VictorJuiz/thesis huggingface dataset:
Concentration polarization at microfluidic-nanofluidic interfaces [electronic resource]
Keywords: Mechanical Engineering

Nanofluidic devices have the potential to offer unique functionality by exploiting length scales comparable to the Debye length or the size of individual biomolecules. Integration of nanofluidics with microfluidics also has potential benefits as a system can thereby draw from the benefits of both technologies. To leverage these functionalities, the physics associated with interfacing microchannels and nanochannels needs to be understood rigorously. In particular, when current is applied across a microchannel-nanochannel interface, surface charge effects inside the nanochannel often lead to an imbalance of fluxes of positive and negative species. This, in turn, creates a region of high ionic strength on one side of the nanochannel and low ionic strength on the other side, a phenomena known as concentration polarization (CP). Prior work on the physics of microchannel-nanochannel interfaces has neglected several key issues which we will address in this work. We review an analytical model of propagating CP and present experimental and computational validation of this model. In particular, our results show that enrichment and depletion regions propagate as 'shockwaves' of concentration which can profoundly change the flow and electric field conditions in a microfluidic system. Additionally, we present new analytical model which predicts the behavior of analyte ions in a microchannel-nanochannel system with CP. This work shows that CP can restrict the transport of analyte ions such that they cannot reach all regions of a microfluidic-nanofluidic system. The effects of CP, therefore, must be considered in the design of microfluidic-nanofluidic systems for biological or chemical analysis. Finally we present the first simultaneous visualization of nanochannel ionic strength and conductance. Our experiments show that, for some cases, the propagating CP model is a fair predictor of trends in nanochannel concentration. However, in some cases, the concentration inside the nanochannel reaches a temporary 'meso' state before transitioning to a final, significantly different concentration which is not described by theory. The latter shows that there is yet much room for further studies of this phenomenon.
Constructing agency [electronic resource] : the role of language
Keywords: Psychology

Speakers of the world's languages differ in how they typically describe the same events. For example, to describe the same physical event in some languages it would be natural to say "He broke the vase" while in others one would say "The vase broke itself." Do such patterns in language matter for how people construe and remember the same events? Do patterns in language shape whether we construe someone as being an agent, whether we attend to and remember who was involved, and how much we blame and punish those involved? Evidence from several populations - speakers of English, Spanish, and Japanese; adults and children -- suggests that the answer to these questions is "Yes". There are cross-linguistic differences in eye-witness memory for the same events, and language influences judgments of blame and punishment. The effects of language appear to be strong: Patterns in one's linguistic environment affect thinking even when people are not required to use language in a task and even when other rich sources of non-linguistic information are available.
Constructing genealogies in early modern England and the Mediterranean [electronic resource]
Keywords: Comparative Literature.

My dissertation uncovers how and why authors in early modern English and Mediterranean literature construct explanations of their own or their societies' origins. The framework for my analysis is the notion of "genealogies"--a term that may signify bloodlines, imperial lineages, religious genealogies, imagined genealogies of heroic conquerors, or literary genealogies of authors. I further argue that competing Muslim and Christian claims to the same genealogies complicate (or even render unsustainable) many of the assumed distinctions between "East" and "West" that have endured from the Renaissance to the present day. Chapter one discusses how both Leo Africanus and his _Descrizione dell'Africa_ both reify Muslim and Christian geographical distinctions while simultaneously challenging them. I conclude the chapter with a discussion of the afterlife of Africanus' work through a European "isnad" in Luis del Mármol Carvajal's _Descripción general de Africa_. Mármol unwittingly adapts Africanus' hybrid literary genealogy in a hostile manner unintended by Africanus and, in effect, writes Africanus out of his own history. Chapter two deals with ideologies of empire, comparing consanguineal and heroic genealogies in Ludovico Ariosto's _Orlando furioso_ and Edmund Spenser's _Faerie Queene_. I address why Ariosto makes Ruggiero (the "ancestor" of Ariosto's patrons) Muslim and how Spenser manipulates genealogies to provide a solution for the aging, heirless Queen Elizabeth by collapsing time and place within his poem. Chapter three notes two competing genealogies of English kingship in Shakespeare's Henriad--Christian divine right and heroic Greco-Roman genealogies. Fluellen's comparison of Henry V with Alexander "the Pig, " even as it relies upon Plutarch's paralleled lives of Alexander and Julius Caesar, demonstrates that if Shakespeare's handling of Henry V's "Turkishness" is subversive, it is because it is emulative, not slanderous. Finally, to make a larger point about mixed blood and religion in seventeenth-century Spain, I take Cervantes' suggestion literally, that his readers imagine Sidi Hamete Benengeli as the "true author" of _Don Quijote_ and explore how, similar to Mármol's appropriation of Leo Africanus' open-ended genealogy, Avellaneda, the author of an apocryphal sequel, engages in unauthorized continuation Sidi Hamete's "verdadera historia.".
Construction of Time-and-Angle-Resolved Photoelectron Spectroscopy on Correlated Materials
Keywords: Physics
Angle-Resolved Photoelectron Spectroscopy
ARPES
Femtosecond Time-Resolved ARPES
Thesis

