1,720,993 research outputs found
Linker permethylation as a means to foster valence tautomerism and thwart dimerization in ferrocenyl-triarylmethylium cations
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Redox Isomeric Ferrocenyl Styrylruthenium Radical Cations with Diphenyl-Substituted β-Ketoenolato Ligands
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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
Heterobimetallic Mn/Co hybrid complexes composed of proximate organometallic and classical coordination sites
No full textA series of highly unsymmetric heterobinuclear Mn/Co complexes is reported, in which an organometallic CpMn(CO)(2) fragment and a classical Werner-type cobalt(II) subunit are arranged in close proximity by means of a bridging pyrazolate. Two ligand scaffolds are employed that differ by the chelate size of the tripodal tetradentate {N4} binding site for cobalt. Molecular structures of three complexes with either nitrate or acetate coligands have been characterized by X-ray crystallography. IR and UV-Vis-spectroelectrochemistry reveals that oxidation of the heterobimetallic systems is highly localized at the organometallic manganese site, while electrochemical reduction occurs at cobalt. Structural and spectroscopic features as well as trends for the redox potentials of the Mn-I/Mn-II couple suggest that changes at the cobalt(II) Werner-type subunit have only minor effects on the properties of the organometallic site. (C) 2007 Elsevier B.V. All rights reserved
Tailoring Valence Tautomerism by Using Redox Potentials: Studies on Ferrocene‐Based Triarylmethylium Dyes with Electron‐Poor Fluorenylium and Thioxanthylium Acceptors
No full textThree new electrochromic ferrocenyl triarylmethylium dyes with fluorenylium ( 1a + , 1b + ) or thioxanthylium ( 1c + ) residues were selected in order to keep the intrinsic differences of redox potentials for ferrocene oxidation and triarylmethylium reduction small and to trigger valence tautomerism. UV/Vis/NIR and quantitative EPR spectroscopy identified paramagnetic diradical isomers 1a +•• ‐1c +•• alongside diamagnetic forms 1a + ‐1c + , which renders these complexes magnetochemical switches. The diradical forms 1a +•• ‐1c +•• as well as the one‐electron reduced triarylmethyl forms of the complexes were found to dimerize in fluid solution. For radical 1a • , dimerization occurs on the timescale of cyclic voltammetry, which allowed us to determine the kinetics and equilibrium constant for this process by digital simulation. Mößbauer spectroscopy indicated that 1a + and 1b + retain VT even in the solid state. UV/Vis/NIR spectroelectrochemistry revealed the polyelectrochromic behaviour of these complexes by establishing distinctly different electronic absorption profiles of the corresponding oxidized and reduced form s.publishe
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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