Physics Commons^™

The Aging And Impacts Of Atmospheric Soot: Closing The Gap Between Experiments And Models, Ogochukwu Yvonne Enekwizu

Dissertations

The main goal of this dissertation is to generate data and parameterizations to accurately represent soot aerosols in atmospheric models. Soot from incomplete combustion of fossil fuels and biomass burning is a major air pollutant and a significant contributor to climate warming. The environmental impacts of soot are strongly dependent on the particle morphology and mixing state, which evolve continuously during atmospheric transport via a process known as aging. To make predictions of soot impacts on the environment, most atmospheric models adopt simplifications of particle structure and mixing state, which lead to substantial uncertainties. Using an experimentally constrained modeling approach, …

Live Cell Super-Resolution Microscopy Quanitifies An Interaction Between Influenza Hemagglutinin And Phosphatidylinositol 4,5-Bisphosphate, Jaqulin N. Wallace

Electronic Theses and Dissertations

Influenza virus, colloquially known as the flu, is an acute respiratory disease that infects several millions of individuals each year in the U.S. and kills tens of thousands of those infected. Yearly viral vaccines are widely available, however, due to the virus’s high mutation rate, their efficacy varies greatly. Due to the variability in vaccine efficiency against seasonal influenza, and the potential for even more pathogenic versions of influenza to emerge at any time, there is a high demand for a universal treatment option.

Influenza virus hijacks a variety of host cell components in order to replicate. The glycoprotein hemagglutinin …

Parametric Model Development For Heterogeneous Atmospheric Conditions, Daniel Paul Greenway

Electronic Theses and Dissertations

No abstract provided.

Laser-Induced Breakdown Spectroscopy And Plasmas Containing Cyanide, Christopher Matthew Helstern

Doctoral Dissertations

This dissertation focuses on laser-induced plasma of diatomic molecular cyanide. Optical breakdown plasma generation is produced by high-peak-power 1064 nm Q-switched nanosecond pulsed radiation. Laser-induced breakdown is performed on a 1:1 molar gas mixture of carbon dioxide and nitrogen held at a fixed pressure of 760 Torr, a 1:1 molar gas mixture of carbon dioxide and nitrogen held at a fixed pressure of 2069 Torr, and a flowing 1:1 molar gas mixture of carbon dioxide and nitrogen flowing at a rate of 100 mL per minute. Plasma shockwave measurements in laboratory air are shown to determine the shock front geometry …

Characterization Of A Digital Holography Diagnostic For In Situ Erosion Measurement Of Plasma-Facing Components In Fusion Devices, Cary Dean Smith

Doctoral Dissertations

Fusion energy devices, particularly tokamaks, face the challenge of interior surface damage occurring over time from the heat flux of the high-energy plasma they generate. The ability to monitor the rate of surface modification is therefore imperative, but to date no proven technique exists for real-time erosion measurement of planar regions of interest on plasma-facing components in fusion devices. In order to fill this diagnostic gap, a digital holography system has been established at ORNL [Oak Ridge National Laboratory] for the purpose of measuring the erosion effects of plasma-material interaction in situ.

The diagnostic has been designed with the …

Using Second Harmonic Generation To Study Gram-Positive Bacterial Membranes, Lindsey N. Miller

Doctoral Dissertations

Understanding how small-molecules, such as drugs, interact with bacterial membranes can quickly unravel into much more perplexing questions. No two bacterial species are alike, especially when comparing their membrane compositions which can even be altered by incorporating fatty acids from their surrounding environment into their lipid-membrane composition. To further complicate the comparison, discrete alterations in small-molecule structures can result in vastly different membrane-interaction outcomes, giving rise to the need for more "label-free" studies when analyzing drug mechanisms. The work presented in this dissertation highlights the benefits to using nonlinear spectroscopy and microscopy techniques for probing small-molecule interactions in living bacteria. …

Characterization Of Fiber Bragg Grating Based, Geometry-Dependent, Magnetostrictive Composite Sensors, Edward Lynch

