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2014

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Articles 241 - 270 of 434

Full-Text Articles in Astrophysics and Astronomy

Developing Microwave-Generated Hydrogen Atoms As A Reducing Agent For Tungsten Atomic Layer Deposition, Jason Kyle Anderson, Dr. David Allred Apr 2014

Developing Microwave-Generated Hydrogen Atoms As A Reducing Agent For Tungsten Atomic Layer Deposition, Jason Kyle Anderson, Dr. David Allred

Journal of Undergraduate Research

Traditional micro fabrication processes are confined to a small subset of possible materials due to limitations on etching and are confined to low aspect ratio fabrication due to limits in both etching and stability of thicker film deposition processes.

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Generation Of A Low Velocity Controlled Beam Of Sr Ions, Jarom Jackson, Dr. Dallin Durfee Apr 2014

Generation Of A Low Velocity Controlled Beam Of Sr Ions, Jarom Jackson, Dr. Dallin Durfee

Journal of Undergraduate Research

The purpose of this project was to produce a slow controlled beam of Strontium (Sr) ions. This is a key step in a proposed experiment to build an ion interferometer capable of measuring electric fields to a degree of sensitivity that has never been done before. This device will be useful in conducting a number of new experiments and will help test and push the boundaries of modern electromagnetic theory.

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Modeling Supernovae Light Curves: A Vital Step Toward Photometric Classification, Brittany Spencer, Dr. Shane Reese Apr 2014

Modeling Supernovae Light Curves: A Vital Step Toward Photometric Classification, Brittany Spencer, Dr. Shane Reese

Journal of Undergraduate Research

Type Ia supernovae play a critical role in understanding the nature of the evolving universe. The Dark Energy Survey is currently investigating the expansion rate of the universe, with the intent to gain insight into the nature of dark energy. One of their primary measures of expansion is Type Ia supernovae (DES Projects, 2011). Due to this type of supernova’s uniformity in formation, most supernova of this type explode to approximately the same absolute brightness (Goobar, 2011).

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Development Of A Surface Magneto-Optic Kerr Effect Magnetometer, Susan Stoffer Sorensen, Dr. Karine Chesnel Apr 2014

Development Of A Surface Magneto-Optic Kerr Effect Magnetometer, Susan Stoffer Sorensen, Dr. Karine Chesnel

Journal of Undergraduate Research

The Kerr effect is a phenomenon in which as polarized visible light reflects off of a magnetized surface it experiences a small rotation in polarization. This is known as the Kerr rotation, denoted Δθ. This rotation is proportional to the magnetization of the sample, to a first-order approximation (Δθ∝M). The surface magneto-optic Kerr effect (SMOKE) is a subset of the Kerr effect which probes the magnetization of the surface of the sample. Since the samples measured by our SMOKE apparatus are as thin as 10 nm to 100 nm the surface magnetization equals the total magnetization. These samples can be …

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Superparamagnetic Behavior Of Magnetite Nanoparticles: Preparation And Characterization, Matea Trevino, Dr. Karine Chesnel Apr 2014

Superparamagnetic Behavior Of Magnetite Nanoparticles: Preparation And Characterization, Matea Trevino, Dr. Karine Chesnel

Journal of Undergraduate Research

Magnetite (Fe3O4) nanoparticles have the unique ability of being superparamagnetic. When no field is applied to the nanoparticles, the nanoparticles’ assembly has a net magnetization of zero, meaning that the nanoparticles’ magnetic moments align in random positions leading to a net magnetization of zero. When a field is applied, the particles’ magnetic moments align with the magnetic field. This is considered superparamagnetic because this is looked at on the nanometer (nm) scale and not the atomic scale. Being able to understand this phenomenon will open up many doors in technology and medical usage. Nanocrystals, such as Fe3O4 particles, are good …

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Femtosecond Frequency Comb Lock, Daniel Thrasher, Dr. Scott Bergeson Apr 2014

