MSpace

MSpace is the University of Manitoba’s Institutional Repository. The purpose of MSpace is to acquire, preserve and provide access to the scholarly works of University faculty and students within an open access environment.

 

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Open Access
Design and development of a multimodal nonlinear optical microscope for applications in biosciences
(2024-12-16) Montero Collado, Vladimir; Sherif, Sherif (Electrical and Computer Engineering); Lin, Francis (Physics and Astronomy); Major, Arkady
Nonlinear optical microscopy is an expanding field in the area of optical microscopy applied to biosciences. Methods such as Two-Photon Excited Fluorescence (2PEF or TPEF), Second Harmonic Generation (SHG), Third Harmonic Generation (THG), and Coherent Anti-Stokes Raman Scattering (CARS) constitute an improvement over classical (single-photon) fluorescence microscopy. With them, the need for the use of exogenous labelling agents disappears together with issues such as phototoxicity and photobleaching. These techniques can provide detailed structural images and chemical information from unstained samples. The laser wavelengths used in these methods penetrate deeper into the biological tissues and allow us to obtain images with sub-micron lateral and axial resolution. In the present work, a multimodal nonlinear optical microscope was designed and developed. In the instrument, the following nonlinear methods were implemented: 2PEF, SHG, THG with CARS being added in the near future. A compact, reliable, and cost-efficient Yb:KGW laser was used as a light source. The low energy (12 nJ) per pulse decreases the amount of damage to the surrounding sample areas. The ultrashort laser pulses provide us with a broad spectrum that makes it easier to find lines that coincide with the absorption spectra of different biological materials. The software for controlling the instrument was also developed in two versions (single-tile and multi-tile). The multi-tile version allows the scanning of larger sample areas by joining several tiles. Finally, conditions were created for future implementation of CARS using the Yb:KGW radiation to provide the Stokes beam and a Photonic Crystal Fiber to generate the pump beam.
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Open Access
Direct numerical simulation of turbulent flow and heat transfer within a wavy-channel
(2024-12-19) Opperman, Taylor C.; Tachie, Mark F. (Mechanical Engineering); Jian, Fuji (Biosystems Engineering); Wang, Bing-Chen
In this thesis, the effects of varying amplitude-to-period ratio (A/P=0.15, 0.2 and 0.4) on turbulent flow and heat transfer in a wavy-channel at a fixed nominal Reynolds number Reb,nom=5600 have been studied by means of direct numerical simulation (DNS). The results of these flows are further compared with those of a plane-channel flow at a similar Reynolds number. The impact of the wavy wall on the turbulent transport of momentum and thermal energy has been thoroughly investigated through the analyses of the first- through fourth-order statistical moments of the velocity and temperature fields, joint probability density function (JPDF) of the velocity and temperature fluctuations, budget balance of both the turbulence kinetic energy (TKE) and turbulence scalar energy (TSE) transport equations, swirling strength iso-surfaces, 2-D spatial two-point cross- and auto-correlation coefficients of the velocity and temperature fluctuations, and pre-multiplied energy spectra of the velocity fluctuations. A separation region is observed in the wave troughs, resulting in a mean flow recirculation bubble where the convective heat transfer is greatly impacted. It is also observed that the wavy wall induces a strong shear layer at the wave peak that envelope the recirculation bubble and further enhances the transport of turbulence kinetic and scalar energy between the high-momentum hot outer flow and low-momentum cold near-wall flow. Furthermore, it is interesting to observe that as the wave steepness increases, the characteristic length scales of turbulence structures become increasingly shortened in the streamwise direction while aligning more prominently in the vertical direction. Analysis of key performance parameters such as the Nusselt number and total drag coefficient reveal that the thermohydraulic efficiency decreases as the value of A/P increases.
