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今井 陽介大学院工学研究科 機械工学専攻教授
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■ 受賞- 2019年12月 Asian Pacific Association for Computational Mechanics, APACM Award for Young Investigators in Computational Mechanics
- 2019年05月 日本計算工学会, 第24回計算工学講演会 グラフィックスアワード優秀賞国内学会・会議・シンポジウム等の賞
- 2019年05月 日本計算工学会, 第24回計算工学講演会 グラフィックスアワード特別賞（Meshman賞）国内学会・会議・シンポジウム等の賞
- 2018年07月 Japan Association for Computational Mechanics, JACM Fellows Award国内学会・会議・シンポジウム等の賞
- 2017年09月17日 日本機械学会, 日本機械学会計算力学部門 業績賞日本国国内学会・会議・シンポジウム等の賞
- 2015年12月04日 青葉工学振興会, 第9回青葉工学振興会賞日本国出版社・新聞社・財団等の賞
- 2014年07月 Dynamics of Capsules, Vesicles, and Cells in Flow, Best Poster Award国際学会・会議・シンポジウム等の賞
- 2014年04月 文部科学省, 平成26年度科学技術分野の文部科学大臣表彰 若手科学者賞日本国国内外の国際的学術賞
- 2014年03月 Advances in Computation Fluid-Structure Interaction and Flow Simulation, Poster Award (Second Place)日本国国際学会・会議・シンポジウム等の賞
- 2013年08月 7th Asian Pacific Conference on Biomechanics, APCB2013 Award for Excellent Thesis国際学会・会議・シンポジウム等の賞
- 2013年03月 Journal of Biomechanical Science and Engineering, JBSE Graphics of the Year Award日本国学会誌・学術雑誌による顕彰
- 2012年06月 日本計算工学講演会, 第17回計算工学講演会 ベストペーパーアワード日本国国内学会・会議・シンポジウム等の賞
- 2012年01月 日本機械学会バイオエンジニアリング部門, 日本機械学会バイオエンジニアリング部門 瀬口賞日本国国内学会・会議・シンポジウム等の賞
- 2011年11月 Journal of Biomechanical Science and Engineering, JBSE Papers of the Year Award日本国学会誌・学術雑誌による顕彰
- 2010年07月 日本計算力学連合, JACM Award for Young Investigators in Computational Mechanics日本国出版社・新聞社・財団等の賞
- 2010年04月 日本機械学会, 日本機械学会奨励賞（研究）日本国出版社・新聞社・財団等の賞
- 2010年01月 青葉工学振興会, 第15回青葉工学研究奨励賞日本国出版社・新聞社・財団等の賞
- 2008年12月 International Conference on Biomedical Engineering, Young Investigator Award Merit Prize国際学会・会議・シンポジウム等の賞
- 2007年02月 財団法人手島工業教育資金団, 手島記念研究賞（博士論文賞）日本国出版社・新聞社・財団等の賞
- 2006年12月 第20回数値流体力学シンポジウム実行委員会, 第20回数値流体力学シンポジウム ベストCFDグラフィックス・アワード最優秀賞日本国国内学会・会議・シンポジウム等の賞
- 2006年11月 日本機械学会計算力学部門, 日本機械学会第19回計算力学講演会 ビジュアリゼーションコンテスト優秀作品賞日本国国内学会・会議・シンポジウム等の賞
- 2005年12月 第19回数値流体力学シンポジウム実行委員会, 第19回数値流体力学シンポジウム ベストCFDグラフィックス・アワード最優秀賞日本国国内学会・会議・シンポジウム等の賞
- 2005年11月 日本機械学会計算力学部門, 日本機械学会第18回計算力学講演会 ビジュアリゼーションコンテスト最優秀作品賞日本国国内学会・会議・シンポジウム等の賞
- 2004年12月 第18回数値流体力学シンポジウム実行委員会, 第18回数値流体力学シンポジウム ベストCFDグラフィックス・アワード優秀賞日本国国内学会・会議・シンポジウム等の賞
- This study evaluates gastric electrophysiology in relation to the menstrual cycle using a novel noninvasive high-resolution methodology, revealing substantial variations in gastric activity with menstrual cycling and menopause. Gastric slow-wave frequency is significantly higher in the luteal versus follicular menstrual phase. Computational modeling predicts that this difference translates to higher rates of gastric mixing and liquid emptying in the luteal phase, which is consistent with previous experimental data evaluating menstrual cycling effects on gastric emptying.American Physiological Society, 2024年07月, American Journal of Physiology-Gastrointestinal and Liver Physiology, 327(1) (1), G47 - G56研究論文（学術雑誌）
- Understanding the growth-induced deformation of soft materials in viscous environments is important for a variety of problems in nature and engineering. Here, we focus on the fluid–structure interaction of a hyperelastic sheet growing in an incompressible Newtonian fluid in the Stokes flow regime. We develop a computational framework for simulating this problem, where the isogeometric boundary integral method is used with the Kirchhoff–Love shell formulation and elastic–plastic decomposition of the deformation gradient tensor. We quantify the relative effects of the growth rate, the sheet bending rigidity, and the fluid viscosity on the fold formation and development of the growing sheet. Our results suggest that the viscous resistance to in-plane deformation promotes fold formation, whereas the viscous resistance to out-of-plane deformation suppresses fold development. We also investigate the effects of the thickness and aspect ratio of the rectangular sheet. Finally, we compare the growth- and prestrain-induced deformations to find a common behavior of sheets under viscous environments.AIP Publishing, 2024年05月, Physics of Fluids, 36(5) (5)研究論文（学術雑誌）
- Effects of magnetic field applied perpendicular to a shear plane in shear flow on the deformation of a ferrofluid droplet are numerically investigated. The boundary integral method is employed to solve the two-phase Stokes flow under a uniform magnetic field. When the magnetic field is applied perpendicular to the shear plane, the deformation of the droplet in the shear plane decreases. The magnetic field causes the droplet to elongate in the y-direction, and its cross-sectional radius in shear plane decreases. Consequently, the apparent capillary number in the shear plane decreases, thereby suppressing the droplet deformation. Droplet breakup is also suppressed by imposing a magnetic field perpendicular to the shear plane, thereby increasing the critical capillary numbers. The critical capillary numbers for the magnetic Bond numbers Bo = 2.0 and 4.0 increase to approximately 110% and 130%, respectively, than those without magnetic field. Furthermore, an equation for the theoretical prediction of the droplet deformation under a magnetic field in shear flow is presented, which is based on the small deformation theory, the decrease in the cross-sectional radius, and the boundary conditions at the droplet interface. The theoretical prediction agrees well with the numerical results for the variation in the magnetic susceptibility of the droplet as well as the viscosity ratio between the external fluid and the ferrofluid droplet under a small deformation. The critical capillary numbers under a magnetic field can also be predicted by using the numerical results without a magnetic field.AIP Publishing, 2024年03月, Physics of Fluids, 36(3) (3)研究論文（学術雑誌）
- Elsevier BV, 2024年03月, Journal of Fluids and Structures, 125, 104081 - 104081研究論文（学術雑誌）
- Elsevier BV, 2024年01月, Journal of Fluids and Structures, 124, 104022 - 104022研究論文（学術雑誌）
- 一般社団法人 日本機械学会, 2023年, バイオフロンティア講演会講演論文集, 2023.34, 2B05, 日本語
- 一般社団法人 日本機械学会, 2023年, バイオフロンティア講演会講演論文集, 2023.34, 2G09, 日本語
- 一般社団法人 日本機械学会, 2023年, バイオフロンティア講演会講演論文集, 2023.34, 1B02, 日本語
- The amplitude and frequency of peristaltic contractions are two major parameters for assessing gastric motility. However, it is not fully understood how these parameters affect the important functions of the stomach, such as gastric mixing and emptying. This study aimed to quantify the effects of peristaltic amplitude and frequency on gastric mixing and emptying using computational fluid dynamics simulation of gastric flow with an anatomically realistic model of the stomach. Our results suggest that both the increase and decrease in peristaltic amplitude have a significant impact on mixing strength and emptying rate. For example, when the peristaltic amplitude was 1.2 times higher than normal, the emptying rate was 2.7 times faster, whereas when the amplitude was half, the emptying rate was 4.2 times slower. Moreover, the emptying rate increased more than proportionally with the peristaltic frequency. The nearest contraction wave to the pylorus and the subsequent waves promoted gastric emptying. These results suggest the importance of maintaining parameters within normal ranges to achieve healthy gastric function.The Royal Society, 2023年01月, Journal of The Royal Society Interface, 20(198) (198)[査読有り]研究論文（学術雑誌）
- Peristaltic pumping is the primary mechanism of food transport in the human intestine. Intestinal contents are often modeled as power-law fluids with low-behavior indices ( n < 1). Peristaltic flows were studied for periodic contraction waves ([Formula: see text]) with infinitely long wavelengths ([Formula: see text]) in the Stokes flow regime ([Formula: see text]). However, the peristaltic flow generated by an isolated contraction wave with a short wavelength at nonzero Reynolds numbers is more relevant to physiological conditions. In this study, we investigated the peristaltic transport of a power-law fluid with a low behavior index of n = 0.21 at nonzero Reynolds numbers up to Re = 10, generated by a single short contraction wave. First, we investigated the analytical solution for the peristaltic transport of the power-law fluid for [Formula: see text] and [Formula: see text]. The analytical solution shows that the discharge flow rate of a power-law fluid generated by a single contraction wave is much smaller than that of a Newtonian fluid ( n = 1). Next, we investigated the peristaltic transport for [Formula: see text] 10 using the cumulant lattice Boltzmann method. The numerical results demonstrate that the discharge flow rate for the power-law fluid sharply increased owing to the inertia effect. The power-law fluid induces an asymmetric flow field with respect to the contraction wave at smaller Reynolds numbers than Newtonian fluids. The inertia effect was increased by the sharpness of the contraction wave. These results suggest that intestinal contents can be transported more quickly by an isolated contraction wave with a shorter wavelength when the contents have low consistency indices or when the contraction wave has a large propagation velocity.AIP Publishing, 2022年11月, Physics of Fluids, 34(11) (11), 111911 - 111911[査読有り]研究論文（学術雑誌）
- Ciliary motility disorders are known to cause hydrocephalus. The instantaneous velocity of cerebrospinal fluid (CSF) flow is dominated by artery pulsation, and it remains unclear why ciliary dysfunction results in hydrocephalus. In this study, we investigated the effects of cilia-induced surface velocity on CSF flow using computational fluid dynamics. A geometric model of the human ventricles was constructed using medical imaging data. The CSF produced by the choroid plexus and cilia-induced surface velocity were given as the velocity boundary conditions at the ventricular walls. We developed healthy and reduced cilia motility models based on experimental data of cilia-induced velocity in healthy wild-type and Dpcd-knockout mice. The results indicate that there is almost no difference in intraventricular pressure between healthy and reduced cilia motility models. Additionally, it was found that newly produced CSF from the choroid plexus did not spread to the anterior and inferior horns of the lateral ventricles in the reduced cilia motility model. These findings suggest that a ciliary motility disorder could delay CSF exchange in the anterior and inferior horns of the lateral ventricles.The Royal Society, 2022年08月, Journal of The Royal Society Interface, 19(193) (193)[査読有り]研究論文（学術雑誌）
- American Physical Society (APS), 2022年06月, Physical Review Fluids, 7(6) (6)[査読有り]研究論文（学術雑誌）
- 一般社団法人 日本機械学会, 2022年, バイオフロンティア講演会講演論文集, 2022.33, 1F15, 日本語
- 一般社団法人 日本機械学会, 2022年, バイオフロンティア講演会講演論文集, 2022.33, 1F18, 日本語
- American Physical Society (APS), 2021年09月, Physical Review Fluids, 6(9) (9)[査読有り]研究論文（学術雑誌）
- Wiley, 2021年01月, Physiological Reports, 8(24) (24)[査読有り]研究論文（学術雑誌）
- The cerebral vasculature has a complex and hierarchical network, ranging from vessels of a few millimeters to superficial cortical vessels with diameters of a few hundred micrometers, and to the microvasculature (arteriole/venule) and capillary beds in the cortex. In standard imaging techniques, it is difficult to segment all vessels in the network, especially in the case of the human brain. This study proposes a hybrid modeling approach that determines these networks by explicitly segmenting the large vessels from medical images and employing a novel vascular generation algorithm. The framework enables vasculatures to be generated at coarse and fine scales for individual arteries and veins with vascular subregions, following the personalized anatomy of the brain and macroscale vasculatures. In this study, the vascular structures of superficial cortical (pial) vessels before they penetrate the cortex are modeled as a mesoscale vasculature. The validity of the present approach is demonstrated through comparisons with partially observed data from existing measurements of the vessel distributions on the brain surface, pathway fractal features, and vascular territories of the major cerebral arteries. Additionally, this validation provides some biological insights: (i) vascular pathways may form to ensure a reasonable supply of blood to the local surface area; (ii) fractal features of vascular pathways are not sensitive to overall and local brain geometries; and (iii) whole pathways connecting the upstream and downstream entire-scale cerebral circulation are highly dependent on the local curvature of the cerebral sulci.2020年06月, PLoS computational biology, 16(6) (6), e1007943, 英語, 国際誌[査読有り]研究論文（学術雑誌）
- Japan Society of Mechanical Engineers, 2020年, Journal of Biomechanical Science and Engineering[査読有り]研究論文（学術雑誌）
- This study investigated hemodynamic changes in the thoracic aorta and aortic arch branches before and after aortic valve replacement (AVR) by 4D-flow MRI in patients with aortic valve stenosis (AS). Thoracic 4D-flow MRI was performed in 10 AS patients before and after AVR (mean 27 ± 1.9 days). Fifteen aortic planes and 3 aortic arch branches planes were set to evaluate the mean volume flow rate in each plane during a cardiac cycle and the angle between the main flow direction in a specified plane and the axial direction of the aorta. We also focused on the distribution and magnitude of helicity density to evaluate the flow complexity. A significant increase in the volume flow rate after AVR was found in the ascending aorta (before 59.2 ± 8.7 mL/s vs after 77.3 ± 6.2 mL/s, P < 0.05) and the aortic arch branches (before 26.5 ± 2.8 mL/s vs after 35.8 ± 3.3 mL/s, P < 0.001). The flow angle significantly decreased in the ascending aorta (before 39.2 ± 2.7 degree vs after 25.2 ± 1.7°, P < 0.0001) and the arch aorta (before 19.3 ± 2.0 degree vs after 13.4 ± 0.9°, P < 0.001). The volume flow rate in the ascending aorta and the arch branches increased within 1 month after AVR, showing an increased blood supply to the upper body, including to the brain. The postoperative change was accompanied with an increased blood flow in the ascending aorta and a decreased flow complexity proximal to the arch branches.2020年, Seminars in thoracic and cardiovascular surgery, 32(1) (1), 25 - 34, 英語, 国際誌[査読有り]研究論文（学術雑誌）
- 2019年11月, Physical Review Fluids, 4, 113601, 英語[査読有り]研究論文（学術雑誌）
- © 2019 The Japan Society of Mechanical Engineers. Studies on platelet margination have shown that the platelets can effectively marginate at the microvessel wall in a multi-file flow of red blood cells (RBCs), whereas axially migrated RBCs push platelets toward the wall. However, it is unclear whether these results can be extended to capillaries, which potentially cause a single-file line of RBCs, or a so-called bolus flow. Our previous numerical results (Takeishi and Imai, 2017) showed that microparticles with a diameter of 1 m (1-m-MPs) were captured by a bolus flow of RBCs, instead of being marginated in capillaries. Herein we perform numerical simulations to clarify whether platelets are captured or escape from the vortex-like flow structures between RBCs. We demonstrate that platelets are also captured in a capillary whose diameter is 25% larger than that of RBCs at a physiologically-relevant hematocrit (Hct 0.2), but the number of captured platelets is smaller than that of 1-m-MPs. When the capillary diameter is comparable to that of RBCs, however, many platelets flow near the wall due to an unstable bolus flow resulting in a less number of captured platelets. These results suggest that the size effect reduces platelet capture events compared to 1-m-MPs. We also investigate the effect of Hct and the non-dimensional shear rate (capillary number) on capture events. These findings may help not only to understand platelet adhesion in capillaries but also to develop therapeutic drug carriers.2019年11月, Journal of Biomechanical Science and Engineering, 14(3) (3), 18 - 00535, 英語[査読有り]研究論文（学術雑誌）
- Common practices to improve the ability to swallow include modifying physical properties of foods and changing the posture of patients. Here, we quantified the effects of the viscosity of a liquid bolus and patient posture on the bolus pathway and pharyngeal residue using a computational fluid dynamics simulation. We developed a computational model of an impaired pharyngeal motion with a low pharyngeal pressure and no pharyngeal adaptation. We varied viscosities from 0.002 to 1 Pa·s and postures from -15° to 30° (from nearly vertical to forward leaning). In the absence of pharyngeal adaptation, a honey-like liquid bolus caused pharyngeal residue, particularly in the case of forward-leaning postures. Although the bolus speed was different among viscosities, the final pathway was only slightly different. The shape, location, and tilting of the epiglottis effectively invited a bolus to two lateral pathways, suggesting a high robustness of the swallowing process.NEW & NOTEWORTHY Thickening agents are often used for patients with dysphagia. An increase in bolus viscosity not only reduces the risk of aspiration but also can cause a residual volume in the pharynx. Because information obtained from videofluoroscopic swallowing studies is only two-dimensional, measurement of pharyngeal residue is experimentally difficult. We successfully quantified the three-dimensional bolus pathway and the pharyngeal residual volume using computational modeling and simulation.2019年11月, American Journal of Physiology Gastrointestinal and Liver Physiology, 317(6) (6), G784 - G792, 英語, 国際誌[査読有り]研究論文（学術雑誌）
