122 research outputs found
Investigation 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
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
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)
PHARMACOKINETIC (PK) AND PHARMACODYNAMIC ANALYSES OF ONCE- AND TWICE-DAILY DARUNAVIR/RITONAVIR (DRV/r) IN THE ODIN TRIAL
No full textHeerlicke nievwe tidinghe vande gelvckige veroveringe van der stadt ende casteele van Bredevoort, gheleghen inden graeffschappe van Zutphen.
No full textVingerafdruk: 000004 - b1=b2 vrunden e$NederVerpakt met de steun van Fonds Inbev-Latour (2010-2012)Herkomst: Vignet Isaac MeulmanMachiels, J. Catalogus van de boeken gedrukt vóór 1600 ; M 305Tiele, P. A. Bibliotheek van Nederlandsche pamfletten. Verzameling Frederik Muller ; 399Valkema Blouw, P. Typographia Batava ; 2318Europeana-GoogleBook
Processamento de dados maregráficos – estação de Viana do Castelo
No full textA clássica questão da qualidade dos dados maregráficos tornou-se mais importantes na última década, pois surgiram novas tecnologias e as redes maregráficas foram modernizadas. Este trabalho permitiu avaliar não só o desempenho dos marégrafos da rede maregráfica, mas também apresentar técnicas de controle de qualidade para dados de marés registados em tempo quase-real que implica a necessidade de implementação de software automático de deteção e sinalização de erros. O controle de qualidade consiste na deteção de valores anómalos, atribuição errada de data e hora e cálculo de
resíduos. Para avaliar o desempenho de medição dos equipamentos maregráficos, o teste de Van de Casteele foi revisitado. A validação das observações in situ do nível do mar foi baseada em procedimentos de controlo de qualidade sugeridos por normativos internacionais
How aligned are the perspectives of EU regulators and HTA bodies? A comparative analysis of regulatory-HTA parallel scientific advice
No full textBackgroundIn 2010, the European Medicines Agency (EMA) initiated a pilot project on parallel scientific advice with Health Technology Assessment bodies (HTABs) that allows manufacturers to receive simultaneous feedback from both the European Union (EU) regulators and HTABs on their development plans for medicines.AimsThe present retrospective qualitative analysis aimed to explore how the parallel scientific advice system is working and levels of commonality between the EU regulators and HTABs, and among HTABs, when applicants obtain parallel scientific advice from both a regulatory and an HTA perspective.MethodsWe analysed the minutes of discussion meetings held at the EMA between 2010, when parallel advice was launched, and 1 May 2015, when the cutoff date for data extraction was set. The analysis was based on predefined criteria and conducted at two different levels of comparison: the answers of the HTABs vs. those of the regulators, and between the answers of the participating HTA agencies.ResultsThe analysis was based on 31 procedures of parallel scientific advice. The level of full agreements was highest for questions on patient population (77%), while disagreements reached a peak for questions on the study comparator (30%). With regard to comparisons among HTABs, there was a high level of agreement for all domains.ConclusionsThere is evident commonality, in terms of evidence requirements between the EU regulators and participating HTABs, as well as among HTABs, on most aspects of clinical development. Indeed, regardless of the question content, the analysis showed that a high level of overall agreement was reached through the process of parallel scientific advice
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