Direct mechanical conveying

Bulk displacement may be caused by fluid flow or direct mechanical conveying of a complete phase or fraction from one location or vessel to another. Consider, for example, the mechanical decantation of the upper phase from vessel A to vessel B. In vessel B, additional separation takes place because of the redistribution of components of the upper phase in vessel A between itself and the lower phase in vessel B (Figure 3.1.1). But all the components in the upper phase of vessel A are displaced to the new vessel B at the same rate and in a nonselective fashion. Such a procedure is followed in laboratory decantations as well as in industrial decanters. 

Bulk flow via direct mechanical conveying can also allow the achievement of bulk flow parallel to the direction of the force. Consider, for example, a liquid phase y = 2 of volume V2 in a vessel containing species i = 1,2. Add a certain volume Vi of an immiscible Uquid phase y = 1 on top of this liquid phase j = 2. This liquid phase will extract preferentially one of the species i. After equilibrium has been achieved, this top Uquid... 

Not all materials or products have the same flow characteristics. Some have plastic characteristics and flow easily. Others do not self-adhere and tend to separate when pumped or mechanically conveyed. As a result, the volumetric efficiency is directly affected by the properties of each product. This also impacts screw performance. 

Two general mechanisms have been considered by which a depleted intracellular Ca2+ pool might communicate with the plasma membrane [4]. There is evidence that the IP3 receptor is associated with the cytoskeleton, and this association may tether the IP3 receptor to the plasma membrane. Depletion of intracellular calcium stores might cause a conformational change in the IP3 receptor, which could be conveyed to the plasma membrane via the cytoskeleton or by a more direct protein-protein interaction. Alternatively, signaling could occur... 

This examination of the available information on the structure and function of hemopexin, the mechanisms of hemopexin-mediated heme transport, and the biological consequences of this specific transport system is intended to convey a sense of the considerable information available on this system, to show how past and present results combine to provide a coherent picture of the system, and to point to the many exciting new directions for continued research. 

Positive-displacement pump—A pump that conveys fluid by directly moving it using a suitable mechanism such as a piston, plunger, or screw. 

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