Bayesian experimental design for nonlinear mixed-effects models with application to HIV dynamics

Bayesian experimental design is investigated for Bayesian analysis of nonlinear mixed-effects models. Existence of the posterior risk for parameter estimation is shown. When the same prior distribution is used for both design and inference, existence of the preposterior risk for design is also proven. If the prior distribution used in design is different from that used for inference, sufficient conditions are established for existence of the preposterior risk for design. A case study of design for an experiment in population HIV dynamics is provided.     

Optimal Experimental Design and Accuracy of Parameter Estimation for Nonlinear Regression Models Used in Long-term Selection

An experimental design problem is considered for the analysis of long-term selection experiments with nonlinear regression models. For a 3-parametric exponential regression function whose parameters have also a reasonable biological interpretation approximate formulas for the determination of the necessary number of observations at each generation are constructed in such a way that the half expected length of an (1 — α)-confidence interval for a chosen parameter is not greater than a given value. In this sense the accuracy of the parameter estimators can be described.     

Mutation and control of the human immunodeficiency virus

We examine the dynamics of infection by the human immunodeficiency virus (HIV), as well as therapies that minimize viral load, restore adaptive immunity, and use minimal dosage of anti-HIV drugs. Virtual therapies for wild-type infections are demonstrated; however, the HIV infection is never cured, requiring continued treatment to keep the condition in remission. With high viral turnover and mutation rates, drug-resistant strains of HIV evolve quickly. The ability of optimal therapy to contain drug-resistant strains is shown to depend upon the relative fitness of mutant strains.     

苜蓿人工草地节肢动物群落的时间格局

调查了甘肃省庄浪县苜蓿人工草地节肢动物群落的组成及多样性变化,应用主分量分析和最优分割法对节肢动物群落的时间格局进行了研究。结果表明,苜蓿人工草地节肢动物群落的物种丰富度,多样性和均匀度指标在时间过程中的变化有明显的差异和规律性,6月下旬害虫和天敌的物种丰富度均达到最大值,但天敌的个体数量高峰明显落后于害虫,在时间变化过程中,影响节肢动物群落的主导因素和时间格局分化明显,根据研究结果,将苜蓿人工草地节肢动物群落在时间动态中的变化划分为5月上旬以前,5月中旬-6月上旬,6月中旬-7月中旬,7月中旬以后4个阶段,并结合气候,物候变化,分析了各阶段内主要害虫和天敌的发生特点,提出了害虫的治理对策。     

非线性森林发展系统研究进展

就近年来国内外对非线性森林发展系统的研究进展做一综述,介绍了一些非线性森林发展系统模型,分析了非线性森林系统的研究结果。     

Dynamic membrane structure induces temporal pattern formation

The understanding of temporal pattern formation in biological systems is essential for insights into regulatory processes of cells. Concerning this problem, the present work introduces a model to explain the attachment/detachment cycle of MARCKS and PKC at the cell membrane, which is crucial for signal transduction processes. Our model is novel with regard to its driving mechanism: Structural changes within the membrane fuel an activator–inhibitor based global density oscillation of membrane related proteins. Based on simulated results of our model, phase diagrams were generated to illustrate the interplay of MARCKS and PKC. They predict the oscillatory behavior in the form of the number of peaks, the periodic time, and the damping constant depending on the amounts of MARCKS and PKC, respectively. The investigation of the phase space also revealed an unexpected intermediate state prior to the oscillations for high amounts of MARCKS in the system. The validation of the obtained results was carried out by stability analysis, which also accounts for further enhanced understanding of the studied system. It was shown, that the occurrence of the oscillating behavior is independent of the diffusion and the consumption of the reactants. The diffusion terms in the used reaction–diffusion equations only act as modulating terms and are not required for the oscillation. The hypothesis of our work suggests a new mechanism of temporal pattern formation in biological systems. This mechanism includes a classical activator–inhibitor system, but is based on the modifications of the membrane structure, rather than a reaction–diffusion system.     

Spatial information enhanced by non-spatial information in hippocampal granule cells

The hippocampus organizes sequential memory composed of non-spatial information (such as objects and odors) and spatial information (places). The dentate gyrus (DG) in the hippocampus receives two types of information from the lateral and medial entorhinal cortices. Non-spatial and spatial information is delivered respectively to distal and medial dendrites (MDs) of granule cells (GCs) within the molecular layer in the DG. To investigate the role of the association of those two inputs, we measured the response characteristics of distal and MDs of a GC in a rat hippocampal slice and developed a multi-compartment GC model with dynamic synapses; this model reproduces the response characteristics of the dendrites. Upon applying random inputs or input sequences generated by a Markov process to the computational model, it was found that a high-frequency random pulse input to distal dendrites (DDs) and, separately, regular burst inputs to MDs were effective for inducing GC activation. Furthermore, when the random and theta burst inputs were simultaneously applied to the respective dendrites, the pattern discrimination for theta burst input to MDs that caused slight GC activation was enhanced in the presence of random input to DDs. These results suggest that the temporal pattern discrimination of spatial information is originally involved in a synaptic characteristic in GCs and is enhanced by non-spatial information input to DDs. Consequently, the co-activation of two separate inputs may play a crucial role in the information processing on dendrites of GCs by usefully combing each temporal sequence.     

湖南壶瓶山国家级自然保护区哺乳动物多样性的时空格局

<正>对生物多样性的定量分析,是生态学、生物地理学和保护生物学的中心议题之一(Purvis and Hector,2000; Brooks et al.,2006; Pavoine and Bonsall,2011)。自然保护地(protected area)不仅是地球生物多样性的\"诺亚方舟\",更应该是探索人与自然和谐共存方式、维持地球可持续发展的示范地(Higgins et al.,2004)。     

应用试验设计提高蝮蛇抗栓酶产量的研究

试验设计是研究使试验过程科学化、合理化的一门学科。本文介绍了应用试验设计方法寻找生产蝮蛇抗栓酶的最佳工艺,从而有效地提高了产品产量,并取得明显经济效益