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1.
Mohamad Sh. Ramadan Nabila M. El-Mallah Sherif M. Abd-Elmenem 《Journal of Dispersion Science and Technology》2013,34(8):1110-1120
AbstractThe interaction between anionic dyes [Reactive Orange 122 (R.O 122), Reactive Blue 19 (R.B 19), Reactive Violet 5 (R.V 5) and Acid Green 20 (A.G 20)] with cationic surfactant cetyltrimethylammoniun bromide (CTAB) has been investigated by spectrophotometry and conductance technique. The used dyes are characterized by tautomeric behavior which affects the mechanism of the interaction. Various parameters such as dye structure, surfactant composition, solvent composition, temperature and pH of the medium were studied. The spectral data were applied for calculating the binding constant between dye and surfactant (Kb), fraction of micellization (?mic), and standard free energy change of binding (ΔG°b) in 0,10,20 and 30 v/v % acetonitile (AN). Conductance technique was constructed to estimate the ion pairing constant (Ka) at different temperatures and v/v % AN. Thermodynamic parameters (ΔG°, ΔH° and ΔS°) for ion pair formation were evaluated. The role of hydrophobic and electrostatic effect on dye-surfactant interaction was discussed. 相似文献
2.
Mohamed Lamei El-Mallah 《Journal of Algebra》1983,80(2):314-322
Let A denote a prehilbert absolute valued real algebra such that (x, x, x) = 0 for all x ε A; for this algebra we obtain the same results we have previously obtained for the flexible absolute valued algebra. Our main theorem is: A has a finite dimension 1, 2, 4 or 8, and is isotopic to
or C. One of the results concerning the isomorphism between A and
, C*,
or C shows that if for every two idempotents e1 and e2 in
, then A is isomorphic to
, C*,
or C. The example of infinite dimensional Hilbert absolute valued algebra given by Urbanik and Wright indicates that the assumption, (x, x, x) = 0 for all x ε A, is essential. 相似文献
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The rate constants for the reactions of 4-halomethyl-3-nitrobenzoic acids, the nonnitro derivatives, and their ethyl esters with arylthiolates were measured at different temperatures. It was found that the retardation in rate constants compared to benzyl halides is due to the electrostatic repulsion between the electronegative substituents (COO− and/or NO2) in the substrates and thiolate ions. Good correlations between log k2 values of the acids and carbon basicities of thiolates were found while log k2 values of the esters show good straight lines with Hammett σ constants, pka, and carbon basicities of arylthiolates. © 1996 John Wiley & Sons Inc 相似文献
5.
Magda F. Fathalla Mohamed Sh. Ramadan Nabila M. El-Mallah Gehan M. Nabil 《Journal of Dispersion Science and Technology》2014,35(4):528-534
Pseudo-first-order reaction rate for alkaline hydrolysis of 2-chloroquinoxaline (2-CQX) is carried out in acetonitrile (AN)-water (H2O) mixtures at 35°C. Cationic surfactants as dodecyltrimethylammonium bromide (DOTAB) and an anionic surfactant as sodium dodecylsulphate (SDS) are used above their critical micelle concentration (cmc) to study the effect of micelles on reaction rate. When increasing the percentage of volume of AN, the rate profiles with DOTAB are shown to slightly increase with increasing surfactant concentration, while that with SDS are found to smoothly decrease. The micellar effect is explained in terms of a modified pseudo-phase ion exchange model. The binding constant (KS) between 2-CQX and DOTAB as micelle showed a decrease by increasing percentage of volume of AN, while that with SDS increased. The counterion micellar coverage degrees (β) are found to be 0.55 and 0.85 with DOTAB and SDS systems, respectively, at all range of volume percentage of AN. Finally, the calculated ratio between rate constants in water to that in the micelle region kw/kM at different volume percentage of AN indicated that DOTAB enhances the reaction rate while SDS inhibits it. 相似文献
6.
Mohamed Lamei El-Mallah 《Archiv der Mathematik》1982,38(1):432-437
Sans résumé 相似文献
7.
An approach to evaluate the efficiency of γ-ray detectors to determine the radioactivity in environmental samples
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Mohamed. S. Badawi Ahmed. M. El-Khatib Samah. M. Diab Sherif. S. Nafee Ekram. A. El-Mallah 《中国物理C(英文版)》2014,38(6):066203-066203
This work provides an approach to determine the efficiency of γ-ray detectors with a good accuracy in order to determine the concentrations of either naturally occurring or artificially prepared radionuclides. This approach is based on the efficiency transfer formula (ET), the effective solid angles, the self- absorptions of the source matrix, the attenuation by the source container and the detector housing materials on the detector efficiency. The experimental calibration process was done using radioactive (Cylindrical & Marinelli) sources, in different dimensions, that contain aqueous 152Eu radionuclide. The comparison point to a fine agreement between the experimental measured and calculated efficiencies for the (NaI & HPGe) detectors using volumetric radioactive sources. 相似文献
8.
Nabila M. El-Mallah Abdel-Monem M. Ahmed 《Journal of Dispersion Science and Technology》2013,34(11):1579-1590
The rates of electrodeposition of copper plates were determined by measuring cathodic limiting current in the absence and in the presence of carbohydrates (glucose, fructose, mannose, sucrose, lactose, and maltose). It is found that the rate of electrodeposition decreases in the presence of organic additives by an amount ranging from 1.89% to 35.85%, and depending on the types of additives and its concentrations. Our investigation of adsorption isotherm indicates that the inhibition fits both the Langmuir adsorption isotherm and Flory-Huggins adsorption isotherm; we found that the rate of electrodeposition decreases by increasing height and increasing CuSO4 concentrations. Thermodynamic parameters are given and show that electrodeposition process is diffusion controlled. The rate of deposition and its equations are represented:
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Sh = 0.099Re0.715 Sc0.33 for glucose with average deviation: ±0.158%
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Sh = 0.097Re0.715 Sc0.33 for fructose with average deviation: ±0.058%
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Sh = 0.099Re0.715 Sc0.33 for mannose with average deviation: ±0.108%
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Sh = 0.098Re0.713 Sc0.33 for sucrose with average deviation: ±0.003%
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Sh = 0.099Re0.714 Sc0.33 for lactose with average deviation: ±0.018%
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Sh = 0.099Re0.713 Sc0.33 for maltose with average deviation: ±0.097%.
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Nabila M. El-Mallah Hind M. Hassouba 《Journal of Dispersion Science and Technology》2014,35(1):130-142
The kinetics and dynamics of nickel ions adsorption on activated carbon and bentonite were studied. The influence of parameters (pH, amount of adsorbent, adsorbate concentration, solution volume, rotation speed, and temperature) were investigated. Kinetic models of pseudo-first, pseudo-second and Weber-Morris models were applied. The data was better reported by the pseudo-second order model. Freundlich, Langmuir, and D-R models were utilized for the analysis of adsorption equilibrium. Evaluation of thermodynamic parameters reveal that adsorption is spontaneous and endothermic in nature. From the experimental data, it was concluded that bentonite has more efficiency for the adsorption of nickel ions than activated carbon. 相似文献