Conservatoire national des arts et métiers

About: Conservatoire national des arts et métiers is a education organization based out in Paris, France. It is known for research contribution in the topics: Population & Context (language use). The organization has 3573 authors who have published 7127 publications receiving 141430 citations. The organization is also known as: CNAM & Conservatoire des arts et métiers.

Ocean tide loading (OTL) displacements from global and local grids: comparisons to GPS estimates over the shelf of Brittany, France

Abstract: In this paper we examine OTL displacements detected by GPS stations of a dedicated campaign and validate ocean tide models. Our area of study is the continental shelf of Brittany and Cotentin in France. Brittany is one of the few places in the world where tides provoke loading displacements of ∼10-12 cm vertically and a few cm horizontally. Ocean tide models suffer from important discrepancies in this region. Seven global and regional ocean tide models were tested: FES2004 corrected for K2, TPXO.7.0, TPXO.6.2, GOT00.2, CSR4.0, NAO.99b and the most recent regional grids of the North East Atlantic (NEA2004). These gridded amplitudes and phases of ocean tides were convolved in order to get the predicted OTL displacements using two different algorithms. Data over a period of 3.5 months of 8 GPS campaign stations located on the north coast of Brittany are used, in order to evaluate the geographical distribution of the OTL effect. We have modified and implemented new algorithms in our GPS software, GINS 7.1. GPS OTL constituents are estimated based on 1-day batch solutions. We compare the observed GPS OTL constituents of M2, S2, N2 and K1 waves with the selected ocean tide models on global and regional grids. Large phase-lag and amplitude discrepancies over 20° and 1.5 cm in the vertical direction in the semi-diurnal band of M2 between predictions and GPS/models are detected in the Bay of Mont St-Michel. From a least squares spectral analysis of the GPS time-series, significant harmonic peaks in the integer multiples of the orbital periods of the GPS satellites are observed, indicating the existence of multipath effects in the GPS OTL constituents. The GPS OTL observations agree best with FES2004, NEA2004, GOT00.2 and CSR4.0 tide models.

Lanthanum(III) and gadolinium(III) separation by cloud point extraction.

Abstract: In the present study, cloud point extraction (CPE) is used with lipophilic chelating agents, 8-hydroxyquinoline (HQ) and Kelex 100 (K100), to extract and separate lanthanum(III) and gadolinium(III) from aqueous solutions. The methodology used is based on the formation of lanthanide(III) organic complexes that are soluble in a micellar phase of a non-ionic surfactant, Triton X-114. The lanthanide(III) complexes are then extracted into the surfactant-rich phase at a temperature above the cloud-point temperature. Influence of pH of the solution, structure of the chelating agent, chelating agent/lanthanides(III) molar ratio, on extraction efficiency and selectivity is studied. High extraction efficiency and selectivity for Gd(III) is observed using HQ whereas K100 is a poor extractant. By pH switching, yields of Gd(III) recovery higher than 95% were obtained with selectivity factors up to 37 against La(III), indicating the feasibility of separating Gd(III) from La(III) using CPE.

Limitations of Long-Term Stability in a Coherent Population Trapping Cs Clock

Abstract: Vapor cell atomic clocks exhibit reduced frequency stability for averaging time between about one hundred and a few thousand seconds. Here we report a study on the impact of the main parameters on the mid-to-long term instability of a buffer-gas vapor cell Cs clock, based on coherent population trapping (CPT). The CPT signal is observed on the Cs $D1$ line transmission, using a double $\Lambda$ scheme and a Ramsey interrogation technique. The effects on the clock frequency of the magnetic field, the cell temperature, and the laser intensities are reported. We show in particular that the laser intensity shift is temperature dependent. Along with the laser intensity ratio and laser polarization properties, this is one of the most important parameters.

Ion-responsive fluorescent compounds - V. Photophysical and complexing properties of coumarin 343 linked to monoaza-15-crown-5

Abstract: The photophysical and complexing properties of a fluoroionophore consisting of coumarin 343 linked to monoaza-15-crown-5 are reported in acetonitrile and ethanol. The amide link between the coumarin and the crown precludes pH sensitivity of the tertiary amine bridging group. Upon complexation by calcium and magnesium cations, the photophysical properties undergo marked changes, whereas the effects are insignificant or very weak with alkali metal ions. I.R. spectra were recorded in deuterated acetonitrile in order to unravel the participation of the carbonyl groups in the complexation. The stoichiometry of the complexes is 1:1 apart from the case of complexation with calcium in acetonitrile where two complexes can be formed. The stability constants of the complexes were determined in acetonitrile and ethanol.

Response of CsI(Tl) scintillators over a large range in energy and atomic number of ions. Part II: calibration and identification in the INDRA array

Abstract: The light output of the 324 CsI(Tl) scintillators of INDRA has been measured over large ranges in energy: 1– 80 AMeV and in atomic number of incident ions: Z =1–60. An analytical expression for the non-linear total light response as a function of the energy and the identity of the ion is developed. It depends on four parameters. For three of them, connected to CsI(Tl) intrinsic characteristics, fixed values are proposed. Two applications are presented: energy calibration and fragment identification in telescopes using a CsI(Tl) crystal as residual energy detector.