Physics Commons^™

Electronic & Magnetic Properties Of Ba(Fe,Co)2as2 & Uru2si2, Travis J. Williams

Open Access Dissertations and Theses

This thesis details a collection of experiments performed on two condensed matter systems, Co-doped BaFe₂As₂ and URu₂Si₂. These two materials are related by their structural type (ThCr₂Si₂-type) serving as great examples of the diversity of material properties present in this family. They are also both superconducting materials and belong to the collection of strongly-correlated electron systems. The interest in studying the Ba(Fe,Co)₂As₂ group of materials is due to the high superconducting transition temperature in these (and related) materials, while the compound URu₂Si_{2 ...}

Phase Field Crystal Studies Of Strain-Mediated Effects In The Thermodynamics And Kinetics Of Interfaces, Jonathan F E Stolle

Open Access Dissertations and Theses

In this dissertation, the Phase Field Crystal (PFC) Method is used to study a number of problems in which interfaces and elastic effects play important roles in alloys. In particular, the three topics covered in this work are grain boundary thermodynamics in alloys, dislocation-mediated formation of clusters in binary and ternary alloys, and solutal effects in explosive crystallization. Physical phenomena associated with grain boundaries, such as Read-Shockley-like behaviour and Gibbs adsorp- tion theorem, were shown to be accurately captured in both PFC- and XPFC-type models. In fact, a connection between the solute segregation behaviour and physical properties of the system ...

Neutron Scattering Studies Of Magnetic Oxides Based On Triangular Motifs, Katharina Fritsch

Open Access Dissertations and Theses

The following dissertation presents neutron scattering studies on three specific magnetic insulating oxide materials whose lattice is based on triangular structural motifs. Each of the three materials studied, LuCoGaO₄, Co₃V₂O₈ and Tb₂Ti₂O₇, displays an interesting disordered ground state that is reached by different mechanisms: site disorder, geometric frustration, and quantum fluctuations induced by a transverse magnetic field. The main focus of this work is the characterization of the resulting magnetic ground states and magnetic excitations within these systems.

Chapters 3, 4 and 5 contain original work in the form ...

Development Of A Thgem Imaging Detector With Delay Line Readout, Andrei Hanu

Open Access Dissertations and Theses

Position sensitive detectors represent a class of particle detectors widely used in high-energy physics, astrophysics, biophysics and medicine for imaging the spatial distribution of various radioactive sources. In recent years, a new class of gas based detectors, so-called micropattern gas detectors (MPGDs), has emerged. While modern MPGDs rival solid state detectors in terms of spatial and temporal resolution, their cost of production is significantly lower. A Thick Gaseous Electron Multiplier (THGEM) imaging detector, with a two-dimensional delay line readout, has been constructed as a concept for a large area imaging detector with reasonable spatial resolution. The delay line based THGEM ...

In-Package Atmospheric Pressure Cold Plasma Treatment Of Strawberries, Nn Misra, Paula Bourke, Patrick J. Cullen, Sonal Patil

Articles

The ability to generate low temperature plasma at atmospheric pressure offers new opportunities to decontaminate biological materials, including fresh foods. In this study, strawberries were treated with atmospheric cold plasma (ACP), generated with a 60 kV dielectric barrier discharge (DBD) pulsed at 50 Hz, across a 40 mm electrode gap, generated inside a sealed package containing ambient air (42% relative humidity). The current-voltage characteristics revealed that the plasma operated in the filamentary regime. The background microflora (aerobic mesophillic bacteria, yeast and mould) of strawberries treated for 5 min was reduced by 2 log 10 within 24 h of post-ACP treatment ...

Multicomponent Dark Matter: Possible Signatures At Colliders, Satellites, And Underground Experiments, Gregory Peim

Physics Dissertations

Collider and dark matter phenomenology of the Higgs boson, Supersymmetry, Stueckelberg extensions to the Standard Model as well as to the Minimal Supersymmetric Standard Model, and exotic TeV size scalars with naturalness implications in the context of multicomponent dark matter and asymmetric dark matter models are investigated. The measurement of signals of new physics at dark matter direct detection experiments as well as colliders (Large Hadron Collider, TeVatron, and a future muon collider) were discussed and explored in depth with a focus on the prospects for the discovery of new physics. The details of multicomponent dark matter models and each ...

Vibrational Spectroscopy: Disease Diagnostics And Beyond, Hugh Byrne, Kamila Ostrowska, Haq Nawaz, Jennifer Dorney, Aidan Meade, Franck Bonnier, Fiona Lyng

Books/Book Chapters

Summary

This chapter outlines some developments in the applications of vibrational spectroscopy for disease diagnostics and demonstrates how the applications of the spectroscopic techniques can be extended to the analysis and evaluation of disease aetiology and the mechanisms of interaction and the cellular and subcellular responses to, for example chemotherapeutic agents and nanoparticles. The primary emphasis is on Raman spectroscopy, although some examples are based on infrared absorption spectroscopy. The studies presented are chosen to illustrate how a range of multivariate analytical techniques can be employed to maximize the potential benefits of the complex spectral information obtained from tissue or ...

