| 1. |
- Moberg, Christina, et al.
(författare)
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De unga gör helt rätt när de stämmer staten
- 2022
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Ingår i: Aftonbladet. - 1103-9000.
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Tidskriftsartikel (populärvet., debatt m.m.)abstract
- 1 620 forskare och lärare i forskarvärlden: Vi ställer oss bakom Auroras klimatkrav
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| 2. |
- Beghin, Christian, et al.
(författare)
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Modeling of CLUSTER's electric antennas in space : application to plasma diagnostics
- 2005
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Ingår i: Radio Science. - 0048-6604 .- 1944-799X. ; 40:6, s. RS6008-
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Tidskriftsartikel (refereegranskat)abstract
- [1] The main characteristics of the long-boom electric antennas installed on board the Cluster satellites are derived from finite element modeling in a kinetic and isotropic space plasma, in the frequency range of about 1–100 kHz. The model is based on the surface charge distribution method in quasi-static conditions. The impedances of both types of antenna, i.e., the double-wire and the double-probe, are computed versus the frequency normalized with respect to the local plasma frequency and for several different Debye lengths. Most of the code outputs are checked using analytic estimations for better understanding of the involved physical mechanisms. As a by-product, the effective length of the double-probe antenna and the mutual impedance between the two antennas are computed by the code. It is shown that if it had been possible to implement such measurements on board, one would have been able not only to determine accurately the electric characteristics of the antennas but also to estimate the local plasma parameters. Nevertheless, an interesting feature predicted by the model has been checked recently in orbit by running a special mode of operation for testing the mutual impedance measurement. The preliminary results are globally consistent with the predictions, except that they suggest that our Maxwellian model for the electron distribution should be revised in order to explain the unexpected low-frequency response. After analysis of the electron flux measurements obtained simultaneously, it appears that a rough adjustment of the electron distribution with a two-component distribution allows us to account for the observations.
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| 3. |
- Heith-Stade, David, et al.
(författare)
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Den gudomliga liturgins editionshistoria
- 2014
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Ingår i: Chrysostomosliturgin - förda anteckningar. - 9789197871990 ; , s. 146-151
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Bokkapitel (populärvet., debatt m.m.)
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| 4. |
- Retinò, Alessandro, et al.
(författare)
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In situ evidence of magnetic reconnection in turbulent plasma
- 2007
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Ingår i: Nature Physics. - : Springer Science and Business Media LLC. - 1745-2473 .- 1745-2481. ; 3:4, s. 235-238
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Tidskriftsartikel (refereegranskat)abstract
- Magnetic reconnection is a universal process leading to energy conversion in plasmas. It occurs in the Solar System, in laboratory plasmas and is important in astrophysics . Reconnection has been observed so far only at large-scale boundaries between different plasma environments . It is not known whether reconnection occurs and is important in turbulent plasmas where many small-scale boundaries can form. Solar and laboratory measurements as well as numerical simulations indicate such possibility. Here we report, for the first time, in situ evidence of reconnection in a turbulent plasma. The turbulent environment is the solar wind downstream of the Earths bow shock. We show that reconnection is fast and electromagnetic energy is converted into heating and acceleration of particles. This has significant implications for laboratory and astrophysical plasmas where both turbulence and reconnection should be common.
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| 8. |
- Sundkvist, David, et al.
(författare)
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Dissipation in turbulent plasma due to reconnection in thin current sheets
- 2007
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Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 99:2, s. 025004-
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Tidskriftsartikel (refereegranskat)abstract
- We present in situ measurements in a space plasma showing that thin current sheets the size of an ion inertial length exist and are abundant in strong and intermittent plasma turbulence. Many of these current sheets exhibit the microphysical signatures of reconnection. The spatial scale where intermittency occurs corresponds to the observed structures. The reconnecting current sheets represent a type of dissipation mechanism, with observed dissipation rates comparable to or even dominating over collisionless damping rates of waves at ion inertial length scales ( X 100), and can have far reaching implications for small-scale dissipation in all turbulent plasmas.
