Graduate Theses & Dissertations

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Temporal variation of dissolved organic matter and diffusive gradient in thin films-labile mercury in the Quesnel river, BC, and the Goose Creek tributary of Churchill river, MB
This study examined dissolved organic matter (DOM) and labile Mercury (from diffusive gradient in thin films (DGT)) in the Quesnel river, British and the Goose creek tributary of the Churchill river, Manitoba. DOM properties were measured with optical measurements of absorption coefficient (a254), spectral slopes (S275-295, SR) and fluorescence indices (HIX, BIX, FI). The DOC proxy measurements (a254) were almost 10 times higher at the Churchill site (Mean a254 116.77 cm-1) compared with the Quesnel river site (Mean a254 12.06 cm-1) during the study periods. While DGT labile Hg concentrations at the Quesnel site (2.17 to 98.97ppt) were almost 10 times more than the levels reported at the Churchill site (0.03 to 9.06 ppt). Fluorescence indices and the rise of labile Hg concentrations in spring indicated mostly terrestrial sources of DOM at both the sites. Spectral slopes and fluorescence indices substantiated that Churchill site had high molecular weight, complex and more humic DOM compared with Quesnel. DOM at both the sites was prone to temporal variation and affected by environmental conditions. Correlation between DGT labile-Hg and DOM parameters suggested that DGT collected Hg-organic complexes along with inorganic labile-Hg complexes. Author Keywords: Churchill, Diffusive gradient in thin films, Dissolved organic matter, Labile Hg, Mercury, Quesnel
Solving Differential and Integro-Differential Boundary Value Problems using a Numerical Sinc-Collocation Method Based on Derivative Interpolation
In this thesis, a new sinc-collocation method based upon derivative interpolation is developed for solving linear and nonlinear boundary value problems involving differential as well as integro-differential equations. The sinc-collocation method is chosen for its ease of implementation, exponential convergence of error, and ability to handle to singularities in the BVP. We present a unique method of treating boundary conditions and introduce the concept of the stretch factor into the conformal mappings of domains. The result is a method that achieves great accuracy while reducing computational cost. In most cases, the results from the method greatly exceed the published results of comparable methods in both accuracy and efficiency. The method is tested on the Blasius problem, the Lane-Emden problem and generalised to cover Fredholm-Volterra integro-differential problems. The results show that the sinc-collocation method with derivative interpolation is a viable and preferable method for solving nonlinear BVPs. Author Keywords: Blasius, Boundary Value Problem, Exponential convergence, Integro-differential, Nonlinear, Sinc
Icelandic Dust Entrainment, Emission & Deposition
Extremely active dust sources within selected areas of Iceland that are comprised of particles supplied from both glacio-fluvial outwash systems and volcanic eruptions (Bullard et al., 2016; Gassó et al., 2018). The supply of sediments, sparsity of vegetation, high frequency of surface winds, and lack of adequate gravel pavement to reduce sand drifting are believed to influence the duration, frequency, and magnitude of these dust events in Iceland. Apart from recent collaborative efforts to measure and model dust entrainment, emission and deposition (Prospero et al., 2012; Zwaaftink et al., 2017), several underlying physical mechanisms that are unique to cold, humid climates and the geology of Iceland are not well understood. This study specifically aims to assess and understand the physics of Icelandic dust entrainment and deposition with an emphasis on the influence of climate and the physical characteristics of the particles. A series of laboratory experiments of different configurations were carried out on several sediments collected from some of the most emissive sources in Iceland in order to understand these dust processes. The results from this study show that the increasing particle sphericity is associated with progressively smaller particle size; and an abundance of amorphous glass increases the surface area and roughness of the particles, which contributes to high porosity that alters the particle skeletal density. The particle features and climate are interlinked with the entrainment and deposition rates. For instance, coarse sediments emit higher PM concentrations than sediments containing more clay. The strong wind shear at the bed surface acts to disperse many of the tiny particle aggregates and coated liquid droplets contained within a splash structure created by the impact of a single water droplet. The deposition of suspended dust particulates is dependent on the particle characteristics and relative humidity. The retreat of glaciers and ice-cap masses in Iceland are expected to expose new dust particulate sources as the global mean temperature continues to rise (Cannone et al., 2008; Radic and Hock, 2011). Therefore, the influence of the particle characteristics and climate on the dust entrainment, emission and de- position must be accounted for in the parameterization of dust dispersion models related to suspended volcaniclastic particles. Author Keywords: High latitude cold climate environments, Icelandic dust particle characteristics, Laser Doppler anemometer, Rain droplet impact, Settling velocity, Wind tunnel
