Results for "Matthijs H. D. van der Wiel"

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Characterizing star formation activity in infrared dark cloud MSXDC G048.65-00.29Jul 23 2008Nov 18 2008Infrared Dark Clouds (IRDCs), condensed regions of the ISM with high column densities, low temperatures and high masses, are suspected sites of star formation. Thousands of IRDCs have already been identified. To date, it has not been resolved whether ... More
Gas signatures of Herbig Ae/Be disks probed with Herschel SPIRE spectroscopyOct 22 2013Herbig Ae/Be objects, like their lower mass counterparts T Tauri stars, are seen to form a stable circumstellar disk which is initially gas-rich and could ultimately form a planetary system. We present Herschel SPIRE 460-1540 GHz spectra of five targets ... More
Chemical stratification in the Orion Bar: JCMT Spectral Legacy Survey observationsFeb 09 2009Feb 23 2010Photon-dominated regions (PDRs) are expected to show a layered structure in molecular abundances and emerging line emission, which is sensitive to the physical structure of the region as well as the UV radiation illuminating it. We aim to study this layering ... More
Hydrogen Fluoride in High-Mass Star-forming RegionsJul 02 2012Hydrogen fluoride has been established to be an excellent tracer of molecular hydrogen in diffuse clouds. In denser environments, however, the HF abundance has been shown to be approximately two orders of magnitude lower. We present Herschel/HIFI observations ... More
Tracing the cold and warm physico-chemical structure of deeply embedded protostars: IRAS 16293-2422 versus VLA 1623-2417May 14 2018Much attention has been placed on the dust distribution in protostellar envelopes, but there are still many unanswered questions regarding the structure of the gas. We aim to start identifying the factors that determine the chemical structure of protostellar ... More
The HIFI spectral survey of AFGL 2591 (CHESS). III. Chemical structure of the protostellar envelopeDec 18 2014We aim to understand the rich chemical composition of AFGL 2591, a prototypical isolated high-mass star-forming region. Based on HIFI and JCMT data, the molecular abundances of species found in the protostellar envelope of AFGL 2591 were derived with ... More
The ALMA-PILS survey: The sulphur connection between protostars and comets: IRAS 16293-2422 B and 67P/Churyumov-GerasimenkoFeb 08 2018The evolutionary past of our Solar System can be pieced together by comparing analogous low-mass protostars with remnants of our Protosolar Nebula - comets. Sulphur-bearing molecules may be unique tracers of the joint evolution of the volatile and refractory ... More
Modulation of conductance and superconductivity by top-gating in LaAlO3/SrTiO3 2-dimensional electron systemsJun 24 2013We report the electrical top-gating of a 2-dimensional electron gas (2DEG) formed at the LaAlO3/SrTiO3 interface, using electron-beam evaporated Au gate electrodes. In these structures, epitaxial LaAlO3 films grown by pulsed laser deposition induce the ... More
Three-dimensional distribution of hydrogen fluoride gas toward NGC6334 I and I(N)May 19 2016Aims. We investigate the spatial distribution of a collection of absorbing gas clouds, some associated with the dense, massive star-forming core NGC6334 I, and others with diffuse foreground clouds. For the former category, we aim to study the dynamical ... More
Far-infrared/sub-millimetre properties of pre-stellar cores L1521E, L1521F and L1689B as revealed by the Herschel SPIRE instrument -- I. Central positionsFeb 22 2016Dust grains play a key role in the physics of star-forming regions, even though they constitute only $\sim$1 % of the mass of the interstellar medium. The derivation of accurate dust parameters such as temperature ($T_{dust}$), emissivity spectral index ... More
The HIFI spectral survey of AFGL2591 (CHESS). I. Highly excited linear rotor molecules in the high-mass protostellar envelopeMar 14 2013We aim to reveal the gas energetics in the circumstellar environment of the prototypical high-mass protostellar object AFGL2591 using space-based far-infrared observations of linear rotor molecules. Rotational spectral line signatures of CO, HCO+, CS, ... More