- Proper coordination of gastric motor functions is required for healthy gastric emptying. However, pyloric function may be impaired by functional disorders or surgical procedures. Here, we show how coordination between pyloric closure and antral contraction affects the emptying of liquid contents. We numerically simulated fluid dynamics using an anatomically realistic gastrointestinal geometry. Peristaltic contractions in the proximal stomach resulted in gastric emptying at a rate of 3-8 ml min-1. When the pylorus was unable to close, the emptying rate increased to 10-30 ml min-1, and instantaneous retrograde flow from the duodenum to the antrum occurred during antral relaxation. Rapid emptying occurred if the pylorus began to open during the terminal antral contraction, and the emptying rate was negative if the pylorus only opened during the antral relaxation phase. Our results showed that impaired coordination between antral contraction and pyloric closure can result in delayed gastric emptying, rapid gastric emptying and bile reflux.2019年08月, Journal of the Royal Society Interface, 16(157) (157), 20190266 - 20190266, 英語, 国際誌[査読有り]研究論文（学術雑誌）
- © Cambridge University Press 2019 We present a numerical analysis of the rheology of a suspension of red blood cells (RBCs) in a wall-bounded shear flow. The flow is assumed as almost inertialess. The suspension of RBCs, modelled as biconcave capsules whose membrane follows the Skalak constitutive law, is simulated for a wide range of viscosity ratios between the cytoplasm and plasma, λ = 0.1-10, for volume fractions up to φ = 0.41 and for different capillary numbers (Ca). Our numerical results show that an RBC at low Ca tends to orient to the shear plane and exhibits so-called rolling motion, a stable mode with higher intrinsic viscosity than the so-called tumbling motion. As Ca increases, the mode shifts from the rolling to the swinging motion. Hydrodynamic interactions (higher volume fraction) also allow RBCs to exhibit tumbling or swinging motions resulting in a drop of the intrinsic viscosity for dilute and semi-dilute suspensions. Because of this mode change, conventional ways of modelling the relative viscosity as a polynomial function of φ cannot be simply applied in suspensions of RBCs at low volume fractions. The relative viscosity for high volume fractions, however, can be well described as a function of an effective volume fraction, defined by the volume of spheres of radius equal to the semi-middle axis of a deformed RBC. We find that the relative viscosity successfully collapses on a single nonlinear curve independently of λ except for the case with Ca > 0.4, where the fit works only in the case of low/moderate volume fraction, and fails in the case of a fully dense suspension.2019年08月, Journal of Fluid Mechanics, 872, 818 - 848, 英語[査読有り]研究論文（学術雑誌）
- Understanding the behavior of capsules in flow and the rheology of capsule suspensions is of fundamental importance for diverse problems in nature and engineering. The particle Reynolds number of capsules is often small, and the flow field is given by the boundary integral formulation of the Stokes equations. The boundary element method (BEM) based on the boundary integral formulation is thus one of the most accurate methods for simulating capsules under Stokes flow regime. A high computational cost of BEM, however, has limited its application to relatively small scale problems. We have developed a graphics process unit (GPU) computing of BEM for capsules and biological cells in Stokes flow. We have investigated rheological properties of capsules, and those of capsule suspensions using the GPU-accelerated BEM. Here, we provide an overview of our recent studies, particularly focusing on the shear viscosity of dense suspensions of capsules in simple shear flow an overshoot phenomenon of the capsule deformation in oscillating shear flow and the sedimentation of red blood cells.Springer Basel, 2018年, Modeling and Simulation in Science, Engineering and Technology, 213 - 251, 英語論文集(書籍)内論文
- Cytoadhesion of red blood cells infected by Plasmodium falciparum (Pf-IRBCs) is predominantly found in postcapillary venules, rather than in arterioles. However, factors influencing this phenomenon remain unclear. Here, we conduct a systematic study using a numerical model coupling the fluid and solid mechanics of the cells and cellular environment with the biochemical ligand-receptor interaction. Our results show that, once a Pf-IRBC adheres to the vascular wall, the Pf-IRBC can withstand even arteriole shear stresses, and exhibits either rolling or firm adhesion. We also perform a simulation of the multistep process of cytoadhesion, consisting of flow, margination, capture, and rolling or firm adhesion. This multistep simulation suggests that a lower probability of contact with the vascular wall at high shear rates may diminish adherent Pf-IRBCs in the arterioles.CELL PRESS, 2017年09月, BIOPHYSICAL JOURNAL, 113(5) (5), 1163 - 1172, 英語[査読有り]研究論文（学術雑誌）
- 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.ELSEVIER SCI LTD, 2017年08月, JOURNAL OF BIOMECHANICS, 61, 242 - 249, 英語[査読有り]研究論文（学術雑誌）
- A BOUNDARY ELEMENT METHOD FOR CELLULAR SCALE PHYSIOLOGICAL FLOW PROBLEMS: PASSIVE MOTIONS OF RED BLOOD CELLS AND ACTIVE MOTIONS OF CILIA AND FLAGELLAYamaguchi Medal 受賞講演2017年07月, The 26th Congress of the International Society of Biomechanics (ISB 2017), 英語[招待有り]
- Previous studies have concluded that microparticles (MPs) can more effectively approach the microvessel wall than nanoparticles because of margination. In this study, however, we show that MPs are not marginated in capillaries where the vessel diameter is comparable to that of red blood cells (RBCs). We numerically investigated the behavior of MPs with a diameter of 1 mu m in various microvessel sizes, including capillaries. In capillaries, the flow mode of RBCs shifted from multi-file flow to bolus (single-file) flow, and MPs were captured by the bolus flow of the RBCs instead of being marginated. Once MPs were captured, they rarely escaped from the vortex-like flow structures between RBCs. These capture events were enhanced when the hematocrit was decreased, and reduced when the shear rate was increased. Our results suggest that microparticles may be rather inefficient drug carriers when targeting capillaries because of capture events, but nanoparticles, which are more randomly distributed in capillaries, may be more effective carriers.NATURE PUBLISHING GROUP, 2017年07月, SCIENTIFIC REPORTS, 7, 5381, 英語[査読有り]研究論文（学術雑誌）
- ObjectiveSIPA, which is mediated by vWF, is a key mechanism in arterial thrombosis under an abnormally high shear rate of blood flow. We investigated the influence of SIPA on thrombogenesis, focusing on alterations in blood flow at stenotic vessels. MethodsWe carried out a computer simulation of thrombogenesis in stenotic vessels at three different injury positions (ie, upstream, apex, and downstream of the stenosis) to evaluate the effect of SIPA. ResultsThe results demonstrated that thrombus volume increased downstream of the stenosis. In particular, growth was enhanced significantly as blood flow velocity and severity of stenosis increased. The influence of SIPA was induced by continuous exposure to high shear rate; thus, SIPA had a greater effect from the apex to downstream of the stenosis along the vessel wall. The asymmetry of the impact of SIPA contributed to the distribution of the thrombus. Furthermore, we found that the degree of SIPA was prolonged in a stenotic vessel with a distal injury, whereas it was moderate with thrombus growth in a nonstenosed vessel. This occurred because platelets and vWF that underwent a high shear rate around the apex were transported to the region downstream of the stenosis. ConclusionsThese results suggest that thrombus formation downstream of the stenosis is easily affected by SIPA and hemodynamics.WILEY, 2017年05月, MICROCIRCULATION, 24(4) (4), e12355, 英語[査読有り]研究論文（学術雑誌）
- 2017年04月, 19th International Conference on Finite Elements in Flow Problems, 英語Integrated nanobiomechanics of the living system
- 2016年12月, Abstracts Book of the 16th International Conference on Biomedical Engineering, 167, 英語RELATIONSHIP BETWEEN PERISTALTIC CONTRACTION AND GASTRIC MIXING
- 2016年12月, Abstracts Book of the 16th International Conference on Biomedical Engineering, 163, 英語DEVELOPMENT OF A BIOMECHANICAL MODEL OF CELL BEHAVIOR SUBJECTED TO CYCLIC STRETCH
- 2016年12月, Abstracts Book of the 16th International Conference on Biomedical Engineering, 54, 英語A NUMERICAL ANALYSIS OF THE LATERAL MIGRATION OF FLOWING CELLS
- 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.AMER PHYSIOLOGICAL SOC, 2016年12月, AMERICAN JOURNAL OF PHYSIOLOGY-GASTROINTESTINAL AND LIVER PHYSIOLOGY, 311(6) (6), G1114 - G1121, 英語[査読有り]研究論文（学術雑誌）
- 2016年11月, The 69th Annual Meetin g of The American Physical Society, Bulletin of the American Physical Society, DED 2016, 61, 72, 英語Numerical analysis of cell adhesion in capillary flow
- 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.CAMBRIDGE UNIV PRESS, 2016年11月, JOURNAL OF FLUID MECHANICS, 806, 102 - 128, 英語[査読有り]研究論文（学術雑誌）
- High-resolution (HR) mapping has been used to study gastric slow-wave activation; however, the specific characteristics of antral electrophysiology remain poorly defined. This study applied HR mapping and computational modeling to define functional human antral physiology. HR mapping was performed in 10 subjects using flexible electrode arrays (128-192 electrodes; 16-24 cm(2)) arranged from the pylorus to mid-corpus. Anatomical registration was by photographs and anatomical landmarks. Slow-wave parameters were computed, and resultant data were incorporated into a computational fluid dynamics (CFD) model of gastric flow to calculate impact on gastric mixing. In all subjects, extracellular mapping demonstrated normal aboral slow-wave propagation and a region of increased amplitude and velocity in the prepyloric antrum. On average, the high-velocity region commenced 28 mm proximal to the pylorus, and activation ceased 6 mm from the pylorus. Within this region, velocity increased 0.2 mm/s per mm of tissue, from the mean 3.3 +/- 0.1 mm/s to 7.5 +/- 0.6 mm/s (P < 0.001), and extracellular amplitude increased from 1.5 +/- 0.1 mV to 2.5 +/- 0.1 mV (P < 0.001). CFD modeling using representative parameters quantified a marked increase in antral re-circulation, resulting in an enhanced gastric mixing, due to the accelerating terminal antral contraction. The extent of gastric mixing increased almost linearly with the maximal velocity of the contraction. In conclusion, the human terminal antral contraction is controlled by a short region of rapid high-amplitude slow-wave activity. Distal antral wave acceleration plays a major role in antral flow and mixing, increasing particle strain and trituration.AMER PHYSIOLOGICAL SOC, 2016年11月, AMERICAN JOURNAL OF PHYSIOLOGY-GASTROINTESTINAL AND LIVER PHYSIOLOGY, 311(5) (5), G895 - G902, 英語[査読有り]研究論文（学術雑誌）
- 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.AMER PHYSIOLOGICAL SOC, 2016年08月, AMERICAN JOURNAL OF PHYSIOLOGY-HEART AND CIRCULATORY PHYSIOLOGY, 311(2) (2), H395 - H403, 英語[査読有り]研究論文（学術雑誌）
- 2016年07月, Summer Biomechanics, Bioengineering and Biotransport Conference, 742, 英語Similarities and differences between flow mode of a leukocyte and circulating tumor cell in microvessels
- 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.ELSEVIER SCI LTD, 2016年07月, JOURNAL OF BIOMECHANICS, 49(11) (11), 2221 - 2228, 英語[査読有り]研究論文（学術雑誌）
- 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.ELSEVIER SCI LTD, 2016年07月, JOURNAL OF BIOMECHANICS, 49(11) (11), 2249 - 2254, 英語[査読有り]研究論文（学術雑誌）
- Springer New York LLC, 2016年04月, Annals of Biomedical Engineering, 44(4) (4), 1323, 英語
- Severe asphyxiating thoracic dystrophy (Jeune syndrome) is usually fatal. The authors used distraction osteogenesis in a severe case and achieved 45mm distraction of the sternum and improvement in tidal volume, lung compliance, and mean airway pressure.Taylor and Francis Ltd, 2016年03月, Journal of Plastic Surgery and Hand Surgery, 50(3) (3), 180 - 183, 英語[査読有り]研究論文（学術雑誌）
- 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.CAMBRIDGE UNIV PRESS, 2016年02月, JOURNAL OF FLUID MECHANICS, 789, 481 - 499, 英語[査読有り]研究論文（学術雑誌）
- 2016年, The World Congress on Engineering 2016, ICSBB15, 515 - 518, 英語Bio-Micropump by Using A Flagellate Propulsive Force of Escherichia coli[査読有り]研究論文（国際会議プロシーディングス）
- 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 >= 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.CAMBRIDGE UNIV PRESS, 2016年01月, JOURNAL OF FLUID MECHANICS, 786, 110 - 127, 英語[査読有り]研究論文（学術雑誌）
- 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.ROYAL SOC, 2016年01月, PROCEEDINGS OF THE ROYAL SOCIETY A-MATHEMATICAL PHYSICAL AND ENGINEERING SCIENCES, 472(2185) (2185), 20150604, 英語[査読有り]研究論文（学術雑誌）
- 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]TAYLOR & FRANCIS LTD, 2016年, SCIENCE AND TECHNOLOGY OF ADVANCED MATERIALS, 17(1) (1), 454 - 461, 英語[査読有り]研究論文（学術雑誌）
- 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.AMER PHYSICAL SOC, 2015年12月, PHYSICAL REVIEW E, 92(6) (6), 063011, 英語[査読有り]研究論文（学術雑誌）
- 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.AMER PHYSICAL SOC, 2015年12月, PHYSICAL REVIEW E, 92(6) (6), 063027, 英語[査読有り]研究論文（学術雑誌）
- 2015年11月, 68th Annual Meeting of the Division of Fluid Dynamics, Bulletin of the American Physical Society, DFD 2015, 60, 116, 英語Quantification of hydrodynamic factors influencing cell lateral migration
- 2015年11月, 68th Annual Meeting of the Division of Fluid Dynamics, Bulletin of the American Physical Society, DFD 2015, 60, 72, 英語Deformable micro torque swimmer
- 2015年10月, The 3rd International Workshops on Advances in Computational Mechanics(IWACOM-III), 128, 英語Rheological analysis of dense capsule suspensions – effect of volume fraction
- 2015年10月, The 3rd International Workshops on Advances in Computational Mechanics(IWACOM-III), 47, 英語Graphics processing unit computing of cellular flow and adhesion in microvessels
- 2015年09月, The 8th Asian-Pacific Conference on Biomechanics, PS8-15, 英語Mechanics of Nodal Cilia in Early Mouse Embryo
- 2015年09月, The 8th Asian-Pacific Conference on Biomechanics, PS3-7, 英語Development of a Numerical Model of Cytoskeleton Dynamics
- 2015年09月, The 8th Asian-Pacific Conference on Biomechanics, PS3-6, 英語Clarification of Relationship between Gastric Mixing and Movement of Wall
- 2015年09月, The 8th Asian-Pacific Conference on Biomechanics, PS3-2, 英語Orientation Angle of a Single Red Blood Cell during Sedimentation
- 2015年09月, The 8th Asian-Pacific Conference on Biomechanics, PS3-1, 英語Hydrodynamic Interaction between the Small Microparticles and Red Blood Cells in Microchannel
- 2015年09月, The 8th Asian-Pacific Conference on Biomechanics, PS1-10, 英語Swimming Behavior of a Model Ciliate near a Fluid-Air or a Fluid-Solid Interface
- 2015年09月, The 8th Asian-Pacific Conference on Biomechanics, OS2-2, 英語A Numerical Simulation of Cytoadhesion and Rosette Formation of Red Blood Cells Infected by Malaria
- 2015年09月, The 8th Asian-Pacific Conference on Biomechanics, OS2-1, 英語Effect of Flow Curvature on the Migration of Blood Cells
- 2015年09月, Computational Fluid Dynamics (CFD) in Medicine and Biology II, 英語Simulations of a swimming microorganism near an fluid-air or an fluid-solid interface
- 2015年09月, Computational Fluid Dynamics (CFD) in Medicine and Biology II, 英語Separation of motile bacteria using drift force near a wall
- BioMed Central Ltd., 2015年07月, Cilia, (1) (1), 英語[査読有り]研究論文（学術雑誌）
- 2015年07月, 13th U.S. National Congress on Computational Mechanics, 英語Cellular Scale Physiological Flow: Active Swimming Sperm Cells and Passive Flowing Red Blood Cells
- 2015年07月, 13th U.S. National Congress on Computational Mechanics, 英語Viscosity Reduction in Bimodal Suspensions of Two Types of Capsules
- 2015年06月, SB3C2015, 223, 英語Peclet Number Of Ciliary Transport On The Surface Of The Tracheal Lumen
- 2015年06月, SB3C2015, 256, 英語A Computational Study Of Red Blood Cells In Stokes Flow: From Single Cellular Mechanics To Suspension Rheology
- 2015年03月, The 18th International Conference on Finite Elements in Flow Problems FEF2015, 23, 英語Rheology of A Red Blood CEll Suspension Computing with A Boundary Element-Finite Wlement Coupled Method
- 2015年, International Symposium on Integrated Nanobiomechanics, 英語Visualization of intestinal peristalsis of mosquito midgut by using micro x-ray imaging研究論文（国際会議プロシーディングス）
- 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.SPRINGER, 2015年01月, ANNALS OF BIOMEDICAL ENGINEERING, 43(1) (1), 238 - 257, 英語[査読有り]研究論文（学術雑誌）
- 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.CAMBRIDGE UNIV PRESS, 2015年, JOURNAL OF FLUID MECHANICS, 762, 288 - 301, 英語[査読有り]研究論文（学術雑誌）
- 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.The Japan Society of Mechanical Engineers, 2014年12月, Journal of Biomechanical Science and Engineering, 9(3) (3), 14-00039 - 00039-14-00039, 英語[査読有り]研究論文（学術雑誌）
- 2014年11月, The Sixth International Symposium on Aero Aqua Bio-mechanisms, 37, 英語Swimming behavior of a model microorganism at a fluid-air interface
- © 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.2014年10月, Physical Review E - Statistical, Nonlinear, and Soft Matter Physics, 90(4) (4)[査読有り]研究論文（学術雑誌）
- 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.SPRINGER, 2014年10月, COMPUTATIONAL MECHANICS, 54(4) (4), 933 - 941, 英語[査読有り]研究論文（学術雑誌）
- 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.AMER PHYSICAL SOC, 2014年10月, PHYSICAL REVIEW E, 90(4) (4), 043009, 英語[査読有り]研究論文（学術雑誌）
- 2014年09月, THE FOURTH JAPAN-SWITZERLAND WORKSHOP ON BIOMECHANICS, 102, 英語Modeling of Flow in the Stomach
- 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.Japan Soc. of Med. Electronics and Biol. Engineering, 2014年08月, Transactions of Japanese Society for Medical and Biological Engineering, 52, 45, 英語[査読有り]研究論文（学術雑誌）
- 2014年07月, 11th World Congress on Computational Mechanics, 303, 英語A numerical method for simulating gastricflow
- 2014年07月, 11th World Congress on Computational Mechanics, 303, 英語Rheological analysis of capsule suspensions containing different size capsules
