Polymorphism and Mechanical Behavior in Hot-Pressed 3D-Printed Polyamide Composite: Effects of Pressure and Temperature

The aim of this work is to study the effect of high-temperature compaction (HTC) upon the polymorphism and the mechanical behavior of an additively manufactured (AM) carbon fiber-reinforced polyamide (PA6). Different pressure and temperature levels during HTC were tested to determine the overall effect on the mechanical behavior and material crystalline composition. Treated, carbon fiber-reinforced PA6 samples were analyzed using differential scanning calorimetry, X-ray diffraction, thermogravimetric analysis, scanning electron microscopy, and three-point bending testing. When considered with respect to as-printed samples, an HTC temperature of 190 ◦C combined with 80 psi pressure resulted in an increased flexural modulus and strength of 47% and 58%, respectively. This increase was attributed to the decrease in AM-induced cracking, voids (both inside and between the beads), and crystalline solid-state transition in the PA6. The effect of pressure and temperature on the crystalline structure was discussed in terms of an increased degree of crystallinity and the amount of α-phase. Therefore, HTC can help overcome some limitations of traditional annealing, which can result in recrystallization-induced cracking which can lead to material embrittlement. The proposed HTC method demonstrates the potential in improving the mechanical behavior of AM thermoplastic composites.Applied Science, Faculty ofNon UBCMaterials Engineering, Department ofReviewedFacultyResearche

Classifying riparian forests of the Okanagan Basin, British Columbia, Canada, through random forest modelling with LiDAR and spectral derived parameters

Riparian forests are integral components of landscapes due to their ecological significance and the services they provide to both terrestrial and aquatic ecosystems. These unique ecosystems act as buffers, regulating water quality, stabilizing streambanks, providing habitat for diverse flora and fauna, and influencing local microclimates. Accurate assessment and classification of riparian forests are essential for effective land management and conservation efforts, especially in regions like the Okanagan Basin, where water resources are particularly vulnerable to anthropogenic impacts and climate change. Recent advancements in remote sensing (RS) technologies, particularly the integration and availability of multispectral and LiDAR data, offer opportunities to predict and delineate riparian forest composition at larger scales and over potentially inaccessible terrain, enabling comprehensive assessments of these ecosystems' spatial distribution, structural attributes, and species composition. This study integrated fine-scale RGB RS imagery with LiDAR data to classify riparian forest tree species in select fish-bearing streams within the Okanagan River system, to develop a reproducible and cost-effective process for predicting ten native tree species classes and one infrastructure class. To inform the random forest (RF) classification model, a total of 23 explanatory covariates created from LiDAR and RGB data were incorporated. The model was trained using 1,611 observations, collected through in-situ field visits and supplemented by open-access tree inventory data, sourced from various reaches of the study area, encompassing diverse locations, elevations, and ecosystem types. The RF model achieved an overall accuracy of 96.03%, evaluated through a confusion matrix. In the 100 m buffers used to describe riparian environments of the study area, (129,802 ha), 85,679 ha (66% of the area) were classified into 11 classes. The spruce class was the most predicted class (54.16% of classified cells), followed by western redcedar (15.01%), and lodgepole pine (7.46%). Of the 23 explanatory covariates used, LiDAR-derived covariates were found to be more influential than RGB-derived covariates. This research provides valuable insights for land management strategies and conservation efforts, especially in regions like the Okanagan Basin, where water resources are particularly vulnerable to anthropogenic impacts and climate change.Science, Irving K. Barber Faculty of (Okanagan)Earth, Environmental and Geographic Sciences, Department of (Okanagan)Graduat

