VictorJuiz/thesis huggingface dataset:
Sociodemographic Predictors of Patient Migration and Waitlist Outcome for Liver Transplantation in the United States
Keywords:  Department of Health Research & Policy
Mannalithara, Ajitha
Liver transplantation
geographic disparity
organ allocation
Thesis

Background: Faced with ongoing organ shortage and regional differences in organ availability, patients requiring liver transplantation may relocate to improve their chance of transplantation.
Objective: To identify predictors of patient migration for liver transplantation in the United States (US), and to evaluate the effect of migration on waitlist outcome.
Design: This is a retrospective cohort study of adult liver transplant candidates and recipients from 2004 to 2016.
Setting: The Organ Procurement and Transplantation Network database represents all transplant and waitlist events in the US.
Patients: Eligible patients included adults living in a zip code with available median income data. Patients listed or transplanted for multi-organ transplantation other than liver-kidney, as Status 1 priority, or with insurance through the Veterans Affairs system, were excluded.
Measurements: Migration was defined as travel to a transplant center greater than 500 miles from a patient’s zip code and outside their home transplant region. We identified sociodemographic factors associated with migration and assessed the impact of migration on waitlist outcomes.
Results: Of 61,007 eligible recipients, 2,066 (3.4%) migrated for transplantation. Migration was associated with non-black race, non-Medicaid payer, residence in a higher income area, and education beyond high school. Of 104,914 primary waitlist registrations during the same period, 2,930 (2.8%) were listed at a distant center. In multivariable competing risk analysis, with liver transplantation as a competing event, distant listing was associated with reduced 1-year waitlist mortality (subdistribution hazard ratio 0.80, 95% CI 0.71-0.90).
Conclusion: Listing at a distant center, which often involves considerable travel and resources, is associated with reduced waitlist mortality. Geographic disparity in access to liver transplantation disproportionately affects minority patients with lower income and public insurance.
Solidarity in action : a case study of journalistic humanizing techniques in the San Francisco homeless project
Keywords: Communication.

Solidarity is a political commitment to social justice that translates into action, and is a longstanding, though unacknowledged, ideal within American journalism that humanizes marginalized communities. To explain the role and significance of solidarity in journalism that humanizes marginalized communities, this dissertation explicates the concept of solidarity, applies solidarity to journalism, and develops an empirical case study of a 2016 journalistic collaboration called the San Francisco Homeless Project to demonstrate how journalistic humanizing techniques invite and impede solidarity. Based on semistructured interviews with participating journalists paired with textual analysis of their stories, this dissertation finds that journalists humanize homeless people through personalization techniques that appeal to empathy by representing homeless people's personal problems, and do so at the expense of solidarity. Empathy becomes a barrier to solidarity in journalism because it individualizes social injustice. On the other hand, journalists also rely on politicization techniques that invite solidarity by representing homeless people as living within unjust conditions produced by systemic factors that they cannot individually surmount. This dissertation concludes by arguing that solidarity provides a news value for guiding journalistic practice in the direction of social justice.
Solid-state architecture for an elevated-temperature photoelectrochemical cell
Keywords: Materials Science and Engineering.

Solar fuels can be utilized to overcome the storage and distribution limitations of solar energy by using sunlight to convert water into hydrogen fuel. Photoelectrochemical cells (PECs) have been investigated as a tool for solar-to-hydrogen conversion for several decades, and the majority of PECs used for solar water splitting operate near room temperature with a liquid or polymeric electrolyte. These devices are typically limited by slow kinetics and thermodynamic losses at interfaces, and have often suffered from severe stability concerns. My colleagues and I have recently shown that even a small temperature increase can substantially improve the minority carrier collection efficiency of PECs, thus increasing the photocurrent density output by the cell. Additionally, using a detailed-balance approach, we have shown that a solid-state composite device operating at 450 C could achieve solar-to-hydrogen efficiencies as high as 17%. In this dissertation, I first review our experimental work confirming enhanced water-splitting performance for modest increases in temperature up to 70 C. These enhancements are observed for multiple metal-oxide systems, including iron oxide and bismuth vanadate. I then describe how we developed a composite, solid-state architecture for elevated temperature photoelectrochemistry using an oxide-based solid electrolyte. Since the oxygen evolution reaction is typically limiting due to its catalytic complexity, most of the subsequent work focuses on this reaction at the photoanode surface. Next, I discuss the fabrication and characterization of a solid-state PEC composed of a bismuth vanadate light absorber and a yttria-stabilized zirconia thin-film solid electrolyte. Our cell design has enabled us to achieve photocurrent densities above 100 mA/cm^2 at temperatures between 300 to 400 C -- among the highest current densities observed in literature for a solid-state photoelectrochemical cell. Throughout, I highlight my work on optimizing the oxide layers, current collector morphology, and deposition techniques to improve cell performance. To better understand the results, I share our findings regarding the role of thermal effects on the observed performance, and I demonstrate my initial results for future materials of interest like titanium oxide. Ultimately, my thesis conveys the benefits of elevated temperature on PEC performance, the role of heterojunctions on enhanced charge-separation, and the opportunity provided by thin-film solid electrolytes to enable high photocurrent densities for photon-assisted oxygen evolution.
Solvolysis of enantioenriched dihalides and its application to the synthesis of the brominated chamigrene sesquiterpenes
Keywords: Chemistry.

