Imaging techniques

actin out

Quick: what’s the difference between an ‘amu’ (atomic mass unit) and a ‘Da’ (Dalton)? Answer: Nothing. They both represent one-twelfth of the rest mass of an unbound carbon-12 atom in its nuclear and electronic ground state, a.k.a 1.66×10−27 kg. This is very slightly less than the mass of a proton or a neutron (approximately 1.67×10-27 kg). When first invented, the Dalton was intended to be a fundamental unit such that one hydrogen atom had a mass of one Dalton. Helium would be two Daltons, lithium would be three Daltons, etc. Of course, then we realized that every atom had different numbers of protons, neutrons and electrons, which mean that there was no simple universal mass. It would be so much easier to memorize if everything on the periodic table was a simple multiple of a fundamental quantity.

helium: a weighty question

My research focuses on how magnets behave when you make them very, very small. (The broad answer is: really interestingly and often unpredictably.) Like many people who study the physical world, it is much easier to get at the basic nature of a material if you cool the material to very low temperatures. Cooling literally “freezes out” many effects, making the system simpler to understand.

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