1,720,985 research outputs found
Phylogeny and karyotype evolution of the Iberian Leptynia attenuata species complex (Insecta Phasmatodea).
No full textAn in-depth analysis of the Leptynia attenuata species complex has been performed by cytochrome oxidase subunit 2 (cox2) gene sequencing as well as karyotype and allozyme analysis. The whole set of data allows to largely resolve the taxonomy of the group and suggests an overall trend of chromosomal repatternings through a progressive reduction of the chromosome number. A previously suggested new species has been also confirmed on a genetic basis. Data are discussed in order to depict a phylogenetic and phylogeographic scenario fitting the observed genetic relationships between the different species of the group. Chromosome rearrangements are proposed as the major speciation driving force within the group and androgenetic reproduction is suggested as a shortcut to overcome the problem of fixing chromosomal rearrangements that are strongly underdominant in heterozygotes
Parental species and hybrid descendants of Bacillus (Insecta Phasmatodea) show different patterns of highly amplified, colocalized ribosomal and telomeric sequences
Full text linkWe investigated by dual-color fluorescence in situ hybridization (FISH) with 28S ribosomal and (TTAGG)n telomeric probes all species of the circum-Mediterranean genus Bacillus encompassing bisexual and parthenogenetic taxa, namely the three parental species (B. grandii, B. atticus, B. rossius) and the two derived hybrids (B. whitei, B. lynceorum). Specimens were collected in Italian mainland, Sardinia and Sicily. In all species the presence of colocalized, highly amplified ribosomal and telomeric sequences was demonstrated by the double labelling of the cytological satellites. These satellites varied in size, number and location both among and within species. In B. grandii and B. atticus a maximum of two FISH-labeled locations were observed, whereas in B. rossius and in the two hybrids up to 11 different positions were recorded. Moreover, our investigations showed a significant occurrence of chromosome breakages and rearrangements. The overall meaning of the ribosomal and telomeric sequence colocalization as well as the Nucleolar Organizer Region mobility and activity are discussed in both the ancestors and their hybrid descendants. It is noteworthy that the same trait has been shown in seven additional phasmid species belonging to distantly related genera. This trait could be a shared ancestral character in phasmids
Co-localization of ribosomal and telomeric sequences in Leptynia (Insecta: Phasmatodea)
No full textStick insects have been studied mainly for non-conventional reproduction modes, such as parthenogenesis, hybridogenesis and androgenesis. Parallel karyological investigations have evidenced extensive numerical and structural chromosome re-patterning, particularly evident in hybrid parthenogenetic taxa. Chromosome sets of bisexual Leptynia (Pantel) species show an evolutionary trend from 40 to 36 chromosomes and are characterized by cytological atellites of variable size and localization. We performed fluorescence in situ hybridization (FISH) analysis using 45S ribosomal genes and pentameric (TTAGG)n telomere sequences as probes in two strictly related but karyotypically distinct species, L. montana Scali (2n = 38/37; XX/XO) and L. attenuata Pantel (2n = 36). L. attenuata has recently been split into three subspecies (L. attenuata attenuata, L. attenuata iberica and L. attenuata algarvica), and found to share an XX/XY sex chromosome formula, unusual for stick insects. FISH by 45S rDNA sequences consistently labelled the short arm of the 4th chromosome pair, often of a variable size. Silver staining showed that nucleolar organizer regions (NORs) are active. FISH of the telomeric repeats, besides ordinary telomeres, also labelled the short arm of this same pair. The use of both probes in double FISH analysis fully confirmed the co-localization of ribosomal and telomeric
highly repeated sequences. Since it is increasingly emerging that the co-localization of NORs and telomeric sequences appears to be a feature shared by evolutionarily distant animals, its possible role is discussed
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
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