466 research outputs found

    Cusp plasma intrusion and Pc 5

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    第2回極域科学シンポジウム/第35回極域宙空圏シンポジウム 11月16日(水) 統計数理研究所 3階リフレッシュフロ

    A case study of a radially polarized Pc4 event observed by the Equator-S satellite

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    International audienceA 16 mHz Pc4 pulsation was recorded on March 17, 1998, in the prenoon sector of the Earth's magnetosphere by the Equator-S satellite. The event is strongly localized in radial direction at approximately L = 5 and exhibits properties of a field line resonance such as an ellipticity change as seen by applying the method of the analytical signal to the magnetic field data. The azimuthal wave number was estimated as m \approx 150. We discuss whether this event can be explained by the FLR mechanism and find out that the change in ellipticity is more a general feature of a localized Alfvén wave than indicative of a resonant process

    Observation of a New Type of Low Frequency Waves at Comet 67P/Churyumov-Gerasimenko

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    We report on magnetic field measurements made in the innermost coma of 67P/Churyumov-Gerasimenko in its low activity state. Quasi-coherent, large-amplitude (δB/B1\delta B/B \sim 1), compressional magnetic field oscillations at \sim 40 mHz dominate the immediate plasma environment of the nucleus. This differs from previously studied comet-interaction regions where waves at the cometary ion gyro-frequencies are the main feature. Thus classical pick-up ion driven instabilities are unable to explain the observations. We propose a cross-field current instability associated with newborn cometary ion currents as a possible source mechanism.Comment: 6 pages, 3 Figure

    Utilização do custo-meta por empresas brasileiras como estratégia de gestão: alguns estudos setoriais utilizando o método da causalidade de Granger

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    This article aims to develop, based on the Granger-causality test, a research technique to assess, in business sectors and as an alternative for case studies, the price strategies adopted by Brazilian companies. It focuses on the differentiation between those companies which use target costing as a strategy from those using the cost plus margin, or yet, from companies without a clear strategy for establishing prices and costs. Forty-seven companies from eight different segments were analyzed through Granger causality. In most cases, the results revealed a lack of strategy in terms of company price and cost management. Target costing was only predominant in the electric power distribution sector. The research results suggest possibilities for future studies.Este artigo tem como objetivo básico desenvolver, com apoio no teste de causalidade de Granger, uma técnica de pesquisa que possa avaliar, no agregado de empresas e como uma alternativa ao estudo de caso, as estratégias de preços adotadas por empresas brasileiras. Em especial, busca-se distinguir aquelas empresas que adotam o custometa como estratégia, em relação àquelas empresas que adotam o custo mais margem ou, ainda, daquelas que não apresentam uma estratégia clara de preços e custos. Quarenta e sete empresas, de oito setores distintos, foram analisadas mediante a utilização do método de causalidade de Granger. Os resultados evidenciaram a falta de estratégia com relação à gestão de preços e custos das empresas, na maioria dos casos. Em particular, a hipótese da estratégia de custo-meta predominou somente no setor de distribuição de energia elétrica. Os resultados apresentados são suscetíveis a várias contribuições e podem servir como uma agenda para futuras pesquisas

    Report of the ICES\NAFO Joint Working Group on Deep-water Ecology (WGDEC), 11–15 March 2013, Floedevigen, Norway.

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    On 11 February 2013, the joint ICES/NAFO WGDEC, chaired by Francis Neat (UK) and attended by ten members met at the Institute for Marine Research in Floedevi-gen, Norway to consider the terms of reference (ToR) listed in Section 2. WGDEC was requested to update all records of deep-water vulnerable marine eco-systems (VMEs) in the North Atlantic. New data from a range of sources including multibeam echosounder surveys, fisheries surveys, habitat modelling and seabed imagery surveys was provided. For several areas across the North Atlantic, WGDEC makes recommendations for areas to be closed to bottom fisheries for the purposes of conservation of VMEs

    The role of marine reserves in achieving sustainable fisheries (One contribution of 15 to a Theme Issue 'Fisheries: a Future?')

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    Many fishery management tools currently in use have conservation value. They are designed to maintain stocks of commercially important species above target levels. However, their limitations are evident from continuing declines in fish stocks throughout the world. We make the case that to reverse fishery declines, safeguard marine life and sustain ecosystem processes, extensive marine reserves that are off limits to fishing must become part of the management strategy. Marine reserves should be incorporated into modern fishery management because they can achieve many things that conventional tools cannot. Only complete and permanent protection from fishing can protect the most sensitive habitats and vulnerable species. Only reserves will allow the development of natural, extended age structures of target species, maintain their genetic variability and prevent deleterious evolutionary change from the effects of fishing. Species with natural age structures will sustain higher rates of reproduction and will be more resilient to environmental variability. Higher stock levels maintained by reserves will provide insurance against management failure, including risk-prone quota setting, provided the broader conservation role of reserves is firmly established and legislatively protected. Fishery management measures outside protected areas are necessary to complement the protection offered by marine reserves, but cannot substitute for it

    Drawing lines at the sand: evidence for functional vs. visual reef boundaries in temperate Marine Protected Areas.

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    Marine Protected Areas (MPAs) can either protect all seabed habitats within them or discrete features. If discrete features within the MPA are to be protected humans have to know where the boundaries are. In Lyme Bay, SW England a MPA excluded towed demersal fishing gear from 206 km(2) to protect rocky reef habitats and the associated species. The site comprised a mosaic of sedimentary and reef habitats and so 'non reef' habitat also benefited from the MPA. Following 3 years protection, video data showed that sessile Reef Associated Species (RAS) had colonised sedimentary habitat indicating that 'reef' was present. This suggested that the functional extent of the reef was potentially greater than its visual boundary. Feature based MPA management may not adequately protect targeted features, whereas site based management allows for shifting baselines and will be more effective at delivering ecosystem goods and services
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