If a fluid is moving past a body with velocity, v, the same resistance tensor in Eq. ( ) also governs the forces (and torques) experienced by the body, although the sign of the velocity is reversed. Similarly, if the surrounding fluid is exhibiting a vortex flow, this same tensor will govern torques (and forces) on the body. To illustrate this point, consider the 'propeller'-shaped molecules, Λ-tris(2,2'-bipyridine) ruthenium (II) and ∆-tris(2,2'-bipyridine) ruthenium (II) shown in Fig. .