1,721,108 research outputs found
TRANSPUTER-BASED PARALLEL SYSTEM FOR ACQUISITION AND ONLINE ANALYSIS OF SINGLE-FIBER ELECTROMYOGRAPHIC SIGNALS
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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
Luminescence of the surface nonbridging oxygen hole center: Spectral and decay properties
No full textWe investigated the red luminescence in a porous film of silica nanoparticles, originating from surface nonbridging oxygen hole centers. The excitation spectrum was measured from 1.8 to 8.0 eV by a tunable laser system and a synchrotron radiation source; this spectrum evidences a peak at 2.0 eV, nearly overlapping with
the emission, and an ultraviolet broadband with peaks at 4.8 and 6.0 eV. The emission is characterized by a spectrum with two subbands split by 0.07 eV, its decay occurs with lifetime longer than 30 microsec and undergoes
a thermal quenching by a factor aboout 2 with increasing temperature from 10 to 290 K. The optical characteristics of surface and bulk centers are discussed on the basis of the reported experimental results and quantum
chemical calculations
Unraveling exciton dynamics in amorphous silicon dioxide: Interpretation of the optical features from 8 to 11 eV
No full textWe introduce a model comprehensively describing the optical features of amorphous silicon dioxide (a-SiO2)
in the spectral range from 8 up to 11 eV. Our model is grounded on the critical analysis of the temperature
dependence of Kramers-Kronig-derived absorption spectra in the range from 8 up to 17.5 eV, together
with the features of the Urbach absorption tail and of self-trapped exciton emission. In a paper we recently
published [Phys. Rev. Lett. 105, 116401 (2010)] we showed the 10.4-eV resonance in the absorption spectra
to feature a close Lorentzian line shape, thus implying a delocalized nature for excitons in a-SiO2. Here we
provide estimations of the main parameters ruling exciton dynamics in SiO2, such as the energy of the mean
lattice vibrational mode coupled to excitons ( ̄hω0 = 0.083 eV), the half width of the excitonic energy band
(B = 2 eV), the root-mean-square amplitude of site-to-site energy fluctuations of exciton energy (D = 0.7 eV),
and the exciton-phonon coupling constant (g = 2.1). The quantum yield of excitonic emission (η = 10−3) at
T = 10 K in a-SiO2 is determined as well. Our model suggests that a-SiO2 features an indirect gap near 9
eV and a direct one near 11 eV, and allows a coherent description of the properties of the intrinsic Urbach
absorption tail. The latter results are satisfactorily explained as arising from the momentary self-trapping of the
10.4-eV exciton. As far as near-edge absorption properties are concerned, our model places SiO2 in the wider
context of wide-band-gap solids, such as LiF or NaF, where excitons are weakly scattered, but strongly coupled
to phonons. On the whole, the present study shows that exciton dynamics accounts for all optical properties of
a-SiO2 from 8 up to 11 eV
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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