失重后血量减少致立位应激时心血管反应改变的仿真研究

我们将计算机仿真的实验方法引入重力重力生理学研究领域。以Melchior（1994)工作为基础，建立一个仿真立位应激（下体负压）时心血管反应的数学模型，模型包括血液重新分配、左室充盈、左室工作、外周循环、心率调节调节、外周阻力调节、静脉紧张程度调节等七个模型。然后仿真人体在下体负压时血压和心率变化，结果与同步进行的人体下体负压实验结果吻合。基于此模型，仿真研究了血量减少对立位应激时血压、心率和休克指数的影响。结果表明，超过总血量15%的血量减少将导致立位应激时心血管反应的明显改变；但是当血容量减少低于总血量的5%条件下，心血管系统可以通过压力反射调节作用维持LBNP时正常的HR和BP。本结果证明血量减少是失重后人体立位耐力不良的主要因素之一。     

人体脉搏线性传播特性的仿真研究

人体脉搏的传播特性与心血管系统中相关力学参数的变化密切相关。本文根据弹性管近端与远端血压理论和心搏出量理论,利用软件开展传播特性的仿真研究。首先给定弹性管近端的脉搏压力波数组以及相关参数和周期、时间延迟,然后仿真得出弹性管远端的脉搏波的波形图及相关参数,并由此计算得到相应的心搏出量数值。最后通过图形表达出心搏出量与各个参数的关系。通过数值仿真,讨论理论计算与实验结果的区别。     

人体乳腺组织电阻抗特性的研究

以人体乳腺组织电阻抗特性为依据的乳腺电阻抗扫描成像技术的出现,为乳腺癌的早期检查与辅助诊断开辟了一个新的方向。人体乳腺组织的电阻抗特性反映了乳腺组织的病理生理状态,而对它的测量成为乳腺电阻抗扫描成像技术的前提和基础。主要讨论了人体乳腺组织电阻抗特性的测量方法、测量结果以及存在的问题,对乳腺电阻抗成像技术的应用前景进行了展望。     

磁刺激人体可兴奋组织的建模及其感应电场的三维分析

磁刺激是利用时变电流流入线圈,产生时变磁场,从而在组织内感应出电流使某些可兴奋性组织产生兴奋的一种无创的诊断和治疗技术.本文建立了磁刺激可兴奋性组织的一般模型.确定了一些无量纲参数,对感应电场的分布函数进行无量纲化,并给出了电场强度三维分布的计算机仿真.文中分析和讨论了决定刺激聚焦和刺激深度的因素,确定了设计合理的磁刺激线圈和可以使刺激效果和磁刺激装置都得到优化的依据.     

基于虚拟人体的培训型医学超声成像仿真系统

通过对人体器官超声特征的数学建模和软件设计,实现对医学超声成像过程的仿真,在此基础上研发可用于相关医务人员职业技能培训的医学超声成像仿真系统.此系统可以避开只有在真实患者身上进行试验才能缓慢提高技能这一常规,以达到降低培训成本、缩短培训周期的目的.     

胶囊内窥镜无线能量传输系统的人体安全性研究

采用电磁感应方式为体内胶囊内窥镜供能时,人体必然暴露于发射线圈产生的强电磁场中.本研究采用数值计算的方法,在包含62种人体组织、分辨率为0.33 mm×0.33 mm×2 mm的三维真实人体仿真模型上求解人体不同组织在该电磁场中的感应电流密度和比吸收率,并根据国际非电离辐射防护委员会安全性标准对其进行安全性评估.结果表明,发射功率为25 W,谐振频率为266.5 kHz的能量传输系统产生的电磁场对人体是安全的.本研究为无线能量传输系统奠定了生物安全性基础.     

基于音圈电机振荡源的阻抗测量系统辨识精度评估的研究

基于强迫振荡技术(forced oscillation technology,FOT)的肺功能检查对早期发现气道疾病具有重要意义,但如何提高及评估阻抗测量系统的辨识精度仍是当前难点。针对此问题,本研究以音圈电机为振荡源构建阻抗测量系统,通过对3D打印的气道模型进行阻抗测量,分析了阻抗与支气管堵塞程度的敏感性和分布关系。结果表明,基于音圈电机的阻抗测量系统能够检测到气道模型两个以上小孔径(0.8 cm)截面积堵塞的阻抗变化,并且阻抗与堵塞端口数量近似呈指数分布关系。本研究采用气道模型来量化评估了阻抗测量系统的辨识精度,推进了FOT技术在气道阻塞程度和阻塞部位评估的研究。     

基于微流控芯片的气压驱动进样系统的特性研究

为了精准控制微流控芯片的分选进样速度,本研究设计了一种气压控制的进样系统.通过PID闭环控制,实现了对缓冲溶液瓶中气体容腔的精准压力控制,将样液以平稳的流量推送入微流控芯片中.采用Matlab软件中的Simulink建立数学模型对进样系统仿真,获得了在不同流量信号输入时,微流道中液体流量的动态响应特性.通过对比实验,仿...     

