| 1. |
- Klaric, Lucija, et al.
(författare)
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Mendelian randomisation identifies alternative splicing of the FAS death receptor as a mediator of severe COVID-19.
- 2021
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Ingår i: medRxiv : the preprint server for health sciences. - : Cold Spring Harbor Laboratory. ; , s. 1-28
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Severe COVID-19 is characterised by immunopathology and epithelial injury. Proteomic studies have identified circulating proteins that are biomarkers of severe COVID-19, but cannot distinguish correlation from causation. To address this, we performed Mendelian randomisation (MR) to identify proteins that mediate severe COVID-19. Using protein quantitative trait loci (pQTL) data from the SCALLOP consortium, involving meta-analysis of up to 26,494 individuals, and COVID-19 genome-wide association data from the Host Genetics Initiative, we performed MR for 157 COVID-19 severity protein biomarkers. We identified significant MR results for five proteins: FAS, TNFRSF10A, CCL2, EPHB4 and LGALS9. Further evaluation of these candidates using sensitivity analyses and colocalization testing provided strong evidence to implicate the apoptosis-associated cytokine receptor FAS as a causal mediator of severe COVID-19. This effect was specific to severe disease. Using RNA-seq data from 4,778 individuals, we demonstrate that the pQTL at the FAS locus results from genetically influenced alternate splicing causing skipping of exon 6. We show that the risk allele for very severe COVID-19 increases the proportion of transcripts lacking exon 6, and thereby increases soluble FAS. Soluble FAS acts as a decoy receptor for FAS-ligand, inhibiting apoptosis induced through membrane-bound FAS. In summary, we demonstrate a novel genetic mechanism that contributes to risk of severe of COVID-19, highlighting a pathway that may be a promising therapeutic target.
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| 2. |
- Abou-Taouk, Abdallah, 1982, et al.
(författare)
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CFD analysis of a SGT-800 burner in a combustion RIG
- 2016
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Ingår i: ASME Turbo Expo, June 13 – 17, 2016, Seoul, South Korea.
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Konferensbidrag (refereegranskat)abstract
- This work focuses on 3D turbulent reacting flow modeling of a SGT-800 3rd generation dry low emission (DLE) burner at both atmospheric and engine-like conditions. At atmospheric pressure the burner is fitted in a test rig with high pre-heating of the incoming air. To reduce the computational cost, the M4 mechanism previously developed by Abou-Taouk et al. (2013) is used for operating pressure of 1 bar. A new novel optimized 4-step reaction mechanism for methane-air mixture is developed in the present work at an operating pressure of 20 bar. The mechanism is based on a large sample of detailed chemistry solutions that are processed by an iterative optimization procedure. This leads to a reduced 4-step mechanism, reproducing the targeted detailed chemistry solutions in terms of laminar flame speeds, species profiles and temperatures. The CFD simulations are performed using the combined eddy dissipation model / finite rate chemistry (EDM/FRC) turbulence chemistry interaction model. The turbulence is modeled using both the k-ω SST and the scale adaptive simulation (SAS) turbulence models. A comprehensive testing and measurement campaign carried out at atmospheric pressure for this burner was previously performed in a combustion test rig. The CFD results are compared to measurement data which includes for example flame position and pressure drop.
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| 3. |
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| 4. |
- Andersson, Kristoffer, 1976, et al.
(författare)
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Resistive SiC-MESFET mixer
- 2002
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Ingår i: IEEE Microwave and Wireless Components Letters. - : Institute of Electrical and Electronics Engineers (IEEE). - 1531-1309 .- 1558-1764. ; 12:4, s. 119-121
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Tidskriftsartikel (refereegranskat)abstract
- A single-ended silicon carbide resisitve MESFET mixer with minimum conversion loss (CL) of 10.2 dB and an input third order intercept point of 35.7 dB at 3.3 GHz was designed and characterized. A lumped-element, large-signal model was used for modeling the device. The drain-source resistance was measured by taking the real part of the output port impedence. Analysis suggested that the optimum gate bias for minimum CL was -6.7 V.
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| 5. |
- Andersson, Niklas, 1976, et al.
(författare)
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A Novel Solver Acceleration Technique Based on Dynamic Mode Decomposition
- 2014
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Ingår i: 11th World Congress on Computational Mechanics, WCCM 2014. - 9788494284472 ; , s. 4832-4851
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Konferensbidrag (refereegranskat)abstract
- The speed up of finite-volume solvers for compressible flows is a difficult task. There are several ways to achieve solver speed-up, more or less difficult to implement and more or less suitable for implementation in a parallel, unstructured type of solver. Examples of such techniques are the multi-grid method and implicit residual smoothening. In this article, a solver acceleration technique based on Dynamic Mode Decomposition (DMD) is proposed. The technique does not depend on data or mesh structure and is thus as straightforward to implement in an unstructured parallel code as in a structured sequential code. The main idea behind the proposed method is that one can use the information in flow field modes extracted using the DMD technique to find a correction that will bring the solution closer to a steady state condition, i.e. the method is only applicable to steady-state problems. In the presented work the DMD-based acceleration technique has been implemented in a massively parallel block-structured finite-volume Navier-Stokes solver for compressible flows. The method has been tested on a turbine cascade case with promising results. To the knowledge of the authors, the proposed method is not previously published in the open literature.
