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.
Urea is found dissolved in blood and is excreted by the renal tubules. In addition, a small amount of urea is also excreted in sweat. Therefore, the BUN level may reflect functioning of the liver and/or kidneys. In the United States, blood urea nitrogen (BUN) is measured in mg/dL.To convert BUN to a concentration in mmol/L (SI units), multiply by 0.357 ([10 dL/1 L]/[28 mg of N/mmol of urea] = 0.357).n addition, a small amount of urea is also excreted in sweat. Therefore, the BUN level may reflect functioning of the liver and/or kidneys. The reference range of the BUN level is 3-20 mg/dL. Individual laboratories may have different reference ranges, since the procedure may vary.