Search

Abstract With the aim to establish advantages and limitations of techniques commonly employed for material characterization of Cultural Heritage objects, we performed comparative measurements by LIBS, X-ray Fluorescence (XRF) and Particle Induced X-ray Emission (PIXE) on four typologies of materials. The samples include: 1) egg tempera pigments on gypsum ground; 2) oil paints on gypsum ground with light or dark imprimitura ; 3) fragments of decorated glazed ceramic, and 4) ancient Roman coins. The optimal choice of an analytical instrument depends also on the sample type, its dimensions and transportability, and for these reasons our measurements involved two types of instruments per technique. The LIBS probing was done by a table-top instrument (on coins and ceramics) and by a stand-off system at distance of 9.5 m (on pigments). The XRF measurements involved a laboratory micro-XRF system (on coins) and a portable instrument (on pigments and ceramics). The PIXE analyses were obtained by TOP-IMPLART accelerator at ENEA Frascati, using a low energy line that produces the proton beam with adjustable energy between 3 and 7 MeV (used for the pigments and ceramics), and by INFN-LABEC system with proton energy of 3 MeV and complemented by Elastic Backscattering Spectrometry (EBS), for coin samples. Results relevant to quantitative analysis of major sample constituents, identification of trace components, and stratigraphy are reported and discussed for the examined typologies of samples. Graphical abstract Unlabelled Image Highlights • We compared performances of LIBS, PIXE and XRF techniques applied for cultural heritage. • The samples include tempera or oil pigments, decorated glazed ceramics, and ancient coins. • LIBS detected many more elements in each sample than PIXE and XRF. • By changing the particle energies PIXE is able to identify different layers if sufficiently thick. • LIBS provides well resolved multi-elemental depth profiling also on thin layers. [ABSTRACT FROM AUTHOR]

The laser induced plasma spectroscopy was applied on particles attached on substrate represented by a silica wafer covered with a thin oil film. The substrate itself weakly interacts with a ns Nd:YAG laser (1064 nm) while presence of particles strongly enhances the plasma emission, here detected by a compact spectrometer array. Variations of the sample mass from one laser spot to another exceed one order of magnitude, as estimated by on-line photography and the initial image calibration for different sample loadings. Consequently, the spectral lines from particles show extreme intensity fluctuations from one sampling point to another, between the detection threshold and the detector's saturation in some cases. In such conditions the common calibration approach based on the averaged spectra, also when considering ratios of the element lines i.e. concentrations, produces errors too large for measuring the sample compositions. On the other hand, intensities of an analytical and the reference line from single shot spectra are linearly correlated. The corresponding slope depends on the concentration ratio and it is weakly sensitive to fluctuations of the plasma temperature inside the data set. A use of the slopes for constructing the calibration graphs significantly reduces the error bars but it does not eliminate the point scattering caused by the matrix effect, which is also responsible for large differences in the average plasma temperatures among the samples. Well aligned calibration points were obtained after identifying the couples of transitions less sensitive to variations of the plasma temperature, and this was achieved by simple theoretical simulations. Such selection of the analytical lines minimizes the matrix effect, and together with the chosen calibration approach, allows to measure the relative element concentrations even in highly unstable laser induced plasmas. [ABSTRACT FROM AUTHOR]

Small fragments of the oil paintings "Emmaus Dinner" by Bellini (XVII century) and "Annunciation" by Brughi (XVIII century) were taken to laboratory because of insufficient information collected in-situ. At first, the samples were analyzed by SEM-EDX and FTIR Spectroscopy in order to identify the elemental and molecular composition of the surface layers, mostly covered by Ca-based patina (calcium oxalate and carbonates). Afterwards, the depth profiling by LIBS made possible to distinguish surface contaminations and retouches from the original pictorial materials. Stratigraphic variations of the chemical composition were established by a proper normalization of the element line intensities, necessary due to large changes of overall plasma intensity during ablation of heterogeneous samples. So obtained layer separations were confirmed by Principal Component Analysis (PCA). Studies of the correlations and ratios between intensities of the analytical element lines were effective to identify pigments and priming layers and, in some cases, to indicate also a possible material provenance. In the Bellini's painting we identified Natural Umber, Azurite, Green Earth, Goethite, Lead-Tin Yellow and Lead White, the latter detected in all examined fragments. The surface contamination by debris and retouches by modern pigments containing Ba, Cr and Zn were also detected. The presence of K and Na in the priming layer suggests the use of glass, commonly employed in the XVII century. In the Brughi's painting we identified a thin layer of Ultramarine Blue placed over Green Earth layer while the priming layer was mainly constituted by gypsum. On this painting, we also detected surface restoration by Ba based modern pigments. [Display omitted] • LIBS stratigraphy on small fragments from oil paintings revealed different layers. • The used materials are identified from correlations between the element lines. • Surface contamination and restoration are recognized by monitoring the line ratios. • The realization techniques and probable provenance of some materials are established. • Surface SEM-EDX and FTIR analysis supported the assignments of certain pigments. [ABSTRACT FROM AUTHOR]

