Physics Commons^™

Effects Of Coulomb Collisions On The Structures Of Fast Magnetosonic Shocks, Bo Farnell

Physics and Astronomy Undergraduate Senior Theses

We present fully kinetic particle-in-cell simulations demonstrating qualitative effects of binary Coulomb collisions on fast magnetosonic shocks. We find that with a sufficiently high collisional frequency, shock rippling and reformation can be inhibited, creating stationary, laminar shocks. We see that collisions rapidly bring the reflected population into equilibrium with the upstream population, adding credibility to existing theories that the separation of these two populations create these dynamical behaviors around the shock transition region. We also see that Ohmic heating from Coulomb collisions can suppress instabilities.

Investigation Of Some Structural And Spectroscopic Characteristics Of Inverted Alkali–Bismuth Fluoroborate Glass Containing Holmium Ions, R. M. Ramadan, D. Atta, Ahmed H. Hammad, Ahmed R. Wassel

Nanotechnology Research Centre

An inverted glass system of sodium bismuth fluoroborate with the composition of (30-x)NaF–40Bi2O3–30B2O3–xHo2O3 was successfully fabricated using the traditional melt-quenching method, where the holmium content was introduced at the expense of the sodium fluoride (NaF) modifier to modify the glass structure and improve the optical and spectroscopic properties. The substitution of NaF with Ho2O3 resulted in an increase in the glass density (ρ) from 4.888 to 5.322 g/cm³. The glass structure consists of BiO3, BiO6, BO3, BO2F, BO4, and BO3F units. The incorporation of Ho³⁺ ions into the host glass network …

Spatial Extent And Vertical Structure Of Marine Heatwaves In Chesapeake Bay, Nathan P. Shunk, Piero L. F. Mazzini, Ryan K. Walter, Kyle E. Hinson, Pierre St-Laurent, Marjorie A. M. Friedrichs

Physics

Marine heatwaves (MHWs) adversely impact marine ecosystems globally, yet data scarcity limits our understanding of their subsurface extent, particularly in estuaries. Using a high-resolution regional ocean model, we characterized the horizontal extent and subsurface structure of MHWs across the Chesapeake Bay (CB). Additionally, we developed a supplementary definition for local climatology-identified MHWs, “Vertical MHWs,” which quantifies their water column presence, and developed a new MHW vertical classification scheme. Surface MHWs were generally shorter, more frequent and intense, and impacted ∼5% of the CB surface area, while the deepest MHWs were generally longer, less frequent and intense, and regularly occupied >50% …

Computational-Experimental Synergy As A Predictive And Interpretive Tool Through Metal-Organic Framework Investigations, Cristian Sayers

Graduate Student Theses and Dissertations

In the search for tunable materials platforms capable of addressing both clean energy conversion and viable post-combustion carbon capture, metal-organic frameworks (MOFs) have emerged as a uniquely versatile class of porous solids offering high specific surface area, structural tunability, and chemically addressable metal nodes and organic linkers. Realizing their potential requires understanding behavior that spans atomic-scale electronic structure and bulk-scale property response, a regime in which neither computation nor experiment alone is sufficient. This work attempts to develop a tighter integration between density functional theory (DFT) and laboratory investigation, treating the two modalities as mutually informing probes of the same …

Characterizing Stiffness Dynamics Of Normal And Malignant Breast Spheroids Using Brillouin Microscopy, Razanne Rafat Zaghloul, Karlin Hilai, Chenjun Shi, Jitao Zhang

Medical Student Research Symposium

Background: Breast cancer progression and metastasis are closely linked to alterations in the mechanical properties of tumor cells and their microenvironment. Softer, more deformable cells are often associated with higher metastatic potential. While atomic force microscopy (AFM) is the current gold standard for mechanical characterization, it is limited to surface measurements and can damage 3D cultures. It remains unclear how the mechanical properties evolve over time in normal versus malignant spheroids. This study utilizes Brillouin light-scattering microscopy, a non-contact and label-free optical technique, to assess stiffness changes in normal and malignant breast epithelial spheroids over time. Understanding these mechanical signatures …

