VictorJuiz/thesis huggingface dataset:
Eigenvalue Distributions of Symmetric Group Representations

/n/nFor each k ≥ 1, we study the eigenvalue distributions of permutation representations of the symmetric group ?n on k-tuples and k-subsets as well as the S(n-k,1,...,1) irreducible/nrepresentation of ?n (we will call these k-representations)./n/n/nFirst, we consider the fluctuations of eigenvalue statistics. Endow ?n with the uniform measure and let α and θ be linearly independent irrational numbers over ℚ. Then we show that as n → ∞, the scaled count of the number of eigenangles in a fixed interval (α, θ) of a k-representation evaluated at a random element σ ∈ ?n converges weakly to a compactly supported distribution. In particular, we compute the limiting moments and moreover provide a formula for the limiting density in the case k = 2./n/n/nNext, we study the scaled eigenvalue point process of the k-representations. Here, we endow ?n with the Ewens measure of parameter θ for which the uniform distribution corresponds to the special case θ = 1. The eigenvalue point processes exhibit drastically different behavior depending on whether one “zooms in” at rational angles or irrational angles. We obtain the limiting eigenvalue point process at rational angles as well as angles of irrationality measure 2 for all k-representations. A power series representation for the limiting gap probability is also given./n/n/nFinally, we study the distribution of entries of a random permutation matrix under a “randomized basis.” This means that we conjugate the random permutation matrix by a random orthogonal matrix drawn from Haar measure. Then it is shown that under certain conditions, the linear combination of entries of a random permutation matrix under a “randomized basis” converges to a sum of independent variables sY + Z where Y is Poisson distributed, Z is normally distributed, and s is a constant./n

Advisor: Evans, Steven N.
DESIGN OF LIGHTWEIGHT ASSISTIVE EXOSKELETONS FOR INDIVIDUALS WITH MOBILITY DISORDERS

There are over 270,000 people in the United States suffering from spinal cord injury. Currently, the wheelchair is the most commonly prescribed mobility solution for these individuals. Unfortunately, numerous health problems can be developed as a side effect of extended sitting. Studies have indicated that standing and walking for wheelchair bound individuals can improve overall health and mitigate these secondary health risks. Several passive walking devices exist, however these approaches are impractical due to the high metabolic cost associated with walking. Powered lower extremity exoskeletons have the capacity to substantially improve overall health and mobility of paralyzed individuals. The practicality of previous mobile medical exoskeletons has been limited due to cumbersome walking dynamics, high system mass and high cost. This work introduces the Steven Exoskeleton, a lightweight minimally actuated assistive exoskeleton developed as a device that can be intuitively adopted by manual wheelchair users. This device builds off of the successes of several generations of low cost medical exoskeletons developed at the UC Berkeley Robotics and Human Engineering Laboratory. Several elements of exoskeleton gait have been refined for the Steven Exoskeleton allowing better control of walking speed with more fluid walking dynamics. By smoothing hip trajectories and increasing stride length it has been possible to increase overall speed and pilot comfort. New hardware allows tunable hip and spine flexibility, improving pilot performance and adaptability. Through hardware and control refinement, comfortable walking speed has been increased to 0.48m/s from a previous maximum of 0.27m/s. Higher walking speed makes the device more useful for locomotion and allows greater independence in society. The Steven Exoskeleton was designed to bridge the gap between seated and standing operation by assisting the user in a new range of postures. This approach expands pilot capabilities while seated and increases overall utility as a tool. This work also discusses a new approach to increase the reliability, and safety of standup and sit-down. Consistent standup and sit-down enables individuals to be self-sufficient with the possibility of full operation without a spotter. The adaptability of this device has enabled testing in laboratory and real world environments with pilots exhibiting a variety of medical conditions. The success of the Steven Exoskeleton and associated control and hardware adaptions moves devices of this nature closer to widespread adoption by paraplegics.

