Skin discoloration can be due to changes in melanin. Melanin is a skin pigment that gives color to the skin. Changes in melanin can also cause skin to be patchy. Treatment for skin discoloration includes using topical treatments.
Winglets increase an aircraft's operating efficiency by reducing what is called induced drag at the tips of the wings. An aircraft's wing is shaped to generate negative pressure on the upper surface and positive pressure on the lower surface as the aircraft moves forward.
Aircraft designers also use geometry on a daily basis, as wing geometry has a significant effect on the lift and drag of all types of aircraft. Lift refers to the force that works against an aircraft and holds it in the air. Drag is a mechanical force that opposes the motion of an aircraft when it is in the air.