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Simulating a Stellar Binary Merger
No full textThe discovery of luminous red nova (LRN) V1309 Sco revealed a binary star system prior to its outburst in brightness, with an exponentially decaying orbital separation. This allowed, for the first time, theoretical models of contact stellar mergers to be verified by observations, although a direct comparison had not been made. In this thesis, we simulate the V1309 Sco light curve, thereby bridging the gap between theory and observation, and provide numerical tools that can be applied to other LRNe. I will first provide an overview of LRNe and their connection to stellar mergers, my method for simulating the mergers, and the fundamentals of the radiation physics that I applied to those simulations to obtain the light curves. Following this review, I will detail my process for simulating a V1309 Sco progenitor and show that ray tracing, a common method in SPH for reconstructing the radiation field, cannot give realistic brightness estimations where the simulated fluid transitions from optically thin to optically thick, such as near the surface of a star. I will address this limitation by implementing a new method called envelope fitting, which involves tabulating unique stellar profiles of known surface brightnesses and mapping the simulated mass elements to those profiles. Using envelope fitting, I will show that my simulated progenitor produces synthetic observations comparable to that of V1309 Sco prior to the outburst. Then, I will introduce a novel implementation of flux-limited radiative diffusion to my simulation method and evolve the progenitor dynamically beyond the merger. The resulting light curves will be compared to the V1309 Sco observations to reveal a match in the peak, plateau, and subsequent drop in luminosity. I explore the effects of various progenitor and simulation parameters on the light curves. Finally, I will summarize the main results of my work
The Social Psychology of Assessment
No full textAssessment is deeply embedded in educational practice. While it's typically described in teaching standards as neutral and objective, the real-life experience of assessments—like exams, essays, and presentations—demonstrates that they are emotional, social, and consequential thereby suggesting an important role for social psychology. Despite this, classroom assessment research has largely developed apart from the insights of social psychology. This disconnect is particularly unfortunate given how much social psychology, especially in the realm of theory-based interventions, can contribute to shaping assessments so they reliably support well-being. In this presentation, I will apply Self-Determination Theory to reimagine assessment through a social psychological lens, highlighting how assessments can be deliberately structured to support student well-being while still maintaining its integrity as a measure of learning
Correlation of Scoliotic Parameters from Ultrasound, Surface Topography, and Radiography in Adolescent Idiopathic Scoliosis
No full textAdolescent idiopathic scoliosis (AIS) is a three-dimensional (3D) deformity of the spine, characterized by lateral curvature, axial vertebral rotation, and thoracic hypokyphosis. AIS patients usually have radiographs taken regularly, leading to cumulative radiation exposure and an increased risk of cancer. Ultrasound (US) and surface topography (ST) are the two main radiation-free imaging methods which have been applied for AIS applications. However, no study has investigated if combining US and ST parameters can better estimate scoliotic parameters measured on radiographs. This thesis aimed to investigate the correlation of the four main radiographic parameters, including Cobb angle (CA), axial vertebral rotation (AVR), kyphotic angle (KA), and lordotic angle (LA), with the measurements from US and ST. The specific objectives were to investigate: (1) the accuracy and reliability of US measurements obtained with a newly developed wireless handheld 3D US system, (2) the accuracy and reliability of back surface measurements obtained with a low-cost handheld 3D surface scanner, (3) the correlations between radiographic, US, and ST parameters separately for right thoracic and left lumbar curves, (4) the accuracy of stepwise linear regression equations using the combination US and ST versus using only US to estimate the four main radiographic parameters.
The new 3D US system was first evaluated via a clinical study. The four main scoliotic parameters were measured on radiographs, on US images obtained with a previously validated US system, and with the new US system. When comparing the two US systems, all parameters showed good results, with intra- and inter-rater intra-class correlation coefficient (ICC[2,1]) values ≥ 0.87 and mean absolute differences (MADs) between 1.4° and 3.3°. When comparing the new 3D US system with radiography, CA, AVR, and KA also showed good results with ICC[2,1] values ≥ 0.86 and MADs between 2.3° and 5.0°. However, LA showed a large discrepancy between US images and radiographs with MAD of 14.7° and ICC[2,1] value of 0.30. The discrepancy increased when LA severity increased.
