Results for "C. M. Wood"

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Bending and stretching unit vector fields in Euclidean and hyperbolic 3-spaceDec 11 2006Dec 31 2007New examples of harmonic unit vector fields on hyperbolic 3-space are constructed by exploiting the reduction of symmetry arising from the foliation by horospheres. This is compared and contrasted with the analogous construction in Euclidean 3-space, ... More
Higher-power harmonic maps and sectionsFeb 08 2019The variational theory of higher-power energy is developed for mappings between Riemannian manifolds, and more generally sections of submersions of Riemannian manifolds, and applied to sections of Riemannian vector bundles and their sphere subbundles. ... More
Experimental Issues for Precision Electroweak Physics at a High-Luminosity Z FactoryDec 21 2000We discuss the ultimate precision for ALR, and therefore for the weak mixing angle, at a high-luminosity Linear Collider. Drawing on our experience at the SLC, and considering various machine parameter sets for the NLC and for TESLA, it emerges that a ... More
Higher-power harmonic maps and sectionsFeb 08 2019Mar 15 2019The variational theory of higher-power energy is developed for mappings between Riemannian manifolds, and more generally sections of submersions of Riemannian manifolds, and applied to sections of Riemannian vector bundles and their sphere subbundles. ... More
Soft Gamma Repeaters and Anomalous X-ray Pulsars: Magnetar CandidatesJun 04 2004Nov 04 2004This article is a review of Soft Gamma Repeaters and Anomalous X-ray Pulsars. It contains a brief historical record of the emergence of these classes of neutron stars, a thorough overview of the observational data, a succinct summary of the magnetar model, ... More
Harmonic vector fields on pseudo-Riemannian manifoldsJan 07 2015The theory of harmonic vector fields on Riemannian manifolds is generalised to pseudo-Riemannian manifolds. Harmonic conformal gradient fields on pseudo-Euclidean hyperquadrics are classified up to congruence, as are harmonic Killing fields on pseudo-Riemannian ... More
Harmonic sections of Riemannian vector bundles, and metrics of Cheeger-Gromoll typeFeb 02 2006We study harmonic sections of a Riemannian vector bundle whose total space is equipped with a 2-parameter family of metrics which includes both the Sasaki and Cheeger-Gromoll metrics. This enables the theory of harmonic unit sections to be extended to ... More
Harmonic maps and sections on spheresMar 02 2007The absence of interesting harmonic sections for the Sasaki and Cheeger-Gromoll metrics has led to the consideration of alternatives, for example in the form of a two-parameter family of natural metrics shown to relax existence conditions for harmonicity. ... More
The geometry of generalised Cheeger-Gromoll metricsMar 02 2007Feb 06 2009We study the geometry of the tangent bundle equipped with a two-parameter family of Riemannian metrics. After deriving the expression of the Levi-Civita connection, we compute the Riemann curvature tensor and the sectional, Ricci and scalar curvatures. ... More
Harmonic vector fields on pseudo-Riemannian manifoldsJan 07 2015Oct 28 2016The theory of harmonic vector fields on Riemannian manifolds is generalised to pseudo-Riemannian manifolds. Harmonic conformal gradient fields on pseudo-Euclidean hyperquadrics are classified up to congruence, as are harmonic Killing fields on pseudo-Riemannian ... More
Harmonic Vector Fields on Space FormsJan 25 2013A vector field s on a Riemannian manifold M is said to be harmonic if there exists a member of a 2-parameter family of generalised Cheeger-Gromoll metrics on TM with respect to which s is a harmonic section. If M is a simply-connected non-flat space form ... More
A Novel Potential Field Controller for Use on Aerial RobotsApr 15 2017Unmanned Aerial Vehicles (UAV), commonly known as drones, have many potential uses in real world applications. Drones require advanced planning and navigation algorithms to enable them to safely move through and interact with the world around them. This ... More
Design of Experiments for ScreeningOct 18 2015The aim of this paper is to review methods of designing screening experiments, ranging from designs originally developed for physical experiments to those especially tailored to experiments on numerical models. The strengths and weaknesses of the various ... More
Harmonic contact metric structures, and submersionsAug 31 2007We study harmonic almost contact structures in the context of contact metric manifolds, and an analysis is carried out when such a manifold fibres over an almost Hermitian manifold, as exemplified by the Boothby-Wang fibration. Two types of almost contact ... More
Harmonic morphisms from three-dimensional Euclidean and spherical space formsDec 18 1996P. Baird and the second author studied harmonic morphisms from a three-dimensional simply-connected space form to a surface and obtained a complete local and global classification of them. In this paper, we obtain a description of all harmonic morphisms ... More
