Bulletin of the American Physical Society
APS April Meeting 2013
Volume 58, Number 4
Saturday–Tuesday, April 13–16, 2013; Denver, Colorado
Session S2: Poster Session III (2:00 - 5:00pm) |
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Sponsoring Units: APS Room: Plaza Foyer |
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S2.00001: ASTROPHYSICS |
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S2.00002: SOFOS: The Scanning Observatory For Optical SETI Corbin Covault Since the 1960's scientists have searched for evidence of extraterrestrial civilizations using large radio telescopes. However, signals sent at optical wavelengths may be a more promising means of interstellar communications. Such signals may be sent in the form of very rapid (nanosecond) light pulses generated by large lasers. In principle, optical telescopes equipped with high-speed light sensors can be used to detect such signals. Already, several groups have initiated preliminary search efforts. Here we describe the design for the Scanning Observatory For Optical SETI (SOFOS). Our design is modular and can be implemented based on available technology. We use a set of four individual fixed-heading telescope modules to scan the sky as it moves overhead. Each telescope includes a large area Fresnel lens (3.5 by 3.5 meters) and an array of photomultiplier tubes. The lens sits on a tiltable rotation stage allowing access to the entire northern hemisphere sky for signals. The four telescope modules will be operated in coincidence so as to minimize the chance of recording false signals due to background light fluctuations and cosmic ray events. Our design yields a sensitivity to light flashes of less than 10 photons/m$^2$, a significant improvement over prior searches. [Preview Abstract] |
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S2.00003: Flux-freezing breakdown observed in high-conductivity magnetohydrodynamic turbulence C. Lalescu, G. Eyink, K. Kanov, R. Burns, C. Meneveau, A. Szalay, E. Vishniac, H. Aluie, K. B\"urger Alfven's principle of ``frozen-in'' magnetic field lines for ideal plasmas explains diverse astrophysical phenomena, e.g. how proto-stars shed excess angular momentum. But frozen-in lines also preclude rapid changes in magnetic topology observed at high conductivities, e.g. in solar flares. Microphysical processes at scales below the ion gyroradius are a proposed explanation but it is unclear how these lead to rapid reconnection of astrophysical flux structures very much larger. We propose instead that turbulent Richardson advection brings field-lines implosively together to gyroradius separations from distances far apart. Here we report analysis of a simulation of MHD turbulence at high-conductivity that exhibits Richardson dispersion. This effect of advection by rough velocities leads to line-motions that are completely indeterministic or ``spontaneously stochastic,'' as predicted in analytical studies. The turbulent breakdown of standard flux-freezing at scales greater than the ion gyroradius can explain fast reconnection of large-scale flux structures, e.g. post-CME side-lobe magnetic fields reconnecting to an arcade of flare loops. The thick current sheet observed between flare arcade and CME is explained quantitatively by the stochastic flux-freezing due to turbulence. [Preview Abstract] |
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S2.00004: Foreground Removal Methods for Cosmology Large-Angular Scale Surveyor Maximilian Abitbol, Tobias Marriage The Cosmology Large-Angular Scale Surveyor (CLASS) is a new cosmic microwave background (CMB) polarization survey instrument deploying to the Atacama Desert. CLASS will survey over half of the sky to measure the B-mode polarization on $>$2 degree angular scales at 40, 90, and 150 GHz using transition-edge sensor bolometers. In order to estimate cosmological parameters such as the optical depth to reionization, $\tau$, and the tensor-to-scalar ratio, r, we need to remove the significant foreground emission from thermal dust and synchrotron sources from the signal. In this poster we consider template based polarized foreground removal techniques. For CLASS, the 40 and 150 GHz channels will serve to distinguish the spectrally distinct synchrotron and dust emission from the polarized CMB signal. We reproduce both the temperature and polarization template cleaning procedures used by the Wilkinson Microwave Anisotropy Probe (WMAP) team and consider additional template cleaning methods. We apply these statistical foreground removal methods to simulated CLASS CMB polarization maps and extract the B-mode polarization from these cleaned maps. [Preview Abstract] |
