Results for "Brian Paul Bockelman"

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ROOT I/O compression algorithms and their performance impact within Run 3Jun 11 2019Aug 02 2019The LHCs Run3 will push the envelope on data-intensive workflows and, since at the lowest level this data is managed using the ROOT software framework, preparations for managing this data are starting already. At the beginning of LHC Run 1, all ROOT data ... More
Continuous Performance Benchmarking Framework for ROOTDec 07 2018Feb 21 2019Foundational software libraries such as ROOT are under intense pressure to avoid software regression, including performance regressions. Continuous performance benchmarking, as a part of continuous integration and other code quality testing, is an industry ... More
Extending ROOT through ModulesDec 07 2018Dec 11 2018The ROOT software framework is foundational for the HEP ecosystem, providing capabilities such as IO, a C++ interpreter, GUI, and math libraries. It uses object-oriented concepts and build-time components to layer between them. We believe additional layering ... More
Evolution of ROOT package managementJun 11 2019ROOT is a large code base with a complex set of build-time dependencies; there is a significant difference in compilation time between the "core" of ROOT and the full-fledged deployment. We present results on a "delayed build" for internal ROOT packages ... More
Exploring compression techniques for ROOT IOApr 23 2017ROOT provides an flexible format used throughout the HEP community. The number of use cases - from an archival data format to end-stage analysis - has required a number of tradeoffs to be exposed to the user. For example, a high "compression level" in ... More
Optimizing ROOT IO For AnalysisNov 07 2017The ROOT I/O (RIO) subsystem is foundational to most HEP experiments - it provides a file format, a set of APIs/semantics, and a reference implementation in C++. It is often found at the base of an experiment's framework and is used to serialize the experiment's ... More
Speeding HEP Analysis with ROOT Bulk I/OJun 11 2019Distinct HEP workflows have distinct I/O needs; while ROOT I/O excels at serializing complex C++ objects common to reconstruction, analysis workflows typically have simpler objects and can sustain higher event rates. To meet these workflows, we have developed ... More
Discovering Job Preemptions in the Open Science GridJul 17 2018The Open Science Grid(OSG) is a world-wide computing system which facilitates distributed computing for scientific research. It can distribute a computationally intensive job to geo-distributed clusters and process job's tasks in parallel. For compute ... More
Fast Access to Columnar, Hierarchically Nested Data via Code TransformationAug 20 2017Nov 03 2017Big Data query systems represent data in a columnar format for fast, selective access, and in some cases (e.g. Apache Drill), perform calculations directly on the columnar data without row materialization, avoiding runtime costs. However, many analysis ... More
ROOT I/O compression algorithms and their performance impact within Run 3Jun 11 2019The LHCs Run3 will push the envelope on data-intensive workflows and, since at the lowest level this data is managed using the ROOT software framework, preparations for managing this data are starting already. At the beginning of LHC Run 1, all ROOT data ... More
Designing Computing System Architecture and Models for the HL-LHC eraJul 20 2015This paper describes a programme to study the computing model in CMS after the next long shutdown near the end of the decade.
