Bulletin of the American Physical Society
Spring 2013 Meeting of the APS Ohio-Region Section
Volume 58, Number 2
Friday–Saturday, March 29–30, 2013; Athens, Ohio
Session B1: Poster Session (4:15 - 6:15PM) |
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Chair: Justin Frantz, Ohio University Room: Walter Hall Main Foyer Area, 1st Floor |
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B1.00001: How fast can we walk? Courtney Barker, Melissa Akers, Kurt Baughman, Howard Wetzler, Gabriela Popa We have made a model to find out how fast a person can walk, and figure out the maximum walking speed. Several recordings of walking people of various masses and heights were analyzed using LoggerPro. A force platforme was used to figure out the normal and horizontal forces applied to the floor as walking. [Preview Abstract] |
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B1.00002: Investigation of Rooftop Radiative Cooling for Green Building Design Lin Su, Dennis Kuhl The efficiency of a rooftop radiative cooling system was investigated for the environmental conditions at Marietta, Ohio. A 24''x24''x21.5'' house model was built as test cell. Each wall had 1.5'' of foam insulation in between two 0.5'' thick plywood boards. The roof component consisted of a layer of 7/8'' thick concrete on the bottom, a layer of 1.5'' thick insulation in the middle, and a thin steel plate on the top. Copper tube was embedded in the concrete layer and run on top of the steel plate. Water was circulated in a closed cycle from a reservoir through the concrete and through the radiator. Temperature was monitored inside the house, in the flowing water, outside the house, and inside the concrete layer. Relative humidity was monitored inside the model and outside the model. Results will be presented that indicate that slower water flow rate corresponds to higher radiative cooling efficiency, which is consistent with previously published results. Preliminary results of investigations of the effects of relative humidity will also be presented. [Preview Abstract] |
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B1.00003: Preliminary investigation of a plasma sheath using dust Thomas E. Steinberger, W.L. Theisen, T.E. Sheridan The plasma sheath is the boundary layer that separates a plasma from a material surface. Dust particles in a plasma typically acquire a negative charge and float at the edge of the plasma sheath. The charge on dust in a two-particle cluster can be found from normal mode analysis. The electric field and field gradient can then be determined at the particles' positions. Preliminary results from the Dusty O.N.U. experimenT (D.ONU.T) will be presented. [Preview Abstract] |
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B1.00004: 3-D Simulations of Open Star Cluster Evolution Using The King Model Jennifer Kachel, Ann Bragg, Cavendish McKay We model the evolution of open clusters using the Starlab simulator package with the goal of understanding how the spatial distributions of high and low mass stars within the clusters evolve in time. To accomplish this, we built ensembles of simulated clusters containing different numbers of stars, with initial populations distributed according to the King model and the Salpeter initial mass function. Using these simulated clusters, we examine the timescale on which mass segregation becomes apparent and its variability due to differences in initial populations drawn from the same distribution. We also examine the effect of cluster size on the mass segregation. [Preview Abstract] |
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B1.00005: Simulations of Episodic AGN Feedback Conditions in Elliptical Galaxies David Riethmiller, Thomas Statler The exact nature of mechanisms for AGN feedback and cooling in elliptical galaxies is to date uncertain. However, observed correlations among X-ray properties of ellipticals may allow us to judge how well simulated feedback and cooling prescriptions reproduce X-ray observations. Of particular interest is the coupling of AGN power with X-ray morphology; recent investigations have found that the AGN X-ray luminosity is directly correlated with the morphological asymmetry in the gas, which could be explained by episodic AGN activity. As an initial step in exploring such feedback in ellipticals, we present here a series of hot galactic gas simulations executed with the smoothed particle hydrodynamics (SPH) code GADGET2. Our setup places gas particles inside a fixed static dark matter potential. The gas is disturbed by an accretion-fed AGN which may return energy with varying efficiency, thermally or kinetically (or both), with or without jets. Our aim is to investigate under what conditions we observe episodic AGN activity consistent with the AGN power-morphology relation. [Preview Abstract] |
