Results for "Steven W. Allen"

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Implicit Priors in Galaxy Cluster Mass and Scaling Relation DeterminationsJun 20 2011Deriving the total masses of galaxy clusters from observations of the intracluster medium (ICM) generally requires some prior information, in addition to the assumptions of hydrostatic equilibrium and spherical symmetry. Often, this information takes ... More
Constraining Dark Energy with X-ray Galaxy Clusters, Supernovae and the Cosmic Microwave BackgroundSep 24 2004Apr 05 2005We present new constraints on the evolution of dark energy from an analysis of Cosmic Microwave Background, supernova and X-ray galaxy cluster data. Our analysis employs a minimum of priors and exploits the complementary nature of these data sets. We ... More
The Observed Growth of Massive Galaxy Clusters IV: Robust Constraints on Neutrino PropertiesNov 09 2009Jun 24 2010This is the fourth of a series of papers in which we derive simultaneous constraints on cosmological parameters and X-ray scaling relations using observations of the growth of massive, X-ray flux-selected galaxy clusters. Here we examine the constraints ... More
Hard X-ray emission from elliptical galaxies and its contribution to the X-ray backgroundOct 19 1999We explore the implications of the discovery of hard, power-law X-ray sources in the spectra of nearby elliptical galaxies for the origin of the X-ray background. The spectra of these sources are consistent with models of thermal bremsstrahlung emission ... More
Cosmology and Astrophysics from Relaxed Galaxy Clusters V: Consistency with Cold Dark Matter Structure FormationJul 16 2016Jul 25 2016This is the fifth in a series of papers studying the astrophysics and cosmology of massive, dynamically relaxed galaxy clusters. Our sample comprises 40 clusters identified as being dynamically relaxed and hot in Papers I and II of this series. Here we ... More
Cosmological Parameters from Observations of Galaxy ClustersMar 24 2011Jun 10 2011Studies of galaxy clusters have proved crucial in helping to establish the standard model of cosmology, with a universe dominated by dark matter and dark energy. A theoretical basis that describes clusters as massive, multi-component, quasi-equilibrium ... More
The Observed Growth of Massive Galaxy Clusters III: Testing General Relativity on Cosmological ScalesNov 10 2009Apr 10 2010This is the third of a series of papers in which we derive simultaneous constraints on cosmological parameters and X-ray scaling relations using observations of the growth of massive, X-ray flux-selected galaxy clusters. Our data set consists of 238 clusters ... More
The Observed Growth of Massive Galaxy Clusters I: Statistical Methods and Cosmological ConstraintsSep 16 2009Jun 24 2010(Abridged) This is the first of a series of papers in which we derive simultaneous constraints on cosmological parameters and X-ray scaling relations using observations of the growth of massive, X-ray flux-selected galaxy clusters. Our data set consists ... More
X-ray Cluster Constraints on Non-GaussianityApr 04 2013May 06 2013We report constraints on primordial non-Gaussianity from the abundance of X-ray detected clusters. Our analytic prescription for adding non-Gaussianity to the cluster mass function takes into account moments beyond the skewness, and we demonstrate that ... More
A uniform metal distribution in the intergalactic medium of the Perseus cluster of galaxiesOct 29 2013Most of the metals (elements heavier than helium) ever produced by stars in the member galaxies of galaxy clusters currently reside within the hot, X-ray emitting intra-cluster gas. Observations of X-ray line emission from this intergalactic medium have ... More
Constraints on modified gravity from the observed X-ray luminosity function of galaxy clustersDec 12 2008Sep 16 2009We use measurements of the growth of cosmic structure, as inferred from the observed evolution of the X-ray luminosity function (XLF) of galaxy clusters, to constrain departures from General Relativity (GR) on cosmological scales. We employ the popular ... More
Probing Dark Energy with Constellation-XAug 01 2006Constellation-X (Con-X) will carry out two powerful and independent sets of tests of dark energy based on X-ray observations of galaxy clusters, providing comparable accuracy to other leading dark energy probes. The first group of tests will measure the ... More
