Saint Petersburg State University is a Russian federal state-owned higher education institution based in Saint Petersburg the oldest and one of the largest universities in Russia.It is made up of 22 specialized faculties, 13 research institutes, the Faculty of Military Studies, the Academic Classical School, the Medical College, the College of Physical culture and Sports, Economics and Technology and the Department of Physical Culture and Sports. As of 2014, the university has a teaching staff of 5,800. The university has two primary campuses: one on Vasilievsky Island and the other in Peterhof. During the Soviet period, it was known as Leningrad State University , in 1948–1989 named after Zhdanov. Wikipedia.
Proskurnikov A.,Saint Petersburg State University
Automatica | Year: 2013
Consensus algorithms for multi-agent networks with high-order agent dynamics, time-varying topology, and uncertain symmetric nonlinear couplings are considered. Convergence conditions for these algorithms are obtained by means of the Kalman-Yakubovich-Popov lemma and absolute stability techniques. The conditions are similar in spirit and extend the celebrated circle criterion for the stability of Lurie systems. © 2012 Elsevier Ltd. All rights reserved.
Baluev R.V.,Saint Petersburg State University
Monthly Notices of the Royal Astronomical Society | Year: 2013
We perform a detailed analysis of the latest HARPS and Keck radial velocity data for the planet-hosting red dwarf GJ 581, which attracted a lot of attention in recent time. We show that these data contain important correlated noise component ('red noise') with the correlation time-scale of the order of 10 d. This red noise imposes a lot of misleading effects while we work in the traditional white-noise model. To eliminate these misleading effects, we propose a maximum-likelihood algorithm equipped by an extended model of the noise structure. We treat the red noise as a Gaussian random process with an exponentially decaying correlation function. Using this method we prove that (i) planets b and c do exist in this system, since they can be independently detected in the HARPS and Keck data, and regardless of the assumed noise models; (ii) planet e can also be confirmed independently by both the data sets, although to reveal it in the Keck data it is mandatory to take the red noise into account; (iii) the recently announced putative planets f and g are likely just illusions of the red noise; (iv) the reality of the planet candidate GJ 581 d is questionable, because it cannot be detected from the Keck data, and its statistical significance in the HARPS data (as well as in the combined data set) drops to a marginal level of 2γ, when the red noise is taken into account. Therefore, the current data for GJ 581 really support the existence of no more than four (or maybe even only three) orbiting exoplanets. The planet candidate GJ 581 d requests serious observational verification. © 2012 The Author Published by Oxford University Press on behalf of the Royal Astronomical Society.
Golovnev A.,Saint Petersburg State University
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics | Year: 2014
Recently, an interesting gravitational model was proposed in order to mimic the effect of Dark Matter. Chamseddine and Mukhanov in the arXiv preprint 1308.5410 have separated the conformal mode of a physical metric in the form of a squared gradient of an auxiliary scalar field. Notably, the variational principle has given a more general equation of motion than that of purely Einsteinian relativity theory, with a possibility of reproducing an effective Dark Matter. In this short Letter, we explain the nature of this phenomenon in terms of the class of functions on which the variation takes place. Then we give a more transparent equivalent formulation of the model without an auxiliary metric. Finally, we speculate a bit about possible extensions. © 2013 The Author. Published by Elsevier B.V.
Zapasskii V.S.,Saint Petersburg State University
Advances in Optics and Photonics | Year: 2013
More than 30 years ago, the feasibility of detecting magnetic resonance in the Faraday-rotation noise spectrum of transmitted light was demonstrated experimentally. However, practical applications of this experimental approach have emerged only recently thanks, in particular, to a number of crucial technical advancements. This method has now become a popular and efficient tool for studying magnetic resonance and spin dynamics in atomic and solid-state paramagnets. In this paper, we present a review of research in the field of spin-noise spectroscopy, including its physical basis, its evolution since its first experimental demonstration, and its recent experimental advances. Main attention is paid to the specific capabilities of this technique that render it unique compared to other methods of magnetic and optical spectroscopy. The paper is primarily intended for experimentalists who may wish to use this novel optical technique. © 2013 Optical Society of America.
Golovnev A.,Saint Petersburg State University
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics | Year: 2012
In this Letter we present a very simple and independent argument for the absence of the Boulware-Deser ghost in the recently proposed potentially ghost-free non-linear massive gravity. The limitation is that, in its simple form, the argument is, in a sense, non-constructive and less explicit than the standard approach. However, the formalism developed here may prove to be useful for discussing the formal aspects of the theory. © 2011 Elsevier B.V.
Toukach F.V.,RAS N. D. Zelinsky Institute of Organic Chemistry |
Ananikov V.P.,Saint Petersburg State University
Chemical Society Reviews | Year: 2013
All living systems are comprised of four fundamental classes of macromolecules-nucleic acids, proteins, lipids, and carbohydrates (glycans). Glycans play a unique role of joining three principal hierarchical levels of the living world: (1) the molecular level (pathogenic agents and vaccine recognition by the immune system, metabolic pathways involving saccharides that provide cells with energy, and energy accumulation via photosynthesis); (2) the nanoscale level (cell membrane mechanics, structural support of biomolecules, and the glycosylation of macromolecules); (3) the microscale and macroscale levels (polymeric materials, such as cellulose, starch, glycogen, and biomass). NMR spectroscopy is the most powerful research approach for getting insight into the solution structure and function of carbohydrates at all hierarchical levels, from monosaccharides to oligo- and polysaccharides. Recent progress in computational procedures has opened up novel opportunities to reveal the structural information available in the NMR spectra of saccharides and to advance our understanding of the corresponding biochemical processes. The ability to predict the molecular geometry and NMR parameters is crucial for the elucidation of carbohydrate structures. In the present paper, we review the major NMR spectrum simulation techniques with regard to chemical shifts, coupling constants, relaxation rates and nuclear Overhauser effect prediction applied to the three levels of glycomics. Outstanding development in the related fields of genomics and proteomics has clearly shown that it is the advancement of research tools (automated spectrum analysis, structure elucidation, synthesis, sequencing and amplification) that drives the large challenges in modern science. Combining NMR spectroscopy and the computational analysis of structural information encoded in the NMR spectra reveals a way to the automated elucidation of the structure of carbohydrates. This journal is © The Royal Society of Chemistry 2013.
