Digital Commons Network^™

Fundamental Aspects Of The Interaction Between Light And Nanostructures, Stephen Keith Sanders

Physics & Astronomy ETDs

Recent breakthroughs in nanophotonics have brought new opportunities to control and manipulate light at the nanoscale. The optical properties of metallic nanostructures have attracted particular interest because of their plasmon resonances, which couple strongly with visible light, and generate large near-field enhancements in their vicinity. In the first part of this thesis, we investigate the fundamental limits of the local density of photonic states near nanostructures by analyzing a sum rule relating its spectral integral to the field induced by a static dipole. Next, we analyze how the design of metallic nanoantennas can benefit from incorporating active materials that display …

Simulation Of Light Propagation Captured By Photoemission Electron Microscopy (Peem), Nabila Islam

Dissertations and Theses

The Photoemission electron microscopes (PEEM) is a powerful tool capable of synchronously imaging wave nature of light manifested by interference patterns as well as its particle nature through the energy exchange between the incident photons and the photoemitted imaging electrons. PEEM offers a non-invasive high-resolution approach for studying light propagation and interaction phenomena within a nanophotonic waveguide [7,8]. The electric field intensity variation of the interference pattern yielded by the interaction between the incident light and the guided mode coupled into the waveguide produces varying photoemission yields creating contrast in PEEM image. The guided modes cannot be excited simply by …

Selection Rule For Topological Amplifiers In Bogoliubov De Gennes Systems, Hong Y. Ling, Ben Kain

College of Science & Mathematics Departmental Research

Dynamical instability is an inherent feature of bosonic systems described by the Bogoliubov de Geenes (BdG) Hamiltonian. Since it causes the BdG system to collapse, it is generally thought that it should be avoided. Recently, there has been much effort to harness this instability for the benefit of creating a topological amplifier with stable bulk bands but unstable edge modes which can be populated at an exponentially fast rate. We present a theorem for determining the stability of states with energies sufficiently away from zero, in terms of an unconventional commutator between the number conserving part and number nonconserving part …

The Incubation Effect Among Students Playing An Educational Game For Physics, May Marie P. Talandron-Felipe, Ma. Mercedes T. Rodrigo

Department of Information Systems & Computer Science Faculty Publications

The incubation effect (IE) is a problem-solving phenomenon composed of three phases: pre-incubation where one fails to solve a problem; incubation, a momentary break where time is spent away from the unsolved problem; and post-incubation where the unsolved problem is revisited and solved. Literature on IE was limited to experiments involving traditional classroom activities. This initial investigation showed evidence of IE instances in a computer-based learning environment. This paper consolidates the studies on IE among students playing an educational game called Physics Playground and presents further analysis to examine the incidence of post-incubation or the revisit to a previously unsolved …

3d-Printing Habitable Structures On Mars, Addison Johnson, John Pugsley, Andrew Scherer

Faculty-Mentored Undergraduate Scholarship

This project developed technology to 3D-print habitable structures on Mars from in-situ materials, as part of the push to create a self-sustaining colony on Mars. The team designed a next generation sulfur concrete printhead capable of extruding with greater efficiency and better quality than the previous design.

Determinantal Quantum Monte Carlo Solver For Cluster Perturbation Theory, Edwin W. Huang, Yao Wang

Open Access Publishing Fund

Cluster Perturbation Theory (CPT) is a technique for computing the spectral function of fermionic models with local interactions. By combining the solution of the model on a finite cluster with perturbation theory on intra-cluster hoppings, CPT provides access to single-particle properties with arbitrary momentum resolution while incurring low computational cost. Here, we introduce Determinantal Quantum Monte Carlo (DQMC) as a solver for CPT. Compared to the standard solver, exact diagonalization (ED), the DQMC solver reduces finite size effects through utilizing larger clusters, allows study of temperature dependence, and enables large-scale simulations of a greater set of models. We discuss the …

Biochemical Impact Of Solar Radiation Exposure On Human Keratinocytes Monitored By Raman Spectroscopy; Effects Of Cell Culture Environment, Ulises Lopez Gonzalez, Alan Casey, Hugh Byrne

