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June 1, 2005
Abstract
Within the genus Coniophora , C. puteana and the less common species C. marmorata , C. arida and C. olivacea form a group of domestic brown-rot fungi (“cellar fungi”), which cause considerable decay in the woodwork of buildings. The fungi are difficult to distinguish by their fruit bodies. Traditional methods fail to identify species in a pure culture. Also with regard to decay of wood in use, the basidiomes rarely develop, and the surface mycelium on wood is sparse except for the fine dark strands. Thus, molecular techniques were applied to obtain a reliable method for differentiation and detection and to aquire a greater knowledge of the domestic Coniophora species. Isolates obtained from decayed wood and from culture collections and identified as domestic Coniophora species were used. The internal transcribed spacer (ITS) of the ribosomal DNA was amplified by polymerase chain reaction, sequenced and restricted by the endonuclease Ta qI. The ITS sequences characteristic of C. puteana, C. arida, C. marmorata and C. olivacea were obtained and entered into the international databases. The sequence size ranges from 525 to 729 bp. The data supplement our collection of ITS sequences from domestic wood decay fungi built for the characterization of mycelium in culture. Most isolates belong to C. puteana and some to C. arida, C. marmorata and C. olivacea . Two other isolates belong to a further Coniophora species close to C. olivacea . Obviously, at least five Coniophora species occur within European buildings. Many of the isolates were not correctly identified. Consequently, the traditional characterization methods used, viz. , growth rate, temperature influence and wood weight loss, were less suitable for the differentiation of Coniophora species as formerly anticipated.
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June 1, 2005
Abstract
Seasonal variation of the volatile terpenoids of Pinus pinea Ten and Pinus halepensis Mill, infested and uninfested by the caterpillar Marchalina hellenica , was followed by GC and GC-MS analyses of the pines cortical oleoresin. α-Pinene was found to be the dominant monoterpene in P. halepensis , while in P. pinea limonene was the most abundant compound. A significant decrease in the number of identified volatiles from winter to summer was observed and was more pronounced in the minor metabolites. Variation of the terpenoids according to the depth of the draining (drilling) holes in the trees was also determined. In addition, terpenoids were correlated with the results of cross feeding experiments designed for the study of the host preference of M. hellenica . All results revealed the dependence of M. hellenica on the secondary chemistry of the host. P. pinea , having a high content of limonene, appears to be more resistant to the caterpillar. Canonical discriminant analysis, in the discriminant space of the relative contribution of the ten major terpenes, separated P. pinea from P. halepensis , and infested from uninfested P. halepensis trees.
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June 1, 2005
Abstract
The effect of Trametes hirsuta laccase on isolated spruce wood lignans was evaluated. Lignans were isolated from the heartwood of spruce branches and treated with different laccase dosages and treatment times. The effect of the treatment was monitored by gas chromatography, size exclusion chromatography and ionization difference UV spectroscopy. Lignans were efficiently oxidized by T. hirsuta laccase. About half of the phenolic groups present in lignans remained intact during the treatment. The oxidation of phenolic groups in lignans produced oligomeric structures containing approximately 4–5 lignan units ( i.e. , 8–10 phenyl propane units). Precipitation of the formed oligomeric structures probably prevented further polymerization.
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June 1, 2005
Abstract
Cell-wall dehydrogenation polymers (CW-DHP) were prepared by incubating a mixture of soft xylem (differentiating xylem) from Picea abies , coniferin 13 C-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 13 C-NMR spectra between 13 C-enriched CW-DHP and unenriched CW-DHP, the bond frequencies involving specifically 13 C-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 13 C-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.
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June 1, 2005
Abstract
Six nonphenolic β-0-4 lignin models substituted on the phenyl A-ring [unsubstituted; 3,5-dimethoxyl; 3,4-dimethoxyl; 3-methoxyl; 4-methoxyl; and 4-methyl] were synthesized and the alkaline hydrolysis rates at 170°C determined. Electron-withdrawing substituents enhanced the hydrolysis rate, but this effect was relatively minor. Over 90% of the disappearance of the dimer could be accounted for by appearance of the B-ring phenolic product for all compounds, which suggests that minimal side reactions occurred.
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June 1, 2005
Abstract
Bleached pulps were obtained from a Eucalyptus grandis peroxyformic/formic acid chemical pulp using oxygen, hydrogen peroxide, photosensitizers (methylene blue, Fe (II) 4,4′,4″,4‴-tetrasulfophthalocyanine, hemin, hematoporphyrin) and/or TiO 2 . Residual lignin of unbleached pulp, isolated and characterized by size exclusion chromatography, 31 P NMR and thioacidolysis, was used to study the photochemical reactions occurring during the bleaching process. The main reactions were conversion of phenolic aromatic units into carboxylic acids and cleavage of the β-O-4 ether bonds leading to a depolymerization of the lignin framework into smaller fragments.
