Results for "J. L. M. van Mechelen"

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Tunable localization in an s-electron Kondo system at room temperatureFeb 08 2019To achieve room-temperature superconductivity, a mechanism is needed that provides heavy quasiparticles at room temperature. In heavy fermion systems such localization is prototypically present only at liquid helium temperatures. In these $f$-electron ... More
Stratified dispersive model for material characterization using terahertz time-domain spectroscopyJul 07 2014We propose a novel THz material analysis approach which provides highly accurate material parameters and can be used for industrial quality control. The method treats the inspected material within its environment locally as a stratified system and describes ... More
Spin resonance in EuTiO3 probed by time-domain GHz ellipsometryMay 18 2011We show an example of a purely magnetic spin resonance in EuTiO3 and the resulting new record high Faraday rotation of 590 deg/mm at 1.6 T for 1 cm wavelengths probed by a novel technique of magneto-optical GHz time-domain ellipsometry. From our transmission ... More
Many-body large polaron optical conductivity in SrTi$_{1-x}$Nb$_x$O$_3$Mar 04 2010Recent experimental data on the optical conductivity of niobium doped SrTiO$_{3}$ are interpreted in terms of a gas of large polarons with effective coupling constant $\alpha_{eff}\approx2$. The {theoretical approach takes into account} many-body effects, ... More
Common Fermi-liquid origin of T-squared resistivity and superconductivity in n-type SrTiO3Sep 14 2011A detailed analysis is given of the T^2 term in the resistivity observed in electron-doped SrTiO3. Novel bandstructure data are presented, which provide values for the bare mass, density of states, and plasma frequency of the quasiparticles as a function ... More
Mg-Ni-H films as selective coatings: tunable reflectance by layered hydrogenationJan 07 2004Unlike other switchable mirrors, Mg2NiHx films show large changes in reflection that yield very low reflectance (high absorptance) at different hydrogen contents, far before reaching the semiconducting state. The resulting reflectance patterns are of ... More
Oxygen isotope effect and phase separation in the optical conductivity of (La$_{0.5}$Pr$_{0.5}$)$_{0.7}$Ca$_{0.3}$MnO$_3$ thin filmsOct 13 2005The optical conductivities of films of (La$_{0.5}$Pr$_{0.5}$)$_{0.7}$Ca$_{0.3}$MnO$_3$ with different oxygen isotopes ($^{16}$O and $^{18}$O) have been determined in the spectral range from 0.3 to 4.3 eV using a combination of transmission in the mid-infrared ... More
Electron-phonon interaction and charge carrier mass enhancement in SrTiO3Dec 10 2007We report a comprehensive THz, infrared and optical study of Nb doped SrTiO3 as well as DC conductivity and Hall effect measurements. Our THz spectra at 7K show the presence of a very narrow (<2 meV) Drude peak, the spectral weight of which shows approximately ... More
Surface state charge dynamics of a high-mobility three dimensional topological insulatorMay 04 2011Oct 05 2011We present a magneto-optical study of the three-dimensional topological insulator, strained HgTe using a technique which capitalizes on advantages of time-domain spectroscopy to amplify the signal from the surface states. This measurement delivers valuable ... More
Phononic gaps in the charged incommensurate planes of Sr14Cu24O41Apr 06 2012The terahertz (THz) excitations in the quantum spin-ladder system Sr14Cu24O41 have been determined along the c-axis using THz time-domain, Raman and infrared spectroscopy. Low-frequency infrared and Raman active modes are observed above and below the ... More
Obtaining the CMS Ridge effect with Multiparton InteractionsMar 09 2012May 16 2012We show that the "ridge" phenomenon in the two-particle angular correlation function, as observed by the CMS experiment, can be reproduced by implementing an impact parameter dependent azimuthal correlation of the scattering planes of individual partonic ... More
Universal spin-momentum locking of evanescent wavesApr 23 2015Oct 20 2015We show the existence of an inherent property of evanescent electromagnetic waves: spin-momentum locking, where the direction of momentum fundamentally locks the polarization of the wave. We trace the ultimate origin of this phenomenon to complex dispersion ... More
