1,721,043 research outputs found
Hidden Mediterranean biodiversity: molecular evidence for a cryptic species complex within the reef building vermetid gastropod Dendropoma petraeum (Mollusca: Caenogastropoda)
No full textGenetic assessment of population structure and connectivity in the threatened Mediterranean coral Astroides calycularis (Scleractinia, Dendrophylliidae) at different spatial scales
No full textUnderstanding dispersal patterns, population structure and connectivity among populations is helpful in the management and conservation of threatened species. Molecular markers are useful tools as indirect estimators of these characteristics. In this study, we assess the population genetic structure of the orange coral Astroides calycularis
in the Alboran Sea at local and regional scale, and at three localities outside of this basin. Bayesian clustering methods, traditional F-statistics and Dest statistics were used to
determine the patterns of genetic structure. Likelihood and coalescence approaches were used to infer migration patterns and effective population sizes. The results obtained
reveal a high level of connectivity among localities separated by as much as 1 km and moderate levels of genetic differentiation among more distant localities, somewhat
corresponding with a stepping-stone model of gene flow and connectivity. These data suggest that connectivity among populations of this coral is mainly driven by the biology
of the species, with low dispersal abilities; in addition, hydrodynamic processes, oceanographic fronts and the distribution of rocky substrate along the coastline may
influence larval dispersal
Structure and Absolute Stereochemistry of Stolonoxide A, a Novel Cyclic Peroxide from the Marine Tunicate Stolonica Socialis
No full textStolonoxide A, a novel peroxide possessing an unprecedented molecular arrangement, has been isolated as
its methyl ester from the marine tunicate Stolonica socialis. The structure of stolonoxide A has been fully
elucidated by spectroscopic methods and its relative stereochemistry secured by chemical conversion. The absolute
stereochemistry is suggested on the basis of Mosher’s method on the diol derivative obtained by hydrogenation of
the natural product
The changing biogeography of the Mediterranean Sea: from the old frontiers to the new gradients.
No full textGoing 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
DISTRIBUTION AND CONSERVATION NEEDS OF A NEGLECTED ECOSYSTEM: THE MEDITERRANEAN VERMETID REEF
Full text linkVermetid reefs are a key intertidal habitat in the Mediterranean. Despite recent evidence of local extinction in the Eastern Mediterranean, their role as habitat engineers and the high numbers of ecosystem services they provide, vermetid reefs are among the least known marine habitats of the Mediterranean. Here we present a literature-based study to assess for the first time their distribution inside the basin and provide evidence of a general lack of protection at Mediterranean scale
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
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