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Sökning: WFRF:(Blomberg E) > (2005-2009)

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1.
  • Jallow, Muminatou, et al. (författare)
  • Genome-wide and fine-resolution association analysis of malaria in West Africa.
  • 2009
  • Ingår i: Nature Genetics. - : Springer Science and Business Media LLC. - 1061-4036 .- 1546-1718. ; , s. 657-665
  • Tidskriftsartikel (refereegranskat)abstract
    • We report a genome-wide association (GWA) study of severe malaria in The Gambia. The initial GWA scan included 2,500 children genotyped on the Affymetrix 500K GeneChip, and a replication study included 3,400 children. We used this to examine the performance of GWA methods in Africa. We found considerable population stratification, and also that signals of association at known malaria resistance loci were greatly attenuated owing to weak linkage disequilibrium (LD). To investigate possible solutions to the problem of low LD, we focused on the HbS locus, sequencing this region of the genome in 62 Gambian individuals and then using these data to conduct multipoint imputation in the GWA samples. This increased the signal of association, from P = 4 x 10(-7) to P = 4 x 10(-14), with the peak of the signal located precisely at the HbS causal variant. Our findings provide proof of principle that fine-resolution multipoint imputation, based on population-specific sequencing data, can substantially boost authentic GWA signals and enable fine mapping of causal variants in African populations.
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  • Blomberg, Lars G., et al. (författare)
  • MEFISTO - An electric field instrument for BepiColombo/MMO
  • 2006
  • Ingår i: Advances in Space Research. - : Elsevier BV. - 0273-1177 .- 1879-1948. ; 38:4, s. 672-679
  • Tidskriftsartikel (refereegranskat)abstract
    • MEFISTO, together with the companion instrument WPT, are planning the first-ever in situ measurements of the electric field in the magnetosphere of planet Mercury. The instruments have been selected by JAXA for inclusion in the BepiColombo/MMO payload, as part of the Plasma Wave Investigation coordinated by Kyoto University. The magnetosphere of Mercury was discovered by Mariner 10 in 1974 and will be studied further by Messenger starting in 2011. However, neither spacecraft did or will measure the electric field. Electric fields are crucial in the dynamics of a magnetosphere and for the energy and plasma transport between different regions within the magnetosphere as well as between the magnetosphere and the surrounding regions. The MEFISTO instrument will be capable of measuring electric fields from DC to 3 MHz, and will thus also allow diagnostics of waves at all frequencies of relevance to the Hermean magnetosphere. MEFISTO is a double-probe electric field instrument. The double-probe technique has strong heritage and is well proven on missions such as Viking, Polar, and Cluster. For BepiColombo, a newly developed deployment mechanism is planned which reduces the mass by a factor of about 5 compared to conventional mechanisms for 15 in long booms. We describe the basic characteristics of the instrument and briefly discuss the new developments made to tailor the instrument to flight in Mercury orbit.
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  • Blomberg, L. Mattias, et al. (författare)
  • Reduction of Nitric Oxide in Bacterial Nitric Oxide Reductase : A Theoretical Model Study
  • 2006
  • Ingår i: Biochimica et Biophysica Acta - Bioenergetics. - : Elsevier BV. - 0005-2728 .- 1879-2650. ; 1757:4, s. 240-252
  • Tidskriftsartikel (refereegranskat)abstract
    • The mechanism of the nitric oxide reduction in a bacterial nitric oxide reductase (NOR) has been investigated in two model systems of the heme-b3-FeB active site using density functional theory (B3LYP). A model with an octahedral coordination of the non-heme FeB consisting of three histidines, one glutamate and one water molecule gave an energetically feasible reaction mechanism. A tetrahedral coordination of the non-heme iron, corresponding to the one of CuB in cytochrome oxidase, gave several very high barriers which makes this type of coordination unlikely. The first nitric oxide coordinates to heme b3 and is partly reduced to a more nitroxyl anion character, which activates it toward an attack from the second NO. The product in this reaction step is a hyponitrite dianion coordinating in between the two irons. Cleaving an NO bond in this intermediate forms an FeB (IV)O and nitrous oxide, and this is the rate determining step in the reaction mechanism. In the model with an octahedral coordination of FeB the intrinsic barrier of this step is 16.3 kcal/mol, which is in good agreement with the experimental value of 15.9 kcal/mol. However, the total barrier is 21.3 kcal/mol, mainly due to the endergonic reduction of heme b3 taken from experimental reduction potentials. After nitrous oxide has left the active site the ferrylic FeB will form a μ-oxo bridge to heme b3 in a reaction step exergonic by 45.3 kcal/mol. The formation of a quite stable μ-oxo bridge between heme b3 and FeB is in agreement with this intermediate being the experimentally observed resting state in oxidized NOR. The formation of a ferrylic non-heme FeB in the proposed reaction mechanism could be one reason for having an iron as the non-heme metal ion in NOR instead of a Cu as in cytochrome oxidase.
