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Sökning: WFRF:(Sundkvist D.)

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1.
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2.
  • Andre, M., Behlke, R., Wahlund, J.E., Vaivads, A., Eriksson, A., Tjulin, A., Carozzi, T. D., Cully, C., Gustafsson, G., Sundkvist, D., Khotyaintsev, Y., Cornilleau-Wehrlin, N., Rezeau, L., Maksimovic, M., Lucek, E., Balogh, A., Dunlop, M., Lindqvist, P.A. (författare)
  • Multi-spacecraft observations of broadband waves near the lower hybrid frequency at the Earthward edge of the magnetopause.
  • 2001
  • Ingår i: Annales Geophysicae. ; 19:6, s. 1471-1481
  • Tidskriftsartikel (refereegranskat)abstract
    • Broadband waves around the lower hybrid frequency (around 10 Hz) near the magnetopause are studied, using the four Cluster satellites. These waves are common at the Earthward edge of the boundary layer, consistent with earlier observations, and can have a
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3.
  • Andre, M., et al. (författare)
  • Multi-spacecraft observations of broadband waves near the lower hybrid frequency at the Earthward edge of the magnetopause
  • 2001
  • Ingår i: Annales Geophysicae. - : Copernicus GmbH. - 0992-7689 .- 1432-0576. ; 19:12-okt, s. 1471-1481
  • Tidskriftsartikel (refereegranskat)abstract
    • Broadband waves around the lower hybrid frequency (around 10 Hz) near the magnetopause are studied, using the four Cluster satellites. These waves are common at the Earthward edge of the boundary layer, consistent with earlier observations, and can have amplitudes at least up to 5 mV/m. These waves are similar on all four Cluster satellites, i.e. they are likely to be distributed over large areas of the boundary. The strongest electric fields occur during a few seconds, i.e. over distances of a few hundred km in the frame of the moving magnetopause, a scale length comparable to the ion gyroradius. The strongest magnetic oscillations in the same frequency range are typically found in the boundary layer, and across the magnetopause. During an event studied in detail, the magnetopause velocity is consistent with a large-scale depression wave, i.e. an inward bulge of magnetosheath plasma, moving tailward along the nominal magnetopause boundary. Preliminary investigations indicate that a rather flat front side of the large-scale wave is associated with a rather static small-scale electric field, while a more turbulent backside of the large-scale wave is associated with small-scale time varying electric field wave packets.
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4.
  • Wahlund, J.-E., Yilmaz, A., Backrud, M., Sundkvist, D., Vaivads, A., Winningham, D., Andre, M., Balogh, A., Bonnell, J. Buckert, S. and 9 coauthors (författare)
  • Observations of auroral broadband emissions by CLUSTER
  • 2003
  • Ingår i: Geophysical Research Letters. - : American Goephysical Union. ; 30:11, s. 17-
  • Tidskriftsartikel (refereegranskat)
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5.
