1207-3900_Nir_Spex,
2014
City University of New York (CUNY)
A Digital Backend For The Low Frequency All Sky Monitor,
2014
University of Texas at Brownsville
A Digital Backend For The Low Frequency All Sky Monitor, Louis Percy Dartez
Theses and Dissertations - UTB/UTPA
The Low Frequency All Sky Monitor (LoFASM) is a distributed array of dipole antennas that are sensitive to radio frequencies from 10 to 88 MHz. The primary science goals of LoFASM are the detection and study of low-frequency radio transients, a high priority science goal as deemed by the National Research Council's decadal survey. LoFASM consists of antennas and front-end electronics that were originally developed for the Long Wavelength Array (LWA) by the U.S. Naval Research Lab, the University of New Mexico, Virginia Tech, and the Jet Propulsion Laboratory. LoFASM, funded by the U.S. Department of Defense, will initially consist …
1207-3900_Opt_Mage,
2014
City University of New York (CUNY)
Galaxy Pairs In The Sloan Digital Sky Survey - Ix. Merger-Induced Agn Qctivity As Traced By The Wide-Field Infrared Survey Explorer,
2014
George Mason University
Galaxy Pairs In The Sloan Digital Sky Survey - Ix. Merger-Induced Agn Qctivity As Traced By The Wide-Field Infrared Survey Explorer, Shobita Satyapal, Sara L. Ellison, William Mcalpine, Ryan C. Hickox
Dartmouth Scholarship
Interactions between galaxies are predicted to cause gas inflows that can potentially trigger nuclear activity. Since the inflowing material can obscure the central regions of interacting galaxies, a potential limitation of previous optical studies is that obscured Active Galactic Nuclei (AGNs) can be missed at various stages along the merger sequence. We present the first large mid-infrared study of AGNs in mergers and galaxy pairs, in order to quantify the incidence of obscured AGNs triggered by interactions. The sample consists of galaxy pairs and post-mergers drawn from the Sloan Digital Sky Survey that are matched to detections by the Wide …
Experimental Observation Of Lasing Shutdown Via Asymmetric Gain,
2014
Wesleyan University
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.
Fermi-Normal, Optical, And Wave-Synchronous Coordinates For Spacetime With A Plane Gravitational Wave,
2014
The University of Texas Rio Grande Valley
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 …
Towards A Sustainable Modular Robot System For Planetary Exploration,
2014
University of Nebraska-Lincoln
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 …
Book Review: Cosmic Dawn: The Search For The First Stars And Galaxies,
2014
Embry-Riddle Aeronautical University
Book Review: Cosmic Dawn: The Search For The First Stars And Galaxies, T. D. Oswalt
Publications
This document is Dr. Oswalt’s review of Cosmic Dawn : the Search for the First Stars and Galaxies by George Rhee, springer, 2013. 279p, 9781461478126 $39.99, 9781461478133 $29.99.
Massive Compact Galaxies With High-Velocity Outflows: Morphological Analysis And Constraints On Agn Activity,
2014
University of Wisconsin-Madison
Massive Compact Galaxies With High-Velocity Outflows: Morphological Analysis And Constraints On Agn Activity, P. H. Sell, C. A. Tremonti, R. C. Hickox, A. M. Diamond-Stanic
Dartmouth Scholarship
We investigate the process of rapid star formation quenching in a sample of 12 massive galaxies at intermediate redshift (z~0.6) that host high-velocity ionized gas outflows (v>1000 km/s). We conclude that these fast outflows are most likely driven by feedback from star formation rather than active galactic nuclei (AGN). We use multiwavelength survey and targeted observations of the galaxies to assess their star formation, AGN activity, and morphology. Common attributes include diffuse tidal features indicative of recent mergers accompanied by bright, unresolved cores with effective radii less than a few hundred parsecs. The galaxies are extraordinarily compact for their …
Transition To Order After Hilltop Inflation,
2014
Dartmouth College
Transition To Order After Hilltop Inflation, Marcelo Gleiser, Noah Graham
Dartmouth Scholarship
We investigate the rich nonlinear dynamics during the end of hilltop inflation by numerically solving the coupled Klein-Gordon-Friedmann equations in an expanding universe. In particular, we search for coherent, nonperturbative configurations that may emerge due to the combination of nontrivial couplings between the fields and resonant effects from the cosmological expansion. We couple a massless field to the inflaton to investigate its effect on the existence and stability of coherent configurations and the effective equation of state at reheating. For parameters consistent with data from the Planck and WMAP satellites, and for a wide range of couplings between the inflaton …
Deep Broadband Observations Of The Distant Gamma-Ray Blazar Pks 1424+240,
2014
Department of Physical Sciences, Cork Institute of Technology, Bishopstown, Cork, Ireland
Deep Broadband Observations Of The Distant Gamma-Ray Blazar Pks 1424+240, P. T. Reynolds, Et Al
Physical Sciences Publications
