Arts and Science, Faculty of
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- ItemCardiotoxicity and interspecies sensitivity of early life stage fish to polycyclic aromatic compounds(Lethbridge, Alta. : University of Lethbridge, Dept. of Biological Sciences, 2025) McKenzie, Kristin C. R.; University of Lethbridge. Faculty of Arts and Science; Wiseman, StevePolycyclic aromatic compounds (PACs) are a broad class of organic contaminants that are present in all types of hydrocarbon fuels and produced from the incomplete combustion of organic matter. During early development, PAC exposure induces sublethal and lethal toxicity in fish. Predictive tools such, as the target lipid model (TLM), have been developed to estimate these impacts. Although cardiotoxicity is a well-established outcome of early life stage crude oil and PAC exposure, few studies have compared cardiotoxicity endpoints across freshwater fish species, and applications of cardiotoxicity endpoints within a TLM framework remain limited. Therefore, the aim of this study was to compare lethal and cardiotoxicity endpoints of larval walleye (Sander vitreus), fathead minnow (Pimephales promelas), and rainbow trout (Oncorhynchus mykiss) following exposures to naphthalene, dibenzothiophene and benz(a)anthracene. Larvae from each species were exposed using a passive-dosing system to five serial concentrations of each PAC, with exposures initiated within 24 h post-hatch and terminated at seven days post-hatch. The TLM framework was able to effectively characterize lethality, bradycardia and ventricle to atrium length ratio (walleye only), enabling a critical target lipid body burden (CTLBB) for each endpoint and species. Although walleye exhibited significantly lower sensitivity to acute lethality relative to the other species, no significant differences between species were observed for bradycardia endpoints. Despite their high survival, walleye exhibited significant reductions in ventricle length and diminished cardiac function following exposure to PACs. This study is the first to successfully apply cardiotoxicity endpoints in fish to a TLM and the first to produce CTLBB data for walleye. Results from this study further support the integration of cardiac endpoints into TLM-based approaches for improving the prediction of sublethal impacts from oil spills.
- ItemResiliency and vulnerability of boreal peatlands to wildland fire: identifying patterns through depth of burn, carbon loss, and environmental controls(Lethbridge, Alta. : University of Lethbridge, Dept. of Geography and Environment, 2025) Nelson, Kailyn Dawn; University of Lethbridge. Faculty of Arts and Science; Chasmer, LauraBoreal peatlands are globally significant carbon (C) sinks that have accumulated C over millennia but are increasingly threatened by climate-driven changes in fire regimes and moisture levels. Soil C losses from peat combustion remain uncertain due to challenges in quantifying below-ground combustion, limiting representation in global C budgets and models. This thesis 1) quantifies spatial variability in C loss during boreal peatland fires, and 2) identifies ecological conditions driving variability and peatland resistance or vulnerability to combustion. Research integrates field data, bi-temporal airborne lidar, and statistical modelling from the 2016 Horse River Wildfire in Alberta’s Boreal Plains. A synthesis of existing knowledge produced conceptual models of pre- and post-fire feedbacks impacting peatland combustion and recovery. These frameworks define two conceptual peatlands: resilient – hydrologically connected with low soil bulk density and moderated water tables, resulting in low severity combustion and moisture-retaining negative feedbacks; and vulnerable – fragmented or drained, with high bulk density, fluctuating water tables, and shrub encroachment, resulting in deep burns and drying positive feedbacks. Lidar ground classification accuracy assessments across unburned and burned, regenerating peatlands revealed negligible mean offsets: 0.00 m in burned to 0.01 m in unburned peatlands, with RMSEs of 0.09 m to 0.19 m, respectively. These findings support the utility of lidar for detecting elevation changes from peat combustion. Using these validated data, depth of burn (DOB) was estimated across peatland types and ecotones, averaging 0.08 ± 0.06 m, with deepest combustion in bog ecotones (0.09 ± 0.07 m). Statistical models revealed that top drivers of DOB variability depended on peatland type. In bogs, DOB was associated with topography and morphology, while in fens and swamps, where groundwater connectivity reduces the influence of topography on water tables, differences were associated with vegetation, hydrology, and disturbance. C losses across peatlands estimated using field-based soil C data and lidar-derived DOB showed that soil C losses (-2.11 ± 5.09 kg m-2) were substantially greater than vegetation losses (-0.38 ± 0.32 kg m-2), with bog ecotones identified as hotspots for C combustion loss (-16.5 kg m-2). Comparison with Landsat differenced Normalized Burn Ratio (dNBR) revealed that while vegetation losses related moderately to dNBR, soil losses did not, demonstrating the limitations of optical indices for below-ground combustion. Comparisons with estimates from the Canadian Model for Peatlands highlighted the need to explicitly include ecotones in C models – particularly under a changing climate.
