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Results for “Stationary Population”

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At least 19 recordsLinked to original sources
PubMed1992

Immigrant's ages and the structure of stationary populations with below-replacement fertility.

A sustained regime of low fertility plus immigration yields an unusual kind of stationary population. The author demonstrates that all stationary populations have a common structure, and that the familiar replacement-level fertility population is the youngest among the many stationary populations corresponding to a particular life table. This finding has important consequences for policy because although fertility increase and immigration are equally effective at halting population decline, immigration is inferior as a means of rejuvenating low-fertility populations. In fact, an immigration-based policy could make a low-fertility population older rather than younger. The paper includes examples using U.S. and West German vital rates.

Adolescent↗
PubMedDate not supplied

[The correlation of the indices of animal longevity and mortality in stationary populations with a constant rate of mortality].

Equations have been derived on the basis of general ratios of the numbers of different age groups of animals that allow to estimate the mortality coefficient in populations with stationary age structure and intensity of mortality that does not depend on age at their continuous and discontinuous replenishing by frequency of occurrence of individuals of the maximal age. The proposed method of estimation of mortality has been tested on models with different numbers of animals and age classes. The equation gives a non-biased estimate of mortality coefficient for populations with discontinuous replenishing with young individuals at very small sample sizes (less than 10 individuals).

Aging↗
PubMed1995

Statistical inference in stationary populations.

A fixed ensemble of alternating renewal processes is proposed as a model for stationary populations. This model is applied to explore the relationship between survival times and forward recurrence times. In addition, it is shown that ergodic theory can be applied to the model. An example is presented.

Biometry↗
PubMed1977

Toward stationary populations and beyond.

The world's rate of population growth is declining. Most industrialized societies have achieved or are moving rapidly toward stationary populations, but while birth rates are also declining in many developing countries, continued growth must be expected because of the large proportions of young people in these populations. New evidence of exceptions to the classical demographic transition theory indicate that declining fertility is compatible with high mortality or low socioeconomic development if acceptable means of fertility control are readily available. "Fertility silhouettes" showing differing age-specific fertility rates indicate that present family planning programs have had a demographic impact. A review of the economic and ecologic consequences of rapid population growth justifies the conclusion that considerable effort will be required to again bring the world's population into balance with these systems. The author outlines priorities for this effort, with emphasis on the need to devise acceptable means of fertility control that will not tax the frail health care infrastructures of developing countries.

Adolescent↗
PubMed1999

Network of characterizing functions for stationary populations.

A variety of open systems in nature and society exist under dynamic equilibrium, maintained by statistical counterbalance between the entering and leaving of individuals and the stationarity of the exchange processes. A network of functions characterizing the dynamics of such a stationary population is established and discussed, which allows the mutual transference of system properties without the need of any explicit information about the microdynamic processes. In order to illustrate the potential benefit of these interdependence relations, examples taken from diverse branches of research (adsorption and reaction kinetics, demographic analysis, and coronary blood flow diagnosis) are given.

Journal Article↗
PubMed1978

[Stationary populations of genetically different homonuclear strains of human cells].

Morphological and cytophysiological indices of cells and cellular populations were studied during this stationary phase. In difference from normal cell strains which displayed a definite complex of ontogenetic changes, cells of the strains with chromosomal and gene mutations showed individual differences apparently caused by disturbed differentiation and by expression of features characteristic of malignant cells.

Cell Line↗
PubMed1977

Cell proliferation kinetics and drug sensitivity of exponential and stationary populations of cultured L1210 cells.

Drug sensitivity and cell cycle parameters of L1210 cells in culture in exponential (10(5) to 4 x 10(5) cells/ml) and plateau phase (greater than 8 x 10(5) cells/ml) of growth were compared. The percentage of cells in G1, S, and G2 + M for exponential and plateau-phase cultures was 24.1, 70.0, and 5.9, and 42.5, 45.6, and 11.9, respectively. These values correspond to those reported previously for early and late L1210 mouse leukemia cells. Cell survival (measured by cloning) after drug exposure showed that actinomycin D, 1-(2-chloroethyl)-3-cyclohexyl-1-nitrosourea, chlorozotocin, and streptozocin were all equally lethal to cells in both phases, and 1-beta-D-arabinofuranosylcytosine, high-specific-activity (20Ci/mmole) [3H]thymidine, vincristine, daunomycin, adriamycin, and 5-fluorouracil were more lethal to exponential cells than to plateau-phase cells. The percentage kill by S-phase-specific agents such as 1-beta-D-arabinofuranosylcytosine and[3H]thymidine corresponded well with the percentage of cells in S. Finally, 1,3-bis(2-chloroethyl)-1-nitrosourea was more toxic to plateau cells than to exponential cells.

Amino Acids↗