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Unified Stochastic SIR Model with Parameter Estimation and Application to the COVID-19 Pandemic
Get PDFThis thesis is comprised of three parts which collectively serve as a study of stochastic epidemiological
models, in particular, the susceptible, infected, recovered/removed (SIR) model.
I
We propose a unified stochastic SIR model driven by Lévy noise. The structural model allows for
time-dependency, nonlinearity, discontinuity, demography and environmental disturbances. We
present concise results on the existence and uniqueness of positive global solutions and investigate
the extinction and persistence of the novel model. Examples and simulations are provided to
illustrate the main results.
II
This part is twofold; we investigate the parameter estimation and forecasting of two forms of a
stochastic SIR model driven by small Lévy noises, and we provide theoretical results on parameter
estimation of time-dependent drift for Lévy noise-driven stochastic differential equations. A
novel algorithm is introduced for approximating the least-squares estimators, which lack attainable
closed-forms; moreover, the presented results ensure the consistency of these approximated
estimators.
III
We apply the previous results to study the COVID-19 pandemic using data from New York City,
New York. This application yields parameter estimation and predictive analysis, including the
unknown period for a periodic transmission function and importation/exportation of infection
The Benefits of Circus Arts Practice and Performance on Adolescent Wellbeing
Get PDFABSTRACT
The Benefits of Circus Arts Practice and Performance on Adolescent Wellbeing
Mélanie-Beby Robert
As the circus arts continue to evolve in Quebec rapidly, there is an increasing interest in exploring this domain, particularly regarding its influence on child development. This study aims to understand how circus arts performances affect the wellbeing of adolescents. In this qualitative research, ten adolescents taking classes at the École de Cirque de Verdun were observed with a view to better understand their wellbeing through circus practice and performance. The data collection methods include observations, curated journals, and interviews. The study's findings encompass the participants’ definitions of wellbeing, the importance of healthy relationships, and the significance of having strong role models in their lives during adolescence. The results offer insights into how their circus rehearsal influences their wellbeing. These findings highlight that artistic expression, physical abilities, and personal growth collectively contribute to the comprehensive development of young individuals during this crucial life phase.
Keywords: Circus education, adolescence, wellbeing, play, risk, socializing, circus performance, child development, Quebec circus
Curriculum-Based Dynamic Assessment of Narratives: Benefits for Bilingual Filipino Children
Get PDFIn 2021, people of Filipino origin arriving in Canada reached nearly one million, leading to rising numbers of Filipino children in Canadian schools (Statistics Canada, 2022). Filipino-speaking children who display challenges in learning the language of instruction may be referred for language assessment. However, standardized assessments are often not suited to children acquiring a second language, leading to inaccurate conclusions regarding their abilities. This set of studies examines the benefits of a novel curriculum-based dynamic assessment (CBDA) developed to assess the narrative abilities of children acquiring English as a second language.
Study 1 examined the accuracy of the CBDA in distinguishing typical language development (TD) from language difficulties (LD) for 34 bilingual Filipino children and compared the classification accuracy to the Test of Narrative Language – Second Edition (TNL-2; Gillam & Pearson, 2017). The results showed that the CDBA was an excellent predictor of language ability.
Study 2 examined narrative microstructure for children from Study 1 at pretest and posttest. Children in the TD group scored higher than the LD group on productivity measures at both pretest and posttest and on complexity measures at pretest. The TD group also improved on the productivity measures, while the LD group did not change on either the productivity or complexity measures.
Study 3 explored the modifiability ratings and performance on the TNL-2 of four kindergarten children with LD who participated in the first two studies, using a multiple case-study design. All four children showed difficulties answering wh-questions appropriately and warranted high examiner effort. They displayed differences in their learning preferences and potential and performed differently from one another on the TNL-2.