Polarization-Coupled Transport Behavior In Ultrathin Ferroelectric Heterostructures, Haidong Lu

Theses, Dissertations, and Student Research: Department of Physics and Astronomy

Ferroelectric polarization-coupled resistive switching behavior in ferroelectric tunnel junctions (FTJs), the tunneling electroresistance (TER) effect, is a recently predicted new phenomenon, which attracts interest due to potential application in the next generation non-volatile ferroelectric random access memories (FeRAMs). In this dissertation, we demonstrate the TER effect in FTJ devices by means of scanning probe microscopy (SPM) techniques. We have investigated several device configurations for enhancement of polarization stability and for demonstration of the resistive switching behavior: (i) using the SPM probe as a top electrode; (ii) using heterostructures with engineered interfacial atomic terminations; (iii) using metal electrodes; (iv) adding an ...

An Evaluation Of The Consistency Of Imrt Patient-Specific Qa Techniques, Elizabeth M. Mckenzie

UT GSBS Dissertations and Theses (Open Access)

To ensure the integrity of an intensity modulated radiation therapy (IMRT) treatment, each plan must be validated through a measurement-based quality assurance (QA) procedure, known as patient specific IMRT QA. Many methods of measurement and analysis have evolved for this QA. There is not a standard among clinical institutions, and many devices and action levels are used. Since the acceptance criteria determines if the dosimetric tools’ output passes the patient plan, it is important to see how these parameters influence the performance of the QA device. While analyzing the results of IMRT QA, it is important to understand the variability ...

Near-Infrared Surface-Enhanced Fluorescence Using Silver Nanoparticles In Solution, Michael D. Furtaw

Mechanical (and Materials) Engineering -- Dissertations, Theses, and Student Research

Fluorescence spectroscopy is a widely used detection technology in many research and clinical assays. Further improvement to assay sensitivity may enable earlier diagnosis of disease, novel biomarker discovery, and ultimately, improved outcomes of clinical care along with reduction in costs. Near-infrared, surface-enhanced fluorescence (NIR-SEF) is a promising approach to improve assay sensitivity via simultaneous increase in signal with a reduction in background. This dissertation describes research conducted with the overall goal to determine the extent to which fluorescence in solution may be enhanced by altering specific variables involved in the formation of plasmonactive nanostructures of dye-labeled protein and silver nanoparticles ...

Investigating Fault Structure Using Electrical Resistivity Tomography, Sara Michelle Monahan

Physics

The resolving power of two-dimensional Direct Current (DC) Electrical Resistivity Tomography (ERT) is investigated in the context of shallow faults. Subsurface electrical resistivity data was collected perpendicular to a secondary fault scarp of the Los Osos Fault Zone with a Syscal KID Switch 24 resistivity meter and processed with Prosys II and Res2DInv software to produce two-dimensional cross sections of resistivity values via a smoothness-constrained least-squares optimization method. Comparison of ERT inversion results to a trench wall map of the same fault scarp suggest the location and dip direction of faults is resolvable, while detailed fault structure, such as dip ...

Science Goals And Overview Of The Radiation Belt Storm Probes (Rbsp) Energetic Particle, Composition, And Thermal Plasma (Ect) Suite On Nasa’S Van Allen Probes Mission, Harlan E. Spence, G. D. Reeves, D. N. Baker, J. B. Blake, M. Bolton, S. Bourdarie, A. A. Chan, S. G. Claudepierre, J. H. Clemmons, J. P. Cravens, S. R. Elkington, J. F. Fennell

Physics Scholarship

The Radiation Belt Storm Probes (RBSP)-Energetic Particle, Composition, and Thermal Plasma (ECT) suite contains an innovative complement of particle instruments to ensure the highest quality measurements ever made in the inner magnetosphere and radiation belts. The coordinated RBSP-ECT particle measurements, analyzed in combination with fields and waves observations and state-of-the-art theory and modeling, are necessary for understanding the acceleration, global distribution, and variability of radiation belt electrons and ions, key science objectives of NASA’s Living With a Star program and the Van Allen Probes mission. The RBSP-ECT suite consists of three highly-coordinated instruments: the Magnetic Electron Ion Spectrometer ...

The Magnetic Electron Ion Spectrometer (Mageis) Instruments Aboard The Radiation Belt Storm Probes (Rbsp) Spacecraft, J. B. Blake, P. A. Carranza, S. G. Claudepierre, J. H. Clemmons, W. R. Crain, Y. Dotan, J. F. Fennell, F. H. Fuentes, R. M. Galvan, J. S. George, M. G. Henderson, M. Lalic

Physics Scholarship

This paper describes the Magnetic Electron Ion Spectrometer (MagEIS) instruments aboard the RBSP spacecraft from an instrumentation and engineering point of view. There are four magnetic spectrometers aboard each of the two spacecraft, one low-energy unit (20–240 keV), two medium-energy units (80–1200 keV), and a high-energy unit (800–4800 keV). The high unit also contains a proton telescope (55 keV–20 MeV). The magnetic spectrometers focus electrons within a selected energy pass band upon a focal plane of several silicon detectors where pulse-height analysis is used to determine if the energy of the incident electron is appropriate for ...

