锥形血管内血液脉动流的数值模拟

将锥形血管与人体血液的脉动流动联系起来研究发展中的血液流动问题 ,给出了锥形血管的几何模型、血液流动的理论模型、生理边界条件以及计算条件 ;根据人体生理脉动流条件 ,建立了血流平均速度函数 ,并就此对三维锥形血管内的血液脉动流动进行了数值模拟 ,获得心动周期不同时刻的轴向速度、径向速度、断面压力和轴向压力分布曲线。将数值模拟计算结果与实验和分析计算结果进行对照 ,讨论了锥形血管内血液脉动流的特点。     

流体剪应力对成骨细胞的作用研究

研究了生理范围内不同大小的流体剪切力对成骨细胞增殖分化和功能的影响,从细胞水平验证流体剪切力在骨组织力学适应性中发挥的重要作用.运用流室系统提供精确可控的流体剪切力,对原代培养的大鼠颅骨成骨细胞施以5、10、20、30 mN/cm2的剪切力刺激,分别在加载后的3、6、9、12、24、36 h采集样品,检测细胞周期分布,碱性磷酸酶活性,胞外钙质分泌的变化.5 mN/cm2和10 mN/cm2的剪应力促进细胞增殖,进一步增大会有抑制作用,而5、10和20 mN/cm2的剪应力对ALP活性和胞外钙分泌均有促进作用,并且与静态培养相比ALP活性高峰期提前,30 mN/cm2表现出抑制效应.结果显示成骨细胞的增殖、分化、矿化均能受到剪应力的调节,这种调节表现出对剪应力大小的依赖性.     

3D CFD Simulation of Pulsatile Blood Flow in the Human Aorta

INTRODUCTION　　The human aorta is the majorblood vessel of complex geometry including curva-tures in multiple planes,branches at the apex of the arch,significant tapering andwith distensible vessel wall ( as shown in Fig.1 ) . The blood flow structures in theaorta are very complex and attribute a lot to the development of atherosclerotic le-sions,which always occur in the vicinity of arterial branches,curvatures and bifur-cations〔1～ 5〕.In order to understand the complex nature of the …     

弱脉动血管内速度和温度分布特征的研究

运用Boussinesq近似,以直圆管作为血管模型,导出了在弱脉动条件下轴向速度和温度的径向分布.结果表明,温度波动的幅值与脉动频率成反比;当脉动频率增加时,速度和温度剧烈变化的部分将局限在接近管壁的薄层中.     

圆管狭窄下游湍流场流动分离区流体力学实验模型的设计和调试

研究旨在建立和调试体外圆管狭窄模型 ,使之能够配合粒子成像流速仪 (PIV)进行狭窄下游流动分离区速度、湍流切应力的检测和压力传感器的压力检测。采用粒子成像流速仪和压力传感器 ,对模型狭窄下游定常流湍流场速度、湍流切应力和压力进行定量检测 ,初步认识流动分离区速度、切应力和压力的分布特征。实验模型能够较好地配合 PIV和压力传感器进行流动分离区速度、湍流切应力和压力的定量检测 ;圆管狭窄下游流动分离区边壁局部存在明显的低速度、低压力和低切应力分布。     

Regional Blood Flow in the Left Ventricular Wall of Dogs with a Graded Coronary Artery Stenosis

Blood flow in the circumflex branch of the left coronary artery was recorded by electromagnetic flowmeter. In the area supplied by this branch vasodilatation was produced by progressive constriction until the diastolic reactive hyperemic response to 10 s occlusion disappeared (“optimum” stenosis). This degree of stenosis was accompanied by a 20% decrease in diastolic circumflex flow, while systolic flow remained unchanged. The distribution of blood flow in the left ventricular free wall was evaluated at “optimum” stenosis by counting activity in tissue blocks following bolus injection of Xe-133 into the aortic root. When Xe-133 was injected immediately after occlusion of the left anterior descending branch the Xe-133 concentration of the endocardial part of the area supplied by the circumflex branch was about half the concentration in the epicardial part. The concentrations in the two parts did not, however, differ significantly when occlusion of the left anterior descending branch was omitted. This indicates that the endocardial blood flow reserve is lower than the epicardial, and that, yet, a preferential fall in blood flow in the endocardial part of a post-stenotic area can be rapidly eliminated when blood supply from a neighbouring artery is available.     

