Recursos de colección

CaltechTHESIS (10.133 recursos)


Type = Thesis

Mostrando recursos 1 - 20 de 1.921

  1. A Dual Quark Model with Spin

    Ellis, Stephen Dean

    A dual quark model is developed from the usual Veneziano model by explicitly including the Dirac spin of the quarks. Resonances appear without the parity doubling and new ghosts present in previous models with spin. This is accomplished by eliminating the contributions of the negative parity components (MacDowell-twins) of the spin quarks 1/2 through the introduction of fixed J-plane cuts. The resonances belong to an SU6 symmetric spectrum identical, on the leading trajectory, with that of the usual static symmetrical quark model. All resonances couple via SU6w x O2Lz symmetric vertices and the model factorizes with essentially the same degeneracy as the usual Veneziano model....

  2. Part I. Tyrosinase Induction by Antimetabolites in Neurospora. Part II. Amino Acid Transport in Neurospora

    Pall, Martin Lawrence

    Part I.

    A technique for inducing very high levels of tyrosinase activity with various antimetabol ites is described. A modification of this tech­nique was used for studying tyrosinase induction in Neurospora over periods of a few hours. An amount of the antimetabolite inducer sufficient to induce the enzyme is rapidly taken up into the mycelium. Following uptake, however, there is a lag period of about two hours before tyrosi nase is synthesized. During the lag period, some active, energy requiring process prepares the mycelium for tyrosinase synthesis. Rapid synthesis of tyrosinase then ensues. High concentrations of cycloheximide, an inhibitor of protein synthesis,...

  3. Thymidine Metabolism in Neurospora Crassa

    Williams, Larry Gale

    The metabolism of thymidine by Neurospora crassa was investigated after radioactive labeling experiments showed that thymidine is not specifically incorporated into the DNA of Neurospora; a finding in contrast to the results of labeled thymidine experiments with many other organisms. Labeling experiments in which 2-C14 deoxyuridine, 2-C14 thymidine and 2-C14 thymine were administered to Neurospora revealed that in each case ninety per cent of the nucleic acid label was in the RNA fraction. When thymidine methyl-H3 was administered no label was found in either the RNA or DNA. This and other evidence was taken as proof that Neurospora lacks phosphorylating enzymes for deoxyribose...

  4. Mary and Magdalene Reintegrated Through Sisterhood in a Male-Dominated Goblin Market

    Buhler, Vivian Huang
    In her most celebrated and controversial poem, Goblin Market, Christina Rossetti presents an allegory of her own spiritual journey toward redemption as a woman, a sinner, and a reform worker. Through the stories of three young maidens’ misadventures among the goblin men’s “haunted glen,” Rossetti reveals the unjust Victorian binaries of male versus female, as well as virgin versus prostitute, and proposes an alternative definition of virtue attained through redemption that is accessible to all regardless of gender or social background. Using Jeanie, Lizzie, and Laura as figures for fallen woman, penitent, and sister, Rossetti further recasts the parallel feminine...

  5. Coarse-Grained Simulation Approaches for Protein Integration and Translocation via the Sec Translocon

    Niesen, Michiel Jacobus Maria

    This thesis describes coarse-grained approaches for simulating the co-translational integration and translocation of proteins via the Sec translocon, which is a key step in the biogenesis of membrane and secretory proteins. We present a coarse-grained simulation approach that is capable of simulating minute-timescale dynamics while retaining sufficient chemical and structural detail to capture sequence-specific interactions. The model is validated through comparison to existing experimental data and applied to characterize the forces that act on nascent proteins and drive successful integration and translocation. We also apply coarse-grained simulations of the integration of multi-spanning membrane proteins to understand the effect of sequence...

  6. A Theory for the Hugoniot of Condensed Media

    Salzman, Paul Klenett

    A shock model is developed that leads to an analytical expression for the Hugoniot of condensed media. In the analysis the final state is selected to coincide with the end of the shock transition so that the total energy change across the shock front is evaluated from changes in configurational energy only using an n-6 pair potential (shown to be valid for all n > 0) and a given lattice structure. Thermal energy changes are ignored because the dwell time of the molecules in the shock transition region is less than the thermal relaxation time. The total energy change is equated to...

  7. Studies on Absorptive Transitions Between Rotational Sublevels of Symmetric-Top Molecules in a Static Electric Field

    Thiene, Paul George, Jr.

    The topic of this research is the hitherto uninvestigated absorption of electromagnetic energy by polar symmetric-top molecules in a static electric field, which arises by virtue of direct transitions between sublevels of a single rotational state. A short theoretical treatment of the Stark effect of a rigid molecule is included. The factors governing the absorption of quanta from the surrounding radiation field are discussed in a rudimentary derivation of a formula for the maximum linear absorption coefficient of a gas.

