VictorJuiz/thesis huggingface dataset:
Quantification of optical gain-limiting processes in silicon nanocrystals using microcavities [electronic resource]
Keywords: Electrical Engineering

The past two decades have witnessed a dramatic surge in efforts to elicit active optical functionality out of silicon. Active silicon-compatible devices such as all-optical switches, electro-optic modulators, and high-speed photodetectors have been realized across numerous laboratories. A silicon-based, electrically-pumped laser now remains one of the final obstacles toward ushering in the era of chip-scale nanophotonics and optical interconnects. Among various options, light emitting Si-nanocrystals (Si-nc) and Si-nc sensitized erbium have shown received most attention as a silicon-compatible, near-infrared- (600--1000 nm) and telecom-wavelength (1550 nm) gain-media due to demonstrations of optical gain. Ever since the first and the famous report of optical gain in the year 2000, the measurements have been fraught with controversy with numerous laboratories since then having tried and failed to reproduce these observations. Even in the successful experiments, there exists a considerable spread in the reported conditions required for optical gain. Despite the decade that has nearly elapsed since the first gain measurements, the lack of a Si-nc or a Si-nc sensitized erbium laser remains an experimental fact. Rather than inquiring about the conditions leading to optical gain, such a situation demands for taking a step back and investigating the achievability of the gain itself. The present thesis concerns itself with answering this question in two steps. The first step is an identification of the constraints necessary on the material properties for optical gain to be possible. The second step is a ensuring the satisfaction of these constraints by an accurate measurement of the material properties. Following our identification of free-carrier absorption (FCA) as the fundamental gain-limiting mechanism in semiconductors, we develop a microcavity-based spectroscopic technique for its accurate quantification in Si-nc. We build up to the development of this technique in several intermediate steps including Si-nc synthesis, microcavity modeling, fabrication and testing, and modeling of carrier generation/recombination processes in the quantum dots. Finally we extend our FCA measurement to telecom wavelengths (1550 nm) using pump-probe measurement. Besides enabling us to conclude on the possibility of optical gain in Si-nc sensitized erbium, the pump-probe measurements allow for comparison of the new microcavity-based specroscopy against this well-established technique.
Regulation of gene expression by RNA-binding proteins and microRNAs [electronic resource]
Keywords: Biochemistry.

Circumstantial evidence suggests vast post-transcriptional regulatory networks in eukaryotes. There are scores of examples of mRNAs with rich post-transcriptional lives, and dozens of RNA-binding proteins and noncoding RNAs are suggested to have regulatory functions. While eukaryotic genomes encode hundreds of RNA-binding proteins and metazoans also encode dozens to hundreds of regulatory noncoding RNAs, few RNA-binding proteins or regulatory noncoding RNAs have been studied systematically, leaving unanswered basic questions about the scope and organization of post-transcriptional regulation in any eukaryote. First, I present studies aimed at uncovering some of the basic principles of post-transcriptional regulation in eukaryotes, via searching for the RNA targets of 40 proteins in the yeast Saccharomyces cerevisiae: a selective sample of the approximately 600 annotated and predicted RBPs as well as several proteins not annotated as RBPs. Second, I present a simple biochemical approach to identify direct targets of specific microRNAs, important noncoding regulatory RNAs, that regulate protein synthesis of most mammalian mRNAs. Third, I present experiments that uncover the magnitude and respective contributions of translational repression and mRNA decay of microRNA-mediated regulation. These studies apply simple, yet powerful approaches to systematically dissect various aspects of post-transcriptional regulation and uncover a wealth of novel information regarding regulation by RNA-binding proteins and microRNAs.
Research synthesis for multiway tables of varying shapes and size [electronic resource]
Keywords: Statistics

This thesis will present techniques for synthesizing partially classified contingency tables with complex missing data patterns. Data of this form is prevalent in modern genetics, with disparate research groups performing independent association studies. We will propose models for combining the results of such studies in a single meta- analysis. Two main algorithms are developed in this dissertation. The first is a likelihood-based approach, using the EM algorithm and loglinear models. Secondly, we will propose a Bayesian alternative, utilizing the Data Augmentation algorithm and constrained Dirichlet-Multinomial distributions. These general models will then be extended to deal with data-specific problems; such as retrospective sampling, conditional slices and multiple perspective linked tables. Variance estimation techniques, model-selection criteria and tests for homogeneity are also derived. Mendelian diseases are deterministic in nature, with direct genetic inheritance paths established between parent and offspring. However, the vast majority of inherited diseases are in fact non-Mendelian, such as early-onset Alzheimer's, psoriasis, breast cancer and cystic fibrosis. Here both genetic and non-genetic factors affect inheritance patterns, with multiple genes and environmental factors interacting in a complex fashion. We shall propose methods for the amalgamation of existing clinical research for such diseases. Each study incrementally measures a particular factor or group of factors, but is missing data on the combination of all potentially relevant variables, thereby producing underdetermined results. By integrating these studies into a single meta-analysis, disease prediction can be carried out across the full set of risk factors.
Runtime Automatic Speculative Parallelization of Sequential Programs [electronic resource]
Keywords: Electrical Engineering

