Mn site substitution of La0.67Ca0.33MnO3 with closed shell ions: Effect on magnetic transition temperature

Mn site is substituted with closed shell ions (Al, Ga, Ti, Zr and a certain combination of Zr and Al) and also with Fe and Ru ions carrying the magnetic moment (S=5/2 and 2 respectively) at a fixed concentration of 5 at %. Substitution did not change either the crystal symmetry or the oxygen stoichiometry. All substituents were found to suppress both the metal-insulator and ferromagnetic transition temperatures (T _p(ρ) and T _C, respectively) to varied extents. Two main contributions identified for the suppression are the lattice disorder arising due to difference in the ionic radii between the substituent (r _M) and the Mn³⁺ ion (r _Mn ³⁺) and in the case of the substituents carrying a magnetic moment, the type of magnetic coupling between the substituent and that of the neighboring Mn ion.     

Production of intense positron beams at the VEPP-5 injection complex

A source of positrons allowing 5 × 10⁸ positrons accelerated to the energy of 70 MeV to be produced per pulse has been developed. The process of electron-positron pair production in an electromagnetic shower is used for production of positrons. The electromagnetic shower is generated in a tantalum target by a beam of 2 × 10¹⁰ electrons with energy 270 MeV. A high efficiency of positron collection (positron yield Y ≈ 0.1 GeV^?1) is ensured by a unique design of the matching device.     

Fluorescence assay for monitoring Zn-deficient superoxide dismutase in vitro

A method has been developed for selective detection of the zinc-deficient form of Cu, Zn superoxide dismutase (SOD1) in vitro. Zinc-deficient SOD1 mutants have been implicated in the death of motor neurons leading in amyotrophic lateral sclerosis (ALS or Lou Gerhig's disease). Thus, this method may have applicability for detecting zinc-deficient SOD1 mutants in human ALS patients samples as well as in a transgenic mouse model of ALS and in cultured motor neurons. We determined previously that structural analogs of 1,10 phenanthroline, which react specifically with Cu(I), react with the active Cu(I) of SOD1 when zinc is absent, but not when zinc is also bound, as evidenced by the fact that the reaction is inhibited by pretreatment of the enzyme with zinc. We report herein that bathocuproine, or its water-soluble derivative bathocuproine disulfonate, react with zinc-deficient SOD1 to form a complex which fluoresces at 734 nm when excited at 482 nm. Fluorescent intensity is concentration dependent, thus we propose to use fluorescent confocal microscopy to measure intracellular levels of zinc-deficient SOD1 in situ.     

Controlling the Properties of Spin–Wave Transport in a Semiring Magnon Microwavevguide

Technical Physics - Spin-wave transport along a waveguide structure with disturbed translational symmetry has been investigated. A semiring portion of a magnon microwaveguide has been made of a YIG...     

Controlled Spin-Wave Transport in a Magnon-Crystal Structure with a One-Dimensional Array of Holes

JETP Letters - Spin-wave transport in a lateral system of microwaveguides coupled to each other through a magnonic crystal structure with a one-dimensional array of holes has been analyzed....     

Neuromorphic Calculations Using Lateral Arrays of Magnetic Microstructures with Broken Translational Symmetry

A possibility to control the characteristics of spin waves in a lateral array of magnetic microstructures with broken translational symmetry is demonstrated. The regimes of spatial and frequency selection of the spinwave signal are studied by Brillouin light scattering and by numerical simulations. The micromagnetic simulation is used to study the effect of geometric parameters on the characteristics of dipole-coupled spin waves. The specific features of the coupling between the transverse modes propagating in the system with broken translational symmetry are revealed. The results can be applied to develop multiplexers, power dividers, couplers, and the ultrahigh frequency signal processing circuits using the neuromorphic principles, which are based on the lateral arrays of magnetic microstructures.     

Functional Magnon Network Blocks Based on Structures with Translational Symmetry Violation

Technical Physics - We have studied the properties of spin-wave excitations in a structure that is a junction of two regular magnon waveguides. The proposed structure enables the transmission of...     

Middle-infrared random lasing of Cr doped ZnSe, ZnS, CdSe powders, powders imbedded in polymer liquid solutions, and polymer films

Room temperature (RT) middle-infrared (Mid-IR) random lasing of chromium- (Cr) doped ZnSe, ZnS, and CdSe powders, powders imbedded in perfluorocarbon liquid polymer solutions, and fluorocarbon polymer films is reported. Laser active powders were prepared without a stage of bulk crystal growth by annealing of starting chemicals (pure, mixed ZnSe:CrSe; ZnS:CrS; CdSe:CrSe). Mixture of the different semiconductor hosts allows tuning oscillation wavelength from 2240 to 2630 nm.