The goal of this study was to investigate whether a secondary plasma can be formed on a non-metallic target under water and to give insight into the related processes. The material of choice here was alumina, since its physical, thermal and mechanical properties are substantially different from those of pure Al, only for which secondary plasma formation was recently demonstrated. To achieve this, plasma and bubble formation on alumina under water after single pulse laser excitation were studied using fast photography, shadowgraphy, Schlieren and LIBS techniques. The results show that the secondary plasma caused by backward heating of the target and successive slow target evaporation into the growing vapour bubble also occurs for alumina. The secondary plasma formed on alumina involves only a narrow interaction region on the target resulting in an almost spherical plume shape. In contrast, on thermally conductive and easily melting/evaporating aluminium, the secondary plasma is intense, with a large volume which is flattened on the target surface. Inside the expanded bubble above the alumina target, glowing particles were not observed. Due to less efficient secondary plasma formation on alumina compared to aluminium, its optical emission only slightly increases at a delay of 400 ns from the laser pulse but emission persists during three bubble cycles with a total duration of about 650 μs. The LIBS spectra related to the secondary plasma are almost free from any continuum component and show narrow emission lines from low excited states. Here we discuss the observed differences in the plasma’s spatial, temporal and spectral evolution on the two considered target materials. The obtained results indicate that under water a secondary plasma might be formed on very different materials and that its detection produces a good quality LIBS signal from single pulse excitation using a commercial nanosecond laser source. [ABSTRACT FROM AUTHOR]

The final scope of this work was to determine the elemental composition of different types of decorative layers present on ancient ceramic fragments through depth profiling by laser induced breakdown spectroscopy (LIBS). The measurements were performed by a stand-off LIBS system at distance of 10.5 m, by employing ns laser pulses at 1064 nm and an Echelle spectrometer. The detected plume intensity strongly differs from one sample/coating to another and changes importantly also in repeated measurements on the almost homogeneous bulk materials. Furthermore, the plasma intensity and its parameters widely change during the depth profiling, as evident from the ratio of here monitored Fe I and Fe II spectral lines. Averaging the line intensities over six repeated measurements, also on the bulk material and for a selected consecutive shot number, produces the errors up to 60% around the mean value and this makes impossible to compare composition of the ceramic body with its decorative layers. To overcome this problem, we developed a theoretically supported procedure for the spectral line corrections in presence of variable plasma parameters, which considers the relative changes among a sufficiently large data set. This method allowed improving the measurement precision up to five times, obtaining a flat response during the depth profiling, and measuring composition of the surface layers. The correction factors are specific for one analytical line of the considered element. The proposed procedure could be universally applied for increasing the LIBS precision in repeated samplings or during the depth profiling, without time consuming calculations of the plasma temperature and the electron density, which also suffer from large measurement errors. [ABSTRACT FROM AUTHOR]

In this work we present studies of spatial and temporal plasma evolution after single pulse ablation of an aluminium target in water. The laser ablation was performed using 20 ns long pulses emitted at 1064 nm. The plasma characterization was performed by fast photography, the Schlieren technique, shadowgraphy and optical emission spectroscopy. The experimental results indicate the existence of two distinct plasma stages: the first stage has a duration of approximately 500 ns from the laser pulse, and is followed by a new plasma growth starting from the crater center. The secondary plasma slowly evolves inside the growing vapor bubble, and its optical emission lasts over several tens of microseconds. Later, the hot glowing particles, trapped inside the vapor cavity, were detected during the whole cycle of the bubble, where the first collapse occurs after 475 μs from the laser pulse. Differences in the plasma properties during the two evolution phases are discussed, with an accent on the optical emission since its detection is of primary importance for LIBS. Here we demonstrate that the LIBS signal quality in single pulse excitation underwater can be greatly enhanced by detecting only the secondary plasma emission, and also by applying long acquisition gates (in the order of 10–100 μs). The presented results are of great importance for LIBS measurements inside a liquid environment, since they prove that a good analytical signal can be obtained by using nanosecond pulses from a single commercial laser source and by employing cost effective, not gated detectors. [ABSTRACT FROM AUTHOR]

Experimental estimates of ecologically acceptable single-bath lubricant, are presented and compared to those of classical lubricants in this paper. A device was created for the realisation of the strip ironing test with double thinning and a appropriate definition of the friction coefficient is used. Strips of 2.5 mm-thick low carbon steel sheets were used in the single-phase process with a maximum thinning deformation of 25%. In addition to the single-bath ecological lubricant, a phosphate layer with mineral oil was applied, as was lithium lubricating grease with MoS2 and mineral oil with EP additives. The basic criterion for the estimates was the change in the friction coefficient and the secondary criterion was the level of surface microchanges due to sliding. The applied test procedure enables the clear differences between the lubricating properties of the investigated lubricants to be established. [ABSTRACT FROM AUTHOR]