Transverse Momentum Transfer and Low x Parton Dynamics at HERAJul 12 1999The transverse momentum transfer correlation is introduced as a sensitive probe that can be used to discriminate between models for parton dynamics in low-x deep-inelastic scattering. Expectations for uncorrelated models and models with short-range or ... More
Transverse momentum dependent (TMD) parton distribution functions: status and prospectsJul 19 2015We provide a concise overview on transverse momentum dependent (TMD) parton distribution functions, their application to topical issues in high-energy physics phenomenology, and their theoretical connections with QCD resummation, evolution and factorization ... More
Proceedings of the Sixth International Workshop on Multiple Partonic Interactions at the Large Hadron ColliderJun 18 2015Multiple Partonic Interactions are often crucial for interpreting results obtained at the Large Hadron Collider (LHC). The quest for a sound understanding of the dynamics behind MPI - particularly at this time when the LHC is due to start its "Run II" ... More
Stokes Vector of Photon in the Decays B^0 -> rho^0 gamma and B^0 -> K^* gammaMar 19 2004Apr 08 2004We consider a model for the decay Bbar^0 -> rho^0 gamma in which the short-distance amplitude determined by the Hamiltonian describing b -> d gamma is combined with a typical long-distance contribution Bbar^0 -> D^+ D^- -> rho^0 gamma. The latter possesses ... More
Optimally Designed Digitally-Doped Mn:GaAsDec 15 2006We use the ab initio local-density approximation (LDA) to study of exchange interactions and Tc of Ga1&#8722;xMnxAs grown in digitally doped structures. We analyze the crystallographic dependence of exchange interactions predicted by the LDA in terms ... More
Violation of Time Reversal Invariance in the Decays K_L -> pi^+ pi^- gamma and K_L -> pi^+ pi^- e^+ e^-Aug 20 1999The origin of the large CP-odd and T-odd asymmetry observed in the decay K_L -> pi^+ pi^- e^+ e^- is traced to the polarization properties of the photon in the decay K_L -> pi^+ pi^- gamma. The Stokes vector of the photon S = (S_1, S_2, S_3) is studied ... More
CP-Violation in the decay B^0, (B^0)bar -> pi^+ pi^- gammaAug 23 2002Aug 30 2002The decay (B^0)bar -> pi^+ pi^- gamma has a bremsstrahlung component determined by the amplitude for (B^0)bar -> pi^+ pi^-, as well as a direct component determined by the penguin interaction V_tb V^*_td c_7 O_7. Interference of these amplitudes produces ... More
Time Evolution of Decay Spectrum in K^0, K^0 bar -> pi^+ pi^- e^+ e^-Jun 29 2000Aug 04 2000We consider the decay K^0 (K^0 bar) -> pi^+ pi^- e^+ e^- of a neutral K meson prepared in a state of strangeness +1 (-1). The time evolution of the state produces remarkable time-dependent effects in the angular distribution of the pi^+ pi^- e^+ e^- system. ... More
Optimizing Tc in the (Mn,Cr,Ga)As and (Mn,Ga)(As,P) Ternary AlloysOct 17 2005We explore two possible ways to enhance the critical temperature $T_c$ in the dilute magnetic semiconductor Mn$_{0.08}$Ga$_{0.92}$As. Within the context of the double-exchange and RKKY pictures, the ternary alloys Mn$_{x}$Cr$_{0.08-x}$Ga$_{0.92}$As and ... More
On the mass distribution of neutron stars in HMXBsFeb 16 2005We present the results of a monitoring campaign of three eclipsing high-mass X-ray binaries (HMXBs: SMC X-1, LMC X-4 and Cen X-3). High-resolution VLT/UVES spectra are used to measure the radial velocities of these systems with high accuracy. We show ... More
Abundances in Spiral Galaxies: Evidence for Primary Nitrogen ProductionFeb 11 1998We present the results of nitrogen and oxygen abundance measurements for 185 HII regions spanning a range of radius in 13 spiral galaxies. As expected, the nitrogen-to-oxygen ratio increases linearly with the oxygen abundance for high metallicity HII ... More
The FP420 R&D Project: Higgs and New Physics with forward protons at the LHCJun 02 2008Jan 02 2009We present the FP420 R&D project, which has been studying the key aspects of the development and installation of a silicon tracker and fast-timing detectors in the LHC tunnel at 420 m from the interaction points of the ATLAS and CMS experiments. These ... More
Helicity Amplitudes for Charmonium Production in Hadron-Hadron and Photon-Hadron CollisionsOct 16 2007We present the gluon-gluon and photon-gluon helicity amplitudes for color singlet and octet charmonium production in polarized and unpolarized hadron-hadron and photon-hadron collisions.
