Digital Commons Network^™

Ultrafast Electron Diffraction: Visualizing Dynamic States Of Matter, D. Filippetto, P. Musumeci, R. K. Li, B. J. Siwick, M. R. Otto, Martin Centurion, J. P. F. Nunes

Department of Physics and Astronomy: Faculty Publications

Since the discovery of electron-wave duality, electron scattering instrumentation has developed into a powerful array of techniques for revealing the atomic structure of matter. Beyond detecting local lattice variations in equilibrium structures with the highest possible spatial resolution, recent research efforts have been directed toward the long-sought-after dream of visualizing the dynamic evolution of matter in real time. The atomic behavior at ultrafast timescales carries critical information on phase transition and chemical reaction dynamics, the coupling of electronic and nuclear degrees of freedom in materials and molecules, and the correlation among structure, function, and previously hidden metastable or nonequilibrium states …

Behaviors For Which Deinonychosaurs Used Their Feet, Alexander King

Honors Projects

This paper seeks to show for what purpose deinonychosaurs used their feet. Fowler et al., (2011) showed that D. antirrhopus’s feet were closest in function to accipitrids, as they found it was more built for grasping prey than running.

I answered this question by using 2D images of the feet of three modern birds (Buteo jamaicensis, Phasianus colchicus, and Gallus gallus domesticus), one eudromaeosaur (Deinonychus antirrhopus), and one troodontid (Borogovia gracilicrus). I used ImageJ to apply 73 landmarks to each foot, capturing the variation between species in the metatarsals and pedal phalanges. These data were then uploaded to the software …

Six-Dimensional Single-Molecule Imaging With Isotropic Resolution Using A Multi-View Reflector Microscope, Oumeng Zhang, Zijian Guo, Yuanyuan He, Tingting Wu, Michael D. Vahey, Matthew D. Lew

Electrical & Systems Engineering Publications and Presentations

Imaging of both the positions and orientations of single fluorophores, termed single-molecule orientation-localization microscopy, is a powerful tool for the study of biochemical processes. However, the limited photon budget associated with single-molecule fluorescence makes high-dimensional imaging with isotropic, nanoscale spatial resolution a formidable challenge. Here we realize a radially and azimuthally polarized multi-view reflector (raMVR) microscope for the imaging of the three-dimensional (3D) positions and 3D orientations of single molecules, with precisions of 10.9 nm and 2.0° over a 1.5-μm depth range. The raMVR microscope achieves 6D super-resolution imaging of Nile red molecules transiently bound to lipid-coated spheres, accurately resolving …

Supercontinuum Light Generation Via Non-Linear Effects In Hollow-Core Fiber, Skyler Gulati

Physics Student Works

The field of non-linear optics has gained traction in the last couple decades due to the variable generation of wavelengths which are less deterministic than within traditional optics. Using non-linear mediums, including hollow-core fibers (HCF), generation of wavelengths spanning into the vacuum ultraviolet (VUV) wavelength range is possible. These short wavelengths can be utilized within electron spectroscopy-based methods of material science like angle-resolved photoemission spectroscopy (ARPES). This technique most often uses specific photoemission lines of atoms in discharge lamps, however, with the frequency dispersion capabilities of HCF, broad band creation can allow for variable wavelength selection through filtering specific wavelengths …

Phase Transitions In Evolutionary Dynamics, Adam D. Scott, Dawn M. King, Stephen W. Ordway, Sonya Bahar

Physics Faculty Works

Sharp changes in state, such as transitions from survival to extinction, are hallmarks of evolutionary dynamics in biological systems. These transitions can be explored using the techniques of statistical physics and the physics of nonlinear and complex systems. For example, a survival-to-extinction transition can be characterized as a non-equilibrium phase transition to an absorbing state. Here, we review the literature on phase transitions in evolutionary dynamics. We discuss directed percolation transitions in cellular automata and evolutionary models, and models that diverge from the directed percolation universality class. We explore in detail an example of an absorbing phase transition in an …

Spacecraft Charging Test Considerations For Composite Materials, Allen Andersen, Wousik Kim, J. R. Dennison, Brian Wood, Todd A. Schneider, Jason Vaughn, Kenneth H. Wright Jr., Nelson W. Green, Eric Suh, Joel Schwartz, Abdul-Majeed Azad

Journal Articles

Composite materials present a growing challenge for spacecraft charging assessments. We review some recent lessons learned for charging tests of composite materials using both parallel-plate and electron beam test geometries. We also discuss examples of materials that exhibit significant variations between samples, despite them all having the same trade name.