Angle-Resolved Photoelectron Spectroscopy (ARPES) has been a major experimental technique in studying the electronic band structure of condensed matter systems. The traditional ARPES system resolves binding energies and in-plane electron momenta of electronic systems. It is of great scientific interest to further resolve the information of electron dynamics. In this thesis, I give a brief review of the theoretical and experimental backgrounds of the Femtosecond Time-Resolved ARPES technique. I report the construction of such a system, which consists of an ultrafast 1.5 eV pump beam and 6 eV probe beam, and a Scienta SES200 electron analyzer. An optical autocorrelator verifies that the duration of the pump laser pulse is 75 fs; An ARPES experiment on an Sb sample demonstrates that the angular resolution of the electron analyzer is less than 0:34 [degrees] and that the energy resolution is less than 50 meV.
The contribution of myelin lipids to the failure of central nervous system axon regeneration [electronic resource]
Keywords: Developmental Biology.

CNS myelin is strongly inhibitory to growing axons and is presently thought to be a major contributor to CNS axon regenerative failure. Although a number of proteins present in myelin, including Nogo, MAG and OMgp, have been identified as myelin-associated inhibitors, studies of mice lacking these genes suggest that additional inhibitors present in CNS myelin remain to be identified. Here, I have investigated the hypothesis that myelin lipids contribute to CNS regenerative failure. I identified sulfatide, a major constituent of CNS myelin, as a novel myelin-associated inhibitor of neurite outgrowth. Sulfatide, but not galactocerebroside or ceramide, strongly inhibited the neurite outgrowth of retinal ganglion cells (RGCs) when used as a purified lipid substrate. The mechanism involved in sulfatide-mediated inhibition shared features with other known inhibitors, as the stabilization of GTP-bound Rho was required for inhibition. Myelin in which sulfatide was lacking or blocked using specific antibodies was significantly less inhibitory to RGC neurite outgrowth in vitro than was wild type myelin, indicating that sulfatide is a major component of CNS myelin's inhibitory activity. Mice unable to make sulfatide did not regenerate RGC axons more robustly after optic nerve crush than wild type littermates under normal conditions, but did exhibit a small but significant enhancement in the extent of zymosan-induced regeneration. These results demonstrate that specific lipids can powerfully inhibit axon growth, identify sulfatide as a novel myelin-associated axon growth inhibitor, and provide evidence that sulfatide inhibition contributes to axon regenerative failure in vivo.
Contributions to high-dimensional principal component analysis [electronic resource]
Keywords: Statistics

Principal component analysis is a widely used dimension reduction method, but difficulties can arise when it is applied to very high dimensional data. In this thesis, motivated by examples in chemometrics, signal processing, econometrics, etc., we investigate two aspects of high-dimensional principal component analysis for a class of "low-rank signal plus noise'' models under Gaussian assumption. In the first part, we study rates of convergence for the distributions of extreme sample eigenvalues to their Tracy-Widom limits, when there is no signal in the observations and the sample size and the dimensionality of the feature space grow to infinity proportionally. By careful choice of the rescaling constants, we improve the rate to the second order for the largest eigenvalue. An analogous result is established for the smallest eigenvalue. Numerical experiments show that the asymptotic distributions are informative even when the sample size or the feature dimenionality is as small as 2. In the second part, we consider recovery of principal subspaces under the assumption that the principal axes have a sparse representation. We find that a new iterative thresholding approach recovers the leading principal subspace consistently, and even achieves near optimal rate of convergence, in a wide range of high-dimensional settings. Both statistical and computational properties of the approach are studied. Its competitive performance is demonstrated on a collection of simulated examples.
Control of dynamic maneuvers for bipedal robots [electronic resource]
Keywords: Mechanical Engineering