Femtosecond Frequency Comb Lock, Daniel Thrasher, Dr. Scott Bergeson

Journal of Undergraduate Research

Laser frequency control is imperative for cold atom experimentation. In our lab we use finely tuned lasers to optically cool and trap calcium atoms. Our ability to successfully trap atoms is highly dependent on the stability of the lasers we use to cool them. After trapping the atoms we use more finely tuned lasers to reveal how cold the atoms are and how quickly they leave our trap. Previous to this work our lasers were limited to 20 MHz precision. By installing a femtosecond laser as a standard by which to stabilize the other lasers in our experiment we successfully …

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Dynamics Of Multi-Spin Systems : Landau-Lifshitz-Gilbert Model And Ferromagnetic Pattern Formation, Soyoung Jung, Dr. Manuel Berrondo Apr 2014

Dynamics Of Multi-Spin Systems : Landau-Lifshitz-Gilbert Model And Ferromagnetic Pattern Formation, Soyoung Jung, Dr. Manuel Berrondo

Journal of Undergraduate Research

Modeling has been an important part of many fields of research. Even though it sometimes could be considered to be non-practical, it has sharpened the questions and has been a useful tool for experimental research to understand what is being observed in the laboratory. Likewise, the Heisenberg model constitutes an essential stepping stone to understand anti/ferromagnetism in magnetic materials. We have been able to develop a spin model using Landau-Lifshitz-Gilbert equation enhanced with anisotropy and long range interaction that is comparable to experimental results.

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Optical Isolation Via Pt-Symmetric Nonlinear Fano Resonances, F. Nazari, N. Bender, Hamidreza Ramezani, M. K. Moravvej-Farshi, D. N. Christodoulides, T. Kottos Apr 2014

Optical Isolation Via Pt-Symmetric Nonlinear Fano Resonances, F. Nazari, N. Bender, Hamidreza Ramezani, M. K. Moravvej-Farshi, D. N. Christodoulides, T. Kottos

Physics & Astronomy Faculty Publications

We show that Fano resonances created by twoPT -symmetric nonlinear micro-resonators coupled to a waveguide, have line-shape and resonance position that depends on the direction of the incident light. We utilize these features in order to induce asymmetric transport, up to 47 dBs, in the optical C-window. Our theoretical proposal requires low input power and does not compromise the power or frequency characteristics of the output signal.

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Gravitational Waves From Known Pulsars: Results From The Initial Detector Era, J. Aasi, J. Abadie, B. P. Abbott, Teviet Creighton, Mario C. Diaz, Soma Mukherjee, Walter Ortega Larcher, Volker Quetschke, Malik Rakhmanov, Joseph D. Romano Apr 2014

Gravitational Waves From Known Pulsars: Results From The Initial Detector Era, J. Aasi, J. Abadie, B. P. Abbott, Teviet Creighton, Mario C. Diaz, Soma Mukherjee, Walter Ortega Larcher, Volker Quetschke, Malik Rakhmanov, Joseph D. Romano

Physics & Astronomy Faculty Publications

We present the results of searches for gravitational waves from a large selection of pulsars using data from the most recent science runs (S6, VSR2 and VSR4) of the initial generation of interferometric gravitational wave detectors LIGO (Laser Interferometric Gravitational-wave Observatory) and Virgo. We do not see evidence for gravitational wave emission from any of the targeted sources but produce upper limits on the emission amplitude. We highlight the results from seven young pulsars with large spin-down luminosities. We reach within a factor of five of the canonical spin-down limit for all seven of these, whilst for the Crab and …

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The Link Between Shocks, Turbulence And Magnetic Reconnection In Collisionless Plasmas, H. Karimabadi, V. Roytershteyn, H. X. Vu, Y. Omelchenko, J. Scudder, W. Daughton, A. Dimmock, Katariina (Heidi) Nykyri, Et Al. Apr 2014

The Link Between Shocks, Turbulence And Magnetic Reconnection In Collisionless Plasmas, H. Karimabadi, V. Roytershteyn, H. X. Vu, Y. Omelchenko, J. Scudder, W. Daughton, A. Dimmock, Katariina (Heidi) Nykyri, Et Al.