- 2014年07月, Dyna Caps 2014, 英語Rheological analysis of dense capsule suspension under simple shear flow condition
- 2014年07月, Dyna Caps 2014, 英語Numerical Analysis of Capsule Suspensions Containing Two Different siza Capsules
- 2014年07月, Dyna Caps 2014, 英語Collective swimming of ellipoidal squimers
- 2014年07月, Dyna Caps 2014, 英語Margination of large cells in microchannels
- 2014年07月, 7th WORLD CONGRESS OF BIOMECHANICS, 英語Development of a numerical model for analysis of ciliary motions
- 2014年07月, 7th WORLD CONGRESS OF BIOMECHANICS, 英語Effect of Shear Gradient and Wall on Capsule Lateral Migration
- 2014年07月, 7th WORLD CONGRESS OF BIOMECHANICS, 英語Multi-scale computational study on the formation and destruction of primary thrombus under the influence of the blood flow and red blood cells
- 2014年07月, 7th WORLD CONGRESS OF BIOMECHANICS, 英語A numerical simulation on the motion ofmalaria-infected cells in microcirculatory blood flow
- 2014年07月, 7th WORLD CONGRESS OF BIOMECHANICS, 英語Numerical analysis of hydrodynamic behavior of circulating tumor cells in microchannels
- 2014年07月, Internationnal Symposium on Integrated Nanobiomechanics, 17 - 18, 英語Development of an Intracellular Structure Model for Ciliary Motion Analysis
- 2014年07月, Internationnal Symposium on Integrated Nanobiomechanics, 15 - 16, 英語Nutrient Uptake in a Suspension of Model Microorganisms
- 2014年07月, Internationnal Symposium on Integrated Nanobiomechanics, 13 - 14, 英語Capsule Lateral Migration in an Unbounded Plane Poiseuille Flow and Near-wall Shear Flow
- 2014年07月, Internationnal Symposium on Integrated Nanobiomechanics, 11 - 12, 英語Rheology of a Red Blood Cell Suspension from Dilute to Semi-dilute Regime
- 2014年07月, Internationnal Symposium on Integrated Nanobiomechanics, 9 - 10, 英語Hydrodynamic Interction between a Circulating Tumor Cell and Blood Cells in Microcirculation
- 2014年07月, Internationnal Symposium on Integrated Nanobiomechanics, 7 - 8, 英語Numerical Modeling of the Adhesion of Red Blood Cells Infected by Plasmodium Falciparum Malaria in Microcirculatory Blood Flow
- 2014年07月, Internationnal Symposium on Integrated Nanobiomechanics, 5 - 6, 英語A Numerical Analysis of Cellular Adhesion to Planar Wall Mediated by Ligand-Receptor Interactions
- 2014年07月, Internationnal Symposium on Integrated Nanobiomechanics, 3 - 4, 英語Computational Study on Thrombogenesis
- 2014年07月, Internationnal Symposium on Integrated Nanobiomechanics, 1 - 2, 英語Shear Stress Distribution in the Stomach
- 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.WILEY-BLACKWELL, 2014年07月, CYTOSKELETON, 71(7) (7), 412 - 422, 英語[査読有り]研究論文（学術雑誌）
- 2014年04月, COMPSAFE, 347 - 348, 英語Nutrient uptake in a suspension of model microorganisms
- 2014年03月, Advances in Computational Fluid-Structure Interaction and Flow Simulation, Poster Session, 英語Rheological analysis of dense capsule suspension under Stokes flow condition
- 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.2014年01月, Physical Review E - Statistical, Nonlinear, and Soft Matter Physics, 89(1) (1), 英語[査読有り]研究論文（学術雑誌）
- 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.Kluwer Academic Publishers, 2014年, Lecture Notes in Computational Vision and Biomechanics, 12, 101 - 117, 英語[査読有り]研究論文（学術雑誌）
- 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.AMER PHYSICAL SOC, 2014年01月, PHYSICAL REVIEW E, 89(1) (1), 013008, 英語[査読有り]研究論文（学術雑誌）
- 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.AMER PHYSIOLOGICAL SOC, 2014年01月, AMERICAN JOURNAL OF PHYSIOLOGY-LUNG CELLULAR AND MOLECULAR PHYSIOLOGY, 306(2) (2), L144 - L151, 英語[査読有り]研究論文（学術雑誌）
- 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.ROYAL SOC CHEMISTRY, 2014年, LAB ON A CHIP, 14(5) (5), 1023 - 1032, 英語[査読有り]研究論文（学術雑誌）
- 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.American Physiological Society, 2014年, Physiological Reports, 2(6) (6), e12037, 英語[査読有り]研究論文（学術雑誌）
- 2013年12月, APCOM2013 & ISCM2013 Conference Handbook, 15, 英語A numerical analysis of a capsule containing multiple small capsules in simple shear flow
- 2013年12月, APCOM2013 & ISCM2013 Conference Handbook, 18, 英語Numerical analysis of margination of a cancer cell in microcirculation
- 2013年12月, The15th International Conference on Biomedical Enginnering, 17 - 18, 英語Solid particle motion in the stomach during gastric mixing
- 2013年11月, Bulletin of the American Physical Society, 58, 409, 英語Nutrient uptake in a suspension of squirmers
- 2013年11月, Bulletin of the American Physical Society, 58, 97, 英語Viscoelasticity of dilute capsule suspension under Stokes flows
- 2013年11月, 7th East Asian Consortium on Biomedical Engineering, Proceeding Book, 80 - 81, 英語Viscosity of Dense Capsule Suspension Under Simple Shear FLow Condition
- 2013年11月, 7th East Asian Consortium on Biomedical Engineering, Proceeding Book, 78 - 79, 英語Margination of leukocyte in different sizes of circular micro-channel
- The importance of water-air interfaces (WAI) on microorganism activities has been recognized by many researchers. In this paper, we report a novel phenomenon: the entrapment of ciliates Tetrahymena at the WAI. We first characterized the behavior of cells at the interface and showed that the cells' swimming velocity was considerably reduced at the WAI. To verify the possible causes of the entrapment, we investigated the effects of positive chemotaxis for oxygen, negative geotaxis and surface properties. Even though the taxes were still effective, the entrapment phenomenon was not dependent on the physiological conditions, but was instead affected by the physical properties at the interface. This knowledge is useful for a better understanding of the physiology of microorganisms at interfaces in nature and in industry. © 2013 Ferracci et al.2013年10月, PLoS ONE, 8(10) (10), e75238, 英語[査読有り]研究論文（学術雑誌）
- Thrombogenesis results from the interaction between glycoprotein receptors and their ligands, although a thrombus is affected by multiple factors such as blood flow, platelet interactions, and changes in ligand characteristics. In this study, we propose a platelet adhesion and aggregation model, focusing on the interaction between the glycoprotein receptor and its ligand. First, we conducted thrombogenesis simulations to compare physiological and pathological conditions. The results suggested that simulations of thrombogenesis differed in distribution, volume, and stability of the thrombus based on disorders of platelet adhesion, aggregation, and the activation. For example, distribution and volume were affected by the activation of GPIIb/IIIa with a GPIb/IX/V deficiency. The thrombus was also unstable, but formed from the upstream side of the injured site, with a GPIIb/IIIa deficiency. Second, we investigated thrombogenesis enhanced by the shear-induced platelet aggregation (SIPA) mechanism. The results demonstrated that the degree of SIPA decreased gradually with thrombus growth in a straight vessel. This result suggests that SIPA is a key hemostasis mechanism in an injured healthy arteriole, although it can lead to the formation of an occlusive thrombus in stenosed vessels. (C) 2013 Elsevier Inc. All rights reserved.ACADEMIC PRESS INC ELSEVIER SCIENCE, 2013年09月, MICROVASCULAR RESEARCH, 89, 95 - 106, 英語[査読有り]研究論文（学術雑誌）
- 2013年08月, APCB2013 Proceedings, S12 - 002, 英語Effect of Aeration on the Bioconvection Pattern in a Microalgae Suspension
- 2013年08月, APCB2013 Proceedings, S4 - 3, 英語Modeling of cytoadhesion in malaria infection
- 2013年08月, APCB2013 Proceedings, S4 - 020, 英語Mechanism of capsule migration near a plane wall
- 2013年08月, APCB2013 Proceedings, S4 - 019, 英語Numerical simulation of motion of solid particles in the stomach
- 2013年08月, APCB2013 Proceedings, S4 - 3, 英語Margination of white blood cell in various sizes of circular micro-channel
- 2013年08月, APCB2013 Proceedings, S4 - 014, 英語Collective Swimming of Ellipsoidal Microorganisms
- 2013年08月, APCB2013 The7thAsian Pacific Conference on Biomechanics, ILS4 - 009, 英語Integrated Biomechanics for Physiological Flow Problems
- 2013年06月, COMPDYN 2013, S2090, 英語COMPUTATIONAL BIOMECHANICS ON BLOOD FLOW FROM CELLULAR TO
- 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.2013年06月, Journal of Fluid Mechanics, 724, 154 - 174, 英語[査読有り]研究論文（学術雑誌）
- 2013年03月, 6th East Asian Pacific Student Workshop on Nano-Biomedical Engineering, 52 - 53, 英語The near-wall motion of a capsule in stokes flow研究論文（国際会議プロシーディングス）
- 2013年03月, 6th East Asian Pacific Student Workshop on Nano-Biomedical Engineering, 42 - 43, 英語Simulation of nutrient uptake of a swimming model microorganism by boundary element method研究論文（国際会議プロシーディングス）
- 2013年03月, 6th East Asian Pacific Student Workshop on Nano-Biomedical Engineering, 38 - 39, 英語Numerical simulation of adhesion of malaria-infected red blood cells研究論文（国際会議プロシーディングス）
- 2013年03月, 6th East Asian Pacific Student Workshop on Nano-Biomedical Engineering, 44 - 45, 英語Numerical analysis of swimming microorganisms by a boundary element method研究論文（国際会議プロシーディングス）
- 2013年03月, 6th East Asian Pacific Student Workshop on Nano-Biomedical Engineering, 48 - 49, 英語Numerical analysis of dynamics of solid particles in the stomach研究論文（国際会議プロシーディングス）
- 2013年03月, 6th East Asian Pacific Student Workshop on Nano-Biomedical Engineering, 36 - 37, 英語Margination of various cells in microcirculation研究論文（国際会議プロシーディングス）
- 2013年03月, 6th East Asian Pacific Student Workshop on Nano-Biomedical Engineering, 78 - 79, 英語Gradient diffusion of red blood cells in blood flow through a Y-shape microchannel研究論文（国際会議プロシーディングス）
- 2013年03月, 6th East Asian Pacific Student Workshop on Nano-Biomedical Engineering, 104 - 105, 英語A numerical analysis of complex viscosity of dilute capsule suspension研究論文（国際会議プロシーディングス）
- 2013年03月, 6th East Asian Pacific Student Workshop on Nano-Biomedical Engineering, 106 - 107, 英語A numerical analysis of bimodal capsule suspensions研究論文（国際会議プロシーディングス）
- 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.2013年02月, Journal of Biomechanics, 46(3) (3), 548 - 553, 英語[査読有り]研究論文（学術雑誌）
- 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.2013年, American Journal of Physiology - Gastrointestinal and Liver Physiology, 304(5) (5), G536 - G542, 英語[査読有り]研究論文（学術雑誌）
- 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.ELSEVIER SCI LTD, 2012年12月, MEDICAL ENGINEERING & PHYSICS, 34(10) (10), 1411 - 1420, 英語[査読有り]研究論文（学術雑誌）
- 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.AMER PHYSICAL SOC, 2012年11月, PHYSICAL REVIEW E, 86(5) (5), 056321, 英語[査読有り]研究論文（学術雑誌）
- 2012年11月, Bulletin of the American Physical Society 65th Annual Meeting of the APS Division of Fluid Dynamics, 331 - 331, 英語Off-plane motion of a non-spherical capsule in simple shear flow研究論文（国際会議プロシーディングス）
- 2012年11月, Bulletin of the American Physical Society 65th Annual Meeting of the APS Division of Fluid Dynamics, 334 - 334, 英語Measurement of ciliary flow generated on the surface of tracheal lumen研究論文（国際会議プロシーディングス）
- 2012年11月, Bulletin of the American Physical Society 65th Annual Meeting of the APS Division of Fluid Dynamics, 107 - 107, 英語Hydrodynamical entrapment of ciliates at the air-liquid interface研究論文（国際会議プロシーディングス）
- 2012年11月, Bulletin of the American Physical Society 65th Annual Meeting of the APS Division of Fluid Dynamics, 330 - 330, 英語Gradient diffusion of red blood cells in blood flow through a Y-shape microchannel研究論文（国際会議プロシーディングス）
- 2012年11月, Bulletin of the American Physical Society 65th Annual Meeting of the APS Division of Fluid Dynamics, 330 - 330, 英語Analysis of red blood cell behavior in a narrow tube研究論文（国際会議プロシーディングス）
- 2012年11月, Bulletin of the American Physical Society 65th Annual Meeting of the APS Division of Fluid Dynamics, 49 - 49, 英語3D-PTV measurement of the phototactic movement of algae in shear flow研究論文（国際会議プロシーディングス）
- 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.ELSEVIER SCI LTD, 2012年10月, JOURNAL OF BIOMECHANICS, 45(15) (15), 2684 - 2689, 英語[査読有り]研究論文（学術雑誌）
- 2012年10月, International Computational Mechanics Symposium 2012 (USB), USB Memory, 英語Lateral migration of capsules in a near-wall shear flow研究論文（国際会議プロシーディングス）
- 2012年10月, International Computational Mechanics Symposium 2012, USB Memory, 英語Development of a GPU-Implemented BEM solver for biological cell suspensions研究論文（国際会議プロシーディングス）
- 2012年09月, Computational Modelling of Objects Represented in Images: Fundamentals, Methods and Applications, 239 - 242, 英語GPU computing for patient-specific model of pulmonary airflow
- 2012年09月, 9th International Conference on Flow Dynamics Proceedings, 732 - 733, 英語Role of fluid mechanics in collective motions of bacteria研究論文（国際会議プロシーディングス）
- 2012年09月, ECCOMAS 2012 Congress Proceedings, CD-ROM, 英語Computational analysis on the mechanical interaction between a thrombus and red blood cells研究論文（国際会議プロシーディングス）
- 2012年08月, Abstract Book of the 23rd International Congress of Theoretical and Applied Mechanics, 106 - 106, 英語Reorientation of a non-spherical micro-capsule in shear flow研究論文（国際会議プロシーディングス）
- 2012年07月, Biorheology, 49, 181 - 181, 英語Particle based simulation of microcirculation using a parallel computation研究論文（国際会議プロシーディングス）
- 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.ELSEVIER SCI LTD, 2012年07月, MEDICAL ENGINEERING & PHYSICS, 34(6) (6), 725 - 732, 英語[査読有り]研究論文（学術雑誌）
- 2012年06月, Softflow 2012 – Biological Complex Fluids, 36 - 37, 英語Hydrodynamic entrapment of ciliates at the air-liquid interface研究論文（国際会議プロシーディングス）
- 2012年06月, Softflow 2012 – Biological Complex Fluids, 76 - 76, 英語Dynamics of capsules near a plane wall研究論文（国際会議プロシーディングス）
- 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.ELSEVIER SCI LTD, 2012年06月, JOURNAL OF BIOMECHANICS, 45(10) (10), 1809 - 1815, 英語[査読有り]研究論文（学術雑誌）
- 2012年05月, IFMBE Proceedings, World Congress on Medical Physics and Biomedical Engineering, CD-ROM, 英語Energy efficiency in collective motions of swimming bacteria研究論文（国際会議プロシーディングス）
- 2012年03月, Biological Flow: A Conference to Celebrate the 70th Birthday of Timothy J. Padley FRS, 38, 英語Computational biomechanics of physiological flow
- 2012年03月, 18th 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, 153 - 154, 英語Rheology of a dilute suspention of red blood cells in simple shear flow研究論文（国際会議プロシーディングス）
- 2012年03月, 18th 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, 111 - 112, 英語Quantifying characteristics of blood cell at dense cellullar flow研究論文（国際会議プロシーディングス）
- 2012年03月, 18th 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, 115 - 116, 英語Hydrodynamic entrapment of ciliates at the interface fluid-air研究論文（国際会議プロシーディングス）
- 2012年03月, 18th 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, 145 - 146, 英語Effect of constitutive law on the lateral migration of a capsule near a wall研究論文（国際会議プロシーディングス）
- 2012年03月, 18th 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, 109 - 110, 英語Collective Diffusion of red blood cells from high concentration to low研究論文（国際会議プロシーディングス）
- 2012年03月, 18th 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, 61 - 64, 英語A particle model of cellular flow in microcirculation研究論文（国際会議プロシーディングス）
- 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.AMER PHYSICAL SOC, 2012年03月, PHYSICAL REVIEW LETTERS, 108(13) (13), 138102, 英語[査読有り]研究論文（学術雑誌）
- 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.2012年02月, Journal of Biomechanical Science and Engineering, 7(1) (1), 57 - 71, 英語[査読有り]研究論文（学術雑誌）
- 2012年02月, Nano-Biomedical Engineering, Imperial College Press, 134 - 143, 英語Radial dispersion of tracer particles through high-hematocrit blood flow within a capillary tube研究論文（その他学術会議資料等）
- 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.SPRINGER, 2012年02月, BIOMEDICAL MICRODEVICES, 14(1) (1), 25 - 33, 英語[査読有り]研究論文（学術雑誌）
- 2012年02月, Nano-Biomedical Engineering, Imperial College Press, 70 - 76, 英語Entrapment of fresh water ciliates at the interface fluid-air研究論文（その他学術会議資料等）
- 2012年02月, Nano-Biomedical Engineering, Imperial College Press, 53 - 62, 英語Computational biomechanics of blood flow at macro- and micro-scales研究論文（その他学術会議資料等）
- 2012年02月, Nano-Biomedical Engineering, Imperial College Press, 122 - 127, 英語Behavior of a spherical capsule in simple shear flow near an infinite plane研究論文（その他学術会議資料等）
- 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.Bentham Science Publishers Ltd., 2012年, Single and Two-Phase Flows on Chemical and Biomedical Engineering, 600 - 612, 英語[査読有り]論文集(書籍)内論文
- 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.Bentham Science Publishers Ltd., 2012年, Single and Two-Phase Flows on Chemical and Biomedical Engineering, 513 - 547, 英語[査読有り]論文集(書籍)内論文
- 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.2012年, WIT Transactions on Modelling and Simulation, 53, 201 - 208, 英語[査読有り]研究論文（国際会議プロシーディングス）
- 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.2012年, WIT Transactions on Modelling and Simulation, 53, 191 - 199[査読有り]研究論文（国際会議プロシーディングス）
- Flow visualization of trace particles and Red Blood Cells in a microchannel with a diverging and converging bifurcationThis 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.CRC PRESS-TAYLOR & FRANCIS GROUP, 2012年, COMPUTATIONAL VISION AND MEDICAL IMAGE PROCESSING: VIPIMAGE 2011, 209 - 211, 英語[査読有り]研究論文（国際会議プロシーディングス）
- 一般社団法人 日本機械学会, 2012年, バイオエンジニアリング講演会講演論文集, 2012(0) (0), _8F25 - 1_-_8F25-2_, 日本語[査読有り]研究論文（国際会議プロシーディングス）
- 一般社団法人 日本機械学会, 2012年, バイオエンジニアリング講演会講演論文集, 2012(0) (0), _7E41 - 1_-_7E41-2_, 日本語研究論文（国際会議プロシーディングス）
- AMER SOC MECHANICAL ENGINEERS, 2012年, PROCEEDINGS OF THE ASME SUMMER BIOENGINEERING CONFERENCE, PTS A AND B, CD-ROM, 839 - 840, 英語[査読有り]研究論文（国際会議プロシーディングス）
