Shallow donor states of hydrogen in II-VI oxide and chalcogenide semiconductors, modelled by muon spectroscopy

The nature of hydrogen defect centres in II-VI semiconductors has been inferred by studying implanted positive muons, used to mimic interstitial protons. Neutral paramagnetic centres formed by electron capture fall into three distinct categories. CdS, CdSe, CdTe and ZnO show shallow-donor states, implying that hydrogen may act as an n-type dopant in these materials. ZnS, ZnSe, MgO, BeO and SrO show the more normal trapped-atom states, whilst HgO exhibits a state intermediate between the two extremes, reminiscent of the deep-donor hydrogen state in Si. Preliminary indications of shallow states in CdO and HgS and of a deep state in ZnTe remain to be clarified. In a search for a predictive model and in the light of recent theoretical notions of a common hydrogen pinning level, the systematics of the shallow-to-deep instability are correlated with the depths of the conduction-band minima

Clinopodium gilliesii (Benth.) Kuntze

Clinopodium gilliesii (Benth.) Kuntze is an aromatic species from the Andean region, from southern Peru to northern-central Argentina. It is mainly known as muña-muña and its leaves and tender stems are used as a flavoring and medicinal: stimulant, against mountain sickness, aphrodisiac, digestive, antispasmodic, among others traditional uses. Its bioactive constituents are essential oils, to which the plant owes its aroma and many of its therapeutic properties. The presence of flavonoids and phenolic compounds has also been detected. The essential oil composition of aerial organs is variable according to geographical location and ecological conditions, soil-type, weather-conditions and altitude of the population. Regarding its popular uses, the majority of uses has not been validate by pre-clinical tests, therefore they require experimental founding. Some of its biological activities, e.g.: aphrodisiac (in particular, erectile dysfunction), against some gastrointestinal disorders, antibacterial, antifungal, antiplasmodial, trypanocidal, insect repellent, antioxidant, and cytotoxic activities have already been analyzed. Some data about the similar species: C. bolivianum (Benth.) Kuntze and C. odorun (Griseb.) Harley is additionally commented.Fil: Hurrell, Julio Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; Argentina. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Laboratorio de Etnobotánica y Botánica Aplicada; Argentin