VictorJuiz/thesis huggingface dataset:
Nanostructured Electrocatalysts for CO2 Conversion

Renewables-powered electrochemical activation and conversion of water + CO2 into hydrocarbons and oxygenates could potentially offer a sustainable, low-net-emissions, route to produce many of the world’s most needed commodity chemicals and fuels. In this thesis I report progress in the synthesis, characterization, and computational modelling of electrocatalyst materials for the CO2 reduction reaction. I show how experiment, theory, and spectroscopy can be used together to uncover physicochemical phenomena; I build nanostructured materials to exploit these phenomena; and I integrate these materials into electrocatalytic systems. I first begin by examining the pathways toward industrial implementation of CO2 reduction technology. I give a brief technoeconomic analysis and carbon emissions assessment of certain valuable products. I then describe the concept of Field-Induced Reagent Concentration (FIRC) on gold nanoneedle catalysts. This entails the use of nanostructured morphologies to produce a high local electric field that attracts positively charged cations to stabilize CO2 reaction intermediates to produce CO with Faradaic efficiencies above 90% and overpotentials of 240 mV. I continue with a description of the potential for tandem catalysis between metal-organic frameworks (MOFs) and gold nanoneedles towards tuning CO2 reduction. Next, I describe how thin layers of amorphous sulfide-doped tin catalysts on top of gold nanoneedles can modulate CO2 reduction towards formic acid synthesis with Faradaic efficiencies of 93% and current densities of 55 mA cm−2 over 40 hours. I then demonstrate a new bottom-up synthesis, catalyst electro-redeposition, that allows simultaneous control over morphology and oxidation state of copper to produce ethylene selectively. I use a combination of spectroscopy and computational simulation to explain the electronic structure-property relationships of this new catalyst and report a partial ethylene current density of 160 mA cm–2 and an ethylene/methane ratio of 200. I conclude by describing emerging directions in the field including greater understanding of electrocatalyst evolution, inspiration from biology, and integration into electrolyzer systems. I discuss the wider relevance of nanostructuring as a means to control and enhance catalytic activity.

Keywords: CO2 Conversion
Electrocatalysis
Nanostructured Materials
Renewable Energy
Advisor: Sargent, Edward H
Mobile Phone-based Peer Support in the Prevention of Postpartum Depression Among Adolescent Mothers: A Pilot Randomized Controlled Trial

Background: Adolescent mothers are at three times greater risk for developing postpartum depression (PPD) compared to adult mothers. Lack of social support has been identified as a major risk factor for PPD among adolescent mothers. The objective of this parallel pilot randomized controlled trial was to evaluate the feasibility, acceptability and adherence of a mobile phone-based peer support intervention and obtain preliminary estimates of impact on clinical outcomes to inform a future definitive randomized controlled trial. Methods: Pregnant adolescents 16-24 years old were recruited from the community in Toronto, Canada and randomly allocated into either a mobile phone-based peer support intervention group or a usual care control group using sequentially numbered, opaque, sealed envelopes. Participants in the intervention group received support from a trained peer mentor by mobile phone (voice calling or text messaging) during their last trimester of pregnancy and 12 weeks postpartum. Primary outcomes measured implementation (feasibility, acceptability and adherence). Secondary outcomes measured preliminary effectiveness (depressive symptomatology, anxiety, social support and health service utilization). A research assistant blinded to group allocation collected outcome measures. Results: Forty pregnant adolescents (mean age 21.6, SD 1.8 years) were recruited (intervention n=21, control n=19). Primary outcomes: 33 participants (82.5%) completed outcome measures. A total of 121 contacts were made between participants and peer mentors, with the majority of contacts made by text message (n= 112, 92.6%). Overall, 100% of participants agreed or strongly agreed that they were satisfied with their peer support experience. Secondary outcomes: After controlling for baseline depressive symptomatology, participants in the intervention group demonstrated lower mean depression scores at 12 weeks postpartum compared to participants in the control group (F = 4.25, p = 0.048). There were no group differences in anxiety, social support or health service utlization. No adverse events were reported. Discussion: Mobile phone-based peer support may be a feasible and acceptable way to provide support to adolescents during pregnancy and in the postpartum period. Preliminary evidence suggests that the peer support intervention may be effective in preventing depressive symptomatology among adolescent mothers. A definitive randomized controlled trial with adequate sample size is warranted.

