Brownian motion of a charged particle driven internally by correlated noise

We give an exact solution to the generalized Langevin equation of motion of a charged Brownian particle in a uniform magnetic field that is driven internally by an exponentially-correlated stochastic force. A strong dissipation regime is described in which the ensemble-averaged fluctuations of the velocity exhibit transient oscillations that arise from memory effects. Also, we calculate generalized diffusion coefficients describing the transport of these particles and briefly discuss how they are affected by the magnetic field strength and correlation time. Our asymptotic results are extended to the general case of internal driving by correlated Gaussian stochastic forces with finite autocorrelation times.Comment: 10 pages, 4 figures with subfigures, RevTeX, v2: revise

An exact analytical solution for generalized growth models driven by a Markovian dichotomic noise

Logistic growth models are recurrent in biology, epidemiology, market models, and neural and social networks. They find important applications in many other fields including laser modelling. In numerous realistic cases the growth rate undergoes stochastic fluctuations and we consider a growth model with a stochastic growth rate modelled via an asymmetric Markovian dichotomic noise. We find an exact analytical solution for the probability distribution providing a powerful tool with applications ranging from biology to astrophysics and laser physics

Solos e aptidão edafoclimática para a cultura do cajueiro no Município de Grajaú-MA.

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Correção do solo para cultivo do cajueiro no cerrado piauiense.

Caracteristicas dos solos cultivados com cajueiro no Piaui; Correcao do solo; Recomendacoesbitstream/CNPAT-2010/8606/1/Dc-081.pd

Caracterização e interpretação para uso agrícola dos principais solos da microregião Bico do Papagaio-Tocantins.

A microrregião Bico do Papagaio, localizada no norte do Estado do Tocantins, apresenta deficiencia, principalmente, de solos, em funcao das suas caracteristicas fisicas e quimicas. A area territorial da microrregiao e de 15.722km2, correpondendo a 5,67% do Estado. Os principais produtos agricolas sao o feijao e o milho, geralmente plantados em consorcio nos solos de melhor fertilidade. Mais recentemente nos municipios localizados nesta microrregiao esta sendo cultivado o cajueiro, com grande possibilidade de sucesso do empreendimento. Nesse contexto esse trabalho tem os seguintes objetivos: - Caracterizar quimica e fisicamente os principais solos da microrregiaoBico do Papagaio. - Identificar o potencial de uso dos principais solos e de praticas de manejo adequadas, particulamente, em propriedades de pequenos agricultores.bitstream/item/40453/1/Dc-032.pd

Rural-urban migration in d-dimensional lattices

The rural-urban migration phenomenon is analyzed by using an agent-based computational model. Agents are placed on lattices which dimensions varying from d=2 up to d=7. The localization of the agents in the lattice define their social neighborhood (rural or urban) not being related to their spatial distribution. The effect of the dimension of lattice is studied by analyzing the variation of the main parameters that characterizes the migratory process. The dynamics displays strong effects even for around one million of sites, in higher dimensions (d=6, 7).Comment: 9 pages, 7 figures, to be published in International Journal of Modern Physics C 1

“An ethnographic seduction”: how qualitative research and Agent-based models can benefit each other

We provide a general analytical framework for empirically informed agent-based simulations. This methodology provides present-day agent-based models with a sound and proper insight as to the behavior of social agents — an insight that statistical data often fall short of providing at least at a micro level and for hidden and sensitive populations. In the other direction, simulations can provide qualitative researchers in sociology, anthropology and other fields with valuable tools for: (a) testing the consistency and pushing the boundaries, of specific theoretical frameworks; (b) replicating and generalizing results; (c) providing a platform for cross-disciplinary validation of results

Fertilidade dos solos cultivados com cajueiro no Maranhão.

O presente trabalho avalia os resultados do levantamento das caracteristicas quimicas dos solos cultivados com cajueiro no Estado do Maranhao. O estudo envolve 382 amostras das cinco regioes ecologicas. Os resultados das analises foram colocados em tabelas por municipio em respectivas regioes ecologicas, distribuidas em termos percentuais de amostras nos intervalos pre-estabelecidos para cada parametro analisado. Apos dois anos de estudo, foram observados baixos teores de nutrientes e alta acidez, tendo 80% das amostras apresentado pH entre 4,3 e 5,5. Teores de calcio + magnesio, fosforo e potassio, considerados inadequados em 80%, 90% e 100%, respectivamente, das amostras coletadas. Os resultados obtidos chamaram atencao para a necessidade de correcao dos teores de nutrientes disponiveis e melhoria das condicoes dos solos, no sentido de se obter, a curto prazo, melhores producoes e qualidade de frutos.bitstream/CNPAT-2010/5488/1/Bp-036.pd

O aluminio em solos cultivados com cajueiro (anacardium occidentale L.) no Piauí.

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