617 research outputs found

    Absolute Relativity in Classical Electromagnetism: the Quantisation of Light

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    A rigorous introduction of the underlying nature of space and time forces qualitatively new kinds of solutions in the classical theory of electromagnetism. A class of relativistic wave-functions are derived which are solutions to the first-order, free-space Maxwell equations. These describe all photons from radio to gamma waves and are governed by a single parameter: the exchange frequency. Though the theory remains that of classical, continuous electromagnetism, allowed travelling-wave solutions are quantised in that they come in \lumps" and their characteristic energy is proportional to frequency

    The London Basin superficial and bedrock LithoFrame 50 Model

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    This report describes the methodology and datasets used in the construction of the 1:50 000 resolution superficial and bedrock geological model of the London Basin. The London Basin study area was divided into twelve 20 x 20 km tiles, with construction of the first tiles beginning in 2006 and completion of the combined model in 2014. This time period coincided with the ongoing development of GSI3D software which was used to construct much of the model. The GSI3D software was used to calculate a rockhead (base Quaternary and Anthropocene) surface that was then used as a capping surface for the modelling of the bedrock geology in the GOCAD® software. The model complements the corresponding DiGMapGB-50 tiles of the area and consists of about 80 modelled geological units, comprising mass movement (landslip), artificial, superficial, and bedrock. This report supersedes an earlier report detailing the construction of the superficial part of this model (Burke et al. 2013). A glossary of technical terms used is included at the end of this report

    A geological model of London and the Thames Valley, southeast England

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    Many geological survey organisations have started delivering digital geological models as part of their role. This article describes the British Geological Survey (BGS) model for London and the Thames Valley in southeast England. The model covers 4800 km2 and extends to several hundred metres depth. It includes extensive spreads of Quaternary river terraces and alluvium of the Thames drainage system resting on faulted and folded Palaeogene and Cretaceous bedrock strata. The model extends to the base of the Jurassic sedimentary rocks. The baseline datasets used and the uses and limitations of the model are given. The model has been used to generate grids for the elevation of the base of the Quaternary, the thickness of Quaternary deposits, and enabled a reassessment of the subcrop distribution and faulting of the Palaeogene and Cretaceous bedrock units especially beneath the Quaternary deposits. Digital outputs from the model include representations of geological surfaces, which can be used in GIS, CAD and geological modelling software, and also graphic depictions such as a fence diagram of cross-sections through the model. The model can be viewed as a whole, and be dissected, in the BGS Lithoframe Viewer. Spatial queries of this and other BGS models, at specific points, along defined lines or at a specified depth, can be performed with the new BGS Groundhog application, which delivers template-based reports. The model should be viewed as a first version that should be improved further, and kept up to date, as new data and understanding emerges

    An online digital archive of magnetograms from 1846 to 1987

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    The magnetic measurements from current UK observatories, together with those from their historical predecessors, provide some of the longest running continuous sets of geophysical observations in the world. A campaign to capture high quality digital images of >300,000 analogue magnetograms (front and back) was completed in 2013, with every single image now available to search, view and download from the on-line archive at www.bgs.ac.uk/data/magnetograms. In parallel with the capture of the magnetograms, the related published yearbooks were scanned and are available online as PDF documents at www.geomag.bgs.ac.uk/data_service/data/yearbooks/yearbooks.html. This work has helped to ensure that these valuable long-term data sets are not lost, irrespective of what may happen in the future to the original photographic paper records. The additional benefit of immediate worldwide access to the data contained within these historic documents has also been established. In this paper we present the BGS OpenGeoscience service, which the magnetogram image archive forms part of. We also show some results of on-going work to acquire digital data from the images and the yearbooks. We discuss past and potential future use of the data for scientific research, such as space weather studies of the magnetograms during the period of the Carrington storm and studies into the homogeneity of long term geomagnetic activity indices that are used in space climate research

    Possible symmetries of the superconducting order parameter in a hexagonal ferromagnet

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    We study the order parameter symmetry in a hexagonal crystal with co-existing superconductivity and ferromagnetism. An experimental example is provided by carbon-based materials, such as graphite-sulfur composites, in which an evidence of such co-existence has been recently discovered. The presence of a non-zero magnetization in the normal phase brings about considerable changes in the symmetry classification of superconducting states, compared to the non-magnetic case.Comment: 4 pages, REVTe

    Molecular basis for bacterial peptidoglycan recognition by LysM domains.

