Showing papers by "Kazan Federal University published in 2008"

Modelling of essential fish habitat based on remote sensing, spatial analysis and GIS

Abstract: We review the variety of existing modelling approaches applied to species habitat mapping and we discuss issues arising from the availability and nature of sampled biological data and corresponding ecological and environmental habitat descriptors, as well as the different spatial analysis approaches that are selected according to specific hypotheses. We focus on marine species habitat mapping, presenting an overview of work on modelling fish habitat carried out through a European Communities Policy-Support Action, EnviEFH ‘Environmental Approach to Essential Fish Habitat (EFH) Designation’ (2005–2008). The selection of the appropriate habitat model is dataset-specific and the resulting EFH maps are often similar in spite of using different models. Derived EFH maps are based on either environmental ranges (used as minimum and maximum environmental habitat descriptors) or probability of occurrence values. We apply model outputs to regions larger than sampled areas making use of the capacity of satellite data to cover wide areas.

The mass of the compact object in the X-ray binary her X-1/HZ her

Abstract: We have obtained the first estimates of the masses of the components of the Her X-1/HZ Her X-ray binary system taking into account non-LTE effects in the formation of the H γ absorption line: m x = 1.8 M ⊙ and m v = 2.5 M ⊙. These mass estimates were made in a Roche model based on the observed radial-velocity curve of the optical star, HZ Her. The masses for the X-ray pulsar and optical star obtained for an LTE model lie are m x = 0.85 ± 0.15 M ⊙ and m v = 1.87 ± 0.13 M ⊙. These mass estimates for the components of Her X-1/HZ Her derived from the radial-velocity curve should be considered tentative. Further mass estimates from high-precision observations of the orbital variability of the absorption profiles in a non-LTE model for the atmosphere of the optical component should be made.

Chemically modified electrodes based on noble metals, polymer films, or their composites in organic voltammetry

Abstract: The review deals with the current state of and prospects for the use of electrodes modified with noble metals, polymer films, or composites on their basis, which yield catalytic response in voltammetry. Techniques of applying noble metals, polymer films, or their composites to a conducting support are considered. The catalytic properties of immobilized redox mediators and the analytical, operating, and performance characteristics of this type of modified electrodes are compared.

Slowly rotating scalar field wormholes: The second order approximation

Abstract: We discuss rotating wormholes in general relativity with a scalar field with negative kinetic energy. To solve the problem, we use the assumption about slow rotation. The role of a small dimensionless parameter plays the ratio of the linear velocity of rotation of the wormhole's throat and the velocity of light. We construct the rotating wormhole solution in the second-order approximation with respect to the small parameter. The analysis shows that the asymptotical mass of the rotating wormhole is greater than that of the nonrotating one, and the null energy condition violation in the rotating wormhole spacetime is weaker than that in the nonrotating one.

Slowly rotating wormholes: the first-order approximation

Abstract: We discuss a solution describing a rotating wormhole in general relativity with a scalar field source having negative kinetic energy. To solve the problem, we use the assumption of slow rotation. The role of a small dimensionless parameter is played the ratio of the linear velocity of rotation of the wormhole throat and the velocity of light. The rotating wormhole solution is constructed in the first-order approximation with respect to the small parameter. We analyze the solution obtained and study test particle motion and light propagation in the spacetime of a rotating wormhole.

Strongly correlated variables and existence of a universal distribution function for relative fluctuations

Abstract: If two random values plotted against each other form a curve close to a straight line, these values are defined as strongly correlated with each other. In this paper, we define these two random values as satisfying the linear principle for strongly correlated variables (LPSCV). For variables of such kind, it is possible to find a new and very general class of distribution functions. One can show that detrended random sequences for relative fluctuations presented in the form of the sequences of ranged amplitudes (SRAs) satisfy the LPSCV. The first results of such kind, based on the analysis of the SRAs, confirm the fact that many random sequences are strongly correlated. For detrended sequences (obtained by numerical differentiation), characterized by a large sampling volume (N > 1000), the found distribution function, describing the SRA envelopes, can be written as [1] F(t) = a1tv1 + a2tv2. The results obtained in this study open new possibilities for analysis of many complex systems, where the natural relationships are very difficult to find and in cases where they are not known. Examples based on available data confirm this basic statement and show that the envelopes of relative fluctuations presented in the form of SRAs are described by the general distribution function found here.

