VictorJuiz/thesis huggingface dataset:
Learning with peers [electronic resource] : teams in an online course for teacher professional development
Keywords: Education.

Students can learn from and with peers, and the role of peers varies with the learning environment and with which tools are available. This research examines voluntary online classes that involve teams of participants. The courses were created by Stanford's Understanding Language Online group as professional development for teachers and were available for free. This study describes how social connections and interactions within the class predict course completion. However, an intervention designed to improve teammates' social connections and encourage goal interdependence had no effect on course completion, but rather caused participants currently working as teachers to leave their teams at a higher rate. This dissertation contributes to three scholarly areas. First, it extends the study of peer effects in learning to focus on the structures and contexts that can improve the effects of peer contact. Second, it examines how learners interact in Massive Open Online Courses (MOOCs). In particular, students work in teams on the NovoEd platform. Third, it contributes to our understanding of adult learning and teacher professional development. The dissertation contains an extensive synthesis of theory and evidence on teams and peer effects across academic fields. The main argument, based on this literature review and the results of the study, is that peer effects on learning are shared goods produced through learner interactions, and thus benefits from peers are subject to collective action problems. This implies that there are potential gains from redesigning the structures and contexts around peer learners in ways that encourage voluntary contributions. That is, productivity gains are possible through technologies---for instance, curricula, online tool design, and social contexts---that allow and encourage peers to meet, advise, and motivate each other. This mechanism is especially valuable because peer learners are an abundant, underused resource in a massive course. The study highlights relevant research findings and examples of technologies moving in this direction, and it recommends further study into the design of social online learning. Lastly, this dissertation discusses the particular difficulties that MOOC environments pose for researchers, whether they are conducting experiments or performing causal inference. The attrition and anonymity inherent in these voluntary courses pose problems, but the distributed control of structure and content raise unexpected problems. An appendix explores methods for peer effects in this medium and describes the NovoEd algorithm for assigning teams that was in place during the courses studied.
Life in 2050, Adaptive Technological Innovations, and Their Challenges: An STS Critique
Keywords: Alina Luk
Stanford University
Program in Science Technology and Society
STS
Adaptive Technological Innovations
Honors Thesis
Thesis

The three key changes: a growing population, an aging population, and urbanization, will have significant social, environmental, and economic impacts on the human population. This thesis examines technologies that stem from the challenges of the three global changes. The growing population will lead to increased demands for food, which can be addressed by cultured meat production. By 2050, it is projected that there will be an 80% increase in demand for animal protein, which makes meat production one of the most pressing| challenges the world will face in the coming years. This thesis employs STS frameworks to explore the impact of the projected changes in the global population demographic, identifies how the three emerging technologies could address the rising challenges, and critiques the challenges that these new technologies are facing. A thorough understanding of these technologies will facilitate critical discussions that address how we should tackle some of the largest challenges of the future.I urge people to| overcome the tendency and temptation to resort to simplifying these technologies into their techno-economical impacts, and set higher standards for the technologists, engineers, and corporations creating these technologies to understand the wider implications of the technology more comprehensively. address the demand for meat while also reducing greenhouse gas emissions.
Light-managing nanomaterials for energy efficiency [electronic resource]
Keywords: Materials Science and Engineering.

Sustainable energy is the most important goal for humans in 21st century. While energy is an indispensable factor for our prosperity, the huge demand for energy has also produced excessive greenhouse gas emission, causing global warming and extreme climate change. Therefore, it is crucial to develop sustainable energy to leave a better living environment for the next generation. Energy efficiency, which means to reduce the consumption of energy while maintaining the same life quality, is especially promising due to the quick turnaround and cost-effectiveness. Among all the energy end-use, indoor space heating and cooling contribute to up to 30%. In my PhD study, I explored several nanomaterials that can selectively control the passage of light and electrons to provide energy efficiency solutions for indoor temperature control. In the first part, I will introduce the concept of personal thermal management, which focuses on controlling the temperature around human bodies rather than the entire space. Considering the huge thermal mass of the entire building as compared to the occupants, personal thermal management will have considerable energy saving without sacrificing thermal comfort. My approach is to fabricate light-managing nanomaterials for indoor cloths which is ultra-warm/ultra-cool, so the occupants can feel comfortable even when the indoor temperature is low/high. Chapter 2 describes metallic nanowires coating for textile to enhance the radiation reflectivity and trap the human body infrared radiation (IR) and keep warm. Chapter 3 demonstrates using nanoporous polyethylene (nanoPE) as the textile material which is transparent in infrared and yet remains opaque in visible light. Traditional textile materials are all IR-opaque, so this extra IR-transparency of nanoPE will enhance the radiation heat transfer to the ambience and thus promote human body heat dissipation. Since 50% of human body dissipation is from radiation, this is proven to be very effective to expand the indoor temperature setpoint range by a few Celsius degrees, which should results in 10~30% of energy saving. The second part describes my work on metallic nanowire transparent electrode and electrochromic windows. Electrochromic windows are capable of controlling solar heat input to reduce the dependence on indoor heater or air conditioner, and transparent electrodes directly influences their performance. I will introduce the superior electrical and optical performance metallic nanowire transparent electrode by engineering the wire dimensions, junction resistance, and how to passivate the metal surface. High performance metallic nanowires transparent electrodes will improve the electrochromic windows switching speed, bendability, and cycle life.
Linking the conformational landscape of Huntingtin to proteostasis and neurotoxicity in Huntington's disease [electronic resource]
Keywords: Biology.

