1,990 research outputs found
Generating Entangled Microwave Radiation Over Two Transmission Lines
Using a superconducting circuit, the Josephson mixer, we demonstrate the
first experimental realization of spatially separated two-mode squeezed states
of microwave light. Driven by a pump tone, a first Josephson mixer generates,
out of quantum vacuum, a pair of entangled fields at different frequencies on
separate transmission lines. A second mixer, driven by a -phase shifted
copy of the first pump tone, recombines and disentangles the two fields. The
resulting output noise level is measured to be lower than for vacuum state at
the input of the second mixer, an unambiguous proof of entanglement. Moreover,
the output noise level provides a direct, quantitative measure of entanglement,
leading here to the demonstration of 6 Mebit.s (Mega entangled bits per
second) generated by the first mixer.Comment: 5 pages, 4 figures. Supplementary Information can be found here as an
ancillary fil
Viriato: a Fourier-Hermite spectral code for strongly magnetised fluid-kinetic plasma dynamics
We report on the algorithms and numerical methods used in Viriato, a novel
fluid-kinetic code that solves two distinct sets of equations: (i) the Kinetic
Reduced Electron Heating Model (KREHM) equations [Zocco & Schekochihin, Phys.
Plasmas 18, 102309 (2011)] (which reduce to the standard Reduced-MHD equations
in the appropriate limit) and (ii) the kinetic reduced MHD (KRMHD) equations
[Schekochihin et al., Astrophys. J. Suppl. 182:310 (2009)]. Two main
applications of these equations are magnetised (Alfvenic) plasma turbulence and
magnetic reconnection. Viriato uses operator splitting (Strang or Godunov) to
separate the dynamics parallel and perpendicular to the ambient magnetic field
(assumed strong). Along the magnetic field, Viriato allows for either a
second-order accurate MacCormack method or, for higher accuracy, a
spectral-like scheme composed of the combination of a total variation
diminishing (TVD) third order Runge-Kutta method for the time derivative with a
7th order upwind scheme for the fluxes. Perpendicular to the field Viriato is
pseudo-spectral, and the time integration is performed by means of an iterative
predictor-corrector scheme. In addition, a distinctive feature of Viriato is
its spectral representation of the parallel velocity-space dependence, achieved
by means of a Hermite representation of the perturbed distribution function. A
series of linear and nonlinear benchmarks and tests are presented, including a
detailed analysis of 2D and 3D Orszag-Tang-type decaying turbulence, both in
fluid and kinetic regimes.Comment: 42 pages, 15 figures, submitted to J. Comp. Phy
Diagnostic accuracy of a brief screening tool forAttention Deficit/Hyperactivity Disorder in UK prison inmates
BackgroundAttention deficit hyperactivity disorder (ADHD) is overrepresented in prison, making it imperative to identify a screening tool that can be quickly applied to efficiently detect the disorder. We explored the discrimination ability of a widely used ADHD screen, the Barkley Adult ADHD Rating Scale (BAARS-IV), against a clinical diagnostic interview. A brief version of the screen was then developed in order to simplify its use in the prison context, and maximize its diagnostic properties.MethodA cross-sectional study of 390 male prison inmates was performed in the UK, all participants were screened and interviewed via the Diagnostic Interview for ADHD in Adults 2.0 (DIVA-2).ResultsA total of 47 (12.1%) inmates screened positive for ADHD using the full BAARS-IV, and 96 (24.6%) were clinically diagnosed, for a sensitivity of 37.9 and a specificity of 96.3. Our models identified the six items that most predicted ADHD diagnosis, with adjusted odds ratios ranging from 2.66 to 4.58. Sensitivity, specificity and accuracy were 0.82, 0.84 and 0.84, respectively, for the developed brief scale, and 0.71, 0.85 and 0.81 for its validation. Weighted probability scores produced an area under the curve of 0.89 for development, and 0.82 for validation of the brief scale.ConclusionsThe original BAARS-IV performed poorly at identifying prison inmates with ADHD. Our developed brief scale substantially improved diagnostic accuracy. The brief screening instrument has great potential to be used as an accurate and resource-effective tool to screen young people and adults for likely ADHD in the criminal justice system.</jats:sec
Thioglycolate de méthyle comme matière première pour la synthèse de beta-alcoxythiophènes
National audienc
Entrepreneurial orientation and firm performance in the context of upper echelon theory.
Entrepreneurial Orientation (EO) is a firm-level phenomenon, which
involves the firm’s prospects to take risks, be proactive, and be innovative.
