| 1. |
- Eriksen, Niklas, 1974-, et al.
(författare)
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Diagonal checker-jumping and Eulerian numbers for color-signed permutations
- 2000
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Ingår i: The Electronic Journal of Combinatorics. - Clemson, USA : Electronic Journal of Combinatorics. - 1097-1440 .- 1077-8926. ; 7
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Tidskriftsartikel (refereegranskat)abstract
- We introduce color-signed permutations to obtain a very explicit combinatorial interpretation of the q-Eulerian identities of Brenti and some generalizations. In particular, we prove an identity involving the golden ratio, which allows us to compute upper bounds on how high a checker can reach in a classical checker-jumping problem, when the rules are relaxed to allow also diagonal jumps.
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| 2. |
- 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
-
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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| 3. |
- Örlén, Hanna, et al.
(författare)
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SPG11 mutations cause Kjellin syndrome, a hereditary spastic paraplegia with thin corpus callosum and central retinal degeneration.
- 2009
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Ingår i: American Journal of Medical Genetics. Part B, Neuropsychiatric Genetics. - : Wiley. - 1552-485X .- 1552-4841. ; 150B:7, s. 984-992
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Tidskriftsartikel (refereegranskat)abstract
- Autosomal recessive hereditary spastic paraplegia (ARHSP) with thin corpus callosum (TCC) is genetically heterogenous and approximately 35% of patients carry mutations in either of the SPG11 or SPG15 genes. Disease onset is during the first three decades of life with spastic paraplegia and mental impairment. Peripheral neuropathy and amyotrophy may occur. Kjellin syndrome is characterized by central retinal degeneration in addition to ARHSP-TCC and the disease is associated with mutations in the SPG15 gene. We identified five patients in four unrelated kindreds with spastic paraplegia and mental impairment. Magnetic resonance imaging revealed TCC, atrophy elsewhere in the brain and increased T2 signal intensity in the periventricular white matter. Probands from the four kindreds were screened for mutations in the SPG11 gene. All patients were found homozygous or compound heterozygous for truncating SPG11 mutations of which four are reported for the first time. Ophthalmological investigations revealed that the four index cases have central retinal degeneration consistent with Kjellin syndrome. PET examinations with N-[11C-methyl]-L-deuterodeprenyl (DED) and fluor-18 2-fluorodeoxyglucose (FDG) were performed in two patients with Kjellin syndrome. We observed a reduced glucose uptake in the thalami, anterior cingulum, and sensorimotor cortex indicating neuronal loss, and an increased DED binding in the thalami and pons which suggests astrogliosis. From our results we extend the SPG11 associated phenotype to comprise also Kjellin syndrome, previously found to be associated with mutations in the SPG15 gene. We anticipate that degeneration of the central retina is a common and previously unrecognized feature in SPG11 related disease.
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| 4. |
- Abé, Christoph, et al.
(författare)
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Brain structure and clinical profile point to neurodevelopmental factors involved in pedophilic disorder
- 2021
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Ingår i: Acta Psychiatrica Scandinavica. - : John Wiley & Sons. - 0001-690X .- 1600-0447. ; 143:4, s. 363-374
-
Tidskriftsartikel (refereegranskat)abstract
- Objective: Pedophilic disorder (PD) is characterized bypersistent, intense sexual attraction to prepubertal children that the individual has acted on, or causes marked distress or interpersonal difficulty. Although prior research suggests that PD has neurodevelopmental underpinnings, the evidence remains sparse. To aid the understanding of etiology and treatment development, we quantified neurobiological and clinical correlates of PD.Method: We compared 55 self-referred, help-seeking, non-forensic male patients with DSM-5 PD with 57 age-matched, healthy male controls (HC) on clinical, neuropsychological, and structural brain imaging measures (cortical thickness and surface area, subcortical and white matter volumes). Structural brain measures were related to markers for aberrant neurodevelopment including IQ, and the 2nd to 4th digit ratio (2D:4D).Results: PD was associated with psychiatric disorder comorbidity and ADHD and autism spectrum disorder symptoms. PD patients had lower total IQ than HC. PD individuals exhibited cortical surface area abnormalities in regions belonging to the brain's default mode network and showed abnormal volume of white matter underlying those regions. PD subjects had smaller hippocampi and nuclei accumbens than HC. Findings were not related to history of child-related sexual offending. IQ correlated negatively with global expression of PD-related brain features and 2D:4D correlated with surface area in PD.Conclusions: In the largest single-center study to date, we delineate psychiatric comorbidity, neurobiological and cognitive correlates of PD. Our morphometric findings, their associations with markers of aberrant neurodevelopment, and psychiatric comorbidities suggest that neurodevelopmental mechanisms are involved in PD. The findings may need consideration in future development of clinical management of PD patients.
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| 5. |
- Abou-Taouk, Abdallah, 1982, et al.
(författare)
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CFD analysis of a SGT-800 burner in a combustion RIG
- 2016
-
Ingår i: ASME Turbo Expo, June 13 – 17, 2016, Seoul, South Korea.
-
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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| 6. |
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| 7. |
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| 8. |
- Almqvist, Erik, et al.
(författare)
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Solving the ADAPT Benchmark Problem - A Student Project Study
- 2010
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Konferensbidrag (refereegranskat)abstract
- This paper describes a solution to the Advanced Diagnosis and Prognostics testbed (ADAPT) diagnosis benchmark problem. One main objective was to study and discuss how engineering students, with no diagnosis research background, would solve a challenging diagnosis problem. The study was performed within the framework of a final year project course for control engineering students. A main contribution of the work is the discussion on the development process used by the students. The solution is based on physical models of components and includes common techniques from control theory, like observers and parameter estimators, together with established algorithms for consistency based fault isolation. The system is fully implemented in C++ and evaluated, using the DXC software platform, with good diagnosis performance.
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| 9. |
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| 10. |
- Ancillotti, Mirko, 1981-, et al.