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S2.00005: The Helium and Lead Observatory and the Supernova Early Warning System Justin Vasel, Alec Habig, Clarence Virtue A core collapse in the Milky Way will produce an enormous burst of neutrinos that are detectable on Earth. One such detector is the Helium and Lead Observatory (HALO) located at SNOLAB in Ontario, Canada and is the first detector to use lead as an interaction medium for supernova neutrinos. HALO is designed to be a low-maintenance, high-uptime detector dedicated solely to the search for galactic supernova neutrinos. Along with several detectors around the world, HALO will serve as a member of the Supernova Early Warning System (SNEWS), a network designed to alert astronomers as soon as possible after the detected neutrino signal. [Preview Abstract] |
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S2.00006: Local Environmental Characterization using Gamma Ground Survey Network Marc Litz, David Burns, Dimos Katsis, James Carroll Inexpensive gamma detectors with GPS and wireless communications have been developed and installed to provide a ground survey network for detection of environmental levels of gamma radiation from naturally occurring events (i.e. radon, lightening, solar flares, etc.) and unintended gamma radiation on the battlefield and along transport routes. Signals from lightening and cosmic rays have pulse widths less than 100 us. Pedestrian borne and vehicle borne radiation sources have signatures from millseconds to seconds. The large energy associated with solar initiated disruptions (10$^{20}$J) generates a variety of ground level events that can last for hours. Data collected during the 24/7 operation of this gamma network is compared to xray, electron, and ion flux from satellite sensors. Local rainfall data is also utilized to make comparisons to local radon intensity levels. This paper will discuss the time and intensity correlations with corroborating environmental data. If the gamma signals characteristics from local environments and space-based environments can be described with enough detail, it is hoped that automated warning of unexpected radiation events can offer early warning protection to power and energy grid avoiding potentially damaging surges as well as offer local radiation health warning as necessary. [Preview Abstract] |
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S2.00007: ABSTRACT WITHDRAWN |
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S2.00008: Testing Solar Energetic Particle Origin and their Correlations with $\gamma $-ray Flares Using COMPTEL Christopher Wing Impulsive solar particle events, which are short, electron-rich, enriched with $^{\mathrm{3}}$He, are thought to originate from magnetic reconnections low in the corona. During a flare, particles either react in or escape the solar atmosphere, but in any event leave signatures in the form of neutral radiation and in-situ observations. Particles which travel back on closed magnetic field lines may emit $\gamma $-rays as a result. They can be measured by the solar detector COMPTEL. Electrons produce hard X-ray emission and leave signatures of escape in Type III radio burst emission. The goal of this project is to find out whether small impulsive flares are related to the small $^{\mathrm{3}}$He-rich SEPs observed in-situ, using the highly sensitive COMPTEL instrument. The relationship between Gamma Ray Lines (GRL's) and solar energetic particles (SEP) would help us understand where flare particles are accelerated, and how they escape into the interplanetary medium. [Preview Abstract] |
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S2.00009: Measuring Optical Properties of Water in HAWC Stoian Borissov The attenuation properties of water inside the tanks at HAWC affect the detection of Cherenkov photons due to gamma ray induced air showers. Understanding the attenuation properties of the water enables better modeling of the detector response. A Geant4 simulation has been written to describe light propagation in the device used for determining optical attenuation length at HAWC. We discuss systematic uncertainties of the current HAWC method of attenuation measurement. These relate to geometry, such as the diameter of the sensor used to measure attenaution and optical effects such as total internal reflection. We will provide alternative methods of measuring water properties that allow the independent measurement of scattering and absorption length. [Preview Abstract] |