Investigation Of Gaas Double Heterostructures For Photonic Heat Engines, Nathan Giannini-Hutchin

Optical Science and Engineering ETDs

The creation of a laser cooled semiconductor device has been a long sought achievement. GaAs-based devices have emerged as a promising candidate for the realization of this goal. Efforts to improve the efficiency of such devices have enabled the material to exhibit external quantum efficiencies (EQE, a measure of the probability that an excitation leads to the emission of a photon) of 99.5\%. Despite this impressive feat, a laser coolable device remains elusive.

To investigate the obstacles to such a device, the material characteristics of GaAs-based double heterostructures (DHS) are theoretically and experimentally examined. Through this study, a GaAs $\vert$ …

Turning Density Functional Theory Calculations Into Molecular Mechanics Simulations : Establishing The Fluctuating Density Model For Rna Nucleobases, Christopher A. Myers

Legacy Theses & Dissertations (2009 - 2024)

Molecular mechanics (MD) simulations and density functional theory (DFT) have been the backbone of computational chemistry for decades. Due to its accuracy and computational feasibility, DFT has become the go-to method for theoretically predicting interaction energies, polarizability, and other electronic properties of small molecules at the quantum mechanical level. Although less fundamental than DFT, molecular mechanics (MM) algorithms have been just as influential in the fields of biology and chemistry, owing their success to the ability to compute measurable, macroscopic quantities for systems with tens of thousands to hundreds of thousands of atoms at a time. Nevertheless, MD simulations would …

Building Structures From Mycelium, Noah M. Brown

Physics

The purpose of this project was to develop a method for creating bricks from mycelium and agricultural waste. The bulk of the research happened in two parts, the first part being a period in which different substrates, strains, and methods were used build the bricks. This research took place in San Luis Obispo and was aided by a group of students in PSC392 under Dr. Pete Schwartz in early 2022. After developing a method for constructing these bricks, the research was moved to St. Thomas, Jamaica, in collaboration with an ecovillage called The Source Farm from July to September. The …

A Method For Exploring The Habitability Of Earth-Like Exoplanets: Applications To Tess Objects Of Interest 203 B, 256 B, And 700 D, Paul Bonney

Graduate Theses and Dissertations

The Transiting Exoplanet Survey Satellite (TESS) has and is continuing to discover a multitude of potentially habitable planet candidates. As more planets are detected and confirmed, it becomes increasingly important to strategically search for signs of habitability with which to differentiate and prioritize them for further observation, in particular with the James Webb Space Telescope (JWST). To facilitate this, I have created a method for prioritizing TESS planet candidates based on parameters derived from their light curves and have applied the method to the TESS Candidate Target List (CTL). This data set uses preliminary fits to transit modeling which can …

First-Principles Study Of Doping Effects On Ferroelectricity And On Rashba Spin Splitting, Zegnet Yimer Muhammed

Graduate Theses and Dissertations

In this dissertation, we have thoroughly studied the effect of chemical and charge dopingon ferroelectrics (PbTiO3 and BaTiO3) and Rashba type semiconductor (BiTeI). In the first project, We investigate the polar instability and soft modes in electron-doped PbTiO3 using linear-response density functional calculations. Because, metallicity and ferroelectric-like polar distortion are mutually non-compatible, and their coexistence in the same system is an intriguing subject of fundamental interest in the field of structure phase transition. However, it is unclear what mechanism may extend the limit of metallicity that allows polar distortion. We find that ferroelectric instability can remarkably sustain up to an …

Strong Constraints On New Physics From The Icecube South Pole Neutrino Observatory, Grant Kendrick Parker

Physics Dissertations - Archive

The IceCube Neutrino Observatory, a gigaton-scale ice Cherenkov detector located deep within the Antarctic glacier, has detected hundreds of thousands of atmospheric neutrinos at energies from a few GeV to 100 TeV. Above 100 GeV, where ordinary oscillation effects become vanishingly small, this data sample is particularly sensitive to a wide range of beyond-standard-model (BSM) neutrino oscillation mechanisms. This thesis presents two searches for such BSM physics: flavor-changing nonstandard neutrino interactions (NSI) and neutrino oscillation decoherence (decoherence). The first analysis constrains the mu-tau flavor-changing NSI parameter with eight years of IceCube atmospheric neutrino data ranging from 500 GeV to 1 …

