The nature of black stains in Lascaux Cave,France, as revealed by surface‐enhanced Raman spectroscopy

We used surface‐enhanced Raman spectroscopy to investigate the chemical composition of the black stains threatening the rock‐art paintings of Lascaux Cave, Montignac, France. The stains are mainly composed of melanin from the fungus Ochroconis sp. and the faecal pellets of the collembolan Folsomia candida. Surface‐enhanced Raman spectroscopy is a useful technique for revealing the structure of unknown macromolecules in cultural heritage research. Copyright © 2011 John Wiley & Sons, Ltd.     

Adsorption and catalysis of flavonoid quercetin on different plasmonic metal nanoparticles monitored by SERS

Raman and surface‐enhanced Raman scattering spectroscopy were used to follow the chemical modification of quercetin (QUC) on silver nanoparticles. Different metallic systems were fabricated to check the influence of the interface, in terms of electric charge or total available surface, on the catalytic change undergone by QUC. The effect of QUC surface coverage was crucial to reveal information about the different orientation and the interaction mechanism with the metal at different concentrations of this flavonoid. Surface‐enhanced Raman scattering spectra of good quality of QUC were observed at concentrations down to 10^–8 M. Chemical modifications in the presence of nanostructure metal surfaces include oxidation followed by a subsequent polymerization via a condensation of rings whereas different chemical species have been recognized under different experimental conditions. The assignment of the new species formed on the metal surface was conducted. Copyright © 2012 John Wiley & Sons, Ltd.     

Effect of different additives on the performance of V?Mg?O catalysts in the oxidative dehydrogenation of propane

The addition of K₂O, Cr₂O₃, Sm₂O₃ or Nb₂O₅ to V–Mg–O catalyst decreased both activity and selectivity in propane oxydehydrogenation. By comparing these results with the characterization data, a relationship between propylene selectivity and catalyst reducibility was revealed. The most easily reduced catalyst was the most selective.     

Affinity chromatography of frog epidermis dopa-oxidase

Benzoic acid is a competitive inhibitor of the enzyme dopa-oxidase. p-Aminobenzoic acid was coupled by a single-step reaction of the amino group to: (1) CNBr-activated Sepharose 4B: (2) Enzacryl AA, by reaction with thiophosgene (pH 10.0); and (3) CM-Sephadex G-50, modified to azide by the Curtis procedure. These three solid supports were used as affinity adsorbents in the dopa-oxidase purification. The enzyme was obtained from frog epidermis, and was retained at pH 4.7 with 0.1 M acetate buffer. The enzyme elution was carried out using a linear pH gradient with 0.1 M phosphate buffer pH 8.0. We have examined the interaction of the enzyme with the immobilized PABA in relation to the nature of the support, the lengthening of the “arm” of the ligand, bathwise adsorption, and the enzyme activation by immobilized trypsin.     

Speciation of activators in electroluminescent thin films: an EXAFS study of cerium and terbium doped strontium sulfide

Extended X-ray absorption fine structure (EXAFS) was used to determine the local structure of the luminescent centers in Tb³⁺ and Ce³⁺ -doped strontium sulfide thin films deposited by Atomic Layer Epitaxy (ALE). The rare earths were observed to enter mainly the substitutional sites but at the same time a part of the atoms form RES clusters (RE = rare earth). The presence of both substitutional sites and RES clusters has been observed for the first time in this study for rare earths in II–VI compounds. Received: 9 February 1998 / Revised: 22 May 1998 / Accepted: 29 May 1998     

Development and Applications of an Automated In-Column Pyrolysis Gas Chromatography-Mass Spectrometry System

A novel system for sample introduction into a Gas Chromatograph (GC) using an automated in-column pyrolysis device has been developed. The in-column pyrolysis device is suitable for use with any GC or GC-MS system. Solid samples are dissolved or emulsions can be diluted and injected into the system. Because the system is designed for introducing liquid samples, a better control of the injected sample amounts is achieved. This leads to high reproducibility of the peak areas, offering new opportunities for quantitation of polymers or other high molecular weight materials. In addition, a better statistical representation of the material to be analyzed is given if the samples are dissolved in a solvent. The system can be operated both in a normal GC injection mode, and in the pyrolysis mode. As a conventional GC injector working in on-column or Programmed Temperature Vaporization (PTV) injection mode, (without the pyrolysis function), information on the volatile fraction of a sample can be obtained. Once the volatile materials in the sample have been separated, a second analysis on the non-volatile matrix can be performed by initiating the pyrolysis sequence, yielding information on the non-volatile fraction of the sample. Both features, on column or PTV injection mode and in-column pyrolysis can be used separately or in combination. This new technology is expected to be useful for the determination of additives, monomers, solvents and other volatile components in a non volatile matrix, such as polymers, as well as in the characterization of the non-volatile matrix itself, in a single run. Revised: 20 June and 21 July 2005     

Characterization of an X‐ray mirror mechanical bender for the European XFEL

One of the classical devices used to tune a mirror on an X‐ray optical setup is a mechanical bender. This is often designed in such a way that the mirror is held with clamps on both ends; a motor is then used to put a torque on the clamps, inducing a cylindrical shape of the mirror surface. A mechanical bender with this design was recently characterized, to bend a 950 mm‐long mirror up to a radius of curvature of 10 km. The characterization was performed using a large‐aperture Fizeau interferometer with an angled incidence setup. Some particular and critical effects were investigated, such as calibration, hysteresis, twisting and long‐term stability.     

Background vapor from six ionic liquids and the partition coefficients and limits of detection for 10 different analytes in those ionic liquids measured using headspace gas chromatography

The concentration and identity of the compounds detected in the vapor above six ionic liquids by headspace gas chromatography (HS-GC) at 100 degrees C are reported. In addition, the partition coefficients for 10 different compounds in these ionic liquids and limits of detection were measured. These results provide quantitative guidance for the application of ionic liquids for HS-GC.