Graduate Theses & Dissertations

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Asserting sexual (dis)interest
Sexual assertiveness encompasses skills in refusing unwanted sexual situations and bringing about wanted sexual situations. Measures of sexual assertiveness typically assess both refusal and initiation aspects, yet there is a dearth of research examining these skills in relation to one another. The present study examined the relationship between these skillsets in women, exploring predictors of each. Initiation and refusal assertiveness were moderately correlated. Additionally, the relationship between them was not entirely explained by general assertiveness, indicating that there is something unique to assertiveness in the sexual context. Committed relationship context and erotophilic disposition specifically predicted initiation assertiveness. Less endorsement of the sexual double standard and fewer approach motivations for engaging in unwanted sex specifically predicted refusal assertiveness. Few differences emerged in predictors of assertiveness types when comparing sexual orientation groups, yet non-heterosexual women reported slightly lower levels of refusal assertiveness. Implications for sexual education, therapy, and future research are discussed. Author Keywords: sexual assertiveness, sexual autonomy, sexual compliance, sexual double standard, sexual satisfaction, sexual self-disclosure
Positive Solutions for Boundary Value Problems of Second Order Ordinary Differential Equations
In this thesis, we study modelling with non-linear ordinary differential equations, and the existence of positive solutions for Boundary Value Problems (BVPs). These problems have wide applications in many areas. The focus is on the extensions of previous work done on non-linear second-order differential equations with boundary conditions involving first-order derivative. The contribution of this thesis has four folds. First, using a fixed point theorem on order intervals, the existence of a positive solution on an interval for a non-local boundary value problem is obtained. Second, considering a different boundary value problem that consists of the first-order derivative in the non-linear term, an increasing solution is obtained by applying the Krasnoselskii-Guo fixed point theorem. Third, the existence of two solutions, one solution and no solution for a BVP is proved by using fixed point index and iteration methods. Last, the results of Green's function unify some methods in studying the existence of positive solutions for BVPs of nonlinear differential equations. Examples are presented to illustrate the applications of our results. Author Keywords: Banach Space, Boundary Value Problems, Differential Equations, Fixed Point, Norm, Positive Solutions
Thinking Ahead
The present thesis entails a qualitative investigation of the unique notion to transition media change from the current paper-based system to the potential use of information technology innovation for communication between health care providers and employers during return to work. Stakeholder perspectives on relevant communication phenomena were gathered from workers, employers, and health care providers with experience in return to work. Methods for analysis involved critical realist grounded theory, as well as the use of a prototype innovation, named the Return to Work Expert App, as a platform for participant evaluation and discourse. The study’s findings provided comprehensive and in-depth understanding of return to work communication, beyond its empirical regularities. The generative mechanisms of common communication problems that were discovered included situated reasoning, media as information (“the medium is the message”), epistemological disjuncture, egoism-altruism-collectivism quandary, and perspective taking. A novel theoretical framework based on ecological psychology was also advanced to offer a coherent and systematic understanding of the situated nature of health care providers’ reasoning and information development. Media change via the Return to Work Expert App was argued to be limited in handling and resolving many of the communication problems that can occur. However, the app had perceptible value and benefits to prospective users that suggested a distinct advantage over current paper-based practices. Opportunities for further development and research exist to address relevant challenges, most notable of all being the need to address the app’s burden of proof. For the interested reader, this thesis advances research and knowledge of provider-employer communication to a state that is truly fitting of the importance acknowledged of it in the field of return to work. Author Keywords: critical realism, ecological psychology, media change, return to work, stakeholder communication, technological acceptance
Effect of the neonicotinoid imidacloprid on embryogenesis and anuran survivorship in frog virus 3 infected tadpoles
Exposure of pre-metamorphic amphibians to neonicotinoid insecticides may be contributing to the global decline in amphibian populations. In this study, anuran embryos and tadpoles of the African clawed frog (Xenopus laevis) and the North American leopard frog (Lithobates pipiens) were used to determine the effects of embryonic exposure to neonicotinoids. In addition, Xenopus was used to determine if prolonged exposure to neonicotinoids influenced tadpole sensitivity to frog virus 3 (FV3). Exposure of anuran embryos to concentrations of the neonicotinoid insecticide, imidacloprid, ranging from 1 -20 ppm induced a concentration dependent increase in malformations of the retina in Xenopus embryos. However, similar responses were not observed with embryos of leopard frogs. Exposure of Xenopus tadpoles to 500 ppb concentration of imidacloprid followed by challenge with FV3 showed that pesticide exposure unexpectedly decreased the rates of mortality, although total mortalities by the end of the experiment were not significantly different from controls. This unexpected observation may be attributed to a reduced inflammatory response induced by exposure to imidacloprid. Despite the low acute toxicity of neonicotinoid insecticides to vertebrates, these studies indicate that exposure to this class of insecticides causes sublethal effects in anuran species during early life stages. Author Keywords: embryogenesis, Lithobates pipiens, neonicotinoid, ranavirus, tadpole, Xenopus laevis
