| 1. |
- Choquet, Isabelle, 1965-, et al.
(författare)
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Clogging and lump formation during atmospheric plasma spraying with powder injection downstream the plasma gun
- 2007
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Ingår i: Journal of thermal spray technology (Print). - : Springer Science and Business Media LLC. - 1059-9630 .- 1544-1016. ; 16:4, s. 512-523
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Tidskriftsartikel (refereegranskat)abstract
- This study aimed to numerically and experimentally investigate lump formation during atmospheric plasma spraying with powder injection downstream the plasma gun exit. A first set of investigations was focused on the location and orientation of the powder port injector. It turned out impossible to keep the coating quality while avoiding lumps by simply moving the powder injector. A new geometry of the powder port ring holder was designed and optimized to prevent nozzle clogging, and lump formation using a gas screen. This solution was successfully tested for applications with Ni-5wt.%Al and ZrO2-7wt.%Y2O3 powders used in production. The possible secondary effect of plasma jet shrouding by the gas screen, and its consequence on powder particles prior to impact was also studied.
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| 2. |
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| 3. |
- Liu, Yan, et al.
(författare)
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Long crack behavior in a thermal barrier coating upon thermal shock loading
- 2005
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Ingår i: Journal of Thermal Spray Technology. - : Springer Science and Business Media LLC. - 1544-1016 .- 1059-9630 .- 0000-0000. ; 14:2, s. 258-263
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Tidskriftsartikel (refereegranskat)abstract
- The behavior of macroscopic long cracks in the ceramic top coat of a thermal barrier coating (TBC) system subjected to thermal shock loading and the influence of the cracks on the coating durability were investigated experimentally and numerically. Thermal shock testing was conducted until coating failure. Comparisons were made with coating samples without macroscopic cracks. The experimental results revealed that the presence of macroscopic cracks reduces the life of the TBC. The finite-element method, with a fracture mechanics approach, was applied to analyze preexisting long cracks, and the calculations correlate well with the experimental findings. It was found that the life of the coating is reduced with crack length as well as with maximum cycle temperature. It was also found that the stress-intensity factors for long cracks are initially high and decrease with the number of temperature cycles, which indicates that rapid crack growth occurs during the first number of cycles.
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| 4. |
- Lyphout, Christophe, 1981, et al.
(författare)
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Characterization of Adhesion Strength and Residual Stresses of HVOF Sprayed Inconel 718 for Aerospace Repair Applications
- 2007
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Ingår i: Proceedings of the International Thermal Spray Conference (ITSC), Beijing, China. ; , s. 588-593
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Thermally sprayed Inconel 718 coatings have been deposited by high velocity oxy-fuel (HVOF) spraying on Inconel 718 substrates. The aim of the on-going study is to understand and control the adhesion mechanisms and the residual stress state of the deposit/substrate system, in order to build up thick coatings for maintenance purposes. The coating adhesion strength was evaluated by the standard ASTM C633 tensile test. Coating shear strength was evaluated by the recently developed prEN15340 Shear Test. A modified Layer Removal Method (MLRM) test was carried out to measure residual stresses. The work is a part of an ongoing study for evaluation of relationships between process parameters, residual stress distribution and adhesion strength.
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| 5. |
- Markocsan, Nicolaie, et al.
(författare)
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Effect of heat treatment on low conductive thermal barrier coatings
- 2009
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Ingår i: Proceedings of the 22nd International Conference on Surface Modification Technologies. - 9780981706511 ; , s. 139-147
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Konferensbidrag (refereegranskat)abstract
- Development of Thermal Barrier Coating (TBC) systems will allow higher combustion temperature which is of interest for all manufactures since it results in higher fuel efficiency and environmentally cleaner emissions. Low thermal conductivity and long service life are the most important properties of these coatings. The objective of the work presented in this paper was to study the influence of a long-term heat treatment (i.e. 1200°C/2000h) on different characteristics of atmospheric plasma sprayed TBCs. Two zirconia feedstock materials were evaluated, namely yttria partially stabilised zirconia and dysprosia partially stabilised zirconia. Several spray conditions were designed and employed in order to achieve different coating morphologies. Microstructure analyses revealed that the coating microstructure was significantly dependent on both operating conditions and heat treatment conditions. Significant changes in coatings porosity occurred during heat treatment. The lowest thermal conductivity was reached with the dysprosia partially stabilised zirconia material. All TBC systems experienced decomposition of the metastable t´ phase during long heat treatment at 1200°C.
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| 6. |
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| 7. |
- Markocsan, Nicolaie, 1967-, et al.
(författare)
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Thermal spraying in Europe’s Nordic region
- 2007
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Ingår i: Journal of thermal spray technology (Print). - : Springer. - 1059-9630 .- 1544-1016. ; 16:4, s. 463-464
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Tidskriftsartikel (refereegranskat)
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| 8. |
- Nilsson, Jan, et al.
(författare)
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Regulatory T cells and the control of modified lipoprotein autoimmunity-driven atherosclerosis.
