Crescimento da bananeira cv. Prata Anã sob diferentes regimes de irrigação com déficit.

A escassez dos recursos hídricos obriga cada vez mais o uso eficiente do recurso água, isto é, incrementar a produção por unidade de água consumida. Sendo assim, o objetivo desse trabalho foi avaliar o crescimento vegetativo e as variáveis de produção da cultivar Prata Anã submetida a déficit hídrico em diferentes fases fenológicas. O presente trabalho foi conduzido nos campos experimentais da Embrapa Mandioca e Fruticultura, no município de Cruz das Almas ? BA (12º48?S; 39º06?W; 225 metros)

Deteccao de doencas na cultura do pimentao no submedio do Vale Sao Francisco-1998 a 2000.

A deteccao de doencas em 172 amostras de pimentao, provenientes de areas do Submedio do Vale do Sao Francisco, foi realizada no Laboratorio de Fitopatologia da Embrapa Semi-Arido, Petrolina, PE, no periodo de 1998 a 2000. Em 162 (94,2% ) amostras foram detectados fungos, bacterias e virus e em 7 (4,07%) amostras foram verificados danos causados por insetos, deficiencia nutricional e danos causados por herbicidas. Em 3 (1,7%) amostras, as causas dos sintomas nao foram identificadas. Infeccoes causadas por bacterias e por fungos foram detectadas em 32 (18,6%) e 27 ( 15,7% ) amostras, respectivamente. Cinco genero de fungos -Leveil,ula 9 ( 15,2% ), Cercospora 7 (11,8%), Colletotrichum 6 (10,2%), Rhizoctonia 4 (6,8%) e Sclerotium 1 ( l'7% ) -e tres de bacteria -Xanthomonas 26 ( 44, 1% ), Erwinia 3 ( 5, 1% ) e Ralstonia 3 (5,1%) -foram identificados nas amostras analisadas. A especie de tospovirus Groundnut ringspot virus foi detectada em 103 amostras.Suplemento. Edição do 41 Congresso Brasileiro de Olericultura; 1 Encontro sobre Plantas Medicinais, Aromáticas e Condimentares, Brasília, DF, jul. 2001

Cosmological constant constraints from observation-derived energy condition bounds and their application to bimetric massive gravity

Among the various possibilities to probe the theory behind the recent accelerated expansion of the universe, the energy conditions (ECs) are of particular interest, since it is possible to confront and constrain the many models, including different theories of gravity, with observational data. In this context, we use the ECs to probe any alternative theory whose extra term acts as a cosmological constant. For this purpose, we apply a model-independent approach to reconstruct the recent expansion of the universe. Using Type Ia supernova, baryon acoustic oscillations and cosmic-chronometer data, we perform a Markov Chain Monte Carlo analysis to put constraints on the effective cosmological constant $\Omega^0_{\rm eff}$. By imposing that the cosmological constant is the only component that possibly violates the ECs, we derive lower and upper bounds for its value. For instance, we obtain that $0.59 < \Omega^0_{\rm eff} < 0.91$ and $0.40 < \Omega^0_{\rm eff} < 0.93$ within, respectively, $1\sigma$ and $3\sigma$ confidence levels. In addition, about 30\% of the posterior distribution is incompatible with a cosmological constant, showing that this method can potentially rule it out as a mechanism for the accelerated expansion. We also study the consequence of these constraints for two particular formulations of the bimetric massive gravity. Namely, we consider the Visser's theory and the Hassan and Roses's massive gravity by choosing a background metric such that both theories mimic General Relativity with a cosmological constant. Using the $\Omega^0_{\rm eff}$ observational bounds along with the upper bounds on the graviton mass we obtain constraints on the parameter spaces of both theories.Comment: 11 pages, 4 figures, 1 tabl

D3 instantons in Calabi-Yau orientifolds with(out) fluxes

We investigate the instanton effect due to D3 branes wrapping a four-cycle in a Calabi-Yau orientifold with D7 branes. We study the condition for the nonzero superpotentials from the D3 instantons. For that matter we work out the zero mode structures of D3 branes wrapping a four-cycle both in the presence of the fluxes and in the absence of the fluxes. In the presence of the fluxes, the condition for the nonzero superpotential could be different from that without the fluxes. We explicitly work out a simple example of the orientifold of $K3 \times T^2/Z_2$ with a suitable flux to show such behavior. The effects of D3-D7 sectors are interesting and give further constraints for the nonzero superpotential. In a special configuration where D3 branes and D7 branes wrap the same four-cycle, multi-instanton calculus of D3 branes could be reduced to that of a suitable field theory. The structure of D5 instantons in Type I theory is briefly discussed.Comment: 17 pages; Typos corrected, arguments improved and references adde

Germinação de sementes de dendê (Elaeis guineensis, Jacq.), utilizando o método de calor seco.