Observing Extended Sources with the \Herschel SPIRE Fourier Transform SpectrometerJun 24 2013The Spectral and Photometric Imaging Receiver (SPIRE) on the European Space Agency's Herschel Space Observatory utilizes a pioneering design for its imaging spectrometer in the form of a Fourier Transform Spectrometer (FTS). The standard FTS data reduction ... More
The JCMT Spectral Legacy Survey: physical structure of the molecular envelope of the high-mass protostar AFGL2591Jan 28 2011The understanding of the formation process of massive stars (>8 Msun) is limited, due to theoretical complications and observational challenges. We investigate the physical structure of the large-scale (~10^4-10^5 AU) molecular envelope of the high-mass ... More
Understanding partition comparison indices based on counting object pairsJan 07 2019In unsupervised machine learning, agreement between partitions is commonly assessed with so-called external validity indices. Researchers tend to use and report indices that quantify agreement between two partitions for all clusters simultaneously. Commonly ... More
Magnetic effects at the interface between nonmagnetic oxidesMar 01 2007Jun 04 2007The electronic reconstruction at the interface between two insulating oxides can give rise to a highly-conductive interface. In analogy to this remarkable interface-induced conductivity we show how, additionally, magnetism can be induced at the interface ... More
The Spatial Variation of the Cooling Lines in the Reflection Nebula NGC7023Jan 30 2015Context: The north-west photo-dissociation region (PDR) in the reflection nebula NGC 7023 displays a complex structure. Filament-like condensations at the edge of the cloud can be traced via the emission of the main cooling lines, offering a great opportunity ... More
Herschel SPIRE FTS Spectral Mapping CalibrationJan 09 2014The Herschel SPIRE Fourier transform spectrometer (FTS) performs spectral imaging in the 447-1546 GHz band. It can observe in three spatial sampling modes: sparse mode, with a single pointing on sky, or intermediate or full modes with 1 and 1/2 beam spacing, ... More
Surface Acoustic Wave induced Transport in a Double Quantum DotJan 09 2006We report on non-adiabatic transport through a double quantum dot under irradiation of surface acoustic waves generated on-chip. At low excitation powers, absorption and emission of single and multiple phonons is observed. At higher power, sequential ... More
Direct Coulomb and Exchange Interaction in Artificial AtomsJan 18 2000We determine the contributions from the direct Coulomb and exchange interactions to the total interaction in semiconductor artificial atoms. We tune the relative strengths of the two interactions and measure them as a function of the number of confined ... More
The ALMA-PILS survey: Stringent limits on small amines and nitrogen-oxides towards IRAS 16293-2422BAug 01 2018Hydroxylamine (NH$_{2}$OH) and methylamine (CH$_{3}$NH$_{2}$) have both been suggested as precursors to the formation of amino acids and are therefore of interest to prebiotic chemistry. Their presence in interstellar space and formation mechanisms, however, ... More
Spin injection and perpendicular spin transport in graphite nanostructuresMay 21 2010Organic and carbon-based materials are attractive for spintronics because their small spin-orbit coupling and low hyperfine interaction is expected to give rise to large spin-relaxation times. However, the corresponding spin-relaxation length is not necessarily ... More
Magnetoresistance oscillations and relaxation effects at the SrTiO3-LaAlO3 interfaceJun 27 2008We present low-temperature and high-field magnetotransport data on SrTiO3-LaAlO3 interfaces. The resistance shows hysteresis in magnetic field and a logarithmic relaxation as a function of time. Oscillations in the magnetoresistance are observed, showing ... More
Inelastic tunneling in a double quantum dot coupled to a bosonic environmentJul 12 2000Coupling a quantum system to a bosonic environment always give rise to inelastic processes, which reduce the coherency of the system. We measure energy dependent rates for inelastic tunneling processes in a fully controllable two-level system of a double ... More
Microwave spectroscopy on a quantum-dot moleculeSep 09 1998Quantum dots are small conductive regions in a semiconductor, containing a variable number of electrons (N=1 to 1000) that occupy well defined discrete quantum states. They are often referred to as artificial atoms with the unique property that they can ... More
