Graduate Theses & Dissertations

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Stability Properties of Disease Models under Economic Expectations
Comprehending the dynamics of infectious diseases is very important in formulating public health policies to tackling their prevalence. Mathematical epidemiology (ME) has played a very vital role in achieving the above. Nevertheless, classical mathematical epidemiological models do not explicitly model the behavioural responses of individuals in the presence of prevalence of these diseases. Economic epidemiology (EE) as a field has stepped in to fill this gap by integrating economic and mathematical concepts within one framework. This thesis investigated two issues in this area. The methods employed are the standard linear analysis of stability of dynamical systems and numerical simulation. Below are the investigations and the findings of this thesis: Firstly, an investigation into the stability properties of the equilibria of EE models is carried out. We investigated the stability properties of modified EE systems studied by Aadland et al. [6] by introducing a parametric quadratic utility function into the model, thus making it possible to model the maximum number of contacts made by rational individuals to be determined by a parameter. This parameter in particular influences the level of utility of rational individuals. We have shown that if rational individuals have a range of possible contacts to choose from, with the maximum of the number of contacts allowable for these individuals being dependent on a parameter, the variation in this parameter tends to affect the stability properties of the system. We also showed that under the assumption of permanent recovery for disease coupled with individuals observing or not observing their immunity, death and birth rates can affect the stability of the system. These parameters also have effect on the dynamics of the EE SIS system. Secondly, an EE model of syphilis infectivity among &ldquo men who have sex with men &rdquo (MSM) in detention centres is developed in an attempt at looking at the effect of behavioural responses on the disease dynamics among MSM. This was done by explicitly incorporating the interplay of the biology of the disease and the behaviour of the inmates. We investigated the stability properties of the system under rational expectations where we showed that: (1) Behavioural responses to the prevalence of the disease affect the stability of the system. Therefore, public health policies have the tendency of putting the system on indeterminate paths if rational MSM have complete knowledge of the laws governing the motion of the disease states as well as a complete understanding on how others behave in the system when faced with risk-benefit trade-offs. (2) The prevalence of the disease in the long run is influenced by incentives that drive the utility of the MSM inmates. (3) The interplay between the dynamics of the biology of the disease and the behavioural responses of rational MSM tends to put the system at equilibrium quickly as compared to its counterpart (that is when the system is solely dependent on the biology of the disease) when subjected to small perturbation. Author Keywords: economic and mathematical epidemiology models, explosive path, indeterminate-path stability, numerical solution, health gap, saddle-path stability, syphilis,
First Time…A Second Time
The purpose of the current study was to explore virginity loss experiences in lesbian, gay, and bisexual individuals (LGB), specifically those who have had both a sexual experience with a member of a different sex and a member of the same sex. This phenomenon is what the current study is defining as second virginity loss. Participants consisted of 645 LGB self-identified individuals, the sample was approximately half women (53%) and ages ranged from 18-65. Further, six semi-structured interviews were conducted to gain a clearer understanding of LGB individuals virginity loss experiences. Of the sample, approximately 60% of each sexual orientation reported having two sexual experiences they equated with virginity loss, one with a member of a different sex, and one with a member of the same sex. Analyses of both the qualitative and quantitative data were conducted in an attempt to gain an understanding in three main areas: (1) definitions of virginity loss, (2) virginity beliefs, and (3) motivations. It was found that LGB individuals continue to hold heteronormative definitions of virginity loss, i.e. penile-vaginal intercourse, though these definitions were found to be transitional in nature. LGB individuals also seem to hold more gift related beliefs toward their same-sex experience and more stigma related beliefs toward their different sex experience, however, as shown by previous research (Carpenter, 2001, 2002), most LGB individuals highly endorsed process beliefs. Finally, motivations for virginity loss were found to be consistent with two main themes: validation and drive. Overall, this research suggests that the LGB community has a fairly complicated relationship with virginity but certainly do not feel exempt from the concept or the pressures attached. The current study is the first to explore the phenomenon of second virginity loss in LGB individuals and should be used as a foundation for future research in both first sexual experience and LGB fields to build upon. Author Keywords: first sexual experience, LGB, mixed-methods, second virginity loss, virginity
