Small Solute Removal

Small solute removal during HD occurs almost exclusively by diffusion. To quantify a particular membrane's diffusive capabilities, its mass transfer resistance is frequently used:

In the above equation, the overall resistance to diffusive mass transfer of a particular solute (RO) has three components: blood compartment resistance (Rb), resistance due to the membrane itself (RM) and dialysate compartment resistance (RD). Minimizing the mass transfer resistance in the blood compartment primarily requires the use of relatively high flow rates (i.e. shear rates) that decrease unstirred layers. Dialysate-side mass transfer resistance is likewise decreased by increasing flow rate but optimal dialysate perfusion of fibre bundles is also a consideration. Although increasing dialysate flow rate may itself improve fibre bundle perfusion (see below), another mechanism by which this can be achieved is the inclusion of spacer yarns. These devices are spacing filaments placed external to the fibres and are designed to facilitate dialysate distribution and reduce channelling. The resistance related to the membrane itself actually has two components:

where XM is the effective diffusion path-length for a solute and DM is the solute-specific membrane diffusivity. This equation indicates that a decrease in membrane resistance can be achieved either by a decrease in membrane thickness or an increase in membrane diffusivity, the latter of which is influenced strongly by membrane porosity.

Solar Panel Basics

Solar Panel Basics

Global warming is a huge problem which will significantly affect every country in the world. Many people all over the world are trying to do whatever they can to help combat the effects of global warming. One of the ways that people can fight global warming is to reduce their dependence on non-renewable energy sources like oil and petroleum based products.

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