Experimental evaluation of the performance of a wireless sensor network in agricultural environments

The aim of this study was to perform an experimental study to evaluate the proper operation distance between the nodes of a wireless sensor network available on the market for different agricultural crops (maize, physic nut, eucalyptus). The experimental data of the network performance offers to farmers and researchers information that might be useful to the sizing and project of the wireless sensor networks in similar situations to those studied. The evaluation showed that the separation of the nodes depends on the type of culture and it is a critical factor to ensure the feasibility of using WSN. In the configuration used, sending packets every 2 seconds, the battery life was about four days. Therefore, the autonomy may be increased with a longer interval of time between sending packets.

Evapotranspiração real diária em sub-bacias do Paracatu, utilizando produtos do sensor Modis

A evapotranspiração define a perda total de água do sistema solo-planta para a atmosfera. Nas áreas agrícolas, particularmente onde se pratica algum tipo de irrigação, a determinação da evapotranspiração, por via de sensoriamento remoto, vem ganhando cada vez mais importância, pois possibilita identificar a eficiência com que a água tem sido utilizada. Nesse contexto, este trabalho tem o objetivo de determinar a evapotranspiração real diária (ETr diária), com a utilização de produtos do sensor MODIS, nas sub-bacias do Ribeirão Entre Ribeiros e Rio Preto, que ficam entre os Estados de Goiás e Minas Gerais. O SEBAL (Surface Energy Balance Algorithm for Land) foi utilizado para a obtenção da ETr diária em quatro dias diferentes, no período de julho a outubro de 2007. Os resultados encontrados foram compatíveis com os citados em outras literaturas e a comparação entre a evapotranspiração, obtida pelo SEBAL, e a evapotranspiração da cultura (ETc) demonstraram que esse algoritmo pode ser utilizado como boa opção para determinar, com a utilização de produtos do sensor MODIS, a evapotranspiração diária nas condições das sub-bacias do ribeirão Entre Ribeiros e rio Preto.

Use efficiency of variable rate of nitrogen prescribed by optical sensor in corn

ABSTRACT The efficiency of nitrogen fertilizer in corn is usually low, negatively affecting plant nutrition, the economic return, and the environment. In this context, a variable rate of nitrogen, prescribed by crop sensors, has been proposed as an alternative to the uniform rate of nitrogen traditionally used by farmers. This study tested the hypothesis that variable rate of nitrogen, prescribed by optical sensor, increases the nitrogen use efficiency and grain yield as compared to uniform rate of nitrogen. The following treatments were evaluated: 0; 70; 140; and 210 kg ha-1 under uniform rate of nitrogen, and 140 kg ha -1 under variable rate of nitrogen. The nitrogen source was urea applied on the soil surface using a distributor equipped with the crop sensor. In this study, the grain yield ranged from 10.2 to 15.5 Mg ha-1, with linear response to nitrogen rates. The variable rate of nitrogen increased by 11.8 and 32.6% the nitrogen uptake and nitrogen use efficiency, respectively, compared to the uniform rate of nitrogen. However, no significant increase in grain yield was observed, indicating that the major benefit of the variable rate of nitrogen was reducing the risk of environmental impact of fertilizer.

Mapeamento do uso e cobertura da terra a partir da segmentação e classificação de imagens-fração solo, sombra e vegetação derivadas do modelo linear de mistura aplicado a dados do sensor TM/Landsat5, na região do reservatório de Tucuruí - PA

Técnicas de sensoriamento remoto são fundamentais para o monitoramento das mudanças de uso da terra, principalmente em áreas extensas como a Amazônia. O mapeamento de uso da terra, geralmente é realizado por métodos de classificação manual ou digital pixel a pixel, os quais consomem muito tempo. Este estudo aborda a aplicação do modelo linear de mistura em uma imagem Landsat-TM segmentada para o mapeamento das classes de uso da terra na região do reservatório de Tucuruí-PA para os anos de 1996 e 2001.

