Results for "Jason M. Allred"

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Stimulating STDP to Exploit Locality for Lifelong Learning without Catastrophic ForgettingFeb 08 2019Stochastic gradient descent requires that training samples be drawn from a uniformly random distribution of the data. For a deployed system that must learn online from an uncontrolled and unknown environment, the ordering of input samples often fails ... More
ASP: Learning to Forget with Adaptive Synaptic Plasticity in Spiking Neural NetworksMar 22 2017Jun 08 2018A fundamental feature of learning in animals is the "ability to forget" that allows an organism to perceive, model and make decisions from disparate streams of information and adapt to changing environments. Against this backdrop, we present a novel unsupervised ... More
Electron doped Ca10(Pt3As8)(Fe2As2)5 and Ca10(Pt4As8)(Fe2As2)5 - High Tc superconductors with skutterudite intermediary layersJun 10 2011It has been argued that the very high transition temperatures of the highest Tc cuprate superconductors are facilitated by enhanced CuO2 plane coupling through the (Bi,Tl,Hg)-O intermediary layers. Whether enhanced coupling through intermediary layers ... More
Solar Ellerman Bombs in 1-D Radiative HydrodynamicsJan 16 2017Recent observations from the Interface Region Imaging Spectrograph (IRIS) appear to show impulsive brightenings in high temperature lines, which when combined with simultaneous ground based observations in H$\alpha$, appear co-spatial to Ellerman Bombs ... More
From Radio to X-ray: The Quiescent Atmosphere of the dMe Flare Star EV LacertaeApr 11 2006We report on multi-wavelength observations spanning radio to X-ray wavelengths of the M dwarf flare star, EV Lacertae, probing the characteristics of the outer atmospheric plasma from the upper chromosphere to the corona. We detect the star at a wavelength ... More
Brownmillerite Ca2Co2O5: Synthesis, Stability, and Re-entrant Single-Crystal-to-Single-Crystal Structural TransitionsNov 20 2014Ca2Co2O5 in the brownmillerite form was synthesized using a high-pressure optical-image floating zone furnace, and single crystals with dimensions up to 1.4x0.8x0.5 mm3 were obtained. At room temperature, Ca2Co2O5 crystallizes as a fully ordered brownmillerite ... More
Anisotropic $H_{c2}$ determined up to 92 T and the signature of multi-band superconductivity in Ca$_{10}$(Pt$_{4}$As$_{8}$)((Fe$_{1-x}$Pt$_{x}$)$_{2}$As$_{2}$)$_{5}$ superconductorFeb 22 2012The upper critical fields, $H_{c2}$($T$), of single crystals of the superconductor Ca$_{10}$(Pt$_{4-\delta}$As$_{8}$)((Fe$_{0.97}$Pt$_{0.03}$)$_{2}$As$_{2}$)$_{5}$ ($\delta$ $\approx$ 0.246) are determined over a wide range of temperatures down to $T$ ... More
Complete Analysis of a Random Forest ModelMay 07 2018Sep 21 2018Random forests have become an important tool for improving accuracy in regression problems since their popularization by [Breiman, 2001] and others. In this paper, we revisit a random forest model originally proposed by [Breiman, 2004] and later studied ... More
Bi2Te1.6S1.4 - a Topological Insulator in the Tetradymite FamilyMay 14 2012We describe the crystal growth, crystal structure, and basic electrical properties of Bi2Te1.6S1.4, which incorporates both S and Te in its Tetradymite quintuple layers in the motif -[Te0.8S0.2]-Bi-S-Bi-[Te0.8S0.2]-. This material differs from other Tetradymites ... More
Bulk Intergrowth of a Topological Insulator with a Room Temperature FerromagnetFeb 22 2012We demonstrate that the layered room temperature ferromagnet Fe7Se8 and the topological insulator Bi2Se3 form crystallographically oriented bulk composite intergrowth crystals. The morphology of the intergrowth in real space and reciprocal space is described. ... More
Coincident structural and magnetic order in BaFe$_2$(As$_{1-x}$)P$_x$)$_2$ revealed by high-resolution neutron diffractionOct 09 2014We present neutron diffraction analysis of BaFe$_2$(As$_{1-x}$P$_x$)$_2$ over a wide temperature (10 to 300 K) and compositional ($0.11 \leq x \leq 0.79$) range, including the normal state, the magnetically ordered state, and the superconducting state. ... More
