Soil phosphorus properties and management for perennial crops in the central Amazon.

Predominant soils in the Brazilian Amazon. Phosphorus constraints to continuous soil use in the Brazilian Amazon. Phosphorus fertilization to perennial crops in the central Amazon. Phosphorus budgets in perennial crop plantations

Fabrication and Electrical Characterization of Translucent Bi 12

The production of high-density Bi12TiO20 ceramics, their transmission spectrum, and impedance features are reported. The samples were synthesized at 700°C/6 h and sintered at 800°C/3 h. This procedure yielded translucent ceramics with relative density of 99.2±0.5% and average grain size of 3.1±1.6 μm. Samples with 0.5 mm thickness were translucent with optical transmission of about 30% at 800 nm. The electrical and dielectric properties of the high-density ceramics were studied and compared with those measured for samples with lower density and also with the literature about Bi12TiO20 single crystals. The activation energy for the conduction process in high-density ceramic was 0.99 eV, and the dielectric permittivity was 40 at 200°C. These values are comparable to those reported for single crystals

Mata ciliar é vida.

bitstream/item/26693/1/Mata-Ciliar-vida-Portal-Dia-de-Campo.pd

Improving light harvesting in polymer photodetector devices through nanoindented metal mask films

To enhance light harvesting in organic photovoltaic devices, we propose the incorporation of a metal (aluminum) mask film in the system’s usual layout. We fabricate devices in a sandwich geometry, where the mask (nanoindented with a periodic array of holes of sizes d and spacing s) is added between the transparent electrode and the active layer formed by a blend of the semiconducting polymer P3HT and substituted fullerene. Its function is to promote trapping of the incident light into the device’s cavity (the region corresponding to the active layer). For d, we set a value that allows light diffraction through the holes in the relevant absorption range of the polymer. To optimize the mask structure, we consider a very simple model to determine the s leading to trapped fields that are relatively intense and homogeneous within the device. From measurements of the action spectra, we show that, indeed, such architecture can considerably improve the resulting photocurrent efficiencies—one order of magnitude in the best situation studied.

Caracterização de sintomas de deficiências em mudas de teca (Tectona grandis L. f.).

Este estudo teve por objetivo caracterizar os sintomas visuais de deficiência de macro e micronutrientes em mudas de teca.bitstream/item/24801/1/ct90-teca.pd

Solo: um patrimônio ameaçado.

bitstream/item/26700/1/Solo-um-patrimnio-ameaado-Portal-Dia-de-Campo.pd