Results for "Andrew J. Higgins"

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Reconciling a Reactionless Propulsive Drive with the First Law of ThermodynamicsMay 07 2015A "space drive" is a hypothetical device that generates a propulsive force in free space using an input of power without the need for a reaction mass. Any device that generates photons (e.g., a laser) would qualify as a propellantless "photon rocket," ... More
Influence of Discrete Sources on Detonation Propagation in a Burgers Equation Analog SystemFeb 01 2015An analog to the equations of compressible flow that is based on the inviscid Burgers equation is utilized to investigate the effect of spatial discreteness of energy release on the propagation of a detonation wave. While the traditional Chapman-Jouguet ... More
Propagation Distance Required to Reach Steady-State Detonation Velocity in Finite-Sized ChargesJul 08 2014The decay of a detonation wave from its initial CJ velocity to its final, steady state velocity upon encountering a finite thickness or diameter charge is investigated numerically and theoretically. The numerical simulations use an ideal gas equation ... More
Geometric Scaling for a Detonation Wave Governed by a Pressure-Dependent Reaction Rate and Yielding ConfinementMay 30 2014Jul 09 2014The propagation of detonation waves in reactive media bounded by an inert, compressible layer is examined via computational simulations in two different geometries, axisymmetric cylinders and two dimensional, planar slabs. For simplicity, an ideal gas ... More
Effect of Spatial Heterogeneity on Near-Limit Propagation of a Stable DetonationJun 04 2014The effect of introducing a spatial heterogeneity into an explosive medium is studied computationally by examining the detonation velocity near the limit to propagation in a thin explosive layer. The explosive system studied is an ideal gas with a single ... More
The Influence of Spatial Discreteness on the Thermo-Diffusive Instability of Flame Propagation with Infinite Lewis NumberDec 04 2015Jun 13 2016The dynamics of flame propagation in systems with infinite Lewis number and spatially discretized sources of heat release is examined, which is applicable to the combustion of suspensions of fuel particles in air. The system is analyzed numerically using ... More
Effect of spatial discretization of energy on detonation wave propagationAug 27 2016Detonation propagation in the limit of highly spatially discretized energy sources is investigated. The model of this problem begins with a medium consisting of a calorically perfect gas with a prescribed energy release per unit mass. The energy release ... More
Thin Elements and Commutative Shells in Cubical omega-categoriesAug 23 2004The relationships between thin elements, commutative shells and connections in cubical omega-categories are explored by a method which does not involve the use of pasting theory or nerves of omega-categories (both of which were previously needed for this ... More
The Effect of Particle Strength on the Ballistic Resistance of Shear Thickening FluidsJul 04 2012Apr 01 2013The response of shear thickening fluids (STFs) under ballistic impact has received considerable attention due to its field-responsive nature. While efforts have primarily focused on the response of traditional ballistic fabrics impregnated with fluids, ... More
Ballistic Impact of Dense Particle SuspensionsOct 14 2011The ballistic impact of various dense particle suspensions is of interest for the development of superior materials for personal protective equipment. The dynamic response of the fluids under impact of a fragment simulating projectile at various incident ... More
Propagation of gaseous detonation waves in a spatially inhomogeneous reactive mediumMar 27 2017Detonation propagation in a compressible medium wherein the energy release has been made spatially inhomogeneous is examined via numerical simulation. The inhomogeneity is introduced via step functions in the reaction progress variable, with the local ... More
Meso-resolved simulations of shock-to-detonation transition in nitromethane with air-filled cavitiesMay 14 2019Two-dimensional, meso-resolved numerical simulations are performed to investigate the complete shock-to-detonation transition (SDT) process in a mixture of liquid nitromethane (NM) and air-filled, circular cavities. The shock-induced initiation behaviors ... More
Meso-resolved simulations of shock-to-detonation transition in nitromethane with air-filled cavitiesMay 14 2019May 15 2019Two-dimensional, meso-resolved numerical simulations are performed to investigate the complete shock-to-detonation transition (SDT) process in a mixture of liquid nitromethane (NM) and air-filled, circular cavities. The shock-induced initiation behaviors ... More
Dynamical Regimes Induced by Spin Transfer in Magnetic NanopillarsJun 29 2008Jul 16 2008We demonstrate the predicted out-of-plane precession induced by spin transfer in magnetic nanostructures with in-plane magnetic field. We show that other magnetic excitations have a significant effect on the stability of the out-of plane precession, making ... More
