VictorJuiz/thesis huggingface dataset:
Trouble in our Fields: Health and Human Rights among Mexican and Caribbean Migrant Farm Workers in Canada

For many years Canada has quietly rationalized importing temporary “low-skilled” migrant labour through managed migration programs to appease industries desiring cheap and flexible labour while avoiding extending citizenship rights to the workers. In an era of international human rights and global competitive markets, the Canadian Seasonal Agricultural Workers Program (SAWP) is often hailed as a “model” and “win-win” solution to migration and labour dilemmas, providing employers with a healthy, just-in-time labour force and workers with various protections such as local labour standards, health care, and compensation. Tracing migrant workers’ lives between Jamaica, Mexico and Canada (with a focus on Ontario’s Niagara Region), this thesis assesses how their structural vulnerability as non-citizens effectively excludes them from many of the rights and norms otherwise expected in Canada. It analyzes how these exclusions are rationalized as permanent “exceptions” to the normal legal, social and political order, and how these infringements affect workers’ lives, rights, and health. Employing critical medical anthropology, workers’ health concerns are used as a lens through which to understand and explore the deeper “pathologies of power” and moral contradictions which underlie this system. Particular areas of focus include workers’ occupational, sexual and reproductive, and mental and emotional health, as well as an assessment of their access to health care and compensation in Canada, Mexico and Jamaica. Working amidst perilous and demanding conditions, in communities where they remain socially and politically excluded, migrant workers in practice remain largely unprotected and their entitlements hard to secure, an enduring indictment of their exclusion from Canada’s “imagined community.” Yet the dynamics of this equation may be changing in light of the recent rise in social and political movements, in which citizenship and related rights have become subject to contestation and redefinition. In analyzing the various dynamics which underlie transnational migration, limit or extend migrants’ rights, and influence the health of migrants across borders, this thesis explores crucial relationships between these themes. Further work is needed to measure these ongoing changes, and to address the myriad health concerns of migrants as they live and work across national borders.

Keywords: migrant workers
migrant farm workers
seasonal agricultural workers
farmworkers
temporary foreign workers
health
human rights
migration
medical anthropology
Canada
Jamaica
Mexico
occupational health
sexual health
mental health
health care
workers compensation
Seasonal Agricultural Workers Program
structural violence
agriculture
Advisor: Cunningham, Hilary
The Regulatory Properties of α5 Subunit-Containing γ-Aminobutyric Acid Subtype A Receptors in Learning and Synaptic Plasticity

Synaptic plasticity, which is thought to represent the neuronal substrate for learning and memory is influenced by the degree of GABAergic inhibitory tone. In particular, γ-aminobutyric acid subtype A receptors (GABAARs), which mediate the majority of inhibitory neurotransmission in the mammalian brain regulate learning and plasticity. In these studies I examined a subpopulation of α5 subunit-containing GABAA receptors (α5GABAARs), which are preferentially expressed in the hippocampus, to determine whether they have a specific role in memory processes. I hypothesized that α5GABAAR-activity constrains hippocampus-dependent learning and CA1 synaptic plasticity. The main research objective of this thesis was to investigate the electrophysiological changes within the hippocampus that accompany genetic and pharmacological targeting of α5GABAARs and how these changes impact behaviour. I found that the general anesthetic etomidate enhanced a tonic inhibitory conductance generated by α5GABAARs, and this action correlated with an impairment of long-term potentiation (LTP) and hippocampus-dependent memory performance for fear-associated memory and spatial navigation. Mice with a genetic deletion of the α5 subunit gene (Gabra5–/–) were resistant to the LTP- and memory-impairing effects of etomidate. Additionally, the LTP- and memory-impairing effects of etomidate were rescued by pharmacologically inhibiting α5GABAARs. Genetic and pharmacological inhibition of α5GABAARs enhanced associative learning in trace fear but not contextual fear conditioning tasks. Interestingly, genetic deletion and pharmacological inhibition of α5GABAARs did not result in the common adverse side-effects associated with non-selective inhibition of GABAARs such as anxiogenesis or seizures. Further, I found that blocking the tonic inhibition generated by α5GABAARs lowered the threshold for LTP, such that lower stimulation frequencies enhanced LTP. Synaptic changes within this frequency band were modified independently of phasic GABAAR inhibition. Inhibiting the α5GABAAR-dependent membrane conductance was associated with an increase in the depolarizing envelope during 10 Hz stimulation. These experiments provide new insights into the in vitro and in vivo physiology of α5GABAARs and suggest that a tonic inhibition generated by α5GABAARs constrains learning and glutamate plasticity through regulation of the membrane’s electrical properties.

