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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
The effects of self-compassion on responses to social stressors among individuals with social anxiety
(2025-05-20) Brais, Nicolas; Bailis, Dan (Psychology); Li, Johnson (Psychology); Alcolado, Gillian (Clinical Health Psychology); Kocovski, Nancy (Wilfrid Laurier University); Johnson, Edward
Self-compassion is a healthy way to interact with oneself in response to difficult situations. Interventions designed to increase self-compassion have focused on individuals writing self-compassionately about past negative events. It remains unclear if self-compassionate writing about anxiously anticipated events can help manage future-oriented distress. One population for whom this approach might prove beneficial are socially anxious people, for whom distress about the future is relevant. Study 1 explored whether describing anxiously anticipated events could elicit distress and whether self-compassionate writing was more effective than control writing in addressing such distress. Socially anxious participants were randomly assigned to write about an anticipated anxiety-provoking event (n = 236) or a neutral event (n = 50). The former group (n = 224) were then randomly assigned to write about that event again, in either a self-compassionate (n = 133) or neutral (n = 91) manner. Writing about the anxiety-provoking event proved effective at eliciting distress. Subsequent self-compassionate writing about the event increased state self-compassion, positive affect and determination to engage in the event. Study 2 evaluated whether writing about an anxiously anticipated task (i.e., the Trier Social Stress Test: TSST) in a self-compassionate manner would promote objective performance on the TSST and a subjective sense of success. Socially anxious university students (n = 85) completed the online study in three phases: 1) baseline self-report measures; 2) random assignment to self-compassionate writing (n =34), control writing (n = 26), or no writing (n = 25), then the TSST, and state self-report measures; and 3) one-month follow-up (e.g., social anxiety). Participants in the self-compassionate writing condition had higher confidence, eye contact, and state self-compassion compared to those in the control writing, but not the no writing condition. Exploratory analyses found that greater levels of fear of the upcoming task attenuated the effect of self-compassionate writing. Overall, results suggest that self-compassionate writing about a future anxiously anticipated event may be beneficial and that a fruitful direction for future research is to elucidate the utility of self-compassion for coping with anticipated difficulties.
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Open Access
Atomistic exploration of deformation mechanisms in metallic nanowires. ABC as a promising approach to overcome timescale limitations of molecular dynamics
(2025-05-12) Sun, Cheng; Liang, Xihui (Mechanical Engineering); Wang, Jay (Mechanical Engineering); Deng, Chuang
This thesis provides an atomistic exploration of deformation mechanisms in single-crystal metallic nanowires subjected to bending and shear stresses. A significant aspect of the work involves evaluating the ABC method as a promising computational approach to overcome the inherent timescale limitations of Molecular Dynamics (MD) simulations. Through comparative analyses, distinct deformation mechanisms such as dislocation nucleation and propagation, twinning, detwinning, twin-boundary migration, and five-fold twin (FFT) boundary formation were systematically identified. While MD simulations were constrained by short simulation timescales, ABC successfully captured slow, time-dependent plastic deformation phenomena such as gradual twin-boundary migrations and stacking fault formations. Additionally, both methods revealed the formation of FFT boundaries, occurring rapidly in MD and gradually in ABC simulations, highlighting ABC’s capability to mimic long-term deformation behaviors. This work emphasizes the directional dependence of deformation modes and underscores ABC’s potential to significantly extend computational capabilities. Ultimately, these findings provide critical insights into nanowire deformation mechanisms, laying the groundwork for future research focused on optimizing nanomaterial reliability and performance.