This paper provides an overview of the laser induced breakdown spectroscopy (LIBS) inside liquids, applied for detection of the elements present in the media itself or in the submerged samples. The processes inherent to the laser induced plasma formation and evolution inside liquids are discussed, including shockwave generation, vapor cavitation, and ablation of solids. Types of the laser excitation considered here are single pulse, dual pulse and multi-pulse. The literature relative to the LIBS measurements and applications inside liquids is reviewed and the most relevant results are summarized. Finally, we discuss the analytical aspects and release some suggestions for improving the LIBS sensitivity and accuracy in liquid environment. [ABSTRACT FROM AUTHOR]

Abstract: Influence of time delay between two laser pulses on the LIBS (laser induced breakdown spectroscopy) signal inside liquids was investigated and the results are compared with data from literature. Plasma was produced by laser ablation (LA) of aluminum inside water and its emission after the second laser pulse was characterized by spectrally and time resolved detection. Light propagation through the vapor bubble formed by the first laser pulse was studied by measurements of beam scattering and transmission. Optical absorption by the evolving bubble is not significant, but its growth is accompanied by lowering of its refraction index nb with respect to surrounding liquid; this effect increases defocusing both of the incident beam and of the out-coming plasma radiation. Collection efficiency of the secondary plasma emission rapidly degrades with the cavity growth, but close to its full expansion the LIBS signal partially recovers through Snell''s reflections at the liquid–vapor interface, which produce a bright spot close to the bubble center. Such a light redistribution allows detecting of the emission from external plasma volume, otherwise deflected out of the collection system. Except for strong line transitions from the main sample constituents, self-absorbed inside the high-pressure cavity, we observed the highest LIBS signal when sending the second pulse well before the bubble is fully expanded. Transitions of the pressure wave through the focal volume, formed by the first laser pulse and reflected from the cell''s walls and sample back-plane, enhances the LIBS signal importantly. The measured lifetime of the secondary plasma rapidly decreases with the bubble expansion. Here, we also discuss the optimization of the optical collection system and some analytical aspects of double-pulse (DP) LIBS inside liquids. [Copyright &y& Elsevier]

Abstract: Plasma and vapor bubble formation and evolution after a nanosecond laser pulse delivered to aluminum targets inside water were studied by fast photography. This technique was also applied to monitor the plasma produced by a second laser pulse and for different interpulse delays. The bubble growth was evident only after 3μs from the first laser pulse and the bubble shape changed during expansion and collapse cycles. The evolution and propagation of the initial shockwave and its reflections both from the back sample surface and cell walls were detected by Schlieren photography. The primary plasma develops in two phases: violent particle expulsion and ionization during the first μs, followed by slow plasma growth from the ablation crater into the evolving vapor bubble. The shape of the secondary plasma strongly depends on the inner bubble pressure whereas the particle expulsion into the expanded bubble is much less evident. Both the primary and secondary plasma have similar duration of about 30μs. Detection efficiency of the secondary plasma is much reduced by light refraction at the curved bubble–water interface, which behaves as a negative lens; this leads to an apparent reduction of the plasma dimensions. Defocusing power of the bubble lens increases with its expansion due to the lowering of the vapor''s refraction index with respect to that of the surrounding liquid (Lazic et al., 2012 [1]). Smell''s reflections of secondary plasma radiation at the expanded bubble wall redistribute the detected intensity on a wavelength-dependent way and allow gathering of the emission also from the external plasma layer that otherwise, would not enter into the optical system. [Copyright &y& Elsevier]

Light transmission through a laser formed bubble (LFB) following ablation of a metallic target inside water was studied. During the early expansion and late collapsing phases, the refraction index nb of the hot high-pressure vapor bubble is higher than 1.23 and close to that of the surrounding liquid. The cavity growth lowers nb down to 1.00 and causes strong defocusing of the incident laser beam with consequent enlargement of the ablation crater diameter, here overcoming factor two. Inhomogeneous water vapor clustering inside the cool expanded bubble further perturbs the light transmission and induces irregular ablation by the successive laser pulse. [ABSTRACT FROM AUTHOR]

