920 research outputs found

    Economic evaluation of LIFE methodology

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    Background: The LIFE project (Lifecycle Information For E-Literature) was carried out during 2004-2006 by a consortium consisting of The British Library and University College London Library Services . The project was joint venture funded by JISC under the programme area Institutional Management Support and Collaboration. The project has received favourable feedback, for instance during a workshop organised at the end of it, and JISC has agreed to fund a second phase during 2007-2008. The consortium has been strengthened by three associate partners (SHERPA-LEAP Consortium, SHERPA-DP and the Medical Research Council). In addition some funds were reserved for the use of an outside economic consultant for an evaluation of the life-cycle models that emerged as the key results from the first phase. The LIFE-2 project consists of five work packages, and this report is part of the first of these. The objective of WP 1 is formulated in the LIFE 2 Project proposal as follows: Validation of the economic modelling and methodology for the Lifecycle and Generic Preservation formulae developed in Phase 1 of the LIFE project, with technical and presentational development of the models. Cloudlake Consulting Oy has been commissioned by the consortium to carry out this validation. The report has been written by Bo-Christer Björk. He is professor of Information Systems Science at the Swedish School of Economics and Business Administration in Helsinki, Finland. He has been conducting research concerning the scientific publishing process since 2000 and has published several peer reviewed journal articles as well as conference papers on the subject. He is often an invited speaker at international workshops in this area

    Open Access 2007 - 2017: Country and University Level Perspective

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    Each year the number of Open Access (OA) papers is gradually increasing. We carried out a study investigating 400 universities from 8 countries to examine: i) the total number of OA papers per country, ii) proportion of OA papers published by representative universities in each country classified into three tiers of research quality: high, middle and low, iii) how universities within the same country compare to each other and iv) the growth of OA papers in countries per year. We conclude that among the analysed countries the UK and USA rank first and second respectively, while Russia and India are positioned towards the bottom of the list. We observe no link between the proportion of OA papers published by authors at a university and the university ranking, with some universities in the middle university rank tier having a larger proportion of OA papers than those in the high tier

    On the structure of the sets of mutually unbiased bases for N qubits

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    For a system of N qubits, spanning a Hilbert space of dimension d=2^N, it is known that there exists d+1 mutually unbiased bases. Different construction algorithms exist, and it is remarkable that different methods lead to sets of bases with different properties as far as separability is concerned. Here we derive the four sets of nine bases for three qubits, and show how they are unitarily related. We also briefly discuss the four-qubit case, give the entanglement structure of sixteen sets of bases,and show some of them, and their interrelations, as examples. The extension of the method to the general case of N qubits is outlined.Comment: 16 pages, 10 tables, 1 figur

    Two-photon imaging and quantum holography

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    It has been claimed that ``the use of entangled photons in an imaging system can exhibit effects that cannot be mimicked by any other two-photon source, whatever strength of the correlations between the two photons'' [A. F. Abouraddy, B. E. A. Saleh, A. V. Sergienko, and M. C. Teich, Phys. Rev. Lett. 87, 123602 (2001)]. While we believe that the cited statement is true, we show that the method proposed in that paper, with ``bucket detection'' of one of the photons, will give identical results for entangled states as for appropriately prepared classically correlated states.Comment: 4 pages, 2 figures, REVTe

    Many-Body Effects on Tunneling of Electrons in Magnetic-Field-Induced Quasi One-Dimensional Electron Systems in Semiconductor Nanowhiskers

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    Effects of the electron-electron interaction on tunneling in a semiconductor nanowhisker are studied in a magnetic quantum limit. We consider the system with which bulk and edge states coexist. In bulk states, the temperature dependence of the transmission probability is qualitatively similar to that of a one-dimensional electron system. We investigate contributions of edge states on transmission probability in bulk states. Those contributions can be neglected within our approximation which takes into account only most divergent terms at low temperatures.Comment: 9 pages, 6 figure

    Open-access mega-journals: A bibliometric profile

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    In this paper we present the first comprehensive bibliometric analysis of eleven open-access mega-journals (OAMJs). OAMJs are a relatively recent phenomenon, and have been characterised as having four key characteristics: large size; broad disciplinary scope; a GoldOA business model; and a peer-review policy that seeks to determine only the scientific soundness of the research rather than evaluate the novelty or significance of the work. Our investigation focuses on four key modes of analysis: journal outputs (the number of articles published and changes in output over time); OAMJ author characteristics (nationalities and institutional affiliations); subject areas (the disciplinary scope of OAMJs, and variations in sub-disciplinary output); and citation profiles (the citation distributions of each OAMJ, and the impact of citing journals). We found that while the total output of the eleven megajournals grew by 14.9% between 2014 and 2015, this growth is largely attributable to the increased output of Scientific Reports and Medicine. We also found substantial variation in the geographical distribution of authors. Several journals have a relatively high proportion of Chinese authors, and we suggest this may be linked to these journals’ high Journal Impact Factors (JIFs). The mega-journals were also found to vary in subject scope, with several journals publishing disproportionately high numbers of articles in certain sub-disciplines. Our citation analsysis offers support for Björk & Catani’s suggestion that OAMJs’s citation distributions can be similar to those of traditional journals, while noting considerable variation in citation rates across the eleven titles. We conclude that while the OAMJ term is useful as a means of grouping journals which share a set of key characteristics, there is no such thing as a “typical” mega-journal, and we suggest several areas for additional research that might help us better understand the current and future role of OAMJs in scholarly communication

    Entanglement measure for general pure multipartite quantum states

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    We propose an explicit formula for an entanglement measure of pure multipartite quantum states, then study a general pure tripartite state in detail, and at end we give some simple but illustrative examples on four-qubits and m-qubits states.Comment: 5 page

    Conditional generation of N-photon entangled states of light

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    We propose a scheme for conditional generation of two-mode N-photon path-entangled states of traveling light field. These states may find applications in quantum optical lithography and they may be used to improve the sensitivity of interferometric measurements. Our method requires only single-photon sources, linear optics (beam splitters and phase shifters), and photodetectors with single photon sensitivity.Comment: 4 pages, 2 figures, RevTeX

    Certainty relations between local and nonlocal observables

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    We demonstrate that for an arbitrary number of identical particles, each defined on a Hilbert-space of arbitrary dimension, there exists a whole ladder of relations of complementarity between local, and every conceivable kind of joint (or nonlocal) measurements. E.g., the more accurate we can know (by a measurement) some joint property of three qubits (projecting the state onto a tripartite entangled state), the less accurate some other property, local to the three qubits, become. We also show that the corresponding complementarity relations are particularly tight for particles defined on prime dimensional Hilbert spaces.Comment: 4 pages, no figure

    Assessing the Polarization of a Quantum Field from Stokes Fluctuation

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    We propose an operational degree of polarization in terms of the variance of the projected Stokes vector minimized over all the directions of the Poincar\'e sphere. We examine the properties of this degree and show that some problems associated with the standard definition are avoided. The new degree of polarization is experimentally determined using two examples: a bright squeezed state and a quadrature squeezed vacuum.Comment: 4 pages, 2 figures. Comments welcome
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