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Mathematical Model For The Role Of Multiple Pericentromeric Repeats On Heterochromatin Assembly, Puranjan Ghimire, Mo Motamedi, Richard Joh

Physics Publications

Although the length and constituting sequences for pericentromeric repeats are highly variable across eukaryotes, the presence of multiple pericentromeric repeats is one of the conserved features of the eukaryotic chromosomes. Pericentromeric heterochromatin is often misregulated in human diseases, with the expansion of pericentromeric repeats in human solid cancers. In this article, we have developed a mathematical model of the RNAi-dependent methylation of H3K9 in the pericentromeric region of fission yeast. Our model, which takes copy number as an explicit parameter, predicts that the pericentromere is silenced only if there are many copies of repeats. It becomes bistable or desilenced if …

Simulation Studies Of Topological Defect Behavior In Rank-2 Anti-Symmetric Tensor Fields, Wyatt Carbonell

Physics, Astronomy and Geophysics Honors Papers

Lorentz-violating models are a class of theories in which a fundamental field breaks the underlying Lorentz symmetry of a system action by assuming a nonzero vacuum expectation value. In this work, we consider a model which achieves such a Lorentz violation through a rank-2, anti-symmetric tensor field. We present a derivation of the equations governing the time evolution of this tensor field, the specifications of a program capable of numerically simulating this evolution through the solving of differential equations, evidence for the success of our simulation in accurately representing the model, and evidence against the physical viability of such a …

Nuclear Physics And Neutron Stars: Structure Of Compact Stellar Objects, Michel Geralddi Coria Magaña

2024 REYES Proceedings

The Tolman-Oppenheimer-Volkoff (TOV) equations provide a theoretical framework for modeling the structure of neutron stars and white dwarfs in hydrostatic equilibrium. Using Python and MATLAB, we simulate the mass-radius relationship, pressure, and density profiles of these compact stars, focusing on how ionized plasma dynamics contribute to their stability. By incorporating particle simulations into the visualization process, we model the internal forces of neutron stars and white dwarfs, demonstrating how computational tools offer unique insights into these celestial objects. The results align well with theoretical predictions and provide a solid foundation for future studies incorporating additional physical effects such as magnetic …

A Computational Study On The Structural Limits Of Neutron Stars Under Relativistic Conditions And Nuclear Phenomena, Marcelo Siles

2024 REYES Proceedings

This project investigates the modeling of neutron stars and white dwarfs using polytropic equations of state and relativistic corrections. By integrating relativistic effects into the Tolman-Oppenheimer-Volkoff (TOV) equations, we obtain more accurate predictions of neutron star properties, including mass-radius relationships and neutron degeneracy pressure. Non-relativistic models are inadequate under high pressures. Considering nucleon-nucleon interactions suggests that neutron stars can surpass the Tolman-Oppenheimer-Volkoff limit, theoretically reaching masses up to 2.3 𝑀_⊙. However, empirical data supports a more realistic mass range of 1.5 to 2.3 𝑀_⊙. The inclusion of neutron star crust modeling refines these predictions, indicating possible …

Topological Robustness Revealed By Real-Time Longitudinal And Transverse Studies, Hoai Anh Ho

Wayne State University Dissertations

For a long time, phases of matter were interpreted through order parameters based on specific symmetries, with phase transitions involving symmetry breaking. However, the discovery of Integer Quantum Hall Effect (IQHE) with the Hall quantized resistances h/(ne^2) (n is a filling factor) has reshaped our understanding of phases and transitions. The effectis characterized by dissipationless edge states and insulating bulk states. These exotic properties are determined by a nontrivial topological invariant rather than an order parameter, and unchanged in the presence of perturbations. However, when measuring IQHE, there are two variations that require explanation. First, it is precision level of …

Imaging Shapes Of Atomic Nuclei In High-Energy Nuclear Collisions, Star Collaboration

Physics and Astronomy Faculty Publications

Atomic nuclei are self-organized, many-body quantum systems bound by strong nuclear forces within femtometre-scale space. These complex systems manifest a variety of shapes1–3 , traditionally explored using non-invasive spectroscopic techniques at low energies4,5 . However, at these energies, their instantaneous shapes are obscured by long-timescale quantum fluctuations, making direct observation challenging. Here we introduce the collective-flow-assisted nuclear shape-imaging method, which images the nuclear global shape by colliding them at ultrarelativistic speeds and analysing the collective response of outgoing debris. This technique captures a collision-specific snapshot of the spatial matter distribution within the nuclei, which, through the hydrodynamic expansion, imprints patterns …

