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141.
E. A. Dem’yanov E. V. Djukova 《Computational Mathematics and Mathematical Physics》2007,47(3):518-526
New estimates are derived for the computational complexity of the problem of constructing irredundant coverings of an integer matrix (search for maximal conjunctions of a special logical function). 相似文献
142.
Andrej T. Il’ichev 《Zeitschrift für Angewandte Mathematik und Physik (ZAMP)》2006,57(4):547-566
Stability of solitary waves in a thin inextensible and unshearable rod of infinite length is studied. Solitary-wave profile
of the elastica of such a rod without torsion has the form of a planar loop and its speed depends on a tension in the rod.
The linear instability of a solitary-wave profile subject to perturbations escaping from the plane of the loop is established
for a certain range of solitary-wave speeds. It is done using the properties of the Evans function, an analytic function on
the right complex half-plane, that has zeros if and only if there exist the unstable modes of the linearization around a solitary-wave
solution. The result follows from comparison of the behaviour of the Evans function in some neighbourhood of the origin with
its asymptotic at infinity. The explicit computation of the leading coefficient of the Taylor series of the Evans function
near the origin is performed by means of the symbolic computer language.
Received: April 6, 2004; revised: December 12, 2004 相似文献
143.
The electron transfer from aniline and its N-methyl as well as N-phenyl substituted derivatives (N-methylaniline, N,N-dimethylaniline, diphenylamine, triphenylamine) to parent solvent radical cations was studied by electron pulse radiolysis in n-butyl chloride solution. The ionization results in the case of aniline (ArNH2) and the secondary aromatic amines (Ar2NH, Ar(Me)NH) in the synchronous and direct formation of amine radical cations, as well as aminyl radicals, in comparable amounts. Subsequently, ArNH2*+ deprotonates in a delayed reaction with the present nucleophile Cl-, and forms further ArNH*. In contrast, tertiary aromatic amines such as triphenylamine and dimethylaniline yield primarily the corresponding amine radical cations Ar3N*+ or Ar(Me2)N*+, only. The persistent Ar3N*+ forms a charge transfer complex (dimer) with the parent amine molecule, whereas Ar(Me2)N*+ deprotonates to carbon-centered radicals Ar(Me)NCH2*. 相似文献
144.
Vasil"ev L. S. Sheremetev A. B. Khoa N. K. Dem"yanets Z. K. Dmitriev D. E. Dorokhov V. A. 《Russian Chemical Bulletin》2001,50(7):1280-1286
In the presence of nickel acetylacetonate, -dicarbonyl compounds readily add at the nitrile group of 4-R-3-cyanofurazans to form enaminofurazans. The adducts obtained from 4-amino-3-cyanofurazan underwent intramolecular cyclization on heating with AcOH in EtOH to give furazano[3,4-b]pyridine derivatives in high yields. 相似文献
145.
Dr. Andrej Jančařík Daniel Mildner Dr. Yuuya Nagata Dr. Marzena Banasiewicz Joanna Olas Dr. Boleslaw Kozankiewicz Dr. Jan Holec Dr. André Gourdon 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(48):12388-12394
Acenes, polyaromatic hydrocarbons composed of linearly fused benzene rings have received immense attention due to their performance as semiconductors in organic optoelectronic applications. Their appealing physicochemical properties, such as extended delocalization, high charge carrier mobilities, narrow HOMO-LOMO gaps and partially radical character in the ground state make them very attractive targets for many potential applications. However, the intrinsic synthetic challenges of unsubstituted members such as high reactivity and poor solubility are still limiting factors for their wider exploitation. Herein, we report a simple general synthesis of a new family of angularly fused acenoacenes with improved stability compared to their isoelectronic linear counterparts. The synthesis and comprehensive characterization of pentacenopentacene, pentacenohexacene and hexacenohexacene, with lengths between decacene and dodecacene, are disclosed. 相似文献
146.
Lucia Kovacikova Marta Soltesova Prnova Magdalena Majekova Andrej Bohac Cimen Karasu Milan Stefek 《Molecules (Basel, Switzerland)》2021,26(10)
Aldose reductase (AR, ALR2), the first enzyme of the polyol pathway, is implicated in the pathophysiology of diabetic complications. Aldose reductase inhibitors (ARIs) thus present a promising therapeutic approach to treat a wide array of diabetic complications. Moreover, a therapeutic potential of ARIs in the treatment of chronic inflammation-related pathologies and several genetic metabolic disorders has been recently indicated. Substituted indoles are an interesting group of compounds with a plethora of biological activities. This article reviews a series of indole-based bifunctional aldose reductase inhibitors/antioxidants (ARIs/AOs) developed during recent years. Experimental results obtained in in vitro, ex vivo, and in vivo models of diabetic complications are presented. Structure–activity relationships with respect to carboxymethyl pharmacophore regioisomerization and core scaffold modification are discussed along with the criteria of ‘drug-likeness”. Novel promising structures of putative multifunctional ARIs/AOs are designed. 相似文献
147.
Noyori–Ikariya-type ruthenium(II)-catalysts for asymmetric transfer hydrogenation (ATH) have been known for 25 years and have proved as a well-behaved and user-friendly platform for the synthesis of chiral secondary alcohols. A progress has been made in the past five years in understanding the asymmetric reduction of complex ketones, where up to four stereocenters can be controlled in a single chemical transformation. Intriguing multi-chiral molecular architectures are therefore available in few well understood and robust synthetic steps from commercially available building blocks and possess handles for additional functionalization. The aim of this Review is to showcase the availability of three-dimensional scaffolds and homochiral lead-like compounds via ATH and inspire their direct use in drug discovery endeavors. Basic mechanistic insights are provided to demystify the stereo-chemical outcomes, as well as examples of diastereoselective transformations of enantiopure alcohols to give a feeling of how these rigid non-planar molecules can be further elaborated. 相似文献
148.
JPC – Journal of Planar Chromatography – Modern TLC - Thin layer chromatography with flame-ionization detection has been used for analysis of oligosaccharides. We report preliminary... 相似文献
149.
150.
Copper(II) coordination compounds with ferulic acid 总被引:1,自引:0,他引:1
The first two molecular structures of the ferulic acid (3-(4-hydroxy-3-methoxyphenyl)-2-propenoic acid, C10H10O4) coordination compounds are presented, namely, [Cu2(C10H9O4)4(CH3CN)2] 1 and [Cu2(C10H9O4)4(C6H6N2O)2]·4CH3CN (C6H6N2O = nicotinamide) 2. Both compounds were synthesised from the starting mixture of Cu2O and CuCl upon copper oxidation in the acetonitrile solution. The single-crystal X-ray diffraction analysis of 1 and 2 reveals the binuclear structure of the ‘paddle–wheel’ type for both complexes. 1 and 2 are unstable outside mother liquid due to loosely bound acetonitrile molecules. The final products of decomposition are [Cu2(C10H9O4)4] 1a and [Cu2(C10H9O4)4(C6H6N2O)2] 2a, which were characterized by several physico-chemical methods. The triplet X-band EPR spectra of 1a and 2a, showing signals BZ1 15 mT, B2 460 mT and BZ2 580 mT, are in agreement with the expected data for the binuclear tetracarboxylate units, found in the structures of the parent complexes 1 and 2. Together with the room temperature magnetic susceptibility data, μeff/B.M. 1.40 (1a), 1.48 (2a), the EPR spectra analysis confirm the antiferromagnetic interaction in 1a and 2a. This is suggesting preservation and stability of the paddle–wheel structures in 1a and 2a. 相似文献