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B1.00006: Analysis of relaxation time from numerical simulation of open star clusters Shelby Lee, Cavendish McKay, Ann Bragg Open clusters exhibit mass segregation such that higher mass stars are more centrally concentrated than lower mass stars. Untangling the effects of primordial distribution and dynamical evolution has proven challenging, as observers only see any given cluster at a single moment in time. We use numerical simulations to study the time evolution of ensembles star clusters drawn from initial distributions consistent with the Plummer model and the Salpeter initial mass function. We discuss the time dependence of mass segregation for clusters of various sizes. [Preview Abstract] |
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B1.00007: Analysis of 2D substructure in radio-loud clusters of galaxies Donald Pleshinger, Jason Pinkney We have produced and refined catalogs of galaxy positions, magnitudes, colors and redshifts in ten, radio-loud clusters of galaxies. The CCD images were taken with the MOSA imager on the Kitt Peak 0.9-m telescope. We use the color-magnitude relation (CMR) in B-V and B-R to select samples of galaxies which are members of the targeted clusters. We also restrict the samples to galaxies within one Abell radius (for Ho=75 km/s/Mpc) of the center, using two approaches for defining the center. We estimate the contamination of the CMR samples by foreground and background galaxies to be about 10\%. We apply four statistical tests for the significance of 2D (plain of the sky) substructure to all of the samples, and obtain significance levels using Monte Carlo simulations. We are able to rule out the null hypothesis of a unimodal distribution with confidence for the majority of clusters. Isopleth contour maps are used to verify the substructure qualitatively. This allows us to address our motivating question: do cluster-subcluster mergers have an influence on radio galaxy morphology? [Preview Abstract] |
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B1.00008: A Radiation-Hydrodynamics Code Comparison for Laser-Produced Plasmas: FLASH versus HYDRA and the Results of Validation Experiments Chris Orban, Milad Fatenejad, Sugreev Chawla, Scott Wilks, Donald Lamb The potential for laser-produced plasmas to yield fundamental insights into High Energy Density Physics (HEDP) and deliver other useful applications can sometimes be frustrated by uncertainties in modeling the properties and expansion of these plasmas using radiation-hydrodynamics codes. In an effort to overcome this and to validate and verify the HEDP capabilities of the publicly available FLASH radiation-hydrodynamics code, we present detailed comparisons of FLASH simulations to previously published results from the HYDRA code used extensively at Lawrence Livermore National Laboratory for the validation experiments investigated by Grava et al., Phys. Rev. E, 78, (2008). Their paper describes the laser irradiation of an Al target and includes both interferometric measurements of electron number densities as well as HYDRA simulations of the target evolution. Despite radically different schemes for determining the computational mesh, and different equation of state and opacity models, the HYDRA and FLASH codes give excellent agreement with the experimental data. [Preview Abstract] |
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B1.00009: A study of the nature of the low frequency vibrational modes of crystalline nucleosides Craig Koontz, Scott Lee Raman spectroscopy was used to study the low-frequency ($\le $ 200 cm$^{-1})$ vibrations in crystalline samples of six nucleosides: deoxythymidine (dT), deoxycytidine (dC), deoxyadenosine (dA), uridine (rU), cytidine (rC), and adenosine (rA). The modes in this frequency range can involve both external modes (in which two molecules of the unit cell ``beat'' against each other) and internal modes. These experiments were performed in order to test the predicted low-frequency vibrational modes of dT, dC and dA of Shishkin \textit{et al.} (in ``Theoretical analysis of low-lying vibrational modes of free canonical 2-deoxyribonucleosides,'' O.V. Shishkin, A. Pelmenschikov, D.M. Hovorun and J. Leszczynski, Chemical Physics, \textbf{260} (2000) 317-325). Our experiments support their theoretical result that the lowest frequency vibrational mode (near 30 cm$^{-1}$) in dA and dC is due to a rotational mode around the C(1')-N bond. [Preview Abstract] |
