1,720,954 research outputs found
Direct seeding of Cerrado native tree species: differences between species and effects of weed competition
No full textFace à expressiva degradação a que o Cerrado brasileiro vem sendo submetido, é de grande importância a investigação e o desenvolvimento de métodos para a sua restauração. Atualmente, há obstáculos ecológicos e tecnológicos para a restauração da vegetação de cerrado, tais como a presença de espécies exóticas invasoras, a estação seca prolongada, a dificuldade para obtenção de mudas de espécies nativas em viveiros e a falta de conhecimento para a escolha de espécies adequadas para cada técnica de restauração. O entendimento acerca do desempenho de diferentes espécies arbóreas nativas semeadas diretamente em campo e dos efeitos da matocompetição sobre o desempenho dessas espécies é altamente relevante para a superação dos obstáculos mencionados. Os objetivos deste estudo foram: (i) comparar o desempenho de espécies arbóreas nativas por meio de semeadura direta, em busca de padrões funcionais que expliquem esse desempenho, (ii) verificar se o desempenho das espécies é comprometido pela matocompetição e (iii) verificar se a semeadura consorciada com gramíneas nativas pode inibir o estabelecimento da matocompetição. Instalamos um experimento fatorial em blocos (5 blocos) com os seguintes fatores: 1) espécies nativas arbóreas (11); 2) controle de matocompetição (sim ou não) e 3) consorciação com um mix de seis gramíneas nativas (sim ou não). O experimento totalizou 110 parcelas de 4 m2 cada, distribuídas nos 5 blocos. Em cada parcela semeamos 100 sementes de uma espécie arbórea aleatoriamente definida, em linhas, com 20 cm entre sementes. Contamos a quantidade de indivíduos arbóreos emergidos e mortos aos 10, 20 e 30 dias após a semeadura e, posteriormente, ao término das estações seca e chuvosa. Após um ano, medimos a altura e o diâmetro do caule dos indivíduos sobreviventes e estimamos a porcentagem de cobertura do terreno por gramíneas nativas e por matocompetição em cada parcela. Adicionalmente, medimos o comprimento e quantificamos a biomassa seca da parte aérea e da parte subterrânea de 11 indivíduos de cada espécie arbórea e apresentamos uma estimativa de custos da semeadura direta. Observamos diferença no desempenho entre tratamentos para algumas espécies que foram prejudicadas pela matocompetição. As espécies Dipteryx alata, Hymenaea stigonocarpa e Plathymenia reticulata apresentaram os maiores valores médios de taxa de sobrevivência (superiores a 60%) e as duas espécies do gênero Stryphnodendron apresentaram os piores desempenhos (ao redor de 20%). A presença de gramíneas nativas não beneficiou nenhuma espécie arbórea nem inibiu a colonização e o desenvolvimento da matocompetição. A interação entre as variáveis massa das sementes, biomassa raiz:parte aérea e comprimento do sistema radicular explicou 93% da variação na sobrevivência das plântulas em campo. Conclui-se que a semeadura direta de espécies arbóreas em cerrado pode ser bem sucedida, especialmente para espécies com sementes grandes, raízes profundas e que investem mais em sistema subterrâneo do que em parte aérea, que são atributos funcionais relacionados com a capacidade de sobreviver em condições de déficit hídrico. Embora algumas espécies possam ter sucesso sob matocompetição, o controle de gramíneas exóticas e ervas ruderais pode viabilizar a semeadura direta para um conjunto maior de espécies.In view of the vast and fast degradation to which Brazilian Cerrado has been submitted, it is of great importance to find adequate restoration techniques to be widely applied. There are currently ecological and technological challenges for the restoration of the cerrado vegetation, such as the presence of invasive alien species, the prolonged dry season, the difficulty to obtain seedlings of native species in nurseries and the lack of knowledge to choose suitable species for each restoration technique. Understanding the performance of different tree species in direct seeding and the interactions between weeds and native grasses is highly relevant to overcome the mentioned obstacles. The objectives of this study were: (i) to evaluate the performance of native tree species in direct sowing, in search for functional patterns related to this performance, (ii) to verify if the consortium of native grasses with tree seeds can help in weed control, positively influencing the performance of tree species, and (iii) to verify if the native grasses are able to inhibit weeds colonization and development (competition). We set up a factorial experiment in blocks with the following levels of variation: 1) species (11); 2) weed control (yes or no) and 3) consortium with a mix of six native grasses (yes or no). The experiment totalled 110 plots of 4 m2 each, distributed in the 5 blocks. In each plot we sowed 100 seeds of an arboreal species, in rows, with 20 cm between seeds. We counted the number of arboreal individuals emerged and dead at 10, 20 and 30 days after sowing; and then at the end of both the dry season and the rainy season. After one year from sowing, we measured stem height and diameter of the surviving individuals, and estimated the percentage of ground cover by native grasses and weeds per plot. In addition, we measured the length and quantified the dry aerial and belowground biomass of 11 individuals of each tree species and we estimated the costs for direct seeding. We observed a difference in performance among treatments for some species that were adversely affected by weed competition. The species Dipteryx alata, Hymenaea stigonocarpa and Plathymenia reticulata had the highest average survival rates (over 60%) and the two species of the genus Stryphnodendron had the worst performances (around 20%). The presence of native grasses did not benefit any tree species nor inhibit colonization and development of weed competition. The interaction of the attributes seed mass, root: shoot ratio and root length, explained 93% of the variation in seedling survival in the field. We concluded that direct seeding of tree species in Cerrado regions can be successful, especially for species with large seeds, deep roots and that invest more in underground structures than in aerial parts, which are functional attributes related to the capacity to survive in conditions of water deficit. Although some species may succeed under weed competition, the control of exotic grasses and ruderal forbs may enable direct seeding for a larger set of species
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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