1,720,970 research outputs found
Amphiphilic Cu(II) Complexes Modeled After the Metal-Complexation Subunit of Bleomycin Antibiotics
No full textTime-resolved EPR investigation of oxygen and temperature effects on synthetic eumelanin
No full textSynthetic eumelanin produced using 5,6-dihydroxyindole-2-carboxylic acid as precursor and H2O2/horseradish peroxidase as oxidative reagent, in form of dry powder, has been investigated under photoexcitation by TR-EPR spectroscopy. The formation of spin polarized radical pairs from triplet excited states of melanin has been obsd. both in absence and in presence of oxygen and has been followed as a function of the temp. in the range 140-290 K. The triplet mechanism explains the obsd. polarization pattern in net emission. In the presence of oxygen new radical pairs are formed by interaction of melanin with mol. oxygen
Time-resolved EPR investigation of oxygen and temperature effects on synthetic eumelanin
No full textSynthetic eumelanin produced using 5,6-dihydroxyindole-2-carboxylic acid as precursor and H2O2/horseradish peroxidase as oxidative reagent, in form of dry powder, has been investigated under photoexcitation by TR-EPR spectroscopy. The formation of spin polarized radical pairs from triplet excited states of melanin has been obsd. both in absence and in presence of oxygen and has been followed as a function of the temp. in the range 140-290 K. The triplet mechanism explains the obsd. polarization pattern in net emission. In the presence of oxygen new radical pairs are formed by interaction of melanin with mol. oxygen
Electrochemical, in silico and time-resolved EPR behaviour of semiconductive π-conjugated poly(p-phenyleneethynylenevinylene)s (PPEV)
No full text
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
Electrochemical, in silico and time-resolved EPR behaviour of semiconductive π-conjugated poly(p-phenyleneethynylenevinylene)s (PPEV)
No full textA series of poly(p-phenyleneethynylenevinylene)s (PPEV), synthesized by step-growth polymerization of 1,4-dialkoxybenzene and 9,9-bis(2'-ethylhexyl)fluorene-diethynyl monomers and featuring aryl-(E)-enyne repeating units were investigated by experimental and computational techniques with respect to their conjugative and conductive properties. HOMO-LUMO band gaps in the range 2.64-2.79 eV were determined by cyclic voltammetry and UV-vis spectroscopy. In agreement with these data, conductivity measurements performed on thin films drop cast from dichloromethane solutions exhibit values in the range 10-4-10-3 S cm-1 depending on the identity of the repeat units and on the length of alkyl chains. A p-type doping of the materials was achieved through exposure of the films to iodine vapor with a relevant increase of conductivity up to 7-folds compared to the undoped polymers. The cationic hole resulting by electron transfer from one PPEV to the electron acceptor PCBM was observed in situ by TREPR spectroscopy. In addition, DFT calculations performed on well-defined oligomeric models of the PPEVs provide HOMO-LUMO band gaps in agreement with the experimental values and disclose the dependence on both the length and type of conformers in the polymeric chain. Plots of the calculated band gaps versus 1/n, with n the number of monomer units, show a linear trend and predict that the maximum values of conductivity of the materials are reached with n as low as & GE; 6-7, which correspond to the average degrees of polymerization achievable by the synthetic procedure
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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