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- Ciamulski, T, et al.
(författare)
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Parallel FDTD Processing on Shared Memory Computers
- 2007
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Ingår i: The 23rd annual review of Progress in Applied computational electromagnetics.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- An ongoing European project on customization of electromagnetic simulation tool is ready to present significantly improved performance of parallel version of a professional FDTD simulator. The first stage of the work is concentrated on solution for computers with the shared memory architecture. The relevance and feasibility study of the solution for contemporary computers is shown. Possible ways to reach further performance improvements as well as solutions for distributed memory machines are discussed.
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| 7. |
- Hjelm, F, et al.
(författare)
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Antibody-mediated regulation of the immune response
- 2006
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Ingår i: Scandinavian Journal of Immunology. - : Wiley. - 0300-9475 .- 1365-3083. ; 64:3, s. 177-184
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Tidskriftsartikel (refereegranskat)abstract
- Antibodies administered in vivo together with the antigen they are specific for can regulate the immune response to that antigen. This phenomenon is called antibody-mediated feedback regulation and has been known for over 100 years. Both passively administered and actively produced antibodies exert immunoregulatory functions. Feedback regulation can be either positive or negative, resulting in >1000-fold enhancement or >99% suppression of the specific antibody response. Usually, the response to the entire antigen is up- or downregulated, regardless of which epitope the regulating antibody recognizes. IgG of all isotypes can suppress responses to large particulate antigens like erythrocytes, a phenomenon used clinically in Rhesus prophylaxis. IgG suppression works in mice lacking the known Fc-gamma receptors (FcgammaR) and a likely mechanism of action is epitope masking. IgG1, IgG2a and IgG2b administered together with soluble protein antigens will enhance antibody and CD4+ T-cell responses via activating FcgammaR, probably via increased antigen presentation by dendritic cells. IgG3 as well as IgM also enhance antibody responses but their effects are dependent on their ability to activate complement. A possible mechanism is increased B-cell activation caused by immune complexes co-crosslinking the B-cell receptor with the complement-receptor 2/CD19 receptor complex, known to lower the threshold for B-cell activation. IgE-antibodies enhance antibody and CD4+ T-cell responses to small soluble proteins. This effect is entirely dependent on the low-affinity receptor for IgE, CD23, the mechanism probably being increased antigen presentation by CD23+ B cells.
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| 8. |
- Hjelm, Mats, et al.
(författare)
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Critical evaluation of scattering models within the full band Monte Carlo simulation framework
- 2005
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Ingår i: Recent Advances in Multidisciplinary Applied Physics. - : Elsevier. - 9780080446486 ; , s. 305-311
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The full band Monte Carlo (MC) simulation framework is regarded as the most accurate method available to study high-field carrier transport in semiconductors. Its potential has been demonstrated in a large number of studies over the years. In this work we focus on how the quantum mechanical uncertainty at high scattering rates affects the validity Fermi's Golden Rule, which traditionally is the basis for the scattering handling in the MC method. Considering the uncertainty is important in for instance silicon carbide, which at moderate energies exhibits a scattering rate exceeding 1014 s-1. The expression for time-dependent scattering rate is presented together with calculated rates for some initial states with acoustic as well as polar-optical phonon interaction. A first-order time-dependent algorithm for handling of scattering events in MC simulators is proposed.
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| 9. |
- Hjelm, Mats, et al.
(författare)
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Interband tunneling description of holes in Wurtzite GaN at high electric fields
- 2007
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Ingår i: Journal of Computational Electronics. - : Springer Science and Business Media LLC. - 1569-8025 .- 1572-8137. ; 6:1-3, s. 163-166
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Tidskriftsartikel (refereegranskat)abstract
- We have studied the time evolution of an ensemble of holes in Wurtzite GaN under the effect of a high electric field. The density matrix equation used as a foundation in the study includes band-to-band tunneling, but disregards collisions. In the description of the ensemble dynamics the full band structure is used. The average energy and group velocity for the ensemble is calculated, as well as velocity components corresponding to the non-diagonal elements of the velocity operator (interference). The calculations have been carried out for the electric field strengths 0.4 and 4 MV/cm. A comparison is presented of the results with and without inclusion of band tunneling in the ensemble dynamics. There is also a comparison of the velocity with and without the non-diagonal elements of the velocity operator terms. A conclusion is that Monte Carlo simulations considering band tunneling, but not interference, can give accurate results.
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