The Observed Growth of Massive Galaxy Clusters II: X-ray Scaling RelationsSep 16 2009Jun 24 2010(Abridged) This is the second in a series of papers in which we derive simultaneous constraints on cosmology and X-ray scaling relations using observations of massive, X-ray flux-selected galaxy clusters. The data set consists of 238 clusters drawn from ... More
Center-Excised X-ray Luminosity as an Efficient Mass Proxy for Future Galaxy Cluster SurveysMay 25 2017Oct 26 2017The cosmological constraining power of modern galaxy cluster catalogs can be improved by obtaining low-scatter mass proxy measurements for even a small fraction of sources. In the context of large upcoming surveys that will reveal the cluster population ... More
Low-temperature surface conduction in the Kondo insulator SmB$_6$Nov 21 2012Dec 02 2013We study the transport properties of the Kondo insulator SmB$_6$ with a specialized configuration designed to distinguish bulk-dominated conduction from surface-dominated conduction. We find that as the material is cooled below 4 K, it exhibits a crossover ... More
A kinematical approach to dark energy studiesMay 29 2006Jan 25 2007We present and employ a new kinematical approach to cosmological `dark energy' studies. We construct models in terms of the dimensionless second and third derivatives of the scale factor a(t) with respect to cosmic time t, namely the present-day value ... More
Cold dark energy constraints from the abundance of galaxy clustersJan 25 2017Nov 22 2017We constrain cold dark energy of negligible sound speed using galaxy cluster abundance observations. In contrast to standard quasi-homogeneous dark energy, negligible sound speed implies clustering of the dark energy fluid at all scales, allowing us to ... More
Accretion onto the Supermassive Black Hole in M87Feb 12 2002Sep 03 2002Chandra X-ray observations of the giant elliptical galaxy M87 resolve the thermal state of the hot interstellar medium into the accretion (Bondi) radius of its central 3 10^9 Msun black hole. We measure the X-ray gas temperature and density profiles and ... More
Cosmology and Astrophysics from Relaxed Galaxy Clusters I: Sample SelectionFeb 20 2015This is the first in a series of papers studying the astrophysics and cosmology of massive, dynamically relaxed galaxy clusters. Here we present a new, automated method for identifying relaxed clusters based on their morphologies in X-ray imaging data. ... More
A unique small-scale gravitational arc in Abell 1201Nov 10 2003We present a snapshot Hubble Space Telescope (HST) image of the galaxy cluster A1201 (z=0.169), revealing a tangential arc 2arcsec from the brightest cluster galaxy (BCG). Keck-ESI spectroscopy confirms that the arc is gravitational in nature and that ... More
Joule heating of dilute 2D holes in a GaAs quantum wellMar 07 2002Mar 12 2002We present measurements of the Joule heating of a 2D hole gas (2DHG) formed in a 30nm GaAs quantum well. The hole density is in the range (4.6-18.9)*10^9cm^-2 and exhibits an apparent metal-to-insulator transition (MIT) with a critical density 6*10^9 ... More
The Metallicity of the Intracluster Medium Over Cosmic Time: Further Evidence for Early EnrichmentJun 05 2017Sep 14 2017We use Chandra X-ray data to measure the metallicity of the intracluster medium (ICM) in 245 massive galaxy clusters selected from X-ray and Sunyaev-Zel'dovich (SZ) effect surveys, spanning redshifts $0<z<1.2$. Metallicities were measured in three different ... More
The properties of cooling flows in X-ray luminous clusters of galaxiesFeb 28 2000We discuss the X-ray properties of the cooling flows in a sample of thirty highly X-ray luminous clusters of galaxies observed with the ASCA and ROSAT satellites. We demonstrate the need for multiphase models to consistently explain the spectral and imaging ... More
Quasi-particles and their absence in photoemission spectroscopyNov 05 2002The elucidation of Landau Fermi liquid quasi-particles and their absence in strongly correlated electron systems lies at the heart of modern research on the quantum mechanics of electrons in condensed matter. Photoemission spectroscopy of the single particle ... More
