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排序方式: 共有119条查询结果,搜索用时 15 毫秒
61.
Tao X Li W Ma X Li X Fan W Xie X Ayad T Ratovelomanana-Vidal V Zhang Z 《The Journal of organic chemistry》2012,77(1):612-616
Various substituted aryl-pyridyl ketones were hydrogenated in the presence of Ru-XylSunPhos-Daipen bifunctional catalytic system with enantiomeric excesses up to 99.5%. Upon introduction of a readily removable ortho-bromo atom to the phenyl ring, enantiomerically enriched 4-chlorophenylpyridylmethanol was obtained by hydrogenation method with 97.3% ee, which provided an important chiral intermediate for some histamine H(1) antagonists. 相似文献
62.
63.
64.
Summary Tin(IV), titanium(IV) and hafnium(IV) chloride complexes of ligands such as salicylidene-4-aminoantipyrine (HL1), 5-chlorosalicylidene-4-aminoantipyrine (HL2), 2,4-dihydroxybenzylidene-4-aminoantipyrine (HL3), 2-hydroxy-1-naphthylidene-4-aminoantipyrine (HL4) and 2-hydroxyacetophenonylidene-4-aminoantipyrine (HL5) have been prepared and characterized. The analytical data show that tin(IV) forms only 1:1 metal complexes when reacted with HL1, HL3 and HL4, whereas it forms 1:1 and 1:2 metal complexes when reacted with HL2, depending on the molar ratio. HL5 produces only the binuclear complex SnHL5Cl4(H2O)SnCl4. Titanium(IV) gives only one type of complex of the general formula [Ti(HL)2Cl2]Cl2-2H2O, whilst hafnium(IV) gives HfHL3Cl4-4H2O and Hf(L5)2Cl2. 相似文献
65.
M.M. Ayad S.E. Khayyal N.M. Farag 《Spectrochimica Acta Part B: Atomic Spectroscopy》1985,40(8):1127-1131
A new method for the determination of nicotine alkaloid has been developed. This method is based on the quantitative precipitation of the alkaloid with metals such as Cu2+, Pb2+, Zn2+ and Hg2+. Then either the equivalent or residual metal is determined.The proposed method was successfully applied to the determination of nicotine in various types of tobaccos. 相似文献
66.
Mohamed Ayad 《manuscripta mathematica》1992,76(1):305-324
67.
Magda M. Ayad Abdalla Shalaby Hisham E. Abdellatef Heba M. Elsaid 《Mikrochimica acta》2002,140(1-2):93-96
The construction of a plasticised PVC matrix-type promazinium cation-selective membrane electrode and its use in the potentiometric
determination of promazine hydrochloride in pharmaceutical preparations are described. It is based on the use of the ion-associate
species, formed by promazinium cation and tetraphenylborate (TPB) counter ion. The basic electrode performance characteristics
are evaluated according to IUPAC recommendations. It exhibited a linear response for 1 × 10−2−1 × 10−5 M of promazine hydrochloride solutions with a cationic Nernstian slope over the pH range 2–6. Common organic and inorganic
cations showed negligible interference. Direct potentiometric determination of 1 × 10−2−1 × 10−5 M aqueous promazine hydrochloride using this membrane electrode system showed an average recovery of 99.5% with a mean standard
deviation of 1.5%. This electrode was successfully used for monitoring the titration of promazine hydrochloride with sodium
tetraphenyl borate and for determining promazine hydrochloride in ampoules.
Received June 15, 2001 Revision November 6, 2001 相似文献
68.
Abdellatef HE Ayad MM Soliman SM Youssef NF 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2007,66(4-5):1147-1151
Thin-layer chromatography, first derivative, ratio spectra derivative spectrophotometry and Vierordt's method have been developed for the simultaneous determination of paracetamol and drotaverine HCl. TLC densitometric method depends on the difference in Rf values using ethyl acetate:methanol:ammonia (100:1:5 v/v/v) as a mobile phase. The spots of the two drugs were scanned at 249 and 308 nm over concentration ranges of 60-1200 microg/ml and 20-400 microg/ml with mean percentage recovery 100.11%+/-1.91 and 100.15%+/-1.87, respectively. The first derivative spectrophotometric method deals with the measurements at zero-crossing points 259 and 325 nm with mean percentage recovery 99.25%+/-1.08 and 99.45%+/-1.14, respectively. The ratio spectra first derivative technique was used at 246 and 305 nm with mean percentage recovery 99.75%+/-1.93 and 99.08%+/-1.22, respectively. Beer's law for first derivative and ratio spectra derivative methods was obeyed in the concentration range 0.8-12.8 and 0.4-6.4 microg/ml of paracetamol and drotaverine HCl, respectively. Vierordt's method was applied to over come the overlapping of paracetamol and drotaverine HCl in zero-order spectra in concentration range 2-26 and 2-40 microg/ml respectively. The suggested methods were successfully applied for the analysis of the two drugs in laboratory prepared mixtures and their pharmaceutical formulation. The validity of the methods was assessed by applying the standard addition technique. The obtained results were statistically agreed with those obtained by the reported method. 相似文献
69.
Ayad Saeed Balachandran Ruthramurthy Wong Hin Yong Ong Boon Hoong Tan Kar Ban Yow Ho Kwang Srimala Sreekantan 《Russian Journal of Electrochemistry》2016,52(8):788-795
Using pulse electrodeposition technique, nano crystalline NiFe films were deposited on conductive copper substrates, under galvanostatic mode in an ultrasonic field at different conditions such as pulse current magnitude, deposition time and ultrasonic bath temperature. As-prepared NiFe/Cu thin films were characterized for phase analysis, surface morphology, surface roughness and resistivity measurements. The results show that the use of ultrasonic bath at room temperature has reduced the surface roughness, resistivity, average grain size and crystallite size of NiFe/Cu thin films. The resistivity is reduced with increasing deposition current from 44.2 µΩ cm at 40 mA to 33.0 µΩ cm at 100 mA. On the other hand, a significant drop of the resistivity from 35.7 to 9.4 µΩ cm is observed if the deposition time was reduced from 5 to 3 min. 相似文献
70.
Stresses and displacements are obtained for an elastic superconductor in the form of an infinitely long, circular cylindrical tube subjected to an initially uniform magnetic field perpendicular to the tube's axis. The effect of the magnetic field penetration on the stressed state is assessed by solving the problem, firstly taking into account this penetration and, secondly, neglecting it. The problem involves the solution of a non-homogeneous biharmonic equation in two dimensions for the stress function. The special case of a circular cylinder is also given. Numerical calculations estimate the variation between the two cases for some quantities of practical interest. It is shown, in particular, that neglecting the penetration of the magnetic field in the elastic superconductor may induce a non negligible error in the appreciation of the stressed state. 相似文献