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61.
This contribution concerns the mechanics of materials with random network microstructures. It develops a general homogenization approach that allows to link the microscopic deformation of fibers in the disordered network with the macroscopic response of the continuous solid. This link is established by a novel micro-macro relation based on the kinematics of maximal advance paths that constrains the unknown microscopic stretch of fibers with respect to the macroscopic strain. This relation accounts for the topology of the network, in particular, its connectivity and takes for the tetrafunctional networks a clearly interpretable tensorial form. In line with the principle of the minimum averaged free energy the elastic response of the network is obtained by the relaxation of the variable fiber stretch subjected to the kinematic constraint. (© 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
62.
Shaotang Song Lulu Wang Jie Su Zhen Xu Chia-Hsiu Hsu Chenqiang Hua Pin Lyu Jing Li Xinnan Peng Takahiro Kojima Shunpei Nobusue Mykola Telychko Yi Zheng Feng-Chuan Chuang Hiroshi Sakaguchi Ming Wah Wong Jiong Lu 《Chemical science》2021,12(35):11659
Deciphering rich non-covalent interactions that govern many chemical and biological processes is crucial for the design of drugs and controlling molecular assemblies and their chemical transformations. However, real-space characterization of these weak interactions in complex molecular architectures at the single bond level has been a longstanding challenge. Here, we employed bond-resolved scanning probe microscopy combined with an exhaustive structural search algorithm and quantum chemistry calculations to elucidate multiple non-covalent interactions that control the cohesive molecular clustering of well-designed precursor molecules and their chemical reactions. The presence of two flexible bromo-triphenyl moieties in the precursor leads to the assembly of distinct non-planar dimer and trimer clusters by manifold non-covalent interactions, including hydrogen bonding, halogen bonding, C–H⋯π and lone pair⋯π interactions. The dynamic nature of weak interactions allows for transforming dimers into energetically more favourable trimers as molecular density increases. The formation of trimers also facilitates thermally-triggered intermolecular Ullmann coupling reactions, while the disassembly of dimers favours intramolecular cyclization, as evidenced by bond-resolved imaging of metalorganic intermediates and final products. The richness of manifold non-covalent interactions offers unprecedented opportunities for controlling the assembly of complex molecular architectures and steering on-surface synthesis of quantum nanostructures.A real-space characterization of dynamic non-covalent interactions in molecular assemblies and chemical reactions at the atomic bond level. 相似文献
63.
The first highly enantioselective catalytic reduction of 1-imino-2,2,2-trifluoroethylphosphonates and the synthesis of enantiomerically enriched biorelevant phosphonotrifluoroalanine is reported. 相似文献
64.
Mykola Kolotylo Volodymyr Holovatiuk Julia Bondareva Oleg Lukin Vladimir Rozhkov 《Tetrahedron letters》2019,60(4):352-354
The synthesis of dendrimers and a chlorosulfo-dendron possessing a unique combination of 1?→?2 and 1?→?4 branching types is described. The procedure consists of a two-step preparation of 3,5-dinitrobenzene-1-sulfonyl chloride, which was used for the persulfonylation of p-toluidine and 4-(benzylthio)aniline. The obtained tetranitro compounds were reduced to the corresponding tetraamines. The latter were decorated with eight 4-toluene sulfonyl groups each to furnish the corresponding dendrimers. Oxidation of the dendrimer possessing a 4-(benzylthio)phenylene core with N-chlorosuccinimide resulted in the formation of a dendron with a sulfonyl chloride functionality at the focal point. 相似文献
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68.
Yu. A. Kabachii S. Yu. Kochev S. S. Abramchuk P. M. Valetskii 《Russian Chemical Bulletin》2016,65(2):414-418
Photocatalytic properties of Pt-promoted CdS nanocrystals functionalized by the polymer coating were investigated. Deposition of Pt on the surface of the nanoparticles followed by polymer functionalization provides a high photocatalytic activity (1.45 mmol h–1 mg–1 at 0.93 W cm–2) and apparent quantum yield (7%, λ = 445 nm) of the particles. Dependence of the rate of H2 evolution on Pt loading is described by a curve with the maximum, whereas the quantum yield decreases with an increase in the light flux density. The photocatalytic activity of the nanocrystals increases more than 2 times with polymer coatining. 相似文献
69.
Dubrovin EV Voloshin AG Kraevsky SV Ignatyuk TE Abramchuk SS Yaminsky IV Ignatov SG 《Langmuir : the ACS journal of surfaces and colloids》2008,24(22):13068-13074
Atomic force microscopy (AFM) was used to study the process of infection of bacterial cells by bacteriophages, for which purpose experimental protocols were elaborated. Three types of bacteriophages were characterized with AFM and transmission electron microscopy (TEM). Bacteriophage interaction with cells was studied for three bacterial hosts: Gram-negative Escherichia coli 057 and Salmonella enteritidis 89 and Gram-positive Bacillus thuringiensis 393. Depending on the phase of lytic cycle, different cell surface changes are observed in AFM images of infected cells in comparison with intact cells: from phage adsorption on the cells and flagella to complete lysis of the cells, accompanied by the release of a large number of newly formed phages. Control experiments (cells without phages and cells with nonspecific phages) did not reveal any surface changes. Penetration of phages inside obligate aerobe Bacillus thuringiensis was shown to be oxygen-dependent and required aeration in laboratory conditions. Our results show great potential of using AFM for numerous fundamental and applied tasks connected with pathogen-host interaction. 相似文献
70.
Vyacheslav O. Khavrus Nataliia V. Lemesh Svitlana V. Gordijchuk Andriy I. Tripolsky Tetyana S. Ivashchenko Mykola M. Biliy Peter E. Strizhak 《Reaction Kinetics and Catalysis Letters》2008,93(2):295-303
A simple method for producing unsupported nickel catalyst that can be used to synthesize multi-wall carbon nanotubes (MWNT)
has been developed. The yield of purified MWNTs is about 1.8 gmwnt/(gcat×h). 相似文献