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B1.00010: Femoral bone strength and running speeds in emus (\textit{Dromaius novaehollandiae}) Scott Lee Large, flightless birds provide the best extant model for the study of the locomotion abilities of extinct, bipedal dinosaurs. The ability of the femur to resist bending stresses is determined by its midlength cross-sectional geometry, its length and the elastic properties of the mineral part of the bone. The animal's athletic ability, determined by a ``bone strength index,'' is limited by this femoral bending strength in relation to the loads on the femur. As part of a comprehensive study of the cursorial potential of extinct dinosaurs, we report measurements of femoral bone strength index in emus (\textit{Dromaius novaehollandiae}) and relate this to the running speeds of these animals. [Preview Abstract] |
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B1.00011: Monte-Carlo simulations of single-molecule RNA pulling experiments Dan Le, Jutta Luettmer-Strathmann In many viruses, genetic information is encoded in single-stranded ribonucleic acid (RNA) molecules. These molecules are very long chains with an interesting secondary structure that is still difficult to predict from the sequence of bases along the chain. In this work, we develop a coarse-grained lattice model for RNA with orientation-dependent interactions between hydrogen-bonded base pairs. We perform Monte Carlo simulations for several different chains to investigate chain conformations and determine the collapse transition. We determine force-extension curves under equilibrium conditions for tension forces applied to different segments of the chain. These simulated pulling experiments allow us to investigate the relationship between the mechanical response and the secondary structure of the chain. [Preview Abstract] |
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B1.00012: Phase Transitions and Helix Formation of a Fused Square-Well-Sphere Michael Mroz, Mark Taylor This study involves observing phase transitions of a flexible polymer chain made of N = 20 fused square-well-sphere monomers, with the hard-core diameter d and square-well diameter Rd, connected by bonds of fixed length L less than d. The density of states of the polymer is calculated using the Wang-Landau simulation technique. The density of states is utilized to compute thermodynamic and average structural properties of the chain. A temperature-interaction range (T-R) phase diagram was constructed for a chain of bond length L = 0.625d. With decreasing temperature this chain undergoes a coil-globule (i.e., collapse) transition followed by one or more low temperature transitions to an ordered ground-state structure. For R greater than 1.25 this ground state is a simple helix while for smaller R the ground state is a wrapped structure, in which one end of the chain forms a linear core about which the rest of the chain is helically wound. The low temperature transition takes on a first-order character for R less than 1.1. [Preview Abstract] |
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B1.00013: Central Pattern Generators for Quadrupedal Arboreal Locomotion of Chipmunks [Tamias Sibiricus] Ulrich Zurcher, Alexandra Powers, Andrew Lammers Locomotion requires to coordinated periodic movements of muscles and ligaments, which in turn requires periodic firings of neurons. The patterns are self-generated and do not depend on external stimulus. The corresponding oscillators are known as central pattern generators [CPG]. The CPGs for fore- and hind limb movement have been studied quite extensively in the literature. We focus on CPGs for the motion of the trunk, head, and tail of chipmunks. We observe wave-like behavior, which generates the angular momentum about the mediolateral axis necessary for dynamic, rather than static, stability. [Preview Abstract] |
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B1.00014: Solvation Potentials \& Partition Function Zeros for a Polymer Chain Mark Taylor, Yuting Ye, Pyie Phyo Aung In this poster we present results for model interaction-site polymers built from either Lennard-Jones (LJ) or square-well (SW) sphere monomers. First, we study the conformation of LJ chain polymers in explicit LJ solvent. We compute numerically exact sets of solvation potentials for chains of length five across the LJ solvent phase diagram. We use these exact short chain results to construct accurate solvation potentials for long LJ chains in solvent. These solvation potentials map the many-body chain-in-solvent problem onto a few-body single-chain problem, thereby greatly reducing the computational complexity of studying long chains in explicit solvent. Second, we study phase transitions of an isolated SW polymer chain by examining the zeros of the single-chain partition function. These partition functions are obtained either through exact calculation for short chains (n $\le$ 6) or via Wang-Landau simulation for long chains (up to length n = 256). Maps of the partition function zeros provide insight into the location and nature of the single-chain collapse and freezing transitions. Of particular interest is the disappearance of the collapse transition for a sufficiently short SW interaction range, analogous to the disappearance of the liquid phase in a SW monomer fluid. [Preview Abstract] |