XMM-Newton X-ray and HST weak gravitational lensing study of the extremely X-ray luminous galaxy cluster ClJ120958.9+495352 ($z=0.902$)Aug 23 2017Nov 24 2017Observations of relaxed, massive and distant clusters can provide important tests of standard cosmological models e.g. using the gas mass fraction. We study the very luminous, high redshift ($z=0.902$) galaxy cluster ClJ120958.9+495352 using XMM-Newton ... More
Revealing the properties of dark matter in the merging cluster MACSJ0025.4-1222Jun 13 2008Jul 23 2008We constrain the physical nature of dark matter using the newly identified massive merging galaxy cluster MACSJ0025.4-1222. As was previously shown by the example of the Bullet Cluster (1E0657-56), such systems are ideal laboratories for detecting isolated ... More
The Kondo Resonance in Electron SpectroscopyFeb 15 2005The Kondo resonance is the spectral manifestation of the Kondo properties of the impurity Anderson model, and also plays a central role in the dynamical mean-field theory (DMFT) for correlated electron lattice systems. This article presents an overview ... More
Resolving the discrepancy between X-ray and gravitational lensing mass measurements for clusters of galaxiesOct 21 1997We present a detailed comparison of mass measurements for clusters of galaxies using ASCA and ROSAT X-ray data and constraints from strong and weak gravitational lensing. Our results for a sample of 13 clusters provide a consistent description of the ... More
Cosmology and Astrophysics from Relaxed Galaxy Clusters II: Cosmological ConstraintsFeb 25 2014Mar 21 2014We present cosmological constraints from measurements of the gas mass fraction, $f_{gas}$, for massive, dynamically relaxed galaxy clusters. Our data set consists of Chandra observations of 40 such clusters, identified in a comprehensive search of the ... More
Robust Weak-lensing Mass Calibration of Planck Galaxy ClustersFeb 11 2014Oct 09 2014In light of the tension in cosmological constraints reported by the Planck team between their SZ-selected cluster counts and Cosmic Microwave Background (CMB) temperature anisotropies, we compare the Planck cluster mass estimates with robust, weak-lensing ... More
Weighing the Giants V: Galaxy Cluster Scaling RelationsJun 10 2016Sep 26 2016We present constraints on the scaling relations of galaxy cluster X-ray luminosity, temperature and gas mass (and derived quantities) with mass and redshift, employing masses from robust weak gravitational lensing measurements. These are the first such ... More
New constraints on $f(R)$ gravity from clusters of galaxiesNov 29 2014Aug 08 2015The abundance of massive galaxy clusters is a powerful probe of departures from General Relativity (GR) on cosmic scales. Despite current stringent constraints placed by stellar and galactic tests, on larger scales alternative theories of gravity such ... More
The XXL Survey: XVII. X-ray and Sunyaev-Zel'dovich Properties of the Redshift 2.0 Galaxy Cluster XLSSC 122Mar 23 2017We present results from a 100 ks XMM-Newton observation of galaxy cluster XLSSC 122, the first massive cluster discovered through its X-ray emission at $z\approx2$. The data provide the first precise constraints on the bulk thermodynamic properties of ... More
The Millennium Galaxy Catalogue: morphological classification and bimodality in the colour-concentration planeFeb 10 2006Using 10 095 galaxies (B < 20 mag) from the Millennium Galaxy Catalogue, we derive B-band luminosity distributions and selected bivariate brightness distributions for the galaxy population. All subdivisions extract highly correlated sub-sets of the galaxy ... More
Weighing the Giants II: Improved Calibration of Photometry from Stellar Colors and Accurate Photometric RedshiftsAug 02 2012Apr 19 2014We present improved methods for using stars found in astronomical exposures to calibrate both star and galaxy colors as well as to adjust the instrument flat field. By developing a spectroscopic model for the SDSS stellar locus in color-color space, synthesizing ... More
Weighing the Giants - I. Weak-lensing masses for 51 massive galaxy clusters: project overview, data analysis methods and cluster imagesAug 02 2012Apr 18 2014This is the first in a series of papers in which we measure accurate weak-lensing masses for 51 of the most X-ray luminous galaxy clusters known at redshifts 0.15<z<0.7, in order to calibrate X-ray and other mass proxies for cosmological cluster experiments. ... More
