VictorJuiz/thesis huggingface dataset:
Facile Grown Native Oxide Based Passivation of Crystalline Silicon: A Novel Approach for Low-Temperature Synthesis of Silicon Photovoltaics

Passivation of the crystalline silicon surface is central to the attainment of high-efficiency silicon solar cells and even more so as the silicon absorber is thinned. Moreover, the current predominantly high temperature processing of thin silicon wafers gives rise to defect migration-creation and thermal stresses in a typical multi-layered photovoltaic (PV) device. The development of a simple and effective low temperature passivation scheme would aid immensely in the synthesis of next generation low-cost high-efficiency thin silicon solar cells. This research proposes, investigates and demonstrates the efficacy of a novel low-temperature passivation scheme for crystalline silicon surface which consists of a facile grown native oxide (SiOx) layer and a silicon nitride (SiNx) over layer. A systematic experimental study of the interfacial passivation quality reveals that high quality surface passivation is obtained at a saturation native oxide thickness of ~10Å. The passivation quality is uniform over a large silicon surface with a surface recombination velocity (SRV) of 8 cm/s. Recombination modelling of the interface shows that the interfacial defect density diminishes with increasing native oxide thickness while the trapped charge density is essentially unchanged. In light of the new passivation scheme, this research investigates theoretically and experimentally a legacy photovoltaic cell concept, the Back Amorphous-Crystalline silicon Heterojunction (BACH) PV device, and proposes a novel PV cell concept - the Lateral Inherently Thin (LIT) amorphous-crystalline silicon heterojunction PV device. Benchmarked theoretical studies of the devices, using Sentaurus - a device modelling code, indicate a maximum BACH cell and LIT cell efficiency of 24.4% and 23.9%, respectively, for a 100µm thick textured cSi substrate with attainable (10 cm/sec) passivation quality. BACH and LIT PV devices, integrating the new facile grown SiOx passivation scheme, were fabricated using n-type double-side polished 280µm thick (100) FZ cSi wafers. An optimal untextured cell efficiency of 16.7% and 11.6% are obtained for a 1 cm2 BACH and LIT devices, respectively, under AM1.5 solar irradiation. Development of the high quality facile grown oxide based passivation scheme, a paradigm shift relative to conventional thermal oxide passivation, paves the path for low-temperature synthesis of oxide-based high quality semiconductor devices on thin silicon - including high-efficiency silicon photovoltaics.

Keywords: Solar Cell
Crystalline Silicon
Amorphous Silicon
Passivation
Back contact
Photovoltaic
BACH
LIT
Native oxide
PECVD
Silicon nitride
Low temperature
Advisor: Kherani, Nazir P.
Deciphering X-chromosome inactivation and the role of MECP2e1 in Rett Syndrome patient induced pluripotent stem cells

Rett Syndrome (RTT) is a neurodevelopmental disorder that affects girls due primarily to heterozygous mutations in the gene encoding methyl-CpG binding protein 2 (MECP2). MECP2 encodes four exons that are alternatively spliced into two isoforms, MECP2e1 and MECP2e2. MECP2 isoform-specific functions are unknown, but due to the higher abundance in the brain and MECP2e1-specific mutations associated with RTT, MECP2e1 is hypothesized to be the functional isoform in the brain. MECP2 is an X-linked gene subject to random X-chromosome inactivation (XCI) resulting in mosaic expression of mutant MECP2. The lack of readily accessible human brain tissue motivates the need for alternative human cellular models to study RTT. In this thesis, I established a novel human in vitro model of RTT by isolating human induced Pluripotent Stem cells (hiPSCs) from RTT patient fibroblasts. RTT-hiPSCs retained the MECP2 mutation, are pluripotent and fully reprogrammed, and retained an inactive X-chromosome in a nonrandom pattern. Taking advantage of the latter characteristic, I obtained a pair of isogenic wild-type and mutant MECP2 expressing RTT-hiPSC lines that retained this MECP2 expression pattern upon differentiation into neurons. Phenotypic analysis of mutant RTT-hiPSC-derived neurons demonstrated a reduction in soma size compared with the isogenic control RTT-hiPSC-derived neurons from the same RTT patient validating RTT-hiPSC-derived neurons for disease phenotyping. To further understand the role of MECP2e1 in RTT, I took advantage of RTT-hiPSCs carrying a MECP2 mutation that specifically disrupts MECP2e1 while MECP2e2 remains intact (RTTe1). RTTe1-hiPSC-derived neurons exhibited a soma size defect compared to wild-type neurons. Furthermore, this phenotype was rescued by MECP2e1 vectors in a cell autonomous manner suggesting that disruption of MECP2e1 alone is sufficient to cause a cellular RTT phenotype. Altogether, in this thesis, I isolated mutant and isogenic control RTT-hiPSCs by taking advantage of their unique XCI pattern. Upon differentiation, mutant RTT-hiPSC-derived neurons exhibited a RTT phenotype compared to isogenic control hiPSC-derived neurons from the same patient. Analysis of mutant and isogenic control hiPSC-derived neurons represents a novel human in vitro model for understanding the pathogenesis of RTT and the role of MECP2 and its isoforms in human neurons.