    A new microwave Stark-effect spectrometer constructed for an exploratory investigation is described. The instrument operates in an unusual manner whereby the spectral position of the absorption line is varied, while the frequency...

  8. On Bacterial and ØX-174 Messenger-RNA

    Sedat, John W.

    General methods for the chromatography of nucleic acids on benzoylated (naphthoylated) DEAE cellulose are described. This procedure results in well-resolved peaks with good recovery and seems to separate nucleic acids on the basis of their secondary structure almost independently of their molecular weight. These methods have proved to be useful in the analysis of the replicative intermediates of MS-2 RNA, ØX RFDNA, and ØX single stranded DNA, for example.

    Specific methods for the purification of E. coli. pulse-labeled RNA based on the chromatography on benzoylated DEAE cellulose at pH 7.5 and pH 3.5 were developed. Greater than 60% of the pulse label with...

  9. Mechanisms of Transcriptional Silencing by the Nuclear Piwi Protein in Drosophila Germ Cells

    Rogers, Alicia Kathryn

    An important characteristic for life is the ability to persist – to reproduce and defend oneself against different stresses. The ability of a species to persist from one generation to the next heavily depends on the integrity of the genetic material being passed down, and thus organisms have developed strategies to ensure the integrity of their genomes remain in tact. In Metazoan germlines, piwi proteins and their associated piwi-interacting RNAs (piRNAs) provide a RNA-interference (RNAi) based defense system against the expression of transposable elements (TEs). TE expression is detrimental to an organism’s genome – resulting in disruption of genes, double-stranded...

  10. Failure of Liquid Storage Tanks Due to Earthquake Excitation

    Shih, Choon-Foo
    Above ground liquid storage tanks have suffered serious damage during earthquakes. The damage of tanks can vary from local yielding or buckling of the tank wall, to loss of contents, or to collapse which leads to an unrepairable tank. Considerable work has been carried out on this problem with varying degree of success. However, the results are largely directed toward response rather than failure prediction. The information on failure mechanisms is very limited. The present work consists of scale model testing, correlation with existing analysis and failure prediction with laboratory verification. The scale model testing incorporates dynamic similarity of the fluid/structure...

  11. Magnetism in an Amorphous Fe-Pd-P Alloy System

    Sharon, Thomas Edward

    Amorphous alloys of composition FexPd80-xP20 (13 ≤ x ≤ 44) have been prepared by rapid quenching from the liquid state. The Mössbauer effect in Fe57 has been used to study the magnetic properties of these materials. The hyperfine field distributions have been determined from these experiments, as a function of composition and temperature. The results indicate that the electronic state of Fe in these alloys remains essentially constant throughout the composition range, and that the Pd d band is filled by electron transfer from phosphorus.

    The variation of the magnetic transition temperature with composition has been determined by combining the Mössbauer effect results with complementary magnetic measurements. There is a sharp...

  12. Crystallographic Studies of Iodide-Containing Quasi-One-Dimensional Conductors

    Ma, Charlotte K. Lowe

    The crystal structures of three iodide-containing quasi-one-dimensional conductors, (tetrathiotetracene)2(iodide)3 (high disorder), tetrathiotetracene-iodide, and (hexamethylenetetraselenofulvalene)-(iodide)x were solved by single crystal X-ray diffraction methods. These three iodides are single charge-carrier conductors and allow a comparison of such competing effects as disorder, interchain coupling, and overlap.

    The crystal structure of metallic (tetrathiotetracene)2(iodide)3 (high disorder), TTT2I3 (h.d.), was solved at room temperature (~294° K), 164° K, 74° K, and at 19° K. At all four temperatures the lattice symmetry remained orthorhombic and the structures were successfully refined in the space group Cmca. During slow cooling the diffuse layer lines were also carefully monitored. In contrast...

  13. Applications of Model Theory to Complex Analysis

    Stroyan, Keith Duncan

    We use a nonstandard model of analysis to study two main topics in complex analysis.

    UNIFORM CONTINUITY AND RATES OF GROWTH OF MEROMORPHIC FUNCTIONS is a unified nonstandard approach to several theories; the Julia-Milloux theorem and Julia exceptional functions, Yosida's class (A), normal meromorphic functions, and Gavrilov's Wp classes. All of these theories are reduced to the study of uniform continuity in an appropriate metric by means of S-continuity in the nonstandard model (which was introduced by A. Robinson).

    The connection with the classical Picard theorem is made through a generalization of a result of A. Robinson on S-continuous *-holomorphic functions.

    S-continuity offers considerable simplifications over the standard sequential approach and permits a...

