12,735 research outputs found
Immunization and Aging: a Learning Process in the Immune Network
The immune system can be thought as a complex network of different
interacting elements. A cellular automaton, defined in shape-space, was
recently shown to exhibit self-regulation and complex behavior and is,
therefore, a good candidate to model the immune system. Using this model to
simulate a real immune system we find good agreement with recent experiments on
mice. The model exhibits the experimentally observed refractory behavior of the
immune system under multiple antigen presentations as well as loss of its
plasticity caused by aging.Comment: 4 latex pages, 3 postscript figures attached. To be published in
Physical Review Letters (Tentatively scheduled for 5th Oct. issue
Comportamento de híbridos de milho nos Tabuleiros Costeiros e Agreste Estados de Sergipe e Alagoas no ano agrícola de 2003.
Gaussian phase-space representations for fermions
We introduce a positive phase-space representation for fermions, using the
most general possible multi-mode Gaussian operator basis. The representation
generalizes previous bosonic quantum phase-space methods to Fermi systems. We
derive equivalences between quantum and stochastic moments, as well as operator
correspondences that map quantum operator evolution onto stochastic processes
in phase space. The representation thus enables first-principles quantum
dynamical or equilibrium calculations in many-body Fermi systems. Potential
applications are to strongly interacting and correlated Fermi gases, including
coherent behaviour in open systems and nanostructures described by master
equations. Examples of an ideal gas and the Hubbard model are given, as well as
a generic open system, in order to illustrate these ideas.Comment: More references and examples. Much less mathematical materia
Efeito da irrigação no estabelecimento de plântulas de Manduvi transplantadas Em pastagens cultivadas.
O esforço para a conservação da arara-azul no Pantanal deve enfocar a manutenção de populações viáveis de Manduvi. Caso seja diagnosticado que o recrutamento populacional de Manduvi desta árvore no Pantanal é insatisfatório para a reposição de adultos, torna-se urgente o desenvolvimento de um programa de manejo e conservação de populações de Manduvi. Neste sentido, este trabalho investigou o estabelecimento de plântulas de Manduvi, com 60 dias de semeadura, transplantadas em pastagens cultivadas, que substituíram a vegetação original na área da fazenda Nhumirim. The effort to conserve hyacinth macaws in the Pantanal should focus on the maintenance of viable populations of Manduvi. If it is diagnosed that the recruitment of this tree population in the Pantanal is unsatisfactory for the replacement of adults, it becomes urgent to develop a program management and conservation of populations of Manduvi. Thus, this study investigated the establishment of seedlings of Manduvi, with 60 days of sowing, transplanting in cultivated pastures, which replaced the original vegetation in the area of the Nhumirim Farm
Identificacao de fontes de resistencia a xanthomonas vignicola, agente causal da mancha bacteriana do Caupi.
Abstract; Introducao; Material e Metodos; Resultados e Discussao; Conclusoes.bitstream/CNPAT-2010/6362/1/Bp-028.pd
Reação de genótipos de feijão-de-corda ao ataque da cigarrinha-verde, no Estado do Ceará.
Abstract; Introducao; Material e metodos; Resultados e discussao; Conclusoes.bitstream/CNPAT-2010/6363/1/Bp-030.pd
Avaliação de sobrevivência e desempenho de "SEEDLINGS" de Umbuzeiro ( Spondias tuberosa ) após dois períodos de incubação de substrato contendo farelo de mamona.
O umbuzeiro (Spondias tuberosa Arruda Câmara) é uma frutífera nativa da região Nordeste do Brasil, representando fonte de emprego e renda no período da safra, para as populações na área de ocorrência natural das plantas. Estudos indicam que o uso racional de farelo de mamona poderá disponibilizar às plantas quantidades suficiente de nutrientes, dispensando o uso complementar de fertilizante mineral, em especial os nitrogenados
Ising Spin Glass in a Transverse Magnetic Field
We study the three-dimensional quantum Ising spin glass in a transverse
magnetic field following the evolution of the bond probability distribution
under Renormalisation Group transformations. The phase diagram (critical
temperature {\em vs} transverse field ) we obtain shows a finite
slope near , in contrast with the infinite slope for the pure case. Our
results compare very well with the experimental data recently obtained for the
dipolar Ising spin glass LiHoYF, in a transverse field.
This indicates that this system is more apropriately described by a model with
short range interactions than by an equivalent Sherrington-Kirkpatrick model in
a transverse field.Comment: 7 pages, RevTeX3, Nota Cientifica PUC-Rio 23/9
Estabilidade de cultivares de milho nos Estados de Sergipe e Alagoas no ano agrícola de 2003.
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