| 1. |
- Blomberg, Lars G., et al.
(författare)
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EMMA - the electric and magnetic monitor of the aurora on Astrid-2
- 2004
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Ingår i: Annales Geophysicae. - : Copernicus GmbH. - 0992-7689 .- 1432-0576. ; 22:1, s. 115-123
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Tidskriftsartikel (refereegranskat)abstract
- The Astrid-2 mission has dual primary objectives. First, it is an orbiting instrument platform for studying auroral electrodynamics. Second, it is a technology demonstration of the feasibility of using micro-satellites for innovative space plasma physics research. The EMMA instrument, which we discuss in the present paper, is designed to provide simultaneous sampling of two electric and three magnetic field components up to about 1 kHz. The spin plane components of the electric field are measured by two pairs of opposing probes extended by wire booms with a separation distance of 6.7 m. The probes have titanium nitride (TiN) surfaces. which has proved to be a material with excellent properties for providing good electrical contact between probe and plasma. The wire booms are of a new design in which the booms in the stowed position are wound around the exterior of the spacecraft body. The boom system was flown for the first time on this mission and worked flawlessly. The magnetic field is measured by a tri-axial fluxgate sensor located at the tip of a rigid. hinged boom extended along the spacecraft spin axis and facing away from the Sun. The new advanced-design fluxgate magnetometer uses digital signal processors for detection and feedback, thereby reducing the analogue circuitry to a minimum. The instrument characteristics as well as a brief review of the science accomplished and planned are presented.
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| 4. |
- Cumnock, J. A., et al.
(författare)
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Interplanetary magnetic field control of theta aurora development
- 2002
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Ingår i: Journal of Geophysical Research. - : American Geophysical Union (AGU). - 0148-0227 .- 2156-2202. ; 107:A7
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Tidskriftsartikel (refereegranskat)abstract
- [1] We ascertain the influence of the B-y component of the interplanetary magnetic field (IMF) on theta aurora evolution. During most cases where a transpolar arc is observed to move across the polar region, and form a theta aurora, there are brief (minutes) southward excursions of IMF B-z, however northward IMF is required prior to theta aurora formation. Observations show that theta aurora can form during strictly northward IMF with its motion consistent with a change in sign of IMF B-y. It is important to note that since transpolar arcs can persist for 20-30 min after the IMF turns southward, errors will occur in assigning instantaneous IMF conditions to snapshots'' of particular auroral patterns. We consider the entire evolution of the theta aurora and the changing IMF conditions. The influence of IMF B-y is best illustrated by examples which occur during steady northward IMF as compared to times when the IMF is northward on average. We show examples, provided by the Polar UV imager, when the IMF is steady northward. For one case, DMSP F13 and F14 provide in situ measurements of precipitating particles, ionospheric plasma flows and ion density. This unique data set enables us to analyze in detail the evolution of a theta aurora, in one case crossing the entire polar region. No sign change in B-z is needed for theta aurora formation.
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| 5. |
- Feldstein, Y. I., et al.
(författare)
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Structure of the auroral precipitation region in the dawn sector : relationship to convection reversal boundaries and field-aligned currents
- 2001
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Ingår i: Annales Geophysicae. - : Copernicus GmbH. - 0992-7689 .- 1432-0576. ; 19:5, s. 495-519
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Tidskriftsartikel (refereegranskat)abstract
- Simultaneous DMSP F7 and Viking satellite measurements of the dawnside high-latitude auroral energy electron and ion precipitation show that the region of the low and middle altitude auroral precipitation consists of three characteristic plasma regimes. The recommendation of the IAGA Working Group IIF/III4 at the IAGA Assembly in Boulder, July 1995 to decouple the nomenclature of ionospheric populations from magnetospheric population is used for their notation. The most equatorial regime is the Diffuse Auroral Zone (DAZ) of diffuse spatially unstructured precipitating electrons. It is generated by the plasma injection to the inner magnetosphere in the nightside and the subsequent drift plasma to the dawnside around the Earth. Precipitating par tides have a hard spectrum with typical energies of electrons and ions of more than 3 keV. In the DAZ, the ion pitch-angle distribution is anisotropic. with the peak near 90 degrees. The next part is the Auroral Oval (AO), a structured electron regime which closely resembles the poleward portion of the nightside auroral oval. The typical electron energy is several keV, and the ion energy is up to 10 