基于有限元方法的心脏除颤仿真研究

临床动物电击除颤实验无法精确测量放电电场在心脏上的实际分布情况,且存在诸多不便利和不安全因素.鉴于此,提出了一种基于心脏建模及有限元求解的心脏除颤电场分布仿真研究方法,心脏模型包含了完整的心房心室解剖结构和左右心腔,考虑了心肌细胞和血液的电阻率,然后采用有限元方法进行分析,并使用Abaqus集成环境进行求解,求解结果与文献报道的参考标准进行对比.仿真结果在除颤电压阈值和能量阈值方面与目前的植入式心脏复律除颤器( ICD)的临床应用效果具有相当的吻合度,能量阈值相对误差仅为10％,验证了所提出方法的可行性.     

三维心电场仿真模型及计算机仿真Ⅲ——心脏模型在仿真心肌异常中的应用

本文利用作者构造完成的三维心电场仿真模型,研究了它在心肌异常仿真中的应用,其中包括束支传导阻滞、心肌缺血等,仿真结果与临床实测良好一致。     

三维心电场仿真模型及计算机仿真——Ⅰ心电场仿真模型的理论基础

心电场计算机仿真是心理论研究的重要手段,也是心电理论研究的前沿课题之一。本文介绍了我们新近在IBM PC机上开发完成的心电仿真模型,其各项指标均达到了国外同类模型的水平,它能完成以往在大型机上实现的仿真模型所能完成的研究工作。     

心肌细胞电脉冲作用下电场分布仿真结果与分析

目的 细胞电脉冲刺激仿真是研究心脏电脉冲消融的一种仿真方式，本文建立椭球形细胞电脉冲刺激仿真模型，模拟心肌细胞受到电脉冲刺激下的情况，研究电场入射方向和细胞长度对其电场分布和跨膜电位的影响。方法 通过COMSOL5.5软件进行仿真，以球形细胞模型为基础，在边长60μm的立方体空间中建立椭球形细胞模型。于垂直于Z轴的两面施加2.4 V电压，用以模拟心肌细胞在外加匀强电场作用下的电压分布情况。改变脉冲电场与细胞长轴的夹角，研究0°、30°、60°、90°的不同电场入射角度对心肌细胞电压分布和跨膜电位的影响。保持入射角为0，研究跨膜电位最大值与细胞长轴直径的关系。结果 对于椭球形的心肌细胞，电场的入射角从0°增大到90°时，跨膜电位从1.068 V减小至0.373 V，同时最大跨膜电位的位置也发生改变。入射角为0°时，跨膜电位最大值V与细胞长轴直径D的线性回归方程为V=81.191 6+38.607 9D,r²=0.998 1。结论 电场入射角越大，细胞跨膜电位越低；细胞长轴直径越长，跨膜电位最大值越大。该研究对后续心肌细胞电脉冲刺激实验及心脏电脉冲消融的临床试验具有参...     

基于动态心脏模型的体表心电图仿真研究

以往的电生理心脏模型大多是静态的,而非动态模型.这样在用准静电场理论求解体表电位时,整个心动周期中等效心电偶极子（源点）与体表（场点）之间的距离假设为恒定不变,从而会引入较大的系统误差.因此,为了更准确仿真心电图,有必要采用动态或跳动的心脏模型.基于原来静态心脏模型,构造了一个动态心脏模型,并对体表12导联心电图进行仿真比较研究.在动态心脏模型中考虑了心肌电兴奋引起的心脏机械力学收缩,通过计算心动周期中心室壁的位移,从而将心脏与体表之间的相对距离变化考虑进体表电位计算过程.仿真结果表明,对于正常心电图,基于动态心脏模型的仿真结果比基于静态心脏模型的仿真结果更符合临床记录心电图,特别是V1-V6胸导联的ST段和T波.对于前壁轻微缺血情况,在动态心脏模型的仿真心电图中能明显看出ST段和T波的变化,而在静态心脏模型的仿真心电图中与正常心电图相比看不出什么变化.本研究的仿真研究证实了动态心脏模型的确能更准确地仿真体表心电图.     

