1,721,001 research outputs found
Meiofaunal diversity and assemblage structure in a shallow-water hydrothermal vent in the Pacific Ocean
No full textConcerted proton electron transfer or hydrogen atom transfer? an unequivocal strategy to discriminate these mechanisms in model systems
No full textConcerted proton electron transfer (CPET) and hydrogen atom transfer (HAT) are two important mechanisms in many fields of chemistry, which are characterized by the transfer of one proton and one electron. The distinction between these mechanisms may be challenging in several reactions; thus, different computational methods have been developed for this purpose. In this work, we present a computational strategy to distinguish the two mechanisms, rationalizing the factors controlling the reactivity in four different model reactions. Fist, the transition state SOMO (singly occupied molecular orbital) is visualized, presenting all the limits and ambiguities of this analysis. Then, the electron flow along the reaction path is evaluated through the intrinsic bond orbitals (IBOs); this analysis allows to describe correctly the mechanism of each reaction in agreement with previous studies. Furthermore, some structural modifications are applied to the transition state of each system and the energetic differences are rationalized in the framework of the activation strain analysis to understand the geometrical and electronic factors governing the reactivity and the selection of CPET or HAT mechanism. Lastly, the effect of the donor-acceptor distance is evaluated. It emerges that a combined computational analysis is crucial to understand not only the distinction between the two mechanisms, but also the molecular reasons why one mechanism is operative in a specific reaction
Organic matter composition, metazoan meiofauna and nematode biodiversity in Mediterranean deep-sea sediments
No full textTo identify the relationships between the abundance and biodiversity of deep-sea meiofauna and their food resources in the Tyrrhenian Sea (Mediterranean Sea), we have investigated the quantity and biochemical composition of sediment organic matter, the metazoan meiofauna abundance and biomass, and the nematode biodiversity at meso- (>50 km) and/or local (<1 km) scales. Sediment samples were collected at four deep-sea sites (from 3430 to 3581 m in depth), two of which were close to two seamounts. The analysis of variance revealed significant differences at both the meso- and local scales (i.e. between sites and between stations at each site), and showed that the variability at the mesoscale was much higher than that at the local scale. The values of all of the investigated variables were generally lowest in sediments surrounding the seamounts, suggesting a role for these submersed structures in the abundance of the metazoan meiofauna and their resources. The nematode assemblage composition changed significantly across the four sites. Among the 96 identified nematode species, 14 were exclusively seen in sediments around the two seamounts, and only three species were present at all sampling stations. Differences in the trophic structures of the nematode assemblages were also linked with differences in the biochemical composition of sediment organic matter. These results indicate that high β-diversity in soft sediments around deep seamounts is associated with diversification of the benthic food webs, and suggest that while making the sediments poorer for food availability for benthic consumers, the presence of seamounts enhances the biodiversity in neighbouring sediment
Metazoan meiofauna in deep-sea canyons and adjacent open slopes: A large-scale comparison with focus on the rare taxa
No full textα-, β-, γ-, δ- and ε-diversity of deep-sea nematodes in canyons and open slopes of Northeast Atlantic and Mediterranean margins.
No full textOrganic matter composition, metazoan meiofauna and nematode biodiversity in Mediterranean deep-sea sediments
No full text
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
- …