  • Bakhtadze, Ekaterine, et al. (författare)
  • Common variants in the TCF7L2 gene help to differentiate autoimmune from non-autoimmune diabetes in young (15-34 years) but not in middle-aged (40-59 years) diabetic patients
  • 2008
  • Ingår i: Diabetologia. - : Springer Science and Business Media LLC. - 0012-186X .- 1432-0428. ; 51:12, s. 2224-2232
  • Tidskriftsartikel (refereegranskat)abstract
    • Type 1 diabetes in children is characterised by autoimmune destruction of pancreatic beta cells and the presence of certain risk genotypes. In adults the same situation is often referred to as latent autoimmune diabetes in adults (LADA). We tested whether genetic markers associated with type 1 or type 2 diabetes could help to discriminate between autoimmune and non-autoimmune diabetes in young (15-34 years) and middle-aged (40-59 years) diabetic patients. In 1,642 young and 1,619 middle-aged patients we determined: (1) HLA-DQB1 genotypes; (2) PTPN22 and INS variable-number tandem repeat (VNTR) polymorphisms; (3) two single nucleotide polymorphisms (rs7903146 and rs10885406) in the TCF7L2 gene; (4) glutamic acid decarboxylase (GAD) and IA-2-protein tyrosine phosphatase-like protein (IA-2) antibodies; and (5) fasting plasma C-peptide. Frequency of risk genotypes HLA-DQB1 (60% vs 25%, p =9.4x10(-34); 45% vs 18%, p= 1.4x10(-16)), PTPN22 CT/TT (34% vs 26%, p=0.0023; 31% vs 23%, p=0.034), INS VNTR class I/I (69% vs 53%, p=1.3x10(-8); 69% vs 51%, p=8.5x10(-5)) and INS VNTR class IIIA/IIIA (75% vs 63%, p=4.3x10(-6); 73% vs 60%, p=0.008) was increased in young and middle-aged GAD antibodies (GADA)-positive compared with GADA-negative patients. The type 2 diabetes-associated genotypes of TCF7L2 CT/TT of rs7903146 were significantly more common in young GADA-negative than in GADA-positive patients (53% vs 43%; p=0.0004). No such difference was seen in middle-aged patients, in whom the frequency of the CT/TT genotypes of TCF7L2 was similarly increased in GADA-negative and GADA-positive groups (55% vs 56%). Common variants in the TCF7L2 gene help to differentiate young but not middle-aged GADA-positive and GADA-negative diabetic patients, suggesting that young GADA-negative patients have type 2 diabetes and that middle-aged GADA-positive patients are different from their young GADA-positive counterparts and share genetic features with type 2 diabetes.
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6.
  • Chasapis, A., et al. (författare)
  • Thin Current Sheets and Associated Electron Heating in Turbulent Space Plasma
  • 2015
  • Ingår i: Astrophysical Journal Letters. - : Institute of Physics Publishing (IOPP). - 2041-8205 .- 2041-8213. ; 804:1
  • Tidskriftsartikel (refereegranskat)abstract
    • Intermittent structures, such as thin current sheets, are abundant in turbulent plasmas. Numerical simulations indicate that such current sheets are important sites of energy dissipation and particle heating occurring at kinetic scales. However, direct evidence of dissipation and associated heating within current sheets is scarce. Here, we show a new statistical study of local electron heating within proton-scale current sheets by using high-resolution spacecraft data. Current sheets are detected using the Partial Variance of Increments (PVI) method which identifies regions of strong intermittency. We find that strong electron heating occurs in high PVI (>3) current sheets while no significant heating occurs in low PVI cases (<3), indicating that the former are dominant for energy dissipation. Current sheets corresponding to very high PVI (>5) show the strongest heating and most of the time are consistent with ongoing magnetic reconnection. This suggests that reconnection is important for electron heating and dissipation at kinetic scales in turbulent plasmas.
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7.
  • Gottsäter, A., et al. (författare)
  • Proinsulin secretion during the first 3 years after diagnosis in diabetic patients with and without islet cell antibodies
  • 1996
  • Ingår i: Diabetes Care. - : American Diabetes Association. - 0149-5992 .- 1935-5548. ; 19:6, s. 659-662
  • Tidskriftsartikel (refereegranskat)abstract
    • OBJECTIVE - To evaluate proinsulin secretion in different types of NIDDM. RESEARCH DESIGN AND METHODS - Proinsulin and insulin were evaluated at diagnosis of diabetes and 3 years later (fasting and after stimulation with intravenous glucose and glucagon) in 10 NIDDM patients without islet cell antibodies (ICAs) at diagnosis (age 52 ± 4 years), 11 NIDDM patients with ICAs at diagnosis (age 50 ± 5 years), and 21 healthy control subjects (age 53 ± 4 years). RESULTS - At diagnosis, fasting proinsulin was higher in NIDDM patients without ICAs than in control subjects (39.6 ± 10.0 vs. 12.8 ± 1.6 pmol/l, P < 0.01). Proinsulin response to intravenous glucose decreased in NIDDM patients with ICAs (from 35.6 ± 6.2 to 13.5 ± 5.4 pmol/l, P < 0.05), but remained unchanged in those without ICAs. At 3 years after diagnosis, fasting proinsulin (10.0 ± 3.7 vs. 59.1 ± 17.0 pmol/l) and proinsulin responses to intravenous glucose (13.5 ± 5.4 vs. 103.9 ± 35.1 pmol/l) and to intravenous glucagon (7.4 ± 3.9 vs. 36.0 ± 7.7 pmol/l) were much lower (P < 0.01) in NIDDM patients with ICAs than in those without ICAs. CONCLUSIONS - After diagnosis of diabetes, proinsulin secretion decreases significantly in NIDDM patients with ICAs and remains constant in those without.
