Physical Sciences and Mathematics Commons^™

High Pressure X-~Ray Absorption Spectroscopy Studies Of Heavy-~Fermion Cerium And Uranium Compounds, Daniel Antonio

UNLV Theses, Dissertations, Professional Papers, and Capstones

Investigations into f- electron heavy-fermion materials have revealed a wide range of novel behavior. Hydrostatic pressure is a valuable "clean" non-thermal parameter that can be used to systematically study them by tuning their ground state properties. The rare earth compound CeCu2Ge2 shows an unusual two-domed region of unconventional superconductivity under pressure, similar to its isostructural counterpart CeCu2Si2. While the lower pressure dome at about 10 GPa is caused by a magnetic quantum critical point (QCP), the higher one at about 16 GPa is less well understood. Previous structural measurements have indicated that it may be caused by critical valence fluctuations, …

Validation Of Argon From Underground Sources For Use In The Darkside-50 Detector, Thomas R. Alexander

Masters Theses

Liquid argon is an attractive target for dark matter searches due to its low cost and exemplary event discrimination. However, atmospherically derived argon contains the beta-emitter 39Ar which confounds the growth of dual-phase time projection chamber (TPC) style detectors to the ton-scale. The DarkSide Collaboration seeks to bypass this limitation by extracting argon from deep underground, from a location known to contain significantly less 39Ar than atmospherically derived argon. This thesis will summarize the e orts taken to produce the first batch of underground argon, focusing on the first operation of the underground argon in a dual-phase TPC to validate …

Multiwavelength X-Ray Diffraction, Maziar Saleh Ziabari

College of Science and Health Theses and Dissertations

The central problem of diffraction theory is determining the structure of an object given only the intensity of its diffraction pattern. In general, both the amplitude and phase must be known to uniquely solve a structure; however a coherent radiation source is usually required in order to measure the diffacted phases (e.g. in holography). In many important cases, coherent sources are unavailable and other assumptions or methods must be employed to substitute for the missing phase information. One method that has been successfully applied to the specific problem of determining atomic structure from X-ray diffraction intensity patterns has been the …

Bayesian Model Selection And Parameter Estimation For Gravitational Wave Signals From Binary Black Hole Coalescences, Alexander L. Lombardi

Masters Theses

In his theory of General Relativity, Einstein describes gravity as a geometric property of spacetime, which deforms in the presence of mass and energy. The accelerated motion of masses produces deformations, which propagate outward from their source at the speed of light. We refer to these radiated deformations as gravitational waves. Over the past several decades, the goal of the Laser Interferometer Gravitational-wave Observatory (LIGO) has been the search for direct evidence of gravitational waves from astrophysical sources, using ground based laser interferometers. As LIGO moves into its Advanced era (aLIGO), the direct detection of gravitational waves is inevitable. With …

The Relationship Of Childhood Stress To Adult Health And Mortality Among Individuals From Two U.S. Documented Skeletal Collections, Late 19Th To Early 20Th Centuries, Rhonda Coolidge

USF Tampa Graduate Theses and Dissertations

Although the association between social inequality and poor adult health is well established, the mechanisms by which inequality is translated into poor adult health are less clear. Increasingly, evidence suggests that many adult health problems and health disparities have their origins in early life; the developmental origins of health and disease (DOHaD) hypothesis provides an explanatory mechanism linking adverse early life conditions with permanent structural or functional changes that increase the risk for disease. This hypothesis is consistent with bioarchaeological research noting reduced lifespan among individuals exhibiting signs of childhood stress.

