711 research outputs found

    Quantitative Phase Analysis in Semicrystalline Materials Using the Rietveld Method

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    Wustite as a new precursor of industrial ammonia synthesis catalysts

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    Contradictory results about the best oxidic precursor of Fe ammonia synthesis catalyst prompted the present comparative investigation on wustite- and magnetite-based catalysts. Many physical (density, porous texture, crystalline phases, reduction rate, metal surface, abrasion loss) and catalytic (kinetic constants, thermoresistancy) properties have been determined on both catalysts. The wustite-based catalyst proved to be much more active, especially at lower temperatures, approaching the performances of Ru/C catalyst, except at high conversion. Possible reasons for such a behavior of the wustite-based catalyst are discussed, suggesting that a reconsideration of the present consolidated knowledge on Fe ammonia synthesis catalyst might be convenien

    Stabilization of cubic Na-modified ZrO 2

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    Home and Work Physical Activity Environments: Associations with Cardiorespiratory Fitness and Physical Activity Level in French Women

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    The influence of the physical activity environment in the home and at work on cardiorespiratory fitness (CRF) and objectively-measured physical activity has not been extensively studied. We recruited 147 women with a (mean ± SD) age of 54 ± 7 years and without evidence of chronic disease. The physical activity environment was assessed by self-report (Assessing Levels of PHysical Activity or ALPHA questionnaire), CRF using a submaximal step test, usual physical activity using combined heart rate and accelerometry, as well as by a validated questionnaire (Recent Physical Activity Questionnaire). Summary scores of the home environment and the work environment derived from the ALPHA questionnaire were positively correlated with CRF after adjustment for age (rr = 0.18, pp = 0.03 and rr = 0.28, pp < 0.01, respectively). Women owning a bicycle or having a garden (which may prompt physical activity) had higher CRF; those with a bicycle at home also had a higher physical activity energy expenditure. Similarly, women who had access to fitness equipment at work had higher CRF. In conclusion, these results provide new insights into potential environmental influences on physical capacity and physical activity that could inform the design of physical activity promotion strategies.European Union (Integrated Project LSHM-CT-2006-037197 in the Framework Programme 6 of the European Community), Medical Research Council (Grant ID: MC_UU_12015/3

    Pd-Fe/SiO2 Catalysts in the Hydrogenation of 2,4-Dinitrotoluene

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    Pd-Fe/SiO2 bimetallic catalysts with a constant amount of Pd and a different Fe/Pd ratio were prepared by sequential wet mpregnation and the hydrogenation of 2,4-dinitrotoluene was arried out at 25'C in a batch reactor. The presence of Fe nhances the Pd catalytic activity. The formation of a disperse Pd-Fe alloy was evidenced through X-ray powder diffraction nd is consistent with the data observed by FTIR analysis, TPR, nd chemisorption features. The increase of the Fe total conten f the catalysts results in the increase of the dispersion of the metallic phase and in the presence of partially oxidized Fe pecies. FTIR analysis shows that nitrocompounds chemisorb mainly on the support rather than on the metal surface. It is uggested that the Pd-Fe alloy formation is responsible for the ncrease of the catalytic activity because of a cooperative effect of Fe in the hydrogen transfer step

    Fractal properties of a partially crystalline zirconium oxide aerogel

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    Raleio químico: balanço de carboidratos na cultura da macieira.

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    Abusca constante do agricultor é sempre por maior lucratividade na sua atividade. Essa lucratividade pode ser alcançada aumentando a produtividade, melhorando a qualidade da produção e, melhor ainda, através de ambas. Nos sistemas de economia globalizada da atualidade, onde a competitividade está sempre presente, a busca por maior produtividade deve sempre estar associada à alta qualidade. O raleio se insere neste contexto como uma das práticas culturais mais importantes, com influência direta na produtividade e na qualidade dos frutos (Camilo e Pereira, 2006). O raleio é comercialmente realizado a fim de maximizar o valor das culturas por meio da otimização do tamanho dos frutos, a coloração, a forma e a qualidade dos frutos destinados a comercialização, bem como promover o retorno da floração e reduzir o vigor da parte aérea das plantas (Byers, 2003).bitstream/item/200832/1/13850-2012-p.24.pd
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