This dissertation presents Runtime Automatic Speculative Parallelization (RASP), a technique for the dynamic extraction of speculative threads from a running application in a user-transparent fashion. By leveraging the idle cores in a CMP to analyze, optimize, and participate in the execution of a running sequential program, RASP enables a collection of simpler cores to achieve sequential performance on par with a significantly more complex core. In contrast to other systems for automatic speculative parallelization, RASP uses dynamic binary translation to optimize applications on-the-fly, without any need for recompilation or source code. RASP achieves these speedups without relying on special-purpose hardware support; RASP's dynamic profiling uses a clever variation on conventional performance-monitoring, while RASP's speculative execution relies on the same simple hardware support for speculation that has been proposed for simplifying parallel programming. On a simulated cluster of four in-order cores, RASP accelerates SPEC2006 integer benchmarks by an average of 49%, with promising results for scientific and multimedia workloads as well.
Security from location [electronic resource]
Keywords: Aeronautics and Astronautics

The emergence of the Internet and personal computers has led to an age of unprecedented information access. The proliferation of Internet connectivity, personal computers, and portable, high density data storage has put volumes of data at one's fingertips. While the spread of such technology has increased efficiency and knowledge, it has also made information theft easier and more damaging. One common expression of information theft is a data storage disk or equipment containing sensitive or valuable information. For example, the U.K. government lost computer disks that contain personal information on almost half of the country's population. The information includes names, addresses, insurance numbers, bank account details, etc. These emerging problems have made the field of information security grow significantly in recent years. This thesis develops a new means to provide more protection against information loss, named geo-security or location-based security. This new technology is well suited to help mitigate the above described data loss scenario. Precise location and time information can be used to restrict access of the system or equipment at certain locations and time frames. This study bridges the two fields of navigation and security, and provides experimental support for the concept using location information for security. This thesis designs a theoretical framework that provides a general analysis of geo-security, and quantifies the reliability and security of a geo-security system. The qualitative part of this analysis includes navigation signal definition, system design, performance standards, threat model and attack scenarios, and mitigation of the threats/attacks. The quantitative part of this analysis measures and quantifies location-dependent navigation parameters based on information theory, and evaluates the consistency, spatial decorrelation, and entropy of these parameters for a variety of relevant navigation systems. Next, this thesis demonstrates geo-security using Long Range Navigation (Loran) and Wi-Fi as case studies. Experiments were conducted to evaluate the performance based on the designed framework. They illustrate the trade space between permitting access to authorized users and denying access to attackers. Finally, error-tolerant algorithms, named fuzzy extractors, are developed to improve the availability and reliability of location-based security systems given the constraints of real-world navigation systems and signal propagation characteristics.
Starting big [electronic resource] : the role of multi-word phrases in language learning and use
Keywords: Linguistics

Why are children better language learners than adults despite being worse at other cognitive tasks? Previous accounts have focused on biological, cognitive or neural differences between children and adults. In this dissertation, I suggest the answer lies, at least in part, in the linguistic units that children and adults learn from and how those shape subsequent learning. I propose the Starting Big Hypothesis: children learn from units that are larger and less analyzed than the ones adults learn from. Children's early inventory includes multi-word fragments (e.g., give-it) and short multi-word utterances (e.g., I-don't-know, It's-my-turn). These multi-word units facilitate grammatical and lexical learning and are part of the native adult inventory as well. I argue that adults' prior knowledge and experience with language leads them to 'break language down' in a way that hinders the learning process. I explore three concrete predictions of this hypothesis 1) that children's morphological knowledge is facilitated in frequent sentence-frames 2) that multi-word phrases are part of the native adult lexicon, and 3) that L2 learning of grammatical gender will improve when learners are first exposed to larger chunks of language. I test these predictions using several experimental tasks: corpus studies of natural speech, elicited production with children, lexical decision, and artificial language learning in adults. The combined findings offer a novel perspective on the difficulty that adults experience in learning a second language. The findings enhance a usage-based view of first language learning that emphasizes the importance of multi-word phrases in the construction of grammar, and present evidence in support of an emergentist view of language where all linguistic experience (be it atomic or complex) is processed by the same cognitive mechanism.
State, market, and bureau-contracting in reform China [electronic resource]
Keywords: Political Science.