- Analysis of a suspension of microorganisms is important in environmental and biomedical engineering. Previous studies had problems of high computational load in simulating many-body interaction of non-spherical swimmers. In this study, we propose a boundary element method (BEM), based on the double-layer representation, for calculating interactions of two squirmers in Stokes flow regime. By comparing the trajectories of squirmers calculated by both single- and double-layer representations, we show the accuracy of the method. The developed method has potential to deal with many-body interactions of non-spherical microorganisms.AMER SOC MECHANICAL ENGINEERS, 2012年, PROCEEDINGS OF THE ASME SUMMER BIOENGINEERING CONFERENCE, PTS A AND B, CD-ROM, 777 - 778, 英語[査読有り]研究論文（国際会議プロシーディングス）
- AMER SOC MECHANICAL ENGINEERS, 2012年, PROCEEDINGS OF THE ASME SUMMER BIOENGINEERING CONFERENCE, PTS A AND B, CD-ROM, 823 - 824, 英語[査読有り]研究論文（国際会議プロシーディングス）
- AMER SOC MECHANICAL ENGINEERS, 2012年, PROCEEDINGS OF THE ASME SUMMER BIOENGINEERING CONFERENCE, PTS A AND B, CD-ROM, 787 - 788, 英語[査読有り]研究論文（国際会議プロシーディングス）
- 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.WIT PRESS, 2012年, BOUNDARY ELEMENTS AND OTHER MESH REDUCTION METHODS XXXIV, 53, 201 - 208, 英語[査読有り]研究論文（国際会議プロシーディングス）
- 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.WIT PRESS, 2012年, BOUNDARY ELEMENTS AND OTHER MESH REDUCTION METHODS XXXIV, 53, 191 - 199, 英語[査読有り]研究論文（国際会議プロシーディングス）
- 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.TAYLOR & FRANCIS LTD, 2012年, COMPUTER METHODS IN BIOMECHANICS AND BIOMEDICAL ENGINEERING, 15(7) (7), 771 - 778, 英語[査読有り]研究論文（学術雑誌）
- 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.ROYAL SOC CHEMISTRY, 2012年, LAB ON A CHIP, 12(21) (21), 4336 - 4343, 英語[査読有り]研究論文（学術雑誌）
- 2011年12月, 5th East Asian Pacific Student Workshop on Nano-Biomedical Engineering, 72 - 73, 英語Multi-GPU computing of capsule flow using boundary integral method研究論文（国際会議プロシーディングス）
- 2011年12月, 5th East Asian Pacific Student Workshop on Nano-Biomedical Engineering, 152 - 153, 英語GPU-based simulation of blood flow in complex microvessels研究論文（国際会議プロシーディングス）
- 2011年12月, 5th East Asian Pacific Student Workshop on Nano-Biomedical Engineering, 120 - 121, 英語Entrapment of fresh water ciliates at the interface fluid-air研究論文（国際会議プロシーディングス）
- 2011年12月, 5th East Asian Pacific Student Workshop on Nano-Biomedical Engineering, 76 - 77, 英語Computation of near-wall capsule flow using boundary integral method研究論文（国際会議プロシーディングス）
- 2011年12月, 5th East Asian Pacific Student Workshop on Nano-Biomedical Engineering, 32 - 33, 英語Collective diffusion of red blood cells from high concentration to low研究論文（国際会議プロシーディングス）
- 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]AMER INST PHYSICS, 2011年12月, BIOMICROFLUIDICS, 5(4) (4), 044120, 英語[査読有り]研究論文（学術雑誌）
- 2011年12月, 5th East Asian Pacific Student Workshop on Nano-Biomedical Engineering, 150 - 151, 英語A numerical computation on gastric mixing using GPU研究論文（国際会議プロシーディングス）
- 2011年12月, 5th East Asian Pacific Student Workshop on Nano-Biomedical Engineering, 34 - 35, 英語Analysis of fluid flow on the surface of tracheal lumen through effective ciliary motion研究論文（国際会議プロシーディングス）
- 2011年11月, Bulletin of the American Physical Society, DFD2011, 56, 388, 英語Energy transport in a concentrated suspension of bacteria研究論文（国際会議プロシーディングス）
- 2011年11月, 5th Shanghai Int. Conf. Biophysics and Molecular Biology Abstract Book, 125, 英語Development of GPU computing for simulating dense suspension of capsules研究論文（国際会議プロシーディングス）
- 2011年09月, The International Conference on BioTribology Conference Abstracts, CD-ROM, 英語Swallowing simulation based on videofluorography研究論文（国際会議プロシーディングス）
- 2011年09月, Proc. ECCOMAS SIMBIO 2011, CD-ROM, 英語Modelling of red blood cell motion and deformation using particle based method研究論文（国際会議プロシーディングス）
- 2011年08月, 3rd Micro and Nano Flows Conference, CD-ROM, 英語Particle based modeling and simulation of the red blood cell infected by malaria -mechanism of the margination of the infected red blood cell研究論文（国際会議プロシーディングス）
- 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.AMER PHYSICAL SOC, 2011年07月, PHYSICAL REVIEW LETTERS, 107(2) (2), 028102, 英語[査読有り]研究論文（学術雑誌）
- 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.ACADEMIC PRESS LTD- ELSEVIER SCIENCE LTD, 2011年06月, JOURNAL OF THEORETICAL BIOLOGY, 279(1) (1), 63 - 73, 英語[査読有り]研究論文（学術雑誌）
- 2011年06月, Proc Japan-Portugal Nano-BME Symp, 7 - 10, 英語Numerical simulation on margination of malaria-infected red blood cells in microvessels研究論文（国際会議プロシーディングス）
- 2011年06月, Proc. Japan-Portugal Nano-BME Symp, 15 - 16, 英語Numerical simulation of cell depleted peripheral layer and red blood cells motion in microvascular blood flow研究論文（国際会議プロシーディングス）
- 2011年06月, Proc. Japan-Portugal Nano-BME Symp, 29 - 30, 英語Motions of trace particles and red blood cells in a PDMS microchannel with a converging bifurcation研究論文（国際会議プロシーディングス）
- 2011年06月, Proc. Japan-Portugal Nano-BME Symp, 19 - 22, 英語High performance GPU computing of capsule flow using boundary integral method研究論文（国際会議プロシーディングス）
- 2011年06月, Proc. Japan-Portugal Nano-BME Symp, 17 - 18, 英語Gradient diffusion of red blood cells in a Y-shape microchannel研究論文（国際会議プロシーディングス）
- 2011年06月, Proc. Japan-Portugal Nano-BME Symp, 49 - 50, 英語Development of a microfluidic device for partial cell separation研究論文（国際会議プロシーディングス）
- 2011年06月, Proc Japan-Portugal Nano-BME Symp, 1 - 4, 英語Computational biomechanics for respiratory and micro-circulation systems研究論文（国際会議プロシーディングス）
- 2011年06月, Proc. Japan-Portugal Nano-BME Symp, 11 - 14, 英語Analysis of ciliary motion and fluid flow on the surface of tracheal cells研究論文（国際会議プロシーディングス）
- 2011年05月, Microscale Modeling in Biomechanics and Mechanobiology Program and Abstract, 英語Computational analysis of the margination of malaria-infected red blood cells in microcirculation研究論文（国際会議プロシーディングス）
- 2011年05月, Microscale Modeling in Biomechanics and Mechanobiology Program and Abstract, 英語Effect of red blood cells on dynamics of microvascular blood flow研究論文（国際会議プロシーディングス）
- 2011年05月, Microscale Modeling in Biomechanics and Mechanobiology Program and Abstract, 英語Capsule flow analysis using GPU computation研究論文（国際会議プロシーディングス）
- 2011年05月, Microscale Modeling in Biomechanics and Mechanobiology Program and Abstract, 英語Diffusion of red blood cells from high concentration to low in a blood flow microchannel研究論文（国際会議プロシーディングス）
- We investigated numerically the mechanism of margination of Plasmodium falciparum malaria-infected red blood cells (Pf-IRBCs) in micro-scale blood flow. Our model illustrates that continuous hydrodynamic interaction between a Pf-IRBC in the trophozoite stage (Pf-T-IRBC) and healthy red blood cells (HRBCs) results in the margination of the Pf-T-IRBC and, thus, a longer duration of contact with endothelial cells. The Pf-T-IRBC and HRBCs first form a "train". The volume fraction of RBCs is then locally increased, to approximately 40%, and this value is maintained for a long period of time due to the formation of a long train in high-hematocrit conditions. Even in low-hematocrit conditions, the local volume fraction is instantaneously elevated to 40% and the Pf-T-IRBC can migrate to the wall. However, the short train formed in low-hematocrit conditions does not provide continuous interaction, and the Pf-T-IRBC moves back to the center of the channel. (C) 2011 Elsevier Ltd. All rights reserved.ELSEVIER SCI LTD, 2011年05月, JOURNAL OF BIOMECHANICS, 44(8) (8), 1553 - 1558, 英語[査読有り]研究論文（学術雑誌）
- 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.AMER PHYSICAL SOC, 2011年04月, PHYSICAL REVIEW E, 83(4) (4), 041918, 英語[査読有り]研究論文（学術雑誌）
- 2011年03月, 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, 英語Novel methods for the computational biomechanics study of respiratory and micro-circulatory systems研究論文（国際会議プロシーディングス）
- 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.WILEY-BLACKWELL, 2011年03月, INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN BIOMEDICAL ENGINEERING, 27(3) (3), 424 - 435, 英語[査読有り]研究論文（学術雑誌）
- 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.SPRINGER, 2011年02月, BIOMEDICAL MICRODEVICES, 13(1) (1), 159 - 167, 英語[査読有り]研究論文（学術雑誌）
- 2011年, Trends & Challenges in Computational Mechanics Program and Abstracts, 43 - 44, 英語Particle based simulation of the microvascular blood flow in the malaria infection研究論文（国際会議プロシーディングス）
- 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.SPRINGER-VERLAG BERLIN, 2011年, COMPUTATIONAL VISION AND MEDICAL IMAGE PROCESSING: RECENT TRENDS, 19, 297 - 309, 英語研究論文（国際会議プロシーディングス）
- 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.ELSEVIER SCI LTD, 2011年01月, JOURNAL OF BIOMECHANICS, 44(1) (1), 170 - 175, 英語[査読有り]研究論文（学術雑誌）
- 2011年, ASME 2011 6th Frontiers in Biomedical Devices Conference and Exhibition, BioMed 2011, CD-ROM, 25 - 26, 英語[査読有り]研究論文（国際会議プロシーディングス）
- 2011年, ASME 2011 6th Frontiers in Biomedical Devices Conference and Exhibition, BioMed 2011, CD-ROM, 13 - 14, 英語[査読有り]研究論文（国際会議プロシーディングス）
- We investigated the gradient diffusion of red blood cells (RBCs) in blood flow in a microchannel. The effects of flow rates, and hematocrit (Hct) on the gradient diffusion were investigated experimentally. Under the same hematocrit condition, the gradient dispersion coefficient was increased almost linearly to the flow rate. The gradient diffusion dominated over Brownian diffusion in most of high hematocrit conditions. These findings provide useful information in understanding mass transport in small vessels.一般社団法人 日本機械学会, 2011年, バイオフロンティア講演会講演論文集, 2011(0) (0), 63 - 64, 英語研究論文（その他学術会議資料等）
- 2010年12月, Proc. 4th East Asian Pacific Stu. Workshop Nano-Biomed. Eng, 98 - 99, 英語Large-scale numerical simulation of blood flow in microvessels研究論文（国際会議プロシーディングス）
- INFORMA HEALTHCARE, 2010年11月, JOURNAL OF INTERPROFESSIONAL CARE, 24(6) (6), 738 - 741, 英語[査読有り]研究論文（学術雑誌）
- 2010年09月, KIST-Tohoku Joint Symp Nanobiomed Eng, 75 - 76, 英語Separation of cancer cells from blood by using a micro fluidic device研究論文（国際会議プロシーディングス）
- 2010年09月, KIST-Tohoku Joint Symp Nanobiomed Eng, 67 - 68, 英語Effects of rosette formation and cytoadhesion on hemodynamics in malaria infection研究論文（国際会議プロシーディングス）
- 2010年09月, KIST-Tohoku Joint Symp Nanobiomed Eng, 15 - 16, 英語A numerical study on migration of malaria infected red blood cells[査読有り][招待有り]研究論文（国際会議プロシーディングス）
- 2010年08月, 6th World Congress of Biomechanics Abstracts, 581, 英語Parallel 3-D Code to Investigate the Pathophysiology of Malaria on Distributed Memory Systems研究論文（国際会議プロシーディングス）
- 2010年08月, 6th World Congress of Biomechanics Abstracts, 561, 英語Micro-flow Visualization of in vitro Blood through a Microchannel with a Bifurcation and Confluence研究論文（国際会議プロシーディングス）
- 2010年08月, 6th World Congress of Biomechanics Abstracts, 472, 英語Measuring the Cell-Free Layer in circular Microchannels研究論文（国際会議プロシーディングス）
- 2010年08月, IFMBE Proceedings, 31, 1067 - 1070, 英語Measurement of the red blood cell (RBC) dispersion in microchannels: the effect of the temperature研究論文（国際会議プロシーディングス）
- 2010年08月, 6th World Congress of Biomechanics Abstracts, 470, 英語Effect of Membrane Modeling on the Capsule Deformation: Comparison between a Spring Network and Continuum Models研究論文（国際会議プロシーディングス）
- 2010年08月, 6th World Congress of Biomechanics Abstracts, 503, 英語Effect of Adhesive Properties of Malaria-infected Red Blood Cells in Microcirculation研究論文（国際会議プロシーディングス）
- 2010年08月, 6th World Congress of Biomechanics Abstracts, 471, 英語Diffusion of Fluid Particles in High Hematocrit Blood Flow in a Capillary Tube研究論文（国際会議プロシーディングス）
- 2010年08月, 6th World Congress of Biomechanics Abstracts, 164, 英語Development of a Micro Fluidic Device to Separate Cancer Cells from Blood研究論文（国際会議プロシーディングス）
- 2010年08月, 6th World Congress of Biomechanics Abstracts, 471, 英語A Numerical Study on the Behavior of Cells in Micro-scale Blood Flows研究論文（国際会議プロシーディングス）
- 2010年08月, 6th World Congress of Biomechanics Abstracts, 575, 英語A Numerical Study on Fluid Motion in the Stomach研究論文（国際会議プロシーディングス）
- 2010年08月, 6th World Congress of Biomechanics Abstracts, 165, 英語Analysis of Swallowing Motion based on Videofluorography研究論文（国際会議プロシーディングス）
- 2010年07月, ESB2010 Abstracts CD-ROM, 英語Blood flow and cancer cell adhesion in a microchannel with bifurcation and confluence研究論文（国際会議プロシーディングス）
- 2010年06月, CFD2010 Proceedings (CD-ROM), 英語Confocal micro-flow visualization of blood cells研究論文（国際会議プロシーディングス）
- 2010年05月, 22nd International Conference on Parallel Computational Fluid Dynamics (ParCFD 2010) (CD-ROM), 英語Efficient parallel code for simulating malaria infected blood flow研究論文（国際会議プロシーディングス）
- 2010年05月, Proc. 4th ECCM, CD-ROM, No.269, 英語Numerical simulation of interaction among malaria-infected red blood cells, healthy red blood cells, and endothelial cells[査読有り][招待有り]研究論文（国際会議プロシーディングス）
- 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.ELSEVIER SCI LTD, 2010年05月, JOURNAL OF BIOMECHANICS, 43(7) (7), 1386 - 1393, 英語[査読有り]研究論文（学術雑誌）
- 2010年05月, Proc. 4th ECCM, No. 781, 英語Impact of membrane modeling in analysing deformation of a capsule:comparison between a spring network model and constitutive laws[査読有り]研究論文（国際会議プロシーディングス）
- 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 Ca(2+) and other extracellular substances involved in caspase activation.SPANDIDOS PUBL LTD, 2010年05月, ONCOLOGY REPORTS, 23(5) (5), 1425 - 1433, 英語[査読有り]研究論文（学術雑誌）
- 2010年03月, 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, 英語Effect of pneumothorax on morphology and hemodynamic of pulmonary artery研究論文（国際会議プロシーディングス）
- 2010年03月, 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, 英語Radial dispersion of tracer particles in blood flow in a capillary tube研究論文（国際会議プロシーディングス）
- 2010年03月, The 2nd Biosupercomputing symposium, 118 - 119, 英語Comprehensive application of particle methods to the diseases of the blood研究論文（国際会議プロシーディングス）
- 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.SPRINGER, 2010年03月, ANNALS OF BIOMEDICAL ENGINEERING, 38(3) (3), 1225 - 1235, 英語[査読有り]研究論文（学術雑誌）
- 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.SPRINGER, 2010年03月, ANNALS OF BIOMEDICAL ENGINEERING, 38(3) (3), 927 - 934, 英語[査読有り]研究論文（学術雑誌）
- 2010年02月, Nano-Biomedical Engineering 2009, 41 - 50, 英語Computational biomechanics for investigating cardiovascular diseases
- 一般社団法人日本機械学会, 2010年, 年次大会講演論文集, 2010, 51 - 52, 日本語
- Red Blood Cell Dispersion in 100 mu m Glass Capillaries: The Temperature EffectThe 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.SPRINGER, 2010年, 6TH WORLD CONGRESS OF BIOMECHANICS (WCB 2010), PTS 1-3, 31, 1067 - +, 英語[査読有り]研究論文（国際会議プロシーディングス）
- We developed a numerical model of blood flow in malaria infection. Our model was based on a particle method. All the components of blood were represented by finite number of particles. The membrane of red blood cells was modeled by triangular network of membrane particles. Stretch resistance and bending resistance were considered. The force generated by the deformation of membrane was substituted into the force term of Navier-Stokes equations only for membrane particles. The malaria parasite was assumed as a rigid object. Some interesting behavior of the infected and healthy red blood cells were simulated. © 2010 American Institute of Physics.2010年, AIP Conference Proceedings, 1281, 591 - 593, 英語研究論文（国際会議プロシーディングス）
- 2010年01月, SMART-Tohoku GCOE joint Workshop on Micro & Nano Bioenginering, 50 - 50, 英語Cellular behaviours in high hematocrit blood flow in micro-channels研究論文（国際会議プロシーディングス）
- We develop a numerical model of hemodynamics arising from Plasmodium falciparum malaria. A free-mesh particle method is employed for simulating complex interactions among red blood cells infected by Plasmodium falciparum, healthy red blood cells, and endothelial cells. The deformability of red blood cells is expressed by a spring model. Cytoadherent and rosetting property of infected red blood cells are also modeled by using local spring models. We present the behavior of IRBCs and rosettes in shear flow, and the migration and cytoadhesion of IRBCs in micro-scale blood flow.SPRINGER, 2010年, 6TH WORLD CONGRESS OF BIOMECHANICS (WCB 2010), PTS 1-3, 31, 1145 - +, 英語研究論文（国際会議プロシーディングス）
- 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.2010年, Journal of Biomechanical Science and Engineering, 5(5) (5), 485 - 498, 英語[査読有り]研究論文（学術雑誌）
- (株)医学書院, 2009年12月, 呼吸と循環, 57(12) (12), 1219 - 1227, 日本語
- 2009年12月, 3rd East Asian Pacific Student Workshop on Nano-Biomedical Engineering, 124 - 125, 英語Patient specific morphological and hemodynamic analysis of pulmonary artery in the case of severe deformations of the lung研究論文（国際会議プロシーディングス）
- 2009年12月, 3rd East Asian Pacific Student Workshop on Nano-Biomedical Engineering, 122 - 123, 英語Impact of membrane modeling on the deformation analysis of a capsule研究論文（国際会議プロシーディングス）
- 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.JOHN WILEY & SONS INC, 2009年12月, INTERNATIONAL JOURNAL OF MEDICAL ROBOTICS AND COMPUTER ASSISTED SURGERY, 5(4) (4), 471 - 478, 英語[査読有り]研究論文（学術雑誌）
- 2009年11月, Dynein International Workshop 2009, p.11, 英語Fluid flow analysis of the surface of tracheal ciliary cells
- 2009年11月, International Journal of Computational Fluid Dynamics, 23, 583 - 593, 英語[査読有り]研究論文（学術雑誌）
- 2009年11月, VIPIMAGE2009, Computational Vision and Medical Image Processing, 335 - 338, 英語Patient-specific blood flow analysis of pulmonary artery affected by severe deformations of the lung[査読有り]研究論文（国際会議プロシーディングス）
- 2009年11月, VIPIMAGE2009, Computational Vision and Medical Image Processing, 339 - 342, 英語Motions of particles and red blood cells in a bifurcation: comparison between experiments and numerical simulations[査読有り]研究論文（国際会議プロシーディングス）
- 2009年11月, VIPIMAGE2009, Computational Vision and Medical Image Processing, 357 - 360, 英語Determination of the cell-free layer in circular PDMS microchannels[査読有り]研究論文（国際会議プロシーディングス）
- 2009年09月, Book of Abstracts BIOENGINEERING 09, 48 - 48, 英語Simulation of rosette formation and destruction of malaria infected red blood cells研究論文（国際会議プロシーディングス）
- 2009年09月, Book of Abstracts BIOENGINEERING 09, 92 - 92, 英語Pulmonary airflow simulation of inspiration and expiration using a patient-specific model研究論文（国際会議プロシーディングス）
- 2009年09月, Book of Abstracts BIOENGINEERING 09, 126 - 126, 英語On the sensitivity of a hemodynamic index for cerebral aneurysm initiation, the GON, to flow input waveform研究論文（国際会議プロシーディングス）
