VictorJuiz/thesis huggingface dataset:
Deviation inequalities for eigenvalues of deformed random matrices [electronic resource]
Keywords: Mathematics.

We consider two models of deformed random matrices. The first model is the deformed GOE. Let G be a n by n matrix in the Gaussian Orthogonal Ensemble (GOE) with off diagonal entries having variance $\frac{\sigma^2}{n}$ and let P be a n by n real symmetric matrix whose non zero eigenvalues are $\theta_1 \geq \cdots \geq \theta_r > 0$. We establish non-asymptotic deviation inequalities for the extreme eigenvalues of A = P + G of the following type: $P(\lambda_i (A) - \lambda_{\theta_i}[vertical line] \geq t) \leq C_1 n^{r-i+1} e^{-C_2 nt^2 / \sigma^2}, 1\leq i \leq r$, where $\lambda_{\theta_i} = \theta_i + \frac{\sigma^2}{\theta_i}$ or
Device engineering for efficient dye-sensitized solar cells [electronic resource]
Keywords: Applied Physics.

Dye-sensitized solar cells (DSCs) offer a variety of advantages to typical silicon and thin film solar cells. And while the advantages of ease-of-processing and fabrication from low-cost, earth-abundant materials make DSCs an attractive technology, the efficiency of DSCs (13%) is still too low to compete with the current inorganic incumbents. Hence, new 'outside-of-the-box' strategies must be used to render DSCs competitive with current commercial technologies. This thesis describes my work on identifying losses in DSCs and 2 strategies to improve the efficiency of DSCs: the use of highly-soluble energy relay days to broaden the spectral response of DSCs, and the fabrication of semi-transparent solid-state DSCs to help improve the efficiency of inorganic devices in a tandem solar cell. Solid-state dye-sensitized solar cells (ssDSCs) have historically lagged behind their liquid-electrolyte counterparts in efficiency. To gain a better understanding of why this is so, we have developed accurate internal quantum efficiency (IQE) measurements for ssDSCs. By analyzing the IQE, it is found that while charge collection is efficient in ssDSCs, often charge injection is not. This analysis also shows that parasitic absorption by the Spiro-OMeTAD is an important loss mechanism in ssDSCs and suggests that stronger absorbing sensitizers are the most promising path to higher efficiencies. In DSCs, the roles of absorbing light, injecting charge, and blocking recombination are all given to the sensitizing dye, resulting in a myriad of design rules for DSC sensitizers. An energy relay dye (ERD) is a second dye that helps relax these design rules by providing complementary absorption and then transferring energy to a sensitizing dye. However, such ERDs come with their own design rules, including the need for high solubility for full light absorption, and high photoluminescence for efficient energy transfer. We have designed and synthesized two such dyes, and characterized them as ERDs in DSCs, yielding a 65% increase in efficiency. Finally, even if DSCs are unable to reach efficiencies that render them competitive against traditional inorganic solar cells, DSCs can be used in conjunction with an inorganic solar cell in a hybrid tandem photovoltaic (HTPV). High open-circuit voltages and cheap processing render DSCs attractive top cells in HTPVs, and such devices can exceed efficiencies of 20%. However, in order to be used in HTPVs, a DSC must be fabricated such that below bandgap light can pass through the device and be absorbed by the inorganic bottom cell. Toward that end, we have developed a transparent top contact for solid-state dye-sensitized solar cells that renders ssDSCs attractive candidates for HTPVs.
Dialectic of spectrality [electronic resource] : a transpacific study on being in the age of cyberculture, 1945~2012
Keywords: Comparative Literature.

The recent rise of digital media and human-machine interfaces has redefined survival for the conscious human subject. The most advanced technological apparatuses run on the principle of ambiguity and fluidity, countering the long-standing nostalgia towards an illusory state of totality seen in the history of Western ontology. Drawing on psychoanalytic, postmodern and cognitive theories, I reinterpret the fragmented, transgressive and incomprehensible aspects of digital communication and interaction as the fundamental modes, not objects, of individual and collective existence. I situate my discourse in a transcultural framework through Korean, Japanese and American literature and visual media, including works by Neal Stephenson (U.S.), Murakami Haruki (Japan) and Kim Young-ha (Korea).
Dialogic constructions of new black aesthetics [electronic resource] : East Africa and African America, 1952-1979
Keywords: Theater and Performance Studies.

