48,214 research outputs found

    Some remarks on the attractor behaviour in ELKO cosmology

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    Recent results on the dynamical stability of a system involving the interaction of the ELKO spinor field with standard matter in the universe have been reanalysed, and the conclusion is that such system does not exhibit isolated stable points that could alleviate the cosmic coincidence problem. When a constant parameter δ\delta related to the potential of the ELKO field is introduced in the system however, stable fixed points are found for some specific types of interaction between the ELKO field and matter. Although the parameter δ\delta is related to an unknown potential, in order to satisfy the stability conditions and also that the fixed points are real, the range of the constant parameter δ\delta can be constrained for the present time and the coincidence problem can be alleviated for some specific interactions. Such restriction on the ELKO potential opens possibility to apply the ELKO field as a candidate to dark energy in the universe, and so explain the present phase of acceleration of the universe through the decay of the ELKO field into matter.Comment: 17 pages, section III with minor changes and section IV rewritten with a new analysi

    Análise da distribuição espacial dos recursos do Pronaf em Sergipe no período 2000-2006.

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    bitstream/CPATC/20046/1/f_03_2008.pd

    Modeling and simulation of a socioterritorial system: an exploratory analysis of the Southern Rural Territory of Sergipe, Brazil.

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    This work presents an application of the Soclab framework on the task of modeling and simulation of a socioterritorial system. The aim of this work was to identify the general social structure and relevant social power relations in the Southern Rural Territory of Sergipe, Brazil. The results show that this territory is stable, the social actors search for cooperative partnership, but presents unbalanced structure and inequalities among social actors according to the capacity of action and power

    Crozier & Luhmann: social theory as a support for a systemic socioterritorial modeling and simulation.

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    This paper shows how a socioterritorial system could be computationally modeled by means of two social theories, Sociology of Organized Action (SOA) and Social Systems (SS) to study power relations among social actors. It is concluded that both approaches helps the empirical research and that they complement each other, while SOA emphasizes the power relations, the SS focuses on the generative process of communication

    Impacto do aquecimento global na aptidão da laranjeira no Estado da Bahia.

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    O Brasil produziu aproximadamente 18,5 milhões de toneladas de frutos de laranjeira no ano de 2008, sendo que a Bahia contribuiu como segundo maior produtor brasileiro (6%), seguido pelos Estados de Sergipe (4%) e Minas Gerais (3%) e atrás apenas de São Paulo (78%) (IBGE, 2008). As produtividades médias obtidas na Bahia (17 t/ha) inferiores às alcançadas em São Paulo (24 t/ha) refletem tanto a aptidão das regiões onde estão situados os pomares no Estado, apresentando transição acentuada do clima úmido para o subúmido seco, bem como as deficiências nas práticas agrícolas e manejo agronômico da cultura (plantio de mudas de qualidade, espaçamentos adequados, diversificação de porta-enxertos, adubação, monitoramento e manejo fitossanitário, irrigação, dentre outros).O cultivo da laranjeira na Bahia é caracterizado por ser desenvolvimento predominantemente em condições de sequeiro, e o estresse por deficiência de água no solo é o maior limitador da expansão, sendo este o principal critério utilizadonos trabalhos de zoneamentos climático no Nordeste brasileiro. A distribuição irregular das chuvas interfere na qualidade e produtividade de frutos e esses riscos podem ser aumentados com as previsões futuras de ocorrência de eventos extremos (seca e enchentes) e maior restrição hídrica no solo, devido ao aumento da evapotranspiração das culturas, relacionadas ao aquecimento global (Assad & Pinho, 2008; Semenov, 2009).O presente trabalho teve o objetivo de avaliar os impactos do aquecimento global (aumento de temperatura) na aptidão da cultura da laranja no Estado da Bahia.pdf 236

    Caracterização da vegetação e uso da terra da bacia Quitéria em 2007.

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    O objetivo deste trabalho é identificar os principais tipos de uso da terra e vegetação natural da bacia Quitéria em 2007.SBSR 2013

    Experimental evidence of laser power oscillations induced by the relative Fresnel (Goos-Haenchen) phase

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    The amplification of the relative Fresnel (Goos-Haenchen) phase by an appropriate number of total internal reflections and the choice of favorable incidence angles allow to observe full oscillations in the power of a DPSS laser transmitted through sequential BK7 blocks. The experimental results confirm the theoretical predictions. The optical apparatus used in this letter can be seen as a new type of two-phase ellipsometric system where the phase of the complex refractive index is replaced by the relative Fresnel (Goos-Haenchen) phase.Comment: 7 pages, 3 figures, 1 tabl
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