VictorJuiz/thesis huggingface dataset:
E-Cigarettes: Biomarkers of Exposure and the Development and Validation of a Research Toolkit

Electronic nicotine delivery systems (ENDS) have gained worldwide popularity. Even so, there is limited research on the potential effects of regular ENDS use on health. Moreover, little is known about ENDS dependence and studies are often limited by a lack of validated research tools. Current measures of ENDS dependence are adapted from cigarette dependence questionnaires and do not consider concepts unique to ENDS vaping. Similarly, there are currently no validated ENDS-related stimuli for use in the research of drug reward and addictive behaviors. This thesis therefore directly compared the urinary cotinine levels, a biomarker of nicotine exposure, in individuals who use ENDS exclusively, use ENDS in conjunction with smoking tobacco cigarettes (dual users), and smoke cigarettes exclusively. We found no significant differences in cotinine levels between genders [F(2,84)=0.46, p=0.636], and between participant groups [F(2,84)=0.12, p=0.892]. In exclusive ENDS users, individuals with higher levels of cotinine also reported shorter times before vaping after waking [r(21)=-0.46, p=0.028]. Additionally, this thesis developed and validated a questionnaire to assess ENDS dependence and a database of 120 ENDS-related image cues. Exploratory factors analysis reduced an initial pool of 28 ENDS dependence items to 15 that were included in the final ENDS Nicotine Dependence Questionnaire (ENDS-DQ). Further analyses found that the ENDS DQ has high internal consistency (Cronbach α=0.84), external validity, and test-retest reliability (ICC=0.87). Regarding the development of an ENDS-related cue database, findings from our preliminary and follow-up validation studies were consistent with one another and with literature. Desire-to-vape ratings of ENDS-related images were correlated with valence (r=0.55, p

Keywords: biomarkers
dependence
e-cigarette
nicotine
questionnaire
stimuli
Advisor: Zawertailo, Laurie
Learning Conflict in the Midst of Violence. Urban Youth and School Life in Colombia’s (Post)Conflict Transition

This thesis explores the (dis)encounters between youths’ lived experiences and understandings of conflict and violence and the curricular intentions and practices in their schools. Participating youth attend two schools in marginalized urban areas of Colombia that are differently affected by violence and the armed conflict. One school is located in a municipality directly affected by armed conflict violence. The other is in a traditional neighborhood in a large city, affected by insecurity and urban criminality but located away from the direct effects of the armed conflict. Soon after the 2016 peace agreement between the Colombian state and the largest guerrilla organization, I conducted three months of participant observations, focus groups with youth from grades 8 to 10, interviews with teachers, and follow-up visits in each field site. I show that, despite young people’s different locations in relation to war, intimate expressions of direct violence—interpersonal, criminal, domestic, and drug-related—were prominent in students’ narratives about the social conflicts affecting their lives in both field sites. These concerns overrode both the visibility of armed conflict and indirect socio-cultural and structural forms of violence in their understandings of social conflict. I also show how the prevalent practices embedded in these schools’ curriculum, based on convivencia [peaceful coexistence] and (global) citizenship education discourses and guidelines, emphasized a similarly individualized, depoliticized, and ahistorical framing of violence and conflict. I argue that school life is a symbolic device that contributes to the normalization of violence in the everyday life of these (school) communities. While it provides a space for stability, inclusion, and young people’s personal visions of their future paths, it also undermines their ability to understand the Colombian conflict as a social process, with causes, actors, and a history. By contrasting youths’ and schools’ conceptions and practices of conflict and violence in two different geographies, this dissertation shows how predominant approaches to convivencia as securitization and order, conceptions of citizenship that blame others for violence, and skepticism towards peace (building) and collective action hinder youth-oriented peacebuilding pedagogies efforts for conflict transformation and reconciliation during Colombia’s transition from war to post-conflict.

Keywords: Colombia
Peace
Pedagogy
School
Violence
Youth
Advisor: Bickmore, Kathy K
Gaztambide-Fernandez, Ruben R
Structures Strike Back: Their Significance for Our Models of Opinion Formation

