1,720,962 research outputs found
Self-assembly of polyoxoselenitopalladate nanostars [Pd15(μ3-SeO3)10(μ3-O)10Na]9- and their supramolecular pairing in the solid state
No full textAn anionic Pd15-oxo-cluster [Pd15(l3-SeO3)10(l3-O)10Na]9- has
been synthesized. It is the result of an unprecedented selfassembly
of Pd2+ and Na+ cations, SeO3
2- and oxo anions.
It has been found for the first time, that selenito groups can
give rise to supramolecular interactions in the solid state with
palladium atoms, through the selenium electron lone pairs
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
Coordination properties of the multifunctional S,N,S zwitterionic ligand EtNHC(S)Ph2P=NPPh2C(S)NEt
No full textThe reaction of trialkylphoshanes and amino-phosphanes with isothiocyanates yields adducts containing
the zwitterionic thioamidyl-phosphonium P+C(S)N− functional group. Ligands containing this group were
not previously studied, probably due to their instability towards dissociation, in the presence of metal
species able to coordinate the P atom. The ligand EtNHC(S)Ph2P NPPh2C(S)NEt (HEtSNS) was obtained
by reaction of Ph2PNHPPh2 with ethylisothiocyanate and proved to be very versatile: it can be protonated
giving cation H2EtSNS+ and deprotonated forming the dianion–cation EtSNS−. HEtSNS and its derivatives
behave as ligands showing five possible coordination fashions, S,N,S tridentate and S,S-bidentate (with a
bite-angle varying from 180◦ to 90◦), S-monodentate, S,S bridging andN,N,Ninteraction. Here we describe
the coordination chemistry of HEtSNS, in particular towards Rh, Cu, Ag and Au, and some properties of
its complexes which are still the only examples containing the P+C(S)N− zwitterionic grou
Suppression of β-Hydride Chain Transfer in Nickel(II)-Catalyzed Ethylene Polymerization via Weak Fluorocarbon Ligand–Product Interactions
No full textThe synthesis and characterization of two neutrally charged Ni(II) ethylene polymerization catalysts, [2-tert-butyl-
6-((2,6-(3,5-dimethylphenyl)phenylimino)methyl)phenolato]nickel(II) methyl trimethylphosphine ((CH3)FI-Ni) and [2-tertbutyl-
6-((2,6-(3,5-bis(trifluoromethyl)phenyl)phenylimino)methyl)phenolato]nickel(II) methyl trimethylphosphine ((CF3)FINi)
are reported. In the presence of a Ni(COD)2 cocatalyst, these catalysts produce markedly different polyethylenes: densely
branched oligomers with Mw = 1.4 × 103 g mol−1 for (CH3)FI-Ni vs lightly branched polyethylenes with Mw = 92 × 103 g mol−1 for
(CF3)FI-Ni and with ∼6.5× the polymerization activity and with much greater performance thermal stability. HOESY 2D 19F,1H
NMR spectra of a model Ni-ethyl compound, [2-tert-butyl-6-((2,6-(3,5-bis(trifluoromethyl)phenyl)phenylimino)methyl)phenolato]-
nickel(II) ethyl 2,4-lutidine ((CF3)FI-Ni-Et), indicate non-negligible Cβ−Hβ···F3C through-space dipolar interactions, and molecular
modeling reveals that Cβ−Hβ···F(C) distances can be as small as ∼2.61 Å during the polymerization process. Furthermore, there is no
structural or spectroscopic evidence for fluorocarbon inductive effects on the structure, bonding, and reactivity of these complexes, and
a catalyst with CF3 introduced β to the imino N produces only low-Mw oligomers with low activity. These results argue that weak
(ligand)C−F···H−C(polymer) interactions can significantly influence the chain transfer characteristics of these catalysts
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
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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