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Saint Petersburg, Russia

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.

Malyshev A.V.,Complutense University of Madrid | Malyshev A.V.,Zernike Institute for Advanced Materials | Malyshev V.A.,Zernike Institute for Advanced Materials | Malyshev V.A.,Saint Petersburg State University
Physical Review B - Condensed Matter and Materials Physics | Year: 2011

Optical response of an artificial composite nanodimer comprising a semiconductor quantum dot and a metal nanosphere is analyzed theoretically. We show that internal degrees of freedom of the system can manifest bistability and optical hysteresis as functions of the incident field intensity. We argue that these effects can be observed for real-world systems, such as a CdSe quantum dot and an Au nanoparticle hybrid. These properties can be revealed by measuring the optical hysteresis of Rayleigh scattering. We also show that the total dipole moment of the system can be switched abruptly between its two stable states by small changes in the excitation intensity. The latter promises various applications in the field of all-optical processing at the nanoscale, the most basic of them being the volatile optical memory. © 2011 American Physical Society.

Slesarenko V.,Saint Petersburg State University
Materials Today: Proceedings | Year: 2015

The mechanical behavior and the physical properties of shape memory alloys (SMAs) considerably depend on their structural state. The current research was devoted to the amorphous-crystalline shape memory composites produced by means of the partial isothermal crystallization from melt-spun ribbons. Previous works revealed that such composites contain amorphous matrix with embedded spherical crystalline inclusions and this structure was simulated in the current study with the help of the simple nucleation and growth model. In addition, some aspects of pseudoelastic behavior of the amorphous-crystalline composites were simulated by means of finite element analysis by ANSYS FEA software. This study revealed that pseudoelastic behavior significantly depended on the volume fraction of crystalline phase in the amorphous-crystalline shape memory composite. © 2015 The Authors.

Potapov D.K.,Saint Petersburg State University
Journal of Computer and Systems Sciences International | Year: 2013

Optimal control problems for higher order elliptic distributed systems with a spectral parameter and nonlinearity that is discontinuous in the phase variable are considered. Sufficient conditions for the nonemptiness of the set of acceptable ?control-state? pairs are found by using the variational method; topological properties of this set are studied. Existence theorems for the solution of optimization problems are proved. The optimal control in the Gol?dshtik problem of the separated flows of incompressible fluid is obtained as an application of the results. © 2013 Pleiades Publishing, Ltd.

Davydov S.Y.,RAS Ioffe Physical - Technical Institute | Sabirova G.I.,Saint Petersburg State University
Physics of the Solid State | Year: 2011

A simple M-shaped model has been proposed for the density of states of the π bands of the graphene. The model has been used to derive the expression for the local density of states on the adsorbed atom and to calculate the corresponding occupation numbers for different model parameters. Additional simplifications have made it possible to represent the band contribution n b to the total occupation number of the adatom n a in the analytical form. The contributions of local states n l to n a = n b+n l have been calculated for different parameters. The charge has been numerically evaluated for the case of adsorption of alkali metal atoms on the graphene. The results obtained have been verified using the model of a surface diatomic molecule calculated by the Harrison bond-orbital method. The verification has demonstrated that the charges calculated in terms of radically different models are in good agreement. © 2011 Pleiades Publishing, Ltd.

Krivulin N.,Saint Petersburg State University
Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics) | Year: 2014

We present a multidimensional optimization problem that is formulated and solved in the tropical mathematics setting. The problem consists of minimizing a nonlinear objective function defined on vectors over an idempotent semifield by means of a conjugate transposition operator, subject to constraints in the form of linear vector inequalities. A complete direct solution to the problem under fairly general assumptions is given in a compact vector form suitable for both further analysis and practical implementation. We apply the result to solve a multidimensional minimax single facility location problem with Chebyshev distance and with inequality constraints imposed on the feasible location area. © 2014 Springer International Publishing.

Leonov G.A.,Saint Petersburg State University | Kuznetsov N.V.,University of Jyvaskyla
International Journal of Bifurcation and Chaos | Year: 2013

From a computational point of view, in nonlinear dynamical systems, attractors can be regarded as self-excited and hidden attractors. Self-excited attractors can be localized numerically by a standard computational procedure, in which after a transient process a trajectory, starting from a point of unstable manifold in a neighborhood of equilibrium, reaches a state of oscillation, therefore one can easily identify it. In contrast, for a hidden attractor, a basin of attraction does not intersect with small neighborhoods of equilibria. While classical attractors are self-excited, attractors can therefore be obtained numerically by the standard computational procedure. For localization of hidden attractors it is necessary to develop special procedures, since there are no similar transient processes leading to such attractors. At first, the problem of investigating hidden oscillations arose in the second part of Hilbert's 16th problem (1900). The first nontrivial results were obtained in Bautin's works, which were devoted to constructing nested limit cycles in quadratic systems, that showed the necessity of studying hidden oscillations for solving this problem. Later, the problem of analyzing hidden oscillations arose from engineering problems in automatic control. In the 50-60s of the last century, the investigations of widely known Markus-Yamabe's, Aizerman's, and Kalman's conjectures on absolute stability have led to the finding of hidden oscillations in automatic control systems with a unique stable stationary point. In 1961, Gubar revealed a gap in Kapranov's work on phase locked-loops (PLL) and showed the possibility of the existence of hidden oscillations in PLL. At the end of the last century, the difficulties in analyzing hidden oscillations arose in simulations of drilling systems and aircraft's control systems (anti-windup) which caused crashes. Further investigations on hidden oscillations were greatly encouraged by the present authors' discovery, in 2010 (for the first time), of chaotic hidden attractor in Chua's circuit. This survey is dedicated to efficient analytical-numerical methods for the study of hidden oscillations. Here, an attempt is made to reflect the current trends in the synthesis of analytical and numerical methods. © 2013 The Author(s).

Bobylev V.V.,Saint Petersburg State University | Bajkova A.T.,Russian Academy of Sciences
Astronomy Letters | Year: 2012

To study the peculiarities of the Galactic spiral density wave, we have analyzed the space velocities of Galactic Cepheids with propermotions from the Hipparcos catalog and line-of-sight velocities from various sources. First, based on the entire sample of 185 stars and taking R 0 = 8 kpc, we have found the components of the peculiar solar velocity (u ⊙, v ⊙) = (7.6, 11.6) ± (0.8, 1.1) km s -1, the angular velocity of Galactic rotation Ω 0 = 27.5 ± 0.5 km s -1 kpc -1 and its derivatives Ω′ 0 = -4.12 ± 0.10 km s -1 kpc -2 and Ω″ 0 = 0.85 ± 0.07 km s -1 kpc -3, the amplitudes of the velocity perturbations in the spiral density wave f R = -6.8 ± 0.7 and f θ = 3.3 ± 0.5 km s -1, the pitch angle of a two-armed spiral pattern (m = 2) i = -4.6° ± 0.1° (which corresponds to a wavelength λ = 2.0 ± 0.1 kpc), and the phase of the Sun in the spiral density wave χ ⊙ = -193° ± 5°. The phase χ ⊙ has been found to change noticeably with the mean age of the sample. Having analyzed these phase shifts, we have determined the mean value of the angular velocity difference Ω p - Ω, which depends significantly on the calibrations used to estimate the individual ages of Cepheids. When estimating the ages of Cepheids based on Efremov's calibration, we have found {pipe}Ω p - Ω 0{pipe} = 10 ± 1 stat ± 3 syst km s -1 kpc -1. The ratio of the radial component of the gravitational force produced by the spiral arms to the total gravitational force of the Galaxy has been estimated to be f r0 = 0.04 ± 0.01. © 2012 Pleiades Publishing, Ltd.

Altenbach H.,Otto Von Guericke University of Magdeburg | Eremeyev V.A.,Otto Von Guericke University of Magdeburg | Eremeyev V.A.,Scientific University of the South | Morozov N.F.,Saint Petersburg State University
International Journal of Engineering Science | Year: 2012

We discuss the influence of surface viscoelasticity effects on the effective properties of materials such as effective bending stiffness of plates or shells. Viscoelastic properties in the vicinity of the surface can differ from the properties of the bulk material. This difference influences the behavior of nanostructural elements. In particular, the surface viscoelastic stresses are responsible for the size-depended dissipation of nanosized structures. Using the extension of the Gurtin-Murdoch model and the correspondence principle of linear viscoelasticity we derive the expressions of the stress and couple stress resultant tensors for shear deformable plates and shells. © 2012 Elsevier Ltd. All rights reserved.

Bogdanov S.P.,Saint Petersburg State University
Glass Physics and Chemistry | Year: 2011

The capabilities of the iodide transport method for the deposition of coatings on powders have been investigated. It has been demonstrated that this process is affected by different factors, such as the temperature, time, structure of the substrate material, and its dispersity. © 2011 Pleiades Publishing, Ltd.

A new tribe, Iscini tr. n., comprising the Oriental genera Isca Gillies 1951 and Notophlebia Peters & Edmunds 1970, is established. A new species, Notophlebia ganeshi sp. n., is described based on male and female imagos reared from larvae. The new species markedly differs from N. jobi Sivaramakrishnan & Peters 1984 by its non-specialized larval mouth apparatus. The larva of N. jobi has a highly specialized mouth apparatus of the «Dilatognathus- type»; this type of mouth apparatus has evolved independently in several non-related leptophlebiid taxa. © Copyright 2014 Magnolia Press.

Ovid'Ko I.A.,Saint Petersburg State University
Reviews on Advanced Materials Science | Year: 2012

Conventional curved carbon nanostructures such as fullerenes, capped nanotubes and cones can be produced by insertion of pentagons-sources of highly concentrated curvature - Into initially flat hexagonal lattice of single crystalline graphene. This paper is focused on a new approach (suggested and biefly discussed earlier [I.A. Ovid'ko II Rev. Adv. Mater. Sci. 30 (2012) 201]) which potentially allows one to fabricate principally new curved carbon nanostructures with arbitrary geometries/shapes. The approach represents insertion of special defects into grain boundaries (GBs) of initially flat polycrystalline graphene. Since special defects typically serve as flexible sources of weakly concentrated curvature, this approach opens intriguing possibilities to fabricate new carbon nanostructures with novel properties controlled by their curvature. In particular, elastic strains created by weakly varying curvature in polycrystalline graphene can effectively tailor its electronic properties and thus be exploited in electronics based on design of moderately curved graphene. Also, in this paper, technological schemes/strategies are outlined which can be potentially exploited in the fabrication of new curved carbon nanostructures through GB engineering in graphene. © 2012 Advanced Study Centre Co. Ltd.

Syromyatnikov A.V.,Saint Petersburg State University
Physical Review B - Condensed Matter and Materials Physics | Year: 2012

We discuss spin-12 one-dimensional (1D) and quasi-1D magnets with competing ferromagnetic nearest-neighbor J 1 and antiferromagnetic next-nearest-neighbor J exchange interactions in a strong magnetic field H. It is well known that, due to attraction between magnons, quantum phase transitions (QPTs) take place at H=H s from the fully polarized phase to the nematic phase if J>|J 1|/4. Such a transition at J>0.368|J 1| is characterized by a softening of the two-magnon bound-state spectrum. Using a bond-operator formalism we propose a bosonic representation of the spin Hamiltonian containing, aside from bosons describing one-magnon spin-1 excitations, a boson describing spin-2 excitations whose spectrum coincides at H≥H s with the two-magnon bound-state spectrum obtained before. The presence of the bosonic mode in the theory that softens at H=H s makes the QPT consideration substantially standard. In the 1D case at H

Sidorenko M.S.,Saint Petersburg State University | Perel M.V.,RAS Ioffe Physical - Technical Institute
Physical Review B - Condensed Matter and Materials Physics | Year: 2012

A simple analytical explanation of the directed diffraction phenomenon is presented. This phenomenon is shown to be associated with the hyperbolic points of a dispersive surface. The simplest one-dimensional model of the photonic crystal is taken to demonstrate the theory. The hyperbolic points correspond to the lower boundaries of band gaps. The phenomenon was observed both analytically and numerically by using FDTD simulation. © 2012 American Physical Society.

Kol'tsov A.B.,Saint Petersburg State University
Geochemistry International | Year: 2010

In this paper, we consider numerical simulation of mineral deposition from hydrothermal solutions under variable temperature and pressure conditions. The influence of solution source temperature depth, composition, and degree of oxidation on the composition of the products of mineral formation was evaluated. Conditions and reasons for the development of solution supersaturation/undersaturation with respect to major vein minerals were analyzed. Coupled variations in the degrees of dissociation of acids and complexes of major elements play the leading role in the formation of particular mineral assemblages. Chemical composition and degree of oxidation of the source of solutions modify vein mineralization but do not fundamentally change its character. The cooling, heating, and decompression of solutions result in the formation of distinctive mineral assemblages. This allows the use of data on the qualitative and quantitative composition of veins for the estimation of the conditions of solution evolution and its source. © 2010 Pleiades Publishing, Ltd.

Lyalin A.,Hokkaido University | Lyalin A.,Saint Petersburg State University | Taketsugu T.,Hokkaido University
Faraday Discussions | Year: 2011

The specific role played by small gold nanoparticles supported on the rutile TiO2(110) surface in the processes of adsorption and dissociation of H2 is discussed. It is demonstrated that the molecular and dissociative adsorption of H2 on Aun clusters containing n = 1, 2, 8 and 20 atoms depends on cluster size, geometry structure, cluster flexibility and the interaction with the support material. Rutile TiO2(110) support energetically promotes H2 dissociation on gold clusters. It is demonstrated that the active sites towards H2 dissociation are located at corners and edges on the surface of the gold nanoparticle in the vicinity of the support. The low coordinated oxygen atoms on the TiO2(110) surface play a crucial role for H2 dissociation. Therefore the catalytic activity of a gold nanoparticle supported on the rutile TiO2(110) surface is proportional to the length of the perimeter interface between the nanoparticle and the support. © 2011 The Royal Society of Chemistry.

Kukushkin V.Yu.,Saint Petersburg State University
Journal of Organic Chemistry | Year: 2010

Chemical Equation Presented 1,3-Dipolar cycloadditions of a series of 12 allyl-anion type 1,3-dipoles X=Y+-Z- (X, Z = CH 2, NH, O.; Y = N(Me), O) to acetonitrile MeC≡N, both free and coordinated to PtII and PtIV in the complexes trans-[PtCln(NCMe)2] (n = 2, 4), were investigated by theoretical methods. The reactivity increases along the following sequence of dipoles, the first three being inert toward nitriles: ON(Me)O < NHN(Me)O < NHN(Me)NH < CH2N(Me)O < OOO ≈ NHONH < CH 2N(Me)NH < NHOO < CH2N(Me)CH2 < CH 2OCH2RSCH2ONH < CH2OO. The thermodynamic stability of the cycloaddition products (reaction energies) inversely correlates with the activation energies with exception of dioxadiazoles N=C(Me)OONH which cannot exist in the uncoordinated state. A complete ortho selectivity of these reactions is predicted. Coordination of MeCN to platinum accelerates the reactions of CH2N(Me)CH2, CH2ONH, and particularly CH2N(Me)O and CH2N(Me)NH and stabilizes the corresponding products. Coordination accelerates the reactions of CH2OCH2, CH2OO, and NHONH only slightly and inhibits the reactions of NHOO and OOO. The cycloadditions of nitrones to nitriles are potentially interesting for dynamic combinatorial chemistry. The details of the reaction mechanisms and correlations of activation and reaction energies, synchronicity, and charge transfer vs dipole nature, FMO energies, atomic charges, HSAB properties, distortion energies, and regioisomeric pathways are discussed. C© 2010 American Chemical Society.

Rusanov A.I.,Saint Petersburg State University
Nanoscale | Year: 2014

The theory presented enables calculating the cohesive energy and line energy (the work of formation of the unit border line length) of graphene from the first-principles data, which also yields estimate of the line tension of graphene at zero temperature. Contributions from chemical bonds and dispersion forces have been estimated separately to give a summary value of 16.7 × 10-10 J m-1 for the line energy of graphene. The significance of line energy and line tension for nanotube formation is discussed. © 2014 the Partner Organisations.

Armenise I.,CNR Institute of Inorganic Methodologies and Plasmas | Kustova E.V.,Saint Petersburg State University
Chemical Physics | Year: 2014

In the present paper, state-to-state model of vibrational-chemical kinetic and transport processes is applied to study heat and mass transfer in non-equilibrium flows of CO2 and air mixtures under atmospheric entry conditions. Different contributions to the heat flux typical for the state-to-state approach are considered: fluxes due to heat conduction, mass diffusion, thermal diffusion, and diffusion of vibrational energy. For several test cases, vibrational distributions, chemical composition, temperature profiles as well as the transport coefficients and heat flux are calculated along the stagnation line. Various models for diffusion velocities are considered. For a non-catalytic surface, the role of thermal diffusion process is found to be important in some test cases. Prandtl and Schmidt numbers are calculated along the stagnation line, and it is shown that they are essentially non-constant. The influence of Prandtl and Schmidt numbers on the diffusion velocities and heat flux is evaluated. © 2013 Elsevier B.V. All rights reserved.

Voshchinnikov N.V.,Saint Petersburg State University | Hirashita H.,Academia Sinica, Taiwan
Monthly Notices of the Royal Astronomical Society | Year: 2014

We apply the time evolution of grain size distributions through accretion and coagulation found in our previous work to the modelling of the wavelength dependence of interstellar linear polarization. We focus in particular on the parameters of the Serkowski curve K and λmax, characterizing the width and maximum wavelength of this curve, respectively. We use aligned silicate and non-aligned carbonaceous spheroidal particles with different aspect ratios a/b. The imperfect alignment of grains with sizes larger than a cut-off size rV,cut is considered. We find that the evolutionary effects on the polarization curve are negligible in the original model with commonly used material parameters (hydrogen number density nH =103 cm-3, gas temperature Tgas =10 K and sticking probability for accretion Sacc =0.3). Therefore, we apply the tuned model, where the coagulation threshold of silicate is removed. In this model, λmax displaces to longerwavelengths and the polarization curve becomes wider (K reduces) on timescales ~(30-50)(nH/103cm-3)-1 Myr. The tuned models at T ≲ 30(nH/103cm-3)-1 Myr and different values of the parameters rV,cut can also explain the observed trend between K and λmax. It is significant that the evolutionary effect appears in the perpendicular direction to the effect of rV,cut on the K - λmax diagram. Very narrow polarization curves can be reproduced if we change the type of particles (prolate/oblate) and/or vary a/b. © 2014 The Authors.

Abakumov E.V.,Saint Petersburg State University
Eurasian Soil Science | Year: 2010

Original data on humus-forming substances and their elemental and biochemical compositions in Antarctic soils are discussed. Mosses, lichens, algae, remains of higher vascular plants, and penguin guano of two types differ considerably in their chemical compositions. This leads to significant differences in the formation of humic substances in plant materials themselves in the course of their transformation. However, no significant differences in the composition of humus in the fine earth of soils developing under different humus-forming materials have been revealed, which may be related to the extremely low rates of humification. Significant differences between the soils of Antarctic landscapes proper and the soils of the Subantarctic King George Island are only observed in the humus enrichment with nitrogen. The soils of Antarctica are low-humus soils with the humate-fulvate or fulvate types of humus. © 2010 Pleiades Publishing, Ltd.

Hubrig S.,Leibniz Institute for Astrophysics Potsdam | Scholler M.,European Southern Observatory | Kholtygin A.F.,Saint Petersburg State University
Monthly Notices of the Royal Astronomical Society | Year: 2014

Our recent search for the presence of a magnetic field in the bright early A-type supergiant HD 92207 using FOcal reducer low dispersion spectrograph (FORS) 2 in spectropolarimetric mode indicated the presence of a longitudinal magnetic field of the order of a few hundred gauss. Assuming the ideal case of a non-variable star, this discovery has recently been questioned in one work trying to demonstrate the importance of non-photon noise in FORS 2 observations. The assumption of non-variability of HD 92207 can, however, not be held since substantial profile variations of diverse lines on a time-scale of minutes or maybe even a fraction of a minute are detected in FORS 2 spectra. The presence of short-term spectral variability in blue supergiants, which are considered as Type II supernova progenitors, has not been a subject of systematic studies before and is critical for the current theoretical understanding of their physics. Given the detected short-term variability, the question of the presence of a magnetic field cannot be answered without proper modelling of the impact of such a variability on the measurements of the magnetic field. Since the short-term periodicity does not fit into the currently known domain of non-radially pulsating supergiants, its confirmation is of great importance for models of stellar evolution. © 2014 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society.

Ovid'ko I.A.,Saint Petersburg State University
Reviews on Advanced Materials Science | Year: 2013

This article briefly summarizes the information now available, from recent experiments, computer simulations and theoretical models, addressing the outstanding mechanical properties of graphene. In particular, experimental data on superior strength and extremely high in-plane stiffness of pristine graphene are presented. The role of dislocations as carriers of plastic flow in graphene is discussed. Special attention is devoted to the effects of grain boundaries in polycrystalline graphene on its strength.Also, enhancement of fracture toughness due to graphene inclusions in nanocomposites is considered. Finally, important unsolved problems in interdisciplinary fundamental science and applied research of the mechanical properties exhibited by graphene are outlined. © 2013 Advance Study Center Co. Ltd.

Malkin Z.,Saint Petersburg State University
Monthly Notices of the Royal Astronomical Society | Year: 2014

During the last few years, much attention has been paid to the astrometric implications of the galactic aberration in proper motions (GA). This effect causes systematic errors in astrometric measurements at a μas level. Some authors consider it so serious that it requires redefinition of the Celestial Reference Frame (CRF). We argue that such attention to the GA is exaggerated too much. It is just a small astrometric correction that must be taken into account during highly accurate astrometric and geodetic data processing. The accuracy of this correction depends on the accuracy of the Galactic rotation parameters and, for most applications, on the ccuracy of the rotation matrix between Galactic and equatorial systems. Our analysis has shown that our current knowledge of these two factors is sufficient to compute the correction of the GA with an accuracy better than 10 per cent. The remaining effect at the level of a few tenths μas yr-1 is negligible nowadays. Another consequence of introducing the GA correction is the necessity to return to classical astrometric modelling of the extragalactic radio source position - derived by very-long-baseline interferometry (VLBI) - by the linear trend model. Changing the current paradigm of the VLBI-derived CRF, based on the assumption of zero motion of radio sources, to classical one leads to bias in the radio source positions of up to several tens of μas for a catalogue at epoch J2000.0. © 2014 The Author Published by Oxford University Press on behalf of the Royal Astronomical Society.

Zaitsev A.N.,Saint Petersburg State University
Geology of Ore Deposits | Year: 2010

The extinct Quaternary Kerimasi volcano located in the southern part of the Gregory Rift, northern Tanzania, contains both intrusive and extrusive calciocarbonatites. One carbonate mineral with a high content of Na and Ca has been found in a sample of volcanic carbonatite, which is probably a cumulate rock. On the basis of Raman spectroscopy and SEM/EDS, this mineral was identified as nyerereite, ideally Na2Ca(CO3)2. It occurs as solid inclusions up to 300 × 200 μm in size in magnetite and contains (wt. %) 25.4-27.4 Na2O, 26.0-26.8 CaO, 1.6-1.9 K2O, 0.6-1.8 FeO, 0.3-0.6 SrO, <0.4 BaO, 1.4-2.3 SO3, and 0.6-0.9 P2O5. The average mineral formula is (Na1.84K0.08)Σ1.92(Ca1.00Fe0.03Sr0.01)Σ1.04[(CO3)1.91(SO4)0.05(PO4)0.02]Σ1.98. A few inclusions in magnetite also contain calcite, which is considered here to be a late-stage, subsolidus mineral. The occurrence of nyerereite in carbonatite supports Hay's (1983) idea that some of the extrusive carbonatites at the Kerimasi volcano were originally alkaline rich and contained both calcite and nyerereite as primary minerals. © 2010 Pleiades Publishing, Ltd.

Sorokin A.O.,RAS Petersburg Nuclear Physics Institute | Syromyatnikov A.V.,Saint Petersburg State University
Physical Review B - Condensed Matter and Materials Physics | Year: 2012

We carry out Monte Carlo simulations to discuss critical properties of a classical two-dimensional XY frustrated helimagnet on a square lattice. We find two successive phase transitions upon the temperature decreasing: the first one is associated with breaking of a discrete Z 2 symmetry and the second one is of the Berezinskii-Kosterlitz-Thouless (BKT) type at which the SO(2) symmetry breaks. Thus, a narrow region exists on the phase diagram between lines of the Ising and the BKT transitions that corresponds to a chiral spin liquid. © 2012 American Physical Society.

Pitjeva E.V.,Russian Academy of Sciences | Pitjev N.P.,Saint Petersburg State University
Solar System Research | Year: 2012

More than 635 thousand positional observations of planets and spacecraft of various types (mostly radiotechnical ones, 1961-2010) were used to estimate possible changes in the gravitational constant, Sun's mass, and semi-major axes of planetary orbits, as well as the associated value of the astronomical unit. The observations were analyzed based on the EPM2010 ephemerides constructed at the Institute of Applied Astronomy (Russian Academy of Sciences) in a post-Newtonian approximation as a result of simultanious numerical integration of the equations of motion of nine major planets, the Sun, the Moon, asteroids, and trans-Neptunian objects. The heliocentric gravitational constant GM ⊙ was found to vary with a rate of (GṀ ⊙/GM ⊙ = (-5.0 ± 4.1)) × 10 -14 per year (at the 3σ level). The positive secular changes in the semimajor axes ȧ i/a i were found for Mercury, Venus, Mars, Jupiter, and Saturn provided by high-precision observations. These changes also correspond to the decrease in the heliocentric gravitational constant. The changing of GM ⊙, itself is probably caused by the loss of the mass M ⊙ of the Sun due to its radiation and solar wind; these effects are partly compensated by the material falling onto the Sun. Allowing for the maximum bounds on the possible change in the Sun's mass M ⊙, it has been found from the change obtained in GM ⊙ that the annual change Ġ/G of the gravitational constant G falls within the interval -4.2 × 10 -14 < ȧ/G < +7.5 × 10 -14 with a 95% probability. The astronomical unit (AU) is connected by its definition only with the heliocentric gravitational constant. The decrease of GM ⊙ obtained in this paper should correspond to a secular decrease in the AU. It is shown, however, that the modern level of accuracy does not allow us to determine a change in the AU. The attained posibility of determining changes in GM ⊙ using high-accuracy observations encourages us to have a relation between GM ⊙ and the AU fixed for a certain moment in time, since it is inconvenient to have a time-dependent length for the AU. © 2012 Pleiades Publishing, Ltd.

Kozlov V.V.,Saint Petersburg State University | Rosanov N.N.,S. I. Vavilov State Optical Institute
Physical Review A - Atomic, Molecular, and Optical Physics | Year: 2013

Generation of single-cycle pulses from a laser passively mode locked by the technique of coherent mode locking is theoretically demonstrated for the case when resonant lines of both the gain and absorbing media are inhomogeneously broadened. In contrast to conventional mode-locked lasers, for which the inhomogeneous nature of line broadening sets a severe limitation on their performance, here, the stable single-cycle pulse operation is shown to persist even when the spectral widths of the inhomogeneously broadened lines of the amplifier and the absorber become nearly as wide as the central resonance frequency of their two-level transitions. This study is aimed at showing the potential for application of the coherent-mode-locking technique for quantum-dot lasers, which are typically characterized by a great amount of inhomogeneous broadening. © 2013 American Physical Society.

Bajkova A.T.,Russian Academy of Sciences | Bobylev V.V.,Saint Petersburg State University
Astronomy Letters | Year: 2012

To redetermine the Galactic spiral density wave parameters, we have performed a spectral (Fourier) analysis of the radial velocities for 44 masers with known trigonometric parallaxes, proper motions, and line-of-sight velocities. The masers are distributed in awide range of Galactocentric distances (3.5 kpc < R < 13.2 kpc) and are characterized by a wide scatter of position angles θ in the Galactic XY plane. This has required an accurate allowance for the dependence of the perturbation phase both on the logarithm of the Galactocentric distances and on the position angles of the objects. To increase the significance of the extraction of periodicities from data series with large gaps, we have proposed and implemented a spectrum reconstruction method based on a generalized maximum entropy method. As a result, we have extracted a periodicity describing a spiral density wave with the following parameters from the maser radial velocities: the perturbation amplitude f R = 7.7 -1.5 +1.7km s -1, the perturbation wavelength λ = 2.2 -0.1 +0.4kpc, the pitch angle of the spiral density wave i = -5 -0.9° +0.2°, and the phase of the Sun in the spiral density wave χ ⊙ = -147 -17° +3°. © 2012 Pleiades Publishing, Ltd.

