VictorJuiz/thesis huggingface dataset:
Pursuing Credit: Sovereign Debtors’ Economic and Political Motivations to Oscillate in Creditor Selection

In a decade and a half, three Presidential administrations in the Republic of Ecuador have led the country to oscillate three times in its selection of sovereign and private creditors. Beginning in 2007 with the election of President Rafael Correa, Ecuador foreclosed any possibility of borrowing from Western multilaterals and bond markets following a puzzling decision to default on bonds. Over the next ten years, Ecuador became one of the 30-most indebted countries to the People’s Republic of China. Then, when Correa’s successor President Lenín Moreno was elected in 2017, a process many described as a parricide marked a re-embrace of multilaterals, though the administration also continued to borrow heavily from China. Finally, in 2021, President Guillermo Lasso aligned himself, and therefore, the country, closer once more with multilaterals, and finally qualified Chinese lending to Ecuador as detrimental to the country’s growth. In this thesis, I seek to determine what a country’s guiding and principal motivations are when choosing with which creditor to engage. I examine each of these three Presidential administrations as distinct time periods in Ecuador’s history of sovereign borrowing, and seek to answer the aforementioned question through interviews with seven high-ranking officials in the Ecuadorian government or regional and international multilaterals. I also leverage qualitative analysis of public declarations, government decrees, and contracts. I find that, broadly, incentives to oscillate between creditors can be split into economic and political motivations. Each of these in turn can be subdivided further into considerations. These are availability of capital, cost of capital, ideological affinity, geopolitical considerations, and political and electoral benefits. I concluded that while these considerations vary in importance from one administration to the next, availability of capital and ideological affinity were central across all three administrations. I also highlight how creditor selection can be used to garner political and electoral benefits, particularly through the use of signaling mechanisms for voters. This is an element that escapes the literature and is a new contribution to the field.

Keywords: Sovereign debt; sovereign debt default; Ecuador
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Thesis
Putting Things in the Right Perspective: liberating the mind through the performative Zhuangzi

This thesis offers an English translation and interpretive analysis of the Inner Chapters of the Zhuangzi. I examine how the text resets the reader's firmly established beliefs and behaviors to transport the mind and free the spirit from the shackles of culture and language frameworks, prejudices, and distinctions through the narrative force of language. I present my own interpretation of what the text accomplishes, showing how crucial the presentation of Zhuangzi’s dialogues, stories and poems is to the text’s very substance and how the Zhuangzi effectively leads its audience toward positive change by the process of interacting with it.

Keywords:  Stanford Global Studies
East Asian Studies
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Thesis
Advisor: Sun Chaofen
Quantifying hydrologic change in tropical peatlands

Tropical peatlands are a globally significant carbon sink that store over 100 Gt of carbon. In pristine peatlands, this sink is enabled by unique hydrologic characteristics that keep peat soils waterlogged year-round, in turn slowing down the decomposition of organic matter and protecting peat soil from burning. But Southeast Asian peatlands, which store about half of all tropical peatland carbon, have experienced extensive deforestation, drainage, and conversion to agricultural use in recent decades. Already, this degradation has resulted in devastating impacts. Deadly fires during drought years release massive amounts of carbon dioxide and smoke, and there is also evidence of increased decomposition rates throughout the region. Climate change threatens to further disrupt the hydrologic and carbon balance in peatlands. In this dissertation, I quantified changes in Southeast Asian peatland hydrology by developing the first datasets for two key hydrologic variables: surface soil moisture and drainage canals. This was made possible with new satellite-based sensors and advances in retrieval algorithms and computer vision. In Chapter 2, I showed that soil moisture can be measured with sufficient accuracy using data from NASA's Soil Moisture Active Passive satellite (counter to previous understanding), and found it can be used for predicting peat fire risk up to a month later. In Chapter 3, I created the first regional map of drainage canals. I found that drainage density correlates with higher carbon emissions rates, and counter to previous assumptions, does not correlate one-to-one with land use. In Chapter 4, I built a model to predict future soil moisture regimes under climate change, and found that drier climatic conditions may cause significant decreases in soil moisture, implying more severe fire regimes in the future. Thus, this dissertation provides new tools for studying and modeling changes in peatland hydrology, and the implications that these changes have for earth's carbon cycle