Why and how has China succeeded as a developmental state despite a seemingly rents-ridden bureaucracy? Following conventional wisdom, "Weberian" bureaucracies are an institutional precondition for development, especially in interventionist states like China. However, my research finds that China's fast-growing economy has not been governed by a purely salaried civil service. Instead, Chinese bureaucracies still remain partially prebendal; at every level of government, each office systematically appropriates authority to generate income for itself. My study unravels the paradox of "developmentalism without Weberianness" by illuminating China's unique path of bureaucratic adaptation in the reform era -- labeled as bureau-contracting -- where contracting takes place within the state bureaucracy. In a bureau-contracting structure, the state at each level contracts the tasks of governance to its own bureaucracies, assigning them revenue-making privileges and property rights over income earned in exchange for services rendered. Contrasting previous emphases on the prevalence of illicit corruption in China, my study shows how and why bureaucracies in this context are actually authorized by the state to profit from public office. Specifically, I identify two factors that constrain arbitrary and excessively predatory behavior among Chinese bureaucracies: first, mechanisms of rents management, and second, the mediation of narrow departmental interests by local developmental incentives. In short, I argue that it is the combination of an incentive-compatible fiscal design and increasingly sophisticated instruments of oversight that have sustained an otherwise unorthodox structure of governance in China. In a phrase, bureau-contracting presents a high-powered but opportunistic alternative to the Weberian ideal-type. The Chinese experience suggests that "market-compatible" bureaucratic institutions need not necessarily conform to -- and may even diverge significantly -- from standard Western models, at least at early stages of development. My research draws on interviews with 165 cadres across different regions and governmental sectors, as well as statistical analysis of previously unavailable budget data.
Studies of the cathode-electrolyte interface of solid oxide fuel cells [electronic resource]
Keywords: Materials Science and Engineering

Concerns about global climate change remain a significant driving force for research of energy conversion devices. Solid oxide fuel cells (SOFCs) are one such device. Several recent advances in SOFCs have focused on reducing the ohmic losses of the device, either through thinner electrolyte membranes, or higher ionic conductivity of the electrolyte. As these advances allow for the operation of SOFCs at lower temperatures, the major source of loss within these devices shifts to the interfaces. In particular, the activation losses at the cathode and cathode-electrolyte interface become the dominant bottleneck in the operation of SOFCs at lower temperatures. In this work, three studies on the cathode or cathode-electrolyte interface of SOFCs will be presented. Additionally, electrochemical impedance spectroscopy (EIS) is used as a tool for interpreting the types and amount of loss present in SOFCs under various fabrication and operational conditions. In the first study, thin films of LSCF, a mixed electronic-ionic conducting (MEIC) material, are deposited by pulsed laser deposition (PLD) and used as the cathode material for SOFCs. Research results indicate the presence of an optimal cathode thickness for maximum power performance, which is obtained by minimizing the sum of the electronic and ionic resistances of the cathode material. However, the results indicate the catalytic activity of this material severely limits SOFC performance at lower temperatures. In the second study, the effects of ion irradiation at the cathode-electrolyte interface of SOFCs are studied. In particular, the IV performance is observed as a function of irradiation energy for both xenon and sodium ions at a dose of 1E16 ions per square centimeter. Results indicate that xenon ion irradiation at low energy (70keV and below) produces an increase of more than 100% in the peak power density at 310°C, by reducing the activation losses of the SOFCs, while sodium irradiation produces little effect. Both xenon and sodium ion irradiation result in significantly worse performance at high irradiation energy (150 keV and above). Secondary ion mass spectrometry (SIMS) was used to verify the depth profile of the implanted ions, which compared favorably with simulations performed using a Kinetic Monte Carlo (KMC) model. Additionally, transmission electron microscopy (TEM) was used to visualize the damage created in the electrolyte substrates under various irradiation conditions. The final study looks at the role of electrolyte grain-boundaries at the cathode-electrolyte interface. Results from EIS measurements, quantum simulations, and SIMS analysis indicate that oxide ion incorporation from the cathode into the electrolyte is enhanced at grain boundaries of the electrolyte.
Taking Up, Getting Better and Crowding Out: Evaluating Local Effects of the California Healthy Kids Insurance Program
Keywords:  Department of Economics
Stanford Department of Economics
California Healthy Kids Insurance Program
public health insurance
children
health outcomes
private insurance
Federal Poverty Level
Thesis

