1,720,973 research outputs found
Water acidification: effects on the macroalgal community
No full textRecent researches, performed in a naturally acidified site (Castello Aragonese d’Ischia - Gulf of Naples, Italy) where volcanic carbon dioxide vents cause long-term changes in seawater carbonate chemistry, lowering the pH from 8.17 down to 6.57, reveal winners and losers within the benthic community. In the same site, we chose to address the impact of ocean acidification on the algal community with an integrated approach by means of ecological, physiological and molecular tools. Qualitative and quantitative changes in algal composition have been detected. Results showed a less structured community at low pH, characterized by few dominant species and the lack of calcareous taxa. Due to their different tolerance to pH variations, three target species (Sargassum vulgare, Dictyota dichotoma and Jania rubens) have been selected to carry out transplant experiments in order to detect short term stress signals. Variations in fluorometry-derived parameters of the photosynthetic performance of these species were detected in situ at different pH conditions by means of a Diving-PAM. In order to understand if the chronic lowering of pH of this site has promoted any local adaptations (morphological and/or genetic), the Dictyota complex species have been selected. Results indicate that our integrated approach is the key factor leading to understand how these changes can drive deteriorations in the structure and function of algal assemblages under the effects of water acidification
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
Physiological responses of a population of Sargassum vulgare (Phaeophyceae) to high pCO2/low pH: implications for its long-term distribution.
No full textOcean Acidification (OA) is likely to affectmacroalgal diversity in the futurewith species-specific responses shaping macroalgal communities. In this framework, it is important to focus research on the photosynthetic response of habitat-forming species which have an important structural and functional role in coastal ecosystems. Most of the studies on the impacts of OA involve short-term laboratory or micro/mesocosmexperiments. It is more challenging to assess the adaptive responses of macroalgal community to decreasing ocean pH over long-term periods, as they represent the basis of trophic dynamics in marine environments. This work aims to study the physiological traits of a population of Sargassum vulgare that lives naturally in the high pCO2 vents system in Ischia (Italy), in order to predict the species behaviour in a possible OA future scenario. With this purpose, the photosynthetic
performance of S. vulgare was studied in a wild, natural population living at lowpH (6.7) as well as in
a population transplanted fromnative (6.7) to ambient pH (8.1) for threeweeks. The main results show that the photochemical activity and Rubisco expression decreased by 30% after transplanting, whereas the non-photochemical dissipation mechanisms and the photosynthetic pigment content increased by 50% and 40% respectively, in order to compensate for the decrease in photochemical efficiency at low pH. Our data indicated a stress condition for the S. vulgare population induced by pH variation, and therefore a reduced acclimation capability at different pH conditions. The decline of the PSII maximum quantum yield (Fv/Fm) and the increase of PARP enzyme activity in transplanted thalli further supported this hypothesis. The absence of the species at ambient pH conditions close to the vent system, as well as the differences in physiological traits, suggest a local adaptation of S. vulgare at pH 6.7, through optimization of photosynthetic performance
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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