Structure function ratios: Recent results from NMC

Ratios of structure functions are determined in measurements of deep inelastic muon scattering. The ratio F,n /Ff( x) has been measured using hydrogen and deuterium targets and incoming muons with energies of 274 Ge V and 89 Ge V. The ratios F,He /Ff, F,C /Ff and F,C" /Ff have been measured at 197 Ge V. The measurements cover a wide range in x and Q'. Due to a complementary target system systematic errors are small. The ratio F;' /Fi( x ) , together with a deuteron structure function obtained from a fit to the world data, is also used to calculate the Gottfried sum rule. With the heavy target data the variation of the EMC effect with A and the momentum conservation sum rule are studied