Effect of Ionosphere on the Excitation of Electromagnetic Field at Extremely Low and Lower Frequencies in the Near-Field Zone

Excitation of electromagnetic fields at extremely low and lower frequencies in the near-field zone of the Earth–ionosphere waveguide is considered. Variations in the field amplitude in the lower part of the extremely low frequency (ELF) range and lower frequencies are experimentally determined under different geophysical conditions in the absence of variations in the ultralow frequency (ULF) range. The effects related to such variations are analyzed with the aid of theoretical calculations that show significant effect of ionosphere in the near-field zone at relatively low terrestrial conduction.     

Quasi-one-dimensional Fulde-Ferrell-Larkin-Ovchinnikov-like state in Nb/Cu0.41Ni0.59 bilayers

In a ferromagnet (F) being in contact with a superconductor (S) an unconventional finite-momentum pairing of electrons forming Cooper pairs occurs. As a consequence, interference effects of the pairing wave function, leading to an oscillation of the critical temperature for increasing F-layer thickness in S/F bilayers, including extinction and recovery of the superconducting state, were predicted by theory. We observed experimentally all types of this behavior, calculated theoretically, in Nb/Cu_{1 ? x} Ni _x bilayers (x = 0.59) of nanometer film thickness, prepared by magnetron sputtering (utilizing a moving magnetron deposition technique to provide a superb homogeneity of the ultrathin Nb layers), including a double extinction of superconductivity, giving evidence for a multiple reentrant state.     

Evidence of orbital reconstruction at interfaces in ultrathin La0.67Sr0.33MnO3 films

Linear dichroism (LD) in x-ray absorption, diffraction, transport, and magnetization measurements on thin La(0.7)Sr(0.3)MnO(3) films grown on different substrates, allow identification of a peculiar interface effect, related just to the presence of the interface. We report the LD signature of preferential 3d-e(g)(3z(2)-r(2)) occupation at the interface, suppressing the double exchange mechanism. This surface orbital reconstruction is opposite to that favored by residual strain and is independent of dipolar fields, the chemical nature of the substrate and the presence of capping layers.     

Self-ionization of an atom in <Emphasis Type="Italic">β</Emphasis><Superscript>−</Superscript> decay

The dependence of the yield of near-zero-energy electrons (e ₀ electrons) from the surface of a ⁴⁶Sc source on the energy of β ^? particles is measured with the use of the method of eγ and eβ coincidences. The self-ionization of an atom in β ^? decay owing to shake-off and direct collisions is determined. It is found that the probability of shake-off is independent of the energy of a β ^? particle, whereas the probability of direct collisions is inversely proportional to its velocity. The results of the measurements are discussed in the approximation of the sudden perturbation of an atomic electron by the moving β ^? particle.     

Asymptotic solution of the Turán problem for some hypergraphs

Taking an ordinary graphL ² and replacing each of its vertices by a group ofr/2 vertices (r is even), we get anr-uniform hypergraphL′. In the casex(L ²)=2^m+1, we solve asymptotically the Turán problem forL′. Ifx(L ²)#2^m+1, the upper bound is still valid but proper constructions are not known.     

Non-newtonian viscosity of complex-plasma fluids

Investigations of shear flows in three-dimensional complex-plasma fluids produced in a dc discharge were carried out. The shear was induced either by an inhomogeneous gas flow or by a laser beam. The viscosity of complex plasmas was measured over a broad range of shear rates, up to the hydrodynamic limit when the discreteness becomes important. Analysis of the measurements reveals non-Newtonian behavior of complex plasmas accompanied by substantial shear thinning.