Test for Pluralism
This study intervenes into the debate regarding the definition of pluralism in ecological economics and how that definition affects various characterizations of ecological economics. The methodological pluralist camp argue for the inclusion of neoclassical economics into the ecological economics fold, while the critical pluralist camp argue against the inclusion of neoclassical economics. This study provides a critical exposition of the preanalytical visions of neoclassical and ecological economics that includes their respective ontological and epistemological foundations. Those foundations are critically scrutinized for coherence, realism and relevance, and their respective ability to analyze complex systems. It is argued that combining neoclassical and ecological economics renders ecological economics incoherent, and that neoclassical economics fails the test of realism, and its conceptual apparatus is only capable of analyzing simple systems. It is also argued that ecological economics is coherent, passes the test of realism because it is ontologically, socio-historically, and descriptively realistic, and the conceptual apparatus of institutionalist ecological economics incorporates complex systems. It is concluded that practitioners of ecological economics ought to reject and jettison neoclassical economics from their fold and to develop closer connections to and alliances with practitioners of heterodox economics. Keywords: Ecological Economics, Ontology, Coherence, Realism, Systems Thinking. Author Keywords: Coherence, Ecological Economics, Ontology, Systems Thinking
Talking it out
The literature to date that investigates the development of social perspective taking in children primarily focuses on preschool aged children. These studies provide evidence that implicates language as being crucial for social perspective taking in young children but less is known about the importance of language to social perspective taking during middle childhood and early adolescence. The current study uses Selman's theory of socio-cognitive development to investigate the maturation of social perspective taking and the importance of language to social problem solving in 8 year olds (n = 111) and 12 year olds (n = 112). Analysis of variance and scalogram analysis shows a developmental progression of social perspective taking across the social problem solving process. Children may be able to demonstrate reciprocal perspective taking when generating strategies before they are able to demonstrate reciprocal perspective taking for other steps of social problem solving. Flexibility in interpersonal orientation is shown to be a predictor of social problem solving ability. Correlations and multiple regression analysis demonstrate that language is important to overall social problem solving but that the role of semantic and syntactic language may differ at age 8 compared to age 12. Author Keywords: interpersonal orientation, language, Selman, social cognition, social perspective taking, social problem solving
Phosphorus forms and response to changes in pH in acid-sensitive soils on the Precambrian Shield
Catchment soil acidification has been suggested as a possible mechanism for reducing phosphorus (P) loading to surface waters in North America and northern Europe, but much of the research that has been conducted regarding P immobilization in pH manipulated soils has been performed at high P concentrations (> 130 μM). This study investigated how soil acidity was related to P fractionation and P sorption at environmentally relevant P concentrations to evaluate the potential influence of long term changes in soil pH on P release to surface waters. Total phosphorus (TP) concentrations declined between 1980 and 2000 in many lakes and streams in central Ontario; over the same time period forest soils in this region became more acidic. Soils were collected from 18 soil pits at three forested catchments with similar bedrock geology but varying TP export loads. The soil pH at the 18 study soil pits spanned the historic soil pH range, allowing for `space for time' comparison of soil P factions. Soils were analysed by horizon for P fractions via Hedley P fractionation. Batch P sorption experiments were performed on selected B-horizon soils at varied solution pH. Soil P fractions varied by horizon but were comparable among the three catchments, with only apatite (PHCl) differing significantly across catchments. Contrary to expectation, both soluble and labile P showed negative relationships with pH in some horizons. Mineral soils were able to sorb almost all (> 90 %) of the P in solution at environmentally relevant P concentrations (4.5 - 45.2 μM). Phosphorus sorption at environmentally relevant P concentrations was unrelated to solution pH but at high P concentration there was a positive relationship between P sorption and solution pH, suggesting a P concentration dependant P sorption mechanism. Phosphorus budgets indicate that P is accumulating within catchments, suggesting that P is being immobilized in the terrestrial environment. An alternative hypothesis, which attempts to explain both the decline in stream TP export and terrestrial P accumulation, is discussed. The results from this study suggest that acidification induced P sorption in upland soils are not a contributing factor to decreases in stream TP concentration in the study catchments. Author Keywords: central Ontario, Hedley fractionation, phosphorus, podzols, soil acidification, sorption
