First principles calculation of L21+A2 coherent equilibria in the Fe–Al–Ti system

By combining first-principles density functional total energy calculations and statistical mechanics the ground state and the phase equilibria at finite temperatures of the ternary system Fe–Al–Ti have been investigated. Total energy calculations have been performed by means of the Wien 2k code to establish the ground state energetic. A cluster expansion method was therewith used to describe solid solutions. At several chosen finite temperatures the cluster variation method in the irregular tetrahedron approximation was employed in order to calculate the iron rich ternary bcc equilibria. It is confirmed that there are two kinds of phase separations of the bcc phase, A2+L2₁ and B2+L2₁.     

Effects of water and electric field on atomic oxygen adsorption on Pt–Co alloys

Density functional theory is used to study the effect of atomic oxygen adsorption at various coverages with and without the presence of water on ordered and Pt-segregated PtCo surfaces. The strength of O adsorption, as well as surface reconstruction effects due to the adsorbate are strongly influenced by the presence of the oxygen-philic transition metal on the surface or subsurface. At high O coverage, buckling of the Co atom on PtCo surfaces is much smaller than that of Pt on Pt(1 1 1) surfaces, and buckling of Pt atoms on Pt-skin surfaces is negligible. Also, the effect of an electric field perpendicular to the surface on adsorbed water and atomic oxygen is investigated. Spontaneous water dissociation is not found on the ordered and segregated alloy surfaces within the entire applied electric field range (−0.51 to 0.51 V/Å). Water changes orientation under strong negative fields, switching from a metal–O to a metal–H interaction, and the effect is much more pronounced in the low-coordination sites of cluster models.     

Py-GC/MS, GC/MS and FTIR investigations on LATE Roman-Egyptian adhesives from opus sectile: New insights into ancient recipes and technologies

An analytical protocol based on optical microscopy, Fourier transforms infrared spectroscopy (FTIR), analytical pyrolysis in the presence of hexamethyldisilazane followed by gas chromatographic/mass spectrometric analysis (Py-GC/MS) and gas chromatography/mass spectrometry after alkaline hydrolysis, solvent extraction and trimethylsilylation (GC/MS) was used in the chemical characterisation of the original adhesives used to fix monochrome and mosaic glass and stone plaques coming from the Late Roman archaeological site of Antinoopolis (Egypt).FTIR analysis demonstrated the presence of calcite fragments, and Py-GC/MS and GC/MS analyses provided detailed molecular compositions, highlighting the presence of a wide range of compound classes including diterpenoid acids, tricyclic abietanes with a high degree of aromatisation, mid- and long-chain monocarboxylic fatty acids, mono- and di-hydroxy acids, α,ω-dicaboxylic fatty acids, n-alkanols, and n-alkanes. Characteristic biomarkers and their distribution patterns indicated the presence of pine pitch in all the adhesives, which in some cases was admixed with beeswax and brassicaceae seed oil.The results provided new insights into the complex recipes used by artisans in ancient Egypt in the production of adhesives and in the sophisticated manufacture of opus sectile decorations.     

The development of a gas chromatographic–mass spectrometric analytical procedure for the determination of lipids,proteins and resins in the same paint micro-sample avoiding interferences from inorganic media

This paper presents a GC–MS analytical procedure for determining proteinaceous materials, glycerolipids, natural waxes and terpenoid resins in the same paint micro-sample. The procedure is also reliable when high amounts of interfering inorganic pigments, dryers and charges are present. The characterisation of proteinaceous binders in a paint sample can be subject to analytical interferences by inorganic materials. Such materials may form complexes with functional groups of proteins, thus preventing their efficient derivatisation, which is necessary prior to GC analysis. For this reason an analytical procedure has been developed based on two extractions and a clean-up step, in order to obtain two fractions: a lipid-resinous fraction and a proteinaceous fraction. The lipid-resinous fraction is subjected to salification/saponification assisted by microwaves, followed by acidification, extraction, derivatisation and GC–MS analysis. The proteinaceous fraction is analysed by GC–MS after hydrolysis and derivatisation of the freed amino acids. The desalting step is applied before the hydrolysis, and is based on the use of the monolithic sorbent tip technology with a C4 stationary phase. Reference paint replicas of egg, casein and animal glue were prepared with and without several metals containing pigments, and used to develop and validate the analytical procedure. The procedure proved to be efficient in desalting the proteinaceous materials both from cations and anions. Although non quantitative, it is reliable in the analysis of samples whose content of extractable proteins is <1 μg, thus showing it to be suitable for the characterisation of paint samples. An example of how the analytical procedure was used to characterise a sample from a 15th century panel painting is also discussed.     