(författare)
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Uncritical and unbalanced coverage of synthetic biology in the Nordic press
- 2017
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Ingår i: Public Understanding of Science. - : Sage Publications. - 0963-6625 .- 1361-6609. ; 26:2, s. 235-250
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Tidskriftsartikel (refereegranskat)abstract
- Synthetic biology will probably have a high impact on a variety of fields, such as healthcare, environment, biofuels, agriculture, and so on. A driving theme in European research policy is the importance of maintaining public legitimacy and support. Media can influence public attitudes and are therefore an important object of study. Through qualitative content analysis, this study investigates the press coverage of synthetic biology in the major Nordic countries between 2009 and 2014. The press coverage was found to be event-driven and there were striking similarities between countries when it comes to framing, language use, and treated themes. Reporters showed a marked dependence on their sources, mainly scientists and stakeholders, who thus drives the media agenda. The media portrayal was very positive, with an optimistic look at future benefits and very little discussion of possible risks.
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| 11. |
- Andersen, Niklas, et al.
(författare)
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Wind turbines’ end-of-life : Quantification and characterisation of future waste materials on a national level
- 2016
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Ingår i: Energies. - : MDPI AG. - 1996-1073. ; 9:12
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Tidskriftsartikel (refereegranskat)abstract
- Globally, wind power is growing fast and in Sweden alone more than 3000 turbines have been installed since the mid-1990s. Although the number of decommissioned turbines so far is few, the high installation rate suggests that a similarly high decommissioning rate can be expected at some point in the future. If the waste material from these turbines is not handled sustainably the whole concept of wind power as a clean energy alternative is challenged. This study presents a generally applicable method and quantification based on statistics of the waste amounts from wind turbines in Sweden. The expected annual mean growth is 12% until 2026, followed by a mean increase of 41% until 2034. By then, annual waste amounts are estimated to 240,000 tonnes steel and iron (16% of currently recycled materials), 2300 tonnes aluminium (4%), 3300 tonnes copper (5%), 340 tonnes electronics (<1%) and 28,000 tonnes blade materials (barely recycled today). Three studied scenarios suggest that a well-functioning market for re-use may postpone the effects of these waste amounts until improved recycling systems are in place.
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| 12. |
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| 13. |
- Andersson, Dennis, 1980-
(författare)
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Mission Experience : How to Model and Capture it to Enable Vicarious Learning
- 2013
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Organizations for humanitarian assistance, disaster response and military activities are characterized by their special role in society to resolve time-constrained and potentially life-threatening situations. The tactical missions that these organizations conduct regularly are significantly dynamic in character, and sometimes impossible to fully comprehend and predict. In these situations, when control becomes opportunistic, the organizations are forced to rely on the collective experience of their personnel to respond effectively to the unfolding threats. Generating such experience through traditional means of training, exercising and apprenticeship, is expensive, time-consuming, and difficult to manage.This thesis explores how and why mission experience should be utilized in emergency management and military organizations to improve performance. A multimedia approach for capturing mission experience has further been tested in two case studies to determine how the commanders’ experiences can be externalized to enable vicarious learning. These studies propose a set of technical, methodological, and ethical issues that need to be considered when externalizing mission experience, based on two aforementioned case studies complemented by a literature review. The presented outcomes are (1) a model aligning abilities that tactical organizations need when responding to dynamic situations of different familiarity, (2) a review of the usefulness of several different data sources for externalization of commanders’ experiences from tactical operations, and (3) a review of methodological, technical, and ethical issues to consider when externalizing tactical military and emergency management operations. The results presented in this thesis indicate that multimedia approaches for capturing mission histories can indeed complement training and exercising as a method for generating valuable experience from tactical missions.
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| 14. |
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| 15. |
- 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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| 16. |
- Andersson, Niklas, 1976, et al.
(författare)
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A Novel Solver Acceleration Technique Based on Dynamic Mode Decomposition
- 2014
-
Ingår i: 11th World Congress on Computational Mechanics, WCCM 2014. - 9788494284472 ; , s. 4832-4851
-
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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| 17. |
- 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
-
Ingår i: AIAA 2004-3024, proc. of 10th AIAA/CEAS Aeroacoustics Conference, May 10-12, 2004.
-
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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| 18. |
- Andersson, Niklas, 1976, et al.
(författare)
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Effects of Inflow Conditions and Subgrid Model on LES for Turbulent Jets
- 2005
-
Ingår i: AIAA 2005-2925, proc. of 11th AIAA/CEAS Aeroacoustics Conference, May 23-25, 2005, Monterey, California.
-
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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| 19. |
- Andersson, Niklas, 1976, et al.
(författare)
-
Investigation of an Isothermal Mach 0.75 Jet and its Radiated sound Using Large-Eddy Simulation and Kirchhoff Surface Integration
- 2005
-
Ingår i: International Journal of Heat and Fluid Flow. ; 26, s. 393-410
-
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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| 20. |
- Andersson, Niklas, 1976, et al.
(författare)
-
Large-Eddy Simulation of a Mach 0.75 Jet
- 2003
-
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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| 21. |
- Andersson, Niklas, 1976, et al.
(författare)
-
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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| 22. |
- Andersson, Niklas, 1976, et al.
(författare)
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LES Prediction of Flow and Acoustic Field of a Coaxial Jet
- 2005
-
Ingår i: AIAA 2005-2884, proc. of 11th AIAA/CEAS Aeroacoustics Conference, May 23-25, 2005, Monterey, California.
