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  • 201.
    Friman, Linda
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Höglund, Hans
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Högberg, Hans-Erik
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Agnemo, Roland
    Tannin-iron impregnated thermomechanical pulp: Part II: Bleachability and brightness reversion2004Ingår i: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 19, nr 4, s. 525-531Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Tannins are polymeric, phenolic constituents found in the bark of pine and spruce. When reacting with iron ions, tannins form strongly coloured complexes. Thus, the presence of bark in the mechanical pulping process leads to decreased brightness of the pulp. In order to evaluate the effects of the presence of iron on the properties of pulp, we have impregnated thermomechanical pulp (TMP) with 30 parts per million (ppm i.e. mg/kg) iron either as Fe3+ or as tannin-iron complexes and studied how such treatments affect bleachability and heat-induced brightness reversion. The bleaching agents studied are hydrogen peroxide and sodium dithionite. Treatment of the tannin-iron impregnated pulp with 1% by weight of diethylenetriaminepentaacetic acid (DTPA) before bleaching with 4% hydrogen peroxide almost eliminated the brightness loss caused by the impregnation. Such a treatment also removed all of the added iron from both the tannin-iron and FeCl3 impregnated pulps. Approximately 5% more of the added peroxide was required for oxidation of the tannins in the tannin-iron impregnated pulp. Contrary to what was observed with peroxide bleaching, dithionite bleaching did not reduce the amount of iron in the pulps. Instead, the added iron and tannin-iron negatively affected the dithionite bleaching, even if the pulps were extracted with DTPA before bleaching. It should therefore be advantageous to first bleach with peroxide, which removes most of the iron, and then with dithionite. Compared with dithionite, peroxide yields a more efficient bleaching. The reason for this is that the former reduces the light absorption coefficient, the k-value, more efficiently in the whole visible spectrum, whereas dithionite reduces it mainly at shorter wavelengths. In our experiments, the addition of tannin-iron or FeCl3 to the untreated pulp did not increase heat-induced brightness reversion. This is Supported by the fact that although extraction of the samples with DTPA before bleaching lowered the iron content slightly, it-did not affect the brightness reversion. The initial brightness reversion of the dithionite bleached pulps was larger than that observed for the peroxide bleached pulps.

  • 202.
    Friman, Linda
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Logenius, Louise
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Agnemo, Roland
    Högberg, Hans-Erik
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Comparison of metal profiles in thermomechanical pulping processes in which either hydrogen peroxide or dithionite bleaching is used2003Ingår i: Paperi ja Puu/Paper and timber, ISSN 0031-1243, Vol. 85, nr 6, s. 334-339Artikel i tidskrift (Refereegranskat)
  • 203. Fuganti, C.
    et al.
    Grasselli, P.
    Servi, S.
    Högberg, Hans-Erik
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Fermenting Bakers' yeast reduction of a-methyl-b-(2-furyl)acrolein1992-1997Ingår i: Preparative biotransformations: whole cell and isolated enzymes in organic systems, 1992-1997, s. 1-7Kapitel i bok, del av antologi (Övrigt vetenskapligt)
  • 204.
    Fäldt, J.
    et al.
    Royal Institute of Technology, Department of Chemistry, Organic Chemistry, Group of Ecological Chemistry, SE-100 44 Stockholm.
    Sjödin, Kristina
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Persson, M.
    Royal Institute of Technology, Department of Chemistry, Organic Chemistry, Group of Ecological Chemistry, SE-100 44 Stockholm.
    Valterová, I.
    Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic, Flemingovo nám. 2, 166 10 Prague 6, Czech Republic.
    Borg-Karlson, Anna-Karin
    Royal Institute of Technology, Department of Chemistry, Organic Chemistry, Group of Ecological Chemistry, SE-100 44 Stockholm.
    Correlations between selected monoterpene hydrocarbons in the xylem of six Pinus (pinaceae) species2001Ingår i: Chemoecology, ISSN 0937-7409, E-ISSN 1423-0445, Vol. 11, nr 2, s. 97-106Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The compositions of 23 monoterpene hydrocarbons of six pine species (Pinus sylvestris, P. yunnanensis ll,ris, P. armandii, P. tropicalis, P. cubensis and P. caribaca) were compared, using multivariate data analysis. Four of the six species were clearly different from the other species in a Principal Components Analysis (PCA) model, based on the relative amounts (selective normalization) of the monoterpenes. The correlation coefficients between constituents were determined separately for each species and the strongest correlations were found between (+)-alpha -pinene and (+)-camphene and between the corresponding (-)-enantiomers, in all species. This pattern, i.e. a good correlation in all species, was neither shown by the correlation of the structurally more similar (+)-alpha/beta -pinenes, nor by the (-)-alpha/beta -pinenes or within the enantiomeric pairs of alpha -pinene and beta -pinene. For these pairs of monoterpenes, good correlations were found in some species. None of the species showed good correlations in all the investigated monoterpene pairs presented here. Correlations between monoterpenes in insect-attacked trees (P. cubensis and P. caribaea, attacked by Dioryctria horneana, and P. yunnanensis, attacked by Tomicus piniperda) were also determined. The results are discussed from chemotaxonomic and biosynthetic points of view.

  • 205.
    Fält, Susanna
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Model Studies of Cellulose Fibers and Films and Their Relation to paper Strenght2003Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
  • 206.
    Fält, Susanna
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Wågberg, Lars
    Influence of electrolytes on the swelling and strength of kraft-liner pulps2003Ingår i: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 18, nr 1, s. 69-73Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In the present paper, the effect of common process electrolytes NaCl, Na2SO4 and CaCl2 on fibre swelling and paper strength has been investigated. Results show that there is an initial increase in the water retention value (WRV) of the fibres when the salt concentration is increased at a pH of 5 in the solution surrounding the fibres. At higher salt concentrations, the WRV decreases. This behaviour is most pronounced for Na2SO4 and smaller for NaCl and CaCl2.The increase in swelling is explained as being due to an increase in pH in the fibre wall and a subsequent increased dissociation of the carboxyl groups during the initial increase in ionic strength. When the electrolyte concentration is further increased, the difference in osmotic pressure between the interior of the fibre wall and the surrounding solution decreases and eventually the pressure difference drops to zero. It is also found that there is no unique relationship between the WRV and the strength of paper formed from the fibres treated with different electrolyte concentrations.

