Many types of ecological studies require identification of individual animals. I developed and evaluated an automated identification system for polar bears (Ursus maritimus) based on their whisker spot patterns. First, I measured the reliability of using whisker spot patterns for identification from polar bear photographs taken in western Hudson Bay. This analysis involved estimating the complexity of each whisker spot pattern in terms of its information content. I found that 98% of patterns contained enough information to be reliable, and this result varied little among three different observers. Based on these results, I implemented a computer-aided identification system for polar bears based on whisker spot pattern recognition. I used standard computer vision techniques to pre-process images and the Chamfer distance transform to compute similary scores between images. In addition, I evaluated the system by testing the effects of photographic quality and angle on system accuracy. I found that excellent and moderate quality/angle provided best results, with system accuracy of 90-95%. These findings suggest that individual identification of polar bears in the field based on whisker spot pattern variation is possible. Researchers studying polar bear behavior or estimating population parameters should benefit from this noninvasive technique.

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The United States Fish and Wildlife Service (USFWS) expressed the need to develop appropriate management strategies for apparently high-density, growing black bear populations in the Roanoke-Neuse-Tar-Cape Fear ecosystem in coastal North Carolina and Virginia. In order to provide the scientific information necessary to develop these strategies, I investigated population densities and genetic structure of black bears at 3 national wildlife refuges [Great Dismal Swamp (GDSNWR), Pocosin Lakes (PLNWR), and Alligator River (ARNWR)]. Density estimates were derived from DNA samples collected noninvasively at each of the 3 refuges for 2 consecutive summers. Hair samples were analyzed for individual identification using 6-7 microsatellite markers. Estimated densities were some of the highest reported in the literature and ranged from 0.56-0.63 bears/km2 at GDSNWR to 0.65-1.12 bears/km2 at ARNWR to 1.23-1.66 bears/km2 at PLNWR. Sex ratios were male-biased in all areas of all refuges. Genetic variability and structure of bears at these refuges was assessed using 16 microsatellite markers for 40 bears from each refuge. Genetic variability of the 3 refuge populations was substantially high compared to other bear populations in North America, with observed heterozygosities ranging from 0.6729 at GDSNWR to 0.7219 at ARNWR. FST and DS values were relatively low (0.0257-0.0895 and 0.0971-0.3640, respectively), indicating movement of bears and gene flow across the landscape is adequate to prevent high levels of genetic differentiation and structure among the refuge bears. Genetic statistics at GDSNWR indicate that this population is isolated to some degree by geography (i.e., the Albemarle Sound) and encroaching urban development (i.e., the towns of Suffolk and Chesapeake). ARNWR has the potential to become isolated in the future if movement corridors to the south of the refuge are not maintained. Harvest of bears is likely warranted at PLNWR and ARNWR, though extreme caution must be taken the first few seasons as hunter success will be extremely high. Further research is needed to determine population growth rates, reproductive parameters, and survival rates at all 3 refuges, particularly if a hunting season will be established and maintained in these areas. Methods for regularly monitoring bear populations at these refuges also should be incorporated into biological programs, as bears comprise a significant component of the ecosystem at these refuges and cannot be ignored when outlining management goals. / Master of Science

Ultrasound waves are mechanical undulations above the threshold for human hearing, and have been used widely in both the human body and brain for diagnostic and therapeutic purposes. Ultrasound can be controlled using specially designed transducers into a focus of a few millimeters in diameter. Low intensity ultrasound, such as used in imaging applications, appears to be safe in adults. It is also known that ultrasound waves can penetrate through the skull and be focused within the brain for ablation purposes, employing the heat generation properties of high intensity focused ultrasound. High intensity focused ultrasound is thus used to irreversibly ablate brain tissue in localized areas without observable damage to intermediate tissue and vasculature. Ablation with high intensity focused ultrasound guided by magnetic resonance imaging is used for abolishing brain tumors, and experimentally for pain. Low intensity ultrasound can be utilized beyond imaging in neuroscience and neurology by focusing the ultrasound beam to investigate the structure and function of discrete brain circuits. In contrast to high intensity focused ultrasound, the effects of low intensity focused ultrasound on neurons are reversible. Considering the volume of work on high intensity focused ultrasound, low intensity focused ultrasound remains decidedly underdeveloped. Given the great potential for impact of low intensity focused ultrasound in both clinical and scientific neuromodulation applications, we sought to advance the use of low intensity focused ultrasound for noninvasive, transcranial neuromodulation of human cortex. This dissertation contains novel research on the use of low intensity transcranial focused ultrasound for noninvasive neuromodulation of human cortex. The importance of mechanical forces in the nervous system is highlighted throughout to expand beyond the stigma that nervous function is governed chiefly by electrical and chemical means. Methods of transcranial focused ultrasound are applied to significantly modulate human cortical function, shown using electroencephalographic recordings and behavioral investigations of sensory discrimination performance. This dissertation also describes computational models used to investigate the insertion behavior of ultrasound across various tissues in the context of transcranial neuromodulation, as ultrasound's application for neuromodulation is relatively new and crudely understood. These investigations are critical for the refinement of device design and the overall advancement of ultrasound methods for noninvasive neuromodulation. / Ph. D.

