Recursos de colección

CaltechTHESIS (10.335 recursos)


Type = Thesis

Mostrando recursos 1 - 20 de 2.139

  1. Synthesis of Functionalized Polymers by Ring-Opening Metathesis Polymerization (ROMP)

    Maughon, Bob Robinson, Jr.

    In Chapter 1, the ROMP of 5-methacrylate-1-cyclooctene and the copolymerization of this monomer with cyclooctadiene using the initiator (PCy3)2Cl2Ru=CHCH=CPh2 were investigated to produce polymers with cross-linkable side-chains. The impact of concentration, monomer to initiator ratio, and the amount of inhibitor in the polymerization was examined. These polymers were cross-linked through the methacrylate side-chains with either thermal or photochemical initiation, and the incorporation of these polymers into poly(methyl methacrylate) (PMMA) to produce AB cross-linked materials was accomplished. A comparison of the physical properties of PMMA and these new materials demonstrated that these materials had higher thermal stability and solvent resistance than pure PMMA.

    As an extension of the work presented in...

  2. Tensile Failure and Fracture of Three-Dimensional Brittle Nanolattices

    Mateos Arrieta, Arturo Jose
    The emergence of a new class of cellular solids, i.e., nano- and micro-architected materials, poses the question of whether they can be characterized as a continuum solid. Extensive research has shown that these ultralight and strong structural metamaterials are particularly attractive for mechanically-demanding applications; yet their susceptibility to flaws, fracture behavior, and discrete-continuum duality remains relatively unexplored. In the course of this work, we report the fabrication and tensile-to-failure response of three-dimensional ceramic nanolattices, comprised of 50nm-thick alumina tubes that are arranged into periodic 5um-wide octet-truss unit cells, with and without pre-fabricated through-thickness center notches oriented at different angles to...

  3. An Electrophysiological Study Of Voluntary Movement and Spinal Cord Injury

    Urban, Luke Stuart

    Voluntary movement is generated from the interaction between neurons in our brain and the neurons in our spinal cord that engage our muscles. A spinal cord injury destroys the connection between these two regions, but parts of their underlying neural circuits survive. A new class of treatment (the brain-machine interface) takes advantage of this fact by either a) recording neural activity from the brain and predicting the intended movement (neural prosthetics) or b) stimulating neural activity in the spinal cord to facilitate muscle activity (spinal stimulation). This thesis covers new research studying the brain-machine interface and its application for spinal...

  4. Micrometric and Petrofabric Studies of the Val Verde Tonalite, Southern California

    Osborn, Elburt Franklin

    The Val Verde tunnel of the Metropolitan Water District of Southern California, located thirteen miles south of Riverside, California, passes through 27,000 feet of a single tonalite intrusive and across the intrusive contact into a body of quartz-biotite schist.

    Micrometric analyses of the tonalite along the line of the tunnel have shown no progressive variation in the percentage of minerals present; but the albite content of the plagioclase increases toward the contact with the schist, and this correlates directly with the radioactivity and zircon content of the tonalite. The more acid border of the intrusive is believed to be due to...

  5. A Study of the Energy Contained in the Seismic Waves P and pP

    Mooney, Harold Morton
    The energy observed in the seismic waves P and pP in a large number of earthquakes is compared with the theoretical energy calculated from a standard equation, using two partly independent methods. The results are analyzed using as variables depth of focus, distance from epicenter to recording station, geographical location of epicenter and azimuth from station. When compared with the theoretical value, the ratio of the energy in pP to the energy in P averaged over a distance range 60°-90° is observed to decrease with depth, by 0.5 on a logarithmic scale of energy between 100 and 600 km. depth...

  6. Analysis of Metal-oxide Protected Photoelectrochemical Systems for Water Splitting

    Lichterman, Michael Yang
    The photoelectrochemical splitting of water into oxygen and hydrogen gas is one pathway toward the renewable and economic generation of a fuel which is sufficiently scalable to power a large fraction, or even a majority, of the power requirements of modern society. In order to make such a device economically promising, it must be sufficiently cheap, have sufficiently high efficiency, or some combination thereof. In this work, two primary routes toward such a device are discussed; the first is the use of a cheaply prepared photoanode material, BiVO4, the interactions of this material with cobalt oxide based catalysts, and the use of such structures in more extreme...

  7. Computational and Neural Mechanisms Underlying Decision-Making in Humans

    Adachi, Ryo

    How do we make economic decisions in everyday life? How do we make decisions in the face of uncertainty regarding the statistics of the environment? These are the questions that played a pivotal role in the formation of the field "Decision Neuroscience". In each chapter of this thesis, we investigated the computational and neural mechanisms to tackle these questions using behavioral and neural data acquired through fMRI experiments.

