[en] Selenium (Se) is an essential micronutrient for human health, but its deficiency may affect at least one billion people worldwide. Plants and plant-derived products transfer the soil-uptaken Se to humans through the food chain, which is hardly enough when soils have been always poor or already exhausted in bioavailable Se species. Other than agronomic approaches for enhancing Se levels in cereals, such as soil and foliar supplements, seed enrichment may be viewed as an alternative Se-biofortification technique. This study addresses the protocol for preparing Se-enriched wheat seeds, with the specific purpose of optimizing the administration of Se to the seeds prior to sowing. The first step was to soak an amount of bread-wheat seeds in an active Se solution, made with irradiated [Na₂O₄Se], and then monitoring ⁷⁵Se in periodically-retrieved samples from that original amount. To avoid losing Se to soil (after sowing), and, especially, to ensure that Se gets really absorbed into the seeds - and not just adsorbed onto them - the washing time of the seeds should be optimized as well. This was carried out by washing Se-treated seeds several times, until no significant amount of the radiotracer could be detected in the washing water. In what concerns the full optimization procedure, the overall results of the present study point to an optimum time of 48 h for soaking and 24 h for washing. (author)

[en] Sulfur and selenium isotopes are used for labeled compounds and as precursors for radioisotope production; however, both limited availability and high costs are problems. A new method is needed for large-scale separation of theses isotopes. Experimental distillation columns were used to measure isotopic separations for sulfur and selenium compounds. The maximum total isotope separations of ³²S vs. ³⁴S were 1.127 for H₂S, 1.048 for COS, 0.838 for SF₄, and 1.058 for CH₃SH. Relative volatilities of ³²S and ³⁴S are 1.0006 for COS and 0.9976 for SF₄. There is a reverse isotope effect for carbon in COS. No isotopic separation was observed for dimethyl selenide. The lower mass selenium isotopes in H₂Se are more volatile. Distillation is a promising method for separating sulfur isotopes on a production scale. Existing distillation technology produces separated isotopes with an effect similar to that found for sulfur in SF₄. (author). 8 refs.; 2 tabs

[en] A comprehensive set of shell model calculations for ⁷⁸⁻⁸⁴Se isotopes have been performed with recently derived interactions, namely JUN45 and jj44b for f_5/2pg_9/2 space. To study the importance of the proton excitations across a Z = 28 shell, in this region mentioned by Cheal et al (2010 Phys. Rev. Lett. 104 252502), calculations for fpg_9/2 valence space using an fpg effective interaction with ⁴⁸Ca as the core, and imposing a truncation, have also been performed. Comparison of the calculations with experimental data show that the predicted results of the jj44b interaction are in good agreement with experimental data. (paper)

[en] The separated isotopes of selenium may be used as stable precursors for the synthesis of radio-bromine isotopes for positron emitter tomographic diagnostics. As part of a project to find a suitable distillation method for separating selenium isotopes, the need arose to study the organo-metallic compound dimethyl selenide. The complexity of the mass spectrum tended to obscure the isotope effect with 35 major peaks being measured. A least-squares fitting procedure was developed for the 13 fragmentation factors as well as a few hundredths of a percent, yet no sizeable separation was observed across the test column. According to these measurements, the effect of one mass unit increase in the selenium isotope results in less than 10 ppM in the vapor pressure of the compound. 4 figures

[en] This work contains the results of research on the complete process for the centrifuge enrichment of all selenium isotopes. The centrifuge cascade that was used to obtain the first selenium isotope Selenium (⁷⁴Se) in the world with an enrichment of more than 99% in gram quantities is described. The same cascade was used to obtain small quantities of all others isotopes of selenium. As a result of this work, nearly 2 kg of elemental ⁷⁴Se with an enrichment of 96-99.8% were obtained

No abstract available

[en] A good understanding of the migration of selenite, Se(IV), through deep granitic layers depends on a good understanding of the geochemistry of these layers. Chemical sequential extraction is applied herein to evaluate the ability of granite to adsorb Se(IV) in DW, GW and SW systems. The experimental results indicate that the removal of crystalline Fe oxides reduces the adsorption of Se(IV), suggesting its importance in granite. The normalized concentrations of Se(IV) adsorbed onto crystalline Fe oxides is approximately 0.0301, 0.0330 and 0.0335 mole Se(IV) adsorbed/mole of Fe in DW, GW and SW systems. Kinetic adsorption experiments are conducted to elucidate the results of the chemical sequential extraction. Both the treated and the untreated granite take the same time to reach their equilibrium, suggesting that crystalline Fe oxides dominate the adsorption of Se(IV). Meanwhile, the one-site model suffices to simulate the kinetics of adsorption. (author)

No abstract available

[en] The recently measured experimental data of ^79,81,83Se isotopes have been interpreted in terms of shell model (SM) calculations. The calculations have been performed in f_5/2pg_9/2 space with the recently derived interactions, namely JUN45 and jj44b. To study the importance of the proton excitations across the Z = 28 shell in this region, we have also performed calculation in fpg_9/2 valence space using an fpg effective interaction with ⁴⁸Ca core and imposing a truncation. Excitation energies, B(2) values, quadrupole moments and magnetic moments are compared with the experimental data available. Present study reveals the importance of proton excitations across the Z = 28 shell for predicting quadrupole and magnetic moments. (author)

[en] A number of values for systematization of the isotope charge density distribution diffusibility phenomenon is proposed. Apart from the charge distribution by volume β(r), charge distribution by spherical layers dQ/dr=4πρ(r)r² is considered. The behaviour of the values considered is demonstrated taking selenium and chromium isotopes as an example. For selenium isotopes diffusibility characteristics of theoretic distributions of charge density, calculated by Hartree-Fock and final Fermi-system method are presented. 8 refs.; 8 figs.; 2 tabs