Heterogeneous High Throughput Scientific Computing with APM X-Gene and Intel Xeon PhiOct 10 2014Electrical power requirements will be a constraint on the future growth of Distributed High Throughput Computing (DHTC) as used by High Energy Physics. Performance-per-watt is a critical metric for the evaluation of computer architectures for cost- efficient ... More
SciTokens: Capability-Based Secure Access to Remote Scientific DataJul 12 2018The management of security credentials (e.g., passwords, secret keys) for computational science workflows is a burden for scientists and information security officers. Problems with credentials (e.g., expiration, privilege mismatch) cause workflows to ... More
Increasing Parallelism in the ROOT I/O SubsystemApr 10 2018When processing large amounts of data, the rate at which reading and writing can take place is a critical factor. High energy physics data processing relying on ROOT is no exception. The recent parallelisation of LHC experiments' software frameworks and ... More
Data Access for LIGO on the OSGMay 17 2017During 2015 and 2016, the Laser Interferometer Gravitational-Wave Observatory (LIGO) conducted a three-month observing campaign. These observations delivered the first direct detection of gravitational waves from binary black hole mergers. To search for ... More
SciTokens: Demonstrating Capability-Based Access to Remote Scientific Data using HTCondorMay 22 2019The management of security credentials (e.g., passwords, secret keys) for computational science workflows is a burden for scientists and information security officers. Problems with credentials (e.g., expiration, privilege mismatch) cause workflows to ... More
The Tetrahedron algebra, the Onsager algebra, and the $\mathfrak{sl}_2$ loop algebraNov 02 2005Let $K$ denote a field with characteristic 0 and let $T$ denote an indeterminate. We give a presentation for the three-point loop algebra $\mathfrak{sl}_2 \otimes K\lbrack T, T^{-1},(T-1)^{-1}\rbrack$ via generators and relations. This presentation displays ... More
On the Geometric Interpretation of N = 2 Superconformal TheoriesSep 19 1994Dec 09 1994We clarify certain important issues relevant for the geometric interpretation of a large class of N = 2 superconformal theories. By fully exploiting the phase structure of these theories (discovered in earlier works) we are able to clearly identify their ... More
Any Data, Any Time, Anywhere: Global Data Access for ScienceAug 06 2015Data access is key to science driven by distributed high-throughput computing (DHTC), an essential technology for many major research projects such as High Energy Physics (HEP) experiments. However, achieving efficient data access becomes quite difficult ... More
HEPCloud, a New Paradigm for HEP Facilities: CMS Amazon Web Services InvestigationSep 29 2017Historically, high energy physics computing has been performed on large purpose-built computing systems. These began as single-site compute facilities, but have evolved into the distributed computing grids used today. Recently, there has been an exponential ... More
Machine Agency in Human-Machine Networks; Impacts and Trust ImplicationsFeb 26 2016We live in an emerging hyper-connected era in which people are in contact and interacting with an increasing number of other people and devices. Increasingly, modern IT systems form networks of humans and machines that interact with one another. As machines ... More
Error Floor Approximation for LDPC Codes in the AWGN ChannelFeb 13 2012Jun 09 2013This paper addresses the prediction of error floors of low-density parity-check (LDPC) codes with variable nodes of constant degree in the additive white Gaussian noise (AWGN) channel. Specifically, we focus on the performance of the sum-product algorithm ... More
Generalized Sharp Bounds on the Spectral Radius of DigraphsApr 27 2012Mar 04 2013The spectral radius {\rho}(G) of a digraph G is the maximum modulus of the eigenvalues of its adjacency matrix. We present bounds on {\rho}(G) that are often tighter and are applicable to a larger class of digraphs than previously reported bounds. Calculating ... More
Numerical Issues Affecting LDPC Error FloorsAug 07 2012Numerical issues related to the occurrence of error floors in floating-point simulations of belief propagation (BP) decoders are examined. Careful processing of messages corresponding to highly-certain bit values can sometimes reduce error floors by several ... More
