Faculty of Graduate Studies Online Theses

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Open Access
Sustaining Soil Organic Carbon and Soil Health in Intensively Tilled Short Crop Rotations
(2025-05-29) Lavergne, Stéphanie; No; Doctor of Philosophy; Department of Plant, Food and Environmental Sciences; Received; Meagan E. Schipanski; Yes; Andrew M. Hammermeister; David L. Burton; Derek H. Lynch; Caroline Halde
Soils in Canada are under degradation due to the intensification of agricultural systems. Intensive field crop rotations are characterized by low crop diversity and crop residues, and high tillage frequency and external nutrient inputs. However, the impact of these intensive short rotations on soil health, earthworm communities, and soil organic carbon (SOC) has been little investigated and is the focus of this thesis. A field survey was conducted over three years on eleven organic grain farms in Québec, Canada, to assess the impact of short crop rotations without forages (corn [Zea mays L.] -soybean [Glycine max (L.) Merr.] – small grain) on the earthworm community and soil health. Earthworm abundance and richness were generally low in both fields and field margins, with earthworm communities in cropped fields primarily dominated by endogeic species. Our findings suggest that long-term manure application, along with frequent use of cover crops, plus inversion tillage favours endogeic species in these systems. In contrast anecic and epigeic species increased under winter cereals. Legacy (prior three years) management practices were characterized using indices for crop diversity (CDI), soil tillage intensity rating (STIR) and organic amendment use (OAI). In-season management indices, in particular CDI (increased by cover crops and winter crops) and STIR, varied across crop fields and had a greater effect on soil health outcomes. A replicated potato (Solanum tuberculum L.) experiment in Prince Edward Island, Canada, compared the impact of contrasting three-year rotations including one full season cover crop on SOC dynamics and distribution. Treatments failed to differ in soil profile (0-45cm) SOC. Our results indicate that, carbon (C) inputs from full season cover crops were insufficient to offset SOC loss due to high tillage intensity in these rotations, affecting both topsoil and subsoil SOC stocks. Overall, this research has shown that reducing tillage intensity by increasing crop diversity was the main driver of earthworm community diversity and soil health. Rotations that enhance C inputs, such as via winter cover crops and cash crops residues, could buffer the earthworm community, and soil health and SOC, against the impacts of greater tillage intensity in short rotation cropping systems.
Open Access
FUNCTIONALIZING GOLD NANOPARTICLES WITH A DNA APTAMER FOR BIOSENSING 25-HYDROXYVITAMIN D3
(2025-05-29) Hansson, Benjamin; Not Applicable; Master of Science; Department of Physics & Atmospheric Science; Not Applicable; n/a; Not Applicable; Laurent Kreplak; Alan Fine; Kimberley Hall; Kevin Hewitt
Vitamin D influences over 400 processes in the human body and its deficiency is associated with several diseases such as uterine fibroids. Accessible point-of-need tools are required to detect 25-hydroxyvitamin D3 (25(OH)D3), a Vitamin D biomarker. This thesis investigated conjugation methods for the specific, yet structurally complex 25(OH)D3 aptamer, VDBA14, to gold nanoparticles (AuNPs), common biosensor transducers. Initial approaches using salt-aging, low pH, and freeze conjugation, evaluated with UV-Vis, fluorescence, and salt stability assays, were ineffective due to poor aptamer conjugation and the resulting AuNP aggregation. A promising development was the inclusion of an 18atom hexa-ethyleneglycol spacer between the aptamer and disulphide linker. Freeze conjugation of the modified aptamer improved AuNP stability, with conjugation confirmed by UV-Vis redshift and DNA FT-IR bands. Future experiments are required to demonstrate conjugation without destabilizing AuNPs. This work represents a foundation for functionalizing AuNPs with VDBA14, and the first step towards point-of-need 25(OH)D3 biosensors.
