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WAVE2 and Tpm3.1/3.2 : actin dynamics, B-cell biology, and targeting B-cell lymphomas
No full textActivation of the B cell requires dynamic remodeling of the actin cytoskeleton upon interaction with antigen-presenting cells. This enables cell spreading on antigen-bearing surfaces, immune synapse formation, and sustained B-cell receptor signaling. A central regulator of these events is the Arp2/3 complex, which drives the formation of branched actin networks in response to antigen stimulation. Of the nucleation-promoting factors that activate the Arp2/3 complex, the
roles of WASp and N-WASp in B cells have been well-studied, but the contribution of WAVE2
has not been investigated. My work showed that WAVE2 and the Arp2/3 complex colocalize at
the peripheral F-actin ring formed during B cell spreading. siRNA-mediated knockdown of
WAVE2 led to impaired and delayed B cell spreading, reduced actin retrograde flow, and disrupted formation of actomyosin arcs. These defects diminished BCR signaling at the immune
synapse and impaired B cell activation in response to antigen-presenting cells. In parallel, I
investigated the role of tropomyosin isoforms Tpm3.1 and Tpm3.2, which stabilize actin
filaments and regulate the recruitment of myosin. Tropomyosin function in B cells had not been
studied previously. Using ATM-3507, a selective small-molecule inhibitor of Tpm3.1/3.2, I
showed that disrupting Tpm3.1/3.2 function severely impaired BCR-induced actin remodeling,
cell spreading, and actomyosin arc assembly, consistent with its localization at the cell periphery
and actin arcs. Moreover, treating diffuse large B-cell lymphoma cells with ATM-3507 inhibited
their growth, induced G2/M arrest, and reduced CXCL12-induced chemotaxis and motility on
fibronectin. Collectively, these findings highlight WAVE2 and Tpm3.1/3.2 as key regulators of
B cell actin architecture and B cell function, while positioning Tpm3.1/3.2 as a promising
therapeutic target for B cell malignancies such as DLBCL.Science, Faculty ofMicrobiology and Immunology, Department ofGraduat
Minimal thermal treatment of cellulosic biomass to produce torrefied pellets
No full textThe production of solid biofuels from torrefied biomass holds significant potential for renewable energy applications. Pelletizing torrefied biomass offers advantages over its ground or loose form, though it often requires a binding agent to enhance pellet durability, thus increasing costs and energy use. This research aimed to produce durable pellets from torrefied loblolly pine (Pinus taeda) residues without using external binders or adjusting pelletization parameters, leveraging the benefits of torrefaction such as greater heating value and hydrophobicity. Experiments that involve various combinations of mild torrefaction temperature (230°C and 250°C) and shorter residence time (10, 15, and 30 minutes) across four particle size ranges (as-received, 1mm) were conducted to determine the effects of these factors on the physicochemical properties of the biomass. The torrefied materials were then subjected to pelletization, and the influence of torrefaction on the mechanical durability and fuel characteristics of pellets was examined. Thermogravimetric analysis of the pyrolysis and combustion behaviour of torrefied pellets indicated the improvement of fuel characteristics in terms of a higher comprehensive pyrolysis index and greater thermal stability with reduced risk of spontaneous combustion. The Response Surface Methodology (RSM) was employed for optimizing these factors to produce durable pellets from biomass, with an aim to minimize dry matter loss while maximizing the benefits of torrefaction. Results of RSM along with a predicted desirability of 0.674 indicated that the optimal treatment conditions are 250°C torrefaction temperature and 10 min residence time regardless of the particle size range. Under these conditions, the pellets can be produced with less mass loss at 14.5 wt% and pellet quality indicators which include single pellet durability of 63.4% that corresponds to tumbler durability of 87.1%, HHV (higher heating value) of 20.5 MJ/kg db, and EMC (equilibrium moisture content) of 12.5%. Overall, the study demonstrated that mild torrefaction temperature and shorter residence time preserved wood polymers, enhancing the physicochemical properties of the pellets, and enabling pellets to be produced with improved moisture resistance and fuel characteristics compared to untreated pellets. Besides, shorter torrefaction time would not only reduce energy consumption and operational costs but also minimize mass loss.Applied Science, Faculty ofChemical and Biological Engineering, Department ofGraduat
Upcycling plastic waste into electrode materials for energy storage applications
No full textThe accumulation of plastics in the environment poses a major threat to ecosystems, as discarded plastics release toxic chemicals or degrade into microplastics that enter food chains. Since 1950, over 6.3 billion tonnes of plastic waste have been produced, with about 80% ending up in landfills or the environment. Conventional waste management methods are ineffective for plastics with crosslinked structures and complex compositions, while incineration generates significant pollution. This research presents a sustainable route for upcycling non-recyclable plastic waste into electrode materials for energy storage applications. A plastic foam waste containing vulcanized rubber (60%), polyvinyl chloride (35%), and additives was selected due to its non-recyclable nature. The waste was pyrolyzed into carbon and chemically activated with potassium hydroxide at 500–800 °C to develop porous carbon materials (PWC). Increasing activation temperature enhanced porosity, producing larger pores, a more disordered graphitic structure, and higher charge transfer resistance.