Chironomids (Diptera: Chironomidae) in lakes of central Yakutia and their indicative potential for paleoclimatic research

Abstract: A study of chrionomid fauna was carried out in two regions of central Yakutia. Fossilized remnants of head capsules were sampled from shallow layers of the bottom sediments of lakes. Seventy five taxa of chironomids have been determined. Statistical analysis shows that the spatial distribution of chironomid taxa in the study regions is mainly controlled by ions of aluminium and magnesium, mean July temperature, transparency and content of oxygen in water. The obtained results serve as the base for development of a chironomid temperature model used for reconstruction of Holocene and Pleistocene paleotemperatures of the Russian North.

Optical identifications of five INTEGRAL hard X-ray sources in the Galactic plane

Abstract: The results of optical identifications of five hard X-ray sources in the Galactic plane from the INTEGRAL all-sky survey are presented. The X-ray data on one source (IGR J20216+4359) are published for the first time. The optical observations were performed with the 1.5-m RTT-150 telescope (Turkish National Observatory, Antalya, Turkey) and the 6-m BTA telescope (Special Astrophysical Observatory, Nizhny Arkhyz, Russia). A blazar, three Seyfert galaxies, and a high-mass X-ray binary are among the identified sources.

Aptasensor for Thrombin Based on Carbon Nanotubes-Methylene Blue Composites

Abstract: The amperometric and EQCM aptasensors based on DNA aptamers immobilized by avidin-biotin method or by electrostatic adsorption onto multiwalled carbon nanotube layer contained methylene blue (MB) have been developed and examined for thrombin detection in buffer and in spiked blood serum. The presence of MB increases the binding capacity of the surface layer and enhances the range of thrombin concentrations to be determined. This results in significant improvement of analytical characteristics of thrombin detection. The EQCM aptasensors allowed us to detect 0.3–100 nM and amperometric aptasensors 10–1000 nM of thrombin.

Chemically modified electrodes with amperometric response in enantioselective analysis

Abstract: Estimation of the enantiomeric purity of chiral biologically active compounds, as well as the determination of particular optical isomers, is very important for the control of medicines, food, and biological fluids. The main approaches to the development of electrochemical enantioselective sensors with the amperometric detection of the signal are considered in this review. Examples of the use of biochemical and supramolecular receptors providing enantiomer recognition and techniques of their inclusion into the corresponding sensors are given. The main characteristics of enantioselective sensors for the determination of optically active medicines, organic acids, aminoacids, carbohydrates, alcohols, and other biologically important compounds are considered.

Postbuckling elastoplastic state analysis of three-dimensional bodies taking into account finite strains

Abstract: A technique for analyzing the stress strain state of elastoplastic bodies taking into account large displacements, rotations, finite strains, and buckling is presented. The step-by-step loading method with formulation of the resolvent variation equation in the current configuration is used. The governing equations for elastoplastic bodies that connect the Jaumann derivative of the Cauchy-Euler stress tensor with the velocity strain are applied. The spatial discretization is based on the finite element method (FEM) in the framework of the polylinear three-dimensional isoparameteric approximation. The numerical solutions of the problems are given.

New active galactic nuclei among the INTEGRAL and SWIFT X-ray sources

Abstract: We present the results of our optical identifications of a set of X-ray sources from the INTEGRAL and SWIFT all-sky surveys. The optical data have been obtained with the 1.5-m Russian-Turkish Telescope (RTT-150). Nine X-ray sources have been identified with active galactic nuclei (AGNs). Two of them are located in the nearby spiral galaxies MCG-01-05-047 and NGC 973 seen almost edge-on. One source, IGR J16562-3301, is probably a BL Lac object (blazar). The remaining AGNs are observed as the starlike nuclei of spiral galaxies whose spectra exhibit broad emission lines. The relation between the hard X-ray (17–60 keV) luminosity and the [O III] 5007 line luminosity, log Lx/L[O III] ≈ 2.1, holds good for most of the AGNs detected in hard X rays. However, the luminosities of some AGNs deviate from this relation. The fraction of such objects can reach ∼20%. In particular, the [O III] line flux is lower for two nearby edge-on spiral galaxies. This can be explained by the effect of absorption in the galactic disks.