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B1.00015: Active layer morphologies for device simulations Jutta Luettmer-Strathmann, Kiran Khanal The morphology of the active layer has a strong effect on charge generation and transport in organic photovoltaics. In bulk heterojunction devices, amorphous and crystalline regions with varying compositions coexist due to microphase separation and crystallization of the blend components. Accounting for these effects in device simulations is difficult since the size of the active layer is too large to generate realistic morphologies from molecular simulations of the constituents. In this work we perform Monte Carlo simulations of a coarse-grained lattice model of polymer mixtures to generate microphase separated layers with ordered and disordered regions. [Preview Abstract] |
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B1.00016: Sensory Neuron Terminals in Paddlefish Electroreceptors: Where Do Spikes Start? Desmon Rogers, Lilia Neiman, David F. Russell We studied the branching terminals of sensory neuron axons at electroreceptors in the skin of paddlefish. They respond to weak electric fields in nearby water, from prey. FOCUS PROBLEM: Where are spikes initiated? Since a sensory neuron branches repeatedly to receive input from 3-30 ``sensors,'' is there a separate spike initiation zone for each sensor? Or do all the sensors sum to drive spiking at a single zone? APPROACH: (i) 3-Color fluorescent antibody labeling and light microscopy revealed the locations of specific cell components known to be involved in action potential generation, including voltage-gated sodium channels, and neurofilament-H inside sensory axons, and myelin around axons. (ii)Fluorescent lipophilic tracers DiI and DiO revealed the membrane of sensory axon branches. RESULTS: (i) Antibody labeling showed that as a sensory axon branched repeatedly, each sub-branch remained myelinated until 100 microns from the sensors, where each sub-branch had a classic ``hemi-node'' organization, with a final cluster of sodium channels (the last node), beyond which unmyelinated neurites, not showing voltage-gated sodium channels, branched profusely to innervate a pair of adjacent sensors. (ii) Lipophilic tracers confirmed this organization. We used 2-color tracing to ask if the 3-6 sensory axons in an electroreceptor co-innervate all of its sensors. CONCLUSION: A sensory axon can have multiple spike initiation zones, e.g. up to 15 (one for each pair of sensors) in paddlefish electroreceptors. [Preview Abstract] |
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B1.00017: The Role of Bidirectional Coupling in the bullfrog' saccular inner hair cells Rami M. Amro, Alexander B. Neiman Mechanical vibrations of the hair bundle and somatic membrane potential oscillation are strongly correlated through bidirectional coupling. Hodgkin-Huxley type model was used to study the dynamical properties of the isolated (Otolithic membrane removed) bullfrog's inner ear saccular hair cells. We hypothesize the existence of the bidirectional coupling and investigating the effects of the coupling strength on the hair cell's main characteristics. The forward coupling is proportional to the magnitude of the transduction current, while backward coupling parameter is in proportion to the calcium concentration near the motor complexes' sites. Different types of these hair cells were studied. Model parameters are chosen to reflect realistic situations. This study shows that sensitivity and frequency selectivity are greatly enhanced within limited ranges of the coupling parameters' space. Also; we show that non-oscillating hair bundles undergo spontaneous activity if bidirectional coupling exists [Preview Abstract] |
