Bulletin of the American Physical Society
78th Annual Meeting of the Southeastern Section of the APS
Volume 56, Number 9
Wednesday–Saturday, October 19–22, 2011; Roanoke, Virginia
Session LA: Poster Session (6:00PM-8:00PM) |
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Room: Roanoke Foyer |
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LA.00001: Network Theoretical Approach to Partitioning of Real Power Grids Brett Israels, Per Arne Rikvold, Ibrahim Abou Hamad, Svetlana Poroseva Power grids are innately susceptible to electrical faults. Here we present various network-theoretical approaches to achieve intentional intelligent islanding of a power grid in order to limit cascading power failures in case such a fault occurs. The methods we use can partition networks into communities with local generating capacity. Here we discuss results of using spectral matrix methods along with Monte Carlo methods to analyze and partition the Floridian and Italian high-voltage power grids, as well as the power distribution system for a conceptual all-electric naval vessel. We contrast the effects of approximating the generating capacity of generators according to degree of the generators versus using actual generating capacities. [Preview Abstract] |
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LA.00002: Calculation of Stationary, Free Molecular Flux Distributions in General 3D Environments Jesse Labello This article presents an application of the angular coefficient method for diffuse reflection to calculate stationary molecular flux distributions in general three dimensional environments. The method of angular coefficients is reviewed and the integration of the method into Blender, a free, open-source, 3D modeling software package, is described. Some example calculations are compared to analytical and Direct Simulation Monte Carlo (DSMC) results with excellent agreement. [Preview Abstract] |
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LA.00003: A Muon Tomography Station with GEM Detectors for Nuclear Threat Detection Michael Staib, Kondo Gnanvo, Leonard Grasso, Marcus Hohlmann, Judson Locke, Filippo Costa, Sorin Martoiu, Hans Muller Muon tomography for homeland security aims at detecting well-shielded nuclear contraband in cargo and imaging it in 3D. The technique exploits multiple scattering of atmospheric cosmic ray muons, which is stronger in dense, high-Z nuclear materials, e.g. enriched uranium, than in low-Z and medium-Z shielding materials. We have constructed and operated a compact Muon Tomography Station (MTS) that tracks muons with six to ten 30 cm $\times$ 30 cm Triple Gas Electron Multiplier (GEM) detectors placed on the sides of a 27-liter cubic imaging volume. The 2D strip readouts of the GEMs achieve a spatial resolution of $\sim $130 $\mu $m in both dimensions and the station is operated at a muon trigger rate of $\sim $20 Hz. The 1,536 strips per GEM detector are read out with the first medium-size implementation of the Scalable Readout System (SRS) developed specifically for Micro-Pattern Gas Detectors by the RD51 collaboration at CERN. We discuss the performance of this MTS prototype and present experimental results on tomographic imaging of high-Z objects with and without shielding. [Preview Abstract] |
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LA.00004: A New Viewpoint (The expanding universe, Dark energy and Dark matter) Daniel Cwele Just as the relativity paradox once threatened the validity of physics in Albert Einstein's days, the cosmos paradox, the galaxy rotation paradox and the experimental invalidity of the theory of dark matter and dark energy threaten the stability and validity of physics today. These theories and ideas and many others, including the Big Bang theory, all depend almost entirely on the notion of the expanding universe, Edwin Hubble's observations and reports and the observational inconsistencies of modern day theoretical Physics and Astrophysics on related subjects. However, much of the evidence collected in experimental Physics and Astronomy aimed at proving many of these ideas and theories is ambiguous, and can be used to prove other theories, given a different interpretation of its implications. The argument offered here is aimed at providing one such interpretation, attacking the present day theories of dark energy, dark matter and the Big Bang, and proposing a new Cosmological theory based on a modification of Isaac Newton's laws and an expansion on Albert Einstein's theories, without assuming any invalidity or questionability on present day cosmological data and astronomical observations. [Preview Abstract] |
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LA.00005: Dissociative Electron-Ion Recombination of the Protonated Interstellar Species Glycolaldehyde, Acetic Acid, and Methyl Formate Patrick Lawson, Nigel Adams Recently, the prebiotic molecule and primitive sugar glycolaldehyde and its structural isomers acetic acid and the abundant methyl formate have been detected in the interstellar medium(ISM). Understanding the processes involving these molecules is vital to understand the ISM, where stars are formed. The rate constants, $\alpha _{e}$, for dissociative electron-ion recombination of protonated gycolaldehyde, (HOCH$_{2}$CHO)H$^{+}$, and protonated methyl formate, (HCOOCH$_{3})$H$^{+}$, have been determined at 300K in a variable temperature flowing afterglow using a Langmuir probe to determine the electron density. The $\alpha _{e}$ at 300K are 3.2 x 10$^{-7}$ cm$^{3}$ s$^{-1}$ for protonated methyl formate and 7.5 x 10$^{-7}$ cm$^{3}$ s$^{-1}$ for protonated glycolaldehyde. The $\alpha _{e}$ of protonated acetic acid could not be directly measured due to difficulty in producing the ion, but it appears to have a recombination rate constant, $\alpha _{e}$, on the $\sim $10$^{-7}$ cm$^{3}$ s$^{-1}$ scale. Additional temperature dependence information was obtained. The astrochemical implications of the $\alpha _{e}$ measurements and protonation routes are also discussed. [Preview Abstract] |
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LA.00006: Towards Modeling Self-Consistent Core Collapse Supernovae Merek Chertkow, W. Raphael Hix, Stephen Bruenn, Eric Lentz, John Blondin, O.E. Bronson Messer, Ching-Tsai Lee, Anthony Mezzacappa, Pedro Marronetti, Konstantin Yakunin Core-collapse supernovae (CCSN) are multi-dimensional events and the codes we develop to model them must follow suit. Our group at the Oak Ridge National Lab has successfully generated self-consistent explosions in 2D of 12-25 solar mass stars using our code CHIMERA. This code is made up of three essentially independent parts designed to evolve the stellar gas hydrodynamics (VH1/MVH3), the ``ray-by-ray-plus'' multi-group neutrino transport (MGFLD-TRANS), and the nuclear kinetics (XNET). Incorporation of passive tracer particles, for post-processing nucleosynthesis, allows us to explore effects that stem from anisotropies, instabilities, and mixing. An extension of our alpha-nuclear network to 150 species, has enabled us to identify nuclear processes such as the nu-p process and better follow the neutronization during the explosion. These advances also allow us to investigate lower mass limit O-Ne-Mg CCSN and possible sites for the production of weak r-process elements. In this poster, we will present results of these efforts. [Preview Abstract] |
