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31.
Alexander O. Terent’ev Igor B. Krylov Vera A. Vil’ Zhanna Yu. Pastukhova Sergey A. Fastov Gennady I. Nikishin 《Central European Journal of Chemistry》2012,10(2):360-367
It was found that oximes undergo deoximation in the presence of the H2O2aq-HBraq system to form ketones and bromo ketones. This reaction provided the basis for the synthesis of dibromo ketones in yields
varying from 40% to 94%. This method is environmentally friendly, sustainable, and easy to perform. The results of this investigation
extend the potential of the use of oximes for the protection of carbonyl group, thus offering the ability to perform not only
conventional deoximation but also the subsequent bromination of ketones. The reaction is easily scaled up and dibromo ketones
can be prepared in gram amounts.
相似文献
32.
A railway wheelset rolling on rails without slip is studied with consideration of the creep hypothesis. The wheelset is represented
by two cones having a common base; the rails are represented by two circular cylinders with parallel axes. The kinematic characteristics
of undisturbed rolling for the wheelset are determined when its center of mass moves along a straight line; these characteristics
are also determined in the case of disturbed motion when the mass center of the wheelset moves along a sinusoidal trajectory.
For these modes of motion, the constraint reactions are found with an accuracy up to the second order of smallness with respect
to the values of disturbed variables. When the absolutely rigid point contact is replaced by the elastic contact, the creep
hypothesis is used, the method of averaging with respect to the fast variables is applied, and a critical velocity above which
the rectilinear rolling becomes unstable is determined on the basis of the averaged equations. 相似文献
33.
Alberto H. V. Vilão R. C. Piroto Duarte J. Gil J. M. Ayres de Campos N. Lichti R. L. Davis E. A. Cottrell S. P. Cox S. F. J. 《Hyperfine Interactions》2001,136(3-8):471-477
The hyperfine spectroscopy of muonium in II–VI semiconductors is reviewed, suggesting that whereas hydrogen is a deep-level
defect in ZnS, ZnSe and ZnTe, it constitutes a shallow donor in ZnO, CdS, CdSe and CdTe. Shallow and deep states coexist in
CdTe. Using new data for ZnO, it is shown that the principal values of the muonium hyperfine tensor may be obtained with equal
facility from measurements in longitudinal or in transverse magnetic field, and from samples that are polycrystalline powders
or single crystals. Spin density on the central muon in the shallow states correlates with the electron binding energy or
donor depth.
This revised version was published online in September 2006 with corrections to the Cover Date. 相似文献
34.
Dr. Ludmila Krejčová Dr. Terza Leonhardt Dr. Filip Novotný Dr. Vilém Bartůněk Dr. Vlastimil Mazánek Prof. David Sedmidubský Prof. Zdeněk Sofer Prof. Martin Pumera 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(15):3828-3834
Nature and its highly sophisticated biomaterials are an endless source of inspiration for engineers and scientists across a wide range of disciplines. During the last decade, concepts of bioinspired synthesis of hierarchically structured nano- and micromaterials have been attracting increasing attention. In this article, we have utilized the natural ability of fungi to absorb metal ions for a bioinspired synthesis of carbonaceous material doped by selected transition metals. As an all-around metal accumulator, Hebeloma mesophaeum was selected, and it was cultivated in the presence of three transition-metal ions: NiII, FeII, and MnII. The metal-doped carbonized biomaterial possessed enhanced catalytic activity toward hydrazine oxidation, oxygen reduction, and cumene hydroperoxide reduction. Thus, we have shown possible transformation of a waste product (fungi grown on a contaminated soil) into a value-added carbonaceous material with tailored catalytic properties. This bioinspired synthesis can outline an attractive route for the fabrication of catalysts for important industrial applications on a large scale. 相似文献
35.
S. F. J. Cox J. S. Lord S. P. Cottrell H. V. Alberto J. M. Gil J. Piroto Duarte R. C. Vilão A. Keren D. Prabhakaran 《Hyperfine Interactions》2004,158(1-4):313-316
Muonium centres in Cu2O, Ag2O and CdO show hyperfine parameters spanning four orders of magnitude. They exemplify the three different categories of hydrogen
defect centre in semiconducting and dielectric solids, with very different electronic structure and electrical activity, namely
quasi-atomic (possibly deep acceptor), deep donor and shallow donor. 相似文献
36.