Fitting Solar Panel Brdf Parameters To Out-Of-Plane Empirical Data, Michael R. Gross

Theses and Dissertations

The bidirectional reflectance distribution function (BRDF) describes material reflectance by describing how incident irradiance reflects into all possible scatter angles as a function of incident angle. However, a solar panel has unique features that are not featured in any of these previously known models. A previous project at the Air Force Institute of Technology (AFIT) created a novel microfacet-like BRDF to model a solar panel with a prominent diffractive feature present which had not been previously modeled. This BRDF was coded into MATLAB for modeling purposes and C++ to test its speed with a MEX function call. A previous thesis …

Denoising And Deconvolving Sperm Whale Data In The Northern Gulf Of Mexico Using Fourier And Wavelet Techniques, Kendal Mccain Leftwich

LSU New Orleans Theses and Dissertations

The use of underwater acoustics can be an important component in obtaining information from the oceans of the world. It is desirable (but difficult) to compile an acoustic catalog of sounds emitted by various underwater objects to complement optical catalogs. For example, the current visual catalog for whale tail flukes of large marine mammals (whales) can identify even individual whales from their individual fluke characteristics. However, since sperm whales, Physeter microcephalus, do not fluke up when they dive, they cannot be identified in this manner. A corresponding acoustic catalog for sperm whale clicks could be compiled to identify individual …

Dual Energy Electron Storage Ring Cooler Design For Relativistic Ion Beams, Bhawin Dhital

Physics Theses & Dissertations

Collider experiments demand small beam emittances in order to achieve high luminosity. For light particles such as electrons, there exists a natural synchrotron radiation damping resulting in low emittance beams at equilibrium. In the case of heavy particle beams such as proton or ion beams, there is no significant synchrotron radiation damping effect and some cooling mechanism is needed to get to low emittance beams. A dual energy storage ring cooler is a novel concept proposed to cool hadron beams at higher energies. The design consists of two rings: a low energy ring and a high energy ring connected by …

Quantifying The Magnitude Of To Tal Dose Deviation Caused By Various Sources Of Error Among Iroc Phantom Irradiation Results, Sharbacha S. Edward

Dissertations and Theses (Open Access)

The Imaging and Radiation Oncology Core (IROC) phantoms are used as an end-to-end test of an institution’s radiotherapy processes, and for clinical trial credentialing. Phantoms are treated like patients, and evaluation of the doses received by the thermoluminescent dosimeters (TLDs) inside the phantom, reflects the accuracy with which an institution can image, plan and irradiate a phantom or patient. Recent phantom results show that among the hundreds of various IROC phantoms irradiated annually, 8-17% of institutions fail this test. The purpose of this work was to investigate the various types of errors that may occur during the treatment process and …

Application Of Flo-Sic To F-Electron Systems: Sixth Row Elements And Ligated Molecules, Alexander Irun Johnson

Open Access Theses & Dissertations

Density functional theory - the most widely used theoretical method to study atoms,molecules, and solids - suffers from the well-known self-interaction error. A solution to the problem was suggested by Perdew and Zunger [1], who showed the self-interaction error can be removed with self-interaction correction. In 2014, Pederson showed a unitary transformation can be performed on the Kohn-Sham orbitals to generate Fermi-Löwdin orbitals which improve atomization energies, and avoid the computational costs of solving the localization equations.[2] This method is known as the Fermi-Löwdin Orbital Self-Interaction Correction (FLO-SIC). Until now, the FLO-SIC methodology has been used for atoms not containing …

Oil Particle Analysis Using Machine Learning And Holography Imaging, Daniel Cruz

Open Access Theses & Dissertations

Holographic cameras show potential as a sensor to monitor oil spills. Holographic cameras record the light interference from particles in a volume of space, producing an image called a hologram. Processing these holograms is known as hologram reconstruction. It produces a representation of particles located in three-dimensional space. These cameras can record precise shapes and sizes of particles in a volume of water. However, it is very time-consuming and resource-intensive to process the images. Most algorithms that perform particle analysis require the hologram reconstruction step. The well-documented hybrid method is one such algorithm. Machine learning is one possible technique that …

