In a “normal” electrocardiogram (ECG), the transition of the QRS axis in the precordial leads occurs between leads V 3 and V 4 (i.e., there is a dominant S in V 3 and a dominant R in V 4).

Nagoya University scientists in Japan and colleagues at Yale University in the US have uncovered details of how the bacterial propeller, known as the flagellum, switches between counterclockwise and ...