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Improved prediction and physiological understanding of methylated sulfur cycling in the northeast subarctic Pacific and Southern Ocean
No full textThe methylated sulfur compounds dimethyl sulfide (DMS), dimethyl sulfoniopropionate (DMSP), and dimethyl sulfoxide (DMSO; colloquially referred to together as DMS/O/P) are essential components to the marine sulfur cycle. These compounds are ubiquitous in oceanic waters and have putative roles ranging from regulating cellular physiology to facilitating multi-trophic interactions and regulating regional climate. Despite over three decades of intense study, there remains significant uncertainty in the mechanisms and processes influencing DMS/O/P cycling and distributions. This PhD thesis focuses on applying novel machine learning techniques and isotopic shipboard experiments to better characterize DMS distributions and DMS/O/P cycling within the NE subarctic Pacific (NESAP) and Southern Oceans, two “hotspot” regions for DMS/O/P cycling globally. Chapters 2 and 3 applied ensembled random forest regression and artificial neural networks to build surface ocean DMS climatologies in the NESAP and Southern Oceans, representing smaller-scale (20-27 km) variability. Results from these chapters demonstrated significantly improved predictive accuracy over traditional empirical models, although later in situ work in Chapter 5 revealed limitations in these models. Nonetheless, this modelling work revealed several oceanographic factors, including irradiance, nutrient availability, and mixing, as key drivers of DMS variability in these regions, with temperature gradients and sea surface height anomalies controlling finer-scale DMS features. Chapters 4 and 5 further explored the mechanisms and processes underpinning the relationships between DMS/O/P cycling, mixing, irradiance and temperature. Ship-board irradiance manipulation and photosynthetic inhibition experiments in the NESAP revealed that DMSO reduction is upregulated in low-light acclimated phytoplankton assemblages exposed to surface level irradiance, and this pathway was linked to photosynthetically derived electrons. From these results, a novel electron scavenging hypothesis was proposed as a physiological function for DMSO in phytoplankton. In Chapter 5, DMS/O/P cycling was examined in response to a marine heatwave event in the NESAP, providing evidence for an indirect influence of temperature through floristic shifts towards high-DMS producing species, and notable coastal-oceanic transitions in sulfur metabolism. Collectively, the chapters in this thesis provide new insights into the application of novel statistical methods to characterize DMS distributions, as well as the mechanisms and processes underpinning DMS/O/P cycling within two globally significant ocean regions.Science, Faculty ofEarth, Ocean and Atmospheric Sciences, Department ofGraduat
Improving planetary health through healthcare foodservices transformation
No full textHealthcare systems have both an ethical responsibility and a mandate to decarbonize. Integrating plant-rich diets, such as the EAT-Lancet Planetary Health Diet, in healthcare settings could advance climate change mitigation, provide an opportunity to improve the food served to patients, and support a societal transition to healthier and more sustainable diets by changing social norms. Yet, their adoption in the healthcare sector have been limited. This PhD thesis therefore aims to explore how more plant-rich diets could be adapted in an acute inpatient setting, focusing on the experience at Vancouver General Hospital.
After providing context for this work, in Chapters 2 and 3, I endeavour to better characterise the current state of patient satisfaction, nutrition, food waste and environmental impacts with the existing menu by conducting a hospital-wide survey and a prospective cohort study of surgical inpatients. I find substandard levels of patient satisfaction, insufficient nutrition, rates of food waste as high as 59%, and a prevalence of animal-based proteins in meal offerings which account for the largest proportion of the menu’s greenhouse gas emissions and land use.
Then, I describe the development and implementation of a more sustainable menu developed by an interdisciplinary team, which comprises members from food services, clinical dietetics, sustainability teams, patient partners, and an Executive Chef. The novel menu features 18 new appealing dishes with plant-based or low-impact animal-based proteins, is more culturally diverse, nutritionally sound, better aligned with the Planetary Health Diet, and associated with considerable environmental benefits. This novel menu is then implemented across Vancouver General Hospital to assess patient acceptability with in-person patient surveys and waste audits. I find that the menu, served to the majority of patients, results in an increase of plant-based meals served from 8% to 25% of all dishes served at lunch and dinner. Patient acceptability scores are on average 84%, and food waste rates are lower across most protein types with the novel menu.
