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排序方式: 共有818条查询结果,搜索用时 15 毫秒
791.
M. S. El-Shahawi M. W. Kadi S. H. El-Khouly A. Abd El-Mohty S. M. Saad N. E. A. Eweda 《Journal of Radioanalytical and Nuclear Chemistry》2013,295(1):15-22
A new zirconium vanadate (Zr–V) ion-exchanger was synthesized and characterized for fast and selective separation procedure of 90Y from 89Sr. The method was based on 90Y(III) sorption from aqueous HCl solution containing 89Sr(II) onto Zr–V gel exchanger. The kinetics of Y(III) sorption from HCl solution by Zr–V exchanger was subjected to Weber–Morris, Lagergren, Bhattacharya and Venkobachar, and Bt models. Initially, the uptake of Y(III) onto the exchanger was fast followed by kinetically first-order sorption with an overall rate constant, K Lager = (3.55 ± 0.03) × 10?4 min?1. Film and intraparticle transport are the two steps that might influence Y(III) sorption. The negative values of ΔG of 90Y retention dictate that, the process is a spontaneous. The negative values of ΔH and ΔS reflect the exothermic nature of 90Y(IIsorption and the random uptake of 90Y(III) onto Zr–V sorbent. Zr–V exchanger offers unique advantages of 90Y(III) retention over conventional solid sorbents in rapid and effective separation of traces of 90Y(III) from Sr. The exchanger was successfully packed in column for an effective separation of 90Y. 相似文献
792.
M. S. El-Shahawi M. W. Kadi S. H. El-Khouly A. Abd El-Mohty S. M. Saad N. E. A. Eweda 《Journal of Radioanalytical and Nuclear Chemistry》2013,295(3):1873-1880
A low cost and selective method has been developed for the separation of trace concentrations of 90Y3+ from its parent 89Sr2+. The proposed procedure is based upon complete retention of 90Y3+ onto zirconium-vanadate (Zr-V) gel ion exchanger packed column from aqueous solutions containing HCl (1.0 × 10?5mol dm?3). Under these conditions, 89Sr2+ species were not retained onto Zr-V sorbent. The retained 90Y3+ species were then recovered with HCl. The performance of Zr-V sorbent packed column was determined via the height equivalent to the theoretical plates (HETP) and the number of plates (N). Validation of the developed method was checked by calculating the radionuclidic purity in terms of purification factor (P f = A/A0) and radiochemical purity of the eluted 90Y from the column. Zr-V sorbent packed column offers unique advantages of retention and quantitative separation of 90Y from retention over conventional solid sorbents in rapid and effective separation of trace concentration of 90Y3+ from 89Sr2+ in their aqueous equilibrium media. 相似文献
793.
Gamal R. Saad Nagwa H.S. Ahmed Abdelgawad A. Fahmi Mohamed M. Kaddah 《Liquid crystals》2013,40(8):1285-1297
ABSTRACTThe effect of introducing a lateral methyl substitution into the previously investigated laterally neat four-ring analogues, 4-substituted phenylazo phenyl 4?-(4?-alkoxyphenylazo) benzoates (Ina–e), on their mesophase behaviour was investigated for the newly prepared five homologous series of 4-substituted phenylazo phenyl 4?-(3?-methyl-4?-alkoxyphenylazo) benzoates (IIna–e). Within each homologous series, the alkoxy group varies between 6, 8, 10, 12, 14, and 16 carbons, while the substituent, X, is a polar group that alternatively changes between the electron-donating (CH3O and CH3) groups, and the electron-withdrawing (Br and NO2) groups, including the unsubstituted homologues (IInc). Their mesophase stabilities were determined by DSC and phases identified by PLM. The results showed that independent of the alkoxy-chain length or the polarity of the substituent X, the nematic phase is predominant with relatively high stability and wide temperature ranges. All compounds show a good thermal stability in the mesophases domain, except the nitro and Br substituted derivatives bearing short alkoxy chain length. Comparison of the mesophase behaviour was also made between the present series and corresponding three-ring laterally CH3-substituted azo/ester analogues. UV-vis absorption spectra revealed that derivatives with electron donating or an electron withdrawing groups exhibited redshifts of the π→π* transition compared with unsubstituded derivative. 相似文献
794.
Alan R. Katritzky Saad El-Zemity Hengyuan Lang Ezzat A. Kadous Abdallah M. El-Shazly 《合成通讯》2013,43(2):357-365
1-(α-Aminomethyl)-1,2,4-triazoles readily add to enol ethers or enamides to give novel classes of compounds, 1-(γ-amino-α-alkoxy)propyl- (8) and 1-(γ-amino-α-amido)propyl- (10) substituted 1,2,4-triazoles, in excellent yields. 相似文献
795.
