30921 research outputs found
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Switching On Emission in Zn(II) Coordination Complexes by Tempering Namido Character
No full textA series of four-coordinate zinc(II) complexes is presented in which the amido vs imino character of a ligated nitrogen donor correlates to the luminescence intensity. DFT analysis points to a distinct mechanism for this trend wherein emission can be switched on by restricting non-radiative decay pathways through the resonance-induced delocalization of amido ligand lone-pairs
Safety, security and well-being of trans students in Canadian public schools
No full textThis dissertation examines the safety, security, and well-being of trans students in Canadian schools, using data from the First and Second Canadian National School Climate Surveys. All students in Canada should have a safe and secure learning environment which supports their well-being. However, trans, nonbinary and/or gender nonconforming students ('trans students') are harassed and disrespected at school (Peter et al., 2021; Peter et al., 2017). Comparing trans students' experiences to cisgender peers is typically challenging due to limited sample sizes. This dissertation (informed by feminist theory, intersectionality theory, and queer theory) fills an important gap in the literature by comparing trans students' safety, security and well-being at school to their cisgender peers (using ANCOVA and logistic regression). Further analyses examine whether racialized trans students' experiences differ on the same outcomes, and whether these outcomes have significantly changed in the roughly ten years between the First and Second School Climate Surveys. Results showed trans students have significantly lower safety, security and well-being than many of their peer groups (though racialized trans students do not differ) and no significant differences within the ten years between the First and Second Surveys. Trans students face an unwelcoming and even threatening school environment, and the lack of improvement in the last ten years suggests current interventions are not effectively promoting change.Scholarship from Community Health Sciences (Research Manitoba)October 202
Changes in psychiatric admissions in the first year of COVID-19 in Ontario, Canada
No full textAbstract Background Several studies showed strong evidence that the COVID-19 pandemic disrupted mental health service use, with changes in emergency department visits, and psychiatric hospital admissions. It is not clear, however, whether the pandemic caused an increase or decrease in use of services for people with different diagnoses and symptoms. Methods We used data from all individuals admitted to psychiatric units in Ontario, Canada (259,620 individuals) from January 1st 2015 to December 31st, 2020 and compared the number of admissions, length of stay, symptoms, and clinical characteristics of this population in 2020 to the average of those who were admitted between 2015 and 2019. Results Total number of admissions declined sharply (44%) during the first lockdown period but returned to pre-pandemic levels within about 2 months. This trend, however, was not observed for all types of mental health problems. Admissions for symptoms such as risk of harm to others and addictions were consistently higher after the first wave in May 2020 compared to the same month in the previous 5 years, while symptoms such as social withdrawal, and depression were consistently lower. Conclusion Taken together, these results suggest that the impact of the pandemic on the use of mental health services were symptom-specific, which is likely a result of the heterogeneity of mental health problems within this population. This variation in the changes in psychiatry admissions for patients with different clinical profiles should be considered when preparing for future service interruptions
V/f controlled low frequency high voltage ac transmission for the grid integration of offshore wind
No full textLow frequency high voltage alternating current (LF-HVac) transmission has been proposed as a bulk power transfer alternative to either the conventional 50/60 Hz HVac or the high voltage direct current (HVdc) transmission schemes. In LF-HVac transmission, the proposition is to use ac operating frequency values that would be fractional quantities of the nominal 50/60 Hz frequency used in the conventional HVac. In comparison to HVac, LF-HVac would considerably increase the power transfer capacity of a given transmission link, extend the power transmission distance (without compensation), reduce losses, and improve the voltage and the dynamic stability of the power transmission system. Grid integration of remote offshore wind farms has been identified as the most viable application of the LF-HVac transmission scheme. Unlike HVdc, it would only require one converter station, which would be conveniently sited onshore.
Wind, unlike conventional electricity sources such as hydro or thermal, is an intermittent and non-dispatchable energy resource. Thus, it would be logical that any power transmission scheme applied to a remote offshore wind facility is practical for the expected variability of its output. This thesis proposes and investigates the feasibility and the merits of V/f controlled LF-HVac transmission scheme for offshore wind. In submarine export cables, it was determined that voltage is a more consequential quantity than frequency f in limiting the amount of useful power that could be delivered to the grid. With a defined V/f ratio, simultaneous adjustment of system V and f would allow for non-saturation operation of power transformers and reactors. The LF-HVac system would operate at the optimally selected V/f set for the rated output power. However, for most of the times, when the wind output is below the rated power, the system would operate at the energy-output-level applicable, lower, V/f set, thereby maximizing energy delivery to the grid for that wind output level.
