Treesearch

Despite the rather random and heterogeneous nature of isolated lignins, many of their intimate structural details are revealed by diagnostic NMR experiments. 13C-NMR was recognized early-on as a high-resolution method for detailed structural characterization, aided by the almost exact agreement between chemical shifts of carbons in good low-molecular-mass model compounds and in the polymer (1, 2). Although this correspondence cannot generally be expected for proton NMR, lignin dimers and their counterpart units in the polymer also closely match proton NMR chemical shifts and coupling...

This report describes the history and current status of wood collections housed in the Center for Wood Anatomy Research at the Forest Products Laboratory, USDA Forest Service. The collections include the original Madison collection (MADw.) and the collection formerly housed at the Yale School of Forestry, Yale University (SJRw.) and the Chicago Field Museum (Fw.). General statistics are provided for MADw collection, including the Fw collection. Prospects and hopes for the future of xylaria at the Forest Products Laboratory are discussed.

Peroxidase/H2O2-mediated radical coupling of hydroxycinnamaldehydes produced 81O14-, 8-5-, 818-, and 5-5dimers as had been documented earlier (although we found that the 815-dimer is produced in its cyclic phenylcoumaran form at neutral pH). Spectral data from dimers and oligomers has allowed a more substantive assignment of aldehyde components in lignins isolated from a CAD-deficient pine mutant and an antisense-CAD-downregulated transgenic tobacco. The CAD-deficient pine lignin shows the typical benzaldehyde and cinnamaldehyde peaks at levels significantly enhanced over the corresponding...

During the course of restoring and maintaining forest ecosystem health and function in the western interior of the United States, many small-diameter stems are removed from densely stocked stands. In general, these materials are considered nonusable or underutilized. Information on the properties of these resources is needed to help managers understand when timber sales are a viable option to accomplish ecosystem management objectives. Pulp is a logical use for this small-diameter material. In this study, chemithermomechanical pulps (CTMP) were prepared and evaluated from lodgepole pine...

This paper describes the design, modeling, and testing of two portable timber bridges, each consisting of two noninterconnected longitudinal glued-laminated timber (glulam) deck panels 1.8 m (6 ft) wide. One bridge is 12.2 m (40 ft) long while the other bridge is 10.7 m (35 ft) long. The deck panels are fabricated in a unique double-tee cross section. The bridges exhibited linear elastic behavior in static bending tests. When actual lumber property data were used in transformed section and finite element models, the models overpredicted the stiffness of the bridge panels. The transformed...

Combining kenaf fiber with other resources provides a strategy for producing advanced composite materials that take advantage of the properties of both types of resources. It allows the scientist to design materials based on end-use requirements within a framework of cost, availability, recyclability, energy use, and environmental considerations. Kenaf fiber is a potentially outstanding reinforcing filler in thermoplastic composites. The specific tensile and flexural moduli, for example, of a 50% by volume of kenaf-polypropylene (PP) composite compares favorably with a 40% by weight of...

Bridge railing systems in the United States have historically beers designed based on static load criteria given in the American Association of State Highway and Transportation 0fficials (AASHTO) Standard Specifications for Highway Bridges. In the past decade, full-scale vehicle crash testing has been recognized as a more appropriate and reliable method of evaluating bridge railing acceptability. In 1993, the National Cooperative Highway Research Program published Report 350, Recommended Procedures for the Saftey Performance Evaluation of Highway Features, which provides new criteria for...

The structural reliability of plank decks designed by the AASHTO codes are determined. Inadequacies in load distribution and plank resistance in the current specifications are identified.

The xylose-utilizing yeast, Pichia stipitis, has a complex respiratory system that contains cytochrome and non-cytochrome alternative electron transport chains in its mitochondria. To gain primary insights into the alternative respiratory pathway, a cytochrome c gene (PsCYC1, Accession No. AF030426) was cloned from wild-type P. stipitis CBS 6054 by cross-hybridization to CYC1 from Saccharomyces cerevisiae. The 333 bp open reading frame of PsCYC1 showed 74% and 69% identity to ScCYC1 and ScCYC7, respectively, at the DNA level. Disruption of PsCYC1 resulted in a mutant that uses the salicylhy...

This paper discusses efforts to characterize the rheological properties of pulps that include low-grade wastepapers and papermill sludges to determine their potential for extrusion and conversion into useful products. We investigated apparent changes in viscosity associated with the addition of typical inorganic paper fillers (calcium carbonate, kaolin clay, and titanium dioxide) to bcleanc pulps. Addition of calcium carbonate significantly increased apparent pulp viscosity, but clay and titanium dioxide had minimal effects. When high molecular weight sodium carboxymethyl cellulose (CMC)...