Faculty of Graduate Studies Online Theses
Permanent URI for this collectionhttps://hdl.handle.net/10222/11163
Browse
Recent Submissions
Item Embargo HYPOXIA MEDIATES N-METHYL-D-ASPARTATE SIGNALING RELATED SUSCEPTIBILITY TO TRAUMATIC BRAIN INJURY(2025-07-02) Muradov, Jamil; Not Applicable; Doctor of Philosophy; Department of Medical Neuroscience; Received; Jamie Hutchison; Yes; Lutz Weise; William Baldridge; Alon FriedmanCortical spreading depolarizations (CSDs) are an early hallmark of traumatic brain injury (TBI) and are associated with poor clinical outcomes, yet their underlying mechanisms remain poorly understood. We hypothesized that post-traumatic hypoxia promotes CSDs and impairs neurovascular responses. This study examined how hypoxia and CSDs affect neurobehavioral outcomes post-TBI and evaluated the effects of NMDAR antagonists as potential therapeutics. Using an animal model of single moderate TBI (N=67), we assessed its outcome variability (Chapter 2). TBI impaired neurological scores at 48 h post-impact (p<0.0001) and disrupted the neurovascular response to CSDs. Behavioral scores showed a bimodal distribution (R²=0.88; trough=7.01), categorizing animals into “susceptible” and “resilient” groups. Susceptible animals exhibited early cardiorespiratory dysfunction (lower HR and SpO₂ at hind paw and neck; p=0.02, p<0.001, p=0.01) and a significantly reduced neurovascular response to triggered CSDs, along with prolonged post-CSD oligemia. To explore the relationship between hypoxia and CSDs (Chapter 3), I used epidural electrodes and cranial window surgery. Animals that developed CSDs had lower mean SpO₂ (83.6%) compared to those that did not (92.2%). The co-occurrence of CSDs and hypoxia significantly altered the neurovascular response, with a 16% reduction in cerebral blood flow during the expected hyperemic phase, suggesting potential hypoperfusion and ischemia. In Chapter 4, I studied CSD-induced vascular responses in resilient vs. susceptible animals under hypoxia or following NMDAR antagonist treatment. Memantine reduced CSD incidence by 42–73% and mitigated cortical hypoperfusion. In a randomized pre- clinical trial, memantine treatment improved behavioral outcomes and preserved neurovascular function. This multi-modal investigation identified post-impact hypoxia as a key driver of CSDs and demonstrated that hypoxia and CSDs synergistically impair neurovascular regulation. Targeting these processes through oxygen support and NMDAR antagonism prevented secondary injury and improved outcomes. These findings may inform mechanism-based strategies for mitigating TBI susceptibility across injury severities.Item Open Access Assessing The Associations Between Asbestos Exposure and Breast Cancer Incidence Among Nova Scotian Females in a Longitudinal Cohort Study(2025-06-26) Ring, Ethan; Not Applicable; Master of Science; Department of Community Health & Epidemiology; Not Applicable; n/a; Not Applicable; Dr. Ellen Sweeney; Dr. Nathalie St-Jacques; Dr. Cindy Feng; Dr. Robin UrquhartBreast cancer is common among female populations worldwide. While many risk factors for breast cancer are well-established, potential associations between asbestos exposure and breast cancer incidence remains a subject of ongoing investigation. This population-based study utilized data from 8,808 cancer-free females in Nova Scotia. Multivariable logistic regression was used to assess associations between three binary indicators of asbestos exposure (at work, at home and overall) and breast cancer incidence, adjusting for various confounders. Increased odds of breast cancer among participants reporting prior asbestos exposure in the workplace was noted (AOR = 1.75, 95% CI: 1.00 – 3.06). Elevated risks were observed for following occupational asbestos exposure (AOR = 2.18, 95% CI: 1.21 – 3.92) and overall asbestos exposure (AOR = 1.82, 95% CI: 1.06 – 3.11) among females 50 years of age or older. These results warrant further investigation to uncover potential biological mechanisms and confirm observations among other populations.Item Embargo Assessment of Functional Recovery in Experimental Autoimmune Encephalomyelitis by Putative Remyelinating Drugs(2025-06-24) Kasheke, Gracious; Yes; Doctor of Philosophy; Department of Pharmacology; Received; Dr. Jack Antel; Yes; Dr. Patrice Côté; Dr. Corey Baimel; Dr. George RobertsonCurrent immune-based therapies for multiple sclerosis (MS) reduce disease relapses but have limited value in slowing disease progression. Remyelination in the central nervous system (CNS) is considered essential for functional recovery in MS. This has driven an intense search for drugs that promote myelin repair. This thesis compared the efficacy of four putative remyelinating drugs at promoting motor recovery in a mouse model of MS termed experimental autoimmune encephalomyelitis (EAE). EAE recapitulates many pathophysiological features of MS including autoimmune mediated demyelination and axonal damage. Furthermore, we have shown that EAE produces MS-like gait deficits in mice. Kinematic gait analysis was therefore employed to identify drugs that promote functional recovery in