Results for "Alex K. Lew"

total 94307took 0.15s
Few-Shot Bayesian Imitation Learning with Logic over ProgramsApr 12 2019We describe an expressive class of policies that can be efficiently learned from a few demonstrations. Policies are represented as logical combinations of programs drawn from a small domain-specific language (DSL). We define a prior over policies with ... More
Collapsibility of simplicial complexes of hypergraphsOct 28 2018Let $\mathcal{H}$ be a hypergraph of rank $r$. We show that the simplicial complex whose simplices are the hypergraphs $\mathcal{F}\subset\mathcal{H}$ with covering number at most $p$ is $\left(\binom{r+p}{r}-1\right)$-collapsible, and the simplicial ... More
Spectral gaps of simplicial complexes without large missing facesJun 01 2017Let $X$ be a simplicial complex on $n$ vertices without missing faces of dimension larger than $d$. Let $L_{j}$ denote the $j$-Laplacian acting on real $j$-cochains of $X$ and let $\mu_{j}(X)$ denote its minimal eigenvalue. We study the connection between ... More
Spectral gaps, missing faces and minimal degreesJul 04 2018Let $X$ be a simplicial complex with $n$ vertices. A missing face of $X$ is a simplex $\sigma\notin X$ such that $\tau\in X$ for any $\tau\subsetneq \sigma$. For a $k$-dimensional simplex $\sigma$ in $X$, its degree in $X$ is the number of $(k+1)$-dimensional ... More
Constraints on radio source clustering towards galaxy clusters: application for cm-wavelength simulations of blind sky surveysApr 16 2015We constrain radio source clustering towards $Planck$-selected galaxy clusters using the NVSS point source catalogue. The constraint can be utilised for generating realistic Sunyaev-Zeldovich effect (SZE) mocks, and for predicting detectable clusters ... More
Hemispherical power asymmetry: parameter estimation from CMB WMAP5 dataAug 21 2008Nov 10 2008We reexamine the evidence of the hemispherical power asymmetry, detected in the CMB WMAP data using a new method. At first, we analyze the hemispherical variance ratios and compare these with simulated distributions. Secondly, working within a previously-proposed ... More
Improving pointing of Toruń 32-m radio telescope: effects of rail surface irregularitiesJul 27 2017Jan 31 2018Over the last few years a number of software and hardware improvements have been implemented to the 32-m Cassegrain radio telescope located near Toru\'n. The 19-bit angle encoders have been upgraded to 29-bit in azimuth and elevation axes. The control ... More
Real space tests of the statistical isotropy and Gaussianity of the WMAP CMB dataMar 10 2008Aug 10 2008ABRIDGED: We introduce and analyze a method for testing statistical isotropy and Gaussianity and apply it to the WMAP CMB foreground reduced, temperature maps, and cross-channel difference maps. We divide the sky into regions of varying size and shape ... More
Starbugs: all-singing, all-dancing fibre positioning robotsNov 28 2013Starbugs are miniature piezoelectric 'walking' robots with the ability to simultaneously position many optical fibres across a telescope's focal plane. Their simple design incorporates two piezoceramic tubes to form a pair of concentric 'legs' capable ... More
Baryogenesis through Collapsing String Loops in Gauged Baryon and Lepton ModelsJun 30 1993A scenario for the generation of the baryon asymmetry in the early Universe is proposed in which cosmic string loops, predicted by theories where the baryon and/or lepton numbers are gauged symmetries, collapse during the friction dominated period of ... More
To P or not to P: on the evidential nature of P-values and their place in scientific inferenceNov 01 2013The customary use of P-values in scientific research has been attacked as being ill-conceived, and the utility of P-values has been derided. This paper reviews common misconceptions about P-values and their alleged deficits as indices of experimental ... More
Precision in ground based solar polarimetry: Simulating the role of adaptive opticsNov 02 2012Accurate measurement of polarization in spectral lines is important for the reliable inference of magnetic fields on the Sun. For ground based observations, polarimetric precision is severely limited by the presence of Earth's atmosphere. Atmospheric ... More
