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Search Results: 1 - 10 of 40 matches for " Suvorov "
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Facing the Challenge of Data Transfer from Animal Models to Humans: the Case of Persistent Organohalogens
Alexander Suvorov, Larissa Takser
Environmental Health , 2008, DOI: 10.1186/1476-069x-7-58
Abstract: The history of research on a group of persistent, bioaccumulating organohalogen environmental contaminants, namely polychlorinated biphenyls (PCBs), shows serious delays in the accumulation of necessary data for the purpose of toxic-substance policy making and regulatory action [1]. Delays averaging some 50 years, depending on the country, have brought on far-reaching consequences with damage to human health, natural ecosystems and the economy [2]. The ever-increasing accumulation of industrial contaminants in biota, the influence of which is of yet unknown to human health, is one reason why speeding up policy making and regulatory action is becoming an important goal in the field of toxicology.Could delays in regulatory action be at least partly attributable to the low coherence between experimental studies of toxic effects in animal models and human studies? In other words, to what extent the outputs of animal studies aid in the design of human studies? Animal models play an important role in studying the toxic effects of hazardous substances, determining dose-response relationships, and pinpointing the most susceptible developmental stages. The results of animal experiments form an important input for human studies which influence directly the policy making process. Any discordance between them may slow down the regulatory process. Hence, an important question is to what extent the outputs of existing animal experiments correspond to the input requirements for human studies?To answer this question, we compared the animal-study histories of two groups of well known organohalogen contaminants: PCBs and PBDEs (polybrominated diphenyl ethers). PCBs have been relatively well studied compared to PBDE which are a relatively new group with a much shorter history of studies. In addition, we also ask what lessons, if any, are to be drawn from history?We reviewed PubMed titles, abstracts and full texts selected with the terms "PCB" or "PBDE" as search criteria on May 15th,
New Generation of LTCC Materials
Valant, Matjaz,Suvorov, Danilo
Boletín de la Sociedad Espa?ola de Cerámica y Vidrio , 2004,
Abstract: To reduce the complexity of LTCC systems and so accelerate the development of LTCC tapes with new functionalities it is necessary to reduce the number of phases within a particular tape. This can best be done by using glass-free single-phase ceramic systems. Such a material system consisting of low- and high-permittivity LTCC materials was developed based on Bi eulytite (permittivity; k’=16) and sillenite (k’=40) compounds and the δ-Bi2O3 solid solution with Nb2O5 (k’=90). The Ge and Si analogues of the sillenites and eulytites, and the 0.75Bi2O3 0.25Nb2O5 solid solution meet the main requirements for LTCC with respect to their sintering behavior (Ts=850-900oC), their mutual chemical compatibility, their compatibility with a silver electrode as well as their dielectric properties. Para reducer la complejidad de los sistemas LTCC y así acelerar el desarrollo de láminas de LTCC con nuevas funcionalidades es necesario reducir el número de fases dentro de una determinada lámina. La mejor manera de hacer esto es usar sistemas cerámicos monofásicos libres de fase vítrea. Dicho sistema que consiste en materiales LTCC de baja- y alta-permitividad se ha desarrollado en base a compuestos de Bieulitita (permitividad; k’=16) y silenita (k’=40) y la solución sólida de δ-Bi2O3 con Nb2O5 (k’=90). Los análogos de Ge y Si de las silenitas y eulititas, y la solución sólida 0.75Bi2O3 0.25Nb2O5 cumplen los principales requerimientos de los LTCC respecto a su comportamiento de sinterización (Ts=850-900oC), su compatibilidad química mutua y su compatibilidad con electrodos de plata, así como en lo concerniente a sus propiedades dieléctricas.
