| 1. |
- Brodin, Gert, et al.
(författare)
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Excitation of electromagnetic wake fields in a magnetized plasma
- 1998
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Ingår i: Physical Review E. Statistical, Nonlinear, and Soft Matter Physics. - 1063-651X .- 1095-3787. ; 57:6, s. 7041-7047
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Tidskriftsartikel (refereegranskat)abstract
- We consider propagation of short electromagnetic pulses in a magnetized plasma. A self-consistent system of equations describing wake-field generation in the weakly nonlinear limit is derived. Due to the external magnetic field, the generated wake field becomes partially electromagnetic. The equations are applicable for arbitrary directions of propagation as compared to the external magnetic field. The conservation laws for the system are discussed in detail. The energy decrease rate and the frequency decrease rate of the short pulse are determined
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| 2. |
- Lundberg, Fredrik, et al.
(författare)
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Presence of vitronectin and activated complement factor C9 on ventriculoperitoneal shunts and temporary ventricular drainage catheters
- 1999
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Ingår i: Journal of Neurosurgery. - : Journal of Neurosurgery Publishing Group (JNSPG). - 0022-3085. ; 90:1, s. 101-108
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Tidskriftsartikel (refereegranskat)abstract
- Object. The pathogenesis of cerebrospinal fluid (CSF) shunt infection is characterized by staphylococcal adhesion to the polymeric surface of the shunt catheter. Proteins from the CSF-fibronectin, vitronectin, and fibrinogen-are adsorbed to the surface of the catheter immediately after insertion. These proteins can interfere with the biological systems of the host and mediate staphylococcal adhesion to the surface of the catheter. In the present study, the presence of fibronectin, vitronectin, and fibrinogen on CSF shunts and temporary ventricular drainage catheters is shown. The presence of fragments of fibrinogen is also examined. Methods. The authors used the following methods: binding radiolabeled antibodies to the catheter surface, immunoblotting of catheter eluates, and scanning force microscopy of immunogold bound to the catheter surface. The immunoblot showed that vitronectin was adsorbed in its native form and that fibronectin was degraded into small fragments. Furthermore, the study demonstrated that the level of vitronectin in CSF increased in patients with an impaired CSF-blood barrier. To study complement activation, an antibody that recognizes the neoepitope of activated complement factor C9 was used. The presence of activated complement factor C9 was shown on both temporary catheters and shunts. Conclusions. Activation of complement close to the surface of an inserted catheter could contribute to the pathogenesis of CSF shunt infection.
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| 3. |
- Lundberg, Jonas, et al.
(författare)
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Perturbation method for the Vlasov-Poisson system
- 1998
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Ingår i: Journal of Plasma Physics. - 0022-3778 .- 1469-7807. ; 60, s. 181-192
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Tidskriftsartikel (refereegranskat)abstract
- A perturbation method for the Vlasov-Poisson system is presented. It is self-consistent and entirely based on Lie transformations, which are considered as active transformations, generating the dynamics of the particle distribution function in the space of distribution functions. The main result is a set of three equations that forms a good starting point for a wide variety of problems concerning nonlinear wave propagation. Besides being efficient, the new perturbation method is systematic and therefore also suited for the use of computer algebra.
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| 4. |
- Stollenwerk, Maria, et al.
(författare)
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Quantitation of bacterial adhesion to polymer surfaces by bioluminescence
- 1998
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Ingår i: Zentralblatt fur Bakteriologie. - 0934-8840. ; 287:1-2, s. 7-18
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Tidskriftsartikel (refereegranskat)abstract
- Quantitation of microbes adhering to a surface is commonly used in studies of microbial adhesion to different surfaces. We have quantified different staphylococcal strains adhering to polymer surfaces by measuring bacterial ATP (adenosine triphosphate) by bioluminescence. The method is sensitive, having a detection limit of 104 bacterial cells. Viable counting of bacterial cells may yield falsely low results due to the presence of 'dormant' and adherent bacteria. By using bioluminescence, this can be avoided. Cells of different bacterial species and cells of strains of the same species were shown to differ significantly in their basal ATP content (8.7 x 10-13 - 5.2 x 10-22 MATP). The size of adherent and planktonic bacteria decreased with time (0.7 μm → 0.3 μm, 20 days). During incubation in nutrient-poor buffer ('starvation'), the ATP content of adherent bacteria decreased after 24-96 h whereas that of planktonic bacteria was stable over 20 days. The presence of human serum or plasma did not interfere significantly with the test results. Since the ATP concentration of bacterial strains of different species varies and is also influenced by the growth conditions of bacteria (solid or liquid culture medium), a species-specific standard curve has to be established for bacteria grown under the same culture conditions. We conclude that the method is a sensitive tool to quantify adherent bacteria during experiments lasting for less than 6 h and constitutes a valuable method to be used in conjunction with different microscopical techniques.
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