La conservazione e il restauro di manufatti in argento e sue leghe di interesse storico, artistico e archeologico sono uno dei temi di attenzione e dibattito nel campo dei beni culturali. In passato, l’insieme delle operazioni finalizzate al restauro di un qualsivoglia manufatto storico-artistico, non sempre si sono rivelate adeguate a rallentarne il naturale processo di degrado nel tempo. Da qui la consapevolezza di impostare e perfezionare tecniche di restauro sulla base di conoscenze scientifiche sempre più approfondite e con conseguente impiego di metodi d’indagine non distruttivi. La caratterizzazione qualitativa e quantitativa degli elementi e dei composti del manufatto, non solo rappresenta uno strumento prezioso nel campo della ricerca storica (origine, datazione, ecc.), ma è anche di fondamentale importanza per una migliore comprensione e prevenzione dei processi di alterazione cui il manufatto è soggetto. Contemporaneamente lo studio e l’identificazione dei prodotti di corrosione rappresentano un prerequisito essenziale per il corretto restauro di antichi manufatti argentei e un basilare contribuito nel campo della conservazione. Il presente lavoro è finalizzato alla conoscenza approfondita e completa dell’applicabilità e dell’efficacia della tecnica di pulitura di manufatti archeologici in argento e sue leghe usando un laser UV (laser cleaning). A tale scopo gli interventi di pulitura laser sono stati monitorati da indagini di diffrattometria e fluorescenza a raggi X condotte prima, durante e dopo i trattamenti laser. Tali indagini hanno permesso di valutare la concentrazione superficiale degli elementi costituenti le patine e gli effetti fotochimici indotti dal laser.

Silver artefacts and particularly ancient silver artefacts present the serious problem of the black look due to ambient contamination. The black colour is the consequence of the layer forming on the surface made of acanthite and jalpaite, both compounds are sulphur composts. Recently UV laser cleaning technique has demonstrated to be very promising in processing of cultural artefacts. To operate on artefacts without to contaminate the bulk, first we determined the laser fluence threshold of the bulk, second we controlled the surface compounds and at the end we operated the laser irradiation. In this work we utilised certified silver and silver/copper samples in order to perform preliminary studies. The threshold fluence we found were 780 and 510 mJ/cm2 for the Ag pure and for the Ag/Cu alloy, respectively. The jalpaite concentration on Ag/Cu sample increased after the laser dose of 25 J/cm2, while for higher laser dose its value lowered pointing out that complex processes take part during the laser application. As a successful of our studies we applied the technique on a Carlino coin made of silver coined in 1689 under King Carlo II. The analyses were performed by two different techniques able to find the percentage of elements and the chemical compounds; the EDXRF and the XRD. We found that the sulphur concentration decreased on laser dose. Operating on the coin up to a dose of 280 J/cm2 the sulphur concentration deceases up to 20 %, while the coin look becomes clear just after a 50 J/cm2.

In this study, the evidence of electron-dense magnetic inclusions with polyhedral shape in the cytoplasm of Harveyi clade Vibrio strain PS1, a bioluminescent bacterium living in symbiosis with marine organisms, led us to investigate the behavior of this bacterium under exposure to static magnetic fields ranging between 20 and 2000 Gauss. When compared to sham-exposed, the light emission of magnetic field-exposed bacteria growing on solid medium at 18°C ±0.1°C was increased up to two-fold as a function of dose and growth phase. Stimulation of bioluminescence by magnetic field was more pronounced during the post-exponential growth and stationary phase, and was lost when bacteria were grown in the presence of the iron chelator deferoxamine, which caused disassembly of the magnetic inclusions suggesting their involvement in magnetic response. As in luminescent Vibrio spp. bioluminescence is regulated by quorum sensing, possible effects of magnetic field exposure on quorum sensing were investigated. Measurement of mRNA levels by reverse transcriptase real time-PCR demonstrated that luxR regulatory gene and luxCDABE operon coding for luciferase and fatty acid reductase complex were significantly up-regulated in magnetic field-exposed bacteria. In contrast, genes coding for a type III secretion system, whose expression was negatively affected by LuxR, were down-regulated. Up-regulation of luxR paralleled with down-regulation of small RNAs that mediate destabilization of luxR mRNA in quorum sensing signaling pathways. The results of experiments with the well-studied Vibrio campbellii strain BB120 (originally classified as Vibrio harveyi) and derivative mutants unable to synthesize autoinducers suggest that the effects of magnetic fields on quorum sensing may be mediated by AI-2, the interspecies quorum sensing signal molecule.

Ion production

In this paper we report the experimental results of the study of evaluation of an UV laser cleaning treatment on a bronze bell outdoor, dating from the second half of the 600. Energy dispersive X-ray fluorescence (EDXRF) non-destructive analysis was performed on the bell before, during and after the cleaning treatment in order to assess the laser ablation threshold, to define the efficiency of laser cleaning process, to avoid possible damage of laser on the bell, to determine the concentration of the constituents of both the patina and the alloy. In particular, an EDXRF portable apparatus was used in order to evaluate the variation of concentration of sulfur, chlorine, calcium, copper, lead and tin during the laser cleaning.

In this work, we performed experiments of absorption of hydrogen and deuteriumgas by Pd thin films, and we compared the behavior of these samples to unprocessed films. We also employed a continuous wave He–Ne laser to irradiate the samples inside the chamber during the treatment, in order to increase the gas absorption. Using a scanning electron microscope (SEM) and an electron probe micro-analyzer (EDX), we observed structures like spots on the surface of the treated samples. Inside the spots, elements other than Pd were found. Based on these results, we determined that gas loading is an effective way to transmute elements, and the laser action has been a very effective way to increase morphological changes in the treated samples.

This work enters in an interdisciplinary research project involving the archaeometrical analysis of ancient silver coins minted in the Greek colony of Taras (the modern south Italian town of Taranto) between the V century BC and the III century BC. In this work, by comparing the results obtained from X-ray microanalysis data acquired from the least corroded surface areas and the cross- section of coins from SEM-EDX and from XRF analysis, we have demonstrated that analysed coins exhibited a corrosion layer no more than 25 m and that surface silver enrichment was less than 1 wt%. Thus, the data obtained by using X-ray microanalysis from surface may not significantly differ from the original bulk composition. Our results demonstrate that the silver content in the coins decreases considerably ranging from about 97% for the older down to 80% for the ones of 3rd Evans period (300–270 BC), corresponding to the significant social change in the period.