CNET News: A mini-atom-based magnetic sensor has successfully tracked a human heartbeat, say physicists at NIST, who are working with researchers at a German national metrology institute. A key advantage, says principal investigator John Kitching, is that the magnetic signals detected by magnetocardiograms aren’t affected by fluids in the body, as are the electric signals used with electrocardiograms; MCGs also do not require contact with the body. Nevertheless, such a device would require powerful shielding from Earth’s magnetic field. Kitching and coworkers have published their findings in Applied Physics Letters.