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LA.00007: Trends in Ion-Electron Dissociative Recombination of Benzene Analogs David Osborne, Nigel Adams The Kepler Spacecraft successfully identified five new planets within the Habitable zones of stars in our region of the Milky Way. In our own planetary system the Cassini Spacecraft obtained mass spectra of the atmosphere of Saturn's moon Titan. To convert the mass spectra to molecular composition a great deal of kinetic rate data is required. These data are used to explain the processes by which small molecules form larger compounds within the Titan atmosphere. The models have indicated that larger ringed hydrocarbon species are present, like benzene. This makes the Titan atmosphere similar to the atmosphere of Early Earth and of interest to NASA. To help in the modeling, we have studied the kinetics of ion-electron recombination of various single ringed hydrocarbon analogs, like benzene. These data were obtained using a Variable Temperature Flowing Afterglow fitted with a Langmuir Probe to determine kinetic rates for ion-electron recombination. This technique was used for benzene analogs with varying degrees of nitrogen and methyl substitutions. From the data, it has been possible to determine trends which will reduce the amount of data needed in the modeling of the Titan atmosphere. [Preview Abstract] |
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LA.00008: On-line Java Tools for Analyzing AGN Outflows Carter Chamberlain We present six interactive programs created to aid in the analysis of outflows from Active Galactic Nuclei. 1. An interactive plot showing the ionic fraction versus the ionization parameter, for each ion of several elements and for different SEDs. 2. An interactive plot showing the excitation ratio versus electron number density for several elements. 3. A tool for finding the ionization parameter solution from the measured column densities. The user provides the measured ionic column densities and chooses an SED. Then the program displays the locus of possible models in a plot of Hydrogen column density versus ionization parameter. The program also calculates and overlays a chi-squared map for one- or two-ionization parameter solutions. 4. A spectral identification tool displays a spectrum, and allows the user to interactively identify the absorption features. This will give the redshift of each outflow and intervening system along the line of sight to the quasar. 5. Two calculators a) Calculate the velocity of an outflow given the systemic redshift and the absorber redshift. b) Convert GALEX flux to units of $10^{-15}$ergs/s/$\mathrm{cm}^2$/{\AA}. [Preview Abstract] |
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LA.00009: A statistical analysis of the environments of extragalactic water masers Thomas Redpath, Anca Constantin, Nathan DiDomenico, James Corcoran Water megamasers provide crucial tools for accurate determinations of masses of black holes lurking in galaxy centers, and of extragalactic distances without the need for indirect cosmological assumptions. Current searches have detected masers in only 3 -- 4{\%} of the galaxies surveyed and require refinement of their survey criteria. Motivated by current models linking galaxy environment and black hole accretion and the possibility that maser activity correlates with black hole accretion, we undertook a study of the properties of the small-scale environments of galaxies hosting masers. Using samples of maser detections and non-detections provided by the Megamaser Cosmology Project together with SDSS DR7 photometric and spectroscopic observations we performed a comparative analysis of near-neighbor statistics that include distances to first and third neighbors, neighbor counts and color distributions for both flux and absolute magnitude limited volumes. We present results that provide potential constraints for maser surveys, which may increase their detection rate. [Preview Abstract] |
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LA.00010: Radio Detection of Neutron Star Binary Mergers Brandon Bear, Brett Cardena, Dana Dispoto, Joanna Papadopoulos, Michael Kavic, John Simonetti Neutron star binary systems lose energy through gravitational radiation, and eventually merge. The gravitational radiation from the merger can be detected by the Laser Interferometer Gravitational-Wave Observatory (LIGO). It is expected that a transient radio pulse will also be produced during the merger event. Detection of such radio transients would allow for LIGO to search for signals within constrained time periods. We calculate the LWA-1 detection rate of transient events from neutron star binary mergers. We calculate the detection rate of transient events from neutron star binary mergers for the Long Wavelength Array and the Eight-meter-wavelength Transient Array. [Preview Abstract] |
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LA.00011: Afterglow photometry and Modeling GRB 091018 Apurva Oza We focus on continuing the modeling of GRB (Gamma-ray Burst) 091018. Our data is mostly collected across 4 bands (BVRI) from PROMPT (Panchromatic Robotic Optical Monitoring and Polarimetry Telescopes) approximately 4.1 hours after the trigger. We have added NIR, UVOT, X-ray, and more optical points to our datasets. After rejecting the orginal assertion of dust evolution by linking extinction parameters with Galapagos (a software that employs genetic algorithms to output the best fit model with our circum-burst GRB parameters we have settled on a model with the circumburst density index k, at -1.75 (which is close to the wind-blown medium of k=-2). In addition to k, the results of our baseline fit indicate that the cooling break is above the data, and may be crossing the synchrotron peak during the early UVOT data. This cross-over will yield interesting results about the circumburst medium of a GRB at early times. Photometring GRBs live was also conducted along with instrumentation techniques. [Preview Abstract] |
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LA.00012: A Search for Astrophysical Meter Wavelength Radio Transients Sean Cutchin, John Simonetti, Michael Kavic Astrophysical phenomena such as exploding primordial black holes (PBHs), gamma-ray bursts (GRBs), compact object mergers, and supernovae are expected to produce a single pulse of electromagnetic radiation detectable in the low-frequency end of the radio spectrum. Detection of any of these pulses would be significant for the study of the objects themselves, their host environments, and the interstellar/intergalactic medium. Furthermore, a positive detection of an exploding PBH could be a signature of an extra spatial dimension, which would drastically alter our perception of spacetime. However, even upper limits on the existence of PBHs, from searches, would be important to discussions of cosmology. We describe a method to carry out an agnostic single dispersed pulse search, and apply it to data collected with ETA. Applying the single pulse search procedure to 30 hours worth ETA data yielded no compelling detections with $S/N \ge 6$. However, with $\approx 8$ hours of interference free data, we find an observational upper limit to the rate of exploding PBHs $r \approx 8 \times 10^{-8} \,\rm{pc}^{-3}\,\rm{y}^{-1}$ for a PBH with a fireball Lorentz factor $\gamma_f = 10^{4.3}$. [Preview Abstract] |
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LA.00013: Searching for Low-Frequency Radio Transients from Supernovae Jr-Wei Tsai, Sean Cutchin, Manthan Kothari, Christian Schmitt, Michael Kavic, John Simonetti Supernovae events may be accompanied by prompt emission of a low-frequency electromagnetic transient. These transient events are created by the interaction of a shock wave of charged particles created by SN core-collapse with a stars ambient magnetic field. Such events can be detected in low-frequency radio array. Here we discuss an ongoing search for such events using two radio arrays: the Long Wavelength Array (LWA) and Eight-meter-wavelength Transient Array (ETA). [Preview Abstract] |
