Bulletin of the American Physical Society
79th Annual Meeting of the APS Southeastern Section
Volume 57, Number 16
Wednesday–Saturday, November 14–17, 2012; Tallahassee, Florida
Session KA: Poster Session (6:00-10:00PM) |
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Room: DoubleTree Ballroom, Adams-Park, and adjacent hallways |
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KA.00001: LiF Thermoluminescent Detectors for Proton and Neutron Dosimetry Erin Chambers, Chris Allgower, Susan Klein Measurements of proton and secondary neutron dose have been taken using LiF:Mg,Ti thermoluminescent dosimeters at the Indiana University Health Proton Therapy Center at Bloomington, IN. These measurements provide evidence for a lower secondary neutron dose from active beam modulation as opposed to passive modulation. An unexplained inconsistency in TLD proton dose response was identified. This research was funded by the National Science Foundation and supported by the Indiana University REU program. [Preview Abstract] |
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KA.00002: Width and Spacing Distributions in Nuclear Data T.L. Johnson, J.F. Shriner, Jr., G.E. Mitchell A recent study focusing on neutron resonance widths\footnote{P. E. Koehler, Phys. Rev. C \textbf{84}, 034312 (2011).} has called into question whether the Gaussian orthogonal ensemble (GOE) version of random matrix theory describes nuclear resonance data. The conclusion that the data are inconsistent with GOE seems in contradiction with the analysis of resonance spacing data. We wish to test the possibility that the distribution is not truly GOE but the spacing data by themselves still appear to be described by the GOE. We have simulated both width and spacing distributions that differ by varying amounts from the GOE distribution and determined how one estimate of GOE behavior, the fraction of missing levels, behaves as we deviate increasingly from a GOE distribution. Results will be presented. [Preview Abstract] |
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KA.00003: Minimum-Bias Studies Using the Energy Scan Data from the Fermilab Tevatron Collider David Wilson, Craig Group, Rick Field We report on an analysis of the minimum-bias event data (that is, events with the least selective trigger criteria) taken at the Tevatron collider at Fermilab, in particular an energy scan recording collisions at $\sqrt{s}$ = 0.3, 0.9, and 1.96 TeV. This data set represents a rare chance to analyze the energy dependence of several minimum-bias observables; for example, the pseudorapidity ($dN/d\eta$) distribution. We present the results of a comparison of these observables with the PYTHIA Monte Carlo simulation. [Preview Abstract] |
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KA.00004: Studies of Silicon Photomultipliers for their use in the Mu2e Experiment at Fermilab Alyssa Henderson, Craig Group, Yuri Oksuzian, Paul Rubinov Silicon Photomultipliers (SiPMs), a relatively novel technology, are able to detect single photons and convert them into electrical signals when used within a proper voltage range. In order to learn more about SiPMs for their use in the Mu2e experiment, we find a few characteristics of the SiPM at the Silicon Detector facility at Fermilab. We connected several SiPMs, one at a time, to a Keithely 2400 Sourcemeter that was programmed to vary the voltage automatically. In this way, we were able to apply our desired voltage range and the sourcemeter provided the corresponding current. We also conducted these experiments with the SiPMs in a dark chamber, which we used to control the temperature of the environment. We applied a voltage and measured the corresponding current at four temperatures and measured three characteristics: breakdown voltage, the operating voltage range, and the resistor value at each, as well as how they vary with temperature, time, and between two brands. [Preview Abstract] |
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KA.00005: Nuclear Effects in Polarized $^3$He Structure Functions and Asymmetries Jacob Ethier, Wally Melnitchouk In polarized electron-nucleon scattering, spin structure functions (SSFs) give information about quark spin contributions to the total nucleon spin. Since free neutron targets are nonexistent, nuclei such as $^3$He (two protons and one neutron) and deuterium (one proton and one neutron) are commonly used as effective neutron targets to gather SF data. Given that the neutron is not free but is bound inside the nucleus results in consequences for its internal quark structure. The aim of this work was to study theoretical models of $^3$He SSFs and polarization asymmetries (ratios of polarized to unpolarized SFs) that account for these bound nucleon effects so that neutron information can be reliably extracted from nuclear data. The $^3$He SSFs and asymmetries can be calculated by smearing the proton and neutron SSFs with the light-cone momentum distributions of the nucleons in the nucleus. The full calculations of the $^3$He SSFs and asymmetries reveal a distinct difference in resonance structure compared to the free nucleon SSFs. [Preview Abstract] |
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KA.00006: Metropolis-Hastings Algorithm Optimization Using Lag-1 Correlation Time and Chain Power Spectrum to Generate Nuclear Coordinates from Nuclei with Neutron Halo Emily Gordon, Ivan Novikov We extract parameters of nuclear density distribution for the $^{11}$Li nucleus by calculating interaction and reaction cross sections and comparing the results to experimental data. The cross section calculations are done in the framework of Glauber theory using Monte Carlo integration technique. The Metropolis-Hastings algorithm and other Markov Chain Monte Carlo (MCMC) approaches are used to create sequences of random numbers distributed according to a predefined distribution. The algorithm efficiency depends on exact expressions of the distribution of interest and proposal distribution. The goal of this study is to find the parameters of proposal distribution which maximize the efficiency of the Metropolis-Hastings algorithm. The algorithm performance was optimized using lag-1 correlation time and the shape of the power spectrum of the random number sequence. [Preview Abstract] |
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KA.00007: Implementing a New Ion Chamber Design for Neutron Spin Rotation Hannah Gardiner, Eamon Anderson, Jason Fry, Adam Holley, Mike Snow The quark-quark weak interaction is difficult to measure due to the presence of the strong force. However, low energy neutrons passing through liquid Helium-4 can be used to probe the nucleon-nucleon weak interaction, which is induced by the quark-quark weak interaction. The neutron spin rotation experiment seeks to measure the spin rotation angle of neutrons due to their weak interaction with Helium-4 nuclei. This rotation angle is translated into a neutron flux asymmetry with a neutron polarizer/analyzer pair. A segmented Helium-3 gas ionization chamber was developed to measure the resultant neutron flux. We report on the design and initial tests of that ionization chamber. This work is supported by the National Science Foundation REU program and NSF grant {\#}PHY-0969490. [Preview Abstract] |
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KA.00008: Use of Computational Simulations for Analysis of Parity Violation Experiments with Neutrons Jonathan Serpico, Ivan Novikov We developed and analyzed the results of computer simulations of experiments in which parity violating and parity conserving asymmetries are measured in nuclear reactions with neutrons. The software utilizes parallel computing technologies. The value of the parity violating and parity conserving asymmetries and their accuracies were obtained for various neutron beam parameters, targets, and configurations of detection systems. The energy dependence of parity violating and parity conserving amplitudes were obtained in the framework of reaction theory. [Preview Abstract] |
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KA.00009: Characterization of a polymer based drug delivery system for the enhancement of wound healing Ryan Widejko, Keith Moore, Jay Potts The field of Regenerative Medicine has seen an increase in the need to improve long term implant compatibility. To address this need we have combined microencapsulation and beneficial wound healing agents. The aim of the project was to develop and characterize a delivery system for the agent $\alpha $CT1. To enable the extended release of this peptide, alginate microcapsules coated in poly-l-ornithine (PLO) were explored as a means of delivery. These capsules were created via electro-spraying and characterized by phase contrast microscopy, scanning electron microscopy (SEM), atomic force microscopy (AFM), and release profiles. SEM analysis showed the addition of PLO did not change the overall geometry or topology of the microcapsules. AFM analysis showed that PLO affected the rigidness of the capsules by decreasing it from 54.26 pN to 46.11 pN. The release profile analysis revealed that over an 8 hr period the addition of PLO extended the $\alpha $CT-1 released by 146{\%} over the release of alginate alone. Phase contrast microscopy revealed that the addition of PLO changed the average size of the capsules from 209 $\mu $m to 187 $\mu $m. The results of this project indicate that the use of alginate microcapsules as a drug delivery system for $\alpha $CT-1 is a viable method. This material is based upon the work performed in association with an REU Program hosted by the Biomedical Engineering Program at USC and supported by the NSF under the grant {\#}EEC-1005138. [Preview Abstract] |
