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91.
Mohamed Hilmy Elnagdi Shereif Mahmoud Fahmy Ebtisam Abdel Aziz Hafez Mohamed Riffaat Hamza Elmoghayar Samir Abdel Rahman Amer 《Journal of heterocyclic chemistry》1979,16(6):1109-1111
Benzoylacetonitrile (II) reacted with trichloroacetonitrile (III) to yield the β-amino-β-trichloromethylacrylonitrile IV. Compound IV reacted with hydrazine hydrate to yield 5-amino-4-cyano-3-phenylpyrazole (V) and with 2-aminopyridine to yield the aminopyridine derivative VIII (cf., Chart I). Compound IV reacted with III to yield 2,4-bis(trichloromethyl)-5-cyano-6-phenylpyrimidine (I) which could be converted into a variety of pyrazolo[4,3-d]pyrimidine derivatives by treatment with hydrazine hydrate under a variety of different experimental conditions (cf., Chart II). 相似文献
92.
Waleed E. Mahmoud S.A. Mansour M. Hafez M.A. Salam 《Polymer Degradation and Stability》2007,92(11):2011-2015
Acrylonitrile butadiene rubber (NBR) compounds filled with 40 phr of high abrasion furnace black (HAF) and HAF (20 phr)/graphite (20 phr) were experimentally investigated. The stress-strain curves of the composites were studied, which are described by applying Ogden's model. The effect of cyclic fatigue and hysteresis was also examined. The dissipation energy that indicates the vibration damping capacity for all samples was determined. A continuum damage model is used to investigate the fatigue damage behavior for elastomers. Experiments on the cyclic fatigue of a carbon-filled NBR rubber and carbon/graphite filled NBR rubber were conducted to determine the relation between the number of cyclic fatigue and the strain amplitude. The results indicate that the theoretical formula for the number of cyclic fatigue as a function of the strain amplitude, derived from the damage model, can describe experimental data for the prepared samples very well. 相似文献
93.
Mohamed Tarek Mohamed Zaki Nabil Hafez A. Y. El-Sayed 《Monatshefte für Chemie / Chemical Monthly》1992,123(6-7):477-486
The complexation reactions of cerium(III and IV) with 9-phenyl-2,3,7-trihydroxy-6-fluorone (H3
PF) have been studied in the presence and absence of some surfactants and protective colloids. Maximum enhancement of the chelate absorbances is obtained with the cationic surfactant cetylpyridinium bromide (CPB) or cetyltrimethylammonium bromide (CTAB). In thepH ranges 8.2–9.0 and 9.8–10.8 the ternary 1:3:3 and 1:4:3 cerium(III)-PF-CPB complexes are formed with molar absorptivities of 9.02 × 104 and 9.86 · 104 lmol–1 cm–1 at 570 and 590 nm, respectively. The corresponding 1:4:2 and 1:3:2 complexes of cerium(IV) are formed in thepH ranges 8.4–9.0 and 9.8–10.6 in the presence ofCTAB andCPB, respectively. Their molar absorptivities are 8.00·104 and 8.56·104lmol–1 cm–1 at 570 and 590 nm, respectively. The stability constants of the studied complexes have been determined and a spectrophotometric method has been developed to determine the cerium content in monazite concentrate.
Komplexierungsreaktionen von Cer(III und IV) mit 9-Phenyl-2,3,7-trihydroxy-6-fluoron in Gegenwart kationischer oberflächenaktiver Stoffe
Zusammenfassung Es wurden Komplexierungsreaktionen von Cer(III und IV) mit 9-Phenyl-2,3,7-trihydroxy-6-fluoron (H3 PF) in Gegenwart und auch ohne oberflächenaktive Stoffe und Schutzkolloide untersucht. Maximale Verstärkung der UV-VIS-Absorption wurde mit den kationischen oberflächenaktiven Verbindungen Cetylpyridiniumbromid (CPB) und Cetyltrimethylammoniumbromid (CTAB) erreicht. ImpH-Bereich von 8.2–9.0 und 9.8–10.8 bildeten sich die ternären 1:3:3 und 1:4:3 Cer(III)-PF-CPB-Komplexe mit molaren Extinktionskoeffizienten von 9.02·104, bzw. 9.86·104lmol–1 cm–1 bei 570 bzw. 590 nm. Die entsprechenden 1:4:2 und 1:3:2 Cer(IV)-Komplexe wurden impH-Bereich 8.4–9.0 und 9.8–10.6 in Gegenwart vonCTAB undCPB gebildet, wobei die Extinktionskoeffizienten bei 8.00·104, bzw. 8.56·104 lmol–1 cm–1 bei 570 bzw. 590 nm lagen. Es wurden die Stabilitätskonstanten der Komplexe bestimmt und es wurde eine spektrophotometrische Methode zur Bestimmung von Cer in Monazitkonzentrat entwickelt.相似文献
94.