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June 1, 2005
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4-Ethylguaiacol is a phenolic model compound used to study the oxidation of lignin. A new method was developed to determine 4,4′-diethyl-6,6′-biguaiacol, an unwanted side-product, in the oxidation of 4-ethylguaiacol. The sample is extracted with ethyl acetate to separate 4,4′-diethyl-6,6′-biguaiacol from the water-soluble oxidation catalyst. No other treatment is required before analysis with a standard UV-Vis spectrophotometer. The spectrophotometer is calibrated to measure concentrations of 4,4′-diethyl-6,6′-biguaiacol up to 0.3 mM. With the new method, the concentrations of 4,4′-diethyl-6,6′-biguaiacol can be reliably determined over a wide alkaline pH range. The performance of the method was demonstrated in experiments investigating the formation of 4,4′-diethyl-6,6′-biguaiacol in the autoxidation and cobalt-sulphosalen catalysed oxidation of 4-ethylguaiacol. In the conditions of the studies (1 bar oxygen pressure and 50°C), a low (0.01 mM) concentration of Co-sulphosalen clearly increased the total conversion of 4-ethylguaiacol. However, relative to autoxidation, the conversions achieved in the presence of the catalyst were just as sensitive to pH, and the yields of the undesired dimeric product, 4,4′-diethyl-6,6′-biguaiacol, were higher.
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June 1, 2005
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In modern structural analysis of complex mixtures of wood polysaccharides, methylation analysis is still a valuable and powerful tool for linkage analysis. In this paper, methylation analysis is described for the procedure methylation, methanolysis, silylation and GC/MS. The retention time indexes for the partly methylated methyl glycosides of the relevant wood polysaccharides are listed together with the ratios of the isomers of the different structural units. A calculation model for relative molar response factors is suggested based on a published model for FID detection and on experimental data. Tested for oligosaccharides of known structure including xylotetraose, mannotriose and 6 3 , 6 4 -α-D-galactosyl-mannopentaose, the model gives reproducible and sufficiently correct results. The fate of xylose units substituted with 4- O -methyl glucuronic acid at position 2 is investigated with a model compound.
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June 1, 2005
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The surface chemistry of Eucalyptus grandis wood pulp fibres was investigated using the sessile drop apparent contact angle, XPS and TOF-SIMS techniques. Pulp fibres were studied using different chemical pulping conditions. The pulping affected the surface coverage of lignin and extractives, as indicated by XPS, and the work of adhesion with water, as estimated from contact angle determinations. The amount of surface lignin decreased while surface extractives and work of adhesion with water increased in relation to the amount of active alkali used in the pulping. Desorption and analysis of surface extractives by TOF-SIMS showed sterols, fatty acid calcium and sodium salts. After acetone extraction the spectra obtained by TOF-SIMS showed changes. However, calcium and sodium salts of fatty acids were still detected, indicating their resistance to solvent extraction. This resistance to extraction can affect the lignin and extractive surface coverage estimations using XPS due to the contribution of the carbon content after extraction. The extent of interference was, however, uncertain.
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June 1, 2005
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A phenolic β-O -4 type lignin model compound, guaiacylglycerol- β -guaiacyl ether, was treated with 70 wt % aq 1,4-butanediol solution at 180°C to investigate the delignification mechanism under high-boiling solvent (HBS) pulping conditions. Thirteen compounds including four monomers, six dimers, two trimers and a tetramer were isolated from the reaction products. Most of these products were generated by recombination of phenoxy radicals formed by homolysis of the β -aryl ether. The results suggest that phenolic β-O -4 linkages in lignin are cleaved homolytically (radical mechanism) via quinone methide intermediates under HBS pulping conditions.
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June 1, 2005
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Pinus radiata sapwood stakes were treated with ellagic acid and tetraguanidinium, tetracholine and tetrakis-benzyltrimethylammonium ellagates. The effect of these treatments upon moisture movement and uptake was investigated by wick action. Given that chemical reactions within the wood substrate between nutrients and treatment solutions may alter the properties of the wood with regard to moisture movement, the presence of Cu 2+ in the system was also examined. Water-soluble ellagates reduced water loss by 25–35%, but had no effect upon water uptake. Ellagic acid in N -methylpyrrolidone significantly reduced both water loss and moisture uptake. The effect of Cu 2+ upon moisture movement and uptake in the treated stakes was negligible.
