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91.
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
92.
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.
93.
94.
95.
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
96.
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i) We have edℚ(ℤ/8ℤ)=4, a result which was conjectured by Buhler and Reichstein in 1995 (unpublished).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
97.
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
98.
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
99.
Given a connected surface \({\mathbb {F}}^2\) with Euler characteristic \(\chi \) and three integers \(b>a\ge 1<k\), an \((\{a,b\};k)\)-\({\mathbb {F}}^2\) is a \({\mathbb {F}}^2\)-embedded graph, having vertices of degree only k and only a- and b-gonal faces. The main case are (geometric) fullerenes (5, 6; 3)-\({\mathbb {S}}^2\). By \(p_a\), \(p_b\) we denote the number of a-gonal, b-gonal faces. Call an \((\{a,b\};k)\)-map lego-admissible if either \(\frac{p_b}{p_a}\), or \(\frac{p_a}{p_b}\) is integer. Call it lego-like if it is either \(ab^f\)-lego map, or \(a^fb\)-lego map, i.e., the face-set is partitioned into \(\min (p_a,p_b)\) isomorphic clusters, legos, consisting either one a-gon and \(f=\frac{p_b}{p_a}\,b\)-gons, or, respectively, \(f=\frac{p_a}{p_b}\,a\)-gons and one b-gon; the case \(f=1\) we denote also by ab. Call a \((\{a,b\};k)\)-map elliptic, parabolic or hyperbolic if the curvature \(\kappa _b=1+\frac{b}{k}-\frac{b}{2}\) of b-gons is positive, zero or negative, respectively. There are 14 lego-like elliptic \((\{a,b\};k)\)-\({\mathbb {S}}^2\) with \((a,b)\ne (1,2)\). No \((\{1,3\};6)\)-\({\mathbb {S}}^2\) is lego-admissible. For other 7 families of parabolic \((\{a,b\};k)\)-\({\mathbb {S}}^2\), each lego-admissible sphere with \(p_a\le p_b\) is \(a^fb\) and an infinity (by Goldberg–Coxeter operation) of \(ab^f\)-spheres exist. The number of hyperbolic \(ab^f\,(\{a,b\};k)\)-\({\mathbb {S}}^2\) with \((a,b)\ne (1,3)\) is finite. Such \(a^f b\)-spheres with \(a\ge 3\) have \((a,k)=(3,4),(3,5),(4,3),(5,3)\) or (3, 3); their number is finite for each b, but infinite for each of 5 cases (a, k). Any lego-admissible \((\{a,b\};k)\)-\({\mathbb {S}}^2\) with \(p_b=2\le a\) is \(a^f b\). We list, explicitly or by parameters, lego-admissible \((\{a,b\};k)\)-maps among: hyperbolic spheres, spheres with \(a\in \{1,2\}\), spheres with \(p_b\in \{2,\frac{p_a}{2}\}\), Goldberg–Coxeter’s spheres and \((\{a,b\};k)\)-tori. We present extensive computer search of lego-like spheres: 7 parabolic (\(p_b\)-dependent) families, basic examples of all 5 hyperbolic \(a^fb\) (b-dependent) families with \(a\ge 3\), and lego-like \((\{a,b\};3)\)-tori. 相似文献
100.
Nguyen Tle A Devic T Mialane P Rivière E Sonnauer A Stock N Demir-Cakan R Morcrette M Livage C Marrot J Tarascon JM Férey G 《Inorganic chemistry》2010,49(22):10710-10717
A high-throughput methodology combined with X-ray powder diffraction measurements was used to investigate the reactivity of the TetraThiaFulvalene TetraCarboxylic acid ((TTF-TC)H(4)) with divalent metals (M = Ni, Co) under various reaction conditions (stoichiometry, pH, temperature). Two new crystalline phases were identified and then studied by single crystal X-ray diffraction. Whereas the first one appears to be a simple salt, the second one, formulated {[M(H(2)O)(4)](2)(TTF-TC)}·4H(2)O, is built of 2:1 M:TTF-TC molecular complexes and labeled MIL-136(Ni, Co) (MIL stands for Materials Institute Lavoisier). The combination of thermogravimetric analysis and thermodiffraction studies reveals that MIL-136(Ni) exhibits a complex dehydration behavior. Indeed, a partial dehydration/rehydration process led to the single-crystal-to-single-crystal transformation of the molecular compound in a two-dimensional coordination polymer formulated {[Ni(2)(H(2)O)(5)(TTF-TC)]}·H(2)O (MIL-136'(Ni)). Magnetic and redox properties of MIL-136(Ni, Co) were investigated. Magnetic measurements indicate that all the magnetic coupling, intra- and intermolecular, are very weak; thus, the magnetic data of MIL-136(Ni, Co) have been interpreted in term of single-ion spin orbit coupling. Solid state cyclic voltammetry of MIL-136(Ni, Co) presents three reversible waves which were assigned to the redox activity of the TTF core and the metallic cations. In contrast to solids based on TTF linkers and alkaline ions, the MIL-136(Ni, Co) complexes do not act as excellent positive electrode materials for Li batteries, but present two reversible electron oxidation of the TTF core. These observations were tentatively related to the strength of the metal-carboxylate bond. 相似文献