Investigations into the electrical characteristics and performance of high voltage cross-linked polyethylene (XLPE) export cables, with respect to the ac operating frequency, underscore the advantages of adopting LF-HVac in lieu of the conventional HVac. The results show that at lower nominal operating frequency, a given cable system would support greater current/power capacity while losses, per energy transferred, are reduced. With the developed frequency-dependent steady-state LF-HVac transmission model, analysis of the voltage, current, and power flow in the export cable show that for an intermittent energy resource like wind, the optimum operating V/f pair would be variable, dependent on the prevailing wind conditions and thus, the energy output.
Finally, the feasibility and the technical requirements of applying modular multilevel converter (MMC) technology in the frequency conversion of the V/f controlled LF-HVac transmission scheme is investigated. The results support the adoption of MMC as the frequency converter. Nevertheless, it is important to appropriately determine the energy storage requirement, i.e., the minimum capacitor sizing, of the MMC at each operating point, and for the applicable V/f pair. Failure to do so could result in dc overvoltage. Results from the detailed time domain simulations of the V/f controlled LF-HVac transmission system for offshore wind in PSCAD/EMTDC provide validation to the thesis theory and the analytically derived results of the offshore wind system.October 202
Exploring the environmental factors controlling iceberg season severity along the east coast of Canada
No full textMass loss from Greenland’s marine-terminating glaciers occurs largely through solid discharge, that is, the calving of icebergs. Some of these icebergs reach the east coast of Canada and pose navigation hazards to offshore industries, especially during the peak iceberg season (February to August). Increasing marine activity heightens the need for accurate predictions of iceberg occurrence off the east Canadian coast. However, an abrupt increase in the iceberg count variability in recent decades has reduced the predictability of the season. Therefore, a thorough understanding of processes influencing the iceberg severity is essential to understand which process(es) dominate. Studies suggest multiple factors such as oceanic conditions along the Labrador region, upstream environment, as well as calving rates. However, the most significant governing factor is still a matter of debate. Moreover, scarcity of observational data outside the International Ice Patrol-monitored region obscures understanding of the roles played by potential upstream governing factors. Therefore, an improved model representation of the connections between the processes and iceberg severity is imperative. With this motivation, we evaluate NEMO-ICB (v3.6) outputs against observations and test the model’s sensitivity to atmospheric forcing and simulation period. Majority of the seasons with higher iceberg severity found to coincide with concentrated sea ice and colder Labrador shelf waters. The model outputs identified another driver affecting the iceberg counts in the shipping lanes which has not yet been considered in the literature: Baffin Bay gyre strength, which is interlinked to the sea surface height gradient. The energy of Baffin Bay circulation controls the transport of the icebergs out of Baffin Bay into the northern Labrador coast, and in turn the downstream iceberg severity. The temporal evolution of the correlations among the iceberg presence and environmental factors suggests that the importance of the major drivers of the iceberg season severity varies over time with the environment’s mean state. Despite potential biases from model simplifications, with the novel finding this study narrows down the environmental factors influencing iceberg occurrence along eastern Canada and improves understanding of the processes driving seasonal variability.University of Manitoba Graduate Fellowship
University of Manitoba International Graduate Student Entrance Scholarship
University of Manitoba Research Completion Award
University of Manitoba D. G. and V. E. Memorial Barber Fellowship in Arctic Research
University of Manitoba Baryla AwardOctober 202
A numerical investigation into the impact of Mi-cromechanics models on the stiffness parameters of cross-ply laminates
Get PDFLaminate plate and shell structures with symmetric cross-ply configurations are widely used due to their high stiffness-to-weight ratio. However, conventional lamination theo-ries rely on simplifying assumptions that may introduce inaccuracies, and experimental data is often limited and expensive to obtain. Therefore, having a reliable and accurate numerical model as a reference is valuable for evaluating and improving the analytical approach.
