Results for "D. M. Bowman"

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Suppression of Spin-Orbit Scattering in Strong-Disordered Gold NanojunctionsFeb 02 2004Mar 20 2005We discovered that spin-orbit scattering in strong-disordered gold nanojunctions is strongly suppressed relative to that in weak-disordered gold thin films. This property is unusual because in weak-disordered films, spin-orbit scattering increases with ... More
Spin-Based Magnetofingerprints and Dephasing in Strongly Disordered Au-NanobridgesMar 20 2005Dec 01 2005We investigate quantum interference effects with magnetic field (magnetofingerprints) in strongly disordered Au-nanobridges. The magnetofingerprints are unconventional because they are caused by the Zeeman effect, not by the Aharonov-Bohm effect. These ... More
Electrostatically Assembled Metallic Point ContactsDec 12 2001We describe a method for creating atomic-scale electric contacts. A metal source is deposited on two insulating substrates separated by a 70 nm gap. Electric conductance across the gap is monitored, while protrusions from the bulk extend into the gap ... More
Localization and Capacitance Fluctuations in Disordered Au Nano-junctionsFeb 02 2004Nano-junctions, containing atomic-scale gold contacts between strongly disordered leads, exhibit different transport properties at room temperature and at low temperature. At room temperature, the nano-junctions exhibit conductance quantization effects. ... More
Differences in Personal and Professional Tweets of ScholarsMay 06 2015Purpose: This study shows that there were differences in the use of Twitter by professors at universities in the Association of American Universities (AAU). Affordance use differed between the personal and professional tweets of professors. Framing behaviors ... More
HI and Cosmology: What We Need To KnowJan 05 2009There are three distinct regimes in which radio observations of the redshifted 21 cm line of HI can contribute directly to cosmology in unique ways. The regimes are naturally divided by redshift, from high to low, into: inflationary physics, the Dark ... More
Electron Transport in Metallic GrainsFeb 21 2002Sep 03 2002We discuss electron transport in individual nanometer-scale metallic grains at dilution refrigerator temperatures. In the weak coupling regime, the grains exhibit Coulomb blockade and discrete energy levels. Electron-electron interactions lead to clustering ... More
Multiple Polylogarithms: A Brief SurveyOct 05 2003We survey various results and conjectures concerning multiple polylogarithms and the multiple zeta function. Among the results, we announce our resolution of several conjectures on multiple zeta values. We also provide a new integral representation for ... More
Infinite Volume and Continuum Limits of the Landau-Gauge Gluon PropagatorJan 19 2001May 31 2001We extend a previous improved action study of the Landau gauge gluon propagator, by using a variety of lattices with spacings from $a = 0.17$ to 0.41 fm, to more fully explore finite volume and discretization effects. We also extend a previously used ... More
K2 space photometry reveals rotational modulation and stellar pulsations in chemically peculiar A and B starsMay 04 2018May 11 2018The physics of magnetic hot stars and how a large-scale magnetic field affects their interior properties is largely unknown. Few studies have combined high-quality observations and modelling of magnetic pulsating stars, known as magneto-asteroseismology, ... More
The Algebra and Combinatorics of Shuffles and Multiple Zeta ValuesOct 06 2003The algebraic and combinatorial theory of shuffles, introduced by Chen and Ree, is further developed and applied to the study of multiple zeta values. In particular, we establish evaluations for certain sums of cyclically generated multiple zeta values. ... More
Resolution of Some Open Problems Concerning Multiple Zeta Evaluations of Arbitrary DepthOct 05 2003We prove some new evaluations for multiple polylogarithms of arbitrary depth. The simplest of our results is a multiple zeta evaluation one order of complexity beyond the well-known Broadhurst-Zagier formula. Other results we provide settle three of the ... More
Gluon Propagator on Coarse Lattices in Laplacian GaugesJun 14 2002Jun 21 2002The Laplacian gauge is a nonperturbative gauge fixing that reduces to Landau gauge in the asymptotic limit. Like Landau gauge, it respects Lorentz invariance, but it is free of Gribov copies; the gauge fixing is unambiguous. In this paper we study the ... More
Nanometer-Scale Metallic Grains Connected with Atomic-Scale ConductorsOct 28 2002We describe a technique for connecting a nanometer-scale gold grain to leads by atomic-scale gold point contacts. These devices differ from previous metallic quantum dots in that the conducting channels are relatively well-transmitting. We investigate ... More