Biology and Management of Stratiotes Aloides in the Trent River, Ontario
Invasive aquatic plants can create negative ecological, economic and social impacts when they displace local vegetation, interfere with shipping and navigation and inhibit water-based recreational activities. In 2008, the first North American occurrence of the invasive plant Stratiotes aloides (Water soldier) was identified in the Trent River, Ontario. This research measured offset photosynthesis and turion germination to determine the light compensation point (5.2-5.4m) and maximum depth of colonization (4-6m) for S. aloides propagules using in situ incubations and controlled growth experiments. The effects of spring and fall chemical (Diquat) and physical (hand raking) treatments on S. aloides biomass, local macrophyte recovery and community dynamics in the Trent River were also measured. The target of a 75% minimum reduction in S. aloides biomass was not attained using any of the treatment methods and no perceivable recovery of the local plant community was observed. Significant S. aloides regrowth was recorded for both treatment methods regardless of application timing. Author Keywords: herbicide, invasive species, macrophyte, photosynthesis, propagule
Real-space renormalization group approach to the Anderson model
Many of the most interesting electronic behaviours currently being studied are associated with strong correlations. In addition, many of these materials are disordered either intrinsically or due to doping. Solving interacting systems exactly is extremely computationally expensive, and approximate techniques developed for strongly correlated systems are not easily adapted to include disorder. As a non-interacting disordered model, it makes sense to consider the Anderson model as a first step in developing an approximate method of solution to the interacting and disordered Anderson-Hubbard model. Our renormalization group (RG) approach is modeled on that proposed by Johri and Bhatt [23]. We found an error in their work which we have corrected in our procedure. After testing the execution of the RG, we benchmarked the density of states and inverse participation ratio results against exact diagonalization. Our approach is significantly faster than exact diagonalization and is most accurate in the limit of strong disorder. Author Keywords: disorder, localization, real-space renormalization, strong correlations
Bank Swallow (Riparia riparia) Breeding in Aggregate Pits and Natural Habitats
I examined Bank Swallow (Riparia riparia) colony persistence and occupancy, in lakeshore, river and man-made aggregate pit habitat. Habitat persistence was highest on the lakeshore and lowest in aggregate pits, likely due to annual removal and relocation of aggregate resources. Bank Swallow colonies in aggregate pit sites were more likely to persist if a colony was larger or if burrows were located higher on the nesting face. I also compared nest productivity and health factors of Bank Swallows in lakeshore and aggregate pit habitats. While clutch size was the same in both habitat types, the number of fledglings from successfully hatched nests was significantly higher in aggregate pit sites than from lakeshore sites. Mass of fledgling Bank Swallows did not differ significantly between habitat types, however mass of adults from aggregate pits decreased significantly over the nesting season. Parasite loads on fledgling Bank Swallows were significantly lower in aggregate pits than in lakeshore sites. According to these indicators, aggregate pits appear to provide equivalent or higher quality habitat for Bank Swallows than the natural lakeshore sites, making them adequate and potentially key for this species’ recovery. Aggregate pit operators can manage for swallows by (1) creating longer, taller faces to attract birds and decrease predation, and (2) supplementing their habitat with water sources to encourage food availability. Author Keywords: Aerial insectivore, aggregate pits, Bank Swallow, colony persistence, ectoparasites, substitute habitat
Habitat Preferences and Feeding Ecology of Blackfin Cisco (Coregonus nigripinnis) in Northern Algonquin Provincial Park
Blackfin Cisco (Coregonus nigripinnis), a deepwater cisco species once endemic to the Laurentian Great Lakes, was discovered in Algonquin Provincial Park in four lakes situated within a drainage outflow of glacial Lake Algonquin. Blackfin habitat preference was examined by analyzing which covariates best described their depth distribution using hurdle models in a multi-model approach. Although depth best described their distribution, the nearly isothermal hypolimnion in which Blackfin reside indicated a preference for cold-water habitat. Feeding structure differentiation separated Blackfin from other coregonines, with Blackfin possessing the most numerous (50-66) gill rakers, and, via allometric regression, the longest gill rakers and lower gill arches. Selection for feeding efficiency may be a result of Mysis diluviana affecting planktonic size structure in lakes containing Blackfin Cisco, an effect also discovered in Lake Whitefish (Coregonus clupeaformis). This thesis provides insight into the habitat preferences and feeding ecology of Blackfin and provides a basis for future study. Author Keywords: allometric regression, blackfin cisco, habitat, hurdle models, lake whitefish, mysis
Assessing Canada Lynx Dispersal Across an Elevation Barrier
