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Abstract: We consider the boundary-value problem on a finite interval for a class of second-order operator-differential equations with a linear operator in one of its boundary conditions. We obtain sufficient conditions for the regular solvability of the boundary-value problem under consideration; these conditions are expressed only in terms of its operator coefficients.

A procedure for the radiochemical neutron activation analysis of rhenium and ammonium perrhenate samples was developed. The procedure provides the determination of about 30 impurity elements present in concentrations of n× 10–4to n× 10–8mass % with RSD of 20–30%. An AV-17 anion exchanger–nitric acid solution system was used, which allows the selective separation of rhenium from a wide variety of elements.

A new synthesis of 1H-2,3,4,5-tetrahydro-1,5-benzodiazepin-2-ones (I) by the reductive cyclization of o-nitro derivatives of N-phenyl-ß-alanine is described. It is more convenient to use the amide of acrylic acid rather than acrylic acid itself, its nitrile, or ester for the synthesis of I from the appropriate o-phenylenediamines.

The dipole moments of N-(2-hydroxy-5-alkylbenzyl)-piperidines, NN'-bis-(2-hydroxy-5-tert-amylbenzyl)-piperazine, ?-hydroxyethyl aryl sulfides, and arylmercaptoacetic acids have been determined experimentally, and also calculated by the vector method. On the basis of the results obtained, and on the IR spectra, it is shown that intramolecular hydrogen bonds exist in the above compounds, with the exception of the arylmercaptoacetic acids.

A spectrophotometric technique was used to determine the association equilibrium constants of phenol, o-isopropylphenol, p-tert-butylphenol, 3,4-, 2,5-, 2, 6-dimethylphenols, and thymol with triethylamine (in an n-heptane medium). The ultraviolet spectra recorded serve as proof of the formation of a hydrogen bond between the hydrogen atoms of the hydroxyl group and the nitrogen atom of triethylamine in these systems (phenol-triethylamine-n-heptane).