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| 6. |
- Andersson, Niklas, 1976, et al.
(författare)
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A Study of Mach 0.75 Jets and Their Radiated Sound Using Large-Eddy Simulation
- 2004
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Ingår i: AIAA 2004-3024, proc. of 10th AIAA/CEAS Aeroacoustics Conference, May 10-12, 2004.
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Konferensbidrag (refereegranskat)abstract
- Large-Eddy Simulations (LES) of a compressible nozzle/jet configuration have been carried out. Two jets were simulated, an isothermal jet and a jet with a higher temperature than the quiescent surrounding air. The Mach number was in both cases 0.75 and the jet Reynolds number was 50,000. Sound pressure levels in far-field observer locations were evaluated using Kirchhoff surface integration. The Favre filtered Navier-Stokes equations were solved using a finite volume method solver with a low-dissipation third-order upwind scheme for the convective fluxes, a second-order centered difference approach for the viscous fluxes and a three-stage second-order Runge-Kutta technique in time. The computational domain was discretized using a block structured boundary fitted mesh with approximately 3,000,000 cells. The calculations were performed on a parallel computer, using message-passing interface (MPI). A compressible form of Smagorinsky's subgrid scale model was used for computation of the subgrid scale stresses. Absorbing boundary conditions based on characteristic variables were adopted for all free boundaries. Velocity components specified at the entrainment boundaries were estimated from corresponding Reynolds Averaged Navier-Stokes (RANS) calculations, which enable the use of a rather narrow domain. This, furthermore, ensures that the correct amount of fluid is entrained into the domain. Two-point space-time correlations were obtained for locations in the shear layer center, from which length and time scales of turbulence structures were evaluated. Predicted near-field flow statistics and far-field sound pressure levels (SPL) are both in good agreement with experiments. Predicted (SPL) are for all observers locations, where evaluated, within a 3.0 [dB] deviation from measured levels and for most locations within a 1.0 [dB] deviation. Experimental data used for validation were provided by Laboratoire dEtude Aeròdynamiques, Poitiers, France.
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| 7. |
- Andersson, Niklas, 1976, et al.
(författare)
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Effects of Inflow Conditions and Subgrid Model on LES for Turbulent Jets
- 2005
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Ingår i: AIAA 2005-2925, proc. of 11th AIAA/CEAS Aeroacoustics Conference, May 23-25, 2005, Monterey, California.
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Konferensbidrag (refereegranskat)abstract
- The turbulent mixing process prescribing the spreading rate of the jet and the length of the potential core region is influenced by a number of factors. Using large-eddy simulation (LES), the four factors that are believed to be the most important in this respect are: subgrid-scale properties, the accuracy of the numerical scheme, the entrainment boundary conditions, and the inflow conditions. In a previously performed study of a subsonic (Mach 0.75) jet, the turbulence mixing was found to be too efficient and hence the length of the potential core region was underpredicted. In that study indications were found of that the overpredicted mixing was due to the inflow conditions. For a model nozzle, capturing the initial turbulent shear flow might not be of that great importance for accurate prediction of radiated sound since most of these effects will appear in the high-frequency range. When dealing with real engine geometries, however, it becomes quite important. Moreover, methods for industrial use have to cope with complex geometries and high temperature and velocity ratios making the ability to capture the initial flow physics even more important. In the present work LES has been used for the same Mach 0.75 jet. The acoustic field is extracted to the far field using Kirchhoff surface integration. The effects of inflow conditions, Reynolds number, and subgrid-scale model on flowfield and acoustic signature are investigated.The Favre-filtered Navier-Stokes equations were solved using a finite-volume method solver with a low-dissipation third-order upwind scheme for the convective fluxes, a second-order centered difference approach for the viscous fluxes and a three-stage second-order Runge-Kutta technique in time. The computational domain was discretized using a block-structured boundary-fitted mesh with approximately 3,000,000 cells. The calculations were performed on a parallel computer, using message-passing interface (MPI). A compressible form of Smagorinsky's subgrid-scale model was used to compute the subgrid-scale stresses. Absorbing boundary conditions based on characteristic variables were adopted for all free boundaries.
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| 8. |
- Andersson, Niklas, 1976, et al.
