Physical Sciences and Mathematics Commons^™

Relativistic Particle-In-Cell Simulation Of Prompt And Early Afterglows From Grbs, K.-I. Nishikawa, P. Hardee, Y. Mizuno, M. Medvedev, B. Zhang, Dieter H. Hartmann, G. J. Fishman

Publications

Nonthermal radiation observed from astrophysical systems containing relativistic jets and shocks, e.g., gamma-ray bursts (GRBs), active galactic nuclei (AGNs), and microquasars commonly exibit power-law emission spectra. Recent PIC simulations of relativistic electro-ion (or electron-positron) jets injected into a stationary medium show that particle acceleration occurs within the downstream jet. In collisionless, relativistic shocks, particle (electron, positron, and ion) acceleration is due to plasma waves and their associated instabilities (e.g., the Weibel (filamentation) instability) created in shock region. The simulations show that the Weibel instability in responsible for generating and amplifying highly non-uniform, small-scale magnetic fields. These fields contribute to the …

Implications Of Cosmological Gamma-Ray Absorption. Ii. Modifications Of Gamma-Ray Spectra, Dieter H. Hartmann, T. M. Kneiske, T. Bretz, K. Mannheim

Publications

Bearing on the model for the time-dependent metagalactic radiation field developed in the first paper of this series, we compute the gamma-ray attenuation due to pair production in photon-photon scattering. Emphasis is on the effects of varying the star formation rate and the fraction of UV radiation assumed to escape from the star forming regions, the latter being important mainly for high-redshift sources. Conversely, we investigate how the metagalactic radiation field can be measured from the gamma-ray pair creation cutoff as a function of redshift, the Fazio-Stecker relation. For three observed TeV-blazars (Mkn501, Mkn421, H1426+428) we study the effects of …

Exist's Gamma-Ray Burst Sensitivity, D. L. Band, J. E. Grindlay, A. Garson Iii, H. Krawczynski, Dieter H. Hartmann, S. Barthemy, N. Gehrels, G. Skinner

Publications

We use semianalytic techniques to evaluate the burst sensitivity of designs for the EXIST hard X-ray survey mis-sion. Applying these techniques to the mission design proposed for the Beyond Einstein program,we find that with its very large field of view and faint gamma-ray burst detection threshold, EXIST will detect and localize approximately two bursts per day, a large fraction of which may be at high redshift. We estimate that EXIST’s maximum sensitivity will be ~4 times greater than that of Swift’s Burst Alert Telescope. Bursts will be localized to better than 40" at thresh-old, with a burst position as good …

Equivalences On Acyclic Orientations, Matthew Macauley, Henning S. Mortveit

Publications

The cyclic and dihedral groups can be made to act on the set Acyc(Y ) of acyclic orientations of an undirected graph Y , and this gives rise to the equivalence relations ∼κ and ∼δ, respectively. These two actions and their corresponding equivalence classes are closely related to combinatorial problems arising in the context of Coxeter groups, sequential dynamical systems, the chip-firing game, and representations of quivers.

In this paper we construct the graphs C(Y ) and D(Y ) with vertex sets Acyc(Y ) and whose connected components encode the equivalence classes. The number of connected components …

Over-Ocean Validation Of The Global Convective Diagnostic, David W. Martin, Richard A. Kohrs, Frederick R. Mosher, Carlo Maria Medaglia, Claudia Adamo

Publications

The global convective diagnostic (GCD) is a bispectral (infrared and water vapor), day–night scheme for operationally mapping deep convection by means of geostationary satellite images. This article describes a test of GCD performance over tropical and subtropical waters near North America. The test consists of six cases, each involving a convective cloud complex. A seventh case treats convection over land. For each case, a map of deep convection was constructed from image pairs from Geostationary Operational Environmental Satellite-12 (GOES-12). Case by case and for all maritime cases together, the GCD map was compared with a convective parameter derived …

A Magnetohydrodynamic Boost For Relativistic Jets, Yosuke Mizuno, Phillip Hardee, Dieter H. Hartmann, Ken-Ichi Nishikawa, Bing Zhang

Publications

We performed relativistic magnetohydrodynamic simulations of the hydrodynamic boosting mechanism for relativistic jets explored by Aloy & Rezzolla (2006) using the RAISHIN code. Simulation results show that the presence of a magnetic field changes the properties of the shock interface between the tenuous, overpressured jet (Vzj) flowing tangentially to a dense external medium. Magnetic fields can lead to more efficient acceleration of the jet, in comparison to the pure-hydrodynamic case. A "polodial" magnetic field (Bz), tangent to the interface and parallel to the jet flow, produces both a stronger outward moving shock and a stronger inward moving rarefaction wave. This …

On Existence And Uniqueness Results For The Bbm Equation With Arbitrary Forcing Terms, Timothy A. Smith

Publications

The problem of classical solutions for the regularized long-wave equation is considered where various additional forcing terms are introduced which are often required for physical modifications in the wave theory. Sufficient conditions of solvability and existence are established and then these conditions are related to the structure of the forcing terms under consideration.

