Graduate Theses & Dissertations

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Near-road assessment of traffic related air pollutants along a major highway in Southern Ontario
The spatial and temporal variation in atmospheric nitrogen dioxide (NO2), ammonia (NH3), and 17 elements (V, Cr, Fe, Ni, Cu, Zn, As, Cd, Pb, Mg, Al, Ca, Co, Se, Sb, Mn, and Na) were measured at 40 road side locations along a ~250 km traffic density gradient of 40,000–400,000 vehicles on the King’s Highway 401, in Ontario, Canada. Elemental concentrations were measured over a year, using moss bags as passive samplers, for four quarterly three-month exposure periods (October 2015 – October 2016). Gaseous NO2 and NH3 concentrations were measured using Willem’s badge passive diffusive samplers for twelve one-week exposure periods (one per month: October 2015–October 2016). Dry deposition of nitrogen was estimated using the inferential method. There were significant linear relationships between NO2 and NH3 and average annual daily traffic (AADT) volumes across the study area; higher concentrations corresponded to higher volume traffic sites. Average NO2 concentrations at sites ranged from 23.5 to 73 μg/m3, with an annual average of 43.7 μg/m3. Ammonia ranged from 2.56 to 13.55 μg/m3, with an annual average of 6.44 μg/m3. There were significant quarterly variations in NO2, with concentrations peaking during the winter months. In contrast, NH3 showed no significant quarterly variation, but a slight peak occurred during the summer. Gaseous NO2 and NH3 were highly positively correlated (r = 0.63), suggesting a common emission source from traffic. Concentrations in exposed moss were determined by subtracting the total concentration of each metal in the exposed sample from the background concentration present in the moss. Relative accumulation factors (RAF) and contamination factors were also calculated to determine the anthropogenic influence on tissue concentrations in exposed moss. All metals showed elevated levels versus background concentrations, with all metals except Ni and Co showing considerable enrichment. The highest levels of contamination were from V, Cr, Fe, Zn, Cd, Sb, Pb and Na. Principal component analysis indicated 5 clear clusters of related elements, with PC1 accounting for 36.2% and PC2 accounting for 25.6% of the variance. Average annual daily traffic was significantly related to Cr, Fe, Cu, Sb, Mn, Al, and Na. Road side monitoring shows consistently higher concentrations than active monitoring sites located further from the edge of the road, indicating a need for increased road side monitoring in Ontario, Canada. Author Keywords:
Role of Dielectric Screening in SrTiO3-Based Interfaces
We build a theoretical model for exploring the electronic properties of the two-dimensional (2D) electron gas that forms at the interface between insulating SrTiO3 (STO) and a number of perovskite materials including LaTiO3, LaAlO3, and GdTiO3. The model treats conduction electrons within a tight-binding approximation, and the dielectric polarization via a Landau-Devonshire free energy that incorporates STO's strongly nonlinear, nonlocal, field-, and temperature-dependent dielectric response. We consider three models for the dielectric polarization at the interface: an ideal-interface model in which the interface has the same permittivity as the bulk, a dielectric dead-layer model in which the interface has permittivity lower that the bulk, and an interfacial-strain model in which the strain effects are included. The ideal-interface model band structure comprises a mix of quantum 2D states that are tightly bound to the interface, and quasi-three-dimensional (3D) states that extend hundreds of unit cells into the STO substrate. We find that there is a substantial shift of electrons away from the interface into the 3D tails as temperature is lowered from 300 K to 10 K. We speculate that the quasi-3D tails form the low- density high-mobility component of the interfacial electron gas that is widely inferred from magnetoresistance measurements. Multiple experiments have observed a sharp Lifshitz transition in the band structure of STO interfaces as a function of applied gate voltage. To understand this transition, we first propose a dielectric dead-layer model. It successfully predicts the Lifshitz transition at a critical charge density close to the measured one, but does not give a complete description for the transition. Second, we use an interfacial-strain model in which we consider the electrostrictive and flexoelectric coupling between the strain and polarization. This coupling generates a thin polarized layer whose direction reverses at a critical density. The transition occurs concomitantly with the polarization reversal. In addition, we find that the model captures the two main features of the transition: the transition from one occupied band to multiple occupied bands, and the abrupt change in the slope of lowest energy band with doping. Author Keywords:
Hybridization dynamics in cattails (Typha spp.,) in northeastern North America
