Reconstruction of the Green function in problems of resonance acoustic spectroscopy

A possibility for reconstruction of the Green function for a three-dimensional elastic body (resonator) is considered. The initial data are the elasticity tensor for the resonator material that is measured by the technique of resonance acoustic spectroscopy and its complex vibration response. Possibility for the response reconstruction and determination of the coordinates for a force source of vibration excitation according to the measured data is demonstrated. The difference between the measured and synthesized responses is small that provides an opportunity to perform continuous calibration of acoustic measurements and determine the distribution of stress and strain within a solid.     

Electroreduction of Phthalazines and 1,2,5-Thiadiazoles: Structural Factors Determining the Opening of Heterocycle

Electrochemical reduction of phthalazines and 1,2,5-thiadiazoles containing nucleofugaceous groups at the carbon -atoms are studied in aprotic and proton-donating media. Heteroatoms, substituents, and media are found to affect potentials and reaction path for the electroreduction. The factors determining the reductive opening of heterocycles are revealed. In diazines the heterocycle opening in annelated systems is induced by the electron transfer, provided there exist (a) a heteroatom–heteroatom bond and (b) an easily splitting-off group at the carbon -atom, whose nucleofugacity is comparable with or exceeds that of the chloride ion. Stability of the 1,2,5-thiadiazole cycle toward its reduction is determined by the substituent and the medium nature. On adding a nucleofugaceous group to the molecule, the transfer of two electrons in an aprotic medium results in the heterocycle opening with the formation of iminonitrile; when two easily splitting-off groups are present, the electron transfer makes the cycle decompose into inorganic anions.     

Structure of surface-active bubblets in electrolytes

The possibilities of formation and details of architecture of bubblets that arise in an electrolyte in the presence of a hydrophobic effect at the vapor/liquid interface for one of the ions is discussed. It is demonstrated that the competition of this effect and the image forces leads to the emergence, around a cavity of radius R that materialized for some reason or another, of a charged double layer, which is capable of stabilizing the bubble dimensions. A relationship is determined between radius R and parameters pertaining to the problem: the energy of localization of “hydrophobic” ions, the surface tension at the vapor/liquid interface, the dielectric constant of the liquid, and so on. It is mentioned that the scenario under discussion has no threshold that would interfere with the emergence of dipole-charged bubblets in weak electrolytes.     

Cyclic phosphorochloridites (chloridates) based on chiral butane-2,3-diol and dihydrobenzoin as reagents for the analysis of enantiomeric compositions of alcohols by31P NMR spectroscopy

The use of cyclic phosphorochloridites which were prepared based on PCl₃ and chiral butane-2,3-diol or hydrobenzoin as possible reagents for the analysis of the enantiomeric composition of chiral alcohols by³¹P NMR spectroscopy is considered. The diastereomeric dispersion of chemical shifts of the resulting phosphites as well as of derived phosphates and thiophosphates is compared with that of structurally similar reagents. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 308–311, February, 2000.     

Synthesis,hypolipidemic and antifungal activity of tetrahydroberberrubine sulfonates

The paper describes the synthesis of new tetrahydroberberrubine derivatives containing polyfl uorophenyl- or alkylsulfonate groups at the O(9) position as well as those containing or not containing a bromine atom at the C(12) position. In a model of acute Triton-induced hyperlipidemia, tetrahydroberberrubine 9-O-(heptafluoro-4’-toluene)sulfonate was shown to reduce the cholesterol level by 23.5%, which is comparable with the eff ect of Simvastatin. At a concentration of 32 μg mL^?1, tetrahydroberberrubine 9-O-pentafluorobenzenesulfonate inhibits the growth of the fungus Cryptococcus neoformans by 81.3±3.5%.