From one environment to many: The problem of replicability of statistical inferencesApr 22 2019The environment in which an experiment is conducted is unique to each experiment. While the statistical inferences that are drawn from the analysis of experimental data apply only to the environment in which the experiment is conducted, it is almost always ... More
Imaging ferroelectric hysteresis and domain wall pinningDec 31 2009Simultaneous imaging of the piezoresponse phase, amplitude and bare surface topography of displacive ferroelectric thin films by scanning probe microscopy directly shows the nature of domain wall pinning and its relation to morphological disorder. Strong ... More
The fundamental groupoid of the quotient of a Hausdorff space by a discontinuous action of a discrete group is the orbit groupoid of the induced actionDec 19 2002The main result is that the fundamental groupoid of the orbit space of a discontinuous action of a discrete group on a Hausdorff space which admits a universal cover is the orbit groupoid of the fundamental groupoid of the space. We also describe work ... More
Current-Induced Dynamics in Almost Symmetric Magnetic NanopillarsOct 05 2008Magnetic nanodevices usually include a free layer whose configuration can be changed by spin-polarized current via the spin transfer effect, and a fixed reference layer. Here, we demonstrate that the roles of the free and the reference layers interchange ... More
Rotational stabilisation of the Rayleigh-Taylor instabilityApr 25 2019A number of applications utilise the energy focussing potential of imploding shells to dynamically compress matter or magnetic fields, including magnetised target fusion schemes. This paper examines the effect of fluid rotation on the Rayleigh-Taylor ... More
Cubical abelian groups with connections are equivalent to chain complexesDec 11 2002The theorem of the title is deduced from the equivalence between crossed complexes and cubical $\omega$-groupoids with connections proved by the authors in 1981. In fact we prove the equivalence of five categories defined internally to an additive category ... More
Thermal Dynamics in Symmetric Magnetic Nanopillars Driven by Spin TransferJan 11 2008We study the effects of spin transfer on thermally activated dynamics of magnetic nanopillars with identical thicknesses of the magnetic layers. The symmetric nanopillars exhibit anomalous dependencies of switching statistics on magnetic field and current. ... More
A Statistical Study of Distant Consequences of Large Solar Energetic EventsSep 18 2015Large solar flares and eruptions may influence remote regions through perturbations in the outer-atmospheric magnetic field, leading to causally related events outside of the primary or triggering eruptions that are referred to as "sympathetic events." ... More
Structures Produced by the Collision of Extragalactic Jets with Dense CloudsApr 01 1999We have investigated how several parameters can affect the results of a collision between an extragalactic jet and a dense, intergalactic cloud, through a series of hydrodynamic simulations. Such collisions are often suggested to explain the distorted ... More
Flow Induced Organization and Memory of a Vortex LatticeApr 09 1999Apr 10 1999We report on experiments probing the evolution of a vortex state in response to a driving current in 2H-NbSe$_2$ crystals. By following the vortex motion with fast transport measurements we find that the current enables the system to reorganize and access ... More
Metastability and Glassy Behavior of a Driven Flux-Line LatticeJun 11 1996Aug 06 1996Strong metastability and history dependence are observed in DC and pulsed transport studies of flux-line lattices in 2H-$NbSe_{2}$, leading to the identification of two distinct states of the lattice with different spatial ordering. The metastability ... More
Plastic Motion of a Flux-line Lattice Driven by Alternating CurrentMay 01 1998We have measured the response of the flux-line lattice in the low T$_c$ superconductor, 2H-NbSe$_2$, to finite frequency drives. In a well-defined range of fields, temperatures, and driving amplitudes the system exhibits a variety of novel non-linear ... More
Suppression of the Melting Line in a Weakly Disordered Flux-line SystemNov 10 2011An analytic formula describing the suppression of the equilibrium melting line by quenched point pinning disorder is compared to data from ac susceptibility and magnetization measurements in the mixed phase of the layered dichalcogenide low T_c superconductor ... More
Generalized Full MatchingMar 11 2017Matching methods are used to make units comparable on observed characteristics. Full matching can be used to derive optimal matches. However, the method has only been defined in the case of two treatment categories, it places unnecessary restrictions ... More
Coexistence of Antiferromagnetism and Superconductivity in Electron-doped High-Tc SuperconductorsMay 30 2007We present magnetotransport evidence for antiferromagnetism in films of the electron-doped cuprates Pr$_{2-x}$Ce$_x$CuO$_4$. Our results show clear signature of static antiferromagnetism up to optimal doping x=0.15, with a quantum phase transition close ... More
Blocking estimators and inference under the Neyman-Rubin modelOct 05 2015We derive the variances of estimators for sample average treatment effects under the Neyman-Rubin potential outcomes model for arbitrary blocking assignments and an arbitrary number of treatments.
