Physical Sciences and Mathematics Commons^™

The Black-To-White Hole Transition, Farshid Soltani

Electronic Thesis and Dissertation Repository

Classically, an isolated black hole is a stable gravitational object. If however semiclassical effects are taken into account, an isolated black hole can be shown to slowly radiate its mass away in a process called evaporation. At the end of the evaporation process, when the size of the horizon becomes Planckian, the quantum nature of the gravitational field can no longer be neglected and the dynamics of the horizon is governed by quantum gravity. The main objective of this thesis is the systematic investigation of a tentative scenario for the “end of the life” of a black hole: the black-to-white …

Luminescence And Structural Properties Of Silicon-Germanium Quantum Structures Fabricated By Ion Implantation, Matheus Coelho Adam

Electronic Thesis and Dissertation Repository

The advancement of semiconductor materials has played a crucial role in driving positive technological breakthroughs that impact humanity in numerous ways. The presence of defects significantly alters the physical properties of semiconductors, making their analysis essential in the fabrication of semiconductor devices. I presented a new method to quantify surface and near-surface defects in single crystal semiconductors. Epitaxially-grown silicon was measured by low energy electron diffraction (LEED) to obtain the surface Debye temperature (θ_D). The results showed the surface θ_D of bulk Si (001), 1.0 μm, and 0.6 μm Si on sapphire of 333 K, 299 K, …

Modeling Thermosyphon And Heat Pipe Performance For Mold Cooling Applications, Dwaipayan Sarkar

Electronic Thesis and Dissertation Repository

Thermosyphons are enhanced heat transfer devices that can continuously transfer very large amounts of heat rapidly over long distances with small temperature differences. The high heat transfer rate is achieved through simultaneous boiling and condensation of the working fluid and the continuous heat transfer is achieved through recirculation of the working fluid in its liquid and vapor phase. A potentially important application of the thermosyphons has been towards reducing the cycle times of the mold cooling processes which would provide economic incentives to the automotive industry.

Different operational and geometrical parameters such as the input heating power, fill ratio (FR), …

High-Performance Computing In Covariant Loop Quantum Gravity, Pietropaolo Frisoni

Electronic Thesis and Dissertation Repository

This Ph.D. thesis presents a compilation of the scientific papers I published over the last three years during my Ph.D. in loop quantum gravity (LQG). First, we comprehensively introduce spinfoam calculations with a practical pedagogical paper. We highlight LQG's unique features and mathematical formalism and emphasize the computational complexities associated with its calculations. The subsequent articles delve into specific aspects of employing high-performance computing (HPC) in LQG research. We discuss the results obtained by applying numerical methods to studying spinfoams' infrared divergences, or ``bubbles''. This research direction is crucial to define the continuum limit of LQG properly. We investigate the …

Patterned Heating Induced Propulsion, Saajid A. Aman

Electronic Thesis and Dissertation Repository

This study explores propulsion effects generated by patterned heating acting on smooth and corrugated surfaces. The model problem assumes that the upper plate moves freely, and the lower plate is stationary, equipped with grooves, and exposed to spatially distributed heating. Our findings identify two distinct propulsion effects: thermal streaming and thermal drift. Thermal streaming occurs when given sufficient heating intensity with net flow in the left or right direction characterized by a pitchfork bifurcation. The efficiency of this technique can be controlled using the wavelength of heating. Thermal drift represents a pattern interaction effect. Its strength depends on the relative …

On The Origins Of Life — Modelling The Initial Stages Of Complex Coacervate Droplet Formation, Yixuan Wu

Western Libraries Undergraduate Research Awards (WLURAs)

Coacervate droplets are considered a plausible model for protocells due to their spontaneous formation and ability to compartmentalize macromolecules such as nucleic acid and peptides. Although experimental studies have observed and synthesized coacervates under different laboratory conditions, little is known about their structure. Here we present atomistic molecular dynamic simulations of the interactions between water and oppositely charged proteins that cluster together in a salt-dependent process. Observing such liquid-liquid phase separation on an atomic level would serve as a model for the initial stages of complex coacervate formation. Molecular Dynamics was used to compute diagnostics of the structure at different …

