181 research outputs found

    ЭЛЕКТРОДИАЛИЗНЫЙ ГЕНЕРАТОР ГИДРОКСИДНОГО ЭЛЮЕНТА ДЛЯ ИОННОЙ ХРОМАТОГРАФИИ

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    The electrodialysis alkaline eluent generator with membrane-electrode assemblies was invented.  Using this generator allows to generate a stable-content hydroxide carbonate-ions free eluent  in the flow line of chromatograph and raise the limit of  anions determination in more than 5 times, comparing to  methods, using standard eluents (carbonate / bicarbonate, borate, etc.).Keywords: ion chromatography, hydroxide eluent generator, anion analysis.(Russian)DOI: http://dx.doi.org/10.15826/analitika.2013.17.1.010 V. Gursky1, O. Kurtova2 1Federal Unitary Enterprise, Scientific Research Technological Institute “NITI imeni Alexandrova”, Sosnovy Bor, Leningrad Region, Russian Federation2Saint-Petersburg State University, Saint-Petersburg, Russian Federation Разработан электродиализный генератор щелочного элюента для ионной хроматографии с использованием мембранно-электродных блоков. Применение разработанного устройства  позволяет генерировать в гидравлической линии хроматографа стабильный по составу гидроксидный элюент, не содержащий карбонат-ионов, и более чем в 5 раз улучшить предел определения анионов по сравнению с методиками, использующими стандартные элюенты. Разработанный генератор устанавливается в линии высокого давления хроматографа и не требует установки специального дегазатора  для удаления электролизных газов.Ключевые слова: ионная хроматография, электродиализный  генератор элюента, анионный анализ.  DOI: http://dx.doi.org/10.15826/analitika.2013.17.1.01

    INTEGRAL observations of the black hole candidate H 1743-322 in outburst

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    INTEGRAL made 3 observations in 2003 April of the black hole candidate H 1743-322 during the rising part, and close to the maximum, of an outburst. H 1743-322 was previously observed in outburst in 1977-1978. The source is located in a crowded region of the sky (l = 357 deg, b = -2 deg) and at least 18 sources are clearly detected in the field of view of the gamma-ray imager during a 277 ksec exposure. These are well known persistent X-ray binaries and 3 transient sources in outburst. The combined 5-200 keV JEM-X and SPI spectrum of H 1743-322 is well fit with an absorbed ((2.5 10E22 atom/cm2) soft (photon index 2.70 +/- 0.09) power-law model consistent with J 1743-322 being in a high/soft state.Comment: 5 pages. Figs. 2 and 3 are best viewed in color. To appear in INTEGRAL special edition of A&A

    The study of the negative pion production in neutron-proton collisions at beam momenta below 1.8 GeV/c

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    A detailed investigation of the reaction np -> pp\pi^{-} has been carried out using the data obtained with the continuous neutron beam produced by charge exchange scattering of protons off a deuterium target. A partial wave event-by-event based maximum likelihood analysis was applied to determine contributions of different partial waves to the pion production process. The combined analysis of the np -> pp\pi^{-} and pp -> pp\pi^{0} data measured in the same energy region allows us to determine the contribution of isoscalar partial waves (I=0) in the momentum range from 1.1 up to 1.8 GeV/c. The decay of isoscalar partial waves into (^1S_0)_{pp}\pi$ channel provides a good tool for a determination of the pp S-wave scalar scattering length in the final state which was found to be a_{pp}=-7.5\pm 0.3 fm.Comment: 6 pages, 6 figure

    Discrete molecular dynamics simulations of peptide aggregation

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    We study the aggregation of peptides using the discrete molecular dynamics simulations. At temperatures above the alpha-helix melting temperature of a single peptide, the model peptides aggregate into a multi-layer parallel beta-sheet structure. This structure has an inter-strand distance of 0.48 nm and an inter-sheet distance of 1.0 nm, which agree with experimental observations. In this model, the hydrogen bond interactions give rise to the inter-strand spacing in beta-sheets, while the Go interactions among side chains make beta-strands parallel to each other and allow beta-sheets to pack into layers. The aggregates also contain free edges which may allow for further aggregation of model peptides to form elongated fibrils.Comment: 15 pages, 8 figure

