School of Agriculture, Food and Ecosystem Sciences - Theses
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ItemNo Preview AvailableThe chemical modification of Pinus radiata (D.Don.) with furfuryl alcohol(University of Melbourne, 2006)Wood blocks impregnated with furfuryl alcohol required a standing time of 48 hours to ensure complete swelling of the wood. Total penetration of the blocks was required for maximum swelling and water resistance in treated blocks. The presence of water in the treatment solution caused rapid swelling of the wood block, whereas 100% furfuryl alcohol created a slow rate of swelling. The presence of water in the cell walls accelerated the rate of swelling of 100% furfuryl alcohol, but not to the extent as when the water was present in the treatment solution. Dimensional stability decreased as the water content in the treating solution increased, but compared to the controls (6 - 8%) there was significant improvement in dimensional stability (2.5 - 4%). The resin forming efficiency varied with the amount of water present, but never dropped below 85%. Treated wood samples compressed to a density of 1200 � 1400 kg/m3 were more stable when exposed to water, and had increased hardness and MOE compared to untreated compressed samples. The curing of furfuryl alcohol in beakers gave a clear indication of catalyst performance with variable catalyst concentration and curing temperature. An increase in catalyst concentration increased the resin forming efficiency which was dependant upon the catalyst strength and number of pKa values. Of the catalysts stable at room temperature, oxalic acid, maleic acid and zinc chloride were the best performed for wood impregnation, with respect to the parameters investigated. The higher the resin forming efficiency the lower the volumetric swelling. The initial moisture content of the wood had a direct effect upon the swelling of wood blocks. All samples with an initial moisture content of 12% performed better than the corresponding treatments used with oven-dried blocks. Further, higher catalyst concentrations and curing temperatures improved performance. Oxalic acid at a 4% concentration with furfuryl alcohol and a 2% concentration with furfuryl alcohol � formaldehyde formulations produced the best resin forming efficiency, permanent swelling and water property results. Conditioning time between pressure impregnation and curing was unnecessary with no improvement in properties with the cured wood block. Furfuryl alcohol with a 4% oxalic acid concentration produced the most desirable overall results with resin forming efficiency (111%), permanent swelling (8%), water uptake (8%) and dimensional stability (2.8%), when cured for 24 hours at 120�C. Analysis of leachate by GCMS suggested that a minimum curing time of 12 hours is required with furfuryl alcohol and 6 hours with a furfuryl alcohol � formaldehyde formulation to substantially reduce the amount of leachable material from a treated wood block, confirmed by dimensional stability trials.
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ItemNo Preview AvailableThe chemical modification of Pinus radiata (D.Don.) with furfuryl alcohol(University of Melbourne, 2006)Wood blocks impregnated with furfuryl alcohol required a standing time of 48 hours to ensure complete swelling of the wood. Total penetration of the blocks was required for maximum swelling and water resistance in treated blocks. The presence of water in the treatment solution caused rapid swelling of the wood block, whereas 100% furfuryl alcohol created a slow rate of swelling. The presence of water in the cell walls accelerated the rate of swelling of 100% furfuryl alcohol, but not to the extent as when the water was present in the treatment solution. Dimensional stability decreased as the water content in the treating solution increased, but compared to the controls (6 - 8%) there was significant improvement in dimensional stability (2.5 - 4%). The resin forming efficiency varied with the amount of water present, but never dropped below 85%. Treated wood samples compressed to a density of 1200 � 1400 kg/m3 were more stable when exposed to water, and had increased hardness and MOE compared to untreated compressed samples. The curing of furfuryl alcohol in beakers gave a clear indication of catalyst performance with variable catalyst concentration and curing temperature. An increase in catalyst concentration increased the resin forming efficiency which was dependant upon the catalyst strength and number of pKa values. Of the catalysts stable at room temperature, oxalic acid, maleic acid and zinc chloride were the best performed for wood impregnation, with respect to the parameters investigated. The higher the resin forming efficiency the lower the volumetric swelling. The initial moisture content of the wood had a direct effect upon the swelling of wood blocks. All samples with an initial moisture content of 12% performed better than the corresponding treatments used with oven-dried blocks. Further, higher catalyst concentrations and curing temperatures improved performance. Oxalic acid at a 4% concentration with furfuryl alcohol and a 2% concentration with furfuryl alcohol � formaldehyde formulations produced the best resin forming efficiency, permanent swelling and water property results. Conditioning time between pressure impregnation and curing was unnecessary with no improvement in properties with the cured wood block. Furfuryl alcohol with a 4% oxalic acid concentration produced the most desirable overall results with resin forming efficiency (111%), permanent swelling (8%), water uptake (8%) and dimensional stability (2.8%), when cured for 24 hours at 120�C. Analysis of leachate by GCMS suggested that a minimum curing time of 12 hours is required with furfuryl alcohol and 6 hours with a furfuryl alcohol � formaldehyde formulation to substantially reduce the amount of leachable material from a treated wood block, confirmed by dimensional stability trials.
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ItemTowards association studies in Pinus radiata D.Don - populations and wood property candidate-genes( 2006)In Australia and New Zealand Pinus radiata D. Don wood quality is receiving increasing interest from tree breeders. This is partly due to declining resource wood quality associated with more advanced generation breeds leading to increased rejection and product downgrading in processing. While log segregation and wood grading at mill-door yields immediate benefits to processors the underlying cause is not addressed. The only long-term solution is to include wood quality in breeding programs. Wood quality traits are costly and difficult to measure. Marker-assisted selection offers a potential solution and quantitative trait loci (QTL) mapping studies have been undertaken with the aim of facilitating this. It is becoming increasingly clear that in widely outcrossing species with long generation times and very large genomes these approaches will not work. The identification of the underlying genetic sites, or tightly linked marker sites, would rectify this and in model species linkage-map based cloning has been used extensively. This approach is also not practical in species such as P. radiata. Association testing combined with a candidate-gene approach is therefore widely believed to be one of the only methods remaining. This approach uses a priori information to select and then test the phenotypic effects of variants within candidate-gene loci. Implementation of these studies relies heavily on the results of other investigations, especially those that generate DNA sequence information. Also required is detailed knowledge of the genetic population structure, the patterns of nucleotide diversity and the patterns of linkage disequilibrium. On a more practical level suitable populations need to be identified while the current methods for the collection and handling of samples for molecular investigations are limiting. The selection of candidate genes is also a non-trivial process. For candidate-gene association studies to be successful in P. radiata all these factors need to be addressed. This formed the main aim of this thesis. A multi-pronged approach was used. Firstly, at the population level, the genetic resources available for association studies were identified and the underlying genetic population structure of these resources and the patterns of nucleotide diversity and linkage disequilibrium were investigated. Secondly, improved methods for the collection and isolation of genomic DNA were developed and thirdly, a small set of wood quality candidate-genes were selected and further characterised with the aim of identifying those with the most promise of harbouring causative variation for inclusion in future association studies. This was achieved by literature based review, linkage mapping onto wood property QTL maps and neutrality testing. Results include support for previous population genetic studies showing P. radiata to have a complex genetic structure compared to most pine species. This study also indicated significant levels of migration between the three mainland populations. Within the candidate-genes two, cinnamyl alcohol dehydrogenase and sucrose synthase, showed interesting patterns of population differentiation and/or nucleotide diversity while the results for one other gene, korrigan, did not agree with previous investigations.
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