VictorJuiz/thesis huggingface dataset:
On Baccharis pilularis DC. (coyote brush, Asteraceae) Water Relations During Succession Into Coastal Grasslands in a Changing Climate

In California, the common native shrub, Baccharis pilularis DC. (coyote brush, Asteraceae) readily invades grasslands in the absence of fire and grazing. Research shows that water availability is important in regulating B. pilularis seedling establishment in grasslands, with late spring rainfall providing a timely source of moisture that helps B. pilularis roots compete with neighboring grassland plants. The ecohydrology of B. pilularis, particularly during invasion into grasslands, remains largely unexplored. For this research I investigated 1) intraspecific variation in water relations between the prostrate B. pilularis ssp. pilularis and erect B. pilularis ssp. consanguinea (herein B. pilularis) in a mature common garden, 2) seasonal water relations and use of experimentally planted B. pilularis seedlings with and without neighboring plants in cool, fog-prone, perennial-dominated and warm, dry annual-dominated coastal grasslands, and 3) seasonal water relations between experimental B. pilularis seedlings and naturally-occurring adults in the two contrasting grassland types. For these studies I measured a suite of water relations traits including stomatal conductance, stem water potentials, leaf stable carbon isotope composition, tissue-level parameters that reflect cell hydration, stable isotope composition of xylem water, and whole stem hydraulic conductance. First, I found that despite the decreasing water availability during the rainless summer, both B. pilularis morphotypes increased rates of stomatal conductance and photosynthesis. These increases are likely a strategy to meet increased carbon demands before B. pilularis’ fall blooming period, so the plants can produce adequate numbers of wind-pollinated and wind-dispersed flowers to ensure successful dispersal and establishment into neighboring grasslands. Second, a manipulative neighbor removal treatment demonstrated that grassland neighbors harvest fog for use by B. pilularis seedlings when fog water is present but not in the warm, dry annual grassland with very little fog where seedlings grew significantly better. Third, as expected, adults showed greater tolerance for water deficit and seedlings readily used fog water when fog was present. As in Chapter One, plants in both age classes show the same increased demand for carbon before the onset of the blooming period as demonstrated by increased stomatal conductance, osmotic adjustment, bulk leaf δ13C during the rainless summer. These results provide evidence that B. pilularis is well adapted to withstand water deficits yet plant water status can benefit from neighbors in fog-prone areas. In a warmer and drier climate, this shrub will likely become an increasingly dominant presence throughout the California Floristic Province.

Advisor: McBride, Joe R
Dawson, Todd E
New Taxes and the American States: The Social Origins of Fiscal Citizenship Debates, 1945-1970

Scholars have documented that a new type of fiscal compact took hold in the United States during the twentieth century as taxpayers supported progressive taxation on incomes in exchange for public investments by government aimed at securing widespread prosperity. Yet by focusing primarily on the national level, existing literature examining the link between tax structure and social policy in the United States has missed a key element of American fiscal exceptionalism. By moving to the state level, my analysis finds that very different fiscal bargains, or models of “fiscal citizenship,” developed across the American states between the late 1940s and early 1970s, in many cases dramatically departing from the national model. Indeed, in some states, taxes were understood not as a way to underwrite progressive investments but rather as a means to force groups “escaping” taxation to contribute more toward the cost of government, as a way of preserving an exclusionary social order, or as a tool for purchasing autonomy from federal intervention./nUnderstanding the factors shaping this period of reforms is critical for strengthening theories of the exceptional American welfare state, particularly since the United States is distinctive in its strong reliance on state-level revenue generation to support social policy expenditures. In this dissertation, I examine what factors were responsible for the development of such diverse fiscal compacts across the American states by undertaking a comparative historical analysis of four key cases of state tax reform: New York, Texas, Georgia, and South Carolina. I find that types of social contracts negotiated between taxpayers and the American states during these critical tax debates depended on the balance of power between labor and business groups and the prevailing racial order in each state.

