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991.
R. S. Kumeev M. Yu. Nikiforov E. D. Totchasov G. A. Al’per 《Journal of Structural Chemistry》2008,49(6):1120-1123
Chemical shifts (c.s.) of 1H nuclei in methanol are measured for methanol-benzene and methanol-phenanthrene systems. A method to determine the equilibrium constant of the molecular association reaction by NMR spectroscopy data is proposed for systems with low solubility of a compound when the dependence of c.s. on the composition is close to a straight line. The equilibrium constants for the formation of molecular complexes in methanol-benzene and methanol-phenanthrene systems are found. 相似文献
992.
Ohne Zusammenfassung 相似文献
993.
O. G. Al’tshuler L. P. Abramova L. A. Sapozhnikova G. N. Al’tshuler 《Russian Journal of Applied Chemistry》2009,82(3):391-395
New phosphoric acid cation exchanger was synthesized on the basis of immobilized calix[4] resorcinolarene and its service characteristics were determined. 相似文献
994.
995.
In this investigation, the peristaltic flow of a third order fluid in an asymmetric channel is considered in the presence of a slip condition. The series solution of the stream function and longitudinal pressure gradient is given under long wave length and low Reynolds number approximations. Pressure rise and frictional forces per wave length are analyzed through numerical integration. Pumping and trapping phenomena are examined and the obtained results are compared with those of no-slip condition. Comparison is made with the results of no-slip and viscous fluid cases. 相似文献
996.
G. A. Zenkovets G. N. Kryukova S. V. Tsybulya E. M. Al’kaeva T. V. Andrushkevich O. B. Lapina E. B. Burgina L. S. Dovlitova V. V. Malakhov G. S. Litvak 《Kinetics and Catalysis》2000,41(4):572-583
The formation of vanadia-titania catalysts was studied with a complex of physicochemical methods. The use of highly dispersed
anatase with a defect structure results in the formation of coherent boundaries of coalescence of the V2O5 and TiO2 crystallites with the ratio V : Ti =1 : 1 in a wide range of vanadium and titanium concentrations. The catalysts containing
coherent boundaries are active and selective in Β-picoline oxidation to nicotinic acid. 相似文献
997.
Dynamics of a Cubic Nonlinear Vibration Absorber 总被引:1,自引:0,他引:1
We study the dynamics of a nonlinear active vibration absorber. We consider a plant model possessing curvature and inertia nonlinearities and introduce a second-order absorber that is coupled with the plant through user-defined cubic nonlinearities. When the plant is excited at primary resonance and the absorber frequency is approximately equal to the plant natural frequency, we show the existence of a saturation phenomenon. As the forcing amplitude is increased beyond a certain threshold, the response amplitude of the directly excited mode (plant) remains constant, while the response amplitude of the indirectly excited mode (absorber) increases. We obtain an approximate solution to the governing equations using the method of multiple scales and show that the system possesses two possible saturation values. Using numerical techniques, we perform stability analyses and demonstrate that the system exhibits complicated dynamics, such as Hopf bifurcations, intermittency, and chaotic responses. 相似文献
998.
Mohamed Rafat Mahmoud Maher Mohamed Ahmed Hamed Ali Mohamed Shaker 《Journal of solution chemistry》1986,15(9):765-776
Kinetics of base hydrolysis of new heterocyclic azomethines derived from active methyl quaternary salts and aromatic nitroso compounds were investigated in the presence of 70% (wt/wt) water-methanol. The base hydrolysis of these compounds is strictly first-order with respect to OH– and azomethine. The rate determining step is suggested to be the attack of the hydroxide ion on the free base. Effects of water content and nature of organic hydroxylic solvent have been studied. It is concluded that specific solute-solvent interactions through dispersion forces play a major role in the base hydrolysis rate of the azomethines investigated. The effect of pH (2.98 – 12.24) on hydrolysis rates of compounds having a diethylamino substituent in the presence of 30% methanol has been studied. In acidic media, the rate determining step is probably the water attack on the protonated substrate. 相似文献
999.
We present a direct and rather elementary method for defining and analyzing one-dimensional Schrödinger operators H = −d2/dx2 + μ with measures as potentials. The basic idea is to let the (suitably interpreted) equation −f′′ + μ f = zf take center stage.We show that the basic results from direct and inverse spectral theory then carry over to Schrödinger operators with measures. 相似文献
1000.
Muhammad Saleem Naseem Akhter Muhammad Shaiq Ali Mamona Nazir Naheed Riaz Muhammad Moazzam Muhammad Arshad Abdul Jabbar 《Magnetic resonance in chemistry : MRC》2009,47(3):263-265
Chromatographic analysis of the alcoholic extract from Salsola imbricata yielded two new secondary metabolites, salisomide (1) and salisoflavan (2). Their structures were established with the help of spectroscopic techniques including COSY, HMQC and HMBC NMR experiments. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献