颞部骨块形态形成模型极限环的唯一性

本文研究了颞部骨块形态形成的Gierer-Meinhardt模型,并得到该模型在大范围内极限环的唯一性．     

On the length distribution of external branches in coalescence trees: genetic diversity within species

Let Z(n) denote the length of an external branch, chosen at random from a Kingman n-coalescent. Based on a recursion for the distribution of Z(n), we show that nZ(n) converges in distribution, as n tends to infinity, to a non-negative random variable Z with density x--> 8/(2+x)(3), x>or=0. This result facilitates the study of the time to the most recent common ancestor of a randomly chosen individual and its closest relative in a given population. This time span also reflects the maximum relatedness between a single individual and the rest of the population. Therefore, it measures the uniqueness of a random individual, a central characteristic of the genetic diversity of a population.     

一类三次Kolmogorov系统极限环的存在性和唯一性

研究一类三次Ｋｏｌｍｏｇｏｒｏｖ系统,获得了系统存在极限环和存在唯一极限环以及不存在极限环的条件。     

一类生化反应系统极限环的存在唯一性

讨论一类具有二重饱和反应速度的生化反应模型,给出了该系统极限环的不存在性、存在性和唯一性的充分条件,并与具有米氏饱和反应速度的生化模型的定性性质进行比较。     

一类微生物连续培养竞争模型的定性分析

研究一类微生物连续培养竞争模型的解的结构,分析了平衡点的稳定性及平衡点附近极限环存在唯一性,证明系统存在正向不变集。     

二次自催化反应系统的极限环

本文用化学动力学的理论建立了一个二次自催化反应的数学模型,并用定性理论对模型作了定性分析,得到了该模型在大范围内极限环的唯一性的结果．     

Maximum likelihood for interval censored data: Consistency and computation

Standard convex optimization techniques are applied to the analysisof interval censored data. These methods provide easily verifiableconditions for the self-consistent estimator proposed by Turnbull(1976) to be a maximum likelihood estimator and for checkingwhether the maximum likelihood estimate is unique. A sufficientcondition is given for the almost sure convergence of the maximumlikelihood estimator to the true underlying distribution function.     

Functional and phylogenetic uniqueness of helminth and flea assemblages of two South African rodents

The loss of a particular species from a community may have different effects on its functioning, depending on the presence or absence of functionally similar or phylogenetically close species in that community (redundancy). Redundancy is thus defined as the fraction of species diversity not expressed by functional or phylogenetic diversity. We assessed functional and phylogenetic alpha- and beta-redundancy in helminth and flea assemblages of two species of South African rodents, Rhabdomys dilectus and Rhabdomys pumilio, using community uniqueness as the inverse indicator of redundancy. We asked whether patterns of functional and phylogenetic alpha- and beta-uniqueness differed between (i) parasite groups (endo- versus ectoparasites), (ii) host species within parasite groups, and (iii) biomes within host species. We found differences between the two hosts in the functional and phylogenetic alpha-uniqueness (but not beta-uniqueness) of flea, but not helminth, assemblages. Significant correlations between the alpha-uniqueness of parasite assemblages and the total parasite prevalence were found only for phylogenetic uniqueness and only in helminths. Pairwise site-by-site dissimilarities in uniqueness (beta-uniqueness) and pairwise dissimilarity in prevalence were significantly associated (positively) in helminths but not in fleas. A between-biome difference in functional (but not phylogenetic) alpha-uniqueness was found in both helminth and flea assemblages harboured by R. pumilio. We conclude that the resilience of parasite assemblages in terms of the effect on hosts depends not only on their transmission strategy but also on traits of host species and environmental factors.     

具有非线性密度制约HollingⅢ类功能反应Predator-Prey系统模型的定性分析

用定性分析的方法讨论了一类具有非线性密度制约的HollingⅢ型功能反应的predator-prey模型,分析了模型平衡点的性态,得出了模型极限环的存在性与惟一性的充分条件.