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1.	Bengtsson, Charlotte, et al. (author) Bending creep of high-temperature dried spruce timber 2003 In: Holzforschung. - 0018-3830 .- 1437-434X. ; 57:1, s. 95-100 Journal article (peer-reviewed)abstract In this paper, bending creep test results from high-temperature (HT) dried Norway Spruce timber are presented. The results are compared with creep tests of conventional low-temperature (LT) dried timber. The HT drying was performed at 115°C and the LT drying was performed at 70°C. The creep tests were performed in a varying climate with 20°C and 30–90% relative humidity. A total number of 24 specimens, 45 × 70 × 1100 mm, were loaded in bending during approximately 240 days. Both the HT-dried and the LT-dried material were cut from the same four trees to have as equal raw material as possible for the two drying methods. The results show smaller bending creep deformations of HT-dried timber (approximately 30%) as compared to the LT-dried timber. The variation in magnitude of creep for HT-dried timber was equal to or smaller than for LT-dried timber. Additionally, the variation in deformation between the moisture cycles was smaller for HT-dried timber. These observations indicate a less pronounced mechano-sorptive effect for HT-dried timber. The free shrinkage in the grain direction was significantly smaller for the HT-dried material than for the LT-dried material.
2.	Bengtsson, Peter, 1974-, et al. (author) Evaluation of hydrocarbon emissions from heart- and sapwood of Scots pine using a laboratory-scale wood drier 2004 In: Holzforschung. - : Walter de Gruyter. - 1437-434X .- 0018-3830. ; 58:6, s. 660-665 Journal article (peer-reviewed)abstract The subject of study is the emission of Volatile Organic Compounds (VOC) during the drying of wood. Heartwood and sapwood from Scots pine were dried at different temperatures (50, 70 and 90°C) in a laboratory kiln. The sampling method, Solid Phase Microextraction was used to collect the different volatile organic compounds during the drying. The gas chromatograph and mass spectrometer was used to identify and quantify the organic matter. The total hydrocarbons were measured with a flame ionization detector. Primarily, different monoterpenes were released during the drying process. 3-carene and α-pinene were most common and were also analytically quantified. The diterpene, pimaral, was found in an estimated large amount in the later stage of the drying process but was not exactly quantified. Large differences in both release behaviour and total amount of released hydrocarbon between heart- and sapwood were obtained. Emissions of VOC from heartwood were of a magnitude approximately three times higher than that from sapwood.
3.	Blom, Åsa, et al. (author) Durability of Untreated Norway Spruce (Picea abies) Exposed Outdoors Above Ground for Nine Years. 2004 In: Holzforschung. - 0018-3830 .- 1437-434X. ; 58:2, s. 167-172 Journal article (peer-reviewed)abstract Moisture dynamics and durability during weather exposure as affected by origin and production method were studied for nine years on 113 untreated spruce samples. The moisture content was measured on 67 occasions. The weight loss was determined for each sample at the end of the sampling period. The most important factors, affecting both moisture content and weight loss, were origin and drying technique. The samples originating from central Sweden had the best durability, followed by the southern stand, while the northern stand had the lowest durability in terms of weight loss. Airdrying had a negative impact on the performance of samples from all three stands, but to different degrees. Samples from the northern stand were most sensitive to airdrying, in terms of both weight loss and moisture content, followed by the southern stand, while the central stand was least sensitive. Why the samples from the northern stand were more sensitive to airdrying and showed the largest weight losses is unknown; it can only be suggested that the origin of the wood can be of importance for the durability.
4.	Carlsson, Peter (author) Distributed optimization with a two-dimensional drying model of a board, built up by sapwood and heartwood 2001 In: Holzforschung. - 0018-3830 .- 1437-434X. ; 55:4, s. 426-432 Journal article (peer-reviewed)abstract Optimization with distributed computing is performed on a two-dimensional orthotropic drying model which allows boards with arbitrary outtake of the log and sapwood/heartwood distribution in the cross section. Drying schedules with an optimized variation of temperature and humidity which yields minimized drying time are created at the same time as moisture, stress and deformation levels are considered. A numerical example with distributed computing of a board with a mixture of sapwood and heartwood is presented. Drying starts from the fibre saturation point.
5.	Durbeej, Bo, et al. (author) A density functional theory study of coniferyl alcohol intermonomeric cross linkages in lignin – three-dimensional structures, stabilities and the thermodynamic control hypothesis 2003 In: Holzforschung. - : Walter de Gruyter. - 0018-3830 .- 1437-434X. ; 57:2, s. 150-164 Journal article (peer-reviewed)abstract Density functional theory methods are utilized to investigate structural features and stabilities of the most common lignin dimerization products. It is found that intra-molecular hydrogen bonding acts as a stabilizing force in the lowest-energy conformer(s) of several different dimeric lignin structures. Furthermore, the calculations show that the hypothesis of thermodynamic control of monolignol dimerization accounts for some of the results obtained in experimental studies aimed at determining the ratios of intermonomeric linkages. A quantitative correlation between experimentally observed ratios and calculated relative energies cannot, however, be pointed out.
