VictorJuiz/thesis huggingface dataset:
Assessments of Hypothetical Community Service Components in High Schools

The current study seeks to address some debates surrounding the imposition of mandatory volunteer programs in high schools by directly engaging students with interviews about their own reasoning surrounding matters of autonomy and the fostering of prosocial beliefs that are affected by the composition of a mandatory volunteer program. Participants were asked to evaluate five different vignettes depicting a different program. Results indicated that older youth tend to evaluate programs which offer choice more positively, while younger students make few distinctions. All age groups prefer mandatory programs to a voluntary program. No effect of program (service learning vs. community service) was present, although forced-choice data indicate a preference for service learning components. Implications for autonomy and prosocial development are discussed.

Keywords: Volunteerism
Autonomy
Advisor: Helwig, Charles C.
Implantable Biosensors for Neural Imaging: A Study of Optical Modeling and Light Sources

We aim to develop an implantable, optical neural imaging device by fabricating lasers and photodiodes onto a gallium arsenide substrate. Some studies suggest that lasers exhibit higher noise than light emitting diodes (LEDs) due to coherence effects – my studies aim to quantify this noise and to guide device development. To this end, I developed a model of a fluorescent imaging device which agreed with experiment. Noise analysis performed in phantom showed that laser sources exhibit temporal and spatial noise up to 10x higher than LED sources, and in vivo noise analysis also demonstrated this trend. I studied a neural injury model called cortical spreading depression in vitro in mouse brain slices and in vivo in the rat brain using laser and LED sources. Signal magnitudes in vitro are on the order of 10% and in vivo results are inconclusive. Future work will aim to reduce coherence related noise.

Keywords: Laser
Brain
Imaging
Modeling
Coherence noise
Neurophotonics
Biophotonics
Biosensor
Optical
Light source
Speckle
Light emitting diode
Advisor: Levi, Ofer
Detection of Movement Intention Onset for Brain-machine Interfaces

The goal of the study was to use electrical signals from primary motor cortex to generate accurate predictions of the movement onset time of performed movements, for potential use in asynchronous brain-machine interface (BMI) systems. Four subjects, two with electroencephalogram and two with electrocorticogram electrodes, performed various movements while activity from their primary motor cortices was recorded. An analysis program used several criteria (change point, fractal dimension, spectral entropy, sum of differences, bandpower, bandpower integral, phase, and variance), derived from the neural recordings, to generate predictions of movement onset time, which it compared to electromyogram activity onset time, determining prediction accuracy by receiver operating characteristic curve areas. All criteria, excepting phase and change-point analysis, generated accurate predictions in some cases.

Keywords: brain-machine interface
neural engineering
rehabilitation engineering
neuroprosthetics
brain-computer interface
synchronous
EEG
ECoG
Advisor: Popovic, Milos R.
Xenotransplantation of Human Umbilical Cord Perivascular Cells in a Femoral Defect

This work examines the osteogenic potential and immune-privileged properties of human umbilical cord perivascular cells (HUCPVCs) in normal Wistar rats and athymic rnu/rnu rats for up to 60 days. HUCPVCs demonstrated a mesenchymal stromal cell phenotype, assayed through flow cytometry, and RT-PCR analysis detected their expression of osteogenic genes. A bone tissue engineering construct was developed through centrifugal seeding of HUCPVCs onto calcium phosphate-coated PLGA scaffolds. These cell-scaffold constructs were transplanted into bilateral femoral defects. HUCPVCs did not induce any systemic biological response in normal rats; however, they did not engraft and impaired bone healing up to 60 days. When transplanted into athymic rats, HUCPVCs were detected up to 30 days in the femoral defects, improved bone regeneration at 15 and 30 days, as measured by micro computed tomography, and expressed osteogenic proteins. These findings demonstrate that HUCPVCs are suitable for bone tissue engineering studies in larger animals.

