Treesearch

Round guardrail posts may provide an important value added option for small-diameter thinnings. Such posts require minimum processing and have been shown to have higher strength compared to the equivalent rectangular volume. The resulting value-added product may bring a higher return compared to lumber. The obstacles to immediate utilization of ponderosa pine and Douglas-fir guardrail posts are the need for full-scale crash testing, a visual grading rule, and an installation guide. This paper reports on the static and dynamic tests performed at the USDA Forest Products Laboratory in...

To determine if there was a delignification behavior difference between secondary wall (S2) and middle lamella (cell corner or CC) lignin, black spruce cross-sections were acid-chlorite delignified and the tissue was evaluated in-situ by Raman imaging. Lignin concentration in S2 and CC was determined in numerous latewood cell areas in the two hour delignified cross section. In all instances, compared to the S2-lignin the CC-lignin reacted more rapidly. This result contradicted what has been reported previously. The Raman approach to study the topochemistry of delignification is better...

Anisotropy of cellulose organization in mature black spruce wood cell wall was investigated by Raman imaging using a 1 [mu]m lateral-resolution capable confocal Raman microscope. In these studies, wood cross sections (CS) and radial longitudinal sections (LS) that were partially delignified by acid chlorite treatment were used. In the case of CS where latewood cells were examined, Raman images of S2 and S1 regions, produced using cellulose contribution at 1098 and 2773-3045 cm-1, showed significant differences. While the spectra associated with the S2 images indicated the microfibrillar...

Wood-plastic composites (WPCs) have been gaining market share in the residential construction industry as lumber for decking, roof tiles, and siding. The durability of these materials in exterior environments is just beginning to be understood. Current research suggests that controlling moisture absorption by the composite is key to improving durability. Methods to improve moisture resistance of WPCs have met with limited success. Co-extrusion involves the simultaneous extrusion of two dissimilar materials as a single profile. In this study, co-extrusion was used to improve the moisture...

The deterioration of heartwood from live and dead Alaska yellow-cedar trees was evaluated by exposing ministakes in soils at field sites in Alaska and Mississippi for 2 and 4 year intervals. Southern yellow pine sapwood served as a control. The vastly greater deterioration, as measured by weight loss, in Mississippi compared to Alaska (60 and 10 percent after 4 years, respectively) was attributed to warmer temperatures, a longer growing season, and perhaps the presence of termites. The wood from Alaska yellow-cedar trees dead 26 years did not differ in deterioration from the wood from live...

Saccharomyces cerevisiae L2612 transformed with genes for xylose reductase and xylitol dehydrogenase (XYL1 and XYL2) grows well on glucose but very poorly on D-xylose. When a gene for D-xylulokinase (XYL3 or XKS1) is overexpressed, growth on glucose is unaffected, but growth on xylose is blocked. Spontaneous or chemically induced mutants of this engineered yeast that would grow on xylose could, however, be obtained. We therefore used insertional transposon mutagenesis to identify two loci that can relieve this xylose-specific growth inhibition. One is within the open reading frame (ORF) of...

Tensile and the moisture-induced thickness swelling properties of wood strands are among the most fundamental parameters in modeling and predicting engineering constants of strand-based composites such as oriented strandboard (OSB). The effects of hot-pressing and resin-curing on individual strand properties were investigated in this study. Strands from four Louisiana-grown species—willow (Salix spp.), yellow-poplar (Liriodendron tulipifera L), red oak (Quercus spp.) and southern yellow pine (Pinus taeda L.)—were tested. It was found that the properties of strands were different from the...

The anisotropy of wood creates a complex problem for solving heat and mass transfer problems that require analyses be based on fundamental material properties of the wood structure. Most heat transfer models for softwood use average thermal properties across either the radial or tangential direction and do not differentiate the effects of cellular alignment or differences in earlywood and latewood. A two-dimensional finite element model that considers these basic structural characteristics was developed to determine the effective thermal conductivity as a function of cell alignment, cell...

Biocides must be developed for controlling mould establishment on cellulose-based building materials. Accordingly, biocides intended for indoor applications must be non- toxic, non-volatile, odourless, hypoallergenic, and able to provide long-term protection under conditions of high humidity. Multi-component biocide systems were tested in American Wood-Preservers’ Associations oil block tests for inhibition of brown-rot and white-rot decay fungi and American Society for Testing and Materials standard tests for inhibition of mould fungi and termites. Multi-component systems combining a...