One of the most important standards that the API has set is the method used for measuring the density of petroleum. This standard is called the API gravity. Specific gravity is a ratio of the density of one substance to the density of a reference substance, usually water.
The most common symptoms of RSI include: 1  Pain. 2  Tingling. 3  A feeling of restlessness in the joint. 4  Weakness. 5  Throbbing. 6  Stiffness or cramp.
Typical symptoms resemble the common cold. However, RSV infection can also result in pneumonia, especially in the very young, the very old or those with weakened immune systems. However, mild or unnoticeable illness may occur. Symptoms may persist for a few days to a number of weeks.