The likelihood principle does not entail a `sure thing', `evil demon' or `determinist' hypothesisJul 30 2015Aug 24 2015The likelihood principle makes strong claims about the nature of statistical evidence but is controversial. Its claims are undermined by the existence of several examples that are assumed to show that it allows, with unity probability, domination of all ... More
Understanding the atmospheric properties and chemical composition of the ultra-hot Jupiter HAT-P-7b: I. Cloud and chemistry mappingJun 19 2019Ultra-hot Jupiters have recently attracted interest from observers and theoreticians alike, as they provide observationally accessible test cases. We apply a hierarchical modelling approach as a virtual laboratory to study cloud formation and gas-phase ... More
Analysis of Using Browser-native Technology to Build Rich Internet Applications for Image ManipulationDec 31 2010In this work we investigate whether browser-native technologies can be used to perform photo manipulation tasks e.g cropping, resizing or rotating an image within the current mainstream browser. By the use of a case study we will analyze problems that ... More
Binary and nonbinary description of hypointensity in human brain MR imagesDec 31 2010Accumulating evidence has shown that iron is involved in the mechanism underlying many neurodegenerative diseases, such as Alzheimer's disease, Parkinson's disease and Huntington's disease. Abnormal (higher) iron accumulation has been detected in the ... More
Static and Dynamic Properties of Type-II Composite Fermion Wigner CrystalsJun 10 2011The Wigner crystal of composite fermions is a strongly correlated state of complex emergent particles, and therefore its unambiguous detection would be of significant importance. Recent observation of optical resonances in the vicinity of filling factor ... More
Gamow-Teller Strength in the Region of $^{100}$SnJun 01 1994New calculations are presented for Gamow-Teller beta decay of nuclei near $^{100}$Sn. Essentially all of the $^{100}$Sn Gamow-Teller decay strength is predicted to go to a single state at an excitation energy of 1.8 MeV in $^{100}$In. The first calculations ... More
Finer-grained Locking in Concurrent Dynamic Planar Convex HullsFeb 09 2017The convex hull of a planar point set is the smallest convex polygon containing each point in the set. The dynamic convex hull problem concerns efficiently maintaining the convex hull of a set of points subject to additions and removals. One algorithm ... More
Discrete quark-lepton symmetry need not pose a cosmological domain wall problemSep 28 1992Quarks and leptons may be related to each other through a spontaneously broken discrete symmetry. Models with acceptable and interesting collider phenomenology have been constructed which incorporate this idea. However, the standard Hot Big Bang model ... More
Clear sky atmosphere at cm-wavelengths from climatology dataMay 31 2015Oct 29 2015We utilise ground-based, balloon-borne and satellite climatology data to reconstruct site and season-dependent vertical profiles of precipitable water vapour (PWV). We use these profiles to solve radiative transfer through the atmosphere, and derive atmospheric ... More
A Solution to the Isolatitude, Equi-area, Hierarchical Pixel-Coordinate SystemSep 22 2004Nov 10 2004Gorski et al (1999b) have earlier presented the outline of a pixelisation-to-spherical-coordinate transformation scheme which simultaneously satisfies three properties which are especially useful for rapid analyses of maps on a sphere: (i) equal spacing ... More
The comptonization parameter from simulations of single-frequency, single-dish, dual-beam, cm-wave observations of galaxy clusters and mitigating CMB confusion using the Planck sky surveyAug 11 2016Nov 18 2016Systematic effects in dual-beam, differential, radio observations of extended objects are discussed in the context of the One Centimeter Receiver Array (OCRA). We use simulated samples of Sunyaev-Zel'dovich (SZ) galaxy clusters at low ($z<0.4$) and intermediate ... More
Universal Meshes: A new paradigm for computing with nonconforming triangulationsJan 24 2012We describe a method for discretizing planar C2-regular domains immersed in non-conforming triangulations. The method consists in constructing mappings from triangles in a background mesh to curvilinear ones that conform exactly to the immersed domain. ... More