effects of environmental variables and dissolved organic matter characteristics on the diffusion coefficient of dissolved organic matter using diffusive gradients in thin films
The efficacy of the diffusive gradients in thin films (DGT) passive samplers to provide accurate measurements of free metal ions and those complexed with dissolved organic matter (DOM) was investigated. DOM controls the diffusive properties of DOM-complexed metal species in natural systems. Knowing the diffusion coeiffiecent (D) for DOM of different molecular weights (MW) and the major environmental variables influencing D is critical in developing the use of DGT passive samplers and understanding labile species. D and MW were determined for natural and standard DOM. No noticeable changes in DOM MW were observed during the diffusion process, suggesting that DOM remains intact following diffusion across the diffusive gel. Data analysis revealed that MW had the greatest influence on D, with a negative relationship between D and MW, except in tidal areas where ionic strength influence on D was significant. This study provides further characterization of the variables influencing D using the DGT technique. Author Keywords: Diffusion coefficient, Diffusive gradients in thin films, Dissolved organic matter, Flow field-flow fractionation, Principal Component Analysis, UV-Vis Spectroscopy
'This is where the poetry comes out'
Since 1984, poetry slams have emerged as a politicized expressive movement of performing the personal and political through poetry competitions. Slams are also discursively spatialized, often represented as “spaces” that are “safe,” “inclusive,” etc. In this thesis, I investigate how, why, and to what effect the Peterborough Poetry Slam produces, consolidates, and challenges such “resistant spaces.” Drawing on interviews and participant observation, I consider how the slam’s reiterative practices facilitate its space-making by encouraging performances that resist, reimagine, and sometimes inadvertently reify dominant societal norms. I argue that this space-making is imperfect yet productive: though not resistant space in any straightforward or static way, the slam continuously produces possibilities to challenge norms and confront power. This thesis contributes to scholarship on performative space and creative resistance movements. In an era when political resistance to power structures is often silenced, this research offers insights of potential significance to other resistant space-makings. Author Keywords: Nogojiwanong Peterborough, performative space, poetry slam, resistance, space-making, spoken word
Effects of biodiversity and lake environment on the decomposition rates of aquatic macrophytes in the Kawartha Lakes, Ontario
Decomposition of aquatic macrophytes has an important role in defining lake carbon (C) storage and nutrient dynamics. To test how diversity impacts decomposition dynamics and site-quality effects, I first examined whether the decomposition rate of aquatic macrophytes varies with species richness. Generally, I found neutral effects of mixing, with initial stoichiometry of component species driving decomposition rates. Additionally, external lake conditions can also influence decomposition dynamics. Therefore, I assessed how the decomposition rate of a submersed macrophyte varies across a nutrient gradient in nine lakes. I found decomposition rates varied among lakes. Across all lakes, I found Myriophyllum decomposition rates and changes in stoichiometry to be related to both nutrients and water chemistry. During the incubation changes in detrital stoichiometry were related to lake P and decomposition rates. Aquatic plant community composition and stoichiometry could alter decomposition dynamics in moderately nutrient enriched lakes. Author Keywords: Aquatic Plants, Decomposition, Diversity, Littoral, Macrophytes, Nutrients
Disability-Mitigating Effects of Education on Post-Injury Employment Dynamics
Using data drawn from the Workplace Safety and Insurance Board’s (WSIB) Survey of Workers with Permanent Impairments, this thesis explores if and how the human capital associated with education mitigates the realized work-disabling effects of permanent physical injury. Using Cater’s (2000) model of post-injury adaptive behaviour and employment dynamics as the structural, theoretical, and interpretative framework, this thesis jointly studies, by injury type, the effects of education on both the post-injury probability of transitioning from non-employment into employment and the post-injury probability of remaining in employment once employed. The results generally show that, for a given injury type, other things being equal, higher levels of education are associated with higher probabilities of both obtaining and sustaining employment. Author Keywords: permanent impairment, permanent injury, post-injury employment