Assessing limnological characteristics of subarctic Québec thaw ponds and mercury methylation and methylmercury demethylation within their sediments
Thawing permafrost due to increasingly warm temperatures in northern subarctic regions is releasing mercury. The consequent formation of thaw ponds in the peatland palsa valley of the Sasapimakwananisikw (SAS) river in Whapmagoostui-Kuujjuarapik, Québec may provide a pool for MMHg formation and a potential risk to aquatic and human life, if these ponds facilitate MMHg export through hydrological connections to nearby waterways. Hg methylation and MMHg demethylation activities were examined in thaw pond sediments using a Hg tracer isotope incubation experiment. Analysis by coupling gas chromatography cold-vapor atomic fluorescence spectrophotometry (GC-CVAFS) with inductively coupled mass spectrometry (ICP-MS) techniques showed that MMHg was produced at a higher rate and within the first 2 h of incubation for both summer and winter seasons. For thaw ponds SAS1A, SAS1B and SAS2A, MMHg was formed at 0.0048 % h-1, 0.0012 % h-1, and 0.0008 % h-1, respectively during winter and at 0.0001 % h-1, 0.0016 % h-1, and 0.0010 % h-1, respectively during summer. Detection of MMHg losses were not as expected likely due to limitations of the combined tracer spike and overestimation of the in situ ambient mercury levels. Physical and chemical properties vary within ponds, among ponds and between winter and summer. SAS1B’s location nearby an organic carbon rich palsa may be ideal to study DOC – Hg interactions. Variability in pond characteristics including depth, surface area, age, pH, temperature, colour, oxygen concentration, total dissolved and suspended solids, conductivity, carbon, mercury, ammonium, calcium, magnesium, sulfate, total phosphorous, potassium, and sodium between seasons indicate the challenge of predicting future environmental impacts of climate change related thaw pond creation in the north. Author Keywords: demethylation, mercury, methylation, methylmercury, SAS, thaw ponds
Use Of Rapid Amygdala Kindling With Corticosterone Supplementation As A Model Of Epilepsy-Depression Comorbidity
Temporal lobe epilepsy increases risk for developing major depression, and conversely, depression increases risk for development of epilepsy. The mechanisms responsible for the widely observed bi-directional relationship between epilepsy and depression are currently poorly understood. One reason why our understanding of shared etiology has had little improvement is due to the lack of availability of a reliable animal model for inducing depression in epileptic animals. The development of a reliable model of epilepsy-depression comorbidity would greatly improve the ability to mechanistically evaluate shared pathophysiology between the conditions. Recently there has been evidence that rapid kindling of the basolateral amygdala can evoke a behavioural phenotype that is comparable to the symptoms of anxiety and depression observed in depressed epileptic patients. However, this work has yet to be replicated, leaving question as to whether or not the behavioural phenotype can be reliably evoked. In the following series of experiments we assessed rapid amygdala kindling as a potential model of epilepsy-depression comorbidity and sought to improve the model with inclusion of the glucocorticoid corticosterone. Our findings may improve our understanding of the unique relationships between epilepsy and depression. Author Keywords: animal models, depression, hippocampus, kindling, stress, temporal lobe epilepsy
Achieving Equity in Mathematics Education
Little thought is given to how equitable mathematics would better the lives of those marginalized, or how the increased inclusion of marginalized voices improves the practice of mathematics. The purpose of this narrative research is to explore students’ voices and analyze aspects of math identity: the reported beliefs and practices of a group of elementary urban students who identify as Black/Brown. Understanding voice through counter-narrative is a methodology for the equitable practice of teaching/learning mathematics. CRRP describes participants engaged in the metacognitive task of writing untold stories as it relates to their beliefs, practices, and experiences in mathematics learning. The findings offer meaningful and appropriate insights to math educators about student competency, belongingness, and agency. Keywords: Black and Brown, marginalized students, student engagement, math identity, mathematical competence, sense of belonging to mathematics, mathematical agency, gateway, gatekeeper, fixed mindset, growth mindset, STEM pipeline, counter narrative. Author Keywords: Black and Brown, marginalized students, mathematical competence, math identity, sense of belonging to mathematics, student engagement
Novel Aliphatic Amides from Vegetable Oils as Bio-Based Phase Change Materials
