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11.
A systematic study is presented on Pu IV extraction with tri-n-butyl phosphate and trilaurylamine from binary mixtures of H2SO4 with HCl and HBr. The addition of sulfuric acid to the mentioned mineral acid solutions, was found to affect appreciably DPu, which recommended some useful purification procedures. The effect of water-miscible alcohols on the extraction of plutonium from HCl and HNO3 solutions was also investigated. 相似文献
12.
4-Amino-3-hydroxy-2-(2-chlorobenzene)-azo-1-naphthalene sulfonic acid (AHCANSA) was used as a chelating modifier to improve the reactivity of the silica gel surface in terms of selective binding and extraction of heavy metal ions. The surface coverage values were found to be 0.488 and 0.473mmolg–1 for the newly modified physically adsorbed silica gel phase (I) and chemically immobilized-AHCANSA phase (II), respectively. The modified silica gel phases (I, II) were tested for stability in different acidic buffer solutions (pH 1–6) and found to be highly resistant to hydrolysis and leaching by buffer solutions above pH 2. The application of these two phases as solid extractors for a series of mono-, di-, and tri-valent metal ions from aqueous solutions was also performed with different controlling factors such as the pH value of metal ion solutions and equilibrium shaking time. The mmolg–1 metal capacity values determined by silica gel phases (I, II) were found to confirm high affinity and selectivity characters for binding with heavy metal ions such as Cr3+, Ni2+, Cu2+, Zn2+, Cd2+ and Pb2+ in a range of 0.250–0.483. The tested alkali and alkaline earth metals, Na+, K+, Mg2+ and Ca2+, were found to exhibit little interaction and binding ability with the modified silica gel phases. The selectivity characters incorporated into the modified silica gel phases were further utilized and applied in solid phase extraction and pre-concentration of trace concentration levels (1.0µgmL–1 and 2.00–2.50ngmL–1) from real seawater samples. The percentage recovery values determined for Cr3+, Cu2+, Zn2+, Cd2+ and Pb2+ were found to be in the range of 95.2–98.1±2.0–5.0%, and the pre-concentration recovery values for the same tested heavy metal ions were found to be in the range of 92.5–97.1±3.0–6.0% for the two newly modified silica gel phases with a pre-concentration factor of 500.Received December 20, 2002; accepted May 14, 2003
published online September 1, 2003 相似文献
13.
Ensemble averaging measurements obscure the link between the electrochemical performance and the specific properties of an individual because of the interplay of inhomogeneity and heterogeneity. Nanocollision electrochemistry has attracted increasing interest because of its extremely high sensitivity, revealing the intrinsic properties of individual entities that are masked in the traditional ensemble measurements. In this perspective review, we summarized the recent developments in nanocollision-based single entity electrochemistry and photoelectrochemistry, the combined nanocollision electrochemistry with the other complementary techniques, as well as accurate data process. In closing, future challenges, opportunities, and destinations related to nanocollison electrochemistry were discussed. 相似文献
14.
Azza A. Shoukry Mohamed M. Shoukry Mohamed N. Hafez 《Central European Journal of Chemistry》2010,8(4):797-805
The kinetics of base hydrolysis of glycine, histidine, and methionine methyl esters in the presence of [Pd(pip)(H2O)2]2+ complex, where pip is piperazine, is studied in aqueous solutions, at T = 25°C, and I = 0.1 mol dm−3. The rate of ester hydrolysis for glycine methyl ester is studied at different temperature and dioxane/water solutions of
different compositions. The kinetic data are fit under the assumption that the hydrolysis proceeds in one step. The activation
parameters for the base hydrolysis of the complexes are evaluated
相似文献
15.
A. B. A. Elgazzar A. M. Gafaar H. N. Hafez A. S. Aly 《Phosphorus, sulfur, and silicon and the related elements》2013,188(8):1859-1883
Pyridopyrimidine derivatives 2 reacted with hydrazonoylchloride derivatives and yielded triazolopyridopyrimidines 6a–f. Compound 4b reacted with aliphatic acids and afforded triazolo-pyridopyrimidines 7a,b, and the reaction with carbon disulfide afforded 10-mercapto-triazolopyridopyrimidine (10). Moreover, the reaction of 4b with β -ketoesters afforded 10-pyrazolyl-pyridopyrimidines derivatives 11, 13, 14, and 15. Compound 4b reacted with nitrous acid to give tetrazolopyridopyrimidine 16, which reduced to 10-amino-derivative 17. On the other hand, the reaction of 4b with aromatic aldehydes afforded arylidines derivatives 18a–c, which were later cyclized to triazolo-pyridopyrimidines deivatives 19a–c. Finally, 4b reacted with α-haloketones to give triazines derivativrs 20, with new ring systems. 相似文献
16.
