Graduate Theses & Dissertations

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Neonatal Environment Influences Behavioural and Physiological Reactivity to Stressors, and Mammary Gland Development in BALB/c Mice
Using rodent models, it is possible to study the behavioural and physiological outcomes of early life stress and the influences on normal mammary gland development and carcinogenic risk. Results demonstrate that the experience of three weeks of prolonged maternal separation (LMS; 4 hrs/day) increased the susceptibility of adult, but not pubertal, female BALB/c mice to engage in higher levels of depressive-related immobility behaviour and lower levels of active floating (a suggested adaptive coping behaviour) in the acute forced swim test, than offspring that experienced three weeks of brief separation (BMS; 15 min/day) events. Despite the increased immobility behaviour, adult LMS female offspring demonstrated lower basal corticosterone levels relative to BMS females. However, the experience of chronic early-life stress, regardless of the length, results in greater changes between non-stressed and stressed corticosterone levels (i.e. stressor reactivity) in adult females compared to their male counterparts. These changes were associated with decreased glucocorticoid receptor and coactivator-associated arginine methyltransferase 1 protein expression in mammary gland of female LMS mice at young adulthood, highlighting potential mechanisms underlying their heightened risk of mammary tumourigenesis. These data suggest that early life environments can induce behavioural and physiological alterations observed in adulthood, which may have an influence on the likelihood of malignancies developing in the breast. Author Keywords: coping, early life stress, mammary gland development, mother-infant interactions, steroid receptors, stressor reactivity
Ice age fish in a warming world
In the face of climate change, the persistence of cold-adapted species and populations will depend on their capacity for evolutionary adaptation of physiological traits. As a cold-adapted Ice Age relict species, lake trout (Salvelinus namaycush) are ideal for studying potential effects of climate change on coldwater fishes. I studied the thermal acclimation capacity and aerobic metabolism of age 2+ lake trout from four populations across four acclimation temperatures (8ºC, 11ºC, 15ºC, and 19ºC). One population had marginally significant higher active metabolic rate (AMR) and metabolic scope across all temperatures. There was no interpopulation variation for critical thermal maximum (CTM), standard metabolic rate (SMR), or thermal acclimation capacity. Acclimation resulted in a 3ºC increase in thermal tolerance and 3-fold increase in SMR for all populations. At 19ºC, SMR increased and AMR declined, resulting in sharply reduced metabolic scope for all populations. The limited intraspecific variation in thermal physiology suggests that climate change may threaten lake trout at the species rather than population level. Author Keywords: Climate Change, Lake Trout, Metabolic Rate, Salvelinus namaycush, Temperature, Thermal Acclimation
Speciation of Aluminum and Zinc in Three Streams of a Forested Catchment of the Boreal Zone
This study presents a detailed assessment of the chemical speciation of aluminum and zinc in three streams of a small, acid-sensitive forested catchment on the southern edge of the Precambrian Shield. Speciation analysis was achieved using an in-situ analytical technique known as Diffusive Gradient in Thin film (DGT) which measures labile metals, and a predictive computer algorithm (WHAM VI) which calculates metal species concentrations. Three types of DGT with different metal scavenging capabilities were used and a total of 11 deployments performed across four seasons. WHAM VI predictions showed that the organic fraction of aluminum was the main contributor to the dissolved concentrations in the main inflow stream (PC1) (~ 80 %) and the lake's outflow (PCO) (~ 75%); in the upland stream (PC1-08) the inorganic fraction contributed ~ 75%. For zinc the free ion was the single most important contributor to the dissolved concentration (< 90%) in all three streams. A comparative study of the DGT and WHAM methods showed an agreement between their inorganic concentrations during the spring season. Both methods indicate the greatest environmental impact for Al takes place during snow melt period in PCO and PC1-08 and in the summer for PC1. The greatest environmental impact for Zn predicted with WHAM VI, occurs during the spring in all three streams. Author Keywords: Aluminum, DGT, Metal speciation, WHAM, Zinc
Cytokinin Oxidase/Dehydrogenase (CKX) Gene Family in Soybeans (Glycine max)
