生命表的进一步研究及应用

一、数学公式的推证一般的生物生命表由发育期、进入该发育期的存活数、死亡原因、死亡数目、死亡率、存活率等六栏组成。计算简单,但不能充分表达生存规律。现引入生存率函数S(t),积累死亡率函数F(t),死亡密度函数f(t),危险率函数λ(t),以弥补其不足。计算一组生物体进入某一发育期的死亡率公式是: 某一发育期的死亡率=在该发育期的死亡数 进入该发育期的活体总数。根据这一思想定义一个随机变量T及随机     

Some Extensions of Buser and Baroni-Urbani's Clustering Method

We consider that the algorithm of numerical taxonomy focused upon the concept of “homogeneity”, proposed by Buser and Baroni-Urbani (1982) for binary data, satisfies best from all the other algorithms known by us, the conditions of classification in biology formulated by Beckner in 1959. Therefore the paper proposes and studies homogeneities for binary and for ordered multi-states data, which model explicitly Beckner's conditions. From all these, the homogeneity denoted by h* has the remarkable quality of generalizing the famous Jaccard's similarity coefficient. Moreover, using h* in this algorithm “naturally” improved by us, we can achieve the performance of a correct classification of the remarkable example proposed by Watanabe (1969).     

The Importance of Stochastic Transitions for the Origin of Life

We discuss the origin of life in terms of an RNA World scenario in which the creation of autocatalytic sequences is the key step. Our computational models illustrate that life arises by a rare stochastic event that occurs due to spatially localized concentration fluctuations. This allows the chemical system to jump from a non-living state with very low ribozyme concentration to a living state that is controlled by ribozymes. Once the living state is established locally, it can spread deterministically through the rest of the system. These are generic features also possessed by more complex models with a greater degree of chemical realism.     

A Note on Life Table Construction

In this article a modification to the CHIANG'S method of construction of the current life table is presented by using a new set of estimates of n^ax, derived under certain simplified assumptions.     

Extensions to gene set enrichment

MOTIVATION: Gene Set Enrichment Analysis (GSEA) has been developed recently to capture changes in the expression of pre-defined sets of genes. We propose number of extensions to GSEA, including the use of different statistics to describe the association between genes and phenotypes of interest. We make use of dimension reduction procedures, such as principle component analysis, to identify gene sets with correlated expression. We also address issues that arise when gene sets overlap. RESULTS: Our proposals extend the range of applicability of GSEA and allow for adjustments based on other covariates. We have provided a well-defined procedure to address interpretation issues that can raise when gene sets have substantial overlap. We have shown how standard dimension reduction methods, such as PCA, can be used to help further interpret GSEA. SUPPLEMENTARY INFORMATION: Supplementary data are available at Bioinformatics online.     

Impact of Pregnancy-Related Deaths on Female Life Expectancy in Zambia: Application of Life Table Techniques to Census Data

Introduction

Since 2000, the world has been coalesced around efforts to reduce maternal mortality. However, few studies have estimated the significance of eliminating maternal deaths on female life expectancy. We estimated, based on census data, the potential gains in female life expectancy assuming complete elimination of pregnancy-related mortality in Zambia.

Methods

We used data on all-cause and pregnancy-related deaths of females aged 15–49 reported in the Zambia 2010 census, and evaluated, adjusted and smoothed them using existing and verified techniques. We used associated single decrement life tables, assuming complete elimination of pregnancy-related deaths to estimate the potential gains in female life expectancy at birth, at age 15, and over the ages 15–49. We compared these gains with the gains from eliminating deaths from accidents, injury, violence and suicide.

Results

Complete elimination of pregnancy-related deaths would extend life expectancy at birth among Zambian women by 1.35 years and life expectancy at age 15 by 1.65 years. In rural areas, this would be 1.69 years and 2.19 years, respectively, and in urban areas, 0.78 years and 0.85 years. An additional 0.72 years would be spent in the reproductive age group 15–49; 1.00 years in rural areas and 0.35 years in urban areas. Eliminating deaths from accidents, injury, suicide and violence among women aged 15–49 would cumulatively contribute 0.55 years to female life expectancy at birth.

