ETD (Electronic Theses and Dissertations)

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For information on how to submit your thesis to this collection, please go to our ETD website on the UVic Libraries Website.

Access to the full text of some theses may be restricted at the request of the author.

All theses from 2011 to the present are in this collection, as well as some from 2010 and earlier years.

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    Sexism and Ts'msyen Law: A Critical Analysis of the Gendered Exclusion in Holding the Name of Chief in Ts'msyen Society
    (2024) Gray, Christina; Napoleon, Val; Pérez Piñán, Astrid
    Sexism exists in relation to women holding the highest-ranking name of chief within Ts’msyen society (also spelled Tsimshian and Tsimpsean). There are limited historic examples of Ts’msyen women holding the chief names. Some of these examples occurred with colonialism at a time when there was greater church influence in Ts’msyen communities. Today, the sexist pattern persists within Ts’msyen society, including within legal and governance systems where women are excluded based on their gender from holding the highest-ranking names. Despite the sexist pattern, women have legal agency, and they are at the centre of the Ts’msyen matrilineal society. My legal research demonstrates that these exclusionary patterns do not result from legitimate legal reasoning and do not constitute valid Ts’msyen law. First, I engage with Indigenous theories on sources of law. Second, I suggest a path forward based on Jennifer Nedelsky’s four-step relational approach to creating transformative change which I apply to the Ts’msyen legal principle of equality for application to gender equality of chiefs’ names.
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    Comparisons of Ramp Functions and Michaelis-Menten Functions in Biochemical Dynamical Systems
    (2024) Dore-Hall, Skye; Edwards, Roderick
    Analysis of nonlinear dynamical systems, such as those modeled using Michaelis-Menten kinetics, can be difficult. Thus, it is natural to consider whether such systems can be simplified in a way that facilitates analysis while preserving qualitative behaviour. Previously, we showed that when the Michaelis-Menten terms in a model of plant metabolism are replaced by piecewise linear approximations called ramp functions, the qualitative behaviour of the model is maintained. We then defined a limited class of systems containing ramp functions called biochemical ramp systems and studied their properties, including the existence and stability of equilibria and global flow. Here, we expand on our previous work by reforming the definition of a biochemical ramp system to describe a wider class of systems. We study the properties of several types of biochemical ramp systems that were previously not covered by the definition, and show that their qualitative behaviour is similar to that of their Michaelis-Menten counterparts. We then introduce concepts from chemical reaction network theory, such as the Deficiency Zero and Deficiency One Theorems, and explain how they are applicable to the analysis of biochemical ramp functions, but cannot be applied to the corresponding Michaelis-Menten systems. In the last chapter, we show that when ramp functions are used in systems that do not fall under the expanded definition of a biochemical ramp system, there can be qualitative differences in behaviour between these ramp systems and their Michaelis-Menten counterparts. We end with a look at periodic behaviour in ramp systems by studying a version of the Lotka-Volterra predator-prey model containing ramp functions.
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    Impacts of marine shipping on the underwater soundscape and Chinook salmon behaviour
    (2024) Murchy, Kelsie; Juanes, Francis; Rountree, Rodney
    With the persistent growth of the shipping industry, the underwater soundscape across the globe has been changing. The prevalence of low-frequency noise from shipping activities has led to a noticeable increase in ambient underwater noise levels. Research to date has focused on large commercial vessels in motion, but commercial vessels are also anchoring in coastal ecosystems and there is a high presence of small commercial vessels that might be altering the marine soundscape. In this dissertation, these underrepresented anthropogenic noise sources are explored in Cowichan Bay, and Campbell River, British Columbia using underwater hydrophones. Results from these chapters (2 and 3) demonstrated significant changes to the underwater soundscape from anchored commercial bulk carriers and tugboats, highlighting the need to understand these noise sources further. Additionally, the growing body of literature on the impacts of anthropogenic noise on the underwater soundscape has generated concern about the impacts of the elevated noise on marine species. In the Northeast Pacific Ocean, many ecologically important species have been declining since the 1970s including Chinook salmon Oncorhynchus tshawytscha). Although behavioural changes including modified sound production behaviours have been documented in response to anthropogenic activities for some fishes, there has been little research on the impacts of shipping on Chinook salmon. Furthermore, Chinook salmon sound production has received little attention and only limited information on frequency and amplitude has been reported. To better understand the impacts of shipping on Chinook salmon vocal behaviour, understanding of salmon sound production, Chinook and other Pacific salmon, is required. Sound production in three species of Pacific salmon (Chinook, pink, O. gorbuscha and coho salmon, O. kisutch) was evaluated at Big Qualicum Hatchery (chapter 4). Chinook and coho salmon were found to produce air movement, hydrodynamic and pulse sounds, while pink salmon were shown to likely produce all these sounds. However, because pink salmon were always recorded in mixed schools with Chinook salmon, further work is required to validate their sound production. Additionally, the impacts of shipping on Chinook salmon movement and behaviour have never been evaluated, but vessel noise and other anthropogenic sources like pile driving have been shown to produce spatial displacement and behavioural changes in other salmonids. To begin to address this issue, changes in Chinook salmon behaviour in the presence of shipping noise were evaluated using acoustic tags in Cowichan Bay, British Columbia (chapter 5). Significant changes in depth for tagged salmon were observed with increased sound pressure levels and number of AIS-equipped vessels present. However, the influence of the number of AIS-equipped vessels present on the overall activity levels of Chinook did not appear linear and further work is needed to understand vessel noise effects on activity levels. This chapter represents the first study demonstrating the impacts of increased underwater noise levels on Chinook salmon. Collectively this dissertation highlights the impacts of anchored commercial vessels and tugboats on the underwater soundscape and the influence of shipping noise on Chinook salmon behaviour, demonstrating the importance of developing mitigation methods to help reduce the noise produced by shipping activities to protect these ecologically, and culturally important species.