Interplay Of Forces In Impinging Jet Flow And Circular Hydraulic Jump, Abdelkader Baayoun

Electronic Thesis and Dissertation Repository

The circular liquid jet impingement with subsequent hydraulic jump formation is studied theoretically using boundary-layer and thin-film approaches. Three different scenarios are tackled, namely, an accelerated Newtonian jet impinging on a stationary disk, a steady Newtonian jet impinging on a rotating disk, and a steady viscoelastic liquid jet impinging on a stationary disk. Accordingly, the effects of jet acceleration, gravity, centrifugal forces, and fluid elasticity on the flow behaviour and the jump are examined. The results are validated against numerical simulation and existing measurements. The findings show that the thickness of the boundary layer developing near impingement diminishes with jet …

Feasibility Of Functional Mri On Point-Of-Care Mr Platforms, Arjama Halder

Electronic Thesis and Dissertation Repository

Magnetic resonance imaging (MRI) has proven to be a clinically valuable tool that can produce anatomical and functional images with improved soft tissue contrast compared to other imaging modalities. There has recently been a surge in low- and mid-field scanners due to hardware developments and innovative acquisition techniques. These compact scanners are accessible, offer reduced siting requirements and can be made operational at a reduced cost.

This thesis aims to implement blood-oxygen-level-dependent (BOLD) resting-state functional MRI (fMRI) at such a mid-field point-of-care scanner. The availability of this technique can be beneficial to get neurological information in cases of traumatic brain …

Towards Clinical Microscopic Fractional Anisotropy Imaging, Nico Jj Arezza

Electronic Thesis and Dissertation Repository

Microscopic fractional anisotropy (µFA) is a diffusion-weighted magnetic resonance imaging (dMRI) metric that is sensitive to neuron microstructural features without being confounded by the orientation dispersion of axons and dendrites. µFA may potentially act as a surrogate biomarker for neurodegeneration, demyelination, and other pathological changes to neuron microstructure with greater specificity than other dMRI techniques that are sensitive to orientation dispersion, such as diffusion tensor imaging. As with many advanced imaging techniques, µFA is primarily used in research studies and has not seen use in clinical settings.

The primary goal of this Thesis was to assess the clinical viability of …

Effect Of Morphology And An Upstream Tall Building On A Street Canyon Flow, Haoran Du

Electronic Thesis and Dissertation Repository

The effects of the morphological model and the existence of an upstream tall building on the turbulent street canyon flow and the overlying boundary layer are investigated in a wind tunnel, using Stereoscopic Particle Image Velocimetry (S-PIV) measurements. The velocity variances, Reynolds shear stress, and turbulent kinetic energy are found to be larger than in a similar idealized street canyon model. Increasing building height results in a decrease in vertical mass fluxes across the opening of the canyon, at least in the canyon portion directly downstream of the building. The interaction between the large-scale structures in the overlying boundary layer …

The Magnetic Field Of Protostar-Disk-Outflow Systems, Mahmoud Sharkawi

Electronic Thesis and Dissertation Repository

Recent observations of protostellar cores reveal complex magnetic field configurations that are distorted in the innermost disk region. Unlike the prestellar phase, where the magnetic field geometry is simpler with an hourglass configuration, magnetic fields in the protostellar phase are sculpted by the formation of outflows and rapid rotation. This gives rise to a significant azimuthal (or toroidal) component that has not yet been analytically modelled in the literature. Moreover, the onset of outflows, which act as angular momentum transport mechanisms, have received considerable attention in the past few decades. Two mechanisms: 1) the driving by the gradient of a …

Modelling Cell Population Growth, Mahmood Mazarei

Electronic Thesis and Dissertation Repository

The growth of biological matter, e.g., tumor invasion, depends on various factors, mainly the tissue’s mechanical properties, implying elasticity, stiffness, or apparent viscosity. These properties are impacted by the characteristics of the tissue’s extracellular matrix and constituent cells, including, but not limited to, cell membrane stiffness, cell cytoskeleton mechanical properties, and the intensity and distribution of focal adhesions over the cell membrane. To compute and study the mechanical properties of tissues during growth and confluency, a theoretical and computational framework, called CellSim3D, was developed in our group based on a three-dimensional kinetic division model.

