Digital Commons Network^™

Electrical Characterization Of Crystalline Uo2, Tho2 And U0.71Th0.29O2, Christina L. Dugan

Theses and Dissertations

Uranium dioxide (UO₂), thorium dioxide (ThO₂), and U_xTh_1-xO₂ alloys are characterized for suitability in uranium-based neutron detectors. ThO₂ was studied for an envisioned UO₂/ThO₂ heterojunction. A U_0.71Th_0.29O₂ alloy was studied because of its resistance to oxidation and potential use in surface passivation. The U_0.71Th_0.29O₂ effective Debye temperature of 217± 24 K was measured using temperature-dependent x-ray photoemission spectroscopy (XPS). The specific heat capacity for the U_0.71Th_0.29O₂ alloy was calculated from the Debye …

Optical Micro-Seismometer Based On Evanescent Field Perturbation Of Whispering Gallery Modes, Jaime Da Silva

Mechanical Engineering Research Theses and Dissertations

This thesis proposes a light-weight, compact, and accurate optical micro-seismometer that could be used in many applications, such as planetary exploration. The sensor proposed here is based on the principle of whispering gallery optical mode (WGM) resonance shifts of a dielectric micro-resonator due to disturbances of its evanescent field. The micro-seismometer could be used in place of the traditional bulky seismometers. The design of a waveguide-resonator and mechanical structure to disturb the evanescent field are presented. A proof-of-concept a seismometer model that uses a 5µm ring resonator is numerically tested with actual seismic data. The results show that a WGM-based …

Fast Objective Coupled Planar Illumination Microscopy, Cody Jonathan Greer

Arts & Sciences Electronic Theses and Dissertations

Among optical imaging techniques light sheet fluorescence microscopy stands out as one of the most attractive for capturing high-speed biological dynamics unfolding in three dimensions. The technique is potentially millions of times faster than point-scanning techniques such as two-photon microscopy. This potential is especially poignant for neuroscience applications due to the fact that interactions between neurons transpire over mere milliseconds within tissue volumes spanning hundreds of cubic microns. However current-generation light sheet microscopes are limited by volume scanning rate and/or camera frame rate. We begin by reviewing the optical principles underlying light sheet fluorescence microscopy and the origin of these …

Studies Of Inner-Shell Chemistry Of Mercury Based Compounds At Extreme Conditions, Sarah Schyck

UNLV Theses, Dissertations, Professional Papers, and Capstones

It has been theoretically predicted that when mercury difluoride (HgF2) is pressurized to above 50 GPa in the presence of molecular fluorine, it will most likely transform into mercury tetrafluoride (HgF4), thus mercury will behave as a transition element at high pressure. However, there is no experimental evidence verifying this prediction yet. To begin with, the crystalline properties of pure HgF2 at high pressure were not experimentally established. In this thesis, the high pressure structural properties of HgF2 are investigated by means of synchrotron X-ray powder diffraction. Our results reveal that the predicted, ambient cubic structure of HgF2 with the …

Design, Layout, And Testing Of Sige Apds Fabricated In A Bicmos Process, Dane Laurence Gentry

UNLV Theses, Dissertations, Professional Papers, and Capstones

This Thesis is concerned with the design, layout, and testing of avalanche photodiodes (APDs). APDs are a type of photodetector and, thus, convert light signals into electrical signals (current or voltage). APDs can be fabricated using silicon (Si). In this Thesis, however, three integrated circuit (IC) chips containing various silicon-germanium (SiGe) APDs with different sizes, structures, and geometries were designed, laid out, and fabricated using the Austriamicrosystems (AMS) 0.35μm SiGe BiCMOS (S35) process. This was done in order to compare SiGe APDs to Si only APDs and investigate the hypothesis that SiGe APDs are capable of detecting longer wavelengths than …

