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- Author or Editor: B. Eichler x
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Abstract
The Hg-, Cd- and UO2-targets bombarded by protons have been treated using the sublimation and evaporation techniques. The Hg and Cd nuclei have been separated from non-isotopic products by distillation in the hydrogen stream. The separation of the groups of Re, Os, Ir, Mo, Tc and Ru oxides has been carried out in the air stream. No monotonic temperature dependence of the Tl, Ru, Mo, Tc, Te, Pb and Po release has been observed in the oxidation of the UO2-ceramics in the air stream. The values of (−ΔH a 0 ) of volatile products adsorbed on quartz have been determined from the chromatographic data. The relation between the adsorption heat (−ΔH a 0 ) and the standard sublimation heat (ΔH 298 0 subl.) has been found to be linear, i.e. −ΔH a 0 =(4.04±1.97)+(0.69±0.04)ΔH 298 0 (subl.). As an example of the thermochromatographic generator of isotopes, the separation of99Mo to99mTc has been investigated.
Abstract
Starting from tabulated thermodynamic data of stable compounds in the Mo−O−Cl system, phase diagrams for the Mo−O−Cl system were developed on the basis of GIBBS' phase law by means of thermodynamic calculations. The behaviour of molybdenum trioxide in a temperature gradient tube was investigated experimentally under chlorinating conditions, using99Mo as indicator. The thermochromatografically separated compounds were characterized by their deposition temperature in the temperature gradient tube and by an activation analytical determination of their Mo/Cl ratio. The experimental results were compared with the calculated phase diagram.
The effects of genotypes, nutrient and water supply on the dry matter production and potassium uptake dynamics of maize (Zea mays L.) were studied on chernozem soil in the Debrecen-Látókép long-term field experiment (Eastern Hungary).According to the experimental results and calculations it can be concluded that — in addition to the previously used and considered soil and plant nutrient contents — the calculation of the plant-extracted nutrient amount (depending on the applied hybrid, NPK nutrient levels and water supply) is suggested to enable the characterization of the growth and nutrient demand dynamics of maize genotypes. This parameter gives information not only about the available nutrient amount at a given sampling time, but about the supply level of plants up to the sampling time as well. For the proper characterization of the mentioned dynamics of maize plants authors suggest to take the following sampling times into consideration: the intensive vegetative growth period, the switch between the vegetative and generative growth phases (silking), and the grain filling phase.
Abstract
Selenium nuclides are available from thermal neutron induced nuclear fission of 235U at the gas-jet facility at the Swiss spallation neutron source (SINQ) at Paul Scherrer Institute, Switzerland. The formation of stable selenium compounds, their transport yields using the gas-jet system and their relative thermal decomposition temperature were investigated under oxidizing and reducing conditions in the target chamber. Using O2, H2, CO, and propene as additional gases, the selenium isotopes are suggested to form H2SeO3, H2Se, COSe, and C3H6Se, respectively, with overall 84Se yields of 1.5%, 4.7%, 6.3%, and 21.9%, respectively. Adsorption enthalpy, vapour pressure, solubility and acidity data for these species were collected from the literature or estimated from other known thermochemical properties. Carrier free bromine isotopes (84Br, 86Br) in the form of HOBr were obtained by thermally decomposing H2SeO3 and retaining elemental Se under oxygen rich conditions on quartz at 400 K.
Summary
Guanabara Bay, located at Rio de Janeiro, is an example of an impacted coastal environment due to the high influx of industrial and domestic effluents. Four sediment cores were sampled in areas with different levels of pollution and were analyzed for trace elements and foraminifera for abundance. Instrumental neutron activation analysis (INAA) was used to determine As, Ba, Co, Cr, Fe, Sb, Sc, and Zn. The effects of metal concentrations in the benthic foraminifera were studied. The low concentrations of the benthic foraminifera and the dominance of opportunistic species in coastal regions such as Ammonia may be correlated to natural stress or anthropogenic impact.