Modulation Of Non-Diffracting Hermite Gaussian Beams And Nonlinear Optical Microscopy For Nanoscale Sulfur Imaging, Gilberto Navarro

Open Access Theses & Dissertations

Hermite Gaussian beams are the solutions of the scalar paraxial wave equation in Cartesian coordinates. A method was developed to modulate the intensity profile of non-diffracting Hermite Gaussian (HG) beams. The original HG beamâ??s intensity profile consists of high intense corner lobes and low intense central lobes which is not ideal for structured illumination in light-field microscopy. The modulated HG beams were generated by multiplying the original HGâ??s beam envelope by a super-Gaussian envelope to modify the intensity profile to attain equal intensity lobes. The propagation of the original HG beam and modulated HG beam were compared to determine that …

Two-Step Single Qubit Gates For Superconducting Qubits, Edward Takyi

Open Access Theses & Dissertations

Why quantum information processing? Contemporary manipulation and transmission of information is executed through physical machines (computers, routers, scanners, etc.) in which Classical Mechanics is used to describe the embodiment and transformation of information. However, the physical theory of the world is not Classical Mechanics. And so, there is no reason to suppose that machines following the laws of Classical Mechanics would have the same computational power like quantum machines. Quantum computers would break the rules of classical computers and they would be able solve problems that are intractable on conventional supercomputers.

In order to fabricate quantum computers and make significant …

Magnetic Structures Of Sawtooth Olivines Mn2six 4 (X = S, Se) Determined Through Neutron Powder Diffraction, Melaku Sisay Tafere

Open Access Theses & Dissertations

In olivine chalcogenide Mn2SiX 4 (X = S, Se) compounds, the Mn lattice produces a sawtooth, which is of critical significance in magnetism due to the potential for manifesting at bands in the magnon spectrum, a crucial component in magnonics. The compounds Mn2SiS4 and Mn2SiSe4 in Mn2SiX 4 family undergo antiferromagnetic phase transitions at T â?? 85 K and â?? 66 K, respectively, as determined from the specific heat, Cp(T). The average and local crystal structuresare determined using synchrotron X-ray, neutron diffraction, and X-ray total scattering data followed by Rietveld and pair distribution function (PDF) analysis. It is found from …

Bifurcations And Hysteresis In The Dynamics Of Small Populations Of Spherical Magnets, Peter T. Haugen

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

If you heat up some kinds of metals and then cool them down next to a magnet, they will be a magnet when they cool, but if they cool down away from a magnet, they will just be a lump of metal. This is an example of hysteresis and it’s very important for lots of technology. Another example of hysteresis might be a water tower pump that turns on when the tower is nearly empty and keeps going until the tower is nearly full. Whether or not the pump is on when the tower is half full depends on what …

Investigating Atmospheric Gravity Waves Using 3-Dimensional Spectral Analysis, Kenneth I. Zia

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

Atmospheric gravity waves (GW) are generated from the ground and go into the upper layers of the atmosphere where space begins. These waves have strong effects on the temperature and circulation of the Earth’s atmosphere. The temperature changes caused by these waves are observed through special cameras looking at light that the Earth’s atmosphere naturally emit at night. One of these cameras is placed at McMurdo Station, Antarctica where the long nights are used to see these waves longer than anywhere else. The images captured there are automatically analyzed to determine wave properties to better understand how often they are …

Relativistic, Continuum Drift-Kinetic Capability In The Nimrod Plasma Fluid Code, Tyler Markham

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

A ”runaway” electron is an electron that, through a self-reinforcing process, accelerates to relativistic speeds. At multiple points during tokamak discharges, relativistic runaway electron (RE) beams can form. RE beams pose a serious risk in the form of severe damage to plasma facing components in ITER and future burning plasma reactors. Early RE studies used simplified geometric and transport models, but enabled feedback on the overall plasma evolution. This feedback is important for understanding the evolution of the RE current column. The work in this thesis is an important step toward self-consistently evolving an RE distribution in the plasma fluid …

Towards The Electronic Response Of Carbon-Based Van Der Waals Heterostructures In A Diamond Anvil Cell, George Thomas Foskaris

