| 1. |
- Kasimir, Johannes, et al.
(författare)
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An finite volume based multigrid preconditioner for dg-sem for convection-diffusion
- 2021
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Ingår i: Fluid Dynamics and Transport Phenomena. - : CIMNE. ; 600, s. 1-12
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Konferensbidrag (refereegranskat)abstract
- The goal of our research is the construction of efficient Jacobian-free preconditioners for high order Discontinuous Galerkin (DG) discretizations with implicit time integration. We are motivated by three-dimensional unsteady compressible flow applications, which often result in large stiff systems. Implicit time integrators overcome the impact upon restrictive CFL conditions on explicit ones but leave the problem to solve huge nonlinear systems. In this paper we consider a multigrid preconditioning strategy for Jacobian-free Newton-Krylov (JFNK) methods for the solution of algebraic equation systems arising from implicit Discontinuous Galerkin (DG) discretizations. The preconditioner is defined by an auxiliary first order Finite Volume (FV) discretization that refines the original DG mesh, but can still be implemented algebraically. Different options exist to define the grid transfer between DG and FV. We suggest an ad hoc assignment of the unknowns as well as L2 projections. We present new numerical results for the two-dimensional convection-diffusion equation in combination with the different transfer options, which demonstrate the quality and efficiency of the suggested preconditioner with regards to convergence speed up and CPU time. The suggested L2 projection from this paper result in the best convergence speed up.
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| 2. |
- Kloss, Frank, et al.
(författare)
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The role of oxygen termination of nanocrystalline diamond on immobilisation of BMP-2 and subsequent bone formation
- 2008
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Ingår i: Biomaterials. - : Elsevier BV. - 0142-9612 .- 1878-5905. ; 29:16, s. 2433-2442
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Tidskriftsartikel (refereegranskat)abstract
- Medical implants are increasingly often inserted into bone of frail patients, who are advanced in years. Due to age, severe trauma or pathology-related bone changes, osseous healing at the implant site is frequently limited. We were able to demonstrate that coating of endosseous implants with nanocrystalline diamond (NCD) allows stable functionalization by means of physisorption with BMP-2. Strong physisorption was shown to be directly related to the unique properties of NCD, and BMP-2 in its active form interacted strongly when NCD was oxygen-terminated. The binding of the protein was monitored under physiological conditions by single molecule force spectroscopy, and the respective adsorption energies were further substantiated by force-field-calculations. Implant surfaces refined in such a manner yielded enhanced osseointegration in vivo, when inserted into sheep calvaria. Our results further suggest that this technical advancement can be readily applied in clinical therapies with regard to bone healing, since primary human mesenchymal stromal cells strongly activated the expression of osteogenic markers when being cultivated on NCD physisorbed with physiological amounts of BMP-2.
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| 3. |
- Sharapov, S.E., et al.
(författare)
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Energetic particle instabilities in fusion plasmas
- 2013
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Ingår i: Nuclear Fusion. - : IOP Publishing. - 1741-4326 .- 0029-5515. ; 53:10, s. 104022-
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Tidskriftsartikel (refereegranskat)abstract
- Remarkable progress has been made in diagnosing energetic particle instabilities on present-day machines and in establishing a theoretical framework for describing them. This overview describes the much improved diagnostics of Alfvén instabilities and modelling tools developed world-wide, and discusses progress in interpreting the observed phenomena. A multi-machine comparison is presented giving information on the performance of both diagnostics and modelling tools for different plasma conditions outlining expectations for ITER based on our present knowledge.
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| 6. |
- Steinmüller-Nethl, Doris, et al.
(författare)
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Strong binding of bioactive BMP-2 to nanocrystalline diamond by physisorption
- 2006
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Ingår i: Biomaterials. - : Elsevier BV. - 0142-9612. ; 27, s. 4547-4556
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Tidskriftsartikel (refereegranskat)abstract
- Nano-crystalline diamond (NCD)-coated surfaces were efficiently functionalized with bone morphogenetic protein-2 (BMP-2) by means of physisorption. Due to their randomly oriented texture, NCD-coated surfaces appear to bind complex molecules firmly. Applying various highly sensitive analytical methods, the interaction was found extremely stable. The strength of the experimentally measured adherence between BMP-2 and NCD was further corroborated by theoretical calculations. Oxygen treatment rendered NCD hydrophilic by the appearance of surface oxygen containing groups. This particular NCD surface exhibited even higher binding energies towards BMP-2 than the hydrophobic surface, and this surface was also favoured by cultured cells. Most importantly in this context, bound BMP-2 was found fully active. When cultured on BMP-2-treated NCD, osteosarcoma cells strongly up-regulated alkaline phosphatase, a specific marker for osteogenic differentiation. Hence, this simple method will allow generating highly versatile surfaces with complex biomimetic coatings, essentials for novel medical devices and implants as well as for innovative scaffolds in tissue engineering.
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