No description available.

Denna avhandling behandlar den svenska trähusbranschens behov och möjligheter att erhålla trämaterial med egenskaper som uppfyller de krav som produktion och slutkund ställer. Ett gemensamt problem för den svenska trähusbranschen är de kvalitetsbrister hos det virke sombranschens företag köper för sin produktion, som kan resultera i merkostnader för branschen med 100 MSEK årligen. Trähusföretagen uttrycker en viss uppgivenhet över bemötandet från virkesleverantörerna. Virkesleverantörerna å sin sida menar att köparna av trämaterial inklusive företagen i trähusbranschen i ringa utsträckning genomför reklamationer. Avgörande för genomförda virkesaffärer är ofta priset – det blir affär med den som erbjuder lägst pris. Sammantaget innebär detta att det inte blir någon dialog mellan leverantör och köpare som utvecklar synsättet på trämaterialkvalitet. Avhandlingsarbetet har bland annat behandlat beredning av träråvaran till färdiga ämnen t.ex. studier vid tillverkning av kvistfria ämnen. Resultatet av arbetet visar på vikten av att genomföra utvärderingar av material och leverantörer. Resultatet visar vidare att kapkostnaden för färdiga träämnen inkl. spill är ca 1/3 av ämneskostnaden. Dock är kostnaden för trämaterialet låg i relation till totalkostnaden för det färdiga huset vilket innebär att ett högre pris för ett virke som fullt ut motsvarar kravspecifikationerna i liten utsträckning påverkar totalkostnaden för huset. Råd till trähusbranschen är att ställa krav på virkesråvaran, utvärdera material och leverantörer samt att trähusbranschen ska sikta mot att bli en modern tillverkningsindustri i likhet med de mest framgångsrika inom verkstadsindustrin. / This thesis investigates the needs and opportunities for the Swedish wood house industry to obtain wood material with properties meeting demands of both producers and final customers. A common problem within the Swedish wood house industries is the insufficient quality of the wood material that companies purchase for their production. These flaws in quality can render an additional annual cost for the industry of approximately 10 million Euros. Wood house companies express a certain resignation regarding communication with wood material suppliers. However, timber suppliers claim that they rather receive very few complaints regarding timber quality from wood house companies and other purchasers. For a timber supplier, being able to offer an acceptable price is often a determining factor, since most deals will go to the supplier offering the lowest price. This has led to a non-existent dialogue between suppliers and purchasers regarding how to approach the wood quality issue. This study has, among other things, studied the preparation of sawn wood into finished components, for instance, the production of knotfree boards. The results illustrate the importance of carrying out evaluations of raw material and suppliers. Furthermore, results show that the cutting cost for wood components, including waste is approximately 1/3 of the total cost for ready-made components. However, in relation to the total cost of the house the timber cost is low. This means that a higher price for wood that fully meets the target specifications, will have limited impact on the total cost for the house. The wood house industry is recommended to present firm demands for a high-quality material and to evaluate material and suppliers. In addition to this, the wood house industry should aim towards becoming a modern manufacturing industry, like those most successful manufacturing industries in other fields.

Timber with its natural appearance and glass with its transparency may be appealing material for architects and users of modern buildings. Glass is a brittle material, but it is about six times stiffer than timber. Combined appropriately, the materials could form different types of composite products, e.g. beams or shear walls, that can be included in the load-carrying structure of buildings. e knowledge on load- carrying timber/glass components is limited. e intention of this research has been to contribute to the knowledge required for the industry to be willing to produce timber/glass components for the market. The thesis includes experimental testing accompanied with complementary nite element simulations, which provide more details and information about the test results. Tests were performed on small-scale specimens with a bond area of 800 mm2 as well as on I-beam and shear wall prototypes. For the small-scale specimens tested in standard climate, three different adhesives were used for the bond line between timber and glass. ese specimens were tested in both tension and shear. In addition, one of the adhesives was used for small-scale shear specimens which were exposed to different humidity levels before the tests were performed. e 4 m long I-beam prototypes designed with a web of glass and wooden anges were tested in four- point bending. e shear wall prototypes were tested by applying either a vertical load, a horizontal load or a combination of these, all being applied in the plane of the shear wall. Of the three adhesives used in the small-scale testing, an acrylate adhesive had the largest strength, both in tension and in shear. e study on the effect of humidity was performed with this adhesive. is study indicates that the adhesive properties do not change dramatically in indoor climate. is adhesive was also used for twelve of the fourteen tested I-beams. e results from the beams show that a signi cant redundancy is obtained; the load at the nal failure was around 240 % of the load when the rst crack in the glass web appeared. e shear walls were glued using the acrylate adhesive and for a few cases a 2-component silicone based adhesive. e results from the shear wall tests showed the shear wall to behave in a much more brittle manner, without any noticeable redundancy.

