Atherosclerosis in the carotid arteries, two large arteries in the neck that carry blood to the brain, is a major risk factor for ischemic stroke. Symptoms of stroke include: 1  Sudden numbness, weakness, or paralysis of face, arm or leg, especially on one side of the body. carotid endarterectomy is a surgical procedure in which a doctor removes fatty deposits blocking one of the two carotid arteries, the main supply of blood for the brain.
Polar stratospheric cloud. Polar stratospheric clouds or PSCs, also known as nacreous clouds (/ËneÉªkriË.És/, from nacre, or mother of pearl, due to its iridescence), are clouds in the winter polar stratosphere at altitudes of 15,000â25,000 meters (49,000â82,000 ft).
The stratosphere defines a layer in which temperatures rises with increasing altitude. At the top of the stratosphere the thin air may attain temperatures close to 0 C. This rise in temperature is caused by the absorption of ultraviolet (UV) radiation from the Sun by the ozone layer.he lowest layer of the atmosphere is called the troposphere. It ranges in thickness from 8km at the poles to 16km over the equator. The troposphere is bounded above by the tropopause, a boundary marked by stable temperatures. Above the troposphere is the stratosphere.