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  • Author or Editor: M. Shehata x
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Abstract  

The distribution of Mo(VI) and the interfering radiocontaminants U(VI), Zr(IV) and Nb(V) have been investigated between chromatographic alumina and aqueous hydrochloric acid solutions of concentrations ranging from 0.5M to 11M. At low acidities (less than 1M HCl) the distribution coefficients increase with the decrease of acid concentration, while in the region of 2–4M they increase with the increase of the acid concentration. Above 4M HCl, the increase inK D continues with the acid concentration for both Zr(IV) and Nb(V), but constant values are reached for U(VI) and Mo(VI).

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Abstract  

Dissolution of a neutron-irradiated uranium target in a medium of 6N HCl containing a few drops of very dilute HNO3 yielded a matrix solution which on running on a silica gel column allowed the complete adsorption of the95Zr−95Nb activity formed in the fission process. The95Zr−95Nb activity is cleanly and totally eluted with 0.5% oxalic acid solution. None of the uranium or the activity of the other fission products was found to be adsorbed on the column.

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Abstract  

The radioisotope99Mo generated through the fission of neutron-irradiated uranium targets was separated in an extremely radiochemically pure state. The target dissolution mixture was run on a silica gel column whereby the95Zr−95Nb activity, the serious radiocontaminants of99Mo, was adsorbed on the gel. The effluent from the gel column was processed and treated with sodium dihydrogen phosphate. The processed solution was run on an activated alumina column whereby99Mo was adsorbed as phospho-molybdate complex ion, then desorbed from the column as the molybdate ion by eluting with 10% NaOH solution. By recycling the adsorption and desorption steps on alumnia,99Mo was finally obtained totally free from all other radiocontaminants.

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Abstract  

The sorption behavior of Th(IV) from intermediate acidic solutions (0.5–1.5N HCl) of Arsenazo-III with three different types of ion exchangers, namely Dowex-50 W×8, AG-2×8 and Chelex-100 is studied at different concentrations of Arsenazo-III corresponding to metal: reagent ratio of 11 to 13. The sorption behavior of Arsenazo-III with AG-2×8 and Chelex-100 under various experimental conditions is studied as well. Complete sorption of the reagent on AG-2×8 under all studied conditions is found. The sorption process from solutions at high pH-values is found to be relatively slow. Complete sorption of reagent on Chelex-100 is found from acidic solutions. The percent uptake decreases sharply with increasing pH value. While partial sorption of Th(IV) or Th(IV)-Arsenazo-III complexes on Dowex-50 W×8 or AG-28, respectively, is found, Chelex-100 is found to be selective for concentrating thorium as coloured Arsenazo-III complex which may be useful in ion exchange phase absorptiometry. The sorbed complex from 0.5N HCl solutions of Arsenazo-III is proved to be ThL.

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Abstract  

The extraction of UO 2 2+ from nitrate solution has been carried out using DHDECMP. Different parameters affecting the distribution coefficient of UO 2 2+ have been determined. The extraction of UO 2 2+ was found to have second order dependency on both extractant and H+ concentrations. Addition of some bases as TBP and TOPO to the phosphonate extractant increased the distribution of UO 2 2+ to a great extent. LogD for UO 2 2+ with respect to both synergistic bases was found to be a first order dependent. The thermodynamic parameters have been calculated and the extraction mechanisms have been suggested.

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Abstract  

A method for the separation of no-carrier-added arsenic radionuclides from the bulk amount of proton-irradiated GeO2 targets as well as from coproduced radiogallium was developed. The radionuclides 69Ge and 67Ga produced during irradiation of GeO2 were used as tracers for Ge and Ga in the experiments. After dissolution of the target the ratio of As(III) to As(V) was determined via thin layer chromatography (TLC). The extraction of radioarsenic by different organic solvents from acid solutions containing alkali iodide was studied and optimized. The influence of the concentration of various acids (HCl, HClO4, HNO3, HBr, H2SO4) as well as of KI was studied using cyclohexane. The optimum separation of radioarsenic was achieved using cyclohexane with 4.75 M HCl and 0.5 M KI and its back-extraction with a 0.1% H2O2 solution. The separation leads to high purity radioarsenic containing no radiogallium and <0.001% [69Ge]Ge. The overall radiochemical yield is 93 ± 3%. The practical application of the optimized procedure in the production of 71As and 72As is demonstrated and batch yields achieved were in the range of 75–84% of the theoretical values.

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Abstract  

The radiochemical separation of radiogallium from radiogermanium was studied using ion-exchange chromatography (Amberlite IR-120) and solvent extraction (Aliquat 336 in o-xylene). Both Amberlite IR-120 and Aliquat 336 in o-xylene have been used for the first time in separations involving radiogallium and radiogermanium. For tracer studies the radionuclides 68Ge (t 1/2 = 270.8 days), 69Ge (t 1/2 = 39 h) and 67Ga (t 1/2 = 78.3 h) were used. They were produced by the nuclear reactions natGa(p,xn)68,69Ge and natZn(p,xn)67Ga, respectively, and separated from their target materials in no-carrier-added form. Several factors affecting the separation of radiogallium from radiogermanium were studied and for each procedure the optimum conditions were determined. The solvent extraction using Aliquat 336 was found to be better. The separation yield of radiogallium was >95%, the time of separation short, the contamination from radiogermanium <0.008% and the final product was obtained in 0.5 M KOH. This method was adapted to the separation of n.c.a. 68Ga from its parent n.c.a. 68Ge. The quality of the product thus obtained is discussed.

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This study describes the antistaphylococcal mechanism of the ethanolic extract of Algerian propolis on Staphylococcus aureus ATCC 25923. To investigate the underlying mechanism of action of the ethanolic extract of propolis, bacteriolysis, bacterial death, leakage of potassium, proteins, nucleic components, and scanning electron microscopic studies were conducted. The results showed that the minimum inhibitory concentration (MIC) of ethanolic extract of propolis against Staphylococcus aureus ATCC 25923 was 39 μg ml–1. The extract displayed significant bactericid activity against S. aureus in a time and concentration dependant manner. Its mode of action was evident from the increase of K+ efflux and nucleotide leakage. These results were confirmed by Scanning Electron Microscopy (SEM) that showed remarkable morphological and ultrastructural changes in S. aureus after exposure to 1MIC and 2MIC concentrations. The overall study contributed to the understanding of the antistaphylococcal mechanism of ethanolic extract of propolis. It emphasizes its potential to be used as an important natural bio-preservatives in food products.

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