Advisor: Weir, Margaret
Retinal Image-Based Eye-Tracking Using the Tracking Scanning Laser Ophthalmoscope

The tracking scanning laser ophthalmoscope (TSLO) was designed, built and characterized for high-resolution eye-tracking, imaging, and targeted retinal stimulus delivery. Eye-tracking is done via an image-based software program that monitors the image of the retina over time while simultaneously logging the displacements of the eye. Currently, this system is the most accurate, fast and functional eye-tracking system used in a standard ophthalmic instrument. The TSLO has the ability to non-invasively track the eye at 960 Hz (with an accuracy of 0.2 arcminutes or roughly 1 micron) and present stimuli to the retina at the resolution of single cone photoreceptors (0.66 arcminutes, which is roughly 3 microns). The combination of structural imaging and functional testing allows one to begin to more thoroughly understand retinal disease progression, as well probe specific retinal locations in order to test new treatment efficacies. This level of accuracy is unprecedented in the clinic and is crucial when monitoring minute changes in eye motion, structure, and function. Additionally, the system is capable of providing external eye-tracking for other high-resolution imaging systems, such as optical coherence tomography (OCT) and adaptive optics scanning laser ophthalmoscope (AOSLO) systems through the active steering of an imaging beam. This feature allows the imaging raster or stimuli to stay on target during fixational eye motion. This dissertation steps through all of the above-mentioned uses of the TSLO and further elaborates on the optimal design and system test performance capabilities of the system.

Advisor: Roorda, Austin
Unified Multi-Cue Depth Estimation from Light-Field Images: Correspondence, Defocus, Shading, and Specularity

Light-field cameras have recently become available to the consumer market. An array of micro-lenses captures enough information that one can refocus images after acquisition, as well as shift one's viewpoint within the sub-apertures of the main lens, effectively obtaining multiple views. Thus, depth cues from defocus, correspondence, specularity, and shading are available simultaneously in a single capture. Previously, defocus could be achieved only through multiple image exposures focused at different depths; correspondence and specularity cues needed multiple exposures at different viewpoints or multiple cameras; and shading required very well controlled scenes and low-noise data. Moreover, all four cues could not easily be obtained together./nIn this thesis, we will present a novel framework that decodes the light-field images from a consumer Lytro camera and uses the decoded image to compute dense depth estimation by obtaining the four depth cues: defocus, correspondence, specularity, and shading. By using both defocus and correspondence cues, depth estimation is more robust with consumer-grade noisy data than previous works. Shading cues from light-field data enable us to better regularize depth and estimate shape. By using specularity, we formulate a new depth measure that is robust against specularity, making our depth measure suitable for glossy scenes. By combining the cues into a high quality depth map, the results are suitable for a variety of complex computer vision applications.

Advisor: Ramamoorthi, Ravi
Dynamics of Electron Relaxation Studied Using Time-Resolved Photoelectron Spectroscopy in Liquid Microjets

The solvated electron, an isolated electron in polar solution, is a species of fundamental interest to the physics of solvation and to the understanding of condensed phase reactions in the presence of ionizing radiation. In radiation chemistry and biology, the solvated electron acts as a powerful reductant and has been shown to act as a reagent in a wide range of processes from atmospheric chemistry to radiation-induced DNA damage. As the "simplest'' quantum mechanical solute, the solvated electron serves as a fundamental probe of solute-solvent interaction and thus has been used as a model system for studying solvation processes./nHere, time-resolved photoelectron spectroscopy is used to study the binding motifs and solvation dynamics of solvated electrons in various polar solvents. This thesis is separated into three parts: first, an introduction to the research and description of the apparatus, second, results from experiments on the relaxation dynamics of the solvated electron after photoexciation and after generation by charge-transfer-to-solvent and, third, preliminary designs and proposed experiments for a liquid jet photoelectron spectrometer with attosecond time resolution.

