31,079 research outputs found

    Pruning deciduous fruit trees /

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    Island transport, car ownership and use: A focus on practices in Cuba, Malta, Mauritius and Singapore

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    Car ownership is growing in many countries and this growth results in further car use and increasing emissions – a trend diametrically opposed to a reduction of transport energy and longer term sustainability targets, and a problem that is particularly acute in island states across the world. The aim of this paper is to consider how various contextual factors influence the development of transport systems in four island states. Within this, the paper seeks to explore how transport systems have developed in Cuba, Mauritius, Malta and Singapore. The paper finds that a number of contextual factors have combined to result in four rather interesting transport outcomes

    Diffusiophoresis in non-adsorbing polymer solutions: the Asakura-Oosawa model and stratification in drying films

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    A colloidal particle placed in an inhomogeneous solution of smaller non-adsorbing polymers will move towards regions of lower polymer concentration, in order to reduce the free energy of the interface between the surface of the particle and the solution. This phenomenon is known as diffusiophoresis. Treating the polymer as penetrable hard spheres, as in the Asakura-Oosawa model, a simple analytic expression for the diffusiophoretic drift velocity can be obtained. In the context of drying films we show that diffusiophoresis by this mechanism can lead to stratification under easily accessible experimental conditions. By stratification we mean spontaneous formation of a layer of polymer on top of a layer of the colloid. Transposed to the case of binary colloidal mixtures, this offers an explanation for the stratification observed recently in these systems [A. Fortini et al, Phys. Rev. Lett. 116, 118301 (2016)]. Our results emphasise the importance of treating solvent dynamics explicitly in these problems, and caution against the neglect of hydrodynamic interactions or the use of implicit solvent models in which the absence of solvent backflow results in an unbalanced osmotic force which gives rise to large but unphysical effects.Comment: 11 pages, 6 figure
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