| 1. |
- Berg, Anna-Karin, et al.
(författare)
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Enterovirus Markers and Serum CXCL10 in Children With Type 1 Diabetes
- 2010
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Ingår i: Journal of Medical Virology. - : Wiley. - 0146-6615 .- 1096-9071. ; 82:9, s. 1594-1599
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Tidskriftsartikel (refereegranskat)abstract
- Most patients with type 1 diabetes are considered to have a T-cell mediated autoimmune disease. The chemokine CXCL10 promotes the migration of activated T-cells. Virus infections might contribute to the pathogenesis of type 1 diabetes and enterovirus protein and/or genome have been detected in beta-cells from a majority of tested newly diagnosed children with type 1 diabetes. The chemokine CXCL10 is induced in human islet cells by enterovirus infections in vivo and in vitro, but is not expressed in islets from normal organ donors. Since CXCL10 is a chemokine known to be induced by virus infections and/or cellular damage, our aim was to study if levels of CXCL10 are elevated in serum from children with type 1 diabetes and whether it correlates to the presence of enterovirus markers. CXCL10, neutralizing antibody titer rises against certain enterovirus, and antibodies against GAD65 were measured in serum, and enterovirus PCR was performed on whole blood from 83 type 1 diabetes patients at onset, 48 siblings and 69 controls. CXCL10 was also measured in serum from 46 patients with proven enterovirus infection and in serum from 46 patients with other proven virus infections. The CXCL10 serum levels were not elevated in children at onset of type 1 diabetes and there was a considerable overlap between the groups with 99(8-498) pg/ml in serum from children with type 1 diabetes, 120 (17-538) pg/ml in serum from controls, and 117 (7-448) pg/ml in siblings of the children with type 1 diabetes. The CXCL10 serum levels in patients with proven enterovirus infection were slightly increased compared to the levels in the other groups, 172 (0-585) pg/ml but there was no statistically significant difference. In contrast, CXCL10 serum levels in patients with other proven virus infections were clearly elevated 418 (34-611) pg/ml. Despite that elevated CXCL10 levels have been demonstrated in some groups of patients with type 1 diabetes, in this study the mean CXCL10 serum levels were not elevated in patients with type 1 diabetes neither in patients with proven enterovirus infection. In contrast, in patients with other virus infections the CXCL10 levels were elevated, presumably reflecting the severity or the site of infection. This suggests that local production of CXCL10 in the affected organ cannot be measured reproducible in serum and that its potential use in clinical practice is limited.
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| 2. |
- Chasoglou, Dimitris, et al.
(författare)
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Computational predictions with coupled experimental investigations of the effect of alloying elements on microstructure in PM-HIP alloys
- 2013
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Ingår i: International Powder Metallurgy Congress and Exhibition, Euro PM 2013. - : European Powder Metallurgy Association (EPMA). - 9781899072408
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Konferensbidrag (refereegranskat)abstract
- Steel produced by the PM-HIP route has a more homogenous microstructure compared with that obtained in conventionally produced material. This is an important advantage in many applications, and is therefore of interest to predict. The homogeneity of the microstructure is possible due to the rapid solidification of the powder grains in the atomization and the small size of the powder grains. Computational predictions of the variations of composition in powder grains, compacted material and conventionally produced material are compared with microstructure investigations. The microstructure is investigated in SEM with coupled composition analysis by EDS/WDS. The computational predictions are based on a description of the equilibria in the steel, and of the kinetics of segregation on solidification. The effect of alloying elements is discussed, and the effect in a stainless steel and in a tool steel is calculated.
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| 3. |
- Frisk, Karin, et al.
(författare)
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Compound materials by PM-HIP
- 2014
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Ingår i: Powder Metallurgy. - 0032-5899 .- 1743-2901. ; 57:5, s. 341-347
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Tidskriftsartikel (refereegranskat)abstract
- There are many applications where compound materials can be of interest, for example when different properties are needed in different parts of a component. Compound materials can be produced by hot isostatic pressing (HIP) of powder metallurgical materials. One aspect that should be considered in the design is the quality of the interface between the two different material compositions. Diffusion during HIP can cause formation of brittle phases in the interface or deteriorate properties by diffusion of alloying elements. The present work shows results from a study where different steel types were joined (quench and temper steel/air hardening steel/bearing steel with a tool steel/corrosion resistant martensitic steel). The evaluation was performed by computational predictions and by small scale HIP experiments that were evaluated by microstructure analysis and chemical analysis. © 2014 Institute of Materials, Minerals and Mining.
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| 4. |
- Frisk, Karin, et al.
(författare)
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Oxygen in pilot-scale gas atomised powders - Study of oxygen uptake and oxide characterisation
- 2011
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Ingår i: Proceedings of the Euro International Powder Metallurgy Congress and Exhibition, Euro PM 2011. - : European Powder Metallurgy Association (EPMA). - 9781899072200
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Konferensbidrag (refereegranskat)abstract
- Properties of steel are detrimentally affected by oxygen and the content should be minimised. The effect of oxygen on steel properties depends on the type of steel, on the amount of dissolved oxygen and on the type and size of oxides, and on microstructure. In steel produced from powder, surface oxides on the powder grains, dissolved oxygen as well as oxide inclusions originating from the melt contribute to the total oxygen content. It is therefore interesting to investigate under what conditions oxygen uptake takes place, and how oxides are formed and can be characterised. A lab scale atomizer with a maximum charge weight of approximately 10 kg has been used. Powder atomisations have been performed, using an oxysensor to monitor the oxygen levels at different positions in the atomisation equipment, and melt samples have been extracted. Oxygen in the powder is characterised using Photo Acoustic Spectroscopy (PAS), by analysing oxygen contents in powder and in compacted samples, and by microstructure investigations.