6.	Durbeej, Bo, et al. (author) Formation of β-O-4 lignin models – a theoretical study 2003 In: Holzforschung. - : Walter de Gruyter. - 0018-3830 .- 1437-434X. ; 57:5, s. 466-478 Journal article (peer-reviewed)abstract The formation of two different β-O-4 lignin models is investigated by means of density functional calculations. It is found that the coupling of two coniferyl alcohol radicals forming a quinone methide proceeds by an energy barrier of ~2–5 kcal/mol, and that the associated reaction energy is negative by more than 20 kcal/mol. On the basis of the corresponding results obtained for the coupling of a coniferyl alcohol radical to a coniferyl alcohol, it is argued that the resulting radical, albeit being formed in an energetically less favourable process, might play an important role in lignin polymerisation. Finally, two different reaction mechanisms for the conversion of a quinone methide into a guaiacylglycerol-β-coniferyl ether dilignol through the addition of water are explored.
7.	Durbeej, Bo, et al. (author) Spin distribution in dehydrogenated coniferyl alcohol and associated dilignol radicals 2003 In: Holzforschung. - : Walter de Gruyter. - 0018-3830 .- 1437-434X. ; 57:1, s. 59-61 Journal article (peer-reviewed)
8.	Elustondo, Diego, et al. (author) Estimation of green moisture content distribution in hemfir timber by stochastic simulation 2004 In: Holzforschung. - 0018-3830 .- 1437-434X. ; 58:4, s. 413-417 Journal article (peer-reviewed)abstract This paper describes an improved stochastic model designed to simulate systems, such as green timbers, that cannot be analyzed as a unit but as a collection of a large number of similar components. The stochastic model provides a piecewise green moisture content frequency distribution curve by using nondestructive measurements such as of timber weight. A new, relatively simple two-parameter function was designed to describe the log-normal moisture concentration distribution above the fiber saturation point, and the parameters of this function were determined by fitting the experimental timber weights with the results of the stochastic model. The simulated green moisture content distributions showed good agreement with the experimental data for Pacific coast hemlock (hemfir) timbers, thus providing a piece of information that is indispensable for applying stochastic simulation to industrial drying of timbers.
9.	Elustondo, Diego, et al. (author) Non-deterministic description of wood radio frequency vacuum drying 2003 In: Holzforschung. - 0018-3830 .- 1437-434X. ; 57:1, s. 88-94 Journal article (peer-reviewed)abstract A numerical method is proposed to predict the stochastic dispersion of data that unavoidably occurs in a real drying process. The method is based on the use of discrete frequency distribution curves to predict a random variation on some parameters of the process and is applied to the case of radio frequency vacuum (RFV) drying of wood. Experimental data of RFV drying of western hemlock timbers were used to obtain the numeric values of the stochastic parameters and their standard deviation. A mathematical model was designed to simulate the final moisture content dispersion on hypothetical examples. Results were quantified using three indices: average, range and standard deviation.
10.	Gellerstedt, Göran, et al. (author) Bleachability of alkaline pulps - Part 1. The importance of beta-aryl ether linkages in lignin 2000 In: Holzforschung. - 0018-3830 .- 1437-434X. ; 54:6, s. 609-617 Journal article (peer-reviewed)abstract Analytical and structural studies were done on different types of alkaline pulps and their isolated residual lignins. Although having the same degree of delignification after cooking, some pulps were easier to bleach than others. All isolated residual lignins were found to contain beta -aryl ether (beta -O-4) structures in reasonable amounts when analysed by thioacidolysis (greater than or equal to 10% of the native lignin value). At decreasing kappa numbers, there was also a corresponding decrease in the amount of beta -aryl ether structures in the residual lignin. Moreover, a high beta -aryl ether content in the unbleached residual lignin after cooking was found to contribute to a better bleachability of the pulp, especially when hydrogen peroxide stages were involved. At the same degree of delignification, the superior bleachability of alkaline sulfite pulps over kraft pulps was shown to be attributable to a higher content of beta -aryl ether linkages in the further type of pulps.
11.	Hafrén, Jonas, et al. (author) Formation of 13C-enriched cell-wall DHP using isolated soft xylem from Picea abies 2002 In: Holzforschung. - 0018-3830 .- 1437-434X. ; 56:6, s. 585-591 Journal article (peer-reviewed)abstract Cell-wall dehydrogenation polymers (CW-DHP) were prepared by incubating a mixture of soft xylem (differentiating xylem) from Picea abies, coniferin 13C-enriched at the side-chain β-carbon and unenriched coniferin, both with and without the addition of β-glucosidase and glucose oxidase, which causes an in situ polymerisation of the coniferyl alcohol in the cell wall. From difference solid state 13C-NMR spectra between 13C-enriched CW-DHP and unenriched CW-DHP, the bond frequencies involving specifically 13C-enriched carbon can be quantitatively determined. The sub-structures in CW-DHP prepared without the addition of β-glucosidase and glucose oxidase showed more similarity to protolignin than CW-DHP prepared with the addition of extraneous enzymes. The CW-DHP obtained without the addition of enzymes contained 36% β-O-4-derived sub-structures, 44% combined β-β, β-5 and β-1 sub-structures and 20% coniferyl alcohol/coniferaldehyd end groups. After acetone/water extraction of the CW-DHP, the content of β-β, β-5 and β-1 structures decreased by 4%, and the β-O-4 dominating peak increased by 4%. The 13C-enriched CW-DHP material can be used to study lignin reactions in a solid wood matrix, and is also a powerful system for detailed studies on in vivo lignification mechanisms and the effects on lignification conditions on lignin structure.
