  Self-consistent modelling based on local spin-density formalism is employed
to calculate conductance of quantum point contacts at finite temperatures. The
total electrostatic potential exhibits spin-dependent splitting, which persists
at temperatures up to 0.5 K and gives rise to the anomalies at 0.4 and 0.7 of
the conductance quantum $2e^2/h$ occurring simultaneously in the absence of
external magnetic fields.