Quantum baroque. Muddy transcendence and baroque obsession

This research examines a perspective of Baroque in the 20th and 21st century. The thesis is that Baroque is more than an artistic style in the 17th century, or that it simply appears in moments of crisis. It can be understood that the appearance of Baroque as an irregular pearl covers its true manifestation, which is formed by a group of minerals known as amphiboles and, hence, its ambiguous structure. Making an analogy between Baroque and theoretical physics, it seeks to find the modus operandi of Baroque as a system of mechanisms that operate as morbid phenomena within culture, politics, art, religion and society. Baroque exists as a series of expanded fields that allow the control and manipulation of the social ethos, and through an analysis of it, an attempt is made to find emancipatory solutions that seek the liberation from a neocolonial, tecno-feudal, and imperialist apparatus in our global era.Graduate and Postdoctoral StudiesGraduat

Emulsion-Based Encapsulation of Fibrinogen with Calcium Carbonate for Hemorrhage Control

Hemorrhage, particularly non-compressible torso bleeding, remains the leading cause of preventable death in trauma. Self-propelling hemostats composed of thrombin-calcium carbonate (CaCO₃) particles and protonated tranexamic acid (TXA⁺) have been shown to reduce blood loss and mortality in severe bleeding animal models. To further enhance both hemostatic and self-propelling properties, this study was to investigate fibrinogen-CaCO₃ particles prepared via a water-oil-water (W/O/W) emulsion method. The particles were characterized using light and fluorescence microscopy, gel electrophoresis, rotational thromboelastometry (ROTEM), and video motion tracking. The method produced spherical micrometer-sized particles with various yields and fibrinogen content, depending on the preparation conditions. The highest yield was achieved with sodium carbonate (SC), followed by ammonium carbonate (AC) and sodium bicarbonate (SBC). AC and paraffin generated smaller particles compared to SC and heptane, which were used as the carbonate source and oil phase, respectively. Fibrinogen incorporation led to an increase in particle size, indicating a correlation between fibrinogen content and particle size. Fluorescence microscopy confirmed successful fibrinogen encapsulation, with various amounts and hemostatic effects as assessed by gel electrophoresis and ROTEM. Combining fibrinogen-CaCO₃ particles with TXA+ and thrombin-CaCO₃ particles showed synergistic hemostatic effects. All fibrinogen-encapsulated particles exhibited self-propulsion when mixed with TXA⁺ and exposed to water, regardless of fibrinogen content. This study advances current hemostatic particle technology by demonstrating enhanced self-propulsion and fibrinogen incorporation via the W/O/W emulsion method. Further optimization of the encapsulation method could enhance the effectiveness of fibrinogen-CaCO₃ particles for hemorrhage control.Medicine, Faculty ofNon UBCBiochemistry and Molecular Biology, Department ofReviewedFacultyResearche

Mixed Bioconvection Flow Around a Vertical Thin Needle with Variable Surface Fluxes

This study investigates mixed convection flow over a vertical thin needle with variable surface heat, mass, and microbial flux, incorporating the influence of gyrotactic microorganisms. The governing partial differential equations are transformed into ordinary differential equations using appropriate similarity transformations and then solved numerically by employing MATLAB’s Bvp4c solver. The primary focus lies in examining the influence of various dimensionless parameters, including the mixed convection parameter, power-law index, buoyancy parameters, bioconvection parameters, and needle size parameters, on the velocity, temperature, concentration, and microbe profiles. The results indicate that these parameters significantly affect the surface (wall) temperature, fluid concentration, and motile microbe concentration, as well as the corresponding velocity, temperature, concentration, and microorganism profiles. The findings provide insights into the intricate dynamics of mixed convection flow with bioconvection and have potential applications in diverse fields such as biomedicine and engineering.Applied Science, Faculty ofNon UBCMechanical Engineering, Department ofReviewedFacultyResearche

Transformations in teaching practices during the COVID-19 pandemic : faculty perspectives at Université Laval