12.	Hafrén, Jonas, et al. (author) Ultrastructural changes in the compound middle lamella of Pinus thunbergii during lignification and lignin removal 2000 In: Holzforschung. - 0018-3830 .- 1437-434X. ; 54:3, s. 234-240 Journal article (peer-reviewed)abstract The structure of the middle lamella in Pinus thunbergii has been studied by the rapid-freeze deep-etching (RFDE) technique in combination with transmission electron microscopy (TEM). The ultrastructure of the compound middle lamella was studied in the early phases of the development of woody tissue in the cambial and differentiating xylem, before the heavy incrustation with lignin had occurred. Lignified middle lamella in the xylem was studied both directly and after delignification. It was found that the structure of the unlignified middle lamella in the cambium/developing xylem consists of a fine irregular network probably containing pectin and hemicellulose. As a result of lignin incrustation, the middle lamella becomes increasingly dense and the surface structure of the fully lignified middle lamella appeared to be compact and partly covered with globular structures. After delignification of the lignified middle lamella a thin network with a different structure was revealed. This network probably mainly consists of hemicellulose. No microfibrils of the type that occurs in the primary and secondary walls were found in the middle lamella.
13.	Hogberg, N., et al. (author) Identification of Serpula lacrymans and other decay fungi in construction timber by sequencing of ribosomal DNA - A practical approach 2004 In: Holzforschung. - 0018-3830 .- 1437-434X. ; 58:2, s. 199-204 Journal article (peer-reviewed)abstract We have approached species identification of wood decay fungi in construction wood by means of sequencing ribosomal DNA. Sequencing of the Internal Transcribed Spacer (ITS), which includes the 5.8S rDNA, is straightforward and provides a basis for species identification. Identification was either by BLAST search on sequences in GenBank or phylogenetic analysis. A number of important wood decay fungi such as Serpula lacrymans, S. himantioides, Antrodia serialis, A. sinuosa, Gloeophyllum sepiarium, Fomitopsis pinicola, Resinicium bicolor and Junghuhnia collabens have been successfully identified from fruitbodies and directly from wood samples. Sequence variants were found within the species sampled including S. himantioides, the close relative of S. lacrymans. But, among 27 samples from fruitbodies and mycelium of S. lacrymans, unexpectedly, no sequence variation was detected.
14.	Jernkvist, L.O., et al. (author) Experimental determination of stiffness variation across growth rings in Picea abies 2001 In: Holzforschung. - 0018-3830 .- 1437-434X. ; 55:3, s. 309-317 Journal article (peer-reviewed)abstract The radial and tangential deformations in a single growth ring of Norway spruce, which was subjected to moderate tensile loading in its radial direction, were measured by use of digital speckle photography. From the measured displacement field, the transverse coefficients of elasticity ER, ET, GRT and vTR we determined with respect to radial position in the growth ring. As a result of the abrupt change in stiffness from latewood to earlywood in the growth ring, it was possible to establish all four coefficients solely from the radial tension test. The elastic modulus ET was found to be a factor 15 larger in latewood than in early wood, whereas the corresponding variation for ER was merely a factor 3. The measured variations were in reasonable agreement with predictions from simple two-dimensional honeycomb models of the growth ring cellular structure.The average elastic moduli of the growth ring were found to be twice as large as ER and ET measured in conventional tests on macroscale specimens, whereas the reverse was true for the shear modulus. An explanation to these differences is sought by analysing the loading conditions and deformation behaviour of macroscale specimens used in transverse stiffness testing of wood.
15.	Josefsson, T., et al. (author) Steam explosion of aspen wood. Characterisation of reaction products 2002 In: Holzforschung. - 0018-3830 .- 1437-434X. ; 56:3, s. 289-297 Journal article (peer-reviewed)abstract The steam explosion process was used to separate the components of aspen wood. The main goal was to obtain a material with a molecular weight distribution similar to that of dissolving pulp. To achieve variations in fibre structure and molecular weight, two series of steam explosions were made in which the time and temperature were varied according to factorial designs. The resulting pulps were very dark and were therefore bleached with hydrogen peroxide. The bleaching was sufficient to increase the brightness of the exploded material significantly The resulting lignocellulosic materials as well as the washing water were characterised by carbohydrate analysis. lignin analysis and size-exclusion chromatography. A large variation in the pulp composition as well as in cellulose and hemicellulose molecular weight was obtained merely by varying the time and temperature of the explosions. The results showed that pulps with properties ranging from a high xylan content (7%) and high molecular weight cellulose (900 000) to a low xylose content (<1%) and low molecular weight cellulose (<40 000) were produced. The exploded material consisted mainly of cellulose, hemicellulose and degraded polysaccharides. The degraded polysaccharides showed up as lignin in the Klason lignin analysis and in measurements of kappa number.
