29,949 research outputs found

    A new formulation of compartmental epidemic modelling for arbitrary distributions of incubation and removal times

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    The paradigm for compartment models in epidemiology assumes exponentially distributed incubation and removal times, which is not realistic in actual populations. Commonly used variations with multiple exponentially distributed variables are more flexible, yet do not allow for arbitrary distributions. We present a new formulation, focussing on the SEIR concept that allows to include general distributions of incubation and removal times. We compare the solution to two types of agent-based model simulations, a spatially homogeneous one where infection occurs by proximity, and a model on a scale-free network with varying clustering properties, where the infection between any two agents occurs via their link if it exists. We find good agreement in both cases. Furthermore a family of asymptotic solutions of the equations is found in terms of a logistic curve, which after a non-universal time shift, fits extremely well all the microdynamical simulations. The formulation allows for a simple numerical approach; software in Julia and Python is provided.Comment: 21 pages, 11 figures. v2 matches published version: improved presentation (including title, abstract and references), results and conclusions unchange

    Prospects and status of quark mass renormalization in three-flavour QCD

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    We present the current status of a revised strategy to compute the running of renormalized quark masses in QCD with three flavours of massless O(a) improved Wilson quarks. The strategy employed uses the standard finite-size scaling method in the Schr\"odinger functional and accommodates for the non-perturbative scheme-switch which becomes necessary at intermediate renormalized couplings as discussed in [arXiv:1411.7648].Comment: 7 pages, 3 figures, 1 table; Proceedings of the 33rd International Symposium on Lattice Field Theory, 14-18 July 2015, Kobe, Japa

    Shear-melting of a hexagonal columnar crystal by proliferation of dislocations

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    A hexagonal columnar crystal undergoes a shear-melting transition above a critical shear rate or stress. We combine the analysis of the shear-thinning regime below the melting with that of synchrotron X-ray scattering data under shear and propose the melting to be due to a proliferation of dislocations, whose density is determined by both techniques to vary as a power law of the shear rate with a 2/3 exponent, as expected for a creep model of crystalline solids. Moreover, our data suggest the existence under shear of a line hexatic phase, between the columnar crystal and the liquid phase

    THROES: a caTalogue of HeRschel Observations of Evolved Stars. I. PACS range spectroscopy

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    This is the first of a series of papers presenting the THROES (A caTalogue of HeRschel Observations of Evolved Stars) project, intended to provide a comprehensive overview of the spectroscopic results obtained in the far-infrared (55-670 microns) with the Her- schel space observatory on low-to-intermediate mass evolved stars in our Galaxy. Here we introduce the catalogue of interactively reprocessed PACS (Photoconductor Array Camera and Spectrometer) spectra covering the 55-200 microns range for 114 stars in this category for which PACS range spectroscopic data is available in the Herschel Science Archive (HSA). Our sample includes objects spanning a range of evolutionary stages, from the asymptotic giant branch to the planetary nebula phase, displaying a wide variety of chemical and physical properties. The THROES/PACS catalogue is accessible via a dedicated web-based inter- face (https://throes.cab.inta-csic.es/) and includes not only the science-ready Herschel spectroscopic data for each source, but also complementary photometric and spectroscopic data from other infrared observatories, namely IRAS (Infrared Astronomical Satellite), ISO (Infrared Space Observatory) or AKARI, at overlapping wavelengths. Our goal is to create a legacy-value Herschel dataset that can be used by the scientific community in the future to deepen our knowledge and understanding of these latest stages of the evolution of low-to-intermediate mass stars.Comment: 38 page

    Attitude towards gender equality and coeducation among Secondary School teachers: a case study in Madrid, Spain

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    Introduction. In spite of the education reform and the introduction of mixed schools, there are still obstacles to gender equality in Spain. Sexist attitudes and values continue to influence personal development and career choices, limiting women''s participation in many spheres. The opinions, beliefs, ideas, conceptions, expectations and personal attitude of teaching professionals exert a great influence on the students who perceive them, which calls for up-to-date information on teaching staff’s perceptions towards gender equality and coeducation. Method. In this work, results from a survey distributed to 105 teachers in three Secondary Schools in the Autonomous Community of Madrid are presented. The retrieved data was analyzed by using parametric (ANOVA) and non-parametric (Kruskal-Wallis) tests. Results. Significant differences were found among the respondents in terms of their views on gender equality for the gender and gender*age factors, and for the gender and years of teaching experience factors in the case of their perceptions about coeducation. Discussion and Conclusion. Although the tendency toward a true status of equality was more pronounced in women than in men, an adequate predisposition of the majority of teachers of both sexes towards the achievement of a social equality model based on the promotion of peer roles and coeducational practices was found. Teaching staff appears to be aware of the importance of adopting policies and laws that favor effective and real equality between men and women. © 2021. Universidad de Almería and Ilustre Colegio Oficial de la Psicología de Andalucía Oriental (Spain). All Rights Reserved

    Intrinsic structure of two-phonon states in the interacting boson model

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    A general study of excitations up to two-phonon states is carried out using the intrinsic-state formalism of the Interacting Boson Model (IBM). Spectra and transitions for the different dynamical symmetries are analyzed and the correspondence with states in the laboratory frame is established. The influence of multi-phonon states is discussed. The approach is useful in problems where the complexity of the IBM spectrum renders the analysis in the laboratory frame difficult.Comment: 22 pages, TeX (ReVTeX). 7 eps figures. Submitted to Nucl. Phys.
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