keV. Ion distributions are predominantly isotropic. In some cases, this plasma regime may be absent in the prenoon sector. Poleward of the Auroral Oval, there is the Soft Small Scale Luminosity (SSSL) regime. It is caused by structured electron and ion precipitation with typical electron energy of about 0.3 keV and ion energy of about 1 keV. The connection of these low-altitude regimes with plasma domains of the distant magnetosphere is discussed. For mapping of the plasma regimes to the equatorial plane of the magnetosphere, the empirical model by Tsyganenko (1995) and the conceptual model by Alexeev et al. (1996) are used. The DAZ is mapped along the magnetic field lines to the Remnant Layer (RL), which is located in the outer radiation belt region: the zone of structured electrons and isotropic ion precipitation (AO) is mapped to the dawn periphery of the Central Plasma Sheet (CPS); the soft small scale structured precipitation (SSSL) is mapped to the outer magnetosphere close to the magnetopause, i.e. the Low Latitude Boundary Layer (LLBL). In the near-noon sector, earthward fluxes of soft electrons, which cause the Diffuse Red Aurora (DRA), are observed. The ion energies decrease with increasing latitude, The plasma spectra of the DRA regime are analogous to the spectra of the Plasma Mantle (PM). In the dawn sector, the large-scale field-aligned currents flow into the ionosphere at the SSSL latitudes (Region 1) and flow out at the AO or DAZ latitudes (Region 2). In the dawn and dusk sectors, the large-scale Region 1 and Region 2 FAC generation occurs in different plasma domains of the distant magnetosphere. The dawn and dusk FAC connection to the traditional Region 1 and Region 2 has only formal character, as FAC generating in various magnetospheric plasma domains integrate in the same region (Region 1 or Region 2). In the SSSL, there is anti-sunward convection in the DAZ and the AO, there is the sunward convection. At PM latitudes, the convection is controlled by the azimuthal IMF component (By) It is suggested to extend the notation of the plasma pattern boundaries, as proposed by Newell et al. (1996), for the nightside sector of the auroral oval to the dawn sector.
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| 7. |
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| 11. |
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| 15. |
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| 16. |
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| 17. |
- Blomberg, Lars G., et al.
(författare)
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On electromagnetic phenomena in Mercury's magnetosphere
- 2004
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Ingår i: Mercury, Mars and Saturn. - OXFORD : Pergamon Press. ; , s. 2161-2165
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Konferensbidrag (refereegranskat)abstract
- Mercury has a small but intriguing magnetosphere. In this brief review, we discuss some similarities and differences between Mercury's and Earth's magnetospheres. In particular, we discuss how electric and magnetic field measurements can be used as a diagnostic tool to improve our understanding of the dynamics of Mercury's magnetosphere. These points are of interest to the upcoming ESA-JAXA BepiColombo mission to Mercury.
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| 18. |
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| 19. |
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| 20. |
- Blomberg, Lars G., et al.
(författare)
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Solar windmagnetosphere-ionosphere coupling : an event study based on Freja data
- 2004
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Ingår i: Journal of Atmospheric and Solar-Terrestrial Physics. - : Elsevier BV. - 1364-6826 .- 1879-1824. ; 66:5, s. 375-380
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Tidskriftsartikel (refereegranskat)abstract
- Freja data are used to study the relative contributions from the high-latitude (reconnection/direct entry) and low-latitude (viscous interaction) dynamos to the cross-polar potential drop. Convection streamlines which are connected to the high-latitude dynamo may be identified from dispersed magnetosheath ions not only in the cusp/cleft region itself but also several degrees poleward of it. This fact, together with Freja's orbital geometry allows us to infer the potential drop from the high-latitude dynamo as well as to obtain a lower limit to the potential drop from the low-latitude dynamo for dayside Freja passes. All cases studied here are for active magnetospheric conditions. The Freja data suggest that under these conditions at least one third of the potential is generated in the low-latitude dynamo. These observations are consistent with earlier observations of the potential across the low-latitude boundary layer if we assume that the low-latitude dynamo region extends over several tens of Earth radii in the antisunward direction along the tail flanks, and that the majority of the potential drop derives from the sun-aligned component of the electric field rather than from its cross-boundary component, or equivalently, that the centre of the dynamo region is located quite far down tail. A possible dynamo geometry is illustrated.
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| 21. |
- Blomberg, Lars G., et al.
