PHOTO

Takuji Ishikawa
Section
Graduate School of Biomedical Engineering
Job title
Professor
Degree
  • 博士(工学)(東京工業大学)

  • 修士(工学)(東京工業大学)

Education 2

  • Tokyo Institute of Technology Graduate School, Division of Engineering

    - 1999/03

  • Tokyo Institute of Technology

    - 1994/03

Committee Memberships 45

  • 日本機械学会バイオエンジニアリング部門 副部門長

    2023/04 - Present

  • Asian-Pacific Association for Biomechanics Treasure

    2022/04 - Present

  • 日本国際学生技術研修協会(IAESTE JAPAN) 理事

    2022/04 - Present

  • Asian-Pacific Association for Biomechanics Council Member

    2021/12 - Present

  • 日本機械学会バイオエンジニアリング部門 国際ジャーナル委員会 委員長

    2019/04 - Present

  • Journal of Biomechanical Science and Engineering Editor in Chief

    2019/04 - Present

  • 日本学術会議 連携会員

    2018/04 - Present

  • World Congress of Biomechanics Council Member

    2014/07 - Present

  • BioMedical Engineering Online Associate Editor

    2016/10 - 2022/03

  • 日本機械学会バイオエンジニアリング部門 幹事

    2018/04 - 2020/03

  • 17th International Conference on BioMedical Engineering Member of International Scientific Committee

    2019/01 - 2019/12

  • 日本機械学会東北支部 表彰幹事

    2017/03 - 2019/03

  • 日本機械学会バイオエンジニアリング部門 第93期国際ジャーナル編集委員会 幹事

    2016/04 - 2019/03

  • Journal of Biomechanical Science and Engineering Chief Editor

    2010/04 - 2019/03

  • Journal of Biomechanical Science and Engineering Chief Editor

    2010/04 - 2019/03

  • 日本機械学会表彰部会 委員

    2017/05 - 2018/03

  • 日本機械学会表彰部会 委員

    2017/05 - 2018/03

  • 日本機械学会バイオエンジニアリング部門 2017年度計算力学部門運営委員会 委員

    2017/04 - 2018/03

  • 日本機械学会学術誌編集部会 2017年度英文ジャーナル編修委員会 幹事

    2017/04 - 2018/03

  • 日本機械学会バイオエンジニアリング部門 2017年度計算力学部門運営委員会 委員

    2017/04 - 2018/03

  • 日本機械学会学術誌編集部会 2017年度英文ジャーナル編修委員会 幹事

    2017/04 - 2018/03

  • 5th Switzerland-Japan Workshop on Biomechanixs (SJB 2017) Scientific Committee

    2017/02 - 2017/09

  • 5th Switzerland-Japan Workshop on Biomechanixs (SJB 2017) Scientific Committee

    2017/02 - 2017/09

  • 日本機械学会バイオエンジニアリング部門 第93期国際ジャーナル編集委員会 幹事

    2016/04 - 2017/03

  • 日本機械学会バイオエンジニアリング部門 2016年度計算力学部門運営委員会 委員

    2016/04 - 2017/03

  • 日本機械学会バイオエンジニアリング部門 2016年度計算力学部門運営委員会 委員

    2016/04 - 2017/03

  • The 8th Asian-Pacific Conference on Biomechanics Local Committee member

    2015/09 - 2017/03

  • 日本機械学会バイオエンジニアリング部門 国際委員会 委員長

    2014/04 - 2016/03

  • 日本機械学会流体工学部門 運営委員会 運営委員

    2014/04 - 2016/03

  • 日本機械学会バイオエンジニアリング部門 国際委員会 委員長

    2014/04 - 2016/03

  • 日本機械学会流体工学部門 運営委員会 運営委員

    2014/04 - 2016/03

  • 日本機械学会バイオエンジニアリング部門 企画委員会 委員

    2013/04 - 2015/03

  • 日本機械学会バイオエンジニアリング部門 企画委員会 委員

    2013/04 - 2015/03

  • 日本機械学会バイオエンジニアリング部門 運営委員会 運営委員

    2010/04 - 2012/03

  • 日本機械学会バイオエンジニアリング部門 広報委員会 幹事

    2010/04 - 2012/03

  • 日本機械学会バイオエンジニアリング部門 運営委員会 運営委員

    2010/04 - 2012/03

  • 日本機械学会バイオエンジニアリング部門 広報委員会 幹事

    2010/04 - 2012/03

  • Journal of Biomechanical Science and Engineering Editor

    2009/04 - 2010/03

  • Journal of Biomechanical Science and Engineering Editor

    2009/04 - 2010/03

  • 日本機械学会バイオエンジニアリング部門 運営委員会 運営委員

    2007/04 - 2009/03

  • 日本生体医工学会専門別研究会 バイオメカニクス研究会 幹事

    2007/04 - 2009/03

  • 日本機械学会バイオエンジニアリング部門 運営委員会 運営委員

    2007/04 - 2009/03

  • 日本生体医工学会専門別研究会 バイオメカニクス研究会 幹事

    2007/04 - 2009/03

  • Journal of Biomechanical Science and Engineering Guest Editor

    2007/04 - 2008/03

  • Journal of Biomechanical Science and Engineering Guest Editor

    2007/04 - 2008/03

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Professional Memberships 4

  • 日本流体力学会

  • American Physical Society

  • エアロ・アクアバイオメカニズム学会

  • 日本機械学会

Research Interests 3

  • Biophysics

  • Biomechanics

  • Biological Fluid Mechanics

Research Areas 1

  • Life sciences / Biomedical engineering /

Awards 14

  1. 業績賞

    2023/06 日本機械学会バイオエンジニアリング部門

  2. フェロー

    2023/02 日本機械学会

  3. 流体科学研究賞

    2022/11 一般財団法人 機器研究会 遊泳微生物の流体力学および行動力学に関する研究

  4. JBSE Papers of the year award

    2019/04 Journal of Biomechanical Science and Engineering Elastohydrodynamic phase-lock in two rotating cilia

  5. 可視化情報学会 アートコンテスト金賞

    2015/07/01 可視化情報学会

  6. JBSE Graphics of the year award

    2013/03/30 JSME Bioengineering Division

  7. 青葉工学振興会賞

    2011/12 青葉工学振興会

  8. JBSE Papers of the year award

    2011/11/01 JSME Bioengineering Division

  9. 日本工学教育協会 論文・論説賞

    2010/08 日本工学教育協会

  10. みやぎ産業科学振興基金 研究奨励賞

    2010/05 みやぎ産業科学振興基金

  11. 科学技術分野の文部科学大臣表彰 若手科学者賞

    2010/04 文部科学大臣

  12. 日本機械学会バイオエンジニアリング部門 瀬口賞

    2007/01/07 日本機械学会

  13. 日本機械学会教育賞

    2003/04/01 日本機械学会 子どもの科学技術および理科離れ解消のための公開講座と出前講座 (「賢い主婦への出発」と「機械工学大好き講座」)

  14. 日本機械学会奨励賞

    1999/04/01 日本機械学会 動脈狭窄部を通る血流の研究

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Papers 543

  1. Glucose stockpile in the intestinal apical brush border in C. elegans

    Takumi Saito, Kenji Kikuchi, Takuji Ishikawa

    Biochemical and Biophysical Research Communications 706 2024/04

    DOI: 10.1016/j.bbrc.2024.149762  

    ISSN:0006-291X

    eISSN:1090-2104

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    Revealing the mechanisms of glucose transport is crucial for studying pathological diseases caused by glucose toxicities. Numerous studies have revealed molecular functions involved in glucose transport in the nematode Caenorhabditis elegans, a commonly used model organism. However, the behavior of glucose in the intestinal lumen-to-cell remains elusive. To address that, we evaluated the diffusion coefficient of glucose in the intestinal apical brush border of C. elegans by using fluorescent glucose and fluorescence recovery after photobleaching. Fluorescent glucose taken in the intestine of worms accumulates in the apical brush border, and its diffusion coefficient of ∼10−8 cm2/s is two orders of magnitude slower than that in bulk. This result indicates that the intestinal brush border is a viscous layer. ERM-1 point mutations at the phosphorylation site, which shorten the microvilli length, did not significantly affect the diffusion coefficient of fluorescent glucose in the brush border. Our findings imply that glucose enrichment is dominantly maintained by the viscous layer composed of the glycocalyx and molecular complexes on the apical surface.

  2. Fluid dynamics of squirmers and ciliated microorganisms Invited Peer-reviewed

    Takuji Ishikawa

    Annual Review of Fluid Mechanics 56 95-121 2024/01

  3. High shear flow prevents bundling of bacterial flagella and induces lateral migration away from a wall Peer-reviewed

    Jinyou Yang, Kenji Kikuchi, Takuji Ishikawa

    Communications Physics in press 2023/11

  4. Swimming, Feeding and Inversion of Multicellular Choanoflagellate Sheets Peer-reviewed

    Lloyd Fung, Adam Konkol, Takuji Ishikawa, Ben T. Larson, Thibaut Brune, Raymo, E. Goldstein

    Physical Review Letters 131 168401 2023/10

  5. 50-year History and Perspective on Biomechanics of Swimming Microorganisms: Part II. Collective Behaviours Invited Peer-reviewed

    Journal of Biomechanics 160 111802 2023/09

  6. Computational Fluid Dynamics of Swimming Microorganisms Invited Peer-reviewed

    Toshihiro Omori, Takuji Ishikawa

    Journal of the Physical Society of Japan 92 121002 2023/09

  7. 50-year History and perspective on biomechanics of swimming microorganisms: Part I. Individual behaviours Invited Peer-reviewed

    Takuji Ishikawa, T.J. Pedley

    Journal of Biomechanics 158 111706-111706 2023/09

    Publisher: Elsevier BV

    DOI: 10.1016/j.jbiomech.2023.111706  

    ISSN:0021-9290

  8. Endotracheal tube, by the venturi effect, reduces the efficacy of increasing inlet pressure in improving pendelluft International-journal Peer-reviewed

    Kazuhiro Takahashi, Hiroaki Toyama, Yutaka Ejima, Jinyou Yang, Kenji Kikuchi, Takuji Ishikawa, Masanori Yamauchi

    PLOS ONE 18 e0291319 2023/09

    DOI: 10.1371/journal.pone.0291319  

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    In mechanically ventilated severe acute respiratory distress syndrome patients, spontaneous inspiratory effort generates more negative pressure in the dorsal lung than in the ventral lung. The airflow caused by this pressure difference is called pendelluft, which is a possible mechanisms of patient self-inflicted lung injury. This study aimed to use computer simulation to understand how the endotracheal tube and insufficient ventilatory support contribute to pendelluft. We established two models. In the invasive model, an endotracheal tube was connected to the tracheobronchial tree with 34 outlets grouped into six locations: the right and left upper, lower, and middle lobes. In the non-invasive model, the upper airway, including the glottis, was connected to the tracheobronchial tree. To recreate the inspiratory effort of acute respiratory distress syndrome patients, the lower lobe pressure was set at -13 cmH2O, while the upper and middle lobe pressure was set at -6.4 cmH2O. The inlet pressure was set from 10 to 30 cmH2O to recreate ventilatory support. Using the finite volume method, the total flow rates through each model and toward each lobe were calculated. The invasive model had half the total flow rate of the non-invasive model (1.92 L/s versus 3.73 L/s under 10 cmH2O, respectively). More pendelluft (gas flow into the model from the outlets) was observed in the invasive model than in the non-invasive model. The inlet pressure increase from 10 to 30 cmH2O decreased pendelluft by 11% and 29% in the invasive and non-invasive models, respectively. In the invasive model, a faster jet flowed from the tip of the endotracheal tube toward the lower lobes, consequently entraining gas from the upper and middle lobes. Increasing ventilatory support intensifies the jet from the endotracheal tube, causing a venturi effect at the bifurcation in the tracheobronchial tree. Clinically acceptable ventilatory support cannot completely prevent pendelluft.

  9. Flow-induced diffusion in a packed lattice of squirmers Peer-reviewed

    Yu Kogure, Toshihiro Omori, Takuji Ishikawa

    Journal of Fluid Mechanics 971 A17-1 2023/09

  10. Biophysical Analysis of Mechanical Signals in Immotile Cilia of Mouse Embryonic Nodes Using Advanced Microscopic Techniques Peer-reviewed

    Takanobu Katoh, Toshihiro Omori, Takuji Ishikawa, Yasushi Okada, Hiroshi Hamada

    BIO-PROTOCOL 13 (14) 2023/07/20

    Publisher: Bio-Protocol, LLC

    DOI: 10.21769/bioprotoc.4715  

    ISSN:2331-8325

  11. Effectiveness of substantial shortening of the endotracheal tube for decreasing airway resistance and increasing tidal volume during pressure-controlled ventilation in pediatric patients: a prospective observational study. International-journal Peer-reviewed

    Kazuhiro Takahashi, Hiroaki Toyama, Ryosuke Kubo, Norifumi Yoshida, Yutaka Ejima, Kenji Kikuchi, Takuji Ishikawa, Masanori Yamauchi

    Journal of clinical monitoring and computing 37 1513-1519 2023/06/08

    DOI: 10.1007/s10877-023-01038-w  

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    The endotracheal tubes (ETTs) used for children have a smaller inner diameter. Accordingly, the resistance across ETT (RETT) is higher. Theoretically, shortening the ETTs can decrease total airway resistance (Rtotal), because Rtotal is sum of RETT and patient's airway resistance. However, the effectiveness of ETT shortening for mechanical ventilation in the clinical setting has not been reported. We assessed the effectiveness of shortening a cuffed ETT for decreasing Rtotal, and increasing tidal volume (TV), and estimated the RETT/Rtotal ratio in children. In anesthetized children in a constant pressure-controlled ventilation setting, Rtotal and TV were measured with a pneumotachometer before and after shortening a cuffed ETT. In a laboratory experiment, the pressure gradient across the original length, shortened length, and the slip joint alone of the ETT were measured. We then determined the RETT/Rtotal ratio using the above results. The clinical study included 22 children. The median ETT percent shortening was 21.7%. Median Rtotal was decreased from 26 to 24 cmH2O/L/s, and median TV was increased by 6% after ETT shortening. The laboratory experiment showed that ETT length and the pressure gradient across ETT are linearly related under a certain flow rate, and approximately 40% of the pressure gradient across the ETT at its original length was generated by the slip joint. Median RETT/Rtotal ratio were calculated as 0.69. The effectiveness of ETT shortening on Rtotal and TV was very limited, because the resistance of the slip joint was very large.

  12. Immotile cilia mechanically sense the direction of fluid flow for left-right determination Peer-reviewed

    Takanobu A. Katoh, Toshihiro Omori, Katsutoshi Mizuno, Xiaorei Sai, Katsura Minegishi, Yayoi Ikawa, Hiromi Nishimura, Takeshi Itabashi, Eriko Kajikawa, Sylvain Hiver, Atsuko H. Iwane, Takuji Ishikawa, Yasushi Okada, Takayuki Nishizaka, Hiroshi Hamada

    Science 379 (6627) 66-71 2023/01/06

    Publisher: American Association for the Advancement of Science (AAAS)

    DOI: 10.1126/science.abq8148  

    ISSN:0036-8075

    eISSN:1095-9203

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    Immotile cilia at the ventral node of mouse embryos are required for sensing leftward fluid flow that breaks left-right symmetry of the body. However, the flow-sensing mechanism has long remained elusive. In this work, we show that immotile cilia at the node undergo asymmetric deformation along the dorsoventral axis in response to the flow. Application of mechanical stimuli to immotile cilia by optical tweezers induced calcium ion transients and degradation of Dand5 messenger RNA (mRNA) in the targeted cells. The Pkd2 channel protein was preferentially localized to the dorsal side of immotile cilia, and calcium ion transients were preferentially induced by mechanical stimuli directed toward the ventral side. Our results uncover the biophysical mechanism by which immotile cilia at the node sense the direction of fluid flow.

  13. Reciprocating intestinal flows enhance glucose uptake in C. elegans. International-journal Peer-reviewed

    Yuki Suzuki, Kenji Kikuchi, Keiko Numayama-Tsuruta, Takuji Ishikawa

    Scientific reports 12 (1) 15310-15310 2022/09/21

    DOI: 10.1038/s41598-022-18968-1  

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    Despite its physiological and pathological importance, the mechanical relationship between glucose uptake in the intestine and intestinal flows is unclear. In the intestine of the nematode Caenorhabditis elegans, the defecation motor program (DMP) causes reciprocating intestinal flows. Although the DMP is frequently activated in the intestines, its physiological function is unknown. We evaluated the mechanical signature of enhanced glucose uptake by the DMP in worms. Glucose uptake tended to increase with increasing flow velocity during the DMP because of mechanical mixing and transport. However, the increase in input energy required for the DMP was low compared with the calorie intake. The findings suggest that animals with gastrointestinal motility exploit the reciprocating intestinal flows caused by peristalsis to promote nutrient absorption by intestinal cells.

  14. Instability of an active fluid jet Peer-reviewed

    Takuji Ishikawa, Thanh-Nghi Dang, Eric Lauga

    Physical Review Fluids 7 (9) 2022/09/13

    Publisher: American Physical Society (APS)

    DOI: 10.1103/physrevfluids.7.093102  

    eISSN:2469-990X

  15. Self-sustaining oscillation of two axonemal microtubules based on a stochastic bonding model between microtubules and dynein Peer-reviewed

    T. Omori, S. Munakata, T. Ishikawa

    Physical Review E 106 (1) 2022/07/07

    Publisher: American Physical Society (APS)

    DOI: 10.1103/physreve.106.014402  

    ISSN:2470-0045

    eISSN:2470-0053

  16. Bacterial behaviors in confined diorama environments Peer-reviewed

    Takuji Ishikawa

    Biophysical Journal 121 (13) 2487-2489 2022/07

    Publisher: Elsevier BV

    DOI: 10.1016/j.bpj.2022.05.045  

    ISSN:0006-3495

  17. Soft Microswimmer Powered by Fluid Oscillation Peer-reviewed

    Takuji Ishikawa, Takeru Morita, Toshihiro Omori

    Journal of Robotics and Mechatronics 34 (2) 298-300 2022/04/20

    Publisher: Fuji Technology Press Ltd.

    DOI: 10.20965/jrm.2022.p0298  

    ISSN:0915-3942

    eISSN:1883-8049

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    In this letter, we review the results of our recent studies on a soft microswimmer powered by fluid oscillations. The microswimmer consists of an elastic membrane with a prolate spheroidal reference shape containing a rigid sphere. The swimming direction can be controlled by appropriately applying fluid oscillations. The obtained knowledge will be useful for future artificial microswimmer designs.

  18. Immotile cilia of the mouse node sense a fluid flow–induced mechanical force for left-right symmetry breaking

    Takanobu A. Katoh, Toshihiro Omori, Katsutoshi Mizuno, Xiaorei Sai, Katsura Minegishi, Yayoi Ikawa, Hiromi Nishimura, Takeshi Itabashi, Eriko Kajikawa, Sylvain Hiver, Atsuko H. Iwane, Takuji Ishikawa, Yasushi Okada, Takayuki Nishizaka, Hiroshi Hamada

    2022/04/12

    Publisher: Cold Spring Harbor Laboratory

    DOI: 10.1101/2022.04.11.487968  

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    Immotile cilia of crown cells at the node of mouse embryos are required for sensing of a leftward fluid flow<sup>1</sup> that gives rise to the breaking of left-right (L-R) symmetry<sup>2</sup>. The flow-sensing mechanism has long remained elusive, however, with both mechanosensing and chemosensing models having been proposed<sup>1, 3–5</sup>. Here we show that immotile cilia at the mouse node respond to mechanical force. In the presence of a leftward flow, immotile cilia on the left side of the node bend toward the ventral side whereas those on the right side bend toward the dorsal side. Application of mechanical stimuli to immotile cilia along the dorsoventral axis by optical tweezers induced Ca<sup>2+</sup> transients and degradation of Dand5 mRNA—the first known L-R asymmetric molecular events—in the targeted cells. The Pkd2 channel protein was found to be preferentially localized to the dorsal side of immotile cilia on both left and right sides of the node, and the observed induction of Ca<sup>2+</sup> transients preferentially by mechanical stimuli directed toward the ventral side could explain the differential response of immotile cilia to the directional flow. Our results thus suggest that immotile cilia at the node sense the direction of fluid flow in a manner dependent on a flow-generated mechanical force.

  19. Lubrication theory and boundary element hybrid method for calculating hydrodynamic forces between particles in near contact Peer-reviewed

    Takuji Ishikawa

    Journal of Computational Physics 452 110913-110913 2022/03

    Publisher: Elsevier BV

    DOI: 10.1016/j.jcp.2021.110913  

    ISSN:0021-9991

  20. Pairwise scattering and bound states of spherical microorganisms Peer-reviewed

    C. Darveniza, T. Ishikawa, T. J. Pedley, D. R. Brumley

    Physical Review Fluids 7 (1) 2022/01/31

    Publisher: American Physical Society (APS)

    DOI: 10.1103/physrevfluids.7.013104  

    eISSN:2469-990X

  21. Rheotaxis and migration of an unsteady microswimmer Peer-reviewed

    T. Omori, K. Kikuchi, M. Schmitz, M. Pavlovic, C.-H. Chuang, T. Ishikawa

    Journal of Fluid Mechanics 930 2022/01/10

    Publisher: Cambridge University Press (CUP)

    DOI: 10.1017/jfm.2021.921  

    ISSN:0022-1120

    eISSN:1469-7645

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    Rheotaxis and migration of cells in a flow field have been investigated intensively owing to their importance in biology, physiology and engineering. In this study, first, we report our experiments showing that the microalgae Chlamydomonas can orient against the channel flow and migrate to the channel centre. Second, by performing boundary element simulations, we demonstrate that the mechanism of the observed rheotaxis and migration has a physical origin. Last, using a simple analytical model, we reveal the novel physical mechanisms of rheotaxis and migration, specifically the interplay between cyclic body deformation and cyclic swimming velocity in the channel flow. The discovered mechanism can be as important as phototaxis and gravitaxis, and likely plays a role in the movement of other natural microswimmers and artificial microrobots with non-reciprocal body deformation.

  22. Influence of Respiratory Gas Density on Tidal Volume During Pressure-Controlled Ventilation: A Laboratory Investigation and Observational Study in Children.

    Kazuhiro Takahashi, Hiroaki Toyama, Yutaro Funahashi, Shin Kawana, Yutaka Ejima, Kenji Kikuchi, Takuji Ishikawa, Masanori Yamauchi

    The Tohoku journal of experimental medicine 256 (4) 271-281 2022

    DOI: 10.21203/rs.3.rs-711979/v1  

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    Fluid mechanics show that high-density gases need more energy while flowing through a tube. Thus, high-density anesthetic gases consume more energy to flow and less energy for lung inflation during general anesthesia. However, its impact has not been studied. Therefore, this study aimed to investigate the effects of high-density anesthetic gases on tidal volume in laboratory and clinical settings. In the laboratory study, a test lung was ventilated at the same pressure-controlled ventilation with 22 different gas compositions (density range, 1.22-2.27 kg/m3) using an anesthesia machine. A pneumotachometer was used to record the tidal volume of the test lung and the respiratory gas composition; it showed that the tidal volume of the test lung decreased as the respiratory gas density increased. In the clinical study, the change in tidal volume per body weight, accompanied by gas composition change (2% sevoflurane in oxygen and with 0-30-60% of N2O), was recorded in 30 pediatric patients. The median tidal volume per body weight decreased by 10% when the respiratory gas density increased from 1.41 kg/m3 to 1.70 kg/m3, indicating a significant between-group difference (P < 0.0001). In both settings, an increase in respiratory gas density decreased the tidal volume during pressure-controlled ventilation, which could be explained by the fluid dynamics theory. This study clarified the detailed mechanism of high-density anesthetic gas reduced the tidal volume during mechanical ventilation and revealed that this phenomenon occurs during pediatric anesthesia, which facilitates further understanding of the mechanics of ventilation during anesthesia practice and respiratory physiology.

  23. Microbial Brazil nut effect. International-journal Peer-reviewed

    Atul Srivastava, Kenji Kikuchi, Takuji Ishikawa

    Soft matter 17 (46) 10428-10436 2021/12/01

    DOI: 10.1039/d1sm01327k  

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    The Brazil nut effect (BNE) is a counter-intuitive process of segregation of a large object inside a vibrated granular medium (GM), which has been studied widely by subjecting GMs to various kinds of shears and vibrations. In this article, we report a new kind of BNE which occurs as a consequence of granular fluctuations induced by microbe-generated gas bubbles. We call it the 'microbial Brazil nut effect'. The paper demonstrates microbial BNE for a bidisperse granular mixture as well as for intruder segregation. Furthermore, using X-ray μCT and a simple scaling argument for segregation velocity, the paper clarifies the transport mechanics of an intruder inside a bubbly granular bed. We think the reported phenomenon should be ubiquitous in the microbe-populated wet sandy floors of waterbodies and may have some implication on the distribution of material near the floors.

  24. 工学的アプローチによるモデル生物の流動の医学・生物学的理解

    菊地 謙次, 石川 拓司

    細胞 53 (13) 858-863 2021/11

    Publisher: (株)ニュー・サイエンス社

    ISSN:1346-7557

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    生体における生理的現象は、細胞スケールでの熱的ゆらぎや生化学的反応が支配的なシステムから、組織・臓器スケールでの流動拡散現象が支配的なシステムまで幅広い物理スケールで恒常的に行われている。生体外においては、個体と外界(周囲流体:空気や水など)との干渉は、巨視的な確率論(個体の遭遇確率や数密度)や周囲の構造的制約、周囲流動場により変化し、数理的また工学的に理解されうることが多い。本稿では、モデル生物を用いた生体流動の医学的・生物学的機能を推し量る方法論として、これまでに筆者らが工学的手法を用いて解析してきた研究の概略を解説したい。医学的知見として、ゼブラフィッシュ稚魚を用いた「食後の消化器蠕動運動の変化と腸内における輸送と撹拌」の研究と、ブタ皮膚を用いた「皮膚上皮への機械的摩擦刺激によって生ずる皮膚の物質透過脆弱化」の研究を紹介する。また、生物学的知見として、線虫C.elegansを用いた「餌捕食量と生存率」の研究と、酵母を用いた「生物誘起流れの細胞増殖への自己還元」の研究を紹介する。(著者抄録)

  25. Near-wall rheotaxis of the ciliate <i>Tetrahymena</i> induced by the kinesthetic sensing of cilia Peer-reviewed

    Takuya Ohmura, Yukinori Nishigami, Atsushi Taniguchi, Shigenori Nonaka, Takuji Ishikawa, Masatoshi Ichikawa

    Science Advances 7 (43) 2021/10/22

    Publisher: American Association for the Advancement of Science (AAAS)

    DOI: 10.1126/sciadv.abi5878  

    eISSN:2375-2548

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    Kinesthetic sensing of cilia results in upstream motility for Tetrahymena pyriformis , a typical freshwater microorganism.

  26. Impact of rheological properties on bacterial streamer formation Peer-reviewed

    Hiroki Kitamura, Toshihiro Omori, Takuji Ishikawa

    Journal of The Royal Society Interface 18 (183) 2021/10/20

    Publisher: The Royal Society

    DOI: 10.1098/rsif.2021.0546  

    eISSN:1742-5662

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    Bacterial biofilms, which can be found wherever there is water and a substrate, can cause chronic infections and clogging of industrial flow systems. Despite intensive investigation of the dynamics and rheological properties of biofilms, the impact of their rheological properties on streamer growth remains unknown. We numerically simulated biofilm growth in a pillar-flow and investigated the effects of rheological properties of a filamentous flow-shaped biofilm, called a ‘streamer’, on its formation by varying the viscoelasticity. The flow-field is assumed to be a Stokes flow and is solved by a boundary element method. A Maxwell model is used for extracellular matrix-mediated streamer growth to express the fluidity of streamer formations. Both high elastic modulus and viscosity are needed for streamer formation, and high viscosity promotes streamer growth at low cell concentrations. Our findings are consistent with experimental observations and can explain the relationship between the cell concentrations and viscosity at which streamers form.

  27. Non-biodegradable objects may boost microbial growth in water bodies by harnessing bubbles Peer-reviewed

    Atul Srivastava, Kenji Kikuchi, Takuji Ishikawa

    Royal Society Open Science 8 (9) 210646-210646 2021/09/15

    Publisher: The Royal Society

    DOI: 10.1098/rsos.210646  

    eISSN:2054-5703

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    Given the ubiquity of bubbles and non-biodegradable wastes in aqueous environments, their transport through bubbles should be widely extant in water bodies. In this study, we investigate the effect of bubble-induced waste transport on microbial growth by using yeasts as model microbes and a silicone rubber object as model waste. Noteworthily, this object repeatedly rises and sinks in fluid through fluctuations in bubble-acquired buoyant forces produced by cyclic nucleation, growth and release of bubbles from object's surface. The rise–sink movement of the object gives rise to a strong bulk mixing and an enhanced resuspension of cells from the floor. Such spatially dynamic contaminant inside a nutrient-rich medium also leads to an increment in the total microbe concentration in the fluid. The enhanced concentration is caused by strong nutrient mixing generated by the object's movement which increases the nutrient supply to growing microbes and thereby, prolonging their growth phases. We confirm these findings through a theoretical model for cell concentration and nutrient distribution in fluid medium. The model is based on the continuum hypothesis and it uses the general conservation law which takes an advection–diffusion growth form. We conclude the study with the demonstration of bubble-induced digging of objects from model sand.

  28. Rheology of a concentrated suspension of spherical squirmers: monolayer in simple shear flow Peer-reviewed

    Takuji Ishikawa, D. R. Brumley, T. J. Pedley

    Journal of Fluid Mechanics 914 A26 2021/03

  29. Zigzag instability of biased pusher swimmers Peer-reviewed

    Eric Lauga, Thanh Nghi Dang, Takuji Ishikawa

    EPL 133 44002 2021/02

  30. Cilia and centrosomes: Ultrastructural and mechanical perspectives Invited Peer-reviewed

    Takuji Ishikawa, Hironori Ueno, Toshihiro Omori, Kenji Kikuchi

    Seminars in Cell & Developmental Biology 110 61-69 2021/02

    Publisher: Elsevier BV

    DOI: 10.1016/j.semcdb.2020.03.007  

    ISSN:1084-9521

  31. Swimming microorganisms acquire optimal efficiency with multiple cilia Peer-reviewed

    Toshihiro Omori, Hiroaki Ito, Takuji Ishikawa

    Proceedings of the National Academy of Sciences of the United States of America 117 30201-30207 2020/12

  32. The bubble induced population dynamics of fermenting yeasts Peer-reviewed

    Atul Srivastava, Kenji Kikuchi, Takuji Ishikawa

    Journal of the Royal Society Interface 17 20200735 2020/10

  33. Bacterial Biomechanics - From Individual Behaviors to Biofilm and the Gut Flora - Invited Peer-reviewed

    Takuji Ishikawa, Toshihiro Omori, Kenji Kikuchi

    APL Bioengineering 4 041504 2020/10

  34. Elasto-hydrodynamic interaction of two swimming spermatozoa Peer-reviewed

    Nanami Taketoshi, Toshihiro Omori, Takuji Ishikawa

    Physics of Fluids 32 101901 2020/09

  35. Stability of dancing Volvox Peer-reviewed

    Takuji Ishikawa, T. J. Pedley, K. Drescher, R. E. Goldstein

    Journal of Fluid Mechanics 903 A11 2020/09

  36. Vulnerability of the skin barrier to mechanical rubbing Peer-reviewed

    Kenji Kikuchi, Shunsuke Shigeta, Keiko Tsuruta-Numayama, Takuji Ishikawa

    International Journal of Pharmaceutics 587 119708 2020/07

  37. Active droplet driven by a collective motion of enclosed microswimmers Peer-reviewed

    Zhihan Huang, Toshihiro Omori, Takuji Ishikawa

    Physical Review E 102 022603 2020/07

  38. How do C. elegans worms survive in highly viscous habitats? International-journal Peer-reviewed

    Yuki Suzuki, Kenji Kikuchi, Keiko Numayama-Tsuruta, Takuji Ishikawa

    The Journal of experimental biology 224 jeb.224691 2020/06/25

    DOI: 10.1242/jeb.224691  

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    The nematode Caenorhabditis elegans is a filter feeder, which lives in various viscous habitats such as soil, the intestines of slugs, and rotting materials such as fruits and stems. C. elegans draws in suspensions of bacteria and separates bacteria from water using the pharyngeal pump. Although these worms often live in highly viscous habitats, it is still unclear how they survive in these environments by eating bacteria. In this study, we investigated the effects of suspension viscosity on the survival rate of malnutritioned worms by combining live imaging and scaling analyses. We found that survival rate decreased with increases in viscosity because the high viscosity suppressed the amount of food ingested. The same tendency was found in two feeding defective mutants, eat-6(ad467) and eat-6(ad997). We also found that the high viscosity weakened pump function, but the velocities in the pharynx were not zero, even in the most viscous suspensions. Finally, we estimated the amount of ingested food using scaling analyses, which provided a master curve of the experimental survival rates. These results illustrate that the survival rate of C. elegans worms is strongly dependent on the ingested bacteria per unit time associated with physical environments, such as the viscosity of food suspensions and the number density of bacteria. The pump function of the C. elegans pharynx is not completely lost even in fluids that have 105 times higher viscosity than water, which may contribute to their ability to survive around the world in highly viscous environments.

  39. Rheology of a dilute suspension of deformable microswimmers Peer-reviewed

    Hitomu Matsui, Toshihiro Omori, Takuji Ishikawa

    Physics of Fluids 32 071902 2020/06

  40. Harnessing random low Reynolds number flow for net migration Peer-reviewed

    Takeru Morita, Toshihiro Omori, Yohei Nakayama, Shoichi Toyabe, Takuji Ishikawa

    Physical Review E 101 063101 2020/06

  41. Mechanical roles of anterograde and retrograde intestinal peristalses after feeding in a larval fish (Danio rerio). International-journal Peer-reviewed

    Kenji Kikuchi, Hyeongtak Noh, Keiko Numayama-Tsuruta, Takuji Ishikawa

    American journal of physiology. Gastrointestinal and liver physiology 318 (6) G1013-G1021 2020/04/13

    DOI: 10.1152/ajpgi.00165.2019  

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    Transport in gut is important not only for digestion, metabolism and nutrient uptake but also for microbiotic circumstance in the digestive tract, however, the effects of mixing and pumping in the intestine have not been fully clarified. Therefore, in this study, we quantitatively explored intestinal mixing and pumping represented using a dispersion coefficient and pressure rise in zebrafish larvae, which is a model organism for vertebrate digestive studies, over time by measuring transport phenomena after feeding. Here we provide the first quantitative evidence of the roles of anterograde and retrograde intestinal peristalses in the larval fish of Danio rerio after feeding in terms of digestive pumping and mixing functions by an in vivo imaging of intestinal propagation waves in the larval intestine. Peristaltic velocities in the anterior and posterior intestines change considerably after feeding for 5 hours, while the intervals and amplitudes remain almost constant. The intestinal transport is successively visualized after feeding to elimination. Moreover, the particle tracking velocimetry in the chyme leads our quantitative understanding of outstanding mixing and pumping functions in the anterior and posterior intestines by adopting physical parameters of diffusivity and pressure rise, respectively. From scaling analysis, we found that the anterior intestine maintains mixing for 5 hours from feeding, whereas the posterior intestine activates gradually pumping up. These results suggest that time change of pumping and mixing functions of intestinal peristalsis could considerably influence the nutrient uptake and microbiotic circumstance in the larval fish intestine.

  42. Hydrodynamic interaction of two deformable torque swimmers Peer-reviewed

    Hitomu Matsui, Toshihiro Omori, Takuji Ishikawa

    Journal of Fluid Mechanics 894 A9 2020/04

  43. The shape effect of flagella is more important than bottom-heaviness on passive gravitactic orientation in Chlamydomonas reinhardtii. International-journal Peer-reviewed

    Azusa Kage, Toshihiro Omori, Kenji Kikuchi, Takuji Ishikawa

    The Journal of experimental biology 223 (Pt 5) jeb205989 2020/03

    DOI: 10.1242/jeb.205989  

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    The way the unicellular, biflagellated, green alga Chlamydomonas orients upward has long been discussed in terms of both mechanics and physiology. In this study, we focus on the mechanics, i.e. the 'passive' mechanisms, of gravitaxis. To rotate the body upwards, cellular asymmetry is critical. Chlamydomonas can be depicted as a nearly spherical cell body with two anterior, symmetric flagella. The present study looks at the question of whether the existence of the flagella significantly affects torque generation in upward reorientation. The 'density asymmetry model' assumes that the cell is spherical and bottom-heavy and that the shape and weight of the flagella are negligible, while the 'shape asymmetry model' considers the shape of the flagella. Both our experimental and simulation results revealed a considerable contribution from shape asymmetry to the upward orientation of Chlamydomonas reinhardtii, which was several times larger than that of density asymmetry. From the experimental results, we also quantified the extent of bottom-heaviness, i.e. the distance between the centers of gravity and the figure when the cell body is assumed to be spherical. Our estimation was approximately 30 nm, only one-third of previous assumptions. These findings indicate the importance of the viscous drag of the flagella to the upward orientation, and thus negative gravitaxis, in Chlamydomonas.

  44. Shape matters: Entrapment of a model ciliate at interfaces Peer-reviewed

    Junichi Manabe, Toshihiro Omori and Takuji Ishikawa

    Journal of Fluid Mechanics 892 A15 2020/03

  45. Motility and Phototaxis of Gonium, the Simplest Differentiated Colonial Alga Peer-reviewed

    Helene de Maleprade, Frederic Moisy, Takuji Ishikawa, Raymond E. Goldstein

    Physical Review E 101 022416 2020/02

  46. Particle selectivity of filtering by C. elegans Peer-reviewed

    Yuki Suzuki, Kenji Kikuchi, Keiko Tsuruta-Numayama, Takuji Ishikawa

    Theoretical & Applied Mechanics Letters 9 61-65 2019/11

  47. Swimming mediated by ciliary beating: Comparison with a squirmer model Peer-reviewed

    Hiroaki Ito, Toshihiro Omori, Takuji Ishikawa

    Journal of Fluid Mechanics 874 774-796 2019/07

  48. Swimming of ciliates under geometric constraints Invited Peer-reviewed

    Takuji Ishikawa

    Journal of Applied Physics 125 200901 2019/05

  49. Shear-induced migration of a transmembrane protein within a vesicle Peer-reviewed

    Koyo Nakamura, Toshihiro Omori, Takuji Ishikawa

    Biophysical Journal 116 1483-1494 2019/04

  50. Depth measurement of molecular permeation using inclined confocal microscopy International-journal Peer-reviewed

    Kenji Kikuchi, Shunsuke Shigeta, Takuji Ishikawa

    PLoS ONE 14 (3) e0214504 2019/04

    DOI: 10.1371/journal.pone.0214504  

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    We report a new technique for the high time-resolved depth measurement of molecular concentration distribution in a permeable hydrogel film with micro-depth precision. We developed an inclined observation technique in a laser-induced fluorescence (LIF) system, based on confocal microscopy, which measures the concentration distribution in the depth direction at less than micrometre intervals. The focal plane of confocal microscopy was tilted to enable simultaneous depth scanning in the microscopic field of view inside the permeable substrate. Our system achieved real-time and non-contact depth measurement of concentration distribution in the permeable hydrogel film. Simultaneous depth concentration measurement was realised with < 1 μm/pixel resolution over a maximum depth range of 570 μm, depending on the tilt angle of the stage and optical conditions. Our system measured the concentration of fluorescence materials based on the fluorescence intensities at several depth positions with a minimum concentration resolution of 1.3 nmol/L. Applying the proposed system to real-time concentration imaging, we successfully visualised unsteady concentration transport phenomena, and estimated the mass transport coefficient through the liquid-hydrogel interface. Our findings are useful for investigating the mass transport of physical, biological, and medical phenomena in permeable substrates.

  51. Bacterial detachment from a wall with a line of bump Peer-reviewed

    Jinyou Yang, Yuji Shimogonya, Takuji Ishikawa

    Physical Review E 99 023104 2019/02

  52. Swimming of spermatozoon in a Maxwell fluid Peer-reviewed

    Toshihiro Omori, Takuji Ishikawa

    Micromachines 10 78 2019/01

  53. Stability of a dumbbell micro-swimmer Peer-reviewed

    Takuji Ishikawa

    Micromachines 10 33 2019/01

  54. Biaxial fluid oscillations can propel a micro-capsule swimmer in an arbitrary direction Peer-reviewed

    Takeru Morita, Toshihiro Omori, Takuji Ishikawa

    Physical Review E 98 063102 2018/12

  55. Elastohydrodynamic phase-lock in two rotating cilia Peer-reviewed

    Toshihiro OMORI, Mingming LU, Takuji ISHIKAWA

    Journal of Biomechanical Science and Engineering 13 17-00699 2018/12

  56. Passive swimming of a micro-capsule in vertical fluid oscillation Peer-reviewed

    Takeru Morita, Toshihiro Omori, Takuji Ishikawa

    Physical Review E 98 023108 2018/08

  57. Influence of cellular shape on sliding behavior of ciliates Peer-reviewed

    Yukinori Nishigami, Takuya Ohmura, Atsushi Taniguchi, Shigenori Nonaka, Junichi Manabe, Takuji Ishikawa, Masatoshi Ichikawa

    Communicative & Integrative Biology 11 e1506666 2018/08

  58. Simulation of the nodal flow of Dpcd and Rfx3 mutant embryo: comparison of mechano-sensing and morphogen transport hypotheses Peer-reviewed

    Toshihiro Omori, Katja Winter, Kyosuke Shinohara, Hiroshi Hamada, Takuji Ishikawa

    Royal Society Open Science 5 180601 2018/08

  59. Asymmetry in cilia configuration induces hydrodynamic phase locking Peer-reviewed

    Keiji Okumura, Seiya Nishikawa, Toshihiro Omori, Takuji Ishikawa, Atsuko Takamatsu

    Physical Review E 97 032411 2018/03

  60. Simple mechanosense and response of cilia motion reveal the intrinsic habits of ciliates Peer-reviewed

    Takuya Ohmura, Yukinori Nishigami, Atsushi Taniguchi, Shigenori Nonaka, Jun-ichi Manabe, Takuji Ishikawa, Masatoshi Ichikawa

    Proceedings of the National Academy of Sciences of the United States of America 115 3231-3236 2018/03

  61. What causes the spatial heterogeneity of bacterial flora in the intestine of zebrafish larvae? Peer-reviewed

    Jinyou Yang, Yuji Shimogonya, Takuji Ishikawa

    Journal of Theoretical Biology 446 101-109 2018/03

    DOI: 10.1016/j.jtbi.2018.03.007  

  62. Collective spreading of red blood cells flowing in a microchannel. International-journal Peer-reviewed

    Cheng-Hsi Chuang, Kenji Kikuchi, Hironori Ueno, Keiko Numayama-Tsuruta, Takami Yamaguchi, Takuji Ishikawa

    Journal of biomechanics 69 64-69 2018/03/01

    DOI: 10.1016/j.jbiomech.2018.01.009  

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    Due to recent advances in micro total analysis system technologies, microfluidics provides increased opportunities to manipulate, stimulate, and diagnose blood cells. Controlling the concentration of cells at a given position across the width of a channel is an important aspect in the design of microfluidic devices. Despite its biomedical importance, the collective spreading of red blood cells (RBCs) in a microchannel has not yet been fully clarified. In this study, we experimentally investigated the collective spreading of RBCs in a straight microchannel, and found that RBCs initially distributed in one side of the microchannel spread to the spanwise direction during downstream flow. Spreading increased considerably as the hematocrit increased, though the flow rate had a small effect. We proposed a scaling argument to show that this spreading phenomenon was diffusive and mainly induced by cell-cell interactions. The dispersion coefficient was approximately proportional to the flow rate and the hematocrit. These results are useful in understanding collective behaviors of RBCs in a microchannel and in microcirculation.

  63. Biomechanics of Tetrahymena escaping from a dead end Peer-reviewed

    Takuji Ishikawa, Kenji Kikuchi

    Proceedings of the Royal Society B 285 20172368 2018/02

  64. Active particles in periodic lattices Peer-reviewed

    Alexander Chamolly, Takuji Ishikawa, Eric Lauga

    New Journal of Physics 19 115001-1-115001-13 2017/11/07

  65. Swimming Behavior of Neutral Squirmer against Non-Slip Boundary

    T. Ohmura, Y. Nishigami, J. Manabe, T. Ishikawa, M. Ichikawa

    International Symposium on Fluctuation and Structure out of Equilibrium 2017 (SFS2017) 2017/11

  66. Biomechanics of Tetrahymena escaping from dead ends

    TAKUJI ISHIKAWA, KENJI KIKUCHI

    Bulletin of the American Physical Society DFD2017 62 (14) 407-407 2017/11

  67. Micro-navigation in complex periodic environments

    ALEXANDER CHAMOLLY, TAKUJI ISHIKAWA, ERIC LAUGA

    Bulletin of the American Physical Society DFD2017 62 (14) 58-58 2017/11

  68. Transport phenomena in the intestine of zebrafish larvae

    Jinyou Yang, Yuji Shimogonya, Takuji Ishikawa

    5th Switzerland-Japan Workshop on Biomechanics (SJB2017) 46-46 2017/09

  69. Nodal cilia-driven flow: Development of a computational model of the nodal cilia axoneme Peer-reviewed

    T. Omori, H. Sugai, Y. Imai, T. Ishikawa

    JOURNAL OF BIOMECHANICS 61 242-249 2017/08

    Publisher: ELSEVIER SCI LTD

    DOI: 10.1016/j.jbiomech.2017.07.025  

    ISSN:0021-9290

    eISSN:1873-2380

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    Cilia-driven nodal flow is important in the determination of left-right asymmetry in the body. Several theoretical and computational models have been proposed to explain the mechanics of ciliary motion, although the full mechanism remains unknown. Here, we developed a three-dimensional nodal cilia axoneme model using a finite element-boundary element coupling method, and investigated the mechanics of nodal ciliary motion. We found that the rotational orbit was strongly dependent on the dynein activation frequency. We also investigated flow field generated by the ciliary rotation, and the flow strength decayed as r(-3) at the far field from the cilium. Our numerical results also suggest that experimentally observed tilt angle theta = 2 pi/9 is sufficiently large to make a leftward flow. These findings are helpful in better understanding ciliary motion and nodal flow. (C) 2017 Elsevier Ltd. All rights reserved.

  70. VISCOUS LOAD CHANGES THE CILIARY FORCE AND FLOW ON A TRACHEAL LUMEN

    Takuji Ishikawa, Kenji Kikuchi, Tomofumi Haga, Keiko Numayama-Tsuruta, Hironori Ueno

    The 26th Congress of the International Society of Biomechanics (ISB 2017) 2017/07

  71. TRANSDERMAL DRUG DELIVERY ENHANCEMENT BY UNIDIRECTIONAL SKIN EXTENSION

    Sho Sugawara, Kenji Kikuchi, Shunsuke Shigeta, Keiko Numayama-Tsuruta, Takuji Ishikawa

    The 26th Congress of the International Society of Biomechanics (ISB 2017) 2017/07

  72. UPSTREAM SWIMMING OF A SPERM CELL IN SHEAR FLOW

    Toshihiro Omori, Takuji Ishikawa

    The 26th Congress of the International Society of Biomechanics (ISB 2017) 2017/07

  73. A BOUNDARY ELEMENT METHOD FOR CELLULAR SCALE PHYSIOLOGICAL FLOW PROBLEMS: PASSIVE MOTIONS OF RED BLOOD CELLS AND ACTIVE MOTIONS OF CILIA AND FLAGELLA Invited

    Toshihiro Omori, Yohsuke Imai, Takami Yamaguchi, Takuji Ishikawa

    The 26th Congress of the International Society of Biomechanics (ISB 2017) 2017/07

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    Yamaguchi Medal 受賞講演

  74. Shear-induced platelet aggregation and distribution of thrombogenesis at the stenotic vessel Peer-reviewed

    Hiroki Kamada, Yohsuke Imai, Masanori Nakamura, Takuji Ishikawa, Takami Yamaguchi

    Microcirculation 24 (4) e12355-1-e12355-8 2017/05/15

  75. Integrated nanobiomechanics of the living system

    T. Yamaguchi, Y. Imai, T. Ishikawa

    19th International Conference on Finite Elements in Flow Problems 2017/04

  76. Mixing and pumping functions of the intestine of zebrafish larvae Peer-reviewed

    Jinyou Yang, Yuji Shimogonya, Takuji Ishikawa

    JOURNAL OF THEORETICAL BIOLOGY 419 152-158 2017/04

    Publisher: ACADEMIC PRESS LTD- ELSEVIER SCIENCE LTD

    DOI: 10.1016/j.jtbi.2017.02.004  

    ISSN:0022-5193

    eISSN:1095-8541

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    Due to its transparency, the intestine of zebrafish larvae has been widely used in studies of gastrointestinal diseases and the microbial flora of the gut. However, transport phenomena in the intestine of zebrafish larvae have not been fully clarified. In this study, therefore, transport caused by peristaltic motion in the intestine of zebrafish larvae was investigated by numerical simulation. An anatomically realistic three-dimensional geometric model of the intestine at various times after feeding was constructed based on the experimental data of Field et al. (2009). The flow of digested chyme was analyzed using the governing equations of fluid mechanics, together with peristaltic motion and long-term contraction of the intestinal wall. The results showed that retrograde peristaltic motion was the main contributor to the mixing function. The dispersion caused by peristalsis over 30 min was in the order of 10(-12) m(2)/s, which is greater than the Brownian diffusion of a sphere of 0.4 mu m diameter. In contrast, anterograde peristaltic motion contributed mainly to the pumping function. The pressure decrease due to peristalsis was in the order of millipascals, which may reduce the activation and maintenance heat of intestinal muscle. These findings enhance our understanding of the mixing and pumping functions of the intestine of zebrafish larvae.

  77. Effect of Fluid Viscosity on the Cilia-Generated Flow on a Mouse Tracheal Lumen Peer-reviewed

    Kenji Kikuchi, Tomofumi Haga, Keiko Numayama-Tsuruta, Hironori Ueno, Takuji Ishikawa

    ANNALS OF BIOMEDICAL ENGINEERING 45 (4) 1048-1057 2017/04

    Publisher: SPRINGER

    DOI: 10.1007/s10439-016-1743-y  

    ISSN:0090-6964

    eISSN:1573-9686

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    Mucous flow in a tracheal lumen is generated by the beat motion of ciliated cells to provide a clearance function by discharging harmful dust particles and viruses. Due to its physiological importance, the cilia-generated flow and the rheological properties of mucus have been investigated intensively. The effects of viscosity on the cilia-generated flow, however, have not been fully clarified. In this study, we measured bulk background velocity of ciliary flow using a micro particle tracking velocimetry method under various viscosity conditions in mice. The results showed that the flow velocity decreased as the increase with viscosity of ambient fluid. Moreover, no previous study has clarified the pump power generated by cilia, which provides important information with regard to understanding the molecular motor properties of cilia. Measurements of both the ciliary flow and the ciliary motion were conducted to determine the cilia pump power. Our results indicated that the cilia pump during the effective stroke did not drive the ciliary flow efficiently under high viscosity conditions; these findings are necessary to resolve the clearance function.

  78. Extending Whole Slide Imaging: Color Darkfield Internal Reflection Illumination (DIRI) for Biological Applications Peer-reviewed

    Yoshihiro Kawano, Kana Namiki, Atsushi Miyawaki, Takuji Ishikawa

    PLoS ONE 12 (1) e0167774-1-e0167774-10 2017/01/13

  79. RELATIONSHIP BETWEEN PERISTALTIC CONTRACTION AND GASTRIC MIXING

    Yohsuke Imai, Taimei Miyagawa, Shunichi Ishida, Takami Yamaguchi, Takuji Ishikawa

    Abstracts Book of the 16th International Conference on Biomedical Engineering 167 2016/12

  80. DEVELOPMENT OF A BIOMECHANICAL MODEL OF CELL BEHAVIOR SUBJECTED TO CYCLIC STRETCH

    Fumiyasu Saito, Yohsuke Imai, Shunichi Ishida, Toshihiro Omori, Takuji Ishikawa

    Abstracts Book of the 16th International Conference on Biomedical Engineering 163 2016/12

  81. A NUMERICAL ANALYSIS OF THE LATERAL MIGRATION OF FLOWING CELLS

    Stephanie Nix, Yohsuke Imai, Takuji Ishikawa

    Abstracts Book of the 16th International Conference on Biomedical Engineering 54 2016/12

  82. NUMERICAL STUDY ON MIXING AND PUMPING FUNCTIONS GENERATED BY PERISTALSIS IN A ZEBRAFISH INTESTINE

    Jinyou Yang, Yuji Shimogonya, Takuji Ishikawa

    Abstracts Book of the 16th International Conference on Biomedical Engineering 44 2016/12

  83. NUMERICAL SIMULATION OF A SPERM CELL IN SHEAR FLOW NEAR AN INFINITE BOUNDARY WALL

    Toshihiro Omori, Takuji Ishikawa

    Abstracts Book of the 16th International Conference on Biomedical Engineering 34 2016/12

  84. Relationship between gastric motility and liquid mixing in the stomach Peer-reviewed

    Taimei Miyagawa, Yohsuke Imai, Shunichi Ishida, Takuji Ishikawa

    AMERICAN JOURNAL OF PHYSIOLOGY-GASTROINTESTINAL AND LIVER PHYSIOLOGY 311 (6) G1114-G1121 2016/12

    Publisher: AMER PHYSIOLOGICAL SOC

    DOI: 10.1152/ajpgi.00346.2016  

    ISSN:0193-1857

    eISSN:1522-1547

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    The relationship between gastric motility and the mixing of liquid food in the stomach was investigated with a numerical analysis. Three parameters of gastric motility were considered: the propagation velocity, frequency, and terminal acceleration of peristaltic contractions. We simulated gastric flow with an anatomically realistic geometric model of the stomach, considering free surface flow and moving boundaries. When a peristaltic contraction approaches the pylorus, retropulsive flow is generated in the antrum. Flow separation then occurs behind the contraction. The extent of flow separation depends on the Reynolds number (Re), which quantifies the inertial forces due to the peristaltic contractions relative to the viscous forces of the gastric contents; no separation is observed at low Re, while an increase in reattachment length is observed at high Re. While mixing efficiency is nearly constant for low Re, it increases with Re for high Re because of flow separation. Hence, the effect of the propagation velocity, frequency, or terminal acceleration of peristaltic contractions on mixing efficiency increases with Re.

