ALBERT

Notes: Summary Linear viscoelastic properties of laboratory handsheets have been investigated from the two dimensional aspect. According to the linear theory of viscoelasticity, the behavior of transverse isotropic materials such as handsheets subjected to plane stresses is fully described by the two in-plane relaxation functions G11 (t) and G12 (t). In the present paper, some viscoelastic characteristic functions describing responses to in-plane deformation histories are derived from G11 (t) and G12 (t) determined by strip biaxial stress relaxation testing. The predicted uniaxial relaxation function curve was in good agreement with the experimental one, and the viscoelastic Poisson's ratios in uniaxial stress relaxation and in uniaxial constant strain rate extension were decrease functions of time. Effects of beating on the areal dilatation and shear relaxation functions are discussed by introducing the classical concept of relaxation spectrum.

Notes: Summary This electron microscopy study is concerned with the dormant cambial cells in compression wood of Picea abies (L.) Karst. The cambial zone comprised 4–8 rows of fusiform cells. Each radial file contained the group known as Sanio's four, namely an initial, a mother, and two daughter cells. Groups of three, resulting from a failure of a mother or a daughter cell to divide, were also present. Undifferentiated xylem tissue cells occurred singly, in pairs, or in groups of four. These cells and the last-formed tracheids were often enclosed by a common primary wall. The fusiform cells had a large, elongated nucleus, numerous small vacuoles, and a frequently infolded plasma membrane. Golgi apparatus and endoplasmic reticulum were rare, while plastids, amyloplasts, and lipid droplets were common. Cambial ray cells contained much lipid material. The tissues were similar to cambial tissues in normal wood of conifers. The present results can only be interpreted in terms of the single layer of initials and sequence of cell divisions established by Sanio. The initial can be located by several criteria in dormant and active cambial regions in conifers. It could be shown that the existence of the group of Sanio's four is better documented in the literature than has so far been recognized. The occurrence of a variable number of primary cell walls is discussed with reference to the concentration of lignin in the middle lamella of mature xylem.

Notes: Summary The technology and chemistry of recent advances in alkaline pulping are reviewed from the standpoint of the authors' work over the past few years. Topics reviewed include soda-amine [particularly soda-ethylenediamine (EDA)], soda-anthraquinone (AQ), kraft-AQ, and soda-AQ/EDA pulping and their effects on pulp strength properties and bleachability. There is evidence to support the concept that the rates of all alkaline delignification reactions, including kraft, are controlled by a reductive step which transfers electrons to the degrading lignin.

Notes: Summary A lignin-carbohydrate material from black spruce (Picea mariana) was treated with a hemicellulase mixture. The carbohydrates in the remaining material were studied by the following methods. a) Treatment with 0.1 M NaOH in the presence of sodium borohydride followed by selective hydrolysis of the furanosidic bonds, b) Smith degradation (periodate oxidation followed by mild acid hydrolysis). The results obtained indicate that lignin is bound to all types of sugar units in the hemicelluloses. For arabino-4-O-methylglucuronoxylan, linkages to the side-chain units seem to dominate. The links to the 4-O-methylglucuronic acid units are ester bonds, probably benzyl ester bonds. Those to the other sugar units in the hemicelluloses are ether bonds, probably benzyl ether bonds. The results suggest, furthermore, that fractions of cellulose are linked to lignin.

Notes: Summary NPA, applied in a 2–3 cm band around the middle protion of 2- or 3-year-old internodes of three vertically-oriented six-year-old Sugi trees (Cryptomeria japonica D. Don), brought about abnormal thickening all over the upper segment from the NPA treatment. Xylem tissues above and below the treatment, as well as at the treated area itself, was examined by ordinary light microscopy and by scanning electron microscopy. The results obtained seemed to indicate that the tissue formed after treatment in the upper segment of the stem was true compression wood. In the lower segment of the stem, no abnormal tissue but a small amount of latewood-like tissue was produced after treatment. Referring to the previous studies in which morphactin, another IAA transport inhibitor, has induced compression wood, we consider it likely that compression wood formation must be induced by high concentrations of endogenous IAA, which could be brought about by blockage created not only by NPA and morphactins, but also by IAA transport inhibitors in general.

Notes: Summary Tangential latewood sections (60 μm) of Scots pine sapwood were differently treated with chlorite. The subsequently incubated two strains of Bacillus polymyxa caused a weight loss up to about 25%, including a loss of lignin of about 42%. UV-microspectrophotometry of 1 μm-cross-sections prepared from the cultured woody tissues demonstrated that bacteria caused neither quantitative nor qualitative changes of the remaining lignin. The lignin, which was dissociated from the pretreated woody cell wall by bacteria, could not be respired, suggesting that the lignin is a ‘ballast’ to these bacteria that inhibits the dissimilation of the carbohydrates in the wood.

Notes: Summary That the behavior of wood in service results from its “structure” is generally accepted by wood scientists. No doubt this acceptance is due to the broad interpretation of such a term. Structure can refer to the organization of elements on a macro scale, such as in a laminated beam, as well as to the arrangement of cellulose molecules in the crystalline region of an elementary fibril. This presentation focuses on a structural domain that appears increasingly to be a critical one in wood behavior-ultrastructure. The spectrum of terminology that has been used in profusion during the “electron microscopic era” must first be defined so that confusion is minimized. Then a historical evolution of the field of wood ultrastructure can be presented to provide perspective. Structures that have been shown to affect or indeed to control certain processes can be identified. The role of a “non-structure”, the elusive transient capillary, can be illustrated. Microfibrillar organization and cell wall archictecture fall into the realm of ultrastructure as well. The past decade of research in wood science has been productive to a significant extent because of scanning electron microscopy and its accessory tools and techniques. The exploration of wood penetration by wood preservatives, pulping liquors and coatings using this approach has yielded much new evidence. One can speculate about the anticipated contributions of computer-driven SEM, stereology, STEM, and even higher resolution microscopy in the near future.

Notes: Summary Problems associated with handling non-steady liquid flow data are discussed. It is shown that the Darcian flow model is fundamentally imprecise when applied to non-steady state flow in wood due to: 1) the observed decrease in permeability with increased specimen length 2) the wide range of diameters encountered in wood pores. Because of this wide range of pore sizes, liquid penetrates some flow paths more rapidly than others. This may give rise to the occurrence of surface forces resisting penetration, with both “wetting” and “non-wetting” liquids. It seems unlikely that these various factors can be accurately quantified. Hence the precise prediction of liquid penetration rate from steady state permeability data may be illusory.