The prepared PWC was employed to fabricate cathodes for two types of energy storage devices. First, PWC samples were used to confine selenium (Se) and prepare Se-based cathode composites for lithium-selenium (Li-Se) batteries. The sample activated at 600 °C (PWC600) delivered the best performance, achieving a stable reversible capacity of 655 mAh g⁻¹ at 0.1 C (97% of Se’s theoretical capacity) with excellent cycling stability over 150 cycles. Its superior performance was attributed to low charge transfer resistance and effective Se confinement, which mitigated side reactions. Next, PWC samples were used as active cathode materials in Zn-ion hybrid supercapacitors (ZHSCs). The sample activated at 800 °C (PWC800) exhibited the highest surface area (2300 m² g⁻¹) and the best electrochemical performance, achieving a capacitance of 248.5 F g⁻¹ at 0.5 A g⁻¹, an energy density of 97 Wh kg⁻¹, and a power density of 1600 W kg⁻¹.
Overall, this research demonstrates the potential of converting complex, non-recyclable plastic waste into valuable carbon materials for efficient energy storage systems. It highlights how activation parameters influence carbon morphology and performance, providing insights for the rational design of sustainable carbon-based electrodes.Applied Science, Faculty ofEngineering, School of (Okanagan)Graduat
Mapping vegetation structure and carbon dynamics across the Canadian forest-tundra ecotone using multi-scale remote sensing
No full textClimate change is impacting the stability and livelihoods of northern communities across Canada. Warming is accelerated at high-latitudes which has cascading effects on permafrost, hydrology, vegetation and carbon storage. The transitional area between the boreal and tundra biomes, known as the “forest-tundra ecotone”, is a large, dynamic region of climate-sensitive vegetation, including forests, tall-shrubs and tundra plant communities. Warming temperatures are expected to release reproductive limitations on trees facilitating northward advance of the boreal biome. However, there is significant variation in measurements of treeline advance across different locations, and the timing of advance relative to recent climatic changes are unclear. The primary objective of my dissertation is to use remote sensing datasets to investigate change in vegetation structure and its implications for carbon storage across the Canadian forest-tundra ecotone. To accomplish this, I used spaceborne light detection and ranging (Lidar) measurements and multi-spectral satellite imagery to model vegetation structure across 180 million hectares of northern Canada. These models were used to evaluate whether change in vegetation structure over the past 40-years is consistent with northward advance of the boreal biome. I found that forested area expanded northward by approximately 1 million hectares across Canada, but large parts of the limit were stable over time. Mean annual temperature and total precipitation also increased along the forest limit, indicating that the position of the forest-tundra boundary is out of equilibrium with recent climate warming. A central theme of this dissertation is assessing change across spatial and temporal scales. To this end, I also used high-resolution drone imagery to link fine-scale vegetation structure with measurements of soil organic carbon across northern tree and shrublines. At the regional scale, I paired historic air photos with contemporary satellite imagery to assess long-term patterns in tree and shrub expansion at multiple treeline sites. These patterns were linked back to national mapping products derived from multi-spectral time series to understand potential biases and evaluate strengths in both approaches. Ultimately, this dissertation provides new insights into climate driven impacts on northern vegetation across Canada, and demonstrates the use of novel remotely sensed data to support future research.Forestry, Faculty ofGraduat
Rheology aging and adhesion of aminated polyolefins
No full textAssociating polymers are macromolecules with reversible, non-covalent interaction sites such as hydrogen bonds or ionic interactions. These dynamic associations enable properties like self-healing, stimuli-responsiveness, and enhanced mechanical and adhesive performance. A novel synthetic route for amine-containing associating polymers was developed, among which poly(aryl amine-containing cyclooctene) (P(ACC)), also referred to as aminated polyethylene (APE), stood out for its exceptional adhesion performance on low surface energy substrates like PTFE. This thesis focused on understanding the effects of simple amine–amine associations on polymer dynamics, their aging as well as the adhesion performance of APEs and its applications.
