  A new method for computing hadronic effects on electroweak radiative
corrections to low-energy weak interaction semileptonic processes is described.
It employs high order perturbative QCD results originally derived for the
Bjorken sum rule along with a large N QCD-motivated interpolating function that
matches long and short-distance loop contributions. Applying this approach to
the extraction of the CKM matrix element V_ud from superallowed nuclear beta
decays reduces the theoretical loop uncertainty by about a factor of 2 and
gives V_ud = 0.97377(11)(15)(19). Implications for CKM unitarity are briefly
discussed.
