Restricted Theses and Dissertations

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This collection is the result of a joint project between the Faculty of Graduate Studies and Libraries and Cultural Resources which provides Graduate students with the opportunity to archive their thesis with University Archives in our digital repository.

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Now showing 1 - 5 of 4536
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    Modeling of Antimicrobial-Resistant Enterococci Exposure Risks in Canadian Beef Cattle Production System Using Existing Data
    (2024-04-17) Strong, Kayla; Checkley, Sylvia L.; Checkley, Sylvia L.; Kastelic, John Patrick; Otto, Simon James G.; Reid-Smith, Richard; Waldner, Cheryl Lynne; Lhermie, Guillaume; Noyes, Noelle
    Antimicrobial resistance occurs when microbes change, and antimicrobials previously used to treat them are no longer effective. Antimicrobial resistance presents a global risk to health and food safety, with previously treatable infections becoming increasingly costly and challenging. Antimicrobial resistance is a quintessential One Health issue, given its impact and drivers across human, animal, and environmental health, and requires transdisciplinary interpretations and solutions. This thesis considers methods of risk interpretation using a case study of antimicrobial-resistant Enterococcus spp. within Canadian beef production systems. Five objectives were considered: (1) to identify factors associated with antimicrobial-resistant enterococci within Canadian beef production systems; (2) to construct an integrated assessment model for interpretation of factors potentially associated with antimicrobial-resistant enterococci; (3) to construct a risk profile for interpretation of risks associated with antimicrobial-resistant enterococci in Canadian beef; (4) to construct a Bayesian model for interpretation of enterococci resistance within beef production; and (5) to describe integrated strengths and weaknesses of modeling approaches. Factors assessed for association with antimicrobial-resistant Enterococcus spp. within Canadian beef production systems included antimicrobial and nutritional supplement administration to cattle, environmental factors, and type of processing plant. Resistance trends were often nuanced to unique gene and phenotypic resistance. Patterns varied by species of enterococci. When data were available, the integrated assessment model utilized crude odds ratios extracted from identified factors. Limited data for baseline seeding and factor inclusion limited the model's interpretability. Recommendations and best practices are proposed for future model applications. The risk profile was developed to meet the Codex 77 guidelines and demonstrated the scarce evidence of enterococci resistance transference from beef products, and limited human pathogenicity of enterococci from foodborne consumption. The risk profile highlighted the need for Canadian surveillance studies of enterococci in food products for more informed decision-making. The Bayesian model incorporated available evidence with current estimates of enterococci resistance trends, integrating expert opinion within the model. The model suggests that less than 0.3% of beef products carry antimicrobial-resistant E. faecalis. Individual models and risk discussions uniquely fill niches in resistance discussions and interpretations but were insufficient for providing a holistic interpretation required by stakeholders across the production chain. Drawing findings from multiple reports supported a better understanding and enhanced decision-making.
