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October 7, 2005
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June 1, 2005
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This paper reports on the use of yeast as biological control agents against mould and blue-stain fungi in laboratory-based Pinus sylvestris sapwood wood block incubation tests. All 5 yeast isolates tested significantly reduced discolouration of wood surfaces by moulds and most were also effective against staining fungi. The 2 most promising yeast isolates also significantly reduced radial growth of selected mould and stain fungi in vitro solely through the liberation of volatile compounds. Five bacterial isolates were also tested for antagonism toward mould and stain fungi and were effective biological control agents in wood block tests. Again, volatile production alone by the bacteria was shown to be sufficient to significantly reduce fungal growth in vitro . Most of the bacteria and yeasts significantly reduced wood discolouration by fungi when inoculated onto block surfaces 7 days before, or at the same time as the target fungi, and in some cases even when inoculated 7 days after the fungi. The possibility of using yeasts as biological control agents to prevent wood spoilage during kiln drying and short-term storage at sawmills is considered.
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June 1, 2005
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To investigate the mechanisms by which the isopod Limnoria tolerates copper, chromium and arsenic when tunnelling CCA-treated wood in the marine environment, digestive caecae of specimens of L. quadripunctata from CCA-treated and untreated Pinus sylvestris sapwood were examined using transmission electron microscopy (TEM) and energy dispersive X-ray detection (EDX). Copper-containing granules were found to be present in the small cells of the digestive caecae (midgut) of Limnoria from both treated and untreated wood. However, individuals tunnelling treated timber contained a greater number of granules, with six types of morphology being distinguished of which only two were present in Limnoria from untreated wood. The presence of copper-containing granules in Limnoria from untreated timber may be explained by the ability of this isopod to acquire and store copper from seawater for use in enzymes and blood pigments. The increased number of copper granules in individuals tunnelling treated wood was believed to result from elevated levels of this element in the food substrate. This ability to store copper allows these organisms to tolerate this metal in the wood substrate and may explain how this organism is able to attack CCA-treated wood in service. No chromium, or arsenic, was detected in the digestive caecal cells.
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June 1, 2005
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We have examined chromated copper arsenate (CCA) wood preservative fixation at two selected temperatures in seven common North American hardwood species: red maple ( Acer rubrum L.), white birch ( Betula papyrifera Marsh.), yellow poplar ( Liriodendron tulipifera L.), trembling aspen ( Populus tremuloides Michx.), red oak ( Quercus rubra L.), basswood ( Tilia americana L.) and American beech ( Fagus grandifolia Ehrh.). The softwood red pine ( Pinus resinosa Ait.) was included for comparison. CCA component fixation was monitored by the expressate method at both 21°C and 50°C under non-drying conditions. Hexavalent chromium (CrVI) and total Cr, Cu and As contents of the expressate were determined at different times during fixation. Based on CCA fixation results it was possible to divide the examined hardwoods into a fast fixing group (beech, red oak and red maple), intermediate group (white birch and red pine) and slow fixing group (aspen, yellow poplar and basswood). The variable fixation rates for the different species could not be directly related to different anatomical and chemical attributes of the studied hardwoods, although there was an apparent relationship with density with more dense species fixing faster than low density species. However, the species differences appeared to be mainly influenced by types and amounts of extractives in the woods. In red maple, extraction resulted in a slowing of the fixation rate, while the opposite effect was seen in red oak.