In this work, CellSim3D is …

A Highly Charged Topic: Intrinsically Disordered Proteins And Protein Pka Values, Carter J. Wilson

Electronic Thesis and Dissertation Repository

Intrinsically disordered proteins (IDPs) are known not only for their roles in disease but also for their conformational flexibility, which makes them elusive for experimentation. We consider the role played by theory and simulation in resolving important questions pertaining to IDP structure and dynamics, as well as the nature of the charged residues (e.g., glutamate, lysine, etc.) that enrich them. Specifically, we investigated how the deep learning trained AlphaFold2 (AF2) predictor estimates disorder content, revealing both strong performance in relation to conventional approaches and an important relationship between the AF2 confidence metric and IDP dynamics. We also assessed how modern …

New Aspects Of Scattering Amplitudes, Higher-K Amplitudes, And Holographic Quark Gluon Plasmas, Bruno Giménez Umbert

Electronic Thesis and Dissertation Repository

We present new results on different aspects of quantum field theory, which are divided into three main parts. In part I, we find and prove a new behavior of massless tree-level scattering amplitudes, including the biadjoint scalar theory, the U(N) non-linear sigma model, and the special Galileon, within specific subspaces of the kinematic space. We also derive new formulas for the double-ordered biadjoint scalar and $\phi^p$ amplitudes, which can be obtained as integrals over the positive tropical Grassmannian and under limiting procedures on the kinematic invariants. This reveals surprising connections with cubic amplitudes. We also present alternative versions of the …

Galfit-Ing Agn Host Galaxies In Cosmos: Hst Versus Subaru, Callum Dewsnap, Pauline Barmby, Sarah C. Gallagher, C. Megan Urry, Aritra Ghosh, Meredith C. Powell

Physics and Astronomy Publications

The COSMOS field has been extensively observed by most major telescopes, including Chandra, HST, and Subaru. HST imaging boasts very high spatial resolution and is used extensively in morphological studies of distant galaxies. Subaru provides lower spatial resolution imaging than HST but a substantially wider field of view with greater sensitivity. Both telescopes provide near-infrared imaging of COSMOS. Successful morphological fitting of Subaru data would allow us to measure morphologies of over 104 known active galactic nucleus (AGN) hosts, accessible through Subaru wide-field surveys, currently not covered by HST. The morphological parameters indicate the types of galaxies that host AGNs. …

Solar Cells, Lambert W And The Logwright Functions, Prabhat Lankireddy, Sibibalan Jeevanandam, Aditya Chaudhary, P. C. Deshmukh, Ken Roberts, S. R. Valluri

Physics and Astronomy Publications

Algorithms that calculate the current-voltage (I-V) characteristics of a solar cell play an important role in processes that aim to improve the efficiency of a solar cell. I-V characteristics can be obtained from different models used to represent the solar cell, and the single diode model is a simple yet accurate model for common field implementations. However, the I-V characteristics are obtained by solving implicit equations, which involve repeated iterations and inherent errors associated with numerical methods used. Some methods use the Lambert W function to get an exact explicit formula, but often causes numerical overflow problems. The present work …

Modelling Of Covid-19 Using Fractional Differential Equations, Rishi Patel, P. Sainani, M. Brar, R. Patel, X. Li, J. Drozd, F. A. Chishtie, A. Benterki, T. C. Scott, S. R. Valluri