Keywords: Rett Syndrome
Induced Pluripotence
Advisor: Ellis, James
The Dark and Bright Sides of Anxiety: A Comprehensive Examination of the Relation between State Anxiety, Trait Anxiety, and Job Performance

Research has consistently tapped into a “dark side” of anxiety by demonstrating that anxiety has a negative relation with performance, while neglecting to consider the possibility of a “bright side” of anxiety by examining whether anxiety can benefit performance. The purpose of this research was to conduct a comprehensive examination of the anxiety and job performance relationship by considering the potential for a dark and bright side. First, I developed a dual-process model of anxiety outlining the process through which state and trait anxiety might lead to debilitative and facilitative job performance. Drawing from Interference Theory (Wine, 1980), I predicted that anxiety leads to debilitative performance through off-task cognition. Drawing from the Integrative Resource Model (Kanfer & Ackerman, 1989), Processing Efficiency Theory (Eysenck & Calvo, 1992), and Attentional Control Theory (Eysenck, Derakshan, Santos, & Calvo, 2007), I predicted that anxiety leads to facilitative performance through self-regulatory processing. Second, guided by motivation theory (Vroom, 1964), I extended my theoretical model by specifying a condition under which anxiety might lead to debilitative and facilitative performance. Specifically, motivation is predicted to moderate the relationship between anxiety and off-task cognition, and between anxiety and self-regulatory processing. Two controlled laboratory experiments tested the overall model. Experiment 1 consisted of a simulated work environment with 306 participants. Experiment 2 consisted of a similar work simulation with 327 participants. In both experiments, trait anxiety was assessed through self-report, three levels of state anxiety were induced in participants, and performance on in-basket tasks was examined. Experiment 2 also manipulated two levels of motivation. Findings do not support a bright side of anxiety and suggest that the dark side of anxiety is quite robust. Both trait and state anxiety led to higher levels of off-task cognition, which led to lower performance. Both trait and state anxiety led to lower levels of self-regulatory processing, which led to higher performance. Experiment 2 extended these results by finding that motivation buffered the relationship between state anxiety and self-regulatory processing, and between state anxiety and off-task cognition. Motivation did not have an effect for trait anxiety. Contributions and practical implications are discussed.

Keywords: Anxiety
Job Performance
Motivation
Advisor: McCarthy, Julie
Three Essays on the Impact of Geographic and Social Proximity on Innovation

The ability of an economy to generate and diffuse ideas has a profound influence on its ability to sustain growth. Our understanding of a key economic phenomenon behind agglomeration and modern growth - localization economies - relies on basic assumptions about how knowledge is recombined locally versus over distance. Whereas scholars have extensively studied the effects of proximity on the diffusion of ideas, the micro-foundations of knowledge recombination remain undeveloped. In particular, we know surprisingly little about how geographic, social and knowledge proximity shape the way ideas are generated, recombined, and discovered by others. In the first study, I provide novel empirical evidence grounded in an original theoretical framework to explain how the composition of near-neighbor scientists influences the direction of inventive activity. Co-located individuals are more likely to engage in low expected value but high variance payoffs interactions ("water cooler"). To address endogeneity concerns due to selection into co-location and matching, I exploit an unexpected random relocation of scientists due to asbestos removal at UPMC Paris. Results are consistent with the theory and shed light on how proximity affects innovation: random versus chosen co-location leads to higher levels of experimentation, and has a positive impact on breakthrough ideas for collaborations across academic fields. In the second study I explore the decline in collaboration that follows the separation of previously co-located co-authors. Not all co-author pairs are equally affected by an increase in geographic distance, as social proximity substitutes for it when the returns to collaboration are high. Collaborations that bridge otherwise disconnected communities of experts are the most negatively affected by separation. Finally, the third study examines how social and geographic proximity affect the discovery and funding of creative projects in online crowdfunding. Whereas the internet reduces many distance-related frictions, local and distant investors exhibit different investment patterns. The distance effect is explained by investors who likely have a social relationship with the entrepreneur, and does not persist after the first investment (i.e., it is likely driven by search costs). Thus, crowdfunding seems to eliminate many distance-related frictions, but not those related to social interactions.