Quantitative Assessment of Steady and Pulsatile Flow Fields in a Parallel Plate Flow Chamber

Steady and pulsatile flows were imaged and quantified in a parallel plate flow chamber that was designed to allow constant variation of the volumetric flow rate and to minimize pressure gradients across the width of the flow field. Results indicated that both the steady and pulsatile flow fields were uniform across the width of the flow chamber as shown by linear regression analysis. Further, the dynamic effects of the fluid pulse were transmitted almost instantaneously across the length of the flow field. These findings verify that parallel plate devices designed in this manner are suitable for delivering uniform steady and pulsatile shear stress to adherent cell populations in vitro. © 1999 Biomedical Engineering Society. PAC99: 8780-y, 4780+v, 8718-h     

Vortex Shedding in Steady Flow Through a Model of an Arterial Stenosis and Its Relevance to Mural Platelet Deposition

In this study, the development of unsteady vortical formations in the separated flow region distal to a stenosis throat is presented and compared with the platelet deposition measurements, to enhance our understanding of the mechanisms involved in platelet kinetics in flowing blood. Qualitative and quantitative flow visualization and numerical simulations were performed in a model of a streamlined axisymmetric stenosis with an area reduction of 84% at the throat of the stenosis. Measurements were performed at Reynolds numbers (Re), based on upstream diameter and average velocity, ranging from 300 to 1800. Both the digital particle image visualization method employed and the numerical simulations were able to capture the motion of the vortices through the separated flow region. Periodic shedding of vortices began at approximately Re=375 and continued for the full range of Re studied. The locales at which these vortices are initiated, their size, and their life span, were a function of Re. The numerical simulations of turbulent flow through the stenosis model entailed a detailed depiction of the process of vortex shedding in the separated flow region downstream of the stenosis. These flow patterns were used to elucidate the mechanisms involved in blood platelet kinetics and deposition in the area in and around an arterial stenosis. The unsteady flow development in the recirculation region is hypothesized as the mechanism for observed changes in the distribution of mural platelet deposition between Re=300, 900, and 1800, despite only a marginal variation in the size and shape of the recirculation zone under these flow conditions. © 1999 Biomedical Engineering Society. PAC99: 8719Uv, 8710+e     

一种简化的袖带测量模型及在收缩压测量中的应用研究

传统的波动法血压无创测量技术由于利用了统计学原理，因此必须造成测量时的个体误差。作者对袖带测量的物理进行了研究，根据已有的结论，提出了一种袖带测量过程的物理模型，根据这一模型提出了一种人体血压的无创测量方法，该方法不象传统方法那样采用统计学原理，从而避免了所有个体采用统一的血压判据而导致的个体测量误差，实际实验表明，该技术的测量准确性要优于传统的波动法测量技术，这对改善医学临床血压无创自动测量技术     

Effect of Stenosis Asymmetry on Blood Flow and Artery Compression: A Three-Dimensional Fluid-Structure Interaction Model

A nonlinear three-dimensional thick-wall model with fluid-structure interactions is introduced to simulate blood flow in carotid arteries with an asymmetric stenosis to quantify the effects of stenosis severity, eccentricity, and pressure conditions on blood flow and artery compression (compressive stress in the wall). Mechanical properties of the tube wall are measured using a thick-wall stenosis model made of polyvinyl alcohal hydrogel whose mechanical properties are close to that of carotid arteries. A hyperelastic Mooney–Rivlin model is used to implement the experimentally measured nonlinear elastic properties of the tube wall. A 36.5% pre-axial stretch is applied to make the simulation physiological. The Navier–Stokes equations in curvilinear form are used for the fluid model. Our results indicate that severe stenosis causes critical flow conditions, high tensile stress, and considerable compressive stress in the stenosis plaque which may be related to artery compression and plaque cap rupture. Stenosis asymmetry leads to higher artery compression, higher shear stress and a larger flow separation region. Computational results are verified by available experimental data. © 2003 Biomedical Engineering Society. PAC2003: 8719Uv, 8710+e     

Influence of Adipose Tissue Blood Flow on the Lipolytic Response to Circulating Noradrenaline at Normal and Reduced pH

Hypercapnic acidosis (pH 7.0) inhibits the lipolytic response of canine subcutaneous adipose tissue to i.v. infused noradrenaline (NA) by 80 per cent or more. The response to sympathetic nerve stimulation, on the other hand, is only reduced by 1040 per cent during acidosis. The fate of intravenously infused ³H-labelled NA (0.35 ug × kg^-1× min^-1 for 30 min) was not significantly altered by acidosis. The rate of disappearance of unmetabolized NA from the arterial plasma after an infusion was the same at pH 7.4 and 7.0 and the calculated increase in circulating NA during infusions was 4 ng/ml at both pH:s. I.v. infusion of Na increases adipose tissue blood flow, an effect which is attenuated by acidosis. There was a significant correlation (p< 0.001) between adipose tissue blood flow and the lipolytic response at normal pH. Preventing the NA-induced increase in blood flow by constant flow perfusion reduced the lipolytic response at normal pH. The degree of inhibition by acidosis of the lipolytic response to i.v. NA was significantly reduced (from 79 to 56 per cent, p < 0.05) when the adipose tissue was perfused at constant flow. These data suggest that adipose tissue blood flow is important in determining the lipolytic response to i.v. NA, probably by influencing the delivery of NA to the tissue. The marked inhibition by acidosis of lipolysis due to i.v. infused NA therefore appears to be the combined effect of a direct antilipolytic effect of acidosis and a decreased delivery of N A to the adipose tissue due to the attenuated blood flow response.     