Efficient and automatic methods for flexible regression on spatiotemporal data, with applications to groundwater monitoringOct 29 2013Fitting statistical models to spatiotemporal data requires finding the right balance between imposing smoothness and following the data. In the context of p-splines, we propose a Bayesian framework for choosing the smoothing parameter which allows the ... More
Modelling the quark propagatorSep 17 2002The quark propagator is at the core of lattice hadron spectrum calculations as well as studies in other nonperturbative schemes. We investigate the quark propagator with an improved staggered action (Asqtad) and an improved gluon action, which provides ... More
Period spacings of gravity modes in rapidly rotating magnetic stars I. Axisymmetric fossil field with poloidal and toroidal componentsMar 13 2019Context. Stellar magnetic fields are one of the candidates often invoked to explain the missing transport of angular momentum observed in the models of stellar interiors. However, the properties of an internal magnetic field and the consequences of its ... More
A lower limit of dz > 0.06 for the duration of the reionization epochSep 05 2012Observations of the 21-centimetre line of atomic hydrogen in the early Universe directly probe the history of the reionization of the gas between galaxies. The observations are challenging, though, because of the low expected signal strength (~10 mK), ... More
Interpreting "altmetrics": viewing acts on social media through the lens of citation and social theoriesFeb 19 2015More than 30 years after Cronin's seminal paper on "the need for a theory of citing" (Cronin, 1981), the metrics community is once again in need of a new theory, this time one for so-called "altmetrics". Altmetrics, short for alternative (to citation) ... More
Absolute calibration of a wideband antenna and spectrometer for sky noise spectral index measurementsSep 05 2012A new method of absolute calibration of sky noise temperature using a three-position switched spectrometer, measurements of antenna and low noise amplifier impedance with a vector network analyzer, and ancillary measurements of the amplifier noise waves ... More
Consistency of parity-violating pion-nucleon couplings extracted from measurements in 18F and 133CsFeb 13 1998The recent measurement of the nuclear anapole moment of 133Cs has been interpreted to yield a value of the weak pion-nucleon coupling H_pi^1 which contradicts the upper limit from the 18F experiments. We argue that because of the sensitivity of the anapole ... More
When is an article actually published? An analysis of online availability, publication, and indexation datesMay 04 2015With the acceleration of scholarly communication in the digital era, the publication year is no longer a sufficient level of time aggregation for bibliometric and social media indicators. Papers are increasingly cited before they have been officially ... More
Forward seismic modelling of the pulsating magnetic B-type star HD 43317May 02 2018May 31 2018The large-scale magnetic fields detected at the surface of about 10% of hot stars extend into the stellar interior, where they may alter the structure. Deep inner regions of stars are only observable using asteroseismology. Here, we investigated the pulsating ... More
Spectral Index of the Diffuse Radio Background Measured From 100 to 200 MHzJun 17 2008The mean absolute brightness temperature of the diffuse radio background was measured as a function of frequency in a continuous band between 100 and 200 MHz over an effective solid angle of ~pi str at high Galactic latitude. A spectral brightness temperature ... More
Nearby Doorways, Parity Doublets and Parity Mixing in Compound Nuclear StatesAug 28 1994We discuss the implications of a doorway state model for parity mixing in compound nuclear states. We argue that in order to explain the tendency of parity violating asymmetries measured in $^{233}$Th to have a common sign, doorways that contribute to ... More
Binary Asteroseismic Modelling: isochrone-cloud methodology and application to Kepler gravity-mode pulsatorsOct 01 2018The simultaneous presence of variability due to both pulsations and binarity is no rare phenomenon. Unfortunately, the complexities of dealing with even one of these sources of variability individually means that the other signal is often treated as a ... More
Detection of magnetic fields in chemically peculiar stars observed with the K2 space missionMay 02 2018We report the results of an observational study aimed at searching for magnetic pulsating hot stars suitable for magneto-asteroseismology. A sample of sixteen chemically peculiar stars was selected and analysed using both high-resolution spectropolarimetry ... More
