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611.
Maged A. Osman 《Helvetica chimica acta》1985,68(3):606-609
Liquid crystals with negative Δϵ can be obtained by incorporating a cyano group in the terminal alkyl substituent or in an ethylene bridge between the cyclic units of the rigid core. The clearing points of such compounds are higher than those of the corresponding derivatives where the cyano group is laterally attached to a phenyl moiety. In compounds where both cyclic units of the rigid core are cyclohexyl, this type of substitution leads to an optimal contribution to ϵ⟂ in contrast to the cyanophenyl derivatives. 相似文献
612.
The theory of two-cluster transfer reactions is reconsidered on the basis of a simple semiclassical approximation. The obtained expression for the differential cross section is in a closed form so as to be easily calculated. A theoretical study with calculations for the angular distribution for different incoming and outgoing energies, and also for different angular momentum transfer is introduced. Comparing our theoretical calculations with experimental data, satisfactory agreement is obtained especially in the backward direction. 相似文献
613.
Soad Abdel Meguid Osman Galal Eldin Hamza Elgemeie Galal Abdel Moein Nawar Mohamed Hilmy Elnagdi 《Monatshefte für Chemie / Chemical Monthly》1986,117(1):105-110
A variety of new 6-thiophen-2-yl and 6-furan-2-ylthiazolo[2,3—a]pyridine derivatives could be prepared via the reaction of 2-functionally substituted methyl-2-thiazolin-4-one with cyanomethylenethiophen-2-yl and cyanomethylenefuran-2-yl derivatives. The structure of the reaction products was established based on spectral data.
Aktivierte Nitrile in der Heterocyclen-Synthese: Die Synthese von 6-Thiophen-2-yl-und 6-Furan-2-yl-thiazolo[2,3—a]pyridin-Derivaten
Zusammenfassung Es konnte eine Reihe neuer 6-Thiophen-2-yl- und 6-Furan-2-yl-thiazolo-[2,3—a]pyridine über die Reaktion von 2-funktionell-substituierten Methyl-2-thiazolin-4-onen mit Cyanomethylenthiphen-2-yl bzw. Cyanomethylenfuran-2-yl-Derivaten hergestellt werden. Die Struktur der Reaktionsprodukte wurde mit spektroskopischen Methoden ermittelt.相似文献
614.
Bathini Madhusree S. Tanabe Ayaka Amaha ?ztürk Ryo Tatsukawa Nobuyuki Miyazaki Emin ?zdamar Orhan Aral Osman Samsun Bayram ?ztürk 《Fresenius' Journal of Analytical Chemistry》1997,359(3):244-248
Concentrations of butyltin compounds (BTs) were determined in harbour porpoise (Phocoena phocoena) collected from the Turkish coastal waters of the Black Sea. Total butyltin compounds (∑ BTs) in the liver were in the range
of 89–219 ng/g on a wet weight basis. The dibutyltin (DBT) residues were higher than those of tributyltin (TBT), suggesting
the degradation of TBT to DBT in the liver and the metabolic capacity comparable to other marine mammals. Any sex difference
and age-dependent accumulation of BTs residues were not found in harbour porpoises, but residue levels increased until maturity
and then remained constant. When compared with other marine mammals, the present results indicate that the Black Sea is also
contaminated with butyltin compounds, but to a lesser degree than coastal waters of developed nations. The biomagnification
factor in harbour porpoises was 0.8, which was comparable with pinnipeds and lower than cetaceans.
Received: 23 December 1996 / Revised: 15 April 1997 / Accepted: 16 April 1997 相似文献
615.
J. Korkisch und Maher Osman 《Fresenius' Journal of Analytical Chemistry》1959,171(2):107-111
Zusammenfassung In der vorliegenden Arbeit wird eine rasche und genaue spektrophotometrische Bestimmungsmethode für Mikrogrammengen Zirkonium mittels des Azofarbstoffes Solochrome Violet R besehrieben. Dieser Farbstoff bildet in 0,1 n salzsaurer Lösung mit Zirkonium einen rotvioletten Komplex, der bei einer Wellenlänge von 560 m, maximale Absorption aufweist. Mit dieser Methode kann noch 1 g Zirkonium/10 ml Meßlösung mit ausreichender Genauigkeit bestimmt werden.Wir danken Herrn Prof. Dr. F. Hecht für seine Unterstützung, die für das Zustandekommen dieser Arbeit von großer Bedeutung war.IV. Mitteilung siehe diese Z. 166, 181 (1959). 相似文献
616.