To obtain ST images, a low-cost handheld 3D surface scanner was used. A phantom study was first conducted. ST scans were repeated twice, and 8 distance measurements were performed and compared with measurements using a digital caliper. The mean absolute error (MAE) was 0.33 ± 0.33 mm when comparing the two ST scans, and it ranged from 0.45 mm to 0.49 mm when comparing with caliper measurements. The MAEs were under the threshold of 2 mm which was generally considered when measuring surface images. A pilot clinical study was then conducted in AIS participants, with 10 ST parameters measured, including trunk length (TL-ST), coronal balance (CB-ST), shoulder angle difference (SAD-ST), shoulder level angle (SLA-ST), scapular angle (ScA-ST), waist level angle (WLA-ST), waist asymmetry index (WAI-ST), back surface rotation (BSR-ST), kyphotic angle (KA-ST), and lordotic angle (LA-ST). All parameters showed excellent intra-rater reliability with ICC[2,1] values ≥ 0.95. Some ST parameters demonstrated moderate to good correlations with radiographic measurements (r-values from 0.49 to 0.77), including CB-ST, ScA-ST, SAD-ST, BSRl-ST, and KA-ST.
Finally, a clinical study was conducted to investigate the correlations between the 4 radiographic parameters (CA-XR, AVR-XR, KA-XR, and LA-XR) with US parameters (CA-US, AVR-US, KA-US, and LA-US) and ST parameters (CB-ST, SAD-ST, SAL-ST, ScA-ST, WLA-ST, WAI-ST, BSR-ST, KA-ST, and LA-ST). Multivariate stepwise linear regression was used separately for right thoracic and left lumbar curves. US parameters alone already showed a strong relationship with radiographic parameters, as reported in the literature. Only two ST parameters (ScA-ST and CB-ST) could complement US parameters (CA-US and AVR-US) to better estimate CA-XR and AVR-XR for right thoracic curves, improving MAD from 2.57° to 2.12° for CA-XR and from 3.20° to 1.72° for AVR-XR. ST could not complement US to estimate CA-XR and AVR-XR of left lumbar curves, KA-XR, and LA-XR.
In conclusion, the newly developed wireless handheld 3D US system was able to acquire accurate and reliable images for measuring CA, AVR, and KA. The low-cost handheld 3D surface scanner was also found to be accurate and reliable when measuring different ST parameters, some of which demonstrated moderate to good correlations with radiographic measurements. Combining ST and US would improve the accuracy in estimating CA-XR and AVR-XR of right thoracic curves while providing a comprehensive understanding of both internal and external deformities
The function of plant-plant interactions in community dynamics of a native grassland
No full textPlant-plant interactions are considered an important driver of community assembly and stability. Historically, the role of competition is emphasized, leading to the expectation that plants living together result in competitive exclusion and the dominance of a few species. This is thought to be reflected in patterns of plant traits, the biological and morphological attributes of plants. Functional traits result from and respond to environmental conditions to optimize plant performance and are thus closely tied to the concept of the niche and community assembly. However, plant-plant interactions are not always negative, and there are few direct tests of trait-competition and limiting similarity predictions. In this thesis, I examine the function of plant-plant interactions at multiple scales to better understand their consequences for community dynamics. First, I test the expectation that plants with similar traits should compete more strongly. I find competitive suppression increases when focal plants are dissimilar to their neighbours, indicating a misunderstanding of traits’ function in how individuals experience competition. Second, I ask if competitive ability is a species-level trait resulting in ‘competitive’ plants that cannot facilitate others. Instead, I find species engage in both facilitative and competitive interactions, challenging the idea that competitiveness is a stand-alone plant strategy. Additionally, species specialized at either end of the interaction gradient, suggesting they exhibit competitive or facilitative strategies. Finally, I ask how resource manipulations, community diversity, and plants’ social context (identities and interactions with neighbours) influence species turnover in a native grassland community. I find evidence that resource addition but not light removal influenced species loss, suggesting a decoupling of nutrient and light effects on species loss in this low-nutrient system. Further, plant social context functioned in species gains as communities forming more positive species co-occurrences were less invasible, suggesting evidence of relatively closed ‘modules’ of species exerting biotic resistance. Overall, the results of this thesis clarify when and how plant-plant interactions are functional and their role in community dynamics
Income Inequality and Contraceptive Non-use among Canadian Youths in Canada, 2015/16.