Keywords: Stem cells
Mesenchymal cells
Umbilical cord
Wharton's jelly
Bone tissue engineering
Advisor: Davies, John Edward
The Effect of Repeated Exposure to Unpredictable Reward on Dopamine Neuroplasticity

Drugs of abuse elicit dopamine release unconditionally, sensitizing the reward system to drugs and drug-associated stimuli resulting in compulsive drug-seeking and drug-taking behaviour. It has been discovered that these same dopamine neurons consistently respond to natural rewards when the reward delivery is at maximum uncertainty (50%). Reward uncertainty is a defining feature of gambling. Therefore, chronic increases in dopamine release from gambling-like stimuli could lead to sensitization of the reward pathways and contribute to gambling pathology. This study investigated the effects of repeated exposure to different probabilities of sucrose reward (0, 25%, 50%, 75%, 100%) on sensitivity to an amphetamine challenge (0.5 mg/kg) and development of sensitization after multiple amphetamine doses (5 x 1.0/kg) in Sprague–Dawley and Lewis rats. No significant group differences were found during the amphetamine challenge or amphetamine sensitization in either strain. Opportunities for improvement in the experimental paradigm and for future research are discussed.

Keywords: Unpredictable Reward
Dopamine Neuroplasticity
Advisor: Fletcher, Paul J.
Intakes of Whole and Refined Grains and Dietary Fibre In Relation to Plasma Inflammatory Protein Concentrations

Inflammation contributes to the etiology of type 2 diabetes (T2D) and cardiovascular disease (CVD). Therefore, it is of interest to investigate how diet relates to plasma inflammatory proteins, particularly whole grain and fibre intakes, as these factors have been associated with lower CVD and T2D risk. Only a limited number of observational studies have examined these relationships. The objective of this study was to investigate the cross-sectional relationships of whole and refined grain and dietary fibre intakes with plasma inflammatory proteins. There was a strong inverse relationship between whole grain intake and plasminogen activator inhibitor type 1 (PAI-1) (β =-0.102; SE=0.038; p=0.0077), and a positive relationship between refined grain intake and PAI-1 (β=0.076; SE=0.034; p=0.0251). Additionally, dietary fibre was related to lower concentrations of C-reactive protein (β=-0.034; SE=0.010; p=0.0008) and fibrinogen (β=-1.207; SE=0.505; p=0.0171). This research suggests that whole and refined grain and fibre intakes may influence inflammatory protein concentrations.

Keywords: epidemiologic study
diabetes risk factors
cardiovascular disease risk factors
Advisor: Hanley, Anthony James Gordon
The Evolution of Caenorhabditis elegans Sperm Traits Involved in Reproductive Success by Self-fertilizing Hermaphrodites and in Male-male Post-mating Contests

Sperm play a pivotal role in determining the reproductive success of individuals whose sperm must compete directly with that of others. I used sperm precedence assays and experimental evolution to examine the role of sperm traits in the reproductive success of hermaphrodites and males in the androdioecious nematode Caenorhabditis elegans. First, sperm size and the rate of reproduction were analyzed, in the context of male-male sperm competition, for evidence of natural heritable variation. Sperm size proved to be a strong indicator of second-male sperm precedence in the genotypes examined. Second, I tested the theoretically predicted effect of larval development time on the number of self-sperm produced by hermaphrodites. I demonstrated that a short larval development period favored the evolution of fewer sperm, inline with theoretical predictions. These results provide important insights into C. elegans reproductive biology and more generally to our understanding of the evolution of reproductive systems.

Keywords: experimental evolution
Caenorhabditis elegans
sperm competition
Advisor: Cutter, Asher
The Effects of Competitive Context on Shade Avoidance Syndrome Evolution in Impatiens Capensis

Competition plays a fundamental role in structuring ecological communities, and is a particularly important interaction for sessile organisms such as plants (Goldberg & Fleetwood 1987; Tilman 1994). To mitigate the negative effects of competition on fitness, plants can alter their phenotypes and reproductive traits through plastic responses. For example, decreases in the red to far-red ratio of light signal the presence of competitors, inducing a suite of responses known as shade avoidance syndrome (Franklin 2008). My thesis examines the impact of the competitive environment on reproductive output, the phenotypes Impatiens capensis produce and natural selection acting on shade avoidance responses. I found that heterospecific competitors affect both the phenotypes of I. capensis, and selection on shade avoidance traits. I also found evidence of population differentiation in hypocotyl lengths and flowering time. My thesis elucidates the influence of competition on the evolution of phenotypic plasticity in Impatiens capensis.

