Modeling Strength Loss in Wood by Chemical Composition. Part I. an Individual Component Model for Southern Pine

In this study, we develop models for predicting loss in bending strength of clear, straight-grained pine from changes in chemical composition. Although significant work needs to be done before truly universal predictive models are developed, a quantitative fundamental relationship between changes in chemical composition and strength loss for pine was demonstrated. In particular, this study explored a linear independent-component modeling approach. The models were evaluated across a range of environmental exposure conditions known to cause strength loss and with several chemical treatments capable of causing hydrolytic chemical degradation in wood. Simple linear models developed reasonably accurate predictions of strength loss of clear, straight-grained southern pine wood based on changes in its chemical composition. Side-chain sugars of hemicellulose were the most susceptible to acid hydrolysis. The extent of their degradation was a sensitive predictor of early strength loss. Those sugars associated with the hemicellulose backbone were the next most susceptible, but they were strongly correlated between themselves. This is known as collinearity and, as such, data from either mannose or xylose, or from Klason lignin or glucose, often precluded the need for the other in the models. A linear three-parameter model using changes in a side-chain hemicellulose (arabinose), a main-chain hemicellulose (mannose), and glucose as an indicator of the extent of cellulose degradation reasonably predicted bending strength loss. We believe that with further work, residual strength or serviceability models based on a linear accumulation of the changes in chemical composition of wood during microbiological attack, thermochemical treatments, or severe environmental exposures can be developed to provide sensitive predictors of post-treatment or in-service strength loss

Verification of a Kinetics-Based Model for Long-Term Effects of Fire Retardants on Bending Strength at Elevated Temperatures

This study verifies a single-stage reaction-rate model for the long-term effects of various fire retardants. The adequacy of predictions from our previously reported models was tested using data from fire-retardant-treated wood exposed at 66°C (150°F) and 75% relative humidity for 3 or 4 years. Our analysis showed that if the treated wood experienced significant thermal degradation early during exposure to high temperature, then the previously reported model parameters adequately predicted thermal degradation for up to 4 years of steady-state exposure. However, if the treated wood did not experience significant thermal degradation early during high-temperature exposure, then the previous parameter estimates tended to underpredict degrade. Modified parameter estimates are presented where appropriate. This report also describes the practical implications of running the verified models for up to 10 annual iterations of an actual year of measured roof sheathing temperatures derived from structures exposed in the field. Our results predict that monoammonium phosphate, a generic fire-retardant formulation, can be expected to cause an additional 15% loss in original strength capacity in 10 years if used for roof sheathing under similar conditions

Kinetic Models for Thermal Degradation of Strength of Fire-Retardant-Treated Wood

Several types of kinetics-based thermal degradation models were evaluated to predict strength loss of fire-retardant-treated wood as a function of cumulative thermal exposure. The data were taken from previous tests and reports on small, clear specimens of southern pine treated with six different fire-retardant chemicals and subjected to various durations of a steady-state exposure at different temperatures and relative humidity levels. We found that the single-stage full model approach was superior to traditional two-stage approaches. When constrained to using a two-stage approach, the best alternative two-stage model was a nonlinear model with additive error for each temperature, followed by a weighted regression across temperatures. The advantages of the nonlinear-weighted two-stage model were the maximized fit and more random error structure when compared to other two-stage models

Efficacy of alternative copper-based preservatives in protecting decking from biodegradation

The above-ground performance of decking treated with two alternative copper-based preservative formulations is being evaluated at a test site near Madison, Wisconsin, USA. Southern pine sapwood lumber specimens (38 mm by 140 mm by 910 mm) were pressure treated with 0,93 %, 1,40 % or 2,34 % (oxide basis) actives concentrations of a boron-copper formulation (BC) composed of 7,2 % copper hydroxide and 92,8 % sodium tetraborate decahydrate. Similar specimens were pressure-treated with 0,66 % or 1,32 % actives concentrations of a copper-zinc formulation (CZDP) composed of 18 % copper (CuO basis), 12 % zinc (ZnO basis), 14 % dimethylcocoamine and 56 % propanoic acid. In both cases untreated specimens and specimens treated with a 1% concentration of chromated copper arsenate Type C (CCA-C) were included for comparison.  The specimens were installed on racks approximately 760 mm above the ground and periodically evaluated for extent of fungal decay and surface microbial growth. After 18 years in test specimens treated with the lowest solution concentration of BC (0,93 %) suffered substantial degradation and all but three replicates have failed. Obvious decay has not yet been detected in specimens treated to the highest BC concentration (2,34 %), but decay is suspected in one of these specimens. Decking specimens treated with CZDP exhibited no evidence of decay until year 17 when a fruiting body was observed on one specimen treated with a 0,66 % solution concentration. There has been no evidence of decay in specimens treated with 1,32 % CZDP or in either set of specimens treated with 1 % CCA-C. Both BC and CZDP-treated specimens were at least as effective as 1 % CCA-C in minimizing noticeable surface microbial growth. These decking studies confirm that relatively low copper concentrations can provide substantial protection for decking exposed in a moderate climate, and that the CZDP formulation is potentially more effective than the BC formulation. However, caution is warranted in extrapolating these findings to more severe climates and to construction designs that are more likely to trap moisture

