RESUMO
We report a new cyanide-bridged Csâ{Fe4Co4} box, a soluble model of photomagnetic Prussian blue analogues (PBAs). The Cs+ ion has a high affinity for the box and can replace the K+ ion in the preformed K-cube. This exchange is kinetically impeded at room temperature but is accelerated by heating and using the 18-crown-6 ether. The inserted Cs+ ion confers a high robustness to the cube, which withstands boiling, as shown by variable-temperature NMR studies. The stability of this model complex in solution allows the probing of the electronic interaction between the alkali ion and the cyanide cage by using various techniques. These interactions are known to play a role in the photomagnetic behaviour of PBAs. Firstly, the 133Cs NMR spectroscopy proves that there is an electronic communication between the encapsulated alkali ion and the cyanide cage. The measured up-field signal, observed at ca. -200 ppm at 300 K, reveals that a certain amount of spin density is transferred through the bonds from the paramagnetic Co(ii) ion to the encapsulated cation. Secondly, cyclovoltammetric studies show that the nature of the inserted ions affects the redox properties of the cage and influences the electronic communication between the metal ions. However, the differences in the electrochemical properties of the K-cube and the Cs-cube remain moderate. As the switching properties are influenced by the redox potential of the Fe and Co centers, similar photomagnetic behaviour is observed, with both of them being highly photomagnetic. This result contrasts strikingly with previous studies on the 3D polymeric PBAs, where the PBAs with a high amount of Cs+ show poor photomagnetic behaviour. In that case, cooperative behaviour likely influences the switching properties. Finally, EPR spectroscopy shows that the K-cube is more anisotropic than the Cs-cube. This difference is reflected in the changes occurring in the slow magnetic relaxation (single molecule magnet behaviour) observed in the two cubes.
RESUMO
The school health service in France was attached to the Ministry of national education from 1945-1964, then to the Ministry of health until 1984, and has since returned to the Ministry of national education. From a global service in its beginnings, including physicians, nurses and social workers, it progressively grew into a social service on one hand, as well as a medical service and nursing service on the other, that act in close collaboration. Health and social personnel insure the technical advising of administrative heads of the Ministry of national education, at each level (ministerial, academic, and departmental). The strong coherence of the fundamental texts of the Ministry of national education allows the health and social service personnel to take health into account in the daily lives of establishments. They act as technical advisors in public health among school directors and heads of establishments. School medical centres are organised in districts of more than 5,000 inhabitants. The medical files of students are regrouped in these centres. The provision of personnel remains insufficient. The funds for functioning are sparse. The initial training of nurses and social workers depends on academic initiatives, while doctors benefit from a statuary initial training, either for eight weeks or a year. The school health teams implement new work procedures based on the methods of public health, the systematic health exams having been put into question. The March, 1998 "plan for relaunching school health" focuses on health education and prevention in schools.