LADAR-Based Mover Detection from Moving VehiclesSep 25 2017Detecting moving vehicles and people is crucial for safe operation of UGVs but is challenging in cluttered, real world environments. We propose a registration technique that enables objects to be robustly matched and tracked, and hence movers to be detected ... More
Improving Deep Learning by Inverse Square Root Linear Units (ISRLUs)Oct 27 2017Nov 09 2017We introduce the "inverse square root linear unit" (ISRLU) to speed up learning in deep neural networks. ISRLU has better performance than ELU but has many of the same benefits. ISRLU and ELU have similar curves and characteristics. Both have negative ... More
Using Sparse Semantic Embeddings Learned from Multimodal Text and Image Data to Model Human Conceptual KnowledgeSep 07 2018Nov 14 2018Distributional models provide a convenient way to model semantics using dense embedding spaces derived from unsupervised learning algorithms. However, the dimensions of dense embedding spaces are not designed to resemble human semantic knowledge. Moreover, ... More
A Relationship Between Halo Mass, Cooling, AGN Heating, and the Coevolution of Massive Black HolesOct 23 2015Oct 11 2016We derive X-ray mass, luminosity, and temperature profiles for 45 galaxy clusters to explore relationships between halo mass, AGN feedback, and central cooling time. We find that radio--mechanical feedback power (referred to here as "AGN power") in central ... More
Disorder-Induced Electronic NematicityJun 11 2019We expose the theoretical mechanisms underlying disorder-induced nematicity in systems exhibiting strong fluctuations or ordering in the nematic channel. Our analysis consists of a symmetry-based Ginzburg-Landau approach and associated microscopic calculations. ... More
Binary Black Hole Accretion From a Circumbinary Disk: Gas Dynamics Inside the Central CavityOct 01 2013We present the results of 2D hydrodynamical simulations of circumbinary disk accretion using the finite-volume code DISCO. This code solves the 2D viscous Navier-Stokes equations on a high-resolution moving mesh which shears with the fluid flow, greatly ... More
Binary Black Hole Accretion During Inspiral and MergerSep 17 2014We present the results of 2D, moving mesh, viscous hydrodynamical simulations of accretion onto merging supermassive black hole (SMBH) binaries. We include viscous heating, shock heating, and radiative cooling, and simulate the transition from the "pre-decoupling" ... More
Ultra-deep mid-IR survey of a lensing clusterAug 13 1998We present the first results of mid-infrared (MIR) ultra-deep observations towards the lensing cluster Abell 2390 using the ISOCAM infrared camera on-board ESA's Infrared Space Observatory (ISO) satellite. They reveal a large number of luminous MIR sources. ... More
HEP Software Foundation Community White Paper Working Group - Data Analysis and InterpretationApr 09 2018At the heart of experimental high energy physics (HEP) is the development of facilities and instrumentation that provide sensitivity to new phenomena. Our understanding of nature at its most fundamental level is advanced through the analysis and interpretation ... More
Distributed Error-Function Roughness in Refl1d Reflectometry Fitting ProgramDec 12 2017Jan 19 2018The Refl1d program is used for modeling and fitting data from neutron and X-ray reflectometry experiments. The model of the (thin-film) samples is typically constructed of discrete layers of different scattering-length densities (SLD). Interlayer roughness ... More
Situational Awareness based Risk-Adapatable Access Control in Enterprise NetworksOct 26 2017As the computing landscape evolves towards distributed architectures such as Internet of Things (IoT),enterprises are moving away from traditional perimeter based security models toward so called zero trust networking (ZTN) models that treat both the ... More
An Elusive Z' Coupled to BeautyApr 08 1996Apr 24 1996By extending the standard gauge group to SU(3)_c \times SU(2)_L \times U(1)_Y \times U(1)_X with X charges carried only by the third family we accommodate the LEP measurement of R_b and predict a potentially measurable discrepancy in A_{FB}^{b} in e^+e^- ... More
Rucio - Scientific data managementFeb 26 2019Jun 06 2019Rucio is an open-source software framework that provides scientific collaborations with the functionality to organize, manage, and access their data at scale. The data can be distributed across heterogeneous data centers at widely distributed locations. ... More
