Gas chromatographic-mass spectrometric analysis of acids and phenols in distilled alcohol beverages. Application of anion-exchange disk extraction combined with in-vial elution and silylation

A GC-MS protocol for profiling spirits, based on 19 acids and phenolic compounds, has been proposed and evaluated. The method combined a simple preconcentration procedure based on solid-phase (anion-exchange) disk extraction, and in-vial elution and silylation of the analytes. The derivatized extract was directly injected into the GC-MS system. These analytes were: C6, C8, C10, C12 acids, pyruvic acid, 2-furoic acid, succinic acid, fumaric acid, glutaric acid, lactic acid, glycolic acid, malic acid, tartaric acid, citric acid, vanillin, syringaldehyde, coniferaldehyde, vanillic acid and gallic acid. The profiles of six different spirits were found reproducible from day-to-day with <20% RSD for measurements of most of the analytes at different concentrations. Recoveries of individual analytes appear to be affected by the level of tannins in the spirits, and they varied from sample to sample. The method of standard addition was used to quantify age-related analytes. Good linearity of response with correlation coefficients in the range of 0.992-0.999 was obtained. The results of the study indicate that for spirits of the same brand but of different ages, the amounts of these analytes appear to increase with the ageing period.     

From micro to nano reentrant structures: hysteresis on superomniphobic surfaces

The paper reports on the wetting characterization of two surfaces presenting reentrant shapes at micro- and nanoscale using low surface tension liquids (down to 28 mN/m). On the one hand, mushroom-like microstructures are fabricated by molding poly(dimethylsiloxane) (PDMS) onto a patterned sacrificial photoresist bilayer. On the other hand, zinc oxide nanostructures (ZnO NS) are synthesized by easy and fast chemical bath deposition technique. The PDMS and ZnO NS surfaces are then chemically modified with 1H,1H,2H,2H-perfluorodecyltrichlorosilane in vapor phase. Both PDMS and ZnO NS surfaces exhibit a large apparent contact angle (>150°) and contact angle hysteresis varying from 50° to a quasi-null value. This large discrepancy can be ascribed to the length scale and topography of the structures, promoting either a vertical imbibition or a lateral spreading within the roughness.     

Engineering sticky superomniphobic surfaces on transparent and flexible PDMS substrate

Following the achievement of superhydrophobicity which prevents water adhesion on a surface, superomniphobicity extends this high repellency property to a wide range of liquids, including oils, solvents, and other low surface energy liquids. Recent theoretical approaches have yield to specific microstructures design criterion to achieve such surfaces, leading to superomniphobic structured silicon substrate. To transfer this technology on a flexible substrate, we use a polydimethylsiloxane (PDMS) molding process followed by surface chemical modification. It results in so-called sticky superomniphobic surfaces, exhibiting large apparent contact angles (>150°) along with large contact angle hysteresis (>10°). We then focus on the modified Cassie equation, considering the 1D aspect of wetting, to explain the behavior of droplets on these surfaces and compare experimental data to previous works to confirm the validity of this model.     

On the sigma term in KN scattering

By keeping the kaon on the mass shell, we derive low-energy relations constrained by the kaon-nucleon sigma term, σ_NN^KK. From one of these relations, a threshold calculation shows that σ_NN^KK depends strongly on g_KNΣ′, only, thus allowing a reliable estimate of the sigma term.     

INHIBITION OF OXYGEN EVOLUTION IN CHLOROPLAST PHOTOSYSTEM II BY THE PROTEIN-MODIFYING AGENT TETRANITROMETHANE

Abstract— The protein-modifying agent tetranitromethane (TNM) reacts with tyrosine residues and -SH groups. It was found to inhibit photo synthetic electron transport on the water splitting side of photosystem II (P. V. Sane and U. Johanningmeier, Z. Naturforsch. 35c, 293–297, 1979). In the present work the inhibition by TNM is studied in detail using photosystem II submembrane fractions. It is shown that the action of TNM with membrane-bound proteins could imply the modification of tyrosine residues. At concentrations below 30 μ M and with short incubation periods (<2 min), TNM produces the release of the extrinsic polypeptides involved in the stabilization of the water-splitting complex, this being correlated with inhibition of electron transport at a site prior to H₂O₂ electron donation even though the inhibition cannot be prevented by the addition of Cl or Ca²⁺, which are known cofactors for oxygen evolution. As the incubation period or the concentration of TNM is increased, photosynthetic pigments are bleached, starting with aggregates absorbing at relatively long wavelengths. The inhibition by low concentrations of TNM differs from the effect of most of the previously reported inhibitors acting at the oxygen-evolving complex of photosystem II.     

Reconstruction of the Water-Oxidizing Complex in Manganese-Depleted Photosystem II Preparations Using Mononuclear Manganese Complexes

Abstract— The water-oxidizing complex of chloroplast photosystem II is composed of a cluster of four manganese atoms that can accumulate four oxidizing redox equivalents. Depletion of manganese from the water-oxidizing complex fully inhibits oxygen evolution. However, the complex can be reconstituted in the presence of exogenous manganese in a process called photoactivation. In the present study, mononuclear manganese complexes with ligands derived from either nitrosonaphthol and ethylenediamine (Niten) or from diaminohexane and salicylaldehyde (Salhxn) are used in photoactivation experiments. Measurements of photoinduced changes of chlorophyll fluorescence yield, thermal dissipation using photoacoustic spectroscopy, photoreduction of 2,6-dichorophenolindophenol and oxygen evolution in manganese-depleted and in reconstituted photosystem II preparations demonstrate that photoactivation is more efficient when Niten and Salhxn complexes are used instead of MnCl₂. It is inferred that the aromatic ligands facilitate the interaction of the manganese atoms with photosystem II. The addition of CaCl₂ and of the extrinsic polypeptide of 33 kDa known as the manganese-stabilizing protein during photoactivation further enhances the recovery of electron transport and oxygen evolution activities. It is proposed that mononuclear manganese complexes are able to contribute to re-constitution of the water-oxidizing complex by sequential addition of single ions similarly to the current model for assembly of the tetranuclear manganese cluster and that these complexes constitute suitable model systems to study the assembly of the water-oxidizing complex.     

Novel configuration of processing bulk textured YB2Cu3O7−x superconductor by seeded infiltration growth method

Mono-domain YBa₂Cu₃O_7?x (Y123) bulk superconductors have been processed using seeded infiltration growth technique (SIG). The combination of melt infiltrated liquid source (Ba₃Cu₅O₈) into the Y₂BaCuO₅ (Y211) pre-form and the nucleation of Y123 domain from SmBa₂Cu₃O₇ crystal seed has been investigated. The different configurations of SIG process were compared in this study. In addition, the effect of the starting Y211 particles size has been studied. The results reveal that, the Y211 particle size and different configurations strongly influence the properties of the final bulk superconductor sample.