Performed density gradients, effect

The density change on polymerization is typically about 20%, and this density gradient can cause significant secondary flows and natural convection effects. The experiments cited above for vinyl acetate polymerization were performed in a helical reactor. The centrifugal force in helical reactors induces secondary flows as well. The effects of helical flow have been analyzed, but were found to be less significant than the effects of natural convection [14]. 

Numerous electroanalytical techniques are performed on quiet or stationary solutions. The ideal stationary solution has no convective motion due to vibrations, mechanical stirring, motion of the electrode(s), temperature gradients, or density gradients. At long times only natural convection effects arising from the electrode reaction itself will contribute to nonideality. 

Formation of Steady-State Density Gradient in TLF Experiments. The formation of the density gradient by the effect of electric field on Percoll was evidenced by the appearance of distinct focused zones of density marker beads in TLF cell (13). A similar experiment was performed by using PS latex standard particles suspended in Percoll. Narrow steady-state focused zone was formed, thus indicating that focusing FFF of these particles should appear in the separation channel as well. 

Bulk solids typically have well-bounded values of the reduced density gradient s, and so might be particularly amenable to GGA description. However, the full verdict is not yet in. We emphasize here the importance of performing full-potential all-electron calculations in tests of GGA s, and avoiding as much as possible further approximations, such as pseudopotential or shape approximations, which may lead to errors which mask the effects of the GGA, relative to LSD. 

Depending on the current density a rather non uniform utilization of the catalyst layer can be expected. While at low current density negligible effects are caused by the ionic resistance in the catalyst layer and almost all platinum particles can be used, the reaction concentrates close to the membrane interface at high current densities causing underutilization of the platinum present in the electrode [54, 55]. Optimization of electrode performance can be expected from microstructural optimization for example by designing catalyst layers having gradients in noble metal concentration and porosity. 

From the results of RTD studies it can be concluded that small changes in bowl temperatures above or below the feed temperature have a significant effect on flow patterns in the bowl. This result supports the hypothesis that thermally induced density gradients lead to mixing currents. In addition to temperature, flow patterns are affected by feed flow rate and bowl speed. Separation efficiency and classification studies show that the various flow patterns produced under different operating conditions affect separation performance in both types of separations studied. This fact leads to the conclusion that flow patterns must be better understood and controlled in order to optimize classification of superfine solids. 

Rabbit reticulocytes were incubated with isotopically labeled amino acids in the presence and absence of added hemin after incubation sucrose density gradient analysis was performed to determine the patterns of ribosomes and the radioactivity of the nascent, and completed polypeptide chains (Fig. 6) (Grayzel et al., 1966). The effects... 

The core electrons of all atoms were treated via ultra-soft pseudo potentials [10,11] with a cut-off of 25 Ry for wave function, and 240 for electronic density. The PBE gradient-corrected exchange-correlation function was used in self-consistent DFT calculations. The geometry optimization was performed using a lxlxl /c-point mesh. Because of the natural paired electron occupancies of the adsorbates, spin polarization effects were not considered to be important and were not treated explicitly in this study. 

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