- 2009年09月, Proc. 3rd Switzerland-Japan Workshop on Biomechanics 2009, 47 - 47, 英語Mixing of red blood cells in high hematocrit blood flow in micro-channels研究論文（国際会議プロシーディングス）
- 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.SPRINGER, 2009年08月, ANNALS OF BIOMEDICAL ENGINEERING, 37(8) (8), 1546 - 1559, 英語[査読有り]研究論文（学術雑誌）
- 2009年07月, 10th U.S. National Congress on Computational Mechanics Congress Program, 42 - 42, 英語A particle based modeling and analysis of Malaria infected red blood cell in microcirculation研究論文（国際会議プロシーディングス）
- 2009年07月, 36th International Congress of Physiological Sciences Final Program, 143 - 143, 英語Computational biomechanics of malaria and arterial diseases研究論文（国際会議プロシーディングス）
- 2009年07月, Technology and Health Care, 17, 121 - 131, 英語[査読有り]研究論文（学術雑誌）
- 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'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.AMER PHYSIOLOGICAL SOC, 2009年06月, ADVANCES IN PHYSIOLOGY EDUCATION, 33(2) (2), 91 - 97, 英語[査読有り]研究論文（学術雑誌）
- 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.ELSEVIER SCI LTD, 2009年05月, JOURNAL OF BIOMECHANICS, 42(7) (7), 838 - 843, 英語[査読有り]研究論文（学術雑誌）
- 2009年04月, 10th International Symposium of Tohoku University Global COE Program, Global Nano-Biomedical Engineering Education and Research Network CentreNano-Biomedical Engineering in the East Asian-Pacific Rim Region Jointly Organised with Fourth Asian Pacific Conf, 20 - 21, 英語Numerical simulation of inspiratory and expiratory pulmonary airflow using a patient-specific model研究論文（国際会議プロシーディングス）
- 2009年04月, 10th International Symposium of Tohoku University Global COE Program, Global Nano-Biomedical Engineering Education and Research Network CentreNano-Biomedical Engineering in the East Asian-Pacific Rim Region Jointly Organised with Fourth Asian Pacific Conf, 8 - 9, 英語Effect of the memberane bending stiffeness on the deformation of a red blood cell研究論文（国際会議プロシーディングス）
- 2009年04月, 15th Int. Conf. Finite Elements in Flow Problems (FEF09) Abstracts, 37, 英語Patient-specific pulmonary airflow simulation using cartestian adaptive mesh refinement method研究論文（国際会議プロシーディングス）
- 2009年04月, Proc. AP Biomech 2009, 164 - 165, 英語Numerical simulation of inpiratory and expiratory pulmonary airflow using a patient-specific model研究論文（国際会議プロシーディングス）
- 2009年04月, Proc. AP Biomech 2009, 102 - 103, 英語Motion of individual red blood cells in a concentrated suspension flowing through micro-channels研究論文（国際会議プロシーディングス）
- 2009年04月, Proc. ICCES'09, 244, 英語Motion of individual cells in high hematocrit blood flow in micro-channels研究論文（国際会議プロシーディングス）
- 2009年04月, 15th Int. Conf. Finite Elements in Flow Problems (FEF09) Abstracts, 41, 英語Modeling of the membrane bending rigidity for calculating red blood cell deformation研究論文（国際会議プロシーディングス）
- 2009年04月, Proc. AP Biomech 2009, 154 - 155, 英語Low voltage pulses can induce apoptosis研究論文（国際会議プロシーディングス）
- 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'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.SPRINGER, 2009年04月, ANNALS OF BIOMEDICAL ENGINEERING, 37(4) (4), 702 - 709, 英語[査読有り]研究論文（学術雑誌）
- 2009年04月, Proc. AP Biomech, 196 - 197, 英語Effect of the membrane bending stiffness on the deformation of a red blood cell研究論文（国際会議プロシーディングス）
- 2009年04月, Proc. ICCES'09, 10, 英語Computational biomechanics for investigating various diseases over micro to macro scales[招待有り]研究論文（国際会議プロシーディングス）
- 2009年04月, Proc. ICCES'09, 96, 英語A numerical model to study hemodynamics arising from malaria infection[招待有り]研究論文（国際会議プロシーディングス）
- 2009年04月, Proc. AP Biomech 2009, 100 - 101, 英語A micro scale blood flow model to study pathology of malaria研究論文（国際会議プロシーディングス）
- 2009年03月, 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, 英語Computational simulation of blood flow in pulmonary artery under respiratory disorders研究論文（国際会議プロシーディングス）
- 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.ELSEVIER SCI LTD, 2009年03月, JOURNAL OF BIOMECHANICS, 42(4) (4), 550 - 554, 英語[査読有り]研究論文（学術雑誌）
- We propose a numerical method for simulating three-dimensional hemodynamics arising from malariainfection. Malaria-infected red blood cells (IRBCs) become stiffer and develop the property of cytoadherent and resetting. To clarify the mechanism of microvascular obstruction in malaria, we need to understand the changes of hemodynamics, involving interaction between IRBC, healthy RBCs, and endothelial cells. In the proposed model, all the components of blood are represented by a finite number of particles. The membrane of RBCs is expressed by two-dimensional network. Malaria parasites inside the RBC are represented by solid objects. The motion of each particle is described by the conservation laws of mass and momentum for incompressible fluid. We examine several numerical tests, involving the stretching of IRBCs, and flow in narrow channels, to validate our model. The obtained results agree well with the experimental results. Our method would be helpful for further understandings of pathology of malaria-infection. © 2009 International Federation of Medical and Biological Engineering.2009年, IFMBE Proceedings, 23, 2244 - 2247, 英語[査読有り]研究論文（国際会議プロシーディングス）
- 2009年, ICCB 2009, USB, 83, 英語Simulation of microcirculatory disorder by malaria infection using a particle method研究論文（国際会議プロシーディングス）
- 2009年, Med. Phys. Biomed. Eng. World Cong. 2009, CD-ROM, 131, 英語Particle method simulation of red blood cells infected by malaria研究論文（国際会議プロシーディングス）
- 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.WIT PRESS/COMPUTATIONAL MECHANICS PUBLICATIONS, 2009年, MODELLING IN MEDICINE AND BIOLOGY VIII, 13, 49 - +, 英語研究論文（国際会議プロシーディングス）
- AMER SOC MECHANICAL ENGINEERS, 2009年, PROCEEDINGS OF THE ASME SUMMER BIOENGINEERING CONFERENCE - 2009, PT A AND B, CD-ROM, 765 - 766, 英語[査読有り]研究論文（国際会議プロシーディングス）
- Numerical methods are used to provide quantitative and qualitative information about effects of pulmonary disorders on blood flow. From patient's CT images, arterial geometries are extracted and compared for healthy and unhealthy conditions. We show that pulmonary artery shape is strongly affected by the pulmonary disorders, e.g., the inlet is elongated and the branches are bent. In order to clarify the effect of geometrical change on the blood flow, we performed computational simulation of blood flow in the extracted geometries.AMER SOC MECHANICAL ENGINEERS, 2009年, PROCEEDINGS OF THE ASME SUMMER BIOENGINEERING CONFERENCE - 2009, PT A AND B, CD-ROM, 1037 - 1038, 英語[査読有り]研究論文（国際会議プロシーディングス）
- AMER SOC MECHANICAL ENGINEERS, 2009年, PROCEEDINGS OF THE ASME SUMMER BIOENGINEERING CONFERENCE - 2009, PT A AND B, CD-ROM, 443 - 444, 英語[査読有り]研究論文（国際会議プロシーディングス）
- AMER SOC MECHANICAL ENGINEERS, 2009年, PROCEEDINGS OF THE ASME SUMMER BIOENGINEERING CONFERENCE - 2009, PT A AND B, CD-ROM, 479 - 480, 英語[査読有り]研究論文（国際会議プロシーディングス）
- AMER SOC MECHANICAL ENGINEERS, 2009年, PROCEEDINGS OF THE ASME SUMMER BIOENGINEERING CONFERENCE - 2009, PT A AND B, CD-ROM, 331 - 332, 英語[査読有り]研究論文（国際会議プロシーディングス）
- 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.2009年, Technology and Health Care, 17(2) (2), 121 - 131, 英語[査読有り]研究論文（学術雑誌）
- 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.TAYLOR & FRANCIS LTD, 2009年, INTERNATIONAL JOURNAL OF COMPUTATIONAL FLUID DYNAMICS, 23(8) (8), 583 - 593, 英語[査読有り]研究論文（学術雑誌）
- 2008年12月, GPBE/NUS-Tohoku Graduate Student Conf. Bioeng., Program & Abstract, 99 - 100, 英語Behavior of a red blood cell in a simple shear flow simulated by a boundary element method
- 2008年12月, GPBE/NUS-Tohoku Graduate Student Conf. Bioeng., Program & Abstract, 95 - 96, 英語A novel hemodynamic index for the initiation of cerebral aneurysms: focusing on temporal variation of spatial wall shear stress gradient
- 2008年12月, GPBE/NUS-Tohoku Graduate Student Conf. Bioeng., Program & Abstract, 81 - 82, 英語Numerical simulation of inspiratory and expiratory pulmonary airflow using a subject-specific model
- 2008年11月, Int. Feder. Med. Biol. Eng. (IFMBE) Proc. (CD-ROM), 205, 英語
- 2008年11月, Int. Feder. Med. Biol. Eng. (IFMBE) Proc. (CD-ROM), 234, 英語
- 2008年11月, Int. Feder. Med. Biol. Eng. (IFMBE) Proc. (CD-ROM), 274, 英語
- 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's home; (b) its high extendibility and flexibility facilitate adaptation to a patient'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.MARY ANN LIEBERT INC, 2008年11月, TELEMEDICINE JOURNAL AND E-HEALTH, 14(9) (9), 939 - 945, 英語[査読有り]研究論文（学術雑誌）
- 2008年10月, 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, 英語Three-dimensional simulation of malaria-infected blood研究論文（国際会議プロシーディングス）
- 2008年09月, Book of Abstracts BIOENGINEERING 08, 135 - 135, 英語Behavior of a red blood cell in a simple shear flow simulated by a boundary element method研究論文（国際会議プロシーディングス）
- 2008年09月, Bioengineering 08 Book of Abstracts, 61, 英語Mixing of red blood cells in a micro-channel flow under high hematocrit conditions
- 2008年09月, Bioengineering 08 Book of Abstracts, 166, 英語Confocal micro-PTV Measurements of Blood Flow in a Circular PDMS Microchannel
- 2008年09月, Bioengineering 08 Book of Abstracts, 146, 英語Proposal of a New Hemodynamic Index for Cerebral Aneurysm Initiation: Focusing on Temporal Fluctuation of Spatial Wall Shear Stress Gradient
- 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.ELSEVIER IRELAND LTD, 2008年09月, CANCER LETTERS, 269(1) (1), 93 - 100, 英語[査読有り]研究論文（学術雑誌）
- 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.SPRINGER, 2008年09月, ANNALS OF BIOMEDICAL ENGINEERING, 36(9) (9), 1489 - 1495, 英語[査読有り]研究論文（学術雑誌）
- 2008年09月, Abstracts of Bioengineering 08, 英語A numerical method for simulating micro-scale blood flow in malaria infection[査読有り]研究論文（国際会議プロシーディングス）
- 2008年07月, 8th World Congress on Computational Mechanics (WCCM8) / 5th European Congress on Computational Methods in Applied Sciences and Engineering (ECCOMAS 2008) (PROGRAMME, CD-ROM), 216 - 216, 英語Image-based pulmonary airflow simulation using cartesian adaptive mesh refinement method[査読有り]研究論文（国際会議プロシーディングス）
- 2008年07月, ・16th Congress of the European Society of Biomechanics Conference Program ・Abstract 16th Congress of the European Society of Biomechanics (CD-ROM), 30 - 30, 英語Role of the hematocrit on the radial dispresion of red blood cells in glass capillaries研究論文（国際会議プロシーディングス）
- 2008年07月, IACM/ECCOMAS Congress 2008 CD-ROM, MS194C, 英語Three-Dimensional Simulation of Blood Flow arising from Malaria Infection
- 2008年07月, Journal of Biomechanics, 41, S390, 英語Motion of red blood cells and cell free layer distribution in a stenosed microchannel研究論文（国際会議プロシーディングス）
- 2008年07月, Journal of Biomechanics, 41, S429, 英語Determination of blood cells motions and interactions by a confocal micro-PTV system研究論文（国際会議プロシーディングス）
- 2008年07月, Journal of Biomechanics, 41, S480, 英語A numerical model of blood flow with malariainfected red blood cells研究論文（国際会議プロシーディングス）
- 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.ELSEVIER SCI LTD, 2008年07月, MEDICAL ENGINEERING & PHYSICS, 30(6) (6), 774 - 782, 英語[査読有り]研究論文（学術雑誌）
- 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.ELSEVIER SCI LTD, 2008年07月, JOURNAL OF BIOMECHANICS, 41(10) (10), 2188 - 2196, 英語[査読有り]研究論文（学術雑誌）
- 2008年06月, Int. Symp. Multi-scale Sim. Biol. Soft Mater. (MSBSM2008) Book of Abstracts, 2 - 3, 英語Multi-scale multi-physics simulations of Biological flows
- 2008年06月, Proc. ASME 2008 Summer Bioeng. Conf.CD-ROM, 英語The importance of proliferation of the arterial wall in formation of saccular cerebral aneurysms
- 2008年05月, Proc. Tohoku-NUS Student Joint Symp, 16 - 17, 英語Pulmonary airflow simulation using subject-specific model and Cartesian adaptive mesh refinement method
- 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.SPRINGER, 2008年04月, BIOMEDICAL MICRODEVICES, 10(2) (2), 153 - 167, 英語[査読有り]研究論文（学術雑誌）
- 2008年03月, Fifth International Bio-Fluid Symposium and Workshop, 146 - 147, 英語CT image-based pulmonary airflow simulation using airway scale determined mesh
- 2008年03月, Fifth International Bio-Fluid Symposium and Workshop, 65 - 66, 英語Some uninvestigated directions of computational fluid dynamics studies for flow
- The proposed scheme, which is a conservative form of the interpolated differential operator scheme (IDO-CF), can provide high accurate solutions for both compressible and incompressible fluid equations. Spatial discretizations with fourthorder accuracy are derived from interpolation functions locally constructed by both cell-integrated values and point values. These values are coupled and time-integrated by solving fluid equations in the flux forms for the cell-integrated values and in the derivative forms for the point values. The IDO-CF scheme exactly conserves mass, momentum, and energy, retaining the high resolution more than the non-conservative form of the IDO scheme. A direct numerical simulation of turbulence is carried out with comparable accuracy to that of spectral methods. Benchmark tests of Riemann problems and lid-driven cavity flows show that the IDO-CF scheme is immensely promising in compressible and incompressible fluid dynamics studies. (C) 2007 Elsevier Inc. All rights reserved.ACADEMIC PRESS INC ELSEVIER SCIENCE, 2008年02月, JOURNAL OF COMPUTATIONAL PHYSICS, 227(4) (4), 2263 - 2285, 英語[査読有り]研究論文（学術雑誌）
- We proposed a new hemodynamic indicator for the initiation of cerebral aneurysms, defined by the temporal fluctuations of tension/compression forces acting on endothelial cells. We calculated the proposed hemodynamic indicator and other three hemodynamic quantities (time-averaged wall shear stress (WSS), time-averaged spatial WSS gradient (SWSSG), and potential aneurysm formation indicator (AFI)) for a patient-specific geometry before aneurysm formation by means of computational fluid dynamics technique. The results showed that only the proposed hemodynamic indicator had a significant correlation with the location of aneurysm formation. Our findings suggest that the proposed indicator might be a prospective hemodynamic indicator for the initiation of cerebral aneurysms.一般社団法人日本機械学会, 2008年, 年次大会講演論文集, 2008, 31 - 32, 日本語
- We have numerically analyzed inspiratory and expiratory airflow using an image-based pulmonary airway model. As a result, the image-based analysis provided us with some interesting flow features, which is hardly seen in analyses using idealistic airway models. We have examined relationship between flow rate at trachea and pressure drop between trachea and peripheral airways during inspiraotry and expiratory phase. There was difference of pressure drop between inspiratory and expiratory phase even the flow rate was identical, though pressure loss due to fluid viscosity in inspiratory and expiratory phase was almost identical. Generally, pressure drop in a tube is given from summation of dynamic pressure and pressure loss due to fluid viscosity. We conclude that the difference of pressure drop was occurred due to dynamic pressure caused by the difference of cross sectional area between trachea and peripheral airways.一般社団法人日本機械学会, 2008年, 年次大会講演論文集, 2008, 121 - 122, 日本語
- A capsule endoscope is recently developed for the observation of the digestive system because digestive diseases particularly cancers very frequently occur and became fatal. Despite many advantages, the capsule endoscope has some limitations in the diagnosis, since it only moves passively by the peristaltic motion of the intestine. In order to overcome this problem, locomotive functions are expected to the capsule endoscope. In this study, we report a mechanical crawler system mimicking the pedal locomotion of snails for such a capsule endoscope. The crawler we developed has four joints, five segments and two suction cups. In locomotion experiments on a horizontal plane and on an inclined plane of 10 degrees, we confirmed that the developed crawler could locomote at the speed of 3 mm/s.一般社団法人日本機械学会, 2008年, 年次大会講演論文集, 2008, 59 - 60, 日本語
- Microscale flow dynamics of red blood cells in a circular microchannelThe 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.TAYLOR & FRANCIS LTD, 2008年, COMPUTATIONAL VISION AND MEDICAL IMAGING PROCESSING, 53 - +, 英語[査読有り]研究論文（国際会議プロシーディングス）
- 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.2008年, Journal of Biomechanical Science and Engineering, 3(3) (3), 431 - 442, 英語[査読有り]研究論文（学術雑誌）
- 2007年12月, Proc. 7th Int. Symp. Adv. Fluid Info. & 4th Int. Symp. Transdisciplinary Fluid Integr., 56 - 57, 英語Tracking of red blood cells in microchannel with stenosis by confocal micro PTV system[査読有り]
- 2007年12月, Proc. 3rd Tohoku-NUS Joint Symp. Nano-Biomed. Eng. in the East Asian-Pacific Rim Region, 99 - 100, 英語Blood flow in microchannel with stenosis measured by a confocal micro PTV system[査読有り]
- 2007年12月, Proc. 3rd Tohoku-NUS Joint Symp. Nano-Biomed. Eng. in the East Asian-Pacific Rim Region, 47 - 48, 英語Development of respiration measurement system with conductive rubber for elderly home care[査読有り]
- 2007年12月, Proc. APCOM'07 in conjunction with EPMESC XI, CD-ROM MS22-4-2, 英語Modeling of malaria-infected red blood cell mechanics using a particle method[査読有り]
- 2007年12月, Proc. APCOM'07 in conjunction with EPMESC XI, CD-ROM MS22-3-3, 英語Numerical simulation of cerebral aneurysm growth based on a hemodynamic hypothesis[査読有り]
- 2007年12月, Proc. APCOM'07 in conjunction with EPMESC XI, CD-ROM MS7-1-3, 英語An AMR Method based on the IDO scheme for patient-specific pulmonary airflow simulation[査読有り]
- 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.MARY ANN LIEBERT INC, 2007年12月, TELEMEDICINE JOURNAL AND E-HEALTH, 13(6) (6), 703 - 713, 英語[査読有り]研究論文（学術雑誌）
- 2007年11月, Proc. Int. Conf. Adaptive Modeling & Simulation, 166 - 169, 英語CT Image-Based Respiratory Flow Simulation by using Cartesian Adaptive Mesh Refinement Method[査読有り]
- 2007年11月, Proc. Int. Conf. Adaptive Modeling & Simulation, 128 - 131, 英語A Cartesian Adaptive Mesh Refinement Method for Simulating Physiological Flows[査読有り]