Theses and Dissertations

Optical sensors based on geometry dependent magnetostrictive composite, having potential applications in current sensing and magnetic field sensing are modeled and evaluated experimentally with an emphasis on their thermal immunity from thermal disturbances. Two sensor geometries composed of a fiber Bragg grating (FBG) embedded in a shaped Terfenol-D/epoxy composite material, which were previously prototyped and tested for magnetic field response, were investigated. When sensing magnetic fields or currents, the primary function of the magnetostrictive composite geometry is to modulate the magnetic flux such that a magnetostrictive strain gradient is induced on the embedded FBG. Simulations and thermal experiments reveal the …

Vibration Overtone Hyperpolarizability Measured For H2 Using Electric Field Induced Second Harmonic Generation, Rachel Ellis

UNLV Theses, Dissertations, Professional Papers, and Capstones

The vibrational contribution to the second hyperpolarizability (γ) of gas phase H2 was measured using electric field induced second harmonic generation. Measurements were made for the pure vibrational 3-0 Q(J) overtone transitions (v=0,J → v’=3,J for J = 0,1,2,3). Measured intensities were found to be 4-14% larger than ab initio calculations. The first chapter of this thesis provides an introduction to nonlinear optics, second harmonic generation, and the tensor nature of hyperpolarizabilities. The second chapter provides theoretical expressions for γ and relevant static and Raman polarizabilities. The third chapter covers the experimental design and electric field induced second harmonic generation. …

Optical Properties Of Ultrathin In(Ga)As/Gaas And In(Ga)N/Gan Quantum Wells, Yurii Maidaniuk

Graduate Theses and Dissertations

Recently, structures based on ultrathin quantum wells (QWs) began to play a critical role in modern devices, such as lasers, solar cells, infrared photodetectors, and light-emitting diodes. However, due to the lack of understanding of the formation mechanism of ultrathin QWs during the capping process, scientists and engineers cannot fully explore the potential of such structures. This study aims to investigate how structural parameters of ultrathin QWs affect their emission properties by conducting a systematic analysis of the optical properties of In(Ga)As/GaAs and In(Ga)N/GaN ultrathin QWs. Specifically, the analysis involved photoluminescence measurements combined with effective bandgap simulation, x-ray diffraction, and …

Spontaneous Raman Scattering Enhancement With Microcavities And Multipass Resonators For Trace Gas Detection, Juan Sebastian Gomez Velez

USF Tampa Graduate Theses and Dissertations

The continual increase in production and use of chemicals in an ever-growing field of applications naturally brings forth the necessity to accurately and efficiently measure molecular composition. Spontaneous Raman scattering is a reliable technique which can optically identify molecules based on their intrinsic rotational-vibrational energy structure. The Raman emission from a substance can be spectrally analyzed to detect molecular species simultaneously and with isotopic sensitivity using a single laser source. However, even though the process is non-invasive and effective, the rate at which the emission occurs is notoriously low due to a weak scattering cross-section. Therefore, research into the development …

Control Of Molecular Energetics And Transport Via Strong Light-Matter Interaction, Rong Wu

Dissertations, Theses, and Capstone Projects

Strong light-matter coupling in excitonic systems results in the formation of half-light half-matter quasiparticles called exciton polaritons. These hybrid quasiparticles take on the best of both systems, namely, the long-range propagation and coherence arising from the photonic component and the nonlinear interaction from the excitonic component. We develop methods for making high quality factor cavities and investigate the potential applications of these strongly coupled states arising specifically in organic molecular systems.

In the first project we investigate the potential of organic dye molecules to undergo condensation in an optical cavity at room temperature. The second study involves the use of …

Emulating Condensed Matter Systems In Classical Wave Metamaterials, Matthew Weiner

Dissertations, Theses, and Capstone Projects

One of the best tools we have for the edification of physics is the analogy. When we take our classical set of states and dynamical variables in phase space and treat them as vectors and Hermitian operators respectively in Hilbert space through the canonical quantization, we lose out on a lot of the intuition developed with the previous classical physics. With classical physics, through our own experiences and understanding of how systems should behave, we create easy-to-understand analogies: we compare the Bohr model of the atom to the motion of the planets, we compare electrical circuits to the flow of …

Structural Organization And Chemical Activity Revealed By New Developments In Single-Molecule Fluorescence And Orientation Imaging, Tianben Ding

McKelvey School of Engineering Theses & Dissertations

Single-molecule (SM) fluorescence and its localization are important and versatile tools for understanding and quantifying dynamical nanoscale behavior of nanoparticles and biological systems. By actively controlling the concentration of fluorescent molecules and precisely localizing individual single molecules, it is possible to overcome the classical diffraction limit and achieve 'super-resolution' with image resolution on the order of 10 nanometers.

