1,721,033 research outputs found
Regeneration of the ophiuroid Amphiura filiformis
No full textRegeneration of body parts lost following trauma, predation, or as a result of asexual reproduction has received much attention in recent years. Indeed, there are several reports in current volume, which deal with this problem. In terms of the cell biology of regeneration, most effort has been directed at a rather limited number of species and groups, for example, crinoids, asteroids and holothuroids (Candia Carnevali et al. 1998; Garcia-Arraras et al. 1998; Moss et al. 1998; Thorndyke & Candia Carnevali 2000 and this volume). In sharp contrast the ophiuroids have received scant attention. To a certain extent this is surprising since it is in ophiuroids that arm loss and regeneration is perhaps most common and in terms of their ecology, we know much about the role of autonomy and regeneration (Skold &Rosenberg 1996; Stancyk et al. 1994).
It now seems most timely to re-visit the ophiuroids since they make excellent models for the study of regeneration and in particular the role of the nervous system, especially in terms of its mechanism of renewal and the part it plays in regulating the process itself
Cellular and molecular bases of arm regeneration in Brittlestars
No full textWe have studied arm regeneration in a range of brittlestars with a particular emphasis on the nervous system. Regeneration is common in this group of echinoderms and forms part of their normal life-pattern where body parts may be lost following predator stress. Our approach has been to combine laboratory studies with an analysis of naturally regenerating animals from the field. Regeneration is a remarkably rapid process with as much as 1-2mm of re-growth recorded in Amphiura filiformis over 10 days at 10-110C. As in crinoids the process involves the formation of a blastema. This is produced by the active proliferation of cells, which accumulate at the end of the radial nerve cord. Following blastema formation the arms appear to extend from the tip with segmental maturity occurring in a temporally regulated fashion and posterio-anterior (disk to tip) direction. An advantage of A. filiformis is its natural bioluminescence and this feature has allowed us to assess the extent of functional recovery in the regenerate. Initial results suggest that this system is capable of extensive and rather rapid reformation with function in the regenerated part restored just over one week following ablation. We are also investigating the role of growth factors in this process as well as the expression of patterning genes and are currently analysing cDNA libraries prepared from both regenerating and normally growing arms
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
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
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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