Spectral estimations for Laplace operator for the discrete Heisenberg group
K. Kokhas,A. Suvorov
Mathematics , 1999,
Abstract: Let H be the discrete 3-dimensional Heisenberg group with the standard generators x, y, z. The element Delta of the group algebra for H of the form Delta= (x+x^{-1}+y+y^{-1})/4 is called the Laplace operator. This operator can also be defined as transition operator for random walk on the group. The spectrum of Delta in the regular representation of H is the interval [-1,1]. Let E(A), where A is a subset of [-1,1], be a family of spectral projectors for Delta and m(A)=(E(A)e, e) be the corresponding spectral measure. Here e is the characteristic function of the unit element of the group H. We estimate the value m([-1,-1+t] \cup [1-t,1]) when t tends to 0. More precisely we prove the inequality m([-1,-1+t] \cup [1-t,1]) > const t^{2+alpha} for any positive alpha.
Testing modified gravity and no-hair relations for the Kerr-Newman metric through quasi-periodic oscillations of galactic microquasars
Arthur George Suvorov,Andrew Melatos
Physics , 2015,
Abstract: We construct multipole moments for stationary, asymptotically flat, spacetime solutions to higher-order curvature theories of gravity. The moments are defined using $3+1$ techniques involving timelike Killing vector constructions as in the classic papers by Geroch and Hansen. Using the fact that the Kerr-Newman metric is a vacuum solution to a particular class of $f(R)$ theories of gravity, we compute all its moments, and find that they admit recurrence relations similar to those for the Kerr solution in general relativity. It has been proposed previously that modelling the measured frequencies of quasi-periodic oscillations from galactic microquasars enables experimental tests of the no-hair theorem. We explore the possibility that, even if the no-hair relation is found to break down in the context of general relativity, there may be an $f(R)$ counterpart that is preserved. We apply the results to the microquasars GRS $1915$+$105$ and GRO J$1655$-$40$ using the diskoseismology and kinematic resonance models, and constrain the spins and `charges' [which are not really electric charges in the $f(R)$ context] of their black holes.
Carbohydrase Systems of Saccharophagus degradans Degrading Marine Complex Polysaccharides
Steven W. Hutcheson,Haitao Zhang,Maxim Suvorov
Marine Drugs , 2011, DOI: 10.3390/md9040645
Abstract: Saccharophagus degradans 2-40 is a γ-subgroup proteobacterium capable of using many of the complex polysaccharides found in the marine environment for growth. To utilize these complex polysaccharides, this bacterium produces a plethora of carbohydrases dedicated to the processing of a carbohydrate class. Aiding in the identification of the contributing genes and enzymes is the known genome sequence for this bacterium. This review catalogs the genes and enzymes of the S. degradans genome that are likely to function in the systems for the utilization of agar, alginate, α- and β-glucans, chitin, mannans, pectins, and xylans and discusses the cell biology and genetics of each system as it functions to transfer carbon back to the bacterium.
Phase relations in the La2O3-TiO2-Al2O3 system
?kapin Sre?o D.,Suvorov D.
Science of Sintering , 2002, DOI: 10.2298/sos0201057s
Abstract: A small amount of LaAlO3 added to a La2O3:3TiO2 starting oxide mixture stabilizes the A-deficient La2/3TiO3 perovskite structure. According to XRD and microstructural investigations of samples prepared in the ternary system at 1400oC, only the solid solution along the La2/3TiO3-LaAlO3 tie-line extends from at least 4 mol% LaAlO3 to pure LaAlO3.
Neutron star deformation due to poloidal-toroidal magnetic fields of arbitrary multipole order: a new analytic approach
Alpha Mastrano,Arthur George Suvorov,Andrew Melatos
Physics , 2015, DOI: 10.1093/mnras/stu2671
Abstract: A recipe is presented to construct an analytic, self-consistent model of a non-barotropic neutron star with a poloidal-toroidal field of arbitrary multipole order, whose toroidal component is confined in a torus around the neutral curve inside the star, as in numerical simulations of twisted tori. The recipe takes advantage of magnetic-field-aligned coordinates to ensure continuity of the mass density at the surface of the torus. The density perturbation and ellipticity of such a star are calculated in general and for the special case of a mixed dipole-quadrupole field as a worked example. The calculation generalises previous work restricted to dipolar, poloidal-toroidal and multipolar, poloidal-only configurations. The results are applied, as an example, to magnetars whose observations (e.g., spectral features and pulse modulation) indicate that the internal magnetic fields may be at least one order of magnitude stronger than the external fields, as inferred from their spin downs, and are not purely dipolar.