Percolation Transition in the Heterogeneous Vortex State in NbSe2Mar 02 2005A percolation transition in the vortex state of a superconducting 2H-NbSe2 crystal is observed in the regime where vortices form a heterogeneous phase consisting of ordered and disordered domains. The transition is signaled by a sharp increase in critical ... More
AC Dynamics and Metastability of a Flux-Line LatticeMar 05 1997We have measured the complex surface impedance of 2H-NbSe_2 in the mixed state over a wide range of magnetic field(0-2T) and frequency(10-3000MHz). A crossover between pinned and viscous dynamics of flux-lines is observed at a pinning frequency, $\omega_p$. ... More
A Two Factor Forward Curve Model with Stochastic Volatility for Commodity PricesAug 04 2017Aug 08 2017We describe a model for evolving commodity forward prices that incorporates three important dynamics which appear in many commodity markets: mean reversion in spot prices and the resulting Samuelson effect on volatility term structure, decorrelation of ... More
Stochastic Spot/Volatility Correlation in Stochastic Volatility Models and Barrier Option PricingApr 15 2014Most models for barrier pricing are designed to let a market maker tune the model-implied covariance between moves in the asset spot price and moves in the implied volatility skew. This is often implemented with a local volatility/stochastic volatility ... More
Resonant transport and electrostatic effects in single-molecule electrical junctionsJun 03 2015In this contribution we demonstrate structural control over a transport resonance in HS(CH$_{2}$)$_{n}$[1,4 - C$_{6}$H$_{4}$](CH$_{2}$)$_{n}$SH (n = 1, 3, 4, 6) metal - molecule - metal junctions, fabricated and tested using the scanning tunnelling microscopy-based ... More
The Critical Current Density in Polycrystalline HTS and LTS Superconductors in High Magnetic FieldsNov 14 2012Nov 24 2013Flux pinning scaling laws were developed to explain the observed increase in the critical current density Jc caused by increased density of grain boundaries in polycrystalline low temperature superconductors (LTS) such as Nb3Sn. For four decades they ... More
Multiple-copy state discrimination: Thinking globally, acting locallyDec 16 2010May 20 2011We theoretically investigate schemes to discriminate between two nonorthogonal quantum states given multiple copies. We consider a number of state discrimination schemes as applied to nonorthogonal, mixed states of a qubit. In particular, we examine the ... More
Using weak values to experimentally determine "negative probabilities" in a two-photon state with Bell correlationsDec 15 2011Jan 29 2015Bipartite quantum entangled systems can exhibit measurement correlations that violate Bell inequalities, revealing the profoundly counter-intuitive nature of the physical universe. These correlations reflect the impossibility of constructing a joint probability ... More
Exploring metastability via the third harmonic measurements in single crystals of $2H$-$NbSe_2$ showing anomalous Peak effectSep 20 2005We explore the metastability effects across the order-disorder transition pertaining to the peak effect phenomenonon in critical current density ($J_c$) via the first and the third harmonic ac susceptibility measurements in the weakly pinned single crystals ... More
Hall effect in cobalt-doped TiO$_{2-δ}$Nov 03 2003We report Hall effect measurements on thin films of cobalt-doped TiO$_{2-\delta}$. Films with low carrier concentrations (10$^{18}$ - 10$^{19}$) yield a linear behavior in the Hall data while those having higher carrier concentrations (10$^{21}$ - 10$^{22}$) ... More
Ultrafast dynamics in the presence of antiferromagnetic correlations in electron-doped cuprate La$_{2-x}$Ce$_x$CuO$_{4\pmδ}$Jan 25 2016Aug 17 2016We used femtosecond optical pump-probe spectroscopy to study the photoinduced change in reflectivity of thin films of the electron-doped cuprate La$_{2-x}$Ce$_x$CuO$_4$ (LCCO) with dopings of x$=$0.08 (underdoped) and x$=$0.11 (optimally doped). Above ... More
