Partial-thickness burns (2nd degree burns)-- affect the top 2 layers of skin. Most notable by blisters (which may develop quickly or take 24 hours to form), but also red, mottled, wet and painful skin. Full-thickness burns (3rd degree burn)-- all three layers of skin affected; leathery, dry, charred, gray.
1 Discoveror: known since ancient times. 2  Place of discovery: not known. 3  Date of discovery: unknown. 4  Origin of name: from the Anglo-Saxon word  gold  (the origin of the symbol Au is the Latin word  aurum  meaning  gold ).
The astronomical unit (symbol au, AU or ua) is a unit of length, roughly the distance from Earth to the Sun. However, that distance varies as Earth orbits the Sun, from a maximum (aphelion) to a minimum (perihelion) and back again once a year.