DECal: A Spectrophotometric Calibration System For DECamFeb 22 2013DECal is a new calibration system for the CTIO 4 m Blanco telescope. It is currently being installed as part of the Dark Energy Survey and will provide both broadband flat fields and narrowband (about 1 nm bandwidth) spectrophotometric calibration for ... More
Weighing the Giants - III. Methods and Measurements of Accurate Galaxy Cluster Weak-Lensing MassesAug 02 2012Apr 18 2014We report weak-lensing masses for 51 of the most X-ray luminous galaxy clusters known. This cluster sample, introduced earlier in this series of papers, spans redshifts 0.15 < z_cl < 0.7, and is well suited to calibrate mass proxies for current cluster ... More
Weighing the Giants V: Galaxy Cluster Scaling RelationsJun 10 2016Jan 30 2017We present constraints on the scaling relations of galaxy cluster X-ray luminosity, temperature and gas mass (and derived quantities) with mass and redshift, employing masses from robust weak gravitational lensing measurements. These are the first such ... More
Regulation of Black Hole Winds and Jets Across the Mass ScaleMay 18 2012Nov 21 2012We present a study of the mechanical power generated by both winds and jets across the black hole mass scale. We begin with the study of ionized X-ray winds and present a uniform analysis using Chandra grating spectra. The high quality grating spectra ... More
Extrasolar Planet Transits Observed at Kitt Peak National ObservatoryFeb 13 2012We obtained J-, H- and JH-band photometry of known extrasolar planet transiting systems at the 2.1-m Kitt Peak National Observatory Telescope using the FLAMINGOS infrared camera between October 2008 and October 2011. From the derived lightcurves we have ... More
Presence of a (1x1) oxygen overlayer on bare ZnO(0001) surfaces and at Schottky interfacesJul 27 2011The atomic surface and interface structure of bare and metal-coated ZnO(0001) Zn-polar wafers were investigated via surface x-ray diffraction. All bare samples showed the presence of a (1x1) overlayer of oxygen atoms located at the on-top position above ... More
The Future Landscape of High-Redshift Galaxy Cluster ScienceMar 13 2019Modern galaxy cluster science is a multi-wavelength endeavor with cornerstones provided by X-ray, optical/IR, mm, and radio measurements. In combination, these observations enable the construction of large, clean, complete cluster catalogs, and provide ... More
The dark matter halos of massive, relaxed galaxy clusters observed with ChandraOct 02 2006May 09 2007We use the Chandra X-ray Observatory to study the dark matter halos of 34 massive, dynamically relaxed galaxy clusters, spanning the redshift range 0.06<z<0.7. The observed dark matter and total mass (dark-plus-luminous matter) profiles can be approximated ... More
The Colloquium on Decoupling Civil Timekeeping from Earth RotationNov 29 2011On October 5 and October 6, 2011, the Colloquium on the Decoupling Civil Timekeeping from Earth Rotation was hosted in Exton, Pennsylvania by Analytical Graphics, Inc. (AGI). This paper highlights various technical perspectives offered through these proceedings, ... More
Cactus: Issues for Sustainable Simulation SoftwareSep 07 2013Sep 16 2013The Cactus Framework is an open-source, modular, portable programming environment for the collaborative development and deployment of scientific applications using high-performance computing. Its roots reach back to 1996 at the National Center for Supercomputer ... More
Parasites on parasites: coupled fluctuations in stacked contact processesDec 07 2012Nov 14 2013We present a model for host-parasite dynamics which incorporates both vertical and horizontal transmission as well as spatial structure. Our model consists of stacked contact processes (CP), where the dynamics of the host is a simple CP on a lattice while ... More
Band Structure and Transport Properties of CrO_2Aug 24 1996Local Spin Density Approximation (LSDA) is used to calculate the energy bands of both the ferromagnetic and paramagnetic phases of metallic CrO_2. The Fermi level lies in a peak in the paramagnetic density of states, and the ferromagnetic phase is more ... More
Lower glycolysis carries a higher flux than any biochemically possible alternativeApr 10 2014The universality of many pathways of core metabolism suggests a strong role for evolutionary selection, but it remains unclear whether existing pathways have been selected from a large or small set of biochemical possibilities. To address this question, ... More
