Electrical transport and magnetic ordering in R 2Ti3Ge4 (R=Dy, Ho and Er) compounds

New R ₂Ti₃Ge₄ (R=Dy, Ho and Er) intermetallic compounds have been synthesized and characterized by X-ray diffraction and low temperature ac magnetic susceptibility, electrical resistivity and thermoelectric power measurements were carried out. The compounds crystallize in the parent, Sm₅Ge₄-type orthorhombic structure (space group Pnma) and lanthanide contraction is observed as one moves along the rare-earth series. The changeover from paramagnetic to antiferromagnetic phase happens at low temperatures and the ordering temperature scales with the de Gennes factor. The electrical resistivity is metallic with a negative curvature above 100 K. Thermopower displays a weak maximum at temperatures less than 50 K signifying the possible phonon and magnon drag effects.     

Effect of electric field on activated sludge in water

The results of the study of the effect of a dc electric field on activated sludge of aeration tanks. It is experimentally detected that the specific oxidation rate of organic compounds by activated sludge increases up to 90.5% with electric field processing, and then decreases. The observed effect is substantiated. The results obtained can find wide application in purification of sewage polluted by organic compounds.     

The Optimal Axis-Symmetrical Plasma Potential Distribution for Plasma Mass Separation

The mass separation of chemical element mixtures is a relevant task for numerous applications in the nuclear power industry. One of the promising approaches to solve this problem is plasma mass separation. In a recent study, the efficiency of plasma mass separation in a configuration with a potential well and a homogeneous magnetic field was experimentally demonstrated. This article examines the possibility of increasing the distance between the deposition regions of charged particles with different masses by varying the profile of the electric field potential. Such correlation can be considered as the control in a system of active particles. A cylindrical coordinate system is used. The electric field is axially symmetrical, and the magnetic field is directed along the axis of the symmetry. The corresponding mathematical problem was solved in a general way. The criteria for increasing the distance between the deposition areas of the “light” and “heavy” components of the mixture have been formulated. A high sensitivity of particle trajectories to the electric field potential in the region of the pericentres of the trajectories of charged particles was detected. Recommendations for the practical implementation of the optimal spatial separation of ion fluxes are proposed.     

Visible and near-infrared chemical lasers

We analyze the basic thermodynamic, kinetic, radiative, and spectroscopic properties of halogen and interhalogen molecules which are potentially suitable for the construction of visible and near-IR chemical lasers. We discuss the problem of chemical buildup of electronically excited states (EES) of donor molecules (or atoms). We propose a number of new kinetic schemes with formation of EES of donor particles, for the development of lasers based on electronic transitions (ET). We obtain analytic relations for the lasing condition and for the laser efficiency of a system of a “donor—acceptor” type as applied to ET chemical lasers. Actual results of research into the gain properties and energy characteristics of potential visible-band chemical NF-IF and N₂-IF lasers. The possibility of using atoms in chemical lasers is discussed. Translated from Trudy Fizicheskogo Instituta im. P. N. Lebedeva Akademiya Nauk SSSR, Vol. 194, pp. 171–211, 1989.     

Designing of a lead ion model source for plasma separation of spent nuclear fuel

Plasma sources of model substances are required for solving problems associated with the development of a plasma separation method for spent nuclear fuel (SNF). Lead is chosen as the substance simulating the kinetics and dynamics of the heavy SNF component. We report on the results of analysis of the discharge in lead vapor with a concentration of 10¹²–10¹³ cm^–3. Ionization is produced by an electron beam (with electron energy up to 500 eV) in the centimeter gap between planar electrodes. The discharge is simulated using the hydrodynamic and one-particle approximations. The current–voltage characteristics and efficiencies of single ionization depending on the vapor concentrations and thermoelectron current are obtained. The experimentally determined ion currents on the order of 100 μA for an ionization efficiency on the order of 0.1% are in conformity with the result of simulation.     

Small oscillations of an emulsion of two weakly viscous compressible liquids

The small oscillations of an emulsion of two weakly viscous compressible liquids in an external acoustic field are studied. The structure of the mixture is assumed to be periodic with a sufficiently by small cell size. An integro-differential acoustic equation and an expression for the mean velocity are derived by the two-scale convergence method and the strong convergence of the difference in the velocities and the difference in the velocity gradients of the prelimiting and limiting problems (the initial problem and the averaged problem) to zero in L₂ is proved. The elements of the dynamic “filtration matrix”, that is, of the kernel of the convolution of the acoustic equation, are calculated by the finite volume methods.     

Electronic properties of ultrathin films based on pyrrolofullerene molecules on the surface of oxidized silicon

Results of the investigation into the interface formation during the deposition of the films based on aziridinylphenylpyrrolofullerene (APP-C₆₀) up to 8 nm thick on the surface of the oxidized silicon substrate are presented. The procedure of detecting reflection of testing low-energy electron beam from the surface implemented in the total current spectroscopy mode with a change in the incident electron energy from 0 to 25 eV is used. The structure of maxima in the total current spectra induced by the APP-C₆₀ deposited film is established, and the character of interrelation of these maxima with π* and σ* energy bands in the studied materials is determined. It is revealed due to analyzing the variation in intensities of the total current spectra of the deposited APP-C₆₀ film and the (SiO₂)n-Si substrate that the APP-C₆₀ film is formed at the early deposition stage with the coating thickness thinner than one monolayer without the formation of the intermediate modified organic layer. As the APP-C₆₀/(SiO₂)n-Si interface is formed, the work function of the surface increases by 0.7 eV, which corresponds to the transfer of the electron density from substrate (SiO₂)n-Si toward the film APP-C₆₀. The optical absorption spectra of the APP-C₆₀ films are measured and compared with the spectra of films of unsubstituted C₆₀.