Physics Commons^™

Radiation Exposure Calibration Of The Al2o3:C With Radium-226 And Cesium-137 Using The Osl Method, Selma Tepeli Aydin

All Theses

Optically stimulated luminescence (OSL) dosimetry was utilized to calibrate Al₂O₃:C powder dosimeters, available commercially as the nanoDot® from Landauer Inc., and compare the dosimeter response to radium-226 (²²⁶Ra) and cesium-137 (¹³⁷Cs). The signal from the OSL was quantified using a microSTARii^® OSL reader also produced by Landauer Inc. Dose-response curves were developed for ²²⁶Ra and ¹³⁷Cs experiments (5 dosimeters each) at thirteen absorbed doses. Individual dosimeter response was tracked by serial number. Linear regression analysis was performed to determine if there were significant differences between the intercepts of the …

Apparatus And Instrumentation Design For Investigation Of Surface Impact Effects On Superconductivity, Austin Back

All Theses

The effects of ion irradiation on the physical properties of materials make EBITs an invaluable tool for many scientific and engineering fields. Many experiments rely on the use of these lab setups to test for device reliability, explore surface physics phenomena, and replicate the environment for many physical systems that are not readily accessible. We seek to extend the capabilities of these experiments using the CUEBIT and a new sample holder installed in section 3.

This thesis begins by presenting an overview of the CUEBIT and the basic operations of the equipment. This is followed by a brief explanation of …

The Characterization Of Atmospheric Turbulence And Its Effect On Laser Beam Propagation, Michael Cox

All Theses

Having a controlled environment to measure atmospheric turbulence is essential to understanding its effects on different laser beam characteristics. The Clemson Variable Turbulence Generator (VTG) has the capability to propagate a laser beam up to 100 m and be able to dial many turbulence settings up to a heat flux of 357 W/m². A high-speed camera, power detector, and high-resolution temperature probes characterize the VTG with theoretical turbulence spectrums. The exponent associated with the Rayleigh-Bénard (RB) temperature structure constant equation is studied. Two different laser beam profiles are used throughout this work: Gaussian and Asymmetric Perfect Vortex (APV). …

Oam-Based Wavelets In A High Speed Optical Probing System For Measuring The Angular Decomposition Of The Environment, Justin Free

All Theses

This thesis presents the theoretical development of orbital angular momentum (OAM) based wavelets for the analysis of localized OAM information in space. An optical probing system for generating and detecting these wavelets is demonstrated; individual wavelets can scan the environment in 10µs or less. The probing system was applied to a three-dimensional atmospheric turbulence distribution to obtain a continuous wavelet transform of the angular information of the turbulent propagation path about a fixed radius. An entire continuous wavelet transform was measured in 3.8ms; the measurements are much faster than the turbulence and give insight into the short time scale of …

Developing A Software Defined Radio Based Faraday Receiver, Alvaro J. Guerra

All Theses

The ionosphere can be approximated as a magnetized plasma. This results in wave- particle interactions driving a large quantity of ionospheric phenomena. To understand these phenomena, it is important to quantify and measure certain key plasma parameters. One such parameter is electron density. The Faraday Experiment was developed for the purpose of measuring electron density in the D-region of the ionosphere. This experiment was made popular by Martin Friedrich in the 1970s and is currently one of the only ways to provide high resolution measurements of electron density in the D-region without actively disturbing the surrounding plasma. This thesis aims …

Prediction Of Pathogenic Mutations In Spermine/Spermidine Synthases, Shannon Bonomi

All Theses

As genetic technology and information become continuously more sophisticated and applied to the prevention and treatment of diseases, the need to understand the effects of genetic variants becomes an important task with regards to assessing disease risk. In the specific case of intellectual disabilities, prenatal screenings is an important diagnostic tool that prepares families and health professionals for the arrival of a child who may need immediate, specialized care. Cell Free DNA screenings are routine for determining sex and provide the opportunity to discover genetic anomalies. However, this has little value unless mutations can be recognized as pathogenic and are …

Experimental Investigation Of Interaction Between Proteins And Carbon Nanomaterials, Bishwambhar Sengupta