Incorporation of Density Matrix Wavefunctions in Monte Carlo Simulations: Application to the Frustrated Heisenberg ModelFeb 08 2000Feb 23 2000We combine the Density Matrix Technique (DMRG) with Green Function Monte Carlo (GFMC) simulations. The DMRG is most successful in 1-dimensional systems and can only be extended to 2-dimensional systems for strips of limited width. GFMC is not restricted ... More
QED radiative corrections to virtual Compton scatteringJan 12 2000The QED radiative corrections to virtual Compton scattering (reaction $e p \to e p \gamma$) are calculated to first order in $\alpha_{em} \equiv e^2 / 4 \pi$. A detailed study is presented for the one-loop virtual corrections and for the first order soft-photon ... More
The maximum dimension of a Lie nilpotent subalgebra of M_{n}(F) of index mAug 16 2016The main result of this paper is the following: if F is any field and R is any F-subalgebra of the algebra of nxn matrices over F with Lie nilpotence index m, then the F-dimension of R is less or equal than M(m+1,n), where M(m+1,n) is the maximum of a ... More
Nanostructured superconductor/ferromagnet bilayersJan 17 2002The pinning properties of type-II superconductors can be efficiently controlled by using laterally nanostructured ferromagnet / superconductor bilayers. This will be illustrated by studying the flux pinning in thin superconducting Pb films which are deposited ... More
Benchmarking in cluster analysis: A white paperSep 27 2018Oct 01 2018To achieve scientific progress in terms of building a cumulative body of knowledge, careful attention to benchmarking is of the utmost importance. This means that proposals of new methods of data pre-processing, new data-analytic techniques, and new methods ... More
The Wolf-Rayet counterpart of Cygnus X-3Apr 17 1996We present orbital-phase resolved I and K-band spectroscopy of Cygnus X-3. All spectra show emission lines characteristic of Wolf-Rayet stars of the WN subclass. On time scales longer than about one day, the line strengths show large changes, both in ... More
Ram Pressure Stripping in the Low Luminosity Virgo Cluster Elliptical Galaxy NGC 4476Oct 18 2004We present a deep VLA search for HI emission from the low-luminosity Virgo Cluster elliptical galaxy NGC 4476, which contains 1.1 x 10^8 M_sun of molecular gas in an undisturbed disk in regular rotation. No HI was detected. The rms noise in the final ... More
The Distance to the Isolated Neutron Star RX J0720.4-3125Mar 13 2007We have used a set of dedicated astrometric data from the Hubble Space Telescope to measure the parallax and proper motion of the nearby neutron star RX J0720.4-3125. At each of eight epochs over two years, we used the High Resolution Camera of the Advanced ... More
CP Violation in the Decays B -> K Kbar in the Presence of D Dbar <-> K Kbar MixingJun 01 2004We have recently shown that the large direct CP violation observed in the decay B^0 -> pi^+ pi^-, and the enhanced branching ratio for B^0 -> pi^0 pi^0, can be understood by invoking a small mixing of the pi pi system with the dominant D Dbar channel. ... More
Charm electroproduction viewed in the variable-flavour number scheme versus fixed-order perturbation theoryDec 18 1996Starting from fixed-order perturbation theory (FOPT) we derive expressions for the heavy-flavour components of the deep-inelastic structure functions FL and F2 in the variable-flavour number scheme (VFNS). These expressions are valid in all orders of ... More
Dephasing of entangled electron-hole pairs in a degenerate electron gasJul 09 2003A tunnel barrier in a degenerate electron gas was recently discovered as a source of entangled electron-hole pairs. Here, we investigate the loss of entanglement by dephasing. We calculate both the maximal violation E_max of the Bell inequality and the ... More
Determination of the strong coupling constant $α_s(M_Z)$ in next-to-next-to-leading order QCD using H1 jet cross section measurementsSep 21 2017The strong coupling constant $\alpha_s(M_Z)$ is determined from inclusive jet and dijet cross sections in neutral-current deep-inelastic $ep$ scattering (DIS) measured at HERA by the H1 collaboration using next-to-next-to-leading order (NNLO) QCD predictions. ... More