Bayesian Model Comparisons In Planetary Science, John Henry Boisvert

UNLV Theses, Dissertations, Professional Papers, and Capstones

Model comparison in the modern era allows us to use statistical methods that were previously difficult with older machines. I present a state-of-the-art model comparison code that uses modern Bayesian statistics to measure the Bayes factor between two competing models. The Bayes factor is the ratio of the probability of the data given one model to the probability of the data given another model. My code was used to compare models in five problems in planetary science. The first three pertain to radial velocity exoplanet data. There is a degeneracy in the radial velocity exoplanet signal between a single planet …

Tunable Electronic And Optical Properties Of Low-Dimensional Materials, Shiyuan Gao

Arts & Sciences Electronic Theses and Dissertations

Two-dimensional (2D) materials with single or a few atomic layers, such as graphene, hexagonal boron nitride (h-BN) and transition metal dichalcogenides (TMDCs), and the heterostructures or one-dimensional (1D) nanostructures they form, have attracted much attention recently as unique platforms for studying many condensed-matter phenomena and holds great potentials for nanoelectronics and optoelectronic applications. Apart from their unique intrinsic properties which has been intensively studied for over a decade by now, they also allow external control of many degrees of freedom, such as electrical gating, doping and layer stacking. In this thesis, I present a theoretical study of the electronic and …

Optimization Of Useful Hard X-Ray Photochemistry, David Lewis Goldberger

UNLV Theses, Dissertations, Professional Papers, and Capstones

X-ray induced damage is generally considered a nuisance, but in the field of Useful Hard X-ray Photochemistry we harness the highly ionizing and penetrating properties of hard X-rays (> 7 keV) to initiate novel photochemical decomposition and synthesis at ambient and extreme conditions. Preliminary experiments suggest that the energy of irradiating photons and the sample pressure play roles in determining the nature of X-ray induced damage. Here, we present the X-ray energy dependence of damage induced in strontium oxalate, strontium nitrate, and barium nitrate, as well as the pressure dependence of X-ray induced damage of strontium oxalate. Our results indicate …

Linking Structure And Dynamics In Metallic Liquids: A Combined Experimental And Molecular Dynamics Approach, Robert Ashcraft

Arts & Sciences Electronic Theses and Dissertations

A major outstanding problem in condensed matter physics is the nature of the glass transition, in which a rapidly cooled liquid can bypass the transition into a crystalline state and the liquid structure is "frozen-in" due to kinetic arrest. To characterize the fundamental features behind this transition the liquid, both in the high temperature (equilibrium) and supercooled state, needs to be better understood. By examining the relationship between structure and dynamics a better characterization of the liquid state and a determination of the mechanisms that are ultimately important for the formation of the glass can be gained. In this dissertation, …

Observation Of Medium-Induced Modifications Of Jet Fragmentation In Pb-Pb Collisions At √SNn =5.02 Tev Using Isolated Photon-Tagged Jets, A. M. Sirunyan

Department of Physics and Astronomy: Faculty Publications

Measurements of fragmentation functions for jets associated with an isolated photon are presented for the first time in pp and Pb-Pb collisions. The analysis uses data collected with the CMS detector at the CERN LHC at a nucleon-nucleon center-of-mass energy of 5.02 TeV. Fragmentation functions are obtained for jets with p^jet_T > 30 GeV/c in events containing an isolated photon with p^γ_T > 60 GeV/c, using charged tracks with transverse momentum p^trk_T > 1 GeV/c in a cone around the jet axis. The association with an isolated photon constrains the initial p_{T …}

Investigation Of An Unusual Thin Layer Descending Through The Upper Stratosphere, Houston D. Bentley

Physics Capstone Projects

Lidar observations on the night of 19-20 February 2004 at Logan, Utah (41.74 N, 111.81 W) revealed a strange thin layer which descended from roughly 55 km to 30 km over seven hours. Approximations are made for the dimensions and descent rate of the layer. Although the particle radius and density are unknown, a range can be determined from the descent rate and reference to the sizes of known particles. Several possible sources for the layer are explored, concluding that an object entering the Earth’s atmosphere was the most probable cause.

