1,720,961 research outputs found
A protocol for non-invasive analysis of miniature paintings
No full textThe characterisation of palettes used in medieval manuscript illumination is an important task from the historical-artistic point of view, but a hard one from the scientific point of view: miniatures cannot be sampled, it is unsuitable to use techniques
operating in contact (i.e. IR in ATR mode) and to perform long-lasting analytical sessions, due to the stress that can be inferred to manuscripts. For these reasons it is necessary to use analytical techniques either non-invasive and fast; moreover,
in most of cases it is necessary to work in situ with portable instruments. Among available techniques working in portable versions, Raman spectroscopy is the most informative, due to its diagnostic power; it requires, though, long time of analysis. XRF spectrometry is a powerful alternative but, being an elemental technique, in some cases it does not yield accurate results. UV-visible-NIR spectrophotometry in reflectance mode with fibre optics (FORS) can be promising as preliminary technique with some apparent limits. In this work a protocol of analysis is proposed for characterisation of miniature paintings on manuscripts in non-invasive way, using only portable techniques and performing in situ analysis. The protocol allows identification of colorants by successive application of complementary techniques, exploiting the advantages of each technique. First of all a palette with several pigments, dyes and lakes on parchment
has been prepared with colorants that were in use in Middle Ages; paints have been prepared in gum Arabic and in egg white, according to ancient recipes described in medieval textbooks such as De arte illuminandi by anonymous, Compositiones ad tingenda musiva by anonymous and Il libro dell’arte by Cennino Cennini. This palette is the base on which to build a database of spectroscopic analysis, reproducing a
situation similar to the one present on manuscripts. It is important, therefore, to stress out the fact that spectra collected from this palette are more reliable that spectra obtained from analysis of colorants in powder. Protocol is started with an overall
investigation with FORS, collecting spectra from all painted areas of the manuscript and comparing them with the database. This allows to identify almost 60-70 % of the colorants present. Then visual inspection of the paintings is performed with a digital camera connected with a 10-80x microscope, in order to have a clear image of areas that show uncertain FORS spectra, i.e. mixtures of pigments, altered paints, etc. Then XRF spectrometry is performed in order to characterise metal pigments (i.e. gold, silver and copper pigments), to verify the presence of overlapping layers, to identify mordants for dyes and lakes and to identify contaminants in pigments yielding information useful to study the provenance of raw materials for colorants. At this stage almost 90% of colorants can be identified. Finally Raman spectroscopy is used for the most uncertain cases. After application of these techniques a wealth of information is obtained, causing little or no stress at all to the manuscripts under analysis
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
La spettroscopia di riflettanza UV-visibile con fibre ottiche: luci ed ombre nell'indagine di manoscritti illuminati
No full textUV-visible spectroscopy in diffuse reflectance mode is a simple and fast technique that can be applied advantageously in the characterisation of pictorial artworks, above all in situations in which the range of pigments and dyes be limited by age, geographical zone and painting technique. It is particularly useful in application with optic fibres in the configuration known as FORS (Fibre Optic Reflectance Spectroscopy). Despite of some clear disadvantages, first of all relative difficulty in interpretation of spectra from mixtures and from dyes, FORS can be proposed as technique of preliminary investigation in the analysis of miniatures on manuscripts, a situation in which fastness of analysis and non invasivity are very important features
Non invasive analysis of miniature paintings: proposal for an analytical protocol
No full textThe characterisation of palettes used in manuscript illumination is a hard analytical task, due to value
and fragility of the analysed items. Analysis on miniatures must be necessarily non-invasive and fast
and requires the use of several techniques since no single technique is able to provide all information
needed. In this work a four-step analytical protocol is proposed for non-invasive in situ characterisation
of miniature paintings. The protocol allows the identification of coloured materials through the
use in sequence of complementary techniques, so as to fully exploit the information given by each
instrument. Preliminarily to the instrumental investigations on ancient books and miniatures is the compilation
of spectroscopic databases obtained from “standard” samples prepared on parchment, according
to recipes described in medieval artistic treatises. The protocol starts with an extensive investigation
with UV–visible spectrophotometry in reflectance mode, collecting spectra from all the most significant
painted areas in the manuscript; chemometric classification is then performed on the spectra to highlight
areas possibly containing the same materials. The second step involves in-depth inspection of miniatures
under optical microscopy that guides the interpretation of reflectance spectra. XRF spectrometry is then
performed to characterise pigments and metal layers, to verify the presence of overlapping layers, to
identify mordants in lakes and to recognise minor components that may yield information concerning
provenance; in addition, chemometric classification can be performed on element concentrations to
highlight similar areas. Finally, Raman spectroscopy is used to shed light on the uncertain cases, if still
present. Such a procedure offers a wealth of information without causing stress to the manuscripts under
analysis
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
On the hierarchical use of colourants in a 15th century book of hours
Full text linkAn illuminated Book of Hours (in use in Chalon-sur-Saône) currently owned by the Museo Civico di Arte Antica and displayed in the prestigious Palazzo Madama in Torino (Italy) was investigated by means of optical microscopy, fibre optic reflectance spectroscopy, fibre optic molecular fluorimetry, X-ray fluorescence spectrometry and Raman spectroscopy. The aim of the scientific survey was to expand the knowledge of the manuscript itself and on the materials and techniques employed by Antoine the Lonhy, the versatile itinerant artist who decorated the book in the 15th century. The focus was to reveal the original colourants and to investigate the pigments used in rough retouches which were visible in some of the miniatures. The investigation was carried out in situ by portable instruments according to a non-invasive analytical sequence previously developed. It was evident that the use of different pigments by the master was ruled, at least partially, by a hierarchical scheme in which more precious materials were linked to the most important characters or details in the painted scene
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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