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1.
Summary A thin-layer Chromatographic method was developed for the detection and estimation of the steroid sapogenins of fenugreek seeds and plant at its various stages of growth. It depends on the initial separation of the constituent sapogenins (diosgenin, tigogenin and gitogenin) effectively on silica gel and alumina chromatoplates (n-hexane/ethylacetate as solvent) followed by direct photometric estimation of each product separately with reference to a calibration curve. Errors of ± 6% were found with synthetic mixtures.
Dünnschicht-chromatographischer Nachweis und Bestimmung von Steroidsapogeninen in BockshornkleeSteroidsapogenine. XIV
Zusammenfassung Das Verfahren wurde zur Untersuchung der Samen und der Pflanze (Trigonella foenum graecum L.) in verschiedenen Wachstumsstufen angewendet. Die Sapogenine (Diosgenin, Tigogenin und Gitogenin) wurden auf Dünnschichten aus Silicagel oder Aluminiumoxid mit Hilfe von n-Hexan/Äthylacetat-Gemischen getrennt und anschließend photometrisch mit Phosphormolybdänsäure direkt auf der Platte bestimmt. In synthetischen Gemischen wurden Fehler von ± 6% gefunden.相似文献
2.
Gunnar Aksnes Fayez Y. Khalil Piotr J. Majewski 《Phosphorus, sulfur, and silicon and the related elements》2013,188(2):157-161
Abstract This study reports rate data of the alkoxide promoted decomposition of triphenyl 3-hydroxypropyl phosphonium chloride, diphenyl di(3-hydroxypropyl)phosphonium chloride, and tetraphenyl phosphonium bromide. Comparison of kinetics, rate constants, and activation parameters of the alkoxide promoted decompositions points to different mechanism as compared to the hydroxyl promoted reaction. The alkoxide reaction is believed to proceed via a hexacovalent intermediate. Reasons for the hexacovalent route are discussed. 相似文献
3.
Anne-Marie Caminade Fayez El Khatib Antoine Baceiredo Max Koenig 《Phosphorus, sulfur, and silicon and the related elements》2013,188(2-4):365-367
Abstract The ozonization of various halophosphines 1a-j leads with quantitative yields to the corresponding phosphine oxides 2a-j. Ozonization is a convenient method of oxidation, in particular of compounds with bulky ligands (1c, 1d, 1e). 相似文献
4.
Fayez H. Osman Naglaa M. Abd El-Rahman Fatma A. El-Samahy I. S. Ahmed Farag 《Phosphorus, sulfur, and silicon and the related elements》2013,188(3):531-538
3-Acetyl coumarin ( 1 ) reacts with dialkyl phosphites at 100°;C for 8 h to give the phosphonates 2 . Under the same experimental conditions, 1 reacts with trialkyl phosphites to form a mixture of the phosphonates 2 and 3 . The molecular structures of these products were elucidated by x-ray crystallography. 相似文献
5.
Fayez H.?OsmanEmail author Fatma A.?El-Samahy I. S.?Ahmed Farag 《Monatshefte für Chemie / Chemical Monthly》2004,135(7):823-831
Summary. The reaction of (E)-(2-oxo-1,2-dihydroindol-3-ylidene)acetic acid esters with dry acetone at 70°C in presence of aluminum oxide as a catalyst led to the formation of an addition product as a mixture of two isomers. When the same reaction was carried out in presence of morpholine as a base, the unexpected spiro-product was obtained beside the two isomers. Methylation of the latter with methyl iodide in acetone in presence of anhydrous potassium carbonate yielded the corresponding methylated products, whereas methylation of the starting material by the same procedure gave an N-methylated product and the unexpected dispiro-compound. The reaction mechanisms are considered and the structural assignments of the new compounds are based on the chemical and spectroscopic evidences. The structure of the dispiro-product was derived by X-ray analysis. 相似文献
6.
Fabien Cornillier Fayez F. Boctor Gilbert Laporte Jacques Renaud 《European Journal of Operational Research》2008
In the multi-period petrol station replenishment problem (MPSRP) the aim is to optimize the delivery of several petroleum products to a set of petrol stations over a given planning horizon. One must determine, for each day of the planning horizon, how much of each product should be delivered to each station, how to load these products into vehicle compartments, and how to plan vehicle routes. The objective is to maximize the total profit equal to the revenue, minus the sum of routing costs and of regular and overtime costs. This article describes a heuristic for the MPSRP. It contains a route construction and truck loading procedures, a route packing procedure, and two procedures enabling the anticipation or the postponement of deliveries. The heuristic was extensively tested on randomly generated data and compared to a previously published algorithm. Computational results confirm the efficiency of the proposed methodology. 相似文献
7.
Rare-earth doped fibers suffer from relatively high attenuation in comparison to conventional communication fibers. In order to improve the properties of such fibers, understanding of the mechanisms involved in scattering effects is of great importance. The effect of Nd-doping, Al-codoping and of the drawing temperature on the scattering effect was investigated for several different optical fibers. To this end a measuring setup was realized which allows absolute measurements of the scattering coefficient at different positions along a fiber. Also separation of total attenuation and scattering effects is possible. The presented results indicate scattering effects as primary source for increased attenuation compared with undoped fibers. 相似文献
8.
The heat transfer dissipation from a horizontal rectangular fin embedded with square perforations of two orientations under natural convection is numerically investigated. The parameters considered in this investigation are the geometrical dimensions and the orientations of the perforation. A comparison between heat dissipation of the fin with variable orientations of the perforations is presented. It is found that the heat dissipation enhancement from a fin with square perforation parallel to the fin base was more than that of fin with inclined square perforation. The problem of this study was numerically solved using the variational approach finite element technique. 相似文献
9.
Davar A. Azarafza R. Fayez M. S. Fallahi S. Jam J. E. 《Mechanics of Composite Materials》2021,57(2):181-204
Mechanics of Composite Materials - Equilibrium equations of a rib grid-stiffened composite cylindrical shell reinforced with carbon nanotubes (CNTs) are derived based on the first-order shear... 相似文献
10.
Rare-earth doped fibers suffer from relatively high attenuation in comparison to conventional communication fibers. In order to improve the properties of such fibers, understanding of the mechanisms involved in scattering effects is of great importance. The effect of Nd-doping, Al-codoping and of the drawing temperature on the scattering effect was investigated for several different optical fibers. To this end a measuring setup was realized which allows absolute measurements of the scattering coefficient at different positions along a fiber. Also separation of total attenuation and scattering effects is possible. The presented results indicate scattering effects as primary source for increased attenuation compared with undoped fibers. 相似文献