First Observation Of P-Odd Gamma Asymmetry In Polarized Neutron Capture On Hydrogen, D. Blyth, J. Fry, N. Fomin, R. Alarcon, L. Alonzi, E. Askanazi, S. Baeßler, S. Balascuta, L. Barrón-Palos, Alex Barzilov, J. D. Bowman, N. Birge, J. R. Calarco, T. E. Chupp, V. Cianciolo, C. E. Coppola, C. B. Crawford, K. Craycraft, D. Evans, C. Fieseler, E. Frlež, I. Garishvili, M. T. W. Gericke, R. C. Gillis, K. B. Grammer, G. L. Greene, J. Hall, J. Hamblen, C. Hayes, E. B. Iverson, M. L. Kabir

Mechanical Engineering Faculty Research

We report the first observation of the parity-violating gamma-ray asymmetry A(gamma)(np) in neutron-proton capture using polarized cold neutrons incident on a liquid parahydrogen target at the Spallation Neutron Source at Oak Ridge National Laboratory. A(gamma)(np) isolates the Delta I = 1, S-3(1)-> P-3(1) component of the weak nucleon-nucleon interaction, which is dominated by pion exchange and can be directly related to a single coupling constant in either the DDH meson exchange model or pionless effective field theory… See full text for full abstract.

First Observation Of P-Odd Γ Asymmetry In Polarized Neutron Capture On Hydrogen, D. Blyth, J. Fry, N. Fomin, R. Alarcon, L. Alonzi, E. Askanazi, S. Baeßler, S. Balascuta, L. Barrón-Palos, A. Barzilov, J. D. Bowman, N. Birge, J. R. Calarco, T. E. Chupp, V. Cianciolo, C. E. Coppola, Chrisopher B. Crawford, K. Craycraft, D. Evans, C. Fieseler, E. Frlež, I. Garishvili, M. T. W. Gericke, R. C. Gillis, K. B. Grammer, G. L. Greene, J. Hall, J. Hamblen, C. Hayes, E. B. Iverson, Md Latiful Kabir, Mark Mccrea, R. Milburn, F. Simmons, Aaron P. Sprow, E. Tang

Physics and Astronomy Faculty Publications

We report the first observation of the parity-violating gamma-ray asymmetry A^np_γ in neutron-proton capture using polarized cold neutrons incident on a liquid parahydrogen target at the Spallation Neutron Source at Oak Ridge National Laboratory. A^np_γ isolates the ΔI = 1, ³S₁ → ³P₁ component of the weak nucleon-nucleon interaction, which is dominated by pion exchange and can be directly related to a single coupling constant in either the DDH meson exchange model or pionless effective field theory. We measured A^np_γ = [−3.0 ± 1.4(stat )± 0.2(syst)] × 10^{−8 …}

Investigation Of Flow Disturbances And Multi-Directional Wall Shear Stress In The Stenosed Carotid Artery Bifurcation Using Particle Image Velocimetry, Amanda L. Dicarlo

Electronic Thesis and Dissertation Repository

Hemodynamics and shear forces are associated with pathological changes in the vascular wall and its function, resulting in the focal development of atherosclerosis. Flow complexities that develop in the presence of established plaques create environments favourable to thrombosis formation and potentially plaque rupture leading to stroke. The carotid artery bifurcation is a common site of atherosclerosis development. Recently, the multi-directional nature of shear stress acting on the endothelial layer has been highlighted as a risk factor for atherogenesis, emphasizing the need for accurate measurements of shear stress magnitude as well direction. In the absence of comprehensive patient specific datasets numerical …

Rare Helium-Bearing Compound Feo2he Stabilized At Deep-Earth Conditions, Jurong Zhang, Jian Lv, Hefei Li, Xiaolei Feng, Cheng Lu, Simon A. T. Redferm, Hanyu Liu, Changfeng Chen, Yanming Ma

