1,720,990 research outputs found
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
Unravelling the DNA sequences carried by Streptomyces coelicolor membrane vesicles
Full text linkMembrane vesicles (MVs) are spherical particles with nanoscale dimensions and characterized by the presence of diverse cargos, such as nucleic acids, proteins, lipids, and cellular metabolites. Many examples of (micro)organisms producing MVs are reported in literature. Among them, bacterial MVs are of particular interest because they are now considered as the fourth mechanism of horizontal gene transfer. Streptomyces bacteria are well-known for their ecological roles and ability to synthesize bioactive compounds, with Streptomyces coelicolor being the model organism. It was previously demonstrated that it can produce distinct populations of MVs characterized by different protein and metabolite cargos. In this work we demonstrated for the first time that MVs of S. coelicolor carry both DNA and RNA and that their DNA content represents the entire chromosome of the bacterium. These findings suggest that MV DNA could have a role in the evolution of Streptomyces genomes and that MVs could be exploited in new strain engineering strategies
Cloning of two DNA fragments which complement hisD mutation in Streptomyces coelicolor A3(2).
No full textRehabilitation of Mediterranean anthropogenic soils using symbiotic wild legume shrubs: Plant establishment and impact on the soil bacterial community structure
No full textSusceptibility to desertification in southern Europe is increasing and rehabilitation of desertification-threatened Mediterranean soils is a challenge due to the inhospitality of the environment. In particular, recovery of anthropogenic soils (mainly human-derived artefacts from housing construction and other inert materials or topsoil of terminal phase municipal landfills) cannot rely on spontaneous processes and low-cost/low-impact strategies are needed to prevent desertification. Mediterranean wild legume shrubs have great potential for soil recovery and conservation against desertification, thanks to drought resistance, and their symbiosis with N2-fixing rhizobia and arbuscular mycorrhizal fungi. In this study double inoculated autochthonous wild legume shrubs (the genistea Spartium junceum L. and the thermopsidea Anagyris foetida L.) were used in a long-term trial to recover an anthropogenic hill in a semi-arid site of southern Italy, mainly composed of inert and human-derived artefacts.
Microbial inoculants strongly enhanced plant establishment and growth on the anthropogenic soil in the greenhouse and in the field up to two years. Automated Ribosomal Intergenic Spacer Analysis (ARISA) and bacterial cultivation revealed a dramatic effect of the tripartite symbiosis on the structure of soil bacterial communities that largely overcomes plant species effect and suggests synergism of AMF with the bacterial community of the mycorhizosphere. Our results demonstrate that microsymbiont inoculation on wild legume shrubs is a promising strategy to rehabilitate anthropogenic soils in Mediterranean semi-arid regions
Clonaggio e caratterizzazione di un gruppo di geni biosintetici di istidina Streptomyces coelicolor.
No full textBradyrhizobium sp. nodulating the Mediterranean shrub Spanish broom (Spartium junceum L.)
Full text linkAims: The molecular diversity of 25 strains of rhizobia, isolated in Sicily from root nodules of the Mediterranean shrubby legume Spanish broom (Spartium junceum L.), is presented in relation to the known rhizobial reference strains.
Methods and Results: Our approach to the study of the S. junceum rhizobial diversity combined the information given by the 16S and the intergenic spacer (IGS) 16S–23S rDNA polymorphic region by obtaining them in a single polymerase chain reaction (PCR) step. The PCR fragment size of the S. junceum isolates was 2400–2500 bp and that of the reference strains varied from 2400 in Bradyrhizobium strains to 2800 in Sinorhizobium strains. Inter- and intrageneric length variability was found among the reference strains. Restriction fragment length polymorphisms (RFLP) analysis allowed us to identify eight genotypes among the S. junceum rhizobia that were clustered into two groups, both related to the Bradyrhizobium lineage. Sequencing of representative strains of the two clusters confirmed these data. The 16S–IGS PCR–RFLP approach, when applied to rhizobial reference strains, allowed very close species (i.e. Rhizobium leguminosarum/R. tropici) to be separated with any of the three enzymes used; however, cluster analysis revealed inconsistencies with the 16S-based phylogenesis of rhizobia.
Conclusions: Rhizobia nodulating S. junceum in the Mediterranean region belong to the Bradyrhizobium lineage. Our results confirm the resolution power of the 16S–23S rDNA in distinguishing among rhizobia genera and species, as well as the usefulness of the PCR–RFLP method applied to the entire 16S–IGS region for a rapid tracking of the known relatives of new isolates.
Significance and Impact of the Study: The present paper is, to our knowledge, the first report on rhizobia nodulating a Mediterranean wild woody legume
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