1,720,990 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
THE ELECTRONIC-STRUCTURE AND MOSSBAUER-SPECTRA OF IRON(II)-PHTHALOCYANINE COMPLEXES AS STUDIED BY SEMIEMPIRICAL MO-LCAO CALCULATIONS
No full textDensity functional calculations of magnetic exchange interactions in polynuclear transition metal complexes
No full textVariations 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
A ‘donor-free’ chromophore with a silicon-based acceptor group for second order nonlinear optics
No full textIn this paper we report an investigation on the linear and nonlinear properties of a non-classic push-pull molecule, based on the molecular design concept of a ‘donor-free’ chromophore. Herein a terthiophene unit acts both as a donor and a π-spacer group and a tris(trimethylsiloxy)silane substituent as an acceptor group. This latter can represent a model of a fragment of silica surface and it has been compared with a classic acceptor unit like the nitro group. The ‘donor-free’ chromophores have also been compared to more typical push-pull chromophores by replacing the terthiophene unit with the N,N-dimethylamino donor group. Despite the silane group only slightly impacts on the electronic and linear properties of the terthiophene, our results reveal high μβEFISH values for silane-functionalized derivatives producing a NLO activity stronger than that of the nitro substituted. Finally, the investigated ‘donor-free’ NLO-phore exhibits interesting physical properties relevant in term of nonlinearity/transparency trade-off, a highly desired requirement for second-order NLO materials
Axial Imidazole Distorsion Effects on the Catalytic and Binding Properties of Chelated Deuterohemin Complexes
Full text linkThe effect of strain in the axial coordination of imidazole to the heme has been studied in the chelate complexes
deuterohemin-histidine (DH-His) and deuterohemin-alanylhistidine (DH-AlaHis). Molecular mechanics calculations
indicate that three types of distortion of the axial ligand occur in DH-His, due to the relatively short length
of the arm carrying the donor group: tilting off-axis, tipping, and inclination of the imidazole plane with respect
to the axial Fe-N bond. The effects of tilting (¢ç 10°) and inclination of the imidazole ring (¢ä 17°) are
dominant, while tipping is small and is probably of little importance here. By contrast, the axial imidazole
coordination is normal in DH-AlaHis and other computed deuterohemin-dipeptide or -tripeptide complexes
where histidine is the terminal residue, the only exception being DH-ProHis, where the rigidity of the proline
ring reduces the flexibility of the chelating arm. The distortion in the axial iron-imidazole bond in DH-His has
profound and negative influence on the binding and catalytic properties of this complex compared to DH-AlaHis.
The former complex binds more weakly carbon monoxide, in its reduced form, and imidazole, in its oxidized
form, than the latter. The catalytic efficiency in peroxidative oxidations is also reduced in DH-His with respect
to DH-AlaHis. The activity of the latter complex is similar to that of microperoxidase-11, the peptide fragment
incorporating the heme that results from hydrolytic cleavage of cytochrome
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