Notes: Summary To predict the capillary transport of free liquid during the drying of softwood, it is essential to have knowledge of capillary pressure as a function of moisture content. The dependence of the capillary pressure on the wood's moisture content is predicted with a mechanistic model and measured for isothermal moisture movement in the tangetial direction. The experimental measurements confirm the model which is formulated on the postulate that the menisci that form between the liquid and gas in the tracheid lumens control the magnitude of the capillary pressure. Lumen size variation within an annual growh ring was found to significantly affect the local capillary pressure and indicated that separate flow paths are likely to exist in earlywood and latewood.

Notes: Summary A model for the build up of residual growth stresses in cylindrical tree stems is presented. By using Bessel functions the general equations can be solved to allow for surface strain distributions that vary both in the circumferential as well as longitudinal directions. An arbitrary surface strain distribution can be decomposed into Fourier components and the residual internal stresses can be found by superimposing the component solutions due to each new increment of growth. A numerical simulation leading to the residual stress distribution for a typical hardwood is presented.

Notes: Summary Information is presented on the magnitude of errors associated with various sampling simulation schemes of the distribution of three different populations, representing actual bending strength of dimension lumber. Errors were determined between the simulated and actual distributions. Graphical evaluations indicated good fits with the three-parameter form of the weibull distribution for both original and simulated bending strength data, as well as with the resulting error terms. Error terms, based on the simulated versus actual distributions, were generated for the lower 5% exclusion limit, for the 50% exclusion limit and for the entire distribution curve. Simulations were carried out with the aid of Monte Carlo techniques using distribution functions fitted to actual test data for dimension lumber. The errors are expressed as functions of confidence levels. The comparison of the erro obtained through the various sampling schemes could provide some initial directions to choose an economical sampling plan for the presently ongoing in-grade lumber testing program.

Notes: Summary Paintings on 150 wooden panels accepted and not accepted as authentic Rembrandts were investigated using wood-anatomical and dendrochronological techniques. Paintings on 131 panels came from oaks in the coastal area of the Netherlands and 1 panel came from an oak in the interior. The wood of the remaining 18 panels was from beech, poplar and walnut, presumably from the Netherlands, and from cedrela, mahogany and jequitiba imported from Central and South America. In several cases wood of different panels was from the same trunk. By determining the felling date of a tree, a “terminus post quem” could be set for the production of the panel and the completion of the painting, respectively. The art-historical dating of most paintings could be dendrochronologically confirmed. In some cases the attribution was corrected by a few years. In one case an older panel was re-used.

Notes: Summary Structural factors in a Pinus densiflora tree grown under the influence of strong wind were measured. No $$\overline {DP} $$ difference for cellulose molecules was noticed between compression and opposite wood, but the $$\overline {DP} $$ was somewhat lower in the region where the compression wood was concentrated. The degree of crystallinity of cellulose was 45–50% in compression wood, about 50% in normal wood, and 50–60% in opposite wood. The crystallinity decreased with increasing height above the ground. The maximum point of crystallographic b-axis (fiber axis) orientation distribution for cellulose crystallites in compression wood was located at ϕ≅30°, in normal wood at ϕ≅25° and in opposite wood at ϕ≅0°. The cellulose crystallite dimension in the transverse direction was 3.2 nm, corresponding to four cellulose unit cells, a value that was almost constant throughout the wood. In the longitudinal direction, there were large differences in cellulose crystallite dimensions between compression and opposite woods. In compression wood the cellulose crystallite dimensions was 12 nm corresponding to 11–12 cellulose unit cells. In opposite wood it was 17–32.5 nm corresponding to 17–32 cellulose unit cells. These structural factors were apparently affected by the environmental conditions, and the mechanical properties of the wood were influenced by these factors. Opposite wood had longer crystallites, a higher degree of crystallinity and a better orientation distribution of cellulose crystallites in the longitudinal direction. Compression wood, on the other hand, had shorter crystallites, a lower degree of crystallinity and a large angle between the stem and the direction of the crystallites.

Notes: Summary Wood poles have been traditionally tested by “sounding” — striking with a hammer and making a subjective assessment on the basis of the sound emitted. Various other acoustic methods have been developed and employed for this function but none has been accepted on any regular basis as being successful. The propagation of acoustic waves in poles is examined here, and measurements are made using a pulse echo technique of the two acoustic parameters, velocity and damping, on a selection of poles some of which contain decay and rot. The results suggest that measurement of the acoustic damping of longitudinal compression waves may be useful in detecting the presence of decay and rot within a pole.

Notes: Summary The exposure of wood treated with a commercial fire retardant chemical to fire conditions resulted in different patterns of char and fissure development than are seen in untreated whole wood. In addition microstructural observations demonstrated the existence of particulate fire retardant residues in char from treated wood. The source and mode of growth of these particles is considered as well as effects of fire retardants on crack growth, char development and overall appearance of chars from treated wood.

Notes: Summary Tar and charcoal could be produced in high yields from bagasse by applying a rapid continuous pyrolysis process at a relatively low temperature. The ether extractives of the pyrolytic tar and oil amounted to 9.4% based on bagasse. Phenols represented 79% of these extractives. Gas chromatographic separation showed that guaiacol and its derivatives constituted 38% of the identified simple phenols. There were much smaller amounts of syringol and none at high pyrolysis temperatures. Depithing did not reduce the ash content of the charcoal, but it yielded an environmentally clean charcoal containing practically no sulfur or nitrogen. It was necessary to remove the fine particle size fraction of the bagasse after grinding in order to reduce the ash content of the charcoal. The carbon content of the charcoal increased rapidly with increasing temperature, and reached 96% at 720°C. The charcoal had a remarkably high adsorption capacity despite the fact that it had not been subjected to any activation treatment.

Notes: Summary The alkaline delignification of spruce and beech wood is accomplished in three phases. The first phase results in a decrease of yield down to 83...80%, the second one in a decrease from 83...80% to 64...61% and the third one in a yeld drop from 64...61% to 50...46%. The amount of polysaccharides removed in the first phase was 22%, in the second phase 5...6% and in the third phase 10% of the total polysaccharides in the original wood. The amount of lignin removed in the first phase of delignification was 9...11% in the second phase 53...54% and in the third phase 28% of the total lignin in the original wood. The polysaccharides extracted in the second and third phase amounted to 70...78% of the polysaccharides removed in the first delignification phase. For an entire characterization of the delignification reaction not only the course of lignin removal is of importance but also the course of the polysaccharide extraction. The results show that for a two-stage alkali-oxygen-cooking technology the optimum yield after initial partial alkaline delignification lies in the range of 64...61%.