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Open Access
Incidence of gasoline taxes in Canada: an event study approach to estimating pass-through
(2024-12-11) Vortia, Pooja; Shartaj, Mostafa (Agribusiness and Agricultural Economics); Mann, Janelle (Economics); Lawley, Chad
This study investigates the city-level pass-through rates of provincial and carbon tax changes on wholesale and retail gasoline prices in Canada from 1998 to 2024. Focusing on tax increases and decreases, the analysis measures pass-through rates to explore the impact of tax policies on gasoline prices across Canada. This study also analyses the tax incidence of medium/small cities and large cities separately to examine regional pass-through rates. Data is collected from Kent Marketing Ltd and Statistics Canada to create panel datasets for an event-based difference-in-difference model. Event plots show an immediate response in retail gasoline prices following tax changes; however, retail prices begin to adjust even before the implementation of tax policies. The estimated pass-through rate of gasoline tax increases on retail prices is 100% in the 9-week window and 88% in the 17-week window. For tax decreases, the pass-through rates are even higher, at 120% in the 9-week window and 140% in the 17-week window. The analysis also reveals the significant impact of tax changes on retail prices in medium/small cities and large cities. However, the study finds that the impact of gasoline tax changes on wholesale prices is statistically insignificant for both the 9-week and 17-week windows. Additionally, results from the 9-week window gasoline tax analysis without fixed effects and covariates are insignificant, underscoring the importance of accounting for these factors. In conclusion, the findings of this study emphasize the crucial role of provincial and carbon tax policies in shaping retail gasoline prices, while highlighting the limited impact on wholesale prices in Canada.
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Open Access
Linear and nonlinear characterization of particulate composites using microstructure-free finite element modeling
(2024-12-17) Oli, Sebak; Liang, Xihui (Mechanical Engineering); Zhu, Guo-zhen (Mechanical Engineering); Luo, Yunhua
Particulate reinforced composite materials, particularly metal-matrix based alloys, represent a group of materials widely used across various industrial and engineering sectors due to their unique advantages, such as isotropic properties and ease of manufacturing. The effective properties of particulate composites are primarily determined by the properties and volume fractions of the constituent phases. Effective properties refer to the macroscopic properties of composites resulting from the interaction of their phases. Characterizing these effective properties is a crucial step in designing high-performance particulate composites. However, existing methods face fundamental limitations, especially in the nonlinear characterization regime. In this thesis, the recently developed microstructure-free finite element modeling (MF-FEM) approach is extended to characterize the linear properties of three-phase particulate composites and the nonlinear properties of two-phase particulate composites. The main advantages of MF-FEM include: cost-effectiveness compared to experimental methods; greater reliability than analytical models; and circumventing the complexity of modeling intricate microstructures required in traditional finite element methods. MF-FEM predictions of effective properties closely align with experimental results, particularly in cases where phase materials exhibit significantly mismatched properties. This study demonstrates that MF-FEM is a reliable and cost-effective tool for designing particulate composites.
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Open Access
The agential torrent: an a/r/tographic exploration of face-to-face classroom encounters
(2024-12-18) Clark, Tony; Irwin, Rita (Curriculum and Pedagogy, University of British Columbia); De Oliveira Jayme, Bruno (Curriculum, Teaching and Learning); Black, Joanna
After two years (2019-2021) of frustrating online crisis teaching in response to COVID-19, I came to a new appreciation of what I had previously taken for granted in my classroom teaching experiences. Provoked by a tangible feeling of loss, this thesis investigates the abiding question of how to better understand and describe the experience of bodies participating in an educational setting. Using a/r/tography and self-study research methodologies, and by applying the onto-epistemology of agential realism and an embodied cognition framework, this paper and graphic novel examines the agential and embodied nature of face-to-face classroom interactions (both human and non-human). The paper attempts to describe the intensely interconnected, multifaceted, and overwhelmingly complicated relations (involving actants) continually forming and reforming - a torrent of agency. Three a/r/tographic renderings are employed in the graphic novel: (1) intra-actions between agential classroom bodies are comprised of waves; (2) the nature of these multi-layered and interweaving intra-actions is entangled; and (3) the ongoing and discursive nature of these intra-actions results in emergence. This resplendent maelstrom of classroom phenomena is contrasted with the diminutive and capitalistic neoliberal educational narrative. The research was provoked by the imposed juxtaposition of these two paradigms during the onset of COVID-19 and subsequent moves to sustain society and the education system through online crisis learning. The paper concludes with discussion questions as prompted in the graphic novel to further the reader’s collaborative study of face-to-face learning.