Harmonic almost contact structuresFeb 23 2006An almost contact metric structure is parametrized by a section of an associated homogeneous fibre bundle, and conditions for this to be a harmonic section, and a harmonic map, are studied. These involve the characteristic vector field, and the almost ... More
Compton Polarimetry at a TEV ColliderFeb 06 1998An electron beam polarization of 80% or greater will be a key feature of a 1 TeV Linear Collider. Accurate measurements of the beam polarization will therefore be needed. We discuss design considerations and capabilities for a Compton-scattering polarimeter ... More
Polarimetry at a Future Linear Collider - How Precise?Apr 03 2000Apr 04 2000At a future linear collider, a polarized electron beam will play an important role in interpreting new physics signals. Backgrounds to a new physics reaction can be reduced by choice of the electron polarization state. The origin of a new physics reaction ... More
Electroweak Results from the SLD ExperimentMay 10 1999We present an overview of the electroweak physics program of the SLD experiment at the Stanford Linear Accelerator Center (SLAC). A data sample of 550K Z0 decays has been collected. This experiment utilizes a highly polarized electron beam, a small interaction ... More
The polarized electron beam for the SLAC Linear ColliderNov 09 1996The SLAC Linear Collider has been colliding a polarized electron beam with an unpolarized positron beam at the Z^0 resonance for the SLD experiment since 1992. An electron beam polarization of close to 80% has been achieved for the experiment at luminosities ... More
Bayesian Inference Applied to the Electromagnetic Inverse ProblemJun 16 1998We present a new approach to the electromagnetic inverse problem that explicitly addresses the ambiguity associated with its ill-posed character. Rather than calculating a single ``best'' solution according to some criterion, our approach produces a large ... More
Model selection via Bayesian information capacity designs for generalised linear modelsJan 29 2016Aug 14 2016We provide the first investigation of designs for screening experiments where the response variable is approximated by a generalised linear model. We define the Bayesian information capacity criterion for the selection of designs that are robust to the ... More
Model selection via Bayesian information capacity designs for generalised linear modelsJan 29 2016Oct 26 2016The first investigation is made of designs for screening experiments where the response variable is approximated by a generalised linear model. A Bayesian information capacity criterion is defined for the selection of designs that are robust to the form ... More
The energy of unit vector fields on the 3-sphereMay 31 2000The stability of the 3-dimensional Hopf vector field, as a harmonic section of the unit tangent bundle, is viewed from a number of different angles. The spectrum of the vertical Jacobi operator is computed, and compared with that of the Jacobi operator ... More
Ellipsoidal Variability and the Difference between Sequence D and E Red GiantsFeb 19 2010We have studied a sample of Large Magellanic Cloud red giant binaries that lie on sequence E in the period--luminosity plane. We show that their combined light and velocity curves unambiguously demonstrate that they are binaries showing ellipsoidal variability. ... More
SPH Simulations of Negative (Nodal) Superhumps: A Parametric StudyJun 15 2009Negative superhumps in cataclysmic variable systems result when the accretion disc is tilted with respect to the orbital plane. The line of nodes of the tilted disc precesses slowly in the retrograde direction, resulting in a photometric signal with a ... More
Smoothed Particle Hydrodynamics Simulations of Apsidal and Nodal SuperhumpsApr 12 2000In recent years a handful of systems have been observed to show "negative" (nodal) superhumps, with periods slightly shorter than the orbital period. It has been suggested that these modes are a consequence of the slow retrograde precession of the line ... More
Jacobi fields along harmonic mapsApr 11 2001We show that Jacobi fields along harmonic maps between suitable spaces preserve conformality, holomorphicity, real isotropy and complex isotropy to first order; this last being one of the key tools in the proof by Lemaire and the author of integrability ... More
Physical Mechanisms for the Variable Spin-down of SGR 1900+14Aug 08 1999We consider the physical implications of the rapid spindown of Soft Gamma Repeater 1900+14, and of the apparent "braking glitch", \Delta P/P = l x 10^-4, that was concurrent with the Aug. 27th giant flare. A radiation-hydrodynamical outflow associated ... More
Comments on "A gravitational shielding based upon ZnS:Ag phosphor" and "The gravitational mass at the superconducting state"Apr 11 2002This is a discussion of two recent papers by De Aquino [physics/0112081 (2001) and physics/0201058 (2002)] that put forward an explanation of observations of gravity shielding originally reported by Podkletnov and Nieminen [Physica C 203 441 (1992)].
