1,720,973 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
New highly water-soluble rhodium complexes bearing 1,3,5-triaza-7-phosphaadamantane (PTA) and/or tris(hydroxymethyl) phosphine (THP)
No full textWater soluble ruthenium cyclopentadienyl and aminocyclopentadienyl PTA complexes as catalysts for selective hydrogenation of alpha,beta-unsaturated substrates (PTA=1,3,5-triaza-7-phosphaadamantane)
No full textA series of half-sandwich Ru-cyclopentadienyl derivatives containing the cage-like water soluble monodentate phosphine 1,3,5-triaza-7-phosphaadamantane (PTA) was synthesized and tested in aqueous phase or biphasic homogeneous hydrogenation of activated olefins via hydrogen transfer or under hydrogen pressure at mild conditions. The hydrogen transfer results show higher activity for the Cp* derivatives (Cp* = C5Me5) than for the corresponding Cp complexes (CP = C5H5). Under H, pressure, all complexes show high selectivity to C=C double bond hydrogenation. The X-ray crystal structure featuring a protonated 2-aminoethylcyclopentadienyl Ru complex was also determined
Diffusion NMR Studies on the Self-Aggregation of Ru-Arene CAP Complexes: Evidence for the Formation of H-Bonded Dicationic Species in Acetonitrile
No full textThe self-aggregation of neutral [RuCl2(η6-p-cymene)(CAP)] (2; p-cymene = 1-methyl-4-(propan-2-yl)benzene) and ionic [RuCl(η6-p-cymene)(L)(CAP)](PF6) (3, L = CAP; 4, L = MeCN) and [RuCl2(η6-p-cymene)(CAP-H)](BPh4) (5; CAP-H = monoprotonated CAP) ruthenium(II) arene complexes, bearing the water-soluble phosphine CAP (1,4,7-triaza-9-phosphatricyclo[5.3.2.1]tridecane), in aprotic polar solvents, was investigated by means of PGSE (pulsed field gradient spin-echo) diffusion NMR. In addition, the analogous neutral [RuCl2(η6-p-cymene)(PTA)] (1) and monoprotonated [RuCl2(η6-p-cymene)(PTA-H)](BPh4) (6) PTA (1,3,5-triaza-7-phosphaadamantane) complexes were investigated in acetonitrile-d3. Complexes 1-4 do not exhibit any tendency to self-aggregate in acetonitrile-d3 and acetone-d6. In contrast, 5 and 6 monoprotonated complexes undergo a peculiar self-aggregation process, involving almost exclusively the cation, leading to the main formation of dicationic species held together by intermolecular hydrogen bonds. This has been clearly demonstrated by 1H diffusion NMR experiments, which allowed measurement of an average hydrodynamic volume for the cation that was more than double that expected, whereas that of the counterion is only slightly higher than that of the free anion. The trend of the aggregation number (N+) as a function of the concentration of 5 and 6 was fitted using the equation of the equal K indefinite model of association, leading to ΔG°298 »K = -3.1 and -3.0 kcal mol-1, respectively, for the formation of H-bonded dications. The critical role played by the protonated -NH unit in establishing hydrogen bonding was further supported by the detection of 6+2 dinuclear species in acetonitrile-d3 solutions containing equimolar mixtures of 2 and 6. The self-aggregation free energy of 2 (ΔG°298 »K = -3.1 kcal mol-1) and 6+ (ΔG°298 »K = -2.9 kcal mol-1) in such mixed solutions is practically identical with those of 5 and 6 in acetonitrile-d
A ruthenium-based catalytic system for a mild borrowing-hydrogen process
Full text linkThe alkylation of arylamines using stoichiometric amounts of aliphatic and benzylic alcohols in the presence of tBuOK was carried out at 55 °C using a low catalyst loading of [Ru(cod)-Cl2]n/PTA (1,3,5-triaza-7-phosphaadamantane). The overall borrowing-hydrogen process does not require a controlled nitrogen atmosphere, and it could also be carried out at room temperature using higher loading of base. A wide range of substrates can be used in this transformation, and it has a good tolerance of different substituents. This catalytic system proved also to be efficient for other hydrogen-transfer reactions such as a tandem oxidation/C-C coupling between 1-phenylethanol and primary alcohols
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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