Keywords: Adolescent Mothers
Mobile Phones
Peer Support
Postpartum Depression
Advisor: Dennis, Cindy-Lee
A Study of Plurilingualism and Pluriculturalism Through the Lived Experiences of Three Young Adults in Multigenerational Homes

This qualitative study explored the lived experiences that contribute to plurilingualism and pluricultural identity for three young adults living in multigenerational homes. The research focused on the shared stories of the participants in regard to their language, culture, and identity. The timeline for the study was over various segments of the primary participant’s life, which began with her early bilingual language development as a child in the year 2000. Later, as a young adult, she explored her plurilingual and pluricultural identity through semistructured interviews and stimulated recall (SR). Data for the other two participants were collected over a three month period through one-on-one semistructured interviews. The participants all lived in multigenerational homes, where both Italian and English were spoken. Additionally, all participants received varying amounts of French language instruction at school. At the conclusion of the interviews, data were analyzed through the use of thematic analysis. The themes explored were: family, in particular grandparents; language; and identity. The study found that positive relationships with family and extended family present in the home was a significant factor in the development of plurilingual and cultural identity for all three participants. Greater linguistic ability did not necessarily lead to greater language confidence, nor greater plurilingual self-identification. The interconnectedness of language and the acceptance of the varying degrees of language competency within an individual’s language repertoire was also explored. The data led to the conclusion that all three participants had found a way in which to be both Canadian and Italian in Alberta. Participants shared experiences in which they viewed their identity as linked to more than one language and culture. While the study allowed for a detailed view into which experiences impacted on the development of plurilingual and pluricultural identification, more attention to plurilingualism is needed in order to further develop the research concerning the topic.

Keywords: French Immersion
Identity
Multigenerational
Pluriculturalism
Plurilingualism
Advisor: Piccardo, Enrica
Externalities of Corporate Financial Information and Financial Intermediaries in the Secondary State-Bond Market

This study provides the initial evidence on the roles of corporate financial information and financial intermediaries in the secondary state-bond market that is often characterized by informational opacity. In the first chapter, I investigate the informational role of statewide aggregate earnings and find that corporate-earnings changes that are aggregated at the state level are positively associated with state-bond returns. This finding suggests that statewide aggregate earnings provide bondholders with real-time signals about regional economic performance. In cross-sectional analyses, I show that the effect is especially pronounced when bondholders face greater agency costs, higher credit exposure, and greater information opacity, when corporate earnings are ex-ante more relevant to states’ economic performance, and when corporate managers and business media disseminate earnings news more extensively. In the second chapter, I further examine whether analyst following and media coverage affect the bargaining power over state-bond dealers for small retail state-bond investors, a group that is severely disadvantaged in the over-the-counter market. I find that analyst following and media coverage on local public firms are negatively associated with the small trade premium in the secondary state-bond market, suggesting that financial analysts and the business media provide unique value in facilitating retail state-bond investors' information discovery process. In cross-sectional analyses, I show that this effect is especially pronounced when public firms’ information is ex-ante more precise to states’ economic performance, and mitigated when issuers’ disclosures are more accessible to retail investors. Taken together, the evidence is suggestive of positive externalities of public companies and their financial intermediaries that extend beyond the corporate sector to the state-bond market.

Keywords: Aggregate Earnings
Externalities
Information Transfer
Regional Economic Signals
Secondary State-Bond Market
Small Trade Premium
Advisor: Hope, Ole-Kristian
Negotiating Subjectivities Through Literature: Anticolonial Counternarrative Fiction Book Clubs and Their Possibilities

“Tired of reading straight, racist, colonial fiction?... Want to read meaningful anti-colonial fiction that disrupts racism on Turtle Island?” This is the call I put out to engage participants in this anticolonial book club research project. Reading two books together, I asked: How do five racialized women and one Indigenous woman negotiate their subjectivities during processes of reading anticolonial fiction? This research question was the aim of the project, but the anticolonial political commitments are at the foundation of the anticolonial feminist literacy theoretical framework and feminist Deleuzian methodology used. As a queer, white, settler researcher and educator, I created the project with a desire-based lens, in order to focus on the subversion, persistence, and thriving in the feminist anticolonial space. I recruited the six women with two main goals: examine how reading anticolonial fiction can help facilitate the negotiation of subjectivities and examine how reading fiction that is not white settler colonial in nature can create generative spaces for people to thrive. Using the feminist Deleuzian methodological framework through the anticolonial feminist literacy theoretical lens allowed me to focus on the hot spots of the data that arose in the book club conversations, one-on-one meetings, and reading journals. Focusing on these hot spots, or what ‘glowed,’ I explain how reading and language are embodied processes and allowed one participant to continue becoming bilingual-immigrant-racialized-woman in ways that resist molar/static understandings of her subject positions and a more liveable life. Focusing on a second hot spot, I explain how reading anticolonial counternarrative fiction enabled a space for deep self-reflection which helped the participants build trust in their subject positions and experiences of marginalization, which allowed them to create a new consciousness outside of white settler colonial discourses. In the last data chapter, I explain how this anticolonial book club created an anticolonial community of care to walk alongside Indigenous resurgence initiatives through feminist solidarity and horizontal comradeship. Walking alongside Indigenous resurgence is always contextual, but this research project shows one way in which this is possible in a non-reactionary, productive way.