Spontaneous Emission Spectrum in Double Quantum Dot DevicesAug 10 1998A double quantum dot device is a tunable two-level system for electronic energy states. A dc electron current directly measures the rates for elastic and inelastic transitions between the two levels. For inelastic transitions energy is exchanged with ... More
Signatures of warm carbon monoxide in protoplanetary discs observed with Herschel SPIREAug 22 2014Molecular gas constitutes the dominant mass component of protoplanetary discs. To date, these sources have not been studied comprehensively at the longest far-infrared and shortest submillimetre wavelengths. This paper presents Herschel SPIRE FTS spectroscopic ... More
Photon Assisted Tunneling in Quantum DotsApr 26 1999Apr 03 2002We review experiments on single electron transport through single quantum dots in the presence of a microwave signal. In the case of a small dot with well-resolved discrete energy states, the applied high-frequency signal allows for inelastic tunnel events ... More
Gate-tunable band structure of the LaAlO$_3$-SrTiO$_3$ interfaceOct 07 2016The 2-dimensional electron system at the interface between LaAlO$_{3}$ and SrTiO$_{3}$ has several unique properties that can be tuned by an externally applied gate voltage. In this work, we show that this gate-tunability extends to the effective band ... More
The ALMA-PILS survey: The first detection of doubly-deuterated methyl formate (CHD2OCHO) in the ISMNov 22 2018Studies of deuterated isotopologues of complex organic molecules can provide important constraints on their origin in regions of star formation. In particular, the abundances of deuterated species are very sensitive to the physical conditions in the environment ... More
Josephson supercurrent in a topological insulator without a bulk shuntJun 30 2014A Josephson supercurrent has been induced into the three-dimensional topological insulator Bi1.5Sb0.5Te1.7Se1.3. We show that the transport in Bi1.5Sb0.5Te1.7Se1.3 exfoliated flakes is dominated by surface states and that the bulk conductivity can be ... More
Conductance spectroscopy of a proximity induced superconducting topological insulatorJun 19 2015We study the proximity effect between the fully-gapped region of a topological insulator in direct contact with an s-wave superconducting electrode (STI) and the surrounding topological insulator flake (TI) in Au/Bi$_{1.5}$Sb$_{0.5}$Te$_{1.7}$Se$_{1.3}$/Nb ... More
Translational and rotational dynamics of a large buoyant sphere in turbulenceMar 08 2016We report experimental measurements of the translational and rotational dynamics of a large buoyant sphere in isotropic turbulence. We introduce an efficient method to simultaneously determine the position and (absolute) orientation of a spherical body ... More
The ALMA-PILS survey: First detections of ethylene oxide, acetone and propanal toward the low-mass protostar IRAS 16293-2422Nov 22 2016One of the open questions in astrochemistry is how complex organic and prebiotic molecules are formed. Aims. Our aim is to start the process of compiling an inventory of oxygen-bearing complex organic molecules toward the solar-type Class 0 protostellar ... More
Physical structure of the photodissociation regions in NGC 7023. Observations of gas and dust emission with HerschelOct 08 2014The determination of the physical conditions in molecular clouds is a key step towards our understanding of their formation and evolution of associated star formation. We investigate the density, temperature, and column density of both dust and gas in ... More
First detection of cyanamide (NH$_2$CN) towards solar-type protostarsDec 27 2017Searches for the prebiotically-relevant cyanamide (NH$_2$CN) towards solar-type protostars have not been reported in the literature. We here present the first detection of this species in the warm gas surrounding two solar-type protostars, using data ... More
Coherent single electron spin control in a slanting Zeeman fieldOct 15 2005We consider a single electron in a 1D quantum dot with a static slanting Zeeman field. By combining the spin and orbital degrees of freedom of the electron, an effective quantum two-level (qubit) system is defined. This pseudo-spin can be coherently manipulated ... More