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B1.00018: Controlling Ionic Dissociations Reactions with Isotopic Labeling: Methane Loss in Acetone David Klecyngier, Jim Kercher, Andras Bodi, Tomas Baer, Dan Fakoury Acetone-h$_{6}$ and acetone-d$_{6}$ were fragmented by low energy mass spectrometer to observe the formation of methane and methyl radicals. Methyl and methane loss are competing parallel reaction with activation energies of 78 $\pm$ 2 kJ mol$^{-1}$ and 75 $\pm$ 2 kJ mol$^{-1}$, respectively. The dissociation thresholds for the fragment ions were measured from 10.200 eV to 10.700 eV. A hydrogen transfer is necessary to form CH$_{4}$; this requires tunneling through the potential barrier modeled by the Eckart barrier. The tunneling process was effectively shut off when acetone-d$_{6}$ was used, resulting in only methyl loss. This is due to the isotope effect, given that heavier matter is less likely to tunnel. The measured dissociations were then modeled with theoretical rates determined with high level quantum calculations using the approximate Eckart barrier, thermal energy, and dissociation rates. Time of flight, TOF, files were required to accurately model the dissociation of methane because it is a slow reaction, it dissociates while in flight, this leads to the development of asymmetric peaks in the spectra. A 1-dimensional Eckart barrier was determined to be effective as a rough analysis of this kind of reaction. [Preview Abstract] |
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B1.00019: Evolution of Two Dimensional Surface State Electrons near the Metal-Molecule Boundary Kyaw Zin Latt, Hao Chang, Sajida Khan, Andrew R. Dilullo, Saw Wai Hla The existence of a surface state just below the Fermi level ($\sim$ -65 meV) on Ag(111) surface generate two-dimensional and nearly free electrons gas parallel to the surface. Here, how the surface state electrons evolve at the molecule-metal boundary has been investigated by using low temperature tunneling microscopy, tunneling spectroscopy, and spectroscopic mapping. We choose nanoscale molecular clusters composed of BETS and GaCl$_{4}$ f on Ag(111) surface as the molecular layer. dI/dV tunneling spectroscopy data are then measured across the metal-molecular cluster boundary and the data clearly reveal the expected surface state on-set at -65 $\pm$ 5 mV on bare Ag(111) terrace away from the molecular clusters. However, the intensity of the surface state on-set exponentially decreases starting at $\sim$ 1.5 nm distance from the molecule-metal boundary and decayed under the molecular layer. Moreover, the surface state on-set energy also is shifted towards the Fermi level indicating the depopulation of the surface state electrons near the molecular clusters. [Preview Abstract] |
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B1.00020: Single Molecule Study of Charge Transfer in 6T-TBrPP-Co Molecular Complex Yuan Zhang, U.G.E. Perera, S.-W. Hla When two molecules having tendency to donate or accept electronic charge are put together, charge transfer between the molecules can take place. By a suitable selection of donor and acceptor molecules, it is possible to engineer an entire class of materials having metallic, semiconducting, insulating, or even superconducting properties. Here, we present a low temperature scanning tunneling microscopy and spectroscopy study of single molecule level charge transfer process between $\alpha $-sexithiophene(6T) and TBrPP-Co molecules on a Cu(111) surface. We form molecular clusters composed of both molecular species on Cu(111). The charge transfer between the molecules is directly evident in the tunneling spectroscopy data, which reveals the shift of 6T HOMO towards the surface Fermi level indicating donation of charge from 6T to TBrPP-Co. [Preview Abstract] |
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B1.00021: Synchrotron Assisted Scanning Tunneling Microscopy H. Kersell, V. Rose, S.-W. Hla Scanning tunneling microscopy (STM) provides a wealth of information regarding surface properties of conductive materials by probing the electronic properties of samples under investigation. However, the nature of STM's reliance on the sample density of electronic states often limits the chemical contrast of resulting images. By targeting the sample with high energy X-rays, such as those generated by a synchrotron light source, core level electrons may be promoted and subsequently contribute to the current measured in STM. Since core level excitation energies are chemically specific, this technique can be used to obtain chemical sensitivity in STM imaging, providing deeper insight into molecule-substrate and intermolecular interactions. We present the development of a synchrotron-assisted STM (SXSTM), capable of obtaining chemical resolution. [Preview Abstract] |