  85. Precession in Stokes flow: spin and revolution of a bacterial flagellum

    TAKUJI ISHIKAWA, YOICHIRO SAWANO, HIROMICHI WAKEBE, YUICHI INOUE, AKIHIKO ISHIJIMA, YUJI SHIMOGONYA

    The 69th Annual Meetin g of The American Physical Society, Bulletin of the American Physical Society, DED 2016 61 546 2016/11

  86. Numerical analysis of cell adhesion in capillary flow

    NAOKI TAKEISHI, YOHSUKE IMAI, SHUNICHI ISHIDA, TOSHIHIRO OMORI, ROGER KAMM, TAKUJI ISHIKAWA

    The 69th Annual Meetin g of The American Physical Society, Bulletin of the American Physical Society, DED 2016 61 72 2016/11

  87. Reorientation of a single red blood cell during sedimentation Peer-reviewed

    D. Matsunaga, Y. Imai, C. Wagner, T. Ishikawa

    JOURNAL OF FLUID MECHANICS 806 102-128 2016/11

    Publisher: CAMBRIDGE UNIV PRESS

    DOI: 10.1017/jfm.2016.601  

    ISSN:0022-1120

    eISSN:1469-7645

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    The reorientation phenomenon of a single red blood cell during sedimentation is simulated using the boundary element method. The cell settles downwards due to a density difference between the internal and external fluids, and it changes orientation toward a vertical orientation regardless of Bond number or viscosity ratio. The reorientation phenomenon is explained by a shape asymmetry caused by the gravitational driving force, and the shape asymmetry increases almost linearly with the Bond number. When velocities are normalised by the driving force, settling/drifting velocities are weak functions of the Bond number and the viscosity ratio, while the angular velocity of the reorientation drastically changes with these parameters: the angular velocity is smaller for lower Bond number or higher viscosity ratio. As a consequence, trajectories of the sedimentation are also affected by the angular velocity, and blood cells with slower reorientation travel longer distances in the drifting direction. We also explain the mechanism of the reorientation using an asymmetric dumbbell. From the analysis, we show that the magnitude of the angular velocity is explained by two main factors: the shape asymmetry and the instantaneous orientation angle.

  88. Rheotaxis of a Sperm Cell in Shear Flow Near an Infinite Plane Wall, The 7th International Conference on Computational Methods

    Toshihiro Omori, Takuji Ishikawa

    The 7th International Conference on Computational Methods MS-043 2016/08

  89. Cell adhesion during bullet motion in capillaries Peer-reviewed

    Naoki Takeishi, Yohsuke Imai, Shunichi Ishida, Toshihiro Omori, Roger D. Kamm, Takuji Ishikawa

    AMERICAN JOURNAL OF PHYSIOLOGY-HEART AND CIRCULATORY PHYSIOLOGY 311 (2) H395-H403 2016/08

    Publisher: AMER PHYSIOLOGICAL SOC

    DOI: 10.1152/ajpheart.00241.2016  

    ISSN:0363-6135

    eISSN:1522-1539

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    A numerical analysis is presented of cell adhesion in capillaries whose diameter is comparable to or smaller than that of the cell. In contrast to a large number of previous efforts on leukocyte and tumor cell rolling, much is still unknown about cell motion in capillaries. The solid and fluid mechanics of a cell in flow was coupled with a slip bond model of ligand-receptor interactions. When the size of a capillary was reduced, the cell always transitioned to "bullet-like" motion, with a consequent decrease in the velocity of the cell. A state diagram was obtained for various values of capillary diameter and receptor density. We found that bullet motion enables firm adhesion of a cell to the capillary wall even for a weak ligand-receptor binding. We also quantified effects of various parameters, including the dissociation rate constant, the spring constant, and the reactive compliance on the characteristics of cell motion. Our results suggest that even under the interaction between P-selectin glycoprotein ligand-1 (PSGL-1) and P-selectin, which is mainly responsible for leukocyte rolling, a cell is able to show firm adhesion in a small capillary. These findings may help in understanding such phenomena as leukocyte plugging and cancer metastasis.

  90. Bayesian Inference of Forces Causing Cytoplasmic Streaming in Caenorhabditis elegans Embryos and Mouse Oocytes Peer-reviewed

    Ritsuya Niwayama, Hiromichi Nagao, Tomoya, S. Kitajima, Lars Hufnagel, Kyosuke Shinohara, Tomoyuki Higuchi, Takuji Ishikawa, Akatsuki Kimura

    PLoS ONE 11 (7) e0159917-1-e0159917-18 2016/07/29

  91. Numerical methods for simulating blood flow at macro, micro, and multi scales Peer-reviewed

    Yohsuke Imai, Toshihiro Omori, Yuji Shimogonya, Takami Yamaguchi, Takuji Ishikawa

    Journal of Biomechanics 49 (11) 2221-2228 2016/07/26

    Publisher: Elsevier Ltd

    DOI: 10.1016/j.jbiomech.2015.11.047  

    ISSN:1873-2380 0021-9290

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    In the past decade, numerical methods for the computational biomechanics of blood flow have progressed to overcome difficulties in diverse applications from cellular to organ scales. Such numerical methods may be classified by the type of computational mesh used for the fluid domain, into fixed mesh methods, moving mesh (boundary-fitted mesh) methods, and mesh-free methods. The type of computational mesh used is closely related to the characteristics of each method. We herein provide an overview of numerical methods recently used to simulate blood flow at macro and micro scales, with a focus on computational meshes. We also discuss recent progress in the multi-scale modeling of blood flow.

  92. Asymmetry of Arrangement Induces Phase Synchronization in Mouse Node Cilia

    Keiji Okumura, Seiya Nishikawa, Toshihiro Omori, Takuji Ishikawa, Atsuko Takamatsu

    26th IUPAP International conference on Statistical Physics 421 2016/07

  93. Orientation change of a single red blood cell during sedimentation

    Daiki Matsunaga, Yohsuke Imai, Christian Wagner, Takuji Ishikawa

    Summer School 2016 Active Complex Matter 2016/07

    DOI: 10.1017/jfm.2016.601  

  94. MEASURMENT OF DRUG PERMEATION IN THE SKIN BY A TWO PHOTON MICROSCOPY

    Shunsuke Shigeta, Kenji Kikuchi, Keiko Numayama, Takuji Ishikawa

    22nd Congress of the European Society of Biomechanics OS21-1 2016/07

  95. Bio-Micropump by Using a Flagellate Propulsive Force of Escherichia Coli

    K. Kikuchi, R. Matsuura, H. Ueno, Y Imai, N. Matsuki, T. Yamaguchi, T. Ishikawa

    The 24th World Congress on Engineering 2016 515-518 2016/07

  96. Similarities and differences between flow mode of a leukocyte and circulating tumor cell in microvessels

    Naoki Takeishi, Yohsuke Imai, Takami Yamaguchi, Takuji Ishikawa

    Summer Biomechanics, Bioengineering and Biotransport Conference 742 2016/07

  97. Lateral migration of a capsule in a parabolic flow Peer-reviewed

    S. Nix, Y. Imai, T. Ishikawa

    JOURNAL OF BIOMECHANICS 49 (11) 2249-2254 2016/07

    Publisher: ELSEVIER SCI LTD

    DOI: 10.1016/j.jbiomech.2015.11.038  

    ISSN:0021-9290

    eISSN:1873-2380

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    Red blood cells migrate to the center of the blood vessel in a process called axial migration, while other blood cells, such as white blood cells and platelets, are disproportionately found near the blood vessel wall. However, much is still unknown concerning the lateral migration of cells in the blood; the specific effect of hydrodynamic factors such as a wall or a shear gradient is still unclear. In this study, we investigate the lateral migration of a capsule using the boundary integral method, in order to compute exactly an infinite computational domain for an unbounded parabolic flow and a semi-infinite computational domain for a near-wall parabolic flow in the limit of Stokes flow. We show that the capsule lift velocity in an unbounded parabolic flow is linear with respect to the shear gradient, while the lift velocity in a near-wall parabolic flow is dependent on the distance to the wall. Then, using these relations, we give an estimation of the relative effect of the shear gradient as a function of channel width and distance between the capsule and the wall. This estimation can be used to determine cases in which the effect of the shear gradient or wall can be neglected; for example, the formation of the cell-free layer in blood vessels is determined to be unaffected by the magnitude of the shear gradient. (C) 2015 Elsevier Ltd. All rights reserved.

  98. Enhancing cell-free layer thickness by bypass channels in a wall Peer-reviewed

    M. Saadatmand, Y. Shimogonya, T. Yamaguchi, T. Ishikawa

    JOURNAL OF BIOMECHANICS 49 (11) 2299-2305 2016/07

    Publisher: ELSEVIER SCI LTD

    DOI: 10.1016/j.jbiomech.2015.11.032  

    ISSN:0021-9290

    eISSN:1873-2380

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    When blood flows near a wall, red blood cells (RBCs) drift away from the wall and a cell-free layer (CFL) is formed adjacent to the wall. Controlling the CFL thickness is important for preventing adhesion of cells in the design of biomedical devices. In this study, a novel wall configuration with stenoses and bypass channels is proposed to increase the CFL thickness. We found that the presence of bypass channels modified the spatial distribution of cells and substantially increased the CFL downstream of the stenosis. A single-bypass geometry with 5% hematocrit (Hct) blood flow showed a 1.7 mu m increase in CFL thickness compared to without the bypass. In the case of three bypass channels, a 3 gm increase in CFL thickness was observed. The CFL enhancement was observed up to 10% Hct, but no significant enhancement of CFL was indicated for 20% Hct blood flow. The mechanism of the CFL enhancement was investigated using a numerical simulation of the flow field. The results showed that the distance between each streamline and the corner of the stenosis compared with size of RBC was important parameter in regulating CFL thickness. These results show the potential of the proposed mechanism to prevent adhesion of cells to biomedical devices. (C) 2015 Elsevier Ltd. All rights reserved.

  99. Numerical methods for simulating blood flow at macro, micro, and multi scales Peer-reviewed

    Yohsuke Imai, Toshihiro Omori, Yuji Shimogonya, Takami Yamaguchi, Takuji Ishikawa

    JOURNAL OF BIOMECHANICS 49 (11) 2221-2228 2016/07

    Publisher: ELSEVIER SCI LTD

    DOI: 10.1016/j.jbiomech.2015.11.047  

    ISSN:0021-9290

    eISSN:1873-2380

    More details Close

    In the past decade, numerical methods for the computational biomechanics of blood flow have progressed to overcome difficulties in diverse applications from cellular to organ scales. Such numerical methods may be classified by the type of computational mesh used for the fluid domain, into fixed mesh methods, moving mesh (boundary-fitted mesh) methods, and mesh-free methods. The type of computational mesh used is closely related to the characteristics of each method. We herein provide an overview of numerical methods recently used to simulate blood flow at macro and micro scales, with a focus on computational meshes. We also discuss recent progress in the multi-scale modeling of blood flow. (C) 2015 Elsevier Ltd. All rights reserved.

  100. Response to the Letter to the Editor "Hemodynamics in the Microcirculation" by A. G. Koutsiaris

    Toshihiro Omori, Yohsuke Imai, Kenji Kikuchi, Takuji Ishikawa, Takami Yamaguchi

    ANNALS OF BIOMEDICAL ENGINEERING 44 (4) 1323-1323 2016/04

    Publisher: SPRINGER

    DOI: 10.1007/s10439-016-1570-1  

    ISSN:0090-6964

    eISSN:1573-9686

  101. Upward swimming of a sperm cell in shear flow Peer-reviewed

    Toshihiro Omori, Takuji Ishikawa

    PHYSICAL REVIEW E 93 (3) 032402 2016/03

    Publisher: AMER PHYSICAL SOC

    DOI: 10.1103/PhysRevE.93.032402  

    ISSN:2470-0045

    eISSN:2470-0053

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    Mammalian sperm cells are required to swim over long distances, typically around 1000-fold their own length. They must orient themselves and maintain a swimming motion to reach the ovum, or egg cell. Although the mechanism of long-distance navigation is still unclear, one possible mechanism, rheotaxis, was reported recently. This work investigates the mechanism of the rheotaxis in detail by simulating the motions of a sperm cell in shear flow adjacent to a flat surface. A phase diagram was developed to show the sperm's swimming motion under different shear rates, and for varying flagellum waveform conditions. The results showed that, under shear flow, the sperm is able to hydrodynamically change its swimming direction, allowing it to swim upwards against the flow, which suggests that the upward swimming of sperm cells can be explained using fluid mechanics, and this can then be used to further understand physiology of sperm cell navigation.

  102. Inhomogeneous distribution of Chlamydomonas in a cylindrical container with a bubble plume Peer-reviewed

    Yuki Nonaka, Kenji Kikuchi, Keiko Numayama-Tsuruta, Azusa Kage, Hironori Ueno, Takuji Ishikawa

    BIOLOGY OPEN 5 (2) 154-160 2016/02

    Publisher: COMPANY OF BIOLOGISTS LTD

    DOI: 10.1242/bio.015669  

    ISSN:2046-6390

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    Swimming microalgae show various taxes, such as phototaxis and gravitaxis, which sometimes result in the formation of a cell-rich layer or a patch in a suspension. Despite intensive studies on the effects of shear flow and turbulence on the inhomogeneous distribution of microalgae, the effect of a bubble plume has remained unclear. In this study, we used Chlamydomonas as model microalgae, and investigated the spatial distribution of cells in a cylindrical container with a bubble plume. The results illustrate that cells become inhomogeneously distributed in the suspension due to their motility and photo-responses. A vortical ring distribution was observed below the free surface when the bubble flow rate was sufficiently small. We performed a scaling analysis on the length scale of the vortical ring, which captured the main features of the experimental results. These findings are important in understanding transport phenomena in a microalgae suspension with a bubble plume.

  103. Nutrient uptake in a suspension of squirmers Peer-reviewed

    Takuji Ishikawa, Shunsuke Kajiki, Yohsuke Imai, Toshihiro Omori

    JOURNAL OF FLUID MECHANICS 789 481-499 2016/02

    Publisher: CAMBRIDGE UNIV PRESS

    DOI: 10.1017/jfm.2015.741  

    ISSN:0022-1120

    eISSN:1469-7645

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    Nutrient uptake is one of the most important factors in cell growth. Despite the biological importance, little is known about the effect of cell-cell hydrodynamic interactions on nutrient uptake in a suspension of swimming micro-organisms. In this study, we numerically investigate the nutrient uptake in an infinite suspension of squirmers. In the dilute limit, our results are in good agreement with a previous study by Magar et al. (Q. J. Mech. Appl. Maths, vol. 56, 2003, pp. 65-91). When we increased the volume fraction of squirmers, the nutrient uptake of individual cells was enhanced by the hydrodynamic interactions. The average nutrient concentration in the suspension decayed exponentially as a function of time, and the relaxation time could be scaled using the Sherwood number, the Peclet number and the volume fraction of cells. We propose a fitting function for the Sherwood number, which is useful in predicting nutrient uptake in the non-dilute regime. Furthermore, we analyse the swimming energy consumed by individual cells. The results indicate that both the energetic cost and the nutrient uptake increased as the volume fraction of cells was increased, and that the uptake per unit energy was not significantly affected by the volume fraction. These findings are important in understanding the mass transport and metabolism of swimming micro-organisms in nature and for industrial applications.

  104. Rheology of a dense suspension of spherical capsules under simple shear flow Peer-reviewed

    D. Matsunaga, Y. Imai, T. Yamaguchi, T. Ishikawa

    JOURNAL OF FLUID MECHANICS 786 110-127 2016/01

    Publisher: CAMBRIDGE UNIV PRESS

    DOI: 10.1017/jfm.2015.666  

    ISSN:0022-1120

    eISSN:1469-7645

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    We present a numerical analysis of the rheology of a dense suspension of spherical capsules in simple shear flow in the Stokes flow regime. The behaviour of neo-Hookean capsules is simulated for a volume fraction up to phi = 0.4 by graphics processing unit computing based on the boundary element method with a multipole expansion. To describe the specific viscosity using a polynomial equation of the volume fraction, the coefficients of the equation are calculated by least-squares fitting. The results suggest that the effect of higher-order terms is much smaller for capsule suspensions than rigid sphere suspensions; for example, O(phi(3)) terms account for only 8 % of the specific viscosity even at phi = 0.4 for capillary numbers Ca &gt;= 0.1. We also investigate the relationship between the deformation and orientation of the capsules and the suspension rheology. When the volume fraction increases, the deformation of the capsules increases while the orientation angle of the capsules with respect to the flow direction decreases. Therefore, both the specific viscosity and the normal stress difference increase with volume fraction due to the increased deformation, whereas the decreased orientation angle suppresses the specific viscosity, but amplifies the normal stress difference.

  105. A numerical model of a red blood cell infected by Plasmodium falciparum malaria: coupling cell mechanics with ligand-receptor interactions Peer-reviewed

    Shunichi Ishida, Yohsuke Imai, Yuki Ichikawa, Stephanie Nix, Daiki Matsunaga, Toshihiro Omori, Takuji Ishikawa

    SCIENCE AND TECHNOLOGY OF ADVANCED MATERIALS 17 (1) 454-461 2016

    Publisher: TAYLOR & FRANCIS LTD

    DOI: 10.1080/14686996.2016.1211462  

    ISSN:1468-6996

    eISSN:1878-5514

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    We developed a numerical model of the behavior of a red blood cell infected by Plasmodium falciparum malaria on a wall in shear flow. The fluid and solid mechanics of an infected red blood cell (Pf-IRBC) were coupled with the biochemical interaction of ligand-receptor bindings. We used the boundary element method for fluid mechanics, the finite element method for membrane mechanics, and the Monte Carlo method for ligand-receptor interactions. We simulated the behavior of a Pf-IRBC in shear flow, focusing on the effects of bond type. For slip bonds, the Pf-IRBC exhibited firm adhesion, tumbling motion, and tank-treading motion, depending on the applied shear rate. The behavior of catch bonds resembled that of slip bonds, except for a 'catch' state at high shear stress. When the reactive compliance decreased to a value in the order of 10(-2) nm, both the slip and catch bonds behaved like an ideal bond. Such bonds do not respond to the force applied to the bond, and the velocity is stabilized at a high shear rate. Finally, we compared the numerical results with previous experiments for A4- and ItG-infected cells. We found that the interaction between PfEMP1 and ICAM-1 could be a nearly ideal bond, with a dissociation rate ranging from 30 s(-1) to 100 s(-1).[GRAPHICS]

  106. Deformation of a micro-torque swimmer Peer-reviewed

    Takuji Ishikawa, Tomoyuki Tanaka, Yohsuke Imai, Toshihiro Omori, Daiki Matsunaga

    PROCEEDINGS OF THE ROYAL SOCIETY A-MATHEMATICAL PHYSICAL AND ENGINEERING SCIENCES 472 (2185) 20150604 2016/01

    Publisher: ROYAL SOC

    DOI: 10.1098/rspa.2015.0604  

    ISSN:1364-5021

    eISSN:1471-2946

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    The membrane tension of some kinds of ciliates has been suggested to regulate upward and downward swimming velocities under gravity. Despite its biological importance, deformation and membrane tension of a ciliate have not been clarified fully. In this study, we numerically investigated the deformation of a ciliate swimming freely in a fluid otherwise at rest. The cell body was modelled as a capsule with a hyperelastic membrane enclosing a Newtonian fluid. Thrust forces due to the ciliary beat were modelled as torques distributed above the cell body. The effects of membrane elasticity, the aspect ratio of the cell's reference shape, and the density difference between the cell and the surrounding fluid were investigated. The results showed that the cell deformed like a heart shape, when the capillary number was sufficiently large. Under the influence of gravity, the membrane tension at the anterior end decreased in the upward swimming while it increased in the downward swimming. Moreover, gravity-induced deformation caused the cells to move gravitationally downwards or upwards, which resulted in a positive or negative geotaxis-like behaviour with a physical origin. These results are important in understanding the physiology of a ciliate's biological responses to mechanical stimuli.

  107. Flow of a circulating tumor cell and red blood cells in microvessels Peer-reviewed

    Naoki Takeishi, Yohsuke Imai, Takami Yamaguchi, Takuji Ishikawa

    PHYSICAL REVIEW E 92 (6) 063011 2015/12

    Publisher: AMER PHYSICAL SOC

    DOI: 10.1103/PhysRevE.92.063011  

    ISSN:1539-3755

    eISSN:1550-2376

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    Quantifying the behavior of circulating tumor cells (CTCs) in the blood stream is of fundamental importance for understanding metastasis. Here, we investigate the flowmode and velocity of CTCs interactingwith red blood cells (RBCs) in various sized microvessels. The flow of leukocytes in microvessels has been described previously; a leukocyte forms a train with RBCs in small microvessels and exhibits margination in large microvessels. Important differences in the physical properties of leukocytes and CTCs result from size. The dimensions of leukocytes are similar to those of RBCs, but CTCs are significantly larger. We investigate numerically the size effects on the flow mode and the cell velocity, and we identify similarities and differences between leukocytes and CTCs. We find that a transition from train formation to margination occurs when (R-a)/t(R) approximate to 1, where R is the vessel radius, a is the cell radius, and t(R) is the thickness of RBCs, but that the motion of RBCs differs from the case of leukocytes. Our results also show that the velocities of CTCs and leukocytes are larger than the average blood velocity, but only CTCs move faster than RBCs for microvessels of R/a approximate to 1.5-2.0. These findings are expected to be useful not only for understanding metastasis, but also for developing microfluidic devices.

  108. Shape matters: Near-field fluid mechanics dominate the collective motions of ellipsoidal squirmers Peer-reviewed

    K. Kyoya, D. Matsunaga, Y. Imai, T. Omori, T. Ishikawa

    PHYSICAL REVIEW E 92 (6) 063027 2015/12

    Publisher: AMER PHYSICAL SOC

    DOI: 10.1103/PhysRevE.92.063027  

    ISSN:1539-3755

    eISSN:1550-2376

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    Microswimmers show a variety of collective motions. Despite extensive study, questions remain regarding the role of near-field fluid mechanics in collective motion. In this paper, we describe precisely the Stokes flow around hydrodynamically interacting ellipsoidal squirmers in a monolayer suspension. The results showed that various collective motions, such as ordering, aggregation, and whirls, are dominated by the swimming mode and the aspect ratio. The collective motions are mainly induced by near-field fluid mechanics, despite Stokes flow propagation over a long range. These results emphasize the importance of particle shape in collective motion.

  109. Torque-induced precession of bacterial flagella Peer-reviewed

    Yuji Shimogonya, Yoichiro Sawano, Hiromichi Wakebe, Yuichi Inoue, Akihiko Ishijima, Takuji Ishikawa

    SCIENTIFIC REPORTS 5 18488 2015/12

    Publisher: NATURE PUBLISHING GROUP

    DOI: 10.1038/srep18488  

    ISSN:2045-2322

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    The bacterial flagellar motor is an ion-driven rotary machine in the cell envelope of bacteria. Using a gold nanoparticle as a probe, we observed the precession of flagella during rotation. Since the mechanism of flagella precession was unknown, we investigated it using a combination of full simulations, theory, and experiments. The results show that the mechanism can be well explained by fluid mechanics. The validity of our theory was confirmed by our full simulation, which was utilized to predict both the filament tilt angle and motor torque from experimental flagellar precession data. The knowledge obtained is important in understanding mechanical properties of the bacterial motor and hook.

  110. Quantification of hydrodynamic factors influencing cell lateral migration

    STEPHANIE NIX, YOHSUKE IMAI, TAKUJI ISHIKAWA

    68th Annual Meeting of the Division of Fluid Dynamics, Bulletin of the American Physical Society, DFD 2015 60 116 2015/11/01

  111. Deformable micro torque swimmer

    TAKUJI ISHIKAWA, TOMOYUKI TANAKA, TOSHIHIRO OMORI, YOHSUKE IMAI

    68th Annual Meeting of the Division of Fluid Dynamics, Bulletin of the American Physical Society, DFD 2015 60 72 2015/11/01

  112. Hydrodynamic regulation and control of a micro-swimmer

    Takuji Ishikawa

    The 3rd International Workshops on Advances in Computational Mechanics(IWACOM-III) 133 2015/10/01

  113. Rheological analysis of dense capsule suspensions – effect of volume fraction

    Daiki Matsunaga, Yohsuke Imai, Christian Wagner, Takuji Ishikawa

    The 3rd International Workshops on Advances in Computational Mechanics(IWACOM-III) 128 2015/10/01

  114. Graphics processing unit computing of cellular flow and adhesion in microvessels

    Yohsuke Imai, Naoki Takeishi, Shunichi Ishida, Takuji Ishikawa

    The 3rd International Workshops on Advances in Computational Mechanics(IWACOM-III) 47 2015/10/01

  115. Modeling mechanical behavior of precession of bacterial flagella

    Yuji Shimogonya, Takuji Ishikawa

    Computational Fluid Dynamics (CFD) in Medicine and Biology II 2015/09/01

  116. Intergrated Computational Biomechanics of the Flow Phenomena in the Living Body

    Takami Yamaguchi, Yosuke Imai, Toshihiro Omori, Kenji Kikuchi, Takuji Ishikawa

    Computational Fluid Dynamics (CFD) in Medicine and Biology II 2015/09/01

  117. Mechanics of Nodal Cilia in Early Mouse Embryo

    Toshihiro Omori, Hiroto Sugai, Yohsuke Imai, Takuji Ishikawa

    The 8th Asian-Pacific Conference on Biomechanics PS8-15 2015/09/01

  118. Digest Blood Sucked by a Female Mosquito

    Kenji Kikuchi, Yosuke Imai, Takami Yamaguchi, Takuji Ishikawa

    The 8th Asian-Pacific Conference on Biomechanics PS8-14 2015/09/01

  119. Effect of Mucous Viscosity on Ciliary Beat in the Tracheal Lumen

    Tomofumi Haga, Kenji Kikuchi, Keiko Numayama-Tsuruta, Hironori Ueno, Takami Yamaguchi, Takuji Ishikawa

    The 8th Asian-Pacific Conference on Biomechanics PS8-13 2015/09/01

  120. Development of a Numerical Model of Cytoskeleton Dynamics

    Fumiyasu Saito, Yohsuke Imai, Shunichi Ishida, Toshihiro Omori, Takuji Ishikawa

    The 8th Asian-Pacific Conference on Biomechanics PS3-7 2015/09/01

  121. Clarification of Relationship between Gastric Mixing and Movement of Wall

    Taimei Miyagawa, Yohsuke Imai, Shunichi Ishida, Takami Yamaguchi, Takuji Ishikawa

    The 8th Asian-Pacific Conference on Biomechanics PS3-6 2015/09/01

  122. Orientation Angle of a Single Red Blood Cell during Sedimentation

    Daiki Matsunaga, Yohsuke Imai, Christian Wagner, Takuji Ishikawa

    The 8th Asian-Pacific Conference on Biomechanics PS3-2 2015/09/01

  123. Hydrodynamic Interaction between the Small Microparticles and Red Blood Cells in Microchannel

    Naoki Takeishi, Yohsuke Imai, Takami Yamaguchi, Takuji Ishikawa

    The 8th Asian-Pacific Conference on Biomechanics PS3-1 2015/09/01

  124. Swimming Behavior of a Model Ciliate near a Fluid-Air or a Fluid-Solid Interface

    Junichi Manabe, Toshihiro Omori, Yohsuke Imai, Takuji Ishikawa

    The 8th Asian-Pacific Conference on Biomechanics PS1-10 2015/09/01

  125. Noninvasive Measurement of Drug Permeation in the Skin

    Shunsuke Shigeta, Kenji Kikuchi, Keiko Numayama, Takuji Ishikawa

    The 8th Asian-Pacific Conference on Biomechanics PS1-9 2015/09/01

  126. Hemodynamic Study on the Initiation of Cerebral Aneurysms Using Left-Right Comparison Method

    Yuji Shimogonya, Shunichi Fukuda, Takuji Ishikawa, Takami Yamaguchi

    The 8th Asian-Pacific Conference on Biomechanics OS2-5 2015/09/01

  127. A Numerical Simulation of Cytoadhesion and Rosette Formation of Red Blood Cells Infected by Malaria

    Yohsuke Imai, Yuki Ichikawa, Shunichi Isida, Daiki Matsunaga, Stephanie Nix, Toshihiro Omori, Takami Yamaguchi, Takuji Ishikawa

    The 8th Asian-Pacific Conference on Biomechanics OS2-2 2015/09/01

  128. Effect of Flow Curvature on the Migration of Blood Cells

    Stephanie Nix, Yohsuke Imai, Takuji Ishikawa

    The 8th Asian-Pacific Conference on Biomechanics OS2-1 2015/09/01

  129. Simulations of a swimming microorganism near an fluid-air or an fluid-solid interface

    Junichi Manabe, Toshihiro Omori, Yohsuke Imai, Takuji Ishikawa

    Computational Fluid Dynamics (CFD) in Medicine and Biology II 2015/09/01

  130. Separation of motile bacteria using drift force near a wall

    Takuji Ishikawa, Tatsuya Shioiri, Keiko Numayama-Tsuruta, Hironori Ueno, Yohsuke Imai, Takami Yamaguch

    Computational Fluid Dynamics (CFD) in Medicine and Biology II 2015/09/01

  131. A Stepping Microrobot Controlled by Flow Oscillations Peer-reviewed

    Takuji Ishikawa, V. A. Vladimirov

    JOURNAL OF FLUIDS ENGINEERING-TRANSACTIONS OF THE ASME 137 (8) 84501-1-84501-3 2015/08

    Publisher: ASME

    DOI: 10.1115/1.4029840  

    ISSN:0098-2202

    eISSN:1528-901X

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    A self-locomotive microrobot can be a key technology for medical applications, manufacturing, or micro total analysis systems (mu TAS). Although previous studies have mostly used magnetic, electric, chemical, or optical forces to control microrobots, we utilized flow oscillations. The results showed that the locomotion of the microrobot was stepwise near a wall when the oscillations were applied both horizontally and vertically. The most efficient microrobot was capable of propelling itself about 2 x 10(-3) times its radius during one oscillation period. These results illustrate that the proposed stepping microrobot has great potential for future applications.

  132. Cellular Scale Physiological Flow: Active Swimming Sperm Cells and Passive Flowing Red Blood Cells

    Toshihiro Omori, Takuji Ishikawa, Yohsuke Imai, Takami Yamaguchi

    13th U.S. National Congress on Computational Mechanics 2015/07/01

  133. Viscosity Reduction in Bimodal Suspensions of Two Types of Capsules

    Yohsuke Imai, Hiroki Ito, Daiki Matsunaga, Toshihiro Omori, Takami Yamaguchi, Takuji Ishikawa

    13th U.S. National Congress on Computational Mechanics 2015/07/01

  134. Peclet Number Of Ciliary Transport On The Surface Of The Tracheal Lumen

    Kouki Kiyota, Hironori Ueno, Keiko Numayama-Tsuruta, Yohsuke Imai, Takami Yamaguchi, Takuji Ishikawa

    SB3C2015 223 2015/06/01

  135. A Computational Study Of Red Blood Cells In Stokes Flow: From Single Cellular Mechanics To Suspension Rheology

    Toshihiro Omori, Yohsuke Imai, Takami Yamaguchi, Takuji Ishikawa

    SB3C2015 256 2015/06/01

  136. Rheology of A Red Blood CEll Suspension Computing with A Boundary Element-Finite Wlement Coupled Method

    Toshihiro Omori, Yohsuke Imai, Takuji Ishikawa

    The 18th International Conference on Finite Elements in Flow Problems FEF2015 23 2015/03/01

  137. Expanding Imaging Capabilities for Microfluidics: Applicability of Darkfield Internal Reflection Illumination (DIRI) to Observations in Microfluidics Peer-reviewed

    Yoshihiro Kawano, Chino Otsuka, James Sanzo, Christopher Higgins, Tatsuo Nirei, Tobias Schilling, Takuji Ishikawa

    PLOS ONE 10 (3) e0116925 2015/03

    Publisher: PUBLIC LIBRARY SCIENCE

    DOI: 10.1371/journal.pone.0116925  

    ISSN:1932-6203

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    Microfluidics is used increasingly for engineering and biomedical applications due to recent advances in microfabrication technologies. Visualization of bubbles, tracer particles, and cells in a microfluidic device is important for designing a device and analyzing results. However, with conventional methods, it is difficult to observe the channel geometry and such particles simultaneously. To overcome this limitation, we developed a Darkfield Internal Reflection Illumination (DIRI) system that improved the drawbacks of a conventional darkfield illuminator. This study was performed to investigate its utility in the field of microfluidics. The results showed that the developed system could clearly visualize both microbubbles and the channel wall by utilizing brightfield and DIRI illumination simultaneously. The methodology is useful not only for static phenomena, such as clogging, but also for dynamic phenomena, such as the detection of bubbles flowing in a channel. The system was also applied to simultaneous fluorescence and DIRI imaging. Fluorescent tracer beads and channel walls were observed clearly, which may be an advantage for future microparticle image velocimetry (mu PIV) analysis, especially near a wall. Two types of cell stained with different colors, and the channel wall, can be recognized using the combined confocal and DIRI system. Whole-slide imaging was also conducted successfully using this system. The tiling function significantly expands the observing area of microfluidics. The developed system will be useful for a wide variety of engineering and biomedical applications for the growing field of microfluidics.

  138. Visualization of intestinal peristalsis of mosquito midgut by using micro x-ray imaging

    Kenji Kikuchi, Yohsuke Imai, Takami Yamaguchi, Takuji Ishikawa

    International Symposium on Integrated Nanobiomechanics 2015

  139. Deformation of a spherical capsule under oscillating shear flow Peer-reviewed

    D. Matsunaga, Y. Imai, T. Yamaguchi, T. Ishikawa

    JOURNAL OF FLUID MECHANICS 762 288-301 2015

    Publisher: CAMBRIDGE UNIV PRESS

    DOI: 10.1017/jfm.2014.649  

    ISSN:0022-1120

    eISSN:1469-7645

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    The deformation of a spherical capsule in oscillating shear flow is presented. The boundary element method is used to simulate the capsule motion under Stokes flow. We show that a capsule at high frequencies follows the deformation given by a leading-order prediction, which is derived from an assumption of small deformation limit. At low frequencies, on the other hand, a capsule shows an overshoot phenomenon where the maximum deformation is larger than that in steady shear flow. A larger overshoot is observed for larger capillary number or viscosity ratio. Using the maximum deformation in start-up shear flow, we evaluate the upper limit of deformation in oscillating shear flow. We also show that the overshoot phenomenon may appear when the quasi-steady orientation angle under steady shear flow is less than 9.0 degrees. We propose an equation to estimate the threshold frequency between the low-frequency range, where the capsule may have an overshoot, and the high-frequency range, where the deformation is given by the leading-order prediction. The equation only includes the viscosity ratio and the Taylor parameter under simple shear flow, so it can be extended to other deformable particles, such as bubbles and drops.

  140. Hemodynamics in the Microcirculation and in Microfluidics Peer-reviewed

    Toshihiro Omori, Yohsuke Imai, Kenji Kikuchi, Takuji Ishikawa, Takami Yamaguchi

    ANNALS OF BIOMEDICAL ENGINEERING 43 (1) 238-257 2015/01

    Publisher: SPRINGER

    DOI: 10.1007/s10439-014-1180-8  

    ISSN:0090-6964

    eISSN:1573-9686

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    Hemodynamics in microcirculation is important for hemorheology and several types of circulatory disease. Although hemodynamics research has a long history, the field continues to expand due to recent advancements in numerical and experimental techniques at the micro-and nano-scales. In this paper, we review recent computational and experimental studies of blood flow in microcirculation and microfluidics. We first focus on the computational studies of red blood cell (RBC) dynamics, from the single cellular level to mesoscopic multiple cellular flows, followed by a review of recent computational adhesion models for white blood cells, platelets, and malaria-infected RBCs, in which the cell adhesion to the vascular wall is essential for cellular function. Recent developments in optical microscopy have enabled the observation of flowing blood cells in microfluidics. Experimental particle image velocimetry and particle tracking velocimetry techniques are described in this article. Advancements in micro total analysis system technologies have facilitated flowing cell separation with microfluidic devices, which can be used for biomedical applications, such as a diagnostic tool for breast cancer or large intestinal tumors. In this paper, cell-separation techniques are reviewed for microfluidic devices, emphasizing recent advances and the potential of this fast-evolving research field in the near future.

  141. Swimming behavior of a model microorganism at a fluid-air interface

    Junichi Manabe, Kohei Kyoya, Toshihiro Omori, Yohsuke Imai, Takuji Ishikawa

    The Sixth International Symposium on Aero Aqua Bio-mechanisms 37 2014/11/01

  142. Inhomogeneous distribution of cells in a microalgae suspension with aeration

    Yuki Nonaka, Kenji Kikuchi, Keiko Numayama-Tsuruta, Azusa Kage, Hironori Ueno, Takuji Ishikawa

    The Sixth International Symposium on Aero Aqua Bio-mechanisms 39 2014/11/01

  143. Falling dynamics of immobilized Chlamydomonas reinhardtii

    Azusa Kage, Kenji Kikuchi, Takuji Ishikawa

    The Sixth International Symposium on Aero Aqua Bio-mechanisms 16 2014/11/01

  144. Lateral migration of a spherical capsule near a plane wall in Stokes flow Peer-reviewed

    S. Nix, Y. Imai, D. Matsunaga, T. Yamaguchi, T. Ishikawa

    Physical Review E - Statistical, Nonlinear, and Soft Matter Physics 90 (4) 2014/10/15

    DOI: 10.1103/PhysRevE.90.043009  

    ISSN:1539-3755

    eISSN:1550-2376

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    © 2014 American Physical Society. Lateral migration is the motion of a particle perpendicular to the direction of the surrounding flow. One of the factors leading to the lateral migration of a deformable particle in Stokes flow is the presence of a nearby wall. We numerically investigate the lateral migration of a capsule in a near-wall simple shear flow using a boundary integral method coupled with a finite element method. We find that asymmetrical deformation of the capsule induced by the wall is correlated with a reduction in the lift velocity relative to the lift velocity predicted by a far-field analytical solution. A combination of this asymmetrical deformation, which decreases the lift velocity, and an increase in the value of the capsule stresslet near the wall, which works to increase the lift velocity, leads to a migration velocity that is nearly independent of capillary number and membrane constitutive law at large deformation near the wall.

  145. Lateral migration of a spherical capsule in a near-wall shear flow Peer-reviewed

    S. Nix, Y. Imai, D. Matsunaga, T. Yamaguchi, T. Ishikawa

    Physical Review E 90 043009 2014/10/05

  146. Oxygen supersaturated fluid using fine micro/nanobubbles Peer-reviewed

    N. Matsuki, T. Ishikawa, S. Ichiba, N. Shiba, Y. Ujike, T. Yamaguchi

    International Journal of Nanomedicine 9 1-11 2014/10/02

    DOI: 10.2147/IJN.S68840  

  147. Enhancing Cell Free Layer Thickness by Bypass Channels in a Wall

    Maryam Saadatmand, Takami Yamaguchi, Takuji Ishikawa

    Eleventh International Conference on Flow Dynamics 310-311 2014/10/01

  148. Biological Flow generated by Cilla and Flagella

    Takuji Ishikawa

    Eleventh International Conference on Flow Dynamics 320-321 2014/10/01

  149. Hydrodynamic interaction between two red blood cells in simple shear flow: its impact on the rheology of a semi-dilute suspension Peer-reviewed

    Toshihiro Omori, Takuji Ishikawa, Yohsuke Imai, Takami Yamaguchi

    COMPUTATIONAL MECHANICS 54 (4) 933-941 2014/10

    Publisher: SPRINGER

    DOI: 10.1007/s00466-014-0997-1  

    ISSN:0178-7675

    eISSN:1432-0924

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    Blood is a suspension of red blood cells (RBCs) and its rheology is important when discussing the physiology of the cardiovascular system. In this study, we performed a numerical investigation of the rheological properties of an RBC suspension from the dilute to semi-dilute regime. RBCs were modelled as a capsule with a two-dimensional hyperelastic membrane. Large deformation of the thin membrane was calculated by a finite element method. Due to the small size of the RBC, fluid motion around the RBC was assumed to follow Stokes flow and was solved by a boundary element method. In the dilute limit, cell-cell interactions were omitted and the bulk stress of the suspension was calculated by the stresslet generated on a single RBC. Interestingly, the effective shear viscosity of the dilute suspension decreased with increasing viscosity of the internal liquid. In the semi-dilute regime, cells can be considered as showing pairwise interactions. The effective shear viscosity of the semi-dilute suspension shows a quadratic increase with respect to the volume fraction. These findings are important for understanding the complex phenomena of blood rheology.

  150. Modeling of Flow in the Stomach

    Yohsuke Imai, Ikuma Kobayashi, Taimei Miyagawa, Shunichi Ishida, Takuji Ishikawa, Takami Yamaguchi

    THE FOURTH JAPAN-SWITZERLAND WORKSHOP ON BIOMECHANICS 102 2014/09/01

  151. Biological Flow generated by Cilla and Flagella

    Takuji Ishikawa

    THE FOURTH JAPAN-SWITZERLAND WORKSHOP ON BIOMECHANICS 110 2014/09/01

  152. Dispersion of model microorganisms swimming in a nonuniform suspension Peer-reviewed

    Takuji Ishikawa, T. J. Pedley

    PHYSICAL REVIEW E 90 (3) 033008 2014/09

    Publisher: AMER PHYSICAL SOC

    DOI: 10.1103/PhysRevE.90.033008  

    ISSN:1539-3755

    eISSN:1550-2376

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    Although diffusion properties of a suspension of swimming microorganisms in equilibrium have been studied intensively, those under nonequilibrium conditions remain unclear. In this study, we investigate the spreading of model microorganisms from high concentration to low by the Stokesian dynamics method. The results reveal that the spreading is neither purely diffusive nor ballistic. When the dipole component of the swimming velocity is small, the cells actively direct themselves towards lower concentrations. The concentration distribution shows stronger oscillations than would be expected for ballistic swimmers with constant orientations. The mechanism can be explained by the near-field hydrodynamic interactions between cells and the spatial gradient of the collision rate. Comparison of the numerical results with a simple continuum model and a Monte Carlo simulation shows that those conventional models can capture the basic features of the present results. These new findings pave the way towards a mathematical description of the dispersion of microorganisms in various environments.

  153. Numerical modeling of cellular flow and adhesion in microvessels Peer-reviewed

    Yohsuke Imai, Naoki Takeishi, Akihisa Ami, Takami Yamaguchi, Takuji Ishikawa

    Transactions of Japanese Society for Medical and Biological Engineering 52 45 2014/08/17

    Publisher: Japan Soc. of Med. Electronics and Biol. Engineering

    DOI: 10.11239/jsmbe.52.SY-45  

    ISSN:1347-443X 1881-4379

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    Adhesion of cells flowing in microvessels to the vessel wall is an important process in hemostasis and immune system, and it also relates to malaria and metastasis. This process may depend on the mechanical property of cells, the size and geometry of vessels, the volume fraction of red blood cells, the shear rate, and the biochemical property of ligand-receptor interactions. We have developed a numerical model of cellular flow in microvessels to clarify the effects of these parameters. A cell is modeled as a liquid drop enclosed by a thin membrane. The finite element method for membrane mechanics is coupled with the lattice Boltzmann method for fluid mechanics. A ligand-receptor interaction model is also coupled with those methods. All the procedures are implemented in GPU computing for accelerating simulations. We simulate flow of leukocytes and circulating tumor cells, and rolling motion of malaria-infected red blood cells in microvessels.

  154. Collective swimming of model micro-organisms

    Takuji Ishikawa

    JSMB/SMB Osaka 2014 43 2014/08/10

  155. A numerical method for simulating gastricflow

    Taimei Miyagawa, Yohsuke Imai, Takami Yamaguchi, takuji Ishikawa

    11th World Congress on Computational Mechanics 303 2014/07/10

  156. Rheological analysis of capsule suspensions containing different size capsules

    Hiroki Ito, Yohsuke Imai, Daiki Matsunaga, Toshihiro Omori, Takami Yamaguchi, Takuji Ishikawa

    11th World Congress on Computational Mechanics 303 2014/07/10

  157. Rheological analysis of dense capsule suspension under simple shear flow condition

    Daiki Matsunaga, Yohsuke Imai, Takami Yamaguchi, Takuji Ishikawa

    Dyna Caps 2014 2014/07/10

  158. Numerical Analysis of Capsule Suspensions Containing Two Different siza Capsules

    Hiroki Ito, Yohsuke Imai, Daiki Matsunaga, Toshihiro Omori, Takami Yamaguchi, Takuji Ishikawa

    Dyna Caps 2014 2014/07/10

  159. Collective swimming of ellipoidal squimers

    Takuji Ishikawa, Kohei Kyoya, Daiki Matsunaga, Yohsuke Imai, Toshihiro Omori

    Dyna Caps 2014 2014/07/10

  160. Margination of large cells in microchannels

    Yohsuke Imai, Naoki Takeishi, Takami Yamaguchi, Takuji Ishikawa

    Dyna Caps 2014 2014/07/10

  161. Development of a numerical model for analysis of ciliary motions

    H. Sugai, T. Omori, Y. Imai, T. Ishikawa

    7th WORLD CONGRESS OF BIOMECHANICS 2014/07/10

  162. Effect of Shear Gradient and Wall on Capsule Lateral Migration

    S. Nix, Y. Imai, T. Yamaguchi, T. Ishikawa

    7th WORLD CONGRESS OF BIOMECHANICS 2014/07/10

  163. Multi-scale computational study on the formation and destruction of primary thrombus under the influence of the blood flow and red blood cells

    H. Kmada, Y. Imai, T. Ishikawa, T. Yamaguchi

    7th WORLD CONGRESS OF BIOMECHANICS 2014/07/10

  164. Rheology of a red blood cell suspension in a simpleshear flow

    T. Omori, Y. Imai, D, Mtsunaga, T. Yamaguchi, T, Ishikawa

    7th WORLD CONGRESS OF BIOMECHANICS 2014/07/10

  165. A numerical simulation on the motion ofmalaria-infected cells in microcirculatory blood flow

    Y. Imai, A, Ami, T. Yamaguchi, T, Ishikawa

    7th WORLD CONGRESS OF BIOMECHANICS 2014/07/10

  166. Collective motions of ellipsoidal squirmers in a dense suspension

    T. Ishikawa, K. Kyoya, D. Matsunaga, Y.Imai. T. Omori

    7th WORLD CONGRESS OF BIOMECHANICS 2014/07/10

  167. Numerical analysis of hydrodynamic behavior of circulating tumor cells in microchannels

    N. Takeishi, Y. Imai, T. Yamaguchi, T. Ishikawa

    7th WORLD CONGRESS OF BIOMECHANICS 2014/07/10

  168. Distrlibution of Microalgae Cells in a Tube Container with Aeration

    Yuki Nonaka, Kenji Kikuchi, Keiko Numayama-Tsuruta, Azusa Kage, Hironori Ueno, Takuji Ishikawa

    Internationnal Symposium on Integrated Nanobiomechanics 21-22 2014/07/05

  169. Effect of Rheological Properties on Cilliary Flow in the Airway

    Tomofumi Haga, Kenji Kikuchi, Hironori Ueno, Keiko Numayama-Tsuruta, Takuji Ishikawa

    Internationnal Symposium on Integrated Nanobiomechanics 19-20 2014/07/05

  170. Development of an Intracellular Structure Model for Ciliary Motion Analysis

    Hiroto Sugai, Toshihiro Omori, Yohsuke Imai, Takami Yamaguchi, Takuji Ishikawa

    Internationnal Symposium on Integrated Nanobiomechanics 17-18 2014/07/05

  171. Nutrient Uptake in a Suspension of Model Microorganisms

    Takuji Ishikawa, Shunsuke Kajiki, Yohsuke Imai, Toshihiro Omori

    Internationnal Symposium on Integrated Nanobiomechanics 15-16 2014/07/05

  172. Capsule Lateral Migration in an Unbounded Plane Poiseuille Flow and Near-wall Shear Flow

    Stephanie Nix, Yohsuke Imai, Takami Yamaguchi, Takuji Ishikawa

    Internationnal Symposium on Integrated Nanobiomechanics 13-14 2014/07/05

  173. Rheology of a Red Blood Cell Suspension from Dilute to Semi-dilute Regime

    Toshihiro Omori, Yohsuke Imai, Takami Imai, Takuji Ishikawa

    Internationnal Symposium on Integrated Nanobiomechanics 11-12 2014/07/05

  174. Hydrodynamic Interction between a Circulating Tumor Cell and Blood Cells in Microcirculation

    Naoki Takeishi, Yohsuke Imai, Takami Yamaguchi, Takuji Ishikawa

    Internationnal Symposium on Integrated Nanobiomechanics 9-10 2014/07/05

  175. Numerical Modeling of the Adhesion of Red Blood Cells Infected by Plasmodium Falciparum Malaria in Microcirculatory Blood Flow

    Yohsuke Imai, Akihisa Ami, Takami Yamaguchi, Takuji Ishikawa

    Internationnal Symposium on Integrated Nanobiomechanics 7-8 2014/07/05

  176. A Numerical Analysis of Cellular Adhesion to Planar Wall Mediated by Ligand-Receptor Interactions

    Yuki Ichikawa, Yohsuke Imai, Daiki Matsunaga, Stephanie Nix, Takami Yamaguchi, Takuji Ishikawa

    Internationnal Symposium on Integrated Nanobiomechanics 5-6 2014/07/05

  177. Computational Study on Thrombogenesis

    Hiroki Kamada, Yohsuke Imai, Takuji Ishikawa, Takami Ymaguchi

    Internationnal Symposium on Integrated Nanobiomechanics 3-4 2014/07/05

  178. Shear Stress Distribution in the Stomach

    Taimei Miyagawa, Yohsuke Imai, Sunichi Ishida, Takami Yamaguchi, Takuji Ishikawa

    Internationnal Symposium on Integrated Nanobiomechanics 1-2 2014/07/05

  179. Structure of Dimeric Axonemal Dynein in Cilia Suggests an Alternative Mechanism of Force Generation Peer-reviewed

    Hironori Ueno, Khanh Huy Bui, Takuji Ishikawa, Yohsuke Imai, Takami Yamaguchi, Takashi Ishikawa

    CYTOSKELETON 71 (7) 412-422 2014/07

    Publisher: WILEY-BLACKWELL

    DOI: 10.1002/cm.21180  

    ISSN:1949-3584

    eISSN:1949-3592

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    The mechanism by which the two different heads of the ciliary outer dynein arm produce force to translocate the microtubule during beating is still unknown. In this report we use cryo-electron tomography and image processing to analyze the conformational changes and the relative abundance of each conformation of the two dynein heads from mouse respiratory cilia. In the absence of nucleotides the majority of dynein dimers are in the apo form and both heads are tightly packed, whereas they are dissociated and move independently in the presence of nucleotides. The head of the external outer arm dynein heavy chain has a diagonal shift toward both the neighboring B-tubule and the proximal end of the axoneme, while the head of the internal heavy chain shifts only longitudinally toward the proximal end. In the presence of nucleotides a significant number of the dynein dimers have two heads overlapped in the proximal shifting form or overlapped in the apo form. During ciliary bending axonemal dynein translocates microtubules by moving with short steps and two heads stay at the same position longer than cytoplasmic dynein. This demonstrates that the step of the outer arm dynein dimer is not dominated by the hand-over-hand motion, but also indicates the difference between axonemal dynein and cytoplasmic dynein. (C) 2014 Wiley Periodicals, Inc.

  180. Nutrient uptake in a suspension of model microorganisms

    Takuji Ishikawa, Shunsuke Kajiki, Yohsuke Imai, Toshihiro Omori

    COMPSAFE 347-348 2014/04/02

  181. Fluid mechanics of swimming bacteria with multiple flagella Peer-reviewed

    Philipp Kanehl, Takuji Ishikawa

    PHYSICAL REVIEW E 89 (4) 042704 2014/04

    Publisher: AMER PHYSICAL SOC

    DOI: 10.1103/PhysRevE.89.042704  

    ISSN:1539-3755

    eISSN:1550-2376

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    It is known that some kinds of bacteria swim by forming a bundle of their multiple flagella. However, the details of flagella synchronization as well as the swimming efficiency of such bacteria have not been fully understood. In this study, swimming of multiflagellated bacteria is investigated numerically by the boundary element method. We assume that the cell body is a rigid ellipsoid and the flagella are rigid helices suspended on flexible hooks. Motors apply constant torque to the hooks, rotating the flagella either clockwise or counterclockwise. Rotating all flagella clockwise, bundling of all flagella is observed in every simulated case. It is demonstrated that the counter rotation of the body speeds up the bundling process. During this procedure the flagella synchronize due to hydrodynamic interactions. Moreover, the results illustrated that during running the multiflagellated bacterium shows higher propulsive efficiency (distance traveled per one flagellar rotation) over a bacterium with a single thick helix. With an increasing number of flagella the propulsive efficiency increases, whereas the energetic efficiency decreases, which indicates that efficiency is something multiflagellated bacteria are assigning less priority to than to motility. These findings form a fundamental basis in understanding bacterial physiology and metabolism.