Abstract: With the aim to study and to improve LIBS capability for detecting residues of energetic compounds in air surrounding, nine types of explosives and some potential interferents, placed in small quantities on a metallic support, were interrogated by a laser. Shot-to-shot behavior of the line intensities relative to the sample constituents was studied. The detected plasma was not stoichiometric and the line intensities, as well as their ratios, were changing even for an order of magnitude from one sampling point to another, particularly in the case of aromatic compounds. We explained some sources of such LIBS signal''s behavior and this allowed us to establish a data processing procedure, which leads to a good linearization among the data sets. In this way, it was possible to determine some real differences between the LIBS spectra from explosives and interferents, and to correlate them with molecular formulas, with some known pathways for the molecule''s decomposition and with successive chemical reactions in the plasma. Number spectral parameters, which distinguish the each studied explosive from other organic materials, were also determined and compared with previously published results relative to percentages of correct classifications for the same explosives. Experimental conditions for reliable recognition of the explosives by LIBS in air are also suggested, together with the parameters that should be considered or discarded from the classification procedure. [Copyright &y& Elsevier]

Abstract: With the aim of realizing a compact instrument for detection of energetic materials at trace levels, laser induced breakdown spectroscopy was applied on residues from nine explosives in air surroundings. Different potentially interfering organic materials were also analyzed. The residues were not uniformly distributed on an aluminum support and single-shot discrimination was attempted. For a single residue type, large shot-to-shot fluctuations of the line intensity ratios characteristic for organic samples were observed, which made material classification difficult. It was found that both atomic and molecular emission intensities, as well as their ratios, are strongly affected by an amount of the ablated support material, which mainly determines the plasma temperature. With respect to the spectra from the clean support, emission intensities of atomic oxygen and nitrogen are always reduced in the presence of an organic material, even if its molecules contain these elements. This was attributed to chemical reactions in a plasma containing carbon or its fragments. Hydrogen atomic emission depends strongly on the local humidity above the sampled point and its line intensity shows shot to shot variations up to 50%, also on a homogeneous sample. It is argued that shock waves generated by previous spatially and/or temporally close laser pulses blow away a relatively heavy water aerosol, which later diffuses slowly back towards the sampled point. C2 and CN exhibit a peak emission behavior with atomic Al emission, and their variable ratio indicates an existence of different formation or removal mechanisms from the plasma, depending on the plasma parameters and on the composition of the organic residue. On the basis of these observations, an attempt is made to establish a suitable procedure for data analysis and to determine the optimal experimental conditions, which would allow for discrimination of explosives from other, potentially interfering, residues. [Copyright &y& Elsevier]

Abstract: ExoMars, ESA''s next mission to Mars, will include a combined Raman/LIBS instrument for the comprehensive in-situ mineralogical and elemental analyses of Martian rocks and soils. It is inferred that water exists in the upper Martian surface as ice layers, “crystal” water or adsorbed pore water. Thus, we studied Laser Induced Breakdown Spectroscopy (LIBS) on wet and dry rocks under Martian environmental conditions in the temperature range −60 °C to +20 °C and in two pressure regimes, above and below the water triple point. Above this point, the LIBS signals from the rock forming elements have local minima that are accompanied by hydrogen (water) emission maxima at certain temperatures that we associate with phase transitions of free or confined water/ice. At these sample temperatures, the plasma electron density and its temperature are slightly lowered. In contrast to powder samples, a general increase of the electron density upon cooling was observed on rock samples. By comparing the LIBS signal behavior from the same rock with different grades of polishing, and different rocks with the same surface treatment, it was possible to distinguish between the influence of surface roughness and the bulk material structure (pores and grains). Below the triple point of water, the LIBS signal from the major sample elements is almost independent of the sample temperature. However, at both considered pressures we observed a hydrogen emission peak close to −50 °C, which is attributed to a phase transition of supercooled water trapped inside bulk pores. [Copyright &y& Elsevier]

Abstract: We applied Laser Induced Breakdown Spectroscopy (LIBS) on moist soil/rock samples in simulated Martian conditions. The signal behavior as a function of the surface temperature in the range from +25 °C to −60 °C was studied at pressure of 7 mbar. We observed the strong signal oscillations below 0 °C with different negative peaks, whose position, width and magnitude depend on the surface roughness. In some cases, the signal was reduced for one order of magnitude with consequences for the LIBS analytical capability. We attribute such a signal behavior to the presence of supercooled water inside the surface pores, which freezing point depends on the pore size. On a same rock samples with different grades of the surface polishing, the signal has different temperature dependence. Its decrease was always registered close to 0 °C, corresponding to the freezing/melting of normal disordered ice, which can be present inside larger pores and scratching. An amount of the signal reduction at the phase transition temperatures does not seem to change with the laser energy density in the examined range. Comparative measurements were performed on a frozen water solution. A large depression, for two orders of magnitude, of the LIBS intensity was observed close to −50 °C. The same negative peak, but with a smaller magnitude, was also registered on some rock/soil samples. Ablation rates and plasma parameters as a function of the sample temperature are also discussed, and their consequences for in-situ analyses. [Copyright &y& Elsevier]

