VictorJuiz/thesis huggingface dataset:
Structure-activity relationships in CO2 electroreduction catalysis

Developing structure-activity relationships in CO2 electroreduction catalysts is critical to rationally synthesizing electrode materials with improved performance. While many studies have drawn correlations between the activity, selectivity, and stability of a CO2 electroreduction catalyst and catalyst particle size, shape, composition, roughness, comparatively less had been established about how bulk defects influence surface reactivity. We hypothesized that bulk defects could stabilize reactive surfaces that persist through electrolytic conditions and alter the reactivity of more ordered surfaces. In this dissertation, we detail our efforts to obtain the first direct evidence that CO2 electroreduction in enhanced at the surface terminations of grain boundaries (GBs) and dislocations. We used scanning electrochemical cell microscopy (SECCM) to show that the surface terminations of GBs engender regions of enhanced CO2 electroreduction activity that can be several µms wide. The magnitude of enhancements appeared to depend on local GB structure and ranged between 10%-300% relative to the adjacent grains. In contrast, the competing H2 evolution reaction was relatively insensitive to the presence of these defects. Mapping the lattice deformation of the regions surrounding these bulk defects using electron diffraction suggested that the local density of dislocation surface terminations, instead of local lattice strain, were correlated to the observed enhancements. Beyond electroanalytical SECCM studies, we demonstrated the utility of engineering bulk defects in CO2 electroreduction catalysts by showing that mechanical treatment enhances CO2 electroreduction by introducing new GBs and dislocations, while the H2 evolution reaction remains relatively unaffected. In addition, we report the development and validation of a scanning electron microscope (SEM)-based technique to rapidly and accurately characterize the grain orientation and defect structure of polycrystalline nanoparticles, relieving a bottleneck imposed by the inaccessibility of existing grain mapping techniques. These studies establish a new structure space for electrocatalyst design and motivate the exploration of GB and dislocation engineering to develop improved catalysts for electrochemical transformations

Keywords: Chemistry.
Advisor: Kanan Matthew William
Chidsey Christopher E. D. (Christopher Elisha Dunn)
Dai Hongjie
Struggle, Rebellion, and Transformation: Disease and Patient Representation in Dying to Survive

Released in the summer of 2018, Wen Muye’s Dying to Survive generated heated discussion over China’s healthcare system among the Chinese audience. This paper examines the representation of disease and patients in Dying to Survive, analyzing how the film has reflected, critiqued, and challenged China’s medical and public health reality by bringing a real-life story to the big screen. Through a close analysis of individual patients appearing in the film, the paper demonstrates how the patients redefine the meanings of their life, death, and identity as they confront the disease and rebel against the dark reality blocking their chances of living. Additionally, the film suggests how the patient community may become a momentum of driving positive changes in the extant healthcare system by interacting with and making impacts on the thoughts of those beyond the patient community.

Keywords:  East Asian Languages and Cultures
East Asian Languages and Cultures
East Asian Studies
cancer
leukemia patients
disease metaphor
contemporary Chinese cinema
healthcare policy
medical humanities
Thesis
Advisor: Wang Ban
Student Loan Solutions: Modeling the Financial Impacts of Income Based Repayment

Student loan debt in the United States is a major source of hardship for a large portion of the population. As of September 2019, almost 45 million Americans had outstanding student loans, many with six-figure balances, and there was over $1.5 trillion in outstanding student debt. This paper uses a Copula approach to model income dynamics for college graduates across ages. By simulating incomes for a population- representative sample of student-borrowers, I am able to estimate the financial impacts of enrolling borrowers in the incumbent Income Based Repayment (IBR) plan. I find that enrolling all borrowers who benefit from enrollment would cost the United States federal government $227 billion, which is equivalent to the cost of an 18.3 percent cumulative default rate. In addition, the paper simulates a novel Income Driven Repayment (IDR) program for new borrowers, showing that such a program benefits student borrowers. Based on these findings, I argue that debt is an inherently flawed as a way to support higher education.

Keywords: Department of Economics
student loans
income-based repayment
copula
debt
debt-restructuring
Thesis
Advisor: Admati Anat
A study of laser ignition for hybrid propulsion systems

Hybrid propulsion systems have historically been precluded from finding application due to the extensive development and heritage of liquid and solid alternatives. However, an emerging market for small-satellites and a corresponding need for high performance micro-propulsion systems presents a unique opportunity for the development of small-scale hybrids capable of providing advanced maneuverability to these spacecraft both in Earth orbit and for interplanetary exploration. To that end, this thesis focuses on the development of a novel laser ignition system for these motors that can perform numerous motor restarts while minimizing system mass and volume. This research has pursued two primary goals. The first is in the development and verification of a theory that describes the laser-driven ignition process. This verification has been accomplished through high-speed imaging of the ignition process within an optically accessible combustion chamber. The second goal has involved the demonstration of this laser igniter as a restart-capable device, initially using a laboratory-scale hybrid motor and later with a flight-like hybrid motor in a vacuum chamber. Experimental investigations in the optically accessible combustion chamber resulted in the first images showing laser ignition of hybrid propellants. Restart ignition tests in representative hybrid motor geometries demonstrated the reliability of this technique