-
Konferensbidrag (refereegranskat)abstract
- A compressible high-subsonic coaxial jet has been simulated using large-eddy simulation (LES). The acoustic field was extended to the far field using Kirchhoff surface integration. The jet Mach number based on the local speed of sound is approximately 0.9 for both the primary and secondary stream. The static temperature in the primary stream is three times that of the secondary stream. In order to resolve the acoustic field, it is desirable to have a computational domain with a rather large radial extent and a mesh that is relatively fine even in the far-field regions. Furthermore, the mesh should be as equidistant as possible so as to minimize the introduction of numerical errors. In order to keep the number of cells down, the computational domain was divided into three regions: a well resolved near-wall LES region, a medium-resolution LES region optimized for propagation of acoustic waves, and a coarse LES region. Over the interfaces between these regions, the number of cells is increased by factor two in each direction. Special treatment of the interfaces between the regions is utilized in order to minimize undesirable numerical errors. The radial extent of the computational domain increases downstream such that the flow in the outer boundary region can be assumed to be irrotational and axisymmetric. Hence, the flow outside the three-dimensional computational domain can be represented by a less expensive two-dimensional axisymmetric calculation. The interface between the full 3D LES region and the 2D region is based on azimuthally averaged quantities and acts as an absorbing boundary condition. 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 20,000,000 nodes. 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.
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| 23. |
- Andersson, Niklas, 1976, et al.
(författare)
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Numerical Simulation of Stirling Engines Using an Unsteady Quasi-One-Dimensional Approach
- 2015
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Ingår i: Journal of Fluids Engineering, Transactions of the ASME. - : ASME International. - 1528-901X .- 0098-2202. ; 137:5, s. Art. no. 051104-
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Tidskriftsartikel (refereegranskat)abstract
- An existing computer code for solving the quasi-one-dimensional flow equations governing unsteady compressible flow in tubes with smoothly varying cross-section areas, has been adapted to the simulation of the oscillatory flow in Stirling engines for engine design purposes. By utilizing an efficient smoothing algorithm for the area function that preserves the total volume of the tube, it has been possible to achieve a highly accurate and fully conservative numerical scheme. Sub-models for wall friction and heat transfer have been added, enabling the simulation of gas heaters, gas coolers, and regenerators. The code has been used for the modeling of an alpha-type Stirling engine and validated for a range of operating conditions with good results.
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| 24. |
- Andersson, Niklas, 1976, et al.
(författare)
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Prediction of flowfield and acoustic signature of a coaxial jet using RANS-based methods and large-eddy simulation
- 2008
-
Ingår i: International Journal of Aeroacoustics. - : SAGE Publications. - 1475-472X .- 2048-4003. ; 7:1, s. 23-40
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Tidskriftsartikel (refereegranskat)abstract
- The feasibility of using large-eddy simulation (LES) for jet noise predictions has been discussed in several publications. The vast majority of these studies are, however, restricted to fairly simple geometries and moderate Reynolds numbers flows. Recent studies have shown that LES-based methods can be used for realistic flows and complex geometries with promising results. With continuously increased computer capacity and with the possibility to perform computations in parallel on PC-clusters, the possibility of using LES for industrial applications is increasing. However, although, the complexity of configurations for which LES may be used is approaching that of a real jet engine, due to high demands for computational power and long turn-over times LES is still not feasible for industrial use. For low-noise nozzle design, engineering tools with short turn-over time, accurate enough for prediction of noise trends are therefore needed. In the development of such methods, LES can provide data suitable for method validation. In the present work, the high-subsonic flow in an axisymmetric coaxial nozzle/jet configuration is studied. Flowfield predictions obtained using an axisymmetric RANS solver for compressible flows and predicted acoustic signature obtained using a method based on RANS and Lighthill's acoustic analogy are compared with flowfield and radiated sound predictions obtained using LES combined with Kirchhoff surface integration. In the predicted flow statistics, the most noticeable difference between RANS and LES results is that the RANS calculation gives somewhat lower levels of turbulence kinetic energy in the shear layers in the near-nozzle regions and hence the LES jet mixes somewhat faster and thus the potential core region is shorter in this simulation.
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| 25. |
- Andrews, David, et al.
(författare)
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Control of the topside Martian ionosphere by crustal magnetic fields
- 2015
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Ingår i: Journal of Geophysical Research - Space Physics. - 2169-9380 .- 2169-9402. ; 120:4, s. 3042-3058
-
Tidskriftsartikel (refereegranskat)abstract
- We present observations from the Mars Advanced Radar for Subsurface and Ionospheric Sounding (MARSIS) instrument onboard Mars Express of the thermal electron plasma density of the Martian ionosphere and investigate the extent to which it is influenced by the presence of Mars's remnant crustal magnetic fields. We use locally measured electron densities, derived when MARSIS is operating in active ionospheric sounding (AIS) mode, covering an altitude range from approximate to 300km to approximate to 1200km. We compare these measured densities to an empirical model of the dayside ionospheric plasma density in this diffusive transport-dominated regime. We show that small spatial-scale departures from the averaged values are strongly correlated with the pattern of the crustal fields. Persistently elevated densities are seen in regions of relatively stronger crustal fields across the whole altitude range. Comparing these results with measurements of the (scalar) magnetic field also obtained by MARSIS/AIS, we characterize the dayside strength of the draped magnetic fields in the same regions. Finally, we provide a revised empirical model of the plasma density in the Martian ionosphere, including parameterizations for both the crustal field-dominated and draping-dominated regimes.
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| 26. |
- Asplund, Basse, et al.
