Figure 2.

Conserving and non-conserving energy transmissions. A: the initial state has a linear gradient. We are interested in the energy change of the center piece. B: Energy is transferred from high to low (gradient direction), as indicated by the arrows. C: Result of typical conserving transmission. The center piece receives and gives the same amount of energy, which maintains a solenoidal gradient field. D: Result of dilation-like transmission, which is not energy conserving. The center piece gains energy and a solenoidal gradient field cannot be sustained.