Dynamic Creation and Annihilation of Metastable Vortex Phase as a Source of Excess NoiseMar 14 2002Mar 18 2002The large increase in voltage noise, commonly observed in the vicinity of the peak-effect in superconductors, is ascribed to a novel noise mechanism. A strongly pinned metastable disordered vortex phase, which is randomly generated at the edges and annealed ... More
Entanglement-free Heisenberg-limited phase estimationSep 19 2007Jun 12 2008Measurement underpins all quantitative science. A key example is the measurement of optical phase, used in length metrology and many other applications. Advances in precision measurement have consistently led to important scientific discoveries. At the ... More
Comparison of Phase Boundaries between Kagome and Honeycomb Superconducting Wire NetworksDec 02 2001We measure resistively the mean-field superconducting-normal phase boundaries of both kagome and honeycomb wire networks immersed in a transverse magnetic field. In addition to their agreement with theory about the overall shapes of phase diagrams, they ... More
Warm ISM in the Sgr A Complex. I: Mid-J CO, atomic carbon, ionized atomic carbon,and ionized nitrogen sub-mm/FIR line observations with the Herschel-HIFI and NANTEN2/SMART telescopesJun 14 2016We present large-scale submm observations towards the Sgr A Complex covering ~300 arcmin2. These data were obtained in the frame of the HEXGAL Program with the Herschel-HIFI satellite and are complemented with submm observations obtained with the NANTEN2/SMART ... More
Adaptive Measurements in the Optical Quantum Information LaboratoryApr 14 2009Adaptive techniques make practical many quantum measurements that would otherwise be beyond current laboratory capabilities. For example: they allow discrimination of nonorthogonal states with a probability of error equal to the Helstrom bound; they allow ... More
Entanglement-enhanced measurement of a completely unknown phaseMar 26 2010The high-precision interferometric measurement of an unknown phase is the basis for metrology in many areas of science and technology. Quantum entanglement provides an increase in sensitivity, but present techniques have only surpassed the limits of classical ... More
Stick-slip instability for viscous fingering in a gelJan 09 2002The growth dynamics of an air finger injected in a visco-elastic gel (a PVA/borax aqueous solution) is studied in a linear Hele-Shaw cell. Besides the standard Saffmann-Taylor instability, we observe - with increasing finger velocities - the existence ... More
Effect of pinning and driving force on the metastability effects in weakly pinned superconductors and the determination of spinodal line pertaining to order-disorder transitionOct 28 2005We explore the effect of varying drive on metastability features exhibited by the vortex matter in single crystals of 2H-NbSe$_2$ and CeRu$_2$ with varying degree of random pinning. An optimal balance between the pinning and driving force is needed to ... More
Gapped tunneling spectra in the normal state of Pr$_{2-x}$Ce$_x$CuO$_4$Mar 30 2001We present tunneling data in the normal state of the electron doped cuprate superconductor Pr$_{2-x}$Ce$_x$CuO$_4$ for three different values of the doping $x$. The normal state is obtained by applying a magnetic field greater than the upper critical ... More
Role of oxygen in the electron-doped superconducting cupratesFeb 06 2006We report on resistivity and Hall measurements in thin films of the electron-doped superconducting cuprate Pr$_{2-x}$Ce$_{x}$CuO$_{4\pm\delta}$. Comparisons between x = 0.17 samples subjected to either ion-irradiation or oxygenation demonstrate that changing ... More
Ultrafast dynamics in the presence of antiferromagnetic correlations in electron-doped cuprate La$_{2-x}$Ce$_x$CuO$_{4\pmδ}$Jan 25 2016Feb 09 2017We used femtosecond optical pump-probe spectroscopy to study the photoinduced change in reflectivity of thin films of the electron-doped cuprate La$_{2-x}$Ce$_x$CuO$_4$ (LCCO) with dopings of x$=$0.08 (underdoped) and x$=$0.11 (optimally doped). Above ... More
Manifestation of modulation in spatial order of flux line lattice in weakly pinned superconductors : a vibrating sample magnetometer studyMay 09 2006Aug 15 2006We have investigated the healing of transient disordered vortex states injected into a superconducting sample during the field ramping process in isothermal M-H measurements as a prescription to comprehend the modulation in the state of order of the underlying ... More