In o‐minimal structures, every cell is definably connected and every definable set is a finite union of its definably connected components. In this note, we introduce pseudo definably connected definable sets in weakly o‐minimal structures having strong cell decomposition, and prove that every strong cell in those structures is pseudo definably connected. It follows that every definable set can be written as a finite union of its pseudo definably connected components. We also show that the projections of pseudo definably connected definable sets are pseudo definably connected. Finally, we compare pseudo definable connectedness with (recently introduced) weak definable connectedness of definable sets in weakly o‐minimal structures. 相似文献
95.
Hafez Maghsoudi 《Separation & Purification Reviews》2016,45(3):169-192
Characterization of zeolite membrane defects including SEM, dye permeation, bubble point and permporometry methods are presented. Experimental setup, governing equations and step by step procedure for obtaining pore sizes are discussed for the most useful method, i.e., the permporometry. A complete review on the techniques for elimination of defects including chemical vapor and liquid depositions, coke deposition, surface coatings, and hydrothermal treatments is presented. For each method, experimental setup, various modification conditions as well as performance enhancement of the membranes are comprehensively discussed. Finally, comparison between different methods is performed to find the more efficient techniques. 相似文献
96.
A. E. Amr N. A. A. Hafez K. A. Ali M. A. Al-Omar H. A. Ghabbour 《Russian Journal of General Chemistry》2016,86(8):1944-1947
2-Dimethylamino methylenechromanone 1 reacted with 4H-1,2,4-triazol-3-amine in acetic acid to give only one isolated product which was identified by X-ray study as 6H-chromeno[3,4-e][1,3,4]triazolo[2,3-a]-pyrimidine. The molecular structure of 3, C12H8N4O, was determined to be monoclinic, P21/c, a = 16.3875(5), b = 8.8378(3), c = 13.8392(5) Å, β = 101.190(1)°, V = 1966.22(11) Å3, Z = 8. 相似文献
97.
Polyethylene glycol–polyvinyl alcohol (PEG–PVA) blend is a multifunctional material and controlling its properties is important for various medical and industrial uses. In this paper, we report the influence of carboxymethyl cellulose (CMC) and doping with tin oxide (SnO2) nanoparticles (NPs) on the structural and optical properties of PEG–PVA. The prepared samples were investigated by X-ray diffraction (XRD), high-resolution transmission electron microscopy (HR-TEM), scanning electron microscopy (SEM), Fourier transform infrared (FTIR) and UV–Vis-NIR spectroscopies. SnO2 NPs of rutile structure, average crystallite size of ~30.2 nm and optical band gap (Eg) of 3.68 eV were prepared by a simple sol–gel process. CMC addition enhances the crystallinity of PEG–PVA that then gradually reduced by increasing SnO2 doping ratio. The optical transmittance of PEG–PVA increased from 77 to 90% after mixing with CMC and then decreased to 64% with increasing SnO2 content to 1.5%. Also, the Eg of PEG–PVA increased from 5.20 to 5.28 eV and then decreased to 4.88 eV due to CMC addition and SnO2 incorporation, respectively. The refractive index, the dispersion parameters and the optical conductivity of PEG–PVA, CMC/PEG–PVA and of its nanocomposite films are discussed. The correlation between the structural modifications and the resultant optical properties are reported. 相似文献
98.
A quantitative study of the interaction of some lanthanide ions with 2,2-oxybis-[ethyliminodi /acetic/ acid] or 2,2-bis [aminoethyl]ether-tetraacetic acid /BAETA/ was carried out. Stability constants of the lanthanide chelates containing 11 ratio of metal to ligand were determined. A discussion of the variation of the metal chelates stability constants in the lanthanide series is given. Radiolysis of the formed chelates has also been investigated both in presence and in absence of oxygen. A radiolytic degradation mechanism is proposed and discussed. 相似文献
99.
Willibald Diemair Heinz Janecke und Mohamed Hassib Hafez Ragab 《Fresenius' Journal of Analytical Chemistry》1956,152(1-3):36-44
Zusammenfassung Überblickt man die Ergebnisse noch einmal, so läßt sich feststellen, daß die papierchromatographische Bestimmung von l-Ascorbinsäure, wenn diese in wäßriger Lösung vorliegt, sehr gute Werte liefert. Sie wird jedoch unsicher, wenn die Bestimmung in biologischem Material erfolgen muß. Sie scheint besonders dann nicht geeignet zu sein, wenn behandelte, gefärbte Säfte zu untersuchen sind. Diese Beobachtung legt die Vermutung nahe, daß die l-Ascorbinsäure mit einem anderen Saftbestandteil, eine Verbindung eingeht und sich so der Erfassung entzieht.Herrn Prof. Dr. A. Kurtenacker zum 70. Geburtstage gewidmet. 相似文献
100.
We report a new method for the catalytic, asymmetric synthesis of beta-substituted aspartic acid derivatives in which the nucleophilic catalyst serves up to four discrete roles in a one-pot procedure: catalytic dehydrohalogenation of acid chlorides to form ketenes; catalytic dehydrohalogenation of alpha-chloroamines to form the corresponding imines; catalyzed [2 + 2]-cycloaddition to produce intermediate acyl beta-lactams; and finally, nucleophilic ring opening to afford optically enriched beta-substituted aspartic acids in high enantioselectivity and diastereoselectivity. 相似文献