The Dynamic Behavior of Soft Gamma RepeatersApr 21 2003Soft Gamma Repeaters (SGRs) undergo changes in their pulse properties and persistent emission during episodes of intense burst activity. Both SGR 1900+14 and SGR 1806-20 have shown significant changes in their spin-down rates during the last several years, ... More
Carbon isotope measurements in the Solar SystemJan 28 2009Feb 02 2010I make publicly available my literature study into carbon isotope ratios in the Solar System, which formed a part of Woods & Willacy (2009). As far as I know, I have included here all measurements of 12C/13C in Solar System objects (excluding those of ... More
The Effects of Burst Activity on Soft Gamma Repeater Pulse Properties and Persistent EmissionApr 22 2002Soft Gamma Repeaters (SGRs) undergo changes in their pulse properties and persistent emission during episodes of intense burst activity. SGR 1900+14 has undergone large flux increases following recent burst activity. Both SGR 1900+14 and SGR 1806-20 have ... More
Computing the period of an Ehrhart quasi-polynomialNov 09 2004If P is a rational polytope in R^d, then $i_P(t):=#(tP\cap Z^d)$ is a quasi-polynomial in t, called the Ehrhart quasi-polynomial of P. A period of i_P(t) is D(P), the smallest positive integer D such that D*P has integral vertices. Often, D(P) is the ... More
Luminosity, Energy and Polarization Studies for the Linear Collider: Comparing e+e- and e-e- for NLC and TESLAMar 04 2004We present results from luminosity, energy and polarization studies at a future Linear Collider. We compare e+e- and e-e- modes of operation and consider both NLC and TESLA beam parameter specifications at a center-of-mass energy of 500 GeV. Realistic ... More
Search for Gamma-ray Emission from Galactic Novae with the Fermi-LATOct 12 2017Context. A number of novae have been found to emit high-energy gamma rays (>100 MeV). However, the origin of this emission is not yet understood. We report on the search for gamma-ray emission from 75 optically-detected Galactic novae in the first 7.4 ... More
Characterizing the Population of Bright Infrared Sources in the Small Magellanic CloudDec 14 2016We used Spitzer's Infrared Spectrograph (IRS) to observe stars in the Small Magellanic Cloud (SMC) selected from the Midcourse Space Experiment (MSX) Point Source Catalog. We concentrate on the dust properties of oxygen-rich evolved stars, which show ... More
Normal galaxies in the XMM-Newton fields. X-rays as a star formation indicatorMay 28 2009Jun 01 2009Context: We use the first XMM serendipitous source catalogue (1XMM) to compile a sample of normal X-ray galaxies Aims: We seek to expand the database of X-ray selected normal galaxies at intermediate redshifts and examine the relation between X-ray emission ... More
Efficient Z-Gates for Quantum ComputingDec 02 2016Jun 28 2017For superconducting qubits, microwave pulses drive rotations around the Bloch sphere. The phase of these drives can be used to generate zero-duration arbitrary "virtual" Z-gates which, combined with two $X_{\pi/2}$ gates, can generate any SU(2) gate. ... More
Efficient Z-Gates for Quantum ComputingDec 02 2016For superconducting qubits, microwave pulses drive rotations around the Bloch sphere. Here we show that the phase of these drives can be used to generate zero-duration arbitrary Z-gates which, combined with two $X_{\pi/2}$ gates, can generate any SU(2) ... More
Further Developments in Gold-stud Bump BondingDec 05 2011As silicon detectors in high energy physics experiments require increasingly complex assembly procedures, the availability of a wide variety of interconnect technologies provides more options for overcoming obstacles in generic R&D. Gold ball bonding ... More
