For this telescope, the lenses are a concave convex (one side curved out and the other curved in) and a plano concave (one flat side and one side curved in). The plano concave lens is used as the eyepiece with the plano (flat) side facing the eye.
BUN redirects here. For other uses, see Bun (disambiguation). The liver produces urea in the urea cycle as a waste product of the digestion of protein. Normal human adult blood should contain between 6 and 20 mg of urea nitrogen per 100 ml (6â20 mg/dL) of blood.
BUN (blood urea nitrogen) is a blood test to check kidney function. So is the serum creatinine test. When your doctor talks about BUN/creatinine levels or a BUN-to-creatinine ratio, he or she is referring to the two main blood tests that tell how well the kidneys are filtering waste products from your blood. The ratio of BUN to creatinine is normally in the range of 10:1 to 20:1.