Phase and extraction equilibria in water–polyethyleneglycol ethers of monoethanolamides of synthetic fatty acid–ammonium chloride systems

Phase equilibria in layering systems of water, polyethyleneglycol ethers of monoethanolamides of synthetic fatty acids (SFAs) (synthamide-5), and ammonium chloride are studied. The possibility of using such systems for the liquid extraction of metal ions is evaluated. The effect the nature of salting-out agents has on the processes of segregation of the systems has been considered.     

Propagation of electromagnetic waves in periodic structures with superconducting layers having electrodynamic parameters in the nonlinearity range of the dynamic mixed state

The propagation of electromagnetic waves in type-II superconductor-insulator periodic structures is studied for the case when the superconductor falls into the nonlinearity range of the dynamic mixed state described in the framework of the Larkin-Ovchinnikov theory. A dispersion relation for waves propagating in different directions is derived. It is shown that the electromagnetic waves can be amplified via interaction with a moving lattice of Abrikosov vortexes.     

An efficient approach to azirino and pyrrolo-fused dibenzazepines. Conformations of substituted dibenzo[c,f]pyrrolo[1,2-a]azepines

An effective approach to azepino-fused heterocycles is described. trans-1-Aryl-7,11b-dihydro-1H-azirino[1,2-a]dibenzo[c,f]azepines were synthesised via a domino sequence: isomerization of gem-dichloroaziridine-intramolecular Friedel-Crafts acylation of the tethered benzene ring catalysed by SnCl(4) and subsequent hydride induced intramolecular cyclization. Cycloaddition of dibenzazepinium ylides, generated by heating these aziridines, to activated C[double bond]C, C[triple bond]C dipolarophiles and fullerene C(60), leads to derivatives of dibenzo[c,f]pyrrolo[1,2-a]azepine. The reaction proceeds with complete stereoselectivity via cycloaddition of only W-ylide, which due to the high barrier does not undergo E,Z-isomerization under the reaction conditions. It was found that 2,3,9,13b-tetrahydro-1H-dibenzo[c,f]pyrrolo[1,2-a]azepine systems can exist in conformations of two types depending on the substituents at the pyrrolidine carbons in β-position with respect to nitrogen. Details of cycloaddition reactions and the conformational behavior of cycloadducts were studied by DFT calculations at the B3LYP/6-31G(d) level.     

Spin probe study of acidity of inorganic materials

Acidic characteristics of various inorganic materials, such as silica gel, aluminum, and titanium(IV) oxides, original and modified with F^? and SO ₄ ^2? ions, in the form of hydrogels and nanostructured powders doped by copper(II) ions, are studied. It is shown that pH values inside pores of the studied sorbents (pH_intr) differ from the pH of external solutions by 0.5–1.1 units. In the pores of original γ-Al₂O₃, the pH_intr values are higher, while, in pores of γ-Al₂O₃ samples modified with F^? и SO ₄ ^2? , as well as nonmodified α-Al₂O₃, SiO₂ gel, and TiO₂ hydrogels, pH_intr are lower compared to the pH of the external solution. It is found that pH_intr decreases, as the content of Cu²⁺ ions in the TiO₂ phase grows, and, beginning with a certain moment, it coincides with pH of an equilibrium solution. The pK _a values of functional group dissociation in some materials are determined. It is shown that, using spin probes, that is, pH-sensitive nitroxyl radicals, the electrostatic potential of the surface of nanostructured TiO₂ can be estimated.     

A monopole mass filter with a hyperbolic V-shaped electrode

In this article we compare the classical monopole mass filter of von Zahn and the monopole mass filter with a hyperbolic V-shaped electrode. The experimental results and those of computer simulation for both mass spectrometers are presented. We show that the replacement of a conventional 90 degrees V-shaped electrode by an electrode with a hyperbolic profile substantially improves the peak shape of any given mass, and increases the mass resolution by a factor of 3-4 and the abundance sensitivity by a factor of 100. The potential of high analytical performance combined with electroforming techniques for electrode manufacture indicate future practical uses of such instruments. Copyright 1999 John Wiley & Sons, Ltd.