(författare)
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The martian plasma environment : Electric field and Langmuir probe diagnostics
- 2003
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Ingår i: IEEE Transactions on Plasma Science. - : Institute of Electrical and Electronics Engineers (IEEE). - 0093-3813 .- 1939-9375. ; 31:6, s. 1232-1236
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Tidskriftsartikel (refereegranskat)abstract
- The plasma environment of Mars has been studied by a small handful of spacecraft. From the sparse observations that exist, one may conclude that the solar wind-Martian magnetosphere interaction is different in significant ways from the solar wind's interaction with Earth's magnetosphere. Mars offers an opportunity to make significant advances in our understanding of the fundamentals of the solar wind's interaction with cold celestial bodies, with suitable plasma instrumentation orbiting the planet. We briefly review what is known about Mars' plasma environment and address some scientific topics that can be studied by proper plasma instrumentation in Mars' vicinity, in particular the scientific potential of Langmuir probe measurements. Finally, we exemplify how the studies may contribute to an enhanced understanding not only of the plasma surrounding Mars, but also of the planet itself and its neutral atmosphere.
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| 22. |
- Blomberg, Stina, et al.
(författare)
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Presence of cutaneous interferon-alpha producing cells in patients with systemic lupus erythematosus
- 2001
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Ingår i: Lupus. - : SAGE Publications. - 0961-2033 .- 1477-0962. ; 10:7, s. 484-90
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Tidskriftsartikel (refereegranskat)abstract
- Systemic lupus erythematosus (SLE) patients have increased levels of interferon-alfa (IFN-alpha) in the circulation but a reduced number of functionally intact natural IFN-alpha producing cells (IPC) in peripheral blood. In search for tissue localisation of activated IPC, we investigated skin biopsies from SLE patients for the occurrence of such cells. Eleven SLE patients with inflammatory skin lesions and six healthy controls were biopsied. An immunohistochemical technique (IH) and in situ hybridisation (ISH) were used to detect intracellular IFN-alpha protein and IFN-alpha mRNA, respectively. In all 11 biopsies from SLE lesions, a high number of IPC were detected by IH. In the nonlesional SLE biopsies we could also demonstrate IPC in 10/11 patients. In 6/11 SLE patients, IFN-alpha mRNA containing cells could be detected in the specimens. A low number of IPC were detected in 1/6 healthy controls by IH, but no ISH positive cells were seen. Our results demonstrate that SLE patients have active IPC in both dermal lesions and in noninflammatory skin. A recruitment of IPC from blood to peripheral tissues may explain the low number of circulating natural IPC in SLE patients. Because the type I IFN system is involved in the SLE disease process, these results are of interest for the understanding of the pathogenesis in SLE.
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| 23. |
- Bohlin, Maria, et al.
(författare)
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Affinity-CE with phospholipid and carbohydrate ligands : Binding between heparin and anionic liposomes and the anticoagulant protein, beta-2-glycoprotein I
- 2004
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Konferensbidrag (populärvet., debatt m.m.)abstract
- Binding studies executed by capillary electrophoresis (CE) benefit from flexibility in experimental set-up, wide applicability, and low consumption of reagents. Importantly, the high resolution inherent in CE allows complex mixtures and binding resulting in only small migration changes to be characterized quantitatively. One specific problem, however, that may be encountered when applying CE for the analysis of binding interactions of proteins is the need to avoid interactions other than those between the analyte and the ligand. Thus, protein-wall interactions in unmodified fused-silica capillaries used at neutral pH often invalidate analyses of protein binding. This problem is especially pronounced with basic proteins and proteins containing exposed patches of positive charge. Ways to overcome this are to neutralize the immobilized wall charges e.g. by different wall coatings and/or buffer additives, or by using the pH hysteresis effect, i.e., the slow deprotonation at neutral pH of low pH-treated fused silica. We illustrate the use of the pH-hysteresis effect to avoid adsorption problems in the analysis of a phospholipid- and heparin-binding anticoagulant protein, beta-2-glycoprotein under physiological pH conditions. The approach was useful for characterizing protein-heparin and protein-liposome binding. This will be the basis of using CE methods to evaluate the influence of human thrombogenic autoantibodies against this protein on such interactions and the approach will be also be a useful means to measure the binding activity of different domains and structurally modified variants of this protein and other proteins that suffer from a tendency to stick to fused silica
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| 24. |
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| 25. |
- Bohlin, Maria, et al.
