1,721,070 research outputs found
Shock waves in laser-induced plasmas
Full text linkThe production of a plasma by a pulsed laser beam in solids, liquids or gas is often associated with the generation of a strong shock wave, which can be studied and interpreted in the framework of the theory of strong explosion. In this review, we will briefly present a theoretical interpretation of the physical mechanisms of laser-generated shock waves. After that, we will discuss how the study of the dynamics of the laser-induced shock wave can be used for obtaining useful information about the laser-target interaction (for example, the energy delivered by the laser on the target material) or on the physical properties of the target itself (hardness). Finally, we will focus the discussion on how the laser-induced shock wave can be exploited in analytical applications of Laser-Induced Plasmas as, for example, in Double-Pulse Laser-Induced Breakdown Spectroscopy experiments
Determination of Ash Content of coal by Laser-Induced Breakdown Spectroscopy
No full textIn this work, we report the results on the application of Laser-Induced Breakdown Spectroscopy (LIBS) to the analysis of coal, for the determination of its Ash Content. This parameter is critical for an efficient use of coal to produce electrical energy in power plants. The results obtained are compared with the ones obtained through conventional chemical laboratory analysis. The study here presented, although performed in the Laboratory, was set up trying to reproduce the real industrial conditions, with the purpose of easing the transfer of the results obtained to the on-line monitoring of coal quality at the power plant
Characterization of historical mortars from the bell tower of St. Nicholas church (Pisa, Italy)
No full textComposite gems in medieval era: the art of counterfeiting before the sixteenth century
No full textThis study explores the evolution of gemstone treatments, with a particular focus on composite gems, which consist of two or three layers of natural gems or artificial materials glued together with adhesives and pigments to imitate genuine natural gems (e.g. doublets and triplets). While traditional treatments such as foiling and coating are well documented, composite gems are largely absent from ancient literature. Pliny is the earliest source to mention the practice of gem imitation, even though with some condemnation. After a considerable gap, the first description of doublets and triplets appear in Leonardi (1502) and Cellini (1568), with the first literature reference to composite gems on goldwork dated to the fourth decade of the fifteenth century. The analysis of a collection of goldsmithing artifacts, dating from the late thirtheenth to the fifteenth centuries and preserved in Tuscany museums, revealed—for the first time—the unexpected presence of composite gems alongside a variety of gemstones and treatment methods. Gemological analysis, including Raman spectroscopy, and the study of adhesives using pyrolysis gas chromatography coupled with mass spectrometry, have shed light on their manufacturing processes. The results suggest that composite gemstones, particularly doublets and triplets, have been systematically produced in specialized workshops since the thirteenth century. This production is likely to have coincided with advances in the technology of cutting precious stones and artificial glass. This research not only sheds light on historical gemstone craftsmanship but also opens new perspectives for studying the evolution of gemology, challenging previous assumptions about the timeline and context of composite gemstone production
Graph clustering and portable X-Ray Fluorescence: An application for in situ, fast and preliminary classification of transport amphoras
Full text linkIn the last decade, numerous papers have been delivered on the potential of portable X-Ray Fluorescence (XRF) in archaeological ceramics. Additionally, new chemometric methods have been proposed to manage chemical dataset and facilitate the use of geochemical discrimination for provenance classification of ancient ceramics. In this contribute, the potential of portable Energy Dispersive X-Ray Fluorescence (ED-XRF) analysis and chemical data processing by Graph Clustering is evaluated for provenance classification of archaeological potteries, discussing possible merits and limits of the employed routine. A ceramic assemblage represented by seventy-three transport amphorae classified by typological analysis have been used as testing materials; spectra have been collected on samples simulating in situ analysis conditions (e.g. on fresh cut surfaces without any preparation) and Graph Clustering method has been applied in chemical data processing; comparison with classical Cluster Analysis (CA) and Principal Component Analysis (PCA) is also evaluated. The obtained results favor the use of Graph Clustering for a preliminary classification of ceramics, which can be chemically analyzed in easy, fast and non-destructive way. With a 75.35% of correct attribution, the study shows the suitability of portable ED-XRF in rapid screening of a large number of ceramic samples usually recovered in the framework of archaeological excavation. Misclassifications have been mostly verified for samples exhibiting a coarse-grained clay paste, suggesting that the method is particularly suitable for fine-grained ceramic materials
Raman, surface‐enhanced Raman and density functional theory analyses of poorly soluble pharmaceuticals in water
No full textPharmacologically active compounds can be dispersed in nature during their manufacture, consumption, and disposal. In this study three pharmaceutical ingredients (acetaminophen, indomethacin and acetazolamide), commonly found in wastewaters, were studied in aqueous environment by Raman spectroscopy. Their spectroscopic properties were computed using density functional theory methods, and a combined atomistic/continuum description of the aqueous solution. The theoretical study allowed to explore the potential energy surface, to identify stable structures, and to accurately predict their Raman response in solution. Given the relevance of the determination of these compounds, their spectral information were related to their concentration level in water and synthetic wastewater by Raman multivariate regression models (partial least squares and Gaussian process regression), reaching limit of detection down to millimolar (investigated range 2.5 – 40 mM, 1.25 – 5 mM, and 0.25 – 5 mM for acetaminophen, indomethacin and acetazolamide, respectively). However, since in real samples pharmaceutical ingredients are usually found at trace level, the suitability of a more performing techniques such as surface-enhanced Raman spectroscopy was evaluated, which enabled us to lower the detection limit of one order on magnitude at least. The quality of the obtained surface-enhanced Raman spectra for the selected molecules should also be highlighted respect to those currently available in the literature. Surface-enhanced Raman analysis of acetazolamide, especially, shows promising features for the development of a sensitive (down to nanomolar) and highly specific analytical method
Walking in the Streets of Pisa to Discover the Stones Used in the Middle Ages
No full textThis paper deals with the stones used as building materials in the centre of Pisa during the Middle Age. Most of the stones are quarried from the nearby mountains,Monte Pisano andMonti d’Oltre Serchio, but there are also other ones, coming from Apuan Alps, Elba Island, western Tuscan coast, and from other quarries opened in the Western Mediterranean area. Our goal is to enrich the classic concept of street photography by inserting, in an interpretative context, the analysis and the observation of the geoenvironment in which we are immersed, daily, for the journey home-office, home-school or just for a simple walk. The tools we have are the eyes, the light and an instrument: the camera. Five stops along a city route allow to describe the main types of stones that have been used to construct and ornate the buildings since the 10th and 11th centuries, when Pisa acquired its traditional fame as one of the four historical Maritime Republics of Italy. Monte Pisano marble is the most important stone in the medieval phase of construction of the city of Pisa, often used together with black limestones to give the typical decorative alternate bands, black and white, of the Pisan Romanesque style. Other types of stones were also used, such as Quartzites, Agnano breccia, Panchina,Macigno sandstone as well as Apuan marble, granitoid rocks fromElba Island and Sardinia, and some rocks from ancient quarries of the western Mediterranean area, such as precious marbles from Greece and Turkey
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