Recherche uO, le dépôt numérique de l'Université d'Ottawa, réunit le matériel de recherche et d'enseignement créé par notre communauté universitaire et nos partenaires. Le savoir de l'Université est ainsi disponible à long terme et en accès libre, ce qui lui procure de la visibilité et facilite sa diffusion.

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    Dynamic Modelling and Coordinated Control for Autonomous Path Tracking of Agricultural Wide-Span Implement Carriers
    (Université d'Ottawa / University of Ottawa, 2026-09-28) Li, Xiaopeng; Laguë, Claude
    Agricultural wide-span implement carriers (WSICs) are controlled traffic farming platforms that reduce soil compaction and improve field-operation efficiency through the coordinated motion of two supporting vehicles connected by a long-span truss. This research presents an original, applied systems-engineering integration of vehicle-truss dynamic modelling, control design, adjoint-curve-based leader-follower synchronization, simulation, and experimental evaluation for this configuration. A dynamic model was formulated for the supporting vehicles of the coupled vehicle-truss system, incorporating longitudinal and lateral motion, yaw dynamics, tire-ground interaction, and loads transmitted quasi-statically through the truss and implement. The model served as the basis for a combined control strategy using incremental model predictive control (MPC) for steering, with adaptive weighting evaluated in simulation, and proportional-integral-derivative (PID) control for longitudinal velocity. Inter-vehicle coordination was achieved through a follower synchronization controller based on offset-error regulation, with first-order error dynamics and a Lyapunov-based stability analysis. The strategy was evaluated through MATLAB/Simulink and CarSim co-simulations and experimentally validated on a small-scale WSIC platform equipped with real-time kinematic Global Positioning System (RTK-GPS) receivers, inertial measurement units, and wireless communication modules. The dynamic-model-based strategy was compared with a kinematic approach under demanding simulated conditions, including curved and reverse motion, higher speeds, implement resistance, and initial offset errors, with differences assessed against sensor-based thresholds and application-specific error bounds. On curved paths, the strategy reduced steady-state lateral error from ±0.20 m to ±0.12 m, meeting the ±0.15 m criterion, and reduced distance-based integral absolute error (IAE) for lateral tracking and offset by approximately 46% and 50%, respectively. In curved reverse motion, lateral-error IAE decreased by 34-36%. In straight-line simulations, the principal differences between the controllers were in offset regulation and recovery from a large initial offset. The combined MPC-PID strategy also reduced lateral-error IAE by about 28% relative to unified MPC during curved tracking. Small-scale experiments with fixed MPC weights demonstrated the strategy's feasibility: in two-vehicle cooperation, steady-state lateral errors were 0.02-0.03 m lower than those obtained with the kinematic controller. On sinusoidal paths, offset-error and separation-error IAEs decreased by 33-35%, while steady-state orientation error was approximately 0.02 rad larger. Experimental tracking errors exceeded simulated errors, owing mainly to the slower measured response of the follower velocity loop, together with unmodelled hardware nonlinearities, GPS fluctuations, and surface irregularities. Overall, incorporating vehicle dynamics, predictive steering, and explicit synchronization design provides an effective, experimentally validated foundation for WSIC guidance and future full-scale development.
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    TCF4 Mediates PHF6 Transcriptional Regulation of Neural Stem Cells in the Developing Brain, a Mechanism Disrupted in Börjeson-Forssman-Lehmann Syndrome
    (Université d'Ottawa / University of Ottawa, 2026-09-28) Li, Yunqiao; Jahani-Asl, Arezu
    Intellectual disability (ID) comprises a heterogeneous group of neurodevelopmental disorders characterized by impairments in cognitive function and adaptive behavior. Börjeson Forssman-Lehmann syndrome (BFLS) is a rare X-linked form of ID caused by mutations in plant homeodomain finger protein 6 (PHF6). Individuals with BFLS exhibit moderate-to-severe ID, characteristic craniofacial abnormalities, and seizure susceptibility. Although PHF6 has been implicated in brain development, the mechanisms through which PHF6 deficiency contributes to BFLS pathogenesis remain poorly understood. Using integrated chromatin immunoprecipitation sequencing (ChIP-seq), transcriptomic analyses, molecular and functional assays in embryonic and adult neural stem cells (NSCs), this thesis identifies transcription factor 4 (TCF4), a basic helix-loop-helix transcription factor essential for brain development, as a previously unrecognized downstream target of PHF6. PHF6 was found to directly occupy the Tcf4 regulatory region, promoting Tcf4 transcription. Consistent with this mechanism, TCF4 expression was significantly reduced in multiple BFLS mouse models. Functional studies demonstrated that Tcf4 knockdown phenocopies PHF6 deficiency by enhancing NSC self-renewal, increasing neurosphere formation, and elevating expression of the stem cell markers Nestin and Sox2. Importantly, restoration of TCF4 expression rescued the abnormal NSC phenotypes observed following PHF6 loss, demonstrating that TCF4 is a major functional mediator of PHF6 during neurogenesis. Furthermore, this regulatory relationship persisted in adult NSCs, indicating that PHF6-dependent regulation of TCF4 contributes to stem cell homeostasis beyond embryonic development. Together, these findings establish the PHF6-TCF4 signaling axis as a critical transcriptional pathway regulating NSC fate during corticogenesis and provide a mechanistic insight for how PHF6 mutations disrupt neurodevelopment in BFLS. Beyond identifying TCF4 as a key downstream effector of PHF6, this work expands our understanding of the transcriptional networks governing cortical development and provides a foundation for future studies investigating whether targeting the PHF6-TCF4 pathway may represent a therapeutic strategy for BFLS and other TCF4-associated neurodevelopmental disorders.