Advisor: Neumark, Daniel M.
Before the Eye Moves: Remapping, Visual Stability and Perisaccadic Perception

Our perception is of a stable visual world, yet we make several saccadic eye movements per second – to say nothing of the motion of objects in the world or our own motion through the physical world. Even standing on a stage, looking out at an audience, we have the perception of the crowd in detail, in spite of our less than accurate peripheral input. Standing on this stage, it is a trivial matter to make a series of saccades to the faces of various audience members to find one particular person – how can we do this, since visual crowding makes these faces unidentifiable? How much information is available from peripheral vision prior to a saccade? While making saccades to individual members of the crowd is useful for identifying them, what about gaining a sense of the audience as a whole? We can perceive the ensemble emotion of the audience without examining each and every member, but is this solely possible with peripheral information, the details of which we cannot otherwise access, or does it require foveal information?/nWhile a great deal of information is available from peripheral vision, identifying individual objects is difficult due to visual crowding; we solve this problem by simply making a saccade to the object we wish to identify. The ability to saccade to a crowded object implied that a saccade to a crowded object might reduce crowding before the object was foveated, essentially unlocking peripheral information that is otherwise inaccessible. We performed a series of experiments where subjects made saccades to crowded faces and were not permitted to foveate them; we found that crowding was diminished presaccadically and that this was more effective than covert attention alone. Our crowding result shows that saccade planning can diminish crowding, but what information becomes available to conscious vision? To determine this, we performed a series of experiments to determine whether saccadic remapping acquired object representations or merely constituent features from saccade targets. We found that saccadic remapping was object-selective and tightly tuned to the target of the saccade, suggesting that, prior to a saccade, detailed information is made available to conscious vision. However, there simply is not time to take advantage of this unlocking for each face in a crowd – can the visual system use this inaccessible information to generate a percept of the group as a whole – an ensemble code – and is foveation of individuals required? We occluded foveal input and determined that it was unnecessary for ensemble perception of emotion. In all, these three studies demonstrate that peripheral input is remarkably detailed and that the visual system can use this information to both facilitate identification of individual group members as part of saccade planning, and to provide a useful assessment of the crowd as a whole

Advisor: Whitney, David
Public Opinion and Political Representation

This dissertation considers the relationship between the opinions voters have on issues and the positions politicians take on them. The first chapter makes a methodological intervention into existing literature, showing that to understand these relationships we must examine one issue at a time, not boil down the preferences of voters and politicians to summaries of their ideologies. It then considers some implications of this distinction. The second chapter elaborates one of these implications, the implications of polarization for representation. This chapter argues for a different set of implications than is typically drawn. The final chapter then adopts this approach to bring a new perspective to a neglected question: how do politicians see their constituents? By investigating this question in individual issues, the final chapter illustrates the utility of the approach and raises new questions for scholars to consider.

Advisor: Schickler, Eric
Lewis Acid Mediated Reactions: Electronic Modification of Platinum Complexes and Metal-Free Catalysis