Deep Search For Joint Sources Of Gravitational Waves And High-Energy Neutrinos With Icecube During The Third Observing Run Of Ligo And Virgo, R. Abbasi, M. Ackermann, Mario C. Diaz, Francisco Llamas Villarreal, Soma Mukherjee, Volker Quetschke, Wenhui Wang

Physics & Astronomy Faculty Publications

The discovery of joint sources of high-energy neutrinos and gravitational waves has been a primary target for the LIGO, Virgo, KAGRA, and IceCube observatories. The joint detection of high-energy neutrinos and gravitational waves would provide insight into cosmic processes, from the dynamics of compact object mergers and stellar collapses to the mechanisms driving relativistic outflows. The joint detection of multiple cosmic messengers can also elevate the significance of the common observation even when some or all of the constituent messengers are subthreshold, i.e., not significant enough to declare their detection individually. Using data from the LIGO, Virgo, and IceCube observatories, …

Enhanced No₂ Gas Sensing Using Silver-Doped Cadmium Telluride Nanocrystalline Thin Films, Tunis Balasim Hassan

Karbala International Journal of Modern Science

Nitrogen dioxide (NO₂) is a toxic pollutant that necessitates sensitive and reliable monitoring systems. Conventional gas sensors often lack adequate responsiveness and fast recovery under changing conditions and therefore create a need for semiconductors with enhanced performance, especially at high industrial temperatures (around 250 °C). The study therefore aims to synthesis and evaluate silver-doped cadmium telluride (Ag:CdTe) thin films as NO₂ gas sensors. Pure CdTe and Ag:CdTe with silver concentrations of 5, 10, and 15 wt% were prepared by a co-precipitation process. XRD verified cubic symmetry with a progressive fall in crystallite size (6.67 nm to 5.46 nm at 15 …

An Analytical Framework For Quantifying Urban And Community Resilience To Natural Hazards From Cell-Phone Gps-Location And Traffic-Flow Data, Georgios Chatzikyriakidis

Civil and Environmental Engineering Theses and Dissertations

Urban areas are increasingly exposed to natural hazards while accommodating a growing share of the global population, yet a consistent science-based framework for quantifying urban and community resilience remains lacking. This dissertation develops a physics-based analytical framework grounded in statistical mechanics and the quantitative theory of Brownian motion. A city is conceptualized as a complex medium in which citizens move analogously to Brownian particles within a viscoelastic environment, influenced by socioeconomic interactions and infrastructure functionality.

A central premise is that urban resilience, interpreted as engineering resilience (an outcome), can be quantified through a single metric: the mean-square displacement MSD=⟨r²(t)⟩, of …

Design, Fabrication, And Characterization Of Silicon Nitride Microresonator Optical Frequency Combs, Lala Rukh

Optical Science and Engineering ETDs

Optical frequency combs consist of equidistant optical frequencies and have numerous applications ranging from optical metrology to medical diagnostics. Initially, frequency combs were based on bulky mode-locked lasers, but advancements in integrated photonics enabled the generation of frequency combs in chip-scale resonators (microcombs) using Kerr nonlinearity. These miniaturized systems present various challenges, including increased propagation losses, enhanced thermal effects, and the extension of microcombs to visible wavelengths. In this dissertation, I will focus on addressing these challenges in silicon nitride (SiN) resonators. First, this thesis focuses on the fabrication of high-Q SiN resonators and the impact of fabrication parameters on …

A Quantum Phase Space Description Of Local Noise In Atomic Ensembles, Andrew Kolmer Forbes