(författare)
-
In vitro degradation and in vivo biocompatibility study of a new linear poly(urethane urea)
- 2008
-
Ingår i: Journal of biomedical materials research. Part B: Applied biomaterials. - : Wiley. - 1552-4973 .- 1552-4981. ; 86B:1, s. 45-55
-
Tidskriftsartikel (refereegranskat)abstract
- Segmented poly(urethane urea)s (PUUs) with hard segments derived only from methyl 2,6-diisocyantohexanoate (LDI) without the use of a chain extender have previously been described. These materials, which contain hard segments with multiple urea linkages, show exceptionally high strain capability (1600-4700%). In the study reported here, the rate and effect of hydrolysis of these materials were determined for gamma-sterilized and nonsterilized samples. Materials investigated contained PCL, PTMC, P(TMC-co-CL), P(CL-co-DLLA), or P(TMC-co-DLLA) as soft segments and, as well as their mechanical properties, changes in mass, inherent viscosity (IN.), and thermal properties were studied over 20 weeks. Results showed that the degradation rate was dependant on the soft segment structure, with a higher rate of degradation for the polyester-dominating PUUs exhibiting a substantial loss in IN. A tendency of reduction of tensile strength and strain hardening was seen for all samples. Also, loss in elongation at break was detected, for PUU-P(CL-DLLA) it went from 1600% to 830% in 10 weeks. Gamma radiation caused an initial loss in I.V. and induced more rapid hydrolysis compared with nonsterilized samples, except for PUU-PTMC. A cytotoxicity test using human fibroblasts demonstrated that the material supports cell viability. In addition, an in vivo biocompatibility study showed a typical foreign body reaction after I and 6 weeks.
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| 27. |
- Asplund, Marcus, et al.
(författare)
-
Price Discrimination in Oligopoly : evidence from regional newspapers
- 2008
-
Ingår i: Journal of Industrial Economics. - : Wiley. - 0022-1821 .- 1467-6451. ; 56:2, s. 333-346
-
Tidskriftsartikel (refereegranskat)abstract
- Recent theoretical work has shown that the incentive to target rival firms' customers with low prices can increase price discrimination, and that the strength of the incentive depends on a firm's market position. Using data on Swedish newspaper subscriptions, we find strong support for these predictions. Newspapers with a local competitor sell a larger part of their circulation at a discount than monopoly newspapers. Moreover, in competitive markets, the use of discounts is inversely related to the newspaper's market share. We find no evidence that price discrimination based on observable and exogenous characteristics is influenced by the market structure.
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| 28. |
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| 29. |
- Asplund, Marcus, et al.
(författare)
-
Price Discrimination in Oligopoly: Evidence from Swedish Newspapers
- 2001
-
Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- This paper provides an empirical examination of third degree price discrimination in the Swedish local newspaper markets. We measure the extent of price discrimination by the fraction of subscriptions that a newspaper sells at a discount. The results show that price discrimination is more prevalent in competitive markets and among newspapers with low market shares. We find weak evidence that newspapers operating in markets with larger inflows of new consumers, and those that cover diverse geographical areas, offer more discounts. Overall, our findings are consistent with predictions from recent theoretical work, including Chen (1997) and Villas-Boas (1999), which suggests that firms attempt to poach consumers from rivals by offering targeted discounts.
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| 30. |
- Axheimer, Niklas, et al.
(författare)
-
The middle Cambrian cosmopolitan key species Lejopyge laevigata and its biozone: new data from Sweden
- 2006
-
Ingår i: Geological Magazine. - 0016-7568. ; 143:4, s. 447-455
-
Tidskriftsartikel (refereegranskat)abstract
- The middle Cambrian Lejopyge laevigata Zone is poorly exposed in Scandinavia. Both this zone, however, and the succeeding Agnostus pisiformis Zone are well exposed at a classic locality at Gudhem, Vastergotland, south-central Sweden. The sequences consist of finely laminated alum shale with scattered stinkstone (orsten) lenses. Three measured and sampled sections yielded a diverse fossil fauna, dominated by trilobites, in particular agnostoids, and the bradoriid Anabarochilina primordialis. Fossils are excellently preserved but restricted to the stinkstones. The L. laevigata Zone at Gudhem includes several geographically widespread key agnostoid species, notably Tomagnostella sulcifera, Clavagnostus spinosus, Glaberagnostus altaicus, Lejopyge laevigata and L. armata. The L. laevigata Zone in Scandinavia is here extended to include the traditional Solenopleura? brachymetopa Zone, and its lower boundary is defined by the FAD of L. laevigata. Trilobite evidence shows that the upper part of the Scandinavian L. laevigata Zone approximately correlates with the Proagnostus bulbus Zone of China and elsewhere.
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| 31. |
- Barlind, Anna, 1978, et al.
(författare)
-
Decreased cytogenesis in the granule cell layer of the hippocampus and impaired place learning after irradiation of the young mouse brain evaluated using the IntelliCage platform.
- 2010
-
Ingår i: Experimental brain research. - : Springer Science and Business Media LLC. - 1432-1106 .- 0014-4819. ; 201:4, s. 781-787
-
Tidskriftsartikel (refereegranskat)abstract
- Radiation therapy is used to treat malignant tumors in the brain and central nervous system involvement of leukemia and lymphomas in children. However, ionizing radiation causes a number of adverse long-term side effects in the brain, including cognitive impairment. Hippocampal neurogenesis is important for place learning and has been shown to be decreased by irradiation (IR) in rats and mice. In the present study, 10-day-old male mice received 6-Gy IR to the brain on postnatal day 10. We used BrdU labeling of the granule cell layer (GCL) of the hippocampus to evaluate cell proliferation and survival. An unbiased, automated platform for monitoring of behavior in a group housing environment (IntelliCage) was used to evaluate place learning 2 months after IR. We show that cranial IR impaired place learning and reduced BrdU labeling by 50% in the GCL. Cranial IR also reduced whole body weight gain 5%. We conclude that this experimental paradigm provides a novel and time-saving model to detect differences in place learning in mice subjected to IR. This method of detecting behavioral differences can be used for further studies of adverse effects of IR on hippocampal neurogenesis and possible new strategies to ameliorate the negative effects of IR on cognition.
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| 32. |
- Barlind, Anna, 1978, et al.
(författare)
-
The growth hormone secretagogue hexarelin increases cell proliferation in neurogenic regions of the mouse hippocampus.
