Band compression factor

Band broadening is also affected by the gradient steepness. This effect is expressed in Table 16-14 by a band compression factor C, which is a fnuctiou of the gradient steepness and of equilibrium parameters. Since C < 1, gradient elution yields peaks that are sharper than those that would be obtained in isocratic elution at

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Gritti, E. Guiochon, G. The ultimate band compression factor in gradient elution chromatography. J. Chromatogr. A,... 

The optimum loading factor is higher in gradient elution than in isocratic elution, because the band compression diminishes the tag-along effect of the more retained component. Accordingly, the average concentration of the collected... 

Usually both gradient elution and displacement chromatography offer higher optimum loading factors than isocratic elution, due to the band compression effect of the former two modes. Gradient elution chromatography requires less column efficiency than isocratic elution, ie. shorter columns packed with larger particles can be used which will result in shorter cycle times to the increased flow rate. 

Compression along the grain causes the kinking of cell walls, in much the same way that composites fail in compression (Chapter 25, Fig. 25.5). The kink usually initiates at points where the cells bend to make room for a ray, and the kink band forms at an angle of 45° to 60°. Because of this kinking, the compressive strength is less (by a factor of about 2 - see Table 26.1) than the tensile strength, a characteristic of composites. 

In this book we are particularly interested in simple descriptions of structures that are easily visualized and providing information of the chemical environment of the ions and atoms involved. For metals, there is an obvious pattern of structures in the periodic table. The number of valence electrons and orbitals are important. These factors determine electron densities and compressibilities, and are essential for theoretical band calculations, etc. The first part of this book covers classical descriptions and notation for crystals, close packing, the PTOT system, and the structures of the elements. The latter and larger part of the book treats the structures of many crystals organized by the patterns of occupancies of close-packed layers in the PTOT system. 

On the Osaka University thermionic cathode L-band linac, a time resolution of two picoseconds was achieved using magnetic pulse compression and time jitter compensation systems (Fig. 13). The time jitter between the Cerenkov light from the electron beam and the laser pulse was measured shot-by-shot with a femtosecond streak camera to accurately determine the relative time of each measurement in the kinetic trace. In this way, the time jitter that would otherwise degrade the time resolution was corrected, and the remaining factor dominating the rise time was the electron-light velocity difference over the 2-mm sample depth. 

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