Publications

Global hybrid (electron fluid, kinetic ions) and fully kinetic simulations of the magnetosphere have been used to show surprising interconnection between shocks, turbulence and magnetic reconnection. In particular collisionless shocks with their reflected ions that can get upstream before retransmission can generate previously unforeseen phenomena in the post shocked flows: (i) formation of reconnecting current sheets and magnetic islands with sizes up to tens of ion inertial length. (ii) Generation of large scale low frequency electromagnetic waves that are compressed and amplified as they cross the shock. These 'wavefronts' maintain their integrity for tens of ion cyclotron times but eventually …

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Event-Plane-Dependent Dihadron Correlations With Harmonic VN Subtraction In Au + Au Collisions At √SNn=200 Gev, H Agakishiev, M. M. Aggarwal, Z. Ahammed, A. V. Alakhverdyants, I. Alekseev, J. Alford, B. D. Anderson, C. D. Anson, D. Arkhipkin, G. S. Averichev, Renee H. Fatemi, Robert G. Fersch, Wolfgang Korsch, G. Webb, Wayne Otto Witzke Apr 2014

Event-Plane-Dependent Dihadron Correlations With Harmonic VN Subtraction In Au + Au Collisions At √SNn=200 Gev, H Agakishiev, M. M. Aggarwal, Z. Ahammed, A. V. Alakhverdyants, I. Alekseev, J. Alford, B. D. Anderson, C. D. Anson, D. Arkhipkin, G. S. Averichev, Renee H. Fatemi, Robert G. Fersch, Wolfgang Korsch, G. Webb, Wayne Otto Witzke

Physics and Astronomy Faculty Publications

STAR measurements of dihadron azimuthal correlations (Δϕ) are reported in midcentral (20–60%) Au + Au collisions at √sNN = 200 GeV as a function of the trigger particle's azimuthal angle relative to the event plane, ϕs = |ϕt − ψEP |. The elliptic (v2), triangular (v3), and quadratic (v4) flow harmonic backgrounds are subtracted using the zero yield at minimum (ZYAM) method. The results are compared to minimum-bias d + Au collisions. It is found that a finite near-side (|Δϕ| < π/2) long-range pseudorapidity correlation (ridge) is present in the in-plane direction (ϕs∼0). The …

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Ds/Cft At Uniform Energy Density And A De Sitter “Bluewall”, Diptarka Das, Sumit R. Das, K. Narayan Apr 2014

Ds/Cft At Uniform Energy Density And A De Sitter “Bluewall”, Diptarka Das, Sumit R. Das, K. Narayan

Physics and Astronomy Faculty Publications

We describe a class of spacetimes that are asymptotically de Sitter in the Poincare slicing. Assuming that a dS/CFT correspondence exists, we argue that these are gravity duals to a CFT on a circle leading to uniform energy-momentum density, and are equivalent to an analytic continuation of the Euclidean AdS black brane. These are solutions with a complex parameter which then gives a real energy-momentum density. We also discuss a related solution with the parameter continued to a real number, which we refer to as a de Sitter “bluewall”. This spacetime has two asymptotic de Sitter universes and Cauchy horizons …

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Characterizing The Quiescent X-Ray Variability Of The Black Hole Low-Mass X-Ray Binary V404 Cyg, F Bernardini, E. M. Cackett Apr 2014

Characterizing The Quiescent X-Ray Variability Of The Black Hole Low-Mass X-Ray Binary V404 Cyg, F Bernardini, E. M. Cackett