Electromagnetic Fields And Radiation From Localized Current Source Interacting With A Cosmic Axion Field In The Context Of Massive Axion Electrodynamics, Railing Chang, P. T. Leung

Physics Faculty Publications and Presentations

Electromagnetic fields from localized current source interacting with an oscillatory cosmic axion field are studied, accounting for the possibility of a finite photon mass. In particular, focus will be on the dipole radiation from static current sources. The Proca theory is generalized to include the axion field and solutions to the modified EM field equations are obtained to first order in the axion coupling parameter. Analysis of the interplay between the two vanishingly small parameters – the axion mass (via the coupling constant and the oscillating frequency) and the photon mass – is carried out with reference to possible future …

Development Of Advanced Instrumentation For High-Enthalpy Flow Characterization For The Onr-Uta Arc-Jet ”Leste” Facility, Ian Raybon

Mechanical and Aerospace Engineering Dissertations - Archive

Sustained hypersonic flight is an exceedingly challenging task comprised of a myriad of complex physical processes. At hypersonic speeds, which is defined by the presence of unique phenomena like high-temperature nonequilibrium flow, viscous and vorticity interactions, and thin shock layers, which are not seen in supersonic, transonic, or subsonic vehicles, the vehicle design is principally driven by the high levels of aerodynamic heating caused by the conversion of kinetic energy to internal energy. Gaining an understanding of how these physical processes interact with each other is required to develop a design methodology for this class of vehicles. Arc-jet wind tunnels …

Quantum Interference Enhancement Of The Spin-Dependent Thermoelectric Response, Runa X. Bennett, Joshua R. Hendrickson, Justin P. Bergfield

Faculty publications – Physics

We investigate the influence of quantum interference (QI) and broken spin-symmetry on the thermoelectric response of node-possessing junctions, finding a dramatic enhancement of the spin-thermopower (Ss), figure-of-merit (ZsT), and maximum thermodynamic efficiency (ηsmax) caused by destructive QI. Using many-body and single-particle methods, we calculate the response of 1,3-benzenedithiol and cross-conjugated molecule-based junctions subject to an applied magnetic field, finding nearly universal behavior over a range of junction parameters with Ss, ZsT, and reaching peak values of 2𝜋/ √3(𝑘/𝑒)2𝜋/3(𝑘/𝑒), 1.51, and 28% of Carnot efficiency, respectively. We also find that the …

Sequential Infiltration Synthesis Of Silicon Dioxide In Polymers With Ester Groups─Insight From In Situ Infrared Spectroscopy, Mahua Biswas, Vepa Rozyyev, Anil U. Mane, Amelia Korveziroska, Uttam Manna, Jeffrey W. Elam

Faculty publications – Physics

New strategies to synthesize nanometer-scale silicon dioxide (SiO2) patterns have drawn much attention in applications such as microelectronic and optoelectronic devices, membranes, and sensors, as we are approaching device dimensions shrinking below 10 nm. In this regard, sequential infiltration synthesis (SIS), a two-step gas-phase molecular assembly process that enables localized inorganic material growth in the targeted reactive domains of polymers, is an attractive process. In this work, we performed in situ Fourier transform infrared spectroscopy (FTIR) measurements during SiO2 SIS to investigate the reaction mechanism of trimethylaluminum (TMA) and tri(tert-pentoxy) silanol (TPS) precursors with polymers having ester functional groups (poly(methyl …

Examining Factors Related To Access To Rigorous High School Physics For Black Males: Evidence From The High School Longitudinal Study Of 2009, Jennifer Dacosta

CGU Theses & Dissertations

In the landscape of American education, Black male students face significant barriers in accessing advanced science courses, a challenge that underscores broader issues of equity and inclusion. This study investigated the factors influencing Black male high school students’ access to earn physics credits, focusing on the interplay between school offerings, academic prerequisites, counselor support, personal efficacy in science, and socioeconomic status. Through a detailed analysis of data from the High School Longitudinal Study of 2009, the research adopted a quantitative approach to examine how these variables collectively impact the educational trajectory of these students through multiple regression models which produced …

Exploring The Physical, Structural, Optical, And Gamma Radiation Shielding Properties Of Borate Glasses Incorporating Sb2o3/Moo3, Elsayed Salama, Hesham A. Yousef, Ahmed E. Hannora, Y. Assran