Physics & Astronomy Faculty Research

There is compelling geochemical evidence for primordial helium trapped in Earth’s lower mantle, but the origin and nature of the helium source remain elusive due to scarce knowledge on viable helium-bearing compounds that are extremely rare. Here we explore materials physics underlying this prominent challenge. Our structure searches in conjunction with first-principles energetic and thermodynamic calculations uncover a remarkable helium-bearing compound FeO2He at high pressure-temperature conditions relevant to the core-mantle boundary. Calculated sound velocities consistent with seismic data validate FeO2He as a feasible constituent in ultralow velocity zones at the lowermost mantle. These mutually corroborating findings establish the first and …

Gluon Quasi-Parton-Distribution Functions From Lattice Qcd, Zhou-You Fan, Yi-Bo Yang, Adam Anthony, Huey-Wen Lin, Keh-Fei Liu

Physics and Astronomy Faculty Publications

We present the first attempt to access the x dependence of the gluon unpolarized parton-distribution function (PDF), based on lattice simulations using the large-momentum effective theory approach. The lattice calculation is carried out with pion masses of 340 and 678 MeV on a (2+1)-flavor domain-wall fermion configuration with lattice spacing a = 0.111  fm, for the gluon quasi-PDF matrix element with the nucleon momentum up to 0.93 GeV. Taking the normalization from similar matrix elements in the rest frame of the nucleon and pion, our results for these matrix elements are consistent with the Fourier transform of the global fit …

Application Of Bradford’S Law Of Scattering On Research Publication In Astronomy & Astrophysics Of India, Satish Kumar, Senthilkumar R.

Library Philosophy and Practice (e-journal)

The present study is focused on examining the application of Bradford’s law of scattering on research articles published in the field of Astronomy & Astrophysics by Indian scientist during 1988-2017. The bibliographic data was retrieved from Web of Science (WoS) bibliographic data base for different period of time. Total 18,877 journal’s article have been published by Indian scientist in the field of Astronomy & Astrophysics during 1988-2017 which was further retrieved and analyzed separately for different blocks of 10 years as well as for 30 years consolidated too. The core journal of the field was identified. The Bradford law of …

Search For Sub-Solar Mass Ultracompact Binaries In Advanced Ligo's First Observing Run, B. P. Abbott, R. Abbott, T. D. Abbott, F. Acernese, K. Ackley, C. Adams, T. Adams, Marc Favata, Shaon Ghosh, Rodica Martin

Department of Physics and Astronomy Faculty Scholarship and Creative Works

We present the first Advanced LIGO and Advanced Virgo search for ultracompact binary systems with component masses between 0.2 M-1.0 M using data taken between September 12, 2015 and January 19, 2016. We find no viable gravitational wave candidates. Our null result constrains the coalescence rate of monochromatic (delta function) distributions of nonspinning (0.2 M, 0.2 M) ultracompact binaries to be less than 1.0×106 Gpc-3 yr-1 and the coalescence rate of a similar distribution of (1.0 M, 1.0 M) ultracompact binaries to be less than 1.9×104 Gpc-3 yr-1 (at 90% confidence). Neither black holes nor neutron stars are expected to …

Interactions Between Disciplinary Practices And Joint Work In Undergraduate Physics Research Experiences, Gina Quan, Chandra Turpen, Andrew Elby

Faculty Publications

We analyze how participating in undergraduate research experiences (UREs) influenced physics students’ trajectories of participation within the community of practice of physics researchers. Students in the study participated in an elective seminar in which they were paired with graduate student and faculty mentors on physics research projects and participated in weekly discussions about research. Using video data from student interviews and mentor interviews, we characterize two aspects of students’ engagement in the physics community of practice. First, we find variations in their engagement in physics practice, which we characterize as physics activities that are connected and purposeful. Second, we characterize …

