124,672 research outputs found
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe 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
From Atactic to Isotactic CO/p-Methylstyrene Copolymer by Proper Modifications of Pd(II) Catalysts Bearing Achiral alpha-Diimines
No full textCationic Pd(II) complexes modified with achiral C2v-symmetric α-diimine ligands allow preparation of atactic or isotactic stereoblock CO/p-methylstyrene copolymers; both catalyst activity and polyketone microstructure depend on the choice of α-diimine substituents and counterion
Dispelling the Myths Behind First-author Citation Counts
No full textWe 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
Mechanistic Aspects of Isotactic CO/Styrene Copolymerization Catalyzed by Oxazoline Pd(II) Complexes
No full textCatalytic systems of the type [Pd(CH3)(NCCH3)(N−N)]+[B{3,5-(CF3)2C6H3}4]-, where N−N = (4S,4‘S)-(−)-4,4‘,5,5‘-tetrahydro-4,4‘-bis(1-methylethyl)-2,2‘-bioxazole (BIOX) or N−N = (4S,4‘S)-(−)-2,2‘-(1-methylethylidene)bis[4,5-dihydro-4-(phenylmethyl)oxazole]) (BISOX), afford highly isotactic CO/styrene or p-methylstyrene copolymers. The reactivity of the catalyst with the BIOX ligand toward carbon monoxide was studied and the corresponding methyl carbonyl Pd complex was isolated and identified as the real catalytic species. Starting from this compound the first steps of the copolymerization process were investigated and particular attention was paid to the stereochemistry of the intermediates. Specifically, NOE experiments carried out on the five-membered palladacycle, obtained from the first insertion of p-methylstyrene, indicated that regiochemistry is of the 2,1 type and that one diastereoisomeric species is exclusively generated, with an R configuration of the new −CHAr− stereogenic center. Moreover, the investigation of the intermediate resulting after the second sequence of p-methylstyrene and CO insertion showed the presence of only one diastereoisomer. This evidence indicates that the stereocontrol of the isospecific catalyst is already very efficient at the first stages of copolymerization
Application of NOE and PGSE NMR methodologies to investigate non-covalent intimate inorganic adducts in solution
No full textNOE and PGSE NMR experiments provide crucial information for the structural characterization of non-covalent intimate adducts in solution. The possible presence and the favorite relative orientation of the interacting units can be deduced from NOE results, while the size of the non-covalent adducts can be estimated through PGSE measurements. The complementarity of the two methodologies has been successfully used to investigate transition metal complex ion pairs and, to a lesser extent, intermolecular adducts. The main results concerning the solution structures of non-covalent inorganic adducts are reported and compared with those in the solid state and those from theoretical calculations
Stereochemical Control in CO/p-Methylstyrene Copolymerization Catalyzed by a-Diimine Pd(II) Complexes
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From atactic to isotactic CO/p-methylstyrene copolymerizations by proper modifications of Pd(II) catalysts bearing achiral a-diimines
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