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  • 51. Magara, Kengo
    et al.
    Karlsson, Olov
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Hosoya, Shuji
    Reduction of chloroform emission from hypochlorite-bleaching process2003In: Kami Pa Gikyoshi, ISSN 0022-815X, Vol. 57, no 9, p. 76-83Article in journal (Refereed)
    Abstract [en]

    Chloroform was readily converted to formic acid through the nucleophilic attack of hydroxyl anion under the certain reaction conditions (pH>12, temp.>°C). When guaiacol was reacted with hypochlorite at such reaction conditions, the generation of chloroform was almost completely reduced. Successful reduction of the chloroform generation was also observed in alkaline hypochlorite bleaching of kraft pulps and DIP without any loss in pulp quality. Even when the hypochlorite bleaching was carried out under the open system (no sealing of the reaction vessel), nearly 90% of the generated chloroform was converted to formic acid.

  • 52.
    Kishimoto, Takao
    et al.
    Forestry and Forest Products Research Institute.
    Ikeda, Tsutomu
    Wood Chemistry Laboratory, Forestry and Forest Products Research Institute, 305-8687 Ibaraki.
    Karlsson, Olov
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Magara, Kendo
    Wood Chemistry Laboratory, Forestry and Forest Products Research Institute, 305-8687 Ibaraki.
    Hosoya, Shuji
    Wood Chemistry Laboratory, Forestry and Forest Products Research Institute, 305-8687 Ibaraki.
    Reactivity of secondary hydroxyl groups in methyl β-D-xylopyranoside toward a β-O-4-type quinone methide2002In: Journal of Wood Science, ISSN 1435-0211, E-ISSN 1611-4663, Vol. 48, no 1, p. 32-37Article in journal (Refereed)
    Abstract [en]

    Methyl β-D-xylopyranoside was allowed to react with β-O-4-type quinone methide without a catalyst to elucidate the reactivities of secondary hydroxyl groups at the C2, C3, and C4 positions. Benzyl ether-type lignin-carbohydrate complex (LCC) compounds linked at the C2 and C4 positions were predominant, at a ratio of 2:3. However, the reactivity of the hydroxyl group at the C3 position was quite low. These results strongly suggest that the reactivity of the C2 hydroxyl group in xylan toward quinone methide intermediate is higher than that of the C3 hydroxyl group during biosynthesis of LCCs

  • 53.
    Karlsson, Olov
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Westermark, Ulla
    Resin-free particleboard by oxidation of wood2002In: 6th Pacific Rim Bio-Based Composites Symposium & Workshop on the Chemical Modification of Cellulosics: November 10th to 13th 2002, Portland, Oregon ; proceedings / [ed] P. E. Humphrey, Corvallis, Or: Wood science and engineering department , 2002Conference paper (Refereed)
  • 54.
    Karlsson, Olov
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Pettersson, B.
    Westermark, Ulla
    Linkages between residual lignin and carbohydrates in bisulphite (magnefite) pulps2001In: Journal of Pulp and Paper Science (JPPS), ISSN 0826-6220, Vol. 27, no 9, p. 310-316Article in journal (Refereed)
    Abstract [en]

    The presence of bonds between residual lignin and carbohydrates in bisulphite pulps from hardwoods and softwoods was studied. Results showed that a fraction of the residual lignin was bonded to cellulose in bisulphite pulps of softwood. The treatment with xylanase indicated the existence of alkali-stable lignin-xylan bonds in softwood bisulphite pulps.