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S2.00010: Spin as a Manifestation of a Nonlinear Constitutive Tensor and a Non-Riemannian Geometry Fredrick W. Cotton The electromagnetic constitutive tensor can be used to introduce a classical form of spin. For charged particles at rest, with no external forces, the spin does not affect the energy density of the particle. The particle solutions satisfy a non-Riemannian form of the Einstein-Maxwell equations. [Preview Abstract] |
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S2.00011: QED Near the Decoupling Temperature Samina Masood We study the effective parameters of QED near the decoupling temperature and show that the QED perturbation theory works perfectly fine at temperatures, below the decoupling temperature. Temperature dependent selfmass of electron, at T $=$ m, gives two different values when approached to the same overlapping point. It ia shown that at T $=$ m, change in thermal contribution of the electron selfmass is 1/3 of the low temperature value and 1/2 of the high temperature value. The difference of behavior measures the electron background contributions at T $=$ m. These electrons are emitted through beta decay. This rise in mass affects the QED parameters and change the electromagnetic properties of the medium with temperature also. However, these contributions are ignorable near the decoupling temperature. [Preview Abstract] |
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S2.00012: Dark Energy: As A Fact of Matter Richard Bowen At the current time Dark Energy has been attributed to a property of space itself, ie. the vacuum energy of space. This explanation does not account for the inflationary expansion of the early universe nor does it explain the flatness of the universe. If however, Dark Energy is considered to be a property of matter, these issues are resolved. The Space Production Model of Gravity proposes that matter is converted to and emits space. The amount of space emitted per unit time is proportionate to mass by the formula: 4$\pi $(2G$m$/$c^{2})^{2}(c)$ Where: G $=$ gravitational constant $m =$ mass $c =$ speed of light Using this formula and the observed Hubble constant one can calculate the mass of the universe to be 5.441x10$^{\mathrm{53\thinspace }}$kg. One can also calculate the size of the universe at a given age. 1.36x10$^{20}$ cubic meters of new space is produced per planck time. Therefore one planck time after the Big Bang the radius of the universe was 3164 kilometers; after 1 second 88515 light years; and after 13.7 billion years 67 billion light years. The ``Flatness'' problem is also resolved. More massive gravitationally bound objects will produce more volume per unit time than less massive objects. This means that the rate of expansion of the universe is dependent upon the local mass density, the higher the density the greater the rate of expansion. Over time this produces a universe that is extremely homogenous. If the Space Production Model is true, the current Dark Energy survey should reveal that more massive gravitationally bound objects such as galaxy super-clusters recede slightly faster than much less massive lone galaxies at the same distance. [Preview Abstract] |
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S2.00013: Spiral Galaxy Formation, Shape, Rotation and Evolution: A Perspective withOUT Mysterious Dark Matter C.F. Gallo, James Q. Feng Various models for Spiral Galaxies are compared to arrive at the following viewpoint. (1)Peratt theoretically displays the formation and evolution of galaxies from hot plasma with a combination of gravity and electromagntic plasma effects, particularly circulating currents. The sequence proceeds from Elliptical to Irregular to stable Spiral Disc Galaxies. The spirals are initiated by radial EM plasma jets oriented around magnetic fields. (2)DeSouza observes/analyzes young spiral galaxies in the process of forming their spiral shapes. He observes radial Jets initiating from the central Bulge and evolving into full trailing spirals in agreement with Peratt's EM plasma simulations. (3) Feng and Gallo have successfully analyzed galactic rotation data with Newtonian gravity/dynamics withOUT Mysterious Dark Matter. Our model represents mature spiral disk galaxies whose behavior is dominated by gravity since the plasma has mostly condensed into stars at this late stage. This situation in similar to our gravity dominated Solar System. (4) All three models are based on known verified physics withOUT Mysterious Dark Matter. [Preview Abstract] |