Study 4 explored Filipino-Canadian parents’ views on Filipino children’s narratives and on the usefulness of the CBDA through focus groups. They indicated that the story content was influenced by personal experiences common in the Filipino culture and described “good” stories as elaborated and structured in keeping with story grammar models. Lastly, parents appreciated the CBDA's focus on individual capabilities and its cultural sensitivity.
Together, the studies provide evidence that the CBDA of narratives is valuable for assessing Filipino- and English-speaking children and contributes to research on dynamic assessment for bilingual children
Determining Spatial Organisation and Localization of a Proposed Enterobactin Metabolon in Escherichia coli
No full textTo obtain scarce iron from their environment, bacteria synthesize and secrete high affinity siderophores that chelate ferric ions. Enterobactin is a catecholate siderophore produced by Escherichia coli. Synthesized in the cytoplasm by the concerted action of seven enzymes, EntCBDAEF and EntH, enterobactin is then transported to the periplasm by the inner-membrane protein EntS. We hypothesize that the Ent proteins assemble in a large multiprotein complex to enhance the metabolic flux of the intermediates and prevent their diffusion, and that this assembly localizes at the inner membrane where it interacts with EntS for secretion. The overarching goal of this thesis is to gather further structural evidence of interactions among the biosynthetic enzymes, to determine the manner in which the proposed assembly interacts with the transporter channel, and to initiate characterization of EntS. Herein we demonstrate an interaction between the first two enzymes of the pathway, EntC and EntB. Through in vivo crosslinking with formaldehyde, we captured intracellular complexes comprising both proteins. These results were supported by two-hybrid assays, whereas automated docking of the crystal structures of EntC and EntB resulted in a model where the active sites of EntC and EntB are oriented in apposition and connected by an electropositive surface potentially capable of channeling the negatively charged precursor of enterobactin, isochorismate. We then built on these research outcomes, which suggested that other Ent proteins could interact simultaneously and form complexes in which both EntC and EntB were detected. Using in vivo crosslinking with formaldehyde, we confirmed the presence of proteins EntA and EntE in these higher-order complexes. We also initiated work towards identification of EntS cytosolic interactors, where using an engineered ascorbate peroxidase enzyme fused in frame with EntS as the bait, proximity labeling assays revealed prey proteins localizing within 10 nm of EntS. Finally, we undertook extraction and isolation of EntS in a detergent micelle and in synthetic lipid nanodiscs. We identified two detergents and two copolymers that were efficient in extracting and solubilizing EntS, as well as the optimized conditions for successful extraction. The results obtained also suggest that EntS might assemble as a dimer
Transgressive Positivity in Four Online Multiplayer Games
Get PDFOnline games have a reputation for toxicity. Forms of play that have been theorized as transgressive from the perspective of idealized play have become highly normalized within the toxic space of online gaming. In this context, positivity in online gaming takes on a transgressive quality that challenges the common behaviours, the norms of communication, and their underlying ideologies found within online gaming communities. Through an ethnography of four massively multiplayer online game spaces - DOTA 2, Lost Ark, Destiny 2, and World of Warcraft - this project examines the effects of positivity in play on others who share these game worlds to consider ways that positivity might be leveraged to impact gaming’s toxic culture. Positivity is approached through different scales, from smaller individual actions like friendly greetings and helpful gestures not often seen in these particular games, to larger community formations that promote positivity and inclusivity within these gaming communities.
This study finds that positivity across these scales produces substantial and proportional resistance to positive deviations from the toxic norms within these games and their linked community sites. Players actively trying to resist toxicity through positivity add varying levels of labor to their leisure and are frequent targets for harassment, leading to burnout or self-exclusion from these online games. Transgressive positivity in online play can produce alternatives to self-exclusion from gaming by producing ephemeral connections and networks of support between players. Enclaves built on positivity can form, but they are always under threat when they intersect with the mainstream culture across each of these four games. Ultimately, there are severe systemic issues within these communities - reinforced by trends within the games industry and in online game design - that undercut player-led positivity initiatives. While positivity can be a useful strategy for some to connect with others and to persist in spite of these toxic environments, positivity’s transgressive quality in online play produces substantial vulnerability for those who actively pursue it as a strategy of resistance or cultural intervention
Bearing That in Mind: Canadian Teachers’ Experiences After Mental Health Literacy Training
Get PDFThe rise in the number of mental health disorders in children and young people is a growing concern worldwide. As young people spend much of their time in a school environment, educational institutions and teachers are more frequently being asked to support students struggling with these afflictions. Programs intended to increase teachers’ mental health literacy (MHL) have tried to equip them for this task. Previous research related to MHL has largely focused on quantitative means of assessing teachers’ MHL in the short-term, with little qualitative focus on their long-term teaching experiences, or on the retention and application of these skills in teachers’ day-to-day practice.