Notes: Summary Delignification studies on 0.5 μm sections of Douglas-fir earlywood tracheids pulped by soda, soda-anthraquinone (soda/AQ) and kraft pulping processes were performed by determining bromine concentrations in various morphological regions with SEM-EDXA technique. Soda/AQ pulping was much more selective in removing lignin from the middle lamella regions than either soda or kraft pulping. However, up to 50% delignification, more lignin was removed from the secondary wall by soda or kraft, compared to soda/AQ pulping. The kinetics of lignin removal in the various morphological regions were established. Addition of AQ and sodium sulfide resulted in an earlier transition from a slow initial to a rapid bulk delignification, particularly in the middle lamella, and in an enhanced bulk delignification in the secondary wall. Anthraquinone was also found to promote residual delignification in the secondary wall, where sodium sulfide was not effective. The opposite was observed for the bulk delignification in the middle lamella, where only sodium sulfide addition improved the rate significantly. The great differences observed in the bulk delignification rates between middle lamella and secondary wall in soda pulping as well as their response to additives suggest structural differences between middle lamella and secondary wall lignins.

Notes: Summary The lignification process in different morphological regions of loblolly pine tracheids was studied by the SEM-EDXA technique. Prior to S2 layer formation, lignification was initiated in the cell corner middle lamella and compound middle lamella regions. Subsequently a rapid lignin deposition was observed in both regions, whereas secondary wall lignification was a more gradual process and initiated when the middle lamella lignin concentration was approximately 50% of maximum. Within the secondary wall, the S1 layer is lignified first. Then, lagging just behind cell wall formation, lignification of the S2 layer is initiated adjacent to the S1 layer and extends toward the lumen. Finally, the S3 layer lignified. Upon completion of lignification, the cell walls had a higher concentration of lignin in both the S1 and S3 layers than in the S2 layer.

Notes: Summary Photodegradation of wood surfaces in the presence of oxygen was studied. ESR studies revealed that free radicals were formed at the wood surface during photoirradiation. These wood free radicals readily interacted with oxygen molecules to form peroxide radicals. Iodometry UV absorption studies showed that hydroperoxide was formed in the photoirradiated wood. The hydroperoxide concentration increased when wood was irradiated in the presence of singlet oxygen generators such as Rose Bengal and Methylene Blue. Hydroperoxide concentration decreased when wood was irradiated in the presence of singlet oxygen quenchers such as 1,4-diazobicyclo (2,2,2) octane, β-carotene and triethylamine. These findings imply the participation of singlet oxygen in the photodegradation of wood surfaces. The mechanisms of formation of singlet oxygen and hydroperoxide during photoirradiation are proposed. The consequence of hydroperoxide decomposition reactions on the discoloration and degradation of wood surface is discussed.

Notes: Summary This paper concerns the elaboration of a method for the determination of elastic constants of orthotropic bodies with particular application to wood. It is based on the finite element calculation (displacement pattern) of thin plate samples and on the experimental measurement of the deflections at particular points under a simply imposed load.

Notes: Summary The reaction of enzymatically generated superoxide radical with coniferyl alcohol in aqueous solution at pH 8.0 was studied. In the absence of calcium (II) no reaction occurred, but with a calcium (II) concentration of about 50 mM or more, coniferyl alcohol was oxidized by the superoxide radical. Dehydrodiconiferyl alcohol and pinoresinol were identified in the reaction mixture. From this result it is concluded that in the presence of calcium (II) the superoxide radical can achieve a one electron oxidation of coniferyl alcohol. It is suggested that a superoxide-generating enzyme outside the cell wall is responsible for the lignification. This suggestion is based on knowledge of the pore structure of wood cell walls, the high calcium concentration in non-lignified cells, the course of lignification and the existence of superoxide-producing enzyme systems in plant cell walls.

Notes: Summary A review of the chemistry and topochemistry of compression wood with 200 references. Compression wood contains on the average 30% cellulose, 35–40% lignin, 10% galactan, 9% galactoglucomannan, 8% xylan, and 2% of a 1,3-glucan (laricinan). The cellulose is less crystalline, and the xylan has fewer arabinose side chains than in normal wood. The lignin is composed of guaiacylpropane and p-hydroxyphenylpropane units. It is more condensed, has a higher proportion of carbon-carbon bonds, and contains fewer arylglycerol-β-aryl ether structures than a normal conifer lignin. The ray cells and the primary wall of the tracheids have the same chemical composition in normal and compression woods. The galactan is largely located in the outer region of the secondary wall. Only 5–10% of the lignin in compression wood tracheids is extracellular. The middle lamella is less lignified than in normal wood, while the S1 and inner S2 layers have a lignin concentration of 30–40% which is twice as high as in normal wood. The lignin content of the S2 (L) layer is equal to or higher than that of the intercellular region along the wall. The review is concluded with a brief reference to areas where present information is incomplete or lacking.

Notes: Summary A model for the isothermal transport of bound water through the cell wall of wood is developed, based on the assumption that the driving force for moisture movement is the gradient of “spreading” pressure ϕ, as first proposed by Babbitt (1950). This pressure is a surface phenomenon, derivable from the surface sorption theory of Dent (1977), a modification of the BET sorption theory. The force resisting moisture transport is assumed to be inversely proportional to moisture content and directly proportional to the equivalent viscosity of the sorbed water, calculated to be orders of magnitude larger than that of free water. The coefficients normally used to describe isothermal moisture transport in wood are derived from the model, and their predicted behavior as functions of the relative vapor pressure h of the cell wall are described graphically. An attempt is made to calculate a quantitative magnitude for the diffusion coefficient D, based on an assumed relationship between viscosity and the activation energy for water diffusion.

Notes: Summary To elucidate biochemical features leading to p-hydroxyphenyl-rich lignin in gymnosperm reaction wood the activities of the following five enzymes involved in the biosynthesis of p-hydroxyphenyl lignin were compared in reaction and opposite woods: phenylalanine ammonialyase (EC 4.3.1.5), cinnamate 4-hydroxylase (EC 1.14.13.11), p-hydroxycinnamate: CoA ligase (EC 6.2.1.12), cinnamyl alcohol dehydrogenase (EC 1.1.1.-) and peroxidase (EC 1.11.1.7). The enzyme activities in the reaction woods of Thuja orientalis and Metasequoia glyptostroboides were remarkably higher than those in the opposite woods, reflecting the higher contents of p-hydroxyphenyl lignin in reaction wood.

Notes: Summary The purpose of this paper was to clarify the gluability and adhesion mechanism of polypropylene as a hot melt wood adhesive for plywood bonding. The gluability of plywood glued with nonpolar and modified polypropylene satisfied approximately the specification of the Japan Agricultural Standard, Designation Types 1 and 2. The moisture content (8 to 25 %) of the core veneer had no recognizable effect on gluability. The durability of polypropylene and that of modified polypropylene were the same as that of melamine-formaldehyde resin. Molten polypropylene made good contact with veneer surface, and penetrated into the lumina of wood cells and other spaces. In the separated glue lines, casts of glue which had penetrated into the vessels had many mushroom-like projections which had filled the bordered pit cavities. It was indicated that the anchoring effect of polypropylene which had penetrated into various wood elements and spaces in the veneer contributed dominantly to the gluability.

