Localization versus subradiance in three-dimensional scattering of light

We study the scattering modes of light in a three-dimensional disordered medium, in the scalar approximation and above the critical density for Anderson localization. Localized modes represent a minority of the total number of modes, even well above the threshold density, whereas spatially extended subradiant modes predominate. For specific energy ranges however, almost all modes are localized, yet adjusting accordingly the probe frequency does not allow to address these only in the regime accessible numerically. Finally, their lifetime is observed to be dominated by finite-size effects, and more specifically by the ratio of the localization length to their distance to the system boundaries.Comment: Add figure comparing localization percentage via frequency, fixed text, addition of Ioffe-Regel criterion limits, figure axis were normalize

Comparison of wheat classification accuracy using different classifiers of the image-100 system

Classification results using single-cell and multi-cell signature acquisition options, a point-by-point Gaussian maximum-likelihood classifier, and K-means clustering of the Image-100 system are presented. Conclusions reached are that: a better indication of correct classification can be provided by using a test area which contains various cover types of the study area; classification accuracy should be evaluated considering both the percentages of correct classification and error of commission; supervised classification approaches are better than K-means clustering; Gaussian distribution maximum likelihood classifier is better than Single-cell and Multi-cell Signature Acquisition Options of the Image-100 system; and in order to obtain a high classification accuracy in a large and heterogeneous crop area, using Gaussian maximum-likelihood classifier, homogeneous spectral subclasses of the study crop should be created to derive training statistics

Evaluation of spatial filtering on the accuracy of wheat area estimate

A 3 x 3 pixel spatial filter for postclassification was used for wheat classification to evaluate the effects of this procedure on the accuracy of area estimation using LANDSAT digital data obtained from a single pass. Quantitative analyses were carried out in five test sites (approx 40 sq km each) and t tests showed that filtering with threshold values significantly decreased errors of commission and omission. In area estimation filtering improved the overestimate of 4.5% to 2.7% and the root-mean-square error decreased from 126.18 ha to 107.02 ha. Extrapolating the same procedure of automatic classification using spatial filtering for postclassification to the whole study area, the accuracy in area estimate was improved from the overestimate of 10.9% to 9.7%. It is concluded that when single pass LANDSAT data is used for crop identification and area estimation the postclassification procedure using a spatial filter provides a more accurate area estimate by reducing classification errors

Soil fertility, mineral nitrogen and microbial biomass in upland soils of the Central Amazon under different plant covers.

Amazon is the largest State of Brazil and major area of the State is covered by a largest tropical rainforest of the world. Most soils of the Amazon region soils are characterized as acidic and infertile. When the Amazon forest land is cleared for agricultural use by burning the vegetation, the efficient nutrient recycling mechanism are disrupted. However, nutrient contents in the deforested burn land increased temporarily. The objective of this study was to evaluate the soil fertility, mineral nitrogen and microbial activity of carbon (C), nitrogen (N) and phosphorus (P) resulting from the replacement of the primary forest with pasture (Brachiaria brizantha), commercial plantations of rubber (Hevea spp.), cupuaçu (Theobroma grandiflorum), and citrus trees (Citrus sinensis) cultivated in Xanthic Ferralsol and secondary forest under Acrisols Dystric Nitosols. The results showed that ammonium-N predominates in the 0-10 cm soil depth both in primary forest and areas with secondary forest, citrus plantation and pasture. There was no increase in soil fertility with management of the cultivated areas under secondary forest, but in the pasture there was a significant increase in the stock of organic C and total N and high C/N ratios, the inverse of what occurred with the carbon of the microbial biomass. The primary forest had the highest values of C and P of the microbial biomass and the lowest metabolic quotient. Of the successions studied, the rubber trees were the plant cover with the smallest changes in terms of quality of the organic matter in the soil

Repartição e remobilização de nutrientes na bananeira.

A bananeira demanda grandes quantidades de corretivos e fertilizantes para manter suas exigências nutricionais e obter alta produtividade, porém grande porcentagem aplicada não é disponibilizada, sendo perdida, principalmente, por fixação, lixiviação e volatilização. O objetivo deste trabalho foi verificar a taxa de remobilização e repartição de nutrientes na bananeira cultivar Thap Maeo, cultivada na Amazônia Ocidental. Os resultados mostraram que as maiores proporções de K, Na, Mg, S, B, Cu, Fe e Zn se encontram contidas no pseudocaule. Os restos florais da bananeira constituem forte dreno temporário de nutrientes. A biomassa proveniente dos restos de cultura representa fonte significativa de nutrientes para as plantas. O N e K apresentam o maior índice relativo de remobilização, sendo o inverso observado com o Mn e Fe. Termos para indexação: Musa sp., macronutrientes, micronutrientes, restos culturais

Produção, fontes e nível crítico de boro para alfafa cultivada em Latossolo Vermelho Amarelo distrófico.

Com objetivo de determinar a dose, fontes e o nível crítico de boro que obtivesse a maior produção de matéria seca da alfafa foi realizado um experimento em condições de campo em delineamento em blocos casualisados com duas saturações por base, cinco doses (0, 1, 3, 6 e 9 kg ha-1 de B) e duas fontes [ulexita (9% de B) e ácido bórico (17% de B)], com quatro repetições. Foram realizados seis cortes com intervalos de 30 dias. Os resultados mostraram que o uso da ulexita ocasionou na maior produção de matéria seca da parte aérea (MSPA) da alfafa, sendo a maior produção obtida com aplicação estimada de 6,5 kg ha-1. O teor foliar de B para obtenção da maior produção de MSPA esta na faixa de 35,95 mg kg-1 a 37,35 mg kg-1

Microbial biomass in upland soils of the Central Amazon under different plant covers.

The objective of this study was to evaluate the microbial activity of carbon, nitrogen and phosphorus resulting from the replacement of the primary forest with Brachiaria brizantha, Hevea, cupuaçu, citrus and secondary forest. There was no increase in soil fertility under secondary forest, but in the pasture had an increase in the stock of C and N and high C/N ratios, the inverse occurred with C-microbial biomass. The primary forest had the highest values of C, N and P of the microbial biomass and the lowest metabolic quotient. The Hevea was the plant cover with the smallest changes of C in the soil