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S2.00014: MEST-a special orbit of dark comet Dayong Cao ``Like mass attract, like energy repel each other.'' A mass-energy oscillation can produce a mass-energy wave which can build up a mass-energy field like a space-time field of the mass-energy, because the space-time is frequency and amplitude square. The Big Bang system has an energy center which makes a repulsive gravity and a negative curvature like dark energy. But a light has the space-time of itself. When a light travels in the universe, its quantum space-time will convert to a universal space-time. It will cause Hubble's red shift by itself. So we need find a new balance system of the flat universe. The Sun and Tyche-dark hole build up a system by a conversation of mass-energy and space-time. The dark hole and the dark comet (like a kind of antimatter or Dark matter) are mainly space-time while mass-energy is ancillary. They have their space-time center which is different from a mass-energy center of the solar system, which is mainly mass-energy while space-time is ancillary. The dark comets belt is around the dark hole. When the dark hole goes near the solar system, it will take the dark comets belt and the asteroids belt to impact planets. With a mass-energy and space-time coordinates, a relationship between the sun and the dark hole decides a special elliptical orbit both of a dark comet and asteroid who will hit on the solar system. We need use a space-time effect to change the orbit of dark hole, dark comet and asteroid which will impact our earth to avoid next impaction. A little asteroid hit on the ground of Russia on Feb. 15th, 2013. It authenticates my supposition that ``their new impaction will come in 20 years.'' [Preview Abstract] |
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S2.00015: SEPHIROT: Scenario for Universe-Creation AUTOMATICALLY from Digits On-Average Euler-Bernoulli-Kummer-Riemann-Newcomb-Poincare-Weyl-Benford-Kac-Raimi-Hill-Antonoff-Siegel ``Digit-Physics'' Logarithm-Law: ``It's a Jack-in-the-Box Universe'': EMET/TRUTH!!! Edward Carl-Ludwig Siegel, Frederic Young, Janis Wignall SEPHIROT: Siegel[http://fqxi.org/community/forum/topic/1553]: Ten-[0$\to $9]-Digits; Average Log-Law SCALE-Invariance; Utter-Simplicity: ``Complexity'' (vs. ``Complicatedness''); Zipf-law/Hyperbolicity/ Inevitability SCENARIO AUTOMATICALLY CREATES {\&} EVOLVES a UNIVERSE: inflation, a big-bang, bosons(E)$\to $Mellin-(c\textasciicircum 2)-tranform$\to $fermions(m), hidden-dark-energy(HDE), hidden-dark-matter (HDM), cosmic-microwave-background(CMB), supersymmetry(SUSY), PURPOSELY NO: theories,models,mechanisms,processes, parameters,assumptions,\textellipsis WHATSOEVER: It's a ``Jack-in-the-Box'' Universe!!!: ONLY VIA: Newcomb [Am.J.Math.4(1),39(1881)]\textbraceleft QUANTUM-discovery!!!\textbraceright -Benford-Siegel-Antonoff[AMS.Joint-Mtg.(02)-Abs.{\#}973-60-124!!!] inversion to ONLY BEQS with d$=$0 BEC: ``Digit-Physics''!; Log fixed-point invariance(s): [base$=$units$=$SCALE] of digits classic (not classical!) average [CAUSING] log statistical-correlations $\langle $P(d)$\rangle =$log(1$+$1/d), with physics-crucial d$=$0 BEC singularity/pole, permits SEPHIROT!!!: ``digits are quanta are bosons because bosons are and always were digits!!!'': Digits $=$ Bosons with d$=$0 BEC(!!!) {\&} expansion to \textasciitilde Zipf-law Hyperbolicity INEVITABILITY CMB! [Preview Abstract] |
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S2.00016: Interstellar gamma-ray emission observed by the Fermi Large Area Telescope as a cosmic-ray tracer Elliott Bloom, Luigi Tibaldo The Large Area Telescope (LAT) aboard the Fermi Gamma-ray Space Telescope continuously surveys the high-energy gamma-ray sky in the energy band from 20 MeV to more than 300 GeV. The majority of the photons detected by the LAT are of interstellar origin, produced by interactions of high-energy cosmic rays with gas and low-energy radiation fields. This interstellar gamma-ray emission is a unique tracer of cosmic rays outside the solar system where direct measurements are not possible. I will present the most important results concerning interstellar emission from more than four years of LAT observations. LAT data are granting us access to a wealth of new information on the cosmic-ray environment in the local interstellar medium, in nearby regions of massive-star formation, throughout the Milky Way and up to external galaxies and the intergalactic space. I will discuss how these results are improving our understanding of the century-long puzzle of cosmic-ray origin and propagation. [Preview Abstract] |