Tetragonal magnetic phase in Ba$_{1-x}$K$_x$Fe$_2$As$_2$ from x-ray and neutron diffractionMay 06 2015Combined neutron and x-ray diffraction experiments demonstrate the formation of a low-temperature minority tetragonal phase in Ba$_{0.76}$K$_{0.24}$Fe$_2$As$_2$ in addition to the majority magnetic, orthorhombic phase. A coincident enhancement in the ... More
Charge ordering and ferrimagnetism in the strongly correlated $β$-V$_2$PO$_5$ single crystalDec 28 2017A combined study of transport, thermodynamic, neutron diffraction, nuclear magnetic resonance measurements and first principles calculation were performed for $\beta$-V$_2$PO$_5$ single crystal. It was shown to be a semiconductor with a band gap of 0.48 ... More
Parameterizations of Chromospheric Condensations in dG and dMe Model Flare AtmospheresNov 26 2017The origin of the near-ultraviolet and optical continuum radiation in flares is critical for understanding particle acceleration and impulsive heating in stellar atmospheres. Radiative-hydrodynamic simulations in 1D have shown that high energy deposition ... More
Counting Motifs with Graph SamplingFeb 21 2018Applied researchers often construct a network from a random sample of nodes in order to infer properties of the parent network. Two of the most widely used sampling schemes are subgraph sampling, where we sample each vertex independently with probability ... More
Shell Model of BaTiO3 Derived from Ab-initio Total Energy CalculationsSep 07 2013A shell model for ferroelectric perovskites fitted to results of first-principles density functional theory (DFT) calculations is strongly affected by approximations made in the exchange-correlation functional within DFT, and in general not as accurate ... More
Estimating the Number of Connected Components in a Graph via Subgraph SamplingJan 12 2018Aug 08 2018Learning properties of large graphs from samples has been an important problem in statistical network analysis since the early work of Goodman \cite{Goodman1949} and Frank \cite{Frank1978}. We revisit a problem formulated by Frank \cite{Frank1978} of ... More
A 3D Model of AR 11726 Heated by NanoflaresJul 02 2018The Extreme Ultraviolet Normal Incidence Spectrograph (EUNIS) and the Hinode/ EUV Imaging Spectrometer (EIS) observed AR 11726 on 2013 April 23. We present intensity images in numerous atomic lines constructed from these observations. These lines are ... More
Double-Q spin-density wave in iron arsenide superconductorsMay 22 2015Elucidating the nature of the magnetic ground state of iron-based superconductors is of paramount importance in unveiling the mechanism behind their high temperature superconductivity. Until recently, it was thought that superconductivity emerges only ... More
Decorated Feynman CategoriesFeb 02 2016Nov 13 2017In [KW14], the new concept of Feynman categories was introduced to simplify the discussion of operad--like objects. In this present paper, we demonstrate the usefulness of this approach, by introducing the concept of decorated Feynman categories. The ... More
Detailed magnetic and structural analysis mapping a robust magnetic C4 dome in Sr1-xNaxFe2As2Jan 21 2016The recently discovered $C_4$ tetragonal magnetic phase in hole-doped members of the iron-based superconductors provides new insights into the origin of unconventional superconductivity. Previously observed in Ba$_{1-x}A_x$Fe$_2$As$_2$ (with $A =$ K, ... More
Halpha line profile asymmetries and the chromospheric flare velocity fieldOct 07 2015The asymmetries observed in the line profiles of solar flares can provide important diagnostics of the properties and dynamics of the flaring atmosphere. In this paper the evolution of the Halpha and Ca II 8542 {\AA} lines are studied using high spatial, ... More
Derivative-free optimization for parameter estimation in computational nuclear physicsJun 20 2014Sep 17 2014We consider optimization problems that arise when estimating a set of unknown parameters from experimental data, particularly in the context of nuclear density functional theory. We examine the cost of not having derivatives of these functionals with ... More
