Parallel packing

FIG. 23-25 Typ es of industrial gas/Hqiiid reactors, (a) Tray tower, (h) Packed, counter current, (c) Packed, parallel current, (d) Falling liquid film, (e) Spray tower, if) Bubble tower, (g) Venturi mixer, h) Static in line mixer, ( ) Tubular flow, (j) Stirred tank, (A,) Centrifugal pump, (/) Two-phase flow in horizontal tubes. 

In its simplest presentation, using glass fiber with plastic, if the fibers were packed as closely as possible (like stacked pipe), the glass would occupy 90.6 vol% (volume) or 95.6 wt%. With a square packing (parallel layered fibers so that each layer has fibers 90° to each other) the glass would occupy 78.5 vol% or 88.8 wt%. 

The crystal structure of the mesogenic 4-(3"-pentenyl)-4 -(ethoxy)-l,l -bicyclohexane (PEBCH) was determined by Nath et al. [78]. This compound exhibits a nematic phase. The molecules are packed parallel to each other in an imbricated mode. 

Fig. 4. Phase contrast SFM images of an ultrathin film of dendrimer 22a on HOPG. The dendrimers are grouped in domains in which they are packed parallel to each other, separated by a periodicity of 4.8 ( 0.5) nm. The nature of the dark features is not yet understood... 

The crystal lattices of a series of ternary alkali metal-silver acetylenediide [M Ag(C=C)] (M1 = Li 161, Na, K 162, Rb, Cs 163) have been analyzed by Ruschewitz and co-workers using X-ray powder diffraction.209 Neutron powder diffraction experiments have also been performed on 161-163 for obtaining precise bond lengths. It has been found that for 161 and 162, the [Ag(C C)] chains were packed parallel to each other, whereas for 163, they were aligned in layers that were rotated by 90° with respect to each other (see Figure 51). 

The basic concept behind all models of chiral self-assembly can be stated as follows. In general, chiral molecules do not pack parallel to their neighbors but rather pack at a slight angle with respect to their neighbors. This favored packing can be visualized by the packing of hard screws,6 as illustrated in... 

Chalcedony is a variety of quartz composed of fibrils that are not separable. The fibrils may have variable thickness, and lengths, from a few to hundreds of microns, and may be twisted (Fig. 2.19C). The fiber axis, usually perpendicular to the free or growing surface, is easily detected in the crystalline material consisting of tightly packed, parallel or subparallel fibrils. The range of color, and the mechanisms of inclusion of impurities, and especially of water and (OH) in chalcedony, have been described and discussed by many authors, most recently by Frondel (1978, 1982). 

Mesophase in which disc-shaped molecules, the disc-shaped moieties of macromolecules or wedge-shaped molecules assemble themselves in columns packed parallel on a two-dimensional lattice, but without long-range positional correlations along the columns. 

Mesophase in which board-shaped molecules assemble in stacks packed parallel to one another on a one- or two-dimensional lattice (see Figs. 17 and 18). 

Isotactic PP, which is a commercial variety of PP, exists as a helix instead of an extended planar conformation in order to relieve the strain and thus attain a state of low free energy. Such helical conformations are actually rodlike and thus pack parallel to other rods in the crystal lattice. 

Fig. 2. a. Long molecules packed parallel, b. Long molecules arranged so that there are two different orientations, c. In some crystals composed of monatomic ions,, anisotropy results from the mode of packing of the ions. 

Fig. 167. (a).Long molecules, packed parallel, give plate-like crystals, while (b) flat molecules, packed parallel, give needle-like crystals. 

Cellulose fibres are probably packed parallel to one another lengthwise along the axis to form bundles, so called micelles, which are highly oriented along the fibre axis, thus giving cellulose its characteristic mechanical properties. 

In tissues, microfibrils form loosely packed parallel bundles. X-ray fiber diffraction of hydrated zonular microfibril bundles identified one-third-staggered junctions that may modulate force transmission (Wess et al., 1998a), and quick-freeze deep-etch analysis of zonules has identified molecular links between microfibrils (Davis et al., 2002). 

Figure 21. Cellulose microfibrils in the primary wall and Sj portion of the secondary wall from a longitudinal tracheid. Note the loosely packed ana randomly arranged microfibrils in the primary wall (P). The S layer (S) consists of tightly packed, parallel microfibrils. 12,000X...

Van der Waals forces between the methylene groups orient the monolayer. Such a self-assembly process thus results in well-organized and stable mono-layers, with the hydrocarbon tails packed parallel to each other, tilted at -30° relative to the surface normal (Fig. 4.14). The closely-packed pinhole-free films (surface coverage of 9 x 10 10mol/cm2) block transport of species to the... 

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