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Open Access
Herbivory resistance to generalist feeder Trichoplusia ni of faba bean (Vicia faba) exposed to salinity stress
(2025-03) Lavallée-Shrupka, Caleb; John Markham (Biological Sciences); Kevin Fraser (Biological Sciences); Renault, Sylvie; Avila-Sakar, German
Plants are often exposed to multiple stress factors simultaneously. Exposure to one stress can exacerbate or mitigate the response to a subsequent stress. While salinity and herbivory can impair growth and physiological function individually, their combined effects remain poorly understood. To investigate this interaction and determine if salt tolerance influences resistance to herbivory, Vicia faba (cv. Broad Windsor) plants were grown under salinity (0, 50, 75, 100 mM NaCl) and exposed to cabbage looper (Trichoplusia ni) herbivory. Gas exchange parameters (photosynthesis, stomatal conductance, transpiration) were not significantly affected by salinity after 11 days of treatment. After 20 days, salinity did not affect plant height, stem biomass or water content of most tissues but significantly reduced root and lateral leaf biomass. Total phenolic compounds and total soluble proteins in the leaves were also unchanged. Elemental analysis revealed that salinity significantly increased Na and Cl concentrations in all three tissue types (leaves, stems, and roots), with the highest accumulation in roots. Salinity significantly increased the concentrations of macronutrients (N, P, K, Ca, and Mg) and micronutrients (Fe, Mn, Cu, Zn, and Mo) in the leaves, suggesting efficient nutrient retention in photosynthetically active tissues. Constitutive resistance to herbivory was not significantly affected by salinity. However, induced resistance was significantly impaired in salt-treated plants. Together, these findings indicate that V. faba exhibits moderate tolerance to salinity, maintaining gas exchange and nutrient homeostasis under salt stress while minimizing growth impairments. The compromised induced resistance highlights the vulnerability of inducible defenses and suggests that salinity may force a tradeoff between preserving physiological function and sustaining inducible defences against herbivory. These results emphasize the importance of considering stress interactions when evaluating plant defence.
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Open Access
Numerical investigation of pore distribution patterns on the linear and nonlinear mechanical behavior of porous materials
(2025-05-20) Chakma, Prajjayini; Zhu, Guo-Zhen (Mechanical Engineering); Lin, Francis (Physics and Astronomy); Luo, Yunhua
Porous materials represent a class of materials widely used in various engineering and industrial applications due to their unique properties, such as lightweight and enhanced fluid permeability, which have drawn significant attention in recent years. The effective properties of porous materials are largely influenced by porosity, the spatial distribution of pores, and the interaction between the pores and the surrounding solid matrix. Existing methods, particularly micromechanics-based analytical formulas, exhibit fundamental limitations in handling high-porosity materials and extending the analysis beyond elastic region. In this thesis, the Microstructure-Free Finite Element Method (MF-FEM) is extended to characterize porous materials by modeling two different microstructures: regular and irregular, and analyzing their properties in both elastic and inelastic regimes. The MF-FEM results are compared with analytical approaches, using available experimental results as a baseline. The comparison demonstrates that MF-FEM predictions consistently exhibit strong agreement with experimental results, whereas the accuracy of micromechanics-based formulas remains conditional and highly dependent on their underlying assumptions. Beyond its reliability, MF-FEM also provides a cost-effective numerical approach for predicting and characterizing the mechanical properties of porous materials. Moreover, this study provides a comprehensive understanding of how different pore distributions, such as regular and irregular patterns, affect the overall mechanical properties in both linear and nonlinear regimes. These insights contribute to the efficient design of porous materials for various industrial applications, including automotive, aerospace, and biomedical engineering.
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Open Access
Acute effects of quinoline and 2-methylquinoline on electrical activity of great pond snail (Lymnaea stagnalis) neurons
(2025-04) Tramley, Cameron; Tomy, Gregg (Chemistry); Markham, John (Biological Sciences); Fry, Mark
Polycyclic aromatic compounds (PAC) are organic compounds found ubiquitously in the environment and originate naturally or anthropogenically. They are persistent, bioaccumulative, and toxic (PBT). PACs have been found to modulate voltage gated ion channels in fish cardiomyocytes. Many studies have examined PACs effects, however, there is growing concern about a less studied class of PACs: hetero-polycyclic aromatic compounds (HPACs). Quinoline and its derivative 2-methylquinoline are two-ringed HPACs found in high concentrations in sediment and tissues of fishes from the Great Lakes. Studies investigating synthetic quinoline derivatives used in the pharmaceutical industry have shown HPACs modulate voltage gated sodium, calcium and potassium ion channels in cardiomyocytes of fishes and mollusk neurons. We therefore designed a study investigating the acute neurobiological effects of quinoline and 2-methylquinoline on Great Pond Snail (Lymnaea stagnalis) neurons, a model with a large easily accessible central nervous system and well conserved ion channels. Electrophysiological characteristics were measured by performing suction electrode experiments on the right internal nerve of the right parietal Lymnaea stagnalis ganglion. Extracellular recordings before and after application of various quinoline or 2-methylquinoline concentrations were used to determine the frequency of right parietal nerve activity which we normalized as percent of control. The extracellular recordings revealed that quinoline affects right parietal nerve activity in a dose dependent manner. Quinoline caused a statistically significant effect on right parietal nerve activity at 1000 nM, but not 100 nM, and 10 nM, with mean percent of control values being 89.2 ± 4.3%, 103.9 ± 4.6% and 99.9 ± 3.5% respectively. 2-Methylquinoline had no statistically significant effect on right parietal nerve activity at 1000 nM. These experiments highlight the importance of understanding the neurobiological effect of PBT environmental contaminants quinoline and 2-methylquinoline, as well as demonstrate the utility of suction electrode recordings as an electrophysiology technique to evaluate acute neurotoxicity of environmental contaminants.