- 2010
-
Ingår i: Growth hormone & IGF research. - : Elsevier BV. - 1532-2238 .- 1096-6374. ; 20:1, s. 49-54
-
Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVE: Radiation therapy (RT) to the brain is often used in the treatment of children with different types of malignant diseases affecting the brain. However, RT in childhood may also have severe side effects including impaired brain maturation and intellectual development. For childhood cancer survivors these adverse effects of RT can cause lifelong disability and suffering. Therefore, there is an unmet need to limit late effects after RT. Precursor cells in the subgranular zone of the dentate gyrus (DG) in the hippocampus are particularly sensitive to irradiation (IR). This may be of significance as newly generated neurons in the DG are important for memory and learning. GH secretagogues (GHS) have previously been shown to promote neurogenesis and to have neuroprotective effects. In addition, several parts of the brain, including the hippocampus, have been shown to express the GHS receptor 1a (GHS-R1a). The aim of this study was to evaluate the potential effect of the GHS hexarelin on proliferation and survival of progenitor cells in the hippocampus after brain IR in a mouse model. DESIGN: In the present study, 10-day-old male mice received 6Gy cranial IR. Non-irradiated sham animals were used as controls. We treated one group of irradiated and one sham group with hexarelin (100mug/kg/day) for 28days and used immunohistochemical labeling of bromo-deoxy uridine (BrdU) and phospho-histone H3 of the granular cell layer of the DG to evaluate proliferation and cell survival after IR at postnatal day ten. RESULTS: Our results show that hexarelin significantly increased the number of BrdU-positive cells in the granule cell layer by approximately 50% compared to controls. CONCLUSION: The increased number of BrdU-positive cells in the granule cell layer suggests a partial restoration in the pool of proliferating cells by hexarelin after IR.
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| 33. |
- Barrio, Alvaro Martinez, et al.
(författare)
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Targeted Resequencing and Analysis of the Diamond-Blackfan Anemia Disease Locus RPS19
- 2009
-
Ingår i: PLoS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 4:7, s. e6172-
-
Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: The Ribosomal protein S19 gene locus (RPS19) has been linked to two kinds of red cell aplasia, Diamond-Blackfan Anemia (DBA) and Transient Erythroblastopenia in Childhood (TEC). Mutations in RPS19 coding sequences have been found in 25% of DBA patients, but not in TEC patients. It has been suggested that non-coding RPS19 sequence variants contribute to the considerable clinical variability in red cell aplasia. We therefore aimed at identifying non-coding variations associated with DBA or TEC phenotypes. METHODOLOGY/PRINCIPAL FINDINGS: We targeted a region of 19'980 bp encompassing the RPS19 gene in a cohort of 89 DBA and TEC patients for resequencing. We provide here a catalog of the considerable, previously unrecognized degree of variation in this region. We identified 73 variations (65 SNPs, 8 indels) that all are located outside of the RPS19 open reading frame, and of which 67.1% are classified as novel. We hypothesize that specific alleles in non-coding regions of RPS19 could alter the binding of regulatory proteins or transcription factors. Therefore, we carried out an extensive analysis to identify transcription factor binding sites (TFBS). A series of putative interaction sites coincide with detected variants. Sixteen of the corresponding transcription factors are of particular interest, as they are housekeeping genes or show a direct link to hematopoiesis, tumorigenesis or leukemia (e.g. GATA-1/2, PU.1, MZF-1). CONCLUSIONS: Specific alleles at predicted TFBSs may alter the expression of RPS19, modify an important interaction between transcription factors with overlapping TFBS or remove an important stimulus for hematopoiesis. We suggest that the detected interactions are of importance for hematopoiesis and could provide new insights into individual response to treatment.
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| 34. |
- Bengtsson, Stefan, 1961, et al.
(författare)
-
Carbon-based nanoelectromechanical devices
- 2011
-
Ingår i: International Journal of High Speed Electronics and Systems. - 1793-6438. ; 20:1, s. 195-204
-
Tidskriftsartikel (refereegranskat)abstract
- Carbon-based nanoelectromechanical devices are approaching applications in electronics. Switches based on individual carbon nanotubes deliver record low off-state leakage currents. Arrays of vertically aligned carbon nanotubes or nanofibers can be fabricated to constitute varactors. Very porous, low density arrays of quasi-vertically aligned arrays of carbon nanotubes behave mechanically as a single unit with very unusual material properties.
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| 35. |
- Bergemalm, Daniel, 1977-, et al.
(författare)
-
Systemic Inflammation in Preclinical Ulcerative Colitis
- 2021
-
Ingår i: Gastroenterology. - : AGA Institute. - 0016-5085 .- 1528-0012. ; 161:5, s. 1526-1539.e9
-
Tidskriftsartikel (refereegranskat)abstract
- Background & Aims: Preclinical ulcerative colitis is poorly defined. We aimed to characterize the preclinical systemic inflammation in ulcerative colitis, using a comprehensive set of proteins.Methods: We obtained plasma samples biobanked from individuals who developed ulcerative colitis later in life (n = 72) and matched healthy controls (n = 140) within a population-based screening cohort. We measured 92 proteins related to inflammation using a proximity extension assay. The biologic relevance of these findings was validated in an inception cohort of patients with ulcerative colitis (n = 101) and healthy controls (n = 50). To examine the influence of genetic and environmental factors on these markers, a cohort of healthy twin siblings of patients with ulcerative colitis (n = 41) and matched healthy controls (n = 37) were explored.Results: Six proteins (MMP10, CXCL9, CCL11, SLAMF1, CXCL11 and MCP-1) were up-regulated (P < .05) in preclinical ulcerative colitis compared with controls based on both univariate and multivariable models. Ingenuity Pathway Analyses identified several potential key regulators, including interleukin-1β, tumor necrosis factor, interferon-gamma, oncostatin M, nuclear factor-κB, interleukin-6, and interleukin-4. For validation, we built a multivariable model to predict disease in the inception cohort. The model discriminated treatment-naïve patients with ulcerative colitis from controls with leave-one-out cross-validation (area under the curve = 0.92). Consistently, MMP10, CXCL9, CXCL11, and MCP-1, but not CCL11 and SLAMF1, were significantly up-regulated among the healthy twin siblings, even though their relative abundances seemed higher in incident ulcerative colitis.Conclusions: A set of inflammatory proteins are up-regulated several years before a diagnosis of ulcerative colitis. These proteins were highly predictive of an ulcerative colitis diagnosis, and some seemed to be up-regulated already at exposure to genetic and environmental risk factors.
