1,720,960 research outputs found
Virtual Analysis of a Concretioned Skullcap From S'Omu e S'Orku, an Early Holocene Mesolithic Site of Sardinia
No full textEffects of Saline Solutions on Paper-Based Cultural Heritage: Non-Invasive Techniques for Studying Flooded Ancient Books
Full text linkArchival materials are increasingly vulnerable to damage from chemical, physical, biological, and environmental factors, including climate change-related extreme weather events such as torrential rains and flash floods. These conditions pose significant risks to paper-based cultural heritage, leading to degradation from both water and salt exposure. This study investigates the effects of direct immersion in saline solutions on different types of paper, simulating the impact of flooding events. We focused on how varying levels of salinity affect the crystalline structure of paper, which is crucial for understanding its degradation. This study employed non-invasive, portable optical techniques such as luminescence, reflectivity, and Raman spectroscopy to monitor the changes in the paper structure. Our results showed that salt exposure leads to significant alterations in the paper’s crystalline composition. The study concludes that washing treatments are essential for mitigating further degradation, highlighting the importance of timely intervention in preserving cultural heritage. The non-destructive nature of the methods used also demonstrates their potential for in situ applications in cultural heritage conservation
Degradation of CdS Yellow and Orange Pigments: A Preventive Characterization of the Process through Pump–Probe, Reflectance, X-ray Diffraction, and Raman Spectroscopy
Full text linkCadmium yellow degradation afflicts numerous paintings realized between the XIXth and XXth centuries. The degradation process and its kinetics is not completely understood. It consists of chalking, lightening, flaking, spalling, and, in its most deteriorated cases, the formation of a crust over the original yellow paint. In order to improve the comprehension of the process, mock-up samples of CdS in yellow and orange tonalities were studied by means of structural analysis and optical characterization, with the principal techniques used in the field of cultural heritage. Mock ups were artificially degraded with heat treatment and UV exposure. Relevant colorimetric variation appears in CIE Lab coordinates from reflectance spectra. XRD, SEM-EDS, and Raman spectroscopy revealed the formation of cadmium sulfate, whilst time-resolved photoluminescence and pump–probe transient absorption spectroscopy suggest the formation of a defective phase, compatible with Cd vacancies and the formation of both CdO and CdSO(4) superficial clusters
Defect Related Emission in Calcium Hydroxide: The Controversial Band at 780 cm−1
Full text linkCalcium hydroxide, a crystal involved in the cycle of calcination and carbonation of calcium oxide, finds several applications from cultural heritage to the dentistry branch or to the construction industry. When excited at 1064 nm, Raman spectra of calcium hydroxide show a broad composite band peaked at about 780 cm−1, corresponding to 1170 nm. Since it is not observed with visible excitation, the origin of this band is debated, being assigned to some pre-existent luminescent impurities or some structural defect of the lime formed after the synthesis of the material. To shed light on the formation of this band, we synthetised the lime paste starting from pure calcite powders. The obtained fresh Ca(OH)2 samples did not show any band in the investigated range, irrespective of the laser excitation applied. A detailed analysis of the excitation and emission spectra in the near infrared region did not show the 1170 nm band, supporting the hypothesis of a post-synthesis origin. Thus, we carried out thermal treatments at different temperatures (90–500 °C) and under different environments (in air or under nitrogen flux) on synthesised fresh Ca(OH)2 powders. We also investigated the time evolution of the samples, monitoring the Raman spectra over 90 days after a specific treatment. The collected data support the hypothesis of a defect-related luminescence centre, whose formation depends on the temperature and environment of the treatment, which appears as a preferential site for the carbonation process of the calcium hydroxide. These results can be useful in the field of Cultural Heritage for dating purposes, and to determine the conservation state of Ca(OH)2 containing relics to prevent the possible activation of degradation processes
Innovative method for provenance studies in cultural heritage: A new algorithm based on observables from high-resolution Raman spectra of red ochre