This dissertation creates a dialogue between East African and African American cultural politicians that construct new black aesthetics between 1952 and 1979; these years encompass their respective liberation movements, including the Black Arts Movement, the Black Power Movement, and the National Independence Movements of Kenya, Uganda, and Tanzania. Cultural politicians are artists and ideologues with political influence that engage in the discourse on black cultural liberation through multiple creative and congressional forums. This dissertation considers theatrical, linguistic, sonic, and visual performances of philosophy that constitute radical black aesthetics during this period. First, it examines how both East African and African American cultural politicians stage the topography of a historical Black Nation. Second, how they make a case for Swahili as a cross-cultural black language. Third, how they revise and perform oral traditions to proselytize Black Nationalism. Finally, how they represent their ideologies sartorially, all in an effort to liberate Black people culturally ergo psychologically. I anchor this cross-cultural investigation into constructions of blackness----that is linguistic, aesthetic, and philosophical creations that come to constitute the abstract notion of blackness----with the then contemporaneous discourses on Africa's nature, on Black history, on legacies, and on prophecies. I argue that new black aesthetics emerge dialogically when East Africans engage with radical African American political and cultural ideologies and vice versa. Moreover, juxtaposing the politics of aesthetics in both regions, even when seemingly disparate, elucidates the shared discursive terrain for black identity and aesthetics in the 1950s, 1960s, and 1970s. Thus, by excavating the transnational discourse on cultural liberation in these ethno-geographic regions, I illuminate the overlooked relationship between East African and African American ideas and aesthetics. In so doing, I confront, underscore, and re-value the invention of tradition over and above its retention.
Difference and democracy [electronic resource] : encountering difference in democratic dialogues
Keywords: Communication.

The collection of essays in this dissertation explores the impact of interacting with different others on people's attitudes. In the first chapter, I drew from intergroup contact theory (Allport, 1954; Pettigrew, 1998; Brown & Hewstone, 2005) to study the effect of deliberating with racial and religious minorities in samples of Australians, Bulgarians, and the Northern Irish. My analyses showed that: (1) prior contact was positively associated with greater support for outgroup policies; (2) contact with the outgroup during deliberation increased support for outgroup policies; and (3) the positive effect of deliberative contact was stronger for those who have had negative contact experiences in the past. I also found that perspective taking and argument quality were significant mediators of contact effects, while learning about the outgroup was not. In the second chapter, I focused on another form of difference -- opinion difference -- in the context of face-to-face group discussions. Based on theories of social influence (Asch, 1951; Bassili, 2003; Huge & Glynn, 2012), it was hypothesized that those who hold different opinions from the majority of the group would report greater feelings of constraint and change their opinions more after deliberation. It was also posited that opinion support -- having more people on "your side" of the opinion spectrum -- would moderate the effect of opinion difference and opinion change. Data from the 2011 Deliberative Poll in Korea lent support to these hypotheses. Results showed that opinion minorities were more likely to feel inhibited during deliberation and changed their opinions more to the other side compared to opinion majorities. This effect was mitigated when they had a greater number of people on their side in the group. The results also suggested that the three measures of opinion difference seemed to measure slightly different constructs. In the third chapter, I broadened my perspective to examine the effect of race during the telephone survey interview process that involved an African American candidate. Using data from hundreds of thousands of telephone interviews conducted during the 2008 U.S. Presidential election campaign by major survey organizations (ABC News/Washington Post, CBS News/New York Times, and the Gallup Organization), I found that Africa-American interviewers were indeed more likely to elicit statements of the intent to vote for Mr. Obama than were White interviewers. This effect occurred because African-American interviewers were more likely than White interviewers to elicit participation in the survey by African-American respondents and/or that White interviewers were more likely than African-American interviewers to elicit participation by White respondents. Together, these three studies illuminate different pieces of the puzzle regarding the influence of minorities in different communication contexts.
Directed evolution of small molecules to solve the molecular recognition problem [electronic resource]
Keywords: Biochemistry.