EAE mice. To this end, we compared the effects of oral administration of pioglitazone, VP3.15, olesoxime, or IRX4204 beginning at peak disease on EAE-induced gait deficits. Unlike pioglitazone, VP3.15, and olesoxime, IRX4204 reduced clinical scores, loss of knee average angle, and elevation of knee and ankle RMS differences. These gait improvements in IRX4204-treated EAE mice were associated with transcriptional and histological signs of reduced inflammation, increased remyelination, and enhanced axonal integrity in the spinal cord. Experimentation with a mouse microglial cell line and primary astrocyte cultures showed that IRX4204 suppressed the expression of pro-inflammatory cytokines induced by treatment with lipopolysaccharide. IRX4204 also enhanced mitochondrial function and the phagocytotic activity of microglia. These findings support the potential of IRX4204 to increase functional recovery in MS by stimulating myelin repair. However, IRX4204 suffers from poor CNS uptake and adverse side effects caused by actions on cells outside of the CNS. To overcome these problems, we developed an intranasal nanoparticle formulation of IRX4204 designed to preferentially deliver this drug to the CNS. Our findings suggest that intranasal nanoparticle delivery is a promising strategy to improve the safety and efficacy of IRX4204 but also reveal limitations of this approach.Item Open Access Understanding the global and local evidence on the process of student engagement in Health Promoting Schools(2025-06-23) Kontak, Julia; Yes; Doctor of Philosophy; Faculty of Health; Received; Dr. Antony Card; Yes; Dr. Camille Hancock-Friesen; Dr. Becky Feicht; Dr. Sara KirkHealth Promoting Schools (HPS) is a whole-school approach that facilitates environments for student health and learning. Despite evidence supporting outcomes of student engagement, a key component of HPS, little is known regarding process factors that lead to these benefits. In Nova Scotia, Canada, UpLift (2019 – 2024), a school-community-university partnership was formed to catalyze HPS, with a focus on student engagement. To amplify student engagement, Youth Engagement Coordinators (YECs) were hired, and Student Action Grants were established. The aim of this dissertation was to understand the process of student engagement in HPS at the global and local level. First, a scoping review was conducted to globally map and characterize the process of student engagement in HPS. Of the 50 sources analyzed, process factors related to participatory mechanisms for engagement included reflection and visioning, co-determining priorities and action-oriented learning. Second, a co-design approach using a transformative lens was employed to understand perspectives from students (n = 9, grades 7 - 11) and YECs (n = 6) involved in UpLift. This involved two co-design workshops where participants worked with the research team to gather, analyze, and interpret the data. Methods with students involved the draw, write and tell method, and a participatory focus group. Methods with YECs included a focus group, participatory mapping and a theming exercise. Following the workshops, reflexive thematic analysis was employed, and member reflection was conducted. Findings from the student group outlined the significance of strategies to build motivation for action, a collaborative space for youth, and adult facilitation practices. Findings from the YECs emphasized the importance of reflexivity, school culture, connections with school members, expansion on the concept of health and equitable environments for youth voice. This dissertation provides global and contextual considerations specific to Nova Scotia on the process for student engagement in HPS. Findings highlight factors across the process spectrum, from foundational considerations including adult positioning and school culture, to more specific implementation strategies related to collaborative decision-making. Findings highlight the relationship between student health promotion competencies and youth agency. These findings will directly build the knowledge base and contribute to local student engagement efforts in HPS.Item Embargo Bathymetric Anomaly Detection Towards Simultaneous Localization and Mapping on Autonomous Underwater Vehicles(2025-06-23) Cain, Nolan; Not Applicable; Master of Applied Science; Department of Mechanical Engineering; Not Applicable; na; Not Applicable; Dr. Ted Hubbard; Dr. Guy Kember; Dr. Mae Seto; Dr. Robert BauerAutonomous underwater vehicles (AUVs) are uncrewed vehicles that can dive to deep depths or under ice to map the seafloor in the Arctic. Due to the lack of global navigation satellite systems (GNSS) underwater, AUV's rely on inertial navigation to estimate their position. Inertial navigation suffers from unbounded error drift. Simultaneous localization and mapping (SLAM) can be used to correct the AUV's positional estimate by repeatedly observing landmarks in its surrounding terrain. Bathymetry has been used to define landmarks for underwater navigation using feature extraction techniques designed for optical imagery. This thesis describes the development of a novel