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    “But I Did Not Ask These Questions”: The Soviet Katyn Lie and the Anglo-American Press during the Second World War
    (2024) Zadravec, Eric; Semmens, Kristin
    This thesis explores English-language newspaper reporting on the Katyn massacre during the Second World War. While previous scholars have taken up the subject of Anglo-American complicity in suppressing the Katyn Massacre, there has not been a full examination of the Soviet propaganda put forwards to the Western press during WWII. Firstly, this thesis reexamines the origins of the Katyn massacre in 1940 by highlighting the influence of Soviet foreign policy towards Poland on the Soviet leadership’s decision to undertake the massacre. Secondly, this thesis provides a comprehensive analysis of what historians have termed the “Katyn Lie” as it appeared in the Anglo-American press, and the manner in which the Soviets actively utilized the Western press to spread the Katyn Lie abroad. This thesis demonstrates that Soviet-Polish relations formed the overarching link between the origins of the Katyn massacre and the Soviet falsification of the massacre after 1943. This thesis casts further light on the Anglo-American complicity in silencing the truth about the Katyn massacre, along with further demonstrating the importance the Soviets attached to the international perception of it.
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    Exploration of applications of photon-counting detector computed tomography (CT) using a table-top CT system
    (2024) Richtsmeier, Devon; Bazalova-Carter, Magdalena; Moffitt, Matthew
    Computed Tomography (CT) is an essential diagnostic tool in healthcare, widely used for various applications including cancer detection, vascular disease evaluations, and radiation therapy planning. Recent advancements in photon-counting detector (PCD) technology have led to the development of photon-counting detector CT (PCD-CT), a promising innovation offering high spatial resolution and superior contrast-to-noise ratios compared to traditional CT. PCD-CT excels in detecting and characterizing small structures in various body parts, enhancing tissue differentiation, and material decomposition, thus potentially improving disease diagnosis and radiotherapy treatment planning. This research explores the applications of PCD-CT using a bench-top system, offering insights into its potential benefits over conventional CT systems. Despite its limitations in fully representing a clinical CT system, the bench-top model provides flexibility in assessing clinically useful features. This dissertation investigates four key applications of PCD-CT: material decomposition, multi-contrast imaging, metal artifact reduction, and high-resolution imaging. We investigated the material decomposition capabilities of our bench-top PCD-CT scanner using a dual-energy CT (DECT) method for extracting effective atomic number (Zeff) and relative electron density (ρe) of tissues. We demonstrated that the method with PCD-CT was more accurate in extracting Zeff and ρe for a set of electron density phantom materials with known Zeff and ρe than the method with DECT. In addition, four tissue types were correctly identified in an ex-vivo tissue sample and an injected gold contrast agent was separated from the other four tissue types using K-edge subtraction imaging. Multi-contrast imaging was demonstrated in a phantom model with four contrast agents: gadolinium, dysprosium, lutetium, and gold. The four contrast agents were inserted into the same cylindrical phantom and imaged in one scan. Using K-edge subtraction, we were able to demonstrate complete separation and accurate quantification of the four contrast agents, even of gadolinium and dysprosium, which have K-edge energies of 50.2 keV and 53.8 keV, respectively. Additionally, we optimized the acquisition parameters for the various contrast agents. We also developed a novel metal artifact reduction (MAR) method using PCD-CT. As metal attenuates fewer higher energy x-rays than low energy x-rays, we showed that the high-energy range of 100–110 keV demonstrated fewer metal artifacts. The high energy range is separable from the other x-ray data with the PCD. With this in mind, we developed trace replacement metal artifact reduction (TRMAR). The metal traces in the corrupted conventional CT sinogram space are replaced with the high-energy trace data from the 100-110 keV range. With this, we maintained the contrast and image quality of the full spectrum conventional CT image and also kept the reduced metal artifacts from the high energy data. Finally, we demonstrated the high spatial resolution of our PCD-CT system by imaging coronary artery stents and comparing the same stents imaged with two conventional CT scanners. PCD-CT demonstrated more accurate measurement of the stent strut, or wire, width, stent lumen diameter, and lumen CT number compared to conventional CT. In addition, this led to more accurate 3D representations of the stents. The higher accuracy of strut width and stent visualization is due to the higher spatial resolution of the PCD-CT system and the reduced metal and blooming artifacts it offers over conventional CT. Each of these applications demonstrates the significant potential of PCD-CT in enhancing medical diagnostics and treatment, particularly in cardiovascular imaging, highlighting its diverse contributions to the field of medical imaging.
