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.
Creatinine and BUN levels are important indexes to measure how well kidneys are functioning.If creatinine and BUN levels keep higher than normal for a long time, it may prove that your kidneys are not working well.n general,the normal BUN level ranges from 7 to 20mg/dL(2.5 to 7.1mmol/L).However, the normal BUN levels may vary with the lab, and your age. Urea nitrogen levels tend to increase with age. Infants have lower levels than other people do, and the range in children varies.