Articles

Understanding and amelioration of the effects of solar radiation exposure are critical in preventing the occurrence of skin cancer. Towards this end, many studies have been conducted in 2D cell culture models under simplified and unrealistic conditions. 3D culture models better capture the complexity of in vivo physiology, although the effects of the 3D extracellular matrix have not been well studied. Monitoring the instantaneous and resultant cellular responses to exposure, and the influence of the 3D environment, could provide an enhanced understanding of the fundamental processes of photocarcinogenesis. This work presents an analysis of the biochemical impacts of simulated solar …

Relating Dust Reference Models To Conventional Systems In Manifestly Gauge Invariant Perturbation Theory, Kristina Giesel, Bao-Fei Li, Parampreet Singh

Faculty Publications

Models with dust reference fields in relational formalism have proved useful in understanding the construction of gauge invariant perturbation theory to arbitrary orders in the canonical framework. These reference fields modify the dynamical equations for perturbation equations. However, important questions remain open on the relation with conventional perturbation theories of inflaton coupled to gravity and of multifluid systems, and on understanding modifications in terms of physical degrees of freedom. These gaps are filled in this manuscript for Brown-Kuchar and Gaussian dust models, both of which involve three scalar physical degrees of freedom. We establish a relationship of these models with …

Deep-Learning Based Reconstruction Of The Shower Maximum Xmax Using The Water-Cherenkov Detectors Of The Pierre Auger Observatory, A. Aab, P. Abreu, M. Aglietta, J. M. Albury, I. Allekotte, A. Almela, B. Fick, D. F. Nitz, A. Puyleart, Et. Al.

Michigan Tech Publications, Part 1

The atmospheric depth of the air shower maximum Xmax is an observable commonly used for the determination of the nuclear mass composition of ultra-high energy cosmic rays. Direct measurements of Xmax are performed using observations of the longitudinal shower development with fluorescence telescopes. At the same time, several methods have been proposed for an indirect estimation of Xmax from the characteristics of the shower particles registered with surface detector arrays. In this paper, we present a deep neural network (DNN) for the estimation of Xmax. The reconstruction relies on the signals induced by shower particles in the ground based water-Cherenkov …

Crosssections, Summer 2021, University Of Northern Iowa. Department Of Physics.

CrossSections

Contents:

A Message from the Department Head, Dr. Paul Shand --- 1
Faculty Profile: Dr. Paul Shand --- 3
Department Happenings --- 4
Student Focus --- 6
Student Research --- 8
Alumni Profile --- 9
Alumni News --- 10
Science Education --- 11
In Memoriam --- 12
New Physics --- 15

Estimating Turbulence Distribution Over A Heterogeneous Path Using Time‐Lapse Imagery From Dual Cameras, Benjamin Wilson, Santasri Bose-Pillai, Jack E. Mccrae, Kevin J. Keefer, Steven T. Fiorino

Faculty Publications

Knowledge of turbulence distribution along an experimental path can help in effective turbulence compensation and mitigation. Although scintillometers are traditionally used to measure the strength of turbulence, they provide a path-integrated measurement and have limited operational ranges. A technique to profile turbulence using time-lapse imagery of a distant target from spatially separated cameras is presented here. The method uses the turbulence induced differential motion between pairs of point features on a target, sensed at a single camera and between cameras to extract turbulence distribution along the path. The method is successfully demonstrated on a 511 m almost horizontal path going …

High-Order Positivity-Preserving L2-Stable Spectral Collocation Schemes For The 3-D Compressible Navier-Stokes Equations, Johnathon Keith Upperman

Mathematics & Statistics Theses & Dissertations

High-order entropy stable schemes are a popular method used in simulations with the compressible Euler and Navier-Stokes equations. The strength of these methods is that they formally satisfy a discrete entropy inequality which can be used to guarantee L₂ stability of the numerical solution. However, a fundamental assumption that is explicitly or implicitly used in all entropy stability proofs available in the literature for the compressible Euler and Navier-Stokes equations is that the thermodynamic variables (e.g., density and temperature) are strictly positive in the entire space{time domain considered. Without this assumption, any entropy stability proof for a numerical scheme …

Development And Applications Of Adjoint-Based Aerodynamic And Aeroacoustic Multidisciplinary Optimization For Rotorcraft, Ramiz Omur Icke

Mechanical & Aerospace Engineering Theses & Dissertations

Urban Air Mobility (UAM) is one of the most popular proposed solutions for alleviating traffic problems in populated areas. In this context, the proposed types of vehicles mainly consist of rotors and propellers powered by electric motors. However, those rotary-wing components can contribute excessively to noise generation. Therefore, a significant noise concern emerges due to urban air vehicles in or around residential areas. Reducing noise emitted by air vehicles is critically important to improve public acceptance of such vehicles for operations in densely populated areas.