Advisor: Kazerooni, Homayoon
Scanning Tunneling Microscopy Study of Graphene Electronic Nanostructures

This dissertation focuses on the study of the electronic properties of graphene using scanning tunneling microscopy (STM). A particular focus is the behavior of charge carriers in monolayer graphene around a single Coulomb impurity at the microscopic scale, and the interactions between two vertically stacked graphene layers./nIn order to probe the intrinsic electronic properties of graphene, hexagonal boron nitride (BN) was employed as a new substrate for supporting graphene due to its ultra-flatness and high purity. The surface roughness and charge inhomogeneity of graphene on BN were measured to be significantly smaller than graphene on SiO$_\text{2}$ using STM. The high quality of graphene on BN enables us to investigate the fundamental physics question of how Dirac fermions in graphene respond to a single Coulomb impurity. This problem is divided into two separate regimes (subcritical and supercritical) depending on the strength of the Coulomb potential. The subcritical regime was investigated by using charge-tunable cobalt trimers on graphene, and the graphene LDOS around these charged impurity showed electron-hole asymmetry but no bound states. The supercritical regime was achieved by manipulating calcium dimers into clusters in order to surpass the supercritical charge threshold, and atomic-collapse quasi-bound states were demonstrated. The screening properties of graphene under various doping conditions were also measured using charge-stable calcium monomer adatoms, and the characteristic screening length of graphene was observed to scale inversely with its Fermi wavevector./nBesides depositing charged impurities, the electronic structure of graphene can also be modified via vertical layer stacking. The lattice orientation difference between two contacting layers of graphene induces a series of Moir\'{e} bands which manifest themselves as Van Hove singularities and other higher-order spectroscopic features that can be measured in twisted bilayer graphene./nThe results presented in this dissertation contribute to our understanding of the microscopic electronic structure of graphene under the influence of charged impurities and layer-layer interactions, and shed new insight on how we can tailor graphene properties for use in real world applications.

Advisor: Crommie, Michael F
Bayesian Network Methods for Modeling and Reliability Assessment of Infrastructure Systems

Bayesian Network Methods for Modeling and Reliability Assessment of Infrastructure Systems/nby Iris Tien/nDoctor of Philosophy in Civil and Environmental Engineering/nUniversity of California, Berkeley/nInfrastructure systems are essential for a functioning society. As these systems age, however, system reliability analyses are required to identify the critical components and make decisions regarding inspection, repair, and replacement to minimize the risk of system failure. In this study, we present novel Bayesian network (BN) methodologies for the modeling and reliability assessment of infrastructure systems. In an environment where information about a system is evolving and is oftentimes uncertain, BNs are able to both update the network when new information becomes available, and handle information probabilistically to support engineering decision making under conditions of uncertainty. One of the major limitations of the BN framework, however, is the size and complexity of the system that can be tractably modeled as a BN./nIn this study, we propose a novel compression algorithm that significantly reduces the memory storage requirements for a BN model, along with an inference algorithm that performs both forward and backward inference on the compressed matrices. We also present several heuristics to improve the computational efficiency of the algorithms. Through the application of these algorithms and heuristics to example systems, we show the proposed methodology to achieve significant gains in both memory storage and computation time. Together, these algorithms enable larger systems to be modeled as BNs for system reliability analysis./nIn addition, we propose a methodology based on the dynamic BN (DBN) to assess the response of a structure as it evolves through time under an excitation that is stochastic, e.g., an earthquake ground motion, based on sensor measurements that are uncertain. We look at the maximum response in particular, and derive an analytical solution for estimating the distribution of the peak response. In applying the proposed DBN framework to a multi-story shear-type building, we show the method to be robust relative to uncertainties in the structural characteristics, ground characteristics, and input motion parameters. This work informs decision making in the management of structures subject to seismic hazard and for the development and design of smart structural health monitoring systems.

Advisor: Der Kiureghian, Armen
"According to my bond": Intimacy and Attachment in Early Modernity

This dissertation studies the history of intimacy from late humanism through the Enlightenment by examining how the abstract concept of attachment becomes both a primary preoccupation and a crucial stumbling block in imagining subjectivity throughout the period. Examining a series of authors (Shakespeare, Descartes, Milton, and Rousseau) who ask what it would mean to be essentially without social ties, this project reveals the early modern period's ongoing conflict between a primary solitude associated with autonomy, isolation, and detachment and a primary sociality that assumes a natural order of attachments, bonds, and interdependence. This dissertation challenges the conventional story of the birth of "interiority" or "the invention of the human" with Shakespeare (or even Montaigne) by revealing a resistance to a conception of attachment that assumes inwardness; instead, it uncovers a more gradual historical shift in models of primary attachment from external to internal bonds, from attachments understood to occur outside the subject to those forged by an immanent or internal principle of relationship./nChapter one argues that Shakespeare's The Merchant of Venice and King Lear reveal a commitment to exteriority rather than the interiority so often attributed to Shakespeare as it attempts to conceal the fragility of social bonds and the ease with which they - and social life - can be destroyed. Chapter two examines Descartes' Meditations and locates in the defensive strategies of the meditator an attempt to evade the threats of attachment through a negotiation with poetics that leaves dependency precariously outside the self. Chapter three finds in Milton's Paradise Lost and Paradise Regained a turn to an immanent sociality in the figure of the Son; in Milton's monism, a principle of relation inheres in all matter, suggesting that even total isolation is attended by this principle of relation. Chapter four studies Rousseau's Émile and shows how the autonomy and even the solitude of the subject is secured by placing a relational principle around the subject's soul. Finally, a speculative coda turns to Kant to consider the legacy of solitude and autonomy in the Enlightenment's most famous moral philosopher.