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KA.00010: Measurement of coiled-coil stability by fluorescence resonance energy transfer James Pino, Bomi Kim, Manuel Santiago, Stefanie Whitson, Kristin Whitson Alpha helical coiled-coils are common structural motifs by which proteins assemble into larger complexes. The leucine zipper-like oligomerization domain of heterogeneous nuclear ribonucleoprotein C (CLZ) assembles into an anti-parallel tetramer with a coiled-coil fold. Fluorescently-tagged CLZ peptides were designed and characterized as appropriate to perform measurements using fluorescence resonance energy transfer (FRET) to study the overall stability of the assembly. Experiments revealed that the appearance of FRET in a sample was time dependent and thus reflective of the kinetics of the tetramer's formation. Furthermore, FRET assays using varying concentrations of labeled peptides have allowed the first measurement of the equilibrium dissociation constant (K$_{D})$ of the CLZ tetramer, which is representative of the strength of specific molecular interactions within the oligomer. The method can be used to study effects of mutations in this coiled coil on the thermodynamic stability of the complex. [Preview Abstract] |
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KA.00011: Sensitivity of Rayleigh-Taylor Instability growth rate due to thermal conductivity Ryan Learn, Tomasz Plewa, Andrey Zhiglo In many high energy density and astrophysical systems, the heat conduction plays an important role in the system evolution by redistributing the heat and modifying flow morphology. Thermal conduction is known to induce fluid flows in systems where materials of different densities are in pressure equilibrium. In situations when gravity is present, material discontinuities might be subject to the Rayleigh-Taylor instability. In that case, and in presence of thermal conduction, one may expect the interplay between the thermal conduction and the Rayleigh-Taylor Instability. We explore this possibility and study Rayleigh-Taylor driven mixing in thermally conducting plasmas by means of multidimensional hydrodynamic simulations. The parameters used in our numerical experiments are based on proposed and completed experiments on the OMEGA and National Ignition Facility lasers. [Preview Abstract] |
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KA.00012: Characterization of Zr-V-Fe Non-Evaporable Getter Strips for use in a Miniature Penning Trap Robert Baker, Georg Bollen, David Lincoln, Matt Redshaw, Ryan Ringle, Stefan Schwarz, Adrian Valverde The Low Energy Beam and Ion Trap (LEBIT) group at the National Superconducting Cyclotron Laboratory (NSCL) performs high-precision mass measurements using a Penning trap. The current method involves measuring reference ions of known mass in order to calibrate the magnetic field. Because the reference measurements require us to stop the measurement of a rare isotope, we will optimize the use of beam time by installing a magnetometer to directly measure the magnetic field while conducting a rare isotope measurement. A miniature Penning trap (MiniTrap) will be mounted adjacent to the measurement trap to serve as a magnetometer. To reach the desired precision, the MiniTrap must be operated in very low pressures. We investigate using the SAES St707 (Zr-V-Fe) non-evaporable getter to pump out the MiniTrap to achieve an ultra-high vacuum. Excess hydrogen will be ionized into $H_2^+$ and serve as the reference mass. We report a pumping speed for the activated getter material, partial pressures for the background gases after different pumping intervals, and discuss further work with the MiniTrap. [Preview Abstract] |
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KA.00013: Computational analysis of odorant binding to OBPs Bomi Kim, James Pino, Manuel Santiago, Stefanie Whitson, Kristin Whitson Humans can detect countless odors but the mechanism by which much of the pathway occurs is not elucidated. Odorant binding proteins (OBPs) carry hydrophobic odorants across aqueous mucus to be deposited at olfactory receptors, triggering a neuronal response. The active site within the beta-barrel structure is conducive for hydrophobic odorants, where a lysine residue has been implicated as essential for binding of aldehyde moieties. The studies herein aim to determine the relative stability of various odorant/OBP combinations by energy minimization and computational modeling with ligand docked to active sites in wild-type OBP2A, mutant OBP2A, or OBP2B. The results demonstrate other specific interactions between odorants and protein, revealing wild-type OBP2A may have two binding sites, with initial binding occurring near the barrel opening. Energies indicate protein stability though two ligands are present in the active site. In addition, ligands with similar structures bind the same location on the protein, indicating directionality of the protein in ligand binding. [Preview Abstract] |
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KA.00014: Examination of Concrete with Carbon Nanotubes Using the Large Chamber Scanning Electron Microscope Linda Cruz, Shane Palmquist, Jahi Palmer, Keith Andrew, Edward Kintzel Mechanical properties of concrete are most commonly determined using destructive tests including: compression, flexure, and fracture notch specimen tests. However, nondestructive tests exist for evaluating the properties of concrete such as ultrasonic pulse velocity and impact echo tests. One of major issues with concrete is that unlike steel it is quasi-brittle material. It tends to want to crack when tensile stresses develop. These cracks generally develop at the interfacial transition zone (ITZ) between the cement paste and the aggregate. Fibers have been added to concrete for many years to help with temperature and shrinkage cracks. In more recent years, the concepts of adding fibers with enhanced properties such as carbon nanotubes (CNTs), to concrete have been explored. Some possibilities include developing concrete that may be more durable, flexible, stronger, less permeable, and potentially ``crack free'' than traditional concrete. Based on SEM images and quantitative data taken using the Large Chamber Scanning Electron Microscope at Western Kentucky University, this study examines the ITZ of concrete made with CNTs. Results provide greater understanding on the nature of the ITZ region in concrete made with CNTs. [Preview Abstract] |
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KA.00015: Quantum Magnetism Software Scott Garland, Larry Engelhardt We present an open-source (free), user-friendly computer program that generates theoretical magnetism data based on customizable quantum spin systems. A detailed knowledge of quantum mechanics is not required to use this program, making it suitable for students as well as researchers. FIT-MART, the Fully Integrated Tool for Magnetic Analysis and Research, is available for download as a platform-independent, executable java (.jar) file at: http://www.opensourcephysics.org/items/detail.cfm?ID=12308. [Preview Abstract] |
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KA.00016: Ameliorating Computational Tools and Testing Cosmological Models Ezekiel Shuler The Lambda-Cold Dark Matter (LCDM) model is the standard model for the universe. This model explains some key elements in the universe that cosmologists believe to be true, however this model also has some inconsistencies. Using the CosmoMC code along with the Palmetto Cluster, I will run jobs that will best test the LCDM model. I will also improve an EJS (Easy Java Simulations) program to require GRBs (Gamma-Ray Bursts) as apposed to just SN (Supernovae). Supernovae Type Ia are known as standard candles, and they are used to directly probe the expansion rate of the universe. Recently, GRBs (Gamma-Ray Bursts) have been explored more and have been proposed to be a complementary probe to Supernovae Type Ia. So far, GRBs are the most intense explosions in our universe. For this reason, the GRBs have much higher redshifts up to 8.1, but redshifts close to 10 or larger are expected. This simulation allows the user to discover the cosmological model that best-fits the recent supernovae and GRB datasets. After receiving the results from my jobs on the Palmetto cluster, I will conclude on the stasis of the LCDM model and be able to do a pulmonary test with the GRBs in the EJS program. I found that the LCDM model is a pretty good model for our universe, but we need more conclusive data to rule it out or keep it. The study of the evolution of the universe is extremely important to understand the cause of the accelerated expansion of the universe (cosmic acceleration). [Preview Abstract] |
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KA.00017: Galaxy Collision Modeling Kirubaa Thavayoganathan This project is a study of colliding galaxies. Using a parallelized N-Body code called GADGET-2, we create a model of the collision between Milky Way galaxy and Sagittarius dwarf galaxy (SDG). The SDG system is one of the closet dwarf galaxies to the Milky Way and observations provide very accurate positional and kinematical data for computer modeling. Through varying the parameters of the starting location of the SDG system we are able to study the resulting position of the SDG after 1 billion years has passed. Using the position of the SDG system as observed today we will be able to modify the initial position of the SDG system to produce an even better model. [Preview Abstract] |
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KA.00018: Control Box for Sub-Orbital Telescope Christian Rhodes One of the major obstacles for observational astronomers is the Earth's atmosphere. By sending telescopes outside of the atmosphere we can overcome this problem. However, this can be quite expensive, especially with billion dollar telescopes such as the Hubble. Reasonably, astronomers do not want to risk burning out the CCD on the valuable telescope by pointing it near the sun. Solutions such as using Black Brant rockets have arisen, yet still cost millions of dollars. By utilizing commercial spaceflights offered by XCOR, we can cut this cost to less than a couple hundred thousand dollars and get the telescope back at the end of the flight. To prove that this is possible, we are developing a telescope that can fit onto the passenger side of the spacecraft. Even though the telescope will be hand-steered, a programmed control box was needed to change the filters and to record. The control box sends commands via serial communication to a shell program that controls the CCD program and the filter wheel program. By creating a shell program that controls the CCD and filter program inside the Windows operating system, the shell program is easily adaptable to any CCD or filter wheel program. This control box allows you to manually and automatically change the filters and record as well as document the time in which all the actions occurred. - This project was completed under the Palmetto Academy, a division of the NASA SC Space Grant Consortium [Preview Abstract] |
