Fluoration de l’émail in vitro par laser à rayons ultraviolets

28 samples of human enamel have been studied in order to measure fluoride absorption after treatment with ultraviolet radiations.Samples treated with topical application only presented limited fluoride absorption in enamel surface (up to 0,5 µm deep). The absorption rate was higher, using an U.V. lamp. In samples treated with «excimer» laser, fluoride absorption was much higher in the surface layer and occurred also deeper (3 µm).28 échantillons d’émail dentaire humain ont été analysés afin de quantifier l’absorption du fluor après traitement aux rayons ultraviolets.Les analyses ont montré que les échantillons soumis à une simple application topique présentent une absorption de fluor modeste, uniquement dans les couches superficielles de l’émail (jusqu’à 0,5 µm de profondeur). L’absorption est plus importante en utilisant une lampe à vapeur de mercure. Avec le laser «excimer», comparé aux deux autres méthodes, la fixation du fluor dans le réseau de l’émail est très supérieure en surface et se produit également en profondeur (3 µm)

Thermoelectric power in crystalline boron

The thermoelecric power of mono-crystalline beta-boron (purity >99.9995%, room-temperature resistivity 5 × MegaOhm cm), measured in the dark, increased from 305 to a maximum of 700 µV/K, and then fell to 650 µV/K, respectively, at T = 190, 345, and 435 K. The observed temperature dependence explained assuming two components in the boron conductivity: a p-type conduction in the valence band, and an n-type conduction of electrons hopping in an impurity band

Interdiffusion of thin chromium and gold films deposited on silicon

The backscattering technique was used to study the interdiffusion process of Cr and Au films deposited on Si substrates. The results indicate that Au diffuses in Cr with an effective diffusion coefficient D = const. * exp(-0.68/kT). The activation energy is consistent with a diffusion process that occurs preferentially through grain boundaries. The high value of the diffusion coefficient justifies the presence of Au at the Cr-Si interface after a low-temperature short-time heat treatment. At temperature > 370°C (the eutectic point of the Si-Au system) and after a longenough heat treatment, the Au is completely mixed with Si

Fotoriattivazione, mediante laser (GaAs) ad impulsi, di ATPasi (Na+-K+) e di ATPasi miosinica inattivate

Fotoriattivazione, mediante laser (GaAs) ad impulsi, di ATPasi (Na+-K+) e di ATPasi miosinica inattivat