空间分布型的形成过程研究

具合影个研究了广义空间分布型和复合空间分布型的形成问题,解释了空间分布型的形成机理,并给出了１１种广义空间分布型和９种复事空间分布型;同时提出了空间分布型的３种判定方法：扩散系数法、空间相关法和参数变动法,它们以可用于区分常见的空间分布型,也可以用于判定分布型的形成过程;为研究空间分布型的形成机理和变化规模提供了有力的手段。以马尾松毛虫的空间分布型的研究结果表明,马尾松毛虫幼虫的空间分布型是复合负     

The Non-Central Negative Binomial Distribution

The non-central negative binomial distribution is derived by mixing the POISSON distribution with a certain BESSEL function distribution, or the negative binomial distribution with the POISSON distribution. Some properties of the distribution are discussed, including a characterization. The fitting of the distribution to some data are given together with the efficiency for various procedures of estimation.     

Distribution patterns of some subterranean Crustacea in the territory of the former Yugoslavia

A selection of the most representative distribution patterns of stygobiont animals is presented. The range of a genus may extend beyond the Dinaride karst, while some species exhibit a holo-Dinaric distribution. The mero-Dinaric distribution is organised in two vicarious centres (in the NW and SE) as well as an epilittoral and a paralittoral belt. The paralittoral distribution is a result of paleogeographic rather than present-day ecological conditions. Important differences between the interstitial faunas of Slovenia (and NE Italy) and Macedonia are probably the result of their different sources. Some other distribution patterns are discussed or summarized from the existing literature. The distribution patterns of this stygobiont fauna are extremely diverse, and are influenced by the geological complexity of the territory as well as by the richness of the fauna concerned. New distribution data for some Copepoda, Thermosbaenacea, and Amphipoda are appended.     

Parameter-free testing of the shape of a probability distribution

The Kolmogorov-Smirnov test determines the consistency of empirical data with a particular probability distribution. Often, parameters in the distribution are unknown, and have to be estimated from the data. In this case, the Kolmogorov-Smirnov test depends on the form of the particular probability distribution under consideration, even when the estimated parameter-values are used within the distribution. In the present work, we address a less specific problem: to determine the consistency of data with a given functional form of a probability distribution (for example the normal distribution), without enquiring into values of unknown parameters in the distribution. For a wide class of distributions, we present a direct method for determining whether empirical data are consistent with a given functional form of the probability distribution. This utilizes a transformation of the data. If the data are from the class of distributions considered here, the transformation leads to an empirical distribution with no unknown parameters, and hence is susceptible to a standard Kolmogorov-Smirnov test. We give some general analytical results for some of the distributions from the class of distributions considered here. The significance level and power of the tests introduced in this work are estimated from simulations. Some biological applications of the method are given.     

秦岭种子植物区系科的组成、特点及其地理成分研究

秦岭种子植物区系组成丰富, 共有种子植物198 科、1007 属、3446 种, 区系组成的大科及主要科共16 科, 占秦岭种子植物总数属的50.05%, 总种数的57.25%, 它们构成了秦岭植物区系组成的基本框架, 就其性质来讲, 绝大多数为温带性质。松科、壳斗科、桦木科、杨柳科、蔷薇科、杜鹃花科、禾本科、莎草科等是秦岭植被的区系组成的优势科, 从地理成分上来分析, 本区科的分布型可以划分为世界或亚世界分布科、热带分布科、温带分布科、间断分布科以及东亚和中国特有科, 其区系的起源则有明显的古老性。     

A Suprasystem of Probability Distributions

A set of differential equations is described whose solutions represent a general system of probability distribution functions. Previously reported systems of such distribution functions are special cases of this general system. The differential equations can be used to represent distribution functions and generate their related statistics in cases for which no simple formula for the distribution is known. The generality of this suprasystem of distribution functions and its potential utility are discussed.     

Several appropriate background distributions for entropy-based protein sequence conservation measures

Amino acid background distribution is an important factor for entropy-based methods which extract sequence conservation information from protein multiple sequence alignments (MSAs). However, MSAs are usually not large enough to allow a reliable observed background distribution. In this paper, we propose two new estimations of background distribution. One is an integration of the observed background distribution and the position-specific residue distribution, and the other is a normalized square root of observed background frequency. To validate these new background distributions, they are applied to the relative entropy model to find catalytic sites and ligand binding sites from protein MSAs. Experimental results show that they are superior to the observed background distribution in predicting functionally important residues.     

四川缙云山林下乔木幼苗分布格局的研究

1 引言 研究林下乔木幼苗的分布格局及其与环境因子的相互关系,不仅可以表达植物种群中幼苗群的特征,而且可根据幼苗群对随机性的偏离与环境因子的相互关     

Correlative statistical analysis and computer modelling of intramembraneous particle distributions in human erythrocyte membranes.

