Plate efficiency local

The ratio Emv is shown graphically in Figure 11.56 where for any operating line AB the enrichment that would be achieved by an ideal plate is BC, and that achieved with an actual plate is BD. The ratio BD/BC then represents the plate efficiency. The efficiency may vary from point to point on a tray. Local values of the Murphree efficiency are designated Emv and Emi. 

Three hinds of plate efficiencies may be used for expressing the relationship between the performance of theoretical and actual stages. They are (1) overall column efficiency or overall plate efficiency, (2) Murphree plate efficiency, and (3) point efficiency or local efficiency. 

Because — [ln(l — 0)] /0 is greater than unity, the stage efficiency in cross flow exceeds the local efficiency E Eg- A similar result is found in distillation, where the plate efficiency is greater than the point efficiency when there is cross flow of liquid without mixing across the plate. 

TYPES OF PLATE EFFICIENCY. Three kinds of plate efficiency are used (1) overall efficiency, which concerns the entire column (2) Murphree efficiency, which has to do with a single plate and (3) local efficiency, which pertains to a specific location on a single plate. 

DISTILLATION PLATE EFFICIENCY. The two-film theory can be applied to mass transfer on a sieve tray to help correlate and extend data for tray effieiency. The bubbles formed at the holes are assumed to rise through a pool of liquid that is vertically mixed and has the local composition x. The bubbles change in composition as they rise, and there is assumed to be no mixing of the gas phase in the vertical direction. For a unit plate area with a superficial velocity the moles transferred in a thin slice dz are... 

Gas absorption can be carried out in a column equipped with sieve trays or other types of plates normally used for distillation. A column with trays is sometimes chosen instead of a packed column to avoid the problem of liquid distribution in a large diameter tower and to decrease the uncertainty in scaleup. The number of theoretical stages is determined by stepping off plates on a y-x diagram, and the number of actual stages is then calculated using an average plate efficiency. The plate and local efficiencies are defined in the same way as for distillation [Eqs. 

Point efficiency (Murphree point efficiency). If the vapour and liquid compositions are taken at a point on the plate, equation 11.64 gives the local or point efficiency, Emv. 

Geddes, R. L. Trans. Am. Inst. Chem. Eng. 42 (1946) 79. Local efficiencies of bubble plate fractionators. 

A central tenet to the step-wise model is that the continental lithosphere deforms as a series of small plates, and that plate boundary stresses are sufficient to reactivate old suture boundaries as sites of crustal thickening and mantle subduction far from the plate boundary. The continental crust thickens homogeneously above internally undeformed mantle lithosphere that is partially subducted at these boundaries. Localized strain at sites of strike-slip and mantle subduction also requires a mechanically competent lower crust and mantle lithosphere such that stresses are efficiently transmitted from the mantle lithosphere through the crust. 

Packed-tower efficiency and turndown are strongly dependent on the quality of initial liquid distribution. Uneven distribution may cause local variations in the liquid/gas ratio, localized pinch conditions, and reduced vapor-liquid contact. Figure 14 shows two common liquid distributor types, the ladder type (shown as the top distributor) and the orifice type (shown as the redistributor). The ladder type is a horizontal header of pipes, which are perforated on the underside. The orifice type is a flat perforated plate equipped with round or rectangular risers for gas passage. Other common types of distributors are a header equipped with spray nozzles (spray distributor) and a header of horizontal channels, with V notches cut in the vertical walls of the channels (notched-trough distributor). 

Because surface imperfections can act efficiently as nucleation centers, the defect structure of the surface onto which the metal is plated plays an important role in determining the morphology of the deposit. On a microscopic level, the amount of metal deposited onto a given area depends largely on the density of nuclei, which in return is greatly influenced by both the number of defects and their local arrangement across the surface. Thus, preferential deposition of metal at atomic steps is often seen. 

We developed adenoviral constructs of the human a1B-AR and the oqD-AR coupled with GFP. These constructs infected human aortic smooth muscle cells (Cascade Biologies, Portland, OR) with approx 70% efficiency (35). Confocal images of infected cells (Fig. 4 see Color Plate 1 following p. 148.) show that the a1B-AR/GFP is primarily expressed on the cell surface of vascular smooth muscle cells, although some cytoplasmic expression is also observed. This localization pattern agrees with the work of MacKenzie et al. (34). 

---