anomaly detector, `Bathymetric Anomalies from Anti-Motifs' (BAAM), that is purpose-built to detect unique bathymetric landmarks. BAAM exploits known bathymetric motifs (commonly repeated patterns) to detect bathymetric anomalies which can be used as landmarks for SLAM. Bathymetric motifs were extracted from a region of Delaware Bay bathymetry using a 2-D adapted matrix profile algorithm, geometric transformation- and scale-invariant image matrix profile (GTSI-IMP), that was developed in this thesis. The ability to associate landmarks, of BAAM and existing optical feature extraction algorithms, was evaluated using semi-synthetic sonar images of a separate region of Delaware Bay bathymetry. For the conditions used in this research, the BAAM detector combined with the binary robust invariant scalable keypoints (BRISK) descriptor produced more correct matches than many of the optical feature extraction methods. However, the scale-invariant feature transform (SIFT) detector combined with the BRISK descriptor was found to produce the most correct matches in both the noise-free and noisy semi-synthetic sonar images. Despite SIFT-BRISK's ability to produce more correct matches than BAAM-BRISK on these semi-synthetic sonar images, the landmarks identified in the Delaware Bay bathymetry using BAAM were found to be more unique (anomalous) than those identified using SIFT.Item Embargo Synthesis of Phosphino(Silyl) Ligated Nickel and Manganese Complexes for the Catalytic Hydrofunctionalization of Alkenes(2025-06-17) Saunders, Tyler; Not Applicable; Doctor of Philosophy; Department of Chemistry; Not Applicable; Johanna Blacquiere; Yes; Mark Stradiotto; Saurabh Chitnis; Norman Schepp; Laura TurculetTransition metal catalysts play a key role in the synthesis of value-added products from abundant raw materials. While homogeneous catalysts that feature scarce metals such as Pd, Pt, Rh, and Ru have proven effective, recent focus on sustainability has led to interest in utilizing Earth-abundant 3d-metals such as Mn, Fe, Co, and Ni. Multidentate phosphino(silyl) ligands under investigation in the Turculet group have proven useful in 3d-metal mediated catalysis. This document details the development of new tridentate PSiN and bidentate PSi supported Ni and Mn complexes for application in hydrofunctionalization catalysis. Nickel complexes supported by a new PSiN ligand that features a quinolyl donor, as well as complexes supported by the bidentate CyPSi (CyPSi = κ2-(2-Cy2PC6H4)SiiPr2) ligand were shown to be effective pre-catalysts for alkene tandem isomerization-hydroboration. Deuterium labeling experiments support a Ni-mediated alkene chain-walking mechanism involving reversible alkene insertion/β-hydride elimination. Borylation occurs exclusively at a terminal position, affording high selectivity. Nickel complexes supported by a new PSiInd ligand featuring an indolyl backbone were also pursued, and these complexes along with (CyPSi)Ni species were screened in alkene hydrogenation catalysis. A variety of sterically hindered, unfunctionalized alkenes were readily hydrogenated under mild conditions. Deuteration experiments highlight the occurrence of background chain-walking, similar to that observed in the previous hydroboration studies. The synthesis of chiral phosphino(silyl) Ni complexes for application in asymmetric catalysis was also targeted. In this regard, a new (BIPHEN-SilaPhos)Ni(η3-C8H13) complex is described. This complex and the previously synthesized ((S,S)-TADDOL-SilaPhos)Ni(η3-C8H13) were applied in the asymmetric hydrogenation of (Z)-2-acetamido-3-arylacrylates to access chiral α-amino acid esters. SilaPhos ligation represents a new approach to chiral ligands featuring chirality at a Si donor. The (S,S)-TADDOL-SilaPhos ligated Ni complex afforded the desired products in near quantitative yields with excellent enantioselectivity (up to 98:2 er). Both direct and transfer hydrogenation with iPrOH as the hydrogen source are shown to be viable pathways for this reactivity. Progress towards the synthesis of Mn complexes supported by multidentate phosphino(silyl) ligation is also described. Mn(I) tricarbonyl complexes supported by CyPSiP (CyPSiP = κ3-(2-Cy2PC6H4)2SiMe) and PSiN ligation were synthesized and structurally characterized. The utility of Mn pre-catalysts in alkyne semi-hydrogenation and alkene hydrogenation was investigated. In situ generated Mn(II) dialkyl complexes featuring CyPSiP and PSiN ligation are shown to be active in the catalytic hydrogenation of a range of terminal alkenes.Item Open Access Optogenetic-Based Models of Arrhythmia-Induced Cardiomyopathy in Larval Zebrafish(2025-06-19) Savoie, Emma; Not Applicable; Master of Science; Department of Physiology & Biophysics; Not Applicable; Keith Brunt; Not Applicable; Thomas Pulinilkunnil; Ketul Chaudhary; Alexander QuinnArrhythmia-induced cardiomyopathy (AiCM) has recently emerged as a distinct subset of cardiomyopathy, resulting from chronic tachycardia or high ectopic burden, which leads to structural and functional changes in the heart. Traditional experimental models of AiCM rely on invasive techniques, such as