The principal aim of this dissertation is to contribute …

Optical Communication Using Hybrid Micro Electro Mechanical Structures (Mems) And Commercial Corner Cube Retroreflector (Ccr), Sunny Kedia

USF Tampa Graduate Theses and Dissertations

This dissertation presents a free-space, long-range, passive optical communication system that uses electrostatically modulated microelectromechanical systems (MEMS) structures coupled with a glass total internal reflection (TIR)-type corner cube retroreflector (CCR) as a non-emitting data transmitter. A CCR consists of three mirrors orthogonal to each other, so that the incident beam is reflected back to the incident beam, source. The operational concept is to have a MEMS modulator fusion with TIR CCR, such that the modulators are working periodically to disrupt the evanescent waves at the air interface of one of the three back glass faces of a TIR CCR. The …

In Vacuo Fabrication And Electronic Structure Characterization Of Atomic Layer Deposition Thin Films, Michael Schaefer

USF Tampa Graduate Theses and Dissertations

Improvement of novel electronic devices is possible by tailor-designing the electronic structure at device interfaces. Common problems observed at interfaces are related to unwanted band alignment caused by the chemical diversity of interface partners, influencing device performance negatively. One way to address this problem is by introducing ultra-thin interfacial dipole layers, steering the band alignment in a desired direction. The requirements are strict in terms of thickness, conformity and low density of defects, making sophisticated deposition techniques necessary. Atomic layer deposition (ALD) with its Ångstrom-precise thickness control can fulfill those requirements.

The work presented here encompasses the implementation of an …

Investigation Of Low Thermal Conductivity Materials With Potential For Thermoelectric Applications, Kaya Wei

USF Tampa Graduate Theses and Dissertations

Thermoelectric devices make it possible for direct energy conversion between heat and electricity. In order to achieve a high energy conversion efficiency, materials with a high thermoelectric figure of merit (ZT = S²σT/κ, where S is the Seebeck coefficient, σ is the electrical conductivity, T is the absolute temperature, and κ is the thermal conductivity) are in great demand. The standard approach is to optimize charge carrier transport while at the same time scatter the heat transport, a task that is easier said than done. Improving the electrical properties in order to increase ZT is limited since electrons …

Contact Angles And Contact Lines Around Particles At Isotropic And Anisotropic Liquid Interfaces, Nesrin Senbil

Doctoral Dissertations

Liquid interfaces, capillarity and self-assembly of particles at interfaces are important in nature and technology. When a particle is adsorbed to a liquid interface, the contact line of the particle with the liquid interface and the associated contact angle are the crucial parameters that drive assembly of the particles. We looked at how the shape of the liquid interface and the shape of the particle affect the contact angle and the shape of the contact line. We used millimeter-sized PDMS-coated glass spheres and measured the contact angles at isotropic (planar) and anisotropic interfaces (saddle and cylindrical in shape). Anisotropy of …

Gravitational Wave Astrophysics: Instrumentation, Detector Characterization, And A Search For Gravitational Signals From Gamma-Ray Bursts, Daniel Hoak

Doctoral Dissertations

In the coming years, the second generation of interferometric gravitational wave detectors are widely expected to observe the gravitational radiation emitted by compact, energetic events in the nearby universe. The field of gravitational wave astrophysics has grown into a large international endeavor with a global network of kilometer-scale observatories. The work presented in this thesis spans the field, from optical metrology, to instrument commissioning, to detector characterization and data analysis. The principal results are a method for the precise characterization of optical cavities, the commissioning of the advanced LIGO Output Mode Cleaner at the Hanford observatory, and a search for …

Exact Solutions In Gravity: A Journey Through Spacetime With The Kerr-Schild Ansatz, Benjamin Ett

Doctoral Dissertations

The Kerr-Schild metric ansatz can be expressed in the form $g_{ab} = \gbar_{ab}+\lambda k_ak_b$, where $\gbar_{ab}$ is a background metric satisfying Einstein's equations, $k_a$ is a null-vector, and $\lambda$ is a free parameter. It was discovered in 1963 while searching for the elusive rotating black hole solutions to Einstein's equations, fifty years after the static solution was found and Einstein first formulated his theory of general relativity. While the ansatz has proved an excellent tool in the search for new exact solutions since then, its scope is limited, particularly with respect to higher dimensional theories. In this thesis, we present …

