Flow decay curve

Figure 5 shows the flow decay for the cell suspension concentration step of Figure 3. The flow rate decays gradually with time with an average final rate around 700 ml/min. Inlet pressure was 90 psi, and there was a 4.6X reduction in volume in about 15 minutes. The flow decay curve in Figure 5 is typical for an IS. coli concentration with a new 0.45 micron pore size microporous membrane.

Figure 6 is the corresponding flow decay curve for the sonified lysate suspension. Again, this is a typical flow decay with time. 

Figure 5. Flow decay curve for concentrating E. coli whole cells with a 0.45 pm microporous (Durapore) membrane. Inlet pressure was 90 psi. The initial volume was 22.3 liters the final volume, 4.8 liters.

Figure 8. Protein concentration flow decay curves for two different operating conditions with a 100,000 MWCO UF membrane. Key ...

Stopped-flow experiments of luminol chemiluminescence in the system luminol/pure DMSO/tert.butylate/oxygen 109> with independent variations of the concentrations of reactants confirmed the results obtained previously by E. H. White and coworkers 117> as to pseudo-first-order dependence of the chemiluminescence intensity upon each of the reactants. Moreover, the shapes of the decay curves obtained... 

Back EMF Draw an exponential decay curve (dotted) to show how back EMF is highest when rate of change of current flow is highest. This explains how inductors are used to filter out rapidly alternating current in clinical use. 

The flow response of a gas cell is an important parameter for sensing applications as it defines the actual response time of the system. The theoretical aspects of determining the time constants from the decay component of the response curve are straightforward. The time constants of the gas cell are calculated from the concentration decay curves (Fig. 6). For example, the time constants for CO are 1.23 and 12.4 s for the HWG and the multipass gas cell,... 

Fig. 6 Flow response decay curves for FT-IR spectroscopy with a F1WG gas cell (dotted line) and FT-IR spectroscopy with a 3-m multipass gas cell (dashed line) [43]...

The static experiments show that there is a complex between TBP and PNP at the dodecane/water interface. Even by simply mixing the two solutions it was clear that this interaction was time-dependent. However, the decay rate was sufficiently fast so that given the need to ensure uniform mixing in the bulk phases and the time required to accumulate a reasonable S/N, only the long time tail of the decay curve could be measured. No accurate estimate of the decay rate could be made in the Petri-dish. The solution was to construct a flow cell to measure the kinetics of the TBP and PNP interaction at the dodecane/water interface [48]. 

David and Augsburger (63) studied the decay of compressional forces for a variety of excipients, compressed with flat-faced punches on a Stokes rotary press. They found that initial compressive force could be subject to a fairly rapid decay and that this rate was dependent on the deformation behavior of the excipient for the materials studied, they found that maximum loss in compression force was for compressible starch and MCC, which was followed by compressible sugar and DCP. This was attributed to differences in the extent of plastic flow. The decay curves were analyzed using the Maxwell model of viscoelastic behavior. Maxwell model implies first order decay of compression force. 

Figure 8 displays normalized fluorescence decay curves of single R-6G (a) and rhodamine B zwitterion (b) molecules in aqueous solution. The boldface lines represent fits giving lifetimes of 3.7 and 1.8 ns, respectively, and the fine lines show the instrumental response curves (IRF). These data, however, were not yet obtained in a liquid flow but the solution was contained in a small liquid cell where the molecules diffused freely in and out the diffraction limited excitation focus. 

The present model also allows calculation of the relationship between flow velocity at constant relative conversion and operating time in a fixed bed. In the past linear as well as exponential functions have been proposed for this property. In figure 8 the expected relationships according to the present model, linear decay and exponential decay are shown. The results of one representative experiment have also been shown. The present theory results in a decay curve which is between the linear and exponential relationships. The assumption of linear decay involves an underestimation of the activity half life the assumption of exponential decay, however, overestimates the half life of the initial flow velocity. 

Figure 7 shows the experimental activity decay curve for this immobilized enzyme reactor system. Initial residence time to obtain a 45% converted product from the starting dextrose substrate was in the order of 10.6 min. The first and second half-lives Ct. and t., .) were defined as the times at which the flow rates were 1/2 and 1/4 of the Initial flow rate, respectively. In this particular case, the initial flow rate was... 

In addition to the continuous-flow reactors, we developed a stopped-flow apparatus to study slow reactions of the NO3 radical. In this apparatus, a series of solenoid valves is used to divert and isolate a flow of gas that contains the reaction mixture. These valves were designed and fabricated in this laboratory by the PI, and ensure that only glass is in contact with the flow. Concentrations of NO3 are then followed as a function of time after the flow is cut off, the data being captured by computer. Figure 1 shows the apparatus in schematic form, while Fig. 2 illustrates decay curves for [NO3] in the absence and presence of C2H4. 

The filtration rate of a filter decays over time due to plugging of the filter cloth by small wax crystals. A typical decay curve is shown below. The feed rate measured by flow meter is plotted against the number of DIPS or exposures of the filter cloth to the wax slurry. The shape of the decay curve depends on the filter media, in this case an ExxonMobil proprietary cloth. 

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