Zhong Liu

When a person receives radiation for a tumor in the head or neck, the rays pass through healthy tissue as well. Sometimes the jawbone starts to die afterward — a severe complication called osteoradionecrosis. The question isn't whether it happens, but how much the radiation dose itself increases the risk.

At the center of every atom lies a nucleus — a dense ball of protons and neutrons. These particles don't just crowd together randomly; they fill strict energy levels, much like floors in a skyscraper. When a floor is completely filled, the nucleus becomes especially stable — physicists call this a magic number.

To determine the size of the proton cloud in an atomic nucleus, physicists collide an unstable nucleus with a target and observe how many protons it loses. The larger the projectile nucleus, the more often it grazes target nuclei and loses particles.