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| 5. |
- Frisk, Karin, et al.
(författare)
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Simulation of oxygen reduction in PM-HIP materials
- 2010
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Ingår i: Proceedings of the World Powder Metallurgy Congress and Exhibition, World PM 2010. - : European Powder Metallurgy Association (EPMA). - 9781899072194
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Konferensbidrag (refereegranskat)abstract
- A challenge in the development of powder based materials is to limit the oxygen contents. In the present work reduction of oxygen/oxides in a duplex stainless steel powder was studied. The main mechanisms ruling the reduction of oxygen in a hydrogen atmosphere have been established. A combination of experiments and mathematical modelling was used. Experiments were performed on small samples of powder, as well as powder encapsulated in a 200x200 mm canister. FEM calculations of the heat transfer in the canister, combined with thermodynamic calculations of the stability, and heat of reduction of oxides were used for the modelling. The experimental features: oxide reduction, heat transfer, and hydrogen transport, are reproduced by the calculations. A high-oxygen powder was used for the experiments, and the oxygen content was reduced from 200 ppm O in the powder, to less than 100 ppm O in the compacted material. The results from the modelling could conclude that this was due to a reduction of Fe-oxides at low temperatures, and Cr-oxides at high temperatures.
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| 6. |
- Frisk, Karin
(författare)
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Simulation of precipitation of secondary carbides in hot work tool steels
- 2012
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Ingår i: Materials Science and Technology. - 0267-0836 .- 1743-2847. ; 28:3, s. 288-294
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Tidskriftsartikel (refereegranskat)abstract
- Precipitation of secondary carbides in hot work tool steels during tempering heat treatments has been investigated using simulations based on a thermodynamic description coupled with kinetic parameters through multicomponent nucleation and growth models. The simulations reproduce the measured effects of steel composition on the precipitation of secondary carbides. Both Si and V increase the volume fraction of fine secondary carbides precipitated during tempering provided that the austenitising temperature is adjusted to give the same fraction of retained primary carbides. The most important effect of Si in 5%Cr steels is its influence on the primary carbide stability at austenitisation temperatures, but increasing the V contents has a strong effect on the fraction of secondary carbides, without increasing the size, and can thus improve the yield strength. The most critical input to the calculations is the thermodynamic description of the individual phases. © 2012 Institute of Materials, Minerals and Mining.
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| 7. |
- Garcia, J., et al.
(författare)
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Kinetics of formation of graded layers on cemented carbides : Experimental investigations and DICTRA simulations
- 2011
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Ingår i: International Journal of Refractory Metals and Hard Materials. - : Elsevier BV. - 0263-4368. ; 29:2, s. 256-259
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Tidskriftsartikel (refereegranskat)abstract
- Kinetics of formation of fcc-free layers on Co-W-Ti-Ta-Nb-C-N cemented carbides was investigated by experimental methods and DICTRA simulations. The layer formation obeys a parabolic law, indicating a diffusion-controlled process. For DICTRA simulations, the influence of the mobilities for all diffusing elements in the liquid binder phase at the sintering temperature was investigated. The best agreement between experimental and simulations was obtained considering that the mobility of all metallic elements is two times slower compared with the mobility of the non-metallic elements. © 2010 Elsevier Ltd. All rights reserved.
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| 8. |
- Hervestad, Eleonora, et al.
(författare)
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Tool Steels, Phases and Alloying Elements, Literature survey
- 2014
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Rapport (refereegranskat)abstract
- This report is meant to give a brief introduction to tool steels, phases and alloying elements. The focus is to understand the microstructure, its evolution and how it is altered through processing, heat treatment and alloying. The first part of the report gives a general insight into tool steels, some example of the major tool steels groups and processing. The second part of the report concentrates on the phases that can appear in tool steels. Some phases are given more attention than others depending on regular appearance and level of interest. The last part of the report concerns alloying elements and give an overview of elements and their properties. In the very end a summary of the outcome is given.
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| 9. |
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| 10. |
- Lindwall, Greta, et al.
(författare)
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Assessment and evaluation of mobilities for diffusion in the bcc Cr-Mo-Fe system
- 2012
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Ingår i: Journal of Phase Equilibria and Diffusion. - : ASM International. - 1547-7037 .- 1863-7345. ; 33:5, s. 375-389
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Tidskriftsartikel (refereegranskat)abstract
- An assessment of the diffusion mobility functions for diffusion in the bcc Cr-Fe-Mo system ispresented. The optimization of the mobility parameters is performed by utilizing experimentaldiffusion data available in literature. New diffusion data for the Mo diffusion is produced by adiffusion couple experiment and is accounted for in the optimization. Agreement between calculatedand measured diffusion coefficients is found. An M6C coarsening experiment is performedand the measured coarsening rate can be reproduced by diffusion calculation using the DICTRA software and the developed kinetic description. The mobility parameters are shown tohave a strong influence on the calculated coarsening rate.
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