Amyloid aggregation is one of the main hallmarks of neurodegenerative diseases. However, what triggers this amyloid aggregation and how it results to toxicity are unclear. In Huntington's disease (HD), neurodegeneration correlates with the amyloid aggregation of a mutant protein Huntingtin (Htt). This mutation is an expansion of a polyQ repeat in the Htt protein. While the length of the polyQ repeat has been shown to correlate with severity of neurodegeneration in HD, recent studies have highlighted how regions flanking the polyQ repeat alter Htt aggregation and toxicity in various models. In this work, we investigate the roles the polyQ flanking regions play in controlling complex interplay between the biophysics and cell biology leading to the cellular fate mHtt. We find that these polyQ flanking regions impact the energetics, conformations and fibrillar structure of the Htt protein. Importantly, the impact of these polyQ flanking regions have on the Htt conformational landscape have direct consequences on neuronal toxicity and cellular proteostasis of mutant Htt. Overall, our study provides, for the first time, an integrated view of how the biophysical properties of an amyloidogenic protein are linked to their behavior in the cell. Our work linking the mHtt conformational landscape with neuronal proteostasis and toxicity informs rational avenues to leverage the roles of the polyQ flanking regions for HD therapeutics.
Low dimensional superconductivity in strontium titanate heterostructures [electronic resource]
Keywords: Applied Physics.

The two-dimensional confinement of electrons generates quantized subbands, primarily studied in semiconductor heterostructures, which play important roles determining their electrical properties. Despite the recent interest in the interplay between the subbands and superconductivity, their study has been limited due to the small range of materials candidates and the ability to control them at the atomic scale to form subbands. SrTiO3 is a perfect candidate for such study as it is intrinsically a wide-gap insulator, which becomes an n-type semiconductor by doping, allowing access to a clean well-defined system. In this work, single crystalline SrTiO3 heterostructures were fabricated using pulsed laser deposition, which had crystalline quality equal to bulk single crystals with their thickness controlled on the subnanometer scale. By fully exploiting the capability to form clean interfaces with other complex oxides, we engineered metal/SrTiO3 tunneling junctions which allowed us to address one of the longstanding questions regarding the origin of SrTiO3 superconductivity. From the tunneling spectroscopy of bulk and two-dimensional superconducting ground states in SrTiO3, two contrasting electron-phonon coupling strengths were obtained from the normal and the superconducting states, suggesting an unusual polaron formation in a weak coupling Bardeen-Cooper-Schrieffer superconductor. Furthermore, when two quantum wells are placed in parallel, the coupled quantum wells showed the coexistence of two distinct superconducting components originating from Cooper pairs on the different subbands, as evidenced by systematic variation in the upper critical fields. These results indicate the realization of an artificial multi-band superconductor enabled by two-dimensional confinement. These studies open a unique pathway to design and manipulate superconductivity in two-dimensions using oxide heterostructures.
Luminous words [electronic resource] : prerevolutionary Russian writers on foreign language and the art of translation
Keywords: Slavic Languages and Literatures.