Nuclear magnetic relaxation of 3He in contact with an aerogel above the Fermi temperature

Abstract: The spin kinetics of 3He in an aerogel has been studied above the Fermi temperature. The magnetic relaxation times T1 and T2 of adsorbed, gaseous, and liquid 3He in a 95% silica aerogel at a temperature of 1.5 K have been determined as functions of frequency by means of pulse nuclear magnetic resonance. It has been found that the time T1 is linear in frequency in all three cases, whereas T2 is independent of frequency. To explain the observed behavior of the longitudinal relaxation rate, a theoretical model of relaxation in the adsorbed layer of 3He taking into account the filamentary structure of the aerogel is proposed.

Analysis of fundamental parameters for V477 Lyr

Abstract: We analyze the photometric and spectroscopic observations of the young pre-cataclysmic variable (pre-CV) V477 Lyr. The masses of both binary components have been corrected by analyzing their radial velocity curves. We show that agreement between the theoretical and observed light curves of the object is possible for several sets of its physical parameters corresponding to the chosen temperature of the primary component. The final parameters of V477 Lyr have been established by comparing observational data with evolutionary tracks for planetary nebula nuclei. The derived effective temperature of the O subdwarf is higher than that estimated by analyzing the object’s ultraviolet spectra by more than 10000 K. This is in agreement with the analogous results obtained previously for the young pre-CVs V664 Cas and UU Sge. The secondary component of V477 Lyr has been proven to have a more than 25-fold luminosity excess compared to main-sequence stars of similar mass. Comparison of the physical parameters for the cool stars in young pre-CVs indicates that their luminosities do not correlate with the masses of the objects. The observed luminosity excesses in such stars show a close correlation with the post-common-envelope lifetime of the systems and should be investigated within the framework of the theory of their relaxation to the state of main-sequence stars.

Reactions of 2-sulfanylethanol with mucochloric acid and its derivatives

Abstract: Mucochloric acid reacted with 2-sulfanylethanol in the presence of triethylamine to give 3-chloro-5-hydroxy-4-(2-hydroxyethylsulfanyl)furan-2(5H)-one which underwent acid-catalyzed cyclization to 7-chloro-2,3,4a,6-tetrahydrofuro[2,3-b][1,4]oxathiin-6-one. Likewise, reactions of 5-alkoxy-3,4-dichlorofuran-2(5H)-ones with 2-sulfanylethanol in the presence of triethylamine involved replacement of chlorine in position 4 of the furan ring with formation of the corresponding 4-(2-hydroxyethylsulfanyl) derivatives. The reaction of mucochloric acid with 2-sulfanylethanol in excess aqueous potassium hydroxide resulted in the formation of an acyclic product, 3-(2-hydroxyethylsulfanyl)-2-chloroprop-2-enoic acid. The structure of 7-chloro-2,3,4a,6-tetrahydrofuro[2,3-b][1,4]oxathiin-6-one and 3-(2-hydroxyethylsulfanyl)-2-chloroprop-2-enoic acid was proved by X-ray analysis.

C *-algebras generated by mappings

Abstract: Let X be an infinite set and let φ be a given mapping of it into itself. We consider the C*-algebra C φ (X) with a single generating element T φ on Hilbert space l 2(X). We show that C φ (X) is isomorphic to C*-algebra generated by a finite set of partial isometries of a special kind if T φ is continuous. We give the full description of C φ (X) in case φ is injective mapping. Also we give the examples of C φ (X) if φ is not injective.

An amperometric monoamine oxidase biosensor for determining some antidepressants

Abstract: An amperometric biosensor based on a platinum screen-printed electrode and immobilized monoamine oxidase is developed to determine antidepressants of different classes. Petylyl, pyrazidol, and flu-oxetine can be determined with determination limits of 8 × 10−9, 8 × 10−7, and 8 × 10−10 M, respectively. A procedure is proposed for determining fluoxetine in tablets. It is shown that petylyl can be selectively determined by an immunochemical technique using the developed biosensor and immobilized antibodies in the concentration range from 1 × 10−4 to 1 × 10−8 M.