Notes: Summary The anatomy of periderms in three North American conifers are described and compared. The phellems of balsam fir and eastern hemlock consist of tangential bands of thin-walled phellem (TnP) separated by one, or sometimes more, cell layers of thick-walled phellem (TkP). The phellem of white spruce contains tangential bands of TnP and TkP, as well as one to several cell layers of crystalliferous phellem (CP) abaxially adjacent to every TkP zone. The TkP, and to a lesser extent the TnP, are distinctive for each of the three conifers. The terminations of phellem growth cycles in fir and hemlock are delineated by thickened adaxial suberinic walls in the last-formed layer of TnP cells. In spruce, the adaxial suberinic walls of the last-formed layer of CP cells are thickened. TkP marks the geginning of phellem growth cycles in all three conifers. TkP cells are “true” suberized phellem cells, not phelloids.

Notes: Summary An acoustic resonance technique has been evaluated as a means of detecting deterioration in wood poles. The basis of the technique is that degradation of the pole by rot or other agency will lead to an increase in the damping of longitudinal acoustic waves, which can subsequently be detected by an examination of the acoustic resonance characteristics of the pole. The technique was assessed in a series of field trials conducted on in-situ poles, which were subsequently removed and dissected. The results of the acoustic testing compared favourably with the gradings of the poles following dissection.

Notes: Summary Historically, adhesive development has been a propelling force in the evolution of the forest product industry. The 1973 energy crisis has caused the wood industry to focus its attention on the necessity of adhesive self-sufficiency. Research in the use of bark, pulp waste liquor and foliage for adhesive application is rapidly spreading. In addition, many new adhesives have been proposed by the chemical industry as alternatives for wood bonding. Recently developed physiochemical analytical methods have been successfully applied to this adhesive research area and to durability evaluation. However, there are still enormous difficulties in developing a durable natural product adhesive of low variability as well as a unified international interpretation of bond durability. Phenolic resins have weathered the energy crisis and are gaining importance in the industry. Some examples of recent contributions from phenolic-resin research to panel board and lumber end-joint developments will be discussed in detail.

Notes: Summary The fine structure of inactive eastern white spruce phellogen (Pg) and phelloderm is briefly described. Phellogen cells resemble dormant cambium but contain larger tannin vacuoles. Phelloderm cells contain even more tannin and have much thicker primary walls. Three types of phellem are described: crystalliferous phellem (CP), thin-walled phellem (TnP), and thick-walled phellem (TkP). All three occur in spruce, but only the latter two in balsam fir and eastern hemlock. The TnP cells have thin shared common walls overlain by suberinic and wax extractive layers. True pits are lacking, but plugged plasmodesmatal canals sealed over by the wax extractive layers cross the suberinic layers. Spruce CP and fir and hemlock TnP cells have adaxially-thickened suberinic and wax extractive layers when adjacent to TkP or inactive Pg. The suberin lamellae are much thickened in these suberinic layers, at least in spruce. Spruce CP has a thick wax extractive layer which also sheaths the crystals. The TkP cells of all three species have thick polylamellate abaxial cellin walls perforated by simple pits. The lamellae differ both in structure and composition. Polylamellate wall construction is discussed and a model proposed. The TkP cells have both suberinic and wax extractive layers in fir and hemlock, but only wax extractive layers in spruce. These cells are therefore true phellem cells, not phelloids.

Notes: Summary Deflections of wooden beams loaded repeatedly for seven or two days in every 14 were compared with those of beams under constant load over a period of six months in a constant environment. Four load levels were applied to beams of three species. Loads ranged from 17 to 67 per cent of short-time failing load estimated from matched specimens. The deflections under intermittent loads were lower than the creep deflections under constant load and, with the exception of material under high stress, applicability of Boltzmann's principle of superposition of deformations was confirmed. Non-linearity at high stresses is linked with other signs of weakening after application of loads in excess of about 50 per cent of short-time ultimate.

Notes: Summary A computerised wood densitometer system using X-rays is described. The technique uses 5 mm increment core samples, machined to 2 mm thickness in the axial direction of the fibre, and an isotopic radiation source (Fe 55). Direct measurement of the intensity of radiation passing through the sample enables wood density variations to be recorded automatically and stored on disc file for subsequent analyses with an interactive computer program.

Notes: Summary An equation is derived to describe transverse nonisothermal moisture movement in wood, based upon a gradient of chemical potential. When compared with a previously derived equation based upon a gradient of activated moisture molecules, this new equation predicts an accentuated effect of the thermal gradient relative to the moisture gradient at high wood moisture contents and a decreased effect at low moisture contents. The two equations yield identical results at a moisture content in equilibrium with a relative humidity of approximately 53 percent.

Notes: Summary The hypochlorous acid formed intermediately during the bleaching of an oxygen-prebleached kraft pulp with pure chlorine dioxide (a D0-stage) was captured as N-chlorosulfamic acid by addition of sulfamic acid to the bleaching liquor. The amount of hypochlorous acid captured corresponded to about 50 mol% of the consumed chlorine dioxide. The amount of chlorite formed (20 to 30 mol%) was less than the amount of hypochlorous acid captured. The excess of hypochlorous acid over chlorite suggests that chlorine dioxide is reduced initially not only by a one-electron mechanism to chlorite but also by a two-electron mechanism to monochlorine monoxide, which is then reduced by lignin or by chlorine dioxide to hypochlorous acid. The routes for the further reactions of chlorite, monochlorine monoxide and hypochlorous acid are discussed.

Notes: Summary Ultra-high pressure water jets, operating at 48 300 kPa through a ring-type No. 6 nozzle with 15° fan and 1.57 mm diameter opening, were used in practical trials for debarking several hardwood species. Eucalyptus paniculata, E. agglomerata, E. acmenioides, E. pilularis and Syncarpia glomulifera were tested, as they are known to be difficult to debark. The effects of these jets on the configuration of the detached bark, were also assessed. Except for E. pilularis, all species were effectively debarked, and a classification was made of the relative difficulty with which various barks were removed. In E. pilularis the bark adhered strongly to the timber, the surface of which was extensively damaged by the water jets. The high pressure water often broke and shattered the bark, which sometimes underwent pronounced defibration. In particular, the bark of E. acmenioides and E. paniculata was broken down into a material, which should be readily utilisable without further processing. Finally, these trials have shown that the design of a small-size hydraulic debarker is feasible and should eventually be a commercially viable proposition.

Notes: Summary The purpose of this study was to assess the relationship of oven-dry density, initial moisture content, vascular bundles and shrinkage to stem height and diameter of Cocos nucifera L. High correlations were obtained between initial moisture content and stem height, initial moisture content and oven-dry density, oven-dry density and stem height, vascular bundles per cm2 and stem height, vascular bundles and oven-dry density for cross-sections and shrinkage and vascular bundles per cm2. The high correlations between vascular bundles per cm2 and oven-dry density on the one hand and to shrinkage on the other can be used for visual grading of coconut timber.

