1,720,978 research outputs found
Identification of phytotoxic metabolites of a new Fusarium sp. inhibiting germination of Striga hermonthica seeds
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Development of a rapid and sensitive HPLC method for the identification and quantification of cavoxin and cavoxone in Phoma cava culture filtrates
No full textCavoxin is a tetrasubstituted phytotoxic chalcone and cavoxone is the corresponding chroman-4-one, both produced in vitro by Phoma cava, a fungus isolated from chestnut. Cavoxin showed biofungicide potential against fungal species responsible for food moulding. Therefore, cavoxin has potential to be incorporated into biopolymer to generate ‘intelligent food packaging’. To reach this objective, large-scale production of cavoxin by P. cava fermentation needs to be optimized. A rapid and efficient method for cavoxin analysis, as well as of cavoxone, in the fungal culture filtrates and the corresponding organic extracts is the first experimental step. Thus, a HPLC method was developed and applied to quantify cavoxin and cavoxone production in two different fungal culture conditions. The analysis proved that cavoxin production in stirred culture filtrates is significantly higher than in static ones
Augmented phytotoxic effect of nanoencapsulated ophiobolin A
No full textOphiobolin A is a secondary phytotoxic metabolite produced by some pathogenic fungal species responsible for severe plant diseases, considered to play a role in disease development and symptom appearance. Herein we investigated whether the phytotoxic activities of ophiobolin A against weed species could be improved by nanoencapsulation. Given the rapid natural degradation of the compound, it was hoped that nanoencapsulation would prolong the phytotoxic effects or enhance the bioactivity, thus leading to improved weed control capabilities. This article presents an assessment of the effectiveness of encapsulated ophiobolin A on 11 commonly found weed species, compared to the pure ophiobolin, to the particle alone, and a combination of mixed particles and ophiobolin A, by applying the solution droplets to both intact or injured leaf surface, on the adaxial or abaxial side. The bioassays showed the improved efficacy of the encapsulated ophiobolin, and the need for leaf lesions to diffuse the particles into the tissues.[Formula: see text]
Terpestacin, a toxin produced by Phoma exigua var. heteromorpha, the causal agent of a severe foliar disease of oleander (Nerium oleander L.)
No full textSince 1987, several cytochalasins were isolated from Phoma exigua var. heteromorpha, the causal agent of foliar blight disease of oleander (Nerium oleander L.), and chemically and biologically characterised. During the purification process of a large-scale production of cytochalasins A and B, necessary to continue the study on their anticancer activity, a metabolite having a different carbon skeleton compared to that of cytochalasans, was isolated. It was identified as terpestacin, a well-known toxic fungal stestertepenoid, isolated for the first time from P. exigua var. heteromorpha, by spectroscopic investigation (essentially 1D and 2D 1H and 13C-NMR and ESI MS) and optical methods in comparison with the literature data. Terpestacin and some its derivatives (including a natural one, fusaproliferin) were prepared and tested for their biological activity. Terpestacin and fusaproliferin had some inhibitory effects on seed germination of Phelipanche ramosa, whereas none of the compounds caused phytotoxic effects on weed leaves.[Formula: see text]
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
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