- 2007年11月, Bulletin of the American Physical Society, 52, 245 - 246, 英語The hydrodynamics of interactions between two swimming bacteria[査読有り]
- 2007年11月, Proc. 3rd Asian Pacific Conf. Biomech., S226, 英語Numerical Simulation of Malaria-Infected Blood Flow using a Particle Method[査読有り]
- 2007年11月, Proc. 3rd Asian Pacific Conf. Biomech., S206, 英語Measurement of Respiration by a Hyper Diaper with Conductive Rubber[査読有り]
- 2007年11月, Proc. 3rd Asian Pacific Conf. Biomech., S103, 英語Monitoring Physical and Mental Workloads by a Wearable Computer[査読有り]
- 2007年11月, Proc. 3rd Asian Pacific Conf. Biomech., S92, 英語Measurement of Multi-Red Blood Cells Interactions in Blood Flow by Confocal Micro-PTV[査読有り]
- 2007年11月, Proc. 3rd Asian Pacific Conf. Biomech., S89, 英語Observation of the Blood Flow in Microchannel with Stenosis by Confocal-Micro-PIV[査読有り]
- 2007年11月, Proc. 3rd Asian Pacific Conf. Biomech., S84, 英語Development of a Wearable System for Monitoring Health Condition[査読有り]
- 2007年11月, Proc. 3rd Asian Pacific Conf. Biomech., S76, 英語A Simulation Model for Cerebral Aneurysm Growth based on a Hemodynamic Hypothesis[査読有り]
- 2007年11月, Proc. 3rd Asian Pacific Conf. Biomech., S58, 英語CFD Study on Mass Transport to Saccular Aneurysms at Arterial Bend[査読有り]
- 2007年10月, Proc. 4th Japan-Taiwan Workshop on Mech. & Aerospace Eng., 289 - 294, 英語CFD modeling of pulmonary airflow using IDO-AMR method[査読有り]
- 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.BIOPHYSICAL SOC, 2007年09月, BIOPHYSICAL JOURNAL, 93(6) (6), 2217 - 2225, 英語[査読有り]研究論文（学術雑誌）
- 2007年06月, Biomechanics at micro- and nanoscale levels, World Scientific, 3, 146 - 156, 英語A fluid-solid interactions study of the pulse wave velocity in uniform arteries[査読有り]
- 2007年06月, Proc. 2007 Summer Bioengineering Conference, CD-ROM, 175969, 英語Measurement of erythrocyte motions in microchannels by using a confocal micro-PTV system
- 2007年06月, Proc. 2007 Summer Bioengineering Conference, CD-ROM, 176102, 英語Wall shear stress change due to arterial wall stiffness; fluid-solid interaction study
- 2007年06月, Proc. 2007 Summer Bioengineering Conference, CD-ROM, 176529, 英語Image-based simulation of pulmonary airflow using multi-level voxel modeling
- 2007年06月, Proc. 2007 Summer Bioengineering Conference, CD-ROM, 176106, 英語A simulation study on the growth of cerebral aneurysms
- 2007年06月, Proc. 2007 Summer Bioengineering Conference, CD-ROM, 176556, 英語Effects of arterial geometry on inflow rate into cerebral aneurysms on curved arteries
- 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.The Japan Society of Mechanical Engineers, 2007年05月, Journal of Biomechanical Science and Engineering, 2(2) (2), 58 - 68, 英語[査読有り]研究論文（学術雑誌）
- Two explicit schemes for the numerical solution of the shallow-water equations are examined. The directional-splitting fractional-step method permits relatively large time steps without an iterative process by using a treatment based on the characteristics of the governing equations. The interpolated differential operator (IDO) scheme has fourth-order accuracy in time and space by using a Hermite interpolation function covering local domains, and accurate results are obtained with coarse meshes. It is shown that the two schemes are very efficient for hydrostatic meteorological models from the viewpoints of numerical accuracy and central processing unit time, and the fact that they are explicit makes them suitable for computers with parallel architecture.AMER METEOROLOGICAL SOC, 2007年03月, JOURNAL OF APPLIED METEOROLOGY AND CLIMATOLOGY, 46(3) (3), 388 - 395, 英語[査読有り]研究論文（学術雑誌）
- 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。(一社)呼吸研究, 2007年02月, 呼吸, 26(2Suppl.) (2Suppl.), S7 - S10, 日本語
- 2007年01月, Proc. Final Symp. Tohoku University 21st Century of Excellence Program, 919 - 927, 英語A Fluid-Solid Interaction Study of the Pulse Wave Velocity in Uniform Arteries[査読有り]
- We have developed a new method for respiratory computational fluid dynamics (CFD) simulation using realistic airway models extracted from multi-slice computed tomography (CT) images. Pulmonary airway is multi-scale tube, which is one of the difficulties in respiratory simulation. In the viewpoint of CFD, mesh size must be refined to capture airflow in the small airways. Therefore adaptive mesh refinement (AMR) method based on Interpolated Differential Operator (IDO) scheme is applied to respiratory simulation model. Mesh size is determined by the diameter of the airways in the local domain to maintain accuracy for CFD simulation and adjust computational time. As a result of CFD analysis, we have confirmed accuracy of our new AMR adopted airflow simulation in spite of the number of computational nodes decreased 75%.一般社団法人日本機械学会, 2007年, 年次大会講演論文集, 2007, 271 - 272, 日本語
- To solve an aging problem in the society, it is important that the aged people are encouraged to be independent and spend healthy life. We have proposed the concept of the Hyper Hospital, which is the information support system for patients. In the Hyper Hospital, some units analyze their vital data, and patient's family who lives in the distance, the neighborhood and their doctor share the analyzed data through computer network to know their health condition. In this paper, we present a wearable platform for monitoring health condition. This platform sends the analyzed biomedical signal of a patient to a database server in his/her house. We developed a sensor module to acquire EMG that informs weakening of muscular strength by an underexercise or disease such as a hemiplegia. We confirmed that the sensor module works well with storage module and analysis module through some experiment. We also developed a database server for collecting data from any other sensor module and processing the data from each module separately. The proposed system will be expected monitoring health condition of the elderly.一般社団法人日本機械学会, 2007年, 年次大会講演論文集, 2007, 57 - 58, 日本語
- The mechanism of the growth of cerebral aneurysm has not yet been understood. We focus on biological reactions in addition to purely mechanical process. We propose a simulation model to express the assumption that surface areas of the arterial wall are increased locally where wall shear stress value is much higher. We applied the model to a U-shaped artery with torsion. The resultant shape was consistent with clinical observations. It is concluded that it is necessary to consider biological reactions to understand the growth of the cerebral aneurysm.一般社団法人日本機械学会, 2007年, 年次大会講演論文集, 2007, 91 - 92, 日本語
- This paper focuses on inflow into an aneurysm from its parent artery. Understandings of the inflow are required in designing endovascular devices such as coils and stents. A parametric computational fluid dynamics study of the inflow is performed for saccular cerebral aneurysms at a variety of arterial bends. Numerical results show that the inflow rate is strongly influenced by parent arterial geometry because secondary flow momentum in the parent artery determines the inflow. We also present that the shape of an aneurysm little affects the inflow rate.一般社団法人日本機械学会, 2007年, 年次大会講演論文集, 2007, 89 - 90, 日本語
- Malaria is one of the most serious diseases for all around the world. It is thought that severe symptoms are caused by microvasucular occlusions of parasitized red blood cells (PRBC) that have adhesive property and low deformability. However, the detailed mechanisms of the vascular occlusion caused by red blood cells are still not clear. In this study, the malaria-infected blood is modeled by particles. The adhesive property of PRBC is expressed by local spring. The result shows that the PRBC interacts with some healthy RBCs and move downstream keeping attachment to the vessel wall. This phenomenon induces the high resistance to the flow, which is likely to lead to microvascular obstruction in lower shear flow.一般社団法人日本機械学会, 2007年, 年次大会講演論文集, 2007, 87 - 88, 日本語
- 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.World Scientific Publishing Co., 2007年01月, Biomechanics at Micro- and Nanoscale Levels, 4, 130 - 140, 英語[査読有り]論文集(書籍)内論文
- 2007年01月, The 9th Int. Symp. Future Med. Eng. based on Bio-nanotech., 128 - 129, 英語Effect of Aneurysmal Geometry on the Distribution of ATP Concentration[査読有り]
- 2007年01月, The 9th Int. Symp. Future Med. Eng. based on Bio-nanotech., 126 - 127, 英語Tracking Red Blood Cells in a Circular PDMS Microchannel using a Confocal Micro-PIV System[査読有り]
- 2007年01月, The 9th Int. Symp. Future Med. Eng. based on Bio-nanotech., 94 - 95, 英語Numerical Simulation on the Growth of Saccular Aneurysm[査読有り]
- 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.日本機械学会, 2007年01月, Journal of Biomechanical Science and Engineering, 2(1) (1), 12 - 22, 英語[査読有り]研究論文（学術雑誌）
- 2006年12月, 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, 英語Development of a wearable watch over system for patients home with an accelerometer[査読有り]
- 2006年12月, 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, 英語Numerical analysis of ATP transport in aneurysms[査読有り]
- 2006年12月, 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, 英語Monitoring physical and mental workloads by wearable system for elderly home care[査読有り]
- 2006年12月, Proc. 15th Int. Conf. Mechanics in Medicine and Biology, 187 - 188, 英語Development of a wearable system for an quantification measurment of human motions in daily life[査読有り]
- 2006年12月, Proc. 15th Int. Conf. Mechanics in Medicine and Biology, 422 - 423, 英語Computer simulation of effects of deformabilities of red blood cells on blood flow using particle method[査読有り]
- 2006年12月, Proc. 15th Int. Conf. Mechanics in Medicine and Biology, 80 - 81, 英語An adaptive mesh refinement method for CFD analysis of arterial blood flow[査読有り]
- 2006年12月, Proc. 15th Int. Conf. Mechanics in Medicine and Biology, 420 - 421, 英語Numerinal simulation of a low Hematocrit blood flow in a small artery with stenosis[査読有り]
- 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.The Japan Society of Mechanical Engineers, 2006年10月, Journal of Biomechanical Science and Engineering, 1(1) (1), 29 - 50, 英語[査読有り]研究論文（学術雑誌）
- The numerical accuracy of the Interpolated Differential Operator (IDO) scheme is studied with Fourier analysis for the solutions of Partial Differential Equations (PDEs): advection, diffusion, and Poisson equations. The IDO scheme solves governing equations not only for physical variable but also for first-order spatial derivative. Spatial discretizations are based on Hermite interpolation functions with both of them. In the Fourier analysis for the IDO scheme, the Fourier coefficients of the physical variable and the first-order derivative are coupled by the equations derived from the governing equations. The analysis shows the IDO scheme resolves all the wavenumbers with higher accuracy than the fourth-order Finite Difference (FD) and Compact Difference (CD) schemes for advection equation. In particular, for high wavenumbers, the accuracy is superior to that of the sixth-order Combined Compact Difference (CCD) scheme. The diffusion and Poisson equations are also more accurately solved in comparison with the FD and CD schemes. These results show that the IDO scheme guarantees highly resolved solutions for all the terms of fluid flow equations. (c) 2006 Elsevier Inc. All rights reserved.ACADEMIC PRESS INC ELSEVIER SCIENCE, 2006年09月, JOURNAL OF COMPUTATIONAL PHYSICS, 217(2) (2), 453 - 472, 英語[査読有り]研究論文（学術雑誌）
- 2006年08月, Computational Mechanics, 38(3) (3), 211 - 224, 英語[査読有り]研究論文（学術雑誌）
- The Interpolated Differential Operator (IDO) scheme on collocated grids provides fourth-order discretizations for all the terms of the fluid flow equations. However, computations of fluid flows on collocated grids are not guaranteed to produce accurate solutions because of the poor coupling between velocity vector and scalar variables. A stable coupling method for the IDO scheme oil collocated grids is proposed, where a new representation of first-order derivatives is adopted. It is important in deriving the representation to refer to the variables at neighboring grid points, keeping fourth-order truncation error. It is clear that accuracy and stability are drastically improved for shallow water equations in comparison with the conventional IDO scheme. The effects of the stable coupling are confirmed in incompressible flow calculations for DNS of turbulence and a driven cavity problem. The introduction of a rational function into the proposed method makes it possible to calculate shock waves with the initial conditions of extreme density and pressure jumps. (c) 2005 Elsevier Inc. All rights reserved.ACADEMIC PRESS INC ELSEVIER SCIENCE, 2006年06月, JOURNAL OF COMPUTATIONAL PHYSICS, 215(1) (1), 81 - 97, 英語[査読有り]研究論文（学術雑誌）
- An Interpolated Differential Operator (IDO) scheme using a new interpolation function is proposed. The gradient of the dependent variable is calculated at the position shifted by a half grid size from that of the physical value. A fourth-order Hermite-interpolation function is constructed locally using both the value and the gradient defined at staggered positions. The numerical solutions for the Poisson, diffusion, advection and wave equations have fourth-order accuracy in space. In particular, for the Poisson and diffusion equations, the Gradient-Staggered (G-S) IDO scheme shows better accuracy than the original IDO scheme. As a practical application, the Direct Numerical Simulation (DNS) for two-dimensional isotropic homogeneous turbulence is examined and a comparable result with that of the original IDO scheme is obtained. The G-S IDO scheme clearly contributes to high-accurate computations for solving partial differential equations in computational mechanics.JAPAN SOC MECHANICAL ENGINEERS, 2004年11月, JSME INTERNATIONAL JOURNAL SERIES B-FLUIDS AND THERMAL ENGINEERING, 47(4) (4), 681 - 689, 英語[査読有り]研究論文（学術雑誌）
- We have developed a numerical method on Cartesian grid for image-based blood flow simulation. Cartesian grid has advantages for grid generation for the complex and moving boundary problems. Interpolated Differential Operator (IDO) scheme with Local Mesh Refinement method are effectively introduced for blood flow simulations. In order to simulate flow interacting with elastic vessel on Cartesian grid, a new technique INTERGRID has been developed and it is shown that the simulation of fluid-structure interaction problems that structure does not displace over the resolution of grid is carried out.一般社団法人日本機械学会, 2004年09月, 日本機械学会論文集 Ａ編, 70(697) (697), 1232 - 1239, 日本語[査読有り]研究論文（学術雑誌）
- 東京 : 日本計算工学会, 2024年06月, 計算工学講演会論文集 = Proceedings of the Conference on Computational Engineering and Science / 日本計算工学会 編, 29, 1286 - 1290, 日本語細胞膜の拡大による樹状突起スパインのアイソジオメトリック解析—An isogeometric analysis of dendritic spine morphogenesis induced
- 東京 : 日本計算工学会, 2024年06月, 計算工学講演会論文集 = Proceedings of the Conference on Computational Engineering and Science / 日本計算工学会 編, 29, 1228 - 1230, 日本語アイソジオメトリック境界要素法による超弾性体シートの沈降挙動解析—An analysis of sedimentation of a hyperelastic sheet using isogeometric boundary element method
- 東京 : 日本計算工学会, 2024年06月, 計算工学講演会論文集 = Proceedings of the Conference on Computational Engineering and Science / 日本計算工学会 編, 29, 1225 - 1227, 日本語弾性管の蠕動運動により生じる管内流れのアイソジオメトリック境界要素解析—Isogeometric boundary element analysis of flow driven by peristaltic motion of an elastic tube
- 東京 : 日本計算工学会, 2024年06月, 計算工学講演会論文集 = Proceedings of the Conference on Computational Engineering and Science / 日本計算工学会 編, 29, 1231 - 1236, 日本語粘性流体との相互作用による薄膜の変形の流体構造連成解析—A fluid-structure interaction analysis of the thin film deformation due to interaction with
- 2024年, 計算工学講演会論文集(CD-ROM), 29細胞膜の拡大による樹状突起スパインのアイソジオメトリック解析
- 東京 : 日本計算工学会, 2023年05月, 計算工学講演会論文集 = Proceedings of the Conference on Computational Engineering and Science / 日本計算工学会 編, 28, 761 - 766, 日本語粘性流体中で成長する薄膜の変形のアイソジオメトリック解析—An isogeometric analysis of deformation of a growing thin menbrane in a viscous fluid
- 2019年, 計算工学講演会論文集(CD-ROM), 24全脳循環血流場の大規模並列シミュレーション
- 2019年, バイオエンジニアリング講演会講演論文集(CD-ROM), 32nd全脳循環血流シミュレータの開発
- 2019年, 日本機械学会計算力学講演会論文集(CD-ROM), 32nd脳血管網モデリングと全脳循環血流場の数値計算
- 2018年09月, 8th International Conference on Fluid Mechanics (ICFM8), S10BM0-04, 英語FLUID-STRUCTURE INTERACTIONS OF NODAL CILIA AXONEME[査読有り]研究発表ペーパー・要旨（国際会議）
- (一社)日本耳鼻咽喉科学会, 2018年04月, 日本耳鼻咽喉科学会会報, 121(4) (4), 569 - 569, 日本語
- 2018年, 日本嚥下医学会抄録(Web), 41st嚥下の3D数値流体力学シミュレーションの開発と検討
- Integrated Nano-Biomechanics provides an integrated look into the rapidly evolving field of nanobiomechanics. The book demystifies the processes in living organisms at the micro- and nano-scale through mechanics, using theoretical, computational and experimental means. The book develops the concept of integrating different technologies along the hierarchical structure of biological systems and clarifies biomechanical interactions among different levels for the analysis of multi-scale pathophysiological phenomena. With a focus on nano-scale processes and biomedical applications, it is shown how knowledge obtained can be utilized in a range of areas, including diagnosis and treatment of various human diseases and alternative energy production. This book is based on collaboration of researchers from a unique combination of fields, including biomechanics, computational mechanics, GPU application, electron microscopy, biology of motile micro-organisms, entomological mechanics and clinical medicine. The book will be of great interest to scientists and researchers involved in disciplines, such as micro- and nano-engineering, bionanotechnology, biomedical engineering, micro- and nano-scale fluid-mechanics (such as in MEMS devices), nanomedicine and microbiology, as well as industries such as optical devices, computer simulation, plant based energy sources and clinical diagnosis of the gastric diseases.Elsevier, 2018年01月01日, Integrated Nano-Biomechanics, 1 - 297, 英語その他
