1,341 research outputs found

    Polychaete assemblage of an impacted estuary, Guanabara Bay, Rio de Janeiro, Brazil

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    Thirty-eight stations were sampled in Guanabara Bay, Rio de Janeiro, Brazil, to assess the spatio-temporal diversity and biomass of sublittoral polychaetes. Samples were collected during the dry (September 2000) and rainy season (May 2001) in shallow sublittoral sediments. The polychaete spatial composition showed a heterogeneous distribution throughout the bay. A negative gradient of diversity and biomass was observed towards the inner parts of the bay and sheltered areas. A wide azoic area was found inside the bay. Some high-biomass and low-diversity spots were found near a sewage-discharge point. In these areas, the polychaete biomass increased after the rainy season. A diversified polychaete community was identified around the bay mouth, with no dramatic changes of this pattern between the two sampling periods. Deposit-feeders were dominant in the entire study area. The relative importance of carnivores and omnivores increased towards the outer sector, at stations with coarse sediment fractions. Guanabara Bay can be divided into three main zones with respect to environmental conditions and polychaete diversity and biomass patterns: A) High polychaete diversity, hydrodynamically exposed areas composed of sandy, oxidized or moderately reduced sediments with normoxic conditions in the water column. B) Low diversity and high biomass of deposit and suspension-feeding polychaete species in the middle part of the bay near continental inflows, comprising stations sharing similar proportions of silt, clay and fine sands. C) Azoic area or an impoverished polychaete community in hydrodynamically low-energy areas of silt and clay with extremely reduced sediments, high total organic matter content and hypoxic conditions in the water column, located essentially from the mid-bay towards the north sector. High total organic matter content and hypoxic conditions combined with slow water renewal in the inner bay seemed to play a key role in the polychaete diversity and biomass. Sedimentation processes and organic load coming from untreated sewage into the bay may have negatively affected the survivorship of the fauna.Trinta e oito estações foram amostradas na Baía de Guanabara, Rio de Janeiro, Brasil, no intuito de descrever a diversidade e biomassa de poliquetas sublitorais. As coletas foram realizadas em dois períodos distintos do ano: seco (Setembro 2000) e chuvoso (Maio de 2001). A distribuição espacial dos poliquetas sublitorais demonstrou ser nitidamente heterogênea na Baía de Guanabara. Um gradiente negativo de diversidade e biomassa foi observado em direção as partes internas e protegidas da baía. Foi encontrada uma grande área azóica dentro da baía. Por outro lado, algumas áreas com alta biomassa e baixa diversidade foram encontradas nas proximidades de locais com despejo de esgoto urbano não tratado. Nestas áreas foi observado aumento da biomassa de poliquetas no período chuvoso. Uma comunidade diversificada foi identificada na entrada da baía sem mudanças dramáticas deste padrão entre os dois períodos estudados. Os depositívoros de superfície foram dominantes em toda a área estudada. A importância relativa dos carnívoros e omnívoros aumentou em direção ao setor externo contendo estações de coleta com frações granulométricas mais grosseiras. A Baía de Guanabara pôde ser dividida em três principais regiões levando-se em consideração as condições ambientais, diversidade e biomassa de poliquetas sublitorais: A) área com alta diversidade situada em regiões hidrodinamicamente mais expostas, compostas por areias oxidadas ou pouco reduzidas e com concentrações normais de oxigênio dissolvido na coluna d'água; B) área com baixa diversidade e alta biomassa de poliquetas depositívoras e suspensívoras na porção intermediária da baía próxima a efluentes urbanos, abrangendo estações com contribuições semelhantes de silte, argila e areias finas; C) área azóica ou com emprobecimento da comunidade de poliquetas, apresentando baixa densidade em regiões com baixa energia hidrodinâmica compostas por silte e argila em condição extremamente reduzida, altas concentrações de matéria orgânica total e pouca disponibilidade de oxigênio na coluna d'água, localizada essencialmente do meio até o setor norte da baía. O alto conteúdo de matéria orgânica e as condições de hipoxia da coluna d´água, combinados com a baixa renovação das águas nas áreas protegidas, parecem ter exercido papel fundamental na diversidade e biomassa das poliquetas sublitorais. Os processos de sedimentação e o aporte orgânico intenso a que a Baía de Guanabara está sujeita podem ter contribuído negativamente para a sobrevivência da fauna.CNPq National Council for the Development of Science and TechnologyPETROBRA

