Western University Open Repository

Western University’s Open Repository collects, archives, preserves, and freely disseminates scholarly works by members of the Western University community.

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Faculty and Staff Works 11841
Works by any staff member, including faculty, librarians, archivists, and post-doctoral fellows.
Graduate Student Works 17169
Scholarly works by graduate students, including theses and dissertations.
Undergraduate Student Works 1371
Scholarly works by undergraduate students. Undergraduate students must have faculty support and approval to post their work.

Recent Submissions

Access status: Embargo ,
The Role of Peroxidase in Suberin Assembly in Potato
(The University of Western Ontario, 2026-01-21) Esfandiari, Mina
Suberin is a complex heteropolymer that forms an apoplastic diffusion barrier in plant tissues, protecting against water loss and pathogen invasion. In potato tubers (Solanum tuberosum), suberization is a key wound-healing response that requires coordinated deposition of phenolic and aliphatic monomers. Although suberin biosynthesis has been studied extensively, the specific roles of individual class III peroxidases (PRXs) in catalyzing oxidative polymerization of phenolic monomers remain unclear. Here, we examined the functional contributions of three wound-inducible peroxidase genes—PRX19, PRX55, and PRX105—using RNA interference (RNAi) knockdown to dissect isoform-specific roles in suberin assembly and barrier formation. Transcript analyses confirmed strong (>80%) silencing of each target gene, yet physiological and biochemical consequences varied substantially. PRX19-RNAi tubers showed sharply reduced total peroxidase activity, substantial loss of phenolic suberin, disrupted lamellar ultrastructure, and impaired water-retention capacity. Metabolic profiling revealed altered accumulation of soluble phenolics and defective incorporation of aliphatic monomers, indicating that PRX19 is required to generate phenolic radicals that form the initial poly(phenolic) scaffold necessary for subsequent aliphatic deposition. By contrast, PRX55- and PRX105-RNAi lines displayed only modest or negligible effects on peroxidase activity, suberin chemistry, and barrier integrity, suggesting partial redundancy or supporting roles during wound healing. Together, these findings support a model in which PRX19 acts as a central catalytic hub in early suberin assembly, governing phenolic coupling and lamellar organization. This work advances understanding of the enzymatic and metabolic coordination underlying wound-induced suberization and highlights PRX19 as a potential molecular target for improving postharvest tuber quality, stress tolerance, and disease resistance through targeted modulation of peroxidase activity.
Access status: Embargo ,
Retention of Post-Secondary Graduates in their City of Study
(The University of Western Ontario, 2026-03-30) Mpinda, Isaac
Canada faces a profound demographic crisis characterized by low fertility rates, population aging, and stark regional disparities in growth, with rural and smaller urban communities experiencing acute brain drain and labor shortages. While postsecondary graduates, both domestic and international, represent a strategic pool of skilled labor that could alleviate these pressures, their retention patterns remain poorly understood at the city level, where graduates directly interact with local labor markets and community networks. This dissertation addresses this gap through an integrated article format comprising three empirical chapters that examine graduate retention across multiple scales and populations using linked longitudinal administrative data from Statistics Canada. Drawing on human capital theory, internal migration theory, integration theory, and life course perspectives, the research follows 1.5 million graduates from 2009–2013 cohorts over five years post-graduation. Chapter 2 establishes that retention is shaped by immigration status (permanent residents show 24% lower mobility hazards than Canadians), study location (graduates in non-Census Metropolitan Areas face 3.4 times higher exit risks than those in Toronto, Montreal, and Vancouver), and credential type (non-degree graduates exhibit stronger local attachment than university graduates). Chapter 3 develops a novel study discipline-occupation crosswalk to assess field-of-study alignment with local occupations, finding modest but significant retention benefits when graduates’ disciplines match dominant city-level employment sectors. Chapter 4 introduces a critical dual-scale framework distinguishing national retention (remaining in Canada) from local retention (remaining in the study city), revealing that these processes operate through divergent mechanisms: permanent residency pathways and labor-market-aligned credentials drive national retention, while co-ethnic networks, urban scale, and family formation shape intra-Canadian mobility. The dissertation makes three key contributions: (1) it helps establish the city as a critical yet understudied scale for understanding graduate mobility; (2) it demonstrates that policies successful at the national level may fail locally, exposing tensions between federal immigration objectives and subnational development needs; and (3) it provides evidence-based guidance for place-based retention strategies, particularly for smaller communities struggling to anchor talent. Findings underscore that retaining skilled graduates requires coordinated interventions across immigration policy, labor market development, and family-supportive infrastructure, not education recruitment alone.