16.	Lawoko, Martin, et al. (author) Changes in the lignincarbohydrate complex in softwood kraft pulp during kraft and oxygen delignification 2004 In: Holzforschung. - 0018-3830 .- 1437-434X. ; 58:6, s. 603-610 Journal article (peer-reviewed)abstract Three kraft pulps in the kappa number range between 50 and 20 and the same pulps oxygendelignified to similar lignin contents (kappa approximately 6) were analyzed for lignincarbohydrate complexes (LCC) by a method based on selective enzymatic hydrolysis of the cellulose, and quantitative fractionation of the LCC. Between 85 and 90% of residual lignin in the unbleached kraft pulp and all residual lignin in the oxygendelignified pulps were isolated as LCC. Three types of complexes were found; viz., xylanlignin, glucomannanligninxylan and glucanlignin complexes. After pulping to a high kappa number, most of the residual lignin was linked to xylan. Different delignification rates were observed so that most of the residual lignin was linked to glucomannan when the pulping was extended to a low kappa number. With increasing degree of oxygen delignification, a similar trend in the delignification rates of LCC was observed so that the residual lignin was increasingly linked to glucomannan. Complex LCC network structures seemed to be degraded into simpler structures during delignification. The differences in delignification rates are discussed with reference to the solubility properties and structural differences of LCC, and to morphological aspects of the pulp.
17.	Lawoko, M., et al. (author) Hemicellulase activity of aerobic fungal cellulases 2000 In: Holzforschung. - 0018-3830 .- 1437-434X. ; 54:5, s. 497-500 Journal article (peer-reviewed)abstract Cellulases isolated from Trichoderma reesei and Phanerochaete chrysosporium were screened for hemi-cellulolytic, pectinolytic and cellulolytic activity using locust bean mannan, birchwood xylan, citrus fruit pectin and carboxymethylated cellulose (CMC) as substrates. The purpose of this work was to choose appropriate enzymes to include in a miniature cellulase system with minimal hemicellulase activity for the preparation of lignin-carbohydrate complexes (LCCs). The endoglucanases showed CMC activity whereas activity towards the substrate was not detected for the CBHs. Xylanase activity was observed for EG I and EG 38 whereas mannanase activity was observed for EG 44. None of the enzymes degraded pectin. The results suggest that CBH I, CBH II, CBH 58, EG II and EG III are good candidates for the effective preparation of LCCs. The possible biological function for the hemicellulolytic activity of cellulases is discussed.
18.	Lawoko, Martin, et al. (author) New method for the quantitative preparation of lignin-carbohydrate complex from unbleached softwood kraft pulp : Lignin-polysaccharide networks I 2003 In: Holzforschung. - 0018-3830 .- 1437-434X. ; 57:1, s. 69-74 Journal article (peer-reviewed)abstract A new method for the quantitative preparation of pulp representative lignin-carbohydrate complexes (LCC) has been developed, in which LCC has been systematically prepared at quantitative yield, fractionated and qualitatively determined. At least 90% of residual lignin in softwood kraft pulp is proposed to be chemically bonded to carbohydrates. A major part of LCC (92%) in softwood kraft pulp was observed between lignin, xylan and glucomannan, whereas a minor part (8%) was linked to cellulose. Half of the hemicelullosic LCC is a lignin-glucomannan complex. The other half is lignin-xylan complex and xylan-lignin-glucomannan complex. Thus, part of the residual lignin in softwood kraft pulp crosslinks xylan and glucomannan. The proposed linkages are of covalent type. At most 10% of the residual lignin is not bonded covalently to carbohydrates.
19.	Molin, Ulrika, et al. (author) Effects of refining on the fibre structure of kraft pulps as revealed by FE-SEM and TEM : Influence of alkaline degradation 2004 In: Holzforschung. - 0018-3830 .- 1437-434X. ; 58:3, s. 226-232 Journal article (peer-reviewed)abstract The aim of the study was to evaluate the effect of refining on the ultrastructure of spruce pulp fibres. Pulps with different molar masses of cellulose (estimated as intrinsic viscosity) were studied after PFIrefining. The molar masses of the polymers were decreased by increases in alkali concentration during pulping. Fibre surface structures were examined using Field Emission Scanning Electron Microscopy (FESEM) and Transmission Electron Microscopy (TEM) was used to observe changes in the internal structure of the fibres. Pulps with lower (125 and 329 ml g-1) intrinsic viscosity showed more damaged during refining than pulps with higher (620 and 1120 ml g-1) intrinsic viscosity. Observations showed pulps with lower intrinsic viscosity to have large decreases in fibre length after refining. Fibres with low intrinsic viscosity (i.e., 125 ml g-1) had less primary wall and S1 layer remaining and the external fibrillation and damage of the S2 layer had increased. The S2 wall of fibres with high intrinsic viscosity showed characteristic delamination. Similar delamination was not visible for fibres with low intrinsic viscosity.
