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Potently antiviral polyniobotungstates have been structurally characterized; the dimer A-[alpha]-[Si2Nb6W18O77]8– cleaves cleanly to the monomer A-[alpha]-[SiNb3W9O40]7– within 1 min in aqueous solution buffered at physiological (neutral) pH establishing that the monomer and not the dimer is pharmacologically relevant.

Building codes are critically important in the use of wood products for construction. The codes contain regulations that are prescriptive or performance related for various kinds of buildings and construction types. A prescriptive standard might dictate that a particular type of material be used in a given application. A performance standard requires that a particular building or building component meets a specified strength or fire-resistance characteristic based on code-approved testing procedures. For the wood products industry, a change in a prescriptive or performance standard in a...

This report shows pulpwood receipts at wood pulp mills in the United States for the period 1950 to 1996. It is an update of the General Technical Report FPL1GTR173, bUnited States Pulpwood Receipts: Softwood and Hardwood, Roundwood and Residues, 195011989,c published in 1993. This report continues as a compilation of published and estimated data based on information from various sources, including the American Pulpwood Association and the USDA Forest Service. Data are presented for the Northeast, North Central, total north, Southeast, South Central, total south, and total west regions of...

Round timbers and ties represent some of the most efficient uses of our forest resources. They require a minimum of processing between harvesting the tree and marketing the structural commodity. Poles and piles are debarked or peeled, seasoned, and often treated with preservative prior to use as structural members. Construction logs are usually shaped to facilitate construction. Ties, used for railroads, landscaping, and mining, are slab-cut to provide flat surfaces. Because these products are relatively economical to produce, compared with glulam, steel, and concrete products, they are...

Equations for deformation and stress, which are the basis for tension members and beam and column design, are discussed in this chapter. The first two sections cover tapered members, straight members, and special considerations such as notches, slits, and size effect. A third section presents stability criteria for members subject to buckling and for members subject to special conditions. The equations are based on mechanics principles and are not given in the design code format found in Allowable Stress Design or Load and Resistance Factor Design specifications.

The fibrous nature of wood strongly influences how it is used. Wood is primarily composed of hollow, elongate, spindle-shaped cells that are arranged parallel to each other along the trunk of a tree. When lumber and other products are cut from the tree, the characteristics of these fibrous cells and their arrangement affect such properties as strength and shrinkage as well as the grain pattern of the wood. This chapter briefly describes some elements of wood structure.

Because wood properties vary among species, between trees of the same species, and between pieces from the same tree, solid wood cannot match reconstituted wood in the range of properties that can be controlled in processing. When processing variables are properly selected, the end result can sometimes surpass nature’s best effort. With solid wood, changes in properties are studied at the cellular level. With reconstituted wood materials, changes in properties are studied at the fiber, particle, flake, or veneer level. Properties of such materials can be changed by combining, reorganizing,...

The strength and stability of any structure depend heavily on the fastenings that hold its parts together. One prime advantage of wood as a structural material is the ease with which wood structural parts can be joined together with a wide variety of fastenings— nails, spikes, screws, bolts, lag screws, drift pins, staples, and metal connectors of various types. For utmost rigidity, strength, and service, each type of fastening requires joint designs adapted to the strength properties of wood along and across the grain and to dimensional changes that may occur with changes in moisture...

The primary function of any wood finish (paint, varnish, and stain, for example) is to protect the wood surface, help maintain a certain appearance, and provide a cleanable surface. Although wood can be used both outdoors and indoors without finishing, unfinished wood surfaces exposed to the weather change color, are roughened by photodegradation and surface checking, and erode slowly. Unfinished wood surfaces exposed indoors may also change color; moreover, unfinished wood is more difficult to clean than is finished wood. Wood and wood-based products in a variety of species, grain...

Lumber sawn from a log, regardless of species and size, is quite variable in mechanical properties. Pieces may differ in strength by several hundred percent. For simplicity and economy in use, pieces of lumber of similar mechanical properties are placed in categories called stress grades, which are characterized by (a) one or more sorting criteria, (b) a set of properties for engineering design, and (c) a unique grade name. This chapter briefly discusses the U.S. Department of Commerce American Softwood Lumber Standard PS20 (1994) sorting criteria for two stress- grading methods, and the...