Dynamical Electron Vortices In Attosecond Double Photoionization Of H2, Jean Marcel Ngoko Djiokap, A. V. Meremianin, N. L. Manakov, L. B. Madsen, S. X. Hu, Anthony F. Starace

Anthony F. Starace Publications

We study electron momentum vortices in single-photon double ionization of H2 by time-delayed, counterrotating, elliptically polarized attosecond pulses propagating along kˆ either parallel or perpendicular to the molecular axis R. For kˆ | R, kinematical vortices occur similar to those found for He. For kˆ ⊥ R, we find dynamical vortex structures originating from an ellipticity-dependent interplay of ¹∑⁺_u and ¹∏⁺_u continuum amplitudes. We propose a complete experiment to determine the magnitudes and relative phase of these amplitudes by varying pulse ellipticities and time delays.

Interactions Between Disciplinary Practices And Joint Work In Undergraduate Physics Research Experiences, Gina M. Quan, Chandra Turpen, Andrew Elby

Gina Quan

Four Derivations Of Schrödinger’S Time Dependent Equation, Sydney Swanson

Essential Studies UNDergraduate Showcase

Physics and the natural world have been studied by humans since the first person wondered ‘Why?’ The Schrödinger equation is important because it attempts to describe a relatively new (to us) and unfamiliar part of our universe, behavior of subatomic particles, and helps modern scientists uncover secrets that have proven useful in technology and explaining our origins. The time dependent Schrödinger equation can be derived from various starting points in Classical such as the equation of a wave, the time independent Schrödinger equation, and Hamilton-Jacobi equations. Why Quantum mechanics exists, useful applications, and cases when it fails or is inaccurate …

Transverse Anderson Localization In Optical Fibers: High-Quality Wave Transmission And Novel Lasing Applications, Behnam Abaie

Optical Science and Engineering ETDs

In this dissertation, transverse Anderson localization (TAL) of light mediated by disordered optical fibers is exploited for high-quality optical wave transmission and novel random lasing applications. En route, we first establish a powerful numerical platform for detailed investigation of TAL optical fibers (TALOF). Our approach is based on a modal perspective as opposed to beam propagation method (BPM) which was primarily used in the previous studies of TAL in disordered optical fibers. The versatile numerical tools developed in our simulations result in a potent methodology for simulation of TALOFs; the result is a fast and effective algorithm which can be …

Measurement Of The Γ*Γ* → Η' Transition Form Factor, J.P. Lees, V. Poireau, V. Tisserand, E. Grauges, A. Palano, G. Eigen, D. N. Brown, Yu G. Kolomensky, M. Fritsch, H. Koch, T. Schroeder, C. Hearty, T. S. Mattison, J. A. Mckenna, R. Y. So, V. E. Blinov, A. R. Buzykaev, V. P. Druzhinin, V. B. Golubev, Milind Purohit, Et. Al.

Faculty Publications

We study the process e⁺e⁻→e⁺e⁻η′ in the double-tag mode and measure for the first time the γ^*γ^*→ η′ transition form factor Fη′ (Q ² ₁ , Q² ₂) in the momentum-transfer range 2< Q ² ₁ , Q² ₂ 60 GeV ² . The analysis is based on a data sample corresponding to an integrated luminosity of around 469     fb^{− 1} collected at the PEP-II e ⁺e ⁻ collider with the BABAR detector at center-of-mass energies near 10.6 GeV.

1; Q2 2Þ in the …

Computational Techniques For Scattering Amplitudes, Juliano A. Everett

Publications and Research

Scattering amplitudes in quantum field theory can be described as the probability of a scattering process to happen within a high energy particle interaction, as well as a bridge between experimental measurements and the prediction of the theory.

In this research project, we explore the Standard Model of Particle Theory, it’s representation in terms of Feynman diagrams and the algebraic formulas associated with each combination.

Using the FeynArts program as a tool for generating Feynman diagrams, we evaluate the expressions of a set of physical processes, and explain why these techniques become necessary to achieve this goal.

