Physics Commons^™

Robust Interventions In Network Epidemiology, Erik Weis

Graduate College Dissertations and Theses

Which individual should we vaccinate to minimize the spread of a disease? Designing optimal interventions of this kind can be formalized as an optimization problem on networks, in which we have to select a budgeted number of dynamically important nodes to receive treatment that optimizes a dynamical outcome. Describing this optimization problem requires specifying the network, a model of the dynamics, and an objective for the outcome of the dynamics. In real-world contexts, these inputs are vulnerable to misspecification---the network and dynamics must be inferred from data, and the decision-maker must operationalize some (potentially abstract) goal into a mathematical objective …

Effective Drag Coefficient Prediction On Single-View 2d Images Of Snowflakes, Cameron Hudson

Graduate College Dissertations and Theses

The drag coefficient of snowflakes is an crucial particle descriptor that can quantify the relationships with the mass, shape, size, and fall speed of snowflake particles. Previous studies has relied on estimating and improving empirical correlations for the drag coefficient of particles, utilizing 3D images from the Multi-Angled Snowflake Camera Database (MASCDB) to estimate snowflake properties such as mass, geometry, shape classification, and rimming degree. However, predictions of the drag coefficient with single-view 2D images of snowflakes has proven to be a challenging problem, primarily due to the lack of data and time-consuming, expensive methods used to estimate snowflake shape …

Strain-Enhanced Coherent Exciton-Polaron States In 1d Phthalocyanine Crystalline Thin Films, Libin Liang

Graduate College Dissertations and Theses

Organic semiconductors are at the forefront of materials research, due to their desired electric and mechanical properties. They offer the unique opportunity to modify material properties during synthesis process, opening an avenue to the development of novel flexible and wearable electronic and photonic devices.Molecular excitons are of importance in organic semiconductor properties. While majority of research studies are centered on achieving good control of amorphous or polycrystalline thin film properties, the static disorder effect leads to poor device performance when compared to inorganic semiconductors with superior crystalline ordering. On the other hand, the macroscopic molecular long-range ordering can enhance device …

Tuning Electroluminescence From Resonators Based On Fabry-Pérot Microcavity Oleds, Ekraj Dahal

Graduate College Dissertations and Theses

This thesis comprises a series of methods for controlling the electroluminescence from Fabry-Pérot microcavity OLEDs by varying the resonator geometry and the location of the organic emitter within the resonator. In pursuit of this thesis, I conducted three experimental projects backed by theoretical modeling. First the thickness of the microcavity was varied to observe changes in resonant state wavelength, linewidth of the states, angular dispersion, and polarization splitting. The resulting electroluminescence can be tuned to span the entire color gamut using a single green chromophore. Electroluminescence of this green chromophore was used to pump the optical states of nominally identical …

The Impact Of Prior Exposure To Physics On Students' Transition To Flipped Classrooms With Active Learning, Johnny Gonzalez

Graduate College Dissertations and Theses

The pedagogical approach of the flipped classroom with an active learning model shows great benefit for all students in many disciplines. This study explored the possibility that certain subsets of students may have varying benefits from this model. In this study, we used survey questions to categorize students and analysis of the Forced Concept Inventory (FCI) scores, including normalized gain (NG), to measure learning improvement. In particular, we used a questionnaire with two questions that were used to partition each sub-group. The first group consisted of students that have varying levels of physics knowledge and the second group consisted of …

Pymoocfd - A Multi-Objective Optimization Framework For Cfd, George Martin Cunningham Love

Graduate College Dissertations and Theses

Modern computational resource have solidified the use of computer modeling as an integral part of the engineering design process. This is particularly impressive when it comes to high-dimensional models such as computational fluid dynamics (CFD) models. CFD models are now capable of producing results with a level of confidence that would previously have required physical experimentation. Simultaneously, the development of machine learning techniques and algorithms has increased exponentially in recent years. This acceleration is also due to the widespread availability of modern computational resources. Thus far, the cross-over between these fields has been mostly focused on computer models with low …

Medical Applications Of Ultrasound: T-Cell Drug Delivery, Osteoporosis Diagnosis, And Biofilm Mitigation, Alina Karki