Nernst effect in the electron-doped cuprate superconductor La2-xCexCuO4Jan 25 2018We report a systematic study of the Nernst effect in films of the electron doped cuprate superconductor La2-xCexCuO4 (LCCO) as a function of temperature and magnetic field (up to 14 T) over a range of doping from underdoped (x=0.08) to overdoped (x=0.16). ... More
Effects of asymmetric contacts on single molecule conductances of HS(CH2)nCOOH in nano-electrical junctionsSep 02 2015A scanning tunnelling microscope has been used to determine the conductance of single molecular wires with the configuration X-bridge-X, X-bridge-Y and Y-bridge-Y (X = thiol terminus and Y = COOH). We find that for molecular wires with mixed functional ... More
Embedding in a finite 2-generator semigroupJan 24 2019We augment the body of existing results on embedding finite semigroups of a certain type into 2-generator finite semigroups of the same type. The approach adopted applies to finite semigroups the idempotents of which form a band and also to finite orthodox ... More
Gating of single molecule junction conductance by charge transfer complex formationJan 02 2016The solid-state structures of organic charge transfer (CT) salts are critical in determining their mode of charge transport, and hence their unusual electrical properties, which range from semiconducting through metallic to superconducting. In contrast, ... More
Orthodox semigroups and permutation matchingsDec 10 2018We determine when an orthodox semigroup S has a permutation that sends each member of S to one of its inverses and show that if such a permutation exists, it may be taken to be an involution. In the case of a finite orthodox semigroup the condition is ... More
The scattering of LyA radiation in the intergalactic medium: numerical methods and solutionsJun 28 2012Two methods are developed for solving the steady-state spherically symmetric radiative transfer equation for resonance line radiation emitted by a point source in the Intergalactic Medium. One method is based on solving the ray and moment equations using ... More
The Wouthuysen-Field effect in a clumpy intergalactic mediumNov 07 2008We show that, due to the high optical depth of the intergalactic medium to Lyman-alpha photons before the Epoch of Reionization, the Lyman-alpha scattering rate responsible for the Wouthuysen-Field effect from an isolated source will be negligible unless ... More
New Constraints on the Asteroid 298 Baptistina, the Alleged Family Member of the K/T ImpactorNov 02 2008In their study Bottke et al. (2007) suggest that a member of the Baptistina asteroid family was the probable source of the K/T impactor which ended the reign of the Dinosaurs 65 Myr ago. Knowledge of the physical and material properties pertaining to ... More
Metastable states of a flux line lattice studied by transport and Small Angle Neutron ScatteringNov 29 2004Flux Lines Lattice (FLL) states have been studied using transport measurements and Small Angle Neutron Scattering in low T$_c$ materials. In Pb-In, the bulk dislocations in the FLL do not influence the transport properties. In Fe doped NbSe$_{2}$, transport ... More
NAIVE: A Method for Representing Uncertainty and Temporal Relationships in an Automated ReasonerMar 27 2013This paper describes NAIVE, a low-level knowledge representation language and inferencing process. NAIVE has been designed for reasoning about nondeterministic dynamic systems like those found in medicine. Knowledge is represented in a graph structure ... More
Involution matchings, the semigroup of orientation-preserving and orientation-reversing mappings, and inverse covers of the full transformation semigroupNov 11 2018Feb 07 2019We continue the study of permutations of a finite regular semigroup that map each element to one of its inverses, providing a complete description in the case of semigroups whose idempotent generated subsemigroup is a union of groups. We show, in two ... More