Directed evolution of large combinatorial chemistry libraries is an emerging approach for small-molecule discovery. To advance this field, we have developed a DNA‑programmed chemistry technique that enables breeding of drug-like compounds over multiple generations. The progeny from each cycle of synthesis, selection, and amplification act as the starting point for a subsequent generation; thus the evolutionary cycle can be iterated. The linkage between genotype and phenotype is accomplished by coupling each unique compound to a DNA gene that programs its synthesis. Here we establish the behavior of our technology using a model selection for kinase substrates. We show that the platform behaves in a predictable manner and that it should be capable of identifying useful molecules from very large compound libraries. We then use the technology to discover novel biologically active small molecules by applying a purifying selection to a naive DNA‑programmed library comprising 1.1 billion distinct compounds. Given the comprehensive nature of the combinatorial synthesis and the deep sampling enabled by high throughput sequencing, we can observe the simultaneous enrichment of different chemical families, increasing our chances of identifying a true hit. We have thus identified the first known non-peptidic substrate for protein kinase. This work demonstrates the feasibility to chemically probe the substrate binding sites of kinases. More broadly, we have performed the first directed evolution of a billion member combinatorial library. We anticipate that our approach will lead to the discovery of novel small‑molecule affinity reagents, pharmaceutical compound leads, imaging probes and other high‑value compounds. This could substantially increase global access to small‑molecule reagents, and open up new areas of biological inquiry.
Dissecting fundamental mechanisms of protein translation in Saccharomyces cerevisiae [electronic resource]
Keywords: Biochemistry.

The central dogma of biology states that DNA, the genetic information, is transcribed into RNA, an information containing intermediate, which is then translated into proteins, actionable molecules which perform the majority of tasks required for life. To synthesize proteins, the cell employs a massive, macromolecular machine, the ribosome, and a myriad of protein factors to successfully translate an mRNA. My graduate studies have focused both on the ribosome and the protein translation factors that interact with the ribosome to facilitate translation initiation, elongation, and termination. First, utilizing recent advances in high throughput sequencing, we discovered that sequencing of ribosome protected fragments could illuminate in vivo dynamics of ribosome structural changes in Saccharomyces cerevisiae. We demonstrated that the ribosome protects two distinct sizes of fragments and assigned each fragment population to approximate stages of the translation elongation cycle where large structural rearrangements of the ribosome are known to occur. Once these assignments were made, we were able to model elongation speed and demonstrated that, contrary to previous reports, tRNA abundance and codon optimality were not the major determinants of elongation speed; surprisingly our data indicated that the polarity of the amino acid being decoded dictated elongation rates under these conditions, with polar amino acids acting to slow elongation rates. This study also implicated Dom34, a known NO GO decay factor, as a novel component of canonical translation termination and ribosome recycling. Second, we used another genome-wide assay of translation, "gradient encoding" microarray analysis, to interrogate the genome-wide effects of depleting five individual translation factors. Based on the current understanding of the molecular mechanisms of each translation factor, we hypothesized that the depletion of each factor would result in differential translation of mRNAs based on the physical properties of each mRNA species. However, we were startled to observe that the translational program of S. cerevisiae was relatively unperturbed by the depletion of three initiation factors, one elongation factor, and one termination factor. Further investigation revealed that yeast were actively compensating for the deficiency of each factor by either increasing or decreasing translation initiation rates such that the depleted factor was no longer limiting. This tuning was mediated by changes in eIF2[alpha] phosphorylation levels, a known modulator of translation initiation. Overall, we have leveraged high throughput technologies to provide novel understanding of in vivo structural dynamics of the ribosome and reveal a novel, unexpected robustness of the translational program in S. cerevisiae.
Dissecting the neural circuits of early visual processing in Drosophila [electronic resource]
Keywords: Electrical Engineering.

Visual inputs are high-dimensional, dynamic, and may consist of significant levels of noise. Nevertheless, visual processing systems in many animals are capable of efficiently extracting information out of these signals to guide behavior. Flies, in particular, use visual information to guide behavior in challenging conditions such as during rapid flight maneuvers. In this dissertation we examine how early visual processing cells in the visual system of the Fruit Fly, Drosophila, achieve this feat. In particular, we focus on cells that provide inputs to motion detecting circuits and assess how these cells balance the goal of facilitating computational specializations with the goal of efficiently capturing all visual information. In these studies, we used two-photon calcium imaging in vivo to monitor the responses of specific cells in the fly visual system to visual stimuli. Using this system, we found that two first order interneurons providing inputs to pathways specialized for the detection of moving bright and dark edges nevertheless similarly encode information about both brightening and darkening. However, an in depth study of the functional properties of one of these interneurons revealed that it responds differently to bright and dark moving objects of different sizes in a manner that could facilitate the downstream specialization. Furthermore, via genetic and pharmacological manipulations it was found that GABAergic circuits providing lateral and feedback inputs to this cell enhance its responses to dark stimuli and thus enable it to relay critical information for the downstream pathway. These circuits were found to give rise to a center-surround antagonistic, anisotropic and spatiotemporally coupled RF structure in this cell. Interestingly, our studies uncovered deep similarities between the function of early visual processing cells in the fly and in vertebrate retinas. This suggests that different systems have converged on a similar set of solutions for addressing the challenge of efficiently using the resources available to the nervous system to process visual signals.
The distribution and composition of communities of foliar fungal endophytes in Metrosideros polymorpha [electronic resource]
Keywords: Biology.