Keywords: Aeronautics and Astronautics.
Advisor: Cantwell Brian 
Senesky Debbie 
Wang Hai
Supporting critical computational literacies through interactive storytelling

This dissertation explores how pedagogical uses of interactive storytelling can support the development of youth critical computational literacies, in and out of school. Despite extensive documentation of inequities in K12 computer science education and numerous initiatives working to address them, we lack theoretical accounts and practical tools for how computing itself plays a role in marginalization and oppression. Meanwhile there are few opportunities for literacy educators and researchers, who are centrally concerned with the relationship between language and power, to participate in K12 computer science education. One barrier to interdisciplinary pedagogy and research has been the lack of shared constructs between literacy studies and the learning sciences. This dissertation proposes critical computational literacies as an interdisciplinary construct encompassing cognitive, situated, and critical scales of literacy practice, and the relationship of each scale of practice to the infrastructural media through which it is enacted. Critical computational literacies provides an account of identity authorship and channeling voices, two forms of critical action by which authors can transform literacies through participation to make room for their identities and for their voices. This dissertation focuses on a ten-week curriculum unit in a midwestern US sixth-grade classroom using Unfold Studio, a web application for reading and writing interactive stories written with a combination of prose and programming. Building on three years of participatory design-based research, this study used mixed methods to analyze how authors used affordances of text and code toward rhetorical and critical ends, how they used interactive storytelling to connect across literacies, and the extent to which literacy participation was associated with computer science learning. One primary contribution of the dissertation is an articulation of critical computational literacies grounded in constructs and methods which are important to both the learning sciences and to literacy studies. I show that interactive storytelling can be an effective medium for supporting critical computational literacies which connect youths' existing literacy practices to the classroom, and which support critical action through identity authorship and channeling voices. Unfold Studio and its curriculum are practical tools for teaching with interactive storytelling. Finally, the dissertation offers a theoretical justification for a literacy-based approach to K12 computer science education which centers youths' lives and stories, with empirical evidence of its efficacy

Keywords: Education.
Advisor: Barron Brigid 
Blikstein Paulo
Garcia Antero 
Pea Roy D.
Survival Through Internal Balancing in a Bipolar Environment: An Analysis of North Korea’s Missile Test as a Means of Projecting Balancing Power

Mearsheimer argued that in a bipolar world, a state’s option is to balance the threat externally. However, for states that are threatened by both great powers, the best course of action is internal balancing (self-strengthening) to maximize its self-interest between the great powers. North Korea’s geographical position presents an interesting example of a weaker state surrounded by great powers: China and the United States. North Korea’s acquisition of missiles and WMDs are a form of internal balancing. By understanding when North Korea tests its missiles, it is possible to observe when a state utilizes its success at internal balancing as a mechanism to pressure the great powers. This paper reports that North Korea is more likely to conduct missile tests when its relationships with the United States and China, independently, are weak. I propose that North Korea’s missiles acted as an internal balancing instrument; that missile tests are a method of projecting its success at self-strengthening to signal and instigate a change from the great powers during times of a corroding relationship.

Keywords:  Stanford Global Studies
Balancing
North Korea
United States
China
Missile Tests
Thesis
Advisor: Shin Giwook
Sustaining biodiversity in tropical agricultural landscapes

Anthropogenic lands now dominate much of the globe. While protected areas are critical in the fight against the 6th mass extinction, the conservation of many species will depend on the ability of these novel human landscapes to support life. This dissertation is an examination of the potential for tropical agricultural landscapes to preserve the many dimensions of biodiversity that exist outside of protected areas. I begin by using DNA metabarcoding to infer how the diversity and composition of trophic interactions between birds and their arthropod prey respond to variable land management practices in southern Costa Rica. I show that habitat heterogeneity, rather than the total amount of habitat available, may promote these feeding interactions, providing evidence that increasing landscape complexity is one potential mechanism to increase the diversity of resources available to birds. For the remainder of my dissertation, I take a temporal view to the structuring of tropical wildlife in forest and agricultural landscapes. To do this, I first quantify the role of climatic seasonality in structuring tropical biodiversity dynamics. I show that agricultural intensification degrades the rhythmic seasonal structuring of bird communities. In contrast, I show that diversified farming landscapes serve as an important seasonal habitat for both resident and migratory species. I next quantify population trends for several hundred bird species, and the influence of farming practices and climate change on the regulation of these dynamics. In particular, I provide the first empirical evidence that agricultural intensification and climate change act synergistically to drive population declines in tropical wildlife. Finally, I quantify the degree to which bird communities have changed over the past two decades in Costa Rican forests and agricultural landscapes. I find that communities in intensive agricultural habitats have changed substantially, with marked declines in species of conservation concern. I next show that, in part, these changes are driven by interactions between altered colonization-extinction dynamics, periodic climatic forcing, and species' climatic niches. Taken together, this dissertation demonstrates the potential for integrating biodiversity conservation with food production in tropical landscapes

