1,720,969 research outputs found
The determination of maturity stages in male elasmobranchs (Chondrichthyes) using a segmented regression of clasper length on total length
No full textA novel statistical method for estimating the stages of maturity in male sharks and skates based on a segmented regression (SRM) is proposed. We hypothesize that this method is able to find the transition points in the three-phase relationship between total length (TL) and clasper length (CL). We applied an SRM to TL–CL data of nine species, from large pelagic sharks (e.g., Carcharhinus falciformis) to small coastal skates (e.g., Rioraja agassizi), captured in the southwestern Atlantic and northeastern Pacific. As expected, SRM detected two breakpoints, defining three maturity stages (immature, maturing, and mature), in six out of nine species. For three species, it was not possible to find two breakpoints because of incomplete sampling of TL. This novel method is noninvasive, it is applicable to previously collected data, is easy to use, and provides a reliable tool for increasing our understanding of elasmobranch reproductive strategies
Trace elements and isotopes analysis on historical samples of white sharks (Carcharodon carcharias) from central Mediterranean Sea
No full textBoth trace elements and isotopes analysis were performed on two samples of vertebrae of White Sharks Carcharodon carcharias from Favignana Island (Sicily, central Mediterranean). For the trace elements analysis, the ICP-MS associated by Laser Ablation allowed us to find 36 trace elements. More samples were taken, on the same vertebrae, along a transect that goes from the most central part of the vertebra to the distal one. Among these 36 trace elements we have been detected high concentrations of Pb, Fe, Zn, Sr, Ba and U. Fluctuations of these elements can be caused by different kind of processes such as variations in temperature, nutrition, uptake of urban pollutants and proximity to industrial areas. The stable isotopes (δ15N and δ13C) analysis has been performed through IRMS (Isotope Ratio Mass Spectrometry) and allowed us to understand the trophic levels of individuals. The two white shark vertebrae showed different isotopic values. The first individual (seven growth layers) presented isotopic ranges from 9.6‰ to 10.8‰ (δ15N) and from -16.5‰ to - 13.0‰ (δ13C); this showed a mean ± SD value of 10.3 ± 0.4‰ for δ15N and -14.6 ± 1.3‰ for δ13C. The second individual (five growth layers) presented isotopic ranges from 9.8‰ to 11.1‰ (δ15N) and from -16.9‰ to -15.0‰ (δ13C), displaying a mean ± SD value of 10.8 ± 0.6‰ for δ15N and -15.8 ± 0.8‰ for δ13C. In terms of δ15N values, there were not significant differences (U = 6, p =0.07346) between the two individuals; however, there were significant differences (t = -1.8, p =0.049256) in δ13C values, both at a significance level of 0.05. The absence of differences between the trophic level of the individuals could be related to the trophic level of their preys at the time of age. The differences observed in the case of δ13C are probably correlated to the fact that the first shark was feeding near the coast, while the other feed more offshore
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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