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LA.00014: The Arcminute Morphology of the WIM Toward the Local Perseus Arm of the Galaxy Phillip Nelson, John Simonetti, Brian Dennison We used the Virginia Tech Spectral-Line Imaging Camera (SLIC) to image the warm ionized interstellar medium (WIM) toward the Local Perseus Arm. We obtained a series of images, each of which is 10$^\circ$-wide, and has arcminute-resolution. The images show three basic types of structures --- compact clouds with diameters greater than several degrees, those that are 1$^\circ$ or less in diameter, and extended filaments which span several degrees in length but have thicknesses of only a few tens of arcminutes. The data show that [S {\sc ii}]/H$\alpha$ ratios are, on average, nearly six times higher in the filaments than in the clouds, which indicates that emission from collisionally excited, singly-ionized S$^+$ is the dominant emission source within the filaments. In clouds, the lower [S {\sc ii}]/H$\alpha$ values are evidence that the H$\alpha$ recombination line of photoionized hydrogen dominates. [Preview Abstract] |
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LA.00015: Mid-infrared Molecular Emission Studies from Energetic Materials using Laser-Induced Breakdown Spectroscopy Ei Brown, Uwe Hommerich, Clayton Yang, Sudhir Trivedi, Alan Samuels, Peter Snyder Laser-induced breakdown spectroscopy (LIBS) is a powerful diagnostic tool for detection of trace elements by monitoring the atomic and ionic emission from laser-induced plasmas. The laser-induced plasma was produced by focusing a 30 mJ pulsed Nd:YAG laser (1064 nm) to dissociate, atomize, and ionize target molecules. In this work, LIBS emissions in the mid-infrared (MIR) region were studied for potential applications in chemical, biological, and explosives (CBE) sensing. We report on the observation of MIR emissions from energetic materials (e.g. ammonium compounds) due to laser-induced breakdown processes. All samples showed LIBS-triggered oxygenated breakdown products as well as partially dissociated and recombination molecular species. More detailed results of the performed MIR LIBS studies on the energetic materials will be discussed at the conference. [Preview Abstract] |
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LA.00016: Dianion formation from anion-alkali metal charge exchange reactions: TCNQ$^{-}$ + Na $\to $ TCNQ$^{--}$ + Na$^{+}$ Byron Smith, Robert Compton, Serge Ovchinnikov, Anne Holm, Steen Nielsen The interaction of an electron with an anion is characterized by a long-range coulomb repulsion and a short range polarizability attraction giving rise to a coulomb barrier. The permanent addition of an extra electron to a negatively charged anion requires tunneling through the barrier or attachment of the electron over the top of this coulomb barrier followed by disposal of the excess energy. Charge-exchange collisions of an anion with an alkali atom utilize the latter channel to produce permanent dianions with cross sections of $\sim $1 {\AA}$^{2}$. We have previously examined the reaction TCNQ-F$_{4}^{-}$ + Xe $\to $ TCNQ-F$_{4}^{--}$ + Xe$^{+}$ and reported a delayed threshold and quantum phase interference effects in the charge exchange cross section.\footnote{S. Yu. Ovchinnikov, et al. Phys. Rev. A, 73, 64704(2006)} Employing sodium as the collision partner, the cross section is seen to increase with decreasing energy with a threshold below 180 eV (com). A new apparatus has been constructed to allow measurements down to energies below the expected threshold ($\sim $41 eV, laboratory energy based upon a 1 eV second electron affinity). This method has been used to study the reaction TCNQ$^{-}$ + NA $\to $ TCNQ$^{--}$ + Na$^{+}$ and will provide one of the first measurements of second electron affinities for molecular anions. [Preview Abstract] |
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LA.00017: Upconversion Studies of Er3+ Doped into Low Phonon-Energy Hosts KPb2Cl5 and KPB2Cl5 via 0.97 $\mu$m and 1.5 $\mu$m Laser Excitation A. Bluiett, E. Brown, U. Hommerich, S.B. Trivedi A comparative study of the wavelength dependence of the Er3+ upconversion in low phonon-energy hosts KPb2Cl5 and KPb2 Br5 will be presented. Initial measurements indicate that visible and infrared upconversion was generated under 0.97 $\mu$m and 1.5 $\mu$m laser excitation. Using time resolved emission, spectral emission, and spectral absorption data the dominant upconversion mechanisms involving excited state absorption and/or energy transfer were investigated. In addition, special emphasis was geared toward a comparative study of the detrimental effects of upconversion under resonant pumping conditions (1.5 $\mu$m) for possible applications in the eye-safe wavelengths (1.5 -- 1.6 $\mu$m) region. [Preview Abstract] |
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LA.00018: A study of the chiro-optical properties of Carvone Jason Lambert The intrinsic optical rotatory dispersion (IORD) and circular dichroism (CD) of the conformationally flexible carvone molecule has been investigated in 17 solvents and compared with results from calculations for the ``free'' (gas phase) molecule. The G3 method was used to determine the relative energies of the six conformers. The ORD of (\textit{R})-(-)-carvone at $589$ nm was calculated using coupled cluster and density-functional methods, including temperature-dependent vibrational corrections. Vibrational corrections are significant and are primarily associated with normal modes involving the stereogenic carbon atom and the carbonyl group, whose $n\rightarrow\pi^*$ excitation plays a significant role in the chiroptical response of carvone. However, without the vibrational correction the calculated ORD is of opposite sign to that of the experiment for the CCSD and B3LYP methods. Calculations performed in solution using the PCM model were also opposite in sign to of the experiment when using the B3LYP density functional. [Preview Abstract] |
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LA.00019: Collective excitations in a spinor condensate Jianing Han Bose Einstein Condensates (BECs) confined in a trap allow us to study the excitation between eigenfunctions of a given trap potential, which can be directly calculated from quantum mechanics. Here we study the spinor collective excitations, in other words, the collective excitations of different spin components. Specifically, the spinor collective modes in a 3D harmonic trap will be presented. Moreover, different types of collective excitations in this trap, collective mode mixing as well as their applications will be discussed. [Preview Abstract] |
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LA.00020: Physical properties of unacetylated chromatin as examined by magnetic tweezers Kerry McGill, David Dunlap, John Lucchesi As the source of genetic material, DNA is involved in a variety of biological processes like transcription, cell replication, and more. In these processes, DNA is manipulated into different structures and is subjected to different levels of physical force on a molecular scale. When tension is applied to one hierarchical structure called chromatin, it appears to behave like a Hookian spring. The base component of chromatin is a nucleosome, which is constructed when DNA coils around octamers of histone proteins. The histones can become acetylated---a chemical process in which an acetyl functional group attaches to amino acids of the histones, often lysines. Acetylation may loosen chromatin's coils and therefore lower the amount of tension required to stretch the chromatin. Comparing the levels of tension required to stretch acetylated chromatin could reveal, directly, physical differences in the chromatin fiber that bear ion the function of the DNA molecule. Work presented will be the investigation of unacetylated chromatin. [Preview Abstract] |