Physics & Astronomy ETDs

Nonclassicality in quantum sensors can improve sensitivity, but often increases susceptibility to noise. Thus, modeling physically relevant noise sources and analyzing their effect on quantum metrology are both of importance to the field of quantum sensing. In this dissertation, I demonstrate that local noise sources, which are present in almost all many-spin systems, can be tractably modeled when assuming permutation symmetry of the noise, and we show that many common local noise sources can be mapped to a Fokker-Planck equation on quantum phase space. We apply this description of noise to study quantum sensing using noisy probe states and establish …

Optical Nuclear Spin Detection In Diamond And Varifocal Metasurface Optics, Maxwell D. Aiello

Physics & Astronomy ETDs

This dissertation presents two experimental investigations at the intersection of quantum sensing and precision optical instrumentation. The primary project demonstrates optically detected nuclear magnetic resonance (NMR) of ¹³C nuclear spins in diamond, using state-selective Landau-Zener transitions under microwave frequency sweeping to bidirectionally transfer spin polarization between nitrogen-vacancy (NV) electron spins and remote ¹³C nuclear spins. This enables optical polarization and readout of large ensembles of polarized nuclear spins at low magnetic fields and room temperature, with spin dephasing times limited by longitudinal relaxation of nearby NV electron spins. The secondary project reports the design, fabrication, and characterization of …

Realizing The Long Wavelength Array Swarm, Craig Anthony Taylor

Physics & Astronomy ETDs

Sensitive modern radio interferometers are costly to build and operate at the university level. The `swarm telescope' concept addresses this challenge by enabling the collaborative use of individual telescope systems, overseen by separate institutions, that come together to form a more powerful and manageable facility. This dissertation focuses on demonstrating this concept using the Long Wavelength Array (LWA) by commissioning an aperture synthesis telescope consisting of interconnected LWA stations, called the LWA Swarm. The presented work details building a cost-efficient prototype LWA platform -- the LWA--North Arm station -- to enable synthesis imaging using the 3-element interferometer comprised of LWA1, …

A Multi-Frequency Investigation Of Compact Symmetric Objects, Evan E. Sheldahl

Physics & Astronomy ETDs

Some of the brightest objects in the radio sky are jetted active galactic nuclei (AGN), supermassive black holes in the centers of galaxies that accelerate relativistic electrons into twin radio jets. One of the biggest questions surrounding AGN is how they produce radio jets in the first place. We search for an answer to this question by exploring a class of AGN that have uniquely well-constrained physical properties and are thought to be in an early stage of AGN development: compact symmetric objects (CSOs). Throughout our journey with these remarkable sources, we quantify their efficacy as calibrator sources for radio …

Quantum Control Protocols For Robust Quantum Computing, Leeseok Kim

Electrical and Computer Engineering ETDs

The fundamental goal of quantum computing is to precisely control quantum systems to perform meaningful tasks, including implementing high-fidelity quantum gates for reliable quantum computation and accurately simulating complex quantum many- body dynamics. In this dissertation, we develop improved quantum control protocols for three distinct objectives, quantum error suppression, quantum optimal control, and analog quantum algorithms, achieving performance beyond standard approaches. First, we introduce new dynamical decoupling protocols, including both determin- istic and randomized constructions, that can substantially outperform conventional deterministic sequences. We then extend the randomized approach to dynamically corrected gates. Second, we propose a randomized quantum optimal control …

Surface Directed Microwave Assisted Fabrication Of Znmn2o4 And Its Composite As Anode Materials For Lithium Ion Battery, Anirudh Singh

Electronic Theses & Dissertations

The Lithium-ion batteries (LIBs) are widely utilized in portable electronics and electric/hybrid electric vehicles. However, the limited theoretical capacity of graphite (372 mA h g⁻¹) restricts further advancements. In our recent work, a series of ZnMn₂O₄ materials with various additives were synthesized using the microwave reaction method and evaluated as anodes for LIBs. Additives such as 2-methylimidazole (2MIM), polyvinyl alcohol (PVA), and cetyltrimethylammonium bromide (CTAB) were employed to prepare ZnMn₂O₄ with distinct morphologies. Our findings revealed that ZnMn₂O₄  with pure phases was achieved when 2MIM and CTAB were used as additives. …

