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排序方式: 共有131条查询结果,搜索用时 296 毫秒
91.
Salah Abd El Wanees Ahmed Diab Omar Azazy M. Abd El Azim 《Journal of Dispersion Science and Technology》2014,35(11):1571-1580
N-(Pyridin-2-yl-carbamothioyl)benzamide (PCMB) was newly synthesized and tested as a corrosion inhibitor for C-steel in 0.5 M H2SO4 using chemical and electrochemical techniques. Polarization measurements showed that the synthesized compound acted as a mixed inhibitor. The inhibition efficiencies obtained from the different methods were in good agreement. The inhibitive action of this compound is discussed in terms of blocking the electrode surface by adsorption of the inhibitor according to the Langmuir isotherm. The effect of temperature on the corrosion behavior in the absence and presence of 2.5 × 10?5 M of PCMB was studied (283–308 K). The associated activation energies (E a) and the thermodynamic parameters (ΔH*, ΔS*, K ads, ΔG°ads) for the adsorption process were determined. The ΔG°ads value is ?36.55 kJ/mol, which indicated that the adsorption mechanism of PCMB on C-steel in 0.5 M H2SO4 solution was combined between physisorption and chemisorption processes. 相似文献
92.
93.
High-spin states of nuclei, populated by heavy-ion reactions, are of interest because they reveal changes in the structur of nuclei under stress. In the first part much of our insight into the structure of high-spin states is being provided by electromagnetic strength functions. In the second part, the level scheme of 158Yb has been extended to I = 37 by using the 98Mo (64Ni, 4n) reaction, and the backbending phenomena in Yb isotopes has been discussed. 相似文献
94.
Refractive index profiles have been obtained at different heights in the region above a candle flame both theoretically and experimentally by means of double and multiple exposure speckle photography. Improved fringe visibility has been achieved in the case of the multiple exposure technique giving rise to accurate measurement of the refractive index. Theoretical analysis shows that the resulting speckle pattern is equivalent to the ordinary pattern convolved with a function representing the effect of light deflection, while the interference pattern obtained is modulated by a background representing the autocorrelation function of the diffuser. 相似文献
95.
P. Mison R. Chaabouni Y. Diab A. Laurent R. Martino A. Lopez F. W. Wehrli T. Wirthlin 《Magnetic resonance in chemistry : MRC》1976,8(2):90-94
The configuration and favoured conformations of 1,2-dialkyl-(or alkyl-phenyl)-7-azabicyclo[4.1.0]heptane diastereoisomers have been determined by means of 13C NMR. The substituent in position-2 is ‘pseudo-axial’ in cis isomers and ‘pseudo-equatorial’ in trans isomers. 相似文献
96.
Power series expansions of quantum-mechanical potential surfaces for H2O and LiH2 are generated using conventional valence displacement coordinates and alternative distance [(r-r e)/r] and angle [(sin (θ/2) — sin (θe/2))/sin (θe/2)] variables. Power series in the new variables are demonstrated to be superior in terms of the quality of the fit to the energygeometry data, predicted equilibrium geometry and energy, and stability of expansion coefficients. 相似文献
97.
Maxime Beuvin Maxime Manneveau Sonia Diab Baptiste Picard Morgane Sanselme Serge R. Piettre Julien Legros Isabelle Chataigner 《Tetrahedron letters》2018,59(51):4487-4491
An efficient access to 4-aryl imidazole scaffolds is described in two steps and one operation. Cyanoaryl-imidazolines are easily obtained by a (3?+?2) heterocyloaddition involving cyanobenzenes as dipolarophiles and a non-stabilized azomethine ylide as an electron-rich 1,3-dipole. Oxidation of the crude mixture affords an efficient two-steps access to the corresponding imidazoles. 相似文献
98.
A. B. Moustafa N. A. Ghanem M. A. Diab 《Journal of polymer science. Part A, Polymer chemistry》1975,13(9):1987-1991
The polymerization of methyl methacrylate (MMA) was carried out in water by use of various concentrations of sodium bisulfite as initiator in the presence and absence of colorless and colored soda lime glass at 40°C. The reaction products were filtered, washed with water, methanol and finally dried at 50°C. The glass–polymer combination was subjected to Soxhlet extraction with benzene. The molecular weights of the soluble polymers were determined viscometrically. In the absence of glass, the conversion was lower but the average molecular weights were higher than in presence of soda lime glass. The effect of grain size of the glass on conversion and molecular weights was such that larger grain size of glass resulted in lower conversion and higher average molecular weights. 相似文献
99.
A transient absorption study of the photolysis of methylcobalamin (MeCbl), ethylcobalamin (EtCbl), and n-propylcobalamin (PrCbl) in ethylene glycol spanning six decades in time, from 10 fs to 10 ns, is reported. These measurements probe the influence of solvent on the formation and decay of the metal-to-ligand charge transfer (MLCT) intermediate observed following excitation of MeCbl, the photolysis mechanism in EtCbl and PrCbl, and the rate constants for geminate recombination of the alkyl radicals with cob(II)alamin and for the escape of the alkyl radicals from the initial solvent cage. Earlier investigations probed the dynamics of 5'-dexoyadenosylcobalamin (coenzyme B(12)) in water and ethylene glycol (Yoder, L. M.; Cole, A. G.; Walker, L. A., II; Sension, R. J. J. Phys. Chem. B 2001, 105, 12180-12188) and alkylcobalamins in water (Cole, A. G.; Yoder, L. M.; Shiang, J. J.; Anderson, N. A.; Walker, L. A., II; Banaszak Holl, M. M.; Sension, R. J. J. Am. Chem. Soc. 2002, 124, 434-441). The results of these investigations are discussed in the context of the literature on the frictional influence of solvent on chemical reaction dynamics. The measurements allow a separation of the influence of the solvent on the intrinsic rate constant for geminate recombination and the rate constant for escape from the initial solvent cage. The rate constant for the intrinsic geminate recombination of cob(II)alamin with the alkyl radical is weakly dependent on the solvent and on the nature of the alkyl radical (Me, Et, Pr, or Ado). The Et, Pr, and Ado radicals exhibit the behavior expected for diffusion-controlled escape from the initial solvent cage. In contrast, the magnitude of cage escape for the Me radical is much larger than anticipated on the basis of hydrodynamic arguments. 相似文献
100.
M. Amin Diab 《European Polymer Journal》1984,20(6):599-603
Thermal stability and degradation behaviour have been studied for PVB and VB-MVK copolymers spanning the whole composition range, using thermogravimetric analysis. The reactivity ratios in the radial copolymerization were determined by using an NMR technique, leading to ri(VB) = 3.6 ± 0.2 and r2(MVK) = 0.2 ± 0.1. The introduction of MVK units into the VB chain leads to an interaction with release of methyl bromide. The stability of the copolymers increases with increasing MVK concentration. 相似文献