Population Annealing Monte Carlo Studies Of Ising Spin Glasses, Wenlong Wang

Doctoral Dissertations

Spin glasses are spin-lattice models with quenched disorder and frustration. The mean field long-range Sherrington-Kirkpatrick (SK) model was solved by Parisi and displays replica symmetry breaking (RSB), but the more realistic short-range Edwards-Anderson (EA) model is still not solved. Whether the EA spin glass phase has many pairs of pure states as described by the RSB scenario or a single pair of pure states as described by two-state scenarios such as the droplet/scaling picture is not known yet. Rigorous analytical calculations of the EA model are not available at present and efficient numerical simulations of spin glasses are crucial in …

Elasticity And Geometry In Curved-Filament Assemblies, Luis Cajamarca Ospina

Doctoral Dissertations

In this dissertation we explore the effect of shape, mechanics and geometry in assemblies of tubular filaments by introducing the notion of cohesive contact. We first study the optimal geometry of cohesive interactions in straight flexible tubes by considering two interaction potentials. We find filaments adopt a locally skewed configuration, associated with a twist angle. The interaction energy decreases with the twist angle and ground states are found to be twisted. For pair-wise interactions, we find a generic behavior in the profile of the cohesive energy where the geometry of close-packed double helices dictates the shape of the assembly. By …

Emergent Structure Of Multi-Dislocation Ground States In Frustrated Assemblies, Amir Azadi

Doctoral Dissertations

In this dissertation we study the emergent patterns of multi-dislocation ground states in two geometrically related classes of frustrated assemblies, twisted filament bundles and crystalline spherical cap. We discuss the fundamental role played by characteristic patterns of dislocations in restructuring the ordered phase of theses geometrically frustrated systems in the presence of external stresses. Our analysis on the formation of grain boundary scars leads to universal predictions for the features of defect patterns and their underlying energetic principles.

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 …

Synthesis, Characterization And Ferroelectric Properties Of Ln-Type Znsno3 Nanostructures, Corisa Kons

USF Tampa Graduate Theses and Dissertations

With increasing focus on the ill health and environmental effects of lead there is a greater push to develop Pb-free devices and materials. To this extent, ecofriendly and earth abundant LiNbO₃-type ZnSnO₃, a derivative of the ABO₃ perovskite structure, has a high theoretically predicted polarization making it an excellent choice as a suitable alternative to lead based material such as PZT. In this work we present a novel synthesis procedure for the growth of various ZnSnO₃ nanostructures by combined physical/chemical processes. Various ZnSnO₃ nanostructures of different dimensions were grown from a ZnO:Al template …

Hyperpolarized 129xe Magnetic Resonance Imaging Of Radiation-Induced Lung Injury, Ozkan Doganay

Electronic Thesis and Dissertation Repository

Lung cancer is the largest contributor to cancer-related mortality worldwide. Only 20% of stage III non-small cell lung cancer patients survive after 5-years post radiation therapy (RT). Although RT is an important treatment modality for lung cancer, it is limited by Radiation-Induced Lung Injury (RILI). RILI develops in two phases: (i) the early phase (days-weeks) referred to radiation pneumonitis (RP), and (ii) the late phase (months). There is a strong interest in early detection of RP using imaging to improve outcomes of RT for lung cancer. This thesis describes a promising approach based on ¹²⁹Xe gas as a contrast …

High Resolution Tropospheric Studies With An Mst Type Radar, Marcial Garbanzo-Salas

Electronic Thesis and Dissertation Repository

Applications and results of a variety of studies carried out with the Costa Rican VHF profiler radar are included. This radar is unique because of the wide frequency bandwidth available (5 MHz). During the developing stages of the wind profiler radar new techniques of processing and radar engineering were used.