    In the first chapter, we investigated the computational and neural basis of economic decision-making in a binary choice task between two food items. We analyzed behavioral and neural data in a task...

  8. Redox Signaling in Eukaryotic DNA Replication and Repair

    O'Brien, Elizabeth

    DNA-mediated charge transport chemistry (DNA CT) offers an intriguing regulatory mechanism in biology, as it is long-range, rapid, and sensitive to mismatches and perturbations to base stacking. DNA-processing enzymes in all three domains of life moreover have been shown to contain [4Fe4S] clusters, commonly redox cofactors. Bacterial [4Fe4S] repair proteins have been shown to signal one another using long-range DNA-mediated charge transport (DNA CT), facilitating the redistribution to damaged genomic DNA in cells. The role of metabolically expensive, [4Fe4S] cluster cofactors in eukaryotic systems, however, was less clear than in prokaryotes.

    Here we examine the chemical role of the [4Fe4S] cluster...

  9. Interrogating the Structural Landscape of Malaria Biomarkers with Epitope Targeted Peptide Capture Agents

    Liang, JingXin

    Antibodies have conventionally been used as molecular recognition agents against epitopes, or antigenic regions, for protein capture and detection. The ability of monoclonal and polyclonal antibodies to selectively bind their targets with high affinities makes them excellent agents for specific protein recognition. However, as large proteins themselves (~150 kDa), antibodies are susceptible to changes in pH, temperature, and biochemical environment, particularly proteolytic cleavage. Additionally, epitope binding on antibodies is reliant on their rigid tertiary structure to position key functional groups that facilitation antigen recognition. Retaining the integrity of the protein structure creates rigid limitations against chemical modifications of antibodies to...

  10. Interfacial and Stability Studies of Photocathodes for Hydrogen Evolution

    Jiang, Jingjing

    Photoelectrochemical (PEC) water splitting is a promising way to generate clean hydrogen fuel from water and sunlight. The ideal photocathodes for hydrogen evolution reaction (HER) should have good electrical contact and mechanical adhesion on the interface between the semiconductor and the catalyst, and be stable during operation. However, the interfacial properties and the stability have not been intensively studied. We investigated the electrical and mechanical properties on the nanoscale of the interface of commonly used Si/Pt nanoparticles (Pt-NPs) electrodes with Pt-NPs as a catalyst, and showed that the Pt-NPs have a weaker adhesion in electrolyte than in air, and less...

  11. Theoretical Foundations for Quantum Measurement in a General Relativistic Framework

    Pang, Belinda Heyun
    In this work, we develop theoretical formulations to analyze experimentally relevant quantum measurement schemes in a general relativistic framework, and discuss their implications versus the Newtonian or non-relativistic viewpoints. Specifically, we address (i) matter waves in simple free fall, (ii) the Mach-Zehdner atom interferometer with light-matter interaction and (iii) optomechanical systems. The motivation is to explore the regime of physics where gravity and relativistic effects become pertinent for quantum experiments due to the increase in system size and complexity. Such experiments may illuminate a way forward to reconcile the independently successful but apparently paradoxical theories of gravity and quantum mechanics,...

  12. A Dark Matter Search Using the Final SuperCDMS Soudan Dataset and the Development of a Large-Format, Highly-Multiplexed, Athermal-Phonon-Mediated Particle Detector

    Cornell, Brett Durcan

    Over the past eighty years, numerous complementary observations of our universe have indicated that our current description of physics is far from complete. The "ordinary matter", such as electrons, protons, photons and neutrons, that constitutes the bulk of all human physical experiences is actually only a minority (about 16%) of the total mass of the universe. The remaining 84% is very poorly understood, but has profound effects on the dynamics and evolution of our universe. Because it does not interact with light, and is not observable in telescopes on earth, this extra mass is usually referred to as "dark matter"....

  13. Single-Neuron Correlates of Visual Object Representation in the Human Brain: Effects of Attention, Memory, and Choice

    Minxha, Juri

    Neurons in the medial temporal lobe (amygdala and hippocampus) are known to respond selectively to specific object categories, such as faces. This dissertation investigates two novel extensions of this work: (1) how are such neuronal responses influenced by where we attend; (2) how is category information used by the brain to make decisions.

    The first question evaluated the representation of faces in the primate amygdala during naturalistic conditions, by recording from both human and macaque amygdala neurons during free viewing of arrays of images with concurrent eye tracking. We found that category-selective responses were very strongly modulated by where people, or...