- 2018年, 日本機械学会バイオフロンティア講演会講演論文集(CD-ROM), 29th全脳循環血流場の数値シミュレーションに向けた脳血管構造モデリング
- 2018年, 数値流体力学シンポジウム講演論文集(CD-ROM), 32nd実形状モデルを用いた胃内流動の数値計算
- 2018年, バイオエンジニアリング講演会講演論文集(CD-ROM), 31st胃内容物の撹拌・排出の数値シミュレーション
- 2018年, 日本機械学会計算力学講演会論文集(CD-ROM), 31st胃の撹拌・排出の計算力学解析
- 2017年, 計算工学講演会論文集(CD-ROM), 22胃から十二指腸への食物排出の数値計算
- 2017年, 日本機械学会計算力学講演会論文集(CD-ROM), 30th胃における蠕動運動と流れの関係についての一考察
- 2017年, バイオエンジニアリング講演会講演論文集(CD-ROM), 29th胃壁の運動機能と胃内容物攪拌の関係
- 2017年, バイオエンジニアリング講演会講演論文集(CD-ROM), 29th胃内部の固体粒子挙動の数値計算
- 日本計算工学会, 2016年05月, 計算工学講演会論文集 Proceedings of the Conference on Computational Engineering and Science, 21, 4p, 日本語微小循環内における細胞接着の数値解析
- 2E32 沈降赤血球の再配向現象に関する数値解析When keeping blood inside a static tube, it is well known that the red blood cells (RBCs) start to sediment downward due to the density difference between inner fluid and the outer fluid plasma. In present work, we numerically investigate the orientation angle of settling RBCs. First, we confirm that the RBCs change its orientation toward vertical angle as also reported in previous experimental studies. Secondly, we find that this reorientation is faster for a red blood cell with higher Bond number or lower viscosity ratio. In this report, we also discuss how this reorientation speed would impact the overall trajectories of the RBCs.一般社団法人日本機械学会, 2016年01月09日, バイオエンジニアリング講演会講演論文集, 2016(28) (28), "2E32 - 1"-"2E32-4", 日本語
- 2E24 血球細胞の移動現象に及ぼす流体力学的因子の解明In the blood, cells are observed to move perpendicular to the direction of the blood flow in a process called lateral migration. This lateral migration occurs due to several hydrodynamic factors, such as the presence of the vessel wall, the applied Poiseuille flow within the vessel, and cell-cell interactions. However, the effect of these factors has not been well understood. Thus, using the boundary integral method, we have been numerically investigating the effect of the wall and the effect of the curvature of the applied flow on the lateral migration of a single cell. We have shown that the effect of the wall on cell lateral migration is dominant relative to the effect of the flow curvature, even at large distances between the cell and the wall. We have also derived a semi-analytical equation representing the relative effects of the wall and flow curvature, which allows us to predict the migration velocity in slit flows or microvessels. Our results can also be used to develop simplified models, based on the position of the cell within the vessel, for biophysical phenomena such as cell margination and axial migration.一般社団法人日本機械学会, 2016年01月09日, バイオエンジニアリング講演会講演論文集, 2016(28) (28), "2E24 - 1"-"2E24-4", 英語
- 1C46 気液または固液界面における繊毛虫の遊泳シミュレーション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.一般社団法人日本機械学会, 2016年01月09日, バイオエンジニアリング講演会講演論文集, 2016(28) (28), "1C46 - 1"-"1C46-5", 日本語
- 1E11 細管内における細胞の接着シミュレーション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.一般社団法人日本機械学会, 2016年01月09日, バイオエンジニアリング講演会講演論文集, 2016(28) (28), "1E11 - 1"-"1E11-5", 日本語
- 一般社団法人日本機械学会, 2016年, 講演論文集, 2016(51) (51), 187 - 188, 日本語195 粘弾性流体中を泳ぐ精子の数値シミュレーション
- 2016年, バイオエンジニアリング講演会講演論文集(CD-ROM), 28th蠕動運動と胃内容物攪拌の関係
- 一般社団法人 日本機械学会, 2016年, 東北支部総会・講演会 講演論文集, 2016(0) (0), 191 - 192, 日本語
- 一般社団法人日本機械学会, 2015年10月01日, バイオフロンティア講演会講演論文集, 2015(26) (26), 123 - 124, 日本語B212 細胞骨格運動の数値シミュレーション(B2-3 数理・計算バイオメカニクス2)
- 一般社団法人日本機械学会, 2015年09月16日, Proceedings of the ... Asian Pacific Conference on Biomechanics : emerging science and technology in biomechanics, 2015(8) (8), 366 - 366, 英語PS8-15 Mechanics of nodal cilia in early mouse embryo(PS8: Poster Short Presentation VIII,Poster Session)
- 一般社団法人日本機械学会, 2015年09月16日, Proceedings of the ... Asian Pacific Conference on Biomechanics : emerging science and technology in biomechanics, 2015(8) (8), 365 - 365, 英語PS8-14 Visualization of intestinal peristalsis of mosquito midgut by using micro X-ray imaging(PS8: Poster Short Presentation VIII,Poster Session)
- 一般社団法人日本機械学会, 2015年09月16日, Proceedings of the ... Asian Pacific Conference on Biomechanics : emerging science and technology in biomechanics, 2015(8) (8), 268 - 268, 英語PS3-7 DEVELOPMENT OF A NUMERICAL MODEL OF CYTOSKELETON DYNAMICS(PS3: Poster Short Presentation III,Poster Session)
- 一般社団法人日本機械学会, 2015年09月16日, Proceedings of the ... Asian Pacific Conference on Biomechanics : emerging science and technology in biomechanics, 2015(8) (8), 262 - 262, 英語PS3-1 Hydrodynamic behavior of small particles in a microchannel(PS3: Poster Short Presentation III,Poster Session)
- 日本計算工学会, 2015年06月, 計算工学講演会論文集 Proceedings of the Conference on Computational Engineering and Science, 20, 3p, 英語Capsule lateral migration : shear gradient vs. wall
- 一般社団法人日本機械学会, 2015年01月08日, バイオエンジニアリング講演会講演論文集, 2015(27) (27), 11 - 12, 日本語1A15 マラリア感染赤血球の回転運動・定常接着の数値解析(OS11-1:生体流れの計算バイオメカニクス:疾病の再現および診断・治療への応用(1))
- 一般社団法人日本機械学会, 2015年01月08日, バイオエンジニアリング講演会講演論文集, 2015(27) (27), 13 - 14, 日本語1A16 ダイニンによって駆動するノード繊毛運動の数値計算(OS11-1:生体流れの計算バイオメカニクス:疾病の再現および診断・治療への応用(1))
- 一般社団法人日本機械学会, 2015年01月08日, バイオエンジニアリング講演会講演論文集, 2015(27) (27), 5 - 6, 日本語1A12 カプセル懸濁液中におけるトレーサー粒子の挙動 : トレーサー粒子径の影響(OS11-1:生体流れの計算バイオメカニクス:疾病の再現および診断・治療への応用(1))
- 一般社団法人日本機械学会, 2015年01月08日, バイオエンジニアリング講演会講演論文集, 2015(27) (27), 165 - 166, 日本語1D35 せん断流れ下における赤血球懸濁液のレオロジー(OS3-1:血球運動のバイオメカニクス(1))
- 2015年, バイオエンジニアリング講演会講演論文集, 27th胃内のせん断応力の数値解析
- 2015年, 計算工学講演会論文集(CD-ROM), 20胃内容物攪拌の数値計算:胃壁の運動の影響
- 一般社団法人日本機械学会, 2014年10月02日, バイオフロンティア講演会講演論文集, 2014(25) (25), 21 - 22, 日本語A112 モータタンパクによって駆動する繊毛運動の数値計算(A1-3 数理・計算バイオメカニクス3,分散体バイオメカニクス)
- 一般社団法人日本機械学会, 2014年10月02日, バイオフロンティア講演会講演論文集, 2014(25) (25), 19 - 20, 日本語A111 界面近傍における微生物の振る舞いの数値計算(A1-3 数理・計算バイオメカニクス3,分散体バイオメカニクス)
- 日本計算工学会, 2014年06月, 計算工学講演会論文集 Proceedings of the Conference on Computational Engineering and Science, 19, 4p, 日本語体積率を変化させたカプセル濃厚懸濁液の数値解析
- 一般社団法人日本機械学会, 2014年01月10日, バイオエンジニアリング講演会講演論文集, 2014(26) (26), 539 - 540, 日本語2G34 微生物懸濁液中の物質吸収シミュレーション(OS1-1:自然界のバイオメカニクス・バイオミメティクス(1))
- 一般社団法人日本機械学会, 2014年01月10日, バイオエンジニアリング講演会講演論文集, 2014(26) (26), 245 - 246, 日本語1G43 リガンド-レセプタ相互作用モデルを用いたマラリア感染赤血球の接着シミュレーション(OS5-4:生体流れの計算バイオメカニクス:疾病の再現および診断・治療への応用(4))
- 一般社団法人日本機械学会, 2014年01月10日, バイオエンジニアリング講演会講演論文集, 2014(26) (26), 247 - 248, 日本語1G44 微小血管系における血行性転移に関連したがん細胞の流動解析(OS5-4:生体流れの計算バイオメカニクス:疾病の再現および診断・治療への応用(4))
- 一般社団法人日本機械学会, 2014年01月10日, バイオエンジニアリング講演会講演論文集, 2014(26) (26), 235 - 236, 日本語1G33 胃内の食物の流動の数値計算(OS5-3:生体流れの計算バイオメカニクス:疾病の再現および診断・治療への応用(3))
- 一般社団法人日本機械学会, 2014年01月10日, バイオエンジニアリング講演会講演論文集, 2014(26) (26), 439 - 440, 日本語2E15 微小流路内を流れる赤血球の変形挙動解析(OS3-1:血球運動のバイオメカニクス(1))
- 一般社団法人日本機械学会, 2014年01月10日, バイオエンジニアリング講演会講演論文集, 2014(26) (26), 445 - 446, 日本語2E22 カプセル濃厚懸濁液の体積率に対する粘度の非線形応答のメカニズム(OS3-2:血球運動のバイオメカニクス(2))
- 一般社団法人日本機械学会, 2014年01月10日, バイオエンジニアリング講演会講演論文集, 2014(26) (26), 443 - 444, 日本語2E21 壁近傍のせん断流れにおけるカプセル挙動の数値シミュレーション(OS3-2:血球運動のバイオメカニクス(2))
- 一般社団法人日本機械学会, 2014年, 講演論文集, 2014(49) (49), 131 - 132, 日本語167 気液界面における微生物の遊泳シミュレーション
- J027014 遊泳微生物の物質吸収シミュレーション([J027-01]生物規範メカニクス・システム:生物の運動,力学及びミメティクス(1))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.一般社団法人日本機械学会, 2013年09月08日, 年次大会 : Mechanical Engineering Congress, Japan, 2013, "J027014 - 1"-"J027014-4", 日本語
- J027011 微生物の集団遊泳シミュレーション([J027-01]生物規範メカニクス・システム:生物の運動,力学及びミメティクス(1))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.一般社団法人日本機械学会, 2013年09月08日, 年次大会 : Mechanical Engineering Congress, Japan, 2013, "J027011 - 1"-"J027011-4", 日本語
- 一般社団法人日本機械学会, 2013年03月15日, 講演論文集, 2013(48) (48), 8 - 9, 日本語102 二種類のカプセルを含むサスペンジョンの数値解析(バイオエンジニアリング,一般講演)
- 一般社団法人日本機械学会, 2013年01月08日, バイオエンジニアリング講演会講演論文集, 2013(25) (25), 299 - 300, 日本語2B14 境界要素法を用いたカプセルサスペンジョンのレオロジー解析(OS8-1:生体流れに関わる連成計算の最近の進展(1))
- 一般社団法人日本機械学会, 2013年01月08日, バイオエンジニアリング講演会講演論文集, 2013(25) (25), 387 - 388, 日本語2E02 微小血管における赤血球の挙動解析(GS10-1:循環器系の計算バイオメカニクス(1))
- 一般社団法人日本機械学会, 2013年01月08日, バイオエンジニアリング講演会講演論文集, 2013(25) (25), 307 - 308, 日本語2B19 微小循環における流動する細胞の管壁への移動現象の解析(OS8-2:生体流れに関わる連成計算の最近の進展(2))
- 一般社団法人日本機械学会, 2013年01月08日, バイオエンジニアリング講演会講演論文集, 2013(25) (25), 117 - 118, 日本語1D04 GPUを用いたモデル微生物の遊泳解析(OS10-1:生物の遊泳と飛翔(1))
- 一般社団法人 日本機械学会, 2013年, バイオエンジニアリング講演会講演論文集, 2013(0) (0), 111 - 112, 日本語
- 一般社団法人 日本機械学会, 2013年, バイオエンジニアリング講演会講演論文集, 2013(0) (0), 609 - 610, 日本語
- 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.一般社団法人 日本機械学会, 2013年, 年次大会, 2013(0) (0), _J027013 - 1-_J027013-4, 日本語
- 一般社団法人 日本機械学会, 2013年, バイオフロンティア講演会講演論文集, 2013(0) (0), 45 - 46, 日本語
- 一般社団法人 日本機械学会, 2013年, 東北支部総会・講演会 講演論文集, 2013(0) (0), 10 - 11, 日本語
- バイオメカニズム学会, 2012年12月, バイオメカニズム学術講演会予稿集, 33回, 33 - 34, 日本語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
- 一般社団法人日本機械学会, 2012年10月06日, 計算力学講演会講演論文集, 2012(25) (25), 9 - 10, 日本語806 胃内部の固体粒子運動の数値シミュレーション(OS8-1.工学・医療工学における移動境界問題(1),OS・一般セッション講演)
- 一般社団法人日本機械学会, 2012年10月06日, 計算力学講演会講演論文集, 2012(25) (25), 11 - 12, 日本語807 Double-layerを用いた境界要素法によるモデル微生物の干渉解析(OS8-2.工学・医療工学における移動境界問題(2),OS・一般セッション講演)
- 一般社団法人日本機械学会, 2012年10月06日, 計算力学講演会講演論文集, 2012(25) (25), 3 - 4, 日本語803 マラリア感染中期における感染赤血球と血管内皮細胞の接着シミュレーション(OS8-1.工学・医療工学における移動境界問題(1),OS・一般セッション講演)
- 一般社団法人日本機械学会, 2012年10月04日, バイオフロンティア講演会講演論文集, 2012(23) (23), 13 - 14, 日本語A107 遊泳モデル微生物の物質吸収シミュレーション(A1-2 生体流体工学2)
- 2012年09月01日, 京都大学数理解析研究所講究録, (1808) (1808), 121 - 126, 日本語ストークス流れ中の非球形カプセルの配向現象記事・総説・解説・論説等（大学・研究所紀要）
- 日本計算工学会, 2012年05月, 計算工学講演会論文集 Proceedings of the Conference on Computational Engineering and Science, 17, 4p, 日本語微小循環内血流解析のためのGPU計算手法の開発
- 日本計算工学会, 2012年05月, 計算工学講演会論文集 Proceedings of the Conference on Computational Engineering and Science, 17, 4p, 日本語せん断流れ下における赤血球の変形挙動解析
- 日本計算工学会, 2012年05月, 計算工学講演会論文集 Proceedings of the Conference on Computational Engineering and Science, 17, 4p, 日本語カプセル流動計算のための境界要素法のマルチGPU実装手法の構築
- 一般社団法人日本機械学会, 2012年03月13日, 講演論文集, 2012(47) (47), 28 - 29, 日本語111 境界要素法を用いた遊泳モデル微生物の物質吸収シミュレーション(バイオエンジニアリングII,一般講演)
- 一般社団法人日本機械学会, 2012年03月13日, 講演論文集, 2012(47) (47), 26 - 27, 日本語110 境界要素法による遊泳モデル微生物の干渉解析(バイオエンジニアリングII,一般講演)
- 一般社団法人日本機械学会, 2012年03月13日, 講演論文集, 2012(47) (47), 32 - 33, 日本語113 マラリア感染赤血球の接着現象の計算力学解析(バイオエンジニアリングII,一般講演)
- 一般社団法人日本機械学会, 2012年03月13日, 講演論文集, 2012(47) (47), 24 - 25, 日本語109 境界要素法を用いた流れ中の赤血球の変形解析(バイオエンジニアリングI,一般講演)
- 一般社団法人日本機械学会, 2012年03月13日, 講演論文集, 2012(47) (47), 230 - 231, 日本語212 GPGPUを用いた微小血管内血流モデルの開発(学生賞II,一般講演)
- 一般社団法人日本機械学会, 2012年01月06日, バイオエンジニアリング講演会講演論文集, 2012(24) (24), "8G24 - 1"-"8G24-2", 日本語8G24 GPUを用いた胃内容物撹拌の3次元計算(GS03 生体モデリングとシミュレーション)
- 一般社団法人日本機械学会, 2012年01月06日, バイオエンジニアリング講演会講演論文集, 2012(24) (24), "8F34 - 1"-"8F34-2", 日本語8F34 GPU計算に基づくマラリア感染時の微小循環血流計算モデルの開発(GS02 循環系のバイオメカニクス(モデリング,シミュレーション)1)
- 一般社団法人日本機械学会, 2012年01月06日, バイオエンジニアリング講演会講演論文集, 2012(24) (24), "8F13 - 1"-"8F13-2", 日本語8F13 高精度な大規模細胞流動計算のためのGPU計算基盤の開発(OS16 血球運動と微小環境のバイオニクス1)
- 一般社団法人日本機械学会, 2012年01月06日, バイオエンジニアリング講演会講演論文集, 2012(24) (24), "7H22 - 1"-"7H22-2", 日本語7H22 GPUによる肺内気流・吸入粒子の高速計算(OS15 呼吸系のバイオメカニクス2)
- 2012年, 日本機械学会東北支部総会・講演会講演論文集, 47th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
- 2012年, 日本機械学会計算力学講演会論文集(CD-ROM), 25th胃内部の固体粒子運動の数値シミュレーション
- 一般社団法人日本機械学会, 2011年10月08日, 計算力学講演会講演論文集, 2011(24) (24), 642 - 643, 日本語2306 胃内容物撹拌の数値計算(バイオメカニクス(2),OS・一般セッション講演)
- 一般社団法人日本機械学会, 2011年10月08日, 計算力学講演会講演論文集, 2011(24) (24), 639 - 641, 日本語2305 嚥下造影画像に基づく嚥下の計算力学解析(バイオメカニクス(2),OS・一般セッション講演)
- 一般社団法人日本機械学会, 2011年10月08日, 計算力学講演会講演論文集, 2011(24) (24), 646 - 647, 日本語2308 GPUによるカプセル流動の高速計算(バイオメカニクス(2),OS・一般セッション講演)
- 一般社団法人日本機械学会, 2011年10月08日, 計算力学講演会講演論文集, 2011(24) (24), 644 - 645, 日本語2307 GPU計算に基づく微小循環血流計算モデルの開発(バイオメカニクス(2),OS・一般セッション講演)
- 一般社団法人日本機械学会, 2011年10月06日, バイオフロンティア講演会講演論文集, 2011(22) (22), 61 - 62, 日本語B112 GPUを用いたCapsuleサスペンジョンの大規模計算手法の開発(B1-3 生体流体工学1)
- 一般社団法人日本機械学会, 2011年03月15日, 講演論文集, 2011(46) (46), 170 - 171, 日本語184 血管内皮細胞形状を考慮した血管内血球流動シミュレーション(バイオエンジニアリングII,一般講演)
- 一般社団法人日本機械学会, 2011年01月07日, バイオエンジニアリング講演会講演論文集, 2010(23) (23), 559 - 560, 日本語9G-17 嚥下造影画像に基づく嚥下の数値シミュレーション(GS-2 呼吸と嚥下)
- 一般社団法人日本機械学会, 2011年01月07日, バイオエンジニアリング講演会講演論文集, 2010(23) (23), 557 - 558, 日本語9G-16 胃内容物攪拌の数値流体力学モデルの開発(GS-2 呼吸と嚥下)
- 一般社団法人日本機械学会, 2011年01月07日, バイオエンジニアリング講演会講演論文集, 2010(23) (23), 389 - 390, 日本語9E-08 血液中を流動する細胞挙動の数値解析(OS-1(1) 微小循環器系のバイオエンジニアリング(2))
- 一般社団法人 日本機械学会, 2011年, 東北支部総会・講演会 講演論文集, 2011(0) (0), 166 - 167, 日本語
- 一般社団法人 日本機械学会, 2011年, バイオエンジニアリング講演会講演論文集, 2010(0) (0), 487 - 488, 日本語
- 一般社団法人 日本機械学会, 2011年, 東北支部総会・講演会 講演論文集, 2011(0) (0), 176 - 177, 日本語
- 一般社団法人日本機械学会, 2010年11月11日, バイオフロンティア講演会講演論文集, 2010(21) (21), 13 - 14, 日本語A107 マラリア感染赤血球の接着特性による血流の変化(A1-2 生体流体工学2)
- 一般社団法人日本機械学会, 2010年11月11日, バイオフロンティア講演会講演論文集, 2010(21) (21), 15 - 16, 日本語A108 胃内容物流れの数値シミュレーション : 内容物量の影響(A1-2 生体流体工学2)
- 一般社団法人日本機械学会, 2010年03月12日, 講演論文集, 2010(45) (45), 128 - 129, 日本語164 粒子法を用いた胃内容物攪拌の数値シミュレーション(計算力学/情報・知能・精密機器/交通・物流I,一般講演)
- 一般社団法人日本機械学会, 2010年03月12日, 講演論文集, 2010(45) (45), 184 - 185, 日本語192 血流中のマラリア感染赤血球挙動の3次元シミュレーション(バイオエンジニアリングI,一般講演)
- 一般社団法人日本機械学会, 2010年03月12日, 講演論文集, 2010(45) (45), 192 - 193, 日本語196 大腸菌を用いたバイオマイクロポンプの基礎研究(バイオエンジニアリングII,一般講演)
- 一般社団法人日本機械学会, 2010年03月12日, 講演論文集, 2010(45) (45), 186 - 187, 日本語193 共焦点マイクロPIVシステムによる大腸菌溶液のメゾスケール流動構造の計測(バイオエンジニアリングI,一般講演)
- 一般社団法人日本機械学会, 2010年03月12日, 講演論文集, 2010(45) (45), 188 - 189, 日本語194 微小流路内におけるがん細胞の流動挙動(バイオエンジニアリングII,一般講演)
- 一般社団法人日本機械学会, 2010年01月08日, バイオエンジニアリング講演会講演論文集, 2009(22) (22), 14 - 14, 日本語0205 マラリア感染赤血球の接着特性が血流に与える影響(GS2:血球と微小循環)
- 一般社団法人日本機械学会, 2010年01月08日, バイオエンジニアリング講演会講演論文集, 2009(22) (22), 280 - 280, 日本語0625 Patient-specific morphological and blood flow analysis of pulmonary artery in the case of severe deformations of the lung
- 一般社団法人日本機械学会, 2010年01月08日, バイオエンジニアリング講演会講演論文集, 2009(22) (22), 270 - 270, 日本語0513 小腸内の輸送現象の計算バイオメカニクス(GS14-1:モデリングとシミュレーション)
- 一般社団法人日本機械学会, 2010年01月08日, バイオエンジニアリング講演会講演論文集, 2009(22) (22), 169 - 169, 日本語1005 生体インピーダンス法による体内水分量モニタリングシステムの開発(GS13:生体計測)
- 一般社団法人日本機械学会, 2010年01月08日, バイオエンジニアリング講演会講演論文集, 2009(22) (22), 156 - 156, 日本語0914 要介護者のための自走式トイレの開発(GS15-1:福祉工学1)
- 一般社団法人 日本機械学会, 2010年, バイオフロンティア講演会講演論文集, 2010(0) (0), 105 - 106, 日本語
- 一般社団法人日本機械学会, 2009年11月06日, バイオフロンティア講演会講演論文集, 2009(20) (20), 111 - 112, 英語B210 Patient-specific study on pulmonary blood now in the case of severe deformations of the lung
- 一般社団法人日本機械学会, 2009年11月06日, バイオフロンティア講演会講演論文集, 2009(20) (20), 109 - 110, 日本語B209 がん細胞のレオロジー特性に及ぼす抗がん剤の影響(B2-2 細胞工学・マイクロバイオメカニクス3)
- 一般社団法人日本機械学会, 2009年11月06日, バイオフロンティア講演会講演論文集, 2009(20) (20), 39 - 40, 日本語B106 嚥下造影画像に基づく食塊・喉頭蓋の運動解析(B1-2 生体計測・診断)
- 一般社団法人日本機械学会, 2009年10月10日, 計算力学講演会講演論文集, 2009(22) (22), 544 - 545, 日本語2001 マラリア感染血液流れの三次元計算力学モデルの開発(OS20.細胞・生体分子の計算バイオメカニクス(1),オーガナイズドセッション)
- 2009年10月, ブイヤント航空, 37, 81 - 88, 日本語変形機構を有する室内飛行船の開発記事・総説・解説・論説等（その他）
- FIT(電子情報通信学会・情報処理学会)運営委員会, 2009年08月20日, 情報科学技術フォーラム講演論文集, 8(3) (3), 555 - 556, 日本語K-014 独居老人のための自走式排泄支援システムの開発(教育工学・福祉工学・マルチメディア応用,一般論文)
- 一般社団法人日本機械学会, 2009年03月13日, 講演論文集, 2009(44) (44), 100 - 101, 日本語151 変形して家庭内を巡航する飛行船型見守りシステム(ロボティクス・メカトロニクス/機械力学・計測制御)
- 一般社団法人日本機械学会, 2009年03月13日, 講演論文集, 2009(44) (44), 168 - 169, 日本語187 ガン細胞の転移性と変形能の関係(バイオエンジニアリング)
- 一般社団法人日本機械学会, 2009年03月13日, 講演論文集, 2009(44) (44), 188 - 189, 日本語198 小腸内の消化物の流動解析(流体力学・流体工学I)
- 一般社団法人日本機械学会, 2009年03月13日, 講演論文集, 2009(44) (44), 170 - 171, 日本語188 高齢者のための体内水分量モニタリングシステムに関する基礎的検討(バイオエンジニアリング)
- 一般社団法人日本機械学会, 2009年03月13日, 講演論文集, 2009(44) (44), 174 - 175, 日本語190 嚥下造影画像を用いた嚥下メカニズムの力学的考察(バイオエンジニアリング)
- 一般社団法人日本機械学会, 2009年03月13日, 講演論文集, 2009(44) (44), 172 - 173, 日本語189 Parameciumの回避反応を引き起こす力学的刺激の定量化(バイオエンジニアリング)
- 一般社団法人日本機械学会, 2009年03月13日, 講演論文集, 2009(44) (44), 190 - 191, 日本語199 マラリアにおけるロゼットの計算力学モデルの開発(流体力学・流体工学I)
- 一般社団法人日本機械学会, 2009年01月22日, バイオエンジニアリング講演会講演論文集, 2008(21) (21), 411 - 412, 日本語439 自走式排泄支援ロボットの開発(OS8-2:生活支援と福祉工学(2),OS8:生活支援と福祉工学)
- 一般社団法人日本機械学会, 2009年01月22日, バイオエンジニアリング講演会講演論文集, 2008(21) (21), 401 - 402, 日本語434 在宅介護のための呼吸モニタリングシステムの開発(OS8-1:生活支援と福祉工学(1),OS8:生活支援と福祉工学)
- 一般社団法人日本機械学会, 2009年01月22日, バイオエンジニアリング講演会講演論文集, 2008(21) (21), 87 - 88, 日本語215 微小流路内の分岐部及び合流部における血流の共焦点マイクロPIV計測(OS1-3:循環器系のバイオメカニクス(3),OS1:循環器系のバイオメカニクス)
- 一般社団法人日本機械学会, 2008年09月22日, バイオフロンティア講演会講演論文集, 2008(19) (19), 153 - 154, 日本語B412 呼吸モニタリングに基づく吸入器自動制御システム(福祉工学,リハビリテーション工学)
- 一般社団法人日本機械学会, 2008年09月22日, バイオフロンティア講演会講演論文集, 2008(19) (19), 47 - 48, 日本語B203 境界要素法による定ずり流れ中での赤血球の変形挙動解析(生物流体・熱工学)
- 一般社団法人日本機械学会, 2008年09月22日, バイオフロンティア講演会講演論文集, 2008(19) (19), 58 - 59, 日本語B209 カタツムリの腹足推進を模倣したカプセル型内視鏡の自走機構の開発(バイオミメティクス)
- 1G3-2 自走式排泄支援システムの開発(医療福祉ロボットII,一般講演)A number of elderly people have a difficulty in going to the toilet by themselves. They sometimes wear an adult diaper but it makes the elderly uncomfortable and unsanitary. Moreover, their pride is injured by wearing the diaper. A portable toilet is also used for the elderly requiring assistance to the toilet. The portable toilet is not a sufficient solution because it is also uncomfortable and unsanitary for them. We propose a mobile toilet system for solving this problem. The concept of the proposed system is as follows. The toilet waits for calling signal from the elderly at standby room. When the calling signal is received, the toilet autonomously goes to the bedroom and approaches the elderly. After excreting, the toilet returns to the standby room and automatically disposes feces. This system is also equipped with analyzing function of feces for monitoring their health condition. We have developed a prototype of the toilet.一般社団法人日本機械学会, 2008年09月17日, 福祉工学シンポジウム講演論文集, 2008, 176 - 177, 日本語
- 1G2-2 呼吸器疾患在宅治療のための呼吸モニタリングシステムの開発(医療福祉ロボットI,一般講演)A number of patients are suffering from respiratory diseases, such as dyspnea, sleep apnea syndrome (SAS), asthma and chronic obstructive pulmonary disease (COPD). These patients can be supported by early detection of symptom and administration of milder treatment. However, it is a serious burden for them and their family to care for their respiratory conditions in daily life. We propose a new home-care system for such patients. The system is an automatic inhaler control system based on continuous respiration monitoring. We employ a mask-type unit to install a measurement sensor for respiration together with an inhaler. Respiration is monitored using a thermocouple in the mask. Respiratory rate is measured by counting peaks of temperature change due to expiration and inspiration. The error of respiratory rate at rest in sitting posture was within 2% between the measurement and the reference. Based on the monitored data, the inhaler can be controlled automatically. Moreover, the information of respiration can be shared with family, hospital, and local supporters at a long distance through a computer network.一般社団法人日本機械学会, 2008年09月17日, 福祉工学シンポジウム講演論文集, 2008, 164 - 165, 日本語
