ABSTRACT
The role of the transition metal nature and Al2O3 coating on the surface reactivity of LiCoO2 and LiNi(1/3)Mn(1/3)Co(1/3)O2 (NMC) materials were studied by coupling chemisorption of gaseous probes molecules and X-ray photoelectron (XPS) spectroscopy. The XPS analyses have put in evidence the low reactivity of the LiMO2 materials toward basic gaseous probe (NH3). The reactivity toward SO2 gaseous probe is much larger (roughly more than 10 times) and strongly influenced by the nature of metal. Only one adsorption mode (redox process producing adsorbed sulfate species) was observed at the LiCoO2 surface, while NMC materials exhibit sulfate and sulfite species at the surface. On the basis of XPS analysis of bare materials and previous theoretical work, we propose that the acid-base adsorption mode involving the Ni(2+) cation is responsible for the sulfite species on the NMC surface. After Al2O3 coating, the surface reactivity was clearly decreasing for both LiCoO2 and NMC materials. In addition, for LiCoO2, the coating modifies the surface reactivity with the identification of both sulfate and sulfite species. This result is in line with a change in the adsorption mode from redox toward acid-base after Al/Co substitution. In the case of NMC materials, the coating induced a decrease of the sulfite species content at the surface. This phenomenon can be related to the cation mixing effect in the NMC.
ABSTRACT
Antiepileptic drugs as well epilepsy itself are known to induce some cognitive impairment. Thirty-six epileptic patients under unchanged and reduced therapy conditions were followed from a clinical (seizures' evaluation, reaction times [RTs], memory tests) and neurophysiological (EEG, BAEPs, ERPs) point of view, weekly as inpatients (mean stay 8.9 weeks) and after 1 and 3 months as outpatients. This study showed on one hand no clear correlation between RTs and ERPs components, and on the other hand an improvement of the most complex RT after reduction of polytherapy or stabilization of seizures by the introduction of carbamazepine-CR in newly treated patients. These data suggest that in epileptic patients there exists a slowing of cognitive processes between the stimulus evaluation time and the motor response and that this step is improved when a reduced but efficient therapy is given.
