548 research outputs found

    Development and Validation of a ReaxFF Reactive Force Field for Cu Cation/Water Interactions and Copper Metal/Metal Oxide/Metal Hydroxide Condensed Phases

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    To enable large-scale reactive dynamic simulations of copper oxide/water and copper ion/water interactions we have extended the ReaxFF reactive force field framework to Cu/O/H interactions. To this end, we employed a multistage force field development strategy, where the initial training set (containing metal/metal oxide/metal hydroxide condensed phase data and [Cu(H_2O)_n]^(2+) cluster structures and energies) is augmented by single-point quantum mechanices (QM) energies from [Cu(H_2O)_n]^(2+) clusters abstracted from a ReaxFF molecular dynamics simulation. This provides a convenient strategy to both enrich the training set and to validate the final force field. To further validate the force field description we performed molecular dynamics simulations on Cu^(2+)/water systems. We found good agreement between our results and earlier experimental and QM-based molecular dynamics work for the average Cu/water coordination, Jahn−Teller distortion, and inversion in [Cu(H_2O)_6]^(2+) clusters and first- and second-shell O−Cu−O angular distributions, indicating that this force field gives a satisfactory description of the Cu-cation/water interactions. We believe that this force field provides a computationally convenient method for studying the solution and surface chemistry of metal cations and metal oxides and, as such, has applications for studying protein/metal cation complexes, pH-dependent crystal growth/dissolution, and surface catalysis

    Application of Higher-Order FEM Elements to the Analysis of Microstrip Structures

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    Microstrip structures, formed by metal traces printed on a dielectric substrate above a reference plane, are frequently the object of electromagnetic modeling. In this paper, hybrid FEM/MoM formulations employing conventional Whitney elements and newly developed linear-tangent/linear-normal (LT/LN) tangential vector finite elements (TVFEs) are applied to the analysis of microstrip structures with thin traces. This paper shows that the variation of the electric field below the trace is a significant issue to be addressed in microstrip structure modeling. Different mesh methods are investigated and the advantages of the LT/LN TVFEs are discussed

    An in vivo genetic screen for genes involved in spliced leader trans-splicing indicates a crucial role for continuous de novo spliced leader RNP assembly

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    ACKNOWLEDGEMENTS Some strains were provided by the CGC, which is funded by NIH Office of Research Infrastructure Programs (P40 OD010440). We would also like to thank Prof. Shohei Mitani,at the National Bioresource Project for the Experimental Animal ‘Nematode C. elegans’, Japan, for FX3079. We are grateful to Prof. Tom Blumenthal (University of Colorado, Boulder) for suggestions and support of this work; and to Kathrine Wood for her contribution to the initial stages of part of this work. Author contributions. L.P., G.P., R.F., N.H., J.P. and B.M. performed experiments; B.M., J.P. and B.C. designed and lead the study; B.M. and J.P. drafted the manuscript. All authors reviewed the manuscript. FUNDING Biotechnology and Biological Sciences Research Council (BBSRC) [Project grant BB/J007137/1]; Medical Research Council (MRC) Confidence in Concept 2014 - University of Aberdeen Award(MC PC 14114v.2); University of Aberdeen Elphinstone Scholarship (to R.F.) and TET Fund support through Adekunle Ajasin University, Nigeria (to R.F.). Funding for open access charge: Biotechnology and Biological Sciences Research Council and Medical Research Council.Peer reviewedPublisher PD

    Apostrophe, witnessing and its essentially theatrical modes of address: Maria DermĂŽut on Pattimura and Kara Walker on the New Orleans flooding

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    Apostrophe is best known as a punctuation mark (') or as a key poetic figure (with a speaker addressing an imaginary or absent person or entity). In origin, however, it is a pivotal rhetorical figure that indicates a 'breaking away' or turning away of the speaker from one addressee to another, in a different mode. In this respect, apostrophe is essentially theatrical. To be sure, the turn away implies two different modes of address that may follow upon one another, as is hinted at by the two meanings of the verb 'to witness': being a witness and bearing witness. One cannot do both at the same time. My argument will be, however, that in order to make witnessing work ethically and responsibly, the two modes of address must take place simultaneously, in the coincidence of two modalities of presence: one actual and one virtual. Accordingly, I will distinguish between an address of attention and an address of expression. Whereas the witness is actually paying attention to that which she witnesses, she is virtually (and in the sense Deleuze intended, no less really) turning away in terms of expression. The two come together in what Kelly Oliver called the 'inner witness'. The simultaneous operation of two modes of address suggests that Caroline Nevejan's so-called YUTPA model would have to include two modalities of 'you'. Such a dual modality has become all the more important, in the context of the society of the spectacle. One text will help me first to explore two modes of address through apostrophe. I will focus on a story by Dutch author Maria DermĂŽut, written in the fifties of the twentieth century, reflecting on an uprising and the subsequent execution of its leader in the Dutch Indies in 1817. Secondly, I will move to American artist Kara Walker's response, in the shape of an installation and a visual essay, to the flooding of New Orleans in 2005. The latter will serve to illustrate a historic shift in the theatrical nature and status of 'presence' in the two modes of address. Instead of thinking of the convergence of media, of which Jenkins speaks, we might think of media swallowing up one another. For instance, the theatrical structure of apostrophe is swallowed up, and in a sense perverted, by the model of the spectacle in modern media. This endangers the very possibility of witnessing in any ethical sense of the word

    Learning through social spaces: migrant women and lifelong learning in post-colonial London

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    This article shows how migrant women engage in learning through social spaces. It argues that such spaces are little recognised, and that there are multiple ways in which migrant women construct and negotiate their informal learning through socialising with other women in different informal modes. Additionally, the article shows how learning is shaped by the socio-political, geographical and multicultural context of living in London, outlining ways in which gendered and racialised identities shape, construct and constrain participation in lifelong learning. The article shows that one way in which migrant women resist (post)colonial constructions of difference is by engaging in informal and non-formal lifelong learning, arguing that the benefits are (at least) two-fold. The women develop skills (including language skills) but also use their informal learning to develop what is referred to in this article as 'relational capital'. The article concludes that informal lifelong learning developed through social spaces can enhance a sense of belonging for migrant women
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