5 research outputs found

    Etude des conséquences d'une acidose induite sur le taux butyreux et le profil des acides gras du lait et du sérum chez la vache laitière : relation entre le ph ruminal et le ratio trans- 10 / trans- 11 (c18:1 + c18:2)

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    L'acidose ruminale a non seulement un impact sur les performances laitières, mais également sur la composition en acides gras du lait. En effet, la modification des conditions de fermentation limite la biohydrogénation des acides gras insaturés et favorise la formation des isomères trans-10 au détriment des trans-11, normalement majoritaires. Ce travail, portant sur 2 Prim Holstein pourvues de canule ruminale, est une étude préliminaire qui envisage les modifications du profil de ces acides gras lors de l'ajout de blé à hauteur de 20 puis 35% de la matière sèche d une ration à base d ensilage de maïs. Les résultats montrent que le taux butyreux et le profil des acides gras sont fortement modifiés pour des pH inférieurs à 6,0 et que le pH ruminal est assez bien corrélé au taux butyreux (r2=0,70) et au ratio trans-10 / trans-11 du lait (r2=0,55). D autres études sont cependant nécessaires avant d envisager l'utilisation du dosage des acides gras à des fins diagnostiques

    Effect of the introduction of Na2B4O7 on erbium luminescence in tellurite glasses

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    Compositional dependence of spontaneous emission of Er3+ was studied in borate telluriteglasses. The improvement of the luminescence at 1533 nm while pumping at 980 nm by introducing sodium tetraborate in a telluriteglass host is discussed in Er3+ doped and Yb3+/Er3+ co-doped glasses. From the absorption, emission spectra and lifetime measurements, an optimized sodium tetraborate molar concentration between 1.25% and 2.5% was shown to induce a maximum intensity of the 1533 nm spontaneous emission in correlation with a more efficient non-radiative transfer from the pump level to the emitting level of Er3+. The introduction of Na2B4O7 shortens the radiative lifetime of the erbium pump level (4I1L/2) as well as decreases the visible luminescence resulting from up conversion effect

    Formation and thermo-assisted stabilization of luminescent silver clusters in photosensitive glasses

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    Various photo-induced silver luminescent centres were obtained in photosensitive zinc and phosphate glasses containing silver ions after exposure to gamma or ultraviolet nanosecond pulsed-laser radiation. Gamma-irradiation of the glasses results mainly in the formation within the glass of electron-trapped and hole-trapped silver centres as evidenced by optical absorption, luminescence and electron spin resonance spectroscopies. For the highest irradiation doses silver clusters are obtained. Under ultraviolet nanosecond pulsed-laser exposure similar species are generated along the beam propagation direction as proven by the analogous optical and luminescence signatures. In this case for high irradiation doses few silver clusters are created. The evolution of the luminescence spectra with respect to the temperature and to the duration of the heat treatment after ultraviolet nanosecond pulsed-laser irradiation evidences the presence of potential barriers determining the stability limits of some species such as the Ag2+ hole-trapped centres or the Agmx+ clusters composed of silver ions and silver atoms. A heat treatment of several hundreds of degrees is identified as a the key parameter for tailoring the optical properties and controlling the formation of Agmx+ clusters in the photosensitive glasses.Femtosecond Laser Interaction and Nanostructurin

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