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.
Estivation and Daily Torpor. Estivation is like hibernation in hot weather. Animals that live in deserts or tropical climates practice estivation. It may not occur solely because of food supply issues, as with hibernation, but because the conditions become too hot and dry for the animal to survive.