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| 13. |
- Sundkvist, David, 1975-
(författare)
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Space Plasma Dynamics : Instabilities, Coherent Vortices and Covariant Parametrization
- 2005
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The magnetospheric cusps are two funnel-like regions of Earth's magnetosphere where solar wind plasma can have direct access to the ionosphere. The cusps are very dynamic regions where wave-particle interactions continuously take place and redistribute energy among different particle populations. In this thesis, both low and high frequency plasma waves in the cusp have been studied in detail using data from the Cluster spacecraft mission. The waves were studied with respect to frequency, Poynting flux and polarization. Wavelengths have also been estimated using multi-spacecraft techniques. At low frequencies, kinetic Alfvén waves and nonpotential ion cyclotron waves are identified and at high frequencies, electron cyclotron waves, whistler waves, upper-hybrid and RX-waves are observed. A common generation mechanism called the shell-instability is proposed for several of the wave modes present in the cusp, both at low and high frequencies. The plasma in the cusp is shown to be strongly inhomogeneous. In an inhomogeneous low-frequency magnetoplasma, kinetic Alfvén waves couple to drift-waves. Such drift-kinetic Alfvén waves have long been believed to nonlinearly self-interact and form coherent structures in the form of drift-kinetic Alfvén vortices. In this thesis the first unambiguous direct measurements confirming the existence of such vortices in a turbulent space plasma are presented. Some of the crucial parameters such as the vortex radius are determined. Plasma theory is electrodynamics applied to a large collection of charged particles. In this thesis a new way of looking at the fundamental Maxwell tensor is presented. A covariant spectral density tensor containing information on electromagnetic waves is formed. This tensor is then decomposed into irreducible components by using the spinor formalism for an arbitrary metric. The obtained fundamental tensors are shown to correspond both to well known tensors in Maxwell's theory, as well as several physically interesting new tensors.
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| 14. |
- Sundkvist, Göran, et al.
(författare)
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Autonomic and peripheral nerve function in early diabetic neuropathy. Possible influence of a novel aldose reductase inhibitor on autonomic function
- 1987
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Ingår i: Acta Medica Scandinavica. - 0001-6101. ; 221:5, s. 445-453
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Tidskriftsartikel (refereegranskat)abstract
- Autonomic and peripheral nerve functions as well as the possible short-term effect of a novel aldose reductase inhibitor (ARI) on neuropathy were evaluated in 30 male type I diabetics (age 25-44 years, mean 34; duration of diabetes 10-20 years, mean 34) with neurographic signs of peripheral neuropathy (PN). Autonomic neuropathy (AN) was established by the heart rate reactions to deep breathing (E/I ratio = vagal function) and to tilt (acceleration index = sympathetic and vagal functions; the brake index = vagal function). Twenty-nine patients, 13 with AN, completed the study. Among neurographic variables, only sural nerve function tests correlated with autonomic functions. Patients with AN showed significantly lower mean sensory action potential amplitudes (SAPA) sural, indicating axonal losses, than patients without AN (3.58 +/- 0.79 microV v. 7.34 +/- 1.12 microV; p less than 0.01). PN as measured by neurography did not improve during ARI treatment. On the other hand, vagal function (brake indices) improved (p less than 0.05) during ARI in AN patients.
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| 15. |
- Sundkvist, Göran, et al.
(författare)
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Islet cell antibody reactivity with human fetal pancreatic islets
- 1991
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Ingår i: Diabetes Research and Clinical Practice. - 0168-8227. ; 14:1, s. 1-7
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Tidskriftsartikel (refereegranskat)abstract
- To evaluate the possibility of autoimmune processes against pancreatic islets in fetal life, we tested islet cell antibody (ICA) reactivity with 14 fetal pancreata obtained after abortion at the 15th up to the 19th week of gestation. Pancreatic islets positive for a monoclonal proinsulin antibody but non-reactive with ICA negative control serum were found in 9 14 pancreata and all ( 9 9) of them showed a positive reaction with the ICA standard. It is concluded that ICA reactivity may be detected in fetal human pancreata. Further studies on fetal islet cell antibody reactivity in the development of insulin dependent diabetes mellitus (IDDM) are warranted.
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| 16. |
- Wänman, Johan, et al.
(författare)
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Age, sex, primary tumor type and site are associated with mortality after pathological fractures: an observational study of 1453 patients from the Swedish Fracture Register
- 2023
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Ingår i: Journal of Orthopaedic Surgery and Research. - : Springer Science and Business Media LLC. - 1749-799X. ; 18:1
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Tidskriftsartikel (refereegranskat)abstract
- Background Pathological fractures are challenging in orthopedic surgery and oncology, with implications for the patient's quality of life, mobility and mortality. The efficacy of oncological treatment on life expectancy for cancer patients has improved, but the metastatic pattern for bone metastases and survival is diverse for different tumor types. This study aimed to evaluate survival in relation to age, sex, primary tumor and site of the pathological fractures. Methods All pathological fractures due to cancer between 1 September 2014 and 31 December 2021 were included in this observational study from the Swedish Fracture Register (SFR). Data on age, sex, tumor type, fracture site and mortality were collected. Results A total of 1453 patients with pathological fractures were included (48% women, median age 73, range 18-100 years). Unknown primary tumors were the most common primary site (n = 308). The lower extremities were the most common site of pathological fractures. Lung cancer had the shortest median survival of 78 days (range 54-102), and multiple myeloma had the longest median survival of 432 days (range 232-629). The site at the lower extremity had the shortest (187 days, range 162-212), and the spine had the longest survival (386 days, range 211-561). Age, sex, primary type and site of the pathological fractures were all associated with mortality. Interpretation Age, sex, primary tumor type and site of pathological fractures were associated with survival. Survival time is short and correlated with primary tumor type, with lung cancer as the strongest negative predictor of survival.
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