The planar distribution of intramembranous particles on the P faces of freeze-fractured human erythrocyte membranes is characterized by radial distribution, angular distribution and differential density distribution analysis. Various degrees of intramembranous particle aggregation induced by spectrin removal and low pH are differentiated through computation. Random hard disk models with various disk diameters are built for comparison studies. In all samples, the 80 +/- 10 A particles are found to have a preferred neighboring distance of 100 +/- 10 A, but no preferred angular relation is found between neighboring particles. A pattern recognition process using both radial and density distribution analyses reveals that none of the particle distributions observed may be regarded as random. The fact that the particle distributions observed are neither even nor random suggests that factors other than long range electrostatic force alone are involved in determining the particle distribution.     

On the size distribution of live genera

This article deals with the theoretical size (number of species) distribution of live genera, arising from a simple model of macroevolution in which speciations and extinctions are assumed to occur independently and at random, and in which new genera are formed by the random splitting of existing genera. Mathematically, the distribution is that of the state of a homogeneous birth-and-death process after an exponentially distributed time. An ordinary differential equation for the generating function of the distribution is derived and solved and a recurrence relation for computing the probabilities in the distribution presented. Some properties of the distribution, including asymptotic behaviour, are examined and the distribution of the time since establishment of a genus of a given size derived. Fitting the distribution to empirical taxon size distributions by maximum likelihood is discussed and two examples are presented.     

A stochastic model for chemical equilibrium— asymptotic expectation and variance of the stationary probability distribution of reversible chemical reactions

Reversible second order chemical reactions are described by a birth and death process. The stationary distribution of this process occurs in statistics as a conditional distribution of Bernoulli variables. For large numbers of reacting molecules—by using well-known properties of these Bernoulli variables—it is shown that a normal approximation of the stationary distribution holds. The mean and variance of the stationary distribution are explicitly calculated. For some relatively small numbers of reacting molecules computer output is added in which the distribution function, mean and variance are compared with their approximations.     

叶蜂总科昆虫生物地理研究I叶蜂总科科级阶元的地理分布分析(膜翅目)

本文在科级阶元水平分析了叶蜂总科的地理分布特征。叶蜂总科在科、亚科和族级水平上可分为３种,９种和１６种分布型。在各级水平上,全北界分布型均占有绝对优势,其中东亚地区中南部是主要分布中心。文中还简要阐述了世界膜翅目广腰类群的分布特性;提出了一个简明实用的“类元分布指数Ｉｔ”,用于表示特定地区某一或全部生物类群的各级阶元的分布数量与世界已知阶元总数之比值。此指数稍作修改提出一个类群起源可能性指数Ｉｏ,用于表示某一类群在一特定区域起源的可能性大小。     

秦岭及陕北黄土区辽东栎林群落物种多样性特征

应用５种物种多样性测度指标及４种物种—多度分布模型对秦岭和黄土区辽东栎林种子植物物种多样性及木本植物种—多度分布进行了对比研究,结果表明：秦岭辽东栎林无论是群落物种多样性还是各层次的物种多样性均高于黄土区辽东栎林。秦岭辽东栎林木本植物种—多度分布符合对数正态分布而黄土区辽东栎林则符合对数级数分布,分布区气候差异是造成两类辽东栎林物种多样性差异的主要原因。物种—多度分布分析与物种多样性分析结果是一致的。     

塔里木河上游天然胡杨林种群空间分布格局与动态研究

以新疆塔里木河上游阿瓦提县天然胡杨林为研究对象,采用相邻格子法进行实地调查,应用方差/均值比率法和5种聚集度指标研究了塔里木河上游天然胡杨林主要种群的空间分布格局与动态特征.结果显示:胡杨群落中除草本西北天冬种群空间分布格局呈随机分布外,其它主要种群均呈聚集分布;拟合检验表明,胡杨、灰叶胡杨种群为聚集分布.种群空间分布动态分析表明,灰叶胡杨在小树、中树与大树阶段均为聚集分布;胡杨种群在小树与中树阶段为聚集分布,但聚集强度减弱,到大树阶段为随机分布.研究表明,物种分布格局主要与物种本身的生物生态学特性和生境有关.     