Open Access
The Ovarian Cancer Tumour Microenvironment Modulates Natural Killer Cell Function
(2025-05-28) Nicolela, Anna Pasternak; Not Applicable; Master of Science; Department of Pathology; Received; Gregory Fairn; Not Applicable; David Hoskin; Locke Davenport Huyer; Jeanette Boudreau
Natural killer (NK) cells mediate anti-tumour responses but are inhibited in the high-grade serous carcinoma (HGSC) microenvironment by factors including adenosine (ado) and human leukocyte antigen (HLA)-E/natural killer group 2A (NKG2A) checkpoint. Using flow cytometry, I assessed how ado alters HGSC cells and NK phenotypes. I genotyped HGSC patients for NKG2A polymorphisms and tested their impact on patient outcomes and immune profiles, and I genotyped healthy donors to assess NKG2A polymorphism impact on NK function in vitro. CD16 expression defined two NK subsets with distinct responses to ado; only CD16low NK cells were suppressed by ado-treated targets. NKG2A variant 5 (V5) associated with higher NKG2A expression and stronger responses to HLA-Elow targets. Ado enhanced HLA-E/NKG2A expression and NKG2A polymorphisms dictated ado suppression, revealing a novel link between metabolic and checkpoint inhibition. These findings support dual targeting of ado metabolism and NKG2A to overcome NK suppression in the HGSC microenvironment.
Open Access
ON THE MAGNITUDE AND SEASONAL VARIABILITY OF PCO2 AND AIR-SEA CO2 FLUXES IN THE NORTHWEST ATLANTIC OCEAN
(2025-05-26) Arruda Monteiro da Silva, Ricardo; Not Applicable; Doctor of Philosophy; Department of Oceanography; Not Applicable; Michael DeGrandpre; Yes; Katja Fennel; Eric Oliver; Kumiko Azetsu-Scott; Douglas Wallace
Oceanic uptake of atmospheric CO 2 plays a major role in regulating climate and mitigating the impact of its increasing concentration on global temperature. This thesis is focused on observations of surface-ocean partial pressure of CO2 (pCO2) and air-sea CO2 fluxes, particularly on the Northwest Atlantic Ocean. First, an overview of the marine carbon cycle and air-sea CO 2 fluxes is presented (Chapter 1). Then, a study analysing how new sensor-based pCO2 systems compare with more conventional but complex measuring systems is presented (Chapter 2). This comparison showed promise for a technological change that could be crucial for expanding our observational/monitoring network on ships of opportunity, research vessels, and using new platforms for ocean observation. The next study presented is a compilation of all pCO 2 observations available for the Central Labrador Sea (Chapter 3), where a base-line reference climatology was created for this region and compared against an ensemble of global products, showing large discrepancies between these products and the observational climatology produced here. The last study (Chapter 4) presents a gap-filling reconstruction of pCO2 maps for the Northwest Atlantic, using a neural network approach. These reconstructions were done with new observations and different spatial resolutions, and the effects of additional data and finer resolution on pCO2 and air-sea CO2 fluxes estimates is discussed. Both Chapters 3 and 4 emphasize the problem of poor data coverage, specially in high latitudes regions of the North Atlantic, pin-pointing where and when additional observations are necessary for improving constraints of air-sea CO2 fluxes. Therefore, this thesis contributes to improving potential for future data-coverage by validating a new simpler pCO2 measuring system (DAL-SOOP). The thesis also provides a compilation of pCO2 observations, producing a baseline seasonal climatology for the Central Labrador Sea. Comparison of this reference against other observational-based global products revealed systematic differences in the representation of the seasonal cycle of pCO2 and uncertainties in the magnitude of air-sea CO2 fluxes. Finally, the reconstruction of pCO2 maps in the Northwestern Atlantic Ocean contributes to new estimates of air-sea CO2 fluxes for regions that are poorly sampled. This study highlights the need to increase observation capability, specially in data-poor locations and in regions with high variability of pCO2 and intense CO2 fluxes.