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Open Access
Correction: Role and promise of health policy and systems research in integrating rehabilitation into the health systems
(BMC, 2024-11-08) Ghafar, Abdul; Bachani, Abdulgafoor M.; Hyder, Adnan A.; Cieza, Alarcos; Bhangu, Aneel; Bussières, André; Sanchez-Ramirez, Diana C.; Gandhi, Dorcas B. C.; Verbunt, Jeanine; Rasanathan, Kumanan; Gustafsson, Louise; Côté, Pierre; Reebye, Rajiv; De la Cerna-Luna, Roger; Negrini, Stefano; Frontera, Walter R.; Kamalakannan, Sureshkumar
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Embargo
The modified pressure bulb theory considering boundary effect
(2024-12-10) Raji, Ahmed; Liang, Larry (Mechanical Engineering); Chen, Yuejian (Mechanical Engineering); Wu, Nan
This study investigates the behavior between Finite Element Analysis (FEA) results and the modified Westergaard equation, taking into consideration of the boundary effect on stress distribution around the loading area of a mechanical part with limited dimension. The Westergaard equation, a definitive problem-solving method in elasticity of pavement with ‘boundary at infinity approximation’, serves as the theoretical basis while a modified advancement is introduced to optimize parameters and address differences between theoretical assumptions and FEA results. The study emphatically included boundary effects in the analysis, acknowledging their effect on stress patterns. Parameters, such as stress measurement horizontal location (r) and stress measurement depth (Z), are systematically modified, and a new variable, load-to-boundary distance (LB), is introduced to achieve a more accurate alignment between FEA and the newly tuned Westergaard theoretical results. This finding noted the relevance of the original Westgaard model error as well as the boundary effect in tuning the original Westergaard equation, contributing to real-life engineering applications, especially on mechanical parts with limited dimensions. More specifically, the original Westergaard model is tuned by introducing polynomial constants (A and B factors) to correct its error in the application of mechanical parts with a single material. The boundary effects of mechanical structure with limited dimensions and its induced stress distribution error can be described by a Gaussian function with variable, LB.
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Open Access
Acute and chronic isotonic resistance exercise vs. eccentric quasi-isometric resistance exercise: Exploring sex-differences in physiological, biomechanical, and performance-based measures
(2024-12-18) Henderson, Zachariah; Cornish, Stephen (Applied Health Sciences); Gordon, Joseph (Nursing); Chilibeck, Philip (Kinesiology, University of Saskatchewan); Scribbans, Trisha; Glazebrook, Cheryl
Context: The combination of extended isometric and eccentric muscle actions (i.e., eccentric quasi-isometric resistance exercise (EQI-RE)) is postulated to have advantages over traditional isotonic resistance exercise (TRD-RE), and researchers and practitioners have suggested potential applications in both training and rehabilitation contexts. Studies investigating EQI-RE have yet to evaluate many purported benefits directly, such as greater time under tension, motor unit recruitment, muscle co-contraction/activation, improvements in strength and hypertrophy, and have not compared sex-differences. As females are generally more resistant to fatigue than males, and exercise volume during EQI-RE will be a function of fatiguability, females may exhibit differing neuromuscular responses to EQI-RE, while accruing more exercise volume, potentially leading to sex-differences in musculotendinous adaptations to EQI-RE. Objective: In trained and untrained males and females, the thesis investigated overall and/or sex-related differences in the acute fatigue response, as well as strength and hypertrophy adaptations to unilateral TRD-RE and EQI-RE of the elbow flexors. Methods: Using isokinetic dynamometry and surface electromyography (sEMG), study one examined sex-differences in the acute kinematic, kinetic, and muscle excitation response during successive unilateral EQI-RE elbow flexion sets. Using a unilateral dumbbell protocol, study two compared acute sex-differences in time under tension, muscle excitation, and co-activation between TRD-RE and EQI-RE. With this protocol, study three used b-mode ultrasonography and estimated 1-repetition maximum testing to evaluate elbow flexor hypertrophy and strength after 8-weeks of TRD-RE or EQI-RE, and between males and females. Results: Females were generally less fatigable than males for both TRD-RE and EQI-RE. Greater and faster muscle excitation was produced by TRD-RE, although there were no appreciable differences in agonist-antagonist co-activation. Females accrued more exercise volume from both TRD-RE and EQI-RE, but there were no sex-differences in muscle hypertrophy and strength. TRD-RE produced significantly greater relative increases in muscle hypertrophy and strength than EQI-RE. Conclusion: The thesis does not equivocally support the proposed benefits of EQI-RE. Females were less fatigable than males during EQI-RE and TRD-RE, but this did not lead to sex-differences in muscle hypertrophy or strength. Overall, TRD-RE was more effective for improving strength and hypertrophy, although EQI-RE still produced significant increases in untrained individuals.
