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Nonlinear Mode Coupling Coefficients In Extrasolar Hot Jupiter Systems With Non-Solar Type Host Stars, Niyousha Davachi
Nonlinear Mode Coupling Coefficients In Extrasolar Hot Jupiter Systems With Non-Solar Type Host Stars, Niyousha Davachi
Physics Theses
Short period planets tidally excite internal gravity modes within their host star. These excited modes, known collectively as the dynamical tide, dissipate orbital energy and cause the planet’s orbit to decay. In hot Jupiter systems, resonantly excited gmodes are driven to such large amplitudes in the stellar core that they nonlinearly excite a sea of secondary modes. These secondary modes can greatly enhance the efficiency of tidal dissipation compared to linear theory predictions and thus significantly increase the rate of orbital decay. In this thesis we calculate the three-mode coupling coefficients between the excited g-modes of hot Jupiter host stars. …
Orbital Evolution Studies And Radio Searches Of Extra-Solar Moons, Marialis Rosario-Franco
Orbital Evolution Studies And Radio Searches Of Extra-Solar Moons, Marialis Rosario-Franco
Physics Dissertations
Exoplanetary research has undergone a great deal of development and growth. Achievements in theoretical studies and detection techniques have led to the discovery of 4,000+ exoplanets in ~3, 000 planetary systems to date. Despite this great success, and though candidates have been proposed, the confirmation of the first exomoon is yet to be accomplished. Understanding the constraints under which extrasolar moons form around exoplanets can provide insight into the overall formation of the system, the host planet’s habitability, and could even aid the process of drawing out the best observational candidates for exomoon searches. This work entails the use of …
Studying The Oxygen Effect In Proton Therapy Via Gpu-Based Microscopic Monte Carlo Simulation, Marcos Joseph Guillen
Studying The Oxygen Effect In Proton Therapy Via Gpu-Based Microscopic Monte Carlo Simulation, Marcos Joseph Guillen
Physics Theses
Dissolved oxygen molecules are known to play an important role in radiotherapy. For example, tumor cells can be more radio-resistance under hypoxia than normoxia. There has been multiple hypothesis proposed to explain these phenomena, including the oxygen mediated chemical track evolution. In principle, we can perform microscopic Monte Carlo (MC) simulation to quantitively test this hypothesis. Yet, to avoid the extreme high computational resource consuming, in the current CPU-based MC tools, oxygen is either ignored or taken as a continuous radical-scavenging background. Recently, our research group developed an open-source, GPU-based MC simulation tool, gMicroMC, in which, the oxygen mediated chemical …
Investigations On The Impact Of Spatial Ability And Scientific Reasoning Of Student Comprehension In Physics, State Assessment Test, And Stem Courses, Alfonso Juan Hinojosa
Investigations On The Impact Of Spatial Ability And Scientific Reasoning Of Student Comprehension In Physics, State Assessment Test, And Stem Courses, Alfonso Juan Hinojosa
Physics Dissertations
Physics examines topics that are highly spatial in nature. Students are required to visualize a system, manipulate that system, and then solve a given problem. Doing all of this simultaneously can lead to a cognitive overload, causing the student to be unable to correctly solve the problem. Some difficulties may be rooted in conceptual difficulties, whereas other difficulties may arise from issues with spatial intelligence and visual cognition. In some cases, students might have created an incorrect mental image of the problem to begin with, and it's this misconception, not the lack of content knowledge, that has caused the student …
First Principles Study Of Ga-Stabilized Δ-Pu Bulk And Surfaces, Sarah Christine Hernandez
First Principles Study Of Ga-Stabilized Δ-Pu Bulk And Surfaces, Sarah Christine Hernandez
Physics Dissertations
Plutonium (Pu) metal is highly reactive toward environmental gases and corrodes at a high rate. Due to this inevitable process, containers used to store Pu-based materials may experience catastrophic failure, subsequently releasing Pu particulates into the environment. Such interactions can be probed at the atomic scale using ab initio methods such as density functional theory (DFT). However, previous theoretical studies only examined these reactions with a pure δ-Pu surface. This is not realistic since δ-Pu exists at a high temperature (600K), therefore most technological applications of δ-Pu employ the alloyed form. The alloyed form is achieved with the addition of …