Wood is one of the most important products of world trade, due to its countless uses as a source of timber, fibre, and renewable energy. In addition to its economic importance, the formation of wood represents a global carbon sink which reduces the excess atmospheric CO2 that contributes to global warming. The formation of wood or xylogenesis is a complex example of cell differentiation, controlled by multiple interacting environmental factors and the coordinated expression of hundreds of genes. Genomic studies have proved a valuable tool in identifying the genes associated with xylogenesis. The expression of these genes has been shown to under strict spatial regulation in a developmental-stage specific fashion. Despite recent advances in the understanding of this process, there remains much to learn about the cellular, molecular and developmental processes involved. While the spatial regulation of wood formation has been well described, less attention has been devoted to the temporal regulation of this process. Most organisms are known to match their activities to the daily oscillation of night and day in what is known as a diurnal rhythm. A subset of these diurnal rhythms are termed circadian rhythms, and persist in the absence of environmental time cues, with a period of approximately 24 hours. Circadian rhythms are endogenous in nature, being generated by a small number of central oscillator genes, and illustrate an organism's ability to measure time. Circadian rhythms are found across a wide taxonomic spectrum, and are believed to confer an adaptive benefit, possibly due to the ability to anticipate regular changes in the external environment. As wood formation is a major sink for the products of light driven photosynthesis, it represents a likely target for circadian control in plants. A large proportion of photosynthesis genes themselves are known to be under circadian control, as are several cell wall formation genes. Most studies of temporal rhythms in plants, however, have used the herbaceous model species Arabidopsis, which does not have a woody stem. It is likely, therefore, that the circadian control of many wood formation genes remains to be discovered. We used a spotted cDNA mIcroarray carryIng 2608 elements to quantitatively measure daily changes in transcript abundance in the wood-forming tissues of a fast growing, Eucalyptus hybrid. Eucalyptus is a large genus of tree species, many of which are of great economic importance, and are widely grown in plantations for solid timber and pulp production. We found that almost ten percent of the genes on the microarray showed significant daily changes in expression (-loglOP>3.74). These genes included Eucalyptusorthologues of the Arabidopsis central clock genes CCA1 (CIRCADIAN CLOCK ASSOCIATED 1) and GIGANTEA (GI) which cycled with a period and phase matching that seen in Arabidopsis. The remaining genes were involved in pathways including carbohydrate metabolism, hormone signalling, transcription regulation and wood formation. The types of genes that were seen to be diurnally influenced, suggests a role for circadian control of various important plant metabolic pathways, including aspects of carbon allocation to wood formation. / Dissertation (MSc)--University of Pretoria, 2008. / Genetics / unrestricted

No description available.

In this study anaerobic toxicity assays were used to quantify the relative toxicity of resin acids to the total toxicity in bleached chemithermomechanical wastewater. Fiber toxicity was also compared to raw bleached chemithermomechanical wastewater toxicity. Resin acids were found to be toxic to anaerobic bacteria but were not found to be responsible for all the toxicity in the wastewater. Toxicity associated with the fiber is soluble in methanol. The bulk of the fiber which is not methanol soluble exhibits no toxicity. Transfer of information obtained from batch modified anaerobic toxicity assays to continuous anaerobic treatment systems was also evaluated. Modified anaerobic toxicity assay data was compared to continuous toxicity assays using an upflow anaerobic sludge bed reactor. The continuous reactor was relatively unaffected by acute or chronic exposure to resin acids at concentrations that invoked inhibition in bath tests. Inferences from these tests indicated that batch modified anaerobic toxicity assay results may be unreliable when applied to continuous systems. (Abstract shortened by UMI.)

Abstract not available.