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    Study of Electrochemical Methane Oxidation to Oxygenates
    (2024-04-10) Al-Attas, Tareq Ali Salem; Kibria, Md Golam; Thangadurai, Venkataraman; Karan, Kunal; Roberts, Edward (Ted) PL; Birss, Viola Ingrid; Morales Guio, Carlos Gilberto
    Methane (CH4), a primary component of natural gas, plays a vital role in energy and chemical production. However, conventional methods of chemical production tend to be resource-intensive and often result in the release of CH4 through venting or flaring in oil and gas operations. Decentralized technologies that leverage renewable energy can mitigate CH4 emissions while generating revenue. Electrochemical oxidation of CH4 (eCH4OR) into valuable fuels and materials offers a flexible solution that can operate in varied conditions. Nevertheless, achieving desirable outcomes at scale is challenging due to the high energy requirements for breaking the C–H bonds of CH4. This thesis focuses on developing catalysts for high-rate and selective electrooxidation of CH4 while also aiming to deepen our understanding of the reaction mechanism. Drawing inspiration from iron (IV)-oxo (FeIVO) metalloenzymes that activate C–H bonds, a copper-iron-nickel (CuFeNi) catalyst for selectively oxidizing CH4 into formate using a peroxide-assisted pathway is presented. The synergistic effect of the metals to selectively oxidize CH4 is explored by in situ spectroelectrochemical studies (i.e. XANES and UV-Vis) and density functional theory (DFT) calculations. Specifically, the analyses revealed the presence of high valent FeIV as the active site for CH4 oxidation, attained by the reactive oxygen species generated during the partial oxidation of H2O2 at low overpotentials compared to water oxidation reaction (OER) on nickel. Furthermore, the critical role of copper in preventing the overoxidation of valuable oxygenates to CO2 was revealed. We achieved a formate faradaic efficiency of ~42% at a current density of 32 mA cm−2 (i.e., partial current of ~13 mA cm−2) and a low applied potential of 0.9 VRHE. Additionally, the thesis examines the reaction pathways of the eCH4OR using hematite (α-Fe2O3) as an electrocatalyst. Different electrochemical and in situ spectroelectrochemical techniques, including ATR-SEIRAS, EIS, and PTR-TOF-MS, were employed to comprehend the mechanism of this reaction. The electrochemical oxidation current density uncovered non-faradaic adsorption of CH4 molecules at lower applied potentials. The non-faradaic adsorption of CH4 molecules was further confirmed through ATR-SEIRAS. In situ ATR-SEIRAS also revealed the presence of the FeIVO species and CH4 oxidation intermediates, correlating them with the applied potential. Thisanalysis unveiled the formation of oxygenated products, including CH3OH, HCOOH, CH3COOH, and their corresponding intermediate adsorbed species, such as •OCH3, •OCOH, and •OCOCH3. Notably, C–C coupling between –COCH3 and –CH3 via ketonization resulted in CH3COCH3 formation. PTR-TOF-MS supported our findings by confirming that acetone is the primary liquid product generated, achieving a faradaic efficiency of 6.3% at 2.3 VRHE. This result is attributed to its formation by coupling acetate and formate intermediates. Consequently, we developed proposed reaction pathways for the selective electrooxidation of CH4 to C1-C3 products. The thesis extends to present techno-economic and life-cycle assessments of electrification options for CH4 utilization. Initially, the study highlights the economic viability of electrifying reformers and boilers in traditional technology. A futuristic scenario discusses one-step methanol synthesis via the direct eCH4OR and illustrates the impact of cell voltage and electricity prices on the calculated minimum selling price of methanol. For instance, methanol production can be profitable at electricity prices below ¢4 per kWh at a total operating cell voltage of 2.0 V. The analysis establishes electricity emission goals to maintain net CO2 emissions within the acceptable range for current methanol synthesis. It is shown that the emissions intensity of the electricity source must be under 181 kgCO2 per MWh for the electrochemical route.
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    Investigating the Built Environment’s Influence on Child Active Transportation Injury and Prevalence
    (2024-04-11) HubkaRao, Tate; Hagel, Brent; Nettel-Aguirre, Alberto; Cloutier, Marie-Soleil
    Background: Motor-vehicle collisions (MVCs) are a leading cause of Canadian child active transportation injuries. Specific built environment features may reduce child injury risk while increasing active transportation prevalence; however, few studies exist evaluating the effectiveness of these features specific to this age group. Further, it is important to understand how built environment features can influence community and school wide child active transportation injuries and prevalence. Methods: Using a modified stepped-wedge trial, Chapters 3 and 4 investigated the influence of installing specific built environment features on traffic speed and volume, active transportation prevalence, and caregiver perceptions of safety. Chapters 5 and 6 used machine learning recursive partitioning trees to predict the number of child active transportation related MVCs, and the proportion of elementary students using active transportation to school, based on the built environment within respective geographical areas. Results: Chapter 3 found traffic calming curbs and in-street signs were associated with a reduction in traffic speed, depending on time-period. No significant changes in traffic volume were found immediately following installation. In-street signs were associated with a reduction of active transportation prevalence in the morning, and an increase in the afternoon. Chapter 4 found traffic calming curb installation was associated with higher proportions of caregiver perceptions of safety. Some respondents showed higher proportions of reported children walking to school at intervention locations. Chapter 5 found built environment features such as signalized intersections were predictive of annual collisions. Chapter 6 showed population density to be important in predicting active transportation prevalence to school. Conclusions: Results of this thesis support calls for a systems approach to road safety. The variability in characteristics of the urban environment that are associated with child active transportation safety and prevalence suggests that no single intervention would be as effective as a more holistic and comprehensive approach. Specific features such as traffic calming curbs and in-street signs, coupled with reductions of major roadways and increases in population density, may, together, have a considerable and lasting effect on improving active transportation safety for Canadian children.