Access status: Embargo ,
Cholinergic Modulation of Parvalbumin Neurons in Cognition Relevant to Schizophrenia
(The University of Western Ontario, 2025-12-03) Hamidullah, Shahnaza
Cognitive impairments, particularly deficits in attention and working memory, are a hallmark of schizophrenia and related disorders. These impairments significantly impact daily life and are among the strongest predictors of poor functional outcomes. Understanding the neural mechanisms underlying attention and working memory is crucial for developing therapeutic strategies to improve the quality of life for patients with these disorders. These aspects of cognition rely on the balance between excitatory and inhibitory neurotransmission, particularly in the prefrontal cortex (PFC), where inhibitory parvalbumin neurons (PVNs) play a key role. PVN activity, in turn is subject to modulation by neuromodulators such as acetylcholine (ACh). This work examines how cholinergic signaling and PVNs in the PFC contribute to cognition. Using fibre photometry, we first characterized ACh and PVN dynamics in attention using the rodent continuous performance task (rCPT). ACh and PVN signals showed highly similar event-related patterns, suggesting coordinated activity during attentional processing. These findings support a model in which cholinergic modulation enhances PVN recruitment to facilitate attention. Next, we investigated the receptor mechanisms underlying this modulation. Broad muscarinic receptor (mAChR) blockade with scopolamine impaired discrimination between targets and non-targets and reduced PVN activity, indicating a causal link between muscarinic signaling and PVN recruitment. Selective targeting revealed that M1, but not M4, mAChR antagonism reproduced these effects, identifying M1 mAChRs as critical for sustaining attention by maintaining excitation–inhibition balance. Nicotinic blockade produced only modest effects, suggesting a lesser role on modulation of PVN activity and attention. Finally, we explored the role of PVNs in working memory using the trial-unique delayed nonmatching-to-location (TUNL) task. We found that PVN activity was associated with greater task demands, particularly when delay length or interference was increased. Furthermore, optogenetic inhibition impaired performance under demanding conditions, whereas gamma-frequency stimulation improved accuracy. Together, these findings demonstrate that PVNs are recruited in a demand-dependent manner during working memory performance. Our findings indicate that M1 mAChR modulation of PVNs plays a key role in cognition relevant to schizophrenia and related disorders. Targeting specific mAChRs may provide a promising therapeutic avenue for these conditions.
Access status: Open Access ,
Analysis of Risk in Real-World Driving Scenarios: Implications for Advanced Driving Assistance Systems
(The University of Western Ontario, 2026-04-02) Bhowmik, Moumita
This thesis presents a dynamic risk assessment algorithm for Advanced Driver Assistance Systems (ADAS) using real urban driving data. The goal is to estimate how risky a current traffic situation is by combining information about the ego vehicle, surrounding objects, and their interactions. To achieve this, a YOLOv8m-DeepSORT pipeline detects and tracks surrounding road users and combines that with CAN bus and IMU signals to obtain ego-vehicle and object states. From these, Time-to-Collision (TTC), Time-to-Materialization (TTM), geometric intersection points, and a set of critical scenarios (crossing traffic, head-on collision, intersection turning, parked/occluded vehicles, not following traffic signs, construction speed-limit violations, and emergency braking) are derived. These inputs feed a Severity–Exposure–Controllability (SEC) model that outputs a continuous risk score R ∈ [0, 10] and LOW, MEDIUM, or HIGH risk classes. The results show realistic scenarios and risk distributions, and a qualitative validation confirms that the proposed SEC-based risk assessment algorithm can provide an interpretable, runtime measure of driving risk that is consistent with established safety concepts and suitable as an input for future ADAS decision-making.
Access status: Embargo ,
Examining the Role of the NAc-PFC Pathway in the Link Between Examining the Role of the NAc-PFC Pathway in the Link Between Adolescent Nicotine Exposure and Adulthood Depression
(The University of Western Ontario, 2026-02-19) Harrison, Robin
There is a frequent association between nicotine exposure in adolescence and adulthood depression, but this relationship is poorly understood from a biological perspective. The nucleus accumbens and prefrontal cortex often display dysfunction during reward-based neuroimaging studies in nicotine users and depressed individuals. To explore these regions’ roles in this relationship, this project investigated activation of these areas during monetary reward through functional magnetic resonance imaging in individuals with (n=25) and without (n=25) adolescent nicotine exposure who may also have had a lifetime diagnosis of depression. This analysis found that individuals with a history of adolescent nicotine use displayed heightened activation to monetary reward in the prefrontal cortex compared to those without, and this phenotype was also present in nicotine-exposed individuals with a history of depression. These findings contribute to our understanding of nicotine’s influence on the adolescent brain, and may help elucidate the common association between nicotine use and depression.