1,720,954 research outputs found
Análise de supressores da fermentação de xilose em saccharomyces cerevisiae
Get PDFO Brasil se destaca como o segundo maior produtor mundial de bioetanol, sendo detentor do processo de produção mais eficaz e rentável, baseado exclusivamente na utilização da cana-de-açúcar. Porém, apenas um terço de sua biomassa é utilizado para produção de bioetanol. O restante da biomassa (bagaço, folhas e palha) é queimado para a produção de vapor e eletricidade. Estes materiais são compostos majoritariamente de fibras de lignocelulose que são extremamente ricas em açúcares, apresentando grande potencial para produção adicional de bioetanol. A levedura Saccharomyces cerevisiae é o microrganismo mais amplamente utilizado na produção industrial de etanol, sendo capaz de fermentar eficientemente açúcares como a sacarose (principal açúcar presente na cana-de-açúcar) e hexoses. No entanto, essa levedura, em sua condição natural, é incapaz de fermentar pentoses como a xilose, o segundo açúcar mais abundante na biomassa da cana-de-açúcar. O sucesso das tecnologias de produção de biocombustíveis de segunda geração depende, portanto, de leveduras capazes de fermentar tanto as hexoses quanto as pentoses presentes na biomassa lignocelulósica. Recentemente, alguns estudos têm reportado que os genes BUD21 e PHO13 funcionam como possíveis supressores da metabolização de xilose em S. cerevisiae. O objetivo do presente estudo foi avaliar o efeito da deleção dos referidos genes em linhagens industriais diploides utilizadas para a produção de etanol combustível no Brasil. Para tanto, utilizou-se técnicas de biologia molecular baseadas em recombinação homóloga para deletar do genoma de S. cerevisiae o(s) gene(s) BUD21 e PHO13. Nossos resultados mostraram que linhagens de laboratório com deleção do gene BUD21 (bud21?) foram incapazes de utilizar xilose como fonte de carbono, sugerindo que este gene não é um supressor da metabolização de xilose nas leveduras analisadas. Numa segunda abordagem, o gene PHO13 foi deletado numa levedura industrial diploide recombinante que sobre-expressa os genes necessários à metabolização de xilose (genes XYL1, XYL2 e XKS1). A linhagem industrial pho13? / pho13? foi capaz de crescer em meios sólidos contendo altas concentrações de xilose, e em cultivos em frascos agitados, a deleção do gene PHO13 melhorou significativamente oconsumo da xilose, bem como a produção de biomassa e de etanol pela linhagem industrial recombinante. No entanto, ensaios de fermentação em batelada simples em condições microaeróbias revelaram que a deleção do PHO13 não melhora a fermentação da xilose. Resultados semelhantes foram encontrados nos ensaios de co-fermentações de xilose/glicose e xilose/sacarose.Abstract : Brazil stands as the second largest world producer of bioethanol, having the most efficient and profitable production process, based exclusively on the use of sugarcane. However, only a third of its biomass is used for bioethanol production. The remaining biomass (bagasse, leaves and straw) is burned to produce steam and electricity. These materials are composed mostly of lignocellulosic fibers that are extremely rich in sugars, with great potential for further production of bioethanol. The yeast Saccharomyces cerevisiae is the microorganism most widely used in the industrial production of ethanol, been able to efficiently ferment sugars such as sucrose (the principal sugar present sugarcane) and hexoses. However, this yeast, in its natural condition, is unable to ferment pentoses such as xylose, the second most abundant sugar in the sugarcane biomass. The success of the technologies of second generation biofuels production, therefore, depends on yeast capable of fermenting hexoses as well as pentoses present in the lignocellulosic biomass. Recently some studies have reported that the BUD21 and PHO13 genes function as potential suppressors of xylose metabolism in S. cerevisiae. The aim of this study was to evaluate the effect of the deletion of these genes in diploid industrial strains used for the production of fuel ethanol in Brazil. For this, we used molecular biology techniques based on homologous recombination to delete the BUD21 and PHO13 gene(s) from the S. cerevisiae genome. Our results showed that laboratory strains deleted in the BUD21 gene (bud21?) were unable to use xylose as a carbon source, suggesting that this gene is not a suppressor of xylose metabolism in the analyzed yeasts. In a second approach, the PHO13 gene was deleted in a recombinant diploid industrial yeast overexpressing the genes required for xylose metabolism (XYL1, XYL2 and XKS1 genes). The industrial pho13? / pho13? strain was able to grow on solid media containing high concentrations of xylose, and in flasks cultivations, the deletion of the PHO13 gene significantly improved xylose consumption, as well as production of biomass and ethanol by the industrial recombinant strain. However, assays in simple batch fermentation under conditions of limited oxygen revealed that deletion of PHO13 no improvement ofxylose fermentation. Similar results were found in assays of co-fermentation of xylose / glucose and xylose / sucrose
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
Author Under Sail The Imagination of Jack London, 1893-1902
No full textIn Author Under Sail, Jay Williams offers the first complete literary biography of Jack London as a professional writer engaged in the labor of writing. It examines the authorial imagination in London's work, the use of imagination in both his fiction and nonfiction, and the ways he defined imagination in the creative process in his business dealings with his publishers, editors, and agents. In this first volume of a two-volume biography, Williams traverses the years 1893 to 1902, from London's "Story of a Typhoon" to The People of the Abyss. The Jack London who emerges in the pages of Author Under Sail is a writer whose partnership with publishers, most notably his productive alliance with George Brett of Macmillan, was one of the most formative in American literary history. London pioneered many author models during the heyday of realism and naturalism, blurring the boundaries of these popular genres by focusing on absorption and theatricality and the representation of the seen and unseen. London created an impassioned, sincere, and extremely personal realism unlike that of other American writers of the time. Author Under Sail is a literary tour de force that reveals the full range of London as writer, creative citizen, and entrepreneur at the same time it sheds light on the maverick side of machine-age literature.Intro -- Title Page -- Copyright Page -- Dedication -- Contents -- Acknowledgments -- Introduction -- 1. Spirit Truth -- 2. From Absorption to Theatricality and Back Again -- 3. "I Will Build a New Present" -- 4. Sons as Authors -- 5. Fathers as Publishers -- 6. The Daughter as Author -- 7. Lovers as Authors -- 8. At Sea with the Family -- 9. Yellow News, Yellow Stories -- 10. The Return Home -- Notes -- Bibliography -- Index -- About Jay WilliamsIn Author Under Sail, Jay Williams offers the first complete literary biography of Jack London as a professional writer engaged in the labor of writing. It examines the authorial imagination in London's work, the use of imagination in both his fiction and nonfiction, and the ways he defined imagination in the creative process in his business dealings with his publishers, editors, and agents. In this first volume of a two-volume biography, Williams traverses the years 1893 to 1902, from London's "Story of a Typhoon" to The People of the Abyss. The Jack London who emerges in the pages of Author Under Sail is a writer whose partnership with publishers, most notably his productive alliance with George Brett of Macmillan, was one of the most formative in American literary history. London pioneered many author models during the heyday of realism and naturalism, blurring the boundaries of these popular genres by focusing on absorption and theatricality and the representation of the seen and unseen. London created an impassioned, sincere, and extremely personal realism unlike that of other American writers of the time. Author Under Sail is a literary tour de force that reveals the full range of London as writer, creative citizen, and entrepreneur at the same time it sheds light on the maverick side of machine-age literature.Description based on publisher supplied metadata and other sources.Electronic reproduction. Ann Arbor, Michigan : ProQuest Ebook Central, YYYY. Available via World Wide Web. Access may be limited to ProQuest Ebook Central affiliated libraries
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