Physics and Astronomy Faculty Research Publications

We conducted the first long-term (75 d) X-ray monitoring of the black hole low-mass X-ray binary V404 Cyg, with the goal of understanding and characterizing its variability during quiescence. The X-ray light curve of V404 Cyg shows several flares on time-scales of hours with a count rate change of a factor of about 5–8. The root-mean-square variability isFvar = 57.0 ± 3.2 per cent. The first-order structure function is consistent with both a power spectrum of index −1 (flicker noise), or with a power spectrum of index 0 (white noise), implying that the light curve is variable on …

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Design And Implementation Of A Laser Locking Apparatus, Jarom Jackson, Dr. Dallin Durfee Apr 2014

Design And Implementation Of A Laser Locking Apparatus, Jarom Jackson, Dr. Dallin Durfee

Journal of Undergraduate Research

The experiment which we are building here in Dr. Durfee’s lab is a novel one, the key part of which is an ion interferometer. The interferometer consists of a beam of Sr+ ions which will be split in half. The two halves of the beam will travel along different paths, and then be recombined. Depending on the difference of phase of the two beams on recombining they may either constructively or destructively interfere with each other. Since the phase change of each beam depends on the potential energy along the path that beam follows, this will allow us to very …

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The Calculation Of H-Beta Indices For Delta Scuti Variable Stars, Kelsey Jorgenson, Dr. Eric Hintz Apr 2014

The Calculation Of H-Beta Indices For Delta Scuti Variable Stars, Kelsey Jorgenson, Dr. Eric Hintz

Journal of Undergraduate Research

A large part of astronomical research involves gathering information about celestial objects and drawing conclusions about that information. Astronomers commonly gather data for research projects via sweeping surveys, either of particular regions of the sky or of specific kinds of stars or celestial objects. Data from these surveys are often arranged into catalogues. The aim of my research project was to fill in information gaps in the catalogue of information of known delta Scuti variable stars, particularly in the form of the hydrogen beta, or H-beta, index. I will give introductory information about delta Scuti stars as well as the …

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A Chandra Grating Observation Of The Dusty Wolf-Rayet Star Wr 48a, Svetozar A. Zhekov, Marc Gagne, Stephen L. Skinner Apr 2014

A Chandra Grating Observation Of The Dusty Wolf-Rayet Star Wr 48a, Svetozar A. Zhekov, Marc Gagne, Stephen L. Skinner

Earth & Space Sciences Faculty Publications

No abstract provided.

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Lensed Type Ia Supernovae As Probes Of Cluster Mass Models, J Nordin, David Rubin, J Richard, E Rykoff, Greg Aldering, R Amanullah, H Atek, K Barbary, S Deustua, H K. Fakhouri, A S. Fruchter, A Goobar, I Hook, E Y. Hsiao, Xiaosheng Huang, J P. Kneib, C Lidman, J Meyers, S Perlmutter, C Saunders, A L. Spadafora, N Suzuki Apr 2014

Lensed Type Ia Supernovae As Probes Of Cluster Mass Models, J Nordin, David Rubin, J Richard, E Rykoff, Greg Aldering, R Amanullah, H Atek, K Barbary, S Deustua, H K. Fakhouri, A S. Fruchter, A Goobar, I Hook, E Y. Hsiao, Xiaosheng Huang, J P. Kneib, C Lidman, J Meyers, S Perlmutter, C Saunders, A L. Spadafora, N Suzuki

Physics and Astronomy

Using three magnified Type Ia supernovae (SNe Ia) detected behind CLASH (Cluster Lensing and Supernovae with Hubble) clusters, we perform a first pilot study to see whether standardizable candles can be used to calibrate cluster mass maps created from strong lensing observations. Such calibrations will be crucial when next-generation Hubble Space Telescope cluster surveys (e.g. Frontier) provide magnification maps that will, in turn, form the basis for the exploration of the high-redshift Universe. We classify SNe using combined photometric and spectroscopic observations, finding two of the three to be clearly of Type Ia and the third probable. The SNe exhibit …

