Assessing Poisson variation of intestinal tumour multiplicity in mice carrying a Robertsonian translocation

Summary.  Tumour multiplicity is a frequently measured phenotype in animal studies of cancer biology. Poisson variation of this measurement represents a biological and statistical reference point that is usually violated, even in highly controlled experiments, owing to sources of variation in the stochastic process of tumour formation. A recent experiment on murine intestinal tumours presented conditions which seem to generate Poisson-distributed tumour counts. If valid, this would support a claim about mechanisms by which the adenomatous polyposis coli gene is inactivated during tumour initiation. In considering hypothesis testing strategies, model choice and Bayesian approaches, we quantify the positive evidence favouring Poisson variation in this experiment. Statistical techniques used include likelihood ratio testing, the Bayes and Akaike information criteria, negative binomial modelling, reversible jump Markov chain Monte Carlo methods and posterior predictive checking. The posterior approximation that is based on the Bayes information criterion is found to be quite accurate in this small n case-study.     

Approximation and Exact Algorithms for Constructing Minimum Ultrametric Trees from Distance Matrices

An edge-weighted tree is called ultrametric if the distances from the root to all the leaves in the tree are equal. For an n by n distance matrix M, the minimum ultrametric tree for M is an ultrametric tree T = (V, E, w) with leaf set {1,..., n} such that d_T(i, j) M[i, j] for all i, j and is minimum, where d_T(i, j) is the distance between i and j on T. Constructing minimum ultrametric trees from distance matrices is an important problem in computational biology. In this paper, we examine its computational complexity and approximability. When the distances satisfy the triangle inequality, we show that the minimum ultrametric tree problem can be approximated in polynomial time with error ratio 1.5(1 + log n), where n is the number of species. We also develop an efficient branch-and-bound algorithm for constructing the minimum ultrametric tree for both metric and non-metric inputs. The experimental results show that it can find an optimal solution for 25 species within reasonable time, while, to the best of our knowledge, there is no report of algorithms solving the problem even for 12 species.     

大熊猫发情期繁殖行为的研究

本文从圈养大熊猫的活动节律、活动量、食欲、叫声、遗留气味标志,蹭阴频率和方式的变化;雌体独自抬尾出现的时间和频率、阴阜膨肿度和颜色、阴道角化细胞百分比的变化;雌雄个体相互影响和引诱等行为方面,探索大熊猫行为与发情高潮的关系.     

拓扑分子格的远域系公理和远域基公理

本文在拓扑分子格中讨论了基与远域基的关系,给出了拓扑分子格的远城系公理和远城基公理,得到分子格上余拓扑的两种刻划。     

Response to Commentaries:

It is time to bring nature (genetics) together with nurture (environment) in the study of social development. Following a brief overview of behavioral genetic theory and methods, three examples are described of new genetic research especially relevant to social developmentalists. First, initial research findings on three key domains of social development (attachment, empathy, and social competence) suggest that genetic factors contribute to individual differences in social development. Second, research on widely used measures of social environment implicates a genetic contribution, which opens up new directions for research at the interface of nature and nurture in social development. Third, by the turn of the century, it is predicted that behavioral genetic research will be conducted using DNA markers that assess genetic variation among individuals directly rather than resorting to indirect estimates based on twin and adoption methods. This will revolutionize behavioral genetic research and make it more accessible and applicable to developmentalists. As a first step in the direction of behavioral genetics, social developmentalists are encouraged to include siblings in their research.     

烯烃分子结构与凝聚型性能关系的三级结构信息法研究

根据分子结构的特点,用图论方法探讨了烯烃凝聚型性能与其分子结构之间的关系,提出了一个结构基础明确的定量关系.对大量烯烃的沸点、密度和折光指数进行了计算,结果与实验值拟合较好.应用本文定量关系,不仅能够预测烯烃的凝聚型性能,而且有助于揭示物质结构与性能间关系的奥秘.     

生物免疫机理在网络入侵检测中的应用

基于生物免疫学的网络入侵检测是近年来入侵检测领域研究的热点,它的突出特点是利用生物物免疫学的原理、规则与机制来实现对入侵行为的检测和反应。网络入侵检测系统与生物免疫系统具有本质的相似性:生物免疫系统负责识别生物体的"自我"(Self)与"非自我"(Non-self)细胞,并清除异常细胞;网络入侵检测系统则辨别正常与异常行为模式,采取适当的措施阻止对系统的入侵行为。文中围绕生物免疫系统的算法、原理和运行机制在网络入侵检测中的应用并结合入侵检测系统自身的特点进行了深入研究。     

Impact factors of purse seine net and dip net fisheries on a chub mackerel population

There are two major kinds of fisheries for the chub mackerel in Japan. The purse seine net fishery exploits young and adult fish during the foraging season, while the dip net fishery exploits fish before and during the spawning season. To compare the damage to the chub mackerel stock caused by purse seine net and dip net fisheries, we introduced impact factors of the two kinds of fisheries on the two kinds of fisheries and estimated number of eggs spawned in 1982. We defined the impact factor as the ratio of the average reproductive value of individuals caught by each fishery to the reproductive value at maturity. The number of individuals caught by the purse seine net fishery was 66 times larger than the number caught by the dip net fishery, while the impact factor of the former was 84% of that of the latter. Thus, the total damage caused by the purse seine net fishery was much higher than the damage caused by the dip net fishery. We can evaluate the damage caused by mortality factors on endangered species using this method.     

Extinction of populations due to inbreeding depression with demographic disturbances

The process of population extinction due to inbreeding depression with constant demographic disturbances every generation is analysed using a population genetic and demographic model. The demographic disturbances introduced into the model represent loss of population size that is induced by any kind of human activities, e.g. through hunting and destruction of habitats. The genetic heterozygosity among recessive deleterious genes and the population size are assumed to be in equilibrium before the demographic disturbances start. The effects of deleterious mutations are represented by decreases in the growth rate and carrying capacity of a population. Numerical simulations indicate rapid extinction due to synergistic interaction between inbreeding depression and declining population size for realistic ranges of per-locus mutation rate, equilibrium population size, intrinsic rate of population growth, and strength of demographic disturbances. Large populations at equilibrium are more liable to extinction when disturbed due to inbreeding depression than small populations. This is a consequence of the fact that large populations maintain more recessive deleterious mutations than small populations. The rapid extinction predicted in the present study indicates the importance of the demographic history of a population in relation to extinction due to inbreeding depression.     

传播学视野中的网络生态研究

网络生态学是以人为关注焦点,贯彻整体观、互动观、平衡观、循环观和资源观的指导原则,将网络作为人的生存环境来展开研究的一门交叉学科。它由信息因子、主体因子和环境因子构成,三者相互影响,呈现开放与内敛的发展态势,并具有开放性、系统性、动态性和可控性等特征。但信息污染、资源失衡、行为失范、文化危机等网络失衡问题影响着网络生态的发展,这是网络主体因子和环境因子异变的结果。因此,维护网络信息多样化,优化网络生态的结构与功能,保障系统能量与物质的均衡流动,加强网络生态的自我调节和净化能力就显得尤为必要;而且在治理过程中还要倡导网络伦理、完善网络法规和加速技术研发,以实现网络生态的平衡和可持续发展。