Open Access
EFFECTS OF ENHANCED EFFICIENCY NITROGEN FERTILIZERS ON THE AGRONOMIC AND ENVIRONMENTAL PERFORMANCE OF GRAIN CORN
(2025-05-21) Lynds, Baillie; Not Applicable; Master of Science; Department of Plant, Food and Environmental Sciences; Not Applicable; n/a; Not Applicable; Dr. Nancy McLean; Dr. David Burton; Dr. Rhea Lumactud; Dr. Yunfei Jiang
Proper nutrient management is crucial for high yields, economic viability and environmental sustainability in agriculture. Nitrogen fertilizers enhance grain corn yields, but excess application can lead to N loss. Enhanced efficiency nitrogen fertilizers (EENFs) could mitigate this loss, but their effects on grain yields, quality, and the environment in Maritime Canada is under-researched. This study investigated the effects of EENFs on the agronomic and environmental performance of grain corn at three sites in the Canadian Maritimes, through four main comparisons: urea vs. EENFs, reduced vs. standard application rate, split vs. single applications, and EENFs applied alone vs. mixed with urea. Urea acted as a control, while three EENFs (PurYield™, SuperU®, and EENF_X) were evaluated. Results suggest PurYield™ and SuperU® can replace urea at a standard application rate without yield penalty, while EENF_X may cause a marginal yield reduction. PurYield™ reduced N2O emissions marginally compared to urea, but EENF_X exacerbated post-harvest soil NO3- N concentrations compared to all other fertilizers. PurYield™ maintained yields at a reduced rate of 100 kg N ha-1 while SuperU® reduced Truro-2023 yields at this rate. An application rate of 75 kg N ha-1 presented marginal yield reductions for both PurYield™ and SuperU®. Various application rates of EENF_X show no significant effect on yields. PurYield™ and SuperU® reduced N2O emissions at a rate of 100 kg N ha-1 compared to standard rates at Truro-2023 and Truro-2024 respectively. SuperU® showed marginally lower yields for a single application at Truro-2023, but otherwise, there were no yield, protein, or environmental differences between single and split applications. Mixing EENFs with urea showed no yield differences compared to applying EENFs or urea alone, but urea had higher N2O emissions than all treatments containing EENFs at Truro-2024, and higher NO3- N concentrations than certain EENFs in some cases, although results were inconsistent. Upon performing a return on investment analysis, 125U2T (125 kg N ha-1 urea split applied at planting and V6-V8), 100PY2T (split application of 100 kg N ha-1 PurYield™), 125USU2T (split application of 125 kg N ha-1 mixture of SuperU® and urea), and 125UPY2T (split application of 125 kg N ha-1 mixture of PurYield™ and urea) were consistently in the top five highest, suggesting these may be the most economical choices for producers. These findings provide farmers with recommendations on fertilizer products and management techniques to reduce environmental impact while maintaining grain yield, quality, and profitability, thereby enhancing agricultural sustainability.
Open Access
Integration of iGPMP2 and iSDF for Manipultor Motion Planning in a Partially-Unknown Semi-Dynamic Environment
(2025-05-21) Buchanan, Scott; Not Applicable; Master of Applied Science; Department of Mechanical Engineering; Not Applicable; n/a; Not Applicable; Clifton Johnston; Issam Hammad; Ya-Jun Pan; Robert Bauer
The use of high degree-of-freedom (DoF) manipulators in industrial manufacturing is well established. Traditionally, manipulators operate in isolated, well-defined work cells with little need for flexibility. Increasingly, however, manipulators are being extended to tasks in unpredictable and, at times, dynamic environments. This thesis presents an approach which enables the Franka Emika (FE) Panda 7-DoF manipulator, to which an Intel RealSense D435i RGB-D camera is mounted, to navigate in partially-unknown semi-dynamic environments. This goal is achieved through the integration of the popular optimization-based motion planner iGPMP2 with a neural network (NN) based environment estimation module iSDF. The main contributions of this thesis are the proposed modifications to iSDF and iGPMP2 to address their limitations in the application considered in this thesis, the integration of iSDF with iGPMP2, and the experimental validation of the proposed approach. The proposed modification to iSDF extends iSDF for use in non-static environments through the identification ...
Open Access
Physical Activity and Executive Functions in Young Adults: A Systematic and Empirical Investigation
(2025-05-19) Leckey, Jennifer; Not Applicable; Doctor of Philosophy; Department of Psychology and Neuroscience; Received; Dr. Travis J Saunders; Yes; Dr. Margo Watt; Dr. David Westwood; Dr. Sophie Jacques; Dr. Shannon Johnson
Young adults rely on executive functions (EFs) to navigate the transition to adulthood, and poorer EFs are associated with greater challenges during this period. Understanding factors that enhance young adults’ EFs will inform intervention strategies. Physical activity (PA), particularly exercise, is a promising strategy for enhancing EFs, though optimal PA parameters for young adults are unclear. A systematic review of 44 randomized controlled trials (N=3,124, ages 18–30) revealed that moderate-intensity and moderate-duration exercise of various types generally benefited young adults’ EFs in the short-term, while longer-term effects have been understudied. A follow-up cross-sectional study with undergraduate students (N=212) indicated that PA had a limited role in predicting EFs, whereas musical training, positive affect, and sleep quality were stronger predictors. Findings highlight the short-term benefits of exercise for young adults’ EFs, and suggest that other lifestyle factors, such as musical training, may be important for cognitive health promotion strategies.