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  • Alexeev, I. I., et al. (författare)
  • Magnetopause mapping to the ionosphere for northward IMF
  • 2007
  • Ingår i: Annales Geophysicae. - : Copernicus GmbH. - 0992-7689 .- 1432-0576. ; 25:12, s. 2615-2625
  • Tidskriftsartikel (refereegranskat)abstract
    • We study the topological structure of the magnetosphere for northward IMF. Using a magnetospheric magnetic field model we study the high-latitude response to prolonged periods of northward IMF. For forced solar wind conditions we investigate the location of the polar cap region, the polar cap potential drop, and the field-aligned acceleration potentials, depending on the solar wind pressure and IMF B-y and B-x changes. The open field line bundles, which connect the Earth's polar ionosphere with interplanetary space, are calculated. The locations of the magnetospheric plasma domains relative to the polar ionosphere are studied. The specific features of the open field line regions arising when IMF is northward are demonstrated. The coefficients of attenuation of the solar wind magnetic and electric fields which penetrate into the magnetosphere are determined.
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  • Blomberg, C, et al. (författare)
  • Pattern of Accessory Regions and Invasive Disease Potential in Streptococcus pneumoniae.
  • 2009
  • Ingår i: Journal of Infectious Diseases. - : Oxford University Press (OUP). - 1537-6613 .- 0022-1899. ; 199, s. 1032-1042
  • Tidskriftsartikel (refereegranskat)abstract
    • Background. The invasive disease potential (IDP) of Streptococcus pneumoniae differs between serotypes, but the reason for this is unknown. Methods. A total of 47 pneumococcal isolates from 13 serotypes with different IDPs in humans that belonged to 37 multilocus sequence types were compared by whole genome microarrays and mutant analyses. Results. Approximately 34% of the genes were variable, including 95 genes previously shown by signature-tagged mutagenesis (STM) to be required for invasive disease in mice. Many variable genes were localized to 41 accessory regions (ARs), of which 24 contained genes previously identified by STM as required for invasive disease. Only AR6 and AR34 were preferentially found in isolates of serotypes with high IDPs. Neither AR6, which carries a gene previously identified by STM as required for invasive disease and encodes a 6-phospho-beta glucosidase, nor the putative adhesin expressed by AR34 was required for mouse virulence in TIGR4. Conclusions. Pneumococci possess a repertoire of ARs that differ between clones and even between isolates of the same clone. The ARs required for invasive disease in humans may be redundant, as no unique pattern distinguished the most invasive clones from others. The ARs that contained genes previously identified by STM as required for virulence in mice were frequently absent from invasive human isolates. Only 1 AR (AR6) was present in almost all isolates from the serotypes with the highest IDP (1, 4, and 7F), whereas it was missing from many others.
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  • Blomberg, Lars G., et al. (författare)
  • Electric fields in the Hermean environment
  • 2006
  • Ingår i: Advances in Space Research. - : Elsevier BV. - 0273-1177 .- 1879-1948. ; 38:4, s. 627-631
  • Tidskriftsartikel (refereegranskat)abstract
    • Returning to Mercury with the BepiColombo mission will provide a unique opportunity to obtain in situ information on the electric field in Mercury's magnetosphere. The electric field plays a crucial role for plasma transport in the magnetosphere, for transfer of energy between different parts of the system, and for propagation of information. Measuring the electric field, we will be able to better understand plasma motion and wave propagation in Mercury's magnetosphere. Together with knowledge of the magnetic field a better understanding will be derived of the magnetospheric current systems and their closure at or near the planetary surface. Further, insight into possible substorms at Mercury will be gained. We here focus on the expected amplitudes and frequencies of the electric fields concerned and the requirements for instrument capability that they pose.
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  • Blomberg, Lars G., et al. (författare)
  • Transpolar aurora : time evolution, associated convection patterns, and a possible cause
  • 2005
  • Ingår i: Annales Geophysicae. - : Copernicus GmbH. - 0992-7689 .- 1432-0576. ; 23:5, s. 1917-1930
  • Tidskriftsartikel (refereegranskat)abstract
    • We present two event studies illustrating the detailed relationships between plasma convection, field-aligned currents, and polar auroral emissions, as well as illustrating the influence of the Interplanetary Magnetic Field's y-component on theta aurora development. The transpolar are of the theta aurorae moves across the entire polar region and becomes part of the opposite side of the auroral oval. Electric and magnetic field and precipitating particle data are provided by DMSP, while the POLAR UVI instrument provides measurements of auroral emissions. Ionospheric electrostatic potential patterns are calculated at different times during the evolution of the theta aurora using the KTH model. These model patterns are compared to the convection predicted by mapping the magnetopause electric field to the ionosphere using the Paraboloid Model of the magnetosphere. The model predicts that parallel electric fields are set up along the magnetic field lines projecting to the transpolar aurora. Their possible role in the acceleration of the auroral electrons is discussed.