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B1.00022: Measuring the Thermal Fluctuations in Bulk YBCO and BSCCO Superconductors Jeremy Massengale, Paul Voytas High temperature $(HT_{c})$ superconductors have been studied rigorously for over twenty years because of their potential for both research-driven and industrial applications, as well as emerging technologies such as smart grids and power transmission. Their unique ability to become superconducting at high temperatures $(T > 77K)$ has ignited much interest in the development of new materials that push the critical temperature, $T_{c}$, to ever higher limits. Due to the high transition temperatures, short coherence length and layered structure, thermal fluctuations near the transition temperature are unusually large. We explore these effects in measurements of the resistivity as a function of temperature in bulk YBCO and BSCCO using equipment standard in most undergraduate universities. The experimental arrangement and results to date will be presented. [Preview Abstract] |
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B1.00023: Topological insulating state in bismuth doped with antimony and arsenic: infrared and magneto-optical studies G.M. Foster, S.V. Dordevic, N. Stojilovic, V.M. Nikolic, S.S. Vujatovic, Z.Z. Djuric, P.M. Nikolic, Z. Chen, Z.Q. Li Bismuth and its alloys with antimony have attracted attention in recent years due to the possibility of having a topological insulating state. In this study we have used infrared and magneto-optical spectroscopies to probe the electrodynamic response of bismuth doped with of antimony and arsenic. The spectra will be presented for temperatures down to 5 K, and in magnetic fields as high as 18 Tesla. The results have revealed a strong magneto-optical activity, especially around the plasma minimum in reflectance. These findings will be compared and contrasted with magneto-optical results from other 3D topological insulators. [Preview Abstract] |
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B1.00024: Local Work Function Approximation at Tip Induced Surface Vacancies by STM Andrew DiLullo, Danda Pani Acharya, Saw-Wai Hla Local surface work functions are important for many surface interactions including surface chemistry, site-specific adsorbate binding, and macromolecule self-assembly. The scanning tunneling microscope can act as a probe of the local work function by measurement of resonances that occur in the field-emission regime, which are Stark-shifted image potential resonances. The energetic positions of field emission resonances are extracted from bias dependent topographic sequences. Using this technique, surface regions with step edges, and surface vacancies created by controlled probe vertical manipulations, had their field-emission resonance energies measured throughout the imaged regions. The extracted resonance energies were fit by Gundlach's equation resulting in reasonable approximations for local surface work function, probe work function, and absolute probe height. The induced surface vacancies are interesting, considering industrial approaches to nanoindentation, with use for independent determination of the work functions for these nearly zero-dimensional objects. [Preview Abstract] |
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B1.00025: Sulfur adsorption on gold - an exercise in computational low-energy electron diffraction Ashley Ernst, Nathan Grieser Gold - one of the less reactive elements in nature - has recently sparked the interest of the scientific community through the properties of its surface. The Au(111) surface, under UHV conditions, reconstructs into a (22x$\surd $3) structure. Nevertheless, even a small amount of sulfur adsorbed on the Au(111) surface is enough to lift the reconstruction. As the amount of adsorbed sulfur increases, a succession of S/Au structures are formed, as recognized in low-energy electron diffraction (LEED) patterns. We report on the LEED computational analysis of one such phase: ($\surd $3x$\surd $3)R30$^{\mathrm{0}}$ which corresponds, theoretically, to a 0.33ML sulfur coverage. Experimental evidence places this phase in coexistence with other phases on the Au substrate, therefore there is little expectation for a such a LEED investigation to answer the main question of the actual adsorption site of the atomic sulfur on the gold substrate. Still, as an exercise in computational LEED, we investigated several models for the ($\surd $3x$\surd $3)R30$^{\mathrm{0}}$ structure, testing various adsorption sites for the sulfur atoms. We also considered the possibility of sulfur bonding to additional Au atoms, placed on top of the regular surface, forming Au-S entities. [Preview Abstract] |