The Chandra LETG and XMM-Newton Spectra of HR 1099Jan 31 2002The X-ray luminous RS CVn binary system HR 1099 has been observed on several occasions in the early phases of \textit{Chandra} and \textit{XMM-Newton}. A very hot (up to 40 MK) dominant coronal plasma has been identified from the high-resolution spectroscopic ... More
Swift X-ray Telescope study of the Black Hole Binary MAXI J1659-152: Variability from a two component accretion flowJun 11 2015We present an energy dependent X-ray variability study of the 2010 outburst of the black hole X-ray binary MAXI J1659-152 with the Swift X-ray Telescope (XRT). The broad-band noise components and the quasi periodic oscillations (QPO) observed in the power ... More
From gas to galaxiesNov 02 2004The unsurpassed sensitivity and resolution of the Square Kilometer Array (SKA) will make it possible for the first time to probe the continuum emission of normal star forming galaxies out to the edges of the universe. This opens the possibility for routinely ... More
LHC Forward PhysicsNov 15 2016Dec 09 2017The goal of this report is to give a comprehensive overview of the rich field of forward physics, with a special attention to the topics that can be studied at the LHC. The report starts presenting a selection of the Monte Carlo simulation tools currently ... More
LHC Forward PhysicsNov 15 2016The goal of this report is to give a comprehensive overview of the rich field of forward physics, with a special attention to the topics that can be studied at the LHC. The report starts presenting a selection of the Monte Carlo simulation tools currently ... More
Modelling recorded crime: a full search for cointegrated modelsApr 29 2008Oct 30 2008A modelgenerator is developed that searches for cointegrated models among a potentially large group of candidate models. The generator employs the first step of the Engle-Granger procedure and orders cointegrated models according to the information criterions ... More
Parameter estimation of a Levy copula of a discretely observed bivariate compound Poisson process with an application to operational risk modellingDec 01 2012A method is developed to estimate the parameters of a Levy copula of a discretely observed bivariate compound Poisson process without knowledge of common shocks. The method is tested in a small sample simulation study. Also, the method is applied to a ... More
Compression of sub-relativistic space-charge-dominated electron bunches for single-shot femtosecond electron diffractionJun 10 2010We demonstrate compression of 95 keV, space-charge-dominated electron bunches to sub-100 fs durations. These bunches have sufficient charge (200 fC) and are of sufficient quality to capture a diffraction pattern with a single shot, which we demonstrate ... More
Shapiro steps in a superconducting film with an antidot latticeJul 27 1999Shapiro voltage steps at voltages V_n=nV_0 (n integer) have been observed in the voltage-current characteristics of a superconducting film with a square lattice of perforating microholes (antidots)in the presence of radiofrequent radiation. These equidistant ... More
Jamming, Yielding and Rheology of Weakly Vibrated Granular MediaJun 15 2011Jul 17 2011We establish that the rheological curve of dry granular media is non-monotonic, both in the presence and absence of external mechanical agitations. In the presence of weak vibrations, the non-monotonic flow curves govern a hysteretic transition between ... More
Scalability and Resilience of Software-Defined Networking: An OverviewAug 28 2014Software-Defined Networking (SDN) allows to control the available network resources by an intelligent and centralized authority in order to optimize traffic flows in a flexible manner. However, centralized control may face scalability issues when the ... More
Bistable hysteresis and resistance switching in hydrogen gold junctionsJun 26 2009Aug 03 2009Current-voltage characteristics of H2-Au molecular junctions exhibit intriguing steps around a characteristic voltage of 40 mV. Surprisingly, we find that a hysteresis is connected to these steps with a typical time scale > 10 ms. This time constant scales ... More