  14. The Primordial Origin and Dynamical Sculpting of Close-In Planetary System Architectures

    Spalding, Christopher

    For centuries, planet formation theories were tuned to reproduce the remarkable coplanarity of our Solar System. Specifically, the eight planetary orbital planes exhibit mutual inclinations limited to ~1−2 degrees. Furthermore, the misalignment between the Sun's spin axis and the orbital planes of the planets – the 'spin-orbit misalignment'– is only about 6 degrees. However, observational characterization of close-in extrasolar planetary systems has revealed an abundance of spin-orbit misalignments ranging all the way from 0 to 180 degrees (Winn et al. 2010). Particularly among the hot Jupiters (giant planets with orbital periods shorter than ~1 week), spin-orbit misalignments are more prevalent...

  15. Heat Flow near Major Strike-Slip Faults in Central and Southern California

    Henyey, Thomas Louis

    Seventeen heat flow measurements have been made near the San Andreas, San Jacinto, and Garlock faults of California in regions representative of several levels of seismic activity. Data from these measurements in conjunction with results of other heat flow investigations in central and southern California show no maxima directly attributable to the fault zones. This negative result along with stress-drop results from earthquakes suggests an upper bound of the order of 200 bars for the absolute stress in the vicinity of the San Andreas fault. In addition, the average heat flow in the four regions investigated (San Bernardino Mountains - Lake Hughes,...

  16. Part 1. Dynamic Response of Phase Boundaries in the Earth to Surface Loading. Part 2. Pleistocene Glaciation and the Viscosity of the Lower Mantle

    O'Connell, Richard John

    Part 1. Analytic approximate solutions have been found for the response of a phase change to pressure loading. These solutions allow the behavior of the system to be analyzed in terms of simple parameters of the system. Different characteristic types of behavior are shown to obtain for short times and long times, and criteria for defining these characteristic time scales are given in terms of known parameters. The distribution of heat sources and convective heat transport are shown to generally have only minor influence on the solution, and may be neglected in many cases. The important parameters are the latent heat...

  17. Amplitudes of Seismic Waves Reflected and Refracted at the Earth's Core

    Dana, Stephen Winchester

    The Zoeppritz equations are used to determine the energy partition in seismic waves reflected and refracted at the earth's core. First, the assumption is made that the core is fluid and hence does not transmit any shear waves. Then the four possible cases are treated; an incident longitudinal wave in the mantle against the core, an incident longitudinal wave in the core against the mantle, and an incident shear wave both of the SV type (particles vibrating in the plane of incidence) and of the SH type (particles vibrating perpendicular to the plane of incidence) in the mantle against the core. The square...

  18. Part I. The Effect of Temperature and Partial Melting on Velocity and Attenuation in a Simple Binary System. Part II. Effect of Temperature and Pressure on Elastic Properties of Polycrystalline and Single Crystal MgO

    Spetzler, Hartmut A. W.

    A possible explanation of the low-velocity, low-Q zone in the upper mantle is partial melting, but laboratory data has not been available to test this conjecture. As a first step in obtaining an idea of the role that partial melting plays in affecting seismic variables, the longitudinal and shear velocities and attenuations were measured in a simple binary system that is completely solid at low temperatures and involves 17% melt at the highest experimental temperature. The system investigated was NaCl•H2O. At temperatures below the eutectic the material is a solid mixture of H2O (ice) and NaCl•H2O. At higher temperatures the system is...

  19. Surface Wave Propagation and Source Studies in the Gulf of California Region

    Thatcher, Wayne Raymond

    A number of aspects of seismic surface wave propagation and earthquake mechanism in the Gulf of California region are investigated in this thesis. In addition, several associated problems raised by this study are also explored in some detail.

    Surface wave dispersion and P-wave travel time delays are measured to delineate the crust and upper mantle structure in the Imperial Valley-Gulf of California region. Crustal thicknesses beneath Baja California and Sonora are comparable and near 25 km, while within the Gulf crustal structure varies laterally from nearly oceanic on the western side to continental shelf thicknesses (~20 km) towards the north and east. Love...

  20. The Low-Frequency Frontier: Cosmology with Future 21cm Experiments

    Mishra, Abhilash

    This thesis presents theoretical and observational investigations in two areas of cosmology: the detection of inflationary gravitational waves using the circular polarization of the redshifted 21cm line from neutral hydrogen during the Dark Ages, and the study of galactic foregrounds at low-frequencies using the Owens Valley Radio Observatory Long Wavelength Array (OVRO LWA).

    In the theoretical part of this thesis, we propose a new method to measure the tensorto-scalar ratio r using the circular polarization of the 21 cm radiation from the Dark Ages. In Chapter II we discuss the basic principles of inflationary physics, which is now accepted as a...

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