Keywords: Learning
GABA
alpha5
fear conditioning
Advisor: Orser, Beverley
Dimension Groups and C*-algebras Associated to Multidimensional Continued Fractions

Thirty years ago, Effros and Shen classified the simple dimension groups with rank two. Every such group is parametrized by an irrational number, and can be constructed as an inductive limit using that number's continued fraction expansion. There is a natural generalization of continued fractions to higher dimensions, and this invites the following question: What dimension groups correspond to multidimensional continued fractions? We describe this class of groups and show how some properties of a continued fraction are reflected in the structure of its dimension group. We also consider a related issue: an Effros-Shen group has been shown to arise in a natural way from the tail equivalence relation on a certain sequence space. We describe a more general class of sequence spaces to which this construction can be applied to obtain other dimension groups, including dimension groups corresponding to multidimensional continued fractions.

Keywords: dimension group
C*-algebra
continued fraction
multidimensional continued fraction
Advisor: Elliott, George Arthur
Effects of Infliximab Therapy on Hospitalization, Surgery and Healthcare Consumption in Crohn’s Disease: A Population Based Propensity Score Matched Analysis

Background : The majority of patients with Crohn’s Disease (CD) will be hospitalized and receive surgery for their disease. Hospitalizations and surgical procedures account for the majority of the direct costs of CD. Purpose : Our objective was to use population-based administrative data from the province of Quebec, Canada, to estimate the effectiveness of infliximab therapy in reducing CD-related surgery, hospitalization and health care resource consumption in subjects with CD. Methods : We obtained patient level prescription data, physician billing claims and hospitalization data from the Régie de l'Assurance Maladie du Québec (RAMQ) a Canadian provincial health care provider. Subjects who were enrolled in the system for a minimum of two years and who received prescription drug benefits for each year they participated in the study were identified as being affected by CD using a validated algorithm. For each subject treated with infliximab, up to two closely matched comparison subjects were selected using propensity score methods. We compared time to first CD-related intra-abdominal surgery and hospitalization as well as total hospitalized days and physician visits between infliximab users and non-users. Results : We were able to match 319 (77%) out of the 414 infliximab users to comparison subjects using propensity score matching; 300 were matched to two infliximab non-users and 19 were matched to one non-user to create 619 matched-pair sets. Subjects who received infliximab therapy had a significantly reduced risk of experiencing a CD-related intra-abdominal surgery (HR=0.674, 95%CI 0.533-0.853, p=0.001), any hospitalization (HR=0.753, 95%CI 0.619-0.917 p=0.005), and CD-related hospitalization (HR=0.726, 95%CI 0.565-0.934 p=0.013). Infliximab users experienced lower rates of hospitalized days (RateR=0.6418, 95%CI 0.4399-0.9362; P=0.021) and gastroenterologist visits (RateR=0.810, 95% CI 0.700-0.937; P=0.005). Infliximab users and non-users had similar rates of non-gastroenterologist physician visits (RateR=0.928, 95% CI 0.851-1.057; P=0.262). Conclusion : Infliximab therapy was associated with significant reductions in CD-related intra-abdominal surgeries, hospitalizations, hospitalized days and gastroenterologist visits. Our results confirm the population-based effectiveness of infliximab beyond the ideal conditions of clinical trials.

Keywords: infliximab
pharmacoepidemiology
Advisor: Einarson, Thomas Ray
Nod1 and Nod2 in Innate Immune Responses, Adaptive Immunity and Bacterial Infection

The last decade has been witness to a number of seminal discoveries in the field of innate immunity. The discovery that microbial molecules and endogenous danger signals can be detected by germ-line encoded receptors has changed the way we study the immune system. Indeed, the characterization of Toll in Drosophila as a sensor of microbial products in 1997 then led to the discovery of a family of Toll Like Receptors (TLRs) in mammals. TLRs are critical for the induction of inflammatory responses and the generation of a successful adaptive immune response. The array of ligands that these transmembrane proteins recognized mediates defense against bacteria, viruses, fungus and parasites, as well as, possibly, cancerous cells. In addition to this membrane-bound family of recognition proteins, two families of pattern recognition receptors have been recently shown to respond to microbial and chemical ligands within the cytosol. These represent the Nod Like Receptors (NLRs) and RIGI-like helicase receptor (RLH) families. Nod1 and Nod2 are members of the NLR family of proteins, which are responsible for the recognition of components derived from the bacterial cell wall, more precisely, moieties of peptidoglycan. As such, Nod1 and Nod2 are implicated in the recognition and the defense against bacterial pathogens. Importantly, the genes encoding these two proteins have also been linked to the etiology of several inflammatory disorders such as Crohn’s disease and asthma. In this thesis, we show that recognition of Nod1 and Nod2 ligands generates a rapid and transient inflammatory response in vivo. When co-injected with a model protein, Nod1 and Nod2 ligands exhibit adjuvant properties that lead to the generation of an antigen-specific Th2 type adaptive immune response. Surprisingly, recognition of the Nod1 ligand in non-hematopoietic cells is critical for the generation of this immune response. In contrast, TLRs classically tip the balance towards a Th1 response and interestingly, co-injection of TLR and Nod ligands synergize to generate a more potent immune response characterized by the generation of Th1, Th2 and Th17 T cell respones. To study the role of Nod1 and Nod2 in the context of a bacterial infection in vivo, we used an intestinal mouse pathogen, Salmonella enterica serovar Typhimurium. We were able to show that Nod1-deficient mice, but not Nod2-deficient mice, are more susceptible to the strain of this bacterium, which enters the host through the active pickup in the intestinal lumen by underlying myeloid cells. This sampling mechanism is mediated by a subset of dendritic cells that populate the intestinal lamina propria. Accordingly, the defect seen in Nod1-deficient mice localizes to the mucosal barrier where these dendritic cells appear to have an impaired response towards the bacteria. Taken together, these results increase our knowledge on the general role of Nod1 and Nod2 in immunity and might generate new avenues of research and potential therapeutic targets.

