Phosphorimetric determination of pyrene in gasoline and gasoline-contaminated soil samples

The determination of pyrene in gasoline and gasoline-contaminated soils using room-temperature phosphorimetry (RTP) in micellar solutions of sodium dodecyl sulfate was studied. It was found that pyrene can be selectively determined by RTP in the above materials. The accuracy of the procedure was verified by gas chromatography with mass-selective detection.     

Transmission-Type Harmonic Mixers of MM-wave Range

A new kind of harmonic mixer for use in phase locking systems for MM-wave oscillators is presented. The mixer has compact design and combines directional coupler and conventional harmonic mixer in one element. Construction and features of the mixer are discussed. Experimentally measured main characteristics of the mixer are presented. Possibility of continuous frequency scan of phase locked MM-wave oscillator within a full waveguide band is demonstrated.     

Modeling process operations in the forming of parts made of flat metal-polymer composites

The forming of complex three-dimensional parts (tubular structures, sections, shells) from flat sheets of metal-polymer composites is examined. Results are reported from a series of experimental studies of the strain and strength characteristics of these composites, and features of the fabrication of shells of single and double curvature are analyzed. One method of solving the problem of bending shells of complex shape with large displacements (deflections) beyond the elastic limit of the material is proposed and substantiated empirically.Paper to be presented at the IX International Conference on the Mechanics of Composite Materials (Riga, October, 1995).Translated from Mekhanika Kompozitnykh Materialov, Vol. 31, No. 3, pp. 417–427, May–June, 1995.     

Complexation and Self-Assembling of Sulfonatomethylated Calix[4]resorcinarene with Both Organic and Lanthanide Ions in Aqueous Media

The stoichiometry and binding constant of the paramagnetic lanthanide ion(Gd³⁺) with sulfonatomethylated calix[4]resorcinarene (H₈Xna₄) were evaluated from the NMR relaxation data. Both ¹H NMR spectroscopy and NMR relaxation data indicate that interaction of tetramethylammonium (TEMA) and N-methylpyridinium (MePy) cations with H₈Xna₄ in the presence of Ln³⁺ (Lu³⁺ or Gd³⁺) results in theformation of ternary complexes [Ln(G)H₈X] with lanthanide ions,coordinated via sulfonate groups and organic cation included intothe cavity of H₈Xna₄. The inclusion of long-chainedN-decyl-(DePy) and N-cetylpyridinium (CPy) ions into H₈Xna₄ cavity leads to self-assembling which can be revealed by NMR relaxation method with Gd³⁺ probe ions. The excess of alkylpyridinium or TEMA cations leads to disassembling of (Gd)_n(H₈X)_m(RPy)_maggregates.     

Asymptotic periodicity of trajectories of an interval

We consider dynamical systems generated by continuous mappings of an interval I into itself. We prove that the trajectory of an interval J ⊂ I is asymptotically periodic if and only if J contains an asymptotically periodic point.     

Stereochemical transformations of some seven-membered pyridoxine dimethyl ketals

According to the data of single crystal X-ray diffraction analysis and computational methods, the seven-membered rings of acylated pyridoxine acetonides have C ₂ symmetry. Two stereochemical transformations in solutions, enantiotopomerization of P-, M-conformations with spiral chirality of twist-boat forms and diastereotopomerization of structures that differ in the configuration of the phenolic oxygen substituents, were revealed by dynamic ¹H NMR spectroscopy.     

Dearomative (3+2) cycloaddition of 2-substituted 3,5-dinitropyridines and N-methyl azomethine ylide

Chemistry of Heterocyclic Compounds - 1,3-Dipolar cycloaddition of various 2-substituted 3,5-dinitropyridines and unstabilized N-methyl azomethine ylide has been studied. It was found that,...     

Crystal structure of boron difluoride acetylnaphtholates

The crystal structure of luminescent isomeric boron difluoride acetylnaphtholates: 2-acetyl-1-naphthoboron difluoride (1) and 1-acetyl-2-naphthoboron difluoride (2) has been studied. Molecules of 1 make infinite stacks of coplanar molecules in crystals, and molecules of 2 are arranged in the crystalline cell in the form of isolated π-dimers. Unlike a planar molecule of 1, the methyl group in α-position of the diketonate ring drops out of the molecule plane in a molecule of 2, thus forcing the chelate ring to bend considerably along the line C(11)-B. The structure features of 1 cause a bathochromic shift of the luminescence band in comparison with 2.