Buffer or generation zone

As the fluid s velocity must be zero at the solid surface, the velocity fluctuations must be zero there. In the region very close to the solid boundary, ie the viscous sublayer, the velocity fluctuations are very small and the shear stress is almost entirely the viscous stress. Similarly, transport of heat and mass is due to molecular processes, the turbulent contribution being negligible. In contrast, in the outer part of the turbulent boundary layer turbulent fluctuations are dominant, as they are in the free stream outside the boundary layer. In the buffer or generation zone, turbulent and molecular processes are of comparable importance. 

Contrary to classical packed beds, fluidization of beads provides a practical option to process very crude material containing particles in suspension such as protein aggregates, cells, or cell debris. In this separation mode, microbeads are lifted inside a column by an upward liquid stream generated by buffers and sample solutions. The particles leave larger empty zones between beads where the feedstock and particles in suspension pass through. 

An injection-related artifact can occur in gel buffers with consecutive electroki-netic injections from the same, low volume (10-200 mL) sample progressively smaller amounts of sample are introduced into the capillary, resulting in peak heights or areas that decrease with each injection (Schwartz et al., 1995). This effect is due to the migration of cations (e.g., Tris) from the gel buffer into the sample, changing its relative ionic strength. One solution to this problem is to perform an electrokinetic injection from a water vial prior to sample injection. This water injection generates a zone of ion depletion (i.e., rela-... 

Electrophoretic separation on agarose gels or cellulose acetate membranes is the procedure most commonly used to demonstrate LD isoenzymes." After the isoenzymes have been separated by electrophoresis, a reaction mixture is layered over the separation medium. The mixture (typically D, L-lactate> 500mmol/L, and NAD, 13mmol/L, often dissolved in a suitable pH 8.0 buffer) is applied as a liquid or in a gel. The NADH generated over the LD zones is detected either by its fluorescence, when excited by long-wave ultraviolet light (365 nm), or by its reduction of a tetrazolium salt to form a colored formazan. 

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