微循环流速测量技术的发展与临床应用简况

微循环速流测量技术在基础医学研究和临床实践中正发挥着日益重要的作用。本文着重介绍微循环流速测量技术的国内外进展，包括显微电视系统法、激光多普勒和微光散斑技术，在掌握祥实资料的基础上，对这些微循环流速测量技术在临床实践中的应用发展情况也作了清晰简要的介绍。     

Comparison of a Simplified Whole Blood and Isolated Lymphocyte Stimulation Technique

Whole blood and isolated lymphocyte stimulation in healthy men were compared utilizing PHA, ConA, and PWM. Dose response curves with each of the 3 mitogens were found to differ with the two techniques of lymphocyte stimulation. When incubation time was lengthened PWM responses increased markedly in both the whole blood and isolated lymphocyte assays. Increased incubation time had no effect on PHA cultures and increased the responses with ConA in the whole blood method. In each study, responses with ³H-thymidine were comparable to responses utilizing ¹²⁵IUdR.     

手臂组织的简化力传递模型及其应用

为了探索一种有理论依据的无创定量测量血压的方法,本文从力学原理出发,提出了一个理想化的手臂活组织力传递模型,以便识别动脉壁内外侧压力平衡的特征信息,用动脉壁外侧压力 测量 脉内压力。通过模型在无创测量动脉血压中的初步应用,从理论和实践两方面探讨了该模型的实用价值。     

Comparison of a Simplified Whole Blood and Isolated Lymphocyte Stimulation Technique

Whole blood and isolated lymphocyte stimulation in healthy men were compared utilizing PHA, ConA, and PWM. Dose response curves with each of the 3 mitogens were found to differ with the two techniques of lymphocyte stimulation. When incubation time was lengthened PWM responses increased markedly in both the whole blood and isolated lymphocyte assays. Increased incubation time had no effect on PHA cultures and increased the responses with ConA in the whole blood method. In each study, responses with ³H-thymidine were comparable to responses utilizing ¹²⁵IUdR.     

Finite Element Modeling of Three-Dimensional Pulsatile Flow in the Abdominal Aorta: Relevance to Atherosclerosis

The infrarenal abdominal aorta is particularly prone to atherosclerotic plaque formation while the thoracic aorta is relatively resistant. Localized differences in hemodynamic conditions, including differences in velocity profiles, wall shear stress, and recirculation zones have been implicated in the differential localization of disease in the infrarenal aorta. A comprehensive computational framework was developed, utilizing a stabilized, time accurate, finite element method, to solve the equations governing blood flow in a model of a normal human abdominal aorta under simulated rest, pulsatile, flow conditions. Flow patterns and wall shear stress were computed. A recirculation zone was observed to form along the posterior wall of the infrarenal aorta. Low time-averaged wall shear stress and high shear stress temporal oscillations, as measured by an oscillatory shear index, were present in this location, along the posterior wall opposite the superior mesenteric artery and along the anterior wall between the superior and inferior mesenteric arteries. These regions were noted to coincide with a high probability-of-occurrence of sudanophilic lesions as reported by Cornhill et al. (Monogr. Atheroscler. 15:13--19, 1990). This numerical investigation provides detailed quantitative data on hemodynamic conditions in the abdominal aorta heretofore lacking in the study of the localization of atherosclerotic disease. © 1998 Biomedical Engineering Society. PAC98: 8745Hw, 0270Dh, 8710+e     

微循环容积脉搏血流信号的频率特性分析

本文利用微循环模型来研究容积脉搏血流的频率响应特性 ,从伯德图中找到影响模型频率响应的两个特征参数 ,即阻尼比 ξ和转角频率ωn。通过分析这两个特征参数的数值及其变化 ,可以确认出微循环的不同优劣状态。实验结果证实了模型分析结果。     

血压的多频率生物节律特性及其受内外因素作用变化的机制探讨

本文旨在探索生物节律的起源,内外因素对生物节律的影响机制。从新生儿到老人(共245人)着手,连续24小时以上检测其血压,其中68人被连续检测七日以上。采用Halberg等的余弦法对上述血压的时序数据作24,168小时为周期的余弦曲线拟合,所获得的振幅作相关和回归分析。还分别对24,168小时以上的时序数据作最佳拟合。其结果是近日节律的节律性随年龄增大而增强;近七日节律随年龄增大而减弱。在新生儿中,近日节律的最佳拟合周期很少有24小时,而其他年龄组几乎均在24小时,近七日节律,新生儿最佳拟合周期远离168小时,其他人非常接近168小时。结论是:近日节律和近七日节律是内源性的,但是它们不一定是24小时和168小时,在外界环境的刺激和影响下,内在节律与外环境节律发生整合,结果使内在节律调整得更接近于外环境节律。