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排序方式: 共有187条查询结果,搜索用时 609 毫秒
41.
Abdullah S. Babaqi Mohamed T. Mohamed Salah S. Massoud Mohamed F. Amira 《Transition Metal Chemistry》1988,13(3):201-204
Summary The aquation of chloropentamminecobalt(III) ion has been studied in ethylene glycol-water mixtures up to 80% by weight at five temperatures from 35 to 55°C. Specific solvent effects on the reaction rate and mechanism have been investigated and discussed. The validity of our previously proposed equations, correlating the specific reaction rate with the dielectric constant of the medium has been examined. The thermodynamic parameters of activation have been calculated and presented as evidence for the solvation effects and in support of the proposed reaction mechanism. 相似文献
42.
Nabil A. Abdel-salam Nabila M. Ghazy Shaimaa M. Sallam Mohamed M. Radwan Amira S. Wanas Mahmoud A. ElSohly 《Natural product research》2018,32(6):702-706
Alcea rosea L. is widely cultivated in gardens of Egypt as an ornamental plant and it has a great history of folkloric medicinal uses. In the present work, phytochemical investigation of the alcoholic extract of the flowers of A. rosea L. led to the isolation of six flavonoids (1–6). Dihydrokaempferol-4′-O-β-d-glucopyranoside (1), dihydrokaempferol (2), kaempferol-3-O-[6″-(E-coumaroyl)]-β-d-glucopyranoside (3), kaempferol-3-O-β-d-glucopyranoside (4), Apigenin (5) and kaempferol-3-O-α-l-rhamnopyranosyl-(1′″→6″)-β-d-glucopyranoside (6). Four of the isolated compounds were evaluated for their antioxidant, immunostimulant and cytotoxic activities against HepG-2 cell line. Compound (3) showed potent cytotoxic activity against HepG-2 cell line with high selectivity towards hepatocellular carcinoma in vitro (with IC50 = 3.8 μg/mL). Compounds 1 and 2 exhibited significant antioxidant activity and compound 4 showed a significant immune stimulant activity. Compound 1 is isolated for the first time from genus Alcea and this is the first report for its biological investigation. 相似文献
43.
Rabeay Y. A. Hassan Amira M. Kamel Mona S. Hashem Hassan N. A. Hassan Mahmoud A. Abd El-Ghaffar 《Journal of Solid State Electrochemistry》2018,22(6):1817-1823
The development of new techniques for rapid and continuous monitoring of urea in biomedical and clinical analysis is very important. Thus, conductive polymer-supported carbon nanotube as an effective electrochemical biosensing platform for direct detection of urea in blood samples was designed. For the assay optimization, several conductive polymers were synthesized and tested as electrode modifiers; among the tested polymers, poly-o-toluidine (PoT) showed the highest electrochemical signals. However, after the enzyme immobilization, direct bioelectrochemical signals were not obtained when the PoT was used alone. Due to the lower electrocatalytic feature of PoT, integration of carbon nanotube, to form a composite with the PoT, was exploited to enable the direct electron transfer. Successfully, using the hybrid, the catalytic activity of the immobilized urease enzyme was retained. Consequently, a sensitive and specific chronoamperometric signals were achieved after the bioassay optimization. Eventually, a standard calibration curve for urea determination was obtained. A linear range was found from 0.1 to 11 mM with the limit of detection of 0.03 mM. Successfully, several blood samples were analyzed and urea level was correlated with the reference analytical method. 相似文献
44.
Mohamed F. Amira Shawky A. El-Shazly Mohamed M. Khalil Fathy M. Abdel-Halim 《Transition Metal Chemistry》1986,11(2):72-74
Summary Rate coefficients, k, for aquation of [Cr(NH3)5Cl]2+ in 10% ethanol solutions of some dicarboxylates have been determined by potentiometric titration methods. The dissociation constants of ion-pairs so formed have been obtained from e.m.f.s. of a cell comprising glass and calomel electrodes. A wide range of k(ion) and k(ion-pair) values and dissociation constants has been obtained and a new correlation between k(ion-pair) and association constants among the dicarboxylate series studied has been established. 相似文献
45.
