So how many stars are there in the Universe? It is easy to ask this question, but difficult for scientists to give a fair answer! Stars are not scattered randomly through space, they are gathered together into vast groups known as galaxies. The Sun belongs to a galaxy called the Milky Way.
Reverse osmosis. Reverse osmosis (RO) is a water purification technology that uses a semipermeable membrane to remove ions, molecules, and larger particles from drinking water.
Reactive oxygen species (ROS) are chemically reactive molecules containing oxygen. Examples include peroxides. superoxide, hydroxyl radical, and singlet oxygen. In a biological context, ROS are formed as a natural byproduct of the normal metabolism of oxygen and have important roles in cell signaling and homeostasis.