| 11. |
- Lindbom, John, 1960-, et al.
(författare)
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Wear particles generated from studded tires and pavement induces inflammatory reactions in mouse macrophage cells
- 2007
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Ingår i: Chemical Research in Toxicology. - : American Chemical Society (ACS). - 0893-228X .- 1520-5010. ; 20:6, s. 937-946
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Tidskriftsartikel (refereegranskat)abstract
- Health risks associated with exposure to airborne particulate matter (PM) have been shown epidemiologically as well as experimentally, pointing to both respiratory and cardiovascular effects. These health risks are of increasing concern in society, and to protect public health, a clarification of the toxic properties of particles from different sources is of importance. Lately, wear particles generated from traffic have been recognized as a major contributing source to the overall particle load, especially in the Nordic countries where studded tires are used. The aim of this study was to further investigate and compare the ability to induce inflammatory mediators of different traffic-related wear particles collected from an urban street, a subway station, and studded tire-pavement wear. Inflammatory effects were measured as induction of nitric oxide (NO), IL-6, TNF-α, arachidonic acid (AA), and lipid peroxidation after exposure of the murine macrophage like cell line RAW 264.7. In addition, the redox potential of the particles was measured in a cell-free system. The results show that all particles tested induce IL-6, TNF-α, and NO, and those from the urban street were the most potent ones. In contrast, particles collected from a subway station were most potent to induce lipid peroxidation, A A release, and formation of ROS. Particles from studded tire-pavement wear, generated using a road simulator, were able to induce inflammatory cytokines, NO, lipid peroxidation, and ROS formation. Interestingly, particles generated from pavement containing granite as the main stone material were more potent than those generated from pavement containing quartzite as the main stone material.
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| 12. |
- Nordebo, Sven, et al.
(författare)
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Fisher information analysis for two-dimensional microwave tomography
- 2007
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Ingår i: Inverse Problems. - : IOP Publishing. - 0266-5611 .- 1361-6420. ; 23:3, s. 859-877
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, a Fisher information analysis is employed to establish some important physical performance bounds in microwave tomography. As a canonical problem, the two-dimensional electromagnetic inverse problem of imaging a cylinder with isotropic dielectric losses is considered. A fixed resolution is analysed by introducing a finite basis, i.e., pixels representing the material properties. The corresponding Cramer-Rao bound for estimating the pixel values is computed based on a calculation of the sensitivity field which is obtained by differentiating the observed field with respect to the estimated parameter. An optimum trade-off between the accuracy and the resolution is defined based on the Cramer-Rao bound, and its application to assess a practical resolution limit in the inverse problem is discussed. Numerical examples are included to illustrate how the Fisher information analysis can be used to investigate the significance of measurement distance, operating frequency and losses in the canonical tomography set-up.
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| 13. |
- Nordebo, Sven, et al.
(författare)
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Sensitivity analysis for antenna near-field imaging
- 2007
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Ingår i: IEEE Transactions on Signal Processing. - 1053-587X. ; 55:1, s. 94-101
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Tidskriftsartikel (refereegranskat)abstract
- Although imaging and inverse scattering problems have been thoroughly studied during the last century, there is only a partial understanding of these complex problems. Most of the efforts have been placed on the development of efficient inversion algorithms and mathematical uniqueness results. In comparison, there are very few results and a limited knowledge about the information content in the inversion data. In this paper, we provide a mathematical framework for sensitivity analysis of antenna near-field imaging problems, based on the multipole expansion of the electromagnetic field and the Fisher information to quantify the quality of data. By exploiting this framework, a fundamental relation for accuracy and resolution is formulated based on the Cramer-Rao bound (CRB). The sensitivity analysis is illustrated using a relevant example with cylindrical measurement data.
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| 14. |
- Rodriguez, J.V., et al.
(författare)
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Frequency selective wallpaper for reducing interference while increasing the MIMO capacity in indoor environments
- 2007
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Ingår i: The Second European Conference on Antennas and Propagation, EuCAP 2007. - : Institution of Engineering and Technology. - 0537-9989. - 9780863418426
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Konferensbidrag (refereegranskat)abstract
- The design and features of frequency-selective wallpaper created for attachment onto regular walls in order to filter out signals operating at 5 GHz while at the same time allowing the desired radio communication services to propagate through such walls are presented. An analysis of the characteristics of the radio channel evaluated in a typical indoor environment, when considering either regular walls or walls with the designed wallpaper, is performed through a ray-launching programme for both single input single output (SISO) and multiple input multiple output (MIMO) systems. In this way, parameters such as the signal to interference ratio, power delay profile, and channel capacity are obtained and compared for the two mentioned scenarios (with and without wallpapers).
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| 15. |
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| 16. |
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| 17. |
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| 18. |
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| 19. |
- Sohl, Christian, et al.
(författare)
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Bounds on metamaterials in scattering and antenna problems
- 2007
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Ingår i: ; , s. 1-4
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Konferensbidrag (refereegranskat)abstract
- This paper reports on physical limitations on metamaterials in scattering and antenna problems. A dispersion relation for the extinction cross section is derived from the holomorphic properties of the forward scattering dyadic. The result states that for a given volume, there is only a limited amount of scattering and absorption available in the entire frequency range. The dispersion relation is verified numerically for the perfectly conducting circular disk, and theoretical bounds are illustrated for a plasmonic stratified sphere.
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| 20. |
- Sohl, Christian, et al.
(författare)
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Physical limitations on antennas: isoperimetric inequalities and the effect of metamaterials
- 2007
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Ingår i: [Host publication title missing]. - 9789536037506 ; , s. 75-79
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Konferensbidrag (refereegranskat)abstract
- In this paper, physical limitations on antennas are presented based on the holomorphic properties of the forward scattering dyadic. As a direct consequence of causality and energy conservation, a forward dispersion relation for the extinction cross section is established, and isoperimetric inequalities for the partial realized gain and partial directivity are derived for antennas of arbitrary shape. Closed-form expressions for the prolate and oblate spheroids are compared with Chu's classical result for the sphere, and the effect of invoking metamaterials in the antenna design is discussed. The theory is illustrated by numerical simulations of a monopole antenna with a finite ground plane.
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