Post-concussion syndrome. Post-concussion syndrome, also known as postconcussive syndrome or PCS, is a set of symptoms that may continue for weeks, months, or a year or more after a concussion â a mild form of traumatic brain injury (TBI).
The Equatorial (Celestial) Coordinate System. Equatorial coordinates, also called simply celestial coordinates, are the standard coordinate system for the sky. It is meant for the fixed sphere of the stars within which the Earth and Sun move.
Spherical Coordinates Spherical coordinates, also called spherical polar coordinates (Walton 1967, Arfken 1985), are a system of curvilinear coordinates that are natural for describing positions on a sphere or spheroid.