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B1.00026: Simulating Blazar SEDs using a Time Dependent Leptonic Model Christopher Diltz, Markus Boettcher We present simulations for a time dependent leptonic model to reproduce characteristics found in spectral energy distributions of flat spectrum radio quasars (FSRQ's) and BL Lac objects. Blazars are known for their lack of emission lines and relatively featureless continuum radiation emission. Conversely, FSRQ's present with emission lines as well as contributions from external radiation fields surrounding a supermassive black hole (SMBH). We simulate time evolved SEDs from a series of different input parameters to understand the effects these input parameters have on the output. Our model is able to produce continuum radiation from synchrotron and synchrotron self-comptonization (SSC) from a time evolved distribution of electrons moving relativistically along the axis of the blazar jet. The model also considers contributions from external radiation fields and their subsequent scattering to higher energies due to external Compton processes. The results of our simulations agree well with the expected normalization and power law dependencies for the overall flux of the spectral energy distributions from the input parameters involved. [Preview Abstract] |
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B1.00027: Plasmon Interactions in a Lattice of Nanospheres Andrew Wasil, Doug Armstead A surface plasmon is an oscillation in the electron gas at the surface of a metal. Surface plasmons can couple with a photon to become a surface plasmon polariton (SPP) which has the ability to propagate along the surface of the metal and eventually re-emit the photon. We look at a simulation of SPPs on the surface of conducting spheres, first for an individual sphere and then for a square lattice of spheres using the MIT Electromagnetic Equation Propagation (MEEP) package. We seek to characterize the dispersion of the re-emitted photons, characterized by a map of the electromagnetic field, and determine the relationship between this dispersion and the spacing of the lattice. We also look for the spacing at which an SPP begins to exhibit gap plasmon polariton (GPP)-like behavior. [Preview Abstract] |
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B1.00028: Atomistic origin of doping-enhanced rapid crystallization in Ag-doped Ge-Sb-Te alloys: a joint experimental and theoretical study Binay Prasai, David Drabold, Gang Chen We have applied extended X-ray absorption fine structure (EXAFS) analyses and \textit{ab-initio} molecular dynamics (AIMD) simulations to study the atomic structure of Ag-doped (up to 42{\%}) Ge$_{1}$Sb$_{2}$Te$_{4}$ alloys. Analysis of the models that are consistent with the EXAFS experiment reveals that the Ge environment is significantly modified by Ag doping whereas those of Sb and Te are barely affected (except for high Ag concentrations), and suggests that Ag prefers bonding with Te to Ge or Sb. Doping with Ag promotes the conversion of tetrahedral Ge sites to octahedral Ge sites and enhances the speed of crystallization of Ge-Sb-Te (GST) alloys as evidenced directly from the MD simulations. Our study shed light on the atomistic mechanism of rapid crystallization of GST alloys enhanced by Ag doping. [Preview Abstract] |
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B1.00029: Two-probe Electrical and Thermal Transport Measurements on 50-micron Long Single Crystal ZnGeN$_{2}$ Rods John R. Colvin, Paul C. Quayle, Kathleen Kash, Jeffrey S. Dyck While many modern electrical devices are based on III-nitride semiconductors such as GaN, these devices have some challenges related to the strong polarity of the wurtzite crystal structure and a difficulty in doping them p-type. ZnGeN$_{2}$ is a II-IV-nitride analog to GaN, and the two share very similar crystal structures, lattice parameters, and band-gap energies. ZnGeN$_{2}$ has a number of distinctly different predicted properties, however; in particular, its doping and defect properties and lower spontaneous polarization coefficients. So far, the electrical transport properties of ZnGeN$_{2}$ are not well studied. Recently, high quality, 50-micron long single crystal rods have been grown by a vapor-liquid-solid method. Electrical transport measurements are difficult on such small crystals. In this work, we will present a novel sample stage designed to perform 2-probe electrical measurements under the influence of a temperature gradient on these small crystals, enabling measurements of Seebeck coefficient and resistance. We will discuss modeling of Seebeck coefficient data for ZnGeN$_{2}$ and the design, fabrication, and performance of sample stage prototypes. [Preview Abstract] |