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| 36. |
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| 37. |
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| 38. |
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| 39. |
- Bernerstedt, Thomas, et al.
(författare)
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3500 kyrkor : Problem eller möjlighet. 8 Restuareringsexempel
- 2014
-
Rapport (populärvet., debatt m.m.)abstract
- I kyrkorna finner man de högsta kvaliteterna av arkitektur och konst som har stått i mänsklig makt att uppbringa. Kulturarvets värde är högt. Arkitektur är en konstart som förstärker funktionen/verksamheten – på samma sätt som t.ex. musik, poesi, skulptur eller måleri. Konstarterna går utöver funktionerna/verksamheterna, därför finns det alltid nya möjligheter att bearbeta. Restaureringskonstens uppgift är att tillvara arkitekturkvaliteterna, utveckla dem och förhöja dem. Det finns ungefär 3 500 kyrkor inom Svenska kyrkan, en tredjedel medeltida och entredjedel från 1950–60-talen. Sammantaget är det en komplex samling byggnader. Majoriteten av 6,4 miljoner medlemmar i Svenska kyrkan är intresserade av att kyrkobyggnaderna tas om hand. Färre säger sig vara intresserade av att aktivt delta i kyrkans kärnverksamhet. Men kyrkobyggnaden och verksamheten hänger samman; de enda byggnader som haft enoch samma användning i 1000 år är kyrkor. Att vårda och utveckla kyrkobyggnadsmiljöernaingår inte i kyrkans kärnverksamheter. Varför inte? Sedan relationsförändringen år 2000 då kyrkan skildes från staten har inga långsiktiga visioner eller strategier om förvaltningen av Sveriges mest tillgängliga kulturskatt framkommit. Inget drastiskt hände år 2000; antalet gudstjänstbesökare började minska långt tidigare. Varför ska vi vara så oroliga nu när vi inte var det förut? Våra kyrkor är i bättre skick än i något annat land i Europa, vi har aldrig haft det så bra som nu, ändå är det först nu som vi inte anser oss ha råd att sköta denna del av kulturarvet. Andra länder har en mängd olika sätt att finansiera och arbeta med kyrkobyggnader. Sverige har bara ett sätt, statsbidrag. En mängd oprövade möjligheter finns – ett gyllene ägg att förvalta! 20 studenter i Restaureringskonst har arbetat med kunskapsuppbyggnad i teori och praktik under året. Våra studier har innefattat tre innerstadskyrkor och fem andra kyrkor i Stockholms stift, praktiskt nåbara för våra studier. Vi är väl medvetna om de helt olikartade förutsättningar som finns i vårt avlånga land med Europas snabbaste urbaniseringstakt, även om vi haft ett begränsat antal fallstudier när vi tränat arbetsprocess och metodik. Året har förutom projektarbete omfattat föreläsningar, seminarier, workshops och studieresor inom restaureringshistoria, dokumentation med 3D-laserscanning, kulturhistoriskvärdering och analys, material och metoder för restaurering, gestaltning och bevarande,presentation och kommunikation. Av årets studenter är tio arkitekter, en ingenjör, sex antikvarier, två konservatorer och en förvaltare. Tack vare kursens blandade professioner är inledningdiskussionerna och det interna kunskapsutbytet en viktig del av utbildningen, liksom det nätverk som erbjuds genom inbjudna föreläsare och specialister inom praktisk restaurering och i forskningsfronten. Genom studiebesök och studieresor får studenterna kontakter ochintryck av hur restaurering tillämpas och diskuteras i olika sammanhang. I år har vi gjort studieresor till Tyskland och England samt inom Sverige. Kyrkan har i alla tider stått för högsta kvalitet i arkitektur och konst – årets kurs vill visa värdet av denna resurs och hur vi kan arbeta med uppgiften att upprätthålla och gärna öka kulturarvets kvaliteter genomrestaureringskonst.Vi tackar alla som bidragit till genomförandet av vår kurs i år; särskilt Stockholms stift och de församlingar som har gett oss tillgång till sina kyrkor.
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| 40. |
- Björck, Niclas, et al.
(författare)
-
Keramik : I: UV GAL Rapport 200:14. Snåret.Aspekter på sten-, brons och järnålder i Vendel, Väg E4, sträckan Uppsala-Mehedeby, Uppland, Vendels socken, Fallsboda 1:2, Karby 29:5, RAÄ 291
- 2007
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Rapport (populärvet., debatt m.m.)abstract
- Arkeologisk undersökning av boplats med lämningar från neolitikum, yngre bronsålder och vendeltid. På platsen fanns även sannolika gravar. Analyser görs av hus, keramik, pollen mm. Platsen har under vendeltid utnyttjats för tjärframställning
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| 41. |
- Björk, Mikael, et al.
(författare)
-
Marinarkeologisk undersökning och dokumentation av skeppsvraket Constantia : RAÄ Torhamn 96 (L1978:1899)
- 2024
-
Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Blekinge museum har på uppdrag av Länsstyrelsen i Blekinge undersökt och dokumenterat vraket efter flöjtskeppet Constantia (1676), beläget öster om Inlängan i Blekinge skärgård. Lämningen dokumenterades genom fotogrammetri och manuell uppmätning. Därutöver sågades fem prov för dendrokronologisk analys och ett fyra tegelstenar bärgades för ICP-analys. Området runt vraket metalldetekterades och flera större utslag noterades, möjligtvis kanoner. På lämningen påträffades en träsked samt flera metallfragment från en klocka vilka skyddsbärgades efter samråd med Länsstyrelsen. Undersökningen visar att lämningen trots sitt nedbrutna tillstånd innehåller flera välbevarade och orörda arkeologiska kontexter vilka kan ge en unik inblick i livet ombord på ett krigsfartyg under stormaktstiden och inte minst användningen av bestyckade handelsfartyg. Därutöver illustrerar hela händelseförloppet kring Constantias förlisning på det strategiska behovet av en flottbas i södra Östersjön, ett behov som Karlskrona därefter kommit att tillgodose.
