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51.
Belkacem Benmerad Achoura Guehria‐Laidoudi Fadila Balegroune Henrik Birkedal Gervais Chapuis 《Acta Crystallographica. Section C, Structural Chemistry》2000,56(7):789-792
The structure of the title compound, [La(C5H6O4)(C5H7O4)‐(H2O)]·H2O, consists of dense layers formed by chains of one‐edge‐sharing LaO9(H2O) polyhedra, linked together by the glutarate ligand. The three‐dimensional polymeric structure, built up through connection of these layers by the hydrogen glutarate ligand, exhibits cavities accommodating a guest water molecule. The lanthanum ion is tenfold coordinated by four glutarates, acting as bridging–chelating carboxylate groups, by three hydrogen glutarates, three times monodentate, and by one water molecule. Its coordination polyhedron is highly distorted and intermediate between a bicapped dodecahedron and a tetracapped trigonal prism. Hydrogen bonding links the two water molecules and the framework built up from this polynuclear coordination polymer. A very short hydrogen bond, D?A = 2.484 (3) Å, links the protonated with the deprotonated acid groups in the hydrogen glutarate. 相似文献
52.
Gervais B Giglio E Jacquet E Ipatov A Reinhard PG Suraud E 《The Journal of chemical physics》2004,121(17):8466-8480
We present a theoretical model to study the dynamics of metallic clusters embedded in a rare gas matrix. We describe the active electrons of the embedded cluster using time dependent density functional theory, while the surrounding matrix is described in terms of classical molecular dynamics of polarizable atoms. The coupling between the cluster and the rare gas atoms is deduced from the work of Gross and Spiegelmann [J. Chem. Phys. 108, 4148 (1998)] and reformulated explicitly in a simple and efficient density functional form. The electron rare gas interaction takes the form of an averaged dipole fluctuation term, which retains the van der Waals long range interaction, and a short range repulsive pseudopotential, which accounts for the Pauli repulsion of the electron by the rare gas atom. We applied our model to Na clusters embedded in Ar matrix. For the latter we developed an efficient local pseudopotential, which allows studying systems containing more than 10(3) Ar atoms. We show that large systems are indeed necessary to account properly for long range polarization of the matrix, that competes with the matrix confinement effect. We focus our study on Na(2), Na(4), and Na(8). For each system, we have determined the geometry of the most favorable trapping site by means of damped molecular dynamics. We present the effect of matrix embedding on the optical absorption spectrum. For Na(2), the trapping site can be unambiguously identified by comparison of the absorption spectrum with experiment. For Na(4) the spectrum of the embedded cluster is significantly different from the free cluster spectrum, while for Na(8) differences are less pronounced. 相似文献
53.
Jamila El Jabri Solange De Lauzon Nicole Cittanova Patrice Gervais Jacques Mugnier Jacques Pouget Bernard Valeur 《Analytica chimica acta》1989
A small, highly sensitive, inexpensive fluorimeter for the detection of very low fluorescence intensities for analytical and clinical purposes is described. High sensitivity is achieved by use of an inexpensive continuous wave laser with a power of a few milliwatts. The optical arrangement of the instrument has been thoroughly designed so that the effects of Rayleigh and Raman scattering are minimized. Fluorescence is dected through optical filters with a side-on photomultiplier. Concentrations of rhodamine B in ethanol as low as 10?11 M can be measured. To use this instrument for a fluoroimmunoassay of urinary estrogens (10?9?10?7 M), a purified monoclonal IgG, raised against estradiol, was labelled with RITC (rhodamine isothiocyanate) in a 1:1 molar ratio. It was possible to measure IgG-RITC concentrations between 10?9 and 10?10 M with good accuracy and reproducibility. 相似文献
54.
Sylviane Sabo Bruno Chaudret Daniele Gervais 《Journal of organometallic chemistry》1983,255(1):C19-C22
Reactions of NaMn(CO)3 with RuCl2(PMe3)4, RuCl2(dppm)2 and RuCl2(PPh3)3 lead either to an ionic species [Ru2Cl3(PMe3)6]+[Mn(CO)5]? or to metal—metal bonded RuMn compounds such as RuMn(μ-CO)2(CO)3(μ-dppm)2 Cl, and, quite unexpectedly, to the μ-phosphido complex RuMn(μ-PPh2)(CO)6(PPh3)2 via a hydride intermediate. 相似文献
55.