Salar Hafez Ghoran Fatemeh Taktaz Ali Akbar Mozafari Murat Tuntürk Nazim Sekeroglu Anake Kijjoa 《Molecules (Basel, Switzerland)》2022,27(3)
The search for new bioactive compounds from plant sources has been and continues to be one of the most important fields of research in drug discovery. However, Natural Products research has continuously evolved, and more and more has gained a multidisciplinary character. Despite new developments of methodologies and concepts, one intriguing aspect still persists, i.e., different species belonging to the same genus can produce different secondary metabolites, whereas taxonomically different genera can produce the same compounds. The genus Salvia L. (Family Lamiaceae) comprises myriad distinct medicinal herbs used in traditional medicine worldwide that show different pharmacological activities due to the presence of a variety of interesting specialized metabolites, including mono-, sesqui-, di-, sester-, tri-, tetra-, and higher terpenoids as well as phenylpropanoids, phenolic acid derivatives, lignans, flavonoids, and alkaloids. We herein summarize the research progress on some uncommon terpenoids, isolated from members of the genus Salvia, which are well recognized for their potential pharmacological activities. This review also provides a current knowledge on the biosynthesis and occurrence of some interesting phytochemicals from Salvia species, viz. C23-terpenoids, sesterterpenoids (C25), dammarane triterpenoids (C30), and uncommon triterpenoids (C20+C10). The study was carried out by searching various scientific databases, including Elsevier, ACS publications, Taylor and Francis, Wiley Online Library, MDPI, Springer, Thieme, and ProQuest. Therefore, 106 uncommon terpenoids were identified and summarized. Some of these compounds possessed a variety of pharmacological properties, such as antibacterial, antiviral, antiparasitic, cytotoxic and tubulin tyrosine ligase inhibitory activities. Due to the lack of pharmacological information for the presented compounds gathered from previous studies, biological investigation of these compounds should be reinvestigated. 相似文献
17.
Zaghloul E. Kandeel Ebtisam A. Hafez Maghraby A. Sleim Fawi M. Abdelatif Mohamed H. Elnagdi 《Heteroatom Chemistry》1995,6(4):305-309
4-Arylmethylene-2-phenyl-2-oxazolin-5-ones 1a , b reacted with some active methylene reagents to afford pyrrolidine-3,5-dione, pyrrolo[2,3-b]pyridine and pyrrolinone derivatives. The cinnamate ester, obtained from 1a and sodium ethoxide, could be converted into a pyrrolidinone derivative having an active methylene group. This compound coupled with diazonium salts to afford the corresponding azo coupling products. 相似文献
18.
M. Hafez I. S. Yahia S. Taha 《Applied Physics A: Materials Science & Processing》2014,116(3):1445-1453
Optical, microstructural, and thermal properties of the investigated silver nitrate samples were characterized by various techniques, such as X-ray analysis, scanning electron microscopy, UV–Vis–NIR absorption and differential scanning calorimetry (DSC). The presence of structural phase transition [orthorhombic structure (phase II) to rhombohedral structure (phase I)] was checked by DSC and X-ray analysis measurements. The thermal energy required for such transformation is found to be 11.6 J/g. The optical band gaps of AgNO3 are 1.4 and 2.02 eV for phase II and phase I, respectively, at the low-energy region. But at high-energy region, the optical band gaps are 3.41 and 3.43 eV for phase II and phase I, respectively. Characteristic peaks for AgNO3 corresponding to (2 1 1), (0 0 4) and (3 5 1) for phase II and (0 0 4), (3 1 1) and (0 2 4) for phase I have been observed. The average crystalline size for AgNO3 samples and the values of dislocation density δ and the strain ε for the planes of two phases II and I are calculated and also the texture coefficient is determined. Such information can considerably aid in understanding the process of phase transformations in AgNO3. 相似文献
19.
Fixation mechanism between zeolite and some radioactive elements 总被引:1,自引:0,他引:1
M. B. Hafez A. F. Nazmy F. Salem M. Eldesoki 《Journal of Radioanalytical and Nuclear Chemistry》1978,47(1-2):115-119
Fixation of some fission products and actinide elements from aqueous solutions on zeolite was investigated. Studies showed
that the interaction between the radionuclides and zeolite followed the exchange and the adsorption mechanisms. The relative
importance of each depends on the type, the nature, and the size of the radioelement. 相似文献
20.
Dimensional analysis and overlap arguments lead to a prediction of a region in the streamwise velocity spectrum of wall-bounded turbulent flows in which the dependence on the streamwise wave number, kappa(1), is given by kappa(1)(-1). Some recent experiments have questioned the existence of this region. In this Letter, experimental spectra are presented which support the existence of the kappa(1)(-1) law in a high-Reynolds-number boundary layer. This Letter presents the experimental results and discusses the theoretical and experimental issues involved in examining the existence of the kappa(1)(-1) law and the reasons why it has proved so elusive. 相似文献