  182. Rheological analysis of dense capsule suspension under Stokes flow condition

    Daiki Matsunaga, Yohsuke Imai, Takami Yamaguchi, Takuji Ishikawa

    Advances in Computational Fluid-Structure Interaction and Flow Simulation Poster Session 2014/03/02

  183. Numerical analysis of a red blood cell flowing through a thin micropore Peer-reviewed

    Toshihiro Omori, Haruki Hosaka, Yohsuke Imai, Takami Yamaguchi, Takuji Ishikawa

    Physical Review E - Statistical, Nonlinear, and Soft Matter Physics 89 (1) 2014/01/13

    DOI: 10.1103/PhysRevE.89.013008  

    ISSN:1539-3755 1550-2376

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    Red blood cell (RBC) deformability plays a key role in microcirculation, especially in vessels that have diameters even smaller than the nominal cell size. In this study, we numerically investigate the dynamics of an RBC in a thin micropore. The RBC is modeled as a capsule with a thin hyperelastic membrane. In a numerical simulation, we employ a boundary element method for fluid mechanics and a finite element method for membrane mechanics. The resulting RBC deformation towards the flow direction is suppressed considerably by increased cytoplasm viscosity, whereas the gap between the cell membrane and solid wall becomes smaller with higher cytoplasm viscosity. We also measure the transit time of the RBC and find that nondimensional transit time increases nonlinearly with respect to the viscosity ratio, whereas it is invariant to the capillary number. In conclusion, cytoplasmic viscosity plays a key role in the dynamics of an RBC in a thin pore. The results of this study will be useful for designing a microfluidic device to measure cytoplasmic viscosity. © 2014 American Physical Society.

  184. Flow-induced deformation of a capsule in unbounded stokes flow Peer-reviewed

    Toshihiro Omori, Takuji Ishikawa, Yohsuke Imai, Takami Yamaguchi

    Lecture Notes in Computational Vision and Biomechanics 12 101-117 2014

    Publisher: Kluwer Academic Publishers

    DOI: 10.1007/978-94-007-7769-9_6  

    ISSN:2212-9413 2212-9391

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    Dynamics of deformable capsules in fluid flow is great interest in chemical engineering, bioengineering, and food industry. To investigate the motion and deformation of a capsule, both the fluid mechanics of the internal and external liquids and the solid mechanics of the membrane must be solved precisely. To express the elastic behaviours of the solid membrane, two different kinds of modelling are commonly used. One is a continuum constitutive law and the other is a discrete spring network model. This study first examines the correlations between the mechanical properties of the discrete spring network model and those of continuum constitutive laws. We also derive the relationships between the spring constant and continuum properties, such as Young modulus, Poisson ratio, area dilation modulus, and shear elastic modulus. Next, we investigate the motion and deformation of a capsule in simple shear flow. Especially, we analyze the dynamics of a non-spherical capsule in shear. In the absence of inertia effect of fluid motions, a boundary element method is used to compute the internal and external Stokes flow. The results show that the orientation of a non-spherical capsule is variant under time reversal, though that of a rigid particle is invariant. Interestingly, the alignment of a non-spherical capsule over a long time duration shows a transition depending on the shear rate.

  185. Fluctuation of cilia-generated flow on the surface of the tracheal lumen Peer-reviewed

    Kouki Kiyota, Hironori Ueno, Keiko Numayama-Tsuruta, Tomofumi Haga, Yohsuke Imai, Takami Yamaguchi, Takuji Ishikawa

    AMERICAN JOURNAL OF PHYSIOLOGY-LUNG CELLULAR AND MOLECULAR PHYSIOLOGY 306 (2) L144-L151 2014/01

    Publisher: AMER PHYSIOLOGICAL SOC

    DOI: 10.1152/ajplung.00117.2013  

    ISSN:1040-0605

    eISSN:1522-1504

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    Although we inhale air that contains many harmful substances, including, for example, dust and viruses, these small particles are trapped on the surface of the tracheal lumen and transported towards the larynx by cilia-generated flow. The transport phenomena are affected not only by the time-and space-average flow field but also by the fluctuation of the flow. Because flow fluctuation has received little attention, we investigated it experimentally in mice. To understand the origin of flow fluctuation, we first measured the distribution of ciliated cells in the trachea and individual ciliary motions. We then measured the detailed flow field using a confocal micro-PTV system. Strong flow fluctuations were observed, caused by the unsteadiness of the ciliary beat and the spatial inhomogeneity of ciliated cells. The spreading of particles relative to the bulk motion became diffusive if the time scale was sufficiently larger than the beat period. Finally, we quantified the effects of flow fluctuation on bulk flow by evaluating the Peclet number of the system, which indicated that the directional transport was an order of magnitude larger than the isotropic diffusion. These results are important in understanding transport phenomena in the airways on a cellular scale.

  186. Numerical analysis of a red blood cell flowing through a thin micropore Peer-reviewed

    Toshihiro Omori, Haruki Hosaka, Yohsuke Imai, Takami Yamaguchi, Takuji Ishikawa

    PHYSICAL REVIEW E 89 (1) 013008 2014/01

    Publisher: AMER PHYSICAL SOC

    DOI: 10.1103/PhysRevE.89.013008  

    ISSN:2470-0045

    eISSN:2470-0053

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    Red blood cell (RBC) deformability plays a key role in microcirculation, especially in vessels that have diameters even smaller than the nominal cell size. In this study, we numerically investigate the dynamics of an RBC in a thin micropore. The RBC is modeled as a capsule with a thin hyperelastic membrane. In a numerical simulation, we employ a boundary element method for fluid mechanics and a finite element method for membrane mechanics. The resulting RBC deformation towards the flow direction is suppressed considerably by increased cytoplasm viscosity, whereas the gap between the cell membrane and solid wall becomes smaller with higher cytoplasm viscosity. We also measure the transit time of the RBC and find that nondimensional transit time increases nonlinearly with respect to the viscosity ratio, whereas it is invariant to the capillary number. In conclusion, cytoplasmic viscosity plays a key role in the dynamics of an RBC in a thin pore. The results of this study will be useful for designing a microfluidic device to measure cytoplasmic viscosity.

  187. Leukocyte margination at arteriole shear rate Peer-reviewed

    Naoki Takeishi, Yohsuke Imai, Keita Nakaaki, Takami Yamaguchi, Takuji Ishikawa

    Physiological Reports 2 (6) e12037 2014

    Publisher: American Physiological Society

    DOI: 10.14814/phy2.12037  

    ISSN:2051-817X

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    We numerically investigated margination of leukocytes at arteriole shear rate in straight circular channels with diameters ranging from 10 to 22 lm. Our results demonstrated that passing motion of RBCs effectively induces leukocyte margination not only in small channels but also in large channels. A longer time is needed for margination to occur in a larger channel, but once a leukocyte has marginated, passing motion of RBCs occurs continuously independent of the channel diameter, and leukocyte margination is sustained for a long duration. We also show that leukocytes rarely approach the wall surface to within a microvillus length at arteriole shear rate.

  188. A full GPU implementation of a numerical method for simulating capsule suspensions Peer-reviewed

    Daiki Matsunaga, Yohsuke Imai, Toshihiro Omori, Takuji Ishikawa, Takami Yamaguchi

    Journal of Biomechanical Science and Engineering 9 (3) 1-16 2014

    Publisher: Japan Society of Mechanical Engineers

    DOI: 10.1299/jbse.14-00039  

    ISSN:1880-9863

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    Although boundary element (BE) based methods are highly accurate for simulating capsule suspensions in Stokes flows, computational time has been a major issue, even when only a few capsules are simulated. We propose a full graphics processing unit (GPU) implementation of a numerical method coupling the BE method of fluid mechanics with the finite element method of membrane mechanics. In single GPU computing, the performance achieves 0.12 TFlop/s when computing one capsule (2562 nodes and 5120 elements) and 0.29 TFlop/s for two capsules. The performance increases with the number of capsules, achieving a maximum of 0.59 TFlop/s. We also implement a multi-GPU method with the data communication overlapping the computation. A weak scaling test shows perfect scalability for any number of computational nodes per GPU, indicating that the communication time is completely hidden. For a practical use of the present results, we estimate the computational time required for 10000 time steps. When we simulate one capsule and two capsules on one GPU, only 2.0 and 9.1 minutes are required to complete the simulation, respectively, and a simulation with 256 capsules on 16 GPUs takes 3.8 days.

  189. A full GPU implementation of a numerical method for simulating capsule suspensions Peer-reviewed

    Daiki Matsunaga, Yohsuke Imai, Toshihiro Omori, Takuji Ishikawa, Takami Yamaguchi

    Journal of Biomechanical Science and Engineering 9 (3) 1-16 2014

    Publisher: Japan Society of Mechanical Engineers

    DOI: 10.1299/jbse.14-00039  

    ISSN:1880-9863

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    Although boundary element (BE) based methods are highly accurate for simulating capsule suspensions in Stokes flows, computational time has been a major issue, even when only a few capsules are simulated. We propose a full graphics processing unit (GPU) implementation of a numerical method coupling the BE method of fluid mechanics with the finite element method of membrane mechanics. In single GPU computing, the performance achieves 0.12 TFlop/s when computing one capsule (2562 nodes and 5120 elements) and 0.29 TFlop/s for two capsules. The performance increases with the number of capsules, achieving a maximum of 0.59 TFlop/s. We also implement a multi-GPU method with the data communication overlapping the computation. A weak scaling test shows perfect scalability for any number of computational nodes per GPU, indicating that the communication time is completely hidden. For a practical use of the present results, we estimate the computational time required for 10000 time steps. When we simulate one capsule and two capsules on one GPU, only 2.0 and 9.1 minutes are required to complete the simulation, respectively, and a simulation with 256 capsules on 16 GPUs takes 3.8 days.

  190. Separation of motile bacteria using drift velocity in a microchannel Peer-reviewed

    Takuji Ishikawa, Tatsuya Shioiri, Keiko Numayama-Tsuruta, Hironori Ueno, Yohsuke Imai, Takami Yamaguchi

    LAB ON A CHIP 14 (5) 1023-1032 2014

    Publisher: ROYAL SOC CHEMISTRY

    DOI: 10.1039/c3lc51302e  

    ISSN:1473-0197

    eISSN:1473-0189

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    Separation of certain bacteria from liquids is important in the food, water quality management, bioengineering, and pharmaceutical industries. In this study, we developed a microfluidic device for the hydrodynamic separation of motile bacteria (Escherichia coli) using drift velocity. We first investigated drift tendencies of bacteria and found that cells tended to move in a spanwise direction with similar velocities regardless of the flow rate. When the drift distance was small compared to the wetted perimeter of the cross section, the cells were not separated efficiently. We then investigated the drift phenomenon in more detail using a numerical simulation. Interestingly, the drift phenomenon was observed even without a wall boundary, indicating that drift was caused mainly by the interaction of moving cells with the background shear flow. Finally, we developed a microfluidic device to separate motile bacteria from tracer particles or less motile cells. By decreasing the channel height, the device could successfully separate motile bacteria from other particles or cells with a separation efficiency of about 40%. Connecting microchannels in a series was also found to be effective, which achieved the separation efficiency of about 60%. The knowledge obtained in this study will facilitate the development of other microfluidics devices for use with bacteria.

  191. A numerical analysis of a capsule containing multiple small capsules in simple shear flow

    Yuki Ichikawa, Yohsuke Imai, Daiki Matsunaga, Takami Yamaguchi, Takuji Ishikawa

    APCOM2013 & ISCM2013 Conference Handbook 15 2013/12/11

  192. Numerical analysis of margination of a cancer cell in microcirculation

    N. Takeishi, Y. Imai, T. Yamaguchi, T. Ishikawa

    APCOM2013 & ISCM2013 Conference Handbook 18 2013/12/11

  193. Solid particle motion in the stomach during gastric mixing

    Taimei Miyagawa, Yohsuke Imai, Takami Yamaguchi, Takuji Ishikawa

    The15th International Conference on Biomedical Enginnering 17-18 2013/12/04

  194. Collective Swimming in a Suspension of Ellipsoidal Squirmers

    Kohei KYOYA, Daiki MATSUNAGA, Yohsuke IMAI, Takami YAMAGUCHI, Takuji ISHIKAWA

    Bulletin of the American Physical Society 58 410 2013/11/26

  195. Nutrient uptake in a suspension of squirmers

    Shunsuke Kajiki, Yohsuke Imai, Takami Yamaguchi, Takuji Ishikawa

    Bulletin of the American Physical Society 58 409 2013/11/26

  196. Viscoelasticity of dilute capsule suspension under Stokes flows

    Daiki Matsunaga, Yohsuke Imai, Takami Yamaguchi, Takuji Ishikawa

    Bulletin of the American Physical Society 58 97 2013/11/24

  197. Viscosity of Dense Capsule Suspension Under Simple Shear FLow Condition

    Daiki Matsunaga, Yohsuke Imai, Takami Yamaguchi, Takuji Ishikawa

    7th East Asian Consortium on Biomedical Engineering, Proceeding Book 80-81 2013/11/19

  198. Margination of leukocyte in different sizes of circular micro-channel

    Naoki takeishi, Yohsuke Imai, Takami Yamaguchi, Takuji Ishikawa

    7th East Asian Consortium on Biomedical Engineering, Proceeding Book 78-79 2013/11/19

  199. Hydrodynamical entrapment of ciliates at the air-liquid interface Peer-reviewed

    J. Ferracci, H. Ueno, K. Numayama-Tsuruta, Y. Imai, T. Yamaguchi, T. Ishikawa

    PLoS ONE 8 e75238 2013/10/01

    DOI: 10.1371/journal.pone.0075238  

  200. Behavior of red blood cells in a hyperbolic microchannel: the extensional flow effect Peer-reviewed

    T. Yaginuma, M. S. N. Oliveira, R. Lima, T. Ishikawa, T. Yamaguchi

    Biomicrofluidics 7 054110-106 2013/09/02

    DOI: 10.1063/1.4820414  

  201. Human red blood cell behavior under homogeneous extensional flow in a hyperbolic-shaped microchannel Peer-reviewed

    T. Yaginuma, M. S. N. Oliveira, R. Lima, T. Ishikawa, T. Yamaguchi

    BIOMICROFLUIDICS 7 (5) 2013/09

    Publisher: AMER INST PHYSICS

    DOI: 10.1063/1.4820414  

    ISSN:1932-1058

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    It is well known that certain pathological conditions result in a decrease of red blood cells (RBCs) deformability and subsequently can significantly alter the blood flow in microcirculation, which may block capillaries and cause ischemia in the tissues. Microfluidic systems able to obtain reliable quantitative measurements of RBC deformability hold the key to understand and diagnose RBC related diseases. In this work, a microfluidic system composed of a microchannel with a hyperbolic-shaped contraction followed by a sudden expansion is presented. We provide a detailed quantitative description of the degree of deformation of human RBCs under a controlled homogeneous extensional flow field. We measured the deformation index (DI) as well as the velocity of the RBCs travelling along the centerline of the channel for four different flow rates and analyze the impact of the particle Reynolds number. The results show that human RBC deformation tends to reach a plateau value in the region of constant extensional rate, the value of which depends on the extension rate. Additionally, we observe that the presence of a sudden expansion downstream of the hyperbolic contraction modifies the spatial distribution of cells and substantially increases the cell free layer (CFL) downstream of the expansion plane similarly to what is seen in other expansion flows. Beyond a certain value of flow rate, there is only a weak effect of inlet flow rates on the enhancement of the downstream CFL. These in vitro experiments show the potential of using microfluidic systems with hyperbolic-shaped microchannels both for the separation of the RBCs from plasma and to assess changes in RBC deformability in physiological and pathological situations for clinical purposes. However, the selection of the geometry and the identification of the most suitable region to evaluate the changes on the RBC deformability under extensional flows are crucial if microfluidics is to be used as an in vitro clinical methodology to detect circulatory diseases. (C) 2013 AIP Publishing LLC.

  202. Simulation of nutrient uptake of swimming model microorganisms

    S. Kajiki, D. Matsunaga, Y. Imai, T. Yamaguchi, T. Ishikawa

    APCB2013 Proceedings S12 2013/08/30

  203. Effect of Aeration on the Bioconvection Pattern in a Microalgae Suspension

    Y. Nonaka, H. Ueno, K. Numayama, T. Omori, Y. Imai, T. Yamaguchi, T. Ishikawa

    APCB2013 Proceedings S12-002 2013/08/30

  204. Modeling of cytoadhesion in malaria infection

    A. Ami, Y. Imai, T. Ishikawa, T. Yamaguchi

    APCB2013 Proceedings S4-3 2013/08/30

  205. Mechanism of capsule migration near a plane wall

    S. Nix, Y. Imai, D. Matsunaga, T. Yamaguchi, T. Ishikawa

    APCB2013 Proceedings S4-020 2013/08/30

  206. Numerical simulation of motion of solid particles in the stomach

    T. Miyagawa, Y. Imai, T. Yamaguchi, T. Ishikawa

    APCB2013 Proceedings S4-019 2013/08/30

  207. Margination of white blood cell in various sizes of circular micro-channel

    N. Takeishi, Y. Imai, T. Ishikawa, T. Yamaguchi

    APCB2013 Proceedings S4-3 2013/08/30

  208. Collective Swimming of Ellipsoidal Microorganisms

    K. Kyoya, D. Matsunaga, Y. Imai, T. Yamaguchi, T. Ishikawa

    APCB2013 Proceedings S4-014 2013/08/30

  209. A Numerical Analysis of the Rheorogy of Capsule Suspensions Containing Different Size Capsules

    H. Ito, Y. Imai, D. Matsunaga, T. Yamaguchi, T. Ishikawa

    APCB2013 Proceedings S4-015 2013/08/30

  210. Integrated Biomechanics for Physiological Flow Problems

    T. Yamaguchi, Y. Imai, T. Omori, H. Ueno, K. Numayama-Tsuruta, T. Ishikawa

    APCB2013 The7thAsian Pacific Conference on Biomechanics ILS4-009 2013/08/29

  211. COMPUTATIONAL BIOMECHANICS ON BLOOD FLOW FROM CELLULAR TO

    T. yamaguchi, Y. Imai, T. Ishikawa

    COMPDYN 2013 S2090 2013/06/13

  212. Shear-induced diffusion of red blood cells in a semi-dilute suspension Peer-reviewed

    T. Omori, T. Ishikawa, Y. Imai, T. Yamaguchi

    Journal of Fluid Mechanics 724 154-174 2013/06/10

    DOI: 10.1017/jfm.2013.159  

    ISSN:0022-1120 1469-7645

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    The diffusion of red blood cells (RBCs) in blood is important to the physiology and pathology of the cardiovascular system. In this study, we investigate flow-induced diffusion of RBCs in a semi-dilute system by calculating the pairwise interactions between RBCs in simple shear flow. A capsule with a hyperelastic membrane was used to model an RBC. Its deformation was resolved using the finite element method, whereas fluid motion inside and outside the RBC was solved using the boundary element method. The results show that shear-induced RBC diffusion is significantly anisotropic, i.e. the velocity gradient direction component is larger than the vorticity direction. We also found that the motion of RBCs during the interaction is strongly dependent on the viscosity ratio of the internal to external fluid, and the diffusivity decreases monotonically as the viscosity ratio increases. The scaling argument also suggests that the diffusivity is proportional to the shear rate and haematocrit, if the suspension is in a semi-dilute environment and the capillary number is invariant. These fundamental findings are useful to understand transport phenomena in blood flow. © 2013 Cambridge University Press.

  213. Computational simulation of thrombus formation regulated by platelet membrane receptors and blood shear Peer-reviewed

    H. Kamada, Y. Imai, M. Nakamura, T. Ishikawa, T. Yamaguchi

    Microvascular Research 89 95-106 2013/06/02

    DOI: 10.1016/j.mvr.2013.05.006  

  214. Hydrodynamic Phase Locking in Mouse Node Cilia Peer-reviewed

    Atsuko Takamatsu, Kyosuke Shinohara, Takuji Ishikawa, Hiroshi Hamada

    PHYSICAL REVIEW LETTERS 110 (24) 248107 2013/06

    Publisher: AMER PHYSICAL SOC

    DOI: 10.1103/PhysRevLett.110.248107  

    ISSN:0031-9007

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    Rotational movement of mouse node cilia generates leftward fluid flow in the node cavity, playing an important role in left-right determination in the embryo. Although rotation of numerous cilia was believed necessary to trigger the determination, recent reports indicate the action of two cilia to be sufficient. We examine cooperative cilia movement via hydrodynamic interaction. Results show cilia to be cooperative, having phases locked in a certain relation; a system with a pair of nonidentical cilia can achieve phase-locked states more easily than one with a pair of identical cilia.

  215. Asymmetric rotational stroke in mouse node cilia during left-right determination Peer-reviewed

    Atsuko Takamatsu, Takuji Ishikawa, Kyosuke Shinohara, Hiroshi Hamada

    Physical Review E - Statistical, Nonlinear, and Soft Matter Physics 87 (5) 050701(R) 2013/05/15

    DOI: 10.1103/PhysRevE.87.050701  

    ISSN:1539-3755 1550-2376

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    Rotational movement of isolated single cilia in mice embryo was investigated, which generates leftward fluid flow in the node cavity and plays an important role in left-right determination. The leftward unidirectional flow results from tilting of the rotational axis of the cilium to the posterior side. By combining computational fluid dynamics with experimental observations, we demonstrate that the leftward stroke can be more effective than expected for cases in which cilia tilting alone is considered with the no-slip condition under constant driving torque. Our results suggest that the driving torque is asymmetric. © 2013 American Physical Society.

  216. The near-wall motion of a capsule in stokes flow

    S. Nix, Y. Imai, D. Matsunaga, T. Ishikawa, T. Yamaguchi

    6th East Asian Pacific Student Workshop on Nano-Biomedical Engineering 52-53 2013/03

  217. Numerical simulation of adhesion of malaria-infected red blood cells

    A. Ami, Y. Imai, T. Ishikawa, T. Yamaguchi

    6th East Asian Pacific Student Workshop on Nano-Biomedical Engineering 38-39 2013/03

  218. Numerical analysis of swimming microorganisms by a boundary element method

    K. Kyoya, D. Matsunaga, Y. Imai, T. Yamaguchi, T. Ishikawa

    6th East Asian Pacific Student Workshop on Nano-Biomedical Engineering 44-45 2013/03

  219. Numerical analysis of dynamics of solid particles in the stomach

    T. Miyagawa, Y. Imai, T. Ishikawa, T. Yamaguchi

    6th East Asian Pacific Student Workshop on Nano-Biomedical Engineering 48-49 2013/03

  220. Margination of various cells in microcirculation

    N. Takeishi, Y. Imai, T. Ishikawa, T. Yamaguchi

    6th East Asian Pacific Student Workshop on Nano-Biomedical Engineering 36-37 2013/03

  221. Gradient diffusion of red blood cells in blood flow through a Y-shape microchannel

    C. Chuang, T. Ishikawa, H. Ueno, K. Numayama-Tsuruta, Y. Imai, T. Yamaguchi

    6th East Asian Pacific Student Workshop on Nano-Biomedical Engineering 78-79 2013/03

  222. A numerical analysis of complex viscosity of dilute capsule suspension

    D. Matsunaga, Y. Imai, T. Ishikawa, T. Yamaguchi

    6th East Asian Pacific Student Workshop on Nano-Biomedical Engineering 104-105 2013/03

  223. A numerical analysis of bimodal capsule suspensions

    H. Ito, Y. Imai, D. Matsunaga, T. Ishikawa, T. Yamaguchi

    6th East Asian Pacific Student Workshop on Nano-Biomedical Engineering 106-107 2013/03

  224. Active Suspensions of Swimming Microorganisms Invited

    T. Ishikawa

    Int. Symp. Self-organization and Emergent Dynamics in Active Soft Matter Abstracts 14 2013/02/01

  225. Membrane tension of red blood cells pairwisely interacting in simple shear flow Peer-reviewed

    Toshihiro Omori, Takuji Ishikawa, Yohsuke Imai, Takami Yamaguchi

    Journal of Biomechanics 46 (3) 548-553 2013/02/01

    DOI: 10.1016/j.jbiomech.2012.09.017  

    ISSN:0021-9290 1873-2380

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    Flow-induced membrane tension contributes to the release of molecules by red blood cells (RBCs), and extremely high tension may cause haemolysis. Here, we investigated the membrane tension of RBCs during pairwise interactions in simple shear flow, given that pairwise interactions form the basis of many-body interactions. RBCs were modelled as capsules with a two-dimensional hyperelastic membrane, and large deformations were solved by the finite element method. Due to the small size of the RBCs, surrounding fluid motion was estimated as a Stokes flow and solved by the boundary element method. The results showed that the maximum isotropic tension appeared around the dimple of the biconcave surface and not around the rim. A comparison of the results with solitary cases indicated that the maximum principal tension and isotropic tension were significantly increased by cell-cell interaction effects. As the volume fraction of RBCs is large under physiological conditions, as well as in blood flow in vitro, cell-cell interactions must be analysed carefully when considering mechanotransduction and haemolysis in blood flow. © 2012 Elsevier Ltd.

  226. Membrane tension of red blood cells pairwisely interacting in simple shear flow Peer-reviewed

    Toshihiro Omori, Takuji Ishikawa, Yohsuke Imai, Takami Yamaguchi

    Journal of Biomechanics 46 (3) 548-553 2013/02/01

    DOI: 10.1016/j.jbiomech.2012.09.017  

    ISSN:0021-9290 1873-2380

    More details Close

    Flow-induced membrane tension contributes to the release of molecules by red blood cells (RBCs), and extremely high tension may cause haemolysis. Here, we investigated the membrane tension of RBCs during pairwise interactions in simple shear flow, given that pairwise interactions form the basis of many-body interactions. RBCs were modelled as capsules with a two-dimensional hyperelastic membrane, and large deformations were solved by the finite element method. Due to the small size of the RBCs, surrounding fluid motion was estimated as a Stokes flow and solved by the boundary element method. The results showed that the maximum isotropic tension appeared around the dimple of the biconcave surface and not around the rim. A comparison of the results with solitary cases indicated that the maximum principal tension and isotropic tension were significantly increased by cell-cell interaction effects. As the volume fraction of RBCs is large under physiological conditions, as well as in blood flow in vitro, cell-cell interactions must be analysed carefully when considering mechanotransduction and haemolysis in blood flow. © 2012 Elsevier Ltd.

  227. Antral recirculation in the stomach during gastric mixing Peer-reviewed

    Yohsuke Imai, Ikuma Kobayashi, Shunichi Ishida, Takuji Ishikawa, Martin Buist, Takami Yamaguchi

    American Journal of Physiology - Gastrointestinal and Liver Physiology 304 (5) G536-G542 2013

    DOI: 10.1152/ajpgi.00350.2012  

    ISSN:0193-1857 1522-1547

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    We investigate flow in the stomach during gastric mixing using a numerical simulation with an anatomically realistic geometry and freesurface flow modeling. Because of momentum differences between greater and lesser curvatures during peristaltic contractions, timeaveraged recirculation is generated in the antrum, with retropulsive flow away from the pylorus and compensation flow along the greater curvature toward the pylorus. Gastric content in the distal stomach is continuously transported to the distal antrum by the forward flow of antral recirculation, and it is then mixed by the backward retropulsive flow. Hence, the content inside the antral recirculation is well mixed independently of initial location, whereas the content outside the recirculation is poorly mixed. Free-surface modeling enables us to analyze the effects of posture on gastric mixing. In the upright, prone, and right lateral positions, most of the antrum is filled with content, and the content is well mixed by antral recirculation. In contrast, in the supine and left lateral positions, most of the content is located outside antral recirculation, which results in poor mixing. The curved, twisted shape of the stomach substantially supports gastric mixing in fluid mechanical terms. © 2013 the American Physiological Society.

  228. Computational analysis on the mechanical interaction between a thrombus and red blood cells: Possible causes of membrane damage of red blood cells at microvessels Peer-reviewed

    Hiroki Kamada, Yohsuke Imai, Masanori Nakamura, Takuji Ishikawa, Takami Yamaguchi

    MEDICAL ENGINEERING & PHYSICS 34 (10) 1411-1420 2012/12

    Publisher: ELSEVIER SCI LTD

    DOI: 10.1016/j.medengphy.2012.01.003  

    ISSN:1350-4533

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    Previous studies investigating thrombus formation have not focused on the physical interaction between red blood cells (RBCs) and thrombus, although they have been speculated that some pathological conditions such as microangiopathic hemolytic anemia (MAHA) stem from interactions between RBCs and thrombi. In this study, we investigated the mechanical influence of RBCs on primary thrombi during hemostasis. We also explored the mechanics and aggravating factors of intravascular hemolysis. Computer simulations of primary thrombogenesis in the presence and the absence of RBCs demonstrated that RBCs are unlikely to affect the thrombus height and coverage, although their presence may change microvessel hemodynamics and platelet transportation to the injured wall. Our results suggest that intravascular hemolysis owing to RBC membrane damage would be promoted by three hemodynamic factors: (1) dispersibility of platelet thrombi, because more frequent spatial thrombus formation decreases the time available for an RBC to recover its shape and enforces more severe deformation; (2) platelet thrombus stiffness, because a stiffer thrombus increases the degree of RBC deformation upon collision; and (3) vessel size and hemocyte density, because a smaller vessel diameter and higher hemocyte density decrease the room for RBCs to escape as they come closer to a thrombus, thereby enhancing thrombus-RBC interactions. (C) 2012 IPEM. Published by Elsevier Ltd. All rights reserved.

  229. Computational analysis on the mechanical interaction between a thrombus and red blood cells: Possible causes of membrane damage of red blood cells at microvessels Peer-reviewed

    Hiroki Kamada, Yohsuke Imai, Masanori Nakamura, Takuji Ishikawa, Takami Yamaguchi

    MEDICAL ENGINEERING & PHYSICS 34 (10) 1411-1420 2012/12

    Publisher: ELSEVIER SCI LTD

    DOI: 10.1016/j.medengphy.2012.01.003  

    ISSN:1350-4533

    More details Close

    Previous studies investigating thrombus formation have not focused on the physical interaction between red blood cells (RBCs) and thrombus, although they have been speculated that some pathological conditions such as microangiopathic hemolytic anemia (MAHA) stem from interactions between RBCs and thrombi. In this study, we investigated the mechanical influence of RBCs on primary thrombi during hemostasis. We also explored the mechanics and aggravating factors of intravascular hemolysis. Computer simulations of primary thrombogenesis in the presence and the absence of RBCs demonstrated that RBCs are unlikely to affect the thrombus height and coverage, although their presence may change microvessel hemodynamics and platelet transportation to the injured wall. Our results suggest that intravascular hemolysis owing to RBC membrane damage would be promoted by three hemodynamic factors: (1) dispersibility of platelet thrombi, because more frequent spatial thrombus formation decreases the time available for an RBC to recover its shape and enforces more severe deformation; (2) platelet thrombus stiffness, because a stiffer thrombus increases the degree of RBC deformation upon collision; and (3) vessel size and hemocyte density, because a smaller vessel diameter and higher hemocyte density decrease the room for RBCs to escape as they come closer to a thrombus, thereby enhancing thrombus-RBC interactions. (C) 2012 IPEM. Published by Elsevier Ltd. All rights reserved.

  230. Models and Numerical Methods for a Suspension of Swimming Microorganisms: Review Peer-reviewed

    Takuji Ishikawa

    INTERNATIONAL JOURNAL OF OFFSHORE AND POLAR ENGINEERING 22 (4) 270-275 2012/12

    Publisher: INT SOC OFFSHORE POLAR ENGINEERS

    ISSN:1053-5381

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    Microorganisms play a vital role in many ecological, environmental and engineering phenomena: Examples include plankton blooms in the oceans and bioreactors for algae fuels. In the last decade, the mathematical models and numerical methods used in this field have improved significantly. In this paper, we review recent advances in the simulation of the individual and collective behaviors of swimming microorganisms, as well as discrete modeling of individual microorganisms for simulating large-scale flow structures. Because we have recently reviewed the biomechanical aspects of suspensions of swimming microorganisms (Ishikawa, 2009), we mainly focus on methodological aspects here.

  231. 3D-PTV measurement of the phototactic movement of algae in shear flow

    T. Maeda, T. Ishikawa, H. Ueno, K. Numayama-Tsuruta, Y. Imai, T. Yamaguchi

    Bulletin of the American Physical Society 57 49 2012/11/20

  232. Measurement of ciliary flow generated on the surface of tracheal

    K. Kiyota, H. Ueno, T. Ishikawa, K. Numayama-Tsuruta, Y. Imai, T. Omori, T. Yamaguchi

    Bulletin of the American Physical Society 57 334 2012/11/20

  233. Off-plane motion of a non-spherical capsule in simple shear flow

    T. Omori, T. Ishikawa, Y. Imai, T. Yamaguchi

    Bulletin of the American Physical Society 57 331 2012/11/20

  234. Analysis of red blood cell behavior in a narrow tube

    H. Hosaka, T. Omori, Y. Imai, T. Yamaguchi, T. Ishikawa

    Bulletin of the American Physical Society 57 330 2012/11/20

  235. Hydrodynamical entrapment of ciliates at the air-liquid interface

    J. Ferracci, H. Ueno, K. Numayama-Tsuruta, Y. Imai, T. Yamaguchi, T. Ishikawa

    Bulletin of the American Physical Society 57 107 2012/11/20

  236. Gradient diffusion of red blood cells in blood flow through a Y-shape microchannel

    C. Chuang, T. Ishikawa, H. Ueno, K. Numayama-Tsuruta, Y. Imai, T. Yamaguchi

    Bulletin of the American Physical Society 65th Annual Meeting of the APS Division of Fluid Dynamics 330-330 2012/11

  237. Tension of red blood cell membrane in simple shear flow Peer-reviewed

    T. Omori, T. Ishikawa, D. Barthes-Biesel, A. -V. Salsac, Y. Imai, T. Yamaguchi

    PHYSICAL REVIEW E 86 (5) 056321 2012/11

    Publisher: AMER PHYSICAL SOC

    DOI: 10.1103/PhysRevE.86.056321  

    ISSN:1539-3755

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    When a red blood cell (RBC) is subjected to an external flow, it is deformed by the hydrodynamic forces acting on its membrane. The resulting elastic tensions in the membrane play a key role in mechanotransduction and govern its rupture in the case of hemolysis. In this study, we analyze the motion and deformation of an RBC in a simple shear flow and the resulting elastic tensions on the membrane. The large deformation of the red blood cell is modelled by coupling a finite element method to solve the membrane mechanics and a boundary element method to solve the flows of the internal and external liquids. Depending on the capillary number Ca, ratio of the viscous to elastic forces, we observe three kinds of RBC motion: tumbling at low Ca, swinging at larger Ca, and breathing at the transitions. In the swinging regime, the region of the high principal tensions periodically oscillates, whereas that of the high isotropic tensions is almost unchanged. Due to the strain-hardening property of the membrane, the deformation is limited but the membrane tension increases monotonically with the capillary number. We have quantitatively compared our numerical results with former experimental results. It indicates that a membrane isotropic tension O(10(-6) N/m) is high enough for molecular release from RBCs and that the typical maximum membrane principal tension for haemolysis would be O(10(-4) N/m). These findings are useful to clarify not only the membrane rupture but also the mechanotransduction of RBCs.

  238. Lateral migration of capsules in a near-wall shear flow

    S. Nix, Y. Imai, D. Matsunaga, T. Ishikawa, T. Yamaguchi

    JSME-CMD ICMS2012 USB 2012/10/20

  239. Development of a GPU-Implemented BEM solver for biological cell suspensions

    Y. Imai, D. Matsunaga, K. Kyoya, T. Omori, T. Ishikawa, T. Yamaguchi

    JSME-CMD ICMS2012 USB 2012/10/20

  240. Mouse respiratory cilia with the asymmetric axonemal structure on sparsely distributed ciliary cells can generate overall directional flow Peer-reviewed

    Hironori Ueno, Takuji Ishikawa, Khanh Huy Bui, Kohsuke Gonda, Takashi Ishikawa, Takami Yamaguchi

    NANOMEDICINE-NANOTECHNOLOGY BIOLOGY AND MEDICINE 8 (7) 1081-1087 2012/10

    Publisher: ELSEVIER SCIENCE BV

    DOI: 10.1016/j.nano.2012.01.004  

    ISSN:1549-9634

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    Mucociliary clearance on the surface of the tracheal lumen is an important component of lung defense against dust mites and viruses. However, the axonemal structure that achieves effective ciliary motion, and the mechanisms by which discretely distributed ciliary cells generate directional flow are unknown. In this study, we examined individual ciliary motion with 7- to 9-nm spatial precision by labeling the ciliary tip with quantum dots and detected an asymmetric beating pattern. Cryo-electron tomography revealed that the densities of two inner dynein arms were missing from at least 2 doublet microtubules in the axonemal structure. Although the flow directions generated by individual ciliated cells were unsteady and diverse, the time- and space-averaged velocity field was found to be directional. These results indicate that the asymmetric ciliary motion is driven by the asymmetric axonemal structure, and it generates overall directional flow from the lungs to the oropharynx on sparsely distributed ciliated cells. From the Clinical Editor: The authors of this study utilized quantum dots in determining the kinetics of ciliary motion in mouse respiratory cilia with 7- to 9-nm spatial precision. (C) 2012 Elsevier Inc. All rights reserved.

  241. Quantification of red blood cell deformation at high-hematocrit blood flow in microvessels Peer-reviewed

    Davod Alizadehrad, Yohsuke Imai, Keita Nakaaki, Takuji Ishikawa, Takami Yamaguchi

    JOURNAL OF BIOMECHANICS 45 (15) 2684-2689 2012/10

    Publisher: ELSEVIER SCI LTD

    DOI: 10.1016/j.jbiomech.2012.08.026  

    ISSN:0021-9290

    eISSN:1873-2380

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    The deformation of red blood cells in microvessels was investigated numerically for various vessel diameters, hematocrits, and shear rates. We simulated blood flow in circular channels with diameters ranging from 9 to 50 mu m, hematocrits from 20% to 45%, and shear rates from 20 to 150 s(-1) using a particle-based model with parallel computing. The apparent viscosity predicted by the simulation was in good agreement with previous experimental results. We quantified the deformation of red blood cells as a function of radial position. The numerical results demonstrated that because of the shape transition in response to local shear stress and the wall effect, the radial variation of red blood cell deformation in relatively large microvessels could be classified into three different regions: near-center, middle, and near-wall regions. Effects of the local shear stress and wall varied with vessel diameter, hematocrit, and shear rate. (C) 2012 Elsevier Ltd. All rights reserved.

  242. Role of fluid mechanics in collective motions of bacteria

    T. Ishikawa, N. Yoshida, H. Ueno, M. Wiedeman, Y. Imai, T. Yamaguchi

    9th International Conference on Flow Dynamics 732-733 2012/09/20

  243. Computational analysis on the mechanical interaction between a thrombus and red blood cells

    H. Kamada, Y. Imai, M. Nakamura, T. Ishikawa, T. Yamaguchi

    ECCOMAS 2012 Congress CD-ROM 2012/09/20

  244. Vertical dispersion of model microorganisms in horizontal shear flow Peer-reviewed

    Takuji Ishikawa

    JOURNAL OF FLUID MECHANICS 705 98-119 2012/08

    Publisher: CAMBRIDGE UNIV PRESS

    DOI: 10.1017/jfm.2012.116  

    ISSN:0022-1120

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    Microorganisms often swim upwards due to the cell's phototaxis, chemotaxis or geotaxis, in flow fields with vertical velocity gradients. In this study, the vertical dispersion of model microorganisms was investigated under horizontal shear conditions. A microorganism was modelled as a spherical squirmer with or without bottom-heaviness. First, the three-dimensional movement of 100 identical squirmers in a homogeneous suspension was computed by the Stokesian dynamics method. The results show that the dispersion of squirmers is strongly affected by the swimming velocity and bottom-heaviness of the cells and the shear rate of the background flow. The vertical diffusion is considerably smaller than the horizontal diffusion. Interestingly, the vertical diffusion decreases as the volume fraction and the stresslet of squirmers decrease, which is opposite of the tendency in diffusion with no background flow. Next, a continuum model of a suspension of squirmers was developed using the diffusion tensor and the drift velocity to simulate the spatial distribution of squirmers in macroscopic flow fields. The results of the continuum model illustrate that the gyrotactic trapping found by Durham, Kessler & Stocker (Science, vol. 323, 2009, pp. 1067-1070) also appears in the present model considering cell cell hydrodynamic interactions. In the case of horizontal Poiseuille flow, the volume fraction of bottom-heavy cells in the channel becomes considerably larger than that at the inlet. These fundamental findings are helpful for understanding the distribution of microorganisms in various water regimes in nature and industry.

  245. Particle based simulation of microcirculation using a parallel computation

    T. Yamaguchi, Y. Imai, T. Ishikawa

    14th Int.l Cong. Biorheology and 7th Int. Conf. Clinical Hemorheology 181 2012/07/20

  246. Reorientation of a non-spherical capsule in shear flow

    T. Ishikawa, T. Omori, Y. Imai, T. Yamaguchi

    Abstracts 23rd Int. Cong. Theor. Appl. Math. 106 2012/07/20

  247. Hemodynamics in the pulmonary artery of a patient with pneumothorax Peer-reviewed

    J-J Christophe, T. Ishikawa, Y. Imai, K. Takase, M. Thiriet, T. Yamaguchi

    MEDICAL ENGINEERING & PHYSICS 34 (6) 725-732 2012/07

    Publisher: ELSEVIER SCI LTD

    DOI: 10.1016/j.medengphy.2011.09.016  

    ISSN:1350-4533

    eISSN:1873-4030

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    Pneumothorax is characterized by lung collapse and an alteration of lung geometry, resulting in alterations of the pulmonary artery blood flow. Though many clinical studies and animal experiments have investigated the effects of pneumothorax on the hemodynamics of pulmonary arteries, its precise effects remain unclear. In this patient-specific study, we investigated the effects of lung deformation and vascular resistance increases due to pneumothorax on the pulmonary blood flow during the acute phase and after recovery. Arterial geometry was extracted up to the fifth generation from computed tomography images, and reconstructed. Computational fluid dynamic analysis was performed, for an unsteady laminar flow with resistance at the outlets, in a reconstructed domain. The results demonstrated a change in flow structure during systole between the acute phase and recovery, and were associated with variations in the flow rate ratio between the right and left lungs. We observed a parabolic-like decrease of the volume flow rate ratio in the affected lung as the resistance increased. Thus, the systemic artery blood oxygenation will rely more on the unaffected lung leading to improved oxygenation of the blood under high resistance in the affected lung. These findings are significant in our understanding of ventilation function under a pneumothorax. (C) 2011 IPEM. Published by Elsevier Ltd. All rights reserved.

  248. Hydrodynamic entrapment of ciliates at the air-liquid interface

    J. Ferracci, H. Ueno, K. Numayama-Tsuruta, Y. Imai, T. Yamaguchi, T. Ishikawa

    Softflow 2012 - Biological Complex Fluids 36-37 2012/06/22

  249. Dynamics of capsules near a plane wall

    S. Nix, Y. Imai, T. Ishikawa, T. Yamaguchi

    Softflow 2012 - Biological Complex Fluids 76 2012/06/22

  250. Analysis of ciliary motion and the axonemal structure in the mouse respiratory cilia Peer-reviewed

    H. Ueno, T. Ishikawa, K. H. Bui, K. Gonda, T. Ishikawa, T. Yamaguchi

    ASME 2012 Summer Bioengineering Conference CD-ROM 2012/06/20

    DOI: 10.1115/SBC2012-80232  

  251. Dynamics of a spherical capsule in a near-wall shear flow Peer-reviewed

    S. Nix, Y. Imai, D. Matsunaga, T. Ishikawa, T. Yamaguchi

    ASME 2012 Summer Bioengineering Conference CD-ROM 2012/06/20

    DOI: 10.1115/SBC2012-80518  

  252. Development of a numerical model for micro-scale blood flow simulation using GPGPU Peer-reviewed

    N. Takeishi, Y. Imai, K. Nakaaki, T. Ishikawa, T. Yamaguchi

    ASME 2012 Summer Bioengineering Conference CD-ROM 2012/06/20

    DOI: 10.1115/SBC2012-80028  

  253. Development of a multi-phase flow model for simulating solid particle motion in the stomach Peer-reviewed

    T. Miyagawa, Y. Imai, I. Kobayashi, T. Ishikawa, T. Yamaguchi

    ASME 2012 Summer Bioengineering Conference CD-ROM 2012/06/20

    DOI: 10.1115/SBC2012-80891  

  254. Double-layer representation of model microorganisms by a boundary element method Peer-reviewed

    K. Kyoya, Y. Imai, T. Yamaguchi, T. Ishikawa

    ASME 2012 Summer Bioengineering Conference CD-ROM 2012/06/20

    DOI: 10.1115/SBC2012-80234  

  255. Transport Phenomena in Suspensions of Swimming Microorganisms

    T. Ishikawa

    Biological Complex Fluids 53 2012/06/20

  256. Blood oxygenation using microbubble suspensions Peer-reviewed

    Noriaki Matsuki, Shingo Ichiba, Takuji Ishikawa, Osamu Nagano, Motohiro Takeda, Yoshihito Ujike, Takami Yamaguchi

    EUROPEAN BIOPHYSICS JOURNAL WITH BIOPHYSICS LETTERS 41 (6) 571-578 2012/06

    Publisher: SPRINGER

    DOI: 10.1007/s00249-012-0811-y  

    ISSN:0175-7571

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    Microbubbles have been used in a variety of fields and have unique properties, for example shrinking collapse, long lifetime, efficient gas solubility, a negatively charged surface, and the ability to produce free radicals. In medicine, microbubbles have been used mainly as diagnostic aids to scan various organs of the body, and they have recently been investigated for use in drug and gene delivery. However, there have been no reports of blood oxygenation by use of oxygen microbubble fluids without shell reagents. In this study, we demonstrated that nano or microbubbles can achieve oxygen supersaturation of fluids, and may be sufficiently small and safe for infusion into blood vessels. Although Po-2 increases in fluids resulting from use of microbubbles were inhibited by polar solvents, normal saline solution (NSS) was little affected. Thus, NSS is suitable for production of oxygen-rich fluid. In addition, oxygen microbubble NSS effectively improved hypoxic conditions in blood. Thus, use of oxygen microbubble (nanobubble) fluids is a potentially effective novel method for oxygenation of hypoxic tissues, for infection control, and for anticancer treatment.

  257. Deposition of micrometer particles in pulmonary airways during inhalation and breath holding Peer-reviewed

    Yohsuke Imai, Takahito Miki, Takuji Ishikawa, Takayuki Aoki, Takami Yamaguchi

    JOURNAL OF BIOMECHANICS 45 (10) 1809-1815 2012/06

    Publisher: ELSEVIER SCI LTD

    DOI: 10.1016/j.jbiomech.2012.04.017  

    ISSN:0021-9290

    eISSN:1873-2380

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    We investigated how breath holding increases the deposition of micrometer particles in pulmonary airways, compared with the deposition during inhalation period. A subject-specific airway model with up to thirteenth generation airways was constructed from multi-slice CT images. Airflow and particle transport were simulated by using GPU computing. Results indicate that breath holding effectively increases the deposition of 5 mu m particles for third to sixth generation (G3-G6) airways. After 10 s of breath holding, the particle deposition fraction increased more than 5 times for 5 mu m particles. Due to a small terminal velocity, 1 mu m particles only showed a 50% increase in the most efficient case. On the other hand, 10 mu m particles showed almost complete deposition due to high inertia and high terminal velocity, leading to an increase of 2 times for G3-G6 airways. An effective breath holding time for 5 mu m particle deposition in G3-G6 airways was estimated to be 4-6 s, for which the deposition amount reached 75% of the final deposition amount after 10 s of breath holding. (C) 2012 Elsevier Ltd. All rights reserved.

  258. Energy efficiency in collective motions of swimming bacteria

    T. Ishikawa, N. Yoshida, H. Ueno, M. Wiedeman, Y. Imai, T. Yamaguchi

    World Cong. Med. Phys. Biomed. Eng CD-ROM, TH.07/05.1-5 2012/05/20

  259. Computational biomechanics of physiological flow

    T. Yamaguchi, T. Ishikawa, Y. Imai, H. Ueno, K. Numayama-Tsuruta, T. Omori

    Biological Flow: A Conference to Celebrate the 70th Birthday of Timothy J. Padley FRS 38 2012/03/20

  260. Rheology of a dilute suspention of red blood cells in simple shear flow

    T. Omori, T. Ishikawa, Y. Imai, T. Yamaguchi

    Proc. 18th International Symposium of Tohoku University Global COE Program 153-154 2012/03/20

  261. Effect of constitutive law on the lateral migration of a capsule near a wall

    S. Nix, Y. Imai, D. Matsunaga, T. Ishikawa, T. Yamaguchi

    Proc. 18th International Symposium of Tohoku University Global COE Program 145-146 2012/03/20

  262. Hydrodynamic entrapment of ciliates at the interface fluid-air

    J. Ferracci, T. Ishikawa, H. Ueno, K. Numayama, Y. Imai, T. Yamaguchi

    Proc. 18th International Symposium of Tohoku University Global COE Program 115-116 2012/03/20

  263. Quantifying characteristics of blood cell at dense cellullar flow

    D. Alizadehrad, Y. Imai, T. Ishikawa, T. Yamaguchi

    Proc. 18th International Symposium of Tohoku University Global COE Program 111-112 2012/03/20

  264. Collective Diffusion of red blood cells from high concentration to low

    C. Chuang, T. Ishikawa, H. Ueno, K. Numayama, Y. Imai, T. Yamaguchi

    Proc. 18th International Symposium of Tohoku University Global COE Program 109-110 2012/03/20

  265. A particle model of cellular flow in microcirculation

    T. Yamaguchi, T. Ishikawa, Y. Imai

    Proc. 18th International Symposium of Tohoku University Global COE Program 61-64 2012/03/20

  266. Radial dispersion of tracer particles through high-hematocrit blood flow within a capillary tube Invited

    M. Saadatmand, T. Ishikawa, N. Matsuki, H. J. Abdekhodaie, Y. Imai, H. Ueno, T. Yamaguchi

    Nano-Biomedical Engineering, Imperial College Press 134-143 2012/03/01

  267. Behavior of a spherical capsule in simple shear flow near an infinite plane Invited

    S. Nix, Y. Imai, D. Matsunaga, T. Ishikawa, T. Yamaguchi

    Nano-Biomedical Engineering, Imperial College Press 122-127 2012/03/01

  268. Entrapment of fresh water ciliates at the interface fluid-air Invited

    J. Ferracci, T. Ishikawa, H. Ueno, K. Numayama-Tsuruta, Y. Imai, T. Yamaguchi

    Nano-Biomedical Engineering, Imperial College Press 70-76 2012/03/01

  269. Gradient diffusion of red blood cells flowing in a straight microchannel Invited

    C. Chuang, T. Ishikawa, H. Ueno, K. Numayama-Tsuruta, Y. Imai, T. Yamaguchi

    Nano-Biomedical Engineering, Imperial College Press 63-69 2012/03/01

  270. Computational biomechanics of blood flow at macro- and micro-scales Invited

    T. Yamaguchi, T. Ishikawa, Y. Imai

    Nano-Biomedical Engineering, Imperial College Press 53-62 2012/03/01

  271. Reorientation of a Nonspherical Capsule in Creeping Shear Flow Peer-reviewed

    Toshihiro Omori, Yohsuke Imai, Takami Yamaguchi, Takuji Ishikawa

    PHYSICAL REVIEW LETTERS 108 (13) 138102 2012/03

    Publisher: AMER PHYSICAL SOC

    DOI: 10.1103/PhysRevLett.108.138102  

    ISSN:0031-9007

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    The dynamics of a capsule and a biological cell is of great interest in chemical engineering and bioengineering. Although the dynamics of a rigid spheroid is well understood by Jeffery's theory, that of a spheroidal capsule remains unclear. In this Letter, the motion of a spheroidal capsule or a red blood cell in creeping shear flow is investigated. The results show that the orientation of a nonspherical capsule is variant under time reversal, though that of a rigid spheroid is invariant. Surprisingly, the alignment of a nonspherical capsule over a long time duration shows a transition depending on the shear rate, which can be utilized for a particle-alignment technique. These findings form a fundamental basis of the suspension mechanics of capsules and biological cells.

  272. Parallel simulation of cellular flow in microvessels using a particle method Peer-reviewed

    Davod Alizadehrad, Yohsuke Imai, Keita Nakaaki, Takuji Ishikawa, Takami Yamaguchi

    Journal of Biomechanical Science and Engineering 7 (1) 57-71 2012/02/29

    DOI: 10.1299/jbse.7.57  

    ISSN:1880-9863

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    We developed a numerical method for large-scale simulations of cellular flow in microvessels. We employed a particle method, where all blood components were modeled using a finite number of particles. Red blood cell deformation was modeled by a spring network of membrane particles. A domain decomposition method was used for parallel implementation on distributed memory systems. In a strong scaling test up to 64 CPU cores, we obtained a linear speedup with the number of CPU cores, and demonstrated that our model can simulate O(10 3) red blood cells in vessels a few tens of micrometers in diameter. For quantitative validation, we analyzed the Fåhræus effect and the formation of a cell-depleted peripheral layer. Simulations were performed for tube hematocrit ranging from 20 to 45%, and microvessel diameters from 9 to 50 μm. Our numerical results were in good agreement with previous experimental results both for the discharge hematocrit and cell-depleted peripheral layer thickness. © 2012 by JSME.

