Alkyd paints in art: Characterization using integrated mass spectrometry

Alkyd resins have been commonly used as binders in artist paints since the 1940s. The characterization of alkyds in samples from artworks can help to solve attribution and dating issues, investigate decay processes, and contribute to the planning of conservation strategies. Being able to assess the components of industrially formulated paint materials and to differentiate between different trademarks and producers is extremely interesting and requires multi-analytical approaches.     

Discovering the composition of ancient cosmetics and remedies: analytical techniques and materials

This article reviews the analytical techniques and procedures used in the study of ancient cosmetics, therapeutic chemicals, and remedies found in historical and archaeological sites. Well consolidated techniques based on molecular and atomic spectroscopy, for example FT-IR, Raman, SEM-EDX, and XRD, and analytical procedures based on high-performance chromatography and mass spectrometry, for example GC–MS and HPLC–MS are reviewed. The advantages of recently introduced techniques based on synchrotron radiation and on direct mass spectrometric techniques are also discussed. The possibility of extracting information about composition, preparation techniques, and the degradation processes of ancient cosmetics, pharmaceutics, and ritual balms is analysed by use of several case studies.     

First chemical evidence of royal purple as a material used for funeral treatment discovered in a Gallo�CRoman burial (Naintr��, France, third century AD)

Violet-purple residues collected from a Gallo-Roman burial dated back to the second half of the third century A.D. and excavated at Naintré (France) were chemically investigated by multi-analytical methodology involving the use of Raman spectroscopy, direct exposure-mass spectrometry (DE-MS) and high-performance liquid chromatography (HPLC-UV-visible). Little is known about funeral treatment and rituals during Roman times. Retrieving valuable information on these by chemical analysis of organic residues was thus a key aspect of this work. Analyses demonstrated the presence of the very precious purple colorant obtained from shellfish glands commonly known as Tyrian or royal purple and its exceptional preservation. Chemical investigation and archaeological evidence have shown that purple was widely spread after the deposition of the body for burial. These results are the earliest chemical evidence of purple colorant used during funeral rituals (not as textile dye) and enabled us to highlight new aspects of funeral practices in Roman times.     

Analytical pyrolysis with in situ thermally assisted derivatisation, Py(HMDS)-GC/MS, for the chemical characterization of archaeological birch bark tar

An analytical method based on pyrolysis in the presence of hexamethyldisilazane followed by gas chromatographic/mass spectrometric analysis, Py(HMDS)-GC/MS, was used for the first time to study birch bark tar, an adhesive that has been used since the Palaeolithic period. Py(HMDS)-GC/MS enabled us to obtain information simultaneously both on polymerised and solvent soluble fractions of birch bark tar. A very particular chromatographic pattern was obtained, which was mainly characterised by the presence of homologous series of linear saturated and unsaturated monocaboxylic fatty acids, and homologous series of straight-chain alkenes and alkanes. The pattern can be linked to suberin and suberan, which are known to be present in birch barks. In addition, lupane-type triterpenoids were also revealed. Py(HMDS)-GC/MS was initially applied to a reference material, and was then used to study the archaeological adhesives from a wooden spindle recovered in a Gallo-Roman burial (3rd century AD) and from the golden sheath of a Thracian dagger (8th-7th centuries BC) recovered in Belogradets (Bulgaria).     

Unimolecular rearrangements of ketene-O,O-acetals and fragmentations occurring in the gas phase

Gas phase skeletal rearrangements of regioisomeric 3‐cyano‐2‐methoxy‐3a‐alkylfuro[2,3‐b]‐ and [3,2‐b]indoles were evidenced by product ions [M ? 32]^+?, consistent with loss of methanol, on electron ionization in their mass spectra. The rearranged products occurring in gas phase were demonstrated to have elemental composition and fragmentation properties identical to those of authentic samples of 2‐indolyl cyanomalonates. Isotopic labeling experiments support the formation mechanism of the [M ? 32]^+? ion. Additional thermal gas‐phase reaction products were characterized by comparison with an authentic sample. Copyright © 2011 John Wiley & Sons, Ltd.     

Interrupted Intramolecular Hydroaminomethylation of N-Protected-2-vinyl Anilines: Novel Access to 3-Substitued Indoles or Indoline-2-ols

A new synthetic alternative to the synthesis of 3-methyl indoles and 3-methyl indoline-2-ols with an excellent atomic economy is presented in this study. It is demonstrated that the intramolecular interrupted hydroaminomethylation (HAM) reaction is a powerful tool for the formation of these compounds, which exhibit wide-ranging biological activity. Several N-Protected-2-vinyl anilines were synthesized and involved in the reaction producing the corresponding 3-methylindole or 3-methyl indoline-2-ol depending on the nature of the N-protecting groups.     

On the motive of certain subvarieties of fixed flags

We compute the Chow motive of certain subvarieties of the Flags manifold and show that it is an Artin motive.     

Catalytic activity tuning of a biomimetic HO-FeV=O oxidant for methane hydroxylation by substituents on aromatic rings: theoretical study

HO-(TPA)FeV=O (TPA = tris(2-pyridylmethyl)amine) has been proposed in the literature as the key high-valent iron-oxo intermediate involved in alkane hydroxylation. Here the structure of this species is investigated theoretically in the framework of density functional theory (DFT). A detailed electronic structure analysis leads to the presumption that the properties of the FeV=O bond can be modified by introducing substituents to the aromatic rings of TPA and thus the reactivity of HO-(TPA)FeV=O for the hydrogen atom abstraction of methane hydroxylation can be tuned on the quartet potential energy surface. The validity of our presumption is verified by DFT calculations. According to the rebound mechanism, the H-abstraction step is examined by using five complexes with TPA and TPA-derivative ligands and the corresponding reaction energies and energy barriers are obtained and compared with each other. The results are fully in agreement with our qualitative model, showing that electron-withdrawing groups are able to lower the barrier and facilitate the reaction, whereas the electron-donating groups increase the barrier and reduce the reactivity.     

The ring of global sections of multiples of a line bundle on a toric variety

In this article we prove that for any complete toric variety, and for any Cartier divisor, the ring of global sections of multiples of the line bundle associated to the divisor is finitely generated.