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

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 $T_c$ {\em vs} transverse field $\Gamma$) we obtain shows a finite slope near $T=0$, 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 LiHo$_{0.167}$Y$_{0.833}$F$_4$, 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