UNLV Theses, Dissertations, Professional Papers, and Capstones

The nanoscale regime of materials has been at the forefront of research and interest in condensed matter physics for many years. In a merger of the fields of two-dimensional (2D) materials and high pressure physics, we present an investigation of the electronic response of carbon-based, van der Waals (vdW) heterostructures in a diamond anvil cell (DAC). Combining these fields presents us with the ability to study the characteristics of such systems both optically, and through electrical transport. Properties such as conductance, band structure, and layer number are considered. The samples in this study are assembled using exfoliation and stacking techniques …

Braiding Properties Of Worldline Configurations In Hardcore Lattice Bosons, Fabio Lingua, Wei Wang, Liana Shpani, Barbara Capogrosso-Sansone

Physics

In this manuscript, we study braiding properties of worldline configurations for a variety of ground-states of hardcore Bose–Hubbard models in two dimensions. Configurations are collections of particle paths and result from the path-integral formulation of statistical mechanics. For hard-core bosons, configurations can be seen as geometric braids and therefore can be assigned a certain topological structure, i.e. a way to classify braiding events among worldlines. By means of Monte Carlo calculations, we study superfluid phase and a variety of insulating phases and observe that ground-states of different quantum phases correspond to different probability distributions of braiding properties.

An Author Correction …

A Mechanically Intelligent Hosing-Drone, Blake Hament

UNLV Theses, Dissertations, Professional Papers, and Capstones

This manuscript presents a ”mechanically intelligent” approach to designing a Hosing-Drone for heavy-duty pressure washing. Spraying a hose creates strong reaction forces and torques. Previously demonstrated spraying robots are over-engineered to be very massive with huge inertias. These high inertias ”wash out” the reaction from the spraying. In the proposed approach, the contributions from all observable fluid dynamics, fluid structure interactions, and aerodynamics are studied individually and for the coupled system. Experimental data is collected and fit to dynamic models. These models are used to design a smaller, lighter, more agile vehicle than has been previously demonstrated. An impedance controller …

Optical Properties And Simulated X-Ray Near Edge Spectra For Y2o2s And Er Doped Y2o2s, Nicholas Dimakis, Eric Baldemar Rodriguez Jr., Kofi Nketia Ackaah-Gyasi, Madhab Pokhrel

Physics & Astronomy Faculty Publications

The electronic and optical properties of Y2O2S and its Er+3 doped counterparts at various concentrations are analyzed using density functional theory (DFT) and simulated x-ray near edge (XANES) spectra. Our simulations are complemented by absorption experiments, which show Y2O2S:Er+3 light emissions in the visible and near infrared. These emissions correspond to Er f–f intraband transitions. We use DFT and DFT+U to calculate the band structure of the Y2O2S and its Er+3 doped counterparts, whereas optical properties are calculated using the independent particle approximation (IPA). The host Y2O2S optical properties are also calculated using the random phase approximation (RPA) and …

High Fidelity Universal Gates Performed On A Continuously-Decoupled Coherence Enhanced Transmon Qubit, Michael Senatore

Dissertations - ALL

Decoherence is the primary limiting factor for the utility of modern qubits and qubit networks; most chiefly, pure dephasing which limits the operational time any gate-sequence can produce a high-fidelity result. In this dissertation, I present the results of my experiment, performing fast, high fidelity, universal single-qubit gates, on a qubit which has been decoupled from pure dephasing resulting from environmental noise. This technique can expand operational ranges of qubits–such as allowing the high-coherence operation of a flux-tunable qubit far away from its flux-insensitive sweet-spot; broadening our selection of viable qubits by making otherwise low-coherence qubits operable with high coherence, …

All-Sky Search For Continuous Gravitational Waves From Isolated Neutron Stars Using Advanced Ligo And Advanced Virgo O3 Data, R. Abbott, H. Abe, M. G. Benjamin, Teviet Creighton, Mario C. Diaz, Francisco Llamas, Soma Mukherjee, Gaukhar Nurbek, Volker Quetschke, Wenhui Wang

Physics & Astronomy Faculty Publications

We present results of an all-sky search for continuous gravitational waves which can be produced by spinning neutron stars with an asymmetry around their rotation axis, using data from the third observing run of the Advanced LIGO and Advanced Virgo detectors. Four different analysis methods are used to search in a gravitational-wave frequency band from 10 to 2048 Hz and a first frequency derivative from −10−8 to 10−9  Hz/s. No statistically significant periodic gravitational-wave signal is observed by any of the four searches. As a result, upper limits on the gravitational-wave strain amplitude h0 are calculated. The best upper limits …