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| 42. |
- Björkström, Niklas K, et al.
(författare)
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Characterization of natural killer cell phenotype and function during recurrent human HSV-2 infection.
- 2011
-
Ingår i: PloS one. - : Public Library of Science (PLoS). - 1932-6203. ; 6:11
-
Tidskriftsartikel (refereegranskat)abstract
- Human natural killer (NK) cell differentiation, characterized by a loss of NKG2A in parallel with the acquisition of NKG2C, KIRs, and CD57 is stimulated by a number of virus infections, including infection with human cytomegalovirus (CMV), hantavirus, chikungunya virus, and HIV-1. Here, we addressed if HSV-2 infection in a similar way drives NK cell differentiation towards an NKG2A(-)NKG2C(+)KIR(+)CD57(+) phenotype. In contrast to infection with CMV, hantavirus, chikungunya virus, and HIV-1, recurrent HSV-2 infection did not yield an accumulation of highly differentiated NK cells in human peripheral blood. This outcome indicates that human HSV-2 infection has no significant imprinting effect on the human NK cell repertoire.
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| 43. |
- Bonninghoff, Niklas, et al.
(författare)
-
ZrCuAlNi thin film metallic glass grown by high power impulse and direct current magnetron sputtering
- 2021
-
Ingår i: Surface & Coatings Technology. - : ELSEVIER SCIENCE SA. - 0257-8972 .- 1879-3347. ; 412
-
Tidskriftsartikel (refereegranskat)abstract
- High-power impulse magnetron sputtering (HiPIMS) is a thin film deposition technique that combines the advantages of energetic deposition methods with magnetron sputtering. HiPIMS has so far mostly been utilized for the growth of crystalline coatings. Here we offer a study devoted to metallic glasses, in which we compare Zr60Cu25Al10Ni5 (target composition) thin films deposited by conventional direct current magnetron sputtering (DC) and HiPIMS. Film microstructure is strongly dependent on the choice of the sputtering method. The DC layers show a columnar structure with intra-columnar porosity, which provides a pathway for oxygen diffusion into the film. In contrast, HiPIMS films are column-free and possess about 4% higher density, as revealed by X-ray reflectivity. Electron diffraction reveals a decrease in average atomic spacing for the latter film of about 12%. These differences in film properties and morphology can be attributed to an increase in ad-atom mobility during HiPIMS caused by an increase in ion energy and flux of the film-forming species enabling a more efficient energy and momentum transfer to the growing film surface. The relative contribution of metallic and hence film forming ions to the overall ion flux of the DC plasma compared to the HiPIMS plasma is 13% and 96%, respectively. Additionally, a substrate bias causes the ionized film forming species during HiPIMS to arrive close to the substrate normal reducing shadowing effects. Different microstructures have a direct effect on the average roughness values, which for DC and HiPIMS films are 1.4 nm and 0.2 nm, respectively. The indentation hardness H and Youngs modulus E are higher for the HiPIMS sample, at 9.2 +/- 0.3 GPa and 131.6 +/- 3.6 GPa, respectively. The increase in hardness for the HiPIMS sample as compared to the DC sample (similar to 35%) can be attributed to higher film density, compressive (HiPIMS) as opposed to tensile (DC) stress and the lack of a columnar structure.
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| 44. |
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| 45. |
- Bremer, Johan, 1991, et al.
(författare)
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Analysis of Lateral Thermal Coupling for GaN MMIC Technologies
- 2018
-
Ingår i: IEEE Transactions on Microwave Theory and Techniques. - 0018-9480 .- 1557-9670. ; 66:10, s. 4430-4438
-
Tidskriftsartikel (refereegranskat)abstract
- This paper presents a study of the lateral heat propagation in an aluminum gallium nitride/gallium nitride (AlGaN/GaN) heterostructure grown on a silicon carbide substrate. The study is enabled by the design of a temperature sensor that utilizes the temperature-dependent I-V characteristic of a semiconductor resistor, making it suitable for integration in GaN monolithic microwave integrated circuit technologies. Using the sensor, we are able to characterize the thermal transient response and extract lateral thermal time constants from the measurements. Time constants in the range from 25 mu s to 1.2 ms are identified. Furthermore, the heat propagation properties are characterized for heat source-to-sensor distances of 86-484 mu m, resulting in delay times from 3.5 to 111 mu s. It is shown that both the time constants and propagation delay increase with temperature. An empirical model of the sensor current versus temperature and voltage is proposed and used to predict the junction temperature of the sensor. The study provides knowledge for heat management design and proposes an integrated temperature measurement solution for future highly integrated GaN applications.
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| 46. |
- Brorsson, Annelie, 1963, et al.
(författare)
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Recovery of calf muscle endurance 3 months after an Achilles tendon rupture.
- 2016
-
Ingår i: Scandinavian journal of medicine & science in sports. - : Wiley. - 1600-0838 .- 0905-7188. ; 26:7, s. 844-853
-
Tidskriftsartikel (refereegranskat)abstract
- The purpose of this study was to evaluate calf muscle endurance in a seated position 3 months after an Achilles tendon rupture and to evaluate how the ability to perform standardized seated heel-rises correlated to the single-leg standing heel-rise test and to patient-reported symptoms evaluated with the Achilles tendon Total Rupture Score (ATRS) 3 and 6 months after the injury. Ninety-three patients were included from a cohort of 101 patients participating in a prospective, randomized controlled trial comparing surgical and nonsurgical treatment after Achilles tendon rupture. Forty-seven patients were treated surgically and 46 nonsurgically. Ninety-one patients out of 93 (98%) could perform the standardized seated heel-rises. At the 3-month follow-up, there was a significant difference (P<0.001) between the injured and the healthy side performing standardized seated heel-rises. There were also significant correlations (r=0.29-0.37, P=<0.05) between the standardized seated heel-rises and ATRS 3 and 6 months after injury in the group who could not perform single-leg standing heel-rises. There were no significant differences between the surgical and nonsurgical treatment groups. The evaluation of standardized seated heel-rises appears to be a useful tool to quantify progress and predict future functional performance and patient-reported symptoms.