ARIANNA: A New Concept for UHE Neutrino DetectionOct 20 2006The ARIANNA concept utilizes the Ross Ice Shelf near the coast of Antarctica to increase the sensitivity to cosmogenic neutrinos by roughly an order of magnitude when compared to the sensitivity of existing detectors and those under construction. Therefore, ... More
Physics and Operation of the AMANDA-II High Energy Neutrino TelescopeNov 13 2002Nov 15 2002This paper briefly describes the principle of operation and science goals of the AMANDA high energy neutrino telescope located at the South Pole, Antarctica. Results from an earlier phase of the telescope, called AMANDA-B10, demonstrate both reliable ... More
Detecting Life-bearing Extra-solar Planets with Space TelescopesOct 07 2007Mar 29 2008One of the promising methods to search for life on extra-solar planets (exoplanets) is to detect life's signatures in their atmospheres. Spectra of exoplanet atmospheres at the modest resolution needed to search for oxygen, carbon dioxide, water, and ... More
The Influence of Electrostatic Truncation on Simulations of Polarizable SystemsSep 16 1999Sep 17 1999Different schemes for the treatment of long-ranged electrostatic interactions will be examined for water simulations using the polarizable fluctuating charge potential. Several different methods are compared, including Ewald sums, potential shifting, ... More
High Energy Cosmic NeutrinosMar 31 1999While the general principles of high-energy neutrino detection have been understood for many years, the deep, remote geographical locations of suitable detector sites have challenged the ingenuity of experimentalists, who have confronted unusual deployment, ... More
The REgolith X-Ray Imaging Spectrometer (REXIS) for OSIRIS-REx: Identifying Regional Elemental Enrichment on AsteroidsSep 25 2013The OSIRIS-REx Mission was selected under the NASA New Frontiers program and is scheduled for launch in September of 2016 for a rendezvous with, and collection of a sample from the surface of asteroid Bennu in 2019. 101955 Bennu (previously 1999 RQ36) ... More
Vector Positronium States in QED3Sep 18 1996Apr 13 1997The homogeneous Bethe-Salpeter equation is solved in the quenched ladder approximation for the vector positronium states of 4-component quantum electrodynamics in 2 space and 1 time dimensions. Fermion propagator input is from a Rainbow approximation ... More
Positronium States in QED3Dec 21 1995The $e^-$-$e^+$ bound state spectrum of QED3 is investigated in the quenched ladder approximation to the homogeneous Bethe-Salpeter equation with fermion propagators from a rainbow approximation Schwinger-Dyson equation. A detailed analysis of the analytic ... More
The relationship between cooling flows and metallicity measurements for X-ray luminous clustersFeb 17 1998Mar 02 1998We explore the relationship between the metallicity of the intracluster gas in clusters of galaxies, determined by X-ray spectroscopy, and the presence of cooling flows. Using ASCA spectra and ROSAT images, we demonstrate a clear segregation between the ... More
X-rays from Clusters of GalaxiesApr 01 2003The X-ray emission from clusters of galaxies enables them to be used as good cosmological probes and as an example for massive galaxy formation. The gas mass fraction in clusters should be a universal standard which by means of Chandra observations enables ... More
Polynomial Monogamy RelationsFeb 17 2015Like concurrence, negativity reflects the monogamous nature of entanglement among multiple qubits. Both satisfy a linear inequality involving a party's entanglement with other parties. We show that negativity only saturates the inequality in trivial cases, ... More
On the thermodynamic self-similarity of the nearest, most relaxed, giant ellipticalsMay 08 2012Aug 14 2012We present detailed spatially resolved measurements of the thermodynamic properties of the X-ray emitting gas in the inner regions of the five nearest, X-ray and optically brightest, and most X-ray morphologically relaxed giant elliptical galaxies known. ... More
Chandra measurements of non-thermal-like X-ray emission from massive, merging, radio-halo clustersNov 05 2008Jul 16 2009We report the discovery of spatially-extended, non-thermal-like emission components in Chandra X-ray spectra for five of a sample of seven massive, merging galaxy clusters with powerful radio halos. The emission components can be fitted by power-law models ... More