Keywords: Earth System Science.
Advisor: Konings Alexandra
Gorelick Steven
Naylor Rosamond
Quantifying the diversity of sulfate-reducing microbes in the human gut

Sulfate-reducing microbes (SRM) are a diverse group of bacteria and archaea that utilize sulfate as the terminal electron acceptor in anaerobic respiration and are hypothesized to contribute to gut inflammation in humans. The presence of common SRM have been correlated to chronic gastrointestinal inflammatory diseases such as Crohn’s Disease, Ulcerative Colitis, Inflammatory Bowel Disease, and Irritable Bowel Syndrome in geographically homogeneous, adult, Western populations. However, little is understood of the full diversity of the SRMs within the human gut, especially outside of adult, Western populations. This study aims to characterize the full diversity of the SRMs in the human gut by comprehensively identifying SRM species from a wide set of metagenomic data. This study utilizes a computational approach to search publicly available metagenomes from human gut samples for dsrAB, an SRM-specific gene encoding for dissimilatory sulfite reductase. Using dsrAB genes from a manually curated database, we constructed a profile hidden Markov model (HMM) and applied a commonly used bioinformatics tool, HMMER, to identify homologous sequences from 14,286 gut metagenomes. The returned sequences were then phylogenetically classified using Random Axelerated Maximum Likelihood Evolutionary Placement Algorithm (RAxML-EPA) on a reference dsrAB tree. Phylogenetic analyses of collected dsrAB sequences suggests the presence of diverse SRM in the gut from various taxa, including the Desulfovibrionaceae family, the Firmicutes group sensu lato, and the Archaeoglobus cluster. The analysis showed that most common SRM were Desulfovibrio piger, Bilophila wadsworthia, and an uncultured relative of Desulfovibrio desulfuricans, confirming the widely accepted presumption that Desulfovibrionaceae is the most common family of gut-SRM. Many dsrAB sequences from SRM not previously catalogued in the gut environment were found at lower frequencies. These results indicate the SRMs in the human gut are more diverse than previously hypothesized. The results of this study comprehensively characterize an understudied microbial group with implications in gut health, determine the prevalence of different SRM taxa within the human gut, and inform future studies in assessing causality between SRM and gut inflammation.

Keywords:  Department of Biology
sulfate-reducing microbes
biology
microbiology
human gut
phylogeny
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Thesis
Advisor: Spormann Alfred
Long Sharon
Quantifying the effects of polar lipid proportions on the stability of model tear films

Dry eye Disease (DED) is one of the most widespread ocular surface disorders across the world and is thought to affect hundreds of millions of people worldwide, including costs of over $50 billion annually to the United States alone. However, despite DED’s widespread prevalence, there are very few effective clinical treatments for the syndrome, in part due to the complexity of the thin liquid coating – i.e. tear film – over the surface of the eye.
One hallmark of DED is premature destabilization of the tear film, which can be caused by many different mechanisms. Although we have an extensive knowledge of the various underlying biological causes for DED, we know relatively little about the resulting physical processes that lead to DED, which makes it difficult to design targeted treatment options.
Particularly little is known about tear film lipids – which are thought to sit on the surface of the tear film. Deficiencies in certain types of polar lipids are thought to be linked to an increased risk of DED, but we do not yet understand why this is the case. Finally, despite a wide array of literature on lipid chemistry, structure, and rheology, no clear link has been made yet between lipid composition on the surface of the eye and the severity of DED.
To address these deficiencies in knowledge, this thesis aims to improve our understanding of the role of polar lipids in the stability of the tear film. We test the stability of model tear films supplemented with varying amounts of the phospholipid “dipalmitoyl phosphatidylcholine” (DPPC) and the wax ester “stearyl stearate,” both of which are comparable to common lipids found natively in the eye. We find that model tear films can be stabilized by both DPPC and SS, likely through a combination of lipid-specific physical mechanisms. When model tear films are created with combined DPPC and SS lipid layers, we find that large increases in the DPPC composition can increase the stability of the model films. Finally, we find that mixed lipid layers have physical properties that differ from the pure lipid components, implying that a more nuanced understanding of lipid interactions is required.
Altogether, this data indicates that large changes to lipid compositions in the tear film could play a role in reducing tear film stability, as is thought to occur in patients with DED. However, a more advanced understanding of multi-component lipid layers is necessary before well-targeted therapeutics can be developed. DED remains a pressing health and societal problem, but this work improves our understanding of the lipid layer of the tear film and provides a basis for future research on the role of lipids in dry eye disease.