Two main objectives of the present dissertation are: (1) to expand the multidisciplinary optimization to …

Electrohydrodynamic Simulations Of Capsule Deformation Using A Dual Time-Stepping Lattice Boltzmann Scheme, Charles Leland Armstrong

Mathematics & Statistics Theses & Dissertations

Capsules are fluid-filled, elastic membranes that serve as a useful model for synthetic and biological membranes. One prominent application of capsules is their use in modeling the response of red blood cells to external forces. These models can be used to study the cell’s material properties and can also assist in the development of diagnostic equipment. In this work we develop a three dimensional model for numerical simulations of red blood cells under the combined influence of hydrodynamic and electrical forces. The red blood cell is modeled as a biconcave-shaped capsule suspended in an ambient fluid domain. Cell deformation occurs …

Large-NC Constraints For One- And Two-Nucleon Currents In Effective Field Theory, Thomas Richardson

Theses and Dissertations

There is a long-standing goal of understanding nuclear physics in terms of quarks and gluons, the constituent particles of nucleons. However, the underlying theory is strongly coupled at the scales relevant for nuclear physics; therefore, this goal can only be achieved through nonperturbative calculations. Additionally, nuclear targets are employed in a variety of experiments ranging from electroweak processes to Beyond the Standard Model physics. Thus, it is important to have a strong theoretical foundation for nuclear physics in the presence of external fields in order to interpret experimental results. Effective field theory (EFT) for nuclear physics constitutes a systematic and …

Two Aspects Of Magnetic Nanoparticle Self-Assembly On Thin-Film Multilayers: Custom Media Properties And Accurate Determination Of Nanoparticle Anisotropy Constant, Sara L. Fitzgerald

Theses and Dissertations

ZFC/FC moment versus temperature measurements are a common technique to determine magnetic properties of nanoparticles. In this work, I varied both applied field strength and nanoparticle concentration to study resulting changes in blocking temperature, T_B, and anisotropy constant, K. T_B and K values were obtained using both existing and new analytic methods. Accurate determination of these parameters helps researchers optimize the use of magnetic nanoparticles for a variety of applications, including magnetic heating, drug delivery, and magnetic field-directed self-assembly. For magnetic self-assembly particularly, not only nanoparticle properties, but also the magnetic properties of the substrate alter …

Π+Π- Electroproduction Off Protons In Deuterium: Measurements Of Quasi-Free Cross Sections And Kinematic Probing Of Final State Interactions, Iuliia Skorodumina

Theses and Dissertations

In this study, the process of π⁺π^- electroproduction off protons bound in deuterium nuclei is explored. The exploration is performed through the analysis of experimental data on electron scattering off the deuteron target, collected in Hall B at Jefferson Lab with the CLAS detector. As a main result, the set of integrated and single-differential cross sections of the reaction $\gamma_{v}p(n) \rightarrow p' (n')\pi^{+}\pi^{-}$ is obtained. The cross sections are extracted in the quasi-free regime, which implies that only events not affected by final state interactions are subject to selection. The measurements are performed in the kinematic region …

J/Ψ Photoproduction Near Threshold With Clas12, Joseph Newton

Physics Theses & Dissertations

The structure of the proton is comprised of quarks and a sea of gluons. A mechanism that can extract the characteristics of the hidden-color correlations of the nuclear wavefunction is the production of charm near threshold. Due to the fact that momentum transfer is large near threshold in the production of J/ψ , all three valence quarks must act coherently to ex- change energy for the reaction to occur. Models have been developed to predict the nature of J/ψ photoproduction at these specific energies. These include production mechanisms with the two-gluon and three-gluon exchanges. The transferred momentum dependence of the …