Precision Higgs Coupling Measurements In H→Ww*→Lνlν Final State With The Atlas Detector At The Lhc, Hee Yeun Kim
Precision Higgs Coupling Measurements In H→Ww*→Lνlν Final State With The Atlas Detector At The Lhc, Hee Yeun Kim
Physics Dissertations
The Standard Model (SM) is a gauge theory that describes the fundamental particles of matter and the forces between these particles. It has been tested to a very high precision in the past several decades, except for observation of the Higgs particle, a ramification of the Higgs mechanism. After discovery of the Higgs particle in July 2012, at the Large Hadron Collider (LHC) at the European organization for Nuclear Research (CERN), subsequent studies have focused on confirming whether the newly discovered particle is consistent with the SM Higgs. In particular its spin and its couplings have been measured. In this …
A Density Functional Theory Guide To High Quality Modification Of Mixed Metal Oxides Used For Photocatalytic Water Splitting, Cedric Leon Mayfield
A Density Functional Theory Guide To High Quality Modification Of Mixed Metal Oxides Used For Photocatalytic Water Splitting, Cedric Leon Mayfield
Physics Dissertations
Phase stability and charge transport of pristine and transition metal alloyed bismuth titanate (Bi2Ti2O7, a.k.a. BTO), a photocatalytic water splitter, has been studied using the generalized gradient approximated density functional theory (GGA-DFT). The primary goals of this work were to predict the effective conditions for pure phase synthesis of the modified ternary multi-metal oxide and to determine the most suitable modifications for enhancing its photocatalytic properties. To understand the details of phase stability and photoconduction, we have derived the formation enthalpies, defect formation energies, electronic structures, spectral absorptions and polaron activation energies for pristine and transition metal doped bismuth titanate …
Laser-Assisted Transfection, Optogenetic Stimulation And Its Detection In Mammalian Cells, Kamal Raj Dhakal
Laser-Assisted Transfection, Optogenetic Stimulation And Its Detection In Mammalian Cells, Kamal Raj Dhakal
Physics Dissertations
Stimulation of cells, especially neurons is of significant interest both for basic understanding of neuronal circuitry as well as clinical intervention. Existing electrode-based methods of stimulation is invasive and non-specific to single cells or cell type. Recently, optical stimulation of targeted neurons expressing light-sensitive proteins (opsins) has surfaced as an emerging and a powerful technique (Optogenetics) in neuroscience. Various transfection methods such as viral-based, lipofection, electroporation have been developed to express the opsin. However, these methods are not suitable for transfection of a single cell. In order to achieve single cell transfection, we have used femtosecond pulsed laser microbeam to …
Investigation Of Kev Beta Particle Transportation In Matter, Bright Chukwudi Izudike
Investigation Of Kev Beta Particle Transportation In Matter, Bright Chukwudi Izudike
Physics Theses
Nuclear imaging is widely used in medicine for more accurate diagnoses and more effective treatment for cancer. Current emission tomography techniques used in clinics may not efficiently detect cancer at a very early stage partly because of the weak signals from small tumors. Portable nuclear imaging devices can more effectively reveal these small tumors in a close proximity for complete malignant tissue destruction. With the advance of detector technology in high energy physics, the detection of beta particles (positron and electron) from clinical/pre-clinical radiotracers, such as those labeled with Cu-64, may open a new avenue for imageguided treatment of cancer. …
Analysis Of Equatorial F-Region Vertical Neutral Winds From Brazil Fpi Observations, Jose De La Garza
Analysis Of Equatorial F-Region Vertical Neutral Winds From Brazil Fpi Observations, Jose De La Garza
Physics Theses
Understanding the neutral dynamics of our upper atmosphere is an essential component of space weather prediction. In order to come up with better climatological models that describe upper atmospheric variations, an accurate description of vertical neutral winds is needed. Hence, observations of thermospheric winds must be continually made in order to fulfill this need. Vertical winds are generally smaller than horizontal winds, but even small vertical winds can have a significant effect on the ionosphere and thermosphere because of the large vertical density gradients that exist throughout the atmosphere. Recent observation deployments of Fabry-Perot Interferometers (FPIs) in Brazil have allowed …