Keywords: Huang, Yogi
Dry eye syndromes
Tear film
Interfacial science
Rheology (Biology)
Interfacial lipid layer
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Thesis
Advisor: Fuller Gerald G
Myung David
Quantitative phase contrast imaging with a nonlocal angle-selective metasurface

Phase contrast microscopy has played a central role in the development of modern biology, geology, and nanotechnology. It can visualize the structure of translucent objects that remains hidden in regular optical microscopes. The optical layout of a phase contrast microscope is based on a 4f image processing setup and has essentially remained unchanged since its invention by Zernike in the early 1930s. Here, we propose a conceptually new approach to phase contrast imaging that harnesses the non-local optical response of a guided-mode-resonator metasurface. We highlight its benefits and demonstrate the imaging of various phase objects, including biological cells, polymeric nanostructures, and transparent metasurfaces. Our results showcase that the addition of this non-local metasurface to a conventional microscope enables quantitative phase contrast imaging with a 0.02π phase accuracy. At a high level, this work adds to the growing body of research aimed at the use of metasurfaces for analog optical computing

Keywords: Electrical Engineering.
Advisor: Brongersma Mark L.
Fan Shanhui
Miller D. A. B.
Quantum control and entanglement of nanomechanical oscillators

The quantum behavior of macroscopic objects is not readily apparent in our everyday experience, although the governing equations are present nevertheless. Towards studying this regime, solid-state mechanical objects provide a promising testbed, but quantum control of acoustic devices has been a significant experimental challenge to date. Here, we describe efforts to build a hybrid quantum device composed of nanomechanical resonators coupled to a superconducting qubit. In this device, the mechanical resonators consist of phononic crystals made from thin-film lithium niobate, enabling both acoustic confinement and strong piezoelectric coupling. By using the qubit to control and measure these resonators, we can access nonclassical states of motion, find new ways to process quantum information, and study the quantum nature of sound. In this thesis, we present a series of experiments illustrating the capabilities of this quantum acoustics platform. First, we successfully demonstrate strong dispersive coupling between the qubit and nanomechanical resonator, allowing resolution of phonon number states. This result represents the first direct observation of the quantization of sound in a mechanical oscillator's energy levels. Next, we characterize superconducting, acoustic, and two-level system loss channels in the phononic crystal devices, with the goal of achieving coherence times that exceed conventional planar superconducting circuits. Finally, we build a small-scale quantum acoustic processor that not only achieves control at the single-phonon level, but also performs non-demolition measurements to probe the quantum states of motion. By extending these techniques to two nanomechanical resonators simultaneously, we deterministically synthesize mechanical Bell-states and characterize the resulting quantum entanglement between macroscopic objects. Ultimately, this demonstration provides a hardware-efficient approach towards scaling today's quantum computers

Keywords: Physics.
Advisor: Safavi-Naeini Amir H.
Fejer Martin M. (Martin Michael)
Feldman Ben (Benjamin Ezekiel)
Irwin Kent
Quantum phases on ladders and cylinders