(författare)
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Capillary electrophoresis-based analysis of phospholipid- and glycosaminoglycan-binding by human beta-2-glycoprotein I
- 2004
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Konferensbidrag (populärvet., debatt m.m.)abstract
- Human beta-2-glycoprotein I (b2gpI) is a phospholipid- and heparin-binding plasma glycoprotein involved in autoimmune diseases characterized by blood clotting disturbances (thrombosis) together with the occurrence of autoantibodies against b2gpI. With the final goal of assessing autoantibody influence on binding interactions of b2gpI we have studied the development of capillary electrophoresis (CE)-based assays for interactions of negatively charged ligands with b2gpI. Binding studies executed by capillary electrophoresis benefit from flexibility in experimental set-up, wide applicability, and low consumption of reagents.Importantly, the high resolution inherent in CE allows complex mixtures and binding resulting in only small migration changes to be characterized quantitatively. One specific problem, however, that may be encountered when applying CE for the analysis of binding interactions of proteins is the need to avoid interactions other than those between the analyte and the ligand. Thus, protein-wall interactions in unmodified fused-silica capillaries used at neutral pH often invalidate analyses of protein binding. This problem is especially pronounced with basic proteins and proteins containing exposed patches of positive charge. In the development of suitable conditions for analysis at neutral pH of b2gpI we found the pH hysteresis behavior of fused silica surfaces useful since the protonated surface after an acid pre-wash counteracted protein adsorption efficiently in contrast to more laborious procedures including acrylamide/dimethylacrylamide coatings that did not permit analysis of this particular protein. This approach made quantitative studies of heparin-b2gpI interactions possible and the principle was shown also to work for detection of b2gpI binding to anionic phospholipids. Utilizing the pH hysteresis effect may be a simple solution to the adsorption problems often encountered in analyses of proteins by CE.
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| 26. |
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| 27. |
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| 28. |
- Bohlin, Maria, et al.
(författare)
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Use of Dimethylacrylamide Coated Capillaries for the Study of beta2-Glycoprotein I with Affinity Capillary Electrophoresis
- 2003
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Konferensbidrag (populärvet., debatt m.m.)abstract
- The purpose of this work is to develop a solution method for examining interactions of human beta2-Glycoprotein I (b2gpI) with antibodies and natural ligands under nondenaturing conditions. In the approach, a physiological pH was applied because our intention was to study the interactions between b2gpI and antibodies and the protein must thus be kept in its native state. Preliminary experiments have shown that the recovery of the protein, when analyzed in an uncoated capillary, is poor. At physiological pH the protein is positively charged and most likely it was adsorbed at the negatively charged capillary wall in these experiments. Therefore dimethylacrylamide (DMA) coated capillaries1 are used and analyses could be performed with acceptable recovery. Interaction studies are performed simply by adding the antibody or ligand to the running buffer. The method showed good repeatability and efficiency
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| 29. |
- Cumnock, Judy A., et al.
(författare)
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Transpolar arc evolution and associated potential patterns
- 2004
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Ingår i: Annales Geophysicae. - : Copernicus GmbH. - 0992-7689 .- 1432-0576. ; 22:4, s. 1213-1231
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Tidskriftsartikel (refereegranskat)abstract
- We present two event studies encompassing detailed relationships between plasma convection, field-aligned current, auroral emission, and particle precipitation boundaries. We illustrate the influence of the Interplanetary Magnetic Field B, component on theta aurora development by showing two events during which the theta originates on both the dawn and dusk sides of the aurora] oval. Both theta then move across the entire polar region and become part of the opposite side of the aurora] oval. Electric and magnetic field and precipitating particle data are provided by DMSP, while the Polar UVI instrument provides measurements of auroral emissions. Utilizing satellite data as inputs, the Royal Institute of Technology model provides the high-latitude ionospheric electrostatic potential pattern calculated at different times during the evolution of the theta aurora, resulting from a variety of field-aligned current configurations associated with the changing global aurora.
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| 30. |
- Cumnock, Judy, et al.
(författare)
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POLAR UVI Observations of Auroral Oval Intensifications During a Transpolar Arc Event on December 7, 1996
- 2000
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- The evolution of the northern hemisphere aurora is examined during a time when the IMF makes three brief southward excursions after a change in the sign of By during an extended period of northward IMF. POLAR UVI provides images of the aurora while DMSP F13 and F14 provide in situ measurements of precipitating particles, ionospheric plasma flows and ion density. Three different intensifications located in the nightside auroral oval occur during northward turnings of the IMF after brief periods of southward IMF. Spatial expansion, intensity of emissions and their duration are related to the length of time the IMF is southward prior to the northward turning. Thus the longer the period of enhanced magnetospheric convection the more intense the ionospheric response. Observations of a transpolar arc indicate that when the transpolar arc reaches highest latitudes it is located on a spatially narrow region of closed field lines, which extends along the noon-midnight meridian. UV observations indicate a connection between the transpolar arc and the nightside auroral enhancements. Precipitating particles associated with both features are attributed to a plasma sheet boundary layer source in the magnetotail implying a magnetospheric connection between the transpolar arc and the nightside auroral oval intensification.