This thesis explores the lived experiences of seven Canadian teachers from a variety of teaching environments, and at various stages of their careers, who have taken MHL training. It investigates how their understanding of this MHL training has informed their teaching through semi-structured phone interviews that were recorded, transcribed, and analyzed using Interpretative Phenomenological Analysis (IPA). Four themes emerged from the research, including the need for 1) contextually relevant training, 2) role acceptance, 3) the feasibility of applying knowledge, and 4) self-efficacy.
The findings of this study are intended to improve future MHL programming, implementation, and ultimately early and improved mental health outcomes for students while also outlining directions for future research
Design and Development of LapBot: An Interactive Mobile Game for Mastering Safe Laparoscopic Cholecystectomy
Get PDFMajor bile duct injuries during laparoscopic cholecystectomy (LC) are a significant source of morbidity, mortality, disability, and healthcare costs. These injuries are primarily due to errors in surgical judgment and visual misperception of critical anatomy and tissue planes. To facilitate learning of safe LC we designed and developed LapBot Safe Chole, a novel mobile game integrating artificial intelligence (AI) feedback to enhance intraoperative decision-making during LC training.
LapBot Safe Chole offers an engaging learning experience through short video clips of LC scenarios. Users identify optimal dissection zones, with real-time AI-generated annotations delivering accuracy scores and immediate feedback. The game comprises five progressively challenging levels aligned with the Parkland grading scale. Progression to the next level necessitates over 50% accuracy across five consecutive responses.
Beta-testing (n = 22) results indicate improvement in game scores with each round, with attendings and senior trainees reaching top-scores earlier than junior residents per level. Our testing also showed that candidates can be distinguished by their learning curves and learning progression which can facilitate a competency-based curriculum. A statistically significant correlation (p=0.003) between user experience and score was observed. Furthermore, user feedback highlighted the game’s
ease of use (80% agreement) and its effectiveness in making learning enjoyable (100% agreement).
LapBot Safe Chole introduces and reinforces safe LC principles through an easily accessible and free gaming platform. Positive beta-testing outcomes suggest its potential adoption among surgical trainees. Future directions involve broader validation
An Effective Method for Milling Tool Condition Monitoring Using On-machine Measurement
Get PDFSmart machining technology is now under intensive research worldwide. As a kernel technique of smart machining, on-machine measurement (OMM) technology can automatically measure tool diameter and length with laser tool setters on machine so that the machine controller compensates for the tool wear while machining, which can improve part accuracy without manual tool measurement on tool pre-setters. However, there is a dilemma that the OMM technique cannot predict tool failure so that the operator can replace tools before it fails. To address this problem, this research proposes a new approach to predict failure of round-insert face mill in rough and finish machining to automatically change tools right before their failure. First, the geometric equation of flank wear land width of round-insert face mill is formulated; second, after a tool diameter is measured, the flank wear width is calculated. Third, an experimental method is proposed to determine the tool radius reduction threshold and the tool location of measurement, and then the tool failure can be predicted in rough machining. Then, a new method is established to determine the criteria of tool radius reduction in finish machining according to the machined surface roughness. Finally, several experiments are conducted to verify this approach, and it is applied to a practical example. This approach can be directly applied in industry, and it can advance the smart machining technology
Alzheimer Model on Chip: Mechanobiology Study of Microglia Cells
