Determination of aqueous plutonium oxidation states by solvent extraction

The reliability of two solvent extraction techniques for the determination of Pu oxidation states in solution was tested with low-ionic-strength solutions and with high-Na and high-Mg brines that contained Pu concentrations sufficient for spectrophotometric analysis. One procedure only differentiates between reduced Pu [Pu(III) and Pu(IV)] and oxidized Pu [Pu(V) and Pu(VI)], whereas the second procedure was designed to differentiate between Pu(IV), Pu(V), and Pu(VI) in solution. Both procedures successfully differentiated between oxidized and reduced Pu in both dilute solutions and brines when tested with samples that contained only the Pu(IV), Pu(V), or Pu(VI) oxidation states. However, when the second solvent extraction procedure, which differentiates between Pu(V) and Pu(VI), was employed for solutions that did not contain a strong oxidant to maintain the Pu(VI) oxidation state, significant quantities of Pu(VI) were reduced to Pu(V) during extraction, indicating that accurate quantification of Pu(V) and Pu(VI) is not possible with this procedure.Work supported by the U. S. Department of Energy under Contract DE-ACO6-76RLO 1830.     

Positron-lifetime study of vacancy annealing in neutron-irradiated GaAs

Positron-lifetime measurements have been used to study the annealing of vacancies in neutron-irradiated GaAs. The vacancies which are interpreted as defects in the Ga sublattice disappear in a single annealing stage (at 500°C in GaAs doped with Si or Zn, and at 600°C in Cr-doped GaAs).     

An asymmetric Ellis theorem

In 1957 Robert Ellis proved that a group with a locally compact Hausdorff topology T making all translations continuous also has jointly continuous multiplication and continuous inversion, and is thus a topological group. The theorem does not apply to locally compact asymmetric spaces such as the reals with addition and the topology of upper open rays. We first show a bitopological Ellis theorem, and then introduce a generalization of locally compact Hausdorff, called locally skew compact, and a topological dual, Tk, to obtain the following asymmetric Ellis theorem which applies to the example above:Whenever (X,⋅,T) is a group with a locally skew compact topology making all translations continuous, then multiplication is jointly continuous in both (X,⋅,T) and (X,⋅,Tk), and inversion is a homeomorphism between (X,T) and (X,Tk).This generalizes the classical Ellis theorem, because T=Tk when (X,T) is locally compact Hausdorff.     

Mössbauer study on LiFePO4 cathode material for lithium ion batteries

Crystalline LiFePO₄ has been synthesized using solid-state, spray pyrolysis, and wet chemical methods. The crystal parameters were obtained from Rietveld’s refinement methods of the X-ray diffraction patterns. A detailed investigation of the Fe valency carried out using Mössbauer spectroscopy at room temperature indicates that Fe is predominantly present in its bivalent state.     

MEASUREMENT OF CONTACT ANGLE IN A CLEARANCE-FIT PIN-LOADED HOLE

A simple experimental technique using an instrumented pin was developed for the measurement of the load-contact variation in a clearance-fit, pin-loaded hole. The method is applicable to both conducting and nonconducting materials.     

Isobar separation at FRS-ESR – a development towards pure isomeric stored beams

One important goal of the ILIMA project at FAIR is the study of masses and decay properties of relativistic isomeric beams stored and cooled in the planned storage-ring complex. A new scheme is described, where a storage-cooler ring is used for high-resolution mass separation. Experimental results on the separation of the isobaric pair ¹⁴⁰Pr-¹⁴⁰Ce are presented. P. Beller, deceased.