Graduate College Dissertations and Theses

The ability of ultrasound to localize acoustic energy deposition and induce a biological effect within a target is examined in three novel biomedical applications: sonoporation, osteoporosis diagnosis, and biofilm mitigation.Ultrasound can excite encapsulated microbubbles, causing an acoustic cavitation effect in the vicinity of cells, temporarily increasing membrane permeability, and allowing cells to uptake foreign molecules. This non-viral transfection technique is called sonoporation. Our experimental study demonstrated that it could be effective for small interfering RNA (siRNA) delivery into an isolated mouse and human T-cells, which is a complex process despite its importance in treating numerous diseases. T-cells are non-proliferating, while …

Resonant Trojan Emris With Lisa, Vanessa Myhaver

Graduate College Dissertations and Theses

Extreme--mass--ratio inspirals (EMRI) are prospective sources for the detection of observational signals with the Laser Interferometer Space Antenna (LISA) mission, built to accurately detect and measure gravitational waves -- ripples in the curvature, and fabric of space--time. EMRIs are typically comprised of a supermassive black hole (SMBH) one million times more massive than our Sun, and a stellar--origin black hole several orders of magnitude smaller. As the smaller black hole spirals into the supermassive black hole, thousands of cycles of the gravitational waveform serve as a precision probe for the extreme space-time curvature of the system. The goal of this …

Small-Scale Roll Coating As A Transitional Stage In The Scaling Of Organic Electronic Device Fabrication Techniques, Jared Benson

Graduate College Dissertations and Theses

Incredible achievements have been made in the field of organic electronics in small-scale laboratory settings. A topic of increasing importance is the realization of the potential for these technologies to be applied in an industrial setting. This is a deceptively challenging process, considering that many of the procedures used to attain exceptional results in a laboratory setting are not viable for translation to larger scale fabrication efforts. Moreover, upscaling fabrication is further complicated by the enormous barrier of entry due to the expensive equipment required to fabricate organic electronics at larger scale as well as the exponentially greater quantity of …

Transient Effects In Solution-Processed Organic Thin Films, Jing Wan

Graduate College Dissertations and Theses

Due to the weak van der Waals forces between organic semiconductor molecules, the molecular packing depends sensitively on the processing methods and conditions. Thus, understanding the crystallization mechanisms during solution deposition are essential for fundamental studies and reproducible fabrication of electronic devices.The performance of Organic field effect transistors (OFETs) also depends heavily on extrinsic factors such as contact resistance and interfacial defects, which can produce a different kind of transient effect at the metal-semiconductor contact. We have observed structural transient effects during the crystallization process of two small molecule organic semiconductors made from solution. We report in situ X-ray scattering …

Nonlinear Impedance Spectroscopy To Characterize Hole Transport And Recombination Dynamics In Organic Semiconductor Devices, Robin Rice

Graduate College Dissertations and Theses

Impedance Spectroscopy (IS) is an increasingly common technique to characterize both solid state and electrochemical systems including solar cells and light emitting diodes (LEDs). However, IS relies on a system response being linear with its input such that a time invariant impedance can be defined. This is usually achieved by a small amplitude input. However, doing so suppresses responses of the nonlinear processes which are of considerable interest to those designing and optimizing these devices, such as charge carrier recombination and space charge effects. This investigation employs the recently developed nonlinear extension to IS (NLIS) based in Fourier analysis of …

Two-Dimensional Bose–Hubbard Model For Helium On Graphene, Jiangyong Yu

Graduate College Dissertations and Theses

An exciting development in the field of correlated systems is the possibilityof realizing two-dimensional (2D) phases of quantum matter. For a systems of bosons, an example of strong correlations manifesting themselves in a 2D environment is provided by helium adsorbed on graphene. We construct the effective Bose-Hubbard model for this system which involves hard-core bosons (U ≈ ∞) and repulsive nearest-neighbor (V > 0) interactions. In this work, we focus on the calculations of single particle properties of the model such as the hopping parameter t. This is accomplished via Wannier Theory and Band structure calculations, which proves to be reliable …