Physics and Astronomy Publications

In this work, we have described the mathematical modeling of COVID-19 transmission using fractional differential equations. The mathematical modeling of infectious disease goes back to the 1760s when the famous mathematician Daniel Bernoulli used an elementary version of compartmental modeling to find the effectiveness of deliberate smallpox inoculation on life expectancy. We have used the well-known SIR (Susceptible, Infected and Recovered) model of Kermack & McKendrick to extend the analysis further by including exposure, quarantining, insusceptibility and deaths in a SEIQRDP model. Further, we have generalized this model by using the solutions of Fractional Differential Equations to test the accuracy …

The Role Of R-Modes In Pulsar Spindown, Pulsar Timing And Gravitational Waves, Varenya Upadhyaya, Xiyuan Li, Xiyang Zhang, S. R. Valluri

Physics and Astronomy Publications

Pulsars are fast spinning neutron stars that lose their rotational energy via various processes such as gravitational and magnetic radiation, particle acceleration and mass loss processes. This dissipation can be quantified by a spin-down equation that measures the rate of change of the frequency as a function of the rotational frequency itself. We explore the pulsar spin-down and consider the spin-down equation upto the seventh order in frequency. This seventh order term accounts for energy loss due to the gravitational radiation caused by a current type quadrupole in the pulsar due to r-modes. We derive the rotational frequency due to …

The Physical Properties Of Low-Redshift Felobal Quasars. I. Spectral-Synthesis Analysis Of The Broad Absorption-Line (Bal) Outflows Using Simbal, Hyunseop Choi, Karen M. Leighly, Donald M. Terndrup, Collin Dabbieri, Sarah C. Gallagher, Gordon T. Richards

Physics and Astronomy Publications

We present the first systematic study of 50 low-redshift (0.66 < z < 1.63) iron low-ionization broad absorption-line quasars (FeLoBALQs) using SimBAL, which represents a more than five-fold increase in the number of FeLoBALQs with detailed absorption line spectral analyses. We found the outflows have a wide range of ionization parameters, − 4 ≲ log U ≲ 1.2 and densities, 2.8 ≲ log n ≲ 8 [ cm − 3 ] . The objects in our sample showed FeLoBAL gas located at a wide range of distances 0 ≲ log R ≲ 4.4 [pc], although we do not find any evidence for disk winds (with R ≪ 0.01 pc) in our sample. The outflow strength primarily depends on the outflow velocity with faster outflows found in quasars that are luminous or that have flat or redder spectral energy distributions. We found that ∼18% of the FeLoBALQs in the sample have the significantly powerful outflows needed for quasar feedback. Eight objects showed overlapping troughs in the spectra, and we identified eleven loitering outflow objects, a new class of FeLoBALQs that are characterized by low outflow velocities and high column density winds located log R ≲ 1 [pc] from the central engine. The FeLoBALs in loitering outflows objects do not show properties expected for radiatively driven winds, and these objects may represent a distinct population among FeLoBALQs. We discuss how the potential acceleration mechanisms and the origins of the FeLoBAL winds may differ for outflows at different locations in quasars.

Pressure-Induced Modifications To The Structural And Optoelectronic Properties Of 2d Hybrid Organic-Inorganic Perovskites, Jesse Ratte

Electronic Thesis and Dissertation Repository

Recently, 2D hybrid organic-inorganic perovskites (HOIP) have garnered lots of research interest for their applications in optoelectronic devices, especially in solar cells. The optoelectronic properties of 2D HOIPs have yet to be optimized for these applications. High external pressure is well known to induce structural modifications to 2D HOIPs, and thus modify their optoelectronic properties. Herein, we report a study of the effects of high pressure (HP) on the structures and optoelectronic properties of cyclohexane methylamine (CMA) lead iodide (CMA2PbI4) and the structures of N,N-dimethylphenylene-p-diammonium (DPDA) lead iodide (DPDAPbI4).