Abstract: Laser Induced Breakdown Spectroscopy (LIBS) was applied on sediments directly under water. The aim of the research was to develop a method for measuring the sediment elemental composition, including minor elements, which could be implemented in-situ. The plasma was generated by a double-pulse, Q-Switched Nd:YAG laser operated at 1064 nm. For signal detection, both ICCD and non-gated, compact detectors were used. The major difficulties in underwater sediment analyses are related to the natural and laser induced surface roughness, and to the sample softness. The latter is responsible for the formation of particle clouds above the surface, which scatter both the laser and plasma radiation, and often results in breakdown formation above the analyzed surface. In such cases, a broad sonoluminescence emission from water, formed during the gas bubble collapse was sometimes registered. Under optimized experimental conditions, even by using a non-gated detector and single shot acquisition, it was possible to detect several minor sediment constituents, such as titanium, barium, manganese and others. A crude estimation of the Limit of Detection (LODs) for these elements was performed by underwater measurements on certified soils/sediments. Due to strong shot-to-shot fluctuations in the plasma temperature, well correlated calibration curves, aimed for quantitative analyses, could only be obtained after applying an appropriate data processing procedure. The latter selects automatically only the spectra characterized by similar plasma parameters, which are related to their continuum spectral distribution. Application of such a procedure improves the measurement accuracy also in other surroundings and on samples different from the ones analyzed here. [Copyright &y& Elsevier]

Abstract: The detection of different materials immersed in seawater has been studied by means of Laser Induced Breakdown Spectroscopy. The plasma emission was produced by a Q-Switched Nd:YAG laser operated at 1064 nm in a dual pulse mode. Different classes of materials potentially found in the undersea archaeological parks, such as iron, copper-based alloys, precious alloys, marble and wood have been examined. Data acquisition and processing were optimized for better signal control and in order to improve the detection threshold. In all the examined cases but wood, qualitative analysis was successful and allowed for the material recognition. The spectral features necessary to clearly distinguish marble materials from calcareous rocks have been also established. It was found that these characteristic spectral intervals could be also used for the recognition of sedimentary layers deposited on the underwater findings. Quantitative chemical analysis was also performed on submerged bronze samples, after generating calibration curves with standards of similar matrix composition. [Copyright &y& Elsevier]

Abstract: Laser-induced breakdown spectroscopy (LIBS) has been performed on immersed solid samples with different grades of surface roughness and material homogeneity and on bulk water solutions. The underwater plasma was produced by applying double-pulse excitation at 1064 nm, with different sets of laser pulse energies. LIBS spectra were recorded separately for each couple of laser pulses in order to monitor shot-to-shot plasma behavior and to apply signal post processing. The latter was aimed at improving the detection limits for elemental analyses. Except in the case of flat homogeneous solid samples at high laser pulse energies, the measurements were affected by strong shot-to-shot signal oscillations. Automatic elimination of low intensity spectra reduced the detection limit up to a factor of seven. The optimum level for spectral filtering depends strongly on sample properties. For bulk water, a poor correlation was observed between the peak line intensities and the plasma continuum emission, making the peak-to-background ratio unsuitable for internal standardization purposes. The analytical performance of LIBS for bulk liquid was also affected by the spatial fluctuations of the breakdown location, a phenomenon known as “moving breakdown” in the literature, which was responsible for the signal depletion in the detection region. In preliminary measurements on water solutions, the detection limit of 0.2 mg/l for magnesium has been obtained after applying data post processing. [Copyright &y& Elsevier]

Single and double pulse laser-induced breakdown spectroscopy (LIBS) was carried out on aluminum samples in air. In the case of double pulse excitation, experiments were conducted by using the same laser source operated at the same wavelength (1064 nm in most cases here presented). A lowering of the second pulse plasma threshold was observed, together with an overall enhancement in line emission for the investigated time delay between the two pulses (40–60 μs). The laser-induced plasma originated by a single and double pulse was investigated near ignition threshold with the aim to study possible dynamical mechanisms in different regimes. Currently available spectroscopic diagnostics of plasma, such as the line broadening and shift due Stark effects, have been used in the characterization in order to retrieve electron densities, while standard temperature measurements were based on Boltzmann plot. Plasma relevant parameters, such as temperature and electron density, have been measured in the plasma decay on a long time scale, and compared with crater shape (diameter and inferred volume). The comparison of double with single pulse laser excitation was carried out while keeping constant the energy per pulse; the influence of laser energy was investigated as well. Results here obtained suggest that use of the double pulse technique could significantly improve the analytical capabilities of LIBS technique in routine laboratory experiments. [Copyright &y& Elsevier]

Malignant tumors of the salivary glands are rare malignancies and most of them affect major salivary glands. The aim of this study was to analyze trends in age-standardized incidence rates of major salivary glands tumors among the Belgrade population. Data were obtained from The Serbian Cancer Registry. We analyzed all cases of malignant tumors of major salivary glands registered in Belgrade from January 1st 1999 to December 31st 2010. Joinpoint regression analysis was used to define trends and annual percentage change (APC). A total number of 283 (168 in men and 115 in women) major salivary glands tumors were reported to The Registry during the study period. Age-standardized incidence rate (ASR) for entire period and for both sex was 0.87/100.000 person, 1.13 for men and 0.67 for women. ASR increased with APC of 6.4% in both sexes (p

