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X-ray Diffraction, UV Photoelectron, and ab initio Study of Intramolecular Interactions in β-Carbonyl Sulfones
No full textInformation on the geometric and electronic structures of β-carbonylsulfones, XC(O)CH2SO2R (1-10, X = Et2N, EtS, EtO, alkyl and aryl, and R' = alkyl and aryl) are obtained for different pairs of the X and R substituents. The results of the x-ray diffraction and of the PE spectra analyses fully agree with the results of optimized ab initio 3-21G* calculations. The electron charge distribution at various atoms and/or groups is discussed in connection with the other observables. In the compounds studied the CH2-S bond is gauche to the carbonyl group irrespective of the X and R substituents and of the gas or solid phase. This conformation is dictated by the interplay of the electronic interactions between the XC(O) and SO2R groups with two strong non bonded interactions between pairs of oppositely charged atoms. The negatively charged carbonyl oxygen and one of the sulfonyl oxygen atoms lie at distances shorter than the sum of the corresponding van der Waals radii from the positively charged sulfur and carbonyl carbon atoms, respectively. The interaction of the sulfonyl oxygen with the carbonyl carbon atom is the stronger of the two and partially offsets the strong inductive effect of the sulfonyl group. The presence of both through-bond and through-space interactions between the carbonyl and the sulfonyl groups in the ground and ionized states is confirmed by eigenvector analysis and by the shifts in the MO energies with respect to reference compounds. The conformation of compound 5, in solid phase, is in part determined by crystal packing forces
Conformational and Electronic Interaction Studies of some beta-ketosulfoxides
No full textThe analysis of the carbonyl I.R. band and the U.V. phoelectron spectroscopic data along with the ab-initio calculations and X-ray diffraction of alfa (methylsulfinyl)- and alfa-(phenylsulfinyl)-acetophenones indicated the predominance of the cis rotamers aver the gauche ones
Comparative conformational and electronic interaction studies of some alpha-diethoxy-phosphoryl-carbonyl compounds and their alpha-ethylsulfonyl analogues
No full textThe analysis of the IR, 13C NMR data along with the ab-initio calculations of some α-diethoxyphosphoryl- and α-ethylsulfonyl-carbonyl compounds indicated that the most stable gauche rotamer for both series is stabilized by charge transfer
UV-photoelectron, electron transmission, and dissociative electron attachment spectroscopies of acetone oximes
No full textThe conformation and the electronic structure of several α-heterosubstituted acetone oximes (XCH2(CH3)C=NOH (X = H (1), F (2), Cl (3), CH3O (4), C2H5S (5) and (CH3)2N (6)) have been determined by means of a multidisciplinary approach based on ultraviolet photoelectron (UP), electron transmission (ET) and dissociative electron attachment (DEA) spectroscopies and fully optimized ab initio 6-31G** and MP2/6-31G** calculations. The vertical ionization energy (IE) and electron affinity (EA) values related to the HOMO (πC=N) and LUMO (π∗C=N) have been determined by the ΔSCF and ΔMP2 (IE only) procedures. The studied compounds prefer an anti (E) configuration between the OH and the CH2X group, and a gauche conformation of the C-X bond with respect to the double bond, except 2 and 4 for which a syn (Z) planar structure is nearly degenerate with the E one. The spectral data, coupled with the results of the calculations indicate that the properties of the acetone oximes are mainly governed by the mixing between the orbitals localized at the X and C=N fragments and by electrostatic interactions between hydrogen and electronegative atoms. When X has poor donor and poor mesomeric acceptor properties (X = F and OMe), the prevailing interaction is the strong charge transfer mixing of the hydroxyl oxygen lone pair with the π∗C=N orbital, and the X group moves in the main molecular plane
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
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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