Analysis of a method to parameterize planar curves immersed in triangulationsSep 16 2011Feb 17 2013We prove that a planar $C^2$-regular boundary $\Gamma$ can always be parameterized with its closest point projection $\pi$ over a certain collection of edges $\Gamma_h$ in an ambient triangulation, by making simple assumptions on the background mesh. ... More
Reconstructing comptonization parameters using simulations of single frequency, dual-beam observations of galaxy clustersAug 11 2016Aug 12 2016Systematical effects in dual-beam, differential, radio observations of extended objects are discussed in the context of the One Centimeter Receiver Array (OCRA). We use simulated samples of Sunyaev--Zel'dovich (SZ) galaxy clusters at low ($z<0.4$) and ... More
NP vs PSPACESep 30 2016We present a proof of the conjecture $\mathcal{NP}$ = $\mathcal{PSPACE}$ by showing that arbitrary tautologies of Johansson's minimal propositional logic admit "small" polynomial-size dag-like natural deductions in Prawitz's system for minimal propositional ... More
Dynamic Feature Description in Human Action RecognitionDec 31 2010This work aims to present novel description methods for human action recognition. Generally, a video sequence can be represented as a collection of spatial temporal words by detecting space-time interest points and describing the unique features around ... More
Variational integrators for the dynamics of thermo-elastic solids with finite speed thermal wavesMar 15 2014This paper formulates variational integrators for finite element discretizations of deformable bodies with heat conduction in the form of finite speed thermal waves. The cornerstone of the construction consists in taking advantage of the fact that the ... More
A test of the Poincare dodecahedral space topology hypothesis with the WMAP CMB dataJan 09 2008Apr 24 2008It has been suggested by Roukema and coworkers (hereafter R04) that the topology of the Universe as probed by the ``matched circles'' method using the first year release of the WMAP CMB data, might be that of the Poincar\'e dodecahedral space (PDS) model. ... More
Quark-Lepton SymmetryNov 20 1992Quark-lepton symmetric models are a class of gauge theories motivated by the similarities between the quarks and leptons. In these models the gauge group of the standard model is extended to include a ``color'' group for the leptons. Consequently, the ... More
The route to high temperature superconductivity in transition metal oxidesOct 07 2010The discovery of high temperature superconductivity in cuprates was possible only through an intimate knowledge of perovskite oxides which have been synthesized and characterized for decades at the IBM in the Z\"urich laboratoty. Especially SrTiO3 and ... More
Crossover behavior in a mixed mode fiber bundle modelMay 19 2004Dec 06 2004We introduce a mixed-mode load sharing scheme in fiber bundle model. This model reduces exactly to equal load sharing (ELS) and local load sharing (LLS) models at the two extreme conditions of the load sharing rule. We identify two distinct regimes: a) ... More
Effects of Rotation and Relativistic Charge Flow on Pulsar Magnetospheric StructureMay 09 2005We propose an analytical 3-D model of the open field-line region of a neutron star (NS) magnetosphere. We construct an explicit analytic solution for arbitrary obliquity (angle between the rotation and magnetic axes) incorporating the effects of magnetospheric ... More
High-Altitude Particle Acceleration and Radiation in Pulsar Slot GapsFeb 19 2004We explore the pulsar slot gap electrodynamics up to very high altitudes, where for most relatively rapidly rotating pulsars both the standard small-angle approximation and the assumption that the magnetic field lines are ideal stream lines break down. ... More
Extended Acceleration in Slot Gaps and Pulsar High-Energy EmissionJan 02 2003Jan 03 2003We revise the physics of primary electron acceleration in the "slot gap" (SG) above the pulsar polar caps (PCs), a regime originally proposed by Arons and Scharlemann (1979) in their electrodynamic model of pulsar PCs. We employ the standard definition ... More