Detecção de cicatrizes de áreas queimadas baseada no modelo linear de mistura espectral e imagens índice de vegetação utilizando dados multitemporais do sensor MODIS/TERRA no estado do Mato Grosso, Amazônia brasileira

O objetivo desta pesquisa foi avaliar os dados do sensor MODIS para detectar e monitorar cicatrizes de áreas recém queimadas. Utilizamos imagens da reflectância de superfície do sensor MODIS: produto MOD09 (dia 5 de outubro) e produto MOD13A1 (meses de outubro e novembro). Foi avaliada também uma série temporal de um ano dos índices de vegetação (IV) EVI e NDVI (produto MOD13A1). Uma imagem do sensor ETM+ (dia 5 de outubro) foi utilizada como base para a delimitação dos polígonos amostrais e avaliação dos dados MODIS devido a sua melhor resolução espacial. A metodologia focou na aplicação do modelo linear de mistura espectral nas imagens reflectância para a geração das imagens fração sombra. Análises de regressão foram efetuadas para comparação entre o percentual de sombra derivado da imagem ETM+ e das imagens MODIS. As alterações multitemporais nas imagens IV foram avaliadas com base no teste de Tukey. Os resultados mostraram que a imagem fração sombra gerada a partir do produto MOD09 apresentou um R² = 0,66 (p < 0,01) em relação aos dados ETM+. Para as imagens do produto MOD13A1 não foram identificadas relações significativas. Os IV dentro dos mesmos polígonos apresentaram uma variação sazonal durante o ano. No entanto, não houve uma diminuição significativa dos valores destes índices nos meses onde foram observadas as cicatrizes de áreas recém queimadas. Portanto, o produto MOD09 mostrou-se mais eficiente que o produto MOD13A1 para a detecção de cicatrizes de áreas recém queimadas. A análise multitemporal dos IV sugeriu que não foi possível detectar este mesmo padrão na área de estudo.

Mapeamento da antiga cobertura vegetal de várzea do Baixo Amazonas a partir de imagens históricas (1975-1981) do Sensor MSS-Landsat

Este estudo apresenta um mapa da cobertura vegetal da planície de inundação do Rio Amazonas entre as cidades de Parintins (AM) e Almeirim (PA), com base em imagens Landsat-MSS adquiridas entre 1975 e 1981. O processamento digital dessas imagens envolveu a transformação para imagens-fração de vegetação, solo e água escura (sombra), seguido da aplicação de técnicas de segmentação e classificação por região. O mapa resultante da classificação foi organizado em quatro classes de cobertura do solo: floresta de várzea, vegetação não-florestal de várzea, solo exposto e água aberta. A precisão do mapa foi estimada a partir de dois tipos de informações coletadas em campo: 1) pontos de descrição: para validação das classes de cobertura não sujeitas a grandes alterações, como é o caso dos corpos d'água permanentes, e identificação de indicadores dos tipos de cobertura original presentes na paisagem na ocasião da obtenção das imagens (72 pontos); 2) entrevistas com moradores antigos para a recuperação da memória sobre a cobertura vegetal existente há 30 anos (44 questionários). Ao todo foram coletadas informações em 116 pontos distribuídos ao longo da área de estudo. Esses pontos foram utilizados para calcular o Índice Kappa de concordância entre os dados de campo e o mapa resultante da classificação automática, cujo valor (0,78) indica a boa qualidade do mapa de cobertura vegetal da várzea. Os resultados mostram que a região possuía uma cobertura florestal de várzea de aproximadamente 8.650 km2 no período de aquisição das imagens.