Glycine max (soybean) is an economically important plant species that registers a relatively low yield/seed weight compared to other food and oil seed crops due to higher rates of flower and pod abortion. Alleviation of this abortion rate can be achieved by altering the sink strength of the reproductive organs of soybeans. Cytokinin (CK) plays a fundamental role in promoting growth of sink organ (flowers and seeds) by increasing the assimilate demand. Cytokinin oxidase/dehydrogenase (CKX) is an enzyme that catalyses the irreversible breakdown of active CKs and hence reduce the cytokinin content. The current thesis uncovers the members of CKX gene family in soybeans and the natural variations among CKX genes within soybean varieties with different yield characteristics. The identification of null variants of OsCKX2 that resulted in large yield increases by Ashikari et al. (2005) provided a rationale for current thesis. The soybean CKX genes along with the ones from Arabidopsis, Rice and Maize were used to construct a phylogenetic tree. Using comparative phylogeny, protein properties and bioinformatic programs, the potential effect of the identified natural variations on soybean yield was predicted. Five genes among the seventeen soybean CKXs identified, showed polymorphisms. One of the natural variations, A159G, in the gene GmCKX16 occurred close to the active site of the protein and was predicted to affect the activity of enzyme leading to higher accumulation of CKs and hence increased seed weight. Use of such natural variations in marker assisted breeding could lead to the development of higher yielding soybean varieties. Author Keywords: CKX, Cytokinins, Seed weight, Seed Yield, SNPs, Soybeans
Molecular Dynamics Simulations of Aqueous and Confined Systems Relevant to the Supercritical Water Cooled Nuclear Reactor
Supercritical water (SCW) is the intended heat transfer fluid and potential neutron moderator in the proposed GEN-IV Supercritical Water Cooled Reactor (SCWR). The oxidative environment poses challenges in choosing appropriate design materials, and the behaviour of SCW within crevices of the passivation layer is needed for developing a corrosion control strategy to minimize corrosion. Molecular Dynamics simulations have been employed to obtain diffusion coefficients, coordination number and surface density characteristics, of water and chloride in nanometer-spaced iron hydroxide surfaces. Diffusion models for hydrazine are evaluated along with hydration data. Results demonstrate that water is more likely to accumulate on the surface at low density conditions. The effect of confinement on the water structure diminishes as the gap size increases. The diffusion coefficient of chloride decreases with larger surface spacing. Clustering of water at the surface implies that the SCWR will be most susceptible to pitting corrosion and stress corrosion cracking. Author Keywords: Confinement, Diffusion, Hydration, MD Simulations, Supercritcal Water
Unexpected Journeys
The last two decades have seen thousands of Canadian university graduates go to teach English in places such as China, South Korea, and Japan. In this thesis, drawing on Clandinin and Connelly's concept of narrative inquiry, I situate the stories I heard about the experiences of 15 teachers who taught English as a Second Language in South Korea between 2003 and 2012. While my interviewees expressed intrinsically personal reasons for taking on such temporary professional employment, they also acknowledged that they felt somewhat forced to do so by an increasingly bleak job market at home. I position their decisions in the neoliberal employment context in Canada over the past two decades, highlighting the personal and socioeconomic factors that influenced them to take up such opportunities. Additionally, I examine how these experiences shifted their views of Canada and what it meant to be Canadian, both while they were away and upon their return home by revealing the contradictions between expectation and the lived realities of young Canadians. These contradictions unmask the deceptive nature of dominant narratives in Canadian society. Author Keywords: Canadian Identity, Canadian Job Market, Narrative, Neoliberalism, Teaching Abroad
Return to "The Child"
Despite - or perhaps because of - her popularity as a best-selling poet, the work of Mary Oliver has been minimized and marginalized within the academy. Nevertheless, Oliver's readership is an expansive and devout one made up of a wired yet insular North American public in search of reconnecting with the natural world. I propose that through Oliver's poetry readers access the affective, sensory responses to nature first encountered during childhood. This return to "the child" is deliberately used by various publics to share communal goals. Drawing from such frameworks as ecocritical and trauma theory, I explore environmental memory, ecstatic places, and the sensuousness of nature and language to consider ways in which diverse publics claim and use Oliver's work. I provide a close reading of selections of Oliver's poems to argue that her work's appeal speaks to a revived perception of the necessity of nature to the human spirit Author Keywords: Attentiveness, Childhood, Language, Mary Oliver, Nature Poetry, Senses
Role of Multiple Nights of Sleep in the Consolidation of an Engaging and Complex Motor Learning Task
The present study examined the role of multiple nights of sleep in the consolidation of a complex motor learning task. Participants were 24 Trent undergraduates, 12 in the learning group (Mage = 20.33, SD = 1.87, 10 female) and 12 in the control group (Mage = 21.92, SD = 3.42, 7 female). Participants underwent 5 consecutive nights of polysomnographic recordings, with a Rock Band learning session on the third night. A series of 2(group)x4(night) ANOVAs were performed on the sleep variables. Interactions were found in the number of spindles detected at Pz, F(333) = 9.19, p <.01, and in the density of spindles detected at Pz, F(3,33) = 4.06, p <.05. The pattern of changes from baseline was significantly different between the two groups; spindles increased in the learning group and decreased in the control group. The novel finding was that spindle number/density remained elevated at the third post-learning night of sleep. Author Keywords: Motor Learning, Procedural Memory, Sleep, Sleep Spindles