Conclusion

Eliminating pregnancy-related mortality would extend female life expectancy in Zambia substantially, with more gains among adolescents and females in rural areas. The application of life table techniques to census data proved very valuable, although rigorous evaluation and adjustment of reported deaths and age was necessary to attain plausible estimates. The collection of detailed high quality cause-specific mortality data in future censuses is indispensable.     

Two Approaches to the Study of the Origin of Life

This paper compares two approaches that attempt to explain the origin of life, or biogenesis. The more established approach is one based on chemical principles, whereas a new, yet not widely known approach begins from a physical perspective. According to the first approach, life would have begun with—often organic—compounds. After having developed to a certain level of complexity and mutual dependence within a non-compartmentalised organic soup, they would have assembled into a functioning cell. In contrast, the second, physical type of approach has life developing within tiny compartments from the beginning. It emphasises the importance of redox reactions between inorganic elements and compounds found on two sides of a compartmental boundary. Without this boundary, “life” would not have begun, nor have been maintained; this boundary—and the complex cell membrane that evolved from it—forms the essence of life.     

Morphobiochemical Adaptations to Life on Littoral in Some Sedentary Gastropods

Adaptations to attachment, respiration, nutrition, and pollution of sedentary gastropods with cowl-shaped shell living in littoral conditions and prone to the influence of abiotic factors are analyzed. Weight properties of individual parts of the radular apparatus related to scrapping mode of nutrition are discussed. The content of hemoglobin in radular tissues of some representatives of Patellidae, Acmaeidae, and Siphonariidae families is comparatively evaluated.     

干旱环境中褐家鼠的种群数量动态研究

动物种群数量动态研究是种群生态学研究的主要对象之一．借用Leslei矩阵建立数学模型对分布在新疆北部干旱环境中的褐家鼠种群数量动态进行了预测．同时经计算得新疆北部干旱环境中褐家鼠种群的特征根(λ),及其对应的特征向量(ns)．结果表明,12年后雌体总数达到29 801．686 28,同时根据褐家鼠种群增长曲线,发现该种群的增长属于稳定型的指数增长类型．     

On Some Stochastic Problems in Epidemiology under the Binomial Damage Model

The present paper discusses some probability problems in epidemiology in which a community is divided into two parts by means of the binomial damage model. The community size N is an integer-valued random v?ariable and p denotes the incidence rate of a certain disease such that conditional on N=n, the number B of infected individuals in the community follows a binomial distribution with parameters n and p. Let C denote the number of the susceptibles, where B + C = N. Probabilities are found of the events, such as, only half the community is hit by the disease, or there are n more susceptibles than are infected for n=0, 1, 2,…, or the susceptibles exceed the infected, or the susceptibles exceed (m-1) times the number of infected individuals for m = 2, 3,…, etc. These probabilities play an useful role when a public health official wishes to ascertain that only a given proportion 1/m of the community is infected with the disease. Only the cases when the community size N follows the geometric, negative binomial or FISHER'S logarithmic series distributions are considered with the mathematics being manageable.     

柏小爪螨实验种群生命表的组建与分析

组建并分析了柏小爪螨实验种群生命表。在25℃恒温条件下,种群的内禀增长力rm为0．1274,周限增长率λ为1．1358／d,净增殖率Ro为12．8746代,平均世代周期T为20．0586d,种群增长一倍需要的时间t为5．4407d。     

A Life Table Regression Analysis for Complex Survey Data

A methodology for obtaining maximum likelihood estimates of life table regression coefficients from complex survey data is presented. Certain of the issues of writing a likelihood for survey data are presented and discussed. The proposed methodology includes consideration of the sampling design in any inference by using design based variance estimates for the parameters. An example is given using data from the 1973 United States National Survey of Family Growth.