Advisor: Kahn, Victoria
Essays on Information and Beliefs in Credit Markets

This dissertation is a collection of three essays in financial economics, specifically focused on the role of information and beliefs in credit markets. The first chapter establishes that private bank information about customers in primary lending markets exists. The second chapter shows that private information hinders banks' capacities to sell loans on secondary markets, unless the purchaser believes that the bank has committed to remain uninformed. The third chapter explores the welfare consequences of incorrect borrower beliefs about the economic environment on financial product choice./nIn the first chapter, my co-author and I hypothesize that while lending to a firm, a bank receives signals that allow it to learn and better understand the firm's fundamentals; and that this learning is private; that is, it is information that is not fully reflected in publicly-observable variables. We test this hypothesis using data from the syndicated loan market between 1987 and 2003. We construct a variable that proxies for firm quality and is unobservable by the bank, so it cannot be priced when the firm enters our sample. We show that the loading on this factor in the pricing equation increases with relationship time, hinting that banks are able to learn about firm quality when they are in an established relationship with the firm./nIn the second chapter, I present new evidence that lemon problems hinder trade on secondary mortgage markets. Using the geographic distance from lenders to borrowers as a proxy for the absence of private bank information, I document a systematic positive link between distance and the mortgage sale rate. Mortgage sale rates are higher when the originating lender is less likely to be informed about the borrower. I further show that the private mortgage sale rate locally depends on lender-borrower distance only above the conforming loan limit, in the illiquid jumbo market where the GSEs are barred from purchasing mortgages. This is consistent with the familiar tradeoff between market liquidity and seller incentives to acquire information./nIn the third chapter, I investigate how borrowers' incorrect beliefs about future inflation might bias their choice between fixed-rate and adjustable-rate mortgages. Borrowers who have experienced recent periods of greater inflation pay more for fixed-rate mortgage contracts and pay more in interest, at least over the first six yeras of the mortgage's life. That is, incorrect beliefs about future inflation are welfare-reducing both ex ante and ex post.

Advisor: Malmendier, Ulrike
Bees in a Changing World: How land surface phenology, bee community distributions, and pollinator-plant interactions are impacted by urbanization and agriculture

Background/nUrbanization and agricultural intensification of landscapes are influential drivers of global change, resulting in direct impacts on ecological communities and leading to shifts in species distributions and interactions. These landscapes are novel for many reasons, but an often overlooked aspect is how the phenology of vegetation can vary between land use types. Because such differences can impact floral-dependent species, I explored how human-altered landscapes affect bees, a group of high economic and ecological importance. I measured the phenological diversity of vegetation across a human-altered landscape, compared these findings to a spatio-temporal pollinator distribution dataset, and investigated how pollinator visitation translates to seed set./nApproach/nI collected and observed bees for three field seasons in a peri-urban landscape on the outskirts of the San Francisco Bay Area, California, where urban, agricultural, and natural land use types interface. To assess patterns of phenological change, I used seasonal remote sensing data from MOD13Q1 vegetation indices, which I complimented with collections of 91 bee species groups across different land use types. I examined how differences in bee populations between land use types impacted plant-pollinator interactions by making standardized observations of floral visitation and measuring seed set of yellow starthistle (Centaurea solstitialis), a common grassland invasive abundant in all land use types./nResults & Conclusion/nI found phenological patterns in vegetation indices, total bee abundance, and species richness of human-altered landscapes to be out of sync between urban, agricultural, and natural areas. Vegetation indices were significant predictors of total bee abundance, a relationship that improved when time lags were included. Bee visitation was highest in urban and agricultural land use contexts, but seed set rates in these human-altered landscapes were lower than in natural sites. These results emphasize the importance of differences in temporal dynamics between land use types, a previously overlooked mechanism of global change.