  14. The Avatar Paradigm in Granular Materials

    Kawamoto, Reid Y.
    Granular materials are ubiquitous in both everyday life and various engineering and industrial applications, ranging from breakfast cereal to sand to rice to medical pills. However, despite the familiarity of granular materials, their behavior is complex and efforts to characterize them are currently broad research areas in physics and engineering. Research of granular materials, as is the case with the research of other engineering materials such as rocks and metals, is beset with two gaps: the gap between reconciling macroscopic behavior with microscale (particle-scale, in the case of granular materials) behavior, and the gap between reconciling experimental and computational results....

  15. A Planetary Perspective of Life

    Wong, Michael L.

    Join me on my journey to Jupiter, Titan, Pluto, Earth, and Mars as I seek a deeper understanding of life through the lessons that I learn from each world. How should we define life? What does life do? Why does life exist, and how did it begin? And what do the answers to these questions mean for the prospect of life beyond Earth? No, you’re not going to get any spoilers here. Yes, you actually have to read the manuscript. I spent a lot of time weaving this story together, adding supplementary material to each chapter, connecting the dots between...

  16. The Effective Field Theory of Fermi Surfaces in the Vicinity of Van Hove Singularities

    McKinney, Tristan

    The use of effective field theories to attack new and seemingly disparate problems has proliferated in the past several decades. In this thesis, we develop effective field theories for systems of fermionic quasiparticles possessing Fermi surfaces, with a particular focus on Fermi surfaces proximal to Van Hove singularities. Such systems are a fruitful source of complex and novel behavior in condensed matter physics. We begin with an overview of the renormalization group procedure at the heart of effective field theory by analyzing a simple example. We emphasize the concept that the RG relates the observables of one theory to those...

  17. Synthesis and Self-Assembly of Bottlebrush Block Polymers: Molecular Architecture and Materials Design

    Chang, Alice B.

    Bottlebrush polymers represent a unique molecular architecture and a modular platform for materials design. However, the properties and self-assembly of bottlebrush polymers remain relatively unexplored, in large part due to the synthetic challenges imposed by the sterically demanding architecture. This thesis describes our work to close this gap, connecting (1) the synthesis of polymers with precisely tailored molecular architectures, (2) the study of fundamental structure-property relationships, and (3) the design of functional materials.

    Chapter 1 introduces key concepts related to polymer architecture and block polymer phase behavior. Recent developments in the synthesis and self-assembly of bottlebrush block polymers are highlighted in...

  18. Engineering Novel Rhodopsins for Neuroscience

    Bedbrook, Claire Nicole

    The overarching goal of my PhD research has been engineering proteins capable of controlling and reading out neural activity to advance neuroscience research. I engineered light-gated microbial rhodopsins, primarily focusing on the algal derived, light-gated channel, channelrhodopsin (ChR), which can be used to modulate neuronal activity with light. This work has required overcoming three major challenges. First, rhodopsins are trans-membrane proteins, which are inherently difficult to engineer because the sequence and structural determinants of membrane protein expression and plasma membrane localization are highly constrained and poorly understood (Chapter 3-5). Second, protein properties of interest for neuroscience applications are assayed using...

  19. Astrophysical Applications of Quantum Mechanics

    Murchikova, Elena M.
    From an outside point of view, astrophysics and quantum mechanics as subclasses of the physical sciences could not be further from each other. Yet these two sides of nature are deeply intertwined. The influence of quantum mechanics on astrophysics and astrophysics on quantum mechanics has been profound: spectral lines as diagnostics, radiative transport, the interiors of celestial bodies, neutrino oscillations, constraints on neutrino mass and graviton mass. In this work, I discuss several applications of quantum mechanics in astrophysics: (1) I examine the use of submm recombination lines of H, He and He+ to probe the extreme ultraviolet luminosity of...

  20. Towards a priori Models for Differential Diffusion in Turbulent Non-Premixed Flames

    Burali, Nicholas

    In this work, progress is made towards the correct modeling of differential diffusion, both for resolved simulations, and for reduced-order combustion models. For resolved simulations, the validity and the limitations of the constant non-unity Lewis number approach in the description of molecular mixing in laminar and turbulent flames is studied. Three test cases are selected, including a lean, highly unstable, premixed hydrogen/air flame, a lean turbulent premixed n-heptane/air flame, and a laminar ethylene/air coflow diffusion flame. For the hydrogen flame, both a laminar and a turbulent configuration are considered. The three flames are characterized by Lewis numbers which are less...

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