Non-covalent columnar cyclodextrin-based structures

Examples of the formation of ordered ensembles of α-, β-, and γ-cyclodextrins (CDs) molecules with a columnar packing of macrocycles are reported. These ensembles are formed by (1) the supramolecular dissociation of polymer inclusion complexes under the action of organic solvents that are selective with respect to a polymer guest and (2) the fixation of columnar CD aggregates self-organized in aqueous solutions at high temperatures upon the precipitation from water into organic solvents. Specific features of the organization of cyclodextrins in the thus-synthesized structures are studied by X-ray diffraction. Preliminarily oriented polymer inclusion complexes based on corresponding CDs are used as a model with the columnar arrangement of macrocycles.     

Ionizing-Radiation Ignition of a Hydrogen–Air Mixture

The behavior of a hydrogen–air mixture under the action of ionizing radiation was studied. A kinetic model for radiation-chemical processes in the H₂–O₂–N₂ system was constructed, and the effects of the main parameters of radiolysis on shifting its flammability limits were analyzed. It was found that, under normal conditions (p = 0.1 MPa, T ₀ = 300 K), the ignition of the stoichiometric mixture began at a radiation intensity of about 0.1 kGy/s. The induction period of the chain H₂ oxidation reaction shortened with increasing radiation dose rate and pressure.     

Tautomerism,electronic structures,and electronic spectra of indolo[2,3-b]quinoxaline and its derivatives

The tautomerism, electronic spectra, and electronic structures of the ground and excited states of indolo [2,3-b]quinoxaline and its 2,3- and 1,4-dibutoxy derivatives were investigated by the Pariser-Parr-Pople (PPP) method. It is shown that these compounds exist primarily in the 6H form; the long-wave s^* transition is due to transfer of charge from the indole fragment to the quinoxaline fragment, and in the first excited state many of the bonds in the quinoxaline fragment are loosened significantly. The effect of butoxy substituents on the first s^* transition of indolo [2,3-b] quinoxaline was analyzed by means of perturbation theory within the framework of the Hückel MO method.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1259–1263, September, 1982.     

Synthesis and Properties of Copolymers Having Polyconjugated Blocks in the Macromolecules. III Thermal Behavior of Polyisoprene-Containing Polyazophenylene Fragments in the Main Chains

The thermal and thermooxidative stability of polyisoprene containing polyazophenylene fragments of different composition was investigated. Elevated inhibiting activity of polyazophenylene -methane fragments was found to be caused by the intramolecular synergism due to the combination of the reaction of peroxy radicals with mobile hydrogen atoms of methylene bridge groups and decomposition of hydroperoxides under the influence of polyconjugated blocks.     

Structure of the Mo-Containing Dispersed Catalyst During Heavy Oil Upgrading in the Presence of Steam And Hydrogen

XRD, TEM, EXAFS/XANES methods are first used to study the structure and morphology of Mocontaining phases of carbon residues of heavy oil refining during catalytic steam cracking, catalytic cracking without water, and hydrocracking. According to the results obtained from physical and chemical studies of Mo-based catalytic phases, the reaction medium affects structural features of Mo-containing phases, e.g. the amount of oxide and sulphide forms, the particle size, and particle morphology.     

Fluorosiloxane sealants

Fluorosiloxane sealants of domestic and foreign production that have found wide application in aircraft engineering are reviewed. Their main performance characteristics and application features are presented.     

Impact of amorphization on the magnetic state and magnetocaloric properties of Gd3Ni

Rapid quenching and ball milling have been used to modify the magnetic state and magnetocaloric properties of the intermetallic compound Gd₃Ni. The melt-spun and ball-milled Gd₃Ni samples are found to exhibit a soft ferromagnetic-like behavior below 120 K, whereas in the crystalline state, the Gd₃Ni compound is an antiferromagnet with a Néel temperature of about 99 K. The reduced value of the saturation magnetization observed in amorphous Gd₃Ni samples is ascribed to the appearance of a magnetic moment on Ni atoms. After amorphization, the Gd₃Ni samples exhibit substantially improved magnetocaloric properties in a low field region in comparison with crystalline Gd₃Ni.     

Optimization of supersonic flows past thin bodies by using external effects on the flow

Problems of optimization of flows past a thin body of revolution and a slender profile at a small angle of attack in the presence of local energy release zones and an external force acting on the flow near the surface are considered. Analysis is based on an analytic theory of supersonic flow past thin bodies presented in previous papers. The following problems are considered: drag reduction of a thin body of revolution, lift force enhancement of a profile with infinite aspect ratio, attenuation of acoustic noise generated by supersonic flows past bodies.