Absorption of the $ω$ and $φ$ Mesons in NucleiJun 17 2010Due to their long lifetimes, the $\omega$ and $\phi$ mesons are the ideal candidates for the study of possible modifications of the in-medium meson-nucleon interaction through their absorption inside the nucleus. During the E01-112 experiment at the Thomas ... More
New constructions of twistor lifts for harmonic mapsJun 09 2011Nov 23 2013We show that given a harmonic map $\varphi$ from a Riemann surface to a classical compact simply connected inner symmetric space, there is a $J_2$-holomorphic twistor lift of $\varphi$ (or its negative) if and only if it is nilconformal. In the case of ... More
Harmonic maps into the exceptional symmetric space $G_2/SO(4)$Mar 28 2013Oct 22 2014We show that a harmonic map from a Riemann surface into the exceptional symmetric space $G_2/{\mathrm SO}(4)$ has a $J_2$-holomorphic twistor lift into one of the three flag manifolds of $G_2$ if and only if it is `nilconformal', i.e., has nilpotent derivative. ... More
Harmonic morphisms and bicomplex manifoldsOct 06 2009Mar 11 2010We use functions of a bicomplex variable to unify the existing constructions of harmonic morphisms from a 3-dimensional Euclidean or pseudo-Euclidean space to a Riemannian or Lorentzian surface. This is done by using the notion of complex-harmonic morphism ... More
Filtrations, factorizations and explicit formulae for harmonic mapsSep 30 2009Aug 11 2010We use filtrations of the Grassmannian model to produce explicit algebraic formulae for all harmonic maps of finite uniton number from a Riemann surface, and so all harmonic maps from the 2-sphere, to the unitary group for a general class of factorizations ... More
Twistorial harmonic morphisms with one-dimensional fibres on self-dual four-manifoldsMay 07 2003Apr 08 2005We introduce a general notion of twistorial map and classify twistorial harmonic morphisms with one-dimensional fibres from self-dual four-manifolds. Such maps can be characterised as those which pull back Abelian monopoles to self-dual connections. In ... More
Dynamics and Thermodynamics of a Novel Phase of NaAlH4Oct 15 2009We characterize a novel orthorhombic phase (gamma) of NaAlH4, discovered using first-principles molecular dynamics, and discuss its relevance to the dehydrogenation mechanism. This phase is close in energy to the known low-temperature structure and becomes ... More
Harmonic morphisms between almost Hermitian manifoldsDec 18 1995We obtain conditions on the Lee form under which a holomorphic map between almost Hermitian manifolds is a harmonic map or morphism. Then we discuss under what conditions (i) the image of a holomorphic map from a cosymplectic manifold is also cosymplectic, ... More
Harmonic morphisms, conformal foliations and shear-free ray congruencesMar 13 1996Equivalences between conformal foliations on Euclidean $3$-space, Hermitian structures on Euclidean $4$-space, shear-free ray congruences on Minkowski $4$-space, and holomorphic foliations on complex $4$-space are explained geometrically and twistorially; ... More
Hermitian structures and harmonic morphisms in higher dimensional Euclidean spacesOct 13 1994Oct 17 1994We construct new complex-valued harmonic morphisms from Euclidean spaces from functions which are holomorphic with respect to Hermitian structures. In particular, we give the first global examples of complex-valued harmonic morphisms from ${\bf R}^n$ ... More
Harmonic morphisms with one-dimensional fibres on Einstein manifoldsJun 13 2001We prove that, from an Einstein manifold of dimension greater than or equal to five, there are just two types of harmonic morphism with one-dimensional fibres. This generalizes a result of R.L. Bryant who obtained the same conclusion under the assumption ... More
