Digital Commons Network^™

Solar Modulation Of The Cosmic Ray Intensity And The Measurement Of The Cerenkov Reemission In Nova’S Liquid Scintillator, Philip James Mason

Doctoral Dissertations

The NOνA (NuMI Off-axis electron neutrino Appearance) experiment is a long baseline neutrino oscillation experiment at Fermi National Accelerator Laboratory. Its purpose is to observe the oscillation of ν_μ (muon neutrino) to ν_e (electron neutrino) and to investigate the neutrino mass hierarchy and CP violation in the neutrino sector. Two detectors have been built for this purpose, a Near Detector 300 feet underground at Fermilab, and a Far Detector, on the surface at Ash River, Minnesota.

The completion of NOνA’s Far Detector in October 2014 enabled not only the recent measurement of neutrino oscillations, but an array of …

Geometry And Thermodynamics Of Filament Bundles, Isaac Bruss

Doctoral Dissertations

In this dissertation I present a study of the geometry and energetics of bundles composed of flexible cohesive filaments. This is a general class of materials, both biological and artificial, existing across many length scales. The aim of this thesis is to investigate the interdependence between the 2D organization of filaments in a bundle’s cross section, and the 3D structure, with an emphasis on the twisting mode of deformation. First we present a model of filament contacts and interactions, which we employ in numerical simulations to study the connection between the ground state energies of constant-pitch bundles and their interior …

Nonlinear Waves On A String With Inhomogeneous Properties, Robert Arredondo

Doctoral Dissertations

Nonlinear waves on an infinite string with a rapid change in properties at one location are treated. The string is an idealized version of more complex configurations in both fluids and solids. This idealized version treats the property change as an interface with a discontinuity in properties. Packets of waves are then considered with a reduced model, here a set of nonlinear Schr¨odinger (NLS) equations. The stress and the displacement must both be matched at the interface, resulting in dynamic and kinematic interfacial conditions. The dynamic condition produces an inhomogeneous effect that cannot be treated successfully with separation-of-variables. This inhomogeneity …

The Directed Molecular Self-Assembly Of A Novel Pentacene Derivative On Gold Surfaces: An Experimental And Computational Study, Amanda Margaret Larson

Doctoral Dissertations

Understanding electronic devices down to the atomic scale is essential for the development of novel organic molecule based nanotechnologies. Utilizing scanning tunneling microscopy (STM), new organic molecules can be imaged to understand their structural and electronic properties at the molecular level. 5,6,7-trithiapentacene-13-one (TTPO) is a promising organic semiconductor with potential applications in high temperature photovoltaic devices as an electron donor. My STM investigation of TTPO on the close-packed stepped Au(788) surface reveals interesting nanoscale surface structures ranging from molecular chains at low coverage to an ordered self-assembled monolayer. I have utilized density functional theory (DFT) to further probe this unique …

A Study Of Interplanetary Shock Geoeffectiveness Controlled By Impact Angles Using Simulations And Observations, Denny Oliveira

Doctoral Dissertations

In this dissertation, we study the influence of interplanetary (IP) shock impact angles in the IP shock geoeffectiveness focusing on simulations and observations. In our simulations, we use OpenGGCM global MHD code to study the nightside magnetospheric, magnetotail, and ionospheric responses to IP fast forward shocks. Three cases are presented in this study: two inclined oblique shocks, hereafter IOS-1 and IOS-2, where the latter has a Mach number twice stronger than the former. Both shocks have impact angles of 30$^o$ in relation to the Sun-Earth line. Lastly, we choose a frontal perpendicular shock, FPS, whose shock normal is along the …

The Study Of Ionospheric Response To Precipitation Using Sounding Rocket Observations, Ian James Cohen

Doctoral Dissertations

Understanding the role that the ionosphere plays in phenomena such as the development of auroral arcs and ion outflow is basic to the investigation of these processes and critical to the advancement of the broader study of magnetosphere-ionosphere coupling. Sounding rockets present an optimal platform for such studies, allowing low-cost access to altitudes that are difficult to reach by other means. Additionally, these measurements are key to validating current models and furthering understanding of the near-Earth space environment. This thesis highlights two particular rocket-borne instruments that measure electron populations in the ionosphere: the Electron Retarding Potential Analyzer (ERPA) and the …

A Supercell, Bloch Wave Method For Calculating Low-Energy Electron Reflectivity With Applications To Free-Standing Graphene And Molybdenum Disulfide, John Francis Mcclain

Doctoral Dissertations

This dissertation reports on a novel theoretical and computational framework for calculating low-energy electron reflectivities from crystalline surfaces and its application to two layered systems of two-dimensional materials, graphene and molybdenum disulfide. The framework provides a simple and efficient approach through the matching of a small set of Fourier components of Bloch wave solutions to the Schrodinger Equation in a slab-in-supercell geometry to incoming and outgoing plane waves on both sides of the supercell. The implementation of this method is described in detail for the calculation of reflectivities in the lowest energy range, for which only specular reflection is allowed. …

Using Computer Simulations As A Pre-Training Activity In A Hands-On Lab To Help Community College Students Improve Their Understanding Of Physics, Blanca Pineda

Doctoral Dissertations

The purpose of this study was to investigate the effectiveness of using computer simulations as a pre-training activity to a hands-on lab to improve students’ understanding of induction topics in physics. The computer simulation activity was compared to an overview presentation. Conceptual understanding and spatial ability were measured. A two-group descriptive repeated measures design was implemented with a convenience sample of 35 community college physics students in the Bay Area. Participants were randomly assigned to a simulation group (n = 17) or a presentation group (n = 18). A 30-item spatial ability assessment was given to all participants one week …