What are the spectator in 2H^ + +SO 4 ^ 2 +Co^ 2+ +2l CoSO 4 +2H^ 4 +21

The  grandmother cell  is a hypothetical  neuronthat represents a complex but specific concept or object.[1]  it activates when a person "sees, hears, or otherwise sensibly discriminates"[2]  a specific entity, such as his or her grandmother. the term was in use at least as early as 1966 amongst staff and students in the department of experimental psychology, university of cambridge, england. a similar concept, that of the  gnostic neuron, was proposed two years later

It is a body of knowledge gained  using  inquiry and experimentation 

Aquantity of that isotope to decay to 1/2 of  its original value