Limits on variations in fundamental constants from 21-cm and ultraviolet quasar absorption lines

Quasar absorption spectra at 21-cm and UV rest wavelengths are used to estimate the time variation of x equivalent to alpha(2)g(p)mu, where alpha is the fine structure constant, g(p) the proton g factor, and m(e)/m(p)equivalent to mu the electron/proton mass ratio. Over a redshift range 0.24 less than or similar to z(abs)less than or similar to 2.04, (weighted)(total)=(1.17 +/- 1.01)x10(-5). A linear fit gives x/x=(-1.43 +/- 1.27)x10(-15) yr(-1). Two previous results on varying alpha yield the strong limits Delta mu/mu=(2.31 +/- 1.03)x10(-5) and Delta mu/mu=(1.29 +/- 1.01)x10(-5). Our sample, 8x larger than any previous, provides the first direct estimate of the intrinsic 21-cm and UV velocity differences similar to 6 km s(-1).