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91.
Spectra of single tetra-tert-butylterrylene chromophore molecules embedded in an amorphous polyisobutylene matrix as microprobes were recorded. The individual temperature dependences of the spectral linewidths for the same single molecules (SMs) in a broad temperature interval (1.6 < T < 40 K) have been measured. This enabled us to separate the contributions of tunneling two-level systems and quasilocalized low-frequency vibrational modes (LFMs) to the observed linewidths. The analysis of the T dependences yields the values of LFM frequencies and SM-LFM coupling constants for the LFMs in the local environment of a given chromophore. Pronounced distributions of the observed parameters of LFMs were found. This result can be regarded as the first direct experimental proof of the localized nature of LFMs in glasses. 相似文献
92.
A bimetallic titanium(salen) complex has been used to catalyze the asymmetric addition of potassium cyanide to aldehydes attached to Wang resin giving polymer supported cyanohydrin propionates with up to 91% enantiomeric excesses. 相似文献
93.
94.
Chemical Bonding and Pressure‐Induced Change of the Electron Configuration of Ytterbium in β‐YbAgGa2
Ulrich Schwarz Marcus Schmidt Roman Gumeniuk Walter Schnelle Michael Hanfland Konstantin Klementiev Yuri Grin 《无机化学与普通化学杂志》2004,630(1):122-126
Single‐phase polycrystalline samples of the intermetallic compound β‐YbAgGa2 were synthesized by inductive heating and subsequent annealing for eight weeks at 670 K. Magnetic properties were characterized by susceptibility measurements and indicated intermediate valence of ytterbium at ambient pressure. Angle‐dispersive X‐ray powder diffraction data of orthorhombic β‐YbAgGa2 indicate stability of the phase in the investigated pressure range from 0.1 MPa (ambient pressure) to 19 GPa. The pressure‐induced volume decrease is accompanied by an increase of the effective valence from 2.17 at ambient conditions to 2.71 at 16 GPa as evaluated by X‐ray absorption spectroscopy at the Yb LIII threshold. Analysis of the chemical bonding in β‐YbAgGa2 by integrating the electron density of the polyanion in basins as defined by the electron localization function results in an electron count Yb2.7+[(Ag0.2—)(Ga1(3b)1.0—)(Ga2(4b)1.5—)]. This finding is close to the expected values calculated by means of the Zintl rules and fits well the results of magnetic susceptibility measurements and XAS investigations. 相似文献
95.
96.
Optimal process control with control constraints is a challenging task related to many real-life problems. In this paper, a single input continuous time constrained linear quadratic regulator problem, is defined and fully solved. The constraints include both bilinear inequality constraints and customary control force bounds. As a first step, the problem is reformulated as an equivalent constrained bilinear biquadratic optimal control problem. Next, Krotov’s method is used to solve it. To this end, a sequence of improving functions suitable to the problem’s new formulation is constructed and the corresponding successive algorithm is derived. The required computational steps are arranged as an algorithm and proof outlines for the convergence and optimality of the solution are given. The efficiency of the suggested method is demonstrated by numerical example. 相似文献
97.
Skripnikova Tatiana A. Starikova Anna A. Shumilova Galina I. Ermolenko Yuri E. Pendin Andrey A. Mourzina Yulia G. 《Journal of Solid State Electrochemistry》2017,21(8):2269-2279
Journal of Solid State Electrochemistry - We report a new type of solid-state electrode (type I) of a simple design with polyvinyl chloride membranes based on Mn(III) tetraphenylporphyrin and with... 相似文献
98.
99.
V. N. Andreev V. A. Grinberg A. G. Dedov A. S. Loktev N. A. Mayorova I. I. Moiseev A. A. Stepanov 《Russian Journal of Electrochemistry》2013,49(10):996-1000
The electrooxidation of a (~3: 1) mixture of trifluoroacetic and 10-undecylenic acids in MeCN with an aqueous KOH addition on different anodic catalysts was studied. The oxidation of trifluoroacetate ions that forms trifluoromethyl radicals is the key stage of the process, while 10-undecylenic acid seems to be merely an acceptor of the electrogenerated radicals, i.e., shows the chemical properties characteristic of olefins. The galvanostatic electrolysis of trifluoroacetic and 10-undecylenic acids led to a mixture of the products of trifluoromethylation of the latter and the products of coupling of the formed radical species. According to a qualitative estimation, the total yield of these products was 74%. 相似文献
100.
The work deals with the obtaining by the vacuum gas-jet technique of the metal-polymer composites consisting of silver nanoparticles introduced into a fluorocarbon polymer matrix and the investigation of their optical properties. The dependence of the optical density in the visible range of frequencies on the structure of obtained samples has been investigated. The obtained composites are found to possess the plasmon resonance effect. 相似文献