Keywords: Anti-colonialism
Book Club
Constitutive Subjectivities
Feminist Deleuzian Methodology
Indigenous Resurgence
white settler colonial discourse
Advisor: Sykes, Heather
Integrated Genetic and Epigenetic Profiling of Wilms Tumors and Beckwith Wiedemann Syndrome

Wilms tumor is the most common renal tumor arising in childhood. Although cure rates are high, several clinical difficulties remain including the fact that a subset of children may receive more chemoradiotherapy than is required to cure their disease, that there are few options available for patients who relapse, and that surgical treatment for bilateral disease can increase the risk of renal failure. As well, identification of children who are predisposed to Wilms tumor can be difficult and imprecise. Although certain congenital syndromes such as Beckwith-Wiedemann syndrome are well-described to predispose to Wilms tumors, it is unclear what the exact magnitude of the risk is for each child with the syndrome. My thesis approaches these issues by exploring the genomic and epigenomic landscape of Wilms tumors. I hypothesize that Wilms tumors comprise of several distinct subgroups each with distinctive molecular and clinical features that can be used to predict clinical outcomes. I focus first on DNA methylation as multiple lines of evidence indicate that DNA methylation is dysregulated in Wilms tumor but has not been fully explored. RNA expression data are then explored in the context of these epigenetic features. The relationship between genetic features that have previously been described in the disease to epigenetic and expression profiles are also investigated. I describe a combination of genome-wide DNA methylation and RNA expression profiles that define three distinct subgroups of Wilms tumors with different clinical features and with implications for the development of the disease. I also explore the utility of using epigenotypes in Beckwith-Wiedemann Syndrome to delineate tumor risk and enumerate drawbacks to utilizing such an approach clinically.

Keywords: Beckwith Wiedemann syndrome
DNA methylation
Epigenetics
Molecular profiling
Next generation sequencing
Wilms tumor
Advisor: Weksberg, Rosanna
Discovery of Novel Human Biomarkers using Variable Lymphocyte Receptor Antibodies of the Sea Lamprey

Diversity, specificity, and memory are the fundamentals of vertebrate immunity – an intricate system that arose in response to the necessary cohabitation of vertebrates with the most ancient forms of life as we know it, namely microbial life. Although microorganisms are a cause of disease, another critical postulate or determinant is the capacity or capability of one’s immune system. In other words, the same pathogen will not be harmful to all individuals and disease can arise from the immune system itself. Notably, cancer, autoimmunity, and viral infection expose the limitations of human immunity. Not unlike how we observe interindividual variation in disease susceptibility and immune capacity, differences are amplified when we compare different species. Can the strengths of an alternate immune system address the restrictions of ours?   Recently, immunologists have acknowledged that organisms as evolutionarily distant as jawless vertebrates are also endowed with adaptive immunity. Pancer and colleagues were the first to elucidate the molecular origins of adaptive immunity in a lamprey. Adaptive immunity in this jawless fish functions through cells and mechanisms of shared ancestry with those of other vertebrates. In stark contrast however, lampreys rely upon distinct antigen receptors analogous but not homologous to T cell receptors and immunoglobulins. For research and therapeutic purposes, lamprey antibodies are potentially novel tools that may target markers of disease not readily recognized by mammalian immune systems and to which immunoglobulin antibodies are not easily elicited. We hypothesize that the evolutionary distance separating sea lampreys and humans, as well as the unique architecture of lamprey variable lymphocyte receptor antibodies can address tolerogenic constraints of mammalian immune systems, and structural constraints of immunoglobulins. Here, we detail strategies for isolating serum biomarker-specific variable lymphocyte receptor antibodies that may detect, diagnose, or prognose disease. Additionally, we characterize the variable lymphocyte receptor VLRB N8 antibody whose binding specifically to antigen-experienced human B cells is unlike that of any known antibody. Thus, we have described a potential plasma and memory B cell-specific modification of human leukocyte antigen class I, the antigen bound by VLRB N8, and gained insight into B cell biology.