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KA.00019: Optical Strain Indicators Jonathan Heath, Dakotah Anderson, Jeffrey Anker Remote non-destructive methods to measure strain are need for many NASA projects e.g. for astronauts to check on exterior equipment without having to be exposed to space, ground observatories to monitor tension of bolts miles away in the sky, and scientists to monitor how effective an airbag would stand against full impact of 200lb individual. We designed prototype optical strain indicators to accurately measure the strain of various objects and materials through nondestructive measures. These indicators may be used to label structural components, such as bolts, so that improper strain can be seen by the eye or camera. Strain gauges with alternating bands of red and blue were created that appeared to change color when a ``window pattern'' with transparent and opaque regions was displaced relative to the colored bands below. The strain gauges were attached to various objects/materials as they moved, stretched, or bent. The fabricated optical strain gauges were found to be quite versatile for many applications. Future work includes minimalizing the alternating color lines printed on the indicators, constructing and testing a screw design, and pursuing additional tests that involve expansion and bending. [Preview Abstract] |
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KA.00020: Development of a Pattern Simulator for Benchmarking a Near-field Holographic Image Processor Kate Martin, Christopher Beaudoin Deformations of the reflector optics comprising a radio telescope can introduce station position errors that are significant in the context of VLBI2010. Radio holographic imaging is a technique that can be utilized to detect such deformations. In experiments involving large reflector antennas at relatively high frequencies, geosynchronous satellites are observed to conduct far-field radio holography since the stand-off ranges satisfy the far-field requirement. However, these sources are relatively fixed with respect to the radio telescope and this limitation does not facilitate the ability to characterize the deformations over the telescope's full field-of-view. The near-field holographic imaging technique overcomes this limitation of the satellite-based far-field technique since the source is under the control of the observer and may be placed in close proximity to the radio telescope in question. Additional complexities arise in this near-field scenario but these considerations have been addressed in the literature. In this report, a near-field antenna pattern simulator was developed to facilitate testing of a near-field holographic image processor. The results of this simulator have been compared against independent expectations to validate the simulator. [Preview Abstract] |
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KA.00021: Utilizing On-Chip Resonant Cavities for Magnetic Resonance Studies Kyle Serniak, Mathew Martens, Sylvain Bertaina, Irinel Chiorescu We studied an Electron Spin Resonance (ESR) setup utilizing a balanced bridge in conjunction with a lock-in detector to be used at the low temperature attained by a dilution refrigerator. ESR measurements were performed on a spin 1/2 DPPH sample at room temperature. The setup uses a microstrip line, which has recently attracted a lot of interest due to its high sensitivity and low noise baseline. Electronic spin excitation of the sample was achieved through use of an ``omega'' shaped microstrip cavity with resonant frequency of 17.4 GHz, which concentrates the magnetic field in a small region where the sample is placed. A homemade heterodyne detector was used for signal detection with and without a balanced magic-T bridge and lock-in amplifier. Direct measurements were also performed using a fast digital acquisition card. [Preview Abstract] |
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KA.00022: Four Harmonic Buncher For FSU LINAC Daniel Moerland, Ingo Wiedenh\"over Florida State University's John D. Fox Superconducting Accelerator Laboratory is operating a Tandem-Linac system for heavy ion beams at energies of 5-10 MeV/u. Recently, the accelerator has been used as the driver for the radioactive beam facility RESOLUT, which poses new demands on its high-intensity performance and time-resolution. These demands motivated us to optimize the RF bunching system and to switch the bunch frequency from 48.5 to 12.125MHz. We installed a four-harmonic resonant transformer to create 3-4 kV potential oscillations across a pair of wire-mesh grids. This setup is modulating the energy of the beam injected into the tandem accelerator, with the aim to create short bunches of beam particles. A sawtooth-like wave-form is created using the Fourier series method, by combining the basis sinusoidal wave of 12.125MHz and its 3 higher order harmonics, in a manner similar to the systems used at ATLAS and other RF-accelerators. A new aspect of our setup is the use of a digital 1GHz function generator, which allows us to optimize and stabilize the synthesized waveform. The control system was realized using LabView and integrated into the controls of the accelerator. [Preview Abstract] |
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KA.00023: Lagrange Meshes in Nuclear Physics Taylor Hynds We examine different methods of solving the Schr\"{o}dinger equation for two and three-body systems. We begin by constructing variational wave functions, as expansions in a basis of orthogonal polynomials. This method has been found to give accurate results, given a sufficiently large basis. However, computationally this can become very cumbersome. We therefore employ the Lagrange-mesh method, which leads to a simple calculation of both potential and kinetic matrix elements that is both computationally efficient and results in little to no loss in accuracy. This method has been applied to several problems with well known analytical solutions, and has given excellent results. The effectiveness of this method in analyzing bound states of quarks has yet to be demonstrated. In the future this method will be applied to the quantum-mechanical three-body problem. [Preview Abstract] |
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KA.00024: Lagrange Mesh in Hadronic Physics Spencer Rosenfeld, Winston Roberts We used a variational method to solve a quantum mechanical three body problem. This is accomplished by computing the matrix representation of the Hamiltonian operator in a Lagrange mesh basis an minimizing the appropriate energy eigenvalues. The method was applied to an approximate potential for quark-quark interactions. [Preview Abstract] |
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KA.00025: Characterization of $^{10}$B Lined Proportional Counters and Moderator Design J.A. Silano An SA-B1-0824-101 $^{10}$B lined neutron counter from G.E. Reuter-Stokes was characterized and moderator was designed and tested for detecting fast neutrons. The neutron counters are single-wire cylindrical proportional counters with a Boron tube lining enriched to 92\% $^{10}$B and are filled with Ar gas. Thermalized neutrons interact with the Boron layer through the $^{10}$B(n,$\alpha$)$^{7}$Li reaction, and the reaction products deposit energy in the Ar gas. The deposited energy pulse is amplified by a proportional counter bias potential of 800 V, resulting in a detectable signal. The detector consisting of four tubes was simulated in Geant4 and the dependence of the detector efficiency on the thickness of the $^{10}$B layer was determined. The detector efficiency was measured experimentally with a $^{241}$AmBe source of known neutron activity. A modular design for the high density polyethylene moderator allows the detector to be composed of four proportional counters for optimum efficiency, or be split into two separate detectors for ($\gamma$, n) polarization measurements. [Preview Abstract] |
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KA.00026: Effective R-matrix parameters of the Woods-Saxon nuclear potential Dylan Abrahamsen, Alexander Volya, Ingo Wiedenh\"over The phenomenological R-matrix approach is one of the most practical tools for the analysis of the multi-channel resonant scattering data. However, the relatively unconstrained phenomenological parameters of the R-matrix approach have been subjects of a continuous criticism. The goal of this research is to study the connection between the R-matrix channel radius and the reduced width and the parameters of the actual potential model. We evaluate the scattering observables of the Woods-Saxon potential [1] and do an R-matrix fit which allows for the reduced width and channel radius to be determined. The dependence of the R-matrix parameters on the diffuseness, spin-orbit interaction and on other parameters of the nuclear potential is discussed. \\[4pt] [1] N. Schwierz, I. Wiedenh\"over, A. Volya, http://arxiv.org/abs/0706.1628 [Preview Abstract] |
