Physics Commons^™

Lepton Flavor Violation And Lepton Flavor Universality Violation: Opportunity For New Physics Beyond The Standard Model, Fang Xu

Arts & Sciences Electronic Theses and Dissertations

The Standard Model (SM) of Particle Physics has been remarkably successful in explaining the fundamental forces and classifying elementary particles. However, there are various experimental and theoretical indications that suggest the need to go beyond the SM (BSM) and expand our understanding of the fundamental nature of the universe. From a theoretical perspective, there are several limitations of the SM that suggest the existence of a more fundamental theory. For example, the SM does not incorporate gravity, and it fails to explain the hierarchy problem. Additionally, the nature of dark matter and the origin of the mass hierarchy of elementary …

The Physics Of Associative Polymers And Applications To Biomolecular Condensates, Furqan Dar

Arts & Sciences Electronic Theses and Dissertations

Biomolecular condensates represent a new and ubiquitous class of membraneless organelles (MLOs) that are essential for healthy cellular functioning. The constituent molecules of such condensates span a vast bio-macromolecular gamut from intrinsically disordered regions and proteins (IDPs/IDRs), to RNA and RNA-binding proteins (RNPs), to polymerases and DNA etc. Apart from being part of the regular healthy cell cycle, these condensates are also implicated in many diseases, most notably progressive neurodegenerative diseases like Amyotropic Lateral Sclerosis (ALS) and Huntingtin's Disease (HD). Since the constituent molecules of these condensates span a broad range of length scales and modes of interaction, uncovering a …

Quasiparticle And Excitonic Effects In Two-Dimensional Van Der Waals Materials, Linghan Zhu

Arts & Sciences Electronic Theses and Dissertations

Since their discovery, low dimensional van der Waals materials have attracted increasing research interests. They serve as ideal platforms to study novel physics in reduced-dimensional systems, and are critical in nowadays’ nanotechnology applications. Due to the reduced dielectric screening in low dimensions, strong excited state properties dictate their electronic, transport and optical properties, the study of which calls for a description of the many-particle interactions beyond the traditional density functional theory. This is where the many-body perturbation theory comes into play. In this thesis, I will present a comprehensive study of the quasiparticle and excitonic properties of a variety of …

Systems Level Analysis Of Organelle Biogenesis In Saccharomyces Cerevisiae, Kiandokht Panjtan Amiri

Arts & Sciences Electronic Theses and Dissertations

Eukaryotic cells contain hundreds of subcellular structures that serve different functions to maintain cellular homeostasis. A hallmark of Eukaryotic cells is its compartmentalization into membrane-bound organelles. One of the grand challenges in quantitative cell biology is understanding the precision with which cells assemble and maintain subcellular organelles. Despite identification of numerous molecular factors that regulate organelle sizes we lack insight into the quantitative principles underlying organelle size control. We examine organelle sizes from Saccharomyces cerevisiae and human iPS cells with mathematical theory to show that cells can robustly control average fluctuations in organelle size. By demonstrating that organelle sizes obey …

The Effect Of Ionization Density In Applications Of Radiation Detection, Dosimetry, And Therapy, Daniel Mulrow

Arts & Sciences Electronic Theses and Dissertations

This dissertation covers a wide range of topics but is linked by the common theme of radiation interacting with materials and studying the result of those interactions. The introduction describes the fundamentals of how radiation interacts with material and how we are able to detect that radiation and the application of how we use those interactions in radiation oncology. The thesis starts with a chapter detailing the temperature dependence of the photophysics in two organic scintillators. This chapter is the foundation for a future study that will look the degree to which these scintillators can distinguish between gammas and neutrons …

Electronic, Optical, And Thermal Probes Of The Layered Mott Insulator Α-Rucl3 In The Atomically Thin Limit, Jesse Balgley

Arts & Sciences Electronic Theses and Dissertations

Alpha-ruthenium(III) chloride (α-RuCl3) is a layered Mott insulator and van der Waals material that can be cleaved down to a single atomic layer. This material is a promising candidate to realize the Kitaev quantum spin liquid, a strongly correlated phase of matter expected to host fractionalized quasiparticles and a potential platform for topological quantum computation. When α-RuCl3 is placed in direct contact with the layered semimetal graphene we observe a strong charge transfer between the two materials despite the electrically insulating nature of α-RuCl3, which absorbs ≈ 4 × 10^13 electrons/cm^2 from the graphene. Remarkably, this charge transfer persists and …

