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131.
Mikhail E. Elyashberg Kirill A. Blinov Eduard R. Martirosian Sergey G. Molodtsov Antony J. Williams Gary E. Martin 《Journal of heterocyclic chemistry》2003,40(6):1017-1029
Characteristic features of a new expert system StrucEluc are described. The system is intended for the structure elucidation of complex organic molecules using a variety of spectroscopic data including 2D NMR. We review here the results of challenging this system with over 100 structure elucidation problems where the 2D NMR peak tables presented in original journal publications provided the input data. This contribution is focused on methods to overcome difficult situations that can arise when contradictions are present in the input data and/or when the structure is underdetermined as a result of insufficient 2D NMR correlations. Methods by which to address these situations are examined. It has been shown that synergy between the spectroscopist and the expert system allows the solution of problems that seemed to be hopeless at the outset of the structure elucidation process. 相似文献
132.
133.
Lidia S. Konstantinova Maxim A. Bastrakov Aleksei M. Starosotnikov Ivan V. Glukhov Kirill A. Lysov Oleg A. Rakitin Svyatoslav A. Shevelev 《Mendeleev Communications》2010,20(6):353-354
1,3-Dipolar cycloaddition of 4,6-dinitrobenzo[c]isothiazole to (N-methyl-N-methylideneammonio)methanide (2 equiv.) gives 5,8-dimethyl-3b,6b-dinitrodecahydroisothiazolo[3,4-e]pyrrolo[3,4-g]isoindole, whose structure was confirmed by X-ray diffraction analysis. 相似文献
134.
135.
Dr. Shannon J. Lee Gayatri Viswanathan Dr. Scott L. Carnahan Dr. Colin P. Harmer Dr. Georgiy Akopov Prof. Dr. Aaron J. Rossini Prof. Dr. Gordon J. Miller Prof. Dr. Kirill Kovnir 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(9):e202104319
Centrosymmetric skutterudite RhP3 was converted to a nonsymmorphic and chiral compound RhSi0.3P2.7 (space group P212121) by means of partial replacement of Si for P. The structure, determined by a combination of X-ray crystallography and solid state 31P NMR, exhibits branched polyanionic P/Si chains that are unique among metal phosphides. A driving force to stabilize the locally noncentrosymmetric cis-RhSi2P4 and fac-RhSi3P3 fragments is π-electron back-donation between the Rh t2g-type orbitals and the unoccupied antibonding Si/P orbitals, which is more effective for Si than for P. In situ studies and total energy calculations revealed the metastable nature of RhSi0.3P2.7. Electronic structure calculations predicted centrosymmetric cubic RhP3 to be metallic which was confirmed by transport properties measurements. In contrast, the electronic structure for chiral orthorhombic RhSi0.3P2.7 contained a bandgap, and this compound was shown to be a narrow gap semiconductor. 相似文献
136.
Dr. Oleg G. Salnikov Dr. Dudari B. Burueva Dr. Larisa M. Kovtunova Prof. Valerii I. Bukhtiyarov Dr. Kirill V. Kovtunov Prof. Igor V. Koptyug 《Chemphyschem》2022,23(7):e202200072
In this work the mechanism of methylenecyclobutane hydrogenation over titania-supported Rh, Pt and Pd catalysts was investigated using parahydrogen-induced polarization (PHIP) technique. It was found that methylenecyclobutane hydrogenation leads to formation of a mixture of reaction products including cyclic (1-methylcyclobutene, methylcyclobutane), linear (1-pentene, cis-2-pentene, trans-2-pentene, pentane) and branched (isoprene, 2-methyl-1-butene, 2-methyl-2-butene, isopentane) compounds. Generally, at lower temperatures (150–350 °C) the major reaction product was methylcyclobutane while higher temperature of 450 °C favors the formation of branched products isoprene, 2-methyl-1-butene and 2-methyl-2-butene. PHIP effects were detected for all reaction products except methylenecyclobutane isomers 1-methylcyclobutene and isoprene implying that the corresponding compounds can incorporate two atoms from the same parahydrogen molecule in a pairwise manner in the course of the reaction in particular positions. The mechanisms were proposed for the formation of these products based on PHIP results. 相似文献
137.