Topological crystalline Kondo insulators and universal topological surface states of SmB$_6$Jul 26 2013We prove theoretically that certain strongly correlated Kondo insulators are topological crystalline insulators with nontrivial topology protected by crystal symmetries. In particular, we find that SmB$_6$ is such a material. In addition to a nontrivial ... More
Osmosis in a minimal model systemJul 30 2012Jun 14 2013Osmosis plays a central role in the function of living and soft matter systems. While the thermodynamics of osmosis is well understood, the underlying microscopic dynamical mechanisms remain the subject of discussion. Unraveling these mechanisms is a ... More
Point-Form Analysis of Elastic Deuteron Form FactorsMay 17 2000Oct 11 2000Point-form relativistic quantum mechanics is applied to elastic electron-deuteron scattering. The deuteron is modeled using relativistic interactions that are scattering-equivalent to the nonrelativistic Argonne $v_{18}$ and Reid '93 interactions. A point-form ... More
The spatial distributions of cooling gas and intrinsic X-ray absorbing material in cooling flowsDec 03 1996We present the results from a study of the spatial distributions of cooling gas and intrinsic X-ray absorbing material in a sample of nearby, X-ray bright cooling flow clusters observed with the Position Sensitive Proportional Counter (PSPC) on ROSAT. ... More
iQ Cavity for Material Permittivity CharacterizationApr 20 2016We present an X-band waveguide (WR90) and UHF waveguide (WR1500) measurement method that permits the extraction of the complex permittivity for low dielectric loss tangent material specimen. The extraction method relies on computational electromagnetic ... More
Character of Atomic Vibrations in a Lennard-Jones GlassJul 17 2003Jul 22 2003Lennard-Jones glasses (made on a computer by quenching from liquid state coordinates) are studied in harmonic approximation. Vibrational eigenfrequencies and eigenvectors are found by exact diagonalization for models with periodic boundaries and N=(500, ... More
Osmosis with active solutesFeb 06 2014Despite much current interest in active matter, little is known about osmosis in active systems. Using molecular dynamics simulations, we investigate how active solutes perturb osmotic steady states. We find that solute activity increases the osmotic ... More
Weighing the Giants IV: Cosmology and Neutrino MassJul 16 2014Nov 26 2014We employ robust weak gravitational lensing measurements to improve cosmological constraints from measurements of the galaxy cluster mass function and its evolution, using X-ray selected clusters detected in the ROSAT All-Sky Survey. Our lensing analysis ... More
Magnetotransport Measurements of the Surface States of Samarium Hexaboride using Corbino StructuresSep 29 2014Oct 09 2015The recent conjecture of a topologically-protected surface state in SmB$_6$ and the verification of robust surface conduction below 4 K have prompted a large effort to understand the surface states. Conventional Hall transport measurements allow current ... More
Hysteretic Magnetotransport in SmB6 at Low Magnetic FieldsOct 27 2014Utilizing Corbino disc structures, we have examined the magnetic field response of resistivity for the surface states of SmB6 on different crystalline surfaces at low temperatures. Our results reveal a hysteretic behavior whose magnitude depends on the ... More
Baryons at the Edge of the X-ray Brightest Galaxy ClusterFeb 11 2011Studies of the diffuse X-ray emitting gas in galaxy clusters have provided powerful constraints on cosmological parameters and insights into plasma astrophysics. However, measurements of the faint cluster outskirts have become possible only recently. ... More
Gauge gravity and discrete quantum modelsSep 06 2013Jan 10 2014The gauge gravity action for general relativity in any dimension using a connection for the Euclidean or Poincar\'e group and a symmetry-breaking scalar field is written using a particularly simple matrix technique. A discrete version of the gauge gravity ... More
Feature Selection Facilitates Learning Mixtures of Discrete Product DistributionsNov 25 2017Feature selection can facilitate the learning of mixtures of discrete random variables as they arise, e.g. in crowdsourcing tasks. Intuitively, not all workers are equally reliable but, if the less reliable ones could be eliminated, then learning should ... More