Interspecific hybridization is an important evolutionary process which can contribute to the invasiveness of species complexes. In this dissertation I used the hybridizing species complex of cattails (Typha spp., Typhaceae) to explore some of the processes that could contribute to hybridization rates. Cattails in northeastern North America comprise the native T. latifolia, the non-native T. angustifolia, and their fertile hybrid, T. × glauca. First, I examined whether these taxa segregate by water depth as habitat segregation may be associated with lower incidence of hybridization. I found that these taxa occupy similar water depths and therefore that habitat segregation by water depth does not promote mating isolation among these taxa. I then compared pollen dispersal patterns between progenitor species as pollen dispersal can also influence rates of hybrid formation. Each progenitor exhibits localized pollen dispersal, and the maternal parent of first generation hybrids captures more conspecific than heterospecific pollen; both of which should lead to reduced hybrid formation. I then conducted controlled crosses using all three Typha taxa to quantify hybrid fertility and to parameterize a fertility model to predict how mating compatibilities should affect the composition of cattail stands. I found that highly asymmetric formation of hybrids and backcrosses and reduced hybrid fertility should favour the maintenance of T. latifolia under certain conditions. Finally, I used a population genetics approach to characterize genetic diversity and structure of Typha in northeastern North America to determine the extent to which broad-scale processes such as gene flow influence site-level processes. I concluded that hybrids are most often created within sites or introduced in small numbers rather than exhibiting broad-scale dispersal. This suggests that local processes are more important drivers of hybrid success than landscape-scale processes which would be expected to limit the spread of the hybrid. Though my findings indicate some barriers to hybridization in these Typha taxa, hybrid cattail dominates much of northeastern North America. My results therefore show that incomplete barriers to hybridization may not be sufficient to prevent the continued dominance of hybrids and that active management of invasive hybrids may be required to limit their spread. Author Keywords: fertility model, genetic structure, Hybridization, invasive species, niche segregation, pollen dispersal
Nineteenth-Century Aesthetics of Murder
This dissertation examines how sex crime and serial killing became a legitimate subject of aesthetic representation and mass consumption in the nineteenth century. It also probes into the ethical implications of deriving pleasure from consuming such graphic representations of violence. Taking off from Jack the Ripper and the iconic Whitechapel murders of 1888, it argues that a new cultural paradigm – the aesthetics of murder – was invented in England and France. To study the ‘aesthetics of murder’ as countless influential critics have done is not to question whether an act of murder itself possesses beautiful or sublime qualities. Rather, it is to determine precisely how a topic as evil and abject as murder is made beautiful in a work of art. It also questions what is at stake ethically for the reader or spectator who bears witness to such incommensurable violence. In three chapters, this dissertation delves into three important tropes – the murderer, corpse, and witness – through which this aesthetics of murder is analyzed. By examining a wide intersection of visual, literary, and cultural texts from the English and French tradition, it ultimately seeks to effect a rapprochement between nineteenth-century ethics and aesthetics. The primary artists and writers under investigation are Charles Baudelaire, Thomas De Quincey, Oscar Wilde, and Walter Sickert. In bringing together their distinctive styles and aesthetic philosophies, the dissertation opts for an interdisciplinary and comparative approach. It also aims to absolve these writers and artists from a longstanding charge of immorality and degeneracy, by firmly maintaining that the aesthetics of murder does not necessarily glorify or justify the act of murder. The third chapter on the ‘witness’ in fact, elucidates how writers like De Quincey and Wilde transferred the ethical imperative from the writer to the reader. The reader is appointed in the role of a murder witness who accidentally discovered the corpse on the crime scene. As a traumatized subject, the reader thus develops an ethical obligation for justice and censorship. Author Keywords: Censorship, Jack the Ripper, Murder, Trauma, Victorian, Wilde
Assessing Emotion Processing Deficits in Youth
It is well-established that alexithymia in adulthood is a critical risk factor for numerous negative mental health and well-being outcomes. Although this area of research has begun to receive interest in earlier developmental stages, significant methodological limitations have been noted with current measures of alexithymia for adolescence. As such, the aim of the current thesis was to provide empirical evidence on the psychometric strength of a new adolescent measure of alexithymia, the Toronto Alexithymia Scale – Adolescent Version (TAS-A). Study 1 examined the construct validity of the TAS-A in relation to self and informant reported emotional intelligence (EI), while study 2 examined the predictive validity of the TAS-A in relation to adolescent problematic gambling and academic achievement. Adolescents completed self-reports of alexithymia, EI, and gambling behaviour, parents completed informant reports regarding their child’s EI, and academic records were obtained. Confirmatory factor analyses revealed significant relationships between adolescent alexithymia, and self and informant reported EI, indicating significant overlap in constructs. Adolescent alexithymia was also shown to be a significant predictor of problematic gambling and academic achievement; however, some interesting gender differences were observed (a pattern of results reported consistently in the adult alexithymia literature). Results are discussed in terms of methodological and clinical implications during the vulnerable developmental transition of adolescence. Author Keywords: adolescence, alexithymia, psychometrics