Keywords: evolutionary ecology
phenotypic plasticity
Advisor: Stinchcombe, John
Aero-structural Optimization of Divergence-critical Wings

This study investigates the use of the divergence speed as an additional constraint to a multi-disciplinary optimization (MDO) problem. The goal of the project is to expand the MDO toolbox by adding an aeroelastic module used where the aeroelastic characteristics present a possible safety hazard. This paper examines aeroelastic theory and MDO disciplines. The divergence constraint function is developed on a BAH wing. The optimization problem is executed on the HANSA HFB 320 transport jet using the FEAP structural solver and a Vortex Lattice Method as the aerodynamic solver. The study shows that divergence speed can function as a safety constraint but the stress constraints determine the optimum design. Furthermore, obtaining a true divergence constraint will require a finer mesh, a more efficient aerodynamic solver and non-finite difference approach to gradient determination. Thus, the addition of the divergence constraint does not yet directly benefit this MDO framework.

Keywords: Optimization
Divergence
HANSA
Aerostructural
Advisor: Martins, Joaquim R. R. A.
Numerical Determination Of The Transition Boundary Between Regular and Mach Reflection For Planar Shocks Striking Wedges and Cones in Air

A numerical investigation of the interaction of a planar shock wave with a rigid wedge and cone in an air-filled shock tube is performed by computing the unsteady flow field of the interaction process. The Euler and Navier-Stokes equations are solved in two dimensions to produce flow solutions for regular and Mach reflections with and without the viscous and thermal boundary layer on the inclined surface. The transition boundary between these two patterns is determined by changing both the shock strength and the angle of the inclined surface so that the simulations are perpendicular to the theoretical transition boundary. The numerically determined boundaries are compared to the theoretical boundaries predicted by two- and three- shock theories and with results obtained from experiments. The results show that the transition boundary between regular and Mach reflection is different not only for wedges and cones but also for inviscid and viscous numerical solutions.

Keywords: numerical investigation
transition
regular reflection
Mach reflection
Advisor: Gottlieb, James J.
Real-time Neuro-fuzzy Trajectory Generation for Robotic Rehabilitation Therapy

This thesis proposes a method for the design of a real-time neuro-fuzzy trajectory generator for the robotic rehabilitation of patients with upper limb dysfunction due to neurological diseases. The system utilizes a fuzzy-logic schema to introduce compliance into the human-robot interaction, and to allow the emulation of a wide variety of therapy techniques. This approach also allows for the fine-tuning of system dynamics using linguistic variables. The rule base for the system is trained using a fuzzy clustering algorithm and applied to experimental data gathered during traditional therapy sessions. The compliance rule base is combined with a hybrid neuro-fuzzy compensator to automatically tune the dynamics of the system. The trajectory generator is packaged as a platform-independent solution to facilitate the rehabilitation of patients using multiple manipulator configurations.

Keywords: Neuro-fuzzy
Rehabilitation Robotics
Advisor: Emami, Mohammad Reza
The Role of Notch Signaling in Learning and Memory

The Notch receptor and its ligands constitute a ubiquitous signaling pathway found throughout all multicellular animal life. In addition to its highly conserved function in development, a growing body of evidence suggests Notch signaling has important roles to play in adult processes, including long-term memory (LTM) formation. Building on previous work showing a specific requirement for the Notch1 receptor in spatial memory in mice, I show here a similar requirement for the Notch ligand Jag1. Mice with mutations to Dll1 (another Notch ligand) and Lfng (a Notch regulatory protein) do not display such phenotypes. I propose a model in which signaling between Notch pathway components found in the adult mouse hippocampus (such as Notch1 and Jag1) is required for LTM encoding, with no requirement for pathway components not expressed in this tissue (such as Dll1 and Lfng).

Keywords: memory
Notch
Advisor: Josselyn, Sheena
Investigating the Mechanisms of Rupture and Dewetting of Quiescent Thin Films

Controlling and predicting rupture and dewetting of quiescent thin water films, hundreds of microns thick, was studied experimentally. Wax, polycarbonate, steel and aluminium surfaces were immersed in water; the water level was lowered to form thin films above the surfaces. Spontaneous film rupture only occurred on wax, a low-energy surface. Films ruptured at the edges of the other—high-energy—surfaces. Increased surface roughness decreased chances of rupture and dewetting in the film. Introducing large wax or steel protrusions (on the order of millimetres) on smooth surfaces showed films rupturing above the protrusions and adhering to them; further thinning caused rupture and dewetting away from the protrusions. Entrapped air bubbles, injected through the surface and into the film, ruptured as they breached the film surface to form stable holes in the film if it was sufficiently thin. Entrapped air was the best means of rupturing films on all surfaces.

