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81.
Masoud MS Khalil EA Hindawy AM Ali AE Mohamed EF 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2004,60(12):2807-2817
Synthesis and characterization of [o-carboxy phenylazo] moiety of barbituric acid, thiobarbituric acid, thiouracil, citrazinic acid, and disodium chromotropate and their complexes derived from cobalt (II), nickel (II), and copper (II) salts were done. The stereochemistry and the mode of bonding of the complexes were achieved based on elemental analysis, NMR, UV-Vis, IR and ESR. The dissociation constants of the free azo ligands are evaluated by spectrophotometric methods. 相似文献
82.
Alaa S. Amin 《光谱学快报》2013,46(6):424-431
ABSTRACT A cloud-point extraction (CPE) process using the nonionic surfactant Triton X-114 to extract bismuth from aqueous solutions was investigated. The method is based on the complexation reaction of Bi(III) with 4-(2-benzothiazolylazo)2,2′-biphenyldiol (BTABD) and micelle-mediated extraction of the complex. The optimal extraction and reaction conditions (e.g., pH, reagent concentration, surfactant concentration, and effect of time) were studied. The analytical characteristics of the method (e.g., linear range, molar absorptivity, Sandell sensitivity, optimum Ringbom concentration ranges, limits of detection and quantification, preconcentration factor, and improvement factors) were obtained. Linearity was obeyed in the range of 2.50–85.0 ng mL?1 of Bi(III) ion. The detection limit of the method was 0.75 ng mL?1 of Bi(III) ion. The interference effect of some anions and cations was also tested. The method was applied to the determination of bismuth in environmental water, human hair, and urine samples. 相似文献
83.
Alaa J. Ghazai Wisam J. Aziz H. Abu Hassan Z. Hassan 《Superlattices and Microstructures》2012,51(4):480-485
Quaternary n-type Al0.08In0.08Ga0.84N grown on p-Si using molecular beam epitaxy technique was fabricated as a pn-junction and an anti-reflection coating (ARC) of solar cells. The structural properties and surface morphology of the solar cells were investigated using scanning electron and atomic force microscopy. Optical reflectance was obtained using an optical reflectometery system (Filmetric F20-VIS). Current–voltage characteristics were examined under 100 mW cm?2 illumination conditions. Quaternary n-type Al0.08In0.08Ga0.84N coating was found to be an excellent ARC against incident light compared with other ARCs. This material also exhibited good light trapping over a wide wavelength spectrum, which produced highly efficient solar cells. The unique and strong polarization, as well as the piezoelectric effect, of the quaternary-nitrides was employed to reduce surface recombination velocities and enhance the solar cell performance. A solar cell with reasonable conversion efficiency of 9.74% was obtained when the n-Al0.08In0.08Ga0.84N/p-Si was employed. 相似文献
84.
A simple, rapid, selective and sensitive method for the micro amount determination of phenylephrine hydrochloride either in pure form (raw material) or in pharmaceutical formulations is described. The method is based on the development of violet colour charge transfer complex with haematoxylin in alkaline medium with 10 min after heating at 65 °C. The wavelength and maximum absorption range was found in the range from 640 to 620 nm. Molar absorptivity and Sandell sensitivity were found to be 2.38 × 104 L mol− 1 cm− 1 and 8.6 ng cm− 2 respectively. A linear correlation was found between absorbance (at the λmax) and concentration. The resulting colour is stable for more than 10 h. Results of the analyses of pure drug and dosage forms by the proposed method are in good agreement with those of the official BP 1998 procedure. 相似文献
85.
Masoud MS Ali AE Mohamed RH El Zaher Mostafa MA 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2005,62(4-5):1114-1119
A bright green CoCu(PMP)(OH)2(H2O)2 complex was synthesized. Its structure was elucidated and characterized by different spectroscopic techniques. Both cobalt and copper atoms attain tetrahedral geometry. The complex was investigated by the dielectric relaxation spectroscopy. The dielectric parameters are discussed in terms of temperature and frequency changes. The conductivity of the complex decreased as the temperature increased in the temperature range 30-100 degrees C, while above this temperature range stepwise increase in the conductivity was observed. 相似文献
86.