In conclusion, I find in this thesis that more plant-rich diets can be adapted to a healthcare setting in a way that meets patient preferences and nutritional requirements, while resulting in considerable environmental benefits.Science, Faculty ofResources, Environment and Sustainability (IRES), Institute forGraduat
Copper ionophores as inducers of immunogenic cell death : a mechanistic and therapeutic evaluation
No full textImmunotherapy, particularly immune checkpoint inhibition (ICI), has transformed cancer treatment and led to durable responses in subsets of patients. However, response rates remain low across many tumour types, and strategies to improve ICI efficacy are urgently needed. Metal-based chemotherapies, such as platinum (Pt)-containing agents like cisplatin and oxaliplatin, have long been used in oncology. Although oxaliplatin induces ICD, its systemic toxicity and inconsistent benefit in combination with ICI have limited its clinical applicability. Copper (Cu), unlike Pt, is a bioessential trace element required for mitochondrial respiration and redox regulation. These cellular processes are frequently upregulated in Cu-enriched tumour cells to support proliferation and metastasis. Historically, Cu chelation has been explored as a way to deprive tumour cells of this essential nutrient. More recently, an alternative strategy has emerged: delivering Cu therapeutically to induce a form of regulated cell death known as cuproptosis. This mechanism, and its potential to enhance anticancer immunity, remains underexplored in the context of immunotherapy.
This thesis presents a systematic investigation of Cu in anticancer immunity, focusing on both therapeutic delivery and the influence of baseline Cu levels in the tumour microenvironment (TME). A liposomal formulation of the Cu complex of diethyldithiocarbamate (Cu(DDC)₂) was developed and shown to activate adaptive immune responses in syngeneic mouse tumour models. A comparative screen of Cu-binding compounds revealed that the ability to transport Cu intracellularly (ionophore-like activity) was associated with ICD induction. Although both Cu(DDC)₂ and a Cu complexation of clioquinol (Cu(CQ)₂) activated ICD markers, they elicited distinct transcriptional responses, suggesting compound-specific effects on cell death and immune activation. To assess the influence of baseline Cu content, CT26 and MC38 tumour models were characterized as high- and low-Cu environments with distinct isotopic signatures. Treatment with Cu(DDC)₂ or Cu(CQ)₂ in combination with ICI led to markedly different outcomes. CT26 showed enhanced therapeutic response, particularly during acute treatment, whereas MC38 displayed an antagonistic interaction. These findings support the therapeutic potential of Cu-based agents in cancer immunotherapy and highlight the importance of Cu carrier chemistry and tumour-specific Cu biology in guiding clinical development of Cu-based adjuncts to ICI.Medicine, Faculty ofGraduat
Tracing the evolution of the Archean cratonic mantle using Lu-Hf isotopes
No full textThe formation, evolution, and long-term stability of the cratons are central to understanding how the first continents formed and how the Earth operated before the onset of modern plate tectonics. The cratonic mantle keel – the subcontinental lithospheric mantle – plays a critical role in stabilizing the continental lithosphere. However, the timing and nature of processes that shaped the SCLM remain poorly constrained due to the limited availability of geochronological tools applicable to peridotitic mantle rocks. This dissertation addresses this gap by refining and applying high-precision Lu-Hf geochronology to garnet-bearing mantle xenoliths, and by integrating Hf isotope data from tonalite-trondhjemite-granodiorite (TTG) rocks, the earliest products of continental crust formation. This work presents the first large-scale systematic application of low-dispersion internal Lu-Hf isochron dating to mantle xenoliths from the Slave, Kaapvaal, and Siberian cratons. The resulting ages spans over three billion years and demonstrate that preservation of ancient Lu-Hf ages depends on lithology, texture, and metasomatic history. A case study of a recrystallized orthopyroxenite-harzburgite xenolith reveals successive Archean metasomatic events recorded at the grain scale. Complementary TTG zircon data show globally consistent, mildly suprachondritic initial Hf isotope values, suggesting derivation from a long-lived, mildly depleted mantle reservoir. This convergence of mantle and crustal Hf signatures supports the existence of a chemically stable Archean mantle source. Beyond geodynamic implications, this dissertation introduces new methods for handling low-concentration samples and analyzing small-volume garnet separates, improving the feasibility of dating even the most refractory mantle materials. The results support a model of episodic SCLM modification, involving long-lived carbonatitic metasomatism followed by short-lived, localized hydrous overprints prior to kimberlite magmatism. These findings provide new constraints on the geodynamic processes that shaped early Earth and contribute to our broader understanding of mantle reservoirs and crust formation in the Archean.Science, Faculty ofEarth, Ocean and Atmospheric Sciences, Department ofGraduat