Tests of the Invasional Meltdown Hypothesis in invasive herbaceous plant species in southern Ontario
According to the Invasional Meltdown Hypothesis (IMH), invasive species may interact in their introduced range and facilitate future invasions. This study investigated the possibility that Alliaria petiolata, an invasive allelopathic herbaceous plant in Ontario, is facilitating invasions by additional alien species. Two allelopathic focal species were chosen for this study: the native Solidago canadensis and the invasive A. petiolata. Field surveys in southern Ontario that quantified plant biodiversity in plots that included one or both focal species revealed no support for the IMH, although fewer species co-existed with A. petiolata than with S. canadensis. A year-long recruitment experiment in Peterborough, Ontario, also produced results inconsistent with the IMH, although did provide some evidence that A. petiolata limited recruitment of other species. These results collectively show negative impacts on regional biodiversity by A. petiolata, even in the absence of an invasional meltdown. Author Keywords: allelopathy, Alliaria petiolata, co-occurrence surveys, invasional meltdown hypothesis, invasive species, Solidago canadensis
Using a real-world chopping task to study motor learning and memory
Typically task interference is studied using reaching adaptation tasks (visuomotor rotation and/or force-field learning). Participants in these experiments are already experts at the base task (point-to-point, planar reaching) and their ability to adapt reaching to the imposed perturbation is studied. The pattern of data induced by the perturbation is used to make inferences about the nature and neural correlates of our learning and memory for reaching perturbations, specifically, and motor performance in general. We wanted to see if it is possible to demonstrate this same interference pattern using a novel vegetable-chopping task, where we can easily recreate natural performance settings using a task for which we can easily identify non-experts. Participants performed a chopping task in which they are asked to chop a sweet potato into 5 mm-wide slices, matching the beat of a metronome (120 bpm). Following this initial learning, participants were exposed to an interference condition. Participants then performed trials of the original task again. Interference was inferred if the second performance of the original task was impaired, compared to initial performance. Experiment 1 involved novice choppers, and either the force or frequency of chops was manipulated. Only the altered frequency task produced interference effects. In Experiment 2, competent and expert choppers had to manage either a faster or slower frequency. We found evidence for interference in competents, but not experts. These results support the idea that the vulnerability to interference of motor memory changes with practice, and so any inferences made about memory structure must take into account not only expert performance, but every level of skill. Author Keywords: expertise, interference, motor learning, reaching adaptation
Towards a Critical Pedagogy of Globality
In this thesis, I use “Trump’s Wall” between Mexico and the US to resist Eurocentrism and the challenges Eurocentric pedagogy poses to the research-practitioner. In my method, I reimagine C. Alejandra Elenes’ borderlands theory as a zone of empowerment within a multicultural Canadian classroom, and braid it in a hybrid assemblage with the rhizome. The “rhizo-borderlands” assemblage uses selected field notes gleaned from my teaching practice to develop themes of a critical pedagogy of globality in personal, local and international dimensions. These are further braided with a “day-in-the-life” narrative of a fictionalized student (Ellie) who navigates her way towards a world literature classroom where the focus is The Kite Runner by Khaled Hosseini. This assemblage affirms my belief that teaching and learning provides a context where students become “border crossers” and navigate points of intersection between their local and global selves, in order to develop intercultural competencies. Author Keywords: Action Narrative, Critical Pedagogy, Rhizomes
Socio-Ecology and the Sacred
Within the complex socio-ecological systems of South and Southeast Asia, ancient sacred natural sites were created by, and imbued with, cultural and ideological values. These landscapes are liminal spaces or threshold environments between cultivated areas and wilder spaces; the practice of creating and maintaining them persists from ancient to modern times. This thesis examines sacred natural sites in three early state formations from 800 – 1400 CE: the Khmer (Cambodia), the Sinhalese (Sri Lanka) and the Chola (South India), why they persisted over time, and what significance they held. Several ancient sacred natural sites are active parts of societies today, and the ones chosen for this study span several categories: mountains, rivers, forests/groves, and caves. Using the paradigm of entanglement theory in a comparative context, this thesis analyzes sacred natural sites acting as key socio-ecological nodes enmeshed in complex dependent relationships within the landscapes of the South and Southeast Asia. Author Keywords: Comparative study, Entanglement theory, Sacred natural sites, Socio-ecological systems, South Asia, Tropical Societies
