Biomimetic cyclization of Е,Е-germacranolide (+)-hanphilline

Russian Journal of General Chemistry -     

Mathematical Analysis of Inertial Waves in Rectangular Basins with One Sloping Boundary

We consider the problem of small oscillations of a rotating inviscid incompressible fluid. From a mathematical point of view, new exact solutions to the two‐dimensional Poincaré–Sobolev equation in a class of domains including trapezoid are found in an explicit form and their main properties are described. These solutions correspond to the absolutely continuous spectrum of a linear operator that is associated with this system of equations. For specialists in Astrophysics and Geophysics, the existence of these solutions signifies the existence of some previously unknown type of inertial waves corresponding to the continuous spectrum of inertial oscillations. A fundamental distinction between monochromatic inertial waves and waves of the new type is shown: usual characteristics (frequency, amplitude, wave vector, dispersion relation, direction of energy propagation, and so on) are not applicable to the last. Main properties of these waves are described. In particular, it is proved that they are progressive. Main features of their energy transfer are described.     

Modifications based on coumarins III. Synthesis of diesters of karatavic and galbanic acids and mixed diesters of coumarin acids and salicylic acid with sucrose

The synthesis of 6,6′-diesters of sucrose with natural coumarins — karatavic and galbanic acids — has been achieved by the transesterification of methyl esters of these acids with monosucrose esters of the same acids, and so has that of mixed 6,6′-diesters of these coumarin acids and salicylic acid by a reaction between methyl salicylate and a monoester of the corresponding coumarin acid. The structures of the compounds obtained have been confirmed by IR, UV, PMR, and¹³C NMR spectroscopies. A. B. Bektorov Institute of Chemical Sciences, Academy of Sciences, Republic of Kazakhstan, Almaty, fax (3272) 61 57 65. Translated from Khimiya Prirodnykh Soedinenii, No. 4, pp. 461–465, July–August, 1998.     

Observation of fine structure in the photoluminescence spectrum of an Er3+ ion in an amorphous silicon matrix

A multicomponent Stark structure corresponding to a 4I _13/2→4I _15/2 transition in the 4f ¹¹ shell of Er³⁺ ions is observed in hydrogenated amorphous silicon (a-Si:H) subjected to low-temperature (150 °C) anneal. The observation of narrow, strong components indicates that the erbium ions form a highly ordered local surrounding (Er-O-Si nanoclusters) in the labile, disordered structural network of a-Si:H. Pis’ma Zh. éksp. Teor. Fiz. 70, No. 12, 780–783 (25 December 1999) Deceased.     

Synthesis of D-Mannite Esters of Aliphatic and Aromatic Acids

Mono- and diesters of D-mannite with aliphatic acids and mixed diesters with aliphatic and aromatic acids were synthesized by transesterification of their methyl esters. The structures of the products are confirmed by PMR, ¹³ C NMR, and IR spectra     

Smooth titania nanotubes: Self-organization and stabilization of anatase phase

We present transmission electron microscopy and Raman scattering measurements showing that niobium inhibits the processes of nucleation and growth of anatase crystallites in the initial amorphous titania nanotubes and thus shifts the temperature of the complete amorphous-to-anatase phase transition to higher values up to 550 °C. Niobium dopants stabilize the anatase phase in titania nanotubes up to 650 °C. The size of anatase crystallites can reach 30–50 nm. Excess niobium atoms which are pulled off from the volume of anatase crystallite form polymeric or monomeric Ti–O–NbO groups at the interface area. Slight shift and broadening of E_g (144 cm^?1), A_1g (515 cm^?1) and E_g (630 cm^?1) modes in Raman spectra can be explained by niobium insertion into the anatase structure.     

Synthesis of D-Mannite Esters

Mono- and diesters of D-mannite with aromatic acids are synthesized. The structures of the resulting compounds are confirmed by IR spectroscopy, PMR, and ¹³ C NMR.