Plate efficiency number

The literature is less extensive on the use of protoplasts in stress-tolerance investigations however, some applications have been attempted. For example, in one study protoplasts were isolated from the leaves of a wild relative of tomato shown to be salt tolerant and from a salt-sensitive, cultivated species (Rosen Tal, 1981). In the presence of NaCI the plating efficiency (number of surviving cells/number of cells applied to the plate) of the wild relative was greater than the cultivated, sensitive cultivar. Proline, when added to the culture media, was found to enhance the plating efficiency of the salt-sensitive cultivar but not the wild, salt-tolerant relative. These results suggest that traits related to salt tolerance are expressed by the isolated protoplasts and that the response of protoplasts to environmental stress can be manipulated, i.e. the proline response. 

Cells were seeded at 1 X 10" cells/dish, treated test chemical for 24 h, washed and cultured for 5 weeks with biweekly media changes. Cells were fixed (methanol), stained 10% aqueous Giemsa), and scored for type II and type III foci. Plating efficiency, (number of colonies counted/ number of cells plated) X 100, of control cells was 35%... 

This is the one case where the overall column efficiency can be related analytically to the Murphree plate efficiency, so that the actual number of plates is calculable by dividing the number of theoretical plates through equation 86 ... 

Nonisothermal Gas Absorption. The computation of nonisothermal gas absorption processes is difficult because of all the interactions involved as described for packed columns. A computer is normally required for the enormous number of plate calculations necessary to estabUsh the correct concentration and temperature profiles through the tower. Suitable algorithms have been developed (46,105) and nonisothermal gas absorption in plate columns has been studied experimentally and the measured profiles compared to the calculated results (47,106). Figure 27 shows a typical Hquid temperature profile observed in an adiabatic bubble plate absorber (107). The close agreement between the calculated and observed profiles was obtained without adjusting parameters. The plate efficiencies required for the calculations were measured independendy on a single exact copy of the bubble cap plates installed in the five-tray absorber. 

Column efficiency (number of theoretical plates) As in batch chromatography, one needs to determine the efficiency of the column in order to evaluate the dispersion of the fronts due to hydrodynamics dispersion or kinetics limitations. The relationship of N proportional to L can be expressed in terms of the equation for height equivalent to a theoretical plate (HETP) as ... 

In some methods, the Murphree plate efficiencies can be incorporated into the procedure for calculating the number of stages and the number of real stages determined directly. 

The Murphree efficiency EmV is only equal to the point efficiency Emv if the liquid on the plate is perfectly mixed. On a real plate this will not be so, and to estimate the plate efficiency from the point efficiency some means of estimating the degree of mixing is needed. The dimensionless Peclet number characterises the degree of mixing in a system. For a plate the Peclet number is given by ... 

The relation between the plate efficiency and point efficiency with the Peclet number as a parameter is shown in Figure 11.16a and b. The application of the AIChE method is illustrated in Example 11.12. 

The theoretical plates may be stepped off as shown and 9 theoretical plates are shown. If the plate efficiency is 70 per cent, the number of actual plates = (9/0.7) = 12.85,... 

A distillation column is fed with a mixture of benzene and toluene, in which the mole fraction of benzene is 0.35. The column is to yield a product in which the mole fraction of benzene is 0.95, when working with a reflux ratio of 3.2, and the waste from the column is not to exceed 0.05 mole fraction of benzene. If the plate efficiency is 60 per cent, estimate the number of plates required and the position of the feed point. The relation between the mole fraction of benzene in liquid and in vapour is given by ... 

The use of a plate efficiency correction enables the simulation of columns with a real number of plates to be simulated. This may be important in the study of real columns, when incorporating an allowance for plate hydrodynamic behaviour. 

If the plate efficiency is 60 per cent, estimate the number of plates required and the position of the feed point. The relation between the mole fraction of benzene in liquid and in vapour is given by ... 

Equilibrium data and material-and heat-balances to determine the number of equilibrium stages (theoretical plates or transfer units) required for the desired separation. The required height of the column can be calculated if data are available for the specific rate of transfer of material between the two phases, expressed in terms of the plate-efficiency or the height of one transfer unit. 

The efficiency is sometimes quantified by the number of the theoretical plates, the number of effective vaporisation and condensation steps that are required to achieve a condensate of given composition form a given distillate. 

Generally, trays work better in applications requiring high flows, because plate efficiencies increase with increased vapor velocities, and therefore increase the influence of the reflux to feed ratio on overhead composition. Column dynamics is a function of the number of trays, because the liquid on each tray must overflow its weir and work its way down the column. Therefore, a change in composition will not be seen at the bottoms of the tower until some time has passed. 

The number of cells per microcarrier bead, the concentration of beads and the initial stirring conditions can vary dramatically. The following is a suggested protocol but if plating efficiency is poor the culture volume and speed of stirring can be decreased and the number of cells per microcarrier increased. 

For measuring plating efficiency a similar procedure is adopted and the colonies are fixed and stained (with Giemsa) and their number compared with the initial input. The plating efficiency of primary cells is low, but plating efficiencies of up to 100% can be achieved with cell lines or cell strains. 

Release cells with 0.25% trypsin in PBS or BSS (the divalent ions improve plating efficiency) and disperse by gently pipetting up and down the minimum number of times. Trypsinisation at 4°C for 2-10 min has been recommended especially for cloning cells in low serum. 

The most common performance indicator of a column is a dimensionless, theoretical plate count number, N. This number is also referred to as an efficiency value for the column. There is a tendency to equate the column efficiency value with the quality of a column. However, it is important to remember that the column efficiency is only part of the quality of a column. The calculation of theoretical plates is commonly based on a Gaussian model for peak shape because the chromatographic peak is assumed to result from the spreading of a population of sample molecules resulting in a Gaussian distribution of sample concentrations in the mobile and stationary phases. The general formula for calculating column efficiency is... 

As discussed in the first part of this chapter, the design of mass-transfer equipment often requires evaluation of the number of theoretical stages necessary to accomplish a desired separation. To complete the design, information must be available that shows the relationship between these ideal values and the actual performance of the equipment. The translation of ideal stages into actual finite stages can be accomplished by the use of plate efficiencies. 

The required number of actual plates, Ap, is larger than the number of theoretical plates, App, because it would take an infinite contacting time at each stage to establish equilibrium. The ratio Aj Ap is called the overall column efficiency. This parameter is difficult to predict from theoretical considerations, however, or to correct for new systems and operating conditions. It is therefore customary to characterize the single plate by the so-called Alurphree vapor plate efficiency, Ey (98) ... 

Tray I5fficiencies in Plate Absorbers and Strippers Computations of the number of theoretical plates N assume that the liquicl on each plate is completely mixed and that the vapor leaving the plate is in equilibrium with the liquid. In actual practice a condition of complete equilibrium cannot exist since interphase mass transfer requires a finite driving-force difference. This leads to the definition of an overall plate efficiency... 

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