The Reactivity of C–H Bonds in the Cyclohexyloxy Moiety of Cyclohexyl Acetate toward the tert-Butylperoxy Radical

The effect of the functional group on the partial rate constants of the reactions of the tert-butylperoxy radical with CH bonds in the cyclohexyloxy moiety of cyclohexyl acetate at 333 K was studied by the Howard–Ingold method. The ester group activates the CH bond at the 1-position and deactivates the CH bonds at the 3-position and, especially, the 2-position. The reactivity of CH bonds at the 4-position is close to the reactivity of CH bonds in cyclohexane.     

Electrophysical properties of polymers based on Ni(II) complexes

Thin-layer organometallic films synthesized from the monomer [NiSalen] have been studied. The presence of the oxidized and reduced forms of a redox polymer has been established by cyclic voltammetry and electronic absorption spectroscopy. The temperature-frequency dispersion of dielectric characteristics has been discovered, and the possible mechanisms of relaxation polarization in poly[NiSalen] on solid supports have been considered. Based on the temperature-frequency dependences of conductivity, the energy of the thermal activation of electrical conductivity is determined. The feasibility of the hopping mechanism of charge transfer in the polymer under study is discussed.     

Calculation of the unsteady burning velocity according to a known law of pressure variation during transient processes in a solid-propellant rocket engine

The burning velocity during pressure decay in a model solid-propellant engine caused by the opening of an additional nozzle concurrently with the operation of the main nozzle is calculated; i.e., the inverse problem of internal ballistics is solved. The calculations are performed using experimental pressure versus time dependences and the laws of conservation of mass and energy in the thermodynamic and isothermal approximations. The problem is solved in two formulations: using the basic parameters of the combustion chamber before depressurization and in a formulation based on using initial conditions for pressure decay. In the latter case, the unsteady burning velocities are smaller than the corresponding steady-state velocities at the same pressures and close to the calculated velocities obtained for the same pressure decays by solving the direct problem.     

Temperature sensitivity of the burning velocity of nitroglycerin-based propellants

An analysis of the temperature sensitivity of the burning velocity for nitrocellulose and a number of model nitroglycerin-based propellants was performed. The dependences of the temperature sensitivity of the burning velocity on the pressure were obtained: at initial temperatures of below −50°C the pressure dependence of this parameter was virtually absent, whereas at temperatures above −50°C, it decreases sharply with increasing pressure.     

Rapid growth of α-LiIO3 crystal

A fundamental possibility of significantly increasing the growth rate of α-LiIO₃ crystals without the formation of visible defects in them is demonstrated. The corresponding equipment is designed and a technique for obtaining intermediate-size samples is developed. The crystals grown with an average rate of up to 4 mm/days along the Z axis are of high enough quality to be used as materials of optical elements for laser frequency doubling. α-LiIO₃ crystals have been grown both in an open volume via natural faceting and in a rectangular habit, where growth occurs basically through the pyramid (101) face. It is shown that that amount of limiting impurities in the raw material used can be reduced and that the applicability of this material for rapid growth can be verified.     

Evaluation of the Reactivity of Cyclohexanone СН Bonds in Reactions with tert-Butylperoxy Radical by Quantum Chemical Methods

Kinetics and Catalysis - The effective charges on hydrogen and carbon atoms and the Fukui functions for the electrophilic and radical attacks for the hydrogen atoms of the chair and boat...     

Estimation of the $$boldsymbol{p+textrm{He}}$$ Fraction in the Mass Composition of Primary Cosmic Radiation the Energy Range of $$boldsymbol{E_{0}=1}$$ –100 PeV according to Gamma-Ray Families Featuring Halo

Physics of Atomic Nuclei - The present article reports on an analysis of the properties that gamma-ray families featuring a halo exhibit in the cores of extensive air showers (EAS). The events...     

Neutron diffraction study of polycrystalline 4He in a porous medium

The elastic (diffraction) component of the neutron scattering cross section, which carries information on the atomic structure of solid helium confined in silica aerogel, has been studied. Analysis of the crystalline structure of solid helium in a porous medium, which is determined from the existing neutron diffraction data, indicates that the superfluid phase is localized inside a hexagonal close-packed phase and is not present in a body-centered cubic crystal. It has also been revealed that the addition of the ³He isotope changes the structure of solid helium and hardly affects the formation of a superfluid phase.     

Effect of ketones on the equilibrium between peroxy radicals carrying the chains of cyclohexanol oxidation with molecular oxygen

The influence of methyl phenyl ketone and diphenyl ketone on the kinetics of cyclohexanol oxidation initiated by cumyl peroxide at 373 K was studied. The ratio of the chain propagation rate constant involving the 1-hydroxy-1-phenylethylperoxy radical to the equilibrium constant of radical dissociation into methyl phenyl ketone and hydroperoxy radical (k _2.3/K′₂ = 900 L² mol^?2 s^?1) was determined by the selective inhibition method.     

Energy spectra of secondary particles in γ families and their sensitivity to the spectrum of primary cosmic rays

Spectra of secondary particles (γ-rays) in γ-families detected in the X-ray chambers in the Pamirs (H = 600 g cm^?2) have been analyzed. These γ-ray spectra show a bend at the energy E* _γ ≈ (ΣE _γ )^min, where (ΣE _γ )^min is the lowest total energy of γ-rays in the families above which γ-families were selected. The bend is not related to the knee in the spectrum of primary particles; it is due to the use of the ΣE _γ selection criterion. The E _γ spectrum slope is sensitive to the spectrum of the primary cosmic rays in the region E _γ ≥ (ΣE _γ )^min.