To date, more than 2,000 natural products have been isolated and structurally characterized which contain either a chlorine- or bromine-bearing stereocenter. Of these secondary metabolites, approximately 500 contain a brominated five-, six-, or seven-membered cyclic scaffold that is often further embedded within a larger terpene-derived polycyclic architecture. Despite the abundance of these motifs in nature, synthetic technologies providing enantioselective access to these structures are largely deficient. To access such structural motifs, we developed a methodology wherein enantioenriched bromochlorides were subjected to ionizing media (hexafluoroisopropanol) to generate a non-racemizing bromonium ion, which could be captured intramolecularly leading to a cyclized product with near-perfect enantiospecificity. This solvolytic bromonium-initiated cyclization was used to access numerous natural product-relevant scaffolds. The analogous enantioenriched dibromides were found to rapidly racemize under these ionizing conditions. This methodology was applied to the synthesis of several brominated chamigrene sesquiterpenes, a class of approximately 100 red algal-derived secondary metabolites. The flagship member of this class, (+)-aplydactone, and its putative biosynthetic precursor, (--)-dactylone, were synthesized enantioselectively for the first time.
Songs of empire : embedded hymns and the Latin hymnic tradition
Keywords: Classics.

Our understanding of the Latin hymnic tradition has long been impeded by a number of challenges ranging from basic evidential scarcity to formal analytical bias. In this dissertation, I argue for a common set of themes and contexts that unites the Latin hymnic genre. Though our earliest Latin hymns (the carmina of the Salii and Fratres Arvales) are only fragmentary, I show in the first portion of the dissertation that we can nevertheless identify in them themes of war, agriculture, and liminality, the former two in particular idealized cornerstones of early Roman society. As a result, later Latin authors had a vested interest in portraying the Latin hymnic tradition as an indigenous Roman genre, despite its obvious Greek influences. In the latter half of my work, I take case studies of embedded hymns from early imperial authors and show how in both the Augustan and Flavian periods, hymns staged concerns around political continuity with this idealized Roman past. Through its diachronic study of Latin hymns from roughly the 3rd century BCE to its Common Era counterpart, this dissertation ultimately argues that the thematic unity and formal flexibility inherent to the Latin hymn allowed Roman authors to turn work in any poetic genre into a song of empire—in the late Republic and early Empire, poets used embedded hymns to accommodate the changing Roman political landscape, styling their hymnic praise as carmina 'condita' and the refined refoundation of Rome's mythic past.
Space acts : performance, architecture, and the mise-en-scène
Keywords: Theater and Performance Studies.

By analyzing case studies occurring at the intersection of architecture and performance, this dissertation asserts spatial design's role as a critical and performative activity. I argue that these modes of spatial design and activity, while establishing themselves in the built environment, actively perform in real time, refusing to stagnate in the still plan. To describe this spatial activity I draw from the concept of the mise-en-scène. I define the mise-en-scène as a means, method, and medium through which visual and spatial relations structure the sensorium of the stage and the built environment at large. The examples I enlist demonstrate how mise-en-scène engages with the politics of space. By framing them through the mise-en-scène, I analyze design practices by architects Oskar Hansen, Lawrence Halprin, Rem Koolhaas, and Elia Zenghelis; as well as political interventions on architecture. The demonstrations I address range from pictorial to destructive: the graphic interventions of the Atelier Populaire in France in 1968, the symbolic action of the Pentagon levitation in 1967, and the bombings of the Weather Underground from 1969 to 1975. Each case explores the pressure placed upon social performance by architecture, and demonstrates the importance of mise-en-scène as a dynamic concept in contemporary architectural theory.
Speaker systems
Keywords: Philosophy.