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S2.00017: First Very High-Energy Gamma-Ray Observations of the Eclipsing Millisecond Pulsar PSR J1023+0038 Andrew Loo The eclipsing millisecond pulsar PSR J1023+0038 exhibits many similar characteristics to PSR B1259-69 but at a smaller scale, making it an ideal candidate for the study of high-energy non-thermal emission. We present here the first very high-energy (VHE) gamma-ray observations of PSR J1023+0038, carried out by VERITAS between December 2010 and February 2011. No gamma-ray signal has been detected either from a steady search of the whole data or in any of the orbital phases during this observational period. The prospects for detecting this type of system with more sensitive detectors will also be discussed. [Preview Abstract] |
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S2.00018: Using CCI to unravel the states of GRS 1915+105 Charith Peris, Stewart Buchan, Saeqa Vrtilek We use Color-Color-Intensity (CCI) diagrams (Vrtilek \& Boroson, 2012) to explore the states of the black hole binary (BHB) system GRS 1915+105. Assuming the changes in the loci of these states in the CCI phase space to be due to intrinsic properties of the sources (such as mass accretion rate and radio jets), we analyze the regions of CCI phase space and its relation to these properties. We explore the possible correlation of mass accretion rate and X-ray color. We find no simple trend in mass accretion rate on the HR1-HR2 plane. We also plot the jet-line proposed by Fender et al. (2004) in CCI phase space and compare the jet and non-jet states of another GRS-like system, 4U 1630-472. We find that the states of 4U 1630-472 are compatible with the jet-line. [Preview Abstract] |
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S2.00019: Two bodies gravitational systems with variable mass and damping-antidamping effect due to star wind Gustavo Lopez Velazquez, Esmeralda Juarez We study two-bodies gravitational problem where the mass of one of the bodies varies and suffers a damping-anti damping effect due to star wind during its motion. A constant of motion, a Lagrangian and a Hamiltonian are given for the radial motion of the system, and the period of the body is studied using the constant of motion of the system. An application to the comet motion is given, using the comet Halley as an example. [Preview Abstract] |
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S2.00020: Dark Matter, Dark Energy and General Relativity Jacques Leibovitz From an earlier model of DM, we derived: An equation of state for DM. An equation governing the coupled distributions of baryonic and dark matters; galactic flat rotation curves; the Tully-Fisher relation; Milgrom's MOND relation; and a mechanism for the accelerated expansion of the Universe (J of Modern Physics, Dec. 2011). In the present paper, we add the derivation of: a mechanism for the formation of a super massive black hole at the center of every large galaxy; a rational for the finding (by Oort) that the Sun mass on the Solar Neighborhood scale is twice that found on the Solar System scale. Results are discussed; we conclude that general relativity may neither be applied to DM nor to the description of the Universe and its evolution. The correct description must be based not on General Relativity but on Newton's Gravitation, on the proposed model of DM, and on Einstein's relativity of 1905. [Preview Abstract] |