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Open Access
Evaluating Nitrogen Utilization Strategies in Chlamydomonas reinhardtii
(2025-04) Tibule, Miku; Doering, Jennifer (Biological Sciences); Markham, John (Biological Sciences); Lee, Jae-Hyeok
Nitrogen (N) is a common, yet essential macronutrient required for nucleic acid and amino acid synthesis for cell growth and biomass of photosynthetic eukaryotes which includes algae and plants. Understanding how organisms strategically use N for growth will allow development of economical use of N fertilizer being invested into croplands, which in return mitigates anthropogenic contribution to environmental pollution. This honours thesis explores N-use strategies by examining the N-sensing mechanisms within Chlamydomonas reinhardtii to investigate its necessity for optimal growth under N-limited and N-repleted conditions through comparative growth within individual N source provision of NH4Cl, KNO3, and urea. Using photobioreactor and nitrogen quantification experiments, I obtained biomass productivity data and residual N within the cultures, which allowed for an understanding of algal growth under various N-source concentration conditions. Through a comprehensive data analysis of growth biomass OD and residual N concentrations, my study uncovered that there is a regulatory mechanism of C. reinhardtii that allows for a reduction in N consumption rate under extreme N limitation stress, which in turn allows the algae to shift its metabolic priorities to internal N-use. These insights contribute to the existing literature by highlighting the significance of the N-sensing mechanism within C. reinhardtii, for N-use strategies, discovering a temporal switch in metabolic function, and offering potential further investigations into how the algae prioritize cellular N contents for growth and cellular division. Ultimately, this study provides a deeper understanding of N assimilation and cellular use, paving the way for future research and developments in the field.
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Open Access
Regulation of gene expression by growth differentiation factor 15 in the developing mouse and human neocortex
(2025-04) Mohamad, Ruby; Docker, Margaret (Biological Sciences); Lee, Jae-Hyeok (Biological Sciences); Xing, Lei
The evolution of the neocortex, specifically its expansion, is the key advancement that made higher cognitive abilities possible. Humans today have a neocortex that constitutes up to two-thirds of their overall brain mass. This expansion reflects increased and prolonged activity of neural progenitor cells (NPCs), which give birth to neurons during fetal cortical development. Growth differentiation factor 15 (GDF15) is a cell-extrinsic signal that has previously been found to promote basal progenitor proliferation, one of the main classes of NPCs critical to human brain development and evolution. Previously, the Xing Lab discovered several potential downstream targets that could be regulated by GDF15 in the fetal human neocortex, including Dachshund Family Transcription Factor 1 (DACH1), Glypican 6 (GPC6), Semaphorin 5A (SEMA5A), and Shroom Family Member 3 (SHROOM3). All of which have been reported to have various roles in neurodevelopment. In this study, we manipulated GDF15 levels in the developing mouse and human neocortex to understand its regulatory effect on the potential downstream targets. My range-finding experiment indicated a concentration-dependent increase in mRNA levels of the downstream targets, with the most increase observed in fetal human neocortical tissue incubated with 100ng/ml recombinant human GDF15 protein. Knockout of the GDF15 gene in embryonic mice revealed decreased mRNA levels of all the downstream targets. Furthermore, adult GDF15 knockout transgenic mice exhibited a decrease in interneuron and deep-layer neuron numbers. My findings are consistent with the notion that GDF15 regulates NPC proliferation through these downstream targets, contributing to long-term effects on neuron abundance in the adult brain.