implantable pacemakers, which are low-throughput and technically challenging. In contrast, optogenetics allows for light-based cardiac pacing, which, in transparent zebrafish larvae, offers a non-invasive, high-throughput platform for studying AiCM and identifying novel pharmacological treatments. In this study, we aimed to develop in vivo optogenetic models of AiCM using larval zebrafish to investigate the effects of arrhythmias on cardiac function, structure, and gene expression. We utilized zebrafish with cardiac-specific expression of cation-nonspecific channelrhodopsin-2 (ChR2) or chloride-specific anion channelrhodopsin-1 (ACR1) and exposed them to three arrhythmia protocols: intermittent tachypacing, a 33% ectopic burden, or a 50% ectopic burden through programmed light pulses at 2-7 days post-fertilization. GFP-expressing zebrafish exposed to the same light patterns served as controls. The mechanical function of the atrium and ventricle was assessed in live zebrafish at 7 dpf through brightfield recordings, while structural changes were evaluated in fixed samples using fluorescent microscopy. Additionally, we examined the expression of genetic biomarkers associated with cardiomyopathy using qRT-PCR. Our findings revealed that both tachypacing and ectopic pacing induced significant changes in cardiac structure, function, and gene expression. Intermittent tachypacing induced the most severe dysfunction, followed by the 50% ectopic burden and 33% ectopic burden. Across all protocols, ChR2-expressing fish showed more pronounced changes than ACR1-expressing fish. Specifically, both tachypacing and ectopic pacing resulted in increased end-diastolic area (EDA), end systolic area (ESA), stroke area (SA), and decreased ejection fraction (EF), with changes in gene expression indicative of chamber wall stretch, hypertrophy, inflammation, and fibrosis. To explore the therapeutic potential of this model, we tested the effects of fimasartan on tachypacing-induced dysfunction. Preliminary results demonstrated that 50µM fimasartan improved cardiac function and attenuated structural remodeling in the zebrafish heart, highlighting the potential of this model as a high-throughput platform for therapeutic drug screening.Item Open Access ADDRESSING CLASS IMBALANCE IN HIERARCHICAL MULTILABEL CLASSIFICATION WITH NODE-WISE WEIGHTING(2025-06-13) Sharma, Ayushi; Not Applicable; Master of Computer Science; Faculty of Computer Science; Not Applicable; N/A; Not Applicable; Dr. Israat Haque; Dr. Gabriel Spadon De Souza; Dr. Thomas TrappenbergClass imbalance is a persistent challenge in hierarchical multilabel (HML) classification tasks where labels form parent-child relationships and samples contain more than one label. It hampers learning as the majority classes dominate training while minority classes are neglected, which is amplified due to hierarchical dependencies. We introduce an adapted node-wise weighting method that enforces hierarchical constraints and reimagine HML imbalance as defined by node frequencies in a dataset. We benchmark it on several HML datasets including functional genomics datasets and an oceanographic dataset. We analyze which evaluation metrics provide a comprehensive assessment that is specifically suited for assessing HML tasks. The experimental results show that our node-wise weighting method consistently improves recall for minority classes without sacrificing much precision on majority classes, outperforming prior techniques for handling class imbalance. These findings show the potential of our method to address class imbalance in HML settings applicable to diverse real-world HML tasks.Item 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 HaldeSoils 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.Item 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 HewittVitamin 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.Item 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 BoudreauNatural 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.Item 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 WallaceOceanic 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.Item 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 JiangProper 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.Item 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 BauerThe 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 ...Item 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 JohnsonYoung 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.Item 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 OoreMajor 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.Item 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 BruntAcute 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.Item 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 MacIntyreOcean 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.Item 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-MallahiThe 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.Item 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 CampbellThis 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.