1,720,979 research outputs found
Calculation of electric dipole hypershielding at the nuclei in diatomic molecules
No full textThe third-rank electric hypershielding at the nuclei of eight diatomic molecules and carbon dioxide has beenevaluated at the Hartree–Fock level of accuracy (i) by straightforward use of its definition within the Rayleigh–Schr€odinger perturbation theory and (ii) by a pointwise procedure for geometrical derivatives of electric dipole polarizability.The connection between these quantities is provided by the Hellmann–Feynman theorem. Extended ad hocbasis sets of big size and high flexibility have been employed in a numerical test of the theory to assess its practicality. Itis shown that constraints for rototranslational invariance and conditions provided by the virial theorem yield a naturalcriterion for near Hartree–Fock quality of nuclear electric hypershieldings computed by procedure (i)
Geometry distortion of the benzene molecule in a strong magnetic field
Full text linkThe electrostatic Lorentz force acting on the H and C nuclei of a benzenemolecule in the presence of a strong magnetic field with flux density B has been estimated via Rayleigh-Schrödinger perturbation theory to second order in B. In stationary conditions, a new equilibrium configuration is reached, at which the total force has been entirely transferred to the nuclei, and the force on the electrons vanishes. The distortion of the molecular geometry is rationalized in terms of third-rank electric hypershielding at the nuclei, induced by strong magnetic fields applied along three Cartesian axes. The nuclear hypershielding has been evaluated at near Hartree-Fock level of accuracy by its definitionwithin the Rayleigh-Schrödinger perturbation theory, and by a pointwise procedure for the geometrical derivatives of magnetic susceptibilities. The connection between these two quantities is provided by the Hellmann-Feynman theorem. A field along the C6 symmetry axis causes a symmetric contraction of the carbon ring and an elongation of the CH bonds.Afield along one of the C2 symmetry axis containing two CH bond acts to shorten them, to widen the ring, and to bend the four remaining CH bonds towards C2. A field along one of the C2' symmetry axis through the midpoint of two opposite CC bonds causes a spindle effect, by squeezing the molecule toward the center of mass. Constraints for rotational and translational invariance and hypervirial theorems provide a natural criterion for Hartree-Fock quality of computed nuclear electric hypershielding. However, the molecular distortion is negligible for applied fields usually available in a laboratory
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
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
Resolution of alkane molecular polarizabilities into atomic terms
Full text linkTwo additive schemes for resolving average molecular electric dipole polarizabilities into atomic contributions, based on the acceleration gauge for the electric dipole, are outlined. Extended calculations have been carried out for a few terms of the alkane series to test the reliability of the partition method. Gross atomic isotropic contributions evaluated for carbon, alpha(Av)(C)approximate to 5.7 a.u., and hydrogen, alpha(Av)(H)approximate to 2.7 a.u., are actually transferable from molecule to molecule, and can be used to predict fairly accurate average polarizabilities of higher homologous molecules in the alkane series. (C) 1998 American Institute of Physics. [S0021-9606(98)30732-1]
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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