  273. Inertial migration of cancer cells in blood flow in microchannels Peer-reviewed

    Tatsuya Tanaka, Takuji Ishikawa, Keiko Numayama-Tsuruta, Yohsuke Imai, Hironori Ueno, Takefumi Yoshimoto, Noriaki Matsuki, Takami Yamaguchi

    BIOMEDICAL MICRODEVICES 14 (1) 25-33 2012/02

    Publisher: SPRINGER

    DOI: 10.1007/s10544-011-9582-y  

    ISSN:1387-2176

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    The circulating tumor cell test is used to evaluate the condition of breast cancer patients by counting the number of cancer cells in peripheral blood samples. Although microfluidic systems to detect or separate cells using the inertial migration effect may be applied to this test, the hydrodynamic forces acting on cancer cells in high hematocrit blood flow are incompletely understood. In the present study, we investigated the inertial migration of cancer cells in high hematocrit blood flow in microchannels. The maximum hematocrit used in this study was about 40%. By measuring the cell migration probability, we examined the effects of cell-cell interactions, cell deformability, and variations in cell size on the inertial migration of cancer cells in blood. The results clearly illustrate that cancer cells can migrate towards equilibrium positions up to a hematocrit level of 10%. We also performed simple scaling analysis to explain the differences in migration length between rigid particles and cancer cells as well as the effect of hematocrit on cancer cell migration. These results will be important for the design of microfluidic devices for separating cells from blood.

  274. Micro-flow visualization of magnetic nanoparticles for biomedical applications Peer-reviewed

    R. Lima, R. J. Joseyphus, T. Ishikawa, Y. Imai, T. Yamaguchi

    Single and Two-Phase Flows on Chemical and Biomedical Engineering 600-612 2012

    Publisher: Bentham Science Publishers Ltd.

    DOI: 10.2174/978160805295011201010600  

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    An investigation to measure the flow behavior of magnetic nanoparticles through a 100? m microchannel is conducted. The magnetic field is applied externally by a permanent magnet and by using a micro-PTV system it was possible to measure the flow behavior of magnetic nanoparticles at different flow rates and magnetic fields through a 100?m glass capillary. A strong dependence on both magnetic and hydrodynamic force is observed on the nanoparticles fluidic paths. Based on these in vitro studies, important parameters and issues that require further understanding and investigation are point out. © 2012 Bentham Science Publishers. All rights reserved.

  275. Blood flow behavior in microchannels: Past, current and future trends Peer-reviewed

    R. Lima, T. Ishikawa, Y. Imai, T. Yamaguchi

    Single and Two-Phase Flows on Chemical and Biomedical Engineering 513-547 2012

    Publisher: Bentham Science Publishers Ltd.

    DOI: 10.2174/978160805295011201010513  

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    Over the years, various experimental methods have been applied in an effort to understand the blood flow behavior in microcirculation. Most of our current knowledge in microcirculation is based on macroscopic flow phenomena such as Fahraeus effect and Fahraeus-Linqvist effect. The development of optical experimental techniques has contributed to obtain possible explanations on the way the blood flows through microvessels. Although the past results have been encouraging, detailed studies on blood flow behavior at a microscopic level have been limited by several factors such as poor spatial resolution, difficulty to obtain accurate measurements at such small scales, optical errors arisen from walls of the microvessels, high concentration of blood cells, and difficulty in visualization of results due to insufficient computing power and absence of reliable image analysis techniques. However, in recent years, due to advances in computers, optics, and digital image processing techniques, it has become possible to combine a conventional particle image velocimetry (PIV) system with an inverted microscope and consequently improve both spatial and temporal resolution. The present review outlines the most relevant studies on the flow properties of blood at a microscale level by using past video-based methods and current micro-PIV and confocal micro-PIV techniques. Additionally the most recent computational fluid dynamics studies on microscale hemodynamics are also reviewed. © 2012 Bentham Science Publishers. All rights reserved.

  276. Boundary element analysis of the multi-capsule flow using an ultra-high speed GPGPU computation Peer-reviewed

    D. Matsunaga, Y. Imai, T. Ishikawa, T. Yamaguchi

    WIT Transactions on Modelling and Simulation 53 201-208 2012

    DOI: 10.2495/BE120181  

    ISSN:1743-355X

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    A capsule is a liquid drop enclosed by a thin membrane. Understanding the mechanics of capsule suspension is important in a variety of applications. However, computational time is still a barrier against successful simulations for dense suspension of capsules. We have developedan ultra-highspeed computation method based on Graphics Processing Unit (GPU) computing for simulatin gmulti-capsule flow. In the case of using single GPU, the performance achieves 1. 20 TFlops that correspondsto a 550-foldspeed up comparedwith a CPU core. We also developed an algorithm of multi GPUs that hide data communication by overlapping with computational time. Since our method enables us to simulate from one to a few hundredcapsules in a realistic computationaltime, the methodcouldbe a powerful solution for simulating the capsule suspension. © 201 WIT Press.

  277. Boundary element analysis of deformation and movement of a capsule and a red blood cell close to the wall Peer-reviewed

    S. Nix, Y. Imai, T. Ishikawa, T. Yamaguchi

    WIT Transactions on Modelling and Simulation 53 191-199 2012

    DOI: 10.2495/BE120171  

    ISSN:1743-355X

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    Acapsuleis definedas aliquiddropenclosedbyanelastic membrane. Thestudyof capsule behavior near a stationary surface has a numberof biological applications, such as red blood cells in the cardiovascular system. However, near-wall behavior of capsules has not been established well. In this study, we investigate the motion of initially spherical and biconcave capsules in simple shear flow near an infinite plane using a boundary integral method coupled to a finite element method. We find that the deformation of a capsule depends on its initial shape, orientation, and capillary number (Ca). However, the lift velocity of a capsule is dependent on its steady state deformation and distance from the wall. The dependence of lift velocity on deformation may help to explain phenomena such as leukocyte margination. © 201 WIT Press.

  278. Flow visualization of trace particles and Red Blood Cells in a microchannel with a diverging and converging bifurcation Peer-reviewed

    V. Leble, C. Fernandes, R. Dias, R. Lima, T. Ishikawa, Y. Imai, T. Yamaguchi

    COMPUTATIONAL VISION AND MEDICAL IMAGE PROCESSING: VIPIMAGE 2011 209-211 2012

    Publisher: CRC PRESS-TAYLOR & FRANCIS GROUP

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    This paper aims to investigate the effect of both diverging and converging bifurcations on the flow behaviour of Pure Water (PW) and Red Blood Cells (RBCs). A confocal micro-PTV system is used to visualize and measure the flow characteristics of the working fluids. The results show no formation of a Cell-Free Layer (CFL) around the apex of the bifurcation. In contrast, there is a clear formation of a triangular CFL just downstream of the confluence apex. As a result, this triangular CFL seems to play an important role on the in vitro blood flow characteristics at this region.

  279. Flow of Red Blood Cells through a microfluidic extensional device: An image analysis assessment Peer-reviewed

    T. Yaginuma, A. I. Pereira, P. J. Rodrigues, R. Lima, M. S. N. Oliveira, T. Ishikawa, T. Yamaguchi

    COMPUTATIONAL VISION AND MEDICAL IMAGE PROCESSING: VIPIMAGE 2011 217-220 2012

    Publisher: CRC PRESS-TAYLOR & FRANCIS GROUP

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    The present study aims to assess the deformability of Red Blood Cells (RBCs) under extensionally dominated microfluidic flows using an image based technique. For this purpose, a microchannel having a hyperbolic shaped-contraction was used and the images were captured by a standard high-speed microscopy system. The images acquired display RBCs with various light intensity levels and image analysis was used to quantify the Deformation Index (DI) of the RBCs considering these light intensity differences. Additionally, the velocities of different intensity-level RBCs flowing along the centerline of the channel were measured using particle tracking velocimetry. The preliminary results at two different flow rates reveal a highly deformable nature of RBCs when submitted to strong extensional flows. It was also observed that the low intensity cells exhibit a slightly higher velocity than intermediate intensity cells, which we attribute to the cells being located in different planes.

  280. Boundary element analysis of deformation and movement of a capsule and a red blood cell close to the wall

    S. Nix, Y. Imai, T. Ishikawa, T. Yamaguchi

    BOUNDARY ELEMENTS AND OTHER MESH REDUCTION METHODS XXXIV 53 191-199 2012

    Publisher: WIT PRESS

    DOI: 10.2495/BE120171  

    ISSN:1746-4064

    More details Close

    A capsule is defined as a liquid drop enclosed by an elastic membrane. The study of capsule behavior near a stationary surface has a number of biological applications, such as red blood cells in the cardiovascular system. However, near-wall behavior of capsules has not been established well. In this study, we investigate the motion of initially spherical and biconcave capsules in simple shear flow near an infinite plane using a boundary integral method coupled to a finite element method. We find that the deformation of a capsule depends on its initial shape, orientation, and capillary number (Ca). However, the lift velocity of a capsule is dependent on its steady state deformation and distance from the wall. The dependence of lift velocity on deformation may help to explain phenomena such as leukocyte margination.

  281. Boundary element analysis of the multi-capsule flow using an ultra-high speed GPGPU computation

    D. Matsunaga, Y. Imai, T. Ishikawa, T. Yamaguchi

    BOUNDARY ELEMENTS AND OTHER MESH REDUCTION METHODS XXXIV 53 201-208 2012

    Publisher: WIT PRESS

    DOI: 10.2495/BE120181  

    ISSN:1746-4064

    More details Close

    A capsule is a liquid drop enclosed by a thin membrane. Understanding the mechanics of capsule suspension is important in a variety of applications. However, computational time is still a barrier against successful simulations for dense suspension of capsules. We have developed an ultra-high speed computation method based on Graphics Processing Unit (GPU) computing for simulating multi-capsule flow. In the case of using single GPU, the performance achieves 1.20 TFlops that corresponds to a 550-fold speed up compared with a CPU core. We also developed an algorithm of multi GPUs that hide data communication by overlapping with computational time. Since our method enables us to simulate from one to a few hundred capsules in a realistic computational time, the method could be a powerful solution for simulating the capsule suspension.

  282. Patient-specific modelling of pulmonary airflow using GPU cluster for the application in medical practice Peer-reviewed

    T. Miki, X. Wang, T. Aoki, Y. Imai, T. Ishikawa, K. Takase, T. Yamaguchi

    COMPUTER METHODS IN BIOMECHANICS AND BIOMEDICAL ENGINEERING 15 (7) 771-778 2012

    Publisher: TAYLOR & FRANCIS LTD

    DOI: 10.1080/10255842.2011.560842  

    ISSN:1025-5842

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    In this paper, we propose a novel patient-specific method of modelling pulmonary airflow using graphics processing unit (GPU) computation that can be applied in medical practice. To overcome the barriers imposed by computation speed, installation price and footprint to the application of computational fluid dynamics, we focused on GPU computation and the lattice Boltzmann method (LBM). The GPU computation and LBM are compatible due to the characteristics of the GPU. As the optimisation of data access is essential for the performance of the GPU computation, we developed an adaptive meshing method, in which an airway model is covered by isotropic subdomains consisting of a uniform Cartesian mesh. We found that 4(3) size subdomains gave the best performance. The code was also tested on a small GPU cluster to confirm its performance and applicability, as the price and footprint are reasonable for medical applications.

  283. GPU computing for patient-specific model of pulmonary airflow

    T. Yamaguchi, Y. Imai, T. Miki, T. Ishikawa

    COMPUTATIONAL MODELLING OF OBJECTS REPRESENTED IN IMAGES: FUNDAMENTALS, METHODS AND APPLICATIONS III 239-242 2012

    Publisher: CRC PRESS-TAYLOR & FRANCIS GROUP

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    We propose an implementation of Lattice Boltzmann (LB) method on GPUs for simulating airflow in pulmonary airways with complex branches. An adaptive meshing method is developed for optimizing memory accessing, where the global domain comprises unstructured subdomains, while the local subdomain consists of a structured grids. We also develop a multi-GPU computing method based on a domain decomposition. For strong scaling tests with a subject-specific geometry (12 million LB nodes), the performance on 8 GPUs is approximately 200 GFLOPS, which is 100 times faster computation than 8 CPU cores.

  284. Separation of cancer cells from a red blood cell suspension using inertial force Peer-reviewed

    Tatsuya Tanaka, Takuji Ishikawa, Keiko Numayama-Tsuruta, Yohsuke Imai, Hironori Ueno, Noriaki Matsuki, Takami Yamaguchi

    LAB ON A CHIP 12 (21) 4336-4343 2012

    Publisher: ROYAL SOC CHEMISTRY

    DOI: 10.1039/c2lc40354d  

    ISSN:1473-0197

    eISSN:1473-0189

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    The circulating tumor cell (CTC) test has recently become popular for evaluating prognosis and treatment efficacy in cancer patients. The accuracy of the test is strongly dependent on the precision of the cancer cell separation. In this study, we developed a multistage microfluidic device to separate cancer cells from a red blood cell (RBC) suspension using inertial migration forces. The device was able to effectively remove RBCs up to the 1% hematocrit (Hct) condition with a throughput of 565 mu L min(-1). The collection efficiency of cancer cells from a RBC suspension was about 85%, and the enrichment of cancer cells was about 120-fold. Further improvements can be easily achieved by parallelizing the device. These results illustrate that the separation of cancer cells from RBCs is possible using only inertial migration forces, thus paving the way for the development of a novel microfluidic device for future CTC tests.

  285. Asymmetry of red blood cell motions in a microchannel with a diverging and converging bifurcation Peer-reviewed

    Vladimir Leble, Rui Lima, Ricardo Dias, Carla Fernandes, Takuji Ishikawa, Yohsuke Imai, Takami Yamaguchi

    BIOMICROFLUIDICS 5 (4) 044120 2011/12

    Publisher: AMER INST PHYSICS

    DOI: 10.1063/1.3672689  

    ISSN:1932-1058

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    In microcirculation, red blood cells (RBCs) flowing through bifurcations may deform considerably due to combination of different phenomena that happen at the micro-scale level, such as: attraction effect, high shear, and extensional stress, all of which may influence the rheological properties and flow behavior of blood. Thus, it is important to investigate in detail the behavior of blood flow occurring at both bifurcations and confluences. In the present paper, by using a micro-PTV system, we investigated the variations of velocity profiles of two working fluids flowing through diverging and converging bifurcations, human red blood cells suspended in dextran 40 with about 14% of hematocrit level (14 Hct) and pure water seeded with fluorescent trace particles. All the measurements were performed in the center plane of rectangular microchannels using a constant flow rate of about 3.0 x 10(-12) m(3)/s. Moreover, the experimental data was compared with numerical results obtained for Newtonian incompressible fluid. The behavior of RBCs was asymmetric at the divergent and convergent side of the geometry, whereas the velocities of tracer particles suspended in pure water were symmetric and well described by numerical simulation. The formation of a red cell-depleted zone immediately downstream of the apex of the converging bifurcation was observed and its effect on velocity profiles of RBCs flow has been investigated. Conversely, a cell-depleted region was not formed around the apex of the diverging bifurcation and as a result the adhesion of RBCs to the wall surface was enhanced in this region. (C) 2011 American Institute of Physics. [doi:10.1063/1.3672689]

  286. GPU-based simulation of blood flow in complex microvessels Peer-reviewed

    K. Nakaaki, Y. Imai, T. Ishikawa, C. T. Lim, T. Yamaguchi

    5th East Asian Pacific Student Workshop on Nano-Biomedical Engineering 152-153 2011/11/20

  287. A numerical computation on gastric mixing using GPU Peer-reviewed

    I. Kobayashi, Y. Imai, S. Ishida, T. Ishikawa, T. Yamaguchi

    5th East Asian Pacific Student Workshop on Nano-Biomedical Engineering 150-151 2011/11/20

  288. Inertial migration of cancer cells in high hematocrit blood flow Peer-reviewed

    T. Tanaka, T. Ishikawa, K. Numayama-Tsuruta, Y. Imai, H. Ueno, N. Matsuki, T. Yamaguchi

    5th East Asian Pacific Student Workshop on Nano-Biomedical Engineering 146-147 2011/11/20

  289. Entrapment of fresh water ciliates at the interface fluid-air Peer-reviewed

    J. Ferracci, T. Ishikawa, H. Ueno, K. Numayama-Tsuruta, Y. Imai, T. Yamaguchi

    5th East Asian Pacific Student Workshop on Nano-Biomedical Engineering 120-121 2011/11/20

  290. Computation of near-wall capsule flow using boundary integral method Peer-reviewed

    S. Nix, Y. Imai, D. Matsunaga, T. Ishikawa, T. Yamaguchi

    5th East Asian Pacific Student Workshop on Nano-Biomedical Engineering 76-77 2011/11/20

  291. Multi-GPU computing of capsule flow using boundary integral method Peer-reviewed

    D. Matsunaga, Y. Imai, T. Omori, T. Ishikawa, T. Yamaguchi

    5th East Asian Pacific Student Workshop on Nano-Biomedical Engineering 72-73 2011/11/20

  292. Transport phenomena in suspensions of swimming microorganisms Peer-reviewed

    T. Ishikawa

    5th East Asian Pacific Student Workshop on Nano-Biomedical Engineering 50-51 2011/11/20

  293. Analysis of fluid flow on the surface of tracheal lumen through effective ciliary motion Peer-reviewed

    K. Kiyota, H. Ueno, T. Ishikawa, K. Numayama-Tsuruta, Y. Imai, N. Matsuki, T. Yamaguchi

    5th East Asian Pacific Student Workshop on Nano-Biomedical Engineering 34-35 2011/11/20

  294. Collective diffusion of red blood cells from high concentration to low Peer-reviewed

    C. Chuang, T. Ishikawa, H. Ueno, K. Numayama-Tsuruta, Y. Imai, T. Yamaguchi

    5th East Asian Pacific Student Workshop on Nano-Biomedical Engineering 32-33 2011/11/20

  295. Development of a micro fluidic device to separate motile bacteria Peer-reviewed

    T. Shioiri, T. Ishikawa, K. Numayama-Tsuruta, H. Ueno, Y. Imai, T. Yamaguchi

    5th East Asian Pacific Student Workshop on Nano-Biomedical Engineering 12-13 2011/11/20

  296. Development of GPU computing for simulating dense suspension of capsules Peer-reviewed

    Y. Imai, D. Matsunaga, T. Ishikawa, T. Yamaguchi

    5th Shanghai Int. Conf. Biophysics and Molecular Biology Abstract Book 125 2011/11/10

  297. Analysis of ciliary motion and the axonemal structure in the mouse respiratory cilia Peer-reviewed

    H. Ueno, T. Ishikawa, K. H. Bui, K. Gonda, T. Ishikawa, T. Yamaguchi

    5th Shanghai Int. Conf. Biophysics and Molecular Biology Abstract Book 119 2011/11/10

  298. Energy Transport in a Concentrated Suspension of Bacteria Peer-reviewed

    T. Ishikawa, N. Yoshida, H. Ueno, M. Wiedeman, Y. Imai, T. Yamaguchi

    Bulletin of the American Physical Society, DFD 2011 56 388 2011/11/03

  299. Instabilities and global order in concentrated suspensions of spherical microswimmers Peer-reviewed

    A. Evans, T. Ishikawa, T. Yamaguchi, E. Lauga

    Bulletin of the American Physical Society, DFD 2011 56 387 2011/11/03

  300. Orientational order in concentrated suspensions of spherical microswimmers Peer-reviewed

    Arthur A. Evans, Takuji Ishikawa, Takami Yamaguchi, Eric Lauga

    PHYSICS OF FLUIDS 23 (11) 111702 2011/11

    Publisher: AMER INST PHYSICS

    DOI: 10.1063/1.3660268  

    ISSN:1070-6631

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    We use numerical simulations to probe the dynamics of concentrated suspensions of spherical microswimmers interacting hydrodynamically. Previous work in the dilute limit predicted orientational instabilities of aligned suspensions for both pusher and puller swimmers, which we confirm computationally. Unlike previous work, we show that isotropic suspensions of spherical swimmers are also always unstable. Both types of initial conditions develop long-time polar order of a nature which depends on the hydrodynamic signature of the swimmer but very weakly on the volume fraction up to very high volume fractions. (C) 2011 American Institute of Physics. [doi: 10.1063/1.3660268]

  301. Modelling of red blood cell motion and deformation using particle based method Peer-reviewed

    T. Yamaguchi, Y. Imai, T. Ishikawa

    Proc. ECCOMAS SIMBIO 2011 CD-ROM 2011/09/02

  302. Swallowing simulation based on videofluorography Peer-reviewed

    S. Ishida, Y. Imai, T. Ishikawa, A. Kinjyo, N. Matsuki, T. Yamaguchi

    The International Conference on BioTribology Conference Abstracts CD-ROM 2011/09/01

  303. Particle based simulation of the microvascular blood flow in the malaria infection Peer-reviewed

    T. Yamaguchi, Y. Imai, T. Ishikawa

    Trends & Challenges in Computational Mechanics Program and Abstracts 43-44 2011/08/02

  304. Particle based modeling and simulation of the red blood cell infected by malaria -mechanism of the margination of the infected red blood cell- Peer-reviewed

    T. Yamaguchi, T. Ishikawa, Y. Imai

    3rd Micro and Nano Flows Conference CD-ROM MNF2011-87 2011/08/01

  305. Computational Mechanics of Suspensions of Swimming Micro-organisms Peer-reviewed

    Takuji Ishikawa

    Proc. 11th U.S. Nat. Cong. Comp. Mech. CD-ROM 213904 2011/07/01

  306. Energy Transport in a Concentrated Suspension of Bacteria Peer-reviewed

    T. Ishikawa, N. Yoshida, H. Ueno, M. Wiedeman, Y. Imai, T. Yamaguchi

    PHYSICAL REVIEW LETTERS 107 (2) 028102 (Editors’ Suggestions) 2011/07

    Publisher: AMER PHYSICAL SOC

    DOI: 10.1103/PhysRevLett.107.028102  

    ISSN:0031-9007

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    Coherent structures appear in a concentrated suspension of swimming bacteria. While transport phenomena in a suspension have been studied extensively, how energy is transported from the individual cell scale to the larger mesoscale remains unclear. In this study, we carry out the first successful measurement of the three-dimensional velocity field in a dense suspension of bacteria. The results show that most of the energy generated by individual bacteria dissipates on the cellular scale. Only a small amount of energy is transported to the mesoscale, but the gain in swimming velocity and mass transport due to mesoscale coherent structures is enormous. These results indicate that collective swimming of bacteria is efficient in terms of energy. This paper sheds light on how energy can be transported toward smaller wave numbers in the Stokes flow regime.

  307. Suspension biomechanics of swimming micro-organisms Peer-reviewed

    Takuji Ishikawa

    Proc. 21st Int. Offshore Polar Eng. Conf. 235-238 2011/06/02

  308. Development of a microfluidic device for partial cell separation

    R. Lima, M. S. N. Oliveira, T. Yaginuma, T. Ishikawa, Y. Imai, T. Yamaguchi

    Proc. Japan-Portugal Nano-BME Symp. 49-50 2011/06/01

  309. Motions of trace particles and red blood cells in a PDMS microchannel with a converging bifurcation

    V. Leble, R. Dias, R. Lima, C. Fernandes, T. Ishikawa, Y. Imai, T. Yamaguchi

    Proc. Japan-Portugal Nano-BME Symp. 29-30 2011/06/01

  310. High performance GPU computing of capsule flow using boundary integral method

    D. Matsunaga, Y. Imai, T. Omori, T. Miki, T. Ishikawa, T. Yamaguchi

    Proc. Japan-Portugal Nano-BME Symp. 19-22 2011/06/01

  311. Gradient diffusion of red blood cells in a Y-shape microchannel

    C.-H. Chuang, T. Ishikawa, K. Numayama-Tsuruta, Y. Imai, T. Yamaguchi

    Proc. Japan-Portugal Nano-BME Symp. 17-18 2011/06/01

  312. Numerical simulation of cell depleted peripheral layer and red blood cells motion in microvascular blood flow

    D. Alizadehrad, Y. Imai, T. Ishikawa, T. Yamaguchi

    Proc. Japan-Portugal Nano-BME Symp. 15-16 2011/06/01

  313. Analysis of ciliary motion and fluid flow on the surface of tracheal cells

    H. Ueno, T. Ishikawa, K. Gonda, K. H. Bui, T. Ishikawa, Y. Imai, K. Numayama-Tsuruta, T. Yamaguchi

    Proc. Japan-Portugal Nano-BME Symp. 11-14 2011/06/01

  314. Numerical simulation on margination of malaria-infected red blood cells in microvessels

    Y. Imai, K. Nakaaki, T. Ishikawa, T. Yamaguchi

    Proc. Japan-Portugal Nano-BME Symp. 7-10 2011/06/01

  315. Computational biomechanics for respiratory and micro-circulation systems

    T. Yamaguchi, T. Ishikawa, Y. Imai

    Proc. Japan-Portugal Nano-BME Symp. 1-4 2011/06/01

  316. Transport phenomena of microbial flora in the small intestine with peristalsis Peer-reviewed

    T. Ishikawa, T. Sato, G. Mohit, Y. Imai, T. Yamaguchi

    JOURNAL OF THEORETICAL BIOLOGY 279 (1) 63-73 2011/06

    Publisher: ACADEMIC PRESS LTD- ELSEVIER SCIENCE LTD

    DOI: 10.1016/j.jtbi.2011.03.026  

    ISSN:0022-5193

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    The gastrointestinal tract of humans is colonized by indigenous prokaryotic and eukaryotic microbial cells that form a complex ecological system called microbial flora. Although the microbial flora has diverse functions, its homeostasis inside the gastrointestinal tract is still largely unknown. Therefore, creating a model for investigating microbial flora in the gastrointestinal tract is important. In this study, we developed a novel numerical model to explore the transport phenomena of microbial flora in the small intestine. By simultaneously solving the flow field generated by peristalsis, the concentrations of oxygen and nutrient, and the densities of moderate anaerobes and aerobes, the effects of fluid mechanics on the transport phenomena of microbial flora are discussed. The results clearly illustrated that fluid mechanics have considerable influence not only on the bacterial population, but also on the concentration distributions of oxygen and nutrient. Especially, the flow field enhances the radial variation of the concentration fields. We also show scaling arguments for bacterial growth and oxygen consumption, which capture the main features of the results. Additionally, we investigated the transport phenomena of microbial flora in a long tube with 40 constrictions. The results showed a high growth rate of aerobes in the upstream side and a high growth rate of anaerobes in the downstream side, which qualitatively agrees with experimental observations of human intestines. These new findings provide the fundamental basis for a better understanding of the transport phenomena of microbial flora in the intestine. (C) 2011 Elsevier Ltd. All rights reserved.

  317. Computational analysis of the margination of malaria-infected red blood cells in microcirculation

    T. Yamaguchi, T. Ishikawa, Y. Imai

    Microscale Modeling in Biomechanics and Mechanobiology Program and Abstract 2011/05

  318. Effect of red blood cells on dynamics of microvascular blood flow

    D. Alizadehrad, Y. Imai, T. Ishikawa, T. Yamaguchi

    Microscale Modeling in Biomechanics and Mechanobiology Program and Abstract 2011/05

  319. Capsule flow analysis using GPU computation

    D. Matsunaga, Y. Imai, T. Omori, T. Miki, T. Ishikawa, T. Yamaguchi

    Microscale Modeling in Biomechanics and Mechanobiology Program and Abstract 2011/05

  320. Diffusion of red blood cells from high concentration to low in a blood flow microchannel

    C. Chugang, T. Ishikawa, K. Numayama, Y. Imai, H. Ueno, T. Yamaguchi

    Microscale Modeling in Biomechanics and Mechanobiology Program and Abstract 2011/05

  321. Margination of red blood cells infected by Plasmodium falciparum due to local increase in hematocrit Peer-reviewed

    Y. Imai, K. Nakaaki, H. Kondo, T. Ishikawa, C. T. Lim, T. Yamaguchi

    Journal of Biomechanics 44 1553-1558 2011/05/01

    DOI: 10.1016/j.jbiomech.2011.02.084  

  322. Comparison between spring network models and continuum constitutive laws: Application to the large deformation of a capsule in shear flow Peer-reviewed

    T. Omori, T. Ishikawa, D. Barthes-Biesel, A. -V. Salsac, J. Walter, Y. Imai, T. Yamaguchi

    PHYSICAL REVIEW E 83 (4) 041918 2011/04

    Publisher: AMER PHYSICAL SOC

    DOI: 10.1103/PhysRevE.83.041918  

    ISSN:1539-3755

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    A capsule is a liquid drop enclosed by a solid, deformable membrane. To analyze the deformation of a capsule accurately, both the fluid mechanics of the internal and external fluids and the solid mechanics of the membrane must be solved precisely. Recently, many researchers have used discrete spring network models to express the membrane mechanics of capsules and biological cells. However, it is unclear whether such modeling is sufficiently accurate to solve for capsule deformation. This study examines the correlations between the mechanical properties of the discrete spring network model and continuum constitutive laws. We first compare uniaxial and isotropic deformations of a two-dimensional (2D) sheet, both analytically and numerically. The 2D sheet is discretized with four kinds of mesh to analyze the effect of the spring network configuration. We derive the relationships between the spring constant and continuum properties, such as the Young modulus, Poisson ratio, area dilation modulus, and shear modulus. It is found that the mechanical properties of spring networks are strongly dependent on the mesh configuration. We then calculate the deformation of a capsule under inflation and in a simple shear flow in the Stokes flow regime, using various membrane models. To achieve high accuracy in the flow calculation, a boundary-element method is used. Comparing the results between the different membrane models, we find that it is hard to express the area incompressibility observed in biological membranes using a simple spring network model.

  323. Novel methods for the computational biomechanics study of respiratory and micro-circulatory systems

    T. Yamaguchi, T. Ishikawa, Y. Imai

    16th International Symposium of Tohoku University Global COE Program, Global Nano-Biomedical Engineering Education and Research Network Centre, Nano-Biomedical Engineering in the East Asian-Pacific Rim Region 99-102 2011/03

  324. A fourth-order Cartesian local mesh refinement method for the computational fluid dynamics of physiological flow in multi-generation branched vessels Peer-reviewed

    Takahito Miki, Yohsuke Imai, Takuji Ishikawa, Shigeo Wada, Takayuki Aoki, Takami Yamaguchi

    INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN BIOMEDICAL ENGINEERING 27 (3) 424-435 2011/03

    Publisher: WILEY-BLACKWELL

    DOI: 10.1002/cnm.1416  

    ISSN:2040-7939

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    Since abnormal fluid states in our body cause critical diseases, patient-specific computational fluid dynamics (CFD) probably become a standard diagnosis tool in the near future. The vessels in our body are multiple-branched tubes, which makes it difficult to obtain accurate solutions from conventional CFD methods. In this report, we propose a fourth-order local mesh refinement (LMR) method based on an interpolated differential operator scheme for simulating flow in multi-generation branched vessels. The proposed LMR method has the accuracy of fourth-order for three-dimensional advection and diffusion equations, respectively. We describe how to apply the LMR method to patient-specific pulmonary airflow simulations. In our method, the computational mesh size is determined locally by geometrical parameters: the diameter of airways and the distance from the airway wall. To demonstrate our method, an LMR model and a fine mesh model were compared for flow in the central airway, and there was no significant difference between results. We also show the applicability of the method to a maximum eleventh-generation airway model, where the number of computational nodes was reduced by 85% compared with the case using uniform fine meshes. Copyright (C) 2010 John Wiley & Sons, Ltd.

  325. A fourth-order Cartesian local mesh refinement method for the computational fluid dynamics of physiological flow in multi-generation branched vessels Peer-reviewed

    Takahito Miki, Yohsuke Imai, Takuji Ishikawa, Shigeo Wada, Takayuki Aoki, Takami Yamaguchi

    INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN BIOMEDICAL ENGINEERING 27 (3) 424-435 2011/03

    Publisher: WILEY-BLACKWELL

    DOI: 10.1002/cnm.1416  

    ISSN:2040-7939

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    Since abnormal fluid states in our body cause critical diseases, patient-specific computational fluid dynamics (CFD) probably become a standard diagnosis tool in the near future. The vessels in our body are multiple-branched tubes, which makes it difficult to obtain accurate solutions from conventional CFD methods. In this report, we propose a fourth-order local mesh refinement (LMR) method based on an interpolated differential operator scheme for simulating flow in multi-generation branched vessels. The proposed LMR method has the accuracy of fourth-order for three-dimensional advection and diffusion equations, respectively. We describe how to apply the LMR method to patient-specific pulmonary airflow simulations. In our method, the computational mesh size is determined locally by geometrical parameters: the diameter of airways and the distance from the airway wall. To demonstrate our method, an LMR model and a fine mesh model were compared for flow in the central airway, and there was no significant difference between results. We also show the applicability of the method to a maximum eleventh-generation airway model, where the number of computational nodes was reduced by 85% compared with the case using uniform fine meshes. Copyright (C) 2010 John Wiley & Sons, Ltd.

  326. Asymmetry of blood flow and cancer cell adhesion in a microchannel with symmetric bifurcation and confluence Peer-reviewed

    Takuji Ishikawa, Hiroki Fujiwara, Noriaki Matsuki, Takefumi Yoshimoto, Yohsuke Imai, Hironori Ueno, Takami Yamaguchi

    BIOMEDICAL MICRODEVICES 13 (1) 159-167 2011/02

    Publisher: SPRINGER

    DOI: 10.1007/s10544-010-9481-7  

    ISSN:1387-2176

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    Bifurcations and confluences are very common geometries in biomedical microdevices. Blood flow at microchannel bifurcations has different characteristics from that at confluences because of the multiphase properties of blood. Using a confocal micro-PIV system, we investigated the behaviour of red blood cells (RBCs) and cancer cells in microchannels with geometrically symmetric bifurcations and confluences. The behaviour of RBCs and cancer cells was strongly asymmetric at bifurcations and confluences whilst the trajectories of tracer particles in pure water were almost symmetric. The cell-free layer disappeared on the inner wall of the bifurcation but increased in size on the inner wall of the confluence. Cancer cells frequently adhered to the inner wall of the bifurcation but rarely to other locations. Because the wall surface coating and the wall shear stress were almost symmetric for the bifurcation and the confluence, the result indicates that not only chemical mediation and wall shear stress but also microscale haemodynamics play important roles in the adhesion of cancer cells to the microchannel walls. These results provide the fundamental basis for a better understanding of blood flow and cell adhesion in biomedical microdevices.

  327. Preface Peer-reviewed

    Takuji Ishikawa

    Journal of Biomechanical Science and Engineering 6 (2) 63-63 2011

    DOI: 10.1299/jbse.6.63  

    ISSN:1880-9863

  328. Red Blood Cell Deformation in flows through a PDMS Hyperbolic Microchannel Peer-reviewed

    T. Yaginuma, M. S. N. Oliveira, R. Lima, T. Ishikawa, T. Yamaguchi

    NANOTECHNOLOGY 2011: ELECTRONICS, DEVICES, FABRICATION, MEMS, FLUIDICS AND COMPUTATIONAL, NSTI-NANOTECH 2011, VOL 2 505-507 2011

    Publisher: CRC PRESS-TAYLOR & FRANCIS GROUP

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    Red blood cell (RBC) deformability is extremely important in the context of microcirculation as RBCs need to flow through thin capillaries in order to deliver oxygen to the human body. Although most studies on RBC deformability consider the effect of shear flow alone, extensionally-dominated flows are often found in the human circulatory system. This study aims to characterize the deformation of RBCs in microfluidic extensional flows. For this purpose, we designed a microchannel having a hyperbolic shaped-contraction, where the cells experience an extensionally-dominated flow near the centerline. The deformation index (DI) of the RBCs travelling along the central region of the channel were measured in two pre-defmed regions at two different flow rates. The results demonstrate the highly deformable nature of RBCs under strong extensional flows.

  329. Microscale Flow Dynamics of Red Blood Cells in Microchannels: An Experimental and Numerical Analysis

    R. Lima, C. S. Fernandes, R. Dias, T. Ishikawa, Y. Imai, T. Yamaguchi

    COMPUTATIONAL VISION AND MEDICAL IMAGE PROCESSING: RECENT TRENDS 19 297-309 2011

    Publisher: SPRINGER-VERLAG BERLIN

    DOI: 10.1007/978-94-007-0011-6_17  

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    The blood flow dynamics in microcirculation depends strongly on the microvascular networks composed with short irregular vessel segments which are linked by numerous bifurcations. This paper presents the application of a confocal micro-PTV system to track RBCs through a rectangular polydimethysiloxane (PDMS) microchannel with a bifurcation. By using a confocal micro-PTV system, we have measured the effect of bifurcation on the flow behaviour of both fluorescent particles diluted in pure water and RBCs in concentrated suspensions. After performing simulations with the commercial finite element software package POLYFLOW, some experimental results were compared with the numerical results and the limitations of these simulations were outlined.

  330. Development of a microdevice for sorting motile bacteria Peer-reviewed

    T. Shioiri, T. Ishikawa, K. Numayama-Tsuruta, Y. Imai, H. Ueno, T. Yamaguchi

    ASME 2011 6th Frontiers in Biomedical Devices Conference and Exhibition, BioMed 2011 25-26 2011

    DOI: 10.1115/BioMed2011-66035  

  331. Collection of cancer cells from blood samples using inertial migration forces Peer-reviewed

    T. Tanaka, T. Ishikawa, K. Numayama-Tsuruta, Y. Imai, H. Ueno, N. Matsuki, T. Yamaguchi

    ASME 2011 6th Frontiers in Biomedical Devices Conference and Exhibition, BioMed 2011 13-14 2011

    DOI: 10.1115/BioMed2011-66034  

  332. Fluid particle diffusion through high-hematocrit blood flow within a capillary tube Peer-reviewed

    Maryam Saadatmand, Takuji Ishikawa, Noriaki Matsuki, Mohammad Jafar Abdekhodaie, Yohsuke Imai, Hironori Ueno, Takami Yamaguchi

    JOURNAL OF BIOMECHANICS 44 (1) 170-175 2011/01

    Publisher: ELSEVIER SCI LTD

    DOI: 10.1016/j.jbiomech.2010.09.004  

    ISSN:0021-9290

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    Fluid particle diffusion through blood flow within a capillary tube is an important phenomenon to understand, especially for studies in mass transport in the microcirculation as well as in solving technical issues involved in mixing in biomedical microdevices. In this paper, the spreading of tracer particles through up to 20% hematocrit blood, flowing in a capillary tube, was studied using a confocal micro-PTV system. We tracked hundreds of particles in high-hematocrit blood and measured the radial dispersion coefficient. Results yielded significant enhancement of the particle diffusion, due to a micron-scale flow-field generated by red blood cell motions. By increasing the flow rate, the particle dispersion increased almost linearly under constant hematocrit levels. The particle dispersion also showed near linear dependency on hematocrit up to 20%. A scaling analysis of the results, on the assumption that the tracer trajectories were unbiased random walks, was shown to capture the main features of the results. The dispersion of tracer particles was about 0.7 times that of RBCs. These findings provide good insight into transport phenomena in the microcirculation and in biomedical microdevices. (C) 2010 Elsevier Ltd. All rights reserved.

  333. DEVELOPMENT OF A PARTICLE INTERACTION KERNEL FOR CONVECTION-DIFFUSION SCALAR TRANSPORT EQUATION Peer-reviewed

    Chinlong Huang, Tony W. H. Sheu, Takuji Ishikawa, Takami Yamaguchi

    NUMERICAL HEAT TRANSFER PART B-FUNDAMENTALS 60 (2) 96-115 2011

    Publisher: TAYLOR & FRANCIS INC

    DOI: 10.1080/10407790.2011.594389  

    ISSN:1040-7790

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    In this study we derive a mathematically rigorous kernel function, which accounts for the interaction among particles, within the framework of the particle method, to predict a computationally more accurate solution for the convection-diffusion equation investigated at low as well as high Peclet numbers. Determination of the functional dependence of the kernel function on the distance vector between the particles is therefore a key to the success of the interaction model. The smoothed quantity for a scalar or for a vector at a particle location is mathematically identical to its collocated value provided that the kernel function is chosen as the delta function. Such a kernel is unfortunately not computable in a discrete context. Our guideline for developing the modified kernel function is therefore to make it closer to the delta function as much as possible in cases when diffusion dominates convection. To achieve this goal, we enforce five constraint conditions in a derivation of the kernel function for the pure diffusion equation. In addition, this kernel function has no effect on the particles outside of the disk, which has the user's specified radius r(e). To mimic the delta function we demand that the developed kernel function at r=r(e) should smoothly approach zero. It is also desired to acquire the largest possible value for the kernel function near r=0. As flow convection prevailingly dominates its diffusion counterpart, particle interaction at the upstream side should be more favorably taken into account to avoid numerical oscillations due to convective instability. We present in this study a two-dimensional upwind kernel function to enhance numerical stability along the flow direction. The proposed upwind kernel function can render an exact solution for the investigated convection-diffusion equation in the limiting one-dimensional case. The proposed particle interaction model featuring the newly developed kernel function is validated through several problems that are amenable to analytical solutions or have available benchmark solutions. Analysis of the stability condition and spatial accuracy order of the proposed particle interaction model are also provided in details.

  334. Computational study on effect of stenosis on primary thrombus formation Peer-reviewed

    Hiroki Kamada, Ken-ichi Tsubota, Masanori Nakamura, Shigeo Wada, Takuji Ishikawa, Takami Yamaguchi

    BIORHEOLOGY 48 (2) 99-114 2011

    Publisher: IOS PRESS

    DOI: 10.3233/BIR-2011-0585  

    ISSN:0006-355X

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    The purpose of this study was to evaluate the effects of stenosis geometry on primary thrombogenesis with respect to the dynamics of the blood flow. A two-dimensional computer simulation was carried out to simulate the formation of a primary thrombus under blood flow in two geometrically different blood vessels: one straight and the other stenosed. In the simulation, blood was modeled by particles that have characteristics of plasma and of platelets. Plasma and platelet flow was analyzed using the Moving Particle Semi-implicit (MPS) method, while the motion of adhered and aggregated platelets was expressed by mechanical spring forces. With these models, platelet motion in the flowing blood and platelet aggregation and adhesion were successfully coupled with viscous blood flow. The results of the simulation demonstrated that the presence of a stenosis induced changes in blood flow and thereby altered the formation, growth, and destruction of a thrombus. In particular, whereas in the absence of stenosis, the thrombus evenly covered the injured site, in the presence of a stenosis, thrombus formation was skewed to the downstream side. The number of platelets that adhered to the injured site increased earlier as the stenosis became more severe. These results suggest that dynamic changes in blood flow due to the presence of a stenosis affect primary thrombogenesis.

  335. Large-scale numerical simulation of blood flow in microvessels

    D. Alizadehrad, Y. Imai, T. Ishikawa, T. Yamaguchi

    Proc. 4th East Asian Pacific Stu. Workshop Nano-Biomed. Eng. 98-99 2010/12

  336. Hydrodynamic interaction of two unsteady squirmers

    T. Ishikawa, D. Giacche

    Bulletin of the American Physical Society, DFD 2010 55 94 2010/11/21

  337. Designing a clinical education program for engineers: The ESTEEM Project Peer-reviewed

    Noriaki Matsuki, Motohiro Takeda, Masahiro Yamano, Yohsuke Imai, Takuji Ishikawa, Takami Yamaguchi

    JOURNAL OF INTERPROFESSIONAL CARE 24 (6) 738-741 2010/11

    Publisher: INFORMA HEALTHCARE

    DOI: 10.3109/13561820903564714  

    ISSN:1356-1820

  338. Hydrodynamic interaction of two unsteady model microorganisms Peer-reviewed

    Davide Giacche, Takuji Ishikawa

    JOURNAL OF THEORETICAL BIOLOGY 267 (2) 252-263 2010/11

    Publisher: ACADEMIC PRESS LTD- ELSEVIER SCIENCE LTD

    DOI: 10.1016/j.jtbi.2010.08.003  

    ISSN:0022-5193

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    The study of pair-wise interactions between swimming microorganisms is fundamental to the understanding of the rheological and transport properties of semi-dilute suspensions. In this paper, the hydrodynamic interaction of two ciliated microorganisms is investigated numerically using a boundary-element method, and the microorganisms are modeled as spherical squirmers that swim by time-dependent surface deformations. The results show that the inclusion of the unsteady terms in the ciliary propulsion model has a large impact on the trajectories of the interacting cells, and causes a significant change in scattering angles with potential important consequences on the diffusion properties of semi-dilute suspensions. Furthermore, the analysis of the shear stress acting on the surface of the microorganisms revealed that the duration and the intensity of the near-field interaction are significantly modified by the presence of unsteadiness. This observation may account for the hydrodynamic nature of randomness in some biological reactions, and supersedes the distinction between intrinsic randomness and hydrodynamic interactions, adding a further element to the understanding and modeling of interacting microorganisms. (C) 2010 Elsevier Ltd. All rights reserved.

  339. Hydrodynamic entrapment of bacteria swimming near a solid surface Peer-reviewed

    Davide Giacche, Takuji Ishikawa, Takami Yamaguchi

    PHYSICAL REVIEW E 82 (5) 056309 2010/11

    Publisher: AMER PHYSICAL SOC

    DOI: 10.1103/PhysRevE.82.056309  

    ISSN:1539-3755

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    The near-surface motility of bacteria is important in the initial formation of biofilms and in many biomedical applications. The swimming motion of Escherichia coli near a solid surface is investigated both numerically and experimentally. A boundary element method is used to predict the hydrodynamic entrapment of E. coli bacteria, their trajectories, and the minimum separation of the cell from the surface. The numerical results show the existence of a stable swimming distance from the boundary that depends only on the shape of the cell body and the flagellum. The experimental validation of the numerical approach allows one to use the numerical method as a predictive tool to estimate with reasonable accuracy the near-wall motility of swimming bacteria of known geometry. The analysis of the numerical database demonstrated the existence of a correlation between the radius of curvature of the near-wall circular trajectory and the separation gap. Such correlation allows an indirect estimation of either of the two quantities by a direct measure of the other without prior knowledge of the cell geometry. This result may prove extremely important in those biomedical and technical applications in which the near-wall behavior of bacteria is of fundamental importance.

  340. Particle method computation of the red blood cell motion in malaria infection

    T. Yamaguchi, Y. Imai, T. Ishikawa

    International Conference on Numerical Analysis and Applied Mathematics 2010 (CD-ROM) 2010/09

    DOI: 10.1063/1.3498545  

  341. Fluid particle diffusion in a semi-dilute suspension of model micro-organisms Peer-reviewed

    T. Ishikawa, J. T. Locsei, T. J. Pedley

    Physical Review E 82 021408 2010/09/01

  342. Separation of cancer cells from blood by using a micro fluidic device

    T. Tanaka, T. Ishikawa, N. Matsuki, Y. Imai, H. Ueno, K. N-Tsuruta, T. Yamaguchi

    KIST-Tohoku Joint Symp. Nanobiomed. Eng. 75-76 2010/08/02

  343. Effects of rosette formation and cytoadhesion on hemodynamics in malaria infection

    K. Nakaaki, Y. Imai, H. Kondo, T. Ishikawa, C. T. Lim, T. Yamaguchi

    KIST-Tohoku Joint Symp. Nanobiomed. Eng. 67-68 2010/08/02

  344. Suspension biomechanics of swimming micro-organisms

    T. Ishikawa

    KIST-Tohoku Joint Symp. Nanobiomed. Eng. 27-28 2010/08/02

  345. A numerical study on migration of malaria infected red blood cells Invited

    Y. Imai, K. Nakaaki, H. Kondo, T. Ishikawa, C. T. Lim, T. Yamaguchi

    KIST-Tohoku Joint Symp. Nanobiomed. Eng. 15-16 2010/08/02

  346. Measurement of the Red Blood Cell (RBC) Dispersion in Microchannels: The Effect of the Temperature

    D. Pinho, A. Pereira, R. Lima, T. Ishikawa, Y. Imai, T. Yamaguchi

    IFMBE Proceedings 31 1067-1070 2010/08/01

  347. Numerical Modeling of Microvascular Hemodynamics in Plasmodium Falciparum Malaria

    Y. Imai, K. Nakaaki, H. Kondo, T. Ishikawa, C. T. Lim, T. Yamaguchi

    IFMBE Proceedings 31 1145-1148 2010/08/01

    DOI: 10.1007/978-3-642-14515-5_291  

  348. Micro-flow Visualization of in vitro Blood through a Microchannel with a Bifurcation and Confluence

    R. Lima, M. Oliveira, T. Ishikawa, N. Matsuki, Y. Imai, T. Yamaguchi

    6th World Congress of Biomechanics Abstracts 561 2010/08/01

  349. Measuring the Cell-Free Layer in circular Microchannels

    C. Fidalgo, A. Sa, R. Lima, M. Oliveira, T. Ishikawa, Y. Imai, T. Yamaguchi

    6th World Congress of Biomechanics Abstracts 472 2010/08/01

  350. A Numerical Study on Fluid Motion in the Stomach

    I. Kobayashi, Y. Imai, S. Ishida, T. Ishikawa, T. Yamaguchi

    6th World Congress of Biomechanics Abstracts 575 2010/08/01

  351. Parallel 3-D Code to Investigate the Pathophysiology of Malaria on Distributed Memory Systems

    D. Alizadehrad, Y. Imai, T. Ishikawa, T. Yamaguchi

    6th World Congress of Biomechanics Abstracts 581 2010/08/01

  352. Diffusion of Fluid Particles in High Hematocrit Blood Flow in a Capillary Tube

    M. Saadatmand, T. Ishikawa, N. Matsuki, M. J. Abdekhodaie, Y. Imai, H. Ueno, T. Yamaguchi

    6th World Congress of Biomechanics Abstracts 471 2010/08/01

  353. Analysis of Swallowing Motion based on Videofluorography

    S. Ishida, Y. Imai, A. Kinjo, N. Matsuki, T. Ishikawa, T. Yamaguchi

    6th World Congress of Biomechanics Abstracts 165 2010/08/01

  354. A Numerical Study on the Behavior of Cells in Micro-scale Blood Flows

    Y. Matsumoto, Y. Imai, T. Ishikawa, T. Yamaguchi

    6th World Congress of Biomechanics Abstracts 471 2010/08/01

  355. Effect of Membrane Modeling on the Capsule Deformation: Comparison between a Spring Network and Continuum Models

    T. Omori, T. Ishikawa, D. Barthes-Biesel, A.-V. Salsac, Y. Imai, T. Yamaguchi

    6th World Congress of Biomechanics Abstracts 470 2010/08/01

  356. Development of a Micro Fluidic Device to Separate Cancer Cells from Blood

    T. Tanaka, T. Ishikawa, N. Matsuki, Y. Imai, H. Ueno, T. Yamaguchi

    6th World Congress of Biomechanics Abstracts 164 2010/08/01

  357. Effect of Adhesive Properties of Malaria-infected Red Blood Cells in Microcirculation

    K. Nakaaki, Y. Imai, H. Kondo, T. Ishikawa, C. T. Lim, T. Yamaguchi

    6th World Congress of Biomechanics Abstracts 503 2010/08/01

  358. Stable Swimming of Bacteria near a Flat Wall

    D. Giacche, T. Ishikawa, T. Yamaguchi

    6th World Congress of Biomechanics Abstracts 176 2010/08/01

  359. Hydrodynamic entrapment of bacteria swimming near a solid wall

    T. Ishikawa, D. Giacche, T. Yamaguchi

    Individual and Collective Fluid Mechanics of Swimming Microorganisms, Talk and poster abstracts, p.6 2010/07

    DOI: 10.1103/PhysRevE.82.056309  

  360. Blood flow and cancer cell adhesion in a microchannel with bifurcation and confluence

    T. Ishikawa, H. Fujiwara, N. Matsuki, T. Yoshimoto, Y. Imai, H. Ueno, T. Yamaguchi

    17th Congress of the European Society of Biomechanics, ESB2010 Abstracts CD-ROM 2010/07

  361. Confocal micro-flow visualization of blood cells

    R. Lima, T. Ishikawa, Y. Imai, T. Yamaguchi

    CFD2010 Proceedings (CD-ROM) 2010/06

  362. Efficient parallel code for simulating malaria infected blood flow

    D. Alizadehrad, Y. Imai, T. Ishikawa, T. Yamaguchi

    22nd International Conference on Parallel Computational Fluid Dynamics (ParCFD 2010) (CD-ROM) 2010/05

  363. Impact of membrane modeling in analysing deformation of a capsule:comparison between a spring network model and constitutive laws

    T. Omori, T. Ishikawa, D. Barthes-biesel, A. V. Salsac, Y. Imai, T. Yamaguchi

    Proc. 4th Euro. Conf. Comp. Mech., CD-ROM No.781 2010/05

  364. Hydrodynamic entrapment of bacteria near a solid surface

    D. Giacche, T. Ishikawa, T. Yamaguchi

    Proc. 4th Euro. Conf. Comp. Mech., CD-ROM No.411 2010/05

  365. Numerical simulation of interaction among malaria-infected red blood cells, healthy red blood cells, and endothelial cells

    Y. Imai, K. Nakaaki, H. Kondo, T. Ishikawa, C. T. Lim, T. Yamaguchi

    Proc. 4th Euro. Conf. Comp. Mech., CD-ROM No.269 2010/05

  366. Activation of caspases and apoptosis in response to low-voltage electric pulses Peer-reviewed

    Noriaki Matsuki, Motohiro Takeda, Takuji Ishikawa, Aki Kinjo, Tomoaki Hayasaka, Yohsuke Imai, Takami Yamaguchi

    Oncology Reports 23 (5) 1425-1433 2010/05

    DOI: 10.3892/or-00000780  

    ISSN:1021-335X 1791-2431

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    Few studies have examined apoptosis induced by low-voltage electric pulses (LVEPs). LVEP-induce changes in membrane potential that are below the membrane breakdown threshold and increase membrane permeability without electroporation (pore formation) through the transport of extracellular substances via phagocytosis. We demonstrated that propidium iodide uptake and apoptosis increased in accordance with the duration and number of LVEPs in B16 cells, which showed relatively good viability under mild electric field conditions. We showed that LVEP-induced apoptosis was achieved through caspase-8 and -9 activation and subsequent caspase-3 activation. Long-duration LVEPs caused only mild cell damage, such that the apoptosis ratio (apoptosis/total cell death) in electric pulse-treated cells was similar to that in non-treated control cells. To assess the relative degree of caspase dependency in LVEP-induced apoptosis, the apoptosis rate and caspase-3 activity were analyzed using a pan-caspase inhibitor (Z-VAD-FMK). Z-VAD-FMK treatment inhibited, but did not abolish, LVEP-induced apoptosis, indicating that caspases other than caspase-3 participate in this pathway. Moreover, LVEP treatment inhibited cell growth, suggesting that LVEP treatment may be a valuable anticancer therapy. Although the mechanism of LVEP-induced apoptosis remains unclear, it may be related to dysfunctional membrane transport of Ca2+ and other extracellular substances involved in caspase activation.

