Recursos de colección

CaltechTHESIS (10.025 recursos)


Type = Thesis

Mostrando recursos 1 - 20 de 1.691

  1. High Alumina Metamorphic Rocks of the Kings Mountain District, North Carolina and South Carolina

    Potter, Donald Brandreth

    The Kings Mountain district is located in the center of the Piedmont province at the North Carolina-South Carolina border. The district consists of two areas which are underlain by high alumina metamorphic rocks including kyanite quartzite and sillimanite quartzite. The southern area covers about 35 square miles and lies just southeast of the city of Kings Mountain; the northern area covers about 20 square miles and is located 15 miles northeast of the city of Kings Mountain. The two areas are separated by the Yorkville granodiorite. A detailed geologic map was made of the southern area; in the northern area only...

  2. The Diffusion of Ions in Agar Gel Suspensions of Red Blood Cells

    Chilcote, Dennis Don

    A method was developed for measuring the self-diffusion coefficient of solutes in agar gel suspensions of red cells. The purpose was to investigate the influence of the red cell on the diffusion of ions which are important in blood solute transport.

    The capillary diffusion method was employed. The diffusion coefficient was calculated from the initial and final concentration of tracer in the capillary. The results are discussed in terms of a modified Maxwell equation for the average conductivity in a granular medium in which a discontinuous boundary condition is employed to account for the observed partition coefficients.

    The results indicate the ration of the diffusivity of solute in the red cell suspension...

  3. The Effects of Selective Doping on Electron Transport in Two-Dimensional Electron Gases

    Olsen, Ben Andrew
    Recent research on bilayer two-dimensional electron gasses (2DEG) indicates the possibility of excitonic superfluidity, though experiments have measured small dissipation due to motion of unpaired vortices. In regular superconductors, carriers flow without dissipation beacuse vortices are "pinned" by impurities. This research investigates the effects of C and Si dopants within the quantum well of a single quantum well 2DEG. These dopants are candidates for improving vortex pinning in bilayer 2DEG systems. Four C-doped samples, with dopant density ranging from 3.5 x 10^(14) cm^(-3) to 2.5 x 10^(16) cm^(-3) , and one Si-doped sample, with 2.3 x 10^(15) em- :\ Si ions are studied by electron...

  4. Effects of Ca-Doping on the Vortex Properties and Pairing Symmetry of (Y1-xCax)Ba2Cu3O7-δ

    Moehle, Austin Michael

  5. From Sequence to Function through Secondary Structure Kinetics of RNA and DNA

    Meruelo, Alejandro Daniel
    A number of efforts to determine function from sequence of RNA and DNA have been made with varying success. Here we study the determination of function from sequence of DNA and RNA through their secondary structure kinetics, specifically the series of transitions between secondary structures. This series of transitions or microscopic structure can be described by a system of ordinary differential equations that can be approximating using balanced truncation to determine the macroscopic structure. By doing so, we have been able to identify signature topological features of microscopic structure and mathematically characterize the corresponding classes of macroscopic structure. Thus we are now able to take large, complex systems,...

  6. Device Architecture for Improved Redox Couple Mass Transport in Silicon Microwire Photoelectrodes and Electrical Contacts to Silicon Microwire Photovoltaics

    Meng, Andrew Chengsi
    Applications of silicon microwires to solar energy conversion are investigated in this thesis, which is divided into two chapters. In the first chapter, silicon microwires are investigated as photoelectrodes in photoelectrochemical cells. The mass transport limitations of redox couple is studied in these liquid junction solar cells, and a device architecture proposed and successfully demonstrated to improve device performance. This work was recently published in the Proceedings of the National Academy of Sciences and is reproduced in chapter one (32). In the second chapter, the device architecture developed to improve redox couple mass transport in liquid junction solar cells is explored as a possible method to make electrical...

  7. Experimental Apparatus for Measuring Ultralow Thermal Conductivity Structures

    Liu, Shiyi

    Ultralow thermal conductivity materials play an important role in many applications such as space exploration and thermal insulation. One of the primary challenges in studying heat conduction in these materials is performing basic thermal conductivity measurements, because even a small amount of steady heating results in enormous temperature increases. While methods do exist to measure the thermal conductivities of macroscopic materials, these techniques are difficult to apply to the microscopic samples that are the only samples available for some materials.

    In this thesis, we describe an optical, non-contact experimental system for measuring ultralow thermal conductivities. The system we designed and built is a modified pump-and-probe system. With this system, we...