Superabsorption of light via quantum engineeringJun 06 2013Feb 26 2014Almost 60 years ago Dicke introduced the term superradiance to describe a signature quantum effect: N atoms can collectively emit light at a rate proportional to N^2. Even for moderate N this represents a significant increase over the prediction of classical ... More
Evolution in the split-peak structure across the Peak Effect region in single crystals of $2H$-NbSe$_2$Feb 16 2006May 09 2006We have explored the presence of a two-peak feature spanning the peak effect (PE) region in the ac susceptibility data and the magnetization hysteresis measurements over a wide field-temperature regime in few weakly pinned single crystals of $2H$-NbSe$_2$, ... More
Fermi Surface reconstruction and anomalous low temperature resistivity in electron-doped La2-xCexCuO4Jun 23 2017We report ab-plane Hall Effect and magnetoresistivity measurements on La2-xCexCuO4 thin films as a function of doping for magnetic fields up to 14T and temperatures down to 1.8K. A dramatic change in the low temperature (1.8 K) normal state Hall coefficient ... More
Mixed state discrimination using optimal controlSep 08 2009Dec 04 2009We present theory and experiment for the task of discriminating two nonorthogonal states, given multiple copies. We implement several local measurement schemes, on both pure states and states mixed by depolarizing noise. We find that schemes which are ... More
How to perform the most accurate possible phase measurementsJun 30 2009Oct 15 2009We present the theory of how to achieve phase measurements with the minimum possible variance in ways that are readily implementable with current experimental techniques. Measurements whose statistics have high-frequency fringes, such as those obtained ... More
Demonstrating Heisenberg-limited unambiguous phase estimation without adaptive measurementsSep 19 2008Aug 31 2010We derive, and experimentally demonstrate, an interferometric scheme for unambiguous phase estimation with precision scaling at the Heisenberg limit that does not require adaptive measurements. That is, with no prior knowledge of the phase, we can obtain ... More
V-I characteristics in the vicinity of order-disorder transition in vortex matterJul 01 2002Jul 02 2002The shape of the V-I characteristics leading to a peak in the differential resistance r_d=dV/dI in the vicinity of the order-disorder transition in NbSe2 is investigated. r_d is large when measured by dc current. However, for a small Iac on a dc bias ... More
Why pinning by surface irregularities can explain the peak effect in transport properties and neutron diffraction results in NbSe2 and Bi-2212 crystals?Feb 28 2006The existence of a peak effect in transport properties (a maximum of the critical current as function of magnetic field) is a well-known but still intriguing feature of type II superconductors such as NbSe2 and Bi-2212. Using a model of pinning by surface ... More
Free-space quantum key distribution to a moving receiverMay 01 2015Dec 17 2015Technological realities limit terrestrial quantum key distribution (QKD) to single-link distances of a few hundred kilometers. One promising avenue for global-scale quantum communication networks is to use low-Earth-orbit satellites. Here we report the ... More
Cube Handling In Backgammon Money Games Under a Jump ModelMar 26 2012Apr 23 2012A variation on Janowski's cubeful equity model is proposed for cube handling in backgammon money games. Instead of approximating the cubeful take point as an interpolation between the dead and live cube limits, a new model is developed where the cubeless ... More
Burrows-Wheeler transformations and de Bruijn wordsJan 24 2019We formulate and explain the extended Burrows-Wheeler transform of Mantaci et al from the viewpoint of permutations on a chain taken as a union of partial order-preserving mappings. In so doing we establish a link with syntactic semigroups of languages ... More
Permutations of a semigroup that map to inversesJan 16 2019We investigate the question as to when the members of a finite regular semigroup may be permuted in such a way that each member is mapped to one of its inverses. In general this is not possible. However we reformulate the problem in terms of a related ... More