Measuring Small Distances in N=2 Sigma ModelsNov 08 1993We analyze global aspects of the moduli space of K\"ahler forms for $N$=(2,2) conformal $\sigma$-models. Using algebraic methods and mirror symmetry we study extensions of the mathematical notion of length (as specified by a K\"ahler structure) to conformal ... More
Multiple Mirror Manifolds and Topology Change in String TheoryJan 12 1993Jan 15 1993We use mirror symmetry to establish the first concrete arena of spacetime topology change in string theory. In particular, we establish that the {\it quantum theories} based on certain nonlinear sigma models with topologically distinct target spaces can ... More
Approximating invariant densities of metastable systemsMay 02 2009We consider a piecewise smooth expanding map of the interval possessing two invariant subsets of positive Lebesgue measure and exactly two ergodic absolutely continuous invariant probability measures (ACIMs). When this system is perturbed slightly to ... More
Synchronization in networks of networks: the onset of coherent collective behavior in systems of interacting populations of heterogeneous oscillatorsJun 29 2007Jan 24 2008The onset of synchronization in networks of networks is investigated. Specifically, we consider networks of interacting phase oscillators in which the set of oscillators is composed of several distinct populations. The oscillators in a given population ... More
Measurement and modeling of polarized specular neutron reflectivity in large magnetic fieldsOct 27 2015Apr 28 2016The presence of a large applied magnetic field removes the degeneracy of the vacuum energy states for spin-up and spin-down neutrons. For polarized neutron reflectometry, this must be included in the reference potential energy of the Schr\"odinger equation ... More
Search for plant biomagnetism with a sensitive atomic magnetometerJun 17 2010Aug 16 2011We report what we believe is the first experimental limit placed on plant biomagnetism. Measurements with a sensitive atomic magnetometer were performed on the Titan arum (Amorphophallus titanum) inflorescence, known for its fast bio-chemical processes ... More
Simulation of Drosophila Circadian Oscillations, Mutations, and Light Responses by a Model with VRI, PDP-1, and CLKJan 23 2004A model of Drosophila circadian rhythm generation was developed to represent feedback loops based on transcriptional regulation of per, Clk (dclock), Pdp-1, and vri (vrille). The model postulates that histone acetylation kinetics make transcriptional ... More
HEP Software Foundation Community White Paper Working Group -- Data Organization, Management and Access (DOMA)Nov 30 2018Without significant changes to data organization, management, and access (DOMA), HEP experiments will find scientific output limited by how fast data can be accessed and digested by computational resources. In this white paper we discuss challenges in ... More
Estimating the contribution of Galactic sources to the diffuse neutrino fluxOct 01 2014Dec 03 2014Motivated by recent IceCube observations we re-examine the idea that microquasars are high energy neutrino emitters. By stretching to the maximum the parameters of the Fermi engine we show that the nearby high-mass X-ray binary LS 5039 could accelerate ... More
XMM-Newton view of MS0735+7421: the most energetic AGN outburst in a galaxy clusterNov 08 2006We discuss the possible cosmological effects of powerful AGN outbursts in galaxy clusters by starting from the results of an XMM-Newton observation of the supercavity cluster MS0735+7421.
Vision-Based High Speed Driving with a Deep Dynamic ObserverDec 05 2018Dec 10 2018In this paper we present a framework for combining deep learning-based road detection, particle filters, and Model Predictive Control (MPC) to drive aggressively using only a monocular camera, IMU, and wheel speed sensors. This framework uses deep convolutional ... More
Calibration and flight performance of the long-slit imaging dual order spectrographJun 10 2008We present a preliminary calibration and flight performance of the Long-Slit Imaging Dual Order Spectrograph (LIDOS), a rocket-borne instrument with a large dynamic range in the 900 - 1700A bandpass. The instrument observes UV-bright objects with a CCD ... More
Multi-channel entanglement distribution using spatial multiplexing from four-wave mixing in atomic vaporJul 08 2015Four-wave mixing in atomic vapor allows for the generation of multi-spatial-mode states of light containing many pairs of two-mode entangled vacuum beams. This in principle can be used to send independent secure keys to multiple parties simultaneously ... More