Jacobi fields along harmonic 2-spheres in ${\bf C}P^2$ are integrableApr 24 2001Dec 17 2001We show that any Jacobi field along a harmonic map from the 2-sphere to the complex projective plane is integrable (i.e., is tangent to a smooth variation through harmonic maps). This provides one of the few known answers to this problem of integrability, ... More
Topological restrictions for circle actions and harmonic morphismsJul 24 2000Oct 19 2000Let $M^m$ be a compact oriented smooth manifold which admits a smooth circle action with isolated fixed points which are isolated as singularities as well. Then all the Pontryagin numbers of $M^m$ are zero and its Euler number is nonnegative and even. ... More
Hydrogen Dynamics in Superprotonic CsHSO4Feb 25 2007We present a detailed study of proton dynamics in the hydrogen-bonded superprotonic conductor CsHSO4 from first-principles molecular dynamics simulations, isolating the subtle interplay between the dynamics of the O--H chemical bonds, the O...H hydrogen ... More
Dynamical Structure, Bonding, and Thermodynamics of the Superionic Sublattice in alpha-AgIMar 24 2006Using extensive first-principles molecular dynamics calculations, we characterize the superionic phase transition and the lattice and electronic structures of the archetypal Type-I superionic conductor alpha-AgI. We find that superionicity is signalled ... More
Jacobi fields along harmonic 2-spheres in $S^3$ and $S^4$ are not all integrableSep 10 2007Dec 20 2007In a previous paper, we showed that any Jacobi field along a harmonic map from the 2-sphere to the complex projective plane is integrable (i.e., is tangent to a smooth variation through harmonic maps). In this paper, in contrast, we show that there are ... More
Harmonic morphisms and shear-free ray congruencesJun 27 2003We describe the relationship between complex-valued harmonic morphisms from Minkowski 4-space} and the shear-free ray congruences of mathematical physics. Then we show how a horizontally conformal submersion on a domain of Euclidean 3-space gives the ... More
A new construction of Einstein self-dual metricsSep 24 2001We give a new construction of Ricci-flat self-dual metrics which is a natural extension of the Gibbons--Hawking ansatz. We also give characterisations of both these constructions, and explain how they come from harmonic morphisms.
Harmonic morphisms and the Jacobi operatorNov 01 1999We prove that harmonic morphisms preserve the Jacobi operator along harmonic maps. We apply this result to prove infinitesimal and local rigidity (in the sense of Toth) of harmonic morphisms to a sphere.
Weierstrass representations for harmonic morphisms on Euclidean spaces and spheresDec 20 1995May 24 1996We construct large families of harmonic morphisms which are holomorphic with respect to Hermitian structures by finding heierarchies of Weierstrass-type representations. This enables us to find new examples of complex-valued harmonic morphisms from Euclidean ... More
On the space of harmonic $2$-spheres in ${\bf C}P^2$Oct 06 1995Mar 12 1996Carrying further work of T.A. Crawford, we show that each component of the space of harmonic maps from the $2$-sphere to complex projective $2$-space of degree $d$ and energy $4 \pi E$ is a smooth closed submanifold of the space of all $C^j$ maps $(j ... More
Bayesian design of experiments for generalised linear models and dimensional analysis with industrial and scientific applicationJun 19 2016Sep 02 2016The design of an experiment can be always be considered at least implicitly Bayesian, with prior knowledge used informally to aid decisions such as the variables to be studied and the choice of a plausible relationship between the explanatory variables ... More