The underlying cause was sought for "inactivation", a heat-induced change in the surface of veneer that inhibits diffusion of moisture into the wood. It was demonstrated, by the use of Douglas fir wood, that the formation of an inactivated surface could be prevented by extraction with certain organic solvents, but not with water, either before or after the wood was dried. When the extractable materials were removed, or were originally absent, no specimen examined showed degradation, through the effect of heat, of the potential for forming strong glue bonds. The frequently postulated statement related to formation of ether linkages from hydroxyl groups, in heated wood, was found to be not correct. Although oxidation had been suggested as a contributing factor, inactivated surfaces were prepared in the absence of oxygen in anything but minute amounts. Veneer was collected from Coastal and Interior type Douglas fir trees that exhibited severe, moderate or no susceptibility to the development of inactivation. Representative samples were extracted with simple alkanes and a complete separation of the various components carried out, using the techniques of gas/liquid, paper and thin-layer chromatography. Qualitative variability was found, between and within trees. Strong correlation was found between the formation of an inactivated surface and the presence of saturated fatty acids with carbon-chain lengths in excess of eighteen atoms. The role of long-carbon-chain, saturated fatty acids as the causal agent of inactivation was substantiated by the application of commercially-prepared acids, of various chain lengths, to veneer that had proven insusceptible. When heated, this veneer developed an inactivated surface. A theory was proposed, based on the work described in this thesis, and the information available in the literature, to explain the mechanism of surface modification. It states that removal of some or all of the last molecular layer of water from the wood surface, and the application of heat, permits the saturated long-chain fatty acids to hydrogen-bond with the hydroxyl groups contained in the wood cellulose. The surface of the wood is then shielded by a hydrocarbon layer with very low free surface energy that is not- readily wet-table by the water contained in applied glue. / Forestry, Faculty of / Graduate

The phenolic extractives from western hemlock wood (Tsuga heterophylla (Raf.) Sar.) have been examined. The total extractive content of the wood amounted to 1.5% of the dry weight. A leucoanthocyanidin and two lignans, conidendrin and hydroxymatairesinol, were isolated from the phenolic fraction by precipitation of a methanol solution into peroxide-free ether followed by separation on silicic acid-calcium sulphate chromatobars. The pigment produced by acid treatment of the isolated leucoanthocyanidin was shown by spectral studies and alkaline degradation to be a mixture of cyanidin and an unidentified anthocyanidin. The two anthocyanidins had identical Rf values in different solvents and similar ultra-violet spectra in ethanol-hydrochloric acid solution but the shift of the absorption maxima caused by addition of aluminium chloride was negligible in the case of the unknown compound and amounted to 30 mµ for cyanidin. Similar separations of the absorption maxima after complexing with aluminium ion were observed with the 3-methyl and 3-isopropyl ethers of the two anthocyanidins. The alkaline degradation products from the leucoanthocyanidin contained protocatechuic acid but no phloroglucinol. Degradation products of phloroglucinol, however, were present in the reaction mixture. These results suggested that the leucoanthocyanidin occurred in the wood in dimeric form and that alkaline degradation of this structure produced a symmetrical hexahydroxyhenzophenone derivative which split up directly into fragments identical to those obtained from phloroglucinol under the same conditions. New information on the structure of hydroxymatairesinol was obtained by comparison of the infrared spectra of the fully acetylated hydroxymatairesinol with that of the reduced compound and by neutral potassium permanganate oxidation of trimethylhydroxymatairesinol. The results obtained were in good agreement with only one of the two structures previously proposed for hydroxymatairesinol by other workers. The NMR spectra of hydroxymatairesinol and structurally related compounds were compared, but the interpretation of the spectrum of hydroxymatairesinol proved to be difficult because broad, incompletely resolved lines were obtained due to the complexity and asymmetry of the molecule. / Science, Faculty of / Chemistry, Department of / Graduate

It was the purpose of this study to compare pulps prepared from normal, sound wood with those prepared from juvenile wood, compression wood, tension wood and decayed wood with regard to their apparent degree of crystallinity. The crystallinity index and crystallinity ratio of the pulps prepared from these woods were determined by two different X-ray methods. In method A, the principle of the Debye-Scherrer powder technique was applied and the crystallinity index of the pulp was evaluated from the 002 peak of the X-ray diffraction pattern. In method B a Geiger-counter X-ray spectrometer was used and the crystallinity ratio of holocellulose was evaluated from the (101 +101¯) combination peak. It was found that the apparent crystallinity of wood pulp and holocellulose prepared from normal western hemlock wood increased significantly through successive growth rings from the pith to about 15 years, after which it reached a more or less constant value. The crystallinity of wood pulp and holocellulose of summerwood was significantly higher than that of springwood. The crystallinity of wood pulp and holocellulose of compression wood from Douglas fir was considerably lower than that of normal wood, whereas the crystallinity of tension wood from cottonwood was significantly higher than that of normal wood. The crystallinity of cottonwood and Douglas fir holocellulose increased significantly during the incipient stage of decay. The rate of increase in crystallinity was very rapid during the incipient stage of decay represented by a six percent weight loss, but became very slow and showed an almost constant value thereafter. The relative value of crystallinity after decay depends mainly on the initial crystallinity rather than the history of decay. / Forestry, Faculty of / Graduate