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A novel structure, δ-doped NaYF4:Yb,Er, has been proposed for significantly enhancing the fluorescence efficiency of up-conversion phosphors. Theoretical calculations indicate that these new δ-doped NaYF4:Yb,Er structures will suppress the Yb3+-defect energy transfer rate while effectively preserving or enhancing the Yb3+ to Er3+ energy transfer. To investigate this effect δ-doped NaYF4:Yb,Er nanocrystals have been synthesized according to the designed structure model and the prepared samples characterized physically by transmission electron microscopy (TEM), high-resolution TEM (HRTEM), X-ray diffraction (XRD), energy dispersed spectroscopy (EDS) and optically by photoluminescence (PL) spectroscopy. Well-defined doping geometries of the order of 3–5 nm in width were clearly identified, both spatially and chemically. The up-converted emission spectra data were consistent with the theoretical predictions.

Surgical antimicrobial prophylaxis is used to decrease postoperative wound infection. We assessed the compliance to surgical antimicrobial prophylaxis guidelines in our hospital and the impact of an information program.Observational study of clean or clean contamined surgery, during two 3-week periods, separated by a targeted information period. The following data were collected prospectively: prophylaxis indication, antimicrobial agent, timing, dose, route and duration of prophylaxis. Chi square test was used for analysis or Fischer test when available.Four hundred seventy-seven patients were enrolled - 270 and 207 for each period respectively. For both periods only 49% of prophylaxis was appropriated. When prophylaxis should be administered - 15 and 13% of patients for each period - it was antibioprophylaxy was strictly adequate with recommandations. The most common error was administration timing. Only the choice of antimicrobial agent was optimized after information period.These results are consistent with previous studies. Information program alone have no effect on the good use of antimicrobial for surgical prophylaxis. Only a policy associating organization, restriction and education could improve practices.