Long Secondary Periods in Variable Red GiantsJul 17 2009We present a study of a sample of LMC red giants exhibiting Long Secondary Periods (LSPs). We use radial velocities obtained from VLT spectral observations and MACHO and OGLE light curves to examine properties of the stars and to evaluate models for the ... More
Complex patterns of spontaneous initiations and terminations of reentrant circulation in a loop of cardiac tissueMar 18 2008May 06 2008A two-component model is developed that consists of a discrete loop of cardiac cells that circulates action potentials together with a cardiac pacing mechanism. Physiological properties of cells such as restitutions of refractoriness and of conduction ... More
Improved V II log($gf$) Values, Hyperfine Structure Constants, and Abundance Determinations in the Photospheres of the Sun and Metal-poor Star HD 84937Aug 18 2014New experimental absolute atomic transition probabilities are reported for 203 lines of V II. Branching fractions are measured from spectra recorded using a Fourier transform spectrometer and an echelle spectrometer. The branching fractions are normalized ... More
Temporal and Spectral Characteristics of Short Bursts from the Soft Gamma Repeaters 1806-20 and 1900+14May 07 2001We study the temporal and coarse spectral properties of 268 bursts from SGR 1806-20 and 679 bursts from SGR 1900+14, all observed with the Rossi X-Ray Timing Explorer/Proportional Counter Array. Hardness ratios and temporal parameters, such as T_90 durations ... More
Abundances in intermediate-mass AGB stars undergoing third dredge-up and hot-bottom burningApr 15 2007High dispersion near-infrared spectra have been taken of seven highly-evolved, variable, intermediate-mass (4-6 Msun) AGB stars in the LMC and SMC in order to look for C, N and O variations that are expected to arise from third dredge-up and hot-bottom ... More
Properties of post-AGB stars with IRAS colors typical of planetary nebulaeOct 26 2000We have investigated the infrared properties of a sample of objects with IRAS colors typical of planetary nebulae. The selected objects have not yet evolved to the planetary nebula stage since they have no detectable radio continuum emission and they ... More
Properties of Fr-like Th3+ from spectroscopy of high-L Rydberg levels of Th2+Apr 22 2011Binding energies of high-L Rydberg states (L^3 7) of Th2+ with n=27-29 were studied using the Resonant Excitation Stark Ionization Spectroscopy (RESIS) method. The core of the Th2+ Rydberg ion is the Fr-like ion Th3+ whose ground state is a 5 2F5/2 level. ... More
Improved Ni I log(gf) Values and Abundance Determinations in the Photospheres of the Sun and Metal-poor Star HD 84937Feb 18 2014Atomic transition probability measurements for 371 Ni I lines in the UV through near IR are reported. Branching fractions from data recorded using a Fourier transform spectrometer and a new echelle spectrograph are combined with published radiative lifetimes ... More
Improved Ti II log(gf) Values and Abundance Determinations in the Photospheres of the Metal-Poor Star HD 84937Sep 05 2013Atomic transition probability measurements for 364 lines of Ti II in the UV through near IR are reported. Branching fractions from data recorded using a Fourier transform spectrometer and a new echelle spectrometer are combined with published radiative ... More
Near-infrared and Br_gamma observations of post-AGB starsAug 01 2000We investigate the infrared properties of the IRAS sources not confirmed as PNe in Van de Steene & Pottasch (1993). We observed 28 objects in the N-band of which 20 were detected and 5 were resolved. We obtained medium resolution Br_gamma spectra and ... More
Cartesian Bicategories IIAug 14 2007The notion of cartesian bicategory, introduced by Carboni and Walters for locally ordered bicategories, is extended to general bicategories. It is shown that a cartesian bicategory is a symmetric monoidal bicategory.