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    Dis-Connected: Young Adults’ Experience of Growing Up With a Canadian Service Member Parent With an Operational Stress Injury
    (2024-04-09) Iverson, Heather; Robertson, Sharon Elaine; Robertson, Sharon Elaine; Domene, José F.; Kawalilak, Colleen
    Military-connected families in Canada have expressed concerns regarding the impact of having a parent with an operational stress injury (OSI), such as posttraumatic stress disorder (PTSD), on their children’s well-being. A recent trend in research has been focused on examining the impacts of parents’ PTSD on the mental health of military-connected children (MCC). However, there remains a paucity of studies that capture the perspective of the MCC themselves, particularly within a Canadian context. This study aimed to explore how young adult children of Canadian Armed Forces (CAF) veteran service members make sense of their experience of growing up with a parent with an OSI. Individual, semi-structured interviews were conducted with five young adults aged 19 to 23 years, and the transcripts were analyzed using interpretive phenomenological analysis (IPA). From this analysis, five Group Experiential Themes (GETs) emerged: (a) In a Way, I Lost My Dad, (b) Turbulent Waters at Home, (c) Don’t Rock the Boat, (d) In the Dark, and (e) Duty to Care. The participants’ accounts shed light on the complexity of dealing with a father who was present juxtaposed with a father who was absent. Participants’ narratives depicted tumultuous home environments where maintaining family harmony was a honed skill. Moreover, the pervasive uncertainty surrounding their father’s OSI during their upbringing called for participant resilience and resourcefulness in coping with a situation marked by limited information and communication. Furthermore, amidst the confusion and destabilizing circumstances, participants remained steadfast in their commitment to their families. These findings are discussed in the context of relevant literature. The strengths and limitations of the study are considered and implications for practice and research are presented.
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    Fear of Cancer Recurrence Experienced by Pediatric Survivors of Childhood Cancer
    (2024-03-14) Russell, Karleen Brooke; Tomfohr-Madsen, Lianne; Schulte, Fiona; von Ranson, Kristin; Guilcher, Greg; McDonough, Meghan; Galica, Jacqueline
    Introduction: Fear of cancer recurrence (FCR) is a common and sometimes debilitating concern among survivors of cancer. While much is known about FCR experienced by adults, research exploring FCR experienced by children and adolescents has only begun to emerge. Importantly, given the dynamic development of cognitive and social factors throughout childhood, pediatric survivors may experience FCR differently than adults. Method: A scoping review was undertaken to evaluate the existing literature on pediatric FCR. Additionally, given the absence of available tools to measure pediatric FCR, the psychometric properties of an adult FCR measure, the Cancer Worry Scale, was evaluated in a pediatric sample. Results: The scoping review identified 19 studies that met inclusion criteria. FCR was explored as a primary aim in only six. The prevalence of FCR in identified samples ranged from 43% to 90%. FCR was positively associated with somatic symptoms and negatively associated with quality of life and emotional functioning. Evaluation of the Cancer Worry Scale demonstrated acceptable psychometric properties for use with youth but pointed towards the utility of developing a new FCR measure intended specifically for use with youth. Conclusion: FCR is a prevalent and important concern for this population. Additional research is needed to better characterize and understand pediatric FCR.