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L’athérosclérose est un problème de santé publique majeur puisque elle représente aujourd’hui la principale cause de décès dans les pays occidentalisés. Il est donc important de comprendre les mécanismes participant à la progression et aux complications de cette entité anatomoclinique. Nous nous sommes attachés dans ce travail de thèse à démontrer la place et l’apport potentiel de l’imagerie non invasive non expérimentale dans la mise en exergue des particularités de l’athérosclérose carotidienne et/ou coronarienne, et dans la stratégie de dépistage de ses complications chez le sujet non diabétique et diabétique de type 2, en fonction de l’existence ou non d’une stéatose hépatique non alcoolique. Nous présentons notamment dans ce travail, issu en partie de l’exploitation des données cliniques, biologiques et radiologiques de trois protocoles hospitaliers de recherche clinique, les différentes publications scientifiques internationales auxquelles il a donné lieu. / Atherosclerosis is a major public health problem and is one of the major causes of death in the developed western world today. It is therefore of utmost importance that we understand the mechanisms involved in the evolution and progression of this disease and its associated complications. With the work done for this thesis, we tried to bring forth the importance of non invasive clinical imaging to study the pattern of evolution of atherosclerosis involving the carotid and/or coronary arteries. We also present the role played by imaging in prevention and early diagnosis of associated complications in non diabetic and type 2 diabetic patients, presenting with or without non alcoholic hepatic steatosis. In this study, we evaluated three different clinical research protocols used involving the clinical findings, biochemical as well as radiological examination results. The results of these protocols have been the basis for several peer reviewed international publications till date.

A Pressão intracraniana (PIC) é um dos principais parâmetros fisiológicos em animais e humanos e sua morfologia é extremamente importante. Entretanto, todos os métodos de monitoramento existentes no mercado são invasivos, existindo uma ampla demanda por sistemas não invasivos, expandindo assim o campo de pesquisas acerca desse importante parâmetro neurológico, que só não é melhor estudado devido a forma invasiva de ser monitorado. A motivação é fazer com que o monitoramento da PIC seja tão comum e tão essencial quanto é hoje o monitoramento da pressão arterial, facilitando o diagnóstico e até prognóstico de diversas doenças. Este trabalho analisa e implementa melhorias de um sistema não invasivo de monitoramento da pressão intracraniana, baseado em extensometria. Um dos objetivos, no que tange o desenvolvimento do produto, é analisar o equipamento como um todo - Sensor, Hardware, Firmware e Software - e propor melhorias a partir dos testes realizados. Os testes realizados In vivo mostraram uma boa correlação do sinal com um sistema Gold Stardard, evidenciando o potencial promissor do método. / The intracranial pressure (ICP) is one of the main physiological parameters in animals and humans and its morphology is extremely important. However, all monitoring methods available in the market are invasive and there is a large demand for non-invasive systems, thus expanding the scope of research on this important neurological parameter, that just is not further studied because of the invasive method of monitoring. The motivation is to make monitoring the ICP as common and as essential, as monitoring the blood pressure is nowadays, facilitating diagnosis and even prognosis of various diseases. This work analyzes and implements improvements in a non-invasive intracranial pressure monitoring system based on extensometer. One of the goals, regarding product development, is to analyze the unit as a whole- Sensor, Hardware, Firmware and Software- and propose improvements from the tests. The in vivo tests showed a good correlation with a Gold Stardard system signal showing the promising potential of the method.