Comparative neurobiological investigations of sensory representation in diverse species
No full textThis dissertation applies a comparative neuroethological framework to investigate how diverse animals process behaviorally relevant sensory information in the central nervous system. Specifically, I focus on three case studies: somatosensation in birds, vision in frogs, and gustation in mosquitoes. In Chapter 2, in vivo extracellular recordings were used to map tactile responses in two avian forebrain regions, the nucleus basorostralis (Bas) and rostral Wulst (rWulst), of Anna’s hummingbirds and zebra finches. Both species exhibited modular, topographic representations, with cranial and post-cranial regions mapped separately in Bas and rWulst. Hummingbirds displayed lower mechanosensory thresholds and smaller receptive fields than finches, and both species showed heightened sensitivity in behaviorally important areas such as the beak and feet. Building on earlier research, these findings add comparative data from two discrete taxa, contributing to a broader understanding of avian somatosensory organization. Chapter 3 examined a deceptive visual signal, the pedal lure, in cannibalistic South American horned frogs. Behavioral experiments showed that the visual lure is triggered specifically by moving conspecifics, and kinematic analysis identified a dual-frequency hindlimb movement pattern mimicking insect prey. Electrophysiological recordings in the optic tectum showed representation of upper frontal visual field occupied much of the tectal surface, and many of these neurons responded to both prey and the lure. Behaviorally, pedal lure elicited rapid, accurate predatory strikes, supporting its role as an aggressive mimicry signal that co-opts an ancestral prey-detection circuit. In Chapter 4, the central projection patterns of gustatory receptor neurons expressing five distinct receptors (GR4, GR14, PPK301, IR25a, IR76b) were examined through 2D visualization and 3D registration in the subesophageal zone (SEZ) and ventral nerve cord (VNC) of Aedes aegypti. The projection patterns generally reflected receptor expression in peripheral taste organs. However, unlike Drosophila, the large overlap of projections in the SEZ among the five genotypes suggests reduced modality segregation in mosquitoes. Sexual dimorphism was also unexpectedly minimal, despite pronounced behavioral differences. These results warrant further research to better understand gustatory coding in insects. Overall, this study shows that a comparative approach can reveal both conserved coding strategies and specializations reflecting the unique sensory demands of each species.Science, Faculty ofZoology, Department ofGraduat
Dietary analysis of wild and hatchery juvenile Chinook salmon (Oncorhynchus tshawytscha) in the Fraser River estuary reveals differences in ontogenetic shifts
No full textThe Fraser River is the major producer of Pacific salmon (Oncorhynchus spp.) in Canada with millions of juveniles out-migrating through its estuary each year. Estuaries provide critical rearing habitat for juveniles, in particular Chinook salmon (O. tshawytscha), which can reside in estuaries for several weeks. The diet of juvenile Chinook salmon in this habitat is a crucial component of their early development and survival. In 2021 and 2022, I examined size, stomach contents, and stomach fullness of 142 juvenile Chinook salmon of wild and hatchery origin from eelgrass habitat at Roberts Bank (Fraser River estuary). I examined an additional 37 wild Chinook salmon from marsh and sandflat habitats. GSI analyses revealed 83% of all wild fish originated from lower Fraser River populations and PBT analyses revealed 91% of all hatchery fish originated from lower Fraser River populations. In eelgrass habitat, hatchery fish were on average 6.1 mm (~7%) longer than wild fish. Stomach fullness increased with fish size and was ~34% higher in wild fish compared to hatchery fish. Wild fish trended towards fuller stomachs in marsh habitat and emptier stomachs in sandflat habitat compared to those in eelgrass habitat. Stomach content analysis suggested size and time of year were indicators of juvenile Chinook’s transition to a primarily piscivorous diet, which was seen in wild fish with fork lengths as small as 63 mm. Liver and dorsal muscle samples from 130 wild and hatchery Chinook salmon captured in eelgrass habitat were analyzed for δ¹⁵N and δ¹³C revealing overlapping trophic ellipses. Wild fish had greater niche widths compared to hatchery fish and tended to consume higher-quality prey and utilized more diverse habitats compared to hatchery fish highlighting the importance of conserving eelgrass and marsh habitats and the prey they support. To improve foraging competency of hatchery fish in estuaries, naturalization of feeding systems in rearing facilities should be implemented.Forestry, Faculty ofGraduat
