Proton Magnetic Resonance of Western Red Cedar
Keywords:Western red cedar, proton magnetic resonance, heartwood, sapwood, moisture content
AbstractThe potential of proton magnetic resonance techniques, in particular magnetic resonance imaging, for analysis of western red cedar has been investigated. Proton magnetic resonance experiments were carried out on normal sapwood, heartwood and juvenile wood and on rotten juvenile wood from western red cedar logs at a range of hydration levels. Signals from the solid wood and the water were readily distinguishable, and the solid wood signal was characterized by its second moment, which was about 5 x 109 s-2 above the saturation point for all samples and increased by about 20% below the fiber saturation point. The water signal was separated into earlywood tracheid lumen water, latewood tracheid and ray lumen water, and bound water on the basis of spin-spin relaxation times. In the normal log, heartwood and juvenile wood had substantially less water and also shorter spin-spin relaxation times than the sapwood. The rot sample had considerably more water than normal juvenile wood. With proton NMR the sapwood/heartwood boundary of western red cedar can be distinguished easily, but the heartwood/juvenile wood boundary is more difficult to discern. Rot should be identifiable from surrounding normal wood, especially if in heartwood or juvenile wood. With current technology, magnetic resonance imaging facilities can produce cross-sectional images of whole cedar logs; however these images are mainly of earlywood tracheid lumen water and hence show only about 60% of the water in a normal western red cedar log.
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