Lexico-minimum Replica Placement in MultitreesSep 17 2017In this work, we consider the problem of placing replicas in a data center or storage area network, represented as a digraph, so as to lexico-minimize a previously proposed reliability measure which minimizes the impact of all failure events in the model ... More
Pulsar Pair Cascades in a Distorted Magnetic Dipole FieldDec 02 2010Dec 03 2010We investigate the effect of a distorted neutron star dipole magnetic field on pulsar pair cascade multiplicity and pair death lines. Using a simple model for a distorted dipole field that produces an offset polar cap, we derive the accelerating electric ... More
Minimal Massive 3D Gravity Unitarity ReduxNov 07 2014Mar 18 2015A geometrical analysis of the bulk and anti-de Sitter boundary unitarity conditions of 3D "Minimal Massive Gravity" (MMG) (which evades the "bulk/boundary clash" of Topologically Massive Gravity) is used to extend and simplify previous results, showing ... More
Pulsar Pair Cascades in Magnetic Fields with Offset Polar CapsNov 07 2011Neutron star magnetic fields may have polar caps (PC) that are offset from the dipole axis, through field-line sweepback near the light cylinder or non-symmetric currents within the star. The effects of such offsets on electron-positron pair cascades ... More
Smear correction of highly-variable, frame-transfer-CCD images with application to polarimetryJun 11 2015Image smear, produced by the shutter-less operation of frame transfer CCD detectors, can be detrimental for many imaging applications. Existing algorithms used to numerically remove smear, do not contemplate cases where intensity levels change considerably ... More
Pair-Starved Pulsar MagnetospheresOct 16 2008We propose a simple analytic model for the innermost (within the light cylinder of canonical radius) structure of open-magnetic-field lines of a rotating neutron star (NS) with relativistic outflow of charged particles (electrons/positrons) and arbitrary ... More
Particle Acceleration in Pair-Starved PulsarsAug 20 2004We investigate the physical situation above the pulsar polar cap (PC) where the accelerating primaries (electrons) are not capable of producing sufficient numbers of electron-positron pairs at low altitudes (within 1-2 stellar radii above the PC surface) ... More
Failure Processes in Elastic Fiber BundlesAug 09 2008Jul 17 2009The fiber bundle model describes a collection of elastic fibers under load. the fibers fail successively and for each failure, the load distribution among the surviving fibers change. Even though very simple, the model captures the essentials of failure ... More
Unbroken versus broken mirror world: a tale of two vacuaJun 02 2000If the Lagrangian of nature respects parity invariance then there are two distinct possibilities: either parity is unbroken by the vacuum or it is spontaneously broken. We examine the two simplest phenomenologically consistent gauge models which have ... More
A Framework for Real-Time Face and Facial Feature Tracking using Optical Flow Pre-estimation and Template TrackingDec 31 2010This work presents a framework for tracking head movements and capturing the movements of the mouth and both the eyebrows in real-time. We present a head tracker which is a combination of a optical flow and a template based tracker. The estimation of ... More
Supercloseness of Orthogonal Projections onto Nearby Finite Element SpacesAug 18 2014We derive upper bounds on the difference between the orthogonal projections of a smooth function $u$ onto two finite element spaces that are nearby, in the sense that the support of every shape function belonging to one but not both of the spaces is contained ... More
High-Order Finite Element Methods for Moving Boundary Problems with Prescribed Boundary EvolutionMay 08 2014We introduce a framework for the design of finite element methods for two-dimensional moving boundary problems with prescribed boundary evolution that have arbitrarily high order of accuracy, both in space and in time. At the core of our approach is the ... More
Across Browsers SVG ImplementationDec 31 2010In this work SVG will be translated into VML or HTML by using Javascript based on Backbase Client Framework. The target of this project is to implement SVG to be viewed in Internet Explorer without any plug-in and work together with other Backbase Client ... More
