Physical Sciences and Mathematics Commons^™

Timing And Spectroscopy Requirements For A Plastic Scintillating Fiber Bundle Time-Of-Flight Neutron Spectrometer, Paul A. Clement

Theses and Dissertations

The design parameters of a Time-of-Flight (TOF) neutron spectrometer composed of BCF-12 plastic scintillating fibers were investigated. A GEANT4 transport model was developed for analyzing the interaction of 2.5 MeV neutrons with a 14 x 14 BCF-12 fiber bundle. The bundle simulation demonstrated that 0.359% of all neutrons incident on the bundle will double scatter. The timing and data collection e efficiencies of a Tektronix DPO7104 series digital oscilloscope were examined to determine the signal processing requirements for future fiber bundle measurements. The minimum detectable neutron energy was computed by taking into account the bundle scintillation e efficiency, light collection …

Development And Validation Of An Automated Directivity Acquisition System Used In The Acquisition, Processing, And Presentation Of The Acoustic Far-Field Directivity Of Musical Instruments In An Anechoic Space, Nicholas J. Eyring

Theses and Dissertations

A high spatial resolution acoustic directivity acquisition system (ADAS) has been developed to acquire anechoic measurements of the far field radiation of musical instruments that are either remote controlled or played by musicians. Building upon work performed by the BYU Acoustic Research Group in the characterization of loudspeaker directivity, one can rotate a musical instrument with sequential azimuthal angle increments under a fixed semicircular array of microphones while recording repeated notes or sequences of notes. This results in highly detailed and instructive directivity data presented in the form of high-resolution balloon plots. The directivity data and corresponding balloon plots may …

Structure And Function Of Proteins Investigated By Crystallographic And Spectroscopic Time-Resolved Methods, Namrta Purwar

Theses and Dissertations

Biomolecules play an essential role in performing the necessary functions for life. The goal of this thesis is to contribute to an understanding of how biological systems work on the molecular level. We used two biological systems, beef liver catalase (BLC) and photoactive yellow protein (PYP). BLC is a metalloprotein that protects living cells from the harmful effects of reactive oxygen species by converting H2O2 into water and oxygen. By binding nitric oxide (NO) to the catalase, a complex was generated that mimics the Cat-H2O2 adduct, a crucial intermediate in the reaction promoted by the catalase. The Cat-NO complex is …

Extracting The Structure And Conformations Of Biological Entities From Large Datasets, Ali Dashti

Theses and Dissertations

In biology, structure determines function, which often proceeds via changes in conformation. Efficient means for determining structure exist, but mapping conformations continue to present a serious challenge. Single-particles approaches, such as cryogenic electron microscopy (cryo-EM) and emerging "diffract & destroy" X-ray techniques are, in principle, ideally positioned to overcome these challenges. But the algorithmic ability to extract information from large heterogeneous datasets consisting of "unsorted" snapshots - each emanating from an unknown orientation of an object in an unknown conformation - remains elusive.

It is the objective of this thesis to describe and validate a powerful suite of manifold-based algorithms …

Beyond The Standard Model: Lhc Phenomenology, Cosmology From Post-Inflationary Sources, And Dark Matter Physics, Brian J. Vlcek

Theses and Dissertations

It is the goal of this dissertation to demonstrate that beyond the standard model, certain theories exist which solve conflicts between observation and theory -- conflicts such as massive neutrinos, dark matter, unstable Higgs vacuum, and recent Planck observations of excess relativistic degrees of freedom in the early universe. Theories explored include a D-brane inspired construct of U(3) × Sp(1) × U(1) × U(1) extension of the standard model, in which we demonstrate several possible observables that may be detected at the LHC, and an ability to stabilize the Higgs mechanism. The extended model can also explain recent Planck data …

Protein Association In Living Cells Using Fret Spectrometry: Application To G-Protein Coupled Receptors, Suparna Patowary

Theses and Dissertations

Recent advancements in fluorescence microscopy coupled with newly developed fluorescent tags have transformed Fluorescence (Förster) Resonance Energy Transfer (FRET) into a powerful tool studying in vivo molecular interactions with improved spatial (angstrom) resolution. Though widely used to study protein-protein interactions, generalizing and testing the FRET theory for oligomeric complexes containing multiple donors and acceptors has only become possible in recent years. Therefore, many aspects of it are yet unexplored.

