1,721,135 research outputs found
Accelerated light-induced necrosis in an Arabidopsis thaliana triple mutant deficient in vitamin C and stromal and thylakoid chloroplast ascorbate peroxidases
No full textAscorbate (vitamin C) and ascorbate peroxidases (APXs) are part of a multi-layered defense system that protects the cell from damage by reactive oxygen species (ROS). In this study, we investigated the combined functional significance of the soluble stromal ascorbate peroxidase (SAPX) and the thylakoid bound isoform (TAPX) in chloroplasts of Arabidopsis thaliana. In addition, an APX-like protein is present in the thylakoid lumen. We generated homology models for these three chloroplast APXs, and showed that the lumenal APX-like protein is not a bona fide ascorbate peroxidase. A null mutant in this lumenal APX behaved as wild-type under different light regimes. Single and double T-DNA-tagged null mutants in SAPX and TAPX were obtained and were each crossed with vtc2, partially deficient in ascorbate accumulation (Conklin et al, 2000). The single mutants (sapx, vtc2 and tapx), double mutants (sapx-vtc2, tapx-vtc2, and tapx-sapx), and the triple mutant (tapx-sapx-vtc2) were all viable on soil. We determined levels of α-tocopherol, ascorbate and glutathione, as well as growth parameters, photosynthetic activity and H2O2 accumulation in the mutants. All vtc2 genotypes accumulated more glutathione, most likely to compensate for the 80% loss of ascorbate. Anthocyanin accumulation increased under light stress conditions, but was strongly reduced in the vtc2 background. Surprisingly, single, double and triple mutants did not show significant differences in light sensitivity when constantly grown under moderate or high light intensities. However, when mutants were shifted from moderate to high light (120 to 1000 μmol photons m-2sec-1), fully expanded leaves in the triple mutant rapidly showed necrotic lesions in the mesophyll but not in the vasculature. Necrosis in the triple mutant was concomitant with accumulation of H2O2 in the cell. tapx-vtc2 and sapx-vtc2 also showed signs of necrosis, but significantly less than the triple mutant. Importantly, tapx-sapx did not show any light stress symptoms, or H2O2 accumulation upon shift to high light, suggesting that other peroxidase activities are sufficient to detoxify H2O2 when cellular ascorbate concentration is not limiting
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
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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