Rapidly rotating Rayleigh-Bénard convection is studied by combining results from direct numerical simulations (DNS), laboratory experiments and asymptotic modeling. The asymptotic theory is shown to provide a good description of the bulk dynamics at low, but finite Rossby number. However, large deviations from the asymptotically predicted heat transfer scaling are found, with laboratory experiments and DNS consistently yielding much larger Nusselt numbers than expected. These deviations are traced down to dynamically active Ekman boundary layers, which are shown to play an integral part in controlling heat transfer even for Ekman numbers as small as 10 −7 . By adding an analytical parameterization of the Ekman transport to simulations using stress-free boundary conditions, we demonstrate that the heat transfer jumps from values broadly compatible with the asymptotic theory to states of strongly increased heat transfer, in good quantitative agreement with no-slip DNS and compatible with the experimental data. Finally, similarly to non-rotating convection, we find no single scaling behavior, but instead that multiple well-defined dynamical regimes exist in rapidly-rotating convection systems.

No abstract

No abstract

The blood-brain barrier (BBB) comprises the microvascular endothelial cells, pericytes, and astrocytes, which are connected by the extracellular matrix (ECM). Current BBB models focus solely on the microvascular endothelial cells which constitute a physical barrier by formation of tight junctions (TJs), while the impact of pericytes on barrier regulation is poorly understood. We established a coculture model from primary porcine brain capillary endothelial cells (PBCECs) and pericytes (PBCPs) to approach the in vivo situation. This model allows the examination of pericyte impact on pharmacological, transport, migration, and metabolic activity of the BBB. In vivo the interaction between pericytes and endothelial cells is partly controlled by the ECM which is remodeled by matrix metalloproteinases (MMPs). Both endothelial cells and pericytes secrete MMPs which are important not only for ECM remodeling but also for TJ cleavage. In this chapter, current methods to study the interactions of these cell types by ECM signaling as well as MMP secretion are described.

No abstract