Exploring The Solar System Through Space And Time Via Laboratory Investigations Of Extraterrestrial Material, Kainen Lee Utt

Arts & Sciences Electronic Theses and Dissertations

This dissertation reports the results of laboratory studies of lunar soil samples, gas-to-solid filamentary enstatite grains from a likely-cometary interplanetary dust particle (IDP), and exogenous clasts in the CH3 chondrite Acfer 182 that likely originated from a differentiated basaltic planetesimal. These studies were performed using multi-instrument analyses involving high-resolution scanning and transmission electron microscopy (SEM/TEM) techniques, nanoscale secondary ion mass spectrometry (NanoSIMS), synchrotron infrared nanospectroscopy (SINS), electron probe microanalysis (EPMA), and Raman spectroscopy. The results of these analyses are used to examine space weathering phenomena, energetic processing and radial transport in the protoplanetary disk, and the origins of igneous inclusions …

Computational Methods For Analysis Of Data For Conformational And Phase Equilibria Of Disordered Proteins, Jared Michael M Lalmansingh

Arts & Sciences Electronic Theses and Dissertations

Intrinsically disordered proteins and regions (IDPs / IDRs) are a class of proteins with diverse conformational heterogeneity that do not fold into a tertiary structure due to the lack of a native structural state. Consequently, disordered proteins are remarkably flexible and exhibit multivalent properties that enable them to adopt myriad functional roles within the cell such as: signaling transduction, transcription, enzymatic catalysis, translation, and many more. Due to their multivalency, some IDPs undergo monomeric and heterotypic interactions which can drive phase separation. Such IDPs can form membraneless organelles with specific regulatory roles within the cell which include, but are not …

Probing New Physics Beyond The Standard Model Via New Neutrino Interactions, Garv Chauhan

Arts & Sciences Electronic Theses and Dissertations

The Standard Model (SM) of Particle Physics provides a self-consistent quantum field theoretic framework to explain three of the four known fundamental forces (electromagnetic, weak, strong) along with classifying all known elementary particles. Since its conception in the 1960s, the SM has been one of the most tested theories of physics and has withstood all experimental batterings. In spite of these successes, there are compelling indications, both experimental and theoretical, that require us to expand our understanding of the nature beyond the SM (BSM). Arguably the most glaring indication of BSM physics is the observation of neutrino oscillations, which implies …

A Systematic Study Of Neutron Production In Two Versions Of The Mevion Proton-Therapy System, Nima Tatari

Arts & Sciences Electronic Theses and Dissertations

This thesis presents a study of neutron production in two types of proton-therapy systems: passive scattering Mevion S250, and active scanning Mevion S250i. The scattering system has been operating at Washington University in St. Louis since 2013. The scanning system was installed in the same building in 2020. The scanning system has the advantage of producing fewer neutrons due to a focused scanned beam and the absence of beam scatterers, collimators, and a static brass aperture. A systematic particle transport Monte Carlo analysis using the Geant4 toolkit has been performed to track the neutrons produced in various components of each …

Modeling Hyperpolarized Nmr Phenomena In Optically Pumped Semiconductors, Michael Eric West

Arts & Sciences Electronic Theses and Dissertations

Nuclear magnetic resonance (NMR) is a widely-used technique that measures the local environments of nuclei. It is able to detect small differences in energy, making it a highly-valued tool. However, the technique is challenged by inherently low sensitivities, requiring either large sample volumes or long periods of time to overcome this. In semiconductors, optical pumping (OP) can overcome this low sensitivity by creating incredibly large and dynamic nuclear spin polarizations (``hyperpolarization''), which is detectable as a large NMR signal. The combined technique of optically-pumped NMR (OPNMR) is a valuable tool that can explore electronic and nuclear phenomena within semiconductors. In …

Neural Representation In The Primary Visual Cortex Amid High Neural Variability, Ji Xia

Arts & Sciences Electronic Theses and Dissertations

Animals process high-dimensional sensory information constantly. How does neural activityin sensory cortices represent this information? Recent advances in large-scale recordings allow us to monitor activity of hundreds or thousands of neurons simultaneously across a long period of time. Population recordings showed that cortical neuronal responses to repeated sensory stimulation is highly variable from trial to trial. However, how neurons in neocortex represent sensory information amid high neural variability is not well understood. To answer this question, we used two-photon calcium imaging to record from hundreds of excitatory neurons simultaneously from mouse primary visual cortex. We analyzed neural responses to repeated …

