OBJECTIVE: The brain reserve hypothesis was examined in a secondary analysis of cross-sectional data from a community-based sample of 468 older adults residing in Charlotte County, Florida. The objective of the analysis was to determine the association between head circumference and eight cognitive outcomes and to assess any potential effect modification of existing associations by Apolipoprotein E (APOE) genotype. METHODS: Cognitive outcomes include scores from the Modified Mini-Mental State Exam (3MS), the Hopkins Verbal Learning Test-Revised (HVLT-R), Stroop Color-Word Test, Trail-Making Test A and B, and a word-stem completion task measuring implicit memory. Descriptive statistics were calculated for each variable. Head circumference and dependent cognitive outcomes were modeled as dichotomous variables using logistic regression, adjusting for gender, age, education, income, height, and Spot The Word test score, a measure of pre-morbid IQ. For dichotomized test scores, poor outcomes (cases) were defined as having scores in the lowest quintile; the remaining top four quintiles were considered non-cases. RESULTS: small head circumference was significantly associated with low 3MS scores [OR(95%CI): 2.97 (1.12, 7.89), p=0.03], after adjustment for age, income and pre-morbid IQ. The association remained statistically significant after adjustment for gender and education as well. After adjustment, head circumference was not found to be statistically significantly associated with any other cognitive outcome. No effect modification was found by APOE genotype or years of education. CONCLUSION: This analysis confirms previous findings that exposure to low head circumference significantly impacts cognition in late life.

This dissertation develops Bayesian methods to analyze data from auctions and produce policy recommendations for auction design. The essay, "Auction Design Using Bayesian Methods," proposes a decision theoretic method to choose a reserve price in an auction using data from past auctions. Our method formally incorporates parameter uncertainty and the payoff structure into the decision procedure. When the sample size is modest, it produces higher expected revenue than the plug-in methods. Monte Carlo evidence for this is provided. The second essay, "Flexible Bayesian Analysis of First Price Auctions Using Simulated Likelihood," develops an empirical framework that fully exploits all the shape restrictions arising from economic theory: bidding monotonicity and density affiliation. We directly model the valuation density so that bidding monotonicity is automatically satisfied, and restrict the parameter space to rule out all the nonaffiliated densities. Our method uses a simulated likelihood to allow for a very exible specification, but the posterior analysis is exact for the chosen likelihood. Our method controls the smoothness and tail behavior of the valuation density and provides a decision theoretic framework for auction design. We reanalyze a dataset of auctions for drilling rights in the Outer Continental Shelf that has been widely used in past studies. Our approach gives significantly different policy prescriptions on the choice of reserve price than previous methods, suggesting the importance of the theoretical shape restrictions. Lastly, in the essay, "Simple Approximation Methods for Bayesian Auction Design," we propose simple approximation methods for Bayesian decision making in auction design problems. Asymptotic posterior distributions replace the true posteriors in the Bayesian decision framework, which are typically a Gaussian model (second price auction) or a shifted exponential model (first price auction). Our method first approximates the posterior payoff using the limiting models and then maximizes the approximate posterior payoff. Both the approximate and exact Bayes rules converge to the true revenue maximizing reserve price under certain conditions. Monte Carlo studies show that my method closely approximates the exact procedure even for fairly small samples.