Most of the research assumes a positive EO-performance relationship
adopting the EO-as-advantage perspective without providing enough
theoretical foundations of the way EO enhances performance. This paper
provides insights into the EO and firm performance relationship looking into
the EO-as-experimentation perspective. Through EO-as-experimentation
perspective, we argue for the importance of looking into the differential
effects of each of the EO dimensions on firm performance in active and
inactive firms. We hypothesized that the effect of each of the proactiveness
and innovativeness dimension of EO on firm performance is positive among
active firms and negative among inactive firms. Whereas risk taking
dimension of EO is negative among active and inactive firms. Based on the
results of firm fixed effect regression some empirical support for the
hypotheses is presented and discussed
Incorporating independent component analysis and multi-temporal sar techniques to retrieve rapid postseismic deformation
This study investigates the ongoing postseismic deformation induced by two moderate mainshocks of Mw 6.1 and Mw 6.0, 2017 Hojedk earthquake in Southern Iran. Available Sentinel-1 TOPS C-band Synthetic Aperture Radar (SAR) images over about one year after the earthquakes are used to analyze the postseismic activities. An adaptive method incorporating Independent Component Analysis (ICA) and multi-Temporal Small BAseline Subset (SBAS) Interferometric SAR (InSAR) techniques is proposed and implemented to recover the rapid deformation. This method is applied to the series of interferograms generated in a fully constructed SBAS network to retrieve the postseismic deformation signal. ICA algorithm uses a linear transformation to decompose the input mixed signal to its source components, which are non-Gaussian and mutually independent. This analysis allows extracting the low rate postseismic deformation signal from a mixture of interferometric phase components. The independent sources recovered from the multi-Temporal InSAR dataset are then analyzed using a group clustering test aiming to identify and enhance the undescribed deformation signal. Analysis of the processed interferograms indicates a promising performance of the proposed method in determining tectonic deformation. The proposed method works well, mainly when the tectonic signal is dominated by the undesired signals, including atmosphere or orbital/unwrapping noise that counts as temporally uncorrelated components.In contrast to the standard SBAS time series method, the ICA-based time series analysis estimates the cumulative deformation with no prior assumption about elevation dependence of the interferometric phase or temporal nature of the tectonic signal. Application of the method to 433 Sentinel-1 pairs within the dataset reports two distinct deformation patches corresponding to the postseismic deformation. Besides the performance of the ICA-based analysis, the proposed method automatically detects rapid or low rate tectonic processes in unfavorable conditions. © Authors 2020. All rights reserved
Single 3 transition metal atoms on multi-layer graphene systems: electronic configurations, bonding mechanisms and role of the substrate
The electronic configurations of Fe, Co, Ni, and Cu adatoms on graphene and
graphite have been studied by x-ray magnetic circular dichroism and charge
transfer multiplet theory. A delicate interplay between long-range interactions
and local chemical bonding is found to influence the adatom equilibrium
distance and magnetic moment. The results for Fe and Co are consistent with
purely physisorbed species having, however, different 3-shell occupancies on
graphene and graphite ( and , respectively). On the other hand,
for the late 3 metals Ni and Cu a trend towards chemisorption is found,
which strongly quenches the magnetic moment on both substrates.Comment: 7 pages, 4 figure
Using Spontaneous Emission of a Qubit as a Resource for Feedback Control
Persistent control of a transmon qubit is performed by a feedback protocol
based on continuous heterodyne measurement of its fluorescence. By driving the
qubit and cavity with microwave signals whose amplitudes depend linearly on the
instantaneous values of the quadratures of the measured fluorescence field, we
show that it is possible to stabilize permanently the qubit in any targeted
state. Using a Josephson mixer as a phase-preserving amplifier, it was possible
to reach a total measurement efficiency =35%, leading to a maximum of 59%
of excitation and 44% of coherence for the stabilized states. The experiment
demonstrates multiple-input multiple-output analog Markovian feedback in the
quantum regime.Comment: Supplementary material can be found as an ancillary objec
Müllerian mimicry of a quantitative trait despite contrasting levels of genomic divergence and selection
Hybrid zones, where distinct populations meet and interbreed, give insight into how differences between populations are maintained despite gene flow. Studying clines in genetic loci and adaptive traits across hybrid zones is a powerful method for understanding how selection drives differentiation within a single species, but can also be used to compare parallel divergence in different species responding to a common selective pressure. Here, we study parallel divergence of wing colouration in the butterflies Heliconius erato and H. melpomene , which are distantly related Müllerian mimics which show parallel geographic variation in both discrete variation in pigmentation, and quantitative variation in structural colour. Using geographic cline analysis, we show that clines in these traits are positioned in roughly the same geographic region for both species, which is consistent with direct selection for mimicry. However, the width of the clines varies markedly between species. This difference is explained in part by variation in the strength of selection acting on colour traits within each species, but may also be influenced by differences in the dispersal rate and total strength of selection against hybrids between the species. Genotyping‐by‐sequencing also revealed weaker population structure in H. melpomene , suggesting the hybrid zones may have evolved differently in each species, which may also contribute to the patterns of phenotypic divergence in this system. Overall, we conclude that multiple factors are needed to explain patterns of clinal variation within and between these species, although mimicry has probably played a central role
Electronic structure of epitaxial graphene layers on SiC: effect of the substrate
Recent transport measurements on thin graphite films grown on SiC show large
coherence lengths and anomalous integer quantum Hall effects expected for
isolated graphene sheets. This is the case eventhough the layer-substrate
epitaxy of these films implies a strong interface bond that should induce
perturbations in the graphene electronic structure. Our DFT calculations
confirm this strong substrate-graphite bond in the first adsorbed carbon layer
that prevents any graphitic electronic properties for this layer. However, the
graphitic nature of the film is recovered by the second and third absorbed
layers. This effect is seen in both the (0001)and 4H SiC
surfaces. We also present evidence of a charge transfer that depends on the
interface geometry. It causes the graphene to be doped and gives rise to a gap
opening at the Dirac point after 3 carbon layers are deposited in agreement
with recent ARPES experiments (T.Ohta et al, Science {\bf 313} (2006) 951)
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