Properties of Two-Dimensional Silicon grown on Graphene SubstrateApr 05 2013The structure and electrical properties of a two-dimensional (2D) sheet of silicon on a graphene substrate are studied using first-principles calculations. A new corrugated rectangular structure of silicon is proposed to be the most energetically favorable ... More
Proof-graphs for Minimal Implicational LogicApr 01 2014It is well-known that the size of propositional classical proofs can be huge. Proof theoretical studies discovered exponential gaps between normal or cut free proofs and their respective non-normal proofs. The aim of this work is to study how to reduce ... More
Trajectory Optimization on Manifolds: A Theoretically-Guaranteed Embedded Sequential Convex Programming ApproachMay 18 2019Sequential Convex Programming (SCP) has recently gained popularity as a tool for trajectory optimization due to its sound theoretical properties and practical performance. Yet, most SCP-based methods for trajectory optimization are restricted to Euclidean ... More
Quantification of spin accumulation causing spin-orbit torque in Pt/Co/Ta stackAug 04 2017Spin accumulation induced by spin-orbit coupling is experimentally quantified in stack with in-plane magnetic anisotropy via the contribution of spin accumulation to Hall resistances. Using a biasing direct current the spin accumulation within the structure ... More
Model for a Light Z' BosonJan 13 1994A model of a light $Z'$ boson is constructed and phenomenological bounds are derived. This $Z'$ boson arises from a very simple extension to the Standard Model, and it is constrained to be light because the vacuum expectation values which generate its ... More
Dynamics of a nanowire superlattice in an ac electric fieldSep 24 2005With a one-band envelope function theory, we investigate the dynamics of a finite nanowire superlattice driven by an ac electric field by solving numerically the time-dependent Schroedinger equation. We find that for an ac electric field resonant with ... More
Simulations of cm-wavelength Sunyaev-Zel'dovich galaxy cluster and point source blind sky surveys and predictions for the RT32/OCRA-f and the Hevelius 100-m radio telescopeOct 14 2014Dec 30 2014We investigate the effectiveness of blind surveys for radio sources and galaxy cluster thermal Sunyaev-Zel'dovich effects (TSZEs) using the four-pair, beam-switched OCRA-f radiometer on the 32-m radio telescope in Poland. The predictions are based on ... More
Twistor description of spinning particles in AdSOct 26 2017Nov 18 2017The two-twistor formulation of particle mechanics in D-dimensional anti-de Sitter space for D=4,5,7, which linearises invariance under the AdS isometry group Sp(4;K) for K=R,C,H, is generalized to the massless N-extended "spinning particle". The twistor ... More
Anti-de Sitter particles and manifest (super)isometriesAug 15 2016Apr 01 2017Starting from the classical action for a spin-zero particle in a D-dimensional anti-Sitter (AdS) spacetime, we recover the Breitenlohner-Freedman bound by quantization. For D=4,5,7, and using an Sl(2;K) spinor notation for K=R,C,H, we find a bi-twistor ... More
Multi-Task Time Series Analysis applied to Drug Response ModellingMar 21 2019Time series models such as dynamical systems are frequently fitted to a cohort of data, ignoring variation between individual entities such as patients. In this paper we show how these models can be personalised to an individual level while retaining ... More
Twistor variables for Anti-de Sitter (super)particlesAug 15 2016Starting from the classical action for a spin-zero particle in a (D + 1)-dimensional anti-Sitter spacetime, we recover the Breitenlohner-Freedman bound by quantization. We then find a twistor form of the action for D = 3, 4, 6 for which the SO(2, D) isometry ... More
Anti-de Sitter particles and manifest (super)isometriesAug 15 2016Oct 07 2016Starting from the classical action for a spin-zero particle in a D-dimensional anti-Sitter (AdS) spacetime, we recover the Breitenlohner-Freedman bound by quantization. For D=4,5,7 we find a simple bi-twistor form of the action; the AdS isometry group ... More
Multi-Qubit Gate with Trapped Ions for Microwave and Laser-Based ImplementationApr 12 2015A proposal for a phase gate and a M{\o}lmer-S{\o}rensen (MS) gate in the dressed state basis is presented. In order to perform the multi-qubit interaction, a strong magnetic field gradient is required to couple the phonon-bus to the qubit states. The ... More