Single molecules also can be considered as nanoscale sensors since their fluorescence changes in response to their local nanoenvironment. This dissertation discusses extending this SM approach to resolve heterogeneity and dynamics of nanoscale materials and biophysical structures by using positions and orientations …

Biomedical Applications Of Polarimetry, Nathaniel Owen King

McKelvey School of Engineering Theses & Dissertations

Non- or minimally-invasive data collection is highly desirable for gathering the broad base of information that facilitates moving technology to the point of care. Polarimetry has been making this transition for years. Early forms of polarization-sensitive optics involved custom multiplexing a series of images to generate a single image, but today’s snapshot polarimeters are readily commercially available.

The research presented in this dissertation advances three areas of polarimetric imaging: First, this research develops a reflectance-based measurement for tracking changes in the alignment of dynamically loaded soft tissue, specifically tendon. This work highlights a range of mounting angles across which signal …

Snow-Albedo Feedback In Northern Alaska: How Vegetation Influences Snowmelt, Lucas C. Reckhaus

Theses and Dissertations

This paper investigates how the snow-albedo feedback mechanism of the arctic is changing in response to rising climate temperatures. Specifically, the interplay of vegetation and snowmelt, and how these two variables can be correlated. This has the potential to refine climate modelling of the spring transition season. Research was conducted at the ecoregion scale in northern Alaska from 2000 to 2020. Each ecoregion is defined by distinct topographic and ecological conditions, allowing for meaningful contrast between the patterns of spring albedo transition across surface conditions and vegetation types. The five most northerly ecoregions of Alaska are chosen as they encompass …

Development And Demonstration Of A Pico-Watt Calorimeter For Optical Absorption Spectroscopy, Behshad Roshanzadeh

Optical Science and Engineering ETDs

An optical calorimeter for sensitive absorption measurements of non-radiative samples at 4 K was designed, built, and demonstrated. It consists of a cryostat cooled by a commercial pulse tube (PTC) refrigerator, a measurement chamber housing the sample and thermometers, and various fiber-coupled light sources. By employing measures to damp mechanical noise from the environment and active temperature stabilization of critical components of the instrument temperature noise as low as 6 nK/√Hz at 50 mHz was achieved under 15 mW of optical excitation. An optical absorption induced temperature increase of the sample as small as 2.5 nK could be resolved using …

Generation Of Correlated Dual Frequency Combs With Pm Fiber Lasers For High-Precision Metrology, Hanieh Afkhamiardakani

Optical Science and Engineering ETDs

Intracavity Phase Interferometry (IPI) using two correlated, counter-propagating frequency combs (pulse trains) in mode-locked lasers has evolved into a powerful technique for high-precision metrology. In this method a physical parameter to be measured imparts a phase shift onto a pulse circulating in the laser cavity. Inside a laser cavity, that phase shift becomes a frequency shift (phase shift/round-trip time) applied to the whole frequency comb created by this pulse as it exits the cavity at each round-trip. This frequency shift is measured by interfering this comb with a reference comb created by a reference pulse circulating in the same mode-locked …

Radiation-Balanced Fiber Lasers And Amplifiers, Esmaeil Mobini Souchelmaei Mr

Optical Science and Engineering ETDs

Over the past decades, high-power fiber lasers and amplifiers have been extensively under research to achieve higher output powers. However, temperature rise in the core of fiber lasers and amplifiers has been a big issue in power-scaling. Radiation-balancing is a viable technique introduced for effective heat mitigation in lasers and amplifiers by S. Bowman in 1995. Radiation-balancing relies on solid-state laser cooling as a self-cooling mechanism to mitigate the generated heat in lasers and amplifiers. To implement the mentioned idea in fiber lasers and amplifiers, a set of issues should be scrutinized; (i) the amenability of silica glass (as the …

Design Of A 5 Degree Of Freedom Kinematic Stage For The Dual Crystal Backlighter Imager Diagnostic, Nicholas Nguyen

Master's Theses

The National Ignition Facility (NIF) is home to the world’s most energetic laser. The facility is one of the leading centers in inertial confinement fusion (ICF) experiments to research and understand sustainable fusion energy. To fully document and understand the physics occurring during experiments, precise diagnostics are used for a wide range of purposes. One diagnostic, the crystal backlighter imager (CBI), allows for X-ray imaging of the target at late stages of its implosion.