Open Access
Pre-training and self-supervised learning for speech-based mental health assessment
(2025-05-08) Dumpala, Sri Harsha; No; Doctor of Philosophy; Faculty of Computer Science; Not Applicable; Dr. Theodora Chaspari; No; Dr. Rudolf Uher; Dr. Frank Rudzicz; Dr. Sageev Oore
Major depressive disorder (MDD), commonly known as depression, is a leading cause of disability, absenteeism, and premature death. Automatic depression assessment from speech is a vital step towards improving the diagnosis and treatment of this condition. While previous research has explored conventional acoustic features for speech-based depression assessment, these methods have not yet achieved clinical-level performance, highlighting the need for further advancements. A significant challenge is the non-availability of large training datasets required to train deep learning models from scratch for automated depression assessment. To address these issues, this thesis proposes the use of self-supervised learning (SSL) models based on speech to enhance the performance of automatic depression assessment systems. The pre-training objective function of SSL models determines the types of information encoded, such as semantic, speaker, and prosodic features. I first demonstrate that combining SSL models, which capture different aspects of speech—both local and global information—leads to improved performance in detecting depression. Additionally, I show that SSL-based speech embeddings are more effective at identifying specific symptoms of depression than traditional speech features. Furthermore, I compare various SSL pre-trained models to identify which aspects of speech contribute most to the detection of different symptoms. Finally, I extend test-time training (TTT) for depression detection to improve model robustness under naturally occurring covariate (distributional) shifts. This work underscores the potential of SSL techniques in developing more accurate and resilient models for depression assessment, thereby fostering further research into automated mental health evaluation.
Open Access
Investigating Experimental and Standard of Care Heart Failure Therapies in Modulating Macrophage-Mediated Myocardial Inflammation
(2025-04-30) Wells, Kyle Richard Douglas; Not Applicable; Master of Science; Department of Pharmacology; Not Applicable; n/a; Not Applicable; Susan Howlett; Christian Lehmann; Keith Brunt
Acute myocardial infarction (AMI) and hypertension continue to be major contributors to heart failure, yet current pharmacological interventions fail to fully address or cure this disease. In experimental models of AMI, hemin, an inducer of heme oxygenase-1 (HMOX1), has been shown to reduce inflammation in the heart. This effect is mediated via macrophages and other immune cells in the peri-infarct and infarct zones. Candesartan or valsartan (both angiotensin receptor blockers, ARBs), or sacubitril/valsartan (angiotensin receptor blocker with neprilysin inhibitor, ARNI) are standard-of-care heart failure therapeutics with anti-inflammatory effects that may be independent of their AT1 blockade effect or natriuretic peptide breakdown ability. Whether hemin, ARB, or ARNI treatment in heart failure are effective in resolving inflammation via macrophages in cardiac tissues is not fully known. In this thesis, we tested if hemin, ARB, and ARNI could alter the accumulation of M2 macrophages in vivo; if these compounds influenced macrophage polarity in an in vitro model, and if cytokines in media from these macrophages could protect AC16 cardiomyocytes from oxidative stress.