Simple modules for the partition algebra and monotone convergence of Kronecker coefficientsJul 28 2016We construct bases of the simple modules for partition algebras which are indexed by paths in an alcove geometry. This allows us to give a concrete interpretation (and new proof) of the monotone convergence property for Kronecker coefficients using stratifications ... More
Pulsational Frequency and Amplitude Modulation in the $δ$\,Sct star KIC\,7106205Aug 04 2014Analysis of the \textit{Kepler} $\delta$\,Sct star KIC\,7106205 showed amplitude modulation in a single pressure mode, whilst all other pressure and gravity modes remained stable in amplitude and phase over the 1470\,d length of the dataset. The \textit{Kepler} ... More
Gluons, quarks, and the transition from nonperturbative to perturbative QCDJul 04 2001Jul 06 2001Lattice-based investigations of two fundamental QCD quantities are described, namely the gluon and quark propagators in Landau gauge. We have studied the Landau gauge gluon propagator using a variety of lattices with spacings from a = 0.17 to 0.41 fm. ... More
TEA: A Code for Calculating Thermochemical Equilibrium AbundancesMay 24 2015We present an open-source Thermochemical Equilibrium Abundances (TEA) code that calculates the abundances of gaseous molecular species. The code is based on the methodology of White et al. (1958) and Eriksson (1971). It applies Gibbs free-energy minimization ... More
The block structure of the partition algebras in characteristic $p\geq 0$Feb 20 2014Jan 21 2015In this paper we describe the blocks of the partition algebra over a field of positive characteristic.
Characterising the observational properties of δ Sct stars in the era of space photometry from the Kepler missionFeb 15 2018The {\delta} Sct stars are a diverse group of intermediate-mass pulsating stars located on and near the main sequence within the classical instability strip in the Hertzsprung-Russell diagram. Many of these stars are hybrid stars pulsating simultaneously ... More
A Spitzer Five-Band Analysis of the Jupiter-Sized Planet TrES-1Nov 12 2014Nov 18 2014With an equilibrium temperature of 1200 K, TrES-1 is one of the coolest hot Jupiters observed by {\Spitzer}. It was also the first planet discovered by any transit survey and one of the first exoplanets from which thermal emission was directly observed. ... More
High-Field Conduction in Barium TitanateSep 22 2004We present current-voltage studies of very thin (ca. 77 nm) barium titanate single crystals up to 1.3 GV/m applied field. These show that the mechanism of leakage current at high fields is that of space charge limited conduction (SCLC) in a regime with ... More
Global and Brazilian carbon response to El Niño Modoki 2011-2010Mar 10 2017The El Ni\~{n}o Modoki in 2010 lead to historic droughts in Brazil. We quantify the global and Brazilian carbon response to this event using the NASA Carbon Monitoring System Flux (CMS-Flux) framework. Satellite observations of CO$_2$, CO, and solar induced ... More
High-fidelity phase and amplitude control of phase-only computer generated holograms using conjugate gradient minimisationJan 30 2017We demonstrate simultaneous control of both the phase and amplitude of light using a conjugate gradient minimisation-based hologram calculation technique and a single phase-only spatial light modulator (SLM). A cost function which incorporates the inner ... More
Progress toward a new measurement of the parity violating asymmetry in n+p-->d+gammaApr 01 1998We outline the motivation and conceptual design for a new experiment aimed at a 10-fold improvement in the accuracy of the parity-violating asymmetry A_gamma in the angular distribution of 2.2 MeV gamma rays from the n+p-->d+gamma reaction. This observable ... More
New precision measurements of free neutron beta decay with cold neutronsAug 20 2014Precision measurements in free neutron beta decay serve to determine the coupling constants of beta decay, and offer several stringent tests of the Standard Model. This paper describes the free neutron beta decay program planned for the Fundamental Physics ... More
Statistical Theory of Parity Nonconservation in Compound NucleiNov 16 1999Sep 27 2000We present the first application of statistical spectroscopy to study the root-mean-square value of the parity nonconserving (PNC) interaction matrix element M determined experimentally by scattering longitudinally polarized neutrons from compound nuclei. ... More
Adapting sentiment analysis for tweets linking to scientific papersJul 07 2015In the context of altmetrics, tweets have been discussed as potential indicators of immediate and broader societal impact of scientific documents. However, it is not yet clear to what extent Twitter captures actual research impact. A small case study ... More
