1,721,053 research outputs found
Medium-term response of microbial community to rhizodeposits of White clover and ryegrass and tracing of active processes induced by C-13 and N-15 labelled exudates
No full textRhizodeposition affects the microbial community in the rhizosphere, and microbial composition and activity may therefore differ in soil depending on plant species. We hypothesised that these differences increase over the plant growth period because roots occupy larger soil volumes and release more rhizodeposits. We tested how such medium-term responses of the microbial community can be explained by the short-term utilisation of root exudates. To test this we analysed N-15 incorporation into microbial biomass, phospholipid fatty acid (PLFA) composition and C-13 incorporation into the PLFAs of specific microbial groups in soil under white clover (Trifolium repens L.) and ryegrass (Lolium perenne L) following leaf-labelling with C-13-bicarbonate and N-15-urea. In this way microbial N and N-15 and the composition of PLFAs reflect the medium-term (two months) response of microorganisms to rhizodeposits, whereas the C-13-label of the PLFAs reflects the short-term (one week) utilisation of root exudates following labelling of shoots. In the medium term, microbial biomass N and N-15 were greater under the ryegrass, whereas total PLFA was higher under white clover. The relative abundance of fungi and actinomycetes was unaffected by plant species, but pool of Gram-negative and Gram-positive bacteria was greater under white clover at the 10 percent significance level. In the short term, microorganisms more actively utilised fresh exudates (C-13-labelled) of ryegrass than of white clover. We expected ryegrass exudates initially to be incorporated into bacterial PLFA and into fungi over time, but surprisingly fungi had the highest utilisation of ryegrass-derived C over the week. At 0-5 cm soil depth, white clover exudates were utilised only by bacteria, whereas fungi dominated at 5-15 cm. This reflects differences in the quality of white clover exudates or differences in the microbial community composition at the two depths. We conclude that despite clear short-term differences in microbial response to the exudates of white clover and ryegrass, this is only to a limited extent transferred into medium-term defects on the composition of the microbial communities under the two plant species. Hence, our study showed that different short-term C utilisation patterns may lead to similar medium-term responses of the microbial community. (C) 2014 Elsevier Ltd. All rights reserved
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
Get PDFWe 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
Get PDFWe 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
Bicarbonate as tracer for assimilated C and homogeneity of C-14 and N-15 distribution in plants by alternative labeling approaches
No full textApplication of carbon (C) and nitrogen (N) isotopes is an essential tool to study C and N flows in plant-soil-microorganisms systems. When targeting single plants in a community the tracers need to be added via e.g., leaf-labeling or stem-feeding approaches. In this study we: (i) investigated if bicarbonate can be used to introduce C-14 (or C-13) into white clover and ryegrass, and (ii) compared the patterns of C-14 and N-15 allocation in white clover and ryegrass to evaluate the homogeneity of tracer distribution after two alternative labeling approaches. Perennial ryegrass and white clover were pulse labeled with N-15 urea via leaf-labeling and C-14 either via a (CO2)-C-14 atm or with C-14 bicarbonate through leaf-labeling. Plants were sampled 4 days after labeling and prepared for bulk isotope analysis and for C-14 imaging to identify plant parts with high and low C-14 activity. Subsequently, plant parts with high and low C-14 activity were separated and analyzed for N-15 enrichment. Bicarbonate applied by leaf-labeling efficiently introduced C-14 into both white clover and ryegrass, although the C-14 activity in particular for white clover was found predominantly in the labeled leaf. Using C-14 imaging for identification of areas with high (hotspots) and low C-14 activity showed that C-14 was incorporated very heterogeneously both when using bicarbonate and CO2 as expected when using pulse labeling. Subsequent analysis of N-15 enrichment in plant parts with high and low C-14 activity showed that N-15 also had a heterogeneous distribution (up to two orders of magnitude). Bicarbonate can efficiently be used to introduce C-14 or C-13 into plant via the leaf-labeling method. Both C-14 and N-15 showed heterogeneous distribution in the plant, although the distribution of N-15 was more even than that of C-14
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
- …