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| 31. |
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| 32. |
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| 33. |
- Eriksson, Stefan, et al.
(författare)
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Comparing a spherical harmonic model of the global electric field distribution with Astrid-2 observations
- 2002
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Ingår i: Journal of Geophysical Research. - : American Geophysical Union (AGU). - 0148-0227 .- 2156-2202. ; 107:A11
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Tidskriftsartikel (refereegranskat)abstract
- [1] Electric field measurements provided by the double probe instrument on the Astrid-2 satellite are compared with the empirical Weimer electric field model for all magnetic local times, except between 11 and 13 MLT, and poleward of 55degrees corrected geomagnetic latitude (CGLat). We focus the model evaluation on its ability to predict the latitudinal locations of the convection reversal boundaries for two-cell convection patterns and to estimate the magnitude of the electric field above 55degrees CGLat. A total number of 780 polar cap passes are employed from the Northern Hemisphere between January and July 1999. The measured average electric field magnitude in the dawn-dusk meridian plane above 55degrees CGLat is generally 25% larger than the predicted field independent of the interplanetary magnetic field (IMF) direction. The model shows a better correspondence with the observed electric field for southward IMF than for northward IMF, with most cases centered around B-z = -1.5 nT and r = 0.88. However, the agreement for northward IMF is promising, and a few examples are shown to corroborate this fact. The observed and predicted convection reversal boundary locations along the satellite track for southward IMF are on the average found 2-3degrees CGLat apart in the dawn-dusk meridian plane but may be as far apart as 9degrees CGLat. An initial investigation of the relative timing of a 20-min averaging window for the IMF along the 20-25 min polar cap crossing suggests that a time-dependent transfer function may be found that applies a higher weight to the input solar wind data early in the pass and a lower weight later in the pass for an IMF window that corresponds to the first half of the crossing and the opposite weight versus time dependence for an IMF window corresponding to the last half of the crossing.
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| 34. |
- Eriksson, Stefan, et al.
(författare)
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Lobe cell convection and field-aligned currents poleward of the region 1 current system
- 2002
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Ingår i: Journal of Geophysical Research. - : American Geophysical Union (AGU). - 0148-0227 .- 2156-2202. ; 107:A8
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Tidskriftsartikel (refereegranskat)abstract
- [1] We present a case and statistical study of plasma convection in the Northern Hemisphere during summer conditions using electric field, magnetic field, and particle data taken during dawn-dusk directed orbits of the FAST satellite. To our knowledge, this set provides the most comprehensive combination of data as yet presented in support of lobe cell convection from an ionospheric perspective this far from the noon sector. In particular, we study the current systems and convection patterns for all passes in July 1997 that show evidence for six large-scale field-aligned currents (FACs) rather than the usual system of four FACs associated with the region 1/region 2 current systems. A total of 71 passes out of 232 in the study had the extra pair of FACs. The extra pair of FACs in 30 of the 71 cases lies either on the dawnside or on the duskside of the noon-midnight meridian, and their position is strongly correlated with the polarity of the IMF By (negative and positive, respectively). This is consistent with the IMF dependence of a three-cell convection pattern of coexisting merging, viscous, and lobe-type convection cells. The occurrence of the asymmetric FAC pair was also strongly linked to conditions of IMF |B-y/B-z | > 1. The extra pair of FACs in these cases was clearly associated with the lobe cell of the three-cell convection system. The remaining 41 cases had the pair of FACs straddling the noon-midnight meridian. The extra pair of FACs was often (20 cases out of 30) observed at magnetic local times more than three hours away from noon, rather than being confined to regions near noon and the typical location of the cusp. Such a current system consisting of a pair of FACs poleward of the nearest region 1 current is consistent with the IMF B-y-dependent global MHD model developed by Ogino et al. [1986] for southward IMF conditions, as well as with other magnetospheric and ionospheric convection models that include the effects of merging occuring simultaneously at both low-latitude dayside and high-latitude lobe and flank magnetopause reconnection sites. Finally, the presence of the additional FACs and three-cell convection well away from noon show that the entire dayside ionosphere is affected by IMF-dependent processes, rather than only a limited region around noon.
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| 35. |
- Eriksson, Stefan, et al.