浙江仙居俞坑森林群落优势种群结构与分布格局研究

以浙江仙居俞坑森林群落为研究对象,用“空间序列代替时间变化”的方法,对该群落优势种群的结构和动态进行了分析,结果是：各优势种群中常绿阔叶树种的大小级分布图的形状基本相似,种群存活曲线均表现为极显著的线性关系,种群的年龄结构为稳定型。地树种拟赤杨的年龄结构为衰退型。甜槠、青冈栎、红楠种群的分布格局均呈集群分布,木荷、虎皮楠种群的分布格局多为随机分布,拟赤杨呈随机分布或均匀分布。甜槠种群的幼苗、幼树的     

Estimating incident population distribution from prevalent data

A prevalent sample consists of individuals who have experienced disease incidence but not failure event at the sampling time. We discuss methods for estimating the distribution function of a random vector defined at baseline for an incident disease population when data are collected by prevalent sampling. Prevalent sampling design is often more focused and economical than incident study design for studying the survival distribution of a diseased population, but prevalent samples are biased by design. Subjects with longer survival time are more likely to be included in a prevalent cohort, and other baseline variables of interests that are correlated with survival time are also subject to sampling bias induced by the prevalent sampling scheme. Without recognition of the bias, applying empirical distribution function to estimate the population distribution of baseline variables can lead to serious bias. In this article, nonparametric and semiparametric methods are developed for distribution estimation of baseline variables using prevalent data.     

Modeling menstrual cycle length using a mixture distribution

In reproductive health studies, epidemiologists are often interested in examining the effects of covariates on menstrual cycle length which is a convenient, noninvasive measure of women's ovarian and reproductive function. Previous literature (Harlow and Zeger, 1991) suggests that the distribution of cycle length is a mixture of a major symmetric distribution and a component featuring a long right tail. Motivated by the shape of this marginal distribution, we propose a mixture distribution for cycle length, representing standard cycles from a Normal distribution and nonstandard cycles from a shifted Weibull distribution. The parameters are estimated using an estimating equation derived from the score function of an independence working model. The fitted mixture distribution agrees well with the distribution estimated using nonparametric approaches. We propose two measures to help determine whether a cycle is standard or nonstandard, developing tools necessary to identify characteristics of the menstrual cycles that are biologically indicative of ovarian dysfunction. We model the effect of a woman's age on the mean and variation of both standard and nonstandard cycle lengths using multiple measurements of women.     

Prediction of surface area in polydisperse gas-suspension systems with variable apparent surface tension,viscosity and density

Bubble size distribution was found to be represented by a modified log-normal distribution with 3 parameters. The parameters are simple functions of suspension properties,viz. surface tension, viscosity and density, and a function of superficial gas rate. Correlations are presented, enabling the prediction of the distribution constants (and thus of the bubble size distribution) from the system properties and gas rate. Model translucent systems can be used, having identical apparent system properties as real suspensions in experimental work. A computer algorithm is presented for (i) prediction of bubble size distribution, defining the region of formation of spherical bubbles, (ii) converting particle size distribution into volume distribution, (iii) determining the actual gas volume from a hold-up correlation, and (iv) giving the surface area of the system of a given predicted distribution.     

k-长DNA子序列频数分布研究

在详细阐述了生成DNA序列分形图像的Hao方法后,提出一种能够直观显示k-长DNA子序列频数分布差异性的三维频数分布图生成方法。把3D频数分布图转化为1D对数频谱图,突出显示了频数分布的局部特征,提出k-长DNA子序列频数区划分准则,并详细研究了甚高频数区的n阶零间隔现象,指出n阶零间隔分布就是基因组进化过程所留痕迹的假设,并给出对数频谱图特征的生物学解释。实验发现许多DNA序列频数概率分布近似服从非中心F分布,对于分布呈多峰现象的基因组序列,可采用多个非中心F分布的叠加来拟合。在比较非中心F分布与Gamma分布后,提出一种结合二者在拟合方面具有互补优势的新分布,实验证明这种新分布能够更好地吻合实际DNA序列的频数分布。最后研究了两种特异出现频数(最高出现频数与出现频数为1的k-长子序列个数)与k值的关系,发现不同物种的这两种关系具有良好的一致性。     

黑龙江省木本植物区系分析

黑龙江省有木本植物392种,隶属于42科90属。其中裸子植物4科8属34种,双子叶植物37科81属357种,单子叶植物1科1属1种。本省为大兴安岭植物区、东北植物区和蒙古草原植物区三区汇集之地,木本植物地理成分复杂,具有非常明显的温带性质：温带分布科虽然与热带分布科数目相同,但所含种数多,优势明显;温带分布属占75.86%,以北温带分布比例最高;温带分布种占80.43%,以东北分布居首位,其次是中国—日本分布。该区系木本植物起源古老,有珍稀濒危植物9种,特有植物14种及红松、黄檗等孑遗植物,为第三纪植物区系系统。