15,709 research outputs found
Chandrasekhar's Dynamical Friction and non-extensive statistics
The motion of a point like object of mass passing through the background
potential of massive collisionless particles () suffers a steady
deceleration named dynamical friction. In his classical work, Chandrasekhar
assumed a Maxwellian velocity distribution in the halo and neglected the self
gravity of the wake induced by the gravitational focusing of the mass . In
this paper, by relaxing the validity of the Maxwellian distribution due to the
presence of long range forces, we derive an analytical formula for the
dynamical friction in the context of the -nonextensive kinetic theory. In
the extensive limiting case (), the classical Gaussian Chandrasekhar
result is recovered. As an application, the dynamical friction timescale for
Globular Clusters spiraling to the galactic center is explicitly obtained. Our
results suggest that the problem concerning the large timescale as derived by
numerical -body simulations or semi-analytical models can be understood as a
departure from the standard extensive Maxwellian regime as measured by the
Tsallis nonextensive -parameter.Comment: 16pp 5 figs, revised and extended version of arXiv:1202.1873 .
Accepted for publication by JCA
Progesterone profiles through the postpartum period in milk buffaloes under poor management conditions.
Levantamento da diversidade de vĂrus em batata-doce do banco ativo de germoplasma da Embrapa Hortaliças.
O presente trabalho teve o objetivo de ralizar um levantamento de vĂrus no Banco Ativo de Germoplasma de batata-doce da Embrapa Hortaliças
Caracterização fĂsico-quĂmica dos frutos dos clones de cajazeira Capuan e Lagoa Redonda submetidos Ă poda.
Levantamento da diversidade de vĂrus em batata-doce no campo experimental da Embrapa Hortaliças
O presente trabalho teve o objetivo de realizar um levantamento de vĂrus no Campo Experimental de Batata-doce para a análise que consistiu inicialmente na enxertia na planta indicadora Ipomoea stosa e posterior detecção viral pela tĂ©cnica NCM-Elisa para dez virus que infectam a batata-doce: Sweet potato feathery mottle virus (SPMMV), Sweet potato virus G (SPVG), Sweet potato C-6.Resumo expandido
Variabilidade patogĂŞnica entre isolados de phaeoisariopsis griseola.
O feijoeiro comum (Phaeolus vulgaris L.) é hospedeiro de vários patógenos. Entre os patógenos que afetam esta cultura destaca-se o fungo Phaeoisariopsis griseola (Sacc.) Ferraris, agente causal da mancha angular. Esta doença pode proporcionar perdas de até 80% na produção..
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