20.	Norgren, Magnus, et al. (author) Dissociation of phenolic groups in kraft lignin at elevated temperatures 2000 In: Holzforschung. - : Elsevier BV. - 0018-3830 .- 1437-434X. ; 54:5, s. 519-527 Journal article (peer-reviewed)abstract The dissociation of the phenolic groups in a polydisperse, low molecular weight kraft lignin (Indulin AT) was studied in alkaline aqueous solutions in the temperature interval 21-70 degrees C, using a UV-spectrophorometric method. It was found that at a constant concentration of hydroxide ions, the degree of dissociation was decreasing when the temperature was elevated. Dissociation curves and apparent pK(0) values were also calculated for the polydisperse sample at the same conditions, using the van't Hoff and the Poisson-Boltzmann equations. At degrees of dissociation exceeding alpha approximate to 0.4, the outcome of the theoretical approach showed to be in good agreement with the experimentally obtained results. Furthermore, calculations were performed for different molecular weights of kraft lignin and from this it was found that the apparent pK(0) is shifted to higher values by increasing molecular weight, due to an increased electrostatic attraction of the hydrogen ions, which is arising from a less curved surface. Predictions of the dissociation behavior at temperatures reached in the kraft process were performed and under these conditions, higher molecular weight lignin fragments seem never to reach the point of complete dissociation. It was also found that an increase in temperature results in phase separation in kraft lignin solutions with high ionic strengths and pH values close to the pK(a) of the phenolic groups.
21.	Norgren, Magnus, et al. (author) Dissociation of Phenolic Groups in Kraft Lignin at Elevated Temperatures. 2000 In: Holzforschung. - 0018-3830 .- 1437-434X. ; 54:5, s. 519-527 Journal article (peer-reviewed)abstract The dissociation of the phenolic groups in a polydisperse, low molecular weight kraft lignin (Indulin AT) was studied in alkaline aqueous solutions in the temperature interval 21-70°C, using a UV-spectrophotometric method. It was found that at a constant concentration of hydroxide ions, the degree of dissociation was decreasing when the temperature was elevated. Dissociation curves and apparent pK0 values were also calculated for the polydisperse sample at the same conditions, using the van't Hoff and the Poisson-Boltzmann equations. At degrees of dissociation exceeding α ≈ 0.4, the outcome of the theoretical approach showed to be in good agreement with the experimentally obtained results. Furthermore, calculations were performed for different molecular weights of kraft lignin and from this it was found that the apparent pK0 is shifted to higher values by increasing molecular weight, due to an increased electrostatic attraction of the hydrogen ions, which is arising from a less curved surface. Predictions of the dissociation behavior at temperatures reached in the kraft process were performed and under these conditions, higher molecular weight lignin fragments seem never to reach the point of complete dissociation. It was also found that an increase in temperature results in phase separation in kraft lignin solutions with high ionic strengths and pH values close to the pKa of the phenolic groups.
22.	Norgren, Magnus, et al. (author) Physico-chemical characterization of a fractionated kraft lignin 2000 In: Holzforschung. - 0018-3830 .- 1437-434X. ; 54:5, s. 528-534 Journal article (peer-reviewed)abstract A kraft lignin was leached from a softwood pulp and fractionated by ultrafiltration. The fractions were characterized in respect to phenolic group content, molecular weight distributions and self-diffusion coefficients. The H-1-Pulsed Field Gradient (PFG) NMR self-diffusion measurements and the High-Pressure Size Exclusion Chromatography (HPSEC) analysis of the fractions, were seen to correlate fairly well. From the self-diffusion measurements, the mass-weighted median hydrodynamic radii of the diffusants in the fractions, were calculated assuming spherical fragments. Furthermore, the content of phenolic groups in the fractions, was found to decrease by increasing hydrodynamic radius and molecular weight, but the calculated median surface charge densities of the macromolecules, were determined to be constant in the range of oligomers up to at least 65 structural units.
23.	Onnerud, H., et al. (author) Inhomogeneities in the chemical structure of hardwood lignins 2003 In: Holzforschung. - 0018-3830 .- 1437-434X. ; 57:3, s. 255-265 Journal article (peer-reviewed)abstract Bauer-McNett fractions of an aspen chemi-thermomechanical pulp showed a significant variation with respect to lignin content and sugar composition, and two of the fractions were found to be particularly rich in middle lamella and secondary wall material, respectively. The secondary wall lignin of aspen was found to contain larger amounts of non-condensed beta-O-4 aryl ether structures than the middle lamella lignin and the difference was attributed to a larger amount of syringyl structures as revealed by thioacidolysis. Size exclusion chromatography of the thioacidolysis products from birch and spruce wood showed a larger part of lignin oligomers being present in the degraded spruce lignin. Moreover, birch lignin had a lower phenolic content than both aspen and spruce lignin. Thioacidolysis followed by Raney-nickel desulphuration was used for the analysis of hardwood lignin trimers.
24.	Onnerud, H., et al. (author) Inhomogeneities in the chemical structure of spruce lignin 2003 In: Holzforschung. - 0018-3830 .- 1437-434X. ; 57:2, s. 165-170 Journal article (peer-reviewed)abstract Thioacidolysis, periodate oxidation and size exclusion chromatography (SEC) were used for the analysis of spruce lignin samples. The standard thioacidolysis method was modified by including a pre-swelling of the lignocellulosic sample before the reaction, and this gave a higher yield of monomer products. Middle lamella and compression wood lignin was found to contain a larger amount of oligomers after thioacidolysis than normal wood lignin. Analysis by thioacidolysis of a thermomechanical pulp (TMP) revealed that approximately 10% of the beta-O-4 structures in the lignin were cleaved due to the mechanical grinding effect. From kraft pulp, the mixture of thioacidolysis products contains a major fraction having a considerably larger molecular mass than the products from spruce wood and TMP. The structure of this material is still unknown.
