1,720,997 research outputs found
Induction and patterning of the telencephalon in Xenopus laevis
No full textWe report an analysis of the tissue and molecular interplay involved in the early specification of the forebrain, and in particular telencephalic, regions of the Xenopus embryo. In dissection/recombination experiments, different parts of the organizer region were explanted at gastrula stage and tested for their inducing/patterning activities on either naive ectoderm or on midgastrula stage dorsal ectoderm. We show that the anterior dorsal mesendoderm of the organizer region has a weak neural inducing activity compared with the presumptive anterior notochord, but is able to pattern either neuralized stage 10.5 dorsal ectoderm or animal caps injected with BMP inhibitors to a dorsal telencephalic fate. Furthermore, we found that a subset of this tissue, the anterior dorsal endoderm, still retains this patterning activity. At least part of the dorsal telencephalic inducing activities may be reproduced by the anterior endoderm secreted molecule cerberus, but not by simple BMP inhibition, and requires the N-terminal region of cerberus that includes its Wnt-binding domain. Furthermore, we show that FGF action is both necessary and sufficient for ventral forebrain marker expression in neuralized animal caps, and possibly also required for dorsal telencephalic specification. Therefore, integration of organizer secreted molecules and of FGF, may account for patterning of the more rostral part of Xenopus CNS
XOtx5b and XOtx2regulate photoreceptor and bipolar fates in the Xenopus retina
No full textPhotoreceptor and bipolar cells are molecularly related cell types in the vertebrate retina. XOtx5b is expressed in both photoreceptors and bipolars, while a closely related member of the same family of transcription factors, XOtx2, is expressed in bipolar cells only. Lipofection of retinal precursors with XOtx5b biases them toward photoreceptor fates whereas a similar experiment with XOtx2 promotes bipolar cell fates. Domain swap experiments show that the ability to specify different cell fates is largely contained in the divergent sequence C-terminal to the homeodomain, while the more homologous N-terminal and homeodomain regions of both genes, when fused to VP16 activators, promote only photoreceptor fates. XOtx5b is closely related to Crx and like Crx it drives expression from an opsin reporter in vivo. XOtx2 suppresses this XOtx5b-driven reporter activity providing a possible explanation for why bipolars do not express opsin. Similarly, co-lipofection of XOtx2 with XOtx5b overrides the latter's ability to promote photoreceptor fates and the combination drives bipolar fates. The results suggest that the shared and divergent parts of these homologous genes may be involved in specifying the shared and distinct characters of related cell types in the vertebrate retina
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
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