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  • Blomberg, Margareta R. A., et al. (författare)
  • O-O bond cleavage in dinuclear peroxo complexes of iron porphyrins : a quantum chemical study
  • 2007
  • Ingår i: Inorganic Chemistry. - : American Chemical Society (ACS). - 0020-1669 .- 1520-510X. ; 46:19, s. 7992-7997
  • Tidskriftsartikel (refereegranskat)abstract
    • To gain insight into the mechanisms of O-2 activation and cleavage in metalloenzymes, biomimetic metal complexes have been constructed and experimentally characterized. One such model complex is the dinuclear peroxo complex of iron porphyrins observed at low temperature in a noncoordinating solvent. The present theoretical study examines the O-O bond cleavage in these complexes, experimentally observed to occur either at increased temperature or when a strongly coordinating base is added. Using hybrid density functional theory, it is shown that the O-O bond cleavage always occurs in a state where two low-spin irons (S = +/- 1/2) are antiferromagnetically coupled to a diamagnetic state. This state is the ground state when the strong base is present and forms an axial ligand to the free iron positions. In contrast, without the axial ligands, the ground state of the clinuclear peroxo complex has two high-spin irons (S = +/- 5/2) coupled antiferromagnetically. Thus, the activation barrier for O-O bond cleavage is higher without the base because it includes also the promotion energy from the ground state to the reacting state. It is further found that this excitation energy, going from 10 unpaired electrons in the high-spin case to 2 in the low-spin case, is unusually difficult to determine accurately from density functional theory because it is extremely sensitive to the amount of exact exchange included in the functional.
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  • Bogefeldt, Johan P, et al. (författare)
  • Diagnostic differences between general practitioners and orthopaedic surgeons in low back pain patients
  • 2007
  • Ingår i: Upsala Journal of Medical Sciences. - 0300-9734 .- 2000-1967. ; 112:2, s. 199-212
  • Tidskriftsartikel (refereegranskat)abstract
    • Background. There is a growing consensus on low back pain treatment. However, whether this extends to diagnostic labelling is still largely unknown. The aim of this report was to compare the diagnostic assessment of low back pain patients between general practitioners trained in manual therapy and orthopaedic surgeons. Methods. Population-based randomized controlled trial in which 160 patients with acute or sub-acute low back pain were assessed and treated by general practitioners or orthopaedic surgeons. Information on diagnoses and use of diagnostic imaging was obtained from medical records and physician questionnaires covering the ten-week treatment period. The Quebec Task Force classification and free text analysis were used to group diagnostic labels. Results: At baseline there were no significant differences in medical history, findings at physical examination and distribution of the Quebec Task Force diagnostic classification between the patient groups, indicating that they were similar. However, there were significant differences in physicians' use of diagnostic labels for local pain and their characterisation of radiating pain. General practitioners used more terms from manual medicine and reported more pseudoradicular pain than orthopaedic surgeons, who used non-specific pain labels, reported more true radicular pain and used more x-ray examinations. Differences were found at all times from first visit to ten week follow-up. Conclusions: There were significant differences in diagnostic assessment and use of diagnostic radiology between general practitioners and orthopaedic surgeons.
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  • Bogefeldt, Johan P, et al. (författare)
  • Sick leave reductions from a comprehensive manual therapy programme for low back pain : the Gotland Low Back Pain Study
  • 2008
  • Ingår i: Clinical Rehabilitation. - : SAGE Publications. - 0269-2155 .- 1477-0873. ; 22:6, s. 529-41
  • Tidskriftsartikel (refereegranskat)abstract
    • OBJECTIVE: To evaluate if a comprehensive manual therapy programme reduces sick leave due low back pain and facilitates return to work more than the conventional optimized activating care. DESIGN: A randomized controlled trial over a 10-week period with a two-year follow-up. SETTING: Primary health care and Visby Hospital, Municipality of Gotland, Sweden. SUBJECTS: One hundred and sixty patients (70 women, 90 men, ages 20-55 years) with acute or subacute low back pain with or without pain radiation into the legs. INTERVENTIONS: Standardized optimized activating care (n = 71) versus a comprehensive pragmatic manual therapy programme including specific corticosteroid injections (n = 89). MAIN MEASURES: Sick leave measured as net sick leave volume, point prevalence and return to work. RESULTS: After 10 weeks, significantly more manual therapy patients than reference patients had returned to work (hazards ratio 1.62, 95% confidence interval (CI) 1.006-2.60, P<0.05), and among those on sick leave at baseline, significantly fewer were still on sick leave (8/58 versus 13/40, ratio 0.35, 95% CI 0.13-0.97, P<0.05). For all other measures there were inconclusive differences in favour of the manual therapy group. No significant differences remained after two years. CONCLUSIONS: The manual therapy programme used in this study decreased sick leave and increased return to work more than the standardized optimized activating care only up to 10 weeks but not up to two years.