Balysheva O.L.,Saint Petersburg State University
Automation and Remote Control | Year: 2016

The modern materials and types of the substrates used for the surface acoustic wave (SAW) devices are considered and their special requirements for the SAW sensors are discussed. A classification of the SAWsensors is given, and the factors of SAWsensors design and materials choice criteria are discussed. © 2016, Pleiades Publishing, Ltd.

The effective differential cross section (DCS) for elastic scattering of electrons by atoms is proposed that reproduces known energy dependences for the first and second transport cross sections but provides a total elastic cross section that is significantly small compared with the known energy dependences. The number of elastic collisions of electrons in matter when using the effective DCS in Monte Carlo simulations is significantly lower than that when using the real DCS. The results of our Monte Carlo simulation of electron propagation in aluminium using the proposed DCS are in good agreement with experimental data. © 2010 The Royal Swedish Academy of Sciences.

Bandura A.V.,Saint Petersburg State University | Kubicki J.D.,Pennsylvania State University | Sofo J.O.,Pennsylvania State University
Journal of Physical Chemistry C | Year: 2011

Plane wave density functional theory (DFT) calculations have been performed to study the atomic structure, preferred H 2O adsorption sites, adsorption energies, and vibrational frequencies for water adsorption on the ?-quartz (101) surface. Surface energies and atomic displacements on the vacuum-reconstructed, hydrolyzed, and solvated surfaces have been calculated and compared with available experimental and theoretical data. By considering different initial positions of H 2O molecules, the most stable structures of water adsorption at different coverages have been determined. Calculated H 2O adsorption energies are in the range ?55 to ?65 kJ/mol, consistent with experimental data. The lowest and the highest O?H stretching vibrational bands may be attributed to different states of silanol groups on the water-covered surface. The dissociation energy of the silanol group on the surface covered by the adsorption monolayer is estimated to be +80 kJ/mol. The metastable states for the protonated surface bridging O atoms (O br), which may lead to hydrolysis of siloxane bonds, have been investigated. The calculated formation energy of a Q 2 center from a Q 3 center on the (101) surface with 2/3 dense monolayer coverage is equal to +70 kJ/mol which is in the range of experimental activation energies for quartz dissolution. © 2011 American Chemical Society.

Pavilaynen G.V.,Saint Petersburg State University
AIP Conference Proceedings | Year: 2015

The results for the bending of a cantilever beam with the SD-effect under a concentrated load are discussed. To solve this problem, the standard Bernoulli-Euler hypotheses for beams and the Ilyushin model of perfect plasticity are used. The problem is solved analytically for structural steel A40X. The SD-effect for elastic-plastic deformations is studied. The solutions for beam made of isotropic material and material with the SD-effect are compared. © 2015 AIP Publishing LLC.

This is a parallelized algorithm performing a decomposition of a noisy time series into a number of sinusoidal components. The algorithm analyses all suspicious periodicities that can be revealed, including the ones that look like an alias or noise at a glance, but later may prove to be a real variation. After the selection of the initial candidates, the algorithm performs a complete pass through all their possible combinations and computes the rigorous multifrequency statistical significance for each such frequency tuple. The largest combinations that still survived this thresholding procedure represent the outcome of the analysis.The parallel computing on a graphics processing unit (GPU) is implemented through CUDA and brings a significant performance increase. It is still possible to run FREDEC solely on CPU in the traditional single-threaded mode, when no suitable GPU device is available.To verify the practical applicability of our algorithm, we apply it to an artificial time series as well as to some real-life exoplanetary radial-velocity data. We demonstrate that FREDEC can successfully reveal several known exoplanets. Moreover, it detected a new 9.8-day variation in the Lick data for the five-planet system of 55Cnc. It might indicate the existence of a small sixth planet in the 3:2 commensurability with the planet 55Cncb, although this detection is model-dependent and still needs a detailed verification. © 2013 Elsevier B.V.

Eremin D.B.,RAS N. D. Zelinsky Institute of Organic Chemistry | Ananikov V.P.,Saint Petersburg State University
Organometallics | Year: 2014

Acetonitrile solutions of nickel(II) acetylacetonate, which is ubiquitously used in different fields of organometallic chemistry and catalysis, were investigated by means of electrospray ionization mass spectrometry (ESI-MS) and tandem mass spectrometry (MS/MS). The detected Ni2(acac)3 + ion with the binuclear Ni2O2 core underwent a wide range of reactions after collision-induced dissociation, leading to a variety of products. Activation of C-H, C-C, and C-O bonds was observed involving the binuclear nickel complex. In sharp contrast, similar ions involving mononuclear and trinuclear nickel species did not show such exceptional behavior. The findings may open a fascinating direction in the field of superatoms to develop new chemical transformations for organometallic chemistry and catalysis. The higher relative stability of binuclear species was also observed in ESI mass spectra of copper and vanadyl complexes with acetylacetonate ligands, Cu2(acac)3 + and (VO)2(acac)3 +. An important point concerns the purity of the studied solutions, since even a trace level of contaminants has drastically diminished the outcome of the mechanistic studies. © 2014 American Chemical Society.

Vassilevich D.V.,Federal University of ABC | Vassilevich D.V.,Saint Petersburg State University
Classical and Quantum Gravity | Year: 2010

It is well known that for a given Poisson structure one has infinitely many star products related through the Kontsevich gauge transformations. These gauge transformations have an infinite functional dimension, corresponding to an infinite number of degrees of freedom per point of the base manifold. We show that on a symplectic manifold this freedom may be almost completely eliminated if one extends the star product to all tensor fields in a covariant way and impose some natural conditions on the tensor algebra. The remaining ambiguity corresponds either to constant renormalizations to the symplectic structure, or to maps between classically equivalent field theory actions. We also discuss how one can introduce the Riemannian metric in this approach and the consequences of our results for noncommutative gravity theories. © 2010 IOP Publishing Ltd.

Andronov I.V.,Saint Petersburg State University
Acoustical Physics | Year: 2010

Waves localized along a periodic set of point inhomogeneities in a thin elastic plate are studied. The cases of point masses and the cases of small-radius holes in an isolated plate and in a plate that is in contact with an acoustic medium are considered. The holes are modeled with the use of generalized point models. © Pleiades Publishing, Ltd., 2010.

Zolotarev V.M.,Saint Petersburg State University
Optics and Spectroscopy (English translation of Optika i Spektroskopiya) | Year: 2012

The possibility of using the derivative transform method in reflectance spectroscopy is analyzed. It is shown that the first derivative of the external-reflectance spectrum obtained under near normal-incidence conditions allows straightforward determination of the position of the absorption-band maximum for low-intensity bands. © Pleiades Publishing, Ltd., 2012.

Glazov M.M.,RAS Ioffe Physical - Technical Institute | Yugova I.A.,Saint Petersburg State University | Efros A.L.,U.S. Navy
Physical Review B - Condensed Matter and Materials Physics | Year: 2012

We predict a new physical mechanism to explain the electron spin precession frequency focusing effect recently observed in singly charged quantum dots exposed to a periodic train of resonant circularly polarized short optical pulses. We show that electron spin precession in an external magnetic field and a field of nuclei creates a Knight field oscillating at the frequency of the nuclear spin resonance. This field drives the projection of the nuclear spin onto the magnetic field to the value that makes the electron spin precession frequency a multiple of the train cyclic repetition frequency, the condition at which the Knight field vanishes. © 2012 American Physical Society.

Ovid'ko I.A.,Saint Petersburg State University | Sheinerman A.G.,Russian Academy of Sciences
European Journal of Mechanics, A/Solids | Year: 2012

A theoretical model is suggested which describes generation and growth of nanoscale cracks (nanocracks) near tips of blunt cracks in nanocrystalline solids. Within the model, stress concentration near pre-existent/growing blunt cracks induces grain boundary sliding which leads to formation of dislocations at triple junctions of grain boundaries. The superposition of the external stress concentrated near tips of blunt cracks and stresses created by these dislocations is capable of initiating generation and growth of nanocracks. The characteristics of the nanocrack generation and growth in nanocrystalline Al and α-Fe are calculated, and the effects of these processes on toughness/ductility of nanocrystalline solids are discussed. © 2011 Elsevier Masson SAS. All rights reserved.

Ovid'Ko I.A.,Saint Petersburg State University
Scripta Materialia | Year: 2012

Crystals are conventionally treated to be deformed through generation and evolution of crystal lattice defects. In this paper, nanoscale amorphization (NA; formation of nanoscale amorphous regions in crystals under mechanical load) is suggested and theoretically described as a special/alternative deformation mode operating in crystalline solids. It is shown that NA can contribute effectively to plastic flow in crystalline Ni and Si nanowires. © 2011 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Miroshnichenko G.P.,Saint Petersburg State University
Optics and Spectroscopy (English translation of Optika i Spektroskopiya) | Year: 2012

A phenomenological Hamiltonian of photons in a single-mode stochastic inhomogeneous optical fiber (OF) is derived. Quantization of radiation is performed in the basis of an ideal OF with proper calibration that ensures transversality of the electric-field-displacement vector. Stochastic parameters of the Hamiltonian are determined by using the reciprocal tensor of the dielectric permittivity averaged over the OF segment volume. The Hamiltonian is parametrized by three phenomenological parameters and preserves the number of photons. It is assumed that the segment of the OF is divided into random subsegments with optical parameters defined by the Wiener process with respect to the longitudinal coordinate. The temporal dynamics of the single-photon density matrix is analyzed in the basis of states with orthogonal polarizations. The relative quantum beat error rate in the sifted quantum key distributed according to the BB84 protocol with polarization coding of information averaged over the scatter of the OF parameters is calculated. © Pleiades Publishing, Ltd., 2012.

Malkin Z.,Saint Petersburg State University
IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control | Year: 2016

The Allan variance (AVAR) was introduced 50 years ago as a statistical tool for assessing the frequency standards deviations. For the past decades, AVAR has increasingly been used in geodesy and astrometry to assess the noise characteristics in geodetic and astrometric time series. A specific feature of astrometric and geodetic measurements, as compared with clock measurements, is that they are generally associated with uncertainties; thus, an appropriate weighting should be applied during data analysis. In addition, some physically connected scalar time series naturally form series of multidimensional vectors. For example, three station coordinates time series X, Y, and Z can be combined to analyze 3-D station position variations. The classical AVAR is not intended for processing unevenly weighted and/or multidimensional data. Therefore, AVAR modifications, namely weighted AVAR (WAVAR), multidimensional AVAR (MAVAR), and weighted multidimensional AVAR (WMAVAR), were introduced to overcome these deficiencies. In this paper, a brief review is given of the experience of using AVAR and its modifications in processing astrogeodetic time series. © 2015 IEEE.

Rusanov A.I.,Saint Petersburg State University
Colloid Journal | Year: 2016

Specific features of surfactant diffusion in micellar systems are described in terms of mobility, i.e., the limiting velocity of a particle under the action of a unit force. Micellar solutions of nonionic and ionic surfactants are analyzed. A relation is established between average surfactant mobility and the mobilities of individual particles. Although micelles have a lower mobility than monomers have, the average mobility of surfactants is shown to increase rather than decrease upon micellization. In parallel, formulas describing diffusion coefficients are derived, with part of the formulas having been available in the literature. © 2016, Pleiades Publishing, Ltd.

Nikiforov K.,Saint Petersburg State University
AIP Conference Proceedings | Year: 2015

The software complex developed in MATLAB allows modelling of function of diode and triode structures based on field emission electron sources with complex sub-micron geometry, their volt-ampere characteristics, calculating distribution of electric field for educational and research needs. The goal of this paper is describing the physical-mathematical model, calculation methods and algorithms the software complex is based on, demonstrating the principles of its function and showing results of its work. For getting to know the complex, a demo version with graphical user interface is presented. © 2015 AIP Publishing LLC.

Tsyganenko N.A.,Saint Petersburg State University
Journal of Geophysical Research: Space Physics | Year: 2010

Four data-based models of the magnetospheric magnetic field were tested for the degree of their consistency with a static balance between the magnetic and plasma stresses. To that end, best fit distributions of the plasma sheet pressure and its anisotropy were derived in the midnight meridian plane, using two specific forms of the particle distribution function. The tailward limit of the modeling region was placed at R = 20 RE, where the condition of pressure balance with the tail lobe field was used to avoid the multiplicity of solutions of the force balance equation. Best fit solutions were derived by minimizing the rms difference between the magnetic and plasma stress vectors over a set of points within the model plasma sheet at distances 5 R 20 R E. The obtained equatorial profiles of P⊥ and P ∥ demonstrate a steep decrease of both pressures from the inner to outer boundary and a strong overall increase from quiet to disturbed conditions. The anisotropy ratio = P∥/P⊥ was found to significantly deviate from unity in the case of TU82 and T87 models, with progressively higher values of at larger tailward distances. By contrast, more recent T89 and T96 models yielded more realistic results with nearly isotropic pressure in the tail and a moderate pancake-type anisotropy in the inner magnetosphere, consistent with observations. © 2010 by the American Geophysical Union.

Lejzerowicz F.,University of Geneva | Voltsky I.,Saint Petersburg State University | Pawlowski J.,University of Geneva
Deep-Sea Research Part II: Topical Studies in Oceanography | Year: 2013

Metagenetics represents an efficient and rapid tool to describe environmental diversity patterns of microbial eukaryotes based on ribosomal DNA sequences. However, the results of metagenetic studies are often biased by the presence of extracellular DNA molecules that are persistent in the environment, especially in deep-sea sediment. As an alternative, short-lived RNA molecules constitute a good proxy for the detection of active species. Here, we used a metatranscriptomic approach based on RNA-derived (cDNA) sequences to study the diversity of the deep-sea benthic foraminifera and compared it to the metagenetic approach. We analyzed 257 ribosomal DNA and cDNA sequences obtained from seven sediments samples collected in the Sea of Japan at depths ranging from 486 to 3665. m. The DNA and RNA-based approaches gave a similar view of the taxonomic composition of foraminiferal assemblage, but differed in some important points. First, the cDNA dataset was dominated by sequences of rotaliids and robertiniids, suggesting that these calcareous species, some of which have been observed in Rose Bengal stained samples, are the most active component of foraminiferal community. Second, the richness of monothalamous (single-chambered) foraminifera was particularly high in DNA extracts from the deepest samples, confirming that this group of foraminifera is abundant but not necessarily very active in the deep-sea sediments. Finally, the high divergence of undetermined sequences in cDNA dataset indicate the limits of our database and lack of knowledge about some active but possibly rare species. Our study demonstrates the capability of the metatranscriptomic approach to detect active foraminiferal species and prompt its use in future high-throughput sequencing-based environmental surveys. © 2012 Elsevier Ltd.

Abakumov E.V.,Saint Petersburg State University
Eurasian Soil Science | Year: 2010

The particle-size distribution in soils sampled near Russian polar stations in West Antarctica has been studied. It is shown that the soils of the Subantarctic zone (the Bellingshausen Station on King George Island) are characterized by a higher content of silt and clay in the fine earth fraction and by a higher content of the fine earth fraction in comparison with the soils of the proper Antarctic tundra barrens near the Lenin-gradskaya Station and the Antarctic cold desert near the Russkaya Station. In the latter soils, the content of rock fragments is higher than that in the soils of the Antarctic tundra barrens. In the soils of the tundra barrens, a considerable accumulation of fine earth may take place in large cavities (hollows) on the stony bedrock surface. Desert pavements are formed in both types of Antarctic landscapes. © Pleiades Publishing, Ltd. 2010.

Usoskin I.G.,University of Oulu | Kovaltsov G.A.,RAS Ioffe Physical - Technical Institute | Mironova I.A.,Saint Petersburg State University | Tylka A.J.,U.S. Navy | Dietrich W.F.,Praxis Inc.
Atmospheric Chemistry and Physics | Year: 2011

Using a new reconstruction of the solar proton energy spectra for Ground Level Enhancement (GLE) events, based on fits to measurements from ground-based and satellite-borne instruments covering a wide energy range, we quantitatively evaluate the possible ionization effects in the low and middle atmosphere for 58 out of the 66 GLE events recorded by the world-wide neutron monitor network since 1956. The ionization computations are based on the numerical 3D CRAC:CRII model. A table of the ionization effect caused by the GLE events at different atmospheric heights is provided. It is shown that the direct ionization effect is negligible or even negative, due to the accompanying Forbush decreases, in all low- and mid-latitude regions. The ionization effect is important only in the polar atmosphere, where it can be dramatic in the middle and upper atmosphere (above 30 km) during major GLE events. © 2011 Author(s).

Rosanov N.N.,S. I. Vavilov State Optical Institute | Kozlov V.V.,University of Brescia | Kozlov V.V.,Saint Petersburg State University | Wabnitz S.,University of Brescia
Physical Review A - Atomic, Molecular, and Optical Physics | Year: 2010

We study the propagation of few-cycle pulses in a two-component medium consisting of nonlinear amplifying and absorbing two-level centers embedded into a linear and conductive host material. First we present a linear theory of propagation of short pulses in a purely conductive material and demonstrate the diffusive behavior for the evolution of the low-frequency components of the magnetic field in the case of relatively strong conductivity. Then, numerical simulations carried out in the frame of the full nonlinear theory involving the Maxwell-Drude-Bloch model reveal the stable creation and propagation of few-cycle dissipative solitons under excitation by incident femtosecond optical pulses of relatively high energies. The broadband losses that are introduced by the medium conductivity represent the main stabilization mechanism for the dissipative few-cycle solitons. © 2010 The American Physical Society.

Moskvin L.N.,Saint Petersburg State University
Separation and Purification Reviews | Year: 2016

A general classification of separation methods is attempted. The two criteria were phase transformations and interfacial transfers. All separation methods of homogenous mixtures were divided into five groups: (i) methods that are based on the formation of new phases by substances to be separated; (ii) methods that are based on differences in the interphase distribution processes, chromatographic methods being singled out as a separate group; (iii) membrane methods that are based on induced transfers of substances from one phase into another one across a third phase, which separates the two; (iv) separation methods within a single phase that are based on velocity and direction differences in spatial displacement of particles of substances to be separated within one fluid phase under the action of various fields; and (v) combined methods working combining previously listed methods. Descriptions of each group of separation methods include their intragroup classification and information on the most important techniques as well as the least known of them. These descriptions are in the form of reviews of fundamental and most important publications, regardless of the time they appeared. For the well-known classical methods of the first group all necessary information can be found in university textbooks. Copyright © 2016 Taylor & Francis Group, LLC.

Zenkevich I.G.,Saint Petersburg State University
Journal of Chemometrics | Year: 2014

The series of substituted alkanecarboxylic acids including insertion homologues of ω-substituted acids X(CH2)nCO2H (n≥1) and isomers that differ in the position of substituents X in the alkyl fragments, k-X(CnH2n)CO2H (n=const≥1, 1≤k≤n+1) is the sub-group most poorly characterized by their acidity constants, pKa, comparing with the acids of the other sub-groups. When the experimental data for such compounds are unavailable, the precalculated estimates should be taken into consideration. The pKa values for such acids can be calculated using the single first-order recurrent relation, pKa(n+1)=apKa(n)+b, using pKa values of other (usually the simpler and, consequently, better characterized) homologues and/or isomers of the same series. This algorithm results from the unique mathematical properties of recurrent relations in chemistry. © 2014 John Wiley & Sons, Ltd.

Use of the Maxwell equation for the conductivity of dielectrics and the theory of mechanical losses in glasses caused by ionic shifts has made it possible to calculate directly the temperature of the "ionic" maximum of mechanical losses using data on direct current conductivity. The Maxwell equation was used without changes, in the view accepted in electromagnetic theory. An intuitive physicochemical interpretation of the nature of ionic conductivity measured at constant voltage as a relaxation process was suggested. Verification of the suggestion equation's validity was performed for one-alkali glasses in silicate, borosilicate, phosphate, borate, and germanate systems. The ratio of calculated and experimental values of the temperature of the "ionic" internal-friction maximum corresponds to 0.995 ± 0.034 and does not depend on the frequency of measurements of internal friction (it changed by four orders) or the parameters characterizing conductivity. These results also confirm the validity of the Maxwell equation for the conductivity of dielectrics. The possibility of describing the direct current ionic conductivity of glasses as a Debye relaxation transition proved in this work is a consequence of the constant voltage condition. The design of a theory for the condition of natural decay of a given potential, when the Kohlrausch relaxation regularity becomes valid, represents a principally important problem of physics and physical chemistry of disordered systems. © 2012 Pleiades Publishing, Ltd.

Pronina Y.G.,Saint Petersburg State University
Mechanics of Solids | Year: 2014

In the framework of the Davis-Nadai deformation theory, we study the problem of a ball with a central cavity subjected to internal and external pressure. The solution is constructed in the reference configuration for the polynomial material deformation law with possible regard to matter conservation inside the cavity. The obtained solution is analyzed; it is mathematically proved that the limit load exists in the case of uniform compression, and a method for determining this load is given. It is also proved that a new void can be formed in a solid ball in the case of its extension, and the critical load of void formation is estimated. It is shown that the already existing spherical void cannot completely disappear under the action of external pressure (assuming that its shape is preserved and remaining in the framework of the continuity hypothesis). © 2014 Allerton Press, Inc.

Braun M.A.,Saint Petersburg State University
European Physical Journal C | Year: 2014

Double inclusive cross sections for gluon production in collision of two nucleons with two nucleons are studied in the BFKL approach. Various contributions include emission from the pomerons attached to the participants, from the BFKL interactions between these pomerons and from the intermediate BKP state. The last contribution may be observable, provided the growth with energy of the pomeron contribution is tamed in accordance with unitarity. The possibility of long-range azimuthal correlations due to the BKP state are discussed. © 2014 The Author(s).

Pusev R.S.,Saint Petersburg State University
Theoretical and Mathematical Physics | Year: 2010

We obtain results on small deviations of Bogoliubov's Gaussian measure occurring in the theory of the statistical equilibrium of quantum systems. For some random processes related to Bogoliubov processes, we find the exact asymptotic probability of their small deviations with respect to a Hilbert norm. © 2010 MAIK/Nauka.

Pilyugin S.Y.,Saint Petersburg State University | Tikhomirov S.,National Taiwan University
Nonlinearity | Year: 2010

We show that the Lipschitz shadowing property of a diffeomorphism is equivalent to structural stability. As a corollary, we show that an expansive diffeomorphism having the Lipschitz shadowing property is Anosov. © 2010 IOP Publishing Ltd & London Mathematical Society.

Shelyapina M.G.,Saint Petersburg State University | Fruchart D.,CNRS Neel Institute | Wolfers P.,CNRS Neel Institute
International Journal of Hydrogen Energy | Year: 2010

MgH2 is one of the most promising materials for hydrogen storage. However, its rather slow hydrogen absorption and desorption kinetics and high dissociation temperature essentially limit its application in this field. Nevertheless mixing Mg or MgH2 with small amount of transition metals or their oxides remarkably accelerates the hydrogen kinetics. Recently a series of new hydrides Mg7TiHx, Mg6.5NbHx and Mg6VHx of Ca7Ge type structure has been synthesized. The hydrogen desorption properties have been found to be better than for pure MgH2. Here, we report on the results of our theoretical study of the electronic structure of these new hydrides carried out within the framework of the full-potential, self-consistent linearized augmented plane-wave method. We use these results, along with calculations of the heat of formation and relative stability, to discuss the bonding of these materials and their hydrogen-storage properties. © 2010 Professor T. Nejat Veziroglu.

Kuzmin A.,University of Latvia | Kalinko A.,University of Latvia | Evarestov R.A.,Saint Petersburg State University
Acta Materialia | Year: 2013

The electronic, structural and phonon properties of antiferromagnetic triclinic CuWO 4 have been studied using the first-principles spin-polarized linear combination of atomic orbital (LCAO) calculations based on the hybrid exchange-correlation density functional (DFT)/Hartree-Fock (HF) scheme. In addition, the local atomic structure around both Cu and W atoms has been probed using extended X-ray absorption fine structure (EXAFS) spectroscopy. We show that, by using the hybrid DFT-HF functional, one can accurately and simultaneously describe the atomic structure (the unit cell parameters and the atomic fractional coordinates), the band gap and the phonon frequencies. In agreement with our EXAFS results, the LCAO calculations reproduce a strong distortion of both the CuO 6 and the WO 6 octahedra, which occur due to the first-order and second-order Jahn-Teller effects, respectively. We found that the HF admixture of 13-16%, which is implemented in the PBE0-13% and WCGGA-PBE-16% functionals, produces the best result for CuWO 4. The calculated properties agree well with the available experimental data provided by diffraction, optical, X-ray photoelectron and Raman spectroscopies. © 2012 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Marscher A.P.,Boston University | Jorstad S.G.,Boston University | Jorstad S.G.,Saint Petersburg State University
Astrophysical Journal | Year: 2011

We present an X-ray image of the BL Lacertae (BL Lac) object OJ287 revealing a long jet, curved by 55° and extending 20″ or 90kpc from the nucleus. This de-projects to >1Mpc based on the viewing angle on parsec scales. Radio emission follows the general X-ray morphology but extends even farther from the nucleus. The upper limit to the isotropic radio luminosity, 2 × 1024WHz-1, places the source in the Fanaroff-Riley 1 (FR 1) class, as expected for BL Lac objects. The spectral energy distribution indicates that the extended X-ray emission is from inverse Compton scattering of cosmic microwave background photons. In this case, the derived magnetic field is B 5 μG, the minimum electron energy is 7-40m e c 2, and the Doppler factor is δ 8 in a knot 8″ from the nucleus. The minimum total kinetic power of the jet is (1-2)×10 45ergs-1. Upstream of the bend, the width of the X-ray emission in the jet is about half the projected distance from the nucleus. This implies that the highly relativistic bulk motion is not limited to an extremely thin spine, as has been proposed previously for FR 1 sources. The bending of the jet, the deceleration of the flow from parsec to kiloparsec scales, and the knotty structure can all be caused by standing shocks inclined by 7° to the jet axis. Moving shocks resulting from major changes in the flow properties can also reproduce the knotty structure, but such a model does not explain as many of the observational details. © 2011. The American Astronomical Society. All rights reserved.

Afonin S.S.,Saint Petersburg State University
International Journal of Modern Physics A | Year: 2010

The AdS/QCD models are known to be closely related to the QCD sum rules in the large-Nc (called also planar) limit. Rewriting the theory of infinite tower of free stable mesons expected in the large-Nc QCD as a five-dimensional theory, we scrutinize to what extend the bottom-up holographic models may be viewed as an alternative language expressing the phenomenology of planar QCD sum rules. It is found that many features of AdS/QCD models can be thereby obtained without invoking prescriptions from the original AdS/CFT correspondence. Under some assumptions, all possibilities leading to simple Regge trajectories are classified, and it is argued that the most phenomenologically consistent model is the one called "soft wall model" in the holographic approach, with a preference to the positive-sign dilaton background. © 2010 World Scientific Publishing Company.

Kulabukhova N.,Saint Petersburg State University
IPAC 2013: Proceedings of the 4th International Particle Accelerator Conference | Year: 2013

High power accelerator facilities lead to necessity to consider space charge forces. It is therefore important to study the space charge dynamics in the corresponding channels. To represent the space charge forces of the beam we have developed special software based on some analytical models for space charge distributions. Because calculations for space charge dynamics become extremely time consuming, we use a special algorithm for predictorcorrector method for evaluation scheme for beam map evaluation including the space charge forces. This method allows us to evaluate the map along the references trajectory and to create the beam envelope dynamics. The corresponding computer codes are realized using CUDA implementation of maps for particle dynamics. Some numerical results for different types of the beam channels are discussed. The survey of advantages and disadvantages of using different methods of parallelization and some parallel approaches will be done.