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    The Social Organization of People’s Experiences Enhancing Health for their Young Children after Declining Vaccines
    (2024) Huel, Christine; MacKinnon, Karen
    In this publication-based dissertation, I describe a Ph.D. research project with three manuscripts that seek to form a better understanding about people’s activities to enhance their family’s health after declining routine childhood vaccinations. My experiences as a registered nurse working with people who choose not to vaccinate their children ignited my interest in this topic. After not fully vaccinating, people have described contributing substantial amounts of time, effort, and financial resources towards activities that aimed to thwart vaccine preventable diseases in their families and enhance their children’s health. Declining vaccines was not just a choice, or a perspective confined inside of people’s minds. Their efforts to do “health work” for their family can be observed in different families and communities, at different times. Recognizing that what people do is as intensive as it is invisible has led me to engage in a dissertation that seeks to form awareness about this facet of vaccine refusal. Using Institutional Ethnography, my dissertation research began illuminating how institutions within ruling relations influence the social organization of people’s experiences of health work that aims to enhance the health in their children while protecting their rights to choose which health treatments their children will receive. In this work, a JBI qualitative systematic review, a key informant interview, and a meta-ethnographic exploratory synthesis provided rich descriptions of informant’s health work for their children. My goal was to produce an understanding that assists people and healthcare providers, like nurses, to recognize potential influencing factors of vaccine hesitancy that may have gone unnoticed. From this understanding, I hope that healthcare providers and researchers recognize that respect for people’s “health work” can exist in tandem with a difference in opinion on the topic of vaccines.
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    Using remote camera traps to monitor population demographics and community ecology of divii (Dall’s sheep): Part of a community-based monitoring program in the Northern Richardson Mountains, NT
    (2024) Goward, Sydney Lee; Fisher, Jason Thomas; Lantz, Trevor Charles
    The warming Arctic is undergoing rapid ecological change, influencing wildlife populations, mammal community interactions, and ultimately, the persistence of many species. Collecting the species monitoring data required for sound stewardship decisions in these remote areas is a major challenge. Remote wildlife cameras, facilitated through community-based monitoring programs, offer a solution to provide these critical data. In this thesis, I employed novel methods in remote camera trapping as part of a community-based monitoring program to investigate Dall’s sheep population demography and predator-prey dynamics with grizzly bears. In Chapter 2, I explored the ability of remote wildlife cameras to estimate population demographics (lamb:nursery, ram:nursery, and ram classification proportions), as compared to currently standardized aerial surveys. These metrics are imperative to assessing population status and predicting population trends. I found that camera data, accumulated sufficiently through time and discretized in appropriate biological seasons produced reliable lamb:nursery, ram:nursery, and ram classification proportions comparable to those obtained from aerial surveys, and produced similar population status trends between the two methods. To my knowledge, this is the first study employing remote cameras to estimate productivity (lamb:nursery ratio) and adult sex ratios in a wild, un-marked sheep population, and marks a significant advancement in wildlife monitoring with remote cameras. In Chapter 3, I examined the temporal coexistence of Dall’s sheep and grizzly bears, in a core habitat area, at different times of the year. I used remote camera data to derive a time-to-event model investigating if and how grizzly bears are tracking nursery groups and ram bands. I also evaluated the differences and similarities in diel activity patterns between the species to estimate temporal niche partitioning. I found clear temporal segregation of nursery groups and grizzly bears, and showed that grizzly bears were more closely tracking nursery groups than ram bands, especially early in the spring when lambs are most vulnerable to predation. The results indicate that camera traps can yield fine-resolution insights into predator-prey relationships. This study provides a new method to monitor Dall’s sheep population demography, as well as new information on Dall’s sheep and grizzly bear relationships. Incorporating a remote camera system into wildlife monitoring programs allows for a more comprehensive examination of demography, while fostering an opportunity to explore further questions related to community-based monitoring and management.
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    Predictive modelling, Anomaly Detection, and Empirical Extraction of Variation Patterns within Longitudinal Data
    (2024) You, Shuai; Zhang, Xuekui; Lesperance, Mary
    This dissertation represents a comprehensive exploration and enhancement of statistical methodologies, addressing complex challenges in transdisciplinary data analysis. It integrates novel techniques across various domains to bridge gaps in existing algorithms, focusing on advancing multitask prediction and anomaly detection. Significant contributions involve extended stacking algorithms for survival and longitudinal data prediction, an innovative unsupervised learning algorithm for real-time spectral anomaly identification and classification, and applications of longitudinal data analytics in multi-decade geospatial marine pollution monitoring data, including paralytic and amnesic shellfish toxins and fecal coliform bacteria. This dissertation emphasizes the collective contributions of these interconnected research findings, aiming to advance predictive modelling methodologies and anomaly detection across disciplines.
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    Optimal Embedding of the Phase Unwrapping Problem onto the Quantum Annealers
    (2024) Kashfi Haghighi, Mohammad; Nikitas, Dimopoulos
    Quantum computers and algorithms are undergoing rapid development, offering promising solutions to complex computational problems. This study focuses on harnessing the potential of quantum annealing to address the challenging phase unwrapping problem. Specifically, we employed D-Wave’s quantum annealers, currently among the most powerful in existence. To effectively utilize these systems, it is crucial to embed the problem onto their underlying structure, the Pegasus graph in the case of the D-Wave Advantage system. A shorter chain-length in the embedding process generally correlates with improved results. In the course of this thesis, we devised an algorithm for efficiently embedding the phase unwrapping problem onto the D-Wave Advantage system. Our approach yielded promising results when compared to D-Wave’s automatic embeddings. Notably, our introduced embedding boasts the minimum chain-length and utilizes the native structure of the target graph. Additionally, we leveraged D-Wave’s hybrid workflow, combining classical and quantum computing capabilities, to tackle larger image problems. Refinements to the hybrid method were implemented, resulting in enhanced performance. Experimental evaluations were conducted on actual quantum annealers, demonstrating that our refined algorithms outperform those provided by D-Wave.