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June 1, 2005
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Medium density fibreboards consisting of blends of the naturally durable wood species white cypress pine ( Callitris glaucophylla ) and non-durable wood species were manufactured in a commercial plant and subjected to a bioassay using the subterranean termite species, Coptotermes lacteus . A board composed of 30% cypress pine, 30% slash pine ( Pinus elliottii ) and 40% of the naturally durable hardwood species spotted gum ( Corymbia maculata ) was also manufactured and bioassayed against C. lacteus . The aims were to determine (i) whether boards containing cypress pine possessed increased resistance to termite attack compared to a control manufactured entirely from non-durable wood species; (ii) the relationship between the cypress pine content of boards and their resistance (if any) to termite attack; (iii) whether the termite resistance of boards containing cypress pine could be further enhanced by the addition of spotted gum fibre. There was an inverse relationship between the cypress pine content of MDF specimens and mass losses of the specimens during the bioassay; the percentage mass losses of specimens containing 11.4, 16.2 and 34.2% cypress pine being 20.3, 13.4 and 8.8%, respectively, compared to 32.8% for the control, which consisted of non-durable slash pine (80%) and hoop pine ( Araucaria cunninghamii ) (20%) fibre. There was strong evidence that the inverse relationship between the cypress pine content of boards and mass losses during the bioassay was linear, although a statistically significant quadratic (curvilinear) effect was also apparent. The addition of spotted gum fibre to boards did not increase their resistance to termite attack. Cypress pine heartwood contains a variety of extractives that are either toxic or repellent to termites, and the increased termite resistance of MDF containing cypress pine compared to the control is probably due to the insecticidal effect of such chemicals on C. lacteus . The incorporation of cypress pine fibre into MDF shows promise as an alternative to chemical biocides for increasing the resistance of MDF to termites. However, the response of termites to heartwood extractives varies between species, and therefore further experimentation is needed to test the resistance of MDF containing cypress pine fibre to attack by greater range of wood destroying termites under test conditions that more closely simulate field conditions.
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June 1, 2005
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Fossil samples of Pinus sylvestris found near Siena (Tuscany, Italy) in geological formations 2–3 million years old were chemically examined in order to solve the problem of the contrast between the age of geological formations and their good degree of preservation. Comparison with a living Pinus sylvestris was carried out on standard wood component analyses, cation exchange capacity and residual terpene content. The analyses of wood components were close to those of the reference pine, whilst the cation exchange capacity values showed remarkable changes. The increase of salt carboxyls suggested the hydrolysis of ester carboxyls originally present, whilst the reduction of total carboxyls revealed a partial loss of hemicelluloses. Both changes were attributed to the percolation of salt-bearing water through the wood, thus causing ester hydrolysis, carboxyl salification and hemicellulose solubilisation. Residual terpene analysis showed, for the first time in a terrestrial fossil, tetrahydroabietic acid which forms by disproportion of the abietic acid. The 14 C dating assigned the fossil to an age of about 18,000 years and suggested a landslide of Wurmian interglacial age occurred inside the geological formations of 2–3 million years old. Transient terpene compounds, formed in incipient diagenesis, are proposed as tracers for the assessment of particular ranges of fossil age, as previously suggested by the analyses of both a Larix decidua 14,500 years old and a Picea abies 100,000 years
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June 1, 2005
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Several chiral neolignan skeletons and a benzodioxane were prepared from a tartrate derivative with the crucial chiral aryl alkyl ether formation being accomplished with cesium phenolate and 18-crown-6. These compounds have greater than 96% enantiomeric excess, and this work represents the first successful synthetic preparation of optically active 8- O -4′ type neolignan skeletons. The chiral aryl alkyl ethers were also synthesized from several protected carbohydrates, which can serve as chiral auxiliaries for a wide variety of target molecules.
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June 1, 2005
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The possibility that preformed dehydrogenation polymer (DHP) could function as a template to induce a structural pattern in DHP more closely resembling that of natural softwood lignin was investigated by oxidizing β- 13 C-labelled coniferyl alcohol in a medium containing preformed unlabelled polymeric DHP. The experiments were performed at pH 4 and pH 6.5. 1D and 2D NMR were used to estimate the distribution of structural units. No such template effect was found in a comparison of unlabelled with uniformly labelled DHP. Indeed, the effect of pH on the coupling pattern of coniferyl alcohol was greater than the effect of the preformed DHP.
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June 1, 2005
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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 β-aryl ether (β-O-4) structures in reasonable amounts when analysed by thioacidolysis (≥10 % of the native lignin value). At decreasing kappa numbers, there was also a corresponding decrease in the amount of β-aryl ether structures in the residual lignin. Moreover, a high β-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 β-aryl ether linkages in the former type of pulps.