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LA.00021: Superconducting Properties of Nb/Mo Bilayers James Veldhorst, Phillip Broussard We studied various electrical properties of Nb/Mo bilayer films at low temperatures as a function of layer proportions with series varying both Nb and Mo (eg. holding Nb constant at 30nm with Mo ranging from 10 to 40 nm). After growing multiple series of Nb/Mo bilayers on silicon substrates at different configurations through magnetron sputtering, the samples were cooled to $\approx$6K, where we explored their critical fields ($H_{c2}$) at low field strengths. Critical fields were measured using both resistive and inductive measurements on the samples under the influence of a magnetic field ranging from 0 to 120 Gauss. We also look at how the transition temperature of the films ($T_{c}$) vary with Nb and Mo layer thicknesses. We will compare our findings to the proximity effect theory for the $T_{c}$ of thin film bilayers. We will also contrast the linearity of our resistive $H_{c2}$ vs T data fits with the non-linearity of our inductive $H_{c2}$ vs T plots. [Preview Abstract] |
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LA.00022: Electrical Characterization of Zn and ZnO Nanowires Grown on PEDOT:PSS Conductive Polymer Thin Films by Physical Vapor Deposition Matthew Chamberlin, Costel Constantin Physical vapor deposition (PVD) techniques offer tremendous possibilities for easy fabrication of nanostructure arrays for use in thin film electronics. In this study we examine inorganic/organic heterojunctions produced by growing conductive Zn and semiconductive ZnO nanowire arrays on organic conductive PEDOT:PSS polymer thin films using simple and cost-effective PVD methods. Understanding the electrical properties of these hybrid films are of particular interest for applications in organic electronics. However, traditional systems for measuring conductivity and resistivity of thin films by the Van Der Pauw method prove problematic when dealing with soft polymeric surfaces. We present here electrical studies of ZnO- and Zn-nanowire/PEDOT:PSS heterojunctions using a modified 2-point probe method constructed from inexpensive and easily available materials. [Preview Abstract] |
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LA.00023: Analysis of Carbon Nanotubes and Graphene Nanoribbons with Folded Racket Shapes Andy Borum, Raymond Plaut, David Dillard When carbon nanotubes and graphene nanoribbons become long, they may self-fold and form tennis racket-like shapes. This phenomenon is analyzed in two ways by treating a nanotube or nanoribbon as an elastica. First, an approach from adhesion science is used, in which the two sides of the racket handle are assumed to be straight and bonded together with constant or no separation. New analytical results are obtained involving the shape, bending energy, and adhesion energy of the self-folded structures. These relations show that the dimensions of the racket loop are proportional to the square root of the flexural rigidity. The second analysis uses the Lennard-Jones potential to model the van der Waals forces between the two sides of the racket. A nanoribbon is considered, and the interatomic forces are integrated along the length and across the width of the nanoribbon. The resulting integro-differential equations are solved using the finite difference method. The racket handle is found to be in compression and the separation between the two sides of the racket handle decreases in the direction of the racket loop. The results for the Lennard-Jones model approximately satisfy the relationship between the dimensions and the flexural rigidity found using the adhesion model. [Preview Abstract] |
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LA.00024: Electronic transport in semiconductors Alexander Larin The ultimate goal of this work is the Monte-Carlo simulation of electronic transport in semiconductors. As a special case, the effect of the adsorbed surface change on conductivity in the ambient air was investigated. The classical equation of electronic transport for semiconductors must be solved numerically since the analytical solution can be derived only for limited number of relatively simple cases. There are several numerical methods to describe the electronic transport in semiconductors. The One particle Monte Carlo simulation is widely used technique to obtain the exact solution for Boltzmann Transport Equation (BTE). During the simulation several assumptions were made: electron is a particle and its motion can be described by classical mechanics equations, the only interactions the electrons have are those with ions, the collisions/scattering of electrons with ions are elastic, and the outside electric field is uniform inside of the semiconductor device. The quantity of interest in the simulation is current density. The current density was calculated as an integrated result from contributions of individual paths of electrons as they travel from one ohmic contact to another. The simulation can also be used to predict the electronic transport under the influence of nonuniform electric and magnetic fields. The special case of oxygen adsorption was investigated in this work. It was found that an increase in the oxygen concentration in the ambient air can decrease the conductivity of some semiconductor materials. [Preview Abstract] |
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LA.00025: Modeling of the pressurized xenon gamma ray scintillation detector Romney Meek, Alexander Barzilov, Ivan Novikov We are developing a high pressure xenon detector for photon measurements. Xenon produces electroluminescence (EL) scintillation emission that we use as the primary signal in our strategy to acquire information. The detector consists of a high pressure chamber, a thin radiation input window with the supporting grid of collimator ribs and electrode grids to create the electric field, and a photo sensor -- the large area silicon avalanche photodiode. The electrode grids are made of thin wire. The modeling of the electric field is a crucial step in developing a working prototype. It has been previously shown that the uniform electric field divided by the number density of xenon gas needs to be above approximately 3 Td to give enough energy to ionize the xenon atoms, but less than 16 Td to prevent electron avalanches from occurring. The electric field was modeled using Comsol Multiphysics. This presentation discusses the results of electric field modeling for the detector (absorption, drift, and EL regions). [Preview Abstract] |
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LA.00026: Neutron Photoproduction from $^{139}$La Using 12-15 MeV Linearly Polarized $\gamma$-Rays R.K. Thrasher, J. Hauver, W.R. Henderson, C.S. Whisnant, M.W. Ahmed, H.J. Karwowski, J.M. Mueller, L.S. Myers, J. Silano, J.R. Tompkins, H.R. Weller, W.R. Zimmerman, B.J. Davis, D.M. Markoff, M. Spraker, R.M. Prior, R.H. France Data have been collected at the High Intensity $\gamma$-ray Source (HI$\gamma$S) to investigate neutron emission from a $^{139}$La target with linearly polarized gamma rays at $E_\gamma$= 12, 13, 14, and 15 MeV. Liquid scintillator detectors were placed at scattering angles of 55$^\circ$, 90$^\circ$ and 125$^\circ$ above, below and to the left and right of the target. Six additional detectors were placed at angles of 72$^\circ$, 107$^\circ$, and 142$^\circ$ above and to the right of the target. The ratio of neutron yields parallel to neutron yields perpendicular to the plane of polarization observed as a function of $E_n$, $E_\gamma$, and $\theta$ characterizes the response of the nucleus and may prove to be a useful observable in nuclear forensics. The results of the experiment will be discussed. [Preview Abstract] |