Microwave Assisted Heating Of A Ferromagnetically-Doped Propellant For Small Satellites: An Efficacy Study, Thomas Joseph Heffernan

Graduate College Dissertations and Theses

In the interest of mitigating high launch costs, small satellites are often chosen as secondary payloads during launch operations. Their lower mission importance dictates stringent restrictions on the propulsion systems which can be implemented as they cannot contain combustible or toxic agents; a common solution to this prob- lem is implementation of micronozzles with cold-gas propellants in order to generate thrust. The present research explores the efficacy of leveraging microwave-assisted decomposition of a ’green’ chemical blowing agent, namely Azodicarbonamide, as a propellant for use in a microthruster. The thermal evolution of a heterogeneous ferromagnetic-doped propellant is analyzed numerically using COMSOL …

Exciton Coherence In 1d Phthalocyanine Based Organic Crystalline Thin Films, Kimngan Burrill

Graduate College Dissertations and Theses

Quantum coherence plays a vital role in the excitonic properties of organic semiconductors. Several theoretical and experimental studies have shown an unprecedented role of coherence in charge transfer and transport processes, which in turn can improve the performance of electronic devices. Specifically, an enhancement of exciton coherence size can result in fast energy transport and efficient charge separation. The ability to tailor the design and performance of organic electronics based on exciton coherence effects represents the possibility of ultrafast electronic applications in communication and information technology.

The objective of this thesis is the excitonic coherence studies of 1D crystalline thin …

Numerical Simulations Of An Inductively Coupled Plasma Torch, Samuel Whitmore

Graduate College Dissertations and Theses

During entry into a planetary atmosphere, a blunt body (e.g. a spacecraft) traveling at hypersonic velocity creates a bow shock in front of it. In the highly energetic post shock environment, the body experiences heat transfer due to convective, chemical, and radiative processes. To protect the payload against this heating, a thermal protection system (TPS) is employed. Because a given propulsion system has a set amount of mass that it can launch to orbit, reducing the amount of mass used for TPS is desirable as this mass is freed up for mission-oriented payload. At the present, uncertainties in the flow …

Measuring And Modeling Information Flow On Social Networks, Tyson Charles Pond

Graduate College Dissertations and Theses

With the rise of social media, researchers have become increasingly interested in understanding how individuals inform, influence, and interact with others in their social network and how the network mediates the flow of information. Previous research on information flow has primarily used models of contagion to study the adoption of a technology, propagation of purchase recommendations, or virality of online activity. Social (or "complex") contagions spread differently than biological ("simple") contagions. A limitation when researchers validate contagion models is that they neglect much of the massive amounts of data now available through online social networks. Here we model a recently …

Quantum Entanglement Of One-Dimensional Spinless Fermions, Emanuel Casiano-Diaz

Graduate College Dissertations and Theses

The constituents of a quantum many-body system can be inextricably linked, a phenomenon known as quantum entanglement. Entanglement can be used as a resource for quantum computing, quantum communication and detecting phase transitions, among others. The amount of entanglement can be quantified via the von Neumann and Rényi entropies, which have their origins in information theory.

In this work, the quantum entanglement between subsystems of a one dimen- sional lattice model of fermions is quantified. The von Neumann and Rényi entropies were calculated for two types of subsystems. In the first study, the subsystems were treated as two subsets of …

A Multi-Frequency Study Of Arecibo Pulsars, Timothy Eugene Edward Olszanski

Graduate College Dissertations and Theses

Compact Objects (Neutron Stars) form in the last moments of a star's life, during the violent events known as supernovae. As the star's core fusion falters, matter undergoes a dramatic gravitational compression resulting in internal densities rivaling subatomic particles. Ever since their discovery in the mid-twentieth century, these highly magnetized and rapidly rotating balls of condensed matter have provided a bountiful playground for astronomers seeking out exotic physics.