Systematic characterisation of the Herschel SPIRE Fourier Transform SpectrometerFeb 19 2015A systematic programme of calibration observations was carried out to monitor the performance of the SPIRE FTS instrument on board the Herschel Space Observatory. Observations of planets (including the prime point-source calibrator, Uranus), asteroids, ... More
The ALMA Protostellar Interferometric Line Survey (PILS): First results from an unbiased submillimeter wavelength line survey of the Class 0 protostellar binary IRAS 16293-2422 with ALMAJul 29 2016The inner regions of the envelopes surrounding young protostars are characterised by a complex chemistry, with prebiotic molecules present on the scales where protoplanetary disks eventually may form. This paper introduces a systematic survey, "Protostellar ... More
The ALMA-PILS survey: First detections of deuterated formamide and deuterated isocyanic acid in the interstellar mediumMay 09 2016May 12 2016Formamide (NH$_2$CHO) has previously been detected in several star-forming regions and is thought to be a precursor for different prebiotic molecules. Its formation mechanism is still debated, however. Observations of formamide, related species and their ... More
The Herschel Comprehensive (U)LIRG Emission Survey (HerCULES): CO Ladders, fine structure lines, and neutral gas coolingJan 13 2015(Ultra) Luminous Infrared Galaxies ((U)LIRGs) are objects characterized by their extreme infrared (8-1000 $\mu$m) luminosities ($L_{LIRG}>10^{11} $L$_\odot$ and $L_{ULIRG}>10^{12}$ L$_\odot$). The Herschel Comprehensive ULIRG Emission Survey (HerCULES; ... More
Calibration of the Herschel SPIRE Fourier Transform SpectrometerMar 05 2014The Herschel SPIRE instrument consists of an imaging photometric camera and an imaging Fourier Transform Spectrometer (FTS), both operating over a frequency range of 450-1550 GHz. In this paper, we briefly review the FTS design, operation, and data reduction, ... More
Incorporating prior information and borrowing information in high-dimensional sparse regression using the horseshoe and variational BayesJan 29 2019We introduce a sparse high-dimensional regression approach that can incorporate prior information on the regression parameters and can borrow information across a set of similar datasets. Prior information may for instance come from previous studies or ... More
Transverse self-interactions within an electron bunch moving in an arc of a circle (generalized)Apr 09 2003Transverse self-interactions within a "line" bunch of electrons moving in an arc of a circle have been studied extensively by us from an electrodynamical viewpoint. Here we treat an electron bunch with a given vertical (i.e. perpendicular to the orbital ... More
Organic SpintronicsMar 19 2007In this paper we review the recent field of organic spintronics, where organic materials are applied as a medium to transport and control spin-polarized signals. The contacts for injecting and detecting spins are formed by metals, oxides, or inorganic ... More
Magnetically induced chessboard pattern in the conductance of a Kondo quantum dotMay 09 2003We quantitatively describe the main features of the magnetically induced conductance modulation of a Kondo quantum dot -- or chessboard pattern -- in terms of a constant-interaction double quantum dot model. We show that the analogy with a double dot ... More
Geometric reduction of dynamical nonlocality in nanoscale quantum circuitsDec 11 2015Nonlocality is a key feature discriminating quantum and classical physics. Quantum-interference phenomena, such as Young's double slit experiment, are one of the clearest manifestations of nonlocality, recently addressed as $dynamical$ to specify its ... More
Estimating the pattern frequency spectrum inside the browserSep 25 2014Sep 30 2014We present a browser application for estimating the number of frequent patterns, in particular itemsets, as well as the pattern frequency spectrum. The pattern frequency spectrum is defined as the function that shows for every value of the frequency threshold ... More
Correcting the extended-source calibration for the Herschel-SPIRE Fourier-Transform SpectrometerAug 30 2017Jan 02 2018We describe an update to the Herschel-SPIRE Fourier-Transform Spectrometer (FTS) calibration for extended sources, which incorporates a correction for the frequency-dependent far-field feedhorn efficiency, $\eta_\mathrm{FF}$. This significant correction ... More