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LA.00027: Neutron Photoproduction from $^{Nat}$Hg Using 11-15 MeV Linearly Polarized $\gamma$-Rays J. Hauver, W.R. Henderson, R.K. Thrasher, C.S. Whisnant, M.W. Ahmed, H.J. Karwowski, J.M. Mueller, L.S. Myers, J. Silano, J.R. Tompkins, H.R. Weller, W.R. Zimmerman, B.J. Davis, D.M. Markoff, M. Spraker, R.M. Prior, R.H. France The linearly polarized photon beam at the High Intensity $\gamma$-ray Source (HI$\gamma$S) was used to study neutron emission from a $^{nat}$Hg target at energies of 11, 12, 13, 14, and 15 MeV. Twelve liquid scintillator detectors were placed at polar angles of 55$^\circ$, 90$^\circ$ and 125$^\circ$ and at azimuthal angles of $\phi=0^\circ, 90^\circ, 180^\circ, 270^\circ$. Six more detectors were placed at polar angles of 72$^\circ$, 107$^\circ$, and 142$^\circ$ at $\phi=0^\circ$ and $90^\circ$. The ratio of neutron yields parallel to neutron yields perpendicular to the plane of polarization were determined as a function of $E_\gamma$, $E_n$, and $\theta$. Results will be discussed. [Preview Abstract] |
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LA.00028: $^{nat}$Dy$(\gamma,n)$ Asymmetry Measurements with Linearly Polarized $\gamma$-rays between 11 and 15 MeV W.R. Henderson, R.K. Thrasher, J. Hauver, C.S. Whisnant, M.W. Ahmed, H.J. Karwowski, J.M. Mueller, L.S. Myers, J. Silano, J.R. Tompkins, H.R. Weller, W.R. Zimmerman, B.J. Davis, D.M. Markoff, M. Spraker, R.M. Prior, R.H. France The $^{nat}$Dy$(\gamma,n)$ reaction was studied at TUNL's High Intensity $\gamma$-ray Source (HI$\gamma$S) using a linearly polarized photon beam at energies 11, 12, 13, 14, and 15 MeV. Measurements were made using liquid scintillator detectors at angles 55$^{\circ}$, 72$^{\circ}$, 90$^{\circ}$, 107$^{\circ}$, 125$^{\circ}$, 142$^{\circ}$. The ratio of neutrons detected parallel to the plane of polarization compared to perpendicular to the plane of polarization was measured as a function of $E_\gamma$, $E_n$, and $\theta$. This ratio may be useful for distinguishing different isotopes from one another, and $^{nat}$Dy is one among many isotopes measured to date. The experimental set-up is discussed, along with the data analysis procedure used to determine the ratio. [Preview Abstract] |
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LA.00029: Discovery of Isotopes Cathleen Fry, Michael Thoennessen Although a few thousand isotopes have been discovered, the limit existence is only known for the lightest elements. Unfortunately, there has not been a comprehensive compilation of all the discoveries. A project has been undertaken to find all of the first discovery papers. Claims of discoveries were investigated and verified, and first publications are listed at http://www.nscl.msu.edu/$\sim$thoennes/2009/discovery.htm. In this project, I investigated isotopes with 66 $\le$ Z $\le$ 70 and 81 $\le$ Z $\le$ 98. [Preview Abstract] |
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LA.00030: Gravity's Weak Force Link and other thoughts Rich Aquilina Gravity is by far the weakest of the known four forces. What if that is because it is the oldest of the forces and the most decayed of them? What if that is what caused the Big Bang? The decay of gravity could no longer hold the singularity (or other forces) in check. We know there is decay, it is known as the ``Weak'' force. The idea of decaying gravity would only serve to unite the ``Weak'' force and ``Gravity.'' What if this is the elusive connection between ``Gravity'' and the ``Other Forces''? What if there have been other forces that are no longer with us because of decay or their own evolutionary process? What if these unknown decayed forces gave rise to newer and ``stronger'' forces or maybe even ``weaker'' ones? What if ``particles'' were actually a threshold of converged points of strings (like on a multi-dimensional graph), and the reason we can't seem to find one for gravity is because the convergence threshold to manifest as a particle hasn't been met, yet the strings and influence are still there. [Preview Abstract] |
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LA.00031: Comparison of Top-Antitop Cross Section Measurement Analyses by SHyFT and Simple Counting Method Erin Chambers, Paul Sheldon Analysis of top events at the CMS (Compact Muon Solenoid) experiment is tested by subjecting a single dataset to both the simple counting method and the newer Simultaneous Heavy Flavor and Top (SHyFT) cross section measurement. Respective statistical and systematic errors associated with the data are then compared. The results of the SHyFT analysis have much smaller overall uncertainties. [Preview Abstract] |
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LA.00032: Studies of Diamond Pixel Detectors for CMS at LHC Thomas Robacker Single-crystalline diamond detectors are radiation hard and conduct heat very well which makes them an ideal choice for particle tracking devices close to the LHC beam. As a first application they will be used in a luminosity telescope (PLT) that is scheduled to be inserted into the CMS detector in 2012. This summer, several diamond detectors have been bump-bonded to the readout-chip of the CMS silicon detector and their detection characteristics have been tested in the 150GeV pion beam of CERN's SPS, with and without a 3Tesla magnetic field. The poster will introduce the luminosity telescope and present results from the beam test. [Preview Abstract] |
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LA.00033: Modeling of CVD Diamond Detectors Travis Tune Diamond's properties make it a prime candidate for future use in particle detectors such as at the Compact Muon Solenoid at the LHC. Diamond is radiation hard, has a low thermal conductivity, and has a large bandgap. When a fast moving particle passes through the diamond, ionization occurs, leaving a trail of charge carriers in the diamond. By applying an external electric field, these secondary particles are induced to move towards the electrodes. The movement of these charge carriers induces a current, which can be measured. This is the detection mechanism for diamond detectors. A simulation of this detection mechanism was created using GEANT, a platform developed by CERN for simulating the passage of particles through materials. The program uses Monte-Carlo methods to simulate the ionization process through the material. It is capable of tracking each secondary produced. By using this information and the Shockley-Ramo theorem, we are able to simulate the detection mechanism. [Preview Abstract] |
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LA.00034: Study of the Sensitivity of Plastic Scintillators to Fast Neutrons David Abbott The Mu2e experiment at Fermilab plans to use a two-out-of-three coincident requirement in a plastic scintillator based detector to veto cosmic ray events. This veto system must operate efficiently in a high-radiation environment. In this investigation, three plastic scintillator bars containing wavelength-shifting fibers represent the veto system. These bars were placed together, in series, in front of a deuterium-deuterium neutron generator, which produced fast neutrons of approximately 2.8MeV, in order to study the sensitivity of the plastic scintillators to fast neutrons. Multi-anode photomultiplier tubes read out the light from the fibers. The collected data was analyzed to determine the rate of interaction, approximate amount of energy deposited, and numerous other aspects of the neutrons' interactions. The rate of coincidental and correlated hits in multiple scintillator bars was the primary reason for the investigation, in order to understand the sensitivity of the plastic scintillators to fast neutrons. [Preview Abstract] |