Keywords: Biology.
Advisor: Fukami Tadashi
Daily Gretchen C.
Dirzo Rodolfo
Mordecai Erin
Synaptic functions of latrophilins and teneurins

The synapse is the fundamental unit of the brain that enables information processing within circuits of interconnected neurons. The molecular mechanisms of synapse formation and function are critical for brain development and function, in health and in disease. Synaptic cell-adhesion is an essential feature of synapses that has been shown to regulate synapse number, control synaptic properties and affect downstream behaviors. Careful study of the molecular participants in synaptic cell-adhesion and how they work to specify and regulate synapses is needed to reach a molecular-level understanding of the synapses underlying particular circuits and behaviors and may lead the way to novel therapeutic approaches for brain disorders. The latrophilins (Lphns) and teneurins (Tens) are two families of cell-adhesion molecules that are expressed at synapses and interact in a trans- conformation. The latrophilin isoforms Lphn2 and Lphn3 have been shown to be postsynaptic regulators of excitatory synapse number and transmission in mouse hippocampus that function in an input-specific manner, while various Ten orthologs have been shown to be important for proper axonal targeting and are capable of inducing postsynaptic structures in vitro. These data suggest that the latrophilin-teneurin interaction may be a critical mechanism underlying synapse formation and function, however much remains to be learned about how latrophilins and teneurins function at synapses. First, it is unclear if the principles of latrophilin function identified in the hippocampus hold true in other neurons and brain regions that exhibit different patterns of latrophilin expression. In addition, no rigorous studies of teneurin function at synapses in vivo have been performed to date. Finally, there is only limited evidence that latrophilins and teneurins act together to control synapse number and/or function from experiments performed at the same synapses in vivo. This dissertation will cover my progress in dissecting the functions of latrophilins and teneurins at synapses. In Chapter 1, I review in detail the importance of studying the molecular code of synaptic cell-adhesion and the literature to date on latrophilins and teneurins. In Chapter 2, I present a study of the functions of Lphn2 and Lphn3 at Purkinje cell synapses in the cerebellum, where I characterize the expression of Lphns in cerebellum and demonstrate that Lphn2/3 are redundant but essential for parallel-fiber synapse number and synaptic transmission. In Chapter 3, I detail introductory work dissecting the function of Ten3 at synapses between proximal CA1 to distal subiculum neurons, where I find that postsynaptic Ten3 in distal subiculum neurons is not important for maintenance of synaptic strength at synapses from proximal CA1. Taken together, this work expands on our understanding of latrophilins and teneurins as critical mediators of synapse number and function

Keywords: Molecular and Cellular Physiology.
Advisor: Südhof Thomas C. 
Chen Lu (Professor of neurosurgery) 
Ding Jun (Jun B.)
Synaptic neurexin-neurexophilin complexes : structural insights, mechanistic regulation by alternative splicing, and the search for the molecular organization of the brain

Abstract Our brains allow us to experience the world, think, and create. Revealing how the brain works is one of the most challenging frontiers in modern science. Yet learning exactly how the brain works is key to understanding cognition and curing neurodegenerative diseases. Recent advances in neurobiology have provided deep insight into how the brain works by deciphering molecular mechanisms of neuronal structure and function (e.g., molecular release of neurotransmitters, specification of synapse formation, and long-term potentiation). However, despite these breakthroughs, we still know very little about how the brain is organized at the molecular level. This work focuses on expanding our molecular understanding of the brain by revealing the molecular details of synaptic neurexin-- neurexophilin interactions. Here, I detail novel crystal structures of neurexin--neurexophilin complexes at near- atomic resolution. These structures consist of neurexophilin-1 in complex with splice variants of the second Laminin-Neurexin-Sex hormone-binding globulin (LNS2) domain of a-neurexin-1. The general architecture of these complexes consists of the b-sandwiches of each molecule essentially fused together to form one large contiguous b-sandwich—a form of protein--protein interaction unlike anything identified before. Furthermore, by combining these structures with biochemical binding experiments, I was able to reveal the molecular mechanism of how alternative splicing of a-neurexin at splice-site #2 modulates the affinity of the neurexin--neurexophilin complexes. These results mark an important step forward in our understanding of neurexin--neurexophilin interactions and how alternative splicing regulates protein--protein interactions. In addition to my structural work, I discuss preliminary binding data from my efforts to discover novel binding partners for neurexophilin-1. These data suggest novel binding partners for neurexophilin-1. Taken together, my structural data and binding data provide new insights into how the brain is likely organized at the molecular level of synaptic neurexin--neurexophilin complexes

