Use of the nitrification inhibitor dicyandiamide (DCD) does not mitigate N2O emission from bovine urine patches under Oxisol in Northwest Brazil

Nutrient Cycling in Agroecosystems - Animal production systems are important sources of greenhouse gases (GHGs), especially methane (CH4) and nitrous oxide (N2O). GHG emissions from urine patches...     

Measurement of the Properties of a Plasma Column Used as a Radiating Element

This paper presents two test benches for the characterization of a plasma column used as a radiating element. In particular, the main parameters to be quantified are the efficiency of the plasma antenna, the turn-on time of the column, and the conductivity of the plasma. The first two parameters are evaluated by measuring the field radiated by the plasma antenna compared with that of an equivalent copper antenna. For the conductivity, a reflectometric technique is used, wherein the plasma column is inserted inside a waveguide. The accuracy of the method is limited by the ill-conditioned relationship between the reflection coefficient and the plasma conductivity; nevertheless, it is sufficient to subdivide the range of the conductivity values into three regions (i.e., low, medium, and high conductivities) to determine the best operating conditions of the antenna.     

Pasture mapping by classification of Landsat TM images. Analysis of the spectral behaviour of the pasture class in a real medium-scale environment: The case of the Piracicaba Catchment (12 400 km 2, Brazil)

Attempts to map vegetation types, especially pasture, from satellite sensor data in tropical and sub-tropical regions very often have limited success. This study analyses the accuracy of two classifications of Landsat Thematic Mapper (TM), with the aim of distinguishing the pastures from other vegetation classes in a meso-scale basin (12 400 km 2, Piracicaba basin, Brazil). The initial classification is based on non-supervised clustering of the images. The delimited classes are interpreted and merged by comparison with standard spectra from NASA. The second classification is a parallelepiped partition based on the merged clusters issued from the first one. The two classifications are compared by validation with 287 random field observations selected within the whole catchment. The results are discussed, analysing the spectral behaviour variability of the pasture class.     

Recent Trends,Applications, and Perspectives in 3D Shape Similarity Assessment

The recent introduction of 3D shape analysis frameworks able to quantify the deformation of a shape into another in terms of the variation of real functions yields a new interpretation of the 3D shape similarity assessment and opens new perspectives. Indeed, while the classical approaches to similarity mainly quantify it as a numerical score, map‐based methods also define (dense) shape correspondences. After presenting in detail the theoretical foundations underlying these approaches, we classify them by looking at their most salient features, including the kind of structure and invariance properties they capture, as well as the distances and the output modalities according to which the similarity between shapes is assessed and returned. We also review the usage of these methods in a number of 3D shape application domains, ranging from matching and retrieval to annotation and segmentation. Finally, the most promising directions for future research developments are discussed.     

Evaluation of electromagnetic power deposition in a spherical multilayer head in the near field of a linear antenna

The canonical problem of the radiation of an elementary dipole close to a stratified sphere representing a simplified model of human head is investigated in this paper. The proposed approach is a flexible method of investigation about the influence on Specific Absorption Rate (S.A.R.) evaluation of tissue dielectric parameters and geometry as well as a useful tool to test numerical codes. The solution of the electromagnetic (e.m.) problem is achieved in a closed form; results highlight the position of maximum S.A.R. values and their dependence on frequency: for particular layer thicknesses and dielectric parameters, the maximum absorption can occur in the frequency range of cellular phones.     

Radiation modes of open microstrip with applications

The well known bound modes of open microstrip do not constitute a complete spectrum, for, continuous radiation and localized (reactive) modes are excited at discontinuities in microstrip circuits and antennas. This part of the spectrum has not been investigated before so that, up to date, radiation problems in microstrip are being investigated by nonmodal methods, such as the moment method. We derive here for the first time the complete spectrum of open microstrip, including one or more bound modes and a continuum, and demonstrate its straightforward application to a practical problem such as the excitation by a cylindrical probe of finite radius. Application of Lorentz's reciprocity principle is now possible in complete analogy to the problem of excitation of a close waveguide by a probe. Mode patterns, the equivalent circuit of a via-hole and its radiation pattern are characterized as a practical application of the foregoing theory     

Nitrogen dynamics during till and no-till pasture restoration sequences in Rondônia,Brazil

The clearing of tropical rain forest in the Amazon basin has created large areas of cattle pasture that are now declining in productivity. Practices adopted by ranchers to restore productivity to degraded pastures have the potential to alter soil N availability and gaseous N losses from soils. We examined how soil inorganic N pools, net N mineralization and net nitrification rates, nitrification potential and NO and N₂O emissions from soils of a degraded pasture responded to the following restoration treatments: (1) soil tillage followed by replanting of grass and fertilization, (2) no-till application of non-selective herbicide, planting of rice, harvest followed by no-till replanting of grass and fertilization, and (3) the same no-till sequence with soybeans instead of rice. Tillage increased soil NH₄⁺ and NO₃^? pools but NH₄⁺ and NO₃^? pools remained relatively constant in the control and no-till treatments. Cumulative rates of net N mineralization and net nitrification during the first 6 months after treatment varied widely but were hightest in the tilled treatment. Emissions of NO and N₂O fluxes increased with tillage and with N fertilization. There were no clear relationships among rates of N fertilizer application, net N mineralization, net nitrification, NO, N₂O and total N oxide emissions. Our results indicate that pasture restoration sequences involving tilling and fertilizing will increase emissions of N oxides, but the magnitude of the increase is likely to differ based on timing of fertilizer application relative to the presence of plants and the magnitude of plant N demand. Emissions of N oxides appear to be decreased by the use of restoration sequences that minimize reductions in pasture grass cover.