An index of spatial distribution

Summary The index , which takes the value of −1 for a perfectly regular distribution, +1 for a highly aggregated distribution and 0 for the distribution implied by the theoretical varianceσ ², is proposed and a significance table provided.     

A distance measure of spatial pattern in a biological population

Summary Suppose thatn individuals locate independently and randomly on a segment of line of finite length (habitat). Let the theoretical and observed ranges of the sites of the individuals on the segment be μ _n-1 andr _n-1, respectively. Then, the degree of dispersion of the individual sites is measured by the ratio, T _n =n _n-1/μ _n-1, as follows: A random spatial pattern forI _r−1 =1 An aggregated spatial pattern for 0≤I _r <1 A uniform spatial pattern for (n+1)/(n−1)≥I _r >1. Another method was derived. Let the probability that an observed range is less thanr _n−1 beI _p , under the hypothesis of a Beta distribution. Then indicates A random spatial pattern forI _p =1/2 An aggregated spatial pattern forI _p <1/2 A uniform spatial pattern forI _p >1/2. The first index can be used for comparing populations having the same number of individuals, whereas the second one can be used for comparing populations with different numbers of individuals.     

Analysis of spatial association between two species based on the interspecies mean crowding

Summary and Conclusion The measurement of spatial association between two species is considered on the basis of interspecies mean crowding. Two indices of overlapping, γ andC _p, are derived as geometric and weighted arithmetic means of the same component ratios related to inter-and intraspecies mean crowdings. Both indices behave in a similar way, ranging from 1 when the distributions of two species are completely overlapped to 0 when they are completely exclusive with each other. The former is essentially identical with indices proposed byKuno (1968) andPianka (1973), and the latter is a modified form ofMorisita's (1959)C _σ index. Indices to measure the degree of spatial correlation between species, Ω andR _μ, are then derived for both kinds of overlapping indices, which vary from 1 in complete overlapping, through 0 in independent occurrence, to −1 in complete exclusion. Various kinds of interspecies association are analyzed using these indices and an extended form of the regression graph which provides a convenient way of indicating the spatial interrelation between two species as well as distribution patterns of respective species. The method presented in this paper may also be applicable to compare temporal distribution patterns between species, similarity between communities, etc. For such a wider application which includes continuous as well as discrete distributions, the interpretation of intra-and interspecies mean crowdings is not necessarily appropriate, and hence the concept of mean concentration with the symbols and for intraspecies relation and and for interspecies relation is suggested. This study was supported by Science Research Fund (No. 148041) from the Ministry of Education.     

On the momentum of population growth

If age-specific birth rates drop immediately to the level of bare replacement the ultimate stationary number of a population will be given by (9): $$\left( {{\textstyle{{b\mathop e\limits^ \bullet {}_0} \over {r\mu }}}} \right)\left( {\frac{{R_0 - 1}}{{R_0 }}} \right)$$ multiplied by the present number, where b is the birth rate, r the rate of increase, \(\mathop e\limits^ \bullet _0 \) the expectation of life, and R ₀ the Net Reproduction Rate, all before the drop in fertility, and μ the mean age of childbearing afterwards. This expression is derived in the first place for females on the stable assumption; extension to both sexes is provided, and comparison with real populations shows the numerical error to be small where fertility has not yet started to drop. The result (9) tells how the lower limit of the ultimate population depends on parameters of the existing population, and for values typical of underdeveloped countries works out to about 1. 6. If a delay of 15 years occurs before the drop of the birth rate to replacement the population will multiply by over 2. 5 before attaining stationarity. The ultimate population actually reached will be higher insofar as death rates continue to improve. If stability cannot be assumed the ultimate stationary population is provided by the more general expression (7), which is still easier to calculate than a detailed projection.     

Variations on two themes: Racial and ethnic patterns in the attainment of suburban residence

To investigate racial and ethnic diversity in suburbanization, we draw on two complementary theoretical traditions, which we label "assimilation" and "stratification." Our analytic model is multilevel, and includes variables characterizing individuals, households, and metropolitan contexts. We use it to analyze the determinants of suburban versus central-city residence for 11 racial/ethnic groups. The analysis reveals that family status, socioeconomic, and assimilation variables influence the suburbanization process rather consistently. We take this finding as evidence in favor of the assimilation model. These effects display group variations, however, in a manner predicted by the stratification model. There are also suburbanization differences among metropolitan areas, particularly related to the relative economic status of cities and their suburbs, and between the northeast/north central regions and the south/west. Finally, we conclude that suburbanization is variable across the groups in a way that is not captured by broad categories such as "Asian" or "Hispanic."     

A note on the time spent on the journey to work

The notions that most people travel to the center of the city to work and that the farther out they live the longer it takes are only appropriate for middle-sized cities. In larger urban areas, many people work outside the center, and it is the speed of travel which most affects the time that it takes to get to work. As a result, those who live in the central cities of the twelve largest metropolitan areas spend the longest time getting to work and back, because the closer one is to the center and the larger the urban area, the slower the travel speeds.     