Advisor: Roderick, George K.
Chemical Tools for Investigating Galectin Dynamics

Pattern recognition is an essential feature governing many biological processes, including metazoan development, infection, and tumorigenesis. Glycans form a unique pattern on the surfaces of cells. There, these branched, intricate structures are poised to direct communication between neighboring cells and tissues. How cells interpret the staggering complexity associated with the glycome, the repertoire of glycan structures expressed in cells and tissues, though is still not well understood. Galectins comprise one family of glycan-binding proteins that are thought to play a role in decoding glycomic patterns. They have been implicated in cell adhesion and signaling, proliferation, membrane organization, and transcript processing. Yet, the mechanistic underpinnings of the pleiotropic functions of galectins remain obscure due to challenges associated with studying lectin-glycan interactions./n/nMonitoring and modulating glycan patterns present on different cell surface glycoconjugates would greatly facilitate our understanding of galectin-dependent phenomena. Unfortunately, glycosylation is a post-translational modification that is dependent on the collective action of hundreds of enzymes. The final glycans appended to proteins and lipids are not directly encoded in the genome, and as such, there is no obvious means to tag or tailor complex, galectin ligands in vivo. This situation is further exacerbated by the properties of galectins themselves. Galectin-1, for instance, self-assembles in vitro and traverses cell membranes, occupying extracellular, cytosolic, and nuclear spaces. Therefore, isolating galectins' dynamic organization in each subcellular context is imperative, yet non-trivial experimentally./n/nThis dissertation describes the development of new chemical and biophysical tools for studying galectin dynamics and their contribution to cellular physiology and pathology. Chapter 1 explores and summarizes recent advances in chemical methodology that report on mammalian lectin function in vivo. In Chapters 2 and 3, I present a platform for monitoring galectin-mediated cross-linking on living cells with synthetic glycoprotein mimics. Chapter 4 outlines a technique to image galectin ligands, i.e. specific protein glycoforms, in cultured cells and tissue slices. Finally, Chapter 5 is dedicated to clarifying galectin's influence on mammary gland morphogenesis and breast cancer progression. Therein, I discuss harnessing the tools described in Chapters 1-4 to reveal an unprecedented, galectin-based mode of information transfer between extracellular glycomic signatures and nuclear transcription machinery that drives mammary epithelial invasion.

Advisor: Bertozzi, Carolyn R.
Scalar and Spinor Excitations in a Ferromagnetic Bose-Einstein Condensate

At low temperatures, the thermodynamic properties of a many-body system are determined by the low energy excursions from the ground state. In quantum degenerate rubidium, the low energy excitations are phonons—phase and density modes—and magnons—spin modes. This thesis reports on the construction of an ultracold rubidium apparatus and techniques to create and image phonons and magnons. We propose and study matter wave interferometry of phonons in a ring trap as a potential rotation sensor in a compact sensor. Precision measurements of coherent magnons allow us to determine the magnon dispersion relation, including a gap induced by magnetic dipole-dipole interactions.

Advisor: Stamper-Kurn, Dan M
Rebordering the Borderlands: Writing Violence, (Im)migration, and Surveillance

This dissertation is a study on the topics of migration, power, and subjectivity in Chicana/o literature. Much critical cultural studies work which focuses on (im)migration in Chicana/o cultural texts has tended to portray it as an emancipatory project, and thus, has forgone a more complex understanding of this movement. I analyze Tomás Rivera's short stories, Arturo Islas's The Rain God, Salvador Plascencia's The People of Paper, and Helena Maria Viramontes's Their Dogs Came With Them to examine how these narratives depict migration not only in its physical and geographical dimensions, but also as a psychological, gendered, queered, often violent, ideological movement that is shaped by contradicting sources of power and material realities. I argue that these narratives embed the various aspects of this migration in their form, including through a migratory narrative structure, metafiction, skeptical fantasy, and editorial excision. Through the lens of women of color, queer, and political theories, I contend that this literature embodies the tension between transnational and global circuits of power on the one hand and the simultaneous reinforcement of sovereignty, territoriality, and the law on the other to reveal within these narratives moments of resistance and complicity in dominant ideologies like patriarchy, cultural nationalism, and limited expressions of citizenship. I contend that this literature necessarily reproduces this tension in fractured narrative forms that theorize power and lay bare how Chicana/o writers posit both literary and embodied protests to hegemonic formations of power.

Advisor: Saldívar, José David