Extraction of strontium using an irradiated extraction agent of crown structure

The partition coefficient of strontium upon its extraction from the aqueous solutions of picric acid into chloroform containing DC-18-crown-6, B-15-crown-5 after their exposition to gamma radiation has been studied. A significant decrease of the partition coefficient in the studied range of doses 10–70 kGy was observed. This effect can be attributed to the radiolytic products of chloroform. The radiation destruction as well as dehydrogenation of crown ethers were not observed.     

Determination of239, 240Pu in environmental samples from surroundings of the atomic power station Jaslovske Bohunice

The development of a rapid and reproducible method for the separation of plutonium from soil samples is described. Tetravalent plutonium is extracted from 8M HNO₃ into 30% Aliquat-336/toluene mixture. Uranium and thorium are removed with nitric and hydrochloric acid washes. Plutonium is backextracted with HCl–H₂C₂O₄ and HCl–HF solutions. Plutonium is coprecipitated with NdF₃ and filtrated onto a 0.1–0.2 m membrane filter to prepare a source for -spectrometry. The chemical yields of separation are about 50–60%.     

The radiolysis of bis/1,2-dicarbollyl/cobalt/III/ acid in H2O−CCl4 two-phase system

The radiation-induced oxidation of bis/1,2-dicarbollyl/cobalt/III/ acid to 8-monohydroxy-, and 8,8-dihydroxy-derivatives was observed in two-phase system of 4 to 96 vol. % of CCl₄ and H₂O. Carbon tetrachloride increases the radiation yields of the oxidation of the acid in the investigated dose region, nature of the radiolytic products being the same. The partial radiation yields in the system were ascertained.     

Theoretical investigation of CO interaction with copper sites in zeolites: periodic DFT and hybrid quantum mechanical/interatomic potential function study

Periodic DFT and combined quantum mechanics/interatomic potential function (QM-pot) models were used to describe the interaction of CO with the Cu+ sites in FER. The CO stretching frequencies were calculated using omega(CO)(CCSD(T))/r(CO)(DFT) scaling method relating frequencies determined using a high-level quantum-chemical (coupled clusters) method for simple model carbonyls to CO bond lengths calculated using periodic DFT and QM-pot methods for the Cu+-zeolite system. Both periodic DFT and QM-pot models together with omega(CO)/r(CO) scaling describe the CO stretching dynamics with the "near spectroscopic accuracy", giving nu(CO) = 2156 cm(-1) in excellent agreement with experimental data. Calculations for various Cu+ sites in FER show that both types of Cu+ sites in FER (channel-wall sites and intersection sites) have the same CO stretching frequencies. Thus, the CO stretching frequencies are not site-specific in the CO/Cu+/FER system. The convergence of the results with respect to the model size was analyzed. When the same exchange-correlation functional is used the adsorption energies from periodic DFT and QM-pot are in good agreement (about 2 kcal/mol difference) but substantially larger than those of the experiment. The adsorption energy calculated with the B3LYP functional agrees with available experimental data. The overestimation of the adsorption energy in DFT calculations (periodic or QM-pot) is related to a red-shift of the CO stretching mode, both result from an underestimation of the HOMO(5sigma)-LUMO(2pi) gap of CO and the consequent overestimation of the Cu(+)(d)-CO(2pi*) back-donation. For the adsorption energy, this can be overcome by the use of hybrid B3LYP exchange-correlation functional. For the frequency calculations, the DFT problem can be overcome by the use of the omega(CO)(CCSD(T))/r(CO)(DFT) correlation.     

Anaerobic Degradation of PCB in Soils

Abstract

The anaerobic degradation of PCB in loamy and clayey soils containing indigeneous microflora was studied. The anaerobic conditions were created by an argon atmosphere in the flasks containing soil flooded by a liquid medium with glucose. GC-ECD analysis of soil extracts after 40 day incubation showed, in addition to the concentration changes of the less chlorinated PCB congeners, a significant decrease in the concentration of highly chlorinated congeners in both soils. The results indicate that in both soil types reductive dehalogenation of PCB congeners was encountered.     

Thin layers of aluminium: A molecular orbital study

Molecular beam epitaxy has been used to prepare thin layers (200 nm thickness) of aluminium grown either on aluminium or gallium arsenide substrates; their He(I) and He(II) photoelectron spectra have been recorded. The quasirelativistic CNDO/1 method has been applied to investigate the band structure of {Al}₁₇₂, {Al}₂₈₄ and {Al}₄₂₄ clusters obtained by a duplication of the unit cell: the DOS profiles and their projections were generated. These data were correlated with the periodic crystal orbitals of the EHT quality. The first excitation energy serves as a better estimate of the vanishing energy gap showing thus a metallic character of aluminium.     

Thin layers of grey arsenic: A molecular orbital study

A thin layer of grey arsenic has been manufactured by molecular beam epitaxy and its He(I) photoelectron spectrum has been recorded. The quasi-relativistic CNDO/1 method has been used to investigate the band structure of {As}₁₁₄ and {As}₂₂₈ clusters: the DOS profiles and their projections are under question. These data were correlated with the periodic crystal orbitals of the EHT quality. The first excitation energy serves as a better estimate of the energy gap between the filled valence band and the empty conduction band.     

2. Internationale Konferenz iiber Methoden der Darstellung and Aufbewahrung markierter Verbindungen

Es wurde die Verteilung von ¹³¹J im Zeitraum von 1/2–24 h nach einer einmaligen Röntgenbestrahlung mit 0,21 C/kg verfolgt, wobei das Radiojod zu zwei verschiedenen Zeitpunkten nach der Exposition verabreicht wurde; 2 Stunden nach der Exposition bei der Gruppe T₂ und 18 Stunden bei der Gruppe T₁₈. Unterschiede in der Verteilung des Radiojods bei den Kontroll- und Versuchstieren weisen auf pathophysioloyische strahlenbedingte Organveränderungen hin.     

Thin layers of gallium-arsenide: A molecular orbital study

The quasirelativistic INDO/1 method has been used to generate molecular orbitals for some {GaAs}_n clusters up to 160 atoms. On the basis of these one-electron energy levels the density of states (DOS) and density of hole functions have been calculated. Various projections of DOS functions are discussed. The calculations are compared with those generated by periodic crystal orbitals of the EHT quality and with experimental ESCA spectra on thin layers of GaAs.