  • 207.
    Fält, Susanna
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Wågberg, Lars
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Vesterlind, Eva-Lotta
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Swellling of model films of cellulose having different charge densities and comparison to the swelling behavior of corresponding fibers2003Ingår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 19, nr 19, s. 7895-7903Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Cellulose model films with different charge densities were prepared by spin-coating dissolved cellulose in N-methylmorpholine-N-oxide onto SiO2 surfaces. The swelling of the model cellulose films due to exposure to solutions of different electrolytes and at different ionic strengths and pH values were studied using QCM-D (quartz crystal microbalance with dissipation monitoring). Results show that at pH 5, there is a swelling of the film at a low electrolyte concentration (10(-4)-10(-2) M), whereas the deswelling of the film was observed at a high electrolyte concentration (10(-1)-1 M). A considerable swelling of the films is seen when they are treated with deionized water with an increasing pH. The swelling of the films is accompanied by an increase in dissipation, that is, a softening of the material, and the deswelling by a decrease in dissipation, that is, a stiffening of the material. Furthermore, exposure of the films to solutions of different electrolytes affected the swelling of the layer. In this respect, the swelling response of Na2SO4 differs from that of NaCl and CaC1(2) by showing simultaneously high swelling and low dissipation values. The results also show that the rate of swelling reaches its lowest value as the electrolyte concentration reaches the detected limit for the deswelling. The QCM-D results are compared to the swelling of the corresponding carboxymethylated fibers, where a similar behavior was found. However, for the fibers a marked deswelling occurred at a high electrolyte concentration, but only a minor deswelling of the cellulose film was observed. This difference between the materials can be ascribed to noncovalent bonds within the film that will not reform when the swelling forces are decreased at high electrolyte concentrations. A direct measurement of the thickness changes was performed using atomic force microscopy, which shows that the change in frequency measured with QCM-D for the films treated with different NaCl electrolyte concentrations corresponds to changes of 1-2%.

  • 208.
    Fält, Susanna
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Wågberg, Lars
    Vesterlind, Eva-Lotta
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Larsson, P.T.
    Model films of cellulose II - Improved preparation method and characterization of the cellulose film2004Ingår i: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882X, Vol. 11, nr 2, s. 151-162Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    An optimization study of the preparation of spin-coated cellulose model films from the NMMO/DMSO system on silicon wafers has been made. The study shows that the cellulose concentration in the solution determines the cellulose film thickness and that the temperature of the solution affects the surface roughness. A lower solution temperature results in a lower surface roughness at cellulose concentrations below 0.8%. Using the described method, it is possible to prepare films with thicknesses of 30-90 nm with a constant surface roughness by changing the cellulose concentration, i.e. by dilution with DMSO. On these films, water has a contact angle less than 20degrees and about 50% of the material can, according to CP/MAS C-13-NMR spectroscopy on corresponding fibrous material, be considered to consist of crystalline cellulose II type material. It has further been shown that AFM can be used to determine the thickness of cellulose films, in both dry and wet states. In this method, the difference in height between the top surface and the underlying wafer has been measured at an incision made into the cellulose film. The cellulose films have also been spin-coated with the same technique as on the silicon oxide wafer onto the crystal in a quartz crystal microbalance (QCM). These model films were found to be suitable for swelling measurements with the QCM. The films were very stable during this type of measurement and films with different amounts of charges gave different swelling responses depending on their charges. As expected, films with a higher charge showed a higher swelling.

  • 209.
    Geibe, Christine
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Effects on soil solution chemistry caused by sampling method, soil treatment and vegetation2005Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
  • 210.
    Geibe, Christine
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Danielsson, Rolf
    Uppsala University.
    van Hees, Patrick A.W
    Örebro University.
    Lundström, Ulla. S
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Comparison of soil solution chemistry sampled by centrifugation, two types of suction lysimeters and zero-tension lysimeters2006Ingår i: Applied Geochemistry, ISSN 0883-2927, E-ISSN 1872-9134, Vol. 21, nr 12, s. 2096-2111Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The choice of sampling method for soil solution is of great importance. In this paper soil solution chemistry sampled by centrifugation, two types of suction lysimeters and zero-tension lysimeters have been studied with the purpose of investigating systematic differences between them. The samples were taken at 4 depths from an acidified forest soil as well as from adjacent lime and ash treated soils. A centrifugation drainage method was compared with two types of suction lysimeters (‘Rhizon’ and ‘Prenart’) and zero-tension lysimeters. About half of the 27 variables measured showed a significant difference between the sampling methods used. Typically the centrifuged samples had lower pH (4.0 vs. 4.4), Ca (21 lM vs. 30 lM) and Mg (25 lM vs. 34 lM) concentrations and higher Cl (330 lM vs. 230 lM) and DOC (4.4 mM vs. 3.2 mM) concentrations than the Rhizon lysimeters. Also the other lysimeters showed significant differences compared to the centrifuged samples for about half the number of analytes. Centrifuged samples had higher concentrations of all analytes except NO3 and PO4 compared to zero-tension lysimeters and also for all analytes except NO3 and Al compared to Prenart lysimeters. Among the environmental factors considered depth showed an influence to some extent, while sampling occasion had a great significant impact on the difference between the centrifugation method and the Rhizon lysimeters. Factors like individual pits or soil treatment did not show any influence on the difference between the methods.

  • 211.
    Geibe, Christine E
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Holmström, Sara J. M
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    van Hees, Patrick A. W
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Lundström, Ulla
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Impact of lime and ash applications on soil solution chemistry of acidified podzolic soils.2003Ingår i: Water, Air and Soil Pollution, ISSN 0049-6979, E-ISSN 1573-2932, Vol. 3, nr 4, s. 77-96Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Soil solution samples were taken from two sites (Horröd and Hasslöv) in the south part of Sweden to evaluate how soil solution chemistry responded to different treatmentswith dolomite and wood ash. At Horröd, samples were taken four years after application of wood ash, 4.28 ton ha-1 and dolomite, 3.25 ton ha-1. At Hasslöv dolomite, 3.45 ton ha-1 and 8.75 ton ha-1 was applied and samples were taken 15 yr later. It was found that treatment with dolomite at one site (Hasslöv) resulted in higher pH values (<2 pH units) and higher nitrification. It was also found at this site that the total Al and the inorganic Al concentrations decreased with dolomite treatment. The Ca, Mg, DOC, Fe, SO4 2- and Cl- concentrations, mainly in the topsoil, were found to be higher at both sites, following dolomite treatment; Ca and Mg concentrations were 2–8 times higher (<820 mgrM) than in controls (<70 mgrM). Wood ash was found to have less impact. The PO4 concentration in the O2 horizon at Hasslöv decreased due to dolomite-treatment. ANOVA (Analyse of Variance) and PLS (Partial Least Square) were used to evaluate the data from the two sites.

  • 212. Gernandt, Renate
    et al.
    Wågberg, Lars
    Gärdlund, Linda
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Dautzenberg, Herbert
    Polyelectrolyte complexes for surface modification of wood fibres I: Preparation and characterisation of complexes for dry and wet strength improvement of paper2003Ingår i: Colloids and Surfaces A: Physicochemical and Engineering Aspects, ISSN 0927-7757, E-ISSN 1873-4359, Vol. 213, nr 1, s. 15-25Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Polyelectrolyte complexes (PEC) were formed between a cationic polyamideamine epichlorohydrine condensate (PAE) and an anionic carboxymethylcellulose (CMC) at different ratios between the polymers, orders of mixing, salt concentrations and polymer concentrations. Firstly the polymers were characterised by polyelectrolyte titration (charge), static light scattering (molecular weight, radius of gyration) and measurements with a scanning interferometric refractometer (refractive index). The complexes were characterised by ocular inspection and static light scattering in combination with a special evaluation algorithm allowing an estimation of the geometric form of the complexes. The results show that the initial complexes have a spherical form and that the size is fairly constant over a large range of charge ratios between the polymers, provided the complexes are formed in deionised water. When the charge mixing ratio exceeded neutrality a secondary agglomeration of the initially formed complexes occurred. The presence of salt during PEC formation caused a dependence of the level of aggregation on the mixing ratio, whereby small amounts of NaCl drastically lowered the particle mass at lower mixing ratios. Subsequent addition of salt to PECs formed in water led to a strong swelling of the complex particles and at a critical salt concentration to dissolution.

