118 research outputs found

    Real-space local polynomial basis for solid-state electronic-structure calculations: A finite-element approach

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    We present an approach to solid-state electronic-structure calculations based on the finite-element method. In this method, the basis functions are strictly local, piecewise polynomials. Because the basis is composed of polynomials, the method is completely general and its convergence can be controlled systematically. Because the basis functions are strictly local in real space, the method allows for variable resolution in real space; produces sparse, structured matrices, enabling the effective use of iterative solution methods; and is well suited to parallel implementation. The method thus combines the significant advantages of both real-space-grid and basis-oriented approaches and so promises to be particularly well suited for large, accurate ab initio calculations. We develop the theory of our approach in detail, discuss advantages and disadvantages, and report initial results, including the first fully three-dimensional electronic band structures calculated by the method.Comment: replacement: single spaced, included figures, added journal referenc

    Use of SMS texts for facilitating access to online alcohol interventions: a feasibility study

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    A41 Use of SMS texts for facilitating access to online alcohol interventions: a feasibility study In: Addiction Science & Clinical Practice 2017, 12(Suppl 1): A4

    Effects of calcium pH, and blockiness on kinetic rheological behaviour and microstructure of HM pectin gels

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    The kinetic behavior during gel formation and the microstructure of 0.75% high methoxyl (HM) pectin gels in 60% sucrose have been investigated by oscillatory measurements and transmission electron microscopy for three comparable citrus pectin samples differing in their degree of blockiness (DB). Ca2+ addition at pH 3.0 resulted in faster gel formation and a lower storage modulus after 3 h for gels of the blockwise pectin A. For gels of the randomly esterified pectin B, the Ca2+ addition resulted in faster gel formation and a higher storage modulus at pH 3.0. At pH 3.5, both pectins A and B were reinforced by the addition of Ca2+. In the absence of Ca2+, the shortest gelation time was obtained for the sample with the highest DB. Microstructural characterization of the gel network, 4 and 20 h after gel preparation, showed no visible changes on a nanometer scale. The microstructure of pectins A and B without Ca2+ was similar, whereas the presence of Ca2+ in pectin A resulted in an inhomogeneous structure
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