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S2.00021: Black Hole Firewalls and Lorentzian Relativity Friedwardt Winterberg In a paper published (Z. f. Naturforsch. 56a, 889, 2001) I had shown that the pre-Einstein theory of relativity by Lorentz and Poincare, extended to the general theory of relativity and quantum mechanics, predicts the disintegration of matter by passing through the event horizon. The zero point vacuum energy is there cut-off at the Planck energy, but Lorentz-invariant all the way up to this energy. The cut-off creates a distinguished reference system in which this energy is at rest. For non-relativistic velocities relative to this reference system, the special and general relativity remain a good approximations, with matter held together in a stable equilibrium by electrostatic forces (or forces acting like them) as a solution of an elliptic partial differential equation derived from Maxwell's equation. But in approaching and crossing the velocity of light in the distinguished reference system, which is equivalent in approaching and crossing of the event horizon, the elliptic differential equation goes over into a hyperbolic differential equation (as in fluid dynamics from subsonic to supersonic flow), and there is no such equilibrium. According to Schwarzschild's interior solution, the event horizon of a collapsing mass appears first as a point in its center, thereafter moving radially outwards, thereby converting all the mass into energy, explaining the observed gamma ray bursters. [Preview Abstract] |
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S2.00022: GRAVITATION |
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S2.00023: Parameter Biases Introduced by Approximate Gravitational Waveforms Benjamin Farr, Scott Coughlin, John Le, Connor Skeehan, Vicky Kalogera The production of the most accurate gravitational waveforms from compact binary mergers require Einstein's equations to be solved numerically, a process far too expensive to produce the $\sim$10$^7$ waveforms necessary to estimate the parameters of a measured gravitational wave signal. Instead, parameter estimation depends on approximate or phenomenological waveforms to characterize measured signals. As part of the Ninja collaboration, we study the biases introduced by these methods when estimating the parameters of numerically produced waveforms. [Preview Abstract] |
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S2.00024: Conformal Gravity and the Alcubierre Warp Drive Metric Gabriele Varieschi, Zily Burstein We present an analysis of the classic Alcubierre metric based on conformal gravity, rather than standard general relativity. The main characteristics of the resulting warp drive remain the same as in the original study by Alcubierre, namely that effective super-luminal motion is a viable outcome of the metric. We show that for particular choices of the shaping function, the Alcubierre metric in the context of conformal gravity does not violate the weak energy condition, as was the case of the original solution. In particular, the resulting warp drive does not require the use of exotic matter. Therefore, if conformal gravity is a correct extension of general relativity, super-luminal motion via an Alcubierre metric might be a realistic solution, thus allowing faster-than-light interstellar travel. [Preview Abstract] |
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S2.00025: ABSTRACT MOVED TO SESSION X10 |
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S2.00026: Characteristic Extraction using Spin-Weighted Spherical Harmonics and Fourier Continuation Casey Handmer Accurate prediction of gravitational wave signatures for LIGO science require simulation of wave propagation over vast distances. The non-linear nature of GR has necessitated research into techniques including Cauchy Characteristic Extraction (CCE), and Matching to allow feedback over the local simulation boundary. Here, we present a spectral approach to CCE using an integral formalism. This is permitted by the recent development of Fourier continuation (FC), an FFT-fast spectrally accurate basis function with uniform collocation points and thus a relaxed Courant condition. [Preview Abstract] |
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S2.00027: The Global Non-Holonomity of the Rotating Space of the Earth Affects Hafele-Keating Experiment Dmitri Rabounski, Larissa Borissova The deviation of time registered in the ``around-the-world clocks experiment'' (Hafele~J. and Keating~R., Science, 14 July 1972, 166-170) is originally explained due to: 1)~General Relativity (gravitation is lower at the flying airplane's altitude); 2)~Special Relativity (the~airplane's speed and the~Earth's rotation). However as was shown in the 1940's by Schouten and then Zelmanov, if the observer cannot be moved to the rotation-free frame, the space rotation is a non-vanishing effect of General Relativity, and is due to the non-holonomity of space (the~non-orthogonality of the three-space to the lines of time). This is the case of Hafele-Keating experiment (the Earth's rotation cannot be stopped). We thus constructed the metric of the real space of the Earth which bears the gravitational field and rotation. We then proved that this metric satisfies Einstein's equations. Finally, an exact formula is deduced for Hafele-Keating experiment. Despite a hundred nanoseconds of the time correction, and the use of the GPS navigation, the obtained result is useful in the case where is no the GPS connexion, in a long-term submarine travel for instance. [Preview Abstract] |
