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CaltechTHESIS (9.394 recursos)


Status = Unpublished

Mostrando recursos 1 - 20 de 8.855

  1. The Diffractive Dissociation Process at π^-p → π^- (π^-π^+p) 14 GeV/c

    Rosenfeld, Leo C.

    We describe an experiment in which a 14 GeV/c π- beam was incident on a hydrogen bubble chamber. Fast forward scattered pions traversed a wire spark chamber spectrometer downstream of the bubble chamber. Events identified as inelastic by the spectrometer induced a trigger of the bubble chamber camera. The film produced contained a heavy enrichment of events of proton diffractive dissociation.

    We have studied a sample from this exposure of 4400 events of the reaction π-p → π-N* → π-π-π+p. In the two body mass spectra the only noteworthy feature is the Δ++(1230). In the N* mass spectrum we observe enhancements at 1.49 GeV, 1.72 GeV, and 2.0 GeV....

  2. A Study of the Reactions π^±p → π^±π^+π^-π^op and π^±p → π^±π^+π^+π^-n at P_(lab) = 14 GeV/c Using a Triggered Hybrid Bubble Chamber

    Nagy, Frank Joseph

    We have studied the reactions π±p → π±π+π-πop and π±π+π+π-n at a beam momentum of 14 GeV/c. A bubble chamber with a downstream wire spark chamber spectrometer was used to record the data. The bubble chamber camera was triggered by identifing inelastic events in an online computer using data from the downstream spectrometer. The film taken represents an exposure of about 80 events/microbarn for the π+ data and 70 events/microbarn for the π- data.

    We find these reactions to be very rich in subprocesses involving baryon and meson resonances. The invariant mass spectra are presented and estimates of the cross sections for the production of known baryon and meson resonances...

  3. Optimal Sensor Placement for Bayesian Parametric Identification of Structures

    Bhattacharyya, Pinaky

    There exists a choice in where to place sensors to collect data for Bayesian model updating and system identification of structures. It is desirable to use an available deterministic predictive model, such as a finite-element model, along with prior information on the uncertain model parameters and the uncertain accuracy of the predictive model, to determine which optimal sensor locations should be instrumented in the structure. In this thesis, an information-theoretic framework for optimality is considered.

    The mutual information between the uncertain model predictions for the data and the uncertain model parameters is presented as a natural measure of reduction in uncertainty...

  4. Forces, Stresses, and the (Thermo?) Dynamics of Active Matter: The Swim Pressure

    Takatori, Sho C.

    A core feature of many living systems is their ability to move, self-propel, and be active. From bird flocks to bacteria swarms, to even cytoskeletal networks, active matter systems exhibit collective and emergent dynamics owing to their constituents' ability to convert chemical fuel into mechanical activity. Active matter systems generate their own internal stress, which drives them far from equilibrium and thus frees them from conventional thermodynamic constraints, and by so doing they can control and direct their own behavior and that of their surrounding environment. This gives rise to fascinating behaviors such as spontaneous self-assembly and pattern formation, but...

  5. Nanophotonic Resonators for Optical Quantum Memories based on Rare-Earth-Doped Materials

    Miyazono, Evan Tsugio

    The growing interest in optical quantum systems has led to the exploration of multiple platforms. Though pioneering experiments were performed in trapped atom and trapped ion systems, solid state systems show promise of being scalable and robust. Rare earth dopants in crystalline hosts are an appealing option because they possess a rich spectrum of energy levels that result from a partially filled electron orbital. While level structure varies across the period, all elements possess crystal field splittings corresponding to near infra-red or optical frequencies, as well as Zeeman and often hyperfine levels separated by radio frequency and microwave frequencies. These...

  6. Solubility of Natural Gas in Various Crude Oils and Preparation of Pure Methane from Natural Gas

    Kircher, Charles Edmund Jr.
    The work reported in this paper is a continuation of experiments begun and carried out by B.H. Sage, and described in his thesis for the Masters degree C.I.T. 1931. The object of the research was to determine as quantitatively as possible the solubility of natural gas in various crude oils, as it was known that by dissolving natural gas in crude oil, the physical properties of the oil could be changed in such a way as to make possible greater recovery of the crude oil from the underground formation. As pointed out by Mr. Sage, the solubility figures presented in his...

  7. Quantum Optics with Single Atoms and Single Photons

    Turchette, Quentin A.
    An atom strongly coupled to a high-finesse resonator forms a microscopic optical system in which the interaction of single atoms with single photons has significant consequences. This is in contrast to a typical optical system in which a field composed of many photons interacts with a medium consisting of many atoms. This unique optical system has been used in studies of the fundamental matter-radiation interaction on the single quantum level, in quantum computation, and in real-time, high-position-resolution detection of single atoms.