  8. Experimental Characterization of Front Propagation by Marangoni Forces in Ultrathin Liquid Films

    Lee, Lisa Mannan
    Italian physicist Carlo Marangoni published a treatise in 1865 which first described the spontaneous flow of a liquid film caused by gradients in surface t ension at a gas/liquid interface. Such gradients are established by variations in surface concentration of molecular species which lower the surface tension in proportion to the interface concentration. While the dynamics and power law behavior of the initial circular advancing front in surfactant coated films has been studied for about two decades, there has been relatively little work conducted on characterizing the fractal spreading patterns which develop behind this front. In this thesis, we examine the dynamics of front propagation and subsequent...

  9. Bandgap Engineering Silicon Nanopillars

    Latawiec, Pawel Michal
    Vertically oriented , bandgap engineered silicon nanopillars were fabricated and addressed. Devices were fabricated via a three dimensional etching process which created sub-5 nm constrictions in silicon radius upon oxidation. This effect was used to create a Coulomb blockade device. Devices were tested at room and liquid nitrogen temperatures. They showed a clear blockade effect distinctive of an asymmetric double tunnel junction at low temperatures which disappeared when tested at higher temperatures. Different device fabrication parameters were also tested to develop high-current devices, including chip anneal time. Furthermore, both device fabrication steps and current flow were modeled and simulated.

  10. Evidence for Strain Induced Conductance Modulations in Single-Layered Graphene on SO2

    Lai, Andrew P.

    The unique physical properties of graphene and its potential uses in nanoscale devices make it a compelling subject of study^1. Graphene, a two dimensional crystal which consists of a single layer of carbon atoms bonded together in a hexagonal lattice, has a conical band structure at low energies. Therefore, the charge carriers of graphene obey the Dirac equation for relativistic particles and can be thought of as massless Dirac fermions 1,2,3 However, recent scanning tunneling microscopy (STM) studies of graphene on silicon dioxide substrates have found corrugations in the graphene samples, and more importantly have observed deviations in the tunneling spectra from the expected Dirac-like behavior ^(4,5,6). Several...

  11. Investigations into the Conditions Necessary for Stochastic Eternal Inflation

    Kuns, Kevin Aaron
    Theories of cosmological inflation, an early exponential expansion of the universe, have solved the horizon, flatness, and monopole problems in addition to successfully predicting properties of the fluctuations in the cosmic microwave background. Many of these theories have the property, known as eternal inflation, where inflation never ends everywhere at the same time and where there are always regions of exponentially expanding inflating space. The details of inflation are not known at this time and it would be interesting to estimate how generic eternal inflation is in the space of possible inflaton potentials. Of the several ways that inflation can be eternal, we focus here on...

  12. X-ray Ionization and the Influence of Magnetic Fields on the Growth of Gas Giant Planets

    Kim, Stacy Yeonchi

    The past two decades have witnessed an explosion in the number of known planets outside our Solar System. The exoplanets' number and diversity are surprising, with many planetary systems quite unlike our own. Naturally, the question of their origins arise. Yet our knowledge of how planetary systems form and evolve are far from complete, and even for our own Solar System, many fundamental questions remain. One puzzle concerns the formation of gas giants with masses intermediate between Jupiter (MJ = 320M, where M = 6 x 1027 g equals the mass of the Earth) and Neptune (MN = 17M ), which...

  13. A Ku-Band Polarimeter for the Owens Valley Radio Observatory 40-Meter Telescope

    Karkare, Kirit Sukrit

    Blazars are active galactic nuclei - small, extremely luminous objects at the center of galaxies powered by material accreting around a supermassive black hole - which emit relativistic jets of highly energetic plasma along our line of sight. There is no accepted model for jet composition, acceleration, and confinement; observations at different wavelengths will help us understand these emission mechanisms. Since 2007, the 40-Meter Telescope at the Owens Valley Radio Observatory has been monitoring over 1100 blazars every two days. The variability in radio light curves is likely to be correlated with gamma-rays, which we are observing with the Fermi Gamma-Ray Space Telescope.


  14. A Spectral Approach to the Relativistic Inverse Stellar Structure Problem

    Indik, Nathaniel Michael
    We present a new method for solving the inverse stellar structure problem, which determines an expression for the high density range of the neutron star equation of state (EOS) based on observations of total masses, M, and radii, R of these stars. This approach determines spectral representations of the EOS that are very accurate and require only a few spectral parameters to converge. This method can determine the underlying high density EOS from just a few mass-radii observations {Mi, R_ii}. While accurate mass-radii data are not available yet, we tested the accuracy of this method to determine the EOS from a set of {Mi, R_ii} values...

