Synthesis and powder X-ray diffraction analysis of new mixed rare-earth and selenium oxychlorides with composition LnSeO3Cl

A series of new mixed rare-earth and selenium oxychlorides with composition LnSeO₃Cl (Ln = La, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Yb, or Y) were prepared by annealing together LnOCl and SeO₂ in sealed silica tubes. The resulting compounds were characterized by powder X-ray diffraction. The unit cell parameters of the phases were determined. Lanthanum—europium oxychlorides crystallized in the tetragonal system to give the Sillen phases analogously to tellurium compounds with the similar formula, whereas Tb—Yb and Y oxychlorides crystallized in the orthorhombic system. It is likely that the latter oxychlorides are not layered compounds.     

Kinetic Regularities of the Kabachnik–Fields Reaction under Catalysis by Sulfonic Cation Exchangers Based on Petroleum Asphaltenes

Kinetics and Catalysis - Strongly acidic cation exchangers were obtained by the sulfonation and successive sulfonation and nitration of petroleum asphaltenes. The cation exchangers were...     

Superbase-Catalyzed Steric-Hindrance-Induced Dimerization of Alkynones to Highly Functionalized Furans

The cascade dimerization of alkynones bearing sterically hindered secondary alkyl groups at the carbonyl function has unexpectedly furnished highly functionalized furans. The reaction efficiently occurs in the presence of potassium tert-butoxide/dimethylsulfoxide superbase catalytic system at room temperature. Alkynones having additional C−H active site at the carbon-carbon triple bond have followed another dimerization pathway to afford 3-alkenylpyran-4-ones. The discovery of these reactions expands the traditional knowledge about the reactivity of alkynones in strong basic medium.     

Decrease in phase density in very bright beams

Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, No. 2, pp. 3–12, March–April, 1992.     

Simulation of a Looptop Hard X-ray Source in Turbulent Plasma of Solar Flares

Technical Physics - The kinetics of electron beams accelerated in the collisional plasma of solar (stellar) flares is considered. The stationary ion-acoustic turbulent mode localized at the...     

On the ππ-scattering lengths in the theory with effective Lagrangian

Use of the effective Lagrangian incorporating both the scalar and pseudoscalar mesons gives a possibility to calculate the ππ-scattering lengths without attraction of the ChPT theory.     

Effect of unitarization on the amplitudes for the decays K10 → π+π? and K+ → π+π+π?

The unitarization of the amplitude for the decay process K ₁⁰ → π⁺π⁻ and allowance for the rescattering of final-state pions in the decay process K ⁺ → π⁺π⁺π⁻ make it possible to evaluate, by using the parameters extracted from data on K → 2π decays, the K ⁺ → π⁺π⁺π⁻ decay width. The result agrees with the experimental width value at a level of a few percent. Allowance for corrections for higher order terms of the momentum expansion of the amplitude for the decay process K ⁺ → π⁺π⁺π⁻ leads to the slope-parameter value of g ₊₊₋^th = 0.2182, which agrees with its experimental counterpart, g ₊₊₋^exp = 0.2154 ± 0.0035.     

On the limit of neutron fluxes in the fission-based pulsed neutron sources

The upper limit of the density of the thermal neutron flux from pulsed sources based on the fission reaction is established. Three types of sources for research on ejected beams are considered: a multiplying target of the proton accelerator (a booster), a booster with the reactivity modulation (a superbooster), and a pulsing reactor. Comparison with other high-flux sources is carried out. The investigation has been performed at the Frank Laboratory of Neutron Physics of JINR.     

谈谈量子力学中的状态叠加原理

以对话的形式,介绍并评论了布洛欣采夫、狄拉克以及朗道和栗弗席茨关于状态叠加原理的不同表述.