Ruban D.A.,Southern Federal University
Proceedings of the Geologists' Association | Year: 2010
Geodiversity, i.e., a diversity of geological heritage sites, can be quantified with an account of geosite types, type counterparts, and their ranks. Higher numbers of geosite types represented within a given territory and their higher ranks indicate a higher geodiversity. Two additional characteristics, namely geoabundance and georichness, allow measure of the quantity of geosites and the diversity-quantity relationship respectively. Geodiversity loss can be evaluated with an accounting of decreases in geosite type ranks linked to the damage of geosites. A calculation of relative and multi-dimensional geodiversity helps in quantitative assessment of the regional geological heritage. © 2010 The Geologists' Association.
Minkin V.I.,Southern Federal University
Russian Chemical Reviews | Year: 2013
Modern concepts of mechanisms of thermal and photochemical rearrangements responsible for the photo-chromic properties of spiropyrans, spirooxazines, spiroper-imidines and metal bis(chelate) complexes have been considered. The most important applications of spiropyrans and spirooxazines as light-controlled molecular switches of physical and biological properties of hybrid molecular and supramolecular structures and macroscopic materials have been discussed. The bibliography includes 185 references. © 2013 Russian Academy of Sciences and Turpion Ltd.
Mazuritskiy M.I.,Southern Federal University
Journal of Synchrotron Radiation | Year: 2012
Here, soft X-ray synchrotron radiation transmitted through microchannel plates is studied experimentally. Fine structures of reflection and XANES Si L-edge spectra detected on the exit of silicon glass microcapillary structures under conditions of total X-ray reflection are presented and analyzed. The phenomenon of the interaction of channeling radiation with unoccupied electronic states and propagation of X-ray fluorescence excited in the microchannels is revealed. Investigations of the interaction of monochromatic radiation with the inner-shell capillary surface and propagation of fluorescence radiation through hollow glass capillary waveguides contribute to the development of novel X-ray focusing devices in the future. © 2012 International Union of Crystallography Printed in Singapore - all rights reserved.
Vorobyov E.I.,University of Vienna |
Vorobyov E.I.,Southern Federal University
Astronomy and Astrophysics | Year: 2013
Aims. We numerically studied the formation of giant planet (GP) and brown dwarf (BD) embryos in gravitationally unstable protostellar disks and compared our findings with the directly imaged, wide-orbit (≳ 50 AU) companions that are known to-date. The viability of the disk fragmentation scenario for the formation of wide-orbit companions in protostellar disks around (sub-)solar mass stars was investigated. We focused on the likelihood of survival of GP/BD embryos formed via disk gravitational fragmentation. Methods.We used numerical hydrodynamics simulations of disk formation and evolution with an accurate treatment of disk thermodynamics. Using the thin-disk limit allowed us to probe the long-term evolution of protostellar disks, starting from the gravitational collapse of a pre-stellar core and ending in the T Tauri phase after at least 1.0 Myr of disk evolution. We focused on models that produced wide-orbit GP/BD embryos that opened a gap in the disk and showed radial migration timescales similar to or longer than the typical disk lifetime. Results.While most models showed disk fragmentation, only 6 models out of 60 revealed the formation of quasi-stable, wide-orbit GP/BD embryos. The low probability for the fragment survival is caused by efficient inward migration/ejection/dispersal mechanisms that operate in the embedded phase of star formation. We found that only massive and extended protostellar disks (≳ 0.2 M), which experience gravitational fragmentation not only in the embedded but also in the T Tauri phases of star formation, can form wide-orbit companions. Disk fragmentation produced GP/BD embryos with masses in the 3.5-43 MJ range, covering the whole mass spectrum of directly imaged, wide-orbit companions to (sub-)solar mass stars. On the other hand, our modeling failed to produce embryos on orbital distances ≲ 170 AU, whereas several directly imaged companions were found at smaller orbits down to a few AU. Disk fragmentation also failed to produce wide-orbit companions around stars with mass ≲ 0.7 M·, in disagreement with observations. Conclusions. Disk fragmentation is unlikely to explain the whole observed spectrum of wide-orbit companions to (sub-)solar-mass stars and other formation mechanisms, for instance, dynamical scattering of closely packed companions onto wide orbits, should be invoked to account for companions at orbital distance from a few tens to ∼150 AU and wide-orbit companions with masses of the host star =0.7 M·. Definite measurements of orbit eccentricities and a wider sample of numerical models are needed to distinguish between the formation scenarios of GP/BD on wide orbits. © 2013 ESO.
Yuzyuk Y.I.,Southern Federal University
Physics of the Solid State | Year: 2012
Raman investigations of the crystal lattice dynamics in classical ferroelectric perovskites SrTiO 3, PbTiO 3, and BaTiO 3 have been analyzed. The specific features revealed in the behavior of soft modes during the phase transitions occurring in ceramics and powders of these compounds, as well as in several related solid solutions, have been described. Particular attention has been paid to the investigations of ferroelectric thin films and superlattices in which the sequences of structural distortions can be radically different from those known for the initial bulk materials. © 2012 Pleiades Publishing, Ltd.