All Theses

The global market for nanomaterials based products is forecasted to reach $1 trillion per annum per annum for 2015. Engineered nanomaterials (ENMs) exhibit unique physicochemical properties with potential to impact diverse aspects of society through applications in electronics, renewable energy, and medicine. While the research and proposed applications of ENMs continue to grow rapidly, the health and safety of ENMs still remains a major concern to the public as well as to policy makers and funding agencies. It is now widely accepted that focused efforts are needed for identifying the list of physicochemical descriptors of ENM before they can be …

Fast Fission Neutron Detection Using The Cherenkov Effect, Matthew Millard

All Theses

The Cherenkov effect in optically clear media of varying indices of refraction and composition was investigated for quantification of fast neutrons. The ultimate application of the proposed detection system is criticality monitoring. The optically clear medium, composed of select target nuclei, was coupled to a photomultiplier tube. Neutron reaction products of the target nuclei contained within the optical medium emit beta particles and gamma rays that produce Cherenkov photons within the medium which can be detected. Assessed media include quartz (SiO2), sapphire (Al2O3), spinel (MgAl2O4), and zinc sulfide (ZnS), which were irradiated with un-moderated 252Cf. Monte Carlo N-Particle (MCNP) code …

Protein Nano-Object Integrator: Generating Atomic-Style Objects For Use In Molecular Biophysics, Nicholas Smith

All Theses

As researchers obtain access to greater and greater amounts of computational power, focus has shifted towards modeling macroscopic objects while still maintaining atomic-level details. The Protein Nano-Object Integrator (ProNOI) presented here has been designed to provide a streamlined solution for creating and designing macro-scale objects with atomic-level details to be used in molecular simulations and tools. To accomplish this, two different interfaces were developed: a Protein Data Bank (PDB), PDB-focused interface for generating regularly-shaped three-dimensional atomic objects and a 2D image-based interface for tracing images with irregularly shaped objects and then extracting three-dimensional models from these images. Each interface is …

Stimulated Raman Scattering In Micro Sphere Resonators, Ruoyu Zhang

All Theses

Micro sphere resonators that hold optical whisper gallery modes (WGMs) provide an innovative option for implementing micro optical resonators. The unique properties of the micro sphere resonator make it capable to introduce resonance for various optical phenomenon, like stimulated Raman scattering (SRS), in micron scale.

This thesis illustrates the characteristics of micro sphere resonators and demonstrates the resonance-enhanced SRS in micro sphere resonators with reduce threshold power. Both theoretical and experimental results are presented. Coupling model for WGM is derived in transfer matrix method. Simulation analyses for mode pattern of WGMs are solved based on mathematic model and finite element …

The Detection Of A Light Echo From Sn 2007af, Dina Drozdov

All Theses

Type Ia supernovae are widely studied for their uniform properties, which make them ideal candidates for cosmological surveys. Although these exploding stars are popular targets, key funda-mental questions about their nature remain, and new techniques need to be developed to investigate the progenitor system and explosion mechanisms. Light echoes are created by light scattering off dust that reaches the observer after the direct path light from the explosion arrived and have been studied for the past 100 years. Light echoes from Type Ia supernovae are rare, with only a few cases being discovered in the past decades. Because light echoes …

Iron Abundances And Atmospheric Parameters Of Red Giants In The Open Cluster Ic 4756, Julie Djordjevic

All Theses

Three red giants were investigated within the open cluster IC 4756 using observations taken from the McDonald Observatory's 2.1m Otto Struve Telescope and the Sandiford Cassegrain Echelle Spectrometer (SES). Iron abundances were calculated for each star based on the equivalent widths of Fe I and Fe II lines measured using the line lists of Bubar and King (2010) and Schuler et al. (2005). Also derived were the basic atmospheric parameters: effective temperature, surface gravity, metallicity, and microturbulence. Her 35, Her 85, and Her 249 were found to have corresponding [Fe I/H] of 0.06 ± 0.04, -0.16 ± 0.03, and -0.16 …

Tidal Heating And Mlt Tidal Wind Variability Due To The El Nino-Southern Oscillation, Kristi Warner