A New Connection between Central Engine Weak Physics and the Dynamics of Gamma-Ray Burst FireballsSep 10 2000Feb 13 2001We demonstrate a qualitatively new aspect of the dynamics of Gamma-Ray Burst (GRB) fireballs: the development of a substantial dispersion in the proton component in fireballs in which neutron decoupling occurs and is sufficiently pronounced. This effect ... More
Light Element Synthesis in High Entropy Relativistic Flows Associated with Gamma Ray BurstsMay 03 2002We calculate and discuss the light element freeze-out nucleosynthesis in high entropy winds and fireballs for broad ranges of entropy-per-baryon, dynamic timescales characterizing relativistic expansion, and neutron-to-proton ratios. With conditions characteristic ... More
A Unified Term for Directed and Undirected Motility in Collective Cell InvasionMar 22 2012In this paper we develop mathematical models for collective cell motility. Initially we develop a model using a linear diffusion-advection type equation and fit the parameters to data from cell motility assays. This approach is helpful in classifying ... More
Local Structure Controlling the Glass Transition in a Prototype Metal-Metalloid GlassJan 21 2019We use a structure analysis technique that quantifies cluster geometries using machine learning to identify a bicapped square antiprism (BSAP) as the nearest-neighbor cluster involved in the glass transition in Pd82Si18, a prototype metal-metalloid metallic ... More
Finite-sample risk bounds for maximum likelihood estimation with arbitrary penaltiesDec 29 2017The MDL two-part coding $ \textit{index of resolvability} $ provides a finite-sample upper bound on the statistical risk of penalized likelihood estimators over countable models. However, the bound does not apply to unpenalized maximum likelihood estimation ... More
Structural, Magnetic, and Superconducting Properties of Ba1-xNaxFe2As2Sep 30 2013We report the results of a systematic investigation of the phase diagram of the iron-based superconductor system, Ba1-xNaxFe2As2, from x = 0.1 to x = 1.0 using high resolution neutron and x-ray diffraction and magnetization measurements. We find that ... More
Single-Shot Terahertz Time-Domain Spectroscopy in Pulsed High Magnetic FieldsAug 29 2016We have developed a single-shot terahertz time-domain spectrometer to perform optical pump/terahertz probe experiments in pulsed, high magnetic fields up to 30 T. The single-shot detection scheme for measuring a terahertz waveform incorporates a reflective ... More
Single-Shot Terahertz Time-Domain Spectroscopy in Pulsed High Magnetic FieldsAug 29 2016Oct 12 2016We have developed a single-shot terahertz time-domain spectrometer to perform optical-pump/terahertz-probe experiments in pulsed, high magnetic fields up to 30 T. The single-shot detection scheme for measuring a terahertz waveform incorporates a reflective ... More
Approximation and Estimation for High-Dimensional Deep Learning NetworksSep 10 2018Sep 18 2018It has been experimentally observed in recent years that multi-layer artificial neural networks have a surprising ability to generalize, even when trained with far more parameters than observations. Is there a theoretical basis for this? The best available ... More
Density distributions and depth in flocksFeb 21 2019Recent experimental evidence suggests that interactions in flocks of birds do not involve a characteristic length scale. Bird flocks have also been revealed to have an inhomogeneous density distribution, with the density of birds near the border greater ... More
Risk Bounds for High-dimensional Ridge Function Combinations Including Neural NetworksJul 05 2016Oct 29 2018Let $ f^{\star} $ be a function on $ \mathbb{R}^d $ with an assumption of a spectral norm $ v_{f^{\star}} $. For various noise settings, we show that $ \mathbb{E}\|\hat{f} - f^{\star} \|^2 \leq \left(v^4_{f^{\star}}\frac{\log d}{n}\right)^{1/3} $, where ... More
On the Minimum Ropelength of Knots and LinksMar 30 2001Mar 01 2002The ropelength of a knot is the quotient of its length and its thickness, the radius of the largest embedded normal tube around the knot. We prove existence and regularity for ropelength minimizers in any knot or link type; these are $C^{1,1}$ curves, ... More