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June 1, 2005
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Solid state NMR spectroscopy has been used in this work to investigate crystallinity of cellulose in spruce wood before and after kraft pulping and TCF bleaching. Effects of refining of the spruce kraft pulp in water and in weak alkali have been studied by determination of the crystallinity of isolated fines and corresponding bulk fibres in order to find out whether the crystallinity in the fibre surface material and inside the fibre wall differ from each other. Also the possible effect of enzymatic endo-1,4-β-galactanase treatment on the crystallinity of some refined pulps has been investigated. It was found that the I α crystalline form of cellulose predominates over the I β form in native spruce and vice versa in all the pulps studied. In pulping part of the cellulose I α is converted to the more stable I β form mainly by heat. Any measurable changes in the degree of crystallinity or in the relative proportions of different crystalline forms of cellulose could not be seen in pulps after refining, TCF-bleaching or galactanase treatment. However, the degree of crystallinity was found to be considerably lower in the fines compared to the corresponding bulk fibres. Therefore it is suggested that the cellulose crystallinity is lower or the size of crystallites smaller on the fibre surface than inside the fibre wall. Slightly higher contents of lignin and hemicelluloses, mainly xylan and mannan, were also found in the fines compared to the bulk fibres.
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June 1, 2005
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Pulping of whole jute plant is done by sodium hydroxide and ethylenediamine (EDA) or monoethanolamine (MEA) within 1 hour of cooking. The pulp yield is considerably higher than for the control soda and kraft pulps. Pulps obtained are better in physical properties as compared to kraft and soda pulps. The apparent density of soda-EDA pulps decreases with the increase of EDA in the soda liquor whereas the apparent density of soda-MEA pulps increases with the increase of MEA in soda liquor.
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June 1, 2005
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The impregnation pattern of alkali in fresh Cottonwood is analysed. Isothermal process, medium alkali-concentration, temperature below 100°C and tangential direction are considered. The degree of deacetylation in the wood is taken as an indicator of the whole chemical action of the alkali. Profiles of alkali concentration, alkali content, liquid content and acetyl content in the wood are experimentally determined. The results show that wood behaves rather like a glassy polymeric solid placed in contact with a solvent. An advancing boundary zone is established which separates an intact inner part from the outer swollen zone. Alkali concentration and acetyl groups content profiles can approximately be described by a model used to analyse the reaction of solids: the shrinking core model. The chemical reaction in the front is the controlling mechanism. The swelling of the cell walls together with the occupation of the hollow cavities of the wood by the liquor make it possible for the wood liquid content to increase up to almost 3 g liquid g wood −1 . The procedure here adopted and the impregnation pattern proposed are valuable tools to analyse the effect of wood direction and process variables such as temperature, alkali concentration and initial wood moisture. They could also be very useful to build a model for alkaline impregnation of wood under moderate conditions.
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June 1, 2005
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The effect of hydrogen peroxide bleaching on the structure of thermomechanical (TMP) and chemothermomechanical (CTMP) wheat straw paper pulps was investigated. The results obtained by thioacidolysis indicated that the TMP treatment did not significantly affect the ß-0-4 structures of lignins whereas, the alkali conditions of sulfonation (CTMP) and bleaching induced the cleavage of the ß-0-4 bonds and an increase in the S/G ratio. Moreover, it was concluded that bleaching and sulfonation are responsible for the partial solubilisation of the p -coumaric and ferulic acid esters. The ethers of p -coumaric acid are not significantly affected by these treatments whereas, the ethers of ferulic acid are degraded, as shown by acidolysis data. These results underline the structural differences of wheat straw pulps compared to wood pulps.
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June 1, 2005
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A general analytical method based on capillary electrophoresis with indirect UV detection has been developed to separate and quantify N -methylmorpholine- N -oxide (NMMO) and its main degradation products N -methylmorpholine (NMM) and morpholine (M). The electrolyte is based on the two major components 4-methylbenzylamine and 2-hydroxy-2-methylpropanoic acid (hydroxy-isobutyric acid, HIBA), the latter being used to adjust the pH to a value below 3.5 which is crucial for the electrophoretic mobility and, thus, for a good detectability of the amine oxide. The present method is widely applicable to monitor kinetics of reaction mixtures containing NMMO. NMM and M can be determined simultaneously even in a 1000-fold excess of NMMO. To monitor the fast and exothermic thermal degradation of NMMO by the electrophoretic method, special reaction conditions had to be developed for separating the initial decomposition step from super-imposed subsequent reactions. Reactive degradation products were removed by flushing with nitrogen, and the reaction rate was decreased by dilution with o -dichlorobenzene as an inert solvent. The initial phase of the decomposition reaction has been shown to follow second-order kinetics.