Characterization Of Planar Wave Guides By Angle-Dependent Excitation Of Guided Modes, Edward D. Lunde

Physics

In this project a high resolution rotation stage was used to measure the angle of coupling of light into planar waveguide modes. Control of the stage and acquisition of light intensity data was done using the commercially available programming environment, MATLAB. Reliable, repeatable excitation of modes was done using prism coupling. We also investigated coupling using a surface grating on the waveguide.

Helium, Oxygen, Proton, And Electron (Hope) Mass Spectrometer For The Radiation Belt Storm Probes Mission, H. O. Funsten, R. M. Skoug, A. A. Guthrie, E. A. Macdonald, J. R. Baldonado, R. W. Harper, K. C. Henderson, K. H. Kihara, J. E. Lake, B. A. Larsen, A. D. Puckett, V. J. Vigil, Harlan E. Spence

Physics Scholarship

The HOPE mass spectrometer of the Radiation Belt Storm Probes (RBSP) mission (renamed the Van Allen Probes) is designed to measure the in situ plasma ion and electron fluxes over 4π sr at each RBSP spacecraft within the terrestrial radiation belts. The scientific goal is to understand the underlying physical processes that govern the radiation belt structure and dynamics. Spectral measurements for both ions and electrons are acquired over 1 eV to 50 keV in 36 log-spaced steps at an energy resolution ΔE FWHM/E≈15 %. The dominant ion species (H+, He+, and O+) of the magnetosphere are identified using ...

Investigation Of Time Varying Nuclear Decay Rates, Peter G. Barton, Rafael F. Lang

The Summer Undergraduate Research Fellowship (SURF) Symposium

Since the discovery of radioactive decay, radioactive decay rates have consistently shown to be constant. Recently, groups of researchers around the world have noticed variation in the decay rates of different radioactive isotopes, while other groups have noticed no such effect. If the variation is truly varying decay rates, this would imply groundbreaking new physics and would have implications for practices such as carbon dating. More sophisticated experiments are required to determine if the variations are truly new physics or systematic effects inherent to nuclear decay experiments. We are building an experiment where activity data from various radioactive sources will ...

Elementary Studies Of Twisted Bilayer Graphene, Branden P. Burns, Yong P. Chen

The Summer Undergraduate Research Fellowship (SURF) Symposium

In the nanotechnology field, some existing materials and applications are harmful to the environment, not efficient for certain tasks, or too expensive to be fully utilized. Graphene is a strong and cheap material that can be used to improve current nanotechnologies for more practical uses in society. Twisted bilayer graphene (TBG) is an orientation of graphene layers that exhibit different properties than regular bilayer graphene. It is made by placing a single layer of graphene on top of another at an angle with respect to the other lattice orientation. Understanding the characteristics of TBG is important to uncover more physics ...

Investigation Of Major Intermolecular Interactions In 7,8-Dihydrobenzo(K)Phenanthridin-6(5h)-One Crystal Using Quantum Calculations And Crystallographic Visualization Programs, Zhiwei Liao, Tonglei Li, Mingtao Zhang

The Summer Undergraduate Research Fellowship (SURF) Symposium

Currently, tablets and capsules are the most common ways of delivering drugs. The active pharmaceutical ingredients and excipients used to make those tablets and capsules are in their crystalline form generally. However, a single molecule can form multiple different crystal structures because of different packing arrangements of the molecules. These different crystal structures have identical chemical composition but different properties such as solubility, density, stability, etc. This phenomenon is called polymorphism. Occurrence of polymorphism could be a disaster for both patients and pharmaceutical companies, as the drug could lose its efficacy due to changes in properties. Studying intermolecular interactions in ...

Fabrication Of Multilayered Structure For Coherent Random Lasing, John Rauchenstein, Young L. Kim

The Summer Undergraduate Research Fellowship (SURF) Symposium

High powered lasers have many applications, including medical treatment and surgery. However, these lasers are extremely expensive and are therefore not widely available. The aim of this study was to demonstrate a method to create such a laser with significantly decreased overall cost and increased efficiency. In order to do this, we explored a phenomenon called random lasing which is a light amplification process. To start with, a low-cost pumping laser is directed at normal incidence toward a multi-layered sample with two alternating layers. At first pearl, a naturally found material that has many organic nano-scale layers (similar to the ...

Characterization Of Polylactic Acid Films For Food Packaging As Affected By Dielectric Barrier Discharge Atmospheric Plasma, S. K. Pankaj, Luke O'Neill, Nn Misra, Paula Bourke

Articles

Dielectric barrier discharge (DBD) air plasma is a novel technique for in-package decontamination of food, but it has not been yet applied to the packaging material. Characterization of commercial polylactic acid (PLA) films was done after in-package DBD plasma treatment at different voltage and treatment time to evaluate its suitability as food packaging material. DBD plasma increased the roughness of PLA film mainly at the site in contact with high voltage electrode at both the voltage levels of 70 and 80 kV. DBD plasma treatments did not induce any change in the glass transition temperature, but significant increase in the ...