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  • 1.
    Alfredsen, Gry
    et al.
    Norwegian Forest and Landscape Institute, Norway.
    Ringman, Rebecka
    RISE., SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, SP – Sveriges Tekniska Forskningsinstitut / Material och produkter (TRm).
    Pilgård, Annica
    RISE., SP – Sveriges Tekniska Forskningsinstitut, SP Hållbar Samhällsbyggnad. Technical University of Munich, Germany.
    Fossdal, Carl Gunnar
    Norwegian Forest and Landscape Institute, Norway.
    New insight regarding mode of action of brown rot decay of modified wood based on DNA and gene expression studies: A review2015Inngår i: International Wood Products Journal, ISSN 2042-6445, E-ISSN 2042-6453, Vol. 6, nr 1, s. 5-7Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Modified wood shows resistance against wood deteriorating fungi, but the mechanisms are still not fully understood. The aim of this paper was to summarise the molecular studies performed on modified wood with regard to brown rot decay fungi. The DNA data showed that fungi are present inside the laboratory wood test samples already after two weeks of inoculation. Generally the fungal DNA content reflects mass loss and wood moisture content. The oxidative gene expression seems to be higher in modified wood than in untreated wood and it tend to increase during incubation. Based on the gene expression data we suggest that the hypothesis of lack of substrate recognition by the fungus should be rejected. In the reviewed studies, total wood moisture content in the samples was generally not low enough to inhibit fungal colonisation. Hence, moisture distribution within the wood should be studied more closely.

  • 2. Ehmcke, Gabriele
    et al.
    Ringman, Rebecka
    RISE., SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, SP – Sveriges Tekniska Forskningsinstitut / Material och produkter (TRm).
    Pilgård, Annica
    RISE., SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, SP Trä.
    Richter, Klaus
    Improvement of a cytochemical method for localization of hydrogen peroxide and adaptation to furfurylated wood2014Inngår i: Proceedings of 10th Meeting of the Northern European Network for Wood Science & Engineering (WSE 2014), Edinburgh Napier University , 2014, , s. 180-186Konferansepaper (Fagfellevurdert)
  • 3.
    Pilgård, Annica
    et al.
    RISE., SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, SP Trä.
    Ringman, Rebecka
    RISE., SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, SP – Sveriges Tekniska Forskningsinstitut / Material och produkter (TRm).
    Kölle, Martina
    Brischke, Christian
    Richter, Klaus
    Expression of Postia placenta wood degradation genes in thermally modified wood2014Inngår i: Proceedings of 10th Meeting of the Northern European Network for Wood Science & Engineering (WSE 2014), Edinburgh Napier University , 2014, , s. 97-103Konferansepaper (Fagfellevurdert)
  • 4.
    Ringman, Rebecka
    et al.
    RISE - Research Institutes of Sweden, Bioekonomi, Biobaserade material.
    Beck, Greeley
    Norwegian Institute of Bioeconomy Research, Norway.
    Pilgård, Annica
    RISE - Research Institutes of Sweden, Bioekonomi, Biobaserade material. Technical University of Munich, Germany.
    The importance of moisture for Brown Rot degradation of Modified Wood: A critical discussion2019Inngår i: Forests, ISSN 1999-4907, E-ISSN 1999-4907, Vol. 10, nr 6, artikkel-id 522Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The effect of wood modification on wood-water interactions in modified wood is poorly understood, even though water is a critical factor in fungal wood degradation. A previous review suggested that decay resistance in modified wood is caused by a reduced wood moisture content (MC) that inhibits the diffusion of oxidative fungal metabolites. It has been reported that a MC below 23%-25% will protect wood from decay, which correlates with the weight percent gain (WPG) level seen to inhibit decay in modified wood for several different kinds of wood modifications. In this review, the focus is on the role of water in brown rot decay of chemically and thermally modified wood. The study synthesizes recent advances in the inhibition of decay and the effects of wood modification on the MC and moisture relationships in modified wood. We discuss three potential mechanisms for diffusion inhibition in modified wood: (i) nanopore blocking; (ii) capillary condensation in nanopores; and (iii) plasticization of hemicelluloses. The nanopore blocking theory works well with cell wall bulking and crosslinking modifications, but it seems less applicable to thermal modification, which may increase nanoporosity. Preventing the formation of capillary water in nanopores also explains cell wall bulking modification well. However, the possibility of increased nanoporosity in thermally modified wood and increased wood-water surface tension for 1.3-dimethylol-4.5-dihydroxyethyleneurea (DMDHEU) modification complicate the interpretation of this theory for these modifications. Inhibition of hemicellulose plasticization fits well with diffusion prevention in acetylated, DMDHEU and thermally modified wood, but plasticity in furfurylated wood may be increased. We also point out that the different mechanisms are not mutually exclusive, and it may be the case that they all play some role to varying degrees for each modification. Furthermore, we highlight recent work which shows that brown rot fungi will eventually degrade modified wood materials, even at high treatment levels. The herein reviewed literature suggests that the modification itself may initially be degraded, followed by an increase in wood cell wall MC to a level where chemical transport is possible.

