83 research outputs found
Concretos secos produzidos com agregados reciclados de RCD separados por densidade
ResumoO uso de agregados reciclados de resÃduos de construção e demolição (RCD) em blocos de concreto permite compatibilizar as diferentes caracterÃsticas de composição e porosidade desses agregados com os diferentes nÃveis de exigência mecânica em uso dos blocos. Paralelamente, concretos secos são pouco estudados porque a energia de prensagem obtida em vibroprensas não é facilmente reprodutÃvel em escala de laboratório; porém, parte dessa limitação pode ser superada, realizando-se a avaliação do comportamento da mistura (sob confinamento) com prensas de laboratório com controle de deformação. Assim, o objetivo deste artigo foi analisar o comportamento do concreto seco (no estado fresco e endurecido) produzido com agregados de RCD (separados ou não por densidade), empregando-se esse método laboratorial de prensagem. Com substituição total do agregado natural pelo agregado reciclado misto obtido por processo de jigagem obteve-se resistências à compressão comparáveis à s dos concretos de referência. A influência das caracterÃsticas dos agregados e das formulações de concretos secos foi identificada pela técnica de compactação laboratorial. A redução da porosidade do agregado reciclado e a otimização da granulometria da mistura seca (cimento e agregados) foram os parâmetros mais importantes para o incremento de resistência observado
In vitro phosphorylation as tool for modification of silk and keratin fibrous materials
An overview is given of the recent work on in vitro enzymatic phosphorylation of silk fibroin and human hair keratin. Opposing to many chemical "conventional" approaches, enzymatic phosphorylation is in fact a mild reaction and the treatment falls within "green chemistry" approach. Silk and keratin are not phosphorylated in vivo, but in vitro. This enzyme-driven modification is a major technological breakthrough. Harsh chemical chemicals are avoided, and mild conditions make enzymatic phosphorylation a real "green chemistry" approach. The current communication presents a novel approach stating that enzyme phosphorylation may be used as a tool to modify the surface charge of biocompatible materials such as keratin and silk
Variability in the analysis of a single neuroimaging dataset by many teams
Data analysis workflows in many scientific domains have become increasingly complex and flexible. To assess the impact of this flexibility on functional magnetic resonance imaging (fMRI) results, the same dataset was independently analyzed by 70 teams, testing nine ex-ante hypotheses. The flexibility of analytic approaches is exemplified by the fact that no two teams chose identical workflows to analyze the data. This flexibility resulted in sizeable variation in hypothesis test results, even for teams whose statistical maps were highly correlated at intermediate stages of their analysis pipeline. Variation in reported results was related to several aspects of analysis methodology. Importantly, meta-analytic approaches that aggregated information across teams yielded significant consensus in activated regions across teams. Furthermore, prediction markets of researchers in the field revealed an overestimation of the likelihood of significant findings, even by researchers with direct knowledge of the dataset. Our findings show that analytic flexibility can have substantial effects on scientific conclusions, and demonstrate factors related to variability in fMRI. The results emphasize the importance of validating and sharing complex analysis workflows, and demonstrate the need for multiple analyses of the same data. Potential approaches to mitigate issues related to analytical variability are discussed
Variability in the analysis of a single neuroimaging dataset by many teams
Data analysis workflows in many scientific domains have become increasingly complex and flexible. To assess the impact of this flexibility on functional magnetic resonance imaging (fMRI) results, the same dataset was independently analyzed by 70 teams, testing nine ex-ante hypotheses. The flexibility of analytic approaches is exemplified by the fact that no two teams chose identical workflows to analyze the data. This flexibility resulted in sizeable variation in hypothesis test results, even for teams whose statistical maps were highly correlated at intermediate stages of their analysis pipeline. Variation in reported results was related to several aspects of analysis methodology. Importantly, meta-analytic approaches that aggregated information across teams yielded significant consensus in activated regions across teams. Furthermore, prediction markets of researchers in the field revealed an overestimation of the likelihood of significant findings, even by researchers with direct knowledge of the dataset. Our findings show that analytic flexibility can have substantial effects on scientific conclusions, and demonstrate factors related to variability in fMRI. The results emphasize the importance of validating and sharing complex analysis workflows, and demonstrate the need for multiple analyses of the same data. Potential approaches to mitigate issues related to analytical variability are discussed
Transient Studies of Oxygen Removal Pathways and Catalytic Redox Cycles during NO Decomposition on Cu−ZSM5
Réseaux de réactions dans l'oxydation catalytique de composés organiques : utilité et limitations
International audienceDes réseaux de réactions-aussi détaillés que nécessaire mais aussi simples que possible- sont utilisés pour quantifier des cinétiques réactionnelles complexes dans le but d'améliorer la conduite du réacteur et de garantir un dimensionnement fiable. L'approche est illustrée à l'aide d'exemples, à savoir : - la postcombustion catalytique de composés organiques volatiles ; - l'oxydation partielle de composés organiques
Réseaux de réactions dans l'oxydation catalytique de composés organiques : utilité et limitations
Des réseaux de réactions-aussi détaillés que nécessaire mais aussi simples que possible- sont utilisés pour quantifier des cinétiques réactionnelles complexes dans le but d'améliorer la conduite du réacteur et de garantir un dimensionnement fiable. L'approche est illustrée à l'aide d'exemples, à savoir : - la postcombustion catalytique de composés organiques volatiles ; - l'oxydation partielle de composés organiques
A solid electrolyte potentiometry aided study of the catalytic reduction of nitric oxide by ammonia on a vanadia/titania catalyst
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