There are many topographies in both the natural and man-made worlds which pose difficulties to machines: rubble fields, collapsed structures, ecologically sensitive areas, and even generally rugged terrain. If mechanical systems could negotiate such environments, the benefit to society would be great, with applications in search and rescue, ecologically friendly harvesting industries, and infantry support. The focus of this thesis is on gait control for bipedal robots. Before developing control algorithms, two areas of a bipedal robotic system are considered: leg design and control architecture. Noting the success of biologic systems in navigating difficult terrains, inspirations are taken from nature in both of these areas. A dynamic simulation method appropriate for systems with varying topology, such as legged robots, is also developed. In order to test the leg design, control architecture, and dynamic simulator, the relatively simple task of monopod hopping is studied. Stable results are achieved in both simulation and hardware, and the leg design, control architecture, and dynamic simulator are validated. Four bipedal maneuvers are then considered: steady-state running, accelerating, decelerating, and turning. Stable simulated results are demonstrated for all of these maneuvers. An experimental biped is also created. When the torso pitch is partially constrained, stable experimental steady-state running is achieved. When the torso pitch is unconstrained, five steps are achieved before falling. This work contains significant contributions in the areas of control architecture, leg design, and dynamic simulation methods for multi-topology systems. Novel control algorithms are presented for monopod hopping and steady-state running. Finally, control algorithms are presented for accelerating, decelerating, and turning, which have not been previously studied in bipedal robots.
Control of transcriptional programs of aging by NF-kappaB [electronic resource]
Keywords: Cancer Biology.

Aging is a degenerative process accompanied by tissue deterioration, decline in function and increased susceptibility to disease. It is now understood to be a genetically and environmentally regulated process, rather than simply the result of wear and tear. We developed a systematic approach to identify combinatorial cis-regulatory motifs that drive age-dependent gene expression across different tissues and organisms, and identified the transcription factor NF-[kappa]B as a candidate regulator of aging. Using multiple independent models, we show a role for NF-[kappa]B in regulating transcriptional programs of aging. First, we found that aged mice subjected to NF-[kappa]B blockade for two weeks exhibit reversion of the tissue characteristics and global gene expression programs to those of young mice. Next, we detected deregulated transcriptional activity of NF-[kappa]B in Sirt6-deficient mice, which exhibit premature aging-like symptoms. We show that Sirt6 interacts with the NF-[kappa]B RelA subunit and deacetylates histone H3 lysine 9 (H3K9) at NF-[kappa]B target gene promoters. Computational genomics analyses revealed increased activity of NF-[kappa]B-driven gene expression programs in multiple Sirt6-deficient tissues in vivo. Moreover, haploinsufficiency of RelA rescues the early lethality and degenerative syndrome of Sirt6-deficient mice, suggesting that hyperactive NF-[kappa]B-dependent transcription in the absence of Sirt6 promotes premature aging-like syndromes. Finally, we performed a genome-scale survey of RelA and Sirt6 location on chromatin in mouse embryonic fibroblasts (MEFs) via chromatin immunoprecipiation (ChIP)-on-chip to understand to what extent Sirt6 and RelA act coordinately to regulate gene expression. These results indicate that RelA and Sirt6 co-occupy the promoters of a large population of genes at sites less than 500kb apart and/or require RelA to enable binding of Sirt6. Expression analysis of these shared targets reveals direct regulation of 301 promoters, including genes such as Shc1 (encoding p66), Cdkn2a (encoding p16), Wnt2 and Jmjd3, which have been separately implicated in the aging process. We propose that hyperactive NF-[kappa]B signaling contributes to premature and normal aging.
Controls on Landscape Denudation Between Lhasa and Namche Barwa, Southeastern Tibet
Keywords:  Department of Geological and Environmental Sciences
School of Earth Energy &amp; Environmental Sciences
Tibet
Thesis

Twenty new 10Be-derived basin-averaged denudation rates from the region upstream of the Namche Barwa massif resolve the relationship between these rates, and tectonic and climatic variables. Denudation rates correlate well with channel steepness and local relief; precipitation, in contrast, serves as a poor predictor of denudation. In the Yarlung River, denudation rates steadily increase from the headwaters towards the Namche Barwa massif, which is apparently undergoing rapid exhumation over the million-year timescales recorded by low-temperature thermochronologic measurements. North of the Yarlung in the Nyang River, accelerated denudation rates somewhat correspond with the location of active footwall uplift associated with extensional structures. My data, in combination with previously reported 10Be-derived denudation rates from the Parlung River, suggest that regional order-of-magnitude variations in denudation rate are associated with profile knickpoints in the vicinity of Namche Barwa and within the Parlung. Thus, it appears that regional base-level changes, as well as local tectonic effects associated with extension within the Plateau and uplift along its margin, act to steepen the landscape, and in doing so, accelerate denudation.
Coordinated execution and goal management in a reactive cognitive architecture [electronic resource]
Keywords: Aeronautics and Astronautics