Chapter 1. A strategy for the control of electron density at a metal center is reported, using a remote chemical switch involving second-sphere Lewis acid binding that modulates electron density in the first coordination sphere. Binding of the Lewis acid B(C6F5)3 at remote nitrogen positions of a bipyrazine-diarylplatinum(II) complex accelerates biaryl reductive elimination by a factor of 64,000./nChapter 2. The silicon and zinc Lewis acids Si(cat)2 (cat = catecholato), Si(catF)2 (catF = tetrafluorocatecholato), and Zn(C6F5)2 bind to the remote ligand site of a 2,2´-bipyrimidyl–platinum diaryl complex. This platinum complex provides a platform to systematically evaluate electronic and reactivity differences triggered by Lewis acid binding. The electron density of the bipyrimidine ligand is substantially depleted upon Lewis acid binding, as evidenced by UV-vis spectroscopy and cyclic voltammetry. Biaryl reductive elimination studies allowed quantification of the effect of Lewis acid binding on reactivity, and Lewis acid binding accelerated reductive elimination rates by up to eight orders of magnitude. Kinetics experiments in combination with DFT studies support an unusual mechanism featuring complete dissociation of the bidentate bipyrimidine ligand prior to reductive elimination./nChapter 3. Z-type interactions between bis(perfluorophenyl)zinc and platinum(II) diaryl complexes supported by phenanthroline (phen), bipyridine (bpy), and bis(dimethylphosphino)ethane (dmpe) ligands are reported. In the solid state, there is an unsupported Pt–Zn bond for the phen complex, while the dmpe derivative features additional bridging aryl interactions. The Pt–Zn complexes featuring phen and bpy ligands undergo facile reductive elimination, whereas aryl exchange between Pt and Zn is observed for the dmpe complex./nChapter 4. Bis(perfluorocatecholato)silane Si(catF)2 was prepared, and stoichiometric binding to Lewis bases was demonstrated with fluoride, triethylphosphine oxide, and N,N'-diisopropylbenzamide. The potent Lewis acidity of Si(catF)2 was suggested from catalytic hydrosilation and silylcyanation reactions with aldehydes. Mechanistic studies of hydrosilation using an optically active silane substrate, R-(+)-methyl(1-napthyl)phenylsilane, proceeded with predominant stereochemical retention at silicon, consistent with a carbonyl activation pathway. The enantiospecificity was dependent on solvent and salt effects, with increasing solvent polarity or addition of NBu4BArF4 leading to a diminished enantiomeric ratio. The medium effects are consistent with an ionic mechanism, wherein hydride transfer occurs prior to silicon–oxygen bond formation.

Advisor: Tilley, T. Don
Bergman, Robert G.
Perceptual artifacts associated with novel display technologies

Stereoscopic 3D displays are able to provide an added sense of depth compared to traditional displays by sending slightly different images to each eye. Although stereoscopic displays can provide a more immersive viewing experience, existing methods have drawbacks that can detract from image quality and cause perceptual artifacts. In this thesis I investigate perceptual artifacts associated with displays, and propose novel techniques that can improve viewing experience compared to existing methods. Chapter 1 presents a broad introduction to the various types of artifacts that can occur in displays, including motion artifacts, depth distortion, flicker, and color breakup. In Chapter 2, I describe a novel display technique, "spatiotemporal interlacing," that combines spatial and temporal interlacing. I demonstrate using psychophysics that this method provides a better viewing experience than existing methods, and I present a computational model that confirms the psychophysical data. In Chapter 3, I present an investigation of perceptual artifacts on a high-frame-rate (240Hz) temporally interlaced OLED display. The high frame rate of this display allows for several unique driving modes. I investigated the perceptual consequences of these driving modes, characterizing the display in terms of motion, depth distortion, flicker, spatial resolution, and luminance. I demonstrate how one's selection of viewing mode can tailor the viewing experience depending on the goals of viewer. Chapter 4 discusses the phenomenon of color breakup, a perceptual artifact that occurs in displays that present colors sequentially in time, such as Digital Light Processing (DLP) projectors. I discuss a novel psychometric procedure to measure the artifact, and a way to model the saliency of the artifact based on known spatiotemporal properties of the human visual system. I also propose a method for reducing color breakup.

Advisor: Banks, Martin S
K(pi, 1) Spaces in Algebraic Geometry

The theme of this dissertation is the study of fundamental groups and classifying spaces in the context of the étale topology of schemes. The main result is the existence of K(pi,1) neighborhoods in the case of semistable (or more generally log smooth) reduction, generalizing a result of Gerd Faltings. As an application to p-adic Hodge theory, we use the existence of these neighborhoods to compare the cohomology of the geometric generic fiber of a semistable scheme over a discrete valuation ring with the cohomology of the associated Faltings topos. The other results include comparison theorems for the cohomology and homotopy types of several types of Milnor fibers. We also prove an l-adic version of a formula of Ogus, describing the monodromy action on the complex of nearby cycles of a log smooth family in terms of the log structure.

