Abstract: Trace elements can influence dental health, possibly by altering tooth resistance during preeruptive development. Therefore, it was investigated whether lead and fluoride would be incorporated into the calcifying matrices or the cellular parts of tooth germs in vitro. Using laser microprobe mass analysis, the localization of lead and fluoride was studied in the different layers or tooth germs that had been cultured in a medium to which PbCl2 of NaF had been added in different concentrations. Both elements could only be detected in the dentine layer. Hence, the enamel organ in the secretory stage of tooth development excludes lead and fluoride from the enamel, even when enamel formation by the ameloblasts is visibly disturbed. Furthermore, there seemed to be a process of saturation in the accumulation of lead and fluoride in the dentine.

Abstract: The structural stability of 2D transition metal dichalcogenide (TMD) formations is of particular importance for their reliable device performance in nano-electronics and opto-electronics. Recent observations show that the CVD-grown TMD monolayers are likely to encounter stability problems such as cracking or fracturing when they are kept under ambient conditions. Here, two different growth configurations are investigated and a favorable growth geometry is proposed, which also sheds light onto the growth mechanism and provides a solution for the stability and fracture formation issues for TMDs specifically for MoS2 monolayers. It is shown that 18 months naturally and thermally aged MoS2 monolayer flakes grown using specifically developed conditions, retain their stability. To understand the mechanism of the structural deterioration, two possible effective mechanisms, S vacancy defects and growth-induced tensile stress, are assessed by the first principle calculations where the role of S vacancy defects in obtaining oxidation resistant MoS2 monolayer flakes is revealed to be rather more critical. Hence, these simulations, time-dependent observations and thermal aging experiments show that durability and stability of 2D MoS2 flakes can be controlled by CVD growth configuration.

Abstract: In this work, the absorption–desorption performance of CO2 in six new solvent blends of amine (diisopropylamine (DPA), 2-amino-2-methyl-1-propanol (AMP), methyldiethanolamine (MDEA), diethanolamine (DEA), diisopropanolamine (DIPA), and ethanolamine (MEA)), sulfolane, and methanol has been monitored using ATR-FTIR spectroscopy. Additionally, NMR-based species confirmation and solvent viscosity analysis were done for DPA solvent samples. The identified CO2 capture products are monomethyl carbonate (MMC), carbamate, carbonate, and bicarbonate anions in different ratios. The DPA solvent formed MMC entirely with 0.88 molCO2/molamine capture capacity, 0.48 molCO2/molamine cyclic capacity, and 3.28 mPa·s CO2-loaded solvent viscosity. MEA, DEA, DIPA, and MDEA were shown to produce a low or a negligible amount of MMC while AMP occupied an intermediate position.

Abstract: MA-XRF is a novel macroscopic imaging technique originally developed for easel paintings and recently made available to glass conservators. This paper discusses the first real-life contribution of MA-XRF imaging to a conservation intervention of stained-glass panels. The six panels under study belong to the cathedral building since their creation in 1555-1559 AD. MA-XRF appeared an outstanding tool for first-line screening of stained-glass windows, providing readily interpretable information on glass type, coloring and alteration processes. In particular, the chemical imaging technique allowed distinguishing unambiguously the surviving original glass panes from later additions, thereby ensuring a correct historical understanding. From a more practical point of view, the experiments supplied accurate schemes that can be directly incorporated in condition reports and assist designing the ensuing conservation approach. (C0 2019 Elsevier Masson SAS. All rights reserved.

Abstract: Scientific research into cultural heritage has significantly grown in importance over the past decades. The growing popularity of macroscopic imaging techniques such as X-ray fluorescence or Fourier transform infrared now means that conservators and restorers have access to highly objective information on the chemical composition of a painting without the necessity for destructive sampling. As many works of art are heterogeneous on the macroscopic scale, it is clear that solely relying on microscopic samples does not provide sufficiently representative information on the condition of a painting and that macroscopic imaging techniques should be considered a crucial part of the analytical toolkit for conservation science. The goal of this research has been to investigate the added value of reflection-mode macroscopic X-ray powder diffraction (MA-XRPD) for scientific and art historical investigations of cultural heritage artefacts. A prototype scanner was developed after careful consideration of the individual components. This mobile instrument allows for the analysis of flat objects such as oil paintings with reflection MA-XRPD. In this manner images can be obtained that show the distribution of crystalline components present at the surface of the stratigraphy. These crystalline materials can originate from different sources and include original pigments and non-original pigments. MA-XRPD offers novel insights into original pigments such as ultramarine, copper sulfates and lead white. In Girl with a Pearl Earring by Vermeer the MA-XRPD instrument was used to prove that Vermeer used multiple subtypes of lead white to achieve subtle optical effects while in the painting The Night Watch by Rembrandt the lead white composition was studied in detail; multiple rare lead-based compounds were identified that could be linked to the usage of specific driers in the oil paint. By investigating the presence of degradation products, MA-XRPD can be used to assess the conservation state of an artwork. Secondary alteration products were identified in paintings by Nellius and Mignon, explaining why the paintings had visually deteriorated over time. MA-XRPD registered the presence of lead arsenates which were formed from the original yellow arsenic-based orpiment. By combining microscopic and macroscopic analysis, a chemical degradation pathway for the conversion of the unstable orpiment pigment was proposed. In this manner, MA-XRPD can also be used to provide highly valuable information for conservators and restorers by pinpointing areas that have undergone degradation and to guide sampling campaigns.