Coordinated execution and goal management are important human-level capabilities studied in cognitive science and psychology. Evidence suggests there are several di erent types of constraints that govern the coordinated execution of multiple, concurrent tasks. We took three of these types - shared objects, logical relations, and resource requirements - and developed an extension to a cognitive architecture, Icarus, that supports coordinated execution under such constraints. The extended architecture assumes that it should consider subgoals in its procedures concurrently unless the constraints prevent such execution. The existing framework supports constraints on shared objects and logical relations, but it requires a new facility to handle resource constraints. We specify resource requirements for each action that Icarus can use in the world, and the system assigns resources to executable skill paths during the skill retrieval process. The architecture prevents the execution of any skill path that requires already assigned resources and ensures that execution is coordinated according to the resource constraints. We are also interested in the ability to manage goals that arise through changes in the environment. Such changes can lead people to pursue a new goal, abandon an old goal, and revise priorities among existing goals. This ability is especially important when executing multiple tasks at the same time, because concurrently pursued goals can interact with each other in both positive and negative ways. An agent should be able to give priority to more important ones if other goals are known to interfere. In response, we made a second extension to the Icarus architecture that lets the system manage its top-level goals in a reactive manner. The revised Icarus distinguishes long-term and short-term goals, and it nominates instantiated versions of long-term goals when the state matches their corresponding relevance conditions. During the nomination process, the architecture computes the degree of match for the relevance conditions and uses it to modulate priority values of nominated goals. Icarus revises the priority of nominated goals based on the modulated values. To evaluate these extensions, we chose a variety of scenarios in an urban driving domain to demonstrate the new abilities. Due to the high-level nature of our research on cognitive architectures, the demonstrations focus on ability and parsimony of the extended Icarus framework. We have also examined connections to earlier work on these topics and explored future directions for research.
Cost-effective wireless architectures achieving enhanced capacity and coverage [electronic resource]
Keywords: Electrical Engineering.

Achieving higher coverage and capacity while at the same time reducing the cost of cell site deployment, maintenance and backhaul is always the goal of wireless operators. Femtocell and relay are two promising architectural candidates for mobile operators to achieve coverage and capacity improvement in a cost-effective manner. The first half of this dissertation focuses on the relay systems. Relay stations are devices that assist transmission from the information source to the destination. The capacity of a wireless relay network composed of a large number of nodes that operate in an amplify-and-forward mode and that divide into a fixed number of levels is analyzed. We consider both cases where the direct link towards destination nodes is present or not. The capacity computation relies on the study of products of large random matrices, whose limiting eigenvalue distribution is computed via a set of recursive equations. The femtocell network is explored in the second half of this dissertation. The idea of femtocells is to overlay low-power and low-cost base station devices, namely Femto-APs, on the existing cellular network, where each Femto-AP provides high speed wireless connection to subscribers within a small range. Simulation results show that significant areal capacity (throughput per unit area) gain can be achieved via intense spatial reuse of the wireless spectrum. However, Femto-APs introduce more interference to the existing cellular network and degrade the coverage. Fractional frequency reuse can be applied for interference mitigation. Acceptable coverage can be provided while retaining similar order of areal capacity gain.
Coupling fluorophores molecules to nanophotonic structures [electronic resource]
Keywords: Applied Physics

Fluorescence imaging and spectroscopy is an important tool in many areas of research. Biology has particularly benefitted from fluorescence techniques, since a single molecule's position, local environment, and even activity can be studied in real time by tagging it with a fluorescent label. It is, therefore, important to be able to understand and manipulate fluorescence. One way to control fluorescence is to shape the local electromagnetic fields that excite the fluorescent molecule. This thesis studies the interaction between fluorescent molecules and two nanophotonic structures that highly modify local electromagnetic fields: the bowtie nanoantenna and the photonic crystal cavity. The study of plasmons, or coherent excitations of free electrons in a metal, has led to the fabrication of antennas at optical frequencies. In particular, gold bowtie nanoantennas have been shown to concentrate light from the diffraction limit at 800 nm (~300 nm) down to ~20 nm, while also enhancing the local electric field intensity by a factor of 1,000. This huge change in the local field greatly alters the absorption and fluorescence emission of nearby molecules. This thesis will show that the fluorescence from an initially-poor single-molecule emitter can be enhanced by a factor of 1,300, allowing for the measurement of one highly enhanced molecule over a background of 1,000 unenhanced molecules. By extending this experiment to molecules in solution, dynamics of single molecules in concentrated solutions can also be measured. While bowtie nanoantennas act to concentrate light, light does not remain in the structure for long. The photonic crystal cavity can be used to trap and store light, which has interesting implications for molecular emitters located nearby. This thesis will show that molecules can be lithographically positioned onto a photonic crystal cavity and that the molecule's fluorescence emission is coupled to the cavity modes.