In this work, we tested the kinetic theory of FRET using linked fluorescent proteins located in the cytoplasm or at the plasma membrane. We used a novel method developed in our …

Directional Thermal Emission And Absorption From Surface Microstructures In Metalized Plastics, Michael D. Seal

Theses and Dissertations

Thermal emission, exhibiting antenna-like directivity, has been generated by a wide variety of both simple and complex micro-structures. The basic demonstrations of directional emission, and specific device performance evaluations, have been conducted at elevated temperatures, typically several hundred degrees Celsius. The most common applications for these high-temperature designs are thermal photo-voltaic and spectroscopic sources. A wide range of lower temperature applications, such as spacecraft thermal management and mid- to far-infrared optical train stray light management, are precluded by the cost and complexity of the fabrication processes employed. In this work, a novel fabrication and physical surface optimization of a seminal …

Solving Virus Structures From Xfel Diffraction Patterns Of Random Particle Orientations Using Angular Correlations Of Intensities, Miraj Uddin

Theses and Dissertations

The world's first x-ray free electron laser (XFEL), the Linac Coherent Light Source (LCLS) at the Stanford Linear Accelerator Center (SLAC) is now creating X-ray pulses not only of unprecendented brilliance; (a billion times brighter than the most powerful previous sources [8]) but also of ex- tremely short duration. Amongst the promised capabilities of this fourth- generation x-ray sources is the ability to record diffraction patterns from individual bio-molecules. The very first XFEL ''diffract and destroy'' exper- iments are being performed on relatively large objects such as viruses. To quote from Caspar and Klug[2], ''there are only a limited number …

Growth Of Zno Thin Films On Polar Oxide Surfaces By Atomic Layer Deposition, Kallol Pradhan

Theses and Dissertations

Polar heterointerfaces of MgO(111) and the II-VI semiconductor ZnO are of technological interest for transparent conducting electrode applications. Growth and structure of thin films on polar surfaces can be different than on non-polar surfaces due to the large surface energy of polar surfaces. We have grown ZnO on unreconstructed MgO(111)-(1x1)-OH terminated and reconstructed MgO(111)-(√3x√3)R30° polar oxide surfaces using atomic layer deposition. A homemade UHV-interfaced viscous-flow atomic layer deposition (ALD) reactor with in-situ quartz crystal monitor was used to grow ZnO thin films on the MgO(111) substrates. Surface morphology studies revealed that the surface roughness increases with ZnO film thickness and …

Analyses Of Nonlinearity Measures In High-Amplitude Sound Propagation, Michael B. Muhlestein

Theses and Dissertations

Military aircraft generate high-amplitude noise which can cause injury to attending personnel. Efforts to mitigate the effects of this noise require a detailed understanding of the propagation of the noise, which was shown previously to be nonlinear. This thesis presents an analysis of high-amplitude noise propagation, emphasizing measures used to quantify the importance of considering nonlinearity. Two measures of the importance of nonlinearity are compared. These measures are the wave steepening factor and a skewness estimate. The wave steepening factor is a measure of how much nonlinear waveform steepening has occurred in a waveform. The skewness estimate is the skewness …

Characterization Of Ingaas Quantum Dot Chains, Tyler Drue Park

Theses and Dissertations

InGaAs quantum dot chains were grown with a low-temperature variation of the Stranski-Krastanov method, the conventional epitaxial method. This new method seeks to reduce indium segregation and intermixing in addition to giving greater control in the growth process. We used photoluminescence spectroscopy techniques to characterize the quality and electronic structure of these samples. We have recently used a transmission electron microscope to show how the quantum dots vary with annealing temperature. Some questions relating to the morphology of the samples cannot be answered by photoluminescence spectroscopy alone. Using transmission electron microscopy, we verified flattening of the quantum dots with annealing …

Spectral Analysis And Metastable Absorption Measurements Of High Pressure Capacitively And Inductively Coupled Radio-Frequency Argon Helium Discharges, Ben Eshel