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8.
  • Madsen, O D, et al. (författare)
  • A two-colour immunofluorescence test with a monoclonal human proinsulin antibody improves the assay for islet cell antibodies
  • 1986
  • Ingår i: Diabetologia. - : Springer-Verlag New York. - 0012-186X .- 1432-0428. ; 29:2, s. 8-115
  • Tidskriftsartikel (refereegranskat)abstract
    • The conventional indirect immunofluorescence assay for islet cell antibodies was compared with a two-colour immunofluorescent assay to detect both islet cell antibodies with fluorescein isothiocyanate-labeled rabbit anti-human IgG and pancreatic B cells with a monoclonal human proinsulin antibody and Texas red-labeled sheep anti-mouse IgG. Determinations of end-point titres showed a correlation between the new two-colour immunofluorescent assay and the conventional indirect immunofluorescent assay in 1) selected sera positive for islet cell antibodies and insulin autoantibodies rs = 0.93 (p less than 0.01) or for islet cell antibodies alone rs = 0.99 (p less than 0.005) and 2) sera from children or young adults with newly diagnosed Type 1 (insulin-dependent) diabetes rs = 0.95 (p less than 0.0001). No interference between the monoclonal human proinsulin antibodies and islet cell antibodies with or without insulin autoantibodies or between the two second fluorescent antibodies was detected. It is concluded that the two-colour immunofluorescence assay is advantageous since it is possible to mix the reagents to avoid a more time-consuming and technically complicated assay, the presence of B cells can be confirmed in each section to permit detection of B cell cytoplasmic antibodies and microscopic evaluation is easier and more accurate, particularly in islet cell antibody negative samples.
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9.
  • Sanjeevi, C. B., et al. (författare)
  • Polymorphic amino acid variations in HLA-DQ are associated with systematic physical property changes and occurrence of IDDM
  • 1995
  • Ingår i: Diabetes. - : American Diabetes Association. - 0012-1797 .- 1939-327X. ; 44:1, s. 125-131
  • Tidskriftsartikel (refereegranskat)abstract
    • The association between human leukocyte antigen (HLA) insulin-dependent diabetes was studied in a large population-based investigation using genotyping of 425 new-onset patients, 0-14 years of age, and 367 matched control subjects. As many as 97% of patients compared with 75% of control subjects were positive for one or several of DQA1*0301, DQA1*0501, DQB1*0302, or DQB1*0201. Asp-57 DQB was present among 28% of patients, indicating that this residue alone does not confer protection. Combining Asp- 57 DQB1 with either Arg-52 DQA1 or Leu-69 DQA1 did not explain susceptibility or protection either. DQA1*0301-DQB1*0302 (DQS) and DQA1*0301-DQB1*0301 (DQ7) are identical except for four amino acid substitutions in the β- chain, but DQ8 was positively (odds ratio 8.07; P < 0.001) and DQ7 negatively (odds ratio 0.38; P < 0.001) associated with the disease. Molecular modeling was used to determine whether physicochemical properties such as steric factors and surface electrostatic potentials also differ in a systematic way for various DQ molecules. Amino acids were substituted systematically at the four polymorphic sites, and the solvent-accessible surfaces and electrostatic potentials were computed for each molecule. Dramatic alterations in electrostatic potential were seen for double substitutions at position 45 (G45E) and 57 (A57D) of DQB1. The variation of physicochemical properties due to polymorphic substitutions may be significant to the mechanism of HLA-DQ association with insulin-dependent diabetes, via the effect these property variations have on peptide antigen binding selectivity and subsequent interactions with specific T-cell receptors.
