Catalysis of the dealkylation of derivatives of 2,6-di-tert-butylphenol by heteropoly acids

Conclusions The tungsten heteropoly acids in acetic acid are the most active in the dealkylation of 4-alkyl-2,6-di-tert-butylphenols. The reaction is first order with respect to the substrate and with respect to the HPA, and water slows the reaction. It has been postulated that the dealkylation reaction is mediated mainly by the undissociated molecules of the HPA.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 4, pp. 752–756, April, 1987.     

CHEMICAL STRUCTURE AND FUNCTIONAL PROPERTIES OF AMORPHOUS BORON CARBONITRIDE FILMS

Journal of Structural Chemistry - We report a comprehensive study of the effect of the chemical structure of boron carbonitride films on the variability of their functional characteristics. The...     

Modification of sulfate lignin with sodium periodate to obtain sorbent of 1,1-dimethylhydrazine

Application of the oxidative modification of sulfate kraft lignin with sodium periodate under mild conditions is suggested in order to obtain a sorbent for detoxication of spillage places of rocket fuels based on 1,1-dimethylhydrazine and to purify wastewaters containing this compound. It was found that processing with the periodate at a temperature of 55°C for 20 h results in a more than twofold increase in the content of carbonyl and quinone groups in a lignin preparation and a rise in its polydispersity due to the appearance of a macromolecular condensed fraction and a threefold increase in the sorption capacity for 1,1-dimethylhydrazine. The sorbent can bind 6.7% of 1,1-dimethylhydrazine and substantially surpasses in this parameter other lignin-based sorbents. It was shown that the firm chemical binding of hydrazines hinders desorption of the highly toxic rocket propellant and products of its oxidative transformation from the surface of lignin both into solution and into the vapor phase, thereby providing safe handling of the spent sorbent.     

Determination of the sorption characteristics of glauconite during extraction of a pharmaceutical from an aqueous medium

A technique for preparing enriched glauconite on the basis of a natural mineral from the Beloozyorskoe field of Saratov oblast has been developed. The results of a study of the chemical composition, surface structure, and certain physicochemical properties of the samples of the sorbent are presented. The sorption of ambroxol hydrochloride ions from aqueous solutions has been studied using natural and enriched glauconite. The sorption isotherms, are approximated by the Langmuir equation, have been obtained, and the values of the maximum sorptive capacities have been calculated. Based on the obtained data, conclusions have been drawn on using the studied natural mineral sorbents to extract the above-mentioned substance from aqueous solutions.     

On operators generated by elliptic boundary problems with a spectral parameter in boundary conditions

General elliptic boundary value problems with the spectral parameter appearing linearly both in the elliptic equation and in boundary conditions are considered. It is proved that the corresponding matrix operator from the Boutet de Monvel algebra is similar to an almost diagonal operator. This result is applied to prove the completeness and the summability (in the sense of Abel) of the root vectors of this operator.The support of the Rashi Foundation is gratefully acknowledged.The support of the Israel Ministry of Science and Technology is gratefully acknowledged.     

On wide-band mirrors for soft X-ray range

The properties of smooth curved surfaces which can deflect the soft X-ray beams to large angles and reflect them effectively are considered. The wave sliding along the curved cylindrical surface has been analysed and the structure of the electromagnetic field has been found both in the medium and in vacuum. Large reflectivity has been predicted in wavelength regions 50 Å < λ < 150 Å and λ < 20 Å for several elements with known optical constants. In contrast to the multilayer structures which are widely used now, the curved mirrors provide a large reflectivity in a broad X-ray wavelength region.     

New half-metallic ferromagnets: Double perovskites SR(FeM)O<Subscript>3</Subscript> (M = Sn,Ti, Zr)

In calculations using the local spin density approximation, a new group of half-metallic ferromagnets is predicted. This group comprises double perovskites Sr₂FeSnO₆, Sr₂FeTiO₆, and Sr₂ FeZrO₆—systems with one type of magnetic ions that can be obtained by diluting the magnetic sublattice of SrFeO₃ with ions of nonmagnetic pⁿ and d⁰ metals.     

Domain structure of a nematic-liquid-crystal layer in low-frequency Couette flow

The spatially periodic structure arising in a homeotropic nematic-liquid-crystal (NLC) layer in low-frequency Couette flow is described theoretically. The analysis of this phenomenon is based on the hydrodynamic equations for NLCs, from which a self-consistent system of equations is selected for perturbations of hydrodynamic variables: the steady-state angle of the molecule rotation, the liquid flow, and the velocity of oscillating vortex flows. The formation of the periodic structure is explained by the phase delay of the velocities of the vortex oscillating flows forming in the deformed structure with respect to the shear velocity in the Couette flow. It is shown that at low frequencies this difference in the velocities is caused by the orientational waves near the layer boundaries. In the case of fixed orientation of molecules at the boundaries, the dependence of the threshold shear amplitude on the frequency and layer thickness is given by the relation u_th ～ (ωh²)^?1/4. The influence of the conditions for the molecule orientation at the layer boundaries on the above phenomenon is analyzed.