Operating region

FIG. 14-23 Stable operating region, plates. (Smith, Design of Equilibrium Stage Processes, McGraw-Hill, New Yoik, 1963.)... 

Calvert found that reentrainment from the baffles was affected by the gas velocity, the liquid-to-gas ratio, and the orientation of the baffles. Horizontal gas flow past vertical baffles provided the best drainage and lowest reentrainment. Safe operating regions with vertical baffles are shown in Fig. 14-112. Horizontal baffles gave the poorest drainage... 

FIG. 14-112 Safe operating region to prevent reentrainment from vertical zigzag baffles with horizontal gas flow. (Calveii, Yung, and Leung, NTIS Puhl. PB-24S050, 1975.)... 

The concepts of shp velocity and characteristic velocity are useful in defining the Flooding point and operational regions of different types of column contactors. The shp (or relative) velocity is given by the equation ... 

Identify better operating regions leading to improved product or operating efficiency. 

Plant Operation The purpose is to maintain and improve performance (i.e., product quality, rate, efficiency, safety, and profits). Examples include identification of plant conditions that limit performance (troubleshooting, debottlenecking) and exploration of new operating regions. 

Figure 5.1 Operating region of torque and current curves...

The shape of the eurve to the right of point B in Figure 6-46 is familiar. This is the normal operating region of the eompressor. The shape of the eurve to the left of point B shows the theoretieal eharae-teristie of the surge region. 

To summarize the importance of the critical speed concept, one should bear in mind that it allows an identification of the operation region of the rotor-bearing system, probable mode shapes, and approximate locations of peak amplitudes. 

Figure 8.1 A region of DNA in the related bacteriophages lambda, 434, and P22 that controls the switch for synthesis of new phage particles. Two structural genes are involved in this switch one coding for a repressor protein and one coding for the Cro protein. Between these genes there is an operator region (OR) that contains three protein binding sites—ORl, OR2, and OR3.

The lysis-lysogeny decision depends upon which of the two promoters in the operator region is able to bind polymerase, and that, in turn, depends upon the binding of the Cro and repressor proteins to three binding sites—ORl, OR2, and OR3—in OR. These binding sites are situated in the middle of the operator in such a way that ORl and OR2 overlap the promoter... 

How do repressor and Cro recognize the specific operator regions and achieve this subtle differential binding to the switch regions The sequences of ORl, 0R2, and OR3 in lambda are similar but not identical (Table 8.1). They are... 

The consequences of these changes were impressive. The parental 434 repressor had no affinity for the P22 operator in vivo, but the redesigned 434 repressor controiled only P22 operators and not 434 operator regions in vivo. Purified redesigned 434 repressor bound specifically to P22 operator DNA in vitro and showed the same hierarchy of affinities for the three regions ORl, 0R2, and OR3 as native P22 repressor. 

By comparing the crystal structures of these complexes with a further complex of the 434 repressor DNA-binding domain and a synthetic DNA containing the operator region OR3, Harrison has been able to resolve at least in part the structural basis for the differential binding affinity of 434 Cro and repressor to the different 434 operator regions. 

Sequence-specific protein-DNA interactions recognize operator regions... 

Figure 8.15 Sequence-specific protein-DNA interactions provide a general recognition signal for operator regions in 434 bacteriophage, (a) In this complex between 434 repressor fragment and a synthetic DNA there are two glutamine residues (28 and 29) at the beginning of the recognition helix in the helix-turn-helix motif that provide such interactions with the first three base pairs of the operator region.

The trp repressor controls the operon for the synthesis of L-tryptophan in Escherichia coli by a simple negative feedback loop. In the absence of L-tryptophan, the repressor is inactive, the operon is switched on and the enzymes which synthesize L-tryptophan are produced. As the concentration of L-tryptophan increases, it binds to the repressor and converts it to an active form so that it can bind to the operator region and switch off the gene. 

The proteins impose precise distortions on the B-DNA in the complexes Sequence-specific protein-DNA interactions recognize operator regions... 

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