The interplay between the reversible association and polymer chain dynamics in APE was mainly assessed through rheological characterization and the application of a modified tube-based reptation model for associating polymers. Complementary insights were provided by thermal analysis and analytical techniques such as FTIR and SAXS. Amine reversible associations were initially found to exert only a weak delay on the chain reptation process in freshly synthesized polymers. Over time, the polymers gradually transitioned from viscoelastic liquid to viscoelastic solid behavior, indicating an increasing influence of the amine associations. The transition could be viewed as a two-step process, first by an increasing number or strength of binary associations which lead to a stronger delay in the reptation process, followed secondly by the emergence of long lifetime sticker aggregations which resulted in a secondary plateau in the viscoelastic response.
The adhesion performance of freshly synthesized APE was characterized with T-peel tests, and the effect of molecular weights and peel rates on peel strength were studied. The peel strength was found to strongly correlated with the samples’ linear and non-linear viscoelastic properties, as characterized by a Universal extensional fixture. A predictive peel strength model was thus developed, and failure criteria were successfully obtained by fitting the model to the experimental results. Finally, APEs were explored as adhesion promoters for commercial polymer bases to enable adhesion on low surface energy substrates. The resulting blend system demonstrated not only high peel strength but also enhanced stability and improved creep resistance compared to pure APE.Applied Science, Faculty ofChemical and Biological Engineering, Department ofGraduat
Spline Gaussian Cluster-Weighted Models
No full textCluster-weighted models (CWMs) are a class of finite mixture models that jointly model the distribution of covariates and the conditional distribution of a response variable given those covariates. They are effective in uncovering latent subpopulations where both the marginal covariate structure and the regression relationship vary across clusters. However, standard Gaussian CWMs require specifying a parametric regression form within each cluster, limiting their ability to capture nonlinear relationships commonly observed in practice.
To address this limitation, we propose a spline-based extension of the Gaussian CWM that uses B-spline functions to model the within-cluster regression structure. A roughness penalty on the spline coefficients is introduced to control smoothness and prevent overfitting, and this penalization is incorporated into estimation through a fully unsupervised Expectation-Maximization (EM) algorithm. The EM procedure updates spline coefficients via weighted penalized least squares while estimating variance and mixing proportions. In addition, we introduce a mixed-type kernel spline Gaussian CWM that extends the framework to datasets with both continuous and categorical covariates. Although not empirically evaluated here, the model is fully formulated, and an EM-based estimation scheme is provided.
We evaluate the spline-based model using simulated and real datasets that capture a range of cluster-specific relationships with varying degrees of overlap and noise. The results indicate that polynomial Gaussian CWMs perform well when the regression structure is globally simple, such as in the Linear Crossover and the real NPreg dataset, where quadratic polynomials recover the generating form effectively. Spline Gaussian CWMs provide greater flexibility in settings with local nonlinearities, such as the Nonlinear Single and Double Crossover datasets, where they align better with the true group-wise regression functions. Penalized spline CWMs show the most stable performance, mitigating overfitting in challenging cases such as the Parallel and Half-Overlapping datasets, and offering improved classification accuracy relative to unpenalized splines. On fluctuating designs,spline-based approaches capture localized variation better than high-degree polynomials, which risk instability at boundaries.
Overall, this thesis develops nonparametric extensions of Gaussian CWMs by integrating spline regression, penalization, and kernel-based methods. These extensions broaden the applicability of CWMs to complex data structures and provide a foundation for future work on mixed-type and nonparametric mixture modelling.Science, Irving K. Barber Faculty of (Okanagan)Computer Science, Mathematics, Physics and Statistics, Department of (Okanagan)Graduat
Comparing the risk of severe infections associated with different classes of biologic or targeted synthetic agents for inflammatory arthritis
No full textThe full abstract for this thesis is available in the body of the thesis, and will be available when the embargo expires.Medicine, Faculty ofMedicine, Department ofGraduat
Forests, farms, and fairness : exploring equity in carbon accounting, forest carbon offsets, and community-level outcomes of land use policies
