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 clouds can also be associated with very high surface winds which may indicate the presence of, or induce, winds and waves in the stratosphere. They form at temperatures of around minus 85ÂºC, colder than average lower stratophere temperatures, and are comprised of ice particles ~10Âµm across. The clouds must be composed of similar sized crystals to produce the characteristic bright iridescent colours by diffraction and interference.