  15. Commissioning of Ultra-Cold Neutron Asymmetry Spectrometer

    Hsiao, Jennifer Ying
    We can feasibly probe for physics beyond the Standard Model of particle physics with more accurate and precise results from neutron beta decay experiments. An ultracold neutron (UCN) beta decay experiment will begin this year at the Los Alamos Neutron Science Center (LANSCE). This experiment will perform a precision measurement of the neutron betaasymmetry (or the A-correlation), which is the correlation between the neutron's spin and the momentum of the emitted decay electron. A precise measurement of the A-correlation, combined with a value for the neutron lifetime, can be used to test the unitarity of the Standard Model's quark-electroweak mixing matrix. Prior to commencement, the 1 Tesla...

  16. Experimental Analysis of Dynamic Interactions between Micrometer-Scale Stainless Steel Spheres

    Hotan, Gladia Chork
    The quasi-static interactions between macroscopic, spherical particles are well described by the Hertzian contact law. However, little is known about the interaction law at the micrometer scale, where the effects of electrostatic and hydrodynamic forces at the contact are no longer negligible. Contact dynamics at the micrometer scale have been relatively unexplored due to experimental challenges, since the particles are too small in size to be excited by actuators but too massive to be manipulated by electromagnetic fields. In this work, we experimentally study the dynamic interactions between two micrometer-scale spheres colliding in a v-shaped groove. From our experiments we determine physical parameters of interest that inform...

  17. Theory and Numerics of Two Synchronized Oscillators

    Grau, Matthew Charles
    Coupled oscillators are used to model systems such as arrays of lasers or detectors whose response is combined to increase signal strength. I investigated a systems of two coupled oscillators using a model incorporating features such as reactive (non-dissipative) force couplings and amplitude-dependent frequencies. I employed careful numerical simulations to build up intuition about the various behaviors of the model and then studied the model analytically to determine regions of synchronization, a phenomenon in which many oscillators lock their relative phase or frequency to a common equilibrium value. The result of this investigation can be used to motivate the choice of parameter values (such as spread of...

  18. Laser Offset Stabilization for Broadly Tunable TeraHertz (THz) Frequency Generation

    Cossel, Kevin
    Spectroscopy and imaging in the terahertz region promises to be useful for a wide variety of applications. For remote sensing, terahertz spectroscopy could help in the identification of explosives and narcotics. In astronomy, terahertz imaging should provide new information about the composition of the interstellar medium and about the processes by which stars and planets are born. In chemistry and molecular biology, terahertz spectroscopy provides new rotational or rovibrational spectra of molecules and is useful in the study of hydrogen-bound clusters that serve as model systems for the quantitative understanding of the intermolecular forces involved in (bio )polymers and aqueous media. However, there are currently no terahertz...

  19. Measurement, Simulation, and Design of the Dispersion-Engineered Traveling-Wave Kinetic Inductance Amplifier

    Chaudhuri, Saptarshi
    Recently, Eom et al. [1 J proposed a new concept for a low-noise cryogenic amplifier known as a Dispersion-Engineered Traveling-Wave Kinetic Inductance (DTWKI) amplifier. This device exploits the nonlinear kinetic inductance of superconducting thin-film nitrides to achieve high gain-bandwidth, near quantum-limited noise, and excellent dynamic range. In this thesis, we describe recent progress toward an experimental realization of the DTWKI; in particular, we focus on improvements in the areas of gain-bandwidth and noise performance. We describe a numerical model of the amplifier, and use this model to interpret experimental results and provide insight into the effects of dispersion-engineering on gain processes. Lastly, based on experimental results and model...

  20. An Investigation of the Cooling Properties of a Sapphire Half-Wave Plate for SPIDER

    Crites, Abigail Tinney
    Specific cryogenic data about the thermal and optical properties of sapphire are required to properly implement the sapphire half-wave plate that will be used to modulate the polarization signal in the next generation of CMB polarimeters. The wave plate must be operated from a base temperature of between 4 and 20 K. Simulations and experiments in a cryostat will determine if the sapphire sample can be radiatively cooled to approximately 20 K when operating from a 4.2K base temperature. These data will be used to design the final wave plate mount and determine how it will be operated.

Aviso de cookies: Usamos cookies propias y de terceros para mejorar nuestros servicios, para análisis estadístico y para mostrarle publicidad. Si continua navegando consideramos que acepta su uso en los términos establecidos en la Política de cookies.