  • 213. Giesler, R.
    et al.
    Ilvesniemi, H.
    Nyberg, L.
    van Hees, P. A. W.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Starr, M.
    Bishop, K.
    Kareinen, T.
    Lundström, Ulla
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Distribution and mobilization of Al, Fe and Si in three podzolic soil profiles in relation to the humus layer.2000Ingår i: Geoderma, ISSN 0016-7061, E-ISSN 1872-6259, Vol. 94, nr 2-4, s. 249-263Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The mobilization of Al, Fe and Si in podzols is often associated with the weathering of silicate minerals in the E horizon, downward migration, and their accumulation lower in the soil profile. This study investigated Al, Fe, and Si concentrations in soil water (centrifugation samples) and estimated leaching losses from the humus layer in comparison with those in the mineral E and B horizon. Concentrations of total soluble Al and Fe in soil water were higher in the O and E horizons than in B horizon samples, but not significantly different between the two uppermost horizons. Si concentrations were higher in the E than in the O horizon. The amount of Al and Fe leaching from the E horizon (i.e. input to the B horizon) compared to amount leaching from the O horizon (i.e. the input to the E horizon) ranged from 92% to 163%. Calculated leaching losses from the lower B horizon were less than 3% of the input to the B horizon. The results suggest that a large part of the illuviated Al and Fe in the Bs horizon is derived from the O horizon. Similar values for the Si ranged from 56% to 61% (comparing E horizon output with E horizon input). Budget estimates available for one of the investigated podzols indicated that biocycling via above-ground litter explained < 12% of the estimated annual input of Al and Fe to the forest floor. Inputs of Al and Fe due to upward flow of capillary water accounted for about 26% of the Al and Fe in the O layer. The results show that there is a considerable pool of Si Al, Fe in the humus layer. This pool plays an important part in the present day biogeochemical cycling of these elements in podzolic soils. Several mechanisms possibly involved in the transfer of Al, Fe and Si from the mineral soil to the humus layer are discussed.

  • 214.
    Glans, Peter
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Gunnelin, K
    Skytt, P
    Guo, J.H.
    Wassdahl, N
    Nordgren, J
    Ågren, H
    Gelmukhanov, F.K.
    Warwick, T
    Rotenberg, E
    Resonant x-ray emission spectroscopy of molecular oxygen1996Ingår i: Physical Review Letters, ISSN 0031-9007, Vol. 76, nr 14, s. 2448-2451Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Resonant soft x-ray emission spectroscopy has been applied to study the issue of symmetry breaking upon core-hole excitation in molecular oxygen. The results provide direct evidence that the inversion symmetry is not broken in the core-excited states. Furthermore, the experiments themselves demonstrate a new experimental technique of broad applicability for studies of electronic structure and excitation dynamics in free atoms and molecules.

  • 215. Gowda, J.H.
    et al.
    Albrectsen, B.R.
    Ball, J.P.
    Sjöberg, M
    Palo, Thomas
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Spines as mechanical defence: The effect of fertiliser treatment on juvenile Acacia tortillis plants2003Ingår i: Acta Oecologica, ISSN 1146-609X, Vol. 24, nr 1, s. 1-4Artikel i tidskrift (Refereegranskat)
  • 216. Gowda, Juan H
    et al.
    Palo, Thomas
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Age related changes in defensive traits of Acacia tortillis2003Ingår i: African Journal of Ecology, ISSN 0141-6707, Vol. 41, nr 3, s. 218-223Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The theory of plant defences proposes that investments in physical and chemical defences are driven by the risk of herbivore damage, and limited by the cost of producing the particular defensive trait in terms of resources that could be directed to other sinks, such as growth and reproduction. We sampled twigs of 18 mature Acacia tortilis trees and their cohort of juveniles to test some predictions of this hypothesis. We expected a higher allocation of defensive traits to leaves and twigs in the young plants than in the mature ones as a result of a higher risk of damage by ungulates at the juvenile stage. Our results show that the juvenile plants produce more spines along their twigs, but have lower concentrations of phenolic compounds in their leaves than in the mature ones. We also expected a negative relation between the concentration of foliar nutrients and phenolic compounds, as predicted by the carbon/nutrient hypothesis. Only mature plants showed this pattern. Reproduction (in mature plants) and water stress (in juvenile plants) did not relate to allocation to secondary compounds as predicted by current hypotheses of plant defence.

  • 217.
    Gradin, Per A
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Acoustic emission monitoring during mechanical-loading of paper: State of the art2004Rapport (Övrigt vetenskapligt)
  • 218.
    Gradin, Per A.
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik, fysik och matematik.
    Johansson, Ola
    Sunds Defibrator AB.
    Berg, Jan-Erik
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Nyström, Staffan
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik, fysik och matematik.
    Measurement of the Power Distribution in a Single Disc Refiner1999Ingår i: Journal of Pulp and Paper Science, ISSN 0826-6220, Vol. 25, nr 11, s. 384-387Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A vital parameter in the production of mechanical pulp through refining is the energy consumption. Until recently, the pulping industry has focused on the total energy consumed, without a full understanding of how this energy is distributed in the refiners. In this paper two methods are suggested by which it is possible to estimate the energy supplied at an arbitrary point along the disc radius on refiner segments. The methods are based on instrumented bar with strain gauges. In the first method, a bar is slotted so that the sensor can be viewed as consisting of a number of cantilever beams separated by slots. In the second method, the sensor consists of one continuous bar along the disc radius. The sensors are calibrated such that influence coefficients are obtained for the slotted case and an influence function is obtained for the continuous one. The tangential forces are obtained directly in the first method, while in the second they are given by an integral equation which can be solved numerically. From the knowledge of the tangential force the power distribution can be calculated. Experimental results from the use of the slotted sensor are also given.

  • 219.
    Gradin, Per
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Backlund, Hans-Olof
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    New sensors for measurement of tangential force distribution in mill-scale TMP chip refinersManuskript (preprint) (Övrigt vetenskapligt)
  • 220. Granberg, H
    et al.
    Edström, Per
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Quantification of the intrinsic error of the kubelka–munk model caused by strong light absorption2003Ingår i: Journal of Pulp and Paper Science (JPPS), ISSN 0826-6220, Vol. 29, nr 11, s. 386-390Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The Kubelka-Munk (KM) model is widely used within the paper industry to interpret diffuse reflectance factor measurements of paper and its components. It has been found in the literature that the addition of a dye colorant to a paper sheet not only increases its KM light absorption coefficient, but for strong absorption also decreases its KM light scattering coefficient. This effect has previously been attributed to the intrinsic error of the KM model induced by light absorption that tends to orient of the light fluxes perpendicular to the sheet. In the present work we have mapped the intrinsic error of the KM model by comparing light scattering calculations from the KM model with the more accurate Discrete Ordinate Radiative Transfer model DORT2002. We found that the models agree within 2.3% in reflectance, and that the intrinsic error in the KM model explains about 1/5 of the previously observed interdependence of the KM coefficients for heavily dyed sheets.