Structure of the flux lines lattice in NbSe2: Equilibrium state and influence of the magnetic historyApr 16 2009We have performed small-angle neutron scattering (SANS) of the flux line lattice (FLL) in a Fe doped NbSe_2 sample which presents a large peak effect in the critical current. The scattered intensity and the width of the Bragg peaks of the equilibrium ... More
Quantum oscillations from the reconstructed Fermi surface in electron-doped cuprate superconductorsApr 17 2018We have studied the electronic structure of electron-doped cuprate superconductors via measurements of high-field Shubnikov-de Haas oscillations in thin films. In optimally doped Pr$_{2-x}$Ce$_{x}$CuO$_{4\pm\delta}$ and La$_{2-x}$Ce$_{x}$CuO$_{4\pm\delta}$, ... More
Genuine time-bin-encoded quantum key distribution over a turbulent depolarizing free-space channelMar 16 2019Networks of quantum information processors, a Quantum Internet, demand the reliable transmission of quantum bits between nodes via optical-fiber or free-space channels. Encoding quantum information in photonic time-bins is often preferred for realizing ... More
Nature of Phase Transitions of Superconducting Wire Networks in a Magnetic FieldDec 06 1995We study $I$-$V$ characteristics of periodic square Nb wire networks as a function of temperature in a transverse magnetic field, with a focus on three fillings 2/5, 1/2, and 0.618 that represent very different levels of incommensurability. For all three ... More
ALMA and GMRT constraints on the off-axis gamma-ray burst 170817A from the binary neutron star merger GW170817Oct 16 2017Nov 03 2017Binary neutron-star mergers (BNSMs) are among the most readily detectable gravitational-wave (GW) sources with LIGO. They are also thought to produce short $\gamma$-ray bursts (SGRBs), and kilonovae that are powered by r-process nuclei. Detecting these ... More
Single crystal investigation of proposed type-II Weyl semimetal CeAlGeAug 13 2018We present details of materials synthesis, crystal structure, and anisotropic magnetic properties of single crystals of CeAlGe, a proposed type-II Weyl semimetal. Single-crystal x-ray diffraction confirms that CeAlGe forms in noncentrosymmetric I4$_1$md ... More
Algebras defined by equationsOct 30 2018Apr 15 2019We show that a class of algebras is closed under the taking of homomorphic images and direct products if and only if the class consists of all algebras that satisfy a set of (generally simultaneous) equations. For classes of regular semigroups in particular ... More
Gateway state-mediated, long-range tunnelling in molecular wiresDec 18 2017If the factors controlling the decay in single-molecule electrical conductance G with molecular length L could be understood and controlled, then this would be a significant step forward in the design of high-conductance molecular wires. For a wide variety ... More
Algebras defined by equationsOct 30 2018We show that a class of algebras is closed under the taking of homomorphic images and direct products if and only if the class consists of all algebras that satisfy a set of (generally simultaneous) equations. For classes of regular semigroups in particular ... More
Ag colloids and arrays for plasmonic non-radiative energy transfer from quantum dots to a quantum wellSep 12 2016Ag nanoparticles in the form of colloids and ordered arrays are used to demonstrate plasmon-mediated non-radiative energy transfer from quantum dots to quantum wells with varying top barrier thicknesses. Plasmon-mediated energy transfer efficiencies of ... More
Influence of Plasmonic Array Geometry on Energy Transfer from a Quantum Well to a Quantum Dot LayerSep 14 2016A range of seven different Ag plasmonic arrays formed using nanostructures of varying shape, size and gap were fabricated using helium-ion lithography (HIL) on an InGaN/GaN quantum well (QW) substrate. The influence of the array geometry on plasmon-enhanced ... More
Stable and Metastable vortex states and the first order transition across the peak effect region in weakly pinned 2H-NbSe_2Jul 27 2000The peak effect in weakly pinned superconductors is accompanied by metastable vortex states. Each metastable vortex configuration is characterized by a different critical current density J_c, which mainly depends on the past thermomagnetic history of ... More
