VictorJuiz/thesis huggingface dataset:
Applications of operations research in finance and healthcare [electronic resource]
Keywords: Management Science and Engineering.

This thesis covers several applications of Operations Research in the domains of finance and healthcare. There are three chapters, each covering a different application. Chapter 1 applies techniques from deep learning to estimate mortgage risk. The near-elimination of feature engineering is substituted by models with several thousand parameters that require large amounts of training data. The predictive performance of these models strongly exceeds that of baseline models, especially for predicting prepayments. This increased accuracy, however, comes at the cost of a more opaque model which is harder for a human to interpret than simpler models like logistic regression, which are currently the industry standard. The work in Chapter 2 explores the design of policies for biometric authentication. It first develops a model for the joint distribution of similarity scores associated with different fingers and irises. In the second step, this model is harnessed to design near-optimal multi-stage policies that would be used for authentication, and are robust to gaming, can be computed in real-time and are personalized for optimal performance. The work shows that a reduction of several orders of magnitude in the error rates is achievable by solely changing the authentication policies -- and leaving the hardware unchanged. Chapter 3 is motivated by a humanitarian cause geared towards helping developing countries -- to reduce mortality in children by identifying effective interventions at the planning stage. It takes a descriptive health model (called LiST), which estimates mortality of children given coverage of interventions, and embeds that into an optimization engine in order to minimize mortality under a fixed budget. In doing so, it allows LiST to be used in a prescriptive framework, where policymakers can identify the optimal intervention set at a fixed budget as well as recognize the trade-off of mortality reduction and budget allocation. We find that a greedy strategy offers near-optimal performance with ease of implementation. The findings also highlight the critical role that optimization plays in mortality reduction.
Articulations of the ineffable : narratives, engagement, and historical anthropology with the Muwekma tribe of the San Francisco Bay Area
Keywords: Anthropology.

This dissertation integrates Indigenous and western theoretical perspectives to refine thought about the individual in the world, which helps us to approach rupture and growth in American Indian communities without taking recourse to traditional western colonial assumptions. This project has been developed through close collaboration with the Muwekma Tribe of the San Francisco Bay Area, descendants of the historically, federally recognized East Bay Ohlone, Verona Band of Alameda County. Although many of the families of the Muwekma Tribe have continued to live in their homeland for generations, their neglected federal status and their physical integration with various waves of settler communities has seemingly hidden their existence, as well as their ways of being. This project has drawn on transcontinental Indigenous theories, as well as Eurasian theoretical perspectives to develop a decolonial narrative articulating Muwekma ways of being in relationship to ancestral narratives, objects, bodies and places. Despite academic assertions of cultural extinction and dilution starting in the 1920s, the Muwekma families have continued traditions and ways of approaching homeland across three consecutive, violent, colonial regimes in central California. Through the interpretation of a series of interviews, historical ethnographic notes, archaeological praxis, and remains, this research illustrates how the Muwekma families weave western practices of research into their way of being autochthonous in their homeland. This dissertation provides an understanding of the significance of the tribal community's ancestral places, whether they be significant places of ancestor's post-European invasion, or ancestors from the deep past. This dissertation also proposes that to conduct a respectful archaeology, which asserts the contemporaneity of interlocating community's perspectives, is tantamount to a becoming, and requires a level of engagement beyond intellectual assent and objectifying the agents in one's study.
Artificial intelligence in healthcare and medicine [electronic resource] : enhancing the expert
Keywords: Electrical Engineering.

Due to a convergence of large open-source datasets, significant improvements in the parallelization capabilities of hardware (notably, multi-thousand core graphics processing units), and renewed academic interest in decades-old neural network algorithms, primary subfields of AI have flourished in the past 5 years. Natural Language Processing, Computer Vision, and robotics have attained impressive performance across many key AI tasks. In this thesis we focus not on the development of new AI algorithms, but on their application to a series of important problems in healthcare and medicine. Machine learning and AI will impact industries that generate significant amounts of data, by extracting insights that humans cannot. Healthcare and medicine are examples of such industries and thus are excellent use cases for AI deployment. Our story is divided into 4 sections - neuroscience, psychiatry, drug screening, and dermatology - all linked by the common thread of using AI to \textit{enhance the expert}, either in-clinic or in the analysis of data. This underlying motif is the connection to a paradigm in AI development popularized as the \textit{virtual cycle of AI}: build a product that has front-facing user value, generate data with it, use that data to train AI algorithms that improve your product, acquire more data, etc.
Ascorbic Acid as an Epigenetic Therapy for Osteosarcoma
Keywords:  Department of Biology
Osteosarcoma
Ascorbic Acid
Vitamin C
Epigenetics
Methylation
Osteogenesis
Apoptosis
Cell Cycle
Stanford Medicine Department of Orthopedic Surgery
Stanford University School of Humanities and Sciences
Stanford University Department of Biology
Thesis