The Yorp Effect In Reboundx, Kaelyn Clement

UNLV Theses, Dissertations, Professional Papers, and Capstones

The Yarkovsky-O’Keefe-Radzievskii-Paddack (YORP) effect is a radiation-induced torque that can affect the spin and rotational obliquity of small bodies. It has been observed to alter the rotation rate of asteroids in the Solar System (Lowry et al. 2007; Taylor et al. 2007). Under extreme circumstances, YORP can cause a body to fragment, inducing a cascade of fissions. This effect may be important in driving the pollution of white dwarf atmospheres in conjunction with other radiative forces. I developed a YORP calculator for REBOUNDX (Tamayo et al. 2020), an extensional library to the N-body integrator REBOUND (Rein & Liu 2012). I …

Validation And Implementation Of Automated Planning Optimization In Utah Valley Hospital, Oluwatobi Adeniji

UNLV Theses, Dissertations, Professional Papers, and Capstones

The increasing complexity of modern radiotherapy demands planning workflows that are efficient, standardized, and dosimetrically robust across diverse disease sites. Knowledge-based planning (KBP) systems such as RapidPlan offer a data-driven approach to automate and improve treatment planning by learning geometric–dosimetric relationships from high-quality clinical plans. In this work, I am evaluating the performance, generalizability, and clinical applicability of vendor-provided RapidPlan models across seven anatomical sites: intracranial SRS, prostate SBRT, right and left lung SBRT, liver SBRT, head and neck, and glioblastoma. Subsequently, a complementary institution-specific SRS model tailored to single-isocenter multitarget workflows was created. Seventy retrospectively selected patients were replanned …

Establishing A Comprehensive Framework For Sfrt Lattice Treatments: Optimization, Planning, And Clinical Evaluation, Gregory M. Gill

UNLV Theses, Dissertations, Professional Papers, and Capstones

Spatially fractionated radiation therapy (SFRT) using lattice radiotherapy (LRT) has emerged as a promising treatment technique for bulky, nonresectable tumors by delivering spatially heterogeneous dose distributions consisting of high-dose vertices embedded within lower-dose regions. Although early clinical experiences have demonstrated potential therapeutic benefit, widespread clinical implementation of LRT remains limited due to the absence of standardized treatment planning workflows, consistent optimization strategies, and clearly defined evaluation metrics for heterogeneous dose distributions. The objective of this study is to develop and evaluate a structured framework to support efficient, reproducible, and safe clinical implementation of LRT.

To address these challenges, a comprehensive …

Micromagnetic Simulations Of Field-Driven Antiferromagnetically Coupled Skyrmions, Aidan D. Kirk

Physics and Astronomy Honors Papers

Competing magnetic interactions can stabilize smooth magnetization textures and can be characterized by a topological winding number. A specific spin configuration/texture, spatially localized within a two-dimensional plane, is commonly known as a skyrmion. On the classical level, the significance of skyrmions for condensed matter physics and their potential for applications, ranging from spintronic devices to qubits, has been intensely investigated in recent years. This thesis focuses on antiferromagnetically (AF) coupled Neel-type magnetic skyrmions, which are comprised of two skyrmions with opposite topological charges, yielding a net topological charge of 0. This configuration results in the cancellation of their respective Magnus …

Cold Plasma Treatment Of Hydroponically Grown Basil: Effects On Essential Oil Composition For Sustainable Applications (Ocimum Basilicum), Judith Serwaa Marfo

Seton Hall University Dissertations and Theses (ETDs)