The mass of the neutron star in Vela X-1Aug 14 2001We measured the radial-velocity curve of HD77581, the B-supergiant companion of the X-ray pulsar Vela X-1, using 183 high-resolution optical spectra obtained in a nine-month campaign. We derive radial-velocity amplitudes for different lines and wavelength ... More
HERA and the LHC - A workshop on the implications of HERA for LHC physics: Proceedings - Part AJan 02 2006Jan 31 2006The HERA electron--proton collider has collected 100 pb$^{-1}$ of data since its start-up in 1992, and recently moved into a high-luminosity operation mode, with upgraded detectors, aiming to increase the total integrated luminosity per experiment to ... More
New Paradigms in Magnetic RecordingJan 26 2012The magnetic hard disc drive industry continues to face serious challenges in its quest for ever decreasing bit size. This review summarizes recent advances and promising new technology which have foundations in fundamental physical principles. Some advantages ... More
Large Direct CP Violation in B^0 -> pi^+ pi^- and an Enhanced Branching Ratio for B^0 -> pi^0 pi^0Mar 04 2004Apr 07 2004Recent measurements of B^0 -> pi pi decays reveal two features that are in conflict with conventional calculations: the channel B^0 (Bbar^0) -> pi^+ pi^- shows a large direct CP-violating asymmetry, and the channel B^0 (B^0) -> pi^0 pi^0 has an unexpectedly ... More
$O(α_s^2)$ corrections to polarized heavy flavour production at $Q^2\gg m^2$Aug 15 1996We present analytic formulae for the heavy flavour coefficient functions for polarized deep inelastic lepton-hadron scattering. The expressions are valid in the kinematical regime $Q^2\gg m^2$ where $Q^2$ and $m^2$ stand for the masses squared of the ... More
Role of Disorder in Mn:GaAs, Cr:GaAs, and Cr:GaNAug 09 2004We present calculations of magnetic exchange interactions and critical temperature T_c in Mn:GaAs, Cr:GaAs and Cr:GaN. The local spin density approximation is combined with a linear-response technique to map the magnetic energy onto a Heisenberg hamiltonion, ... More
H-alpha features with hot onsets. II. A contrail fibrilSep 24 2016The solar chromosphere observed in H-alpha consists mostly of narrow fibrils. The longest typically originate in network or plage and arch far over adjacent internetwork. We use data from multiple telescopes to analyze one well-observed example in a quiet ... More
A deconvolution map-making method for experiments with circular scanning strategiesJun 21 2011Aims. To investigate the performance of a deconvolution map-making algorithm for an experiment with a circular scanning strategy, specifically in this case for the analysis of Planck data, and to quantify the effects of making maps using simplified approximations ... More
Comparison between the various descriptions for charm electroproduction and the HERA-dataJul 07 1997We examine the charm component F_{2,c}(x,Q^2,m^2) of the proton structure function F_2(x,Q^2) in three different schemes and compare the results with the data in the x and Q^2 region explored by the HERA experiments. Studied are (1) the three flavour ... More
Determination of the mass of the neutron star in SMC X-1, LMC X-4 and Cen X-3 with VLT/UVESJul 18 2007We present the results of a spectroscopic monitoring campaign of the OB-star companions to the eclipsing X-ray pulsars SMC X-1, LMC X-4 and Cen X-3. High-resolution optical spectra obtained with UVES on the ESO Very Large Telescope are used to determine ... More
Generating nested quadrature rules with positive weights based on arbitrary sample setsSep 26 2018For the purpose of uncertainty propagation a new quadrature rule technique is proposed that has positive weights, has high degree, and is constructed using only samples that describe the probability distribution of the uncertain parameters. Moreover, ... More
The role of Joule heating in the formation of nanogaps by electromigrationOct 14 2005Jul 13 2006We investigate the formation of nanogaps in gold wires due to electromigration. We show that the breaking process will not start until a local temperature of typically 400 K is reached by Joule heating. This value is rather independent of the temperature ... More
Resonant X-rays at the Cu L-edge as a momentum dependent probe of the magnetic excitation spectrum in cupratesMar 17 2009We show that, contrary to common lore, in resonant inelastic x-ray scattering (RIXS) at the copper L- and M-edge direct spin-flip scattering is in principle allowed. We demonstrate how this possibility can be exploited to probe the momentum dependent ... More