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KA.00027: The Search for Large Extra Dimensions via Single Photon plus Missing Energy Final States Alicia Gomez In high energy particle physics there is a hierarchy problem in the standard mode. The force of gravity is orders of magnitude weaker than the other forces. A theorized solution to this problem is that the Kaluza-Klein graviton carryies much of the gravitational force into another dimension. We are looking for evidence of large extra dimensions by analyzing quark antiquark collisions which result in the production of a single photon and missing transverse energy. The data we are using is from the D0 experiment at the Tevatron collider at Fermilab National Accelerator Laboratory. The method we are using for our analysis is to restrict the data by imposing certain quality requirements which are pertinent to our analysis. From this data sample, we analyze distance of closest approach histograms to determine which events are best for analysis. Using these events we will set limits on the fundamental mass scale for large extra dimensions. [Preview Abstract] |
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KA.00028: W Boson Production Charge Asymmetry in the Electron Channel Ashley Huff, Susan Blessing We present a measurement of W Boson Production Charge Asymmetry in PP(bar) collisions through W $\rightarrow$ e-$\nu_e$ decays. The collision of a u quark and a d(bar)quark will produce a W$+$ Boson while the collision of an u(bar) quark and a d quark will produce a W- Boson. These particles decay rapidly but we are able to measure their asymmetry by studying the resulting electrons and neutrinos. These results will be used to further constrain PDF fits and improve the accuracy of future predictions for new physics. [Preview Abstract] |
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KA.00029: Dipole Magnets for Axion Research Nicholas Fowler, Dipangkar Dutta, Rob Riehle, Prajwal Mohammurthy Axions are hypothetical particles which have been proposed by Peccei and Quinn as a solution to the strong CP problem. The Mississippi State Axion Search (MASS) project has involved the light shining through a wall (LSW) technique to test for the existence of axions particles. The setup involves two tuned vacuum cavities, one with a radio source and one with a radio detector. The two cavities are separated by a lead wall and placed in a very strong magnetic field. At the moment, we are still in the construction phase but we are very close to beginning experimentation. My contribution to the research has mainly involved the construction of the magnet. [Preview Abstract] |
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KA.00030: Mississippi State University Axion Search Amy Ray, Dipangkar Dutta, Mikhail Gaerlan, Prajwal Mohanmmurthy, Mitra Shabestari, Robertsen Riehle The Mississippi State Axion Search is a project that is searching for a dark matter candidate, an axion- like particle. A technique known as the ``light shining through a wall'' is used to search for this particle via the mechanism that two incident photons couple to form an axion which passes through a wall and then decays back into photons on the other side where they are recorded by a detector. The setup of this experiment consists of two vacuum cavities, one containing a strong EM field and the other housing detectors. The project is currently being set up and will soon be ready to record data. We will present an overview of the project, construction and characterization of the integrator electronics, and data acquisition (DAQ) based on National Instrument Lab View. [Preview Abstract] |
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KA.00031: The Construction of Mississippi State Axion Search Adam Powers, Dipangkar Dutta, Robertsen Riehle, Prajwal Mohanmurthy Axions have been proposed by the Peccei-Quinn theory to be the solution to the strong CP problem. A great deal of the research toward axions has been in narrowing the range of the mass and the coupling constant in which they could be observed. The Mississippi State Axion Search is an exotic particle experiment which uses a light shining through a wall (LSW) technique. The experimental setup consists of two tuned vacuum cavities placed under a very strong magnetic field and separated by a lead wall. While one of the cavities houses a strong radio source, the other (dark) cavity houses the detector systems. Currently, we are piecing together the cavity with the magnets and the wall separating the chambers. The presentation will include a run through of the construction thus far and the purpose of our setup. [Preview Abstract] |
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KA.00032: CosmoEJS: Interactive Cosmological Data Fitting Simulations Jacob Moldenhauer, Larry Engelhardt, Keenan Stone, Ezekiel Shuler We present a collection of cosmological modeling programs built with Easy Java Simulations for studying the accelerated expansion of the universe (cosmic acceleration). These interactive programs use real-time plotting and fitting of cosmological models with actual experimental data sets. The user can choose multiple models and data surveys to compare to one another at the same time. These programs can be found at http://www.compadre.org/osp/items/detail.cfm?ID=12406. [Preview Abstract] |
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KA.00033: Core-Collapse Supernova Explosion Mechanisms: SASI vs Neutrino Driven Convection Timothy Handy, Tomasz Plewa, Andrzej Odrzywolek Despite advances in theory and computer models, the explosion mechanisms in core collapse supernovae (ccSN) are still under debate. In particular, the reported relative importance of the standing accretion shock instability (SASI), non-SASI turbulent fluctuations, and bulk convective motion due to neutrino heating varies between research groups, with no current consensus. In this work we offer our own insight into the problem, utilizing an extensive database of 2D and 3D ccSN models tuned to match the energetics of SN 1987A. We propose, implement, and apply novel methods for characterizing the post-bounce evolution of the stellar core. Our analysis focuses on energy transport, convection, morphology of the flow, and statistical properties of fluid motions. We compare the results of our work to those reported by other groups. In particular, we find that our models indicate more vigorous explosions in 3D as compared to 2D for the same neutrino luminosity. [Preview Abstract] |
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KA.00034: One equation describes galaxy redshift, the Pioneer Anomaly, and the Pound-Rebka experiment John Hodge The Scalar Potential Model (SPM) suggests an equation to describe galaxy redshift that has a higher correlation coefficient than the Hubble Law model. The equation was applied to the Pioneer Anomaly (PA) in 2006. The SPM describes all the anomalies of the PA that no other model does. Data analysis in 2011 confirmed predictions of the equation. This paper shows the equation is consistent with the Pound-Rebka experiment result. http://web.comporium.net/$\sim$scjh/ [Preview Abstract] |
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KA.00035: Spheromak Turbulent Physics Experiment: Initial Physics K.M. Williams, Earl Scime, Edward Thomas, Simon Woodruff The Spheromak Turbulent Plasma Experiment (STPX) at Florida A {\&} M University came online July 2012. The STPX is dedicated in part to examining turbulence and stability physics in the spheromak environment. Much of the research on STPX will be applied to astrophysical and fusion systems. In addition the STPX will serve as a platform for the design and testing of novel diagnostic techniques. Also, closely coupled modeling and experimentation will take place using the FAMU computational cluster. The STPX device will make use of a number of diagnostic systems that have been developed in partnership with our research collaborators. For this meeting, initial physics and STPX plasma characteristics will be discussed. [Preview Abstract] |
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KA.00036: Design study for diverging supernova explosion experiment on NIF Markus Flaig, Tomasz Plewa, Michael Grosskopf, Paul Keiter, Paul Drake, Carolyn Kuranz, Hye-Sook Park, Bruce Remington We report on preliminary design simulations for the DivSNRT experiment, which is a spherically-diverging Rayleigh-Taylor experiment scaled to the core-collapse supernova conditions to be carried out at the National Ignition Facility (NIF). The simulations are done in cylindrical geometry, using the block-AMR multi-group radiative diffusion hydrodynamics code CRASH. We assess the sensitivity of the Rayleigh-Taylor instability growth on numerical discretization effects, variations in the laser drive energy and the manufacturing noise at the material interface. We find that for perturbations with well resolved wavelength, the CRASH code is able to account for the effects of the target manufacturing noise as long as its amplitude is larger than a single grid cell. We also explore different designs of the target mount in order to minimize its influence on the Rayleigh-Taylor instability evolution. These results will serve as the basis for more detailed, multi-interface target design optimization studies in the future. [Preview Abstract] |
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KA.00037: Stratospheric Studies Using High Altitude Ballooning Dylan Wood, Justin Oelgoetz Stratospheric balloons serve as a relatively inexpensive and simple method to study a unique environment with extremely low temperatures and pressures, far above most of the atmosphere. Such balloons can be used to carry a wide variety of experiments ranging from Geiger counters for cosmic ray studies to simple environmental sounders. Austin Peay State University has built a flight system and conducted an initial high altitude balloon launch to test hardware and design feasibility. Through use of an Automatic Packet Reporting System (APRS) beacon, the first balloon was successfully tracked to a maximum altitude of approximately 95,000 feet and retrieved from its landing zone in rural Wilson County, TN. Subsequent launches are underway and will test on-board data acquisition hardware. Results of analysis of data from the on-board 3-axis accelerometer, 3-axis magnetometer, temperature probe, Global Positioning System (GPS) units, and camera will be presented, along with a sketch of future experimental plans. [Preview Abstract] |
