Thesis (Ph. D.)--University of Wisconsin--Madison, 1970. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliography.

Thesis--Wisconsin. / Vita. Includes bibliographical references.

Thesis (M.Soc.Sc.)--University of Hong Kong, 1991. / Also available in print.

Estimating wildlife abundance is fundamental for its effective management and conservation. A range of methods exist: total counts, plot sampling, distance sampling and capture-recapture based approaches. Methods have assumptions and their failure can lead to substantial bias. Current research in the field is focused not on establishing new methods but in extending existing methods to deal with their assumptions' violation. This thesis focus on incorporating animal movement into circular plot sampling (CPS) and point transect sampling (PTS), where a key assumption is that animals do not move while within detection range, i.e., the survey is a snapshot in time. While targeting this goal, we found some unexpected bias in PTS when animals were still and model selection was used to choose among different candidate models for the detection function (the model describing how detectability changes with observer-animal distance). Using a simulation study, we found that, although PTS estimators are asymptotically unbiased, for the recommended sample sizes the bias depended on the form of the true detection function. We then extended the simulation study to include animal movement, and found this led to further bias in CPS and PTS. We present novel methods that incorporate animal movement with constant speed into estimates of abundance. First, in CPS, we present an analytic expression to correct for the bias given linear movement. When movement is de ned by a diffusion process, a simulation based approach, modelling the probability of animal presence in the circular plot, results in less than 3% bias in the abundance estimates. For PTS we introduce an estimator composed of two linked submodels: the movement (animals moving linearly) and the detection model. The performance of the proposed method is assessed via simulation. Despite being biased, the new estimator yields improved results compared to ignoring animal movement using conventional PTS.

The capabilities of the equipment for proton induced X-ray emission analysis at the University of Surrey were examined with particular reference to the trace element analysis of biological samples. The study of samples arising from the Guildford Breast Screening Project was continued. The requirements for trace element analysis of biological samples are outlined together with a review of the available physical analysis techniques. Detail is given of the factors to be considered in order to establish that the study of elemental concentrations by PIXE is feasible. The apparatus used for PIXE analysis is described in detail together with recent improvements to the equipment. The development of a spectrum analysis code HISTO, which simulates the processes of manual analysis, was undertaken. The performance of the code was compared favorably to that of the Ge(Li) spectrum analysis code SAMPO. A preliminary study of 20 samples of human breast cyst fluid was undertaken. The minimum detection limits for those elements assayed by comparative analysis were calculated. The methodology of sample preparation was improved after the examination of target homogeneity and contamination. During a more detailed study of 30 samples the concentration of 9 elements relative to the concetration of potassium was calculated. Calculation of the minimum recommended sample size for elements with Z ≥ 26 indicated that a much larger sample size would be required for reliable results. The PIXE microprobe facility is described and the alignment and operation procedures are outlined. The microprobe was used to examine tree ring samples; examples of some 1D scans are presented. Recommendation that the spectrum analysis code is developed to include a peak location capability is made. Progress with the breast cyst fluid analysis programme is reviewed. The requirement to improve the proton beam current measurment equipment and the data analysis facilities is noted.

When investigating the dynamics of an animal population, a primary objective is to obtain reasonable estimates of abundance or population size. This thesis concentrates on the problem of obtaining point estimates of abundance from capture-recapture data and on how such estimation can be improved by using the method of plant-capture. Plant-capture constitutes a natural generalisation of capture-recapture. In a plant-capture study a pre-marked population of known size is added to the target population of unknown size. The capture-recapture experiment is then carried out on the augmented population. Chapter 1 considers the addition of planted individuals to target populations which behave according to the standard capture-recapture model M0. Chapter 2 investigates an analogous model based on sampling in continuous time. In each of these chapters, distributional results are derived under the assumption that the behaviour of the plants is indistinguishable from that of members of the target population. Maximum likelihood estimators and other new estimators are proposed for each model. The results suggest that the use of plants is beneficial, and furthermore that the new estimators perform more satisfactorily than the maximum likelihood estimators. Chapter 3 introduces, initially in the absence of plants, a new class of estimators, described as coverage adjusted estimators, for the standard capture-recapture model M[sub]h. These new estimators are shown, through simulation and real life data, to compare favourably with estimators that have previously been proposed. Plant-capture versions of these new estimators are then derived and the usefulness of the plants is demonstrated through simulation. Chapter 4 describes how the approach taken in chapter 3 can be modified to produce a new estimator for the analogous continuous time model. This estimator is then shown through simulation to be preferable to estimators that have previously been proposed.

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No description available.

Background: Vulnerable populations in Canada shoulder a disproportionately high burden of disease. Transmission of sexually transmitted infections is behaviourally mediated. Previous research indicates an association between depression and sexual risk-taking. Evidence also suggests that social support is an effect modifier. Methods: Data were collected from a population of injection drug users, between 2003 and 2004 in Winnipeg, using respondent driven sampling. Demographic and social behaviors were analyzed to characterize the population, as well as social networks and ego networks. Logistic regression was used to examine the association between depressive symptoms and sexual risk interactions. Social support was examined as an effect modifier. Results: The majority of the study participants and network members were aged between 35 and 44, and a high percentage identified as Native Canadians. The highest percentage of people reported welfare as their primary source of income, and injecting stimulants, as their most frequently injected drug. Logistic regression models indicated an increase in the odds of individuals engaging in high-risk sexual interactions, if they had also self-reported elevated depressive symptoms. It was not possible to conclude that social support was an effect modifier. Conclusion: This research supports a positive association between elevated depressive symptoms, and higher levels of sexual risk interactions. Further research is needed to understand the role of social support.