Bias in the measurement of radon gas using ionization chambers: Application to SIR.
Two main non-destructive techniques can be used to measure standard 222Rn gas ampoules: well-type ionization chambers and gamma-ray spectrometry, the former being used in the Système International de Référence (SIR) for international comparison purposes. The reliability of these techniques requires that the variability of the flame-sealed gas glass ampoules used have a negligible influence on the detector response. This variability is studied in this work by considering three parameters: the volume of the ampoule, the position of the sealing point and the thickness of the glass. Results showed that variability of the gas ampoules induced measurement bias larger than the uncertainty of the standard sources.
Development of the primary measurement standard for gaseous radon-222 activity.
The Korea Research Institute of Standards and Science (KRISS) has developed a primary system for the activity standardization of gaseous radon-222, based on the defined solid angle counting method. The size of adsorbed radon is determined by a Cyclone Storage Phosphor System, and a buffer chamber is introduced between the measurement chamber and the source for the purpose of gas purification. The measured activity of gaseous radon-222 and its associated measurement uncertainty obtained using the system are presented.
A preliminary account of a new tyrannosauroid theropod from the Wessex Formation (Early Cretaceous) of southern England
Abstract A new genus and species of coelurosaurian theropod dinosaur from the Wessex Formation (Early Cretaceous, Barremian) of the Isle of Wight, England, is described and named. Distinctive characters of the premaxilla, its dentition, maxilla and nasals allow it to be diagnosed. The teeth in the premaxilla are D-shaped in cross-section and the nasals are fused. The hands are elongate and slender and the hindlimbs are gracile. Lack of element fusion elsewhere in the skeleton suggests that it is a subadult. Numerous character states are shared with tyrannosaurids but the new taxon appears to be excluded from the group that comprises aublysodontine and tyrannosaurine tyrannosaurids. We conclude that the taxon is a basal tyrannosauroid and as such it is one of the earliest and (with the exception of some teeth and an isolated ilium from Portugal) the first from Europe. Implications for tyrannosauroid biogeography and evolution are discussed. The animal was part of an unusual taphonomic assemblage in which some elements were partially articulated while others were scattered or broken.