  • 55.
    Karlsson, Olov
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Ikeda, Tsutomu
    Magara, Kengo
    Hosoya, Shuji
    Novel method for isolation of a lignin-carbohydrate bond2001In: 11th ISWPC: Symposium on Wood and Pulping Chemistry; Nice, France, June 11 to 14, 2001, Nice, 2001Conference paper (Refereed)
  • 56.
    Karlsson, Olov
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Pettersson, B.
    Westermark, Ulla
    The use of cellulases and hemicellulases to study lignin-cellulose as well as lignin-hemicellulose bonds in kraft pulps2001In: Journal of Pulp and Paper Science (JPPS), ISSN 0826-6220, Vol. 27, no 6, p. 196-201Article in journal (Refereed)
    Abstract [en]

    The combination of carbohydrate-degrading enzymes and size-exclusion chromatography (SEC) has been used to analyze the existence of covalent bonds between lignin and cellulose and/or hemicelluloses in pulps. Cellulases and xylanase were used for degradation of cellulose and xylan, respectively. Analysis of the molecular weight profiles of lignin and carbohydrates before and after enzymic hydrolysis were performed by dissolution of the pulps in LiCl/dimethylacetamide (DMAC). The results indicate that a considerable part of the residual lignin in unbleached pine kraft pulp is bond to cellulose. Bonding of lignin to xylan in the pine kraft pulp could also be detected. Analysis of birch kraft pulp shows that most of the residu lignin in birch kraft pulps is covalently linked to xylan. The combination of carbohydrate-degrading enzymes and SEC in LiCl/DMAC seems to be an excellent way of characterizing bonds between lignin and carbohydrates in chemical pulps.

  • 57.
    Karlsson, Olov
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Ikeda, Tsutomu
    Forestry and Forest Products Research Institute.
    Kishimoto, Takao
    Forestry and Forest Products Research Institute.
    Magara, Kengo
    Forestry and Forest Products Research Institute.
    Matsumoto, Yuji
    Forestry and Forest Products Research Institute.
    Hosoya, Shuji
    Forestry and Forest Products Research Institute.
    Ozonation of a lignin-carbohydrate complex model compound of the benzyl ether type2000In: Journal of Wood Science, ISSN 1435-0211, E-ISSN 1611-4663, Vol. 46, no 3, p. 263-265Article in journal (Refereed)
    Abstract [en]

    Evidence for the presence of lignin-carbohydrate bonds of the benzylic ether type in wood and pulps may be obtained by use of ozonation treatment to selectively degrade the lignin. It was found that the benzyl ether bond in 3-(4-hydroxy-3-methoxyphenyl)-2-(2-methoxy-phenoxy)-3-(methyl--d-glucopyranosid-6-O-yl)-1-propanol was rather stable during ozonation in acetic acid-water-methanol 1631 at 0°C. The corresponding acid, 3,4-dihydroxy-2-(methyl--d-glucopyranosid-6-O-yl)-butanoic acid, was found to be the major reaction product. The use of ozonation followed by acid hydrolysis in connection with studies of lignincarbohydrate linkages is briefly discussed.

  • 58.
    Karlsson, Olov
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Westermark, Ulla
    The significance of glucomannan for the condensation of cellulose and lignin under kraft pulping conditions1997In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 12, no 2, p. 90-Article in journal (Refereed)
  • 59.
    Karlsson, Olov
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Westermark, Ulla
    Evidence for chemical bonds between lignin and cellulose in kraft pulps1996In: Journal of Pulp and Paper Science (JPPS), ISSN 0826-6220, Vol. 22, no 10, p. J397-401Article in journal (Refereed)
    Abstract [en]

    The cellulose solvent system LiCl-dimethylacetamide has been used to dissolve kraft pulps prepared from pine and birch. The dissolved polymers were analyzed using size-exclusion chromatography combined with both RI- and UV-detection systems in order to monitor simultaneously the major wood polymers (cellulose, hemicellulose and lignin). Kraft pulps from birch were completely soluble in the solvent system and the pine kraft pulp about 80% soluble. Analyses of the kraft pulps strongly suggest that a considerable amount of the residual lignin is chemically linked to the high molecular weight cellulose in pine but not in birch. The presence of stable lignin-cellulose bonds will reduce the possibility of achieving a low kappa number by cooking. For comparison, sulphite and bisulphite pulps were also examined. Both pulps were soluble in the solvent system and analyses indicated that lignin-cellulose bonds also exist in these pulps although to a significantly lesser extent than in the pine kraft pulp