  8. Channeling in Semiconductors and its Application to the Study of Ion Implantation

    Picraux, Samuel Thomas

    The channeling characteristics of protons and helium ions in various diamond-type lattices (diamond, Si, Ge, GaP, GaAs, GaSb) have been studied by means of elastic backscattering in the 0.5 to 2 MeV range. Critical angles (ψ½) and minimum yields (ψ½) have been measured and compared to theory. The values of ψ½ for axial channeling have a functional dependence which agrees well with calculations based on the average potential along the row - both for uniform and for non-uniform spacing and (in the case of the compound semiconductors) for mixed atomic composition. Planar critical angles also show a functional dependence in agreement with average potential calculations. However, it is necessary to...

  9. Biophysical Characterization of an ABC L-methionine Transporter

    Li, Qi Wen

    The ATP-binding cassette (ABC) superfamily is pivotal to a number of important biochemical processes and ubiquitous in all kingdoms of life. Previous studies of ABC transporters have been heavily focused on the structural determination of the different intermediates of the transport cycle. In order to characterize the mechanism of an E. coli L-methionine transporter, which is an ABC importer, we first collated previously reported structural information on the conformational states of several well characterized ABC importers and associated binding proteins, and identified four major conformations (i.e., pre-T, outward, post-T, and inward state). We stabilized these intermediates using appropriate mutations, substrates,...

  10. Differential Reactivity at Edge and Terrace Sites of Transition Metal Dichalcogenides

    Wiensch, Joshua David

    This dissertation describes efforts towards understanding the surface reactivity and catalytic properties of a promising class of materials, which have the potential to be integrated as part of a solar-fuels device and help usher-in the solar age. Because of their multifunctional behavior, layered transition metal dichalcogenides are potential candidates for not only light absorption in a solar fuels device, but also as catalysts for the hydrogen evolution reaction.

    We begin in chapter one with an introduction related to global energy sources and trends, highlighting the motivation for the work performed in this dissertation. The second chapter describes a discovery into the...

  11. I. Tin Silsesquioxanes as Analogs for the Open and Closed Sites in Tin-Containing Zeotype Beta and II. Enantiomerically Enriched, Polycrystalline Molecular Sieves

    Brand, Stephen Kramer

    The use of biomass as a resource to produce value-added products has garnered significant interest as a means of reducing reliance on fossil fuels. This task is complicated by the complex, highly functionalized nature of abundant biomass derivatives, such as glucose. Tin-containing zeolite Beta (Sn-Beta) has been investigated as a catalyst for isomerizing aldohexoses into ketohexoses through a Lewis acid mediated hydride shift (1,2-intramolecular hydride shift, 1,2-HS). Recent studies on the reactivities of Lewis base-doped and alkali-exchanged Sn-Beta samples have conclusively demonstrated that the open tin site performs the glucose isomerization reaction. With Lewis base doped Sn-Beta, glucose conversion is...

  12. Online Learning for the Control of Human Standing via Spinal Cord Stimulation

    Sui, Yanan

    Many applications in recommender systems or experimental design need to make decisions online. Each decision leads to a stochastic reward with initially unknown distribution, while new decisions are made based on the observations of previous rewards. To maximize the total reward, one needs to balance between exploring different strategies and exploiting currently optimal strategies within a given set of strategies. This is the underlying trade-off of a number of clinical neural engineering problems, including brain-computer interface, deep brain stimulation, and spinal cord injury therapy. In these systems, complex electronic and computational systems interact with the human central nervous system. A...

  13. A Field and Geochronologic Study of Mantled Gneiss Domes in Central New England

    Naylor, Richard Stevens

    New information on the origin of mantled gneiss domes comes from a study of these structures in Central New England. The domes have cores of massive granite and gneiss encircled by concordant mantles of well-stratified metamorphic rocks, and appear to originate through intense metamorphism of rock sequences in which massive, chiefly quartzo-feldspathic rocks are overlain by less competent strata. Contrary to previous hypotheses, the new work indicates that neither unconformable separation of the core and mantle nor re-mobilization or anatexis of the core rocks are essential elements in the formation of mantled gneiss domes. Two contrasting types of gneiss domes have been identified in central New England.

    Examples of the first...

