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This study presents some results from the numerical simulation of the flow in an industrial solid bowl centrifuge used for particle separation in industrial fluid processing. The computational fluid dynamics (CFD) software Fluent was used to simulate this multiphase flow. Simplified two-dimensional and three-dimensional geometries were built and meshed from the real centrifuge geometry. The CFD results show a boundary layer of axially fast moving fluid at the gas-liquid interface. Below this layer there is a thin recirculation. The obtained tangential velocity values are lower than the ones for the rigid-body motion. Also, the trajectories of the solid particles are evaluated.

The stall forces of processive molecular motors have been widely studied previously in vitro. Even so, in vivo experiments are required for determining the actual performance of each molecular motor in its natural environment. We report the direct measurement of light momentum changes in single beam optical tweezers as a suitable technique for measuring forces inside living cells, where few alternatives exist. The simplicity of this method, which does not require force calibration for each trapped object, makes it convenient for measuring the forces involved in fast dynamic biological processes such us intracellular traffic. Here we present some measurements of the stall force of processive molecular motors inside living Allium cepa cells.

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Centrifugal separation equipment, such as solid bowl centrifuges, is used to carry out an effective separation of fine particles from industrial fluids. Knowledge of the streams and sedimentation behavior inside solid bowl centrifuges is necessary to determine the geometry and the process parameters that lead to an optimal performance. Regarding a given industrial centrifuge geometry, a grid was built to calculate numerically the multiphase flow of water, air, and particles with a computational fluid dynamics (CFD) software. The effect of internal radial baffles on the multiphase flow was investigated. The results show that the baffles are helpful for the acceleration of the fluid, but they disturb the axial boundary layer, making it irregular, and originate a secondary circulating flow which hinders the sedimentation of small particles.