This thesis is primarily concerned with theoretical approaches to quantum condensed matter systems on ladders and cylinders - i.e. geometries that are infinitely long in one direction but finite in another. Ladders and cylinders are extremely interesting systems in their own right, but the theoretical studies carried out here were designed with a very practical goal in mind: to complement density matrix renormalization group (DMRG), a numerical method. We start off in Chapter 1 by motivating the importance of DMRG in treating paradigmatic problems in strongly correlated electron physics, and explaining why DMRG calculations are most naturally carried out on ladder and cylinder geometries. Chapter 2 explores the use of weak-coupling analyses to identify phases at small interaction strengths, where DMRG simulation is most challenging. One of the prob- lems we treat is the half-filled triangular lattice Hubbard cylinder. We explain how our results relate to recent DMRG studies on the same system that apparently detect spin liquid physics. Chapter 3 presents a systematic finite-circumference scaling theory for supercon- ducting cylinders. We explain how our findings can be used to help extrapolate DMRG results to the infinite-circumference limit. Finally, Chapter 4 discusses a different topic in condensed matter physics -- quan- tum oscillations in the cuprate high temperature superconductors. We develop a theory of quantum oscillations in the presence of phase-disordered charge density waves, and use it to interpret key experiments on the material YBCO

Keywords: Physics.
Advisor: Kivelson Steven
Khemani Vedika 
Raghu Srinivas
Quantum photonics with the tin-vacancy center in diamond

Quantum information processing promises to revolutionize computation and communication. Quantum networks, which consist of interconnected quantum nodes, are expected to play an important role in providing secure communication and bolstering the power of quantum computation. Quantum networks have two basic requirements: uniform, long-lived, optically accessible qubits and efficient photonic interfaces. Because of the potential for photonic integration, solid-state quantum emitters have emerged as promising qubit candidates. In particular, atomic-scale defects in diamond known as color centers have garnered much interest for their bright, spin-dependent emission and long spin coherence times. The tin-vacancy (SnV) center in diamond possesses a unique combination of excellent optical properties, inversion-symmetric crystallographic structure, and potential for long spin coherence times at temperatures above 1~K. In this dissertation, I present my work on the SnV center in diamond, from basic optical characterization to photonic integration. We start with a study of the optical and spin properties of single SnV centers isolated in diamond nanopillars. We then demonstrate electrical tuning of the optical transitions of the SnV center via the DC Stark effect, a useful tool for future multi-emitter experiments. We also explore a new approach to generating SnV centers which at once enables site-controlled generation of emitters with a thin, high-resolution implantation mask, mitigates the presence of non-SnV emission, and can be performed without a potentially damaging annealing step. After developing this new color center generation method and a strong understanding of the properties of the SnV center, we proceed to incorporate the SnV center into photonic devices to develop efficient photonic interfaces. We first demonstrate narrow-linewidth emission from SnV centers in nanobeam waveguides, which indicates that we can create photonic structures containing high-quality SnV centers. We then transition from waveguides to cavities. Incorporating SnV centers into photonic crystal cavities, we achieve a 40-fold enhancement in emission intensity, corresponding to a Purcell factor of 25 and a channeling of 90% of the SnV center emission into the cavity mode, a promising result for future SnV center photonic integration. The works presented in this dissertation constitute key developments that have advanced the SnV center from a nascent color center to a competitive optically interfaced qubit candidate

Keywords: Applied Physics.
Advisor: Vuckovic Jelena
Melosh Nicholas A.
Shen Zhi-Xun
“Queremos justicia, no más impunidad”: Transitional Justice in a Post-Ortega Nicaragua

Lindsay Thornton’s capstone project examined the range of transitional justice measures available to address the serious human rights abuses committed by the government of Daniel Ortega in Nicaragua. Her paper focused on the 2018 political unrests experienced across Nicaragua and how these was informed by the contentious rise of Daniel Ortega and his legacy in Nicaraguan politics. Lindsay also analyzed the history of the Nicaraguan Revolution, electoral politics, and public opinion, to show how anti-democratic reforms gave rise to government corruption and brutality across Nicaragua. Lastly, she considers how a transitional justice process implemented in a post-Ortega Nicaragua can help the country secure justice and accountability as well as pave the way for a peaceful and democratic future.
Student project deposited by department for archival purposes. Original work unavailable for public download due to permission restriction preferences of the author.

