1,721,065 research outputs found
Microbial community composition and polysaccharide processing potential in the South Pacific Gyre
No full textThe South Pacific Gyre (SPG) covers 10% of the ocean's surface and is considered a marine biological desert. However, recent investigations have shown that primary production occurs throughout its deep euphotic zone and that this fuels the regeneration of nutrients and the recycling of organic matter. We set out to investigate the SPG's microbial communities' heterotrophic capability to utilize polysaccharides, an important marine organic matter component. Using fluorescently labeled polysaccharide (FLA-PS) incubations (Reintjes, et al., 2017), we analyzed the initial step of organic matter degradation by measuring both the rate of external hydrolysis and the rate of direct uptake of polysaccharides by marine microorganisms. Furthermore, we investigated the change in bacterial abundance and diversity during the FLA-PS incubations using direct cell counts and 16S rRNA sequencing. The presented dataset contains the microbial diversity, total cellular abundance, and direct FLA-PS uptake results generated during the FLA-PS incubations performed with six polysaccharides (laminarin, xylan, chondroitin sulfate, arabinogalactan, fucoidan, and pullulan) over 18 days. The incubations were performed with seawater from the epipelagic and bathypelagic (75 m, 160 m, 1250 m, and 2800 m) in the central gyre, and seawater from the epipelagic (75 m) at two stations adjacent to the gyre. Our study found that the SPG's microbial community showed remarkably high extracellular enzyme activities, and a considerable fraction of the microorganisms were capable of the direct uptake (selfish-uptake) of FLA-PS. Interestingly, a wide variety of bacteria were capable of cycling HMW organic matter using distinct polysaccharide processing mechanisms in the SPG. This research shows that the SPG features not only organisms capable of existing on the fine edge of minimal substrate concentrations but also those capable of taking advantage of abrupt changes in physical conditions and substrate availabilit
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
Depth related amino acid uptake by Prochlorococcus cyanobacteria in the Southern Atlantic tropical gyre
Full text linkAmbient concentrations and turnover rates of two amino acids, leucine and methionine, by total bacterioplankton and Prochlorococcus cyanobacteria were determined along a latitudinal transect across the Southern Atlantic gyre using a combined isotopic dilution and flow cytometric sorting technique. The ambient concentrations of methionine (0.2–0.65 nM) were about 2 times higher than the concentrations of leucine, while the turnover rates of the two amino acids were remarkably similar (0.1–0.7 nM d?1). The concentrations of both amino acids did not vary significantly with depth between 3 and 150 m but their turnover rates were 1.5–2 times higher in the top 3–80 m. Prochlorococcus took up amino acids in situ at high rates. Using a representative 35S-methionine precursor, about 25% of total bacterioplankton consumption of amino acids could be assigned to Prochlorococcus with low red fluorescence (Pro LRF) inhabiting the surface mixed layer down to 80 m and about 50% assigned to Prochlorococcus with high red fluorescence (Pro HRF) living below 100 m. In the same deep waters the cellular amino acid uptake of Pro LRF was less than 6% of that of the Pro HRF, indicating declining metabolic activity of the former. The mean cellular uptake rate of Pro HRF at depths below 120 m was 2.5 amol cell?1 d?1, 4 times higher than the rates of Pro LRF in the top 80 m. The difference could be partially explained by Pro HRF cellular biomass being twice that of Pro LRF. The biomass specific rates of Prochlorococcus were comparable or higher (particular of the Pro HRF) than that of other bacterioplankton. The reported findings could explain ecological success of mixotrophic Prochlorococcus cyanobacteria over both strictly autotrophic algae and heterotrophic bacteria in oligotrophic regions sustained by nutrient remineralisation
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
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