- ItemSomewhere in France: creating a research-based card game about morale in the Canadian Expeditionary Force during the First World War (1914-1918)(Lethbridge, Alta. : University of Lethbridge, Dept. of History, 2025) Braisher, Matthew; University of Lethbridge. Faculty of Arts and Science; Alexander, Kristine; Burton, ChristopherThis thesis examines the experience of Canadian soldiers in the Great War (1914-1918) through their writings, for a closer understanding of soldiers’ morale in the Western Front. The first chapter of this thesis focuses on morale, and what some of soldiers’ writings can tell us about their morale. The second chapter of this thesis discusses the creation, mechanics, and playtesting of the other portion of this project, my card game named Somewhere in France, which was made with the intention of “translating” my research into a new medium, as well as some of the pros and cons of creating a historical research-based board game.
- ItemAdvanced quadratic optimization based smoothing framework for curved path planning in sustainable agricultural operations(Lethbridge, Alta. : University of Lethbridge, Dept. of Mathematics and Computer Science, 2025) Fernando, Weerahannedige Dananjala Pokurumalie; University of Lethbridge. Faculty of Arts and Science; Hossain, Shahadat; Das, SauryaThis research introduces an advanced quadratic optimization framework for the creation of smooth, curvature-continuous, and steerable waylines in precision agriculture. The framework combines curvature control, coverage uniformity, and steering feasibility into a single mathematical model to reduce skips and overlaps during field operations. Three smoothing techniques; B-spline, Bézier, and Non-Uniform Rational B-Spline (NURBS) are applied and compared to determine their impact on curvature continuity and field coverage efficiency. An extensive sensitivity analysis is performed to understand the effect of swath width tolerance, angular deviation, objective function cost weights, number of characteristic points of the spline curve, and solver configurations using IPOPT and Gurobi. Additionally, a versatile reference-line propagation method enables waylines to be created from either the field boundary or an interior line, thus, increasing flexibility in irregular geometries. The findings reveal that the NURBS-based method offers the greatest geometric flexibility and the most effective field utilization when compared to the other tested methods. The framework is shown to be performant and stable across irregular real-world fields, consequently, it is a scalable and practical solution for optimization-driven path planning in agriculture aiming at sustainability.
- ItemRat ultrasonic vocalizations in associative learning tasks(Lethbridge, Alta. : University of Lethbridge, Dept. of Neuroscience, 2025) Walkey, John Benson; University of Lethbridge. Faculty of Arts and Science; Euston, David R.This thesis investigated how rat ultrasonic vocalizations (USVs) relate to reinforcement and associative learning under conditions of electrical brain stimulation and natural reward. Adult male Long-Evans rats received either medial forebrain bundle (MFB) stimulation or sucrose pellets while under mild calorie restriction. The goal was to determine whether the number and subtypes of 50-kHz calls reflected dopaminergic activation and learning across repeated sessions. Analyses demonstrated that MFB stimulation produced a clear and consistent suppression of 50-kHz vocalizations immediately following stimulation, indicating that activation of this pathway temporarily inhibited rather than enhanced vocal behaviour. This effect was observed across animals and sessions, suggesting that stimulation interrupts the emission of USVs rather than eliciting calls associated with positive affect. In contrast, food delivery did not significantly alter the number of ultrasonic calls, and there was no evidence that pellet reward alone generated measurable increases in vocal production. Across days of testing, there was a gradual increase in the overall number of calls made by the rats. This change may reflect increased anticipation of reward as animals became more familiar with the task structure, but it may also represent a non-associative effect of environmental habituation or reduced novelty stress. Together, these findings suggest that while 50-kHz USVs can serve as sensitive indicators of affective and motivational state, their modulation depends critically on experimental context and timing relative to reinforcement. These results contribute to a more nuanced understanding of ultrasonic vocalizations as behavioural indices of affect. Specifically, they indicate that MFB stimulation, though reinforcing in other paradigms, suppresses ongoing vocalization behaviour, and that food reward alone does not evoke strong appetitive USVs within the parameters tested.