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| 47. |
- Brown, Rosemary, 1990, et al.
(författare)
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Surface Composition of a Highly Active Pt3Y Alloy Catalyst for Application in Low Temperature Fuel Cells
- 2020
-
Ingår i: Fuel Cells. - : Wiley. - 1615-6846 .- 1615-6854. ; 20:4, s. 413-419
-
Tidskriftsartikel (refereegranskat)abstract
- Currently, platinum is the most widely used catalyst for low temperature proton exchange membrane fuel cells (PEMFC). However, the kinetics at the cathode are slow, and the price of platinum is high. To improve oxygen reduction reaction (ORR) kinetics at the cathode, platinum can be alloyed with rare earth elements, such as yttrium. We report that Pt3Y has the potential to be over 2 times more active for the ORR compared with Pt inside a real fuel cell. We present detailed photoemission analysis into the nature of the sputtered catalyst surface, using synchrotron radiation photoelectron spectroscopy (SRPES) to examine if surface adsorbates or impurities are present and can be removed. Pretreatment removes most of the yttrium oxide in the surface leaving behind a Pt overlayer which is only a few monolayers thick. Evidence of a substochiometric oxide peak in the Y 3d core level is presented, this oxide extends into the surface even after Ar+ sputter cleaning in-situ. This information will aid the development of new highly active nanocatalysts for employment in real fuel cell electrodes.
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| 48. |
- Carbone, F., et al.
(författare)
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Statistical study of electron density turbulence and ion-cyclotron waves in the inner heliosphere : Solar Orbiter observations
- 2021
-
Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 656
-
Tidskriftsartikel (refereegranskat)abstract
- Context. The recently released spacecraft potential measured by the RPW instrument on board Solar Orbiter has been used to estimate the solar wind electron density in the inner heliosphere. Aims. The measurement of the solar wind's electron density, taken in June 2020, has been analysed to obtain a thorough characterization of the turbulence and intermittency properties of the fluctuations. Magnetic field data have been used to describe the presence of ion-scale waves. Methods. To study and quantify the properties of turbulence, we extracted selected intervals. We used empirical mode decomposition to obtain the generalized marginal Hilbert spectrum, equivalent to the structure functions analysis, which additionally reduced issues typical of non-stationary, short time series. The presence of waves was quantitatively determined by introducing a parameter describing the time-dependent, frequency-filtered wave power. Results. A well-defined inertial range with power-law scalng was found almost everywhere in the sample studied. However, the Kolmogorov scaling and the typical intermittency effects are only present in fraction of the samples. Other intervals have shallower spectra and more irregular intermittency, which are not described by models of turbulence. These are observed predominantly during intervals of enhanced ion frequency wave activity. Comparisons with compressible magnetic field intermittency (from the MAG instrument) and with an estimate of the solar wind velocity (using electric and magnetic field) are also provided to give general context and help determine the cause of these anomalous fluctuations.
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| 49. |
- Carlborg, Niklas, 1990, et al.
(författare)
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The Scope of Autonomy Model – Development of Teaching Materials for Computational Thinking in Primary School
- 2018
-
Ingår i: ACM International Conference Proceeding Series. - New York, NY, USA : ACM. ; Part F137702, s. 37-44, s. 37-44
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Konferensbidrag (refereegranskat)abstract
- During the 21st century there has been an increasing interest in the field of computational thinking as a consequence of the ever faster technical development. However, educating future generations in programming and computational thinking is not trivial. Many different platforms and teaching approaches can be used for this purpose. Inspired by the UK initiative with BBC micro:bit, this paper strives to identify what may be important to consider when designing teaching materials with the micro:bit for training Swedish primary school pupils’ computational thinking skills relating to mathematical and technical school subjects. This has been investigated in an iterative process, by conducting 21 workshops with the goal to support primary school teachers in developing micro:bit teaching materials. The contribution of this paper is the Scope of autonomy model, which is based on the relation between pupils learning potential, their risk of feeling overwhelmed and the amount of choices provided in exercises. The model aim to support teachers in developing material for teaching programming and computational thinking in accordance with the new curriculum.
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- Carlborg, Niklas, et al.
(författare)
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The scope of autonomy when teaching computational thinking in primary school
- 2019
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Ingår i: International Journal of Child-Computer Interaction. - : Elsevier BV. - 2212-8689 .- 2212-8697. ; 21, s. 130-139
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Tidskriftsartikel (refereegranskat)abstract
- During the 21st century, there has been an increased interest in the field of computational thinking as a consequence of the ever faster technical development. However, educating future generations in programming and computational thinking is not trivial. Many different platforms and teaching approaches can be used for this purpose. Inspired by the UK initiative with BBC micro:bit, this paper strives to identify what may be important to consider when designing teaching materials with the BBC micro:bit for training Swedish primary school learners’ computational thinking skills relating to mathematical and technical school subjects. This has been investigated in an iterative process, by conducting 21 workshops with the goal to support primary school teachers in developing BBC micro:bit teaching materials. The contribution of this paper is the Scope of autonomy model, which is based on the relation between learning potential, the risk of feeling overwhelmed, and the amount of choices provided in exercises. The model aim to support teachers in developing and appropriating material for teaching programming and computational thinking with individual progression in accordance with the new curriculum.
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