Future warming for U.S. cities

In this study, a model is developed to predict future warming for metropolitan areas in the United Sates to the year 2035. According to model results, most U.S. cities of 200,000 population or more can expect significant local warming. The average predicted warming for 104 cities analyzed is .34 degrees Farenheit. The greatest warming can be expected in sunbelt cities experiencing rapid population growth. Such localized warming is in addition to any heating which might occur from an enhanced greenhouse effect. Most cities can expect changes in energy demand, human health, and water supply.The author wishes to thank Stuart Simpson of the George Washington University's Center for Administrative and Academic Computing for his generous support and cooperation.     

Variability of Travel Time,Congestion, and the Cost of Travel

The variability of travel time modifies the rush hour traffic and the cost of commuting. The bottleneck model of road congestion with fixed peak-load demand is augmented of an additive random delay. When individuals have (α-β-γ) preferences, there exists a unique Nash equilibrium. The variability of travel time leads to departure rates that are spread more evenly over the rush hour than when travel times are deterministic. This equilibrium mechanism mitigates both congestion and the cost of unreliability. This implies that “single-traveler models,” which treat congestion as an exogenous phenomenon, overestimate the value of reliability for the rush hour. The application with the uniform or with the exponential distribution helps appraise the overestimation.     

Preliminary studies on the respiratory energy loss of a spider,Lycosa pseudoannulata

Summary To elucidate the basic food requirement of spiders, the important polyphagous predators of rice-plant insect pests, an attempt was made to measure the respiratory energy loss of fasting spiders,Lycosa pseudoannulata. Relationship between fresh (y) and dry (x) weights of spiders inhabiting the bottom layer of the rice-plant community was represented by the following allometric equation:y=0.428x ^0.872. The carbon dioxide production by previously fed and unfed females under the dark at 29°C 100% R. H. was measured by a titration technique. The relationship between fresh body weight and CO₂ production by unfed animals could be represented by the equationM=aW ^b, M being the CO₂ output per individual per day andW the fresh body weight. The constantb, which determines the slope of curve, was 0.808. Respiration of the adult female with 100 mg fresh weight was 1.155±0.250 mg CO₂/100 g fresh weight/day or 48.69 mg CO₂/g dry weight/day. This value corresponds to 35.81 cal/g fresh weight/day or 150.94 cal/g dry weight/day. Supposing the calorific content of spiders to be 5820 cal/g dry weight, rate of the respiratory energy loss to total energy of the body was estimated to be 2.60%. This rate did not strongly contradict with the loss of fresh body weight before and after the measurement. The metabolic rate showed remarkable fluctuation with changing food supply. The CO₂ production of starved individuals decreased to 83.63±16.34% as compared with individuals which were fed before the measurement.     

A simple method for projecting or estimating α and β: An extension of the Brass Relational Gompertz Fertility Model

This paper proposes a simple method that analytically links the parameters and , which are not demographically interpretableand measurable in the Brass Relational Gompertz Fertility Model, with demographic measures of median age and interquartile range. We also extend the Brass model that deals only with age-specific fertility to age-parity-specific fertility, first marriage, divorce, remarriage, and leaving the parental home. The method has been successfully tested by fittings to 180 reliable observed demographic schedules in various countries and periods, and to nearly 10,000simulated schedules with various combinations of possible values (including the extremes) of and . Our proposed method that uses median age and interquartile range instead of and as input is useful in the population and family household projections. It releases the traditionalunrealistic assumption in population projections that the curve of the fertility schedule moves to the right or left in a parallel way. Instead, using our proposed method, one can assume that the demographic events would be delayed or advanced, while the curve becomes more spread or more concentrated, or, more specifically, assume that young people delay the events more than the older persons do, or vice versa. Our proposed method is also useful to formulate assumptions on future demographic trends for purposes of policy analysisand planning. It can be used to indirectly estimate demographic schedules when the detailed age-specific data are not currently available, which is useful for developing countries and sub-region studies in developed countries. A crucial point for a successful application of the method is that the standard schedule chosen can capture the general pattern of the demographic process in the population under study.     

The rôle of density as a factor in metropolitan growth in the United States of America

U.S. Census data are used to show that, as the density of a metropolis increases there is a concomitant increase in the movement of population to the suburbs. This relationship is closest for small metropolitan areas. As size of the area increases, the closeness of the relationship decreases until it reverses—the largest areas actually show a slight decline in metropolitanization when density goes up. It is concluded that metropolitan expansion has definite bounds set by technological factors which place a limit on the distance that the commuter can reasonably travel daily.

