Influence de SO2 et de l'acide ascorbique sur l'activité antiradicalaire des tanins, mesurée sur l'anion superoxyde. Application aux vins rouges

Pour des concentrations habituellement utilisées en oenologie, le SO2 ne presente pas d'activité antiradicalaire à l'égard de l'anion superoxyde. L'acide ascorbique est un antiradicalaire dont les performances sont fonction de sa concentration. Les différents tanins testés présentent tous de très importantes activités antiradicalaires. Dans les vins rouges, ce sont donc pour l'essentiel les procyanidines qui captent les radicaux libres superoxydes. Influence of SO2 and ascorbic acid on the scavenger effect of tannins, measured on superoxide anion. Application to red wines At usual oenological concentrations SO2 does not have a scavenger effect on superoxide anion. Ascorbic acid is an antiradical the effect of which varies with concentration. Different tannins, e.g. castalagin, pentagalloylglucose, procyanidins B2 and B4, (+)-catechin and garlic acid, are shown to have significant antiradical effects. In red wines in particular procyanidins have a scavenger effect on free superoxide radicals

Modélisation du courant de seuil de diodes laser GaAlAs à guidage par l'indice

Le comportement d'une diode laser à ruban VSIS au voisinage du seuil est décrit à partir des modèles généraux du guide optique bidimensionnel, du gain optique du matériau, du comportement électrique de la structure. Les propriétés du guidage sont analysées à partir des variations latérales de l'indice effectif complexe. Les relations gain-niveau de courant sont évaluées pour une même famille d'alliages en se basant sur les propriétés du coefficient de création de paires électron-trou. Le courant total qui traverse la structure est calculé à partir des recombinaisons dans la couche active, du courant de conduction et de diffusion dans les couches de confinement, de la répartition latérale des lignes de courant hors du ruban. L'ensemble de ces modèles s'articule pour proposer une méthodologie générale de détermination du courant de seuil, valable pour la plupart des diodes laser à guidage par l'indice

Tunable Ag@SiO2 core-shell nanocomposites for broad spectrum antibacterial applications

Silica encapsulated silver nanoparticle core-shell nanocomposites of tunable dimensions were synthesised via a one-pot reverse microemulsion route to achieve controlled release of Ag+ ions for broad spectrum antibacterial application. Silver release rates and bactericidal efficacy against Gram-positive and Gram-negative bacteria, S. aureus and P. aeruginosa respectively, were inversely proportional to nanoparticle core diameter (3-8 nm) and silica shell (7-14 nm) thickness, and readily tuned through a facile hydrothermal etching protocol employing a PVP stabiliser to introduce mesoporosity

Izolacija i sposobnost hvatanja slobodnih radikala cijanidin 3-O-glikozida iz plodova Ribes biebersteinii Berl.

The reversed-phase preparative high performance liquid chromatographic purification of the methanol extract of the fruits of Ribes biebersteinii Berl. (Grossulariaceae) afforded five cyanidin glycosides, 3-O-sambubiosyl-5-O-glucosyl cyanidin (1), cyanidin 3-O-sambubioside (2), cyanidin 3-O-glucoside (3), cyanidin 3-O-(2G-xylosyl)-rutinoside (4) and cyanidin 3-O-rutinoside (5). They showed considerable free-radical-scavenging properties in the 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay with the RC50 values of 9.29 × 106, 9.33 × 106, 8.31 × 106, 8.96 × 106 and 9.55 × 106 mol L1, respectively. The structures of these compounds were elucidated by various chemical hydrolyses and spectroscopic means. The total anthocyanin content was 1.9 g per 100 g dried fruits on cyanidin 3-glucoside basis.Pet cijanidin glikozida, 3-O-sambubiozil-5-O-glukozil cijanidin (1), cijanidin 3-O-sambubiozid (2), cijanidin 3-O-glukozid (3), cijanidin 3-O-(2G-ksilozil)-rutinozid (4) i cijanidin 3-O-rutinosid (5) izolirani su iz metanolnog ekstrakta plodova Ribes biebersteinii Berl. (Grossulariaceae) koristeći reverzno-faznu preparativnu tekućinsku kromatografiju visoke učinkovitosti. Cijanidin glikozidi pokazali su sposobnost hvatanja slobodnih radikala u pokusu s 2,2-difenil-1-pikrilhidrazilom (DPPH). Dobivene su sljedeće RC50 vrijednosti: 9,29 × 106, 9,33 × 106, 8,31 × 106, 8,96 × 106, odnosno 9,55 × 106 mol L1. Strukture glikozida određene su kemijskom hidrolizom i spektroskopijom masa. Ukupni sadržaj antocijanina bio je 1,9 g na 100 g suhih plodova preračunato na cijanidin 3-glukozid

Silver confined within zeolite EMT nanoparticles: preparation and antibacterial properties

The preparation of pure zeolite nanocrystals (EMT-type framework) and their silver ion-exchanged (Ag+-EMT) and reduced silver (Ag0-EMT) forms is reported. The template-free zeolite nanocrystals are stabilized in water suspensions and used directly for silver ion-exchange and subsequent chemical reduction under microwave irradiation. The high porosity, low Si/Al ratio, high concentration of sodium and ultrasmall crystal size of the EMT-type zeolite permitted the introduction of a high amount of silver using short ion-exchange times in the range of 2–6 h. The killing efficacy of pure EMT, Ag+-EMT and Ag0-EMT against Escherichia coli was studied semi-quantitatively. The antibacterial activity increased with increasing Ag content for both types of samples (Ag+-EMT and Ag0-EMT). The Ag0-EMT samples show slightly enhanced antimicrobial efficacy compared to that of Ag+-EMT, however, the differences are not substantial and the preparation of Ag nanoparticles is not viable considering the complexity of preparation steps

Potential of a multiparametric optical sensor for determining in situ the maturity components of red and white vitis vinifera wine grapes

A non-destructive fluorescence-based technique for evaluating Vitis vinifera L. grape maturity using a portable sensor (Multiplex ®) is presented. It provides indices of anthocyanins and chlorophyll in Cabernet Sauvignon, Merlot and Sangiovese red grapes and of flavonols and chlorophyll in Vermentino white grapes. The good exponential relationship between the anthocyanin index and the actual anthocyanin content determined by wet chemistry was used to estimate grape anthocyanins from in field sensor data during ripening. Marked differences were found in the kinetics and the amount of anthocyanins between cultivars and between seasons. A sensor-driven mapping of the anthocyanin content in the grapes, expressed as g/kg fresh weight, was performed on a 7-ha vineyard planted with Sangiovese. In the Vermentino, the flavonol index was favorably correlated to the actual content of berry skin flavonols determined by means of HPLC analysis of skin extracts. It was used to make a non-destructive estimate of the evolution in the flavonol concentration in grape berry samplings. The chlorophyll index was inversely correlated in linear manner to the total soluble solids (°Brix): it could, therefore, be used as a new index of technological maturity. The fluorescence sensor (Multiplex) possesses a high potential for representing an important innovative tool for controlling grape maturity in precision viticulture

Transmitting a Compositional Process: the Motets Pensis chief enclin and Quant li douz tens

International audienc

Atelier de restauration des polyphonies du Chansonnier de Noailles

International audienc

Copying Motets in a Chansonnier: the Influence of the Songbook and Song Culture on the Noailles Motet Collection (BnF, f.fr.12615)

International audienc