Extraction of uranium from hydrochloric acid solutions by alkylated crown ethers

The extraction recovery of uranium from 1–10 mol/L hydrochloric acid solutions into solutions of alkylated crown ethers di-tert-butyldibenzo-18-crown-6 (DTBDB18C6) and di-tert-butyldicyclohexyl-18-crown-6 (DTBDCH18C6) in organic solvents (nitrobenzene, 1,2-dichloroethane, chloroform, 1-octanol) was studied. It was found that with increasing HCl concentration, the value of the distribution coefficients of uranium (D) between the organic and aqueous phases increased to a maximum value at 9 mol/L HCl for DTBDB18C6 and 6–7 mol/L HCl for DTBDCH18C6. The properties of the solvent also greatly affect the values of D, reaching a maximum in the application of nitrobenzene, dichloroethane, or their mixture. Under these conditions, D for a 0.01 mol/L solution of DTBDCH18C6 in nitrobenzene is 830, which is the highest of known values. It was determined by the slope method and the complete saturation method that the extracted complexes of the studied alkylated crown ethers with uranyl ions have the 2 : 1 composition. Thus, new supramolecular extractants of uranium from hydrochloric acid solutions have been studied, having an extremely high extraction capacity, which can be used in the analytical and preparative chemistry of uranium.     

Spectral and total intensity of radiation of relativistic electrons and positrons with planar channeling

The spectral and total intensity of radiation of relativistic electrons and positrons is considered within the framework of a Langevin approach to the theory of transit of fast charged particles across a crystal. It is shown that one of the terms of the total intensity of radiation increases exponentially rapidly along those segments of the path that are in regions in which the potential of the planar channel of the crystal has negative Gaussian curvature. Surgut State University. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 9, pp. 42–44, September, 1997.     

Separators of hereditarily arcwise connected continua admitting chebyshev systems of complex continuous functions

A decomposition is constructed of a hereditarily arcwise connected continuum containing no open arcs and θ-curves into two subcontinua with connected intersection, one of which has an arc or a simple closed curve as a separator. The results obtained are related to a problem called Overdeck’s conjecture.     

Equipartition Rule for the Electron and Nuclear Energy Losses of Channeled Particles

Using the Langevin approach to the theory of channeling, it is shown that the equipartition rule is valid not only in respect of electron energy losses of channeled particles, but for their nuclear energy losses as well. It is shown that nuclear energy losses of channeled particles are directly proportional to the atomic diffusion coefficient, the numerical value of which is calculated using a computer program.     

Theory of axial channeling of protons and antiprotons at small depths

The theory of channeling of proton and antiproton beams is constructed using Newton's equations with a transverse force resulting from the statistical ensemble of atoms of the crystal. The equations of motion are linearized by expanding time in series of the transverse force fluctuation, which plays the role of the small parameter. Stochastic instability of the transverse motion of the channeled particles, characterized by an exponential growth of the second moments of the distribution function with path length, is observed.Institute of Nuclear Physics at Tomsk State University. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 5, pp. 66–71, May, 1995.     

Chebyshev systems of locally analytic functions

Translated from Matematicheskie Zametki, Vol. 55, No. 4, pp. 35–46, April, 1994.     

Magnesium-Potassium Phosphate Matrix for Immobilization of <Superscript>14</Superscript>C

Possibility of using a low-temperature magnesium-potassium phosphate matrix to solve the problem of immobilizing the radioactive wastes containing radioactive carbon (¹⁴C) in the form of calcium carbonate was examined. The physicochemical characteristics of the compounds obtained were determined. Large values of the ultimate compression strength (22 ± 5 MPa), which satisfy the technical requirements for cemented radioactive wastes (no less than 4.9 MPa), were obtained. The minimum carryover of carbon dioxide into the atmosphere in the course of synthesis and in keeping of samples for 14 days was noted: not more than 3 wt % relative to the starting CaCO₃. The leaching rate of carbonate ions from magnesium-potassium compounds by 28th day of contact with air does not exceed 10?9 g cm^?2 day^?1, with this value for the rest of the compound components not exceeding 10^?4 g cm^?2 day^?1. Thus, it was found that the magnesium?potassium phosphate matrix is an alternative to the cementation for solidification of radioactive wastes containing ¹⁴C.     

Rehybridization of the atomic orbitals and the field electron emission from nanostructured carbon

The field electron emission, structural features, and electronic properties of carbon films obtained by chemical vapor deposition were experimentally studied. It is shown that the field electron emission from the films composed of spatially oriented carbon nanotubes and platelike graphite nanocrystals is observed for the electric field strength lower by one to two orders of magnitude as compared to the values characteristic of the metal emitters. Experimental data reported for the first time are indicative of a local decrease in the electron work function in such carbon film materials as compared to that in graphite. A model of the emission center is proposed and a mechanism of the field electron emission from nanostructured carbon is described.     

Simulation of the deflection of 200- and 450-GeV protons by a bent germanium crystal

It is shown that the result obtained by numerically solving the kinetic Fokker-Planck equation in the transverse-energy space on the basis of computer simulations of channeled-particle trajectories describes well the results of an experiment that studied the deflection of 200- and 450-GeV protons by a bent germanium crystal.