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Open Access
Canadian Society of Allergy and Clinical Immunology position statement: panel testing for food allergies
(BMC, 2024-11-29) Al Ghamdi, Abdulrahman; Abrams, Elissa M.; Carr, Stuart; Hanna, Mariam A.; Herman, Sari M.; Lavine, Elana; Kim, Harold; Vander Leek, Timothy K.; Mack, Douglas P.
Abstract This position statement addresses the critical concerns and recommended practices surrounding the use of panel food testing for diagnosing food allergies. Food allergies are a significant public health concern, and the misdiagnosis of food allergies remains a prevalent concern, made worse by the ongoing use of panel food testing. The practice of screening patients for multiple food allergens, regardless of clinical relevance, is commonly referred to as “panel food testing.” Fundamentally, a panel food test is not simply a single test; a panel food test is a series of several distinct tests for multiple foods, each with its own variable predictive value. These tests have not been adequately validated as screening tests and carry a considerable false positive rate. The resulting false diagnoses lead to unnecessary dietary restrictions, increased healthcare costs, and significant psychosocial distress for patients and their families.
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Open Access
HIV phylogenetic clusters point to unmet hiv prevention, testing and treatment needs among men who have sex with men in kenya
(BMC, 2024-11-20) Cholette, Francois; Lazarus, Lisa; Macharia, Pascal; Walimbwa, Jeffrey; Kuria, Samuel; Bhattacharjee, Parinita; Musyoki, Helgar; Mugambi, Mary; Ongaro, Martin K.; Olango, Kennedy; Musimbi, Janet; Emmanuel, Faran; Isac, Shajy; Pickles, Michael; Becker, Marissa L.; Mishra, Sharmistha; McKinnon, Lyle R.; Blanchard, James; Ho, John; Henry, Omari; Fabia, Rissa; Sandstrom, Paul; Lorway, Robert; Shaw, Souradet Y
Abstract Background The HIV epidemic in Kenya remains a significant public health concern, particularly among gay, bisexual, and other men who have sex with men (GBMSM), who continue to bear a disproportionate burden of the epidemic. This study’s objective is to describe HIV phylogenetic clusters among different subgroups of Kenyan GBMSM, including those who use physical hotspots, virtual spaces, or a combination of both to find male sexual partners. Methods Dried blood spots (DBS) were collected from GBMSM in Kisumu, Mombasa, and Kiambu counties, Kenya, in 2019 (baseline) and 2020 (endline). HIV pol sequencing was attempted on all seropositive DBS. HIV phylogenetic clusters were inferred using a patristic distance cutoff of ≤ 0.02 nucleotide substitutions per site. We used descriptive statistics to analyze sociodemographic characteristics and risk behaviors stratified by clustering status. Results Of the 2,450 participants (baseline and endline), 453 (18.5%) were living with HIV. Only a small proportion of seropositive DBS specimens were successfully sequenced (n = 36/453; 7.9%), likely due to most study participants being virally suppressed (87.4%). Among these sequences, 13 (36.1%) formed eight distinct clusters comprised of seven dyads and one triad. The clusters mainly consisted of GBMSM seeking partners online (n = 10/13; 76.9%) and who tested less frequently than recommended by Kenyan guidelines (n = 11/13; 84.6%). Conclusions Our study identified HIV phylogenetic clusters among Kenyan GBMSM who predominantly seek sexual partners online and test infrequently. These findings highlight potential unmet HIV prevention, testing, and treatment needs within this population. Furthermore, these results underscore the importance of tailoring HIV programs to address the diverse needs of GBMSM in Kenya across different venues, including both physical hotspots and online platforms, to ensure comprehensive prevention and care strategies.