Modeling association between DNA copy number and gene expression with constrained piecewise linear regression splinesDec 06 2013DNA copy number and mRNA expression are widely used data types in cancer studies, which combined provide more insight than separately. Whereas in existing literature the form of the relationship between these two types of markers is fixed a priori, in ... 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
Suppression of the Kondo Effect in a Quantum Dot by Microwave RadiationDec 08 1999We have studied the influence of microwave radiation on the transport properties of a semiconductor quantum dot in the Kondo regime. In the entire frequency range tested (10--50 GHz), the Kondo resonance vanishes by increasing the microwave power. This ... More
Electron transport through double quantum dotsMay 16 2002May 21 2002Electron transport experiments on two lateral quantum dots coupled in series are reviewed. An introduction to the charge stability diagram is given in terms of the electrochemical potentials of both dots. Resonant tunneling experiments show that the double ... More
Short-range spin- and pair-correlations: a variational wave-functionSep 19 2003Sep 23 2003A many-body wavefuction is postulated, which is sufficiently general to describe superconducting pair-correlations, and/or spin-correlations, which can occur either as long-range order or as finite-range correlations. The proposed wave-function appears ... More
Transverse self-fields within an electron bunch moving in an arc of a circleMay 01 2002As a consequence of motions driven by external forces, self-fields (which are different from the static case) originate within an electron bunch. In the case of magnetic external forces acting on an ultrarelativistic beam, the longitudinal self-interactions ... More
Anisotropic Pauli spin blockade in hole quantum dotsJul 30 2016We present measurements on gate-defined double quantum dots in Ge-Si core-shell nanowires, which we tune to a regime with visible shell filling in both dots. We observe a Pauli spin blockade and can assign the measured leakage current at low magnetic ... More
On the Role of Penning Ionization in Photoassociation SpectroscopyMar 31 2006We study the role of Penning ionization on the photoassociation spectra of He(^3S)-He(^3S). The experimental setup is discussed and experimental results for different intensities of the probe laser are shown. For modelling the experimental results we ... More
Integrability of a conducting elastic rod in a magnetic fieldAug 08 2007We consider the equilibrium equations for a conducting elastic rod placed in a uniform magnetic field, motivated by the problem of electrodynamic space tethers. When expressed in body coordinates the equations are found to sit in a hierarchy of non-canonical ... More
Electron Cotunneling in a Semiconductor Quantum DotJul 27 2000Nov 22 2000We report transport measurements on a semiconductor quantum dot with a small number of confined electrons. In the Coulomb blockade regime, conduction is dominated by cotunneling processes. These can be either elastic or inelastic, depending on whether ... More
The Kondo Effect in the Unitary LimitSep 26 2000We observe a strong Kondo effect in a semiconductor quantum dot when a small magnetic field is applied. The Coulomb blockade for electron tunneling is overcome completely by the Kondo effect and the conductance reaches the unitary-limit value. We compare ... More
Kondo effect in an integer-spin quantum dotApr 25 2000The Kondo effect is a key many-body phenomenon in condensed matter physics. It concerns the interaction between a localised spin and free electrons. Discovered in metals containing small amounts of magnetic impurities, it is now a fundamental mechanism ... More
Highly tuneable hole quantum dots in Ge-Si core-shell nanowiresOct 11 2016We define single quantum dots of lengths varying from 60 nm up to nearly half a micron in Ge-Si core-shell nanowires. The charging energies scale inversely with the quantum dot length between 18 and 4 meV. Subsequently, we split up a long dot into a double ... More
