Model-based adaptive spatial sampling for occurrence map construction

In many environmental management problems, the construction of occurrence maps of species of interest is a prerequisite to their effective management. However, the construction of occurrence maps is a challenging problem because observations are often costly to obtain (thus incomplete) and noisy (thus imperfect). It is therefore critical to develop tools for designing efficient spatial sampling strategies and for addressing data uncertainty. Adaptive sampling strategies are known to be more efficient than non-adaptive strategies. Here, we develop a model-based adaptive spatial sampling method for the construction of occurrence maps. We apply the method to estimate the occurrence of one of the world’s worst invasive species, the red imported fire ant, in and around the city of Brisbane, Australia. Our contribution is threefold: (i) a model of uncertainty about invasion maps using the classical image analysis probabilistic framework of Hidden Markov Random Fields (HMRF), (ii) an original exact method for optimal spatial sampling with HMRF and approximate solution algorithms for this problem, both in the static and adaptive sampling cases, (iii) an empirical evaluation of these methods on simulated problems inspired by the fire ants case study. Our analysis demonstrates that the adaptive strategy can lead to substantial improvement in occurrence mapping.     

Illness-death model: statistical perspective and differential equations

The aim of this work is to relate the theory of stochastic processes with the differential equations associated with multistate (compartment) models. We show that the Kolmogorov Forward Differential Equations can be used to derive a relation between the prevalence and the transition rates in the illness-death model. Then, we prove mathematical well-definedness and epidemiological meaningfulness of the prevalence of the disease. As an application, we derive the incidence of diabetes from a series of cross-sections.     

FEAR OF CRIME IN URBAN RESIDENTIAL NEIGHBORHOODS:

Current work on fear of crime centers largely around three dominant theoretical models: indirect victimization, community concern, and incivilities. Previous work (Taylor and Hale 1986) confirms the importance of the central construct in each model and shows that no one model has more explanatory power than another. But work to date has not examined ecological impacts of some key constructs, even though the models clearly imply processes operative at the neighborhood level. This study extends earlier work, combining central predictors from each model and distinguishing between- and within-neighborhood sources of impact, with data from surveys of 1622 residents of 66 Baltimore neighborhoods and from on-site assessments. Findings indicate ways in which these theories, particularly indirect victimization and incivilities, need further theoretical articulation of central constructs. The results also confirm the generalizability of Merry's diversity thesis—developed from field work in a multi-ethnic subsidized housing context—to urban neighborhoods in a major metropolitan area.     

Discrimination indexes and models for studying sensory functioning in aging

A popular paradigm in experimental psychophysics has subjects estimate sensation magnitude by assigning numbers to stimuli in some way. While it is typical to analyze the central tendency (e.g. means and slopes) of the subjects' psychophysical. functions, there is often a greater need to analyze the internal consistency of these functions. A subject who gives increasing mean responses across increasing stimulus intensities and also gives highly consistent responses within stimulus intensities is showing superior sensory discrimination. We propose new discrimination indexes, based on measures of association and lack-of-fit, that summarize monotonic regressions of the subject's data, as well as non-metric and metric-sensitive measures related to Kendall's coefficient of concordance. We use these indexes in quadratic spline regression models for cross-sectional age trends in sensory discrimination, with covariates included to adjust for task demands and gender differences.Because such data are potentially affected by increasing variability with age, we describe a method to assess this and adjust for it using reweighted least squares.     

Do union organizing activities affect decertification?

This paper tests the hypothesis that unions face a trade-off between retaining organized units and organizing new bargaining units. Using cost-benefit analysis, a model is developed which examines the impact of representation elections on the level of decertification activity for the period 1948 to 1979. The results indicate that as unions increase their efforts to organize more employees, they trade-off a loss of membership through decertification. The shift of resources from servicing existing units to organizing new units causes a sufficient change in the benefit/cost ratio for employees to result in loss of union certification.     

THE TRUE SELF METHOD FOR STUDYING THE SELF-CONCEPTION*

An open-ended questionnaire technique for identifying the self-conception which can be used in lieu of or in combination with the TST is described. Respondents are asked to relate experiences in which they felt that their true selves were expressed, and in which their true selves were misrepresented. It is assumed that investigators can make more refined inferences about the social anchorage of the self-conception from accounts of experience than from single words and short phrases, and that understanding the circumstances which evoke vital feelings of true-self and not-self is more fundamental than knowing the self designations that people make on the basis of these experiences. Possible uses of the method are discussed. Preliminary findings from using the method to distinguish between self-anchorage in impulse and in institution are briefly presented.     

Solitude and intimacy: Linking territoriality and privacy experiences

The further advancement of privacy models depends upon clarifying two issues: the relationship between privacy and territoriality and the degree to which different types of privacy have distinct behavioral and cognitive correlates. Two types of privacy experiences—solitude and intimacy—were investigated. Given the divergent function of these two forms of privacy, we expected each would be sought in different types of territories. We also expected that where people seek a form of privacy depends in part upon the quality of the immediate social environment: a territory will be used less for privacy experiences as the understandings that regulate usage of the space erode. Students were asked where they went for solitude, where they went for intimacy, and to describe their experiences in these two places. Results supported the hypotheses. In addition, a substantial and coequal linkage between privacy and territoriality appeared. A two-step process describing this linkage was suggested. Implications of the findings for a more precise conceptualization of privacy behaviors were explored.Portions of a prior version of this paper were presented at the annual meetings of the American Psychological Association, Toronto, 1978. This research was carried out while the first author was affiliated with Virginia Polytechnic Institute and State University. Research funds were provided by a small grant award from the Office of the Dean of Arts and Sciences, Virginia Polytechnic Institute and State University. The authors are indebted to Ed Krupat and Eric Sundstrom for helpful comments on an earlier draft of this paper.     

Market and Direct Allocation of Labor Through Migration*

Recent research suggests that the relationship between migration and labor allocation has changed in two ways: (1) fewer migrations are job-related; and (2) more of the remaining job-related migrations are job transfers instead of purely market-induced mobility. Data from the 1973–77 U.S. Annual Housing Surveys are used to compare characteristics of market-induced and job-transfer migrants/Both forms of migration occur among all income, education, and age groups. However, the income attainment processes for these migrants suggest that relocations are overrepresented among those primary jobs described by dual labor market theory. Since many of the benefits of primary jobs are age-related, both the increasing frequency of occupational relocations and weakening of the American economic position suggest that the benefits expected by those relocated may be difficult to provide.