Whole-genome sequencing of 78 Icelandic parent–offspring trios is used to study the de novo mutation rate at the genome-wide level; the rate is shown to increase by about two mutations a year as a function of the increasing age of the father at conception, highlighting the importance of father’s age on the risk of diseases such as autism and schizophrenia.

An electronic current flowing in one conductor can induce a drag current in another spatially separated conductor by means of Coulomb interactions; when these interactions are sufficiently strong the currents become equal and the drag therefore ‘perfect’, as shown here for a bilayer two-dimensional electron system.