Keywords: Molecular and Cellular Physiology.
Advisor: Brünger Axel T.
Südhof Thomas C.
Garcia K. Christopher
Shen Kang
Syntactic and semantic perspectives on first conjunct agreement in Russian

This dissertation is an investigation into the syntax and lexical semantics of the phenomenon of first conjunct agreement (FCA) as it occurs in Russian. An in-depth look at FCA sheds light on the structure of conjunction and its interaction with predicate-argument agreement, as well as on word order variation and argument realization. FCA occurs only when the apparently conjoined nominative noun phrases are postverbal, leading to a "subject-final" word order. For this reason, this dissertation investigates the derivational paths taken by nominative arguments in the Russian clause. The key to understanding the "subject-final" word order is that nominative marked subjects must occupy the specifier of TP, even when pronounced postverbally; that is, they undergo "covert movement". In the realm of lexical semantics, FCA in Russian bears on the problem of variable unaccusative/unergative syntactic behavior. FCA has been characterized as occurring only when the verb is unaccusative or passive (Babyonyshev, 1996); however, this generalization is not absolute: under specific circumstances, FCA can occur in sentences in which the verb is typically considered unergative. This dissertation presents a solution to the general problem of variable unaccusative/unergative behavior by proposing a model of the relationships among happenings in the real world, verb meaning, and syntactic representation. The model shows how a single verb root can be associated with either unaccusative or unergative syntactic behavior, depending on the type of event it describes. In Russian, a purportedly unergative verb can be in an unaccusative syntactic structure when it is used to describe an existential event, precisely the type of event that is represented in FCA. Finally, FCA in Russian has syntactic properties that differ from those of conjunct-sensitive agreement phenomena in other languages—it is unacceptable in contexts in which the noun phrases must form a single syntactic constituent that is semantically plural. The analysis presented here holds that FCA in Russian arises only when two verb phrases are immediately conjoined and not two noun phrases, as in other languages with FCA. Taken together with the analysis of the syntactic positions of postverbal nominative arguments, this account of FCA helps clarify the appropriate constraints on movement out of a coordinated structure, i.e. the Coordinate Structure Constraint (Ross, 1967). This approach suggests that the phenomenon descriptively referred to as FCA should receive distinct analyses across languages, accounting for variation in its distribution crosslinguistically

Keywords: Linguistics.
Advisor: Gribanova Vera
Levin Beth
Harizanov Boris
Kiparsky Paul
Synthesis and biophysical characterization of chlorosulfolipids and the synthesis of azamerone

Natural product synthesis and methodology development have long enjoyed a symbiotic relationship with the structural complexity observed in natural products inspiring chemists to invent new reactions, as well as providing a proving ground for the utility of existing methods in complex settings. Chapter 1 of this dissertation provides a recent perspective on catalytic methodology developed to enable the synthesis of complex natural products. A focus on the last 20 years of organic chemistry demonstrates the state-of-the-art in methods development and its direct application to accessing complex natural products efficiently. Chapter 2 details our efforts to synthesize three sulfolipid natural products isolated from algae Ochromonas danica. Key features of our synthesis of danicalipin A include the application of our catalytic, enantioselective dichlorination of allylic alcohols and a diastereoselective boron allylation of the dichloroaldehyde fragment. Subsequent syntheses of two biosynthetic precursors of danicalipin A are presented. We also describe the results of an interdisciplinary collaboration enabled by the synthetic sulfolipids to investigate the biophysical properties of these exotic molecules. Chapter 3 describes our efforts towards the total synthesis of napyradiomycin natural product azamerone. Our synthesis required the development of a catalytic, enantioselective chlorocyclization reaction to access a key chlorinated benzopyran intermediate. Subsequent B-alkyl Suzuki cross-coupling between two enantioenriched fragments, followed by the late-stage installation of the pyridazine heterocycle via a tetrazine [4+2] cycloaddition yielded the natural product. This work constitutes the first enantioselective total synthesis of azamerone

Keywords: Chemistry.
Advisor: Burns Noah
Boxer Steven G. (Steven George)
Du Bois Justin