"SDN:P07::7M8RPACU" . "false" . "2018-02-12 16:53:18.0" . . . . . "2018-02-12 16:53:18.0" . "" . "1" . "SDN:P07::7M8RPACU" . "accepted"@en . . "SDN:P07::7M8RPACU" . "The surface called \"surface\" means the lower boundary of the atmosphere. \"Content\" indicates a quantity per unit area. \"Radioactivity\" means the number of radioactive decays of a material per second. \"Pb\" means the element \"lead\" and \"211Pb\" is the isotope \"lead-211\" with a half-life of 2.51e-02 days."@en . "1" . . "surface_radioactivity_content_of_211Pb"@en .