具时滞的捕食与被捕食系统的动力分析

研究了具有时滞的捕食与被捕食系统,分析了系统的正不变集、边界平衡点性质、全局渐近稳定性和持久生存性.当时滞(?)很小时,系统在正平衡点是局部渐近稳定的,当(?)从0增到(?)_0时,系统在正平衡点附近产生Hopf分支.     

一类具有混合时滞的捕食被捕食模型的耗散控制（英文）

本文研究了一类具有离散时滞和分布时滞的捕食被捕食系统的耗散控制问题,讨论了捕食被捕食系统的正平衡点的局部稳定性和Hopf分支,并给出平衡点局部渐近稳定的充分条件.将捕食被捕食系统转化为Cohen-Grossberg神经网络模型,选取适当的Lyapunov函数,运用线性矩阵不等式的方法,设计状态反馈控制器,使得神经网络闭环模型耗散,从而使原捕食被捕食系统变成耗散系统.最后通过数值算例说明了方法的可行性.     

一类捕食者具有阶段结构的捕食系统的全局稳定性分析

本文建立了一类捕食者具有阶段结构的捕食系统,计算得到了不存在食饵种群时捕食者种群模型和食饵种群存在时捕食系统的平衡点,并证明了平衡点的存在性.分析和比较了两个模型平衡点的全局稳定性,最终确定了决定模型全局稳定性的捕食者种群基本再生数、食饵灭绝与否的捕食率阈值以及捕食存在时食饵种群的净增长率.     

一类功能性反应模型在常数收获下的动态特性

具有功能性反应的捕食与被捕食模型具有非常复杂的动态性质．特别是在常数收获下,该模型呈现了各种各样、纷杂多变的动态特性。其中包括正平衡点及其稳定性的变化、各种分叉的产生以及周期解和极限环的出现．本文重点研究了常数收获项对一类功能性反应模型的动态性能的影响,得到了该收获模型存在稳定正平衡点、产生分叉以及在Hopf分叉附近产生周期解和极限环的若干充分条件．     

一类相互干扰的捕食与被捕食种群模型的稳定性

本文运用常微分方程稳定性理论及方法讨论了一类具有相互干扰的捕食与被捕食模型的稳定性,得到了正平衡点的局部稳定性条件,正平衡点在第一象限的全局稳定性条件及解的有界性．     

一类带大参数的二维生物模型的快慢动力学与松弛振动

本文研究一类带大参数、密度依赖的捕食-食饵系统的快慢动力学与松弛振动的存在性.通过对退化系统与层系统流的分析,我们定义了奇异鞍点、奇异结点并考虑其摄动,得到了系统平衡点稳定性及其类型;接着,根据正平衡点的不同位置并基于匹配渐近展开和几何奇摄动理论,我们研究了系统经典松弛振动的存在性问题;数值模拟验证了结论的正确性.     

两捕食-食饵扩散系统正平衡点的存在性与稳定性

本文是《两捕食-食饵自治扩散系统的持续生存》一文的续篇.主要证明了系统正平衡点的存在性与全局稳定性．     

具有捕食正效应的捕食-食饵系统

在经典的捕食食饵系统中考虑到由于捕食效应对食饵种群带来的正向调节作用后,提出了具有捕食正效应的捕食-食饵系统.通过对模型的动力学行为的分析,从理论上说明了正向调节作用对系统的影响,并就第一象限内平衡点存在时的相图解释了捕食正效应的作用.结果表明:(1)捕食系统中适当的正向调节作用会增加系统的稳定性;(2)当捕食正效应达到一定的程度后系统拥有一个不稳定的极限环;(3)当捕食正效应过大时会使系统的稳定性发生变化,使捕食者种群与食饵种群同时趋向无穷,出现了调节放纵现象.这些结果在保护生物学中具有重要的意义.     

食饵具有Smith增长且基于比率依赖捕食系统模型的定性分析

研究一类食饵为Smith增长且基于比率依赖的HollingⅢ型功能反应捕食系统模型,运用示性方程讨论参数变化时奇点(0,0)邻域内轨线的走向,给出系统平衡点为全局吸引子或吸引子的充分条件,得到系统正周期解的不存在性、正平衡点的全局渐近稳定性及系统存在极限环的充分条件.     

一类捕食者与被捕食者模型的持久性与稳定性

研究了一类捕食者与被捕食者模型,该生态系统是一个食饵种群被一个捕食种群捕食.当给定参数满足一定条件下,利用比较原理和构造Lyapunov函数的方法,证明了系统的持久性和全局渐近稳定性,并讨论了正平衡点的渐近稳定性.     