We present deep VERITAS observations of the blazar PKS 1424+240, along with contemporaneous Fermi Large Area Telescope, Swift X-ray Telescope, and Swift UV Optical Telescope data between 2009 February 19 and 2013 June 8. This blazar resides at a redshift of z ≥ 0.6035, displaying a significantly attenuated gamma-ray flux above 100 GeV due to photon absorption via pair-production with the extragalactic background light. We present more than 100 hr of VERITAS observations over three years, a multiwavelength light curve, and the contemporaneous spectral energy distributions. The source shows a higher flux of (2.1 ± 0.3) × 10–7 photons m–2 …
Jet-Hadron Correlations In √SNn=200 Gev P+P And Central Au+Au Collisions,
2014
AGH University of Science and Technology, Poland
Jet-Hadron Correlations In √SNn=200 Gev P+P And Central Au+Au Collisions, L. Adamczyk, James K. Adkins, G. Agakishiev, M. M. Aggarwal, Z. Ahammed, I. Alekseev, J. Alford, C. D. Anson, A. Aparin, D. Arkhipkin, Renee H. Fatemi, Suvarna Ramachandran, G. Webb
Physics and Astronomy Faculty Publications
Azimuthal angular correlations of charged hadrons with respect to the axis of a reconstructed (trigger) jet in Au+Au and p+p collisions at √sNN=200 GeV in STAR are presented. The trigger jet population in Au+Au collisions is biased toward jets that have not interacted with the medium, allowing easier matching of jet energies between Au+Au and p+p collisions while enhancing medium effects on the recoil jet. The associated hadron yield of the recoil jet is significantly suppressed at high transverse momentum (passocT) and enhanced at low passocT in 0%–20% central …
A Comparison Of X-Ray And Optical Emission In Cassiopeia A,
2014
Smithsonian Astrophysical Observatory
A Comparison Of X-Ray And Optical Emission In Cassiopeia A, Daniel J. Patnaude, Robert A. Fesen
Dartmouth Scholarship
Broadband optical and narrowband Si XIII X-ray images of the young Galactic supernova remnant Cassiopeia A (Cas A) obtained over several decades are used to investigate spatial and temporal emission correlations on both large and small angular scales. The data examined consist of optical and near infrared ground-based and Hubble Space Telescope images taken between 1951 and 2011, and X-ray images from Einstein, ROSAT, and Chandra taken between 1979 and 2013. We find weak spatial correlations between the remnant’s X-ray and optical emission features on large scales, but several cases of good optical/X-ray correlations on small scales for features which …
Measuring Mass-Loss Rates And Constraining Shock Physics Using X-Ray Line Profiles Of O Stars From The Chandra Archive,
2014
Swarthmore College
Measuring Mass-Loss Rates And Constraining Shock Physics Using X-Ray Line Profiles Of O Stars From The Chandra Archive, David H. Cohen, Emma E. Wollman , '09, M. A. Leutenegger, J. O. Sundqvist, A. W. Fullerton, J. Zsargó, S. P. Owocki
Physics & Astronomy Faculty Works
We quantitatively investigate the extent of wind absorption signatures in the X-ray grating spectra of all non-magnetic, effectively single O stars in the Chandra archive via line profile fitting. Under the usual assumption of a spherically symmetric wind with embedded shocks, we confirm previous claims that some objects show little or no wind absorption. However, many other objects do show asymmetric and blueshifted line profiles, indicative of wind absorption. For these stars, we are able to derive wind mass-loss rates from the ensemble of line profiles, and find values lower by an average factor of 3 than those predicted by …
Gravitational Wave Hotspots: Ranking Potential Locations Of Single-Source Gravitational Wave Emission,
2014
University of Texas Rio Grande Valley
Gravitational Wave Hotspots: Ranking Potential Locations Of Single-Source Gravitational Wave Emission, Joseph Simon, Abigail Polin, Andrea Lommen, Ben Stappers, Lee Samuel Finn, F. A. Jenet, B. Christy
Physics & Astronomy Faculty Publications
The steadily improving sensitivity of pulsar timing arrays (PTAs) suggests that gravitational waves (GWs) from supermassive black hole binary (SMBHB) systems in the nearby universe will be detectable sometime during the next decade. Currently, PTAs assume an equal probability of detection from every sky position, but as evidence grows for a non-isotropic distribution of sources, is there a most likely sky position for a detectable single source of GWs? In this paper, a collection of Galactic catalogs is used to calculate various metrics related to the detectability of a single GW source resolvable above a GW background, assuming that every …
Concept Of A Reflective Power Limiter Based On Nonlinear Localized Modes,
2014
Wesleyan University
Concept Of A Reflective Power Limiter Based On Nonlinear Localized Modes, Elena Makri, Hamidreza Ramezani, Tsampikos Kottos, Ilya Vitebsky
Physics & Astronomy Faculty Publications
Optical limiters are designed to transmit low-intensity light, while blocking the light with excessively high intensity. A typical passive limiter absorbs excessive electromagnetic energy, which can cause its overheating and destruction. We propose the concept of a photonic reflective limiter based on resonance transmission via a localized mode. Such a limiter does not absorb the high-level radiation, but rather reflects it back to space. Importantly, the nearly total reflection occurs within a broad frequency range and direction of incidence. The same concept can be applied to infrared and microwave frequencies.