Land cover classification of Lago Grande de Curuai floodplain (Amazon, Brazil) using multi-sensor and image fusion techniques

Given the limitations of different types of remote sensing images, automated land-cover classifications of the Amazon várzea may yield poor accuracy indexes. One way to improve accuracy is through the combination of images from different sensors, by either image fusion or multi-sensor classifications. Therefore, the objective of this study was to determine which classification method is more efficient in improving land cover classification accuracies for the Amazon várzea and similar wetland environments - (a) synthetically fused optical and SAR images or (b) multi-sensor classification of paired SAR and optical images. Land cover classifications based on images from a single sensor (Landsat TM or Radarsat-2) are compared with multi-sensor and image fusion classifications. Object-based image analyses (OBIA) and the J.48 data-mining algorithm were used for automated classification, and classification accuracies were assessed using the kappa index of agreement and the recently proposed allocation and quantity disagreement measures. Overall, optical-based classifications had better accuracy than SAR-based classifications. Once both datasets were combined using the multi-sensor approach, there was a 2% decrease in allocation disagreement, as the method was able to overcome part of the limitations present in both images. Accuracy decreased when image fusion methods were used, however. We therefore concluded that the multi-sensor classification method is more appropriate for classifying land cover in the Amazon várzea.

Marcapasso com sensor de contratilidade regulado pelas variações do sistema nervoso autônomo na miocardiopatia chagásica crônica

OBJETIVO: Analisar o desempenho da estimulação cardíaca artificial com marcapasso do tipo VVIR cujo sensor é regulado pelas variações do sistema nervoso autônomo em pacientes chagásicos com distúrbio no sistema de condução. MÉTODOS: Estudados 47 chagásicos, 28 do sexo masculino, com idades entre 24 e 68 anos, 36 tinham bloqueio atrioventricular (AV) total; 8, bloqueio AV de 2º grau 2; e 3 doença do nódulo sinusal, e encontravam-se, de acordo com a NYHA, em classe I (4), II (15), III (16) e IV (12). Após o implante de marcapasso do tipo VVIR os pacientes foram acompanhados durante 12 meses. A resposta de freqüência foi registrada em gravações de Holter de 24h e divididos em dois grupos de acordo com a FC em repouso - grupo 1: >65bpm e grupo 2: <=65bpm, para estudo comparativo, considerando: 1) FC em exercício no período de pós-implante; 2) PA em repouso após o implante e 3) avaliação dos grupos de eletrodos identificados como TIR-60-UP e outros eletrodos. RESULTADOS: O grupo 1 teve em exercício menor variação entre seus valores, do que o grupo 2, indicando que esse tipo de sistema de estimulação permite controlar individualmente cada paciente. Os valores de PA em repouso e em exercício não foram diferentes entre os grupos. O eletrodo do tipo TIR-60-UP, comportou-se como os demais eletrodos. CONCLUSÃO: O marcapasso do tipo VVIR cujo sensor é regulado pelas variações do SNA propicia o restabelecimento dos mecanismos fisiológicos em chagásicos, sendo que 74% deles tiveram melhora de uma ou duas classes funcionais da NYHA.

Quantification of Trypanosoma cruzi in the heart, lymph nodes and liver of experimentally inffected mice, using limiting dilution analysis

Limiting dilution analysis was used to quantify Trypanosoma cruzi in the lymph nodes, liver and heart of Swiss and C57 B1/10 mice. The results showed that, in Swiss and B1/10 mice infected with T. cruzi Y strain, the number of parasites/mg of tissue increased during the course of the infection in both types of mice, although a grater number of parasites were observed in heart tissue from Swiss mice than from B1/10. With regard to liver tissue, it was observed that the parasite load in the initial phase of infection was higher than in heart. In experiments using T. cruzi Colombian strain, the parasite load in the heart of Swiss and B1/10 mice increased relatively slowly, although high levels of parasitization were nonetheless observable by the end of the infection. As for the liver and lymph nodes, the concentration of parasites was lower over the entire course of infection than in heart. Both strains thus maintained their characteristic tissue tropisms. The limiting dilution assay (LDA) proved to be an appropriate method for more precise quantification of T. cruzi, comparing favorably with other direct microscopic methods that only give approximate scores.