(författare)
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Investigation of an Isothermal Mach 0.75 Jet and its Radiated sound Using Large-Eddy Simulation and Kirchhoff Surface Integration
- 2005
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Ingår i: International Journal of Heat and Fluid Flow. ; 26, s. 393-410
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Tidskriftsartikel (refereegranskat)abstract
- A large-eddy simulation (LES) of a compressible nozzle/jet configuration has been carried out. An isothermal Mach 0.75 jet was simulated. The Reynolds number based on the jet velocity at the nozzle exit plane and the nozzle diameter was 50,000. The Favre filtered Navier-Stokes equations were solved using a finite volume method solver with a low-dissipation third-order upwind scheme for the convective fluxes, a second-order centered difference approach for the viscous fluxes and a three-stage second-order Runge-Kutta time marching technique. A compressible form of Smagorinsky's subgrid scale model was used for computation of the subgrid scale stresses. The computational domain was discretized using a block structured boundary fitted mesh with approximately 3,000,000 cells. The calculations were performed on a parallel computer, using message-passing interface (MPI). Absorbing boundary conditions based on characteristic variables were adopted for all free boundaries. Velocity components specified at the entrainment boundaries were estimated from a corresponding Reynolds Averaged Navier-Stokes (RANS) calculation, which enabled the use of a rather narrow domain. In order to diminish disturbances caused by the outlet boundary, a buffer layer was added at the domain outlet. Kirchhoff surface integration using instantaneous pressure data from the LES was utilized to obtain far-field sound pressure levels in a number of observer locations. The predicted sound pressure levels were for all observer locations within a 3dB deviation from the measured levels and for most observer locations within a 1dB deviation. Aerodynamic results and predicted sound pressure levels are both in good agreement with experiments. Experimental data were provided by Laboratoire dEtude Aeròdynamiques, Poiters, France.
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| 9. |
- Andersson, Niklas, 1976, et al.
(författare)
-
Large-Eddy Simulation of a Mach 0.75 Jet
- 2003
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Ingår i: AIAA 2003-3312, proc. of 9th AIAA/CEAS Aeroacoustic Conference, May 12-14, 2003.
-
Konferensbidrag (refereegranskat)abstract
- A large-eddy simulation (LES) of a compressible nozzle/jet configuration has been carried out. A cold Mach 0.75 jet was simulated. The Reynolds number based on the jet velocity at the nozzle exit plane and the nozzle diameter was 50,000. The Favre filtered Navier-Stokes equations were solved using a finite volume method with a low dissipative third order upwind scheme for the convective fluxes, a second order centered difference approach for the viscous fluxes and a three-stage second order Runge-Kutta time marching technique. A compressible form of Smagorinsky's sub-grid scale model was used for computation of the sub-grid scale stresses. The calculations were performed using a block structured boundary fitted mesh with approximately 3,000,000 cells. The calculations have been performed on a parallel computer, using message-passing interface (MPI). Absorbing boundary conditions based on characteristic variables were adopted for all free boundaries. Velocity components specified at the entrainment boundaries were estimated from a corresponding Reynolds Averaged Navier-Stokes (RANS) calculation. In order to diminish disturbances caused by the outlet boundary a buffer layer was added at the domain outlet. Kirchhoff surface integration has been utilized to obtain far-field sound pressure levels in a number of observer locations using instantaneous pressure from the LES. Aerodynamic results and predicted sound pressure levels are both in good agreement with experiments. Experimental data were provided by Laboratoire dEtude Aeròdynamiques, Poiters, France.
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| 10. |
- Andersson, Niklas, 1976, et al.
(författare)
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Large-Eddy Simulation of Subsonic Turbulent Jets and Their Radiated Sound
- 2005
-
Ingår i: AIAA Journal. ; 43:9, s. 1899-1912
-
Tidskriftsartikel (refereegranskat)abstract
- Large-Eddy Simulations (LES) of a compressible nozzle/jet configuration have been carried out. Two jets were simulated, an isothermal jet and a jet with a higher temperature than the quiescent surrounding air. The Mach number was in both cases 0.75 and the jet Reynolds number was 50,000. Sound pressure levels in far-field observer locations were evaluated using Kirchhoff surface integration. The Favre filtered Navier-Stokes equations were solved using a finite volume method solver with a low-dissipation third-order upwind scheme for the convective fluxes, a second-order centered difference approach for the viscous fluxes and a three-stage second-order Runge-Kutta technique in time. The computational domain was discretized using a block structured boundary fitted mesh with approximately 3,000,000 cells. The calculations were performed on a parallel computer, using message-passing interface (MPI). A compressible form of Smagorinsky's subgrid scale model was used for computation of the subgrid scale stresses. Absorbing boundary conditions based on characteristic variables were adopted for all free boundaries. Velocity components specified at the entrainment boundaries were estimated from corresponding Reynolds Averaged Navier-Stokes (RANS) calculations, which enable the use of a rather narrow domain. This, furthermore, ensures that the correct amount of fluid is entrained into the domain. Two-point space-time correlations were obtained for locations in the shear layer center, from which length and time scales of turbulence structures were evaluated. Predicted near-field flow statistics and far-field sound pressure levels (SPL) are both in good agreement with experiments. Predicted (SPL) are for all observers locations, where evaluated, within a 3.0 [dB] deviation from measured levels and for most locations within a 1.0 [dB] deviation. Experimental data used for validation were provided by Laboratoire dEtude Aeròdynamiques, Poiters, France.
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