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    QPLEX: Towards the Integration of Platform Agnostic Quantum Computation into Combinatorial Optimization Software
    (2024) Giraldo Botello, Juan Fernando; Müller, Hausi A.; Villegas Machado, Norha Milena
    Quantum computing has the potential to surpass the capabilities of current classical computers when solving complex problems. Combinatorial optimization has emerged as a pivotal target area for quantum computers, as problems in this field are renowned for their complexity and resource-intensive nature. Moreover, these challenges play a critical role in various industrial sectors, including logistics, manufacturing, and finance. This thesis explores the integration of quantum computation into classical software tools as a means to potentially address combinatorial optimization problems more efficiently and effectively. This work introduces QPLEX, a Python software library that enables practitioners and researchers to implement the general mathematical formulation of a given combinatorial optimization problem once and execute it seamlessly on multiple quantum devices using various quantum algorithms. This software solution automatically adapts a general optimization model to the specific instructions utilized by the target quantum device’s SDK. It offers a versatile execution workflow capable of running gate-based hybrid quantum-classical algorithms for combinatorial optimization in a platform-agnostic manner. This approach reduces the programming overhead required for modeling and experimenting with combinatorial optimization solutions. Within this manuscript, we address and introduce the various aspects associated with the development of QPLEX in a clear and comprehensive manner. These aspects encompass the quantum algorithms and quantum hardware available in the library, along with QPLEX’s system design and implementation. Additionally, we provide a guide on how to use the library and conduct a thorough evaluation of the software solution within a specific use case as part of this thesis.
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    Mechanisms of cerebral artery compliance at sea-level and following acclimatization to high altitude.
    (2024) Underwood, Destiny; Smith, Kurt
    Brain health is dependent on adequate cerebral blood flow (CBF) delivered through healthy compliant vessels that buffer pulsatile hemodynamic stress. Pharmacological interventions at sea-level (SL) and high altitude (HA, 5050m) that increase and lower CBF provide a useful experimental design to assess the mechanisms involved in buffering cerebrovascular hemodynamic stress. We characterized pulsatile hemodynamic damping factors (DFi), as an index of cerebral hemodynamic stress. DFi was calculated from pulsitility (PI) in the internal carotid (ICA) and middle cerebral arteries (MCA) at SL and HA following pharmacological attempts to increase (SL=Dobutamine, DOB; HA = DOB+Actetazolamide, DOB+ACZ) and decrease (Indomethacin; INDO) CBF in healthy lowlander adults (n=12, 4 females). Cerebrovascular hemodynamics in the ICA (flow [QICA], PIICA) and MCA (velocity [MCAv], PIMCA) were measured using ultrasound; DFi=PIICA:PIMCA. Administration of DOB (2-5μg/kg/min) at SL, DOB+ACZ (5μg/kg/min+10 mg/kg) at HA, and INDO (1.45 mg/kg) at SL and HA were performed on separate days in randomized order. No QICA response were observed following DOB, while QICA increased following DOB+ACZ (change+41±24 ml.min-1, p=0.01), and decreased following INDO at SL (change-53± 56 ml.min-1,p=0.04) and HA (change -41± 18 ml.min-1, p=0.004). DOB and DOB+ACZ administration differentially altered HR (change-3 bpm; change+5 bpm, p=0.02), ICAV (change-6 ± 10 cm.s-1; change+10 ± 11 cm.s-1; p=0.04), MCAv (change+0 ± 10 cm.s-1; change+17± 5 cm.s-1), and PIICA (change+0.4 ± 0.2 a.u; change +0.2 ± 0.09 a.u.; p=0.03). DOB reduced DFi (change -0.1± 0.05, p=0.02) at SL. Meanwhile DFi following INDO was significantly lower at HA (change -0.54± 0.3a.u, p=0.02) but not at SL (change -0.26± 0.3 a.u, p=0.18). The results from these two field experiments highlights that reducing CBF via cyclooxygenase inhibition detrimental alters the buffering of cerebrovascular hemodynamic forces. In contrast, at HA when CBF is increased following DOB+ACZ cerebrovascular hemodynamic regulation was preserved.