Keywords: microgeography
idea recombination
low-opportunity cost time
colocation
proximity
Advisor: Ajay, Agrawal
Ambivalent Visions: Dreams, Bereavement, and Belonging in Contemporary Canadian Memoirs

This study examines the prominent intersections between dreams, representations of bereavement, and negotiations of social and geographic belonging in ten contemporary Canadian memoirs. Dreams are a remarkably common device in the genre, most often appearing in accounts of family members' deaths or staging encounters with deceased others and originary landscapes. I argue that these dreams operate as ambiguously authorizing and paradoxically reassuring spaces of contradiction and reconnection that convey the ambivalence of contemporary responses to death and displacement. As such, I suggest that dreams are prevalent in memoirs because they align with the genre's characteristic focus on personal and social relationships and its irresolvable tensions between representations of self and other, private and public, and desire and detachment. The four chapters theorize dreams through the lenses of bereavement studies, elegy studies, diaspora studies, and body and affect studies, considering how they adapt the conventions of literary modes such as dream-vision, elegy, and pastoral to address contemporary concerns. Chapter One argues that memoirs frequently link premonitory dreams, deathbed visions, and dreams of the dead in 'narratives of dying' that assert the possibility of continued subjectivity after death, with reference to memoirs by Daphne Marlatt, Wayson Choy, and Philip Roth. Chapter Two considers the similarities between the use of dreams in memoirs and poetic elegies, analyzing memoirs and poetry by Lorna Goodison and Patrick Lane to argue that dreams problematize the possibility of speaking for the dead and act as a form of elegiac compensation in both genres. Chapter Three examines diasporic memoirs by Wayne Johnston, Janice Kulyk Keefer, and Michael Ondaatje, theorizing the circumscribed, originary landscapes depicted in dreams as sites of simultaneous nostalgia and irony, reminiscent of complex forms of the pastoral. Finally, Chapter Four argues that memoirs' tendency to privilege embodied and affective responses to dream experience enables memoirists such as Choy, Rudy Wiebe, and Sharon Butala to claim affective affiliations that extend beyond the family. Ultimately, this study posits that dreams’ ability to articulate relational tensions within a solipsistic psychological form offers a strategically non-committal and open-ended way of representing loss and belonging in contemporary Canadian memoirs.

Keywords: Memoir
Dreams
Visions
Bereavement
Mourning
Displacement
Advisor: Goldman, Marlene
Inferring Body Mass in Extinct Terrestrial Vertebrates and the Evolution of Body Size in a Model-Clade of Dinosaurs (Ornithopoda)

Organismal body size correlates with almost all aspects of ecology and physiology. As a result, the ability to infer body size in the fossil record offers an opportunity to interpret extinct species within a biological, rather than simply a systematic, context. Various methods have been proposed by which to estimate body mass (the standard measure of body size) that center on two main approaches: volumetric reconstructions and extant scaling. The latter are particularly contentious when applied to extinct terrestrial vertebrates, particularly stem-based taxa for which living relatives are difficult to constrain, such as non-avian dinosaurs and non-therapsid synapsids, resulting in the use of volumetric models that are highly influenced by researcher bias. However, criticisms of scaling models have not been tested within a comprehensive extant dataset. Based on limb measurements of 200 mammals and 47 reptiles, linear models were generated between limb measurements (length and circumference) and body mass to test the hypotheses that phylogenetic history, limb posture, and gait drive the relationship between stylopodial circumference and body mass as critics suggest. Results reject these and instead recover a highly conserved relationship that provides a robust method to estimate body mass in extinct quadrupedal tetrapods. The constrained model is then used to derive a mathematical correction that permits the body mass of bipedal taxa to be estimated from the quadrupedal-based equation. These equations thus form the empirical baseline dataset with which to assess the accuracy of mass estimates derived from volumetric reconstructions, which, although subjective, are crucial for interpreting biomechanical and physiological attributes in extinct forms. The models developed through this research provide accurate and consistent estimates of body size in terrestrial vertebrates, with important implications for generating large datasets aimed at reconstructing macroevolutionary patterns of body size in association with changing Earth systems.