In order to answer to some specific unsolved questions regarding ancient Roman frescoes from Villa della Piscina, already examined by other spectroscopic techniques, LIBS stratigraphic measurements were performed on the most representative sample fragments. We found that taking into account just the line intensities or applying a single normalization approach based on ratio of the element's analytical line and a selected transition from a main sample constituent, here of Ca, might produce misleading results of depth profiling by LIBS. During the laser induced ablation, parameters of the detected plasma might change both due to the crater development and different overlaid matrix materials, as in case of heterogeneous painted samples, possibly realized with different techniques. We performed the theoretical simulations to select the pair of Cu I and Ca I lines less sensitive to variations of the plasma temperature in presence of local thermal equilibrium (LTE). However, when using not gated detectors as here, the experimental results showed that only a partial LTE holds. For this reason, the choice of the optimum normalization line must take into account also the energy gap between the excited levels of the species, which energies affect the emission lifetime and consequently, the intensity captured by not gated detectors. In following, to the each element's analytical line a specific Ca I line was attributed for deducing the relative element distribution in sample. Following this approach and by detecting simultaneously up to 20 elements per laser pulse, it was possible to distinguish clearly by LIBS also thin overpainted layers of similar colour, and to recognize the painting technique used. Through detection of trace and light elements and studies of their correlations with other elements during ablation of on painted layer, in some cases it was possible also to establish the geographical provenance of the material used. Unlabelled Image • In depth profiling the signal normalization should be weakly sensitive on the plasma temperature. • For the plasma in LTE we simulated the normalizations on different Ca I lines. • For not gated detection the energy gap among the excited lines also plays a role in the normalization. • The proper normalization per each element line allowed to distinguish thin layers on fresco samples. • By LIBS profilometry the realization technique and provenience of some pigments were determined. [ABSTRACT FROM AUTHOR]

Abstract: The main aim of this work is to demonstrate the capability of laser-induced breakdown spectroscopy (LIBS) for the recognition and identification of archeological materials submerged in sea water at depths up to 30m. For this purpose, a remote LIBS instrument based on a fiber optic cable to deliver the laser beam energy has been evaluated. An air flux was applied to create a sample–air interface prior to laser ablation. This flux prevents the contact of sea water with the sample surface during the analysis. In this way, good quality LIBS spectra were obtained. Parametric studies in the laboratory such as gas flow pressure, beam focal conditions and angle of incidence, among others, were performed to optimize the best conditions for field analysis. Finally, real samples such as different bronzes containing a high oxidation degree were analyzed underwater in the Mediterranean Sea. The dependence of LIBS signal with the analysis depth was also studied. Results obtained in these field trials confirmed the capability of remote LIBS for in-situ analysis of underwater archeological samples. [Copyright &y& Elsevier]

Abstract: LIBS analyses of deep metallic layers were performed by dual-pulse excitation, where the first laser pulse efficiently ablates material covered by poly-dispersed water aerosol and water droplets, and the second laser pulse generates the analytical plasma on the crater''s bottom. Enhancement of ablation rate in presence of water confinement was studied on various pure metals, namely Sn, Pb, Zn, Al, Cu, Fe, W, Ti and Mo. Crater depths and shapes were measured comparatively for dry surfaces and the same covered with water aerosol and water droplets of various volumes, and at different laser energies. With wet ablation using water droplet the mass removal efficiency was increased up to 20 times with respect to a dry process. The correlation between ablated mass and the thermal and mechanical properties of the examined metals was also studied. [Copyright &y& Elsevier]

In the present work, we report on the analyses of different types of artworks, such as medieval glazed Umbrian pottery and copper based alloys from Roman and modern periods, performed by means of Laser Induced Breakdown Spectroscopy (LIBS). The semi-quantitative analyses on the multi-layered ceramic findings regard glaze, luster and pigment decorations present on the surface. The composition for each decorative layer was determined by estimating the contribution of the ceramic layer beneath the examined one to the whole plasma emission. Two types of ancient luster have been considered: red and gold, while the pigments examined include painted decorations of different blue tonalities. The measured elemental composition of the decorative layers resulted partially correlated with the color of the painted surface, measured by a standard UV-VIS spectrometer. In LIBS analyses of bronze samples, a procedure was developed, which improves data repeatability and extends quantitative measurements to minor elemental constituents. Results of the quantitative analyses gave indications about the manufacturing process of the artwork, its actual degree of conservation and the presence of residual surface decorations. [Copyright &y& Elsevier]