For cities with populations of less than 500,000 there is a correlation of near zero between size of population and density. Such cities therefore maintain a constant density. But for cities with larger populations, size of population and density rise together.

It is concluded that small cities undergo metropolitan expansion with ease. Distances are within technological limits and any increase in population is reflected in an increase in area. But when a certain area is reached, further expansion is curtailed with a resultant increase in internal density. The net result is a stopping or slowing down of the metropolitan process.     

Networks Versus Need: Drivers of Urban Out-Migration in the Brazilian Amazon

As urbanization rates rise globally, it becomes increasingly important to understand the factors associated with urban out-migration. In this paper, we examine the drivers of urban out-migration among young adults in two medium-sized cities in the Brazilian Amazon—Altamira and Santarém—focusing on the roles of social capital, human capital, and socioeconomic deprivation. Using household survey data from 1,293 individuals in the two cities, we employ an event history model to assess factors associated with migration and a binary logit model to understand factors associated with remitting behavior. We find that in Altamira, migration tends to be an individual-level opportunistic strategy fostered by extra-local family networks, while in Santarém, migration tends to be a household-level strategy driven by socioeconomic deprivation and accompanied by remittances. These results indicate that urban out-migration in Brazil is a diverse social process, and that the relative roles of extra-local networks versus economic need can function quite differently between geographically proximate but historically and socioeconomically distinct cities.     

HIV diffusion patterns and mobility: Gender differences among drug users

Researchers have recently expanded the scope of study of transmission patterns of AIDS to incorporate spatial and geographical questions. United States diffusion patterns of this disease appear to indicate that it may emanate from urban area epicenters to areas of low and moderate prevalence. The travel patterns of injecting drug users (IDUs) and the extent to which they engage in high risk drug and sexual activities was examined as an explanation of diffusion of the HIV virus from one community to another. The study population of 49,621 was comprised of subjects recruited from approximately 60 sites nationwide from 1988–1991. While the data are limited in some ways, they partially support a diffusion explanation of HIV transmission for males and females. The analysis demonstrates that low prevalence cities were significantly more likely to have been the destinations of both men and women who engaged in high risk drug and sexual activities. In addition, HIV seropositive drug users who engaged in high risk drug and sexual behaviors in destination cities were more likely than seronegatives to travel to high or low seroprevalence areas than to moderate prevalence areas. The findings suggest a need for effective HIV prevention educational messages about the risks of traveling and participating in high risk activities.     

Transfers to the old,government debt and demographic change

In this paper we take the view that policy makers (representing the interests of the living generations in one way or another) take the relationship between (explicit) intergenerational transfer systems (including public pension schemes) and government deficits into account. It is assumed that policy makers are behaving altruistically towards past and future generations. Given the behavioral model, an analysis is made of the effects of demographic changes (such as the baby-boom of the 1940s and 1950s and the decline of birth rates in the 1970s) on the decisions to be taken with respect to the tax rate of the public pension system and the size of government debt. From the analysis it appears that, with the assumption of altruistic decision-makers, periods of increasing or decreasing debt can occur alternately in periods of demographic change.     

Measuring the Effect of Tourism Services on Travelers’ Quality of Life: Further Validation

Neal, Sirgy and Uysal (1999) developed a model and a measure to capture the effect of tourism services on travelers quality of life (QOL). They hypothesized that travelers overall life satisfaction is derived from satisfaction with the primary life domains (e.g., family, job, health). Specifically, overall life satisfaction is derived from two sources of satisfaction, namely satisfaction with non-leisure life domains and satisfaction with leisure life. Satisfaction with leisure life is derived from satisfaction with leisure experiences that take place at home and satisfaction with travel/tourism experiences. Satisfaction with travel/tourism experiences results from satisfaction with trip reflections of the traveler (e.g., what the traveler remembers regarding perceived freedomfrom control, perceived freedom from work, involvement, arousal, mastery, and spontaneity experienced during the trip) and satisfaction with travel/tourism services. Satisfaction with travel/tourism services was hypothesized further to be derived from satisfaction with the service aspects of travel/tourism phases – pre-trip services, en-route services, destination services, and return-trip services. The model was tested using a study of university faculty and staff. The original model was extended by hypothesizing the moderation effect of length of stay. Specifically, we hypothesized that the relationshipsin the model are likely to be more evident in relation to travelers who have more time to experience the tourism services than those who do not. A survey of 815 consumers of travel/tourism services who reside in Southwest Virginia was conducted. As predicted, the data confirmed hypotheses as established in the original model. Satisfaction with tourism services affects travelers QOL through the mediating effects of satisfaction with travel/tourism experiences, and satisfaction with leisure life. Furthermore, the moderating effect of length of stay was confirmed by the data. In sum, this replication and extension study provided additional validational support of the original tourism services satisfaction measure in relation to QOL-related measures.     

