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Kuehn, Frederick GabrielFinding Gamma Ray Bursts at High Energies and Testing the Constancy of the Speed of Light
Doctor of Philosophy, The Ohio State University, 2008, Physics
This dissertation presents the development of algorithms for the LAT Onboard Science Processing as well as an analysis methodology for determining non-constancy in the speed of light at high energy. The main goal of Onboard Science is to find GRBs in real time onboard the LAT. Detailed studies of the expected performance and documentation of the implementation are provided. Given current knowledge and reasonable assumption on the high energy spectra, the expected number of GRBs that will be observed is 1-2 per month at better than 17#176; of accuracy. Studies presented here map out the performance as a function of GRB parameters. The second part of this thesis focuses on showing that the LAT is sensitive to a Quantum Gravity time delay induced by physics at the Planck scale. Quantitatively, the LAT can distinguish time delays of 𝓞 (10-5) s/MeV.

Committee:

Brian Winer, PhD (Advisor); Richard Hughes, PhD (Committee Member); John Beacom, PhD (Committee Member); James Beatty, PhD (Committee Member); Mark Wewers, PhD (Committee Member)

Subjects:

Astrophysics; Physics

Keywords:

GRB; Lorentz Invariance Violation; Gamma-Rays

Guarendi, Andrew NNumerical Investigations of Magnetohydrodynamic Hypersonic Flows
Master of Science, University of Akron, 2013, Mechanical Engineering
Numerical simulations of magnetohydrodynamic (MHD) hypersonic flow are presented for both laminar and turbulent flow over a cylinder and flow entering a scramjet inlet. ANSYS CFX is used to carry out calculations for steady flow at hypersonic speeds (Mach number > 5). The low magnetic Reynolds number (<<1) calculated based on the velocity and length scales in this problem justifies the quasistatic approximation, which assumes negligible effect of velocity on magnetic fields. Therefore the governing equations employed in the simulations are the compressible Navier-Stokes and the energy equations with MHD-related source terms such as Lorentz force and Joule dissipation. Turbulence effects are accounted for when applicable and multiple turbulence models are compared. The results demonstrate the ability of the magnetic field to affect the flowfield, and variables such as location and magnitude of the applied magnetic field are examined. An examination of future work is provided through the implementation of a semi-discrete central scheme in-house code toward the solution of the Orszag-Tang vortex system.

Committee:

Abhilash Chandy, Dr. (Advisor); Scott Sawyer, Dr. (Committee Member); Alex Povitsky, Dr. (Committee Member)

Subjects:

Aerospace Engineering; Engineering; Fluid Dynamics; Mechanical Engineering

Keywords:

Hypersonic; Hypersonic Flow; Flow over a cylinder; Magnetohydrodynamic; MHD; Lorentz; Hypersonic MHD; Numerical Methods; CFD; Computational fluid dynamics; fluid dynamics; Aerospace;

Yazdani, MaryamC axis optical property of a family of a high temperature superconductors LaSrCuO
Master of Science, University of Akron, 2016, Physics
In this thesis, I investigated c-axis optical properties of a family of high temperature superconductors La2-xSrxCuO4. Eight samples with different dopings, from x = 0.04 to x = 0.20 were studied at temperatures 32 K, 80 K, and 300 K, all in the normal (non-superconducting) state. I used the Fano model to fit their infrared spectra and from the best fits I extracted the parameters of the phonons: oscillator frequency, plasma frequency, scattering rate and Fano frequency. I then compared these results with the results obtained previously on the same data set using the Drude-Lorentz model. The fits obtained using the Fano fit are better, which indicates that electron-phonon coupling in La2-xSrxCuO4 is strong and must be taken into account during band-structure and phonon calculations. I also found that stripe instability in La2-xSrxCuO4, which is known to be strongest at 1/8 doping, has a significant effect on phonon line-shapes.

Committee:

Sasa Dordevic (Advisor); Jutta Luettmer-Strathmann (Committee Member); Alper Buldum (Committee Member)

Subjects:

Physics

Keywords:

Fano mode; Drude Lorentz mode; high temperature superconductors; normal state; stripe phases; doping; phonon; oscillator frequency; plasma frequency, and scattering rate