Transport in partially equilibrated inhomogeneous quantum wiresApr 30 2010Sep 08 2010We study transport properties of weakly interacting one-dimensional electron systems including on an equal footing thermal equilibration due to three-particle collisions and the effects of large-scale inhomogeneities. We show that equilibration in an ... More
Pauli-Lubanski, Supertwistors, and the Superspinning ParticleJan 20 2016Jul 02 2016We present a novel construction of the super-Pauli-Lubanski pseudo-vector for the ${\cal N}=1$ super-Poincar\'e algebra of four-dimensional spacetime. Our construction arises naturally in a supertwistor formulation of superparticle dynamics, and relies ... More
Free Space Optical Polarization De-multiplexing and Multiplexing by means of Conical RefractionJan 08 2013Polarization de-multiplexing and multiplexing by means of conical refraction is proposed to increase the channel capacity for free space optical communication applications. The proposed technique is based on the forward-backward optical transform occurring ... More
Pauli-Lubanski, Supertwistors, and the Superspinning ParticleJan 20 2016Jun 28 2017We present a novel construction of the super-Pauli-Lubanski pseudo-vector for 4D supersymmetry and show how it arises naturally from the spin-shell constraints in the supertwistor formulation of superparticle dynamics. We illustrate this result in the ... More
Thermodynamics of statistical inference by cellsMay 15 2014Oct 06 2014The deep connection between thermodynamics, computation, and information is now well established both theoretically and experimentally. Here, we extend these ideas to show that thermodynamics also places fundamental constraints on statistical estimation ... More
Mitigating Wordline Crosstalk using Adaptive Trees of CountersJun 07 2018High access frequency of certain rows in the DRAM may cause data loss in cells of physically adjacent rows due to crosstalk. The malicious exploit of this crosstalk by repeatedly accessing a row to induce this effect is known as row hammering. Additionally, ... More
A First-Quantized Formalism for Cosmological Particle ProductionNov 19 2003May 12 2004We show that the amount of particle production in an arbitrary cosmological background can be determined using only the late-time positive-frequency modes. We don't refer to modes at early times, so there is no need for a Bogolubov transformation. We ... More
Statistical evolution of quiet-Sun small scale magnetic features using Sunrise observationsAug 30 2016Aug 31 2016The evolution of small magnetic features in quiet regions of the Sun provides a unique window to probing solar magneto-convection. Here we analyze small scale magnetic features in the quiet Sun, using the high resolution, seeing-free observations from ... More
1-100 GeV Emission from Millisecond PulsarsOct 05 2005A number of rotation-powered millisecond pulsars are powerful sources of X-ray emission. We present predictions for the spectral characteristics of these sources at gamma-ray energies, using a model for acceleration and pair cascades on open magnetic ... More
Yang-Mills as massive Chern-Simons theory: a third way to three-dimensional gauge theoriesJan 29 2015Apr 26 2015The Yang-Mills (YM) equation in three spacetime dimensions (3D) can be modified to include a novel parity-preserving interaction term, with inverse mass parameter, in addition to a possible topological mass term. The novelty is that the modified YM equation ... More
A Variable Length Coding Framework for Cost Function Reduction in Non-Volatile Memory SystemsOct 24 2017Variable length coding for Non-Volatile Memory (NVM) technologies is a promising method to improve memory capacity and system performance through compressing memory blocks. However, compression techniques used to improve capacity or bandwidth utilization ... More
Enabling Fine-Grain Restricted Coset Coding Through Word-Level Compression for PCMNov 23 2017Phase change memory (PCM) has recently emerged as a promising technology to meet the fast growing demand for large capacity memory in computer systems, replacing DRAM that is impeded by physical limitations. Multi-level cell (MLC) PCM offers high density ... More
