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- Carlsson, Per-Anders, 1972, et al.
(författare)
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A transient in situ FTIR and XANES study of CO oxidation over Pt/Al2O3 catalysts
- 2004
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Ingår i: Journal of Catalysis. - : Elsevier BV. - 0021-9517 .- 1090-2694. ; 226:2, s. 422-434
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Tidskriftsartikel (refereegranskat)abstract
- We report experimental results for the oxidation of CO over supported Pt/Al2O3 catalysts operating in oxygen excess at atmospheric pressure. To study the reaction kinetics under transient conditions we have employed step changes of the O2 concentration by intermittently switching off the O2 supply at various temperatures ranging from 523 to 623 K. Detailed in situ FTIR and XANES data for CO coverage and the chemical state of Pt, respectively, are presented together with the CO conversion, which in both cases was monitored by mass spectrometry. A red-shift of the vibrational frequency of linearly bonded CO which correlates with a blue-shift of the Pt LIII binding energy indicates that the Pt catalyst initially is partially oxidised and gradually reduced when the O2 supply is switched off. Control experiments with a NO2 oxidised Pt/Al2O3 catalyst support these findings. A hysteresis in the catalytic activity due to the different rates whereby Pt is oxidised and reduced as a function of gas-phase composition is observed. The activation energy for the Pt oxide reduction (decomposition) process is estimated to be about 50 kJ/mol. The results further emphasise that the conventional three-step Langmuir-Hinshelwood (LH) scheme used to interpret CO oxidation on Pt surfaces must be complemented by a Pt oxidation and reduction mechanism during transient conditions. Moreover, FTIR data suggest that during the extinction, the partially oxidised platinum surface is reduced by chemisorbed CO which should be explicitly accounted for in the modeling of the reaction mechanism.
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| 7. |
- Fryk, Emanuel, et al.
(författare)
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Galectin-1 correlates with inflammatory markers and T regulatory cells in children with type 1 diabetes and/or celiac disease
- 2024
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Ingår i: Clinical and Experimental Immunology. - : Oxford University Press. - 1365-2249 .- 0009-9104. ; 215:3, s. 240-250
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Tidskriftsartikel (refereegranskat)abstract
- Type 1 diabetes (T1D) and celiac disease (CeD) are common autoimmune diseases in children where the pathophysiology is not fully characterized. The autoimmune process involves a complex scenario of both inflammatory and regulatory features. Galectin-1 (GAL-1) has a wide range of biological activities e.g. interaction with immune cells. We examined the relationship between GAL-1 and soluble immune markers and T-cell subsets in a cohort of children with T1D and/or CeD relative to healthy children. GAL-1, together with several soluble immune markers [e.g. interleukins (IL)], tumor necrosis factor (TNF), acute phase proteins, and matrix metalloproteinases (MMP) were measured in sera from children with T1D and/or CeD by fluorochrome (Luminex) technique using children without these diseases as a reference. Subgroups of T cells, including T-regulatory (Treg) cells, were analysed by flow cytometry. Association between GAL-1, pro-inflammatory markers, and Treg cells differed depending on which illness combination was present. In children with both T1D and CeD, GAL-1 correlated positively with pro-inflammatory markers (IL-1 beta, IL-6, and TNF-alpha). Composite scores increased the strength of correlation between GAL-1 and pro-inflammatory markers, Th1-associated interferon (IFN)-gamma, and T1D-associated visfatin. Contrary, in children diagnosed with exclusively T1D, GAL-1 was positively correlated to CD25hi and CD25hiCD101+ Treg cells. For children with only CeD, no association between GAL-1 and other immune markers was observed. In conclusion, the association observed between GAL-1, soluble immune markers, and Treg cells may indicate a role for GAL-1 in the pathophysiology of T1D and, to some extent, also in CeD. Type 1 diabetes (T1D) and celiac disease (CeD) are common autoimmune diseases in children where pathophysiology is not fully characterized. The autoimmune process involves a complex scenario of both inflammatory and regulatory features. Galectin-1 (GAL-1) has a wide range of biological activities e.g. interaction with immune cells and the association observed between GAL-1, soluble immune markers, and T regulatory (Treg) cells may indicate a role for GAL-1 in the pathophysiology of children with T1D and, to some extent, also in children with CeD. Graphical Abstract
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| 8. |
- Jansson, Per-Åke, 1949, et al.
(författare)
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Modeling of Ultrasonic Nondestructive Testing of Surface-breaking Cracks
- 2012
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Ingår i: Proceedings 18th World Conference of Non-Destructive Testing, 16-20 April 2012, Durban, South Africa. - 9780620528726
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Konferensbidrag (refereegranskat)abstract
- A complete model of ultrasonic nondestructive testing of defects in thick-walled components has been developed since more than a decade and has resulted in the computer program UTDefect. The program includes models of transmitting ultrasonic probes, and through a reciprocity argument also recieving probes. A number of simply shaped defects are included. Here the focus is on surface-breaking strip-like cracks, and a comparison of these with strip-like interior cracks. Both scattering problems are solved with a hyper-singular integral equation method, where the unknown crack-opening displacement (COD) is expanded into sets of Chebyshev functions. These expansions are different for the two cracks; whereas the interior crack has a COD that behaves as a square root at the tips, the surface-breaking COD has a finite value at the crack mouth, and these behaviours must be taken into account. Numerical comparisons are made between the two cracks, and it seems that the interior crack pushed to the surface behaves very much like the surface-breaking one, except at very low frequencies (crack size less than half a wavelength). Favourable comparisons with experiments are also made.
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| 9. |
- Jansson, Per-Åke, 1949, et al.
(författare)
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Simulation of the 2008 Ultrasonic Benchmark Problems Using UTDefect
- 2009
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Ingår i: AIP Conference Proceedings. - : AIP. - 0094-243X .- 1551-7616. - 9780735406292 ; 28B, s. 1968-1972
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Konferensbidrag (refereegranskat)abstract
- The computer program UTDefect is used to solve some of the 2008 ultrasonic benchmark problems. UTDefect is a program for simulation of ultrasonic testing with applications within the nuclear industry in mind. Scattering from various types of defects, like a side-drilled hole and a flat-bottom hole, is modelled using solutions that are essentially exact. For the benchmark problems the results obtained from UTDefect are in fairly good agreement with the experimental data from CEA.
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- Jansson, Per-Åke, 1949, et al.
(författare)
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Ultrasonic benchmarking with UTdefect
- 2010
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Ingår i: AIP Conference Proceedings. - : AIP. - 1551-7616 .- 0094-243X. - 9780735407480 ; 1211, s. 2149-2156
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Konferensbidrag (refereegranskat)abstract
- UTDefect is a program for simulation of ultrasonic testing with emphasis on applications within the nuclear power industry. The entire testing process, including the ultrasonic transmitter, the receiver, and scattering from various types of defects of simple shape, is modelled. The basic idea behind UTDefect is to use solutions to the elastodynamic wave equation that are esentially exact. For the 2009 benchmark problems the results obtained from UTDefect are in most cases in fairly good agreement with the experimental data from CEA. © 2010 American Institute of Physics.
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