Quasiclassical Computations Of Compton-Scattered Spectra, Erik Scott Johnson

Physics Theses & Dissertations

Quality X-ray sources are crucial to fundamental physics research, medical radiology, humanities research, and materials science. While synchrotron radiation (SR) facilities produce the state-of-the- art emissions with respect to brilliance and frequency tunability, the great expense required to build, maintain, and operate these structures greatly limits their accessibility to researchers. Much of the research conducted at SR facilities, however, may be conducted with inverse Compton sources (ICS). Accelerator-based Compton scattering light sources generate high-energy, high-brilliance emissions. Compton scattering is the process by which a photon scatters off an electron. ICS offer an affordable, in-lab alternative to SR facilities. Even though …

Antimatter Free-Fall Experiments And Charge Asymmetry, Ulrich D. Jentschura

Physics Faculty Research & Creative Works

We propose a method by which one could use modified antimatter gravity experiments in order to perform a high-precision test of antimatter charge neutrality. The proposal is based on the application of a strong, external, vertically oriented electric field during an antimatter free-fall gravity experiment in the gravitational field of the Earth. The proposed experimental setup has the potential to drastically improve the limits on the charge-asymmetry parameter ɛq of antimatter. On the theoretical side, we analyze possibilities to describe a putative charge-asymmetry of matter and antimatter, proportional to the parameters ɛq and ɛq, by Lagrangian methods. We found that …

Erratum: Laser-Induced Electron Diffraction Of The Ultrafast Umbrella Motion In Ammonia (Struct. Dyn. (2021) 8 (014301) Doi: 10.1063/4.0000046), B. Belsa, K. Amini, X. Liu, A. Sanchez, T. Steinle, J. Steinmetzer, Anh-Thu Le, R. Moshammer, T. Pfeifer, J. Ullrich, R. Moszynski, C. D. Lin, S. Gräfe, J. Biegert

Physics Faculty Research & Creative Works

This article was originally published online on 13 January 2021 with an affiliation for J. Ullrich, Physikalisch-Technische Bundesanstalt, Bundesallee 100, 38116 Braunschweig, Germany, omitted. All online versions of the article were corrected on 13 May 2021. All affiliations appear correctly above.

Structural And Electronic Properties Of Few-Layer Monochalcogenides, Brandon Joel Miller

Graduate Theses and Dissertations

This work discusses a new class of materials with novel properties that have only recently begun being studied. These materials are two-dimensional group IV-VI monochalcogenides, so named because they are formed from group IV (carbon group) and group VI (chalcogens) elements. These materials display several interesting physical properties such as ferroelasticity and ferroelectricity, and the contents within Chapters Two, Three, and Four concern a collaborative effort between theory and experiment between our group at the University of Arkansas and Dr. Kai Chang at the Max Planck Institute of Microstructure Physics in Halle, Germany in studying these properties. This thesis is …

Fabrication And Characterization Of Photodetector Devices Based On Nanostructured Materials: Graphene And Colloidal Nanocrystals, Wafaa Gebril

Graduate Theses and Dissertations

Photodetectors are devices that capture light signals and convert them into electrical signals. High performance photodetectors are in demand in a variety of applications, such as optical communication, security, and environmental monitoring. Among many appealing nanomaterials for novel photodetection devices, graphene and semiconductor colloidal nanocrystals are promising candidates because of their desirable and unique properties compared to conventional materials.

Photodetector devices based on different types of nanostructured materials including graphene and colloidal nanocrystals were investigated. First, graphene layers were mechanically exfoliated and characterized for device fabrication. Self-powered few layers graphene phototransistors were studied. At zero drain voltage bias and room …

Characterization And Modeling Of Upward Lightning At The Gaisberg Tower, Naomi Watanabe

Theses and Dissertations

The majority of cloud-to-ground lightning is downward. Upward lightning rarely occurs; less than 1% of cloud-to-ground lightning is upward. Upward lightning differs from its downward counterpart in how it is initiated. Upward lightning is initiated by an upward moving leader from a tall (> 100 m) object on ground that reaches into the charge regions of an overhead thundercloud resulting in a relatively-long-duration (tens to hundreds of milliseconds), low-level (tens to hundreds of amperes) current called the initial continuous current. It is of significant importance to understand in detail the processes associated with upward lightning as it affects ground-based infrastructure …

Computational Modeling Of Black Phosphorus Terahertz Photoconductive Antennas Using Comsol Multiphysics With Experimental Comparison Against A Commercial Lt-Gaas Emitter, Jose Isaac Santos Batista

