7 results for Altaner, C.M.

  • Wood shrinkage: influence of anatomy, cell wall architecture, chemical composition and cambial age

    Leonardon, M.; Altaner, C.M.; Vihermaa, L.; Jarvis, M.C. (2010)

    Journal Articles
    University of Canterbury Library

    The influence of microfibril angle (MfA), density and chemical cell wall composition on shrinkage varied between the longitudinal and tangential directions as well as between wood types, namely compression wood (CW), mature wood (MW) and juvenile wood (JW). At the same MfA, CW exhibited a lower tangential shrinkage than JW, indicating the influence of the chemical composition on wood shrinkage. The chemical composition measured via FTIR micro-spectroscopy has been shown in conjunction with density to be an alternative to MfA data for shrinkage predictions. This was particularly true for wood of young cambial age for which the MfA did not correlate to shrinkage. The results indicate a possibility to reduce distortion of sawn timber by segregation using infrared (IR) and X-ray in-line measurements.

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  • Molecular xylem wall structure of an inclined Cycas micronesica stem, a tropical gymnosperm

    Altaner, C.M.; Jarvis, M.C.; Fisher, J.B.; Marler, T.E. (2010)

    Journal Articles
    University of Canterbury Library

    The molecular structure of tracheid walls of an inclined eccentrically grown stem of Cycas micronesica K.D. Hill did not differ between the upper and lower side. The absence the typical molecular features of compression wood tracheids, i.e. an increased galactose and lignin content as well as an increased microfibril angle, indicated that cycads do not have the ability to form even very mild forms of compression wood, which lacks anatomical features commonly observed in compression wood. Analysis of the sugar monomers in Cycas micronesica tracheids did reveal a rather unique composition of the non-cellulosic polysaccharides for a gymnosperm. The low mannose and high xylose content resembled a cell wall matrix common in angiosperms. The crystalline cellulose structure in Cycas micronesica tracheids closely resembled those of secondary cell walls in Picea sitchensis (Bong.) Carr. tracheids. However, the spacing between the sheets of cellulose chains was wider and the cellulose fibrils appeared to form larger aggregates than in Sitka spruce tracheids.

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  • UC/NZDFI's durable eucalypt research program

    Altaner, C.M. (2015)

    Conference Contributions - Other
    University of Canterbury Library

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  • Screening eucalypts for growth-strain

    Davies, N.T.; Sharma, M.; Altaner, C.M.; Apiolaza, L.A. (2015)

    Conference Contributions - Other
    University of Canterbury Library

    Eucalypt species are fast-growing and can produce high quality timber for appearance and structural products including Laminated Veneer Lumber (LVL). Eucalypts can contain large growth-strains which are associated with log splitting, warp, collapse and brittleheart. These impose substantial costs on processing (Yamamoto 2007). Costly, and only partially effective, mitigation strategies have been developed to reduce wood defects induced by growth-strain. As growth-strain is highly heritable, an alternative approach is to select and grow individuals which display low growth-strain. Until now measurement of growth-strain has been difficult, time consuming and expensive, preventing the assessment of the large number of trees needed by a breeding programme (Altaner 2015). As an example, the largest sample number in any reported growth-strain study was smaller than 230 trees (Solorzano Naranjo 2011). Traditionally selections are made when trees are older, not only increasing costs (e.g. trial management, sample handling) but also substantially extending the breeding cycle and delaying the deployment of improved germplasm (Altaner 2015). Developments at the University of Canterbury have resulted in a unique growth-strain measurement method supported by theoretical analysis (Entwistle 2014) - dubbed the “Splitting” test. It allows for rapid growth-strain assessment on young trees (Chauhan 2010).