Electronic, Optical, And Magnetic Properties Of Novel Two-Dimensional Materials, Xiaobo Lu

Arts & Sciences Electronic Theses and Dissertations

The field of two-dimensional(2D) materials is experiencing rapid growth and attracting tremendous research interests within the condensed matter community due to its ultimate thickness dimension and unique physical properties. The consistently emerging novel 2D materials not only provide extraordinary intrinsic properties of their single layer and multi- layer structures but also exhibit fascinating responses to the tunable external conditions. The fertile contents and boundless possibilities of novel 2D materials make it one of the pivots of modern nanotechnology towards deepening the physics understanding and promising practical applications.

In the first part of the thesis, we reveal the distinct Stark effects …

Computational Design Of Two-Dimensional Transition Metal Dichalcogenide Alloys And Their Applications, John Douglas Cavin

Arts & Sciences Electronic Theses and Dissertations

The discovery of bronze as an alloy of copper and tin is arguably the earliest form of material design, dating back thousands of years. In contrast, two-dimensional materials are new to the 21st century. The research presented in this dissertation is at the intersection of alloying and two-dimensional materials. I specifically study a class of two-dimensional materials known as transition metal dichalcogenides (TMDCs). Because of the large number of transition metals, there are many combinations of TMDCs that can be alloyed, making experimental exploration of the phase space of possible alloys unwieldly. Instead, I have applied first-principles methods to study …

Partial Measurements Of Quantum Systems, Jonathan Tyler Monroe

Arts & Sciences Electronic Theses and Dissertations

Projective measurement is a commonly used assumption in quantum mechanics. However, advances in quantum measurement techniques allow for partial measurements, which accurately estimate state information while keeping the wavefunction intact. We employ partial measurements to study two phenomena. First, we investigate an uncertainty relation—in the style of Heisenberg’s 1929 thought experiment—which includes partial measurements in addition to projective measurements. We find that a weak partial measurement can decrease the uncertainty between two incompatible (non-commuting) observables. In the second study, we investigate the foundation of irreversible dynamics resulting from partial measurements. We do so by comparing the forward and time-reversed probabilities …

Toward An Understanding Of High-Mass Gamma-Ray Binaries: An Investigation Using Current Observatories And The Development Of A Future Gev Instrument, Zachary Daniel Hughes

Arts & Sciences Electronic Theses and Dissertations

The current generation of gamma-ray instruments have produced a treasure trove of astrophysical discoveries. Among them are a new class of objects tentatively designated high-mass gamma-ray binaries (HMGBs). Thought to be systems containing the colliding wind of a massive star and a young pulsar, these objects are distinguished by emission >1 MeV dominating their spectral energy distributions. We present a multiwavelength study of a newly detected gamma-ray source, HESS J1844-030, utilizing Chandra, Fermi, and VERITAS to show that its spatial, spectral, and flux variability properties are compatible with a classification as a HMGB. The current generation of instruments have identified …

X-Rays From Warped Black Hole Accretion Disks, Quincy Abarr

Arts & Sciences Electronic Theses and Dissertations

In this thesis, I present the results from my research to better understand accretion onto black holes and neutron stars based on spectropolarimetric X-ray observations.

I have developed a general relativistic ray-tracing code which simulates X-rays from warped accretion disks around black holes.

I used this to predict the polarization of the thermal X-ray emission and the energy spectrum the reflected power law emission.

Both of these can be used to measure properties of black hole systems, such as the spin parameter and the inclination of the observer to its spin axis.

My results enable the measurement of these parameters …

Production Of Medical Radioisotopes Using Titanium Accelerator Targets, Christopher Shaun Loveless

Arts & Sciences Electronic Theses and Dissertations

Theranostic radiopharmaceuticals enable diagnostic imaging and radionuclide therapy in patients using a single molecular agent labeled with a diagnostic-therapeutic pair (e.g., 68Ga/177Lu) or a theranostic radionuclide (e.g., 131I). This theranostic approach can help inform patient-specific treatment plans and improve clinical outcomes. Radionuclide pairs used in theranostic agents fall into two categories: pseudo matched-pairs (e.g., 68Ga/177Lu) and matched-pairs (e.g., 124I/131I). Pseudo matched-pair radionuclides have similar chemistries and pharmacokinetics when bound to the same bioconjugate molecule. In contrast, identical chemistries and pharmacokinetics can be obtained by using the matched-pair radionuclides.