(författare)
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Magnetospheric response to the solar wind as indicated by the cross-polar potential drop and the low-latitude asymmetric disturbance field
- 2001
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Ingår i: Annales Geophysicae. - : Copernicus GmbH. - 0992-7689 .- 1432-0576. ; 19:6, s. 649-653
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Tidskriftsartikel (refereegranskat)abstract
- The cross-polar potential drop Phi (pc), and the low-latitude asymmetric geomagnetic disturbance field, as indicated by the mid-latitude ASY-H magnetic index, are used to study the average magnetospheric response to the solar wind forcing for southward interplanetary magnetic field conditions. The state of the solar wind is monitored by the ACE spacecraft and the ionospheric convection is measured by the double probe electric field instrument on the Astrid-2 satellite. The solar wind-magnetosphere coupling is examined for 77 cases in February and from mid-May to mid-June 1999 by using the interplanetary magnetic field B-z component and the reconnection electric field. Our results show that the maximum correlation between Phi (pc) and the reconnection electric field is obtained approximately 25 min after the solar wind has reached a distance of II R-E from the Earth, which is the assumed average position of the magnetopause. The corresponding correlation for ASY-H shows two separate responses to the reconnection electric field, delayed by about 35 and 65 min, respectively. We suggest that the combination of the occurrence of a large magnetic storm on 18 February 1999 and the enhanced level of geomagnetic activity which peaks at Kp = 7(-) may explain the fast direct response of ASY-H to the solar wind at 35 min, as well as the lack of any clear secondary responses of Phi (pc) to the driving solar wind at time delays longer than 25 min.
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| 36. |
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| 37. |
- Kullen, A., et al.
(författare)
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Solar wind dependence of the occurrence and motion of polar auroral arcs : A statistical study
- 2002
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Ingår i: Journal of Geophysical Research. - : American Geophysical Union (AGU). - 0148-0227 .- 2156-2202. ; 107:A11
-
Tidskriftsartikel (refereegranskat)abstract
- [1] Polar UV images from a 3-month period in winter 1998-1999 are used for a statistical study of polar arcs. The study covers all auroral arcs that are located poleward of the northern auroral oval, and which are detectable by the UV imager. The arcs are examined with respect to their spatial and temporal behavior as well as to a possible connection to solar wind parameters using ACE satellite data. It is found that the majority of polar arcs appear during northward IMF, strong IMF magnitude, and high solar wind speed. A modified Akasofu-Perreault epsilon parameter with a cosine function instead of a sine function (nuB(2) cos(4) (theta/2)(l(0)(2)/mu(0))) combines these results. It correlates well with the occurrence frequency of polar arcs for long timescales. The location of polar arcs is strongly dependent on the sign of the IMF B-y component. Static polar arcs occur in the Northern Hemisphere on the dawn (dusk) side of the oval for negative (positive) IMF B-y, whereas poleward-moving arcs separate from the opposite side of the oval, and then move in the direction of IMF B-y. All polar arcs are sorted into five different categories according to their spatial structure and evolution: oval-aligned, bending, moving, midnight, and multiple arcs. Each polar arc type occurs for a characteristic combination of solar wind parameters. IMF clock angle changes seem to have a strong influence on what type of arc occurs. Oval-aligned arcs appear mainly during steady IMF, bending arcs after an IMF B-z sign change, and moving arcs after an IMF B-y sign change. For the rare midnight and multiple arc events, no characteristic IMF clock angle dependence has been found. The different types of clear polar arcs are discussed in the context of existing observational studies and transpolar arc models.
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| 38. |
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| 39. |
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| 40. |
- Marklund, Göran T., et al.
(författare)
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Astrid-2, an advanced microsatellite for auroral research
- 2001
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Ingår i: Annales Geophysicae. - : Copernicus GmbH. - 0992-7689 .- 1432-0576. ; 19:6, s. 589-592
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Tidskriftsartikel (refereegranskat)abstract
- The successful launch of the Swedish microsatellite Astrid-2 in December 1998 began a new era of auroral research, with advanced microprobes of 30 kg or less used as research tools. Innovative technologies and low-mass solutions were used for the sensors and deployment systems to allow a fairly complete set of scientific instruments within the 10 kg allocated for the scientific payload. A newly developed wire boom deployment system proved to function excellently. During its seven month lifetime Astrid-2 collected more than 26 Gbytes of high-quality data of auroral electric and magnetic fields, and auroral particle and plasma characteristics from approximately 3000 orbits at an inclination of 83 degrees and an altitude of about 1000 km. Scientific results cover a broad range of topics, from the physics of energization of auroral particles to how the magnetosphere responds to the energy input from the solar wind and global magnetic field modelling. The fulfilment of both the technological and the scientific mission objectives has opened entirely new possibilities to carry out low-budget multipoint measurements in near-Earth space.
