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Magnetic resonance measurements of the transition from normal to anomalous hydrodynamic dispersion in porous media due to biological activity are presented. Fractional advection-diffusion equations are shown to provide models for the measured impact of biofilm growth on porous media transport dynamics.

It has recently been proposed, on the basis of a theoretical analysis, that the folding of the mucosa provides a significant component of airway stiffness. The model predicted that the stiffness of an airway was directly related to the number of epithelial folds that developed. In this study we examine the possibility that the folding pattern is determined by the physical requirements that the folding membrane must stay within the boundary of the smooth muscle wall, that the submucosal mass is constant, and that the strain energy of the folding membrane is the minimum possible within the geometric constraints. Model predictions are compared with morphometric data from the noncartilaginous airways of 17 sheep lungs. The data are in agreement with our predictions, which are based on the assumption that the folding membrane thickness is proportional to the submucosal thickness (in a fully dilated airway). The outcome of this analysis is that the increase in intrinsic stiffness of the folding membrane resulting from the increased thickness outweighs the decrease in stiffness conferred by the fewer folds required by the thicker submucosa. It is suggested that the increase in folding membrane thickness observed in asthma could be viewed as a protective mechanism that tends to reduce hyperresponsiveness.

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We present an experimental and numerical study of immiscible two-phase flow of Newtonian fluids in three-dimensional (3D) porous media to find the relationship between the volumetric flow rate (Q) and the total pressure difference () in the steady state. We show that in the regime where capillary forces compete with the viscous forces, the distribution of capillary barriers at the interfaces effectively creates a yield threshold (), making the fluids reminiscent of a Bingham viscoplastic fluid in the porous medium. In this regime, Q depends quadratically on an excess pressure drop (). While increasing the flow rate, there is a transition, beyond which the overall flow is Newtonian and the relationship is linear. In our experiments, we build a model porous medium using a column of glass beads transporting two fluids, deionized water and air. For the numerical study, reconstructed 3D pore networks from real core samples are considered and the transport of wetting and non-wetting fluids through the network is modeled by tracking the fluid interfaces with time. We find agreement between our numerical and experimental results. Our results match with the mean-field results reported earlier.Electronic supplementary materialThe online version of this article (doi:10.1007/s11242-017-0874-4) contains supplementary material, which is available to authorized users.

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Nanomedicine directed at diagnosis and treatment of infections can benefit from innovations that have substantially increased the variety of available multifunctional nanoplatforms. Here, we targeted a spherical, icosahedral viral nanoplatform to a pathogenic, biofilm-forming bacterium, Staphylococcus aureus. Density of binding mediated through specific protein-ligand interactions exceeded the density expected for a planar, hexagonally close-packed array. A multifunctionalized viral protein cage was used to load imaging agents (fluorophore and MRI contrast agent) onto cells. The fluorescence-imaging capability allowed for direct observation of penetration of the nanoplatform into an S. aureus biofilm. These results demonstrate that multifunctional nanoplatforms based on protein cage architectures have significant potential as tools for both diagnosis and targeted treatment of recalcitrant bacterial infections.