Figure 3
From: Image Location for Screw Dislocation—A New Point of View
Screw dislocation in (a) the first, (b) the second, (c) the third, and (d) the forth quadrant without modification. Screw dislocation in the first quadrant without modification 
Screw dislocation in the second quadrant without modification 
Screw dislocation in the third quadrant without modification 
Screw dislocation in the forth quadrant without modification 