基于小波变换的R波奇异性分析的研究

奇异性是生物信号的基本特征。依据小波变换模在多尺度上的变化特征,研究了信号奇异性分析的基本定理,在此基础上提出了奇异度Lipschitz指数的估计算法,并将之用于心电图(ECG)的R波奇异性分析。研究发现,随机选取的10名健康受试者与10名心律不齐患者的ECG的R波的奇异性存在显著的差异,健康受试者的奇异性结果显著高于心律不齐的患者。     

Global exponential stability of interval general BAM neural networks with reaction-diffusion terms and multiple time-varying delays

In this paper, we first discuss the existence and uniqueness of the equilibrium point of interval general BAM neural networks with reaction-diffusion terms and multiple time-varying delays by means of using degree theory. Then by applying the existence result of an equilibrium point and constructing a Lyapunov functional, we discuss global exponential stability for above neural networks. In the last section, we also give an example to demonstrate the validity of our global exponential stability result for above neural network.     

车前子不同炮制品抗大鼠膜性肾病的比较

目的:比较车前子生品和盐炙品水煎液抗大鼠膜性肾病的活性。方法:热回流法提取车前子不同炮制品;选用改良的Border法应用阳离子化牛血清白蛋白(C-BSA)建立大鼠膜性肾病模型,在给药的第6周末检测大鼠24 h尿蛋白定量(UTP)及血清总胆固醇(TC),甘油三酯(TG),总蛋白(TP),尿素氮(BUN),肌酐(SCr)水平;采用电镜和光镜观察肾脏病理形态学变化,免疫组化法检测各组大鼠肾组织肿瘤坏死因子(TNF)-α,白细胞介素(IL)-1β,转化生长因子(TGF)-β1,核转录因子-κB(NF-κB)p65的表达情况。结果:与空白组比较,模型组大鼠的尿蛋白、肾指数、血清生化指标、肾脏免疫调节因子具有极显著差异(P0.01),肾脏病理形态变化明显;与模型组比较,贝那普利组、盐炙品3个剂量组和生品高剂量组均可显著降低模型大鼠尿蛋白、肾指数(P0.05,P0.01),使血清生化指标呈显著差异(P0.05,P0.01),病理形态结果显示,大鼠肾脏病变有明显的改善,4种细胞因子表达显著降低(P0.01,P0.05);与生品高剂量组比较,贝那普利组和盐炙品高、中剂量组尿蛋白量显著降低(P0.05,P0.01),贝那普利组和盐炙品高剂量组肾指数显著降低(P0.05),贝那普利组、盐炙品高、中剂量组血清中BUN,SCr,TC,TG的含量显著低于生品高剂量组(P0.05,P0.01),低剂量组仅BUN显著低于生品高剂量组(P0.05),贝那普利组、盐炙品高、中剂量组血清中TP显著升高(P0.05),贝那普利组对肾脏4种免疫调节因子的表达显著降低(P0.01),盐炙品3个剂量组中TNF-α,IL-1β的积分吸光度(IA)显著降低(P0.01),盐炙品高剂量组TGF-β1,NF-κB p65的IA表达显著低于生品高剂量组(P0.05,P0.01)。结论:车前子盐炙品对膜性肾病大鼠的肾保护作用和对肾脏中免疫调节因子的调节作用均优于生品,可继续深入车前子盐炙品的物质基础和药效机制研究。     

Nonlinear analyses of heart rate variability in normal and growth-restricted fetuses

BACKGROUND: Many studies on the physiology of the cardiovascular system reported that nonlinear chaotic dynamics may govern the generation of the heart rate signal. OBJECTIVE: To examine whether the heart rate dynamics of an intrauterine growth restricted (IUGR) fetus is different from a healthy normal fetus by nonlinear methods of time series analysis. DESIGN OF THE STUDY: One hundred nineteen fetal heart rate (FHR) recordings from healthy normal fetuses, and 69 recordings from IUGR fetuses were analyzed. Nonlinear analyses included attractor reconstruction, calculation of the largest Lyapunov exponents using the Wolf algorithm, and estimation of correlation dimension. The largest Lyapunov exponents from normal fetuses were checked by means of surrogate-data test. RESULTS: Abnormal FHR patterns of IUGR fetuses such as decreased variability and repetitive late decelerations presented a remarkably different structure in the reconstructed attractor. Surrogate data suggest that the FHR of healthy normal fetuses has unique nonlinear characteristics. The largest Lyapunov exponents were positive for all of 119 healthy normal fetuses, indicating that the FHR control system is sensitive to initial conditions. The values of IUGR fetuses were significantly lower than those of normal subjects. In normal fetuses, significant changes of correlation dimension according to gestational age were observed. In IUGR fetuses, however, such changes were not found. CONCLUSIONS: The heart rate dynamics of IUGR fetuses is less chaotic than that of normal fetuses. Decreased system complexity suggested by correlation dimension may limit the IUGR fetuses' ability to maintain cardiovascular integrity, and therefore, to adapt to the variety of internal and external cardiovascular stresses.     