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June 1, 2005
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The influence of heat and loading time on the mechanical properties of Calamus merrillii Becc. was evaluated by measurement of dynamic Young's modulus and creep compliance at different temperature settings. Young's modulus decreased steadily as temperature was elevated. Creep compliance, on the other hand, increased steadily with loading time, similar to wood. Compliance rates were more or less the same at all temperature settings except for one particular temperature which deviated extremely from the rest. This temperature indirectly represents the softening temperature. Reduction in strength caused by heat was highly influenced by the cellular composition of the stem as well as the sensitivity of its basic chemical constituents, e.g., hemicellulose content, to heat. Knowing this basic behavior of rattan stems will enable manufacturers to design rattan products more efficiently.
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June 1, 2005
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Thermal modification of wood produces a wood material with many interesting properties, such as enhanced dimensional stability, lower equilibrium moisture content and increased biological durability. Changes in the chemical structure of pine ( Pinus sylvestris ) caused by thermal treatment were investigated by studying various components of wood using 13 C CPMAS NMR spectroscopy. Electron spin resonance (ESR) spectroscopy on the same set of samples was used to study the formation and stability of free radicals formed during the treatment. The most remarkable changes revealed by solid state NMR were the increase in relative crystallinity of cellulose and destruction and deacetylation of hemicelluloses. Changes in the lignin fraction were mostly registered as diminishment in the methoxyl content, although the intensity of the aromatic region increased relative to the carbohydrate fraction during the treatment. Increase in the intensities of the ESR signals from thermally treated wood samples proves the formation of stable free radicals. In addition, radical formation is believed to take part in condensation reactions leading to crosslinks within the lignin and possibly between lignin and other wood components. Both of the methods used indicate that the changes are most remarkable when the treatment temperature is over 200°C.
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June 1, 2005
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The temperature and frequency spectra of dielectric constant ε′ and dielectric loss factor ε″ of Sikkim spruce ( Picea spinulosa Griff.) were measured to investigate the change in dielectric relaxation of water in wood during desorption. In order to control the rate of moisture content change, the measurements were carried out in three steps: from fiber saturation point to 80% RH, from 80% RH to 60% RH and from 60% RH to 20% RH, at 25°C. Two dielectric relaxation processes were observed in different temperature and frequency regions which changed their position and strength with the desorption process. Using the ε′ and ε″ spectra, two groups of Cole-Cole plots were obtained, on which basis two groups of dielectric parameters including the static dielectric constant ε S , optic dielectric constant ε ∞ , relaxation strength (ε S –ε ∞ ), and the relaxation time distribution coefficient α were calculated. Both groups of parameters showed similar trends, that is, ε ∞ remained nearly constant during the whole desorption process. ε S and (ε S –ε ∞ )changed little during the first step of desorption, decreased obviously during the second step and declined slightly during the third step. The α value obtained from the lower frequency data changed significantly during the second and third desorption steps, while there was little change in the other group of α values. These differences can be explained by different mechanisms of the relaxation processes in the lower and higher frequency regions.
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June 1, 2005
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The growing concern for the environment and occupational health aspects have led to the development and use of waterborne coatings for architectural applications. These coatings can be considered as a two-phase system with the binder emulsified or dispersed in the water phase. During film formation, phase separation occurs and coating additives can be mobilised and transported into wood, thus changing wood moisture sorption characteristics. In the present study, wood samples were treated with various coating additives, normally used in waterborne coatings, and exposed to various humid conditions. The moisture adsorption and desorption in the treated wood samples was compared to untreated wood samples. It is shown that the presence of substances common in waterborne coatings changes the moisture sorption characteristics of wood. The presence of a surfactant, nonylphenol ethoxyphenoxylate adduct, and the presence of a rheology modifier, hydroxyethyl cellulose, lower the rate of moisture absorption and, to a great extent, delay the release of moisture during desorption. Due to the fact that these substances occur in waterborne coatings, may be mobilised during and after film formation and accumulate at the coating/substrate interface, there is a great probability that these substances change the moisture sorption characteristics of the wood substrate in an unfavourable way and create unexpected moisture conditions at the coating/wood interface.
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June 1, 2005
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To study wood fracture on its cellular level, small tensile specimens of pine ( Pinus sylvestris [L.]) were fractured in situ in tension inside the chamber of an ESEM (Environmental Scanning Electron Microscope). Fractured surfaces of macroscopic tensile test specimens were also studied with an ESEM. The same kind of fracture phenomena were observed in both small and large specimens. The in situ tests proved to be reproducible and the results revealed typical fracture propagation0 directions and order in softwood under longitudinal tension. The gradual change of material properties of wood in the radial direction was found to strongly influence the fracture process.
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