Closed Form Solutions To Bosonic Perturbations In General Relativity
Arthur Suvorov,Anthony W. C. Lun
Physics , 2014,
Abstract: We present some results regarding metric perturbations in general relativity and other metric theories of gravity. In particular, using the Newman Penrose variables, we write down and discuss the equations which govern tensor field perturbations of ranks $0, \pm 1$ and $\pm 2$ (scalar,vector,tensor bosonic perturbations) over certain space-times that admit specific background metrics expressible in isotropic coordinates. Armed with these equations, we are able to develop the Hadamard series which can be associated with the fundamental solution of the equations, wherein we introduce an inhomogeneous singularity at the physical space-time point of the perturbing particle. The Hadamard series is then used to generate closed form solutions by making choices for an appropriate ansatz solution. In particular, we solve for the spin-weighted electrostatic potential for the Reissner-Nordstrom black hole and for the fully dynamical potential for the Friedmann-Robertson-Walker cosmological solution.
Spin paramagnetic deformation of a neutron star
A. G. Suvorov,A. Mastrano,A. Melatos
Physics , 2015, DOI: 10.1093/mnras/stv2718
Abstract: Quantum mechanical corrections to the hydromagnetic force balance equation, derived from the microscopic Schr\"{o}dinger-Pauli theory of quantum plasmas, modify the equilibrium structure and hence the mass quadrupole moment of a neutron star. It is shown here that the dominant effect --- spin paramagnetism --- is most significant in a magnetar, where one typically has $\mu_{B}|\boldsymbol{B}|\gtrsim k_B T_e$, where $\mu_{B}$ is the Bohr magneton, $\boldsymbol{B}$ is the magnetic field, and $T_e$ is the electron temperature. The spin paramagnetic deformation of a nonbarotropic magnetar with a linked poloidal-toroidal magnetic field is calculated to be up to ${{\sim 10}}$ times greater than the deformation caused solely by the Lorentz force. It depends on the degree of Pauli blocking by conduction electrons and the propensity to form magnetic domains, processes which are incompletely modelled at magnetar field strengths. The star becomes more oblate, as the toroidal field component strengthens. The result implies that existing classical predictions underestimate the maximum strength of the gravitational wave signal from rapidly spinning magnetars at birth. Turning the argument around, future gravitational-wave upper limits of increasing sensitivity will place ever-stricter constraints on the physics of Pauli blocking and magnetic domain formation under magnetar conditions.
Interpreting the AXP 1E 2259+586 antiglitch as a change in internal magnetization
Alpha Mastrano,Arthur George Suvorov,Andrew Melatos
Physics , 2015, DOI: 10.1093/mnras/stv1658
Abstract: The sudden spin-down event ('anti-glitch') observed in AXP 1E 2259+586 on 2012 April 21 was arguably caused by a decay of its internal toroidal magnetic field component, which turns a stable prolate configuration into an unstable one. We refine previous models of this process by modelling the star's magnetic field self-consistently as a 'twisted torus' configuration in non-barotropic equilibrium (which allows us to explore a greater range of equilibrium configurations). It is shown that, if the star's magnetic field is purely dipolar, the change in the toroidal field strength required to produce an anti-glitch of the observed size can be ~ 10 times larger than previously calculated. If the star has a quadrupolar magnetic field component, then an anti-glitch of similar magnitude can be produced via a decay of the quadrupole component, in addition to a decay of the toroidal component. We show that, if the quadrupole component decays, the minimum initial toroidal field strength and the change in toroidal field strength needed to produce the observed anti-glitch are lower than in the pure dipole twisted torus. In addition, we predict the maximum anti-glitch sizes, assuming that they are caused by a change in ellipticity, in four glitching magnetars and discuss the implications for energetics of accompanying X-ray bursts.
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