Capacity Achieving Code Constructions for Two Classes of (d,k) ConstraintsNov 03 2004In this paper, we present two low complexity algorithms that achieve capacity for the noiseless (d,k) constrained channel when k=2d+1, or when k-d+1 is not prime. The first algorithm, called symbol sliding, is a generalized version of the bit flipping ... More
Stagewise Learning for Sparse Clustering of Discretely-Valued DataJun 09 2015May 28 2016The performance of EM in learning mixtures of product distributions often depends on the initialization. This can be problematic in crowdsourcing and other applications, e.g. when a small number of 'experts' are diluted by a large number of noisy, unreliable ... More
Binary Masses as a Test for Pre-Main-Sequence ModelsFeb 08 2001Observations of binaries have traditionally provided the means for ascertaining stellar masses. Here, we use the published data on 8 pre-main-sequence pairs to gauge the accuracy of our own, recently calculated, evolutionary tracks (Palla & Stahler 1999). ... More
MDS codes on the erasure-erasure wiretap channelFeb 19 2009This paper considers the problem of perfectly secure communication on a modified version of Wyner's wiretap channel II where both the main and wiretapper's channels have some erasures. A secret message is to be encoded into $n$ channel symbols and transmitted. ... More
Star Formation in Space and Time: Taurus-AurigaAug 30 2002To understand the formation of stellar groups, one must first document carefully the birth pattern within real clusters and associations. In this study of Taurus-Auriga, we combine pre-main-sequence ages from our own evolutionary tracks with stellar positions ... More
An improved approach to measuring H_0 using X-ray and SZ observations of galaxy clustersMay 19 2004We present an improved method for predicting the Sunyaev-Zeldovich (SZ) effect in galaxy clusters from spatially-resolved, spectroscopic X-ray data. Using the deprojected electron density and temperature profiles measured within a fraction of the virial ... More
Chandra observations of RXJ1347.5-1145: the distribution of mass in the most X-ray luminous galaxy cluster knownNov 19 2001Apr 04 2002We present Chandra observations of RXJ1347.5-1145, the most X-ray luminous cluster of galaxies known. We report the discovery of a region of relatively hot, bright X-ray emission, located approximately 20 arcsec to the southeast of the main X-ray peak, ... More
Chandra observations of the galaxy cluster Abell 1835Jul 17 2001We present the analysis of 30 ksec of Chandra observations of the galaxy cluster Abell 1835. Overall, the X-ray image shows a relaxed morphology, although we detect substructure in in the inner 30 kpc radius. Spectral analysis shows a steep drop in the ... More
The X-ray virial relations for relaxed lensing clusters observed with ChandraOct 29 2001We examine the relations linking mass, X-ray temperature and bolometric luminosity for a sample of luminous, relatively relaxed clusters of galaxies observed with the Chandra Observatory, for which independent confirmation of the mass results is available ... More
User Partitioning for Less Overhead in MIMO Interference ChannelsJul 03 2010Feb 08 2012This paper presents a study on multiple-antenna interference channels, accounting for general overhead as a function of the number of users and antennas in the network. The model includes both perfect and imperfect channel state information based on channel ... More
Nonregenerative MIMO Relaying with Optimal Transmit Antenna SelectionJan 21 2008We derive optimal SNR-based transmit antenna selection rules at the source and relay for the nonregenerative half duplex MIMO relay channel. While antenna selection is a suboptimal form of beamforming, it has the advantage that the optimization is tractable ... More
Cooperative Algorithms for MIMO Interference ChannelsFeb 02 2010Oct 04 2010Interference alignment is a transmission technique for exploiting all available degrees of freedom in the interference channel with an arbitrary number of users. Most prior work on interference alignment, however, neglects interference from other nodes ... More