An IR Search for Extinguished Supernovae in Starburst GalaxiesDec 14 1998IR and Radio band observations of heavily extinguished regions in starburst galaxies suggest a very high SN rate associated with such regions. Optically measured supernova (SN) rates may therefore underestimate the total SN rate by factors of up to 10, ... More
AutoRally An open platform for aggressive autonomous drivingJun 02 2018This article presents AutoRally, a 1$:$5 scale robotics testbed for autonomous vehicle research. AutoRally is designed for robustness, ease of use, and reproducibility, so that a team of two people with limited knowledge of mechanical engineering, electrical ... More
Radio Mode Outbursts in Giant Elliptical GalaxiesSep 09 2009Outbursts from active galactic nuclei (AGN) affect the hot atmospheres of isolated giant elliptical galaxies (gE's), as well as those in groups and clusters of galaxies. Chandra observations of a sample of nearby gE's show that the average power of AGN ... More
Spatial and Spectral Modeling of the Gamma-ray Distribution in the Large Magellanic CloudFeb 15 2015Jul 17 2015We perform spatial and spectral analyses of the Large Magellanic Cloud (LMC) gamma-ray emission collected over 66 months by the Fermi Gamma-ray Space Telescope. In our spatial analysis, we model the LMC cosmic-ray distribution and gamma-ray production ... More
The effect of input phase modulation to a phase-sensitive optical amplifierAug 19 2016Many optical applications depend on amplitude modulating optical beams using devices such as acousto-optical modulators (AOMs) or optical choppers. Methods to add amplitude modulation (AM) often inadvertently impart phase modulation (PM) onto the light ... More
Interaction of Cygnus A with its environmentFeb 17 2015Cygnus A, the nearest truly powerful radio galaxy, resides at the centre of a massive galaxy cluster. Chandra X-ray observations reveal its cocoon shocks, radio lobe cavities and an X-ray jet, which are discussed here. It is argued that X-ray emission ... More
Pulsed single-photon spectrometer by frequency-to-time mapping using chirped fiber Bragg gratingsOct 10 2016Jul 29 2017A fiber-integrated spectrometer for single-photon pulses outside the telecommunications wavelength range based upon frequency-to-time mapping, implemented by chromatic group delay dispersion (GDD), and precise temporally-resolved single-photon counting, ... More
A Mixture of Coalesced Generalized Hyperbolic DistributionsMar 10 2014Oct 27 2018A mixture of multiple scaled generalized hyperbolic distributions (MMSGHDs) is introduced. Then, a coalesced generalized hyperbolic distribution (CGHD) is developed by joining a generalized hyperbolic distribution with a multiple scaled generalized hyperbolic ... More
Unsupervised Learning via Mixtures of Skewed Distributions with Hypercube ContoursMar 10 2014Sep 17 2014Mixture models whose components have skewed hypercube contours are developed via a generalization of the multivariate shifted asymmetric Laplace density. Specifically, we develop mixtures of multiple scaled shifted asymmetric Laplace distributions. The ... More
General Bayesian Inference over the Stiefel Manifold via the Givens RepresentationOct 25 2017Jan 14 2019We introduce an approach based on the Givens representation that allows for a routine, reliable, and flexible way to infer Bayesian models with orthogonal matrix parameters. This class of models most notably includes models from multivariate statistics ... More
ICTD for Healthcare in Ghana: Two Parallel Case StudiesMay 02 2009This paper examines two parallel case studies to promote remote medical consultation in Ghana. These projects, initiated independently by different researchers in different organizations, both deployed ICT solutions in the same medical community in the ... More
Cosmological Effects of Powerful AGN Outbursts in Galaxy Clusters: Insights from an XMM-Newton Observation of MS0735+7421Jan 12 2007We report on the results of an analysis of XMM-Newton observations of MS0735+7421, the galaxy cluster which hosts the most energetic AGN outburst currently known. The previous Chandra image shows twin giant X-ray cavities (~200 kpc diameter) filled with ... More