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  • Bolad, Ahmed, et al. (författare)
  • Distinct interethnic differences in IgG class/subclass and IgM antibody responses to malaria antigens but not in IgG responses to non-malarial antigens in sympatric tribes living in West Africa
  • 2005
  • Ingår i: Scandinavian Journal of Immunology. - : Wiley. - 0300-9475 .- 1365-3083. ; 61:4, s. 380-386
  • Tidskriftsartikel (refereegranskat)abstract
    • The well-established relative resistance to malaria observed in the Fulani ascompared with other sympatric tribes in West Africa has been attributed totheir higher levels of serum immunoglobulin (Ig) G antibodies to malarialantigens. In this study, we confirm and extend the previous findings by analysesof the levels of IgM, IgG and IgG subclasses of anti-malarial antibodies inasymptomatic individuals of different sympatric tribes in Burkina Faso(Fulani/Mossi) and Mali (Fulani/Dogon). The Fulani showed significantlyhigher median concentrations of anti-malarial IgG and IgM antibodies thanthe sympatric tribes at both locations. Although the overall subclass pattern ofantibodies did not differ between the tribes, with IgG1 and IgG3 as dominant,the Fulani showed consistently significantly higher levels of these subclasses ascompared with those of the non-Fulani individuals. No significant differenceswere seen in the levels of total IgG between the tribes, but the Fulani showedsignificantly higher levels of total IgM than their neighbours in both countries.While the antibody levels to some nonmalarial antigens showed the same patternof differences seen for antibody levels to malaria antigens, no significant suchdifferences were seen with antibodies to other nonmalarial antigens. In conclusion,our results show that the Fulani in two different countries show higherlevels of anti-malarial antibodies than sympatric tribes, and this appears not tobe a reflection of a general hyper-reactivity in the Fulani.
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  • Brown, J L, et al. (författare)
  • Lower airways inflammation in allergic rhinitics : a comparison with asthmatics and normal controls
  • 2007
  • Ingår i: Clinical and Experimental Allergy. - : John Wiley & Sons. - 0954-7894 .- 1365-2222. ; 37:5, s. 688-695
  • Tidskriftsartikel (refereegranskat)abstract
    • Background: Allergic rhinitis (AR) and asthma represent a continuum of atopic disease. AR is believed to pre‐dispose an individual to asthma. Compared with asthmatics and normal controls, the inflammatory response in the lower airways of rhinitics is not fully elucidated. To test the hypothesis that the inflammatory response in the airways of subjects with AR is at a level intermediate between that in normal controls and asthmatics, we have characterized bronchial inflammation and cytokine mRNA levels in non‐asthmatic allergic rhinitics and compared it with subjects with allergic asthma and with normal controls.Methods: Endobronchial mucosal biopsies were obtained at bronchoscopy from 14 allergic rhinitics, 16 asthmatics and 21 normal controls. Biopsies were embedded into glycol methacrylate resin for immunohistochemical analysis of cellular inflammation and snap frozen for semi‐quantitative PCR analysis of cytokine mRNA levels.Results: Airway inflammation in rhinitic subjects was characterized by an increase in submucosal eosinophils, mast cells and the mRNA expression of TNF‐α, at an intermediate level between healthy and asthmatics. In addition, CD3+ and CD8+ lymphocytes in the epithelium, the endothelial expression of vascular adhesion molecule‐1 and IL‐1β mRNA were higher in the allergic rhinitics compared with both normal controls and asthmatics, whereas growth‐related oncogene α‐mRNA was decreased in AR compared with both healthy and asthmatics. Airway inflammation in the asthmatic group was characterized by higher numbers of eosinophils and mast cells, together with an increase in TNF‐α‐mRNA compared with both healthy and rhinitics. IFN‐γ mRNA was the highest in normal controls and lowest in the asthmatics.Conclusions: In individuals with AR the present data suggest an intermediate state of airway inflammation between that observed in normal individuals and subjects with clinical asthma. It is also indicated that IFN‐γ production by CD8+ T lymphocytes could be protective against the development of airway hyperresponsiveness. Further work is needed to evaluate this hypothesis.