- 2009
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Ingår i: Trends in Cardiovascular Medicine. - : Elsevier BV. - 1873-2615 .- 1050-1738. ; 19:8, s. 272-276
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Tidskriftsartikel (refereegranskat)abstract
- It has long been recognized that arterial inflammation plays a key role in the development of atherosclerosis. More recent evidence has suggested that this inflammation is modulated by autoimmune responses against modified self-antigens, such as oxidized low-density lipoprotein, in the vascular wall. However, the role of the immune system in atherosclerosis appears to be more complex than in classic autoimmune diseases; and a number of protective immune responses have also been identified. One of the most important of these is carried out by the regulatory T cells. Regulatory T cells inhibit the development of autoimmunity by controlling the activity of autoreactive T cells. If the function of regulatory T cells is compromised in hypercholesterolemic mouse models of atherosclerosis, the development of disease becomes much more aggressive. In this review, we will discuss the possibility that the inflammatory activity in atherosclerotic lesions depends on the balance between plaque antigen-specific proinflammatory Th1-type T cells and anti-inflammatory regulatory T cells specific for the same antigen. We will also discuss the role of hypercholesterolemia in generation of these modified self-antigens as well as ongoing research aiming to develop novel immune-modulating therapy for prevention of cardiovascular disease by targeting these processes.
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| 9. |
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| 10. |
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| 11. |
- Ström, Åsa, et al.
(författare)
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Involvement of the CD1d-Natural killer T cell pathway in neointima formation after vascular injury
- 2007
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Ingår i: CIRCULATION RESEARCH. - 0009-7330. ; 101:8
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Tidskriftsartikel (refereegranskat)abstract
- Recent studies have established that the immune system plays an important role in the development of atherosclerosis. However, its role in regulating the arterial response to mechanical injury is less well studied. Arterial injury is associated with local accumulation of antibodies, and mice lacking functional T and B cells exhibit increased neointima formation, indicating that adaptive immune responses to neoantigens in the damaged tissue modulate the vascular repair process. To study the role of lipid antigen presentation in the arterial response to injury, we analyzed neointima formation in mice deficient in the lipid antigen-presenting molecule CD1d using a carotid collar model. As compared with control mice, neointima formation was reduced by >60% (P<0.01) in CD1d-/- mice. Moreover, carotid injury of wild-type C57BL/6 mice was associated with expansion of CD1d-restricted natural killer T cells in the spleen and accumulation of natural killer T cells in the periadventitial space of injured arteries. The results suggest that presentation of lipid antigens through the CD1d-natural killer T cell pathway modulates vascular repair responses.
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| 12. |
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| 13. |
- Wigren, Maria, et al.
(författare)
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Atheroprotective effects of Alum are associated with capture of oxidized LDL antigens and activation of regulatory T cells
- 2009
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Ingår i: Circulation Research. - 0009-7330 .- 1524-4571. ; 104:12, s. e62-70
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Tidskriftsartikel (refereegranskat)abstract
- The immune system represents a promising novel target for prevention of atherosclerosis. Several pilot vaccines that reduce atherosclerosis in experimental animals have been developed. The aluminum hydroxide adjuvant Alum has been shown to have antiatherogenic properties in itself, suggesting that it may be a suitable adjuvant in possible future atherosclerosis vaccines. To characterize the immune pathways mediating this protection, we treated wild-type C57BL/6 and Apoe(-)(/)(-) mice with Alum or PBS. Analyses of splenocytes isolated from 12-week-old mice demonstrated that Alum increased the presence of CD4(+)CD25(+)FoxP3(+) regulatory T cells and downregulated the expression of T cell activation markers CD28 and ICOS in Apoe(-)(/)(-) mice but not in C57BL/6 wild-type mice. A similar immunosuppressive phenotype was found also in 25-week-old Apoe(-)(/)(-) mice and was associated with reduced atherosclerosis. Alum precipitates recovered from the injection site of Apoe(-)(/)(-) mice contained antigens derived from oxidized LDL. These findings demonstrate that treatment of Apoe(-)(/)(-) mice with Alum results in an increase of regulatory T cells and suggest that these are activated by tolerogenic antigen-presenting cells presenting oxidized LDL antigens. Our findings provide improved mechanistic understanding of the atheroprotective properties of aluminum hydroxide adjuvants but also point to the importance of determining if hypercholesterolemia may compromise the efficacy of Alum-containing vaccines used clinically today.
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| 14. |
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| 15. |
- Zoric, Neven, et al.
(författare)
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Quantitative PCR: A promising technique investigating the early bone-implant interface
- 2007
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Ingår i: Abstract, European Association for Osseointegration (EAO), 16th Annual Scientific Meeting, Barcelona, Spain. ; 25-27 October
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Konferensbidrag (refereegranskat)abstract
- Objectives: Studies on the early tissue response to materials are difficult due to the inaccessibility of the interface zone and lack of sensitive techniques. The purpose of the present study was to apply quantitative PCR (qPCR) in combination with LM and SEM for the evaluation of early gene expression response as well as cellular reactions close to titanium implants. Experimental methods: Anodically oxidized titanium (TiUniteTM; Nobel Biocare AB) and machined titanium implants (2mm×2mm) were inserted in the rat tibia. After 1,3, and 6 days, implants were unscrewed and surrounding bone was retrieved. Both the implants and bone were analyzed with qPCR, routine histology and SEM. The amount of mRNA was normalized to 18S protein subunit. Results: After the initial inflammatory response, the tissue located inside the threads became rapidly organized. SEM analysis showed mesenchymal-like cells extending their processes into the pores of the anodically oxidized surface. qPCR demonstrated significantly higher 18S around anodically oxidized screws and in the surrounding tissues. Alkaline phosphatase (osteoblast marker), TRAP and Cathepsin K (osteoclast markers) mRNA, but not the inflammatory markers (TNF-alpha and IL-1beta) were expressed at different levels around the two surfaces. Conclusions: The results demonstrate that the experimental model and qPCR provide interesting possibilities to analyze the mechanisms of osseointegration. Furthermore, remodelling and in particular the molecular processes occur at implant surfaces in vivo already 3 days after implantation. Support: Swedish Research Council and the Institute for Biomaterials and Cell Therapy, Göteborg, Sweden
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