26,608 research outputs found

    On Maltsev digraphs

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    The original publication is available at www.springerlink.com Copyright SpringerWe study digraphs preserved by a Maltsev operation, Maltsev digraphs. We show that these digraphs retract either onto a directed path or to the disjoint union of directed cycles, showing that the constraint satisfaction problem for Maltsev digraphs is in logspace, L. (This was observed in [19] using an indirect argument.) We then generalize results in [19] to show that a Maltsev digraph is preserved not only by a majority operation, but by a class of other operations (e.g., minority, Pixley) and obtain a O(V G4)-time algorithm to recognize Maltsev digraphs. We also prove analogous results for digraphs preserved by conservative Maltsev operations which we use to establish that the list homomorphism problem for Maltsev digraphs is in L. We then give a polynomial time characterisation of Maltsev digraphs admitting a conservative 2-semilattice operation. Finally, we give a simple inductive construction of directed acyclic digraphs preserved by a Maltsev operation.Peer reviewe

    Determining factors in becoming a sustainable smart city: an empirical study in Europe

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    This paper aims firstly to identify differences and similarities between cities according to the activities which are necessary to become a smart city and secondly to identify relevant factors that could influence positions in the smart cities ranking. To achieve these goals, this study uses a quantitative analysis applied to 73 European cities to identify the factors that influence differences between smart cities. The results suggest the formation of clusters around European smart cities and also that cities located geographically in the west of Europe and with governance by women present higher levels in the European Smart Cities rankings.info:eu-repo/semantics/publishedVersio

    Programa de capacitação técnica coletiva em inclusão digital.

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    A Empresa Brasileira de Pesquisa Agropecuária (Embrapa), acompanhando as tendências de mercado, elaborou, em 2010, o Plano Corporativo de Inclusão Digital da Embrapa(PCIDE), que se estruturou por meio de uma análise da demanda, não somente do mercado, mas também do interesse dos funcionários e colaboradores, com o objetivo de proporcionar meios para que empregados pouco ou nada familiarizados com as TIC tivessem acesso às tecnologias e orientações para um uso adequado

    Organophosphorus pesticides residues in cooked tomato (Licopersicum esculentum).

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    The study aimed to evaluate the residual concentrations of OP in tomato after different cooking times

    Introduction to Special Section on Recent Advances in the Study of Optical Variability in the Near-Surface and Upper Ocean

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    Optical variability occurs in the near-surface and upper ocean on very short time and space scales (e.g., milliseconds and millimeters and less) as well as greater scales. This variability is caused by solar, meteorological, and other physical forcing as well as biological and chemical processes that affect optical properties and their distributions, which in turn control the propagation of light across the air-sea interface and within the upper ocean. Recent developments in several technologies and modeling capabilities have enabled the investigation of a variety of fundamental and applied problems related to upper ocean physics, chemistry, and light propagation and utilization in the dynamic near-surface ocean. The purpose here is to provide background for and an introduction to a collection of papers devoted to new technologies and observational results as well as model simulations, which are facilitating new insights into optical variability and light propagation in the ocean as they are affected by changing atmospheric and oceanic conditions

    Constraint on the chemical potentials of hydrogen and proton in recombination

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    In this paper, we revisit the hydrogen recombination history from a novel perspective: the evolution of chemical potentials. We derive expressions for the chemical potentials, which depend on the thermal bath temperature and the ionization degree of the universe. Our main finding reveals a constraint between the chemical potentials of hydrogen and proton at z1200z\approx 1200 when the free electron fraction is Xe1/3X_e\approx 1/3. Furthermore, we present important data on the chemical potentials during recombination, highlighting the differences between the predictions of the Peebles' and CosmoRec code solutions. Finally, we discuss a particular case related to the chemical potential of hydrogen.Comment: 5 pages, 3 figure
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