Neutron Stars that emit electromagnetic radiation are seen by observers as Pulsars, named such for the pulse of intensity as the pulsar's radiation beam passes into our line of sight. These beams …

Some Results On A Class Of Functional Optimization Problems, David Rushing Dewhurst

Graduate College Dissertations and Theses

We first describe a general class of optimization problems that describe many natu- ral, economic, and statistical phenomena. After noting the existence of a conserved quantity in a transformed coordinate system, we outline several instances of these problems in statistical physics, facility allocation, and machine learning. A dynamic description and statement of a partial inverse problem follow. When attempting to optimize the state of a system governed by the generalized equipartitioning princi- ple, it is vital to understand the nature of the governing probability distribution. We show that optimiziation for the incorrect probability distribution can have catas- trophic results, e.g., …

Cargo Transport By Myosin Va Molecular Motors Within Three-Dimensional In Vitro Models Of The Intracellular Actin Cytoskeletal Network, Andrew Thomas Lombardo

Graduate College Dissertations and Theses

Intracellular cargo transport involves the movement of critical cellular components (e.g. vesicles, organelles, mRNA, chromosomes) along cytoskeletal tracks by tiny molecular motors. Myosin Va motors have been demonstrated to play a vital role in the transport of cargos destined for the cell membrane by navigating their cargos through the three-dimensional actin networks of the cell. Transport of cargo through these networks presents many challenges, including directional and physical obstacles which teams of myosin Va-bound to a single cargo must overcome. Specifically, myosin Va motors are presented with numerous actin-actin intersections and dense networks of filaments which can act as a …

Quantum Many - Body Interaction Effects In Two - Dimensional Materials, Sanghita Sengupta

Graduate College Dissertations and Theses

In this talk, I will discuss three problems related to the novel physics of two-dimensional quantum materials such as graphene, group-VI dichalcogenides family (TMDCs viz. MoS2 , WS2, MoSe2 , etc) and Silicene-Germanene class of materials.

The first problem poses a simple question - how do the quantum excitations in a graphene membrane affect adsorption? Using the tools of diagrammatic perturbation theory, I will derive the scattering rates of a neutral atom on a graphene membrane. I will show how this seemingly naive model can serve as a non-relativistic condensed matter analogue of the infamous infrared problem in Quantum Electrodynamics. …

Investigation Of Pyrolysis Gas Chemistry In An Inductively Coupled Plasma Facility, Corey Tillson

Graduate College Dissertations and Theses

The pyrolysis mechanics of Phenolic Impregnated Carbon Ablators (PICA) makes it a valued material for use in thermal protection systems for spacecraft atmospheric re-entry. The present study of the interaction of pyrolysis gases and char with plasma gases in the boundary layer over PICA and its substrate, FiberForm, extends previous work on this topic that has been done in the UVM 30 kW Inductively Coupled Plasma (ICP) Torch Facility. Exposure of these material samples separately to argon, nitrogen, oxygen, air, and carbon dioxide plasmas, and combinations of said test gases provides insight into the evolution of the pyrolysis gases as …

The Role Of N-Terminal Acidic Inserts On The Dynamics Of The Tau Protein., Miranda Redmond

Graduate College Dissertations and Theses

Alzheimer’s disease (AD), the most prevalent neurodegenerative disease, is characterized in part by disruptions in axonal transport. Axonal transport is a process by which motor proteins carry organelles and other cargo made in the neuronal cell body along microtubule tracks to distal regions of the axon. The microtubule-associated protein (MAP) Tau plays a crucial role in regulating axonal transport, and is implicated in the development of AD and other types of dementia collectively known as Tauopathies. Tau is a neuronal-specific MAP that has six isoforms alternatively spliced from a single gene. These isoforms differ by the presence of zero, one, …

Accelerating Quantum Monte Carlo Via Graphics Processing Units, Benjamin Evert Himberg

Graduate College Dissertations and Theses

An exact quantum Monte Carlo algorithm for interacting particles in the spatial continuum is extended to exploit the massive parallelism offered by graphics processing units. Its efficacy is tested on the Calogero-Sutherland model describing a system of bosons interacting in one spatial dimension via an inverse square law. Due to the long range nature of the interactions, this model has proved difficult to simulate via conventional path integral Monte Carlo methods running on conventional processors. Using Graphics Processing Units, optimal speedup factors of up to 640 times are obtained for N = 126 particles. The known results for the ground …

