Some examples of a method for determining key factors from life table data

Summary The method of Manly (1977) for determining key factors in the life cycle of animal populations is illustrated on several sets of published data.     

Competing risk analysis for life table data with known observation times

"Several models have been proposed for the analysis of cohort mortality in the presence of competing risks.... This paper describes a maximum likelihood approach to the analysis of follow up data in life table format for the case of two competing risks--a specific cause and its competing complement. The model developed uses a robust survivorship assumption--the piecewise exponential--and takes into account information on time to death and time to withdrawal." (summary in GER)     

A general theory of life table construction and a precise abridged life table method

"In this paper we lay the foundation of life table construction by unifying the existing life table methods. We also present a new method of constructing current (period) abridged life tables.... The development includes (1) a careful formulation and computation of age-specific death rates, (2) derivation of a new set of formulas for computing the survivorship function from the observed age-specific death rates and populations, (3) estimation of the main life table functions by spline interpolation, integration and differentiation, and (4) use of a quadratic and a Gompertz function to close the life table.... The method is illustrated with construction of abridged life tables using Canadian data."     

Model life table for captive chimpanzees

Mortality statistics from three captive populations of chimpanzees (Pan troglodytes) were combined to generate standard model life tables for each sex in this species. The model is compared to an estimate of survivorship of a group of wild animals, and is applied to an incomplete data set to illustrate how the model may be used to extend estimates of mortality statistics to missing older ages. © 1995 Wiley-Liss, Inc.     

The influence of temperature on the life table of Hyperaspis notata

The coccinellid Hyperaspis notata Mulsant was introduced into Africa for the biological control of the cassava mealybug, Phenacoccus manihoti Matile-Ferrero. Two cohorts of strains, one originating from Southern Brazil and Paraguay feeding on P. manihoti, and one from Colombia feeding on Phenacoccus herreni Cox & Williams were studied at different temperatures between 15 and 34 °C and age-specific life tables were constructed. Although in the areas of origin the climatical conditions and the food sources are different, the survivorship and developmental times at the same temperature differed little among the two strains, the Colombian strain being slightly more tolerant to high temperatures. Jacknife estimates of the intrinsic rates of increase (rm) peaked very close to 30 °C for the two strains.     

The effects of extra chances to live on life table functions

A decline in mortality can be described as a process according to which the earlier forces of mortality become what has been defined here as the forces of debility. The main thesis is that individuals contract debilitating conditions now with the same force that used to result in deaths in the past. The difference in the two situations is that in the latter period, a certain proportion of the population can recover and thus escape death. Based on these assumptions, the relationships between the initial and the resulting life table functions have been developed in this paper. Among other things, the relative gain in life expectancy has been found to be inversely related to its initial value. Further, interesting results are obtained when a fixed proportion of the population can manage to survive a debilitating condition only once, only twice and so on. The limiting situation has been found to be equivalent to one in which the initial forces of mortality at all ages are reduced by a constant proportion.     

In situ life table of a subtropical copepod

• 1 A life table of a subtropical population of Mesocyclops edax(Copepoda: Cyclopoida) was constructed from a cohort of individuals reared in enclosures in a small, eutrophic lake.
• 2 The lake population was sampled concurrently to determine age structure, per capita birth, death and growth rates, body size and clutch size.
• 3 Maturation times of enclosed males and females were 9.3 and 11.4 days, respectively. The population growth rate. r. was estimated to be 0.18 females day^-1 for the enclosed population, but approximated zero on most dates in the lake population. Mortality was low in the enclosures which excluded predators and high in the field population exposed to planktivorous fish and Chaoborus.
• 4 The means and variances of several fitness traits are related to the specific environment. The enclosure approach promises to be a useful tool in the study of zooplankton life history variation.

     

The simulation of aerial movement--I. The determination of orientation angles from film data

Quantitative mechanical analyses of human movement require the time histories of the angles which specify body configuration and orientation. When these angles are obtained from a filmed performance they may be used to evaluate the accuracy of a simulation model. This paper presents a method of determining orientation angles and their rates of change from film data. The stages used comprise the synchronization of data obtained from two camera views, the determination of three-dimensional coordinates of joint centres, the calculation of an angle from a sequence of sine and cosine values and the curve fitting of angles using quintic splines. For each stage, other possible approaches are discussed. Original procedures are presented for obtaining individual error estimates of both the film data and the calculated angles to permit the automatic fitting of quintic splines for interpolation and differentiation and for deriving the time history of an angle as a continuous function from a sequence of sine and cosine values. The method is applied to a forward somersault with 1 1/2 twists and the average error estimate of 17 orientation angles is obtained as 2.1 degrees.     

Village composition implied by a paleodemographic life table: The Libben Site

Lovejoy and colleagues excavated some 1327 skeletons deposited around 800 to 1100 A.D. at a site near Lake Erie in Ohio, called Libben. Examination of the implications of the life table presented for the living group which produced the cemetery shows that it would have had to be an extremely young population, in which many of the children would be orphans, in which the adults would have had to work hard and effectively to support the group, and almost none of whom would have lived long enough to become grandparents. The unusual and implausible features of the population structure can be interpreted as direct evidence on prehistoric living conditions, or alternatively, as a caution that the life table may include sources of error or bias.     

