The antioxidant effects of the ethyl acetate fraction of Dillenia indica bark (DIBEt) and the underlying mechanisms were investigated in tert-butyl hydroperoxide (t-BHP)-stimulated oxidative stress in RAW 264.7 cells. Paper spray ionization-mass spectroscopy with positive-ion mode tentatively revealed 27 secondary metabolites in D. indica bark extract; predominant among them were alkaloids, phenolic acids, and flavonoids. A new triterpenoid (nutriacholic acid) was confirmed in DIBEt for the first time. DIBEt had strong free radical-scavenging capabilities and was also able to reduce t-BHP-induced cellular reactive oxygen species (ROS) generation in RAW 264.7 cells. DIBEt was found to prevent oxidative stress by boosting the levels of heme oxygenase-1 (HO-1) through the up-regulation of nuclear factor erythroid 2-related factor 2 (Nrf2) via the regulation of extracellular signal-regulated kinase (ERK) phosphorylation in RAW 264.7 cells. These results support the potential of DIBEt for defense against oxidative stress-stimulated diseases.

This paper describes a dynamic membrane filtration system that combines crossflow filtration and centrifugal separation in a rotating tubular membrane. Because of the noslip boundary condition, membrane rotation leads to higher centripetal force near the lumen wall than introduction of a rotating flow. In this fundamental exploratory study, hollow glass microspheres (5 to 35 µm diameters) serve as model low-density, separate-phase foulants during filtration of aqueous suspensions through a tubular ceramic membrane (nominal 0.14 µm pore size). At low crossflow rates, membrane rotation at 1725 rpm decreases fouling and shifts the microsphere size distribution in the membrane cake towards smaller diameters. Force balance calculations suggest that centripetal force should move particles with diameters >~17 μm away from the lumen surface. Moreover, azimuthal and longitudinal shear stresses will also selectively remove larger particles from the membrane cake. Computational fluid dynamics (CFD) simulations show that the rotational flow does not fully develop in the membrane lumen and the fluid radial velocity peaks before the membrane wall. Both of these factors will decrease movement of low-density particles away from the lumen wall. Nevertheless, consistent with experimental data, CFD simulations show greatly decreasing encounters of particles with the membrane wall as particle size increases.

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The wall profile of the swirl chamber greatly impacts the internal flow structures and separation efficiency of a liquid-liquid separation hydrocyclone. The objective of this study is to examine the effects of parabolic and hyperbolic wall profiles of hydrocyclone swirl chamber on the internal flow structures and separation efficiency based on the numerical simulations. The internal flow structures observed for the different wall profiles of swirl chamber motivates the redesign of hydrocyclone geometry to achieve enhanced separation efficiency. Results show that, for a dilute system (oil concentration less than 1%), the hyperbolic and parabolic swirl chambers without a tail pipe yield, respectively, 16.5% and 25% higher separation efficiency for a droplet size of 30 μm when compared with a conical swirl chamber without tail pipe. However, the hyperbolic swirl chamber has a greater potential for the reduction of effective length of hydrocyclone with maintaining high separation efficiency. In addition, a hydrocyclone with truncated hyperbolic swirl chamber and tail pipe provides very long reverse flow core and yields 17% and 33% higher efficiency than that of full hyperbolic and conical swirl chambers without tail pipe, respectively.

In this work we examine the internal flow structures within hydrocyclones used for liquid-liquid separation, especially those used for the removal of oil droplets from water. The internal flow structures and patterns are greatly influenced by the geometric shape of the swirl chamber. The effects of parabolic and hyperbolic wall profiles of the swirl chamber on the reverse flow vortex core, short circuit flows, and the separation efficiency are investigated numerically by solving the Reynolds Average Navier-Stokes equations closed by an equation of change for the Reynolds stress. Droplets (forming the dispersed phase) trajectories are predicted by solving a kinematic equation of motion and force balance. Internal flow structures for different geometric conditions have partially motivated the redesign of the hydrocyclone geometry so as to support a longer and stable reverse flow vortex core and for greater separation efficiency. Results indicate that both the parabolic and hyperbolic swirl chambers provide improved separation efficiency. However, the hyperbolic swirl chamber has a greater potential for the reduction of effective length of the hydrocyclone with maintaining the same separation efficiency.