Typical front behavior

Figure 10. Typical front behavior in fixed-pressure gas-surfactant solution displacement in systems favorable to the creation of a gas-blocking foam. (Reproduced with permission from reference 14. Copyright 1993.)...

Overloading a chiral stationary phase leads to a fronting of the peaks, as the adsorption sites necessary for chiral recognition are occupied and the interaction between the analyte and CSP is not sufficient (see Fig. 6). In Fig. 6, typical retention behavior for a racemate at increasing sample volumes is shown. Both and a become smaller at higher injection volumes and ultimately no longer allow for baseline resolution. The retention times become shorter. 

Wave profiles in the elastic-plastic region are often idealized as two distinct shock fronts separated by a region of constant elastic strain. Such an idealized behavior is seldom, if ever, observed. Near the leading elastic wave, relaxations are typical and the profile in front of the inelastic wave typically shows significant changes in stress with time. 

We may contrast this behavior to that found for AOT. As shown in Figure 1, the chromatograms for AOT exhibit sharp fronts and somewhat diffuse tails, intermediate in shape between the symmetrical peaks typical of conventional solutes and the highly asymmetric chromatograms obtained for sodium dodecyl sulfate micelles in water (15). In addition, the concentration dependence of Mp" for AOT is gradual, not abrupt as for lecithin. These differences may be attributed to the lability of the AOT micelles which makes the observed retention time quite sensitive to the initial concentration (12) and leads to broadened chromatograms. 

The concentration distributions found at different times after the start of current flow are shown in Fig. 11.4. It is a typical feature of the solution obtained that the variable parameters x and t do not appear independently but always as the ratio Like Eq. 11.15), this indicates that the diffusion front advances in proportion to the square root of time. This behavior arises because as the diffusion front advances toward the bulk solution, the concentration gradients become flatter and thus diflusion slows down. 

The typical experimental set-up is shown in Fig. 6. Mono-energetic collimated electrons, with energies usually between 20 to 500 eV, are backscat-tered from the crystal surface onto a fluorescent screen, whereby only the elastically scattered electrons are allowed to pass the grids of an electron optic in front of the screen. Because of their wave-like behavior, the electrons are diffracted at the crystal lattice and the interference maxima become visible at the fluorescent screen. 

Typically, a fire growth model is evaluated by comparing its calculations (predictions) of large-scale behavior to experimental HRR measurements, thermocouple temperatures, or pyrolysis front position. The overall predictive capabilities of fire growth models depend on the pyrolysis model, treatment of gas-phase fluid mechanics, turbulence, combustion chemistry, and convective/radiative heat transfer. Unless simulations are truly blind, some model calibration (adjusting various input parameters to improve agreement between model calculations and experimental data) is usually inherent in published results, so model calculations may not truly be predictions. 

From Fig. 5, it is apparent that the adsorption fronts are considerably less steep than the desorption fronts, and that the adsorption fronts simulated for different initial concentrations of the spots overlap. Similar behavior is apparent in the typical experimental densitograms, given in Figs. 3 and 4. In all these densitograms, the adsorption fronts for the different concentrations of acid also overlap. 

Figure 10 Chromatogram for a typical turbulent-flow chromatography experiment (50- l/L injection), showing fronting and tailing behavior. The numbers of theoretical plates (N) for this compound is —350.

Due to the characteristic shape, almost any raw RDF descriptor is skewed It typically exhibits an asymmetric tailing and is leptokurtic (flatted in relation to the Ganssian distribntion knrtosis > 0). Depending on the descriptor type, the size, and the symmetry of a molecule, the skewness or kurtosis of a raw RDF descriptor may also show asymmetric fronting or platykurtic behavior (peaked in relation to the Ganssian distribntion kurtosis < 0). As the general behavior applies to most of the RDF descriptors, it is no fault to neglect this skewness and to assume a skewed standard distribntion within the descriptor set. 

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