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11.
  • Sundkvist, Göran, et al. (författare)
  • Sorbitol and myo-inositol levels and morphology of sural nerve in relation to peripheral nerve function and clinical neuropathy in men with diabetic, impaired, and normal glucose tolerance
  • 2000
  • Ingår i: Diabetic Medicine. - : Wiley. - 0742-3071 .- 1464-5491. ; 17:4, s. 259-268
  • Tidskriftsartikel (refereegranskat)abstract
    • Aims: Sorbitol and myo-inositol levels and morphology of sural nerve were compared with nerve function and clinical neuropathy in men with diabetic, impaired (IGT), and normal glucose tolerance. Methods: After neurography of sural nerve and determinations of sensory thresholds for vibration, warm and cold on the foot, whole nerve sural nerve biopsy was performed in 10 men with Type 1 diabetes mellitus, 10 with IGT, and 10 with normal glucose tolerance. Polyol levels were assessed by gas-liquid chromatography/mass spectrometry. Results: Sural nerve amplitudes were significantly lower and sorbitol levels significantly higher in diabetic patients (median (interquartile range)) (3.7 (3.5) μV and 643 (412) pmol/mg protein, respectively) both compared with IGT (11.3 (10.6) μV; P = 0.04 and 286 (83) pmol/mg protein; P = 0.0032, respectively) and normally glucose tolerant (10.0 (11.6); P = 0.0142 and 296 (250) pmol/mg protein; P = 0.0191, respectively) subjects. There were no differences in nerve morphology between the three groups. Nerve myo-inositol levels correlated, however, positively with cluster density (r(s) = 0.56; P = 0.0054). In diabetic and IGT subjects, sural nerve amplitudes (2.6 (3.8) vs. 12.1 (10.6) μV; P = 0.0246) and myelinated nerve fibre density (MNFD; 4076 (1091) vs. 5219 (668) nerve fibres/mm2; P = 0.0021) were significantly lower in nine subjects with clinical neuropathy than in 10 without. Conclusions: Nerve degeneration (i.e. MNFD) correlated with clinical neuropathy but not with glucose tolerance status whereas nerve myo-inositol levels positively correlated with signs of nerve regeneration (i.e. increased cluster density).
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12.
  • Yordanova, Emiliya, et al. (författare)
  • Energy input from the exterior cusp into the ionosphere : Correlated ground-based and satellite observations
  • 2007
  • Ingår i: Geophysical Research Letters. - 0094-8276 .- 1944-8007. ; 34:4, s. L04102-
  • Tidskriftsartikel (refereegranskat)abstract
    • The energy transport from the exterior cusp into the ionosphere is investigated using coordinated ground-based (EISCAT and MIRACLE) and satellite ( Cluster) observations. EISCAT and MIRACLE data are used to estimate the plasma heating in the F-region and the Joule heating in the E-region. Cluster measurements are used to derive the electromagnetic and particle energy fluxes at the high altitudes. These fluxes are then compared with the energy deposition into the ionospheric cusp during a 30 minutes long time interval in which Cluster and EISCAT are nearly conjugated. It is shown that the particles seen at about 9 Re in the exterior cusp carry an earthward energy flux that corresponds to the observed heating of the F-region. The estimated earthward Poynting flux is more than enough to account for the Joule heating in the E-region.
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