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| 41. |
- Naver, Lars, et al.
(författare)
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Broad spectrum of time of detection, primary symptoms and disease progression in infants with HIV-1 infection
- 2001
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Ingår i: European Journal of Clinical Microbiology and Infectious Diseases. - : Springer Science and Business Media LLC. - 0934-9723 .- 1435-4373. ; 20:3, s. 159-166
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Tidskriftsartikel (refereegranskat)abstract
- The relationship between time of HIV-1 detection, appearance of symptoms and disease progression was studied in all 24 HIV-1-infected infants from a cohort of 117 children who were born to HIV-1-infected mothers and monitored from birth. HIV isolation from plasma and mononuclear cells, HIV-1 DNA PCR (polymerase chain reaction) and, retrospectively, a quantitative assay for HIV-1 RNA were used for virus detection. Two infants possibly exhibited a symptomatic primary HIV infection. More children with than without symptoms during the first year of life progressed to immunological class 3 (P=0.013) and to AIDS or death (P=0.003) during follow-up. HIV-1 was detected within 4 days of age in 4 of 16 infants: 3 of them became symptomatic within 1 year, as did 6 of the remaining 12 infants (not statistically significant). All four infants in whom virus was detected within 4 days of age progressed to severe immunosuppression, compared to 6 of 14 in whom the virus detection test was initially negative prior to the first positive result (n.s.). Two children with previous repeatedly negative HIV detection tests were diagnosed with HIV-1 infection at 8 and 9 months, respectively. Repeated blood sampling is needed for the diagnosis of HIV-1 infection in perinatally exposed infants, and virus detection tests for exclusion of HIV-1 infection must be used with caution.
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| 42. |
- Olsson, Annika, et al.
(författare)
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Statistics of Joule heating in the auroral zone and polar cap using Astrid-2 satellite Poynting flux
- 2004
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Ingår i: Annales Geophysicae. - : European Geosciences Union (EGU). - 0992-7689 .- 1432-0576. ; 22:12, s. 4133-4142
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Tidskriftsartikel (refereegranskat)abstract
- We make a statistical study of ionospheric Joule heating with the Poynting flux method using six months of Astrid-2/EMMA electric and magnetic field data during 1999 (solar maximum year). For the background magnetic field we use the IGRF model. Our results are in agreement with earlier statistical satellite studies using both the Sigma(P)E(2) method and the Poynting flux method. We present a rather comprehensive set of fitted Joule heating formulas expressing the Joule heating in given magnetic local time (MLT) and invariant latitude (ILAT) range under given solar illumination conditions as a function of the K-P index, the AE index, the Akasofu epsilon parameter and the solar wind kinetic energy flux. The study thus provides improved and more detailed estimates of the statistical Joule heating. Such estimates are necessary building blocks for future quantitative studies of the power budget in the magnetosphere and in the nightside auroral region.
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| 43. |
- Sarkar, N., et al.
(författare)
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Effects of intramyocardial injection of phVEGF-A(165) as sole therapy in patients with refractory coronary artery disease - 12-month follow-up : Angiogenic gene therapy
- 2001
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Ingår i: Journal of Internal Medicine. - : Wiley. - 0954-6820 .- 1365-2796. ; 250:5, s. 373-381
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Tidskriftsartikel (refereegranskat)abstract
- Objective. To test the safety and bioactivity of phVEGF-A(165) after intramyocardial injection during 12-month follow-up. Design. Open-labelled study. Subjects. Inclusion criteria were angina pectoris, Canadian Cardiovascular Society (CCS) class III-IV, unamenable to further revascularization, ejection fraction (EF) >30%, perfusion defects extending over >10% of the anterolateral left ventricle wall detectable with adenosine single photon emission computerized tomography (SPECT) and at least one patent vessel visible by coronary angiography. Seven of 39 patients referred for gene therapy were included. Intervention. Via a mini-thoracotomy under general anaesthesia, phVEGF-A(165) was injected directly into the myocardium at four sites in the anterolateral region of the left ventricle. Results. Operative procedures were uneventful. Perioperative release of myocardial markers and electrocardiogram (ECG) changes were detected in two patients. There were no perioperative deaths but one patient died 7 months postoperatively because of myocardial infarction. Plasma vascular endothelial growth factor (VEGF)-A levels increased two to threefold peaking 6 days postoperatively (P<0.004) and returning to baseline by day 30. A significant reduction in angina pectoris was reported. The CCS class improved from 3.30.2 to 1.9 +/-0.3 (P<0.01) and nitroglycerine intake decreased from 3915 to 12 +/-5 tablets week(-1) (P<0.001) 2 months after gene transfer. Improvements remained after 12 months when nitroglycerine consumption approached zero. Improved myocardial function in the phVEGF-A(165) injection region was documented in all patients (P<0.016) by tissue velocity imaging (TVI). Reduced reversible ischaemia was detected by adenosine SPECT in four patients. Improved collateralization was detected in four patients with coronary angiography. Conclusion. Intramyocardial injection of phVEGF-A(165) is safe and may lead to improved myocardial perfusion and function with longstanding symptomatic relief in end-stage angina pectoris. Based on these results this therapeutic potential is being tested in a double-blind placebo controlled multicentre trial, EUROINJECT ONE.
