Wood rings

Another example is illustrated in Figure 9 (27). The outer, sap-wood rings of a western redcedar, Thuja plicata Donn, which grew about 50 miles south of Seattle, show an increase in 14C which lags slightly behind the levels of 14C which prevailed in the atmosphere. This lag is attributed to a holdover of food supply from the previous year a sizeable... 

Fig. 1. Schematic section, where AR = annual ring, BP = bordered pits, F = wood fiber, FWR = fusiform wood ray, HRD = horizontal resin ducts,...

The word "composites" has a modern ring. But using the high strength of fibres to stiffen and strengthen a cheap matrix material is probably older than the wheel. The Processional Way in ancient Babylon, one of the lesser wonders of the ancient world, was made of bitumen reinforced with plaited straw. Straw and horse hair have been used to reinforce mud bricks (improving their fracture toughness) for at least 5000 years. Paper is a composite so is concrete both were known to the Romans. And almost all natural materials which must bear load - wood, bone, muscle - are composites. 

Plastic packing of very low pressure drop (just greater than wood slats), transfer Coefficients about same as 2-inch Raschig rings. Most useful applications in gas cooling systems or biological trickling filters. 

PMDI is produced on an industrial scale by the phosgenation of diamin-odiphenylmethane. Structure and molar mass of PMDI depend on the number of aromatic rings in the molecule. For PMDI the distribution of the three monomeric isomers has a great influence on the quality, because the reactivities of the various isomers (4,4 -, 2,4 - and 2,2 -MDI) differ significantly. The greater the portion of the 2,2 - and 2,4 -isomers, the lower is the reactivity. This can lead to different bonding strengths as well as to residual isomers in the produced wood-based panels. 

Not much performance data available, but in gen- Wood Grids eral slightly better than Raschig ring, pressure drop slightly higher. High side wall thrust. 

Density. Pie wood block has a lower density than water and floats. The ring has a higher density than water and sinks. 

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