LIF/Raman/XRF non-invasive microanalysis of frescoes from St. Alexander catacombs in Rome.

Laser-induced fluorescence (LIF), Raman spectroscopy and X-ray (XRF) fluorescence were used to study two frescoes at the S. Alexander catacombs complex, in Rome. LIF analysis has shown the presence of a transparent protective material probably deposited in previous restoration treatments and allowed to clearly distinguish the areas undergoing the current restoration process from the ones which still have to be treated. Raman and XRF analysis allowed to non-destructively characterizing most of the pictorial materials used for the artworks, including calcite (CaCO3), red ochre (Fe2O3), minium (Pb3O4), yellow ochre (α-FeOOH) and others. Therefore, thanks to the complementarity of the above-mentioned techniques, it was possible to obtain a detailed characterization of the studied frescoes. Finally, the whole ensemble of results constituted a valid tool to effectively plan the restoration of the frescoes.

Management of NORM-containing processing residuals from hydrocarbons extraction and treatment plants.

Eni, in collaboration with ARPA Veneto, laid down a procedure for the exposure assessment of workers and the public to natural radionuclides contained in oil sludge during their future removal from hydrocarbons extraction and treatment plants. Reference legislation for this study is Italian Legislative Decree 241/00, which regulates protection from exposure to ionising radiation also for working activities with naturally occurring radioactive materials.

Influence of laser wavelength on LIBS diagnostics applied to the analysis of ancient bronzes.

In this work the influence of laser wavelength upon the analytical results obtained from applying LIBS diagnostics to bronzes was investigated theoretically and experimentally at 1,064 nm and 355 nm. The laser ablation process was modeled for a set of reference samples of quaternary Cu/Sn/Pb/Zn alloys and the difference between plume composition and known target stoichiometry was estimated for both of the wavelengths considered. LIBS measurements were performed on the same set of reference samples and under the same experimental conditions to validate the model at different wavelengths. Results from the application of the model to calculate sample optical properties during laser irradiation, absorption in the plasma and plasma temperature are also presented.

Computer simulation study of the closure relations in hard sphere fluids.

We study, using Monte Carlo simulations, the cavity and the bridge functions of various hard sphere fluids: one component system, equimolar additive, and nonadditive binary mixtures. In particular, we numerically check the assumption of local dependency of the bridge functions from the indirect correlation functions, on which most of the existing integral equation theories hinge. We find that this condition can be violated either in the region around the first and second neighbors shell, or inside the hard core, for the systems here considered. The violations manifest themselves clearly in the so-called Duh-Haymet plots of the bridge functions versus the indirect correlation functions and become amplified as the coupling of the system increases.

Stability of the iterative solutions of integral equations as one phase freezing criterion.

A recently proposed connection between the threshold for the stability of the iterative solution of integral equations for the pair correlation functions of a classical fluid and the structural instability of the corresponding real fluid is carefully analyzed. Direct calculation of the Lyapunov exponent of the standard iterative solution of hypernetted chain and Percus-Yevick integral equations for the one-dimensional (1D) hard rods fluid shows the same behavior observed in 3D systems. Since no phase transition is allowed in such 1D system, our analysis shows that the proposed one phase criterion, at least in this case, fails. We argue that the observed proximity between the numerical and the structural instability in 3D originates from the enhanced structure present in the fluid but, in view of the arbitrary dependence on the iteration scheme, it seems uneasy to relate the numerical stability analysis to a robust one-phase criterion for predicting a thermodynamic phase transition.

Radon measurements in the Gran Sasso Underground Laboratory.

Systematic radon monitoring in the Gran Sasso Underground Laboratory was performed in order to determine the background radon contribution to the sophisticated experimental apparatus and to check health physics standards for the personnel. As expected, the radon concentrations were found to depend strongly on the ventilation in the three experimental halls. Considerable reductions in the radon concentrations were obtained in 1993, when fresh air was drawn into the laboratory through a pipe and exhaust air was routed into the highway tunnel.

Radiation protection and radioactive scales in oil and gas production.

Low specific-activity scales consisting of alkaline earth metal carbonates and sulfates are often present in some gaseous and liquid hydrocarbon plants. These scales contain a certain concentration of radium, uranium, and thorium which can cause a risk of gamma irradiation and internal radiocontamination when they must be mechanically removed. The gamma dose rates and the 238U, 232Th, 226Ra concentrations were determined in sludges, scales, and waters of some gas and oil hydrocarbon plants located in Italy, Congo, and Tunisia. 238U and 232Th concentrations were were low. The isotopes 238U and 234U resulted in radioactive equilibrium, while 232Th and 228Th were not always equilibrium. A rough correlation was found between the gamma dose rate and the 226Ra concentration. Some considerations and conclusions about radiation protection problems are pointed out.