Blocker-Based Scatter Correction For Cone-Beam Computed Tomography, Cong Zhao
Blocker-Based Scatter Correction For Cone-Beam Computed Tomography, Cong Zhao
Physics Theses
Cone-beam computed tomography (CBCT) imaging is widely used in radiation therapy for treatment planning and image-guided therapy. More x-ray scatter signals are detected by the two-dimensional detector arrays in CBCT than by the one-dimensional detector arrays in fan-beam CT (FBCT). Therefore, scatter contamination significantly degrades the image quality in CBCT and must be corrected for satisfying image quality.One approach for scatter correction is to use lead blockers. In such a method, the signal in the blocked regions is assumed to be the scatter signal and can be used to estimate the scatter signal in the unblocked region. However, this assumption …
Ferroelectric And Ferromagnetic Behavior Of Oxide Containing Thin Films, Hai In Choi
Ferroelectric And Ferromagnetic Behavior Of Oxide Containing Thin Films, Hai In Choi
Physics Theses
Oxide materials are important due to their interesting physical properties for applications in future electronic devices. Thin film oxide materials show a variety of electric and magnetic properties such as ferroelectric, piezoelectric, ferromagnetic and superconducting properties.One intriguing material, bismuth ferrite, has shown room-temperature multiferroic order. It has ferroelectric order below the 1100 K Curie temperature and large remnant polarization. Also, it has antiferromagnetic order below the Néel temperature of 650 K. However, the bismuth ferrite has several defect-related issues such as bismuth volatilization, transition of iron valence electron states and oxygen vacancies. The multiferroic properties are changed by the defect …
Searching For Dark Matter In Neutrino Beams, Crystal Nicole Chumani Red Eagle
Searching For Dark Matter In Neutrino Beams, Crystal Nicole Chumani Red Eagle
Physics Theses
Dark Matter detection is currently a major area of interest for research. For the past 45 years many ideas and experiments have been investigated to explain the existence of and to detect Dark Matter. Since these experiments have yet to yield any wholly affirmative results it may be time to look for other ways to detect Dark Matter. This particular study looks at the possibilities for Dark Matter detection in neutrino beams at the Deep Underground Neutrino Experiment (DUNE). Simulations for specific parameters were run using MadGraph5 and the results for those data runs are presented and discussed. Areas of …
Experimental Studies Of Fundamental Aspects Of Auger Emission Process In Cu(100) And Ag(100), Prasad Vivek Joglekar
Experimental Studies Of Fundamental Aspects Of Auger Emission Process In Cu(100) And Ag(100), Prasad Vivek Joglekar
Physics Dissertations
Auger spectra at the low energies are accompanied by large contributions unrelated to the Auger transition. The Auger unrelated contributions can obscure the Auger peak and affect the quantitative analysis of the materials under investigation. In this dissertation we present a methodology to measure experimentally the Auger unrelated contributions and eliminate it from the Auger spectrum for obtaining an Auger spectrum inherent to the Auger transition. We used Auger Photoelectron Coincidence Spectroscopy (APECS) to obtain the Auger spectrum. APECS measures the Auger spectrum in coincidence with the core energy level and thus discriminating the contributions arising from secondary electrons and …
Cutoff Frequencies For Alfven Waves In The Solar Atmosphere, B L Harsha Kalpanie Perera
Cutoff Frequencies For Alfven Waves In The Solar Atmosphere, B L Harsha Kalpanie Perera
Physics Dissertations
Propagation of linear Alfven waves in the isothermal and non-isothermal solaratmosphere is investigated numerically and analytically. It is shown that thetwo wave variables, the velocity and magnetic field perturbations, behave differently and that there is a range of wave frequencies for which the wave behavior changes from propagating to non-propagating. The so-called transition and turning points corresponding to this change are determined analytically, and their locations in the atmosphere are calculated and verified against the numerical results. The transition and turning points are then used to introduce cutoff frequencies, which are different for different wave variables. The main result is …
