= Position-dependent resistive pulse
{title2=$\Delta\mathcal R(z)\propto\rho\Omega/A(z)^2$}
A small insulating object of excluded <volume> $\Omega$ perturbs an Ohmic pore most strongly where the pore cross-sectional <area> $A$ is small. In a local weak-blockage model, replacing a small conducting <volume> gives the displayed resistance scaling, with a shape-dependent coefficient. At fixed voltage, $\Delta I\simeq-I_0\Delta\mathcal R/\mathcal R_0$. A symmetric pore with narrow ends and a wide middle can therefore resolve two end features in a passage pulse. This is a conditional volume-exclusion model: charged-particle ion transport, surface interactions and bandwidth can change the observed sign, amplitude and shape.
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