  367. Modeling of hemodynamics arising from malaria infection Peer-reviewed

    Yohsuke Imai, Hitoshi Kondo, Takuji Ishikawa, Chwee Teck Lim, Takami Yamaguchi

    JOURNAL OF BIOMECHANICS 43 (7) 1386-1393 2010/05

    Publisher: ELSEVIER SCI LTD

    DOI: 10.1016/j.jbiomech.2010.01.011  

    ISSN:0021-9290

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    We propose a numerical model of hemodynamics arising from malaria infection. This model is based on a particle method, where all the components of blood are represented by the finite number of particles. A two-dimensional spring network of membrane particles is employed for expressing the deformation of malaria infected red blood cells (IRBCs). Malaria parasite within the IRBC is modeled as a rigid object. This model is applied to the stretching of IRBCs by optical tweezers, the deformation of IRBCs in shear flow, and the occlusion of narrow channels by IRBCs. We also investigate the effects of IRBCs on the theological property of blood in micro-channels. Our results indicate that apparent viscosity is drastically increased for the period from the ring stage and the trophozoite stage, whereas it is not altered in the early stage of infection. (C) 2010 Elsevier Ltd. All rights reserved.

  368. Effect of pneumothorax on morphology and hemodynamic of pulmonary artery

    J-J. Christophe, T. Ishikawa, N. Matsuki, Y. Imai, K. Takase, M. Thiriet, T. Yamaguchi

    11th International Symposium of Tohoku University Global COE Program, Global Nano-Biomedical Engineering Education and Research Network Centre, Nano-Biomedical Engineering in the East Asian-Pacific Rim Region 103-104 2010/03

  369. Numerical investigation of bacteria swimming near a solid surface

    D. Giacche, T. Ishikawa, T. Yamaguchi

    11th International Symposium of Tohoku University Global COE Program, Global Nano-Biomedical Engineering Education and Research Network Centre, Nano-Biomedical Engineering in the East Asian-Pacific Rim Region 105-106 2010/03

  370. Radial dispersion of tracer particles in blood flow in a capillary tube

    M. Saadatmand, T. Ishikawa, N. Matsuki, M. J. Abdekhodaie, Y. Imai, H. Ueno, T. Yamaguchi

    11th International Symposium of Tohoku University Global COE Program, Global Nano-Biomedical Engineering Education and Research Network Centre, Nano-Biomedical Engineering in the East Asian-Pacific Rim Region 113-114 2010/03

  371. Comprehensive application of particle methods to the diseases of the blood

    T. Yamaguchi, Y. Imai, H. Kamada, K. Nakaaki, T. Ishikawa

    The 2nd Biosupercomputing symposium 118-119 2010/03

  372. A three-dimensional particle simulation of the formation and collapse of a primary thrombus Peer-reviewed

    Hiroki Kamada, Ken-ichi Tsubota, Masanori Nakamura, Shigeo Wada, Takuji Ishikawa, Takami Yamaguchi

    INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN BIOMEDICAL ENGINEERING 26 (3-4) 488-500 2010/03

    Publisher: JOHN WILEY & SONS LTD

    DOI: 10.1002/cnm.1367  

    ISSN:2040-7939

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    This report presents a technique based on the particle method to simulate the process of thrombogenesis while considering platelet aggregation under the influence of fluid dynamics. In the employed particle method, the blood region was discretized by particles that were assumed to have the characteristics of plasma and platelets. The moving particle semi-implicit (MPS) method developed for incompressible viscous flow was applied to the flow of plasma and platelets. Adhesion of platelets to the injured vessel wall was expressed by a spring force acting between them. The same modeling was applied for the aggregation of platelets. Three-dimensional computer simulation of thrombogenesis was performed in a rectangular flow channel under the condition of Re=0.02. We demonstrated that the proposed method can simulate the formation and destruction of a thrombus with the inclusion of feedback reactions of thrombus development and flow. The results revealed that the growth rate of a thrombus, its height, and time required from the beginning of thrombus formation to its collapse vary according to the flow rate, indicating that flow dynamics plays an important role in regulating the development of a primary thrombus. Copyright (C) 2010 John Wiley & Sons, Ltd.

  373. ATP Transport in Saccular Cerebral Aneurysms at Arterial Bends Peer-reviewed

    Yohsuke Imai, Kodai Sato, Takuji Ishikawa, Andrew Comerford, Tim David, Takami Yamaguchi

    ANNALS OF BIOMEDICAL ENGINEERING 38 (3) 927-934 2010/03

    Publisher: SPRINGER

    DOI: 10.1007/s10439-009-9864-1  

    ISSN:0090-6964

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    ATP acts as an extracellular signaling molecule in purinergic signaling that regulates vascular tone. ATP binds purinergic P2 nucleotide receptors on endothelial cells. Understanding the mass transport of ATP to endothelial cells by blood flow is thus important to predict functional changes in aneurysmal walls. While some clinical observations indicate a difference of wall pathology between ruptured and unruptured aneurysms, no study has focused on the mass transport in aneurysms. We investigated the characteristics of ATP concentration at aneurysmal wall using a numerical model of ATP transport in aneurysms formed at arterial bends. The magnitude of ATP concentration at the aneurysmal wall was significantly smaller than that at the arterial wall. In particular, significantly low concentration was predicted at the proximal side of the aneurysmal sac. A strong correlation was revealed between the inflow flux at the aneurysmal neck and the resultant concentration at the aneurysmal wall.

  374. Computational biomechanics for investigating cardiovascular diseases

    T. Yamaguchi, H. Kondo, Y. Shimogonya, Y. Imai, N. Matsuki, T. Ishikawa

    Nano-Biomedical Engineering 2009 41-50 2010/02/25

  375. Red Blood Cell Dispersion in 100 mu m Glass Capillaries: The Temperature Effect Peer-reviewed

    D. Pinho, A. Pereira, R. Lima, T. Ishikawa, Y. Imai, T. Yamaguchi

    6TH WORLD CONGRESS OF BIOMECHANICS (WCB 2010), PTS 1-3 31 1067-+ 2010

    Publisher: SPRINGER

    ISSN:1680-0737

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    The rheological behaviour of the red blood cells (RBCs) flowing in microvessels and microchannels depend on several effects, such as hematocrit (Hct), geometry, and temperature. Previous in vitro studies have measured the Hct effect on the radial dispersion (D-yy) at both diluted and concentrated suspensions of RBCs. However, according to our knowledge the effect of the temperature on RBC D-yy was never studied. Hence, the main purpose of the present work is to investigate the effect of the temperature on the RBC D-yy. In vitro human blood was pumped through a 100 mu m glass capillary and by using a confocal micro-PTV system the RBC D-yy was calculated at two different temperatures, i.e., 25 degrees C and 37 degrees C.

  376. Cellular behaviours in high hematocrit blood flow in micro-channels

    T. Ishikawa, N. Matsuki, Y. Imai, H. Ueno, T. Yamaguchi

    SMART-Tohoku GCOE joint Workshop on Micro & Nano Bioenginering, p.50 2010/01

  377. Patient-specific morphological and blood flow analysis of pulmonary artery in the case of severe deformations of the lung due to pneumothorax Peer-reviewed

    Jean-Joseph Christophe, Takuji Ishikawa, Noriaki Matsuki, Yohsuke Imai, Kei Takase, Marc Thiriet, Takami Yamaguchi

    Journal of Biomechanical Science and Engineering 5 (5) 485-498 2010

    DOI: 10.1299/jbse.5.485  

    ISSN:1880-9863

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    Pneumothorax is characterized by lung collapse. Its effect on hemodynamics, especially on pulmonary arterial blood flow, remains unclear. This patient-specific study investigated the effects of lung deformation on pulmonary blood flow during acute phase and after recovery. Arterial geometry was extracted up to the fifth generation from computed tomography images in three patients and reconstructed. Different geometrical parameters (artery bores, area ratios, and between-branch angles) were computed. The shapes of the pulmonary trunk and its branches were affected strongly by pneumothorax. To clarify the effect of geometrical perturbations on blood flow, the Navier-Stokes equations for a steady laminar flow of Newtonian incompressible fluid were solved in a reconstructed domain. The change in flow structure between acute phase and recovery was associated with variations in flow rate ratio between the right and left lungs. This study shows, possibly for the first time, that from a patient-specific numerical test, pneumothorax has a considerable impact on pulmonary arterial morphology and hemodynamics. © 2010 by JSME.

  378. Patient specific morphological and hemodynamic analysis of pulmonary artery in the case of severe deformations of the lung

    J-J. Christophe, T. Ishikawa, N. Matsuki, Y. Imai, K. Takase, M. Thiriet, T. Yamaguchi

    3rd East Asian Pacific Student Workshop on Nano-Biomedical Engineering, pp.124-125 2009/12

  379. Impact of membrane modeling on the deformation analysis of a capsule

    T. Oomori, T. Ishikawa, D. Barthes-Biesel, A. V. Salsac, Y. Imai, T. Yamaguchi

    3rd East Asian Pacific Student Workshop on Nano-Biomedical Engineering, pp.122-123 2009/12

  380. Development of a biologically inspired locomotion system for a capsule endoscope Peer-reviewed

    Daisuke Hosokawa, Takuji Ishikawa, Hirohisa Morikawa, Yohsuke Imai, Takami Yamaguchi

    INTERNATIONAL JOURNAL OF MEDICAL ROBOTICS AND COMPUTER ASSISTED SURGERY 5 (4) 471-478 2009/12

    Publisher: JOHN WILEY & SONS INC

    DOI: 10.1002/rcs.284  

    ISSN:1478-5951

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    Background A capsule endoscope has a limited ability to obtain images of the digestive organs because its movement depends on peristaltic motion. To overcome this problem, capsule endoscopes require a propulsion system. Methods This paper proposes a propulsion system for a capsule endoscope that mimics the locomotive mechanism of snails and earthworms. The prototype crawler can elongate and contract itself longitudinally and adhere to a wall via suction cups. Results We investigated the effect of the inclination angle of the propulsion plane, the mucus viscosity between the propulsion plane and the crawler, and the stiffness of the propulsion plane on the locomotion of the prototype crawler. We found that the crawler could move on a rubber sheet and on inclined planes covered with mucus. We discussed advantages and limitations of the prototype crawler compared to the different locomotive systems developed in former studies. Conclusions We believe that the prototype crawler provides a better understanding of the propulsion mechanism for use in the gastrointestinal tract. Copyright (C) 2009 John Wiley & Sons, Ltd.

  381. 準希薄微生物溶液における自己拡散シミュレーション -せん断流れの影響- Peer-reviewed

    石川拓司

    シミュレーション 1 60-65 2009/12/01

    DOI: 10.11308/tjsst.1.60  

  382. Fluid flow analysis of the surface of tracheal ciliary cells

    H. Ueno, K. Gonda, Y. Imai, N. Matsuki, T. Ishikawa, T. Yamaguchi

    Dynein International Workshop 2009, p.11 2009/11

  383. Shear-induced fluid-tracer diffusion in a semi-dilute suspension of spheres

    T. Ishikawa, T. Yamaguchi

    Bulletin of the American Physical Society, DFD 2009 54 293 2009/11

  384. Simulation of saccular cerebral aneurysm formation based on GON indicator Peer-reviewed

    Y. Shimogonya, T. Ishikawa, Y. Imai, N. Matsuki, T. Yamaguchi

    International Journal of Computational Fluid Dynamics 23 583-593 2009/11/01

    DOI: 10.1080/10618560902953575  

  385. Determination of the cell-free layer in circular PDMS microchannels

    T. Cerdeira, F. Monteiro, R. Lima, M. Oliveira, T. Ishikawa, Y. Imai, T. Yamaguchi

    Computational Vision and Medical Image Processing - VipIMAGE 2009, CRC press, pp.357-360 2009/10

  386. Motions of particles and red blood cells in a bifurcation: comparison between experiments and numerical simulations

    M. Lagoela, B. Oliveira, D. Cidre, C. Fernandes, C. Balsa, R. Lima, R. Dias, T. Ishikawa, Y. Imai, T. Yamaguchi

    Computational Vision and Medical Image Processing - VipIMAGE 2009, CRC press, pp.339-342 2009/10

  387. Patient-specific blood flow analysis of pulmonary artery affected by severe deformations of the lung

    J-J. Christophe, T. Ishikawa, N. Matsuki, Y. Imai, K. Takase, M. Thiriet, T. Yamaguchi

    Computational Vision and Medical Image Processing - VipIMAGE 2009, CRC press, pp.335-338 2009/10

  388. Diffusion in concentrated suspensions of biological cells

    T. Ishikawa

    Computational Vision and Medical Image Processing - VipIMAGE 2009, CRC press, pp.327-330 2009/10

  389. Suspension biomechanics of swimming microbes Peer-reviewed

    Takuji Ishikawa

    JOURNAL OF THE ROYAL SOCIETY INTERFACE 6 (39) 815-834 2009/10

    Publisher: ROYAL SOC

    DOI: 10.1098/rsif.2009.0223  

    ISSN:1742-5689

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    Micro-organisms play a vital role in many biological, medical and engineering phenomena. Some recent research efforts have demonstrated the importance of biomechanics in understanding certain aspects of micro-organism behaviours such as locomotion and collective motions of cells. In particular, spatio-temporal coherent structures found in a bacterial suspension have been the focus of many research studies over the last few years. Recent studies have shown that macroscopic properties of a suspension, such as rheology and diffusion, are strongly affected by meso-scale flow structures generated by swimming microbes. Since the meso-scale flow structures are strongly affected by the interactions between microbes, a bottom-up strategy, i.e. from a cellular level to a continuum suspension level, represents the natural approach to the study of a suspension of swimming microbes. In this paper, we first provide a summary of existing biomechanical research on interactions between a pair of swimming micro-organisms, as a two-body interaction is the simplest many-body interaction. We show that interactions between two nearby swimming micro-organisms are described well by existing mathematical models. Then, collective motions formed by a group of swimming micro-organisms are discussed. We show that some collective motions of micro-organisms, such as coherent structures of bacterial suspensions, are satisfactorily explained by fluid dynamics. Lastly, we discuss how macroscopic suspension properties are changed by the microscopic characteristics of the cell suspension. The fundamental knowledge we present will be useful in obtaining a better understanding of the behaviour of micro-organisms.

  390. Particle method simulation of red blood cells infected by malaria

    T. Yamaguchi, Young Ho Kang, H. Kondo, Y. Imai, T. Ishikawa

    Med. Phys. Biomed. Eng. World Cong. 2009, CD-ROM-131 2009/09

  391. Simulation of microcirculatory disorder by malaria infection using a particle method

    T. Yamaguchi, H. Kondo, Y. Imai, T. Ishikawa

    Int. Cong. Computational Bioeng. (ICCB 2009), USB-83 2009/09

  392. Simulation of rosette formation and destruction of malaria infected red blood cells Peer-reviewed

    T. Yamaguchi, Y. Imai, T. Ishikawa

    Book of Abstracts BIOENGINEERING 09, p.48 2009/09

  393. On the sensitivity of a hemodynamic index for cerebral aneurysm initiation, the GON, to flow input waveform Peer-reviewed

    Y. Shimogonya, T. Ishikawa, Y. Imai, N. Matsuki, T. Yamaguchi

    Book of Abstracts BIOENGINEERING 09, p.126 2009/09

  394. Pulmonary airflow simulation of inspiration and expiration using a patient-specific model Peer-reviewed

    T. Miki, Y. Imai, T. Ishikawa, T. Yamaguchi

    Book of Abstracts BIOENGINEERING 09, p.92 2009/09

  395. Mixing of red blood cells in high hematocrit blood flow in micro-channels Peer-reviewed

    T. Ishikawa, H. Fujiwara, R. Lima, N. Matsuki, Y. Imai, T. Yamaguchi

    Proc. 3rd Switzerland-Japan Workshop on Biomechanics 2009, p.47 2009/09

    DOI: 10.1016/j.jbiomech.2009.01.026  

  396. Axisymmetric polydimethysiloxane microchannels for in vitro hemodynamic studies Peer-reviewed

    Rui Lima, Monica S. N. Oliveira, Takuji Ishikawa, Hirokazu Kaji, Shuji Tanaka, Matsuhiko Nishizawa, Takami Yamaguchi

    BIOFABRICATION 1 (3) 035005 2009/09

    Publisher: IOP PUBLISHING LTD

    DOI: 10.1088/1758-5082/1/3/035005  

    ISSN:1758-5082

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    The current microdevices used for biomedical research are often manufactured using microelectromechanical systems (MEMS) technology. Although it is possible to fabricate precise and reproducible rectangular microchannels using soft lithography techniques, this kind of geometry may not reflect the actual physiology of the microcirculation. Here, we present a simple method to fabricate circular polydimethysiloxane (PDMS) microchannels aiming to mimic an in vivo microvascular environment and suitable for state-of-the-art microscale flow visualization techniques, such as confocal mu PIV/PTV. By using a confocal mu PTV system individual red blood cells (RBCs) were successfully tracked trough a 75 mu m circular PDMS microchannel. The results show that RBC lateral dispersion increases with the volume fraction of RBCs in the solution, i.e. with the hematocrit.

  397. Fluid Particle Diffusion in a Semi-dilute Suspension of Model Micro-organisms

    T. Ishikawa, J. T. Locsei, T. J. Pedley

    The 4th International Symposium on Aero Aqua Bio-Mechanisms 2009, CD-ROM S01 2009/08

  398. Measurement of Individual Red Blood Cell Motions Under High Hematocrit Conditions Using a Confocal Micro-PTV System Peer-reviewed

    Rui Lima, Takuji Ishikawa, Yohsuke Imai, Motohiro Takeda, Shigeo Wada, Takami Yamaguchi

    ANNALS OF BIOMEDICAL ENGINEERING 37 (8) 1546-1559 2009/08

    Publisher: SPRINGER

    DOI: 10.1007/s10439-009-9732-z  

    ISSN:0090-6964

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    Developments in optical experimental techniques have helped in elucidating how blood flows through microvessels. Although initial developments were encouraging, studies on the flow properties of blood in microcirculation have been limited by several technical factors, such as poor spatial resolution and difficulty obtaining quantitative detailed measurements at such small scales. Recent advances in computing, microscopy, and digital image processing techniques have made it possible to combine a particle tracking velocimetry (PTV) system with a confocal microscope. We document the development of a confocal micro-PTV measurement system for capturing the dynamic flow behavior of red blood cells (RBCs) in concentrated suspensions. Measurements were performed at several depths through 100-mu m glass capillaries. The confocal micro-PTV system was able to detect both translational and rotational motions of individual RBCs flowing in concentrated suspensions. Our results provide evidence that RBCs in dilute suspensions (3% hematocrit) tended to follow approximately linear trajectories, whereas RBCs in concentrated suspensions (20% hematocrit) exhibited transversal displacements of about 2% from the original path. Direct and quantitative measurements indicated that the plasma layer appeared to enhance the fluctuations in RBC trajectories owing to decreased obstruction in transversal movements caused by other RBCs. Using optical sectioning and subsequent image contrast and resolution enhancement, the system provides previously unobtainable information on the motion of RBCs, including the trajectories of two or more RBCs interacting in the same focal plane and RBC dispersion coefficients in different focal planes.

  399. Computational biomechanics of malaria and arterial diseases Invited

    T. Ishikawa

    37th Int. Cong. Physiol. Sci. PSJ II-7-4 2009/07/02

  400. Development of an Ethernet-linked Wearable System for Monitoring EMG and Acceleration Peer-reviewed

    M. Kishimoto, T. Yoshida, T. Hayasaka, D. Mori, Y. Imai, N. Matsuki, T. Ishikawa, T. Yamaguchi

    Technology and Health Care 17 121-131 2009/07/01

    DOI: 10.3233/THC-2009-0538  

  401. Rheology of Cancer Cells with Different Metastatic Properties

    T. Yoshimoto, T.Ishikawa, N. Matsuki, H. Fujiwara, Y. Imai, H. Ueno, M. Takeda, T. Yamaguchi

    Proc. ASME 2009 Summer Bioeng. Conf. CD-ROM SBC2009-206593 2009/06/02

    DOI: 10.1115/SBC2009-206593  

  402. A Numerical Model of Adhesion Property of Malaria Infected Red Blood Cells in Micro Scale Blood Flows

    Y. Imai, H. Kondo, Y. H. Kang, T. Ishikawa, C. T. Lim, T. Yamaguchi

    Proc. ASME 2009 Summer Bioeng. Conf. CD-ROM SBC2009-206456 2009/06/02

    DOI: 10.1115/SBC2009-206456  

  403. Morphology and Blood Flow Analysis of Pulmonary Arteries Under Respiratory Disorders

    J.-J. Christophe, T. Ishikawa, Y. Imai, N. Matsuki, K. Takase, T. Yamaguchi

    Proc. ASME 2009 Summer Bioeng. Conf. CD-ROM SBC2009-206243 2009/06/02

    DOI: 10.1115/SBC2009-206243  

  404. Individual Motions of Red Blood Cells in High-Hematocrit Blood Flowing in a Microchannel with Complex Geometries

    T. Ishikawa, H. Fujiwara, N. Matsuki, R. Lima, Y. Imai, H. Ueno, T. Yamaguchi

    Proc. ASME 2009 Summer Bioeng. Conf. CD-ROM SBC2009-206462 2009/06/02

    DOI: 10.1115/SBC2009-206462  

  405. Clinical Education for Engineers: ESTEEM Project

    N.Matsuki, M.Takeda, M.Yamano, Y.Imai, T.Ishikawa, T. Yamaguchi

    Proc. ASME 2009 Summer Bioeng. Conf. CD-ROM SBC2009-206594 2009/06/02

    DOI: 10.1115/SBC2009-206594  

  406. Effects of unique biomedical education programs for engineers: REDEEM and ESTEEM projects Peer-reviewed

    Noriaki Matsuki, Motohiro Takeda, Masahiro Yamano, Yohsuke Imai, Takuji Ishikawa, Takami Yamaguchi

    ADVANCES IN PHYSIOLOGY EDUCATION 33 (2) 91-97 2009/06

    Publisher: AMER PHYSIOLOGICAL SOC

    DOI: 10.1152/advan.90120.2008  

    ISSN:1043-4046

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    Matsuki N, Takeda M, Yamano M, Imai Y, Ishikawa T, Yamaguchi T. Effects of unique biomedical education programs for engineers: REDEEM and ESTEEM projects. Adv Physiol Educ 33: 91-97, 2009; doi: 10.1152/advan.90120.2008.-Current engineering applications in the medical arena are extremely progressive. However, it is rather difficult for medical doctors and engineers to discuss issues because they do not always understand one another&apos;s jargon or ways of thinking. Ideally, medical engineers should become acquainted with medicine, and engineers should be able to understand how medical doctors think. Tohoku University in Japan has managed a number of unique reeducation programs for working engineers. Recurrent Education for the Development of Engineering Enhanced Medicine has been offered as a basic learning course since 2004, and Education through Synergetic Training for Engineering Enhanced Medicine has been offered as an advanced learning course since 2006. These programs, which were developed especially for engineers, consist of interactive, modular, and disease-based lectures (case studies) and substantial laboratory work. As a result of taking these courses, all students obtained better objective outcomes, on tests, and subjective outcomes, through student satisfaction. In this article, we report on our unique biomedical education programs for engineers and their effects on working engineers.

  407. Red blood cell motions in high-hematocrit blood flowing through a stenosed microchannel Peer-reviewed

    H. Fujiwara, T. Ishikawa, R. Lima, N. Matsuki, Y. Imai, H. Kaji, M. Nishizawa, T. Yamaguchi

    JOURNAL OF BIOMECHANICS 42 (7) 838-843 2009/05

    Publisher: ELSEVIER SCI LTD

    DOI: 10.1016/j.jbiomech.2009.01.026  

    ISSN:0021-9290

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    We investigated the behavior of red blood cells (RBCs) in a microchannel with stenosis using a confocal micro-PTV system. Individual trajectories of RBCs in a concentrated suspension of up to 20% hematocrit (Hct) were measured successfully. Results indicated that the trajectories of healthy RBCs became asymmetric before and after the stenosis, while the trajectories of tracer particles in pure water were almost symmetric. The asymmetry was greater in 10% Hct than in 20% Hct. We also investigated the effect of deformability of RBCs on the cell-free layer thickness by hardening RBCs using a glutaraldehyde treatment. The results indicated that deformability is the key factor in the asymmetry of cell-free layer thickness. Therefore, the motions of RBCs are influenced strongly by the Hct, the deformability, and the channel geometry. These results give fundamental knowledge for a better understanding of blood flow in microcirculation and biomedical microdevices. Crown Copyright (C) 2009 Published by Elsevier Ltd. All rights reserved.

  408. Effect of the membrane bending stiffness on the deformation of a red blood cell

    T. Omori, T. Ishikawa, D. Birthes-Biesel, Y. Imai, T. Yamaguchi

    Proc. AP Biomech 2009 196-197 2009/04/03

  409. Numerical Simulation of Inpiratory and Expiratory Pulmonary Airflow using a Patient-specific Model

    T. Miki, Y. Imai, T. Ishikawa, S. Wada, T. Yamaguchi

    Proc. AP Biomech 2009 164-165 2009/04/03

  410. Low voltage pulses can induce apoptosis

    N. Matsuki, T. Ishikawa, Y. Imai, T. Yamaguchi

    Proc. AP Biomech 2009 154-155 2009/04/03

  411. Motion of individual red blood cells in a concentrated suspension flowing through micro-channels

    T. Ishikawa, H. Fujiwara, N. Matsuki, R. Lima, Y. Imai, T. Yamaguchi

    Proc. AP Biomech 2009 102-103 2009/04/03

  412. A Micro Scale Blood Flow Model to Study Pathology of Malaria

    Y. Imai, H. Kondo, Y. H. Kang, T. Ishikawa, C. T. Lim, T. Yamaguchi

    Proc. AP Biomech 2009 100-101 2009/04/03

  413. A numerical model to study hemodynamics arising from malaria infection

    Y. Imai, H. Kondo, Y. H. Kang, T. Ishikawa, C. T. Lim, T. Yamaguchi

    Proceedings of ICCES’09 96 2009/04/02

  414. Motion of individual cells in high hematocrit blood flow in micro-channels Invited

    T. Ishikawa, H. Fujiwara, N. Matsuki, R. Lima, Y. Imai, T. Yamaguchi

    Proceedings of ICCES’09 244 2009/04/02

  415. Computational biomechanics for investigating various diseases over micro to macro scales Invited

    T. Yamaguchi, T. Ishikawa, Y. Imai

    Proceedings of ICCES’09 10 2009/04/02

  416. Modeling of the membrane bending rigidity for calculating red blood cell deformation

    T. Omori, T. Ishikawa, D. Birthes-Biesel, Y. Imai, T. Yamaguchi

    15th Int. Conf. Finite Elements in Flow Problems (FEF09) Abstracts 41 2009/04/01

  417. Patient-specific pulmonary airflow simulation using cartestian adaptive mesh refinement method

    T. Miki, Y. Imai, T. Ishikawa, S. Wada, T. Yamaguchi

    15th Int. Conf. Finite Elements in Flow Problems (FEF09) Abstracts 37 2009/04/01

  418. Hemodynamic Analysis of Microcirculation in Malaria Infection Peer-reviewed

    Hitoshi Kondo, Yohsuke Imai, Takuji Ishikawa, Ken-ichi Tsubota, Takami Yamaguchi

    ANNALS OF BIOMEDICAL ENGINEERING 37 (4) 702-709 2009/04

    Publisher: SPRINGER

    DOI: 10.1007/s10439-009-9641-1  

    ISSN:0090-6964

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    Malaria-infected red blood cells (IRBCs) show various changes in mechanical properties. IRBCs lose their deformability and develop properties of cytoadherence and rosetting. To clarify how these changes advance microvascular occlusion, we need qualitative and quantitative information on hemodynamics in malaria infection, including the interaction among IRBCs, healthy RBCs, and endothelial cells. We developed a numerical model of blood flow with IRBCs based on conservation laws of fluid dynamics. The deformability and adhesive property of IRBCs were simply modeled using springs governed by Hook&apos;s law. Our model could express the basic behavior of IRBCs, including the rolling motion due to cytoadhesive interaction with endothelial cells and complex interaction with healthy RBCs. We confirmed that these types of interactions significantly increase the flow resistance, particularly when knobs develop.

  419. Dancing Volvox: Hydrodynamic Bound States of Swimming Algae Peer-reviewed

    Knut Drescher, Kyriacos C. Leptos, Idan Tuval, Takuji Ishikawa, Timothy J. Pedley, Raymond E. Goldstein

    PHYSICAL REVIEW LETTERS 102 (16) 168101 (cover) 2009/04

    Publisher: AMER PHYSICAL SOC

    DOI: 10.1103/PhysRevLett.102.168101  

    ISSN:0031-9007

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    The spherical alga Volvox swims by means of flagella on thousands of surface somatic cells. This geometry and its large size make it a model organism for studying the fluid dynamics of multicellularity. Remarkably, when two nearby Volvox colonies swim close to a solid surface, they attract one another and can form stable bound states in which they "waltz" or "minuet" around each other. A surface-mediated hydrodynamic attraction combined with lubrication forces between spinning, bottom-heavy Volvox explains the formation, stability, and dynamics of the bound states. These phenomena are suggested to underlie observed clustering of Volvox at surfaces.

  420. Computational simulation of blood flow in pulmonary artery under respiratory disorders

    J-J. Christophe, T. Ishikawa, Y. Imai, N. Matsuki, K. Takase, T. Yamaguchi

    9th International Symposium of Tohoku University Global COE Program, Global Nano-Biomedical Engineering Education and Research Network Centre, Nano-Biomedical Engineering in the East Asian-Pacific Rim Region 100-101 2009/03

  421. Can temporal fluctuation in spatial wall shear stress gradient initiate a cerebral aneurysm? A proposed novel hemodynamic index, the gradient oscillatory number (GON) Peer-reviewed

    Yuji Shimogonya, Takuji Ishikawa, Yohsuke Imai, Noriaki Matsuki, Takami Yamaguchi

    JOURNAL OF BIOMECHANICS 42 (4) 550-554 2009/03

    Publisher: ELSEVIER SCI LTD

    DOI: 10.1016/j.jbiomech.2008.10.006  

    ISSN:0021-9290

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    We propose a new hemodynamic index for the initiation of a cerebral aneurysm, defined by the temporal fluctuations of tension/compression forces acting on endothelial cells. We employed a patient-specific geometry of a human internal carotid artery (ICA) with an aneurysm, and reconstructed the geometry of the ICA before aneurysm formation by artificially removing the aneurysm. We calculated the proposed hemodynamic index and five other hemodynamic indices (wall shear stress (WSS) at peak systole, time-averaged WSS, time-averaged spatial WSS gradient, oscillatory shear index (OSI), and potential aneurysm formation indicator (AFI)) for the geometry before aneurysm formation using a computational fluid dynamics technique. By comparing the distribution of each index at the location of aneurysm formation, we discussed the validity of each. The results showed that only the proposed hemodynamic index had a significant correlation with the location of aneurysm formation. Our findings suggest that the proposed index may be useful as a hemodynamic index for the initiation of cerebral aneurysms. (c) 2008 Elsevier Ltd. All rights reserved.

  422. Fluid dynamics of a suspension of micro-organisms Invited

    T. Ishikawa

    Int. Comf. Nonlinear Sci. Abstracts 25 2009/02/01

    DOI: 10.1007/978-3-540-92841-6_533  

  423. 東北大学における「次世代医療関連産業中核人材育成のための実践的教育システム」の開発と実証研究 Peer-reviewed

    山野 真裕, 松木 範明, 沼山 恵子, 武田 元博, 早坂 智明, 石川 拓司, 山口 隆美

    工学教育 57 13-21 2009/02/01

    DOI: 10.4307/jsee.57.2_13  

  424. Microscale Flow Dynamics of Red Blood Cells in Microchannels: An Experimental and Numerical Analysis Invited Peer-reviewed

    R. Lima, M. Nakamura, T. Omori, T. Ishikawa, S. Wada, T. Yamaguchi

    Advances in Computational Vision and Medical Image Processing, Springer 13 203-220 2009/01/10

  425. An internet-based wearable watch-over system for elderly and disabled utilizing EMG and accelerometer Peer-reviewed

    M. Kishimoto, T. Yoshida, T. Hayasaka, D. Mori, Y. Imai, N. Matsuki, T. Ishikawa, T. Yamaguchi

    Technology and Health Care 17 (2) 121-131 2009

    DOI: 10.3233/THC-2009-0538  

    ISSN:0928-7329

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    An effective way for preventing injuries and diseases among the elderly is to monitor their daily lives. In this regard, we propose the use of a "Hyper Hospital Network", which is an information support system for elderly people and patients. In the current study, we developed a wearable system for monitoring electromyography (EMG) and acceleration using the Hyper Hospital Network plan. The current system is an upgraded version of our previous system for gait analysis (Yoshida et al. [13], Telemedicine and e-Health 13 703-714), and lets us monitor decreases in exercise and the presence of a hemiplegic gait more accurately. To clarify the capabilities and reliability of the system, we performed three experimental evaluations: one to verify the performance of the wearable system, a second to detect a hemiplegic gait, and a third to monitor EMG and accelerations simultaneously. Our system successfully detected a lack of exercise by monitoring the iEMG in healthy volunteers. Moreover, by using EMG and acceleration signals simultaneously, the reliability of the Hampering Index (HI) for detecting hemiplegia walking was improved significantly. The present study provides useful knowledge for the development of a wearable computer designed to monitor the physical conditions of older persons and patients. © 2009 - IOS Press and the authors. All rights reserved.

  426. A realistic simulation of saccular cerebral aneurysm formation: focussing on a novel haemodynamic index, the gradient oscillatory number Peer-reviewed

    Y. Shimogonya, T. Ishikawa, Y. Imai, N. Matsuki, T. Yamaguchi

    INTERNATIONAL JOURNAL OF COMPUTATIONAL FLUID DYNAMICS 23 (8) 583-593 2009

    Publisher: TAYLOR & FRANCIS LTD

    DOI: 10.1080/10618560902953575  

    ISSN:1061-8562

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    Although how cerebral aneurysms initiate and grow is still unclear, haemodynamics is thought to play an important role. In order to better understand the aneurysm formation mechanism, we performed a computational analysis of aneurysm formation for a patient-specific arterial geometry. First, CFD was used to perform a pulsatile blood flow analysis and calculate a novel haemodynamic index, the gradient oscillatory number (GON). Then, using aneurysm growth model in which the proliferation of the wall was hypothesised, we performed an aneurysm formation analysis based on the GON index distribution. The result showed that a saccular cerebral aneurysm could appear based on our hypothesis for a patient-specific arterial geometry. On the other hand, a saccular aneurysm was not observed when assuming only strength degradation of the wall. Our findings have suggested that an arterial biological process, such as the proliferation of the wall, may play a vital role in saccular aneurysm formation.

  427. Microvascular disorders induced by malaria infected red blood cells: a computational mechanical study using the biological particle method Invited

    T. Yamaguchi, H. Kondo, Y. Imai, T. Ishikawa

    MODELLING IN MEDICINE AND BIOLOGY VIII 13 49-+ 2009

    Publisher: WIT PRESS/COMPUTATIONAL MECHANICS PUBLICATIONS

    DOI: 10.2495/BIO090051  

    ISSN:1743-3525

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    We simulated malarial microvascular blood flow disturbances by using a new particle method of biological solid-fluid interaction analysis especially developed for the analysis of malaria infection. Particle based spatial discretization and the sub time step time integration could provide us with stable computations for micro scale blood flow involving interaction with many cells. We performed numerical simulation of the stretching of infected red blood cells and the results agreed well with experimental results. Our model successfully simulated the flow of infected red blood cells into narrow channels.

  428. Behavior of a red blood cell in a simple shear flow simulated by a boundary element method

    T. Omori, T. Ishikawa, D. Barthes-Biesel, Y. Imai, T. Yamaguchi

    GPBE/NUS-Tohoku Graduate Student Conf. Bioeng., Program & Abstract 99-100 2008/12/01

  429. A novel hemodynamic index for the initiation of cerebral aneurysms: focusing on temporal variation of spatial wall shear stress gradient

    Y. Shimogonya, T. Ishikawa, Y. Imai, N. Matsuki, T. Yamaguchi

    GPBE/NUS-Tohoku Graduate Student Conf. Bioeng., Program & Abstract 95-96 2008/12/01

  430. Numerical simulation of inspiratory and expiratory pulmonary airflow using a subject-specific model

    T. Miki, Y. Imai, T. Ishikawa, S. Wada, T. Yamaguchi

    GPBE/NUS-Tohoku Graduate Student Conf. Bioeng., Program & Abstract 81-82 2008/12/01

  431. Three-dimensional Simulation of Blood Flow in Malaria Infection

    Y. Imai, H. Kondo, T. Ishikawa, C. T. Lim, K. Tsubota, T. Yamaguchi

    Proc. 13th Int Conf. Biomed. Eng. 133 2008/12/01

  432. Biomechanics of a suspension of micro-organisms Invited

    T. Ishikawa

    Proc. 13th Int Conf. Biomed. Eng. 14 2008/12/01

  433. 東北大学における「医療工学技術者創成のための再教育システム」の実践 Peer-reviewed

    山野 真裕, 松木 範明, 沼山 恵子, 武田 元博, 早坂 智明, 石川 拓司, 山口 隆美

    工学教育 56 (6) 125-132 2008/12/01

    Publisher: Japanese Society for Engineering Education

    DOI: 10.4307/jsee.56.6_125  

    ISSN:1341-2167

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    Tohoku University promotes the "REDEEM" project, which is a national project of Recurrent Education for the Development of Engineering Enhanced Medicine. This education system provides a curriculum for engineers who belong to bio-medical R. In Japan, most of industrial engineers have been excluded from systemized bio-medical education, while medical and co-medical personnel lack engineering education. This difference of backgrounds causes a discrepancy between medicine and engineering bringing difficulty in collaboration for development of medical equipments or drugs. In this project, we focus on the engineering side, and we try to develop and provide a bio-medical engineering course for engineers. In this paper, we report and discuss on the outline and the progress of the "REDEEM" project.

  434. Development of a Wearable System Module for Monitoring Physical and Mental Workload Peer-reviewed

    Sinbae Kim, Hiromi Nakamura, Toshihiko Yoshida, Masamichi Kishimoto, Yohsuke Imai, Noriaki Matsuki, Takuji Ishikawa, Takami Yamaguchi

    TELEMEDICINE JOURNAL AND E-HEALTH 14 (9) 939-945 2008/11

    Publisher: MARY ANN LIEBERT INC

    DOI: 10.1089/tmj.2008.0019  

    ISSN:1530-5627

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    The population of most developed countries is rapidly aging, which has created a growing demand for home care. A key issue in medicine is supporting the increasing number of elderly patients, both physically and mentally. In this study, we developed a wearable computer that contained modules for measuring electrocardiograms (ECGs) and femoral artery pulse waves using an accelerometer. This system has several benefits: ( a) it can provide a database server in each patient&apos;s home; (b) its high extendibility and flexibility facilitate adaptation to a patient&apos;s needs; and ( c) it allows patients to keep their own data, thus protecting the privacy of personal information. To clarify the capabilities and reliability of the system, we applied it to 8 healthy young volunteers during states of physical and mental work. This system successfully detected clear ECGs and femoral artery pulse waves to calculate important bioinformation, including heart rate, pulse wave velocity, and the power spectral density of spontaneous beat-to-beat oscillations in the R-R interval. In this study, we proposed the way to provide an assessment of the physical and mental condition of the subject using analysis of the bio-information with respect to the physical and mental workloads. The present study provides useful knowledge for the development of a wearable computer designed to monitor the physical and mental conditions of older persons and patients.

  435. Development of coherent structures in concentrated suspensions of swimming model micro-organisms Peer-reviewed

    Takuji Ishikawa, J. T. Locsei, T. J. Pedley

    JOURNAL OF FLUID MECHANICS 615 401-431 2008/11

    Publisher: CAMBRIDGE UNIV PRESS

    DOI: 10.1017/S0022112008003807  

    ISSN:0022-1120

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    A swimming micro-organism is modelled as a squirming sphere with prescribed tangential surface velocity and referred to as a squirmer. The centre of mass of the sphere may be displaced from the geometric centre, and the effects of inertia and Brownian motion are neglected. The well-known Stokesian dynamics method is modified in order to simulate squirmer motions in a concentrated suspension. The movement of 216 identical squirmers in a concentrated suspension without any imposed flow is simulated in a cubic domain with periodic boundary conditions, and the coherent structures within the suspension are investigated. The results show that (a) a weak aggregation of cells appears as a result of the hydrodynamic interaction between cells; (b) the cells generate collective motions by the hydrodynamic interaction between themselves; and (c) the range and duration of the collective motions depend on the volume fraction and the squirmers&apos; stresslet strengths. These tendencies show good qualitative agreement with previous experiments.

  436. Waltzing Volvox: Orbiting Bound States of Flagellated Multicellular Algae

    K. Drescher, K. Leptos, T. J. Pedley, R. E. Goldstein, T. Ishikawa

    Bulletin of the American Physical Society, DFD 2008 53 238 2008/11/01

  437. Numerical analysis of a stable waltzing pair of Volvox

    T. Ishikawa, K. Drescher, K. Leptos, T. J. Pedley, R. E. Goldstein

    Bulletin of the American Physical Society, DFD 2008 53 279 2008/11/01

  438. Development of automatic respiration monitoring for home-care patients of respiratory diseases with therapeutic aids

    M. Okubo, Y. Imai, T. Ishikawa, T. Hayasaka, S. Ueno, T. Yamaguchi

    Int. Feder. Med. Biol. Eng. (IFMBE) Proc. (CD-ROM) 205 2008/11/01

    DOI: 10.1007/978-3-540-89208-3_267  

  439. Development of a mobile toilet system servicing elderly on call

    S. Ueno, T. Hayasaka, Y. Imai, M. Okubo, T. Ishikawa, T. Yamaguchi

    Int. Feder. Med. Biol. Eng. (IFMBE) Proc. (CD-ROM) 234 2008/11/01

    DOI: 10.1007/978-3-540-89208-3_416  

  440. A locomotive system mimicking pedal locomotion of snails for the capsule endoscope

    D. Hosokawa, T. Ishikawa, H. Morikawa, Y. Imai, T. Yamaguchi

    Int. Feder. Med. Biol. Eng. (IFMBE) Proc. (CD-ROM) 274 2008/11/01

    DOI: 10.1007/978-3-540-89208-3_393  

  441. Three-dimensional simulation of malaria-infected blood

    H. Kondo, Y. Imai, T. Ishikawa, K. Tsubota, C.T. Lim, T. Yamaguchi

    Interntional Symposium on Nano-Biomedical Engineering7th Intrnational Symposium of 2007 Tohoku University Global COE Program "Global Nano-Biomedical Engineering Education and Research Network Centre"Nano-Biomedical Engineering in the East Asian-Pacific Ri 42-43 2008/10

  442. Low voltage pulses can induce apoptosis Peer-reviewed

    Noriaki Matsuki, Takuji Ishikawa, Yousuke Imai, Takami Yamaguchi

    CANCER LETTERS 269 (1) 93-100 2008/09

    Publisher: ELSEVIER IRELAND LTD

    DOI: 10.1016/j.canlet.2008.04.019  

    ISSN:0304-3835

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    Electroporation is used for gene transfection, drug delivery, and cell fusion. While studies have shown that high voltage electroporation induces apoptosis in. vitro, a strong electric field can lower cell survival rates. As there are no published reports which have examined apoptotic properties associate with low voltage electric charges, we demonstrated for the first time that consecutive low voltage pulses with a voltage lower than the membrane breakdown threshold of human cells can increase the membrane potential to the threshold required to induce electroporation. This led to apoptosis through caspase pathways. Moreover, necrotic cell damage was less than that caused by high voltage pulses. Therefore, low voltage electroporation can be a suitable anticancer method. (C) 2008 Elsevier Ireland Ltd. All rights reserved.

  443. Inflow into saccular cerebral aneurysms at arterial bends Peer-reviewed

    Yohsuke Imai, Kodai Sato, Takuji Ishikawa, Takami Yamaguchi

    ANNALS OF BIOMEDICAL ENGINEERING 36 (9) 1489-1495 2008/09

    Publisher: SPRINGER

    DOI: 10.1007/s10439-008-9522-z  

    ISSN:0090-6964

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    To identify shortcomings in the design of conventional endovascular devices, we investigated the inflow features of untreated aneurysms at a variety of arterial bends using computational fluid dynamics. As a preliminary study, we analyzed the steady-state inflow for aneurysms created at U-shaped, twisted, and S-shaped arteries. Both the inflow pattern and inflow flux were strongly influenced by the shape of the artery and the configuration angle of the aneurysm to the artery. We revealed that the secondary flow generated in the parent artery is the dominant factor affecting the inflow. Our results suggest that the arterial geometry and secondary flow should be considered in the design of endovascular devices.

  444. Mixing of red blood cells in a micro-channel flow under high hematocrit conditions

    T. Ishikawa, R. Lima, H. Fujiwara, Y. Imai, N. Matsuki, T. Yamaguchi

    Bioengineering 08 Book of Abstracts 61 2008/09/01

  445. A Numerical Method for Simulating Micro-Scale Blood Flow in Malaria Infection

    Y. Imai, H. Kondo, T. Ishikawa, K. Tsubota, C. T. Lim, T. Yamaguchi

    Bioengineering 08 Book of Abstracts 125 2008/09/01

  446. Behavior of a Red Blood Cell in a Simple Shear Flow Simulated by a Boundary Element Method

    T. Omori, T. Ishikawa, D. Barthes-Biesel, Y. Imai, T. Yamaguchi

    Bioengineering 08 Book of Abstracts 135 2008/09/01

  447. Confocal micro-PTV Measurements of Blood Flow in a Circular PDMS Microchannel

    R. Lima, T. Ishikawa, H. Kaji, Y. Imai, S. Wada, M. Nishizawa, T. Yamaguchi

    Bioengineering 08 Book of Abstracts 166 2008/09/01

  448. Proposal of a New Hemodynamic Index for Cerebral Aneurysm Initiation: Focusing on Temporal Fluctuation of Spatial Wall Shear Stress Gradient

    Y. Shimogonya, T. Ishikawa, Y. Imai, N. Matsuki, T. Yamaguchi

    Bioengineering 08 Book of Abstracts 146 2008/09/01

  449. The importance of parent artery geometry in intra-aneurysmal hemodynamics Peer-reviewed

    Kodai Sato, Yohsuke Imai, Takuji Ishikawa, Noriaki Matsuki, Takami Yamaguchi

    MEDICAL ENGINEERING & PHYSICS 30 (6) 774-782 2008/07

    Publisher: ELSEVIER SCI LTD

    DOI: 10.1016/j.medengphy.2007.09.006  

    ISSN:1350-4533

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    We show the importance of arterial geometry in intra-aneurysmal hemodynamics. Using a new geometric parameterized saccular aneurysm model including parameters for parent artery shape and the configuration of the aneurysm in the parent artery, we performed a parametric computational fluid dynamics study. We examined lateral saccular aneurysm models with different aneurysm shapes (i.e., the ratio of aneurysm height to aneurysm neck diameter) and different configurations (i.e., the torsion angle of the aneurysm to the upstream part of the parent artery). The aneurysm lateral to the curve of the parent artery had significantly higher wall shear stress than the aneurysm inside or outside the curve of the artery, even with the same shape of the aneurysm. Our findings SUI-est the important role played by the configuration of the aneurysm relative to the parent artery in intra-aneurysmal hemodynamics. (C) 2007 IPEM. Published by Elsevier Ltd. All rights reserved.

  450. Radial dispersion of red blood cells in blood flowing through glass capillaries: The role of hematocrit and geometry Peer-reviewed

    Rui Lima, Takuji Ishikawa, Yohsuke Imai, Motohiro Takeda, Shigeo Wada, Takami Yamaguchi

    JOURNAL OF BIOMECHANICS 41 (10) 2188-2196 2008/07

    Publisher: ELSEVIER SCI LTD

    DOI: 10.1016/j.jbiomech.2008.04.033  

    ISSN:0021-9290

    eISSN:1873-2380

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    The flow properties of blood in the microcirculation depend strongly on the hematocrit (Hct). microvessel geometry. and cell properties. Previous ill vitro studies have measured the radial displacement of red blood cells (RBCs) at concentrated Suspensions using conventional microscopes. However, to measure the RBSs motion they used transparent suspensions of ghost red cells. which may have different physical properties than normal RBCs. The present Study introduces a new approach (confocal micro-PTV) to measure the motion of labeled RBCs flowing in concentrated Suspensions of normal RBCs. The ability of confocal systems to obtain thin in-focus planes allowed US to measure the radial position of individual RBCs accurately and to consequently measure the interaction between multiple labeled RBCs. All the measurements were performed in the center plane of both 50 and 100 mu m glass capillaries at Reynolds numbers (Re) front 0.003 to 0.005 using Hcts front 2% to 35%. To quantify the Motion and interaction of multiple RBCs, we used the RBC radial dispersion (D-yy). Our results clearly demonstrate that D-yy strongly depends on the Het. The RBCs exhibited higher D-yy at radial positions between 0.4 and 0.8 R and lower D-yy at locations adjacent to the wall (0.8-1 R) and around the middle of the capillary (0-0.2 R) The present work also demonstrates that D-yy tends to decrease with a decrease in the diameter. The information provided by this study not only complements previous investigations oil microhemorheology of both dilute and concentrated Suspensions of RBCs. but also shows the influence of both Hct and geometry on the radial dispersion of RBCs. This information is important for a better Understanding of blood mass transport mechanisms under both physiological and pathological conditions. (C) 2008 Elsevier Ltd. All rights reserved.

