On the Stokes number and characterization of aerosol deposition in the respiratory airways

Aerosol deposition in the respiratory airways has traditionally been examined in terms of the Stokes number based on the reference flow timescale. This choice leads to large scatter in deposition efficiency when plotted against the reference Stokes number because the velocity and length scales experienced by advected particles deviate considerably from the reference values. A time-average of the particle local Stokes number should be adopted instead. Our results demonstrate that this average, or effective, Stokes number can deviate significantly from the reference value, in particular in the intermediate Stokes number range where variation across subjects is largest

Trusting outgroup, but not ingroup members, requires control: neural and behavioral evidence.

Trust and cooperation often break down across group boundaries, contributing to pernicious consequences, from polarized political structures to intractable conflict. As such, addressing such conflicts require first understanding why trust is reduced in intergroup settings. Here, we clarify the structure of intergroup trust using neuroscientific and behavioral methods. We found that trusting ingroup members produced activity in brain areas associated with reward, whereas trusting outgroup members produced activity in areas associated with top-down control. Behaviorally, time pressure-which reduces people's ability to exert control-reduced individuals' trust in outgroup, but not ingroup members. These data suggest that the exertion of control can help recover trust in intergroup settings, offering potential avenues for reducing intergroup failures in trust and the consequences of these failures

The Effect of wake Turbulence Intensity on Transition in a Compressor Cascade

Direct numerical simulations of separating flow along a section at midspan of a low-pressure V103 compressor cascade with periodically incoming wakes were performed. By varying the strength of the wake, its influence on both boundary layer separation and bypass transition were examined. Due to the presence of small-scale three-dimensional fluctuations in the wakes, the flow along the pressure surface undergoes bypass transition. Only in the weak-wake case, the boundary layer reaches a nearly-separated state between impinging wakes. In all simulations, the flow along the suction surface was found to separate. In the simulation with the strong wakes, separation is intermittently suppressed as the periodically passing wakes managed to trigger turbulent spots upstream of the location of separation. As these turbulent spots convect downstream, they locally suppress separation. © 2014 Springer Science+Business Media Dordrecht

Prediction of flow and aerosol deposition in the extrathoracic airways using an implicit immersed boundary method

The effect of intrasubject variation on the turbulent flow and aerosol deposition in the extrathoracic airways is studied in two realistic mouth-throat geometries from the same subject. An immersed boundary method is applied which simplifies the task of grid generation for the complex extrathoracic geometries and allows the use of a structured grid solver. Curvilinear grids that roughly follow the shape of the geometries are adopted, allowing for much higher resolution within the geometries than Cartesian grids commonly used in IB methods. An added advantage is that the grid lines are approximately aligned with the streamlines, which reduces numerical diffusive errors. The numerical simulations allow us to explain in vitro aerosol deposition data in the literature for the same mouth-throat models. The position of the tongue during inhalation is shown to have a significant impact on both the mean flow patterns and the turbulence intensities, which in turn affects extrathoracic deposition