Spiral thickenings

Annulo-spiral, with both ring and spiral thickenings. 

Spiral Thickenings. The fibers of a very few species of softwoods and hardwoods are lined with helically oriented ridges of wall material (Figure 23). These ridges, which can be ropelike in certain woods, are associated with, and are an integral part of, the S3 wall... 

Figure 23. SEM of spiral thickenings in the fibers of Douglas-fir wood radial surfaces. Key A, spirals in the vicinity of ray cross-field pits in early wood and B, nigh magnification of spirals in the last latewood fiber of one year and the first earlywood fiber of the next year. Pits shown in B are interfiber-bordered pits.

Spiral Thickening s, These structures are common in the vessels of many hardwoods (e.g., maple, cherry, basswood, buckeye, southern magnolia, and madrone). The particular form is valuable to the wood anatomist for species identification, but the presence or absence of spirals has no apparent effect on wood behavior (2). 

Figure 11. SEM photo showing spiral thickening (ST) in sample of Douglas fir from Chaco Canyon. No obvious differences were apparent between this sample and the recent wood shown in Figure 12. Bar 4.0 pm.

Power requirements for spiral plants are low, consisting primarily of pumping energy and possibly a thickener or other pulp-handling equipment associated with the flowsheet. 

As a thickener (as opposed to a gel), it is amylose that has the main function. The long water-soluble chains increase the viscosity, which doesn t change much with temperature. Amylose chains tend to curl up into helixes (spirals) with the hydrophobic parts inside. This allows them to trap oils, fats, and aroma molecules inside the helix. 

The micromorphology of the ordered phases depends upon the conditions of crystallization and may be characteristic of that of flat dendrite crystals, lamellae, fibrillar and globular aggregates, and rhombohedric single crystals. The thickening of these crystals may be the result of either superimposition of lamellae or spiral growth originating from screw dislocations [281]. 

Spiral CT of gastric lymphoma discloses a less enhanced and a markedly thickened wall or discrete masses. Three-dimensional reconstructions also provide an accurate depiction of these features. 

Within focal regions where fenestration of the alveolar wall and some confluence of air spaces were identified, Belton et al. (1977) found randomised electron dense collagen fibrils, whereas the normal alveolar septa contained uniformly parallel collagen fibrils. Many of the randomised fibrils had sufficient swelhng to display prominent internal spiralling. When the thickened fibrils were cut transversely, the appeared as a stack of flattened, electron dense lamellae. 

Chromosomes consist of two (or a multiple of two) strands (chromosomes or chromatids), capable of spiralization and despi-ralization, and in some cases visible under the optical microscope. For this reason the physical state of the chromosomes may vary in different stages of mitosis and interphase. Toward the moment of division they become compact and thickened in shape during formation of the interphase nucleus, despiralization is observed accompanied by increased intensity of functional processes in the chromosomes. 

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