This dissertation is concerned with the question of what it means to be a speaker, by which I mean the kind of thing which can perform speech acts. It is, in this way, a study in the foundations of speech act theory. The first two chapters are mainly concerned with conceptual engineering while the last two make use of the framework in understanding other thorny kinds of speech act. Ch.1 lays out the central problem and establishes some of the fundamental distinctions and tools that will help us understand what it is that goes into the production and performance of a speech act. Ch. 2 examines proxy speech (when one agent ``speaks for'' another), using such cases to motivate some more essential distinctions. Ch.3 applies the tools introduced in the earlier chapters to the analysis of group speech acts, in particular marking important differences between group collaboration through speech acts, group co-authoring of speech acts, and group speech proper. These differences register when we take into account the different speaker roles and their normative significance. Finally, Ch.4 examines the way in which one may manipulate speaker systems, and thereby anonymize a speech act in a communicatively significant manner.
Speciation of Metal Ions Associated with Fine Fe(III)-oxyhydroxide Particles in Cement Creek Basin, Colorado after the 2015 Gold King Mine Spill
Keywords:  Department of Geological Sciences
Stanford School of Earth Energy &amp; Environmental Sciences
acid mine drainage
Gold King Mine Spill
Geological Sciences
Thesis

The Gold King Mine Spill on August 5th, 2015 released 3,000,000 gallons of acid mine waters and 880,000 pounds of metals to the Animas River Watershed. The initial impacts of the spill appear to have been naturally mitigated, in part, by the presence of iron-oxyhydroxide particles, which are known to sorb metals from aqueous solutions. Hydrated metal ions can form inner- and outer-sphere sorption complexes on Fe(III)-oxyhydroxide particles, and their sorption is dependent on several factors, including pH, aqueous silica content, and the presence of Fe(II) and As(III)-oxidizing bacteria. We apply laboratory-based x-ray diffraction (XRD), x-ray fluorescence (XRF), inductively coupled plasma-mass spectrometry (ICP-MS), and synchrotron-based micro x-ray fluorescence mapping (µXRF) and x-ray absorption spectroscopy (XAS) on water, sediment (upper 6 cm), and fine particle samples from 15 sites in Cement Creek Basin to determine the effect of pH on the association of Pb(II), Cu(II), and Zn(II) with Fe(III)-oxyhydroxide particles. Solid phase analyses show pH-dependent partitioning of Cu, Pb, and Zn occurs between sediment and fine particle phases. Goethite (Fe3+O(OH)) and ferrihydrite (Fe3+2O3 •.5(H2O)), two Fe(III)-oxyhydroxides that sorb metals from solution as a function of pH, comprise 31-66 percent of the iron species identified in extended x-ray absorption fine structure (EXAFS) fitting of the fine particle samples. The pH-dependent partitioning of metal ions suggests that changes in pH could have a major impact on the speciation of metal cations, including the mobilization of Pb(II) if the pH decreased to ~2.7 in Cement Creek Basin, and mobilization of Zn(II) and Cu(II) if pH decreased to 5.6 or 4.5, respectively, at the Animas River confluence. Such changes could pose significant environmental hazards to aquatic organisms and the human population in the Animas River Watershed, which is used by six states and twelve Native American tribes for water, recreation, and agriculture.
Spectrally and power efficient optical communication systems
Keywords: Electrical Engineering.

Increased traffic demands globally and in particular in short-reach links in data centers will require optical communication systems to continue scaling at an accelerated pace. Nevertheless, energy constraints start to limit the bit rate that can be practically transmitted over optical systems both at the shortest distances in data centers and at the longest distances in ultra-long submarine links. Short-reach links in data centers face strict constraints on power consumption, size, and cost, which will demand low-power solutions that scale to bit rates beyond 100 Gbit/s per wavelength, while accommodating increased losses due to longer fiber plant, multiplexing of more wavelengths, and possibly optical switching. At the longest distances, submarine optical cables longer than about 5,000 km face energy constraints due to power feed limits at the shores, which restricts the electrical power available to the undersea optical amplifiers, ultimately limiting the optical power and throughput per fiber. This dissertation presents strategies to mitigate these limitations. For short-reach links in data centers, we propose low-power coherent receiver architectures that completely avoid high-speed analog-to-digital converters and digital signal processors. For long-haul submarine links, we demonstrate how optimizing the channel power allocation under a constraint on the amplifier power maximizes the information-theoretic capacity per fiber.
Spectroscopic studies on electronic correlation and lattice coupling in hole-doped high-Tc cuprates
Keywords: Applied Physics.

