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81.
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
82.
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
83.
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
84.
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.
85.
86.
87.
Luca Stabellini Wei Lu Alfredo De Rossi Thomas Antoni Mathieu Carras Stefano Trillo Gaetano Bellanca 《Optical and Quantum Electronics》2008,40(14-15):1085-1090
A Finite Difference Time Domain approach is used to design and to optimize quantum-well based infrared photodetectors. Results showing the influence of some parameters on the performance of these devices are presented and discussed. 相似文献
88.
Mathieu Florence 《Inventiones Mathematicae》2008,171(1):175-189
Let p be a prime number, let K be a field of characteristic not p, containing the p-th roots of unity, and let r≥1 be an integer. We compute the essential dimension of ℤ/p
r
ℤ over K (Theorem 4.1). In particular,
i) We have edℚ(ℤ/8ℤ)=4, a result which was conjectured by Buhler and Reichstein in 1995 (unpublished).
ii) We have edℚ(ℤ/p
r
ℤ)≥p
r-1. 相似文献
89.
This work presents the synthesis of novel unsymmetrical bolaamphiphiles bearing a sugar residue and a cationic glycine betaine moiety connected to both ends of a C22 or C32 oligomethylene bridging chain possessing or not a diacetylenic unit. Preliminary transmission electron microscopy (TEM) studies revealed the polymorphism of these bola lipids with regard to their self-assembled morphologies in water depending on the presence or not of the diacetylenic functionality and on alkyl chain length. 相似文献
90.
Mathieu Toumi 《Tetrahedron letters》2008,49(7):1175-1179
A practical synthesis of enantiopure substituted 3-hydroxy-pyrrolidines is reported. In four steps, starting from commercially available amino acids as chiral educts, this method allows for an efficient preparation of a variety of 3-hydroxy-pyrrolidines, as well as 3-hydroxy-piperidines and azepanes. Application of this methodology for a straightforward asymmetric synthesis of (−)-bulgecinine is also described. 相似文献