Open Access
Using Variable Chlorophyll-a Fluorescence to Assess the Impact of Ocean Alkalinity Enhancement on the Photochemical Efficiency of Phytoplankton
(2025-04-30) Egert, Marie; Not Applicable; Master of Science; Department of Oceanography; Not Applicable; Tammi Richardson; Not Applicable; Patrick McGinn; Ruth Musgrave; Zoe Finkel; Hugh MacIntyre
Ocean Alkalinity Enhancement (OAE) is a potential carbon dioxide removal strategy to mitigate climate change by enhancing oceanic carbon uptake. This thesis contributes to the biological risk assessment of OAE by examining its effects on phytoplankton photophysiology through laboratory and field experiments. In vitro studies (Chapter 3) revealed species-specific responses to elevated pH (~8.7), with varying resilience among phytoplankton. Mesocosm experiments (Chapter 4) showed changes in beam attenuation, particle size distribution, and pH following magnesium hydroxide additions, but no clear biological responses. Similarly, field trials with brucite altered optical properties but did not impair photosynthetic function. However, scattering artifacts in bio-optical sensors affected chlorophyll-a fluorescence readings, emphasizing the need for careful methodological consideration. Instrument design influenced sensitivity to scattering, affecting data reliability. Overall, findings support existing evidence that OAE, when applied at appropriate scales, is unlikely to pose significant risks to marine phytoplankton but highlight challenges in measurement accuracy.
Open Access
TOWARDS DEVELOPING STANDARDIZED PRECISION AGRICULTURE BOOM SPRAYER VIA HYBRID COMMUNICATION NETWORK FOR REAL-TIME SPOT APPLICATION
(2025-04-30) Motalab, Mozammel Bin; Not Applicable; Doctor of Philosophy; Faculty of Agriculture; Not Applicable; Viacheslav Adamchuk; Not Applicable; Alex Martynenko; Karama Al-Tamimi; Ahmad Al-Mallahi
The transition of boom spraying towards spot application under precision agriculture schemes faces challenges due to the large volume of data generated by a large number of sensing and actuation devices. This research focuses on developing a universal communication network for real-time spot application, using Controller Area Network (CAN) at its core, offering the advantages of potentially error-free communication and seamless integration of machine vision systems into different boom sprayers. To handle the narrow bandwidth characteristic of CAN, a novel electronic control unit (ECU) was developed to encapsulate pest detection results into CAN data frames based on detected pest locations in images received from one machine vision system consisting of multiple cameras. The machine vision data were transmitted through UART to identify the number of nozzles to be actuated via CAN. The ECU was designed to accommodate different machine vision systems with varying camera counts and image resolutions. For real-time control, the ECU extracted data every 40 ms and constructed CAN frames in two separate threads simultaneously. Field tests demonstrated that the ECU managed nozzle actuation for targets distributed across diverse scenarios, including spatial and temporal successions. Since the conditions on wide boom sprayers require multiple machine vision systems to actuate dozens of nozzles, an upgraded communication protocol was built at the interface of the machine vision with the ECU based on Ethernet. An application layer based on ISO 11783 was added to the CAN interface, widely used in agricultural machinery including sprayers. These upgrades allowed handling nozzle actuation at variable sprayer speeds up to 9.66 kph with a minimum spray length of 345 mm per detection, processing over 30 data frames every 40 ms. Finally, a new ISO 11783-compliant CAN bus with 60 nozzles was installed on a 36 m boom sprayer, used as a case study. This new bus featured two additional ECUs: one to communicate with other buses in the sprayer to import data like speed, and another to store pest detection and nozzle actuation data for further analysis. The case study demonstrated that a complete real-time spot application mechanism, including 30 cameras, would require an additional 4034 W for full functionality.
Open Access
VIRTUAL MENTAL HEALTH CARE FOR CHILDREN AND ADOLESCENTS: A SCOPING REVIEW OF THE LITERATURE AND EMPIRICAL EVIDENCE FROM CHILDREN AND ADOLESCENTS LIVING IN NOVA SCOTIA DURING THE COVID-19 PANDEMIC
(2025-04-30) Lang, Kaleigh; Not Applicable; Master of Science; Department of Community Health & Epidemiology; Not Applicable; n/a; Not Applicable; Dr. Debbie Emberly; Dr. Jill Hayden; Dr. Leslie Anne Campbell
This thesis aimed to identify factors influencing the implementation, delivery, and uptake of formal virtual mental health services for children and adolescents and related research gaps. A scoping review was conducted to map existing literature on virtual mental health care for children and adolescents with findings mapped using the Consolidated Framework for Implementation Research. As formal studies often exclude children and youth who do not access services, a secondary analysis was performed using data from a cross-sectional survey of youth and parents in Nova Scotia, collected between June 2021 and April 2022. Virtual care was widely implemented in response to the COVID-19 pandemic and may be a means of overcoming some barriers to care. Our findings highlight the importance of continued research to support effective and sustainable integration of virtual mental health services for children and adolescents.