Abstract Essential oils are known to have medicinal benefits and pharmaceutical applications. This study investigates the impact of cold plasma treatment on hydroponically cultivated basil (Ocimum basilicum), focusing on physical growth traits, and essential oil composition. Preliminary trials validated our solvent extraction protocol using IPA, hexanes, and methanol without heat on store-bought basil. Rotary evaporation and GC-FID analysis successfully identified key compounds; eugenol, estragole, eucalyptol, and linalool. Plasma-treated hydroponic plants exhibited enhanced physical characteristics, including larger leaves and intensified green pigmentation, compared to untreated controls under identical conditions. The plasma treatment didn't just increase how much oil was extracted, but …

Phase Identification Of (La, Sr)Coo3 Solid Oxide Cell Electrode Films Using Dft Based Exafs, Musab A. Siddiqui

Seton Hall University Dissertations and Theses (ETDs)

Perovskite structured mixed ionic electronic conductor (MIEC) materials formed as films by metal-organic precursor deposition have excellent electrochemical performance in solid oxide cell (SOC) air electrode applications due to the large surface area provided by the manufacturing approach. MIEC films created by metal organic precursor deposition are often multi-phased due to low heat treatment temperatures and locally generated low oxygen partial pressures caused by the release of carbonaceous gases during the drying step of the fabrication process. In this work, we use extended x-ray absorption fine structure spectroscopy (EXAFS) to examine the phase contents of La0.8Sr0.2CoO3 (LSC82) and La0.6Sr0.4CoO3 (LSC64) …

Constructing A Laser Stabilization System For Frequency Metrology, Stephanie Letourneau

UNLV Theses, Dissertations, Professional Papers, and Capstones

Frequency metrology and quantum control, which uses light as a tool for measurement and manipulation, relies on spectrally narrow, stable lasers. Often thought of as being perfectly monochromatic and coherent, in reality, the free-running instantaneous linewidth of lasers can be on the order of hundreds of kHz in the millisecond time-frame and drift on the order of tens of MHz over hours. To correct for these instabilities in real-time, a variety of laser stabilization methods have been implemented, including the Pound-Drever-Hall (PDH) method, saturation absorption spectroscopy (SAS), and dichroic atomic vapor laser locking (DAVLL). All of these methods rely on …

Relativistic Transients From Compact Objects: Radiation Processes And Geometric Effects, Connery Chen

UNLV Theses, Dissertations, Professional Papers, and Capstones

Relativistic transients from compact objects probe the most extreme regimes of physics, where strong gravity, ultra-relativistic outflows, and high-energy radiation operate simultaneously; understanding the underlying radiation mechanisms and extrinsic geometric and relativistic effects is essential for interpreting observations and constraining source properties. I develop theoretical and computational frameworks to quantify how geometry and relativistic motion shape observed emission from fast radio bursts, gamma-ray bursts, and neutron star mergers. I analyze fast radio bursts from the Galactic magnetar SGR J1935+2154 and show that emission geometry strongly governs burst energetics and detection probability, and influences the link between radio and X-ray emission. …

Strongly Confined Bismuth Antimonide Quantum Dots, Min Khadka, Rajendra Subedi, Qiaohui Zhou, Xin Lu, Joelin A. Agyei-Mensah, Miguel José-YacamáN, Guillaume Lang, Etienne Herth, Gregory Guisbiers

Faculty Scholarship

Bismuth antimonide (Bi1–xSbx) has emerged as a highly promising material for quantum applications due to its complex band structure. In this study, spherical Bi1–xSbx quantum dots (QDs), with a diameter of around 8 ± 2 nm, were successfully synthesized by pulsed laser ablation in liquids. The energy bandgap was determined at 2.02 ± 0.27 eV, which is significantly higher than the bulk value (∼0.025 eV). The strong confinement nature of the dots was confirmed by the Raman peak shifts. The chemical composition of the Bi1–xSbx QDs was measured to be around 77 ± 2 at. % of Bi and 23 …

Modeling Velocity Distributions Of Interstellar Neutral Hydrogen In The Heliosphere, Lucas Robert Dyke