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LA.00035: A modified thermodynamic model to estimating the secondary particle source radius, and coalescence radius, in heavy ion collisions Mahmoud PourArsalan, Lawrence Townsend In an abrasion-ablation model of high energy heavy ion collisions as the extremely hot and dense participating region expands, and cools off, light high energy particles are emitted in the sphere regions where the relative momentum of the nucleons is less than the coalescence radius in momentum space. The probability of the light particle emission and the source radius of the region emitting these light particles may be related with a thermodynamic coalescence models. At the high beam energies, the Coulomb repulsion does not effect our thermodynamic coalescence model estimates, how ever at energies below 25 MeV/nucleon, the Coulomb repulsion must be considered. The objective of our study is to estimate the emitting source radius and the coalescence radius at beam energies less than 25 MeV/Nucleon by using a modified thermodynamic coalescence model which includes Coulomb repulsion. The coalescence radius is inversely proportional to the emitting source radius. Emitting source radii and coalescence radii for light energetic particles from many sets systems are estimated for both symmetric and asymmetric systems. [Preview Abstract] |
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LA.00036: Detector Performance in the SLHC era at CMS Brian Francis The future upgrade in instantaneous luminosity at the Large Hadron Collider, the Super LHC, introduces challenging demands on existing and future instrumentation at the Compact Muon Solenoid experiment. The increased particle and radiative flux, especially in the forward regions, requires extensive study to understand aging effects of the detector and any future materials to be considered. Additionally with increased luminosity, the incidence of multiple events in a single beam crossing poses difficulties in detector performance and energy resolution in the calorimeter sub-system. This poster presents the University of Virginia's efforts in understanding these effects in the SLHC era, with a focus on the electromagnetic calorimeter subsystem. [Preview Abstract] |
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LA.00037: Studies of the Performance of Radiatino Hard GaAs Photodetectors Joseph Goodell Gallium Arsenide (GaAs) photodetectors are a type of semiconducting photodetector that should be able to withstand much higher levels of radiation than commonly used silicon photomultipliers (SIPMs). At the University of Virginia we are characterizing GaAs devices as compared to SIPMs by studying the I/V curve in breakdown region, the breakdown voltage, dark noise, and response to photons. Measurements of single photon avalanche diodes (SPADs) and PMC (multiple SPAD chips) are being made focusing on the breakdown region for hardness tests. The SPADs and PMCs will be exposed to high levels of radiation in test beam environments so that post-irradiation performance can be characterized as well. Ultimately GaAs photodetectors could prove to be effective radiation-hard detectors with applications in high radiation environments like those found at the upgraded high-luminosity Large Hadron Collider (LHC). [Preview Abstract] |
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LA.00038: Lifetime Performance Studies on Vacuum Photo-Triodes in the ECAL at CMS John Wood The electromagnetic calorimeter (ECAL) is a crucial sub-detector of the Compact Muon Solenoid (CMS) at the Large Hadron Collider (LHC). It uses scintillation light fr om approximately 83,000 Lead Tungstate (PbWO$_4$) crystals to make precision measurements of high energy photons and electrons. In the endcaps of the ECAL this scinti llation light is collected at the rear of the crystal and converted to an analog electric current with radiation hard, single stage photmultipliers known as Vacuum Pho to-Triodes (VPTs). The response of the VPTs is dependent on several effects including orientation within the magnetic field, calibration and scintillation light expos ure rates, and time between successive exposures. The High Energy Physics group at the University of Virginia (UVa) uses a 3.8 T large-bore superconducting solenoid m agnet to simulate conditions at the LHC and to study the long term behavior of these VPTs under various light and magnetic field conditions. Also, using the ECAL lase r and LED calibration system, UVa is also able to study the response of the VPTs in situ at the CMS detector in order to understand and quantitatively assess the perfo rmance of the VPTs over time. Herein we will report on these remote and in-situ studies of VPT characteristics and performance. [Preview Abstract] |
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LA.00039: First Neutrino Results from the NOvA Near Detector Zukai Wang The NO$\nu$A collaboration is building a long-baseline neutrino spectrometer optimized to study the appearance of electron neutrinos in a muon neutrino beam. A full-sized prototype of the Near Detector has been fabricated on the surface and is presently taking data with the Fermilab NUMI neutrino beam. A description of the Near Detector will be given and its performance will be shown. [Preview Abstract] |
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LA.00040: Identifying Electromagnetic Events in the Forward Hadron Calorimeter Christopher Frye The Forward Hadron Calorimeter (HF) of the Compact Muon Solenoid (CMS) at the Large Hadron Collider (LHC) lies in a region not covered by an inner tracking system, and we can rely only on the shapes of showers that hit the HF to determine whether or not they are due to electromagnetic particles. We review the current method of distinguishing shower types in the HF, and we bring attention to a drawback that will become present as the luminosity of the LHC increases and creates a need for tighter shower-shape cuts. We provide a method to correct this drawback, and we analyze the effectiveness of various tight cuts at isolating signal from background. [Preview Abstract] |
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LA.00041: Open and Solved Elementary Questions in Astronomy Florentin Smarandache Some school scientific problems are posed: 1) Let's consider a tunnel getting from one side to the other of a planet and passing through the planet center. An object is dropped into the tunnel. Is the object oscillating about the center as a pendulum? What happens if the tunnel gets from a side to another side of the planet but doesn't pass through the planet center, would the midpoint of the tunnel play a similar role as the planet center? How will Coriolis force influence this? 2) Is it possible to accelerate a photon (or another particle traveling at, let's say, 0.999c) and thus to get a speed greater than c? [Preview Abstract] |
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LA.00042: Periodicity of the Benjamin-Feir Instability and Linear Superposition Justin Cutrer, Kedric Hayes, Jessica Graber Freak waves are waves of great height that appear out of nowhere from otherwise ordinary, if rough, seas. The steepness of these waves can cause an enormous amount of damage to ships and oil platforms. Understanding the cause of freak waves will help us to predict dangerous conditions, and engineer structures better able to withstand such waves. A number of mechanisms have been studied as the source of freak waves, including linear focusing, refraction of waves through a current field, and nonlinear effects. The Benjamin-Feir instability solves the nonlinear Schrodinger equation when a carrier band of frequency $\omega _0 $ is perturbed by sidebands of $\omega _0 \pm \Delta \omega $. These solutions are periodic, or ``breather,'' solutions under the condition that $\Delta \omega <\omega ka\sqrt 2 $, where \textit{ka} is the wave steepness determined by $k,$ the wavenumber, and $a$, the wave amplitude. In this poster, we will compare the period of these breather solutions with the period of the envelope of the linear superposition of the same carrier wave and sideband perturbations using MatLab movies. [Preview Abstract] |