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  • Wood quality assessment of Pinus radiata (radiata pine) saplings by dynamic mechanical analysis

    Sharma, M.; Brennan, M.; Chauhan, S.S.; Entwistle, K.M.; Altaner, C.M.; Harris, P.J. (2015)

    Journal Articles
    University of Canterbury Library

    The use of dynamic mechanical analysis was explored as a possible method of screening for wood quality in breeding programmes. Viscoelastic properties along the grain of wood from 18-month-old Pinus radiata saplings were measured using a humidity-controlled dynamic mechanical analyser. Storage modulus and tanδ were determined independently for opposite wood (OW) and compression wood (CW) in 25 trees in the temperature range from 10 to 45 °C at 5 °C intervals at three frequencies (0.1, 1 and 10 Hz) at constant moisture content of 9 %. Storage modulus and tanδ were frequency and temperature dependent. The two wood types did not differ significantly in their storage modulus. But OW exhibited significantly higher tanδ values than CW. The relationship of viscoelastic properties with physical (acoustic velocity, basic density and longitudinal shrinkage) and chemical wood properties was explored. There was a strong correlation (R = 0.76) between storage modulus and dynamic MOE (measured by acoustics). In addition, tanδ was positively correlated with longitudinal shrinkage. Monosaccharide compositions of the cell wall polysaccharides and lignin contents were determined and showed significant differences in the relative proportion of major cell wall components in OW and CW. Correlations between tanδ and xylose, originating from heteroxylans, and lignin content were found for CW, suggesting that the damping behaviour of cell walls is controlled by the matrix between cellulose fibril aggregates.

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  • Structure and spacing of cellulose microfibrils in woody cellwalls of dicots

    Thomas, L.H.; Forsyth, V.T.; Martel, A.; Grillo I.; Altaner, C.M.; Jarvis, M.C. (2014)

    Journal Articles
    University of Canterbury Library

    The structure of cellulose microfibrils in situ in wood from the dicotyledonous (hardwood) species cherry and birch, and the vascular tissue from sunflower stems, was examined by wide-angle X-ray and neutron scattering (WAXS and WANS) and small-angle neutron scattering (SANS). Deuteration of accessible cellulose chains followed by WANS showed that these chains were packed at similar spacings to crystalline cellulose, consistent with their inclusion in the microfibril dimensions and with a location at the surface of the microfibrils. Using the Scherrer equation and correcting for considerable lateral disorder, the microfibril dimensions of cherry, birch and sunflower microfibrils perpendicular to the [200] crystal plane were estimated as 3.0, 3.4 and 3.3 nm respectively. The lateral dimensions in other directions were more difficult to correct for disorder but appeared to be 3 nm or less. However for cherry and sunflower, the microfibril spacing estimated by SANS was about 4 nm and was insensitive to the presence of moisture. If the microfibril width was 3 nm as estimated by WAXS, the SANS spacing suggests that a non-cellulosic polymer segment might in places separate the aggregated cellulose microfibrils.

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  • Diffraction evidence for the structure of cellulose microfibrils in bamboo, a model for grass and cereal celluloses

    Thomas, L.H.; Forsyth, T.; Martel, A.; Grillo, I.; Altaner, C.M.; Jarvis, M.C. (2015)

    Journal Articles
    University of Canterbury Library

    Background: Cellulose from grasses and cereals makes up much of the potential raw material for biofuel production. It is not clear if cellulose microfibrils from grasses and cereals differ in structure from those of other plants. The structures of the highly oriented cellulose microfibrils in the cell walls of the internodes of the bamboo Pseudosasa amabilis are reported. Strong orientation facilitated the use of a range of scattering techniques. Results: Small-angle neutron scattering provided evidence of extensive aggregation by hydrogen bonding through the hydrophilic edges of the sheets of chains. The microfibrils had a mean centre-to-centre distance of 3.0 nm in the dry state, expanding on hydration. The expansion on hydration suggests that this distance between centres was through the hydrophilic faces of adjacent microfibrils. However in the other direction, perpendicular to the sheets of chains, the mean, disorder-corrected Scherrer dimension from wide-angle X-ray scattering was 3.8 nm. It is possible that this dimension is increased by twinning (crystallographic coalescence) of thinner microfibrils over part of their length, through the hydrophobic faces. The wide-angle scattering data also showed that the microfibrils had a relatively large intersheet d-spacing and small monoclinic angle, features normally considered characteristic of primary-wall cellulose. Conclusions: Bamboo microfibrils have features found in both primary-wall and secondary-wall cellulose, but are crystallographically coalescent to a greater extent than is common in celluloses from other plants. The extensive aggregation and local coalescence of the microfibrils are likely to have parallels in other grass and cereal species and to influence the accessibility of cellulose to degradative enzymes during conversion to liquid biofuels

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