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- Author or Editor: J. Gascón x
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Abstract
In radiochemical analysis, the storage of a tracer solution is an important issue to bear in mind. The evaporation of the tracer solution depends on the type of container used for storing. In this paper the evaporation rate in four kinds of containers, i.e., flame-sealed glass ampoule, sealed glass flask, flame-sealed polyethylene ampoule and screw glass vial was studied. It is concluded that the evaporation rate depends on the system of closing.
Abstract
In radiochemical analysis, specially by using high resolution alpha-spectrometry, a key issue is the determination of the radiochemical yield. Radiochemical yield allows to determine the concentration of the radionuclide of interest and the quality of the chemical separation. To determine the radiochemical yield it is necessary to know the solid state detector efficiency, which can be obtained by calibration with a circular calibrated source. In this paper the optimization of the parameters affecting both the calibration and measurement of a source by alpha-spectrometry is described. The optimization is based on two sets of data: experimental and theoretical. Experimental data were obtained from the calibration of the solid state detector with four calibrated 241Am sources. Theoretical data were calculated by geometry formulas and were verified experimentally.
Abstract
In this paper the authors present a study of the adsorption of thorium on manganese dioxide by batch equilibration and cartridge experiments. Some anomalies in the use of MnO2 to concentrate thorium have been found. So the use of this technique is limited for the determination of thorium in natural waters.
Abstract
Adsorption of americium with manganese-dioxide-impregnated filters has been studied. The adsorption of americium decreases as the pH increases due to its hydrolysis. From the reported laboratory experiments, it can be concluded that the adsorption on manganese-dioxide filters is not a reliable method to determine americium in natural waters.
Abstract
The determination of Am and Cm in typical waste streams from nuclear power plants using anion exchange chromatography has some drawbacks like the contamination by Pu and Po. This improved procedure solves these problems, and it has been applied with success to the analysis of Am and Cm in nuclear waste samples: ion exchange resins, ion exchange resins solidified with cement and evaporator concentrates.
The aim of this study was to evaluate and compare the dynamics of plant, crustacean, and coleopteran assemblages living in Mediterranean temporary wetlands. We measured assemblage parameters (species richness, diversity and abundance) and succession rates during the hydroperiod for each assemblage analysed. Moreover, the species were classified according to their affinity to the temporary aquatic habitats in order to study if each assemblage had similar patterns among species groups of habitat affinity. Only among plants, the temporary water species were dominant in terms of species richness, diversity or abundance. Cross-taxon congruence between plants and crustaceans, previously reported, was not confirmed when temporal succession was taken into account, suggesting different temporal patterns for the studied taxa. Plants showed the lowest level of successional changes and significant differences between local and regional diversity. In contrast, coleopterans had the highest level of successional changes and a different relationship between local and regional diversity, with regard to the hydroperiod phase. Finally, crustaceans had intermediate levels of successional changes and the relationship between the local and regional diversity during the hydroperiod was dependent on the type of organism (generalist vs. temporary water species). All of this gave evidence of the difficulties to use one taxonomic group in order to elucidate the ecological patterns of other groups.
Pluripotent stem cells (PSCs), already described in human beings, are fibroblast-like cells that exhibit a CD34 marker specific for haematopoietic stem cells. In this work we have demonstrated the presence of PSCs in the peripheral blood of pigs, a species frequently used in transplantation studies as an animal model for human diseases. Differentiation into haematopoietic colonies (granulomacrophagic colonies, erythroid colonies and mixed colonies) has been carried out with the peripheral blood of adult and newborn pigs, using solely human commercial media. Peripheral blood mononuclear cells (PBMNCs) were cultured in semisolid methylcellulose based media enriched with recombinant human cytokines, achieving granulomacrophagic-colony forming unit (GM-CFU) and mixed-colony forming unit (Mix-CFU) growth with erythroblastic lineage proliferation in the presence of erythropoietin (Epo). In all the samples CFU growth was associated with the presence of recombinant human cytokine. No evidence of proliferation in control plates without cytokines was found. From liquid medium culture, a population of macrophages and CD34+ fibroblast like cells were retrieved 21 days after sowing. These findings allow us to think about the direct application of this simple and standardised method in several work fields such as the study of pharmacological effects of many drugs over the haematopoietic line and in the study of new strategies in cellular therapy for some human diseases.