Osteosarcoma is an aggressive primary tumor of the bone, often presenting itself in childhood and adolescence. Treatments in the last 30 years have not improved considerably due to the genetic complexity and genomic instability of osteosarcoma. Therefore, it is necessary to consider epigenetic modifications that may contribute to osteosarcomagenesis. One set of epigenetic modifications are regulated by Ten-eleven translocation (TET) family enzymes, which oxidize 5-methylcytosines (5mC) to 5-hydroxymethylcytosines (5hmC). Current models propose that 5hmc is an intermediate base in the DNA demethylation process that operates during important reprogramming phases of mammalian development. We show that loss of TET affects osteoblast maturation by depleting 5hmc levels in the genome and can prime the epigenetic landscape of osteoblasts towards oncogenesis. Consequently, increasing TET activity in osteosarcoma patient-derived xenografts by adding its co-factor, ascorbic acid (AsA) rescues this decrease in 5hmc and abrogates cell proliferation. By investigating levels of global gene expression before and after AsA treatment, gains in 5hmc were observed in specific subsets of genes associated with apoptosis and cell cycle dynamics, which seem to mitigate the cancerous phenotype. Such results contribute to a better understanding of epigenetic regulation of osteosarcoma, and furthermore implicate AsA as a potential epigenetic therapy for osteosarcoma.
Aspects of three-dimensional gravity and two-dimensional conformal field theory
Keywords: Physics.

In this thesis, we study aspects of three-dimensional gravity in Anti de Sitter (AdS) space by studying the holographically dual two-dimensional conformal field theory (CFT). We begin by describing general constraints on the elliptic genus of a two-dimensional supersymmetric conformal field theory which has a gravity dual with large radius in Planck units. We discuss the distinction between theories with supergravity duals and those whose duals have strings at the scale set by the AdS curvature, using symmetric orbifolds as a case study. We then move on to study extremal theories, conjectured to be dual to "pure" three-dimensional gravity. We first provide an example of an extremal chiral N=2 superconformal field theory at c=24. We then consider extremal CFTs at large central charge, and consider the quantum corrections to the classical spectrum. Our conjecture passes various consistency checks, especially when generalized to include theories with supersymmetry. Finally, we examine a specific top-down construction of AdS3/CFT2 from string theory, called the D1/D5 system. We examine the low-lying quarter BPS spectrum of the K3 symmetric orbifold CFT at various points in moduli space, and look at a more refined count than the ordinary elliptic genus. We do a decomposition of the spectra into N=4 characters, and show that at large N the character decomposition satisfies an unusual property, in which the degeneracy only depends on a certain linear combination of left- and right-moving quantum numbers, suggesting deeper symmetry structure.
Asymptotics of Gaussian processes and Markov chains
Keywords: Mathematics.

In this thesis, we present several results on the asymptotic behavior of Gaussian processes and Markov chains. In the first part, focused on Gaussian processes, we prove a central limit theorem for the sum of i.i.d. high-dimensional random vectors. Surprisingly, not much is known about the optimal dependence of the convergence rate on the dimension of the vectors. Our main contribution is to prove a convergence rate in quadratic transportation distance that is close to optimal in both the dimension and the number of summands. We next prove a result (based on joint work with Jian Ding and Ronen Eldan) about general Gaussian processes: we show that if the maximum of a Gaussian process is strongly concentrated around its expectation (called "superconcentration"), then with high probability the process has many near-maximal values with low pairwise correlations (called "multiple peaks"). Such phenomena naturally arise in the analysis of disordered systems in statistical physics, where the Gaussian process values correspond to energy levels. Our result adds to an overall picture of the behavior of superconcentrated Gaussian processes described by Chatterjee. The second part of the thesis contains results concerning asymptotic behavior of Markov chains. For random walk on a graph, we prove a sharpening of a relationship established by Ding, Lee, and Peres between the cover time and the Gaussian free field. In particular, our estimate implies that in families of graphs (of size growing to infinity) where the hitting time is asymptotically much smaller than the cover time, the cover time is exponentially concentrated around its expectation, and this expectation has a simple asymptotic formula in terms of the Gaussian free field. We also analyze the mixing time of a Markov chain, known as the product replacement walk, on n-tuples of elements of some finite group. One step of the walk involves randomly choosing two of the elements a and b and multiplying a by either b or the inverse of b, with equal probability. The product replacement walk has been extensively studied in the context of random generation of group elements and is part of a larger class of Markov chains that includes random walks on matrix groups over finite fields and certain interacting particle system models. Based on joint work with Yuval Peres and Ryokichi Tanaka, we prove that the product replacement walk exhibits a cutoff phenomenon as n goes to infinity: the chain rapidly transitions from being unmixed to mixed after around 3/2 n log(n) steps.
At Arm's Length: Controlling State-Funded Militants in Civil War
Keywords: Center for International Security and Cooperation
Stanford University
Syria
Militant Groups
Insurgents
foreign financing
Thesis

