472 research outputs found

    Asymptotic-induced numerical methods for conservation laws

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    Asymptotic-induced methods are presented for the numerical solution of hyperbolic conservation laws with or without viscosity. The methods consist of multiple stages. The first stage is to obtain a first approximation by using a first-order method, such as the Godunov scheme. Subsequent stages of the method involve solving internal-layer problems identified by using techniques derived via asymptotics. Finally, a residual correction increases the accuracy of the scheme. The method is derived and justified with singular perturbation techniques

    A fast solver for systems of reaction-diffusion equations

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    In this paper we present a fast algorithm for the numerical solution of systems of reaction-diffusion equations, tu+au=Δu+F(x,t,u)\partial_t u + a \cdot \nabla u = \Delta u + F (x, t, u), xΩR3x \in \Omega \subset \mathbf{R}^3, t>0t > 0. Here, uu is a vector-valued function, uu(x,t)Rmu \equiv u(x, t) \in \mathbf{R}^m, mm is large, and the corresponding system of ODEs, tu=F(x,t,u)\partial_t u = F(x, t, u), is stiff. Typical examples arise in air pollution studies, where aa is the given wind field and the nonlinear function FF models the atmospheric chemistry.Comment: 8 pages, 3 figures, to appear in Proc. 13th Domain Decomposition Conference, Lyon, October 200

    Iron and bismuth bound human serum transferrin reveals a partially-opened conformation in the N-lobe

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    Human serum transferrin (hTF) binds Fe(III) tightly but reversibly, and delivers it to cells via a receptor-mediated endocytosis process. The metal-binding and release result in significant conformational changes of the protein. Here, we report the crystal structures of diferric-hTF (Fe N Fe C-hTF) and bismuth-bound hTF (Bi N Fe C-hTF) at 2.8 and 2.4 Å resolutions respectively. Notably, the N-lobes of both structures exhibit unique 'partially-opened' conformations between those of the apo-hTF and holo-hTF. Fe(III) and Bi(III) in the N-lobe coordinate to, besides anions, only two (Tyr95 and Tyr188) and one (Tyr188) tyrosine residues, respectively, in contrast to four residues in the holo-hTF. The C-lobe of both structures are fully closed with iron coordinating to four residues and a carbonate. The structures of hTF observed here represent key conformers captured in the dynamic nature of the transferrin family proteins and provide a structural basis for understanding the mechanism of metal uptake and release in transferrin families. © 2012 Macmillan Publishers Limited. All rights reserved.published_or_final_versio

    Formative orientation for families of children aged 11-12 years Sport of Athletics of the municipality Caimanera

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    The research provides a system of training for family counseling in Northern Popular advice to children of Athletics who do not fulfill their duties. The actions provide suggestions and recommendations from the preparation, discussion and reflection, family-oriented, with a series of tools to give adequate attention to the school. The evaluation was made feasible the proposal satisfactory results in guiding the family and their impact on the transformation of the school from their duties by the method of expert judgment

    Structural blueprint and ontogeny determine the adaptive value of the plastic response to competition in clonal plants: a modelling approach

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    International audienceLocal competitive interactions strongly influence plant community dynamics. To maintain their performance under competition, clonal plants may plastically modify their network architecture to grow in the direction of least interference. The adaptive value of this plastic avoidance response may depend, however, on traits linked with the plant's structural blueprint and ontogeny. We tested this hypothesis using virtual populations. We used an Individual Based Model to simulate competitive interactions among clones within a plant population. Clonal growth was studied under three competition intensities in plastic and non-plastic individuals. Plasticity buffered the negative impacts of competition at intermediate densities of competitors by promoting clone clumping. Success despite competition was promoted by traits linked with (1) the plant's structural blueprint (weak apical dominance and sympodial growth) and (2) ontogenetic processes, with an increasing or a decreasing dependence of the elongation process on the branch generation level or length along the competition intensity gradient respectively. The adaptive value of the plastic avoidance response depended on the same traits. This response only modulated their importance for clone success. Our results show that structural blueprint and ontogeny can be primary filters of plasticity and can have strong implications for evolutionary ecology, as they may explain why clonal plants have developed many species-specific plastic avoidance behaviours
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