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"In this paper we [propose] a new procedure for estimating population density functions under conditions that the exact location of the CBD [central business district] is unknown or uncertain. As such it can also be utilized as a method for identifying the location of the CBD....[We apply] this method to cross-sectional data from Tel-Aviv-Yafo [Israel] during 1961 through 1990...."
Population density in plants and animals is thought to scale with size as a result of mass-related energy requirements. Variation in resources, however, naturally limits population density and may alter expected scaling patterns. We develop and test a general model for variation within and between species in population density across the order Carnivora. We find that 10,000 kilograms of prey supports about 90 kilograms of a given species of carnivore, irrespective of body mass, and that the ratio of carnivore number to prey biomass scales to the reciprocal of carnivore mass. Using mass-specific equations of prey productivity, we show that carnivore number per unit prey productivity scales to carnivore mass near -0.75, and that the scaling rule can predict population density across more than three orders of magnitude. The relationship provides a basis for identifying declining carnivore species that require conservation measures.
The paper presents data on the population density of active ticks in different landscape zones of West Sykhote-Alyn as well as the material on the absolute abundance of ticks in four experimental 400 m2 areas. The abundance of active Ixodes persulcatus and Haemaphysalis japonica on vegetation at the peak of their activity was found to amount to half of all hibernated adult ticks.
Mosquito surveillance was conducted near the Korean Demilitarized Zone (Paju County, Gyeonggi Province) from April to October, 1999, where malaria cases were reported. Adult mosquito surveillance, using black light and CDC UV light traps, was conducted at five and two sites, respectively. Weekly larval collections were made at five rice paddies located adjacent to the adult collection sites. Anopheles sinensis was the most abundant mosquito of 11 species collected throughout the surveillance period in 1999, comprising 47 - 48% of the total number of mosquitoes collected at cow sheds and residence. At all five sites surveyed by CDC UV light traps, anophelines appeared early in the year (May 3) and were most abundant in the cow sheds followed by the hillside forest, residence, stream/river bank, and were least abundant in rice fields. The population density of the larvae and the adults of An. sinensis increased steadily in June and reached their peaks during the second week of July (mean 112 females/trap/night). The parity rates were higher in July and September, when populations were highest. The probabilities of daily survival of An. sinensis were 0.804 in June to 0.895 in July. Cross-correlation showed a significant relationship between the number of adult anopheline mosquitoes and the number of larvae collected on the previous day, the same day, and also three and seven days later, which may be useful for determining treatment thresholds.
"Based on 1969 and 1982 census data, this paper examines the spatial association between high rural population density and development potential in Zimbabwe and its significance for national development policy. A 1982 grid cell density map was compiled on the same geographical frame as an existing 1969 density map, yielding an intercensal density change map. A land classification map and a composite map of development constraints were rasterized on the same spatial framework and subjected to computer analysis. Areas of critically high (and generally increasing) densities showed strong spatial associations with areas of severe development constraints...."
Two trials were conducted with broiler chicks to determine the effects of population density on the growth, feed efficiency, and several physiological parameters associated with stress in birds. Chicks were brooded in batteries at 116, 232, 348, and 697 cm2/chick. Chicks brooded at 348 cm2/chick grew and utilized feed significantly better than those brooded at 697 cm2/chick during the first week. For maximum growth and feed efficiency, 116 cm2/chick was adequate for the first week; 232 cm2/chick was adequate during the second and third weeks. Increasing cage density significantly decreased percentage heart and spleen weights (g/100 g body weight) and plasma corticosterone at 3 weeks.
We continued to study the diversity of responses of the grass moth Loxostege sticticalis L. to variations of density. We estimated the dynamics of the internal state of individuals and considered the influence of the population prehistory on ecological characteristics of the phytophage. In experiments on studying the structure of flower forms of the larval stage, we showed the dependence of the parameters of the internal state of individuals on prehistory, specifically on the conditions of life and type of individuals of the preceding generation. At the same time, comparison of the experimental results of 1991 and 1994 revealed a drift of the parameters of the reaction to variations in the grass moth population density by the structure of the larval flower forms and actual fertility of the imago. On the whole, the data obtained suggests that the studied species is characterized by a complex system of endogenous mechanisms underlying the regulation of numbers. The dynamics of environmental parameters is mediated by a cascade of endogenous rearrangements, as a result of which transition from depression to mass reproduction is realized through succession of the types of individuals in the population, when instead of a single phase, the flock phase starts to dominate.
