5,190 research outputs found

    1WHSP: an IR-based sample of \sim1,000 VHE γ\gamma-ray blazar candidates

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    Blazars are the dominant type of extragalactic sources at microwave and at γ\gamma-ray energies. In the most energetic part of the electromagnetic spectrum (E>100GeV) a large fraction of high Galactic latitude sources are blazars of the High Synchrotron Peaked (HSP) type, that is BL Lac objects with synchrotron power peaking in the UV or in the X-ray band. HSP blazars are remarkably rare, with only a few hundreds of them expected to be above the sensitivity limits of currently available surveys. To find these very uncommon objects, we have devised a method that combines ALLWISE survey data with multi-frequency selection criteria. The sample was defined starting from a primary list of infrared colour-colour selected sources from the ALLWISE all sky survey database, and applying further restrictions on IR-radio and IR-X-ray flux ratios. Using a polynomial fit to the multi-frequency data (radio to X-ray) we estimated synchrotron peak frequencies and fluxes of each object. We assembled a sample including 992 sources, which is currently the largest existing list of confirmed and candidates HSP blazars. All objects are expected to radiate up to the highest γ\gamma-ray photon energies. In fact, 299 of these are confirmed emitters of GeV γ\gamma-ray photons (based on Fermi-LAT catalogues), and 36 have already been detected in the TeV band. The majority of sources in the sample are within reach of the upcoming Cherenkov Telescope Array (CTA), and many may be detectable even by the current generation of Cherenkov telescopes during flaring episodes. The sample includes 425 previously known blazars, 151 new identifications, and 416 HSP candidates (mostly faint sources) for which no optical spectra is available yet. The full 1WHSP catalogue is on-line at http://www.asdc.asi.it/1whsp/ providing a direct link to the SED building tool where multifrequency data can be easily visualised

    Treatment of bimodality in proficiency test of pH in bioethanol matrix

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    The pH value in bioethanol is a quality control parameter related to its acidity and to the corrosiveness of vehicle engines when it is used as fuel. In order to verify the comparability and reliability of the measurement of pH in bioethanol matrix among some experienced chemical laboratories, reference material (RM) of bioethanol developed by Inmetro - the Brazilian National Metrology Institute - was used in a proficiency testing (PT) scheme. There was a difference of more than one unit in the value of the pH measured due to the type of internal filling electrolytic solutions (potassium chloride, KCl or lithium chloride, LiCl) from the commercial pH combination electrodes used by the participant laboratories. Therefore, bimodal distribution has occurred from the data of this PT scheme. This work aims to present the possibilities that a PT scheme provider can use to overcome the bimodality problem. Data from the PT of pH in bioethanol were treated by two different statistical approaches: kernel density model and the mixture of distributions. Application of these statistical treatments improved the initial diagnoses of PT provider, by solving bimodality problem and contributing for a better performance evaluation in measuring pH of bioethanol.Comment: 20 pages, 6 figures, Accepted for publication in Accreditation and Quality Assurance (ACQUAL

    Bioética, formação em valores e doutrinação : visão de licenciandos de ciências e biologia

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    A presente pesquisa, integrante de um projeto de doutorado, teve como foco a formação inicial de professores de Ciências e Biologia. O objetivo foi analisar se tal formação tem contribuído para a tematização e construção de valores e verificar sob a ótica dos licenciandos seu papel na formação ético-moral dos futuros estudantes. O percurso metodológico consistiu na análise de relatos de graduandos de três Instituições de Ensino Superior obtidos através de questionário. A partir da literatura voltada à educação em valores, constatou-se que os sujeitos reconhecem a contribuição das disciplinas científicas como espaço de promoção de valores ético-morais. Identificou-se fatores que favorecem e que inviabilizam a inserção da dimensão (bio)ética no ensino de ciências e a preparação desses futuros profissionais, entre eles o perigo da doutrinação

    Patterns of innovation diffusion and technological competition in Portuguese manufacturing and service industries