Get PDFAlzheimer's Disease (AD) is a leading cause of death in Canada, contributing to a significant number of annual fatalities. In 2021, it was estimated that more than 50 million Canadians had dementia, with the majority of cases attributed to AD. This condition also places a substantial burden on individuals, families, and the healthcare system. These statistics demand studying AD and developing effective and practical approaches for diagnosing, predicting, and treating the disease. Microglia cells, recognized as immune cells in the brain, have multifunctional roles and play a crucial part in brain health and AD. However, most research on microglia cells has focused on the impact of chemokines, cytokines, and cell-cell interactions. Conversely, our understanding of microglia migration and adhesion as mechanobiological properties is limited. Microfluidic chips have been increasingly used to characterize these mechanobiological properties due to their unique advantages, such as high controllability for fluid flow, portability, minimal reagent volume, and reproducibility. This dissertation focuses on developing an AD model on chip for the diagnosis and progression of AD through amyloid beta oligomers (AβO) as a biomarker using the mechanobiology study of microglia. Exploring these aspects could provide valuable insights for developing cell-based immune therapeutic strategies for AD.
Firstly, in the present thesis, a bi-functional microfluidic chip was developed to be capable of quantifying the adhesion and migration of microglial BV2 cells by combining two assays: cell adhesion assay and wound-healing migration assay. The chip could create the cell-free area (wounding) under either chemical stimuli with trypsin in chemical assays or mechanical stimuli with Phosphate-Buffered Saline (PBS) flow, as in the case of mechanical assays. As a wound-healing migration assay, this microfluidic device, with a simple microstructure and fabrication, can mimic any conditions between chemical and mechanical wound-healing migration assays using around 50 chips. During mechanical wounding, the cell removal was characterized to quantify the cell adhesion under various shear stresses of PBS flow at inlet Reynold number (Re)= 25, 50, and 100. It allowed the investigation of microglia adhesion dynamics during the wounding process and the effect of mechanical stress on cell migration. In chemical wound generation, laminar trypsin flowed within the device using gravity without any peripheral equipment (such as an external pump and microfluidic tubing), making the cell migration quantification cost-effective compared to previous approaches. The wounding study with our microfluidic chip has shown that cell migration in cell-free generated chemically with trypsin highly improved compared to mechanical cell-free creations with PBS flow and the scratch assay. The effect of shear stress variations and geometry on chemical and mechanical wounding performance is predicted in detail in this thesis.
Microglia cells, as highly active cells, always migrate in the brain and encounter various extracellular matrixes (ECMs), including various substrate elasticities (stiffness) of central nervous system (CNS) tissue in both healthy and diseased conditions of the brain. However, conventional migration assays, such as scratch assays, quantify cell migration, which removes ECMs from the substrate. Therefore, this dissertation also focuses on developing microfluidic migration assays to assess microglia BV2 without removing ECM coatings. This migration assay could generate a cell-free area by creating a laminar trypsin flow over the confluent cell monolayer. The trypsin was flown by gravity without using the syringe pump and microfluidic tubing, which makes cell migration assessment affordable and feasible in the wound-healing method compared to previous methods. Microglia BV2 migration was studied using 40 chips on the substrate coated with different ECMs, such as collagen, fibronectin, Poly-L-Lysine (PLL), and gelatin, and also on the substrate with various physical properties, including polystyrene, Polydimethylsiloxane (PDMS), and glass. It was found that PLL and gelatin had a stimulatory-migration effect compared to fibronectin, collagen, and the control condition (glass). Our findings demonstrated that among polystyrene, PDMS, and glass substrates with different physical properties, microglia BV2 cell migration improved on the petri dish coated with plasma compared to PDMS and glass. There was a migration enhancement on the substrate with lower elasticity when their migration on the PDMS was higher than glass.
