Channeling of Neutrons in a Nonmagnetic Planar Waveguide

Journal of Experimental and Theoretical Physics - The propagation of neutrons in the middle layer of a planar waveguide, which is a three-layer thin film, has been studied. Neutrons emitted from...     

Electric Field Mechanism of Thin Plasma Jet Formation in an Open Atmospheric Discharge

Russian Physics Journal - Experimental and theoretical investigations of a new form of pulsed periodic discharge burning in the form of a thin plasma jet – apokamp – have been carried...     

Application of the hidden local symmetry effective chiral Lagrangian to evaluation of the <Emphasis Type="Italic">ω</Emphasis>(782), <Emphasis Type="Italic">ϕ</Emphasis>(1020) → 5<Emphasis Type="Italic">π</Emphasis> decay widths

The amplitudes obtained from the effective chiral Lagrangian with anomalous terms based on hidden local symmetry are applied to the evaluation of the partial widths of the decays ω → 2π⁺2π^?π⁰ and ω → π⁺π^?3π⁰. Combining the Okubo-Zweig-Iizuka rule, applied to the five-pion final state, with the Adler condition of vanishing of the amplitude at the vanishing of four-momentum of any final pion in the chiral limit, the ? → 2π⁺2π^?π⁰ and ? → π⁺π^?3π⁰ decay amplitudes are also calculated. The partial widths of the above decays are evaluated, and the resonance excitation curves in e⁺e^? annihilation are obtained, assuming reasonable particular relations among the free parameters characterizing the anomalous terms of the Lagrangian. The evaluated branching ratios \(Br_{\phi \to \pi + \pi - 3\pi ^0 } \approx 2 \times 10^{ - 7} \) and \(Br_{\phi \to 2\pi + 2\pi - \pi ^0 } \approx 5 \times 10^{ - 7} \) are such that with the luminosity L = 500 pb^?1, attained at the DAΦNE ? factory, one may already possess about 1340 events of the decays ? → 5π.     

The rolling of a wheel with a reinforced tyre along a plane without slip

A model of a wheel with a reinforced tyre, whose surface is simulated by a flexible strip (tread) attached to parts of two tori (the sidewalls of the tyre) is considered. The disk of the wheel (a rigid body) has six degrees of freedom and is in contact with the plane along part of the tread. Based on several assumptions, the potential energy functional of the deformed wheel is found as a function of the deformations of the centre line of the tread. On the assumption that the wheel is rolling without slip in the region of contact of the tread with the plane along a previously unknown section of the tread, the complete system of equations of motion is obtained. The equilibrium of the wheel and the steady state of rolling in a straight line with given swivel and tilt are investigated, and all characteristics of the motion are found (the contact region, the tyre deformation, and the forces and torques applied to the wheel disk).     

Genesis of the electronic spectrum and magnetic properties of a high-temperature phase of nonstoichiometric strontium ferrite SrFeO<Subscript>3–δ</Subscript> (0 ≤ δ ≤ 0.5)

The genesis of the electronic spectrum and magnetic properties of a high-temperature cubic phase of SrFeO_3–δ with the disordered distribution of oxygen vacancies under the variation of their concentration has been studied in the coherent-potential approximation within the LDA + U formalism. Experimental tendencies of the fundamental electron-energy and magnetic characteristics in SrFeO_3–δ under the variation of oxygen nonstoichiometry within the homogeneity region, 0 ≤ δ ≤ 0.5, have been described.     

Polarized neutron channeling as a tool for the investigations of weakly magnetic thin films

We present and apply a new method to measure directly weak magnetization in thin films. The polarization of a neutron beam channeling through a thin film structure is measured after exiting the structure edge as a microbeam. We have applied the method to a three-layer thin film structure acting as a planar waveguide for polarized neutrons. The middle guiding layer is a rare earth based ferrimagnetic material TbCo₅ with a low magnetization of about 20 mT. We demonstrate that the channeling method is more sensitive than the specular neutron reflection method.     

Transalkylation of phenols over heteropoly acids

Transalkylation of 2,6-di-tert-butyl-4-R-phenols over solid heteropoly acids (H₃PW₁₂O₄₀, H₄SiW₁₂O₄₀, H₃PW₁₂O₄₀/SiO₂, H₄SiW₁₂O₄₀/SiO₂) in the presence of toluene or o-xylene as acceptors of a tert-butyl group at 100–140 °C produces 4-R-phenols with 92–98% yield (R = H, alkyl, aryl, etc.). HPAs are effective catalysts for the transalkylation of p-cresol and 2, 6-ditert-butyl-4-methylphenol.

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2,6----4-R- (H₃PW₁₂O₄₀, H₄SiW₁₂O₄₀, H₃PW₁₂O₄₀/SiO₂, H₄SiW₁₂O₄₀/SiO₂) 0- - 100–140°C 4-R- 92–98% (R = H, , ..). - 2,6----4-.

     

Oxygen non-stoichiometry,high-temperature properties,and phase diagram of CaMnO<Subscript>3–<Emphasis Type="Italic">δ</Emphasis></Subscript>

The oxygen content in CaMnO_3–δ is studied by a coulometric titration technique depending on temperature and oxygen partial pressure variations in the ambient atmosphere. The δ–T phase diagram is derived from the obtained data where single-phase fields are outlined for orthorhombic, tetragonal, and cubic structures. The thermal expansion coefficient considerably larger in the cubic phase than in the tetragonal one is related with formation of large Mn³⁺ cations at depletion of oxygen from the crystalline lattice. Negative thermopower is explained by concomitant reactions of oxygen loss and charge disproportionation, 2Mn^{4 +} = Mn^{3 +} + Mn^{5 +} {\hbox{2M}}{{\hbox{n}}^{{{4 + }}}}{\hbox{ = M}}{{\hbox{n}}^{{{3 + }}}}{\hbox{ + M}}{{\hbox{n}}^{{{5 + }}}}{ } . The forbidden energy gap in CaMnO_3–δ is evaluated to be about 0.5 eV.     

Efficient hydrodeoxygenation of biomass-derived ketones over bifunctional Pt-polyoxometalate catalyst

Acidic heteropoly salt Cs(2.5)H(0.5)PW(12)O(40) doped with Pt nanoparticles is a highly active and selective catalyst for one-step hydrogenation of methyl isobutyl and diisobutyl ketones to the corresponding alkanes in the gas phase at 100 °C with 97-99% yield via metal-acid bifunctional catalysis.