A thorough analysis of a data-dependent method (Capon's) commonly used in radar was carried out. This method is analyzed based on a reference established by Fourier theory. Disadvantages of using data-dependent methods with small filters were found. A small filter size will cause Capon's method to underestimate the number of …

Numerical Studies And Optimization Of Magnetron With Diffraction Output (Mdo) Using Particle-In-Cell Simulations, Alireza Majzoobi

Electrical & Computer Engineering Theses & Dissertations

The first magnetron as a vacuum-tube device, capable of generating microwaves, was invented in 1913. This thesis research focuses on numerical simulation-based analysis of magnetron performance. The particle-in-cell (PIC) based MAGIC software tool has been utilized to study the A6 and the Rising-Sun magnetron structures, and to obtain the optimized geometry for optimizing the device performance. The A6 magnetron is the more traditional structure and has been studied more often. The Rising-Sun geometry, consists of two alternating groups of short and long vanes in angular orientation, and was created to achieve mode stability.

The effect of endcaps, changes in lengths …

Optimal Measurements Tasks And Their Physical Realizations, Vadim Yerokhin

Dissertations, Theses, and Capstone Projects

This thesis reflects works previously published by the author and materials hitherto unpublished on the subject of quantum information theory. Particularly, results in optimal discrimination, cloning, and separation of quantum states, and their relationships, are discussed.

Our interest lies in the scenario where we are given one of two quantum states prepared with a known a-priori probability. We are given full information about the states and are assigned the task of performing an optimal measurement on the incoming state. Given that none of these tasks is in general possible to perform perfectly we must choose a figure of merit to …

Accurate Deterministic Solutions For The Classic Boltzmann Shock Profile, Yubei Yue

Dissertations, Theses, and Capstone Projects

The Boltzmann equation or Boltzmann transport equation is a classical kinetic equation devised by Ludwig Boltzmann in 1872. It is regarded as a fundamental law in rarefied gas dynamics. Rather than using macroscopic quantities such as density, temperature, and pressure to describe the underlying physics, the Boltzmann equation uses a distribution function in phase space to describe the physical system, and all the macroscopic quantities are weighted averages of the distribution function. The information contained in the Boltzmann equation is surprisingly rich, and the Euler and Navier-Stokes equations of fluid dynamics can be derived from it using series expansions. Moreover, …

Growth And Characterization Of Type-Ii Submonolayer Zncdte/Zncdse Quantum Dot Superlattices For Efficient Intermediate Band Solar Cells, Siddharth Dhomkar

Dissertations, Theses, and Capstone Projects

In this thesis, we discuss the growth procedure and the characterization results obtained for epitaxially grown submonolayer type-II quantum dot superlattices made of II-VI semiconductors. The goal behind this study is to show the feasibility of this novel material system in fabricating an efficient intermediate band solar cell.

Intermediate band solar cells can potentially have an efficiency of 63.2% under full solar concentration, but the material systems investigated until now are far from optimum and are fraught with growth related issues including low quantum dot densities, presence of wetting layers, strain driven dislocations etc. Here, we have investigated a novel …

Biophysical Characterization Of A De Novo Elastin, Kelly Nicole Greenland

Dissertations, Theses, and Capstone Projects

Natural human elastin is found in tissue such as the lungs, arteries, and skin. This protein is formed at birth with no mechanism present to repair or supplement the initial quantity formed. As a result, the functionality and durability of elastin's elasticity is critically important. To date, the mechanics of this ability to stretch and recoil is not fully understood. This study utilizes de novo protein design to create a small library of simplistic versions of elastin-like proteins, demonstrate the elastin-like proteins, maintain elastin's functionality, and inquire into its structure using solution nuclear magnetic resonance (NMR).

Elastin is formed from …

Studies On Bell's Theorem, Veli Ugur Guney

Dissertations, Theses, and Capstone Projects

In this work we look for novel classes of Bell's inequalities and methods to produce them. We also find their quantum violations including, if possible, the maximum one.