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KA.00038: Integrated Printed Moisture Sensors in Composite Structures Karen Bermes, Jin Gyu Park, Zhiyong Liang Moisture that is present in the ambient environment can break down composite structures, such as boats and aircraft, if they are subject to extended exposure. Therefore, these effects need to be monitored over the lifetime of the structure. We are attempting to do this by producing a moisture sensor that can be integrated into composite structures and have little impact on the structural integrity. To achieve a thin sensor, both printed electronics and nanotechnology were utilized. An open circuit was printed on polyimide (PI) using Ag nanoparticle ink. For some sensors, bucky paper (BP) was laid on top using acetone to flatten it, and on the others carbon nanotube (CNT) ink was printed on top of the Ag printed network. The samples were sintered and testing began in a Controlled Environment Chamber (CEC). We hypothesized that resistance would increase with increasing humidity because the water would impede current in the circuit. This is what occurred in the BP sensors; however the CNT printed sensor displayed the opposite behavior. We are currently looking into why printed materials exhibited opposite behaviors. [Preview Abstract] |
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KA.00039: Analysis of residual stress in welds using electronic speckle-pattern interferometry (ESPI) Sean Craft, Bishwas Ghimire, Bidhan Thapa, T. Sasaki, Sanichiro Yoshida Residual stress is stress which is locked-in inside of a material and is independent of external load/force. The material under consideration is a welded metal sample consisting of two different constituent metals. In this case, the cause of the residual stress is the fact that the two metals, when cooled down from the high temperatures of the welding process, will contract at different rates and to differing degrees due to a difference in their respective coefficients of linear expansion. Of course, because they are now attached, the metals will try to deform one another, which creates internal forces at the weld site. The technique we will be using to analyze this residual stress is electronic speckle-pattern interferometry (ESPI). In unrelated experiments, ESPI has been successfully utilized to show areas of concentrated stress when external forces are applied to a sample metal. Our conjecture is that it can also be used to analyze the areas where residual stress is located within a sample such as that described above. Our method of analysis is based on the following hypothesis: if a slight tensile force is applied to the welded sample perpendicular to the weld, this will cause the sample to contract parallel to the weld. Near the weld site, on one side of the weld, the sample will resist this deformation, due to the fact that it is already deformed in this direction by the residual stress. And conversely, on the other side of the weld, the sample should welcome this deformation. [Preview Abstract] |
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KA.00040: Measurement and Analysis of C$_2$ Swan Spectra Following Breakdown of Nitro Compound Simulants M. Witte, C.G. Parigger, N.A. Bullock, J.A. Merten, S.D. Allen Recent measurements of micro-plasma following laser-induced optical breakdown on 3-nitrobenzoic acid show well developed molecular spectra during the first several hundreds of nanoseconds. Analysis of Carbon Swan spectra for well-above breakdown threshold energy/pulse is accomplished using an accurate line strength file. Moreover, presence of hydrogen-beta allows us to infer electron density in the plasma evolution. Computational challenges include accounting for background variation and appropriate modeling of hydrogen embedded in molecular spectra. Recorded and computed spectra agree nicely for time delays on the order of 1600 ns from optical breakdown when using a single temperature for local thermodynamic equilibrium plasma. [Preview Abstract] |
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KA.00041: Self-absorption of hydrogen Balmer lines in laser induced plasma. M.R. Rezaee, C.G. Parigger In the study of self-absorption phenomena in laser-induced hydrogen plasma we focus on H$_\alpha$, H$_\beta$ and H$_\gamma$ of the Balmer series. Broadened line profiles, shifts and line intensity ratios are commonly measured for plasma characterization and diagnostics in laboratory scale micro-plasma, for example, laser-induced plasma but are also measured to explore inductively coupled plasma and extraterrestrial plasma. One can infer the electron density and plasma temperature from measured spectra. Accurate diagnostics is important for applications in magnetically confined plasma devices as well as in quantitative laser-induced breakdown spectroscopy. Moreover, stability of plasma in Tokamak chambers is a function of electron density and temperature, and optical spectroscopy is utilized to find these values. Self-absorption however can cause extra broadening and distortion in line profiles. Here we present results that reveal evidence of self-absorption in H$_\alpha$. We compare the electron density obtained from H$_\alpha$ with the ones obtained from H$_\beta$ and H$_\gamma$, and we also discuss the determination of temperature from Balmer Series lines. [Preview Abstract] |
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KA.00042: Acquisition and Analysis of Titanium Monoxide Spectra in Plasma A.C. Woods, C.G. Parigger The recent use of titania (TiO$_2$) nanoparticles for thin-film production has raised interest in the environment and properties of Ti containing particles in plasma. As a precursor to TiO$_2$ in rapidly cooling plasma, the titanium monoxide (TiO) molecule provides insight into the environment in which TiO$_2$ nanoparticles are produced. The spectral transitions of the TiO molecule have long been studied and observed by astronomers. We discuss our efforts in the calculation of predicted spectra for the TiO $\gamma$ ($A \, ^3\Phi - X \, ^3\Delta$), $\gamma^\prime$ ($B \, ^3\Pi - X \, ^3\Delta$), and E-X $\Delta v$=0 transitions as well as laser-induced breakdown spectroscopy (LIBS) as a technique for collecting time-resolved spectra. By nonlinear fitting to TiO molecular transitions measured in laser-induced plasma, computed spectra are used to infer the temperature of the observed TiO. [Preview Abstract] |
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KA.00043: Investigation Into The Design Of An Accelerator Drive Reactor Daniel Jones, Phillip Womble Using the Monte Carlo N Particle (MCNP-4C2) code, we attempted to simulate an accelerator driven reactor that did not employ any highly enriched nuclear materials and used only high Z materials as reflector/moderators. We will discuss the results of a ``toy model'' that we created using Th, Pb, and U. Using a rectangular parallel-piped design, 55 MeV neutrons impinged upon a plate of $^{232}$Th to create fission neutrons. The fission neutrons out of the $^{232}$Th plate were moderated to energies around 1 MeV. These slower neutrons were introduced into a mass of fissionable material (such as $^{235}$U) where the primary criticality would occur. We calculated the relative neutron yield from each section and investigated the practicality of a Pb neutron reflector assembly. [Preview Abstract] |
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KA.00044: Characterization of adhesion mechanism of thin-film systems using two independent, but correlating techniques Bishwas Ghimire, Sushovit Adhikari, Sanichiro Yoshida, Konrad Kabza Adhesion strength of thin-films to the substrate has been studied using two methods. The first is characterization of dynamic behavior of the film relative to the substrate surface based on an opto-acoustic technique. The thin-film specimen is configured as an end-mirror of a Michelson interferometer, and oscillated from the rear with an acoustic transducer. The resultant film surface displacement relative to the substrate is evaluated from the fringe shift of interference pattern behind the beam splitter. The second is surface energy analysis based on Young's contact angle measurement. Small drops of solutions with various surface tensions are placed on the substrate surface. The contact angle of each drop is measured, and its cosine is plotted as a function of the surface tension. The surface energy of the substrate is estimated through extrapolation of the plot to the zero-surface tension limit. These methods have been applied to pairs of thin-film specimens of the same film (Au, Pt) and substrate material (Si) prepared with different pre-coating surface conditions (plasma-treated and untreated). The two methods show clear correlation indicating that the plasma-treatment strengthens the adhesion. [Preview Abstract] |
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KA.00045: A Spontaneous Parametric Downconverion Source for Tests of Single Photon Quantum Mechanics R. Seth Smith During the spontaneous parametric downconversion process, a single photon of one frequency is converted into two photons of lower frequency in a nonlinear crystal. The input wave is referred to as the ``pump'' and the output waves are referred to as the ``signal'' and ``idler''. The process is said to be ``spontaneous'' because there are no input signal or idler fields. Rather, these fields are generated spontaneously inside the nonlinear crystal. The process is ``parametric'' because it depends on the electric fields, rather than just their intensities. This creates a definite phase relationship between the input and output fields. It is called ``downconversion'' because the signal and idler fields are at a lower frequency than the pump field. The setup, operation, and performance of a spontaneous parametric downconversion source will be described, as well as future applications of this source for tests of single photon quantum mechanics. [Preview Abstract] |