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Dipole Bound Excited States Of Polycyclic Aromatic Hydrocarbons Containing Nitrogen And Their Relation To The Interstellar Medium, Mallory L. Theis Apr 2014

Dipole Bound Excited States Of Polycyclic Aromatic Hydrocarbons Containing Nitrogen And Their Relation To The Interstellar Medium, Mallory L. Theis

Honors College Theses

Polycyclic aromatic hydrocarbons (PAHs) are the most abundant type of molecule present in the interstellar medium (ISM). It has been hypothesized that nitrogen replacement within a ring is likely for PAHs present in the ISM. Additionally, electrons, protons, and hydrogen atoms are readily added to or removed from PAHs creating a truly diverse set of chemistries in various interstellar regions. The presence of a nitrogen within a PAH (called a PANH herein) that is additionally dehydrogenated leads to a neutral radical with a large dipole moment. It has recently been shown through the use of high-level quantum chemical computations for …

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Single Spin Asymmetries Of Inclusive Hadrons Produced In Electron Scattering From A Transversely Polarized 3He Target, K. Allada, Y. X. Zhao, K. Aniol, J. R. M. Annand, T. Averett, F. Benmokhtar, W. Bertozzi, P. C. Bradshaw, P. Bosted, A. Camsonne, C. Dutta, Ameya Suresh Kolarkar, Wolfgang Korsch Apr 2014

Single Spin Asymmetries Of Inclusive Hadrons Produced In Electron Scattering From A Transversely Polarized 3He Target, K. Allada, Y. X. Zhao, K. Aniol, J. R. M. Annand, T. Averett, F. Benmokhtar, W. Bertozzi, P. C. Bradshaw, P. Bosted, A. Camsonne, C. Dutta, Ameya Suresh Kolarkar, Wolfgang Korsch

Physics and Astronomy Faculty Publications

We report the first measurement of target single spin asymmetries (AN) in the inclusive hadron production reaction, e+3He↑→h+X, using a transversely polarized 3He target. The experiment was conducted at Jefferson Lab in Hall A using a 5.9-GeV electron beam. Three types of hadrons (π±, K±, and proton) were detected in the transverse hadron momentum range 0.54 <pT< 0.74 GeV/c. The range of xF for pions was −0.29 <xF< −0.23 and for kaons was −0.25 <xF< −0.18. The observed asymmetry strongly depends on the type of hadron. A positive asymmetry is observed for π+ and K+. A negative asymmetry is observed for π−. The …

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Constraints On Cosmic Strings From The Ligo-Virgo Gravitational Wave Detectors, Tiffany Summerscales, Ligo Scientific Collaboration And Virgo Collaboration Apr 2014

Constraints On Cosmic Strings From The Ligo-Virgo Gravitational Wave Detectors, Tiffany Summerscales, Ligo Scientific Collaboration And Virgo Collaboration

Faculty Publications

Cosmic strings can give rise to a large variety of interesting astrophysical phenomena. Among them, powerful bursts of gravitational waves (GWs) produced by cusps are a promising observational signature. In this Letter we present a search for GWs from cosmic string cusps in data collected by the LIGO and Virgo gravitational wave detectors between 2005 and 2010, with over 625 days of live time. We find no evidence of GW signals from cosmic strings. From this result, we derive new constraints on cosmic string parameters, which complement and improve existing limits from previous searches for a stochastic background of GWs …

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Survey Of ‘Low-Z’ Particles From The Interplanetary Dust Collection In Search Of Idps, Harison Wiesman Apr 2014

Survey Of ‘Low-Z’ Particles From The Interplanetary Dust Collection In Search Of Idps, Harison Wiesman