Notes: Summary In the present paper a hydrothermolysis apparatus is described. The reaction vessel is of the percolator type with a volume of 560 cm3 and permits the hydrolysis of biomass materials up to 100 g. The optimum degradation conditions of pure cellulose (filter paper) were determined in dependence on temperature, flow rate of the eluting water and influence of stirring on the reaction mixture. Up to 52% glucose can be obtained by hydrolysing cellulose with pure water at 265°C at a flow rate of 12 cm3/min. Biomass materials such as poplar wood and wheat straw were hydrolysed in two stages, using temperatures of about 200°C for the easily hydrolysable polysaccharides and about 260°C for the polysaccharides, which are more difficult to hydrolyse. In the first stage on an average 45% of the initial amount is converted into soluble products, whereas in the second stage this value amounts to 48%.

Notes: Summary The use of ammonium sulfide in aqueous ethanol and methanol was investigated for pulping of wood. Hemlock chips required 21% ammonium sulfide (equivalent to 19% Na2O) at 180°C to become delignified to the kappa range 35–50. The yields exceeded those of conventional kraft pulps by 14% on dry wood basis. Over 75% of the original glucomannan was recovered in the pulp as the consequence of end group stabilization by ammonium sulfide. The intrinsic viscosity of the pulps, measured in cadoxen was 10.65 dl/g — approximately double the value for softwood kraft pulps. The pulps were readily bleached and possessed higher tensile and burst strengths but lower tear strengths than kraft pulps. Ammonium sulfide pulps from cottonwood were likewise obtained in high yields and with adequate strength properties.

Notes: Summary Changes in the submicroscopic porosity in southern pine latewood resulting from pyrolysis at temperatures through 600°C were measured using small-angle X-ray scattering. Two types of scattering curves were observed: the first was obtained for wood and for less intense heat treatment; and the second, for samples heated above 300°C. This change was found to be associated with the thermal degradation of crystalline cellulose in the sample. Specific surfaces and the average dimensions of macropores and micropores were calculated from the second type of scattering curve. The specific surface was found to increase from 1.2 to 2.3 m2/gm as the temperature and heating time increased. The average dimensions of the macropores calculated from the scattering curves was about 15 nm. The first effect of heating sufficiently to decompose the crystalline cellulose was found to be the production of micropores with average diameters of about 0.7 nm. Micropore volume increased from 0.06 cm3/gm for the lower heating temperatures to about 0.13 cm3/gm for samples heated to 600°C. The average micropore dimension increased as the temperature was raised and the samples were heated for longer times.

Notes: Summary In a typical sawmill, about 12% of the wood which is cut is reduced to sawdust. Further material is lost during subsequent planing. A substantial part of this large loss of a costly natural resource can be saved by the use of thin, stable sawblades, but only if proper saw tensioning conditions are developed. The thickness of a stable sawblade can be minimized through optimal tensioning, an increasingly urgent objective because of sharply rising raw material costs. A theoretical model is presented which accurately describes the development of residual stresses in a roll tensioned circular sawblade and the resulting changes in saw critical speed. This model is essential for the reliable prediction of optimal tensioning conditions for any given saw operating state, and for the development of automated control of the tensioning process. An example is presented of an optimally tensioned circular sawblade for which a 40% thickness reduction is achieved compared with an equivalent untensioned sawblade with the same critical speed.

Notes: Summary The structure of coniferous wood is characterized by pronounced differences in density between earlywood and latewood. This could result in disadvantages in wood strength especially against bending. A summary of the observations in this paper leads to the following hypothesis: Coniferous trees meet this danger by forming numerous stiffenings especially in broad annual rings with a high percentage of earlywood. Such stiffenings may be produced by more or less slight fluctuations of density or chemistry within annual rings in radial as well as in tangential directions. The question remains open which anatomical or chemical reasons, upon sandblasting, locally cause radial or radially branched ribs and craters in cross sections, waviness in radial sections and “cloudy” structures in tangential sections.

Notes: Summary The reasons for changes in wood quality and utilization are related to the trends toward harvesting smaller, younger and lower-quality timber, wider use of formerly waste wood, unconventional uses of wood, and improved forest management and new wood manufacturing techniques. 1. An unequal distribution of timber along with increasing costs of forest ownership and management is forcing short-rotation forestry, which results in small-sized timber, low-quality wood, and a high proportion of juvenile wood and knots. This is true for almost all forest regions although it has been most evident in tropical plantations. The economic pressures for short-rotation ages will become increasingly great, especially in those areas where a timber imbalance in age class distribution occurs. 2. Especially in the Tropics, many forestry organizations are planting exotic species on a massive scale and are producing a large volume of “different” wood. The trend toward using exotics is very strong. The trees attain a merchantable size at young ages, with thinning being standard; this produces a large proportion of juvenile wood. Such wood is not desirable for some products, based on current quality criteria, and may be distinctly different from the wood that the same species produces in its indigenous environment. Huge amounts of it are now becoming available, requiring a reassessment of both manufacturing techniques and product type and quality. 3. Better utilization in forest harvesting operations results in the use of mill residues of bark and sawdust and forest residues of bark, limbs, leaves, stumps and roots that formerly were considered to be waste. There is also greater utilization of previously unwanted species, including some which were once considered to be of limited value and often were destroyed during regeneration programs. Of great importance are the technological developments that are enabling a greater utilization of the grossly differing woods found growing together in tropical forests, rather than using only a few species and destroying the rest. 4. Wood quality is very responsive to both silvicultural and genetic manipulation. The improvements possible in wood will partially offset some quality declines caused by young wood and lower quality trees. The quickest and easiest method of changing wood quality is to control age of harvest. 5. New industries are developing which use wood as a source of energy and organic chemicals. In some areas, wood for energy is primarily obtained from large forests being planted solely for energy needs and is secondarily obtained as a salvage product from the forest. From 20 to 50% of the wood harvested in the world is for firewood, which often results in a marked reduction of the quality of the wood used for industrial purposes. Currently some research is focused to grow trees which will yield improved energy and chemicals. 6. New manufacturing techniques, such as oriented strand-board and the endgluing of short, clear wood segments from low-quality logs, are enabling the production of high-quality products from low-quality timber. These manufacturing techniques result in products that differ markedly from those previously available but they are stable and of excellent quality. However, a strong sales program will be needed to assure acceptance of the different products.

