1 Leaf shutters are usually fitted within a lens assembly (central shutter), or more rarely immediately behind (behind-the-lens shutter) or, even more rarely, in front of a lens, and shut off the beam of light where it is narrow. 2  Focal-plane shutters are mounted near the focal plane and move to uncover the film or sensor.
DHEA levels begin to naturally decline by the age of 30. While normal levels for women in their 20s fall between 65 and 380 Âµg/dL, for women in their 30s and 40s, the average normal range is 45 to 270 and 32 to 240 Âµg/dL, respectively.
Results of the blood urea nitrogen test are measured in milligrams per deciliter (mg/dL) in the United States and in millimoles per liter (mmol/L) internationally. In general, around 7 to 20 mg/dL (2.5 to 7.1 mmol/L) is considered normal. But normal ranges may vary, depending on the reference range used by the lab, and your age. Ask your doctor to explain your results. Urea nitrogen levels tend to increase with age. Infants have lower levels than other people do, and the range in children varies. Generally, a high blood urea nitrogen level means your kidneys aren't working well.