All Theses

Tides forced by large-scale weather systems in the tropical troposphere in- troduce significant longitudinal and local time variability in the upper atmosphere. This thesis presents the latent tidal heating variability for 2002-2011 due to variation in tropospheric deep convection associated with the El Niño-Southern Oscillation (ENSO) and the tidal wind response in the mesosphere/lower thermosphere (MLT) region. Emphasis is on the strong ENSO cycle 2009-2011. Latent tidal heating rates are computed from TRMM satellite precipitation data, with added radiative heating from MERRA reanalysis, as functions of time, latitude, and altitude. The heating rates for the two most affected nonmigrating tides …

Spectroscopic Investigation Of Protein Corona, Poonam Choudhary

All Theses

Nanotechnology has revolutionalized the landscape of modern science and technology, including materials, electronics, therapeutics, bioimaging, sensing, and the environment. Research in the past decade has examined the fate of nanomaterials in vitro and in vivo, as well as the interactions between nanoparticles and biological and ecosystems using primarily toxicological and ecotoxicological approaches. However, due to the versatility in the physical and physicochemical properties of nanoparticles, and due to the vast complexity of their hosting systems, the solubility, transformation, and biocompatibility of nanomaterials are still poorly understood. Nanotechnology has been undergoing tremendous development in recent decades, driven by realized perceived applications …

Newtonian Semiclassical Gravity In Three Ontological Quantum Theories That Solve The Measurement Problem: Formalisms And Empirical Predictions, Maaneli Derakhshani

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In this thesis, we consider the implications of solving the quantum measurement problem for the Newtonian description of semiclassical gravity. First we review the formalism of the Newtonian description of semiclassical gravity based on standard quantum mechanics - the Schroedinger-Newton theory - and two well-established predictions that come out of it, namely, gravitational 'cat states' and gravitationally-induced wavepacket collapse. Then we review three quantum theories with 'primitive ontologies' that are well-known known to solve the measurement problem - Schroedinger's many worlds theory, the GRW collapse theory with matter density ontology, and Nelson's stochas- tic mechanics. We extend the formalisms of …

Pair Production By Primordial Black Hole Evaporation, Shaun Hampton

All Theses

Here we investigate the evaporation of a 8.2 _ 1010 kg primordial black hole. This mass is shown to
satifisfy the compactness parameter constraint L/R ≥ 1031 ergscm−1s−1. We assume only photon-photon
production according to a Planck distribution. We calculate the distance from the black hole at which the
optical depth due to photon-photon collisions to produce positron/electron pairs becomes unity in which a
pair plasma is produced within a volume of inner radius of 90RS and outer radius 123000R_S respectively.
We then calculate corresponding positron/electron production rates, production rate densities, and optical
depth rates due to subsequent Compton …

Ultraluminous X-Ray Sources In Andromeda Galaxy: Two Recent Discoveries And Their Implications, Amanpreet Kaur

All Theses

Ultraluminous X-ray sources are believed to be associated with X-ray binaries, in which an accreting black hole generates X-ray luminosities in excess of 10 39 erg/s. The nature of the companion star and the underlying physics of the accretion process is not yet established with certainty. In particular, whether or not the accretion is super/sub Eddington is an open question, as is the mass of the companion star. We discuss the first two ULXs recently discovered in M31 and investigate the nature of their underlying sources. We present the X-ray observations for ULX-1 in detail and discuss its implications for …

Intense And Highly Energetic Atmospheric Pressure Plasma Jet Arrays, John Furmanski

All Theses

This thesis documents the efforts taken to produce highly ionized and concentrated atmospheric pressure plasma using an arrayed atmospheric pressure plasma jet (APPJ) system. The honeycomb-shaped array features seven plasma jets operating in close enough proximity to one another to exhibit jet-to-jet coupling behavior. Optimal gas flow rates for the system were determined and intense plasma plumes composed of argon and/or helium are generated. Optical emission spectroscopy was employed to observe the charged particles responsible for the emissions of each gas discharge and APPJ operation mode. Plasma etching of indium tin oxide glass was conducted to verify the highly energetic …