Keywords: Evolution
Body Size
Body Mass Estimation
Limb Scaling
Volumetric Reconstructions
Dinosauria
Tetrapoda
Quadrupedal
Bipedal
Macroevolution
Adaptive Radiation
Cope's Rule
Island Rule
Ornithopoda
Hadrosauridae
Theropoda
Regression
Evolutionary Models
Mammalia
Reptilia
Aves
Advisor: Evans, David C.
Reisz, Robert R.
Characterization of the Zebrafish Logelei Mutant Reveals a Conserved Requirement for MED14 in the Maintenance of Stem Cell Populations

The Mediator Complex links the RNA polymerase II transcriptional machinery to enhancer bound regulatory factors that in turn establish and maintain cell fate. However, the in vivo consequences of loss of function of many Mediator subunits are largely unknown. Through positional cloning analysis we have identified med14, which encodes a tail component of the Mediator complex, as the gene affected in zebrafish logelei mutants. A slight developmental delay is noticeable by 1.5 dpf in med14 mutants and the gap in development compared to their wild-type siblings continues to widen thereafter. Ultimately, med14-/- embryos progress only as far as the long-pec stage (normally 2.0 dpf) by 3.0 dpf and expire before hallmark events of the hatching period commence (i.e. pectoral fin elongation and formation of the semi-circular canals). Interestingly, transcription is not broadly affected in mutants, with only ~2% of genes assayed by mircoarray being differential expressed relative to their wild-type siblings at 2.25 dpf (764/34858 with ≥ 2 fold difference). More striking still, there is little difference in cell death or proliferation despite the observed “arrest” in development. To gain further insight, RNAi knockdown of med14 in planarians was pursued. Homeostasis and regeneration assays implicate med14 specifically in maintenance of the planarian adult stem cell population. Further analysis of zebrafish embryonic stem cell populations suggests that this could be an evolutionarily conserved role. Finally, preliminary results of an expanded RNAi knockdown screen for multiple Mediator subunits (covering all structural Domains (Head, Middle, Tail and Kinase)), indicate that stem cell maintenance is a general property of the Mediator Complex in vivo. Taken together, these results reveal a specific function for Mediator in stem cell maintenance distinct from its role in general transcription.

Keywords: MED14
Stem Cells
Zebrafish
Logelei
Advisor: Scott, Ian
Mécanismes d’impasse communicative dans le drame familial chez Michel Tremblay, Marie Laberge, Jean Marc Dalpé et Michel Marc Bouchard