空气消毒剂对流感病毒消毒效果检测

[目的 ]　探讨“空气消毒气雾剂”对流感病毒的消毒效果。 [方法 ]　用试管法和模拟现场喷雾试验检测“空气消毒气雾剂”对流感病毒的消毒效果。 [结果 ]　试管法对A/汉防 /3 5 9/95 (H3N2 )毒株感染力的灭活指数 >10 0 0 0 0 ,病毒灭活率 >99.999% ,模拟现场喷雾试验对鸡胚的感染力降低 76.9% ,χ2 =10 .42 ,P <0 .0 0 5。 [结论 ]　在实验室内“空气消毒气雾剂”对流感病毒的消毒效果显著     

分维的概念和应用

本文介绍了拓扑维数、拓扑指数、Ｈａｕｓｒｄｏｒｆｆ维、信息维、关联维的概念和它们在医学科研中的应用。提出了如何制作一个测量这些维数的分维测量器的办法，以便医务工作者对形态作定量研究时应用。     

利用Lyapunov指数提取心电动态生理及病理信息的研究

对心电信号的研究，一般都集中在对个别异常波形进行检测和识别从而判断心脏病变方面。而心电波形及其Ｒ－Ｒ间期序列的Ｌｙａｐｕｎｏｖ指数反映了心脏的总体动态特征。利用ＭＩＴ－ＢＩＨ数据库进行的初步研究表明：１）正常人、室性失常病人和束支传导阻滞病人的心电波形的Ｌｙａｐｕｎｏｖ指数有显著差别；２）正常人和室性失常病人的Ｒ－Ｒ间期序列的Ｌｙｓｐｕｎｏｖ指数有显著差别，正常人和束支传导阻滞病人的Ｒ－Ｒ间期序列的Ｌｙａｐｕｎｏｖ指数没有显著差别。值得指出的是，这一研究的前景在于，当心电信号中的异常波形还不足以被识别时，有可能利用Ｌｙａｐｕｎｏｖ指数进行早期诊断。     

Deterministic chaos and noise in three in vitro hippocampal models of epilepsy

Recent reports have suggested that chaos control techniques may be useful for electrically manipulating epileptiform bursting behavior in neuronal ensembles. Because the dynamics of spontaneous in vitro bursting had not been well determined previously, analysis of this behavior in the rat hippocampus was performed. Epileptiform bursting was induced in transverse rat hippocampal slices using three experimental methods. Slices were bathed in artificial cerebrospinal fluid containing: (1) elevated potassium ([K⁺]_o=10.5 mM), (2) zero magnesium, or (3) the GABA_A-receptor antagonists bicuculline (20 M) and picrotoxin (250 M). The existence of chaos and determinism was assessed using two different analytical techniques: unstable periodic orbit (UPO) analysis and a new technique for estimating Lyapunov exponents. Significance of these results was assessed by comparing the calculations for each experiment with corresponding randomized surrogate data. UPOs of multiple periods were highly prevalent in experiments from all three epilepsy models: 73% of all experiments contained at least one statistically significant period-1 or period-2 orbit. However, the expansion rate analysis did not provide any evidence of determinism in the data. This suggests that the system may be globally stochastic but contains local pockets of determinism. Thus, manipulation of bursting behavior using chaos control algorithms may yet hold promise for reverting or preventing epileptic seizures. © 2001 Biomedical Engineering Society. PAC01: 8719Nn, 8719Xx, 0545Gg, 8717Nn, 8719La     

Exponential stability and stabilization of positive T-S fuzzy delayed systems

The analysis of positive nonlinear delayed systems is of great importance for many real-world applications. Such systems' stability and stabilization assessment is still an open topic, and there is limited literature on this field. Moreover, further convergence conditions should be considered for many experimental processes, such as exponential stability analysis, which is highly important. Considering the above, we deal in this study with the problem of exponential stability and stabilization of nonlinear fuzzy positive systems with delay. We establish exponential stability criteria using Lyapunov–Krasovskii functional (LKF) and a delay bi-decomposition approach for bounded and time-varying delayed systems. The obtained results are then extended to the exponential stabilization case. The control law is designed using Parallel distributed compensation (PDC). The proposed approach, formulated in terms of linear matrix inequalities (LMIs), allows reducing the conservativeness of the delay-dependent conditions. A comparative study is presented to illustrate the superiority of our method. Moreover, simulation results for the two tanks process show the advantages of the proposed control design.     

The reliability of local dynamic stability in walking while texting and performing an arithmetical problem

In the recent years, local dynamic stability of walking was frequently used to quantify motor control. Particularly, dual-task paradigms are used to assess a shift in gait control strategy to test walking in real life situations. Texting short messages while walking is a common motor-cognitive dual task of daily living. To able to monitor possible intervention effects on motor-cognitive dual-task performance, the test-retest reliability of the measure has to be evaluated. Since the reliability of the effects of cognitive tasks including texting while walking on local dynamic gait stability has not been assessed yet, this will be evaluated in the current study. Eleven young individuals were included. Gait data was registered twice (test-retest interval: seven days) using an inertial sensor fixed on the subjects’ trunks in three conditions: normal walking, walking while texting a message and walking while reciting serials of 7. Short-term finite maximum Lyapunov Exponents were quantified to assess local dynamic stability. The test-retest reliability was calculated using intra-class correlation coefficients and Bland and Altman Plots (bias and limits of agreement). ICC values of the current study show that in normal walking and walking while texting, outcomes are comparable and indicate mostly good to excellent reliability. The reliability values were almost always the lowest in walking while reciting serials of 7. Local dynamic stability derived from kinematic data of walking while cell phone texting can be reliably collected and, in turn, be used as an outcome measure in clinical trials with repeated measures design.