The paper presents benchmark solutions for the mechanochemical corrosion of an elastic-perfectly plastic thick-walled spherical shell under internal and external pressure with possible inhibition of corrosion being taken into account. The rates of inner and outer corrosion are linear with equivalent tensile stress at the related surface when the stress increases beyond a certain threshold. The time of initial and complete yielding is determined and compared with the same results for a cylindrical tube that were obtained earlier. © 2014 Elsevier Ltd.

Krasnova N.K.,Saint Petersburg State University
Technical Physics | Year: 2011

The electronic and optical characteristics of 2D electric fields with a complex potential of the type Ω = i(x + iy)n, where n is a real number, are investigated. Particle dynamics is studied in the symmetry plane and in its neighborhood for constructing an effective spectrograph of electron flows. It is shown that in the range of exponents 0 < n < 1, spatial focusing in the angles of incidence of conical bunches is effected in the system, which has second order in the symmetry plane and at least the first order across it. The line of images of a point source (focal line) is a straight line lying in the symmetry plane, the focusing order being independent of particle energy W. Thus, the spectrographic principle holds, and partial electron fluxes can be detected simultaneously by a position-sensitive detector in a wide range of energy variation. The electrode configuration of these systems is quite simple and can be used in practice for constructing spectrographs. The prospects of application of such spectrographs in energy analysis are considered. © 2011 Pleiades Publishing, Ltd.

Igoshev A.P.,Saint Petersburg State University | Popov S.B.,Moscow State University
Monthly Notices of the Royal Astronomical Society | Year: 2013

We analyse different possibilities to explain the wide initial spin period distribution of radio pulsars presented by Noutsos et al. With a population synthesis modelling, we demonstrate that magnetic field decay can be used to interpret the difference between the recent results by Noutsos et al and those by Popov and Turolla, where a much younger population of neutron stars associated with supernova remnants with known ages has been studied. In particular, an exponential field decay with Τ mag = 5 Myr can produce a 'tail' in the reconstructed initial spin period distribution up to P0 > 1 s starting with a standard Gaussian with P0 = 0.3 s and σ = 0.15 s. Another option to explain the difference between initial spin period distributions from Noutsos et al. and Popov and Turolla - the emerging magnetic field - is also briefly discussed. © 2013 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society.

Baluev R.V.,Saint Petersburg State University
Monthly Notices of the Royal Astronomical Society | Year: 2013

We consider the 'multifrequency' periodogram, in which the putative signal is modelled as a sum of two or more sinusoidal harmonics with independent frequencies. It is useful in cases when the data may contain several periodic components, especially when their interaction with each other and with the data sampling patterns might produce misleading results. Although themultifrequency statistic itself was constructed earlier, for example by G. Foster in his CLEANest algorithm, its probabilistic properties (the detection significance levels) are still poorly known and much of what is deemed known is not rigorous. These detection levels are nonetheless important for data analysis.We argue that to prove the simultaneous existence of all n components revealed in a multiperiodic variation, it is mandatory to apply at least 2n - 1 significance tests, among which most involve various multifrequency statistics, and only n tests are single-frequency ones. The main result of this paper is an analytic estimation of the statistical significance of the frequency tuples that the multifrequency periodogram can reveal. Using the theory of extreme values of random fields (the generalized Rice method), we find a useful approximation to the relevant false alarm probability. For the double-frequency periodogram, this approximation is given by the elementary formula (π/16)W2e-zz2, where W denotes the normalized width of the settled frequency range, and z is the observed periodogram maximum. We carried out intensive Monte Carlo simulations to show that the practical quality of this approximation is satisfactory. A similar analytic expression for the general multifrequency periodogram is also given, although with less numerical verification. © 2013 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society.

Veremey E.I.,Saint Petersburg State University
Journal of Computer and Systems Sciences International | Year: 2011

Problems of synthesis of feedbacks providing H ∞-norm- maximal suppression of disturbances, acting on a linear stationary SISO system with account of limitedness of control resources, are considered. Two methods for solving are proposed. The first one is based on the Nevanlinna-Pick interpolation, and the second one is constructed on the ground of guaranteeing singularities of controllers. Within the framework of these approaches, simple computation algorithms that do not require solving Riccati equations or linear matrix inequalities are generated. The application of the developed algorithms is illustrated by an example. © 2011 Pleiades Publishing, Ltd.

Baluev R.V.,Saint Petersburg State University
Monthly Notices of the Royal Astronomical Society | Year: 2013

This paper introduces an extension of the linear least-squares (or Lomb-Scargle) periodogram for the case when the model of the signal to be detected is non-sinusoidal and depends on unknown parameters in a non-linear manner. The problem of estimating the statistical significance of candidate periodicities found using such non-linear periodograms is examined. This problem is related to the task of quantifying the distributions of the maximum values of these periodograms. Based on recent results in the mathematical theory of extreme values of a random field (the generalized Rice method), a general approach is provided to find a useful analytic approximation for these distributions. This approximation has the general form e-z} P(√z), where P is an algebraic polynomial and z is the periodogram maximum.The general tools developed in this paper can be used in a wide variety of astronomical applications, for instance in the study of variable stars and extra-solar planets. With this in mind, we develop and consider in detail the so-called von Mises periodogram - a specialized non-linear periodogram in which the signal is modelled by the von Mises periodic function exp (ν cos ωt). This simple function with an additional non-linear parameter ν can model the light curves of many astronomical objects that show various types of periodic photometric variability. We prove that our approach can be perfectly applied to this non-linear periodogram.We provide a package of auxiliary C++ programs, attached as online-only material. These programs should facilitate the use of the von Mises periodogram in practice. © 2013 The Author. Published by Oxford University Press on behalf of the Royal Astronomical Society.

Barsukov D.P.,Saint Petersburg State University | Goglichidze O.A.,RAS Ioffe Physical - Technical Institute | Tsygan A.I.,RAS Ioffe Physical - Technical Institute
Monthly Notices of the Royal Astronomical Society | Year: 2013

We investigate the neutron stars spin evolution (breaking, inclination angle evolution and radiative precession), taking into account the superfluidity of the neutrons in the star core. The neutron star is treated as a two-component system consisting of a 'charged' component (including the crust and the core protons, electrons and normal neutrons) and a core superfluid neutron component. The components are supposed to interact through the mutual friction force. We assume that the 'charged' component rotates rigidly. The neutron superfluid velocity field is calculated directly from linearized hydrodynamical equations. It is shown that the superfluid core accelerates the evolution of inclination angle and makes all pulsars evolve to either the orthogonal or coaxial state. However, rapid evolution seems to contradict the observation data. Obtained results together with the observations may allowus to examine the superfluidmodels. © 2013 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society.

Pitjeva E.V.,Russian Academy of Sciences | Pitjev N.P.,Saint Petersburg State University
Monthly Notices of the Royal Astronomical Society | Year: 2013

The high precision of the latest version of the planetary ephemeris Ephemerides of the Planets and the Moon (EPM2011) enables one to explore more accurately a variety of small effects in the Solar system. The processing of about 678 thousand of position observations of planets and spacecraft for 1913-2011 with the predominance of modern radar measurements resulted in improving the PPNparameters, dynamic oblateness of the Sun, secular variation of the heliocentric gravitational constant GM⊙, and the stronger limits on variation of the gravitational constant G. This processing made it possible to estimate the potential additional gravitational influence of dark matter on the motion of the Solar system bodies. The density of dark matter dm, if any, turned out to be substantially below the accuracy achieved by the present determination of such parameters. At the distance of the orbit of Saturn the density ρdm is estimated to be under 1.1 × 10-20 g cm-3, andthe mass of dark matter in the area inside the orbit of Saturn is less than 7.9 × 10-11 M⊙ even takinginto account its possible tendency to concentrate in the centre. © 2013 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society.

Berezin A.S.,St Petersburg State Chemical Pharmaceutical Academy | Skorik Y.A.,Saint Petersburg State University
Carbohydrate Polymers | Year: 2015

Novel water-soluble chitosan-isoniazid conjugates were synthesized by two methods: (1) the carbodiimide method using isoniazid (INH) and N-(2-carboxyethyl)chitosan (CEC), and (2) the reaction between INH and N-(3-chloro-2-hydroxypropyl)chitosan (CHPC). The solubility of the conjugates under physiological conditions was enhanced by phosphorylation. Method (1) is preferable in terms of obtaining conjugates with a high content of active substance; depending on reaction conditions, the degree of substitution in the INH-CEC conjugates varies from 0.08 to 0.39. Ultrasound treatment increased the reaction rate by a factor of 1.3-1.5, but caused partial degradation of the polymer. Consecutive modification led to a considerable decrease in polymer biodegradability in the following order: chitosan > CEC or CHPC > conjugate. In vitro screening of the antimicrobial activity against Mycobacterium tuberculosis H37Rv demonstrated a comparable or slightly higher minimum inhibitory concentration for conjugates than for INH itself (0.20, 0.25, and 1.05 μg INH/mL for INH, CEC-INH, and CHPC-INH, respectively). A slug mucosal irritation test employing Limax flavus revealed a lower toxicity for the conjugates than for INH by a factor of 3-4; the most noticeable toxicity decrease was observed for the conjugates obtained by method (1). Studies of acute toxicity in mice revealed a 3-4-fold increase in median lethal dose for the conjugates compared with INH (LD50 210, 850, and 650 mg INH/kg for INH, CEC-INH, and CHPC-INH, respectively). © 2015 Elsevier Ltd. All rights reserved.

Lopatin A.,Russian Academy of Sciences | Averianov A.,Saint Petersburg State University
Journal of Mammalian Evolution | Year: 2014

There are two species of Gobiconodon in the Early Cretaceous Khoboor locality of Mongolia: G. borissiaki Trofimov, 1978, and G. hoburensis (Trofimov, 1978). The smaller G. hoburensis has i2 half the size of i1, double-rooted dp2, and two generations of molariforms (m1-5 and m1r-4r). In the larger G. borissiaki, i2 is about ¾ size of i1, dp2 is single-rooted, and there are three generations of molariforms (m1-5, m1r-5r, m1rr-2rr). In larger G. ostromi Jenkins and Schaff, 1988, there are three molariforms of the third generation (m1rr-3rr). The anterior lower dentition of Gobiconodon is interpreted as i1-3, c, and dp1-2. The replacement of dp1 by p1 is known only in G. hoburensis. The dp2 is not replaced and may be lost in some specimens (G. hoburensis, G. ostromi) with its alveolus plugged by bone. Gobiconodon includes five valid species: G. borissiaki, G. hoburensis, G. ostromi, G. hopsoni Rougier et al., 2001, and G. zofiae Li et al., 2001 (=G. luoianus Yuan et al., 2009, syn. nov.). The holotype upper maxilla of G. hopsoni is not diagnostic and a new diagnosis for this species is provided based on lower dentitions from the type locality. Repenomamus Li et al., 2001, and Meemannodon Meng et al., 2005, are the only other members of the Gobiconodontidae. The dental formula of Repenomamus is reinterpreted as I1-3, C, P1, M1-5/i1-2, c, p1-2, m1-5 and thus it differs from Gobiconodon by lack of i3 and P2. Meemannodon is different from Gobiconodon by lack of i3 (the upper dentition is unknown). The Early Cretaceous Jeholodens, Yanoconodon, and Liaoconodon are closer to the Gobiconodontidae than to the Amphilestidae by having only two premolars. Liaoconodon with modified anterior dentition is likely the closest relative to the Gobiconodontidae. The Gobiconodontidae is likely the sister taxon for the clade Amphilestidae + Trechnotheria. © 2014, Springer Science+Business Media New York.

Krivovichev S.,Saint Petersburg State University
Acta Crystallographica Section A: Foundations of Crystallography | Year: 2012

The topological complexity of a crystal structure can be quantitatively evaluated using complexity measures of its quotient graph, which is defined as a projection of a periodic network of atoms and bonds onto a finite graph. The Shannon information-based measures of complexity such as topological information content, IG , and information content of the vertex-degree distribution of a quotient graph, I vd, are shown to be efficient for comparison of the topological complexity of polymorphs and chemically related structures. The IG measure is sensitive to the symmetry of the structure, whereas the I vd measure better describes the complexity of the bonding network. © 2012 International Union of Crystallography Printed in Singapore - all rights reserved.

Kudrev A.G.,Saint Petersburg State University
Biophysics (Russian Federation) | Year: 2012

In the present study, the experimental data on the pH-induced formation of the i-motif structure in the nucleotide sequence 5′-CCTTTCCTTTTCCTTTCC-3′ (25°C, pH 3.3-8.9) obtained by spectroscopic techniques, such as UV molecular absorption and circular dichroism, has been analyzed using the chemometric soft modeling-based MCR-ALS approach and the hard modeling-based matrix method. Soft modeling using 2 or 3 spectral species correctly reproduced the spectral variations observed experimentally. The use of hard chemical modeling has allowed proposing an equilibrium model, which describes spectral changes as functions of solution acidity. Additionally, the intrinsic protonation constant Kin and the cooperativity parameter ω have been calculated from fitting of the circular dichroism as well as the molecular absorption spectra. The results indicated that folding was accompanied by a cooperative process, i. e. the enhancement of protonated structure stability upon protonation. © 2012 Pleiades Publishing, Ltd.

Shtukenberg A.G.,New York University | Punin Y.O.,Saint Petersburg State University | Gujral A.,New York University | Kahr B.,New York University
Angewandte Chemie - International Edition | Year: 2014

Crystals of a variety of substances including elements, minerals, simple salts, organic molecular crystals, and high polymers forgo long-range translational order by twisting and bending as they grow. These deviations have been observed in crystals ranging in size from nanometers to centimeters. How and why so many materials choose dramatic non-crystallographic distortions is analyzed, with an emphasis on crystal chemistries that give rise to stresses operating either on surfaces of crystallites or within the bulk. Twisted crystals: Crystals of many substances, including hippuric acid (see picture), will bend or twist as they grow under some conditions. These deviations are often activated by particular additives. How and why so many materials choose dramatic non-crystallographic distortions is analyzed for molecular crystals, high polymers, minerals, elements, and salts. Copyright © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Pevzner L.M.,Saint Petersburg State University
Russian Journal of General Chemistry | Year: 2016

Using alkyl 4,5-bis(diethoxyphosphorylmethyl)furan-3-carboxylate as examples, we have demonstrated the possibility of synthesis of a phosphorylated analog of aglycone of the glycoside regulator of cellulose and callose synthesis, bis(phosphorylated) furoyl derivatives of natural amino acids, and phosphorus-containing derivatives of N-furyl-N′-hydroxyethylurea; these compounds are of interest for pharmacology. © Pleiades Publishing, Ltd., 2016.

Gerchikov L.,Saint Petersburg State Polytechnic University | Sheinerman S.,Saint Petersburg State University
Physical Review A - Atomic, Molecular, and Optical Physics | Year: 2011

Atomic inner-shell photoionization followed by double Auger decay is investigated. The focus of our study is the effect of post-collision interaction (PCI) on the photoelectron energy distribution. A semi-classical approach is employed to describe the PCI distortion of the photoelectron line shapes associated with both direct and cascade double Auger decays. This approach is shown to be valid at low photoelectron energies, whereas for large incident photon energies it reduces to the eikonal approximation. The theory is applied to the case of Ar 2p photoionization spectra and good agreement with available experimental data is achieved. © 2011 American Physical Society.

The southern green stink bug Nezara viridula (L.) (Heteroptera: Pentatomidae) has long attracted attention not only as a serious pest of numerous agricultural crops, but also as a species expanding its range in many parts of the world. Nezara viridula has also been widely used as a model in different experimental studies. The present review focuses on reproductive (i.e. adult) winter diapause, which is the pivotal element of the species' seasonal cycle. Results from numerous field experiments and observations, as well as laboratory ecophysiological investigations conducted during the few last decades, are analyzed and interpreted. Experimental findings are used to describe in detail the dynamics of physiological changes during overwintering. Reproductive diapause in N. viridula is controlled in both sexes by photoperiodic conditions. The induction of diapause is associated with a reversible change of body colour from green or yellow to russet (or brown). The proper timing of adult emergence and the induction of diapause, as well as the size of adults, is vitally important for successful overwintering. Nezara viridula has been shown to respond strongly to the current trend in climate change by shifting the limit of its northern range, particularly in central Japan. Analysis of historic climate data suggests that the environmental conditions during the last few decades have become more favourable for the overwintering survival of N. viridula in many locations in central Japan. This has likely promoted the northward spread of the species. The relationships between reproductive diapause, reversible body colour change, overwintering success and the recent range expansion are analyzed. Perspectives of the range dynamics of the species are discussed in light of further predicted climate change. © 2012 The Author. © 2012 The Royal Entomological Society.

Desnitskiy A.G.,Saint Petersburg State University
Russian Journal of Developmental Biology | Year: 2014

This paper presents a brief survey and preliminary classification of embryonic cleavage patterns in the class Amphibia. We use published data on 41 anuran and 22 urodele species concerning the character of the third cleavage furrow (latitudinal or longitudinal) and the stage of transition from synchronous to asynchronous blastomere divisions in the animal hemisphere (4-8-celled stage, 8-16-celled stage or later). Based on this, four patterns of amphibian embryonic cleavage are recognized, and an attempt to elucidate the evolutionary relationships among these patterns is undertaken. The so-called "standard" cleavage pattern (the extensive series of synchronous blastomere divisions including latitudinal furrows of the third cleavage) with the typical model species Ambystoma mexicanum and Xenopus laevis seems to be derived and probably originated independently in the orders Anura and Caudata. The ancestral amphibian cleavage pattern seems to be represented by species with longitudinal furrows of the third cleavage and the loss of synchrony as early as the 8-celled stage (such as in primitive urodele species from the family Cryptobranchidae). © 2014 Pleiades Publishing, Inc.

Proskurnikov A.V.,Saint Petersburg State University
IFAC Proceedings Volumes (IFAC-PapersOnline) | Year: 2013

We consider consensus algorithms for multi-agent networks with high-order and delayed dynamics of agents. The topology is assumed to be fixed and undirected, however the couplings may be nonlinear and uncertain, we assume only the symmetry condition to be valid. We obtain conditions of stability for such algorithms that are similar in spirit to the celebrated Popov criterion for the stability of Lurie systems. © IFAC.

Monakov A.,Saint Petersburg State University
Signal Processing | Year: 2013

The problem of signal waveform estimation using an antenna array in case of uncertainties about the steering vector is considered. New asymptotically (in sample size) optimum estimators are derived. In contrast to the known optimal solutions, the employed method of synthesis yields non-iterative direct-form estimators. Simulation results are provided to evaluate the performance of the synthesized estimators. It is shown that the proposed asymptotic estimators perform as well as the iterative optimal estimators and they outperform the MVDR estimator in a wide range of input signal-tonoise and uncertainty ratios. © 2013 Elsevier B.V. All rights reserved.

Telnov D.A.,Saint Petersburg State University | Chu S.-I.,University of Kansas | Chu S.-I.,National Taiwan University
Physical Review A - Atomic, Molecular, and Optical Physics | Year: 2011

Recent experimental observations of above-threshold ionization of rare gas atoms and diatomic molecules by midinfrared laser fields revealed a prominent maximum in the electron energy spectrum very close to the ionization threshold which is not reproduced by widely used Keldysh-Faisal-Reiss theories. We have performed fully ab initio theoretical analysis and precision calculations to explore the quantum origin of the low-energy structure (LES) observed in the experiments. Our study shows that an important role in shaping of LES is played by the effect of Coulomb attraction in the final electron state and the Coulomb threshold effect. © 2011 American Physical Society.

Malev V.V.,Saint Petersburg State University
Electrochimica Acta | Year: 2015

As known, polaron quasi-particles of conducting polymers contain from 3 to 6 monomer fragments (repeat units) of polymer chains. This is the reason why the widely accepted approach to treating the polaron conductance assumes that the reduced forms of polarons have the same number of repeat units as included into polarons and, moreover, treats such reduced formations as separate quasi-particles. The latter obviously means that charge transfer from a polaron to a neighboring reduced quasi-particle proceeds with simultaneous transformations of all the fragments of these quasi-particles. In other words, the distance of charge transfer in such transitions is assumed to be exactly equal to the polaron size. In contrast to such treatment, the main feature of the proposed approach is a polaron flux reformulation, which assumes a unit polaron translocation to be of a one monomer size independently of number m of monomer fragments included into polaron quasi-particles. As a result, material balance equations of polaron-conducting films take a more complicated form than that accepted in the existing approach. It is shown that, at equilibrium conditions, the obtained equations, as it must be, lead to the relationships being in accordance with thermodynamic ones. At the same time, a proper analysis reveals some differences between quantitative results that follow from the proposed and traditional approaches for both quasi-equilibrium and non-equilibrium conditions. Possible directions of the further development of the represented approach are shortly discussed. © 2015 Elsevier Ltd.

Belash T.,Saint Petersburg State University
Procedia Engineering | Year: 2015

One of the serious problems in field of building seismic stability provision is the restriction of dangerous displacements occurring due to low-frequency seismic impact. Restriction of these displacements would be possible by means of application of special damping elements placed at the levels of floors. Dry friction dampers are considered to be such elements. © 2015 Published by Elsevier Ltd.

Polev D.,Saint Petersburg State University
Journal of Theoretical Biology | Year: 2012

As novel genes emerge in the evolution of species, pre-existing genes expand their expression patterns to diversify their functions and the expression patterns of gene duplicates diverge to pursue functional specialization. All these processes require genes to be expressed, however, the level and specificity of gene expression at the early stages of these processes are unclear. In this study, I propose that transcriptional noise is a mechanism to test genes for new functions, and I hypothesize the 'in-service' mechanism of gene evolution. In contrast to other hypotheses that suggest that there are specialized sites for gene evolution, such as tumors (Kozlov, 2010) or the testis (Kaessmann, 2010) this hypothesis proposes that emerging genes are expressed nonspecifically in many normal tissues, due to transcriptional noise. New genes are continuously 'tested' in various cells and under various conditions, thereby allowing the genes to evolve functions at the sites of their future work. The hypothesis of 'in-service' gene evolution also proposes that pre-existing genes are continuously tested under extrinsic conditions, due to transcriptional noise; this testing facilitates the emergence of alternative promoters and the diversification of the genes' expression patterns and functions. © 2011 Elsevier Ltd.

Kurasov V.,Saint Petersburg State University
Advances in Optical Technologies | Year: 2016

The method to get the glass media with necessary optical characteristics is proposed. This method is based on inserting a necessary number of heterogeneous centers of given activity into the system. The theoretical description of the nucleation process in such situation is given and the resulting formulas allow choosing the characteristics of heterogeneous centers necessary to get the required optical characteristics of the media. © 2016 Victor Kurasov.

Paston S.A.,Saint Petersburg State University
Journal of High Energy Physics | Year: 2014

We discuss for which smooth global embeddings of a metric into a Minkowskian spacetime the Hawking into Unruh mapping takes place. There is a series of examples of global embeddings into the Minkowskian spacetime (GEMS) with such mapping for physically interesting metrics. These examples use Fronsdal-type embeddings for which time-lines are hyperbolas. In the present work we show that for some new embeddings (non Fronsdal-type) of the Schwarzschild and Reissner-Nordström metrics there is no mapping. We give also the examples of hyperbolic and non hyperbolic type embeddings for the de Sitter metric for which there is no mapping. For the Minkowski metric where there is no Hawking radiation we consider a non trivial embedding with hyperbolic timelines, hence in the ambient space the Unruh effect takes place, and it follows that there is no mapping too. The considered examples show that the meaning of the Hawking into Unruh mapping for global embeddings remains still insufficiently clear and requires further investigations. © 2014 The Author(s).

Krasavin M.,Saint Petersburg State University
European Journal of Medicinal Chemistry | Year: 2014

2-Imidazolines are well known as pharmacophores for various isoforms of adrenergic (α) and imidazoline (I) receptors. The biological activities exerted through the modulation of these targets, mostly in the central nervous system, have found utility in the development of many drug candidates - and even marketed drugs - for hypertension, diabetes and various CNS disorders. However, there is a growing evidence for the general privileged character of the 2-imidazoline scaffold, considering the documented success in the development of numerous biologically active compounds acting outside of the α/I receptor domain. In this review, we provide an overview of these, less traditional areas of medicinal applications of 2-imidazolines. © 2014 Elsevier Masson SAS.

Demidov V.I.,Saint Petersburg State University | Kudryavtsev A.A.,Saint Petersburg State University of Information Technologies, Mechanics and Optics
Physics of Plasmas | Year: 2014

This paper discusses the spatial resolution that is required to study inhomogeneous, low-temperature plasmas and is based on a review of low-temperature plasma electron kinetics and methods for probe measurements of electron energy distribution functions (EEDFs). It is stated that EEDFs can be extracted from probe measurements by applying an appropriate probe theory. The Druyvesteyn formula is most commonly used for this extraction and has been used in numerous publications, but more general theory can be used for a wider range of gas pressures. It is demonstrated that the Druyvesteyn formula can be obtained from the general theory as a limiting case. This paper justifies the application of wall probes in plasma studies of an energetic part of EEDFs. This justification is made for an idealized probe. We briefly review the methods for studying anisotropic plasmas and their usefulness in plasma research. It is demonstrated that to determine anisotropic electron energy distribution functions, a planar, one-sided probe is most convenient. © 2014 AIP Publishing LLC.

Alekseev V.A.,Saint Petersburg State University
Journal of Physics B: Atomic, Molecular and Optical Physics | Year: 2014

The electronic structures of the Ne2F, Ar2F, Kr 2F, Xe2F, Ar2Cl, Kr2Cl, Xe 2Cl, Kr2Br, Xe2Br, and Xe2I molecules have been studied on the CASSCF/CASPT2 level, with inclusion of the spin-orbit interaction. For the lowest strongly bound Rg2X (4 2) state we report RRg-Rgand RRg-Xequilibrium bond lengths, dissociation energy, radiative lifetime and frequencies of three vibrational modes. Except for the antisymmetric stretch mode, a similar set of results was obtained for another five bound states above Rg2X(4 2). To compare equilibrium bond lengths and some other molecular properties, calculations were also performed for Rg2 +and RgX diatomics on the same level of theory and using the same basis sets. The ab initio results obtained in this work are of interest for experimental and theoretical studies of Rg2X (42) formation mechanisms. © 2014 IOP Publishing Ltd.

Utkin L.V.,Saint Petersburg State University
Neurocomputing | Year: 2015

A new algorithm for ensemble construction based on adapted restricting a set of weights of examples in training data to avoid overfitting and to reduce a number of iterations is proposed in the paper. The algorithm called IDMBoost (Imprecise Dirichlet Model Boost) applies Walley's imprecise Dirichlet model for modifying the restricted sets of weights depending on the number and location of classification errors. Updating of weights within the restricted set (simplex) is carried out by using its extreme points. The proposed algorithm has a double adaptation procedure. The first adaptation is carried out within every restricted simplex like the AdaBoost. The second adaptation reduces and changes the restricted sets of possible weights of examples. Various numerical experiments with real data illustrate the proposed algorithm. © 2014 Elsevier B.V.

Mironova I.A.,Saint Petersburg State University | Usoskin I.G.,University of Oulu
Environmental Research Letters | Year: 2014

This letter presents a summary of a phenomenological study of the response of the polar stratosphere to strong solar energetic particle (SEP) events corresponding to ground level enhancements (GLEs) of cosmic rays. This work is focused on evaluation of the possible influence of the atmospheric ionization caused by SEPs upon formation of aerosol particles in the stratosphere over polar regions. Following case studies of two major SEP/GLE events, in January 2005 and September 1989, and their possible effects on polar stratospheric aerosols, we present here the results of an analysis of variations of the daily profiles of the stratospheric aerosol parameters (aerosol extinction for different wavelengths, as well as Ångstrom exponent) for both polar hemispheres during SEP/GLE events of July 2000, April 2001 and October 2003, which form already five clear cases corresponding to extreme and strong SEP/GLE events. The obtained results suggest that an enhancement of ionization rate by a factor of about two in the polar region with night/cold/winter conditions can lead to the formation/growing of aerosol particles in the altitude range of 10-25 km. We also present a summary of the investigated effects based on the phenomenological study of the atmospheric application of extreme SEP events. © 2014 IOP Publishing Ltd.

