Determination of partial-wave inelasticities for elastic pion-nucleon scattering with the aid of experimental data on π N → ππ N processes in the beam-momentum range 300 < P beam < 500 MeV/ c

The partial-wave inelasticity parameters of the amplitude for elastic pion-nucleon scattering are determined with the aid of the phenomenological amplitude for inelastic πN → ππN processes in the energy range extending to the threshold for the production of two pions. The resulting inelasticity parameters are compared with their counterparts derived from modern partial-wave analyses. The largest inelastic-scattering cross section in the P11 wave is in excellent agreement with the analogous value from the analysis performed at the George Washington University in 2006. For other waves, however, the present results differ in the majority of cases from respective values given by partial-wave analyses (the distinctions are especially large for the isospin-3/2 amplitudes). Original Russian Text ? V.A. Kozhevnikov, S.G. Sherman, 2008, published in Yadernaya Fizika, 2008, Vol. 71, No. 11, pp. 1891–1909.     

On Minimum Static Breakdown Voltage for a Gasfilled Gap

Russian Physics Journal - Relying on the condition of the discharge self-sustainment, a theoretical analysis is performed aimed at identifying the lowest possible discharge voltage. It is shown...     

Structure and Mechanical Properties of 3D-Printed Ceramic Specimens

Russian Physics Journal - The paper presents the research results of the structure, phase composition and mechanical properties of aluminum oxide ceramic specimens obtained by the additive...     

Inverse and implicit function theorems on carnot manifolds

We obtain some analogs of the Euclidean inverse and implicit function theorems for continuously hc-differentiable mappings on Carnot manifolds.     

General laws of X-ray reflection from rough surfaces: I. Optical theorem and energy conservation law

The optical theorem is generalized for the general case of X-ray wave reflection from an arbitrary layered rough medium. It is proven strictly that in the absence of absorption the energy conservation law is exactly satisfied within the distorted wave Born approximation if the angular scattering distribution is calculated taking into account only the single wave scattering from the inhomogeneities of the medium and if the specular reflectance and transmittance are calculated with allowance for both single and double scattering.     

Polydentate phosphine oxides as external electron donors for titanium-magnesium catalysts for propylene polymerization

The possibility of using R _n P(O)(CH₂OR′)_3—n (R = alkyl, R′ = methyl or acyl, n = 0–2) polydentate phosphine oxides as external electron donors for the titanium-magnesium catalysts for isotactic polypropylene synthesis is demonstrated for the first time. The kinetics of propylene polymerization in liquid monomer at 70°C and the isotacticity and molecular-weight characteristics of the resulting polypropylene are studied as functions of the nature of the substituents at the phosphorus atoms in the external donor and the molar ratio of the cocatalyst AlEt₃ to the external electron donor. Among the compounds examined, isoamyldi(methoxymethyl)phosphine oxide (R = iso-Am, R′ = Me, n = 1) is the most efficient. The isotacticity index of the polypropylene (PP) synthesized on the titanium-magnesium catalyst with this external donor is as high as 94–95%, and the activity of the catalyst (Cat) in the absence of hydrogen is 5.0–6.5 (kg PP) (g Cat)^?1 h^?1. With the optimum combination, the activity of this catalyst is ≈5 (kg PP) (g Cat)^?1 h^?1 and the isotacticity index is 94%. These parameters are close to those obtained for propylene polymerization in the absence of hydrogen on the same titanium-magnesium catalyst with phenyltriethoxysilane (external donor used in the industrial synthesis of PP): the activity is 5.6 (kg PP) (g Cat)^?1 h^?1, and the isotacticity index is 95%. The introduction of hydrogen into the reaction zone makes it possible to efficiently control the molecular weight of PP, increases the catalyst activity by a factor of 1.5–2.5, and somewhat decreases the isotacticity index (from 94 to 91–92%).