Statistical Guarantees for Estimating the Centers of a Two-component Gaussian Mixture by EMAug 07 2016Recently, a general method for analyzing the statistical accuracy of the EM algorithm has been developed and applied to some simple latent variable models [Balakrishnan et al. 2016]. In that method, the basin of attraction for valid initialization is ... More
Fermi surface topology and low-lying electronic structure of a new iron-based superconductor Ca10(Pt3As8)(Fe2As2)5Oct 21 2011We report a first study of low energy electronic structure and Fermi surface topology for the recently discovered iron-based superconductor Ca10(Pt3As8)(Fe2As2)5 (the 10-3-8 phase, with Tc = 8K), via angle-resolved photoemission spectroscopy (ARPES). ... More
Hubble Space Telescope Far Ultraviolet Spectroscopy of the Dwarf Nova VW Hyi in SuperoutburstMar 02 2007We obtained three consecutive HST spectroscopic observations of a single superoutburst of the dwarf nova VW Hydri. The spectra cover the beginning, middle, and end of the superoutburst. All of the spectra are dominated by strong absorption lines due to ... More
Information Security Plan for Flight Simulator ApplicationsNov 07 2011The Department of Defense has a need for an identity management system that uses two factor authentications to ensure that only the correct individuals get access to their top secret flight simulator program. Currently the Department of Defense does not ... More
Approximation by Combinations of ReLU and Squared ReLU Ridge Functions with $ \ell^1 $ and $ \ell^0 $ ControlsJul 26 2016May 23 2018We establish $ L^{\infty} $ and $ L^2 $ error bounds for functions of many variables that are approximated by linear combinations of ReLU (rectified linear unit) and squared ReLU ridge functions with $ \ell^1 $ and $ \ell^0 $ controls on their inner and ... More
On prime non-primitive von Neumann regular algebrasMar 21 2011Let $E$ be any directed graph, and $K$ any field. We classify those graphs $E$ for which the Leavitt path algebra $L_K(E)$ is primitive. As a consequence, we obtain classes of examples of von Neumann regular prime rings which are not primitive.
Strong Electron Correlation in Nitrogenase Cofactor, FeMocoMay 22 2018FeMoco, MoFe$_7$S$_9$C, has been shown to be the active catalytic site for the reduction of nitrogen to ammonia in the nitrogenase protein. An understanding of its electronic structure including strong electron correlation is key to designing mimic catalysts ... More
Holographic algorithms without matchgatesApr 02 2009The theory of holographic algorithms, which are polynomial time algorithms for certain combinatorial counting problems, yields insight into the hierarchy of complexity classes. In particular, the theory produces algebraic tests for a problem to be in ... More
Complexity, Statistical Risk, and Metric Entropy of Deep Nets Using Total Path VariationFeb 02 2019Feb 06 2019For any ReLU network there is a representation in which the sum of the absolute values of the weights into each node is exactly $1$, and the input layer variables are multiplied by a value $V$ coinciding with the total variation of the path weights. Implications ... More
On the uniqueness of promotion operators on tensor products of type A crystalsJun 19 2008May 05 2009The affine Dynkin diagram of type $A_n^{(1)}$ has a cyclic symmetry. The analogue of this Dynkin diagram automorphism on the level of crystals is called a promotion operator. In this paper we show that the only irreducible type $A_n$ crystals which admit ... More
Observations and simulations of the Na I D1 line profiles in an M-class solar flareSep 26 2016We study the temporal evolution of the Na I D1 line profiles in the M3.9 flare SOL2014-06-11T21:03 UT, using high spectral resolution observations obtained with the IBIS instrument on the Dunn Solar Telescope combined with radiative hydrodynamic simulations. ... More
Ruprecht 147: The oldest nearby open cluster as a new benchmark for stellar astrophysicsJun 27 2012Jan 05 2013Ruprecht 147 is a hitherto unappreciated open cluster that holds great promise as a standard in fundamental stellar astrophysics. We have conducted a radial velocity survey of astrometric candidates with Lick, Palomar, and MMT observatories and have identified ... More
