Structure and properties of imidazole-2-thiones (review)

Literature data on the structure, physicochemical properties, and transformations of imidazole-2-thiones and their benzo analogs are correlated.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 12, pp. 1587–1599, December, 1988.Original Article submitted November 19, 1986: revision submitted March 18, 1988.     

The role of local phonon modes in high-temperature ferroelectromagnet-superconductors

A theoretical study is made of the role of local phonon modes in a high-temperature ferroelectromagnet-superconductor. Angular states of magnetic moments of ions in the magnetic structure of a high-T_C superconductor are shown to be possible. A model of ferroelectric and superconducting transition is proposed. Theoretical estimates of the physical parameters are made and compared with experimental data.Deceased.Donetsk Physicotechnical Institute, Academy of Sciences of the Ukraine. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 7, pp. 5–19, July, 1993.     

Supersonic longitudinal flow past a cylinder in the presence of a second coaxial cylinder in the wake

The compressible-gas complete Navier-Stokes equations are applied for a numerical analysis of the flow structure between two coaxial cylinders of equal radius set in tandem in a supersonic flow. The results for Re_∞=10⁴, M_∞=3 ω=0.75, Tw=1.08, when the distance between the coaxial cylinders is equal to two blunt-nose radii, show that the flow between the cylinders is subsonic and quasiperiodic. Translated from Obratnye Zadachi Estestvoznaniya, Published by Moscow University, Moscow, 1997, pp. 199–203.     

13C nuclear magnetic resonance spectroscopy of selected adenine nucleosides: Structural correlation and conformation about the glycosidic bond

Structural correlations have been carried out from ¹³C chemical shifts (δ) and by analysis of ¹J(CH) coupling constants, and the conformation about the glycosidic bond has been studied by means of the ³J(CH) vicinal coupling constants between C-8 and H-1′ of some adenine nucleosides such as adenosine (Ado), N(7)-β-D-ribofuranosyladenine (N(7)-Ado), N(9)- and N(7)-β-D-xylofuranosyladenine (N(9)-xylAde and N(7)-xylAde), N(9)-(3-chloro-3-deoxy-β-D-xylofuranosyl)adenine (3′-Cl-xylAde) and N(9)-(2-chloro-2-deoxy-β-D-arabinofuranosyl)adenine (2′-Cl-araAde). The analysis of the influence on δ¹³C of the nature and configuration of the substituent in the carbohydrate fragment of the molecule has revealed two types of effects, namely, 1,2-cis and 1,2-trans. This approach, as well as the ³J(CH) values and the analysis of the C-3′-endo?C-2′-endo equilibrium of the carbohydrate fragment of nucleosides, and circular dichroism (CD) data, provides important information on the conformation about the glycosidic bond. The magnitudes of ³J(C-4, H) are indicative of the position of attachment of the carbohydrate fragment to the heterocyclic base.