Recursive Neural Networks Can Learn Logical SemanticsJun 06 2014May 14 2015Tree-structured recursive neural networks (TreeRNNs) for sentence meaning have been successful for many applications, but it remains an open question whether the fixed-length representations that they learn can support tasks as demanding as logical deduction. ... More
Gravitational Lensing Signatures of Supermassive Black Holes in Future Radio SurveysJun 24 2004Aug 13 2004Observational measurements of the relationship between supermassive black holes (SMBHs) and the properties of their host galaxies are an important method for probing theoretical hierarchical growth models. Gravitational lensing is a unique mechanism for ... More
Constraints on Fundamental Cosmological Parameters with Upcoming Redshifted 21 cm ObservationsDec 12 2005Feb 16 2007Constraints on cosmological parameters from upcoming measurements with the Mileura Widefield Array-Low Frequency Demonstrator (MWA-LFD) of the redshifted 21 cm power spectrum are forecast assuming a flat LCDM cosmology and that the reionization of neutral ... More
Improving Foreground Subtraction in Statistical Observations of 21 cm Emission from the Epoch of ReionizationOct 03 2005Jun 12 2006Statistical observations of the Epoch of Reionization using the 21 cm line of neutral hydrogen have the potential to revolutionize our understanding of structure formation and the first luminous objects. However, these observations are complicated by ... More
Observing Neutral Hydrogen Above Redshift 6: The "Global" PerspectiveJan 05 2009Above redshift 6, the dominant source of neutral hydrogen in the Universe shifts from localized clumps in and around galaxies and filaments to a pervasive, diffuse component of the intergalactic medium (IGM). This transition tracks the global neutral ... More
Toward Empirical Constraints on the Global Redshifted 21 cm Brightness Temperature During the Epoch of ReionizationOct 12 2007Preliminary results are presented from a simple, single-antenna experiment designed to measure the all-sky radio spectrum between 100 and 200 MHz. The system used an internal comparison-switching scheme to reduce non-smooth instrumental contaminants in ... More
A large annotated corpus for learning natural language inferenceAug 21 2015Understanding entailment and contradiction is fundamental to understanding natural language, and inference about entailment and contradiction is a valuable testing ground for the development of semantic representations. However, machine learning research ... More
Bright Source Subtraction Requirements For Redshifted 21 cm MeasurementsMay 21 2010The \hi 21 cm transition line is expected to be an important probe into the cosmic dark ages and epoch of reionization. Foreground source removal is one of the principal challenges for the detection of this signal. This paper investigates the extragalactic ... More
Multi-wavelength holography with a single Spatial Light Modulator for ultracold atom experimentsJan 06 2015Mar 25 2015We demonstrate a method to create arbitrary intensity distributions of multiple wavelengths of light, which can be useful for ultracold atom experiments, by using regional phase-calculation algorithms to find a single hologram which is illuminated with ... More
Tree-structured composition in neural networks without tree-structured architecturesJun 16 2015Nov 09 2015Tree-structured neural networks encode a particular tree geometry for a sentence in the network design. However, these models have at best only slightly outperformed simpler sequence-based models. We hypothesize that neural sequence models like LSTMs ... More
Foreground Contamination in Interferometric Measurements of the Redshifted 21 cm Power SpectrumJul 25 2008Jan 05 2009Subtraction of astrophysical foreground contamination from "dirty" sky maps produced by simulated measurements of the Murchison Widefield Array (MWA) has been performed by fitting a 3rd-order polynomial along the spectral dimension of each pixel in the ... More
The Sensitivity of First Generation Epoch of Reionization Observatories and Their Potential for Differentiating Theoretical Power SpectraJul 14 2005Statistical observations of the epoch of reionization (EOR) power spectrum provide a rich data set for understanding the transition from the cosmic "dark ages" to the ionized universe we see today. EOR observations have become an active area of experimental ... More
Learning Distributed Word Representations for Natural Logic ReasoningOct 15 2014Natural logic offers a powerful relational conception of meaning that is a natural counterpart to distributed semantic representations, which have proven valuable in a wide range of sophisticated language tasks. However, it remains an open question whether ... More
Quark propagator from an improved staggered action in Laplacian and Landau gaugesDec 17 2001Studies of gauge dependent quantities are afflicted with Gribov copies, but Laplacian gauge fixing provides one possible solution to this problem. We present results for the lattice quark propagator in both Landau and Laplacian gauges using standard and ... More