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LA.00043: Acoustic measurement of the granular density of state Eli Owens, Karen Daniels Measurements of the vibrational density of states (DOS) in glasses reveal that an excess number of low-frequency modes, as compared to the Debye scaling seen in crystalline materials, is associated with a loss of mechanical rigidity. An excess number of modes have also been observed experimentally in colloids and in simulations of idealized granular materials near the jamming point. However, there have not been any experimental measurements in an athermal granular system. We experimentally probe the material by mimicking thermal motion with acoustic waves, thereby allowing us to measure a DOS like quantity by analogy with conventional solid state techniques. Our system is made up of two dimensional photoelastic disks which allow visualization of the internal force structure, and a voice coil driver provides a white noise signal to excite a broad spectrum of vibrations. The sound is then detected with piezoelectric sensors embedded inside a subset of the particles. These measurements give us the particle velocities, from which we are able to compute a DOS by taking the Fourier transform of the velocity autocorrelation function. We measure this DOS as a function of the confining pressure and degree of disorder and find that the peak in the density of states shifts to higher frequency as the system pressure is increased. [Preview Abstract] |
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LA.00044: Photon diffraction John Hodge A particle model of light that exhibited wave--like behavior was proposed at SESAPS log. No. SES09-2009-000064. The model combined the Bohm interpretation with the Scalar Potential Model (SPM) of photons. The model simulation is expanded with a slight modification to allow for different color photons through a single slit experiment, Young's experiment, and coherent light from large distances. [Preview Abstract] |
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LA.00045: The Coffee and Cream Dilemma Brandon Minor, Gerald Feldman Many coffee drinkers take cream with their coffee and often wonder whether to add the cream earlier or later. With the objective of keeping their coffee as hot as possible over a moderate time period (10-15 minutes), this is a question that most of them can never answer definitively. We investigated this problem empirically using hot and cold water, with special emphasis on the calorimetry of the mixture. Assuming a coffee:cream (hot:cold) ratio of 3:1, we began with two identical styrofoam coffee cups containing hot water and then added cold water at $t$ = 200 s in one cup and $t$ = 700 s in the other cup. Using two Vernier temperature probes to simultaneously track the temperature change during the cool-down period of the water in both cups over $\Delta t$ = 1000 s, we obtained a real-time graphical account of which process achieved the higher temperature over this time period. In addition, the effect of evaporation was explored by comparing trials with and without a lid on the coffee cup. The application of Newton's Law of Cooling, as compared to the graphical temperature data acquired, will leave no doubt as to the best strategy for adding cool cream to hot coffee. [Preview Abstract] |
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LA.00046: Characterization of large-scale velocity fluctuations in the Princeton MRI experiment W. Love, A. Roach, E. Spence, P. Sloboda, H. Ji The Princeton MRI Experiment is a modified Taylor-Couette device that uses GaInSn as its working fluid. An Ultrasonic Doppler Velocimetry (UDV) system allows the measurement of internal fluid velocities. Starting from both hydrodynamically stable and unstable background flow states, prior work has demonstrated the existence of large-scale, large-amplitude, coherent, nonaxisymmetric velocity fluctuations when a sufficiently strong magnetic field is applied. Characterizations of these oscillations are made by looking at the dominant fluctuations in the azimuthal and radial velocity field components and matching these features to different model velocity profiles. These profiles are calculated by starting with a model azimuthal and radial flow and calculating the vertical term in the continuity equation. The relative magnitudes of the calculated azimuthal and radial flows are compared to experimental UDV data to determine the validity of the model. Additional calculated properties such as final velocity current density profiles will be presented. [Preview Abstract] |
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LA.00047: Emission Spectroscopy of RF Helicon Heated Plasmas Tim Younkin, T.M. Biewer, R.H. Goulding, D.L. Hillis, R. Isler In order to study plasma-material interfaces under high power and particle flux, large linear machines are being constructed that can effectively simulate conditions that will be found in fusion-grade toroidal devices such as ITER and DEMO. A 15 cm diameter, 1.5 m long linear machine has been built at ORNL using a new helicon antenna designed for input powers up to 100 kW, producing a plasma that will be used to bombard material targets. Visible spectroscopy has been used to measure emission line spectra of the helicon heated plasma from 200 nm to 1100 nm at low resolution. The spectrometer is thoroughly calibrated for wavelength and intensity in order to determine electron density and temperature using the ratios of spectral line intensities. A variety of gas species have been heated, including hydrogen, deuterium and helium. Residual amounts of foreign materials can be monitored near the plasma-wall interface. Results on how magnetic field scans, probe scans, and power scans affect the plasma will be analyzed and presented. [Preview Abstract] |
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LA.00048: Two definitions for genders Philip Shin By my definition, man and woman are the same fact to say. So man and woman have the same thinkings and same existence. But when I say again for man and woman, they are different for sex as the two different persons. They are different each two persons. As an example, by quantum, sex and color is different (the same existence and also different kind with quantum way-push and pull at the same time), also they are the same as they are our ID (hormones) and also dream matter. The same way, I hope we go to heaven and god will say you are the truth like it to be after the end of the world. I wish man and woman are different as it is more fun. [Preview Abstract] |
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LA.00049: Magnetization Dynamics in Magnetic Nanoparticle Chains Suvojit Ghosh, Ishwar Puri Magnetic nanoparticles (MNPs) exhibit superparamagnetism when the energy changes due to thermal fluctuations $(\sim k_B T)$ are comparable to or larger than the anisotropy potential barrier \textit{KV}. Thermal fluctuations produce frequent magnetization reversals in such a situation causing the net MNP magnetization to approach zero. If thermal oscillations are relatively small, the odds of magnetization reversal diminish significantly implying that an MNP is permanently magnetized. In this study we explore the influence of the magnetostatic coupling of moments in neighboring MNPs in an idealized two-particle system. The anisotropic nature of such coupling adds to the magnetocrystalline anisotropy to augment the potential barrier for magnetization reversal. A two particle system of MNPs therefore has a more stable magnetization than an isolated particle. This is analyzed by a scaling analysis of the interaction energies concerned. Numerical simulations of mangetization dynamics of MNPs using a stochastic form of the Landau-Lifshitz-Gilbert equation confirm the hypothesis. The phenomena is explored to determine a range of radii within which an MNP exhibits superparamagnetism in isolation while forming permanently magnetized chains upon self-assembly. [Preview Abstract] |