Energy storage efficiency and sustainability require advanced technologies and novel materials. Recently, bio-based phase change materials (PCMs) have received significant attention for thermal energy storage (TES) uses. Vegetable oils are versatile renewable feedstocks that are well suited for the development of sustainable, functional PCMs. PCMs derived from vegetable oil, which compares favorably with paraffin waxes, the industry standard, are currently available. However, their melting points are typically below 80 °C preventing their wider integration in TES applications, particularly those requiring higher temperatures. The present work manipulated the structural building blocks of fatty acids to advantageously affect the intermolecular forces and increase the properties relevant to TES. The polar amide functional group was incorporated into fatty moieties to take advantage of the strong hydrogen bonds that it forms to increase intermolecular attractions and hence increase the phase change temperature and enthalpy as well as to improve thermal stability and thermal conductivity. A series of carefully designed lipid-derived monoamides and four series of lipid-derived diamides were synthesized via benign and simple amidation reactions. The purity of the amides and the intermolecular hydrogen bond strength were assessed using 1H NMR and FTIR. The properties relevant to TES such as thermal transition, crystal structure and polymorphism, thermal stability and thermal conductivity were measured using DSC, XRD, TGA and a thermal conductivity analyzer, respectively. The complex roles of the PCM’s constituting molecular building blocks in the phase behavior were elucidated and correlations between structure, processing conditions and macroscopic physicochemical properties, never before elucidated, were assembled in predictive relationships, drawing a unified picture of the rules that generally govern the phase behavior of lipid-derived PCMs. Practically, the prepared amides demonstrated desirable TES properties with substantial performance improvement over current bio-based PCMs. They presented increased phase change temperatures (79 - 159 °C), enthalpies of fusion (155 - 220 J/g) and thermal stability (234 - 353 °C). More importantly, the predictive structure-function relationships established in this work will allow the straightforward engineering of lipid-derived amide PCM architectures with judicious selection of molecular building blocks to extend the range of organic PCMs and deliver thermal properties desirable for TES applications. Author Keywords: LATENT HEAT THERMAL ENERGY STORAGE, LIPID-DERIVED AMIDES, PHASE CHANGE MATERIALS, RENEWABLE, SOLID LIQUID AMIDE PCMS, THERMAL PROPERTIES
Influence of Action Potentiation on the Perception of Objects Presented Near Hand
For currently-debated reasons, perception of visual stimuli is enhanced in near-hand space compared to far-hand space. According to the action potentiation hypothesis, near-hand effects result from automatically generated potential motor responses produced upon viewing objects presented in near-hand space. This hypothesis was tested by crossing hand manipulations with two separate techniques designed to elicit action potentiation. The first series of experiments presented participants with a cueing task where images of handled objects served as the cue, and its handle compatibility was manipulated. A consistent near-hand effect was observed, but there was no evidence that the images potentiated action as there was no handle-compatibility effect. The second experiment used a visuomotor competition reaching task, which required participants to initiate reaches toward a distractor display and adjust their trajectory on the fly so as to end the reach at a later indicated target location. For every distractor presented simultaneous and competing motor responses were generated, and differences in how hand presence influenced the resolution of this competition were examined. Based on predictions made, action potentiation is unlikely to be the root cause of the near-hand effect; however, was not possible to rule out this explanation entirely. The findings of these experiments shed light both on the importance and consistency of the near-hand effect, and the difficulties associated with uncovering its nature in human populations. Author Keywords:
Predictive Digital Mapping of Soils in Kitimat, British Columbia
Soil is an essential natural resource that supports provisioning services such as agriculture, silviculture, and mining. However, there is limited knowledge on forest soil properties across Canada. Digital soil mapping may be used to fill these data gaps, as it can predict soil properties in areas with limited observations. The focus of this study was to develop predictive maps of select soil physicochemical properties for the Kitimat Valley, British Columbia, and apply these maps to assess the potential impacts of sulphur dioxide emissions from an aluminum smelter, on soil properties in the Valley. Exchangeable [Ex.] magnesium, organic matter, pH, coarse fragment, Ex. potassium, bulk density, Ex. calcium, Ex. acidity, and Ex. sodium were all mapped with acceptable confidence. Time to depletion of base cation pools showed that ~240 km2 of the study area had a depletion time of 50 years or less. However, sources of base cations such as atmospheric deposition and mineral weathering were not considered. Author Keywords: acidification, buffering capacity, Digital soil mapping, predictive mapping, regression kriging, soil properties