BACKGROUND PRACTICES, AFFORDANCES, AND THE FRAME PROBLEM
This project is a Heideggerian critique of the subject/object metaphysic presupposed in the Representationalist claim that the world is made intelligible solely in virtue of internal states that bear representations. It is comprised of two sections. The first is a critique of the ontological primacy of representational-intentionality/action in which I argue that where Brentano, Husserl, and Searle have erred is not in their model of intentionality/action, but in assigning a priori status to a derivative mode of being. The second is a critique of representation-driven artificial intelligence whereby I argue that belief-fixation and action selection that is context-dependent produces an insurmountable problem that prevents the parsing of context-specifying relevance; the corollary being that the world is not disclosed despite that system having a structurally isomorphic internal constitution to that which is purported by the Representationalist to obtain in human beings. With the issue thus framed, I conclude by arguing that this problem is dissolved within a Heideggerian phenomenological framework. Author Keywords: Artificial Intelligence, Heidegger, Phenomenology, Representationalism, Skillful Coping, The Frame Problem
(un)Natural Provocation
My thesis examines anthropomorphism and many avenues in which humans represent nonhumans to evaluate their own lives. Using Isabella Rossellini's Green Porno webseries, a collection of two-minute films starring Rossellini as a multitude of nonhumans with costumes transforming her into nonhuman, I posit that a new form of anthropomorphism -- one that values the nonhuman in all his or her nonhumanity -- is emerging in contemporary media. Rossellini describes the mating, seduction, and maternal instincts of these nonhumans, regularly drawing parallels between nonhuman and human behavior and uncovering crucial intersections in femininity, masculinity, queer theory, and abjection. In more recent films, I see Rossellini performing certain nonhumans to critique particular characteristics of Western human society and incredulously addressing the human viewer as a member of a species that might not be as high in the caste system of living beings as he or she is led to believe. In turning this sense of grotesque Otherness onto the human, I identify Rossellini as engaging in counterabjection, or the reversal of extreme degradation often projected upon nonhuman bodies by humans. Author Keywords: abjection, animal studies, nonhuman, queer studies
American Acropolis, American Ruins
Since 1979, photographer and sociologist Camilo José Vergara has taken repeat photographs of American cities in decline, focusing on evolving landscapes of postindustrial decay. Vergara's images subscribe to an aesthetic of ruin while providing a record of America's crumbling ghettos rooted in social documentary concerns. Vergara's work diverges from the ahistorical tendencies of contemporary ruin porn photography: by challenging the photograph's temporal stasis Vergara bears witness to the ongoing reality of disenfranchisement, assembling an archive that takes up the Benjaminian task of doing history in images. Vergara's photographs challenge standard photojournalistic portrayals of violence, particularly the ways in which `violent' African American and Hispanic inner city populations have been erroneously cast as the cause of their own economic misfortune. The Invincible Cities website assists Vergara in drawing attention to forgotten places but also complicates his mandate to engage outside viewers by distancing them from the real-­world environments his photographs portray. Author Keywords: Camilo José Vergara, imagistic history, postindustrial decline, repeat photography, ruin porn, Walter Benjamin
Carbon and Nitrogen Isotope Changes in Streams along an Agricultural Gradient
Nitrogen is a major constituent of agricultural fertilizers, and nitrogen inputs to stream water via runoff and groundwater lead to a variety of negative environmental impacts. In order to quantify the movement of nitrogen through aquatic food webs, fourteen streams with varying land uses across South-Central Ontario were sampled for two species of fish, freshwater mussels, and water for measurement of isotope ratios of δ15N and δ13C. I found that nitrogen isotopes in fish, water, and mussels were related to the percentage of riparian monoculture, and that carbon isotopes were unrelated to monoculture. Though all species were enriched as monoculture increased, the rate of δ15N enrichment as monoculture increased did not vary between species. This study has improved our understanding of how monoculture affects nutrient enrichment in stream food webs, and assesses the validity of using nitrogen isotopes to measure trophic positions of aquatic organisms across an environmental gradient. Author Keywords: agriculture, fish, food webs, nitrogen, stable isotopes, streams

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Graduate student theses produced at Trent University. You may also browse theses and dissertations by year, program, or author.

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1973 - 2033
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