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Results for “Optimum Population”

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At least 73 records · Page 4Linked to original sources
PubMed1988

City size, quality of life, and the urbanization deflator of the GNP: 1910-1984.

The authors attempt to determine the net effect of city size on quality of life by developing a welfare measure of urbanization. "The estimation procedure suggested in the theoretical part of the paper (section II) is implemented in the empirical part (section III) using 1980 census data from the [U.S.] PUMS (Public Use Micro Data Sample). The results indicate there is no single optimal city size, but rather a worst city size, and about 90 percent of the U.S. population reside in cities smaller than worst city size. If quality of life is related to the degree of urbanization, then long-term trends in the locational distribution of the population should be accounted for in any welfare-oriented measure of national income. One application of our results is, as indicated, the derivation of a GNP welfare deflator reflecting changes in the degree of urbanization (section IV). The findings suggest an urban deflator on the order of six to seven percentage points, which is steadily increasing at a rate of about half a percentage point per decade."

Americas↗
PubMed1985

Migration efficiency ratios and the optimal distribution of population.

The authors present a theoretical description of the migration process and criticize the conventional interpretation of the migration efficiency ratio, which is defined as the ratio of the net number of moves of individuals between areas to the gross number of moves that take place. "The conventional interpretation of the migration efficiency ratio is that the closer it lies to zero the less efficient the migration process....However, [the authors] feel that this is a somewhat misleading conception of the notion of efficiency in migration in that it emphasizes the physical efficiency of the migration process rather than focusing on the contribution of migration to a socially efficient allocation of population. Thus, to redirect attention, [they] have chosen to judge migration efficiency on the basis of its contribution to producing an equilibrium population distribution." The focus is on internal migration.

Demography↗
PubMedDate not supplied

Population dynamics and rural poverty.

An overview of the relationship between demographic factors and rural poverty in developing countries is presented. The author examines both the micro- and macro-level perspectives of this relationship and the determinants and consequences of population growth. The author notes the prospects for a rapid increase in the rural labor force and considers its implications for the agricultural production structure and the need for institutional change. Consideration is also given to the continuing demand for high fertility at the family level and the role of infant and child mortality in the poverty cycle. "The paper concludes by drawing attention to the need for developing the mechanism for reconciliation of social and individual optima with respect to family size and population growth." The need for rural development projects that take demographic factors into account is stressed as is the need for effective population programs. (summary in FRE, ITA)

Agriculture↗
PubMed1996

Dispersion of human Y chromosome haplotypes based on five microsatellites in global populations.

We have analyzed five microsatellite loci from the nonrecombining portion of the human Y chromosome in 15 diverse human populations to evaluate their usefulness in the reconstruction of human evolution and early male migrations. The results show that, in general, most populations have the same set of the most frequent alleles at these loci. Hypothetical ancestral haplotypes, reconstructed on the basis of these alleles and their close derivatives, are shared by multiple populations across racial and geographical boundaries. A network of the observed haplotypes is characterized by a lack of clustering of geographically proximal populations. In spite of this, few distinct clusters of closely related populations emerged in the network, which are associated with population-specific alleles. A tree based on allele frequencies also shows similar results. Lack of haplotypic structure associated with the presumed ancestral haplotypes consisting of individuals from almost all populations indicate a recent common ancestry and/or extensive male migration during human evolutionary history. The convergent nature of microsatellite mutation confounds population relationships. Optimum resolution of Y chromosome evolution will require the use of additional microsatellite loci and diallelic genetic markers with lower mutation rates.

Alleles↗
PubMed1983

Activation and germination characteristics observed in endospores of thermophilic strains of Bacillus.

The properties of endospores of some thermophilic strains of Bacillus were examined. Included were strains isolated from thermal pools and springs in Yellowstone National Park, a strain of B. thermodenitrificans and two strains of B. stearothermophilus, ATCC 7953 (smooth) and T-10. The spores of thermophilic strains of Bacillus contained relatively high levels of dipicolinic acid ranging from 11-14.8% of the spore dry weight, while the calcium levels were similar to those observed in other bacterial endospores including mesophilic bacilli and thermophilic actinomycetes. Spore populations of thermophilic bacilli could not be effectively germinated in solutions of sodium phosphate alone but germinated well in solutions supplemented with one of a variety of organic compounds. Solutions containing L-valine or L-leucine were particularly effective. A wide range of pH permitted the germination of fractions of spore populations, however, optimum germination was observed only at pH values of 6.0 and above. A range in incubation temperatures of less than 25 degrees C permitted 50% or more of the spores of each of the organisms to germinate. Freshly prepared spore did not germinate, but these spores germinated rapidly and completely if they were heated for 30 min at 100 degrees C just prior to germination testing, i.e., the spores were heat activatable. However, spores of thermophilic bacilli could also be activated by shifting them to and holding them at temperatures below their optimum growth temperature of 65 degrees C. Of the ten temperatures tested, ranging from 4 degrees C through 50 degrees C, the optimum reduced temperature for spore activation was 30 degrees C.

Bacillus↗