White-Tailed Fear
The primary method used to maintain white-tailed deer (Odocoileus virginianus) populations at densities that are ecologically, economically, socially, and culturally sustainable is hunter harvest. This method considers only the removal of animals from the population (the direct effect) and does not conventionally consider the costs imposed on deer as they adopt hunter avoidance strategies (the risk effect). The impact of risk effects on prey can exceed that of direct effects and there is interest in applying this concept to wildlife management. Deer are potential candidates as they have demonstrated behavioural responses to hunters. I explored the potential of such a management practice by quantifying how human decisions around hunting create a landscape of fear for deer and how deer alter their space use and behaviour in response. I used a social survey to explore the attitudes of rural landowners in southern and eastern Ontario towards deer and deer hunting to understand why landowners limited hunting on their property. I used GPS tracking devices to quantify habitat selection by hunters and hunting dogs (Canis familiaris) to better understand the distribution of hunting effort across the landscape. I used GPS collars to quantify the habitat selection of deer as they responded to this hunting pressure. I used trail cameras to quantify a fine-scale behavioural response, vigilance, by deer in areas with and without hunting. Human actions created a highly heterogeneous landscape of fear for deer. Landowner decisions excluded hunters from over half of the rural and exurban landscape in southern and eastern Ontario, a pattern predicted by landowner hunting participation and not landcover composition. Hunter decisions on whether to hunt with or without dogs resulted in dramatically different distributions of hunting effort across the landscape. Deer showed a high degree of behavioural plasticity and, rather than adopting uniform hunter avoidance strategies, tailored their response to the local conditions. The incorporation of risk effects into white-tailed deer management is feasible and could be done by capitalizing on a better understanding of deer behaviour to improve current management practices or by designing targeted hunting practices to elicit a landscape of fear with specific management objectives. Author Keywords: Brownian bridge movement models, hunting, landscape of fear, resource utilization functions, risk effects, white-tailed deer
Fraud Detection in Financial Businesses Using Data Mining Approaches
The purpose of this research is to apply four methods on two data sets, a Synthetic dataset and a Real-World dataset, and compare the results to each other with the intention of arriving at methods to prevent fraud. Methods used include Logistic Regression, Isolation Forest, Ensemble Method and Generative Adversarial Networks. Results show that all four models achieve accuracies between 91% and 99% except Isolation Forest gave 69% accuracy for the Synthetic dataset. The four models detect fraud well when built on a training set and tested with a test set. Logistic Regression achieves good results with less computational eorts. Isolation Forest achieve lower results accuracies when the data is sparse and not preprocessed correctly. Ensemble Models achieve the highest accuracy for both datasets. GAN achieves good results but overts if a big number of epochs was used. Future work could incorporate other classiers. Author Keywords: Ensemble Method, GAN, Isolation forest, Logistic Regression, Outliers
Problem-Solving and Cognitive Flexibility in Older Adolescents and Young Adults
Ill-structured problems have changing components that solvers need to adapt their solutions to. Well-structured problems have strict, well-defined procedures, and solvers must know which procedures to apply and when. Research has suggested that these two types of problems utilize different problem-solving skills. The current study focused on the relation between ill-structured interpersonal problem solving, novel well-structured problem-solving, and cognitive flexibility in young adults and older adolescents. It was predicted that because of the changing components of ill-structured problems, cognitive flexibility would more strongly predict these compared to well-structured problems. The current study sample consisted of 73 undergraduates with an average age of 20.43 years. The results showed that cognitive flexibility is equally associated with ill-structured problem-solving and well-structured problem-solving. This suggests that cognitive flexibility may support the perspective coordination involved in solving ill-structured problems and that cognitive flexibility may support switching between search strategies when solving a novel well-structured problem. Author Keywords: adolescent, adult, cognitive flexibility, ill-structured problem-solving, novel problems, well-structured problem-solving

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Format: 2020/10/24