Depletion-mode Quantum Dots in Intrinsic SiliconSep 21 2017Feb 03 2018We report the fabrication and electrical characterization of depletion-mode quantum dots in a two-dimensional hole gas (2DHG) in intrinsic silicon. We use fixed charge in a SiO$_2$/Al$_2$O$_3$ dielectric stack to induce a 2DHG at the Si/SiO$_2$ interface. ... More
Spatial chaos of an extensible conducting rod in a uniform magnetic fieldMay 08 2009The equilibrium equations for the isotropic Kirchhoff rod are known to form an integrable system. It is also known that the effects of extensibility and shearability of the rod do not break the integrable structure. Nor, as we have shown in a previous ... More
An empirical Bayes approach to network recovery using external knowledgeMay 24 2016Reconstruction of a high-dimensional network may benefit substantially from the inclusion of prior knowledge on the network topology. In the case of gene interaction networks such knowledge may come for instance from pathway repositories like KEGG, or ... More
Growth of degrees of integrable mappingsMay 12 2010We study mappings obtained as s-periodic reductions of the lattice Korteweg-De Vries equation. For small s=(s1,s2) we establish upper bounds on the growth of the degree of the numerator of their iterates. These upper bounds appear to be exact. Moreover, ... More
Somos-4 and Somos-5 are arithmetic divisibility sequencesMay 01 2015We provide an elementary proof to a conjecture by Robinson that multiples of (powers of) primes in the Somos-4 sequence are equally spaced. We also show, almost as a corollary, for the generalised Somos-4 sequence defined by $\tau_{n+2}\tau_{n-2}=\alpha\tau_{n+1}\tau_{n-1}+\beta\tau_n^2$ ... More
On the Fourier transform of the greatest common divisorJan 16 2012The discrete Fourier transform of the greatest common divisor is a multiplicative function that generalises both the gcd-sum function and Euler's totient function. On the one hand it is the Dirichlet convolution of the identity with Ramanujan's sum, and ... More
Gene network reconstruction using global-local shrinkage priorsOct 13 2015Reconstructing a gene network from high-throughput molecular data is often a challenging task, as the number of parameters to estimate easily is much larger than the sample size. A conventional remedy is to regularize or penalize the model likelihood. ... More
Computer-mediated communication in adults with high-functioning Autism Spectrum ConditionsOct 04 2014It has been suggested that people with Autism Spectrum Conditions (ASC) are attracted to computer-mediated communication (CMC). In this study, several open questions regarding CMC use in people with ASC which are investigated. We compare CMC use in adults ... More
Global classification of two-component approximately integrable evolution equationsOct 11 2007Aug 11 2008We globally classify two-component evolution equations, with homogeneous diagonal linear part, admitting infinitely many approximate symmetries. Important ingredients are the symbolic calculus of Gel'fand and Dikii, the Skolem-Mahler-Lech theorem, results ... More
The order completion method for systems of nonlinear PDEs revisitedMar 03 2008Apr 23 2008In this paper we presents further developments regarding the enrichment of the basic Theory of Order Completion. In particular, spaces of generalized functions are constructed that contain generalized solutions to all systems of continuous, nonlinear ... More
Doping dependent optical properties of Bi2201Apr 15 2009An experimental study of the in-plane optical conductivity of (Pb$_{x}$,Bi$_{2-x}$)(La$_{y}$Sr$_{2-y}$)CuO$_{6+\delta}$ (Bi2201) is presented for a broad doping and temperature range. The in-plane conductivity is analyzed within a strong coupling formalism. ... More
Lithographic mechanical break junctions for single-molecule measurements in vacuum: possibilities and limitationsFeb 05 2008Jul 01 2008We have investigated electrical transport through the molecular model systems benzenedithiol, benzenediamine, hexanedithiol and hexanediamine. Conductance histograms under different experimental conditions indicate that measurements using mechanically ... More
Two-stage Kondo effect in a quantum dot at high magnetic fieldOct 20 2001We report a strong Kondo effect (Kondo temperature ~ 4K) at high magnetic field in a selective area growth semiconductor quantum dot. The Kondo effect is ascribed to a singlet-triplet transition in the ground state of the dot. At the transition, the low-temperature ... More