Dendrite inhibition strategy using hetero-epitaxy in thin film deposition mechanics
No full textDendrite formation is a long-standing problem for the commercial application of rechargeable metal anode batteries. The well-controlled coating on anodes can solve the problem of instability and uncontrolled reactions between electrodes and electrolytes. Understanding the effects of pre-stressed (residual stress) electrodes with an artificial solid-electrolyte inter-phase layer (thin film) on dendrite formation is crucial for the successful application of stable anodes. This thesis presents a combined experimental and computational investigation to elucidate the effect of coatings on the electro-chemo-mechanical performance of zinc (Zn) batteries through the incorporation of mechanical stresses and their effect on dendrite formation. To understand the underlying mechanism of how coating affects battery anodes, we used density functional theory-informed continuum modeling and phase-field modeling to unveil the impacts of residual stresses on surface evolution. First, the chemo-mechanical stability of alucone-coated Zn surfaces was examined using density functional theory, revealing strong chemisorption and the development of in-plane compressive surface stress. These stresses, arising from interfacial reconstruction, were found to be orientation-dependent and correlated with reduced surface stiffness, highlighting the mechanical impact of thin-film adhesion at the atomic level. Building on these insights, a continuum model was developed to quantify hetero-epitaxial residual stress due to lattice mismatch between the coating and the Zn substrate. Analytical predictions, supported by finite element simulations and wafer curvature experiments, confirmed the presence of substantial compressive stress (ranging from ~3–5 GPa for alumina to ~0.85–1.2 GPa for alucone). Finally, the effect of residual stress on dendrite growth was explored using in-situ optical microscopy and phase-field modeling. Experiments demonstrated that ultrathin-coated Zn anodes exhibit more uniform electrodeposition and suppressed dendritic features than bare anodes. Phase-field simulations containing stress effects revealed that compressive stresses lower the local electrochemical potential at dendrite tips, redirecting ion flux and smoothing the deposition front. Together, these results provide mechanistic evidence that residual stress, particularly hetero-epitaxial stress induced by nanometric coatings, can serve as a controllable design parameter to inhibit dendrites. The methodologies and findings in this work are broadly extendable to other metal anodes such as lithium and sodium, offering a generalizable framework for engineering stable interfaces in next-generation batteries.Applied Science, Faculty ofMechanical Engineering, Department ofGraduat
Iitsim’kaatsita : enhancing relations between Indigenous women and registered nurses : journeying toward transformative reconciliation to foster maternal health equity
No full textIitsimákaatsita: Enhancing Relations between Indigenous Women and Registered Nurses was a four-phase, Indigenous-led mixed-methods study that investigated how nursing contributes to and/or mitigates perinatal health inequities experienced by Blackfoot women in southern Alberta. Grounded in Siksikaitsitapi (Blackfoot ways of knowing), Indigenous Research Methodologies (IRM), and guided by Critical Indigenous Feminism (CIF) and Red Intersectionality (RI), this dissertation centers Indigenous women’s voices, knowledge systems, and sovereignty to disrupt colonial framings of health and care.
In Phase 1, a culturally specific survey tool was co-developed in partnership with a Blackfoot Advisory Circle to reflect community priorities, relational ethics, and Blackfoot understandings of health and wellbeing. The survey was used to capture Blackfoot women’s perinatal experiences and serve as a foundation for later phases. Phase 2 involved administering the survey with 107 Blackfoot women, whose responses revealed widespread experiences of racism, surveillance, and cultural exclusion in nursing care, alongside expressions of strength, resistance, and the women’s ongoing engagement with Blackfoot perinatal traditions. These findings challenge deficit-based narratives and offer a sovereignty-affirming framework for understanding Indigenous women’s health experiences. Phase 3 engaged 27 perinatal nurses across five focus groups to reflect on the survey findings and explore their roles in reinforcing or disrupting systemic harm. Nurses identified the limitations of cultural competency frameworks and described both institutional constraints and moments of relational care rooted in kinship (understood here not simply as familial ties, but as relational accountability and ethical responsibilities to others), advocacy, and anti-colonial intent. Across community and hospital settings, nurses enacted—and at times resisted—the systemic structures that shape care for Indigenous families. Phase 4 returned findings to Blackfoot communities through knowledge-sharing gatherings to support accountability, relational repair, and community-led action.