三维心电场的有限元仿真方法—心电场仿真三维模型的理论基础

心电场仿真是心电的前没课题。本文提出了心电场耗散能量的数学模型及有限元求解方程揭示 场活动规律。     

Kubicek每搏心输出量计算公式的三维有限元仿真研究

我们从 Kubicek模型三维有限元仿真的角度对 Kubicek每搏心输出量计算公式的临床应用价值进行了研究。在计算机仿真研究中 ,我们对比了模型仿真结果、具体采用 Kubicek每搏心输出量计算公式所得结果以及所设模型的理论计算结果。仿真结果表明 :模型中阻抗改变与主动脉中血液容积改变之间存在着近似的线性关系 ,证明了 Kubicek每搏心输出量计算公式具有一定的临床应用价值 ,同时也为心阻抗血流图基础理论提供了新的研究途径。     

Kubicek每博心输出量计算公式的三维有限元仿真研究

我们从Kubicek模型三维有限元仿真的角度对Kubicek每搏心输出量计算公式的临床应用价值进行了研究。在计算机仿真研究中，我们对比了模型仿真结果、具体采用Kubicek每搏心输出量计算公式所得结果以及所设模型的理论计算结果。仿真结果表明：模型中阻抗改变与主动脉中血液容积改变之间存在着近拟的线性关系，证明了Kubicek每搏心输出量计算公式具有一定的临床应用价值，同时也为心阻抗血流图基础理论提供了新的研究途径。     

三维心电场的有限元仿真方法─—心电场仿真三维模型的理论基础

心电场仿真是心电理论的前沿课题，本文提出心电场耗散能量的数学模型及有限元求解方程，揭示心电场活动规律．     

三维心电场仿真模型及计算机仿真——Ⅱ.模型的实现原理及仿真结果

本文讨论了利用心电模型仿真心脏兴奋传播过程的方法,并给出了正常心脏的仿真结果。     

人体步行运动的关节力学研究

利用角度传感器和步态测力板,本文观察了人体的步行运动,采用Fourier数字滤波拟合出各关节的运动规律,依据多刚体动力变分原理建立了适合作实时计算和模型修改的人体步行动力学方程。对于步行中双脚着地时出现的闭环结构,作者借助测力板测出的脚底反力曲线,提出了由力——位移组成的混合求解法。用文中计算方法编制的软件可用于人体下肢疾病的临床医学诊断。     

复合树脂耐磨耗性能的研究—20种复合树脂耐磨耗性能的评价和比较

本研究测试了十九种商品复合树脂(包括大填料、微细填料和混合型填料以及嵌体材料等四种类型)和一种本研究室研制的试验性复合树脂的耐磨耗性能。磨耗性能测试采用本研究室开发的、以橡胶板为对磨偶件的三体磨耗试验机。对磨耗表面的显微结构进行了扫描电镜观察。本研究的目的在于通过对各种类型的复合树脂的体积磨耗量及其磨耗表面微观结构的对比分析,去寻找、发现影响复合树脂耐磨性能的各种因素。实验结果表明,嵌体材料具有较高的耐磨耗性能。而含有相同填料类型的产品,其磨耗性能有很大差异(体积磨耗量可以相差3—4倍)。耐磨耗性能与填料类型之间无明显相关性。本研究将对如何提高复合树脂耐磨性能提供一些有价值的信息。     

一种非线性呼吸力学模型及其参数估计

本文报道了一个非线性呼吸力学模型,该模型可以反映深呼吸过程中呼吸气体流率、跨肺压力及肺容积变化之间的动态关系。模型参数分别反映气道阻力状态及肺弹性特性。敏感度分析表明,该模型肺弹性参数估计值的准确度高于气道阻力。实验测定了10名被试者的呼吸气体流率、食道压力及肺容积。参数估计结果表明,动、静态肺弹性参数之间存在显著差异(P<0.01)。我们认为肺组织及肺泡表面活性物质的应力松驰机制是造成这种差异的主要原因。     