Vasilyev N.,Saint Petersburg State University
Journal of Luminescence | Year: 2014

Intra-center luminescence dynamics has been investigated under low excitation density in Cd0.6Mn0.4Te/Cd0.5Mg 0.5Te superlattices and Cd0.5Mn0.5Te thin film both experimentally and by Monte-Carlo simulation. A model developed earlier by the author for bulk Cd1-xMnxTe is applied to the superlattices with quantum wells of different width. It was demonstrated that under low temperature hopping-assisted quenching has been neglected in distinct of the significant quenching which was previously stated in bulk samples. In the superlattices with narrower quantum wells a homogeneous broadening is stated to be remarkably enhanced. To make clear an origin of the enhancement more experimental data are required. Noticeable non-exponential decay in Mn 2+-luminescence transients is explained by stochasticity in decay rates, which are found to be completely correlated with the ions' energies. Partial correlation is stated to take place for the Mn2+-ions' energies of 4T1- and 4T2-states participating in the excitation process. The correlation loss is claimed to be originated from symmetry breakdown. Validity of the model applied to the superlattices is proved by good agreement of the experimental data and calculations under temperature rise from 13 to 77 K. © 2013 Elsevier B.V.

Baluev R.V.,Saint Petersburg State University | Beauge C.,National University of Cordoba
Monthly Notices of the Royal Astronomical Society | Year: 2014

We carry out a new analysis of the published radial velocity data for the planet-hosting star HD 82943. We include the recent Keck/HIRES measurements as well as the aged but much more numerous CORALIE data. We find that the CORALIE radial velocity measurements are polluted by a systematic annual variation which affected the robustness of many previous results. We show that after purging this variation, the residuals still contain a clear signature of an additional ~1100 d periodicity. The latter variation leaves significant hints in all three independent radial velocity subsets that we analysed: the CORALIE data, the Keck data acquired prior to a hardware upgrade and the Keck data taken after the upgrade. We mainly treat this variation as a signature of a third planet in the system, although we cannot rule out other interpretations, such as long-term stellar activity. We find it easy to naturally obtain a stable three-planet radial velocity fit close to the three-planet mean-motion resonance 1:2:5, with the two main planets (those in the 1:2 resonance) in an aligned apsidal corotation. The dynamical status of the third planet is still uncertain: it may reside in as well as slightly out of the 5:2 resonance. We obtain the value of about 1075 d for its orbital period and ~0.3MJup for its minimum mass, while the eccentric parameters are uncertain. © 2014 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society.

Samsonov A.A.,Saint Petersburg State University | Sibeck D.G.,NASA | Yu Y.,University of Michigan
Journal of Geophysical Research: Biogeosciences | Year: 2010

We use results from a global MHD simulation to study the interaction of an interplanetary shock with the Earth's magnetosphere for a northward interplanetary magnetic field orientation. We connect intensifications of the transient northward Bz (NBZ) and Region 1 currents in the ionosphere with the appearance of two strong dynamo regions in the magnetosphere: the first on the high-latitude magnetopause near and behind the cusps and the second near the equatorial plane on the flanks. The ionospheric and magnetospheric transients are well synchronized and move antisunward gradually. According to the results obtained, the source of energy for the transient NBZ current is related to shock-intensified lobe reconnection, while the transient Region 1 current corresponds to the reflected fast shock predicted by Samsonov et al. (2007). We speculate that the electric circuits for the quasi-stationary field-aligned currents are similar to the transient electric circuits obtained in this paper. Copyright 2010 by the American Geophysical Union.

Rebane T.K.,Saint Petersburg State University
Physics of Atomic Nuclei | Year: 2012

The problem of boundness of a+b+c-d- four-particle Coulomb systems (quadrions) is studied versus the masses of the particles involved. Inequalities that make it possible to deduce that, if some reference quadrions form a bound state, the same is true for a large number of quadrions formed by particles having various masses were derived. A compendium of calculations for energies of reference systems that possess various symmetries [positronium molecules (e+e+e-e-) and quadrions of the a+b+b-b-, a+b+a-b-, and a+a+b-c- types] is given, and groups of bound asymmetric quadrions corresponding to them are determined. An inequality for kinetic energies of particles that makes it possible to find out, by using asymmetric reference systems, whether specific quadrions are bound is obtained. It is shown that the boundness of many quadrions is ensured by the boundness of respective three-particle systems. The entire body of the present results permits proving that, of the total number of 406 quadrions containing electrons, muons, pions, kaons, protons, deuterons, and tritons and their antiparticles, 227 quadrions are bound. © 2012 Pleiades Publishing, Ltd.

Filatov S.K.,Saint Petersburg State University
Crystallography Reports | Year: 2011

A general concept of the symmetry transformation of a material during its thermal expansion and final polymorphic transition is proposed based on numerous experimental data. Within this concept, the atomic nature of the transformation of the crystal structure with a change in temperature is considered. Particular attention is paid to the thermal expansion of materials, along with the well-known tendency of a thermally induced increase in the crystal symmetry, which is generally considered to be the directionality of material transformation during polymorphic transitions. © Pleiades Publishing, Inc., 2011.

Heberger K.,Hungarian Academy of Sciences | Zenkevich I.G.,Saint Petersburg State University
Journal of Chromatography A | Year: 2010

The comparison of different polarity measures (parameters, descriptors, variables, scales, etc.) indicates that evaluation of interrelations between these measures is important for better understanding and interpretation of chemical and/or analytical data, especially for chromatographic separation. The best linear correlation between gas chromatographic and non-chromatographic polarity descriptors is revealed for the first time: this pair of variables is the difference of gas chromatographic retention indices on standard polar and non-polar phases as well as the difference between non-dimensional indices of boiling points (known in chromatography since mid-1980s as dispersion indices) and indices of molar refractions. The correlation helps chromatographers to find preferable chemical variables (features) to understand better the separation phenomena and to find better correlations in QSRR models. Principal component analysis (PCA) of ten frequently applied polarity measures shows their similarity and, at the same time, it shows the absence of anomalies within the set of simple organic molecules. A novel ranking method for ten polarity parameters points out that the two most informative polarity measures are (i) the non-dimensional index for boiling point and (ii) the difference in chromatographic retention indices on standard polar and non-polar stationary phases. On the other hand, the hydrophobicity parameter, log P, sometimes considered as polarity parameter in HPLC seems to be the worst one in description of "polarity" in gas chromatography. Surprisingly, such polarity measures like dipole moment and permittivity used often in organic chemistry does not provide the best correlation with gas chromatographic polarity measures. © 2010 Elsevier B.V.

Kutcherov D.,Saint Petersburg State University
Journal of Asia-Pacific Entomology | Year: 2016

Insect development times can only be compared over a relatively wide range of permissible temperatures. Both basic and applied branches of entomology widely adopt linear regression that describes the temperature-dependence of developmental rate, which is a reciprocal of time. There is a wealth of literature reporting these parameters for hundreds of economically important species, including leaf beetles. This study begins with a suspicion that the previously published parameters for the temperature-dependent development in the walnut leaf beetle Gastrolina depressa may be imprecise because they disagree with the general variation pattern typical of the family Chrysomelidae. Thus, the immature development in G. depressa is re-studied in order to verify the values of the lower temperature threshold and the slope of developmental rate on temperature. It is found that G. depressa requires 220.2 degree-days accumulated above the threshold of 8.2 °C for total immature development. For example, at 28 °C, the developmental period from oviposition to adult eclosion is as short as 11.4 days. Although development in G. depressa is indeed unusually fast, it does not depart from the general tendencies observed at the family level. Therefore, with extensive published evidence at hand, it has now become possible to approximately predict developmental rates in unstudied species and reveal questionable results in previous studies. In addition, rearing temperature is found to affect adult body mass and sex ratio in this species with males being less abundant at higher temperatures. The latter phenomenon is discussed in light of possible activity of a male-killing microorganism. © 2016 Korean Society of Applied Entomology, Taiwan Entomological Society and Malaysian Plant Protection Society.

Zhou X.-Z.,University of California at Los Angeles | Angelopoulos V.,University of California at Los Angeles | Sergeev V.A.,Saint Petersburg State University | Runov A.,University of California at Los Angeles
Journal of Geophysical Research: Space Physics | Year: 2011

Earthward propagating dipolarization fronts, interpreted as thin, vertical current sheets that separate plasmas of different origins in the Earth's magnetotail, are embedded within flow bursts, often near the leading edge of bursty bulk flows. Observations have also shown that bursty bulk flow onset typically precedes dipolarization front arrival by ∼1 min. Ion distribution functions reveal that earthward flows in advance of front arrival are often caused by the appearance of a new ion population atop a preexisting plasma sheet component. Particle simulations suggest that this second population, which contributes most to the plasma velocity, is composed of ions that have been reflected at and accelerated by the approaching front. We propose that in the presence of a finite upstream Bz field, the reflected ions would be confined in a region with a size comparable to the ion thermal gyroradius over the upstream Bz. THEMIS observations confirm that the measured time difference δt between the appearance of earthward plasma flows and the dipolarization front arrival is consistent with the predicted size of the ion accessibility region. Copyright 2011 by the American Geophysical Union.

Zhou X.-Z.,University of California at Los Angeles | Angelopoulos V.,University of California at Los Angeles | Sergeev V.A.,Saint Petersburg State University | Runov A.,University of California at Los Angeles
Journal of Geophysical Research: Space Physics | Year: 2010

We report on the evolving ion distributions associated with the arrival of an earthward propagating dipolarization front in the near-Earth magnetotail using Time History of Events and Macroscale Interactions during Substorms (THEMIS). Ion distributions exhibit steady duskward anisotropy well before the front arrival, suggesting thin current sheet formation at ∼11 RE, during the growth phase of a moderate geomagnetic substorm. As the dipolarization front moves closer, an additional, earthward streaming ion population appears, resulting in an earthward velocity moment. This population eventually overwhelms the preexisting duskward anisotropy and merges with the earthward convecting bulk flow once the dipolarization front arrives. Test-particle simulations show that the observed ion evolution is consistent with a picture of ions reflected and accelerated by the approaching front and moving ahead of it. Copyright 2010 by the American Geophysical Union.

Desnitskiy A.G.,Saint Petersburg State University
Russian Journal of Developmental Biology | Year: 2011

Literary data on the peculiarities of the egg cleavage process in various representatives of the order of caudate amphibians consisting of 10 families have been considered. It has been recognized that in considerable number of species of Plethodontidae, Cryptobranchidae, and some other families, the synchrony of divisions is lost already after the 8-celled stage of the cleavage in large, yolk-rich and unpigmented eggs. A "standard" cleavage of early embryos of caudate amphibians, which had been described in the text-books on developmental biology and consists approximately of 10 synchronous divisions of comparatively small eggs, is characteristic only of the families Ambystomatidae and Salamandridae including 19.3% of species within the order Caudata. However, within each of these families there seems to be a number of species with a "non-standard" type of early cleavage. The evolutionary relationships between two main types of early embryogenesis within the order Caudata are discussed. © 2011 Pleiades Publishing, Ltd.

Ivanov A.,Saint Petersburg State University
RuPAC 2012 Contributions to the Proceedings - 23rd Russian Particle Accelerator Conference | Year: 2012

An approach based on matrix formalism for solving differential equations is described. Effective in sense of performance matrix formalism can be tested with less efficient, but accurate traditional algorithm of numerical simulation based on the Runge-Kutta scheme. In both cases the symplectic version of the algorithms are used. The results coincide to analytical calculations, but some disagreements have been identified. The approach implementation is demonstrated in the problem of long-term spin dynamics in electrostatic fields. Copyright © 2012 by the respective authors.

Kozynchenko S.A.,Saint Petersburg State University
RuPAC 2012 Contributions to the Proceedings - 23rd Russian Particle Accelerator Conference | Year: 2012

In this paper the program for simulation and optimization of beam dynamics in injection systems is considered, which at the same time allows the choice of parameters of the accelerating-focusing system. This permits designing the injection system during optimization process, taking into account the required output characteristics of the beam. The given program is based on Win 32 API dialog boxes and is developed in standard C++, using parallel programming tools based on the MPI-1. Copyright © 2012 by the respective authors.

Yanovskaya T.B.,Saint Petersburg State University
Izvestiya, Physics of the Solid Earth | Year: 2012

A method for three-dimensional (3D) ray tomography that uses the data on the travel time residuals of body waves is suggested. The underlying assumption of the method is smoothness of horizontal velocity variations. The region under study is divided into layers, and the velocity correction in each layer is assumed to only depend on the horizontal coordinates. The starting velocity model is specified as a function of depth. The numerical implementation of the method is noticeably simpler if the velocity-depth distribution is described by a linear function. The solution is determined by minimizing the functional that contains the sum of the integrals of the square gradients of the velocity corrections. The procedure is reduced to solving the two-dimensional (2D) problem in a way similar to the way previously developed for surface wave tomography (Ditmar and Yanovskaya, 1989). The obtained solution is smoothed, and the degree of smoothing is estimated jointly with the reconstruction of the solution. This approach does not require adaptive parameterization of the medium, i. e., division of the region into the blocks each of which is intersected by a sufficiently large number of rays. The efficiency of the method is demonstrated by the example of synthetic data and on the data on real traveltime residuals of the P waves in the Black Sea basin. © 2012 Pleiades Publishing, Ltd.

Mironova I.A.,Saint Petersburg State University | Usoskin I.G.,University of Oulu | Kovaltsov G.A.,RAS Ioffe Physical - Technical Institute | Petelina S.V.,La Trobe University
Atmospheric Chemistry and Physics | Year: 2012

Energetic cosmic rays are the main source of ionization of the low-middle atmosphere, leading to associated changes in atmospheric properties. Via the hypothetical influence of ionization on aerosol growth and facilitated formation of clouds, this may be an important indirect link relating solar variability to climate. This effect is highly debated, however, since the proposed theoretical mechanisms still remain illusive and qualitative, and observational evidence is inconclusive and controversial. Therefore, important questions regarding the existence and magnitude of the effect, and particularly the fraction of aerosol particles that can form and grow, are still open. Here we present empirical evidence of the possible effect caused by cosmic rays upon polar stratospheric aerosols, based on a case study of an extreme solar energetic particle (SEP) event of 20 January 2005. Using aerosol data obtained over polar regions from different satellites with optical instruments that were operating during January 2005, such as the Stratospheric Aerosol and Gas Experiment III (SAGE III), and Optical Spectrograph and Infrared Imaging System (OSIRIS), we found a significant simultaneous change in aerosol properties in both the Southern and Northern Polar regions in temporal association with the SEP event. We speculate that ionization of the atmosphere, which was abnormally high in the lower stratosphere during the extreme SEP event, might have led to formation of new particles and/or growth of preexisting ultrafine particles in the polar stratospheric region. However, a detailed interpretation of the effect is left for subsequent studies. This is the first time high vertical resolution measurements have been used to discuss possible production of stratospheric aerosols under the influence of cosmic ray induced ionization. The observed effect is marginally detectable for the analyzed severe SEP event and can be undetectable for the majority of weak-moderate events. The present interpretation serves as a conservative upper limit of solar energetic particle effect upon polar stratospheric aerosols. © 2012 Author(s). CC Attribution 3.0 License.

The possibility of using a garnet-biotite geothermometer to estimate the nucleation temperature of zoned crystals is considered. The data on the temperature evolution of mineral systems in the course of porphyroblast growth estimated with different methods are compared for a number of metamorphic provinces. The temperatures for garnet core and rim growth calculated by the program THERMOCALC are systematically overestimated compared to those derived using the garnet-biotite geothermometer (Kaneko and Miyano, 2004; Gulbin, 2011a, 2011b). The discrepancy reaches 40-70°C for the isopleth method and 60-90°C for the average PT method. © 2012 Pleiades Publishing, Ltd.

Skutschas P.P.,Saint Petersburg State University | Gubin Y.M.,Russian Academy of Sciences
Acta Palaeontologica Polonica | Year: 2012

A new neotenic salamander, Seminobatrachus boltyschkensis gen. et sp. nov., is described based on 14 skeletons of late Paleocene-early Eocene age preserved on drill core slabs from the Cherkassy Region, central Ukraine. The new taxon is diagnosed by the following unique combination of characters: dorsal process of premaxilla posteriorly elongate and overlaps frontal; maxilla greatly reduced in size; parietalsquamosal contact absent; vomerine tooth row long and parallel to maxillary arcade; pterygoid has long anterior process; quadrate ossified; marginal and palatal teeth pedicellate; trunk vertebrae amphicoelous, each having a subcentral keel, anterior basapophysis, and spinal nerve foramina; ribs bicipital; carpals and tarsals unossified; and phalangeal formulae of 2-2-3-2 and 2-2-3-4-2 for manus and pes, respectively. Phylogenetic analysis nests S. boltyschkensis within Urodela (i.e., crown-clade salamanders), but its exact phylogenetic position is equivocal, resolving in one of three ways: (1) in an unresolved trichotomy with Salamandra and (Ambystomatidae + (Dicamptodon + Rhyacotriton)) (results obtained in NONA v. 2.0, with the WINCLADA v. 1.00.08 interface; the parsimony ratchet (island hopper) algorithm), (2) as a sister taxon of (Salamandra + (Ambystomatidae + (Dicamptodon + Rhyacotriton))) clade (results obtained in TNT v. 1.1; the implicit enumeration search algorithm) or (3) as a sister taxon of Ambystomatidae (results obtained in PAUP v. 4.0b10; the branch-and-bound search algorithm).

Pilyugin S.Y.,Saint Petersburg State University
Journal of Dynamical and Control Systems | Year: 2015

We give general sufficient conditions for lower semicontinuity of invariant sets for some generalizations of classical dynamical systems, such as nonautonomous processes and skew products. It is shown that under these conditions, the invariant set is trajectorically lower semicontinuous, i.e., for any of its trajectory, there exists a close trajectory of the perturbed process. We also give conditions under which the mapping which takes a trajectory of the invariant set to a close trajectory of the perturbed process is continuous. © 2015, Springer Science+Business Media New York.

Brodskaya E.,Saint Petersburg State University
Journal of Physical Chemistry B | Year: 2012

The surface layer of a direct ionic micelle with explicit solvent was simulated by the molecular dynamics method. Local properties of the system were calculated in the spherical micellar cell. The results for the local electric potential show that the contribution of a polar solvent makes the potential short-ranged, in contrast to predictions of the Poisson-Boltzmann theory. © 2012 American Chemical Society.

Timoshkin A.Y.,Saint Petersburg State University | Morokuma K.,Kyoto University
Physical Chemistry Chemical Physics | Year: 2012

Structures of group 13 Lewis acids ER 3 and group 15 Lewis bases YR′ 3 as well as respective hydrogen splitting products [HER 3] - and [HYR′ 3] + (E = B, Al, Ga; Y = N, P, As; R 3 = (C 6F 5) 3, (C 6H 2F 2) 3CF; R′ = H, C 6H 5, 2,6-Me 2C 6H 3) have been fully optimized at B3LYP/pVDZ and B3LYP/def2-TZVPP levels of theory. Energetic characteristics of the hydrogen-splitting process ER 3 + YR′ 3 + H 2 = [HYR′ 3] + + [HER 3] - have been obtained. Energetics for the ion formation does not depend on the nature of group 13 element E. However, the Lewis acid environment (pyramidal vs. planar) and nature of Lewis base play a significant role in the energetics of heterocyclic hydrogen splitting. The endothermicity of the heterolytic hydrogen splitting process is reduced by about 80 kJ mol -1 by using pyramidal Lewis acids E(C 6H 2F 2) 3CF, and by 40 kJ mol -1 by using Lewis bases with 2,6-Me 2C 6H 3 substituents. Thus, the overall process of the heterolytic hydrogen splitting is predicted to be endothermic by only 130 kJ mol -1 for the E(C 6H 2F 2) 3CF-P(2,6-Me 2C 6H 3) 3 combinations (compared to 450 kJ mol -1 for E(C 6F 5) 3-PH 3). It is shown that H 2 splitting in the gas phase by nitrogen-containing DA cryptands, featuring group 13 element acceptor centers with a pyramidalized environment, is highly exothermic. This journal is © 2012 the Owner Societies.

L'vov B.V.,Saint Petersburg State University | Galwey A.K.,Rhodes University
International Reviews in Physical Chemistry | Year: 2013

The kinetic compensation effect (KCE), unexplained by the Arrhenius activation model, is interpreted in the framework of the novel thermochemical approach to kinetics of heterogeneous reactions. Unlike the activation model, this theory includes the process of congruent dissociative vaporisation of solids described by the Langmuir quasi-equilibrium equations and consideration of the two different reaction regimes: equimolar and isobaric (with the external pressure of gaseous product, respectively, below and above its equilibrium pressure). Change of regimes is shown to be the reason for the mutual variations of the Arrhenius parameters in the equation: ln A = a + bE. This theoretical interpretation of the KCE is quantitatively supported by experimental observations for the following different types of heterogeneous reactions: high temperature atomisation of metal oxides, low-temperature solid-state decompositions, NiO reduction by H2 and catalytic oxidations of CO and of H2 on PtO2. Fundamental reasons for the shortcomings of the activation model in the interpretation of mechanisms and kinetics of heterogeneous reactions are identified. © 2013 Copyright Taylor and Francis Group, LLC.

Zenkevich I.G.,Saint Petersburg State University
Journal of Analytical Chemistry | Year: 2013

A dangerous tendency in the presentation of the results of the GC-MS identification of complex mixture components is discussed. This is an increasing number of publications where unacceptable results are presented. The main signs of them are the absence of a correspondence between the lists of identified compounds and the general principles of chromatographic retention, the indication of erroneous retention indices and chemical names, the unreliable chemical origin of analytes, etc. The main criteria for revealing such errors are the control of the chromatographic elution order of analytes and the absolute values of their retention indices. © 2013 Pleiades Publishing, Ltd.

Pyrkin A.A.,Saint Petersburg State University
Automation and Remote Control | Year: 2010

A new adaptive algorithm for compensation of parametrically uncertain biased harmonic disturbance was proposed. In contrast to the existing counterparts, consideration was given to the case of disturbance compensation where the relative degree of the plant model may be anyone, only the controlled output is measured, and the control channel is characterized by a delay. © Pleiades Publishing, Ltd., 2010.

Rusanov A.I.,Saint Petersburg State University
Russian Chemical Reviews | Year: 2016

As materials science studies physicochemical properties of materials, it needs a support of thermodynamics, which predicts general regularities for physicochemical properties of matter. This survey deals with solid materials the thermodynamic description of which is especially complicated. The achievements of last years provide better insight in the chemical potential anisotropy and, on this grounding, in the anisotropy of chemical affinity governing all processes in solid materials. The survey summarizes novel approaches and thermodynamic equations and then exhibits their use in materials science. As examples, the solubility, creep and corrosion of materials are analyzed. A newly discovered phenomenon, the strain sign effect in corrosion under stress (e.g., a difference in the corrosion rate on the opposite sides of a bent metallic plate), is described and explained thermodynamically.Amodern theory of the strength of materials developed during last years is also presented with the characterization of crack properties, the mechanisms of crack propagation and estimation of the ultimate stress. The development of this area required the introduction of a novel thermodynamic potential that formed the basis for the theory of strength. © 2015 Russian Academy of Sciences and Turpion Ltd.

Vasilyev A.V.,Saint Petersburg State University
Russian Chemical Reviews | Year: 2013

Published data on the reactions of vinyl type cations generated upon protonation of the carbon - carbon triple bond of acetylene compounds in proton-donor Brønsted superacids and conjugate Brønsted -Lewis systems: HSO3F, CF3SO3H, HSO3F- SbF5, CF3SO3H- SbF5, HF- SbF 5, HBr -AlBr3, etc., are summarized. Charasteristics of vinyl type cations by physicochemical methods (NMR spectroscopy, X-ray diffraction analysis, IR spectroscopy) are given. The bibliography includes 88 references. © 2013 Russian Academy of Sciences and Turpion Ltd.

Kharitonov V.L.,Saint Petersburg State University
Automatica | Year: 2010

A necessary and sufficient condition for the existence and uniqueness of Lyapunov matrices for neutral type single delay systems is presented. © 2010 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.

Markov A.G.,Saint Petersburg State University | Amasheh S.,Free University of Berlin
Frontiers in Physiology | Year: 2014

Pleura consists of visceral and parietal cell layers, producing a fluid, which is necessary for lubrication of the pleural space. Function of both mesothelial cell layers is necessary for the regulation of a constant pleural fluid volume and composition to facilitate lung movement during breathing. Recent studies have demonstrated that pleural mesothelial cells show a distinct expression pattern of tight junction proteins which are known to ubiquitously determine paracellular permeability. Most tight junction proteins provide a sealing function to epithelia, but some have been shown to have a paracellular channel function or ambiguous properties. Here we provide an in-depth review of the current knowledge concerning specific functional contribution of these proteins determining transport and barrier function of pleural mesothelium. © 2014 Markov and Amasheh.

Bobylev V.V.,Saint Petersburg State University | Bajkova A.T.,Russian Academy of Sciences
Monthly Notices of the Royal Astronomical Society | Year: 2013

To estimate the parameters of the Galactic spiral structure - namely the pitch angle i and the number of spiral arms - data on Galactic masers with known trigonometric parallaxes were used. We applied the well-known method based on analysis of the 'position angle - distance logarithm' diagram. Estimates of the pitch angle i obtained from four segments of different arms belonging to the global Galactic structure are self-consistent and close to i=-13° ± 1°. The segment which is most interesting is that of the Outer arm. It contains only three masers. Hence, in order to obtain correct estimates, we also used the data on 12 very young star clusters with distances determined by Camargo et al. from infrared photometry. The estimates obtained allow us to conclude in favour of the four-armed model of the Galactic spiral structure. © 2013 The Authors.

The fluid regime of medium-grade metapelitic systems was studied with mineral fugometers. It has been established that at least some of the rocks under consideration contain mineral assemblages equilibrated with the participation of fluids with an appreciably lowered mole fraction of the aqueous component (0.4-0.7). The data obtained are used to explain the systematic discrepancy between the temperature estimated with the garnet-biotite geothermometer and the program THERMOCALC. It has been suggested that the negative correlation between the temperature intervals of crystallization and the nucleation temperature of the studied garnets is related to the kinetic features of porphyroblast growth. © 2012 Pleiades Publishing, Ltd.

The model of the positive column (PC) of a moderate-pressure (5-30 Torr) glow discharge in a mixture of inert gases and chlorine under currents of up to 50 mA/cm2 extends the existing models of discharges in electronegative gases. The novelty of the model is the inclusion of radial nonuniformity in the gas temperature and dissociation of chlorine molecules into atoms, as well as allowance for heating of ions by the electric field and step ionization. As a result, the calculated radial profiles of charged particle concentrations are not only in qualitative agreement with earlier-developed theories of electronegative discharges, but also in quantitative agreement with experimental data. It is shown that allowance for dissociation of chlorine molecules and the effect of longitudinal field Ez on the ion temperatures is essential for this conformity in the model of the PC of a glow discharge in the mixture of inert gases and chlorine. However, radial field Er can be disregarded in estimating the ion temperatures. The smallness of the contribution of the ion current to the total current of the discharge, which had earlier only been postulated, is demonstrated. It is shown that diffusion-aided removal is the predominant mechanism of perishing of electrons and positive ions; for this reason, electron-ion recombination (as well as ion-ion recombination in the balance of positive ions) can be disregarded. © 2011 Pleiades Publishing, Ltd.

Przhibel'skii S.G.,Saint Petersburg State University
Technical Physics | Year: 2011

Analytical and numerical studies of the energy density spatial distribution of a fluctuating electric field near the model ionic crystal surface as a function of temperature are carried out. It is established that the fluctuating field energy density decreases as h-3.3 with increasing distance h from the crystal surface. The fluctuating field energy increases with temperature and differs from zero at -273°C due to quantum zero-point vibrations of ions in the lattice. © 2011 Pleiades Publishing, Ltd.

