  Suppression of electron current $ \Delta I$ through a 1D channel of length
$L$ connecting two Fermi liquid reservoirs is studied taking into account the
Umklapp electron-electron interaction induced by a periodic potential. This
interaction causes Hubbard gaps $E_H$ for $L \to \infty$. In the perturbative
regime where $E_H \ll v_c/L$ ($v_c:$ charge velocity), and for small deviations
$\delta n$ of the electron density from its commensurate values $- \Delta I/V$
can diverge with some exponent as voltage or temperature $V,T$ decreases above
$E_c=max(v_c/L,v_c \delta n)$, while it goes to zero below $E_c$. This results
in a nonmonotonous behavior of the conductance.

Strongly Correlated Electrons