The Laser-induced Breakdown Spectroscopy technique was applied on board the R/V Italica during the XVI Antarctic campaign (2000–2001) to carry out elemental chemical analysis of marine sediments collected using different sampling systems. To this end, a compact system has been built, which was suitable to operate also in the presence of mechanical vibrations, induced by the ship motion. Qualitative and quantitative analyses were performed on dried samples, without any further pre-treatment. Qualitative analyses have shown similar elemental composition among different collected sediments, except for significant differences in the case of rock fragments and manganese nodule. The latter also contains some heavy metals that in sediment layers were detected only in traces. The methodology to retrieve relative or absolute elemental concentration in heterogenous samples has been optimized and is scarcely sensitive to variations of sediment physical properties with depth, and to experimental parameters such as laser defocusing because of surface irregularities, and laser energy fluctuations. The relative distribution of the major elemental constituents, both from a bio-organic and mineral origin, was measured as a function of sediment depth. Measurements, once limited to specific spectral sections, and data analyses are fast and very reproducible. Most of the elements show a gradually varying distribution along the sampled core, except for silicon and barium, whose steep decrease with depth is strongly related to their biogenic origin. Quantitative LIBS analyses were performed on a limited number of samples and the results reported here, are comparable to the certified element contents in a reference sample of Antarctic sediments. [Copyright &y& Elsevier]

Abstract: Since its early applications, Laser Induced Breakdown Spectroscopy has been recognized as a useful tool for solid state chemical analysis. However the quantitative accuracy of the technique depends on the complex processes involved in laser induced plasma formation, ablation, atomization, excitation and ion recombination. Problems arising from laser target coupling, matrix effect, fractionation in target vaporization, local thermodynamic equilibrium assumption and interferences from additional air ionization should be properly addressed in order to obtain reliable quantitative results in laboratory to be used as starting point during field campaigns. As selected case studies carried out within the authors'' research team show, a proper selection of laser parameters and, in general of experimental conditions, for laboratory data acquisition is required in order to minimize the mentioned problems both in case of calibration curves and calibration free approaches. In particular, the choice of reference samples for measuring calibration curves is of crucial importance in laboratory experiments, in relation both to matrix effect and local thermodynamic equilibrium, to be carried out at comparable conditions in terms of temperature and electron density. A model for the ablation process aimed to the optimization of experimental conditions in some case studies (copper alloys) has been specifically developed in order to account for the target stoichiometry in the plasma. Problems related to the limit of detection for quantitative trace analysis have been considered in analyzing data collected both inside and outside the local thermodynamic equilibrium window, in cases characterized by a fixed contamination threshold. [Copyright &y& Elsevier]

Abstract: A theoretical model for nanosecond laser ablation at 1064 nm of quaternary bronze alloys containing Cu, Sn, Zn and Pb was developed. Starting from a known sample composition, the model provides the element concentrations in the laser produced plasma, and therefore the plasma stoichiometry, here studied for different laser energies on the target. For the considered laser excitation, plasma stoichiometry cannot be achieved in the ablation of bronze materials; however, stable element ratios in the plasma occur for a laser fluence above 600 J/cm2, corresponding to an irradiance of 75 GW/cm2. The calculated plasma concentrations were then used to simulate calibration plots in the range of element concentrations corresponding to the standards available. Different kinds of internal standardization were theoretically considered and successively applied to the experimental data obtained. Good agreement between experimental results and model predictions was observed, allowing establishing the optimal method for LIBS calibration of bronze alloys. Further validation of the model was attempted by comparing the predicted element concentrations in the plasma with the experimental results obtained by using the Calibration-Free (CF) approach (Corsi et al., Eur.Phys.J. D13, 2001, 373). The results obtained are in excellent agreement between themselves. However, the estimated element concentrations largely differ from those in samples, and the reasons for the discrepancy are discussed. [Copyright &y& Elsevier]

