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June 1, 2005
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The internal transcribed spacer (ITS) of the nuclear ribosomal DNA (rDNA) of the main fungal species causing wood rot damages in European buildings was amplified by the polymerase chain reaction (PCR). After sequencing the ITS, fungus-specific oligonucleotide primers were designed for taxon-specific priming PCR. These DNA marker molecules were suitable for the differential diagnosis of the Dry rot fungus, Serpula lacrymans , the Wild merulius, S. himantioides , the Oak polypore, Donkioporia expansa , the Brown cellar fungus, Coniophora puteana , the Broad-spored white polypore, Antrodia vaillantii , the Sap polypore, Tyromyces placenta , and the Yellow-red gill polypore, Gloeophyllum sepiarium . Each specific marker identified isolates of its respective target species. Cross reaction with ‘foreign’ fungi was the exception. Species detection from rot samples in buildings was possible, since DNA from contaminating organisms does not response to the marker molecules. The diagnosis was rapid, since preceding fungal pure cultures, special DNA extraction/purification and restriction by endonucleases are not required.
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This paper presents results of a study on the chemical nature of kiln brown stain (KBS) that develops in kiln dried radiata pine ( Pinus radiata D. Don) sapwood. KBS is a chocolate brown discolouration which develops approximately 0.5 mm under the timber surface. Stain free radiata pine was achieved during drying trials on “green” radiata pine sapwood which had been treated to extensive cold and hot water extraction. Differences in chemical composition between the sap and hot water extract were observed. Chemical analyses (of the water-soluble extracts) by a combination of chromatographic and spectroscopic techniques, demonstrated that carbohydrates, cyclitols, amino acids, protein, and phenolics were the main compound classes present. The presence of reducing sugars (glucose and fructose) and amino acids (glutamic acid) in the sap and hot water extracts support the theory that Amadori-Maillard type reactions significantly contribute to the formation of colour in KBS. Furthermore, lignin was also detected and is suspected to contribute to KBS formation. The relative contributions of colour formation to KBS intensity from either phenolics or Maillard-Amadori mechanisms is unknown.
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June 1, 2005
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The microdistribution of copper and zinc in the cell walls of spruce wood treated with water borne copper chloride, ammoniacal copper octanoate, ammoniacal zinc octanoate and with copper carboxylates dissolved in an organic solvent was studied using transmission electron microscopy with X-ray microanalysis. The highest content of copper and zinc was measured in cell corners and middle lamellae, that is in the constituents with the highest proportions of lignin. The same feature was observed also in the case of copper carboxylates dissolved in white spirit. On the basis of these results it was presumed that, within wood, lignin functional groups are preferential adsorption sites for transition metal ions irrespective of the carrier solvent.
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X-ray diffraction (XRD) technique was used to analyze qualitatively and semi-quantitatively solid crystal deposits in wood treated with some preservatives. Chromated copper arsenate type-C (CCA), copper ethanolamine (Cu-EA), copper naphthenate (Cu-N), copper dimethyldithiocarbamate (CDDC) and boric acid treated southern pine was investigated. The solid deposit in post-treatment steamed Cu-N and Cu-EA treated wood samples was identified as cuprous oxide (Cu 2 O) by using XRD. The presence of CDDC crystals was observed in CDDC treated wood samples. The XRD pattern of boric acid treated wood shows that crystalline boric acid is present in the treated wood. After washing boric acid treated wood with distilled water, the crystalline signal of boric acid disappeared. An XRD technique was also developed to semi-quantify the amount of solid crystals in post-treatment steamed Cu-N treated and CDDC treated samples. It was estimated that about 50% of cupric copper was converted to cuprous oxide (Cu 2 O) in Cu-N treated wood after post treatment steaming whereas no cuprous oxide was found in non post-treatment steamed Cu-N treated samples. The CDDC content determined by XRD was consistently 10–20% lower than the value calculated from the copper content using atomic absorption spectroscopy (AAS) analysis.
