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No abstract available

[en] UBe₁₃ has unusual electronic and magnetic properties due to a narrow band of U 5f states near the Fermi energy. We have used EXAFS to compare the interatomic forces in UBe₁₃ with those in ThBe₁₃, which has the same structure but no 5f electrons. From measurements made over the range 10 to 308 K, we have determined the temperature dependences of the mean square relative displacements (MSRD's) for the first actinide-beryllium and actinide-actinide shells in each material. The MSRD's for the corresponding shells in the two compounds were found to be quite similar. The thermal motion of the nearest-neighbor actinide-actinide pairs is shown to be due entirely to a single Einstein mode, the square of whose frequency is proportional to the actinide-Be force constant. We conclude that the presence or absence of 5f electrons on the actinide has very little effect on the actinide-beryllium bonding

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[en] The effect of nitrogen in solid solution on the plastic deformation of polycrystalline thorium was studied by measuring the flow stress from 4.2 to 773⁰K at several strain rates. Nitrogen was found to behave similarly to carbon in thorium and increased the thermally activated component of the flow stress. The activation energy was 1.3 eV for overcoming nitrogen atoms in solution. Aging the higher nitrogen alloys produced an age hardening contribution to the flow stress which was a thermally activated component at about 600⁰K but became an athermal component at lower temperatures. (13 fig) (U.S.)

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[en] Chromium (partially filled 3d shell) as an impurity depresses the superconducting transition temperature T/sub c/ of Th significantly faster than any of the rare earths (4f) or even U (5f). It is speculated that ThCr is a Kondo system. Measurements of T/sub c/ on ThCr alloys under hydrostatic pressures up to 20 kbar show the rate of depression through a maximum

[en] The effects of proton, thorium and uranium on the bioaccumulation of thorium and uranium from the solution (pH 3.5) containing uranium and thorium using Streptomyces levoris cells were examined. The amount of thorium accumulated using the cells decreased by the pre-contact between the cells and the solution (pH 3.5) containing no metals, whereas that of uranium was almost unaffected by the treatment. The amount of thorium was almost unaffected by the existence of uranium. On the other hand, the amount of uranium accumulated was strongly affected by the thorium, especially thorium addition after uranium accumulation. The decrease of uranium accumulated by the addition of thorium after the accumulation of uranium was higher than that from the solution containing both elements. Therefore, the contribution of uranium-thorium exchange reaction was higher than that of competition reaction. Accordingly, proton-uranium-thorium exchange reaction was occurred in the accumulation of thorium from the solution containing thorium and uranium. The gram-positive bacteria, such as Micrococcus luteus, Arthrobacter nicotianae, Bacillus subtilis and B. megaterium, has a much higher separation factor as thorium/uranium than that of actinomycetes. These gram-positive bacterial strains can be used for the accumulation of thorium from the solution containing uranium and thorium

[en] The nature (itinerant vs localized) of the 5f electrons in the actinides determines their magnetic properties. Extensive optical de Haas--van Alphen data which exist only for Th, the simplest actinide with no occupied 5f states, allow detailed comparisons to be made between theory and experiment. The 5f bands were found, by means of ab initio RAPW energy band calculations, to lie above the Fermi energy, to be itinerant in character, and to significantly affect the reflectivity measurements of Veal, et al. [Phys. Rev. Letters; 30: 1061(1973)]. It is found that the 5f bands when included in the RAPW calculations, give excellent agreement with the de Haas--van Alphen results of Boyle and Gold [Phys. Rev. Letters; 22: 461(1969)], for all sections of the ''lungs'', ''dumbbell'', and ''superegg'' Fermi surfaces, in contrast with calculations based on artificially removing the 5f resonance. Simple overlap charge density impurity scattering potential model calculations are used to discuss the possible occurrence of impurity local moment formation in Th based alloys. (U.S.)

No abstract available