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941.
(2-Quinoxalylthio)acetic acids have been found to cyclize on treatment with acetic anhydride to give the mesoionic thiazolo[3,2-a]quinoxalinium oxides. Some reactions of these compounds have been studied, and the relationship of the color of the compounds to their chemical structure examined.For Communication 18, see [1].Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 12, pp. 1680–1684, December, 1989. 相似文献
942.
U. Kreibig K. Fauth M. Quinten D. Schönauer 《Zeitschrift für Physik D Atoms, Molecules and Clusters》1989,12(1-4):505-514
First, some general remarks concerning macroscopic “cluster matter” are given. In the second part, three recent, mainly optically and electron-microscopically performed investigations are discussed which deal with special properties of noble metal cluster systems forming the building units of this kind of matter:(1) dressed Au-55 clusters,(2) electromagnetic coupling effects among coagulated clusters,(3) the transition towards compact inhomogeneous matter caused by coalescence of clusters. 相似文献
943.
944.
945.
V. G. Kokacheva L. V. Menshikova S. K. Talitskikh P. G. Khalatur 《Journal of Structural Chemistry》1995,36(5):734-738
A system of Ornstein-Zernike integral equations is solved numerically to determine the heats of vaporization ΔHV of liquid ethane, propane, and n-butane. It is shown that the calculations (the deformations of valence bonds and bond angles
in the liquid-phase molecules are ignored) give rather accurate values of ΔHV, which are in agreement with the corresponding experimental data. On the other hand, it is established that if there are
intramolecular rotational degrees of freedom, ΔHV depends on the angle of internal rotation ϕ. The function ΔHV(ϕ) is minimum for trans-conformations (ϕ=0) and maximum for cis-conformations (ϕ=180°). Hence, intermolecular interactions
stabilize compact (convolute) conformations. The energy of this effect is of the order of 1 kJ/mole.
Tver State University. Translated fromZhurnal Strukturnoi Khimii, Vol. 36, No. 5, pp. 808–813, September–October, 1995.
Translated by I. Izvekova 相似文献
946.
947.
A. Gopalan S. Paulrajan S. Vaidyanathan K. Venkatarao N.R. Subbaratnam 《European Polymer Journal》1984,20(10):971-973
The kinetics of polymerization of acrylamide initiated by potassium peroxomonosulphate, in the presence and absence of Ag+, were studied. Rates of polymerization and oxone disappearance were followed. From the rate law for the polymerization, a mechanism has been proposed. 相似文献
948.
949.
A selected ion monitoring (SIM) method has been devised for the determination of metabolites of dydrogesterone, 20 alpha-hydroxy-9 beta,10 alpha-pregna-4,6-dien-3-one (DHD) and DHD glucuronide, in plasma. Using testosterone as an internal standard (IS), DHD and IS were extracted with n-hexane and were purified by means of magnesium oxide column chromatography. The purified DHD and IS were converted to their diheptafluorobutyryl derivatives (DHD diHFB and testosterone diHFB) with heptafluorobutyric anhydride in acetone for analysis by SIM. SIM was carried out with a 2% OV-17 column (1 m) at 230 degrees C by monitoring the molecular ions of the derivatives (m/z 706 for DHD diHFB, m/z 680 for testosterone diHFB). DHD was determined from a calibration curve using a peak area method. The determination limit of the devised method was about 5 ng DHD per ml of plasma and the reproducibility was within +/- 6% of the coefficient of variation for 30 ng of DHD per ml of plasma or above. 相似文献
950.
The single comparator method in neutron activation analysis has been applied to the investigation of the purity of silicon
single-crystals of different origins. The following impurities were determined: Au, Sb, Co, Cu and Na. Studies were also carried
out on the surface contamination of silicon samples introduced through steps of sample preparation and irradiation. Up to
nineteen elements on the surface of samples were analysed and found to be easily reduced to low levels or detection limits
by washing and etching. 相似文献