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Open Access
Measuring the Active Learning Gains of Students In Undergraduate Biology Labs Using Peer Review
(2025-03) Bantel, Joseph; Joy Stacey (Biological Sciences); Tamara Kelly (York University); Debets, Cassandra
The peer-review process allows students to engage in the valuable exercise of critically thinking about how they generate and judge the validity of an idea. This is a cornerstone of the scientific community and a core component of biological sciences. Some students in undergraduate studies routinely underperform in the traditional educational experience and benefit greatly from active learning. In a first-year introductory biological science course at the University of Manitoba, I studied the population by using an online peer-review platform called Peerceptiv to study the standardized learning gains of different demographic groups of students to determine if any subgroups experienced a disproportional benefit in this learning exercise compared to any others. I hypothesized that peer-to-peer feedback on scientific graphing would raise the measurable graded assignment scores of URM students in undergraduate biological science, and therefore predicted that there would be no significant difference between URM and non-URM students' graded performance after peer-to-peer input. Students in certain groups did have higher learning gains over the course of the semester when averaged however, these results were not significantly different from the rest of the population. Overall, the reception of the exercise was very positive in student perceptions with 79% of respondents saying that it helped them understand the concepts they learned about. The strongest response was from students saying that getting reviews of their work was the most useful, with 87%. Ultimately, this study shows that students learn from the peer review process and have learning gains associated with it however, additional testing is necessary to definitively say which groups may or may not benefit the most from this activity.
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Open Access
Impacts of a flea beetle double-stranded RNA-based insecticide on the ground beetle Pterostichus melanarius
(2025-04) Lampimaki, Silas; Belmonte, Mark (Biological Sciences); Lee, Jae-Hyeok (Biological Sciences); Whyard, Steve
Flea beetles (Phyllotreta cruciferae and P. striolata) are the most damaging insect pests of canola, one of Canada’s most economically valuable crops. Chemical insecticides are currently the primary method of flea beetle control, but concerns about their impact on non-target organisms highlight the need for safer alternatives. RNA interference (RNAi) has been recognized for its ability to selectively kill insect pests by silencing target genes through sequence-specific exogenous double-stranded RNA (dsRNA). However, sequence similarity between pest and beneficial insects continue to pose risks about potential off-target effects. In this study, two dsRNAs targeting the UBE2L3 and Snf7 gene in P. cruciferae were evaluated for off-target effects in the predatory ground beetle Pterostichus melanarius. A bioinformatic analysis was used to identify the similarity between the dsRNA sequences and their respective orthologs in P. melanarius. Beetles were then injected with the dsRNAs, and relative gene expression and mortality were measured. Following injection of the UBE2L3 dsRNA, which shares 83.4% similarity and a 29 bp matching segment with P. melanarius, target gene expression was reduced by 69.9%. Conversely, injection of the Snf7 dsRNA, which only shares 62.6% similarity, did not induce gene knockdown. Despite the knockdown of UBE2L3, no significant mortality was observed in any treatment group, including the positive control, suggesting that an insufficient dose of dsRNA was used. These findings demonstrate that sequence similarity influences the off-target effects of dsRNA, which can be predicted using a bioinformatic assessment. Continued sequencing of beneficial insects is required so that dsRNA can be designed to have minimal similarity with other species to reduce off-target effects.
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Open Access
Investigating the impact of helminths on mercury in Arctic foxes
(2025-04) Whiteside, Kayla; Detwiler, Jillian (Biological Sciences); Davoren, Gail (Biological Sciences); Roth, Jim
Mercury (Hg) pollution in the Arctic poses a growing threat to the health of local wildlife, yet many factors behind Hg bioaccumulation remain poorly understood. Primarily ingested through diet, Hg bioaccumulates in animal tissues and can impair neurological and reproductive functions. Intestinal helminths have demonstrated the ability to take up Hg while residing in their hosts and have consequently been suggested to benefit their hosts through mitigating toxin exposure. In this study, I used Arctic foxes harvested over five years from Churchill, MB to analyze fox muscle total mercury concentrations ([THg]) (ng/g), intestinal helminth [THg], and helminth biomasses to determine if (i) helminth group (taxa and size) influences helminth Hg uptake, and (ii) helminths benefit their host by decreasing host Hg uptake. Results showed that [THg] did not significantly vary with fox sex, age, or harvest year. Cestodes demonstrated higher [THg] than nematodes, though size did not influence [THg] for either taxon. Both cestodes and nematodes demonstrated [THg] increases relative to host [THg], though only the cestodes had significantly higher [THg] than their hosts, and no significant effect was seen for either cestode or nematode biomass on fox [THg]. Overall, this study provides valuable insight into host-helminth-Hg dynamics. Further research is needed to elucidate the mechanisms and significance of helminth Hg uptake to help understand their potential applications in mitigating toxin exposure in wildlife.