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41.
Raman spectroscopy is used in this work to reveal an increase in the size of anatase crystallites in the process of drying
of hydrated titanium dioxide gel and ordering of the structure of primary particles of hydrated tin dioxide gel under drying.
Raman spectra are interpreted with account of dimensional effects. It is found that mechanical stresses that arise in the
materials under drying have a great effect on the structural changes found there.
TERMOXIDE Research and Production Company, 624051 Zarechnyi, Sverdlovsk Region, P/O Box 94, Russia. Translated from Zhurnal
Prikladnoi Spektroskopii, Vol. 64, No. 2, pp. 266–268, March–April, 1997. 相似文献
42.
We propose an approach to synthesis of N,O,S-containing 6- and 7-membered heterocycles based on using 4-nitrophenyl N-(1-aryl-2,2,2-trifluoroethylidene)urethanes as the electrophilic components in heterocyclizations with bifunctional nucleophilic reagents. 相似文献
43.
Given here are the results of experimental investigations of wave processes in earth under the action of explosions of charges surrounded by sheaths of air, and some general laws are established.Translated from Zhurnal Prikladnoi Mekhaniki i Tekhnicheskoi Fiziki, No. 2, pp. 105–110, March–April, 1972. 相似文献
44.
45.
Squaric acid dimethyl ester (C(6)O(4)H(6); 3,4-dimethoxycyclobut-3-ene-1,2-dione; DCD) was studied by matrix isolation infrared spectroscopy and by density functional theory (B3LYP) and ab initio (MP2) calculations with the 6-31++G(d,p) and 6-311++G(d,p) basis sets. Three conformers of the compound were theoretically predicted. The two most stable conformers were identified in low-temperature argon matrixes and the energy gap between them was determined. The trans-trans conformer (C(2)(v)) was found to be more stable than the cis-trans form (C(s)) by 4.2 kJ mol(-1), in consonance with the theoretical predictions (MP2 calcd = 3.9 kJ mol(-1)). In situ broadband UV irradiation (lambda > 337 nm) of the matrix-isolated compound was found to induce the ring-opening reaction leading to production of the bisketene, 2,3-dimethoxybuta-1,3-diene-1,4-dione as well as the trans-trans --> cis-trans conformational isomerization. The latter phototransformation allowed separation of the infrared spectra of the two conformers initially trapped into a low-temperature matrix. Upon higher energy irradiation (lambda > 235 nm), the main observed photoproducts were CO and deltic acid dimethyl ester (C(5)O(3)H(6); 2,3-dimethoxycycloprop-2-en-1-one), the latter being obtained in two different conformations (trans-trans and cis-trans). According to the experimental data, deltic acid dimethyl ester is produced by decarbonylation of the initially formed bisketene and not by direct CO extrusion from DCD. 相似文献
46.
The behavior of special classes of isometric foldings of the Riemannian sphere S
2 under the action of angular conformal deformations is considered. It is shown that within these classes any isometric folding
is continuously deformable into the standard spherical isometric folding f
s
defined by f
s
(x, y, z) = (x, y, |z|). 相似文献
47.
V. N. Baumer T. G. Deineka T. A. Korshikova E. A. Vovk M. B. Kosmyna B. P. Nazarenko V. M. Puzikov Z. P. Sergienko V. F. Tkachenko A. V. Tolmachev A. N. Shekhovtsov 《Crystallography Reports》2008,53(7):1191-1193
The physical and technical conditions for reproducible production of nanodispersed yttrium aluminum garnet (Y3Al5O12, YAG) and yttrium oxide (Y2O3) powders by chemical coprecipitation have been investigated. It is established that the obtained YAG nanopowders have enhanced
reactivity, which significantly decreases the temperature range of interaction in the Y2O3-Al2O3 system in comparison with ceramic synthesis. It is shown that vacuum heat treatment may lead to reversible transformation
of the YAG crystal structure from cubic to tetragonal. 相似文献
48.
Ivanna Yu. Danyliuk Ruslan I. Vas’kevich Alla I. Vas'kevich Eduard B. Rusanov Mykhailo V. Vovk 《Phosphorus, sulfur, and silicon and the related elements》2019,194(1-2):156-162
Heterocyclization of N-(pyrazol-3-yl)styrylacetamides with arenesulfenyl chlorides yields the corresponding tetrahydrofuran-2-iminium perchlorates isolable after chromatography as trans-5-aryl-4-(arylthio)tetrahydrofuran-2-ones and 5-aryl-4-(arylthio)-1-(pyrazol-3-yl)pyrrolidin-2-ones, with the latter predominating. N-(Pyrazol-4-yl)styrylacetamides react under analogous conditions to give 5-aryl-4-(arylthio)-1-(pyrazol-4-yl)pyrrolidin-2-ones, 4-aryl-3-(arylthio)-4-chloro-N-(1-methylpyrazol-4-yl)butanamides, and tetrahydrofuran-2-iminium perchlorates which, when chromatographed, produce 5-aryl-4-(arylthio)dihydrofuran-2(3H)-ones and 4-aryl-3-(arylthio)-4-methoxy-N-(1-methyl-1H-pyrazol-4-yl)butanamides. 相似文献
49.
Diego Fontana de Andrade Louise Jank Vitor Breda Rego Roberto Minozzo Marcus Vinícius Burgel Sfoggia Álvaro Bavaresco Fabiano Barreto 《Biomedical chromatography : BMC》2020,34(9):e4873
Saponins from Quillaja saponaria have been commonly used as immunomodulatory adjuvants in foot-and-mouth disease vaccines (FMDVs). However, due to the lack of consensus over the possible exacerbation of local inflammatory responses in cattle and its economic impacts, their use has been discouraged by Brazilian authorities. A qualitative method intended to determine the presence of saponins from Q. saponaria bark extracts in FMDVs was developed and validated. Instrumental analysis was performed using an liquid chromatography (LC) coupled to a quadrupole–time-of-flight–mass spectrometry (TOF-MS) system. The method was validated according to the International Conference on Harmonization Harmonized Tripartite Guideline Q2 (R1) and Brazilian Ministry of Agriculture, Livestock and Food Supply Analytical Quality Assurance Guidelines. Validation parameters were determined and considered suitable to the established criteria. The validated method has been applied in routine analysis in the National Agricultural Laboratory at Rio Grande do Sul (LANAGRO-RS). All results obtained were in agreement with the vaccine's composition described by the manufacturer. The method is easy and adequate for analysis in routine laboratories. To the best of the authors' knowledge, this is the first report of a method which intends to investigate the presence of saponins from Q. saponaria bark extracts in veterinary vaccines. 相似文献