Cohesive properties are calculated for the AnIr2 and AnRh3 series of intermetallic systems. The positive and negative deviations from Vegard's law found in both series are emphasized. The development of magnetism and 5f localization as a function of increasing actinide atomic number is studied in detail for the two classes of compounds. A relativistic formulation of the Stoner criterion for ferromagnetism is presented and applied to a number of actinide systems. Finally the ferromagnetism of UFe2, NpFe2 and PuFe2 is treated theoretically. For these intermetallic compounds it is found necessary to implement all three Hund's rules into the calculations, before agreement with experiment is obtained.
Authors:M. Johansson, R. Malmbeck, B. Wierczinski and G. Skarnemark
A study of the extraction of polonium from aqueous solutions containing -hydroxyisobutyric acid (-HIBA) was performed with four different extractants, di-n-octyl sulphide (DOS), Cyanex 272, Cyanex 301 and Cyanex 302, dissolved in toluene. The extracted complex for DOS at low -HIBA concentrations is most likely PoO(-HIB)2·2DOS, while at higher -HIBA concentrations there seems to be a solvating effect implicating an extracted complex of the type PoO(-HIB)2(-HIBA)2·2DOS. For the extraction of polonium with Cyanex 272 the results are inconclusive. The extracted complex is either PoOA2 or PoO(-HIB)2·2HA. For extraction with Cyanex 301 or Cyanex 302 the major extracted species does not contain any -HIBA molecules. The neutral species in both cases is PoOA2, extracted at low extractant concentrations, while at higher extractant concentrations a complex of the type PoOA2·xHA is extracted. The extraction of polonium increases in the order Cyanex 272 < DOS < Cyanex 302 < Cyanex 301.
Authors:B. Husenov, S. Asaad, H. Muminjanov, L. Garkava-Gustavsson, A. Yorgancillar and E. Johansson
Wheat seed-borne diseases are among the major constraints reducing crop yield and the quality of seed and grain. In this study we aimed to evaluate the type and prevalence of fungal seed-borne diseases in Tajik wheat seed samples. Particular emphasis was given to common bunt resistance in advanced wheat breeding materials. Furthermore, we aimed to identify options for improving the seed quality. Seed samples collected from two different locations in Tajikistan were tested by conventional seed-health testing methods for presence of seed-borne diseases. Nineteen advanced wheat breeding lines and three varieties collected from the Tajik wheat breeding program were screened using an artificial inoculation test for their response to common bunt. Significant differences were found between the locations and genotypes concerning presence of common bunt and black point. Fourteen fungal species, where most of them are pathogenic for wheat, were identified in the seed samples. Tilletia laevis, T. tritici, Bipolaris sorokiniana, Stemphylium spp., and Drechslera spp. were the major pathogenic fungi observed in collected wheat samples. Common bunt was predominantly represented by T. laevis. No strong resistance was found in the studied Tajik wheat material, although a low percentage of infection was found in one line (SHARK/ F4105W2.1), while the material was evaluated for common bunt resistance. In managing seed-borne diseases, breeding of resistant varieties should be given a priority, while cultural practices such as preventing contamination and monitoring seed health status should also be considered, as a last resort the use of chemical seed treatments are advised.