803 research outputs found
The French State and Nautical Cartography
The following paper was presented as the inaugural address at the 12th International Congress of Cartography (Paris, 7-10 September 1987). It opens with general views on the connections between the nautical chart and the Administration, then gives a general idea of the strong relationship in France between the State and nautical cartography before concluding with the main reasons for the continued existence of this connection
Analysis of Multijunction solar cells: Electroluminescence study
This paper describes the principle of the study which is based on electroluminescence to extract the parameters characterizing the recombination centers induced by irradiation in a solar cell. This technique is able to provide direct information on each individual junction constituting the multijonctions. The results are compared with those obtained by electrical methods.This paper describes the principle of the study which is based on electroluminescence to extract the parameters characterizing the recombination centers induced by irradiation in a solar cell. This technique is able to provide direct information on each individual junction constituting the multijonctions. The results are compared with those obtained by electrical methods
Electron transport through a metal-molecule-metal junction
Molecules of bisthiolterthiophene have been adsorbed on the two facing gold
electrodes of a mechanically controllable break junction in order to form
metal-molecule(s)-metal junctions. Current-voltage (I-V) characteristics have
been recorded at room temperature. Zero bias conductances were measured in the
10-100 nS range and different kinds of non-linear I-V curves with step-like
features were reproducibly obtained. Switching between different kinds of I-V
curves could be induced by varying the distance between the two metallic
electrodes. The experimental results are discussed within the framework of
tunneling transport models explicitly taking into account the discrete nature
of the electronic spectrum of the molecule.Comment: 12 pages, 12 figures to appear in Phys. Rev. B 59(19) 199
First-principles calculation of intrinsic defect formation volumes in silicon
We present an extensive first-principles study of the pressure dependence of
the formation enthalpies of all the know vacancy and self-interstitial
configurations in silicon, in each charge state from -2 through +2. The neutral
vacancy is found to have a formation volume that varies markedly with pressure,
leading to a remarkably large negative value (-0.68 atomic volumes) for the
zero-pressure formation volume of a Frenkel pair (V + I). The interaction of
volume and charge was examined, leading to pressure--Fermi level stability
diagrams of the defects. Finally, we quantify the anisotropic nature of the
lattice relaxation around the neutral defects.Comment: 9 pages, 9 figure
Targeting the Metabolism and Receptors of Sphingosine-1- Phosphate for the Treatment of Rheumatoid Arthritis
Electron transport through rectifying self-assembled monolayer diodes on silicon: Fermi level pinning at the molecule-metal interface
We report the synthesis and characterization of molecular rectifying diodes
on silicon using sequential grafting of self-assembled monolayers of alkyl
chains bearing a pi group at their outer end (Si/sigma-pi/metal junctions). We
investigate the structure-performance relationships of these molecular devices
and we examine to what extent the nature of the pi end-group (change in the
energy position of their molecular orbitals) drives the properties of these
molecular diodes. For all the pi-groups investigated here, we observe
rectification behavior. These results extend our preliminary work using phenyl
and thiophene groups (S. Lenfant et al., Nano Letters 3, 741 (2003)).The
experimental current-voltage curves are analyzed with a simple analytical
model, from which we extract the energy position of the molecular orbital of
the pi-group in resonance with the Fermi energy of the electrodes. We report
the experimental studies of the band lineup in these silicon/alkyl-pi
conjugated molecule/metal junctions. We conclude that Fermi level pinning at
the pi-group/metal interface is mainly responsible for the observed absence of
dependence of the rectification effect on the nature of the pi-groups, even
though they were chosen to have significant variations in their electronic
molecular orbitalsComment: To be published in J. Phys. Chem.
Turbulent transport of material particles: An experimental study of finite size effects
We use an acoustic Lagrangian tracking technique, particularly adapted to
measurements in open flows, and a versatile material particles generator (in
the form of soap bubbles with adjustable size and density) to characterize
Lagrangian statistics of finite sized, neutrally bouyant, particles transported
in an isotropic turbulent flow of air. We vary the size of the particles in a
range corresponding to turbulent inertial scales and explore how the turbulent
forcing experienced by the particles depends on their size. We show that, while
the global shape of the intermittent acceleration probability density function
does not depend significantly on particle size, the acceleration variance of
the particles decreases as they become larger in agreement with the classical
scaling for the spectrum of Eulerian pressure fluctuations in the carrier flow
Ionizationâenhanced diffusion: Ion implantation in semiconductors
A model for the diffusion of implanted interstitials during implantation is introduced and shown to be able to account for the tails observed in ion profiles. It is argued that mechanisms of ionizationâenhanced diffusion can explain some of the anomalous diffusion mechanisms observed in semiconductors. Indications for the existence of such mechanisms in the field of ion implantation in semiconductors are discussed
- âŠ