Notes: Summary The wettability of four Asian meranti species (dark red, light red, white, and yellow) in various liquids was studied by a cone-immersion technique. Wettability was expressed in terms of the area under the force-immersion curve and referred to as the wettability index. Wettability was strongly influenced by the pH of the solution, generally increasing with increasing pH. Surfactant type affected wettability, with the cationic type yielding the greatest wettability followed by anionic and nonionic types. Among the liquids used, distilled water gave the lowest, and acetone-isopropyl alcohol solution gave the greatest wettability. Of the meranti species, yellow meranti showed the greatest wettability, followed by white, light red, and dark red meranti. A plot of the relative amount of liquid absorbed into the wood sample versus wettability index yielded two regions, one attributed mainly to liquid trapped in crevices on the wood surface, and another which may be more indicative of wood-liquid interactions. A highly significant linear correlation between wettability index and liquid surface tension was found for those species with low and medium wettability, while that with high wettability showed no correlation. A new empirical approach of determining the critical surface tension of wood is discussed. Limited data for the present method indicated close agreement with result from the literature obtained by the use of the well-known Zisman's contact angle approach.

Notes: Summary A culm sample of Phyllostachys makinoi was investigated by analysis of its chemical composition, and by electron microscopic observations of the cell wall structure before and after extraction and degradation procedures. Quantitative determination of the components resulted in 2.6% extractives, 25.5% lignin, 45.3% alpha-cellulose, and 24.3% polyoses. The main polyose is an arabinoxylan with a Xyl: Ara ratio of about 17:1. The electron micrographs show a lamellar deposition of lignin and polyoses within the secondary walls. Lignin is obviously soluble by parts in alkaline as well as in acidic reagents. Sodium hydroxide solution removes cell wall substance mainly from the secondary walls, whereas trifluoroacetic acid removes substance from compound middle lamellae.

Notes: Summary Basic density and extractives content, of the sapwood and outer heartwood respectively, were compared for a fast-and a slow-grown tree in five, 40 year old, coppice clumps of each of six eucalypt species. Rate of growth did not appreciably influence extracted wood density, although outer heartwood extractives levels were significantly (P〈0.05) higher in the larger stems. The juvenile core, as defined by radial variation in basic density, occupied a similar proportion of the tree diameter in the fast-and slow-grown trees, suggesting that sampling was effected in tissues of similar maturity in both tree groups.

Notes: Summary With the emergence of probabilistic design procedures, the need for precise knowledge of the entire probability distributions of load effects and material resistance has never been greater. In order to evaluate these distributions, simulation techniques have provided a reliable and cost and time effective alternative to large scale destructive testing. With the use of the Johnson's SB probability distribution, a closed-form, analytic procedure has been developed to model the inherent variability in strength, given some nondestructively evaluated parameter. This modeling procedure serves as the basis of a verified simulation process to predict a strength distribution, given a probability distribution of the NDE parameter. The approach presented here, represents a closed-form, analytic solution to a problem which has heretofore been treated in a more subjective fashion. This simulation procedure is complemented by a stratified sampling scheme.

Notes: Summary Pole figures were described for (101), (101), (002) and (040) crystallographic planes of cellulose crystallites in opposite, normal and compression woods of Pinus densiflora. The orientation functions for these planes were plotted on the equilateral triangular coordinate. The orientation factors were calculated from the functions. It was found that the cellulose crystallites in the S2 layer contributed to the orientation distribution although those in the other layers also contributed to some extent. From the equilateral triangular coordinate plots it was found that the orientation distributions of cellulose crystallites in wood varied in some kind of regular fashion. This was more clearly confirmed by the variations of the orientation factors.

Notes: Summary The transport of heat and moisture during the convective drying of southern pine was examined experimentally. Moisture distribution within the wood samples was measured using gamma attenuation. The accuracy of these measurements was found to be moisture content dependent with estimated uncertainties ranging from 29.5% at 10% moisture content to 6.8% at 120% moisture content. Local moisture content measurements reveal large inflections at high moisture contents. Peaks in moisture content are closely correlated with low fwood density and vice versa. Above the fiber saturation point the measured drying rate is not a well defined function of the moisture content. This is perhaps due to the biological variability of wood as well as grain orientation, although no definite conclusions could be drawn from the data with regard to the effect of grain orientation. The drying rate does not appear to be highly temperature dependent at high moisture contents. Below the fiber saturation point where diffusion is expected to be the dominant transport mechanism, the drying rate is less affected by biological variability and grain orientation, however, the effects of temperature are evident.

Notes: Summary The increasing supplies of fast-grown woods grown on short roations contain significantly higher proportions of juvenile wood with properties different from those of mature wood. Improved processes will be required to produce dried wood that is satisfactorily stable with few distortional or dimensional changes. The basic wood features affecting different forms of instability are considered. Variations in the amounts of cellulose, hemicelluloses and lignins in wood, the changes in them and the degradation products formed under different conditions are discussed. Changes in the nature of hemicelluloses appear to play an important role in conveying stability. The different volumes of heartwood in green timber have an effect on moisture levels and other properties. As industry is increasing kiln temperatures for high-temperature drying, the effect of time-temperature-moisture relationships on stability and degradation are discussed. The effect of ammonia and other chemicals on stability is considered.

Notes: Summary During treatment of wood meal with nitrogen dioxide and oxygen the major proportion of the nitrogen dioxide and the intermediate nitric oxide is consumed within a few minutes. On prolonged treatment the concentrations decrease slowly due to regeneration of nitrogen dioxide by reactions between the modified lignin and nitric acid formed in the process. The conversion to nitric acid increases with an increased addition of nitrogen dioxide, a decreased dry content, and temperature. An appreciable proportion of the nitric acid is consumed on prolonged treatment.

Notes: Summary The interaction between molecular orbital theory and materials science has yielded fruitful insights into the fundamental properties of many substances. The application of these calculations to the chemical constituents of wood may provide an understanding of macroscopic properties by their examination at the molecular and atomic level. The semi-empirical, self-consistent fields method of modified neglect of diatomic overlap (MNDO) was used to study the dehydrogenation of coniferyl alcohol and the electronic structure of the reactive free radicals which form the lignin polymer.

Notes: Summary Kraft and ethanol organosolv lignins from Picea abies and Fagus sylvatica were carboxymethylated with bromoacetic acid. Of the total hydroxyl groups in the lignins, 60–70% were carboxymethylated. The reaction led to an increase of the number-average molecular weights. The moisture adsorption of the carboxymethylated products is about one and a half as high as that of the original lignins. There are no remarkable differences between the solubilities of the treated and untreated products.

Notes: Summary The reactions of quinone methide intermediates during the initial biosynthesis and also the subsequent aging of lignin are reviewed. The reactions during aging should lead to enhanced lignin-carbohydrate bonding and may explain the structural and analytical differences found between DHP and isolated milled wood lignins.