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LA.00050: It may be possible to use Capillary Action as a Cooling method Richard Kriske It is well known that it takes no work for water to rise in a Capillary tube. It only takes work for the water to be removed from the top of the tube. It may be possible for this water to be removed using individual photons of the size needed to break the water to water hydrogen bond. This bond is often broken in evaporation of water from surfaces. As this bond is broken at the top of the Capillary tube the water makes a phase transition and makes room for another water molecule to move up the column. The phase transition cools the column and another molecule moves up the column with no work being done. There is a net energy loss in this system, and the entire system is cooled. This may be one of the mechanisms that plants use to cool themselves and the soil around the plant. This mechanism may be used to explain the slight temperature regulating effect of plants and the areas around large plant populations. Photons of other sizes may also be used in this mechanism if there are the proper molecules (Chlorophyll for instance) in a chain reaction linked to this mechanism. This chimney like effect could also be used as a precise balancing method to transport materials based on mass and chemical composition, like a chromatograph. The ``Einstein Refrigerator'' can be viewed as a similar idea. [Preview Abstract] |
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LA.00051: Acoustic Radiation from Smart Foam for Various Foam Geometries Nishkala Shivakumar Smart foam is an emerging active-passive noise control technology with many applications. Smart foam consists of passive foam with an embedded curved piezoelectric (PZT) film. We experimented with three geometries of varying film curvatures and a constant cross-sectional area of 58 cm$^{2}$, constructed using melamine foam covered with 28 $\mu $m thick polyvinylidene fluoride (piezoelectric) films with Cu-Ni surface electrodes. An AC voltage provided by a signal generator and amplifier drives the smart foam. An omnidirectional microphone mounted at a distance 100mm from the foam surface measured the sound level (dB) and harmonic distortion generated by the smart foam. Experiments were repeated for voltages, 40V-140V, and frequencies, 300Hz-2000Hz. The result show that the sound level generated by the smart foams has a characteristic frequency response common to all geometries and a peak sound level between 900 to 1,100 Hz. [Preview Abstract] |
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LA.00052: Use of Spray Adhesives for the Manufacture of 3-D Capillary Origami Microstructures Mithi de los Reyes The method of ``capillary origami''---using the surface tension of an evaporating water droplet to fold a flexible membrane into a 3-D polyhedron, as investigated by Py et al.---has shown promise as a way to create fully 3-D microstructures. However, the origami re-opens past a critical evaporation point, and previous attempts to prevent this re-opening have proven to be expensive and time-consuming. We therefore investigated the use of various spray adhesives in keeping these origami microstructures closed. Three characteristics were measured: efficiency, tackiness, and strength of the adhesive. Measurements of these three characteristics point to 3M Super 77 Spray Adhesive as an optimal adhesive for spraying microstructures. Furthermore, we designed a new method to measure adhesive strength by using an analytical balance to measure force applied by a micrometer to a microstructure. We also developed novel procedures to create uniformly-sized microstructures and to accelerate the folding process, all of which improve upon the original capillary origami method. These novel procedures, combined with measurements that indicate 3M Super 77 as an optimum adhesive, suggest a potential method for the mass-production of truly 3-D microstructures. Py, Charlotte, et al. ``Capillary origami: Spontaneous wrapping of a droplet with an elastic sheet.'' \textit{Physical Review Letters}. 98.156103 (2007) [Preview Abstract] |
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LA.00053: e/m Experiment Analysis Refinement Michael Harmon, Bryce Pruitt, Kevin Velasquez, Rich Schelp Thomson's $e/m$ experiment is widely popular in undergraduate courses to help gain an understanding of the properties of the electron. Our results using a standard apparatus, however, reveal significant systematic errors. We examine possible reasons for the discrepancy with the aim of modeling effects that were not included in the original analysis. We conclude that the energy loss of the electron beam as it travels through the helium and the distortion of the beam radius measurement by the curved glass of the tube are the two factors which dominate the discrepancy. [Preview Abstract] |
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LA.00054: Pac-Man: Lock and Key Colloid Particles Ashley Taylor, Lei Zhang, Stefano Sacanna, David Pine The lock and key models using Pac-man particles is an alternative identification mechanism for directing the assembly of combined structures. The system was guided by Fischer's lock- and key principle which consisted of colloidal spheres as keys and monodisperse colloidal particles with a spherical cavity as locks that bind. What makes this so specific is the fact that the assembly is controlled by how closely the size of a spherical colloidal key particle matches the radius of the spherical cavity of the lock particle. Viscosity measurements were also looked at because nano-particles are known to change the resistance of the fluid. [Preview Abstract] |
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LA.00055: Testing General Relativity at Cosmological Scales using \texttt{ISiTGR} Jacob Moldenhauer, Jason Dossett, Mustapha Ishak With the plethora of incoming and future cosmological data, the testing of general relativity at cosmological scales has become a possible and timely endeavor. It is not only motivated by the pressing question of cosmic acceleration but also by the proposals of some extensions to general relativity that would manifest themselves at large scales of distance. To test the consistency of current and future data with general relativity, we introduce the package: \texttt{ISiTGR}, {\it\textbf{I}ntegrated \textbf{S}oftware \textbf{i}n \textbf{T}esting \textbf{G}eneral \textbf{R}elativity}, an integrated set of modified modules for the publicly available packages \texttt{CosmoMC} and \texttt{CAMB}, including a modified version of the ISW-galaxy cross correlation module of Ho et al and a new weak lensing likelihood module for the refined HST-COSMOS weak gravitational lensing tomography data. We provide the equations for the parameterized modified growth equations and their evolution. We implement a functional form approach, a binning approach, as well as a new hybrid approach to evolve the modified gravity parameters in redshift (time) and scale. Examples calculating current constraints on modified gravity parameters are given for illustration and showing again that current data is consistent with general relativity. [Preview Abstract] |
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