No full textThe land‑use sector must deliver large and rapid greenhouse‑gas reductions if the Paris Agreement is to be met. Yet the sector’s role and how to manage a just, sustainable transition within it remains controversial. This dissertation addresses three interconnected gaps: (i) how alternative carbon‑accounting conventions reshape national mitigation duties in the land‑use sector; (ii) the extent of the mitigation‑deterrence risk associated with forest‑carbon offsets and the additional regional costs that may follow; and (iii) how forest‑restoration policies impact rural communities. In Chapter 2, I examine the implications of shifting from production‑ to consumption‑based accounting in agriculture. By modeling two future scenarios across 27 regions, I demonstrate substantial shifts in national responsibilities for emission reductions depending on the chosen accounting framework. Under consumption‑based accounting, net‑importing, typically wealthier nations assume greater responsibility, highlighting important equity implications for international climate policy. Chapter 3 assesses forest‑carbon offsets, investigating their impact on energy‑transition strategies. Using an integrated assessment model, I show that offsets may reduce investments in direct emission reductions (mitigation deterrence) and quantify the additional costs that arise when mitigation deterrence intersects with exogenous failures of forest carbon sinks. I argue that, without robust safeguards and regulations, offsets can undermine genuine climate progress and exacerbate inequalities. Chapter 4 explores how forest‑restoration policies affect rural households in tropical forest areas, using empirical analysis and case studies. My research reveals that, even when restoration projects enhance local livelihoods, they can still pose socio‑economic risks, such as forced migration and the marginalization of certain community groups. Three cross‑cutting insights emerge: (i) accounting choices are normative decisions that materially affect equity; (ii) carbon markets must strictly constrain where, when, and for which emissions offsets may substitute, or they risk undermining climate ambition; and (iii) landscape‑scale climate policies succeed only when environmental goals align with local economic realities. This thesis provides new datasets and proposes analytical tools to help policymakers integrate equity and justice into land‑sector climate strategies, ensuring interventions are both effective and fair.Forestry, Faculty ofGraduat
The relationship between embodiment and social media usage among 8-9-year-old girls in gymnastics
No full textIn popular media and some scholarly domains, there is a moral panic surrounding girls and social media, where girls are assumed to be at risk of online predators or body-related disorders (e.g., poor body image, eating disorders). However, literature that explores how pre-adolescent girls engage with this type of social media content is lacking, despite there being evidence that they are using social media platforms. This study used a poststructural feminist lens to examine how girls (8-9 years old) who are gymnasts navigate social media in forming their embodied subjectivities. Theoretically, the study was grounded in feminist poststructuralism and the new sociology of childhood, wherein I aimed to understand the experiences of young girls when engaging with body-related social media content, through their voices directly. Because the feminine body is central to the sport of gymnastics, it is especially important to consider how the consumption of body-related discourses on social media intersect with those circulating within gymnastics in shaping the embodied subjectivities of young female gymnasts. To achieve these research aims, this study utilized an adapted photo elicitation methodology with eight-to-nine-year-old girls, with the hopes of empowering the voices of young participants within this topic of research.Education, Faculty ofKinesiology, School ofGraduat
Dynamics of microdroplets under oscillatory and quasi-static deformation
No full textSoft microparticles are deformable ("squishy") microscale entities that are ubiquitous in nature and technology. Unlike macroscopic particles, the force response of microparticles under external loading depends on both bulk material properties and interfacial tension, allowing force measurements to probe these properties. Traditional devices such as the biomembrane force probe, optical and magnetic tweezers, the atomic force microscope and the microcantilever tensiometer each have limitations in force range, accessible particle size, reliability of attachment, or commercial availability. Consequently, even simple microparticle subclasses such as Newtonian and viscoelastic microdroplets remain challenging to characterize accurately at the single-particle level.
The cantilevered capillary force apparatus (CCFA) overcomes these limitations by fixing soft microparticles via capillary rim pinning or gentle suction, imposing controlled quasi-static or oscillatory deformations and resolving the resulting forces with high accuracy. However, analytical frameworks for interpreting CCFA force signals and inferring material properties under these deformations have been lacking. To address this, we first perform a small-strain regular perturbation expansion of the Young–Laplace equation, the force response, and the bridge volume-conservation constraint to obtain the leading nonlinear force and shape of an initially spherical Newtonian microdroplet quasi-statically deformed while pinned between two coaxial substrates. Comparison with numerical solutions demonstrates excellent agreement and substantially extends the range of validity of earlier analytical models, enabling accurate interfacial tension measurements over a wider range of deformations.
Second, we develop an asymptotic model for the small-strain oscillatory deformation of an initially cylindrical Maxwell viscoelastic microdroplet pinned between two coaxial substrates. Regular perturbation in strain amplitude and aspect ratio gives a force response with a static capillary part and a dynamic part comprising in-phase contributions from bulk elasticity and interfacial curvature, and an out-of-phase contribution from bulk viscosity. In time-resolved CCFA measurements, the force offset yields the interfacial tension, while the amplitude and phase lag yield the storage and loss moduli. Together, these models provide a unified analytical framework for extracting interfacial and bulk material properties of single microdroplets using the CCFA, and they can be extended to more complex soft microparticles and related instruments.Applied Science, Faculty ofChemical and Biological Engineering, Department ofGraduat