Overall, the study offers an Indigenous-led, community-engaged model for health research and nursing practice. It demonstrates how equity-oriented, culturally grounded care must be rooted in Indigenous sovereignty and relational responsibility. This dissertation contributes to nursing scholarship and Indigenous Peoples’ health by illuminating pathways to transform perinatal care in ways that uphold the voices, values, and well-being of Indigenous women.Applied Science, Faculty ofNursing, School ofGraduat
A linguistic attitudinal study towards Halkomelem and French among French learners of British Columbia
No full textCette thèse porte sur les attitudes linguistiques des apprenants de français envers deux langues minoritaires de la Colombie-Britannique : le halkomelem et le français. Bien que ces deux langues ne soient pas les seules langues minoritaires de la province, elles sont parmi les moins représentées dans l'espace public et elles voient émerger un nombre croissant de locuteurs. Le halkomelem est une langue autochtone et une langue menacée, parlée historiquement dans la région actuelle de la Colombie-Britannique, et le français est une langue coloniale et l'une des langues officielles du Canada. L’objectif principal de cette recherche est d’explorer les attitudes linguistiques des apprenants de français envers ces deux langues. Une meilleure compréhension des attitudes des apprenants du français envers ces langues est cruciale pour examiner les dynamiques du pouvoir linguistique entre ces deux langues minoritaires de Colombie-Britannique. À l’aide d’une approche mixte combinant des données quantitatives et qualitatives, cette étude explore les attitudes de 35 anciens élèves d'immersion française qui ont grandi dans la région de Métro Vancouver. Les participants ont complété un questionnaire en ligne. Les données quantitatives ont été analysées avec ChartExpo et les données qualitatives ont fait l’objet d’une analyse thématique. Les résultats révèlent que les participants associent le halkomelem avec une importance culturelle, le liant à la justice historique et au patrimoine autochtone. En revanche, les participants perçoivent le français comme une langue avantageuse sur les plans économique et professionnel.Arts, Faculty ofFrench, Hispanic, and Italian Studies, Department ofGraduat
Slicer based trajectory planning for 3D printing with novel kinematically redundant (6+3)-DOF parallel robots
No full textAdditive manufacturing (3D printing) has evolved from a prototyping tool into a mainstream production technology capable of creating complex, customized parts. However, printing freeform or overhanging geometries without support structures remains a major challenge. Support generation increases material use, post-processing effort, and limits the design freedom that defines the promise of 3D printing.
Conventional serial robots and gantry printers are constrained by cumulative joint errors, limited orientation range, and discontinuous trajectories. Parallel robotic systems offer greater stiffness and positional accuracy by distributing loads among multiple actuators, yet they suffer from restricted rotational workspace and complex singularity behaviour. Addressing these limitations is essential for enabling multi-axis, support-free manufacturing.
This research develops and integrates the hardware and software foundations for robotic 3D printing using two complementary platforms: a novel kinematically redundant (6+3)-DOF gantry-type robot developed for modeling and trajectory planning, and a kinematically redundant (6+3)-DOF Gosselin-style parallel robot used for simulation and framework validation. A unified framework was implemented that includes (i) inverse-kinematic and Jacobian-based formulations for both robots, (ii) a cubic-polynomial trajectory planner with a Jacobian-aware cost function to ensure smooth, feasible motion, and (iii) a Python-based slicer that converts digital models into joint-space trajectories.
Simulation studies verified the continuity, constraint satisfaction, and feasibility of the generated paths for both planar and non-planar geometries. Hardware implementation validated extrusion control and pilot printing using a DYZE system with PID-regulated thermal stability. While synchronized, multi-axis support-free printing remains future work, the integrated results confirm the functional readiness of the trajectory-planning and control framework.
The principal contribution of this thesis lies in demonstrating how redundancy-aware trajectory planning and custom slicing can bridge the gap between conventional 3D printing and fully support-free, non-planar fabrication. The developed models, software, and verified hardware platform provide a reproducible foundation for future studies in robotic additive manufacturing, trajectory optimization, and precision multi-axis material deposition.Applied Science, Faculty ofMechanical Engineering, Department ofGraduat