Stokes imaging polarimetry using image restoration at the Swedish 1-m Solar TelescopeMay 28 2008Aims: We aim to achieve high spatial resolution as well as high polarimetric sensitivity, using an earth-based 1m-class solar telescope, for the study of magnetic fine structure on the Sun. Methods: We use a setup with 3 high-speed, low-noise cameras ... More
Flux pinning in a superconducting film by a regular array of magnetic dotsOct 26 1999We have studied flux pinning in thin superconducting Pb films covering a triangular array of submicron magnetic Au/Co/Au dots with in-plane magnetization. The rectangular dots can have two possible in-plane magnetic states: a single-domain state where ... More
Asymmetric flux pinning in laterally nanostructured ferromagnetic / superconducting bilayersDec 22 2000Jan 09 2002We investigated the pinning of flux lines in a superconducting film by a regular array of magnetic antidots. The sample consists of a Co/Pt multilayer with perpendicular magnetic anisotropy in which a regular pattern of submicron holes is introduced and ... More
A Distance-Based Approach to Strong Target Control of Dynamical NetworksAug 07 2016This paper deals with controllability of dynamical networks. It is often unfeasible or unnecessary to fully control large-scale networks, which motivates the control of a prescribed subset of agents of the network. This specific form of output control ... More
The X-ray Counterpart of the High-B Pulsar PSR J0726-2612Nov 11 2011Nov 15 2011Middle-aged, cooling neutron stars are observed both as relatively rapidly spinning radio pulsars and as more slowly spinning, strongly magnetized isolated neutron stars (INSs), which stand out by their thermal X-ray spectra. The difference between the ... More
The Parallax and Proper Motion of RX J1856.5-3754 RevisitedNov 08 2001Jan 31 2002RX J1856.5-3754, a bright soft X-ray source believed to be the nearest thermally emitting neutron star, has commanded and continues to command intense interest from X-ray missions. One of the main goals is to determine the radius of this neutron star. ... More
HERA and the LHC - A workshop on the implications of HERA for LHC physics: Proceedings - Part BJan 02 2006Mar 19 2007The HERA electron--proton collider has collected 100 pb$^{-1}$ of data since its start-up in 1992, and recently moved into a high-luminosity operation mode, with upgraded detectors, aiming to increase the total integrated luminosity per experiment to ... More
Ellerman bombs at high resolution. IV. Visibility in Na I and Mg IJun 14 2015Ellerman bombs are transient brightenings of the wings of the solar Balmer lines that mark reconnection in the photosphere. Ellerman noted in 1917 that he did not observe such brightenings in the Na I D and Mg I b lines. This non-visibility should constrain ... More
Micromagnetic simulations of sweep-rate dependent coercivity in perpendicular recording mediaMar 15 2012The results of micromagnetic simulations are presented which examine the impact of thermal fluctuations on sweep rate dependent coercivities of both single-layer and exchange-coupled-composite (ECC) perpendicular magnetic recording media. M-H loops are ... More
The critical behaviour of the 2D Ising model in Transverse Field; a Density Matrix Renormalization calculationSep 09 1997We have adjusted the Density Matrix Renormalization method to handle two dimensional systems of limited width. The key ingredient for this extension is the incorporation of symmetries in the method. The advantage of our approach is that we can force certain ... More
Determinants for nxn matrices and the symmetric Newton formula in the 3x3 caseOct 18 2012Jan 06 2015One of the aims of this paper is to provide a short survey on the Z2-graded, the symmetric and the left (right) generalizations of the classical determinant theory for square matrices with entries in an arbitrary (possibly non-commutative) ring. This ... More
