The Re-Os isotopic system is currently limited as a chronometer because of the lack of accurate gravimetric standards for Os spike calibration and uncertainty of the Re half-life, which is also dependent on the accuracy of Os spike calibration. We demonstrate that the concentration of an Os spike can be calibrated accurately to 60.2%. The accuracy of this calibration was achieved by using a hig...

BACKGROUND Many explanatory models of obsessive-compulsive disorders (OCD) support the idea that compulsive behaviours are an attempt to avoid an aversive situation. There are few experimental studies carried out on the onset of repetitive behaviours. This study tries to create a repetitive checking behaviour as an analogue explaining similar OCD behaviours. METHOD An inter-group design with ...

Recent detailed simulations of Galactic Chemical Evolution have shown that the heavy elements, in particular [Fe/H], are expected to exhibit a weak, or absent, correlation with stellar ages in the early Galaxy due to the lack of efficient mixing of interstellar material enriched by individual Type II supernovae. A promising alternative “chronometer” of stellar ages is suggested, based on the ex...

Written by Ernst Zinner Washington University, St. Louis, MO Our solar system formed 4.6 billion years ago. Primitive meteorites provide samples that were formed in its earliest days and thus can give us information about this period. To establish the sequence of events during solar system formation on a time scale of a million years radioactive isotopes that decay with half-lives comparable to...