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KA.00046: ABSTRACT WITHDRAWN |
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KA.00047: Spectroscopy of Aluminum Monoxide in Flames D.M. Surmick, A.C. Woods, C.G. Parigger, J. Height, A.B. Donaldson, W. Gill Application of optical spectroscopy is discussed in studies of combustion phenomena. Here we present recent experimental results from flame pool measurements. Analysis is accomplished using accurate line strength files. One of the goals of the current study is to infer temperature of combusting aluminum particles from the $B \, {^2\Sigma}^+ \rightarrow X \, {^2\Sigma}^+$ transition of aluminum monoxide (AlO). An indicator of aluminum combustion is presence of AlO bands. The temperature of the flame for various positions is determined by fitting measured with computed spectra. Moreover, the background radiation is modeled using grey-body rather than standard black-body emissions. Computational efforts include comparisons of results from fitting diatomic AlO with results from fitting broadband background emissions.\\[4pt] *Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy's National Nuclear Security Administration under contract DEAC0494AL85000. [Preview Abstract] |
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KA.00048: DNA electrophoresis in tri-block copolymer gels Ling Wei, David Van Winkle Double-stranded DNA ladders were first separated in conventional agarose gel at room temperature. The lanes of well-separated DNA ladders in agarose were cut and trimmed before transferring to Pluronic$^{\textregistered}$ F 127, which is a triblock copolymer forming a gel-like phase of micelles arranged with cubic order at room temperature with concentrations higher than 18{\%}. The electrophoresis in F 127 was performed with the electric field perpendicular to the separation direction in agarose. A 10 bp DNA ladder consisting of 10 base pair repeats (10 bp-330 bp), 25 bp DNA ladder consisting of 19 blunt fragments ranging in length from 25 bp-450 bp (at 25 bp increments) plus a 500 bp band, and 250 bp DNA ladder consisting of 14 blunt fragments ranging in length from 250 bp-3500 bp (at 250 bp increments), were used as samples for this two dimensional gel electrophoresis. The continuously decreasing mobility with increasing length observed in the agarose separation is not duplicated in the Pluronic$^{\textregistered}$ F 127 separation. Rather, a complicated dependence of mobility on DNA length is observed whereby 100 -- 125 bp fragments have the highest mobility and there is also a variation of mobility with length correlated to the micelle diameter. [Preview Abstract] |
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KA.00049: An Investigation of Surface-Plasmon Mediated Emission from Functionalized Zinc Oxide Nanowires Daniel Mayo, Richard Mu, Richard Haglund The exciton-plasmon coupling mechanisms responsible for enhancing photoluminescence in a three-dimensional, metal-coated ZnO nanowire architecture are examined using an insulating MgO interlayer. Vertically-oriented ZnO nanowires are grown by a modified vapor-solid method inside a vertical furnace. The sides of the nanowires are then coated with MgO and functionalized with Ag nanoparticles via electron-beam evaporation using a glancing-angle deposition apparatus. By varying the thickness of the MgO spacer layer, it is possible to elucidate the exciton-plasmon coupling mechanisms that mediate ZnO photoluminescence. For the visible emission, strong quenching occurs independent of the MgO thickness. In contrast, the band-edge emission displayed an enhancement factor of 20 as the nominal thickness of the MgO spacer was increased from 10 to 60 nm. [Preview Abstract] |
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KA.00050: Nonlinear Plasmonics of Gold Nanospirals Roderick B. Davidson, II, Jed I. Ziegler, Guillermo Vargas, Richard F. Haglund, Jr. Archimedean nanospirals have been shown to have complex optical interactions characterized by wavelength- and polarization-sensitive intraparticle resonances. Due to their lack of any axis of inversion symmetry, nanospirals should also exhibit highly nonlinear behavior, such as second- and third-harmonic generation. The gold nanospirals in these experiments were created using electron beam lithography; the 4$\pi $ nanospirals have overall dimensions below 500 nm. The characteristic angular dependence of second harmonic emission (SHG) as a function of polarization angle is observed for linearly polarized light. The differences in SHG emission using linear and circular polarized excitation are also explored. Through these measurements we will characterize the strength of the second-order nonlinearity of the gold nanospirals relative to GaAs calibration materials. These measurements characterize an efficient second order non linear nanoparticle that does not have to meet the phase matching requirements of nonlinear crystals. [Preview Abstract] |
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KA.00051: Cavity Perturbation Technique: The Effects of Crystal Size on the EPR Spectra of Fe8 Muhandis Shiddiq, Junjie Liu, Christopher Beedle, Stephen Hill The Cavity Perturbation Technique (CPT) is a contact-free technique that measures the change of the characteristics of a cavity resonator upon the introduction of a foreign body (the sample under investigation). In this experiment, we study the effect of crystal size with regards to the CPT transmission spectra for single crystals of the single-molecule magnet Fe8. We have found that the frequency shift and transmission suppression become larger when the size of the sample is increased, suggesting a classical coupling between the Fe8 crystal and the resonator. From cavity perturbation theory, these phenomena may be explained by the following classical formula: $\Delta \omega $/$\omega \quad =-\beta \chi $, where $\omega $ is the complex frequency, $\beta $ is the filling factor that depends on the sample volume and the resonant mode of the cavity, and $\chi $ is the complex susceptibility. [Preview Abstract] |
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KA.00052: Tailoring electronic properties of SnO2 nanobelts via thermal annealing Jorge Barreda, Timothy Keiper, Joon-Il Kim, Peng Xiong, Jim P. Zheng Nanostructures of semiconducting metal oxides display many desirable characteristics for nano-electronics and sensing applications. Nanobelts (NBs) of SnO$_2$ have been synthesized using catalyst-free chemical vapor deposition of SnO powder. Channel-limited field-effect transistors (FETs) have been produced from the NBs and their use as effective gas [1], pH [2], and protein [3] sensors has been demonstrated. We investigate the control and optimization of the electronic properties of the NBs for biosensing applications by varying the oxygen stoichiometry via thermal annealing in oxygen and vacuum. Annealing our NBs in O$_2$ environment at 800$^{\circ}$C for 2hrs prior to the FET fabrication produces devices with conductance in the range of millisiemens, suggesting an increase in oxygen vacancies. Subsequent vacuum annealing allows tuning of the conductivity of the NBs. We demonstrate significant modulation of the current through the FET channel with an applied backgate voltage, indicating our devices are acceptable candidates for sensing charged biomolecules. Silane chemistry is used for the selective biofunctionalization of the NB-FETs. Antibody-antigen binding is detected by a change in the NB conductance after exposure to an analyte containing the specific antigen. [Preview Abstract] |
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KA.00053: Novel Sensor Design based on Switchable Electromagnetic-Induced Transparency Christina McGahan, Kannatassen Appavoo, Ethan Paul Shapera, Richard F. Haglund Jr. We can increase detector sensitivity past that of conventional surface plasmon resonance (SPR) detectors by changing the local dielectric environment. Here we demonstrate a novel sensor design that combines SPR detection with a phase-changing element to increase detector sensitivity. Vanadium dioxide (VO$_{2})$ modulates the near-field dielectric environment of the electromagnetically induced transparency (EIT) nanostructures via its insulator-to-metal transition, which shifts the nanostructures' plasmonic response. We obtain a sensor design using three-dimensional, finite-difference time-domain (FDTD) simulations to optimize the dimensions of a gold pi nanostructure exhibiting EIT due to its dipole-quadrupole interaction. To verify our simulations, we use electron-beam lithography to fabricate arrays of optimal structures on VO$_{2}$ films deposited on ITO covered glass by pulsed laser deposition or electron-beam evaporation. We tune the EIT by varying the dimensions of the pi structures, thus changing the strength of the dipole-quadrupole interaction. The resonance of the structures of different separation distances is experimentally verified through measuring broadband white-light transmission while the VO$_{2}$ is thermally modulated. [Preview Abstract] |
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KA.00054: Iron Nanoparticle M\"{o}ssbauer Spectroscopy with Rare-Earth Permanent Magnets L.D. Swafford, C.G. Parigger, H.-Y. Hah, S. Gray, M. Cole, D. Warnberg, C.E. Johnson, J.A. Johnson, E. Shafranovsky Properties of materials can be determined with a high degree of precision from M\"{o}ssbauer spectra. Due to the recoil energy of free particles, M\"{o}ssbauer spectroscopy is useful when the atoms are contained in a lattice structure. Resonance with the nucleus is achieved using gamma radiation. The Doppler effect is utilized by oscillating the radiation source thus modulating the energy of the gamma radiation. The recorded spectra show hyperfine splitting with intensities that depend on the angle of the gamma radiation with respect to the nuclear spin moment. For ferri- and ferro-magnets, the orientation of the magnetization and strength of the applied field can be inferred. For most paramagnets the magnetic susceptibility is on the order of 10$^{-6}$, and application of M\"{o}ssbauer spectroscopy requires low (a few Kelvin) temperature and large (a few Tesla) magnetic fields that are usually generated with superconducting magnets. However, for single-domain nanoparticles, or super-paramagnets, with susceptibility on the order of 10$^{-1}$ to 10$^{-2}$, a sizeable magnetization can be produced at room temperature in 1 Tesla fields. Such magnetic fields are obtainable with Nd-Fe-B permanent magnets. We present results of recent measurements on nanoparticles of iron. [Preview Abstract] |
