Further detailing of the Bose-Einstein negative-U state in the high   temperature superconducting cuprates
  The cause of the sharp and universal optimization of the HTSC condensation energy at the hole doping concentration of p = 0.19 is identified within the context of the boson-fermion negative-U modelling and stripe phase electronic organization. Some recent structural, optical and positron annihilation experiments adding further support to this type of modelling of HTSC are briefly examined. 
John A Wilson