Recombination dynamics in bacterial photosynthetic reaction centers

The time dependence of magnetic field effects on light absorption by triplet-state and radical ions in quinone-depleted reaction centers of Rhodopseudomonas sphaeroides strain R-26 has been investigated. Measurements on the time scale of the hyperfine interaction in the radical pair [(BChl)2+. ...BPh-.)] provided kinetic data characterizing the recombination process. The results have been interpreted in terms of a recently proposed model that assumes an intermediate electron acceptor (close site) between the bacteriochlorophyll "special pair" (BChl)2 and the bacteriopheophytin BPh (distant site). Recombination is assumed to proceed through this intermediate acceptor. The experiments led to effective recombination rates for the singlet and triplet channel: k(Seff) = 3.9 . 107 s-1 and k(Teff) = 7.4 . 10(8) s-1. These correspond to recombination rates ks = 1 . 10(1) s-1 and kT = 7.1 . 10(11) s-1 in the close configuration. The upper bound of the effective spin dephasing rate k2eff approximately equal to 1 . 10(9) s-1 is identical with the rate of the electron hopping between the distant site of zero spin exchange interaction and the close site of large interaction. Interpretation of data for the case of direct recombination yields the recombination rates, spin dephasing rate, and exchange interaction in a straightforward way

Les toutes nouvelles évolutions du Bending Art System™

Le Système SureSmile (Orametrix™) a été développé sur la base du Bending Art System™ (BAS), introduit en 1994. Il présente à plusieurs égards d'importantes évolutions par rapport au système de base. Le Système SureSmile™ combine en effet de manière réfléchie un traitement tridimensionnel de l'image, un diagnostic assisté par ordinateur ainsi que la planification et l'application du traitement. L'objectif est de proposer une orthodontie de très grande qualité basée sur des méthodes précises et hautement reproductibles. Cet article vise à présenter le Système SureSmile™