A nonparametric control chart based on the Mann-Whitney statisticMay 15 2008Nonparametric or distribution-free charts can be useful in statistical process control problems when there is limited or lack of knowledge about the underlying process distribution. In this paper, a phase II Shewhart-type chart is considered for location, ... More
Time-dependent R-matrix theory applied to two-photon double ionization of HeApr 25 2014We introduce a time-dependent R-matrix theory generalised to describe double ionization processes. The method is used to investigate two-photon double ionization of He by intense XUV laser radiation. We combine a detailed B-spline-based wavefunction description ... More
Symmetry condition in terms of Lie bracketsFeb 14 2008Feb 09 2009A passive orthonomic system of PDEs defines a submanifold in the corresponding jet manifold, coordinated by so called parametric derivatives. We restrict the total differential operators and the prolongation of an evolutionary vector field v to this submanifold. ... More
Initial value problems for quad equationsOct 04 2012We describe a method to construct well-posed initial value problems for not necessarily integrable equations on not necessarily simply connected quad-graphs. Although the method does not always provide a well-posed initial value problem (not all quad-graphs ... More
Printed Circuit Board Metal Powder Filters for Low Electron TemperaturesApr 11 2013Apr 17 2013We report the characterisation of printed circuit boards (PCB) metal powder filters and their influence on the effective electron temperature which is as low as 22 mK for a quantum dot in a silicon MOSFET structure in a dilution refrigerator. We investigate ... More
Kondo effect out of equilibrium in a mesoscopic deviceMar 07 2002Mar 15 2002We study the non-equilibrium regime of the Kondo effect in a quantum dot laterally coupled to a narrow wire. We observe a split Kondo resonance when a finite bias voltage is imposed across the wire. The splitting is attributed to the creation of a double-step ... More
Local Subspace-Based Outlier Detection using Global NeighbourhoodsNov 01 2016Outlier detection in high-dimensional data is a challenging yet important task, as it has applications in, e.g., fraud detection and quality control. State-of-the-art density-based algorithms perform well because they 1) take the local neighbourhoods ... More
Evolving the Structure of Evolution StrategiesOct 17 2016Various variants of the well known Covariance Matrix Adaptation Evolution Strategy (CMA-ES) have been proposed recently, which improve the empirical performance of the original algorithm by structural modifications. However, in practice it is often unclear ... More
Single-hole tunneling through a two-dimensional hole gas in intrinsic siliconApr 10 2013Apr 17 2013In this letter we report single-hole tunneling through a quantum dot in a two-dimensional hole gas, situated in a narrow-channel field-effect transistor in intrinsic silicon. Two layers of aluminum gate electrodes are defined on Si/SiO$_2$ using electron-beam ... More
Real-time, local spline interpolation schemes on bounded intervalsSep 19 2015Nov 30 2015We develop a local polynomial spline interpolation scheme for arbitrary spline order on bounded intervals. Our method's local formulation, effective boundary considerations and optimal interpolation error rate make it particularly useful for real-time ... More
Hard X-ray Lags in Cygnus X-1Nov 25 1997We have used the Fourier cross spectra of Cyg X-1, as obtained with BATSE during a period of almost 2000 days, to estimate the phase (or time) lags between X-ray flux variations in the 20-50 keV and the 50-100 keV bands as a function of Fourier frequency, ... More
Search For Rapid X-ray Variability from the Black-Hole Candidate GRO J1655-40Mar 27 1996We have examined fifteen days of CGRO/BATSE data, obtained during the first outburst of the black-hole candidate source GRO J1655-40, to search for rapid variability of its X-ray flux. We find no evidence for significant variability of GRO J1655-40 during ... More
Polarization of a Bose-Einstein Condensate of Photons in a Dye-Filled MicrocavityDec 22 2017We measure the polarization of a photon gas in a dye-filled microcavity. The polarization is obtained by a single-shot measurement of the Stokes parameters. We find that the polarization of both the thermal cloud and the Bose-Einstein condensate of photons ... More
