  The impact of the normal-state pseudogap, present in all optimal and
underdoped HTS cuprates, on critical currents and critical temperature is
surveyed. With the opening of the pseudogap around a doping state of p=0.19 the
condensation energy and superfluid density are rapidly suppressed due to
reduction in the normal-state spectral weight. Even by optimal doping (p=0.16)
these measures of the 'strength' of superconductivity are diminished by up to
40%. This results in a sharp reduction in critical currents and irreversibility
field, respectively. The optimal doping state where these properties are
maximised is therefore not at maximum Tc but in the lightly overdoped region
where the pseudogap energy falls to zero at p=0.19. The presence of impurities
and grain boundaries further heightens these effects.