RXTE, ROSAT and ASCA Observations of G347.3-0.5 (RX J1713.7-3946): Probing Cosmic Ray Acceleration by a Galactic Shell-Type Supernova RemnantApr 30 2003(Abridged) We present an analysis of the X-ray spectrum of the Galactic shell-type supernova remnant (SNR) G347.3-0.5 (RX J1713.7-3946). By performing a joint spectral analysis of data from observations made of G347.3-0.5 using the ROSAT PSPC, the ASCA ... More
Knowledge Engineering Within A Generalized Bayesian FrameworkMar 27 2013During the ongoing debate over the representation of uncertainty in Artificial Intelligence, Cheeseman, Lemmer, Pearl, and others have argued that probability theory, and in particular the Bayesian theory, should be used as the basis for the inference ... More
STIRAP in sodium vapor with picosecond laser pulsesOct 14 2015Aug 01 2017Experimental measurements and calculations of STIRAP transfer efficiencies were made on a sodium gas starting from the $3^2{\rm S}_{1/2}$ electronic ground state, passing through the $3^2{\rm P}_{1/2}$ and/or the $3^2{\rm P}_{3/2}$ to the $5^2{\rm S}_{1/2}$ ... More
Infrared Optical Properties of Ferropericlase (Mg1-xFexO): Experiment and TheoryApr 18 2007The temperature dependence of the reflectance spectra of magnesium oxide (MgO) and ferropericlase (Mg1-xFexO, for x=0.06 and x=0.27) have been measured over a wide frequency range (~50 to 32000 cm-1) at 295 and 6 K. The complex dielectric function has ... More
Simplifying Complex Software Assembly: The Component Retrieval Language and ImplementationSep 07 2010Assembling simulation software along with the associated tools and utilities is a challenging endeavor, particularly when the components are distributed across multiple source code versioning systems. It is problematic for researchers compiling and running ... More
Maximum Likelihood de novo reconstruction of viral populations using paired end sequencing dataFeb 14 2015Apr 16 2016We present MLEHaplo, a maximum likelihood de novo assembly algorithm for reconstructing viral haplotypes in a virus population from paired-end next generation sequencing (NGS) data. Using the pairing information of reads in our proposed Viral Path Reconstruction ... More
STIRAP in sodium vapor with picosecond laser pulsesOct 14 2015Apr 04 2016Experimental measurements and calculations of STIRAP transfer efficiencies were made on a sodium gas starting from the $3^2{\rm S}_{1/2}$ electronic ground state, passing through the $3^2{\rm P}_{1/2}$ and/or the $3^2{\rm P}_{3/2}$ to the $5^2{\rm S}_{1/2}$ ... More
Core-collapse supernova enrichment in the core of the Virgo ClusterAug 22 2011Using a deep (574 ks) Chandra observation of M87, the dominant galaxy of the nearby Virgo Cluster, we present the best measurements to date of the radial distribution of metals in the central intracluster medium (ICM). Our measurements, made in 36 independent ... More
VLA Polarimetry Observations of PKS 2322-123; Estimating Magnetic Fields in the Abell 2597 ClusterMar 10 2005We present 5, 8, and 15 GHz total intensity and polarimetric observations of the radio source PKS 2322-123 taken with the Very Large Array (VLA). This small (11 kpc) source is located at the center of the cooling-core cluster Abell 2597. The inner X-ray ... More
A Recommender System to Support the Scholarly Communication ProcessMay 11 2009The number of researchers, articles, journals, conferences, funding opportunities, and other such scholarly resources continues to grow every year and at an increasing rate. Many services have emerged to support scholars in navigating particular aspects ... More
Turbulence driven diffusion in protoplanetary disks - chemical effects in the outer diskMar 03 2006The dynamics and chemistry of protostellar disks are likely to be intricately linked, with dynamical processes altering the chemical composition, and chemistry, in turn, controlling the ionization structure and hence the ability of the magneto-rotational ... More
Dynamical Fluctuating Charge Force Fields: Application to Liquid WaterJun 10 1994A new molecular dynamics model in which the point charges on atomic sites are allowed to fluctuate in response to the environment is developed and applied to water. The idea for treating charges as variables is based on the concept of electronegativity ... More
Magnetic fields in the Centaurus clusterSep 20 2001We present multi-frequency VLA observations of the radio galaxy PKS 1246-410 at the center of the Centaurus Cluster, and compare these results to recent Chandra observations. The unusual radio morphology of PKS 1246-410 probably results from interactions ... More