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S2.00028: ENERGY RESEARCH AND APPLICATIONS |
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S2.00029: The Effect of mechanical alloying on Electrical properties of BaTiO3 Nano crystals Masoud Mollaee, Mahmoud Rezaee, Mahdieh Zaboli In this paper, electrical properties of BaTiO3 Nano crystals have been studied, Barium Titanate Nano crystals are made by mechanical alloying method in a ball mill of SPEX 8000. For determining Curie temperature, the diagrams of dielectric constant variation via temperature and hysteresis are used. Our results show that, there is a relationship between the time of milling and the curie temperature. this means with increasing milling time and decreasing particle size the curie temperature of samples decreases. In addition, with increasing temperature up to the Curie temperature, the hysteresis loop of samples decreases and in the Curie temperature the hysteresis loop changes to a straight line and also the width of hysteresis loops samples decreases when the temperature increases and it reaches to zero at Curie temperature. [Preview Abstract] |
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S2.00030: Preparation and Characterization of SnO2 thin films deposited by Chemical Bath Deposition method Gbadebo T. Yusuf, Adepoju M. Raimi, Timothy O. Familusi, Ayodeji O. Awodugba, Hezekiah O. Efunwole SnO2 thin films have been deposited onto the soda lime glass substrates by the chemical bath deposition method. The structural and optical properties of the SnO2 thin films were investigated. Tin chloride solution (SnCl$_{2})$ and methanol were used as starting materials at substrate temperature 300$^{\circ}$C. The crystal structure and orientation of the SnO$_{2}$ thin films were investigated by X-ray diffraction (XRD) patterns. The average grain size of the films was calculated using the Scherer formula and was found to be 29.6 nm which increased to 30.04nm after annealing in air at 400$^{\circ}$C. The optical absorbance and transmittance measurements were recorded by using spectrophotometer. The average transmittance of the film was around 80 {\%} at wavelength 550 nm. The optical band gap of the thin films was determined and found to be 3.71eV. The gas sensing properties of tin oxide thin films obtained in this work could be performed for different gases like CO, CH4, H2S, H2 etc. [Preview Abstract] |
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S2.00031: Optical Properties of Sputter-Deposited Tungsten-Doped Gallium Oxide Thin Films Ernesto Rubio, C.V. Ramana Gallium oxide (Ga$_{2}$O$_{3})$ finds attractive applications in luminescent phosphors, high temperature sensors, antireflection coatings, and solar cells. With a band gap of $\sim$5 eV, Ga$_{2}$O$_{3}$ has been recognized as a deep ultraviolet transparent conducting oxide, which makes the material a potential candidate for transparent electrode applications in UV optoelectronics. In this work, effect of tungsten (W) doping on the structure and optical properties of Ga$_{2}$O$_{3}$ has been investigated. W-metal doped $\beta $-Ga$_{2}$O$_{3}$ films grown by sputter deposition by varying the sputtering power from 50-100 W to vary tungsten concentration in the films. The samples were deposited on to Si(100) and quartz substrates by keeping the growth temperature constant at 500 $^{\circ}$C. It is seen that increasing W concentration alters the electronic structure of Ga$_{2}$O$_{3}$ while the crystal structure of $\beta $-Ga$_{2}$O$_{3}$ phase is retained. Spectrophotometry analysis indicates that the W-doped Ga$_{2}$O$_{3}$ films are highly transparent. The fundamental absorption edge shifts associated with a decrease in band gap energy. The results will be presented and discussed. [Preview Abstract] |
