1,721,021 research outputs found
Energy Transfer Mechanism in the NaCl:Pb++,Mn++ System along Aggregation Processes
No full textThe non-radiative energy transfer mechanisms between Pb++ (donor) and Mn++ (acceptor) ions in NaCl:Pb++, Mn++ system are examined at different aggregation stages of the impurities. Mn++ ions are characterized by a series of absorption bands partially overlapping the emission bands of Pb++ aggregates peaking at 380, 430, and 500 to 530 nm. The energy transfer mechanism connected with Pb++-380 nm emission band is based on a resonant single pair interaction, while the transfer process connected with 430 nm and 500 to 530 nm emission bands can be explained on the basis of a fast energy migration within the donor system followed by a final transfer, donor–acceptor, that is resonant for the transfer connected with 430 nm band and phonon assisted for the transfer connected with the 500 to 530 nm band
Radiative Energy Transfer Process in the KCl:Pb++,Eu++ System
No full textMeasurements of emission spectra, time decay scheme, and time resolved spectroscopy, in the temperature range 80 to 300 K, show the existence of an energy transfer process in the KCl:Pb++, Eu++ system at low concentrations of the dopants. The experimental results – in particular time decay scheme both of donors and acceptors – indicate that the transfer is of radiative type; the same conclusion is obtained from the comparison between the transfer probability estimated as if the transfer is supported by a non-radiative mechanism and the intrinsic decay probability of the donors
Decay Scheme of 439 and 478 nm Emission Bands in the KCl:Eu2+ System
No full textThe KCl:Eu2+ system is investigated by using optical techniques such as absorption, luminescence, and luminescence decay times in the temperature range 80 to 300 K. The behaviour of quenched samples is examined; furthermore by annealing quenched samples at defined temperature (200 °C) a controlled aggregation is obtained. At some steps of the aggregation process, emission spectra, and luminescence time decay scheme are measured. Possible models responsible for the luminescence decay scheme of aggregates emitting at 439 and 478 nm are discussed
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
Get PDFWe 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
Initial hydration steps in lipase studied by means of water sorption isotherms, FTIR spectroscopy and thermally stimulated depolarization currents
No full textDispelling the Myths Behind First-author Citation Counts
Get PDFWe 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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