A multi-analytical approach to studying binding media in oil paintings

This article presents a multi-analytical approach to investigating the drying, polymerisation and oxidative degradation of linseed oil, which had undergone various treatments known to be undertaken during the nineteenth century in preparation for painting. The oil was mechanically extracted from the same seed lot then processed by different methods: water washing, heat treatments, and the addition of driers, with and without heat. The oil was prepared in 1999 within the framework of the MOLART project. We compared thermogravimetric analysis (TG), which yields macromolecular information, with gas-chromatography mass-spectrometry (GC/MS) and direct exposure mass spectrometry (DE-MS), which provide molecular information. This comparison enabled us to elucidate the role of pre-treatment on the composition of the oil. TG and oxygen uptake curves registered at a constant temperature helped us to identify the different physical behaviour of the oil samples, thus highlighting the presence of hydrolysed, oxidised and crosslinked fractions, as a consequence of the different pre-treatments. GC/MS was used to characterise the soluble and non-polymeric fraction of the oil, to calculate the ratios of palmitic to stearic acid (P/S), and azelaic to palmitic acid (A/P), and to further evaluate the effects of oil pre-treatments. DE-MS using chemical ionisation with CH₄, enabled us to establish the chemical composition of the oil in different stages of ageing. DE-MS proved to be a useful tool for a simultaneous semi-quantitative characterisation of the free fatty acids, monoglycerids, diglycerides and triglycerides present in each sample. The combination of thermal analysis with GC/MS and DE-MS enabled a model to be developed, which unravelled how oil pre-treatments produce binders with different physical–chemical qualities.     

Anti-Inflammatory and Antinociceptive Activities of the Essential Oil of Tagetes parryi A. Gray (Asteraceae) and Verbenone

Tagetes parryi is a plant empirically used to treat gastrointestinal and inflammatory diseases, its essential oil (EOTP) was obtained from the aerial parts, and the composition was elucidated by GC-MS. The in vivo and in vitro anti-inflammatory activities and the antinociceptive activity of EOTP and (1S)-(-)-verbenone (VERB) were assessed. The major compounds identified for EOTP were verbenone (33.39%), dihydrotagetone (26.88%), and tagetone (20.8%). EOTP and VERB diminished the ear oedema induced with TPA by 93.77 % and 81.13 %, respectively. EOTP and VERB decreased inflammation in a 12-O-tetradecanoylphorbol-13-acetate (TPA) chronic model with ED₅₀ = 54.95 mg/kg and 45.24 mg/kg, respectively. EOTP (15 µg/mL) inhibited the in vitro production of the pro-inflammatory mediators NO (67.02%), TNF-α (69.21%), and IL-6 (58.44%) in LPS-stimulated macrophages. In the acetic induced writhing test, EOTP and VERB showed antinociceptive effects with ED₅₀ = 84.93 mg/kg and ED₅₀ = 45.24 mg/kg, respectively. In phase 1 of the formalin test, EOTP and VERB showed no antinociceptive effects, whereas in phase 2, EOTP (ED₅₀ = 35.45 mg/kg) and VERB (ED₅₀ = 24.84 mg/kg) showed antinociceptive effects. The antinociceptive actions of ETOP and VERB were blocked with the co-administration of L-NAME. This study suggests that EOTP and VERB might be used in the treatment of pain and inflammatory problems.     

Simultaneous Exact Control of Quasi-Electrostatic Piezoelectric Systems in Multilayered Media

We consider two quasi-electrostatic models in a multilayered piezoelectric structure. Both models only differ on the boundary conditions. For each one of them we prove a boundary observability inequality which together with the Hilbert Uniqueness Method introduced by J.L. Lions allow us to drive both systems to rest at time T with the same control function. We require suitable geometric conditions on the region and the interfaces as well as monotonicity assumptions on the coefficients of the model.     

Ab initio molecular dynamics simulations of the oxygen reduction reaction on a Pt(111) surface in the presence of hydrated hydronium (H3O)(+)(H2O)2: direct or series pathway?

Car-Parrinello molecular dynamics simulations have been performed to investigate the oxygen reduction reaction (ORR) on a Pt(111) surface at 350 K. By progressive loading of (H3O)(+)(H2O)(2,3) + e- into a simulation cell containing a Pt slab and O2 for the first reduction step, and either products or intermediate species for the subsequent reduction steps, the detailed mechanisms of the ORR are well illustrated via monitoring MD trajectories and analyzing Kohn-Sham electronic energies. A proton transfer is found to be involved in the first reduction step; depending on the initial proton-oxygen distance, on the degree of proton hydration, and on the surface charge, such transfer may take place either earlier or later than the O2 chemisorption, in all cases forming an adsorbed end-on complex H-O-O*. Decomposition of H-O-O* takes place with a rather small barrier, after a short lifetime of approximately 0.15 ps, yielding coadsorbed oxygen and hydroxyl (O + HO*). Formation of the one-end adsorbed hydrogen peroxide, HOO*H, is observed via the reduction of H-O-O*, which suggests that the ORR may also proceed via HOO*H, i.e., a series pathway. However, HOO*H readily dissociates homolytically into two coadsorbed hydroxyls (HO* + HO*) rather than forming a dual adsorbed HOOH. Along the direct pathway, the reduction of H-O* + O* yields two possible products, O* + H2O* and HO* + HO*. Of the three intermediates from the second electron-transfer step, HOO*H from the series pathway has the highest energy, followed by O* + H2O* and HO* + HO* from the direct pathway. It is therefore theoretically validated that the O2 reduction on a Pt surface may proceed via a parallel pathway, the direct and series occurring simultaneously, with the direct as the dominant step.     

Characterisation of proteinaceous binders in artistic paintings by chromatographic techniques

This review discusses the application of chromatographic techniques (GC, HPLC and Py-GC) for the characterisation of proteinaceous materials in artistic paintings. The focus is on the various analytical steps that are needed to determine these natural materials in paint samples, from sampling and sample pre-treatment, including various methods of hydrolysis and derivatisation for GC and HPLC, to approaches for data evaluation.