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    An Intersectionality-Informed Analysis of Loneliness and Discrimination Experienced by 2S/GBTQ+ People Living With Disabilities Before and During the COVID-19 Pandemic
    (2024) Amato, Anthony Theodore; Lachowsky, Nathan; Card, Kiffer
    Introduction: Social inequities such as loneliness and discrimination due to sexual orientation (herein, discrimination) are prevalent across disabled people and Two-Spirit, Gay, Bisexual and Trans men, Queer and Non-Binary (2S/GBTQ+) communities. However, little is known about how loneliness and discrimination were experienced in Canada at the intersection of disability and 2S/GBTQ+ communities, especially before and during the COVID-19 pandemic. Method: To address this knowledge gap, four cycles (2019, 2020, 2021, 2022) of cross-sectional, bilingual, community-based Sex Now survey data were used, which included 2S/GBTQ+ people aged 15 years or older and living in Canada. A total of 12,355 2S/GBTQ+ participants responded to loneliness outcomes, and 11,575 to discrimination outcomes. A multi-stage data analysis was conducted. First, crosstabulations and chi-square tests were used to describe and test for differences across outcomes across the four survey cycles. Second, pooled data were analyzed to describe and test for differences in outcomes based on social determinants of health. Third, stratified analyses were repeated for participants living with and without a disability. Finally, only among 2S/GBTQ+ participants living with disabilities, multivariable logistic regression models of each outcome identified 1) temporal trends by survey year, and 2) social determinants of health correlates. Results: There were statistically significant differences in outcomes across survey cycles, which were greater among 2S/GBTQ+ participants living with a disability. Compared with 2019 (before COVID-19), the odds of reporting loneliness were greater for 2S/GBTQ+ participants living with disabilities in 2020 and 2021 (but not 2022). 2S/GBTQ+ participants living with a disability who reported a racialized identity, financial strain, or a gender-expansive identity had greater odds of reporting loneliness. Compared with 2019 (before COVID-19), decreased odds of reporting discrimination were found in 2021 and 2022 (but not 2020). Generally, older 2S/GBTQ+ participants living with a disability were less likely to experience discrimination. 2S/GBTQ+ participants living with disabilities who were racialized, queer versus bisexual identified, and gender-expansive reported greater odds of discrimination. Conclusions: These findings suggest that 2S/GBTQ+ people living with disabilities were impacted by greater loneliness and lesser discrimination during COVID-19. However, social inequities were also present among 2S/GBTQ+ people living with disabilities. Equitable policy planning is needed to ensure that underserved yet deserving communities are not disproportionally affected by future pandemics and associated public health responses.
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    Paleoenvironmental interpretations of the Late Triassic marine realm across the Canadian Cordillera: Slow burn of the end-Triassic mass extinction
    (2024) Lei, Jerry; Husson, Jon
    Despite representing some of the most pivotal intervals in evolutionary history, the timing and tempo of mass extinction events have remained contentious. Many studies have contributed evidence suggesting that ecosystem disturbance associated with the end-Triassic mass extinction (ETME) began prior to the Triassic/Jurassic boundary (TJB), but the extent and duration of this leadup phase is not well established. This uncertainty is exacerbated by a comparative lack of studies investigating the ETME within the context of long-term Late Triassic trends, as well as by the dominance of Tethyan datasets in paleoenvironmental interpretations of the epoch. The research presented in this dissertation consists of a multi-faceted investigation of Panthalassan paleoenvironmental conditions spanning from the Norian/Rhaetian boundary (NRB) to across the TJB, as recorded in western Canadian marine strata. An instance of coral reef collapse on Mount Sinwa, British Columbia, is associated with the paleoenvironmental disturbance around the NRB via conodont and Re–Os isochron age constraints. Ratios of 87Sr/86Sr are observed to gradually increase across the late Norian, as opposed to the sudden drop previously observed in Tethyan datasets, indicating the NRB disturbance was not triggered by mantle-derived volcanism on a global scale. A 3 – 4‰ negative excursion in δ13C values is captured in the latest Norian on Mount Sinwa, consistent with the global carbon cycling disruption proposed to occur around the NRB by prior studies. The conodont species Mockina carinata and Mockina englandi are especially abundant in the Norian and Rhaetian strata of Panthalassa. Morphometric analyses on these two conodont species demonstrate a gradual reduction of platform width across the NRB. These intraspecific trends are likely a more conservative parallel to concurrent intergeneric morphology shifts observed in Tethyan conodonts, together potentially implying a global shift in conodont diet away from mineralized food sources during this time. This may suggest that the biomineralization pressure typically associated with the ETME began at a lesser severity around the NRB, and that conodont biodiversity underwent only limited recovery between the substantive turnover at the NRB and complete extinction of the class around the ETME. Specimens of both these species that have a mid-platform length to breadth ratio greater than 3:1 are observed exclusively in the Rhaetian, a clear sign of morphotype origination or subspeciation, with implications for improved biostratigraphic utility. The compilation of δ13C values across stratigraphic sections from Williston Lake, Holberg Inlet, and Kyuquot Sound in the Canadian Cordillera develops a comprehensive Panthalassan record spanning from the Norian through into the Hettangian, with representation from a variety of depositional settings across a wide paleogeographic area. Three distinct negative excursions are observed, with one proximal to the NRB, one within the Rhaetian, and another across the TJB. The somewhat variable positions of these excursions suggest that the earliest “precursor” excursion associated with the Rhaetian leadup to the ETME may be indistinguishable from an excursion associated with the NRB. Some of the observed excursions are too large in magnitude to reflect shifts in global ocean water chemistry, necessitating a local-scale amplification mechanism, such as disturbance-triggered organic carbon respiration in a water column with restricted circulation. Nevertheless, this evidence for repeated carbon cycling instability indicates the ecological distress that initiated around the NRB persisted across the Rhaetian, escalating into the TJB. Drawing from a combination of lithological, paleontological, and geochemical evidence from across the Canadian Cordillera, this dissertation supports the hypothesis of a protracted ETME that initiated as early as the NRB. With implications of elevated extinction pressure persisting for millions of years before the climax at the TJB, this research challenges preconceptions of the timescale in which mass extinction events ought to be envisioned.
