Physical Sciences and Mathematics Commons^™

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