1,721,013 research outputs found
Identification Techniques II: X-ray techniques and X-ray fluorescence with portable systems
No full textEnergy-dispersive X-ray fluorescence (EDXRF) portable spectrometers are becoming very popular in many fields for the on-site analysis of elements. This is mainly because EDXRF is a nondestructive, multielemental technique that is extremely well suited for the analysis of any material.
An EDXRF spectrometer mainly consists of an X- or γ -ray excitation source, an X-ray detector with electronics, and a pulse-height analyzer. Recent technological developments have resulted in small, low-power, dedicated X-ray tubes, thermoelectrically cooled semiconductor detectors, and small pulse-height analyzers. Therefore, completelyportable EDXRF spectrometers are available that can be
assembled on-site, having the size of a book and a weight ranging from as light as 500 g (using a radioactive source) to a few kilograms (using an X-ray tube).
This article start with a short introduction to X- ray physics than reviews the present status of the development of X-ray radiograpy, X-ray diffraction and EDXRF portable systems in the field of Cultural heritage. The various components of a portable system are described: the radiation source, i.e. small, low-power, dedicated X-ray
tubes or, alternatively, radioactive sources that emit X-rays
or low-energy γ -rays; and X-ray detectors, i.e. proportional
gas counters and semiconductor detectors, with special emphasis on the more recent thermoelectrically cooled X- ray detectors: Si-PIN (silicon positive-intrinsic-negative), Si-drift, CdTe, CdZnTe, HgI2, and others.
Commercial systems are considered, and finally the most comon and significant applications are described, with particular emphasis to the field of works of art
Pigment layers and precious metal sheets by energy-dispersive x-ray fluorescence analysis
No full textA portable energy-dispersive x-ray fluorescence (EDXRF) equipment was used to measure pigments and precious metal composition. From the x-ray spectra it was also possible to assign each pigment to the correct pigment layer, and in the case of metal sheets (e.g. gildings) to identify the correct layer distribution. Several methods have also been developed to determine the thickness of pigment layers and metal sheets. They were specifically applied to measure gold thickness in Giotto's halos in the Chapel of the Scrovegni in Padua, and in gilded copper objects from the Royal Tombs of Sipán and from the Museum of Sicán
Archaeometallurgical investigations on the Early-Middle Bronze Age finds from the area of Pyrgos (Limassol)
No full textDiagnostic applied to an easel painting by Ferraù Fenzoni (Chatedral of Todi)
No full textOur team has recently applied a set of complementary techniques to obtain analytical information on four large oil paintings on canvas (3.50 m h. x 2.50 m l.) of the artist Ferraù Fenzoni, located in the Todi Cathedral. Results on one of them, not subjected to recent restoration, are here illustrated, as the most suitable to identify pigments and materials used by this author.
Even if more methodologies have been used, we here mainly compare results coming from Mineralogical Microscopy and X-ray Fluorescence Spectroscopy (XRFS), while only the most significant information from UV Fluorescence (UVF) Photography and Reflectance Spectroscopy is reported.
Data have allowed us to identify almost all the pigments as well as the composition of the preparatory layer. A chemometric treatment of the data obtained for all the four paintings, through the techniques quoted above, surely will add further information: this work is now running
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
The Sanctuary of Hera at River Sele Mouth: Non Destructive Analysis of Archaeological Finds
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