Biological Damage Of Uv Radiation In Environments Of F-Type Stars, Satoko Sato
Biological Damage Of Uv Radiation In Environments Of F-Type Stars, Satoko Sato
Physics Dissertations
I investigate the general astrobiological significance of F-type main-sequence stars with special consideration to stellar evolutionary aspects due to nuclear evolution. DNA is taken as a proxy for carbon-based macromolecules following the assumption that exobiology is most likely based on hydrocarbons. The DNA action spectrum is utilized to represent the relative damage of the stellar UV radiation. Planetary atmospheric attenuation is taken into account in the form of parameterized attenuation functions. My work is motivated by previous studies indicating that the UV environment of solar-like stars is one of the most critical elements in determining the habitability of exoplanets and …
Orbital Stability Analysis And Chaotic Dynamics Of Exoplanets In Multi-Stellar Systems, Suman Satyal
Orbital Stability Analysis And Chaotic Dynamics Of Exoplanets In Multi-Stellar Systems, Suman Satyal
Physics Dissertations
The advancement in detection technology has substantially increased the discovery rate of exoplanets in the last two decades. The confirmation of thousands of exoplanets orbiting the solar type stars has raised new astrophysical challenges, including the studies of orbital dynamics and long-term stability of such planets. Continuous orbital stability of the planet in stellar habitable zone is considered vital for life to develop. Hence, these studies furthers one self-evident aim of mankind to find an answer to the century old question: Are we alone?This dissertation investigates the planetary orbits in single and binary star systems. Within binaries, a planet could …
Investigations Of Laser-Based Repulsive Axonal Guidance And Other Novel Biophysical Applications Of Laser Microbeams, Bryan James Black
Investigations Of Laser-Based Repulsive Axonal Guidance And Other Novel Biophysical Applications Of Laser Microbeams, Bryan James Black
Physics Dissertations
Over the past 30 years, the properties of light have been increasingly exploited to probe and manipulate biological samples. The subsequent techniques and technologies, combined with the broadening optical characterization of biological samples (from cells to single molecules), have had a revolutionary impact on the fields of biophysics, bioengineering, chemistry, and molecular biology. Light is now known to be capable of manipulating biological samples with high spatial and temporal precision, and minimal invasiveness. Herein, we offer the findings of several novel, light-based studies as well as novel applications which exploit a laser microbeam as either a potential gradient, a cutting …
First Principles Computational Modeling Of The Surface Properties Of Uranium Dioxide, Megan Hoover
First Principles Computational Modeling Of The Surface Properties Of Uranium Dioxide, Megan Hoover
Physics Theses
The interaction of uranium dioxide (UO₂) with environmental elements occurs at its exposed surface and a fundamental understanding of this interaction process begins at the atomic scale. In this regard, atomic scale modeling of the properties of clean and adsorbate-covered uranium dioxide (UO₂) surfaces can be used to elucidate UO₂ surface mechanisms such as corrosion and the formation of complex species via environmental gas adsorption. In this thesis, structural and electronic properties of clean and adsorbatecovered low index UO₂ surfaces were modeled using regular and hybrid density functional theory. Specifically, the properties of the clean (111) and (110) surfaces were …
A Structural Prediction Of Copper Sulfide And Study Of Its Electronic Properties And Vacancy Forming Trend Using Density Functional Theory, Prashant Khatri
A Structural Prediction Of Copper Sulfide And Study Of Its Electronic Properties And Vacancy Forming Trend Using Density Functional Theory, Prashant Khatri
Physics Theses