Multi-robot Dubins Coverage with Autonomous Surface VehiclesAug 07 2018In large scale coverage operations, such as marine exploration or aerial monitoring, single robot approaches are not ideal, as they may take too long to cover a large area. In such scenarios, multi-robot approaches are preferable. Furthermore, several ... More
Theory of Rabi interaction between an infrared-active phonon and cavity-resonant modesDec 29 2006Jan 05 2007We present the theory of interaction between a polar vibration in a semiconductor and an electromagnetic mode of a surrounding cavity. Tuning the cavity frequency near the transverse optical phonon frequency couples the phonon-induced polarization field ... More
On Steady State Neutrino Heated Ultra-Relativistic Winds from Compact ObjectsMar 27 2001Mar 28 2001We study steady state winds from compact objects in the regime where the wind velocity at infinity is ultra-relativistic. This may have relevance to some models of Gamma-Ray-Bursts (GRB's). Particular attention is paid to the case where neutrinos provide ... More
FEMSIM+HRMC: Simulation of and Structural Refinement using Fluctuation Electron Microscopy for Amorphous MaterialsJul 14 2016FEMSIM, a Fortran code, has been developed to simulate the fluctuation electron microscopy signal, the variance, V(k), from a model atomic structure. FEMSIM has been incorporated into a hybrid-reverse Monte Carlo code that combines an embedded atom or ... More
Generalized Continued Logarithms and Related Continued FractionsJun 22 2016We study continued logarithms as introduced by Bill Gosper and studied by J. Borwein et. al.. After providing an overview of the type I and type II generalizations of binary continued logarithms introduced by Borwein et. al., we focus on a new generalization ... More
Anatomy of $\varepsilon'/\varepsilon$ beyond the Standard ModelAug 01 2018We present for the first time a model-independent anatomy of the ratio $\varepsilon'/\varepsilon$ in the context of the $\Delta S = 1$ effective theory with operators invariant under QCD and QED and in the context of the Standard Model Effective Field ... More
Stovepiping and Malicious Software: A Critical Review of AGI ContainmentNov 08 2018Awareness of the possible impacts associated with artificial intelligence has risen in proportion to progress in the field. While there are tremendous benefits to society, many argue that there are just as many, if not more, concerns related to advanced ... More
A Global Likelihood for Precision Constraints and Flavour AnomaliesOct 17 2018Feb 11 2019We present a global likelihood function in the space of dimension-six Wilson coefficients in the Standard Model Effective Field Theory (SMEFT). The likelihood includes contributions from flavour-changing neutral current B decays, lepton flavour universality ... More
Ferromagnetic resonance phase imaging in spin Hall multilayersNov 25 2015We experimentally image the magnetic precession phase of patterned spin Hall multilayer samples to study the rf driving field vector using time-resolved anomalous Nernst effect (TRANE) microscopy. Our ferromagnetic resonance (FMR) measurements quantify ... More
A decade of transitional millisecond pulsarsNov 28 2017Transitional millisecond pulsars (tMSPs), which are systems that harbor a pulsar in the throes of the recycling process, have emerged as a new source class since the discovery of the first such system a decade ago. These systems switch between accretion-powered ... More
An Assessment of the Energy Budgets of Low-Ionization Nuclear Emission RegionsJan 17 2010Using the SEDs of the weak AGNs 35 LINERs presented in a companion paper, we assess whether photoionization by the weak AGN can power the emission-line luminosities measured through the large (few-arcsecond) apertures used in ground-based spectroscopic ... More
The graphs with all but two eigenvalues equal to $-2$ or $0$Jan 21 2016Jul 08 2016We determine all graphs for which the adjacency matrix has at most two eigenvalues (multiplicities included) not equal to $-2$, or $0$, and determine which of these graphs are determined by their adjacency spectrum.