Microwave Bessel-Beam Propagation Through Spatially Inhomogeneous Media, Ryan Francis Grecco

Graduate College Dissertations and Theses

Long range wireless power transmission (WPT) is a critical technology for the development of remote power systems for air and space vehicles as well as for point-to-point transmission on Earth. This can be achieved using either a laser for transmission in the infrared to optical frequency domain or by using microwaves. The objective of this research is to study the application of microwave power transmission (MPT) through the use of a so-called Bessel-beam whose unique propagation properties include a self-healing ability as well as non-diffractive properties. These two unique properties lead to an increase in the efficiency of microwave power …

Wronskian And Gram Solutions To Integrable Equations Using Bilinear Methods, Benjamin Wiggins

Graduate College Dissertations and Theses

This thesis presents Wronskian and Gram solutions to both the Korteweg-de Vries and Kadomtsev-Petviashvili equations, which are then scalable to arbitrarily large numbers of interacting solitons.

Through variable transformation and use of the Hirota derivative, these nonlinear partial differential equations can be expressed in bilinear form. We present both Wronskian and Gram determinants which satisfy the equations.

N=1,2,3 and higher order solutions are presented graphically; parameter tuning and the resultant behavioral differences are demonstrated and discussed. In addition, we compare these solutions to naturally occurring shallow water waves on beaches.

Excitonic States In Crystalline Organic Semiconductors: A Condensed Matter Approach, Lane Wright Manning

Graduate College Dissertations and Theses

In this work, a new condensed matter approach to the study of excitons based on crystalline thin films of the organic molecule phthalocyanine is introduced. The premise is inspired by a wealth of studies in inorganic semiconductor ternary alloys (such as AlGaN, InGaN, SiGe) where tuning compositional disorder can result in exciton localization by alloy potential fluctuations. Comprehensive absorption, luminescence, linear dichroism and electron radiative lifetime studies were performed on both pure and alloy samples of metal-free octabutoxy-phthalocyanine and transition metal octabutoxy-phthalocyanines, where the metal is Mn, Co, Ni, and Cu. Varying the ratios of the metal to metal-free phthalocyanines …

Polarization Charge Density In Strained Graphene, Noah Wilson

Graduate College Dissertations and Theses

Graphene, the world's first truly two-dimensional material, is unique for having an electronic structure described by an effective Lorentz invariant theory. One important consequence is that the ratio or Coulomb energy to kinetic energy is a constant, depending only on conditions within the lattice rather than on the average charge density as in a typical Galilean invariant material. Given this unusual property, a natural question would be how do phenomena, such as screening of a Coulomb impurity, happen in graphene? Moreover, how does the addition of uniaxial strain enhance or diminish this behavior? Here I discuss our work to calculate …

Exchange Mechanisms In Macroscopic Ordered Organic Magnetic Semiconductors, Naveen Rawat

Graduate College Dissertations and Theses

Small molecule organic semiconductors such as phthalocyanines and their derivatives represent a very interesting alternative to inorganic semiconductor materials for the development of flexible electronic devices such as organic thin field effect transistors, organic Light Emitting Diodes and photo-voltaic cells. Phthalocyanine molecules can easily accommodate a variety of metal atoms as well in the central core of the molecule, resulting in wide range of magnetic properties. Exploration of optical properties of organic crystalline semiconductors thin films is challenging due to sub-micron grain sizes and the presence of numerous structural defects, disorder and grain boundaries. However, this can be overcome by …

Numerical Simulations Of Reacting Flow In An Inductively Coupled Plasma Torch, Maximilian Dougherty

Graduate College Dissertations and Theses

In the design of a thermal protection system for atmospheric entry, aerothermal heating presents a major impediment to efficient heat shield design. Recombination of atomic species in the boundary layer results in highly exothermic surface-catalyzed recombination reactions and an increase in the heat flux experienced at the surface. The degree to which these reactions increase the surface heat flux is partly a function of the heat shield material. Characterization of the catalytic behavior of these materials takes place in experimental facilities, however there is a dearth of detailed computational models for the fluid dynamic and chemical behavior of such facilities. …