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B1.00030: Eccentricity Distribution of the Initial Conditions for Uranium-Uranium Collisions Andrew Goldschmidt, Zhi Qiu, Ulrich Heinz We provide a case study illustrating how the analysis of relativistic uranium-uranium collisions requires paying careful attention to the collision geometry. Because of the football-like shape of uranium, U-U collisions probe a much larger space of collision geometries than collisions between spherical nuclei such as Pb. In central uranium events, where the colliding nuclei fully overlap with each other, collision orientations can range between two extremes. In side-side events, the major axes of the elliptic uranium nuclei point perpendicular to the beam line, while in tip-tip events the major axes are parallel to the beam direction. These orientations affect both the overlap area of the Lorentz contracted nuclei and the number of collisions between nucleon pairs. Our study looks at these variables in a comparison of the dependence of the initial fireball eccentricity and nuclear overlap area on the total observed multiplicity with what was traditionally found in spherically symmetric gold-gold or lead-lead collisions, where orientation played no role. [Preview Abstract] |
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B1.00031: Measurement of the $^{3}{\rm H}(d,\gamma)$/$^{3}{\rm H}(d,n)$ Branching Ratio at Low Energy Cody Parker, Carl Brune, Thomas Massey, Daniel Sayre, John O'Donnell The branching ratio $^{3}{\rm H}(d,\gamma)^{5}{\rm He}$/$^{3}{\rm H}(d,n)\alpha$ has been measured using a 500-keV pulsed deuteron beam incident on a stopping titanium tritide target, producing a cross-section-weighted average energy of 196 keV. The time-of-flight technique has been used to distinguish the $\gamma$-rays from the neutrons in the bismuth germinate $\gamma$-ray detector. Two stilbene scintillators and an NE-213 scintillator have been used to detect the neutrons using both the pulse-shape discrimination and time-of-flight techniques. The branching ratio has been measured to be (6.9$\pm$1.6)$\times$10$^{-5}$. [Preview Abstract] |
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B1.00032: Other Relations between Distorted Angles vs. Original Angles of a Traveling General Triangle in Special Relativity Florentin Smarandache Let's consider a traveling general triangle $\Delta $\textit{ABC,} with the speed $v$, along its side \textit{BC }on the direction of the $x-$axis; angles $B$ and $C$ are adjacent to the motion direction, while angle $A$ is of course opposite. After the contraction of the side \textit{BC} with the Lorentz factor $C(v)=\sqrt {1-\frac{v^{2}}{c^{2}}} $, and consequently the contractions of the oblique-sides \textit{AB} and \textit{AC} with the oblique-contraction factor \[ OC(v,\theta )=\sqrt {C(v)^{2}\cos^{2}\theta +\sin^{2}\theta } , \] where $\theta $ is the angle between respectively each oblique-side and the motion direction, one gets the general triangle $\Delta A'B'C'$ with the following trigonometric relations between distorted angles \textit{A', B', C'} vs. original angles $A, B, C$ of the general triangle: \[ \frac{\sin A'}{\sin A\cdot C\left( v \right)}=\frac{\sin B'}{\sin B\cdot OC\left( {v,C} \right)}=\frac{\sin C'}{\sin C\cdot OC\left( {v,B} \right)}; \] \[ \cos A'=\cos A\cdot \frac{-\alpha^{2}\cdot C\left( v \right)^{2}+\beta ^{2}\cdot OC\left( {v,C} \right)^{2}+\gamma^{2}\cdot OC\left( {v,B} \right)^{2}}{\left( {-\alpha^{2}+\beta^{2}+\gamma^{2}} \right)\cdot OC\left( {v,C} \right)\cdot OC\left( {v,B} \right)}; \] \[ \tan A'=\frac{\tan A}{C\left( v \right)}\cdot \frac{1-\tan B\cdot \tan C}{1-\tan B\cdot \tan C\cdot C\left( v \right)^{2}}. \] [Preview Abstract] |
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B1.00033: Changing the gravity Philip Shin We can figure out the reason for the world shape by the gravity. The world is not changing as we believe in the gravity. If we change the gravity, the world is changing into the alien. Also the atomic bomb is blowing so the red color is changing into another color, so there is no rule. Before the eschatology, the ant is moving randomly, so there is no standard rule for its moving. When the eschatology comes, the random moving is finished. So we build the gravity as the standard by one. We live the reason to build the gravity, forever. [Preview Abstract] |
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B1.00034: The Law of Density Gravitation Yongquan Han In nature any two objects attract each other mutually and the size of gravitation is determined by gravitational units. The size of the gravitation of gravitational units is directly proportional to the product of the density of these two objects' gravitational units and inversely proportional to the square of the distance between these two objects' gravitational units. The resultant force of all gravitational units between these two objects is the gravitation between these two objects. The calculation formula is F$ = H \cdot \frac{p_{1} \cdot p_{2} }{r^{2}}$. In the nucleus density gravitation is greater than electrostatic force. [Preview Abstract] |
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