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    Ancient abundance, distribution, and size of Olympia Oysters (Ostrea lurida) in the Salish Sea: a perspective from the Lekwungen village of Kosapsom (DcRu-4), southern Vancouver Island, British Columbia
    (2024) Vollman, Taylor; McKechnie, Iain
    Olympia oysters (Ostrea lurida) are the only oyster species native to the Northwest Coast of North America and are currently a focus of restoration and management following a collapse over the past 150 years. This thesis examines 42 archaeological assemblages containing Olympia oysters in the Salish Sea to better understand Indigenous uses, changes in abundance and distribution between ancient and modern and develops a method to estimate ancient size-at-harvest from partial valves. I observe that Olympia oysters are not a particularly abundant species in archaeological sites when measured by weight and MNI (<15% relative frequency) except in a few sites with high abundance in specific nearshore habitats and locations. Additionally, I examine the size and abundance of Olympia oysters from the Kosapsom Village site (DcRu-4), a site with exceptionally high Olympia oyster frequency (~68 % MNI) located on Southern Vancouver Island in British Columbia in the traditional territories of Esquimalt and Songhees Nations. I compare oyster size ranges from Kosapsom to modern restoration sites and observe that sizes are larger than modern oysters in the same waterway but are similar to a 20+ year restoration site in Fidalgo Bay, Washington. Both abundance and size at Kosapsom increased over 1800 years. I interpret these increased sizes (~14% increase) as reflective of harvesting restrictions and population enhancement strategies, which are consistent with maintaining long-term harvest stability. This research contributes to the growing recognition that archaeological records of traditional Indigenous shellfish use and management hold great potential to expand historical baselines and inform modern coastal restoration and conservation strategies.
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    A Laboratory Study on the Influence of Guided Drop Tower Carriage Mass and Kinematic Differences to Full-Surrogate Free Falls Toward Enhanced Helmet Certification Methods
    (2024) Brice, Aaron; Dennison, Christopher
    Falling from height presents a significant risk for military personnel due to the frequency at which they perform high exposure maneuvers, such as walking along unstable structures, repelling from buildings or aircrafts, and low altitude egressing. Traumatic brain injury (TBI) resulting from falls from height (FFH) account for approximately 20% of TBIs with a reported cause in the military, despite the presence of protective head gear. This is likely because current certification testing performed on military helmets emphasize protection against ballistic threats over blunt impacts, such as falls. Military personnel have identified the need for the next generation of helmets to provide better protection against blunt impacts. To develop such helmets, a method for helmet evaluation in scenarios that are representative of real-life falls must be established as the new standard for helmet impact testing. Guided vertical drop towers are a test device commonly used to evaluate the impact attenuating properties of protective headgear in headfirst falls during certification testing. These devices provide a simple, low cost, repeatable means for conducting certification tests over using full-body surrogates to replicate a person experiencing a headfirst fall. However, there are some limitations to the guided drop tower that may limit their ability to properly replicate a fall from height. The most notable limitations are that guided drop towers are constrained to only a single degree of freedom and the impact mass of a drop tower assembly typically only includes the mass of a human head and neck rather than the mass of a full-body. At present there is little work on how these limitations may yield a differing kinematic response between a guided drop tower and that of an actual fall. The objectives of this thesis was to determine if kinematic differences exist between a guided drop tower and a free-falling person, in unhelmeted and helmeted scenarios. The outcomes of this thesis will contribute toward the development of enhanced test standards that evaluate protective headgear in scenarios that are more representative of real-life falls. iii A custom guided drop tower equipped with a Hybrid III head/neck and adjustable weight drop carriage along with a full-body Hybrid III 50th percentile male surrogate, to represent a falling person, were subjected to two experimental series 1) unhelmeted impacts at four angles between 30° and 75° and four impact velocities between 1.50 m/s and 3.00 m/s and, 2) helmeted impacts at 30° and 75° with impact velocities of 3.00 m/s and 4.50m/s. Impacts in both series were conducted onto a rigid impact surface and kinematic measures of head center of gravity linear acceleration, angular acceleration, and angular velocity were measured. Results of the unhelmeted impact series identified that the drop tower can provide an acceptable approximation of the linear acceleration but not the angular velocity that is likely to be experienced by a person in a headfirst frontal impact. This is due to the angular velocity differing in either the magnitude of the peak angular velocity or direction and time instance of peak measures. Changes to the mass of the drop carriage, to be closer to that of a full dummy, did not bring angular velocity closer to that measured for the full dummy. The helmeted impact study identified that a drop tower is likely to yield an underestimate of peak kinematics in shallow angle impacts and an overestimate of peak kinematics in steep angle impacts. This suggests that the drop tower, in its current form, provides a varying estimate of the resultant peak kinematics in helmeted impacts which is dependent on impact angle. These differences in response are primarily attributable to variances in helmet liner engagement when comparing the drop tower and a person falling. The results of this research found that in their current form guided drop towers do not provide a true representation of the kinematic response that is likely to result in a headfirst fall, either unhelmeted or helmeted. Further the addition of mass to the drop carriage in either scenario did not alter the drop tower’s response to a point where it matched the measured response of the falling surrogate .These differences in kinematic responses between the drop tower and what is likely to be experienced by a falling person, specifically in the case of underestimated responses in shallow angle helmeted falls emphasizes the need to further develop testing methods to ensure that future helmets are evaluated in a way that effectively tests the helmet’s impact-attenuating abilities in an actual fall.
