1,720,979 research outputs found
Microchemical investigation of archaeological copper-based artefacts used for currency in ancient Italy before the coinage
No full textBy means of the combined use of XPS and scanning electron microscopy + energy dispersive spectrometry (SEM + EDS), the microchemical structure of long-term corrosion products grown on Aes Rude, i.e. archaeological unworked lumps of Cu-based materials, has been carried out. In ancient Italy, these materials have been used as currency, as a medium of exchange and as a form of saving, from the sixth to the third centuries BC before the use of the struck metallic coins. The results of the microchemical investigation disclose their apparently unusable nature for any functional applications or possible use, being constituted of highly ferruginous leaded copper, and demonstrate that Aes Rude were a primitive form of currency as suggested by archaeologists. Furthermore, XPS and SEM + EDS results give evidence on the corroded external region of the presence of Cu (II) hydrates mixed with hydrated iron oxide and aluminium-silicon phases coming from the soil that have been incorporated into the patina. This information is useful to identify the material nature of these archaeological artefacts and to select tailored conservation strategies finalized to ensure long life to these relevant ancient materials
Combined use of surface and micro-analytical techniques for the study of ancient coins
No full textBy means of the combined use of surface and micro-analytical techniques the surface chemical composition of ancient coins and some aspects of their manufacturing techniques and of degradation mechanisms have been elucidated. Two case histories are described concerning silver Roman Republican coins and some coins plated with thin films of silver and gold. In particular, the coinage methods, the silvering and gilding techniques and the origin of the embrittlement of these selected Roman coins have been studied by means of the combined use of selected-area X-ray photoelectron spectroscopy (SA-XPS) and scanning electron microscopy and energy-dispersive spectrometry (SEM+EDS). This innovative approach has been utilised in order to gain further insight into the microchemical structure of the external regions of the coins as well as of the bulk features. The results show the use of mercury to coat a copper or silver core with a thin film of precious metals that could be considered the most important advance in the technology of gilding to be made in antiquity. Furthermore, the microchemical investigation of brittle Roman silver coins has allowed us to identify the origin of this troublesome problem. The microchemical results indicate that brittleness is induced by the presence of a low amount of lead that is retained in supersaturated solution when the cast blank was produced. This latter element segregates at the grain boundaries during the coin production and the subsequent long-term ageing at room temperature, thus inducing the alloy fracturing along the weakened grain boundaries
Microchemical investigation of Greek and Roman silver and gold plated coins: coatings techniques and corrosion mechanisms
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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
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
Combined use of SEM-EDS, OM and XRD for the characterization of corrosion products grown on silver roman coins
No full textIn the framework of the PROMET project (European Commission contract No. 509126) aimed to develop new analytical techniques and materials for monitoring and protecting metal artefacts and monuments from the Mediterranean region, the corrosion products grown on silver Roman coins during archaeological burial is studied by means of scanning electron microscopy combined with energy dispersive spectrometry (SEM-EDS), X-ray diffraction (XRD) and optical microscopy (OM) technique
Archaeometry of Sicilian glazed pottery
No full textPetrographic and chemical analyses of the “ceramic body” of 114 majolica artefacts manufactured in Sicily over a wide time range (16th–-19th century) are presented. All the
analysed samples, which belong to museums and private collections,were previously attributed to Sicilian workshops based on stylistic features evaluated by expert historians of art. Unambiguous identification of the production sites of majolica handicrafts in Sicily remains, however, open to question when this relies only on purely stylistic considerations. To this end
compositional and/or textural markers have been searched for in the “ceramic body” of the majolica artefacts in order to differentiate
between the centres of manufacture which were active in Sicily in previous centuries. The study of thin sections has allowed the characterization of the raw materials as well as the microscopic “fabric” of manufacture from four of the more relevant Sicilian production sites, namely: Caltagirone, Sciacca, Palermo and Santo Stefano di Camastra. Chemical data, including minor and trace elements, have been submitted to computer
assisted multivariate statistical techniques. Principal component analysis (PCA) and linear discriminant analysis (LDA) have defined compositional “ceramic reference groups” and, consequently, have enabled a more realistic discrimination of provenance. These data have documented several imports of majolica from Naples, while the same artefacts were previously attributed to Sicilian workshops, based on stylistic considerations
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