  • 221.
    Grönlund, Erik
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik, fysik och matematik.
    Johansson, E
    Hanaeus, J
    Falk, Stefan
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Seasonal microalgae variation in a subarctic wastewater stabilization pond using chemcial precipitation2004Ingår i: Vatten, ISSN 0042-2886, Vol. 60, nr 4, s. 239-249Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Surface water microalgae samples were collected during the ice-free period in a small subarctic wastewater stabilization pond system, complemented with chemical precipitation during the winter period (fellingsdam), and serving 310 persons. In the primary pond microalgae dominance alternated between the Cryptophyte Cryptomonas and green algae (Chlorophyta). In the second and third pond the general pattern was that Cryptomonas dominated during summer but was replaced by green algae in autumn and the following spring. Estimations of the microalgae part of the effluent COD and phosphorus showed that microalgae dominated these parameters for only 3-4 weeks of 12 evaluated. This does not support the reasoning behind the European Union directive of the use of filtered samples for effluent BOD, COD and SS from stabilization ponds, in contrast to other wastewater treatment methods. The reasons behind the EU's procedure for ponds are based on the assumption that stabilization ponds convert "sewage BOD" to "algal BOD". The results of this study suggest that further investigations of the microalgae function in subarctic wastewater stabilization ponds and fellingsdams should be conducted, before implementing the EC directive into Swedish law, or into similar laws in other countries with subarctic regions.

  • 222. Gunnars, S.
    et al.
    Wågberg, Lars
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Cohen Stuart, M. A.
    Model films of cellulose: I. Method development and initial results2002Ingår i: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882X, Vol. 9, nr 3/4, s. 239-249Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This report presents a new method for the preparation of thin cellulose films. NMMO (N- methylmorpholine- N-oxide) was used to dissolve cellulose and addition of DMSO (dimethyl sulfoxide) was used to control viscosity of the cellulose solution. A thin layer of the cellulose solution is spin- coated onto a silicon oxide wafer and the cellulose is precipitated in deionised water. The cellulose film is anchored onto the silicon oxide wafer by a saturated polymer layer. Among many different polymers tested, PVAm (polyvinylamine) and G- PAM (glyoxalated- polyacrylamide) worked well. The preparation of cellulose model films described in this paper resulted in films with thicknesses in the range 20- 270 nm and the thickness can be controlled by altering the concentration of cellulose solution by addition of different amounts of DMSO. The films were cleaned in deionised water and were found to be free from solvents by ESCA analysis and contact angle measurements. The molecular weight distribution of the cellulose surface material shows that there is only minor breakdown of the cellulose chains, mainly by cleavage of the longest molecular mass fraction and without creation of low molecular mass oligomers of glucose.

  • 223. Gustafsson, Jon Petter
    et al.
    van Hees, Patrick
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Starr, Michael
    Karltun, Erik
    Lundström, Ulla
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Partitioning of base cations and sulphate between solid and dissolved phases in three podzolized forest soils2000Ingår i: Geoderma, ISSN 0016-7061, E-ISSN 1872-6259, Vol. 94, nr 2-4, s. 311-333Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The cation and SO4 adsorption properties of O and B horizons of three podzolised soils in Sweden and Finland were studied through analysing the soil solution at six different sampling occasions and through a set of batch experiments. High concentrations of dissolved organic carbon and cations were found in centrifuged soil solutions from the O horizon, especially during autumn. An analysis using the WHAM-S model suggested that most of the dissolved Ca, Mg, K and Mn were counter-ions, residing in the diffuse layers of dissolved fulvic acids. Hence, the solubility of these cations depended on the solubility of organic matter. Model exercises suggested that the solubility of humics in turn was influenced by seasonal differences in hydrophobicity and by the water content. Furthermore, the model results showed that only a low proportion of the B horizon organic matter was involved in calcium binding. This is probably due to the interaction between organic matter and oxide surfaces in this horizon. In the case of sulphate adsorption in the B horizons, a surface complexation model was tested for its ability to describe batch experiment data and temporal differences in soil water chemistry. This model was based on the diffuse-layer model and it was optimised by adjusting the surface site concentration and the point of zero charge. However, the interaction between Ca2+ and SO4/2- could not be modelled. Comparisons between the model and the field observations proved to be difficult due to a considerable soil heterogeneity. (C) 2000 Elsevier Science B.V.

  • 224.
    Gustavsson, Leif
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik, fysik och matematik.
    Joelsson, Anna
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik, fysik och matematik.
    Uddin, Noim
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Large scale biomass-based heating systems and energy conservation2004Ingår i: Biomass for energy, industry and climate protection : Second World Biomass Conference; proceedings of the world conference held in Rome, Italy, 10 - 14 May 2004; [held jointly with the 13th European Conference on Biomass for Energy, Industry and Climate Protection]: World Conference on Biomass for Energy, Industry and Climate Protection ; 2 (Rome) : 2004.05.10-14, Florens and Munich: ETA , 2004, s. 1978-1983Konferensbidrag (Refereegranskat)
  • 225.
    Gustavsson, Leif
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik, fysik och matematik.
    Uddin, Noim
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Efficient Use of Forest Resources2003Ingår i: International Nordic Bioenergy Conference, September 3-5, 2003, Finland, 2003, s. 165-170Konferensbidrag (Övrigt vetenskapligt)
  • 226.
    Gylle, A Maria
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Isaksson, Dan
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Ekelund, Nils
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    THE CONCENTRATIONS OF MANNITOL IN FUCUS VESICULOSUS AS A RESPONSE TO DIFFERENT SALINITIES2005Ingår i: PHYCOLOGIA, 2005, s. 42-42Konferensbidrag (Refereegranskat)
  • 227.
    Gylle, A. Maria
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Isaksson, Dan
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Ekelund, Nils G. A.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Seasonal variations in photosynthetic capacity and osmotic adjustment in Fucus vesiculosus and F. radicans (Phaeophyceae) with respect to salinityManuskript (preprint) (Övrigt vetenskapligt)
    Abstract [en]

    The marine intertidal Fucus vesiculosus from the Norwegian Sea (34 practical salinity units, psu) and the sublittoral F. vesiculosus and F. radicans from the brackish Bothnian Sea (5 psu) have been compared physiologically with respect to changes in salinity and seasons. The initial maximum quantum yield of photosystem II photochemistry (Fv/Fm) did not vary between the marine and brackish ecotypes or between the seasons but showed different responses to the experiment condition at different seasons. In general, there were no differences in the ability to withstand salinity changes, measured as Fv/Fm, between the marine and brackish ecotype. The tolerance is in a broad range for both of the ecotypes. The marine ecotype of F. vesiculosus had 30 % more mannitol than the brackish F. vesiculosus and there was 35 % more mannitol in May compared to November. The mannitol content in the marine ecotype responded differently to salinity changes in May compared to November, probably partly due to different initial concentrations. No changes in mannitol content could be detected in brackish F. vesiculosus. No significant differences were shown in Fv/Fm and mannitol content between brackish F. vesiculosus and F. radicans.