Keywords: Innate immunity
Bacterial infection
Inflammation
Advisor: Philpott, Dana Jean
The Neuropsychological Mechanisms of Avoidant Coping Post Traumatic Brain Injury

Many people who sustain traumatic brain injuries (TBI) have poor psychosocial outcomes. Previous research has indicated that poor outcomes are related to the use of avoidant coping following TBI, although the mechanisms of this relationship are not clear. The major pathological consequence of TBI is damage to the frontal lobes and/or their connections, resulting for most people in executive and/or affective dysfunction. The purpose of this dissertation study was to delineate the neuropsychological, psychiatric, personality and physiological mechanisms of avoidant coping following TBI. Controls and people with TBI completed the Baycrest Psychosocial Stress Test (BPST), where coping behaviour was observed directly, and physiological measures were recorded. Participants also completed a neuropsychological test battery, and a series of questionnaires assessing coping, psychiatric status, personality and outcomes. There were no significant differences between groups in self reported coping. However, the control and mild TBI group engaged in more planful than avoidant behaviour on the BPST. As a group, individuals with moderate-to-severe injury, in contrast, engaged in more avoidant than planful behaviour. However, analysis of individual differences in coping behaviour within the moderate-to-severe group revealed a bimodal distribution, allowing classification of people in this group as ‘planners’, or ‘avoiders’ (this distribution was not evident in the mild TBI group). Within the moderate-to-severe group, planners had better executive function, were more reactive to stress (psychologically and physiologically), performed better on the speech task during the BPST, and had greater return to productivity. However, planners also had worse psychosocial outcomes as compared to the avoiders. This was the first study, to the author’s knowledge, to examine coping behaviour during a simulated real-world stress test. Results indicate that behavioural measures of coping, such as the BPST, are more sensitive to changes in coping post TBI than are self and significant other reported questionnaires. Results also demonstrate that executive function and psychological and physiological reactivity are important factors that contribute to coping following moderate-to-severe TBI. These data raise important questions about the challenges of targeting coping through rehabilitation.

Keywords: Traumatic Brain Injury
Coping
Executive Function
Affective Function
Advisor: Nicole, Anderson
Donald, Stuss
Design and Devlopment of a Biostretch Apparatus for Tissue Engineering

Tissue engineering has emerged as a promising approach to repair, replace or regenerate damaged tissues using tissue constructs created in vitro. The standard procedure of the strategy to create a functional tissue is to seed cells on a 3-D biodegradable and biocompatible scaffold, to grow them under precisely controlled culture conditions provided by a bioreactor system, and to deliver the matured construct into the patient’s body to induce and direct the growth of the new and healthy tissue. In this thesis, a novel bioreactor system is designed and developed, which can provide uniaxial cyclic stretch to the tissue patch during culture process. The biostretch apparatus employs non-contact electromagnetic force to cyclically stretch a cell-seeded three-dimensional scaffold. The non-contact driving force and the specially designed mount allow researchers to use standard Petri dishes and commercially available CO2 incubators to culture an engineered tissue patch with precisely controlled strain. The device greatly simplifies the procedure to deliver mechanical stimulation during engineering a tissue patch. Since the applied mechanical stimulus is generated by a magnetic force, the engineered tissue construct is not only affected by a mechanical force, but also exposed to a magnetic field. Thus, the effects of the time-varying magnetic field during the culture process are investigated. The flux density of the field is modeled by COMSOL, and verified by a Gaussmeter. In addition, one side effect of using electromagnets, that of a temperature increase, is also investigated. The biomedical experiment results show that neither a weak low frequency magnetic field (0.1T, 1Hz) nor an increase of 1℃ in temperature has a significant effect on the cell culture. The performance of the designed apparatus is verified by the biomedical experiments from the aspects of cell proliferation and reorganization. Moreover, the mechanical parameters (strain distribution, strain rate, and stretch force) provided by the apparatus have also been quantitatively investigated.

