April 2014 issue
Cover illustration: A trajectory plot showing the gradient vector field of electron density through the pyridine ring of the isoniazid molecule. Gradient trajectories originate at the atomic centres and terminate at the bond critical points. The thick solid lines represent the boundaries of the atomic basins. See Fig. 7 in Rajalakshmi et al. [(2014), Acta Cryst. B70, 331-341].