Decomposition numbers for the cyclotomic Brauer algebras in characteristic zeroMay 15 2012We study the representation theory of the cyclotomic Brauer algebra via truncation to idempotent subalgebras which are isomorphic to a product of walled and classical Brauer algebras. In particular, we determine the block structure and decomposition numbers ... More
Magnetization of 2.6T in gadolinium thin filmsSep 25 2012There is renewed interest in rare-earth elements and gadolinium in particular for a range of studies in coupling physics and applications. However, it is still apparent that synthesis impacts understanding of the intrinsic magnetic properties of thin ... More
Combining WASP and Kepler data: the case of the $δ$ Sct star KIC 7106205Feb 19 2015Ground-based photometric observations from WASP have been calibrated, scaled and combined with Kepler observations of the $\delta$ Sct star KIC 7106205, allowing us to extend the time base of the study of the unexplained amplitude and frequency variation ... More
Lattice Quark Propagator in Landau and Laplacian GaugesOct 14 2001We present results for the lattice quark propagator in both Landau and Laplacian gauges using standard and improved staggered quark actions. The standard Kogut-Susskind action has errors of \oa{2} while the improved ``Asqtad'' action has \oa{4}, \oag{2}{2} ... More
Lattice quark propagator with staggered quarks in Landau and Laplacian gaugesMar 01 2002We report on the lattice quark propagator using standard and improved Staggered quark actions, with the standard, Wilson gauge action. The standard Kogut-Susskind action has errors of \oa{2} while the ``Asqtad'' action has \oa{4}, \oag{2}{2} errors. The ... More
Role of defects in determining the magnetic ground state of ytterbium titanateFeb 19 2019Pyrochlore systems are ideally suited to the exploration of geometrical frustration in three dimensions, and their rich phenomenology encompasses topological order and fractional excitations. Classical spin ices provide the first context in which it is ... More
Improved Landau Gauge Fixing and Discretisation ErrorsSep 14 1999Dec 17 1999Lattice discretisation errors in the Landau gauge condition are examined. An improved gauge fixing algorithm in which order a^2 errors are removed is presented. Order a^2 improvement of the gauge fixing condition displays the secondary benefit of reducing ... More
Forward asteroseismic modeling of stars with a convective core from gravity-mode oscillations: parameter estimation and stellar model selectionJun 18 2018We propose a methodological framework to perform forward asteroseismic modeling of stars with a convective core, based on gravity-mode oscillations. These probe the near-core region in the deep stellar interior. The modeling relies on a set of observed ... More
Brauer algebras of Type $C$ are Cellularly Stratified AlgebrasFeb 02 2011In a recent paper Cohen, Liu and Yu introduce the Type $C$ Brauer algebra. We show that this algebra is an iterated inflation of hyperoctahedral groups, and that it is cellularly stratified. This gives an indexing set of the standard modules, results ... More
An Observational Test of the Critical Earthquake ConceptMar 16 1998We test the concept that seismicity prior to a large earthquake can be understood in terms of the statistical physics of a critical phase transition. In this model, the cumulative seismic strain release increases as a power-law time-to-failure before ... More
Discretisation Errors in Landau Gauge on the LatticeMay 06 1999Jun 09 1999Lattice discretisation errors in the Landau gauge condition are examined. An improved gauge fixing algorithm in which ${\cal O}(a^2)$ errors are removed is presented. ${\cal O}(a^2)$ improvement of the gauge fixing condition improves comparison with continuum ... More
Photometric detection of internal gravity waves in early-type stars observed by CoRoTNov 30 2018Early-type stars are predicted to excite an entire spectrum of internal gravity waves (IGWs) at the interface of their convective cores and radiative envelopes. Numerical simulations of IGWs predict stochastic low-frequency variability in photometric ... More
On the photometric detection of Internal Gravity Waves in upper main-sequence stars I. Methodology and application to CoRoT targetsNov 19 2018Context. Main sequence stars with a convective core are predicted to stochastically excite Internal Gravity Waves (IGWs), which effectively transport angular momentum throughout the stellar interior and explain the observed near-uniform interior rotation ... More
Bases of quasi-hereditary covers of diagram algebrasFeb 03 2011Jul 16 2012We extend the the combinatorics of tableaux to the study of diagram algebras and give a uniform construction of their quasi-hereditary covers.
