1,720,999 research outputs found
The integrity of lichen cell membrane is a suitable parameter for monitoring early biological effects of nitrogen pollution
No full textThis study aimed at testing the suitability of cell membrane integrity in the lichen Evernia prunastri (L.) Ach. as sensitive indicator of nitrogen (N) stress, to set up a rapid and effective method for monitoring biological effects of acute N pollution. Lichen samples were incubated in solutions of potassium nitrate, ammonium nitrate and ammonium sulphate at different concentrations, and cell membrane damage, expressed in terms of increased electrolyte leakage, was measured after 0, 24, 48 and 96 h. Cell membrane damage was observed in E. prunastri in the presence of high or very high N concentrations, irrespective of the compound supplied. Since the mycobiont represents the large majority of a lichen biomass, it is reasonable to assume that ion leakage mainly occurred from fungal cells. Although in biomonitoring studies the photobiont is usually regarded as the most sensitive partner of the lichen symbiosis, our findings suggest that the mycobiont is most affected in the case of N-excess, and that this feature can be used as suitable indicator of acute N stress episodes
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
Time- and dose-dependency of the effects of nitrogen pollution on lichens
No full textThe present work aims at testing if exposure time and dose play a role in the response of lichen species to nitrogen (N) pollution. To this purpose, samples of the N-sensitive Evernia prunastri and the N-tolerant Xanthoria parietina were treated for 5 weeks either with solutions of NH4NO3 0.05 and 1M, or (NH4)2SO4 0.025 and 0.5M. Photosynthetic efficiency was measured as an indicator of sample vitality. The results showed that the lowest concentrations were ineffective at the beginning, but after several supplies both compounds inhibited photosynthetic activity of E. prunastri. The highest concentrations had a deleterious effect, but with a temporal trend. For X. parietina no effect was found for the lowest concentrations, while the same trend shown by E. prunastri was instead observed following treatments with the highest concentrations. It was concluded that the response of lichens to N supply is not only species-specific, but also time- and dose-dependent. The results give a clue on field studies on the relationships between lichens and N pollution
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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