INDEX Packing

Figure Bl.21.1. Atomic hard-ball models of low-Miller-index bulk-temiinated surfaces of simple metals with face-centred close-packed (fee), hexagonal close-packed (licp) and body-centred cubic (bcc) lattices (a) fee (lll)-(l X 1) (b)fcc(lO -(l X l) (c)fcc(110)-(l X 1) (d)hcp(0001)-(l x 1) (e) hcp(l0-10)-(l X 1), usually written as hcp(l010)-(l x 1) (f) bcc(l 10)-(1 x ]) (g) bcc(100)-(l x 1) and (li) bcc(l 11)-(1 x 1). The atomic spheres are drawn with radii that are smaller than touching-sphere radii, in order to give better depth views. The arrows are unit cell vectors. These figures were produced by the software program BALSAC [35]-...

Figure Bl.21.1 shows a number of other clean umeconstnicted low-Miller-index surfaces. Most surfaces studied in surface science have low Miller indices, like (111), (110) and (100). These planes correspond to relatively close-packed surfaces that are atomically rather smooth. With fee materials, the (111) surface is the densest and smoothest, followed by the (100) surface the (110) surface is somewhat more open , in the sense that an additional atom with the same or smaller diameter can bond directly to an atom in the second substrate layer. For the hexagonal close-packed (licp) materials, the (0001) surface is very similar to the fee (111) surface the difference only occurs deeper into the surface, namely in the fashion of stacking of the hexagonal close-packed monolayers onto each other (ABABAB.. . versus ABCABC.. ., in the convenient layerstacking notation). The hep (1010) surface resembles the fee (110) surface to some extent, in that it also...

Kovat s retention index (p. 575) liquid-solid adsorption chromatography (p. 590) longitudinal diffusion (p. 560) loop injector (p. 584) mass spectrum (p. 571) mass transfer (p. 561) micellar electrokinetic capillary chromatography (p. 606) micelle (p. 606) mobile phase (p. 546) normal-phase chromatography (p. 580) on-column injection (p. 568) open tubular column (p. 564) packed column (p. 564) peak capacity (p. 554)... 

Free-swelling tests are commonly used to measure a coal s caking characteristics. A sample of coal is packed in a cmcible or tube, without compaction, and heated at a fixed rate to about 800°C. Infusible coals distill without changing appearance or state of agglomeration. The fusible coals soften, fuse, and usually sweU. The profile of the resultant coke is compared to a series of reference profiles so that a swelling index can be assigned. The profiles represent indexes between 0 and 9. The best cokes come from coals having indexes between 4 and 9. 

In design practice, a less rigorous parameter, HETP, is used as an index of packing efficiency. Tne HETP is the height of packed bed required to achieve a theoretical stage. The terms Hoe and HETP may be related under certain conditions ... 

As indicated above, packed column internals include hqiiid distributors, packing support plates, redistributors (as needed), and holddown plates (to prevent movement of packing under flow conditions). Costs of these internals for columns with random packing are given in Fig. 14-80, based on early 1976 prices, and a Marshall and Swift cost index of 460. 

The transparency and refractive power of the lenses of our eyes depend on a smooth gradient of refractive index for visible light. This is achieved partly by a regular packing arrangement of the cells in the lens and partly by a smoothly changing concentration gradient of lens-specific proteins, the crystallins. 

Four column systems are available from Amersham Pharmacia Biotech that can be used to pack SEC media for various applications at the laboratory scale. These include C, XK, SR, and HR column systems. All of the laboratory-scale columns are constructed with borosilicate glass tubes. Columns for larger scale process applications include INdEX, BPG, EineLINE, BPSS, and Stack columns. The larger scale columns are constructed to meet stringent validation requirements for the production of biopharmaceuticals. Each of the column types are described. 

A third parameter to consider is the column construction. Thus the sample applicator should provide optimal sample application to give the most performance possible out of the packed bed. Constructions should also allow simple, fast, and reproducible packing of the column. Because costs for repacking of columns are a substantial operating cost item in industrial chromatography, the selection of column construction from this point of view is also important. Some novel column constructions allow very simple procedures both for laboratory and for industrial scale (e.g., INdEX columns, see Section V). 

Degassed and preswelled Bio-Gel P-6 and Sephacryl S-200 were packed in self-made glass columns (70 X 1.5 cm 140 X 1.5 cm) and equilibrated for 20 hr with H20(dest.) -t- 0.002% NaN3 to prevent microbial growth. The mass of eluted fractions was detected with a differential refractive index detector (Waters 403 RI, sensitivity 8). 

Soil specific weight is the measure of the concentration of packing of particles in a soil mass. It is also an index of compressibility. Less dense, or loosely packed, soils are much more compressible under loads. Soil specific weight may be expressed numerically as soil ratio and ptorosity (porosity for soils being basically the same definition as that for rocks discussed earlier in this section). Soil porosity e is... 

The index n was found to vary from about 0.4 to 0.8 according to the type of packing. It will be noted that when n 0.75, there is close agreement with the results given by equation 13.57. 

The distance of each reflection from the center of the pattern is a function of the fiber-to-film distance, as well as the unit-cell dimensions. Therefore, by measuring the positions of the reflections, it is possible to determine the unit-cell dimensions and, subsequently, index (or assign Miller indices to) all the reflections. Their intensities are measured with a microdensitometer or digitized with a scanner and then processed.8-10 After applying appropriate geometrical corrections for Lorentz and polarization effects, the observed structure amplitudes are computed. This experimental X-ray data set is crucial for the determination and refinement of molecular and packing models, and also for the adjudication of alternatives. 

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