Spectrally-accurate quadratures for evaluation of layer potentials close to the boundary for the 2D Stokes and Laplace equationsOct 08 2014Dense particulate flow simulations using integral equation methods demand accurate evaluation of Stokes layer potentials on arbitrarily close interfaces. In this paper, we generalize techniques for close evaluation of Laplace double-layer potentials in ... More
Statistical evolution of quiet-Sun small scale magnetic features using Sunrise observationsAug 30 2016Nov 09 2016The evolution of small magnetic features in quiet regions of the Sun provides a unique window to probing solar magneto-convection. Here we analyze small scale magnetic features in the quiet Sun, using the high resolution, seeing-free observations from ... More
New calculations of the PNC Matrix Element for the $J^πT$ 0$^{+}1,0^{-}1$ doublet in $^{14}$NMar 08 1994A new calculation of the predominantly isoscalar PNC matrix element between the $J^{\pi}T$ $0^{+}1,0^{-}1$ (E$_{x} \approx$ 8.7 MeV) states in $^{14}$N has been carried out in a (0+1+2+3+4)$\hbar \omega$ model space with the Warburton-Brown interaction. ... More
Learning warps object representations in the ventral temporal cortexApr 01 2016The human ventral temporal cortex (VTC) plays a critical role in object recognition. Although it is well established that visual experience shapes VTC object representations, the impact of semantic and contextual learning is unclear. In this study, we ... More
Non-equilibrium supercurrent through a quantum dot: current harmonics and proximity effect due to a normal metal leadAug 07 2009Dec 02 2009We consider a Hamiltonian model for a quantum dot which is placed between two superconducting leads with a constant bias imposed between these leads. Using the non-equilibrium Keldysh technique, we focus on the subgap current, where it is known that multiple ... More
Worldline CPT and massless supermultipletsJul 02 2016Sep 08 2016The action for a massless particle in 4D Minkowski space has a worldline time-reversing symmetry corresponding to CPT invariance of the quantum theory. The analogous symmetry of the N-extended superparticle is shown to be anomalous when N is odd, in the ... More
High-Energy Emission From Millisecond PulsarsNov 30 2004The X-ray and gamma-ray spectrum of rotation-powered millisecond pulsars is investigated in a model for acceleration and pair cascades on open field lines above the polar caps. Although these pulsars have low surface magnetic fields, their short periods ... More
Statistical evolution of quiet-Sun small scale magnetic features using Sunrise observationsAug 30 2016Dec 08 2016The evolution of small magnetic features in quiet regions of the Sun provides a unique window to probing solar magneto-convection. Here we analyze small scale magnetic features in the quiet Sun, using the high resolution, seeing-free observations from ... More
A microstructurally informed model for the mechanical response of three-dimensional actin networksFeb 26 2008We propose a class of microstructurally informed models for the linear elastic mechanical behavior of cross-linked polymer networks such as the actin cytoskeleton. Salient features of the models include the possibility to represent anisotropic mechanical ... More
A Physical Model-based Correction for Charge Traps in the Hubble Space Telescope's Wide Field Camera 3 Near-IR Detector and Applications to Transiting Exoplanets and Brown DwarfsMar 03 2017Mar 16 2017The Hubble Space Telescope (HST) Wide Field Camera 3 (WFC3) near-IR channel is extensively used in time-resolved observations, especially for transiting exoplanet spectroscopy and brown dwarf and directly imaged exoplanet rotational phase mapping. The ... More
Matter coupling in 3D "Minimal Massive Gravity"Jul 04 2014Oct 02 2014The "Minimal Massive Gravity" (MMG) model of massive gravity in three spacetime dimensions (which has the same anti-de Sitter (AdS) bulk properties as "Topologically Massive Gravity" but improved boundary properties) is coupled to matter. Consistency ... More
A new approach for constraining the Hubble constant from proper motions of radio jetsSep 07 2005Feb 26 2006Withdrawn due to a mistake in jets' Doppler factor modeling. An updated version will appear after revisiting this work.
