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.
By Mayo Clinic Staff. Some people who have ischemia don't experience any signs or symptoms (silent ischemia). When signs and symptoms occur, the most common is chest pressure or pain, typically on the left side of the body (angina pectoris). Other signs and symptoms â which might be experienced more commonly by women, older people and people with diabetes â include: Neck or jaw pain. Shoulder or arm pain.