Properties Of Si Quantum Dots, Carolyn C. F Cadogan

Electronic Thesis and Dissertation Repository

The fundamental properties of matter in confined particles change dramatically due to quantum effects. In this work, we have explored the optical properties of silicon quantum dots (Si-QDs) embedded in Si₃N₄; and the role of crystallinity on the optical properties and formation of Si-QDs in Al₂O₃. This work examined the role of (1) annealing temperature and the composition of the film, (2) Al doping of the host Si₃N₄ film, (3) doping Si-QDs and (4) Al and P passivation of Si-QDs on the PL intensity of Si-QDs embedded in Si …

Improving The State Selectivity Of Field Ionization With Quantum Control, Vincent C. Gregoric, Jason Bennett, Bianca R. Gualtieri, Ankitha Kannad, Zhimin Cheryl Liu, Zoe A. Rowley, Thomas J. Carroll, Michael W. Noel

Physics and Astronomy Faculty Publications

The electron signals from the field ionization of two closely spaced Rydberg states of rubidium-85 are separated using quantum control. In selective field ionization, the state distribution of a collection of Rydberg atoms is measured by ionizing the atoms with a ramped electric field. Generally, atoms in higher energy states ionize at lower fields, so ionized electrons which are detected earlier in time can be correlated with higher energy Rydberg states. However, the resolution of this technique is limited by the Stark effect. As the electric field is increased, the electron encounters numerous avoided Stark level crossings which split the …

Model For Scattering With Proliferating Resonances: Many Coupled Square Wells, Nirav P. Mehta, Kaden R. A Hazzard, Christopher Ticknor

Physics and Astronomy Faculty Research

We present a multichannel model for elastic interactions, composed of an arbitrary number of coupled finite square-well potentials, and derive semianalytic solutions for its scattering behavior. Despite the model's simplicity, it is flexible enough to include many coupled short-ranged resonances in the vicinity of the collision threshold, as is necessary to describe ongoing experiments in ultracold molecules and lanthanide atoms. We also introduce a simple but physically realistic statistical ensemble for parameters in this model. We compute the resulting probability distributions of nearest-neighbor resonance spacings and analyze them by fitting to the Brody distribution. We quantify the ability of alternative …

Revisiting The Paleomagnetism Of The Neoarchean Uauá Mafic Dyke Swarm, Brazil: Implications For Archean Supercratons, J. Salminen, E. P. Oliveira, Elisa J. Piispa, Aleksey Smirnov, R. I. F. Trindade

Michigan Tech Publications

The original connections of Archean cratons are becoming traceable due to an increasing amount of paleomagnetic data and refined magmatic barcodes. The Uauá block of the northern São Francisco craton may represent a fragment of a major Archean craton. Here, we report new paleomagnetic data from the 2.62 Ga Uauá tholeiitic mafic dyke swarm of the Uauá block in the northern São Francisco craton, Eastern Brazil. Our paleomagnetic results confirm the earlier results for these units, but our interpretation differs. We suggest that the obtained characteristic remanent magnetization for the 2.62 Ga swarm is of primary origin, supported by a …

Digital Plasmonic Holography, Joseph W. Nelson, Greta R. Knefelkamp, Alexandre G. Brolo, Nathan C. Lindquist

Physics and Engineering Faculty Publications

We demonstrate digital plasmonic holography for direct in-plane imaging with propagating surface-plasmon waves. Imaging with surface plasmons suffers from the lack of simple in-plane lenses and mirrors. Lens-less digital holography techniques, however, rely on digitally decoding an interference pattern between a reference wave and an object wave. With far-field diffractive optics, this decoding scheme provides a full recording, i.e., a hologram, of the amplitude and phase of the object wave, giving three-dimensional information from a two-dimensional recording. For plasmonics, only a one-dimensional recording is needed, and both the phase and amplitude of the propagating plasmons can be extracted for high-resolution …