| 1. |
- Andersson, Per, 1964-, et al.
(författare)
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Freedom with reservations : The work of the Swedish folk high school teacher
- 2023
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Ingår i: The Nordic folk high school teacher. - Zürich : LIT Verlag. - 9783643912404 - 9783643962409 ; , s. 143-156
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Bokkapitel (refereegranskat)abstract
- Folk high school teachers work many hours in fluid ways with no clear distinction between working hours and leisure time. Pedagogically, they are often described as being value driven and participant focused. Creating interests, involving, motivating, giving recognition to, challenging, and creating possibilities for participants to grow as human beings is important for the teachers. In this chapter, we mobilise empirical examples to explore if these aspects are connected to a particular understanding of what learning is and should be, a mutual/embedded exploration process where both participants and teachers are challenged and grow as persons and where collaboration and the collective are prerequisites. This particular perspective on learning appears far removed from the traditional subject-based classroom of child education. We describe and discuss the work of folk high school teachers in Sweden, and problematise the work conditions of this diverse group of teachers.
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| 2. |
- Carlsson, Jenny, 1984-, et al.
(författare)
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Investigating tool engagement in groundwood pulping : finite element modelling and in-situ observations at the microscale
- 2020
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Ingår i: Holzforschung. - : Walter de Gruyter GmbH. - 0018-3830 .- 1437-434X. ; 74:5, s. 477-487
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Tidskriftsartikel (refereegranskat)abstract
- With industrial groundwood pulping processes relying on carefully designed grit surfaces being developed for commercial use, it is increasingly important to understand the mechanisms occurring in the contact between wood and tool. We present a methodology to experimentally and numerically analyse the effect of different tool geometries on the groundwood pulping defibration process. Using a combination of high-resolution experimental and numerical methods, including finite element (FE) models, digital volume correlation (DVC) of synchrotron radiation-based X-ray computed tomography (CT) of initial grinding and lab-scale grinding experiments, this paper aims to study such mechanisms. Three different asperity geometries were studied in FE simulations and in grinding of wood from Norway spruce. We found a good correlation between strains obtained from FE models and strains calculated using DVC from stacks of CT images of initial grinding. We also correlate the strains obtained from numerical models to the integrity of the separated fibres in lab-scale grinding experiments. In conclusion, we found that, by modifying the asperity geometries, it is, to some extent, possible to control the underlying mechanisms, enabling development of better tools in terms of efficiency, quality of the fibres and stability of the groundwood pulping process.
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| 3. |
- Carlsson, Jenny, 1984-
(författare)
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On Crack Dynamics in Brittle Heterogeneous Materials
- 2020
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Natural variation, sub-structural features, heterogeneity and porosity make fracture modelling of wood and many other heterogeneous and cellular materials challenging. In this thesis, fracture in such complicated materials is simulated using phase field methods for fracture. Phase field methods have shown promise in simulations of complex geometries as well as dynamics and require few additional parameters; only the material toughness and a length parameter, determining the width of a regularised crack, are needed.First, a dynamic phase field model is developed and validated against experiments performed on homogeneous brittle polymeric materials, wood fibre composites and polymeric materials with different hole patterns. Then, a high-resolution model of wood is developed and related to experiments, this time without considering fracture. Attention is finally focussed on high-resolution numerical analyses of fracture in wood and other cellular microstructures, considering both heterogeneity and relative density.The phase field model is found to reproduce crack paths, velocities and energy release rates well in homogeneous samples both with and without holes. In more complicated heterogeneous and porous materials, the model is also able to simulate crack paths, but the interpretation of the length scale is complicated by the inherent lengths of the micro-structural geometry. In sum, the thesis points to possibilities with the proposed method, as well as limitations in our current understanding of both quasistatic and dynamic fracture of heterogeneous and cellular materials. The findings of this thesis can contribute to an improved understanding of fracture in such materials.
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| 4. |
- Cid Gomes, Leandro, et al.