The focus of this research is on the material challenges in photovoltaic. Copper Sulfide (Cu2 S) has been regarded as a potential solar absorber materials in photovoltaic industry. Despite its simple composition, it is a complex material. Copper atoms are mobile in Cu2 S crystals facilitating copper vacancies; hence promote Cu-deficient non-stoichiometric Cux S. Majority of the present work is directed towards understanding the stability issue related with Cu2 S/Cux S. We used density functional theory systematically to predict acanthite like structure as ground state structure of Cu2 S. The crystal structure of acanthite Cu2 S is much simpler than …
Evidence Of A Positron Bound State On The Surface Of A Topological Insulator, Karthik Shastry
Evidence Of A Positron Bound State On The Surface Of A Topological Insulator, Karthik Shastry
Physics Dissertations
We describe experiments aimed at probing the sticking of positrons to the surfaces of topological insulators performed at university of Texas at Arlington using the Positron Annihilation induced Auger electron Spectrometer. A magnetically guided beam was used to deposit positrons at the surface of Bi₂Te₂Se sample at energy of ~2eV. Peaks observed in the energy spectra and intensities of electrons emitted as a result of positron annihilation showed peaks at energies corresponding to Auger peaks in Bi and Te providing clear evidence of Auger emission associated with the annihilation of positrons in a surface bound state. Theoretical estimates of the …
Phenomenological Studies Of Dark Matter, Miguel Alejandro Gomez Ramirez
Phenomenological Studies Of Dark Matter, Miguel Alejandro Gomez Ramirez
Physics Dissertations
It is common knowledge that eighty percent of the matter in our Universe consists of a mysterious substance called ``dark matter'' (DM) which has only been detected through its gravitational interactions. The ``Standard Model'' (SM) of particle physics, despite its extremely impressive successes, does not have a good candidate particle to fit the DM requirements. If DM is made up of a particle which interacts weakly and it has a mass on the same scale as other SM particles, it should be detectable.In this work, two different phenomenological studies of DM are performed. The first possibility is a weakly-interacting particle …
Investigating The Global Geospace Response To A Period Of Solar Wind High Speed Streams Using The Lyon-Fedder-Mobarry Mhd Simulation, Kevin Pham
Physics Dissertations
As the solar wind flows past the Earth, it interacts with the Earth's magnetic field and transfers energy and momentum to the geospace environment. During times when the solar cycle is near a minimum, there is a tendency for the Sun to produce high speed streams (HSSs), which are solar wind flows that are faster than the ambient solar wind. The HSSs contain properties that are not typically found in slower ambient solar wind, such as large amplitude Alfvén waves, that affect the transfer of energy and momentum. Large transfers of energy and momentum into the geospace environment that could …
Interaction Of The Geomagnetic Field With Northward Interplanetary Magnetic Field, Shree K. Bhattarai
Interaction Of The Geomagnetic Field With Northward Interplanetary Magnetic Field, Shree K. Bhattarai
Physics Dissertations
The interaction of the solar wind with Earth's magnetic field causes the transfer of momentum and energy from the solar wind to geospace. The study of this interaction is gaining significance as our society is becoming more and more space based, due to which, predicting space weather has become more important. The solar wind interacts with the geomagnetic field primarily via two processes: viscous interaction and the magnetic reconnection. Both of these interactions result in the generation of an electric field in Earth's ionosphere. The overall topology and dynamics of the magnetosphere, as well as the electric field imposed on …
Search For The Standard Model Higgs Boson In Eτ Final States, Ian James Howley
Search For The Standard Model Higgs Boson In Eτ Final States, Ian James Howley
Physics Dissertations
Presented in this dissertation is a search for the standard model (SM) Higgs boson using the DØ detector at Fermilab in Batavia, IL. The SM is a fantastically accurate theory describing the fundamental interactions and particles of the Universe. The only undiscovered particle in the SM is the Higgs boson, which is hypothesized to be responsible for electroweak symmetry breaking and giving mass to all other particles. Considered in this search is the process H + X -> eτhjj, where e is an electron, τh is the hadronic decay of a τ, and j is a jet, using pp̄ collisions …
The Electronic Properties Of Noble Metal Doped Silicon Nanocrystals Using Hybrid Density Functional Theory, Cedric Leon Mayfield