H alpha emission line profiles of selected post-AGB starsOct 01 1999Dec 16 1999We present H alpha emission line spectra of 7 post-AGB stars. Typically, they have a P-Cygni type profile with a very strong emission component and a relatively narrow absorption component. These lines are formed in the fast post-AGB wind which in most ... More
The shocking transit of WASP-12b: Modelling the observed early ingress in the near ultravioletJun 15 2011Near ultraviolet observations of WASP-12b have revealed an early ingress compared to the optical transit lightcurve. This has been interpreted as due to the presence of a magnetospheric bow shock which forms when the relative velocity of the planetary ... More
Bayesian design of experiments for generalised linear models and dimensional analysis with industrial and scientific applicationJun 19 2016Oct 26 2016The design of an experiment can be always be considered at least implicitly Bayesian, with prior knowledge used informally to aid decisions such as the variables to be studied and the choice of a plausible relationship between the explanatory variables ... More
Preserving the 7x7 surface reconstruction of clean Si(111) by graphene adsorptionAug 10 2015We employ room-temperature ultrahigh vacuum scanning tunneling microscopy (UHV STM) and {\em ab-initio} calculations to study graphene flakes that were adsorbed onto the Si(111)$-$7$\times$7 surface. The characteristic 7$\times$7 reconstruction of this ... More
Casimir Forces and Graphene SheetsJul 07 2010The Casimir force between two infinitely thin parallel sheets in a setting of $N$ such sheets is found. The finite two-dimensional conductivities, which describe the dispersive and absorptive properties of each sheet, are taken into account, whereupon ... More
Medium-energy ion-scattering study of strained holmium silicide nanoislands grown on silicon (100)Jul 29 2008We have used medium-energy ion scattering (MEIS) to quantitatively analyze the structure of holmium silicide islands grown on the Si(100) surface. Structure fitting to the experimental data unambiguously shows that the tetragonal silicide phase is present ... More
Benzene formation in the inner regions of protostellar disksDec 08 2006Benzene (c-C6H6) formation in the inner 3 AU of a protostellar disk can be efficient, resulting in high abundances of benzene in the midplane region. The formation mechanism is different to that found in interstellar clouds and in protoplanetary nebulae, ... More
Emission line diagnostics to constrain high temperature populations in early-type galaxiesNov 07 2013Jan 12 2014Once thought to be devoid of warm and cold interstellar matter, elliptical galaxies are now commonly observed to host extended regions of neutral and ionized gas. Outside of the innermost nuclear regions of these galaxies, the favoured candidate ionizing ... More
Carbon isotope fractionation in protoplanetary disksDec 01 2008We investigate the gas-phase and grain-surface chemistry in the inner 30 AU of a typical protoplanetary disk using a new model which calculates the gas temperature by solving the gas heating and cooling balance and which has an improved treatment of the ... More
Where are all of the nebulae ionized by supersoft X-ray sources?Oct 20 2015Accreting, steadily nuclear-burning white dwarfs are associated with so-called close-binary supersoft X-ray sources (SSSs), observed to have temperatures of a few$\times 10^{5}$K and luminosities on the order of $10^{38}$erg/s. These and other types of ... More
Long-term X-ray changes in the emission from the anomalous X-ray pulsar 4U 0142+61Aug 21 2007Aug 21 2007We present results obtained from X-ray observations of the anomalous X-ray pulsar (AXP) 4U 0142+61 taken between 2000-2007 using XMM-Newton, Chandra and Swift. In observations taken before 2006, the pulse profile is observed to become more sinusoidal ... More
Long and faint GRBs in archival BeppoSAX-WFC dataMay 20 2003In an ongoing effort to search for X-ray transients on diverse time scales in the data archive of the BeppoSAX Wide Field Cameras we have identified four GRBs that are long (between 540 and at least 2550 s) and faint (with 3 events having peak fluxes ... More
Designs for Generalized Linear ModelsOct 18 2015This paper reviews the design of experiments for generalised linear models, including optimal design, Bayesian design and designs for models with random effects.