  • 5.
    Ringman, Rebecka
    et al.
    RISE., SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, SP – Sveriges Tekniska Forskningsinstitut / Material och produkter (TRm).
    Pilgård, Annica
    RISE., SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, SP Trä.
    Alfredsen, Gry
    Goodell, Barry
    Richter, Klaus
    Possible targets of wood modification in brown rot degradation2014Inngår i: Proceedings IRG Annual Meeting 2014 - IRG/WP 14, 2014, , s. 13Konferansepaper (Annet vitenskapelig)
  • 6.
    Ringman, Rebecka
    et al.
    RISE., SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, SP – Sveriges Tekniska Forskningsinstitut / Material och produkter (TRm).
    Pilgård, Annica
    RISE., SP – Sveriges Tekniska Forskningsinstitut, SP Hållbar Samhällsbyggnad.
    Brischke, Christian
    Leibniz University, Germany.
    Richter, Klaus
    Technische Universität München, Germany.
    Mode of action of brown rot decay resistance in modified wood: a review2014Inngår i: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 68, nr 2, s. 239–246-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Chemically or physically modified wood materials have enhanced resistance to wood decay fungi. In contrast to treatments with traditional wood preservatives, where the resistance is caused mainly by the toxicity of the chemicals added, little is known about the mode of action of nontoxic wood modification methods. This study reviews established theories related to resistance in acetylated, furfurylated, dimethylol dihydroxyethyleneurea- treated, and thermally modified wood. The main conclusion is that only one theory provides a consistent explanation for the initial inhibition of brown rot degradation in modified wood, that is, moisture exclusion via the reduction of cell wall voids. Other proposed mechanisms, such as enzyme nonrecognition, micropore blocking, and reducing the number of free hydroxyl groups, may reduce the degradation rate when cell wall water uptake is no longer impeded.

  • 7.
    Ringman, Rebecka
    et al.
    RISE - Research Institutes of Sweden, Samhällsbyggnad, Byggteknik.
    Pilgård, Annica
    RISE - Research Institutes of Sweden, Samhällsbyggnad, Byggteknik. Technical University of Munich, Germany.
    Brischke, Christian
    University of Göttingen, Germany.
    Windeisen, Elizabeth
    Technical University of Munich, Germany.
    Richter, Klaus
    Technical University of Munich, Germany.
    Incipient brown rot decay in modified wood: patterns of mass loss, structural integrity, moisture and acetyl content in high resolution2017Inngår i: International Wood Products Journal, ISSN 2042-6445, E-ISSN 2042-6453, Vol. 8, nr 3, s. 172-182Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The study of degradation and growth patterns of fungi in modified wood may increase the understanding of their mode of action and may lead to more accurate service-life predictions. The aim of this paper was to study the degradation and growth patterns of brown rot fungi in modified wood and to measure moisture content (MC), structural integrity and the acetyl content by frequent monitoring over 300 days. Mass loss (ML) in the modified wood materials increased slowly up to 3% for 50–100 days after which it flattened out and remained constant during the remainder of the test. Structural integrity and acetyl content were maintained in the modified wood materials and MC was lower compared to untreated wood throughout the decay test. ML results of untreated wood indicate that fungi in solid wood go through distinct phases; the degradation patterns in the modified wood materials were more difficult to interpret.

  • 8.
    Ringman, Rebecka
    et al.
    RISE., SP – Sveriges Tekniska Forskningsinstitut, SP Hållbar Samhällsbyggnad.
    Pilgård, Annica
    RISE., SP – Sveriges Tekniska Forskningsinstitut, SP Hållbar Samhällsbyggnad. Technical University of Munich, Germany.
    Kölle, Martina
    Technical University of Munich, Germany.
    Brischke, Christian
    Leibniz University Hannover, Germany.
    Richter, Klaus
    Technical University of Munich, Germany.
    Effects of thermal modification on Postia placenta wood degradation dynamics: measurements of mass loss, structural integrity and gene expression2016Inngår i: Wood Science and Technology, ISSN 0043-7719, E-ISSN 1432-5225, Vol. 50, nr 2, s. 385-397Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The mechanism by which modified wood resists decay has long been discussed, but is still not fully understood. A better understanding of decay resistance mechanisms could improve wood protection processes and product properties. In this study, the dynamics of brown rot decay in thermally modified wood was examined through measurements of mass loss, strength loss and gene expression. Close monitoring of mass loss over 120 days in thermally modified wood exposed to Postia placenta showed a delay in the onset of degradation compared to untreated wood, and once the degradation had started, the rate was lower. Thermally modified wood did not inhibit expression of wood degradation-related genes before mass loss and was similar to that in untreated wood once mass loss could be detected. Comparing gene expression as well as strength loss at the same stage of decay rather than at the same time after exposure showed smaller differences in decay patterns between thermally modified and untreated wood than previous results indicate. It is concluded that the key to understanding degradation resistance in thermally modified wood is to compare the decay patterns in thermally modified wood and untreated wood before mass loss occurs.

