1,720,975 research outputs found
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
Olefin Trifluoroacetato Derivatives of Copper(I) and Their Olefin/CO Exchange Reaction
No full textCompounds of general formula Cu(CF3COO)(olefin) (olefin = cyclooctene (coe), 1,5-cyclooctadiene (cod), diethylfumarate (defu), methylcinnamate (meci)) have been prepared and the molecular structures have been solved by X-ray diffraction in the case of olefin = coe, defu, meci. The complexes are characterized by a dimeric [Cu2(ƒÝƒ{CF3CO2)2(olefin)2] core with bridging trifluoroacetates and a ƒØ2-bonded olefin. In the case of the defu and meci complexes, [Cu2(ƒÝƒ{CF3CO2)2(olefin)2] dimeric units are linked by the oxygen atom of a carbonyl group of the ester to give polymeric chains. The compound [Cu2(ƒÝƒ{CF3COO)2(meci)2]n is the first structurally characterized example of a metal-bonded methylcinnamate. By recrystallization of [Cu2(CF3COO)2(cod)2], a derivative featuring a cod / Cu molar ratio of 0.5 has been isolated and structurally characterized as [Cu2(ƒÝ-CF3COO)2(ƒÝ-cod)]n, which represents the first example of a polymeric metal complex containing a bridging cod ligand. The carbo..
Synthesis, Characterization and Olefin/CO Exchange Reactions of Copper(I) Derivatives Containing Bidentate Oxygen Ligands
No full textNew hexafluoroacetyalacetonato- (hfacac) and trifluoroacetato olefin complexes of copper(I) of the general formula Cu(hfacac)(olefin) and Cu(CF3CO2)(olefin) have been prepared from Cu2O / hfacacH / olefin or Cu(CF3CO2)(toluene)0.5 / olefin systems. The structures of [Cu(hfacac)(coe)], [Cu(hfacac)(van)], [Cu(μ-CF3COO)(tbve)]n and [Cu(μ-CF3COO)(van)]2•C7H8, have been determined by X-ray diffraction methods, where coe = cyclooctene , van = 4-vinylanisole and tbve = t-butylvinylether. In the solid state, the 4-vinylanisole / trifluoroacetate complex, [Cu(CF3COO)(van)]2, is dimeric with two carboxylato groups symmetrically bridging two copper atoms, while the t-butylvinylether derivative, [Cu(μ-CF3COO)(tbve)]n, is polymeric with single [CF3COO]− bridges between adjacent copper atoms. Olefin hfacac complexes are monomeric and considering the two oxygen atoms and the midpoint of the double bond of the coordinated olefin, the copper atom lies in a nearly trigonal..
Trifluoromethyl-substituted Bis(Pyrazolyl)Methanes as Ligands for Copper and Silver: Synthesis and Spectroscopic and Structural Characterization
No full textNew fluorinated bis(pyrazolyl)methanes with the general formula RCH(PzF)2 [R ) H,
PzF ) 3-(trifluoromethyl)pyrazolyl, 3,5-bis(trifluoromethyl)pyrazolyl; R ) Ph, PzF ) 3,5-bis(trifluoromethyl)
pyrazolyl] have been prepared, and their reactivity with copper and silver salts has been
studied. Copper derivatives Cu[RCH(PzF)2](L)(OTf) [R ) H, PzF ) 3-(trifluoromethyl)pyrazolyl,
3,5-bis(trifluoromethyl)pyrazolyl; R ) Ph, PzF ) 3,5-bis(trifluoromethyl)pyrazolyl, L ) CO, cyclooctene
(coe); R ) Ph, PzF ) 3,5-bis(trifluoromethyl)pyrazolyl, L ) coe, 4-vinylanisole (van), and triethylvinylsilane
(tevs)] have been isolated by reacting Cu(OTf)(toluene)0.5 with the bis(pyrazolyl)methane
ligand in the presence of olefin or CO. Some of them have been structurally characterized (R ) H, PzF
) 3-(trifluoromethyl)pyrazolyl, 3,5-bis(trifluoromethyl)pyrazolyl, L ) CO). These compounds
are monomeric and show strong interactions between copper and one oxygen atom of the triflate
moiety. [Bis[3,5-bis(trifluoromethyl)pyrazolyl]methyl]silver complexes have been prepared from
AgBF4 and the ligand. The coe derivative [Ag{CH2(3,5-(CF3)2Pz)2}(coe)]BF4 has been obtained in good
yields
Trifluoromethyl-Substituted Bis(pyrazolyl)methanes as Ligands for Copper and Silver: Synthesis and Spectroscopic and Structural Characterization
No full textVariations 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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