The purpose of the present paper is to reveal some conformities to natural universal laws allowing to advance the theory of evolutionary economics. The second law of thermodynamics, Le Chatelie–Brown principle as universal laws are applied for nonlinear dynamical economic systems. The ergodic hypothesis is applied for dynamical economic systems as one from principles of economic forecasting. From the point of view of statistical physics, entropy is applied as universal function of a condition for economic systems. The evolution of economic dynamical systems at macro and microeconomic levels from the point of view of thermodynamics, statistical physics, and diffusion processes is investigated. The law of money circulation is formulated as one of the forms of display of energy conservation law in economic space. The concept of parametric economic space is introduced. The concepts of energy and number of degrees of freedom of a dynamical economic system allow substantiated cause and effect connections between the evolution of the system and a number of economic factors (forces), influencing on the system (degree of an openness, freedom of an economic system). The character of the development of technologies and the product life cycle are investigated as a nonlinear economic process. The concept of a wave function describing a technological wave connected with the entropy of a system of economic cells is introduced. 相似文献
138.
Simulations of blood flows in arteries require numerical solutions
of fluid-structure interactions involving Navier-Stokes equations
coupled with large displacement visco-elasticity for the vessels.
Among the various simplifications which have been proposed, the
surface pressure model leads to a hierarchy of simpler models
including one that involves only the pressure. The model exhibits
fundamental frequencies which can be computed and compared with the
pulse. Yet unconditionally stable time discretizations can be
constructed by combining implicit time schemes with
Galerkin-characteristic discretization of the convection terms in
the Navier-Stokes equations. Such problems with prescribed pressure
on the walls will be shown to be efficient and accurate as an
approximation of the full fluid structure interaction problem. 相似文献
139.
Zaikina JV Mori T Kovnir K Teschner D Senyshyn A Schwarz U Grin Y Shevelkov AV 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(42):12582-12589
The creation of thermoelectric materials for waste heat recovery and direct solar energy conversion is a challenge that forces the development of compounds that combine appreciable thermoelectric figure‐of‐merit with high thermal and chemical stability. Here we propose a new candidate for high‐temperature thermoelectric materials, the type‐III Si172?xPxTey cationic clathrate, in which the framework is composed of partially ordered silicon and phosphorus atoms, whereas tellurium atoms occupy guest positions. We show that the utmost stability of this clathrate (up to 1500 K) in air is ensured by the formation of a nanosized layer of phosphorus‐doped silica on the surface, which prevents further oxidation and degradation. As‐cast (non‐optimized) Si‐P‐Te clathrates display rather high values of the thermoelectric figure‐of‐merit (ZT=0.24–0.36) in the temperature range of 700–1100 K. These ZT values are comparable to the best values achieved for the properly doped transition‐metal‐oxide materials. The methods of the thermoelectric efficiency optimization are discussed. 相似文献
140.
Kirill Kolmakov Dr. Vladimir N. Belov Dr. Jakob Bierwagen Dipl.‐Chem. Christian Ringemann Dr. Veronika Müller Dipl.‐Phys. Christian Eggeling Dr. Stefan W. Hell Prof. Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(1):158-166
Fluorescent markers emitting in the red are extremely valuable in biological microscopy since they minimize cellular autofluorescence and increase flexibility in multicolor experiments. Novel rhodamine dyes excitable with 630 nm laser light and emitting at around 660 nm have been developed. The new rhodamines are very photostable and have high fluorescence quantum yields of up to 80 %, long excited state lifetimes of 3.4 ns, and comparatively low intersystem‐crossing rates. They perform very well both in conventional and in subdiffraction‐resolution microscopy such as STED (stimulated emission depletion) and GSDIM (ground‐state depletion with individual molecular return), as well as in single‐molecule‐based experiments such as fluorescence correlation spectroscopy (FCS). Syntheses of lipophilic and hydrophilic derivatives starting from the same chromophore‐containing scaffold are described. Introduction of two sulfo groups provides high solubility in water and a considerable rise in fluorescence quantum yield. The attachment of amino or thiol reactive groups allows the dyes to be used as fluorescent markers in biology. Dyes deuterated at certain positions have narrow and symmetrical molecular mass distribution patterns, and are proposed as new tags in MS or LC‐MS for identification and quantification of various substance classes (e.g., amines and thiols) in complex mixtures. High‐resolution GSDIM images and live‐cell STED‐FCS experiments on labeled microtubules and lipids prove the versatility of the novel probes for modern fluorescence microscopy and nanoscopy. 相似文献