Keywords: Transitional justice
Nicaragua
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Thesis
Racial Disparities in Childhood Cancer Survival and the Role of Time to Treatment

Background: Survival disparities of childhood cancers among racial and ethnic minorities continue to persist despite significant advancements in care. While partially mitigated when accounting for socioeconomic status (SES) and stage at diagnosis, the persistence of these disparities suggests that additional factors need investigation. There have been suggestions that delays in treatment may contribute to differences in mortality among pediatric and young adult cancer patients.
Methods: Using cancer registry data from the Surveillance, Epidemiology, and End Results (SEER) program, we investigated the role of time from diagnosis to treatment in racial survival disparities among patients diagnosed with a primary malignancy at ages 19 years and under. We compared mortality hazard ratios from regression models with and without time to treatment to assess its specific role in risk of mortality. We also compared race-specific unadjusted survival curves to those adjusted for other known determinants of survival, socioeconomic status and stage at diagnosis.
Results: A total of 47,661 patients were included in the analysis, with 24,696 (51.82%) Non-Hispanic White patients, 5,032 (10.56%) Non-Hispanic Black patients, 3,636 (7.63%) Non-Hispanic Asian/Pacific Islander patients, and 14,297 (30.00%) Hispanic patients. Overall, time to treatment had no statistically significant effect on survival, and it did not affect the risk of mortality in any race group. We then assessed the degree to which stage and SES contribute to known racial survival disparities and found there was partial reduction in survival gaps between minority racial groups compared to Non- Hispanic White patients for lymphomas, central nervous system cancers, and other solid tumors but not for leukemias.
Conclusions: Time from diagnosis to treatment does not appear to act as a significant driver of survival outcomes among children with cancer, and despite adjustment for socioeconomic status and stage, there remain significant racial survival disparities.

Keywords: Department of Epidemiology and Population Health
Stanford University School of Medicine
Master’s of Science in Epidemiology and Clinical Research
healthcare disparities
pediatrics
pediatric oncology
childhood cancer
survival disparities
race/ethnicity
socioeconomic status
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Thesis
Advisor: Whittemore Alice
Partap Sonia
Radar sounding of ice sheet near-surface processes

Ice-penetrating radar is powerful tool for imaging the englacial and subglacial conditions that modulate mass loss and sea level contributions from Earth's ice sheets. Instrument design, data collection, and quantitative data analysis efforts have traditionally focused on resolving the conditions at the ice-bed interface that influence ice velocity. However, the structure and water storage capacity of the glacial near-surface are also important sources of uncertainty in projections of future mass loss from the runoff of surface meltwater, as well as potential impediments to deeper radar imaging. This is because the top of the ice column consists of a 50-100m thick layer of porous, compacting snow known as firn. Firn structure is controlled by past and present temperatures, accumulation rates, and surface melt rates, and this direct coupling to atmospheric conditions makes the firn one of the most heterogeneous and rapidly changing components of the ice sheet system. Here, I develop glaciologically-informed electromagnetic models that link physical conditions in the ice-sheet near-surface to their expressions in measurable properties of airborne ice-penetrating radar data. I combine these models with inverse methods to study the impact of near-surface heterogeneity on the performance of orbital radar ice sounders, characterize the long-term impact of extreme melt seasons on the near-surface structure and hydrology of the Greenland Ice Sheet, and constrain the physical processes governing double ridge formation on Europa based on an analog feature observed in Northwest Greenland

Keywords: Electrical Engineering.
Advisor: Schroeder Dustin
Wetzstein Gordon
Zebker Howard A.