神经元的慢动力学活动

近年来发现离子通道和突触的慢活动对突触响应和细胞放电以及网络行为有很大的影响 ,进而影响到大脑节律等等 ,成为研究的热点。增强兴奋性慢活动或减弱抑制性慢活动 ,都可使兴奋性突触后电位增大或延长 ,造成突触传递易化 ,引起神经元阵发和网络振荡 ,成为大脑正常和 /或异常节律性活动的基础 ,为进一步揭示大脑的认知和记忆功能以及某些疾病 (如癫 )的发病机制 ,提供了重要的线索。

基于慢速时变动力学的空间结构施工过程精细化分析方法研究

针对空间结构施工过程模拟问题,依据时变力学基本原理,提出了基于慢速时变动力学的动态施工过程精细化分析方法。该新方法通过设置与实际施工动态过程相一致的分析时长,引入惯性力和阻尼力,实现时变结构几何、物理及边界等因素间的动态耦联,以达到真正意义上的施工全过程精细化分析。由此给出了该方法的求解思路和实现流程。通过对复杂大跨斜交连廊结构的施工过程分析,并对比施工实测数据,结果表明:该方法的计算值与传统静力施工过程分析方法相吻合,且总体上更接近工程实际,因此可用于空间结构的施工过程分析与安全评估;与传统静力施工过程分析方法相比,该方法一方面能够更准确反映实际施工过程中结构响应的动态累积效应,并获取任意时刻的结构受力和变形情况,另一方面,还可适用于强非线性的复杂施工过程分析(大变形、超大位移、机构位移等),从而避免了传统静力施工过程分析方法中非线性求解的收敛性难题。

聚焦钙钛矿光伏器件中慢速动力学机制研究进展

利用光伏效应直接将太阳能转化为电能,是获取可持续清洁能源的重要途径之一。近年来,钙钛矿太阳能电池成为光伏领域的研究热点,随着结构调控和制备工艺的不断发展,目前其光电转换效率已经突破25%。虽然钙钛矿光伏器件具有制备条件温和、成本低、效率高等优点,但该类光伏器件呈现出秒量级甚至分钟量级的慢速动力学现象,这对钙钛矿光伏器件性能以及正确认识光电转换动力学造成较大的影响。迄今对慢速动力学的认识仍处于猜测阶段,尚缺乏系统认识。其中离子迁移和缺陷态属性被当作慢速动力学的主要研究目标。本文从钙钛矿光伏器件原初的电荷分离开始,分析了钙钛矿太阳能电池在多时间跨度内的载流子动力学行为;讨论了可能造成钙钛矿光伏器件慢速动力学的原因,认为可以从关键的钙钛矿活性层切入;揭示了钙钛矿活性层结构对慢速动力学的影响机理;为全新认识钙钛矿太阳能电池光电转换过程提供新思路,从而进一步指导器件设计和制备。

一类Filippov型HR神经元模型的全局动力学分析

基于电磁辐射下的HR神经元模型,引入一种以膜电位为阈值的非光滑控制策略,即确定与电磁感应强度和外部刺激电流相对应的切换函数,从而建立一类四维Filippov型HR神经元模型。利用稳定性理论和数值模拟方法讨论2个子系统平衡点的存在性、稳定性和全局分岔行为。另外,基于双参数分岔分析,研究子系统的双稳态行为和演化模式。进一步,利用Filippov凸组合方法和Utkin等度控制方法分析系统的各类平衡点和滑膜动力学的存在性。最后,采用快-慢动力学的方法揭示阈值控制策略下的滑动放电模式和多稳态特征。

日冕中EUV波的研究进展

日冕极紫外(EUV)波是Thompson等人1998年首先在EIT的观测资料中发现的,在日冕中以几百km/s的速度传播的扰动现象,在1 h之内扫过了大部分太阳表面,所以这个现象开始被称为"EIT波"。首先介绍了EUV波的研究背景;然后介绍了EUV波的观测特征;第3章分别介绍了EUV波与Moreton波、耀斑及CME的关系;第4章介绍了从发现EUV波以来提出的各种理论和模型;第5章讨论到目前为止已发现的EUV波成分:一个较快的波在前面传播,一个较慢的波在后面传播;最后,对EUV波研究的未来方向及发展趋势进行了总结和展望。