Notes: Summary Crystalline inclusions were observed in more than 50%, silica in nearly 20% of about 1500 wood specimens representing ±750 species from 40 genera of the laurel family. Both types of inorganic cell deposits are described and classified with regard to composition, habit, size, degree of isolation and location. Their diagnostic value and taxonomic implications on the specific, generic and suprageneric level are discussed with respect to intra as well as extrafamiliar relationships.

Notes: Summary The longitudinal permeability of Abies grandis wood swollen to varying degree by water vapour sorption has been measured using a non-swelling liquid. The results obtained show that cell wall swelling causes a reversible decrease in permeability in both air dried and solvent exchange dried specimens. Direct microscopic measurements have shown that change in lumen diameter cannot explain the observed effect. Mathematical analysis of the data suggests that the permeability decrease may be due to increase in thickness of bordered pit membrane fibrils resulting from sorption of water.

Notes: Summary Slow speed wood cutting tests were carried out in which cutting forces were measured as a function of applied tool-work electrical potential. The cutting tool and workpiece were electrically insulated so that there was no current flow. Applied potential had no discernible effect on the cutting forces measured in the cutting of unextracted and extracted wet wood.

Notes: Summary The acoustic velocities of a wide range of particle boards were determined from measurements of the transit times of wave packets through the materials. Velocities measured along the plane of the board are dependent on the properties of the board's skin layer, and are reasonably well correlated with the board's modulus of elasticity (r=0.73) and modulus of rupture (r=0.65). Velocities measured perpendicular to the plane of the board are not so well correlated with the mechanical properties of the board — the most significant being the Z strength parameter (r=0.56). The results suggest that this form of non destructive testing would be more suited to production line monitoring than to replacing or complementing existing test methods.

Notes: Summary The study is concerned with the possibility of demonstrating in the transmission electron microscope components such as copper, chromium and arsenic of preservative salts in the wood cell walls using secondary reactions with chemicals. Among the 18 substances tested only 9 showed a substantial positive effect, which was established on the basis of the electron contrast or depositions obtained within the various wall layers. It is suggested that copper is adsorbed onto the matrix substances of the wood cell wall rather than on cellulose.

Notes: Summary The reduction in hygroscopicity as spruce wood is impregnated with linseed oil may be accounted for using a molecular exclusion model. On the basis of the model, each linseed oil molecule appears to displace 90 water molecules and occupy 6 hydrogen bonding sites in the wood.

Notes: Summary Kraft pulping is interpreted in chemical terms on the basis of results from extensive qualitative and quantitative model experiments. In essence, the behavior of lignin is explained as a competition between degradation reactions, mainly involving aryl ether cleavage with participation of neighboring groups, and condensation reactions, comprising conjugate addition of carbanions to quinone methide intermediates. The initial phase of technical delignification is tentatively ascribed to the cleavage of α- and β-aryl ether bonds in phenolic lignin units, whereas the cleavage of β-aryl ether bonds in non-phenolic lignin units is considered to be the rate-determining reaction of the bulk phase. The residual phase may possibly be attributed to the rupture of C-C linkages and to aryl ether cleavage without neighboring group participation. Experimental support for these correlations is provided. The interplay of the various lignin reactions, illustrated in a summarizing scheme, explains some known observations in kraft pulping. Attention is drawn to analogies between reactions involved in the degradation of carbohydrates and those reponsible for the degradation of lignin. From the chemical standpoint, therefore, the selectivity of delignification is due to differences in the reactivity of the wood polymers, rather than to differences in the mechanisms of the degradation reactions. This fact explains the limitations of selective delignification.

Notes: Summary Previous methods for measuring residual longitudinal growth strain distributions in logs are reviewed. An extension is given of Jacobs' method for measuring growth strains which yields residual strain information at many points in the cross section other than along the diametrical plank. Some of the longitudinal growth strain distributions measured using the new method are presented.

Notes: Summary A method for the derivatization of low molecular weight lignin acidolysis product by reduction-acetylation is described. Borane dimethyl sulfide complex has been used as reducing agent. The derivatives could be analysed by gas chromatography.

Notes: Summary Geographical location (north/south latitude), social position of trees in a forst stand (dominant, codominant, suppressed) and site quality were investigated as to their effect on tracheid length, proportion of latewood and wood density of black pine indigenous to Greece. Tracheid length was fund greater in the northern location, in dominant trees and at intermediate site qualities. Proportion of latewood was higher in the southern location, in suppressed trees and at intermediate site qualities. Density was higher in the southern location, in codominant trees and at good or intermediate site qualities. Statistically, however, many differences at P = 95 % and all differences at P = 99% are not significant. The present study is based on the sampling of 331 trees, 55 years old and older; the probes were taken only from the 10 outer rings, at breast height. The findings from 6 trees, sampled from pith to bark, present disagreement with the above results.

Notes: Summary Orifice flow and drag theory are found theoretically to be generally inapplicable to axial gas flow through conifer wood under the conditions normally used for gas permeability studies of the material. However, orifice flow theory might be applicable at higher mean pressures or at higher applied pressure drops. Methods of testing this possibility experimentally are discussed.

Notes: Summary The maximum torsional-shear stress of 5 softwoods and 4 hardwoods were tested in the radial and tangential planes. These tests were carried out in glycerin which was preheated to different temperatures between 22°C and 150°C, inclusively. The dense hardwoods possess 2.4 times higher shear stress than softwoods at 22°C. However, at elevated temperatures, the same degree of shear stress reduction (77 %) is obtained for hardwoods and softwoods in both radial and tangential failure. Thus, the reduction in shear stress is independent of physical and structural wood variables.

Notes: Summary Past research on the combustion and pyrolysis of wood have often indicated a link between wood microstructure and its observed properties in fire exposure. The present research, after utilizing an instrumented fire exposure shown to simulate actual fire conditions, examines the microstructure of fire damaged wood and considers the implications of microstructural changes seen on the burning process. Differences in microstructural detail between wood and char, as well as fissure geometry, were shown to be consistent. The demarcation between damaged and undamaged wood was shown to be extremely small (several cell layers in thickness). The resulting microstructural observations are considered in light of published kinetic data on wood combustion and current theories and data on thermal degradation of wood.

Notes: Summary Radial pattern of variation in the first-formed earlywood tracheid length in blue pine shows that it increases outwards from the pith at first rapidly up to the 10th ring, then more slowly up to about the 40th ring and thereafter it remains more or less constant. It is correlated significantly and positively with both age and distance from the pith up to 40 years. In the mature wood zone i.e. after 40 years, tracheid length is not affected by either age or distance from the pith. The mean tracheid length of mature wood is significantly and positively correlated with the mean tracheid length of juvenile wood and also with the tracheid length of each of the juvenile wood rings. Based on the results of this study some guidelines for sampling are proposed. Trees with greater than 51 cm d.b.h. or above 40 years of age can be compared by sampling only four outermost consecutive mature wood annual rings; and those with less than 51 cm d.b.h. or below 40 years of age can be compared by sampling any of the juvenile wood rings.

