1,721,021 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
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Mechanisms of Stem Cell Maintenance and Cell Differentiation in the Intestinal Epithelium
No full textConstant regeneration of the intestinal epithelium, a dynamic tissue with vital digestive and barrier functions, depends on proliferation of resident stem cells and their differentiation into mature cell types. This epithelium thus provides an ideal model to study stem cells and mechanisms of cell differentiation in an adult tissue.
The identification of a proliferative population of intestinal stem cells (ISCs) at the base of intestinal crypts presents the prospect of understanding their regulation by extrinsic and intrinsic factors. Although activation of Wnt signaling in ISCs is thought to be one crucial function of the ISC niche, the cellular source of Wnt ligands is uncertain. Chapter 2 addresses this question through genetic elimination of Wnt ligand secretion in candidate niche cell populations. The data reveal that Wnts originating in any of the sources considered in the literature – the epithelium (including Paneth cells) and sub-epithelial myofibroblasts – are not required for ISC function. These data support models of highly complex cell redundancy or alternative, non-Wnt ligands. Chapter 3 investigates the cell-intrinsic contributions of an intestine-restricted transcription factor (TF), CDX2, to important ISC behaviors. Cdx2 loss in vivo perturbs ISC proliferation and differentiation, distinct from its functions in mature enterocytes. Analysis of candidate direct CDX2 target genes in ISCs suggests that CDX2 modulates Fibroblast Growth Factor signaling, thus opening new avenues of investigation.
Although cells that differentiate from ISCs rely on gene expression changes mediated by TFs, loss of several individual TFs in vivo has modest effects on intestinal function. Chapter 4 characterizes the functional interactions of CDX2, which has many properties of a master regulator, with two other intestinal TFs: GATA4 and Hepatocyte Nuclear Factor 4 alpha (HNF4A). Analysis of compound mutant mouse intestines elucidated combinatorial roles for CDX2 with GATA4 in crypt cell proliferation and with HNF4A in enterocyte differentiation. Building on this foundation, Chapter 5 describes preliminary investigations into another TF, HNF1A, in intestinal gene regulation and its relationship with CDX2 in controlling cell differentiation and tissue architecture. These studies highlight the complexities of TF interactions and the functions of diverse TF complexes in controlling tissue-specific genes during cell differentiation.Medical SciencesMedical SciencesIntestinal epithelium; intestinal stem cell; cell differentiation; transcription factors; CDX2; HNF4A; HNF1A; GATA; Wnt pathwa
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
Mutation mapping and identification by whole-genome sequencing
Get PDFGenetic mapping of mutations in model systems has facilitated the identification of genes contributing to fundamental biological processes including human diseases. However, this approach has historically required the prior characterization of informative markers. Here we report a fast and cost-effective method for genetic mapping using next-generation sequencing that combines single nucleotide polymorphism discovery, mutation localization, and potential identification of causal sequence variants. In contrast to prior approaches, we have developed a hidden Markov model to narrowly define the mutation area by inferring recombination breakpoints of chromosomes in the mutant pool. In addition, we created an interactive online software resource to facilitate automated analysis of sequencing data and demonstrate its utility in the zebrafish and mouse models. Our novel methodology and online tools will make next-generation sequencing an easily applicable resource for mutation mapping in all model systems.Harvard Stem Cell Institute (Junior Faculty Grant)National Institutes of Health (U.S.) (Grant 1R01DK090311)National Institutes of Health (U.S.) (Grant 5R01MH084676
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
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