  451. Role of the hematocrit on the radial dispersion of red blood cells in glass capillaries

    R. Lima, T. Ishikawa, Y. Imai, M. Takeda, S. Wada, T. Yamaguchi

    Journal of Biomechanics 41 S334 2008/07/01

    DOI: 10.1016/j.jbiomech.2008.04.033  

  452. Motion of red blood cells and cell free layer distribution in a stenosed microchannel

    H.Fujiwara, T. Ishikawa, R. Lima, Y. Imai, N. Matsuki, D. Mori, T. Yamaguchi

    Journal of Biomechanics 41 S390 2008/07/01

  453. Determination of blood cells motions and interactions by a confocal micro-PTV system

    R. Lima, T. Ishikawa, Y. Imai, M. Takeda, S. Wada, T. Yamaguchi

    Journal of Biomechanics 41 S429 2008/07/01

  454. A numerical model of blood flow with malariainfected red blood cells

    Y. Imai, H. Kondo, T. Ishikawa, K. Tsubota, T. Yamaguchi

    Journal of Biomechanics 41 S480 2008/07/01

  455. Stokesian-Dynamics Simulation of a Suspension of Swimming Micro-Organisms Invited Peer-reviewed

    T. Ishikawa, J. T. Locsei, T. J. Pedley, T. Yamaguchi

    IACM/ECCOMAS Congress 2008 CD-ROM MS194D 2008/07/01

  456. Image-based pulmonary airflow simulation using cartesian adaptive mesh refinement method

    T. Miki, Y. Imai, M. Nakamura, C. Iwamura, T. Ishikawa, S. Wada, T. Yamaguchi

    IACM/ECCOMAS Congress 2008 CD-ROM MS070B 2008/07/01

  457. Three-Dimensional Simulation of Blood Flow arising from Malaria Infection

    H. Kondo, Y. Imai, T. Ishikawa, K. Tsubota, C. T. Lim, T. Yamaguchi

    IACM/ECCOMAS Congress 2008 CD-ROM MS194C 2008/07/01

  458. Multi-scale multi-physics simulations of Biological flows

    T. Yamaguchi, T. Miki, Y. Shimogonya, H. Kondo, D. Mori, Y. Imai, M. Nakamura, C. Iwamura, S. Wada, T. Ishikawa

    Int. Symp. Multi-scale Sim. Biol. Soft Mater. (MSBSM2008) Book of Abstracts 2-3 2008/06/01

  459. The importance of proliferation of the arterial wall in formation of saccular cerebral aneurysms

    Y. Shimogonya, T. Ishikawa, Y. Imai, D. Mori, T. Yamaguchi

    Proc. ASME 2008 Summer Bioeng. Conf.CD-ROM 2008/06/01

  460. Pulmonary airflow simulation using subject-specific model and Cartesian adaptive mesh refinement method

    T. Miki, Y. Imai, S. Wada, T. Ishikawa, T. Yamaguchi

    Proc. Tohoku-NUS Student Joint Symp 16-17 2008/05/01

  461. Collective motions of locomotive cells in a suspension Invited

    T. Ishikawa

    Proc. Tohoku-NUS Student Joint Symp 18-19 2008/05/01

  462. In vitro blood flow in a rectangular PDMS microchannel: experimental observations using a confocal micro-PIV system Peer-reviewed

    Rui Lima, Shigeo Wada, Shuji Tanaka, Motohiro Takeda, Takuji Ishikawa, Ken-ichi Tsubota, Yohsuke Imai, Takami Yamaguchi

    BIOMEDICAL MICRODEVICES 10 (2) 153-167 2008/04

    Publisher: SPRINGER

    DOI: 10.1007/s10544-007-9121-z  

    ISSN:1387-2176

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    Progress in microfabricated technologies has attracted the attention of researchers in several areas, including microcirculation. Microfluidic devices are expected to provide powerful tools not only to better understand the biophysical behavior of blood flow in microvessels, but also for disease diagnosis. Such microfluidic devices for biomedical applications must be compatible with state-of-the-art flow measuring techniques, such as confocal microparticle image velocimetry (PIV). This confocal system has the ability to not only quantify flow patterns inside microchannels with high spatial and temporal resolution, but can also be used to obtain velocity measurements for several optically sectioned images along the depth of the microchannel. In this study, we investigated the ability to obtain velocity measurements using physiological saline ( PS) and in vitro blood in a rectangular polydimethysiloxane (PDMS) microchannel (300 mu m wide, 45 mu m deep) using a confocal micro-PIV system. Applying this combination, measurements of trace particles seeded in the flow were performed for both fluids at a constant flow rate (Re = 0.02). Velocity profiles were acquired by successive measurements at different depth positions to obtain three-dimensional (3-D) information on the behavior of both fluid flows. Generally, the velocity profiles were found to be markedly blunt in the central region, mainly due to the low aspect ratio (h/w = 0.15) of the rectangular microchannel. Predictions using a theoretical model for the rectangular microchannel corresponded quite well with the experimental micro-PIV results for the PS fluid. However, for the in vitro blood with 20% hematocrit, small fluctuations were found in the velocity profiles. The present study clearly shows that confocal micro-PIV can be effectively integrated with a PDMS microchannel and used to obtain blood velocity profiles along the full depth of the microchannel because of its unique 3-D optical sectioning ability. Advantages and disadvantages of PDMS microchannels over glass capillaries are also discussed.

  463. Shear-induced fluid-tracer diffusion in a semidilute suspension of spheres Peer-reviewed

    Takuji Ishikawa, Takami Yamaguchi

    PHYSICAL REVIEW E 77 (4) 041402 2008/04

    Publisher: AMER PHYSICAL SOC

    DOI: 10.1103/PhysRevE.77.041402  

    ISSN:1539-3755

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    We calculated tracer diffusion in a sheared suspension of non-Brownian rigid spheres and propose a numerical method based on a boundary element method and Stokesian dynamics method. We present details of the numerical method and examine the accuracy of the method. The limitation of semidiluteness is due to the accuracy of the tracer velocity calculation. The results show that the diffusivity of fluid tracers is greater than that of suspended spheres in the semidilute regime. The diffusivity of the velocity gradient direction is about threefold greater than that in the vorticity direction. Simple scaling demonstrates that the diffusivity of fluid tracers increases with the square of the volume fraction of spheres in the semidilute regime, which is confirmed numerically.

  464. CT image-based pulmonary airflow simulation using airway scale determined mesh

    T. Miki, Y. Imai, M. Nakamura, C. Iwamura, T. Ishikawa, S. Wada, T. Yamaguchi

    Fifth International Bio-Fluid Symposium and Workshop 146-147 2008/03/01

  465. Computational mechanical analysis of primary thrombus formation in a blood flow

    D. Mori, K. Yano, K. Tsubota, T. Ishikawa, S. Wada, T. Yamaguchi

    Fifth International Bio-Fluid Symposium and Workshop 110-111 2008/03/01

  466. Some uninvestigated directions of computational fluid dynamics studies for flow

    T. Yamaguchi, T. Miki, Y. Shimogonya, H. Kondo, D. Mori, Y. Imai, M. Nakamura, C. Iwamura, S. Wada, T. Ishikawa

    Fifth International Bio-Fluid Symposium and Workshop 65-66 2008/03/01

  467. Coherent structures in monolayers of swimming particles Peer-reviewed

    Takuji Ishikawa, T. J. Pedley

    PHYSICAL REVIEW LETTERS 100 (8) 088103 2008/02

    Publisher: AMER PHYSICAL SOC

    DOI: 10.1103/PhysRevLett.100.088103  

    ISSN:0031-9007

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    We report various types of coherent structures in suspensions of spherical particles swimming in a monolayer. We solve the fluid dynamics precisely from far-field hydrodynamic interactions to lubrication between two near-contact surfaces. The simulation results clearly illustrate that coherent structures, such as aggregation, mesoscale spatiotemporal motion, and band formation, can be generated by purely hydrodynamic interactions.

  468. Microscale flow dynamics of red blood cells in a circular microchannel Peer-reviewed

    R. Lima, M. Nakamura, T. Ishikawa, S. Tanaka, M. Takeda, Y. Imai, K. Tsubota, S. Wada, T. Yamaguchi

    COMPUTATIONAL VISION AND MEDICAL IMAGING PROCESSING 53-+ 2008

    Publisher: TAYLOR & FRANCIS LTD

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    The blood flow dynamics in microcirculation depends strongly on the motion, deformation and interaction of RBCs within the microvessel. This paper presents the application of a confocal micro-PTV system to track RBCs through a circular polydimethysiloxane (PDMS) microchannel. This technique, consists of a spinning disk confocal microscope, high speed camera and a diode-pumped solid state (DPSS) laser combined with a single particle tracking (SPT) method. By using this system detailed motions of individual RBCs were measured at a microscale level. Our results showed that this technique can provide detailed information about microscale disturbance effects caused by RBCs in flowing blood.

  469. Simulation of platelet adhesion and aggregation regulated by fibrinogen and von Willebrand factor Peer-reviewed

    Daisuke Mori, Koichiro Yano, Ken-ichi Tsubota, Takuji Ishikawa, Shigeo Wada, Takami Yamaguchi

    THROMBOSIS AND HAEMOSTASIS 99 (1) 108-115 2008/01

    Publisher: SCHATTAUER GMBH-VERLAG MEDIZIN NATURWISSENSCHAFTEN

    DOI: 10.1160/TH07-08-0490  

    ISSN:0340-6245

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    We propose a method to analyze platelet adhesion and aggregation computationally, taking into account the distinct properties of two plasma proteins, von Willebrand factor (vWF) and fibrinogen (Fbg). In this method, the hydrodynamic interactions between platelet particles under simple shear flow were simulated using Stokesian dynamics based on the additivity of velocities. The binding force between particles mediated by vWF and Fbg was modeled using the Voigt model. Two Voigt models with different properties were introduced to consider the distinct behaviors of vWF and Fbg. Our results qualitatively agreed with the general observation of a previous in-vitro experiment, thus demonstrating that the significant development of thrombus formation in height requires not only vWF, but also Fbg. This agreement of simulation and experimental results qualitatively validates our model and suggests that consideration of the distinct roles of vWF and Fbg is essential to investigate the physiological and pathophysiological mechanisms of thrombus formation using a computational approach.

  470. A Rule-Based Computational Study on the Early Progression of Intracranial Aneurysms Using Fluid-Structure Interaction: Comparison between Straight Model and Curved Model Peer-reviewed

    Yixiang Feng, Shigeo Wada, Takuji Ishikawa, Ken-Ichi Tsubota, Takami Yamaguchi

    Journal of Biomechanical Science and Engineering 3 (2) 124-137 2008

    DOI: 10.1299/jbse.3.124  

    ISSN:1880-9863

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    Study of the development of aneurysm is a difficult task due to lack of experimental and clinical data. The current study takes advantage of fluid-structure interaction (FSI) to simulate the formation and growth of aneurysms by focusing on the interplay between the wall shear stress, degeneration of the vessel wall, and the wall deformation. We construct numerical aneurysm models arisen from both straight and curved arteries, under the hypothesis that high local wall shear stress larger than a certain threshold value will lead to a linear decrease in the wall mechanical properties. In the straight model, the growth of aneurysm is small and only at the distal neck region, and the aneurysm stops growing after several steps. In contrast, in the curved model, the aneurysm continues to grow in height and width. Our computer simulation study shows that even if the wall shear stress inside an aneurysm is low, aneurysm development can occur due to degeneration of the wall distal and proximal to the aneurysm. Our study demonstrates the potential utility of rule-based numerical methods in the investigation of developmental biology of cardiovascular diseases. © 2008, The Japan Society of Mechanical Engineers. All rights reserved.

  471. Computational study on effect of red blood cells on primary thrombus formation Peer-reviewed

    Daisuke Mori, Koichiro Yano, Ken-ichi Tsubota, Takuji Ishikawa, Shigeo Wada, Takami Yamaguchi

    THROMBOSIS RESEARCH 123 (1) 114-121 2008

    Publisher: PERGAMON-ELSEVIER SCIENCE LTD

    DOI: 10.1016/j.thromres.2008.03.006  

    ISSN:0049-3848

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    The primary thrombus formation is a critical phenomenon both physiologically and pathologically. It has been seen that various mechanical factors are involved the regulation of primary thrombus formation through a series of physiological and biochemical processes, including blood flow and intercellular molecular bridges. However, it has not been fully understood how the existence of red blood cells contributes to the process of platelet thrombus formation. We computationally analyzed the motions of platelets in plasma layer above which red blood cells flow assuming a background simple shear flow of a shear rate of 1000 s(-1) using Stokesian dynamics. In the computation, fluid mechanical interactions between platelets and red blood cells were taken into account together with the binding forces via plasma proteins between two platelets and between a platelet and injured vessel wall. The process of the platelets aggregation was significantly dependent on whether red blood cells were present. When red blood cells were absent, the aggregate formed grew more vertically compared to the case with red blood cells. Conversely, when red blood cells were present, the aggregate spread more horizontally because the red blood cells constrained the vertical growth when the height of the aggregate reached the level of the red blood cells. Our results suggest that red blood cells mechanically play a significant role in primary thrombus formation, which accelerates the horizontal spread of the thrombus, and point out the necessity of considering the presence of red blood cells when investigating the mechanism of thrombus formation. (C) 2008 Elsevier Ltd. All rights reserved.

  472. Formation of Saccular Cerebral Aneurysms May Require Proliferation of the Arterial Wall: Computational Investigation Peer-reviewed

    Yuji Shimogonya, Takuji Ishikawa, Yohsuke Imai, Daisuke Mori, Noriaki Matsuki, Takami Yamaguchi

    Journal of Biomechanical Science and Engineering 3 (3) 431-442 2008

    DOI: 10.1299/jbse.3.431  

    ISSN:1880-9863

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    We have performed numerical simulations to examine saccular cerebral aneurysm formation at the outer curve of a bent artery. A U-shaped arterial geometry with torsion, which was modeled on part of the human internal carotid artery, has been employed. A new numerical model was proposed to take into account proliferation as well as degradation of the arterial wall. Proliferation of the arterial wall was modeled by surface area expansion in high wall shear stress region. Based on wall shear stress distribution on the artery, we have investigated aneurysm formation for the following three conditions: (a) strength degradation of the wall, (b) proliferation of the wall, and (c) both strength degradation and proliferation of the wall. A saccular aneurysm shape was not observed when considering only arterial wall degradation up to 90%. However, the saccular shape formed when proliferation of the arterial wall was also taken into consideration. The resultant shape was consistent with clinical observations. Our findings have suggested that a saccular aneurysm may not be formed by degradation of the arterial wall alone, but also require its proliferation. © 2008, The Japan Society of Mechanical Engineers. All rights reserved.

  473. Tracking of red blood cells in microchannel with stenosis by confocal micro PTV system Peer-reviewed

    H. Fujiwara, T. Ishikawa, R. Lima, Y. Imai, N. Matsuki, H. Kaji, D. Mori, M. Nishizawa, T. Yamaguchi

    Proc. 7th Int. Symp. Adv. Fluid Info. & 4th Int. Symp. Transdisciplinary Fluid Integr. 56-57 2007/12/01

  474. Blood flow in microchannel with stenosis measured by a confocal micro PTV system Peer-reviewed

    H. Fujiwara, T. Ishikawa, R. Lima, Y. Imai, N. Matsuki, H. Kaji, D. Mori, M. Nishizawa, T. Yamaguchi

    Proc. 3rd Tohoku-NUS Joint Symp. Nano-Biomed. Eng. in the East Asian-Pacific Rim Region 99-100 2007/12/01

  475. Development of respiration measurement system with conductive rubber for elderly home care Peer-reviewed

    M. Okubo, M. Kishimoto, Y. Imai, T. Ishikawa, T. Yamaguchi

    Proc. 3rd Tohoku-NUS Joint Symp. Nano-Biomed. Eng. in the East Asian-Pacific Rim Region 47-48 2007/12/01

  476. Modeling of malaria-infected red blood cell mechanics using a particle method Peer-reviewed

    H. Kondo, Y. Imai, K. Tsubota, T. Ishikawa, T. Yamaguchi

    Proc. APCOM'07 in conjunction with EPMESC XI CD-ROM MS22-4-2 2007/12/01

  477. Numerical simulation of cerebral aneurysm growth based on a hemodynamic hypothesis Peer-reviewed

    Y. Shimogonya, T. Ishikawa, Y. Imai, T. Yamaguchi

    Proc. APCOM'07 in conjunction with EPMESC XI CD-ROM MS22-3-3 2007/12/01

  478. Suspensions of swimming micro-organisms Peer-reviewed

    T. Ishikawa

    Proc. APCOM'07 in conjunction with EPMESC XI CD-ROM MS22-1-2 2007/12/01

  479. An AMR Method based on the IDO scheme for patient-specific pulmonary airflow simulation Peer-reviewed

    Y. Imai, T. Miki, T. Ishikawa, M. Nakamura, S. Wada, T. Yamaguchi

    Proc. APCOM'07 in conjunction with EPMESC XI CD-ROM MS7-1-3 2007/12/01

  480. Development of a wearable surveillance system using gait analysis Peer-reviewed

    Toshihiko Yoshida, Fumio Mizuno, Tomoaki Hayasaka, Kenichi Tsubota, Yousuke Imai, Takuji Ishikawa, Takami Yamaguchi

    TELEMEDICINE JOURNAL AND E-HEALTH 13 (6) 703-713 2007/12

    Publisher: MARY ANN LIEBERT INC

    DOI: 10.1089/tmj.2007.0015  

    ISSN:1530-5627

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    An aging society is a reality in developed countries. An aging population requires more health-care workers and facilities. To reduce this social problem, it is worthwhile to develop a wearable computer for elders or patients to watch over them. In this study, we developed a wearable computer, in which accelerometers were installed to detect variations of posture, falls, and gait disability. The advantages of this system include a designated database server in each patient's home, scalability and flexibility to adapt to patient's needs, and full patient access to their own information. As a first step, we adopted this system for healthy young volunteers with or without impediments to validate the system. The results show that this system can successfully detect variations in posture and falls. We also succeeded in real-time automatic gait analysis by using the Hampering Index. The present study gives useful knowledge for the development of a wearable computer to support the care of elders or other patients.

  481. CT Image-Based Respiratory Flow Simulation by using Cartesian Adaptive Mesh Refinement Method Peer-reviewed

    T. Miki, Y. Imai, M. Nakamura, T. Ishikawa, S. Wada, T. Yamaguchi

    Proc. Int. Conf. Adaptive Modeling & Simulation 166-169 2007/11/30

  482. A Cartesian Adaptive Mesh Refinement Method for Simulating Physiological Flows Peer-reviewed

    Y. Imai, T. Miki, T. Aoki, M. Nakamura, T. Ishikawa, S. Wada, T. Yamaguchi

    Proc. Int. Conf. Adaptive Modeling & Simulation 128-131 2007/11/30

  483. The role of near field interactions in the collective behaviour of model swimming micro-organisms Peer-reviewed

    T. Locsei, T. Ishikawa, T. J. Pedley

    Bulletin of the American Physical Society 52 245 2007/11/21

  484. The hydrodynamics of interactions between two swimming bacteria Peer-reviewed

    T. Ishikawa, G. Sekiya, Y. Imai, T. Yamaguchi

    Bulletin of the American Physical Society 52 245-246 2007/11/21

  485. Relaxation Time of Bottom-Heavy Squirmers in a Semi-Dilute Suspension Peer-reviewed

    T. Ishikawa, T. J. Pedley, T. Yamaguchi

    Proc. 3rd Asian Pacific Conf. Biomech. S227 2007/11/01

  486. Numerical Simulation of Malaria-Infected Blood Flow using a Particle Method Peer-reviewed

    H. Kondo, Y. Imai, K. Tsubota, T. Ishikawa, T. Yamaguchi

    Proc. 3rd Asian Pacific Conf. Biomech. S226 2007/11/01

  487. Computational Study of Platelet Thrombus Formation in a Blood Flow Peer-reviewed

    D. Mori, K. Yano, K. Tsubota, T. Ishikawa, S. Wada, T. Yamaguchi

    Proc. 3rd Asian Pacific Conf. Biomech. S225 2007/11/01

  488. Measurement of Respiration by a Hyper Diaper with Conductive Rubber Peer-reviewed

    M. Okubo, M. Kishimoto, S. Kim, Y. Imai, T. Ishikawa, T. Yamaguchi

    Proc. 3rd Asian Pacific Conf. Biomech. S206 2007/11/01

  489. Monitoring Physical and Mental Workloads by a Wearable Computer Peer-reviewed

    S. Kim, H. Nakamura, M. Kishimoto, Y. Imai, N. Matsuki, T. Ishikawa, T. Yamaguchi

    Proc. 3rd Asian Pacific Conf. Biomech. S103 2007/11/01

  490. Measurement of Multi-Red Blood Cells Interactions in Blood Flow by Confocal Micro-PTV Peer-reviewed

    R. Lima, T. Ishikawa, H. Fujiwara, M. Takeda, Y. Imai, K. Tsubota, N. Matsuki, S. Wada, T. Yamaguchi

    Proc. 3rd Asian Pacific Conf. Biomech. S92 2007/11/01

  491. Observation of the Blood Flow in Microchannel with Stenosis by Confocal-Micro-PIV Peer-reviewed

    H. Fujiwara, T. Ishikawa, R. Lima, H. Kaji, N. Matsuki, Y. Imai, M. Nishizawa, T. Yamaguchi

    Proc. 3rd Asian Pacific Conf. Biomech. S89 2007/11/01

  492. Development of a Wearable System for Monitoring Health Condition Peer-reviewed

    M. Kishimoto, T. Yoshida, H. Nakamura, M. Okubo, Y. Suzuki, S. Kim, T. Hayasaka, Y. Imai, K. Tsubota, T. Ishikawa, T. Yamaguchi

    Proc. 3rd Asian Pacific Conf. Biomech. S84 2007/11/01

  493. A Simulation Model for Cerebral Aneurysm Growth based on a Hemodynamic Hypothesis Peer-reviewed

    Y. Shimogonya, T. Ishikawa, Y. Imai, T. Yamaguchi

    Proc. 3rd Asian Pacific Conf. Biomech. S76 2007/11/01

  494. CFD Study on Mass Transport to Saccular Aneurysms at Arterial Bend Peer-reviewed

    Y. Imai, K. Sato, T. Ishikawa, A. Comerford, T. David, T. Yamaguchi

    Proc. 3rd Asian Pacific Conf. Biomech. S58 2007/11/01

  495. Orientational relaxation time of bottom-heavy squirmers in a semi-dilute suspension Peer-reviewed

    T. Ishikawa, T. J. Pedley, T. Yamaguchi

    JOURNAL OF THEORETICAL BIOLOGY 249 (2) 296-306 2007/11

    Publisher: ACADEMIC PRESS LTD ELSEVIER SCIENCE LTD

    DOI: 10.1016/j.jtbi.2007.07.033  

    ISSN:0022-5193

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    One of the important quantities to characterize unsteady behaviour of a cell suspension is the orientational relaxation time, which is the time scale for a micro-organism to re-orientate to its preferred direction from disorientated conditions. In this paper, a swimming micro-organism is modelled as a squirming sphere with prescribed tangential surface velocity, in which the centre of mass of the sphere is displaced from the geometric centre (bottom-heaviness). The orientational relaxation time of bottom-heavy squirmers in a suspension is investigated both analytically and numerically. The three-dimensional movement of 64 identical squirmers in a fluid otherwise at rest, contained in a cube with periodic boundary conditions, is dynamically computed, for random initial positions and orientations. The effects of volume fraction of squirmers, the bottom-heaviness and the squirming mode on the relaxation time are discussed. The results for a semi-dilute suspension show that both the mean stresslet strength and the orientational relaxation time decrease from those for a dilute suspension. We also observe a stress overshoot in some cases. The mechanism for this is different from that for a visco-elastic fluid, and is explained by the change with time of the orientation of squirmers. (C) 2007 Elsevier Ltd. All rights reserved.

  496. Properties of a Semi-dilute Suspension of Swimming Micro-organisms Peer-reviewed

    T. Ishikawa, T. Yamaguchi, T. J. Pedley

    Bio-mechanisms of Swimming and Flying, Springer-Verlag 17-28 2007/10/01

  497. CFD modeling of pulmonary airflow using IDO-AMR method Peer-reviewed

    Y. Imai, T. Miki, S. Wada, M. Nakamura, T. Ishikawa, T. Yamaguchi

    Proc. 4th Japan-Taiwan Workshop on Mech. & Aerospace Eng. 289-294 2007/10/01

  498. Properties of a suspension of swimming micro-organisms Peer-reviewed

    T. Ishikawa

    Proc. 4th Japan-Taiwan Workshop on Mech. & Aerospace Eng. 265-274 2007/10/01

  499. The rheology of a semi-dilute suspension of swimming model micro-organisms Peer-reviewed

    Takuji Ishikawa, T. J. Pedley

    JOURNAL OF FLUID MECHANICS 588 399-435 2007/10

    Publisher: CAMBRIDGE UNIV PRESS

    DOI: 10.1017/S0022112007007835  

    ISSN:0022-1120

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    The theological properties of a cell suspension may play an important role in the flow field generated by populations of swimming micro-organisms (e.g. in bioconvection). In this paper, a swimming micro-organism is modelled as a squirming sphere with prescribed tangential surface velocity, in which the centre of mass of the sphere may be displaced from the geometric centre (bottom-heaviness). Effects of inertia and Brownian motion are neglected, because real micro-organisms swim at very low Reynolds numbers but are too large for Brownian effects to be important. The three-dimensional movement of 64 identical squirmers in a simple shear flow field, contained in a cube with periodic boundary conditions, is dynamically computed, for random initial positions and orientations. The computation utilizes a database of pairwise interactions that has been constructed by the boundary element method. The restriction to pairwise additivity of forces is expected to be justified if the suspension is semi-dilute. The results for non-bottom-heavy squirmers show that the squirming does not have a direct influence on the apparent viscosity. However, it does change the probability density in configuration space, and thereby causes a slight decrease in the apparent viscosity at O(c(2)), where c is the volume fraction of spheres. In the case of bottom-heavy squirmers, on the other hand, the stresslet generated by the squirming motion directly contributes to the bulk stress at O(c), and the suspension shows strong non-Newtonian properties. When the background simple shear flow is directed vertically, the apparent viscosity of the semi-dilute suspension of bottom-heavy squirmers becomes smaller than that of inert spheres. When the shear flow is horizontal and varies with the vertical coordinate, on the other hand, the apparent viscosity becomes larger than that of inert spheres. In addition, significant normal stress differences appear for all relative orientations of gravity and the shear flow, in the case of bottom-heavy squirmers.

  500. Diffusion of swimming model micro-organisms in a semi-dilute suspension Peer-reviewed

    Takuji Ishikawa, T. J. Pedley

    JOURNAL OF FLUID MECHANICS 588 437-462 2007/10

    Publisher: CAMBRIDGE UNIV PRESS

    DOI: 10.1017/S0022112007007847  

    ISSN:0022-1120

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    The diffusive behaviour of swimming micro-organisms should be clarified in order to obtain a better continuum model for cell suspensions. In this paper, a swimming micro-organism is modelled as a squirming sphere with prescribed tangential surface velocity, in which the centre of mass of the sphere may be displaced from the geometric centre (bottom-heaviness). Effects of inertia and Brownian motion are neglected, because real micro-organisms swim at very low Reynolds numbers but are too large for Brownian effects to be important. The three-dimensional movement of 64 or 27 identical squirmers in a fluid otherwise at rest, contained in a cube with periodic boundary conditions, is dynamically computed, for random initial positions and orientations. The computation utilizes a database of pairwise interactions that has been constructed by the boundary element method. In the case of non-bottom-heavy squirmers, both the translational and the orientational spreading of squirmers is correctly described as a diffusive process over a sufficiently long time scale, even though all the movements of the squirmers were deterministically calculated. Scaling of the results on the assumption that the squirmer trajectories are unbiased random walks is shown to capture some but not all of the main features of the results. In the case of bottom-heavy squirmers, the diffusive behaviour in squirmers&apos; orientations can be described by a biased random walk model, but only when the effect of hydrodynamic interaction dominates that of the bottom-heaviness. The spreading of bottom-heavy squirmers in the horizontal directions show diffusive behaviour, and that in the vertical direction also does when the average upward velocity is subtracted. The rotational diffusivity in this case, at a volume fraction c = 0.1, is shown to be at least as large as that previously measured in very dilute populations of swimming algal cells (Chlamydomonas nivalis).

  501. Hydrodynamic interactions between two swimming bacteria Peer-reviewed

    T. Ishikawa, G. Sekiya, Y. Imai, T. Yamaguchi

    BIOPHYSICAL JOURNAL 93 (6) 2217-2225 2007/09

    Publisher: BIOPHYSICAL SOC

    DOI: 10.1529/biophysj.107.110254  

    ISSN:0006-3495

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    This article evaluates the hydrodynamic interactions between two swimming bacteria precisely. We assume that each bacterium is force free and torque free, with a Stokes flow field around it. The geometry of each bacterium is modeled as a spherical or spheroidal body with a single helical flagellum. The movements of two interacting bacteria in an infinite fluid otherwise at rest are computed using a boundary element method, and the trajectories of the two interacting bacteria and the stresslet are investigated. The results show that as the two bacteria approach each other, they change their orientations considerably in the near field. The bacteria always avoided each other; no stable pairwise swimming motion was observed in this study. The effects of the hydrodynamic interactions between two bacteria on the rheology and diffusivity of a semidilute bacterial suspension are discussed.

  502. A fluid-solid interactions study of the pulse wave velocity in uniform arteries Peer-reviewed

    T. Fukui, Y. Imai, K. Tsubota, T. Ishikawa, S. Wada, T. Yamaguchi

    Biomechanics at micro- and nanoscale levels, World Scientific 3 146-156 2007/06/01

  503. Numerical simulation of a suspension of swimming micro-organisms

    T. Ishikawa, T. J. Pedley, T. Yamaguchi

    Proc. 2007 Summer Bioengineering Conference CD-ROM 175256 2007/06/01

  504. Measurement of erythrocyte motions in microchannels by using a confocal micro-PTV system

    R. Lima, T. Ishikawa, M. Takeda, S. Tanaka, Y. Imai, K. Tsubota, S. Wada, T. Yamaguchi

    Proc. 2007 Summer Bioengineering Conference CD-ROM 175969 2007/06/01

  505. Wall shear stress change due to arterial wall stiffness; fluid-solid interaction study

    T. Fukui, K. H. Parker, Y. Imai, K. Tsubota, T. Ishikawa, S. Wada, T. Yamaguchi

    Proc. 2007 Summer Bioengineering Conference CD-ROM 176102 2007/06/01

  506. Image-based simulation of pulmonary airflow using multi-level voxel modeling

    Y. Imai, T. Miki, M. Nakamura, T. Ishikawa, S. Wada, T. Yamaguchi

    Proc. 2007 Summer Bioengineering Conference CD-ROM 176529 2007/06/01

  507. A simulation study on the growth of cerebral aneurysms

    Y. Shimogonya, Y. Imai, T. Ishikawa, T. Yamaguchi

    Proc. 2007 Summer Bioengineering Conference CD-ROM 176106 2007/06/01

  508. Effect of the red blood cells on the primary thrombus formation

    K. Yano, D. Mori, K. Tsubota, T. Ishikawa, S. Wada, T. Yamaguchi

    Proc. 2007 Summer Bioengineering Conference CD-ROM 176360 2007/06/01

  509. Effects of arterial geometry on inflow rate into cerebral aneurysms on curved arteries

    Y. Imai, K. Sato, T. Ishikawa, T. Yamaguchi

    Proc. 2007 Summer Bioengineering Conference CD-ROM 176556 2007/06/01

  510. Effect of the wall motion on arterial wall shear stress Peer-reviewed

    T. Fukui, K. H. Parker, Y. Imai, K. Tsubota, T. Ishikawa, S. Wada, T. Yamaguchi

    Journal of Biomechanical Science and Engineering 2 (2) 58-68 2007/05/01

    Publisher: The Japan Society of Mechanical Engineers

    DOI: 10.1299/jbse.2.58  

    ISSN:1880-9863

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    The distribution of wall shear stress (WSS) in arteries is affected by both blood and wall motion. Most studies have ignored wall motion by assuming that the artery wall is rigid. To investigate the influence of wall motion we have solved the coupled fluid-solid problem in a straight homogeneous tube. The inlet boundary condition of the tube was given as a pulse of velocity imposed at the inlet of the tube upon a steady flow of Reynolds number 1000. A commercial code (Radioss, Altair Engineering) was used to solve the fluid-solid interactions. Two kinds of waves are generated on the wall by the pulse imposed in the inlet flow; a wave of longitudinal motion of the wall (the longitudinal wave) and a wave of radial motion of the wall (the elastic wave). The ends of the vessel are assumed to be fixed which results in the reflection of both waves. The longitudinal wall motion reduces the relative speed of the blood, reducing WSS by up to 0.5 Pa. The largest effect of wall motion occurs when the longitudinal and elastic waves coincide, where the peak WSS is reduced by 1.0 Pa, which is a significant fraction of the observed WSS. Thus we can say that the effect of wall motion is important in considering physiological response of arterial wall to the blood flow.

  511. Analysis of destruction process of the primary thrombus under the influence of the blood flow Peer-reviewed

    K. Yano, D. Mori, K. Tsubota, T. Ishikawa, S. Wada, T. Yamaguchi

    Journal of Biomechanical Science and Engineering 2 (1) 34-44 2007/04

    Publisher: The Japan Society of Mechanical Engineers

    DOI: 10.1299/jbse.2.34  

    ISSN:1880-9863

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    Stokesian dynamics method based on the approximation of the additivity of velocities was employed to analyze the mechanical behavior of the primary thrombus under the blood flow. The mechanical interactions in the platelet-platelet aggregation and the platelet-surface adhesion via biological macromolecules such as von Willebrand factor and fibrinogen was modeled by the Voigt model. The process of the primary thrombus destruction was simulated under different levels of the mechanical interaction using the developed method. When the binding force was weak, which corresponds to the decline of the platelet function in the bleeding diseases, it was demonstrated that the platelets did not efficiently reside on the injured site of the vessel wall. The results show that our modeling can qualitatively demonstrate the effect of the mechanical interaction via adhesive macromolecules on the destruction process of the primary thrombus. Our modeling could be a powerful tool to better understand the physiological hemostatic mechanism as well as the pathology of the thrombosis and the bleeding disorders.

  512. 64チャンネルマルチスライスCTを用いた肺気道形態の計測

    三木 貴仁, 中村 匡徳, 須田 祐司, 田村 弦, 今井 陽介, 石川 拓司, 山口 隆美, 和田 成生

    呼吸 26 (2Suppl.) S7-S10 2007/02

    Publisher: (一社)呼吸研究

    ISSN:0286-9314

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    CT画像から形態を定量的に計測するためのアルゴリズムを確立すると共に、最新の医療用64チャンネルマルチスライスCT装置を用いて、気管から細部の気道までを撮影し、得られたCT画像から肺気道形態の計測を試みた。アルゴリズムを実際の気道形態計測に適用する際にはファントムを用い実験を行った。ファントムはアクリル製の板で、直径0.5〜4.5mmの穴を0.5mm間隔で開けたものを用いた。アルゴリズムを用いて穴の直径を求めたところ、直径1.0mm以上の穴については全ての穴において計測値が設計値を10%程度上回る結果となった。また0.5mmの穴についてはCT画像が不鮮明で穴直径を求めることができなかった。58歳男の肺について形態計測を行ったが今回の方法で第14世代迄の気道を抽出することができた。

  513. Numerical simulation of a low-hematocrit blood flow in a small artery with stenosis Peer-reviewed

    T. Ishikawa, N. Kawabata, Y. Imai, K. Tsubota, T. Yamaguchi

    Journal of Biomechanical Science and Engineering 2 (1) 12-22 2007/02/01

    Publisher: The Japan Society of Mechanical Engineers

    DOI: 10.1299/jbse.2.12  

    ISSN:1880-9863

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    The blood flow in a large artery is commonly analyzed by means of constitutive equations. However, it is not appropriate to use these equations for small arteries because of the heterogeneity of the blood. In this study, we use a bead-spring model for an erythrocyte to simulate a low-hematocrit blood flow in a small artery with a stenosis. The flow field is solved using Euler coordinates, whereas the motion of the erythrocyte is solved using Lagrangian coordinates (two-way coupling). The results show that the erythrocytes are considerably deformed around the stenosis and that the separated region downstream of the stenosis is weakened by the erythrocytes.

  514. A Fluid-Solid Interaction Study of the Pulse Wave Velocity in Uniform Arteries Peer-reviewed

    T. Fukui, Kim. H. Parker, Y. Imai, K. Tsubota, T. Ishikawa, S. Wada, T. Yamaguchi

    Proc. Final Symp. Tohoku University 21st Century of Excellence Program 919-927 2007/01/02

  515. Velocity Fields of Blood Flow in Microchannels Using a Confocal Micro-PIV System Peer-reviewed

    R. Lima, T. Ishikawa, S. Tanaka, M. Takeda, K. Tsubota, S. Wada, T. Yamaguchi

    Proc. Final Symp. Tohoku University 21st Century of Excellence Program 973-980 2007/01/02

  516. Computational biomechanics of blood flow in cardiovascular diseases Peer-reviewed

    T. Yamaguchi, T. Ishikawa, K. Tsubota, Y. Imai, D. Mori, N. Matsuki

    Biomechanics at Micro- and Nanoscale Levels 4 130-140 2007/01/01

    Publisher: World Scientific Publishing Co.

    DOI: 10.1142/9789812771322_0012  

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    Variations in both spatial and temporal scales must be considered to fully understand cardiovascular diseases. Given these considerations, we investigated the cardiovascular system from the micro- to macroscale using computational biomechanics. This paper presents our findings on mass transport in cerebral aneurysms, platelet aggregation in blood flow, and a particle method for computing microcirculation. Ultimately, these models will help to clarify the biological phenomena surrounding disease processes and will provide a framework for integrating future developments in understanding macro- and microscale biomechanics.

  517. Effect of Aneurysmal Geometry on the Distribution of ATP Concentration Peer-reviewed

    K. Sato, Y. Imai, T. Ishikawa, A. Comerford, T. David, T. Yamaguchi

    The 9th Int. Symp. Future Med. Eng. based on Bio-nanotech. 128-129 2007/01/01

  518. Tracking Red Blood Cells in a Circular PDMS Microchannel using a Confocal Micro-PIV System Peer-reviewed

    R. Lima, T. Ishikawa, S. Tanaka, M. Takeda, Y. Imai, K. Tsubota, S. Wada, T. Yamaguchi

    The 9th Int. Symp. Future Med. Eng. based on Bio-nanotech. 126-127 2007/01/01

  519. Numerical Simulation on the Growth of Saccular Aneurysm Peer-reviewed

    Y. Shimogonya, Y. Imai, T. Ishikawa, T. Yamaguchi

    The 9th Int. Symp. Future Med. Eng. based on Bio-nanotech. 94-95 2007/01/01

  520. Development of a wearable watch over system for patients home with an accelerometer Peer-reviewed

    T. Yoshida, H. Nakamura, M. Kishimoto, F. Mizuno, T. Hayasaka, K. Tsubota, Y. Imai, T. Ishikawa, T. Yamaguchi

    Proc. 2nd Tohoku-NUS Joint Symp. Future Nano-med. Bioeng. in the East Asian Region as the 8th Int. Symp. Future Med. Eng. Based on Bio-nanotech. 120-121 2006/12/01

  521. Numerical analysis of ATP transport in aneurysms Peer-reviewed

    K. Sato, Y. Imai, T. Ishikawa, A. Comerford, T. David, T. Yamaguchi

    Proc. 2nd Tohoku-NUS Joint Symp. Future Nano-med. Bioeng. in the East Asian Region as the 8th Int. Symp. Future Med. Eng. Based on Bio-nanotech. 118-119 2006/12/01

  522. Monitoring physical and mental workloads by wearable system for elderly home care Peer-reviewed

    H. Nakamura, T. Yoshida, Y. Imai, T. Ishikawa, T. Yamaguchi

    Proc. 2nd Tohoku-NUS Joint Symp. Future Nano-med. Bioeng. in the East Asian Region as the 8th Int. Symp. Future Med. Eng. Based on Bio-nanotech. 122-123 2006/12/01

  523. Development of a wearable system for an quantification measurment of human motions in daily life Peer-reviewed

    M. Kishimoto, H. Nakamura, T. Yoshida, F. Mizuno, T. Hayasaka, Y. Imai, K. Tsubta, T. Ishikawa, T. Yamaguchi

    Proc. 15th Int. Conf. Mechanics in Medicine and Biology 187-188 2006/12

  524. Computer simulation of effects of deformabilities of red blood cells on blood flow using particle method Peer-reviewed

    K. Tsubota, S. Wada, Y. Imai, T. Ishikawa, T. Yamaguchi

    Proc. 15th Int. Conf. Mechanics in Medicine and Biology 422-423 2006/12

  525. An adaptive mesh refinement method for CFD analysis of arterial blood flow Peer-reviewed

    Y. Imai, T. Aoki, T. Ishikawa, K. Tsubota, T. Yamaguchi

    Proc. 15th Int. Conf. Mechanics in Medicine and Biology 80-81 2006/12

  526. Numerinal simulation of a low Hematocrit blood flow in a small artery with stenosis Peer-reviewed

    T. Ishikawa, N. Kawabata, Y. Imai, K. Tsubota, T. Yamaguchi

    Proc. 15th Int. Conf. Mechanics in Medicine and Biology 420-421 2006/12

  527. Hydrodynamic interaction of two swimming model micro-organisms Peer-reviewed

    Takuji Ishikawa, M. P. Simmonds, T. J. Pedley

    JOURNAL OF FLUID MECHANICS 568 119-160 2006/12

    Publisher: CAMBRIDGE UNIV PRESS

    DOI: 10.1017/S0022112006002631  

    ISSN:0022-1120

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    In order to understand the rheological and transport properties of a suspension of swimming micro-organisms, it is necessary to analyse the fluid-dynamical interaction of pairs of such swimming cells. In this paper, a swimming micro-organism is modelled as a squirming sphere with prescribed tangential surface velocity, referred to as a squirmer. The centre of mass of the sphere may be displaced from the geometric centre (bottom-heaviness). The effects of inertia and Brownian motion are neglected, because real micro-organisms swim at very low Reynolds numbers but are too large for Brownian effects to be important. The interaction of two squirmers is calculated analytically for the limits of small and large separations and is also calculated numerically using a boundary-element method. The analytical and the numerical results for the translational-rotational velocities and for the stresslet of two squirmers correspond very well. We sought to generate a database for an interacting pair of squirmers from which one can easily predict the motion of a collection of squirmers. The behaviour of two interacting squirmers is discussed phenomenologically, too. The results for the trajectories of two squirmers show that first the squirmers attract each other, then they change their orientation dramatically when they are in near contact and finally they separate from each other. The effect of bottom-heaviness is considerable. Restricting the trajectories to two dimensions is shown to give misleading results. Some movies of interacting squirmers are available with the online version of the paper.

  528. A simple model for the diffusion of swimming model microorganisms

    T. Locsei, T. Ishikawa, T. J. Pedley

    Bulletin of the American Physical Society, DFD 51 (9) 54 2006/11

  529. Microstructure of concentrated suspensions of swimming model micro-organisms

    T. Ishikawa, T. Yamaguchi, T. J. Pedley

    Bulletin of the American Physical Society, DFD 51 (9) 53 2006/11

  530. Interaction of two swimming Paramecia Peer-reviewed

    Takuji Ishikawa, Masateru Hota

    JOURNAL OF EXPERIMENTAL BIOLOGY 209 (22) 4452-4463 2006/11

    Publisher: COMPANY OF BIOLOGISTS LTD

    DOI: 10.1242/jeb.02537  

    ISSN:0022-0949

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    The interaction between two swimming Paramecium caudatum was investigated experimentally. Cell motion was restricted between flat plates, and avoiding and escape reactions were observed, as well as hydrodynamic interactions. The results showed that changes in direction between two swimming cells were induced mainly by hydrodynamic forces and that the biological reaction was a minor factor. Numerical simulations were also performed using a boundary element method. P. caudatum was modelled as a rigid spheroid with surface tangential velocity measured by a particle image velocimetry (PIV) technique. Hydrodynamic interactions observed in the experiment agreed well with the numerical simulations, so we can conclude that the present cell model is appropriate for describing the motion of P. caudatum.

  531. From passive motion of capsules to active motion of cells Invited Peer-reviewed

    D. Barthes-Biesel, T. Yamaguchi, T. Ishikawa, E. Lac

    Journal of Biomechanical Science and Engineering 1 (1) 51-68 2006/10/01

    Publisher: The Japan Society of Mechanical Engineers

    DOI: 10.1299/jbse.1.51  

    ISSN:1880-9863

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    In the past three decades, there has been great progress in the mathematical modeling and computational methods for fluid mechanics of suspensions of micron-scale particles. In medical or biological applications, the particles can be very deformable, self propelled or both. Research on mathematical and computational methods for the modelling of suspensions of such particles is currently very active. In this review paper, we introduce some of the concepts that are used to analyse suspensions of either passive deformable particles or active locomotive particles. To simplify matters, we consider simple model particles that are initially spherical. In one case, the particle is a liquid droplet enclosed by a thin deformable membrane (a 'capsule') and is deformed by hydrodynamic forces. In the other case, the particle remains spherical but propels itself by means of a velocity wave on its surface. Athough the basic equations for locomotive spherical cells and for capsules are similar, the resulting suspension characteristics are quite different owing to the different boundary conditions on the surface of the particles.

  532. Computational Blood Flow Analysis-New Trends and Methods Invited Peer-reviewed

    T. Yamaguchi, T. Ishikawa, K. Tsubota, Y. Imai, M. Nakamura, T. Fukui

    Journal of Biomechanical Science and Engineering 1 (1) 29-50 2006/10/01

    Publisher: The Japan Society of Mechanical Engineers

    DOI: 10.1299/jbse.1.29  

    ISSN:1880-9863

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    Over the past few decades, a large number of novel numerical methods have been proposed to analyze blood flows and to understand the relationship between vascular diseases and hemodynamics. In this paper, we review recent computational fluid dynamics studies on macroscale hemodynamics such as blood flow in the heart and large arteries, microscale blood flows in small vessels in which blood is assumed to be a suspension of red blood cells in plasma, and single red blood cell motions in an induced flow field. The advantages and disadvantages of numerical methods are discussed, and current trends in these research fields are introduced.

  533. Velocity measurements of blood flow in a rectangular PDMS microchannel assessed by confocal micro-PIV system

    R. Lima, S. Wada, S. Tanaka, M. Takeda, K. Tsubota, T. Ishikawa, T. Yamaguchi

    IFMBE Proc. World Congress on Medical Physics and Biomedical Engineering 278-281 2006/09

  534. Hydrodynamic aggregation and diffusion in populations of model micro-organisms

    T. J. Pedley, T. Ishikawa

    J. Biomechanics 39 S349 2006/08

  535. Hydrodynamic interaction of two swimming Caudatum

    T. Ishikawa, M. Hota, T. J. Pedley

    J. Biomechanics 39 S349 2006/08

  536. Deformation of a capsule in a low Re number simple shear flow Peer-reviewed

    T. Ishikawa, K. Kamemoto, N. Kawabata

    Transactions of the Japan Society of Mechanical Enginees, B 72 1927-1934 2006/08/01

    DOI: 10.1299/kikaib.72.1927  

  537. Collective Motion of Swimming Model Micro-organisms in a Concentrated Suspension

    T. Ishikawa, T. J. Pedley

    Proc. 3rd Int. Symp. Aero Aqua Bio-mech. (CD-ROM) S04 2006/07

  538. Modelling populations of swimming micro-organisms

    T. J. Pedley, T. Ishikawa

    Oberwolfach Report (24) 31-32 2006/05

  539. Mass transport in pulsatile flow through asymmetric stenosis Peer-reviewed

    Takuji Ishikawa, Shuzo Oshima, Ryuichiro Yamane, Hiroshi Wada

    JSME International Journal, Series C: Mechanical Systems, Machine Elements and Manufacturing 44 (4) 1005-1012 2001/12

    DOI: 10.1299/jsmec.44.1005  

    ISSN:1344-7653

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    The characteristics of a pulsatile flow through stenosis are already well known, however, mass transport around stenosis is not yet well understood. In this study, mass transport in the pulsatile flow between flat plates with asymmetric stenosis is analyzed numerically. The effects of the pulsation and asymmetry of the stenosis on the mass transport are investigated. Flow pattern, concentration pattern and the distribution of the wall concentration are obtained. It is found that an asymmetry of the stenosis increases the wall concentration downstream of the stenosis. In the asymmetric stenosis case, the wall concentration downstream of the stenosis recovers at a lower pulsatile frequency than the symmetric stenosis case.

  540. Proposal of a deformable erythrocyte model and numerical analysis of shear flow of blood Peer-reviewed

    T Ishikawa, N Kawabata, M Tachibana

    JSME INTERNATIONAL JOURNAL SERIES C-MECHANICAL SYSTEMS MACHINE ELEMENTS AND MANUFACTURING 44 (4) 964-971 2001/12

    Publisher: JAPAN SOC MECHANICAL ENGINEERS

    ISSN:1344-7653

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    Blood flow in a large artery is commonly analyzed by means of constitutive equations. However, it is not appropriate to use constitutive equations for Small arteries because of the heterogeneity of the blood. In this paper, a new method to model an erythrocyte using beads and springs is proposed as an alternative way to analyze the blood flow, which is called a deformable erythrocyte model. The behavior of a single erythrocyte is computed under a constant shear field. The rotating attitude of the erythrocyte model and rheological property of the blood are discussed. The results show that the deformable erythrocyte model can appropriately Simulate the tank tread motion of ail erythrocyte and the shear thinning, property under high shear-rate conditions. It is, therefore, considered that the present model is able to consistently express the blood flow characteristics.

  541. Vortex enhancement in blood flow through stenosed and locally expanded tubes Peer-reviewed

    Takuji Ishikawa, Shuzo Oshima, Ryuichiro Yamane

    Fluid Dynamics Research 26 (1) 35-52 2000/01

    Publisher: Elsevier Science B.V.

    DOI: 10.1016/S0169-5983(98)00047-1  

    ISSN:0169-5983

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    It is well known that fluid dynamical phenomena in arterial blood flow can play an important role in arterial diseases. Periodic blood flow through stenosed and locally expanded tubes is analyzed numerically. The fluid is assumed to be non-Newtonian and incompressible, and the flow is assumed to be periodic in time and axisymmetric. It is found that the vortex downstream of stenosis or expansion becomes strongest at a certain frequency of pulsation. This phenomenon is called vortex enhancement in this paper. The flow pattern, separated region and the distributions of pressure and shear stress on the wall are obtained. The results show that the vortex enhancement occurs in both tubes. The vortex enhancement occurs where the difference between the adverse pressure and the friction on the wall is a maximum.

  542. Modeling and numerical simulation of axisymmetric stenosis growth in an artery Peer-reviewed

    Takuji Ishikawa, Shuzo Oshima, Ryiuchiro Yamane

    Nihon Kikai Gakkai Ronbunshu, B Hen/Transactions of the Japan Society of Mechanical Engineers, Part B 65 (637) 2982-2989 1999

    Publisher: Japan Society of Mechanical Engineers

    DOI: 10.1299/kikaib.65.2982  

    ISSN:0387-5016

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    There are several hypotheses as to why stenosis appears in an artery. However, there is no accepted theory as yet. In this study, axisy mmetric stenosis growth in an artery is modeled based on three hypotheses (1) high wall shear stress theory (2) low wall shear stress theory (3) oscillatory shear index theory. In each hypothesis, stenosis growth is simulated numerically. Flow-is assumed to be periodic, incompressible and axisymmetric. Non-Newtonian viscosity of blood and movement of arterial wall are considered. Flow pattern, concentration pattern and distribution of mass flux on the wall are computed. By using these results, stenosis growth process is obtained. It is found that the stenosis growth process based on the high wall shear stress theory is consistent with the clinical case. However, stenosis does not grow so much in the case of the low wall shear stress theory and the oscillatory shear index theory.

  543. Resonance of vortex in pulsatile flow through asymmetric stenosis Peer-reviewed

    Takuji Ishikawa, Shuzo Oshima, Ryuichiro Yamane

    Nihon Kikai Gakkai Ronbunshu, B Hen/Transactions of the Japan Society of Mechanical Engineers, Part B 65 (639) 3546-3553 1999

    Publisher: Japan Society of Mechanical Engineers

    DOI: 10.1299/kikaib.65.3546  

    ISSN:0387-5016

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    It is well known that fluid dynamical phenomena in arterial blood flow can play an important role in arterial diseases. Flow between flat plates with asymmetric stenosis is analyzed numerically. The fluid is assumed to be Newtonian and incompressible, and the flow is assumed to be periodic in time. It is found that the vortex downstream of asymmetric stenosis becomes strongest at a certain frequency of pulsation. This phenomenon is called vortex resonance in this paper. The flow pattern, the vortex strength and the distributions of wall shear stress are obtained. The results show that the resonance frequency changes with wall configuration and Reynolds number. The vortex resonance occurs where the difference between the adverse pressure and the friction on the wall is maximum.