Notes: Summary Crosslinking of wood with gaseous formaldehyde improves its hygroscopic and dimensional behaviour and its resistance against microorganisms. However, this formaldehyde crosslinking reaction takes place only in the presence of an acid catalyst, which results in losses in mechanical strength. Electron microscopic analysis of poplar samples treated under various conditions of reaction revealed severe degradation of cell wall substances. The formaldehyde gaseous nonomer is shown to have some hydrolytic action on cellular structure. Sulphur dioxide and particularly hydrochloric acid used as catalysts caused substantial extraction of matrix substances from fibre walls. Walls of vessels and ray parenchyma cells seemed to become less degraded. Strong exposure of cellulose fibrils during formaldehyde crosslinking reactions, illustrated by highly electron transparent zones in the S1 and inner S2 layers, occurred for both the SO2 and HCl catalyzed treatments. In general a more extensive degradation was observed for the formaldehyde-hydrochloric acid reaction and for the formaldehyde sulfur dioxide treatments using a high acid concentration. From these observations it might be concluded that the reduced mechanical strength of formaldehyde-treated woods are partially based on the hydrolysis of the carbohydrate backbone of the cell wall.

Notes: Summary The structure of the non-cyclic benzyl aryl (α-0-4) ethers 4 and 5, proposed by Freudenberg and Friedmann (1960) and recently boubted by Leary (1980), is discussed on the basis of previously published experimental results. Further evidence in favor of the occurrence of non-cyclic α-0-4 bonds in lignin is provided. A critical comment is, however, given on the formation of non-cyclic α-0-γ bonds in lignin according to Leary (1980).

Notes: Summary A method has been developed for the determination of lignin distribution in wood cell walls by studying bromine concentrations in 0.5 μm sections with scanning electron microscopy coupled with energy dispersive X-ray analysis (SEM-EDXA) technique. Evaluation of backscattering, absorption and fluorescence effects on quantitative assay of lignin distribution indicated that these effects may all be ignored, if relative comparisons are made. Thus, a relative ratio of the measured Br-L X-ray intensities directly provides bromine concentration ratio, from which the ratio of lignin concentrations in different morphological regions can be estimated. Additionally, the effect of electron beam bombardment on bromine was found to be negligible. Therefore, the SEM-EDXA technique provides quantitative information of lignin distribution with relatively high accuracy. The potential and limitations of this technique were also elucidated.

Notes: Summary Acoustic emission (AE) monitoring is a non-destructive testing technique widely used to detect flaw development and crack propagation in metals, ceramics, polymers and composite materials. This paper relates the AE-strain characteristics from three softwoods tested in tension to mechanisms of deformation observed by scanning electron microscopy. All wood specimens are identical in size and radial-longitudinal in orientation, enabling the path of failure through planes of earlywood and latewood to be examined. It is found that the proportion of earlywood to latewood in each species has a marked effect on the shape of the AE-strain curves. Parana pine, containing very few latewood tracheids, exhibits a close to linear relationship between log cumulative emissions and strain until close to failure when the count rate increases rapidly. Douglas-fir, which has well-defined earlywood-latewood boundaries generates many AEs at low strain and there is greater variation in the shape of the AE characteristic between samples. Parana pine and Douglas-fir are tested at 20 °C (12.5 % EMC). Scots pine is also stressed at 20°C (12.5%EMC), 20°C (0.7%EMC) and 80°C (0.7%EMC), to assess the effect of moisture content on AE. Values of Young's modulus, stress at failure and work of fracture for the three softwoods are compared with the AE-strain data. Although the work of fracture is related to the total AEs to failure, no direct proportionality exists between the two parameters. Finally, the AE-strain data for plywood and glass-reinforced plastic (GRP), both man-made composite materials, are compared with those of wood, the natural composite material.

Notes: Summary A reply to the note by Nimz (1981) on the occurrence of benzyl non-cyclic ether bonds in lignin.

Notes: Summary An extension is made to a previously proposed reliability-based procedure for characterizing the duration of load properties of wood. This extension provides a methodology for testing if two disjoint nominal populations of wood specified by modulus of elasticity have significantly different time to failure distributions at a given applied stress. This extension has practical application in the assignment of grades to structural lumber and in determining the dependence of time to failure on grade, species, and size.

Notes: Summary Structural changes in spruce and aspen wood samples subjected to axial compression were examined by means of the scanning electron microscope. For comparison, macroscopic model experiments were carried out on tube-shaped samples made of paper so as to represent segments of fibriform xylem cells. The results show that there are fracture patterns characteristic of wood in general and others characteristic of the species of wood. The phenomena characteristic of wood in general are prevalent at the cellular level and in the fracture behaviour of the cell wall layers and perforations. The characteristics of the various species of wood dominate at the level of the growth rings and are decisively influenced by the composition and arrangement of the tissues. The model experiments show that the failure morphology of the individual cells of the xylem may be explained to some extent by their geometry.

Notes: Summary In order to elucidate a previously reported discrepancy in the ratio of the lignin concentration in the middle lamella to that in the secondary wall as determined by ultraviolet (UV) microscopy and bromination combined with EDXA, the ultraviolet absorptivity of the lignin and the lignin reactivity towards bromination were compared for black spruce wood (Picea mariana Mill.). In addition, UV microscopy and EDXA techniques were applied to the determination of lignin distribution in the tracheids in order to establish the relationship between the two techniques. The results indicated that, although the ultraviolet absorptivity in different morphological regions is essentially the same, the secondary wall lignin was 1.70 times more reactive towards bromination than the middle lamella lignin. By applying the value of 1.70 as a correction to the EDXA results, the estimated lignin distribution by EDXA was in fairly good agreement with that from UV microscopy.

Notes: Summary Aspen wood was ball milled for times as long as 10 days. The change in wood morphology was examined in the ultraviolet microscope. The accessibility of the milled wood to cellulase was also determined. Soon after the commencement of the milling, part of the wood took on a characteristic appearance in which the cell wall material was completely broken down. The proportion of this disordered wall material (DWM) increased with increased time of milling. The accessibility to cellulase increased with the proportion of DWM produced by the milling.

Notes: Summary The movements of branches or control stem girdled white pine (Pinus strobus L.) were analyzed using beam theory. The stresses generated in the compression wood (CW) produced bending moments to counter the added bending moments due to new branch growth. The branches on the treated trees produced additional CW after untreated trees stopped elongation and diameter growth. The intensity of the stresses in this additional CW was greater than in the other CW. Thus, branches on treated trees moved up vertically well beyond their initial orientation due to both more CW and more active CW. The branches on untreated trees all deflected downward as branch weight continued to increase after CW production stopped.