Fermi-Frenet coordinates for space-like curves

We generalize Fermi coordinates, which correspond to an adapted set of coordinates describing the vicinity of an observer's worldline, to the worldsheet of an arbitrary spatial curve in a static spacetime. The spatial coordinate axes are fixed using a covariant Frenet triad so that the metric can be expressed using the curvature and torsion of the spatial curve. As an application of Fermi-Frenet coordinates, we show that they allow covariant inertial forces to be expressed in a simple and physically intuitive way.Comment: 7 page

Efeitos de herbicida sobre animais em pastejo.

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The Ecosystem Approach to Fisheries: Issues, Terminology, Principles, Institutional Foundations, Implementation and Outlook

Ecosystems are complex and dynamic natural units that produce goods and services beyond those of benefit to fisheries. Because fisheries have a direct impact on the ecosystem, which is also impacted by other human activities, they need to be managed in an ecosystem context. The meaning of the terms 'ecosystem management', 'ecosystem based management', 'ecosystem approach to fisheries'(EAF), etc., are still not universally defined and progressively evolving. The justification of EAF is evident in the characteristics of an exploited ecosystem and the impacts resulting from fisheries and other activities. The rich set of international agreements of relevance to EAF contains a large number of principles and conceptual objectives. Both provide a fundamental guidance and a significant challenge for the implementation of EAF. The available international instruments also provide the institutional foundations for EAF. The FAO Code of Conduct for Responsible Fisheries is particularly important in this respect and contains provisions for practically all aspects of the approach. One major difficulty in defining EAF lies precisely in turning the available concepts and principles into operational objectives from which an EAF management plan would more easily be developed. The paper discusses these together with the types of action needed to achieve them. Experience in EAF implementation is still limited but some issues are already apparent, e.g. in added complexity, insufficient capacity, slow implementation, need for a pragmatic approach, etc. It is argued, in conclusion, that the future of EAF and fisheries depends on the way in which the two fundamental concepts of fisheries management and ecosystem management, and their respective stakeholders, will join efforts or collide

Adaptive Optics Observations of the Galactic Center Young Stars

Adaptive Optics observations have dramatically improved the quality and versatility of high angular resolution measurements of the center of our Galaxy. In this paper, we quantify the quality of our Adaptive Optics observations and report on the astrometric precision for the young stellar population that appears to reside in a stellar disk structure in the central parsec. We show that with our improved astrometry and a 16 year baseline, including 10 years of speckle and 6 years of laser guide star AO imaging, we reliably detect accelerations in the plane of the sky as small as 70 microarcsec/yr/yr (~2.5 km/s/yr) and out to a projected radius from the supermassive black hole of 1.5" (~0.06 pc). With an increase in sensitivity to accelerations by a factor of ~6 over our previous efforts, we are able to directly probe the kinematic structure of the young stellar disk, which appears to have an inner radius of 0.8". We find that candidate disk members are on eccentric orbits, with a mean eccentricity of = 0.30 +/- 0.07. Such eccentricities cannot be explained by the relaxation of a circular disk with a normal initial mass function, which suggests the existence of a top-heavy IMF or formation in an initially eccentric disk.Comment: 7 pages, 4 figures, SPIE Astronomical Telescopes and Instrumentation 201

Germinacao de sementes de leguminosas forrageiras nativas submetidas a tratamentos para a quebra da impermeabilidade do tegumento.

Foi testado o efeito de escarificacao com lixa, do tratamento com acido sulfurico (98o) durante l, 5, 10, 15 e 20 minutos e com agua quente (80oC) durante l, 5,10, 15 e 20 minutos sobre a germinacao das sementes das seguintes leguminosas forrageiras nativas: Stylosanthes capitata, Canavalia obtusifolia, Dioclea lasiophylla, Cratylia floribunda, Calopogonium velutinum e Desmanthus virgatus. O delineamento foi de blocos ao acaso, com tres repeticoes, com 50 sementes por repeticao. Em todas as especies testadas a percentagem de germinacao da testemunha (sem escarificacao) foi muito baixa (0 a 8% aos sete dias e 8 a 16% aos 30 dias) com excecao da C. floribunda (56 e 100% aos 7 e 30 dias). A escarificacao com lixa foi eficiente para S.capitata, C. obtusifolia, C.floribunda e C. velutinum. Os tratamentos com acido sulfurico durante 10, 15 e 20 minutos foram eficazes para D. virgatus (90 a 98% e 94 a 100% de germinacao aos 7 e aos 30 dias) e, durante 5, 10 e 15 minutos foram eficazes para C. floribunda (82 a 92% aos sete dias). Os tratamentos com agua quente so foram eficientes para C. obtusifolia (64 a 90% de germinacao aos 7 e 62 a 100% aos 30 dias). S. capitata teve as mais baixas percentagens de germinacao, em todos os tratamentos, tanto aos 7 como aos 30 dias. C. velutium e D. lasiophylla tiveram germinacao relativamente baixa aos 7 dias, porem bastante aumentada entre o setimo e o trigesimo dia.bitstream/item/40919/1/Bolp50001.pd

Testing for periodicities in near-IR light curves of Sgr A

We present the results of near-infrared (2 μm) monitoring of Sgr A*-IR with 1 minute time sampling using laser guide star adaptive optics (LGS AO) system at the Keck II telescope. Sgr A*-IR was observed continuously for up to three hours on each of seven nights, between 2006 May and 2007 August. Sgr A*-IR is detected at all times and is continuously variable. These observations allow us to investigate Nyquist sampled periods ranging from about 2 minutes to an hour. Of particular interest are periods of ~20 min, which corresponds to a quasi-periodic (QPO) signal claimed based upon previous near-infrared observations and interpreted as the orbit of a ’hot spot’ at or near the last stable orbit of a spinning black hole. We investigate these claims by comparing periodograms of the light curves with models for red noise and find no significant deviations that would indicate QPO activity at any time scale probed in the study. We find that the variability of Sgr A* is consistent with a model based on correlated noise with a power spectrum having a frequency dependence of ~ f^(2.5), consistent with that observed in AGNs. Furthermore, the periodograms show power down to the minimum sampling time of 2 min, well below the period of the last stable orbit of a maximally spinning black hole, indicating that the Sgr A*-IR light curves observed in this study is unlikely to be from the Keplerian motion of a single ’hot spot’ of orbiting plasma

Estudos preliminares para a obtenção de híbridos intra e interespecíficos de açaizeiro.

Plantios de açaizeiro (Euterpe oleracea Mart.) precisam aumentar a produtividade e a qualidade dos frutos. A obtenção de híbridos intra e interespecíficos é uma nova estratégia a ser adotada com vista a complementar características desejáveis entre espécies do gênero Euterpe. Objetivou-se realizar a polinização controlada em espécies do gênero Euterpe para a obtenção de híbridos intra e interespecíficos. Inflorescências de cinco plantas mais produtivas de E. oleracea da cultivar BRS Pará foram identificadas, emasculadas, isoladas e polinizadas. Houve 100 % de fecundação, inclusive na autopolinização. Noventa dias após foi constatada a perda de 100% dos frutos recém formados em três cruzamentos. Os cruzamentos entre plantas da espécie E. oleracea apresentam alta fecundação com pouco registro de perdas completas de frutos recém formados. A ocorrência de autopolinização é viável nessa espécie.PIBIC-2011