Origins of diamond surface noise probed by correlating single spin measurements with surface spectroscopyOct 31 2018The nitrogen vacancy (NV) center in diamond exhibits spin-dependent fluorescence and long spin coherence times under ambient conditions, enabling applications in quantum information processing and sensing. NV centers near the surface can have strong interactions ... More
Transport fluctuations in integrable models out of equilibriumDec 05 2018We present exact results for the full counting statistics, or the scaled cumulant generating function, pertaining to the transfer of arbitrary conserved quantities across an interface in homogeneous integrable models out of equilibrium. We do this by ... More
Secular and orbital variability of Cir X-1 observed in optical spectraSep 11 2001We have observed variations in the optical emission lines from the X-ray binary Circinus X-1. These variations may be attributed both to orbital variations and to long term secular changes in line strength. We have detected double-peaked H-alpha emission ... More
Unambiguous separation of the inverse spin Hall and anomalous Nernst Effects within a ferromagnetic metal using the spin Seebeck effectJul 24 2014The longitudinal spin Seebeck effect is measured on the ferromagnetic insulator Fe$_3$O$_4$ with the ferromagnetic metal Co$_{0.2}$Fe$_{0.6}$B$_{0.2}$ (CoFeB) as the spin detector. By using a non-magnetic spacer material between the two materials (Ti), ... More
Spectral Energy Distributions of Weak Active Galactic Nuclei Associated With Low-Ionization Nuclear Emission RegionsJan 17 2010We present a compilation of spectral energy distributions of 35 weak AGNs in LINERs using recent data from the published literature. We make use of previously published compilations of data, after complementing and extending them with more recent data. ... More
The graphs with all but two eigenvalues equal to $\pm 1$Oct 24 2013We determine all graphs whose adjacency matrix has at most two eigenvalues (multiplicities included) different from $\pm 1$ and decide which of these graphs are determined by their spectrum. This includes the so-called friendship graphs, which consist ... More
Floyd-Warshall Reinforcement Learning: Learning from Past Experiences to Reach New GoalsSep 25 2018Jan 04 2019Consider mutli-goal tasks that involve static environments and dynamic goals. Examples of such tasks, such as goal-directed navigation and pick-and-place in robotics, abound. Two types of Reinforcement Learning (RL) algorithms are used for such tasks: ... More
Constraints and tensions in testing general relativity from Planck and CFHTLenS including intrinsic alignment systematicsJan 13 2015Jun 19 2015We present constraints on testing general relativity (GR) at cosmological scales using recent data sets and assess the impact of galaxy intrinsic alignment (IA) in the CFHTLenS lensing data on those constraints. We consider CMB temperature data from Planck, ... More
The Dixmier-Moeglin equivalence for Leavitt path algebrasMay 24 2010Jun 04 2010Let $K$ be a field, let $E$ be a finite directed graph, and let $L_K(E)$ be the Leavitt path algebra of $E$ over $K$. We show that for a prime ideal $P$ in $L_K(E)$, the following are equivalent: \begin{enumerate} \item $P$ is primitive; \item $P$ is ... More
Effect of a weak ion collisionality on the dynamics of kinetic electrostatic shocksOct 04 2018Feb 06 2019In strictly collisionless electrostatic shocks, the ion distribution function can develop discontinuities along phase-space separatrices, due to partial reflection of the ion population. In this paper, we depart from the strictly collisionless regime ... More
Demonstration of a Cold Atom Fountain Electron Electric Dipole Moment ExperimentFeb 01 2006Mar 14 2006A Cs fountain electron electric dipole moment (EDM) experiment using electric-field quantization is demonstrated. With magnetic fields reduced to 200 pT or less, the electric field lifts the degeneracy between hyperfine levels of different|mF| and, along ... More
Near-field coupling of gold plasmonic antennas for sub-100 nm magneto-thermal microscopyMay 04 2017The development of spintronic technology with increasingly dense, high-speed, and complex devices will be accelerated by accessible microscopy techniques capable of probing magnetic phenomena on picosecond time scales and at deeply sub-micron length scales. ... More
RRT+ : Fast Planning for High-Dimensional Configuration SpacesDec 21 2016Dec 24 2016In this paper we propose a new family of RRT based algorithms, named RRT+ , that are able to find faster solutions in high-dimensional configuration spaces compared to other existing RRT variants by finding paths in lower dimensional subspaces of the ... More