The paper studies closure properties of classes of fuzzy structures defined by fuzzy implicational theories, i.e. theories
whose formulas are implications between fuzzy identities. We present generalizations of results from the bivalent case. Namely,
we characterize model classes of general implicational theories, finitary implicational theories, and Horn theories by means
of closedness under suitable algebraic constructions. 相似文献
37.
The analog of Fisher information for discrete lattice distributions is introduced. The variational problems of minimization
of Fisher information are solved for the discrete analogs of the classes of finite distributions, nonsingular densities and
ε-contaminated distributions.
Translated fromStatisticheskie Metody Otsenivaniya i Proverki Gipotez, pp. 14–18, Perm, 1991. 相似文献
38.
The paper presents generalizations of results on so-called Horn logic, well-known in universal algebra, to the setting of
fuzzy logic. The theories we consider consist of formulas which are implications between identities (equations) with premises
weighted by truth degrees. We adopt Pavelka style: theories are fuzzy sets of formulas and we consider degrees of provability
of formulas from theories. Our basic structure of truth degrees is a complete residuated lattice. We derive a Pavelka-style
completeness theorem (degree of provability equals degree of truth) from which we get some particular cases by imposing restrictions
on the formulas under consideration. As a particular case, we obtain completeness of fuzzy equational logic. 相似文献
39.
Dr. Samuel Ahoulou Dr. Neus Vilà Dr. Sébastien Pillet Prof. Cédric Carteret Prof. Dominik Schaniel Dr. Alain Walcarius 《Chemphyschem》2021,22(23):2464-2477
Silica matrices hosting transition metal guest complexes may offer remarkable platforms for the development of advanced functional devices. We report here the elaboration of ordered and vertically oriented mesoporous silica thin films containing covalently attached tris(bipyridine)iron derivatives using a combination of electrochemically assisted self-assembly (EASA) method and Huisgen cycloaddition reaction. Such a versatile approach is primarily used to bind nitrogen-based chelating ligands such as (4-[(2-propyn-1-yloxy)]4’-methyl-2,2’-bypiridine, bpy’) inside the nanochannels. Further derivatization of the bpy’-functionalized silica thin films is then achieved via a subsequent in-situ complexation step to generate [Fe(bpy)2(bpy’)]2+ inside the mesopore channels. After giving spectroscopic evidences for the presence of such complexes in the functionalized film, electrochemistry is used to transform the confined diamagnetic (S=0) species to paramagnetic (S=1/2) oxidized species in a reversible way, while blue light irradiation (λ=470 nm) enables populating the short-lived paramagnetic (S=2) excited state. [Fe(bpy)2(bpy’)]2+-functionalized ordered films are therefore both electro- and photo-active through the manipulation of the oxidation state and spin state of the confined complexes, paving the way for their integration in optoelectronic devices. 相似文献
40.
Boris Orel Robi Ješe Aljaž Vilčnik Urška LavrenčIč Štangar 《Journal of Sol-Gel Science and Technology》2005,34(3):251-265
The aim of this study was, at first, to re-consider the IR spectra of methyltriethoxysilane (MTEOS) catalysed with HCl (hydrolysis) and to compare them with IR spectra of MTEOS catalysed with trifluoroacetic acid (TFAcOH). TFAcOH as a strong carboxylic acid performs non-hydrolytic sol-gel process based on the condensation between the alkoxide and the acid function, liberating ester molecules (solvolysis). We assessed from the time-dependent IR attenuated reflection spectroscopic (IR ATR) measurements the solvolysis and hydrolysis reactions, formation of the oligomeric species and final condensation products. Additional evidence for the formation of these species was obtained from the spectra of films dip-coated from sols aged to different extent. The results of the IR spectral analysis showed that the structure of both xerogels consisted of irregular Tn (n = 8, 10, 12) cube-like species bridged via the ladder-like oligomers (in the case of MTEOS/TFAcOH) and open-chain trisiloxane species (for MTEOS/HCl). 29Si NMR spectra of MTEOS/TFAcOH showed only signals of T3 while MTEOS/HCl spectra showed beside T3 also T2 signals, in agreement with IR spectra results. From the XRD peaks at low Bragg angles (∼ 9–10°) we inferred that both xerogels consisted of nanocrystalline CH3-SiO3/2 species. In addition, the surface energy values of the films deposited from the corresponding sols were measured and the dispersive and polar portions correlated with the spectral features noted in the films. 相似文献