  We investigate sequential tunneling through a multilevel quantum dot
confining multiple electrons, in the regime where several channels are
available for transport within the bias window. By analyzing solutions to the
master equations of the reduced density matrix, we give general conditions on
when the presence of a second transport channel in the bias window quenches
transport through the quantum dot. These conditions are in terms of distinct
tunneling anisotropies which may aid in explaining the occurrence of negative
differential conductance in quantum dots in the nonlinear regime.
