Treesearch

[Beta]-[SiW12O40]4- (C3v symmetry) is sufficiently higher in energy than its [alpha]-isomer analogue that effectively complete conversion to [alpha]-[SiW12O40]4- (Td) is observed. By contrast, [beta]- and [alpha]-[AlW12O40]5- ([beta]- and [alpha]-1; C3v and Td, respectively) are sufficiently close in energy that both isomers are readily seen in 27Al NMR spectra of equilibrated ([alpha]−[beta]) mixtures. Recently published DFT calculations ascribe the stability of [beta]-1 to an electronic effect of the large, electron-donating [AlO4]5- (Td) moiety encapsulated within the polarizable,...

Fifty-one Brazilian species and varieties of Swartzia Schreber and eight other genera from the tribe Swartzieae were examined. Features with the greatest diagnostic value for the tribe are intervascular pit size, ray width and frequency, storied structure, axial parenchyma strand length, parenchyma band width, and vessel diameter. We analyzed the wood anatomical data using average linkage cluster analysis and canonical discriminant analysis. With weighted features, cluster analysis grouped the species and varieties of Swartzia into four distinct groups and tribe Swartzieae into seven...

Incising is used to increase exposed wood surface and improve uptake and penetration of preservative during pressure treatment of refractory species. However, incising may also cause increased leaching of preservative when the wood is placed in service. This study compared the rate of leaching from unincised eastern hemlock to that of wood that had been incised to two depths and with two density patterns. Incising greatly increased both the penetration and retention of preservative in the incised wood compared to unincised wood. Doubling the depth of the incisions further improved retention...

Noted forest products industry researcher and writer says the conversion factor traditionally used to convert logs measured in board feet to cubic meters has risen. In the U.S., most timber is measured in terms of board feet. The log scales currently in use to estimate lumber recovery from roundwood, however, were created in the 19th century according to sawmill technology, timber resource and lumber sizes used at the time. Because log scales have not been modified since to reflect changes in these factors, they are outdated and inadequately serve their purpose of accurately determining...

This study describes a method for dual protection of wood against fungal and fire degradation in one treatment. The method consists of impregnating wood with aqueous solution of glucose-diammonium phosphate at pH 9, followed by heating the treated wood at temperatures of 160 °C and 190 °C for various lengths of time to form water insoluble products in wood.

Currently, after logging or thinning operations much of the low value timber is either left standing or is felled and left on the ground, chipped, or burned because most North American mills are not equipped to handle this material. In many areas of Western U.S., this forest residue does not decompose if felled and it soon becomes susceptible to forest insect or disease if partially damaged or injured during logging. Two research projects are currently in their second year of a three-year project funded under the USDA Forest Service “National Fire Plan” (Hunt 2000). The goal of these two...

The role of moisture in the biological decay of wood-plastic composites was investigated. Southern pine wood fiber and ponderosa pine wood flour were chemically modified using either acetic anhydride (AA), butylene oxide (BO), or propylene oxide (PO). A 50:50 mixture of high density polyethylene and either chemically modified fiber or flour, or untreated fiber or flour was compounded (blended) and then compression molded. After preconditioning specimens either by a 2-week water soaking or a 5-day boil/dry cycling, a modified soil block test with the brown rot fungus Gloeophyllum trabeum...

Aspen fiber/polypropylene composites were made using several different levels of aspen fiber (0 to 60% by weight) with and without the addition of a compatibilizer (maleic anhydride grafted polypropylene, MAPP). These composites were tested under various relative humidity conditions and in water soaking, boiling water, cyclic liquid water and oven drying tests. In all moisture test conditions, as the level of fiber increased in the composites, the rate and extent of moisture sorption increased as compared to pure polypropylene. The presence of MAPP in the composites, in general, decreased...

This review summarizes patents related to paper recycling that were issued during the last six months of 2001. Two on-line databases, Claims/U.S. Patents Abstracts and Derwent World Patents Index, were searched for this review. This semiannual feature is intended to inform readers about recent developments in equipment design, chemicals and process technology for recycling paper, and alternative products derived from postconsumer paper. Only brief summaries of individual inventions are given in this review. For more complete information, readers will need to access the full text of a...

This report presents eight case studies of successful urban wood waste recycling projects and businesses. These studies document the success of recovered products such as lumber and lumber products, mulch, boiler fuel, and alternative cover for landfills. Overall, wood waste accounts for about 17% of the total waste received at municipal solid waste landfills in the United States. In 1998, the amount of urban wood waste generated was more than 160 million tons, with 29.6 million tons available for recovery. Similarly, in 1998, new construction in the United States generated 8.7 million...