Theses and Dissertations

Characterization of the excited state argon population in an argon-helium discharge is of crucial importance to the development of a continuous wave Discharge Assisted Noble Gas Laser. Experiments were conducted in the Richard W. Davis Advanced Laser Facility at AFRL on Kirtland Air Force Base, Albuquerque, NM. During these tests the capability to maintain a capactively-coupled and inductively-coupled radio-frequency discharge at pressures of 300 Torr was demonstrated. Optical Emission Spectroscopy experiments were conducted in order to examine the population distribution of the p-state in argon. The population distributions for these high-pressure and high-power cases were compared to a low-pressure, low-power …

Chip-Scale Magnetic Source Of Cold Atoms, Eric A. Imhof

Theses and Dissertations

Numerous disruptive technologies are being hampered by the insufficient modern methods of cooling electrically neutral atoms and molecules. Microchip-based magnetic deceleration provides a cooling mechanism to slow most neutral atoms and molecules within the cost and size requirements of a real-world device. Simulations of a novel deceleration technique show 90% removal of kinetic energy from an atomic beam. An experiment is built which creates a time-dependent, decelerating magnetic field to slow an atomic beam. An atomic beam is magnetically guided 800 microns above the surface of a microchip at pressures of 10^-9 Torr. A 60 independent wire microchip is …

Simulation Of 810 Nm Light Propagation Through The Human Finger For Non-Invasive Blood Analysis, Nichole Millward Maughan

Theses and Dissertations

Non-invasive blood analysis devices that can measure characteristics less prominent than the oxygenation of hemoglobin are of interest in the medical community. An important step in creating these devices is to model the interaction of photons with human tissue in increasingly greater physiological detail. We have modeled, using a Monte Carlo technique, the interaction of photons through epidermis, blood and water arranged both in layers and in a homogeneous mixture. We confirm the expected linear relation between photon attenuation and material volumetric percentage in our two-layer models. We discovered that this relationship becomes non-linear in the homogeneously mixed models where …

Cluster Expansion Models Via Bayesian Compressive Sensing, Lance Jacob Nelson

Theses and Dissertations

The steady march of new technology depends crucially on our ability to discover and design new, advanced materials. Partially due to increases in computing power, computational methods are now having an increased role in this discovery process. Advances in this area speed the discovery and development of advanced materials by guiding experimental work down fruitful paths. Density functional theory (DFT)has proven to be a highly accurate tool for computing material properties. However, due to its computational cost and complexity, DFT is unsuited to performing exhaustive searches over many candidate materials or for extracting thermodynamic information. To perform these types of …

The Effect Of Temperature On The Electrical And Optical Properties Of P-Type Gan, Joy Mcnamara

Theses and Dissertations

The development of gallium nitride (GaN) light emitting devices has reached extraordinary echelons. As such, the characterization and analysis of the behavior of GaN materials is essential to the advancement of GaN technology. In this thesis, the effect of temperature on the optical and electrical properties of p-type GaN is investigated. The GaN samples used in this work were grown by various methods and studied by Kelvin probe and photoluminescence (PL) techniques. Specifically, the surface photovoltage (SPV) behavior and PL data were analyzed at different temperatures and illumination intensities. Using the SPV results, we show that p-type GaN exhibits n-type …

Probing Bonding And Dynamics At Heterogeneous Adsorbate/Graphene Interfaces, Eric Charles Mattson

Theses and Dissertations

Graphene-based materials are becoming an astoundingly promising choice for many relevant technological and environmental applications. Deriving graphene from the reduction of graphene oxide (GO) is becoming a popular and inexpensive route toward the synthesis of these materials. While the desired product from GO reduction is pristine graphene, defects and residual oxygen functional groups inherited from the parent GO render reduced graphene oxide (RGO) distinct from graphene. In this work, the structure and bonding for GO and RGO is investigated to the end of a working understanding of the composition and properties of these materials. In situ selected area electron diffraction …

Multimessenger Approach To Search For Cosmic Ray Anisotropies, Larry David Buroker

