  The Knight shift and the nuclear spin-lattice relaxation rate 1/T1 of Ga-71
nuclei are measured in GaAs quantum wells at Landau level filling factor nu =
1/2 using optically pumped NMR. The temperature dependences of these data are
compared with predictions of a weakly-interacting composite fermion model. Our
measurements of the electron spin polarization and spin dynamics near the
transition between fully and partially spin-polarized ground states provide new
constraints on the theoretical description of nu = 1/2.
