<?xml version="1.0" encoding="UTF-8"?><xml><records><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Gil, A M</style></author><author><style face="normal" font="default" size="100%">Lopes, M H</style></author><author><style face="normal" font="default" size="100%">Pascoal Neto, C</style></author><author><style face="normal" font="default" size="100%">Callaghan, P T</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">An NMR microscopy study of water absorption in cork</style></title><secondary-title><style face="normal" font="default" size="100%">Journal of Materials Science</style></secondary-title></titles><keywords><keyword><style  face="normal" font="default" size="100%">13C NMR</style></keyword><keyword><style  face="normal" font="default" size="100%">cell structure (voyant)</style></keyword><keyword><style  face="normal" font="default" size="100%">Cork</style></keyword><keyword><style  face="normal" font="default" size="100%">suberin</style></keyword><keyword><style  face="normal" font="default" size="100%">WATER ABSORPTION</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">2000</style></year></dates><volume><style face="normal" font="default" size="100%">5</style></volume><pages><style face="normal" font="default" size="100%">1891-1900</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">NMR Microscopy is used to measure the imbibition of water into natural cork, extractives-free cork and desuberised cork. The results clearly indicate that suberin is the key constituent which determines the ability of cork to resist water uptake. Furthermore, a particular suberin with distinct spectral properties as viewed by 13C NMR is shown to be the component responsible for cork resistance to water absorption. Laser confocal microscopy suggests that this function is associated with the role of suberin in preserving cell wall structure but the highly hydrophobic nature of suberin may also play an important role. The NMR microscopy study shows that the water absorbed by natural cork, after soaking for three days, is confined to the lenticels, narrow channels on the order of 1000 to 1500 μm in diameter. One incidental outcome is the observation of a clear down-field shift in NMR frequency for water near the cut transverse surfaces of the cork, an effect~associated with susceptibility inhomogeneity.</style></abstract></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Gil, A M</style></author><author><style face="normal" font="default" size="100%">Lopes, M H</style></author><author><style face="normal" font="default" size="100%">Pascoal Neto, C</style></author><author><style face="normal" font="default" size="100%">Rocha, J</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Very high-resolution 1H MAS NMR of a natural polymeric material</style></title><secondary-title><style face="normal" font="default" size="100%">Solid State Nuclear Magnetic Resonance</style></secondary-title></titles><keywords><keyword><style  face="normal" font="default" size="100%">1H MAS NMR</style></keyword><keyword><style  face="normal" font="default" size="100%">Cellulose</style></keyword><keyword><style  face="normal" font="default" size="100%">Cork</style></keyword><keyword><style  face="normal" font="default" size="100%">Lignin</style></keyword><keyword><style  face="normal" font="default" size="100%">Relaxation</style></keyword><keyword><style  face="normal" font="default" size="100%">suberin</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1999</style></year></dates><volume><style face="normal" font="default" size="100%">15</style></volume><pages><style face="normal" font="default" size="100%">59-67</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">The use of ultrafast magic angle spinning (&amp;gt;30 kHz) in tandem with delayed echo acquisition is shown to yield very high-resolution 1H MAS NMR spectra of complex natural organic materials. For the first time, very high-resolution 1H MAS NMR spectra are reported for cork and wood components, two natural materials with great economic importance. The effect of the spinning rate on the 1H NMR spectra was evaluated with single-pulse acquisition and delayed-echo acquisition. The delayed-echo acquisition spectra presented linewidths as sharp as 67 and 25 Hz. The narrow peaks, characterised by proton spin–spin and spin–lattice relaxation, were assigned to the isotropic chemical shifts and the general spectral features were shown to correlate with the sample chemical structure. The tentative assignments of cork 1H MAS NMR signals were presented.</style></abstract></record></records></xml>