  Low temperature specific heat of the electron-doped (n-type) infinite-layer
cuprate $Sr_{0.9}La_{0.1}CuO_{2}$ has been measured. The quasiparticle density
of states (DOS) in the mixed state is found to be consistent with the feature
of the s-wave pairing symmetry, agreeing very well with the earlier tunnelling
measurement, but being contrary to the d-wave symmetry well confirmed for the
hole-doped (p-type) cuprates. Our results indicate that the electronic DOS are
mainly contributed by the vortex cores in the present sample being contrast to
the p-type cuprates in which the vortex cores are abnormal and contribute very
limited low energy DOS as evidenced by many means.