Estimating the Coefficients of a Mixture of Two Linear Regressions by Expectation MaximizationApr 26 2017Oct 16 2018We give convergence guarantees for estimating the coefficients of a symmetric mixture of two linear regressions by expectation maximization (EM). In particular, we show that the empirical EM iterates converge to the target parameter vector at the parametric ... More
Survey for Galaxies Associated with z~3 Damped Lyman alpha Systems II: Galaxy-Absorber Correlation FunctionsJul 07 2006We use 211 galaxy spectra from our survey for Lyman break galaxies (LBGs) associated with 11 damped Lyman alpha systems (DLAs) to measure the three-dimensional LBG auto-correlation and DLA-LBG cross-correlation functions with the primary goal of inferring ... More
Cyber Security Awareness Campaigns: Why do they fail to change behaviour?Jan 09 2019The present paper focuses on Cyber Security Awareness Campaigns, and aims to identify key factors regarding security which may lead them to failing to appropriately change people's behaviour. Past and current efforts to improve information-security practices ... More
NRC-Canada at SMM4H Shared Task: Classifying Tweets Mentioning Adverse Drug Reactions and Medication IntakeMay 11 2018Our team, NRC-Canada, participated in two shared tasks at the AMIA-2017 Workshop on Social Media Mining for Health Applications (SMM4H): Task 1 - classification of tweets mentioning adverse drug reactions, and Task 2 - classification of tweets describing ... More
Reproducing Type II White-Light Solar Flare Observations with Electron and Proton Beam SimulationsJun 01 2018We investigate the cause of the suppressed Balmer series and the origin of the white-light continuum emission in the X1.0 class solar flare on 2014 June 11. We use radiative hydrodynamic simulations to model the response of the flaring atmosphere to both ... More
Topological Surface States and Dirac point tuning in ternary Bi2Te2Se class of topological insulatorsJun 04 2012Dec 14 2012Using angle-resolved photoemission spectroscopy, we report electronic structure for representative members of ternary topological insulators. We show that several members of this family, such as Bi2Se2Te, Bi2Te2Se, and GeBi2Te4, exhibit a singly degenerate ... More
ChromaStarPy: A stellar atmosphere and spectrum modeling and visualization lab in pythonJan 22 2018We announce ChromaStarPy, an integrated general stellar atmospheric modeling and spectrum synthesis code written entirely in python V. 3. ChromaStarPy is a direct port of the ChromaStarServer (CSServ) Java modeling code described in earlier papers in ... More
Berkeley Supernova Ia Program II: Initial Analysis of Spectra Obtained Near Maximum BrightnessFeb 09 2012May 04 2012In this second paper in a series we present measurements of spectral features of 432 low-redshift (z < 0.1) optical spectra of 261 Type Ia supernovae (SNe Ia) within 20 d of maximum brightness. The data were obtained from 1989 through the end of 2008 ... More
Estimation of convex supports from noisy measurementsApr 26 2018A popular class of problem in statistics deals with estimating the support of a density from $n$ observations drawn at random from a $d$-dimensional distribution. The one-dimensional case reduces to estimating the end points of a univariate density. In ... More
Semi-Supervised Nonlinear Distance Metric Learning via Forests of Max-Margin Cluster HierarchiesFeb 23 2014Metric learning is a key problem for many data mining and machine learning applications, and has long been dominated by Mahalanobis methods. Recent advances in nonlinear metric learning have demonstrated the potential power of non-Mahalanobis distance ... More
Leavitt path algebras satisfying a polynomial identityAug 17 2014Leavitt path algebras L of an arbitrary graph E over a field K satisfying a polynomial identity are completely characterized both in graph-theoretic and algebraic terms. When E is a finite graph, L satisfying a polynomial identity is shown to be equivalent ... More
Anatomy of $\varepsilon'/\varepsilon$ beyond the Standard ModelAug 01 2018Mar 18 2019We present for the first time a model-independent anatomy of the ratio $\varepsilon'/\varepsilon$ in the context of the $\Delta S = 1$ effective theory with operators invariant under QCD and QED and in the context of the Standard Model Effective Field ... More
Wrangling Rogues: Managing Experimental Post-Moore ArchitecturesAug 20 2018Apr 09 2019The Rogues Gallery is a new experimental testbed that is focused on tackling "rogue" architectures for the Post-Moore era of computing. While some of these devices have roots in the embedded and high-performance computing spaces, managing current and ... More
Beyond the Knudsen number: assessing thermodynamic non-equilibrium in gas flowsJan 10 2012For more than 150 years the Navier-Stokes equations for thermodynamically quasi-equilibrium flows have been the cornerstone of modern computational fluid dynamics that underpins new fluid technologies. However, the applicable regime of the Navier-Stokes ... More