Coherent Cherenkov radiation and laser oscillation in a photonic crystalAug 23 2016We demonstrate that photonic crystals can be used to generate powerful and highly coherent laser radiation when injecting a beam of free electrons. Using theoretical investigations we present the startup dynamics and coherence properties of such laser, ... More
Coherent Cerenkov radiation and laser oscillation in a photonic crystalAug 23 2016Oct 26 2016We demonstrate that photonic crystals can be used to generate powerful and highly coherent laser radiation when injecting a beam of free electrons. Using theoretical investigations we present the startup dynamics and coherence properties of such laser, ... More
The nuclear ring in the unbarred galaxy NGC 278: result of a minor merger?May 06 2004We present fully sampled high angular resolution two-dimensional kinematics in the H alpha spectral line, optical and near-infrared imaging, as well as 21 cm atomic hydrogen data of the spiral galaxy NGC 278. This is a small non-barred galaxy, which has ... More
Atomic level micromagnetic model of recording media switching at elevated temperaturesFeb 06 2012An atomic level micromagnetic model of granular recording media is developed and applied to examine external field-induced grain switching at elevated temperatures which captures non-uniform reversal modes. The results are compared with traditional methods ... More
Spectroscopy of Outlying H II Regions in Spiral Galaxies: Abundances and Radial GradientsAug 27 1998We present the results of low dispersion optical spectroscopy of 186 H II regions spanning a range of radius in 13 spiral galaxies. Abundances for several elements (oxygen, nitrogen, neon, sulfur, and argon) were determined for 185 of the H II regions. ... More
Physical Properties of a Sunspot Chromosphere with Umbral FlashesApr 02 2013We present new high-resolution spectro-polarimetric Ca II 8542 observations of umbral flashes in sunspots. At nearly 0.18", and spanning about one hour of continuous observation, this is the most detailed dataset published thus far. Our study involves ... More
Mass protection via translational invarianceJul 23 1998Oct 25 1999We propose a way of protecting a Dirac fermion interacting with a scalar field from acquiring a mass from the vacuum. It is obtained through an implementation of translational symmetry when the theory is formulated with a momentum cutoff, which forbids ... More
Spatial population expansion promotes the evolution of cooperation in an experimental Prisoner's DilemmaNov 11 2013Cooperation is ubiquitous in nature, but explaining its existence remains a central interdisciplinary challenge. Cooperation is most difficult to explain in the Prisoner's Dilemma game, where cooperators always lose in direct competition with defectors ... More
Radio Continuum Imaging of High Redshift Radio GalaxiesOct 21 1996We present sensitive radio continuum images at high resolution of 37 radio galaxies at z > 2. The observations were made with the Very Large Array (VLA) at 4.7 GHz and 8.2 GHz, with typical resolutions of 0.45'' and 0.25'', respectively. Images of total ... More
Neutral Gas Distribution and Kinematics of the Nearly Face-on Spiral Galaxy NGC 1232Jul 20 1999We have analyzed high velocity resolution HI synthesis observations of the nearly face-on Sc galaxy NGC 1232. The neutral gas distribution extends well beyond the optical extent of the galaxy. As expected, local peaks in the HI column density are associated ... More
Single atom adhesion in optimized gold nanojunctionsFeb 26 2008Apr 30 2008We study the interaction between single apex atoms in a metallic contact, using the break junction geometry. By carefully 'training' our samples, we create stable junctions in which no further atomic reorganization takes place. This allows us to study ... More
Spin Stiffness in the Hubbard modelOct 25 1995The spin stiffness $\rho_{\rm s}$ of the repulsive Hubbard model that occurs in the hydrodynamic theory of antiferromagnetic spin waves is shown to be the same as the thermodynamically defined stiffness involved in twisting the order parameter. New expressions ... More
Ito's formula in UMD Banach spaces and regularity of solutions of the Zakai equationApr 02 2008Using the theory of stochastic integration for processes with values in a UMD Banach space developed recently by the authors, an Ito formula is proved which is applied to prove the existence of strong solutions for a class of stochastic evolution equations ... More