25.	Onnerud, H., et al. (author) Investigation of lignin oligomers using electrospray ionisation mass spectrometry 2003 In: Holzforschung. - 0018-3830 .- 1437-434X. ; 57:1, s. 37-43 Journal article (peer-reviewed)abstract Electrospray ionisation Fourier transform ion cyclotron resonance mass spectrometry (MS) and size exclusion chromatography (SEC) was utilised for analysis of milled wood lignin (MWL) and lignin model compounds degraded by thioacidolysis. MS and SEC showed that thioacidolysis was an efficient method for degradation of the beta-O-4 bond in lignin. Moreover, the molecular weight of thioacidolysed pinoresinol and MWL were analysed using matrix assisted laser desorption ionisation time-of-flight mass spectrometry. Tandem MS was successfully applied for the structural determination of thioacidolysed pinoresinol with and without acetylation of the product. The MS results of thioacidolysis on MWL resulted in the identification of a tetrameric lignin structure containing a 5-O-4,5-5, beta-1 linkage pattern.
26.	Parkås, Jim, et al. (author) Solid state NMR analysis of β-13C-enriched lignocellulosic material during light-induced yellowing 2001 In: Holzforschung. - 0018-3830 .- 1437-434X. ; 55:3, s. 276-282 Journal article (peer-reviewed)abstract Photoyellowing of lignocellulosic materials has been studied with a new technique based on solid state 13C-NMR analysis of 13C-enriched DHP in cell wall tissue. The selectively 13C-enriched cell wall-dehydrogenation polymer (CW-DHP) was prepared directly on differentiating xylem from spruce (Picea abies) at pH 6.0 by administering β-13C-enriched coniferin in an enzymatic system consisting of glucose oxidase, β-glucosidase, and the naturally occurring water-insoluble enzymes remaining in the cell wall. The bonding pattern of the formed CW-DHP was found to be: 42% β-β, β-5, and β-1 substructures; 36% β-O-4 derived substructures; and 22% coniferyl alcohol and coniferaldehyde end-groups. The 13C-NMR analysis of unirradiated and irradiated tissue revealed a decrease in the relative amount of coniferaldehyde and/or coniferyl alcohol end-groups during irradiation. Prolonged irradiation also introduced new signals centered at 37, 70, and 102 ppm. The results indicate that the present technique, with the formation of DHP in a naturally lignifying carbohydrate environment, has the potential of being a valuable tool for the study of structural changes of lignin during light-induced yellowing.
27.	Roost, C., et al. (author) Structural changes in residual kraft pulp lignins. Effects of kappa number and degree of oxygen delignification 2003 In: Nordic Pulp & Paper Research Journal. - : Walter de Gruyter GmbH. - 0283-2631 .- 2000-0669. ; 18:4, s. 395-399 Journal article (peer-reviewed)abstract Softwood kraft pulps in the kappa number range of approximately 10-50 were prepared in the laboratory. On subsequent oxygen delignification using single or double oxygen stages, the conditions were chosen such that all pulps reached a similar kappa number. As a consequence, different brightness values were obtained after the oxygen stage. The darker pulps were found to require considerably more hydrogen peroxide to reach full brightness (89% ISO). On selected pulps, the content of phenolic hydroxyl groups and the general structural features of the residual lignin were determined by periodate oxidation and 2D NMR respectively. It was found that the number of phenolic groups increased as a function of cooking time and that oxygen delignification led to a decrease which was related to the severity of the oxygen stage. Furthermore, a continuous decrease in the number some of the major lignin inter-unit linkages was found to occur during the cooking stage. After the oxygen stage, however, an apparent increase in the number of these linkages was observed in some of the pulp lignins. These results are discussed with reference to the known features of residual lignins in kraft pulps and an attempt is made to rationalize the structural changes that occur during pulping and oxygen delignification.
28.	Rosenkilde, Anders (author) Measurement of moisture content profiles during drying of Scots pine using magnetic resonance imaging 2004 In: Holzforschung. - 0018-3830 .- 1437-434X. ; 58:2, s. 138-142 Journal article (peer-reviewed)abstract Moisture content profiles with high spatial pixel resolution, 21 µm, were measured in Scots pine heartwood while drying from wet conditions to near equilibrium in the surface layer, (0–300 µm). The measuring technique used was Magnetic Resonance Imaging. In order to obtain magnetic resonance profiles with a high pixel resolution at both high and low moisture contents, a highg-radient permanent magnet was used. The results presented show one-dimensional moisture content profiles and mean moisture content development in the surface layer. In Scots pine heartwood, almost flat moisture content profiles were observed when the moisture content was above the fibre saturation level. When the mean moisture content in the surface layer decreases to the fibre saturation level, gradients start to build up from the surface towards the bulk of the sample although the bulk moisture content is far above the fibre saturation. Furthermore, the results presented in this study imply that a dry shell forms in the surface layer shortly after drying has begun. This dry shell controls the drying rate until the mean moisture content in the bulk decreases to the fibre saturation level.
