2,097 research outputs found

    Local conditions vs regional context: variation in composition of bird communities along the Middle Paraná River, an extensive river-floodplain system of South America

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    We studied spatial changes in species composition (i.e., beta diversity) of local assemblages of birds along ∼450 km of the Middle Paraná River, an extensive fluvial system of South America. Point counts were used to survey birds at 60 plots located in shrub swamps and marshes of the floodplain within four sites (15 plots per site). Two sites were surrounded by each of the two upland ecoregions. Beta diversity of bird assemblages was high and was more important than alpha diversity in shaping regional diversity (i.e., gamma diversity) of the fluvial system. Compositional changes were related to species turnover among plots, while nestedness dissimilarity was not important for shaping diversity patterns. Variation-partitioning analysis showed that local conditions (i.e., landscape composition within a radius of 200 m from the center of each plot) accounted for more spatial variation in assemblage composition than did location along the fluvial system. Adjacent upland ecoregions did not account for spatial changes in bird composition within the fluvial system. In conclusion, environmental heterogeneity created by flood pulses is an important factor for sustaining regional diversity of birds within the fluvial system through effects on beta diversity

    The Planck-LFI flight model composite waveguides

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    The Low Frequency Instrument on board the PLANCK satellite is designed to give the most accurate map ever of the CMB anisotropy of the whole sky over a broad frequency band spanning 27 to 77 GHz. It is made of an array of 22 pseudo-correlation radiometers, composed of 11 actively cooled (20 K) Front End Modules (FEMs), and 11 Back End Modules (BEMs) at 300K. The connection between the two parts is made with rectangular Wave Guides. Considerations of different nature (thermal, electromagnetic and mechanical), imposed stringent requirements on the WGs characteristics and drove their design. From the thermal point of view, the WG should guarantee good insulation between the FEM and the BEM sections to avoid overloading the cryocooler. On the other hand it is essential that the signals do not undergo excessive attenuation through the WG. Finally, given the different positions of the FEM modules behind the focal surface and the mechanical constraints given by the surrounding structures, different mechanical designs were necessary. A composite configuration of Stainless Steel and Copper was selected to satisfy all the requirements. Given the complex shape and the considerable length (about 1.5-2 m), manufacturing and testing the WGs was a challenge. This work deals with the development of the LFI WGs, including the choice of the final configuration and of the fabrication process. It also describes the testing procedure adopted to fully characterize these components from the electromagnetic point of view and the space qualification process they underwent. Results obtained during the test campaign are reported and compared with the stringent requirements. The performance of the LFI WGs is in line with requirements, and the WGs were successfully space qualified.Comment: this paper is part of the Prelaunch status LFI papers published on JINST: http://www.iop.org/EJ/journal/-page=extra.proc5/jins

    Confluence via strong normalisation in an algebraic \lambda-calculus with rewriting

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    The linear-algebraic lambda-calculus and the algebraic lambda-calculus are untyped lambda-calculi extended with arbitrary linear combinations of terms. The former presents the axioms of linear algebra in the form of a rewrite system, while the latter uses equalities. When given by rewrites, algebraic lambda-calculi are not confluent unless further restrictions are added. We provide a type system for the linear-algebraic lambda-calculus enforcing strong normalisation, which gives back confluence. The type system allows an abstract interpretation in System F.Comment: In Proceedings LSFA 2011, arXiv:1203.542

    Fenologia da goiabeira 'Paluma' sob diferentes sistemas de cultivos, épocas e intensidades de poda de frutificação.

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    O trabalho teve como objetivo avaliar os efeitos de diferentes épocas e intensidades de poda de frutificação sobre a fenologia da goiabeira 'Paluma', em dois sistemas de cultivo, em Pedro Canário (ES). O delineamento experimental foi o de blocos ao acaso, em esquema de parcelas sub-subdivididas. As parcelas foram os sistemas de cultivo irrigado e sequeiro; as subparcelas foram as épocas de poda (10/11/2005, 9/12/2005, 13/1/2006 e 10/2/2006); e as sub-subparcelas foram as intensidades de poda (curta, média e longa). O ciclo da goiabeira 'Paluma', entre a poda até o início da colheita dos frutos, variou de 182 (poda em novembro e dezembro) a 203 dias (poda em fevereiro). A queda fisiológica dos frutos ocorreu até os 56 dias após o final do florescimento. A irrigação e a poda longa proporcionaram maior brotação e estabelecimento dos ramos. As plantas submetidas à poda longa em fevereiro produziram maior número de frutos por ramo. Independentemente da época de poda, as plantas submetidas à poda curta apresentaram menor número de frutos por ramo e menor índice de pegamento de frutos. A irrigação e as podas realizadas em dezembro e janeiro favoreceram a produção de frutos maiores

    In vitro fermentation patterns and methane production of sainfoin (Onobrychis viciifolia Scop.) hay with different condensed tannin contents.

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    Sainfoin (Onobrychis viciifolia Scop.) is a perennial legume recently reappraised for some positive charac- teristics leading to highly satisfactory animal perfor- mance. Sainfoin’s characteristics may be partly explained by the presence of moderate levels of condensed tannins (CTs) able to protect dietary protein from microbial degradation in the rumen. Decreased CH4 emissions have been reported for ruminants consuming CT-containing forage. The aim of this study was to evaluate the effects of CT content on the in vitro fermentation characteristics and kinetics and methane production of four samples of O. viciifolia cut at different phenological stages. Sainfoin hays and one sample of alfalfa hay were incubated at 39C in anaerobiosis using the in vitro gas production technique. The chemical composition, tannin content and fermentation charac- teristics and kinetics of sainfoin samples were signifi- cantly affected by phenological stage. After 48 h, the CH4 production in sainfoin hays showed a tendency to increase with the advancement of phenological stage [from 38Æ6 to 49 Æ8 mL g )1 of degraded organic matter (OM)]. The best period to cut sainfoin for hay making is between early and late flowering, when the forage combines high OM digestibility, low CH4 production and more efficient microbial fermentation
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