In AD, Amyloid beta (Aβ) monomers are overproduced and accumulated in the brain, which can cause the formation of toxic amyloid beta oligomers (AβO). AβO are most potent for AD pathogenesis, and the variation of AβO levels is one of the major biomarkers in AD progression. This type of toxic protein can affect microglia mechanobiology properties as the cells are responsible for clearing AβO. Therefore, a quantitative method can be developed to assess microglia-substrate adhesion as a mechanobiology marker to indicate AD progression. In this dissertation, a simple microfluidic device was developed to assess microglia BV2 cells-substrate adhesion without using labeling when the cells were exposed to AβO. Microglia BV2 cells were subjected to fluid shear stresses to analyze microglia-substrate adhesion using microfluidic AD models to characterize the cell removal using time-lapse microscopy. For a comprehensive analysis of microglia cells in AD conditions, 96 chips were used to expose microglia cells in 32 conditions. Shear stresses of 3 Pa and 7.5 Pa were applied to the cells through the inlet flow of the device when the cells were exposed to various AβO concentrations of 1 µM, 2.5 µM, and 5 µM for 1 h, 6 h, 12 h, and 24 h, then compared to their control conditions. Our data showed that quantifying the cell-substrate adhesion could successfully represent various conditions created by increasing AβO concentrations exposed to the cells. It was revealed that increasing the time of the cells exposed to AβO, the binding strength of cells to the substrate reduced. Our present study demonstrated that advancing AβO concentrations caused cell-substrate interaction to lose strength. The result showed that all cells were dead after 24 h incubation of microglia BV2 cells exposed AβO 5 µM.
The quantitative information of this dissertation using the proposed microfluidic chips can provide a better understanding of microglial mechanobiology properties in the control conditions and also the diagnosis and progression of AD through AβO as a biomarker
A Practical On-Machine Tool Condition Monitoring Approach to Predicting Reamer Tool Life
Get PDFOn-machine tool measurement (OMTM) is an emerging technique that can automatically measure cutting tool diameter and length in the machining process with a laser tool setter on the machine table. Tool condition monitoring (TCM) is to measure the width of the flank wear land as tool wear and detect tool failure during machining. Unfortunately, no TCM technique has been developed, tool wear cannot be detected, and tool failure cannot be predicted in machining. It is in high demand that tool wear is measured and compensated, and tools are replaced right before they fail. However, different types of tools wear in different pattern; measuring the tool diameter at a height with OMM cannot well represent tool wear, not even to predict tool failure. To realize TCM with the OMM technique, this research proposes a new approach to predicting a reamer’s life so that the reamer can be changed before it fails. It he relationship between tool wear and tool failure has not been thoroughly investigated, especially since there are various cutting tool types, each with its unique failure mode, which means different tool types require specific methods for evaluating tool failure based on wear detection through TCM. This research propose an approach to predicting the tool life of reamer, a type of metal cutting tool, in hole machining. The study begins by examining the geometry of reamers and the cutting principles underlying the reaming process. This analysis aids in investigating the relationship between the geometric changes in reamers resulting from wear and the occurrence of reamer failure.
Additionally, the research extensively explores the main forms of reamer wear and carefully examines their impact on the quality of hole reaming. A comprehensive understanding of these wear forms is crucial for accurately predicting tool life. Moreover, a selection of reamer geometries has been identified, directly influencing the quality of reaming operations. The corresponding effective dimensional tolerances for these geometries are also determined.
This research successfully develops the fusion technology of On-Machine Monitoring (OMM) and Tool Condition Monitoring (TCM), which enables real-time tool wear assessment and facilitates timely maintenance interventions. The proposed approach has notable benefits for the manufacturing industry, including enhanced production efficiency, reduced downtime, and improved machining quality. The findings of this research contribute to advancing reamer tool life prediction methodologies and hold practical implications for optimizing manufacturing processes. The advanced OMM-TCM fusion technology is a valuable tool for ensuring efficient and reliable hole-reaming operations, benefiting the whole manufacturing industry