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  • Cumnock, Judy A., et al. (författare)
  • Simultaneous polar aurorae and modelled convection patterns in both hemispheres
  • 2006
  • Ingår i: Advances in Space Research. - : Elsevier. - 0273-1177 .- 1879-1948. ; 38:8, s. 1685-1693
  • Tidskriftsartikel (refereegranskat)abstract
    • We present an event study illustrating the relationships between plasma convection and polar auroral emissions, as well as illustrating the influence of the interplanetary magnetic field's y-component on theta aurora development in both hemispheres. Transpolar arcs (TPAs) are often observed during northward IMF with duskside (dawnside) formation of the TPA and dawnward (duskward) motion occurring when B-y changes from positive to negative in the northern (southern) hemisphere. POLAR UVI provides images in the northern hemisphere while DMSP provides ionospheric plasma flow and precipitating particle data in both hemispheres. Concurrent solar wind plasma and interplanetary magnetic field measurements are provided by the ACE satellite. Utilizing the satellite data as inputs, the Royal Institute of Technology (KTH) numerical model provides the high-latitude ionospheric electrostatic potential patterns in both hemispheres 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. These model patterns are compared to the convection predicted by mapping the magnetopause electric field to the ionosphere using the Moscow State University's (MSU) paraboloid model of the magnetosphere. The model predicts that parallel electric fields are set up along the magnetic field lines projecting to the transpolar aurora. Their possible role in the acceleration of the auroral electrons is discussed.
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  • Dagnell, C, et al. (författare)
  • Neurotrophins in COPD
  • 2009
  • Ingår i: RESPIRATORY MEDICINE. - 0954-6111. ; 103, s. S4-S4
  • Konferensbidrag (övrigt vetenskapligt/konstnärligt)
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  • Eriksson, Anders, et al. (författare)
  • RPC-LAP : The Rosetta Langmuir probe instrument
  • 2007
  • Ingår i: Space Science Reviews. - : Springer Science and Business Media LLC. - 0038-6308 .- 1572-9672. ; 128:04-jan, s. 729-744
  • Forskningsöversikt (refereegranskat)abstract
    • The Rosetta dual Langmuir probe instrument, LAP, utilizes the multiple powers of a pair of spherical Langmuir probes for measurements of basic plasma parameters with the aim of providing detailed knowledge of the outgassing, ionization, and subsequent plasma processes around the Rosetta target comet. The fundamental plasma properties to be studied are the plasma density, the electron temperature, and the plasma flow velocity. However, study of electric fields up to 8 kHz, plasma density fluctuations, spacecraft potential, integrated UV flux, and dust impacts is also possible. LAP is fully integrated in the Rosetta Plasma Consortium (RPC), the instruments of which together provide a comprehensive characterization of the cometary plasma.
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  • Farouk, Salah E., et al. (författare)
  • Different antibody and cytokine-mediated responses to Plasmodium falciparum parasite in two sympatric ethnic tribes living in Mali
  • 2005
  • Ingår i: Microbes and infection. - : Elsevier SAS. - 1286-4579 .- 1769-714X. ; 7:1, s. 110-117
  • Tidskriftsartikel (refereegranskat)abstract
    • The Fulani are known to be less susceptible to Plasmodium falciparum malaria infections and to have lower parasitaemia despite living under similar malaria transmission intensity compared with other ethnic tribes. The aim of the present study was to examine whether the Fulani were more polarised towards Th2 as reflected by higher numbers of malaria-specific IL-4- and IL-10-producing cells and lower numbers of IFN-γ- and IL-12-producing cells as compared to their neighbour ethnic tribe, the Dogon of Mali. Total IgE and both anti-malaria IgE and IgG antibodies were measured by ELISA and the numbers of IL-4-, IFN-γ-, IL-10- and IL-12-producing cells were enumerated using enzyme-linked ImmunoSpot assay (ELISPOT). Numbers of parasite clones were detected by polymerase chain reaction (PCR). The study was performed outside the transmission period and all individuals included were asymptomatic. The results revealed that the Fulani were less parasitised, had fewer circulating parasite clones in their blood, had significantly higher anti-malaria IgG and IgE antibodies and higher proportions of malaria-specific IL-4- and IFN-γ-producing cells compared to the Dogon. The higher antigen-specific production of IL-4 among the Fulani was statistically significant both before and after adjustment for level of spontaneous cytokine production, while greater IFN-γ production only attained statistical significance after adjustment for spontaneous levels. Taken together, the association of higher anti-malarial IgE and IgG antibodies and increased numbers of specific IL-4- and IFN-γ-producing cells compared to the ethnic sympatric tribe, the Dogon, may assist in explaining the lower susceptibility to malaria observed in the Fulani.
