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51.
V. M. Buznik L. N. Ignat’eva V. G. Kuryavyi E. B. Merkulov N. N. Savchenko A. Yu. Ustinov A. B. Slobodyuk L. N. Nikitin 《Polymer Science Series A》2010,52(12):1334-1343
Microsized spherical core-shell particles consisting of hydrocarbon cores encapsulated into fluoropolymer shells are obtained
in supercritical carbon dioxide. Paraffins serve as a core material, while the polymer shell is formed from ultradispersed
polytetrafluoroethylene. The morphology and molecular structure in the bulk and on the surface of the particles and the influence
of conditions of particle formation on the shell thickness and the thermal properties of the materials are studied. The materials
are composites comprised of paraffin cores coated with shells of loosened globular fluoropolymer particles with sizes of 0.2–1.7
μm. The shells is built of low- and high-molecular-mass fractions consisting of CF3(CF2)nCF3 molecular chains with different lengths. The shell thickness is governed by preparation conditions, exposure time, and the
percentage of the polymer in the initial dispersion. 相似文献
52.
53.
T. F. Antokhina N. N. Savchenko L. N. Ignat’eva T. A. Kaidalova 《Russian Journal of Inorganic Chemistry》2010,55(5):655-660
Ammonium-containing mixed-alkali-metal fluoro complexes NH4NaNbF7 and NH4MNbOF5 (M = Li and Na) crystallizing in orthorhombic system were synthesized and characterized for the first time. Unit cell parameters
for these complexes were determined. Their IR absorption spectra were measured and characterized in the range 4000-350 cm−1. 相似文献
54.
László Csaba Bencze Csaba Paizs Monica Ioana Toşa Maria Trif Florin Dan Irimie 《Tetrahedron: Asymmetry》2010,21(16):1999-2004
A highly stereoselective enzymatic kinetic resolution of novel various substituted racemic furylbenzthiazole-2-yl-ethanols and their acetates has been developed. Both processes, the enzymatic acylation of the racemic alcohols and the enzymatic methanolysis of racemic acetates yielded highly enantiomerically enriched (ee >98%) resolution product, when CaL-B was used as a biocatalyst in acetonitrile. The absolute configuration of the obtained (R)-(+)-1-(5-(4-chlorobenzo[d]thiazol-2-yl)furan-2-yl)ethanol was determined by a detailed 1H NMR study of rac- and (+)-1-(5-(4-chlorobenzo[d]thiazol-2-yl)furan-2-yl)ethanol Mosher derivatives. 相似文献
55.
A. V. Ignat’ev T. A. Velivetskaya S. Yu. Budnitskii 《Journal of Analytical Chemistry》2010,65(13):1347-1355
A new method for the measurement of the argon isotope composition in a continuous helium flow using isotope mass spectrometers is described for potassium-argon geochronology. Argon was extracted from the samples in a chamber with a multiple-sample holder by successively heating the samples with a continuous infrared laser. Argon extracted in the chamber was preconcentrated in a capillary, separated on a chromatographic capillary column in a helium flow, and then injected into the ion source of a mass spectrometer through an open splitter. Measurements of the 36Ar, 38Ar, and 40Ar isotopes were carried out on isotope mass spectrometers in a dynamic mode using a triple-collector ion detector and three electrometric amplifiers. Preliminary experiments on the developed device for measuring argon isotopes in a continuous helium flow have shown that the proposed method can be used for the determination of radiogenic argon in an amount of n × 10?12 g with the accuracy satisfying the solution of many geochronological problems. In sensitivity and reproducibility, the proposed method is highly competitive to the isotope dilution method for measuring argon and simpler than the conventional methods for measuring radiogenic argon. 相似文献
56.
Tibor Rozsa Mihaela Duma Laurian Vlase Ioana Ionuţ Adrian Pîrnău Brînduşa Tiperciuc Ovidiu Oniga 《Journal of heterocyclic chemistry》2015,52(4):999-1006
Thiazole and bisthiazole derivatives represent a prevalent scaffold in the antimicrobial drug discovery. Therefore, we have decided to synthesize some new series of 4,5′‐bisthiazoles. A total of 17 compounds were synthesized, their structural elucidation being based on elemental analysis (C,H,N,S) and spectroscopic data (MS and 1H NMR). Their in vitro antimicrobial activities were assessed against several Gram‐positive and Gram‐negative bacteria strains and also against one fungal strain (Candida albicans) using the difusimetric method. Some of the compounds showed modest to good antibacterial activity against Gram‐negative Escherichia coli and Salmonella typhimurium and Gram‐positive Staphylococcus aureus and Bacillus cereus bacterial strains. All of the synthesized compounds showed moderate to very good antifungal activity against C. albicans. 相似文献
57.
The electrosurface characteristics of titanium oxide nanoparticles synthesized by the sol-gel method are studied in relation
to the pH and concentration of solutions of sodium, potassium, barium, and lanthanum chlorides. The surface charges and electrokinetic
potentials are found, and the positions of the points of zero charge are analyzed as depending on the type and concentration
of cations. The absence of a negative region of the electrokinetic potential, which results from the superequivalent adsorption
in the Stern layer, is revealed for BaCl2 and LaCl3 solutions. 相似文献
58.
A. O. Ignat’ev 《Ukrainian Mathematical Journal》2011,62(11):1680-1689
A system of linear differential equations with pulse action at fixed times is considered. We obtain sufficient conditions
for the existence of a positive-definite quadratic form whose derivative along the solutions of differential equations and
whose variation at the points of pulse action are negative-definite quadratic forms regardless of the times of pulse action. 相似文献
59.
We deal with a nonconvex and nonlocal variational problem coming from thin-film micromagnetics. It consists in a free-energy functional depending on two small parameters ε and η and defined over vector fields m:Ω⊂R2→S2 that are tangent at the boundary ∂Ω. We are interested in the behavior of minimizers as ε,η→0. They tend to be in-plane away from a region of length scale ε (generically, an interior vortex ball or two boundary vortex balls) and of vanishing divergence, so that S1-transition layers of length scale η (Néel walls) are enforced by the boundary condition. We first prove an upper bound for the minimal energy that corresponds to the cost of a vortex and the configuration of Néel walls associated to the viscosity solution, so-called Landau state. Our main result concerns the compactness of vector fields {mε,η}ε,η↓0 of energies close to the Landau state in the regime where a vortex is energetically more expensive than a Néel wall. Our method uses techniques developed for the Ginzburg-Landau type problems for the concentration of energy on vortex balls, together with an approximation argument of S2-vector fields by S1-vector fields away from the vortex balls. 相似文献
60.
Ioana Diaconu Hassan Y. Aboul-Enein Mohammed A. Al-Omar Gheorghe Nechifor Elena Ruse Andrei A. Bunaciu Eugenia Eftimie Totu 《Arabian Journal of Chemistry》2011,4(1):99-103
The paper presents experimental data obtained in the study of liquid–liquid partition equilibriums in biphasic system in order to optimize the process of transport through bulk liquid membranes (triphasic partition systems). The partition equilibriums of some nitrophenols using chloroform as extraction solvent and membranary solvent, respectively, were studied. The influence of the pH on the partition equilibriums was investigated. The repartition constants and the pKa values of the studied nitrophenols were calculated. Nitrophenols were transferred in triphasic system from a feed phase with pH 2, through a chloroform liquid membrane, into a receiving phase with pH 12, with efficiencies over 90%. 相似文献