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131.
Geometrical parameters associated with N-H ... N types of hydrogen bonds have been analysed using crystal structure data on
nucleic acids, amino acids and related compounds. Histograms depicting the frequency distribution of N-H ... N length (l) and H-N ... N angle (θ) have been drawn and conclusions on the favoured geometry of such bonds have been arrived at. The
distribution ofl shows a pronounced maximum in the range between 2.9? and 3.0? with an overall average of 2.98 ?. The θ distribution shows
a pronounced maximum for the hydrogen bond angle in the range 0°-10°, with a rapid fall-off in frequency for nonlinear hydrogen
bonds. The frequency shows a cos6θ dependence as compared to cos2θ dependence term used earlier to predict the angular dependence of hydrogen bond potential energy in proteins and polypeptides. 相似文献
132.
The ostwald absorption coefficient of argon was measured in aqueous solutions of two surfactants; sodium n-octanoate and in sodium dodecylsulfate, at several concentrations and at a few temperatures between 10–25°C. The free energies, entropies and enthalpies of solution were computed. A tentative interpretation of the results is given, based on a competition between the solubilization and the salting-out effects of the surfactants. 相似文献
133.
134.
直链醇链长对层状液晶结构与稳定性的影响 总被引:8,自引:4,他引:8
作为助表面活性剂,直链醇在层状溶致液晶的制备中是非常重要的。本文以层状液晶的相行为和小角度X射线衍射测量,研究了直链醇链长对层状液晶结构与稳定的影响。 相似文献
135.
T. Vlase Gabriela Vlase N. Doca C. Bolcu 《Journal of Thermal Analysis and Calorimetry》2005,80(1):59-64
Decomposition of dichlorodifluoromethane in thermal plasma was investigated theoretically by computing the equilibrium composition of the gas mixtures involving carbon, chlorine and fluorine in presence of argon (which is assumed to be the main plasma gas) and/or in addition of hydrogen and calcium together with hydrogen. The calculations were carried out for the temperature range between 500 and 6000 K and for the total pressure of the system of 1 bar. Use is made of the fact that a thermal plasma is a plasma in (local) thermal equilibrium, which makes possible the theoretical determination of its equilibrium composition at definite temperature by employing Gibbs free energy data for the compounds present in the system and assuming that the equilibrium of the system corresponds to its minimum energy state. The results of calculations show that toxic molecules and radicals can be, under convenient conditions (appropriate temperature and amount of added substances), converted into stable non-toxic species like CaF2 and CaCl2. 相似文献
136.
Karel Strnský Tom Jursík Antonín Vítek Jií Skoepa 《Journal of separation science》1992,15(11):730-740
A method has been developed for calculating more accurate and reproducible equivalent chain length (ECL) values of 33 straight-chain fatty acids (FA), with various positions and numbers of cis double bonds, chromatographed on DB-Wax and DB-1 columns. The dependence of ECL values on the position and the number of double bonds is described, as is a method of utilizing these relationships for the characterization of FA by gas chromatography. 相似文献
137.
异丁烷与丁烯烷基化反应的热力学分析 总被引:1,自引:0,他引:1
对异丁烷与丁烯烷基化反应进行了较为详尽的热力学分析和计算,得到了不同反应温度下的焓值、吉布斯自由能和反应平衡常数,并且对温度、压力和惰性物质对热力学平衡的影响进行了分析。得到了详细的烷基化反应热力学基础数据,这些数据对研究异丁烷与丁烯的烷基化反应具有重要的参考价值。 相似文献
138.
Todd B. Kreutzian Khalid S. A. Seraj Larry G. Anderson Donald C. Zapien 《Electroanalysis》2007,19(23):2479-2482
In this work, long optical path length thin‐layer electrochemical cell was constructed using indium‐tin oxide on glass as the electrode material. Iron release from ferritin adsorbed on the electrode was induced by applying a negative potential sweep in the presence of 1,10‐phenanthroline. The usefulness of spectroelectrochemistry as a means of determining the quantity of iron released from an adsorbed layer of ferritin is demonstrated. 相似文献
139.
T. M. Roshchina V. Ya. Davydov K. B. Gurevich A. A. Mandrugin N. M. Khrustaleva 《Russian Chemical Bulletin》1997,46(3):431-436
The adsorption properties of silica gel with grafted aminopropyl and guanidinoethanethiol (GET) groups were studied by the
techniques of adsorption under static conditions and gas chromatography. It was shown that molecules capable of forming hydrogen
bonds are adsorbed on all modified samples more weakly than on the initial silica gel. The grafting of GET radicals on the
surface results in a noticiable increase in the dispersion interaction with adsorbed molecules. Calculation of the contributions
of molecular groups to the constant of adsorption equilibrium showed that the thermodynamic characteristics of adsorption
on aminosilochromes and aminosilicas with a polymeric layer of the modifying agent have similar values. Such adsorbents can
be used for investigation of polar compounds, including organic bases.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 452–457, March, 1997. 相似文献
140.