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61.
Noha Fathalla Mokhtar Bishr Abdel Nasser Singab Osama Salama 《Natural product research》2019,33(19):2878-2881
The aim of this work is to characterize the active constituents present in the ethyl acetate fraction of Senna tora, L. Roxb. seeds. Due to the fact that the main biological activity of S. tora, L seeds is attributed to its phenolic compounds which are mainly isolated from Ethyl acetate fraction, to avoid repetition of work and to save time, it was deemed necessary to confirm the identity of these phenolic compounds. This was done by GC-MS and LC-MS analysis of the ethyl acetate fraction where the structures of the isolated compounds were established on the basis of molecular ion peak and their fragmentation pattern. They were identified as Chrysophanol, Chrysarobin, 10-hydroxy-5-methoxy-2-methyl-1, 4-anthracenedione, Rubrofusarin, Parietin, Griseoxanthone-B, Isotorachrysone, and Cumbiasin B.
62.
以二氯-1,3-双(二苯基磷)丙烷基镍(Ⅱ)为催化剂,通过3,6-二氯哒嗪格氏试剂与3,6-二溴-N-戊烷基咔唑共聚得到了一种新型共轭聚合物,并使用IR和1H-NMR等测试手段对单体和聚合物的结构进行了表征。该合成方法所得的共聚物收率为75%,共聚物在N,N-二甲基酰胺(DMF)、二甲基亚砜(DMSO)等极性溶剂和CF3COOH、CH3SO3H、HCOOH等常用有机酸中具有较好的溶解性。用红外(FT-IR)、紫外-可见吸收光谱(UV-vis)、荧光光谱(PL)、X射线衍射、循环伏安(CV)等对聚合物的吸收光谱特性、结晶性和电化学活性进行了探讨。结果表明:聚合物具有较高的发光强度,是一种还原型聚合物,结晶性比较差。 相似文献
63.
H. M. Mokhtar Z. M. El-Shafei H. S. El Khadem D. L. Swartz 《Journal of heterocyclic chemistry》1977,14(5):927-929
4-Phenyl-2,3-dioxobutyro-1,4-lactone ( 1 ) gave with phenylhydrazine and ils p-Cl, p-Br, p-I and p-NO2 derivatives, bishydrazones which were eyclized to 1-aryl-3-(α-hydroxybenzyl)-4,5-dione-4-arylhydrazones. With o-phenylene diamine, compound 1 gave either a Schiff base or a substituted quinoxaline, depending upon the ratio of the reactants. 相似文献
64.
In this article we consider a class of first order nonlinear integro-differential equations with delay. We propose new approach for investigating local and global existence of the solutions of its Cauchy problem. This approach gives new results. 相似文献
65.
We study the backward problem for non-linear (semilinear) parabolic partial differential equations in Hilbert spaces. The problem is severely ill-posed in the sense of Hadamard. Under a weak a priori assumption on the exact solution, we propose a new Fourier truncated regularization method for stabilising the ill-posed problem. In comparison with previous studies on solving the nonlinear backward problem, our method shows a significant improvement. 相似文献
66.
67.
Lanthanum cobaltite oxide, LaCoO3, was prepared by the evaporation technique and the amorphous metal complex method. Powders were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, and surface area measurements. The effect of the synthesis route on the phase purity, particle size, surface area, and morphology of the powders was studied. A single perovskite phase was synthesized at 700°C using the amorphous metal complex route. However, the evaporation technique required higher temperature for LaCoO3 crystallization. Based on the characterization results, low temperature formation of LaCoO3 was attributed to the homogeneity of the precursors. Such behavior also results in different microstructures. Powder synthesized by the amorphous metal complex method exhibited the highest surface area and the lowest particle size. 相似文献
68.
Mokhtar Kirane 《Nonlinear Analysis: Theory, Methods & Applications》2010,73(12):3723-235
We investigate the profile of the blowing-up solutions to the nonlinear nonlocal system (FDS):
69.
G. A. El-Shobaky Th. El-Nabarawy G. A. Fagal M. Mokhtar 《Journal of Thermal Analysis and Calorimetry》1996,46(5):1473-1481
V2O5/Al2O3 solids of varying compositions were prepared, dried at 100°C and calcined in air at 400–1000°C. The solid-solid interactions between the mixed oxides were investigated by means of DTA, TG and XRD techniques.The results revealed that ammonium metavanadate and aluminium hydroxide decomposed at 260 and 290°C, respectively, to yield an ammonium vanadium intermediate compound and Al2O3 as solids. The intermediate compound readily decomposed at 360°C to give V2O5.Solid V2O5 generally catalyses the crystallization of Al2O3 to an extent proportional to its amount present. The solid-solid interactions between Al2O3 and V2O3 to produce AlV2O4 and AlVO4 took place at 750 and 900°C. These solids decomposed entirely at 1000°C, producing V2O5 and alpha-corundum. The pure Al2O3 samples employed existed as amorphous solids even when heated in air at 750°C, but in the presence of V2O5 (7–18 wt.%) they crystallized to thetaalumina at 600°C. The pure solid alumina crystallized at 1000°C to a mixture of theta and kappa-alumina. In the presence of V2O5, alpha-corundum together with kappa and theta phases was obtained on heating at 900°C. 相似文献
70.
New selective and sensitive Spectrophotometric methods for quinone determination are described. Quinone samples are treated with either methanolic solution of rhodanine, fluorene in ammoniacal media or aqueous semicarbazide hydrochloride solution. Semicarbazide is the most sensitive reagent for the determination of 1,4-benzoquinone, 1,4-naphthoquinone and 2-methyl-1,4-naphthoquinone. Quinones substituted with electron withdrawing groups are better determined using rhodanine. The average recovery is 99.1%, 98.7% and 99.2% using rhodanine, fluorene and semicarbazide as reagents, respectively. 相似文献