Loginov D.K.,Saint Petersburg State University
Physics of the Solid State | Year: 2010

A theoretical model has been developed to describe the behavior of exciton polaritons in a wide quantum well for structures with the zinc blende symmetry in a transverse magnetic field (the Voigt geometry). The model takes into account the mixing of the 1s-1s and 1s-2p states of heavy excitons by the magnetic field and makes it possible to explain and quantitatively describe the activation of optically inactive states in the reflection spectra and the magnetic-field-induced increase in the translational mass of the exciton. The quantitative calculations of the spectra have been preformed using typical parameters for CdTe/ZnCdTe quantum-well structures. © Pleiades Publishing, Ltd., 2010.

Zvereva G.N.,Saint Petersburg State University
Optics and Spectroscopy (English translation of Optika i Spektroskopiya) | Year: 2010

The electron energy-distribution functions, the rates of plasmochemical reactions, and the densities of various plasma components have been calculated for a microwave discharge (f = 1000 MHz, P = 100-700 mW) in krypton plasma (p = 0.5 atm) excited by an electron beam with an energy of 12 keV. It has been found that the heating by a microwave field shifts the peak of the electron energy-distribution function (EEDF) from 0.5 to 2 eV, which leads to higher rates of reactions with excitation thresholds lying near the EEDF peak. As a result, the population of excited levels increases by two to three times. © 2010 Pleiades Publishing, Ltd.

Kutcherov D.,Saint Petersburg State University
Journal of Thermal Biology | Year: 2015

Chrysomela vigintipunctata (Scopoli) is a univoltine leaf beetle commonly encountered on willows across the Palearctic forest zone. The preimaginal development in this species takes place during a short time period, from May to June, because larvae are unable to consume mature leaves of the host plant. Therefore, the diet quality imposes a time constraint, and it was expected that the temperature dependence of development in C. vigintipunctata should be adaptively adjusted to the shortness and cool conditions of the favorable season. It was experimentally determined that this leaf beetle was stenothermal at the larval stage, required 275.5 degree-days above the threshold of 9.0. °C for total development from oviposition to adult emergence, and attained greater body mass at lower temperatures. However, in all of these aspects, the thermal ecology of C. vigintipunctata was similar to that of two related multivoltine species, C. populi and C. scripta. The interspecific similarity of thermal reaction norms for development rate and body size suggests that these reaction norms in C. vigintipunctata were unlikely to have been shaped by selection favoring faster development or growth early in the season. The results are discussed in terms of the "ecological fitting" concept, which states that a species may be successful in exploiting novel environments while retaining ecophysiological traits evolved elsewhere. © 2015 Elsevier Ltd.

Andronov I.V.,Saint Petersburg State University
IEEE Antennas and Wireless Propagation Letters | Year: 2013

New high-frequency asymptotic formulas are presented for electromagnetic and acoustic problems of scattering by asymptotically strongly elongated spheroids. Numerical computations show that when spheroids becomes less elongated, scattering cross sections tend to the classical high-frequency limit. © 2002-2011 IEEE.

Butikov E.I.,Saint Petersburg State University
Advances in Space Research | Year: 2015

Several possibilities of launching a space vehicle from the orbital station are considered and compared. Orbital maneuvers discussed in the paper can be useful in designing a trajectory for a specific space mission. The relative motion of orbiting bodies is investigated on examples of spacecraft rendezvous with the space station that stays in a circular orbit around the Earth. An elementary approach is illustrated by an accompanying simulation computer program and supported by a mathematical treatment based on fundamental laws of physics and conservation laws. Material is appropriate for engineers and other personnel involved in space exploration, undergraduate and graduate students studying classical physics and orbital mechanics. © 2015 COSPAR. Published by Elsevier Ltd. All rights reserved.

Blagoveshchensky D.V.,Saint Petersburg State University
Geomagnetism and Aeronomy | Year: 2016

Two high-latitude high-frequency (HF) paths of oblique-incidence ionospheric sounding were selected: Gor’kovskaya (GRK)–Dixon Island (DIK) and GRK–Lovozero (LOZ).The following propagation parameters were studied: F2MOF and F2MUF for the main signal, F2MOFl for lateral signals, EsMOF for a signal reflected from the sporadic ionospheric layer, and MOFm for the propagation modes of the M (or N) type. Here MOF and MUF are the maximum observed and usable frequencies, respectively. It was found that the reciprocal theorem is satisfied on two radio paths depending on the studied propagation parameter: the path length and location, time of day, and degree of magnetospheric disturbance. It was found that the reciprocal theorem is satisfied in 78, 50, and 30% of cases on the first path for the F2MUF values in the daytime under moderately disturbed conditions, in the morning, and at night, respectively. For the MOFm and moderately disturbed conditions on this path, the reciprocal theorem is satisfied in 40, 35, and 20% of cases in the daytime, morning, and at night, respectively. For the F2MUF values on the second path, reciprocity is satisfied in 73% of cases in the daytime and under moderately disturbed conditions and in 30% of cases at night during a quiet period. On this path, reciprocity is satisfied in 33% of all cases at night under strongly disturbed conditions. An unusual fact was also detected when ionograms of oblique-incidence ionospheric sounding were analyzed: the F2MUF values in the LOZ–GRK direction are almost always slightly (by 1–4%) larger than in the GRK–LOZ direction. A similar difference in the F2MUF values in the forward and backward directions can apparently be explained by the steep horizontal gradient in the electron density distribution from north to south in the reflection region of this path. Such a situation is not observed on the DIK–GRK line. © 2016, Pleiades Publishing, Ltd.

Bekryaev R.V.,Saint Petersburg State University | Polyakov I.V.,University of Alaska Fairbanks | Alexeev V.A.,University of Alaska Fairbanks
Journal of Climate | Year: 2010

This study uses an extensive dataset of monthly surface air temperature (SAT) records (including previously unutilized) from high-latitude (>60°N) meteorological land stations. Most records have been updated by very recent observations (up to December 2008). Using these data, a high-latitude warming rate of 1.36°C century -1 is documented for 1875-2008-the trend is almost 2 times stronger than the Northern Hemisphere trend (0.79°C century -1), with an accelerated warming rate in the most recent decade (1.35°C decade -1). Stronger warming in high-latitude regions is a manifestation of polar amplification (PA). Changes in SAT suggest two spatial scales of PA-hemispheric and local. A new stable statistical measure of PA linking high-latitude and hemispheric temperature anomalies via a regression relationship is proposed. For 1875-2008, this measure yields PA of ~1.62. Local PA related to the ice-albedo feedback mechanisms is autumnal and coastal, extending several hundred kilometers inland. Heat budget estimates suggest that a recent reduction of arctic ice and anomalously high SATs cannot be explained by ice-albedo feedback mechanisms alone, and the role of large-scale mechanisms of PA of global warming should not be overlooked. © 2010 American Meteorological Society.

Rodziewicz P.,The Interdisciplinary Center | Rutkowski K.S.,Saint Petersburg State University | Meyer B.,The Interdisciplinary Center
Physical Chemistry Chemical Physics | Year: 2011

For isolated fluoroform (F3CH) molecules adsorbed on a hexagonal ice (0001) surface the properties of blue- and red-shifting hydrogen bonds were studied using static density functional theory (DFT) calculations and Car-Parrinello molecular dynamics (CP-MD) simulations. A systematic search by starting from many initial configurations was performed to determine the lowest-energy structures of F3CH on the ice surface, and for the optimized geometries the vibrational frequencies were calculated. The local minima structures are analyzed in terms of their coordination to the surface, with special focus on identifying blue-shifting hydrogen bonds via their spectroscopic signature of an increased frequency of the C-H fundamental stretching vibration. Subsequently, by CP-MD simulations the stability of the lowest-energy configurations at finite temperatures was verified and possible transformation pathways connecting the local minima structures were explored. © the Owner Societies 2011.

Lukin V.V.,Arctic and Antarctic Research Institute | Vasiliev N.I.,Saint Petersburg State University
Annals of Glaciology | Year: 2014

This paper considers the state of the deep ice borehole 5G at the Russian Antarctic Vostok station after penetration to the surface water of Vostok Subglacial Lake. It discusses the peculiar features of drilling the 'fresh frozen' lake water that has risen in the borehole and the technology for subsequent study of the lake water layer via borehole 5G filled with a kerosene-Freon®mixture. The extremely high rise of lake water via the borehole is attributed to a hydraulic fracture at the side of the borehole, which diverted a large amount of drilling fluid. The proposed technology for the study of the water layer envisages minimal environmental impact and excludes penetration of any of the kerosene-Freon1 mixture to the water layer. This technology has been presented several times at different international forums. There was no critical comment on the Environmental Impact Assessment of the technology at the 37th Antarctic Treaty Consultative Meeting in 2014 and it was adopted for implementation.

Tsyganenko N.A.,Saint Petersburg State University
Journal of Geophysical Research: Space Physics | Year: 2014

The paper presents first results of the data-based modeling of the geomagnetospheric magnetic field, using the data of Polar, Geotail, Cluster, and Time History of Events and Macroscale Interactions during Substorms satellites, taken during the period 1995-2012 and covering 123 storm events with SYM-H ≥ -200 nT. The most important innovations in the model are (1) taking into account the interplanetary magnetic field (IMF)-dependent shape of the model magnetopause, (2) a physically more consistent global deformation of the equatorial current sheet due to the geodipole tilt, (3) symmetric and partial components of the ring current are calculated based on a realistic background magnetic field, instead of a purely dipolar field, used in earlier models, and (4) the validity region on the nightside is extended to ∼40-50 R E. The model field is confined within a magnetopause, based on Lin et al. (2010) empirical model, driven by the dipole tilt angle, solar wind pressure, and IMF Bz. A noteworthy finding is a significant dependence of the magnetotail flux connection across the equatorial plane on the model magnetopause flaring rate, controlled by the southward component of the IMF. Key Points A data-based magnetosphere model with IMF-dependent magnetopause is developed The variable magnetopause flaring affects the magnetotail field stretching Mutually consistent deformations of the equatorial current and the magnetopause ©2014. American Geophysical Union. All Rights Reserved.

Cherepanov G.O.,Saint Petersburg State University
Paleontological Journal | Year: 2014

The scute mosaic (pholidosis) in the turtle shell is characterized by two phenomena: phylogenetic stability of the general body plan and wide individual variability. The study of turtle morphogenesis allowed this phenomenon to be explained. It is shown that scute rudiments are formed in embryogeny as local epidermal thickenings, placodes; the positions of placodes is strictly confined to certain parts of the body and their foundation is realized in strict sequence. In particular, in the carapace, placodes are formed exclusively opposite the transverse trunk myosepta, in septal depressions of the embryonic integument; at the same time, marginal placodes are formed in each septal depression (i.e., segment by segment); placodes of pleural and central series are formed in alternate position in the even and odd depressions, respectively. The stability of the scute pattern is connected with the basic mechanisms of morphogenesis, providing the maintenance of bilateral symmetry and determination of scute positions by the primary embryonic segmentation. The main sourse for pholidosis variability is the presence in turtle embryos of vacant septal depressions, in which extraordinary placodes could have developed in the case of minor disturbances of embryogenesis. These aberrations are rather frequent and usually result in asymmetry of the scutation. The breaking of turtle pholidosis symmetry is connected with deviations in ontogenesis, such as asymmetrical formation of epidermal placodes, with a shift to one body side for a segment or more, the formation of additional placodes in the vacant septal depressions, atypical fusion of neighboring epidermal placodes, the absence of regular epidermal placodes in typical body segments. © 2014, Pleiades Publishing, Ltd.

Meyer M.,Friedrich - Alexander - University, Erlangen - Nuremberg | Klemd R.,Friedrich - Alexander - University, Erlangen - Nuremberg | Konopelko D.,Saint Petersburg State University
Lithos | Year: 2013

The Makbal Complex in the western Tianshan Mountains of Kazakhstan and Kyrgyzstan consists of HP/UHP metasedimentary host rocks which enclose various HP mafic blocks or boudins. These mafic rocks comprise rare eclogites (sensu stricto and sensu lato), garnet amphibolites (retrograded eclogites) and a newly discovered glaucophanite (glaucophane-garnet-omphacite bearing rock).So far the Makbal Complex has been interpreted to predominantly consist of continental lithologies and the mafic rocks were considered as dismembered dikes intruding continental metasediments. This interpretation is mainly based on the geological relationship and bulk rock chemistry of the different rock types. It was further suggested that the continental lithologies of the Makbal Complex underwent eclogite-facies metamorphism in a former subduction zone.In the present study we combined conventional geothermometry, P-T pseudosection modeling and major and trace element whole rock geochemistry for different mafic samples (glaucophanite and eclogites (sensu lato)) in order to shed light on both the metamorphic evolution and the protoliths of the mafic HP rocks in the Makbal Complex.Prograde to peak-pressure clockwise P-T paths of glaucophanite and eclogites (sensu lato) were modeled using garnet isopleth thermobarometry. The results show that the glaucophanite and eclogite (sensu lato) samples experienced similar prograde P-T paths and slightly different peak metamorphic conditions at ~. 560. °C at 2.4. GPa for the former and between ~. 520. °C at 2.2. GPa and ~. 555. °C at ~. 2.5. GPa for the latter, corresponding to burial depths between 70 and 85. km.Whole rock major and trace element analyses and petrological evidence imply that the various rock types at the Makbal Complex most likely originated from different precursor rocks. Eclogites (sensu lato) are believed to represent strongly retrogressed former eclogite-facies rocks that had never been eclogites (sensu stricto, i.e. >70 vol.% garnet and omphacite) due to an unfavorable alkali-poor bulk composition (Na2O <1wt.%). The four high-pressure mafic samples investigated in this study originated from oceanic crust (Zr/Hf ratio of 33 to 35) which contradicts all previous studies suggesting a continental protolith for all mafic HP/UHP rocks at Makbal.The present study indicates that the mafic high-pressure rocks represent incoherent segments of exhumed oceanic crust. Juxtaposition of different mafic oceanic (this study) and continental rocks is suggested to be due to buoyancy-driven exhumation of the metasedimentary host rock in the subduction channel where dismembered fragments of the subducted oceanic crust were captured in different depths. © 2013 Elsevier B.V.

Gavrilov N.M.,Saint Petersburg State University | Kshevetskii S.P.,Immanuel Kant Baltic Federal University
Advances in Space Research | Year: 2013

Acoustic-gravity waves (AGWs) observed in the upper atmosphere may be generated near the Earth's surface due to a variety of meteorological sources. Two-dimensional simulations of vertical propagation and breaking of nonlinear AGWs in the atmosphere are performed. Forcing near the Earth's surface is used as the AGW source in the model. We use a numerical method based on finite-difference analogues of fundamental conservation laws for solving atmospheric hydrodynamic equations. This approach selects physically correct generalized solutions of the wave hydrodynamic equations. Numerical simulations are performed in a representative region of the Earth's atmosphere up to altitude 500 km. Vertical profiles of temperature, density, molecular viscosity and heat conductivity were taken from the standard atmosphere model MSIS-90 for January. Calculations were made for different amplitudes and frequencies of lower boundary wave forcing. It is shown that after activating the tropospheric wave forcing, the initial pulse of AGWs may very quickly propagate to altitudes of 100 km and above and relatively slowly dissipate due to molecular viscosity and heat conduction. This may increase the role of transient nonstationary waves in effective energy transport and variations of atmospheric parameters and gas admixtures in a broad altitude range. © 2012 COSPAR. Published by Elsevier Ltd. All rights reserved.

Krivovichev S.V.,Saint Petersburg State University
Acta Crystallographica Section B: Structural Science, Crystal Engineering and Materials | Year: 2016

Using a statistical approach, it is demonstrated that the complexity of a crystal structure measured as the Shannon information per atom [Krivovichev (2012). Acta Cryst. A68, 393-398] represents a negative contribution to the configurational entropy of a crystalline solid. This conclusion is in full accordance with the general agreement that information and entropy are reciprocal variables. It also agrees well with the understanding that complex structures possess lower entropies relative to their simpler counterparts. The obtained equation is consistent with the Landauer principle and points out that the information encoded in a crystal structure has a physical nature.Structural complexity measured as the Shannon information per atom represents a negative contribution to the configurational entropy of a crystalline solid. © International Union of Crystallography, 2016.

Manida S.N.,Saint Petersburg State University
Theoretical and Mathematical Physics | Year: 2011

We propose a method for deforming an extended Galilei algebra that leads to a nonstandard realization of the Poincaré group with the Fock-Lorentz linear fractional transformations. The invariant parameter in these transformations has the dimension of length. Combining this deformation with the standard one (with an invariant velocity c) leads to the algebra of the symmetry group of the anti-de Sitter space in Beltrami coordinates. In this case, the action for free point particles contains the dimensional constants R and c. The limit transitions lead to the ordinary (R → ∞) or alternative (c → ∞) but nevertheless relativistic kinematics. © 2011 Pleiades Publishing, Ltd.

Popov I.Yu.,Saint Petersburg State University
Physica Scripta | Year: 2011

The problem of flow through a nanotube is considered. Classical fluid mechanics does not give an adequate description of the process. Modified hydrodynamic equations are derived from a microscopic model using the dynamical Bogolyubov approach and the Zwanzig projection operator method. © 2011 The Royal Swedish Academy of Sciences.

Brusnitsyn A.I.,Saint Petersburg State University
Geochemistry International | Year: 2013

The Parnok ferromanganese deposit is confined to the black shales of the western slope of the Polar Urals. The deposit area is made up of weakly metamorphosed terrigenous-carbonate rocks formed in a marine basin at a passive continental margin. Ore-bearing sequence is composed of coaliferous clayey-siliceous-calcareous shales comprising beds and lenses of pelitomorphic limestones, and iron and manganese ores. The iron ores practically completely consist of micrograined massive magnetite. The manganese ores are represented by lenticular-bedded rocks consisting of hausmannite, rhodochrosite, and diverse manganese silicates. With respect to relations between indicator elements (Fe, Mn, Al, Ti), the shales are ascribed to pelagic sediments with normal concentrations of Fe and Mn, the limestones correspond to metalliferous sediments, ferruginous sediments are ore-bearing sediments, while manganese rocks occupy an intermediate position. It was found that the concentrations of trace elements typical of submarine hydrothermal solutions (As, Ge, Ni, Pb, Sb, Zn, etc.) in both the ore types are in excess of those in lithogenic component. At the same time, the indicator elements of terrigenous material (Al, Ti, Hf, Nb, Th, Zr, and others) in the ores are several times lower than those in the host shales (background sediments). REE distribution patterns in iron ores show the positive Eu anomaly, while those in manganese ores, the positive Ce anomaly. In general, the chemical composition of the ores indicates their formation in the hydrothermal discharge zone. The peculiar feature of the studied object is the manifestation of hydrothermal vents in sedimentary basin without evident signs of volcanic activity. Hydrothermal solutions were formed in terrigenous-carbonate sequence mainly at the expense of buried sedimentation waters. The hydrothermal system was likely activated by rejuvenation of tectonic and magmatic processes at the basement of sedimentary sequences. Solutions leached iron, manganese, and other elements from sedimentary rocks and transported them to the seafloor. Their discharge occurred in relatively closed marine basin under intermittent anaerobic conditions. Eh-pH variations led to the differentiation of Fe and Mn and accumulation of chemically contrasting ore-bearing sediments. © 2013 Pleiades Publishing, Ltd.

Yegorova T.,Ukrainian Academy of Sciences | Gobarenko V.,Ukrainian Academy of Sciences | Yanovskaya T.,Saint Petersburg State University
Geophysical Journal International | Year: 2013

The backarc Black Sea (BS) basin was formed in the Late Cretaceous-Palaeocene at the hinterland of the Pontide magmatic arc due to subduction of the Neotethys ocean below the southern Eurasian continental margin.At present the BS consists of two large depressions-the West-and East-Black Sea basins (WBS and EBS) filled with thick (up to 12 km) Cretaceous and younger sediments and underlain by a crust of oceanic/suboceanic type. The sediments mask poorly investigated crystalline crust that is thought to comprise an accretional collage of microplates and terranes of different affinities. To investigate the lithospheric structure of the BS we performed a 3-D gravity analysis and local seismic tomography study. 3-D gravity backstripping analysis allowed us to separate the gravity signal from different parts of the crustal model and then, by subtracting the crustal effect from the observed field, to obtain gravity anomalies of presumed mantle origin only. The broad positive long wavelength component of this might be indicative of good isostatic equilibrium of the deep structure of the Black Sea, that is, that the negative gravity effect of sediments is almost totally compensated by the strong positive gravity impact of Moho shallowing. Velocity structure of the BS lithosphere has been studied by P-wave local seismic tomography. It uses the traveltimes of the earthquakes occurring inside the study region and recorded by permanent seismic stations around the BS. Initial data were corrected for the effect of the crust. The resulting model shows the BS lithosphere as being rather heterogeneous with two domains of increased velocity in its western and eastern parts. The gravity analysis and seismic tomography approaches were integrated by calculating the upper-mantle gravity effect of the tomography model and comparing this to the mantle gravity signature inferred from the gravity analysis itself. The integrated results suggest the presence of rheologically strong and cold continental lithosphere below the BS, similar to Precambrian lithosphere of the East European Platform. © The Authors 2013. Published by Oxford University Press on behalf of The Royal Astronomical Society.

Malkin Z.,Saint Petersburg State University
Journal of Geodynamics | Year: 2013

Variations in free core nutation (FCN) are associated with different processes in the Earth's fluid core and core-mantle coupling. The same processes are generally caused the variations in the geomagnetic field (GMF) particularly the geomagnetic jerks (GMJs), which are rapid changes in GMF secular variations. Therefore, the joint investigation of variations in FCN and GMF can elucidate the Earth's interior and dynamics. In this paper, we investigated the FCN amplitude and phase variations derived from VLBI observations. Comparison of the epochs of the changes in the FCN amplitude and phase with the epochs of the GMJs indicated that the observed extremes in the FCN amplitude and phase variations were closely related to the GMJ epochs. In particular, the FCN amplitude begins to grow one to three years after the GMJs. Thus, processes that cause GMJs are assumed as sources of FCN excitation. © 2013 Elsevier Ltd.

Gulbin Y.L.,Saint Petersburg State University
Geology of Ore Deposits | Year: 2013

The kinetics of zoned garnet porphyroblast growth is exemplified in a sample of garnet-staurolite-biotite schist from the northern Ladoga region. The diffusion-controlled porphyroblast growth was accompanied by a decrease in the kinetic coefficient during phase reactions. Even at insignificant (1-2°C) thermal overstepping, the leading role of diffusion as a factor that controls kinetics of porphyroblast growth in medium-grade metapelites is consistent with the parameters of metamorphic crystallization: T = 500-650°C, t = 1 Ma; DA1 app = 10-14 cm2/s, L = 0.2-0.6 cm, r = 1-3 mm, ΔC Al = 1.5 × 10-4-1.5 × 10-3 mol/cm3. © 2013 Pleiades Publishing, Ltd.

Approaches for estimations of effective turbulent diffusion and energetic parameters from characteristics of anisotropic and isotropic spectra of perturbations of atmospheric refractivity, density and temperature are developed. The approaches are applied to the data obtained with the GOMOS instrument for measurements of stellar scintillations on-board the Envisat satellite to estimate turbulent Thorpe scales, LT, diffusivities, K, and energy dissipation rates, ϵ, in the stratosphere. At low latitudes, effective values are LT ∼ 1-1.1 m, ϵ ∼ (1.8-2.4) × 10-5 W kg-1, and K ∼ (1.2-1.6) × 10-2 m2 s-1 at altitudes of 30-45 km in September-November 2004, depending on different assumed values of parameters of anisotropic and isotropic spectra. Respective standard deviations of individual values, including all kinds of variability, are δLT ∼ 0.6-0.7 m, δϵ ∼ (2.3-3.5) × 10-2 W kg-1, and δK ∼ (1.7-2.6) × 10-2 m2 s-1. These values correspond to high-resolution balloon measurements of turbulent characteristics in the stratosphere, and to previous satellite stellar scintillation measurements. Distributions of turbulent characteristics at altitudes of 30-45 km in low latitudes have maxima at longitudes corresponding to regions of increased gravity wave dissipation over locations of stronger convection. Correlations between parameters of anisotropic and isotropic spectra are evaluated.

Tsiganov A.V.,Saint Petersburg State University
Journal of Physics A: Mathematical and Theoretical | Year: 2011

We discuss the concept of natural Poisson bivectors, which allows us to consider the overwhelming majority of known integrable systems on the sphere in the framework of bi-Hamiltonian geometry. © 2011 IOP Publishing Ltd.

Remenets G.F.,Saint Petersburg State University | Beloglazov M.I.,Russian Academy of Sciences
Journal of Geophysical Research: Space Physics | Year: 2013

The rare phenomenon of ultrarelativistic electron precipitation into the middle polar atmosphere, prevalent under calm geophysical conditions, was established from ground-based radio wave measurements during the period of 1982-1992. Precipitating electrons with energy ∼ 100 MeV and sufficient density to generate X- and gamma-ray bremsstrahlung create a sporadic layer of ionization in the atmosphere under the regular D layer of the ionosphere. Very low frequency radio waves reflect from this sporadic layer with abnormal weakening and with an unusually low height of reflection. The layer has a horizontal linear scale of about several thousand kilometers, with a thickness in altitude of about 20-30 km, and persists for several hours. Due to this layer of electric conductivity, the effective height of this "ground-ionized atmosphere" waveguide diminishes in exceptional cases by 2-2.5 times. The auroras of X-ray bremsstrahlung have been detected by the reflection of radio waves with wavelengths of 30-20 km. This phenomenon may be termed "a polar cap absorption effect of the second kind" as an electron analog of proton precipitation. Key Points Intesive sporadic layer of conductivity in atmosphere and X-ray bremsshtrahlung The ~ 100 MeV electron precipitation into polar atmosphere On ground sensing of the changes of atmosphere conductivity ©2013. American Geophysical Union. All Rights Reserved.

Astakhov V.I.,Saint Petersburg State University
Boreas | Year: 2013

The size, age and dynamics of Pleistocene glaciers, especially ice sheets that periodically covered the northern seaboard of Eurasia, are crucial for understanding the evolution of arctic climates, sea-level changes, the biota and tectonism. General ideas on the glacial history of the vast areas of northern Russia between 48° and 148°E, beyond the limits of the Fennoscandian glaciation, have considerably changed during the last two decades. The change towards modern views may even be considered as a paradigm shift from the conventional wisdom of the previous half-century. The transformation of the main landmarks of late Quaternary glacial history started in the 1970s and accelerated after 1993 as a result of international collaboration in the Russian Arctic. A wealth of new sedimentological, geomorphic and stratigraphic data has recently accumulated for the sedimentary record of the last 200ka. This information, together with data collected from native geological surveys, has been synthesized in the form of digital maps of ice limits based on key stratigraphic sites. The results have been published as contributions to the international programs QUEEN and APEX and also as parts of global compilations. These publications give general overviews of the Eurasian glacial history, but some important modern data are reported only in the Russian literature and therefore are hardly known to the international community. In this paper I will first consider the background material on the non-Scandinavian glaciations and then follow this with a review of the modern results obtained in the course of international cooperation. The outcome is inevitably influenced (or biased) by my long-term experience in studying the Pleistocene of northern Russia. I will not discuss here the extreme northeast of Siberia (western Beringia), as this is a distinct topic partly overviewed in recent publications. © 2012 The Author. Boreas © 2012 The Boreas Collegium.

Obi T.,Waseda University | Ishmatova D.,Saint Petersburg State University | Iwasaki N.,Waseda University
International Journal of Medical Informatics | Year: 2013

Objective: The paper aims to explore effective measures and strategies for the promotion of ICT-enabled innovations for the elderly and people with special needs. Methods: The paper begins by reviewing current government initiatives in the field of e-health and accessibility that are addressing challenges faced by Japan's rapidly ageing society. It then evaluates the results of Japanese government efforts in the promotion of ICT solutions for its older population against the availability of special infrastructure, device interfaces, and services and applications that meet five essential needs of the elderly with regard to quality of life in highly developed countries. Results and conclusion: The results of the study suggest that more efforts are needed to exploit ICT to transform all domains of society in order to meet the challenges produced by a rapidly ageing population. For that purpose the paper proposes 12 main areas in which to facilitate ICT innovations for an ageing population. It then outlines a number of strategic directions for the formulation of specific measures that will place Japan in the forefront of societal transformation. © 2012 Elsevier Ireland Ltd.