The Identification And Verification Of Hazardous Convective Cells Over Oceans Using Visible And Infrared Satellite Observations, Michael F. Donovan, Earle R. Williams, Cathy Kessinger, Gary Blackburn, Paul H. Herzegh, Richard L. Bankert, Steve Miller, Frederick R. Mosher

Publications

Three algorithms based on geostationary visible and infrared (IR) observations are used to identify convective cells that do (or may) present a hazard to aviation over the oceans. The performance of these algorithms in detecting potentially hazardous cells is determined through verification with Tropical Rainfall Measuring Mission (TRMM) satellite observations of lightning and radar reflectivity, which provide internal information about the convective cells. The probability of detection of hazardous cells using the satellite algorithms can exceed 90% when lightning is used as a criterion for hazard, but the false-alarm ratio with all three algorithms is consistently large (40%), thereby exaggerating …

Models Of Phototransduction In Rod Photoreceptors, Harihar Khanal, Vasilios Alexiades

Publications

Phototransduction is the process by which photons of light generate an electrical response in retinal rod and cone photoreceptors, thereby initiating vision. We compare the electrical response in salamander rods from increasingly more (spacialy) detailed models of phototransduction: 0-dimensional (bulk), 1-dimensional (longitudinal), 2-dimensional (axisymmetric), and 3-dimensional (with incisures). We discuss issues of finding physical parameters for simulation and validation of models, and also present some computational experiments for rods with geometry of mouse and human photoreceptors.

Book Review: Mac Os X, Ipod, And Iphone Forensic Analysis Dvd Toolkit, Gary C. Kessler

Publications

This document is Dr. Kessler's review of MAC OS X, iPod, and iPhone Forensic Analysis DVD Toolkit, edited by Jesse Varsalone. Syngress, 2009. ISBN: 978-1-59749-297-3.

Book Review: The Dotcrime Manifesto: How To Stop Internet Crime, Gary C. Kessler

Publications

This document is Dr. Kessler's review of The dotCrime Manifesto: How to Stop Internet Crime, by Phillip Hallam-Baker. Addison-Wesley, 2008. ISBN: 0-321-50358-9

White Dwarf Luminosity And Mass Functions From Sloan Digital Sky Survey Spectra, Steven Degennaro, Ted Von Hippel, D. E. Winget, S. O. Kepler, Atsuko Nitta, Detlev Koester, Leandro Althaus

Publications

We present the first phase in our ongoing work to use Sloan Digital Sky Survey (SDSS) data to create separate white dwarf (WD) luminosity functions (LFs) for two or more different mass ranges. In this paper, we determine the completeness of the SDSS spectroscopic WD sample by comparing a proper-motion selected sample of WDs from SDSS imaging data with a large catalog of spectroscopically determined WDs. We derive a selection probability as a function of a single color (g − i) and apparent magnitude (g) that covers the range −1.0 < g − i < 0.2 and 15 < g < 19.5. We address the observed upturn in log g for WDs with Teff 12,000 K and offer arguments that the problem is limited to the line profiles and is not present in the continuum. We offer an empirical method of removing the upturn, recovering a reasonable mass function for WDs with Teff < 12,000 K. Finally we present a WD LF with nearly an order of magnitude (3358) more spectroscopically confirmed WDs than any previous work.

Book Review: The Telescope: Its History, Technology, And Future, T. D. Oswalt

Publications

This document is Dr. Oswalt’s review of The Telescope : Its History, Technology, and Future by Geoff Andersen. Princeton, 2007 248p, 0691129797 $29.95, 9780691129792 $29.95.

Book Review: Your Cosmic Context: An Introduction To Modern Cosmology, T. D. Oswalt

Publications

This document is Dr. Oswalt’s review of Your Cosmic Context : an Introduction to Modern Cosmology by Todd Duncan and Craig Tyler Pearson Addison-Wesley, 2008 466p, 0132400103 $80.00, 9780132400107 $80.00.

