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Fungal metabolites. 44 - Isolation of a new caryophyllane ester from Lactarius subumbonatus: Conformational analysis and absolute configuration
No full text(1R,GR,SS)-6-Hydroxycaryophyllene (S)-6-hydroxystearate, a sesquiterpene alcohol esterified by the unusual fatty acid (S)(+)-6-hydroxystearic acid, has been isolated from the fruiting bodies of the Basidiomycete Lactarius subumbonatus. Both NMR data and AM1 calculations indicate that the caryophyllene macrocyclic ring adopts a beta beta conformation. The absolute configuration of the sesquiterpene moiety has been established by theoretical Circular Dichroism calculations (De Voe coupled oscillators theory) and that of the Salty acid by NMR studies of the (R)-2-methoxy-2-naphthylacetic acid (2-NMA) ester
Late Seventeenth-Century ‘Scientific’ Academies in Rome and the Cimento’s Disputed Legacy
No full textAb initio and density functional evaluations of the molecular conformations of beta-caryophyllene and 6-hydroxycaryophyllene
No full textThe four conformations of beta -caryophyllene (alpha alpha, alpha beta, beta alpha, and beta beta) were investigated ab initio at the 6-31G*/HF and MP2 levels and additionally hth density functional methods (B3LYP/6-31G*), as it concerns their relative thermodynamic stabilities. The alpha alpha is predicted to be the most stable geometry, in agreement with low-temperature NMR measurements. In the case of 6-hydroxycaryophyllene, the alpha alpha is still the most stable conformation when the configuration at C-6 is S, but when the configuration is reversed to R the beta beta geometry becomes the most stable one. This is again in agreement with NMR data. On the other hand, for both molecules the AM1 semiempirical model Hamiltonian fails to predict the alpha alpha as a low-energy geometry, mainly due to an incorrect description of the cyclobutane ring puckering. The interconversion paths among the different minima are also analyzed and discussed. The solvent effect (either chloroform or water) on the stability of the different conformers of beta -caryophyllene and 6-hydroxycaryophyllene was studied in the polarizable continuum model framework
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
Fungal metabolites. Part 45: The sesquiterpenes of Collybia maculata and Collybia peronata
No full textThe sesquiterpenes of Collybia maculata and C. peronata (Basidiomycetes) have been reinvestigated. In addition to collybolide, isocollybolide and deoxycollybulidol, five new structurally related sesquiterpene lactones have been isolated. The structures have been established by spectroscopic methods. Stereochemical assignments required a derailed conformational investigation, which has been carried out at the AM1 level fur all compounds, and at the B3LYP level for some of them. This led to the inversion of the previously proposed C-7 configuration of deoxycollybolidol. The absolute configuration of collybolides could tentatively be inferred from CD studies. (C) 2001 Elsevier Science Ltd. All rights reserved
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
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