  • 9.
    Ringman, Rebecka
    et al.
    RISE., SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, SP – Sveriges Tekniska Forskningsinstitut / Material och produkter (TRm).
    Pilgård, Annica
    RISE., SP – Sveriges Tekniska Forskningsinstitut, SP Hållbar Samhällsbyggnad.
    Richter, Klaus
    Technische Univerität München, Germany.
    Effect of wood modification on gene expression during incipient Postia placenta decay2014Inngår i: International Biodeterioration & Biodegradation, ISSN 0964-8305, E-ISSN 1879-0208, Vol. 86, nr B, s. 86-91Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The mode of action of nontoxic wood modifications and the fungal response to modified wood are not fully elucidated. The aim of this study was to investigate the reaction of Postia placenta in terms of gene expression of selected genes upon the encounter of acetylated, DMDHEU-treated and thermally modified wood. Quantitative PCR (qPCR) showed that the investigated P.placentagenes involved in oxidative degradation were expressed at higher levels in modified wood than in untreated wood, while expression levels in modified wood for the investigated genes involved in enzymatic degradation were slightly lower than those in untreated wood. The results indicate that the response of P.placenta upon the encounter of modified wood is to up-regulate the expressionof the oxidative degradation machinery. In addition, our results support the theory that the decay resistance of the herein studied modified woods is due to inhibition of fungal molecules, needed for oxidative degradation of wood polymers, to penetrate the wood cell wall.

  • 10.
    Ringman, Rebecka
    et al.
    RISE., SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, SP – Sveriges Tekniska Forskningsinstitut / Material och produkter (TRm).
    Pilgård, Annica
    RISE., SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, Trätek.
    Richter, Klaus
    Effects of wood modification on gene expression during incipient Postia Placenta decay2013Inngår i: Proceedings of the 9th Meeting of the Northern European Network for Wood Science and Engineering, 2013, , s. 221-227Konferansepaper (Annet vitenskapelig)
  • 11.
    Ringman, Rebecka
    et al.
    RISE., SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, SP – Sveriges Tekniska Forskningsinstitut / Material och produkter (TRm).
    Pilgård, Annica
    RISE., SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, SP Trä.
    Richter, Klaus
    Technische Universität München, Germany.
    In vitro oxidative and enzymatic degradation of modified wood2014Inngår i: The seventh European Conference on Wood Modification : Book of Abstracts, 2014, Vol. 6, s. 36-39, artikkel-id 1Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Fungal cellulases have been shown to be less efficient in modified wood than in untreated wood (Lekounogou et al. 2008; Vena°s 2008). However, Verma and Mai (2010) showed that cellulase efficacy is partly restored in 1,3-dimethylol-4,5-dihydroxyethyleneurea (DMDHEU) treated wood by pre-treatment with Fenton's reagent, simulating the oxidative degradation phase in initial brown rot decay. In this study, we examined whether Fenton derived hydroxyl radicals (OH) and cellulases are able to cleave polysaccharides in furfurylated and acetylated wood and to what extent enzyme efficacy is increased by oxidative pre-treatment of these materials. The results show that fungal cellulases were able to degrade acetylated wood and that the cellulase efficacy was increased by oxidative pre-treatment by 20%, which is half of the increase in untreated wood. Furthermore, the results indicate that poly(furfuryl alcohol) is degraded by Fenton derived OH. This indicates a possible route for the eventual degradation of modified wood.

  • 12.
    Ringman, Rebecka
    et al.
    RISE., SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, SP – Sveriges Tekniska Forskningsinstitut / Material och produkter (TRm).
    Pilgård, Annica
    RISE., SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, SP Trä.
    Richter, Klaus
    Postia placenta cellulase gene expression in modified wood during incipient decay2013Inngår i: s. 9-Artikkel i tidsskrift (Annet vitenskapelig)
  • 13.
    Ringman, Rebecka
    et al.
    RISE., SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, SP – Sveriges Tekniska Forskningsinstitut / Material och produkter (TRm).
    Pilgård, Annica
    RISE., SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, Trätek.
    Richter, Klaus
    Postia placenta decay mechanisms and effects of wood modification2012Inngår i: The Sixth European Conference on Wood Modification Proceedings, University of Ljubljana , 2012, , s. 119-126Konferansepaper (Fagfellevurdert)
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