1,720,991 research outputs found
Constituents of Cupuliferae. XIII. New and revised structures of acylated flavonoids from Quercus suber L
No full textFrom leaves of Quercus suber L. in addition to ten known glycosides, two new acylated flavonoids have been isolated and identified as 3-O-kaempferol 2-O-(trans-p-coumaroyl)-beta-D-glucopyranoside (1) and 3-O-kaempferol 2,3-di-O-acetyl-4-O-(cis-p-coumaroyl)-6-O-(trans-p-coumaroyl)-beta-D-glucopyranoside (3). The structures of the previously described 3-O-kaempferol 2,4-di-O-(trans-p-coumaroyl)-beta-D-glucopyranoside2) and 3-O-kaempferol 3,6-di-O-acetyl-2,4-di-O-(trans-p-coumaroyl)-beta-D-glucopyranoside3) were revised to 3-O-kaempferol 2,6-di-O-(trans-p-coumaroyl)-beta-D-glucopyranoside (4) and 3-O-kaempferol 3,4-di-O-acetyl-2,6-di-O-(trans-p-coumaroyl)-beta-D-glucopyranoside (5)
Constituents of Fagaceae (Cupuliferae). Triterpene saponins and acylated flavonoids from Quercus robur stenocarpa.
No full textIn addition to four known glycosides from leaves of Quercus robur L. var. stenocarpa Beck. a new triterpene saponin has been isolated and identified as 28-beta-D-glucopyranosyl ester of the 2 alpha,3 beta,19 alpha-trihydroxy-olean-12-ene-24,28-dioic acid (1)
Analisi delle popolazioni siciliane di Helichrysum: propagazione in vitro e indagini fitochimiche
No full textThe Sicilian populations of Helichisum have got a germoplasm from which it is possible to select ornamental plants to be placed in a mediterranean and/or dry climate. The in vitro trials show an attitude for microprapagation
and multiplication for commerciaI productions that can be used also for the re·introduction in the natural habitat. The highest multiplication rate belongs to three genotypes: H. hyblaeum (clone S6), H. nebrodense (Clone Cli) and H.
rupestre var. rupestre (clone S2, S11). The height and the feature of the vitro plants are pecuIiar for each different clone. The clone S11 is suitable for the production of pot plants or bushes, the clone S2 and S6 for garden edge. The
clones S2 and S11 of H. rupestre develop plants which are morphologically well differentiated showing that the wild population is characterized by genetic variability intrapopulation which is reflected phenotypical by variability.
The buthanolic extract shows the presence mainly of flavonoidic substances, their distribution inside the sampled populations shows a specific quality pattern which can contribute to taxonomic studies on Helichrysum genus. The
richest populations in order or flavonoids can be referred to H. italicum, H. litoreum e H. scandens
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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