Holomorphic Flexibility Properties of Spaces of Elliptic FunctionsSep 22 2016Let $X$ be an elliptic curve and $\mathbb{P}$ the Riemann sphere. Since $X$ is compact, it is a deep theorem of Douady that the set $\mathcal{O}(X,\mathbb{P})$ consisting of holomorphic maps $X\to \mathbb{P}$ admits a complex structure. If $R_n$ denotes ... More
K2 photometry and HERMES spectroscopy of the blue supergiant rho Leo: rotational wind modulation and low-frequency wavesFeb 02 2018We present an 80-d long uninterrupted high-cadence K2 light curve of the B1Iab supergiant rho Leo (HD 91316), deduced with the method of halo photometry. This light curve reveals a dominant frequency of $f_{\rmrot}=0.0373$d$^{-1}$ and its harmonics. This ... More
On the sensitivity of gravito-inertial modes to differential rotation in intermediate-mass main-sequence starsJun 10 2018Jun 26 2018Context. While rotation has a major impact on stellar structure and evolution, its effects are not well understood. Thanks to high- quality and long timebase photometric observations obtained with recent space missions, we are now able to study stellar ... More
K2 photometry and HERMES spectroscopy of the blue supergiant rho Leo: rotational wind modulation and low-frequency wavesFeb 02 2018Feb 13 2018We present an 80-d long uninterrupted high-cadence K2 light curve of the B1Iab supergiant rho Leo (HD 91316), deduced with the method of halo photometry. This light curve reveals a dominant frequency of $f_{\rmrot}=0.0373$d$^{-1}$ and its harmonics. This ... More
Infrared Behavior of the Gluon Propagator on a Large Volume LatticeFeb 18 2000Jul 29 2000The first calculation of the gluon propagator using an order a^2 improved action with the corresponding order a^2 improved Landau gauge fixing condition is presented. The gluon propagator obtained from the improved action and improved Landau gauge condition ... More
Scaling Behavior of the Landau Gauge Overlap Quark PropagatorSep 11 2003The properties of the momentum space quark propagator in Landau gauge are examined for the overlap quark action in quenched lattice QCD. Numerical calculations are done on three lattices with different lattice spacings and similar physical volumes to ... More
Irreducible Modules for the Quantum Affine Algebra $U_q(g)$ and its Borel subalgebra $U_q(g)^{\geq 0}$Jun 24 2006We prove a bijection between finite-dimensional irreducible modules for an arbitrary quantum affine algebra $U_q(g)$ and finite-dimensional irreducible modules for its Borel subalgebra $U_q(g)^{\geq 0}$.