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    This article uses data from the Portuguese Community Innovation Survey (CIS III) to analyse the inter-industry heterogeneity in the diffusion of innovations and level of technological competition in Portuguese manufacturing and service industries. The industries are classified with reference to the relationship between the level of participation in innovation and the strategies of innovative firms. Methods of multivariate statistics are used to synthesize the data and to group the observations into subsets. Four distinctive innovation patterns are identified, defined along the following dimensions: output-orientation of innovation, importance of disembodied innovation, role of technologically advanced innovation and level of innovation opportunities. It is also found that high levels of technological competition tend to occur in sectors with relatively low dimension, productivity and overall investment

    Mathematical modelling of intensified extraction for spent nuclear fuel reprocessing

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    Small scale extractors seem to be a promising intensified alternative to the conventional solvent extraction technologies, because of the well described hydrodynamics, enhanced mass transfer, and good phase separation at the end. One of the most interesting applications of intensified extractions is the reprocessing of spent nuclear fuel. Operating in small channels can reduce the volumes of involved hazardous materials and the residence times, thus minimising the degradation of the solvent and its regeneration cost. Finally, nuclear criticality safety may be easily achieved. In this paper, the application of small channels on spent nuclear fuel reprocessing has been investigated. A mathematical model of a multi-component liquid-liquid extraction has been developed. The multi-component system consists of U, Pu, HNO 3 , HNO 2 , Zr, Ru, Tc, Np(IV), Np(V) and Np(VI), the organic solvent is a mixture of 30% (v/v) Tri-Butyl Phosphate (TBP) and a paraffinic diluent. A segmented flow pattern, with the aqueous phase dispersed in a continuous organic phase, has been assumed. Calculations for the estimation of mass transfer, redox reactions, pressure drop, nuclear criticality and TBP hydrolysis have been included in the model. To increase the flow rates, the number of small channels was increased (scale out) and a comb-like manifold was considered to ensure good flow distribution in each channel. The problem is formulated as a mixed integer nonlinear programming problem and is implemented in the General Algebraic Modeling System (GAMS). The results show that this alternative technology for liquid-liquid extraction offers advantages, especially in terms of solvent degradation and low holdup volume

    A relaxed version of the Kofoidian system of thecal plate nomenclature based on plate homologies

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    More than a century ago, Kofoid proposed a system to label thecal plates of dinoflagellates based on series from apical to antapical. Thanks to this system it was possible to develop the taxonomy of armoured dinoflagellates as it was generally accepted by dinoflagellate taxonomists. Nevertheless, when different species or genera are compared it soon appears that homologous plates receive different names when the Kofoid system is strictly applied. In 1978 at the Penrose Conference on Modern and Fossil Dinoflagellates which was the first of the DINO series, this problem was addressed and discussed, and as a consequence several alternatives were published as an attempt to conciliate plate labels with homologies. Although the proposals were very logic they were not used by taxonomist, probably due to laziness instead of disagreement with the systems. Here, a relaxed version of the Kofoidian system taking into account homologies among plates is applied to some Gonyaulacales genera: Alexandrium, Ceratocorys, Coolia, Fragilidium, Gambierdiscus, Gonyaulax and Ostreopsis

    Process intensification applied to spent nuclear fuel reprocessing: An alternative flowsheet using small channels

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    Commercial plants for spent nuclear fuel reprocessing rely on the Plutonium Uranium Extraction (PUREX) process, based on traditional liquid–liquid extraction technologies. In this paper, an alternative flowsheet for spent nuclear fuel reprocessing is proposed, based on small-scale extractors to overcome some of the issues related to the conventional technologies, such as solvent degradation, size and nuclear criticality control. The main goal of the process is to preclude the risk of nuclear proliferation, hence a mixed uranium/plutonium oxide is produced instead of pure plutonium. A superstructure optimisation based framework has been used to identify a process with several benefits over the conventional process. Novel flow configurations and organic solvent composition have been investigated. A large number of components and chemical reactions are included in the framework. The resulting model is a mixed integer nonlinear optimisation problem, implemented in the General Algebraic Modeling System (GAMS). The most promising flowsheet identified is more cost effective than the conventional one. Furthermore, advantages in terms of safety and separation efficiency have been achieved. It was found that increasing the inner diameter of the small channels up to 2.5 mm, as well as increasing the tributyl phosphate fraction in the organic solvent, are advantageous
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