Improved measurement of two-mode quantum correlations using a phase-sensitive amplifierAug 28 2017We demonstrate the ability of a phase-sensitive amplifier (PSA) to pre-amplify a selected quadrature of one mode of a two-mode squeezed state in order to improve the measurement of two-mode quantum correlations that exist before degradation due to optical ... More
Space-Time Graph Modeling of Ride Requests Based on Real-World DataJan 23 2017This paper focuses on modeling ride requests and their variations over location and time, based on analyzing extensive real-world data from a ride-sharing service. We introduce a graph model that captures the spatial and temporal variability of ride requests ... More
Emergent defect states as a source of resistivity anisotropy in the nematic phase of iron pnictidesJul 01 2014We consider the role of potential scatterers in the nematic phase of Fe-based superconductors above the transition temperature to the (pi,0) magnetic state but below the orthorhombic structural transition. The anisotropic spin fluctuations in this region ... More
High-quality, large-grain MoS2 films grown on 100 mm sapphire substrates using a novel molybdenum precursorNov 12 2018Two-dimensional MoS2 is a crystalline semiconductor with high potential for numerous technologies. Research in recent years has sought to exploit the direct band gap and high carrier mobility properties of monolayer MoS2 for functional applications. To ... More
Noise reduction of a Libbrecht--Hall style current driverMar 30 2016Jun 15 2016The Libbrecht--Hall circuit is a well-known, low-noise current driver for narrow-linewidth diode lasers. An important feature of the circuit is a current limit to protect the laser diode. As the current approaches the maximum limit, however, the noise ... More
A reduced orbital period for the supermassive black hole binary candidate in the quasar PG 1302-102?Feb 10 2015Jul 31 2015Graham et al. (2015) have detected a 5.2 year periodic optical variability of the quasar PG 1302-102 at redshift $z=0.3$, which they interpret as the redshifted orbital period $(1+z)t_{\rm bin}$ of a putative supermassive black hole binary (SMBHB). Here ... More
The Migration of Gap-Opening Planets is not Locked to Viscous Disk EvolutionMay 14 2014Aug 01 2014Most standard descriptions of Type II migration state that massive, gap-opening planets must migrate at the viscous drift rate. This is based on the idea that the disk is separated into an inner and outer region and gas is considered unable to cross the ... More
The Rearrangement NumberDec 22 2016How many permutations of the natural numbers are needed so that every conditionally convergent series of real numbers can be rearranged to no longer converge to the same sum? We show that the minimum number of permutations needed for this purpose, which ... More
Counterintuitive Reconstruction of the Polar O-Terminated ZnO Surface With Zinc Vacancies and HydrogenFeb 01 2017Understanding the structure of ZnO surface reconstructions and their resultant properties is crucial to the rational design of ZnO-containing devices ranging from optoelectronics to catalysts. Here, we are motivated by recent experimental work which showed ... More
Reducing Cascading Failure Risk by Increasing Infrastructure Network InterdependencyOct 24 2014Jun 23 2015Increased coupling between critical infrastructure networks, such as power and communication systems, will have important implications for the reliability and security of these systems. To understand the effects of power-communication coupling, several ... More
Isotropic Band Gaps and Freeform Waveguides Observed in Hyperuniform Disordered Photonic SolidsNov 11 2013Recently, disordered photonic media and random textured surfaces have attracted increasing attention as strong light diffusers with broadband and wide-angle properties. We report the first experimental realization of an isotropic complete photonic band ... More
A Mixture of Coalesced Generalized Hyperbolic DistributionsMar 10 2014Jun 04 2015A mixture of coalesced generalized hyperbolic distributions (GHDs) is developed by joining a finite mixture of generalized hyperbolic distributions with a novel mixture of multiple scaled generalized hyperbolic distributions (MSGHDs). After detailing ... More
The Rearrangement NumberDec 22 2016May 13 2019How many permutations of the natural numbers are needed so that every conditionally convergent series of real numbers can be rearranged to no longer converge to the same sum? We define the \emph{rearrangement number}, a new cardinal characteristic of ... More
