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Recent Submissions

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    Optimization of Cellulose Nanocrystal Stabilized Emulsions through Surface Modification and Oil Phase Interactions
    (University of Waterloo, 2026-08-31) De Silva, Mahima
    Cellulose nanocrystals (CNCs) have emerged as promising bio-based Pickering emulsion stabilizers owing to their renewability, high aspect ratio, and excellent colloidal stability. This thesis explores strategies in optimizing CNC-stabilized emulsions through surface modification of CNCs and elucidating their interactions with oil-phase amphiphilic molecules. Pristine anionic CNCs were modified by grafting quaternary ammonium groups and quaternary ammonium surfactants to produce cationic CNC (P-CNC) and surfactant CNC (S-CNC), respectively. These materials were evaluated as stabilizers for hexane-in-water emulsions in combination with dodecylamine (DDA) and lauric acid (LA). Pristine CNCs exhibited strong synergistic interactions with DDA, producing highly stable emulsions with decreasing droplet size and enhanced viscoelasticity with increasing CNC concentration. In contrast, pristine CNC–LA emulsions displayed antagonistic interactions, where increasing CNC concentration produced larger emulsion droplets with better resistance to creaming and enhanced viscoelasticity. Surface modification to produce P-CNC reversed these trends, demonstrating that particle surface charge governs interactions with oil-phase amphiphiles through electrostatic interactions. S-CNC possessed substantially higher interfacial activity than pristine or cationic CNCs. It yielded stable emulsions with the smallest droplets. However, these emulsions possessed comparatively weak rheological properties despite their small droplet size. Overall, these findings demonstrate that modifying CNC surface chemistry provides a versatile strategy for tailoring emulsion droplet size, rheology, and stability. This work also reveals previously unexplored interactions between aqueous-phase cellulose nanoparticles and oil-phase amphiphilic molecules, providing new insights into the rational design of sustainable emulsions with tunable interfacial and bulk properties for diverse applications.
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    Experimental Comparison of Ultrasound -Derived Deformation Measurements for Soft Tissue Impact Biomechanics
    (University of Waterloo, 2026-08-31) Puzio, Katarzyna
    Background: Fall-related hip fractures represent a critical public health concern, with falls causing 95% of hip fractures in older adults and resulting in 25% mortality within one year. The global incidence of hip fractures is projected to nearly double by 2050, with particularly significant increases anticipated in Canada's aging population. Trochanteric soft tissue thickness plays a crucial role in impact dynamics during lateral falls by absorbing up to 70% of impact energy. From an epidemiology perspective, increased thickness is associated with reduced hip fracture risk. However, current understanding of soft tissue deformation during high-speed impact events remains limited, hindering the development of more effective fracture prevention interventions. Objective: This thesis aims to design and assess a dynamic ultrasound imaging protocol for quantifying soft tissue deformation during controlled, high-speed mechanical loading. The primary objectives are: (1) to design a 2D ultrasound motion tracking system using a linear actuator as a controlled mechanical loading standard, (2) to assess how ultrasound system sampling frequency affects measurement accuracy during rapid tissue deformation and (3) to evaluate the performance of the 2D ultrasound motion tracking system in a biologically representative porcine tissue specimen, assessing its accuracy under conditions that more closely mimic in vivo tissue complexity. Methods: A custom linear actuator system was used to deliver controlled compressive loading to a tissue-mimicking gel phantom at 0.5 m/s (low-speed) and 1.0 m/s (high-speed), while tissue deformation was simultaneously recorded using a Verasonics Vantage NXT 64LE ultrasound system. High-frame-rate B-mode ultrasound sequences were acquired using a 6 MHz transducer and processed via beamforming before motion tracking analysis. An Optotrak motion capture system served as the reference standard and provided synchronized displacement measurements by receiving a trigger from the ultrasound system. Ultrasound-derived displacement measurements were obtained using image-based motion tracking in ProAnalyst and compared with motion capture-derived deformation profiles. The protocol was further assessed using a biologically representative porcine tissue specimen. The effect of sampling frequency on measurement accuracy was assessed through direct ultrasound acquisition at multiple native frame rates and retrospective downsampling of 4000 fps acquisitions to evaluate the influence of temporal resolution independent of acquisition method. Statistical Analysis: Agreement between ultrasound-derived and motion capture-derived deformation measurements was assessed using Pearson’s correlation coefficient (r), root mean square error (RMSE), and peak deformation error. The effects of sampling frequency and loading velocity were evaluated using two-way and mixed-design analyses of variance. Independent-samples t-tests were used to compare direct acquisition and downsampled acquisitions at matched sampling frequencies. Statistical significance was defined as α = 0.05 with 95% confidence intervals. Results: Ultrasound-derived displacement measurements demonstrated strong agreement with motion capture measurements during phantom gel validation, with Pearson correlation coefficients of r = 0.970 at 0.5 m/s and r = 0.874 at 1.0 m/s. Sampling frequency significantly affected peak deformation accuracy, with the greatest errors occurring at sampling frequencies of 100 fps and below, particularly during faster loading conditions. At 1.0 m/s, peak deformation error increased to −78.40 ± 7.86% at 30 fps and −41.29 ± 35.55% at 100 fps, whereas sampling frequencies of 1000 fps and above maintained substantially lower errors. Downsampling analysis demonstrated that peak deformation accuracy was preserved from 4000 to 1000 fps, with significant degradation occurring only at 100 fps and 30 fps, indicating a threshold effect rather than a progressive decline with decreasing sampling frequency. Direct acquisition and downsampled acquisitions produced comparable peak deformation measurements between 100 and 3000 fps, although differences were observed at 30 fps. Porcine tissue results demonstrated the feasibility of using B-mode ultrasound motion tracking to quantify deformation and characterize layer-specific tissue responses during dynamic loading. Conclusion: High-frame-rate B-mode ultrasound combined with image-based motion tracking provides a reliable approach for quantifying soft tissue deformation during controlled dynamic loading. Accurate peak deformation estimation was maintained at sampling frequencies of approximately 1000 fps and above, whereas lower sampling frequencies resulted in substantial errors, particularly during rapid deformation events. These findings highlight the importance of sufficient temporal resolution for dynamic ultrasound deformation measurements and demonstrate the potential of high-frame-rate ultrasound for investigating tissue-specific mechanical responses. Significance: This research addresses critical gaps in understanding soft tissue deformation during high-speed impact events relevant to hip fracture biomechanics. By assessing dynamic ultrasound imaging protocols under controlled conditions, this thesis establishes a foundation for future in vivo studies of soft tissue behavior during falls and inform the development of more optimized hip protector designs and improved finite element models that account for subject-specific soft tissue properties.