Spectrum of Morphologic Changes of Lymph Nodes in HIV Infection

Cervical lymph nodes biopsies from 31 HIV positive patients (with or without AIDS) were studied by histologic methods and immunohistochemistry (StreptABC staining of paraffin sections) to identify cellular and extracellular matrix components. The results were the following: (1) the biopsies were included in the stages of follicular hyperplasia without fragmentation FH-FF (4 cases); follicular hyperplasia with follicular fragmentation FH+FF (16 cases); follicular involution FI (6 cases) and diffuse pattern DP (5 cases); (2) the most important alteration was the germinal centers disruption due to follicle lysis, which began in the light zone; (3) there was coincidence between intrafollicular hemorrhages and segmental hyaline mycroangiopathy; (4) during the progression of the disease occurred: (a) an increase in the number of mast cells, CD68+ and Mac387+ macrophages; (b) a diffuse augment of collagen III, elastic fibers, laminin, fibronectin and proteoglycans; (c) maintenance of Factor VIII - related antigens in the vascular endothelial cells, with decrease in the expression of Ulex-Europeus I lectin. Follicular hyperplasia (FH-FF or FH+FF) was the most common histologic pattern recognized in the lymph nodes of patients without AIDS and follicular involution and difuse pattern were seen in those who had AIDS. The results indicate that the lymph node biopsies may provide important information about the evolutive stage of the disease and its prognosis.

Involvement of regional lymph nodes after penetration of Schistosoma mansoni cercariae in naive and infected mice

The parotid lymph nodes of naive and previously infected Balb/c mice were studied after, respectively, infection and re-infection with cercariae of Schistosoma mansoni via the ears. Schistosomula were able to pass through the lymph node by following the lymph flow or by penetrating the veins of the medullary cords. The number of nodal mast cells was higher from day 2 to 6 of primary infection; and from day 5 to 11 of re-infection. The amount of degranulating mast cells was significantly higher at day 4 of infection and at day 1 of re-infection. Eosinophils characterized the nodal inflammatory processes observed after day 5 in both primarily-infected and re-infected mice. However, only in the latter the eosinophils were able to adhere to the larval surface. In primarily-infected mice, no intranodal larva presented signs of degeneration. In contrast, in re-infected animals, some degenerating larvae were found inside eosinophilic infiltrates. The eosinophils reached the nodal tissue by migrating through the high endothelial venules and their collecting veins.

Evaluation of local immune response to Fasciola hepatica experimental infection in the liver and hepatic lymph nodes of goats immunized with Sm14 vaccine antigen

Protection against Fasciola hepatica in goats immunized with a synthetic recombinant antigen from Schistosoma mansoni fatty acid-binding protein 14 (rSm14) was investigated by assessing worm burdens, serum levels of hepatic enzymes, faecal egg count and hepatic damage, which was evaluated using gross and microscopic morphometric observation. The nature of the local immune response was assessed by examining the distribution of CD2+, CD4+, CD8+ and γ´+ T lymphocytes along with IgG+, IL-4+ and IFN-γ+ cells in the liver and hepatic lymph nodes (HLN). The goats used consisted of group 1 (unimmunized and uninfected), group 2 [infected control - immunized with Quillaia A (Quil A)] and group 3 (immunized with rSm14 in Quil A and infected), each containing seven animals. Immunization with rSm14 in Quil A adjuvant induced a reduction in gross hepatic lesions of 56.6% (p < 0.001) and reduced hepatic and HLN infiltration of CD2+, CD4+, CD8+ and γ´+ T lymphocytes as well as IL-4+ and IFN-γ+ cells (p < 0.05). This is the first report of caprine immunization against F. hepatica using a complete rSm14 molecule derived from S. mansoni. Immunization reduced hepatic damage and local inflammatory infiltration into the liver and HLN. However, considering that Quil A is not the preferential/first choice adjuvant for Sm14 immunization, further studies will be undertaken using the monophosphoryl lipid A-based family of adjuvants during clinical trials to facilitate anti-Fasciolavaccine development.