一种新型人工机械心瓣——双叶翼型瓣的开发研究

本文着重从仿生医学和血流动力学研究方面,论述了由成都科技大学及华西医科大学共同研制开发并已投入临床试用的一种新型人工机械心瓣——双叶翼型瓣。 该瓣具有两个叶片,这些叶片具有基于有铰薄翼理论设计的翼型瓣叶形状。该瓣是中心流道型,具有良好的功能仿生性及血流动力学性能。特别是,它的翼型形状,具有独特的早期关闭性能。该瓣使用了具有良好生物相容性的热解碳及类金刚石膜材料,耐久性及可靠性好,对人体没有危害。 综合分析以及实验和临床初步结果均显示出该瓣具有良好的应用前景。     

Eosinophil chemotactic factor release from neutrophils induced by stimulation with Schistosoma japonicum eggs

 The neutrophil is one of the sources of eosinophil chemotactic factor (ECF) in the presence of some stimulants. In the present study we showed that guinea-pig neutrophils could release ECF upon stimulation with Schistosoma japonicum eggs. ECF release from neutrophils began as early as 5 min after the stimulation and reached a peak at 20 min. When homogenate of the eggs was separated into a water-soluble fraction as soluble egg antigen (SEA) and a water-insoluble fraction (eggshell), both preparations possessed a potent neutrophil-stimulating activity to release ECF. The ECF release was dependent on the concentration of eggshells or SEA or on the number of neutrophils. The neutrophil-stimulating activity of eggshells was stable to heat, HCl, or pronase treatment but sensitive to NaOH treatment. When the eggs or eggshells were washed with acetone or Tween-20, they lost the neutrophil-stimulating activity to release ECF, indicating that the neutrophil-stimulating factor (NSF) possesses a lipid nature. The molecular weight of NSF extracted from the eggshells was estimated to be about 1000 Da by gel chromatography on Sephadex G25. The possible role of eggshells in the formation of eosinophil-rich granulomatous lesions in schistosomiasis japonica is discussed. Received: 13 May 1996 / Accepted: 25 July 1996     

人甲襞毛细血管的流体力学研究

本文应用流体力学模拟实验的方法研究了甲襞微循环中输入枝→袢顶→输出枝的流动规律。结果表明:①正常管袢沿流线方向压力和速度的变化较为平稳。异常管袢中当管径改变时压力曲线出现明显的拐点。速度分布较为复杂:当输入枝管径变细时,袢顶的流速最快,而输出枝变细时,袢顶的流速低于其下游的流速。②同一截面上的压力和速度以靠近管壁缘的变化稍大一些,轴心处较为平稳,在流线方向改变时外缘的变化较内缘更为剧烈。③短路枝开通后压力和速度曲线较开通前要平滑得多,被短路的管袢中压力略有增加,速度略有降低。④甲襞管袢内的压力和速度的分布主要受管径改变的影响,而对管袢形状、构型的改变并不敏感。     

Subcellular localization of the eosinophil chemotactic factor (ECF) and its inactivator in human polymorphonuclear leucocytes (PMN).

An eosinophil chemotactic factor (ECF) of low MW can be released from human polymorphonuclear leucocytes (PMN) on stimulation with the Ca-ionophore, arachidonic acid and during phagocytosis. After a rapid rise of ECF activity in the supernatant a steep fall of in its activity occurred at the later times of secretion suggesting a mechanism of ECF inactivation. ECF obtained at the later times of secretion represents a stable biological activity and does not decrease on further incubation. In addition, intact PMN and ECF combined do not lead to its inactivation, while incubation of homogenized PMN with ECF decreased its activity. These data suggest the presence of an inactivator for ECF within human PMN. The purpose of the study was to localize ECF and its inactivator within human PMN. After cell disruption, differential and equilibrium gradient centrifugation, subcellular components of human PMN can be obtained which reveal eosinophilotactic (ECF) or ECF-inactivating activity. ECF activity can be recovered (in a structurally bound state) from the microsomal fraction of unstimulated and stimulated PMNs, while another portion is obtainable as a soluble, low mol. wt ECF. The PMN-derived ECF inactivator can be recovered from the peroxidase positive (azurophilic) granules and has a mol. wt of 60,000 and less. We suggest that low mol. wt ECF is derived from the plasma membrane of PMN which can be inactivated by components of the azurophilic granules. The mechanism of inactivation is still unresolved.     