Objective: Aboriginal children are disproportionately affected by obesity, as they are twice as likely to be classified as obese compared to their non-Aboriginal Canadian counterparts. Research indicates that income, food insecurity, and diet quality are important predictors of weight status, however these factors are not well explored among Aboriginal children living off reserve. This study aims to identify associations between food insecurity and diet on obesity status among off-reserve First Nations and Métis children. Methods: This study used both quantitative and qualitative research methods. Data from the 2006 Aboriginal Peoples Survey (APS) – Children and Youth component were analyzed using binary logistic regression and the proportional odds model to assess relationships between food insecurity, diet, and body mass index (BMI). Fruit and vegetable intake, as well as junk food consumption, were used as proxy measures for children’s diet quality. Additional analyses involving income instead of food insecurity, as well as food insecurity interaction terms, were also explored. Focus groups were conducted with caregivers of Métis and off-reserve First Nations children in Midland-Penetanguishene and London, Ontario, respectively. The focus groups were planned and carried out in partnership with the Métis Nation of Ontario (MNO) and the Southwest Ontario Aboriginal Health Access Centre (SOAHAC). A thematic analysis was conducted with the qualitative data, and the focus group discussions provided important contextual information to complement the statistical results. Results: Approximately 11% of First Nations and 6.8% of Métis children were food insecure according to the 2006 APS. The quantitative analysis did not find a significant association between food insecurity and diet, or food insecurity and BMI for First Nations or Métis children. Income was a better predictor of weight status than food insecurity. For First Nations children, having a household income higher than $60,000 decreased the risk of being overweight/obese. For Métis children, a household income of less than $20,000 increased the risk of overweight/obesity. Food insecurity was only significant as an interaction with parental education for First Nations children, and with parental education and number of people living in the household for Métis children. The proportional odds model produced similar results to the binary logistic regression procedure, and food insecurity remained insignificant in the analyses. Contrary to the quantitative findings, the focus group discussions indicated that caregivers perceived a positive relationship between low income and food insecurity, as well as adverse impacts on their children’s diets. While caregivers did not use the term “food insecurity” explicitly, conversations about not having enough food or money for food, as well as coping strategies for when these situations occurred, suggested that food insecurity manifests itself in different ways. Caregivers mentioned decreased variety of foods, compromised fruit and vegetable intake, as well as decreased traditional food consumption as examples of how families’ food consumption and purchasing patterns changed when food insecure. Food insecurity negatively impacted children’s diets, and many caregivers attributed the rise in overweight and obesity to poor diet quality. Some of the key barriers to children eating healthfully were unaffordability and limited access to healthy foods. Caregivers also discussed the role of various programs for improving child health within their communities. Conclusions: While food insecurity was not significantly associated with obesity in the quantitative analyses, discussions with caregivers of First Nations and Métis children identified food insecurity and low income as important predictors of poor diet, and consequently decreased well-being. Several limitations associated with the 2006 APS design may have prevented food insecurity from being significantly associated with obesity risk; however, it is clear from both the quantitative and qualitative components of this study that income consistently affects diet and child obesity risk. Findings from this study can inform necessary improvements to existing programs, interventions, and policies targeting obesity and health of Aboriginal children.

No description available.

No description available.

Terracettes are a widely occurring form of micro-relief found throughout regions displaying various climatic and environmental conditions. Much speculation surrounds the processes responsible for their formation and development. An investigation of these micro-forms, their associated soil physical properties, sustaining mechanisms, and their relationship to slope stability was undertaken in Giant's Castle Game Reserve, KwaZulu - Natal Drakensberg, South Africa. The study showed that relationships between terracette morphology and soil physical properties within the Reserve are few, and that current soil conditions cannot be used to infer process related to terracette formation. However dry bulk density data indicated that soil creep is the dominant formative mechanism within the Reserve. Throughflow at riser surfaces was the dominant sustaining mechanism, with needle ice growth, wind, surfacewash and animal disturbance contributing minor retreat at both treads and risers. Aspect played an important role in determining soil physical characteristics. It was inferred that terracettes imparted stability to the slopes on which they are found, and with continued retreat at both treads and risers the slope was again placed under conditions of instability. / Thesis (M.Sc.)-University of Natal, Pietermaritzburg, 1998.

