Birch fibers

A wood xylan was prepared from birch fibers that had been subjected to acetone extraction and chlorite delignification. The xylan fraction was extracted with a solution of 6.5% KOH in a nitrogen atmosphere at 20 C for 3.7 hours. The extract was acidified and the xylan was precipitated with ethanol. 

The potential for using multiplexed single-photon counting to acquire fluorescence lifetime data from a distributed array of optical fiber sensors, each sensing a different analyte, has recently been demonstrated by Birch etal.(39,47) Figure 12.9 illustrates such a network to be used in conjunction with the arrangement shown in Figure 12.6. 

Zaman, A., Alen, R. and Kotilainen, R. (2000) Thermal behaviour of Scots pine Pinus sylvestris) and silver birch (Betula pubescens) at 200-230 deg C. Wood and Fiber Science, 32(2), 138-143. 

The pulp and paper industries use three types of raw materials, namely, hard wood, soft wood, and nonwood fiber sources (straw, bagasse, bamboo, kenaf, and so on). Hard woods (oaks, maples, and birches) are derived from deciduous trees. Soft woods (spruces, firs, hemlocks, pines, cedar) are obtained from evergreen coniferous trees. 

Castoreum is an unpleasantly sharp-smelling, oily substance secreted by special glands of beavers. Castor fiber L. (Castoridae), living in Canada, Alaska, and Siberia. Both sexes secrete the substance, which accumulates in an abdominal pouch, also called castoreum. Dilute castoreum (e.g., as a tincture in ethanol) smells pleasantly of birch tar and musk and is slightly fruity. 

Hardwoods contain several cell types, specialized for different functions (Fig. 1-9). The supporting tissue consists mainly of libriform cells, the conducting tissue of vessels with large cavities, and the storage tissue of ray parenchyma cells. In addition, hardwood contains hybrids of the above-mentioned cells which are classified as fiber tracheids. Although the term fiber is frequently used for any kind of wood cells, it more specifically denotes the supporting tissue, including both libriform cells and fiber tracheids. In birch these cells constitute 65 to 70% of the stem volume. 

Libriform cells are elongated, thick-walled cells with small cavities containing some simple pits. The dimensions of birch libriform fibers are 0.8-1.6 mm or on an average 1.1 -1.2 mm (length), 14 40 /xm (width), and 3-4 /xm... 

Table 6.2.8. Alkaline nitrobenzene oxidation products of the fiber fraction from birch wood soft xylemd...

A protein with a similar dumbell shape and structure is troponin C of skeletal muscles. Troponin C binds to a complex of proteins that assemble on the thin actin filaments of muscle fibers and control con-trachon in response to changes in the calcium ion con-centrahon (Chapter 19). Other proteins that contain EF-hand mohfs and are therefore responsive to Ca + include spectrin of cell membranes, clathrin light chains from coated vesicles, the extracellular osteonectin of bones and teeth, ° and a birch pollen anhgen. 2 Another group of 17 or more small SlOO EF-hand proteins play a variety of other roles. One of these, which has a high affinity for Zn +, has been named psoriasin because of its 5-fold or greater... 

Commercial wood fiber from aspen, birch, maple, and spruce typically has a length of 0.4-3.5 mm, that is, 400-3500 pm (spruce is the longest one), and width 50-27 pm. Average aspect ratio values for fiber from these species are 35 (maple), 60 (aspen), 100 (birch), and 130 (spruce). 

Tritiated Water. Exchange with tritiated water and subsequent scintillation analysis of the tritium content is a very useful method for accessibility measurements when the samples are not transparent to IR and visible light. Thin shives of sapwood from black spruce (a common softwood), and white birch (a common hardwood) where studied before and after delignification by treatment with peracetic acid (17). Also wood cambium from the same softwood was studied. The cambium is the recently formed fiber layer, located close to the bark and not yet lignified. Spruce and birch wood contain about the same amounts of cellulose, 42 and 44%, respectively. Spruce wood has more lignin (28 vs. 18% ), while birch has more hemicellulose (35 vs. 2S% ), in particular more pentosans than spruce (24 vs. 14%). 

Table I. Composition of Cotton and Typical Angiospermous (Birch) and Gymnospermous (Spruce) Fibers...

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