A. A. Abd El Raheem Abdel Aziz Amin Farouk A. Osman 《Fresenius' Journal of Analytical Chemistry》1959,171(6):420-431
Summary Omega Chrome Black Blue G has been found to be a suitable colorimetric reagent for the detection of cobalt and for the determination of copper, cobalt, cadmium, lead and magnesium. The effects of time, pH, temperature, and foreign ions on the absorbancy are investigated. The reagent is practically suitable for the determination of microgram amounts of cobalt in presence of nickel and other ions which evoke a red colour.The reagent is not suitable for the determination of nickel, calcium, strontium, and zinc. 相似文献
617.
Kekulé indices and conjugated circuits are computed for 36 Kekulé structures, together with two VB quantities associated with the corresponding factor graphs (previously called submolecules). These latter quantitites are nonadjacent numbers of Hosoya and the reciprocal of the connectivity indices of Randi?. It was found that the index of Hosoya successfully orders a set of Kekulé structures belonging to the same hydrocarbon in a parallel order as their Kekulé indices and branching indices. This substantiates the relation between VB and MO theories. A code is derived by summing contributions of nonadjacent numbers in all Kekulé stuctures of a hydrocarbon. The order of the resulting codes is found to be identical to the order of the molecular properties (resonance energies, π-energies, and eigenvalues) of the hydrocarbons. 相似文献
618.
The reaction of 3,3-diphenylindan-1,2-dione with trimethyl phosphite in dry benzene at room temperature for about 15 h led
to the formation of a mixture containing dimethyl (3,3-diphenyl-2-methoxy-1-indenyl)phosphate and dimethyl (3,3-diphenyl-1H-2-oxo-1-indanyl)phosphate, whereas with triisopropyl phosphite, diisopropyl (3,3-diphenyl-2-isopropoxy-1-indenyl)phosphate
is the only product. Treatment of the dione with dialkyl phosphites under different experimental conditions gave dialkyl (3,3-diphenyl-1-hydroxy-2-oxo-1-indanyl)phosphates.
Reaction mechanisms are presented which account for the experimental results. Structural assignments of the new compounds
are based on the spectroscopic evidences and two examples were elucidated by X-ray crystallography. 相似文献
619.
Analysis of diffusion-controlled adsorption and surface tension in one-dimensional planar coordinates with a finite diffusion length and a nonlinear isotherm, such as the Langmuir or Frumkin isotherm, requires numerical solution of the governing equations. This paper presents three numerical methods for solving this problem. First, the often-used integral (I) method with the trapezoidal rule approximation is improved by implementing a technique for error estimation and choosing time-step sizes adaptively. Next, an improved finite difference (FD) method and a new finite element (FE) method are developed. Both methods incorporate (a). an algorithm for generating spatially stretched grids and (b). a predictor-corrector method with adaptive time integration. The analytical solution of the problem for a linear dynamic isotherm (Henry isotherm) is used to validate the numerical solutions. Solutions for the Langmuir and Frumkin isotherms obtained using the I, FD, and FE methods are compared with regard to accuracy and efficiency. The results show that to attain the same accuracy, the FE method is the most efficient of the three methods used. 相似文献
620.
Osman Tiryaki 《Accreditation and quality assurance》2006,11(10):514-513
Method validation is an important requirement in the practice of pesticide residue analysis and is the process of verifying that a method is fit for its purpose. To make a correct decision on the validity of the method, the following method performance parameters have to be taken into consideration: scope, specificity, limit of detection, limit of quantification, linear range, accuracy, precision, repeatability, reproducibility, recovery, ruggedness and robustness. The goal of this study was to validate previously adapted thin-layer chromatographic methods for the pesticide residue analysis in grain. Confirmation of validation parameters for some compounds was also performed by gas chromatographic analysis. 相似文献