Treesearch

Early transition-metal oxygen-anion clusters (polyoxometalates, POMs) are a large and rapidly growing class of versatile and tunable oxidation catalysts. All key molecular properties of these clusters (composition, size, shape, charge density, reduction potential, solubility, etc.) can be systematically altered, and the clusters themselves can serve as tunable ligands for controlling the reactivity of a wide variety of transition-metal cations.

Southern pine solid wood and fiber were chemically modified with epichlorohydrin to help in understanding the role of moisture in the mechanism of biological effectiveness of chemically modified wood. The solid wood had weight gains from 11% to 34%, while the fiber had weight gains from 9% to 75%. After modification, part of the specimens were water leached for 2 weeks or extracted for 2 hours with a toluene:ethanol (2:1) solution. The equilibrium moisture content (EMC) at 30%, 65%, and 90% relative humidity (RH) and 27 °C was determined on all specimens. Laboratory soil block decay...

Lodgepole pine chips were pulped to Kappa numbers of about 70 using soda–AQ, soda–ODiMAQ, and kraft methods. At a catalyst level of 0.20% (oven-dry wood basis), cooking times for the soda cooks were significantly shorter than that for the kraft cook. The ODiMAQ catalyzed cooking time was much shorter than that of the AQ cook. It might be possible to replace the kraft process with a soda–ODiMAQ process for production of linerboard grade pulps. Delignification of the high Kappa soda–ODiMAQ pulp with oxygen and also with a polyoxometalate (POM) to Kappa numbers of about 30 resulted in higher...

Production of mechanical pulp is expected to increase significantly to meet the growing global demand for paper. Mechanical pulping uses wood resources more efficiently with less negative impact on the environment than does chemical pulping. However, several problems related to mechanical pulping need to be resolved: high energy consumption, low paper strength properties, problems with pitch, and color reversion. Biopulping, an alternative pulping method, resolves the energy, strength, and pitch limitations but does not address brightness or color reversion. Optical properties can be...

Pulp extrusion at ultra-high consistencies (20% to 40% solids) is a new process developed at USDA Forest Service, Forest Products Laboratory (FPL) to convert recovered papers, wastepaper, and papermill residuals into solid sheets or profiles for compression molding. This process requires adding a water-soluble polymer (WSP) to alter the rheological properties of the pulp and generate a paste that can be extruded. The variety of fibrous raw materials can have a significant impact on the efficiency of a WSP to alter viscosity. Therefore, an appropriate WSP must be selected that will rapidly...

Bridges require periodic inspections to ensure the safety of those using the structure. A visual inspection has historically been the most common form of investigation for timber bridges. This poses many problems when inspecting bridge timbers since often the damage is internal, leaving no visible signs of decay on the surface. Localized nondestructive evaluation (NDE) techniques have been developed to allow assessment of the internal parts of timber structural members. Testing an entire structure in this manner can be tedious and time consuming. Steel structures have long been tested from...

Conventional compression strength formulas for corrugated fiberboard boxes are limited to geometry and material that produce an elastic postbuckling failure. Inelastic postbuckling can occur in squatty boxes and trays, but a mechanistic rationale for unifying observed strength data is lacking. This study employs a finite element model, instead of actual experiments, to generate experimentally designed data and a smoothed model. Results lead to a better understanding of how to unify elastic and inelastic failure data and form a more general box strength formula. The objective of this study...

The use of recovered paper has an influence on the amount of timber harvested as well as the feasibility of expanded recycling programs. During the 1990’s markets and prices for recovered materials have fluctuated widely. There are a number of factors driving these market changes including economic conditions domestically and internationally. The objective of this study was to develop recovered paper supply functions for the five principal grades of recovered paper by focusing on the effects of the spot and contract markets in establishing domestic prices for recovered paper. Two supply...

Glutathione-dependent formaldehyde dehydrogenase (FLD) is a key enzyme required for the catabolism of methanol as a carbon source and certain primary amines, such as methylamine as nitrogen sources in methylotrophic yeasts. Here we describe the molecular characterization of the FLD1 gene from the yeast Hansenula polymorpha. Unlike the recently described Pichia pastoris homologue, the H. polymorpha gene does not contain an intron. The predicted FLD1 product (Fld1p) is a protein of 380 amino acids (ca. 41 kDa) with 82% identity to P. pastoris Fld1p, 76% identity to the FLD protein sequence...

The annual rings of softwoods are visually obvious and represent cylindrical layers of primarily cellulosic material that possess significantly different properties. For simplicity, wood construction products are designed assuming a material homogeneity that does not exist. As rapidly grown plantation trees are used for wood products, fewer rings are contained in an individual wood product with the outcome of each individual ring playing a greater role in product structural performance. The magnitudes of these earlywood and latewood property differences are largely unknown because of the...