Localized states in advanced dielectrics from the vantage of spin- and symmetry-polarized tunnelling across MgO.

Research on advanced materials such as multiferroic perovskites underscores promising applications, yet studies on these materials rarely address the impact of defects on the nominally expected materials property. Here, we revisit the comparatively simple oxide MgO as the model material system for spin-polarized solid-state tunnelling studies. We present a defect-mediated tunnelling potential landscape of localized states owing to explicitly identified defect species, against which we examine the bias and temperature dependence of magnetotransport. By mixing symmetry-resolved transport channels, a localized state may alter the effective barrier height for symmetry-resolved charge carriers, such that tunnelling magnetoresistance decreases most with increasing temperature when that state is addressed electrically. Thermal excitation promotes an occupancy switchover from the ground to the excited state of a defect, which impacts these magnetotransport characteristics. We thus resolve contradictions between experiment and theory in this otherwise canonical spintronics system, and propose a new perspective on defects in dielectrics.

Tissue distribution of sex steroids: concentration of 17beta-oestradiol and cyproterone acetate in selected organs of female Wistar rats.

The tissue distribution of 17beta-oestradiol and cyproterone acetate was investigated after intravenous and intragastric administration to female Wistar rats by measuring the time course of the concentration of the sex steroids in plasma, liver, kidney, brain, and heart by radioimmunoassay. Test substances were administered intravenously in doses of 0.1 mg/kg each and intragastrically in doses of 10 mg/kg (17beta-oestradiol) and 0.1 mg/kg (cyproterone acetate) corresponding to the expected oral bioavailability. Tissue distribution was assessed within each mode of administration by AUCorgan/AUCplasma-quotients (Q-values), and between both routes of administration by F-values representing (bio- and organ availability) and R-values, which express the organ load after intragastric compared to intravenous administration if the same amount of drug has been made bioavailable in the plasma after both routes (for explanation see next page). The absolute bioavailability of 17beta-oestradiol after intragastric administration of 10 mg/kg was ca. 8%. The oestradiol liver load after intragastric administration was about 20 times higher than after intravenous administration, whereas the drug load of other organs was independent of the administration route. Cyproterone acetate was completely bioavailable after intragastric administration in a dose of 0.1 mg/kg. Cyproterone acetate levels and AUC-values in all organs investigated were higher when compared to the plasma with highest levels in the liver. The organ distribution of cyproterone acetate including the drug liver load was independent of the route of administration.

[Child abuse and dentists]. / Kindermishandeling en tandartsen.

A questionnaire on the recognition and reporting of child abuse was sent to a random sample of Dutch dental practitioners (N = 250). The response rate was 54%. Eighty-six percent had never seen a case of child abuse. The percentage of dentists reporting a (suspicious) case of child abuse (6%) was lower than the percentage of dentists detecting a case of suspicious child abuse (14%). The most important reason for this discrepancy seems to be a lack of knowledge and/or skills to properly identify child abuse. More professional education about child abuse is desired.