(författare)
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Light-driven (cross-)dimerization of terpenes as a route to renewable C15-C30 crudes for fuel and lubricant oil applications
- 2023
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Ingår i: Sustainable Energy & Fuels. - : Royal Society of Chemistry. - 2398-4902. ; 7:3, s. 868-882
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Tidskriftsartikel (refereegranskat)abstract
- Non-fossil hydrocarbons are desirable for transport fuels and lubricant oils to reach a fossil carbon neutral economy. Herein, we show the production of such end-products from crude raw materials via the photosensitized dimerization of terpenes. Terpenes are hydrocarbons originating from renewable sources, such as forestry, industrial bio-waste and photosynthetically active microorganisms. Under irradiation at 365 nm, we observed high conversions of terpenes with conjugated diene segments into their dimers (e.g. 96.1 wt%, 12 h for α-phellandrene), and remarkable results were obtained using simulated and natural sunlight (90.8 wt% and 46.6 wt%, respectively, for α-phellandrene). We show that the lower reactivities of some isomeric monoterpenes could be overcome by a cross-photodimerization with α-phellandrene. We also utilized the cross-photodimerization approach to obtain C15 and C30 products, combining mixtures of isoprene, monoterpenes and sesquiterpenes. Hydrogenation of the terpene dimers gave materials with physical properties suitable as high energy density fuels and lubricant oils. Finally, our preliminary analysis based on recent literature points to the commercial viability of this route to produce fuels and lubricant oils, as well as to a potential for reduction of the environmental impact compared to fossil-based routes.
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| 5. |
- Forsström, David, et al.
(författare)
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Gamblers' Perception of the Playscan Risk Assessment : A Mixed-Methods Study
- 2022
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Ingår i: Journal of Gambling Studies. - : Springer Science and Business Media LLC. - 1050-5350 .- 1573-3602. ; 38:2, s. 591-606
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Tidskriftsartikel (refereegranskat)abstract
- Responsible gambling (RG) tools are globally widespread; they aim to prevent or decrease the harm caused by gambling. However, existing research suggests that several included features do not decrease gambling or significantly reduce the subsequent harm. Most of the previous studies have used gambling data to understand the changes in gambling behavior. However, the literature lacks research regarding gamblers' experience and perception of RG tools, which may provide insight into increasing the usage and effectiveness of RG tools. This mixed-methods study aimed to explore gamblers' perception of their risk assessment in the RG tool Playscan regarding developing harmful gambling problems. Overall, 757 participants rated the perceived accuracy of their risk assessment and their perception of the overall RG tool that conducted the assessment. Participants were also allowed to leave a comment providing feedback, which was analyzed using thematic analysis. Quantitative data was analyzed using logistic regression and structural equation modeling. Qualitative analyses revealed that most of the participants were pleased with the risk assessment and found it helpful. Moderated mediation analysis showed that participants' assessment agreement partially mediated the association between expressing a negative view and their general view of Playscan. These results highlight the need to decrease the level of disagreement for promoting a better general view of RG tools to potentially increase their usage and effectiveness.
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| 6. |
- Gerth, Julia, et al.
(författare)
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Assessing the hardness and residual stress at the very edge of a TiAlN coated cutting insert
- 2024
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Ingår i: Surface and coatings technology. - : Elsevier. - 0257-8972.
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Tidskriftsartikel (refereegranskat)abstract
- A method for determining residual stresses through nanoindentation has been used in order to evaluate the local residual stress in a PVD Ti0.5Al0.5N coating. The influence of residual stress on the measured hardness is obtained by comparing the hardness of as deposited, residually stressed, coating and stress relieved pillars made in the very same coating. The technique offers high lateral resolution, and it can be applied on complex geometries where conventional stress measurements fall short. In this work, the method proved useful for estimating the residual stress at such a complex geometry as a sharp cutting edge. Edges with two different radii were analysed and it was concluded that the nominal residual compressive stress given to a coating can locally, on the very cutting edge, become significantly reduced by elastic relaxation .This effects the cohesion of the coating at that position which, together with the lift-off stress generated at the edge, make the coating in that region especially vulnerable to damage. The experimental results correlated very well with finite element simulations of the residual stress state around cutting edges with the same geometries.
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| 7. |
- Holmberg, Anders, et al.
(författare)
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Crack initiation and early propagation in case hardened sintered PM steels under cyclic load
- 2023
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Ingår i: Powder Metallurgy. - : Taylor & Francis Group. - 0032-5899 .- 1743-2901. ; 66:2, s. 164-175
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Tidskriftsartikel (refereegranskat)abstract
- In the present study, crack propagation through the case hardened region of two different PM steels manufactured with different powder size distributions and sintered at different temperatures has been investigated. EBSD was used to study the microstructure before and after case hardening, revealing the relationship between powder particle grains after sintering and prior austenite grains after case hardening. A novel approach was used to achieve short cracks (10–20 µm) with high repeatability. The cracks were then analysed using EBSD and SEM, revealing detailed and novel information about the crack propagation route in the materials. Both tested materials show the same crack propagation behaviour. If a prior grain/prior austenite boundary is present within an angle from the crack initiation site, the cracks will follow the boundary and thus propagate intergranular, suggesting that the preferred route of crack propagation in case hardened sintered steel is along these boundaries.
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| 8. |
- Malyshev, Dmitry, et al.