Open Access
Enhancing Sustainable Crop Production: Biostimulatory Effects of Fish Hydrolysate and Nano-Sized Fish Hydrolysate on Kale and Lettuce Growth, Yield, and Phytochemical Composition
(2025-04-30) Pradeep Kumar, Anagha; No; Master of Science; Faculty of Agriculture; Not Applicable; Dr Lakshman Galagedara; No; Dr Gurpreet Singh Selopal; Dr Mumtaz Cheema; Dr Lord Abbey; Dr Svetlana Yurgel
As global food demand increases, and environmental issues become more pressing, sustainable agriculture practices are essential for improving crop output while reducing ecological effects. This study investigated the efficacy of fish hydrolysate (FH) and nano-sized fish hydrolysate (nFH) as biostimulants to enhance the growth and development of kale (Brassica oleracea var. sabellica) and lettuce (Lactuca sativa L.). Kale seeds and seedlings were subjected to FH concentrations of 0% (control), 0.25%, 0.5%, 1%, and 2% during germination and seedling growth experiments, while both crops received nFH treatment at sonication durations of 0, 15, 20, 25, and 30 mins, administered via soil drench and foliar application methods. The germination study indicated that 0.25% FH significantly increased kale germination by 15% compared to the control, resulting in an increase in root surface area. Greenhouse findings demonstrated that 2% FH boosted kale fresh weight by 43.35%, along with an increase in leaf count and photosynthetic efficiency compared to the control. In nFH, the 25-min soil drench application optimized biomass in both species, with lettuce exhibiting a 30% greater rosette diameter than the foliar treatment. Soil drench applications consistently outperformed foliar sprays, ensuring sustained nutrient delivery. Analytical techniques, such as scanning electron microscopy, validated that sonication diminished particle sizes, hence improving nutrient availability, while mineral analysis indicated elevated concentrations of key minerals, including potassium (1610 mg/L) and calcium (1410 mg/L) in FH. This study revealed that FH and nFH, especially at optimal concentrations and sonication durations, significantly enhanced plant growth and resistance, providing a sustainable method for utilizing fish waste in agriculture.
Open Access
Innovative Time-Domain Approaches for High-Performance Readout Circuits
(2025-04-30) Zareie, Mahsa; Yes; Doctor of Philosophy; Department of Electrical & Computer Engineering; Not Applicable; Dr. Rashid Rashidzadeh; Yes; Dr. Hamed Aly; Dr. Ya-Jun Pan; Dr. Kamal El-Sankary; Dr. Ezz El-Masry
The scaling of Complementary Metal-Oxide Semiconductor (CMOS) technology presents challenges for low-power, low-frequency sensor readout interfaces, particularly in nonlinearity, noise, and power efficiency. This dissertation explores time-domain signal processing (TMSP) to overcome these limitations, introducing two key contributions: a linearized open-loop Voltage-Controlled-Oscillator (VCO) Analog-to-Digital Converter (ADC) and a time-domain Goertzel-based frequency analyzer for low-frequency applications. The first contribution presents an ultra-low-power open-loop VCO-ADC, designed for direct digitization of low-frequency signals. A pseudo-differential transconductance, (G_M), stage linearization technique effectively suppresses even-order and third-order harmonics distortion, enhancing linearity and Dynamic Range (DR). Fabricated in 180 nm CMOS, the design achieves an Spurious-Free Dynamic Range (SFDR) of 81.48 dB, Total Harmonic Distortion (THD) of -76.8 dB, and Signal-to-Noise-and-Distortion Ratio (SNDR) of 70.9 dB (equivalent to 11.48 Effective Number of Bits (ENOB)) over a 3.6 kHz Bandwidth (BW), with low flicker noise achieved through a chopper-based noise suppression technique. The ADC operates at 1 V, consuming only 20.3 μW, making it highly efficient for low-frequency sensor readout. The second contribution introduces a time-domain Goertzel-based frequency analyzer, implemented for the first time in the analog time domain. A set of proposed TMSP arithmetic circuits, including a single-step time-register (TR) and time-amplifier (TA), enables real-time magnitude and phase extraction with less than 5% error for input frequencies up to 400 Hz. The CMOS 180 nm implementation consumes less than 24 μW, demonstrating superior power efficiency compared to conventional ADC + FFT architectures. These findings establish time-domain architectures as a scalable, low-power alternative for low-frequency sensor interfaces.