Show all ︎Show first 5

Misc. 153

  1. Collision of two deformable torque swimmers

    Hitomu Matsui, Toshihiro Omori, Takuji Ishikawa

    72nd Annual Meeting of the APS Division of Fluid Dynamics P31.00009 2019/11

  2. How do colonial micro-algae swim towards light?

    Helene De Maleprade, Frederic Moisy, Takuji Ishikawa, Raymond E. Goldstein

    72nd Annual Meeting of the APS Division of Fluid Dynamics H31.00003 2019/11

  3. Pump Function of C. elegans Pharynx in Highly Viscous Environments

    Yuki Suzuki, Kenji Kikuchi, Keiko Numayama-Tsuruta, Takuji Ishikawa

    72nd Annual Meeting of the APS Division of Fluid Dynamics G29.00004 2019/11

  4. Mixing and pumping functions in a zebrafish larval intestine

    Kenji Kikuchi, Hyeongtak Noh, Keiko Numayama-Tsuruta, Takuji Ishikawa

    72nd Annual Meeting of the APS Division of Fluid Dynamics G29.00003 2019/11

  5. Harnessing low Reynolds number flow for net migration: Locomotion of a deformable microcapsule by random fluid forces

    Takuji Ishikawa, Takeru Morita, Toshihiro Omori, Yohei Nakayama, Shoichi Toyabe

    72nd Annual Meeting of the APS Division of Fluid Dynamics C35.00008 2019/11

  6. Towards the rheology of a concentrated array of spherical squirmers

    Tim Pedley, Takuji Ishikawa, Douglas Brumley

    72nd Annual Meeting of the APS Division of Fluid Dynamics C32.00003 2019/11

  7. Numerical Simulation of Hydrodynamic Interaction Between Swimming Spermatozoa

    Nanami Taketoshi, Toshihiro Omori, Takuji Ishikawa

    10th Asian-Pacific Conference on Biomechanics PO02 2019/11

  8. Numerical Simulation of a Droplet Propelled by Collective Swimming of Microorganisms

    Zhihan Huang, Toshihiro Omori, Takuji Ishikawa

    10th Asian-Pacific Conference on Biomechanics S1-1 2019/11

  9. Inflamed Intestinal Flow in Zebrafish Larva

    Masahiro Takahashi, K. Numayama-Tsuruta, Kenji Kikuchi, Takuji Ishikawa

    10th Asian-Pacific Conference on Biomechanics S1-4 2019/11

  10. On Transport of Yeasts

    Atul Srivastava, Kenji Kikuchi, Takuji Ishikawa

    10th Asian-Pacific Conference on Biomechanics S1-3 2019/11

  11. Pumping Function for a Fresh-water Sponge

    S. Koyama, K. Kikuchi, K. Numayama-Tsuruta, T. Ishikawa

    16th International Conference on Fluid Dynsmics OS8-10 2019/11

  12. Simulation of a Biofilm-Formation in a Microfluidic Channel

    H. Kitamura , T. Omori, T. Ishikawa

    16th International Conference on Fluid Dynsmics OS11-6 2019/11

  13. High Viscous Fluid Flow in C. elegans Pharynx

    Y. Suzuki, K. Kikuchi, K. Numayama-Tsuruta, T. Ishikawa

    16th International Conference on Fluid Dynsmics OS11-4 2019/11

  14. Enhancement of Transdermal Drug Delivery by Rotational Stimulation Device

    Y. Kurosawa, K. Kikuchi, K. Numayama-Tsuruta, T. Ishikawa

    16th International Conference on Fluid Dynsmics OS9-15 2019/11

  15. Micro-capsule swimmer controlled by flow oscillations

    T. Morita, T. Omori, T. Ishikawa

    Bulletin of the American Physical Society, DFD 2018 63 (13) 540 2018/11

  16. Hydrodynamics of ciliate swimming revealed by individual ciliary motions

    H. Ito, T. Omori, T. Ishikawa

    Bulletin of the American Physical Society, DFD 2018 63 (13) 341 2018/11

  17. Flow-induced transport of a membrane protein on vesicle surface

    K. Nakamura, T. Omori, T. Ishikawa

    Bulletin of the American Physical Society, DFD 2018 63 (13) 205 2018/11

  18. Drug Permeation Measurement through the Skin by using a Two-Photon Laser Induced Fluorescent Microscopy Peer-reviewed

    Kenji Kikuchi, Shunsuke Shigeta, Keiko Tsuruta-Numayama, Takuji Ishikawa

    8th International Conference on Fluid Mechanics (ICFM8) S10BM0-04 2018/09

  19. FLUID-STRUCTURE INTERACTIONS OF NODAL CILIA AXONEME Peer-reviewed

    Toshihiro Omori, Hiroto Sugai, Yohsuke Imai, Takuji Ishikawa

    8th International Conference on Fluid Mechanics (ICFM8) S10BM0-04 2018/09

  20. A NUMERICAL SIMULATION OFSWIMMING SPERMATOZOA Peer-reviewed

    N. Taketoshi, T. Omori, T. Ishikawa

    8th International Conference on Fluid Mechanics (ICFM8) S10BM0-02 2018/09

  21. Behavior of motile unicellular alga flowing in a microchannel Peer-reviewed

    Cheng-Hsi Chuang, Kenji Kikuchi, Azusa Kage, Takuji Ishikawa

    8th International Conference on Fluid Mechanics (ICFM8) S10BM0-01 2018/09

  22. Locomotion mechanism of microcapsele using flow oscillation

    Takeru Morita, Toshihiro Omori, Takuji Ishikawa

    The Seven International Symposium on Aero Aqua Bio-mechanisms ISABMEC 2018 44 2018/09

  23. Gut Bacterial Flow in Zebrafish Larva

    Masahiro Takahashi, Kenji Kikuchi, Keiko Numayama-Tsuruta, Takuji Ishikawa

    26 2018/08

  24. Spatial heterogeneity of bacterial flora in the intestine of zebrafish larvae

    Jinyou Yang, Yuji Shimogonya, Takuji Ishikawa

    8th World Congress of Biomechanics P2051 2018/07

  25. Computational study of the nodal flow with a small number of cilia: comparison of mechanosensing and vesicle transport hypotheses

    Toshihiro Omori, Kyosuke Shinohara, Hiroshi Hamada, Takuji Ishikawa

    8th World Congress of Biomechanics O0636 2018/07

  26. Biomechanics can provide a new perspective on microbiology Invited

    Takuji Ishikawa

    8th World Congress of Biomechanics Plen04 2018/07

  27. FILTRATION FLOW BY CHOANOFLAGELLATE CHAMBERS OF FRESH-WATER SPONGES

    K. Kikuchi, H. Maleprade, R. E. Goldstein, T. Ishikawa

    18th International Symposium on Flow Visualization 11.1.1 2018/06

  28. Anomalous swimming of a ciliary microorganism adjacent to wall

    Takuya Ohmura, Yukinori Nishigami, Junichi Manabe, Takuji Ishikawa, Masatoshi Ichikawa

    APS March Meeting 2018, Abstract K46.00001 2018/03

  29. 「細胞スケールの流れ」の研究動向

    石川拓司

    日本機械学会誌 120 (1182) 26-31 2017/05/05

  30. 胃内部の固体粒子挙動の数値計算

    石田駿一, 今井陽介, 宮川泰明, 石川拓司

    バイオエンジニアリング講演会講演論文集(CD-ROM) 29th 2017

    ISSN:2424-2829

  31. 1C46 Numerical simulation of a swimming ciliate near a water-air or a water-wall interface

    MANABE Junichi, OMORI Toshihiro, IMAI Yohsuke, ISHIKAWA Takuji

    2016 (28) "1C46-1"-"1C46-5" 2016/01/09

    Publisher: The Japan Society of Mechanical Engineers

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    Swimming behavior of microorganism near an interface is important to understand how to prevent bio-film formation, which can be a cause of medical instrument pollution. Recently, we found that a ciliate can be trapped at a water-air interface, though swims away from a water-wall interface. We conducted numerical simulation of swimming microorganism near an interface from hydrodynamic perspective, to reveal the entrapment mechanism. By mimicking microorganism shape in detail, our microorganism model reproduced entrapment phenomena for the first time in the world. We concluded that shape of a ciliate dominates the entrapment phenomena.

  32. 1E11 Numerical simulation of cell adhesion in microchannels

    TAKEISHI Naoki, IMAI Yohsuke, YAMAGUCHI Takami, Kamm Roger D., ISHIKAWA Takuji

    2016 (28) "1E11-1"-"1E11-5" 2016/01/09

    Publisher: The Japan Society of Mechanical Engineers

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    We numerically investigate the velocity of an adherent cell in various sizes of microchannels. The velocity drastically decreases as decreasing the size of microchannels. When the channel size becomes smaller, the motion of the adherent cell changes from a "rolling motion" to a "bullet motion", where the cell rotates on side wall in rolling motion, while the cell adhere its circular arc to the wall in bullet motion. Larger adhesion force is generated in rear parts of rolling cell, and existed bonds experience rupturing with higher probability because of slip bond. Because cell cannot move forward unless the ligand-receptor bonds in rear parts rupture, frequent rupturing allows the rolling cell to move faster than the cell exhibiting bullet motion. As getting smaller in channel diameter, the surface area attached to the wall is larger and then the number of ligand-receptor bonds is larger for smaller microchannels, resulting in a lower velocity. Our numerical model allows us to investigate the effect of various parameters on adherent cell velocity.

  33. 1C45 A Numerical Simulation of Sperm Cell Locomotion in Shear Flow

    OMORI Toshihiro, ISHIKAWA Takuji

    2016 (28) "1C45-1"-"1C45-3" 2016/01/09

    Publisher: The Japan Society of Mechanical Engineers

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    A sperm cell is a flagellated cell and it can swim in a fluid by beating flagellum. Locomotion of a sperm cell is strongly affected by surrounding fluid flow, and recently rheotaxis of sperm cells was found experimentally. Fluid mechanics then becomes a subject of growing importance in sperm motility. In this study, we numerically investigate sperm cell behavior in shear flow near a plane wall to quantitatively understand how fluid mechanics affects on swimming of sperm cell. Due to the small size of sperm cells, inertia effects of fluid motion can be neglected and we assume Stokes flow around the cell. Flow field is then expressed by boundary integral equation and which is solved by a boundary element method. As a result, the sperm cell shows reorient to upstream and keeps on swimming against the fluid flow. This result suggests that fluid mechanics plays a key role in navigation of sperm cells towards the ovum, which is located upstream in the oviduct.

  34. 195 Numerical simulation of a sperm cell swimming in a viscoelastic fluid

    SHIMOMURA Eisaku, OMORI Toshihiro, IMAI Yhosuke, ISHIKAWA Takuji

    2016 (51) 187-188 2016

    Publisher: The Japan Society of Mechanical Engineers

  35. 197 Measurement of the behavior of cancer cells cultivated on a collagen gel

    Iwasaki Yuwa, Imai Yohsuke, Kikuchi Kenji, Numayama-Tsuruta Keiko, Shigeta Shunsuke, Ishikawa Takuji

    The Proceedings of Conference of Tohoku Branch 2016 (0) 191-192 2016

    Publisher: The Japan Society of Mechanical Engineers

    DOI: 10.1299/jsmeth.2016.51.191  

  36. 201 Real Time Visualization of Intestinal Peristalsis of the Zebrafish

    NOH Hyeongtak, KIKUCHI Kenji, NUMAYAMA Keiko, ISHIKAWA Takuji

    The Proceedings of Conference of Tohoku Branch 2016 (0) 199-200 2016

    Publisher: The Japan Society of Mechanical Engineers

    DOI: 10.1299/jsmeth.2016.51.199  

  37. PS8-14 Visualization of intestinal peristalsis of mosquito midgut by using micro X-ray imaging(PS8: Poster Short Presentation VIII,Poster Session)

    Kikuchi Kenji, Imai Yohsuke, Numayama-Tsuruta Keiko, Yamaguchi Takami, Ishikawa Takuji

    Proceedings of the ... Asian Pacific Conference on Biomechanics : emerging science and technology in biomechanics 2015 (8) 365-365 2015/09/16

    Publisher: The Japan Society of Mechanical Engineers

  38. PS1-9 Noninvasive Measurement of Drug Permeation in the Skin(PS1: Poster Short Presentation I,Poster Session)

    Shigeta Shunsuke, Kikuchi Kenji, Numayama Keiko, Ishikawa Takuji

    Proceedings of the ... Asian Pacific Conference on Biomechanics : emerging science and technology in biomechanics 2015 (8) 230-230 2015/09/16

    Publisher: The Japan Society of Mechanical Engineers

  39. 循環器のバイオメカニクス

    石川拓司

    日本機械学会誌 118 14 2015/08/01

  40. 微小生物流れ

    石川拓司

    日本機械学会誌 118 31 2015/08/01

  41. クラミドモナスの鞭毛は上向きトルク発生に寄与する Invited

    鹿毛あずさ, 菊地謙次, 石川拓司

    京都大学数理解析研究所講究録 1940 110-111 2015/04

  42. 1A15 A numerical simulation of rolling and adhesion of red blood cells infected by malaria

    ICHIKAWA Yuki, IMAI Yohsuke, MATSUNAGA Daiki, NIX Stephanie, ISHIKAWA Takuji, YAMAGUCHI Takami

    2015 (27) 11-12 2015/01/08

    Publisher: The Japan Society of Mechanical Engineers

  43. 1A16 Numerical Simulation of the Nodal Ciliary Motion Driven by the Dynein Motor Protein

    SUGAI Hiroto, Omori Toshihiro, IMAI Yohsuke, ISHIKAWA Takuji

    2015 (27) 13-14 2015/01/08

    Publisher: The Japan Society of Mechanical Engineers

  44. 1A12 Behavior of tracer particles in capsule suspensions : the effect of size of tracer particles

    ITO Hiroki, IMAI Yohsuke, MATSUNAGA Daiki, Omori Toshihiro, YAMAGUCHI Takami, ISHIKAWA Takuji

    2015 (27) 5-6 2015/01/08

    Publisher: The Japan Society of Mechanical Engineers

  45. 胃内のせん断応力の数値解析

    宮川泰明, 今井陽介, 石田駿一, 山口隆美, 石川拓司

    バイオエンジニアリング講演会講演論文集 27th 2015

    ISSN:1348-2920

  46. 胃内容物攪拌の数値計算:胃壁の運動の影響

    宮川泰明, 今井陽介, 石田駿一, 山口隆美, 石川拓司

    計算工学講演会論文集(CD-ROM) 20 2015

    ISSN:1342-145X

  47. 22pBL-8 Synchronized oscillation in a model of three nodal cilia with hydrodynamic interaction

    Okumura K, Nishikawa S, Omori T, Ishikawa T, Takamatsu A

    Meeting Abstracts of the Physical Society of Japan 70 (0) 3030-3030 2015

    Publisher: The Physical Society of Japan

    DOI: 10.11316/jpsgaiyo.70.1.0_3030  

    ISSN:2189-079X

  48. 2B35 Effect of aeration on the distribution of Chlamydomonas

    NONAKA Yuki, KIKUCHI Kenji, NUMAYAMA-TSURUTA Keiko, KAGE Azusa, UENO Hironori, ISHIKAWA Takuji

    The Proceedings of the Bioengineering Conference Annual Meeting of BED/JSME 2015 (0) 371-372 2015

    Publisher: The Japan Society of Mechanical Engineers

    DOI: 10.1299/jsmebio.2015.27.371  

  49. 2B41 Effect of Rheological Properties on Ciliary motion and Flow in the airway

    HAGA Tomofumi, KIKUCHI Kenji, UENO Hironori, NUMAYAMA Keiko, YAMAGUCHI Takami, ISHIKAWA Takuji

    The Proceedings of the Bioengineering Conference Annual Meeting of BED/JSME 2015 (0) 373-374 2015

    Publisher: The Japan Society of Mechanical Engineers

    DOI: 10.1299/jsmebio.2015.27.373  

  50. 1316 Flow on a ciliary respiratory epithelium

    HAGA Tomofumi, KIKUCHI Kenji, UENO Hironori, NUMAYAMA Keiko, YAMAGUCHI Takami, ISHIKAWA Takuji

    The Proceedings of the Fluids engineering conference 2015 (0) _1316-1_-_1316-2_ 2015

    Publisher: The Japan Society of Mechanical Engineers

    DOI: 10.1299/jsmefed.2015._1316-1_  

    ISSN:1348-0251

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    We have studied experimentally about the flow on a ciliary respiratory epithelium with the relation between a viscosity of mucus and a generated flow velocity using μPTV measurement. We used a fresh dissected mouse respiratory epithelium for our experiment, and observed a flow on it by using a confocal microscopy for tracing micro fluorescent particles, which dispersed in the mucus on the ciliary cells. The frequency of ciliary motions and velocity of mucus were measured in several cases with different viscosity of mucus. The driven force for generating ciliary flow has a non-linearity with an increasing of viscosity. Our findings would play a medical role to clarify a mechanism of mucus flow on a ciliary respiratory epithelium with its viscous changing.

  51. J0260202 Dispersion of red blood cells in a micro channel

    CHENG-HSI Chuang, KIKUCHI Kenji, NUMAYAMA Keiko, YAMAGUCHI Takami, ISHIKAWA Takuji

    The Proceedings of Mechanical Engineering Congress, Japan 2015 (0) _J0260202--_J0260202- 2015

    Publisher: The Japan Society of Mechanical Engineers

    DOI: 10.1299/jsmemecj.2015._J0260202-  

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    We have been focused on the dispersion of cells in micro channel flow, especially red blood cells (RBCs). When RBCs are dispersed in a micro channel with a Y-shape junction, the dispersion of cells would occur from denser to thinner direction according with concentration of cells. It is regarding to clarify the dispersion phenomena in micro channel for designing of lab-on-a-chip applications. The detailed mechanism of cell dispersion, however, has not been fully clarified yet. We performed the quantitative dispersion measurement in the Y-shape micro channel, in which two layers with and without RBCs flow in parallel, and investigated the effects of flow rates and hematocrit. Our results suggest that the dispersion in micro channel would be more dominant than Brownian diffusion, and depends on the hematocrit and the flow rate. These findings provide us useful information on mass transport in cell suspensions.

  52. A104 Behavior of Yorticella in shear flow

    YOSHIDA Naoto, KIKUCHI Kenji, KAGE Azusa, NUMAYAMA Keiko, NAGAI Moeto, ISHIKAWA Takuji

    The Proceedings of the JSME Conference on Frontiers in Bioengineering 2015 (0) 7-8 2015

    Publisher: The Japan Society of Mechanical Engineers

    DOI: 10.1299/jsmebiofro.2015.26.7  

    ISSN:1348-2939

  53. A108 Drug concentration measurement in a skin using two-photon microscopy

    SHIGETA Shunsuke, KIKUCHI Kenji, NUMAYAMA Keiko, ISHIKAWA Takuji

    The Proceedings of the JSME Conference on Frontiers in Bioengineering 2015 (0) 15-16 2015

    Publisher: The Japan Society of Mechanical Engineers

    DOI: 10.1299/jsmebiofro.2015.26.15  

    ISSN:1348-2939

  54. A112 Numerical Simulation of the Ciliary Motion Driven by the Motor Protein

    SUGAI Hiroto, OMORI Toshihiro, IMAI Yohsuke, ISHIKAWA Takuji

    Proceedings of the ... JSME Conference on Frontiers in Bioengineering 2014 (25) 21-22 2014/10/02

    Publisher: The Japan Society of Mechanical Engineers

    ISSN:1348-2939

  55. A111 A numerical simulation of a microorganism behavior near an interface

    Manabe Junichi, Kyouya Kouhei, Omori Toshihiro, Imai Yohsuke, Ishikawa Takuji

    Proceedings of the ... JSME Conference on Frontiers in Bioengineering 2014 (25) 19-20 2014/10/02

    Publisher: The Japan Society of Mechanical Engineers

    ISSN:1348-2939

  56. 動物のからだの左右を決める回転繊毛間の流体相互作用 (生物流体力学における流れ構造の解析と役割)

    高松 敦子, 石川 拓司, 篠原 恭介, 濱田 博司

    数理解析研究所講究録 1900 97-104 2014/06

    Publisher: 京都大学

    ISSN:1880-2818

  57. Bottom-up Approaches in Biological Flow Studies

    ISHIKAWA Takuji

    2014 (89) "8-5"-"8-8" 2014/03/18

    Publisher: The Japan Society of Mechanical Engineers

  58. 27aAD-4 Decoherence in an isolated system and the disappearance of quantum multiverse

    Ishikawa Takuji

    Meeting abstracts of the Physical Society of Japan 69 (1) 285-285 2014/03/05

    Publisher: The Physical Society of Japan (JPS)

    ISSN:1342-8349

  59. 2G34 A simulation of nutrient uptake in a suspension of squirmers

    KAJIKI Shunsuke, IMAI Yohsuke, Yamaguchi Takami, Ishikawa Takuji

    2014 (26) 539-540 2014/01/10

    Publisher: The Japan Society of Mechanical Engineers

  60. 1G43 A numerical simulation of the cytoadhesion of malaria-infected red blood cells using a ligand-receptor interaction model

    AMI Akihisa, IMAI Yohsuke, ISHIKAWA Takuji, YAMAGUCHI Takami

    2014 (26) 245-246 2014/01/10

    Publisher: The Japan Society of Mechanical Engineers

  61. 1G44 A numerical analysis of the behavior of cancer cells related to hematogenous metastasis in microvasculature

    TAKEISHI Naoki, IMAI Yohsuke, YAMAGUCHI Takami, ISHIKAWA Takuji

    2014 (26) 247-248 2014/01/10

    Publisher: The Japan Society of Mechanical Engineers

  62. 1G33 A numerical simulation of motion of food in the stomach

    MIYAGAWA Taimei, IMAI Yohsuke, YAMAGUCHI Takami, ISHIKAWA Takuji

    2014 (26) 235-236 2014/01/10

    Publisher: The Japan Society of Mechanical Engineers

  63. 2E15 Numerical analysis of a red blood cell flowing through a micro flow channel

    OMORI Toshihiro, ISHIKAWA Takuji, IMAI Yohsuke, YAMAGUCHI Takami

    2014 (26) 439-440 2014/01/10

    Publisher: The Japan Society of Mechanical Engineers

  64. 2E22 Mechanism of the non-linear response of viscosity to volume fraction in dense capsule suspension

    MATSUNAGA Daiki, IMAI Yohsuke, YAMAGUCHI Takami, ISHIKAWA Takuji

    2014 (26) 445-446 2014/01/10

    Publisher: The Japan Society of Mechanical Engineers

  65. 2E21 A numerical simulation of capsule behavior in a near-wall shear flow

    Nix Stephanie, IMAI Yohsuke, MATSUNAGA Daiki, YAMAGUCHI Takami, ISHIKAWA Takuji

    2014 (26) 443-444 2014/01/10

    Publisher: The Japan Society of Mechanical Engineers

  66. J0220101 Effect of aeration on the distribution of micro algae cells

    NONAKA Yuki, UENO Hironori, NUMAYAMA-TSURUTA Keiko, KIKUCHI Kenji, ISHIKAWA Takuji

    The Proceedings of Mechanical Engineering Congress, Japan 2014 (0) _J0220101--_J0220101- 2014

    Publisher: The Japan Society of Mechanical Engineers

    DOI: 10.1299/jsmemecj.2014._J0220101-  

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    When culturing microalgae, we often use aeration for mixing the culture fluid. However, it is not clear how microalgae and aeration interact each other. In order to understand transport phenomena in a microalgae suspension, it is important to clarify the distribution of cells in a container. In this study, we visualized the distribution of microalgae in a tube container with aeration. In the case without aeration, we observed the bioconvection with chaotic pattern. In the case with aeration, on the other hand, we observed cells aggregated in specific regions.

  67. J027014 Simulation of nutrient uptake by swimming microorganisms in a suspension

    KAJIKI Shunsuke, IMAI Yohsuke, YAMAGUCHI Takami, ISHIKAWA Takuji

    Mechanical Engineering Congress, Japan 2013 "J027014-1"-"J027014-4" 2013/09/08

    Publisher: The Japan Society of Mechanical Engineers

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    Little is known about the mass transport in microbial suspension in previous studies. The aim of this study is to analyze the effect of the swimming motion on the nutrient uptake. We modeled a microorganism as a squirmer and calculated its locomotion by boundary element method . Moreover we simulated the nutrient uptake by tracking nutrient particles. The results show that the nutrient uptake is strongly affected by the swimming mode of a microorganism.

  68. J027011 A Numerical Simulation of Collective Swimming of Microorganisms

    KYOYA Kohei, MATSUNAGA Daiki, IMAI Yohsuke, YAMAGUCHI Takami, ISHIKAWA Takuji

    Mechanical Engineering Congress, Japan 2013 "J027011-1"-"J027011-4" 2013/09/08

    Publisher: The Japan Society of Mechanical Engineers

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    Microorganisms play a vital role in many biological, medical and engineering phenomena. Some recent research efforts have demonstrated the importance of biomechanics in understanding certain aspects of microorganism behaviors such as locomotion and collective motions of cells. Previous studies had problems of high computational load in simulating many-body interaction of swimmers. In this study, we propose a boundary element method, based on the double-layer representation, for calculating interactions of many-body swimmers in Stokes flow regime. We use Graphic Processing Unit (GPU) to speed up the computation. We then analyze interactions of 100 swimmers.

  69. 2B14 Rheological analysis of capsule suspension using boundary element method

    MATSUNAGA Daiki, IMAI Yohsuke, ISHIKAWA Takuji, Yamaguchi Takami

    2013 (25) 299-300 2013/01/08

    Publisher: The Japan Society of Mechanical Engineers

  70. 2E02 Analysis of Red Blood Cell Behavior in a Narrow Tube

    HOSAKA Haruki, OMORI Toshihiro, IMAI Yohsuke, ISHIKAWA Takuji, YAMAGUCHI Takami

    2013 (25) 387-388 2013/01/08

    Publisher: The Japan Society of Mechanical Engineers

  71. 2B19 A numerical analysis of the cell migration in microcirculatory blood flow

    TAKEISHI Naoki, IMAI Yohsuke, NAKAAKI Keita, ISHIKAWA Takuji, Yamaguchi Takami

    2013 (25) 307-308 2013/01/08

    Publisher: The Japan Society of Mechanical Engineers

  72. 1D04 Numerical analysis of swimming model microorganisms by GPU

    KYOYA Kohei, MATSUNAGA Daiki, IMAI Yohsuke, YAMAGUCHI Takami, ISHIKAWA Takuji

    2013 (25) 117-118 2013/01/08

    Publisher: The Japan Society of Mechanical Engineers

  73. 1D01 3D-PTV measurement of the phototactic movement of algae in the shear flow

    MAEDA Tatsuyuki, ISHIKAWA Takuji, UENO Hironori, NUMAYAMA-TSURUTA Keiko, IMAI Yosuke, YAMAGUCHI Takami

    The Proceedings of the Bioengineering Conference Annual Meeting of BED/JSME 2013 (0) 111-112 2013

    Publisher: The Japan Society of Mechanical Engineers

    DOI: 10.1299/jsmebio.2013.25.111  

  74. 3E15 Measurement of ciliary flow generated on the surface of tracheal lumen

    KIYOTA Koki, UENO Hironori, ISHIKAWA Takuji, NUMAYAMA Keiko, IMAI Yohsuke, OMORI Toshihiro, YAMAGUCHI Takami

    The Proceedings of the Bioengineering Conference Annual Meeting of BED/JSME 2013 (0) 609-610 2013

    Publisher: The Japan Society of Mechanical Engineers

    DOI: 10.1299/jsmebio.2013.25.609  

  75. J027013 Effect of aeration on the bio-convection of micro algae cells

    NONAKA Yuki, UENO Hironori, NUMAYAMA Keiko, OMORI Toshihiro, IMAI Yohsuke, YAMAGUCHI Takami, ISHIKAWA Takuji

    The Proceedings of Mechanical Engineering Congress, Japan 2013 (0) _J027013-1-_J027013-4 2013

    Publisher: The Japan Society of Mechanical Engineers

    DOI: 10.1299/jsmemecj.2013._J027013-1  

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    Bioconvection patterns are often observed in microalgae suspensions of randomly, but on average upwardly, swimming microalgae which are little denser than water. When we culture microalgae in the laboratory, we usually add aeration for mixing the culture fluid and supplying oxygen and carbon dioxide. However, the effect of aeration on the bioconvection pattern and the transport phenomena in the suspension is unclear. In this study, we investigated bioconvection pattern in a suspension of Chlamydomonas reinhardtii under the condition with aeration. Bioconvection pattern in a cylindrical container was visualized by red illumination, and white light for phototaxis could be added from above. Small bubbles were injected by a needle connected to a syringe. Observation of bioconvection patterns of microalgae suspension with aeration showed three kinds of flow patterns depending on the bubble flow rate. When there was no bubble flow, conventional bioconvection was dominant. When flow rate was low, observed pattern in the cylindrical container was split into two flow regions, where the bioconvection and the bubble flow were dominant respectively. When flow rate was high, bubble flow became dominant and no clear bioconvection was observed. Such changes in the bioconvection pattern have not been reported before. These findings are important to understand the transport phenomena in algae suspensions in engineering settings.

  76. C107 Bioconvection of micro algae cells under an aeration condition

    NONAKA Yuki, UENO Hirinori, NUMAYAMA Keiko, OMORI Toshihiro, IMAI Yosuke, YAMAGUCHI Takami, ISHIKAWA Takuji

    The Proceedings of the JSME Conference on Frontiers in Bioengineering 2013 (0) 45-46 2013

    Publisher: The Japan Society of Mechanical Engineers

    DOI: 10.1299/jsmebiofro.2013.24.45  

    ISSN:1348-2939

  77. 103 Aggregation structure of algae in forced circulation bubbly flow

    NONAKA Yuki, UENO Hironori, NUMAYAMA-TSURUTA Keiko, OMORI Toshihiro, IMAI Yosuke, YAMAGUCHI Takami, ISHIKAWA Takuji

    The Proceedings of Conference of Tohoku Branch 2013 (0) 10-11 2013

    Publisher: The Japan Society of Mechanical Engineers

    DOI: 10.1299/jsmeth.2013.48.10  

  78. 計算生体力学シミュレーションによるミクロからマクロスケールの生体機能の解析

    山口 隆美, 今井 陽介, 水野 文雄, 大森 俊宏, 上野 裕則, 沼山 恵子, 石川 拓司

    バイオメカニズム学術講演会予稿集 33回 33-34 2012/12

    Publisher: バイオメカニズム学会

  79. 806 Numerical simulation of dynamics of solid particles in the stomach

    MIYAGAWA Taimei, IMAI Yohsuke, ISHIKAWA Takuji, YAMAGUCHI Takami

    The Computational Mechanics Conference 2012 (25) 9-10 2012/10/06

    Publisher: The Japan Society of Mechanical Engineers

    ISSN:1348-026X

  80. 807 Numerical analysis of swimming model microorganisms by a boundary element method based on the double-layer representation

    KYOYA Kohei, MATSUNAGA Daiki, IMAI Yohsuke, YAMAGUCHI Takami, ISHIKAWA Takuji

    The Computational Mechanics Conference 2012 (25) 11-12 2012/10/06

    Publisher: The Japan Society of Mechanical Engineers

    ISSN:1348-026X

  81. 803 Numerical simulation of adhesive phenomena of Pf-T-IRBC and the endothelial cells

    AMI Akihisa, IMAI Yohsuke, NAKAAKI Keita, ISHIKAWA Takuji, YAMAGUCHI Takami

    The Computational Mechanics Conference 2012 (25) 3-4 2012/10/06

    Publisher: The Japan Society of Mechanical Engineers

    ISSN:1348-026X

  82. ストークス流れ中の非球形カプセルの配向現象

    石川拓司, 大森俊宏, 今井陽介, 山口隆美

    京都大学数理解析研究所講究録 (1808) 121-126 2012/09/01

  83. 111 Simulation of mass absorption of swimming model microorganisms by a boundary element method

    KAJIKI Shunsuke, MATSUNAGA Daiki, IMAI Yohsuke, YAMAGUCHI Takami, ISHIKAWA Takuji

    2012 (47) 28-29 2012/03/13

    Publisher: The Japan Society of Mechanical Engineers

  84. 110 Numerical analysis of swimming model microorganisms by a boundary element method

    Kyoya Kohei, MATSUNAGA Daiki, IMAI Yohsuke, YAMAGUCHI Takami, ISHIKAWA Takuji

    2012 (47) 26-27 2012/03/13

    Publisher: The Japan Society of Mechanical Engineers

  85. 113 Numerical analysis of adhesive phenomena of malaria-infected red blood cells

    AMI Akihisa, IMAI Yohsuke, NAKAAKI Keita, ISHIKAWA Takuji, YAMAGUCHI Takami

    2012 (47) 32-33 2012/03/13

    Publisher: The Japan Society of Mechanical Engineers

  86. 109 Analysis of Red Blood Ce11 Deformation in Flow Field Using a Boundary Element Method

    Hosaka Haruki, Ishikawa Takuji, Omori Toshihiro, Imai Yohsuke, Yamaguchi Takami

    2012 (47) 24-25 2012/03/13

    Publisher: The Japan Society of Mechanical Engineers

  87. 212 Development of a numerical model for blood flow in microvessels using GPGPU computing

    Takeishi Naoki, IMAI Yohsuke, NAKAAKI Keita, ISHIKAWA Takuji, YAMAGUCHI Takami

    2012 (47) 230-231 2012/03/13

    Publisher: The Japan Society of Mechanical Engineers

  88. 第5回青葉工学振興会賞 細胞レベルから構築した微生物サスペンジョン力学の創生

    石川拓司

    翠巒 (28) 3 2012/03/02

  89. 生命現象の予測を目指して

    石川拓司

    青葉工業会ニュース (50) 17 2012/03/02

  90. 細胞レベルから構築した微生物サスペンジョン力学による藻類の分布予測モデルの革新

    石川拓司

    東北大学機械系同窓会ニュース (17) 2 2012/03/01

  91. 8F34 Development of a numerical model of microcirculatory blood flow in malaria infection based on GPU

    NAKAAKI Keita, IMAI Yohsuke, ISHIKAWA Takuji, Lim Chwee Teck, YAMAGUCHI Takami

    2012 (24) "8F34-1"-"8F34-2" 2012/01/06

    Publisher: The Japan Society of Mechanical Engineers

  92. 8F13 Development of a GPU computing platform for accurate simulations of large-scale cellular flow

    IMAI Yohsuke, MATSUNAGA Daiki, ISHIKAWA Takuji, YAMAGUCHI Takami

    2012 (24) "8F13-1"-"8F13-2" 2012/01/06

    Publisher: The Japan Society of Mechanical Engineers

  93. 7H22 A fast simulation of pulmonary airflow and inhaled particles by GPU

    IMAI Yohsuke, MIKI Takahito, ISHIKAWA Takuji, YAMAGUCHI Takami

    2012 (24) "7H22-1"-"7H22-2" 2012/01/06

    Publisher: The Japan Society of Mechanical Engineers

  94. 固体成分を含む胃内容物の攪拌の数値シミュレーション

    宮川泰明, 今井陽介, 小林生馬, 石川拓司, 山口隆美

    日本機械学会東北支部総会・講演会講演論文集 47th 2012

  95. 胃内部の固体粒子運動の数値シミュレーション

    宮川泰明, 今井陽介, 石川拓司, 山口隆美

    日本機械学会計算力学講演会論文集(CD-ROM) 25th 2012

    ISSN:2424-2799

  96. 2306 A numerical computation on gastric mixing

    KOBAYASHI Ikuma, IMAI Yohsuke, ISHIDA Shunichi, ISHIKAWA Takuji, YAMAGUCHI Takami

    The Computational Mechanics Conference 2011 (24) 642-643 2011/10/08

    Publisher: The Japan Society of Mechanical Engineers

    ISSN:1348-026X

  97. 2305 Numerical simulation of swallowing based on videofluorography

    ISHIDA Shunichi, IMAI Yohsuke, ISHIKAWA Takuji, KINJO Aki, MATSUKI Noriaki, YAMAGUCHI Takami

    The Computational Mechanics Conference 2011 (24) 639-641 2011/10/08

    Publisher: The Japan Society of Mechanical Engineers

    ISSN:1348-026X

  98. 2308 A fast simulation of capsule motion in flow by GPU computing

    IMAI Yohsuke, MATSUNAGA Daiki, ISHIKAWA Takuji, YAMAGUCHI Takami

    The Computational Mechanics Conference 2011 (24) 646-647 2011/10/08

    Publisher: The Japan Society of Mechanical Engineers

    ISSN:1348-026X

  99. 2307 Development of GPU simulation of microcirculatory blood flow

    NAKAAKI Keita, IMAI Yohsuke, ISHIKAWA Takuji, Lim Chwee Teck, YAMAGUCHI Takami

    The Computational Mechanics Conference 2011 (24) 644-645 2011/10/08

    Publisher: The Japan Society of Mechanical Engineers

    ISSN:1348-026X

  100. B112 Development of GPU computing method for capsule suspension

    MATSUNAGA Daiki, IMAI Yohsuke, OMORI Toshihiro, MIKI Takahito, ISHIKAWA Takuji, YAMAGUCHI Takami

    Proceedings of the ... JSME Conference on Frontiers in Bioengineering 2011 (22) 61-62 2011/10/06

    Publisher: The Japan Society of Mechanical Engineers

    ISSN:1348-2939

  101. Preface : For the “Joint Issue of JSME (Japan Society of Mechanical Engineers) and KSB (Korean Society of Biomechanics)”

    S. Park, K. Rhee, T. Ishikawa

    Journal of Biomechanical Science and Engineering 6 in press 2011/07

  102. Preface : For the “Subject Issue on Biofluid and Biothermal Engineering”

    T. Ishikawa

    Journal of Biomechanical Science and Engineering 6 63 2011/04

  103. 184 Numerical simulation of red blood cell flow in micro vessels : effects of endothelial cell geometry

    FUJIWARA Masaki, IMAI Yohsuke, NAKAAKI Keita, ISHIKAWA Takuji, YAMAGUCHI Takami

    2011 (46) 170-171 2011/03/15

    Publisher: The Japan Society of Mechanical Engineers

  104. 9J-07 Analysis of cancer cell membrane protein movement by confocal PTV system

    YOSHIMOTO Takefumi, ISHIKAWA Takuji, NUMAYAMA Keiko, MATSUKI Noriaki, TANAKA Tatsuya, UENO Hironori, IMAI Yohsuke, YAMAGUCHI Takami

    The Proceedings of the Bioengineering Conference Annual Meeting of BED/JSME 2010 (0) 487-488 2011

    Publisher: The Japan Society of Mechanical Engineers

    DOI: 10.1299/jsmebio.2010.23.487  

  105. 187 Flow measurement of bacterial suspensions in a tube by a confocal micro-PIV system

    MAEDA Tatsuyuki, ISHIKAWA Takuji, NUMAYAMA Keiko, IMAI Yosuke, UENO Hironori, YAMAGUCHI Takami

    The Proceedings of Conference of Tohoku Branch 2011 (0) 176-177 2011

    Publisher: The Japan Society of Mechanical Engineers

    DOI: 10.1299/jsmeth.2011.46.176  

  106. 流れを見る ― 細胞周りの流れの共焦点マイクロPIV計測 ―

    石川拓司

    生物の科学 遺伝 64 78-84 2010/11

  107. 論文・論説賞:「次世代医療関連産業中核人材育成のための実践的教育システム」の開発と実証研究

    山野真裕, 松木範明, 沼山恵子, 武田元博, 早坂智明, 石川拓司, 山口隆美

    工学教育 58 21-22 2010/11

  108. 21pEC-7 Suspension Dynamics of swimming microorganisms

    Ishikawa Takuji

    Meeting abstracts of the Physical Society of Japan 65 (1) 305-305 2010/03/01

    Publisher: The Physical Society of Japan (JPS)

    ISSN:1342-8349

  109. Particle-Based Methods for Multiscale Modeling of Blood Flow in the Circulation and in Devices: Challenges and Future Directions Peer-reviewed

    Takami Yamaguchi, Takuji Ishikawa, Y. Imai, N. Matsuki, Mikhail Xenos, Yuefan Deng, Danny Bluestein

    ANNALS OF BIOMEDICAL ENGINEERING 38 (3) 1225-1235 2010/03

    Publisher: SPRINGER

    DOI: 10.1007/s10439-010-9904-x  

    ISSN:0090-6964

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    A major computational challenge for a multiscale modeling is the coupling of disparate length and timescales between molecular mechanics and macroscopic transport, spanning the spatial and temporal scales characterizing the complex processes taking place in flow-induced blood clotting. Flow and pressure effects on a cell-like platelet can be well represented by a continuum mechanics model down to the order of the micrometer level. However, the molecular effects of adhesion/aggregation bonds are on the order of nanometer. A successful multiscale model of platelet response to flow stresses in devices and the ensuing clotting responses should be able to characterize the clotting reactions and their interactions with the flow. This paper attempts to describe a few of the computational methods that were developed in recent years and became available to researchers in the field. They differ from traditional approaches that dominate the field by expanding on prevailing continuum-based approaches, or by completely departing from them, yielding an expanding toolkit that may facilitate further elucidation of the underlying mechanisms of blood flow and the cellular response to it. We offer a paradigm shift by adopting a multidisciplinary approach with fluid dynamics simulations coupled to biophysical and biochemical transport.

  110. B210 Development of a micro fluidic device to sort circulating tumor cells from a blood sample

    TANAKA Tatsuya, ISHIKAWA Takuji, MATSUKI Noriaki, IMAI Yohsuke, UENO Hironori, NUMAYAMA-TSURUTA Keiko, YAMAGUCHI Takami

    The Proceedings of the JSME Conference on Frontiers in Bioengineering 2010 (0) 105-106 2010

    Publisher: The Japan Society of Mechanical Engineers

    DOI: 10.1299/jsmebiofro.2010.21.105  

    ISSN:1348-2939

  111. 1409 Shear-induced fluid-tracer diffusion in a semidilute suspension of spheres

    Ishikawa Takuji, Yamaguchi Takami

    Fluids engineering conference ... 2009 443-444 2009/11/06

    Publisher: The Japan Society of Mechanical Engineers

    ISSN:1348-2882

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    We calculated tracer diffusion in a sheared suspension of non-Brownian rigid spheres and propose a new numerical method based on a boundary element method and Stokesian dynamics method. We present details of the numerical method and examine the accuracy of the method. The limitation of semi-diluteness is due to the accuracy of tracer velocity calculation. The results show that the diffusivity of fluid tracers is greater than that of suspended spheres in the semi-dilute regime. The diffusivity of velocity gradient direction is about threefold greater than that in the vorticity direction. Simple scaling demonstrates that the diffusivity of fluid tracers increases with the square of the volume fraction of spheres in the semi-dilute regime, which is confirmed numerically.

  112. 変形機構を有する室内飛行船の開発

    広瀬量平, 今井陽介, 石川拓司, 山口隆美

    ブイヤント航空 37 81-88 2009/10

  113. 2201 Biomechanics of suspensions of micro-organisms

    Ishikawa Takuji

    The Computational Mechanics Conference 2007 (20) 407-408 2007/11/25

    Publisher: The Japan Society of Mechanical Engineers

    ISSN:1348-026X

  114. 303 Application of a High-Order AMR Method to Pulmonary Airflow Simulations

    IMAI Yohsuke, MIKI Takahito, ISHIKAWA Takuji, NAKAMURA Masanori, WADA Shigeo, YAMAGUCHI Takami

    The Computational Mechanics Conference 2007 (20) 583-584 2007/11/25

    Publisher: The Japan Society of Mechanical Engineers

    ISSN:1348-026X

  115. 瀬口賞を受賞して

    石川拓司

    Bioengineering News 36 17 2007/09/01

  116. 微生物の濃厚溶液の数値シミュレーション

    石川拓司

    計算数理工学レビュー 2007-2 41-46 2007/09/01

  117. Preface : Special Issue on Cardiovascular Flow

    T. Yamaguchi, T. Ishikawa

    Journal of Biomechanical Science and Engineering 2 45 2007/05/01

  118. 27pSB-14 Study of Quantum Decoherence in a finite system : Three Schrodinger cats and the Nuclear collective motion

    ISHIKAWA Takuji

    Meeting abstracts of the Physical Society of Japan 62 (1) 47-47 2007/02/28

    Publisher: The Physical Society of Japan (JPS)

    ISSN:1342-8349

  119. 331 Meso-scale structure in a concentrated suspension of micro-organisms

    Ishikawa Takuji, Pedley T.J., Imai Yohsuke, Tsubota Ken-ichi, Yamaguchi Takami

    2006 (19) 318-319 2007/01/06

    Publisher: The Japan Society of Mechanical Engineers

  120. Interference of Fire Smoke between Successive Tunnels with a Snow-Shed

    Kawabata Nobuyoshi, Sano Akinori, Kikumoto Tomoki, Ishikawa Takuji, Sato Tadao, Kanou Tatuo

    Transactions of the Society of Heating,Air-conditioning and Sanitary Engineers of Japan 29 (94) 61-68 2004

    Publisher: 公益社団法人 空気調和・衛生工学会

    DOI: 10.18948/shase.29.94_61  

    ISSN:0385-275X

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    When a fire accident occurs in the upstream tunnel of successive tunnels connected by a Snow-Shed, it is necessary to control the ventilation so that damage does not expand by smoke flowing downstream. We analyze this phenomenon by means of a three-dimensional simulator using Large Eddy Simulation to examine the interference between successive tunnels, and defined the interference rate I as the ratio of smoke densities in successive tunnels. From comparisons between simulation results and experimental results we confirmed that the simulations have reasonable accuracy. In this way, the rate of interference of fire smoke between the two tunnels was almost in agreement. Many simulation results carried out under various conditions confirmed that the interference rate is governed by the Froude Number, the ratio of longitudinal ventilation velocities of the two tunnels, the dimensionless distance between the tunnels, and the inclination of the Snow-Shed. Each parameter was examined for its influence on the interference rate. Finally we derived the evaluation formula of the interference rate.

  121. Numerical Simulation of Mixing Process of Gaseous Suppressant

    Nobuyoshi Kawabata, Takuji Ishikawa, Yusuke Naito, Youichiro Matsumoto, Naoshi Saito, Takashi Tsuruda

    Nippon Kikai Gakkai Ronbunshu, B Hen/Transactions of the Japan Society of Mechanical Engineers, Part B 69 (688) 2569-2576 2003

    Publisher: Japan Society of Mechanical Engineers

    DOI: 10.1299/kikaib.69.2569  

    ISSN:0387-5016

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    It is important for a fire suppression system to keep the target concentration in all regions of a protected room. In this study, the effects of aspect ratio of the protected region, position and area of the pressure relief port, area of an obstacle in the protected region and the number of nozzles on the mixing process of gaseous suppressant are investigated by large eddy simulation, Besides, the evaluation method of the mixing condition is discussed. The results show that the gaseous suppressant is insufficiently mixed when the aspect ratio of the protected region is large and that the mixing condition can be evaluated by the ratio of the target concentration attainment.

  122. Secondary Flow of Viscoelastic Fluid due to a Rotating Disc Enclosed in a Cylindrical Casing

    FUJIMOTO Masahiro, FUJITA Katushi, ISHIKAWA Takuji, KAWABATA Nobuyoshi

    The Proceedings of Conference of Hokuriku-Shinetsu Branch 2003 (0) 95-96 2003

    Publisher: The Japan Society of Mechanical Engineers

  123. Microscopic Observation of Polymer Solution in Pipe Flow by Freeze-Drying Method

    FUJITA Katsushi, ISHIKAWA Takuji, KAWABATA Nobuyoshi, HASHIMOTO Ryu, BABA Takaaki

    The Proceedings of the Fluids engineering conference 2003 (0) 172-172 2003

    Publisher: The Japan Society of Mechanical Engineers

    ISSN:1348-2882

  124. Numerical analysis of poiseuille flow of polymeric liquid by means of a bead-spring macro model

    Takuji Ishikawa, Nobuyoshi Kawabata, Hirohito Shimizu, Katsushi Fujita

    Nippon Kikai Gakkai Ronbunshu, B Hen/Transactions of the Japan Society of Mechanical Engineers, Part B 68 (676) 3266-3272 2002

    Publisher: Japan Society of Mechanical Engineers

    DOI: 10.1299/kikaib.68.3266  

    ISSN:0387-5016

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    Bead-spring macro model is proposed as a new method to analyze a viscoelastic flow, The tetrahedral structure of beads and springs models a gathering of intertwined polymer chains, and the interaction between gatherings is considered. Poiseuille flow of polymeric liquid is computed simultaneously with the behavior of the bead-spring structure, The numerical results are compared with the experimental results. The results show that the bead-spring macro model can consistently express rheological properties of polymeric liquid such as non-Newtonian viscosity and normal stress differences. Besides, the present model can easily explain the flow field and the stress tensor in terms of the macro model condition. It is found that the present model can consistently simulate a Poiseuille flow, which is a flow field with various shear rates and with walls.

  125. Simulation of Blood Flow in a Small Artery with Stenosis by means of DEM

    ISIKAWA Takuji, KAWABATA Nobuyoshi, TACHIBANA Motoyoshi

    The proceedings of the JSME annual meeting 2002 (0) 93-94 2002

    Publisher: The Japan Society of Mechanical Engineers

    DOI: 10.1299/jsmemecjo.2002.6.0_93  

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    We have proposed a new method to model an erythrocyte by using drag points and springs as an altanative way to analyze a blood flow. In this paper, a blood flow in a small artery with stenosis is simulated by means of DEM. It is found that erythrocyte is strongly deformed around the stenosis and that the vortex downstream of stenosis weakened by erythrocytes.

  126. Influence of the Obstacle on the Backlayering Characteristic of the Thermal Plume in a Tunnel

    HAYASHI Takumi, KAWABATA Nobuyoshi, ISHIKAWA Takuji, MATSUMOTO Tetsuharu

    The Proceedings of Conference of Hokuriku-Shinetsu Branch 2002 (0) 83-84 2002

    Publisher: The Japan Society of Mechanical Engineers

  127. Influence of the obstacle near the tunnel ceiling gives to the back layering characteristic of the thermal plume

    MATSUMOTO Tetsuharu, KAWABATA Nobuyoshi, ISHIKAWA Takuji, OKUGAWA Shingou

    The Proceedings of Conference of Hokuriku-Shinetsu Branch 2002 (0) 81-82 2002

    Publisher: The Japan Society of Mechanical Engineers

  128. Characteristics of Fire Fume in the Tunnel

    SHIOJIMA Ken, KAWABATA Nobuyoshi, ISHIKAWA Takuji

    The Proceedings of Conference of Hokuriku-Shinetsu Branch 2002 (0) 87-88 2002

    Publisher: The Japan Society of Mechanical Engineers

  129. Poiseuille Flow of Viscoelastic Fluids by Bead-Spring MacroModel

    Shimizu Hirohito, ISHIKAWA Takuji, KAWABATA Nubuyoshi, fujita Katsusi

    The Proceedings of Conference of Hokuriku-Shinetsu Branch 2002 (0) 95-96 2002

    Publisher: The Japan Society of Mechanical Engineers

  130. Evaluation of critical velocity employed to prevent the backlayering of thermal fume during tunnel fires

    Qian Wang, Nobuyoshi Kawabata, Takuji Ishikawa

    Nihon Kikai Gakkai Ronbunshu, B Hen/Transactions of the Japan Society of Mechanical Engineers, Part B 67 (656) 911-918 2001

    Publisher: Japan Society of Mechanical Engineers

    DOI: 10.1299/kikaib.67.911  

    ISSN:0387-5016

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    In this paper characteristics of backlayering of thermal fumes induced by emergency fires in tunnels is studied. The critical velocity used to prevent the thermal fume and smoke from backlayering upwind is firstly evaluated by this study using 3 dimensional LES turbulence model. Simulation result shows that under low heat release rate of fire, the critical velocity increases linearly when heat release rate increases, but this dependent relation will become weak under high heat release rate. Result also shows a supercritical velocity valued 2.5-2.7 m/s exists, which agrees to the conventional experimental studies.

  131. Numerical analysis of blood flow under the oscillatory shear field by means of a bead-spring-damper Model

    T. Ishikawa, N. Kawabata, M. Tachibana

    Nihon Kikai Gakkai Ronbunshu, B Hen/Transactions of the Japan Society of Mechanical Engineers, Part B 67 (661) 2180-2187 2001

    Publisher: Japan Society of Mechanical Engineers

    DOI: 10.1299/kikaib.67.2180  

    ISSN:0387-5016

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    The blood flow in large arteries is commonly analyzed by means of the constitutive equations. However, it is not appropriate to use constitutive equations for small arteries because of the heterogeneity of the blood. In this paper, a new method to model an erythrocyte by using beads, springs and dampers is proposed as an alternative to analyze the blood flow. The behavior of a single erythrocyte is computed under an oscillatory shear field. The real and imaginary part of dynamic viscosity, dynamic modulus and normal stress difference are discussed. The results show that the bead-spring-damper model appropriately can express the dynamic characteristics of blood. It is therefore considered that the bead-spring-damper erythrocyte model is able to consistently express blood flow without using constitutive equations.

  132. 1B12 Proposal of Simulation Method for a Blood Flow by means of a Deformable Erythrcyte Model

    ISIKAWA Takuji, KAWABATA Nobuyoshi, TACHIBANA Motoyoshi

    Proceedings of the JSME Bioengineering Conference and Seminar 2001 (0) 47-48 2001

    Publisher: The Japan Society of Mechanical Engineers

    DOI: 10.1299/jsmebs.2001.12.0_47  

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    It is not appropriate to use constitutive equations for a blood now in a small artery because of the heterogeneity of the blood. In this paper, a new method to model an erythrocyte by using drag points and springs is proposed as an altanative way to analyze the blood flow. The progression process of this method and advantages are briefly dicribed. Finally, future view of this method is mentioned.

  133. K-1034 Backlayering Velocity of the Thermal Plume Induced by Tunnel Fires

    ISHIKAWA Masao, KAWABATA Nobuyoshi, ISHIKAWA Takuji, KUNIKANE Yuko

    The proceedings of the JSME annual meeting 1 (0) 9-10 2001

    Publisher: The Japan Society of Mechanical Engineers

    DOI: 10.1299/jsmemecjo.II.01.1.0_9  

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    It is important to clarify the basic characteristics, such as backlayering distance and velocity of the thermal plume generated by the fire accident in a road tunnel in order to design the ventilation system for securing the evacuate environment. In this research, the backlayering velocity and distance are investigated by the experiments which use a reduced scale model tunnel and by the large eddy simulation. The reliability of numerical code is verified by compareing numerical and experimental results. The results show that the backlayering velocity increases with increasing the heat release rate and that the backlayering velocity and distance decrease with increasing the ventilation velocity.

  134. K-1035 Influence of Obstacle on Backlayering Characteristic of Thermal Plume in Model Tunnel

    HAYASHI Takumi, KAWABATA Noboyoshi, ISHIKAWA Takkuji, MATSUMOTO Tetsuharu

    The proceedings of the JSME annual meeting 1 (0) 11-12 2001

    Publisher: The Japan Society of Mechanical Engineers

    DOI: 10.1299/jsmemecjo.II.01.1.0_11  

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    When a tunnel fire happens, the accident vehicle and other vehicles often exist around the fire source. These obstacles influence are exerted on the critical ventilation velocity of the thermal plume from backlaryering and the characteristics of the backlayering distance etc. Then, we install the obstacle in the 1/15 scale model tunnel, and the influence of the obstacle on the backlayering characteristic of the thermal plume was investigated experimentally and numerically

  135. K-1036 Descent of Smoke Moving alone Ceiling at Tunnel Fire

    YAMAMOTO Nobuyuki, KWABATA Nobuyoshi, ISHIKAWA Takuji, KUNIKANE Yuuko

    The proceedings of the JSME annual meeting 1 (0) 13-14 2001

    Publisher: The Japan Society of Mechanical Engineers

    DOI: 10.1299/jsmemecjo.II.01.1.0_13  

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    When the tunnel fire occurred, the damage by smoke and thermal plumes is considerable. The temperature of thermal plumes, which is stratified and moves along the ceiling, decreases because the ceiling gradually absorbs the heat from the thermal plume. The decrease of temperature induces the thermal plume and smoke descending towards the ground. Practically, in order to keep the evacuate environment, fire exits are installed with a certain interval. Therefore, in order to set up fire exit of appropriate interval, it is necessary to clarify the distance where smoke descends to the ground. Consequently, in this research, the influences of various parameters on the descent of smoke were examined by the 3D Large Eddy simulation.

