1,720,958 research outputs found
A simple method for the DNA content assay of culture maintained pancreatic islets of Langerhans
No full textA simple method for assaying DNA content of in vitro culture maintained pancreatic islets is described. By employing lyophilization of the islets and subsequent fluorometric analysis, we have been able to measure DNA from relatively small cell samples. The method may result advantageous, over others, previously reported, since it is less subject to experiment-related interfering conditions. This procedure, which is easy and reliable, even for very low DNA concentrations, seems to be very useful for culture maintained pancreatic islets, since in vitro work conducted with this endocrine tissue is usually associated with small size cell samples. The method may help for a simple assessment of the viable islet cell mass in in vitro studies
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe 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
Full text link“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
Full text linkWe 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
Pancreatic β-cell destruction in non-obese diabetic mice
No full textWe determined the natural history of the widespread pancreatic islet β-cell destruction that precedes the onset of spontaneous putative autoimmune diabetes mellitus in NOD mice. For this purpose, we performed both histological and immunocytochemical examinations of pancreata retrieved from mice at 2 through 30 weeks of age. An overexpression of la antigens was identified on islet β cells at 4 weeks of age, without evidence of mononuclear cell infiltration. The abnormal expression of la antigens was age-related and was associated with hyperexpression of class I antigens and progressive islet cell histologic damage after 17 weeks of age. Immunocytochemical examination of islet cell infiltrate showed that the number of macrophages did not increase during the early phase of islet cell damage in these mice. The L3T4 Lyt-2 ratio increased after 7 weeks of age, but was 1:1 in the late stage of insulitis. These findings suggest that widespread islet β-cell destruction is a process that begins primarily with derangements of the pancreatic β-cell immune pattern, which may trigger a mononuclear cell reaction
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe 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
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