1,720,955 research outputs found
Tasa de evolución molecular y pleiotropía en la trayectoria evolutiva de secuencias codificantes
Get PDFLas investigaciones sobre las variables que modifican la tasa de cambio evolutivo de las macromoléculas han estado en el centro del estudio de la evolución molecular desde sus inicios. En esta línea la pleiotropía, entendida como la capacidad de una mutación de afectar múltiples rasgos fenotípicos, ha sido tratada como un obstáculo para la acumulación de nuevas mutaciones, disminuyendo la tasa evolutiva, debido a que aumenta la probabilidad de que la mutación sea deletérea, a la vez que disminuye su probabilidad de fijación. Si bien esto ha sido demostrado a un nivel teórico bajo condiciones específicas, aún no hay una respuesta satisfactoria de por qué no se ha encontrado esta clara relación negativa en la naturaleza ni tampoco se sabe cómo diferentes condiciones y supuestos pueden cambiar este patrón. Aquí hacemos uso del modelo geométrico de Fisher para estudiar en profundidad los efectos de la pleiotropía sobre la tasa evolutiva e incorporar, por una parte, un seguimiento temporal del proceso evolutivo y, por otra, el rol de la selección natural y la deriva gen ética sobre estos efectos, haciendo uso de una descripción del modelo basado en ecuaciones diferenciales parciales. Adicionalmente, evaluamos las predicciones del modelo a la luz la evolución de las secuencias codificantes de 15 especies de pingüinos y expandimos nuestros resultados para encontrar procesos biológicos significativos en la evolución de estas aves. En el modelamiento, así como en el análisis genómico, encontramos que el efecto de la pleiotropía sobre la tasa evolutiva cambia dinámicamente a lo largo de una trayectoria evolutiva siguiendo tres etapas estereotípicas un efecto negativo inicial, una segunda etapa de efecto positivo de mayor duración y una etapa final de efecto levemente negativo.Research on the variables that modify the rate of evolutionary change of macromolecules has been at the center of the study of molecular evolution since its inception. In this line pleiotropy, understood as the capacity of a mutation to affect multiple phenotypic traits, has been treated as a hindrance to the accumulation of new mutations, decreasing the evolutionary rate, because it increases the probability of the mutation being deleterious while decreasing its probability of fixation. While this has been demonstrated at a theoretical level under specific conditions, there is still no satisfactory answer as to why this clear negative relationship has not been found in nature, nor is it known how different conditions and assumptions can change this pattern. Here we make use of Fisher’s geometric model to study in depth the effects of pleiotropy on the evolutionary rate and incorporate, on the one hand, a temporal follow-up of the evolutionary process and, on the other hand, the role of natural selection and genetic drift on these effects, making use of a description of the FGM based on partial differential equations. In addition, we evaluated the model predictions in light of the evolution of the coding sequences of 15 penguin species and expanded our results to find significant biological processes in the evolution of these birds. In our model, as well as in genomic analysis, we found that the effect of pleiotropy on evolutionary rate changes dynamically along an evolutionary trajectory following three stereotypic stages an initial negative effect, a second stage of longer-lasting positive effect, and a final stage of slightly negative effect.Facultad de Ciencias de la Universidad de Chile, ANID, Instituto Milenio BAS
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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