Advisor: Ogus, Arthur E.
Derived Equivalent Varieties and their Zeta Functions

In order to shed light on Orlov’s conjecture that derived equivalent smooth, projective varieties have isomorphic Chow motives, we examine the zeta functions of derived equivalent varieties over finite fields; in this setting Orlov’s conjecture predicts equality of zeta functions. It is demonstrated that derived equivalent smooth, projective varieties over finite fields that are abelian or satisfy a certain condition on their cohomology. This condition is satisfied, for example, by a surface or Calabi–Yau 3–fold./nOne of our approaches to comparing the zeta functions of derived equivalent varieties over finite fields comes from using the Lefschetz Fixed Point Theorem to turn the question into one of comparing the -adic ́etale cohomology of varieties. Cohomology groups are not in general preserved under the action of Fourier–Mukai equivalences on cohomology, but cohomological structures we call even and odd Mukai–Hodge structures, which are a realization of the Mukai motive, are preserved. Investigation into when isomorphism of these cohomological structures implies equality of zeta functions gives us our cohomological condition for equality of zeta functions./nWe also develop a relative version of the map Fourier–Mukai transforms induce on cohomology and define a relative notion of even and odd Mukai–Hodge structures, and show these structures are preserved in a situation arising from the derived equivalence of smooth, projective varieties with semiample (anti-)canonical bundles. Using this result, it is demonstrated that when derived equivalent smooth, projective varieties have semiample (anti-)canonical bundles, the fibers over any fixed geometric point in their shared (anti-)canonical variety must also have isomorphic even and odd Mukai–Hodge structures. Hence, for any such varieties over finite fields, if their geometric fibers satisfy any of the conditions identified for isomorphism of Mukai–Hodge structures to imply equality of zeta functions, then the varieties themselves also have equal zeta functions.

Advisor: Olsson, Martin C
Literature of Diminishment: American Regionalism and the Writing of Nature

Literature of Diminishment redefines regionalism as a philosophical approach that prefers a partial view of oneself and of others, whether human or nonhuman, rather than the comprehensive view pursued by nineteenth-century science. I show how American regionalist writings from the 1820s to 1910s adapt scientific techniques of observation to the aesthetics of the regionalist sketch. Their "sketchy" view of Nature highlights the deficiencies of knowing and nonetheless opens out to a view of biological processes and succession in which life cedes to life through its casualties. Regionalist literature is, then, less a literature of particular cultural or geographical regions as it is a literature whose principles of diminishment might insist on the roughness and limits of a regional setting. The archive of works I draw upon extends from environmental literature—the nature writings of John James Audubon, Henry David Thoreau, and Celia Thaxter—to less conventionally regionalist texts of the nineteenth and early twentieth centuries such as works by Emily Dickinson, Herman Melville, W.E.B. Du Bois, and Gertrude Stein./nIn regionalist formulations, diminishment is a mode of seeing that relies on imprecise and partial specifications rather than strict definitions. Understanding art and science as approaches that both connote ways of seeing and being in the world, I show how writers like Thoreau, Dickinson, Melville, Thaxter, and Sarah Orne Jewett experiment with partial ways of seeing through concomitantly aesthetic and scientific uses of views, optics, and visual technology. Setting the frame with Thoreau's vista from the eroding shores of Cape Cod, I consider how these writers' engagement with natural history's empirical methods attends to their own perceptual diminishment, and also, critically, to the diminishment of their object of study—Nature, or, more generally, life. The final chapters examine the practice and politics of seeing human races as "species," that is, as part of nature, through what I consider "snapshots" of black workers. Du Bois's and Stein's literary-photographic studies view and review the racialist natural history that pictures African-Americans, as Du Bois writes, "somewhere between men and cattle." Regionalism, I argue, instead affords the succession of life through diminishment, rather than a reduction of life to units of data.

Advisor: Hale, Dorothy