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    Role of the PEST Domains in Proteasomal Degradation of Rett Protein: MeCP2
    (2024) Kalani, Ladan; Ausio, Juan
    Located on the X-chromosome is the gene encoding the nuclear protein Methyl CpG binding protein 2 (MeCP2). The instability of this protein causes pleiotropic neurological abnormalities, including the debilitating neurodevelopmental disease Rett syndrome (RTT). MeCP2, an epigenetic regulator abundant in neurons, is involved in pleiotropic molecular interaction. Many deleterious mutations of MeCP2 impact its mRNA or protein levels. Neuron maturation and dendritic arborization are compromised when MeCP2 levels are out of the homeostatic range. The mechanisms the cell uses to maintain MeCP2 levels within a tight range have yet to be fully understood. Several hypotheses addressed the homeostatic mechanisms of MeCP2, which involve miRNAs, N-terminal degradation signals or N-degrons, and the PEST domains that act as degradation switches upon post-translational modifications (PTMs). Our lab hypothesized the involvement of MeCP2 PEST-mediated degradation as a mechanism of its homeostatic regulation; however, this hypothesis has yet to be experimentally proven. I experimentally tested the PEST-mediated degradation of MeCP2 with Rett-causing mutations by integrating MeCP2 constructs that have an altered or deleted PEST domain and used microscopy, FRAP analysis and western blotting to characterize in vitro how these constructs behave relative to WT and mutated MeCP2. MeCP2 has Rett-causing mutations that cause lower protein levels, such as T158M; the PEST motif expedites its degradation as deleting it results in higher protein levels. Moreover, mutations that result in higher levels of MeCP2, such as R294X, show stronger DNA binding relative to WT, as assessed by NaCl fractionation. For the first time, we report that the Ct-PEST domain of MeCP2 plays a role in its degradation.
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    Pseudoku: A Sudoku Adjacency Algebra and Fractional Completion Threshold
    (2024) Nimegeers, Kate; Dukes, Peter
    The standard Sudoku puzzle is a 9 × 9 grid partitioned into 3 × 3 square boxes and partially filled with symbols from the set {1, 2, ..., 9}, with the goal of the puzzle being to complete the grid so that each symbol appears once and only once in each row, column, and box. We study generalized Sudoku puzzles, set on an n × n grid with cells partitioned into n boxes (sometimes called cages) of height h and width w such that hw = n. Throughout this work, these generalized Sudoku are referred to as (h, w)-Sudoku when h and w are significant, but as simply Sudoku otherwise. The goal of solving a partially filled (h, w)-Sudoku puzzle remains the same; complete the Sudoku by assigning placements in the grid to each symbol from {1, 2, ..., hw} so that each symbol appears once and only once in each row, column, and box. This thesis is specifically concerned with establishing conditions which guarantee a fractional Sudoku completion. A fractional Sudoku completion is an assignment of a set of weights to each symbol-cell incidence, representing the proportion of the symbol for that specific cell. The total weight of symbols for each cell must sum to one, and the sum of the weights for each symbol must be exactly one across the cells from each row, column, and box. These conditions still require a balanced distribution of symbols throughout the grid, but with considerably more flexibility than the typical Sudoku conditions. In order to apply graph theoretic techniques to the problem, we develop a 4-partite graph representation, GP , for a partial Sudoku, P . The 4 parts correspond to the rows, columns, symbols, and boxes of P , and the edges of GP indicate the conditions for a completed Sudoku that remain unsatisfied in P . We then introduce the concept of a tile: a 4-vertex subgraph of GP , which represents a valid symbol placement in P . Completing P is equivalent to decomposing the edges of GP into these tiles. We then use an edge-tile inclusion matrix to relate the existence of such a decomposition to the existence of an solution vector with {0, 1} entries for a specific linear system. It is here that we move to the fractional setting through a relaxation of what constitutes an acceptable solution to the linear system - specifically, we are satisfied with solution vectors for which all entries are non-negative. To find conditions that guarantee such a solution exists we study the Gram matrix of the edge-tile inclusion matrix for the empty (h, w)-Sudoku, denoted M. We show that M is symmetric and that each element of M corresponds to a pair of edges in the graph representation Ghw of the empty (h, w)-Sudoku grid. We then leverage the inherent symmetry of equivalence relations between these edges to establish a Sudoku adjacency algebra which contains M . This allows us to explicitly construct a generalized inverse for M . This generalized inverse, along with some applied perturbation theory, is used to show that given large enough h and w, the linear system for any sufficiently sparse partial (h, w)-Sudoku is a minor perturbation of the linear system for the empty (h, w) Sudoku, and therefore allows a fractional completion. After presenting this main result, we take a brief detour to consider the unique case of Sudoku puzzles with thin boxes, examining how fixing the box width variable w while allowing height h to grow asymptotically influences the density conditions necessary for fractional completion. We also give an overview of our exploratory use of the Schur complement for matrix decomposition. Although this method didn’t directly feed into our primary results, it was instrumental in the discovery of the equivalence relations we used to construct our Sudoku adjacency algebra. Finally, we explore the potential applicability of our methodologies to certain Sudoku variants and acknowledge the limitations inherent in our approach. In the appendices, we provide additional resources that complement the main body of our work. In Appendix A, we give a factorization of the Sudoku matrix M and its eigenvectors as Kronecker products for readers who wish to more directly compare our methodology to algebraic graph theory work done on Sudoku by other researchers. Appendix B presents a series of interactive and educational activities designed to introduce students to the basic principles of Latin squares in a fun spy-themed setting.