Advisor: Zu, Jean W.
Modeling and Control of a Magnetic Fluid Deformable Mirror for Ophthalmic Adaptive Optics Systems

Adaptive optics (AO) systems make use of active optical elements, namely wavefront correctors, to improve the resolution of imaging systems by compensating for complex optical aberrations. Recently, magnetic fluid deformable mirrors (MFDM) were proposed as a novel type of wavefront correctors that offer cost and performance advantages over existing wavefront correctors. These mirrors are developed by coating the free surface of a magnetic fluid with a thin reflective film of nano-particles. The reflective surface of the mirrors can be deformed using a locally applied magnetic field and thus serves as a wavefront corrector. MFDMs have been found particularly suitable for ophthalmic imaging systems where they can be used to compensate for the complex aberrations in the eye that blur the images of the internal parts of the eye. However, their practical implementation in clinical devices is hampered by the lack of effective methods to control the shape of their deformable surface. The research work reported in this thesis presents solutions to the surface shape control problem in a MFDM that will make it possible for such devices to become integral components of retinal imaging AO systems. The first major contribution of this research is the development of an accurate analytical model of the dynamics of the mirror surface shape. The model is developed by analytically solving the coupled system of fluid-magnetic equations that govern the dynamics of the surface shape. The model is presented in state-space form and can be readily used in the development of surface shape control algorithms. The second major contribution of the research work is a novel, innovative design of the MFDM. The design change was prompted by the findings of the analytical work undertaken to develop the model mentioned above and is aimed at linearizing the response of the mirror surface. The proposed design also allows for mirror surface deflections that are many times higher than those provided by the conventional MFDM designs. A third contribution of this thesis involves the development of control algorithms that allowed the first ever use of a MFDM in a closed-loop adaptive optics system. A decentralized proportional-integral (PI) control algorithm developed based on the DC model of the wavefront corrector is presented to deal mostly with static or slowly time-varying aberrations. To improve the stability robustness of the closed-loop AO system, a decentralized robust proportional-integral-derivative (PID) controller is developed using the linear-matrix-inequalities (LMI) approach. To compensate for more complex dynamic aberrations, an Hinf controller is designed using the mixed-sensitivity Hinf design method. The proposed model, design and control algorithms are experimentally tested and validated.

Keywords: Magnetic Fluid Deformable Mirror
Adaptive Optics
Retinal Imaging
Control
Modeling
Advisor: Amara, Foued Ben
The Development and Evaluation of a Model of Time-of-arrival Uncertainty

Uncertainty is inherent in complex socio-technical systems such as in aviation, military, and surface transportation domains. An improved understanding of how operators comprehend this uncertainty is critical to the development of operations and technology. Towards the development of a model of time of arrival (TOA) uncertainty, Experiment 1 was conducted to determine how air traffic controllers estimate TOA uncertainty and to identify sources of TOA uncertainty. The resulting model proposed that operators first develop a library of speed and TOA profiles through experience. As they encounter subsequent aircraft, they compare each vehicle’s speed profile to their personal library and apply the associated estimate of TOA uncertainty. To test this model, a normative model was adopted to compare inferences made by human observers to the corresponding inferences that would be made by an optimal observer who had knowledge of the underlying distribution. An experimental platform was developed and implemented in which subjects observed vehicles with variable speeds and then estimated the mean and interval that captured 95% of the speeds and TOAs. Experiments 2 and 3 were then conducted and revealed that subjects overestimated TOA intervals for fast stimuli and underestimated TOA intervals for slow stimuli, particularly when speed variability was high. Subjects underestimated the amount of positive skew of the TOA distribution, particularly in slow/high variability conditions. Experiment 3 also demonstrated that subjects overestimated TOA uncertainty for short distances and underestimated TOA uncertainty for long distances. It was shown that subjects applied a representative heuristic by selecting the trained speed profile that was most similar to the observed vehicle’s profile, and applying the TOA uncertainty estimate of that trained profile. Multiple regression analyses revealed that the task of TOA uncertainty estimation contributed the most to TOA uncertainty estimation error as compared to the tasks of building accurate speed models and identifying the appropriate speed model to apply to a stimulus. Two systematic biases that account for the observed TOA uncertainty estimation errors were revealed: Assumption of symmetry and aversion to extremes. Operational implications in terms of safety and efficiency for the aviation domain are discussed.

Keywords: Uncertainty
Time-of-Arrival
Interval Estimation
Air Traffic Control
human-centred automation
Advisor: Milgram, Paul