1,721,028 research outputs found

    Pandemie - Virologia, patologia e prevenzione dell'influenza

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    Bollati Boringhieri In tempo di massimo allarme per l'influenza suina, una panoramica scientifica puntuale ed esaustiva sugli aspetti salienti di questo virus e della sua trasmission

    Evidences for bioprecipitation of pedogenic calcite by calcifying bacteria from three different soils of L'Aquila basin (Abruzzi, Central-Italy)

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    To provide further evidences on the role of bacterial soil species in the development of calcium carbonate deposits in soil, we isolated 36 heterotrophic bacterial strains from three soils of L'Aquila basin characterized by different CaCO3 content and tested their ability to precipitate CaCO3 when cultured on a Ca-rich medium. We found that the majority (63.89%) of these isolates could precipitate CaCO3 minerals at 27°C. The aptitude to calcification (time and crystal amount) of each calcifying strains, morphology (SEM) and mineralogy of the formed bioliths were also investigated. X-ray diffraction confirmed the production of calcite. Crystal formation was not observed in the controls. Organic matter, total N and assimilable P, cation exchange capacity and exchangeable Ca2+, Mg2+, K+, Na+, pH, total and active calcium carbonate content, electric conductivity, skeleton, sand, silt and clay fractions of each soil sample were determined and related with its microbiological parameters. We found that the CaCO3 content of soil was significatively related, in particular, to the percentage of calcifying bacterial strains (r = 0.95) and to the heterotrophic bacterial density (r = 0.98) which was found significatively related also with Ca 2+ content of soil (r = - 0.97) and its CEC (r = - 0.97)

    Going Beyond Counting First Authors in Author Co-citation Analysis

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    The present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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