A P.I.V. instrument using two synchronized CCD video cameras is described. The same field of view is imaged onto each CCD
array with an image splitter and one imaging lens. The delay between two exposures can be adjusted from 0.5 to 20 ms depending
on the flow velocity to be measured.
Received: 12 February 1999/Accepted: 20 March 1999 相似文献
56.
We describe the quantum-group structure of two-dimensionalN=1 supergravity in the conformal gauge. The operator-algebra of this (super-Liouville) theory is shown to correspond to a quantum deformation of the super-Möbius group, which provides a new solution of Yang and Baxter's equation. This structure is used to investigate the strong-coupling regime of the theory (1d9). Ford=5, a unitary truncation theorem-similar to the one of the bosonic case-is derived for the fundamental representation.Unité Propre du Centre National de la Recherche Scientifique, associée à l'École Normale Supérieure et à l'Université de Paris-Sud 相似文献
57.
58.
Ali Shahverdi Keun Su Kim Yasaman Alinejad Gervais Soucy 《Journal of nanoparticle research》2012,14(2):660-10
A simple, cost-effective and energy-efficient approach was developed for in situ purity enhancement and surface modification of single-walled carbon nanotubes (SWCNTs) produced using an induction thermal plasma process. In this process, SWCNT-containing materials are thermally treated with oxygen flow inside a filtration chamber, while they are assembled into the sheets during the synthesis process. Owing to selective thermal oxidation, the amount of amorphous carbon was significantly reduced in the final product resulting in higher purity SWCNT-containing materials. Parametric study indicated that the amorphous carbon content was noticeably diminished in the product at an oxygen volume concentration of 10% in the synthesis system. Raman analysis indicated a decrease in the population of the SWCNTs with diameters smaller than 1.3 nm after in situ exposure to 10 vol.% of oxygen. In addition to the successful reduction of amorphous carbon content, the oxygen-functionalized SWCNTs were also observed in the final product using this process. 相似文献
59.
S. Krohns J. Lu P. Lunkenheimer V. Brizé C. Autret-Lambert M. Gervais F. Gervais F. Bourée F. Porcher A. Loidl 《The European Physical Journal B - Condensed Matter and Complex Systems》2009,72(2):173-182
The present work reports synthesis, as well as a detailed and careful characterization of structural, magnetic, and dielectric properties of differently tempered undoped and doped CaCu3Ti4O12 (CCTO) ceramics. For this purpose, neutron and X-ray powder diffraction, SQUID measurements, and dielectric spectroscopy have been performed. Mn-, Fe-, and Ni-doped CCTO ceramics were investigated in great detail to document the influence of low-level doping with 3d metals on the antiferromagnetic structure and dielectric properties. In the light of possible magnetoelectric coupling in these doped ceramics, the dielectric measurements were also carried out in external magnetic fields up to 7 T. At low temperatures the dielectric constant shows a minor but significant dependence on the applied magnetic field. Undoped CCTO is well-known for its colossal dielectric constant in a broad frequency and temperature range. With the present extended characterization of doped as well as undoped CCTO, we want to address the question why doping with only 1% Mn or 0.5% Fe decreases the room-temperature dielectric constant of CCTO by a factor of ~100 with a concomitant reduction of the conductivity, whereas 0.5% Ni doping changes the dielectric properties only slightly. In addition, diffraction experiments and magnetic investigations were undertaken to check for possible correlations of the magnitude of the colossal dielectric constants with structural details or with magnetic properties like the magnetic ordering, the Curie-Weiss temperatures, or the paramagnetic moment. It is revealed, that while the magnetic ordering temperature and the effective moment of all investigated CCTO ceramics are rather similar, there is a dramatic influence of doping and tempering time on the Curie-Weiss constant. 相似文献
60.
Sylvain Gervais 《Transactions of the American Mathematical Society》1996,348(8):3097-3132
We give a presentation of the mapping class group of a (possibly bounded) surface, considering either all twists or just non-separating twists as generators. We also study certain central extensions of . One of them plays a key role in studying TQFT functors, namely the mapping class group of a -structure surface. We give a presentation of this extension.