Gamma-ray flare activity from PSR B1259-63 during 2014 periastron passage and comparison to its 2010 passageSep 09 2015PSR B1259-63/LS 2883 is a gamma-ray binary system containing a radio pulsar in a highly elliptical ~3.4-year orbit around a Be star. In its 2010 periastron passage, multiwavelength emission from radio to TeV was observed, as well as an unexpected GeV ... More
Light Vector Mesons in the Nuclear MediumMar 04 2008The light vector mesons ($\rho$, $\omega$, and $\phi$) were produced in deuterium, carbon, titanium, and iron targets in a search for possible in-medium modifications to the properties of the $\rho$ meson at normal nuclear densities and zero temperature. ... More
Search for medium modification of the $ρ$ mesonJul 16 2007Jul 23 2007The photoproduction of vector mesons on various nuclei has been studied using the CEBAF Large Acceptance Spectrometer (CLAS) at Jefferson Laboratory. The vector mesons, $\rho$, $\omega$, and $\phi$, are observed via their decay to $e^+e^-$, in order to ... More
Laser-driven plasma acceleration in a regime of strong-mismatch between the incident laser envelope and the nonlinear plasma responseApr 10 2017We explore a regime of laser-driven plasma acceleration of electrons where the radial envelope of the laser-pulse incident at the plasma entrance is strongly mismatched to the nonlinear plasma electron response excited by it. This regime has been experimentally ... More
A Luminous and Highly-variable Gamma-ray Flare Following the 2017 Periastron of PSR B1259-63/LS 2883May 09 2018Jul 12 2018Three periastron passages of the PSR B1259$-$63/LS 2883 binary system, consisting of a 48 ms rotation-powered pulsar and a $\sim30$ M$_{\odot}$ Be star, have been observed by the Large Area Telescope (LAT) on board the Fermi Gamma-ray Space Telescope, ... More
The Three-Nucleon System Near the N-d ThresholdJun 27 1997The three-nucleon system is studied at energies a few hundred keV above the N-d threshold. Measurements of the tensor analyzing powers $T_{20}$ and $T_{21}$ for p-d elastic scattering at $E_{c.m.}=432$ keV are presented together with the corresponding ... More
Discovery of a Metal-poor, Luminous Post-AGB Star that Failed the Third Dredge-upOct 12 2017Post-asymptotic giant branch (post-AGB) stars are known to be chemically diverse. In this paper we present the first observational evidence of a star that has failed the third dredge-up (TDU). J005252.87-722842.9 is a A-type ($T_{\rm eff}$ = 8250 $\pm$ ... More
Mid-infrared spectroscopy of carbon stars in the Small Magellanic CloudMar 22 2006We have observed a sample of 36 objects in the Small Magellanic Cloud (SMC) with the Infrared Spectrometer on the Spitzer Space Telescope. Nineteen of these sources are carbon stars. An examination of the near- and mid-infrared photometry shows that the ... More
On the Extended Emission Around the Anomalous X-ray Pulsar 1E 1547.0-5408Jul 14 2011Nov 14 2011We present an analysis of the extended emission around the anomalous X-ray pulsar 1E 1547.0-5408 using four XMM-Newton observations taken with the source in varying states of outburst as well as in quiescence. We find that the extended emission flux is ... More
Modeling spatiotemporal noise covariance for MEG/EEG source analysisMar 08 2005Mar 20 2006We propose a new model for approximating spatiotemporal noise covariance for use in MEG/EEG source analysis. Our model is an extension of an existing model [1,2] that uses a single Kronecker product of a pair of matrices - temporal and spatial covariance; ... More
X-ray Bursts from the Transient Magnetar Candidate XTE J1810-197May 02 2005We have discovered four X-ray bursts, recorded with the Rossi X-ray Timing Explorer Proportional Counter Array between 2003 September and 2004 April, that we show to originate from the transient magnetar candidate XTE J1810-197. The burst morphologies ... More
Emulation of multivariate simulators using thin-plate splines with application to atmospheric dispersionDec 23 2015Aug 23 2016It is often desirable to build a statistical emulator of a complex computer simulator in order to perform analysis which would otherwise be computationally infeasible. We propose methodology to model multivariate output from a computer simulator taking ... More
Silicate features in Galactic and extragalactic post-AGB discsAug 03 2011Aims. In this paper we study the Spitzer and TIMMI2 infrared spectra of post-AGB disc sources, both in the Galaxy and the LMC. Using the observed infrared spectra we determine the mineralogy and dust parameters of the discs, and look for possible differences ... More