1,721,007 research outputs found
Structure–Properties Relationships in Triplet Ground State Organic Diradicals: A Computational Study
No full textTransport properties of binuclear metal complexes of the VIII group using a simplified NEGF-DFT approach
No full textWe report on a theoretical study of the electronic transport properties of binuclear complexes of metals of the VIII group bridged by pyrazine. Metal-porphyrazine units have been combined in order to investigate symmetric and non-symmetric species with particular focus on their current rectification properties. Transmission functions and I-V characteristics of the various species have been computed using a Non-Equilibrium Green Function with a simplified treatment of the molecule-lead interaction. The results obtained show an overall moderate asymmetry in the current along the molecules, which is of the donors- acceptor type and follow the trend of the ionization potential of the metals in the binuclear system. The bias-dependent rectification ratio, which is significant in a limited voltage window, can be explained in terms of the alignment of the occupied orbitals of the metallic fragments that contribute to the HOMO and HOMO - 1 of the supermolecule. The possible improvement of the rectification performance of such a class of molecules has also been investigated exploiting suitable substitution by electron-withdrawing groups
Conformational Effects on the Magnetic Properties of an Organic Diradical: A Computational Study
No full textA theoretical study on the singlet triplet energy splitting in a m-phenylene bridged organic diradical has been performed using an original computational protocol developed in our group. The method is based on post Hatree Fock calculations and has proven to provide accurate results with reasonable computational effort. By virtue of such efficiency, the full PES of both the singlet and triplet states as a function of the two "soft" torsional degrees of freedom at the meta position of the ring has been explored. In agreement with literature findings, we found a pronounced dependence of the sign of the energy gap from the torsional angles. Finally, exploiting the two-dimensional surface, a statistical analysis is carried out at low temperatures and a comparison with available experimental data addressed
Oligomers based on weak hydrogen bond networks: a rotational study of the tetramer of difluoromethane
No full textWe report the rotational spectrum of one conformer of the tetramer of difluoromethane (CH2F2)4 (the first pure rotational spectrum of a tetramer of an asymmetric rotor), and describe the network of weak hydrogen bonds which connect the four subunit
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
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