Basic Science Engineering

The 10 Na2O-(30-x) MoO3- 60H3BO3-xSb2O3 glass system was prepared using the melt-quenching technique, where 30 ≥ x ≥ 10 mol%. X-ray diffraction and Fourier transform infrared spectroscopy were used to investigate the amorphous nature of the glass structure and the impacts of MoO3 and Sb2O3. As the antimony trioxide (Sb2O3) concentration increases at the expense of molybdenum trioxide (MoO3), the density and molar volume increase, and the optical bandgap energy and refractive index also increase. The radiation shielding characteristics were measured using a NaI(Tl) scintillation detector and calculated using the Phy-X/PSD platform. The increase in Sb2O3 concentration increases the values …

Epr Study Of Irradiated Starch: Induced Radicals And Dose Assessment, Elsayed Salama, Ahmed M. Maghraby, Samy A. Anwer, M. El-Sayed

Basic Science Engineering

Irradiation of starch is of much importance to get rid of microbes and for disinfection. EPR study of the ionizing radiation-induced radicals can lead to the assessment of radiation doses delivered during irradiation. The EPR spectra properties, microwave power saturation behavior, short- and long-term temporal dependencies, and other significant factors are studied. Response of EPR spectra of irradiated starch over the range (0.5–10 kGy) was investigated. The time dependence study of the radiation-induced signal radicals of starch showed that variation of the EPR signal can be noticed within ±7.7% relative to the average value over 38 days following irradiation. Results …

Doubly Rotating Coordinates: Wave Functions In Magnetic Resonance Problems, Sunghyun Kim

Graduate Thesis and Dissertation 2023-2024

The nuclear spin response to a rotating field H has been theoretically investigated from the 1930s to the 1950s. Building upon Majorana's probability theory, the behavior of spin 1/2 is well-illustrated in the joint review by Rabi, Ramsey, andSchwinger, and their spin wave function ψ is succinctly restated by Gottfried: ψ(t) = e^-iI_zωt/ℏe^{-i[I_z(ω₀-ω)+I_xω₁]t/ℏ}ψ(0).

However, the complexity involved in evaluating the wave function ψ in terms of probability amplitudes C_m attributed to the noncommutative nature of spin operators [I_x, I …

Optical Seed Development For Yb-Fiber Laser, James G. Brutus

Graduate Thesis and Dissertation 2023-2024

Master Oscillator Power Amplifiers (MOPA) are laser systems that utilize a seed and pump amplification system to boost the output power of high-quality lower power seeding signals. MOPAs can generate high gain while avoiding many of the nonlinearities that negatively affect resonance-based lasers that are known to feature higher internal intensities. Additionally, MOPAs provide an easy alternative to the construction of novel laser technologies for higher output power as they can be easily combined with existing laser sources to amplify their output power.

This thesis outlines the design of an ytterbium-doped fiber laser (YDFL), featuring a MOPA architecture. The YDFL …

Visual Experience Enhancement In Augmented Reality Displays, Qian Yang

Graduate Thesis and Dissertation 2023-2024

In the dynamic arena of display technology, augmented reality (AR) displays represent a pivotal advancement, seamlessly bridging the digital and physical worlds. This dissertation delves into the realm of AR display technologies, spotlighting the challenges and limitations of current systems, including transparent and near-eye displays, and proposes innovative solutions to enhance user experience and display performance. With a focus on overcoming issues such as diffraction-induced image blur, the trade-off between resolution and field of view (FoV) in near-eye displays, and FoV constraints in waveguide-based displays, this research introduces new evaluation methods, optimization techniques, and system designs. First, the dissertation presents …

Dual Frequency Comb Mid-Ir – Thz Spectroscopy, Dmitrii Konnov

Graduate Thesis and Dissertation 2023-2024

The optical frequency comb is a coherent light source whose spectrum consists of hundreds of thousands perfectly equidistant narrow frequency components and precisely expressed in just two radio frequencies. Even though optical frequency combs were developed 25 years ago, that led to the Nobel Prize in Physics 2005, only recently there was a significant progress in generating broadband optical frequency combs in the mid-infrared. These achievements became possible due to the development of new types of robust fiber and solid-state lasers and the efficient downconverting of their frequencies through different techniques based on advanced nonlinear crystals. In this dissertation, I …

Human Visual Search Performance For Close Range Detection Of Static Targets From Moving Sensor Platforms, Jennifer Hewitt