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June 1, 2005
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The effects of steaming were studied on Walnut wood from a hybrid ( Juglans nigra 23 × J. regia ) tree in terms of wood colour and phenolic composition. Wood samples were subjected to treatments at 75, 100 and 125°C for 4, 8, 16 and 24 hours. Colour changes were measured in the CIELCh colour system and phenolics were characterized and quantified by means of HPLC. Steaming mainly resulted in a darkening of wood tissues. Colour changes increased as temperature increased from 75 to 125°C. Lightness L* gradually decreased from 0 to 24 h at 75°C, whereas with higher temperatures, most of the darkening occurred within the first 4 hours of exposure. Contrast in colour, between sapwood and heartwood in particular, could be reduced by steaming at 125°C. The best steaming treatment, leading to a colour of steamed sapwood close to that of natural heartwood, was at 100°C/16 h. Hydrojuglone glucoside (HJG), ellagic and gallic acid derivatives (E1, E2 and G respectively) were gradually degraded by steaming, whereas a new flavonol (F) and oxidation products (OP) increased. Relationships between wood colour and phenolic content are discussed.
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June 1, 2005
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A suite of four samples of xylem tissue from Ginkgo ( Ginkgo biloba L. ) shoots grown in a medium containing coniferin 13 C-labeled at differing side-chain carbon atoms were studied using thermal and chemical degradation methods in combination with molecular-level isotopic analyses. The aims of the study were threefold: (1) to verify conclusions drawn from Nuclear Magnetic Resonance experiments previously performed on the same tissue samples, (2) to investigate degradation mechanisms and (3) to quantify the proportion of labeled material in each sample. Isotopic analysis of specific degradation products revealed the presence of the label exclusively within lignin-derived (phenolic) products and that the label is retained in its original position on the side-chain. These two results clearly indicate that there is no “scrambling” of carbon atoms as a result of thermal or chemical degradation, and thus lend strong support to analytical pyrolysis and chemolysis as viable approaches for structural investigations of the lignin macromolecule. Indeed, the isotopic enrichment of specific degradation products provides new evidence for certain types of linkages within the lignin polymer. The distribution and isotopic composition of the degradation products also strongly suggest an origin from newly-formed lignin as opposed to DHP-type products or unreacted substrate. As such, the data provides added confidence in the selective labeling approach for elucidation of the structure and biosynthesis of lignin. Isotopic mass balance calculations reveal that certain pyrolysis and CuO oxidation products show enhanced labeling which may be indicative of preferential incorporation of their specific precursors into the growing lignin macromolecule or heterogeneous lignin deposition.
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June 1, 2005
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The morphological features of Langmuir-Blodgett (LB) films of pure lignin extracted from sugar cane bagasse and composites of lignin and cadmium stearate have been investigated using atomic force microscopy (AFM). Results indicated that despite the non-amphiphilic nature of lignin and associated relatively poor stability and transferability of the lignin monolayer, the surface of the film is smooth at the micron level and comparable to that of LB films from typical amphiphilic compounds. Distinct domain structures from lignin and cadmium stearate could be visualized in the composite LB film even in one monolayer thick LB films. The mean surface roughness increases with increasing numbers of layers.
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A direct and rapid method for determining the average molecular weight (MW) and content of lignin and hemicelluloses in spent cooking liquor by high performance size-exclusion chromatography (HPSEC) using a cartridge glass column and 2.5 mM NaOH as an eluent was developed. A Uv 290 detector in line with a RI detector was applied to characterise lignin and hemicelluloses, respectively, from liquor during the kraft cooking of grey and black alder wood. During the main delignification stage, the concentration of high-MW wood components in liquor changed through the maximum. The MW values of hemicelluloses in the liquor decreased to DP n = 30 ± 5 and DP w = 55 ± 5. The M̄ n and M̄ w of lignin in spent kraft cooking liquor during the main and final delignification stages did not exceed 3000 and 5000, respectively.
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June 1, 2005
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Aspen wood ( Populus tremula ) as sawdust was chemically modified through a two-step procedure: esterification with maleic anhydride and subsequent oligoesterification with glycidyl methacrylate and maleic anhydride. Chemical analyses and infra-red spectroscopy revealed the differences in the chemical composition and structure of wood as a result of this treatment. These changes were also reflected by a hygroscopicity test and thermal analyses such as thermogravimetry and thermomechanical analysis. The esterified wood showed an increased hygroscopicity and a decreased thermal stability compared to unmodified wood. In contrast, the oligoesterified wood demonstrated a reduced hygroscopicity and a comparable thermal stability up to about 200°C. The thermomechanical analysis of oligoesterified wood clearly showed a significant softening phenomenon in the range 80–140°C, a direct evidence of the thermoplastic properties gained by this chemical modification.