Despite a $500 million investment, most Syrian militants receiving U.S. sponsorship did not attack ISIL. This failure is alarming; as civil wars begin to include more militant groups, states are increasingly interested in influencing their behavior in order to advance national interests. It is also surprising the degree to which militants are able to shirk given the power disparity between states and militants. This thesis asks why strong states struggle to control the weak militant groups they fund in Syria. Most answers rely on principal-agent theory alone, but I incorporate more recent literature on competition and alliances within insurgencies. I also employ a mixed-method analysis of 350 attacks conducted by Sunni militant groups with U.S. or Saudi sponsorship from 2014 to 2016.

Militant group adherence to state goals is highly mediated by participation in alliances. The extent to which Syrian militant groups in alliances obey their sponsors is influenced by the allocation of power within alliances and alliance members’ preferences. Curiously, militant groups are more inclined to follow state sponsor objectives when they ally with other militants who have different aims. Unlike alliances composed entirely of extremists, militant groups can credibly threaten to defect from alliances with groups that have dissimilar goals. In response, these alliances choose a narrow range of targets that conform to the preferences of all members and their state sponsors. This suggests that to avoid further failures, state sponsorship programs must place more consideration on alliances within insurgencies.
Athletic Performance and Bone Stress Injuries in Collegiate Athletes
Keywords: Epidemiology
Stanford
bone stress injuries
performance
running
collegiate
Thesis

Bone stress injuries are a common athletic injury that negatively impact athletes’ performance and well-being; have a high-rate of recurrence; and may reflect poor bone health in some athletes. While many studies have looked at risk factors that modify the load applied to a bone or that modify the ability of a bone to resist load, few have looked about how performance is associated with BSI risk. This study fills that gap by looking at the association between personal-best mile and cross-country times and BSI diagnoses in a large prospective cohort of competitive runners. Student athletes (N=126) from the track and field and cross-country teams at Stanford and UCLA were followed up to 4 years via yearly physical exams and questionnaires to determine which characteristics were associated with BSI events. Analyses looking at the relationship between bone mineral density (BMD) and performance found that a minute slower best mile time was associated with a statistically significant 0.16 standard deviation higher hip BMD in men, after adjusting for known risk factors for low BMD. These analyses also found a statistically significant 0.21 standard deviation higher total body BMD in females, after adjusting for known risk factors. In BSI models for men, a slower mile time was protective against BSIs though this association did not achieve statistical significance; for females, a slower mile time increased BSI rates only after adjusting for known risk factors for low BMD (RR=2.50, p=.06). Models with cross-country times as an exposure showed no association, most likely due to the high variability of cross-country times. Higher performing runners may have reduced BMD.
Atmospheric plasma deposition of optical and optoelectronic materials for photovoltaic applications
Keywords: Materials Science and Engineering.

With global energy consumption expected to rise above 500 quadrillion BTUs by 2030, aggressive research and development is underway to provide sustainable energy production through the proliferation of thin film photovoltaics. In order to build significant momentum towards lowering the cost of solar energy production below 0.03 $/kWhr over the next ten years, we must consider new materials and synthesis routes which better emphasize scalability, do no compromise on material quality, and enhance the overall thermomechanical reliability of the solar module. One such method is atmospheric plasma deposition, an open-air plasma enhanced thin film growth technique. In this dissertation, I present novel atmospheric plasma chemistries for the deposition of several thin film materials, enabling an all open-air processing route for the fabrication of critical layers in thin film solar modules. In the first and second chapter, I introduce and discuss in detail critical concepts used throughout the work, including spectroscopic and mechanical models. Next, I discuss atmospheric deposition of anti-reflective coatings, establishing strategies for controlling the refractive index of coatings derived from metal alkoxide precursors. In the following two chapters, I translate these metal alkoxide chemistries to a scalable, blown arc discharge and discuss both the molecular structure of the coating as well as describe the as-deposited superhydrophilicity of the coatings. In the final chapter, I discuss a new methodology for rapidly crystallizing metal halide perovskite thin films, a solar absorber material. Atmospheric plasma deposition enables open-air thin film deposition of high quality optical and optoelectronic materials.
Atomic Clouds on the Horizon? Russian and Chinese Opposition to U.S. Ballistic Missile Defense Systems
Keywords:  Center for International Security and Cooperation
Center for International Security and Cooperation
missile defense
foreign policy
United States
Russia
China
strategic stability
nuclear deterrence
Thesis