Physiological and pathological role of local and immigrating colonic stem cells

The latest avenue of research is revealing the existence of and role for the colonic stem cells in the physiological renewal of the mucosa and in pathological circumstanc- es where they have both positive and negative effects. In the case of human colon, different levels of stem cell compartments exist. First, the crypt epithelial stem cells, which have a role in the normal crypt epithelial cell dynamics and in colorectal carcinogenesis. Close to the crypts, the second layer of stern cells can be found; the local subepithelial stem cell niche, including the pericryptic subepithelial myofibroblasts that regulate the epithelial cell differentiation and have a crucial role in cancer progression and chronic inflammation-related fibrosis. The third level of stem cell compartment is the immigrating bone-marrow-derived stem cells, which have an important role in wound healing after severe mucosal inflammation, but are also involved in cancer invasion. This paper focuses on stem cell biology in the context of physiological and pathological processes in the human colon.

Comparison of the morphometric dynamics of fast-growing and slow-growing strains of turbot Scophthalmus maximus

The dynamics of changes in body shape of fast-growing and slow-growing strains of turbot Scophthalmus maximus, and of the differences in body shape between the two strains, were evaluated from 3 to 27 months of age. The ratios of total length/body length, body width/body length and total length/body width were used as morphometric indices. The two strains exhibited different temporal trends in total length/body length but similar trends in body width/body length and total length/body width. Generally, body width/body length of the two strains increased with time and total length/body width decreased. Thus, the bodies of both fast-growing and slow-growing strains of turbot changed from a narrow to a more rounded shape. However, the ratio total length/body length was generally lower, body width/body length was mostly higher and total length/body width was consistently lower in the fast-growing strain than in the slowgrowing strain. Correlation analysis of the three shape ratios with body weight showed that total length/body length and total length/body width were unsuitable, and that width/body length was suitable, for use as a phenotypic marker for selective breeding of turbot for growth in weight.

Effects of Bisoprolol on the ventricular function and hemodynamics in patients with atrial fibrillation and chronic heart failure

Background: Recent data suggest that beta-blockers can be beneficial in patients with chronic heart failure (CHF). Atrial fibrillation (AF) is present in a significant number of patients with CHF and is associateing with significant morbidity and increasing mortality rates. Thus it is necessary to establish therapy to improve the poor prognosis in this high-risk population, but a specific benefit of beta-blockers to the subset with concomitant AF and CHF has been little demonstrated. Objective: To examine the effects of Bisoprolol (6 months treatment) on the ventricular function and hemodynamics in patients with AF and CHF. Methods: 84 patients with stable CHF (NYHA≤Ⅲ class) and AF were assigned to Treated Group( n = 37) or Control group Ⅰ ( n = 22, 24-hour heart mean rate < 70/min) or Control Group Ⅱ ( n = 25, 24-hour heart mean rate ≥ 70/min) . All patients were given the basic therapy for CHF, and Treated Group received Bisopolol. Clinical and echocardiographic variables were measured in 3 groups at baseline and after 6 months, and the results were compared . Results: After 6 months of treatment with Bisoprolol, left ventricular ejection fraction (LVEF) and NYHA class had significandy improved (P < 0.05), and a trend towards a reduction in combined end point of death or CHF hospitalization was also observed (P < 0.20) in Treated Group; The increase of LVEF in Treated Group were associated with a reduction in mitral regurgitation degree and left atrial volume; The heart rate in mean 24-hour and at peak exercise decreased in Treated Group, but were similar to that in Control Group Ⅰ. Conclusion: 6 months of Bisoprolol therapy resulted in an improvement in the NYHA class and LVEF, and also showed a trend towards a reduction in hospitalization or death. The beneficial effects of Bisoprolol on patients with AF and CHF may be partly mediated by improvement of ventricular diastolic function.

