Oxidation of U(VI) with oxygen in weakly acidic and neutral solutions

The kinetics of U(IV) oxidation with atmospheric oxygen in solutions with pH 2–7 was studied. In the kinetic curves there is an induction period, which becomes shorter with increasing pH. The induction period is caused by accumulation of U(VI), whose initial presence in the working solution accelerates oxidation. The pseudo-first-order rate constants and bimolecular rate constants of U(IV) oxidation with oxygen were evaluated. The mechanism of U(IV) oxidation is considered. At pH higher than 3, formation of a polymer of hydrolyzed U(IV) with U(VI) plays an important role in oxidation of U(IV), since this prevents formation of U(V). Heating accelerates oxidation of U(IV) at pH 2–2.5, but at a higher pH the process becomes difficultly controllable.     

Synthesis, structure, thermal and mechanical properties of nanocomposites based on linear polymers and layered silicates modified by polymeric quaternary ammonium salts (ionenes)

Polymer–clay composites has been prepared by melt blending an organo-bentonite with linear polymers (polyamide, polysterene and polypropylene) in a disk-screw extruder. In first time organo-clay was prepared by surface treatment of Na-forms bentonite with polymeric quaternary ammonium salts (PQAS). XRD indicated that organo-bentonite layers were exfoliated and dispersed into polyamide and polystyrene. Addition of 2 wt% organo-bentonites (optimal concentration) to polyamide increased tensile strength by 53% and Sharpy impact by 140%. With the incorporation of 2 wt% organo-bentonites (optimal concentration) into polystyrene the tensile strength increased to 28% and the Sharpy impact increased to 25%. For polypropylyne–organo-bentonites composites we did not observe delamination of layered structure, and as result absence of reinforcements. TGA showed that the polyamide and polystyrene nanocomposites have higher decomposition temperature in comparison with the original polymers.     

Verification of backtracking and branch and bound design templates

The design and analysis of computer algorithms is a requirement of computer curricula. It covers many topics, including data structures, complexity theory, and algorithmic design patterns. This course is about the greedy method, divide and conquer, dynamic programming, backtracking, and branch and bound. Naturally, all the listed design patterns are taught, learned, and comprehended using examples. However, they can be semiformalized as design templates, specified by correctness conditions, and manually verified by means of the Floyd method. Moreover, this approach can lead to new insights and better comprehension of the design patterns, specifications, and verification methods. In this paper, we demonstrate the utility of the approach using the study of the backtracking and branch-and-bound design patterns. In particular, we prove the correctness of the suggested templates when the boundary condition is monotone, but the decision condition is antimonotone on sets of “visited” vertices.     

Testing and calculating a two-chamber plasma furnace for processing of radioactive wastes

A two-chamber plasma furnace has been tested and the advantages of the processing of radioactive wastes with the use of plasma-thermal technologies have been demonstrated. A model of a plasma furnace for processing of low-and medium-activity radioactive wastes formed in the process of operation of atomic-power and nuclear-industry plants has been developed. The thermal parameters of such a furnace have been calculated. __________ Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 81, No. 3, pp. 569–576, May–June, 2008.     

Chemical properties of element 104

Using a method of rapid continuous separation of elements of the side groups III and tV of the D. L Mendeleev Periodic System, developed by the authors of this work, the properties of the chlorides of curium, californium, hafnium, and the isotope 104²⁶⁰ were compared. The isotope 104²⁶⁰ had until now been identified only by physical methods. It was established that its chemical properties differ from those of the actinide elements and are close to those of hafnium. An independent confirmation of the atomic number of the new nucleus was obtained, and it was simultaneously demonstrated that the element 104 is a member of group IV. In the experiments, 12 atoms of the isotope 104²⁶⁰ were recorded.Translated from Atomnaya Énergiya, Vol. 21, No. 2, pp. 83–84, August, 1966.