Recent advances in the study of Kaposi's sarcoma-associated herpesvirus replication and pathogenesis

It has now been over twenty years since a novel herpesviral genome was identified in Kaposi's sarcoma biopsies. Since then, the cumulative research effort by molecular biologists, virologists, clinicians, and epidemiologists alike has led to the extensive characterization of this tumor virus, Kaposi's sarcoma-associated herpesvirus(KSHV; also known as human herpesvirus 8(HHV-8)), and its associated diseases. Here we review the current knowledge of KSHV biology and pathogenesis, with a particular emphasis on new and exciting advances in the field of epigenetics. We also discuss the development and practicality of various cell culture and animal model systems to study KSHV replication and pathogenesis.     

The structure, reproduction and taxonomy of Vidalia and Osmundaria (Rhodophyta, Rhodomelaceae)

Comprises species occurring mostly in subtidal habitats in tropical, subtropical and warm-temperate areas of the world. An analysis of the type species, V. spiralis (Sonder) Lamouroux ex J. Agardh, a species from Australia, establishes basic characters for distinguishing species in the genus. These characters are (1) branching patterns of thalli, (2) flat blades that may be spiralled on their axis, (3) width of the blade, (4) primary or secondary derivation of sterile and fertile branchlets and (5) position of sterile and fertile branchlets on the thalli. Application of the latter two characters provides an important basic method for separation of species into three major groups. Osmundaria , a genus known only in southern Australia, was studied in relation to Vidalia , and its separation from the Vidalia assemblage is not accepted. Species of Vidalia therefore are transferred to the older genus name, Osmundaria. Two new species, Osmundaria papenfussii and Osmundaria oliveae are described from Natal. Confusion in the usage of the epithet, Vidalia fimbriala Brown ex Turner has been clarified, and Vidalia gregaria Falkenberg, described as an epiphyte on Osmundaria pro/ifera Lamouroux, is revealed to be young branches of the host, Osmundaria prolifera.     

New or rare chromosome counts in Artemisia L. (Asteraceae, Anthemideae) and related genera from Kazakhstan

Fifteen chromosome counts of six Artemisia taxa and one species of each of the genera Brachanthemum, Hippolytia, Kaschgaria, Lepidolopsis and Turaniphytum are reported from Kazakhstan. Three of them are new reports, two are not consistent with previous counts and the remainder are confirmations of very scarce (one to four) earlier records. All the populations studied have the same basic chromosome number, x = 9, with ploidy levels ranging from 2x to 6x. Some correlations between ploidy level, morphological characters and distribution are noted.     

肝癌中HBV和HCV基因和抗原的分布及意义

采用原位分子杂交方法检测HCV RNA及HBV X基因;采用免疫组织化学方法研究HCV核心抗原,非结构区C33c抗原及HBxAg在肝细胞肝癌中的定位及分布.结果表明(1)HCV RNA、HBV X基因在肝细胞肝癌组织检出率分别为40%(55/136)和82%(112/136).HCV RNA定位于癌细胞的胞浆内,阳性细胞呈散在、灶状及弥漫分布三种形式;HBV X基因在肝癌细胞中的分布呈胞浆型、核型及核浆型,阳性细胞也呈上述三种分布形式;(2)HCV C33c抗原、核心抗原在肝细胞肝癌中的阳性率为81%(133/164)及86%(141/164).C33c抗原定位于癌细胞及肝细胞的胞浆内;核心抗原既定位于癌细胞核中,又可定位于胞浆中.C33c抗原阳性细胞以灶状分布为主;而核心抗原阳性细     

Selection with two alleles and complete dominance

For a plant selection model with frequency-independent viabilities, fertilities and selfing rates, it is shown that apart from global fixation, for certain parameter combinations a protected polymorphism and facultative fixation (either allele may become fixed according to initial frequencies) may both occur. Facultative fixation requires different selling rates for the dominant and recessive type. Protection of the polymorphism requires resource allocation for male and female function. In this connection the problem of purely genetically caused population extinction is discussed.
For general frequency dependence and regular segregation, the chances for establishment of a completely recessive gene are compared to those of a completely dominant gene. It is proven that the process of establishment of the recessive gene, despite a fitness advantage, may be considerably endangered by drift effects if random mating prevails. The recessive gene may reach the same effectivity in establishment as a dominant gene, only if the recessive homozygote mates exclusively with its own type during the period of establishment.