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Aspen wood ( Populus tremula ) as sawdust was chemically modified through a two-step procedure: esterification with maleic anhydride and subsequent oligoesterification with glycidyl methacrylate and maleic anhydride. Simplified techniques consisting of impregnation by immersion followed by thermal treatment using conventional or microwave heating were employed. Chemical analyses and infra-red spectroscopy showed some differences in the chemical composition and structure of the resulting oligoesterified wood depending on the synthesis technique. However, the thermoplastic properties, clearly revealed by thermomechanical analysis, were quite similar and comparable to those exhibited by the oligoesterified wood resulting via classical synthesis. Moreover, similar degrees of chemical modification were obtained for a significantly shorter duration of the process when microwave heating was employed instead of conventional heating.
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June 1, 2005
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The effect of hydrostatic pressure on the density, the ultrasonic velocities and the microstructure of spruce and cherry wood has been studied. Generally speaking, under hydrostatic pressure wood becomes less heterogeneous and less anisotropic than natural wood. In spruce, crushing and buckling of the thin-walled cells in the earlywood takes place. This also has the effect of disrupting the medullary rays, which assume a zig-zag path through the structure. Cherry has a much more homogeneous structure, and the main effect of the hydrostatic pressure is compaction of the vessels by buckling of the walls. The fibres are scarcely affected by the treatment. The width of the earlywood zone decreased after the application of pressure by 26% in spruce, and by 11% in cherry. The average density was increased by the hydrostatic pressure by 26% for spruce and by 46% for cherry. The densitometric profile of spruce demonstrates significant changes following the pressure treatment, with the minimum density D Min increasing and the maximum density D Max decreasing. For cherry, the densitometric profile is shifted rather uniformly towards higher densities, and the annual ring profile is spatially slightly compacted but otherwise similar to that of untreated wood. The anisotropy of wood (expressed by the ratio of acoustic invariants) decreased by 56% for spruce and by 33% for cherry. The structural damage in spruce is predominantly found in the radial (R) direction, and this corresponds to a reduction of 73% in the velocity of the longitudinal ultrasonic waves in the radial direction, V RR . In cherry, the structural damage is mainly in the transverse, T direction. The velocity of the longitudinal ultrasonic waves in the transverse direction, V TT is reduced by 44%. The medullary rays in cherry seem to be the most important anatomical feature influencing the propagation of ultrasonic waves.
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June 1, 2005
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A new resin system was developed by reacting liquefied wood with various epoxy compounds. Examination of the optimum conditions for the synthesis of the resins, and the behavior of liquefied wood in the cured resins were undertaken. Generally, the compatibility and film forming performance of liquefied wood/epoxy resins became better as the wood content increased. The presence of only one broad dispersion peak, due to the glass transition, was observed during dynamic mechanical measurement of resin films suggesting that the different components of the resin were compatible. The glass transition temperature of the cured resins could be modified by changing the kinds of epoxy compounds and the wood contents of liquefied wood. The presence of rubber elasticity at higher temperatures suggests that the resin systems consisted of cross-linking polymer networks.
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The presence of formaldehyde ( 4 ) in solutions of cellulose in N -methylmorpholine- N -oxide (NMMO, 1 ) has been shown by trapping formaldehyde as dimedone adduct 8 in a two-phase system. o -Dichlorobenzene was used as an inert solvent to extract the trapping product as soon as it had formed. Morpholine is a degradation product of NMMO and is always present in systems containing NMMO. Formaldehyde can react with morpholine to form an intermediate carbenium-iminium ion, N -(methylene) morpholinium ( 6 ). The occurrence of 6 in the system cellulose/NMMO was demonstrated by trapping this intermediate in a Mannich type reaction with 2-acetonaphthone ( 9 ). Both formaldehyde and N -(methylene)morpholinium cations are highly reactive species readily undergoing further reactions with nucleophiles. These processes might contribute to the observed discoloration of the reaction mixture, and might also be responsible for the decomposition of NMMO that is inducible by carbenium-iminium ions.
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June 1, 2005
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Creep compliance curves in the radial compression were measured under steam for sugi ( Cryptomeria japonica D. Don) at temperatures up to 200°C. The creep compliance curves for 30 min (I) and those with pre-steaming for 30 min (II) were well connected at 30 min when the structural changes due to the degradation of hemicelluloses or the decomposition of lignin as well as hemicelluloses occurred. However, the creep curves (I) at 30 min differed markedly from creep curves (II) when the structural changes due to the increase in regularity of crystalline lattice spacing of the microfibrils or the formation of cross-linkages between the cell wall polymers occurred. It was concluded that two kinds of structural changes could be detected well by creep measurement.
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