  We explore electron transport properties in a quantum wire attached to two
metallic electrodes. A simple tight-binding model is used to describe the
system and the coupling of the wire to the electrodes (source and drain) is
treated through Newns-Anderson chemisorption theory. In our present model, the
site energies of the wire are characterized by the relation $\epsilon_i=W\cos(i
\lambda^{\nu}\pi)$ where $W$, $\lambda$, $\nu$ are three positive numbers. For
$\nu=0$, the threshold bias voltage of electron conduction across the bridge
can be controlled very nicely by tuning the strength of the potential $W$. On
the other hand, for $\nu \ne 0$, the wire becomes an aperiodic one and quite
interestingly we see that, for some special values of $\nu$, the system
exhibits a {\em metal-insulator} transition which provides a significant
feature in this particular study. Our numerical results may be useful for
fabrication of efficient switching devices.