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    Evaluating the impacts of anthropogenic development on large mammals across protected and industrialized landscapes in Western Canada
    (2024) Smith, Rebecca M; Fisher, Jason T; Shackelford, Nancy
    Anthropogenic landscape development leads to substantial habitat loss and fragmentation, with large mammals among the most strongly impacted. In this thesis, I used wildlife camera traps across landscapes in Western Canada to investigate two landscape-level management actions for development. First, protected areas (PAs) control development within their boundaries, so they provide refuge to wildlife from many anthropogenic disturbances. Despite their prevalence, many PAs fall short of protecting species and habitats. Since PAs are intrinsically linked to their surrounding lands, pressures outside of PAs can be sources of mortality for mammals using habitat that spans boundaries. To improve our understanding, Chapter Two of this thesis examined the relative impacts of landscape development inside and outside of PAs on large mammals. Species occurrences were best predicted by models that comprised both inside- and outside-PA development, demonstrating that PAs do not offer the full protection they are mandated to. Most of the land on earth, however, remains unprotected, so conservation relies on species persistence in unprotected regions with active development. The composition and configuration of habitat resulting from development has been found to influence species distributions, but configuration is often disregarded as influential in landscapes with less than 70% total habitat loss. Chapter Three examines the relative influences of landscape composition and configuration on large mammal species distributions across a petroleum extraction region. Both configuration and composition were revealed as important, and the specific measures of configuration that explained species occurrence showed that resulting landscape configuration from development restructures the ecological mechanics of ecosystems. Together these results can be used to inform landscape management practices across North America to conserve large mammal species.
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    Drivers of Coastal Morphodynamics on a Deltaic Barrier in the Colombian Caribbean
    (2024) Gómez, Juan Felipe; Kwoll, Eva; Walker, Ian J.
    This research presents results from a series of analyses focussed on the overarching goal of identifying and understanding drivers of coastal morphodynamics on a deltaic barrier in the Colombian Caribbean coast, eastward from the Magdalena River mouth. Forcing mechanisms operating at different temporal scales were considered, including the influence of vertical land motion (VLM), storms, river discharge, trade winds, and wave conditions. These forcing mechanisms were related to geomorphic changes determined from satellite imagery taken before and after specific events. Satellite imagery and synthetic aperture radar acquisitions were used to assess decadal-scale coastline changes and VLM for the period 2007–2021. The findings revealed that VLM rates are highly variable alongshore, and that subsidence occurs mainly landward of highly erosive stretches of coastline associated with former mangrove forest. Drivers of coastal morphodynamics operating on time spans from days to seasons were assessed by focusing on four lagoons located along the back-barrier to better understand the interplay between extreme events and the breaching and healing of inlets that are temporarily formed between the lagoons and the ocean. Satellite data in conjunction with hourly readings from weather stations spanning the past 50 years helped to determine the conditions that enabled the breaching and healing processes to transpire in the lagoons. Aligned with the predominantly erosive regime along the study area, the findings indicated that the cumulative effect of the breaching and healing of the lagoons resulted in a deltaic barrier that has rolled over the lagoons, modifying their size over time. The occurrence of meteotsunamis and their role in coastal morphodynamics was investigated using a wavelet analysis applied to water-level readings in three tide gauges for the period 2013–2022. After the discovery of one event with meteotsunami-like characteristics, the atmospheric conditions and total water levels associated with this event were analyzed. The results indicated that total water levels related to the meteotsunami are similar to those produced by moderate storms and both phenomena can induce breaching of lagoons. To date, the barrier has responded to external forcers through a landward displacement of the coastline driven by cycles of lagoon breaching and healing as well as overwashes on lagoons, wetlands, and beaches. Seasonal storms have been critical in forcing these processes and have substantially influenced the barrier evolution during the last 50 years. Taken as a whole, this body of work provides knowledge about the response of deltaic barriers to geomorphologic forcers based on a study area in an understudied region of the Caribbean. At a regional level, the findings are relevant for science-based coastal planning and managing policies. Moreover, this research used a variety of methodological approaches to track causality on coastal landscapes in a manner that can be replicated in other areas with limited pre-existing information and without ongoing monitoring programs.
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    Infrared-Visible Image Fusion in the Gradient Domain
    (2024) Premaratne, Sanduni; Agathoklis, Panajotis; Bruton, Leonard T.
    Due to the complementary properties of the infrared cameras compared to conventional visible imaging cameras, it has become increasingly popular to fuse infrared and visible images of the same scene for better visual understanding. One major application of this is surveillance which involves videos and requires fast processing. Therefore, there is a need for investigating novel low-complexity fusion algorithms that can be implemented in real-time applications. In this study, we address this critical research problem by two-scale fusion in the gradient domain with saliency detection and image enhancement. In the proposed method, the source images are first decomposed in to base and detail layers. Next, the base parts are fused in the gradient domain by choosing the maximum absolute gradient, whereas the gradients of the detail parts are fused using a weighted average where the weights are calculated using saliency maps. Prior to fusion, the detail parts are enhanced using a guided filter-based enhancement approach. Finally, the fused gradients of the base and detail components are added together to obtain the gradients of the fused image, from which the fused image is reconstructed using a reconstruction technique based on wavelets. Experimental results demonstrate that the proposed method achieves very competitive performance in subjective and objective fusion assessments, while also outperforming most methods in terms of computational complexity.
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