Spectral characteristics of solid solutions LiY 1− x Lu x F 4 doped by Ce 3+ ions

Abstract: During crystallization, the LiF-YF3-LuF3 compounds form a continuous series of solid solutions having a scheelite structure at any proportion of the YF3 and LuF3 components. It is established that the crystals conform to the Vegard law and the Rutgers rule. The spectral characteristics of the 5d–4f transitions of Ce3+ ions and color centers induced by ultraviolet radiation in these crystals were studied as a function of the Lu3+ concentration. It is shown that the active media based on LiF-YF3-LuF3: Ce3+ solid solutions are more efficient as compared to LiYF4: Ce3+ and LiLuF4: Ce3+ crystals in possible directional changes in the spectral-kinetic characteristics of impurity ions and the parameters of the losses induced by pumping radiation and in enhancement of energetic and spectral characteristics of lasers on their basis.

Stationary and high-frequency pulsed electron paramagnetic resonance of a calcified atherosclerotic plaque

Abstract: New possibilities of applying high-frequency electron paramagnetic resonance in medicine are demonstrated on an example of the investigation of a calcified atherosclerotic plaque. After the irradiation of the atherosclerotic plaque by x rays, a new type of paramagnetic centers—organomineral radicals—is detected. The spectral and relaxation characteristics of these radicals depend on the calcification degree of the atherosclerotic plaque and can be used for diagnostics.

Non-minimal pp-wave Einstein–Yang–Mills–Higgs model: color cross-effects induced by curvature

Abstract: Non-minimal interactions in the pp-wave Einstein–Yang–Mills–Higgs (EYMH) model are shown to give rise to color cross-effects analogous to the magneto-electricity in the Maxwell theory. In order to illustrate the significance of these color cross-effects, we reconstruct the effective (associated, color, and color-acoustic) metrics for the pp-wave non-minimal seven-parameter EYMH model with parallel gauge and scalar background fields. Then these metrics are used as hints for obtaining explicit exact solutions of the non-minimally extended Yang–Mills and Higgs equations for the test fields propagating in the vacuum interacting with curvature. The influence of the non-minimal coupling on the test particle motion is interpreted in terms of the so-called trapped surfaces, introduced in the Analog Gravity theory.

Complexes of podand-containing bis(dithiophosphonate) ligands with cobalt(II), nickel(II) and cadmium(II): recognition of CH2Cl2

Abstract: Reaction of the potassium salts of podand-containing bis(dithiophosphonate)s [PhO(4-C6H4)P(S)(SH)OCH2CH2]2O (H 2 L) with Co(II), Ni(II) and Cd(II) in aqueous EtOH leads to complexes of formulae M2(L-S,S′)2. The structural formulae of the compounds were deduced by physico-chemical and spectroscopic methods. It was established that complex Ni 2 L 2 recognizes CH2Cl2.

Fundamental parameters of BE UMa revised

Abstract: We have determined a complete set of parameters for the young pre-cataclysmic variable BE UMa from a comprehensive photometric and spectroscopic analysis using model atmospheres. Our precise photometry and spectroscopy were acquired with the 6-m telescope and Zeiss-1000 telescope of the Special Astrophysical Observatory and the 1.5-m Russian-Turkish telescope at a wide range of orbital phases, including times of primary eclipses.We performed a detailed identification of emission lines of ten elements. At phases of minimum brightness, the spectra reveal absorption lines and molecular bands formed in the secondary’s atmosphere, whose effective temperature was determined to be Teff(2) = 4750 ± 150 K. We have studied the radial-velocity curves of the cool star using lines of various elements. All the curves exhibit the previously predicted distortions due to reflection effects in the close binary. The derived component-mass ratio is q = 0.43 ± 0.09, and the component masses are M1 = 0.59 ± 0.07 M⊙ and M2 = 0.25 ± 0.08 M⊙. We analyzed the light curves using model atmospheres for irradiated stars; all the parameters of BE UMa were refined. We demonstrate the validity of our modeling of the binary’s spectra at phases of brightness maximum, which provides a good description of the observed intensities of most lines of heavy elements. The abundances of helium and several light elements (C, N, O, Ne, Mg) in the atmosphere of the cool star are probably higher than the solar values. We conclude that the physical characteristics of the primary are in good agreement with evolutionary tracks for planetary-nebula nuclei, and that the secondary is overluminous by a factor of 30 compared to main-sequence stars of the same mass.

