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91.
Theoretical and Mathematical Physics - We describe the topology of isoenergetic surfaces for an integrable system on the Lie algebra so(3, 1) and the critical points of the Hamiltonian for... 相似文献
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93.
Summary. The three-component condensation of benzaldehyde derivatives, alkyl propiolates, and primary amines catalyzed by silica gel,
zeolite HY, montmorillonite K-10, and acidic alumina under microwave irradiation gave N-substituted 4-aryl-1,4-dihydropyridines
in short reaction times and high yields. The best results were obtained with silica gel.
Received March 26, 2001. Accepted (revised) June 18, 2001 相似文献
94.
The three-component condensation of benzaldehyde derivatives, alkyl propiolates, and primary amines catalyzed by silica gel, zeolite HY, montmorillonite K-10, and acidic alumina under microwave irradiation gave N-substituted 4-aryl-1,4-dihydropyridines in short reaction times and high yields. The best results were obtained with silica gel. 相似文献
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96.
Elahe Moazzen Nasser Daei Seyyedeh Mahdieh Hosseini Homeira Ebrahimzadeh Azam Monfared Mostafa M. Amini Omid Sadeghi 《Mikrochimica acta》2012,178(3-4):367-372
We have developed a technique for the solid-phase extraction of gold using various kinds of pyridine-functionalized nanoporous silica prior to its determination in various samples using FAAS. The effects of solution pH, sample and eluent flow rate, sample volume and of potentially interfering ions are compared. The limits of detections vary from 28 to 53?pg?mL?1. The accuracy and precision are between 99.8% and 98.3?% and 0.7 to 1.6?% (RSD), respectively. The method was successfully applied to several standard reference materials. Figure
A technique has been developed for the solid-phase extraction of gold using various kinds of pyridine-functionalized nanoporous silica prior to its determination in various samples using FAAS. 相似文献
97.
Malek Taher Maghsoodlou Nourallah Hazeri Sayyed Mostafa Habibi‐Khorassani Ghasem Marandi Lotfali Saghatforoush Danial Saravani Niloufar Akbarzadeh Torbati Faramarz Rostami‐Charati Khatereh Khandan‐Barani Brian W. Skelton Mohamed Makha 《Heteroatom Chemistry》2010,21(4):222-227
New phosphonate ester derivatives were obtained by in situ stereo‐specific reaction between triphenyl phosphite and dialkyl acetylenedicarboxylates in the presence of a series of halogenated anilines. Spectroscopic data and X‐ray crystallography analysis are in agreement with the gauche arrangement for the two vicinal protons in the structures. © 2010 Wiley Periodicals, Inc. Heteroatom Chem 21:222–227, 2010; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20600 相似文献
98.
In this study a hot filament chemical vapour deposition (HFCVD) technique was used to prepare Fe-Cr films on Si substrate as catalysts for thermal CVD (TCVD) growing of carbon nanotubes (CNTs) from liquid petroleum gas (LPG) at 800 °C. To characterize the catalysts or CNTs, X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Raman spectroscopy were used. The XPS spectra obtained at different stages of Ar+ sputtering revealed that in the depth of catalyst layers, the relative Fe-Cr concentrations are higher than the top-surface. SEM images of samples after TCVD indicate a significant CNT growing at the backside of catalyst layer compared with its top which is accompanied with morphological changes on catalyst layer such as formation of cone-shape structures, rippling, cracking and rolling of the layer. These observations were attributed to the more catalytic activity of the sub-surface beside the poor activity of the top-surface as well as the presence of individual active islands over the surface of the catalyst thin film. 相似文献
99.
Roya Akbarzadeh Ghazaleh Imani Shakibaei Ayoob Bazgir 《Monatshefte für Chemie / Chemical Monthly》2010,15(1):1077-1081
Abstract
An efficient and simple synthesis of ferrocenyl 3-aminoimidazo[1,2-a]pyridines by the three-component reaction of ferrocenecarboxaldehyde, isocyanides, and 2-aminopyridines in the presence of a catalytic amount of InCl3 in ethanol at room temperature is reported. 相似文献100.
Masoumeh Hasani Masoud Shariati-Rad Elahe Bidad 《Journal of the Iranian Chemical Society》2014,11(4):1137-1145
A simple procedure for the quantitative determination of mixtures of nitrophenols pollutants in environmental and biological samples based on continuous spectrophotometric acid–base titrations and multivariate curve resolution has been proposed. The procedure simultaneously takes into account the spectroscopic and acid–base properties of the nitrophenols, which leads to a higher selectivity. The quantitative determination of analyte in the presence of unknown and uncalibrated interferences is a general benefit of the method. Moreover, only one single synthetic standard containing of the analyte of interest is enough to perform the analysis. Because of the rank-deficiency phenomena, the pure spectra and concentration profiles of the species of interest can only be recovered through matrix augmentation. Even in the presence of the rank deficiencies, in most cases accurate quantitation with relative errors in prediction lower than 5 % was obtained. The percent recoveries obtained (92–108 %) were satisfactory. 相似文献