  • 228.
    Gylle, A. Maria
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Isaksson, Dan
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Ekelund, Nils G A.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    The relation between water soluble organic compounds and salinity in marine and brackish Fucus vesiculosus L. (Phaeophyceae)Manuskript (preprint) (Övrigt vetenskapligt)
    Abstract [en]

    The marine intertidal Fucus vesiculosus from the Norwegian Sea (34 practical salinity units, psu) and the sublittoral F. vesiculosus from the brackish Bothnian Sea (5 psu) have been compared with respect to the production of water soluble organic compounds during treatment in varying salinities. Nuclear magnetic resonance (NMR) 13C spectra revealed that there were differences in the content of water soluble organic compounds between the marine and the brackish F. vesiculosus and that production of these compounds was independent of salinity.

  • 229.
    Gylle, A. Maria
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Nygård, Charlotta A
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Pocock, Tessa
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Ekelund, Nils G. A.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Salinity effect on oxygen evolution and the relative amount of RuBisCO in the brackish Fucus vesiculosus L. (Phaeophyceae)2007Ingår i: Pysiological responses of marine and brackish Fucuc vesiculosus L with respect to salinity, Sundsvall: Mittuniversitetet , 2007, s. 1-8Kapitel i bok, del av antologi (Övrigt vetenskapligt)
    Abstract [en]

    The sublittoral Fucus vesiculosus from the brackish Bothnian Sea is adapted to a salinity of 4-5 practical salinity units (psu). This study investigated the effect of different salinities (5, 10, 20 and 35 psu) on maximum photosynthetic capacity (Pmax) and the relative amount of ribulose 1,5-bisphosphate carboxylase/oxygenase (Rubisco). The results revealed a higher Pmax at higher salinities with the maximum at 10 psu. Higher salinities also resulted in increased relative amounts of Rubisco but this was not well correlated with the increased Pmax. Therefore, the amount of Rubisco doesn�t appear to be the main reason for the increased Pmax in higher salinities.

  • 230.
    Gylle, Maria
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Physiological responses of marine and brackish Fucus vesiculosus L. with respect to salinity2007Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    The intertidal brown alga Fucus vesiculosus L. is mainly a marine species (34 practical salinity units, psu), but the alga also grows in the sublittoral of the brackish Bothnian Sea (part of the Baltic Sea; 5 psu). The conditions at the growth sites are clearly different between the Bothnian Sea and the Norwegian Sea (part of Atlantic) with constant low salinity and a lack of tides in the Bothnian Sea. The objectives of the thesis were to compare the physiology in marine and brackish ecotypes of F. vesiculosus with respect to salinity and the ability of F. vesiculosus to acclimate to different salinities. A study of photosynthetic maximum capacity and relative amount of Rubisco in relation to salinity in brackish F. vesiculosus were also performed. The results showed that both ecotypes of F. vesiculosus have the same potential to use the available excitation energy for photochemistry. The results also suggest that this is relatively independent of salinity changes. There were a higher number of water soluble organic compounds, higher mannitol content (mmol kg‐1 DW), lower chlorophyll (Chl) content (mg g‐1 DW) and higher tolerance to desiccation in the marine ecotype. The number of water soluble carbon compounds did not change when the algae were treated to either high or low salinities and it was suggested that the differences were due to an intertidal or sublittoral acclimation, and not salinity. Both ecotypes showed changed mannitol content as a response to changed salinity but the changes were different between the ecotypes and seasons. The content of mannitol and the osmotic adjustment by mannitol in a longer timescale than 24 h appears to be closely connected to irradiance and photosynthesis in addition to the salinity. The main reason for higher rate of photosynthesis in higher salinity for the brackish ecotype is not clarified because no correlation could be detected between photosynthesis and the relative amount of Rubisco. The Chl content increased in darkness and the differences between the ecotypes are probably due to a compensation for low irradiance in the sublittoral growth site. Higher tolerance for desiccation in marine ecotype was concluded to be due to a lower rate of water loss because of more mannitol and thicker thallus.

  • 231.
    Gylle, Maria
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Nygård, Charlotta
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Ekelund, Nils G. A.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Impacts of UV-radiation on photosynthesis of Fucus vesiculosus at low temperature and different salinities2002Ingår i: Internationale Vereinigung für theoretische und angewandte Limnologie, ISSN 0368-0770, Vol. 28, s. 242-245Artikel i tidskrift (Refereegranskat)
  • 232.
    Gärdlund, Linda
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Polyelectrolyte Complexes: Their Characterization and use for Modification of Wood Fibre Surfaces2006Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    For economical reasons filler particles and less expensive fibre raw materials are more frequently used in papermaking. This influences the mechanical properties of the formed papers in a negative way and it is therefore necessary to add strength-enhancing agents to the papermaking furnish. Traditionally cationic starch has been the dominating additive used for strength enhancement but new techniques are continuously being developed and in the present work the use of polyelectrolyte complexes (PEC) for improvements of different paper strength properties has been evaluated. Large focus has also been given to evaluating the properties of the polyelectrolyte complexes since these properties are largely dependant on molecular mass of the polyelectrolytes, the mixing conditions and ionic strength of the polyelectrolyte solutions. The PEC formation was studied between chemicals already used for strength enhancing purposes in real papermaking systems, i.e. poly (amido-amine) epichlorohydrin (PAE) and carboxymethylcellulose (CMC). The PEC formation was studied with respect to fundamental characteristics and the ability for use as strength additives. The PEC formation was also studied using model polyelectrolytes (PEL) poly(allylamine hydrochloride) (PAH), as the cationic component, and poly(acrylic acid) (PAA) and poly(methacrylic acid) (PMAA), as the anionic components. The fundamental studies involve the PEC formation by varying the mixing ratio between the polyelectrolytes, the charge density or molecular weight of a component, structure of the one polyelectrolyte component, the mixing order, together with solution conditions. The main techniques used for these purposes were the static and dynamic light scattering, AFM tapping mode and Cryo-TEM. The adsorption of PECs onto surfaces of silica and lignin was investigated, using the stagnation point adsorption reflectometry (SPAR) and QCM-D (quartz crystal microgravimetry with dissipation). With these two techniques the amount of adsorbed chemical is obtained an also the viscoelastic properties of the adsorbed layer. The stability of PECs towards an increase in salt concentrations was investigated and the PECs were stable up to 0.2-0.4 M NaCl before complete dissolution, suggesting that the driving force for the formation of the PECs (from CMC-PAE) is a combination of the entropic effect of the released counterions and an enthalpy contribution from the interaction between the polymer segments. The PECs did not change their 3D-structure upon drying. It was also found that the swollen 3D structure of the complexes is achieved by an incorporation of a large amount of water into the complexes. Calculations based on the collected results show that the complexes consist of between 60 % and 95 % water. The PECs formed from PAA and PAH displayed higher water content when formed from low PEL concentration and salt concentrations up to 0.1 M NaCl than the PMAA-PAH PECs. At high PEL concentration and high salt concentration the opposite was observed. The use of the complexes as dry strength additives has two large benefits. First of all the 3D structure of the complexes allows for an efficient bridging between the microscopically rough fibre surfaces. Secondly the complexes allows for a higher saturation adsorption of polyelectrolytes on the fibre surface compared with a single polyelectrolyte addition. The PEC addition also leads to an increase in density, but the PECs showed the same benefits as beating when added to the unbeaten fibres. The effect on the fibre material, with regard to paper properties, varies depending on the pulp used.