Dark Cosmology: Investigating Dark Matter & Exotic Physics in the Dark Ages using the Redshifted 21-cm Global SpectrumFeb 16 2019The Dark Ages, probed by the redshifted 21-cm signal, is the ideal epoch for a new rigorous test of the standard LCDM cosmological model. Divergences from that model would indicate new physics, such as dark matter decay (heating) or baryonic cooling beyond ... More
Intrinsic Dielectric Response in Ferroelectric NanocrystalsJun 08 2004Measurements on 'free-standing' single crystal barium titanate capacitors with thicknesses down to 75nm show a dielectric response typical of large single crystals rather than conventional thin films. There is a notable absence of any broadening or temperature ... More
Towards the Continuum Limit of the Overlap Quark Propagator in Landau GaugeAug 22 2002Sep 12 2002The properties of the momentum space quark propagator in Landau gauge are examined for the overlap quark action in quenched lattice QCD. Numerical calculations were done on two lattices with different lattice spacing $a$ and similar physical volumes to ... More
Realizing a High Magnetic Moment in Gd/Cr/FeCo: The Role of the Rare EarthDec 19 2012The search for materials or systems exhibiting a high magnetic saturation has been of longstanding importance. It has been suggested that increased saturation could be achieved by coupling a transition metal via a spacer to a rare earth. We report Gd/Cr/Fe70Co30 ... More
Improved Measurement of the Spectral Index of the Diffuse Radio Background Between 90 and 190 MHzSep 27 2016Oct 22 2016We report absolutely calibrated measurements of diffuse radio emission between 90 and 190 MHz from the Experiment to Detect the Global EoR Signature (EDGES). EDGES employs a wide beam zenith-pointing dipole antenna centred on a declination of -26.7$^\circ$. ... More
Calibration of the EDGES High-Band Receiver to Observe the Global 21-cm Signature from the Epoch of ReionizationFeb 25 2016Nov 08 2016The EDGES High-Band experiment aims to detect the sky-average brightness temperature of the $21$-cm signal emitted during the Epoch of Reionization (EoR) in the redshift range $14.8 \gtrsim z \gtrsim 6.5$. To probe this redshifted signal, EDGES High-Band ... More
An MCMC approach to extracting the global 21-cm signal during the cosmic dawn from sky-averaged radio observationsJul 15 2011Oct 25 2011Efforts are being made to observe the 21-cm signal from the 'cosmic dawn' using sky-averaged observations with individual radio dipoles. In this paper, we develop a model of the observations accounting for the 21-cm signal, foregrounds, and several major ... More
A Generic and Efficient E-field Parallel Imaging Correlator for Next-Generation Radio TelescopesOct 28 2015Oct 09 2016Modern radio telescopes are favouring densely packed array layouts with large numbers of antennas ($\Nant\gtrsim 1000$). Since the complexity of traditional correlators scales as $\mathcal{O}(\Nant^2)$, there will be a steep cost for realizing the full ... More
A Fast Unified Model for Parsing and Sentence UnderstandingMar 19 2016Jul 29 2016Tree-structured neural networks exploit valuable syntactic parse information as they interpret the meanings of sentences. However, they suffer from two key technical problems that make them slow and unwieldy for large-scale NLP tasks: they usually operate ... More
Scaling behavior of the overlap quark propagator in Landau gaugeJan 17 2003May 11 2004The properties of the momentum space quark propagator in Landau gauge are examined for the overlap quark action in quenched lattice QCD. Numerical calculations are done on three lattices with different lattice spacings and similar physical volumes to ... More
Calibration of the EDGES Receiver to Observe the Global 21-cm Signature from the Epoch of ReionizationFeb 25 2016The EDGES experiment strives to detect the the sky-average brightness temperature from the $21$-cm line emitted during the Epoch of Reionization (EoR) in the redshift range $14 \gtrsim z \gtrsim 6$. To probe this signal, EDGES conducts single-antenna ... More
Limits on Foreground Subtraction from Chromatic Beam Effects in Global Redshifted 21 cm MeasurementsOct 12 2015Foreground subtraction in global redshifted 21 cm measurements is limited by frequency-dependent (chromatic) structure in antenna beam patterns. Chromatic beams couple angular structures in Galactic foreground emission to spectral structures that may ... More