Keywords: Thin Films
Rupture
Dewetting
Surface Roughness
Protrusions
Air Entrapment
Advisor: Chandra, Sanjeev
An Investigation of Metal and Ceramic Thermal Barrier Coatings in a Spark-ignition Engine

Surface temperature and heat flux measurements were made in a single cylinder SI engine piston when uncoated and with two different surface coatings: a metal TBC and YSZ. A new thermocouple was developed to accurately measure surface temperatures. The engine was operated in a standard full load mode and a knock promoting mode featuring heated intake air and advanced spark timing. Cylinder pressures were measured to quantify knock. It was found that average heat flux into the piston substrate was 33 % higher with the metal TBC and unchanged with the YSZ relative to the uncoated surface. The increase with the metal TBC was attributed to its surface roughness. However, the metal TBC and YSZ reduced peak heat flux by 69 and 77 %, respectively. Both the metal TBC and YSZ reduced knock compared to the uncoated surface. After testing, the metal TBC was undamaged and the YSZ was slightly chipped.

Keywords: Thermal Barrier Coatings
Internal Combustion Engine
Advisor: Wallace, James S.
Comparative Energy and Carbon Assessment of Three Green Technologies for a Toronto Roof

Three different green technologies are compared in terms of net energy and carbon savings for a theoretical Toronto rooftop. Embodied energy values are calculated through Life Cycle Analysis and compared to the estimated energies produced and/or saved by each technology. Results show that solar photovoltaics displace the most carbon per m2 of roof space and solar thermal (for hot water) displaces the most energy. An in-depth analysis of an intensive green roof for growing food indicates that the high embodied energy of the materials is not quickly repaid by the sum of six energy savings that were examined (direct and indirect cooling, run-off treatment, transport of food, on-farm energy use, and activities that would otherwise be carried out). However, the energy and carbon benefits are not insignificant, but depend strongly on various assumptions. The methodology used is replicable and therefore useful for other locations.

Keywords: energy
green roof
photovoltaic
solar thermal
embodied energy
Life Cycle Analysis
energy payback
carbon emissions
Toronto
rooftops
Advisor: Harvey, Danny
Assessing Mercury Exposure Risk in the Lake Zapotlán Watershed, Mexico

Mercury is an environmental contaminant of global concern. The distribution of mercury in freshwater systems is poorly characterized in Mexico, despite widespread contamination from industrial and urban effluents. The land use, geology, and hydrology of the Lake Zapotlán basin, Mexico are conducive to the delivery of elevated mercury in water to the lake due to untreated wastewater discharge, deforestation, and local volcanic history. To assess a mercury exposure risk to fish consumers, the concentrations of total Hg (THg) in water inputs, surface waters, sediments, and the commercial catch of tilapia and carp were investigated. Results indicate that despite high particle-bound inputs of THg to the lake in runoff and wastewater, THg in sediments and surface waters were low. Dense Typha latifolia dominated wetlands are believed to retain THg inflow from water inputs. Concentrations of THg in tilapia and carp were low, suggesting low mercury bioavailability in this system.

Keywords: mercury
effluents
Mexico
fisheries
wetland
Advisor: Branfireun, Brian
Vitamin D Deficiency as a Nutritional Child Health Determinant

Objective: This thesis aims to construct a framework for studying vitamin D deficiency in young Canadian children. Methods: A practice based research network was created to collect vitamin D data from children 1-5 years of age in Toronto, Canada (TARGet Kids!). A cross-sectional pilot study was completed and a larger study proposed to determine the prevalence and predictors of low vitamin D. Results: The prevalence of low vitamin D (<50nmol/L) in the pilot study was 32% (29/92, 95% CI: 22-42%). Using multivariable linear regression, lower vitamin D level was associated with lower milk volume, higher BMI and watching TV during snacks. A larger study involving 2400 children 1-5 years of age has been proposed. Interpretation: Pilot data has suggested that 30-80% of toddlers in this setting have low vitamin D. A study to clarify these findings and form the basis of a large longitudinal vitamin D cohort has been proposed.