The Electronic Properties Of Noble Metal Doped Silicon Nanocrystals Using Hybrid Density Functional Theory, Cedric Leon Mayfield
Physics Theses
One of the most challenging issues in semiconductor physics is to engineer band structures for a particular device. Contemporary photovoltaic (PV) and photoelectrochemical (PEC) devices rely on defect energy levels and nano-scaling to customize their band structures. As the length scale of a material becomes comparable to the exciton Bohr radius the free particle behavior of charge carriers transition to bound states where energy levels are quantized. In this thesis, hybrid density functional theory has been used to study the electronic properties of silicon nanocrystals (SiNCs) having 75, 150 and 300 silicon atoms. The atomic coordinates were defined by two …
Nanoscintillators For Radiation Detection, Ryan Gregory Hall
Nanoscintillators For Radiation Detection, Ryan Gregory Hall
Physics Theses
In the search for faster, more effective methods for detection of and protection against radiological weapons, advances in materials for radiation detection are a critical component of any successful strategy. This work focuses on producing inexpensive, but highly sensitive, nanoparticle alternatives to existing single-crystal installations. Attention is given to particular types of promising inorganic scintillators: LaF₃, yttrium-aluminum-garnet (YAG), and SrF₂, each one an inorganic host doped with additional elements that encourage luminescent decay and increase effective Z-value. I examine the possible routes to synthesize these compounds, and the difficulties and benefits of each method. After synthesizing these materials, testing was …
First Principles Study Of Properties Of The Oxidized Cu(100) And Cu(110), Antoine Yongonga Olenga
First Principles Study Of Properties Of The Oxidized Cu(100) And Cu(110), Antoine Yongonga Olenga
Physics Theses
Copper based catalysts are of importance to a number of industrial processes including the synthesis of methanol, the reduction and decomposition of nitrogen oxides, and treatment of waste water. In copper catalysis surface oxidation and oxidic overlayers are believed to play a crucial role. In this work using density functional theory (DFT) within the generalized gradient approximation (GGA) we have studied the stability and associated electronic properties of the oxidized Cu(100) and Cu(110) surfaces. Especially, we have focused on studies of changes in the interlayer spacing, electron work function, binding energy, and density of states with oxygen coverage. We have …
Predicting A New Quaternary Photocatalyst Suitable For Pec Process To Produce Hydrogen And Determnation Of Its Structural, Electronics, And Optical Properties Using Density Functional Theory, Pranab Sarker
Physics Theses
Our present work represents a comprehensive theoretical and computational research in quest for predicting new photocatalysts suitable for photoelectrochemical process (PEC) to produce hydrogen by splitting water. We predict a new photocatalyst, CuBiW₂O₈ that exhibits some promising photocatalytic features seemed elusive to date. It is well known that all physical properties are calculated once ground state structure is known. However, knowing crystal structure is extremely challenging and was considered unpredictable before the material is synthesized. Our density functional theory (DFT) determines the crystal structure of CuBiW₂O₈ to be monoclinic which was later found energetically equivalent to its experimental counterpart. In …
Optimization Of Energy Resolution In The Digital Hadron Calorimeter Using Longitudinal Weights, Jacob Russell Smith
Optimization Of Energy Resolution In The Digital Hadron Calorimeter Using Longitudinal Weights, Jacob Russell Smith
Physics Dissertations
Particle physics seeks to describe matter in its most elementary structure. With lepton colliders; couplings of gauge bosons and heavy quarks, physics beyond the Standard Model, and properties of a recently discovered Higgs boson can be studied with very high precision. Particle Flow Algorithms (PFA), able to achieve necessary jet-energy and di-jet mass resolutions, require fine transverse and longitudinal segmentation from calorimeters. To validate digital imaging calorimetry in this context, a Digital Hadron Calorimeter (DHCAL) with single-bit (digital) readout on imbedded electronics from 1×1 cm2 pads throughout its volume has been constructed and exposed to particle beams as a large …