  • 60.
    Brunow, G.
    et al.
    University of Helsinki.
    Karlsson, Olov
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Lundquist, K.
    Chalmers University of Technology.
    Sipilä, J.
    University of Helsinki.
    On the distribution of the diastereomers of the structural elements in lignins: the steric course of reactions mimicking lignin biosynthesis1993In: Wood Science and Technology, ISSN 0043-7719, E-ISSN 1432-5225, Vol. 27, no 4, p. 281-286Article in journal (Refereed)
    Abstract [en]

    Stereochemical studies on the formation of the diastereomers of arylglycerol-β-aryl ether structures during lignin biosynthesis have been carried out with model compounds. The addition of water to quinone methides of the β-syringyl ether type gives arylglycerol β-syringyl ethers with a predominance of the erythro isomer when the pH of the medium is low. Since erythro forms of arylglycerol β-syringyl ethers are prevalent in hardwood lignins, this indicates that the pH of the medium in which lignin biosynthesis occurs is lower than has been assumed until now. Equilibration studies with non-phenolic model compounds of the arylglycerolβ-guaiacyl ether and β-syringyl ether types under acidolysis conditions indicate that the erythro predominance observed in the syringyl ethers in lignins does not correspond to equilibrium conditions. A remarkable resistance to acidolysis is observed in the model compounds of etherified syringylglycerol β-syringyl ether type.

  • 61.
    Karlsson, Olov
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Lundquist, Knut
    Chalmers University of Technology.
    Stomberg, Rolf
    Chalmers University of Technology.
    Preparation and crystal structure of (+/-)-1,2-Bis(3,4-dimethoxyphenyl)-1,2-ethanediol1993In: Acta Chemica Scandinavica, ISSN 0904-213X, E-ISSN 1902-3103, Vol. 47, p. 728-733Article in journal (Refereed)
  • 62.
    Karlsson, Olov
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Lundquist, Knut
    Acid reactions of hydrobenzoins: effect of catalyst and reaction medium on product composition1992In: Acta Chemica Scandinavica, ISSN 0904-213X, E-ISSN 1902-3103, Vol. 46, p. 283-289Article in journal (Refereed)
  • 63.
    Jönsson, L.
    et al.
    University of Lund.
    Karlsson, Olov
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Lundquist, K.
    Chalmers University of Technology.
    O., Nyman P.
    University of Lund.
    Stereospecificity in enzymic and nonenzymic oxidation of b-O-4 lignin model compounds1990In: FEBS Letters, ISSN 0014-5793, E-ISSN 1873-3468, Vol. 276, no 1,2, p. 45-48Article in journal (Refereed)
  • 64.
    Karlsson, Olov
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Lundquist, Knut
    Stomberg, Rolf
    Studies on hydrobenzoins: preparation, crystal structure and stability of borate complexes1990In: Acta Chemica Scandinavica, ISSN 0904-213X, E-ISSN 1902-3103, Vol. 44, p. 617-624Article in journal (Refereed)
  • 65. Jönsson, L.
    et al.
    Karlsson, Olov
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Lundquist, K.
    Nyman, P. O.
    Trametes versicolor ligninase: isozyme sequence homology and substrate specificity1989In: FEBS Letters, ISSN 0014-5793, E-ISSN 1873-3468, Vol. 247, no 1, p. 143-146Article in journal (Refereed)
    Abstract [en]

    The substrate specificity of three ligninase isozymes from the white-rot fungus Trametes versicolor has been investigated using stereochemically defined synthetic dimeric models for lignin. The isozymes have been found to attack non-phenolic β-O-4 as well as β-1 lignin model compounds. This finding confirms the classification of the isozymes from T. versicolor as ligninases. The amino-terminal residues of the three isozymes from T. versicolor have been determined using Edman degradation. Minor differences found between the sequences suggest the existence of several structural genes for ligninase in T. versicolor. Comparisons have been made with the sequences of three previously reported ligninases from Phanerochaete chrysosporium, another lignin-degrading fungus. One of the sequences from P. chrysosporium is distinctly more similar to the T. versicolor isozymes than to the other two sequences from P. chrysosporium.

12 51 - 65 of 65
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