Variation in the δ15N and δ13C composition of POM in the Lake Simcoe watershed
The purpose of this study was to quantify the variation of baseline carbon and nitrogen stable isotope signatures in the Lake Simcoe watershed and relate that variation to various physicochemical parameters. Particulate organic matter samples from 2009 and 2011 were used as representatives of baseline isotopic values. Temporal data from two offshore lake stations revealed that δ15N of POM was lowest mid-summer and highest after the fall turnover. POM δ13C was variable throughout the summer before declining after fall turnover. Spatial data from the lake and the tributaries revealed that POM stable isotope signatures were highly variable. Various physicochemical parameters indicative of phytoplankton biomass were significantly positively correlated with POM δ15N and significantly negatively correlated with POM δ13C. The correlations were mostly significant in the tributaries, not the lake. Moreover, many of the correlations involving δ15N of POM were driven by extreme values in Cook's Bay and its tributaries. In general, it's likely that different processes or combination of processes were affecting the δ15N and δ13C POM in the Lake Simcoe watershed as physicochemical parameters alone could not explain the variability. Measuring the δ15N of ammonium and nitrate, as well as the δ13C of DIC would help discern the dominant nitrogen and inorganic carbon cycling processes occurring in the Lake Simcoe watershed. Author Keywords: δ13C, δ15N, isotopic baseline, particulate organic matter, spatial variation, stable isotopes
Assessing Connectivity of Protected Area Networks and the Role of Private Lands in the United States
Forestalling biodiversity loss through the establishment of protected areas is a universally accepted conservation strategy, yet despite established guidelines for protected area coverage and placement, much of the world is currently failing to meet its commitments to conservation planning and landscape protection. Calls for the United States to protect more land usually focus on the need for strategic selection of land parcels to bolster protected area coverage and network functionality, but to date there lacks focused research on either the role of private protected areas in conservation planning or the factors affecting individual protected area selection and importance. We determined gaps in conservation planning in the contiguous United States by analyzing the connectivity of protected area networks by state, and assessing the importance of private protected areas in improving linkages in protected area connectivity. We found that all states had low coverage from protected areas (average <8.4% of total land mass), and especially private protected areas (average <1.1% of total land mass), and that the overall contribution of such areas to protected area network connectivity also was low. Terrain ruggedness was identified as the main factor affecting the current location of protected areas, and that protected area spatial layout is a primary influence on landscape connectivity. We conclude that establishment of private protected areas could offer a viable conservation tool for increasing protected area coverage and connectivity, but that current efforts are inadequate to either adequately link existing protected areas or to meet established land protection guidelines. Author Keywords: Aichi Target 11, conservation planning, graph theory, network theory, private conservation, protected areas
Sustainable Development and Environmental Security in the Canadian Arctic
This study identifies and examines interlinkages between climate change and sustainable development, environmental security, and adaptive capacity through a case study of two communities in the Inuvialuit Settlement Region: Inuvik and Tuktoyaktuk. It seeks to understand how these two communities perceive climate change and define sustainable development, particularly in relation to oil and gas development. This thesis discusses the constraints that may be arising for local communities to benefit from emerging opportunities due to competing notions of sustainable development and environmental security. The findings indicate how notions of environmental security and sustainable development act upon multiple levels to impact the adaptive capacity of communities in the Arctic. The general findings also suggest that regionally specific understandings of sustainable development, sustainability, and environmental security need to be acknowledged in order to develop successful governance coordination and cooperation strategies and paradigms related to economic, social, infrastructure and environmental issues in the NWT and the Canadian Arctic. Author Keywords: Arctic, Beaufort Sea, climate change, Environmental Security, Inuvialuit, Sustainable Development

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Format: 2023/12/05