Why do our models of opinion formation work in some situations but fail in others? In this dissertation, I explain that our models of opinion formation work in some cases but fail in others because of the structural level variations that are not accounted for when these models are designed only with individual level variables in mind. By structural level variations, I mean the societal conditions that affect everyone in a given society and which are typically measured by societal level variables. These variables, I argue, are as fundamental to the process of opinion formation as the individual level variations scholars focus on by default. In Chapter 1, I elaborate on the theoretical foundations of this argument and set the tone for the three empirical chapters that test my argument. In Chapter 2, I start testing my argument by engaging with the structural impact of socioeconomic development on elite directed opinion formation at the individual level in MENA countries. I use survey data collected by three waves of the Arab barometer between 2010 and 2016 to show that socioeconomic development reverses the correlation between political awareness and the adoption/rejection of party cues in Islamist publics. In Chapter 3, I address the structural impact of colonization on the model of secularization postulated by modernization theories based on individual material conditions in MENA countries. Based on 42 surveys delivered between 2000 and 2014, my findings suggest that postcolonial MENA societies do indeed break with the pattern predicted by modernization theorists. In Chapter 4, the last empirical chapter of this dissertation, I discuss the structural impact of different immigration systems on patterns of xenophobia predicted by the economic competition theory based on individual social class in MENA countries. Using data from 14 MENA countries gathered between 2000 and 2011, it argues that where immigration systems prevent the social mobility of migrants, as in the case of the kafala system, xenophobic attitudes develop among those with a higher as opposed to a lower socio-economic status. Chapter 5 concludes by outlining some of the key theoretical and methodological implications of these empirical findings.

Keywords: Hierarchical/Multilevel Models
Middle Eastern North African Politics
Opinion Formation
Public Opinion
Quantitative Methods
Survey Data
Advisor: Cochrane, Christopher B.
Ahmad, Aisha
Alteration of Smooth Muscle Cell Polarity Following Arterial Injury: The Role of Mechanotransduction

Smooth muscle cell (SMC) migration from the media to the intima following arterial injury is a hallmark of intimal thickening in vascular disease. Migrating SMCs harvested from the media of normal vessels (M-SMCs) orient the microtubule organizing centre (MTOC) in front of the nucleus in the direction of migration (front-polarized) in vitro. However, following endothelial denudation in vivo, SMCs which migrated to the intima (N-SMCs), were rear-polarized. Rear polarization in N-SMCs is mediated by a PKC-RHAMM-ARPC5 mechanism and correlates with cell division abnormalities and apoptosis. Thus far, the factors inducing rear polarization in N-SMCs have not been identified. In this thesis, I used the rationale that during SMC migration to the intima, they experience significant mechanical forces. The objective of this thesis was to examine the role of mechanotransduction in inducing MTOC rear polarization in migrating SMCs.My first studies addressed the hypothesis that the mechanical stress of migrating through confined fenestrae of the internal elastic lamina, or exposure to shear stress imposed by blood flow, induced MTOC rear polarization in SMCs. Using parallel plate flow chambers, I demonstrated that exposing migrating M-SMC to 12 dyn/cm2 shear stress induced MTOC rear polarization. In the second set of studies, I aimed to elucidate the mechanism by which shear stress induced rear polarization in M-SMC. I tested the hypothesis that flow-induced rear polarization in migrating M-SMC was mediated by a PKC⍺-dependent mechanism. Using bisindolylmaleimide I to inhibit PKC⍺, I found that flow-induced rear polarization was abolished by PKC⍺ inhibition suggesting a key role for PKC⍺ in flow-induced rear polarization. I also observed an increase in RHAMM expression in response to shear stress and this increase was attenuated with PKC⍺ inhibition, suggesting a flow-mediated RHAMM expression regulation via PKC⍺. In summary, my findings suggest that MTOC rear polarization in N-SMC is induced by shear stress via a PKC⍺-dependent mechanism. These are the first studies examining the effect of shear stress on SMC polarity. The findings presented here advance our understanding of mechanotransduction in SMC following vascular injury.

Advisor: Bendeck, Michelle
Measuring Balance Confidence in Youth with Cerebral Palsy: Measure Development, Sensibility, Content Validity, and Initial Psychometric Evaluation

Background: Youth with cerebral palsy (CP) generally participate in less physical activity than typically developing youth. In adults with physical disabilities, balance confidence is a strong predictor of participation. However, balance confidence has not been studied in youth with CP. Research objectives: (1) To explore whether concerns about balance influence physical activity participation of ambulatory youth with CP; (2) to determine how youth with CP feel when they lose their balance; (3) to build a balance confidence measure for this population; (4) to examine the sensibility and content validity of the measure; and (5) to evaluate test-retest reliability and construct validity of the measure. Participants: Eighty-one participants were involved in one or more stages of this measurement study (25 youth with CP, eight parents of youth with CP, 17 typically developing youth, and 31 health care professionals). Methods: Qualitative descriptive methodology with 16 interviews was used to explore balance confidence with ambulatory youth with CP and parents. A multi-step process was used to create the Feelings About Balance–Cerebral Palsy (FAB-CP) youth-report questionnaire and evaluate sensibility, content validity, test-retest reliability, and convergent and discriminant validity. Results: Qualitative analysis demonstrated that ambulatory youth with CP, especially those who do not use gait aids for ambulation, are often concerned about losing their balance during physical activities, which may lead to avoiding physical activities. The FAB-CP, an 11-item computer-based measure was created to investigate balance confidence of this population. Test-retest reliability was excellent (n=21; one-to-four week interval; ICC 0.97 [95% CI 0.93, 0.99]). Convergent validity was good when evaluated against measures of balance capacity (rho=0.74), advanced motor skills (rho=0.83), physical activity enjoyment (rho=-0.61) and participation (rho=0.77). The FAB-CP discriminated among participants of different levels of gross motor function (maximum p