Theses and Dissertations

The origin of the highest energy cosmic rays is still unknown. The discovery of their sources will reveal the workings of the most energetic astrophysical accelerators in the universe. Recent international efforts have brought us closer to unveiling this mystery. Possible ultra-high energy cosmic ray sources have been narrowed down with the confirmation of an "ankle" and the GZKlike spectral feature at the high-end of the energy spectrum. A clear resolution of the ultra-high energy mystery calls for the search of anisotropies in the distribution of arrival directions of cosmic rays. In this thesis, we adopt the so-called "multi-messenger" approach …

How To Think About Indiscernible Particles, Daniel Joseph Giglio

Theses and Dissertations

Permutation symmetries which arise in quantum mechanics pose an intriguing problem. It is not clear that particles which exhibit permutation symmetries (i.e. particles which are indiscernible, meaning that they can be swapped with each other without this yielding a new physical state) qualify as "objects" in any reasonable sense of the term. One solution to this puzzle, which I attribute to W.V. Quine, would have us eliminate such particles from our ontology altogether in order to circumvent the metaphysical vexations caused by permutation symmetries. In this essay I argue that Quine's solution is too rash, and in its place I …

Atomic And Electronic Structure Of A Ligand-Protected Bimetallic Nanocluster, Ag4ni2(Dmsa)4, Anthony F. Pedicini

Theses and Dissertations

An important direction in nanoscale science is to synthesize materials whereby atomic clusters serve as the building blocks. Properties of these clusters can be controlled through size and composition, and such an approach offers a pathway toward designing larger, customized materials. One way to stabilize such materials is through the use of ligated clusters. Ag4Ni2(DMSA)4 is one such cluster, the first with a bimetallic core, and has been stabilized by the experimental group of A. Sen at The Pennsylvania State University. The theoretical studies undertaken in this thesis were directed toward providing information on the atomic structure, nature of electronic …

Premelting Study Of Nickel Nanorod Arrays, Ebtihaj Alrashid Jr.

Theses and Dissertations

In this study, samples of nanoscale structures of nickel (Ni) nanorods were prepared using the glancing angle deposition (GLAD) technique. Annealing was done using a split- top tube furnace at high vacuum chamber pressure. The pre-melting of the nanorods was maintained at 500 °C for 30 minutes in all the samples. Using the samples with 90 minutes of GLAD time, the annealing behavior of the nanorods was studied at 300 °C, 400 °C, 500 °C and 600 °C. The nanorods were then imaged using scanning electron microscopy. Using X-ray diffraction, the crystalline microstructures of the nanorods were studied. It was …

Investigating The Potential Applications Of A Raman Tweezer System, John Wray

Theses and Dissertations

This thesis describes the construction of an Optical Tweezer apparatus to be used in conjunction with a confocal Raman spectrometer. The tweezer utilizes an infrared (λ=1064 nm) laser directed into an inverted microscope with NA=1.4 oil immersion 100x objective lens that strongly focuses the laser light into a sample to function as a single-beam gradient force trap. The long term goal of this research program is to develop a single molecule Raman tweezers apparatus that allows one to control the position of a Raman nanoplasmonic amplifier. This thesis describes the construction of the Raman tweezer apparatus along with several Raman …

Analysis Of Defects In Gan Using Hybrid Density Functional Theory, Ibrahima Castillo Diallo

Theses and Dissertations

In this thesis, we first present a brief overview of various theoretical approaches used to examine the electronic structure of defects in GaN. Using the recently developed hybrid density functional theory (HSE06) along with the experimental measurements, we propose a new explanation of the nature of the yellow luminescence band in carbon-doped GaN. We conduct a systematic study of electronic and optical properties of defects (Carbon, Oxygen, Silicon related) that are candidates for the origin of yellow luminescence. We show that the CN-ON complex is significantly more likely to form compared to isolated carbon configurations. In contrast to the properties …

Experimental Analysis Of Energy-Based Acoustic Arrays For Measurement Of Rocket Noise Fields, Jarom Henry Giraud