Book Review: Challenges To Digital Forensic Evidence, Gary C. Kessler

Publications

This document is Dr. Kessler's review of Challenges to Digital Forensic Evidence, by Fred Cohen. Fred Cohen & Associates, 2008. ISBN 1-878109-41-3

Optical Estimation Of Auroral Ion Upflow: Theory, M. Zettergren, J. L. Semeter, P. L. Blelly, M. Diaz

Publications

This work presents a systematic analysis of optical emissions related to auroral ion upflow. Optical intensities and field‐aligned ion transport are computed for a set of monoenergetic incident electron beams using a combined fluid‐kinetic model. The kinetic portion models the energetic particle transport with a multiple stream approach and provides ionization, excitation, and heating rates to an eight‐moment fluid model of the ionosphere, which then calculates the resulting ion upflow. The analysis is used to develop a technique for estimating upward ion flux from photometric measurements at five discrete wavelengths: 427.8 nm, 557.7 nm, 630.0 nm, 732 nm, and 844.6 …

The General Relativistic Infinite Plane, Preston Jones, Gerardo Muñoz, Michael Ragsdale, Douglas Singleton

Publications

Uniform fields are one of the simplest and most pedagogically useful examples in introductory courses on electrostatics or Newtonian gravity. In general relativity there have been several proposals as to what constitutes a uniform field. In this article we examine two metrics that can be considered the general relativistic version of the infinite plane with finite mass per unit area. The first metric is the 4D version of the 5D “brane” world models which are the starting point for many current research papers. The second case is the cosmological domain wall metric. We examine to what extent these different metrics …

Constraints On An Optical Afterglow And On Supernova Light Following The Short Burst Grb 050813, P. Ferreo, S. F. Sanchez, D. A. Kann, S. Klose, J. Greiner, J. Gorosabel, Dieter H. Hartmann, A. A. Henden, P. Møller, E. Palazzi

Publications

We report early follow-up observations of the error box of the short burst GRB 050813 using the telescopes at Calar Alto and Observatorio Sierra Nevada, followed by deep VLT FORS2 I-band observations obtained under very good seeing conditions 5.7 and 11.7 days after the event. Neither a fading afterglow nor a rising SN component was found, so the potential GRB host galaxy has not been identified based on a comparison of the two VLT images taken at different epochs. We discuss whether any of the galaxies present in the original 1000 XRTerror circle could be the host.In anycase, the optical …

Optimization Of Electrostatic Interactions In Protein-Protein Complexes, Kelly Brock, Kemper Talley, Kacey Coley, Petras Kundrotas, Emil Alexov

Publications

In this article, we present a statistical analysis of the electrostatic properties of 298 protein-protein complexes and 356 domain-domain structures extracted from the previously developed database of protein complexes (ProtCom, http://www.ces.clemson.edu/compbio/protcom). For each structure in the dataset we calculated the total electrostatic energy of the binding and its two components, Coulombic and reaction field energy. It was found that in a vast majority of the cases (>90%), the total electrostatic component of the binding energy was unfavorable. At the same time, the Coulombic component of the binding energy was found to favor the complex formation while …

On Enumeration Of Conjugacy Classes Of Coxeter Elements, Matthew Macauley, Henning S. Mortveit

Publications

In this paper we study the equivalence relation on the set of acyclic orientations of a graph Y that arises through source-to-sink conversions. This source-to-sink conversion encodes, e.g. conjugation of Coxeter elements of a Coxeter group. We give a direct proof of a recursion for the number of equivalence classes of this relation for an arbitrary graph Y using edge deletion and edge contraction of non-bridge edges. We conclude by showing how this result may also be obtained through an evaluation of the Tutte polynomial as T (Y, 1, 0), and we provide bijections to two other classes of acyclic …

Electromagnetic Radiation From Temporal Variations In Space-Time And Progenitors Of Gamma Ray Burst And Millisecond Pulsars, Preston Jones

Publications

A time varying space–time metric is shown to be a source of electromagnetic radiation even in the absence of charge sources. The post-Newtonian approximation is used as a realistic model of the connection between the space–time metric and a time-varying gravitational potential. Rapid temporal variations in the metric from the coalescence of relativistic stars are shown to be likely progenitors of gamma ray burst and millisecond pulsars.