Domain Wall Conductivity in Oxygen Deficient Multiferroic YMnO3 Single CrystalsJan 05 2012The transport properties of domain walls in oxygen deficient multiferroic YMnO3 single crystals have been probed using conductive atomic force microscopy and piezoresponse force microscopy. Domain walls exhibit significantly enhanced conductance after ... More
Dynamic instabilities and memory effects in vortex matterDec 09 1999Recent studies have shown a number of surprising vortex dynamics phenomena both in low and high temperature superconductors, which include: low frequency noise, slow voltage oscillations, history dependent dynamic response, memory of the direction, amplitude, ... More
Co-occurrence of Superparamagnetism and Anomalous Hall Effect in Highly Reduced Cobalt Doped Rutile TiO2 FilmsMar 01 2004We report a detailed magnetic and structural analysis of highly reduced Co doped rutile TiO2 films displaying an anomalous Hall effect (AHE). The temperature and field dependence of magnetization, and transmission electron microscopy clearly establish ... More
Galacticus: A Semi-Analytic Model of Galaxy FormationAug 10 2010We describe a new, free and open source semi-analytic model of galaxy formation, Galacticus. The Galacticus model was designed to be highly modular to facilitate expansion and the exploration of alternative descriptions of key physical ingredients. We ... More
Power Spectrum Estimation II. Linear Maximum LikelihoodMar 29 2005This second paper of two companion papers on the estimation of power spectra specializes to the topic of estimating galaxy power spectra at large, linear scales using maximum likelihood methods. As in the first paper, the aims are pedagogical, and the ... More
Galaxy Morphology in the GTO-NICMOS Northern Hubble Deep FieldJul 14 1999The increased incidence of morphologically peculiar galaxies at faint magnitudes in the optical could be attributable either to "morphological k-corrections" (the change in appearance when viewing high-z objects at shorter rest-frame wavelengths), or ... More
Interferometric computation beyond quantum theoryOct 14 2016Mar 15 2018There are quantum solutions for computational problems that make use of interference at some stage in the algorithm. These stages can be mapped into the physical setting of a single particle travelling through a many-armed interferometer. There has been ... More
Parallel Dither and Dropout for Regularising Deep Neural NetworksAug 28 2015Effective regularisation during training can mean the difference between success and failure for deep neural networks. Recently, dither has been suggested as alternative to dropout for regularisation during batch-averaged stochastic gradient descent (SGD). ... More
Deep Transform: Error Correction via Probabilistic Re-SynthesisFeb 16 2015Errors in data are usually unwelcome and so some means to correct them is useful. However, it is difficult to define, detect or correct errors in an unsupervised way. Here, we train a deep neural network to re-synthesize its inputs at its output layer ... More
Uniform Learning in a Deep Neural Network via "Oddball" Stochastic Gradient DescentOct 08 2015When training deep neural networks, it is typically assumed that the training examples are uniformly difficult to learn. Or, to restate, it is assumed that the training error will be uniformly distributed across the training examples. Based on these assumptions, ... More
"Oddball SGD": Novelty Driven Stochastic Gradient Descent for Training Deep Neural NetworksSep 18 2015Stochastic Gradient Descent (SGD) is arguably the most popular of the machine learning methods applied to training deep neural networks (DNN) today. It has recently been demonstrated that SGD can be statistically biased so that certain elements of the ... More
Parity, eulerian subgraphs and the Tutte polynomialJul 16 2007Sep 20 2007Identities obtained by elementary finite Fourier analysis are used to derive a variety of evaluations of the Tutte polynomial of a graph G at certain points (a,b) where (a-1)(b-1) equals 2 or 4. These evaluations are expressed in terms of eulerian subgraphs ... More