Graduate Thesis and Dissertation 2023-2024

Search models based on human perception have been developed by military researchers over the past few decades and have both military and commercial applications for sensor design and implementation. These models are created primarily for static imagery, and accurately predict task performance for systems with stationary targets and stationary sensors, if the observer is given infinite time to make targeting decisions. To account for situations where decisions must be made on a shortened time scale, the time-limited search model was developed to describe how task performance evolves with time. Recent variations of this model have been made to account for …

Enhancing Scanning Tunneling Microscopy With Automation And Machine Learning, Darian Smalley

Graduate Thesis and Dissertation 2023-2024

The scanning tunneling microscope (STM) is one of the most advanced surface science tools capable of atomic resolution imaging and atomic manipulation. Unfortunately, STM has many time-consuming bottlenecks, like probe conditioning, tip instability, and noise artificing, which causes the technique to have low experimental throughput. This dissertation describes my efforts to address these challenges through automation and machine learning. It consists of two main sections each describing four projects for a total of eight studies.

The first section details two studies on nanoscale sample fabrication and two studies on STM tip preparation. The first two studies describe the fabrication of …

Solutions To The Kaluza-Klein Field Equations, Abel Eshete

All Graduate Theses, Dissertations, and Other Capstone Projects

This Alternate Paper Plan explores Kaluza-Klein theory, a multidimensional framework designed to unify Einstein’s gravitational field theory and Maxwell’s electromagnetic field theory. The objectives of this research can be summarized in two key areas: The first objective is to present a comprehensive introduction to the compactified Kaluza-Klein theory. The second aim involves the application of differential geometry, specifically E ́lie Cartan’s tetrad formalism, to derive exact solutions in two distinct scenarios: a. A Levi-Civita spacetime, b. A general spherical system. Furthermore, Lagrangian and Hamiltonian formalism are utilized to define stability conditions and describe gravitational lensing and Precession of Perihelion within …

Respiratory-Motion Matched Attenuation Correction For Dual-Gated Cardiac Single Photon Emission Computed Tomography (Spect), Christina Xing

Physics Theses - Archive

Cardiac and respiratory dual-gated single-photon emission computed tomography (SPECT) is a promising technique for minimizing the motion artifacts in myocardial perfusion imaging (MPI). However, attenuation correction (AC) for dual-gated SPECT using an attenuation map averaged over the respiratory cycle may lead to mismatched attenuation correction artifacts. In this study, we propose a respiratory motion-matched attenuation correction (RMM-AC) to further improve dual-gated SPECT. For each respiratory gate, RMM-AC uses an attenuation map that matches the SPECT image in a 4D reconstruction framework. Filtered backprojection reconstruction without AC (FBP-nAC) and 4D reconstruction with the attenuation map averaged over all respiratory gates (AVE-AC) …

The Weighty Words Of Lord Rayleigh, John Adam

Mathematics & Statistics Faculty Publications

[First paragraph] Lord Rayleigh, a.k.a. John William Strutt, 3rd Baron Rayleigh (1842–1919), was, in my opinion, a quintessential mathematical and experimental physicist and, indeed, a classical applied mathematician of the highest order for his era. Among the many honors he received, the most prestigious was the 1904 Nobel Prize in Physics “for his investigations of the densities of the most important gases and for his discovery of argon in connection with these studies.” He was one of the very few members of so-called British “higher nobility” who won fame as an outstanding scientist.

Sky Smiley Face: Solutions For Fermi Questions, November 2024, John Adam

Mathematics & Statistics Faculty Publications

Question 2(a): By rotating Fig. 2 counterclockwise by 90°, explain why circumhorizontal arcs (CHAs) [Figs. 1(b) and (c)] form (under favorable conditions) only when the solar altitude exceeds 58° of arc. (In this case, the incoming ray enters a vertical face of an ice crystal and exits via the lower horizontal face.)Question 2(b): By considering the tilt of Earth’s imaginary N–S axis toward the plane of its orbit around the Sun (∼23.5°), explain why in the northern hemisphere CHAs cannot be seen above about latitude 56° N.

