15,706 research outputs found

    Giant magnetic anisotropy at nanoscale: overcoming the superparamagnetic limit

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    It has been recently observed for palladium and gold nanoparticles, that the magnetic moment at constant applied field does not change with temperature over the range comprised between 5 and 300 K. These samples with size smaller than 2.5 nm exhibit remanence up to room temperature. The permanent magnetism for so small samples up to so high temperatures has been explained as due to blocking of local magnetic moment by giant magnetic anisotropies. In this report we show, by analysing the anisotropy of thiol capped gold films, that the orbital momentum induced at the surface conduction electrons is crucial to understand the observed giant anisotropy. The orbital motion is driven by localised charge and/or spin through spin orbit interaction, that reaches extremely high values at the surfaces. The induced orbital moment gives rise to an effective field of the order of 103 T that is responsible of the giant anisotropy.Comment: 15 pages, 2 figures, submitted to PR

    La mediación penal y el nuevo modelo de justicia restaurativa

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    The paper deals with the intersubjective conflict that occurs between two people, perpetrator and victim, and the need to offer a solution to both the conflict itself and those involved in it through penal mediatio

    Van der Waals spin valves

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    We propose spin valves where a 2D non-magnetic conductor is intercalated between two ferromagnetic insulating layers. In this setup, the relative orientation of the magnetizations of the insulating layers can have a strong impact on the in-plane conductivity of the 2D conductor. We first show this for a graphene bilayer, described with a tight-binding model, placed between two ferromagnetic insulators. In the anti-parallel configuration, a band gap opens at the Dirac point, whereas in the parallel configuration, the graphene bilayer remains conducting. We then compute the electronic structure of graphene bilayer placed between two monolayers of the ferromagnetic insulator CrI3_3, using density functional theory. Consistent with the model, we find that a gap opens at the Dirac point only in the antiparallel configuration.Comment: 5 pages, 4 figure

    More Income Equality or Not? An Empirical Analysis of Individuals' Preferences for Redistribution

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    Do people prefer a society with an extensive social welfare system with high taxes, or low taxes but lax redistributive policies? Although economists have for a long time investigated the trade-off mechanism between equity and efficiency, surprisingly little information is available about citizens’ preferences over the distribution of income in a society. The aim of this paper is reduce this shortcoming, investigating in an empirical study working with World Values Survey, what shapes individuals' preferences for income equality in Spain. We present evidence that not only traditional economic variables are relevant to be considered, but also factors such as ideology, political interest, fairness perception about others or trust in institutions, are key determinants to understand preferences towards redistribution and equality. Furthermore, we also find that regional conditions affect the citizens’ preferences for income equality. Higher income inequality leads to stronger preferences for equality. On the other hand, there is the tendency that higher social expenditures reduce the preferences for income equality.redistribution, inequality, welfare state, social capital, regional conditions

    Extended WKB method, resonances and supersymmetric radial barriers

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    Semiclassical approximations are implemented in the calculation of position and width of low energy resonances for radial barriers. The numerical integrations are delimited by t/T<<8, with t the period of a classical particle in the barrier trap and T the resonance lifetime. These energies are used in the construction of `haired' short range potentials as the supersymmetric partners of a given radial barrier. The new potentials could be useful in the study of the transient phenomena which give rise to the Moshinsky's diffraction in time.Comment: 12 pages, 4 figures, 3 table

    Compressed k2-Triples for Full-In-Memory RDF Engines

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    Current "data deluge" has flooded the Web of Data with very large RDF datasets. They are hosted and queried through SPARQL endpoints which act as nodes of a semantic net built on the principles of the Linked Data project. Although this is a realistic philosophy for global data publishing, its query performance is diminished when the RDF engines (behind the endpoints) manage these huge datasets. Their indexes cannot be fully loaded in main memory, hence these systems need to perform slow disk accesses to solve SPARQL queries. This paper addresses this problem by a compact indexed RDF structure (called k2-triples) applying compact k2-tree structures to the well-known vertical-partitioning technique. It obtains an ultra-compressed representation of large RDF graphs and allows SPARQL queries to be full-in-memory performed without decompression. We show that k2-triples clearly outperforms state-of-the-art compressibility and traditional vertical-partitioning query resolution, remaining very competitive with multi-index solutions.Comment: In Proc. of AMCIS'201
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