Stochastic integration in UMD Banach spacesOct 20 2006Aug 13 2007In this paper we construct a theory of stochastic integration of processes with values in $\mathcal{L}(H,E)$, where $H$ is a separable Hilbert space and $E$ is a UMD Banach space (i.e., a space in which martingale differences are unconditional). The integrator ... More
Distances to Galactic methanol masersDec 04 2008Dec 09 2008We present the first EVN parallax measurements of 6.7 GHz methanol masers in star forming regions of the Galaxy. The 6.7 GHz methanol maser transition is a very valuable astrometric tool, for its large stability and confined velocity spread, which makes ... More
Unraveling DNA tori under tensionApr 27 2009Motivated by recent experiments, we develop a model for DNA toroids under external tension. We find that tori are the equilibrium states for our model up to a critical tension, above which they become only metstable. Above this tension, we find a cascade ... More
The circumstellar envelope of AFGL 4106Jul 14 1999We present new imaging and spectroscopy of the post-red supergiant binary AFGL 4106. Coronographic imaging in H-alpha reveals the shape and extent of the ionized region in the circumstellar envelope (CSE). Echelle spectroscopy with the slit covering almost ... More
Adsorbate dynamics on a silica-coated gold surface measured by Rydberg Stark spectroscopyDec 23 2015Trapping a Rydberg atom close to a surface is an important step towards the realisation of many proposals of quantum information or hybrid quantum systems. One of the challenges in these experiments is to overcome the electric field emanating from contaminations ... More
Real-time detection of single electron tunneling using a quantum point contactJul 06 2004We observe individual tunnel events of a single electron between a quantum dot and a reservoir, using a nearby quantum point contact (QPC) as a charge meter. The QPC is capacitively coupled to the dot, and the QPC conductance changes by about 1% if the ... More
AD Leonis: Flares observed by XMM-Newton and ChandraSep 11 2003The M-dwarf AD Leonis has been observed with the Reflection Grating Spectrometers and the European Photon Imaging Camera aboard XMM-Newton and also with the Low Energy Transmission Grating Spectrometer aboard the Chandra X-ray Observatory. In the observation ... More
$K$-band integral field spectroscopy and optical spectroscopy of massive young stellar objects in the Small Magellanic CloudSep 19 2016Sep 20 2016We present $K$-band integral field spectroscopic observations towards 17 massive young stellar objects (YSOs) in the low metallicity Small Magellanic Cloud (SMC) and two YSO candidates in the compact H ii regions N81 and N88 A (also in the SMC). These ... More
Integral Field Spectroscopy of Massive Young Stellar Objects in the N113 H\,{\sc ii} Region in the Large Magellanic CloudOct 19 2015The \textit{Spitzer} SAGE survey has allowed the identification and analysis of significant samples of Young Stellar Object (YSO) candidates in the Large Magellanic Cloud (LMC). However the angular resolution of \textit{Spitzer} is relatively poor meaning ... More
Electromagnetic Corrections to the One-Pion-Exchange PotentialOct 28 1997Leading-order electromagnetic loop corrections to the one-pion-exchange potential are computed within the framework of chiral perturbation theory. These corrections generate an effective nucleon-nucleon potential, $V_{\pi \gamma}$, which supplements the ... More
Radio-Excess IRAS Galaxies: PMN/FSC Sample SelectionJun 27 2003A sample of 178 extragalactic objects is defined by correlating the 60 micron IRAS FSC with the 5 GHz PMN catalog. Of these, 98 objects lie above the radio/far-infrared relation for radio-quiet objects. These radio-excess galaxies and quasars have a uniform ... More
Nonlinear effects in the propagation of optically generated magnetostatic volume mode spin wavesJan 11 2016Jul 08 2016Recent experimental work has demonstrated optical control of spin wave emission by tuning the shape of the optical pulse (Satoh et al.\ Nature Photonics, 6, 662 (2012)). We numerically reproduce these results and expand the scope of the control by investigating ... More