Krivovichev S.V.,Saint Petersburg State University
Crystallography Reports | Year: 2012

Atomic-molecular mechanisms of crystal growth can be modeled based on crystallochemical information using cellular automata (a particular case of finite deterministic automata). In particular, the formation of heteropolyhedral layered complexes in uranyl selenates can be modeled applying a one-dimensional three-colored cellular automaton. The use of the theory of calculations (in particular, the theory of automata) in crystallography allows one to interpret crystal growth as a computational process (the realization of an algorithm or program with a finite number of steps). © 2012 Pleiades Publishing, Ltd.

A brief review is presented of the concepts regarding the nature of α and β relaxation processes in melts and glasses. Experimental data have been used to show that different types of relaxation in oxide systems can be interrelated to each other. The molecular mechanism of viscous flow in inorganic systems has been discussed in detail with the use of continuum theories (elasticity and hydrodynamics) developed in the works by the author in 1967-2007. A rigorous relationship between the volumes of atoms overcoming the activation barrier, the instantaneous shear modulus, and the barrier itself (free activation energy) has been derived. This relationship allows one to calculate the sizes of atoms involved in the viscous flow with a deviation that does not exceed 10% of the values determined by direct structural methods. In this case, empirically chosen con- stants are absent. Based on the results obtained by Anderson and Stewart (1954) and the author (1974), it has been established that the activation energy for ionic conduction can be calculated using similar notions. It has been demonstrated for the first time that the universal relation between the viscosity and conductivity over a wide range of temperatures (for alkali-containing oxide melts) i.e., the Littleton equation, finds a simple quantitative explanation in the framework of the same models, even though the mechanisms of both processes do not depend on each other. © Pleiades Publishing, Ltd., 2010.

Crown-group salamander Kiyatriton leshchinskiyi, from the Lower Cretaceous (Aptian-Albian) Ilek Formation of the Shestakovo locality in Western Siberia, Russia, was the first "lissamphibian" discovered from the Mesozoic of Russia and it is the only Early Cretaceous salamander from Asia which was found outside China. In this paper a detailed redescription of type and newly collected material on Kiyatriton leshchinskiyi, consisting fragmentary cranial and postcranial bones is presented. The structure of the atlas, trunk vertebrae and femur suggest that Kiyatriton leshchinskiyi may be a member of the Cryptobranchoidea. © 2014 Elsevier Ltd.

Anikiev D.,Saint Petersburg State University | Valenta J.,Czech Institute of Rock Structure And Mechanics | Stanek F.,Czech Institute of Rock Structure And Mechanics | Eisner L.,Czech Institute of Rock Structure And Mechanics
Geophysical Journal International | Year: 2014

Seismic monitoring can greatly benefit from imaging events with a low signal-to-noise ratio (SNR) as the number of the events with a low signal grows exponentially. One way to detect weaker events is improvement of a SNR by migration-type stacking of waveforms from multiple stations. We have developed a new method of location of seismic events that involves stacking of seismic phases and amplitudes along diffraction traveltime curves to suppress noise and detect seismic events with a SNR lower than that on individual receivers. The stacking includes polarity correction based on a simultaneous seismic moment tensor inversion and detection algorithm on the stack function. We applied this method to locate microseismicity induced by hydraulic fracturing. First we calibrated the velocity model by locating perforation shots at known locations. Then we processed 3 d of data from microseismic monitoring of shale stimulation and benchmarked migration-type locations of the largest events that were manually located. The detected and located events induced by hydraulic fracturing in this case study are mostly shear events forming narrow bands along the maximum horizontal stress direction approximately 100 m above the injection intervals. The proposed technique is fully automated and feasible for real-time seismic monitoring. © The Authors 2014.Published by Oxford University Press on behalf of The Royal Astronomical Society.

Syasko V.A.,Saint Petersburg State University
Russian Journal of Nondestructive Testing | Year: 2010

Combinations of electroconductive nonferromagnetic coatings and electroconductive nonferromagnetic bases that are used in industry are analyzed. These are divided into five groups depending on the ratios of their electric conductivities. The scheme, design, and principles of operation of eddy-current frequency transducers are considered. The main dependences for determining their parameters (operating frequency, diameter of the winding, sensitivity to the informative parameter, and interfering factors, etc.) are presented. Examples of measurement problems and the optimal application of this method and the achieved metrological characteristics of compact transducers are presented. © Pleiades Publishing, Ltd., 2010.

Shkol'nikov E.V.,Saint Petersburg State University
Russian Journal of Physical Chemistry A | Year: 2016

The effect the pH of an aqueous medium has on the molar solubility of polymorphic TiO2 modifications at 25°C is calculated and experimentally tested thermodynamically with allowance for the formation of hydroxo complexes. It is found that molecular-ionic solubility depends substantially on TiO2 structure and dispersity, increasing by three orders of magnitude upon moving from a stable crystalline to an amorphous modification. © 2016 Pleiades Publishing, Ltd.

Akimkin V.V.,Saint Petersburg State University
Astronomy Reports | Year: 2015

The coagulation of dust particles under the conditions in protoplanetary disks is investigated. The study focuses on the repulsive electrostatic barrier against growth of charged dust grains. Taking into account the photoelectric effect leads to the appearance of a layer at intermediate heights where the dust has a close to zero charge, enabling the dust grains to grow efficiently. An increase in the coagulation rate comes about not only due to the lowering of the Coulomb barrier, but also because of the electrostatic attraction between grains of opposite charge due to the non-zero dispersion of the near-zero charge. Depending on the efficiency of mixing in the disk, the acceleration of the evolution of the dust in this layer could be important, both in the quasi-stationary stage of the disk evolution and during its dispersal. © 2015, Pleiades Publishing, Ltd.

Sunagar K.,University of Porto | Johnson W.E.,U.S. National Cancer Institute | O'Brien S.J.,U.S. National Cancer Institute | O'Brien S.J.,Saint Petersburg State University | And 2 more authors.
Molecular Biology and Evolution | Year: 2012

Cysteine-rich secretory proteins (CRISPs) are glycoproteins found exclusively in vertebrates and have broad diversified functions. They are hypothesized to play important roles in mammalian reproduction and in reptilian venom, where they disrupt homeostasis of the prey through several mechanisms, including among others, blockage of cyclic nucleotide-gated and voltage-gated ion channels and inhibition of smooth muscle contraction. We evaluated the molecular evolution of CRISPs in toxicoferan reptiles at both nucleotide and protein levels relative to their nonvenomous mammalian homologs. We show that the evolution of CRISP gene in these reptiles is significantly influenced by positive selection and in snakes (ω = 3.84) more than in lizards (ω = 2.33), whereas mammalian CRISPs were under strong negative selection (CRISP1 = 0.55, CRISP2 = 0.40, and CRISP3 = 0.68). The use of ancestral sequence reconstruction, mapping of mutations on the three-dimensional structure, and detailed evaluation of selection pressures suggests that the toxicoferan CRISPs underwent accelerated evolution aided by strong positive selection and directional mutagenesis, whereas their mammalian homologs are constrained by negative selection. Gene and protein-level selection analyses identified 41 positively selected sites in snakes and 14 sites in lizards. Most of these sites are located on the molecular surface (nearly 76 in snakes and 79 in lizards), whereas the backbone of the protein retains a highly conserved structural scaffold. Nearly 46 of the positively selected sites occur in the cysteine-rich domain of the protein. This directional mutagenesis, where the hotspots of mutations are found on the molecular surface and functional domains of the protein, acts as a diversifying mechanism for the exquisite biological targeting of CRISPs in toxicoferan reptiles. Finally, our analyses suggest that the evolution of toxicoferan-CRISP venoms might have been influenced by the specific predatory mechanism employed by the organism. CRISPs in Elapidae, which mostly employ neurotoxins, have experienced less positive selection pressure (ω = 2.86) compared with the "nonvenomous" colubrids (ω = 4.10) that rely on grip and constriction to capture the prey, and the Viperidae, a lineage that mostly employs haemotoxins (ω = 4.19). Relatively lower omega estimates in Anguimorph lizards (ω = 2.33) than snakes (ω = 3.84) suggests that lizards probably depend more on pace and powerful jaws for predation than venom. © The Author(s) 2012.

Nazarov S.A.,Saint Petersburg State University | Taskinen J.,University of Helsinki
Zeitschrift fur Angewandte Mathematik und Physik | Year: 2015

We construct a family of periodic piezoelectric waveguides Πɛ, depending on a small geometrical parameter, with the following property: as ɛ → +0, the number of gaps in the essential spectrum of the piezoelectricity problem on Πɛ grows unboundedly. © 2015, Springer Basel.

Peterson M.V.,Saint Petersburg State University
Journal of Optical Technology (A Translation of Opticheskii Zhurnal) | Year: 2010

This paper discusses the task of separating a set of identified reference points on a pair of images of a dynamic scene, using clusters that correspond to observed moving objects. Based on the principle of minimum description length, a criterion is proposed that makes it possible to choose between different classes of transformations and to estimate the clustering quality. This criterion can be used to choose the optimum model of a spatial transformation for each discriminated cluster and to avoid being influenced by outliers in the form of incorrectly identified points. © 2010 Optical Society of America.

Titov V.,Saint Petersburg State University
Astronomische Nachrichten | Year: 2015

Periodic solutions of the general three-body problem are investigated in the shape space. Two different solutions are considered: the first is an extension of the well-known figure-eight orbit, and the second one is from the free-fall problem. Using the shape space, we reduce the dimension of the problem. These orbits are obtained numerically and described on the Euclidean plane and on the shape sphere. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Bozhokin S.V.,Saint Petersburg State University
Technical Physics | Year: 2012

An analytic expression for a continuous wavelet transform (CWT) is obtained for a nonstationary signal with spectral properties varying with time. As a model of the nonstationary signal, a superposition of elementary nonstationary signals is considered, each of which is the product of the Gaussian-shape envelope and an oscillating function. To obtain the CWT, the mother Morlet wavelet is used. The result is compared with the window Fourier transform (Gabor transform). The advantages of the CWT are illustrated by concrete examples. The applications of the exactly solvable model of nonstationary signals for simulating transient processes in physics are considered. © 2012 Pleiades Publishing, Ltd.

Simakov S.K.,Saint Petersburg State University
Journal of Materials Research | Year: 2010

The model of nanosized diamond particles formation at metastable P-T parameters from a C-H-O fluid system is presented. It explains the hydrothermal formation and growth of diamond and the specifics of chemical vapor deposition (CVD) diamond synthesis gas mixtures at low P-T parameters. Further, the model explains the genesis of interstellar nanodiamond formations in space and the genesis of metamorphic microdiamonds in shallow depth Earth rocks. In contrast to models where many possible reactions are considered, the present model makes the simplest possible assumptions about the key processes, and is then able to account for various tendencies seen in experimental data. © 2010 Materials Research Society.

Bankevich A.,Saint Petersburg State University | Pevzner P.A.,University of California at San Diego
Nature Methods | Year: 2016

The recently introduced TruSeq synthetic long read (TSLR) technology generates long and accurate virtual reads from an assembly of barcoded pools of short reads. The TSLR method provides an attractive alternative to existing sequencing platforms that generate long but inaccurate reads. We describe the truSPAdes algorithm (http://bioinf.spbau.ru/spades) for TSLR assembly and show that it results in a dramatic improvement in the quality of metagenomics assemblies. © 2016 Nature America, Inc.

Syromyatnikov A.V.,Saint Petersburg State University
Physical Review B - Condensed Matter and Materials Physics | Year: 2010

We demonstrate that long-range interaction in a system can lead to a very strong interaction between long-wavelength quasiparticles and make them heavily damped. In particular, we discuss magnon spectrum using 1/S expansion in three-dimensional Heisenberg ferromagnet (FM) with arbitrary small dipolar forces at T TC. We obtain that a fraction of long-wavelength magnons with energies k

Kulikov K.G.,Saint Petersburg State University
Technical Physics | Year: 2012

An electrodynamic model of reflection of a plane wave from a layer simulating a biological structure with a slowly varying thickness is constructed with allowance for roughness in the case when the characteristic size of inhomogeneities on the surface is much larger than the wavelength. The model makes it possible to vary the size of inhomogeneities on the rough surface, the electrophysical parameters of the biological sample under investigation, and the geometrical parameters and to establish the dependences between these parameters and the biological properties of the biotissue being simulated. © 2012 Pleiades Publishing, Ltd.

Bobylev V.V.,Saint Petersburg State University
Astronomy Letters | Year: 2015

VLBI measurements of the absolute proper motions of 23 radio stars have been collected from published data. These are stars with maser emission, or very young stars, or asymptotic-giant-branch stars. By comparing these measurements with the stellar proper motions from the optical catalogs of the Hipparcos Celestial Reference Frame (HCRF), we have found the components of the residual rotation vector of this frame relative to the inertial coordinate system: (ωx, ωy, ωz) = (−0.39, −0.51, −1.25) ± (0.58, 0.57, 0.56) mas yr−1. Based on all the available data, we have determined new values of the components of the residual rotation vector for the optical realization of the HCRF relative to the inertial coordinate system: (ωx, ωy, ωz) = (−0.15, +0.24,−0.53) ± (0.11, 0.10, 0.13) mas yr−1. © 2015, Pleiades Publishing, Inc.

Chiu H.-C.,University of California at Riverside | Klimchitskaya G.L.,North West Technical University | Marachevsky V.N.,Saint Petersburg State University | Mostepanenko V.M.,Noncommercial Partnership Scientific Instruments | Mohideen U.,University of California at Riverside
Physical Review B - Condensed Matter and Materials Physics | Year: 2010

The lateral Casimir force, which arises between aligned sinusoidally corrugated surfaces of a sphere and a plate, was measured for the case of a small corrugation period beyond the applicability region of the proximity force approximation (PFA). The increased amplitudes of the corrugations on both the sphere and the plate allowed observation of an asymmetry of the lateral Casimir force, i.e., deviation of its profile from a perfect sine function. The dependences of the lateral force on the phase shift between the corrugations on both test bodies were measured at different separations in two sets of measurements with different amplitudes of corrugations on the sphere. The maximum magnitude of the lateral force as a function of separation was also measured in two successive experiments. All measurement data were compared with the theoretical approach using the proximity force approximation and with the exact theory based on Rayleigh expansions with no fitting parameters. In both cases real material properties of the test bodies and nonzero temperature were taken into account. The data were found to be in a good agreement with the exact theory but deviate significantly from the predictions of the proximity force approximation approach. This provides the quantitative confirmation for the observation of diffraction-type effects that are disregarded within the PFA approach. Possible applications of the phenomenon of the lateral Casimir force in nanotechnology for the operation of micromachines are discussed. © 2010 The American Physical Society.

Nazarov A.,Saint Petersburg State University
JETP Letters | Year: 2012

Schramm-Loewner evolution (SLE) and conformal field theory (CFT) are popular and widely used instruments to study critical behavior of two-dimensional models, but they use different objects. While SLE has natural connection with lattice models and is suitable for strict proofs, it lacks computational and predictive power of conformal field theory. To provide a way for the concurrent use of SLE and CFT, CFT correlation functions, which are martingales with respect to SLE, are considered. A relation between parameters of Schramm-Loewner evolution on coset space and algebraic data of coset conformal field theory is revealed. The consistency of this approach with the behavior of parafermionic and minimal models is tested. Coset models are connected with off-critical massive field theories and implications of SLE are discussed. © 2012 Pleiades Publishing, Ltd.

Jimenez J.B.,University of Geneva | Golovnev A.,Saint Petersburg State University | Karciauskas M.,University of Granada | Koivisto T.S.,University of Oslo
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2012

The bimetric variational principle is a subtle reinterpretation of general relativity that assumes the spacetime connection to be generated by an independent metric. Unlike the so-called Palatini formalism that promotes the connection into a fundamental field, the new variational principle results in a physically distinct theory since the potential for the connection carries new degrees of freedom. Also, the connection-generating metric naturally allows an antisymmetric component. This sets torsion propagating. It is also shown here that while in the most straightforward generalization of the Einstein-Hilbert action the nonmetric degrees of freedom become ghosts, there exists very simple actions which give rise to viable theories at the linearized level when subjected to the bimetric variational principle. However, the nonlinear interactions might bring unpleasant features like the Boulware-Deser ghost. This remains to be explored since this new type of bimetric theories does not, in principle, lie in the class of usual bimetric theories where nonlinear interactions inevitably come in with new ghost-like degrees of freedom. © 2012 American Physical Society.

Trubilko A.I.,Saint Petersburg State University
JETP Letters | Year: 2012

Collective operators corresponding to two different algebras have been introduced for a simple system consisting of a single two-level atom and a high-quality cavity mode. The generators of the first algebra satisfy boson commutation relations, whereas the generators of the second algebra have been obtained by polynomial deformation of su(2) algebra. It has been shown that dual squeezed states identified using the considered commutation relations can be observed in the system placed in an entangled bath with quantum correlations. © 2012 Pleiades Publishing, Ltd.

Rebane T.K.,Saint Petersburg State University
Journal of Experimental and Theoretical Physics | Year: 2012

The energy and eigenstate spectrum of a charged particle in the electric field of a 2D anisotropic oscillator and in a uniform magnetic field is considered. The exact analytic solution to the problem is obtained for an arbitrary magnetic field strength. The characteristic features of variation of the energy spectrum depending on the magnetic field strength are analyzed. The results of this study are of interest for the quantum-mechanical theory of magnetism and can be used to simulate the magnetic properties of atoms and molecules. © Pleiades Publishing, Inc., 2012.

Krivovichev S.V.,Saint Petersburg State University
Zeitschrift fur Kristallographie | Year: 2012

Relationships between the ro and b bond-valence parameters are investigated for ideal and distorted coordination polyhedra. For some ranges of the b values, this relationship can be approximated by linear functions, which are used to derive bond-valence parameters for some cationoxygen pairs (ro, b [Å]): Cu2 +-O (1.679, 0.36), Pb2 +-O (1.963, 0.49), Hg2 +-O (1.924, 0.38), Bi3 +-O (1.990, 0.48), Sb3 +-O (1.885, 0.53), Y3 +-O (2.028, 0.35), La3 +-O (2.086, 0.45), Nd3 +-O (2.021, 0.46). © by Oldenbourg Wissenschaftsverlag, München.

Leonov G.A.,Saint Petersburg State University
International Journal of Bifurcation and Chaos | Year: 2013

For Lorenz-like system, conditions of Shilnikov chaos are obtained. Algorithms for computation of bifurcational values of parameters, which correspond to homoclinic trajectories are formulated. Modified Lorenz, Chen and Lu systems are considered. © 2013 World Scientific Publishing Company.

Kharitonov V.L.,Saint Petersburg State University
Annual Reviews in Control | Year: 2010

In this contribution we present some basic results concerning the computation of quadratic functionals with prescribed time derivatives for linear time delay systems. Some lower and upper bounds for the functionals are given. The functionals are defined by special matrix valued functions. These functions are called Lyapunov matrices. The theory of the matrices is a rather young topic. Therefore, principal results with respect to the existence and uniqueness of the matrices are included. Some important applications of the functionals are pointed out. A brief historical survey ends the contribution. © In this contribution we present some basic results concerning the computation of quadratic functionals with prescribed time derivatives for linear time delay systems. Some lower and upper bounds for the functionals are given. The functionals are defined by special matrix valued functions. These functions are called Lyapunov matrices. The theory of the matrices is a rather young topic. Therefore, principal results with respect to the existence and uniqueness of the matrices are included. Some important applications of the functionals are pointed out. A brief historical survey ends the contribution. © 2010 Elsevier Ltd.

Khryashchev S.M.,Saint Petersburg State University
Nonlinear Phenomena in Complex Systems | Year: 2015

Control systems with a finite number of control parameters (dynamical polysystems) are considered. It is assumed that the control switchings occur at some discrete times. Controllability of the systems is studied. Statistic methods of number theory are applied. Existence of integer control times is established by analysis of Diophantine inequalities. The values of control times can be found by some numerical methods. The statements on controllability are proved. Some examples are considered. © 2015, Education and Upbringing Publishing. All rights reserved.

Kiryanova E.V.,Saint Petersburg State University
Crystal Research and Technology | Year: 2011

Using the examples of aqueous salt solutions NaNO3, KNO 3, RbNO3, K2SO4, NaBr·2H2O, KBr, and NH4NO3, it was experimentally proven that the new phenomena, i.e. temperature-concentration oscillations of crystal-solution phase equilibria detected previously in the range of 15-45 °C remain in the presence of trace impurities (10 -4-10-3 wt. %) of ion-active organic matters. The signs of breaks transformation into pair oscillations of "maximum-minimum" type are established for the K2SO4, NaBr, KBr solutions. The efficiency of influence of trace impurities on phase equilibria sharply rises in the areas of the temperature-concentration oscillations (the saturation temperature ranges up to 10 K). The impurity efficiency is promoted by the presence of the amides in its content (as compared with the sulphates) and an increase in length of the hydrocarbon radical. The phenomenon is absent in case of an addition of ion-inactive compounds. © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Egorov A.V.,Saint Petersburg State University | Lyubartsev A.P.,University of Stockholm | Laaksonen A.,University of Stockholm
Journal of Physical Chemistry B | Year: 2011

To study the effects of water on conformational dynamics of polyalcohols, Molecular Dynamics simulations of glycerol-water liquid mixtures have been carried out at different concentrations: 42.9 and 60.0 wt % of glycerol, respectively. On the basis of the analysis of backbone conformer distributions, it is found that the surrounding water molecules have a large impact on the populations of the glycerol conformers. While the local structure of water in the liquid mixture is surprisingly close to that in pure liquid water, the behavior of glycerols can be divided into three different categories where roughly 25% of them occur in a structure similar to that in pure liquid of glycerol, ca. 25% of them exist as monomers, solvated by water, and the remaining 50% of glycerols in the mixture form H-bonded strings as remains of the glycerol H-bond network. The typical glycerol H-bond network still exists even at the lower concentration of 40 wt % of glycerol. The microheterogeneity of water-glycerol mixtures is analyzed using time-averaged distributions of the sizes of the water aggregates. At 40 wt % of glycerol, the cluster sizes from 3 to 10 water molecules are observed. The increase of glycerol content causes a depletion of clusters leading to smaller 3-5 molecule clusters domination. Translational diffusion coefficients have been calculated to study the dynamical behavior of both glycerol and water molecules. Rotational-reorientational motion is studied both in overall and in selected substructures on the basis of time correlation functions. Characteristic time scales for different motional modes are deduced on the basis of the calculated correlation times. The general conclusion is that the presence of water increases the overall mobility of glycerol, while glycerol slows the mobility of water. © 2011 American Chemical Society.

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.

Wang W.-Z.,Saint Petersburg State University
Journal of Geriatric Cardiology | Year: 2013

Background: Angiotensinogen (AGT) T174M gene polymorphism has been suggested to be linked to risk of coronary artery disease, however, results from studies of this association have been inconsistent. In this study, we assess the relationship between AGT T174M gene polymorphism and coronary artery disease. Methods: We conducted a meta-analysis of 18 case-control studies with 8,147 coronary artery disease cases and 5,344 controls in Google scholar, PubMed, Cochrane Library and China National Knowledge Infrastructure (CNKI) data- bases to identify eligible studies published by July, 2012. Odds ratios (OR) and 95% confidence intervals (95% CI) were calculated from these studies. Results: Overall, a significant association was found between angiotensinogen T174M polymorphism and coronary artery disease risk when all studies were pooled into the meta-analysis (TT vs. MM: OR = 0.53, 95% CI = 0.40-0.71; dominant model: OR = 1.16, 95% CI = 1.01-1.35; recessive model: OR = 0.54, 95% CI = 0.40-0.72). In a stratified analysis, the results indicate a significant association in Caucasians suffering from coronary stenosis (TT vs. MM: OR = 0.38, 95% CI = 0.23-0.63; recessive model: OR = 0.39, 95% CI = 0.23-0.64). No significant increased risk for coronary artery disease was found in Asians. Conclusions: The meta-analysis indicate a significant association of T174M polymorphism with coronary stenosis risk in Caucasians. ©2013 JGC All rights reserved.

Pevzner L.M.,Saint Petersburg State University
Russian Journal of General Chemistry | Year: 2016

Preparative procedure for 4,5-bis(diethoxyphosphorylmethyl)-3-furoate from 4-chloromethyl-3-furoate is developed. It includes substitution of chlorine with iodine, phosphorylation by means of the Arbuzov reaction, chloromethylation of 4-(diethoxyphosphorylmethyl)-3-furoate in the position 5 of the furan ring, substitution of chlorine with iodine in the obtained chloromethyl derivative, and repeated phosphorylation with triethyl phosphite. It was found that ethyl 4-(diethoxyphosphorylmethyl)-5(chloromethyl)-3-furoate reacts with sodium diethyl phosphite by two pathways. Besides usual nucleophilic substitution leading to phosphonate, transfer of the reaction center in the position 2 of the furan ring takes place. The ambident diethylphosphite anion in this case reacts at the oxygen to give tertiary phosphite. The latter is oxidized with the air oxygen to form ethyl 2-(diethoxyphosphoryloxy)-4-(diethoxyphosphorylmethyl)-5-methyl-3-furoate. Unlike that analogous iodomethyl phosphonate is phosphorylated selectively under the conditions of the Arbuzov reaction. © 2016 Pleiades Publishing, Ltd.

Islamova R.M.,Saint Petersburg State University
Russian Journal of General Chemistry | Year: 2016

Experimental data on the application of metal complexes in radical polymerization of vinyl monomers collected over the recent 15 years have been analyzed and generalized. Special attention has been given to (un)substituted ferrocenes, macrocyclic (clathro)chelates, and iron porphyrinates as well as to the approaches to enhance their catalytic activity in controlled synthesis of macromolecules. The mentioned systems have been compared with each other as well as with selected complexes of other transition metals. It has been shown that the electronic and spatial structures of the metal complexes are related to their efficiency in the radical polymerization reactions. © 2016 Pleiades Publishing, Ltd.

Kashin A.S.,RAS N. D. Zelinsky Institute of Organic Chemistry | Ananikov V.P.,Saint Petersburg State University
Journal of Organic Chemistry | Year: 2013

In situ generated catalysts and preformed catalysts are two practical strategies widely used in cross-coupling methodology that have long been considered to involve the same active species in the catalytic cycle. Recent mechanistic studies have revealed two fundamentally different pictures of catalytic reactions in solution. Preformed catalysts with strongly bound ligands initiate transformations mainly involving single type of metal species. In contrast, in situ generated catalysts give rise to cocktail-type systems with different metal species presented in solution. The role of catalyst precursor, interconversions of catalytic species during reaction, stability and recycling of catalyst, catalysis by autocatalyst exhaust and plausible sources of metal-containing contaminants are the key points discussed in this review. © 2013 American Chemical Society.

Ovid'Ko I.A.,Saint Petersburg State University | Skiba N.V.,Saint Petersburg State Polytechnic University
International Journal of Plasticity | Year: 2014

Special mechanisms for formation of nanoscale deformation twins at grain boundaries (GBs) in nanocrystalline and ultrafine-grained materials are suggested and theoretically described. Within our description, nanoscale deformation twins are generated at locally distorted GBs that contain local, deformation-distorted fragments being rich in GB dislocations produced by preceding deformation processes. The twin formation mechanisms represent (i) the successive events of partial dislocation emission from GBs; (ii) the cooperative emission of partial dislocations from GBs; and (iii) the multiplane nanoscale shear generated at GBs. The energy and stress characteristics of the nanoscale twin formation through these special mechanisms in nanocrystalline nickel (Ni), copper (Cu) and silicon carbide (3C-SiC) are calculated and analyzed. Competition between the twin formation mechanisms in nanomaterials is discussed. © 2014 Elsevier Ltd. All rights reserved.