Marriage and mortality: a life table analysis

This paper examines the effects of age at marriage and differential mortality of males and females on the incidence of widowhood between the sexes. Abridged life tables constructed from marital status and death registration data of a rural area of Bangladesh for the period 1974-79 were used. The difference in life expectancy between males and females varies from 0.4 to 2.2 years at the ages 0 to 65 years and over. The mortality differentials show that the probabilities of a male or a female surviving the other spouse would be approximately the same, were there no other influence. But the incidence of widows is about ten times that of widowers. Other relevant factors, under a given regime of mortality, are age at marriage and age difference between husband and wife.     

暗黑齿爪鳃金龟室内种群生命表

组建了室内自然温湿条件下暗黑齿爪鳃金龟的生命期望表和生殖力表。室温下测得该虫的内禀增长率（rm）为0．0106,周限增长率（λ）为1．0107,净增殖率（R_0）为2．2277。模拟了该虫世代种群存活率曲线为Weibull分布曲线I型:Sp（t）＝exP[－（t／2．7082）~(4.6827],种群自然增长过程符合二次三项式,logy＝a＋bx＋cx~2。经验曲线方程：logy＝0．6689＋0．3264。－0．0243x~2。     

Starvation tolerance of rotifers produced from parthenogenetic eggs and from diapausing eggs: a life table approach

Monogonont rotifers have to cope with environmental variationby producing diapausing stages. Cyclically, parthenogeneticrotifers produce females by (i) parthenogenetic eggs and (ii)sexually produced eggs. Parthenogenetic eggs hatch shortly afterovoposition, frequently while they are carried by their mothers.Sexual eggs go into dormancy and hatch in the sediment, in responseto specific environmental cues. Therefore, it is expected thatpost-diapause and parthenogenetic offspring would face differentenvironments. Moreover, resource allocation is higher in diapausingeggs than in parthenogenetic eggs. In this study, the responseto starvation of females obtained from parthenogenetic eggsand from diapausing eggs of the rotifer Brachionus plicatiliswas compared. Starved individuals showed unexpectedly long maximumlongevity (12 days). The average lifespan and the lifespan varianceof individuals hatched from parthenogenetic eggs were higherthan those of individuals hatched from diapausing eggs. Contrastingwith a previous experimental finding, our results do not supportthe hypothesis that high resource allocation in diapausing eggscauses high starvation tolerance. Lower survival of individualshatched from diapausing eggs could be caused by the diversionof energy to other functions (i.e. maintenance during diapauseor the hatching event), or the result of the variance in theallocation of resources in parthenogenetic eggs. We hypothesizethat resource allocation in diapausing eggs follows a conservativepattern, while it is more opportunistic in parthenogenetic eggs. This paper was presented at Plankton Symposium III, held atFiguera da Foz, Portugal between 17 and 20 March 2005, underthe auspices of the University of Coimbra and the Universityof Aveiro, and coordinated by Mário Jorge Pereira andUlisses M. Azeiteiro.     

The determination of the conformational properties of nucleic acids in solution from NMR data

A program, NUCFIT, has been written for simulating the effects of conformational averaging on nuclear Overhauser enhancement (NOE) intensities for the spin systems found in nucleic acids. Arbitrary structures can be generated, and the NOE time courses can be calculated for truncated one-dimensional NOEs, two-dimensional NOE and rotating frame NOE spectroscopy (NOESY and ROESY) experiments. Both isotropic and anisotropic molecular rotation can be treated, using Woessner's formalism (J. Chem. Phys. (1962) 37, 647-654). The effects of slow conformational averaging are simulated by taking population-weighted means of the conformations present. Rapid motions are allowed for by using order parameters which can be supplied by the user, or calculated for specific motional models using the formalism of Tropp (J. Chem. Phys. (1980) 72, 6035-6043). NOE time courses have been simulated for a wide variety of conformations and used to determine the quality of structure determinations using NMR data for nucleic acids. The program also allows grid-searching with least-squares fitting of structures to experimental data, including the effects of spin-diffusion, conformational averaging and rapid internal motions. The effects of variation of intra and internucleotide conformational parameters on NOE intensities has been systematically explored. It is found that (i) the conformation of nucleotides is well determined by realistic NOE data sets, (ii) some of the helical parameters, particularly the base pair roll, are poorly determined even for extensive, noise-free data sets, (iii) conformational averaging of the sugars by pseudorotation has at most second-order influence on the determination of other parameters and (iv) averaging about the glycosidic torsion bond also has, in most cases, an insignificant effect on the determination of the conformation of nucleotides.     

荔枝蝽的实验种群生命表

通过田间笼罩试验 ,排除天敌等生物因子的作用 ,建立了荔枝蝽实验种群生命表 ,分析结果表明 ,荔枝蝽产卵期可持续 1 8周 ,产卵概率呈明显的偏态分布 ,且出现 2个产卵高峰 ;各虫态自然存活率很高 ,均在 95 %以上 ,其实验种群趋势的指数约为 84 0。