Spodumene and garnet luminescence excited by subnanosecond electron beams

Pulsed cathodoluminescence of spodumene and yttrium-aluminum garnet crystals activated by Mn²⁺ and Nd³⁺ ions, respectively, is investigated. The luminescence was excited upon crystal irradiation by electron beams with current densities of 35 and 100 A/cm² and average electron energy of ∼ 50 keV for 0.1, 0.25, and 0.65 ns. It is demonstrated that the electron beam duration decreased to several tenth of a nanosecond does not lead to essential changes of the mechanisms of pulsed cathodoluminescence excitation and character of its spectrum, but in this case, the intensity of luminescence of the hole centers increases compared with the intracenter luminescence.     

Raman scattering and luminescence of yttria nanopowders and ceramics

We have studied Raman scattering in yttria nanopowders and ceramics that was excited by radiation at wavelengths of 514.5 and 632.8 nm. We show that, in undoped nanopowders and cubic phase of doped yttria ceramics, only the Raman scattering by phonons is observed, with no other Raman scattering centers having been revealed. In nanopowders of the monoclinic phase, we have observed an additional Raman line with a Raman shift of 1093 ± 4 cm^?1. If all the objects under investigation are excited by the radiation at a wavelength of 514.5 nm, their spectra exhibit four series of photoluminescence lines, two of which (at λ = 521–523 and 538–564 nm) are emitted by Er³⁺ ions, “impurity” dopants, while the other two lines (at λ = 607–635 and 644–684 nm) are emitted by intrinsic centers. Under excitation by the radiation at a wavelength of 632.8 nm, only a series of bands at λ = 644–684 nm is emitted. In addition to these photoluminescence bands, neodymium-doped ceramics show photoluminescence bands of Nd³⁺ ions. We have shown that intrinsic luminescence centers, which occur in all the examined specimens, are capable of acting as acceptors with respect to neodymium ions excited to the upper laser level.     

A method for calculating the Gibbs energies of hydrophobic effects and specific interactions of nonelectrolytes in aqueous solutions

The thermodynamic characteristics of hydrophobic hydration, the Gibbs energies of hydrophobic effect, were calculated. The method for calculations was based on the division of the Gibbs energy of hydration into contributions of nonspecific interactions, specific interactions between solutes and solvents (if they exist), and hydrophobic effect. In the absence of specific interactions between solutes and water, the Gibbs energy of hydrophobic effect depended linearly on the characteristic molecular volume of the solute for substances with different structures and properties. The universality of this dependence allows the suggestion to be made that it remains valid also in the presence of specific interactions. This allows the Gibbs energy of specific interactions in water to be determined for a wide range of compounds, in particular, for aliphatic alcohols.     

Molecular complexation of uracil with bovine serum albumin and its complex with bilirubin studied by spectroscopic methods

The interactions of uracil (U) with bovine serum albumin (BSA) and its complex with bilirubin (BR·BSA) in phosphate buffer at pH 7.4 were studied by fluorescence and electronic spectroscopy. The parameters of the resulting intermolecular complexes (binding constants, quenching rate constants, the radius of the quenching sphere-of-action, etc.) were determined. The interaction of BSA with U occurs through a static quenching of protein fluorescence and has a predominantly hydrophobic character. The effect of U on the conformational changes of the protein molecule was analyzed by synchronous fluorescence spectroscopy. Uracil binds to BR·BSA more efficiently than to the free protein due to the interaction of U with the tetrapyrrole pigment incorporated in the macromolecular complex.     

Features of the altitude-time distribution of ozone over Moscow during the strong ozone depletion in spring 2011 and during the statospheric warming in 2010 according to observations at millimeter wavelengths

The new observational data at millimeter wavelengths of the vertical distribution of stratospheric ozone over Moscow during the significant ozone depletion in the Northern Hemisphere in spring 2011 and during the circulation disturbance in the mid-winter sudden stratospheric warming in 2010 are presented. Significant interannual variations in the altitude distribution of ozone concentration are detected. The revealed significant ozone variations due to large-scale atmospheric processes show the importance of the monitoring of ozonosphere by radio physical methods for studying its evolution.