The isotopes of Sc include two diagnostic radioisotopes, 43Sc & 44Sc, and …

New Physics With Ultra-High Energy Neutrinos, Yicong Sui

Arts & Sciences Electronic Theses and Dissertations

Ultra-high energy (UHE) astrophysical neutrinos are unique in the sense that they are the

only known particles that could travel through incredibly long distance unattenuated, with

TeV to EeV energy, much higher than the most powerful man-made collider could provide.

The detection of these UHE neutrinos has ushered a new era in neutrino astrophysics, as they

carry important information directly from the inside of energetic astrophysical objects. On the

other hand, from the particle physics point of view, the UHE neutrinos also offer a new window

of opportunity for studying beyond the Standard Model (BSM) phenomena. This is the main …

Peer-Led Team Learning In Calculus-Based Introductory Physics: Implementation And Evaluation, Siera Maia Stoen

Arts & Sciences Electronic Theses and Dissertations

Robust evidence shows that Peer-led Team Learning (PLTL) improves the academic success of college students in introductory Science, Technology, Engineering, and Mathematics (STEM) courses. However, further research is needed to gain a fuller understanding of the benefits of PLTL and the aim of this dissertation is to explore two key and understudied questions surrounding the effects of PLTL. First, does deviating from the optimal implementation of PLTL change its effectiveness? Second, what specific outcomes, in addition to academic success (e.g., exam scores), does PLTL improve? This dissertation will provide a fuller picture of the impact of PLTL by examining its …

Separating Signal From Noise In High-Density Diffuse Optical Tomography, Arefeh Sherafati

Arts & Sciences Electronic Theses and Dissertations

High-density diffuse optical tomography (HD-DOT) is a relatively new neuroimaging technique that detects the changes in hemoglobin concentrations following neuronal activity through the measurement of near-infrared light intensities. Thus, it has the potential to be a surrogate for functional MRI (fMRI) as a more naturalistic, portable, and cost-effective neuroimaging system. As in other neuroimaging modalities, head motion is the most common source of noise in HD-DOT data that results in spurious effects in the functional brain images. Unlike other neuroimaging modalities, data quality assessment methods are still underdeveloped for HD-DOT. Therefore, developing robust motion detection and motion removal methods in …

Specificity Of Ssb Binding To Its Interacting Proteins And Multiple Allosteric Effects Of Ssb C-Terminal Tail On Assembly And Dna Binding Of E. Coli Recor Proteins, Min Kyung Shinn

Arts & Sciences Electronic Theses and Dissertations

The homo-tetrameric E. coli single strand (ss) DNA binding (SSB) protein is an essential component in DNA maintenance for its role in binding and protecting single stranded DNA intermediates via its N-terminal DNA binding domain (DBD). SSB also acts as a hub to recruit at least 17 SSB interacting proteins (SIPs) involved in DNA replication, recombination, and repair via its 9 amino acid C-terminal acidic tip region. A 56 amino acid intrinsically disordered linker connects the DBD and the acidic tip and plays a role in cooperative binding to ssDNA. Using isothermal titration calorimetry, I determined that the SSB-Ct peptides …

Measurement, Dissipation, And Quantum Control With Superconducting Circuits, Patrick Harrington

Arts & Sciences Electronic Theses and Dissertations

The interaction between a superconducting circuit and its environment can cause decoherence. However, interactions with an environment are necessary for quantum state preparation and measurement. Through the dynamics of open quantum systems, the environment is a resource to control and readout superconducting circuit states. I present an experimental result demonstrating qubit state stabilization from engineered dissipation with a microwave photonic crystal. In addition, I discuss the statistical arrow of time in the dynamics of continuous quantum measurement. These results demonstrate an interplay between open quantum system dynamics and statistics, which highlights the role of both dissipation and measurement for quantum …

Applications Of Nonlinear Dynamics, And Critical Phenomena To Measure Neural Populations Using Inputs To Single Neurons, James Kenneth Johnson

