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Micro e Nano Tomografia a raggi X per lo studio della struttura interna di materiali lapidei
No full textX-Ray Computed Tomography as a Non-Destructive Tool for Stone Conservation
No full textLecce stone is a biocalcarenite with a very high content of calcite. It has been used for long-time for the historical building in the south of Italy, especially during the Baroque period, but it is also used in the modern time. As a consequence of its high porosity (typically 40% accessible to water), it can readily take up (rain)water that can facilitate the corrosion of the rock due to the action of acidic pollution gases, such as SOx and NOx. Different kinds of organic products (Paraloid B72, fluorinated rubber or solutions of alkylalkoxysilanes oligomers) are normally applied as hydrophobic coatings (protective agents) with the aim to reduce the damage of the material.
In order to examine thoroughly the distribution of the protectives and the changes of the stone porosity due to these treatments, a number of magnified X-ray computed tomography measurements were performed, using both laboratory instruments and Synchrotron radiation at the beamline ID19 of ESRF.
The product distribution was evaluated by porosity and other morphological parameter measurements: the results reveal that the porosity can be determined with high reproducibility and that there are significant changes of the total porosity and pores size distribution occurring as a consequence of the treatments
Valutazione di Trattamenti Conservativi di Legni Archeologici Imbibiti Mediante Tomografia a Raggi X
No full textInvestigation on porosity changes of Lecce stone due to conservation treatments by means of x-ray nano- and improved micro-computed tomography: preliminary results
No full textCultural heritage materials are subject to continuous chemical and physical changes depending on the establishment of a dynamic equilibrium with the environment in which they are placed. In particular, different phenomena can take place, such as formation of black crusts, corrosion of the material, internal cracks.
Lecce stone, a biocalcarenite mainly used for historical buildings in South Italy, has a high total porosity. In order to prevent its deterioration, different kinds of hydrophobic organic products are applied on the surface of the restored artefacts. Since the efficacy of the treatments depends mostly on the penetration depth and the distribution of the products in the pores, porosity and internal structure of the stone material were mainly investigated in this research. Micro x-ray computed tomography (μ-CT) has been used to study and characterize the internal structure of different samples, untreated and treated with protective products. The porosity and other parameters of the rock were then calculated and compared, before and after the conservation treatment, in order to highlight the changes due to the application of the product.
On the other hand, small pieces of the untreated and treated samples were analysed by sub-micron resolution x-ray tomography where it was possible to see the distribution of the products inside the pores
Investigating morphological changes in treated vs. untreated stone building materials by x-ray micro-CT
No full textCalcareous stones have been largely used to build historical buildings. Among these, the calcarenites are usually characterized by a high content of calcite and a high open porosity, which make them very sensitive to the weathering caused by physical and chemical agents. In order to prevent their deterioration and to retard their decay, different protective products—mainly polymers—are applied on the stone artefact surfaces. In this work we apply the methodology tested in a preliminary study to investigate the morphological changes of the internal structure of a biocalcarenite (Lecce stone) by micro x-ray computed tomography (μ-CT). The porosity and other morphological parameters of the rock before and after the conservation treatment were calculated on a significant number of samples. The Student’s t test was applied for statistical comparison. The results reveal that the treatment with Paraloid B72 (PB 72) is homogenously distributed and causes small changes to the natural properties of the rock, whereas the application of a fluoroelastomer (NH) causes an appreciable decrease in porosity and variation in terms of wall thickness distribution, probably resulting from its inhomogeneous distribution
Evaluation of Conservation Treatments for Archaeological Waterlogged Wooden Artefacts
No full textIn favourable conditions of low temperature and low oxygen concentration, waterlogged wooden artefacts, such as shipwrecks, can survive underwater in relative good condition. Nevertheless, as a result of the action of water and anaerobic bacteria on the cellulose and hemicellulose of the cell walls, the waterlogged wood is very fragile and its consolidation is necessary. These conservation treatments are very often expensive and technically difficult, as they involve the replacement of the waterlogging water with the consolidants, filling the cell walls and all cavities in order to prevent stresses during the drying. Since the effectiveness of the treatment strongly depends on its distribution, the penetration depth and the degree of cavities-filling have been evaluated by micro x-ray tomography (μ-CT). Both laboratory and Synchrotron Radiation-based μ-CT experiments have been performed on different samples coming from findings excavated in the San Rossore archaeological site (Italy), in order to study in detail how the different application parameters can influence the manner in which the conservation products fill the cavities of the wooden structure (i.e. complete or partial volume filling, complete or partial impregnation of the wooden artefact)
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
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