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June 1, 2005
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A series of laccase-mediator treatments (LMS) with 1-hydroxybenzotriazole (HBT) and N -acetyl- Nphenylhydroxylamine (NHAA) (Fig. 1) as the mediators were performed on a laboratory prepared southern softwood conventional kraft pulp (kappa # 75.4). Subsequent to the LMS treatments, the treated pulps were subjected to various oxidatively reinforced alkaline extraction stages (E*). The kappa results suggested that both LMS HBT and LMS NHAA treatments delignified this high-kappa pulp. The E* stages were beneficial in countering the darkening effect observed after the LMS treatments. Structural changes in residual lignins isolated before and after laccase-mediator (LMS NHAA (E*) and LMS HBT (E*)) treatments were explored. The spectral analysis of phosphitylated residual lignins revealed an increase in carboxylic acid content and a depletion of phenolic hydroxyl groups in non-condensed at C-5 lignin moieties. Aliphatic hydroxyl groups were substantially decreased when NHAA was used. Overall, it appears that LMS HBT and LMs NHAA treatments on high-kappa kraft pulps primarily attack phenolic hydroxyl groups in non-condensed at C-5 lignin structures.
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June 1, 2005
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The transverse mechanical properties of the wood fibre play important roles in the use of wood and its fibres in various applications. However, the variation in properties of fibres from different parts of the tree and the relation of these properties to the structure of the fibre is not yet established. This study focuses on the variation in the transverse elastic modulus of the fibre wall and its relation to the fibril structure of the S 2 - and S 1 -layer. For this reason the local fibril angle of radial and tangential fibre walls were measured by polarisation confocal microscopy. It was shown that the variation in fibril angle of the S 2 -layer seems to have very little influence on the transverse modulus of the fibres. Instead the thickness and fibril angle of the S 1 - and thus also the S 3 -layer should contribute to the variation in transverse modulus between earlywood and transition wood fibres. The importance of the ray cells for the transverse elastic properties of the wood was also emphasised.
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June 1, 2005
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June 1, 2005
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The tangential strain on the inner bark of Cryptomeria japonica saplings grown in a growth chamber was continuously measured using strain gauges. Compression wood formation was induced by artificial inclination. The diurnal changes in tangential strain during light/dark cycles in the growth chamber differed from those observed in the field. The total strain increased daily, increasing incrementally during dark periods and decreasing in the light, as observed in the field. In the growth chamber, however, steep increases and rapid decreases in strain were found immediately following lights-off and lights-on. In the inclined saplings, the strain increased more on the lower side of the stem than on the upper side; and the increment of the strain in the dark and the decrement in the light were larger on the lower side than on the upper side. The change in tangential strain on the inner bark surface arises from changes in the volume of differentiating cells, corresponding to turgor pressure changes and cell-wall extensibility changes. Therefore, the differentiating tracheids into compression wood appear to expand at night and shrink in the daytime more than the differentiating tracheids into normal wood.
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June 1, 2005
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The acoustic properties of several chemically modified Sitka spruce samples ( Picea sitchensis Carr.) were evaluated in the longitudinal direction of wood specimens. Sitka spruce treated with glyoxal and carboxymethyl cellulose (CMC) displayed superior acoustic properties to those obtained by the other treatments. The acoustic converting efficiency (ACE) of the glyoxal-CMC treated Sitka spruce was 1.84 times of that of the untreated specimen and the specific dynamic Young's modulus (E′/r) was retained without decrement after such treatment. Changes in the tanδ of Sitka spruce treated with glyoxal and different concentrations of 1,4-butanediol were opposite. With a low concentration of 1,4-butanediol (10%), the tanδ of the treated specimen decreased as a result of the formation of crosslinked cyclic structures. The potential presence of more alkyl hydroxyl groups in the Sitka spruce, after being treated with glyoxal and a high concentration of 1,4-butanediol (20%), resulted in the increment of tanδ and the decrement of ACE. The impairment of the acoustic properties of Sitka spruce was caused by the introduction of free chains with endwise carboxylic acid groups into cell walls after the succinic anhydride treatment. Slight improvement on the ACE of Sitka spruce was achieved by the reaction with acetic anhydride and the decrease in the tanδ was about 15%, which was attributed to the partial formation of crosslinked matrix. These results revealed the improvement of the acoustic properties of chemically modified wood that was probably achieved only by the formation of network structures between wood components and reagents.
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