Informações sobre a germinacao de sementes de dende pelo método de calor seco, envolvendo desde o tratamento das sementes até a recomendação de armazenamento.bitstream/CPAA-2009-09/2728/1/IT_12_98.pd

Constraints on Cold Dark Matter Accelerating Cosmologies and Cluster Formation

We discuss the properties of homogeneous and isotropic flat cosmologies in which the present accelerating stage is powered only by the gravitationally induced creation of cold dark matter (CCDM) particles ($\Omega_{m}=1$). For some matter creation rates proposed in the literature, we show that the main cosmological functions such as the scale factor of the universe, the Hubble expansion rate, the growth factor and the cluster formation rate are analytically defined. The best CCDM scenario has only one free parameter and our joint analysis involving BAO + CMB + SNe Ia data yields ${\tilde{\Omega}}_{m}= 0.28\pm 0.01$ ($1\sigma$) where $\tilde{{\Omega}}_{m}$ is the observed matter density parameter. In particular, this implies that the model has no dark energy but the part of the matter that is effectively clustering is in good agreement with the latest determinations from large scale structure. The growth of perturbation and the formation of galaxy clusters in such scenarios are also investigated. Despite the fact that both scenarios may share the same Hubble expansion, we find that matter creation cosmologies predict stronger small scale dynamics which implies a faster growth rate of perturbations with respect to the usual $\Lambda$CDM cosmology. Such results point to the possibility of a crucial observational test confronting CCDM with $\Lambda$CDM scenarios trough a more detailed analysis involving CMB, weak lensing, as well as the large scale structure.Comment: 12 pages, 3 figures, Accepted for publication by Physical Rev.

New Cosmic Accelerating Scenario without Dark Energy

We propose an alternative, nonsingular, cosmic scenario based on gravitationally induced particle production. The model is an attempt to evade the coincidence and cosmological constant problems of the standard model ($\Lambda$CDM) and also to connect the early and late time accelerating stages of the Universe. Our space-time emerges from a pure initial de Sitter stage thereby providing a natural solution to the horizon problem. Subsequently, due to an instability provoked by the production of massless particles, the Universe evolves smoothly to the standard radiation dominated era thereby ending the production of radiation as required by the conformal invariance. Next, the radiation becomes sub-dominant with the Universe entering in the cold dark matter dominated era. Finally, the negative pressure associated with the creation of cold dark matter (CCDM model) particles accelerates the expansion and drives the Universe to a final de Sitter stage. The late time cosmic expansion history of the CCDM model is exactly like in the standard $\Lambda$CDM model, however, there is no dark energy. This complete scenario is fully determined by two extreme energy densities, or equivalently, the associated de Sitter Hubble scales connected by $\rho_I/\rho_f=(H_I/H_f)^{2} \sim 10^{122}$, a result that has no correlation with the cosmological constant problem. We also study the linear growth of matter perturbations at the final accelerating stage. It is found that the CCDM growth index can be written as a function of the $\Lambda$ growth index, $\gamma_{\Lambda} \simeq 6/11$. In this framework, we also compare the observed growth rate of clustering with that predicted by the current CCDM model. Performing a $\chi^{2}$ statistical test we show that the CCDM model provides growth rates that match sufficiently well with the observed growth rate of structure.Comment: 12 pages, 3 figures, accepted for publication by Phys. Rev. D. (final version, some references have corrected). arXiv admin note: substantial text overlap with arXiv:1106.193

Particle creation due to tachyonic instability in relativistic stars

Dense enough compact objects were recently shown to lead to an exponentially fast increase of the vacuum energy density for some free scalar fields properly coupled to the spacetime curvature as a consequence of a tachyonic-like instability. Once the effect is triggered, the star energy density would be overwhelmed by the vacuum energy density in a few milliseconds. This demands that eventually geometry and field evolve to a new configuration to bring the vacuum back to a stationary regime. Here, we show that the vacuum fluctuations built up during the unstable epoch lead to particle creation in the final stationary state when the tachyonic instability ceases. The amount of created particles depends mostly on the duration of the unstable epoch and final stationary configuration, which are open issues at this point. We emphasize that the particle creation coming from the tachyonic instability will occur even in the adiabatic limit, where the spacetime geometry changes arbitrarily slowly, and therefore is quite distinct from the usual particle creation due to the change in the background geometry.Comment: 12 pages, 2 figures, discussion improved: paragraph added at the end of Sec. V B (published version

Dispersão do material de solo em água para avaliação indireta da erodibilidade de Latossolos.

Os teores de silte e areia muito fina, obtidos da análise granulométrica com dispersão total (NaOH), estão entre os principais parâmetros responsáveis pela erodibilidade dos solos. Sendo os latossolos, por via de regra, pobres em sílte, os índices de erodibilidade, que consideram tais parâmetros relevantes, apresentam para os mesmos acentuada resistência à erosão. Entretanto, quando a dispersão do material de solo é realizada somente em água, os agregados, de elevada estabilidade nesses solos, podem permanecer no tamanho das frações sllte e areia muito fina, permitindo dúvidas sobre a aplicabilidade dos resultados de granulometria com dispersão total na predição do seu comportamento diante da erosão. Neste trabalho, avaliou-se a influência dos teores de partículas e/ou agregados menores de O,lmm (argila, silte e areia muito fina) dispersos em água nos índices de erodibilidade, em amostras de latossolo vermelho-escuro e vermelho-amarelo, coletadas nas profundidades de 0-20 e 60-8Ocm. O emprego das frações granulométricas dispersas em água conduziu a valores mais elevados para a erodibilidade, comparados àqueles obtidos de maneira convencional, notadamente na camada do solo relativa ao horizonte B (60-8Ocm),cujas unidades estruturais são menores e mais estáveis. O latossolo vermelho-escuro, de maneira geral, mostrou-se mais resistente à erosão do que o vermelho-amarelo