MRI of a knee. MRIs employ powerful magnets which produce a strong magnetic field that forces protons in the body to align with that field. When a radiofrequency current is then pulsed through the patient, the protons are stimulated, and spin out of equilibrium, straining against the pull of the magnetic field.
Noun. 1. aestivation - (zoology) cessation or slowing of activity during the summer; especially slowing of metabolism in some animals during a hot or dry period. estivation. zoological science, zoology-the branch of biology that studies animals.
Some metals, like aluminium, stainless steel, and titanium, corrode, but form a layer on their surface that protects them from further corrosion. This is called Passivation. (Stainless steel can't passivate in chlorinated water).