Comunidade infestante no consórcio de milho com leguminosas

Estudou-se o consórcio de milho com adubos verdes: Cajanus cajam, Stizolobium aterrimum, Crotalaria spectabilis e Dolichos lablab, e avaliou-se os efeitos das relações entre comunidade infestante, milho e legumiinosas. Os tratamentos estudados foram: (i) milho em monocultivo mantido no limpo; (ii) milho em monocultivo mantido no mato; (iii) consórcio de milho com leguminosas em semeadura simultânea; (iv) cultivo consorciado de milho com leguminosas semeadas 21 dias após o milho. Brachiaria plantaginea foi a principal planta daninha da área experimental. A produção de matéria seca pelas plantas de milho foi afetada pela presença das plantas daninhas e leguminosas quando a semeadura do milho e leguminosas foi simultânea. A produção de matéria seca pelas leguminosas foi maior quando semeadas 21 dias após o milho. C. espectabilis foi a leguminosa menos apta para conviver no consórcio. Stizolobium aterrimum foi a leguminosa com maior produção de matéria seca, nos dois sistemas de consórcio, a que menos afetou as plantas de milho e, quando semeada simultaneamente ao milho reduziu a densidade de plantas daninhas em relação ao milho em monocultivo. A altura de plantas, a altura de inserção da primeira espiga e a produtividade de milho foram reduzidas pela presença de plantas daninhas e leguminosas quando a semeadura foi simultânea à do milho. As leguminosas reduziram a população de plantas daninhas sem afetar as plantas de milho e nem sua produtividade, quando semeadas 21 dias após o milho.

Nodulation, arbuscular mycorrhizal colonization and growth of some legumes native from Brazil

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

População de plantas e espaçamento entre linhas do feijoeiro irrigado. II: rendimento de grãos e componentes do rendimento

O objetivo deste experimento foi avaliar o efeito de diferentes populações de plantas e espaçamentos entre linhas de cultivo na produção de massa seca, rendimento de grãos e componentes do rendimento da cultura do feijoeiro irrigado. O experimento foi conduzido no ano agrícola 1997/1998, em área do Departamento de Engenharia Rural da Universidade Federal de Santa Maria (UFSM), RS. A cultivar de feijão preto BR-FEPAGRO 44 - Guapo brilhante, habito de crescimento indeterminado (tipo II), foi submetida a três populações de plantas (175, 250 e 325 mil plantas há-1) e três espaçamentos entre linhas de cultivo (35, 50 e 65cm). Utilizou-se o delineamento experimental inteiramente casualizado, bifatorial, com quatro repetições. Irrigações por aspersão foram aplicadas quando a evapotranspiração máxima da cultura, estimada a partir da evaporação do tanque classe A, indicava um valor acumulado de 25mm. Os resultados demonstraram que as diferentes populações de plantas e espaçamentos entre linhas de cultivo não ocasionaram alterações no rendimento de grãos e massa de mil sementes. No entanto, o número de sementes por vagem e de vagens por planta aumentaram com a redução na população de plantas. Na fase do enchimento de grãos, a redução do espaçamento entre linhas de cultivo aumentou a massa seca da parte aérea das plantas. A cultivar de feijoeiro, BR-FEPAGRO 44 - Guapo brilhante, apresenta elevada plasticidade dos componentes do rendimento, havendo compensação no rendimento de grãos nas menores populações de plantas com aumento da produção por planta.

Modelo sistêmico de ocorrência de ações coletivas: um estudo multicaso na comercialização de frutas, legumes e verduras

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Consumo de frutas, verduras e legumes associado à Síndrome Metabólica e seus componentes em amostra populacional adulta