Thermal, Electrical, And Structural Behavior Of Silver Chalcogenide Composites, Jeremy Capps

All Theses

In this thesis and the contained publications, it is demonstrated that it is not only possible to improve the dimensionless figure of merit (ZT) of silver chalcogenide composites, but it is also possible to move the maximum ZT value into a more favorable temperature range for power production. It is shown that by introducing disorder, stress, and phase competition into a system, a reduction in the material's thermal conductivity can be realized. The binaries Ag2Te and Ag2Se are re-examined in detail before moving on to examine Ag2Te1-xSex composites. The maximum ZT (ZT = 0.92) of Ag2Te0.5Se0.5 is measured at T= …

Understanding The Role Of Electrostatics On Protein-Protein Binding, Rooplekha C Mitra

All Theses

Ionized groups carry net charge and thus play a major role in the electrostatic interactions between the ligand and receptor. So understanding the role of electrostatics on protein-protein interactions is crucial for understanding the contribution of ionizable groups to the binding. However, their ionization states depend on many factors including pH of water phase. The complexity comes from the fact that the pKa's of ionizable groups may be quite different from their standard values and even may change due to protein-protein binding. The main difficulty in modeling plausible ionization changes induced by the complex formation arises from the differences in …

Light Beaming From A Single Subwavelength Metal Slit, Pengyu Chen

All Theses

In this thesis, light transmission through a single sub-wavelength slit in a silver thin film with periodic gratings at the exit side of the slit has been studied in both the visible and mid-infrared wavelength ranges.
In the visible wavelength range, we first investigate the enhancement of plasmonic light beaming efficiency by near field resonance in a subwavelength metallic slit-groove beaming structure. We show that by varying the film thickness and the separation distance of the beaming grating, the intensity of the near field can be greatly enhanced by resonance, which leads to the increase of the beaming efficiency. Moreover, …

Structural Role Of Pseudouridines In The Peptidyl Transferase Center Of Human 28s Ribosomal Rna, Chris Mart

All Theses

The human ribosome is an RNA-protein complex responsible for protein synthesis in the cell. Crystal structures of bacterial ribosomes solved to date depict no protein sidechains within the catalytic core, or peptidyl transferase center (PTC). This region of the human ribosome comprises approximately 230 highly conserved nucleotides. Notably, several of the uridine bases clustered within the human PTC are post-transcriptionally modified to pseudouridines, as compared with bacterial analogues. Pseudouridines are base-rotated uridines, linked to their sugar moieties through C5-C1' linkages, affording additional hydrogen-bond donor groups at the N1 position of their rings. A connection was recently made between the absence …

The Thermoelectric Properties Investigation Of X0.05Mo3Sb7-YTeY (X=Mn, Fe, Ni, Co; Y=1.5, 1.6, 1.7), Tim Holgate

All Theses

With ever increasing energy costs, dwindling resources, and terms with the prefix 'green' filling headlines, the need for environmentally friendly energy sources has never been greater. Since the mid-20th century researchers have been pursuing greater efficiency in thermoelectric materials. Thermoelectric materials achieve energy conversion via the Seebeck effect (heat to electric power) and the Peltier effect (electricity to cooling power). Presented herein are the measured electrical and thermal transport properties and phenomenal analysis of the Ir₃Ge₇-type system: X_0.05Mo₃Sb_7-yTe_y (X=Mn, Fe, Ni, Co; y=1.5, 1.6, 1.7) where 'X' are interstitially …

The Origin Of The 511 Kev Positron Annihilation Emission Morphology, Bethany Johns

All Theses

The 511 keV positron annhilation emission from the Galactic bulge has yet to solely be attributed to any astrophysical source of positrons. The 511 keV line, characteristic of electron-positron annihilation, was discovered in 1970 by Johnson and Haymes [1973] almost 40 years ago. Most recently the INTERnational Gamma-Ray Astrophysical Laboratory (INTEGRAL) [Knodlseder 1997] has measured the annihilation rates of both components of the Galaxy. The bulge and disk annihilation rates are (1.5 ± 0.1) x 10^43 e+ s^-1 and(0.3 ± 0.2) x 10^43 e+ s^-1, respectively. The ratio of the bulge rate to that of the disk ranges from 3-9. …

