1,720,978 research outputs found
Biscopyran, a phytotoxic hexasubstituted pyranopyran produced by Biscogniauxia mediterranea, a fungus pathogen of cork oak
No full textA new phytotoxic hexasubstituted pyranopyran, biscopyran, was isolated together with phenylacetic acid and previously isolated 5-methylmellein from the liq. culture filtrates of Biscogniauxia mediterranea, a major fungal pathogen involved in oak decline in Sardinia. Biscopyran was characterized by spectroscopic methods as a new (Z)-2-methoxy-1-[7-((Z)-2-methoxybut-2-enoyl)-3,4,5,6-tetramethyl-2H,7H-pyrano[2,3-b]pyran-2-yl]but-2-en-1-one. Biscopyran assayed at 0.26-0.026 mM concn. range caused epinasty on cork oak cuttings. On a nonhost plant, tomato, biscopyran caused wilting. Phenylacetic acid, assayed at the same concn., was toxic to Quercus suber, while on tomato cuttings it induced internal tissue collapse on the stem
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
Bioactive metabolites produced by the fungal pathogens Diplodia fraxini and Hymenoscyphus fraxineus isolated from infected Fraxinus spp. trees
No full textDuring the last two decades widespread ash population decline has happened in Europe. This epidemic disease, commonly known as ash dieback, is the result of biological invasions by the two ascomycetes fungi Diplodia fraxini and Hymenoscyphus fraxineus. On Fraxinus spp. both fungi are able to cause the same symptoms, corresponding to the typical ones due to the infections of Diplodia
species on woody hosts characterized by V-shaped necrotic sector visible in cross section.1
D. fraxini is a fungus belonging to the Botryosphaeriaceae family. It was found to be a pathogen associated to symptomatic Fraxinus angustifolia trees in South Europe and isolated also from branch and twigs of Fraxinus excelsior in initial and advanced stages of dieback in Poland.
A new phytotoxic isochromanone, named fraxitoxin (1, Fig. 1), was isolated together with (–)-mellein and tyrosol, already known toxic fungal metabolites, from the organic extract of the D. fraxini culture filtrates.1 The structure of fraxitoxin was characterized using spectroscopic methods (essentially NMR and HR-EI-MS) while its absolute configuration was assigned by electronic circular dichroism (ECD) measurements and calculations.
H. fraxineus is a fungus belonging to the Helotiaceae family. It was identified as the pathogen causing the F. excelsior dieback in Europe. H. fraxineus was introduced in Europe from Asia and has gradually spread from East to West continental Europe including the British Isles.2 Viridiol (2, Fig. 1) was isolated as the most abundant and phytotoxic metabolite, from the organic extract of the H. fraxineus culture filtrates.3 The purification and chemical and biological characterization of these two metabolites as well as those of other related compounds will be illustrated in this communication
Viridepyronone, a New Antifungal 6-Substituted 2H-Pyran-2-one Produced by Trichoderma viride
No full textA new antifungal 6-substituted 2H-pyran-2-one, named viridepyronone, has been isolated from a cultural filtrate of a strain of Trichoderma viride showing antagonistic activity in vitro toward Sclerotium rolfsii, which is the causal agent of crown and stem rot of artichoke. Viridepyronone was characterized as 6-(4-oxopentyl)-2H-pyran-2-one 2 with spectroscopic methods. Bioassays showed that viridepyronone had a good antifungal activity against S. rolfsii, and its minimum inhibitory concentration (over 90% inhibition) was found to be 196 μg/mL. This is the first report of viridepyronone produced by any species of fungi
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
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