Black holes, quasars and active galaxies. Black holes are objects so dense, and with so much mass, that even light cannot escape their gravity. The existence of black holes has been theorised for more than 200 years. It is impossible to observe them directly, and astronomers had no way to test their theories until Hubble arrived.
Sequence IIIG Test Method. Sequence IIIG testing for automotive engine oils. The Sequence IIIG Test is a fired-engine, dynamometer lubricant test for evaluating automotive engine oils for certain high-temperature performance characteristics, including oil thickening, varnish deposition, oil consumption, and engine wear.
Polysomnography (PSG), a type of sleep study, is a multi-parametric test used in the study of sleep and as a diagnostic tool in sleep medicine. The test result is called a polysomnogram, also abbreviated PSG. The name is derived from Greek and Latin roots: the Greek ÏÎ¿Î»ÏÏ (polus for many, much, indicating many channels), the Latin somnus (sleep), and the Greek Î³ÏÎ¬ÏÎµÎ¹Î½ (graphein, to write).