On December 13, 2001, President George W. Bush announced that the U.S. would withdraw from the 1972 Treaty on the Limitation of Anti-Ballistic Missile Systems (ABM Treaty). Due to the threat posed by Iran and North Korea, the U.S. has sought to deploy missile defenses in Eastern Europe and Northeast Asia. Russia and China have consistently opposed these deployments, claiming that they threaten strategic stability and seek to counter threats from Russia’s and China’s nuclear arsenals. However, past literature has not thoroughly examined Russia and China together to explain this opposition. This thesis seeks to understand why Russia and China object to the deployment of U.S. missile defense systems and what the U.S. does to address those objections. Through examining government documents, official statements, and expert analysis, this thesis analyzes U.S. missile defense policy since its withdrawal from the ABM Treaty, Russian and Chinese responses, and how allies in Eastern Europe and Northeast Asia view U.S. ballistic missile defense (BMD) policy. This research finds that in the short term, the U.S. is able to strengthen alliances and offer extended deterrence through BMD deployments; precisely for this reason, bolstered U.S. alliances are worrisome for Russia and China. In the longer term, the U.S. sees its evolutionary and adaptable future capabilities as an advantage, but Russia and China view the future of U.S. missile defense as a threat likely to turn into a global missile defense, which includes improved missile defense technology. The alliance finding is particularly consequential, and shows that Russian and Chinese opposition of and U.S. support for BMDs is more political than it is technical. Because missile defense will continue to be a point of contention between the U.S., Russia, and China, it is important to understand why this is an issue.
Automated design of photonic devices
Keywords: Electrical Engineering.

Integrated photonic devices are poised to play a key role in a wide variety of applications, ranging from optical interconnects and sensors to quantum computing. Design methods for photonics, however, lag far behind other areas such as digital electronics and aerospace vehicles. Photonic devices are largely designed by hand using a combination of semi-analytic theory and brute-force parameter sweeps, and as a result only a small library of devices is currently known. In this dissertion, I discuss our recent efforts to automate the design of photonic devices. In particular, we have developed an automated design method that explores the full design space of fabricable devices. This has allowed us to design devices with previously unattainable functionalities, performance, fabrication robustness, and compact footprints. Using this method, we designed, fabricated, and experimentally demonstrated a wide variety of passive silicon photonics devices. These include a wavelength splitting grating coupler, compact waveguide-coupled wavelength splitters, and a 3-way power splitter. The design methods we have introduced have the potential to both revolutionize the integrated photonics industry, and open new avenues of research for photonics.
Automatically distributing and load balancing graphical fluid simulations
Keywords: Electrical Engineering.

Distributing graphical fluid simulations across many machines enables faster and more detailed simulations. However, distributing these simulations efficiently is challenging. First, it requires writing efficient distributed simulation code. Graphical fluid simulations use many diverse, novel and optimized data structures. Existing production libraries contain code developed over decades. It is important to leave low level control over simulation data structures to applications, in order to support these different data structures and existing libraries. Second, even with well written code, it is necessary to distribute work evenly in order to run the simulation efficiently. Fluid simulations exhibit spatial and temporal variation in fluid distribution and computational load. This makes distributing work evenly difficult. Optimal decision making requires knowing future computational load, but computing this state automatically for an arbitrary simulation requires running the simulation itself. As a result, many simulations use a manually specified partitioning, a heuristic, or a reactive approach based on the current load. This dissertation shows that using coarse grained geometric descriptions about data and computations, it is possible for a system to automatically distribute such simulations efficiently by addressing these two challenges. It presents a four layer data model that allows a high level framework to automatically distribute grid-based and hybrid simulations over application owned data structures, and proposes a new approach, speculative load balancing to automatically distribute work evenly. The four layer data model supports complex data structures by providing a simple, geometric abstraction to the simulation author and library. It uses geometric information to translate between geometric views and disjoint system views for efficiently analyzing and enforcing dependencies, and to assemble complex application objects containing data in the format that the simulation library expects from underlying system objects. Speculative load balancing runs the same sequence of computations over a lower resolution grid to estimate future load, and uses these estimates to distribute work evenly. The lower resolution simulation runs orders of magnitude faster and adds negligible execution time overhead. Experimental results show that speculative load balancing outperforms traditional ways of distributing work.