The primary goal of this dissertation is to characterize the factors that shape the distribution and composition of foliar fungal endophytic communities across a tropical landscape. To do so, I have chosen to evaluate communities within a single host tree species, Metrosideros polymorpha (Myrtaceae), across a wide range of environments. In Chapter 2, previously published as Zimmerman and Vitousek (2012) in PNAS, I describe the background and methodology that will be carried through the rest of the dissertation. Sampling broadly across a landscape and sequencing deeply using an amplicon pyrosequencing approach, in this chapter we report high endophyte gamma diversity (more than 4000 fungal OTUs) across a matrix of 13 sites. This high diversity is a consequence of high beta diversity between sites, and we find that this beta diversity to be structured largely by macroenvironmental factors: elevation and rainfall. Chapter 3 extends the study system described in chapter two in order to explicitly account for distance. It does so by incorporating an additional six sites into the design, spanning an 'orthogonal gradient' where elevation and rainfall are held as constant as possible, and distance is varied between sites, from tens to hundreds of kilometers. The primary finding is that while distance does structure communities at these scales, it does so to a much lesser extent than does environmental variation. Chapter 4 focuses on the effects of leaf morphology differences between populations by making use of a common garden of Metrosideros collected from sites across the wet side of the Mauna Loa matrix. The primary finding is that leaf pubescence is a major factor shaping the composition of endophyte communities, even when there is little environmental variation. Chapter 5 moves beyond biogeography to explore how evolution, as well as ecology, may be an important driver of the high endophyte richness across the study system in Hawai'i. It describes the signature of a potential endophyte diversification at high elevation, and proposes that a clade of black meristematic fungi with close phylogenetic affinities to rock-inhabiting ancestors is now living in association with Metrosideros at those sites.
DMRG studies of strongly correlated two-leg ladders [electronic resource]
Keywords: Physics.

High temperature superconductivity of unconventional source (i.e. from repulsive interactions) has been studied for more than 25 years and has created a lot of excitement and interest. In this 25 years many things have been understood and several things still elude us. One controversial issue that belongs to the latter group, is the issue of optimal inhomogeneity and the role it plays. In this thesis, I study the effect of inhomogeneity -- in the sense of a complex periodic, mesoscale structure -- in a variety of inhomogeneous models with initial repulsive on-site interaction on a two-leg ladder geometry, on the superconducting correlations and, in turns, to the critical temperature Tc of a superconductor. The first model presented is the checkerboard Hubbard model and several relatives to it on a two-leg ladder geometry, after previous work done on models like this, has been reviewed. In this subject new and exciting results have been presented, involving great enhancement in the superconducting correlations. Finally I discuss another geometry of a two-leg ladder, namely the honeycomb two-leg ladder. The results in this subject are very interesting and surprising, because this model does not present enhancements in the superconducting correlations but rather a suppression of them.
Double beta decay in xenon-136 [electronic resource] : measuring the neutrino-emitting mode and searching for majoron-emitting modes
Keywords: Physics.

Observations of neutrino flavor oscillations have demonstrated that neutrinos have mass. Since the discovery of these oscillations, much progress has been made at measuring the neutrino mass-squared differences and lepton mixing angles that characterize them. However, the origin and absolute scale of neutrino masses remain unknown. Unique among fermions, neutrinos can be Majorana particles, which could provide an explanation for neutrino masses. Discovery of a hypothetical process known as neutrinoless double beta decay would show that neutrinos are Majorana particles and determine the mass scale for neutrinos. The Enriched Xenon Observatory (EXO) is a series of experiments searching for the neutrinoless double beta decay of xenon-136. The first experiment, EXO-200, began operation in 2011 and makes use of 200 kg of xenon enriched to 80.6% in xenon-136. The analysis presented here makes use of data from EXO-200 to obtain a more precise measurement of the half-life for the two-neutrino-emitting mode of double beta decay than previously reported. The analysis also sets limits on the half-lives for exotic, Majoron-emitting modes of neutrinoless double beta decay. Data from EXO-200 is also used to produce a measurement of the cosmic muon flux at the WIPP underground site where EXO-200 is located.