This study evaluates the predictive capability of lamination theories by integrating multiple micromechanics models with First-Order Shear Deformation Theory (FSDT), and comparing the results against voxel-based finite element modeling (VB-FEM), which serves as a high-fidelity numerical reference. A range of models—including Voigt–Reuss, Chamis, Halpin–Tsai and its modified form, Generalized Self-Consistent, Mori–Tanaka, Bridging, and two iterative isotropized formulations—are assessed for unidirectional laminae. The most accurate micromechanics models are then used in combination with FSDT to assess the stiffness predictions for cross-ply laminates. Pre-dictions are evaluated across a wide range of fiber volume fractions, from approximate-ly 10% to 70%.
Comparison reveals that while all models predict the longitudinal modulus accurate-ly, significant deviations arise in predicting transverse and shear properties. The Bridg-ing model consistently yields the closest agreement with VB-FEM across all five elastic constants, maintaining accuracy even at high volume fractions where the modified Hal-pin–Tsai model begins to fail. Discrepancies in micromechanics-based lamina properties propagate to laminate-level stiffness predictions, highlighting the critical role of model selection. These findings establish VB-FEM as a valuable tool for validating analytical models and guide improved modeling strategies for laminated composite design.February 202
Age-related changes and the one target advantage: multisensory insights into sequential motor control
No full textContext: Coordinating sequential movements requires precise motor planning and effective online control. The “one-target advantage” (OTA), where movements to a single target are executed more quickly than the first movement of a two-target sequence, provides a powerful framework to study these processes. Augmented sensory feedback, such as vibrotactile and auditory cues, can support movement timing, spatial consistency, and smooth transitions. While OTA is well documented in younger adults, there is limited knowledge on how individuals across adulthood incorporate such feedback, particularly in tasks of varying complexity.
Objective: This thesis explored how different forms of sensory feedback; vibrotactile, auditory, or absent, shape OTA-related performance in younger and older adults, examined across sequential aiming tasks that varied in complexity from single-arm movements to limb-switching and directional reversal conditions.
Methods: Right-handed participants performed one- and two-target tasks under No Feedback (NF), Auditory (A), and Vibrotactile (VT) conditions. Movement performance was evaluated through reaction time (RT), movement times (MT1, MT2), peak velocity (PV), time to peak velocity (TTPV), time after peak velocity (TAPV), and endpoint accuracy (constant and variable error) and Pause Time (PT).
Results: Across all tasks, VT feedback consistently supported faster initiation, enhanced movement speed in initial and subsequent segments, and improved spatial accuracy, particularly in multi-segment and higher-complexity conditions. Both younger and older adults demonstrated clear OTAs, with task complexity modulating the size of the advantage. VT feedback was especially effective in promoting smoother transitions between movement segments and refining endpoint precision. Auditory feedback provided selective temporal benefits but less consistent spatial improvements.
Conclusion: OTA is robust across adulthood and can be further optimized through tailored sensory feedback. In particular, vibrotactile feedback enhanced both planning and control processes, offering valuable applications for skill training, daily functional activities, and rehabilitation technologies. Overall, the findings advance out understanding of multisensory contributions to motor performance and highlight the potential of feedback-based approaches to support effective movement strategies across the adult lifespan.February 202
Linking redox homeostasis to gene expression and DNA methylation changes in neuroblastoma cells: role of thioredoxin system
No full textThe thioredoxin-1 (Trx1) system is an important cytoplasmic protein and is essential for maintaining neuronal redox homeostasis. Reduced Trx1 regulates the redox status of a wide range of proteins using two available electrons from its active sites. In this process, Trx1 is oxidized and must be reduced by thioredoxin reductase-1 (TrxR1) to be reused in redox reactions. Disruption of this system has been linked to neurodegenerative diseases pathology as shown by disruption of vital cellular processes including lysosomal autophagy and neuronal nuclear damage.