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    Carbohydrate recognition is essential for growth, cell adhesion and signalling in all living organisms. A highly conserved carbohydrate binding module, LysM, is found in proteins from viruses, bacteria, fungi, plants and mammals. LysM modules recognize polysaccharides containing N-acetylglucosamine (GlcNAc) residues including peptidoglycan, an essential component of the bacterial cell wall. However, the molecular mechanism underpinning LysM-peptidoglycan interactions remains unclear. Here we describe the molecular basis for peptidoglycan recognition by a multimodular LysM domain from AtlA, an autolysin involved in cell division in the opportunistic bacterial pathogen Enterococcus faecalis. We explore the contribution of individual modules to the binding, identify the peptidoglycan motif recognized, determine the structures of free and bound modules and reveal the residues involved in binding. Our results suggest that peptide stems modulate LysM binding to peptidoglycan. Using these results, we reveal how the LysM module recognizes the GlcNAc-X-GlcNAc motif present in polysaccharides across kingdoms

    Dilepton production in heavy ion collisions at intermediate energies

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    We present a unified description of the vector meson and dilepton production in elementary and in heavy ion reactions. The production of vector mesons (ρ,ω\rho,\omega) is described via the excitation of nuclear resonances (RR). The theoretical framework is an extended vector meson dominance model (eVMD). The treatment of the resonance decays RNVR\longmapsto NV with arbitrary spin is covariant and kinematically complete. The eVMD includes thereby excited vector meson states in the transition form factors. This ensures correct asymptotics and provides a unified description of photonic and mesonic decays. The resonance model is successfully applied to the ω\omega production in p+pp+p reactions. The same model is applied to the dilepton production in elementary reactions (p+p,p+dp+p, p+d). Corresponding data are well reproduced. However, when the model is applied to heavy ion reactions in the BEVALAC/SIS energy range the experimental dilepton spectra measured by the DLS Collaboration are significantly underestimated at small invariant masses. As a possible solution of this problem the destruction of quantum interference in a dense medium is discussed. A decoherent emission through vector mesons decays enhances the corresponding dilepton yield in heavy ion reactions. In the vicinity of the ρ/ω\rho/\omega-peak the reproduction of the data requires further a substantial collisional broadening of the ρ\rho and in particular of the ω\omega meson.Comment: 32 pages revtex, 19 figures, to appear in PR

    [Accepted Manuscript] Comparison of Propensity Score Methods and Covariate Adjustment: Evaluation in 4 Cardiovascular Studies.

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    Propensity scores (PS) are an increasingly popular method to adjust for confounding in observational studies. Propensity score methods have theoretical advantages over conventional covariate adjustment, but their relative performance in real-word scenarios is poorly characterized. We used datasets from 4 large-scale cardiovascular observational studies (PROMETHEUS, ADAPT-DES [the Assessment of Dual AntiPlatelet Therapy with Drug-Eluting Stents], THIN [The Health Improvement Network], and CHARM [Candesartan in Heart Failure-Assessment of Reduction in Mortality and Morbidity]) to compare the performance of conventional covariate adjustment with 4 common PS methods: matching, stratification, inverse probability weighting, and use of PS as a covariate. We found that stratification performed poorly with few outcome events, and inverse probability weighting gave imprecise estimates of treatment effect and undue influence to a small number of observations when substantial confounding was present. Covariate adjustment and matching performed well in all of our examples, although matching tended to give less precise estimates in some cases. PS methods are not necessarily superior to conventional covariate adjustment, and care should be taken to select the most suitable method

    A origem das parcerias público-privada na governança global da educação

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    Durante a última década, a globalização da governança educacional por meio de parcerias público-privadas (PPP) tem gerado considerável debate quanto ao seu significado, propósito, status e resultados. Este debate é particularmente aquecido no setor da educação por causa da ampla aceitação da educação como atividade complexa, social e política que deve permanecer, em grande parte, se não totalmente, no setor público, servindo a interesses públicos. O artigo analisa a rápida expansão das parcerias público-privadas em educação (PPPE) articulada à introdução de regras de mercado no setor. Neste estudo nos concentramos sobre o papel de uma rede de desenvolvimento global, fundamental na globalização de um tipo particular de PPPE, indicando que a ideia de PPP encaixa-se em um projeto mais amplo de reconstituição da educação pública no âmbito do setor de serviços, a ser governada como parte da construção de uma sociedade de mercado.Over the past decade, the globalization and governing of education through Public Private Partnerships (PPPs) have generated considerable debate as to their meaning, purpose, status and outcomes. This debate is particularly heated in the education sector because of the widely-held view that education is a complex social and political activity that should remain largely, if not wholly, in the public sector serving public interests. The article analyses the rapid expansion of Education Public Private Partnerships (EPPPs) and the associated introduction of market rules into the education sector. We focus on the role of a key global development network in globalizing a particular kind of ePPPs, and show that the EPPP idea fi ts into a wider project of reconstituting public education as an education services industry to be governed as part of the construction of a market society
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