An investigation of the present levels of inbreeding and the proportion of non-migrants (residents in municipality of birth) in rural districts of Norway reveals a relationship between these two characteristics. There is a steady upward trend from 0.39% first- and second-cousin marriages in municipalities with less than 50% non-migrants to 4.3% such consanguineous matings in municipalities where 85% or more of the inhabitants are non-migrants. There is also a significant negative correlation (rs=-0.86, N=18) between inbreeding and population density per square km by county in Norway. In rural districts of Norway maximum inbreeding is observed in sparsley populated areas with maximum proportion of non-migrants, and the ratio of second- to first-cousin marriages ranges between 3.4 and 4.1. A similar high ratio (3.7) is also encountered in densely populated trading and industrial municipalities and in the smaller towns, whereas the semi-urban municipalities and the larger towns have the lowest inbreeding recorded and also a low ratio (1.9). The lowest proportion of non-migrants (39.3%) is recorded in the semi-urban municipalities.
The specific breast cancer register created in 1988 in the Rhône department demonstrated a high incidence of breast cancer among the women who live in this department (world standardised incidence rate = 79.4). This report presents the results according to two geographical aspects: the urban or rural structure of the area of residence and the population density. These analysis demonstrated an association between the high incidence of female breast cancer and the urban character of the department. However the results of incidence in the urban and rural zone were heterogeneous. The high incidence of breast cancer in the North of the department corresponding to a vineyard region confirmed this association.
The influence of population density in the progression from the nonneoplastic to the neoplastic state has been reassessed. Two twice-cloned, nonneoplastic mouse lines, NCTC 7914 and 7915, were transferred each 3 to 4 days at inoculum sizes selected to minimize or maximize cell-cell contact, 1 X 10(5) or 4 X 10(5) cells/T-15, respectively. As tested by in vivo assay, the regime designed to minimize cell-cell contact did not reproducibly delay transformation, and tumor production was observed in all lines, irrespective of inoculum size. Also, results of tumorigenesis assays correlated with blind evaluation of morphological and cytological alterations, growth in agarose, and susceptibility to killing by activated macrophages. Generally higher saturation densities were seen as a function of period in culture, and no significant differences in glucose utilization or lactic acid production were observed between nonneoplastic and neoplastic cell populations.
The eradication of smallpox was achieved by surveillance and containment vaccination after the failure of mass immunization campaigns. The reasons for this failure are considered in this paper. Comparison of population densities in the Indian subcontinent and Africa show that in highly populated areas even an 80% vaccine coverage will still leave a density of susceptibles high enough to maintain the disease, a finding with important implications for other vaccine campaigns.
I derive two new statistics, Ipop and Ipop*, that adjust Moran's I to study clustering of disease cases in areas (for example, counties) with different, known population densities. A simulation of Lyme disease in Georgia suggests that these new statistics can be more powerful than those currently in use. This is because they consider both spatial pattern and non-binomial variance in rates as evidence supporting disease clusters.
In theory there should be a strong coupling between host and parasite population sizes. Here, we investigated population size and structure in 3 species of acanthocephalans, Corynosoma semerne, C. strumosum and C. magdaleni, in ringed seals (Phoca hispida) from the Bothnian Bay over a period of more than 20 years. During this period, seal numbers first decreased markedly and then increased steadily; at the same time, a paratenic fish host particularly important for C. strumosum has gradually disappeared from the bay due to decreasing salinity. We found no evidence that the mean abundance of any of the 3 acanthocephalan species changed significantly over time, nor was there any relationship between parasite abundance at any point in time and seal numbers in the corresponding year. Based on the proportion of sexually mature female worms per infrapopulation, and on relationships between the sex ratio of worms and infrapopulation size, both C. magdaleni and C. semerme appear to be doing well, independently of the population size of their seal definitive hosts. In contrast, perhaps because of the loss of its main paratenic host, C. strumosum appears more at risk in the Bothnian Bay. Our results show that in complex natural systems, there are not necessarily simple, direct links between definitive host population size or density, and parasite population dynamics.
Previous reports have demonstrated that stressful stimuli markedly influenced physiological conditions and homeostasis. In this study, we examined the influence of high population density environment on barrier function and water retention property of skin in mice. Overcrowding stress induced dramatic body weight reduction and significant increase in adrenal gland weight. Macroscopic skin appearance showed moderate exfoliation and slight wrinkle formation in the stress group. Moreover epidermis hyperplasia not concomitant with inflammatory reactions such as infiltration of immunocytes and vasodilation was observed in the skin from the stress group. Skin surface conductance in the stress group was significantly lower than in the control group. On the other hand, transepidermal water loss in the stress group increased significantly, compared to the control group. Moreover, transdermal penetration of indomethacin and nicotinic acid amide was enhanced significantly. These results suggest that overcrowding stress induced impairment of barrier function and water retention property. To elucidate the mechanism of overcrowding stress-induce dry skin, contents of ceramide and pyrrolidone carboxylic acid, which are the important compounds contributing to those functions were evaluated. Both of them in stratum corneum declined significantly in the stress group. Taken together, these results demonstrate that overcrowding stress induced dry skin, and that the impairment of barrier function and water retention property correlated with decrease in ceramide and pyrrolidone carboxylic acid.