Interfacial solubilization of model amphiphilic molecules in block copolymer micelles 总被引:3,自引:0,他引:3
We investigate the solubilization of 2-nitrodiphenylamine, a hydrophobic but polar dye molecule, in aqueous solutions of polystyrene(310)-b-poly(acrylic acid)(47) micelles. The solubilization capacity of the micelles, which consist of a polystyrene core and poly(acrylic acid) corona, and the micelle-water partition coefficient are evaluated as a function of the solubilizate concentration. The solubilization isotherm shows a nonlinear behavior, and the partition coefficient, instead of being constant, is strongly dependent on the dye concentration. These results are explained by treating solubilization as a binding process, and by fitting the data to a Langmuir adsorption model. In addition, we examine the locus of solubilization of 2-nitrodiphenylamine using its solvatochromic properties and solubility in model solvents, and we identify the micellar interface as the solubilization site. Confirmatory studies, including the dependence of solubilization on the interfacial area of the aggregates, the role of the poly(acrylic acid) corona chains in stabilizing the solubilized molecules, and the effect of the solubilizate structure on the extent of incorporation, were also conducted. The results, consistent with surface localization, show that solubilization is dependent on the interfacial area of the aggregates, and on the affinity of the solubilizate for the micellar interface. 相似文献
46.
Mohamed F. Amira Shawky A. El-Shazly Soad A. Sallam Mohamed M. Khalil 《Transition Metal Chemistry》1987,12(1):25-29
Summary The aquation kinetics of [Co(NH3)5Cl]2+ and [Co(NH3)5Br]2+ ions in acetone-water have been investigated over a wide range of solvent compositions and temperatures. The variation of thermodynamic properties of the activated complex with the mole fraction of acetone reveals the existence of specific solvation. The correlation of the rate constant with dielectric constant of the medium is examined and discussed. A reaction mechanism which describes the solvent effect on reaction rate is proposed. 相似文献
47.
The first and second dissociation constants of tartaric, maleic and phthalic acids have been determined using EMF method in water-ethanol mixed solvents, over a wide range of solvent composition (0-60 wt% ethanol) at six different temperatures (ranging from 30 to 55 degrees C at intervals of 5 degrees C). The thermodynamic parameters (DeltaG degrees , DeltaH degrees and DeltaS degrees ) for the first and the second ionization reactions were calculated from the well known equations. The results have been discussed in terms of the solute-solvent interactions and were compared with those of malic, malonic and succinic acids in the same mixed solvents. 相似文献
48.
Substituted 5-Antipyrinylazo-4-phenyl-2-aminothiazoles as Disperse Dyes for Dyeing Polyester Fabrics
Mohamed A. Metwally Amira Metwally Ebrahim Abdel-Galil Fathy A. Amer 《Monatshefte für Chemie / Chemical Monthly》2008,139(1):35-42
Summary. A series of some new substituted 5-antipyrinylazo-4-phenyl-2-aminothiazole disperse dyes was synthesized by diazocoupling
of 4-antipyrinyldiazonium chloride with aminothiazole derivatives. The synthesized dyes were characterized by UV-Vis absorption,
IR, 1H NMR, and MS spectroscopy. The dyes gave orange to reddish-violet shades with very good depth and levelness when applied
to polyester fabrics as disperse dyes and their fastness properties were evaluated on polyester fibers. Also the position
of color in CIELAB coordinates (L*, a*, b*, H*, and C*) was assessed. 相似文献
49.
A new norcembrane, designated sinularectin 3, was isolated from the Kenyan soft coral Sinularia erecta. Sinularectin is a chlorinated highly oxygenated norcembrane with an unprecedented functionalisation of the cembrane isopropyl group. The structure of sinularectin was elucidated by interpretation of the HRESMS results as well as 1D and 2D NMR spectra. 相似文献
50.
Wanas AS Matsunami K Otsuka H Desoukey SY Fouad MA Kamel MS 《Chemical & pharmaceutical bulletin》2010,58(12):1596-1601
From the EtOAc and 1-BuOH fractions, three new ursane-type and four new lupane-type triterpenes, along with nine known glycosides and glycosyl esters of lupane-type were isolated from the leaves of Schefflera actinophylla. All the isolated compounds were obtained for the first time from this plant. The structures of the new triterpenes were determined through a combination of spectroscopic and chemical analyses. 相似文献