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    Leisure as Pathway to Well-Being and Belonging among Iranian Immigrant Women, 30-55 years of age, in Ottawa, Canada
    (Université d'Ottawa / University of Ottawa, 2026-09-28) Hadidi, Mahsa; O'Connor, Eileen
    This dissertation examines leisure as pathway for well-being, social connection, and belonging among Iranian newcomer immigrant women aged 30 to 55 in Ottawa, Canada. In doing so, this study addresses a gap in the literature and praxis on newcomers and settlement services by exploring how a group of Iranian newcomer women aged 30-55 understand and experience leisure during migration and settlement; what intersecting structural, gendered, and cultural factors constrain or enable their participation; the role a settlement service community-based organization plays in mediating leisure access; and how leisure contributes to their well-being, identity, and belonging. This manuscript-based dissertation produced three studies in collaboration with a local settlement service organization in Ottawa serving Farsi-speaking newcomers. The three distinct but interconnected studies utilized a mixed methods approach including surveys, facilitation of in-person leisure activities, post-activity evaluations, follow-up feedback sessions and participant observation. The first paper examined leisure preferences and structural access conditions among Farsi-speaking immigrant women (n=40) through a bilingual Farsi-English leisure interest survey. The second study co-designed and facilitated three community-based leisure activities: a group walk along the Rideau Canal; a Classical Persian dance workshop; and a visit to the National Gallery of Canada. Data was collected from post-activity evaluations (n=32), participant observation, and follow-up feedback sessions to explore participants' perceptions on leisure and well-being, social connection, and belonging. The third study examined how a settlement organization can play a role in mediating newcomer women's access to leisure. Grounded in an intersectional feminist theoretical framework and a community-based participatory research methodology, we demonstrate that leisure is not peripheral to immigrant settlement but a socially-embedded dimension of everyday life through which women negotiate identity, care, connection, and belonging. Concluding reflections emphasize the importance of participant-informed and community-supported approaches to inclusive leisure programming for newcomers.
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    Characterization of the Mechanisms Underlying Cell Surface ACE2 Receptor Modulation by Seasonal Human Coronavirus NL63
    (Université d'Ottawa / University of Ottawa, 2026-09-28) Silveira Falleiros Silva, Caroline; Langlois, Marc-André
    Seasonal human coronaviruses, including sHCoV-NL63, sHCoV-229E, sHCoV-OC43, and sHCoV-HKU1, belong to the Coronaviridae family. While typically causing mild respiratory infections, sHCoVs can trigger severe complications in vulnerable populations. Among them, sHCoV-NL63 uses the ACE2 receptor, the same entry receptor used by SARS-CoV-2. Previous work from our laboratory showed that sHCoV-NL63 upregulates the ACE2 receptor after infection, potentially increasing the risk of co-infection and of emerging recombinants. The mechanisms underlying this regulation of ACE2 expression remain unknown. This study investigated whether individual sHCoV-NL63 viral proteins modulate ACE2 surface expression. Expression vectors encoding individual sHCoV-NL63 proteins were transfected into HEK293T+ACE2 and LLC-MK2 permissive cell lines. These were used to analyze protein expression and ACE2 receptor levels by fluorescence microscopy, flow cytometry and western blot. While most viral proteins were successfully expressed, none significantly increased ACE2 surface expression, suggesting that ACE2 receptor regulation may depend on coordinated events associated with productive viral infection and/or the cell-intrinsic antiviral response. Further investigation of viral proteases, host cell signalling pathways, and interferon responses may help elucidate the mechanisms responsible for ACE2 receptor modulation.
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    Continued Declines and an Aged Salamander Breeding Population 16-Years After Installation of the First Amphibian Underpass System in a National Park in Canada
    (Université d'Ottawa / University of Ottawa, 2026-09-25) Crews, Christie; Lee-Yaw, Julie A.; Boyle, Sean P.
    Pond-breeding amphibians are highly vulnerable to the effects of roads, prompting the installation of road underpasses and exclusion fencing in many places. Although such systems are often successful at reducing amphibian road mortality, post-installation monitoring is rarely conducted for more than a few years. Consequently, the long-term use and impacts of such infrastructure on amphibian populations is unclear. The first amphibian road mitigation system in a National Park in Canada was installed in 2008 in Waterton Lakes National Park to protect long-toed salamanders (Ambystoma macrodactylum krausei) moving to and from Linnet Lake. However, despite this intervention, surveys of the system shortly after installation pointed to declines of the Linnet Lake population relative to baseline (pre-tunnel) census size. In this study, I used a pitfall trap array and visual surveys to reassess salamander use of this system and associated breeding site 16-years post-installation. Despite observing zero road mortality, I observed just 55 salamanders along the fence and tunnel system and in the terrestrial environment around the lake - a dramatic decrease relative to >500 individuals observed during the last survey and the thousands of individuals present pre-mitigation. Early spring surveys and quantification of migratory orientation around the lake rule out shifts in breeding phenology or changes in migratory routes as explanations for the observed decline in individuals observed. Instead, a high fraction of cross-survey recaptures (i.e. ~35% individuals >13 years old) and lack of successful recruitment (i.e. no young-of-year) suggest that this breeding population has continued to decline and is now at risk of being lost entirely. In addition to the road, salamanders at this site face threats from fish predators and climate and landscape change. My results thus suggest that mitigating road mortality alone may be insufficient for preventing the loss of associated amphibian breeding populations.