Full text linkRed ochre, typically derived from iron oxides and hematite, has been used since Pleistocene times for a range of different applications, practical as well as symbolic, including cave paintings and use in prehistoric burials. The importance to discover new methods for provenance determination, based on non-destructive portable techniques, represents a new challenge in the field of diagnostics of cultural heritage. This study presents the data obtained from the analysis of several non-flaked tools and ochre-stained bones, showing evidence of ochre processing at the Mesolithic site of S'omu e S'Orku in Sardinia (Italy). To investigate the provenance of the ochre (hematite phase) found on a massive stone from the site and also used to cover the bones, we propose three distinct approaches derived from high-resolution Raman spectra of ochres, aiming to identify the maximum number of observables that can be reconducted to unicity criteria. The reliability of this method enables the development of an automatic algorithm of Artificial Intelligence able to recognize the provenance of raw materials used in a range of activities. Furthermore, this study sheds light on one of the earliest and most distinctive Mesolithic burials uncovered in Sardinia to date, providing valuable insights into the human colonization of the island and the symbolic practices of its inhabitants during the Holocene epoch
Fresco Paintings: Development of an Aging Model from 1064 nm Excited Raman Spectra
Full text linkIn this study, we proposed a preliminary kinetic model applied to the carbonation process of fresh lime with the intention to realize a diagnostic tool for aged fresco paintings. The model can be useful, in particular, in the fields of conservation and restoration of ancient lime wall paintings. The dating procedure was achieved through the analysis of 1064 nm excited Raman spectra collected on artificially aged lime samples in addition to ancient samples taken from literature and covering a period of two thousand years. The kinetic model was developed monitoring the concentration of emitting defective centers related to the intensity of 780 cm−1 calcium hydroxide band as a function of the time and depth. This preliminary model shows how Raman spectroscopy, especially NIR micro-Raman, is advantageous for diagnostics and conservation in the cultural heritage field
Application of Raman Spectroscopy to Ancient Materials: Models and Results from Archaeometric Analyses
Full text linkNumerous experimental techniques of analysis find applications in many branches of the archaeometry. Among them, Raman spectroscopy carved out a niche in the field of diagnostic and conservation of cultural heritage. The exceptional ability to predict and discover the structural properties of materials set for Raman spectroscopy, an exclusive role among the analytic techniques, is further boosted when it is coupled with mathematical or statistical models able to deepen the studied phenomena. In this work, we present a review of recent studies where pairing Raman spectroscopy and mathematical models allowed achieving important results in the case of potteries, porcelains, ancient and modern paper, ancient jewelry, and pigment degradation. The potentialities of this approach are evidenced and analyzed in detail
Degradation studies on different pigments and binders: new approaches to diagnostics in cultural heritage
Full text linkStudying the state of degradation, alteration and conservation of an artwork is the starting point of a restoration process. This first step is commonly known in the field of cultural heritage as "diagnostics". A careful diagnosis allows choosing the best restoration approach for a sample under examination. The diagnostics of an artwork permits not only a complete characterization of materials realized by an artist, but also the identification of the degradation products generated over time.
The main intent of this work is to expand the diagnostic research both from a descriptive point of view for the degradation process of the painted surface, and from the point of view of new approaches and methodologies for diagnostics. For what concerns the first one, we worked with two main purposes: kinetics studies in the case of San Giovanni white with the help of a non-invasive technique (Raman spectroscopy), and the characterization of the degradation path and individuation of the respective alteration products in the case of Red vermilion and Cd-pigments, always favouring the choice of a non-destructive techniques, conventional or not, such as non-linear optics. Regarding the development of new approaches and methodologies, we studied the photo-acoustic method coupled with SORS (Spatially Off-set Raman Spectroscopy) as a new tool for stratigraphy analyses of frescoes. This work is carried out in collaboration with the research centre FORTH (Crete) and it has been tested on artificial frescoes mock-ups and on real frescoes fragments, in order to obtain compositional information and stratigraphic imaging on the samples
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
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