小鼠表皮细胞生长因子放射免疫分析的建立及初步应用

目的:建立高特异性和高灵敏度的小鼠表皮细胞生长因子(EGF)放射免疫分析,用于测定小鼠和大鼠血清中EGF水平.方法:用人工重组的小鼠EGF多次免疫兔子获取高效价、高特异的小鼠EGF抗体.用氯氨T法制备<'125>I标记的EGF,经Sephadex G-25纯化.抗原抗体反应采用平衡一步法,4℃温浴24h后经PR试剂分离...     

Extravascular lung water and peripheral volume status in hemodialysis patients with and without a history of heart failure

Determining volume status in hemodialysis patients with a history of congestive heart failure (CHF) is difficult. Extravascular lung water (EVLW) may be derived from blood ultrasound velocity changes following injections of 0.9% and 5% saline. Bioimpedance spectroscopy can measure total body water (TBW) and its intracellular fluid (ICF) and extracellular fluid (ECF) compartments. We studied 29 clinically euvolemic hemodialysis patients, 12 of whom had a history of CHF. The ECF and ICF were measured before dialysis, and EVLW was measured during dialysis. Values of EVLW were similar between patients without CHF and those with CHF (3.55 ml/kg +/- 0.94 SD versus 3.88 ml/kg +/- 0.82 SD, respectively; p = NS). The ECF/ICF ratio was higher among patients with a history of CHF (1.27 +/- 0.29) than among those without such a history (1.04 +/- 0.04; p < 0.05), indicating that ECF volume overload was present in both groups, but was higher in those with a CHF history. There was a positive correlation between EVLW and ECF/ICF ratios (r = 0.54, p < 0.01). Measurements of EVLW were higher in two pulmonary edema patients ((7.95 ml/kg and 5.95 ml/kg; p < 0.05). The results of this study suggest that 1) hemodialysis patients with a history of CHF have more ECF volume overloaded than those without such a history; 2) the degree of ECF expansion is associated with increasing EVLW volume, even in patients without pulmonary edema; and 3) ECF volume expansion eventually exceeds limits and pulmonary edema occurs. These developing technologies of volume measurement may be of value in this challenging clinical area.     

Generation and secretion of eosinophilotactic activity from human polymorphonuclear neutrophils by various mechanisms of cell activation.

An eosinophil chemotactic factor(s) (ECF) can be generated from human polymorphonuclear neutrophils by the calcium ionophore, phagocytosis, arachidonic acid and hypotonic lysis. In kinetic studies it is observed that peak ECF activity is released prior to the maximum of lysosomal enzyme release with the calcium ionophore, phagocytosis and arachidonic acid, while under conditions of hypotonic exposure ECF activity appears after the maximum of enzyme release. The ECF obtained by hypotonic exposure shows a fluctuating pattern with sharp peaks and steep fall-offs in activity. The ECF-release for each stimulus is temperature dependent; extracellular calcium is required when the ionophore or phagocytosis are used as stimuli, while with arachidonic acid and hypotonic exposure no extracellular calcium is necessary for ECF-release. On Sephadex G-25 each preparation of ECF eluted in the low molecular weight range at approximately 500 daltons. Eosinophils can be deactivated and cross-deactivated with the various ECF-preparations indicating either a molecular identity or a common mode of action on eosinophils.