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KA.00055: Upper Critical Fields in Nb/Ni Bilayers Emily Davis, Tim Ahrenholz, Phillip Broussard We studied the upper critical fields ($H_{c2}$) of Nb/Ni bilayers. These bilayers had a constant Nb thickness of 33 nm, and the Ni thicknesses varied from 0-7 nm. For each sample, we took resistive measurements of the superconducting transition under fields ranging from 0-4360 G. From these measurements, we obtained the upper critical field slopes ($H_{c2}^\prime$) of each sample. The $H_{c2}^\prime$ of a simple Nb layer was 3710 G/K, while the $H_{c2}^\prime$ values for the bilayers ranged randomly from 4650-6840 G/K. While the critical temperatures ($T_c$) of the samples seemed to exhibit a particular non-monotonic pattern as a function of Ni thickness (due to proximity effect), the $H_{c2}^\prime$ values as a function of Ni thickness formed no such clear pattern. We also analyzed the curvature of the $H$ vs. $T_c$ plots for each sample. Most of the plots were linear at lower applied fields, but many showed either positive or negative curvature as we applied higher fields. This curvature began anywhere between 2000 and 4000 G. Generally, bilayers with thinner Ni layers produced $H$ vs. $T_c$ plots with negative curvature, and bilayers with thicker Ni layers produced plots with positive curvature. [Preview Abstract] |
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KA.00056: Modeling time-dependent upconversion in Er-Yb doped sol-gel silicate glass Drew Onken, D.G. Hampton, C.J. Trennepohl, D.M. Boye, A.J. Silversmith Examining pulsed IR to visible upconversion in Er$^{3+}$-Yb$^{3+}$ doped sol-gel silicate glass may lead to applications in fiber optic communication due to the similar time scale of its GHz bandwidth. Excited state absorption of Er$^{3+}$ accompanying energy transfer from neighboring Er$^{3+}$ and Yb$^{3+}$ is responsible for the upconversion process. The dynamics of Yb$^{3+}$ to Er$^{3+}$ energy transfer are studied by observing green emission from the $^{4}$F$_{7/2}$ and $^{4}$S$_{3/2}$ levels of Er$^{3+}$ after a 6-ns pulsed laser excitation of the $^{2}$F$_{5/2}$ level of Yb$^{3+}$ at 978nm. This study examines the time-dependence of the fluorescence emission by varying the Yb$^{3+}$ concentrations and the annealing temperature. Our previous work has shown that the rare earth ions reside on the pore surface, and so the nanoporous nature of the sol-gel glass creates a finite reservoir of energy donors in each pore. These finite energy reservoirs foil the application of standard rate equation models and instead necessitate Monte Carlo simulations which can be used to determine the physical parameters of each energy transfer step in the upconversion chain. [Preview Abstract] |
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KA.00057: Spectral Selectivity of Photoinduced Effects in As$_{x}$S$_{100-x}$ Glass Thin Films James York-Winegar, Karel P\'alka, Miroslav Vl\v{c}ek, Justin Oelgoetz, Andriy Kovalskiy Spectral dependence of photoinduced effects in As$_{x}$S$_{100-x}$ ($x=30,35,40$) amorphous thin films were studied using Raman spectroscopy, atomic force microscopy (AFM), and ellipsometry. Samples were exposed to LED light in an argon environment to avoid oxidation on the surface layer. AFM measurements reveal that our samples are of optical quality before and after exposure, allowing for application of these thin films. Ellipsometry was used measure exact penetration depths using the Beer-Lambert law. For all investigated compositions the Raman spectra taken after 375 and 405 nm exposures do not differ noticeably. The same conclusion holds for samples exposed to 450 and 525 nm light, however these two sets experienced different structural transformations. Irradiation of the virgin samples causes photopolymerization effect and significant widening of the vibrational bands. For stoichiometric comparison ($x=40$) the lower ratio between As$_{4}$S$_3$ cages and As$_{4}$S$_{4}$ units is observed for UV exposed sample in comparison with irradiated by band gap light. For all exposure wavelength there is also no evidence for S chains and S$_8$ fragments after irradiation.Theoretical calculations using density functional theory are currently underway. [Preview Abstract] |
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KA.00058: Synthesizing and Size-Characteristics of Ferrofluids Ponn Maheswaranathan, Justin Talbert Ferrofluids are colloidal suspension of magnetic nanoparticles (10-100 nm) utilized in various applications for their unique magnetic and thermodynamic properties. Ferrofluids contain magnetite (Fe (II, III)$_{3}$O$_{4}$ or iron (II, III) oxide), a surfactant, and, in some cases a carrier. All traditional ferrofluid syntheses include a surfactant and establish that the surfactants play a significant role in their properties. In ferrofluid syntheses, a carrier is not always utilized and its role is not clearly investigated. In the presence of a magnetic field, the ferrofluid reacts to the magnetic field by creating ``spikes''of different shapes which depends on the size of the magnetite particles. For this to occur, the magnetite particles must be around ten nanometers in diameter. Therefore, the size of magnetite particles created during synthesis determines the extent of the ferrofluid's magnetic and thermodynamic properties. In this research, ferrofluids were synthesized using different surfactants and carriers. In addition, how the size of magnetite particles affect the ferrofluid's magnetic and thermodynamic properties were analyzed. Preliminary results show that ferrofluids can be synthesized using various methods but the magnetic properties are not the same in each synthesis. Carriers were found to thin out the ferrofluid and provide a medium that creates less friction so that the ferrofluid can move around easier when a magnetic field is applied. Techniques like scanning (SEM) and transmission (TEM) electron microscopy and powder x-ray diffraction (XRD) were utilized to determine magnetite particle size. [Preview Abstract] |
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KA.00059: Mechanochemical Synthesis of ZnFe2O4 as a Function of ``Ball to Powder Ratio'' (BPR) Jari Cabarcas, Ermides Chavez, Yari Babilonia, Oswald Uwakweh Mechanochemical reactions of ZnO and $\alpha $-Fe$_{2}$O$_{3}$ were carried out in a planetary mill to produce zinc ferrite (ZnFe$_{2}$O$_{4})$ nanocrystallites at room temperature by using a ``ball to powder ratio'' (BPR) of 20:1 and 40:1, under identical processing conditions entailing initial addition of 0.6 mL of acetone as surfactant with hardened stainless steel grinding materials. The average crystal sizes of the particles as determined from X-ray diffraction measurements varied as a function of milling time, with the value of 7.36 nm achieved for the 35 hours milled materials. The diffraction peaks of the milled samples are broadened, which can be the result of the reduced grain size and the atomic level strain introduced during milling. The development of superparamagnetic behavior of the particles is confirmed by the presence of a central peak in the M\"{o}ssbauer spectra for 50h and 10h corresponding to BPR= 20:1 and BPR=40:1 respectively. This result has been explained on the basis that at a high BPR, the collision energy is high and therefore leads to enhanced reduction in crystal size and the chemical reaction to single phase ZnFe$_{2}$O$_{4}$ having the particle size dependent superparamagnetic behavior. [Preview Abstract] |
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KA.00060: Stoichiometry of Fe$_3$O$_4$ Nanoparticles Determined by M\"{o}ssbauer Spectroscopy Hien-Yoong Hah, Michael Cole, Sharon Gray, Charles Johnson, Jacqueline Johnson, Vladimir Kolesnichenko, Pavel Kucheryavy, Galina Goloverda The detailed composition of nanoparticles is dependent on the method of preparation. Previous M\"{o}ssbauer studies of Fe$_3$O$_4$ nanoparticles have shown that the samples were not pure Fe$_3$O$_4$. In most cases they were $\gamma$-Fe$_2$O$_3$, which has the same spinel structure as Fe$_3$O$_4$ but with the Fe$^{2+}$ ions oxidized to Fe$^{3+}$ and vacancies to ensure charge neutrality. In other cases the oxidation was incomplete and the structure contained defects on the octahedral (B) sites. In this work the samples of diameters 5.3 and 10.6 nm were prepared from colloidal magnetite in diethylene glycol under an inert atmosphere. The M\"{o}ssbauer spectra showed that they are superparamagnetic with blocking temperatures, T$_B$, of 50 K and 120 K respectively. The spectra at 6 K, the lowest temperature studied, were close to those of bulk crystalline Fe$_3$O$_4$, in particular showing lines due to Fe$^{2+}$ which were absent in many previous studies. [Preview Abstract] |