- 日本計算工学会, 2008年05月19日, 計算工学講演会論文集, 13(2) (2), 827 - 830, 日本語肺内気流計算に対する Adaptive Mesh Refinement 法の有用性
- 日本計算工学会, 2008年05月19日, 計算工学講演会論文集, 13(2) (2), 533 - 536, 日本語マラリア感染血液流れの三次元数値流体モデル
- 一般社団法人日本機械学会, 2008年03月15日, 講演論文集, 2008(43) (43), 53 - 54, 日本語126 自走式インテリジェント便器の開発(バイオエンジニアリング)
- 一般社団法人日本機械学会, 2008年01月24日, バイオエンジニアリング講演会講演論文集, 2007(20) (20), 219 - 220, 日本語608 ウェアラブル温度計測システムによる筋肉負荷の考察(OS8-1:医療福祉と工学(1),OS8:医療福祉と工学)
- 一般社団法人日本機械学会, 2008年01月24日, バイオエンジニアリング講演会講演論文集, 2007(20) (20), 1 - 2, 日本語101 微小流路狭窄部を通る血流のconfocal-micro-PTV計測(OS1-1:循環器系・血流の計測とメカニクス(1),OS1:循環器系・血流の計測とメカニクス)
- 一般社団法人日本機械学会, 2008年01月24日, バイオエンジニアリング講演会講演論文集, 2007(20) (20), 9 - 10, 英語105 DISPERSION OF RED BLOOD CELLS IN MICROCHANNELS : A CONFOCAL MICRO-PTV ASSESSMENT
- 一般社団法人日本機械学会, 2008年01月24日, バイオエンジニアリング講演会講演論文集, 2007(20) (20), 57 - 58, 日本語210 遊泳バクテリアの2体干渉解析(OS3-1:生物遊泳・飛翔とバイオミメティクス(1),OS3:生物遊泳・飛翔とバイオミメティクス)
- 一般社団法人日本機械学会, 2008年01月24日, バイオエンジニアリング講演会講演論文集, 2007(20) (20), 35 - 36, 日本語118 実形状脳動脈モデルにおける嚢状瘤の形成シミュレーション(OS2-5:生体モデリングとシミュレーション(5),OS2:生体モデリングとシミュレーション)
- 一般社団法人日本機械学会, 2007年11月25日, 計算力学講演会講演論文集, 2007(20) (20), 189 - 190, 日本語2304 肺呼吸マルチスケールシミュレーションのための気道-肺実質モデルの構築(OS23.生命体統合シミュレーション(1))
- 一般社団法人日本機械学会, 2007年11月25日, 計算力学講演会講演論文集, 2007(20) (20), 583 - 584, 日本語303 肺内気流計算への高次精度AMR法の応用(OS03.CIP型マルチモーメント・スキームの新展開,ポスターセッションP-5)
- 一般社団法人日本機械学会, 2007年11月25日, 計算力学講演会講演論文集, 2007(20) (20), 341 - 342, 日本語2211 生物学的反応を考慮した嚢状脳動脈瘤の形成シミュレーション(OS22.計算バイオメカニクス(2),ポスターセッションP-3)
- 一般社団法人日本機械学会, 2007年10月05日, バイオフロンティア講演会講演論文集, 2007(18) (18), 127 - 128, 日本語B208 ウェアラブルシステムによる呼吸計測ユニットの開発(B2-2 福祉工学2)
- 2007年07月01日, 可視化情報学会誌 = Journal of the Visualization Society of Japan, 27, 141 - 142, 英語微小流路内の血流における赤血球の挙動と干渉
- 日本計算工学会, 2007年05月, 計算工学講演会論文集, 12(1) (1), 213 - 216, 日本語血管のアダプテーションを考慮した脳動脈瘤の進展シミュレーション
- 一般社団法人日本機械学会, 2007年01月06日, バイオエンジニアリング講演会講演論文集, 2006(19) (19), 140 - 141, 日本語421 適合格子細分化法を用いた実形状肺内気流の計算手法の開発(OS3-2:肺・気道のメカニクス,オーガナイズドセッション3:肺・気道のメカニクス)
- 一般社団法人日本機械学会, 2007年01月06日, バイオエンジニアリング講演会講演論文集, 2006(19) (19), 318 - 319, 日本語331 微生物の濃厚溶液におけるメゾスケール流動構造(OS1-2:生物流体とバイオミメティクス,オーガナイズドセッション1:生物流体とバイオミメティクス)
- 一般社団法人日本機械学会, 2007年01月06日, バイオエンジニアリング講演会講演論文集, 2006(19) (19), 298 - 299, 日本語237 病的血管形状におけるATP輸送の解析(OS2-7:循環系のバイオメカニクス,オーガナイズドセッション12:楽しめるバイオエンジニアリング)
- 一般社団法人日本機械学会, 2006年11月10日, バイオフロンティア講演会講演論文集, 2006(17) (17), 3 - 4, 日本語A101 日常生活の運動量の計測を目的としたウェアラブルシステムの開発(A1-1 福祉工学)
- 一般社団法人日本機械学会, 2006年11月02日, 計算力学講演会講演論文集, 2006(19) (19), 499 - 500, 日本語527 脈波伝播に伴う壁せん断応力変化の流体-固体連成解析(計算バイオメカニクス2,OS25 計算バイオメカニクス)
- 共著, Springer, 2018年11月, 英語Frontiers in Computational Fluid-Structure Interaction and Flow Simulation: A Numerical Analysis of Rheology of Capsule Suspensions Using a GPU-Accelerated Boundary Element Method学術書
- 共著, Elsevier, 2018年07月, 英語Integrated Nano-Biomechanics: 3.2 Gastric Motility and Flow in the Stomach学術書
- 共著, Elsevier, 2018年07月, 英語Integrated Nano-Biomechanics: 3.1 Dynamics of Swallowing学術書
- 共著, Elsevier, 2018年07月, 英語Integrated Nano-Biomechanics: 2.3 Cell Adhesion in Microvessels学術書
- 共編者(共編著者), Elsevier, 2018年07月, 英語Integrated Nano-Biomechanics学術書
- 共編者(共編著者), Springer, 2014年, 英語Visualization and Simulation of Complex Flows in Biomedical Engineering学術書
- Osaka University MEI-Center Summer School 2019, 2019年08月, 英語, Suita, Japan, 国際会議Computation of complex physiological flows[招待有り]口頭発表（招待・特別）
- 29th International Symposium on Cerebral Blood Flow, Metabolism, and Function, 2019年07月, 英語, Yokohama, Japan, 国際会議Development of a numerical model of whole-scale cerebral circulationポスター発表
- 6th International Conference on Computational and Mathematical Biomedical Engineering, 2019年06月, 英語, Sendai, Japan, 国際会議Modeling cerebral vasculatures for analysis of the whole cerebral circulationポスター発表
- 71st Annual Meeting of the APS Division of Fluid Dynamics, 2018年11月, 英語, Atlanta, USA, 国際会議Hemorheology of dense suspension of red blood cells in a wall-bounded shear flow口頭発表（一般）
- 8th World Congress on Biomechanics, 2018年07月, 英語, Dublin, Ireland, 国際会議Relationship between gastric wall motility and mixing of liquid foods in the stomachポスター発表
- 8th World Congress on Biomechanics, 2018年07月, 英語, Dublin, Ireland, 国際会議Perioperative hemodynamic changes in the patient with pulmonary arterial hypertension by use of thoracic 4D-flow MRIポスター発表
- 8th World Congress on Biomechanics, 2018年07月, 英語, Dublin, Ireland, 国際会議Numerical simulation of cytoadhesion of red blood cells infected by Plasmodium falciparum口頭発表（招待・特別）
- Joint Meeting of the European Society for Clinical Hemorheology and Microcirculation, the International Society of Clinical Hemorheology, and the International Society of Biorheology, 2018年07月, 英語, Krakow, Porland, 国際会議Effect of internal viscosity on suspension rheology of red blood cells口頭発表（一般）
- 8th World Congress on Biomechanics, 2018年07月, 英語, Dublin, Ireland, 国際会議Cell adhesion during bullet and rolling motion in capillaries口頭発表（招待・特別）
- 日本機械学会2018年度年次大会, 2018年, 日本語, 吹田, 国内会議微小循環の血液の流れを計算する口頭発表（招待・特別）
- 第14回東北大学REDEEMシンポジウム, 2018年, 日本語, 東京, 国内会議体の中の流れを計算する口頭発表（招待・特別）
- 第90回バイオメクフォーラム, 2018年, 日本語, 豊中, 国内会議体の中の複雑な流れを計算する口頭発表（招待・特別）
- 第50回生物機械システム研究会, 2018年, 日本語, 豊中, 国内会議胃の中の流れを計算する口頭発表（招待・特別）
- 日本学術振興会, 科学研究費助成事業, 基盤研究(A), 神戸大学, 2021年04月05日 - 2024年03月31日流体構造生化学連成解析によるニューロンの移動モードと大脳皮質形成の力学の解明哺乳類の大脳皮質深部で誕生した神経細胞（ニューロン）は，三種類の移動モードを駆使して脳表層に到着し，インサイドアウトと呼ばれる六層構造の大脳皮質を形成する． 本研究の目的は，流体構造生化学連成解析とイン・ビボ細胞実験の統合的な手法によって，ニューロンの移動モードの変化とインサイドアウト構造の形成メカニズムを力学に基づいて明らかにすることである．そのための基盤計算技術として，細胞膜の固体力学，細胞質と細胞外の液体の流体力学，細胞接着タンパクと細胞骨格タンパクの生化学反応を連成するトランススケール流体構造生化学連成解析手法を開発する． ２０２１年度は，ニューロンの先導突起の挙動を再現できるトランススケール流体構造生化学連成解析手法の基礎を構築した．生体組織の成長理論をヒントに，局所的な生体膜の面積増加と薄膜の力学を連成する手法を開発した．非一様有理Ｂスプライン（ＮＵＲＢＳ）関数を用いて高次に表現した曲面に対し，細胞膜に対する代表的な構成則であるスカラックのひずみエネルギー関数（Skalak et al., Biophys. J., 1973）とヘルフリッヒの曲げエネルギー関数（Helfrich, Zeitschrift fur Naturforschung C, 1973）を弱形式で記述し，アイソジオメトリック解析を適用した．マッシュルーム形状の先導突起や長く伸びた先導突起を再現することに成功し，さらに，これらの先導突起の形状を記述する理論解を導出した．
- 日本学術振興会, 科学研究費助成事業, 学術変革領域研究(A), 神戸大学, 2021年09月10日 - 2023年03月31日薄く時間変化する生体建築部材の流体構造連成解析ーからだ建築のCAEの方法生体の組織を構成する建築部材は，多くの場合，繊維と膜と液体であり，例えば，上皮組織の管腔構造などが作られる．これらの建築部材に共通する特徴は，薄い構造であること，部材の数や形が時間変化すること，流体の中で建築作業が進行することである．本研究の目的は，生体建築部材から作られる生体組織のコンピュータ支援エンジニアリング（ＣＡＥ）の手法を開発することである．具体的には，建築部材の変形，成長，結合の変化を考慮して生体構造力学を数理モデル化し，Ｔ－スプライン曲面理論に基づくアイソジオメトリック解析を応用する流体構造連成計算手法を開発する．これを用いて，イン・ビボ実験で得られている螺旋形状の血管形成の再現を試みる． ２０２１年度は，生体建築部材の流体構造連成解析手法として，Ｔースプライン曲面理論に基づくアイソジオメトリック流体構造連成解析のフレームワークを開発した．この手法は曲面の高次表現に特徴があり，薄い構造の曲げ変形を高精度に計算することができる．管腔構造の生体組織に対し，成長を伴う管壁の構造力学を生体組織の成長理論とキルヒホッフ・ラブシェルを用いて定式化している．現在，この手法を用いて，血管を模擬した管腔構造に対する簡易的なパラメトリック解析を実施している．管腔構造が一次元的，二次元的，三次元的に座屈変形するパターンが得られており，それぞれの座屈変形パターンに至る条件を検討し，メカニズムを明らかにしようとしているところである．
- 日本学術振興会, 科学研究費助成事業, 基盤研究(C), 東北大学, 2019年04月01日 - 2023年03月31日腹部大動脈瘤の拡大速度を規定する病理組織学的因子に関する前向きコホート研究昨年度に報告した通り現状ではコロナウイルス感染拡大により、研究計画遂行に大きな支障が生じている。今年度は遅れを取り戻すべく、昨年度と同様に大動脈瘤の拡大速度を規定する病理組織学的因子を解析するため、大動脈瘤血流シミレーション技術の確立と習得、大動脈瘤症例の瘤径の継時的変化の観察、また、大動脈瘤壁の組織サンプルの蓄積、得た技術をもとにした大動脈瘤破裂症例の血流シミレーション等を行う予定であった。しかしながら、今年度も引き続いてコロナ感染は拡大に歯止めがかからず、数回の波も出現した。研究代表者が所属するのが大規模医療機関である事から、大動脈瘤血流シミレーションソフトを開発する予定であった神戸大学との共同研究が、人的交流を含めて困難である状況は変わっていない。それゆえ、現在に至るまでもシミレーションの基盤を確立する段階に至っていない。オンラインミーティングを活用もしているものの、オンラインではその特性からプライバシーに配慮した患者データのやり取りには限界があり、それを元にしたシミレーションデモは行っているものの、数名程度にとどまっている。また、引き続きコロナウイルス感染症の影響で、そもそも大動脈瘤の新規受診症例が減少していることは変わりなく、また、ICU病床・手術室の利用制限も同様であるため、大動脈瘤手術症例の蓄積を行う事が困難である事にも変わりがない。したがって今年度も研究実績は、残念ながらほぼ得られていない。コロナウイルス感染症は収束の糸口が若干見えてきた感があるが、残りの研究期間を考えると、現時点で当初予定していた研究遂行は非常に困難であると言わざるを得ない。従って、次年度最終年度を迎えるにあたり、研究期間の延長申請を行う事を考えている。
- 日本学術振興会, 科学研究費助成事業, 基盤研究(A), 早稲田大学, 2018年04月01日 - 2023年03月31日赤血球の運動に着目した開閉する心臓弁の流体構造連成解析手法の構築心臓弁の開閉に伴い、その内側を流れる赤血球を含む血液は1)流速3 m/sから急激に静止する強い非定常性、2)弁尖同士に挟まれるという 特異性がある。そのため、実験での観測が極めて困難であり、従来の数値計算でも再現できない。従って、弁の開閉やそれに伴う血流動態といった物理の解明には至っていない。本研究では、心臓の弁近傍の血流動態の解明に向け、流体構造連成解析手法を拡張する。具体的には、弁を 含む流体構造連成問題、高速流れ中の赤血球挙動、心臓弁開閉時の赤血球挙動の数値計算手法を順に構築する。統合した手法を用い、赤血球が 弁の開閉時にどのように振る舞うかを詳細に再現することで、血流動態を明らかにする。これにより、心臓弁の機能を損なう疾患の予防・治療 方法に、力学的視点から新たな指針を提示することを目的としている。
本研究では、心臓弁の開閉が起こるようなトポロジー変化が起きる空間を占める流体を、物体適合格子を用いて計算する手法を構築している。この方法は従来の信頼のある解析手法を損なうことなく同時にトポロジー変化も考慮できる方法で、トポロジー変化に特化した手法に比べ信頼性が高い。この方法による計算から、弁が閉じる際に流速は必ずしも徐々に小さくなるわけではないことが示されており、開閉時に生じる速度境界層を捉えることの重要性などがわかる。この事実から、他手法では議論しにくい開閉近傍の現象解明を数値計算により検証ができるようになっている。また赤血球を含む流体解析は多く場合、その影響度合いの高い毛細血管のような低速の箇所であるが、本研究では速度の高い領域での赤血球挙動を議論するために、Navier-Stokes方程式に基づく流体と赤血球の連成問題について取り組んでいる。 - 日本学術振興会, 科学研究費助成事業, 挑戦的研究(萌芽), 神戸大学, 2020年07月30日 - 2022年03月31日細胞実験と数値流体力学の統合的手法による細胞質分裂における細胞の力学状態の解明タリンGFPを発現させたMDA-MB-231細胞の細胞質分裂過程の三次元ライブイメージングを実施し，「タリン二量体の構造変化が細胞質分裂の力学的な特性を変化させるのではないか」という仮説を検証した．タリンGFPを発現したMDA-MB-231細胞は底面に対して斜め方向に分裂する傾向があり，これは，生体分子，細胞，細胞環境の力学的なバランスが変化したためではないかと考えられた．
- 日本学術振興会, 科学研究費助成事業, 新学術領域研究(研究領域提案型), 神戸大学, 2019年04月01日 - 2021年03月31日ニューロンの四つの移動モードの数理・計算モデルの開発本研究課題の目的は，大脳新皮質を構成する興奮性ニューロンの四つの移動モードに対する数理モデルを開発し，大脳新皮質の形成過程を数値解析するための基盤技術を構築することである．大脳新皮質のインサイドアウト構造の形成にはリーリンと呼ばれる分子が必要であり，リーリンはニューロンの四つの移動モード全ての制御に関わっていることが分かっている．ここでは，リーリンによる細胞骨格分子，細胞接着分子の制御に着目し，その効果を細胞骨格分子の重合・脱重合速度の変化，あるいは細胞接着分子の結合・離脱速度の変化としてモデル化する．大規模な数値解析によってこれらのパラメータの変化とニューロンの形態・挙動の変化の関係を力学法則に基づき定量的に理解する．ここでは，細胞を一様な非圧縮の粘弾性体と仮定し，細胞外部の粘性流体との流体構造連成問題としてモデル化した．細胞接着分子のリガンドレセプタ結合にはスリップボンドモデルを採用し，モンテカルロ法を用いて計算した．細胞表面にリガンド，細胞外部の足場にレセプタを分布させ，これらの結合による接着力を埋め込み境界法を用いて流体構造連成計算と連立した．ニューロンのモデルにほとんど同じ物性値を設定し，繊維のネットワーク状の足場とロッド状の足場にそれぞれ配置した．繊維のネットワーク状の足場に配置したニューロンは多極性移動でみられるような挙動を示した．一方，ロッド状の足場に配置したニューロンはロコモーションでみられるような挙動を示した．これらの結果から，多極性移動からロコモーションへの移動モードの変化では，細胞接着の足場となる細胞環境の変化が主な要因であり，細胞の力学特性や生化学特性の変化は二次的な効果となる可能性が示唆された．
- 日本学術振興会, 科学研究費助成事業, 基盤研究(B), 2017年04月01日 - 2021年03月31日計算力学と電気生理学の統合的解析による消化器系バイオメカニクスの開拓数値流体力学，医用画像，電気生理学を用いて，胃・幽門・十二指腸における食物流動の計算モデルを開発した．胃と幽門の運動機能が適切に協調しないことによって，排出速度遅延や十二指腸から胃への逆流が生じることを示した．また，高齢者などにおいて胃体部のスローウェーブの伝播速度が変化しており，これが排出速度に影響を与えている可能性を示した．
- 日本学術振興会, 科学研究費助成事業, 基盤研究(A), 東北大学, 2017年04月01日 - 2021年03月31日微生物バイオメカニクスの深化ナノスケールからマクロスケールへと物理法則を丹念に積み上げる独自の手法を用いることで、力学環境下の精子や微細藻、繊毛虫、大腸菌、酵母などの挙動と生物学的機能を明らかにした。分子モーターで駆動される繊毛軸支の運動から、鞭毛運動の同期、多数の鞭毛が生えた繊毛虫の遊泳と生物学的応答、２体干渉と協調遊泳、連続体としてのレオロジーや拡散特性、細胞増殖と集積など、スケール階層を貫いた解析に成功した。これらの成果は、PNAS誌に２編、Science Adv誌に1編、J Fluid Mech誌に6編など、計48編の査読付き雑誌論文として発表した。また、プレスリリースを８件行い、研究成果を広く社会に公開した。
- 日本学術振興会, 科学研究費助成事業, 挑戦的研究(萌芽), 神戸大学, 2018年06月29日 - 2020年03月31日腸内環境の生理流体力学：過敏性腸症候群の病態メカニズムの革新的理解本研究では，「Rectosigmoid brake」と呼ばれる生理現象に着目して研究を実施した．オークランド大学から提供された大腸の医用画像データに基づき，大腸の形状モデルを作成した．この形状モデルに対し，直腸S状部から発生しS字結腸を伝播する逆行性の蠕動運動を与えた．キュムラント格子ボルツマン法と適合サブドメイン法を応用し，大腸に対する内容物輸送の計算モデルを構築した．逆行性の蠕動運動によって直腸内の時間平均圧力が減少する結果が得られ，逆行性の蠕動運動は「Rectosigmoid brake」として働きえることが示された．
- 日本学術振興会, 科学研究費助成事業, 基盤研究(B), 東北大学, 2016年04月01日 - 2019年03月31日磁気刺激による神経跳躍伝導を電磁界変化で検出する食道がん術中反回神経探索システム食道がん手術を想定した反回神経探索においては、確実な神経探索方法が要求される。そこで、小動物の坐骨神経などを使って、跳躍伝導の発生間隔が約45mmであることと、ランビエ絞輪におけるNa＋チャネルの発火特性を利用した連続パルス刺激を行うことで、神経と他の組織伝導の識別が可能であることを見出した。磁気センサーを使って、ランビエ絞輪におけるNa+チャネルの発火を検出することは、ロックインAMPなどを用いても、実現できなかった。また、磁気刺激についても、連続パルス刺激での跳躍伝導の誘発実現には至らなかった。しかし、跳躍伝導は複数のランビエ絞輪を飛び越えて、発生しているという新しい見解が得られた。
- 日本学術振興会, 科学研究費助成事業, 基盤研究(A), 東北大学, 2014年04月01日 - 2017年03月31日階層を貫く細胞サスペンジョン力学の新展開本研究では、「階層を貫く細胞サスペンジョン力学」を徹底的に追求し、実験・理論解析・数値シミュレーションの手法を統合することで、世界の他の研究グループの追随を許さない高みに引き上げることに成功した。そして、海洋微生物から人体の血球細胞にいたるまで、ナノスケールからマクロスケールまでの生命現象を解明し、生物流れに関わる工学・医工学技術の開発へと展開した。これらの成果は、30編の査読付き英文雑誌論文として公表した。
- 日本学術振興会, 科学研究費助成事業, 特別推進研究, 東北大学, 2013年 - 2017年統合ナノバイオメカニクスの創成分子スケールからのボトムアップアプローチによって，統合ナノバイオメカニクスを構築した．これにより，感染症を始めとする様々な疾患を計算機上で再現することに成功し，疾患の進行や薬効の定量的予測に基づく新しい診断・治療方法を創出した．さらに医療用MEMSデバイスの設計に応用し，がん細胞やバクテリアを分離・検出するバイオチップを開発した．研究成果は，査読付き雑誌論文として50編発表した．
- 日本学術振興会, 科学研究費助成事業, 新学術領域研究(研究領域提案型), 東北大学, 2014年04月01日 - 2016年03月31日実験的に抽出された分子反応パラメータを導入したマラリア感染赤血球モデルの開発マラリアに感染した赤血球は膜表面に接着タンパクを発現する．この分子反応の発現によりマラリア感染赤血球は微小血管内に接着し，周囲の赤血球を巻き込んだ組織レベルの微小循環障害を引き起こす． 細胞の力学と生化学を連立する計算力学モデルを開発し，接着分子の生化学特性とマラリア感染赤血球挙動の関係に対する大規模パラメトリック計算を実施した．まず単体のマラリア感染赤血球挙動の計算を実施し，次に，多数の正常赤血球と相互作用する微小循環内の挙動を計算することで総合的に検討を行った．血管内皮細胞上にTSPやCD36がレセプタとして存在している場合，マラリア感染赤血球は定常接着をすると報告されているが，このような定常接着は離脱頻度が1/s以下の場合に生じることを明らかにした．またレセプタとしてICAM-1が存在する場合，マラリア感染赤血球は回転運動をすることが知られているが，ICAM-1は結合に作用する力にほとんど依存しない結合特性を有することを明らかにした． また，開発した計算力学モデルをより一般的なカプセル懸濁液のレオロジー解析や白血球・腫瘍細胞の流動・接着の問題に応用した．マラリアと同様，白血球の接着は生体防御において，腫瘍細胞の接着はがん転移において重要な過程であり，古くから血管壁面の「Rolling」や定常接着が調べられてきた．我々はセレクチンを発現した毛細血管内の細胞挙動を計算し，毛細血管径が細胞径より小さくなると，細胞は管の中央を移動する「Bullet」挙動を示すことを明らかにした．このときリガンド‐レセプタ結合によって細胞の移動速度は著しく減少し，レセプタ密度が十分低い領域においても定常接着とみなせるような速度となることを示した．
- 日本学術振興会, 科学研究費助成事業, 挑戦的萌芽研究, 東北大学, 2014年04月01日 - 2016年03月31日計算力学による機能性ディスペプシアのメカニズムの解明胃壁の蠕動運動と胃内部の食物流動の関係を理解するため，胃内容物流動の計算力学モデルを開発した．計算力学モデルは，医用画像データから再構築した実形状モデル，蠕動運動のパラメトリックモデル，多相流モデルからなる．胃内部では時間平均的に幽門前庭部を中心とした再循環流れが生じており，蠕動の伝播速度が高くなると再循環流れが強くなるため食物はより効率よく撹拌される．また蠕動の発生周期が短くなると，一つの蠕動によって生じる撹拌の効率が低下することを明らかにした．
- 日本学術振興会, 科学研究費助成事業, 若手研究(A), 東北大学, 2012年04月01日 - 2015年03月31日計算生体力学による微小循環系の細胞の機能と環境の相互作用の解明微小循環における赤血球や白血球など細胞の流動および接着現象を計算機上に再現するため，細胞質・血漿の流体力学，細胞膜の固体力学，接着タンパクの結合を連立し，グラフィックスカードを用いて高速計算する手法を開発した．赤血球の大規模流動によって生じる赤血球の変形や見かけの粘度を定量化し，白血球やがん細胞の微小血管内の流動，血管壁上の回転運動および定常接着を解析した．
- 日本学術振興会, 科学研究費助成事業, 基盤研究(S), 東北大学, 2011年05月31日 - 2014年03月31日生体流れに関わる疾患の診断・治療・予防のための計算ナノバイオメカニクスの新展開平成25年度（平成25年4月1日～平成25年4月25日）の研究内容は，細胞スケールにおける生体力学および分子生物学の融合を目指したシミュレーション技術の開発であり，主な成果は以下のとおりである． (1) 平成24年度に開発した細胞の接着に関連するligand-receptor結合の計算力学モデルについて，これを格子ボルツマン法と有限要素法に基づく流体－膜連成計算手法へと導入し，血小板血栓形成，マラリア感染赤血球の血管内皮細胞上の回転運動，がん細胞の血管内皮細胞への接着を対象としたシミュレーション手法の開発に着手した． (2) 平成24年度にクライオ電子線トモグラフィー法を用いて解明した気管繊毛の三次元内部構造を考慮し，ダイニン分子の滑り運動に由来する個々の気管繊毛の運動と，これによって駆動される周囲の流れ場の連成シミュレーション手法の開発に着手した． (3) 平成24年度までに赤血球の希薄・準希薄懸濁液を対象として，境界要素法と有限要素法に基づく流体－膜連成計算手法を開発し，循環器のマクロスケールの解析で必要となる粒子応力テンソル，自己拡散テンソルを算出している．これを赤血球濃厚懸濁液へと拡張するため，細胞濃厚懸濁液を対象とした大規模GPUシミュレーション手法の開発に着手した． (4) 平成24年度に開発した実形状の胃に対する液体食物流動（食物攪拌）の計算力学モデルについて，これを相の異なる液体や固体運動を連成する手法へと改良し，様々な食物および胃液などの流動を解析するための計算力学モデルの開発に着手した．
- 日本学術振興会, 科学研究費助成事業, 基盤研究(B), 東京工業大学, 2011年04月01日 - 2014年03月31日ＧＰＵスパコンによる気液二相流と物体の相互作用の超大規模シミュレーション気液二相流は気液界面を含んだ複雑な流れのダイナミックスを象徴する流体現象であるが、その数値計算は負荷が大きいにもかかわらず並列化がし難いため、これまでの計算は空間解像度が不十分であった。演算性能の高いGPUを大量に搭載するスパコンを用い、新しいCLSVOF法による界面捕獲、圧力Poisson方程式を解くためのマルチグリッド前処理付BiCGSTAB法などのGPUに適した数値計算手法、複雑形状の物体に対して境界埋込み法を導入し、複数GPU計算での通信と計算をオーバーラップさせることにより、超大規模な気液二相流と物体の相互作用計算を可能にした。
- 日本学術振興会, 科学研究費助成事業, 若手研究(B), 東北大学, 2008年 - 2010年食塊攪拌の計算力学モデルによる胃の機能論の力学的再構成胃における食塊攪拌過程を,流体力学の移動境界問題として取り扱うための計算力学モデルを構築した.胃壁の蠕動運動および食塊-胃内ガスの自由表面を境界条件として与える.食塊の種類や量,および蠕動運動のパターンなどの生理学的条件をパラメータとした解析を行い,これらが攪拌効率や胃内部の応力場にどのように影響しているのかを明らかにした.
- 日本学術振興会, 科学研究費助成事業, 基盤研究(S), 東北大学, 2007年 - 2010年血液・循環器・消化器病の診断・治療・予防のための計算ナノバイオメカニクスの創成本研究では、生命現象の理解と各種疾病の病因の理解、診断手法の開発、治療技術創出のための計算バイオメカニクスを構築した。これにより、脳動脈瘤発生を予測する新しい血行力学指標を発見し、マラリア感染による微小循環障害や血小板血栓形成を解析する手法の開発に成功した。また、遊泳微生物モデルを開発し、腸内細菌フローラの動態の解析などへと展開した。
- 日本学術振興会, 科学研究費助成事業, 基盤研究(B), 東京工業大学, 2007年 - 2009年多モーメント手法による多目的CFDコアの開発次世代の流体解析(CFD)において、流体方程式を格子点上の値、線積分平均値、面積分、体積積分平均値を従属変数として解く多モーメント手法が高精度かつ安定な計算を行うために有効である。直交格子に適合細分化格子法を導入することで解像度制御を行い、保存形IDO法による圧縮性流体計算、非圧縮性流体計算、乱流計算、多相流計算などの様々な流体問題に適用できる高性能な計算コアを開発する。
- 日本学術振興会, 科学研究費助成事業, 若手研究(スタートアップ), 東北大学, 2006年 - 2007年消化管内容物輸送シミュレータによる消化器系疾患の病態生理研究消化管内ガス,食塊,消化液の混相流問題では,領域によって解像するべき流れのスケールが大きく異なる.例えば気相・液相の界面において適切な格子サイズを用いなければ,界面近傍の解が拡散的になる.さらに蠕動運動によって生じる胃壁の移動境界や将来的に導入する食塊の粒子成分の近傍などにおいても同様に,局所的に高解像度の格子が要求される.任意領域の格子解像度を局所的に変化させるAdaptive Mesh Refinement(AMR)法はこのための有望な解決法であるが,粗い格子と細かい格子の境界において流体変数の補間や非等間隔の離散化が必要となるため,2次精度までの手法しか報告されていなかった.Interpolated Differential Operator(IDO)法を適用し,3次元Navier-Stokes方程式に対して4次精度の定式化を行い,医用画像ベースの生体内流動問題に適用し,本手法によって高精度なマルチスケール解析が可能であることを確認した.AMR法を用いた場合,非圧縮性流体の半陰的解法に必要となる圧力のPoisson方程式の係数行列が著しく不規則になるため収束性が悪化する.IDO法の係数行列は非対称な疎行列であるが,従来の差分法と同様,Algebraic Multi-grid(AMG)法を適用することでこれを改善できることを確認した.胃内部の食塊流動問題へ適用するための界面追跡および捕獲法として,Constrained Interpolated Profile-Conservative Semi-Lagrangian3(CIP-CSL3)法およびTangent of Hyperbola for Interface Capturing(THINC)法をIDO法に適合させた,Semi-Lagrange法であるこれらの手法をEuler法として定式化し,記述が簡易になる一方で従来の方法と同等または優れた界面捕獲法となりえることを確認した.2次元の胃内部食塊流動問題に適用し,消化管内ガスの影響に関する基礎的知見を得た.
- 日本学術振興会, 科学研究費助成事業, 基盤研究(A), 東北大学, 2004年 - 2006年血栓の形成・崩壊・移動および塞栓とその成長による重要臓器梗塞の力学的メカニズム本研究では,生体力学に基づいた計算機シミュレーションとin vitro実験を駆使して,重要臓器梗塞の原因となる血栓の形成と崩壊,血栓の血流による移動,および塞栓とその成長といった一連のプロセスのマルチスケールな振る舞いを検討した.まず,ストークス動力学法や粒子法を用いた計算力学シミュレーションにより,血流下で生じる血小板凝集について,生物学的な因子と,血流による流体力学的な因子との関連を明らかとした.同時に,赤血球の変形挙動と見かけの血流抵抗との関連を示し,血球同士の相互作用が血流特性を決定付ける因子であることを明らかとした.また,異なる種類の血球間における力学的および生物学的な相互作用が血栓形成過程を決定することを示した.さらに,マイクロPIV装置を用いて,生体外で微小流路内の血流を定量的に計測する手法を確立した.同装置により,ヘマトクリット値に応じた血流速度の時空間的な揺らぎが計測され,血球の力学的な相互作用が微小循環における血流特性を支配することが示された.一方,地球シミュレーターを援用して,赤血球流動の大規模な計算力学シミュレーションモデルを提案し,血球(μm)から大血管(cm)のスケールに至る血流特性を説明する数理モデルを確立した.左心室と大動脈の統合モデルを開発し,血栓形成に大きな影響を与える血流の渦構造やよどみ点を詳細に評価する上で,同モデルを用いたシミュレーションが実用的な手段として有用であることを確認した.
- 日本学術振興会, 科学研究費助成事業, 特定領域研究, 東北大学, 2003年 - 2006年心臓および脳血管病の発症と進展メカニズムの解明血管におけるマルチスケール/マルチフィジックスの生体力学現象を統合する計算力学アプローチにより,ヒト循環系内の複雑な流れの中の特殊な部位において粥状動脈硬化や動脈瘤が発症・進展し,生命に重篤な危機を及ぼす心筋梗塞や脳卒中,動脈瘤破裂を引き起こすメカニズムを解明するため、医用画像から心臓血管系の形態を抽出してモデル化するソフトウエアを開発し、これに基づき、実形状の血管系について流体力学的計算解析を行うことを目的として研究を実施した。このため、収縮・弛緩する左心室と大動脈および主要分枝のリアリスティックモデルを開発し、その内部の流れを可視化した。また、血管壁・血球などの有形の構造・成分と、血漿などの流体成分の力学的相互作用を解析するために、各種の粒子法による離散的方法を開発し、ミクロレベルにおける流体・固体相互作用を解析した。さらに、質点・バネモデルなどにより成長現象を組み込んだ血管壁モデルと、血流計算を連成することにより、動脈瘤などの発生過程をモデルした。これらから得られる複雑形状の動脈瘤モデルについて、内部の流れとATPなど低分子物質の輸送現象を連成解析した。 この結果、心臓内の流れの乱れや、旋回流、さらに弁口の形状による複雑な流れの影響は、大動脈弓の頂上付近で、ほとんど消失するので、我々が提案している部分的モデリングの技法が有効であることが示された。また、血小板血栓(一次血栓)の形成におけるvWF(von Willebrand Factor)および血小板と血管壁に存在するGP(糖タンパク)レセプタの力学的性質による血小板血栓の形成過程の変化を明らかにした。また、脳動脈瘤の形成における、血管壁の脆弱化の影響を血流との関係で見積もることが可能となり、さらに、これに関与する物質輸送の意義が明らかになった。
研究シーズ
■ 研究シーズ- 細胞・組織・臓器の計算生体流体力学シーズカテゴリ：ライフサイエンス, ものづくり技術（機械・電気電子・化学工業）, 自然科学一般研究キーワード：バイオメカニクス, 計算力学, コンピュータシミュレーション研究内容：血液の流れや食物の消化など生体の機能は生体内で生じる流れと密接に関係しており、流れの変化が病気の原因であることも少なくありません。しかしながら、生体内の流れを実験的に観察することは困難です。我々は、生命現象を力学法則に基づいて数理モデル化し、コンピュータシミュレーションによって、生体の機能や病気のメカニズムを解明することに挑戦しています。
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