The pit does not have any magical properties. What turns the guac brown is the air. If you can keep air from touching the guac then it will stay green. The pit will keep a portion away from the air, but what is more affective is to put plastic wrap over it and push it right down onto the surface.
Denuded skin is just another way of saying that the top layer (epidermis) of skin is gone...either from friction (abrasion or tear), trauma (tape burns), or severe rashes, or from a stage II pressure ulcer.
Compressive stress results in rocks being shortened or flattened. An elongate piece of silly putty may shorten be bending, or folding, wheres a ball of silly putty will flatten by shortening in the direction parallel to the compressive stress and elongating or stretching in the direction perpendicular to it.