Résumé En partant de l’hypothèse qu’il existe, dans le discours dramatique, pris au sens large, un phénomène de piège relationnel qui se produit au sein du conflit familial dramatisé par Michel Tremblay, Marie Laberge, Jean Marc Dalpé et Michel Marc Bouchard, je propose un modèle d’analyse d’interaction conflictuelle qui permet de cerner les composantes de ce phénomène. Dans le premier chapitre de cette thèse, il s’agit du développement de ce modèle. Je m’appuie, en premier lieu, sur les travaux de l’école de Palo Alto, dont la théorie de la communication paradoxale (la « double contrainte » et le « jeu sans fin » et, en deuxième lieu, sur la recherche sur le discours au sens large, c'est-à-dire linguistique et pragmatique, de Austin, Searle, Grice, Ducrot, Brown et Levinson et Kerbrat-Orecchioni, pour ne nommer que ceux-ci. Menée à l’intérieur des paramètres établis par la sémiotique théâtrale, telle que développée par Elam, Ubersfeld, Pavis, Ryngaert et Rosen, entre autres, ainsi qu’à l’intérieur de ceux proposés par l’analyse sociologique et psychanalytique (Goffman, Monroy et Fournier, Jackson, Watzlawick, Leiper et Kent), mon étude de la dynamique interrelationnelle montrera la nature et la fonction de ce que j’appelle « l’impasse communicative », ses trois mécanismes de « conflit dialogal », de « recours monologal » et de « gestualité agonale », ainsi que leurs effets pathétiques sur le moteur dramatique des pièces choisies. Afin de mettre en valeur ce modèle et d’effectuer une analyse approfondie des éléments verbaux et non verbaux de l’interaction conflictuelle, dans les trois chapitres suivants, je procède à l’étude textuelle de cinq pièces à partir de chacun des mécanismes de l’impasse. Dans le chapitre cinq, j’applique mon modèle de l’impasse communicative à l’analyse de l’objet scénique dans la dernière pièce de mon corpus pour montrer le rôle fonctionnel qu’il joue dans la perpétuation du conflit qui écrase les personnages. Dans le contexte de cette étude, les interactions révèlent l’existence d’un cercle vicieux de comportements agonaux qui charpentent les interrelations de sorte que les personnages pérennisent le conflit, produisant une dynamique de piège sans issue.

Keywords: Impasse communicative
Impasse
Communication
Palo Alto
Résistance à la transformation de la relation
Conflit familial
Conflit dialogal
Recours monologal
Gestualité agonale
Family Systems Theory and Literary Study
Chronémique
Proxémique
Littérature québécoise et canadienne-française
Théâtre québécois et canadien-français
Michel Tremblay
Marie Laberge
Jean-Marc Dalpé
Michel Marc Bouchard
Dominé
Dominant
Mécanismes d’impasse communicative
Face négative
Face positive
Signes opaques
Objet scénique
Piège relationnel
Communication impossible
Incommunicabilité
Manque de communication
Monologue
Dialogue
Geste
Attitude
Posture
Advisor: O'Neill-Karch, Mariel
Mapping Worm-Bioavailable Chemical Space for Improved Probe Discovery and Characterization with Caenorhabditis elegans

Small molecule modulators of protein activity are powerful reagents to probe the biology of living systems. Small molecules have been used repeatedly to uncover protein functions that were otherwise hidden from more conventional approaches. One way to find new small molecule probes is to screen libraries of chemicals for those that induce phenotypes in model organisms. Chemical screens in yeast, worms, fish, and plants have all resulted in the discovery of novel probes of protein function. The nematode worm Caenorhabditis elegans has great potential for the discovery and characterization of small molecule probes. Its small size, ease of culture, and genetic tractability make this animal amenable to high‐throughput chemical screens, as well as mode-of-action studies of newly identified bioactives. One drawback to using C. elegans as a screening tool for novel small molecule probes is its resistance to pharmacologically active drug‐like compounds. Given its extensive xenobiotic defenses, poor bioavailability may explain this resistance. Indeed, there are a number of bioactive compounds that are ineffective when applied to whole worms that perturb their target proteins in dissected animals. Thus, target access is likely a major limiting factor for pharmacological efficacy in C. elegans, although this idea has never been tested. In this thesis, I describe a novel HPLC‐based method for measuring the accumulation of exogenous compounds in worms, and I use this method to test the accumulation of hundreds of drug‐like molecules in C. elegans. I show for the first time that worms resist drug‐like compound accumulation, and that accumulation is generally required for bioactivity. I describe the construction of a computer‐based tool that can identify worm‐bioavailable molecules, and I highlight structural features that influence accumulation. I show that screening worm‐bioavailable molecules increases the bioactive discovery rate of C. elegans chemical screens. Next, I describe novel bioactive heterobiaryl amide compounds discovered through a C. elegans chemical screen. I apply insights gleaned from the mapping of worm‐bioavailable chemical space to facilitate their characterization, and preliminary data suggest that these compounds are agonists of the worm metabotropic glutamate receptor MGL‐1. Thus, the worm‐bioavailable chemical space I describe facilitates small‐molecule probe discovery and characterization.

Keywords: Caenorhabditis elegans
chemical genetics
Advisor: Roy, Peter