This dissertation examines the link between language learning and the study of literature in prerevolutionary Russia and illuminates the role of foreign language and translation in the lives of prerevolutionary Russian writers including Mikhail Kuzmin (1872-1936), Konstantin Balmont (1867-1942), and Vladimir Nabokov (1899-1977). I contend that a primary motivation for foreign language study in the prerevolutionary Russian context is an urge to access what is otherwise inaccessible: texts, experiences, cultures. This is in keeping not only with the search for innovation from outside the national tradition that broadly characterizes the history of Russian literature before 1917, but also with the individual cases of the writers I examine, for whom language study and translation become a basis for the development of personal identity through contact with the unknown. The multilingual writers in this study approach foreign languages from experiential perspectives that shed light on the role of subjective factors in language learning and translation that reflect the concerns of their inner lives. The chapters of this dissertation thus approach the urge to access the inaccessible from different angles that span the binary of public and private and speak to concerns of aesthetics, sexual identity, geopolitical power, and the thrill of discovery. Furthermore, my focus on writers' intensely personal experiences with language facilitates an analysis that goes beyond the sociohistorical level to discuss subjective aspects of language learning, translation, and education that cannot be quantified by other parameters. I thereby provide a fuller picture of the encounters between cultures that accounts for the effect of the "luminous words" of others on individuals who engage with the foreign from a position of interest and openness.
Magnesium carbonates in ultramafic rocks [electronic resource] : carbon dioxide transformations in crustal environments
Keywords: Geological Sciences.

Magnesium carbonate mineralization in Earth's crust occurs in a variety of geologic settings, including hydrothermal and mineral ore systems to sedimentary, weathering, and biogenic environments. Tectonic, chemical, and isotopic descriptions of magnesium carbonates and host ultramafic lithologies constrain the geologic conditions of the interaction between CO2-rich fluids with magnesium silicate minerals. Studying carbonate mineralization in ultramafic rocks is important not only for fundamental understanding of Earth processes, but also for assessing the potential of sequestering anthropogenic CO2 in ultramafic rocks. Mineral carbon sequestration, considered to be the longest-lasting mechanism for subsurface storage of anthropogenic CO2, harnesses the reactivity of ultramafic rocks with CO2-rich fluids to form magnesium carbonates. In my thesis, I study natural analogues of mineral carbon sequestration with the objective of determining the geologic parameters that govern magnesium carbonate mineralization in ultramafic rocks. This objective is reached by utilizing (1) equations of state of H2O-CO2 fluid mixtures; (2) hydrogen, carbon, oxygen, and neodymium isotope systematics; and (3) clumped-isotope thermometry to determine the tectonic and geochemical parameters related to the emplacement of magnesite (MgCO3) vein ores in peridotite of the Del Puerto ophiolite within the California Coast Ranges. My study of the transformations of CO2-rich fluids to magnesium carbonates through interaction with ultramafic rocks has applications to other worldwide magnesium carbonate deposits, provides constraints on CO2 sequestration in ultramafic rocks, and illuminates fundamental questions regarding geochemical pathways in weathering, hydrothermal, and mineral ore systems.
Making cultural assets count [electronic resource] : community approaches to problem solving in Yucatec Maya math classrooms
Keywords: Education.

In Yucatec Maya middle schools in the Yucatán, math scores are low and drop out rates are high. Although addressing larger social and economic causes may ameliorate these issues, improving math instruction is a more feasible approach. These three dissertation papers draw from a six-month ethnographic, mixed-methods study that explores community approaches to problem solving in a Yucatec Maya village in the Yucatán. Also, they explore to what extent middle school math instruction capitalizes upon these cultural assets. Findings demonstrate two previously undocumented community approaches to problem solving, autonomy and improvisational expertise, and explore missed opportunities for local teachers to capitalize upon these cultural resources in the math classroom. In addition, the third paper discusses specific recommendations for including more insider perspectives when doing outsider research.
Making It to College in The Time of Recession: How The 2008 Recession Affected Higher Education Enrollment of American and International Students
Keywords:  Department of Economics
Stanford Department of Economics
Higher Education
International Student Enrollment
American Student
The Great Recession
Postsecondary Education
Economics of Education
Thesis

Economic recessions have sweeping and significant impact across multiple industry sectors, including postsecondary education industry. Past literature has found that recession tends to result in increased enrollment of undergraduates to postsecondary institutions, but not much has been done to draw distinctions between American (domestic) and international students. In this paper, I design a difference-in-difference regression model to identify the impact of the 2008 recession on first-time undergraduate enrollment of American and international students. I use the Bureau of Statistics’ unemployment rate as an indicator of recession severity in each state. The findings suggest that the 2008 recession led to increased enrollment of both American and international students in public institutions, but not necessarily in private and for-profit institutions.
Manipulation of sub-micron particles across a patterned plasmonic substrate [electronic resource]
Keywords: Electrical Engineering.

