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cultures of mammalian cells as well as bacteria expressing other ABC transporters—have led most researchers to believe that P-gp operates by directly binding and transporting multiple types of substrate molecules out of cells (6) (see the figure, panel A). Nevertheless, controversy remains. Alternative models have been proposed in which P-gp alters a single(More)
Pellets intended for oral dosing are frequently produced via extrusion/spheronization followed by drying. Typically, the last active process step, i.e., drying, is assumed to have little effect on the final dosage form properties (e.g., dissolution characteristics). Thus, there exist only a few studies of this subject. In the present study, calcium(More)
Blending of powders is a crucial step in the production of pharmaceutical solid dosage forms. The active pharmaceutical ingredient (API) is often a powder that is blended with other powders (excipients) in order to produce tablets. The blending efficiency is influenced by several external factors, such as the desired degree of homogeneity and the required(More)
Fluids sheared between concentric rotating cylinders undergo a series of three-dimensional instabilities. Since Taylor's archetypal 1923 study, these have proved pivotal to understanding how fluid flows become unstable and eventually undergo transitions to chaotic or turbulent states. In contrast, predicting the dynamics of granular systems--from nano-sized(More)
Drying is a common pharmaceutical process, whose potential to alter the final drug properties-even at relatively low temperatures-is often neglected. The present study addresses the impact of drying at 20 and 50 °C on wet-extruded calcium stearate (CaSt) pellets. Drying at 20 °C caused the majority of ibuprofen to accumulate at the pellet surface due to a(More)
Experiments have been carried out to study the behavior of L-threonine (needle-like) crystals during agitated drying. For an L-threonine/water system the morphology of the crystals was monitored using light microscopy and image analysis. Analysis of the transient behavior of the crystal size and shape distribution showed that attrition and agglomeration(More)
Electrostatic interactions between particles can dramatically affect granular flows, creating industrial safety and handling problems [K. N. Palmer, (Chapman and Hall, London, 1973), pp. 388-389]. We present experimental data demonstrating that charging of grains can also cause spontaneous self-assembly that may generate lasting geological patterns under(More)
Unstable waves have been long studied in fluid shear layers. These waves affect transport in the atmosphere and oceans, in addition to slipstream stability behind ships, aeroplanes and heat-transfer devices. Corresponding instabilities in granular flows have not been previously documented, despite the importance of these flows in geophysical and industrial(More)
ecause the majority of active ingredients and excipients in drug products are powders, advances in pharmaceutical technology will be driven by improving the in-dustry's understanding of granular-material processing. In many cases, small amounts of active-drug crystals must be blended with large amounts of excipients with rather different physical(More)
The adhesion of fine particles to surfaces is important for applications ranging from drug delivery to fouling of solar cells. In this letter, we show that powder adhesion can occur in unexpected patterns, concentrating particular grain types in some locations and clearing them from others, and we propose a straightforward traffic model that appears to(More)