Undergraduate Theses—Unrestricted

Micrometeorites are one of the most common types of extraterrestrial material that fall to the Earth, beside meteorites and interplanetary dust particles (IDPs). All of these materials are known to contain presolar grains that, when studied in the laboratory, provide information about the origin of the solar system and help to constrain models of nucleosynthesis in stars. Recent studies of micrometeorites revealed the presence of a group of particles with very high C contents. These ultra-carbonaceous Antarctic micrometeorites (UCAMMs) are fine-grained, fluffy particles dominated by highly disordered carbonaceous matter. The presence of H and N isotopic anomalies, abundant presolar grains, …

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Gravitational Waves From Known Pulsars: Results From The Initial Detector Era, Tiffany Summerscales, The Ligo Scientific Collaboration And The Virgo Collaboration Apr 2014

Gravitational Waves From Known Pulsars: Results From The Initial Detector Era, Tiffany Summerscales, The Ligo Scientific Collaboration And The Virgo Collaboration

Faculty Publications

We present the results of searches for gravitational waves from a large selection of pulsars using data from the most recent science runs (S6, VSR2 and VSR4) of the initial generation of interferometric gravitational wave detectors LIGO (Laser Interferometric Gravitational-wave Observatory) and Virgo. We do not see evidence for gravitational wave emission from any of the targeted sources but produce upper limits on the emission amplitude. We highlight the results from seven young pulsars with large spin-down luminosities. We reach within a factor of five of the canonical spin-down limit for all seven of these, whilst for the Crab and …

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The Stardust Interstellar Dust Collector Crater Origins And Hypervelocity Cratering At Oblique Angles In Aluminum Foil, Harison Wiesman Apr 2014

The Stardust Interstellar Dust Collector Crater Origins And Hypervelocity Cratering At Oblique Angles In Aluminum Foil, Harison Wiesman

Undergraduate Theses—Unrestricted

From 1999 to 2006 the NASA Stardust mission collected cometary particles from the Wild 2 comet and interstellar dust from the interstellar medium in two collectors made from aerogel tiles and aluminum foil. By studying their isotopic compositions, these particles can provide us with information about nucleosynthetic processes in stars. Both collector trays are being studied for traces of these particles, though a number of challenges have arisen in doing so. Identifying impact craters in the aluminum foil on the interstellar collector tray has been incredibly difficult. In addition to being only a few micrometers or less in diameter, many …

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The Physics Of A Space Elevator, Trevor Hamer Apr 2014

The Physics Of A Space Elevator, Trevor Hamer

Thinking Matters Symposium Archive

A space elevator is a hypothetical device consisting of a long cable attached to the surface of the earth that extends upward into space. Its purpose is to provide a tether on which a vehicle could be lifted up into orbit, greatly reducing the cost of space travel. This project explains the physical forces acting on the elevator along with the kinds of materials required to keep such a cable intact. It also examines different design aspects, as well as potential problems facing the construction and usage of the elevator, and whether or not it is something we should expect …

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Transit Timing Analysis In The Hat-P-32 System, M. Seeliger, D. P. Dimitrov, D. Kjurkchieva, M. Mallonn, M. Fernandez, M. Kitze, V. Casanova, G. Maciejewski, J. M. Ohlert, J. G. Schmidt, A. Pannicke, D. Puchalski, E. Gogus, T. Guver, S. Bilir, T. Ak, M. M. Hohle, T. O.B. Schmidt, R. Errmann, E.L.N. Jensen, D. H. Cohen, Laurence A. Marschall, G. Saral, I. Bernt, E. Derman, C. Galan, R. Neuhauser Apr 2014

Transit Timing Analysis In The Hat-P-32 System, M. Seeliger, D. P. Dimitrov, D. Kjurkchieva, M. Mallonn, M. Fernandez, M. Kitze, V. Casanova, G. Maciejewski, J. M. Ohlert, J. G. Schmidt, A. Pannicke, D. Puchalski, E. Gogus, T. Guver, S. Bilir, T. Ak, M. M. Hohle, T. O.B. Schmidt, R. Errmann, E.L.N. Jensen, D. H. Cohen, Laurence A. Marschall, G. Saral, I. Bernt, E. Derman, C. Galan, R. Neuhauser

