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Denitrification, nitrogen fixation, community primary productivity and inorganic-N and oxygen fluxes in an inter-tidal Zostera noltii meadow
No full textDenitrification, nitrogen fixation, community primary productivity and inorganic-N and oxygen fluxes in an intertidal Zostera noltii meadow
No full textRates of denitrification, N-fixation, gross community primary productivity, inorganic-N and oxygen fluxes were determined in February, May and October 1997 in an intertidal Zostera noltii meadow of the Bassin d’Arcachon, French Atlantic coast. Rates of gross community primary productivity were high, 0.09 to 0.40 g C m–2 h–1; high P:R ratios of 1.64 to 2.82 define the system as highly autotrophic and indicate significant losses of carbon via export and/or burial of biomass. Fluxes of DIN, nitrate and ammonium were large (–0.8 to –2.4, –0.1 to –2.2 and –0.1 to –0.7 mmol N m–2 h–1, respectively) and always directed towards the plants/sediment during both light and dark incubations. The contributions of nitrate, nitrite and ammonium to total DIN fluxes reflected their relative abundance in the water column, indicating that there was no assimilatory selection of inorganic-N sources by the plants. The DIN fluxes were dominated by the N-assimilation activity of the plants even during dark incubations, as removal of the plant shoots prior to incubations essentially abolished nitrate fluxes and reversed ammonium fluxes, resulting in substantial effluxes. Thus, inorganic-N fluxes were controlled principally by the Z. noltii and epiphyte biomasses and their primary productivity, rather than the water column concentrations of DIN. Surprisingly, the plant community showed a high dark assimilation activity for inorganic-N, and differences in light and dark fluxes of DIN, nitrate and ammonium were never significant. Data indicate that, whilst DIN fluxes could supply the N-demand of primary production in spring, the plants became increasingly dependent upon sediment N-pools, N-fixation and internal N-reserves through summer into autumn. Denitrification rates determined by the 15N-isotope pairing technique were extremely low, ranging between 2 and 6 μmol N m–2 h–1. Rates of denitrification of nitrate diffusing from the overlying water were consistently below 2 μmol N m–2 h–1 during both light and dark incubations and represented only 0.1 to 0.7% and 0.2 to 1.3% of the total light and dark nitrate fluxes, respectively. Similarly, rates of denitrification coupled to nitrification were consistently low, probably due to the competition between nitrifying bacteria and the Z. noltii roots for ammonium. N-fixation rates varied between 4 and 17 μmol N m–2 h–1 and were substantially greater than N-losses via denitrification in all seasons, with net N2 inputs ranging between 2.5 and 14.6 μmol N m–2 h–1 and 0.5 and 3.8 μmol N m–2 h–1, during light and dark incubations. Overall, our data demonstrate that the Z. noltii meadows represent a highly conservative environment for nitrogen, where the N cycle is dominated by the primary productivity of the plant community and the associated assimilatory demand for fixed-N to support this productivity. Conversely, N-losses via denitrification are extremely low and are more than balanced by N-inputs from N-fixation. Thus, in this macro-tidal lagoon, export of nitrogen as plant biomass and/or N-burial in the sediments are probably the major loss mechanisms for anthropogenic N-inputs
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
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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