Open Access
EXPLORING THE ROLE OF SEX, FRAILTY, OR NEUROPATHOLOGY IN THE ANTIDEPRESSANT-ALZHEIMER’S DISEASE ASSOCIATION: A SCOPING REVIEW AND A SECONDARY DATA ANALYSIS
(2025-04-30) Eum, Lucy; Not Applicable; Master of Science; Medical Research Graduate Program; Received; Ruth Ann Marrie; Not Applicable; Sanja Stanojevic; Sultan Darvesh; Ashley Drohan; Shanna Trenaman; Melissa K Andrew
Background: Depression is a modifiable risk factor of dementia. The antidepressant-dementia association among older adults remains inconsistent. Methods: Two separate studies — a scoping review and a retrospective study — were conducted. The scoping review assessed whether sex or frailty has been studied as an effect modifier (EM) or confounder of the antidepressant-dementia relationship. The retrospective study assessed whether sex, frailty, or neuropathology modifies the antidepressant-dementia relationship. Results: The scoping review found that frailty was not explored as a confounder or EM in the literature. Sex was not explored as an EM. Studies examining sex as a confounder differed widely in their methodologies. The retrospective study found an association between antidepressant use and clinical dementia (odds ratio 2.65, 95%CI: 1.99-3.54). Male sex, frailty, and neuropathologic burden tended to have weaker antidepressant-dementia association, but this was not statistically significant. Conclusion: More studies are needed to explore potential EMs of the antidepressant-dementia relationship.
Embargo
ENERGY TRANSITION IN SMALL COMMUNITIES UNDER UNCERTAINTY
(2025-04-30) Mostafavi Sani, Mostafa; No; Doctor of Philosophy; Department of Industrial Engineering; Not Applicable; Fuzhan Nasiri; No; Uday Venkatadri; Michelle Adams; Hamid Afshari; Ahmed Saif
Transitioning small and remote communities to renewable energy is critical for achieving global net-zero targets. These communities, reliant on costly and emission-intensive fossil fuel systems, require tailored renewable energy frameworks and robust planning strategies to ensure reliable, sustainable, and cost-effective energy solutions. This dissertation addresses these needs through two interconnected themes: designing renewable energy systems specifically suited to local conditions and strategically planning transitions to net zero under uncertainty. In the first theme, advanced optimization models are developed to assess hydrogen's potential as seasonal energy storage, aligning social, economic, and environmental objectives. Results demonstrate significant potential for hydrogen to enhance energy reliability, reduce fossil fuel dependence, and support sustainability. By 2050, strategic deployment of hydrogen and wind power is expected to double capacity, substantially decreasing reliance on external grid connections. Further analyses cluster remote Canadian communities based on resources, climate conditions, and energy demand patterns, revealing hydrogen storage's effectiveness in mitigating seasonal energy fluctuations. Acknowledging the critical role of uncertainties in renewable energy transitions, the second theme introduces multi-stage stochastic robust optimization techniques to handle short-term energy variability and long-term uncertainties such as technology cost developments and evolving carbon policies. The findings highlight that phased investment strategies considerably outperform single-phase transitions, enhancing economic and environmental outcomes. Additionally, assessing the feasibility of waste-to-energy technologies alongside other renewable energy systems is crucial for boosting overall system reliability. Specifically, pyrolysis emerges as an adaptable, cost-effective solution, significantly lowering hydrogen production costs and effectively integrating waste management with broader renewable energy strategies. The thesis delivers frameworks for informed, resilient, and efficient renewable energy transitions in small, remote communities.
