1,721,060 research outputs found
Toxicity evaluation of natural and synthetic phenanthrenes in aquatic systems
No full textSeven natural 9,10-dihydrophenanthrenes were isolated from the common reed Juncus effusus by means of chromatographic processes and identified by spectroscopic means. Furthermore, mimics of natural isolated compounds were synthesized to try to evaluate the influence of functional groups on the dihydrophenanthrene skeleton. Syntheses of compounds were based on the cross-coupling of 1-(2-iodo-5-methoxy)phenyl-ethanol with variously substituted iodobenzenes by zerovalent nickel. All the chemicals were tested to evaluate their effects on freshwater organisms from different trophic levels. Toxicity tests were performed on reducers (the bacterium Escherichia coli); producers (the alga Raphidocelis subcapitata, previously known as Selenastrum capricornutum); and consumers including a rotifer (Brachionus calyciflorus), a cladoceran (Daphnia pulex), and an anostracan (Thamnocephalus platyurus). Results suggested no one organism was uniquely sensitive to the chemicals tested. Toxicity depended on the kind and position of substituents on the aromatic skeleton
Two new polyhydroxylated sterols from Ruppia maritima
No full textTwo new sterols have been isolated from the aquatic plant Ruppia maritima and their structures were established as (24R) ergosta-8,22-diene-3β,6β,7α-triol (1) and (24R) ergosta-8(14),22-diene-3β,6β,7α-triol (2) on the basis of spectroscopic analysis
TETRAHYDROPYRENE GLUCOSIDES FROM JUNCUS-EFFUSUS
No full textTwo tetrahydropyrene glucosides have been isolated from Juncus effuses and their structures determined by spectroscopic analysis and hemisynthesis. © 1995, Taylor & Francis Group, LLC. All rights reserved
Olive Wastes as a High-Potential by-Product: Variability of Their Phenolic Profiles, Antioxidant and Phytotoxic Properties
No full textThe global world olive oil industry produces large amounts of wastes and wastewaters. However, the disposal of these polluting by-products is a significant environmental problem owing to their high polyphenolic compounds. In order to learn possible ways of exploiting this waste, we investigated the phytochemical profiles, the phytotoxicity and the antioxidant activities of olive wastes (leaves, mill wastewater (OMWW) and mill solid waste (OMSW)). Leaf extracts exhibited the highest phytotoxic and antioxidant effects, which are mainly due to its phenolic content. The chromatographic profiles depicted eleven phenolic compounds belonging to secoiridoids, phenyl alcohols, phenolic acids, phenylethanoid glycoside, and flavonoids. Hydroxytyrosol and oleuropein were the main components in leaf methanol and OMWW extracts, respectively, exhibiting an amount of 13.05 and 4.39 mg/g DW. These results will help to demonstrate the possibility of utilizing olive wastes, particularly the leaf, as an inexpensive natural product, in food and agricultural applications. Graphic Abstract: [Figure not available: see fulltext.]
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
New dimeric phenanthrenoids from the rhizomes of Juncus acutus. Structure determination and antialgal activity
No full textIn a study of the allelochemical interactions between the wetland plant Juncus acutus and microalgae some dimeric dihydrophenanthrenoids have been isolated. The structures have been determined on the basis of their spectroscopic properties and their phytotoxicity was evaluated on Selenastrum capricornutum. © 2003 Elsevier Science Ltd. All rights reserved
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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