De mars 2020 à mai 2023, le personnel enseignant des établissements d'enseignement supérieur canadiens a été confronté aux multiples défis posés par la pandémie de COVID-19, tout en étant tenu de maintenir la continuité des activités d'enseignement et d'apprentissage. Dans un contexte d'incertitude sans précédent, les personnes enseignantes ont été contraintes d'adapter leurs approches pédagogiques en réponse aux exigences sanitaires constamment évolutives, naviguant entre fermetures complètes, réouvertures partielles et reprises en présentiel. En conséquence, les pratiques d'enseignement, habituellement sujettes à des transformations qui se déroulent sur des cycles temporels plus longs, ont subi des adaptations rapides en réponse aux impératifs de la pandémie. Dans ce contexte, cette étude a cherché à déterminer dans quelle mesure l'ampleur et la durée de la crise sanitaire ont été suffisantes pour transformer des ajustements temporaires en modifications structurelles des pratiques d’enseignement. Cette recherche, centrée sur la perspective des membres du corps professoral et du personnel enseignant de l'Université Laval, pose la question principale suivante: quelles répercussions la pandémie de COVID-19 a-t-elle eues sur l'évolution des pratiques et des conceptions pédagogiques des personnes enseignantes? Sur la base des entretiens réalisés, cette étude révèle que la pandémie a induit une accélération hétérogène de l'adoption des technologies numériques et une réévaluation notable des croyances pédagogiques des personnes enseignantes. Elle a également favorisé l'élargissement du spectre des approches pédagogiques considérées comme acceptables et efficaces, tout en perturbant les dynamiques historiques de pouvoir qui entouraient traditionnellement le choix des modalités d'enseignement. Ces résultats soulignent l'impact potentiellement durable de la pandémie —dans un avenir encore incertain et variable— sur l'évolution des pratiques et conceptions pédagogiques en éducation supérieure.Education, Faculty ofEducational Studies (EDST), Department ofGraduat

Positive contributors to mental health and wellbeing among youth : findings from a qualitative study in British Columbia, Canada

The full abstract for this thesis is available in the body of the thesis, and will be available when the embargo expires.Medicine, Faculty ofPopulation and Public Health (SPPH), School ofGraduat

Advancements in seismotectonic analysis through relative moment tensor inversion

Large earthquakes often dominate attention due to their significant impact, but the majority of seismic activity consists of smaller and more frequent earthquakes. These smaller earthquakes, when properly analyzed, can produce enormous datasets and greatly enhance ourunderstanding of Earth’s dynamic processes. Through three research projects, this thesis focuses on developing and applying methods to analyze small earthquakes (M < 4) using the relative moment tensor inversion, addressing the challenges of small seismic sources. The first project examines two significant M7.1 intraslab earthquakes in southern Alaska: the 2016 Iniskin (24/01/2016) and the 2018 Anchorage (30/11/2018) earthquakes. The study provides insights into rupture processes and stress evolution by relocating aftershocks, recovering moment tensors, and inverting for stress variation. The aftershock distribution of the Iniskin event suggests a rupture along a steeply dipping fault in the Pacific Plate, with evidence of pre-existing fault reactivation (likely an outer-rise fault) and fluid migration. The Anchorage sequence reveals complex aftershock patterns, likely due to simultaneous rupture on both nodal planes. The second project tackles the challenges of determining moment tensors for small earthquakes recorded by sparse regional networks. Building upon previous work, a simultaneous multiple-event relative moment tensor inversion scheme is developed, leveraging constraints from P-wave polarities, relative P- and S-wave amplitudes, and local magnitude estimates without requiring prior knowledge of a reference moment tensor. This method is validated with synthetic examples and applied to a seismic cluster near San Juan Island, Washington, revealing insights into the local stress regime and fluid migration from the subducting Juan de Fuca Plate. The final project focuses on the Haida Gwaii incipient subduction zone in Canada. The study uses the novel relative moment tensor inversion technique to analyze earthquake groups in this sparsely instrumented area. Moment tensor results for events near the expected Queen Charlotte Fault and thrust zone display reverse mechanisms due to underthrusting of the Pacific Plate. Overall, this thesis advances the understanding of seismic source processes and stress distributions across different tectonic settings, offering valuable insights into fault mechanics, role of geologic structure, fluid presence and regional seismotectonics through innovative inversion methodologies.Science, Faculty ofEarth, Ocean and Atmospheric Sciences, Department ofGraduat