The aim of this project was to increase the current capabilities of the CBI diagnostic with the addition of a second crystal. This thesis focuses on …

Data Assimilation For Conductance-Based Neuronal Models, Matthew Moye

Dissertations

This dissertation illustrates the use of data assimilation algorithms to estimate unobserved variables and unknown parameters of conductance-based neuronal models. Modern data assimilation (DA) techniques are widely used in climate science and weather prediction, but have only recently begun to be applied in neuroscience. The two main classes of DA techniques are sequential methods and variational methods. Throughout this work, twin experiments, where the data is synthetically generated from output of the model, are used to validate use of these techniques for conductance-based models observing only the voltage trace. In Chapter 1, these techniques are described in detail and the …

The Primary Volatile Composition Of Comet C/2015 Er61 (Panstarrs), Aaron Butler

Theses

In the outer edges of the solar system exist two regions: the Kuiper belt and Oort cloud. These two regions have a high amount of icy bodies (comets) orbiting the Sun. Comets located within the Oort cloud and Kuiper belt contain an ancient codex to the solar systems contents, before the formation of our solar system. Presented are near-infrared, high-resolution (λ/Δλ ~40000) data obtained from the immersion-grating echelle spectrograph iSHELL at the 3m NASA Infrared Telescope Facility (IRTF) in Maunakea, Hawaii of the Oort cloud comet C/2015 ER61 (PANSTARRS). Observations took place on April 15 and 17 in 2017 while …

Design And Fabrication Of Biaxial Hyperbolic Metamaterials, Changkee Hong

Graduate Theses - Physics and Optical Engineering

This thesis describes a new method for fabrication of biaxial hyperbolic metamaterials (BHMMs) using layered structures consisting of oblique angle deposited (OAD) titanium dioxide (TiO2) and copper (Cu). An oblique angle deposition (OAD) technique was utilized to deposit dielectric layer composed of nanocolumnar structures in order to provide biaxial property. The biaxial hyperbolic dispersion of the fabricated BHMM was characterized via profilometer and variable angle spectroscopic ellipsometry (VASE) measurements for wavelength between 381 nm and 894 nm. For the fabricated BHMM, a noticeable difference of 0.13 - 0.001 between the in-plane permittivity components and dual epsilon-near-zero (ENZ) regions which are …

An Overview Of Lasers And Their Applications, Luis Cristian Giovanni Guerrero

Physics

This paper is an overview of lasers and their applications. The fundamentals of laser operation are covered as well as the various applications of advanced laser systems. The primary focus is to highlight some of the technological advancements made possible by lasers in the last half-century.

Quantification Of Interactions Between Influenza Hemagglutinin And Host Cell Phosphoinositides By Super-Resolution Microscopy, Matthew T. Parent

Electronic Theses and Dissertations

The influenza viral membrane protein hemagglutinin (HA) forms dense nanoscale clusters on host cell plasma membranes (PM), but the mechanisms that direct HA clustering are not well understood. Previous studies have observed HA associated with actin rich regions of the PM, but there are no known direct interactions between HA and actin. Phosphatidylinositol 4,5-biphosphate (PIP2) is a signaling lipid in the PM which can regulate the actin cytoskeleton, and actin comets initiated by PIP2 are known to be exploited by HA to reach the PM of infected cells. PIP2 is also used by other viruses, such as HIV and Ebola, …

Design Of Submicron Structured Guided-Mode-Resonance Near-Infrared Polarizer, Marzia Zaman