Mironova I.A.,Saint Petersburg State University | Usoskin I.G.,University of Oulu
Atmospheric Chemistry and Physics | Year: 2013

The main ionization source of the middle and low Earth's atmosphere is related to energetic particles coming from outer space. Usually it is ionization from cosmic rays that is always present in the atmosphere. But in a case of a very strong solar eruption, some solar energetic particles (SEPs) can reach middle/low atmosphere increasing the ionization rate up to some orders of magnitude at polar latitudes. We continue investigating such a special class of solar events and their possible applications for natural variations of the aerosol content. After the case study of the extreme SEP event of January 2005 and its possible effect upon polar stratospheric aerosols, here we analyze atmospheric applications of the sequence of several events that took place over autumn 1989. Using aerosol data obtained over polar regions from two satellites with space-borne optical instruments SAGE II and SAM II that were operating during September-October 1989, we found that an extreme major SEP event might have led to formation of new particles and/or growth of preexisting ultrafine particles in the polar stratospheric region. However, the effect of the additional ambient air ionization on the aerosol formation is minor, in comparison with temperature effect, and can take place only in the cold polar atmospheric conditions. The extra aerosol mass formed under the temperature effect allows attributing most of the changes to the "ion-aerosol clear sky mechanism". © 2013 Author(s) .

Bibikov P.N.,Saint Petersburg State University
Annals of Physics | Year: 2015

First and second terms of the low-temperature cluster expansion for the free energy density of a magnetically polarized XXZ spin chain is obtained within the propagator approach suggested by E.W. Montroll and J.C. Ward. All the calculations employ only one- and two-magnon infinite-chain spectrums. In the XXX-point the result reproduces the well known S. Katsura's formula obtained 50years ago by finite-chain calculations. © 2014 Elsevier Inc.

Inge-Vechtomov S.G.,Saint Petersburg State University
Russian Journal of Genetics | Year: 2013

The idea of continuity in living systems, which was initially developed in mid-19th century, reached its peak in 1928 thanks to N. K. Kol'tsov, who proposed the template principle in chromosome reproduction. The determination of genetic functions of nucleic acids and the advent of molecular genetics led to F. Crick's statement of the central dogma of molecular biology in 1958. This dogma became a contemporary version of the template principle (templates of the first order). The discovery of "protein inheritance" underlay the notion of steric or conformational templates (second order) for reproducing conformation in a number of proteins. The template principle supplemented by this notion claims to be the main paradigm of modern genetics. © 2013 Pleiades Publishing, Ltd.

Nikolenko S.I.,Academic University | Korobeynikov A.I.,Saint Petersburg State University | Alekseyev M.A.,University of South Carolina
BMC Genomics | Year: 2013

Error correction of sequenced reads remains a difficult task, especially in single-cell sequencing projects with extremely non-uniform coverage. While existing error correction tools designed for standard (multi-cell) sequencing data usually come up short in single-cell sequencing projects, algorithms actually used for single-cell error correction have been so far very simplistic. We introduce several novel algorithms based on Hamming graphs and Bayesian subclustering in our new error correction tool BAYESHAMMER. While BAYESHAMMER was designed for single-cell sequencing, we demonstrate that it also improves on existing error correction tools for multi-cell sequencing data while working much faster on real-life datasets. We benchmark BAYESHAMMER on both k-mer counts and actual assembly results with the SPADES genome assembler. © 2013 Nikolenko et al.

Solovyev N.D.,Saint Petersburg State University
Journal of Inorganic Biochemistry | Year: 2015

Multiple biological functions of selenium manifest themselves mainly via 25 selenoproteins that have selenocysteine at their active centre. Selenium is vital for the brain and seems to participate in the pathology of disorders such as Alzheimer's disease, Parkinson's disease, amyotrophic lateral sclerosis and epilepsy. Since selenium was shown to be involved in diverse functions of the central nervous system, such as motor performance, coordination, memory and cognition, a possible role of selenium and selenoproteins in brain signalling pathways may be assumed. The aim of the present review is to analyse possible relations between selenium and neurotransmission. Selenoproteins seem to be of special importance in the development and functioning of GABAergic (GABA, γ-aminobutyric acid) parvalbumin positive interneurons of the cerebral cortex and hippocampus. Dopamine pathway might be also selenium dependent as selenium shows neuroprotection in the nigrostriatal pathway and also exerts toxicity towards dopaminergic neurons under higher concentrations. Recent findings also point to acetylcholine neurotransmission involvement. The role of selenium and selenoproteins in neurotransmission might not only be limited to their antioxidant properties but also to inflammation, influencing protein phosphorylation and ion channels, alteration of calcium homeostasis and brain cholesterol metabolism. Moreover, a direct signalling function was proposed for selenoprotein P through interaction with post-synaptic apoliprotein E receptors 2 (ApoER2). © 2015 Elsevier Inc. All rights reserved.

Butikov E.I.,Saint Petersburg State University
American Journal of Physics | Year: 2015

Simple geometric derivations are given for the shape of the "safety domain" boundary for the family of Keplerian orbits of equal energy in a central gravitational field and for projectile trajectories in a uniform field. Examples of practical uses of the envelope of the family of orbits are discussed and illustrated by computer simulations. This material is appropriate for physics teachers and undergraduate students studying classical mechanics and orbital motions. © 2015 American Association of Physics Teachers.

Vechernin V.,Saint Petersburg State University
Nuclear Physics A | Year: 2015

The forward-backward (FB) charged particle multiplicity correlations between windows separated in rapidity and azimuth are analyzed using a model that treats strings as independent identical emitters. Both the short-range (SR) contribution, originating from the correlation between multiplicities produced from a single source, and the long-range (LR) contribution, originating from the fluctuation in the number of sources, are taken into account. The dependencies of the FB correlation coefficient, b, on the windows' rapidity and azimuthal acceptance and the gaps between these windows are studied and compared with the preliminary data of ALICE. The analysis of these dependencies effectively separates the contributions of two above mechanisms. It is also demonstrated that traditional definitions of FB correlation coefficient b have a strong nonlinear dependence on the acceptance of windows. Suitable alternative observables for the future FB correlation studies are proposed. The connection between b and the two-particle correlation function, C2, is traced, as well as its connection to the untriggered di-hadron correlation analysis. Using a model independent analysis, it is shown that measurement of the FB multiplicity correlations between two small windows separated in rapidity and azimuth fully determines the two-particle correlation function C2, even if the particle distribution in rapidity is not uniform. © 2015 Elsevier B.V.

Eylenceolu E.,Middle East Technical University | Rafatov I.,Middle East Technical University | Kudryavtsev A.A.,Saint Petersburg State University
Physics of Plasmas | Year: 2015

Two-dimensional hybrid Monte Carlo-fluid numerical code is developed and applied to model the dc glow discharge. The model is based on the separation of electrons into two parts: the low energetic (slow) and high energetic (fast) electron groups. Ions and slow electrons are described within the fluid model using the drift-diffusion approximation for particle fluxes. Fast electrons, represented by suitable number of super particles emitted from the cathode, are responsible for ionization processes in the discharge volume, which are simulated by the Monte Carlo collision method. Electrostatic field is obtained from the solution of Poisson equation. The test calculations were carried out for an argon plasma. Main properties of the glow discharge are considered. Current-voltage curves, electric field reversal phenomenon, and the vortex current formation are developed and discussed. The results are compared to those obtained from the simple and extended fluid models. Contrary to reports in the literature, the analysis does not reveal significant advantages of existing hybrid methods over the extended fluid model. © 2015 AIP Publishing LLC.

Paston S.A.,Saint Petersburg State University
Classical and Quantum Gravity | Year: 2015

We study the conditions of the existence of Hawking into Unruh mapping for hyperbolic (Fronsdal-type) metric embeddings into the Minkowski space, for which timelines are hyperbolas. Many examples are known for global embeddings into the Minkowskian spacetime (GEMS), with such mapping for physically interesting metrics with some symmetry. However, examples of embeddings, both smooth and hyperbolic, for which there is no mapping, were also given. In the present work we prove that Hawking into Unruh mapping takes place for a hyperbolic embedding of an arbitrary metric with a time-like Killing vector and a Killing horizon if the embedding of such type exists and smoothly covers the horizon. At the same time, we do not assume any symmetry (spherical, for example), except the time translational invariance, which corresponds to the existence of a time-like Killing vector. We show that the known examples of the absence of mapping do not satisfy the formulated conditions of its existence. © 2015 IOP Publishing Ltd.

Alekseev V.A.,Saint Petersburg State University
Journal of Physics B: Atomic, Molecular and Optical Physics | Year: 2015

Luminescence of I2-doped CnF2n+2 (n=1-4) and SF6 cryogenic solids has been studied using an optical-optical double resonance excitation technique. Experiments have shown that the lowest ion-pair state I2(D′) is stable with respect to chemical reaction and fast predissociation in these hosts. The red shift of I2(D′→A′) transition energy relative to the gas phase shows no correlation with the host polarizability and is ∼3500 cm-1 for all studied solids. Besides the I2(D′) solvation energy, a part of the shift is due to a repulsive interaction of I2(A′) with the host molecules. In the CF4 and SF6 solids, the I2(D′→A′) spectrum shows evidence of a coupling between electronic transition in the guest molecule and a vibrational transition in the host molecules. This coupling manifests itself via a satellite of the I2(D′→A′) band, which is shifted to the red by one quantum energy of the strongest IR-active vibrational mode of the CF4 (SF6) molecule. The lifetime of I2(D′) in studied molecular hosts varies from 2.5 ns in CF4 to 13 ns in SF6 solid. © 2015 IOP Publishing Ltd.

Leonov G.A.,Saint Petersburg State University
Physics Letters, Section A: General, Atomic and Solid State Physics | Year: 2015

Existence criterion of homoclinic trajectories in the Glukhovsky-Dolzhansky system, describing three-mode model of rotating fluid convection, is obtained. New applications of the Fishing principle are developed. © 2015 Elsevier B.V.

Syromyatnikov A.G.,Saint Petersburg State University
International Journal of Geometric Methods in Modern Physics | Year: 2015

I give a geometrical description of conformal gauge gravitational theory (CGTG) from the viewpoint of symmetries and affine structure. In the frames of the CGTG incorporating gravitation with torsion space-time into Standard Model of electro-weak interaction (EWI) the multi-muon events produced at the Fermilab Tevatron collider were studied. The CGTG gives the value of the torsion pseudotrace-spinor (muon) universal coupling fT = 4.388 10-17 GF, and with limits from known experiments - torsion mass mT = 0.4700 10-7 eV or mT = 0.445 10-15 muon mass. So the value of the constant of effective four-fermions interaction fT/mT = 0.988, indeed may lead to multi-muon events production. The model of interaction of quantum oscillator with the tensor potential Wμ? of traceless part of the torsion lead to 2 cm displacement of quark-lepton system as a whole in the magnetic field of collider in accordance with a significant sample of events related to b\bar{b} production and decay in which at least one of the muon candidates is produced outside of the beam pipe of radius 1.5 cm. A traceless part of the torsion in CGTG does not vanish in the Newtonian limit of nonzero mass. Torsion gravity potential Wμ? gives conservation of a special conformal current and may be produced in the condition of a spontaneous breaking of gauge symmetry where the gravitation mass MX defect is 1-3 Tev c-2 or 10-13MX. This effect may be possible at known effects on top pair asymmetries at the Tevatron and LHC and takes place as the known energy dissipation above 3 TeV of the Galaxy gamma-ray and neutrino spectrum from two bubbles outside the Galaxy plane. © 2015 World Scientific Publishing Company.

Petrov A.N.,Saint Petersburg State University
Physical Review A - Atomic, Molecular, and Optical Physics | Year: 2015

A method and a code for calculations of diatomic molecules in the external variable electromagnetic field have been developed. The code is applied for calculation of systematics in the electron's electric-dipole-moment search experiment on ThO H3Δ1 state related to geometric phases, including dependence on the Ω doublet, rotational level, and external static electric field. It is found that systematics decrease cubically with respect to the frequency of the rotating transverse component of the electric field. Calculation confirms that experiment on ThO H3Δ1 state is very robust against systematic errors related to geometric phases. © 2015 American Physical Society.

Radina T.V.,Saint Petersburg State University
Physics Letters, Section A: General, Atomic and Solid State Physics | Year: 2015

Abstract The self-consistent problem of the frequency synchronization of counter-propagating waves in a ring laser is rigorously solved. An intrinsic nonlinear mechanism of the phase coupling between the waves is considered for the first time. This ineradicable coupling is provided by modulation of the population difference of the energy levels of the active medium atoms in the electromagnetic field of two counter-propagating waves. The theoretical limit for the range of phase locking between the counter-propagating waves is established. The general equation of phase synchronization is obtained from the solution of a self-consistent problem. The frequency-dependent boundaries of the synchronization band calculated in the framework of this approach show good agreement with experimental results published in the literature. © 2015 Elsevier B.V.

Pismensky A.L.,Saint Petersburg State University
International Journal of Modern Physics A | Year: 2015

The method of calculation of ε-expansion in model of scalar field with φ3-interaction based on conformal bootstrap equations is proposed. This technique is based on self-consistent skeleton equations involving full propagator and full triple vertex. Analytical computations of the Fisher's index η are performed in four-loop approximation. The three-loop result coincides with one obtained previously by the renormalization group equations technique based on calculation of a larger number of Feynman diagrams. The four-loop result agrees with its numerical value obtained by other authors. © 2015 World Scientific Publishing Company.

Skutschas P.P.,Saint Petersburg State University
Acta Palaeontologica Polonica | Year: 2016

The early evolution of salamanders, which are one of the three living groups of lissamphibians, is not well known. Both stem- and crown-group salamanders first appeared in the Middle Jurassic (Bathonian), but subsequently had different evolutionary histories: stem salamanders were thought to have gone extinct in the Late Jurassic, while crown salamanders persist to the present day. Here, I report the discovery of an indeterminate stem salamander in the Lower Cretaceous (Aptian-Albian) Ilek Formation of Western Siberia. This is new evidence that the most basal salamanders survived beyond the Jurassic-Cretaceous boundary and co-existed with crown-group salamanders during approximately the first 40 million years of the known history of salamanders. The recognition of stem salamanders in the Early Cretaceous of Western Siberia adds to the inventory of taxa that suggest this area was a refugium for various groups of vertebrates with Jurassic affinities. Copyright © 2016 P.P. Skutschas.

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.

The shape of spirals formed by the interaction of a circumstellar disk with the magnetosphere in the magnetic propeller regime is examined in the ballistic approximation. The problem is solved analytically. The spirals and their cross sections are illustrated graphically. The possible effect of the magnetic propeller effect on the observed spectra of stars is discussed. © 2015 Springer Science+Business Media New York.

Yerokhin V.A.,Polytechnic University of Mozambique | Shabaev V.M.,Saint Petersburg State University
Physical Review Letters | Year: 2015

We report high-precision calculations of the nuclear recoil effect to the Lamb shift of hydrogenlike atoms to the first order in the electron-nucleus mass ratio and to all orders in the nuclear binding strength parameter Zα. The results are in excellent agreement with the known terms of the Zα expansion and allow an accurate identification of the nonperturbative higher-order remainder. For hydrogen, the higher-order remainder was found to be much larger than anticipated. This result resolves the long-standing disagreement between the numerical all-order and analytical Zα-expansion approaches to the recoil effect and completely removes the second-largest theoretical uncertainty in the hydrogen Lamb shift of the 1S and 2S states. © 2015 American Physical Society.

Tsiganov A.V.,Saint Petersburg State University
Physics Letters, Section A: General, Atomic and Solid State Physics | Year: 2015

We consider a canonical transformation of parabolic coordinates on the plane and suppose that this transformation together with some additional relations may be considered as a counterpart of the auto and hetero Bäcklund transformations associated with the integrable Hénon-Heiles systems. © 2015 Elsevier B.V.

Potekhin A.Y.,Saint Petersburg State University | Pons J.A.,University of Alicante | Page D.,National Autonomous University of Mexico
Space Science Reviews | Year: 2015

Observations of thermal radiation from neutron stars can potentially provide information about the states of supranuclear matter in the interiors of these stars with the aid of the theory of neutron-star thermal evolution. We review the basics of this theory for isolated neutron stars with strong magnetic fields, including most relevant thermodynamic and kinetic properties in the stellar core, crust, and blanketing envelopes. © 2015, Springer Science+Business Media Dordrecht.

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.

Mikhaylov A.M.,Saint Petersburg State University
Journal of Physics: Conference Series | Year: 2013

Endothermic reactions as a method of cooling are considered by many researchers due to the necessity of removal and recovery of large heat fluxes. The main applications of endothermic fuels technology are considered hypersonic aircraft. The increased interest in hydrogen energy, already implemented in specific technical developments, is pushing for consideration of existing developments not only in the spectrum of highly specialized technology of thermal protection, but also in as the hydrogen energy technology. It is proposed the use of endothermic catalytic steam reforming reaction of hydrocarbon fuel in a supercritical state. Summarizes the results achieved in detail both theoretically and experimentally investigated thermal and chemical aspects of the implementation of technology in terms of low pressure in the gaseous or liquid reagents in the light of the supercritical state of the reactants. © Published under licence by IOP Publishing Ltd.

Kuzmin A.,Saint Petersburg State University
International Journal of Aeronautical and Space Sciences | Year: 2013

The sensitivity of transonic flow past a Whitcomb airfoil to deflections of an aileron is studied at free-stream Mach numbers from 0.81 to 0.86 and vanishing or negative angles of attack. Solutions of the Reynolds-averaged Navier-Stokes equations are obtained with a finite-volume solver using the k-ω SST turbulence model. The numerical study demonstrates the existence of narrow bands of the Mach number and aileron deflection angles that admit abrupt changes of the lift coefficient at small perturbations. In addition, computations reveal free-stream conditions in which the lift coefficient is independent of aileron deflections of up to 5 degrees. The anomalous behavior of the lift is explained by interplay of local supersonic regions on the airfoil. Both stationary and impulse changes of the aileron position are considered. © The Korean Society for Aeronautical & Space Sciences.

Dmitriev N.N.,Saint Petersburg State University
Journal of Friction and Wear | Year: 2013

The effect of asymmetric orthotropic friction on the inertial motion of a material point was studied. The assertion of the onset of the motion of the material point under the effect of an active force and on asymmetric friction has been proven. The problems of the equilibrium and the onset of the motion of a two-mass system have been solved. © 2013 Allerton Press, Inc.

Trifonov P.,Saint Petersburg State University
IEEE International Symposium on Information Theory - Proceedings | Year: 2014

Reduced complexity implementation of the successive cancellation decoding algorithm for polar codes with Reed-Solomon kernel is presented. The proposed approach is based on the representation of Reed-Solomon codes as Arikan polar codes over F2m with dynamic frozen symbols, and application of list successive cancellation decoding algorithm. © 2014 IEEE.

Tyukhtin A.V.,Saint Petersburg State University
Journal of Physics: Conference Series | Year: 2012

A new method of determination of charged particle energy is developed. This method consists in use of dependency of waveguide mode frequencies on Lorenz factor of particle. For this method it is principal that the particle bunch generates radiation in waveguide and the mode frequencies depend essentially on the Lorenz factor. Three variants of realization of such technique are considered. The first variant consists in use of a thin dielectric layer in a waveguide. The second variant is based on use of a waveguide containing a system of wires coated with a dielectric material. The third version consists in application of a circular waveguide having a grid wall. For all cases analytical solutions of the problems are obtained (in the case of grid waveguide we use the averaged boundary conditions). Some typical results of computations are given. Advantages and disadvantages of different variants are discussed. It is noted that the grid waveguide can be used as well for generation of microwave radiation. © Published under licence by IOP Publishing Ltd.

Leonov G.A.,Saint Petersburg State University
Systems and Control Letters | Year: 2014

In this paper for the unstable periodic solution of nonlinear differential equation, Pyragas stabilizability problem is studied. An algorithm of stabilization via periodical delayed feedback is obtained. The consideration is based on the theory of nonstationary stabilization. © 2014 Elsevier B.V. All rights reserved.

Churilov A.,Saint Petersburg State University | Medvedev A.,Uppsala University | Mattsson P.,Uppsala University
IEEE Transactions on Automatic Control | Year: 2014

A hybrid mathematical model of endocrine regulation obtained by augmenting the classical continuous Smith model with a pulse-modulated feedback to describe episodic (pulsatile) secretion is considered. Conditions for existence and local orbital stability of periodical solutions with m impulses in the least period (m-cycles) are derived. An important implication of the performed analysis is that the nonlinear dynamics of the pulse-modulated system and not the delay itself cause the sustained closed-loop oscillations. Furthermore, simulation and bifurcation analysis indicate that increasing the time delay in the system in hand typically, but not always, leads to less complex dynamic pattern in the closed-loop system by giving rise to stable cycles of lower periodicity. © 2014 IEEE.

Furtat I.B.,Saint Petersburg State University
Journal of Computer and Systems Sciences International | Year: 2014

The problem of robust control of dynamic networks with non-minimum phase subsystems, where only scalar inputs and outputs are available for measurement, is solved. Conditions on the parameters of the network model and the control system are obtained that ensure that the control algorithm designed for minimum phase network systems remains valid for non-minimum phase network systems as well. Control of the dynamic network in the cases when it includes and does not include a master subsystems is considered. Examples of simulation are presented to illustrate the results. © 2014 Pleiades Publishing, Ltd.

Rozentsvet O.A.,Russian Academy of Sciences | Nesterov V.N.,Russian Academy of Sciences | Sinyutina N.F.,Saint Petersburg State University
Chemosphere | Year: 2012

The paper studies changes in the content and composition of lipids in the membranes of chloroplasts, mitochondria and microsomes of the aquatic plant Hydrilla verticillata exposed to copper ions (100μM; 1, 3, 6 and 24h). The rate of copper accumulation and the coefficient of its extraction by the plant were also determined. The presence of copper in the incubation medium and its accumulation in the plant tissues decreased the content of photosynthetic pigments, stimulated lipid peroxidation and enhanced membrane permeability. The gradual accumulation of copper in the plant tissues was accompanied by specific changes in the composition of lipids: the content of sulfolipids (SQDG) in chloroplasts declined; the content of monogalactosyl diacylglycerols (MGDG), digalactosyl diacylglycerols (DGDG) and phosphatidyl glycerols (PG) in chloroplasts and mitochondria grew after an hour of copper exposure; and the content of all the lipids except phosphatidic acids (PA) decreased after 3h of exposure. The decline in the content of phosphatidyl cholines (PC) was first observed in the membranes of microsomes (after an hour of exposure) and later in the membranes of chloroplasts and mitochondria (after 3-6h of exposure). The experiments with incorporation of [2- 14C]sodium acetate into fatty acids of polar lipids showed that in parallel with lipid destruction, there took place an intensive and specific renewal of the lipid pool of subcellular membrane fractions. © 2012 Elsevier Ltd.

Andronov I.V.,Saint Petersburg State University
Acoustical Physics | Year: 2016

The problem of diffraction by an absolutely soft segment is considered in the high-frequency approximation. The asymptotic field decomposition is obtained, which makes it possible to trace the transition from classical asymptotics valid for grazing incidence to geometrical optics asymptotics, which describes scattering at a finite (not small) angle. © 2016, Pleiades Publishing, Ltd.

Kocharov D.,Saint Petersburg State University
Proceedings of the International Multiconference on Computer Science and Information Technology, IMCSIT 2010 | Year: 2010

An experimental research with a goal to automatically detect prominent words in Russian speech is presented in this paper. The proposed automatic prominent word detection system could be further used as a module of an automatic speech recognition system or as a tool to highlight prominent words within a speech corpus for unit selection text-to-speech synthesis. The detection procedure is based on the use of prosodic features such as speech signal intensity, fundamental frequency and speech segment duration. A large corpus of Russian speech of over 200 000 running words was used to evaluate the proposed prosodic features and statistical method of speech data processing. The proposed system is speaker-independent and achieves an efficiency of 84.2 %. © 2010 IEEE.

Desnitskiy A.G.,Saint Petersburg State University
Russian Journal of Developmental Biology | Year: 2010

Literary data on the comparative embryology of Australian endemic frogs of the family Myobatrachidae have been considered. Six main types of development have been recognized, the important criteria for which are egg size, the site of embryo and tadpole development (in water or on land), the character of larval nutrition (exotrophic or endotrophic), the occurrence of direct development, brooding, etc. An attention has been also paid to the character of the early cleavage process in the embryos of various species. The peculiarities of ontogeny in Myobatrachidae are compared with those in representatives of other families in the order Anura. The perspectives of some further embryological studies of this Australian frog family have been out-lined. © 2010 Pleiades Publishing, Ltd.

Paston S.A.,Saint Petersburg State University
Theoretical and Mathematical Physics | Year: 2011

We propose a formulation of gravity theory in the form of a field theory in a flat space-time with a number of dimensions greater than four. Configurations of the field under consideration describe the splitting of this space-time into a system of mutually noninteracting four-dimensional surfaces. Each of these surfaces can be considered our four-dimensional space-time. If the theory equations of motion are satisfied, then each surface satisfies the Regge-Teitelboim equations, whose solutions, in particular, are solutions of the Einstein equations. Matter fields then satisfy the standard equations, and their excitations propagate only along the surfaces. The formulation of the gravity theory under consideration could be useful in attempts to quantize it. © 2011 Pleiades Publishing, Ltd.

Butikov E.I.,Saint Petersburg State University
Journal of Physics A: Mathematical and Theoretical | Year: 2011

An enhanced and more exact criterion for dynamic stabilization of the parametrically driven inverted pendulum is obtained: the boundaries of stability are determined with greater precision and are valid in a wider region of the system parameters than previous results. The lower boundary of stability is associated with the phenomenon of subharmonic resonances in this system. The relationship of the upper limit of dynamic stabilization of the inverted pendulum with ordinary parametric resonance (i.e. with destabilization of the lower equilibrium position) is established. Computer simulation of the physical system aids the analytical investigation and proves the theoretical results. © 2011 IOP Publishing Ltd.

Smirnov V.V.,Saint Petersburg State University
Journal of Physics A: Mathematical and Theoretical | Year: 2010

Some problems of the application of the saddle point method for the estimation of a path integral are considered. The calculation scheme using the approximation of an integrand with entire functions is represented. © 2010 IOP Publishing Ltd.

Korotyaev E.L.,Saint Petersburg State University
Russian Journal of Mathematical Physics | Year: 2011

The Jacobi operator (Jf)n = an-1fn-1 + anfn+1 + bnfn on ℤ with real finitely supported sequences (an - 1)n∈ℤ and (bn)n∈ℤ is considered. The inverse problem for two mappings (including their characterization): (an, bn, n ∈ ℤ) → {the zeros of the reflection coefficient} and (an, bn, n ∈ ℤ) → {the eigenvalues and the resonances} is solved. All Jacobi operators with the same eigenvalues and resonances are also described. © 2011 Pleiades Publishing, Ltd.

Tsiganov A.V.,Saint Petersburg State University
Journal of Nonlinear Mathematical Physics | Year: 2011

We introduce the concept of natural Poisson bivectors, which generalizes the Benenti approach to construction of natural integrable systems on Riemannian manifolds and allows us to consider almost the whole known zoo of integrable systems in framework of bi-hamiltonian geometry. © 2011 The Author(s).

Syromyatnikov A.G.,Saint Petersburg State University
International Journal of Geometric Methods in Modern Physics | Year: 2016

It was considered within the framework of the conformal gauge gravitational theory CGTG coupling of the standard model fermions to the axial torsion and preliminary discusses the impact of extra dimensions, in particular, in a five-dimensional space-time with Randall-Sundrum metric, where the fifth dimension is compactified on an S1/Z 2 orbifold, which as it turns out is conformally to the fifth dimension flat Euclidean space with permanent trace of torsion, with a compactification radius R in terms of the radius of a CGTG gravitational screening, through torsion in a process Z μ+μ- and LHC data. In general, have come to the correct set of the conformal calibration curvature the Faddeev-Popov diagram technique type, that follows directly from dynamics. This leads to the effect of restrictions on neutral spin currents of gauge fields by helicity and the Regge's form theory. The diagrams reveals the fact of opening of the fine spacetime structure in a process pp γ/Z/T μ+μ- with a center-of-mass energy of 14TeV, indicated by dotted lines and texture columns, as a result of p-p collision on 1.3 → 10-18cm scales from geometric shell gauge bosons of the SM continued by the heavy axial torsion resonance, and even by emerging from the inside into the outside of the ultra-light (freely-frozen in muon's spin) axial torsion. We then evaluate the contribution of the torsion to the muon anomaly to derive new constraints on the torsion parameters. It was obtained that on the N scattering through the exchange of axial torsion accounting, the nucleon anomalous magnetic moment in the eikonal phase leads to additive additives which is responsible for the spin-flip in the scattering process, the scattering amplitude is classical and characterized by a strong the torsion coupling 1. So the scattering of particles, occurs as on the Coulomb center with the charge fT This is the base model which is the g-2 muon anomaly. The muon anomaly contribution due to the heavy axial vector torsion arises from coupling the muon with torsion as external field. This leads to negative energy additive to mass of muons which makes the missing part of the g-2 muon anomaly. It takes place at reasonable values of the transverse front size of the exact solution CGTG equations types of torsion waves with the spin-flip close to the size of the Compton length muon. © 2016 World Scientific Publishing Company.

