Confinement is the physics phenomenon that quarks cannot be isolated. The color-charged quarks are confined with other quarks by the strong interaction to form pairs or triplets so that the net color is neutral. The force between quarks increases as the distance between them increases, so no quarks can be found individually.
... Russian chemist and inventor of the Periodic table
May 19 - Auguste Molinier, French historian
July 14 - Anton Chekhov, Russian playwright and short story ...