Over the past 30 years, light has played an expanding role in the manipulation and processing of materials. Focused beams of light have been used to impart and measure forces on the order of piconewtons, leading to major breakthroughs in the understanding of important biological molecules such as DNA and motor proteins, and novel systems which use light to trap and sort biological materials on a chip have been developed. However, these systems rely on the principles of far-field optics to project optical energy into space, and are thus limited in resolution to approximately 500 nm by the laws of diffraction. Furthermore, the bulky and expensive lens systems that are required to produce tightly focused beams of light limit the deployment of such systems to a laboratory setting. To overcome these limitations, alternative optical trapping techniques have recently been developed which utilize the optical near-field of plasmonic resonators. While these methods can, in principle, improve the resolution of optical traps beyond the limits set by diffraction and overcome the scalability issues associated with far-field optics, they have been hamstrung by their inherently short range of less than 1 μm and are unsuitable for particle transport. The following work presents a novel technique to extend the transport capability of plasmonic resonators by inducing the handoff of a particle from one plasmonic trap to the next. This method uses lithography patterning rather than beam forming to determine transport behavior. We will cover the fundamental basis for this technique and present the first-ever demonstration of the transport of a 390 nm diameter particle along a plasmonic conveyor belt 4.5 μm in length using only a low-NA objective lens (NA < 0.75) and a modest peak beam intensity of 3 mW/μm². While the initial experiment transports a single particle over only a short path, the technique may be scaled to a conveyor of potentially any shape and length and support the simultaneous transport of multiple particles. Critical in the design of such a system is a fast and flexible tool for the calculation of optical forces; we present one such technique and demonstrate a 1000x speedup over traditional methods. We also present a theory for the full generalization of the plasmonic conveyor technique to two dimensions and present a complete class of examples that could be used for the parallel transport and routing of particles across the surface of a chip. We close with a discussion of future work and implications for future lab-on-a-chip technologies.
Mapped finite element methods with applications to the simulation of brittle fracture propagation [electronic resource]
Keywords: Mechanical Engineering.

The thesis presents the development, the mathematical analysis, as well as applications of a computational framework for the simulation of curvilinear crack propagation. At the core of the computational framework lies a novel finite element method, named the Mapped Finite Element Method (MFEM), for the optimal convergence of singular solutions. The main challenges in solving numerically the mathematical description of a propagating fracture can be identified in: the continuously evolving (cracked) domain, the singular nature of the elasticity fields, and the computation of the stress intensity factors for the prediction of crack growth. Current state-of-the-art methods are plagued by low order of accuracy, high computational cost, and complex data structures. The work herein addresses the aforementioned challenges by developing a computationally efficient, rapidly convergent, and non-intrusive algorithm consisting of three key ingredients: Universal Meshes, Mapped Finite Element Methods, and Interaction Integrals. First, Universal Meshes are introduced as a computationally efficient and robust meshing algorithm for the generation of conforming subdivisions of the evolving domain. Second, Mapped Finite Element Methods (MFEM) will be developed for the solution of the singular elasticity fields. The methods are shown to converge with optimal order for the same computational cost, preserving well conditioning and sparsity properties, and with no alteration to the data structure of standard Lagrange finite element methods (known to converge sub-optimally for this class of problems). The optimality of convergence is supported by mathematical analysis and applications of MFEM are showcased beyond brittle fracture (e.g. the resolution of boundary layers in flows around moving obstacle, real-space Kohn-Sham density functional theory calculations, etc). Third, the thesis presents the construct of a family of linear and affine functionals, named Interaction Integral functionals, for the rapidly convergent computation of the stress intensity factors (SIFs) for curvilinear fractures. The distinct feature of the Interaction Integral functionals is their ability to double the rate of convergence of the energy norm of the solution in the evaluation of the SIFs. Sketches of the mathematical analysis are provided to support the observed rapid rates of convergence. The propagation algorithm that combines the developed tools (Universal Meshes, Mapped Finite Element Methods, and Interaction Integrals) is presented and shown to be consistent (in the sense of being able to replicate observed experimental results) and predictive (in the sense of yielding crack paths that converge to a unique solution with refinement of the discretization). Lastly, the capabilities of the developed algorithm are exploited to study the formation of wavy crack patterns when brittle heat conductors are rapidly cooled.