1,720,956 research outputs found
A combined use of FORS, XRF and Raman spectroscopy in the study of mural paintings in the Aosta Valley (Italy)
No full textMural paintings which decorate the external
façade and the internal apsidal wall of a chapel dedicated
to St. Maxime and located at Challand St. Victor in the
Aosta Valley (Italy) have been analysed with a combined
approach involving high-resolution fibre-optic reflectance
spectroscopy (FORS), X-ray fluorescence (XRF) spectrometry
and Raman spectroscopy. The paintings are attributed
to Giacomino from Ivrea, a painter active around the midfifteenth
century. In order to characterise the palette used by
the painter and to yield information useful to restorers, the
cited techniques were used either in situ with portable
instruments and in laboratory, working on micro samples
withdrawn from paintings. The global analytical approach,
though not entirely non-invasive, can indeed be considered
non-destructive as multiple analyses, including SEM-EDX,
could be carried out on the micro samples, exploiting the
features of each technique. On the basis of the information
obtained, the palette was found to be composed of typical
fresco pigments such as calcite, azurite, malachite, vermilion,
red and yellow ochres. A particular situation was noted
for black pigments since the presence of graphite, rather
than wood or lamp carbon, was found, possibly related to
the presence of graphite deposits in the Aosta Valley.
Furthermore, the presence of smalt superimposed to azurite
in areas showing evidence of repainting was detected,
suggesting that paintings were subjected to retouching at a
relatively early stage after the original execution. Finally,
the presence of tin foils, used to decorate haloes of
Evangelists, was ascertained
Identificazione dei coloranti naturali con metodi non invasivi
No full textIl lavoro presenta i risultati preliminari ottenuti da un’indagine sistematica condotta con spettroscopia in riflettanza con fibre ottiche (FORS) nel campo spettrale visibile su un elevato numero di campioni di riferimento in lana e seta tinti con diverse materie prime coloranti naturali (anche in miscela) impiegando vari mordenti e diverse procedure di tintura.
L’analisi degli spettri FORS ottenuti ha consentito di valutare la presenza di caratteristiche spettrali discriminanti per alcune tra le diverse materie prime coloranti considerate (blu e rosse in particolare) e di valutarne le modificazioni associate ai differenti substrati e mordenti, oltre che evidenziarne gli effetti dovuti alla saturazione della tinta
Identification of dyestuffs in historical textiles: strong and weak points of a non-invasive approach
No full textThe dyers of the past exploited a number of natural dyestuffs and dyeing procedures to obtain countless
beautiful colours. It is hard to disclose which dyestuff has been used to dye a historical or an archaeological
textile through non-invasive analytical techniques; therefore invasive analytical strategies, which
require sampling, are generally employed to face this task.
Some useful indication may nevertheless derive from the electronic transitions of dyes supported on
the fibres and the signals can be easily recorded by reflectance spectroscopy in the visible range of the
electromagnetic spectrum. The use of portable instruments equipped with fibre optics allows operation
in-situ directly on the surface of the samples, through a non-invasive approach which is particularly
suitable for the inspection of historical or archaeological samples.
In this paper, the strong and weak points of visible fibre optics reflectance spectroscopy are discussed,
in order to highlight its possible application as a first non-invasive step of a multi-technique analytical
strategy devoted to the recognition of natural dyestuffs in ancient textile artefacts.
Visible fibre optics reflectance spectra were collected from a large set of reference samples (wool and
silk) coloured through various dyestuffs and dyeing procedures, in order to identify the signals of the
coloured species that impregnate the fibres.
The position of minimum, maximum and inflection points in the reflectance spectrawas evaluated and
critically discussed, in order to identify the signals which are not contingent to dyeing procedures or to
the fibre typology, and that can be therefore confidently used for analytical purposes.
In particular, wavelength intervals were defined, in which the characteristic signals of the investigated
dyestuffs (indigo, woad, Saxon blue, logwood, cochineal, madder, brazilwood, old fustic, weld, turmeric
and saffron) are expected. It emerged that visible fibre optics reflectance spectroscopy is poorly selective
for yellow dyes based on curcumins and flavonoids, while it generally succeeds in detecting the other
dyestuffs considered herein.
The information obtained from the reference sample set was then exploited to analyze an embroidered
cloth dated from the seventeenth century. Preliminary information obtained via visible fibre optics
reflectance spectroscopy was confirmed, or integrated, by the results obtained through liquid chromatography
coupled with diode-array detection and mass spectrometry on extracts obtained from some
coloured threads sampled from the historical cloth
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
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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