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S2.00032: Efficient thermophotovoltaic solar cells on bent substrates Gagik Shmavonyan, Ovsanna Zadoyan Thermophotovoltaic devices show promise as a method of reclaiming waste industrial heat and may provide a competitive and quiet low output heat conversion power supply for remote rural areas. GaSb based devices are well matched to a 1500-2000$^{\circ}$C blackbody emission temperature as well as to the solar spectrum when paired with GaAs. The growth of GaSb on GaAs proceeds via the Stranski-Krastanow mechanism, resulting in rectangular islands of GaSb with their edges orientated along the \textless 110\textgreater directions. The size of the islands is dependent on the growth temperature with smaller islands being produced for lower temperatures. The rectification behavior of p-GaSb/n-GaAs heterojunctions is also strongly dependent on the growth temperature. Possible mechanisms for the rectification at low temperature include more rapid turnover of interface dislocations and a corresponding reduction in carrier generation/recombination processes or passivation of defect centres by greater incorporation of impurities such as hydrogen. By optimizing the growth conditions, efficient p-GaSb/n-GaAs thermophotovoltaic devices have been produced. A series of GaSb and GaAs epilayers grown onto substrates has been used to investigate the effect of bent substrate on external quantum efficiency and spectral response. [Preview Abstract] |
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S2.00033: ABSTRACT WITHDRAWN |
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S2.00034: Electrical and thermal conductivity of hybrid nanocomposites with giant strain Kyoung-Yong Chun, Shi Hyeong Kim, Min Kyoon Shin, Geoffrey M. Spinks, Ali E. Aliev, Ray H. Baughman, Seon Jeong Kim The prospect of electronic circuits that are stretchable and bendable promises tantalizing applications such as skin-like electronics, conformable sensors, and lightweight solar cells. The optimization of electronic, thermal, and mechanical properties of conductive and extensible materials is necessary for the application of energy device. Here we demonstrate the theoretical prediction for the electrical conductivity of the nanocomposites compared with experimental results. Also, we present the giant dependence of electrical conductivity on strain and the large positive thermal expansion that can be expected for the elastomer matrix. The percolation threshold (26 vol\% of Ag, average interparticle distance model) and Poisson's ratio (Vt=0.33, Vw=0.2) of nanocomposites are significant factors that can determine the electrical and thermal conductivity with giant strain. The thermal conductivity for the electronically conducting elastomeric film is relatively high at the zero-strain state, and shows a non-metallic temperature dependence consistent with phonon transport. The observed combinational property of a very small dependence of conductivity on temperature with an exponential dependence can be suitable for for the mechanical strain sensing. [Preview Abstract] |
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S2.00035: COMPUTATIONAL PHYSICS |
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S2.00036: Graphics processing units as tools to predict mechanisms of biological signaling pathway regulation Patrick McCarter, Timothy Elston, Michal Nagiek, Henrik Dohlman Biochemical and genomic studies have revealed protein components of \textit{S. cerevisiae} (yeast) signal transduction networks. These networks allow the transmission of extracellular signals to the cell nucleus through coordinated biochemical interactions, resulting in direct responses to specific external stimuli. The coordination and regulation mechanisms of proteins in these networks have not been fully characterized. Thus, in this work we develop systems of ordinary differential equations to characterize processes that regulate signaling pathways. We employ graphics processing units (GPUs) in high performance computing environments to search in parallel through substantially more comprehensive parameter sets than allowed by personal computers. As a result, we are able to parameterize larger models with experimental data, leading to an increase in our model prediction capabilities. Thus far these models have helped to identify specific mechanisms such as positive and negative feedback loops that control network protein activity. We ultimately believe that the use of GPUs in biochemical signal transduction pathway modeling will help to discern how regulation mechanisms allow cells to respond to multiple external stimuli. [Preview Abstract] |
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