29.	Stehr, M., et al. (author) An investigation of the crack tendency on wood surfaces after different machining operations 2000 In: Holzforschung. - 0018-3830 .- 1437-434X. ; 54:4, s. 427-436 Journal article (peer-reviewed)abstract A hypothesis describing tip-crack generation during different machining operations on sapwood of pine surfaces and the differences between the pith side and bark side were investigated. The goal was to determine whether initial tip-cracks are generated already during the machining operation, before weathering. The evaluation of the results showed that about 10 Ic of the annual rings on the pith side and about 1 % of the annual rings on the bark side have cracks after the machining operation. A theoretical analysis of an idealised model using the finite element method (FEM) has also been carried out to investigate the tendency for growth of short initial tip-cracks during a simulation of the compression of a wood piece in a conventional planing operation. The analysis seems to confirm that there is a greater risk for cracks on the pith side than on the bark side.
30.	Terashima, Noritsugu, et al. (author) Nondestructive analysis of lignin structure by NMR spectroscopy of specifically 13C-enriched lignins : Part 1. Solid state study of ginkgo wood 2002 In: Holzforschung. - 0018-3830 .- 1437-434X. ; 56:1, s. 43-50 Journal article (peer-reviewed)abstract Guaiacyl-type lignin is the major component of ginkgo lignin. Specific 13c-enrichment of α, β and γ-carbons of the guaiacylpropane side chains was achieved by administration of coniferin-[α13C], coniferin-[β-13C] and coniferin-[γ13C], respectively, to growing stems of ginkgo trees. Unenriched coniferin was administered as a control. The xylem tissues containing specifically 13C-enriched lignins or unenriched lignin were subjected to analysis by solid state NMR. Subtraction of the spectrum of tissue containing unenriched lignin from the spectra of tissues containing 13C-enriched lignins gave difference spectra exclusively assigned to the enriched side chain carbons of intact protolignin in the cell walls. From the signal intensities determined under quantitative conditions and an estimate of corresponding standard uncertainties, the percentage ranges of the major inter-unit lignin bonds originating from the β-carbon of the coniferin precursor were estimated to be: β-O-4/α-O-R (R = H, polysaccharides or lignols) including β-OH, 53% to 57%; combined β-5, β-β and β-1, 32% to 36%; coniferaldehyde end groups, 2% to 4%; and coniferyl alcohol end groups, 4% to 6%.
31.	Wadenback, J., et al. (author) Variation in content and composition of lignin in young wood of Norway spruce 2004 In: Holzforschung. - 0018-3830 .- 1437-434X. ; 58:2, s. 107-115 Journal article (peer-reviewed)abstract Lignin content and composition are important traits in several tree breeding programs, but very little is known about their natural variation. This study compares the lignin content in 1-yearold plants and 9-yearold trees of Norway spruce belonging to the same fullsib families. It is shown that the lignin content, according to the modified acetyl bromide method, does not vary significantly within or among the different fullsib families either as plants or as young trees. There is, however, on average 4.0% higher lignin content (31.4% versus 27.4%) and lower standard error for the trees than for the plants. The number of C9-units/g(-1) lignin, analyzed by thioacidolysis, ranges from 516 to 1186 mummol C9-units/g(-1) lignin in plants and from 716 to 953 mumol C9-units/g(-1) lignin in trees, with no significant differences among the families. However, the extent of change in C9-units/g(-1) lignin varies among the families with age. The ratio of erythro and threo stereoisomers does not vary significantly among the families. However, the ratio changes differently with age among the families similar to the C9-units g(-1) lignin. Additionally, the content of phydroxyphenyl (H) lignin is 0.6% higher in the trees than in the plants (1.4% versus 0.8%), estimated indirectly from GCMS data by a novel subtractive technique, indicating a higher degree of compression wood in the young trees. In conclusion, the amount and composition of lignin does not vary within or among the families at the same age. However, the amount of lignin increases with age while the change in lignin composition varies between family and age.
32.	Wålinder, Magnus, 1965-, et al. (author) Measurement of wood wettability by the Wilhelmy method - Part 2. Determination of apparent contact angles 2001 In: Holzforschung. - 0018-3830 .- 1437-434X. ; 55:1, s. 33-41 Journal article (peer-reviewed)abstract This work focuses on the determination of apparent contact angles on wood by the Wilhelmy method. In this method, the force acting on an object is measured during a test cycle involving immersion in and withdrawal from a probe liquid. Fresh and aged veneers of extracted and non-extracted heart- and sapwood of pine were investigated. The results indicate that wicking of the probe liquids. into and along the porous wood veneers, occurs during the test cycles and that this strongly affects the determination of contact angles. It is suggested that two different wicking phenomena occur. First, when the veneer contacts the liquid, an instantaneous 'initial wicking' occurs. It is suggested that this initial wicking is influenced primarily by the liquid density and structural properties of the specimen (such as porosity and sur face roughness), and not by surface energetics. An initial wicking constant was therefore estimated for the different veneer samples based on measurements in octane. Second, after the initial wicking, a continuing 'secondary wicking' is observed. In some cases. this may result in zero contact angle after a certain immersion depth. Contact angles should, therefore, be estimated from the initial part of the immersion, where the secondary wicking can be neglected. This may also reduce any contamination of the probe liquids by extractives. The Wilhelmy method stems to be a valuable tool for estimating the wetting properties of wood, permitting reproducible measurements of apparent contact angles provided that there is efficient control of wicking and contamination effects.