(författare)
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Laser induced degradation of bacterial spores during micro-Raman spectroscopy
- 2022
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Ingår i: Spectrochimica Acta Part A - Molecular and Biomolecular Spectroscopy. - : Elsevier. - 1386-1425 .- 1873-3557. ; 265
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Tidskriftsartikel (refereegranskat)abstract
- Micro-Raman spectroscopy combined with optical tweezers is a powerful method to analyze how the biochemical composition and molecular structures of individual biological objects change with time. In this work we investigate laser induced effects in the trapped object. Bacillus thuringiensis spores, which are robust organisms known for their resilience to light, heat, and chemicals are used for this study. We trap spores and monitor the Raman peak from CaDPA (calcium dipicolinic acid), which is a chemical protecting the spore core. We see a correlation between the amount of laser power used in the trap and the release of CaDPA from the spore. At a laser power of 5 mW, the CaDPA from spores in water suspension remain intact over the 90 min experiment, however, at higher laser powers an induced effect could be observed. SEM images of laser exposed spores (after loss of CaDPA Raman peak was confirmed) show a notable alteration of the spores' structure. Our Raman data indicates that the median dose exposure to lose the CaDPA peak was ∼60 J at 808 nm. For decontaminated/deactivated spores, i.e., treated in sodium hypochlorite or peracetic acid solutions, the sensitivity on laser power is even more pronounced and different behavior could be observed on spores treated by the two chemicals. Importantly, the observed effect is most likely photochemical since the increase of the spore temperature is in the order of 0.1 K as suggested by our numerical multiphysics model. Our results show that care must be taken when using micro-Raman spectroscopy on biological objects since photoinduced effects may substantially affect the results.
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| 9. |
- Malyshev, Dmitry, et al.
(författare)
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Mode of action of Disinfection chemicals on the bacterial spore structure and their Raman spectra
- 2021
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Ingår i: Analytical Chemistry. - : American Chemical Society (ACS). - 0003-2700 .- 1520-6882. ; 93:6, s. 3146-3153
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Tidskriftsartikel (refereegranskat)abstract
- Contamination of toxic spore-forming bacteria is problematic since spores can survive a plethora of disinfection chemicals and it is hard to rapidly detect if the disinfection chemical has inactivated the spores. Thus, robust decontamination strategies and reliable detection methods to identify dead from viable spores are critical. In this work, we investigate the chemical changes of Bacillus thuringiensis spores treated with sporicidal agents such as chlorine dioxide, peracetic acid, and sodium hypochlorite using laser tweezers Raman spectroscopy. We also image treated spores using SEM and TEM to verify if we can correlate structural changes in the spores with changes to their Raman spectra. We found that over 30 min, chlorine dioxide did not change the Raman spectrum or the spore structure, peracetic acid showed a time-dependent decrease in the characteristic DNA/DPA peaks and ∼20% of the spores were degraded and collapsed, and spores treated with sodium hypochlorite showed an abrupt drop in DNA and DPA peaks within 20 min and some structural damage to the exosporium. Structural changes appeared in spores after 10 min, compared to the inactivation time of the spores, which is less than a minute. We conclude that vibrational spectroscopy provides powerful means to detect changes in spores but it might be problematic to identify if spores are live or dead after a decontamination procedure.
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| 10. |
- Muresanu, Dafin F., et al.
(författare)
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Diabetes exacerbates brain pathology following a focal blast brain injury : New role of a multimodal drug cerebrolysin and nanomedicine
- 2020
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Ingår i: Neuropharmacology of Neuroprotection. - : ELSEVIER. - 9780128208137 ; 258, s. 285-367
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Bokkapitel (refereegranskat)abstract
- Blast brain injury (bBI) is a combination of several forces of pressure, rotation, penetration of sharp objects and chemical exposure causing laceration, perforation and tissue losses in the brain. The bBI is quite prevalent in military personnel during combat operations. However, no suitable therapeutic strategies are available so far to minimize bBI pathology. Combat stress induces profound cardiovascular and endocrine dysfunction leading to psychosomatic disorders including diabetes mellitus (DM). This is still unclear whether brain pathology in bBI could exacerbate in DM. In present review influence of DM on pathophysiology of bBI is discussed based on our own investigations. In addition, treatment with cerebrolysin (a multimodal drug comprising neurotrophic factors and active peptide fragments) or H-290/51 (a chain-breaking antioxidant) using nanowired delivery of for superior neuroprotection on brain pathology in bBI in DM is explored. Our observations are the first to show that pathophysiology of bBI is exacerbated in DM and TiO2-nanowired delivery of cerebrolysin induces profound neuroprotection in bBI in DM, not reported earlier. The clinical significance of our findings with regard to military medicine is discussed.
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