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  • Feldstein, Y. I., et al. (författare)
  • Auroral electrojets and 3D currents in the ionosphere-magnetosphere system
  • 2006
  • Ingår i: “Physics of Auroral Phenomena”, Proc. XXIX Annual Seminar, Apatity. - : Kola Science Centre, Russian Academy of Science. ; , s. 25-30
  • Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
    • There are shortly described results of the analysis of variations in the location and intensity of the auroral electrojets during magnetic storms and substorms using a numerical method for estimating the equivalent ionospheric currents based on data from meridian chains of magnetic observatories. It is shown that the westward electrojet adjoins to the polar electrojet located at cusp latitudes in the dayside sector. The association of electrojets with the field-aligned currents (FACs), namely Region 1 FAC and Region 2 FAC is considered. During intense disturbances a Region 3 FAC (accompanied with diffuse electron precipitation from the plasma sheet boundary layer) with the downward current was identified. The analysis of observational data is summarized in terms of 2D time-latitude distribution of electrojets at ionospheric altitudes. The magnetic field sawtooth variations generated during the storm main and early recovery phases are also discussed. To follow 3D currents in the magnetosphereionosphere system a clarified view of interrelated 3D currents and magnetospheric plasma domains is presented.
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  • Feldstein, Y. I., et al. (författare)
  • Auroral electrojets and boundaries of plasma domains in the magnetosphere during magnetically disturbed intervals
  • 2006
  • Ingår i: Annales Geophysicae. - : Copernicus GmbH. - 0992-7689 .- 1432-0576. ; 24:8, s. 2243-2276
  • Tidskriftsartikel (refereegranskat)abstract
    • We investigate variations in the location and intensity of the auroral electrojets during magnetic storms and substorms using a numerical method for estimating the equivalent ionospheric currents based on data from meridian chains of magnetic observatories. Special attention was paid to the complex structure of the electrojets and their interrelationship with diffuse and discrete particle precipitation and field-aligned currents in the dusk sector. During magnetospheric substorms the eastward electrojet (EE) location in the evening sector changes with local time from cusp latitudes (Phi similar to 77 degrees) during early afternoon to latitudes of diffuse auroral precipitation (Phi similar to 65 degrees) equatorward of the auroral oval before midnight. During the main phase of an intense magnetic storm the eastward currents in the noon-early evening sector adjoin to the cusp at Phi similar to 65 degrees and in the pre-midnight sector are located at subauroral latitude Phi similar to 57 degrees. The westward electrojet (WE) is located along the auroral oval from evening through night to the morning sector and adjoins to the polar electrojet (PE) located at cusp latitudes in the day-side sector. The integrated values of the eastward (westward) equivalent ionospheric current during the intense substorm are similar to 0.5 MA (similar to 1.5 MA), whereas they are 0.7 MA (3.0 MA) during the storm main phase maximum. The latitudes of auroral particle precipitation in the dusk sector are identical with those of both electrojets. The EE in the evening sector is accompanied by particle precipitation mainly from the Alfven layer but also from the near-Earth part of the central plasma sheet. In the lower-latitude part of the EE the field-aligned currents (FACs) flow into the ionosphere (Region 2 FAC), and at its higher-latitude part the FACs flow out of the ionosphere (Region 1 FAC). During intense disturbances, in addition to the Region 2 FAC and the Region 1 FAC, a Region 3 FAC with the downward current was identified. This FAC is accompanied by diffuse electron precipitation from the plasma sheet boundary layer. Actually, the triple system of FAC is observed in the evening sector and, as a consequence, the WE and the EE overlap. The WE in the evening sector comprises only the high-latitude periphery of the plasma precipitation region and corresponds to the Hall current between the Region 1 FAC and Region 3 FAC. During the September 1998 magnetic storm, two velocity bursts (similar to 2-4 km/s) in the magnetospheric convection were observed at the latitudes of particle precipitation from the central plasma sheet and at subauroral latitudes near the ionospheric trough. These kind of bursts are known as subauroral polarization streams (SAPS). In the evening sector the Alfven layer equatorial boundary for precipitating ions is located more equatorward than that for electrons. This may favour northward electric field generation between these boundaries and may cause high speed westward ions drift visualized as SAPS. Meanwhile, high speed ion drifts cover a wider range of latitudes than the distance between the equatorward boundaries of ions and electrons precipitation. To summarize the results obtained a new scheme of 3-D currents in the magnetosphere-ionosphere system and a clarified view of interrelated 3-D currents and magnetospheric plasma domains are proposed.
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41.
