Estimativa do saldo de radiação sobre um cultivo de videira BRS Clara com e sem tela de sombreamento.

O objetivo deste trabalho foi elaborar modelos de estimativa do saldo de radiação sobre videiras cultivadas na região noroeste de São Paulo a partir da radiação solar global.Resumo

Use of advisory systems and plastic covering in the control of downy mildew on vines of São Paulo, Brazil.

The Northwest region of the State of São Paulo is one of the main producers of table grapes in Brazil. However, the climate of this region is highly favorable for fungal diseases during the growing season. The use of disease advisory systems and plastic covers are promising alternatives for rationalize the use of fungicides for disease control. Thus, the objective of this study was to evaluate the efficacy of the combination of advisory systems and plastic covering in the control of downy mildew (Plasmopara viticola) on vineyards of the Northwest region of State of São Paulo, Brazil. The experiments were carried out at the EMBRAPA - Tropical Viticulture Experimental Station, located in Jales, SP, Brazil. Three rows of 120 m of the seedless grape cultivar ?BRS Morena? (Vitis vinifera), spaced with 3.0 m between plants were conducted during 2012 and 2013 growing seasons. Half of the vineyard was covered with braided polypropylene plastic film installed over a metallic arc-shaped structure and the other half with black screen, with 18% of shading. The experimental design was randomized blocks composed of five treatments, with six repetitions per covered environment. The treatments were defined by the different grapevine downy mildew management : (CO) Control (no sprays against downy mildew); (CA) Conventional control (calendar); (BA) Advisory system 'Rule 3-10'; (MA25) Advisory system with low-infection efficiency - i0 > 25%; and (MA75) Advisory system with high infection efficiency ? i0 > 75%. According to the results, the plastic cover alone was not effective in controlling downy mildew. Under plastic cover, all advisory systems tested were as effective as the control provided by treatment calendar (CA), however, with 75% less fungicide application (MA75) than CA.Resumo expandido

Resposta da videira BRS morena sob cobertura plástica a diferentes sistemas de alerta fitossanitário.

O objetivo deste estudo foi avaliar o efeito do uso de diferentes sistemas de alerta fitossanitário para o controle do míldio na videira cv BRS Morena cultivada sob cobertura plástica impermeável.Resumo expandido

Realistic boundary conditions for stochastic simulations of reaction-diffusion processes

Many cellular and subcellular biological processes can be described in terms of diffusing and chemically reacting species (e.g. enzymes). Such reaction-diffusion processes can be mathematically modelled using either deterministic partial-differential equations or stochastic simulation algorithms. The latter provide a more detailed and precise picture, and several stochastic simulation algorithms have been proposed in recent years. Such models typically give the same description of the reaction-diffusion processes far from the boundary of the simulated domain, but the behaviour close to a reactive boundary (e.g. a membrane with receptors) is unfortunately model-dependent. In this paper, we study four different approaches to stochastic modelling of reaction-diffusion problems and show the correct choice of the boundary condition for each model. The reactive boundary is treated as partially reflective, which means that some molecules hitting the boundary are adsorbed (e.g. bound to the receptor) and some molecules are reflected. The probability that the molecule is adsorbed rather than reflected depends on the reactivity of the boundary (e.g. on the rate constant of the adsorbing chemical reaction and on the number of available receptors), and on the stochastic model used. This dependence is derived for each model.Comment: 24 pages, submitted to Physical Biolog

Downy mildew warning systems for vineyards cultivated under plastic covering - influence on yield and quality

Poste

Spectral and localization properties of the Dirichlet wave guide with two concentric Neumann discs

Bound states of the Hamiltonian describing a quantum particle living on three dimensional straight strip of width $d$ are investigated. We impose the Neumann boundary condition on the two concentric windows of the radii $a$ and $b$ located on the opposite walls and the Dirichlet boundary condition on the remaining part of the boundary of the strip. We prove that such a system exhibits discrete eigenvalues below the essential spectrum for any $a,b>0$. When $a$ and $b$ tend to the infinity, the asymptotic of the eigenvalue is derived. A comparative analysis with the one-window case reveals that due to the additional possibility of the regulating energy spectrum the anticrossing structure builds up as a function of the inner radius with its sharpness increasing for the larger outer radius. Mathematical and physical interpretation of the obtained results is presented; namely, it is derived that the anticrossings are accompanied by the drastic changes of the wave function localization. Parallels are drawn to the other structures exhibiting similar phenomena; in particular, it is proved that, contrary to the two-dimensional geometry, at the critical Neumann radii true bound states exist.Comment: 25 pages, 7 figure

Barriers to Diffusion in Dendrites and Estimation of Calcium Spread Following Synaptic Inputs

The motion of ions, molecules or proteins in dendrites is restricted by cytoplasmic obstacles such as organelles, microtubules and actin network. To account for molecular crowding, we study the effect of diffusion barriers on local calcium spread in a dendrite. We first present a model based on a dimension reduction approach to approximate a three dimensional diffusion in a cylindrical dendrite by a one-dimensional effective diffusion process. By comparing uncaging experiments of an inert dye in a spiny dendrite and in a thin glass tube, we quantify the change in diffusion constants due to molecular crowding as Dcyto/Dwater = 1/20. We validate our approach by reconstructing the uncaging experiments using Brownian simulations in a realistic 3D model dendrite. Finally, we construct a reduced reaction-diffusion equation to model calcium spread in a dendrite under the presence of additional buffers, pumps and synaptic input. We find that for moderate crowding, calcium dynamics is mainly regulated by the buffer concentration, but not by the cytoplasmic crowding, dendritic spines or synaptic inputs. Following high frequency stimulations, we predict that calcium spread in dendrites is limited to small microdomains of the order of a few microns (<5 μm)