Flow Scanning

Flow scans were performed at three axial levels (1.5, 2.5 and 3.5/1) from the top packing surface ( ) being the diameter of the packing), for various flow conditions. Superficial liquid and gas velocities used, denoted as / ), and Ug, respectively, are listed in Table 1. 

In permeate return mode, permeate was recombined with retentate and recirculated. This mode was used to observe the effect on flux of increasing filter pressure (a pressure scan) or increasing transfilter flow (a flow scan). 

A pressure scan was made by holding transfilter flow constant and making a series of trials at differing filter pressures. In similar manner, a flow scan was made by holding filter pressure constant and making a series of trials at different transfilter flows. All pressure and flow scans were 60 min in duration, sufficient to establish flux change. 

So far we have been considering temperature ramping only, with flow rates held constant. In this section we consider the possibility of varying the flow rate during a run. The TS-CSTR turns out to be very simple to deal with, with marvelous possibilities for interactive control. The TS-PFR, as usual, requires much more careful consideration. In both the plug flow and CSTR reactors, flow scanning can be used alone or in combination with temperature scanning. 

Scanning methods described above need not be confined to temperature or flow scanning in chemical kinetics. There may be a variety of other systems, not at all connected with chemical kinetics, where the concept of variablescanning can provide a breakthrough method of data acquisition and lead to a resultant advance in understanding. 

Peak height ratios for different detectors or, e.g., ultraviolet detection at several wavelengths, can be used. Another method is to observe the change in retention times upon derivatization of the sample either by chemical or enzymatic methods. With continuous wavelength detectors stopped flow scanning of ultraviolet or fluorescence spectra is a possibility. Isotopic labelling can be used and, finally, fractions can be collected and characterized by, e.g., spectroscopic methods. 

Rate calodations in flow scanning reactors proceed in exactly the same way as outlined above for the tonpoature scanning case. The only difformce is that care must be taken to keq> trade of Ae various space times t that are cdlected wifli clode time in the data quadn lets -Te ti - t j) they are no longo- constant The resultant sieving is... 

FIGURE 2 (a) UV-vis-NIR spectrum of the as-synthesized PANI-EB solution in NMP (b) FT-IR spectrum (KBr powder diffuse reflectance) of the as-synthesized PANI-EB powder and (c) TGA of the as-synthesized PANI-EB powder under Ar flow (scan rate 20 C/min). 

Deposition point At flow (scan) N2 flow (scan) Pressure X 10 (mbar) Al/N ratio... 

Fig. 20. Effect of KCl and puromycin on the release of ribosomes from mitochondria. Mitochondria isolated from growing cells were incubated for 15 min at 30°C with increasing concentrations of KCl, with and without 2.1 mM puromycin as indicated. The incubation mixtures were layered onto 15-30% linear sucrose gradients and were centrifuged for 2 h at 221,800gniax- Under these conditions, the mitochondria were pelleted, and the released ribosomes remained in the gradient and were quantitated by UV flow scanning. (From Kellems et al )...

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