Tanaka, HirokiDevelopment of MOKE Spectrometer for Magneto-optical Studies of Novel Magnetic Materials and Quantum Structures
Master of Science (MS), Ohio University, 2008, Electrical Engineering (Engineering and Technology)
The progress in modern, widely-defined information technology strongly depends on the ability of precise characterization of variety of materials in the wide range of anticipated parameters. Novel magnetic materials and magnetic structures are the core of the spintronics in which a manipulation of electrons spins opens a door to new concepts of practical applications. The magneto-optic is an interesting approach to effectively assess properties of spintronic materials due to the strong interaction of photons with spins mediated through spin-orbit coupling. This is manifested by observation of Faraday, Voigt and Kerr effects in magnetic materials. These effects crucially depend on the spin-orbit interactions in the starting and/or the ending state of the optical transition considered. In this work we exclusively focused on the magneto-optical Kerr effect through the development of and testing of the automated Magneto-Optical Kerr Effect (MOKE) spectrometer operating in polar and longitudinal geometries at room temperature. The constructed MOKE system has proven to be central to perform magneto-optical and magnetic characterizations of selected test and research samples. In particular, we were able to confirm the functionality of the MOKE by measuring Kerr rotation hysteresis loops of the Pt/Co superlattice test samples. Furthermore, a set of new results was obtained for the different epitaxially grown GaN/Fe material systems. The observed Kerr rotation signal for GaN/Fe was interpreted as the clear evidence for a strong spin-orbit interaction occurring in these novel magnetic materials. In addition to the conducted experimental work, special attention was dedicated to derive an analytically comprehensive description of the Kerr rotation and Kerr ellipticity in the general case of polar and longitudinal geometries. Finally, relying on the expertise gained during the MOKE spectrometer construction and testing, we proposed to upgrade the system necessary to improve its reliability and expand the scope of available magneto-optical measurement techniques at Ohio University.

Committee:

Wojciech M. Jadwisienczak, PhD (Advisor)

Subjects:

Electrical Engineering

Keywords:

MOKE; polar; Longitudinal; Kerr rotation; Kerr ellipticity; Co; Pt;Fe; GaN; LabVIEW; Setup; calibration; Lorentz; Magneto optical Kerr effect

Ahmed, Adam SaiedSkyrmions and Novel Spin Textures in FeGe Thin Films and Artificial B20 Heterostructures
Doctor of Philosophy, The Ohio State University, 2017, Physics
Skyrmions are magnetic spin textures that have a non-zero topological winding number associated with them. They have attracted much interest recently since they can be as small as ~1 nm and could be the next generation of magnetic memory and logic. First, we grow epitaxial films of FeGe by molecular beam epitaxy and characterized the skyrmion properties. This had led us to image skyrmions in real-space with Lorentz transmission electron microscopy for the first time in the United States. Next, from an extensive series of thin and thick films, we have experimentally shown the existence of a magnetic surface state in FeGe and, consequently, any skyrmion material for the first time. Complementary theoretical calculations supported the existence of chiral bobbers—a surface state only predicted in 2015. Next, we fabricated for the first time a new class of skyrmion materials: B20 superlattices. These novel heterostructures of [FeGe/MnGe/CrGe] have now opened the door for tunable skyrmion systems with both Dresselhaus and Rashba Dzyaloshinskii-Moriya interactions. Additionally, we perform resonant soft x-ray scattering to image magnetic spin textures in reciprocal space for FeGe thin films in transmission. We have accomplished the removal of substrate and left an isolated single-crystal FeGe film. Lastly, SrO is grown on graphene as a crystalline, atomically smooth, and pinhole free tunnel barrier for spin injection.

Committee:

Roland Kawakami (Advisor); Chris Hammel (Committee Member); Nandini Trivedi (Committee Member); John Beacom (Committee Member)

Subjects:

Physics

Keywords:

Skyrmions; B20; Chiral bobber; Lorentz Transmission Electron Microscopy; Topological Hall Effect; Magnetic Susceptibility; Molecular Beam Epitaxy; SrO; graphene; FeGe; DMI; Superlattice;

Kim, YoungminOptical studies of the charge localization and delocalization in conducting polymers
Doctor of Philosophy, The Ohio State University, 2005, Physics

A systematic charge transport study on the thermochromism of polyaniline (PAN) doped with a plasticizing dopant, and on a field effect device using conducting poly (3,4-ethylenedioxythiophene) (PEDOT) as its active material, was made at optical (20 — 45,000 cm -1 ) frequencies to probe the charge localization and delocalization phenomena and the insulator to metal transition (IMT) in the inhomogeneous conducting polymer system.

Temperature dependent reflectance [20 — 8000 cm-1 (2.5 meV — 1eV)] of the PAN sample, together with absorbance and dc transport study done by Dr. Pron at the Laboratoire de Physique des Métaux Synthétiques in Grenoble, France, shows spectral weight loss in the infrared region but the reflectance in the very low frequency (below 100 cm -1 ) remains unaffected. There are two localization transitions. The origin of the 200 K localization transition that affect >~ 15% of the electrons is the glass transition emanating from the dopants. The transition principally affects the IR response in the range of 200 — 8000 cm -1 . The low temperature (<75K) localization transition affects the few electrons that provide the high conductivity. It is suggested that these electrons are localized by disorder at the lowest temperature and become delocalized through phonon induced delocalization as the temperature increases to 75K. It is noted that this temperature is typical of a Debye temperature in many organic materials. The thermocromism is attributed to the weak localization to strong localization transition through the glass transition temperature. Below the glass transition temperature (Tg), the lattice is “frozen” in configuration that reduces the charge delocalization and lead to cause increase of strongly localized polarons.