Anisotropic exchange interactions in CuTe2O5

Abstract: Electron paramagnetic resonance (EPR) was used to study CuTe2O5 single crystals at frequencies of 9.4 and 160 GHz. Analytic expressions for the second and fourth moments of the EPR line are deduced with inclusion of the difference between the exchange couplings of the copper spin with its different neighbors. From comparing the calculated and measured EPR linewidths, the positions of copper ions with the strongest exchange interactions are identified. The parameters of the anisotropic exchange interaction between copper ions in a pair are found. The parameter of the exchange interaction between magnetically nonequivalent copper centers is determined from the frequency dependence of the EPR linewidth. The directions of the principal axes of the g tensors are established. The data obtained count in favor of a quasi-one-dimensional model of magnetism in CuTe2O5.

Dynamic Spin Susceptibility of Hole-Doped High-Temperature Superconductors in a Singlet-Correlated Conduction Band Model

Abstract: We have derived an expression for the dynamical spin susceptibility of a hole-doped high-temperature superconductor taking into account a strong correlation between the magnetization of spins of the localized and itinerant electrons. This formula has been used to calculate the imaginary part of the susceptibility as a function of the frequency and wave vector. The results are compared to experimental data on the inelastic neutron scattering in compounds of the YBa2Cu3O6+y type. A peak in the scattering intensity observed at an energy of about 40 meV in the region of wave vectors Q = (π, π) and an arc-shaped dispersion relief are interpreted as manifestations of the collective spin excitations in the system, the energy of which falls within a superconducting gap (spin exciton). The U-shaped divergent relief observed in the neutron scattering intensity is assigned to collective short-rage-order spin oscillations.

Copper valence, structural separation and lattice dynamics in tennantite (fahlore): NMR, NQR and SQUID studies

Abstract: Electronic and magnetic properties of tennantite subfamily of tetrahedrite-group minerals have been studied by copper nuclear quadrupole resonance (NQR), nuclear magnetic resonance (NMR) and SQUID magnetometry methods. The temperature dependences of copper NQR frequencies and line-width, nuclear spin-lattice relaxation rate T 1 −1 and nuclear spin-echo decay rate T 2 −1 in tennantite samples in the temperature range 4.2–210 K is evidence of the presence of field fluctuations caused by electronic spins hopping between copper CuS3 positions via S2 bridging atom. The analysis of copper NQR data at low temperatures points to the magnetic phase transition near 65 K. The magnetic susceptibility in the range 2–300 K shows a Curie–Weiss behavior, which is mainly determined by Fe2+ paramagnetic substituting ions.

A method for calculating the Gibbs energy of nonspecific solvation

Abstract: A method for calculating the Gibbs energy of nonspecific solvation of nonelectrolytes was suggested. The new equation for the Gibbs energy of nonspecific solvation contains one solvent parameter that characterize nonspecific solvent-solute interactions and two experimental Gibbs energies of solvation in two standard solvents. The method is applicable to a wide range of solutes and solvents. It was successfully used to describe some 800 Gibbs energies of solvation for systems without specific solvent-solute interactions.

On the applicability to semirings of two theorems from the theory of rings and modules

Abstract: Problems concerning the extension of the Baer criterion for injectivity and embedding theorem of an arbitrary module over a ring into an injective module to the case of semirings are treated. It is proved that a semiring S satisfies the Baer criterion and every S-semimodule can be embedded in an injective semimodule if and only if S is a ring.

n-Tuple algebras of associative type

Abstract: We study properties of n-tuple algebras of associative type. We show that the nilpotency of an n-tuple algebra of associative type is determined by the nilpotency of each element. In addition, we characterize the nilpotency of an n-tuple algebra of associative type in terms of the trace function. In the final part of the paper, we show that a homogeneously semisimple n-tuple algebra of associative type is the direct sum of two-sided ideals each of which is a homogeneously simple n-tuple algebra of associative type.

A Descent Method with Inexact Linear Search for Nonsmooth Equilibrium Problems

Abstract: A descent method with respect to the gap function is formulated and justified for the nonsmooth equilibrium problem It uses the procedure of inexact linear search of the Armijo type The proposed method converges under the same assumptions as the methods with exact linear search