Furukawa S Takagi N Ikeda T Ono M Nafady AM Nohara T Sugimoto H Doi S Yamada H 《Chemical & pharmaceutical bulletin》2002,50(3):439-440
Two new long-chain alkanoic acid esters of lupeol were isolated together with known triterpenoids, alpha-amyrin, beta-amyrin, cycloartenol, lanosta-7,24-diene-3beta-ol and lupeol from Alecrim-propolis collected in Brazil. The structures were characterized by spectroscopic means. 相似文献
87.
Statistical analysis of HDPE fatigue lifetime 总被引:1,自引:0,他引:1
Fatigue lifetime of HDPE structures such as pipes is recognized to show a large scatter. This study aims to compare different
statistical methods and distributions, in order to give convenient modeling of tensile and fatigue test results of commercially
available polyethylene compression molded sheets. The median rank, the maximum likelihood and the Kolmogorov-Smirnov fitting
are compared for the estimation of Weibull parameters. The choice of the best distribution to fit fatigue lifetime is discussed
on the basis of the goodness-of-fit results. It is found that whether the three-parameter distributions of Weibull and lognormal
types are suitable for lifetime prediction, the two-parameter Weibull is more conservative for probabilistic fatigue design. 相似文献
88.
Three simple and sensitive colorimetric methods (A–C) for the determination of melatonin in bulk samples and in pharmaceutical
formulations are described. They are based on the formation of coloured species by reaction of ninhydrin with the drug (method
A, λmax 397 nm) by oxidation of the indol moiety in melatonin with potassium persulphate (method B, λmax 450 nm) or by reduction of osmium (VIII) (method C, λmax 516 nm). Regression analysis of Beer-Lambert plots showed good correlations in concentration ranges between 0.8–14.2, 70.0–140.0
and 2.0–40.0 μg/mL for methods A, B and C, respectively. The molar absorptivity, Sandell sensitivity and detection limit were
calculated. For more accurate analysis, Ringbom optimum concentration ranges were calculated. The validity of the proposed
methods was tested by analysing pharmaceutical formulations containing melatonin. The relative standard deviations were ≤ 0.95%
with recoveries 99.0–101.33%.
Received October 20, 1999. Revision February 10, 1999. 相似文献
89.
This work provides an insight into the effect of incorporating of magnetite nanoparticles on the rheology of fluids. In this respect, polymer-stabilized magnetite nanoparticles were obtained using sodium salt of poly (2-acrylamido-2-methylpropanesulfonate (PAMPS-Na). Monodisperse polymer coated magnetite nanoparticles Fe3O4/poly(styrene-AMPS) copolymer nanoparticles with diameters of 50–300 nm were prepared by radical polymerization in the presence of a ferrofluid coated with PAMPS-Na. The magnetic nanoparticles were easily separated in a magnetic field. The structure of the obtained magnetic nanoparticles was characterized by Fourier transform infrared spectroscopy (FTIR). The morphology and size of the magnetic nanoparticles were determined by transmission electron microscopy (TEM). FTIR and TEM revealed that the Fe3O4 nanoparticles were incorporated into the shells of poly(styrene-AMPS). Aqueous dispersed solutions of a charged hydrophobically modified Fe3O4/poly(styrene-AMPS) copolymer nanoparticles exhibit high viscosities even at low polymer concentrations (0.1 wt %), which is an interesting feature in connection with enhanced oil recovery. Effects of temperature and addition of sodium chloride on the viscosity properties of a semidilute dispersed solution of Fe3O4/poly(styrene-AMPS) copolymer nanoparticles are examined. The results indicated that Fe3O4/poly(styrene-AMPS) copolymer nanoparticles disclose strong interactions between magnetite and coated polymers of both PAMPS-Na and styrene-AMPS copolymers. 相似文献
90.
Recent Heterocyclic Compounds from (1,3‐Dioxo‐2,3‐dihydro‐1H‐inden‐2‐ylidene)propanedinitrile 下载免费PDF全文
This review summarizes the literatures dealing with the synthesis of some important nitrogen or nitrogen/sulfur heterocyclic, spiroheterocyclic, and fused heterocyclic compounds. 相似文献