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KA.00061: Ytterbium-doped Barium Zirconate Thin Films by Pulsed Laser Deposition for Intermediate Temperature Solid Oxide Fuel Cell Applications Enrico Camata, Alex Skinner, Eric Remington, Renato Camata Ytterbium-doped barium zirconate (BZYb) is predicted to have high protonic conductivity and good potential as a thin-film electrolyte material for intermediate temperature (500-750$^{\circ}$ C) solid oxide fuel cells. We have synthesized BZYb thin films by pulsed laser deposition using ablation targets prepared by mixing barium zirconate (BaZrO$_{3})$ and ytterbium oxide (Yb$_{2}$O$_{3})$ powders. Powders had their masses varied to produce targets with 5, 10, and 15 mol.{\%} of Yb in BaZrO$_{3}$. Targets where pressed at 2800 psi and annealed at 1200$^{\circ}$ C for 12 hours in air. Thin films 1-2 $\mu $m thick were deposited on Si and MgO substrates at 600$^{\circ}$ C using a KrF excimer laser with energy density of 1-2 J/cm$^{2}$ and repetition rate of 30 Hz. Deposition took place at a pressure of 50 mTorr of O$_{2}$ in a vacuum system with base pressure below 5.0x10$^{-7}$ Torr. X-ray diffraction from as-deposited films show patterns of polycrystalline cubic BaZrO$_{3}$ on both, Si and MgO substrates. A substantial amount of amorphous material is present in as-deposited samples. Post-deposition annealing in air at 800\textordmasculine C greatly improves film crystallinity with virtual elimination of the amorphous phase. Energy dispersive X-ray measurements indicate the successful incorporation of Yb in the films in concentrations of 3.1, 5.5, and 8.8 mol.{\%} for targets prepared with 5, 10, and 15 mol.{\%} of Yb, respectively. [Preview Abstract] |
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KA.00062: Effects of Geographical Shape on Power Grid Intentional Islanding Models Aleks Gurfinkel, Yan Xu, Per Arne Rikvold Power grids are interconnected networks of generators and loads that are susceptible to rolling blackouts cascading across the system. To contain the spread of power failures, the {\em intentional islanding} technique deactivates certain electrical connections, partitioning the power grid into temporarily disconnected clusters with the capacity to act as independent power grids with local generating capacity. Optimized choices of intentional islanding clusters for networks of a given topology (pattern of edges) can be found with the application of network theory. We employ a simulated annealing Monte Carlo method to maximize the internal connectivity of the clusters while minimizing the variance of their power surplus. To serve as test cases in the development of adaptable islanding procedures, it is useful to generate large numbers of randomized power grid networks possessing the topological and statistical properties of real power grids. An important factor affecting the topological structure of power grid networks is the geographical shape of the territory in which the network is embedded. In this poster, we compare the success of intentional islanding for models of long, thin geometries (exemplified by the Florida power grid) and geometries with a square aspect ratio. [Preview Abstract] |
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KA.00063: Domain Coarsening on the Hyperbolic Plane Jesse Raffield, Howard Richards, Per Rikvold In statistical physics, the Ising model is used to study systems that vary in application from sociology to condensed matter. With such a rich diversity of use, it has become one of the most studied interacting models. One of its less studied, but also very rich, variations is that of an Ising model that is embedded in the hyperbolic plane. The motivation for this study is to cast light on how systems of negative curvature behave; examples of such are coral growth and the propagation of the internet. The primary characteristic of the hyperbolic Ising model that we seek to study, is the action of domain coarsening using conserved-order-parameter dynamics. That is to say, we are in search of an exponent that determines the behavior of domain coarsening in the hyperbolic plane. Just as a Euclidean lattice requires a Euclidean metric, so too does a hyperbolic lattice require a proper metric of its own. To this end, two such representations are employed; the first is based in graph theory and is known as the ``taxi-cab'' metric while the second involves gyrovectors and analytical geometry. Using Monte-Carlo simulations in conjunction with each geometrical basis, the domain coarsening exponent is estimated to a reasonable degree and is found to be smaller than its Euclidean counterpart. [Preview Abstract] |
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KA.00064: Computational study of the ZGB model with a long-range interaction Chor-Hoi Chan, Per Arne Rikvold The Ziff-Gulari-Barshad (ZGB) model is widely used to study the oxidation of carbon monoxide (CO) on a catalyst surface. The model exhibits a non-equilibrium, discontinuous phase transition between a reactive and a CO poisoned phase. If one allows a nonzero rate of CO desorption (k), the line of phase transitions is terminated at a critical point (k$_{c})$. In this work, instead of restricting the CO and atomic oxygen (O) to react only when they are absorbed in close proximity, we consider a theoretical model that allows CO and O atoms adsorbed far apart on the lattice to react to form carbon dioxide (CO$_{2})$. We employ Monte Carlo simulations to study changes in the physical properties of the system, especially the universality class of the critical point. Through this study we hope to gain further understanding of the ways that a long-range interaction can affect an originally short-range interacting non-equilibrium system. [Preview Abstract] |
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KA.00065: What's in Your Wineglasss Stephen Woolbright, Rich Schelp You probably have done the trick of rubbing the rim of a wineglass, partially filled with water, to produce a crisp tone. We took this old instrument and applied a new question: What would happen to the frequency if we used liquids with different densities? A.P. French constructed a wineglass model which predicts that $(f_0/f)^2 = 1 + kF^4$, where $f_0$ is the frequency of the empty wineglass, $F$ is the wineglass fullness fraction, $f$ is the frequency at that fullness fraction, and $k$ is a constant that is proportional to the density of the liquid [1]. We addressed this question experimentally using five liquids with densities varying from $0.7-1.4\,{\rm g/cm^3}$. To determine how the frequency changed, we filled a wineglass to several different heights for each liquid. At each height, we made a digital recording of the sound produced and used FFT analysis software to determine its frequency. Our results show that the denser a liquid is the lower the frequency of the sound the wineglass produces. The results also confirm that A.P. French's model correctly predicts the relationship between frequency and density.\\[4pt] [1] A.P. French, \textit{In Vino Veritas: A Study of Wineglass Acoustics}, Am. J. Phys. 51, 8 (1983). [Preview Abstract] |
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KA.00066: Angular Momentum Flux in the Scalar Self-Force Problem Samuel Cupp, Peter Diener The scalar self-force problem consists of a scalar point charge orbiting a supermassive black hole. The object is small enough that the perturbation of space-time due to its mass is inconsequential, and the only forces are gravity and the self-force. The self-force is a force on the inspiraling particle that results from the back-scattering of the object's own field off of curved space-time. I derived an accurate calculation of the angular momentum flux for the scalar self-force problem and implemented it into a preexisting (3 spatial +1 time) dimensional code. We then compared our results to very precise frequency domain calculations. The angular momentum flux calculations yield results that converge to the actual value of 0.0124682173 $M^2$. However, the calculations currently converge at about .7 order, and the reason for this extremely slow convergence is currently unknown. [Preview Abstract] |
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KA.00067: Exclusive semileptonic B meson decays at Belle Xiao Long Wang I will report on the results from the Belle experiment on exclusive and inclusive $B$ meson semileptonic decays to charmed mesons as a probe of the CKM matrix element $|V_{cb}|$. The exclusive modes include $B \to D_s^{(*)(*)} \ell \nu$. The discrepancy between the inclusive and sum-of-exclusive branching fractions will be reviewed. [Preview Abstract] |
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KA.00068: The Belle II Experiment at SuperKEKB Xiao Long Wang I will describe the Belle II experiment and the SuperKEKB project under construction at the High Energy Accelerator Research Organization (KEK) in Japan. At this next-generation flavor factory, the Belle II detector will collect about 50 times more data than Belle, i.e., about 50~ab${}^{-1}$. This data set will permit us to search for evidence of new interactions and particles and to make more precise measurements of Standard Model properties such as $CP$ asymmetries in the decays of heavy mesons and leptons, including missing-energy decay modes such as $B \to \tau \nu$ that are inaccessible to the LHC experiments. [Preview Abstract] |
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KA.00069: True Neutrality as a New Type of Flavour Rasulkhozha Sharafiddinov A classification of leptonic currents with respect to C-operation requires the separation of elementary particles into the two classes of vector C-even and axial-vector C-odd character. Their nature has been created so that to each type of lepton corresponds a kind of neutrino. Such pairs are united in families of a different C-parity. Unlike the neutrino of a vector type, any C-noninvariant Dirac neutrino must have his Majorana neutrino. They constitute the purely neutrino families. We discuss the nature of a corresponding mechanism responsible for the availability in all types of axial-vector particles of a kind of flavour which distinguishes each of them from others by a true charge characterized by a quantum number conserved at the interactions between the C-odd fermion and the field of emission of the corresponding types of gauge bosons. This regularity expresses the unidenticality of truly neutral neutrino and antineutrino. Thereby, such a true flavour together with the earlier known lepton flavour predicts the existence of leptonic strings and their birth in single and double beta decays as a unity of symmetry laws. [Preview Abstract] |
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