1,720,984 research outputs found
Note preliminari sullo status tassonomico e la corologia italiana di Chalcolestes parvidens (st. nov.) (Odonata: Lestidae)
No full textMolecular re-examination of the taxonomy of the Meligethes viridescens species-complex (Coleoptera: Nitidulidae).
No full textBiochemical systematics and phylogeography of Percus scrictus subspecies (Coleoptera: Carabidae) endemic to Sardinia
No full textSpecific distinction by allozimic data of sympatric species of anthophagous beetles (Coleoptera: Nitidulidae).
No full textMolecular phylogeny of two lineages of Leuciscinae cyprinids (Telestes and Scardinius) from the peri-Mediterranean area based on cytochrome b data.
Full text linkWe examined phylogenetic relationships in two lineages of Leuciscinae cyprinid fishes based on the sequence data of the complete
mitochondrial DNA region coding for the cytochrome b gene (1140 bp). Telestes includes obligate riverine, moderately cold wateradapted
species whereas Scardinius comprises warm-adapted species living in lowland lakes and still waters of rivers and streams.
We also analysed selected representatives of Leuciscus and Phoxinellus because the taxonomic status of some species belonging to
these genera is dubious and they could be placed in the genus Telestes. The study includes 18 species, 43 populations, and 111
individuals from 9 of the 14 peri-Mediterranean ichthyogeographic districts. Clades recovered from the phylogenetic analyses do not
support previous taxonomic assumptions based on morphology. Telestes, Leuciscus, and Phoxinellus do not form monophyletic
assemblages; phylogenetic analyses suggest that L. polylepis, L. turskyi, P. croaticus, and P. metohiensis should be included in
Telestes. Similarly, populations of Scardinius erythrophthalmus do not cluster together and the endangered S. scardafa, endemic to
central Italy and surviving in a single locality, is nested within them. The radiations of Telestes and Scardinius occurred in different
time periods. A major diversification of Telestes is consistent with a sea dispersal during the freshwater Messinian ‘‘Lago Mare’’
phase of the Mediterranean Sea. Cladogenetic events within Scardinius are likely related to the extension and confluence of river
drainages in lowlands following multiple lowering of the sea level during the Quaternary glaciations
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
Bottleneck effects and the depression of genetic variability in hatchery stocks of Penaeus japonicus (Crustacea, Decapoda)
No full textAquaculture of Penaeus japonicus is developing in Italy at a production level. Genetic analysis of the founder stock and five subsequent hatchery generations revealed a constant reduction in levels of allozyme polymorphism. Average heterozygosity decreased from 0.102 to 0.039. The magnitude of the reduction in heterozygosity was much higher than expected from the numbers of breeders placed into spawning tanks at each reproductive cycle. We estimated, under the assumption of neutrality, that the effective number of parents contributing to each broodstock might have been as low as four, although the number of shrimp pairs held in spawning tanks varied from 50 to 300 after an initial bottleneck occurred in the first generation. This discrepancy may be explained as the combined effect of some common farming practices and it points out the importance of a careful check of the number of spawners actually contributing to each reproductive cycle. © 1986
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
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