High pressure measurements of CMA2PbI4 were performed using Raman spectroscopy, Fourier-transform …

Nustar Observations Of Intrinsically X-Ray Weak Quasar Candidates: An Obscuration-Only Scenario, Chaojun Wang, B. Luo, W. N. Brandt, D. M. Alexander, F. E. Bauer, Sarah C. Gallagher, Jian Huang, Hezhen Liu, D. Stern

Physics and Astronomy Publications

We utilize recent NuSTAR observations (co-added depth ≈55-120 ks) of PG 1001+054, PG 1254+047, and PHL 1811 to constrain their hard X-ray (≳5 keV) weakness and spectral shapes and thus to investigate the nature of their extreme X-ray weakness. These quasars showed very weak soft X-ray emission, and they were proposed to be intrinsically X-ray weak, with the X-ray coronae producing weak continuum emission relative to their optical/UV emission. However, the new observations suggest an alternative explanation. The NuSTAR 3-24 keV spectral shapes for PG 1001+054 and PHL 1811 are likely flat (effective power-law photon indices Γeff=1.0-0.6+0.5 and Γeff=1.4-0.7+0.8, respectively), …

The Physical Properties Of Low-Redshift Felobal Quasars. Iii. The Location And Geometry Of The Outflows, Hyunseop Choi, Karen M. Leighly, Collin Dabbieri, Donald M. Terndrup, Sarah C. Gallagher, Gordon T. Richards

Physics and Astronomy Publications

We present continued analysis of a sample of low-redshift iron low-ionization broad-absorption-line quasars (FeLoBALQs). Choi et al. presented SimBAL spectral analysis of broad-absorption-line (BAL) outflows in 50 objects. Leighly et al. analyzed the optical emission lines of 30 of those 50 objects and found that they are characterized by either a high accretion rate (L Bol/L Edd > 0.3) or low accretion rate (0.03 < L Bol/L Edd < 0.3). We report that the outflow velocity is inversely correlated with the BAL location among the high-accretion-rate objects, with the highest velocities observed in parsec-scale outflows. In contrast, the low-Eddington-ratio objects showed the opposite trend. We confirmed the known relationship between the outflow velocity and L Bol/L Edd and found that the scatter plausibly originates in the force multiplier (launch radius) in the low(high)-accretion-rate objects. A log volume filling factor between −6 and −4 was found in most outflows but was as high as −1 for low-velocity compact outflows. We investigated the relationship between the observed [O iii] emission and that predicted from the BAL gas. We found that these could be reconciled if the emission-line covering fraction depends on the Seyfert type and BAL location. The difference between the predicted and observed [O iii] luminosity is correlated with the outflow velocity, suggesting that [O iii] emission in high-Eddington-ratio objects may be broad and hidden under Fe ii emission. We suggest that the physical differences in the outflow properties as a function of location in the quasar and accretion rate point to different formation, acceleration, and confinement mechanisms for the two FeLoBALQ types.

Wideband And Relativistic Superradiance In Astrophysics, Christopher M. Wyenberg

Electronic Thesis and Dissertation Repository

In the quantum phenomenon of superradiance (SR) a population of inverted particles evolves, through its interaction with the quantized vacuum radiation field, into a highly entangled state capable of generating much greater radiative emission than predicted by the independent spontaneous decay of its constituent particles. The phenomenon has recently been applied to transient astrophysical processes but has thus far been restricted to particles sharing a common velocity. This thesis researches the effects of astrophysical velocity distributions upon SR, which are distinct from conventional regimes of the quantum optics literature in that they may possess extremely wide bandwidths, turbulent statistical properties, …

Rheological Characterization Of Blood-Mimicking Fluids For Use In Particle Image Velocimetry, Anorin S. Ali