In this paper I use county level data from California to estimate the effects of the California Healthy Kids Insurance Program (CHKIP), an optional state county partnership that expands child eligibility for publicly provided health insurance. The paper is split into three sections: the first on the Political Economy of county selection into the program, the second on the program’s effect on child health outcomes, and the third on estimating the degree to which the program “crowds out” private insurance among children eligible for coverage. In the political economy section I find that the most important predictor of county selection into the program is the percentage of the population who are non-citizens. In the health outcomes section I find that CHKIP increases insurance coverage rates and decreases the likelihood that a child will delay medical care. In the crowd out section, I find no evidence for crowding out among children from families with incomes between %250 and %300 of the Federal Poverty Level, but do find evidence for small levels of crowding out among all children from families with incomes less than %300 of the Federal Poverty Level.
Teacher Sorting and Own-Race Teacher Effects in Elementary School
Keywords:  Department of Economics
Stanford Department of Economics
race
teacher quality
teacher sorting
achievement gap
Thesis

I investigate “own-race teacher effects”—the extent that students benefit from having a teacher with the same racial background. Own-race teacher effects may justify recruitment of underrepresented groups in teaching and, in combination with peer effects, help to determine the optimal assignment of students to teachers. However, previous estimates of own-race teacher effects are confounded by the sorting of teachers across schools. Using administrative data from North Carolina public schools, I document that the quality of black teachers relative to white teachers increases with the school’s black enrollment share. To circumvent this endogenous sorting, I develop and estimate a novel teacher-level metric of own-race teacher effects based on teacher fixed effects. I find that own-race teacher effects are present for mathematics achievement, but significantly smaller than previous estimates.
The Determinants of Child Labor and Schooling in the Philippines
Keywords:  Department of Economics
Stanford Department of Economics
multinomial logit
Filipino
poverty
income
household head
education
biological relation
household composition
community infrastructure
female headship
welfare
Thesis

The previous literature suggests that the determinants of child labor are largely country specific, indicating that any policies aimed at reducing child labor must look carefully at the causes of child labor in context. My thesis adds to the empirical work on child labor by investigating what household and community characteristics are most common among working children in the Philippines, using data collected by the International Labour Organization. I use a multinomial logit model with child activity as the dependent variable, where the three possible outcomes are work only, work and study, and study only. I find that poverty has a strong negative impact on the probability a child works full time or part time (relative to study only), especially in rural areas, as do the years of the household head’s education and having electricity and access to drinking water. Having a close biological relation to the head has a significantly positive effect on the probability of studying only for all groups of children, and especially for urban girls. The results also indicate that government programs like welfare and community organizations do little to reduce child labor, probably due to the lack of awareness among the majority of the populace.
The Financial Aid Tax and Student Work Incentives
Keywords:  Department of Economics
Stanford Department of Economics
Financial Aid
Higher Education
Tax Salience
Thesis

This paper investigates whether students account for the financial aid tax when making their decisions to work, and how much four-year university students know about how their financial aid is determined. This paper is divided into two parts. In the first part, I use the NPSAS:2000 data to determine if students respond to the financial aid tax structure by bunching below the point where the tax comes into effect. I find that they do not. In the second part, I survey Stanford undergraduate students on how the financial aid tax has influenced their decisions to work and save. Difference in differences analysis suggests that removing the tax would increase the probability that a student would earn in the tax paying range by 22 percent with a standard error of 12.6 percent. Finally, I suggest reforms that universities could make to improve the financial aid system. These reforms include educating students on how their financial aid is determined, replacing the single 50 percent marginal tax rate on student earnings with a progressive structure similar to that on parent earnings, and allowing low-income students a larger tax exemption.
The Impact of Mobile Phones on the Status of Women in India
Keywords:  Department of Economics
Stanford Department of Economics
mobile phones
gender inequality
domestic violence
autonomy
linear probability
probit
ordered probit
Thesis

Mobile phones have grown at an extraordinary rate throughout the developing world in recent years. They are potentially an invaluable economic asset to the poor and an important tool for strengthening social ties. Mobile phones may also help women overcome physical boundaries, especially in places where they are separated from their support networks and bound within their husband’s social sphere. This paper examines the impact of mobile phones on the status of women in India. Using nation-wide cross-sectional data at the individual level, I build on Jensen and Oster’s model for measuring women’s status. I use domestic violence, decision-making autonomy, child preferences and economic independence as proxies for bargaining power and status of women in their household and society. I find that mobile phones significantly decrease both men and women’s tolerance for domestic violence, increase women’s autonomy in mobility and economic independence, but do not find significant effects on child preferences and other measures of autonomy. Where the effects are significant, they are also large and in some cases equivalent to more than five extra years of education. These results suggest that the Government of India and those of other countries should consider mobile phones as a policy instrument for empowering women.