Enhancement Of Nd: Yag Libs Emission Of A Remote Target Using A Simultaneous Co/Sub 2/ Laser Pulse, Dennis K. Killinger, Susan D. Allen, Robert D. Waterbury, Chris Stefano, Edwin L. Dottery

Publications

For the first time to the best of our knowledge, a simultaneous 10.6 μm CO2 laser pulse has been used to enhance the Laser Induced Breakdown Spectroscopy (LIBS) emission from a 1.064 μm Nd:YAG laser induced plasma on a hard target. The enhancement factor was on the order of 25 to 300 times, depending upon the emission lines observed. For an alumina ceramic substrate the Al emission lines at 308 nm and Fe impurity line at 278 nm showed an increase of 60x and 119x, respectively. The output energy of the Nd:YAG laser was 50 mJ/pulse focused to a 1 …

Shibboleth As A Tool For Authorized Access Control To The Subversion Repository System, Linh B. Ngo, Amy W. Apon

Publications

Shibboleth is an architecture and protocol for allowing users to authenticate and be authorized to use a remote resource by logging into the identity management system that is maintained at their home institution. With Shibboleth, a federation of institutions can share resources among users and yet allow the administration of both the user access control to resources and the user identity and attribute information to be performed at the hosting or home institution. Subversion is a version control repository system that allows the creation of fine-grained permissions to files and directories. In this project an infrastructure, Shibbolized Subversion, has been …

Shibboleth As A Tool For Authorized Access Control To The Subversion Repository System, Amy Apon, Linh B. Ngo

Publications

Shibboleth is an architecture and protocol for allowing users to authenticate and be authorized to use a remote resource by logging into the identity management system that is maintained at their home institution. With Shibboleth, a federation of institutions can share resources among users and yet allow the administration of both the user access control to resources and the user identity and attribute information to be performed at the hosting or home institution. Subversion is a version control repository system that allows the creation of fine-grained permissions to files and directories. In this project an infrastructure, Shibbolized Subversion, has been …

Book Review: Moore On Mercury: The Planet And The Missions, T. D. Oswalt

Publications

This document is Dr. Oswalt’s review of Moore on Mercury : the Planet and the Missions by Patrick Moore. Springer, 2006 139p, 1846282578 $29.95, 9781846282577 $29.95

Gis Assessment Of Environmental Impacts On Urban Forests, Richard Snow, Mary Snow

Publications

No abstract provided.

Wide-Field Survey Of Globular Clusters In M31. I. A Catalog Of New Clusters, Sang Chul Kim, Myung Gyoon Lee, Doug Geisler, Ata Sarajedini, Hong Soo Park, Ho Seong Hwang, William E. Harris, Juan C. Seguel, Ted Von Hippel

Publications

We present the result of a wide-field survey of globular clusters (GCs) in M31 covering a 3^o x 3^o field centered on M31.We have searched for GCs on CCD images taken with Washington CMT₁ filters at the KPNO 0.9 m telescope using the following steps: (1) inspection of morphological parameters given by the SExtractor package such as stellarity, full width at half-maximum, and ellipticity; (2) consulting the spectral types and radial velocities obtained from spectra taken with the Hydra spectrograph at the WIYN 3.5 m telescope; and (3) visual inspection of the images of each object. We …

Testing Lorentz Symmetry With Gravity, Quentin G. Bailey

Publications

In this talk, results from the gravitational sector of the Standard-Model Extension (SME) are discussed. The weak-field phenomenology of the resulting modified gravitational field equations is explored. The application of the results to a variety of modern gravity experiments, including lunar laser ranging, Gravity Probe B, binary pulsars, and Earth-laboratory tests, shows promising sensitivity to gravitational coefficients for Lorentz violation in the SME.

Gis Analysis Of Lightning Strikes Within A Tornadic Environment, Richard Snow, Mary Snow, Nicole Kufa

Publications

Recent research suggests that a maximum rate of lightning strikes occurs at least 15 to 20 minutes prior to tornado formation within a supercell storm. These maxima are associated with strengthening updrafts as they appear in radar measurements. An increase in lightning rates correlates with an increase of shear in the lower part of the storm. In combination with a strong updraft or downdraft, this shear can provide the ingredients for rotation and possibly a tornado. Polarity reversal of lightning around the time of tornado touchdown also has been examined. Thus, increasing lightning flash rates and reversal of lightning strike …

Evolution Of The American Ecological Paideia, Mary Snow, Richard K. Snow

Publications

No abstract provided.