Krivovichev S.V.,Saint Petersburg State University
Angewandte Chemie - International Edition | Year: 2014
The discovery of the diffraction of X-rays on crystals opened up a new era in our understanding of nature, leading to a multitude of striking discoveries about the structures and functions of matter on the atomic and molecular scales. Over the last hundred years, about 150 000 of inorganic crystal structures have been elucidated and visualized. The advent of new technologies, such as area detectors and synchrotron radiation, led to the solution of structures of unprecedented complexity. However, the very notion of structural complexity of crystals still lacks an unambiguous quantitative definition. In this Minireview we use information theory to characterize complexity of inorganic structures in terms of their information content. Cause and complexity: Analysis of inorganic crystal structures using information-based complexity measures indicates that structural complexity is generated by the assembly of nanoscale building blocks, modularity induced by complex chemical compositions, and the formation of superlattices as a result of local atomic ordering or displacive phase transitions. Copyright © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Noskov B.A.,Saint Petersburg State University
Advances in Colloid and Interface Science | Year: 2014
Experimental results on the dynamic dilational surface elasticity of protein solutions are analyzed and compared. Short reviews of the protein behavior at the liquid-gas interface and the dilational surface rheology precede the main sections of this work. The kinetic dependencies of the surface elasticity differ strongly for the solutions of globular and non-globular proteins. In the latter case these dependencies are similar to those for solutions of non-ionic amphiphilic polymers and have local maxima corresponding to the formation of the distal region of the surface layer (type I). In the former case the dynamic surface elasticity is much higher (> 60 mN/m) and the kinetic dependencies are monotonical and similar to the data for aqueous dispersions of solid nanoparticles (type II). The addition of strong denaturants to solutions of bovine serum albumin and β-lactoglobulin results in an abrupt transition from the type II to type I dependencies if the denaturant concentration exceeds a certain critical value. These results give a strong argument in favor of the preservation of the protein globular structure in the course of adsorption without any denaturants. The addition of cationic surfactants also can lead to the non-monotonical kinetic dependencies of the dynamic surface elasticity indicating destruction of the protein tertiary and secondary structures. The addition of anionic surfactants gives similar results only for the protein solutions of high ionic strength. The influence of cationic surfactants on the local maxima of the kinetic dependencies of the dynamic surface elasticity for solutions of a non-globular protein (β-casein) differs from the influence of anionic surfactants due to the heterogeneity of the charge distribution along the protein chain. In this case one can use small admixtures of ionic surfactants as probes of the adsorption mechanism. The effect of polyelectrolytes on the kinetic dependencies of the dynamic surface elasticity of protein solutions is weaker than the effect of conventional surfactants but exceeds the error limits. © 2013 Elsevier B.V.
Rusanov A.I.,Saint Petersburg State University
Surface Science Reports | Year: 2012
Although a crack is a typical detail of a real solid, the theory of cracks in surface science was reduced to studying flat-parallel slits for a long time. The last decade has brought a number of new results related to the thermodynamic and surface science fundamentals of wedge-shaped cracks including the crack line tension. These results, essentially correcting and developing the theory of cracks, could not yet be included in the previous reviews of the author [A.I. Rusanov, Surf. Sci. Rep. 23 (1996) 173247 and A.I. Rusanov, Surf. Sci. Rep. 58 (2005) 111239] and make a subject for reviewing in this paper. Surface characteristics of a crack are described including the crack line tension as a new property that can be important for nanocracks. General thermodynamic relationships are derived, and the calculation of the thermodynamic surface and line tensions for solids with dispersion forces is given as an example. The dependence of the crack line tension on the crack size is analyzed for the conformal change (when a crack changes its size with maintaining its geometrical similarity) and the depth growth (when the distance between the crack lips is fixed). The latter has been found to be more favorable energetically. Since the presence of a crack is more probable for a loaded body, a general and rigorous approach to the thermodynamic description of loaded solids is presented including correcting earlier mistakes and terminology. The thermodynamic consideration presented outputs a useful contribution to the theory of solid strength. A generalized brittle fracture criterion is deduced and the ultimate strength is calculated for both the above mechanisms of the crack growth. The influence of the line tension on the ultimate strength is estimated both for the 2d and 3d cases. © 2012 Elsevier B.V. All rights reserved.
Noskov B.A.,Saint Petersburg State University
Current Opinion in Colloid and Interface Science | Year: 2010
Recent studies show strong influence of the dilational surface rheological properties on the stability and dynamics of foam and emulsions. On the other hand, the dilational dynamic surface elasticity proved to be highly sensitive to conformational transitions of macromolecules at fluid-fluid interfaces and can be used to investigate the adsorption mechanism and aggregate formation in the surface layer. The intention of this review consists in the discussion of recent progress in the dialtional surface rheology of solutions of non-ionic homopolymers, block copolymers, polyelectrolytes, polyelectrolyte/surfactant and protein/surfactant complexes. © 2010 Elsevier Ltd.