Information Theoretic Model Predictive Control: Theory and Applications to Autonomous DrivingJul 07 2017We present an information theoretic approach to stochastic optimal control problems that can be used to derive general sampling based optimization schemes. This new mathematical method is used to develop a sampling based model predictive control algorithm. ... More
Autonomous Racing with AutoRally Vehicles and Differential GamesJul 14 2017Safe autonomous vehicles must be able to predict and react to the drivers around them. Previous control methods rely heavily on pre-computation and are unable to react to dynamic events as they unfold in real-time. In this paper, we extend Model Predictive ... More
A Chandra study of the large-scale shock and cool filaments in Hydra A: Evidence for substantial gas dredge-up by the central outburstFeb 26 2011We present the results of a Chandra study of the Hydra A galaxy cluster, where a powerful AGN outburst created a large-scale cocoon shock. We investigated possible azimuthal variations in shock strength and shape, finding indications for a weak shock ... More
Aggressive Deep Driving: Model Predictive Control with a CNN Cost ModelJul 17 2017We present a framework for vision-based model predictive control (MPC) for the task of aggressive, high-speed autonomous driving. Our approach uses deep convolutional neural networks to predict cost functions from input video which are directly suitable ... More
Graph Filters and the Z-LaplacianJul 18 2017In network science, the interplay between dynamical processes and the underlying topologies of complex systems has led to a diverse family of models with different interpretations. In graph signal processing, this is manifested in the form of different ... More
Atom interferometry in an optical cavitySep 25 2014We propose and demonstrate a new scheme for atom interferometry, using light pulses inside an optical cavity as matter wave beamsplitters. The cavity provides power enhancement, spatial filtering, and a precise beam geometry, enabling new techniques such ... More
The Frequency of Carbon-Enhanced Metal-Poor Stars in the Galaxy from the HERES sampleSep 26 2006We estimate the frequency of Carbon-Enhanced Metal-Poor (CEMP) stars among very metal-poor stars, based on an analysis of 349 stars with available high-resolution spectra observed as part of the Hamburg/ESO R-process Enhanced Star (HERES) survey. We obtain ... More
Large Scale Anisotropy of Cosmic Rays and Directional Neutrino Signals from Galactic SourcesMar 26 2014Mar 27 2014We investigate the neutrino - cosmic ray connection for sources in the Galaxy in terms of two observables: the shape of the energy spectrum and the distribution of arrival directions. We also study the associated gamma ray emission from these sources. ... More
Long-term, Multiwavelength Light Curves of Ultra-cool Dwarfs: I. An Interplay of Starspots & Clouds Likely Drive the Variability of the L3.5 dwarf 2MASS 0036+18Sep 12 2016We present multi-telescope, ground-based, multiwavelength optical and near-infrared photometry of the variable L3.5 ultra-cool dwarf 2MASSW J0036159+182110. We present 22 nights of photometry of 2MASSW J0036159+182110, including 7 nights of simultaneous, ... More
SkyMapper and the Southern Sky Survey: a valuable resource for stellar astrophysicsJun 11 2008Jun 14 2008The Australian National University's SkyMapper telescope is amongst the first of a new generation of dedicated wide-field survey telescopes. Featuring a 5.7 square deg field-of-view Cassegrain imager and 268 Mega-pixel CCD array, its primary goal will ... More
Advanced LIGO Constraints on Neutron Star Mergers and R-Process SitesOct 07 2016Feb 12 2017The role of compact binary mergers as the main production site of r-process elements is investigated by combining stellar abundances of Eu observed in the Milky Way, galactic chemical evolution (GCE) simulations, binary population synthesis models, and ... More
A New Bound on Axion-Like ParticlesMar 21 2017Dec 07 2017Axion-like particles (ALPs) and photons can quantum mechanically interconvert when propagating through magnetic fields, and ALP-photon conversion may induce oscillatory features in the spectra of astrophysical sources. We use deep (370 ks), short frame ... More
Abell 1201: a Minor merger at second core passageMay 08 2012We present an analysis of the structures and dynamics of the merging cluster Abell~1201, which has two sloshing cold fronts around a cooling core, and an offset gas core approximately 500kpc northwest of the center. New Chandra and XMM-Newton data reveal ... More