No full textBackgroundDespite recent efforts to improve access to contraceptive methods for those in need, the non-use of contraceptives among adolescents and youth is a major contributor to the high levels of unintended pregnancy and STIs among this vulnerable population. Income inequality has been reported to beassociated with sexual health behaviour and health outcomes in youth. Given that many countries are actively trying to mitigate the adverse health effects resulting from income inequality, little is known about the role of income inequality in contraceptive non-use. This study’s objectives are: 1) to investigate the relationship between income inequality and modern contraceptive non-use among sexually active youth aged 15 - 24 years in Canada in 2015/2016 and 2) to explore whether thisassociation varies across age groups, gender, household income groups, and immigration status.MethodsData from the 2015-2016 Canadian Community Health Survey (CCHS) respondents aged 15-24 who were sexually active were used. Income inequality was measured using the Gini coefficient from the 2016 Canadian census. Three primary outcomes were derived from self-report and included those who did not use modern contraceptives during their last sexual experience group as follows: non-use of non-prescribed (condoms), prescribed, and overall modern contraceptives. The CCHS and census data were linked using the unique Census Division (CD) identifier. Multilevel binary logistic regression models were applied to assess the association between income inequality and the non-use of modern contraceptive types.ResultsApproximately 39.4% of the 1,763,662 youth at risk reported they did not use non-prescribed modern contraceptives (condoms) during their most recent sexual experience, while 43.2% of youth did not use prescribed modern contraceptives. Overall, 10.3% of sexually active Canadian youth did not use any modern contraceptives during their last sexual experience. The mean Gini coefficient across the 276 census divisions was 0.36 (S.D = 0.03), ranging from 0.28 to 0.47. When fully adjusted for confounders, CD-income inequality was significantly associated with the non-use of prescribed modern contraceptives (OR= 1.37, 95% CI: 1.20, 1.57) but was not with the non-use ofoverall modern contraceptives (OR=1.00, 955 CI: 0.91, 1.10). Conversely, CD-income inequality was significantly associated with a lower likelihood of youth not using condoms (OR= 0.86, 95% CI: 0.78, 0.95). Only youths aged 20-24 had 10% increased odds of not using prescribed moderncontraceptives for every standard deviation increase in income inequality (OR=1.10, 95% CI: 1.02, 1.19). The proportional change in variance showed that about 73.8% of total variations in the odds of non-use contraceptives across the census division were explained by individual and census division-level factors in the model. Moreover, the intraclass correlation showed that about 5.0% of the total variation remained unexplained even after adjustment.ConclusionOverall, about 10% of sexually active Canadian youth at risk did not use contraceptives during recent sexual activities. Census division-level inequality was significantly directly and inversely associated with the non-use of prescribed and non-prescribed modern contraceptives respectively among sexually active Canadian youth. Heterogeneity in the non-use of prescribed modern contraceptives was observed among youth aged 20 – 24 years. Addressing income inequality using variousstrategies like Universal Basic Income and increasing minimum wages as well as targeting youth at risk, especially in high-income inequality areas might benefit the uptake of prescribed moderncontraceptives, especially among dependent youth aged 18 – 24 years. This may improve the uptake of the overall and most effective modern contraceptive methods, especially among this financially dependent population if combined with the implementation of free contraceptives and task-shiftingprograms/services like the prescription of contraceptives to other healthcare professionals in Canada
GrEx-Multi Inter Disciplinary Review
No full textSample Requests for Multi/Interdisciplinary Evaluation from select successful Insight Grants (IG) (2011-2022). The document also includes information on the Tri-Agency Interdisciplinary Peer Review Committee and their evaluation criteria and rating system
Utilization of non-thermal processing technologies to improve pea protein gelation and gelling mechanisms study
Get PDFAs global trends shift towards sustainable and health-conscious diets, pea protein has become a prominent alternative to traditional animal and soy proteins, valued for its high nutritional value, affordability, hypoallergenic properties, non-GMO status, and sustainable production. However, its application in food industry is limited by gelation challenges, as it requires high temperature to open the structure and lacks cysteine for disulfide bonds, resulting in weaker gels compared to soy protein. Despite exploring chemical and enzymatic solutions, concerns over residues and costs persist. Consequently, non-thermal technologies like atmospheric cold plasma (ACP) and high pressure processing (HPP) have attracted increasing interest due to their short exposure time, great energy efficiency, and minimized nutrient loss. This study explored the potential of ACP and HPP to enhance the gelling properties of pea protein and broaden its applications in selected foods.
