Magnetoresistance in dilute p‐Si/SiGe in parallel and tilted magnetic fields

We report the results of an experimental study of the magnetoresistance ρ_xx and ρ_xy in two samples of p‐Si/SiGe with low carrier concentrations p = 8.2 × 10¹⁰ cm^‐2 and p = 2 × 10¹¹ cm^‐2. The research was performed in the temperature range of 0.3–2 K and in the magnetic fields of up to 18 T, parallel or tilted with respect to the two‐dimensional (2D) channel plane. The large in‐plane magnetoresistance can be explained by the influence of the in‐plane magnetic field on the orbital motion of the charge carriers in the quasi‐2D system. The measurements of ρ_xx and ρ_xy in the tilted magnetic field showed that the anomaly in ρ_xx, observed at filling factor ν = 3/2 is practically nonexistent in the conductivity σ_xx. The anomaly in σ_xx at ν = 2 might be explained by overlapping of the levels with different spins 0 ↑ and 1 ↓ when the tilt angle of the applied magnetic field is changed. The dependence of g‐factor g^*(Θ)/g^*(0⁰) on the tilt angle Θ was determined.     

Cross sections and asymmetries for elastic π3He scattering in the energy region around the Δ resonance

For a polarized target, π³He interaction is studied in the fixed-center approximation with all rescatterings included. Only the P ₃₃ wave is taken for the πN interaction. The nuclear wave function is taken either as a sum of Gaussian functions or as a Faddeev wave function in the s-wave approximation. The differential cross sections and asymmetries for elastic π⁺³He scattering at the laboratory energies of T _π, 180, and 256 MeV are calculated. The results are compared with experimental data.     

Effect of electronegative impurities on the generation of ozone in air

A self-consistent numerical model is used to investigate the effect of electronegative impurities on the ozone yield in a dielectric barrier discharge with a pulsed voltage supply, and the range of impurity concentrations giving a substantial (two-or threefold) increase in the ozone yield is established. Sulfur hexafluoride is considered as a representative component having strong electronegative properties. It is shown that a tiny admixture [SF₆]<0.1% can have an appreciable effect on the characteristics of an ozonator. The calculations are compared with published experimental data and given an interpretation. Zh. Tekh. Fiz. 69, 49–52 (January 1999)     

Classical orthogonal polynomials of a discrete variable on nonuniform lattices

A general theory of classical orthogonal polynomials of a discrete variable on nonuniform lattices is developed. The classification of the polynomials under consideration is given.     

Effect of the shape of filler particles on the strength of a polymer composite

When metallic or polymeric powder fillers are introduced into poly(2,6-dimethyl-1,4-phenyleneoxide) (PDPO), the strength of the filled composites is found to decrease, while when glass or polymeric fiber fragments are introduced into PDPO, the effect is reverse. The fracture activation energy of the composites is shown to coincide with the fracture activation energy of PDPO. The variation of the strength is caused by the dependence of structure-sensitive parameter γ of the matrix on the concentration and shape of filler particles. On the one hand, filler particles are stress concentrators and their introduction decreases the strength. This effect prevails in the composites filled by spherical particles. On the other hand, when anisotropic particles are introduced, matrix molecules are arranged parallel to their axis, which decreases γ and increases the strength. This effect is predominant in the composites filled by fiber fragments.     

Reactions of Some Terpenoids with CH-Acids in the Presence of Cs-β Zeolite

Reactions of some ,-unsaturated ketones from terpenoid series with CH-acids in the presence of Cs- zeolite were studied under various conditions. The variation of reaction conditions (heating, ultrasonic irradiation) strongly affected the reaction products ratio, and the effect was singular in each case and gave different results.     

Gell-Mann-Low function in QED

The Gell-Mann-Low function β(g) in QED (g is the fine structure constant) is reconstructed. At large g, it behaves as β_∞ g ^α with α≈1 and β_∞≈1.     

Gell-Mann-Low function in the ϕ4 theory

An algorithm is proposed for the determination of the asymptotics of a sum of a perturbation series from the given values of its coefficients in the strong-coupling limit. When applied to the ?⁴ theory, the algorithm yields the β(g)∝g ^α behavior with α≈1 at large g for the Gell-Mann-Low function.