1,353 research outputs found

    Management Of Fishing Of The Broadband Anchovy (anchoviella Lepidentostole) (fowler, 1911), In South SĂŁo Paulo State, Brazil.

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    The broadband anchovy (Anchoviella lepidentostole) is one of the most important fishery resources for economic and social development of Iguape City and for the whole of the south coast of SĂŁo Paulo state. Nowadays this activity involves over 2,500 fishermen. This paper aims to evaluate its fishing, and discuss how the activity is managed. In order to conduct this study, production data and catch per unit effort (CPUE) data from the 1998-2000 period have been collected, and the characterisation of the activity has also been done. A decline in broadband anchovy abundance had been observed in the region up until 2004, when a new regulation was implemented, in an attempt to recover the resource, with the establishment of closed season fishing (defeso) during the catch season, and adjustments in the employed fishing gear. The results have shown a recovery of the abundance of broadband anchovy throughout the 2005-2010 period, showing thus far that the measures taken for the maintenance of the resource have been successful. The activity has been managed through discussions involving people from the fishing sector in order to determine the controversial actions to be taken, that are hard to enforce. In order to achieve a more satisfactory resource management, it is necessary to keep the participatory process, with adaptive co-management, based on discussion among all the sectors involved (from government and society), and constant monitoring of the activity.73691-

    Nonlinear excitation of zonal flows by rossby wave turbulence

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    We apply the wave-kinetic approach to study nonlinearly coupled Rossby wave-zonal flow fluid turbulence in a two-dimensional rotating fluid. Specifically, we consider for the first time nonlinear excitations of zonal flows by a broad spectrum of Rossby wave turbulence. Short-wavelength Rossby waves are described here as a fluid of quasi-particles, and are referred to as the 'Rossbyons'. It is shown that Reynolds stresses of Rossbyons can generate large-scale zonal flows. The result should be useful in understanding the origin of large-scale planetary and near-Earth atmospheric circulations. It also provides an example of a turbulent wave background driving a coherent structure

    Amplification and generation of ultra-intense twisted laser pulses via stimulated Raman scattering

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    Twisted Laguerre-Gaussian lasers, with orbital angular momentum and characterised by doughnut shaped intensity profiles, provide a transformative set of tools and research directions in a growing range of fields and applications, from super-resolution microcopy and ultra-fast optical communications to quantum computing and astrophysics. The impact of twisted light is widening as recent numerical calculations provided solutions to long-standing challenges in plasma-based acceleration by allowing for high gradient positron acceleration. The production of ultrahigh intensity twisted laser pulses could then also have a broad influence on relativistic laser-matter interactions. Here we show theoretically and with ab-initio three-dimensional particle-in-cell simulations, that stimulated Raman backscattering can generate and amplify twisted lasers to Petawatt intensities in plasmas. This work may open new research directions in non-linear optics and high energy density science, compact plasma based accelerators and light sources.Comment: 18 pages, 4 figures, 1 tabl

    Hand Foot and Mouth Disease in Adults - A Case Report

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    A doença de mãos-pés-boca é uma infecção viral, mais frequentemente causada pelos vírus coxsackie A16 e enterovírus 71, que afecta preferencialmente crianças com idade inferior a 10 anos. Geralmente é uma doença benigna, caracterizada por febre e vesículas na boca e extremidades distais, mas também pode associar-se a complicaçÔes mais graves com meningoencefalite ou miocardite. Os autores reportam um caso de DMPB num adulto imunocompetente, com 27 anos de idade, que apresentava påpulas das mãos, pés e cavidade oral, algumas com progressão posterior para vesículas. A exuberùncia do quadro clínico e curso mais prolongado da doença também constituíram características pouco usuais

    Cutaneous Tuberculosis. A Case Report

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    Apesar de a tuberculose cutĂąnea (TBC) compreender apenas entre 0,1 a 4,4 por cento de todos os casos de tuberculose, Ă© importante para os clĂ­nicos considerarem esta infecção quando confrontados com uma lesĂŁo cutĂąnea de etiologia nĂŁo esclarecida. AlĂ©m do M. tuberculosis, tambĂ©m os bacilos M. bovis e Bacillus Calmette-Guerin (BCG) podem causar infecção da pele. A tuberculose cutĂąnea “verdadeira” pode ser adquirida por via exĂłgena (quando hĂĄ inoculação directa do bacilo na pele), ou endĂłgena, e apresenta um largo espectro de apresentaçÔes clĂ­nicas. Reportamos um caso de escrofuloderma (envolvimento da pele por contiguidade a partir de um outro foco de infecção), com linfadenite tuberculosa e envolvimento da clavĂ­cula, numa mulher imunocompetente

    Amplification and generation of ultra-intense twisted laser pulses via stimulated Raman scattering

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    Twisted Laguerre–Gaussian lasers, with orbital angular momentum and characterized by doughnut-shaped intensity profiles, provide a transformative set of tools and research directions in a growing range of fields and applications, from super-resolution microcopy and ultra-fast optical communications to quantum computing and astrophysics. The impact of twisted light is widening as recent numerical calculations provided solutions to long-standing challenges in plasma-based acceleration by allowing for high-gradient positron acceleration. The production of ultra-high-intensity twisted laser pulses could then also have a broad influence on relativistic laser–matter interactions. Here we show theoretically and with ab initio three-dimensional particle-in-cell simulations that stimulated Raman backscattering can generate and amplify twisted lasers to petawatt intensities in plasmas. This work may open new research directions in nonlinear optics and high–energy-density science, compact plasma-based accelerators and light sources

    Photon-graviton pair conversion

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    We consider the conversion of gravitons and photons as a four-wave mixing process. A nonlinear coupled systems of equations involving two gravitons and two photons is obtained, and the energy exchange between the different degrees of freedom is found. The scattering amplitudes are obtained, from which a crossection for incoherent processes can be found. An analytical example is given, and applications to the early Universe are discussed.Comment: 5 pages, slightly modified as compared to v1, to appear in Class. Quantum Grav. as a Letter to the Edito

    High orbital angular momentum harmonic generation

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    We identify and explore a high orbital angular momentum (OAM) harmonics generation and amplification mechanism that manipulates the OAM independently of any other laser property, by preserving the initial laser wavelength, through stimulated Raman backscattering in a plasma. The high OAM harmonics spectra can extend at least up to the limiting value imposed by the paraxial approximation. We show with theory and particle-in-cell simulations that the orders of the OAM harmonics can be tuned according to a selection rule that depends on the initial OAM of the interacting waves. We illustrate the high OAM harmonics generation in a plasma using several examples including the generation of prime OAM harmonics. The process can also be realized in any nonlinear optical Kerr media supporting three-wave interactions

    High orbital angular momentum harmonic generation

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    We identify and explore a high orbital angular momentum (OAM) harmonics generation and amplification mechanism that manipulates the OAM independently of any other laser property, by preserving the initial laser wavelength, through stimulated Raman backscattering in a plasma. The high OAM harmonics spectra can extend at least up to the limiting value imposed by the paraxial approximation. We show with theory and particle-in-cell simulations that the orders of the OAM harmonics can be tuned according to a selection rule that depends on the initial OAM of the interacting waves. We illustrate the high OAM harmonics generation in a plasma using several examples including the generation of prime OAM harmonics. The process can also be realized in any nonlinear optical Kerr media supporting three-wave interactions.info:eu-repo/semantics/publishedVersio
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