Keywords: balance
balance confidence
cerebral palsy
measurement
participation
self-efficacy
Advisor: Wright, F Virginia
Electrorefining and Electrochemistry of Molten Iron and Iron-Carbon Electrodes in Slag

Despite a perpetual societal need for steel, the industry is facing critical challenges as more steel must be continually recycled to improve sustainability and close material loops in circular economies. A major issue here is producing high-value products and controlling elements like carbon in the face of stringent consumer requirements, volatile markets, low profit margins, and scrap irregularity. In this dissertation, a new electrorefining process was developed where molten iron is decarburized by imposing an electromotive force between it and a slag electrolyte at 1600–1700 °C. Upon anodic polarization, oxygen-containing anions react with carbon dissolved in molten iron, evolving gaseous carbon monoxide. As carbon is oxidized from the iron anode, valuable metallurgical-grade silicon is recovered as a by-product on counter electrodes. Electrorefining trials were conducted over the entire compositional range from 4.5 to 0.005 wt% C and shown capable of producing high-value ultra-low carbon steel containing

Keywords: Decarburization
Electrochemistry
Electrorefining
Impedance
Slag
Steelmaking
Advisor: Azimi, Gisele
Development of a Hydrogel Platform to Model Cellular Invasion in Glioblastoma

Aggressive tumour invasion is a major therapeutic challenge in glioblastoma, leading to poor patient outcomes. This process is facilitated by various factors in the tumour microenvironment (TME), including highly migratory glioma neural stem (GNS) cells and their physical, biochemical and cellular surroundings. Engineered hydrogel-based materials can be used to recapitulate specific aspects of the biochemical composition and physical properties of the extracellular matrix (ECM). Bio-orthogonal click-chemistries enable the functionalization and crosslinking of biomaterials for hydrogel synthesis without side reactions. The Diels-Alder cycloaddition between furan and maleimide functionalized polymers was ameliorated by replacing the furan-moiety with a more electron rich methyl-furan group, resulting in a faster rate of reaction. A series of experimental and computational studies elucidated the factors contributing to the more rapid gelation kinetics, thus enabling the cytocompatible encapsulation of cancer cells.In order to investigate cellular invasion in glioblastoma, we designed a hydrogel conducive to cell invasion by incorporating extracellular matrix (ECM) components upregulated in tumour tissue into the hydrogel. We found that GNS cell lines invade into this material similarly to the way they would in patients. We characterized protease- dependent and independent processes, as well as focal adhesion pathways to be at play in our system. Moreover, we performed bulk-RNA sequencing on cells migrating in the hydrogel and found the invasion process to coincide with apoptotic, stress-response, and immunoregulatory signalling. In order to target cell invasion in glioblastoma, we tested a novel therapeutic platform against the invasion phenotype in our hydrogel model. We exploited the endosomal escape mechanisms of the bacterial toxin, diphtheria toxin, and transformed it into a delivery platform for antisense oligonucleotide therapeutics, specifically, siRNA targeting integrin beta 1. We showed that by targeting an invasion-related gene, a phenotypic change in invasion can be quantified using the hydrogel model developed herein.

Advisor: Shoichet, Molly S
Development of New Methods to Control Redox Conditions in High-pressure Experiments and their Application to Study Ore Metal Solubilities in Sulfur-bearing Magmatic Fluids

This thesis perfected the method of admixing calculated amounts of H2 gas to the argon pressure medium to impose desired fO2 values in hydrous experiments. Using CoPd alloy redox sensors, the method was shown to be accurate within 0.3 log units for the P-T range of 960 – 2060 bar and 800 – 1100⁰C. The rate of progressive oxidation caused by diffusive H2 loss through the Molybdenum Hafnium Carbide (MHC) pressure vessel walls was determined experimentally and the hydrogen permeability constants of the MHC alloy were calculated. At T = 1000⁰C, fO2 at water saturation increased about 0.36 log units/day, and this value approximately doubled for every 100oC increase in T. A prototype MHC pressure vessel apparatus was developed that can be used with a modified Shaw membrane to impose fO2 precisely and accurately while maintaining rapid quench capability. It was shown that 95% of the imposed hydrogen pressure is attained inside the pressure vessel within 2 hours from the start of the experiment at 800 – 1000⁰C, after which a steady state equilibrium is established. Experiments comparing redox-dependent Cu solubilities in silicate melts at fO2 imposed by redox buffers and identical target fO2 imposed by the hydrogen membrane confirmed consistency between the two methods within 0.3 log units fO2 deviation at T=1000⁰C and P=2000 bar. Experiments using Fe(II)-Mg exchange between olivine and water-saturated melt to constrain Fe3+/Fetotal ratios in the silicate melt yielded results mostly consistent within 1σ error with those predicted by the equation of Kress and Carmichael (1991). The relationship between exchange coefficient of Fe-Ti between magnetite and silicate melt (K_(d,Fe-Ti)^(magnetite/melt)) and fO2 in hydrous mafic magmas was also constrained. Using the new experimental apparatus, the solubilities of Cu, Ag and Au in S-rich Cl-bearing magmatic fluids were determined at T = 900 ⁰C and P = 2000 bar covering a wide range of fO2 from NNO – 0.5 to NNO + 2.5 with 7 steps in-between. Thermodynamic model calculations were performed using the HCh software to determine the dominant species of the metals in the fluids.