A síndrome metabólica (SM) aumenta o risco de eventos cardiovasculares e o consumo adequado de frutas, verduras e legumes (FVL) está relacionado a sua prevenção. Objetivo: Identificar o consumo de FVL e sua relação com a SM e seus componentes em amostra populacional adulta. Estudo prospectivo de corte transversal com 636 indivíduos adultos, no período de 2004 a 2008. Foram realizadas avaliações antropométrica, clínica, dietética e bioquímica com todos participantes. A SM foi classificada pelo NCEP ATP-III, modificada para a glicose >100mg/dl. A regressão logística foi utilizada para verificar a razão de chance entre o consumo de FVL com a SM e seus componentes, e o nível de significância adotado foi de 5%. O consumo de frutas adequado se mostrou protetor para obesidade abdominal (OR: 0,77; IC: 0,38-0,93), hipertrigliceridemia (OR: 0,76; IC: 0,35-0,96) e presença de SM (OR: 0,78; IC: 0,39-0,96), e o consumo adequado de FVL apresentou efeito protetor para a presença de SM (OR: 0,79; IC: 0,41-0,95). A análise isolada do consumo adequado de verduras e legumes não mostrou efeitos de proteção/risco para a presença de SM e de seus componentes. O consumo adequado de FVL apresentou efeito protetor para a presença de SM e o consumo adequado de frutas exerceu efeito protetor tanto para a presença de SM e como de seus componentes.

Grain size effect on the electrical response of SnO2 thin and thick film gas sensors

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Grain-boundary segregation and precipitates in La2O3 and Pr2O3 doped SnO2 center dot CoO-based varistors

Structural heterogeneities in SnO2.CoO-based varistors were analyzed by transmission electron microscopy. In SnO2.CoO-based system doped with La2O3 and Pr2O3 two kinds of precipitate phases at grain boundary region were found. Using energy dispersive spectrometry they were found to be Co2SnO4 and Pr2Sn2O7, presenting a defined crystalline structure. It was also identified that such precipitate phases are mainly located in triple-junctions of the microstructure. HRTEM analysis revealed the existence of other two types of junctions, one as being homo-junctions of SnO2 grains and other due to twin grain boundaries inside the SnO2.CoO grain. The role of these types of junction in the overall nonlinear electrical features is also discussed. (C) 2003 Elsevier B.V. Ltd. All rights reserved.

Grain boundary electric characterization of Zn7Sb2O12 semiconducting ceramic: A negative temperature coefficient thermistor

The electrical properties of the grain boundary region of electroceramic sensor temperature based on inverse spinel Zn7Sb2O12 were investigated at high temperature. The zinc antimoniate was synthesized by a chemical route based on the modified Pechini method. The electric properties of Zn7Sb2O12 were investigated by impedance spectroscopy in the frequency range from 5 Hz to 13 MHz and from 250 up to 600 degreesC. The grain boundary conductivity follows the Arrhenius law, with two linear branches of different slopes. These branches exhibit activation energies with very similar values; the low-temperature (less than or equal to350 degreesC) and high-temperature (greater than or equal to400 degreesC) regions are equal to 1.15 and 1.16 eV, respectively. Dissimilar behavior is observed on the relaxation time (tau) curve as a function of temperature, where a single slope is identified. The negative temperature coefficient parameters and nature of the polarization phenomenon of the grain boundary are discussed. (C) 2003 American Institute of Physics.

Investigation of food grain drying with pulsating air flows

In this article we investigate experimentally the potential of using pulsating flows for drying of food grains. A Rijke type oscillator with an electrical heater was used to dry batches of soybean grains. Drying temperatures were 60 degreesC. We observed a decrease on the drying time for pulsating flows when compared with the conventional non-pulsating regime. This decrease depended on sample initial moisture content and weight, and on final sample moisture content. (C) 2004 Elsevier B.V. Ltd.

Do all tannins have similar nutritional effects? A comparison of three Brazilian fodder legumes

Three tropical legumes, namely Leucaena leucocephala, Sesbania sesban and Cajanus cajan, were subjected to chemical analysis plus in vitro, in situ and in vivo evaluations. Three different assays were used to determine total tannins: adsorption to polyvinyl pyrrolidine (PVPP-tannins), radial diffusion (RD-tannins) and protein precipitation capacity (BSA-tannins). Total phenols, total tannins and condensed tannins were highest for Sesbania. RD-tannins were correlated with total phenols (r(2) = 0.93), PVPP-tannins (r(2) = 0.92) and condensed tannins (r(2) = 0.99). The protein precipitation capacity of Sesbania, Leucaena and Cajanus were 25.9, 6.13 and 4.05 mu g BSA/g DM, respectively.Gas production at 24h was negatively correlated with total phenols (r(2) = 0.99), PVPP-tannins (r(2) = 0.99) and condensed tannins (r(2) = 0.91). The RD-, PVPP-tannins and the response to polyethylene glycol (PEG) in the gas production assay appeared to be useful as a first screen for tannins.In situ degradability did not reflect any adverse effects of tannins. However, in vivo experiments showed that the apparent DM digestibility of Sesbania and Leucaena was lower than the basal diet. The apparent protein digestibility was lower for all legumes compared to the basal diet. Most treatments caused a negative nitrogen balance. The problems associated with browse feeding were not only related to tannin contents, other factors such as inherently poor digestibility and low energy intake may also have lead to the poor animal performance on these diets. We propose, given the limitations of current tannin assays, that it is not possible to predict beneficial or harmful nutritional effects from total tannin concentrations per se. (C) 2004 Elsevier B.V. All rights reserved.

