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- Paananen, A., et al.
(författare)
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Interaction between cellulose and xylan : An atomic force microscope and quartz crystal microbalance study
- 2004
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Ingår i: Hemicellulose. - 0841238421 ; , s. 269-290
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Konferensbidrag (refereegranskat)abstract
- The atomic force microscope (AFM) colloidal probe technique has been used to investigate forces between cellulose beads as well as cellulose beads and mica in aqueous solution, and the interaction between cellulose surfaces in xylan solutions. Several observations of the behaviour of the cellulose beads were made. Swelling of the beads in aqueous solutions is rather slow. Thus, it is important to let the beads equilibrate before measurements. The beads are somewhat compressed when forced together to constant compliance, but relax back to their original shape in a few minutes. A long-range electrostatic repulsion between cellulose and mica occurs on approach. The xylan concentration in solution affects the forces between two cellulose surfaces. When the concentration increases from 10-100 mg/l more xylan adsorbs slowly and irreversibly on the cellulose leading to an increasingly long-range and stronger repulsion between the surfaces on approach. Adhesion between the layers is very low and seems to be due to entanglement of polymer chains. Studies of the adsorption of xylan (100 mg/l) on cellulose films with a quartz crystal microbalance with dissipation (QCM-D) verify that a thick, water-swollen layer of xylan is formed by slow adsorption. It has been proposed that adsorbed xylan on fibre surfaces increases paper strength. We conclude that this must be associated with the behaviour of the adsorbed layers of xylan on drying.
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| 3. |
- Allen, T., et al.
(författare)
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Structural responses of high performance sailing yachts to slamming loads
- 2011
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Ingår i: 11th International Conference on Fast Sea Transportation, FAST 2011 - Proceedings. - 9780985066000 ; , s. 585-592
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Konferensbidrag (refereegranskat)abstract
- Experimental measurements of transient strains, local accelerations and pressure were undertaken on the IMOCA Open 60' class sailing yacht Paprec-Virbac III, and on a replica hull panel section tested in a laboratory slam testing facility. The approximately 1m x 0.7m panel for laboratory testing was manufactured on a mould taken from the plug used for the vessel construction, ensuring that the panel had identical curved geometry to the vessel. The laboratory panel included two stringers as on the same region of the vessel. An instrumentation layout including arrays of resistance strain gauges, accelerometers and a transient pressure transducer was used. Linear displacement transducers were used to measure panel deformations during the laboratory tests. The laboratory testing was undertaken at a range of constant impact velocities from 0.5 to 3m/s using a Servohydraulic Slam Testing System. Sea-trials were undertaken in the Hauraki Gulf, Auckland New Zealand. There was good qualitative agreement between the field and laboratory measurements in regard to timing and relative magnitudes of strains at different positions on the structure. Results demonstrate that the hull structure undergoes very complex transient deformations during the slamming events.
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- Milestad, Rebecka, 1973-, et al.
(författare)
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Tensions in future development of organic production—views of stakeholders on Organic 3.0
- 2020
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Ingår i: Organic Agriculture. - : Springer. - 1879-4238 .- 1879-4246.
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Tidskriftsartikel (refereegranskat)abstract
- This study analysed Swedish stakeholders’ views on future developments of organic production and consumption based on Organic 3.0, a strategic initiative by the International Federation of Organic Agriculture Movements (IFOAM). Focus group discussions were carried out with actors representing different parts of the organic value chain in Sweden. These identified a number of tensions, four of which represented an unresolved dichotomy in the way forward for the organic movement and its relevance for organic production in most settings. The first tension was between the drive for increased efficiency to achieve higher yields and an agroecological approach with broader sustainability values. The second concerned availability of plant nutrients in organic agriculture including safe recirculating of nutrients from society. The third tension set new technology against the precautionary principle and the notion of naturalness. The fourth concerned the role of organic as an innovation system; whether organic should be a forerunner, i.e. performing well above average and fostering innovation, or whether organic should be a broader movement including more farmers but then requiring more regulations that may hinder innovation. These tensions will result in important choices on direction for the organic sector as it pursues the Organic 3.0 goal of sustainably feeding a growing population based on farming systems based on organic principles.
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- Stenius, Ivan, et al.
(författare)
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Experimental hydroelastic characterization of slamming loaded marine panels
- 2013
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Ingår i: Ocean Engineering. - : Elsevier BV. - 0029-8018 .- 1873-5258. ; 74, s. 1-15
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Tidskriftsartikel (refereegranskat)abstract
- The paper presents a method to experimentally characterize the significance of hydroelasticity for slamming loaded marine panels. The methodology is based on a large number of systematical experiments of slamming loaded panels from which semi-empiric expressions for the pressure distributions are derived. Finite element simulations are used to obtain rigid/quasi-static reference solutions. Hydroelastic effects are quantified by comparing deflections and strains from experiments with the corresponding non-hydroelastic reference solutions. The study shows that the largest hydro-elastic effects appear to be a time-lag effect, which however does not seem to affect the structural response magnitudes dramatically. The most significant hydroelastic effects can be expected to be close to the panel supports for very flexible structures or sandwich constructions. The results are also discussed with reference to classification rules which indicate that hydroelastic effects are small in the design of conventional ship hull structures.
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- Viluksela, Matti, et al.
(författare)
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Toxicological profile of ultrapure 2,2',3,4,4',5,5'-heptachlorbiphenyl (PCB 180) in adult rats.
- 2014
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Ingår i: PloS one. - : Public Library of Science (PLoS). - 1932-6203. ; 9:8, s. e104639-
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Tidskriftsartikel (refereegranskat)abstract
- PCB 180 is a persistent non-dioxin-like polychlorinated biphenyl (NDL-PCB) abundantly present in food and the environment. Risk characterization of NDL-PCBs is confounded by the presence of highly potent dioxin-like impurities. We used ultrapure PCB 180 to characterize its toxicity profile in a 28-day repeat dose toxicity study in young adult rats extended to cover endocrine and behavioral effects. Using a loading dose/maintenance dose regimen, groups of 5 males and 5 females were given total doses of 0, 3, 10, 30, 100, 300, 1000 or 1700 mg PCB 180/kg body weight by gavage. Dose-responses were analyzed using benchmark dose modeling based on dose and adipose tissue PCB concentrations. Body weight gain was retarded at 1700 mg/kg during loading dosing, but recovered thereafter. The most sensitive endpoint of toxicity that was used for risk characterization was altered open field behavior in females; i.e. increased activity and distance moved in the inner zone of an open field suggesting altered emotional responses to unfamiliar environment and impaired behavioral inhibition. Other dose-dependent changes included decreased serum thyroid hormones with associated histopathological changes, altered tissue retinoid levels, decreased hematocrit and hemoglobin, decreased follicle stimulating hormone and luteinizing hormone levels in males and increased expression of DNA damage markers in liver of females. Dose-dependent hypertrophy of zona fasciculata cells was observed in adrenals suggesting activation of cortex. There were gender differences in sensitivity and toxicity profiles were partly different in males and females. PCB 180 adipose tissue concentrations were clearly above the general human population levels, but close to the levels in highly exposed populations. The results demonstrate a distinct toxicological profile of PCB 180 with lack of dioxin-like properties required for assignment of WHO toxic equivalency factor. However, PCB 180 shares several toxicological targets with dioxin-like compounds emphasizing the potential for interactions.
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