  14. Oxygen and Hydrogen Isotope Ratios in Sedimentary Rocks and Minerals

    Savin, Samuel Marvin

    O18/O16 and D/H measurements were made on a variety of sedimentary rocks and minerals, with special emphasis on the fine-grained, predominantly clay mineral fraction of the sediments. The interlayer water was removed from clay minerals prior to the isotopic analyses. Precision of the measurements was generally ± 0.2 permil for oxygen and ± 0.3 percent for hydrogen. In the case of zeolites the reproducibility was less constant because of difficulty encountered in removing zeolitic water.

    Listed in order of decreasing tendency to concentrate O18, the sedimentary minerals for which such data are available and their approximate isotopic fractionation factors relative to water...

  15. Economic Fluctuations and Capitalistic Production: A Case Study in Robustness Constraints

    Cruz, Gerardo
    A central pursuit of macroeconomic research is to understand the source of short run variations in aggregate economic variables. To this end, the branch of macroeconomics known as Real Business Cycle (RBC) theory emphasizes the role of disturbances to the real economy while abstracting from nominal variables (e.g. money). According to RBC theory, business cycles are the result of optimal responses to exogenous stochastic disturbances on technology in a structure of capitalistic production. In this report, we contend that the structure of capitalistic production per se constrains the ability of the economy to absorb shocks. That is, even if the...

  16. Infrared 8-13µ Spectroscopy of the Moon and Some Cold Silicate Powders

    Goetz, Alexander Franklin Hermann

    Laboratory investigations were made of the spectral emission properties of a limited number of silicate powders in vacuum and surface temperatures of 180-240°K. The effect on the emission spectrum of mineral composition, powder grain-size, surface contamination and thermal gradient was studied.

    The low sample surface temperature enhanced the spectral contrast of quartz but had little effect on spectra of rock materials. In general, there was a decrease in spectral contrast with decreasing sample grain-size. However, this effect was more pronounced for individual mineral samples than for rock samples. When the particle size was reduced to less than 38μ individual rock types could not be identified. However, quartz bearing or generally acidic...

  17. Impact of Climate and Tectonics on the Morphodynamics of Alluvial Piedmonts, Implications for Sediment Transfer and the Stratigraphic Record

    Malatesta, Luca Claude

    Alluvial piedmonts encircle most of the Earth mountain ranges. The erosion product of these mountains must cross the piedmont domain before reaching the basins where they can enter the sedimentary record. The flux of sediment transfers environmental signals, e.g. tectonics and climate, from source to sink, their preservation is critical for the sedimentary record. Alluvial piedmonts are very reactive to external and internal forcing often incise by tens to hundreds of vertical meters over a few thousand years only to subsequently aggrade by roughly the same amount. In my thesis, I set to study the morphodynamics of alluvial piedmonts in...

  18. The Earthquake Response of Deteriorating Systems

    Gates, Nathan Craig

    This thesis is concerned with the earthquake response of deteriorating systems. A model for stiffness degrading or deteriorating systems is used to describe six different single-degree-of-freedom systems. A numerical investigation of the response of these six systems is performed using an ensemble of twelve earthquakes. The response is studied at nine nominal periods of oscillation. The numerical results are presented as response spectra corresponding to six different ductilities.

    An approximate analytical method for calculating the earthquake response of deteriorating systems from a linear response spectrum is presented. The method, called the average stiffness and energy method, is based upon the premise that a linear system may be defined which is in...

  19. Mechanisms and Function of Neural Synchronization in an Insect Olfactory System

    MacLeod, Katrina Marie

    One of the fundamental questions in modem integrative neurobiology relates to the encoding of sensory information by populations of neurons, and to the significance of this activity for perception, learning, memory and behavior. Synchronization of activity across a population of neurons has been observed many times over, but has never been demonstrated to be a necessary component of this coding process. Neural synchronization has been found in many brain areas in animals across several phyla, from molluscs to mammals. Studies in mammals have correlated the degree of neural synchronization with specific behavioral or cognitive states, such as sensorimotor tasks, segmentation and binocular rivalry suggesting a functional link. In...

  20. Terahertz and Microwave Spectroscopy of Liquids and Hydrogen-Bonded Clusters

    Finneran, Ian Alan

    The microwave (MW, 0.3-100 GHz) and terahertz (THz, 0.1-10 THz) regions of the electromagnetic spectrum are replete with a rich set of molecular motions, including soft inter- and intramolecular vibrations, torsions, and rotations. At room temperature these motions are well populated, and play an active role in condensed-phase chemistry on Earth. This work details the development of one MW and two THz spectrometers along with their application to the study of liquids and hydrogen-bonded clusters.

    In the first section, we cover the design and construction of a chirped pulse Fourier transform microwave (CP-FTMW) spectrometer. The instrument relies on a compact, inexpensive...

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