Spin And Orbital Moments And Magnetic Order In Fe3o4 Nanoparticle Assemblies,
2014
Brigham Young University - Provo
Spin And Orbital Moments And Magnetic Order In Fe3o4 Nanoparticle Assemblies, Yanping Cai
Theses and Dissertations
Fe3O4 magnetic nanoparticles of 5 to 11 nm in size were prepared by organic methods. Particle size was analyzed by both X-ray Diffraction (XRD) and Transmission Electron Microscopy (TEM) techniques. Zero Field Cooling (ZFC) / Field Cooling (FC) and magnetization loop measurements were recorded by VSM, and they confirmed superparamagnetic behavior in the sample. The blocking temperature is found to be in the range of 30 K ~ 170 K. It has a dependence on the particle size. ZFC / FC curves also indicate the presence of magnetic coupling between particles. X-ray Magnetic Circular Dichroism (XMCD) measurements of these nanoparticles …
Estimating The Acoustic Power Of Sources In Nonideal Enclosures Using Generalized Acoustic Energy Density,
2014
Brigham Young University - Provo
Estimating The Acoustic Power Of Sources In Nonideal Enclosures Using Generalized Acoustic Energy Density, Daniel Ryan Marquez
Theses and Dissertations
Sound power measurements of acoustic sources are generally made in reverberation or anechoic chambers using acoustic pressure measurements as outlined in specific ISO or other standards. A reverberation chamber produces an approximate diffuse-field condition, wherein the sound power is determined from the spatially averaged squared pressure. An anechoic chamber produces an approximate free-field condition, wherein the sound power is estimated from squared pressure over an enveloping measurement surface. However, in many cases it is desirable to estimate sound power within nonideal semi-reverberant spaces. In these environments, both direct and reverberant energies may contribute significantly to the total acoustic field. This …
Evolution Of Broad-Line Emission From Active Galactic Nuclei,
2014
University of Kentucky
Evolution Of Broad-Line Emission From Active Galactic Nuclei, Moshe Elitzur, Luis C. Ho, Jonathan R. Trump
Physics and Astronomy Faculty Publications
Apart from viewing-dependent obscuration, intrinsic broad-line emission from active galactic nuclei (AGN) follows an evolutionary sequence: type 1 → 1.2/1.5 → 1.8/1.9 → 2 as the accretion rate on to the central black hole is decreasing. This spectral evolution is controlled, at least in part, by the parameter Lbol/M2/3, where Lbol is the AGN bolometric luminosity and M is the black hole mass. Both this dependence and the double-peaked profiles that emerge along the sequence arise naturally in the disc-wind scenario for the AGN broad-line region.
Compton Scattering From 12C Using Tagged Photons In The Energy Range 65–115 Mev,
2014
University of Illinois at Urbana-Champaign
Compton Scattering From 12C Using Tagged Photons In The Energy Range 65–115 Mev, L. S. Myers, Khayrullo Shoniyozov, M. F. Preston, M. D. Anderson, J. R. M. Annand, M. Boselli, W. J. Briscoe, J. Brudvik, J. I. Capone, G. Feldman, K. G. Fissum, K. Hansen, S. S. Henshaw, L. Isaksson, R. Jebali, Michael A. Kovash, K. Lewis, M. Lundin, I. J. D. Macgregor, D. G. Middleton, D. E. Mittelberger, M. Murray, A. M. Nathan, S. Nutbeam, G. V. O'Rielly, B. Schröder, B. Seitz, S. C. Stave, H. R. Weller
Physics and Astronomy Faculty Publications
Elastic scattering of photons from 12C has been investigated using quasimonoenergetic tagged photons with energies in the range 65–115 MeV at laboratory angles of 60∘, 120∘, and 150∘ at the Tagged-Photon Facility at the MAX IV Laboratory in Lund, Sweden. A phenomenological model was employed to provide an estimate of the sensitivity of the 12C(γ,γ)12C cross section to the bound-nucleon polarizabilities.