Optical crop sensor for variable-rate nitrogen fertilization in corn: i - plant nutrition and dry matter production

Variable-rate nitrogen fertilization (VRF) based on optical spectrometry sensors of crops is a technological innovation capable of improving the nutrient use efficiency (NUE) and mitigate environmental impacts. However, studies addressing fertilization based on crop sensors are still scarce in Brazilian agriculture. This study aims to evaluate the efficiency of an optical crop sensor to assess the nutritional status of corn and compare VRF with the standard strategy of traditional single-rate N fertilization (TSF) used by farmers. With this purpose, three experiments were conducted at different locations in Southern Brazil, in the growing seasons 2008/09 and 2010/11. The following crop properties were evaluated: above-ground dry matter production, nitrogen (N) content, N uptake, relative chlorophyll content (SPAD) reading, and a vegetation index measured by the optical sensor N-Sensor® ALS. The plants were evaluated in the stages V4, V6, V8, V10, V12 and at corn flowering. The experiments had a completely randomized design at three different sites that were analyzed separately. The vegetation index was directly related to above-ground dry matter production (R² = 0.91; p<0.0001), total N uptake (R² = 0.87; p<0.0001) and SPAD reading (R² = 0.63; p<0.0001) and inversely related to plant N content (R² = 0.53; p<0.0001). The efficiency of VRF for plant nutrition was influenced by the specific climatic conditions of each site. Therefore, the efficiency of the VRF strategy was similar to that of the standard farmer fertilizer strategy at sites 1 and 2. However, at site 3 where the climatic conditions were favorable for corn growth, the use of optical sensors to determine VRF resulted in a 12 % increase in N plant uptake in relation to the standard fertilization, indicating the potential of this technology to improve NUE.

Optical crop sensor for variable-rate nitrogen fertilization in corn: II - indices of fertilizer efficiency and corn yield

Generally, in tropical and subtropical agroecosystems, the efficiency of nitrogen (N) fertilization is low, inducing a temporal variability of crop yield, economic losses, and environmental impacts. Variable-rate N fertilization (VRF), based on optical spectrometry crop sensors, could increase the N use efficiency (NUE). The objective of this study was to evaluate the corn grain yield and N fertilization efficiency under VRF determined by an optical sensor in comparison to the traditional single-application N fertilization (TSF). With this purpose, three experiments with no-tillage corn were carried out in the 2008/09 and 2010/11 growing seasons on a Hapludox in South Brazil, in a completely randomized design, at three different sites that were analyzed separately. The following crop properties were evaluated: aboveground dry matter production and quantity of N uptake at corn flowering, grain yield, and vegetation index determined by an N-Sensor® ALS optical sensor. Across the sites, the corn N fertilizer had a positive effect on corn N uptake, resulting in increased corn dry matter and grain yield. However, N fertilization induced lower increases of corn grain yield at site 2, where there was a severe drought during the growing period. The VRF defined by the optical crop sensor increased the apparent N recovery (NRE) and agronomic efficiency of N (NAE) compared to the traditional fertilizer strategy. In the average of sites 1 and 3, which were not affected by drought, VRF promoted an increase of 28.0 and 41.3 % in NAE and NRE, respectively. Despite these results, no increases in corn grain yield were observed by the use of VRF compared to TSF.

Determinação da tensão de água em solo agrícola usando um sensor de dissipação de calor

Um estudo foi realizado sob condições de laboratório e de campo objetivando avaliar um sensor de solo utilizado para determinação da temperatura e da tensão da água no solo. Devido à solubilidade do gesso, material poroso utilizado na fabricação dos sensores, houve redução em área da seção transversal e volume, e aumento da porosidade efetiva desses sensores, em relação aos valores observados antes do início dos testes. Os valores médios da temperatura observados com os sensores foram praticamente iguais aos observados com um termômetro de referência com precisão de 0,1°C. Quando sensores saturados foram instalados a 5 cm de profundidade em um solo franco-argilo-siltoso secado ao ar, em relação a valores de Delta T, o tempo de resposta do sensor à secagem foi um pouco superior a 24 horas. Valores de Delta T observados, tanto no laboratório quanto no campo, apresentaram maior variabilidade na faixa representativa de solo seco, em comparação com o solo úmido. Sob condições de campo, não houve diferença estatística (teste F; 5%) entre as médias de Delta T obtidas com os sensores de dissipação de calor instalados a 10 cm de profundidade e as médias de tensão obtidas com tensiômetros e transformadas para Delta T.