The Jordan bases method that we explain in Chapter 2 is about using a pair of certain type of orthonormal bases whose spans are subspaces related to measurement outcomes of incompatible quantities on the same physical system. Jordan vectors are the briefest way of expressing the relative orientation of any two subspaces. This feature helps us to reduce the dimensionality of the parameter space on which we do searches for optimization. The …

Friction, Avalanches And Phase Transitions In Granular Media., Aline Hubard

Dissertations, Theses, and Capstone Projects

We explore the microscopic interactions and properties of dry granular materials in the plane using experiments and simulations. We use statistics of this microscopic information to better understand and predict the bulk behavior and evolution of granular materials.

In the first part, we study the geometric structure of mechanically stable packings of frictional disks in configuration space. Our experimental setup contains frictional disks confined in a vertical plane and subject to a series of small amplitude vibrations that compact the system by reducing the friction between contacts during each vibration step. We find that the evolution of the packings forms …

Another One Busts The Dust, Keiko Hiranaka

Dissertations, Theses, and Capstone Projects

Brown dwarfs are substellar objects with core temperatures insufficient for sustained hydrogen fusion. Their physical properties such as mass, temperature, and radius are similar to those of gas giant planets, so studying brown dwarfs may also benefit exoplanet studies.

There is a population of 'red' L dwarfs, which have redder J - K colors in the near-infrared than normal objects. Red L dwarfs include young, low-gravity objects, which are systematically red, and red field-gravity objects. The observed reddening in L dwarfs is not well explained by current atmosphere models.

We present an analysis of red L dwarfs using our model …

Order And Asymmetry In Jammed Systems, Zhusong Li

Dissertations, Theses, and Capstone Projects

Granular matter is composed of particles that are big enough that thermal effects may be neglected. We studied both granular flow and granular statics using numerical simulation. In granular flow, we simulated 2D granular flow in a hopper. A hopper is a container with an opening at the bottom. Simulated disks are placed in the hopper with the bottom closed and then released. We developed a new tangential force model to simulate hopper flow, that matches experiments and shows that the output flux is proportional to the bottom opening size to the 3/2 power. We also see clogging or jamming …

Metasurfaces For Photon Sorting And Selective Absorption, Isroel Moshe Mandel

Dissertations, Theses, and Capstone Projects

Metamaterials are a recent discovery gaining much interest due to their promising applications to multiple devices in sensing, imaging, photovoltaics, nonlinear optics, heat conversion, sorters, and multitudes of other devices. These metamaterials are made of subunits called meta-atoms which take a role similar to that of atoms in bulk crystals. However, unlike their atom counterparts, these meta-atoms are macroscopic and can be engineered to respond to a driving field in a desired way. Metasurfaces, the 2-dimensional analog of metamaterials, have been shown to possess the ability to control light in novel ways. In this work, we investigate a particular type …

Hybridized Criticality And Elementary Excitations In Lihof4, Haifu Ma

Dissertations, Theses, and Capstone Projects

In this dissertation, I study the magnetic properties of LiHoF₄. Quantum criticality in rare earth ferromagnet LiHoF₄ is complicated by the presence of strong crystal field and hyperfine interactions resulting, e.g., in incomplete mode softening reported by Rønnow et al. We construct a systematic framework for treating elementary excitations in this material across the phase diagram. These excitations interpolate between purely electronic, nuclear and lattice modes and exhibit two-types of quantum critical softening, both complete (as anticipated by elementary treatments, see e.g. Sachdev) but also incomplete, in close correspondence with nuclear scattering results.

Ordering And Topological Defects In Solids With Quenched Randomness, Thomas Chapman Proctor

Dissertations, Theses, and Capstone Projects

We explore multiple different examples of quenched randomness in systems with a continuous order parameter. In all these systems, it is shown that understanding the effects of topology is critical to the understanding of the effects of quenched randomness.

We consider n-component fixed-length order parameter interacting with a weak random field in d = 1,2,3 dimensions. Relaxation from the initially ordered state and spin-spin correlation functions have been studied on lattices containing hundreds of millions sites. At n - 1 < d presence of topological structures leads to metastability, with the final state depending on the initial condition. At n …