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
Astronomical imaging Fourier spectroscopy at far-infrared wavelengthsMar 25 2013May 02 2013The principles and practice of astronomical imaging Fourier transform spectroscopy (FTS) at far-infrared wavelengths are described. The Mach-Zehnder interferometer design has been widely adopted for current and future imaging FTS instruments; we compare ... 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
Resolved images of a protostellar outflow launched by an extended disk windDec 15 2016Young stars are associated with prominent outflows of molecular gas. The ejection of gas via these outflows is believed to remove angular momentum from the protostellar system, thus permitting young stars to grow by accretion of material from the protostellar ... 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
Far-infrared to millimeter data of protoplanetary disks: dust growth in the Taurus, Ophiuchus, and Chamaeleon I star-forming regionsOct 23 2017Far-infrared and (sub)millimeter fluxes can be used to study dust in protoplanetary disks, the building blocks of planets. Here, we combine observations from the Herschel Space Observatory with ancillary data of 284 protoplanetary disks in the Taurus, ... More
Evidence for the start of planet formation in a young circumstellar diskJun 25 2018The growth of dust grains in protoplanetary disks is a necessary first step towards planet formation. This growth has been inferred via observations of thermal dust emission towards mature protoplanetary systems (age >2 million years) with masses that ... 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
The ALMA-PILS survey: The sulphur connection between protostars and comets: IRAS 16293-2422 B and 67P/Churyumov-GerasimenkoFeb 08 2018Feb 21 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
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
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
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
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
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
A thorough view of the nuclear region of NGC 253 - Combined Herschel, SOFIA and APEX datasetApr 29 2018Jun 12 2018We present a large set of spectral lines detected in the $40"$ central region of the starburst galaxy NGC 253. Observations were obtained with the three instruments SPIRE, PACS and HIFI on board the Herschel Space Observatory, upGREAT on board of the ... 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: Complex nitriles towards IRAS 16293--2422Apr 24 2018Complex organic molecules are readily detected in the inner regions of the gaseous envelopes of forming protostars. In particular, molecules that contain nitrogen are interesting due to the role nitrogen plays in the development of life and the compact ... 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
Quantum gravitational corrections to the inflationary power spectra in scalar-tensor theoriesApr 29 2019We derive the first quantum gravitational corrections to the inflationary power spectra for a general single-field scalar-tensor theory which includes a non-minimal coupling to gravity, a non-standard scalar kinetic term and an arbitrary potential of ... 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
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
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
The ALMA-PILS survey: Formaldehyde deuteration in warm gas on small scales toward IRAS 16293-2422 BNov 15 2017[abridged] The enhanced degrees of deuterium fractionation observed in envelopes around protostars demonstrate the importance of chemistry at low temperatures, relevant in pre- and protostellar cores. formaldehyde is an important species in the formation ... More
Quantum gravitational corrections from the Wheeler-DeWitt equation for scalar-tensor theoriesDec 22 2017Jul 11 2018We perform the canonical quantization of a general scalar-tensor theory and derive the first quantum gravitational corrections following from a semi-classical expansion of the Wheeler-DeWitt equation. The non-minimal coupling of the scalar field to gravity ... 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
The ALMA-PILS survey: 3D modeling of the envelope, disks and dust filament of IRAS 16293-2422Dec 19 2017Dec 21 2017Context. The Class 0 protostellar binary IRAS 16293-2422 is an interesting target for (sub)millimeter observations due to, both, the rich chemistry toward the two main components of the binary and its complex morphology. Its proximity to Earth allows ... More
The ALMA-PILS survey: Gas dynamics in IRAS 16293$-$2422 and the connection between its two protostarsMar 29 2019[Abridged] The majority of stars form in binary or higher order systems. The Class 0 protostellar system IRAS16293-2422 contains two protostars, 'A' and 'B', separated by ~600 au and embedded in a single, 10^4 au scale envelope. Their relative evolutionary ... More
Signatures of warm carbon monoxide in protoplanetary discs observed with Herschel SPIREAug 22 2014Molecular gas constitutes the dominant mass component of protoplanetary discs. To date, these sources have not been studied comprehensively at the longest far-infrared and shortest submillimetre wavelengths. This paper presents Herschel SPIRE FTS spectroscopic ... More
The ALMA-PILS survey: The first detection of doubly-deuterated methyl formate (CHD2OCHO) in the ISMNov 22 2018Studies of deuterated isotopologues of complex organic molecules can provide important constraints on their origin in regions of star formation. In particular, the abundances of deuterated species are very sensitive to the physical conditions in the environment ... More
Correlation between Superconductivity, Band Filling and Electron Confinement at the LaAlO$_{3}$-SrTiO$_{3}$ InterfaceJan 09 2018May 24 2018By combined top- and backgating, we explore the correlation of superconductivity with band filling and electron confinement at the LaAlO$_3$-SrTiO$_3$ interface. We find that the top- and backgate voltages have distinctly different effects on the superconducting ... 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
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
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
Bridging the Gap: 3D Real-Space Characterization of Colloidal Assemblies via FIB-SEM TomographyMar 24 2019Insight in the structure of nanoparticle assemblies up to a single particle level is key to understand the collective properties of these assemblies, which critically depend on the individual particle positions and orientations. However, the characterization ... 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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
Charge transport in nanoscale vertical organic semiconductor pillar devicesJan 13 2017We report charge transport measurements in nanoscale vertical pillar structures incorporating ultrathin layers of the organic semiconductor poly(3-hexylthiophene)(P3HT). P3HT layers with thickness down to 5 nm are gently top-contacted using wedging transfer, ... 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
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
Charge Mobility and Dynamics in Spin-crossover Nanoparticles studied by Time-Resolved Microwave ConductivityMar 02 2018We use the electrode-less time-resolved microwave conductivity (TRMC) technique to characterize spin-crossover (SCO) nanoparticles. We show that TRMC is a simple and accurate mean for simultaneously as-sessing the magnetic state of SCO compounds and charge ... 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
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
Improved high-dimensional prediction with Random Forests by the use of co-dataJun 02 2017Prediction in high dimensional settings is difficult due to large by number of variables relative to the sample size. We demonstrate how auxiliary "co-data" can be used to improve the performance of a Random Forest in such a setting. Co-data are incorporated ... 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
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
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
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
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
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
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
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
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
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
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
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
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
Proposal for an analog Schwarzschild black hole in condensates of lightMay 31 2018Mar 26 2019By etching a hole in the mirrors or by placing a scatterer in the center of a cavity, we can create a sink for light. In a Bose-Einstein condensate of photons this sink results in the creation of a so-called radial vortex, which is a two-dimensional analogue ... 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
Interpretable multiclass classification by MDL-based rule listsMay 01 2019Interpretable classifiers have recently witnessed an increase in attention from the data mining community because they are inherently easier to understand and explain than their more complex counterparts. Examples of interpretable classification models ... More
Analogue Schwarzschild Black Hole in Condensates of LightMay 31 2018By etching a hole in the mirrors or by placing a scatterer in the center of the cavity, we can create a sink for light. In a Bose-Einstein condensate of photons this sink results in the creation of a so-called radial vortex, which is in fact a two-dimensional ... 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