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61.
Russian Journal of Organic Chemistry - In this study, three new Schiff bases have been synthesized by the reactions of commercially available phenylglycinol, phenylalaninol, and leuicinol with... 相似文献
62.
Nonlinear Dynamics - Compared with regular-spiking (RS) neurons, the action potentials (APs) of fast-spiking (FS) neurons are characterized by narrow spike durations and unusually fast decay... 相似文献
63.
Dr. Martin Valldor Dr. Bodo Böhme Dr. Yurii Prots Dr. Horst Borrmann Dr. Peter Adler Dr. Walter Schnelle Dr. Yves Watier Dr. Chang Yang Kuo Dr. Tun‐Wen Pi Dr. Zhiwei Hu Prof. Dr. Claudia Felser Prof. Dr. Liu Hao Tjeng 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(13):4626-4631
The novel host–guest compound [Cs6Cl][Fe24Se26] (I4/mmm; a=11.0991(9), c=22.143(2) Å) was obtained by reacting Cs2Se, CsCl, Fe, and Se in closed ampoules. This is the first member of a family of compounds with unique Fe–Se topology, which consists of edge‐sharing, extended fused cubane [Fe8Se6Se8/3] blocks that host a guest complex ion, [Cs6Cl]5+. Thus Fe is tetrahedrally coordinated and divalent with strong exchange couplings, which results in an ordered antiferromagnetic state below TN=221 K. At low temperatures, a distribution of hyperfine fields in the Mössbauer spectra suggests a structural distortion or a complex spin structure. With its strong Fe–Se covalency, the compound is close to electronic itinerancy and is, therefore, prone to exhibit tunable properties. 相似文献
64.
We study two polyhedral lift-and-project operators (originally proposed by Lovász and Schrijver in 1991) applied to the fractional stable set polytopes. First, we provide characterizations of all valid inequalities generated by these operators. Then, we present some seven-node graphs on which the operator enforcing the symmetry of the matrix variable is strictly stronger on the odd-cycle polytope of these graphs than the operator without this symmetry requirement. This disproves a conjecture of Lipták and Tunçel from 2003. 相似文献
65.
Ya Juan Xu Tun Hai Xu Jun Ying Yang Sheng Xu Xie Yue Liu Yun Shan Si Dong Ming Xu 《中国化学快报》2010,21(5):580-583
<正>Two new furostanol glycoside,26-O-β-D-glucopyranosyl-(25S)-5α-furost-3β,22α,26-triol-3-O-β-D-rhamnopyranosyl-(1→2)-[β-D-glucopyranosyl-(1→4)]-β-D-galactopyranoside(1) and 26-O-β-D-glucopyranosyl-(25S)-5α-furost-20(22)-en-2α,3β,26-triol-3-O-β-D-glucopyranosyl-(1→2)-O-β-D-glucopyranosyl-(1→4)-β-D-galactopyranoside(2) were isolated fromthe fruits of Tribulus terrestris L.The structures of two new furostanol saponins were elucidated by spectroscopic methods. 相似文献
66.
67.
4‐Amino‐1‐(2‐deoxy‐β‐D‐ribofuranosyl)quinazolin‐2‐one (4) was prepared by Barton deoxygenation from 4‐amino‐1‐(β‐D‐ribofuranosyl)quinazolin‐2‐one (3) as a 2′‐deoxycytidine analog. 相似文献
68.
69.
Levent Tunçel 《Mathematical Programming》1999,86(1):219-223
Given an m×n integer matrix A of full row rank, we consider the problem of computing the maximum of ∥B
-1
A∥2 where B varies over all bases of A. This quantity appears in various places in the mathematical programming literature. More recently, logarithm of this number
was the determining factor in the complexity bound of Vavasis and Ye’s primal-dual interior-point algorithm. We prove that
the problem of approximating this maximum norm, even within an exponential (in the dimension of A) factor, is NP-hard. Our proof is based on a closely related result of L. Khachiyan [1].
Received November 13, 1998 / Revised version received January 20, 1999? Published online May 12, 1999 相似文献
70.
We consider two notions for the representations of convex cones G-representation and lifted-G-representation. The former represents a convex cone as a slice of another; the latter allows in addition, the usage of auxiliary
variables in the representation. We first study the basic properties of these representations. We show that some basic properties
of convex cones are invariant under one notion of representation but not the other. In particular, we prove that lifted-G-representation is closed under duality when the representing cone is self-dual. We also prove that strict complementarity
of a convex optimization problem in conic form is preserved under G-representations. Then we move to study efficiency measures for representations. We evaluate the representations of homogeneous
convex cones based on the “smoothness” of the transformations mapping the central path of the representation to the central
path of the represented optimization problem.
Research of the first author was supported in part by a grant from the Faculty of Mathematics, University of Waterloo and
by a Discovery Grant from NSERC. Research of the second author was supported in part by a Discovery Grant from NSERC and a
PREA from Ontario, Canada. 相似文献