Physics and Astronomy Faculty Publications

We present the results of 45 transit observations obtained for the transiting exoplanet HATP- 32b. The transits have been observed using several telescopes mainly throughout the YETI (Young Exoplanet Transit Initiative) network. In 25 cases, complete transit light curves with a timing precision better than 1.4 min have been obtained. These light curves have been used to refine the system properties, namely inclination i, planet-to-star radius ratio Rp/Rs, and the ratio between the semimajor axis and the stellar radius a/Rs. First analyses by Hartman et al. suggests the existence of a second planet in the system, thus we tried to …

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Section Abstracts: Astronomy, Mathematics, And Physics With Materials Science Apr 2014

Section Abstracts: Astronomy, Mathematics, And Physics With Materials Science

Virginia Journal of Science

Abstracts of the Astronomy, Mathematics, and Physics with Materials Science Section for the 92nd Annual Meeting of the Virginia Academy of Science, May 13-15, 2014, Virginia Commonwealth University, Richmond, Virginia

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1207-3900_Opt_Mage, Jonathan Gagné Apr 2014

1207-3900_Opt_Mage, Jonathan Gagné

Publications and Research

No abstract provided.

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Towards A Sustainable Modular Robot System For Planetary Exploration, S. G. M. Hossain Apr 2014

Towards A Sustainable Modular Robot System For Planetary Exploration, S. G. M. Hossain

Department of Mechanical and Materials Engineering: Dissertations, Theses, and Student Research

This thesis investigates multiple perspectives of developing an unmanned robotic system suited for planetary terrains. In this case, the unmanned system consists of unit-modular robots. This type of robot has potential to be developed and maintained as a sustainable multi-robot system while located far from direct human intervention. Some characteristics that make this possible are: the cooperation, communication and connectivity among the robot modules, flexibility of individual robot modules, capability of self-healing in the case of a failed module and the ability to generate multiple gaits by means of reconfiguration. To demonstrate the effects of high flexibility of an individual …

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Fermi-Normal, Optical, And Wave-Synchronous Coordinates For Spacetime With A Plane Gravitational Wave, Malik Rakhmanov Apr 2014

Fermi-Normal, Optical, And Wave-Synchronous Coordinates For Spacetime With A Plane Gravitational Wave, Malik Rakhmanov

Physics & Astronomy Faculty Publications

Fermi-normal (FN) coordinates provide a standardized way to describe the effects of gravitation from the point of view of an inertial observer. These coordinates have always been introduced via perturbation expansions and were usually limited to distances much less than the characteristic length scale set by the curvature of spacetime. For a plane gravitational wave this scale is given by its wavelength which defines the domain of validity for these coordinates known as the long-wavelength regime. The symmetry of this spacetime, however, allows us to extend FN coordinates far beyond the long-wavelength regime. Here we present an explicit construction for …

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Experimental Observation Of Lasing Shutdown Via Asymmetric Gain, M. Chitsazi, S. Factor, J. Schindler, Hamidreza Ramezani Apr 2014

Experimental Observation Of Lasing Shutdown Via Asymmetric Gain, M. Chitsazi, S. Factor, J. Schindler, Hamidreza Ramezani

Physics & Astronomy Faculty Publications

Using a pair of coupled RLC cavities we experimentally demonstrate that amplification action can be tamed by a spatially inhomogeneous gain. Under specific conditions we observe the counterintuitive phenomenon of stabilization of the system even when the overall gain provided is increased. This behavior is directly related to lasing shutdown via asymmetric pumping, recently proposed in M. Liertzer et al. [Phys. Rev. Lett. 108, 173901 (2012)]. The analysis of other simple systems reveals the universal nature of the lasing shutdown phenomenon as having its roots in managing impedance matching.

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