Influence of condensed tannins from Brazilian semi-arid legumes on ruminal degradability, microbial colonization and ruminal enzymatic activity in Saanen goats

The present study aimed at determining the influence of condensed tannins present in the Brazilian legume species Mimosa hostilis, Mimosa caesalpinifolia and Bauhinia cheilantha on ruminal degradability, microbial colonization and enzymatic activity. Polyethylene glycol (PEG) was used to reduce the astringency and concentration of soluble condensed tannins. Four ruminally-cannulated Saanen goats (60 +/- 8 kg BW) were fed, in two experimental periods, with a hay diet based on the studied legumes treated or non-treated with PEG. Voluntary intake, microbial colonization, DM, CP, NDF, and ruminal degradability of PEG treated and non-treated forage leaves, as well as pH, ammonia and 1,4 P-endoglucanase activity of the rumen content were evaluated. Astringency and soluble tannin concentration of the studied legumes were reduced by approximately 70% and 50%, respectively, with PEG treatment. Average DM intake was higher for the treated diet (16.76 g DM/kg BW/day against 13.06 g DM/kg BW/day). Percentile values for degradation parameters and for potential and effective degradabilities of DM, CP and NDF were also affected by the tannins, but at different intensities. Electron microscopic observations of ruminally-incubated legume leaves showed a more effective microbial colonization of PEG-treated leaves for all legume species. A decrease in pH and an increase in ammonia concentration and in endoglucanase activity in the ruminal content was also observed for PEG-treated diets at all sampling periods. Condensed tannins of the studied legume species have influenced the adhesion conditions, colonization and enzymatic activity of the microbial ecosystem, and consequently the ruminal degradation of the different dietary fractions. For this reason, the reduction in condensed tannin would be of great importance to improve the nutrition of ruminant feeding of these species. (c) 2005 Elsevier B.V. All rights reserved.

Temperature dependence of fractal dimension of grain boundary region in SnO2 based ceramics

Fractal dimensions of grain boundary region in doped SnO2 ceramics were determined based on previously derived fractal model. This model considers fractal dimension as a measure of homogeneity of distribution of charge carriers. Application of the derived fractal model enables calculation of fractal dimension using results of impedance spectroscopy. The model was verified by experimentally determined temperature dependence of the fractal dimension of SnO2 ceramics. Obtained results confirm that the non-Debye response of the grain boundary region is connected with distribution of defects and consequently with a homogeneity of a distribution of the charge carriers. Also, it was found that C-T-1 function has maximum at temperature at which the change in dominant type of defects takes place. This effect could be considered as a third-order transition.

Ferroelectric state analysis in grain boundary of Na0.85Li0.15NbO3 ceramic

The electric and dielectric properties of the grain boundary of Na0.85Li0.15NbO3 lead-free ferroelectric-semiconductor perovskite were investigated. The impedance spectroscopy was carried out as a function of a thermal cycle. The sodium lithium niobate was synthesized by a chemical route based on the evaporation method. Dense ceramic, relative density of 97%, was prepared at 1423 K for 2 h in air atmosphere. ac measurements were carried out in the frequency range of 5 Hz-13 MHz and from 673 to 1023 K. Theoretical adjust of the impedance data was performed to deriving the electric parameters of the grain boundary. The electric conductivity follows the Arrhenius law, with activation energy values equal to 1.55 and 1.54 eV for heating and cooling cycle, respectively. The nonferroelectric state of the grain boundary and its correlation with symmetry are discussed in the temperature domain. (C) 2003 American Institute of Physics.