Nitrogen-doped graphitic carbon has been intensively studied for potential use as an electrocatalyst in fuel cells for the oxygen reduction reaction (ORR). However, the lack of a mechanistic understanding on the carbon catalysis has severely hindered the progress of the catalyst development. Herein we use a well-defined graphene nanostructure as a model system and, for the first time, reveal an oxygen activation mechanism that involves carbanion intermediates in these materials. Our work shows that the overpotential of the electrocatalytic ORR is determined by the generation of the carbanion intermediates, and the current by the rate the intermediates activate oxygen.

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RESUMOPor sua elevada produção de matéria seca, o capim-elefante tem sido utilizado como fonte de energia renovável. A seleção para a melhoria de características pode influenciar na produção de matéria seca, razão por que se torna necessário o estudo da correlação entre essas características. Assim, os objetivos deste trabalho foram avaliar os coeficientes de correlação e os desdobramentos das correlações genotípicas em efeitos diretos e indiretos das variáveis, como altura das plantas, diâmetro do colmo, número de perfilhos e largura da lâmina foliar na produção de matéria seca em clones de capim-elefante. O experimento foi conduzido em Campos dos Goytacazes-RJ, utilizando-se quarenta genótipos de capim-elefante. O delineamento utilizado foi em blocos ao acaso, com duas repetições. Nos dois cortes avaliados as características de altura da planta, diâmetro do colmo e largura da lâmina foliar apresentaram correlação genotípica positiva e significativa, com a produção de matéria seca. A altura da planta foi a que mais influenciou, direta e positivamente, a produção de matéria seca durante o segundo corte. Já no terceiro corte isto ocorreu para as características diâmetro do colmo e número de perfilhos. Palavras-chave: biomassa, melhoramento de plantas, Pennisetum purpureum Correlations and path analysis in elephant grass for energy ABSTRACTThe elephant grass for its high dry matter production has been used as a source of renewable energy. The selection for the improvement of traits could influence the production of dry matter and therefore it is necessary to study the correlation between these traits. The objectives of this study were to evaluate the correlation coefficients and display genotype correlations into direct and indirect effects of variables such as plant height, stem diameter, number of tillers and leaf blade width in dry matter production in clones of elephant grass. The experiment was conducted in Campos dos Goytacazes-RJ, using forty genotypes of elephant grass. The design was a randomized block with two replications. Evaluated in two cuts, plant height, stem diameter and width of the leaf blade showed positive and significant genotypic correlation with dry matter production. Plant height was the most directly and positively influenced the dry matter production during the second cut. In the third section, it occurred to the characteristics stem diameter and number of tillers.

Elephant grass is a tropical forage plant widely spread in Brazil, used mainly in the livestock sector and in cattle feeding. Because of its high productivity and photosynthetic capacity, this culture has also been considered an alternative source of renewable energy. Six clones of elephant grass (Pennisetum purpureum Schum.) were evaluated under five levels of nitrogen fertilization (100, 200, 400, 800, and 1600 kg•N•ha −1 ), in a randomized-block design with a split-plot arrangement with three replicates, from April 2010 to December 2012, in the city of Campos dos Goytacazes-RJ, Brazil. The objective was to obtain estimates of variation in morpho-agronomic traits and biomass quality. We observed that genotypes Cameroon-Piracicaba and Guaçu I/Z2 have great potential to be used, with maximum dry matter yields of 60.97 and 44.10 t•ha −1 per cut for energy purposes among the studied genotypes.

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0,05) das cultivares de arroz branco, em percentagem de espiguetas férteis por panícula e produtividade de grãos, revelando o potencial agronômico destes genótipos para cultivo em condições de sequeiro.]]>

With a high growth rate and a DM yield of up to 80 t ha -1 yr -1 , elephant grass (Pennisetum purpureum Schumach.) has been utilized as an alternative source of energy. However, genotypes adapted to and productive in the different regions of Brazil need to be developed. Thus, the objectives of the present study were to estimate and evaluate heterotic effects in elephant-grass hybrids obtained in a partial diallel cross (5 × 5), with the aim of assisting the superior hybrids selection for bioenergy production. The experiment was conducted in Campos dos Goytacazes, Rio de Janeiro, Brazil. The following traits were evaluated: plant height (HGT), stem diameter (SD), leaf blade width (LBW), number of tillers per linear meter (NT), percentage of DM (%DM), and DM yield (DMY). The experiment was conducted in a randomized block design, with 35 treatments (five female parents, five male parents, and 25 hybrid combinations) and three replicates. The adopted statistical model was that of Miranda

ABSTRACT. Elephant grass is a tropical forage plant widely distributed throughout Brazil. It was first exclusively used in the livestock sector as cattle feed. The grass is characterized by its high productivity and photosynthetic capacity and is considered as an alternative source of renewable energy. Here, we estimated the general combining ability of the parents and specific combining ability of the hybrids based on morpho-agronomic biomass-quality traits. The experiment was conducted in a randomized block design with 3 replicates. The diallel was composed of 16 hybrids and 2 groups of genitors. In the diallel analysis of variance, we observed a significant difference among treatments. A significant difference was observed among genitors for dry matter production (DMP). For the general combining ability of group 1, the traits leaf blade width, DMP, height, percentage of neutral detergent fiber, percentage of hemicellulose, percentage of lignin, percentage of acid detergent fiber, and percentage of cellulose were significant. For the estimates of general combining ability of DMP, parents Porto Rico