Open Access
Disrupting Carceral Pathways: Experiences of Anti-Youth Ageism and Criminalization in Canadian Child Welfare
(2025-04-30) Amirault, Bryn; Not Applicable; Master of Social Work; School of Social Work; Received; Dr. Brooke Richardson; No; Dr. Michael Ungar; Dr. Nancy Ross
The Canadian child welfare system currently faces a significant issue: youth in care are disproportionately represented in the criminal justice system, a phenomenon known as the care-to-prison pipeline. Quantitative macro-level factors have been well established. What remains underexplored are the micro-level dynamics within group care facilities that may facilitate anti-youth ageism and perpetuate criminalization. Using a qualitative phenomenological design and an intersectional feminist theoretical lens, this research draws on the lived experiences of five former youth in care. In particular, it examines whether anti-youth ageism is present, how intersecting identities impact experiences, and how these factors facilitate criminalization. Ultimately, this study provides a platform for the voices silenced by child welfare to tell their stories and share tactics to disrupt carceral pathways for youth in care.
Open Access
Effect of Hydrogen Absorbent Material in Conductive Coating ICCP System
(2025-04-29) Kashani, Kousha; Not Applicable; Master of Applied Science; Department of Mechanical Engineering; Not Applicable; Dr. Hany El Naggar; Not Applicable; Dr. Zoheir Farhat; Dr. George Jarjoura
Although cathodic protection is widely used for corrosion mitigation, it faces limitations, particularly in protecting parts intermittently exposed to water or shielded from anodes. In complex structures like marine vessels or steel frameworks, traditional systems often fail to protect submerged, buried, or elevated areas effectively. Conductive Coating ICCP (Impressed Current Cathodic Protection) systems address these issues by applying an anode directly onto the substrate surface, reducing power demands, minimizing stray current corrosion, and lowering installation costs. However, overprotection in such systems can cause hydrogen gas evolution at the cathode, leading to blistering and filiform corrosion. This research aims to mitigate hydrogen-related damage by identifying a suitable hydrogen absorbent material and compatible catalyst, optimizing their proportions, and incorporating them into the coating. Performance is evaluated through controlled hydrogen absorption tests, with the ultimate goal of enhancing the long-term durability and effectiveness of Conductive Coating ICCP systems.
Embargo
Exploring the Application of Plasmonic Group IV Transition Metal Nitrides via Surface Modification Strategies
(2025-04-30) Shea, Dreenan Anne; Yes; Doctor of Philosophy; Department of Chemistry; Not Applicable; Dr. Christa Brosseau; Not Applicable; Dr. Peng Zhang; Dr. Norman Schepp; Dr. Ghada Koleilat; Dr. Mita Dasog
The interest in plasmonic transition metal nitrides (TMNs) has expanded recently due to the chemical and thermal stability of their bulk counterparts. While their popularity has grown, the chemical properties of nano-sized TMNs have remained unexplored. As chemical properties such as stability dictate the feasibility of TMNs, this doctoral work first analyzes pH and oxidative stability of these nanomaterials. Amongst investigation via UV-Vis spectroscopy, TiN experienced complete oxidation in 60 days, while ZrN and HfN remained relatively stable. However, all three TMNs showed stable pH ranges of 2-3, observed via zeta potential measurements. Dispersibility studies of TMN nanoparticles showed water as the only functional solvent. The focus of this thesis is stability enhancement of group 4 TMNs (TiN, ZrN and HfN) using surface modification techniques. For surface functionalization studies, multiple silanes (APTES, dimethyldichlorosilane, mPEG-silane) were used as coupling agents due to their reactivity with hydroxy-terminated oxide shells on TMN surfaces.
Open Access
Framing Community Responses to Environmental Disasters: A Case Study of Media Coverage of the Wakashio oil spill in Mauritius
(2025-04-29) Nombro, Emily; Not Applicable; Master of Arts; Department of International Development Studies; Received; n/a; Not Applicable; Dr. John Cameron; Dr. Theresa Ulicki; Dr. Matthew Schnurr
On July 25th, 2020, the MV Wakashio ran aground on the southeastern coral reefs of Mauritius, spilling around one thousand metric tonnes of oil into the sea. The disaster received widespread local and international media coverage, covering both government and civil society response efforts. News media play a significant role in shaping narratives during disasters through frames, influencing public perception of the different response actors. Previous research has demonstrated that both local and international news media can frame the same disaster differently, often reinforcing dominant Western narratives. This thesis uses the Wakashio oil spill to investigate how local versus international news agencies framed the government and civil society responses. Findings show that the local news agencies offered more detailed commentary and critique, particularly of the government response, and, contrary to the literature, the international coverage of the disasters was positive. Finally, implications for future disaster policy and planning are discussed.