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81.
Herein we describe the catalytic activity of 1, a well-defined Re alkylidene complex supported silica, in the reaction of olefin metathesis. This system is highly active for terminal and internal olefins with initial rates up to 0.7 mol per mol Re per s. It also catalyses the self-metathesis of methyl oleate (MO) without the need of co-catalysts. The turnover numbers can reach up to 900 for MO, which is unprecedented for a heterogeneous Re-based catalyst. Moreover the use of silica as a support can bring major advantages, such as the possibility to use branched olefins like isobutene, which are usually incompatible with alumina-based supports; therefore, the formation of isoamylene from the cross-metathesis of propene and isobutene can be performed. All these results are in sharp contrast to what has been found for other silica- or alumina-supported rhenium oxide systems, which are either completely inactive (silica system) or typically need co-catalysts when functionalised olefins are used. Finally the initiation step corresponds to a cross-metathesis reaction to give a 3:1 mixture of 3,3-dimethylbutene and trans-4,4-dimethylpent-2-ene, and make this catalyst the first generation of well-defined Re-based heterogeneous catalysts. 相似文献
82.
Solladié N Walther ME Gross M Duarte TM Bourgogne C Nierengarten JF 《Chemical communications (Cambridge, England)》2003,(19):2412-2413
In addition to the ammonium-crown ether recognition, pi-stacking interactions between the C60 sphere and the porphyrin moiety have been evidenced in a supramolecular complex obtained from a porphyrin-crown ether conjugate and a fullerene derivative bearing an ammonium unit. 相似文献
83.
Ivan Dimitrov Olivier Mathieu Ivan Penkov 《Transactions of the American Mathematical Society》2000,352(6):2857-2869
Given any simple Lie superalgebra , we investigate the structure of an arbitrary simple weight -module. We introduce two invariants of simple weight modules: the shadow and the small Weyl group. Generalizing results of Fernando and Futorny we show that any simple module is obtained by parabolic induction from a cuspidal module of a Levi subsuperalgebra. Then we classify the cuspidal Levi subsuperalgebras of all simple classical Lie superalgebras and of the Lie superalgebra W. Most of them are simply Levi subalgebras of , in which case the classification of all finite cuspidal representations has recently been carried out by one of us (Mathieu). Our results reduce the classification of the finite simple weight modules over all classical simple Lie superalgebras to classifying the finite cuspidal modules over certain Lie superalgebras which we list explicitly.
84.
Density-functional theory is applied to the interaction site model to study gas-liquid nucleation in a partially immiscible binary system consisting of spherical Lennard-Jones atoms (monomers) and dumbbell molecules of two Lennard-Jones atoms (dimers). Increased interaction anisotropy between the dimer sites and monomers is shown to result in mutual enhancement of nucleation. Critical nuclei with a lamellar structure are observed at high dimer activities. 相似文献
85.
F. Buisseret C. Semay V. Mathieu 《The European Physical Journal A - Hadrons and Nuclei》2007,31(4):616-619
A new method to study the retardation effects in mesons is presented. It is based on a generalized rotating string model,
in which a nonzero value of the relative time between the quark and the antiquark is allowed. This approach leads to a retardation
term in the Hamiltonian which behaves as a perturbation of the nonretarded Hamiltonian and preserves the Regge trajectories
for light mesons. The straight-line ansatz is used to describe the string, and the relevance of this approximation is tested.
It is shown that the string is actually curved because of retardation, but this bending does not bring a relevant contribution
to the energy spectrum of the model. 相似文献
86.
Amandine Cournet Marie-Line Délia Alain Bergel Christine Roques Mathieu Bergé 《Electrochemistry communications》2010,12(4):505-508
Most bacteria known to be electrochemically active have been harvested in the anodic compartments of microbial fuel cells (MFCs) and are able to use electrodes as electron acceptors. The reverse phenomenon, i.e. using solid electrodes as electron donors, is not so widely studied. To our knowledge, most of the electrochemically active bacteria are Gram-negative. The present study implements a transitory electrochemical technique (cyclic voltammetry) to study the microbial catalysis of the electrochemical reduction of oxygen. It is demonstrated that a wide range of aerobic and facultative anaerobic bacteria are able to catalyze oxygen reduction. Among these electroactive bacteria, several were Gram-positive. The transfer of electrons was direct since no activity was obtained with the filtrate. These findings, showing a widespread property among bacteria including Gram-positive ones, open new and interesting routes in the field of electroactive bacteria research. 相似文献
87.
Philippe Gros Sabine Choppin Julien Mathieu Yves Fort 《The Journal of organic chemistry》2002,67(1):234-237
The determination of the initial deprotonation site of 2-chloro- and 2-methoxypyridine during reaction with BuLi-LiDMAE has been investigated. A series of experiments on deuterated regioisomers revealed a direct lithiation at C-6 excluding a potential first classical ortholithiation and lithium equilibration in the reaction medium. These results suggested that the formation of lithium aggregates at the neighboring of the pyridinic nitrogen atom favored BuLi delivery at C-6 as well as 6-lithio intermediate stabilization. 相似文献
88.
The osp(N, 2) extension of the AKNS scheme is reconsidered. It leads to a general class of integrable nonlinear evolution equations for 2+N(N–1)/2 commuting and 2N anticommuting fields. by reduction, various osp(N, 2) versions of the Korteweg-de Vries equation can be obtained. One of these is shown to be bi-Hamiltonian and its second Hamiltonian structure corresponds to the classical limit of the so(N) superconformal algebra. The nonlinear Schrödinger and modified Korteweg-de Vries reductions are also briefly discussed.Work supported by NSerc and FCAR. 相似文献
89.
Reda Moubah Silviu Colis Mathieu Gallart Guy Schmerber Pierre Gilliot Aziz Dinia 《Journal of luminescence》2012,132(2):457-460
Recent studies on the physical properties of Ca3Co2O6 nanometric samples have shown that their properties are significantly different from those of the bulk samples. The origin of this change is not trivial. We have carried out optical measurements on Ca3Co2O6 thin films with different thicknesses in order to characterize their electronic structure using optical spectroscopy measurements. The absorption spectra show a dependence on the film thickness that is correlated to the grain size in the polycrystalline layers. We found that the optical band gap increases from 1.3 to 1.55 eV when the thickness changes from 35 to 100 nm. The change in the band gap evolution with the film thickness is discussed in terms of both the amorphous effect and the grain size in the Ca3Co2O6 thin films. Finally, we show that these results are consistent with recent measurements concerning magnetic and electrical properties of Ca3Co2O6 nanometric samples. 相似文献
90.
Mathieu Baillif Alexandre Gabard 《Proceedings of the American Mathematical Society》2008,136(3):1105-1111
We analyze the relationship between Hausdorffness and homogeneity in the frame of manifolds not confined to be Hausdorff. We exhibit examples of homogeneous non-Hausdorff manifolds and prove that a Lindelöf homogeneous manifold is Hausdorff.