In this work we describe a method for preparation and analysis of oils by Laser Induced Breakdown Spectroscopy (LIBS), aimed to minimize the necessary sample volume and the matrix effect while maximizing the detection sensitivity and measurement's repeatability. The preparation procedure consists in stabilizing the oil sample and silica wafer substrate at a fixed temperature, here of 40 °C, and in delivering an oil droplet on the wafer rotated by a spin coater. In this way, a uniform oil film is obtained, which thickness is controlled through the rotation speed. So prepared target is then scanned by using the LIBS instrument. From comparative measurements on the pure oil and oil containing 2100 ppm of various elements, we studied different potentials sources of the matrix effect. During the sample preparation, above a certain rotation speed the thickness of the liquid film is the same for the two oils although their kinematic viscosities are very different, meaning that the volume sampled by LIBS is the same. The measured oil transmissivity at the laser wavelength of 1064 nm significantly decreases with concentration of impurities, but this effect could be neglected when dealing with very thin films. The plasma formation threshold measured on the bulk oil samples decreases with the impurity content. In case of pure oil, also for the maximum laser energy here used (165 mJ), the plasma is mainly initiated on the wafer while the presence of impurities increases screening of the substrate by the plasma formed directly on the oil. The matrix effect disappears on a very thin film, here of 0.74 μm, where the C I line intensity in plasma does not vary with the total concentration of impurities between zero and 2100 ppm; simultaneously, the plasma emission becomes stable from one laser pulse to another, contrary to the case of a thick liquid layer. At 0.5 μs from the laser pulse the plasma electron density is much higher in presence of oil than on the bare substrate because of the initial plume confinement. In the optimized experimental conditions the plasma emission from oil was very intense although the sample volume probed by each laser pulse was of 0.3 nL only. By choosing properly the signal acquisition delay and the calibration procedure, the latter is dependent on the excitation energy of the analytical lines, we obtained the detection limits of 3.9 ppm, 0.49 ppm, 0.16 ppm and 0.082 ppm for Zn, Cd, Cu and Cr in oil, respectively. Unlabelled Image • An intense and stable LIBS signal from oils was obtained by a substrate mediated ablation. • Uniform thin oil films were produced on a wafer substrate rotated at controlled speeds • The optimal calibration procedure is dependent on the excitation energy of the analytical line • The volume sampled by each laser pulse was of 0.3 nL, the matrix effect was absent on <1 μm thin film. • The obtained detection limits for Zn, Cd, Cu and Cr are in range 3.9–0.082 ppm. [ABSTRACT FROM AUTHOR]

Importance: Better understanding of patients' attitudes toward deprescribing specific medications will inform future deprescribing interventions., Objective: To investigate older adults' attitudes toward deprescribing by investigating which medications they would like to have deprescribed, the reasons why, and patient factors associated with interest in deprescribing., Design, Setting, and Participants: This survey study was conducted from May 2022 to December 2023 in primary care settings in 14 countries. Patients aged 65 years or older taking 5 or more medications were consecutively recruited by their general practitioner (GP) and completed the questionnaire., Exposures: Patient characteristics, including gender, number of medications, GP gender, education level, financial status, confidence in completing medical forms, self-rated health, satisfaction with medications, trust in the GP, and country., Main Outcomes and Measures: The primary outcomes were patient attitudes toward deprescribing specific medications, as measured by responses to the question, "Thinking about your current medication list, are there any medications that you would like to stop taking or reduce the dose of?" Multilevel multivariable logistic regression analysis was used, adjusted for clustering effect at the country level, to investigate the association between patient characteristics and interest in deprescribing., Results: Of 1340 patients (mean [SD], 96 [47] patients per country), 736 (55%) were women, 580 (44%) had secondary school as their highest level of education, 1089 (82%) were satisfied with their medications, and 589 (44%) expressed they would like to deprescribe 1 or more of their medications. Patients expressed interest in deprescribing specific medications at varying levels, from 79% (86 of 109 patients) in Poland to 23% (21 of 96 patients) in Bulgaria. The 3 most reported medications patients would like to have deprescribed were diuretics (111 of 1002 medications [11%]), lipid-modifying agents (109 of 1002 medications [11%]), and agents acting on the renin-angiotensin system (83 of 1002 medications [8%]). The odds of naming at least 1 specific medication for deprescribing were lower for patients with higher medication satisfaction (odds ratio, 0.31; 95% CI, 0.21-0.47) and for patients with higher trust in their GP (odds ratio, 0.960; 95% CI, 0.930-0.998)., Conclusions and Relevance: In this survey study with primary care patients aged 65 years and older, patient attitudes toward deprescribing specific medications varied across countries, demonstrating that deprescribing interventions could be more impactful when adapted to specific settings and contexts. These findings highlight the importance of patient-practitioner communication in ensuring appropriate medication use.

In this work, we present a compact LIBS sensor developed for characterization of samples on a crime scene following requirements of law enforcement agencies involved in the project. The sensor operates both in a tabletop mode, for aside measurements of swabbed materials or taken fragments, and in handheld mode where the sensor head is pointed directly on targets at the scene. The sensor head is connected via an umbilical to an instrument box that could be battery-powered and contains also a color camera for sample visualization, illumination LEDs, and pointing system for placing the target in focus. Here we describe the sensor's architecture and functionalities, the optimization of the acquisition parameters, and the results of some LIBS measurements. On nano-plotted traces at silica wafer and in optimized conditions, for most of the elements the detection limits, in term of the absolute element masses, were found to be below 10 picograms. We also show results obtained on some representative materials, like fingerprints, swabbed soil and gunshot residue, varnishes on metal, and coated plastics. The last, solid samples were used to evaluate the depth profiling capabilities of the instrument, where the recognition of all four car paint layers was achieved.