Keywords: Adaptive Immunity
Antibody
Breast Cancer
Human Leukocyte Antigen (HLA)
Sea Lamprey (Petromyzon marinus)
Variable Lymphocyte Receptor (VLR)
Advisor: Ehrhardt, Goetz
Novel Optogenetic Approach Reveals a Function of cGMP in Synaptic Plasticity and Memory

Synaptic plasticity is the activity-dependent structural and functional modulation of the synapse, which is essential for learning and memory. These processes are regulated by signaling pathways involving cAMP and cGMP nucleotide messengers. cAMP signaling is associated with enhanced synaptic structure, function and memory at the hippocampus, but the exact role of cGMP remains elusive. Here, I use a novel optogenetic approach to study the role of cGMP in structural and functional plasticity in hippocampal neurons and memory in the dentate gyrus (DG). Strong synaptic activation induces synapse enlargement called structural long-term potentiation (sLTP), which is further enhanced by cAMP (cAMP-sLTP). By blocking the cGMP/PKG pathway, I demonstrated that postsynaptic cGMP signaling negatively regulates cAMP-sLTP. Using a two-photon optogenetic approach to activate a light-sensitive guanylyl cyclase at targeted dendritic spines, I revealed that an increase in postsynaptic cGMP was sufficient to suppress the cAMP effect on structural potentiation, but not induction of sLTP, suggesting a competitive bidirectional regulation of structural plasticity by cAMP and cGMP. To address the role of cGMP in synaptic plasticity and memory, I adapted the optogenetic technique to manipulate cGMP signaling in neurons of the DG, which is crucial for memory. I demonstrated that postsynaptic cGMP signaling at the perforant path synapses of the dentate gyrus (PP-DG) enhances functional synaptic potentiation. By utilizing a comprehensive battery of tests for mouse behavior, I also revealed that cGMP signaling is associated with enhanced anxiety and reference memory in mice. This project established a novel optogenetic technique for targeted cGMP manipulation and provided the first direct look at cGMP function from the level of the single synapse to the living mouse brain.

Keywords: cGMP
Memory
Optogenetics
Structural plasticity
Synaptic plasticity
Advisor: Okamoto, Kenichi
Magnetic and Topological Aspects of Spin Liquid Candidates with Strong Spin-orbit Coupling

Correlated transition metal compounds with strong spin-orbit coupling have been the subject of great interest to condensed matter physicists recently. They provide an excellent playground in which to explore various quantum phases of matter ranging from exotic magnetism to topological orders. In this thesis, we specifically focus on materials that can be effectively described by a total angular momentum j = 1/2 pseudospin degree of freedom owing to strong spin-orbit coupling. This j = 1/2 pseudospin degree of freedom serves as a building block with which it can be made possible to realize different quantum phases of matter. In particular, we study magnetic and topological aspects of Ir- and Ru-based transition metal compounds that are candidates for a material realization of the long-sought quantum spin liquid phase - a highly entangled state of matter in which the electrons’ spin do not magnetically order, or “freeze,” at low temperature. We begin by investigating possible quantum magnetic orderings arising in layered 2D triangular materials effectively described by j = 1/2 spins, and apply our findings to Ba_3IrTi_2O_9 . We then turn our attention to potential symmetry protected topological phases in single layers of α-RuCl_3 and A_2IrO_3 (A = Li, Na). Finally we show how it is possible to stabilize topological order in correlated honeycomb materials such as the Kitaev spin liquid candidate α-RuCl_3 . We conclude by considering potential avenues for future research.

Advisor: Kee, Hae-Young
Parameter Estimation for Systems of Ordinary Differential Equations

We consider the formulation and solution of the inverse problem that arises when fit- ting systems of ordinary differential equations (ODEs) to observed data. This parameter estimation task can be computationally intensive if the ODEs are complex and require the use of numerical methods to approximate their solution. The thesis focuses on ad- dressing a common criticism of the single shooting approach, which is that it can have trouble converging to the globally optimal parameters if a sufficiently good initial guess for the parameters is unavailable. We demonstrate that it is often the case that a good initial guess can be obtained by solving a related inverse problem. We show that gradient based shooting approaches can be effective by investigating how they perform on some challenging test problems from the literature. We also discuss how the approach can be applied to systems of delay differential equations (DDEs). We make use of parallelism and the structure of the underlying ODE models to further improve the computational efficiency. Some existing methods for the efficient computation of the model sensitivities required by a Levenberg-Marquardt least squares optimizer are compared and implemented in a parallel computing environment. The effectiveness of using the adjoint approach for the efficient computation of the gradient required by a BFGS optimizer is also investigated for both systems of ODEs and systems of DDEs. The case of unobserved components of the state vector is then considered and we demonstrate how the structure of the model and the observed data can sometimes be exploited to cope with this situation.

Keywords: Delay Differential Equations
Inverse Problems
Ordinary Differential Equations
Parameter Estimation
Sensitivities
Advisor: Enright, Wayne H