  • Georgiev, Valentin, 1976-, et al. (författare)
  • A comparison of the reaction mechanisms of iron- and manganese-containing 2,3-HPCD: an important spin transition for manganese
  • 2008
  • Ingår i: Journal of Biological Inorganic Chemistry. - Berlin : Springer. - 0949-8257 .- 1432-1327. ; 13:6, s. 929-40
  • Tidskriftsartikel (refereegranskat)abstract
    • Homoprotocatechuate (HPCA) dioxygenases are enzymes that take part in the catabolism of aromatic compounds in the environment. They use molecular oxygen to perform the ring cleavage of ortho-dihydroxylated aromatic compounds. A theoretical investigation of the catalytic cycle for HPCA 2,3-dioxygenase isolated from Brevibacterium fuscum (Bf 2,3-HPCD) was performed using hybrid DFT with the B3LYP functional, and a reaction mechanism is suggested. Models of different sizes were built from the crystal structure of the enzyme and were used in the search for intermediates and transition states. It was found that the enzyme follows a reaction pathway similar to that for other non-heme iron dioxygenases, and for the manganese-dependent analog MndD, although with different energetics. The computational results suggest that the rate-limiting step for the whole reaction of Bf 2,3-HPCD is the protonation of the activated oxygen, with an energy barrier of 17.4 kcal/mol, in good agreement with the experimental value of 16 kcal/mol obtained from the overall rate of the reaction. Surprisingly, a very low barrier was found for the O-O bond cleavage step, 11.3 kcal/mol, as compared to 21.8 kcal/mol for MndD (sextet spin state). This result motivated additional studies of the manganese-dependent enzyme. Different spin coupling between the unpaired electrons on the metal and on the evolving substrate radical was observed for the two enzymes, and therefore the quartet spin state potential energy surface of the MndD reaction was studied. The calculations show a crossing between the sextet and the quartet surfaces, and it was concluded that a spin transition occurs and determines a barrier of 14.4 kcal/mol for the O-O bond cleavage, which is found to be the rate-limiting step in MndD. Thus the two 83% identical enzymes, using different metal ions as co-factors, were found to have similar activation energies (in agreement with experiment), but different rate-limiting steps.
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42.
  • Gromova, L. I., et al. (författare)
  • High-Latitude Ionospheric Convection Patterns Dependent on the IMF Orientation
  • 2007
  • Ingår i: <em>“</em>Physics of Auroral Phenomena”, Proc. XXX Annual Seminar, Apatity. - : Kola Science Centre, Russian Academy of Science. ; , s. 64-68
  • Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
    • The IZMEM model provides high-latitude ionospheric plasma convection patterns in both hemispheres as a function of the IMF orientation. Model electric potentials are compared with electric field measurements from the DE2, FAST and DMSP satellites along high-latitude passes of the Northern and Southern hemispheres during IMF Bz < 0 and By < 0 (By >0). It has been shown that the IZMEM model electric potentials are in good agreement with measurements along the satellite passes, which makes the IZMEM global spatial convection patterns for these plausible. For small IMF magnitude ionospheric convection patterns generally consist of two cells with a positive potential cell on the dawn-side and a negative potential cell on the dusk-side. For IMF By<0 (By>0) a positive (negative) potential cell becomes dominant in the northern hemisphere, and oppositely in the southern hemisphere. During Bz > 0 the convection pattern changes from the standard two-cell pattern to a more complicated one. IZMEM shows two additional convection cells in the dayside polar cap, positive (negative) potential cell is present duskward (dawnward) of the noon-midnight meridian, and may cause three-cell or four-cell convection pattern depending on By/Bz ratio.
  •  
43.
  • Grunnesjö, Marie I, et al. (författare)
  • The course of pain drawings during a 10-week treatment period in patients with acute and sub-acute low back pain
  • 2006
  • Ingår i: BMC Musculoskeletal Disorders. - : Springer Science and Business Media LLC. - 1471-2474. ; 7, s. 65-
  • Tidskriftsartikel (refereegranskat)abstract
    • Background: Pain drawings are widely used as an assessment of patients' subjective pain in lowback pain patients being considered for surgery. Less work has been done on primary health carepatients. Moreover, the possible correlation between pain drawing modalities and other painassessment methods, such as pain score and functional variables needs to be described. Thus, theobjectives were to describe the course of pain drawings during treatment in primary health carefor low back pain patients.Methods: 160 primary health care outpatients with acute or sub-acute low back pain were studiedduring 10 weeks of a stay active concept versus manual therapy in addition to the stay activeconcept. The patients filled out 3 pain drawings each, at baseline and after 5 and 10 weeks oftreatment. In addition the patients also reported pain and functional variables during the 3measurement periods.Results: The proportion of areas marked, the mean number of areas marked (pain drawing score),mean number of modalities used (area score), and the proportion of patients with pain radiationall decreased during the 10-week treatment period. Most of the improvement occurred during thefirst half of the period. The seven different pain modalities in the pain drawing were correlated topain and functional variables. In case of no radiation some modalities were associated with morepain and disability than others, a finding that grew stronger over time. For patients with painradiation, the modality differences were smaller and inconsistent.Conclusion: Pain modalities are significantly correlated with pain and functional variables. Thereis a shift from painful modalities to less painful ones over time.