    Innovating in open distance teaching with face-to-face retreats within a doctoral program in digital media art

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    INTED 2022. 16ª Conferência Anual, realizada de 7-8 de março de 2022The Portuguese Open University, together with the University of Algarve, both in Portugal, launched a the doctoral program in digital media art taught by a hybrid approach, adopting open distance asynchronous teaching based on an e-learning platform along with face-to-face sessions (doctoral retreats) with a duration of one week at the final of each academic year. This program was established in 2012, pioneering the innovation of applying asynchronous online teaching in practical and labour-intensive disciplines, such as programing sensors or planning art installation exhibitions while creating an online learning community. In this talk, we aim to present the doctoral program by emphasizing not only the overall project but specifically the pedagogic model and strategy adopted while providing examples of concrete teaching/learning scenarios implemented, including the doctoral retreats.N/

    Innovating in open distance teaching with face-to-face retreats within a Doctoral Program in Digital Media Art

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    Conferência realizada de 7-8 de março de 2022.The Portuguese Open University, together with the University of Algarve, both in Portugal, launched a doctoral program in digital media art taught by a hybrid approach, adopting open distance asynchronous teaching based on an e-learning platform along with face-to-face sessions (doctoral retreats) with the duration of one week at the final of each academic year. This program has been established in 2012 pioneering the innovation of applying asynchronous online teaching in practical and some labour intensive disciplines such are programming sensors or planning art installation exhibitions while creating an online learning community. In this article we aim at presenting the doctoral program by emphasizing not only the overall project but specifically the pedagogic model and strategy adopted while providing examples of concrete teaching/learning scenarios implemented including the doctoral retreats.We thank the Foundation for Science and Technology throughout CIAC – Research Centre for Arts and Communication for all the support given to the project (project UIDB/04019/2020); we also thank all the current and past students, teachers and supporting staff of the doctoral program in digital media art.info:eu-repo/semantics/publishedVersio

    First record of the genus Eumunida Smith, 1883 (Crustacea, Decapoda, Eumunididae) from the southwestern Atlantic, with the description of a new species

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    Eumunida picta Smith, 1883, was considered for over a century an amphi-Atlantic species and the only representative of the genus in the Atlantic Ocean, until being split into three species: E. picta sensu stricto (from the northwestern Atlantic), E. bella de Saint Laurent & MacPherson, 1990 and E. squamifera de Saint Laurent & MacPherson, 1990 (from the northeastern and southeastern Atlantic, respectively). Eumunida is now expanded to include a new species, E. notialis, from off the Brazilian coast. Hence, this is the first record of Eumunida and Eumunididae from the southwestern Atlantic. The new species differs from all its Atlantic counterparts in having (1) four hepatic spines; (2) two carapace inframarginal spines; (3) the distal end of the antennal acicle nearly reaching to the articulation between fourth and fifth antennal segments; and (4) the anterolateral spine of the second pleonal tergite obsolete

    Tunneling effects on impurity spectral function in coupled asymmetric quantum wires

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    The impurity spectral function is studied in coupled double quantum wires at finite temperatures. Simple anisotropy in the confinement direction of the wires leads to finite non-diagonal elements of the impurity spectral function matrix. These non-diagonal elements are responsible for tunneling effects and result in pronounced extra peak in the impurity spectral function up to temperatures as high as 20 K.Comment: Accepted in Phys. Rev.

    Editorial

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