Undergraduate Student Research Internships Conference

Blood-mimicking fluids (BMFs) are often used to investigate blood flow using physical replicas of vessels with cardiovascular disease. Particle image velocimetry (PIV) is used with silicone poly-dimethyl siloxane (PDMS) vascular models to visualize this flow. The challenge is creating a blood-mimicking fluid that matches the viscosity profile, viscoelasticity, and density of whole blood while also matching the refractive index (RI) of PDMS. Water-glycerol solutions are commonly used with sodium iodide (NaI) added to increase the RI without changing viscosity. However, NaI is expensive, stains easily, and turns fluids from optically clear to yellow in less than a day. Furthermore, without …

Solving Partial Differential Equations Using The Finite Difference Method And The Fourier Spectral Method, Jenna Siobhan Parkinson

Undergraduate Student Research Internships Conference

This paper discusses the finite difference method and the Fourier spectral method for solving partial differential equations.

Producing And Measuring Oscillatory Shear In A Novel Microfluidic Chip, Sanaz Lordfard, Daniel Lorusso, Tamie L. Poepping, Hristo N Nikolov, Kayla Soon, Stephen Sims, Jeffrey Dixon, David Holdsworth

Undergraduate Student Research Internships Conference

Purpose: To demonstrate the effectiveness of a novel microfluidic device mimicking oscillatory blood flow, allowing cell biologists to examine how endothelial cells respond to a range of oscillatory shear stress levels.

Methods: The microfluidic chip consists of a circular-shaped reservoir, leading to a rectangular channel that is examined under a microscope. The plunger is connected to a speaker system and oscilloscope, allowing the plunger to apply a range of frequencies (5-60Hz) and voltages (5-10 V, leading to a variety in oscillation amplitudes) to the reservoir region. 1.1 um fluorescent particles diluted in distilled water were used for tracking. Processing was …

Polymer Translocation Through A Nanopore: Controlling Capture Conformations Using An Electrical Force, Matthew D. Wei

Undergraduate Student Research Internships Conference

Solid-state nanopore sensors remain a promising solution to the rising global demand for genome sequencing. These single-molecule sensing technologies require single-file translocation for high resolution and accurate detection. This study uses molecular dynamics-lattice Boltzmann simulations of the capture of a single polymer chain under pressure-driven hydrodynamic flow to investigate a method of increasing the single-file capture and translocation rate. By using a model force of two oppositely electrically charged rings, single-file capture in hydrodynamic flow can be amplified from about 45% to 51.5%. This paper found that the optimal values of force location, force strength, and system pressure/flow velocity are …

Travelling Wave Solutions On A Cylindrical Geometry, Karnav R. Raval

Undergraduate Student Research Internships Conference

Fluid equations are generally quite difficult and computationally-expensive to solve. However, if one is primarily interested in how the surface of the fluid deforms, we can re-formulate the governing equations purely in terms of free surface variables. Reformulating equations in such a way drastically cuts down on computational cost, and may be useful in areas such as modelling blood flow. Here, we study one such free-boundary formulation on a cylindrical geometry.

Magnetic Resonance Systems Development For Point-Of-Care Mri Platforms, Eric J. Lessard

Electronic Thesis and Dissertation Repository

Magnetic resonance imaging utilizes electromagnets to produce anatomical images in both clinical and research settings. In the race towards increasing performance head-optimized scanners have begun playing a significant role in providing high quality imaging of the head. However, they are implemented using smaller geometries and as such fail to allow entrance of the patient past their shoulders. This is overcome by designing asymmetric gradient coils which have their imaging region located towards one end of the gradient coil, as opposed to the geometric center, allowing brain imaging. There exists interest in compact configurations which allow imaging further into the cervical …

Complex Energies And The Lambert W Function, A Das, B.G. Sidharth, K. Roberts, Sree Ram Valluri

Physics and Astronomy Publications

We apply the Lambert W function in the context of complex energy values in statistical systems of fermions and bosons. We derive the condition for the transformation connecting fermions and bosons. We discuss the physical significance of these results and investigate the conditions under which bosonization effects take place. The fermion and boson statistical and structural distributions discussed in this work suggest the possibility of their extensions to generalized Planck distributions.