    p3d – Python module for structural bioinformatics

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    <p>Abstract</p> <p>Background</p> <p>High-throughput bioinformatic analysis tools are needed to mine the large amount of structural data via knowledge based approaches. The development of such tools requires a robust interface to access the structural data in an easy way. For this the Python scripting language is the optimal choice since its philosophy is to write an understandable source code.</p> <p>Results</p> <p>p3d is an object oriented Python module that adds a simple yet powerful interface to the Python interpreter to process and analyse three dimensional protein structure files (PDB files). p3d's strength arises from the combination of a) very fast spatial access to the structural data due to the implementation of a binary space partitioning (BSP) tree, b) set theory and c) functions that allow to combine a and b and that use human readable language in the search queries rather than complex computer language. All these factors combined facilitate the rapid development of bioinformatic tools that can perform quick and complex analyses of protein structures.</p> <p>Conclusion</p> <p>p3d is the perfect tool to quickly develop tools for structural bioinformatics using the Python scripting language.</p

    On the pion-nucleon coupling constant

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    In view of persisting misunderstanding about the determination of the pion-nucleon coupling constants in the Nijmegen multienergy partial-wave analyses of pp, np, and pbar-p scattering data, we present additional information which may clarify several points of discussion. We comment on several recent papers addressing the issue of the pion-nucleon coupling constant and criticizing the Nijmegen analyses.Comment: 19 pages, Nijmegen preprint THEF-NYM-92-0

    Bohm and Einstein-Sasaki Metrics, Black Holes and Cosmological Event Horizons

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    We study physical applications of the Bohm metrics, which are infinite sequences of inhomogeneous Einstein metrics on spheres and products of spheres of dimension 5 <= d <= 9. We prove that all the Bohm metrics on S^3 x S^2 and S^3 x S^3 have negative eigenvalue modes of the Lichnerowicz operator and by numerical methods we establish that Bohm metrics on S^5 have negative eigenvalues too. We argue that all the Bohm metrics will have negative modes. These results imply that higher-dimensional black-hole spacetimes where the Bohm metric replaces the usual round sphere metric are classically unstable. We also show that the stability criterion for Freund-Rubin solutions is the same as for black-hole stability, and hence such solutions using Bohm metrics will also be unstable. We consider possible endpoints of the instabilities, and show that all Einstein-Sasaki manifolds give stable solutions. We show how Wick rotation of Bohm metrics gives spacetimes that provide counterexamples to a strict form of the Cosmic Baldness conjecture, but they are still consistent with the intuition behind the cosmic No-Hair conjectures. We show how the Lorentzian metrics may be created ``from nothing'' in a no-boundary setting. We argue that Lorentzian Bohm metrics are unstable to decay to de Sitter spacetime. We also argue that noncompact versions of the Bohm metrics have infinitely many negative Lichernowicz modes, and we conjecture a general relation between Lichnerowicz eigenvalues and non-uniqueness of the Dirichlet problem for Einstein's equations.Comment: 53 pages, 11 figure

    Asymptotic behavior of solutions to the σk\sigma_k-Yamabe equation near isolated singularities

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    σk\sigma_k-Yamabe equations are conformally invariant equations generalizing the classical Yamabe equation. In an earlier work YanYan Li proved that an admissible solution with an isolated singularity at 0Rn0\in \mathbb R^n to the σk\sigma_k-Yamabe equation is asymptotically radially symmetric. In this work we prove that an admissible solution with an isolated singularity at 0Rn0\in \mathbb R^n to the σk\sigma_k-Yamabe equation is asymptotic to a radial solution to the same equation on Rn{0}\mathbb R^n \setminus \{0\}. These results generalize earlier pioneering work in this direction on the classical Yamabe equation by Caffarelli, Gidas, and Spruck. In extending the work of Caffarelli et al, we formulate and prove a general asymptotic approximation result for solutions to certain ODEs which include the case for scalar curvature and σk\sigma_k curvature cases. An alternative proof is also provided using analysis of the linearized operators at the radial solutions, along the lines of approach in a work by Korevaar, Mazzeo, Pacard, and Schoen.Comment: 55 page
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