Time variation of source-drain current, real-time IR reflectance [20 — 8000 cm -1 (2.5 meV — 1eV)] modulation, and real-time UV/VIS/NIR absorbance [380 — 2400 nm (0.5 — 3.3 eV)] modulation were measured to investigate the field induced charge localization of PEDOT field effect device. Layer by layer thin film analysis showed strong localization of free carriers. The temperature dependence of the dc conductivity changes with application of the gate voltage demonstrating that the electric field effect has changed bulk charge transport in the active channel despite the expected screening due to mobile charge carriers. Mid IR (500 — 8000 cm -1 ) reflectance showed little change in the vibrational modes, which distinguish this phenomenon from the doping-dedoping induced electrochemical MIT. UV/Vis/NIR absorbance modulation clearly showed that the increase of the strong localization of charges with the π - π* bandgap transition unchanged. It is proposed that conducting polymer is near the metal to insulator transition and that the applied gate voltage leads to this transition through field induced ion motion.

Committee:

Arthur Epstein (Advisor)

Subjects:

Physics, Condensed Matter

Keywords:

Polyaniline; plastdopant; reflectance; thermochromism; glass transition; PEDOT; PSS; field effect; reflectance; Drude-Lorentz model; absorbance; IRAV mode

Hartz, Jason MichaelThe Plow That Broke the Plains: An Application of Functional Americanism in Music
Doctor of Philosophy (PhD), Ohio University, 2010, Interdisciplinary Arts (Fine Arts)
This dissertation explores the nature of American musical identity in the score from the 1936 documentary film The Plow That Broke the Plains, directed by Pare Lorentz, scored by Virgil Thomson, and created under the auspices of the New Deal‘s Resettlement Administration. While the score offers a study in modernist music and compositional musical Americanism, other approaches may be more suited to positioning this New Deal cultural artifact within its historical context, thus revealing its cultural sources and social intentions. In the spirit of contemporary musicology, this project proposes a new category through which to undertake such studies: functional Americanism. Functional Americanism evaluates American identity in music through the function or utility of music operating in an American setting or for an American purpose. Using this approach to engage with The Plow, this study draws from social history, cultural studies, and musicology in order to understand The Plow within its historical moment as an articulator of American identity.

Committee:

Dora Wilson, PhD (Committee Chair); Condee William, PhD (Committee Member); Gillespie Michael, PhD (Committee Member); Wetzel Richard, PhD (Committee Member)

Subjects:

American Studies; Fine Arts; Music

Keywords:

The Plow That Broke the Plains; Virgil Thomson; Resettlement Administration; Pare Lorentz; New Deal; Dust Bowl; Musical Americanism

Corum, James FrederickAn investigation of the anholonomic nature of the rotating Lorentz transformation with applications to electrodynamics /
Doctor of Philosophy, The Ohio State University, 1974, Graduate School

Committee:

Not Provided (Other)

Subjects:

Engineering

Keywords:

Lorentz transformation;Electrodynamics

Cilwa, Katherine E.Surface Plasmons Polaritons and Single Dust Particles
Doctor of Philosophy, The Ohio State University, 2011, Chemistry
Square nickel mesh perforated with micron scale holes exhibits extraordinary transmission due to propagating surface plasmon polaritions (PSPP) combined with cavity modes. Propagating surface plasmon resonances are known to disperse with the angle of incident light and such experiments yield rich information regarding the plasmonics of the material. More accurate polarized Gamma X dispersion is presented within, as well as the first polarized Gamma M dispersion of square nickel mesh. Calculation of resonance positions within these experiments predicts an effective index of refraction for the asymmetric coupled surface plasmon polaritons to have a value of n’eff = 1.043. Gamma P and Gamma Q dispersion of hexagonal mesh is presented and the coupling of asymmetric plasmonic surfaces examined. Calculations allowing interactions between PSPP states of square mesh are compared with experimental results and traditional predictions of mesh, PSPP transmission maxima; explaining variation from experimental results and traditional predictions and illustrating the polariton, or mixed state, nature of PSPPs. Lastly, scatter free infrared spectra of sixty-three individual micron scale dust particles are presented by placement of each particle in a hole of plasmonic square nickel mesh. The constituents of each particle and the process of quantification of materials is examined by use of Mie scattering, Lorentz dispersion, and Bruggeman effective medium theories. The propagation lengths for PSPP resonances on such mesh are poor (~1-2 hole-to-hole spacings), compared to smooth metal predictions or less absorbing metals, making this mesh ideal for studying individual particles. The PSPPs funnel light through the particles, but they are effectively isolated so long as the neighboring holes are empty. Saturation of absorption peaks at this scale are demonstrated.

Committee:

James Coe, PhD (Advisor); Sherwin Singer, PhD (Committee Member); Barbara Wyslouzil, PhD (Committee Member)

Subjects:

Atmospheric Chemistry; Atmospheric Sciences; Chemistry; Condensed Matter Physics; Environmental Education; Environmental Geology; Environmental Health; Environmental Management; Environmental Science; Environmental Studies; Geochemistry; Mineralogy; Molecular Physics

Keywords:

surface plasmon; surface plasmon polariton; dispersion; Mie; scattering; Lorentz; Bruggeman; micron; particles; particulate; PM10; dust; single particle; interaction; IR; infrared; mesh; hole arrays; extraordinary transmission; hexagonal; absorption