Keywords: magmatic fluids
MHC alloy
porphyry
Pressure vessels
redox
sulfur
Advisor: Zajacz, Zoltan
An Aware and Strongly-coordinated Multi-robot System for Finding Multiple Dynamic Users in Human-centered Environments

Socially assistive robotics considers robots helping people via social interactions. With technological advancements over the past few decades, there has been an increase in the number and types of socially assistive robotic applications. However, these applications have focussed on scenarios in which people begin collocated with the robot. Yet, in real-world environments, people go about their day-to-day lives and robots must first find users prior to assisting. To address this limitation, this thesis considers the multi-robot person search problem, defined herein as the person search team orienteering problem (PSTOP). The PSTOP considers dynamic users with changing locations during the search, a team of robots that may need to search a region multiple times, and a specified search time frame. User locations are modelled by novel activity probability density functions (APDFs) using past location data. The APDF is the only existing model which can determine the probability of a user occupying a region by considering when the region was previously searched. A two-stage multi-robot person search system (2-MRPSS) is introduced to generate team plans specifying when and for how long to search regions. The 2-MRPSS is the only planner which can consider user location data when determining repeated searches of a region. The 2-MRPSS is also the only existing planner which reasons about past user location data, while being both aware and strongly-coordinated. Moreover, this thesis is the first to deploy a multi-robot multi-user person search in a real-world human-centered environment by using a novel centralized architecture to oversee the generation, execution, and monitoring of the team plan. Within the architecture, this thesis introduces a novel low-cost information gathering technique and a navigation technique that adheres to human-etiquette. Simulations have been conducted to evaluate the theoretical contributions of the thesis and experiments have been conducted to evaluate the practical contributions of the thesis. The simulations show that the proposed approach finds more target users than existing state-of-the-art techniques. The experiments show that the architecture, information gathering, navigation, and 2-MRPSS can be used to successfully perform the multi-robot person search in a real-world human-centered environment.

Keywords: Human-Centered Environments
Min-Max Multi-Traveling Salesperson Problem
Multi-Period Multi-Knapsack Problem
Multi-Robot Coordination
Multiple Dynamic People
Search Within a Deadline
Advisor: Nejat, Goldie
The Effect of Vegetation on Student Achievement in the Toronto District School Board

This dissertation builds on past research that has demonstrated positive and significant correlations between student achievement and vegetation. My research extends The Biophillia Hypothesis, which posits that humans receive psychological benefits from being near vegetation, by hypothesizing that schools with greater amounts of nearby vegetation will have better academic outcomes than schools with lesser amounts of vegetation, controlling for key confounders. Data come from student standardized test scores and demographic, obtained from the Toronto District School Board (TDSB) and from measures of satellite images of vegetation surrounding each school, obtained from the Canadian Urban Environmental Health Research Consortium (CANUE). Initial analyses using Pearson’s correlations and OLS regression show positive relationships between vegetation and achievement similar to those found in previous research. However, this dissertation also engages in a unique attempt to investigate whether vegetation has causal effects on school achievement, exploiting a natural experiment made possible by a large ice storm that hit Toronto in 2013 and destroyed approximately 20% of the city’s tree canopy. Several spatial and descriptive statistics were carried out, including Moran’s I, and long-term vegetation change measurements, to examine whether the ice storm was a significant and random event. Fixed Effects (FE) regression models were run to investigate whether proportions of students who met provincial standards in standardized tests dropped due to vegetation loss after the ice storm. These models test for causal impacts of vegetation by comparing levels of achievement before and after the ice storm while controlling for measured confounders such as school-level SES, as well as unmeasured and time-invariant confounders like school climate and culture. Descriptive statistics and OLS regression reveal mixed associations between vegetation and school achievement, while FE regression models did not yield consistent or significant results in support of the initial hypothesis. Implications of these findings for future research are discussed.

Keywords: Achievement
Fixed Effects
NDVI
Vegetation
Advisor: Davies, Scott