Superconducting transition temperature in the (YBa2Cu3Oy)1−x(MeO)x system (MeO=AlO1.5, CeO2, CrO1.5, GaO1.5, GeO2, InO1.5, MgO, MnO2, NbO2.5, SiO2, TaO2.5, TiO2 and ZrO2)