In the thesis, I aimed to examine whether inhibition of Trx1 system by genetic knockdown of TrxR1 in SH-SY5Y neuroblastoma cells can cause chromatin level changes in oxidative stress as induced by serum deprivation. RNA sequencing followed by gene ontology and Protein-protein interaction network analysis revealed that TrxR1KD led to significant gene expression changes. Downregulated genes were involved in synapse organization, synaptic signaling, and DNA methylation, while those upregulated after TrxR1KD were enriched for immune response and extracellular matrix organization pathways. Global DNA methylation status and expression of DNA methylation enzymes was further assessed. TrxR1KD cells exhibited reduced DNMT1 and DNMT3a expression and decreased global 5-methylcytosine, indicating possible epigenetic dysregulation. Notably, despite reduced DNMT levels, global DNA methylation was not significantly changed in TrxR1KD cells following oxidative stress. These findings demonstrate that Trx1 system is critical for preserving neuronal transcriptional and epigenetic integrity, and its deficiency may drive neuronal dysfunction through disrupted methylation and gene expression. Our results further implicate thioredoxin system dysfunction as a potential contributor to the molecular pathology of neurodegenerative diseases.February 202
Replication crisis: pre-post educational video assessing psychology students’ behaviors and attitudes
Get PDFIn the past decade, replication, crises surrounding replication, fraud, and data collection have dominated discussions in psychology. Open Science, a cooperative approach using digital technologies, addresses these issues. This study explored Honours (PSYC 4520) and First - Year (PSYC 1200) Undergraduate Psychology students’ Attitudes Toward Psychology, the Replication Crisis, and their Engagement in proper Open Science Practices. 168 students participated in a pre-test post-test educational video intervention assessing their attitudes and knowledge (post-test only). An 8-item questionnaire was given to Honours students (n = 13) at the end of the academic year related to the Open Science protocols they engaged in (e.g., pre-registration, power analysis, open-data sharing, etc.) for their honours thesis. A repeated-measures t-test examined changes in within-subject participants’ engagement and attitudes pre-to-post intervention, assessing how responses evolved over time. A mixed-design ANOVA was used to investigate the interaction effect between level of study (Honours vs. First-Year) and time points (before and after video) on Engagement in proper Open Science Practices. The intervention led to meaningful changes in students’ Attitudes toward Psychology and their Engagement in proper Open Science practices. However, no significant change was found in Attitudes toward the Replication Crisis. Replication Crisis Knowledge was similar across both academic levels, and students who demonstrated greater understanding of replication issues tended to report more willing Engagement in proper Open Science practices. This study has significant implications on the importance of properly practicing Open Science in one’s undergraduate degree and gaining proper experience for future study management.February 202
Computational and experimental modelling of the human upper airway acoustics with application to obstructive sleep apnea diagnosis during wakefulness
Get PDFObstructive Sleep Apnea (OSA) is a highly prevalent sleep-related breathing disorder characterized by repetitive upper airway collapse during sleep. Despite its clinical significance, current diagnostic techniques remain resource-intensive and often inaccessible. This thesis proposes two modelling approaches aimed at characterizing upper airway acoustics and investigates their potential application as non-invasive, quick and reliable OSA diagnosis during wakefulness.
The first approach involves a hybrid aero-acoustic simulation framework that decouples airflow dynamics and sound propagation. Using patient-specific airway geometries reconstructed from high-resolution CT scans, Large Eddy Simulation (LES) was employed to model unsteady inspiratory flow. Aero-acoustic sources were extracted using Lighthill’s analogy and mapped onto a finite element mesh to solve the wave equation for acoustic propagation. This enabled detailed analysis of how anatomical features—including velopharyngeal, oropharyngeal, and tracheal constrictions—alter airflow patterns, acoustic pressure distribution, and resonance frequencies at the trachea. The results demonstrated strong correlations between geometrical narrowing and frequency shifts in tracheal breathing sound spectra.
The second approach develops an empirical acoustic transfer function estimation between the mouth and the trachea during controlled wakefulness breathing. Participants were exposed to broadband and chirp input signals at the mouth, and tracheal responses were recorded to estimate the transfer function. A novel piezoelectric contact microphone was developed to record the sounds with minimal background interference. Statistical analysis revealed repeatable and individualized transfer functions, with significant spectral variations corresponding to anatomical differences and potential airway obstruction.
Together, these approaches provide a comprehensive understanding of the relationship between the upper airway anatomy, airflow mechanics, and the spectral content of breathing sounds. The findings support the feasibility of using tracheal acoustic responses during wakefulness for OSA diagnosis. In addition, they provide mechanistic insights into OSA pathophysiology by linking specific acoustic signatures to underlying anatomical abnormalities. This enables not only OSA classification, but also identification of the likely anatomical contributors to obstruction in each case. Such individualized insights advance the understanding of the disorder mechanism and pave the way for more targeted, personalized therapeutic strategies. Furthermore, the methodology establishes the groundwork for developing accessible, non-invasive, and personalized screening tools for sleep-disordered breathing.University of Manitoba (UMGF)
Research ManitobaFebruary 202