Degradation of known odor precursors in sludge during anaerobic digestion was systematically studied and simulated using the
Anaerobic Digestion Model Number 1 (ADM1). The degradation of various protein fractions (particulate, soluble, and bound),
volatile fatty acids (VFAs), lipids, and amino acids of primary sludge (PS) and waste-activated sludge (WAS) were monitored
during anaerobic digestion. The degradation kinetic constants of the odor precursors namely, protein, lipid, and VFAs were
determined. Relationships between degradations of protein fractions and volatile suspended solid were established; a strong
relationship between bound protein, a major odor precursor, and volatile suspended solid degradation was found. No statistically
significant difference in bound protein reduction was observed between PS and WAS. ADM1 was successfully used to simulate
the lab scale continuous anaerobic digestion; model results with optimized parameters showed good agreement with the experimental
data for methane production and several other sludge parameters including odor precursors such as lipids, VFAs, and proteins. 相似文献
796.
Wafaa S. Hamama Mohadamed A. Ismail Mamdoh Soliman Saad Shaaban Hanafi H. Zoorob 《Journal of heterocyclic chemistry》2011,48(5):1169-1174
Annulations of 2‐imino‐4‐thiazolidinone ( 5 ) via cycloaddition followed by cyclocondensation reaction with 1,3‐diphenylpropenone ( 6 ), benzylidenemalonate, and 1,2‐bis(chloromethyl)benzene gave 7 , 19 and 20 , respectively. Reaction of 5 with suitable electrophiles (Mannich bases of arylalkanone), 1,4‐dichlorobenzene (diarylmethylation), and formylation afforded 8 / 9 , 21 / 22 , and 23 , respectively. J. Heterocyclic Chem., (2011). 相似文献
797.
Jens Burghaus Moulay T. Sougrati Anne Möchel Andreas Houben Raphaël P. Hermann Richard Dronskowski 《Journal of solid state chemistry》2011,184(9):2315-2321
Prior investigations of the ternary nitride series Ga1-xFe3+xN (0≤x≤1) have indicated a transition from ferromagnetic γ′-Fe4N to antiferromagnetic “GaFe3N”. The ternary nitride “GaFe3N” has been magnetically and spectroscopically reinvestigated in order to explore the weakening of the ferromagnetic interactions through the gradual incorporation of gallium into γ′-Fe4N. A hysteretic loop at RT reveals the presence of a minority phase of only 0.1-0.2 at%, in accord with the sound two-step synthesis. The composition of the gallium-richest phase “GaFe3N” was clarified by Prompt Gamma-ray Activation Analysis and leads to the berthollide formula Ga0.91(1)Fe3.09(10)N1.05(7). Magnetic measurements indicate a transition around 8 K, further supported by Mössbauer spectral data. The weakening of the ferromagnetic coupling through an increasing gallium concentration is explained by a simple Stoner argument. In Ga0.9Fe3.1N, the presence of iron on the gallium site affects the magnetism by the formation of 13-atom iron clusters. 相似文献
798.
Ali A. Alhazime M. ME. Barakat Radiyah A. Bahareth E. M. Mahrous Saad Aldawood S. Abd El Aal and S. A. Nouh 《中国物理 B》2022,31(9):97802-097802
We applied an ex-situ casting procedure to prepare a nanocomposite (NCP) from Makrofol polycarbonate (PC) and CdSe nanoparticles. The CdSe nanoparticles were prepared by a thermolysis procedure in the presence of N2 gas flow. Rietveld refinement of x-ray data illustrated that the CdSe adopts a cubic zinc blend structure of 6.057 Å lattice parameter and 2 nm typical grain size. Samples from the prepared NCP were exposed to γ dosages (20 kGy-250 kGy). The modifications induced in the NCP films owing to γ dosages have been studied. The γ irradiation (50 kGy-250 kGy) causes crosslinks that reduce the optical bandgap from 4.15 eV to 3.81 eV, associated with an increase in dielectric parameters and refractive index. This is attributed to an increase in the mass fraction of the disordered regions as specified by x-ray diffraction. The PC-CdSe NCP was found to have a reaction to color modification which makes it suitable for saleable reproduction on a printing press. 相似文献
799.
A. M. El Atrash E. A. Saad M. S. A. Hamza 《Journal of Radioanalytical and Nuclear Chemistry》1991,149(2):345-349
The extraction of radioactive152–154Eu by ethyl hydrogen benzyl phosphonate (HEBP) and ethyl hydrogen benzoyl phosphonate (HEBOP) in n-hexane from an aqueous solution of ionic strength 0.1M (Na+, HClO4) has been investigated at different temperatures and the thermodynamic functions evaluated. HEBOP was found to be more efficient than HEBP as extractant. In addition, the stability constant of the extracted complexes were determined. 相似文献
800.