Analysis Of The Nonlinear Vibrations Of Electrostatically Actuated Micro-Cantilevers In Harmonic Detection Of Resonance (Hdr), Jonathan Taylor

All Theses

Micro- and nano-cantilevers have the potential to revolutionize physical, chemical, and biological sensing; however, an accurate and scalable detection method is required. In this work, a fully electrical actuation and detection method is presented, known as the Harmonic Detection of Resonance (HDR). In HDR, harmonic components of the current are measured to determine the cantilever's resonance frequency. These harmonics exist as a result of nonlinearities in the system, principally in the electrostatic actuation force. In order to better understand this rich harmonic structure, a theoretical investigation of the micro-cantilever is undertaken. Both a lumped parameter model and a more accurate …

Thermal Coulomb Drag In A Bi-Layer Semiconductor System, Florin Lung

All Theses

In this work, we investigate the existence of a thermoelectric effect that consists of the appearance of an electric field in one layer when a temperature gradient is applied in the other layer of a double quantum well system. This represents a generalization of the Seebeck effect to the case of two spatially separated electron systems allowed to interact only through the Coulomb repulsion. The induced electric field results from the momentum transfer between the electrons driven out of equilibrium by the temperature gradient and the electrons at rest in the passive layer, a mechanism known in the literature as …

Charge Effects In Bilayer Electric Transport, Christopher Czech

All Theses

The mathematical isomorphism between the layer index in a bilayer system and the spin index in a spin-polarized system is used to draw an analogy between phenomena that occur in the two systems as a result of the electron-electron (e-e) interaction. First, the classical case of the Coulomb drag, a phenomenon resulting from momentum transfer through e-e collisions, is reviewed for both bilayer systems and spin-polarized systems. Then, the spin-backflow phenomenon, a result of the interaction-induced changes in the local quasiparticle energy that affects the charge transport in spin-polarized systems is presented. Finally, the iso-spin correlation is exploited to establish …

Comparison Of Thermoelectric Properties Of Arc-Melted And Hot-Pressed Half-Heuslers, Brad Edwards

All Theses

Relatively low thermal conductivity and great electrical properties in combination with wide tuning parameters through doping make half-Heuslers high potential thermoelectric materials. In this study we plan to investigate the effects of hot-pressing and arc-melting on the thermoelectric properties of ZrNiSn_0.975Sb_0.025, and Hf_0.75Zr_0.25NiSn_0.975Sb_0.025 samples. Also, the effects of electron and phonon scattering due to the insertion of small 50 nm particles within the sample were investigated in ZrNiSn_0.975Sb_0.025 +4% Al₂O₃ and Hf_0.75Zr_0.25NiSn_0.975Sb_0.025 +4% Al₂O …

The Thermoelectric Properties Investigation Of Ir3Ge7 Typed Representatives, Huqin Zhang

All Theses

Energy conversion is employed to power generation utilizing the Seebeck effect or cooling utilizing the Peltier effect. Herein, we study several Ir₃Ge₇ typed semiconductor materials for potential thermoelectric energy conversion. Mo₃Sb₇, crystallizing in Ir₃Ge₇ type, can be rendered semiconducting by a partial Sb-Te substitution without noticeable structure changes, resulting in Mo₃Sb₅Te₂ with 55 valence electrons per formula unit. Meanwhile, large cubic voids in the Mo₃Sb₅Te₂ crystal structure provide the possibility of filling the voids with small cations to decrease the …

Comparison Between Steady State And Laser Flash Techniques, Justine Andrews

All Theses

Thermoelectrics is a promising avenue of energy conservation. A material is deemed a good thermoelectric material when it portrays certain material characteristics. These characteristics include a high thermopower and electrical conductivity and a low thermal conductivity. This thesis focuses on the methods of measuring a material's thermal conductivity.
The steady state method is a measurement technique used in the low temperature thermal conductivity measurements. This technique assures that the system and sample are at equilibrium before a measurement point is taken. As a result the measurements are both precise and accurate.
The laser flash technique measures a sample's thermal conductivity …