The first section of the study demonstrated that while untreated pea protein isolate (PPI) (12 wt.%) did not form gel even after heating at 90℃ for 1 h, PPI after ACP did form self-standing gels at 70-90℃ for 30 min. The gels exhibited homogeneous, interconnected macropore network structures with compressive strengths of 0.53 kPa at 70°C, 2.70 kPa at 80°C, and 6.27 kPa at 90°C, with water holding capacities between 80-90%. This enhancement allows pea protein to function effectively as a gelling agent, aligning with an internal food cooking temperature of around 75℃.
However, ACP pretreatment lowered the pH through the generation of reactive species like nitrites pushing it toward the protein isoelectric point and risking functionality loss. This limitation prompted further research into combining ACP with pH-shifting to address this challenge. Specifically, PPI was treated with ACP at pH 12 for 10 min, followed by pH-shifting to neutral. The treated PPI suspension (14 wt.%) formed gels with significantly improved mechanical properties (compressive strength of 2.81 kPa) at 70°C within 10-20 min. The pH-shifting partially unfolded pea protein by altering the tertiary structure. Simultaneously, ACP generated active species such as nitrites and hydrogen peroxides that reacted with the amino acid chains, facilitating aggregate formation. During heating, these aggregates served as active building blocks, forming ordered three-dimensional gel networks via hydrophobic interactions and hydrogen bonding.
HPP is another emerging non-thermal technology used for microbial inactivation and protein modification with minimal effects on food sensory properties. This study systematically examined how variations in pressure level, treatment time, protein concentration, and sample pH impacted the microstructure and strength of PPI gels. Findings demonstrated that HPP could produce a wide range of gel textures, with compressive strengths varying from 0.11 to 130.18 kPa, enabling the simulation of jelly, pudding, and tofu textures at ambient temperatures, depending on processing conditions. Additionally, combining pH-shifting with HPP significantly enhanced freeze-thaw stability, achieving minimum syneresis of 15% after two cycles, demonstrating its suitability for frozen food products.
The gelation mechanisms of PPI with HPP, particularly when combined with polysaccharides, remain underexplored, prompting focused investigations in the final stages of research. Suspensions containing 15% PPI with 0.1-1% κ-carrageenan were subjected to HPP at 100-600 MPa for 5-30 min. The results showed that gels with 1% κ-carrageenan at 600 MPa demonstrated a 27-fold increase in compressive strength compared to PPI alone by HPP and over 5 times the strength of heat-induced counterparts. HPP facilitated protein tertiary structure unfolding, enabling phase separation and uniform distribution of the submicron κ-carrageenan particle in the protein matrix. This, along with a more compact protein network induced by HPP, enhanced gel strength, compensating for limited cysteine in pea protein for disulfide bonds. Conversely, heat-induced gelation caused more random protein aggregation, forming coarser and weaker gels.
Overall, both ACP and HPP effectively modified pea protein structure, significantly enhancing its gelling properties. ACP unfolded proteins and generated reactive species that promote protein aggregate formation, facilitating gel formation at lower temperatures. Similarly, HPP partially unfolded protein structures and exposed reactive sites, enabling improved protein interactions and crosslinking, which enhanced gelation. This study provides innovative and energy-efficient strategies using ACP and HPP to enhance pea protein gelation, essential for developing plant-based alternatives to traditional foods like eggs, cheese, and meat. This research also revealed the gelling mechanisms of pea protein treated by ACP and HPP, fostering further innovations in plant protein applications