Estimation of discriminant analysis error rate for high dimensional data

Methodologies for data reduction, modeling, and classification of grouped response curves are explored. In particular, the thesis focuses on the analysis of a collection of highly correlated, highly dimensional response-curve data of spectral reflectance curves of wood surface features. In the analysis, questions about the application of cross-validation estimation of discriminant function error rates for data that has been previously transformed by principal component analysis arise. Performing cross-validation requires re-calculating the principal component transformation and discriminant functions of the training sets, a very lengthy process. A more efficient approach of carrying out the cross-validation calculations, plus the alternative of estimating error rates without the re-calculation of the principal component decomposition, are studied to address questions about the cross-validation procedure. If populations are assumed to have common covariance structures, the pooled covariance matrix can be decomposed for the principal component transformation. The leave-one-out cross-validation procedure results in a rank-one update in the pooled covariance matrix for each observation left out. Algorithms have been developed for calculating the updated eigenstructure under rank-one updates and they can be applied to the orthogonal decomposition of the pooled covariance matrix. Use of these algorithms results in much faster computation of error rates, especially when the number of variables is large. The bias and variance of an estimator that performs leave-one-out cross-validation directly on the principal component scores (without re-computation of the principal component transformation for each observation) is also investigated

Application of the Dichromatic Reflection Model to Wood

The applicability of the dichromatic reflection model to describe wood-light interactions in Douglas-fir veneer was investigated. Spectral reflectance measurements taken with illumination along and across the fibers were analyzed by the methodology proposed by Lee et al. (1990). Differences between observed and predicted spectral reflectances were small overall, and increased towards the blue end of the spectrum. Transmission through cell walls, interreflection between cell walls, and an optically active interface are possible explanations for these differences. Average reflectances were higher when samples were illuminated across the directions of the fibers. Rotary-peeled veneer, however, presents surface irregularities where the wood fibers have been pulled away from the surface of the material and where the along-fiber brightness is higher than its corresponding across-fiber measurement

Assessing Wood Quality of Borer-Infested Red Oak Logs with a Resonance Acoustic Technique

Large numbers of black oak (Quercus velutina Lam.) and scarlet oak (Quercus coccinea Muenchh.) trees are declining and dying in the Missouri Ozark forest as a result of oak decline. Red oak borer-infested trees produce low-grade logs that become extremely difficult to merchandize as the level of insect attack increases. The objective of this study was to investigate the use of a resonance-based acoustic technique to evaluate the wood quality of infested red oak logs before processing as measured by grade, type and location of defects, and mechanical properties of the resulting boards. Principal component and canonical correlation analyses revealed that relationships do exist between log acoustic measurement and board grade yield, and between a linear combination of log acoustic velocity and diameter at breast height and a linear combination of board defect measurements. Although the acoustic technique was found capable of assessing wood quality at a stand level, the major advantage of the technique lies in segregating logs within the stand

Northeastern united states species treated with copper-based preservatives: Durability in mississippi stake tests

This paper reports on the ground-contact durability of lesser-used wood species of the northeastern United States after treatment with copper-based preservatives. Stakes (19 by 19 by 457 mm) cut from balsam-fir (Abies balsamea), eastern hemlock (Tsuga canadensis), eastern spruce (mixture of Picea glauca, Picea mariana and Picea rubens), red maple (Acer rubrum) or eastern white pine (Pinus strobus) were treated with one of four concentrations of chromated copper arsenate type C (CCA-C), copper citrate (CC), alkaline copper quat type C (ACQ-C) or copper azole type A (CBA-A) and placed into the ground at a test site in southern Mississippi. Similarly treated southern pine (Pinus spp.) stakes were included for comparison. The stakes were rated for decay and termite attack after 1, 2, 3, 4, 5, 8, 10 and 12 years. Eastern white pine and incised eastern hemlock and balsam-fir had durability similar to southern pine when treated with CCA or the other copper-based preservatives. Eastern spruce was less durable than the other softwood species, apparently because of low preservative uptake. Red maple had the least durability at all retentions and for all preservatives. This study indicates that several northeastern softwoods can be adequately durable when pressure-treated with CCA-C or copper-based preservatives

U.S. Billion-ton Update: Biomass Supply for a Bioenergy and Bioproducts Industry

The Report, Biomass as Feedstock for a Bioenergy and Bioproducts Industry: The Technical Feasibility of a Billion-Ton Annual Supply (generally referred to as the Billion-Ton Study or 2005 BTS), was an estimate of “potential” biomass within the contiguous United States based on numerous assumptions about current and future inventory and production capacity, availability, and technology. In the 2005 BTS, a strategic analysis was undertaken to determine if U.S. agriculture and forest resources have the capability to potentially produce at least one billion dry tons of biomass annually, in a sustainable manner—enough to displace approximately 30% of the country’s present petroleum consumption. To ensure reasonable confidence in the study results, an effort was made to use relatively conservative assumptions. However, for both agriculture and forestry, the resource potential was not restricted by price. That is, all identified biomass was potentially available, even though some potential feedstock would more than likely be too expensive to actually be economically available. In addition to updating the 2005 study, this report attempts to address a number of its shortcoming

Finishing the euchromatic sequence of the human genome

The sequence of the human genome encodes the genetic instructions for human physiology, as well as rich information about human evolution. In 2001, the International Human Genome Sequencing Consortium reported a draft sequence of the euchromatic portion of the human genome. Since then, the international collaboration has worked to convert this draft into a genome sequence with high accuracy and nearly complete coverage. Here, we report the result of this finishing process. The current genome sequence (Build 35) contains 2.85 billion nucleotides interrupted by only 341 gaps. It covers ∼99% of the euchromatic genome and is accurate to an error rate of ∼1 event per 100,000 bases. Many of the remaining euchromatic gaps are associated with segmental duplications and will require focused work with new methods. The near-complete sequence, the first for a vertebrate, greatly improves the precision of biological analyses of the human genome including studies of gene number, birth and death. Notably, the human enome seems to encode only 20,000-25,000 protein-coding genes. The genome sequence reported here should serve as a firm foundation for biomedical research in the decades ahead