1,720,965 research outputs found
Analisi faunistiche e biogeografiche sugli Efemerotteri della Sicilia (Insecta, Ephemeroptera).
No full textMorphological and electrophoretic evidence for a new species of Electrogena from central Italy: Description of E-lunaris sp. n. (Ephemeroptera: Heptageniidae)
No full textA population of Electrogena from central Apennine (Italy), previously attributed to E. lateralis (Curtis) proved to be a new species after electrophoretic analysis. Imagines of the new species, named E. lunaris sp. n. differ from E. lateralis only by body and wing colouration. Larvae can be identified by numerical methods. Electrophoresis indicated three loci (Aldh, Gdh, Mpi) that are diagnostic between the syntopic populations of E. lunaris and E. lateralis, and the allele frequencies of three other loci (Est-2, Mdh-1, Pgm) were statistically different between the two species
Estimating genetic variation from larvae and adults of mayflies: An electrophoretic analysis of three species of Heptageniidae (Ephemeroptera)
No full textGenetic variation in larvae and imagines of three species of Heptageniidae from central Italy, Ecdyonurus sp. (venosus group), Electrogena grandiae (Belfiore, 1981), and Electrogenn lateralis (Curtis, 1834) was studied by starch-gel electrophoresis. Thirteen enzyme systems were analysed for a total of 20 loci (Aat, Ada, Adk-1, Adk-2, Ck-1, Ck-2, Est-1, Est-2, alpha-Gpdh, Gpi, La-1, La-2, Mdh-1, Mdh-2, Me-1, Me-2, Mpi, Pap, Pgm-1, Pgm-2), 15 of which were expressed in adults and 16 in the larvae. Only 11 loci (Aat, Ada, Est-2, Gpi, La-2, Mdh-1, Me-2, Mpi, Pap, Pgm-1, Pgm-2) were shared by larvae and adults. Observed heterozygosities were always lower than expected values; higher values were observed in larvae than in adults. Fixation indices and genetic distances were higher in the adults; however, the two genera were better discriminated using the larval samples. In conclusion, comparisons using larvae and adults simultaneously should be avoided, and absolute values of genetic identities and genetic distances to assess systematic levels have to be considered with caution, since they can vary from one developmental stage to another
Genetic variation and its causes in the crested newt, Triturus carnifex (Laurenti, 1768) from Italy (Caudata: Salamandridae)
No full textWe studied genetic variation in 107 individuals from 12 Italian populations of the crested newt, Triturus carnifex, by horizontal starch-gel electrophoresis to test the hypothesis of disjunction along the Central Apennine, as has been found in other animals. Twenty-eight presumptive loci were evidenced, 10 of which were monomorphic. Gene diversity was found to be high for salamandrids (mean percentage of polymorphic loci = 46.4, mean expected heterozygosity = 0.048, mean = 0.358) with about two-thirds due to within-population diversity. Both multidimensional scaling and neighbor-joining analyses on genetic distances (mean Nei's D = 0.131) between populations showed that these can be divided into two units, distributed north and south of the Central Apennines, respectively. Within-population gene diversity was found to be lower in the north-cluster, following a pattern of isolation-by-distance; this pattern was not observed in the south. We conclude that historical events (possibly glaciations) divided the populations into the two cited units. The genetic structure of T. carnifex in central and southern Italy somewhat parallels that of T. italicus from the same areas, thus suggesting a common evolutionary pattern of variation
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
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