Graduate Theses and Dissertations

This thesis presents computational models of terahertz (THz) photoconductive antenna (PCA) emitter using COMSOL Multiphysics commercial package. A comparison of the computer simulated radiated THz signal against that of an experimentally measured signal of commercial reference LT-GaAs emitter is presented. The two-dimensional model (2D) aimed at calculating the photoconductivity of a black phosphorus (BP) PCA at two laser wavelengths of 780 nm and 1560 nm. The 2D model was applied to the BP PCA emitter and the LT-GaAs devices to compare their simulated performance in terms of the photocurrent and radiated THz signal pulse. The results showed better performance of …

Examining Melt Pond Dynamics And Light Availability In The Arctic Ocean Via High Resolution Satellite Imagery, Austin Wesley Abbott

OES Theses and Dissertations

As the Arctic experiences consequences of climate change, a shift from thicker, multi-year ice to thinner, first-year ice has been observed. First-year ice is prone to extensive pools of meltwater (“melt ponds”) forming on its surface, which enhance light transmission to the ocean. Changes in the timing and distribution of melt pond formation and associated increases in under-ice light availability are the primary drivers for seasonal progression of water column primary production and warming. Observations of melt pond development and distribution require meter scale resolution and have traditionally been limited to airborne images. However, recent advances in high spatial resolution …

Simulation Of Self-Heating Effect In Mosfet Based On 2d Mos2, Atabek E. Atamuratov, Xushnudbek Sh. Saparov, A Yusupov, Frank Schwierz

Scientific Bulletin. Physical and Mathematical Research

One of the main trends of today's electronics is the decreasing the sizes of MOSFET up to nanometer scale. In this connection there are two main views to the perspective of scaling. According to one of them limit of scaling is reached at sizes 10 nm order, however according to second view, still there are opportunity to decrease transistor to more lower sizes. In accordance with second approach it is suggested to continue the size scaling by modification the transistor structure or by using the new materials, particularly one or two dimensional materials. One of such suggestions is the designing …

Influence Of A Strong Magnetic Field On Fermi Energy Oscillations In Two-Dimensional Semiconductor Materials, Gafur Gulyamov, Ulugbek Inayatillyevich Erkaboev, Rustam Gulomzhonovich Rakhimov, Nozimjon Sayidov Sayidov, Jasurbek Mirzaev

Scientific Bulletin. Physical and Mathematical Research

This article discusses the effect of a quantizing magnetic field and temperature on Fermi energy oscillations in nanoscale semiconductor materials. A generalized mathematical expression is obtained for calculating the dependence of the Fermi energy oscillations on the magnetic field, temperature, and thickness of the quantum well. It is shown that the Fermi energy in nanoscale semiconductor materials under a quantizing magnetic field is quantized. The proposed theory explains the experimental results in two-dimensional semiconductor structures with a parabolic dispersion law.

A Cauchy-Goursat Problem For A Second Kind Degenerated Equation Of Hyperbolic Type, Doniyor Usmonov

Scientific Bulletin. Physical and Mathematical Research

In the work a Cauchy-Goursta problem has been formulated and investigated for a second kind degenerated equation of hyperbolic type. During the investigation, it was used properties of Gauss’s hyper geometric function and symbol of Pochhammer, the considered problem equivalently reduced to an integral equation with respect to trace of unknown function. Properties of Riemann-Liuvill integral-differential and generalized integral-differential operators have found solution of the taken integral equation. To find solution of the problem it was used general solution of the equation. A class of generalized solutions was introduced for the correctness of the problem. It was found necessary conditions …

Kapitza-Dirac Blockade: A Universal Tool For The Deterministic Preparation Of Non-Gaussian Oscillator States, Wayne Cheng-Wei Huang, Herman Batelaan, Markus Arndt

Department of Physics and Astronomy: Faculty Publications

Harmonic oscillators count among the most fundamental quantum systems with important applications in molecular physics, nanoparticle trapping, and quantum information processing. Their equidistant energy level spacing is often a desired feature, but at the same time a challenge if the goal is to deterministically populate specific eigenstates. Here, we show how interference in the transition amplitudes in a bichromatic laser field can suppress the sequential climbing of harmonic oscillator states (Kapitza-Dirac blockade) and achieve selective excitation of energy eigenstates, cat states, and other non-Gaussian states. This technique can transform the harmonic oscillator into a coherent two-level system or be used …