一维心肌缺血组织中折返发生机制的计算机仿真研究

尖端扭转型（Torsades de Pointes．TdP）室性心动过速是一种严重的心律失常。心肌缺血是诱发TdP的主要原因之一。我们借助计算机仿真技术，利用Noble98心室肌动作电位动力学模型，在一维匀质心肌组织上，定量研究缺血易导致心律失常的机制。首先通过独立减小Na^＋电导、提高细胞外K^＋浓度或减小细胞间缝隙偶联电导构建了缺血时组织兴奋性降低、细胞外K^＋蓄积或偶联减弱的模型，分别研究了各种情况对生理特性的影响。之后将三种参数组合，建立不同程度缺血模型并对其进行了研究。仿真结果显示随缺血程度增大，传导速度明显减慢、动作电位时程明显缩短、易损窗宽度显著增大，极易导致单向传导阻滞，形成折返性心律失常。     

Selection of perturbation parameters for identification of the posture-control system

Postural perturbations are often used in experimental investigations of human balance and postural control. Treating the perturbation as the input and the resulting postural sway response as the output, an input/output model of the posture-control system can be identified. Selection of the perturbation parameters can have a substantial influence on the accuracy of the identification and on the interpretation of the results. Pertinent parameters include type of perturbation, waveform, power spectrum, bandwidth, amplitude and test duration. The selection of these parameters is discussed in the light of general requirements for persistent excitation, accurate identification, stationarity and subject safety. Experimental results are used to illustrate specific issues.     

篮球鞋对主动与被动落地时冲击力特征和肌肉活化的影响

目的探讨人体在主动和被动落地过程中,穿着篮球鞋对落地冲击力特征和下肢相关肌群活化程度的影响。方法选取具备强缓冲性能的篮球鞋作为测试用鞋,并辅以对照鞋。12名球类专项男运动员作为受试者,在翻板器上完成包括由低到高3种下落高度和2种下落方式(主动落地反跳和被动着地)在内的着地动作。利用测力台和肌电分析系统同步采集冲击力和下肢5块主要肌群的EMG信号。结果主动落地反跳时,穿着篮球鞋并没有对冲击力的振幅和频率以及下肢肌群的激活程度产生影响;但被动着地时,穿着篮球鞋却能够显著降低冲击力和负载率的峰值,减小冲击频率(P<0.05),同时显著降低下肢各主要肌群的后激活程度(P<0.05)。结论在主动控制完成动作的情况下,运动鞋影响冲击力和肌肉活化的效果并不明显;然而当人体未完全控制着地状态时,篮球鞋能够改变输入于下肢的冲击力信号,达到缓冲避震并适当减小肌肉活化的效果,为避免落地时运动损伤的发生及机能节省化起到了积极的作用。     

Determination of rate-constants as a method to describe passive expiration

To describe the relaxed expiration by a two-compartment model, we introduced a gas/energy transfer between the lung compartment (V₁) and a second one (V₂). If V₂ were a real volume, the rate-constants (i.e. the flow/volume ratios) of the compartments would describe a real gas-exchange. Alternatively, if a viscoelastic behaviour of the lung or an energy-exchange between compartments was simulated, V₂ would become a "pseudo-volume". We studied nine mechanically ventilated subjects. Changes in volume were transduced by respiratory inductive plethysmography. The rate-constants were assumed (together with the initial volumes of the compartments) as parameters to fit the total volume [V₁(t)+V₂(t)]. Once the best fitting was performed using these "physiological" parameters, the system was directly identified and the compartments were independently analysed. The time profile of the second compartment showed a maximum that depended on the value of the rate-constants. Appropriate tests confirmed the reliability of our procedure. In conclusion, our analysis demonstrated that the energy/volume of the second compartment may increase at the beginning of expiration and then decrease, showing a maximum, even though the total curve can only be a decreasing one. In other words, the slowing down of the curve representing expiratory volume is due not only to the longer emptying of the second compartment, but also to the interaction between the two compartments. As presently proposed, this interaction can be represented by either a gas exchange between two actual volumes, or a mechanical energy transfer between the lung and the tissue compartment.     