Graduate Theses and Dissertations

The objective of this research is to design a larger submicron linear polarizer in the near-infrared wavelength range with a wide bandwidth which can be fabricated using the conventional thin-film microfabrication technology to reduce cost. For this purpose, a gold (Au) wire-grid transmission-type transverse-magnetic (TM) polarizer and a silicon (Si) wire-grid reflection-type TM polarizer, were designed using the guided-mode-resonance filter. The Au wire-grid TM polarizer of 700nm grating width and 1200nm grating period has 95% transmittance at 2400nm, more than 1000nm resonance peak bandwidth, and an extinction ratio (ER) of around 300 with a moderated level of sidebands. The 700nm …

A Study Of Optical Nonlinearities At The Single-Photon Level For Quantum Logic, Balakrishnan Viswanathan

Graduate Theses and Dissertations

In this dissertation, we shall focus on theoretically studying quantum nonlinear optical schemes to construct a conditional phase gate at the single-photon level. With an aim to develop analytical models, we shall carry out a rigorous quantized multimode field analysis of some of these schemes involving only the interacting field operators. More specifically, we shall first study the three-wave mixing process involving two single-photons in a second-order nonlinear medium (x(2)) under two different cases viz. when the photons are traveling with equal velocities and when they are traveling with different velocities, and explore the possibility of using them for building …

Development Of Co2 Laser-Heating For The Study Of Wide Band Gap Oxide Materials, Christian Matthew Childs

UNLV Theses, Dissertations, Professional Papers, and Capstones

The ability to access a vast region of the pressure-temperature landscape using energy density tuning enables exotic states of matter to be probed. A well documented method for such exploration, under static conditions, is the use of the laser-heated diamond anvil cell (LH-DAC), accessing a combination of high pressure (>300 GPa) and high temperature (>5000 K). This thesis presents our development of direct CO2 laser heating techniques to study a series of wide band gap insulators, La2Sn2O7, ZrO2, and CeO2, under high pressure conditions. The lasing frequency of CO2 lasers is such that these wide band gap materials …

Phytoplankton Community Composition In The Surface Ocean: Methods For Detection Using Optical Measurements, Pigment Concentrations, And Flow Cytometry, Alison P. Chase

Electronic Theses and Dissertations

Phytoplankton are microscopic photoautotrophs living in the surface ocean waters and help support all life on earth via photosynthetic production of oxygen. Thousands of species make up the bulk phytoplankton community, and the spatial and temporal distribution of different types of phytoplankton has relevance for many ocean ecosystem questions including marine food web dynamics, and carbon flux and sequestration. Methods to detect phytoplankton community composition (PCC) on the vast scale of the global ocean require estimates of PCC from remote platforms, namely earth-observing satellites. The use of satellite data to observe and interpret PCC in the surface ocean requires significant …

Construction Of A Hyperspectral Imager Using 3d-Printed And Off-The-Shelf Components, Joshua Moorhouse

Mechanical Engineering Undergraduate Honors Theses

The Arkansas Center for Space and Planetary Sciences is working in collaboration with the Mechanical Engineering department to create a relatively cheap and modifiable hyperspectral imager. It is constructed using 3D-printed and off-the-shelf components from Edmund Optics and Amazon. The iteration created in this paper delivers spectrograms in the visible spectrum. The long-term goals of the camera are to create hyperspectral images from these spectrograms and to advance the imager into the infrared and near-infrared spectra. This imager is being developed to be used in the Arkansas Center for Space and Planetary Sciences environmental test chambers to further the scientific …

Applications Of The Negatively-Charged Silicon Vacancy Color Center In Diamond, Forrest A. Hubert

Optical Science and Engineering ETDs

The spatial resolution and fluorescence signal amplitude in stimulated emission depletion (STED) microscopy is limited by the photostability of available fluorophores. Here, we show that negatively-charged silicon vacancy (SiV) centers in diamond are promising fluorophores for STED microscopy, owing to their photostable, near-infrared emission and favorable photophysical properties. A home-built pulsed STED microscope was used to image shallow implanted SiV centers in bulk diamond at room temperature. We performed STED microscopy on isolated SiV centers and observed a lateral full-width-at-half-maximum spot size of 89 ± 2 nm, limited by the low available STED laser pulse energy (0.4 nJ). For a …