Specific features of ethylene polymerization on self-immobilizing catalytic systems based on titanium bis(phenoxy imine) complexes

The kinetics of ethylene polymerization on six methylalumoxane-activated self-immobilizing bis(phenoxy imine) complexes of titanium chloride with allyloxy groups in the m- and p-positions of the N-phenyl ring and with various substituents in the salicylaldehyde fragment was studied. The activity of the complexes in the temperature range 20–60°C and ethylene pressure of 0.4 MPa was evaluated.     

Microwave and UV excitation spectra of 4-fluorobenzyl alcohol at high resolution. S0 and S1 structures and tunneling motions along the low frequency -CH2OH torsional coordinate in both electronic states

Rotationally resolved electronic spectra of several low frequency vibrational bands that appear in the S(1) ← S(0) transition of 4-fluorobenzyl alcohol (4FBA) in the collision-free environment of a molecular beam have been observed and assigned. Each transition is split into two or more components by the tunneling motion of the attached -CH(2)OH group. A similar splitting is observed in the microwave spectrum of 4FBA. Analyses of these data show that 4FBA has a gauche structure in both electronic states, but that the ground state C(1)C(2)-C(7)O dihedral angle of ～60° changes by ～30° when the photon is absorbed. The barriers to the torsional motion of the attached -CH(2)OH group are also quite different in the two electronic states; V(2) ～ 300 cm(-1) high and ～60° wide in the S(0) state, and V(2) ～ 300 cm(-1) high and ～120° wide (or V(2) ～ 1200 cm(-1) high and ～60° wide) in the S(1) state. Possible reasons for these behaviors are discussed.     

The generalized van Laar approximation for free energy

The van Laar equation for the uniform substance phase is analyzed. Based on this, an expression for free energy is found. The structure of the expression allowed us to create a method for determining the free energy in an arbitrary order of the perturbation theory. A generalized equation for free energy is derived based on the using thermodynamic perturbation theory and the accelerated method of convergence of the series of the perturbation theory. This expression agrees well with the asymptotic behavior of the free energy and with the known experimental data. It can be successfully used to describe the behavior of the substance in a super-critical region, as well as to investigate the metastable phase. It is shown that the expression for free energy can be used for a broad class of substances.     

Nonmonotonic variation of the electrical conductivity of C<Subscript>60</Subscript> fullerene crystals dynamically compressed to 300 kbar as evidence of anomalously strong reduction of the energy barrier of C<Subscript>60</Subscript> polymerization at high pressures

The electrical conductivity of a C₆₀ fullerene crystal is measured under the conditions of quasi-isentropic loading by a diffuse shock wave to a pressure of 30 GPa at room temperature. Nonmonotonic behavior of the conductivity of the samples with an increase in pressure is observed: first, conductivity increases by several orders of magnitude and, then, decreases rapidly. An increase in conductivity is explained by a decrease in the band gap under pressure, whereas a decrease in conductivity may be explained under the assumption that the energy barrier of C₆₀ polymerization decreases similarly to the band gap with an increase in pressure. As a result, the rate of C₆₀ polymerization at high pressures increases considerably (by more than seven orders of magnitude).     

The strange-quark distribution

We discuss the latest CCFR determination of the strange sea density of the proton. We comment on the differences with a previous, leading-order, result and point out the relevance of quark mass effects and current non-conservation effects. By taking them into account it is possible to solve the residual discrepancy with another determination of the strange-quark distribution. Two important sources of uncertainties are also analysed.     

Conductivity of C60 fullerene crystals under dynamic compression up to 200 kbar

The conductivity σ of C₆₀ fullerene crystals is measured under quasi-isentropic loading by a spread shock wave to a pressure of 200 kbar at the initial temperatures 293 and 77 K. A sharp increase in σ by seven to eight orders of magnitude is detected: from 10^?6?10^?7 Ω^?1 cm^?1 at normal conditions to 5 Ω^?1 cm^?1 under pressure from 100 to 200 kbar. The conductivity of samples under pressure decreases with decreasing temperature, which is characteristic of semiconductors. On pressure release, σ regains its initial value.     

Preparation of Compounds of Epoxy Resins with Low-Molecular-Weight Carboxyl-containing Rubbers by Activating Mixing

A process was developed for preparing adhesives from a low-molecular-weight carboxyl-containing rubber and an epoxy resin with different oligomer ratios. The process involves the chemical reaction of the components under conditions of activating mixing.     

Synthesis of Phosphate Epoxy Hardener-Flame Retardant and Rheokinetics of Curing of Epoxy Composites with Its Use

The effect of phosphate hardener obtained from phosphoric acid and acetic anhydride on the rheokinetics of extended epoxy composite is studied.__________Translated from Zhurnal Prikladnoi Khimii, Vol. 78, No. 5, 2005, pp. 860–864.Original Russian Text Copyright © 2005 by Nikolaev, Nikolaeva.     

Adsorption behavior of Vulkan-7H graphitized carbon black

The adsorption behavior of Vulkan-7H carbon black graphitized at 3073 K was studied. Benzene adsorption isotherms at 293 K were measured by the static method and by gas chromatography. It was shown that Vulkan-7H carbon black may be considered as a supermicroporous adsorbent with a pore size of 1.05 nm.The sample was provided by N. N. Lezhnev.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1544–1546, September, 1993.     

Twistability of the path of radiation propagating in an absorbing medium

The effect of rotation of the speckle pattern accompanying the propagation of radiation in an absorbing multimode optical fiber is predicted in the geometrical optics approximation. The direction of the angle of rotation of the speckle pattern at the fiber exit is determined by the photon helicity. The absolute value of the angle of rotation is proportional to the square of the fiber length.