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211.
A. V. Tarasov P. O. Yablonsky Yu. A. Moskvichev 《Chemistry of Heterocyclic Compounds》2003,39(1):119-122
Various methods were studied for the oxidation of 2-methyl-5-(phenylsulfonyl)benzenesulfamide and its derivatives. The oxidation by sodium dichromate in sulfuric acid was found most efficient. The effects of temperature, concentration, reagent ratio, and time of the oxidation reaction on the yield of the desired product were investigated. Conditions were proposed for obtaining the desired product in yields up to 95%. A synthesis was developed for a series of new saccharin derivatives. 相似文献
212.
Ha Yong Lee Se Hun Jung Soo Yong Lee Young Ho You Kyung Hyun Ko 《Applied Surface Science》2005,252(5):1891-1898
Al-Al2O3 composite coatings with different Al2O3 particle shapes were prepared on Si and Al substrate by cold spray. The powder compositions of metal (Al) and ceramic (Al2O3) having different sizes and agglomerations were varied into ratios of 10:1 wt% and 1:1 wt%. Al2O3 particles were successfully incorporated into the soft metal matrix of Al. It was found that crater formation between the coatings and substrate, which is typical characteristic signature of cold spray could be affected by initial starting Al2O3 particles. In addition, when the large hard particles of fused Al2O3 were employed, the deep and big craters were generated at the interface between coatings and hard substrates. In the case of pure soft metal coating such as Al on hard substrate, it is very hard to get proper adhesion due to lack of crater formation. Therefore, the composite coating would have certain advantages. 相似文献
213.
214.
In this paper we give the answer to the Gromov's question about the macroscopic dimension of universal coverings of closed manifolds in dimension 3. We prove that the macroscopic dimension of a universal covering of a closed Riemannian 3-manifold cannot be equal to 2. 相似文献
215.
V. Klepko S. Ryabov Yu. Kercha L. Bulavin R. Bila V. Slisenko O. Vasilkevich V. Krotenko 《Journal of Molecular Liquids》2005,120(1-3):67-69
Water molecule mobility in ion-containing and nonionic aqueous solutions of β-cyclodextrin was studied by quasielastic neutron scattering (QENS). The total self-diffusion coefficients and their components corresponding to the contributions from collective (Lagrange type) and single-particle (jump diffusion) parts of molecular motions were determined. From the data obtained, one can conclude that the molecular mobility of free water in nonionic aqueous solutions of β-cyclodextrin with guest molecules (2-aminopyridine) proceeds by a single-particle mechanism. The addition of Pb2+ ions into the solution leads to increase in self-diffusion coefficients and growth of a bound water fraction. 相似文献
216.
217.
Richard P. Kent IV 《Geometriae Dedicata》2004,106(1):145-159
We answer a question of J. Anderson's by producing infinitely many commensurability classes of fibered hyperbolic 3-manifolds whose fundamental groups contain subgroups that are locally free and not free. These manifolds are obtained by performing 0–surgery on a collection of knots with the same properties. 相似文献
218.
219.
Zh. A. Krasnaya E. O. Tret’yakova V. V. Kachala S. G. Zlotin 《Russian Chemical Bulletin》2008,57(8):1671-1675
A reaction of 2,2-disubstituted 1,1-dicyanoethenes with β-dimethylaminoacrolein aminal and 3-dimethylamino-1,1,3-trimethoxypropane
leads to substituted 6,6-dicyano-1-dimethyl-aminohexatrienes and an organic salt containing 1,1,9,9-tetracyano-2,8-diphenylnona-2,4,6,8-tetraenide
as the anion and (dimethylaminopropenylidene)dimethylammonium as the cation, on the basis of which new cation-anionic polymethine
dyes were obtained.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1639–1643, August, 2008. 相似文献
220.
Mohamed Haouas Amine Harrane Mohamed Belbachir Francis Taulelle 《Journal of Polymer Science.Polymer Physics》2007,45(22):3060-3068
Results of multinuclear MAS NMR spectroscopy are reported for poly (ε‐caprolactone)/maghnite nanocomposite formation, with ε‐caprolactone in situ polymerized in the presence of maghnite, a proton exchanged montmorillonite clay. Exfoliated and intercalated materials with different maghnite loading in the range 3–15 wt % were investigated. 1H NMR evidences Brønsted acid hydroxyl groups in the silicate layers and shows that their broad signal at 7.6 ppm present in the parent clay disappears in the nanocomposite material. 27Al MAS NMR results show that beside the hexacoordinated aluminum signal, two additional peaks corresponding to two different tetrahedral Al sites are present in the clay framework. The NMR signal intensity of only one of them was found to be affected in the nanocomposites compared with the parent maghnite, suggesting that these specific aluminum sites are the reactive ones at the initial stages of the polymerization. However almost no changes occurred in the 29Si NMR spectra, confirming that the polymer grafting, as indicated earlier by atomic force microscopy, took place on the aluminum tetracoordinated sites rather than on the silicon sites. A mechanism of maghnite surface catalyzed polymerization of ε‐caprolactone was proposed, involving Brønsted and Lewis acid sites. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 3060–3068, 2007 相似文献