Fig. 7

Péclet number versus apparent diffusivity for various molecules of interest in brain transport. L = 250 μm, \(v\) = 15 μm min⁻¹, and apparent diffusivity (D^*) specific to each molecule. \(Pe = v\) L/D^* is the ratio of convective to diffusive transport rates. For \(Pe \approx 1\), diffusive and convective rates are balanced; for \(Pe > 1\), convection exceeds diffusion. The graph shows for \(v\) = 15 μm min⁻¹ bulk flow is not large enough to be dominant and not small enough to be ignored