We examined the importance of pig-population density in the area of an outbreak of classical swine fever (CSF) for the spread of the infection and the choice of control measures. A spatial, stochastic, dynamic epidemiological simulation model linked to a sector-level market-and-trade model for The Netherlands were used. Outbreaks in sparsely and densely populated areas were compared under four different control strategies and with two alternative trade assumptions. The obligatory control strategy required by current EU legislation was predicted to be enough to eradicate an epidemic starting in an area with sparse pig population. By contrast, additional control measures would be necessary if the outbreak began in an area with high pig density. The economic consequences of using preventive slaughter rather than emergency vaccination as an additional control measure depended strongly on the reactions of trading partners. Reducing the number of animal movements significantly reduced the size and length of epidemics in areas with high pig density. The phenomenon of carrier piglets was included in the model with realistic probabilities of infection by this route, but it made a negligible contribution to the spread of the infection.
The ciliated protozoan, Tetrahymena pyriformis strain GL-C, has been used to study the effect of cell population density during starvation on the synchrony obtained after refeeding and on the number of cells arrested in G2 phase of the cell cycle. At high cell densities two peaks of division indices were observed after refeeding while only one was observed at low cell densities. Cell division began earlier in cultures starved at high cell densities. Most importantly, the proportion of cells in G2 was considerably higher in populations starved at high cell densities. When tritiated thymidine was present during the refeeding period, radioautographs of cell samples at different times showed that the first cells to exhibit division furrows contained unlabeled nuclei. The first peak in the division index after refeeding was observed only at higher cell densities and is attributed to the cells arrested in G2. These results suggest that Tetrahymena is an excellent organism to study the concept of resting stages in the cell cycle and their control.
119 community clusters assembled from contiguous census tracts are investigated in an ecologic study, using as the dependent variable age-adjusted lung cancer in both sexes, 1970 (CA); independent variables are: population density (PD), % white (Anglo) (WH), % Spanish surname (SP), % black (BL), % Oriental (OR), mean income per capita (IN), % of dwelling units with 1+ persons/room (CR), % annoyed by air pollution 1956 (AP), and male/female population ages 55-64 (M/F). Except for CA and AP all data are from 1970 census, compiled by John Chapman and Anne Coulson. Variables given in percent except for AP are arcsine transformed in order to more closely approximate Gaussian normality. AP is approximately normal already. The association of CA with AP is negative and small, and inclusion of other variables and structures never leads to an interesting or significant association. Positive associations with CA are with PD (r = 0.300) and WH (0.228). M/F has the highest negative association with CA (-0.285), and is positively associated with WH (0.273) and IN (0.388). M/F has a strong negative association with PD (-0.549). CR is negatively associated with CA (-0.173). In testing for the independent contribution of PD, we use the strategy of testing whether divergent methods give convergent results. Path analysis is used to reflect a number of structural assumptions among independent variables, and the association of CA and PD remains consistent and positive. After recoding the variables PD, WH, SP, BL, OR, IN, and CR into five classes of 20 and one of 19, a multiple classification analysis (MCA) is performed, using MF as a continuous co-variable. Although the unadjusted PD has a slightly greater eta than the other variables, WH and IN have a larger beta after adjustment, and the multiple R is similar to that found by path analysis, reflecting explained variance of about 0.5. The deviations of PD, CR, and BL are not monotonic but those of WH and IN are. Analysis is repeated for the 20 communities with highest IN and for the 20 with lowest IN, and the correlations (r) of CA with PD are 0.561 and 0.376 respectively. For the 20 communities with highest proportion SP, the association is a non-significant 0.108, for the 20 with highest BL, it is 0.196 and for the the 40 highest WH, the CA association with PD is 0.772. Data for the 40 most white communities are presented in a path analysis.(ABSTRACT TRUNCATED AT 400 WORDS)
Data from the medical birth registries in Norway and Sweden were used to study geographical variations in perinatal mortality in the two countries. The study population comprised 1.4 million single births during 1975-79 and 1985-88. Perinatal death (n=9,834) for infants with a birthweight of 1,000 g or more was the main measure of outcome. In both periods and in both countries, perinatal mortality was inversely associated with population density and annual number of births, with relative risks amounting to 1.4 in Norway and 1.2 in Sweden. Among live births, these gradients were observed in deaths from asphyxia or immaturity in the first time period, and in deaths from congenital malformations in the second time period. As care for premature infants and infants with respiratory problems improves, geographical variations in perinatal mortality may to a larger extent depend on differences in medical care of infants affected by congenital malformations as well as differences in efforts to reduce the prevalence at birth of serious congenital malformations.