What IceCube data tell us about neutrino emission from star-forming galaxies (so far)May 29 2014Jun 10 2014Very recently, the IceCube Collaboration reported a flux of neutrinos in the energy range 50 TeV < E_\nu < 2 PeV, which departs from expectations from atmospheric background at the 5.7\sigma level. This flux is in remarkable agreement with the expected ... More
Effects of Lifshitz Transition on Charge Transport in Magnetic Phases of Fe-Based SuperconductorsAug 08 2014Mar 11 2015The unusual temperature dependence of the resistivity and its in-plane anisotropy observed in the Fe-based superconducting materials, particularly Ba(Fe$_{1-x}$Co$_x$)$_2$As$_2$, has been a longstanding puzzle. Here we consider the effect of impurity ... More
Mass scaling and non-adiabatic effects in photoassociation spectroscopy of ultracold strontium atomsJun 17 2014Jul 30 2014We report photoassociation spectroscopy of ultracold $^{86}$Sr atoms near the intercombination line and provide theoretical models to describe the obtained bound state energies. We show that using only the molecular states correlating with the $^1S_0$$+$$^3P_1$ ... More
Many-body localization in a quantum simulator with programmable random disorderAug 27 2015When a system thermalizes it loses all local memory of its initial conditions. This is a general feature of open systems and is well described by equilibrium statistical mechanics. Even within a closed (or reversible) quantum system, where unitary time ... More
Phase sensing beyond the standard quantum limit with a truncated SU(1,1) interferometerOct 21 2016An SU(1,1) interferometer replaces the beamsplitters in a Mach-Zehnder interferometer with nonlinear interactions and offers the potential of achieving high phase sensitivity in applications with low optical powers. We present a novel variation in which ... More
Resource-Performance Trade-off Analysis for Mobile Robot DesignSep 16 2016Sep 11 2017The design of mobile autonomous robots is challenging due to the limited on-board resources such as processing power and energy. A promising approach is to generate intelligent schedules that reduce the resource consumption while maintaining best performance, ... More
Far-ultraviolet Observations of Comet C/2012 S1 (ISON) from FORTISJun 19 2016We have used the unique far-UV imaging capability offered by a sounding rocket borne instrument to acquire observations of C/2012 S1 (ISON) when its angular separation with respect to the sun was 26.3deg, on 2013 November 20.49. At the time of observation ... More
Time-resolved Absorptance and Melt Pool Dynamics during Intense Laser Irradiation of MetalSep 11 2018High irradiance lasers incident on metal surfaces create a complex, dynamic process through which the metal can rapidly change from highly reflective to strongly absorbing. Absolute knowledge of this process underpins important industrial laser processes ... More
Epoxy-based broadband anti-reflection coating for millimeter-wave opticsJul 30 2013We have developed epoxy-based, broadband anti-reflection coatings for millimeter-wave astrophysics experiments with cryogenic optics. By using multiple-layer coatings where each layer steps in dielectric constant, we achieved low reflection over a wide ... More
Characterization of the X-ray Coherence Properties of an Undulator Beamline at the Advanced Photon SourceFeb 15 2018In anticipation of the increased use of coherent x-ray methods and the need to upgrade beamlines to match improved source quality, we have characterized the coherence properties of the x-rays delivered by beamline 12ID-D at the Advanced Photon Source. ... More
The US Program in Ground-Based Gravitational Wave Science: Contribution from the LIGO LaboratoryMar 11 2019Recent gravitational-wave observations from the LIGO and Virgo observatories have brought a sense of great excitement to scientists and citizens the world over. Since September 2015,10 binary black hole coalescences and one binary neutron star coalescence ... More
Efficient real-time monitoring of an emerging influenza epidemic: how feasible?Aug 18 2016May 03 2019A prompt public health response to a new epidemic relies on the ability to monitor and predict its evolution in real time as data accumulate. The 2009 A/H1N1 outbreak in the UK revealed pandemic data as noisy, contaminated, potentially biased, and originating ... More