Some population characteristics of villages differentiated by size,location, and growth

Selected social characteristics of individuals were examined for groups of villages simultaneously dichotomized by size, location relative to larger cities, and population change. The percent of people having a selected characteristic in each village group of the resulting eight-fold classification was taken as the dependent variable, and difference scores indicating main effects and first order interactions were obtained for each characteristic. The universe is the 375 incorporated places under 2500 in 1950outside the SMSAs of Wisconsin. Size of place was found to be important for the sex ratio, education and income levels, and labor force and occupational variables. Characteristics associated with nearness to a large city included income, male labor force participation, occupation, and industry. Growth was important for age and sex differences, education, income, and some labor force, occupation, and industry variables. An interaction between location and growth was found for several occupation and industry characteristics. The consistency between some of the results and previous research on larger places supports the contention that villages, although classified as rural, share many characteristics of urban centers. The industry and occupation differences by location, and the interaction between location and growth, strongly suggest that location is tied closely to function here. Places near cities over 25,000, especially those that are growing, may serve as residences for commuting blue-collar workers, or perhaps as small manufacturing centers, while most places more remote from cities continue to function as small service centers for a rural hinterland.     

Ecological studies of collembolan populations in a pine forest soil IV. Comparison of distribution patterns

Summary The distribution pattern of ten species of Collembola was studied during the four years period from July 1971 to May 1975 in a pine forest soil. The distribution patterns were analysed for two scales of distribution, i. e., the distribution over the plot of 10×10 m² and the micro-distribution within a block sample consisting of 36 contigious units each 2×2 cm² in area, by applying the -m regression method. The fundamental pattern which appeared was quite similar for the species examined and individuals were aggregated in response to the heterogeneity of habitat conditions. The causes of aggregations were discussed with regard to some environmental factors. The relative abundances of 10 species within the collembolan community was examined in relation to the habitat utilization and the relative abundance was not related to the degree of aggregation but rather to the area occupied by individuals. This suggests that the more numerically abundant species tend to occupy broader micro-habitat. Biological meaning of aggregation was discussed in connection with the population biology and community organization of collembola.     

Interannual fluctuations in recruitment and growth of the sardine,Sardinops melanostictus, in the sea of Japan and adjacent waters

Recruitment and growth of the sardineSardinops melanostictus fluctuated markedly in the Sea of Japan and adjacent waters between 1978 and 1993. Stock size was calculated using Virtual Population Analysis and average body length in each age class was determined by the number of annual rings on the scales. There is an inverse correlation between average water temperature at a depth of 50 m in the coastal area of the mainland of Japan in winter (January to March) and recruitmentR defined as the number of individuals at 1 year old. There is also an inverse correlation between spawning stock sizeE and reproductive success in (R/E). A multiple regression model using spawning stock size and water temperature in winter as independent variables can explain 73% of variance in reproductive success. It suggests that both density-dependent and density-independent factors perform important roles determining reproductive success. There is an inverse correlation between body length and stock size and this suggests that there is a density-dependent effect on the growth of the sardine.     

A new method of sequential sampling to classify populations relative to a critical density

Summary A method of sequential sampling for grading population level in relation to a critical density is proposed. The method is based on the relationship and can be used without restrictions on the distribution patterns. The formulae for simple random sampling as well as for two-stage sampling are given. This research was suported by science research fund from the Ministry of Education.     

Analysis of contagiousness in the action of mortality factors on the western tent caterpillar population by using the \mathop m* - m\mathop m\limits^* - m relationshiprelationship

Summary The contagiousness in the operation of mortality processes on the colonies of the western tent caterpillar,Malacosoma californicum pluviale, was analyzed from two different aspects: successive changes in the frequency distribution of the number of surviving individuals per colony in the course of development, and the distribution pattern of the individuals killed by some biotic mortality factors. Also, for a tachinid parasite,Tachinomyia similis, the analysis was made on the egg-laying pattern on colonies as well as on individual larvae. The methods of these analyses were all based on the relation of mean crowding (m) on mean . A braconid parasite,Rogas sp., tended to kill few individuals together once it attacked a colony, but its effect on host colonies was rather equivalent to the random removal of individuals from all the colonies. Diseases in the late-stage larvae before cocooning was contagious in their action. Nuclear polyhedrosis virus seemed to have no basic contagiousness in its action, but it caused highly contagious distribution of deaths among the colonies when its average incidence was high. A spore-formingBacillus had a tendency to kill several individuals once it appeared in a colony, but the distribution of its incidence (no. of times it appeared per colony) was considered to be nearly at random. The female ofTachinomyia tended to lay more than one egg successively on the same colony. It also attacked individual larvae with a definite tendency for aggregation, which seemed to be resulted from the parasite’s preference to large hosts. When the number of eggs laid on prefered hosts exceeded a certain threshold, however, the fly seemed to change its attention to less attractive, smaller individuals.