  • 233.
    Gärdlund, Linda
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Forsström, Jennie
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Andreasson, Bo
    Wågberg, Lars
    Influence of polyelectrolyte complexes on strength properties of papers made from unbleached kraft pulps with different yields2005Ingår i: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 20, nr 1, s. 36-42Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The properties of the materials combined in corrugated

    board are set to give the board its strength, flexibility

    and protection towards impact and pressure. The raw material is

    of course the single fibre but additives that enhance e.g. the wet

    and dry paper strength are also added. As the strength

    enhancing additives used today are most efficient between pH 4

    and pH 7 there is a need for new types of additives that can be

    used under alkaline conditions. In the present report polyallylamine

    hydrochloride (PAH) and polyelectrolyte complexes

    (PEC) of PAH and polyacrylic acid (PAA) were investigated as

    strength enhancing additives. The components can be used

    under alkaline conditions and results showed that PAH alone or

    incorporated into a PEC gave different effects regarding

    strength properties of sheets from kraft pulps of different yields.

    The results showed that by treating the fibres with PEC´s of

    PAH and PAA it was possible to considerably increase the

    tensile properties, the Z-strength and the compression strength

    of papers made from the treated fibres. The results showed an

    increase of as much as 54 % to 180 % in dry Z-strength and 14

    % to 53 % in compression strength, when using the PEC as an

    additive, indicating an increase in inter-fibre joint strength. It

    was also found that a heat treatment of the non-treated papers

    and of the papers from the PAH treated fibres gave a large

    improvement in tensile properties as well as Z-strength properties

    for the different pulps. For the PEC treated fibres it was not

    necessary to heat-treat the paper to achieve a higher dry

    strength. The molecular mechanism behind the large improvements

    is not identified in the present work but the problem is

    currently being investigated in the lab of the authors.

  • 234.
    Gärdlund, Linda
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Norgren, Magnus
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Wågberg, Lars
    KTH.
    Marklund, Ann
    The use of polyelectrolyte complexes (PEC) as strength additives for different pulps used for production of fine paper2007Ingår i: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 22, nr 2, s. 210-216Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this work the application of polyelectrolyte complexes (PEC) to different pulps, to improve the strength of papers produced from them, is compared with conventional pulp beating. The pulps chosen for the investigation were a fully bleached chemical hardwood pulp (HBK), a fully bleached chemical softwood pulp (SBK), and a peroxide-bleached chemi-thermomechanical pulp (BCTMP). The polyelectrolytes used were a polyamideamine epichlorohydrine condensate (PAE), traditionally used as a wet-strength additive, and carboxymethylcellulose. Since the complexes prepared from these chemicals bear an anionic charge, they can only be used after fibre pre-treatment with the cationic PAE. Results indicate that the addition of 2% PAE and 2% PEC can improve all the measured tensile strength properties of the sheets as much as is commonly achieved by mechanically beating the pulps. In fact, for the chemical pulps, PEC addition at the chosen level produced better results than did traditional beating, since the improved tensile index and tensile energy absorption could be achieved without any significant deterioration in the light scattering coefficient of the papers produced. However, with the BCTMP a significant decrease in light scattering could be detected, especially following the addition of PEC. Adding the chemicals (especially the PEC) increased the sheet density, so chemical treatment left the bending stiffness of the sheets unaffected. However, based on the results, it was suggested that a combination of unbeaten HBK and BCTMP treated with PAE and PEC should be used as the fibre components of a typical fine paper furnish.

  • 235.
    Gärdlund, Linda
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Wågberg, Lars
    KTH, Fiber and Polymer Technology Department, Fibre Technology, S-100 44, Stockholm, Sweden.
    Gernandt, Renate
    Polyelectrolyte complexes for surface modification of wood fibres II: Influence of complexes on wet and dry strength of paper2003Ingår i: Colloids and Surfaces A: Physicochemical and Engineering Aspects, ISSN 0927-7757, E-ISSN 1873-4359, Vol. 218, nr 1-3, s. 137-149Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The current paper presents a way of enhancing paper strength by the use of polyelectrolyte complexes (PEC) of cationic poly (amide, amine) epichlorohydrin condensate (PAE) and anionic carboxymethylcellulose (CMC). In this study the complexes were pre-formed in different mixing ratios, but with an overall anionic charge. The complexes were characterized by means of size, charge, and adsorption properties both to fibres and to model silica surfaces. Finally the PEC�s were applied as strength additive in paper sheet preparation. The main findings are that by changing polymer weight-ratios when preparing the complexes the charge and the amount adsorbed could be altered. Addition of the complexes to the fibres before sheet preparation led to a significant increase in strength of the paper, compared to sheets prepared with only the PAE. The strength improvement depended upon the mixing ratio and a maximum in dry strength was found for complexes where the anionic charge of the CMC had been neutralized to 60%. Paper strength; Polyelectrolyte Complexes; PAE; CMC; Strength additive

  • 236.
    Gärdlund, Linda
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Wågberg, Lars
    Royal Institute of Technology, Stockholm.
    Norgren, Magnus
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    New insights into the structure of polyelectrolyte complexes2007Ingår i: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 312, nr 2, s. 237-246Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The formation of polyelectrolyte complexes (PECs) prepared from oppositely charged linear polyelectrolytes (PELs) was studied by static light scattering at various salt concentrations. The PELs used were poly(allylamine hydro chlorid) (PAH) and the two polyanions poly(acrylic acid) (PAA) and poly(methacrylic acid) (PMAA). Physical characteristics such as radii of gyration and molecular weights as well as water content of the PECs were determined at various molar mixing ratios. In spite of the relatively small difference in chemical structure between PAA and PMAA, fairly large differences in the mentioned parameters were detected. Generally, PECs consisting of PMAA were larger and contained more water. Moreover, by using cryogenic transmission electron microscopy, transmission microscopy and atomic force microscopy, shape and structure of the prepared PECs were investigated both in solution and after drying. The PECs were found to be spherical in solution and the shape was retained after freeze-drying. PECs adsorbed on silica surfaces and dried in air at room-temperature still showed a three-dimensional structure. However, from the relatively low aspect ratios determined, the PECs were found to be significantly collapsed due to interactions with the silica surface during the adsorption and drying processes.