33.	Carlsson, Peter, et al. (author) Optimization of a violin top with a combined laminate and honeycomb model of the wood material 2003 In: Holzforschung. - 0018-3830. ; 57:1, s. 101-105 Journal article (peer-reviewed)abstract Stochastic optimization with the simulated annealing method (SA) is performed on a violin top made of Norway spruce (Picea Abies). A numerical example is presented which shows that it is possible, through changes in thickness variables, to compensate for changes in vibration properties caused by a variation in the material parameters in the top. A material model is also presented for the blank which considers the influence of density variations in the annual rings, the cellular structure of wood and reinforcement from the wood rays.
34.	Durbeej, Bo, et al. (author) A density functional theory study of coniferyl alcohol intermonomeric linkages in lignin - three-dimensional structures, stabilities and the thermodynamic control hypothesis 2003 In: Holzforschung. - 0018-3830. ; 57:2, s. 150-164 Journal article (peer-reviewed)
35.	Durbeej, Bo, et al. (author) Formation of β-O-4 lignin models - a theoretical study 2003 In: Holzforschung. - 0018-3830. ; 57:5, s. 466-478 Journal article (peer-reviewed)
36.	Jönsson, Johan, et al. (author) A contact free measurement method to determine internal stress states in glulam 2004 In: Holzforschung. - 1437-434X. ; 58:2, s. 148-153 Journal article (peer-reviewed)abstract A method to determine the internal stress state across the grain of glued laminated wood (glulam), as well as the experimental equipment for measuring released deformation are described in this paper. The internal stress state is calculated from measured released deformations, which are measured by a contact free method based on a digital camera technique. Nondestructive measurement of the modulus of elasticity in the crossgrain direction is presented and the correlation between dynamic and static modulus of elasticity is shown. Results for a single specimen with induced moisture gradient show that the largest stress found in the tests was about 0.57 MPa, which is higher than the characteristic value of tensile strength perpendicular to the grain. This stress is based on released strain over the total length of the slices cut from the specimens. FEMsimulations evaluating the stress distribution within the specimen to account for end effects indicate that the maximum stress is about 30% higher.
37.	Jönsson, Johan (author) Internal stresses in the cross-grain direction in glulam induced by climate variations 2004 In: Holzforschung. - 1437-434X. ; 58:2, s. 154-159 Journal article (peer-reviewed)abstract Results are presented from an experimental investigation to determine internal stress states perpendicular to grain in glulam induced by moisture variations. The stresses are determined by measuring the released strains before and after cutting. Stress distributions are determined for specimens seasoned in constant humidity, specimens exposed to an artificial single climate change, specimens exposed to cyclic climate change and for specimens exposed to natural climate outdoors under shelter. Results for seasoned specimens show that internal stresses exist in glulam without the presence of moisture gradients. Stresses in specimens with an induced moisture gradient become larger when moistening from a specific climate A to another climate B than when drying from B to A. Tests in an outdoor sheltered climate show large variations in strains and stresses. The tensile stress level in the inner part of the glulam cross section exceeds the characteristic strength of 0.5 MPa during a period of approximately 80 days.
38.	Lawoko, M, et al. (author) Hemicellulase activity of aerobic fungal cellulases 2000 In: HOLZFORSCHUNG. - : WALTER DE GRUYTER & CO. - 0018-3830. ; 54:5, s. 497-500 Journal article (peer-reviewed)abstract Cellulases isolated from Trichoderma reesei and Phanerochaete chrysosporium were screened for hemi-cellulolytic, pectinolytic and cellulolytic activity using locust bean mannan, birchwood xylan, citrus fruit pectin and carboxymethylated cellulose (CMC) as
39.	Mörling, Tommy, et al. (author) A method to estimate fibre length distribution in conifers based on wood samples from increment cores 2003 In: Holzforschung. - 0018-3830. ; 57:3, s. 248-254 Journal article (peer-reviewed)abstract We propose a method to estimate fibre length distribution in conifers based on wood samples from increment cores processed by automatic optical fibre-analysers. Automatic fibre-analysers are unable to distinguish: a) fibres from other tissues, “fines”, and b) cut from uncut fibres. However, our proposed method can handle these problems if the type of distributions that fibre lengths and fines follow is known. In our study the length distributions of fines and fibres were assumed to follow truncated normal distributions, characterised by means and standard deviations of the two distributions. Parameter estimates were obtained by the maximum likelihood method. Wood samples from two 22-year-old Scots pine trees at breast height were used to evaluate the performance of the method. From stem discs at 1.5 m, adjacent samples of 5 mm increment cores and wood pieces were taken. The cores were trimmed 1 mm at each side and samples were, after maceration, analysed in a Kajaani FiberLab 3.0. The results showed that the method works well and gives a possibility to distinguish fine and fibre length distribution.

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