3,691 research outputs found
Mécanismes de Contrôle de la Réactivité d'un Réacteur Orgel de 250 MWe. EUR 4042. = Mechanisms for controlling the reactivity of an Orgel reactor of 250 MWe. EUR 4042.
Establishing National Ocean Service Priorities for Estuarine, Coastal, and Ocean Modeling: Capabilities, Gaps, and Preliminary Prioritization Factors
This report was developed to help establish National Ocean Service priorities and chart new directions for research and development of models for estuarine, coastal and ocean ecosystems based on user-driven requirements and supportive of sound coastal management, stewardship, and an ecosystem approach to management. (PDF contains 63 pages
Electroluminescence from a polythiophene molecular wire suspended in a plasmonic scanning tunneling microscope junction
The electroluminescence of a polythiophene wire suspended between two
metallic electrodes is probed using a scanning tunneling microscope. Under
positive sample voltage, the spectral and voltage dependencies of the emitted
light are consistent with the fluorescence of the wire junction mediated by
localized plasmons. This emission is strongly attenuated for the opposite
polarity. Both emission mechanism and polarity dependence are similar to what
occurs in organic light emitting diodes (OLED) but at the level of a single
molecular wire.Comment: to be published in Physical Review Letter
Performance Measures for Public Transport Accessibility: learning from international practice
There is a growing recognition by city policymakers that urban public transport systems can be developed in such a way that travelers can be offered an alternative to car-based travel. How to evolve the public transport system for this purpose is a significant challenge and raises questions of accessibility and quality largely absent from current planning evaluation. This paper explores the use of accessibility performance measures, both to assess the extent of current public transport accessibility and as a potential metric for future planning and investment. The Spatial Network Analysis for Multimodal Urban Transport Systems (SNAMUTS) tool is employed for analysis of accessibility. A sample of 21 international cities is assessed, representing a range of transport and land-use policy contexts from best to ordinary practice, including those held up as exemplars in public transport infrastructure, service planning, and delivery in Europe and North America. The findings show that the incidence of successful metropolitan public transport systems, as measured by patronage, can be linked to accessibility performance measures of network and service configurations
Optically Probing Spin and Charge Interactions in an Tunable Artificial Molecule
We optically probe and electrically control a single artificial molecule
containing a well defined number of electrons. Charge and spin dependent
inter-dot quantum couplings are probed optically by adding a single
electron-hole pair and detecting the emission from negatively charged exciton
states. Coulomb and Pauli blockade effects are directly observed and
hybridization and electrostatic charging energies are independently measured.
The inter-dot quantum coupling is confirmed to be mediated predominantly by
electron tunneling. Our results are in excellent accord with calculations that
provide a complete picture of negative excitons and few electron states in
quantum dot molecules.Comment: shortened version: 6 pages, 3 figures, 1 table, to appear in Phys.
Rev. Let
Pulling and Stretching a Molecular Wire to Tune its Conductance
A scanning tunnelling microscope is used to pull a polythiophene wire from a
Au(111) surface while measuring the current traversing the junction. Abrupt
current increases measured during the lifting procedure are associated to the
detachment of molecular sub-units, in apparent contradiction with the expected
exponential decrease of the conductance with wire length. \textit{Ab initio}
simulations reproduce the experimental data and demonstrate that this
unexpected behavior is due to release of mechanical stress in the wire, paving
the way to mechanically gated single-molecule electronic devices
Damping of plasmons of closely coupled sphere chains due to disordered gaps
The damping of plasmons due to structural disorder may have important practical consequences. Here, we use spherical harmonic expansions to quantify the damping of plasmons of ensembles of closely coupled sphere chains with moderately disordered gaps. We show that the quadratic shift of average resonance position due to disorder is maintained in the transition from weak to close coupling, but the sensitivity to disorder increases. Further, we find that although the main peak is most often damped and broadened by disorder, it is possible for the optical extinction of disordered gold chains to increase slightly due to red-skew into a region with more favorable metal properties. © 2011 American Chemical Society
Data-Efficient Iterative Training of Gaussian Approximation Potentials: Application to Surface Structure Determination of Rutile IrO<sub>2</sub> and RuO<sub>2</sub>
Machine-learning interatomic potentials like Gaussian Approximation Potentials (GAPs) constitute a powerful class of surrogate models to computationally involved first-principles calculations. At similar predictive quality but significantly reduced cost, they could leverage otherwise barely tractable extensive sampling as in global surface structure determination (SSD). This efficiency is jeopardized though, if an a priori unknown structural and chemical search space as in SSD requires an excessive number of first-principles data for the GAP training.To this end, we present a general and data-efficient iterative training protocol that blends the creation of new training data with the actual surface exploration process. Demonstrating this protocol with the SSD of low-index facets of rutile IrO2 and RuO2 , the involved simulated annealing on the basis of the refining GAP identifies a number of unknown terminations even in the restricted sub-space of (1×1) surface unit-cells. Especially in an O-poor environment, some of these, then metal-rich terminations, are thermodynamically most stable and are reminiscent of complexions as discussed for complex ceramic materials
Childhood-onset Mental Disorders in 6 geographical regions in China: A Systematic Review and Meta-analysis on Attention Deficit Hyperactivity Disorder, Conduct Disorder, Autism Spectrum Disorder, and Autistic Disorder
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