Quantitative characterization of spin-orbit torques in Pt/Co/Pt /Co/Ta/BTO heterostructure on the magnetization azimuthal angle dependenceJun 06 2017Substantial understanding of spin-orbit interactions in heavy-metal (HM)/ferromagnet (FM) heterostructures is crucial in developing spin-orbit torque (SOT) spintronics devices utilizing spin Hall and Rashba effects. Though the study of SOT effective fields ... More
Rare B decays with moving NRQCD and improved staggered quarksOct 06 2008We calculate form factors relevant for rare B decays using moving-NRQCD for the b quark and the AsqTad action for the light quarks. Moving NRQCD allows us to work directly with the physical b quark mass and go to higher recoil momentum compared to standard ... More
Strain-induced energy band gap opening in two-dimensional bilayered silicon filmSep 01 2015This work presents a theoretical study of the structural and electronic properties of bilayered silicon films under in-plane biaxial strain/stress using density functional theory. Atomic structures of the two-dimensional silicon films are optimized by ... More
Learned Video CompressionNov 16 2018We present a new algorithm for video coding, learned end-to-end for the low-latency mode. In this setting, our approach outperforms all existing video codecs across nearly the entire bitrate range. To our knowledge, this is the first ML-based method to ... More
Emergent Geometric Frustration of Artificial Magnetic Skyrmion CrystalsAug 24 2016Magnetic skyrmions have been receiving growing attention as potential information storage and magnetic logic devices since an increasing number of materials have been identified that support skyrmion phases. Explorations of artificial frustrated systems ... More
A big-world network in ASD: Dynamical connectivity analysis reflects a deficit in long-range connections and an excess of short-range connectionsJul 30 2010Over the last years, increasing evidence has fuelled the hypothesis that Autism Spectrum Disorder (ASD) is a condition of altered brain functional connectivity. The great majority of these empirical studies rely on functional magnetic resonance imaging ... More
Universal Meshes for the Simulation of Brittle Fracture and Moving Boundary ProblemsOct 17 2015Universal meshes have recently appeared in the literature as a compu- tationally efficient and robust paradigm for the generation of conforming simpli- cial meshes for domains with evolving boundaries. The main idea behind a univer- sal mesh is to immerse ... More
Electronic structure of wurtzite quantum dots with cylindrical symmetrySep 24 2005This paper presents a six-band k.p theory for wurtzite semiconductor nanostructures with cylindrical symmetry. Our work extends the formulation of Vahala and Sercel [Physical Review Letters 65, 239 (1990)] to the Rashba-Sheka-Pikus Hamiltonian for wurtzite ... More
An Electrochemical Potentiostat Interface for Mobile Devices: Enabling Remote Medical DiagnosticsSep 29 2015An electrochemical potentiostat interface for mobile devices has been designed and implemented. The interface consists of a potentiostat module, a microcontroller module, and a Bluetooth module. The potentiostat module performs electrochemical measurements ... More
The Impact of Galactic Disc Environment on Star-Forming CloudsDec 04 2017We explore the effect of different galactic disc environments on the properties of star-forming clouds through variations in the background potential in a set of isolated galaxy simulations. Rising, falling and flat rotation curves expected in halo dominated, ... More
Augmenting adaptive immunity: progress and challenges in the quantitative engineering and analysis of adaptive immune receptor repertoiresApr 08 2019Apr 09 2019The adaptive immune system is a natural diagnostic and therapeutic. It recognizes threats earlier than clinical symptoms manifest and neutralizes antigen with exquisite specificity. Recognition specificity and broad reactivity is enabled via adaptive ... More
Type I and type II second harmonic generation of conically refracted beamsOct 14 2014Type I and type II second harmonic generation (SHG) of a beam transformed by the conical refraction phenomenon are presented. We show that, for type I, the second harmonic intensity pattern is a light ring with a point of null intensity while, for type ... More
On the dual-cone nature of the conical refraction phenomenonMay 19 2015In conical refraction (CR), a focused Gaussian input beam passing through a biaxial crystal and parallel to one of the optic axes is transformed into a pair of concentric bright rings split by a dark (Poggendorff) ring at the focal plane. Here, we show ... More
Detection of timescales in evolving complex systemsApr 04 2016Most complex systems are intrinsically dynamic in nature. The evolution of a dynamic complex system is typically represented as a sequence of snapshots, where each snapshot describes the configuration of the system at a particular instant of time. Then, ... More