A new cohomological formula for helicity in $\R^{2k+1}$ reveals the effect of a diffeomorphism on helicityMar 08 2009Oct 26 2012The helicity of a vector field is a measure of the average linking of pairs of integral curves of the field. Computed by a six-dimensional integral, it is widely useful in the physics of fluids. For a divergence-free field tangent to the boundary of a ... More
Weak Gravitational Lensing Systematics from Image CombinationOct 12 2013Extremely accurate shape measurements of galaxy images are needed to probe dark energy properties with weak gravitational lensing surveys. To increase survey area with a fixed observing time and pixel count, images from surveys such as the Wide Field ... More
Structural and magnetic phase transitions in Ca$_{0.73}$La$_{0.27}$FeAs$_2$ with electron overdoped FeAs layersMay 21 2015Mar 14 2016We report a study of the Ca$_{0.73}$La$_{0.27}$FeAs$_2$ single crystals. We unravel a monoclinic to triclinic phase transition at 58 K, and a paramagnetic to stripe antiferromagnetic (AFM) phase transition at 54 K, below which spins order 45$^\circ$ away ... More
Radiative hydrodynamic modelling and observations of the X-class solar flare on 2011 March 9Apr 28 2015We investigated the response of the solar atmosphere to non-thermal electron beam heating using the radiative transfer and hydrodynamics modelling code RADYN. The temporal evolution of the parameters that describe the non-thermal electron energy distribution ... More
Suppression of Hydrogen Emission in an X-class White-light Solar FlareFeb 02 2017We present unique NUV observations of a well-observed X-class flare from NOAA 12087 obtained at Ond\v{r}ejov Observatory. The flare shows a strong white-light continuum but no detectable emission in the higher Balmer and Lyman lines. RHESSI and Fermi ... More
Data-driven Radiative Hydrodynamic Modeling of the 2014 March 29 X1.0 Solar FlareMar 16 2016Jun 08 2016Spectroscopic observations of solar flares provide critical diagnostics of the physical conditions in the flaring atmosphere. Some key features in observed spectra have not yet been accounted for in existing flare models. Here we report a data-driven ... More
21 Million Opportunities: A 19 Facility Investigation of Factors Affecting Hand Hygiene Compliance via Linear Predictive ModelsJan 26 2018This large-scale study, consisting of 21.3 million hand hygiene opportunities from 19 distinct facilities in 10 different states, uses linear predictive models to expose factors that may affect hand hygiene compliance. We examine the use of features such ... More
Denominators and Differences of Boundary Slopes for (1,1)-KnotsJan 26 2013Jul 23 2014We show that every nonzero integer occurs in the denominator of a boundary slope for infinitely many (1,1)-knots and that infinitely many (1,1)-knots have boundary slopes of arbitrarily small difference. Specifically, we prove that for any integers m, ... More
The exponential of the spin representation of the Lorentz algebraJan 29 2012As discussed in a previous article, any (real) Lorentz algebra element possess a unique orthogonal decomposition as a sum of two mutually annihilating decomposable Lorentz algebra elements. In this article, this concept is extended to the spin representation ... More
Rotations in three, four, and five dimensionsMar 08 2011The geometry of rotations in dimensions 3, 4, and 5 is discussed using the matrix exponential map. Explicit closed formulas for the exponential of an antisymmetric matrix, as well as the logarithm of a rotation, are given for these dimensions.
Forces on a Clifford bundleMar 29 2019In a companion article, the Clifford bundle over spacetime was used as a geometric framework for obtaining coupled Dirac and Einstein equations. Other forces may be incorporated using minimal coupling. Here the fundamental forces that are allowed within ... More
Learning Parameters for Weighted Matrix Completion via Empirical EstimationDec 31 2014Apr 02 2015Recently theoretical guarantees have been obtained for matrix completion in the non-uniform sampling regime. In particular, if the sampling distribution aligns with the underlying matrix's leverage scores, then with high probability nuclear norm minimization ... More
Iterative Hard Thresholding for Weighted Sparse ApproximationDec 12 2013Jan 07 2015Recent work by Rauhut and Ward developed a notion of weighted sparsity and a corresponding notion of Restricted Isometry Property for the space of weighted sparse signals. Using these notions, we pose a best weighted sparse approximation problem, i.e. ... More
Weak Convergence of the Scaled Median of Independent Brownian MotionsJul 26 2005Aug 02 2006We consider the median of n independent Brownian motions, and show that this process, when properly scaled, converges weakly to a centered Gaussian process. The chief difficulty is establishing tightness, which is proved through direct estimates on the ... More