Robust recipe for low-resistance ohmic contacts to a two-dimensional electron gas in a GaAs/AlGaAs heterostructureJul 17 2014The study of electron transport in low-dimensional systems is of importance, not only from a fundamental point of view, but also for future electronic and spintronic devices. In this context heterostructures containing a two-dimensional electron gas (2DEG) ... More
Optical probes of electron correlations in solidsJul 21 2008Classically the interaction between light and matter is given by the Maxwell relations. These are briefly reviewed and will be used as a basis to discuss several techniques that are used in optical spectroscopy. We then discuss the quantum mechanical ... More
Herschel/HIFI observations of spectrally resolved methylidyne signatures toward the high-mass star-forming core NGC6334IJul 09 2010Jul 27 2010In contrast to extensively studied dense star-forming cores, little is known about diffuse gas surrounding star-forming regions. We study molecular gas in the high-mass star-forming region NGC6334I, which contains diffuse, quiescent components that are ... More
First detection of ND in the solar-mass protostar IRAS16293-2422Jul 27 2010In the past decade, much progress has been made in characterising the processes leading to the enhanced deuterium fractionation observed in the ISM and in particular in the cold, dense parts of star forming regions such as protostellar envelopes. Very ... More
Electro-magnetic Aharonov-Bohm effect in a 2-D electron gas ringJul 23 2001We define a mesoscopic ring in a 2-dimensional electron gas (2DEG) interrupted by two tunnel barriers, enabling us to apply a well-defined potential difference between the two halves of the ring. The electron interference in the ring is modified using ... More
New insights into the electron trapping mechanism in LaAlO_3 / SrTiO3 heterostructuresFeb 20 2019In LaAlO3/SrTiO3 heterostructures, a commonly observed but poorly understood phenomenon is that of electron trapping in back-gating experiments. In this work, by combining magnetotransport measurements and self-consistent Schroedinger-Poisson calculations, ... More
Optimal weighting for false discovery rate controlJul 25 2008Jul 13 2009How to weigh the Benjamini-Hochberg procedure? In the context of multiple hypothesis testing, we propose a new step-wise procedure that controls the false discovery rate (FDR) and we prove it to be more powerful than any weighted Benjamini-Hochberg procedure. ... More
Application of Fractional Fourier Transform in Cepstrum AnalysisJun 04 2012Source wavelet estimation is the key in seismic signal processing for resolving subsurface structural properties. Homomorphic deconvolution using cepstrum analysis has been an effective method for wavelet estimation for decades. In general, the inverse ... More
C-axis optical properties of high Tc cupratesMar 09 2000A review is given of the experimental status of the interlayer coupling energy in the cuprates. A second c-axis plasmon is identified in the double layer compound Y123 for various dopings. The anomalous transport properties along the c-direction and in ... More
New evidence for a massive black hole at the centre of the quiescent galaxy M32Feb 12 1997Massive black holes are thought to reside at the centres of many galaxies, where they power quasars and active galactic nuclei. But most galaxies are quiescent, indicating that any central massive black hole present will be starved of fuel and therefore ... 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
The distribution of water in the high-mass star-forming region NGC 6334IJul 23 2010We present observations of twelve rotational transitions of H2O-16, H2O-18, and H2O-17 toward the massive star-forming region NGC 6334 I, carried out with Herschel/HIFI as part of the guaranteed time key program Chemical HErschel Surveys of Star forming ... More
Unitarity violation at the Wilson-Fisher fixed point in 4-epsilon dimensionsNov 30 2015Jun 01 2016We consider the continuation of free and interacting scalar field theory to non-integer spacetime dimension d. We find that the correlation functions in these theories are necessarily incompatible with unitarity (or with reflection positivity in Euclidean ... More