Systematic, high resolution investigation of the single-particle properties of the heavily overdoped high-Tc superconductor Bi-2212 is carried out with angle-resolved photoemission spectroscopy (ARPES). We find quantitatively that the weak-coupling limit can be reached in this regime, but respectable superconducting fluctuation still persists, and the system is not completely Fermi-liquid which has long been assumed. We measure the particle-hole mixing ratio near the antinode, locate the origin for such fluctuation to the abnormally flat band near the zone boundary in Bi-2212, and explain why Bi-2212 was once considered an example of BCS-BEC crossover system. This provides the first clear momentum perspective to resolve the BCS vs BEC contention in overdoped cuprates. We discover an abrupt change in electron-phonon coupling and the superconducting gap across the critical doping in high-Tc system Bi-2212. This not only reveals the correlation between the mode-coupling and the superconductivity, but also signifies the importance to factor in the lattice degree of freedom when constructing future theories on intertwining electronic orders in the cuprates. Using inelastic x-ray scattering (IXS) and Raman spectroscopy, we also identify of a universal low-energy phonon-broadening in both charge ordered and non-charge ordered region of Bi-2212. Its origin is discussed to favor intrinsic acoustic-optical phonon hybridization rather than the previously suggested charge order induced softening. As a conceptual extension of the previous section, lattice instability may be an indispensable ingredient in the charge order phenomenon in underdoped cuprates. We develop and benchmark a 114nm (11eV) high repetition rate laser as an ARPES lightsource. This setup bridges the application gap between the synchrotron ARPES (access to the full momentum space and valence band) and traditional 6/7eV laser-ARPES (high resolution and high stability).
Stable isotopes of nitrite as a tool for understanding nitrogen cycling and loss in oxygen deficient zones
Keywords: Earth System Science.

Nitrogen (N), a key nutrient in the global ocean, has a complicated biogeochemical cycle. In the ocean, nitrogen is mainly found as nitrate (NO3-), but it also accumulates as nitrite (NO2-) within oxygen deficient zones (ODZs). Nitrite is a key intermediate in several processes that produce nitrous oxide (N2O), a potent greenhouse gas. Using natural abundance stable isotope measurements of NO3- and NO2- help to capture an integrated signal of the N cycle processes. My doctoral work aims to use stable isotopes of N and oxygen (O) in order to further our understanding of the pathways that produce and consume NO2-, which will help us better predict the global impacts of nitrogen cycling both at present and in the future. Many N cycle processes are microbially mediated and impart one or more unique isotope effects on its N substrates and products, and it is important to quantify these isotope effects in order to use numerical models to elucidate relative contributions of different N cycle processes. In Chapter 1, I use pure culture experiments to better constrain estimates of the N and O isotope effects of microbial nitrite reduction, a key step in the process of denitrification, which leads to loss of bioavailable N. I then use the values from this experiment, in conjunction with previous estimates of other N cycle process isotope effects, to model observed NO3- and NO2- data from the Arabian Sea (Chapter 2) and explore the necessity for oxygen-requiring processes within the ODZ. In Chapter 3, I expand upon the results from previous chapters by applying the results to a global 3D inverse model of the N cycle, which includes isotopic fractionation, in order to examine the NO2- production and consumption processes within marine ODZs. I also examine the sensitivity of NO3- and NO2- concentration and isotope profiles to controlling parameters of N cycle processes, such as oxygen thresholds and isotope effects, in order to examine the roles of individual processes in N loss, and their potential for future change.
Stable matchings in metric spaces
Keywords: Electrical Engineering.

Suppose each of $ men and $ women is located at a point in a metric space. A woman ranks the men in order of their distance to her from closest to farthest, breaking ties at random. The men rank the women similarly. An interesting problem is to use these ranking lists and find a stable matching in the sense of Gale and Shapley. This problem formulation naturally models preferences in several real world applications; for example, dating sites, room renting/letting, ride hailing and labor markets. Two key questions that arise in this setting are: (a) When is the stable matching unique without resorting to tie breaks? (b) If $X$ is the distance between a randomly chosen stable pair, what is the distribution of $X$ and what is $E(X)$? These questions address conditions under which it is possible to find a unique (stable) partner, and the quality of the stable matching in terms of the rank or the proximity of the partner. We study dating sites and ride hailing as prototypical examples of stable matchings in discrete and continuous metric spaces, respectively. In the dating site model, each man/woman is assigned to a point on the $-dimensional hypercube based on their answers to a set of $ questions with binary answers ({\it e.g.}\ , like/dislike). We consider two different metrics on the hypercube: Hamming and Weighted Hamming (in which the answers to some questions carry more weight). Under both metrics, there are exponentially many stable matchings when = \lfloor\log n\rfloor$. There is a unique stable matching, with high probability, under the Hamming distance when = \Omega(n^6)$, and under the Weighted Hamming distance when > (2+\epsilon) \log n$ for some $\epsilon> 0$. In the ride hailing model, passengers and cabs are modeled as points on the line and matched based on Euclidean distance (a proxy for pickup time). Assuming the locations of the passengers and cabs are independent Poisson processes of different intensities, we derive bounds on the distribution of $X$ in terms of busy periods at a last-come-first-served preemptive-resume (LCFS-PR) queue. We also study the college admission problem where the goal is to find a stable matching between students and colleges. In our analysis, we consider a utility-based model for the preference lists of colleges and students. We derive sufficient conditions on the utility functions to have a unique stable matching. We also model the interview process in the college admission problem, and show that if conducting interviews are costly, in certain circumstances we may see over-qualification of applicants.