The role of breastmilk IgA in infant gut microbiota and immune development

The gut microbiota is highly dynamic in the first year of life and plays a pivotal role in immune development. Dysbiosis in the gut microbiota during this period has been linked to later development of numerous immune-mediated diseases, including allergies and asthma, but the specific host-microbe interactions that contribute to this phenomenon are still being uncovered. Secretory IgA (SIgA) is the most abundant antibody in the gut, and a key determinant of gut microbiota composition. During the first months of life, infants are not yet able to produce SIgA, receiving it instead through breastmilk. Breastmilk SIgA is known to protect infants against infections previously encountered by the mother. However, the effects of this antibody on infant gut microbiota composition, and thus immune development, have not been defined. This thesis investigates the role of breastmilk SIgA in guiding microbe-mediated immune imprinting in early life. Chapter 2 uses a mouse model of SIgA deficiency to show that maternal milk SIgA targets and limits the immunostimulatory microbe Segmented Filamentous Bacteria (SFB) in the neonatal murine gut, preventing premature activation of the intestinal Th17 cell responses and protecting against Th17-mediated asthma. Chapter 3 characterizes the human breastmilk SIgA repertoire in mothers enrolled in the CHILD Cohort Study, a longitudinal birth cohort in Canada, demonstrating a relationship between breastmilk SIgA-bacteria binding patterns and infant gut microbiota composition. This chapter identifies the bacterium Erysipelatoclostridium ramosum as an immunologically important target of breastmilk SIgA in the infant gut, and a potential human analogue to the well-studied and disease-relevant mouse pathobiont, SFB. Chapter 4 takes advantage of the techniques developed throughout Chapters 2 and 3 to elucidate the relationship between the maternal gut microbiota, breastmilk SIgA, and bacterial colonization dynamics in the offspring. This chapter confirms the ability of SIgA to mediate mother-to-offspring microbiota transfer. In summary, using in vivo models, human samples, longitudinal human health data, and cell culture, this work defines a significant role for breastmilk SIgA in guiding early-life gut microbiota and immune maturation, with important implications for future developments in preventative medicine and infant nutrition.Science, Faculty ofMicrobiology and Immunology, Department ofGraduat

Unsettling education in Stó:lō Téméxw : exploring the particularities of place in curriculum research

The role of place of in education is complex and multifaceted; place is both a topic of inquiry and a context for education. Yet many Western approaches to education continue to be structured around universal approaches to knowledge and skills development that neglect the role of place in education. The result is education operating under the illusion of placelessness, which obscures how Western society exerts power over people and land in the places of education. This dissertation responds to the problem of placelessness by examining the author’s location as an educator in Stó:lō Téméxw, the land of the Stó:lō people, commonly known as British Columbia’s Fraser Valley. This project draws on the curriculum research method of synoptic text, a form of inquiry that explores relevant historical and cultural knowledge on topics in society and education. Synoptic text research is used to explore the historical impacts of possessiveness and superiority in settler colonialism in this region, providing relevant examples from the author’s own practice. This research contributes to the field of place-based education by drawing on concepts from critical place-based and Indigenous land-based education to address the complexities of Indigenous and settler connection to the land. Connection to the land is surveyed within both Stó:lō and settler history. The wisdom of Stó:lō relationship and responsibility to the land is examined alongside the settler assumptions of possessiveness and superiority. By engaging the complicated conversations between Stó:lō and settler perspectives and practices, this curriculum research invites educators to refuse easy solutions to the complexity of decolonization in education. The curriculum research findings lead to discussion on practices of unlearning and relationality that contribute to decolonization in education. Research conversations with Stó:lō educators and leaders and experiments with curriculum examples are included to illustrate ways the relevant knowledge of Stó:lō Téméxw can inform educational practice. The iterative and contextual nature of these conversations and curriculum examples invite educators to consider the implications for unsettling education in their own places of education.Education, Faculty ofEducational Studies (EDST), Department ofGraduat