1,720,958 research outputs found
Chemometrics and elemental mapping by portable LIBS to identify the impact of volcanogenic and non-volcanogenic degradation sources on the mural paintings of Pompeii
Full text linkThis work has been supported by the Spanish Agency for Research AEI (MINECO-FEDER/UE) through the projects MADyLIN (BIA2017-87063-P) and MINECO-17-CTQ2016-77887-C2-1-R, and the Government of the Principality of Asturias (GRUPIN IDI/2018/000186).Pérez-Diez, S., Fernández-Menéndez, L.J., Veneranda, M., Morillas, H., Prieto-Taboada, N., Fdez-Ortiz de Vallejuelo, S., Bordel, N., Martellone, A., De Nigris, B., Osanna, M., Madariaga, J.M., Maguregui, M
Geophysical and geochemical techniques to assess the origin of rising damp of a Roman building (Ostia Antica archaeological site)
No full textA combined approach based on geophysical and geochemical analyses was carried out to determine the sources of rising damp in “Casa di Diana”, a Roman building located in the Ostia Antica archaeological site (Rome, Italy). The studied building is characterized by high humidity values (closed to saturation, > 90% RH) with significant efflorescence and sub-efflorescence phenomena on masonry walls.
Electrical Resistivity Tomography was performed both inside and outside the building to understand the geological setting, to estimate the freshwater-salt water interface, to locate building foundations and consequently, to evaluate the interaction between the structural elements and groundwater. On the other hand, local shallow groundwater was analysed for soluble salts and isotopic analysis (δ18O) to identify the origin of solutes, to isolate the main factors determining the isotopic content and to investigate the aquifer behaviour in terms of movement and distribution processes. The water samples were collected from one well and one tank sited inside and outside the house, respectively.
The geophysical inverted models, were able to detect a freshwater aquifer at the shallower depths (2–5 m) in correspondence to the Roman foundation walls (extended at depth up to 8 m), while below (8–10 m from surface) the salt water presence is likely. The chemical analysis confirmed that groundwater is slightly mineralized even though the salt concentration can be compatible with an interaction with sea salts, maybe due to the depth of the foundation walls.
Therefore, the proposed approach is suitable for understanding the causal relationship between the observed phenomena, assessing the current degree of conservation of the archaeological site and consequently planning the recovery actions
A non-invasive spectroscopic study to evaluate both technological features and conservation state of two types of ancient Roman coloured bricks
No full textThe study of both original and decaying compounds is relevant in understanding the chemistry behind the deterioration processes, above all in open museum contexts where environmental stressors affect the artefacts. In this sense, a combination of non-invasive spectroscopy techniques (Raman spectroscopy, μ-X-ray fluorescence and X-ray diffraction) was applied on an ancient Roman building (130 CE), the “Casa di Diana” Mithraeum at Ostia Antica archaeological site. The aim is to study the raw materials, manufacturing and decaying products of the two observed types of Roman fired bricks (red and yellow) that compose the building.
The present study estimates an illite raw material of carbonate-bearing marine clay likely referring to the common deposits of central/southern Italy, which contain calcite as accessory phase and a-plastic fraction constituted by quartz, feldspar and opaques. This clay material was added with volcanic temper characterised by abundant clinopyroxene and analcime (from analcimization of leucite) that are typical of the Roman Province volcanism. The firing would be probably the result of oxidizing conditions, as proved by the hematite presence. Thanks to the existence of specific neoformed mineral phases during firing it was possible to assess different temperatures ranges. In detail, the red/orange bricks, for the existence of gehlenite (formed from calcite and its reaction with silicates), were fired at 800–900 °C range; whereas, the yellow ones are characterised by the lack of gehlenite and the disappearance of illite/muscovite, which indicates firing temperature at over 900 °C.
Regarding the decaying products, the gypsum covers most of the surface of most bricks, both red and the yellow ones, but these latter are more susceptible to environmental stressors (sulphates and carbonates).
Therefore, this work points out how by integrated non-invasive approaches it is possible trace back to original firing temperature, technology of manufacture, interpreting ceramic data
Analytical techniques for the characterisation of historical building materials. Case study "Casa di Diana" mithraeum (archeological site in Ostia Antica, Italy)
No full textNowadays, a broad range of analytical techniques are available and applied in the preservation of cultural heritage. However, to characterise the historical materials and to obtain quantitative and qualitative information of their composition and structure, it is necessary to choose the appropriate analytical instruments.
In fact, for each study, analytical aim and nature of the analysed materials, it is necessary to combine the scientific and technological knowledge of the devise used in order to define an adequate plan of action.
In the field of cultural heritage conservation, destructive techniques should be avoided, wherever possible, to preserve the integrity of the historical buildings. Therefore, the development of non-invasive, non-destructive and in-situ analysis is extremely important.
Taking all of this into account, this chapter contains the main advantages of the more useful selected analytical techniques to characterise ancient building materials, taking into consideration a particular case study: a roman masonry, dated 130 a. C., found in the Ostia Antica archaeological site. Specifically we will deal with bricks and mortars, the wall building materials of the “Casa di Diana” Mithraeum.
The combined use of techniques such as polarized microscope, X-ray diffraction (XRD), Raman spectroscopy and, X-ray fluorescence (XRF) allow us to extract information in terms of phase identification, quantification of crystalline compounds and complex poly-phasic mixtures (solid solutions), identification of deterioration products and determine their nature.
In this way, it is possible to analyse the complete life-cycle of the manufacturing processes, starting from the raw materials, through to the man-made production and constructive techniques evolution. Moreover, the obtained results enable us to study the forms of degradation, as well as to choose and apply a suitable procedure for the preservation and safeguard of the materials taken into consideration
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
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