Food selection by free-ranging black rhinoceros, eland, giraffe and kudu as well as the utilisation of vegetation types by the latter three browsers were investigated over an entire seasonal cycle, from June 1998 to July 1999, at Weenen Nature Reserve, KwaZulu-Natal. The study was aimed at determining the extent of resource overlap within this browser guild. Feeding habits of eland, giraffe and kudu were studied by direct observations, while a plant-based technique was used for black rhinoceros. Dung counts were conducted to monitor selection for vegetation types. Overlap was estimated by measuring the similarities in resource utilisation patterns. Giraffe were exclusively browsers, feeding mostly on woody foliage, over the complete seasonal cycle. The bulk of the annual diet of kudu also consisted of woody browse, although forbs were important and their use increased from early summer to winter. The annual diet of eland consisted of approximately equal proportions of grass and browse, with pods making up almost a third of the diet. Similar to kudu, forbs were more prominent in the winter diet, while grass use decreased. During winter, overlap in forage types generally increased and was considerable because the browsers did not resort to distinct forage 'refuges'. Overlap in the utilisation of woody plant species, however, decreased as animals diversified their diets. Nonetheless, overlap was extensive, primarily owing to the mutual utilisation of Acacia karroo and Acacia nilotica. The quantity of woody foliage decreased during winter, as indicated by phenological differences, but numerous individual plants still carried leaves. Based on current evidence, food quality was assumed to decline. Under prevailing conditions, eland, giraffe and black rhinoceros suffered no mortalities indicating that they were not food limited, possibly owing to the nutritional advantages conferred by their large body size, and that competition among them was unlikely. By comparison, kudu mortalities were great which may signify that they were constrained by food supply and that the larger browsers exerted a pronounced competitive effect on them. Based on the current study it is hypothesised that during periods of resource scarcity the abundance of high quality foods are limited and if interspecific competition does prevail, which will further limit the availability of these resources, it is the smaller bodied herbivores that will be most affected and suffer the greatest mortalities. Consequences of competitive interactions among these browsers have important management implications, especially in small reserves, which are a key stone for the conservation of mammalian herbivores. / Thesis (M.Sc.)-University of Natal, Pietermaritzburg, 2000.

The main aim of this study was to classify and map the threatened coastal grassland communities of the 3 257 ha Umtamvuna Nature Reserve (UNR) in KwaZulu-Natal (30°07'30" to 300 11'05"E; 30°55'00" to 31°04'30"S). Secondary aims were to relate past management and selected environmental variables to community composition and to develop guidelines for monitoring. Alpha diversity was measured using a Whittaker plot and revealed 119 species. A pilot study to test the efficiency of botanical techniques showed that a point based technique (nearest plant method in a 20 X 20 m plot) was efficient (52 minutes for recording 200 points), but recorded only 23% of the species. By increasing the number of points to six hundred, 34% of the species were recorded in 178 minutes; the same time was required to randomly place 30 quadrats (50 X 50 cm), which revealed 80% of the species. Tests for replicate similarity showed a high retrieval of internal association (PS = 86%), using abundant species only and 100 points per plot. The point based technique was thus efficient in detecting abundant species and was acceptable for producing a classification, especially in this case where a comprehensive species list already existed. Indirect gradient analysis (TWINSPAN) identified six grassland communities. An ordination using detrended correspondence analysis (DCA) contributed towards the community classification and grazing and fire frequency gradients were inferred from this ordination. Protea roupelliae communities were common but did not influence grass species composition . Canonical ordination revealed that, of the eight environmental variables measured, 'distance from the sea' strongly affected species distribution (r= 0.83). Cost effectiveness was considered in the development of a monitoring programme. Point based monitoring techniques favoured by sourveld researchers in KwaZulu-Natal were found to be inefficient, particularly for studies requiring the measurement of both species richness and community composition. Randomly located 100 X 100 cm quadrats, located in selected sites which represent previously identified communities, was more efficient. This study contributed towards a refinement of information on the grassland communities of KwaZulu-Natal and supported the use of point data for the classification of grasslands not previously studied. It also demonstrated that point based techniques were not suitable for meeting all grassland monitoring requirements. / Thesis (M.Sc.)-University of Natal, Pietermaritzburg, 1995.

The St. Lawrence Seaway, constructed between 1954 and 1959, had a significant impact on the Mohawk community of Kahnawake. Located on the shores of the St. Lawrence River, Kahnawake was faced with the expropriation of 1,262 acres of land for the construction of a canal that effectively cut off the community's access to the river and reduced its land base. Regarded by its members as one of the most important events in Kahnawake's history, the Seaway has become part of the everyday discourse of the community. This thesis examines two recurring themes in the discourse about the Seaway---the factionalism in the community at the time of the construction, and memories about the river---and illustrates how this event informs the present political identity of Kahnawake. The Seaway has become a metaphor for the intrusiveness of the Canadian government and the necessity of resisting any encroachment on Kahnawake's autonomy, and as such has played an important part in the development of nationalism in this community.

No description available.