Keywords: Vitamin D deficiency
Child Health
Advisor: Parkin, Patricia C
Linear Feature Extraction with Emphasis on Face Recognition

Feature extraction is an important step in the classification of high-dimensional data such as face images. Furthermore, linear feature extractors are more prevalent due to computational efficiency and preservation of the Gaussianity. This research proposes a simple and fast linear feature extractor approximating the sufficient statistic for Gaussian distributions. This method preserves the discriminatory information in both first and second moments of the data and yields the linear discriminant analysis as a special case. Additionally, an accurate upper bound on the error probability of a plug-in classifier can be used to approximate the number of features minimizing the error probability. Therefore, tighter error bounds are derived in this work based on the Bayes error or the classification error on the trained distributions. These bounds can also be used for performance guarantee and to determine the required number of training samples to guarantee approaching the Bayes classifier performance.

Keywords: Feature Extraction
Classification
Face Recognition
Sufficient Statistic
Advisor: Plataniotis, Konstantinos N.
Timing and Mechanisms Controlling Evaporite Diapirism on Ellef Ringnes Island, Canadian Arctic Archipelago

This thesis investigates the timing and mechanisms involved in the formation of evaporite piercement structures on Ellef Ringnes Island, Canadian Arctic Archipelago. The study includes the interpretation of industry seismic reflection and borehole data to characterize the geometry of the domes, 1D backstripping of wells to investigate the role of tectonic influences on diapirism, and analogue modelling to better understand the mechanisms that drive diapirs with dense anhydrite caps. I propose that basement structures played a significant role in the formation of evaporite domes by triggering and directing salt movement. The domes developed during the Mesozoic by passive growth driven by the differential loading of salt on adjacent fault blocks, which led to their present day asymmetric geometries. Diapir growth rates in the Mesozoic were closely linked to the rate of sedimentation, which was greatly influenced by the amount of accommodation space provided by tectonic subsidence of the basin.

Keywords: evaporite domes
salt tectonics
geodynamics
Canadian Arctic
Advisor: Cruden, Alexander R.
Olanzapine-induced Weight Gain: An Animal Model

Introduction: Using an animal model, we examined weight gain in rats exposed to olanzapine, as well as whether increased weight was associated with food intake, visceral fat and/or locomotion. Methods: Sprague-Dawley rats were chronically treated with olanzapine while being offered diets including standard chow, a high fat (60% fat) diet, and a high fat/high carbohydrate (42% fat; 42.7% carbohydrate) diet. Body weight, food intake, visceral fat and locomotor activity were measured. Results: Our findings related to weight gain are in line with other reports indicating that while olanzapine-induced weight gain can be observed, it does not mirror what is observed in humans on two levels: (i) it is not of the same magnitude, and (ii) it is more gender specific i.e., females greater than males. Conclusions: These data confirm that chronic treatment with olanzapine has varying effects on weight gain, food intake, visceral fat and locomotor activity.

Keywords: olanzapine
weight gain
food intake
locomotor activity
Advisor: Remington, Gary
Geographical Epidemiology of Cardiovascular Disease in India: An Exploratory Study

Cardiovascular Diseases (CVD) have become the leading cause of death in India and other developing countries. The aims of this study were to: (1) describe the geographical epidemiology of CVD in India, (2) provide a graphical display of CVD risk factors and mortality outcomes, and (3) describe the sources of bias. Five large, nationally-representative datasets from India were studied. Cardiovascular death rates were 308/100,000 among males and 198/100,000 among females in middle-age (30-69years). Wide variations between states were noted in the distribution of risk factors and mortality. The selected risk factors explained 49% and 43% of the variation among males and females respectively. Ecologic analysis revealed death rates at state-level were associated with rates of overweight and vegetarianism among males; no such association was found among females. This study has implications for identification of areas with high burden, formulation of hypotheses, and assessing needs for disease control at national/regional levels.

Keywords: epidemiology
cardiovascular disease
geography
India
Advisor: Jha, Prabhat