  136. K-1037 Interference of Ventilation between Two Tunnels connected by Snow Shed

    SANO Akinori, KAWABATA Nobuyoshi, ISIKAWA Takuji

    The proceedings of the JSME annual meeting 1 (0) 15-16 2001

    Publisher: The Japan Society of Mechanical Engineers

    DOI: 10.1299/jsmemecjo.II.01.1.0_15  

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    If fire smoke is generated in the upstream successive tunnel by a traffic accident, the exhausted smoke flows into the downstream tunnel, which may destroy the evacuate environment in the downstream tunnel. It is, therefore, important to discuss the interference rate of successive tunnels. In this paper, the effect of variouse parameters on the interference rate is investigated by large eddy simulation. The reliability of numerical code is verified by comparing with the real scale tunnel experiment. Consequently, the interference rate is expressed by a new equation.

  137. K-1038 Behavior of thermal plume at fire in curvature tunnel

    KAWAI Tomoki, KAWABATA Noboyoshi, ISHIKAWA Takuji

    The proceedings of the JSME annual meeting 1 (0) 17-18 2001

    Publisher: The Japan Society of Mechanical Engineers

    DOI: 10.1299/jsmemecjo.II.01.1.0_17  

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    Recent year, traffic jam often occurs in the urban area. In the urban area, the highways are expected to be constructed under ground as a solution of the traffic jam. Such tunnels have large curvature in the junction area, however the behavior of thermal plume and critical velocity have not been clarified in case of fire accidents. In this research, a fire in the curvature tunnel was simulated, and the behavior of the thermal plume was discussed.

  138. K-1039 Pressure drop at tunnel fire

    ASABATAKE Kimihiro, KAWABATA Nobuyoshi, ISHIKAWA Takuji, SHIMOCHI Miyoshi, TOTTORI Hisaharu

    The proceedings of the JSME annual meeting 1 (0) 19-20 2001

    Publisher: The Japan Society of Mechanical Engineers

    DOI: 10.1299/jsmemecjo.II.01.1.0_19  

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    When tunnel fire occurs, pressure drops at the fire source by the expansion of the air. The strict pressure drop has not been estimated in the discussion of the tunnel ventilation in the emergency fires as yet. In this research, tunnel fires are simulated in one and three dimensionaly and the pressure drop is investigated. The effects of the fire scale and the ventilation velocity on the pressure drop by the fire is clarified.

  139. K-1424 Shear Flow Characteristics of Polymer Solution by Bead-Spring Macro Model

    SAKAMOTO Noriko, FUJITA Katushi, KAWABATA Nobuyoshi, ISHIKAWA Takuji

    The proceedings of the JSME annual meeting 1 (0) 251-252 2001

    Publisher: The Japan Society of Mechanical Engineers

    DOI: 10.1299/jsmemecjo.II.01.1.0_251  

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    The flow of viscoelastic fluid by means of a bead-spring macro model shows non-Newtonian viscosity. The shear flow characteristics of polymer solution are investigated experimentally by using by cone-plate type viscometer. The experimental results are compared with the numerical results by using bead-spring macro model, where three types of models (conventional modeling, present modeling, present modeling + random) are employed. The value and the equation of the spring constant are discussed so that the numerical results show good agreement with the experimental results. It is found that the present modeling + random can consistently express the distribution of polymer chains and the rheological property of viscoelastic fluids.

  140. F-0812 Modeling of Blood Circulatory System by means of Bondgraph

    SUGA Noriyoshi, ISHIKAWA Takuji, KAWABATA Nobuyoshi, TATIBANA Motoyoshi

    The proceedings of the JSME annual meeting 1 (0) 23-24 2001

    Publisher: The Japan Society of Mechanical Engineers

    DOI: 10.1299/jsmemecjo.IV.01.1.0_23  

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    It is difficult for highly accurate methods such as CFD to model all blood circulation of the human body. In this research, bondgraph is used in order to simply model the all blood circulation of the human body, bondgraph is the effective method to express complicated systems and the computational load is small. The heart, the artery, the capillary, and the vein of human body are modeled by the bondgraph, and the change of flow rate and pressure are discussed.

  141. F-0824 Numerical Simulation of Pouseuille Flow of Blood by means of a Deformable Erythrcyte Model

    SAWAZAKI Hiromasa, ISIKAWA Takuji, KAWABATA Nobuyoshi, TACHIBANA Motoyoshi

    The proceedings of the JSME annual meeting 1 (0) 47-48 2001

    Publisher: The Japan Society of Mechanical Engineers

    DOI: 10.1299/jsmemecjo.IV.01.1.0_47  

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    It is not appropriate to use constitutive equitions for small arteries because of the heterogeneity of the blood. In this paper, a new method to model an erythrocyte by using drag point s and springs is proposed as an altanative to analyze the blood flow. The behavior of erythrocytes is computed under Poiseuille flow. The rotating attitude of an erythrocyte under Poiseuille flow, shear-thinning property, first normal stress difference and plasma layer near the wall are discuassed.

  142. Backlayering characteristics of thermal fume during tunnel fires in Hanshin Expressway

    T Ishikawa, N Kawabata, H Tottori, M Ishida

    10TH INTERNATIONAL SYMPOSIUM ON AERODYNAMICS AND VENTILATION OF VEHICLE TUNNELS (43) 597-614 2000

    Publisher: PROFESSIONAL ENGINEERING PUBLISHING LTD

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    Tunnels in expressways between cities have become to employ mostly longitudinal ventilation systems. The longitudinal ventilation system generates a longitudinal wind flow with the same direction to the traffic, so that the upstream vehicles staying near the fire source are protected from the thermal plume and smoke in case of tunnel fires. In order to secure the evacuation environment, it is important to clarify the backlayering characteristics of thermal plume in case of tunnel fires. In this study, backlayering characteristics of thermal plume during the fires in the real city type road tunnel were investigated. The tunnel is managed by Hanshin expressway public corporation and has 9.5 meter in width and 6.2 meter in height. Large eddy simulation was employed for the turbulence model of momentum equation. By this method, backlayering characteristics of thermal plume are simulated accurately, which is confirmed by comparing with the experimental results. The emergency fire was assumed to be caused by a single large bus with the maximum heat release rate of 12MW. The behaviors of thermal plume and smoke were simulated under various longitudinal wind flow conditions. Consequently, it is clarified that the backlayering characteristics of the thermal plume with various longitudinal wind flow and critical longitudinal wind flow that prevents the thermal plume and smoke from backlayering.

  143. Modeling of an erythrocyte by beads and springs and the numerical analysis of blood flow under the constant shear field

    Takuji Ishikawa, Nobuyoshi Kawabata, Motoyoshi Tachibana

    Nihon Kikai Gakkai Ronbunshu, B Hen/Transactions of the Japan Society of Mechanical Engineers, Part B 66 (650) 2642-2649 2000

    Publisher: Japan Society of Mechanical Engineers

    DOI: 10.1299/kikaib.66.650_2642  

    ISSN:0387-5016

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    The blood flow in large arteries is commonly analyzed by means of the constitutive equations. However, it is not appropriate to use constitutive equations for small arteries because of the heterogeneity of the blood. In this paper, a new method to model an erythrocyte by using beads and springs is proposed as an alternative to analyze the blood flow. The behavior of a single erythrocyte is computed under a constant shear field. The rotating attitude of an erythrocyte, shear viscosity, normal stress difference coefficient and stress thinning are discussed. The results show that the bead-spring model appropriately can simulate the tank tread motion of an erythrocyte under a high shear field and stress thinning. It is therefore considered that the bead-spring erythrocyte model is able to consistently express blood characteristics.

  144. Fundamental characteristics of viscoelastic fluid modeled by beeds, springs and dampers (mechanism of second normal stress difference generation by dampers)

    Takuji Ishikawa, Nobuyoshi Kawabata, Katsushi Fujita, Yutaka Miyake

    Nihon Kikai Gakkai Ronbunshu, B Hen/Transactions of the Japan Society of Mechanical Engineers, Part B 66 (648) 2049-2055 2000

    Publisher: Japan Society of Mechanical Engineers

    DOI: 10.1299/kikaib.66.648_2049  

    ISSN:0387-5016

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    Flow of viscoelastic fluid is commonly analyzed by using constitutive equations. In this paper, bead-spring-damper macro model is proposed as an alternative to analyze viscoelastic flow. The tetrahedral structure of beads, springs and dampers models a gathering of intertwined polymer chains. Behavior of the bead-spring-damper structure is computed under simple shear flow condition. Shear-thinning of shear viscosity and the mechanism of second normal stress difference generation are investigated. The results show that the phase lag of the tension, caused by the damper element, is the mechanism of second normal stress difference generation, and that the bead-springdamper macro model can express characteristics of viscoelastic fluid consistently.

  145. Unsteady flow of viscoelastic fluid modeled by beeds, springs and dampers

    Takuji Ishikawa, Nobuyoshi Kawabata, Katsushi Fujita, Yutaka Miyake

    Nihon Kikai Gakkai Ronbunshu, B Hen/Transactions of the Japan Society of Mechanical Engineers, Part B 66 (645) 1287-1294 2000

    Publisher: Japan Society of Mechanical Engineers

    DOI: 10.1299/kikaib.66.1287  

    ISSN:0387-5016

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    Flow of viscoelastic fluid is commonly analyzed by using constitutive equati6ns. In this paper, bead-spring-damper macro model is proposed as an alternative to analyze viscoelastic flow. The tetrahedral structure of beads, springs and dampers models a gathering of interwined polymer chains. Behavior of the bead-spring-damper structure is computed under start-up flow, stop flow and oscillatory flow conditions. Stress overshoot, stress relaxation, dynamic viscosity and dynamic modulus are investigated. The results show that the effect of elasticity appears strongly in the unsteady flow, and that the bead-spring-damper macro model can express characteristics of viscoelastic fluid consistently.

  146. Modeling of an Erythrocyte by Beads and Springs and the Numerical Analysis of Blood Flow under the Constant Shear Field

    ISHIKAWA Takuji, KAWABATA Nobuyoshi, TACHIBANA Motoyoshi

    The proceedings of the JSME annual meeting 2000 (0) 291-292 2000

    Publisher: The Japan Society of Mechanical Engineers

    DOI: 10.1299/jsmemecjo.2000.1.0_291  

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    The blood flow in large arteries is commonly analyzed by means of the constitutive equations. However, it is not appropriate to use constitutive equations for small arteries because of the heterogeneity of the blood. In this paper, a new method to model an erythrocyte by using beads and springs is proposed as an alternative to analyze the blood flow. The behavior of a single erythrocyte is computed under a constant shear field. The results show that the bead-spring model appropriately can simulate the tank tread motion of an erythrocyte under a high shear field and stress thinning. It is therefore considered that the bead-spring erythrocyte model is able to consistently express blood characteristics

  147. Gaseous Fire Suppression Equipment for a high aspect ratio space

    AKINO Takashi, KAWABATA Nubuyoshi, ISHIKAWA Takuji, NAITO Yusuke, TANAKA Kazuhiro, SAKURAI Kenichi

    The proceedings of the JSME annual meeting 2000 (0) 255-256 2000

    Publisher: The Japan Society of Mechanical Engineers

    DOI: 10.1299/jsmemecjo.2000.4.0_255  

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    Gaseous fire suppression equipment is able to extinguish fire without staining spread area and restore the room after the extinguishments early. So, application cases of this extinguishing system increase recently. The purpose of this study is to develop the simulator of gaseous fire extinguishing system that can consider the unsteady change using bond graph. In the case of the high-aspect-ratio space like parking lots, it is difficult to keep a uniform concentration in all area of the protection subdivision. However, the effect of the aspect ratio of protection subdivision is not considered in the conventional designs. Therefore, modeling by using of bond graph and examine the effects of aspect ratio are investigated.

  148. 214 Simulation of human erythrocyte motion in the constant shear field using a disk-spring model

    SAWAZAKI Hiromasa, ISHIKAWA Takuji, KAWABATA Nobuyoshi, TATIBANA Motoyosi

    The Proceedings of Conference of Hokuriku-Shinetsu Branch 2000 (0) 65-66 2000

    Publisher: The Japan Society of Mechanical Engineers

  149. 805 Influence of Discharge Methods on Indoor Diffusion by Gaseous Extinction Equipment

    KASHIGUCHI Tomoaki, ISHIKAWA Yoshiaki, KAWABATA Nobuyoshi, ISHIKAWA Takuji, NAITO Yusuke

    The Proceedings of Conference of Hokuriku-Shinetsu Branch 2000 (0) 301-302 2000

    Publisher: The Japan Society of Mechanical Engineers

  150. 806 Interaction of Exhaust Smoke between Sequential Tunnels

    Shiojima Ken, Shimizu Hirohito, Sano Akinori, Kawabata Nobuyoshi, Ishikawa Takuji

    The Proceedings of Conference of Hokuriku-Shinetsu Branch 2000 (0) 303-304 2000

    Publisher: The Japan Society of Mechanical Engineers

  151. 609 Diffusion of the Gas discharged by Gaseous Extinction Equipment : Numerical Simulation and Real Experiment

    ISHIKAWA Yoshiaki, KAWABATA Nobuyoshi, ISHIKAWA Takuji, NAITO Yusuke, MATSUMOTO Yoichiro, SAITO Naoshi, TSURUDA

    The Proceedings of Conference of Hokuriku-Shinetsu Branch 2000 (0) 225-226 2000

    Publisher: The Japan Society of Mechanical Engineers

  152. 610 Effect of Inclination on the Velocity of Thermal Fume in Emergency Tunnel Fires

    ISHIKAWA Masao, HAYASHI Takumi, KAWABATA Nobuyoshi, ISHIKAWA Takuji, WANG Qian

    The Proceedings of Conference of Hokuriku-Shinetsu Branch 2000 (0) 227-228 2000

    Publisher: The Japan Society of Mechanical Engineers

  153. 608 Modeling of Gaseous Extinction Equipment by using Bond Graph

    AKINO Takashi, KAWABATA Nobuyoshi, ISHIKAWA Takuji, NAITO Yusuke, TANAKA Kazuhiro

    The Proceedings of Conference of Hokuriku-Shinetsu Branch 2000 (0) 223-224 2000

    Publisher: The Japan Society of Mechanical Engineers

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Books and Other Publications 7

  1. Integrated Nano-Biomechanics

    T. Yamaguchi, T. Ishikawa, Y. Imai

    Elsevier 2018/06

  2. 高度物理刺激と生体応答

    編著, 佐藤岳彦, 大橋俊朗, 川野聡恭, 白樫 了

    養賢堂 2017/08/26

  3. はじめての生体工学

    山口昌樹, 石川拓司, 大橋俊朗, 中島 求

    講談社 2016/09/06

  4. メカノバイオロジー

    編 曽我部正博

    化学同人 2015/04/01

  5. Visualization and a simulation of complex flows in biomedical engineering

    Eds. R. Lima, Y. Imai, T. Ishikawa and, M S. N. Oliveira

    Springer 2013/04

  6. 生物流体力学

    編 谷下一夫, 山口隆美

    朝倉書店 2012/03

  7. Handbook of Physics in Medicine and Biology

    Eds. Robert, Splinter

    CRC Press 2010/03

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Presentations 34

  1. Biomechanics can provide a new perspective on microbiology Invited

    Takuji Ishikawa

    Fluid Dynamics Seminar, Imperial College London 2019/06/07

  2. Biomechanics can provide a new perspective on microbiology Invited

    Takuji Ishikawa

    Mathematical Physics Seminar, University of York 2019/06/04

  3. Biomechanics can provide a new perspective on microbiology Invited

    Takuji Ishikawa

    Mathematical Biology and Ecology Seminar, University of Oxford 2019/05/03

  4. Biomechanics can provide a new perspective on microbiology International-presentation Invited

    Takuji Ishikawa

    8th World Congress of Biomechanics 2018/07/10

  5. Understanding motions of cells by mechanics Invited

    石川 拓司

    流れと澱みを語る会2018 2018/06/10

  6. Near-field fluid mechanics alter behaviors of swimming microorganisms International-presentation Invited

    アクティブマター研究会 2018/01/20

  7. 狭い流路内の繊毛虫の遊泳挙動 Invited

    日本機械学会 第30回バイオエンジニアリング講演会 シンポジウム 2017/12/15

  8. バイオエンジニアリング研究の過去と未来 Invited

    日本機械学会 第30回バイオエンジニアリング講演会 イブニングセッション 2017/12/14

  9. Deformation and the resultant motion of a red blood cell International-presentation Invited

    Blood Flow: Current State and Future Prospects 2017/10/10

  10. Hydrodynamic Bound States of a Squirmer International-presentation Invited

    5th Switzerland-Japan Workshop on Biomechanics (SJB2017) 2017/09/15

  11. 行き止まりを避ける微生物の泳ぎ Invited

    違った視点で捉える流れ 2017/09/08

  12. Deformation and Motility of Cells Invited

    第一回アクティブ・ソフトマター研究会 2016/11/14

  13. Modeling and Understanding Biomedical Flows International-presentation Invited

    2nd Global Conference on Biomedical Engineering 2016/08/17

  14. Biological flow studies from cellular to macro scale International-presentation Invited

    International Conference on Future Healthcare and Economic Development in Southeast Asia 2016/08/16

  15. Deformation and Motility of Cells International-presentation Invited

    Summer School 2016 Active Complex Matter 2016/07/13

  16. 遊泳大腸菌の流体力学 Invited

    べん毛研究交流会 2016/03/06

  17. 微小遊泳体の流体力学的な制御機構 Invited

    第5回ソフトマター研究会 2015/12/18

  18. シミュレーションで拓く医工学 Invited

    第18回 血管病態研究会 2015/11/14

  19. Hydrodynamic Regulation and Control of a Micro-swimmer International-presentation Invited

    3rd Int. Workshops Adv. Comp. Mech. 2015/10/12

  20. Separation of motile bacteria using drift force near a wall International-presentation Invited

    Computational Fluid Dynamics in Medicine and Biology II 2015/09/02

  21. Transport Phenomena in Suspensions of Swimming Microorganisms International-presentation Invited

    The Korean Society of Mechanical Engineering 2015/05/21

  22. 微生物溶液のダイナミクス Invited

    京都大学基礎物理学研究所セミナー 2009/10

  23. Mixing of red blood cells in high hematocrit blood flow in micro-channels International-presentation Invited

    3rd Switzerland-Japan Workshop on Biomechanics 2009 2009/09

  24. 微生物溶液のバイオメカニクス Invited

    特定領域研究「ソフトマター物理」 第4回領域研究会 2009/07

  25. Suspension biomechanics of swimming microbes International-presentation Invited

    Workshop on Active Matter – Physics of Biokinetics 2009/07

  26. Computational biomechanics of malaria and arterial diseases International-presentation Invited

    37th Int. Cong. Physiol. Sci. 2009/07

  27. Computational biomechanics for investigating various diseases over micro to macro scales International-presentation Invited

    Int. Conf. Comp. Exp. Eng. Sci. 2009/04

  28. Motion of individual cells in high hematocrit blood flow in micro-channels International-presentation Invited

    Int. Conf. Comp. Exp. Eng. Sci. 2009/04

  29. Fluid dynamics of a suspension of locomotive cells International-presentation Invited

    Int. Conf. Nonlinear Sci. 2009/02

  30. Biomechanics of a Suspension of Micro-Organisms International-presentation Invited

    13th Int. Conf. Biomed. Eng. (ICBME2008) 2008/12

  31. Hydrodynamics of swimming micro-organisms International-presentation Invited

    8th. World Congress on Computational Mechanics, and the 5th. European Congress on Computational Methods in Applied Sciences and Engineering 2008/07

  32. Collective motions of locomotive cells in a suspension International-presentation Invited

    Tohoku-NUS Student Joint Symposium 2008/05

  33. 微生物の濃厚溶液の数値シミュレーション Invited

    第13回計算数理工学フォーラム 2007/09

  34. 微生物溶液の数値シミュレーション Invited

    第18回エアロ・アクアバイオメカニズム研究会 2006/03

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Industrial Property Rights 2

  1. 血液中の粒子分離装置

    石川拓司, 田中達也, 沼山恵子, 上野裕則, 今井陽介, 山口隆美

    Property Type: Patent

  2. 振動針装置及び針の挿入方法

    菊地謙次, 杉山航二郎, 石川拓司, 高瀬圭

    Property Type: Patent

Research Projects 29

  1. Development of non-invasive imaging methods of Biological flow and concentration field for in vivo physiological immune system interference

    Offer Organization: Japan Society for the Promotion of Science

    System: Grants-in-Aid for Scientific Research

    Category: Grant-in-Aid for Scientific Research (B)

    Institution: Tohoku University

    2022/04/01 - 2026/03/31

  2. 環境連成力学を基盤とした微生物行動シミュレータの開発

    石川 拓司, 上野 裕則, 西上 幸範

    Offer Organization: 日本学術振興会

    System: 科学研究費助成事業

    Category: 学術変革領域研究(A)

    Institution: 東北大学

    2021/09/10 - 2026/03/31

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    本年度は研究の立ち上げを行い、大型計算機を入札により導入した。主要な研究実績は以下の通りである。 1.クラミドモナスが流れに逆らって泳ぐ性質(走流性)を示すことを発見した。実験と理論、数値シミュレーションを融合し、そのメカニズムが遊泳の非定常性からくることを明らかにした(Omori, et al., J. Fluid Mech. 2021)。 2.さまざまな遊泳モードを持つ微生物の2体干渉の解析を行い、干渉運動の相図を作成した。これにより、微生物干渉の体系的な理解が進んだ(Darveniza, et al., Phys. Rev. Fluids,2022)。 3.数値解析手法の高度化にも取り組み、汎用性の高い境界要素法と近接場が得意な潤滑理論を融合させたLT-BEMを開発した。この手法を用いることで、微生物運動の解析精度が大幅に改善することを示した(Ishikawa, J. Comp. Phys., 2022)。 4.開発した微生物行動シミュレータをバイオフィルムの形成過程へと展開した。複雑流路内に形成されるストリーマーの形成過程を、細胞スケールからメゾスケールで計算した。そして、マクロなレオロジー特性とストリーマー形状の関係を解明した(Kitamura, et al., J. R. Soc. Interface, 2021)。 5.開発した微生物行動シミュレータを酵母の発酵過程へと展開し、培養時の輸送現象を定量的に調べた。培養容器内にプラスチックごみを模擬した物体を混入させると、ブラジルナッツ効果が現れることを発見した。この成果はSoft Matter誌の背表紙を飾り、プレスリリースされた(Srivastava, et al., Soft Matter, 2021)。

  3. Ethological dynamics to formulate proto-intelligence exerted in diorama environments.

    Offer Organization: Japan Society for the Promotion of Science

    System: Grants-in-Aid for Scientific Research

    Category: Grant-in-Aid for Transformative Research Areas (A)

    Institution: Hokkaido University

    2021/09/10 - 2026/03/31

  4. Study on active transport phenomena for predicting and controlling biological active matter

    Offer Organization: Japan Society for the Promotion of Science

    System: Grants-in-Aid for Scientific Research

    Category: Grant-in-Aid for Scientific Research (S)

    Institution: Tohoku University

    2021/07/05 - 2026/03/31

  5. 薬剤輸送を目指した柔らかいマイクロスイマーの開発

    石川 拓司, 菊地 謙次, ニックス ステファニー, 大森 俊宏

    Offer Organization: 日本学術振興会

    System: 科学研究費助成事業

    Category: 国際共同研究加速基金(国際共同研究強化(B))

    Institution: 東北大学

    2021/10/07 - 2025/03/31

  6. バイオメカニクスで紐解くバイオフィルム形成の仕組み

    石川 拓司, YANG JINYOU

    Offer Organization: 日本学術振興会

    System: 科学研究費助成事業

    Category: 特別研究員奨励費

    Institution: 東北大学

    2021/11/18 - 2024/03/31

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    本年度は、研究環境の整備と、研究の立ち上げを行った。 本来、楊氏は2020年8月に来日予定であったが、コロナ禍の影響で2021年12月まで研究を始められなかった。この間にバイオフィルム研究は日進月歩で深化しているため、最新の研究動向を調査し、研究課題とスケジュールを状況に合わせて軌道修正した。 実験準備として、腸内細菌を観察するためのゼブラフィッシュの実験系を構築した。飼育と産卵、稚魚の観察、麻酔、大腸菌の挿入などの一連のスキルを習得した。また、蛍光顕微鏡によるライブイメージング技術を習得した。微細流体流路を製作するための基礎技術も習得した。これらの技術を基盤とし、ゼブラフィッシュ腸内の大腸菌のライブイメージングに成功した。 さらに、シミュレーションのためのコード開発にも取り組んだ。物理環境下のバクテリア挙動を解析するため、境界要素法を基盤とする解析コードを構築している。東北大学流体科学研究所のスパコンを使用するための事務手続きや、技術習得も行った。計算コードのバグ取りは終了し、試行計算で良好な結果が出ている。

  7. バイオメカニクスで紐解くバイオフィルム形成の仕組み

    石川 拓司, YANG JINYOU

    Offer Organization: 日本学術振興会

    System: 科学研究費助成事業

    Category: 特別研究員奨励費

    Institution: 東北大学

    2021/07/28 - 2023/03/31

  8. バイオメカニクスで紐解くバイオフィルム形成の仕組み

    石川 拓司, YANG JINYOU

    Offer Organization: 日本学術振興会

    System: 科学研究費助成事業

    Category: 特別研究員奨励費

    Institution: 東北大学

    2021/04/28 - 2023/03/31

  9. ノイズで推進する柔らかいマイクロスイマーの開発

    石川 拓司

    Offer Organization: 日本学術振興会

    System: 科学研究費助成事業

    Category: 新学術領域研究(研究領域提案型)

    Institution: 東北大学

    2021/04/01 - 2023/03/31

  10. バイオメカニクスで紐解くバイオフィルム形成の仕組み

    石川 拓司, YANG JINYOU

    Offer Organization: 日本学術振興会

    System: 科学研究費助成事業

    Category: 特別研究員奨励費

    Institution: 東北大学

    2020/11/13 - 2023/03/31

  11. Development of a simulator to evaluate the efficacy of an antibacterial agent to resident and resistant bacteria

    Offer Organization: Japan Society for the Promotion of Science

    System: Grants-in-Aid for Scientific Research

    Category: Grant-in-Aid for Challenging Research (Exploratory)

    Institution: Tohoku University

    2020/07/30 - 2023/03/31

  12. Physiological function generated by biological flow

    Kikuchi Kenji

    Offer Organization: Japan Society for the Promotion of Science

    System: Grants-in-Aid for Scientific Research

    Category: Grant-in-Aid for Scientific Research (B)

    Institution: Tohoku University

    2019/04/01 - 2022/03/31

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    In this research, we thoroughly pursued the "Physiological function generated by biological flow" and succeeded in taking it to heights unparalleled anywhere in the world, utilizing experimental and theoretical analysis and numerical simulation methods. Subsequently, we have elucidated biological phenomena from microorganisms to drug absorption in the skin on scales from microscopic to centimeters, and developed engineering and medical engineering technologies related to biological flow.The results have been published as 9 peer review journal papers.

  13. Modeling a gut flora of a zebrafish by combining experiments, theories and numerical simulations

    Ishikawa Takuji

    Offer Organization: Japan Society for the Promotion of Science

    System: Grants-in-Aid for Scientific Research

    Category: Grant-in-Aid for Challenging Research (Exploratory)

    Institution: Tohoku University

    2018/06/29 - 2021/03/31

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    In this project, we investigated microbial flora in the intestine of a zebrafish larva by combining theories and experiments based on transport phenomena. Three conservation laws (momentum, concentration and cells) are solved simultaneously, and the distribution and growth of bacteria are described. We also conducted experiments using a zebrafish larva. We established the experimental setup, and measured intestinal flow with high temporal and spacial resolutions.

  14. Upgrading Microbial Biomechanics

    Ishikawa Takuji

    Offer Organization: Japan Society for the Promotion of Science

    System: Grants-in-Aid for Scientific Research

    Category: Grant-in-Aid for Scientific Research (A)

    Institution: Tohoku University

    2017/04/01 - 2021/03/31

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    By using an original method that carefully builds up physical laws from the nanoscale to the macroscale, we have clarified the behavior and biological functions of sperm, microalgae, ciliates, E. coli, yeast, and other organisms under mechanical environments. We succeeded in analyzing through the scale hierarchy from the movement of ciliary axonemes driven by molecular motors, synchronization of flagellar movement, swimming and biological responses of ciliates with many flagella, two-body interactions and cooperative swimming, rheology and diffusion properties as a continuum, cell growth and accumulation, and so on. These results were published in a total of 48 peer-reviewed journal articles, including two in PNAS, one in Science Adv, and six in J Fluid Mech. In addition, 8 press releases were issued to widely publicize the research results.

  15. Development of a taxis model of cells: application for medicine and evolutionary biology

    Ishikawa Takuji

    Offer Organization: Japan Society for the Promotion of Science

    System: Grants-in-Aid for Scientific Research

    Category: Fund for the Promotion of Joint International Research (Fostering Joint International Research)

    Institution: Tohoku University

    2018 - 2021

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    The research methodology of the parent project includes the step of "innovating theoretical and analytical methods" for microbial biomechanics. In this study, therefore, the mathematical model of phototaxis of microalgae (Gonium) was developed by combining the experimental and mathematical results of the Goldstein Laboratory at the University of Cambridge with the applicant's simulation technology. We have also conducted swimming and feeding analyses of groups of collar flagellates, the origin of multicellular animals, and has expanded microbial biomechanics into evolutionary biology. Besides, we collaborated with Professors Pedley and Lauga of the same department to analyze the stability of microbial swimming and mathematical modeling of microbial suspensions. These results were published in a total of six refereed journal papers, including two in J Fluid Mech, one in Phys Rev E, and one in J Comp Phys.

  16. Advances in cell suspension mechanics based on the hierarchy structure

    Ishikawa Takuji

    Offer Organization: Japan Society for the Promotion of Science

    System: Grants-in-Aid for Scientific Research

    Category: Grant-in-Aid for Scientific Research (A)

    Institution: Tohoku University

    2014/04/01 - 2017/03/31

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    In this project, we have succeeded to construct a world leading ‘cell suspension mechanics based on the hierarchy structure’ by combining experiment, theory and numerical simulation. We have clarified many phenomena from nano to macro scale using various cells such as algae, bacteria and blood. Then, the obtained knowledge was utilized to develop devices for engineering and biomedical use. The results have been published as 30 peer review journal papers.

  17. Integrated nano-biomechanics

    YAMAGUCHI Takami, ISHIKAWA Takuji, UENO Hironori, MIZUNO Fumio, OMORI Toshihiro, MATSUKI Noriaki, TANAKA Tetsu, SHIMOGONYA Yuji, NIX Stephanie, NUMAYAMA Keiko, IMAI Yohsuke

    Offer Organization: Japan Society for the Promotion of Science

    System: Grants-in-Aid for Scientific Research

    Category: Grant-in-Aid for Specially Promoted Research

    Institution: Tohoku University

    2013 - 2017

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    We have established integrated nano-biomechanics by modeling multi-scale physical and biomedical phenomena from the molecular level. By using the established model, we succeeded to numerically simulate various diseases, such as an infectious disease, and developed novel methodologies for medical diagnosis and treatments based on quantitative predictions. Besides, we developed biochips to separate or detect cancer cells and bacteria. These findings have been published as 50 peer reviewed journal papers.

  18. 気道上皮細胞が作る流れの共焦点マイクロPIV計測

    石川 拓司, SAADATMAND Maryam

    Offer Organization: 日本学術振興会

    System: 科学研究費助成事業

    Category: 特別研究員奨励費

    Institution: 東北大学

    2013/04/01 - 2015/03/31

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    本年度は、マウスから摘出した気道を用い、繊毛が作り出す流れを共焦点マイクロPIVシステムを用いて可視化計測した。特に、粘液粘度の影響に着目し、粘度増加による繊毛打の変化や、繊毛流れの変化を計測した。その結果、高い粘度環境下においても繊毛打は消滅しないが、繊毛打周波数は低下し、繊毛流れが遅くなることを明らかにした。また、気管と気管支における繊毛流れの違いを調べたところ、両者には大きな違いがないことが明らかになった。これらの実験により、病変等で粘液粘度が高くなった条件下における、気道内における繊毛流れの機能、および粒子の輸送効率を議論することが可能となった。こうした成果は、気道のクリアランス機能の病理を理解する上で重要であり、PCDなどの疾患のメカニズムの理解に役立つと考えられる。 さらに、修得したマイクロ流れの計測技術を生かし、微小流体流路内の血液流れなど、他の生物流れの計測も並行して行った。特筆すべきは、PDMSマイクロ流路の壁内にバイパス流路を埋め込むことで、血球成分が壁面から離れ、血漿層の厚みを増幅できることを世界で初めて示した。この壁面形状を、血液に接触する医療機器の表面に応用することで、血液の凝固や溶血などを予防できると期待される。この成果は、国際会議にて口頭発表している。こうした派生的な研究成果も、本課題の研究手法の開発に資するのみならず、特別研究員の将来の活躍の場を広げるものであり、重要である。

  19. Analyses of small molecules behaviors in the body which is emerged by the cooperation of multi-organs.

    SUZUKI Hiroshi, HONMA Masashi, TAKADA Tappei

    Offer Organization: Japan Society for the Promotion of Science

    System: Grants-in-Aid for Scientific Research

    Category: Grant-in-Aid for Scientific Research on Innovative Areas (Research in a proposed research area)

    Institution: The University of Tokyo

    2010/04/01 - 2015/03/31

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    Homeostasis for blood concentrations of various small molecules is one of the most important mechanisms to maintain life. In the present study, we focused on this system which is emerged by the cooperation of multi-organs, aiming to achieve the integrated comprehension of the systems behaviors. In the first half of the study period, we have built novel mathematical models to describe the behavior of small molecules in the body, using drug molecules as models. In the second half of the study, we extended the target ranges to various endogenous small molecules, including highly lipophilic compounds such as cholesterol and fat-soluble vitamins, inorganic salts such as phosphate and calcium, and urate. We have elucidated molecular mechanisms for regulating the behavior of these compounds in the body, and have integrated the information to the multi-organ models.

  20. 細胞サスペンジョン力学による医工学研究の新展開

    石川 拓司

    Offer Organization: 日本学術振興会

    System: 科学研究費助成事業

    Category: 基盤研究(B)

    Institution: 東北大学

    2010 - 2014

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    本研究課題では,実験・理論解析・数値シミュレーションを駆使することで,細胞間の多体干渉現象および複雑流路内での振舞いを新たに解明し,まず始めに細胞サスペンジョン力学を確立することを目的とする.そして細胞サスペンジョン力学を応用し,従来の手法では議論が困難な生命システムを定量的に解明する.これにより,従来は経験的・定性的な議論に留まっていた医工学の分野に,ブレークスルーを生み出すことを目的とする.本年度は主に以下の2つの研究課題を遂行した. 1.細胞間の多体干渉モデルの構築 微生物の2体干渉現象を多体間に拡張し,まず始めに遊泳微生物がどのようなメゾスケール流動構造を示すか実験的に調べた.微生物には大腸菌を用い,共焦点マイクロPIVシステムを用いて高濃度溶液内の大腸菌の運動,および周囲流体の流動を計測した.次に,高濃度バクテリア溶液に対する数理モデルを構築した.本研究では球形以外の形状を取り扱えるよう従来の計算コードを改良し,高濃度バクテリア溶液の数理モデルを提案した.赤血球に対しては,我々の開発してきた境界要素法を赤血球に拡張し,高濃度赤血球サスペンジョンに対する高精度な数理モデルを構築した. 2.複雑流路内の細胞サスペンジョン流動の解明 血液にごく少量のがん細胞を混入し,狭さく部や分岐・合流部における挙動を調べた.そしてがん細胞の軸集中や壁面への集中など,力学的なに引き起こされる特異な流動現象を解明した.次に,開発した多体干渉を表現できる細胞サスペンジョンモデルを用い,実験に対応する複雑流路内の流れのシミュレーションを行った.そしてシミュレーション結果と実験結果を比較検討することにより,信頼性の高い細胞サスペンジョンシミュレータを開発した.

  21. Nano-scale analysis and computational fluid mechanics of the flow on the surface of tracheal lumen

    UENO Hironori, ISHIKAWA Takuji, ISHIKAWA Takashi

    Offer Organization: Japan Society for the Promotion of Science

    System: Grants-in-Aid for Scientific Research

    Category: Grant-in-Aid for Young Scientists (B)

    Institution: Tohoku University

    2009 - 2011

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    Mucociliary clearance on the surface of the tracheal lumen is an important component of lung defense against viruses and bacteria. We analyzed the detail of ciliary movement with high spatial precision by labeling the ciliary tip using quantum dots, and axonemal structure by cryo-electron tomography. We revealed the overall directional flow from the lungs to the oropharynx on tracheal lumen by effective ciliary motion with the asymmetric axonemal structure. Moreover, we discovered that collective swimming of microorganisms is the most energy-efficient way of moving. And also, we developed new program code and GPGPU computational system to analyze the fluid flow mechanism on the surface of tracheal lumen.

  22. Mechanism of the inhibition of cancer cell growth using low voltage electric pulses

    MATSUKI Noriaki

    Offer Organization: Japan Society for the Promotion of Science

    System: Grants-in-Aid for Scientific Research

    Category: Grant-in-Aid for Scientific Research (C)

    2009 - 2011

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    We previously reported that cancer cell apoptosis was induced through electroporation(membrane pore formation) with the application of low voltage electric pulses(LVEPs). In this study, we reported about the apoptosis mechanism of cancer cells that LVEPs impose cell stress and induce apoptosis through caspases activation of both cell death receptor and mitochondrial pathways following intrcellular Ca++elevation. A series of our studies suggest that LVEPs which might be mild damage to the patients could take place of high voltage electrochemtherapy which is studied as a new anti-cancer therapy.

  23. Computational nano-biomechanics for the diagnosis, treatment, and prevention of diseases of blood, circulatory, and digestive organs

    YAMAGUCHI Takami, ISHIKAWA Takuji, IMAI Yohsuke, MORI Daisuke, MATSUKI Noriaki, MIZUNO Fumio

    Offer Organization: Japan Society for the Promotion of Science

    System: Grants-in-Aid for Scientific Research

    Category: Grant-in-Aid for Scientific Research (S)

    Institution: Tohoku University

    2007 - 2010

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    We have developed computational nano-biomechanics for the diagnosis, treatment, and prevention of diseases of blood, circulatory, and digestive organs. We proposed a novel hemodynamic index to predict the initiation of cerebral aneurysms. A numerical model of microvascular blood flow was developed for simulating microvascular occlusion in malaria infection, and thrombogenesis. A model of swimming microorganisms was also developed for analyzing intestinal flora.

  24. Reconstruction of a bio-fluid dynamics model from the cellular level

    ISHIKAWA Takuji

    Offer Organization: Japan Society for the Promotion of Science

    System: Grants-in-Aid for Scientific Research

    Category: Grant-in-Aid for Young Scientists (A)

    Institution: Tohoku University

    2007 - 2009

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    We had developed a numerical model of microorganisms, red blood cells and cancer cells by 2008. We also tried to model biological reaction of cells. In 2009, we utilized these models and computed many body interactions of cells in a suspension. Then we compiled a database for the stress field, diffusion tensor under various conditions. We also developed a mathematical model of these tensor values under simplified conditions. Besides, we develop a numerical model to solve population of bacteria in the human intestine by combining the cellular level models and the macroscopic models. We established a base for the multi-scale and multi-physics simulation for the microbial flora in the intestine.

  25. 病変を伴う小動脈内の血流と血球同士の干渉による特異流動

    石川 拓司

    Offer Organization: 日本学術振興会

    System: 科学研究費助成事業

    Category: 若手研究(B)

    2005 - 2006

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    血球の干渉と血流の数値シミュレーション 実際の血液のヘマトクリット値は40-50%と非常に高く,赤血球同士が結合してルーロー(連銭)を形成するなど複雑な挙動を示すため,赤血球同士の干渉を表現することは実際の血流を取り扱う上で非常に重要なステップである. 申請者はこれまでに,Bradyらが剛体球の濃厚サスペンションを対象に開発したStokesian Dynamics Simulationの手法を微生物溶液に適用し,ミクロスケールの粒子間の流体力学的干渉を厳密に表現することに成功してきた.本年度はその手法を赤血球に適用し,赤血球の濃厚溶液である血液の数理モデル化を行った.特に赤血球の近距離干渉に焦点を当て,高分子の架橋構造による干渉力をばね力でモデル化することに成功した.狭さく部を通る血流の数値シミュレーションも行い,解析結果を実験結果との比較した. 赤血球を用いた血球の干渉実験および血流の可視化実験 シミュレーションの妥当性を検討するには,対応する実験データが不可欠である.そこで本研究では,研究室に既存のconforcal-micro PIVシステムを用い,染色した赤血球の干渉実験および血流の可視化実験を行った.微小血管の狭さく部を模擬した流路は,PDMS micro channelを用いて作成した.実験結果を数値シミュレーション結果と比較検討し,解析手法の妥当性を確認した.

  26. Mechanism of the formation, destruction, and movement of thrombi responsible for ischemia of vital organs

    YAMAGUCHI Takami, WADA Shigeo, TSUBOTA Ken-ichi, ISHIKAWA Takuji, IMAI Yohsuke

    Offer Organization: Japan Society for the Promotion of Science

    System: Grants-in-Aid for Scientific Research

    Category: Grant-in-Aid for Scientific Research (A)

    Institution: Tohoku University

    2004 - 2006

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    We investigated multi-scale behaviors of the formation, destruction, and movement of thrombi under blood flow that are responsible for ischemia of vital organs by using computer simulation and in vitro experiments based on biomechanics. We carried out computer simulations based on a Stokesian Dynamics method and a particle method to characterize the relationships between physiological and fluid mechanical factors in platelet aggregation under blood flow. We determined the relationships between deformation of red blood cells and apparent blood flow resistance. The result indicated that interactions among blood cells play a pivotal role in blood flow properties. It was also shown that biological/mechanical interactions among different types of blood cells determine thrombogenesis process. We established an in vitro quantitative measurement of blood flow through micro channel with micro PIV system, and obtained a spatiotemporal velocity fluctuation in blood flow that depends on hemaetocrit values. This indicated that mechanical interaction among blood cells governs blood flow properties. We proposed a large-scale computer simulation model of flow of red blood cells with the Earth Simulator, and established mathematical formulae of blood flow that can explain hierarchical mechanical behaviors of blood flows from the scale of blood cells (jam) to large vessel (cm). We also developed an integrated computer model of the left ventricle and the aorta, and demonstrated that the model is practically useful in detailed evaluation of the vortex and stagnation, which greatly affects thrombogenesis, in heart and large arteries.

  27. Study on Mechanisms of the Development of Cardiovascular and Cerebrovascular Diseases

    YAMAGUCHI Takami, ISHIKAWA Takuji, TSUBOTA Ken-ichi, IMAI Yohsuke, WADA Shigeo

    Offer Organization: Japan Society for the Promotion of Science

    System: Grants-in-Aid for Scientific Research

    Category: Grant-in-Aid for Scientific Research on Priority Areas

    Institution: Tohoku University

    2003 - 2006

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    Human cardiovascular system is always under the integrated nervous and Humoral control of the whole body, i.e., in homeostasis. Multiple feedback mechanisms with mutual interactions among systems, organs, and even tissues provide integrated control of the entire body. These control mechanisms have different spatial coverage, from the micro- to macroscale, and different time constants, from nanoseconds to decades. Based on this consideration, we investigated the cardiovascular system over micro to macro levels by using conjugated computational mechanics analyzing fluid and solid interactions in the research project. We studied blood flow in the aorta with beating left ventricle as a power source, ATP transport in a cerebral artery with aneurysm, the progress of cerebral aneurysm due to adaptation of arterial wall, the blood flow considering more than 16 thousands of red blood cells' motion, and platelets aggregation in blood flow using a particle method developed for the purpose. The aortic blood flow showed independence from the intraventricular vortices formation downstream from the aortic arch, where the three dimensional configuration of the aorta determined the global flow structure. Transport and distribution of ATP molecule was found to be strongly dependent on the relative position of aneurysms to the mother arteries. The particle method developed in the present study showed its potential to represent the microscale aggregation process of the platelet in the blood flow. In considering clinical applications, however, one needs to include more about biological complexities in the analysis of blood flow, especially with respect to disease processes. A disease is not just a failure of machine. It is an outcome of complex interactions among multi-layered systems and subsystems. We expect that biological phenomena, including disease processes, will be clarified in the future by integrating new understandings of macroscale and microscale hemodynamics.

  28. 動脈硬化症を伴う細動脈を通る血流と赤血球の特異流動

    石川 拓司

    Offer Organization: 日本学術振興会

    System: 科学研究費助成事業

    Category: 若手研究(B)

    Institution: 福井大学

    2002 - 2003

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    細動脈内の動脈硬化症の進展においては,流体力学的要因が重要な役割を果たすことが報告されているため,細動脈狭さく部における血流を解明することは重要である.従来の動脈内の血流を対象とした研究は大半が大動脈を対象としており,小動脈や細動脈を対象とした研究は数少ない.この原因は,血液中に含まれる赤血球の直径は8μm程度であり,直径が0.1mm程度の細動脈においては血液を均質と仮定できず,構成方程式の適用に限界があるためである. そこで本年度は,これまでに申請者が開発してきた赤血球の分布と変形を考慮できる離散的な数値解析手法(DEM)を用い,細動脈内の狭さく部を通る血流を調べるための数値シミュレーションコードを開発した.そして数値シミュレーションをさまざまなケースで実施し,狭さく部周辺での流れの様子や壁面せん断応力などの諸量を調べた.その結果,冠状動脈や脳内の細動脈における動脈硬化症進展のメカニズム解明に有用な知見を得ることができた.この研究成果は,日本機械学会2002年度年次大会講演論文集に発表されている.次年度は,ルーロー(連銭)構造の形成過程を表現できるよう,数値解析コードを改良する予定である. また,本年度は数値解析と平行して模擬赤血球の定ずり速度下の挙動を調べるための実験装置を製作した.多くの種類の模擬赤血球を試作し,本実験に適したマイクロカプセルの作成に成功した.実験装置はほぼ完成しており,次年度に多くの実験を実施し,数値シミュレーションとの対応付けを行う予定である.

  29. 血液のミクロスケール流れを表現できる数値シミュレーション手法の開発

    石川 拓司

    Offer Organization: 日本学術振興会

    System: 科学研究費助成事業

    Category: 奨励研究(A)

    Institution: 福井大学

    2000 - 2001

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    従来の動脈内の血流を対象とした研究は大半が大動脈を対象としており,細動脈や微細動脈を対象とした研究は数少ない.この原因は,血液中に含まれる赤血球の直径は8μm程度であり,直径が0.1mm以下の細動脈においては血液を均質と仮定できず,赤血球の取り扱いが難しいためと考えられる.均質な非ニュートン流体の流れを解く場合には,ずり速度と応力の関係を表す構成方程式を用いてレオロジー的挙動を記述する.しかし細動脈内の血流のように均質を仮定できない場合には,構成方程式の適用には限界があると考えられる.そこで本研究では,球とばね,ダンパを用いたモデルを流体内に多数混入し,構成方程式を用いずに血液の粘弾性的な挙動を表現することを目的として研究を行っている. 平成13年度は血液のポアズイユ流れの数値シミュレーションを行い,日本機械学会2001年度年次大会において「変形する赤血球モデルによる血液のポアズイユ流れのシミュレーション」という題目で講演を行った.また,「Proposal of a Deformable Erythrocyte Model and Numerical Analysis of a Shear Flow of Blood」という題目で,JSME International J.に1編の論文が掲載され,日本機械学会誌にも1編の論文が掲載されている.このように,研究成果は順調に上がっている. また,今年に入り細動脈内狭さく部を通る血液の数値シミュレーションを開始しており,日本機械学会2002年度年次大会において「離散赤血球法による細動脈狭さく部を通る血流のシミュレーション」という題目で講演を行う予定である.

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Social Activities 30

  1. 医療工学技術者創成のための再教育システム

    2006/04/01 - 2018/03/31

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    講師「生体力学」

  2. EMBEE 講師

    EMBEE

    2019/04/01 -

  3. Microorganisms Can Escape from a Dead End by Swimming

    2018/03/23 -

  4. 微生物は危険な場所を巧みに回避することができる

    2018/03/02 -

  5. 東北大、デッドエンドを回避する微生物の仕組みを発見

    2018/03/01 -

  6. 細菌のべん毛は、スピンだけでなく旋回運動もしていた―東北大・下權谷祐氏ら

    2016/01/06 -

  7. 意外と知られていなかった生物の不思議: 細菌のべん毛、付け根も旋回している意外な事実を発見

    2015/12/28 -

  8. 東北大と阪大、細菌のべん毛のコマのような回転挙動のメカニズムを解明

    2015/12/28 -

  9. Fast, Fluid Cells Spread Cancer

    2015/12/16 -

  10. 生き物の明日を予測する ~生物シミュレーションの最前線~

    2014/12/11 -

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    仙台市立仙台青陵中等教育学校・講演会

  11. Featured in Kaleidoscope: Dispersion of model microorganisms swimming in a nonuniform suspension

    2014/10/10 -

  12. 市民講座「未来をツクル ―東北大学機械系若手研究者の挑戦―」

    2013/08/25 -

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    市民講座「未来をツクル ―東北大学機械系若手研究者の挑戦―」

  13. 市民講座「世界をリードする東北大学機械系の若手研究者が目指す未来社会」

    2012/12/27 -

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    市民講座「世界をリードする東北大学機械系の若手研究者が目指す未来社会」

  14. 乳がん細胞 低コスト検出

    2012/03/07 -

  15. 市民講座「世界をリードする東北大学機械系の若手研究者が目指す未来社会」

    2012/03/01 -

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    市民講座「世界をリードする東北大学機械系の若手研究者が目指す未来社会」

  16. Bacteria, live in 3D

    2011/07 -

  17. Tiny travelers take on a viscous world

    2009/07 -

  18. 出会い求め?ダンスを踊る 藻類「ボルボックス」

    2009/05 -

  19. Not Bad For Pond Scum

    2009/04 -

  20. 東北大学、藻類のボルボックスがワルツやメヌエットなどのダンスを踊る姿を発見

    2009/04 -

  21. 团藻运动研究

    2009/04 -

  22. Descubren algas que 'bailan' para mantenerse unidas

    2009/04 -

  23. Study: Algae can form stable groupings

    2009/04 -

  24. Scientists discover 'dancing' algae

    2009/04 -

  25. `Dancing' algae can `waltz' and `minuet'

    2009/04 -

  26. Cientistas britânicos descobrem 'algas dançarinas'

    2009/04 -

  27. Pond Scum to Pond Scum: “Shall we dance?”

    2009/04 -

  28. 藻類、優雅に“ワルツ” 東北大グループ発見

    2009/04 -

  29. Shall we dance?

    2009/04 -

  30. Research Highlights : Dynamics of a dance

    2009/04 -

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Media Coverage 14

  1. 心臓は左…体の「左右」はどう決まる? カギは2種類の「毛」の共演

    朝日新聞デジタル

    2023/01

    Type: Newspaper, magazine

  2. 体の左右非対称を決めるのは、化学物質ではなく「力」と判明

    Newsweek日本版

    2023/01

    Type: Newspaper, magazine

  3. 体の左右非対称を決めるのは、化学物質ではなく「力」と判明

    YahooJapanニュース

    2023/01

    Type: Internet

  4. 哺乳類の体のつくりが左右非対称 その仕組みは?

    NHK NEWS WEB

    2023/01

    Type: TV or radio program

  5. 臓器づくりの左右非対称性 発生初期 機械的な力で決定

    科学新聞

    2023/01

    Type: Newspaper, magazine

  6. Visualization of the "Brazil nut effect," an interesting phenomenon of microbial origin

    Science Japan

    2022/02

    Type: Internet

  7. 流れに逆らって泳ぐ微生物

    読売新聞

    2022/01

    Type: Newspaper, magazine

  8. 大きな粒子が浮上 小さな粒子が沈降 微生物由来の興味深い現象発見

    科学新聞

    2021/12

    Type: Newspaper, magazine

  9. 競争ではなく協力...「精子は助け合って泳ぐ」東北大が発表 不妊治療へ期待

    テレ東ニュース

    2020/11

    Type: TV or radio program

  10. 単細胞から多細胞生物へ、進化の謎を解き明かす鍵を解明 東北大

    BIGLOBEニュース

    2020/11

    Type: Internet

  11. マスクや衣服の擦れによる皮膚の脆弱化メカニズムを解明

    日本学術振興会HP

    2020/09

    Type: Promotional material

  12. ウイルス感染リスクが高まる長時間のマスク着用 - 摩擦刺激で皮膚が脆弱化

    マイナビニュース

    2020/08

    Type: Internet

  13. 過度な摂食制限は寿命を縮める恐れも 線虫で短命化傾向を発見 東北大

    BIGLOBEニュース

    2020/07

    Type: Internet

  14. 小宇宙の中の流れを解析しながら未来への確かな一歩を刻む

    りらく

    2010/08

    Type: Newspaper, magazine

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Other 6

  1. Artificial micro swimmer

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    Artificial micro swimmer

  2. Order in concentrated suspensions of microswimmers

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    Order in concentrated suspensions of microswimmers

  3. ナノイメージングと計算生体力学の融合によるがん転移モデルの構築と薬効評価

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    ナノイメージングと計算生体力学の融合によるがん転移モデルの構築と薬効評価

  4. Flow of malaria infected blood

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    Flow of malaria infected blood

  5. Simulation of deformable red blood cells

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    Simulation of deformable red blood cells

  6. Fluid dynamics of a suspension of micro-organisms

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    Fluid dynamics of a suspension of micro-organisms

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