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911.
An universal function for non-bonded interactions, which takes into account the relative orientation of the bonds is considered in calculating the conformational energies of cycloalkenes and cycloalkadienes. A comparison is made with previous results obtained by using usual 6-exp functions for non-bonded interactions. 相似文献
912.
The monoclinic modification of terbium oxide hydroxide, TbOOH, was prepared using hydrothermal technique. The crystal structure was investigated by three-dimensional single-crystal X-ray analysis and was refined to a conventional R-value of 8.1%. The space group is , No. 11, with a = 6.04 Å, b = 3.69 Å, c = 4.33 Å, and β = 109.0°. The terbium atom is seven coordinated with oxygen atoms, and the structure is not hydrogen bonded.The compound is antiferromagnetic with a Néel temperature of 10°K. Neutron diffraction powder patterns were measured at 300°K and 4.2°K. The magnetic super lattice reflections were indexed on the basis of a monoclinic unit cell with the dimensions aM = 2a, bM = b, cM = c, and βM = β, where a, b, c, and β are the dimensions of the chemical unit cell. The structure contains two independent magnetic atoms. A nonclinear antiferromagnetic arrangement of the spins describes the magnetic structure. The spin at one atom has an angle of 43° with the ac plane and the projection of the spin on the ac plane has an angle of 59° with the a axis. The spin on the other atom has an angle of ?43° with the ac plane, the projection having the same angle of 59° with the a axis. 相似文献
913.
贮氢材料电极循环寿命的定量预测定时放电半衰期法的应用韩剑文,袁满雪,周作祥,赖城明(南开大学化学系天津300071)关键词:贮氢电极,循环寿命,半衰期。前文 ̄[1]讨论了应用定终点电位放电半衰期法来预测贮氢材料电极循环寿命的问题。本文讨论如何采用定时... 相似文献
914.
Hidetake Sakuraba Yoshio Tananaka Fujio Toda 《Journal of inclusion phenomena and macrocyclic chemistry》1991,11(2):195-204
The asymmetric Michael addition of aromatic thiols to 2-cyclohexenone and maleic acid esters has been carried out by utilizing their crystalline cyclodextrin complexes suspended in water. The best chiral induction, 30% enantiomeric excess (ee), was achieved in combinations of 2-cyclohexenone and octyl maleate with the crystalline -cyclodextrin complex of benzenethiol (method A) to afford (S)-3-phenylthiocyclohexanone and (S)-octyl-2-phenylthiosuccinate, respectively, whereas the reaction of benzenethiol with 2-cyclohexenone included in -cyclodextrin (method B) inversely induced the chiral recognition to give the (R)-adduct with 4–9% ee. 相似文献
915.
This study reports on the development of an immunochromatographic flow-injection (FI) method for the quantitation of human serum IgG antibodies to Helicobacter pylori. Patients’ sera were injected into the carrier stream of a FI manifold incorporating an H. pylori immuno-adsorbent reactor. The immuno-adsorbent was prepared by covalently linking H. pylori antigens to periodate oxidized Sepharose CL-4B. Any H. pylori antibody present in the serum is bound to the immuno-sorbent. The bound antibody was quantified by injecting into the carrier stream anti-human IgG peroxidase conjugate followed by TMB/H2O2 as the enzyme substrate. The FI system was optimized with respect to antigen loading (1.0 mg/ml gel), bioreactor length (3.0 cm), enzyme conjugate (0.2 mg/ml) and sample loop size (250 μl). One hundred clinical samples were analyzed for their H. pylori antibody concentrations and the results evaluated with respect to their receiver-operator characteristics (ROC). When a cut-off absorbance of between 0.7 and 0.75 was used for positive and negative samples a specificity (>95%), a sensitivity (>90%)and an overall accuracy (>94%) were obtained. 相似文献
916.
It is shown that 2,2-difluoro-3-hydroxymethylbenzo-1,4-oxathianes are formed together with 3-trifluoromethylbenzo-1,4-oxathianes whenortho-(-trifluoromethyl--chloroethylthio)phenols are boiled with excess aqueous alkali. The mechanism of the reaction is discussed.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1457–1459, August, 1994. 相似文献
917.
A. I. V'yugin E. V. Antina D. V. Chernyshev G. A. Krestov 《Russian Chemical Bulletin》1992,41(7):1190-1192
Features of the solvation of zinctetraphenylporphyrin (ZnTPP) in benzene, toluene,ortho-, meta-, andpara-xylenes were studied by a thermogravimetric method. The temperature ranges of the stability and the compositions of the corresponding specific - complexes were determined from the results of the thermogravimetric investigation of the crystallosolvates of the metalloporphyrin with the solvent molecules, and the energy characteristics of the intermolecular metalloporphyrin—solvent interactions were calculated.Institute of the Chemistry of Nonaqueous Solutions, Russian Academy of Sciences, 153018 Ivanovo. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 7, pp. 1545–1548, July, 1992. 相似文献
918.
The photophysical characteristics of poly 4(2-acryloxybenzophenone), poly-ABP, and its model compound 4(2-methylpropionyloxy)benzophenone, IBP, have been determined by steady state and pulse methods. In IBP the observed properties are mainly due to the n,π1 triplet of the benzophenonic moiety. In poly-ABP, the formation of singlet excimers competes with the intersystem crossing leading to benzophenonic triplet. The triplet lifetime in polymer is reduced, compared to the model compound. This fact is explained in terms of intramolecular hydrogen abstraction of the triplet. 相似文献
919.
Summary The enthalpimetric determination of a series of bases by using the reaction of the bases and sodium tetraphenylboron is described. The accuracy of the method is analytically acceptable, over the range 3×10–5 moles to 7.5×10–4 moles. The upper limit is determined by the bulk of the precipitate.Dosage forms of some physiologically active alkaloids contain more than the upper limit of analyte. Yet, preliminary investigations using silicotungstic acid indicate that this is suitable for thermometric titrations.
Enthalpimetrische und thermometrische Bestimmung stickstoffhaltiger Basen und physiologisch aktiver Alkaloide
Zusammenfassung Die enthalpimetrische Bestimmung einiger N-haltiger Basen erfolgte aufgrund der Reaktion mit Natriumtetraphenyloborat. Die Genauigkeit ist im Bereich von 3 · 10–5-7,5 · 10–4 Mol befriedigend. Eine obere Grenze der Anwendbarkeit ergibt sich aus der Menge des anfallenden Niederschlags. Diese wird bei der Bestimmung von Formulierungen einiger physiologisch aktiver Alkaloide überschritten. Jedoch ist in diesem Fall eine thermometrische Titration mit Hilfe von Silicowolframsäure möglich.
Lecture presented at Euroanalysis I Conference, 28. 8.–1. 9. 1972 in Heidelberg, Germany. 相似文献
920.
A new reaction of organolithium compounds with phosphonium salts is described; reaction of t-butyllithium with dibenzylaminophosphonium or tetraphenylphosphonium bromides takes place through addition of the t-butyl group on a benzene ring at the position para to the phosphorus atom, the ylid formed reacts in a characteristic Wittig reaction with p-tolylaldehyde. 相似文献