Dartmouth College Ph.D Dissertations

As interstellar neutral hydrogen (ISN H) is the most abundant neutral element in the helio- sphere, the region within which the solar wind interacts with the portion of the interstellar medium through which our solar system moves through, it is integral that we aim to under- stand its many properties and interactions within this region. This work details the synthesis and use of a model of ISN H, using trajectory methods to backtrace from a target point at a radial distance of 1 au where explorer probes like Interstellar Boundary Explorer (IBEX) and Interstellar Mapping and Acceleration Probe (IMAP) reside. …

Momentum Space Algorithm For Electronic Structure Of Double-Incommensurate Trilayer Graphene, Kenneth Silver Beard

LSU Doctoral Dissertations

Numerical algorithms for computing the electronic structure of incommensurate 2D-materials using ab initio models are critical for predicting material properties and guiding experiments. For bilayers, momentum space and continuum models have been introduced to approximate observables of ab initio tight-binding models using a momentum description, despite the lack of periodicity in the tight-binding model required for Bloch theory. A similar structure has been introduced for double-incommensurate trilayers using a continuum model, where the three lattices are mutually incommensurate. However, this description leads to a four-dimensional lattice space, and numerical convergence of the density of states has been observed to be …

Geometric Approaches To Memory Formation In Soft Matter, Gentian Muhaxheri

Dissertations - ALL

The primary focus of this dissertation is the development of a geometric framework for understanding memory formation in systems composed of interacting hysteretic elements, or hysterons. Using tools from bifurcation and catastrophe theory, this work provides a description of how complex memory behaviors emerge from the structure of the system's configuration space and the system bifurcations under external driving. As a concrete model system, we study networks of connected rubber balloons subjected to different inflation protocols. Under pressure control, the system maps naturally onto a Preisach-type system of non-interacting hysterons and exhibits return point memory. In contrast, under volume control, …

Quasiparticle Poisoning Of Superconducting Fluxonium Qubits, Kesavan Manivannan

Dissertations - ALL

Superconducting qubits based on Josephson junctions have emerged as a leading hardware platform in the quest to realize large-scale quantum computers. However, qubit decoherence remains a major hurdle on the path toward fault-tolerant quantum computing. In particular, excess quasiparticle (QP) excitations constitute a significant source of dissipation in superconducting quantum devices. The empirically observed QP density in these systems is orders of magnitude larger than that predicted by Bardeen-Cooper-Schrieffer (BCS) theory. Moreover, QP poisoning due to high-energy particle impacts can cause correlated errors that simultaneously affect multiple qubits, thereby impeding quantum error correction. Although QP-induced decoherence has been extensively studied …

Evidence For Environmental Stripping In The Coma Cluster, Richard T. Pomeroy, Juan P. Madrid, Conor R. O’Neill, Alexander T. Gagliano

Physics & Astronomy Faculty Publications

The stability and longevity of globular clusters (GCs) make them effective tracers of the dynamical histories of galaxies in cluster environments. We construct a catalog of 23,351 GC candidates in the Coma Cluster using imaging from the Hubble Space Telescope Advanced Camera for Surveys. We cross-match galaxy data from the SIMBAD, NASA/IPAC Extragalactic Database, and Sloan Digital Sky Survey archives to construct a galaxy sample and model their GC populations using the GC specific frequency. We find several galaxies with significantly smaller GC populations than expected from their luminosities, consistent with either tidal stripping or intrinsically low formation efficiencies. We …

Mapping The Rigid Landscapes Of Disordered Networks And Active Solids, Tyler Hain

Dissertations - ALL

Biological systems are able to exhibit remarkable and exotic mechanical properties by tuning their microscopic internal degrees of freedom in order to accomplish global functions. One of the most interesting mechanical behaviors of some such materials is the ability to transition between stiff solid-like states and soft fluid-like states in order to initiate specific flow patterns or tune their mechanical response. Not only this, but they are able to selectively cross this transition while also being optimized for other functions. In this dissertation I explore numerical and analytical methods for mapping the landscapes of states on the edge of rigidity …