Mountain ranges are often thought to restrict movement of wildlife, yet previous studies evaluating the role of the Rocky Mountains as a dispersal barrier for Canada lynx (Lynx canadensis) have been contradictory. Our study uses neutral microsatellite loci to evaluate the role of the Rocky Mountains as a barrier to gene flow for lynx. Although lynx exhibited low genetic differentiation, we detected a limited effect of the mountains. Furthermore, we inferred the role played by landscape variables in gene flow (genetic differentiation predicted by landscape resistance). Limited gene flow most strongly related to resistance from physical factors (low snow cover and elevation), rather than other topographic and ecological factors (high terrain roughness, low forest cover, low habitat suitability, and geographic distance). Structural connectivity was a relatively poor predictor of functional connectivity. Overall, the Rockies represent an area of reasonably high functional connectivity for lynx, with limited resistance to gene flow. Author Keywords: Canada lynx, connectivity, gene flow, genetic structure, landscape genetics, Rocky mountains
impact of selection harvesting on soil properties and understory vegetation in canopy gaps and skid roads in central Ontario
Tree harvesting alters nutrient cycling and removes nutrients held in biomass, and as a result nutrient availability may be reduced, particularly in naturally oligotrophic ecosystems. Selection harvesting is a silvicultural technique limited to tolerant hardwood forests where individual or small groups of trees are removed creating a “gap” in the forest canopy. In order for harvesting machinery to gain access to these individual trees, trees are felled to create pathways, known as skid roads. The objective of this study was to characterize differences in soil chemical and physical properties in gaps, skid roads and uncut areas following selection harvesting in central Ontario as well as documenting differences in the understory vegetation community and sugar maple (Acer saccharum) seedlings chemical composition post harvest. First year seedlings were collected for elemental analysis from unharvested areas, canopy gaps, and skid roads in 2014, eight months after harvesting. In 2015, first and second year sugar maple seedlings were collected. Soil bulk density and water infiltration were measured in the three areas of the catchment as well as soil moisture, organic matter content, exchangeable base cations, and net nitrification. Seedlings in the disturbed sites had lower concentrations of Mg, K, P, and N compared with unharvested sites and soil nitrification was significantly lower in the skid roads. Water infiltration rates in the gap and skid roads were slower than the control and concentrations of metals (e.g. Fe, Al, Ca) and litter mass increased in litter bags deployed over 335 days, likely reflecting an increase in soil erosion in the skid roads. Understory vegetation was markedly different amongst sites, particularly the dominance of Carex spp. in the skid roads. The sustainability of industrial logging is dependent on successful tree regeneration, however, increased soil compaction, establishment and growth of grasses and shrubs, as well as low nutrient concentrations in seedlings may ultimately restrict forest succession. Author Keywords: Canadian Shield, nitrification, selection harvesting, soil compaction, sugar maple seedling, understory vegetation
Range-Based Component Models for Conditional Volatility and Dynamic Correlations
Volatility modelling is an important task in the financial markets. This paper first evaluates the range-based DCC-CARR model of Chou et al. (2009) in modelling larger systems of assets, vis-à-vis the traditional return-based DCC-GARCH. Extending Colacito, Engle and Ghysels (2011), range-based volatility specifications are then employed in the first-stage of DCC-MIDAS conditional covariance estimation, including the CARR model of Chou et al. (2005). A range-based analog to the GARCH-MIDAS model of Engle, Ghysels and Sohn (2013) is also proposed and tested - which decomposes volatility into short- and long-run components and corrects for microstructure biases inherent to high-frequency price-range data. Estimator forecasts are evaluated and compared in a minimum-variance portfolio allocation experiment following the methodology of Engle and Colacito (2006). Some consistent inferences are drawn from the results, supporting the models proposed here as empirically relevant alternatives. Range-based DCC-MIDAS estimates produce efficiency gains over DCC-CARR which increase with portfolio size. Author Keywords: asset allocation, DCC MIDAS, dynamic correlations, forecasting, portfolio risk management, volatility
Pathogen vs. Predator
Stressors are often an inescapable part of an organism’s life. While the effects of many stressors have been well studied individually, potential interactions between stressors exist that may result in greater than additive negative effects. Stressors may be linked by conflicting demands on energy budgets, interfering with important physiological pathways, or necessitating incompatible adaptive responses. Using Ranavirus (FV3) and larval dragonfly predators (Anax spp.) in a 2x2 factorial experiment on green frog (Lithobates clamitans) tadpoles, I investigate the interactions in behaviour, morphology, and metabolism when both stressors were applied in concert. I demonstrate that activity and feeding are reduced additively by both stressors, and tadpoles increase distance between conspecifics in FV3-exposed tanks, but only in the absence of predators. I also note decreases in mass, and a non-significant marginal increase in metabolic rate of tadpoles exposed to FV3. Interestingly, I provide evidence that FV3 can compromise morphometric responses through antagonistic interactions with perceived predation risk exposure, which may result in significantly elevated mortality even when either stressor is present in sub-lethal quantities. Thus, I conclude that sub-lethal exposure to stressors can nonetheless have substantial impacts on organisms and a more integrative approach to examining the impacts of stressors on individual physiology and fitness is necessary. Author Keywords: Behaviour, Interaction, Morphology, Predation Risk, Ranavirus, Tadpoles

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