Chernysh S.,Saint Petersburg State University | Kozuharova I.,Russian Academy of Sciences
International Immunopharmacology | Year: 2013

Alloferons are a group of naturally occurring peptides primarily isolated from insects and capable of stimulating mouse and human NK cell cytotoxicity towards cancer cells. In this paper we examined anti-tumor activity of alloferon-1 and its novel structural analog referred to as allostatine. The activity was tested in naïve and preventively tumor antigen vaccinated DBA/2 mice subcutaneously grafted with syngenic P388D1 mouse leukemia cells. In naïve animals allostatine demonstrated tumoristatic activity prevailing over alloferon-1 effect. The preventive vaccination caused only weak tumoristatic effect in 27% of vaccinated animals. The vaccination efficacy was dramatically enhanced by allostatine but not alloferon-1 administration: 65% of allostatine treated animals benefitted from tumoristatic effect and 30% was completely cured so that total number of positive responders grew to 95%. Thus, alloferon-1 and especially allostatine are worthy of further consideration as potential anti-cancer drugs. Allostatine seems to be particularly perspective for adjuvant cancer immunotherapy. Sequence similarity search revealed evolutionary conserved allostatine-like pattern inserted to CDR3 region of human and mouse immunoglobulins. By analogy with allostatine, the pattern may execute some unknown so far function in anti-tumor immune response regulation. © 2013 Elsevier B.V.

Antonov N.V.,Saint Petersburg State University | Gulitskiy N.M.,Di Mendeleyev Institute For Metrology
Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics) | Year: 2012

The problem of anomalous scaling in magnetohydrodynamics turbulence is considered within the framework of the kinematic approximation, in the presence of a large-scale background magnetic field. Field theoretic renormalization group methods are applied to the Kazantsev-Kraichnan model of a passive vector advected by the Gaussian velocity field with zero mean and correlation function α δ(t-t′)/k d+ε. Inertial-range anomalous scaling for the tensor pair correlators is established as a consequence of the existence in the corresponding operator product expansions of certain "dangerous" composite operators, whose negative critical dimensions determine the anomalous exponents. The main technical result is the calculation of the anomalous exponents in the order ε 2 of the ε expansion (two-loop approximation). © 2012 Springer-Verlag.

Livshits A.I.,Saint Petersburg State University
Physics Letters, Section A: General, Atomic and Solid State Physics | Year: 2016

The standard equation of diffusion in heterogeneous media is found to be incomplete. The effect of heterogeneity on diffusion phenomena is commonly considered to be caused by only spatial variations of diffusion coefficient while the spatial difference in the potential energy of diffusing particles due to their interactions with the inhomogeneous medium is not taken into consideration. The possibility of new transport phenomena in heterogeneous media follows from the corrected equation. In particular the great increase of hydrogen permeability through the membranes of metallic alloy is turned out possible due to an optimization of spatial distribution of the alloy composition. © 2016 Elsevier B.V. All rights reserved.

Polyakov E.A.,Saint Petersburg State University
Physical Review A - Atomic, Molecular, and Optical Physics | Year: 2016

The time-dependent fermionic Hartree-Fock equations can be stochastically extended in such a way as to become the exact representation of quantum dynamics. This fact was first observed in the work of Juillet and Chomaz [Phys. Rev. Lett. 88, 142503 (2002)PRLTAO0031-900710.1103/PhysRevLett.88.142503]. During the past decade, this observation has led to the emergence of a whole family of stochastic wave-function methods for fermions. The common feature of all these methods is that they are based on the expansion of the density operator over the dyadic product of the two fermionic Slater determinant states. In this work, we develop a unified and rigorous foundation for this family of methods. We find a general form of stochastic equations and describe the sufficient conditions under which these methods converge towards exact quantum dynamics. To achieve these goals, we employ the representation of quantum dynamics in generalized phase space. In particular, we consider the quasiprobability distributions which emerge in these stochastic methods and their master equations. It is shown that the convergence towards exact quantum dynamics is controlled by the problem of boundary terms. We provide an example of stochastic Hartree-Fock method which is well-defined and free from this problem. © 2016 American Physical Society.

Benevolenskaya E.,Saint Petersburg State University | Slater G.,Lockheed Martin | Lemen J.,Lockheed Martin
Solar Physics | Year: 2014

The Solar Dynamics Observatory provides multiwavelength imagery from extreme ultraviolet (EUV) to visible light as well as magnetic-field measurements. These data enable us to study the nature of solar activity in different regions of the Sun, from the interior to the corona. For solar-cycle studies, synoptic maps provide a useful way to represent global activity and evolution by extracting a central meridian band from sequences of full-disk images over a full solar Carrington rotation (≈ 27.3 days). We present the global evolution during Solar Cycle 24 from 20 May 2010 to 31 August 2013 (CR 2097 - CR 2140), using synoptic maps constructed from full-disk, line-of-sight magnetic-field imagery and EUV imagery (171 Å, 193 Å, 211 Å, 304 Å, and 335 Å). The synoptic maps have a resolution of 0.1 degree in longitude and steps of 0.001 in sine of latitude. We studied the axisymmetric and non-axisymmetric structures of solar activity using these synoptic maps. To visualize the axisymmetric development of Cycle 24, we generated time-latitude (also called butterfly) images of the solar cycle in all of the wavelengths, by averaging each synoptic map over all longitudes, thus compressing it to a single vertical strip, and then assembling these strips in time order. From these time-latitude images we observe that during the ascending phase of Cycle 24 there is a very good relationship between the integrated magnetic flux and the EUV intensity inside the zone of sunspot activities. We observe a North-South asymmetry of the EUV intensity in high-latitudes. The North-South asymmetry of the emerging magnetic flux developed and resulted in a consequential asymmetry in the timing of the polar magnetic-field reversals. © 2014 Springer Science+Business Media Dordrecht.

Reshchikov A.V.,Saint Petersburg State University
Journal of the Entomological Research Society | Year: 2011

Lathrolestes is recorded from Turkey for the first time. Three new species are described and illustrated: Lathrolestes acinaces Reshchikov sp. nov., L. fascialis Reshchikov sp. nov., L. zoticus Reshchikov sp. nov. Lathrolestes citrofrontalis Schmiedeknecht, 1912 is considered as junior synonym with L. ungularis (Thomson, 1883).

Kurasov V.,Saint Petersburg State University
Physica A: Statistical Mechanics and its Applications | Year: 2015

Extension of analytical description of the stage of nucleation to the case of the slow growth rates of the embryos growth has been constructed. The metastable phase consumption by the already formed embryos affects the nucleation rate which leads to the non-linear evolution. The power exponentials which are smaller than that for the diffusion growth are chosen as the model laws of the embryos growth. All main characteristics of the nucleation period including the form of the embryos sizes spectrum are found. Analytical description of nucleation in the closed systems as well as in the open systems with the metastable phase influx is presented. It is shown that the relative errors of this description are small. © 2015 Elsevier B.V.All rights reserved.

Pavlova A.V.,Saint Petersburg State University
Journal of Optical Technology (A Translation of Opticheskii Zhurnal) | Year: 2010

In working out a method developed earlier for implementing fuzzy logics, it is proposed to use an approach to the implementation of plausible reasoning, (abductive and inductive inferences) on a two-layer optical neural network with an array of bidirectional connections, implemented by means of Fourier holography. The requirements on the characteristics of the patterns that represent the information to be processed and a phase-conjugate mirror are determined. The results of a numerical simulation are presented. © 2010 Optical Society of America.

Shcherbina T.,Saint Petersburg State University
Journal of Mathematical Physics | Year: 2015

We prove that the asymptotic behavior of the second mixed moment of the characteristic polynomials of the N × N 1D Gaussian real symmetric band matrices with the width of the band W ≫ N1/2 coincides with those for the Gaussian orthogonal ensemble. Here, we adapt the approach of Shcherbina [Commun. Math. Phys. 328, 45-82 (2014)], where the Hermitian case was considered. © 2015 AIP Publishing LLC.

Braun M.,Saint Petersburg State University
European Physical Journal C | Year: 2010

It is shown that in the eikonal scattering of a fast quark in the external field loop corrections to the gluon emission amplitude due to virtual softer gluon after renormalization coincide with a correction due to reggeization of the exchanged gluon in the BFKL picture. © © Springer-Verlag / Società Italiana di Fisica 2010.

Veremey E.I.,Saint Petersburg State University
Optimal Control Applications and Methods | Year: 2015

The paper is devoted to the problem of control law optimization for marine ships, which are steered by autopilots under the action of sea disturbances, mainly determined by bias terms and high-frequency wave components. The essence of the problem is to find a transfer function of the adjustable corrective item (filter) for the autopilot with a special structure, minimizing the functional, which characterizes the intensity of a ship's rudders action. The correspondent dynamic of a closed-loop system provides an economical regime of the ship motion, with the aim to reduce general fuel consumption and to prevent the wear of actuator elements. A specialized approach to the filter design is proposed based on the modern H optimization theory, and its applicability and effectiveness are illustrated by the practical example of autopilot synthesis for a transport ship. © 2015 John Wiley & Sons, Ltd.

Yasnov L.V.,Saint Petersburg State University
Solar Physics | Year: 2014

A number of authors claimed that radio sources above the neutral line of the magnetic field in solar active regions are due to non-thermal emission. This study shows that the thermal mechanism explains the radio emission from such sources. Models similar to those used for interpreting cyclotron lines were used in this study. Such models account for a steep decline in the spectrum at high frequencies and a low degree of polarization. The magnetic field between the two sunspots with an anti-parallel magnetic field has a lower gradient than the field above the sunspots. This, combined with the possibly high temperature in coronal loops connecting the sunspots, leads to the following conclusions. The optical thickness of the gyroresonance layers is increased and leads to more effective radiation at a harmonic number of 4 or 5. The lower gradient of the field between the sunspots also results in more rapid growth of emission intensity with increasing wavelength in this region than in the regions immediately above the sunspots. Additionally, the spatial averaging of the source structure due to the antenna beam pattern leads to a decrease in the degree of polarization in the region between the sunspots. © 2013 Springer Science+Business Media Dordrecht.

Kazarian M.,Steklov Mathematical Institute | Zograf P.,Saint Petersburg State University
Letters in Mathematical Physics | Year: 2015

We compute the number of coverings of ℂP1\{0, 1,∞} with a given monodromy type over ∞ and given numbers of preimages of 0 and 1. We show that the generating function for these numbers enjoys several remarkable integrability properties: it obeys the Virasoro constraints, an evolution equation, the KP (Kadomtsev–Petviashvili) hierarchy and satisfies a topological recursion in the sense of Eynard–Orantin. © Springer Science+Business Media Dordrecht 2015.

Tsiganov A.V.,Saint Petersburg State University
Journal of Geometry and Physics | Year: 2015

We discuss how to get variables of separation, separated relations and the Lax matrix for the Chaplygin system on the sphere with velocity dependent potential starting with the Lax matrix for other integrable system separable in elliptic coordinates on the sphere. © 2015 Elsevier B.V.

Sokolov A.V.,Saint Petersburg State University
Journal of Physics A: Mathematical and Theoretical | Year: 2015

We study relations describing the intertwining of n × n matrix, in general non-Hermitian, one-dimensional Hamiltonians by matrix linear differential operators with nondegenerate coefficients of in the highest degree. Some methods for constructing matrix intertwining operators of the first order of general form are proposed and their interrelations are examined. We construct, as an example, a 2 × 2 matrix Hamiltonian of general form intertwined by an operator of the first order with the Hamiltonian with zero matrix potential. It is shown that one can add, for the final 2 × 2 matrix Hamiltonian with respect to the initial matrix Hamiltonian, with the help of an intertwining operator of first order, up to two bound states for different energy values, or up to two bound states described by vector-eigenfunctions for the same energy value, or up to two bound states described by a vector-eigenfunction and an associated vector-function for the same energy value. © 2015 IOP Publishing Ltd.

Reshchikov A.V.,Saint Petersburg State University
Zootaxa | Year: 2011

Lathrolestes is recorded from Nepal for the first time. Three new species are described and illustrated: L. roerichi sp. nov., L. lidae sp. nov., L. peisseli sp. nov. This is the first record of the tribe Perilissini from Nepal. Copyright © 2011 Magnolia Press.

Hasselmann K.,Max Planck Institute for Meteorology | Kovalevsky D.V.,Saint Petersburg State University
Environmental Modelling and Software | Year: 2013

As a first step towards extending the MADIAM model reported previously to a model hierarchy MADIAMS (Multi-Actor Dynamic Integrated Assessment Model System), we upgrade the basic economic model M2 of the three model levels M1-M3 of MADIAMS to include non-equilibrium processes. The evolution of the economy is governed by the interactions of a few key aggregated actors (a firm, household, a government and a bank). The economy is treated as a nonlinear system described by a set of system-dynamic equations closed by the specification of the actors' control strategies. The model provides a unified framework for studying the dependence of economic growth and transformation on negotiated wage levels, the rate of investment in human capital (technological innovation), consumption versus savings preferences, government policies and various " animal spirit" processes. The latter are " not the outcome of a weighted average of quantitative benefits" (Keynes) and include unstable feedback responses of firms, consumers and investors to changing supply, demand and price signals, leading to business cycles and speculative boom-and-bust events. The inclusion of these dynamic feedback processes in coupled climate-socio-economic models is important for a realistic assessment of the multi-time-scale impact of climate policies. © 2012 Elsevier Ltd.

Zenkevich I.G.,Saint Petersburg State University
Russian Journal of Physical Chemistry A | Year: 2013

It is noted that the pK a values of organic acids can be calculated using the unique recurrence relation pK a(n + 1) = apK a(n) + b from the pK a values of other (usually the simplest and, consequently, better characterized) homologues of the same series. It is shown that this relation is valid within two taxonomic groups: insertion homologues of the ω-substituted acids X(CH2) n CO2H (n ≥ 1) and isomers that differ in the position of substituents X in their alkyl fragments, k-X(C n H2n )CO2H (n ≥ 1, 1 ≤ k ≤ n + 1). It is concluded that this algorithm is a consequence of the unique mathematical properties of recurrence relations. © 2013 Pleiades Publishing, Ltd.

Pevzner L.M.,Saint Petersburg State University
Russian Journal of General Chemistry | Year: 2015

Bromination of ethyl 4-(diethoxyphosphorylmethyl)-5-methylfuran-2-carboxylate and 4-(diethoxyphosphorylmethyl)-5-methylfuran-2-carbonitrile with N-bromosuccinimide followed by phosphorylation via the Arbuzov reaction have yielded the corresponding 2-substituted 4,5-bis(diethoxyphosphorylmethyl)furans. Synthesis and transformations of bisphosphorylated 2-furoic acid and its derivatives are described. © 2015 Pleiades Publishing, Ltd.

Noskov B.A.,Saint Petersburg State University | Loglio G.,MPI fur Kolloid und Grenzflachenforschung | Miller R.,University of Florence
Advances in Colloid and Interface Science | Year: 2011

Recent application of the methods of surface dilational rheology to solutions of the complexes between synthetic polyelectrolytes and oppositely charged surfactants (PSC) gave a possibility to determine some steps of the adsorption layer formation and to discover an abrupt transition connected with the formation of microaggregates at the liquid surface. The kinetic dependencies of the dynamic surface elasticity are always monotonous at low surfactant concentrations but can have one or two local maxima in the range beyond the critical aggregation concentration. The first maximum is accompanied by the generation of higher harmonics of induced surface tension oscillations and caused by heterogeneities in the adsorption layer. The formation of a multilayered structure at the surface for some systems leads to the second maximum in the dynamic surface elasticity. The hydrophobicity and charge density of a polymer chain influence strongly the surface structure, resulting in a variety of dynamic surface properties of PSC solutions. Optical methods and atomic force microscopy give additional information for the systems under consideration. Experimental results and existing theoretical frameworks are reviewed with emphasis on the general features of all studied PSC systems. © 2011 Elsevier B.V. All rights reserved.

Rusanov A.I.,Saint Petersburg State University
Colloid Journal | Year: 2010

The thermodynamic line tension of rectangular edge for amorphous or crystalline bodies with dispersion forces is calculated. The dependence of the local surface tension of the face adjacent to the edge on the distance to the edge is calculated preliminarily and it is shown that the linear tension is practically formed at three intermolecular distances to the edge. The order of magnitude of line tension is determined by the product of surface tension and intermolecular (interplanar for crystals) distance. © 2010 Pleiades Publishing, Ltd.

Stolyarov O.I.,Saint Petersburg State University
Journal of Communications Technology and Electronics | Year: 2016

It is shown that a more efficient use of microwave energy of a source operating into a nonstandard load is possible. As an example, a magnetron operating into a microwave-oven chamber is discussed. Calculation of a matching device with the variation in the amount of food placed in the oven chamber taken into account is presented. The improvement in matching has been experimentally validated by a physical model. © 2016, Pleiades Publishing, Inc.

Petrov M.Yu.,Saint Petersburg State University | Kavokin A.V.,University of Southampton
Physical Review B - Condensed Matter and Materials Physics | Year: 2013

We study theoretically the transport of linearly polarized exciton-polaritons in a quasi-one-dimensional microcavity channel separating two polariton condensates generated by optical pumping. The direction and value of mass and spin currents are controlled by the relative phase and polarization of two condensates, as in the stationary Josephson effect. However, due to dissipation and particle-particle interactions, the current density is inhomogeneous: it strongly depends on the coordinate along the axis of the channel. A stationary spin domain can be created in the channel, its position would be sensitive to the phase difference between two bordering condensates. © 2013 American Physical Society.

Dubrovskii V.G.,Saint Petersburg State University
Technical Physics Letters | Year: 2016

A kinetic model of the formation of axial heterostructures in nanocrystalline wires (nanowires, NWs) of III–V semiconductor compounds growing according to the vapor–liquid–solid (VLS) mechanism is proposed. A general system of nonstationary equations for effective fluxes of two elements of the same group (e.g., group III) is formulated that allows the composition profile of a heterostructure to be calculated as a function of the coordinate and epitaxial growth conditions, including the flux of a group V element. Characteristic times of the composition relaxation, which determine the sharpness of the heteroboundary (heterointerface), are determined in the linear approximation. A temporal interruption (arrest) of fluxes during the switching of elements for a period exceeding these relaxation times must increase sharpness of the heteroboundary. Model calculations of the composition profile in a double GaAs/InAs/GaAs axial heterostructure have been performed for various NW radii. © 2016, Pleiades Publishing, Ltd.

Egorov S.A.,Saint Petersburg State University
Technical Physics | Year: 2016

The influence of hydrostatic pressure in the interval 0-250 MPa on the deformation properties of copper versus its initial state is studied. After liquid nitrogen storage, the torsion strain to fracture is found to increase when the pressure rises to 200 MPa. As the pressure rises further and reaches 250 MPa, the torsion strain to fracture drops. Preliminary torsion to a strain of 5% in opposition to torsion under pressure makes the pressure dependence of the ultimate strain linear. If the prestrain equals 25%, a rise in the pressure to 150MPa increases the ductility of the material. A further increase in the pressure to 250 MPa changes the ductility insignificantly. © 2016, Pleiades Publishing, Ltd.

Athanassoula E.,Aix - Marseille University | Machado R.E.G.,Aix - Marseille University | Machado R.E.G.,University of Sao Paulo | Rodionov S.A.,Aix - Marseille University | Rodionov S.A.,Saint Petersburg State University
Monthly Notices of the Royal Astronomical Society | Year: 2013

We follow the formation and evolution of bars in N-body simulations of disc galaxies with gas and/or a triaxial halo. We find that both the relative gas fraction and the halo shape play a major role in the formation and evolution of the bar. In gas-rich simulations, the disc stays near-axisymmetric much longer than in gas-poor ones, and, when the bar starts growing, it does so at a much slower rate. Because of these two effects combined, large-scale bars form much later in gas-rich than in gas-poor discs. This can explain the observation that bars are in place earlier in massive red disc galaxies than in blue spirals. We also find that the morphological characteristics in the bar region are strongly influenced by the gas fraction. In particular, the bar at the end of the simulation is much weaker in gas-rich cases. The quality of our simulations is such as to allow us to discuss the question of bar longevity because the resonances are well resolved and the number of gas particles is sufficient to describe the gas flow adequately. In no case did we find a bar which was destroyed. Halo triaxiality has a dual influence on bar strength. In the very early stages of the simulation it induces bar formation to start earlier. On the other hand, during the later, secular evolution phase, triaxial haloes lead to considerably less increase of the bar strength than spherical ones. The shape of the halo evolves considerably with time.We confirm previous results of gas-less simulations that find that the inner part of an initially spherical halo can become elongated and develop a halo bar. However we also show that, on the contrary, in gas-rich simulations, the inner parts of an initially triaxial halo can become rounder with time. The main body of initially triaxial haloes evolves towards sphericity, but in initially strongly triaxial cases it stops well short of becoming spherical. Part of the angular momentum absorbed by the halo generates considerable rotation of the halo particles that stay located relatively near the disc for long periods of time. Another part generates halo bulk rotation, which, contrary to that of the bar, increases with time but stays small. Thus, in our models there are two non-axisymmetric components rotating with different pattern speeds, namely the halo and the bar, so that the resulting dynamics have strong similarities to the dynamics of double bar systems. © 2013 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society.

Braun M.A.,Saint Petersburg State University
European Physical Journal C | Year: 2013

Inclusive cross sections for gluon production in collision of two nucleons with two nucleons are studied in the BFKL approach. Various contributions include emission from the pomerons attached to the participants, from the BFKL interactions in between these pomerons and from the intermediate BKP state. The last contribution may be observable provided the growth with energy of the pomeron contribution is tamed in accordance with unitarity. © 2013 Springer-Verlag Berlin Heidelberg and Società Italiana di Fisica.

Equilibrium model of a ligand binding with DNA oligomer has been considered as a process of small molecule adsorption onto a lattice of multiple binding sites. An experimental example has been used to verify the assertion that during saturation of the macromolecule by a ligand should expect effect of cooperativity due to changes in DNA conformation or the mutual influence between bound ligands. Such phenomenon cannot be entirely described by the classical stepwise complex formation model. To evaluate a ligand binding affinity and cooperativity of ligand-oligomer complex formation the statistical approach has been proposed. This new computational approach used to re-examine previously studded ligand binding towards DNA quadruplexes targets with multiple binding sites. The intrinsic equilibrium constants K1-3 of the mesotetrakis-(N-methyl-4-pyridyl)-porphyrin (TMPyP4) binding with the [d(T 4G4)]4 and with the [AG3(T 2AG3)3] quadruplexes and the correction for the mutual influence between bound ligands (cooperativity parameters ω) was determined from the Job plots based upon the nonlinear least-squares fitting procedure. The re-examination of experimental curves reveals that the equilibrium is affected by the positive cooperative (ω>1) binding of the TMPyP4 ligand with tetramolecular [d(T4G4)] 4. However for an intramolecular antiparallel-parallel hybrid structure [AG3(T2AG3)3] the weak anti-cooperativity of TMPyP4 accommodation (ω<1) onto two from three nonidentical sites was detected. © 2013 Elsevier B.V.

Khokhlov V.D.,Saint Petersburg State University
Legal Medicine | Year: 2015

Since 1856 lots of forensic reports, concerning trauma to the hyoid bone and laryngeal cartilages in hanging, have been published. Differences in percentage of injured neck complexes ranged from 0 to 83.3%. Simple arguments suggest that the reason for discrepancy is difference in scientific approach (retro- or prospective) and use of various research methods. Comparative analysis of widely used techniques shows considerable variety in their effectiveness. Plain radiography and palpatory method have fairly low sensitivity (33-60% for different elements of the neck complex) with relatively high specificity (89-98.5%). Reported sensitivity of postmortem CT in identification of different lesions (including fractures) in trauma victims for the head/neck region is higher than 53% in different series with possible false-positive findings. In clinical setting the whole-body CT (pan-scanning) in blunt trauma patients showed sensitivity for head and neck injuries at the level of 84.6%, and specificity - 98.9% (Stengel et al., 2012 [68]). Only complete preparation allows to identify all the damages to the laryngopharynx framework, to avoid false diagnostics and ascertain the exact location, morphology, mechanism and intravital nature of the neck trauma. Currently complete preparation can be regarded as the method of "gold standard". Use of this method shows the frequency of discovered injuries in hanging to be about 70% of cases. In practical use, one should consider radiological techniques and palpation as preliminary and orienting methods (rather excluding, than revealing anterior neck trauma). © 2014 Elsevier Ireland Ltd.

Pronina Y.G.,Saint Petersburg State University
Computational Plasticity XII: Fundamentals and Applications - Proceedings of the 12th International Conference on Computational Plasticity - Fundamentals and Applications, COMPLAS 2013 | Year: 2013

The problem of the equal-rate mechanochemical wear of an elastic-perfectly plastic thick-walled spherical shell under internal and external pressure is solved analytically. The proposed solution allows to assess the time of the initial yielding at the bore of the shell and the time of fully plastic yielding. The obtained formulas are to be used for design purposes and as a benchmark solution for numerical analysis.

Scheer M.,University of Regensburg | Kuntz C.,University of Regensburg | Stubenhofer M.,University of Regensburg | Zabel M.,University of Regensburg | Timoshkin A.Y.,Saint Petersburg State University
Angewandte Chemie - International Edition | Year: 2010

Figure Presented One at a time: Stepwise opening and final removal of the η1 -bound Cp* substituents in the bridged pentelidene complexes [Cp*E{W(CO)5}2] (E=P, As) occurs by the reaction with primary phosphines. Not only novel diphospha- and arsaphosphanorbornenes are obtained, but also diastereomerically pure complexed triphosphines. All reaction steps were monitored by NMR spectroscopy, and compounds structurally characterized chemical equation presentation © 2010 Wiley-VCH Verlag GmbH &. Co. KGaA, Weinheim.

Lyalinov M.A.,Saint Petersburg State University | Zhu N.Y.,University of Stuttgart
IEEE Transactions on Antennas and Propagation | Year: 2013

This paper consists of two parts and deals with the scattering of the wave-field generated by a Hertzian dipole placed over an impedance wedge. Expanding the dipole field into plane waves and extending to complex 'angles of incidence' our recently obtained exact solution of the diffraction of a skew-incident plane wave by an impedance wedge enables us to give an integral representation for the total field. Then by means of asymptotic evaluation of the multiple integral far-field expressions are developed and interpreted. In the present first part (I) of the paper formulation and basic steps of analysis are presented. In particular, the far-field expressions for the reflected and edge waves, including the UAT (uniform asymptotic theory of diffraction) version of the far-field representation, are given. Both numerical computation and physical explanation of the analytic results have been performed. The forthcoming second part (II) of the work will be dedicated to the study of different surface waves excited, as well as to their physical interpretation and numerical calculation. © 1963-2012 IEEE.

Braun M.A.,Saint Petersburg State University
European Physical Journal C | Year: 2013

High-energy collisions of two nucleons on two nucleons are studied in the BFKL approach in the leading approximation in αsNc. Diagrams with redistribution of color are considered. It is found that intermediate BKP states consisting of four reggeized gluons give a contribution which may be leading in deuteron-deuteron scattering and thus experimentally observable. © 2013 Springer-Verlag Berlin Heidelberg and Società Italiana di Fisica.