1,721,048 research outputs found
{4-Bromo-2-[(2-{(ethylsulfanyl)[(2-oxidobenzylidene-κO)amino-κN]methylidene}hydrazinylidene-κN1)methyl]phenolato-κO}(ethanol-κO)dioxidouranium(VI)
No full textIn the title complex, [U(C17H14BrN3O2S)O2(C2H5OH)], the UVI cation has a distorted pentagonal–bipyramidal environment with the pentagonal plane defined by two N and two O atoms of the tetradentate Schiff base ligand and the O atom of the ethanol molecule. Two oxide O atoms occupy the axial positions. The azomethine C=N group and the Br atom are disordered over two positions in a 0.8356 (18):0.1644 (18) ratio. The ethylthiolyl group is disordered over three conformations in a 0.8356 (18):0.085 (6):0.079 (6) ratio, and the ethanol ligand is also disordered over three orientations in a 0.470 (16):0.277 (19):0.253 (18) ratio. In the crystal, molecules form centrosymmetric dimers through hydrogen bonding between ethanol O—H donors and phenolate O-atom acceptors. Weak C—H...O interactions consolidate the crystal packing
Ring to open-chain transformation induced by selective metal coordination in a new dithiocarbazate ligand
No full textBy unsymmetrical derivatization of acetylacetone with S-ethyl-dithiocarbazide, a new tetradentate chelate
ligand (N, N, S, S) has been prepared and studied. The compound can exist in two isomeric forms: an
open tetradentate chelating form and a cyclic dihydropyrazole form. The cyclic form is obtained in the
solid state and is the only one detected even in solution. However, in the presence of metal ions, a competition
between intramolecular cyclization and metal complexation of the open form is active, and monochelate
square planar complexes can be obtained through transformation of the cyclized into the open
ligand form. We have proved this with metal ions prone to square planar coordination such as Ni(II) and
Pd(II). On the other hand, with VO(II), Pb(II), UO2(II), La(III), Ce(III), no complex was obtained and the
cyclized form was recovered from the reaction mixture. This indicates some selectivity of the ligand
towards specific metal ions
Electro-optical properties from CC2 Calculations: A comparison between theoretical and experimental results
No full textThe coupled cluster CC2 method has been employed for the computation of dipole moments and static
first order hyperpolarizability of a large size push–pull molecule with an extended p electron system.
The results are critically compared with the outcomes of electro-optical absorption measurements.
CC2 ground and excited state dipole moments are slightly overestimated with respect to the experimental
ones, but their differences are well reproduced; good agreement has also been found for absorption
wavelengths. Sum of state computations of the static first hyperpolarizability highlight the importance
of at least two excited states
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
Structural, electronic and vibrational properties of N,N'-1H,1H-perfluorobutyl dicyanoperylenecarboxydiimide (PDI-FCN2) crystal
No full textWe present a theoretical and experimental investigation of the crystalline structure of N,N′-1H,1H-perfluorobutyl dicyanoperylenecarboxydiimide (PDI-FCN2) that has been deduced combining experimental XRD data, obtained from powders, with global-optimization algorithms which allow to identify Bravais lattice, primitive cell parameters, and space group of the crystal. The XRD spectrum calculated for the proposed crystalline structure very well reproduces the measured XRD data. Our results suggest the triclinic lattice structure of spatial groups Pmath and P1, respectively, for the crystalline PDI-FCN2-1,7 and PDI-FCN2-1,6 isomers. In both cases, the primitive cell contains a single molecule. On the proposed crystalline structures, KS-DFT cell energy calculations, including van der Waals interactions, have been performed to assign the minimum energy geometrical structure and orientation of the molecule inside the corresponding primitive cell. These calculations evidence the molecular packing that characterizes the strong anisotropy of the PDI-FCN2 crystal. Electronic band-structures calculated for both isomers within the Kohn-Sham density-functional theory indicate that the crystalline P-1 structure is an indirect gap semiconductor, while the P1 structure is a direct gap semiconductor. The electronic band structure calculations on the optimized crystal geometries highlight strong anisotropy in the dispersion curves E(k), which roots at the molecular packing in the crystal. Finally, the vibrational spectrum of both crystalline isomers has been calculated in the harmonic approximation and the dominant vibrational frequencies have been associated to collective motions of selected atoms in the molecules
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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