Structure-controlled slow dynamics in Al−Mg melts

Molecular dynamics simulation was employed to investigate the dynamical and structural properties of Al−Mg melts with the Al concentration systematically changed.The results show that the viscosity of Al67Mg33 abnormally surpasses that of Al85Mg15 below 550 K,inconsistent with the tendency at high temperatures.The evolution of the icosahedral order population is found to account for this dynamic behavior.Structural analysis shows a preferred bonding between Al and Mg atoms in the nearest neighbor shells,while a repelling tendency between them in the second shells,leading to the prepeak emergence in the partial static structure factors.The formation of icosahedral clusters is constrained in the Al-rich compositions because of the lack of sufficient Mg atoms to stabilize the clusters geometrically.These results demonstrate the structural consequence through the interplay between geometric packing and chemical interaction.These findings are crucial to understanding the structure−dynamic properties in Al−Mg melts.

Complex bursting patterns in Van der Pol system with two slowly changing external forcings

This paper investigates the generation of complex bursting patterns in Van der Pol system with two slowly changing external forcings. Complex bursting patterns, including complex periodic bursting and chaotic bursting, are presented for the cases when the two frequencies are commensurate and incommensurate. These complex bursting patterns are novel and have not been reported in previous work. Based on the fast-slow dynamics, the evolution processes of the slow forcing are presented to reveal the dynamical mechanisms undedying the appearance of these complex bursting patterns. With the change of ampli- tudes and frequencies, the slow forcing may visit the spiking and rest areas in different ways, which leads to the generation of different complex bursting patterns.

Dynamics of different compound bursting in two phantom bursting mechanism models

The generic phantom bursting model proposed by Bertram et al.can evoke complex bursting oscillations in collaboration with two generic slow variables with different time scales.Two models with the phantom bursting mechanism are suggested,when these two generic slow variables are provided with some specific biological significances by combining slowly varying intracellular Ca2+concentration of the Chay-Keizer electrical bursting model with two different glycolytic oscillations,respectively.Also,complex dynamic behaviors of different compound bursting occurring in these two models are comprehensively surveyed by two fast/slow analyses for a moderately and a slower slow variable,respectively.

Enhanced External Counterpulsation Inducing Arterial Hemodynamic Variations and Its Chronic Effect on Endothelial Function

To make clear the precise hemodynamic mechanism underlying the anti-atherogenesis benefit of enhanced external couterpulsation(EECP) treatment, and to investigate the proper role of some important hemodynamic factors during the atherosclerotic progress, a comprehensive study combining long-term animal experiment and numerical solving was conducted in this paper. An experimentally induced hypercholesterolemic porcine model was developed and the chronic EECP intervention was subjected. Basic hemodynamic measurement was performed in vivo, as well as the arterial endothelial samples were extracted for physiological examination. Meanwhile, a numerical model was introduced to solve the complex hemodynamic factors such as WSS and OSI. The results show that EECP treatment resulted in significant increase of the instant levels of arterial WSS, blood pressure, and OSI. During EECP treatment, the instant OSI level of the common carotid arteries over cardiac cycles raised to a mean value of 8.58 ×10-2±2.13 ×10-2. Meanwhile, the chronic intervention of EECP treatment significantly reduced the atherosclerotic lesions in abdominal aortas and the endothelial cellular adherence. The present study suggests that the unique blood flow pattern induced by EECP treatment and the augmentation of WSS level in cardiac cycles may be the most important hemodynamic mechanism that contribute to its anti-atherogenesis effect. And as one of the indices that cause great concern in current hemodynamic study, OSI may not play a key role during the initiation of atherosclerosis.

GLOBAL DYNAMICS OF A DELAYED HIV-1 INFECTION MODEL WITH ABSORPTION AND SATURATION INFECTION

In this paper, an HIV-1 infection model with absorption, saturation infection and an intracellular delay accounting for the time between viral entry into a target cell and the production of new virus particles is investigated. By analyzing the characteristic equations, the local stability of an infection-free equilibrium and a chronic-infection equilibrium of the model is established. By using suitable Lyapunov functionals and LaSalle＇s invariance principle, it is proved that if the basic reproduction ratio is less than unity, the infection-free equilibrium is globally asymptotically stable; and if the basic reproduction ratio is greater than unity, sufficient condition is derived for the global stability of the chronic-infection equilibrium.