Anomalous dynamics in two- and three- dimensional Heisenberg-Mattis spin glasses

We investigate the spectral and localization properties of unmagnetized Heisenberg-Mattis spin glasses, in space dimensionalities $d=2$ and 3, at T=0. We use numerical transfer-matrix methods combined with finite-size scaling to calculate Lyapunov exponents, and eigenvalue-counting theorems, coupled with Gaussian elimination algorithms, to evaluate densities of states. In $d=2$ we find that all states are localized, with the localization length diverging as $\omega^{-1}$, as energy $\omega \to 0$. Logarithmic corrections to density of states behave in accordance with theoretical predictions. In $d=3$ the density-of-states dependence on energy is the same as for spin waves in pure antiferromagnets, again in agreement with theoretical predictions, though the corresponding amplitudes differ.Comment: RevTeX4, 9 pages, 9 .eps figure

Psylloidea na fazenda da Brigada Militar, Passo Fundo, Rio Grande do Sul.

Editores técnicos: Joseani Mesquita Antunes, Ana Lídia Variani Bonato, Márcia Barrocas Moreira Pimentel

Dispersão de Leptocybe invasa no Brasil.

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Ocorrência de psilídeos em plantios florestais experimentais e na vegetação nativa na Embrapa Amazônia Ocidental, Manaus/AM.

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New Insights for Benefit of Legume Inclusion in Grazing Systems

The benefits and challenges of legume inclusion in grazing systems have been well documented over time and across different regions. Recent investigations have provided novel insights into the benefits of legume inclusion in grazing systems. Our objective is not to provide a wide overview of the benefits of legume inclusion but to explore novel insights of recent advancements made from studies evaluating legume inclusion in grazing systems. Efficiency of resource use through legume inclusion in grazing systems can reduce the water footprint associated with beef production through improvements in forage nutritive value and animal performance. These efficiencies also translate into improvements in nutrient cycling and nutrient transfer, which are critical for sustaining productivity of grazing systems. Moreover, evidence exists highlighting the importance of root contact between grasses and legumes for sharing N. Provisioning of floral resources from legumes has also been shown to be important for providing habitat for pollinator species. Lastly, soil microbial abundance of microorganisms associated with N2 fixation can be altered according to species present within a pasture, especially when legumes are present. Insights derived from such recent studies continue to provide evidence for the need to continue to develop legume-based grazing agroecosystems

Efeito do silício no aumento da resistência do Eucalyptus camaldulensis ao ácaro Oligonychus punicae (Acari: Tetranychidae)

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Brachiaria plantaginea (Link) Hitchc. as a potential (new) source of shikimic acid. Quantification by NIR and PLS regression.

Shikimic acid is a natural compound, precursor of the antiviral Oseltamivir used against influenza A. It is a scarce and expensive chemical, obtained mainly from seeds of shrubs natives in China and Japan. In this study we propose a fast and clean procedure for the quantification of shikimic acid in B. plantaginea, an alternative source of shikimic acid, using NIR spectroscopy combined with PLS regression

Weed Management Affects Pasture Productivity and Animal Performance

Weed can be defined as any plant growing in undesirable locations. Weeds are considered one of the main challenges in agricultural fields. Weeds affect pasture productivity mainly because of the competition for limited resources such as nutrients, water, and light with forage plants. Weeds encroach pastures spontaneously and spread quickly through the farm and neighboring areas, making their control difficult. In addition, weeds can affect forage nutritive value, grazing behaviour, voluntary forage intake, animal health, and consequently animal performance. The low efficiency of mechanical weeding and the global concern about indiscriminate use of herbicides impose challenges for producers in grazing systems. These factors justify the importance of proper weed management to minimize financial losses and environmental impacts and drive the research effort in this area. Currently, some strategies including grazing management, grass and legumes integration, and site-specific weed spraying have demonstrated potential to improve the efficiency of weed supression and increase the productivity and profitability of livestock systems. This review aims to discuss about the main effects of weed encroachment in grasslands regarding pasture productivity and animal performance, as well as emphasize potential strategies for weed management