Gas Evolution Of A Nickel-Zinc Cell, Niklas Landgraf

Graduate Theses/Dissertations

Batteries are a foundational technology in some of the industries most essential to humanity. Often, their advancement to achieve better performance impacts human lives positively. There are a wide variety of battery chemistries that have been utilized, and the differences in their properties have caused them to be used in many distinct niche applications. Nickel-Zinc (NiZn) batteries are desirable because of their recyclable materials, high cell voltage, and high cycle-life. However, it experiences undesirable shape-change of its electrode materials and gas production due to the electrolysis of the aqueous electrolyte. These can lead to a decrease in capacity over many …

Compton Scattering Of Mammographic Soft X-Ray Beams By Alkali And Transition Metal Salt Filters Produce X-Ray Interference Zones That May Have Treatment Potential For Localized Cancer Lesions, Subhendra N. Sarkar, Eric Lobel, Sabina Rakhmatova, Derbie Desir, Somdat Kissoon, Daler Djuraev, Katie Tam

Publications and Research

In breast x-ray imaging scattered radiation adds 50% of harmful radiation dose from anisotropic Compton scattering mechanism. We have been working with double layered inorganic salt materials that can induce Compton scattering to the incident mammographic x ray beams (in 20-30 kVp range) with adequate isotropy (angular control). Typically metal nitrates and alkali halide salt layers are shown here to cause low energy radiation interference zones with high and low photon intensities and local flux heterogeneity in terms of flux covariance. Spatial variation of low energy photon flux creates concentrated and sparse radiation zones that may be used to induce …

A Method Of Measuring Hot Charge Carrier Drift Mobility In Germanium Detectors, Kyler Kooi

Dissertations and Theses

High purity germanium is a popular radiation detecting medium due to the excellent energy resolution that is achieved. The unique semiconducting properties of germanium allow a small amount of energy to create free charges in the germanium, which are then collected as a signal. Germanium detectors also have good spatial resolution. The shape of the signal can be used to identify the location of energy deposition in the crystal. Both of these properties make germanium detectors a popular choice in many felds, including security, medical, astrophysics, and particle physics. The properties of a germanium crystal should be well understood and …

Development Of Cryogenic Scintillation Detectors For The Search Of New Physics, Keyu Ding

Dissertations and Theses

Coherent elastic neutrino-nucleus scattering (CEvNS) was first proposed in 1974. Despite having the largest cross-section among all low-energy neutrino couplings predicted in the Standard Model (SM), CEvNS detection remains challenging due to its only experimental signature being a low-energy nuclear recoil. In 2017, the COHERENT collaboration successfully observed CEvNS for the first time. A 14.6 kg low-background doped CsI at room temperature was placed 20 meters away from the 1.4 MW Spallation Neutron Source (SNS) at the Oak Ridge National Laboratory (ORNL). The SNS's pulsed proton beam provides exceptional background rejection and high-intensity neutrinos, making it ideal for CEvNS detections. …

Development Of Low Threshold Germanium Detectors For The Search Of Low Mass Dark Matter, Pramod Acharya

Dissertations and Theses

This dissertation explores using high-purity germanium (Ge) crystals for low-mass dark matter (DM) detection, focusing on enhancing crystal quality and identifying key crystal growth parameters. The study assesses the electrical properties of refined Ge materials through Hall Effect measurements and uses machine learning to predict impurity profiles, achieving levels conducive to high-resolution DM detectors. Utilizing a planar Ge detector fabricated at Texas A$\&$M and operated at cryogenic temperatures at the University of Minnesota, the study reveals time-dependent internal charge amplification through impact ionization. Research on charge transport dynamics in a cryogenic p-type Ge detector uncovers evolving charge dynamics and cluster …

Next-Generation High-Performance Virtual Reality And Augmented Reality Light Engines, Zhiyong Yang

Graduate Thesis and Dissertation 2023-2024

The immersive virtual reality (VR) and the optical see-through augmented reality (AR) are expected to revolutionize human lives in work, education, entertainment, healthcare, spatial computing, and digital twins, just to name a few. Next-generation VR/AR devices should exhibit a wide field-of-view (FoV), crisp image without screen-door effect, high dynamic range, compact form factor and lightweight, and low power consumption. Such demanding requirements pose a significant challenge to traditional direct-view display panels. To address these technical challenges, novel approaches need to be proposed. This dissertation is devoted to developing next-generation high-performance display light engines toward high resolution density, high optical efficiency, …

Probing The Ising Model’S Thermodynamics Through Restricted Boltzmann Machines, Xiaobei (Emma) Zhang

HMC Senior Theses

This thesis explores the connection between physics and machine learning by using Restricted Boltzmann Machines (RBMs) to study the thermodynamic properties of the Ising model. The Ising model is a simple but realistic model that captures the magnetic behavior of a system, where spins occupy a lattice of sites and different spin configurations correspond to different energies. The model exhibits phase transitions between ferromagnetic and paramagnetic phases as a function of temperature. RBMs are two-layered neural networks that can learn probability distributions over binary spins. The study generates 2D Ising model data at different temperatures using Monte Carlo simulations, including …