1,721,009 research outputs found
Photo-transferred thermoluminescence from deep traps in quartz
No full textPhoto-transferred thermoluminescence (PTTL) measurements were performed on analytical grade quartz with the aim to study the dependence of the PTTL signal on preheat temperature and light-exposure time. The results proved that, in addition to the well-known contribution due to the electron traps related to the 325 °C thermoluminescence peak, a non-negligible role was played by deep thermally disconnected traps. Moreover, the shape of the time-response curve for the PTTL signal of quartz samples preheated at high temperature values suggested that recombination processes of optically stimulated electrons from deep traps involved also a non-radiative recombination centre
Quantitative XRF analysis in typical archaeometric applications
No full textQuantitative XRF analyses addressed to archaeometric demands are hampered when employing energy dispersive spectroscopy in the three following cases:
i. So called dark matrix sample composed of light elements where absorption correction can be evaluated by resorting to incoherent or coherent to incoherent ratio scattering.
ii. Non homogeneous composition on microscopic scale, as for pigment layers, where quantitative information on pigment dilution can be achieved by proper models where medium absorption is disregarded and grain pigment contribution is evaluated by linear approximation of absorption valid for small volume pigment grains.
iii. Irregular shape of metallic sample and/or incorrect positioning due to the use of portable instruments which prevents from direct comparison with standard reference with plane surface and different position in the experimental set up.
We have already shown that exploiting a geometry where excitation and detection direction are as much coincident as possible one obtains substantial reduction of the error depending on irregular shape in quantitative analysis.
In the present contribution we present the encouraging experimental results achieved employing an annular silicon drift detector so that the condition of coincidence for incoming and out going X-Ray directions is nearly achieved
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
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
A new model for x-ray fluorescence autoabsorption analysis of pigment layers
No full textA new model for describing the x-ray absorption in painting layers is presented. In it we take into account that the painting layer composition consists of small pigment grains embedded in a low Z binding medium. Accordingly, a linear law for autoabsorption inside the grains is assumed (due to the small size) and the x-ray absorption in the medium is completely disregarded. The model developed is based on the fundamental parameter method entering as characteristic parameters of the sample: layer thickness, pigment grain volume and pigment grain volume density (dilution).
We show by experiments, performed on zinc and lead white pigments, that in the thin layer approximation, good agreement with nominal values is obtained for the volume dilution
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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