1,720,974 research outputs found
PHOSPHORUS(III) DOUBLE-BOND SYSTEMS, CARBENE AND ALKENE ANALOGS - THE ELECTRONIC-STRUCTURE OF IMINO-PHOSPHANES AND METHYLENE-PHOSPHANES
Get PDFNIECKE E, GUDAT D, Schoeller W, RADEMACHER P. PHOSPHORUS(III) DOUBLE-BOND SYSTEMS, CARBENE AND ALKENE ANALOGS - THE ELECTRONIC-STRUCTURE OF IMINO-PHOSPHANES AND METHYLENE-PHOSPHANES. JOURNAL OF THE CHEMICAL SOCIETY-CHEMICAL COMMUNICATIONS. 1985;(15):1050-1051
Valence isomerization in the solid state: From 1,3-diphosphacyclobutane-2,4-diyl to 1,2-dihydro-1,2-diphosphete
No full textSchmidt O, Fuchs A, Gudat D, et al. Valence isomerization in the solid state: From 1,3-diphosphacyclobutane-2,4-diyl to 1,2-dihydro-1,2-diphosphete. ANGEWANDTE CHEMIE-INTERNATIONAL EDITION. 1998;37(7):949-952
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
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
Spectroscopic and structural characterization of a phosphavinylidene carbenoid, Mes*-P=C(Cl){Li(DME)(2)}: Stabilization of a carbenanionic center by a cisoid lone pair interaction
No full textNiecke E, Nieger M, Schmidt O, Gudat D, Schoeller W. Spectroscopic and structural characterization of a phosphavinylidene carbenoid, Mes*-P=C(Cl){Li(DME)(2)}: Stabilization of a carbenanionic center by a cisoid lone pair interaction. JOURNAL OF THE AMERICAN CHEMICAL SOCIETY. 1999;121(3):519-522.Characterization of the phosphavinylidene carbenoid DME-solvate (Z)-Mes*-P=C(CI){ Li(DME)(2)} (Z-2a) or the corresponding THF-solvate (Z-2b) by low-temperature X-ray diffractometry and multinuclear NMR studies reveals the presence of discrete monomeric molecules with donor-solvated metal atoms both in solution and the solid state. The structural parameters of solid 2a and the observed intermolecular exchange of Li+ between different carbanion fragments in solution suggest a low degree of covalency for the C-Li bond. This is in accord with a theoretical analysis of the bonding which demonstrates that the electronic structure of the model carbenoids (E/Z)-Me-P=C(Cl){Li(DME)(2)} (5) is very similar to that of the carbanions (E/Z)-[Me-P=C(Cl)](-) (6). In particular, the low degree of covalency in the C-Li bond in 5 is confirmed by natural population analyses and an analysis of the Laplacian of the electron density. On the basis of these results, the bonding situation in the phosphavinylidene carbanion system is discussed in terms of an isolobal analogy to N2F2
NMR spectroscopic and computational study of static and dynamic E/Z isomerism in aminoiminophosphines R2N-P = NMes
No full textGudat D, Hoffbauer W, Rozhenko AB, Schoeller W, Povolotskii MI. NMR spectroscopic and computational study of static and dynamic E/Z isomerism in aminoiminophosphines R2N-P = NMes. MAGNETIC RESONANCE IN CHEMISTRY. 2000;38(10):861-866.The P-31 NMR spectra of the iminophosphines R2N-P=NMes* [R = Me (2a), Et (2b), i-Pr (2c); Mes* = 2,4,6-tri-tert-butylphenyl] were studied in the solid state under magic angle spinning conditions and in solution. Evaluation of the solid-state data in connection with CIAO quantum chemical model calculations allows the characterization of the P-31 nuclear magnetic shielding tensors and leads to assignment of Z-configuration for the double bond in 2a and of the E-configuration for the double bonds in 2b and c. Comparison of the shifts delta(iso) with the chemical shift in solution (delta(soln)) indicates that this configuration is retained in solution only for 2c, whereas solutions of 2a and b contain rapidly exchanging equilibrium mixtures of both E- and Z-isomers. The analysis of the temperature dependence of delta(soln) allows for the first rime the evaluation of Delta H and Delta S for this isomerization. The results reveal that in the case of 2b the configuration of the more stable stereoisomer is opposite to the conformation observed in the solid state. Copyright (C) 2000 John Wiley & Sons, Ltd
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