1,720,996 research outputs found
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
Genetic and evolutionary analysis of diversification and reproductive isolation in yeast
Get PDFIn this thesis, I examine the mechanisms of evolution at different levels, from evolutionary conflict between selfish genes within a single individual (Chapter 1), through social evolution acting within a species (Chapter 2), to genetic divergence and incompatibility between closely related species (Chapters 4 & 5). The thesis therefore investigates how tiny genetic differences occurring in individuals accumulate and produce discontinuous groups. The first chapter explores an interesting form of natural selection, acting independently on different genomes within the same cell. Natural selection can act at the level of individual genes: an allele that promotes its own transmission can increase in frequency despite reducing the fitness of the rest of the genome (Dawkins 1978). This phenomenon, known as intragenomic conflict (Hurst 1992), has long been hypothesized to drive evolution, forcing different lineages to adapt to the genes within their own genomes and therefore causing their genomes to diverge, and potentially, to become incompatible types. Here I test whether intragenomic conflict drives evolutionary change by evolving yeast populations in the laboratory, to see if intra-genomic conflicts would lead genomes in independent populations to become incompatible. After allowing populations to evolve under two treatments of strict vertical transmission of mitochondria, or mixed horizontal/vertical transmission, I tested the evolutionary changes in interactions between mitochondrial and nuclear genomes in the continuum of mutualism and selfishness. As predicted, increasing the independence of mitochondria from their hosts (by increasing outbreeding) reduced the evolved fitness benefit that mitochondria provided to their un-evolved hosts. The results presented in this chapter hint that intra-genomic conflicts can speed up the evolution of cyto-nuclear reproductive isolation between allopatric populations. The second chapter also looks at whether conflict, this time between individuals in a population rather than between genes within an individual, can lead to diversification, not just in the form of single nucleotide replacements but at the under-examined form of copy number variation. The sharing of the secreted enzyme invertase (encoded by SUC genes) by yeast cells is a well-established laboratory model used to test social conflict models. Moreover, yeast populations vary in SUC gene copy numbers. The observed copy number variation has been suggested to be the result of natural selection acting at the level of social conflict. However, genetic variation might instead be explained by adaptation of different populations to different local availabilities of sucrose, the substrate for the SUC gene product. Here, I 6 provide evidence showing that the variation observed in natural populations is better explained by the environmental adaptation hypothesis rather than the social conflict hypothesis (Bozdag & Greig 2014). The final chapters take a different approach: rather than at bottom-up approach testing how natural selection (intra-genomic conflict, social conflict and environmental adaptation) may drive diversification or divergence into different types, I take a top-down approach, testing which genetic changes are responsible for the discontinuities between already established types (between two species of yeast, S. cerevisiae and S. paradoxus). In chapter three, I look at how nucleotide sequence variation can accumulate to such an extent that it prevents the segregation of diverged chromosomes, causing sexual incompatibilities between established types (different species). Here, I have genetically manipulated interspecific hybrids with the aim of inducing crossovers between their diverged chromosomes. This manipulation increased recombination rates significantly compared to unmanipulated hybrids. Increased recombination caused a remarkable increase in the fertility of the yeast hybrids, from 0.5% viable gametes to over 30% viable gametes. I conclude that the reduced recombination in interspecific hybrids is responsible for at least one third of the hybrid gamete death. And finally in chapter four, I determine how individual genetic changes can cause incompatibility, potentially preventing certain individuals from breeding together and therefore allowing the accumulation of further genetic changes. Here I assayed a hybrid strain for two-locus incompatibilities (Bateson-Dobzhansky-Muller genic incompatibilities) between the two parental yeast species. If such genic incompatibilities exist, the proportion of viable offspring bearing the hybrid combination for a pair of loci should be significantly lower than the proportion bearing the non-hybrid (i.e. parental) combination. To check this, I exploited the improved viability of interspecific hybrids obtained in the chapter three. As a result, I present seven putative BDMI regions between the two sibling species of yeast
Die natürliche Ökologie von Saccharomyces Hefen
Get PDFThe extensive existing knowledge about S. cerevisiae based on studies in the lab or in human-made fermentations is unrivaled. Surprisingly almost nothing is known about the natural ecology of the yeast. Wild Saccharomyces are referred as being associated with oak trees especially the bark, which seems surprising considering the high sugar conditions in for example the wine making process. Almost all wild Saccharomyces isolates come from oak but this does not necessarily mean that this is really its primary habitat. There exists a strong bias according to focusing on this environment for sampling as well as to the isolation protocols used. Until now, the yeast / oak association could not be convincingly proved. The aim of this thesis is to shed some light on the natural ecology of Saccharomyces yeast and to specifically search for the natural environment of the yeast. For this approach a combination of field work, next-generation sequencing of the oak bark environment as well as experiments of wild Saccharomyces with naturally co-occurring microorganisms was used.Das ausgeprägte Wissen über S. cerevisiae basierend auf Studien im Labor oder in vom Menschen geschaffenen Fermentationen, ist bemerkenswert. Überraschenderweise ist allerding fast nichts über die natürliche Ökologie der Modellhefe bekannt. Wilde Saccharomyces Hefen werden als assoziiert mit Eichen, vor allem deren Borke, bezeichnet, was überrascht, wenn man die hohen Zuckerkonzentrationen zum Beispiel im Weinherstellungsprozess betrachtet. Fast alle wilde Saccharomyces Isolate kommen von Eichen, was aber nicht bedeutet, dass dies auch wirklich das eigentliche Habitat der Hefe ist. Es existiert eine starke Tendenz sich auf dieses Habitat zu fokussieren, wenn in der Umwelt nach Saccharomyces gesucht wird. Ausserdem führt das Isolationsprotokoll, das normalerweise verwendet wird, zu einer verschobenen Sichtweise. Bis heute konnte die Hefen / Eichen Assoziierung nicht überzeugend bewiesen werden. Das Ziel dieser Dissertation ist es, ein wenig Licht in die natürliche Ökologie von Saccharomyces Hefen zu bringen und vor allem nach der natürlichen Umwelt der Hefe zu forschen. Für diese Fragestellung wurde eine Kombination aus Feldarbeit, Hochdurchsatz Sequenzierung der Eichenborkenumwelt, wie auch Experimente mit wilder Saccharomyces Hefe und natürlicherweise co-existierenden Mikroorganismen verwendet
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
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