  The pole extrapolation method is applied to the semi-inclusive inelastic
electron scattering off the deuteron with tagged spectator protons to extract
the high-x structure function of the neutron. This approach is based on the
extrapolation of the measured cross sections at different momenta of the
spectator proton to the non-physical pole of the bound neutron in the deuteron.
The advantage of the method is in the possibility of suppression of the nuclear
effects in a maximally model-independent way. The neutron structure functions
obtained in this way demonstrate a surprising x dependence at $x\ge 0.6$ and
$1.6 \leq Q^2 \leq 3.38$ GeV$^2$, indicating a possible rise of the neutron to
proton structure function ratio. If the observed rise is valid in the true deep
inelastic region then it may indicate new dynamics in the generation of high-x
quarks in the nucleon. One such mechanism we discuss is the possible dominance
of short-range isosinglet quark-quark correlations that can enhance the d-quark
distribution in the proton.