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    Continuity Through Replacement Spatial Strategies for Reform-Era Housing Redevelopment in Nanjing
    (University of Waterloo, 2026-08-31) Li, Shuyue
    The city of Nanjing, where the author grew up, provides an excellent example of how the transformation of residential areas impacts daily life in modern China. Having lived in both Nanjing and Toronto and observed the differences in the quality of their built environments, the availability of public spaces, and the ways in which residents interact with one another and their surroundings, the author began to consider how housing typologies in the historic core of Nanjing have changed over time and the challenges that many residential neighbourhoods face today. These comparative observations provide a broader perspective for evaluating future housing strategies in Nanjing. This understanding then informs a design proposal that operates from the urban scale to the building scale and, finally, to the individual dwelling unit, addressing the relationship between public and private space within the historic core of the city. The development of housing typologies in Nanjing can be traced from early courtyard settlements, through socialist-era worker housing and later reform-era housing, to the high-rise apartment complexes being built today. Reform-era housing forms an important part of Nanjing’s housing stock but is increasingly unable to meet contemporary needs because of ageing infrastructure, limited accessibility, insufficient communal space, and inflexible layouts, while continuing to accommodate a large number of urban residents. At the same time, the growing demand for vehicle parking has resulted in much of the limited ground-level open space being occupied by cars, reducing pedestrian circulation, landscaping, and opportunities for shared activities. Drawing on several existing precedents related to adaptable design, social continuity, parking integration, and incremental development, this thesis develops a new design methodology for future housing. This methodology informs the design of a mid-rise residential proposal based on the Open Building framework, which includes a permanent structural system and a collection of adaptable residences. The proposal consolidates vehicle parking and service functions at ground level while creating an elevated second ground plane for residential entrances, pedestrian circulation, landscaping, and shared amenities. The implementation strategy includes the phased redevelopment of the existing site, which is intended to reduce construction disruption and allow parts of the neighbourhood to remain in use during the transformation process. Through this phased redevelopment, the proposal seeks to improve housing quality while maintaining the existing residential capacity of the site and providing spatial conditions that may support long-term residential and social continuity within Nanjing’s historic core. Although the design is tested through the redevelopment of two residential buildings, the proposed relationship between ground-level parking, an elevated pedestrian landscape, and adaptable housing is intended as a prototype for similar reform-era residential sites throughout the wider historic urban area.
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    Understanding the Effects of Public Health Measures During COVID-19 on People Who Use Opioids and Service Providers Caring for Them Within Ontario, Canada
    (University of Waterloo, 2026-08-31) Adams, Linda Lee
    The aim of this research is to understand the impact of COVID 19 PHMs from the perspectives of PWUOs and service providers (SPs), while also examining the factors influencing policy decisions related to PHMs and their effects on PWUOs and SPs within a region of Ontario, Canada. Qualitative methodologies using interpretive descriptive approaches—specifically reflexive thematic analysis—to develop themes derived from semi structured interviews with PWUOs and SPs residing within a region of Ontario. An interpretive policy analysis was conducted using the 3I+E framework to elucidate factors influencing policy decisions related to PHMs and their effects on PWUOs and SPs during the first ten months of the pandemic. . Three overarching themes emerged: 1. PHMs worsened conditions for PWUOs residing within NSM; 2. Inequities resulting from the sentiment of the “greater good”; and 3. Failing to learn. Issues of stigma, increased vulnerability, and disparity—and the interplay of a syndemic response—became evident in the themes. Overall, this research may play an important role in informing and preventing similar responses—and resultant harm—for this population in future public health emergencies. There are implications for policy, practice and research evident through the research findings
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    Examining the Association Between Physical Activity and Sleep Duration in a Cohort of Adolescents in Canada: A Linked-Longitudinal Study
    (University of Waterloo, 2026-08-31) Nguyen, Nicole
    sleep duration physical activity adolescents longitudinal