基于心电信号的身份识别方法研究进展

随着人们对信息安全和可靠性的要求日益提高,生物特征识别技术成为信息安全领域中一个重要的研究课题。近年来,由于传统生物特征识别技术正在遭遇伪造、仿制生物特征的挑战,使得基于心电信号的身份识别技术成为一个热门研究领域。自心电信号被作为新的生物特征用于身份识别以来,其研究方法从复杂到简单,本文对其发展史、研究现状以及应用进行了概括。通过心电信号识别个体的方法是可行的,且有其防伪性高的独特优势,但距在实际中广泛应用尚有一段距离。     

肠杆菌科DBI10E点滴生化鉴定系统的评价

目的本研究旨在评价作者研制的DBI10E生化鉴定系统用于临床肠杆菌科的可行性。方法以点滴生化分析为细菌鉴定方法,经过用聚类分析和信息熵分析优选生化项目,选择最新概率数据构建数据库,并采用计算机系统仿真方法进行验证,在数值化鉴定软件支持下运行。结果与API10S进行计算机仿真对照试验的统计表明,DBI10E提高了肠杆菌科细菌鉴定的总体符合率;与API20E进行标准菌株和临床菌株的对照检验后发现,DBI10E点滴生化试验快速、稳定、经济,鉴定到种的概率（％Id）平均提高了24．91个百分点,典型性指数（T值）平均提高了0．19。结论DBI10E为我国临床微生物检验提供了一种新的快速鉴定手段。     

基于心室动作电位的三维心肌组织模型算法研究

心肌电折返是引起心律失常的重要因素之一,它会导致心动过速(VT)乃至室颤(VF)的发生,从而引起心源性猝死。随着计算机仿真在定量电生理研究中的广泛应用,迫切需要建立三维心肌组织实验平台。本文就这种组织模型的数值解方法进行了研究。文中利用Luo-Rudy 1991心室肌细胞模型结合扩散方程形成三维组织模型,利用算子分裂法求其数值解。分别采用ADI格式和七点差分格式求解描述电扩布的偏微分方程,边界条件采用二阶精度的离散格式。实验结果表明,以上两种格式均可成功地解算出细胞膜电位的变化以及电兴奋的活动,且具有良好的稳定性。但ADI格式可较大幅度地缩短计算时间。因此ADI格式下增加时间步长以提高计算效率的方法更具优势。     

Comparison of four methods for rapid identification of Staphylococcus aureus directly from BACTEC 9240 blood culture system

Purpose: Differentiation of Staphylococcus aureus (S. aureus) from coagulase-negative staphylococci is very important in blood stream infections. Identification of S. aureus and coagulase-negative staphylococci (CoNS) from blood cultures takes generally 18–24 h after positive signaling on continuously monitored automated blood culture system. In this study, we evaluated the performance of tube coagulase test (TCT), slide agglutination test (Dry Spot Staphytect Plus), conventional polymerase chain reaction (PCR) and LightCycler Staphylococcus MGrade kit directly from blood culture bottles to achieve rapid identification of S. aureus by using the BACTEC 9240 blood culture system. Materials and Methods: A total of 129 BACTEC 9240 bottles growing gram-positive cocci suggesting Staphylococci were tested directly from blood culture broths (BCBs) with TCT, Dry Spot Staphytect Plus, conventional PCR and LightCycler Staphylococcus MGrade kit for rapid identification of S. aureus. Results: The sensitivities of the tests were 99, 68, 99 and 100%, respectively. Conclusion: Our results suggested that 2 h TCT was found to be simple and inexpensive method for the rapid identification of S. aureus directly from positive blood cultures.     

Impulse response model in reconstruction of insulin secretion by deconvolution: Role of input design in the identification experiment

Insulin secretion rate (ISR)in vivo can be reconstructed by deconvolution of plasma concentration of C-peptide (CP), a peptide co-secreted with insulin but not extracted by the liver and exhibiting linear kinetics. Deconvolution requires the knowledge of the CP impulse response. A two exponential model is usually chosen to describe the CP impulse response but three exponential and one exponential models have also been used. The purpose of this paper is to investigate the role of the CP impulse response model order in reconstructing ISR by deconvolution in three standard physiological/clinical situations: ultradian oscillations, rapid pulses, and biphasic response to a glucose stimulus. By resorting to simulation, we first show that, in each situation, the validity of impulse response models with different orders depends on the input chosen in the impulse response identification experiment. Real data are then used which support the simulation results.     

What methods and process flow can assist in alloantibody identification

When a positive antibody screen is encountered there are many pathways that can be followed for antibody identification and every laboratory should have a policy outlining its standard procedures. It is important that a systematic approach is taken, both to assigning a specificity (ies) and to excluding all clinically significant antibodies that the patient is capable of making. Several reagent red cell panels may be needed to identify some combinations of antibodies. It is useful to know the ethnic background of the patient because some combinations of phenotypes are found almost exclusively in certain populations. Identification of alloantibody specificity is a process undertaken to enable informed decisions to be made regarding suitable blood for transfusion to a patient. It is important to realize that not all antibodies are clinically significant and antigen-negative blood is not always needed. When complex mixtures or antibodies to high incidence antigens are present, resolution can be difficult and time-consuming, thus causing a delay in patient care.