  • 237.
    Göransson, Kristina
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Zhang, Wennan
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    A technical description of BTL laboratory at Mid Sweden University2007Rapport (Övrigt vetenskapligt)
  • 238. Halldin, S
    et al.
    Bergström, H
    Gustafsson, D
    Dahlgren, L
    Hjelm, P
    Lundin, L-C
    Mellander, Per-Erik
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Nord, T
    Jansson, P-E
    Seibert, J
    Stähli, M
    Szilágyi Kishné, A
    Smedman, A S
    Continuous long-term measurements of soil-plant-atmosphere variables at an agricultural site1999Ingår i: Agricultural and Forest Meteorology, ISSN 0168-1923, Vol. 98-99, s. 75-102Artikel i tidskrift (Refereegranskat)
  • 239.
    Halvarsson, Sören
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Norgren, Magnus
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Edlund, Håkan
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Manufacturing of fiber composite Medium Density Fiberboard (MDF) based on annual plant fiber and Urea Formaldehyde Resin2004Ingår i: Proceedings of ICECFOP1: 1st International Conference on Environmentally-Compatible Forest Products, EDICOES UNIV FERNANDO PESSOA , 2004, s. 131-147Konferensbidrag (Refereegranskat)
    Abstract [en]

    Production of fiber composite materials such as Medium Density Fiberboard (MDF) and particleboard (PB) is in general based on wood as a raw material. However, cereal straws and other annual agriculture waste materials have regained an interest as a potential raw material for production of MDF. The cereal straws are among the most common lignocellulosic materials that are easily accessible, non-expensive and renewable. The aim of this investigation was to produce high performance MDF based on wheat straw and urea formaldehyde (UF) resin. The usage of UF-resin for wheat straw MDF-panels has so far resulted in acceptable strength properties but poor moisture resistance and thickness swelling (TS). Application of melamine modified UF-resin for wood based MDF has improved the moisture resistance of produced MDF panels. In this investigation two commercial melamine modified UF-resins were used as binders (adhesives) in the production of wheat straw MDF. Hammer milled wheat straw was treated with water and sulfuric acid (0.6 %) before refining. The reason was to improve the curing, conditions of the UF-resins by a reduction of the pH and the pH-buffering capacity of refined wheat straw fiber. Refining of wheat straw was performed at slightly lower pressure and retention time compared with refining of wood material. However, a lot of fines and dust (wheat straw fibers < 0.5 mm) were generated during refining. A hi-h resin content of the melamine modified UF-resin was necessary (15 %) to compensate for the high ratio of wheat straw fines and dust. Final panel properties of wheat straw MDF could meet the requirements of the MDF standard (EN 622-5:1997), including the TS. Strength properties as internal bond (IB) and modulus of rupture (MOR) were increased as a function of density. Thickness swelling was reduced as a function of density. The usage of wheat straw as a raw material in combination with a melamine modified UF-resin, as an adhesive, is a possible route for manufacturing of high performance Medium Density Fiberboard.

  • 240.
    Halvarsson, Sören
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Norgren, Magnus
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Edlund, Håkan
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Processing of Wheat Straw Materials for Production of Medium Density Fiberboard (MDF) 2005Ingår i: 59th Appita Annual Conference, Aukland, New Zealand 16-19 May 2005, Brunswick East Victoria 3057, Australia: New Genaration Print & Copy , 2005, s. 623-629Konferensbidrag (Övrigt vetenskapligt)
    Abstract [en]

    Wheat straw waste materials were processed in a fully equipped pilot-scale MDF-process. Hammermilled wheat straw was used as a raw material in combination with a commercial melamine modified Urea Formaldehyde (UF) resin. Approximately 15 wt % of the wheat straw particles smaller than 0.7 mm was removed in a sifting operation. Medium density fiberboard was produced in the range of 790 to 860 kg/m3 average densities and at a resin content of 12.5, 13.1 and 14 wt %. The panels produced were approved according to the European Standard for MDF (EN 622-5:1997). Four different wheat straw fractions were investigated and sifted at 1.0 mm, 0.6 mm and 0.2 mm screen hole diameter, including the fine particles less than 0.2 mm. The ash content of the four wheat straw fractions varied between 7 wt % and 15 wt %. The maximum level of ash (15 wt %) was observed for the finest particle fraction based on materials less than 0.2 mm. The silicone (Si) content in corresponding ash samples of the sifted wheat straw was analysed by Energy Dispersive X-ray analysis, EDX. The silicone content increased from 18 % to 24 % at a reduced particle size. Moreover, the pH-buffering capacity of the four wheat straw fractions was reduced as the particle size of the specific fractions was increased.

  • 241. Hansson, B. S.
    et al.
    van der Pers, J. N. C.
    Högberg, Hans-Erik
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Hedenström, Erik
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Sex Pheromone Perception in male pine sawflies, Neodiprion sertifer (Hymenoptera; Diprionidae)1991Ingår i: Journal of Comparative Physiology A, ISSN 0340-7594, Vol. 168, nr 5, s. 533-538Artikel i tidskrift (Refereegranskat)
  • 242. Haslinger, E.
    et al.
    Ottner, F.
    Lundström, Ulla
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Pedogenesis in the Alno carbonatite complex, Sweden2007Ingår i: Geoderma, ISSN 0016-7061, E-ISSN 1872-6259, Vol. 142, nr 1-2, s. 127-135Artikel i tidskrift (Refereegranskat)
  • 243.
    Hedenström, Erik
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Andersson, Fredrik
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Syntheses of female sex pheromone precursors of pine sawflies species and of some structurally related methyl-branched long-chain 2-alkanols2002Ingår i: Journal of Chemical Ecology, ISSN 0098-0331, E-ISSN 1573-1561, Vol. 28, nr 6, s. 1237-1254Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    3,7-Dimethyl-2-undecanol, 3,7,9-trimethyl-2-tridecanol, and 3,7, 11-trimethyl-2-tridecanol were synthesized as racemic mixtures in moderate yields. The alcohols are known precursors of the female sex pheromones of the pine sawfly species Diprion nipponica, Macrodiprion nemoralis, and Microdiprion pallipes, respectively. Stereoisomeric mixtures of 3,8,12-trimethyl-2-tridecanol, erythro-(2R,3R,11R/S)-3,11-dimethyl-2-tetradecanol, 3,5-dimethyl-2-tetradecanol, and 5,7-dimethyl-2-tetradecanol, structurally related to sex pheromone alcohol precursors of pine sawfly species, were also synthesized in moderate yields. The key reaction in the syntheses was the ring opening of γ-butyrolactones by using different alkyl lithiums as nucleophiles.

  • 244.
    Hedenström, Erik
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Andersson, Fredrik
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Hjalmarsson, Mats
    Synthesis of N-propionylated (S)-(-)-2-(pyrrolidin-2-yl)propan-2-ol and its use as a chiral auxiliary and selectivity marker in asymmetric aldol reactions2000Ingår i: Journal of the Chemical Society. Perkin Transactions 1, ISSN 1472-7781, Vol. 2000, s. 1513-1518Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The N-propionylated pyrrolidine derivative and chiral auxiliary, (S)-(-)-2-(pyrrolidin-2-yl)propan-2-ol, was synthesised and used in stereoselective aldol reactions with benzaldehyde. Differences in stereoselectivity were investigated as a function of temperature, solvent, chelating agent and the amount of the chelating agent used by monitoring the 1H NMR spectra of the aldol adducts that were obtained. Among the additives that were investigated, Cp2ZrCl2 induced higher syn-selectivity, while SnCl2 induced higher syn-selectivity respectively. TMSCl was found to induce high selectivity for one syn- and one anti-diastereomer. Varying the ligand sets on titanium additives was found to induce differences in selectivity, with (i-PrO)3TiCl exhibiting syn-selectivity and Cp2TiCl2 exhibiting anti-selectivity. Differences in reactivity and stereoselectivity were also found to depend upon the amount of Lewis acid that was added. Methods for removal of the auxiliary were also investigated. Acidic hydrolysis was used successfully to obtain the desired 3-hydroxy-2-methyl-3-phenylpropionic acids, but was found to give low yields and resulted in a large amount of epimerisation. Furthermore, the ethyl esters of these hydroxy acids are easy to separate into pure syn- and anti-diastereomers by LC. © The Royal Society of Chemistry 2000.