Theses and Dissertations

Microphone arrays are useful for measuring acoustic energy quantities (e.g. acoustic intensity) in the near-field of a full-scale solid rocket motor. Proper characterization of a rocket plume as a noise source will allow for more accurate predictions in engineering models that design for protection of structures, payloads and personnel near the rockets. Acoustic intensity and energy density quantities were measured in three rocket noise fields and have shown that the apparent source region of the rocket becomes smaller and moves upstream as frequency increases. Theoretical results accounting for some scattering and finite-difference errors arising in these types of energy-based measurements …

Discrimination Between Child And Adult Forms Using Radar Frequency Signature Analysis, Stephanie R. Keith

Theses and Dissertations

In this thesis we develop a method to discriminate between adult and child radar signatures. In particular, we examine radar data measured from behind a wall, which introduces radar signal attenuation and multipath effects. To investigate the child/adult discrimination problem in a through-wall, multipath scenario, a previously developed free-space human scattering model was expanded to incorporate multiple paths, and the effects of transmission through, and reflections from, walls and ground. The ground was modeled as a perfectly reflecting surface, while the walls were modeled as homogeneous concrete slabs. Twenty-five reflection paths were identified, involving the direct paths, as well as …

Development Of A Spectropolarimetric Capability, Evan J. Carlson

Theses and Dissertations

A Bomem 200 series Fourier transform infrared spectrometer and FLIR Systems Inc InGaAs infrared (IR) camera was used to measure the degree of linear polarization (DOLP) from a metal and glass surfaces. This was accomplished by placing a wire grid polarizer in front of the aperture of the FTIR and IR camera to measure the polarized reflection from the target material. For the IR camera, an average of pixel counts was collected over the area of the target to measure to DOLP. Factors impacting the accuracy of the measurements from the FTIR are calibration, instrument self emission, and alignment error. …

Electronic Characteristics Of Rare Earth Doped Gan Schottky Diodes, Aaron B. Blanning

Theses and Dissertations

The Schottky barrier height (SBH) was measured on GaN based diodes with three different dopant types; Gd, Er and Yb. Two methods were used to determine the SBH. The first method was the Juergen Werner method to evaluate the I-V characteristics. The calculated SBH of the diodes using this method was 1.41 ± 0.20eV, 1.71 ± 0.25eV and 1.75 ± 0.28eV for the Gd-, Er- and Yb-doped diodes respectively. It was observed that using an ad-hoc effective Richardson constant value of 0.006Axcm^-2xK^-2 to calculate the SBH rendered results that were in no greater than 2% disagreement (neglecting …

Neutron Shielding Effectiveness Of Multifunctional Composite Materials, Anthony D. Marchand

Theses and Dissertations

Composite materials offer a greater degree of flexibility in design and engineering of specialized space vehicle shielding applications compared to aluminum. A new design for shielding materials has been developed by including specific neutron absorbers and conductive materials into the composite structure. In this research, the neutron shielding capability of two types of custom-designed nanocomposite materials are compared to that of T6061 aluminum.

Study Of Laminar Flame 2-D Scalar Values At Various Fuel To Air Ratios Using An Imaging Fourier-Transform Spectrometer And 2-D Cfd Analysis, Andrew J. Westman

Theses and Dissertations

This work furthers an ongoing effort to develop imaging Fourier-transform spectrometry (IFTS) for combustion diagnostics and to validate reactive-flow computational fluid dynamics (CFD) predictions. An ideal, laminar flame produced by an ethylene-fueled (C₂H₄) Hencken burner (25.4 x 25.4 mm² burner) with N₂ co-flow was studied using a Telops infrared IFTS featuring an Indium Antimonide (InSb), 1.5 to 5.5 µm, focal-plane array imaging the scene through a Michelson interferometer. Flame equivalency ratios of Φ = 0.81, 0.91, and 1.11 were imaged on a 128 x 200 pixel array with a 0.48 mm per pixel spatial …

Electron Damage Effects On Carbon Nanotube Thin Films, Jeremy S. Best

Theses and Dissertations

This research investigated the effects of electron damage on single walled carbon nanotube (CNT) thin films. CNT thin films were irradiated by electrons with energies of 500 keV and 1 MeV to determine what damage was created in the CNT thin film structure, how it affected conductivity, and what changes were evident in the Raman spectra.