Astrophysicists on Twitter: An in-depth analysis of tweeting and scientific publication behaviorOct 07 2014This paper analyzes the tweeting behavior of 37 astrophysicists on Twitter and compares their tweeting behavior with their publication behavior and citation impact to show whether they tweet research-related topics or not. Astrophysicists on Twitter are ... More
Measuring Social Media Activity of Scientific Literature: An Exhaustive Comparison of Scopus and Novel Altmetrics Big DataMay 09 2017Jul 17 2017This paper measures social media activity of 15 broad scientific disciplines indexed in Scopus database using Altmetric.com data. First, the presence of Altmetric.com data in Scopus database is investigated, overall and across disciplines. Second, the ... More
Overlap Quark Propagator in Landau GaugeFeb 04 2002Apr 09 2002The properties of the quark propagator in Landau gauge in quenched QCD are examined for the overlap quark action. The overlap quark action satisfies the Ginsparg-Wilson relation and as such provides an exact lattice realization of chiral symmetry. This ... More
Transit and Eclipse Analyses of Exoplanet HD 149026b Using BLISS MappingAug 09 2011May 25 2012The dayside of HD 149026b is near the edge of detectability by the Spitzer Space Telescope. We report on eleven secondary-eclipse events at 3.6, 4.5, 3 x 5.8, 4 x 8.0, and 2 x 16 microns plus three primary-transit events at 8.0 microns. The eclipse depths ... More
A Search for Radio Gravitational Lenses, Using the Sloan Digital Sky Survey and the Very Large ArrayOct 05 2005Nov 25 2005We report on a novel search for radio gravitational lenses. Using the Very Large Array, we imaged ten candidates with both dual redshifts in Sloan Digital Sky Survey spectra and 1.4 GHz radio flux >2 mJy in the FIRST survey. The VLA maps show that in ... More
An Efficient Feedback Calibration Algorithm for Direct Imaging Radio TelescopesMar 07 2016Mar 30 2016We present the E-field Parallel Imaging Calibration (EPICal) algorithm, which addresses the need for a real-time calibration method for direct imaging radio astronomy correlators. Direct imaging involves a spatial fast Fourier transform of antenna voltages, ... More
Tweets as impact indicators: Examining the implications of automated bot accounts on TwitterOct 15 2014This brief communication presents preliminary findings on automated Twitter accounts distributing links to scientific papers deposited on the preprint repository arXiv. It discusses the implication of the presence of such bots from the perspective of ... More
One-Port Direct/Reverse Method for Characterizing VNA Calibration StandardsJun 08 2016This paper introduces a one-port method for estimating model parameters of VNA calibration standards. The method involves measuring the standards through an asymmetrical passive network connected in direct mode and then in reverse mode, and using these ... More
Radiometric Measurements of Electron Temperature and Opacity of Ionospheric PerturbationsDec 06 2014Changes in the sky noise spectrum are used to characterize perturbations in the ionosphere. Observations were made at the same sidereal time on multiple days using a calibrated broadband dipole and radio spectrometer covering 80 to 185 MHz. In this frequency ... More
Calibration of the EDGES High-Band Receiver to Observe the Global 21-cm Signature from the Epoch of ReionizationFeb 25 2016Dec 10 2016The EDGES High-Band experiment aims to detect the sky-average brightness temperature of the $21$-cm signal from the Epoch of Reionization (EoR) in the redshift range $14.8 \gtrsim z \gtrsim 6.5$. To probe this redshifted signal, EDGES High-Band conducts ... More
Improved Measurement of the Spectral Index of the Diffuse Radio Background Between 90 and 190 MHzSep 27 2016We report absolutely calibrated measurements of diffuse radio emission between 90 and 190 MHz from the Experiment to Detect the Global EoR Signature (EDGES). EDGES employs a wide beam zenith-pointing dipole antenna centred on a declination of -26.7$^\circ$. ... More
Impact of Instrument Responses on the Detectability of One-point Statistics from Redshifted 21 cm ObservationsOct 19 2016We study the impact of instrumental systematics on the variance, skewness, and kurtosis of redshifted 21 cm intensity fluctuation observations from the Epoch of Reionization. We simulate realistic 21 cm observations based on the Murchison Widefield Array ... More