  • 245.
    Hedenström, Erik
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Edlund, Helen
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Lund, Susan
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Stereoselective esterification of 2,6-dimethyl-1,7-heptanedioic acid, catalysed by Candida rugosa lipase2003Ingår i: Journal of Molecular Catalysis B: Enzymatic, ISSN 1381-1177, E-ISSN 1873-3158, Vol. 23, nr 1, s. 53-59Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The immobilised Candida rugosa lipase (CRL) displayed S-preference for both stereogenic centres in this sequential esterification of 2,6-dimethyl-1,7-heptanedioic acid (1) (pure meso and meso: (+/-) mixture, 53/47) with n-butanol in cyclohexane at a(w) = 0.8. The reaction was faster when short-chain primary n-alcohols was used and very slow, or even none reactive, when a Ion-chain alcohol was used.

  • 246.
    Hedenström, Erik
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Edlund, Helen
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Lund, Susan
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Abersten, M.
    Persson, D.
    Synthesis and lipase catalysed stereoselective acylation of some 3-methyl-2-alkanols, identified as sex pheromone precursors in females of pine sawfly species2002Ingår i: Journal of The Chemical Society, Perkin Transactions 1, ISSN 1472-7781, Vol. 2002, nr 15, s. 1810-1817Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Several 3-methylalkan-2-ols precursors to sex pheromones of Diprion pini, Gilpinia pallida, Gilpinia frutetorum, Diprion nipponica, Macrodiprion nemoralis and Microdiprion pallipes were synthesised as stereoisomeric mixtures in moderate to good yields. The key reaction sequence in the syntheses was the ring opening of either cis- or racemic trans-epoxybutane using a higher order cyanocuprate as nucleophile followed by a highly efficient lipase catalysed stereoselective acylation of the obtained 3-methylalkan-2-ol. The biologically active species specific stereoisomer was synthesised as a single stereoisomer in high stereoisomeric purity, as one in a mixture of two or as one of four stereoisomers when the appropriate 3-methylalkan-2-ol was stereoselectively acylated using a Pseudomonas sp. lipase as catalyst.

  • 247.
    Hedenström, Erik
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Edlund, Helene
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Wassgren, Ann-Britt
    Göteborg University.
    Bergström, Gunnar
    Göteborg University.
    Anderbrant, Olle
    Lund University.
    Östrand, Fredrik
    Lund University.
    Sierpinski, Andrzej
    Forest Research Institute, Poland.
    Auger-Rozenberg, Marie-Anne
    Institut National de la Recherche Agronomique, France.
    Herz, Marie-Anne
    Technische Universität München, Germany.
    Heitland, Werner
    Technische Universität München, Germany.
    Varama, Martti
    Finnish Forest Research Institute, Finland.
    Sex pheromone of the pine sawfly, Gilpinia pallida: Chemical identification, synthesis, and biological activity2006Ingår i: Journal of Chemical Ecology, ISSN 0098-0331, E-ISSN 1573-1561, Vol. 32, nr 11, s. 2525-2541Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We present the identification of the sex pheromone in the pine sawfly, Gilpinia pallida, including analysis of the female pheromone content, male antennal response and attraction in the field, and synthesis of the most active pheromone component. Several 3,7-dimethyl-2-alkanols were identified from female whole-body extracts, including some compounds with a 2R configuration. This is the first observation of such compounds in a pine sawfly species. Antennae of male G. pallida responded strongly in electroantennograph (EAG) recordings to the (2S,3R,7R)-isomers of the propionates of 3,7-dimethyl-2-tridecanol, 3,7-dimethyl-2-tetradecanol, and 3,7-dimethyl-2-pentadecanol, as well as to the acetates of the tri- and pentadecanols (the acetate of the tetradecanol was not tested). The propionate of (2S,3R,7R)-3,7-dimethyl-2-tetradecanol caught more males in the field than the corresponding isomer of tri- or pentadecanol. We suggest that the (2S,3R,7R)-isomer of 3,7-dimethyl-2-tetradecanol is likely the main sex pheromone precursor in G. pallida, with a subsidiary role for the (2S,3R,7R)-isomer of the tridecanol. Preparation of highly pure (2R,3R,7R)- and (2S,3R,7R)-stereoisomers of 3,7-dimethyl-2-tetradecanol, including the biological active esters, was performed via chemoenzymatic methods and is described in detail.

  • 248.
    Hedenström, Erik
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Högberg, Hans-Erik
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Efficient Opening of trans-2,3-Epoxybutane by a Higher Order Cuprate: Synthesis of erythro-3.7-Dimethylpentadecan-2-yl Acetate, Pheromone of Pine Sawflies1994Ingår i: Tetrahedron, ISSN 0040-4020, Vol. 50, nr 17, s. 5225-5232Artikel i tidskrift (Refereegranskat)
  • 249.
    Hedenström, Erik
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Högberg, Hans-Erik
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Wassgren, A.-B.
    Bergström, G.
    Löfqvist, J.
    Hansson, B.
    Anderbrant, O.
    Sex Pheromone of Pine Sawflies: Chiral Syntheses of some Active Minor Components Isolated from Neodiprion sertifer and of some Chiral Anologues of Diprionyl Acetate1992Ingår i: Tetrahedron, ISSN 0040-4020, Vol. 48, nr 15, s. 3139-3146Artikel i tidskrift (Refereegranskat)
  • 250.
    Hedenström, Erik
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Nguyen, Ba-Vu
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Silks III, L. A.
    Do enzymes recognise remotely located stereocentres?: Highly enantioselective Candida rugosa lipase-catalysed esterification of the 2- to 8-methyldecanoic acids2002Ingår i: Tetrahedron: asymmetry, ISSN 0957-4166, E-ISSN 1362-511X, Vol. 13, nr 8, s. 835-844Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Several racemic methyl decanoic acids have been synthesised and successfully resolved in esterification with 1-hexadecanol at aw=0.8 in cyclohexane using immobilised Candida rugosa lipase (CRL) as the catalyst. The enantiomeric ratios (E=2.8-68) obtained were surprisingly high even when the methyl group was as remotely located as in 8-methyldecanoic acid (E=25). Interestingly, the lipase shows enantiopreference for the S-enantiomer when the methyl group is located on even numbered carbons i.e. for the 2-,4-,6- and 8-methyldecanoic acids and to the R-enantiomer when the methyl group is located on uneven numbered carbons i.e. for the 3-,5- and 7-methyldecanoic acids.

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