Effects of Geographic Factors on the Wild Harvest of Large Mammals across North America
While the harvest of mammals is monitored in each jurisdiction across Canada and the USA, there has been no analysis of this wild harvest at a continental scale across North America. The recreational wild harvest of large mammals varies geographically across North America, and I hypothesized that this variation is influenced by both anthropogenic and other environmental factors on the landscape. I tested this hypothesis using annual harvest tallies collected by Conservation Visions Inc. for mammals for each state, provincial, and territorial jurisdiction in Canada and the USA. I built multiple additive models of the harvest, in one harvest year, 2015 – 2016, to test for landscape gradients that explain the variation in harvest levels for seven large mammal species: white-tailed deer (Odocoileus virginianus), black bear (Ursus americanus), bighorn sheep (Ovis canadensis), elk (Cervus canadensis), mule deer (Odocoileus hemionus), pronghorn (Antilocapra americana), and moose (Alces alces). I built these models from a suite of nine putative predictor variables that comprised landcover, human footprint, and evapotranspiration. For all large mammal species except for pronghorn, anthropogenic influence had a positive effect on the wild harvest density, consistent with the idea that the proximity of human populations and roads are important for fostering wild harvest activity by providing hunters access to hunting areas. The harvest of white-tailed deer, elk, and pronghorn were negatively affected by vegetation structure, urbanization, and primary productivity, respectively. Understanding the recreational wild harvest at a broad-spatial scale provides a unique perspective of the North American model of wildlife conservation and spurs future comparative analyses of the wild harvest across spatial scales. Author Keywords: Anthropogenic Influence, Hunting, Large Mammals, Primary Productivity, Vegetation Structure, Wild Harvest
Experience of Being Jewish in a Small Jewish Community
This thesis explores the experience of Jewish individuals living in a small Jewish community in an urban centre of less than 100,000 in Ontario, Canada. The central question I explore is the ways in which Jewish individuals in a small community enact and perform their identity. What are some of the challenges and obstacles faced by Jews in a small community and what kinds of compromises must be made to accommodate members of the community? Do the benefits of living in a small Jewish community outweigh the shortcomings? This thesis examines how Jewish identity is constructed, maintained and challenged within a smaller urban centre. I begin with a brief historical background of the Jewish presence in Canada. I will look through the lens of Jewish identity within the framework of Canadian multiculturalism, and reasonable accommodation. Jewish identity will then be explored through an intersectional framework. Using qualitative interviews conducted with Jewish individuals, an analysis of common themes and issues pertaining to Jewish identity and maintenance is explored. These themes include Religious observance, cultural identity, Jewish customs and traditions, social action and advocacy. These themes were divided between those of a more individual nature and those of a more communal nature. For participants in this research, managing and maintaining their Jewish identity consisted of balancing their religious and cultural life with their social, work, and other obligations outside the sphere of Jewish identity. The relationship between White identity and Jewish identity is a focal point of study. The synagogue/community centre acts as the primary place in which to express, share, and connect with other Jews. Author Keywords: Assimilation, Community, Intersectionality, Jewish Identity, Multiculturalism, Reasonable Accommodation
Assessing the Clinical Usefulness of Three Tablet-Based Visuomotor Tasks to Evaluate Closed Head Injury
Evidence suggests that visuomotor system behaviour may be more sensitive to the prolonged effects of mild brain injuries than neuropsychological tests. We evaluated whether participants with a mild closed head injury (CHI) would show lingering visuomotor deficits, but not cognitive deficits, up to three years post-injury compared to participants with an orthopaedic injury and healthy controls. All three groups completed a tablet-based visuomotor assessment tool and a brief neuropsychological test battery. The CHI participants scored comparable to the control groups on the neuropsychological tests, but when assessed for visuomotor function requiring adjustment to a changing stimulus, CHI participants showed poorer performance than the control groups. Combined, these findings add to the evidence that CHI can lead to persistent visuomotor deficits that extend beyond those of neuropsychological tests. Therefore, visuomotor assessment should be included in brain injury and recovery evaluation, and this can be accomplished easily using tablet-based tasks. Author Keywords: closed head injury, neuropsychological assessment, recovery, tablet, traumatic brain injury, visuomotor

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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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