Arts & Sciences Electronic Theses and Dissertations

A compelling vision for the future of neuroscience is the ability to sense neural activity throughout the bulk of the brain with exquisite resolution. Popular visions usually include intricate electrode technology intruding into the neuropil, meandering along nerve tracts, and sensing the whole brain. These popular visions stem from the belief that we must always have an outsider’s perspective of neural activity. According to this belief the closest thing neuroscientists can achieve to an insider’s perspective is to shadow every neuron (or almost every neuron) with an electrical or optical recording device. Yet, the brain naturally has an expansive sensor …

Phantoms To Placentas: Mr Methods For Oxygen Quantification, Kelsey Meinerz

Arts & Sciences Electronic Theses and Dissertations

Molecular oxygen (O2) is vital for efficient energy production and improper oxygenation is a hallmark of disease or metabolic dysfunction. In many pathologies, knowledge of tissue oxygen levels (pO2) could aid in diagnosis and treatment planning. The gold standard for pO2 measures in tissue are implantable probes, which are invasive, require surgery for placement, and are inaccessible to certain regions of the body. Methods for determining pO2 both non-invasively and quantitatively are lacking. The slight paramagnetic nature of O2 provides opportunities to non-invasively characterize pO2 in tissue via magnetic resonance (MR) techniques. As such, O2 can be treated as a …

Supertiger Elemental Abundances For The Charge Range $41 \Leq Z \Leq 56$, Nathan Elliot Walsh

Arts & Sciences Electronic Theses and Dissertations

No abstract provided.

Molecular Insights Into Microbial Adhesion, Roger Davies Klein

Arts & Sciences Electronic Theses and Dissertations

Antibiotic-resistant bacterial infections are a serious and immediate threat to global public health. In the United States alone, over 2 million individuals develop antibiotic-resistant infections annually, resulting in 23,000 deaths and $20 billion in excess health care costs. Virulence factors that allow bacteria to invade and persist within the host are promising targets for novel antimicrobial agents that could be used to curb the spread of antibiotic resistance. Development of therapeutics that can selectively eliminate pathogenic bacteria while sparing the beneficial host microbiota requires a detailed molecular understanding of critical virulence factors that facilitate interactions between pathogens and their environments. …

Thermophysical Properties And Phase Transformations In Metallic Liquids And Silicate Glasses, Daniel Christian Van Hoesen

Arts & Sciences Electronic Theses and Dissertations

The first quantitative measurements of the electrical resistivity in binary metallic liquids, used to probe local order in the liquid, are reported in this dissertation. The electrical resistivity is very sensitive to short and medium range ordering because the electron mean free path is approximately the same length scale as the atomic spacing. Particular attention is given to the resistivity value at a crossover temperature that, based on molecular dynamics (MD) simulations, is the onset of cooperative motion in liquid alloys. Experimental evidence for the crossover is found in measurements of the shear viscosity, a dynamical property. An indication of …

Transport In Neutron Star Mergers, Steven Patrick Harris

Arts & Sciences Electronic Theses and Dissertations

Neutron star mergers are the only situation in nature in which we find matter compressed to several times nuclear saturation density and temperatures of several tens of MeV. By observing and numerically simulating neutron star mergers, we can learn about the nature of matter at high temperatures and densities. Neutron star merger simulations evolve Einstein's equations of general relativity coupled to the equations of relativistic hydrodynamics along with a nuclear equation of state, which describes the neutron star matter. Many simulations also take into account neutrino transport and electrodynamics. The purpose of this thesis is to see whether other physical …

Studies Of Maximum Supercooling And Stirring In Levitated Liquid Metallic Alloys, Mark Edward Sellers

Arts & Sciences Electronic Theses and Dissertations

Nucleation—or the formation of some cluster in a medium undergoing a phase transition—is usually the initial step in a phase transition. However, this process is still not fully understood, as outstanding questions related to the role of structure, local order, and diffusion remain unanswered. Systematic supercooling studies on metallic liquids performed using electrostatic and electromagnetic (ESL and EML, respectively) will be presented and discussed within the context of several nucleation theories, such as the Classical Nucleation Theory, Diffuse Interface Theory, and Coupled-Flux theory. To study the role of diffusion on nucleation, studies on the International Space Station using the on-board …