Atomare Fluktuationen und diffusive Bewegungen in Zirkonfluorid-Glaesern

SIGLEAvailable from TIB Hannover: DW 5719 / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman

Nuclear magnetic resonance and ionic motion in fluorozirconate glasses

We have determined NMR linewidths and nuclear spin relaxation rates for 19F, 7Li, and 23Na nuclei, and electrical conductivity in ZrF4-based fluoride glasses as a function of temperature. The results indicate that both Li and F are mobile in the glass containing 20 mole% LiF, whereas only F is mobile in glasses containing NaF (up to 30 mole%) or no alkali ions. Finally we compare and discuss the activation energies for the various parameters.Des mesures de conductivité électrique et de RMN de 19 F, 7Li et 23Na ont été réalisées sur des verres fluorures à base de ZrF4 : les variations des largeurs de raies de résonance et des temps de relaxation ont été étudiées en fonction de la température. Les résultats démontrent que les ions Li et F sont mobiles dans le verre contenant 20% de LiF (en fraction molaire). Dans le cas des verres contenant du NaF (jusqu'à 30% en mole) ou ne contenant pas de cation alcalin, seul l'ion F est mobile. Les énergies d'activation déduites des divers paramètres sont comparées et analysées

Influence of synaptic serotonin level on [18F]altanserin binding to 5HT2 receptor in man

The feasibility of in vivo serotonin 5HT(2) receptor binding measurement using [F-18]altanserin as a radioligand has been well established. In this study, the postsynaptic receptor binding potential of this ligand was examined as a possible indicator of synaptic serotonin content after pharmacological challenge. Studies were performed in 11 subjects with a history of recurrent major depression. Six of them received serotonergic antidepressive treatment at the time of the experiment, the other five patients were untreated. Two PET measurements were carried out in each subject within 2 or 3 days. Before one of the measurements, 25 mg of the serotonin re-uptake inhibitor clomipramine were given intravenously, the other measurement was done without pharmacological challenge. The data were analyzed using non-linear least-square regression and Logan's graphical method. In the whole group of subjects, binding potential and distribution volume of altanserin decreased following clomipramine challenge. The decrease was between 14 (P = 0.03) and 23% (P = 0.004). This effect was mainly seen in subjects not on antidepressive medication. Clomipramine challenge probably increased the synaptic serotonin level, which competed with altanserin leading to the lowered binding potential. The paradigm might, thus, be useful to estimate serotonin release in vivo. Pretreatment with serotonergic antidepressants reduces the effect of clomipramine. (C) 2001 Elsevier Science B.V. All rights reserved