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| 44. |
- Sylven, C., et al.
(författare)
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Myocardial Doppler tissue velocity improves following myocardial gene therapy with VEGF-A(165) plasmid in patients with inoperable angina pectoris
- 2001
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Ingår i: Coronary Artery Disease. - : Ovid Technologies (Wolters Kluwer Health). - 0954-6928 .- 1473-5830. ; 12:3, s. 239-243
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Tidskriftsartikel (refereegranskat)abstract
- Background Myocardial tissue velocity and perfusion were studied in patients with severe angina pectoris following gene therapy by intramyocardial injection of phVEGF-A(165) via thoracotomy. Plasma concentrations of VEGF-A increased postoperatively. Two months after treatment anginal status and myocardial tissue velocity improved and perfusion showed a tendency to improve. Tissue velocity imaging appears to be a sensitive, objective method for detecting changes in myocardial function following gene therapy. Objective To study effects on myocardial tissue velocity and perfusion in patients with angina pectoris following intramyocardial injection of phVEGF-A(165) via thoracotomy. Design Open label, phase I/II. Methods Six patients with Canadian Cardiovascular Society (CCS) angina pectoris functional Glass III - IV and with major defects at adenosine stress single-photon emission computerized tomography (SPECT) were studied. In addition to SPECT, coronary angiography and dobutamine stress echocardiography with tissue Doppler velocity imaging were performed before and two months after gene transfer. Results Plasma concentrations of VEGF-A increased 2 to 3 times (P < 0.04) over baseline from 2 to 14 days after injection with normalization after 4 weeks. The CCS class improved about 40%, from 3.3 +/- 0.2 to 2.0 +/- 0.3 (P < 0.02) and nitroglycerine consumption decreased 30 - 40%, from 44 +/- 17 to 15 +/- 5 tablets per week (P < 0.05). The maximal systolic myocardial tissue velocity increased in all patients about 25% (P < 0.02) but did not reach the reference range. Myocardial perfusion at SPECT improved in four of the six patients. Conclusions Anginal status, myocardial tissue velocity and perfusion can be improved by phVEGF-A(165) intramyocardial injection. Tissue velocity imaging appears to be a sensitive, objective method for detecting changes in myocardial function following gene therapy. Coron Artery Dis 12:239-243
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| 45. |
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| 46. |
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| 47. |
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| 48. |
- Wurz, Peter, et al.
(författare)
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Particle populations in Mercury's magnetosphere
- 2001
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Ingår i: Planetary and Space Science. - 0032-0633 .- 1873-5088. ; 49:14-15, s. 1643-1653
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Tidskriftsartikel (refereegranskat)abstract
- Observations by Mariner 10 during its first and third flybys showed that Mercury possesses an intrinsic magnetic field resulting in a small magnetosphere that can keep the solar wind from directly interacting with the planet's surface under usual conditions. Since Mercury occupies a large fraction of its magnetosphere, regions of trapped charged particles in the inner magnetosphere, the plasmasphere and the energetic radiation belts, would all be absent. During the first flyby, energetic particle bursts were detected and interpreted as hermean substroms analogous to the terrestrial magnetosphere. Moreover, during this flyby, ULF waves and field-aligned currents were detected in the data. Earth-based observations of Na, K, and Ca populations in the exosphere strongly suggest the existence of dynamic magnetospheric processes at high latitudes interacting with the planet's surface.
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| 49. |
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| 50. |
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