  •  
44.
  • Hammarström, Sten, et al. (författare)
  • Peter Perlmann 1919-2005
  • 2006
  • Ingår i: Scandinavian journal of immunology. - : Wiley. - 0300-9475 .- 1365-3083. ; 63:6, s. 487-489
  • Tidskriftsartikel (refereegranskat)
  •  
45.
  • Johansson, Adam Johannes, 1976- (författare)
  • Biomimetic Transition Metal Catalysts : Insights from Theoretical Modeling
  • 2008
  • Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • The scientific interest in the chemistry of synthetic transition metal complexes is motivated by at least two arguments:1.These can be regarded as models of biological transition metal complexes, e.g. metalloenzymes, whose functions can be difficult to reveal in detail due to their complexity.2.Transition metal complexes are used for catalytic purposes in the industrial synthesis of chemicals. There is a large potential for further development of this technology, which can be motivated both by economic and environmental arguments.In the present thesis, density functional theory (a quantum mechanical method) has been applied to model reactions involving synthetic iron and copper complexes in solution. The complexity of the solvent environment is a challenging problem for theoretical investigations and a significant part of the theses has been to investigate the mechanistic effects of metal-coordinating solvent molecules, Lewis bases and counter ions. For example, it is explained why the cleavage of the O-O bond in heme-diiron-peroxides is faster in the presence of a coordinating Lewis base. Furthermore, the experimentally observed structure-activity relationship between the Fe(III)(µ-O)2Fe(IV) and (H2O)Fe(III)(µ-O)Fe(IV)O motifs is given an explanation. In addition, the present thesis presents a systematic investigation of how the self-interaction error in density functional theory (DFT) affects the modeling of transition metal catalysis.
  •  
46.
  • Johansson, Adam Johannes, et al. (författare)
  • Density functional study of the O-2 binding to [Cu-I(TPA(R))](+) (TPA = tris(2-pyridyimethyl)amine) in THF and EtCN
  • 2006
  • Ingår i: Inorganic Chemistry. - : American Chemical Society (ACS). - 0020-1669 .- 1520-510X. ; 45:4, s. 1491-1497
  • Tidskriftsartikel (refereegranskat)abstract
    • Density functional theory using the B3LYP hybrid functional has been employed to study the formation of [Cu-II(TPA(H))(O-2(-))](+) and [Cu-II(TPA(MeO))(O-2(-))](+) (TPA = tris(2-pyridylmethyl)amine) in two different solvents, THF and EtCN. The thermodynamics of solvent coordination as well as that of the overall reactions with O-2 has been computed. The formations of [Cu-II(TPA(H))(O-2(-))](+) in THF and of [Cu-II(TPA(MeO))(O-2(-))](+) in both THF and EtCN are found to be initiated from the [Cu-I(TPAR)]+ species, that is, the Cu complex possessing an empty coordination site. In contrast, the formation of [Cu-II(TPA(H))(O-2(-))](+) in EtCN is found to be initiated from the [Cu-I(TPA(H))(EtCN)](+) species, that is, one solvent molecule being coordinated to Cui. In general, good agreement is found between theoretical and experimental results. The high accuracy of the B3LYP functional in reproducing experimental thermodynamic data for the present type of transition metal complexes is demonstrated by the fact that the differences between measured and computed thermodynamic parameters (Delta G degrees, Delta H degrees, and -T Delta S degrees, in most cases are less than 2.0 kcal mol(-1). An attempt was made to investigate the kinetics of the formation of [Cu-II(TPA(H))(O-2(-))](+) in THF and EtCN. Computed free energies of activation, Delta G(double dagger), are in good agreement with experimental results. However, an analysis of the partitioning of the free energy barriers in enthalpic and entropic contributions indicates that the computationally studied reaction pathway might differ from the one observed experimentally.
  •  
47.
  •  
48.
  • Johansson, Adam Johannes, 1976-, et al. (författare)
  • Quantifying the Effects of the Self-interaction Error in Density Functional Theory : When do the Delocalized States Appear? II. Iron-oxo Complexes and Closed-shell Substrate Molecules
  • 2008
  • Ingår i: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 129, s. 154301-
  • Tidskriftsartikel (refereegranskat)abstract
    • Effects of the self-interaction error (SIE) in approximate density functional theory have several times been reported and quantified for the dissociation of charged radicals, charge transfer complexes, polarizabilities, and for transition states of reactions involving main-group molecules. In the present contribution, effects of the SIE in systems composed of a catalytic transition metal complex and a closed-shell substrate molecule are investigated. For this type of system, effects of the SIE have not been reported earlier. It is found that although the best density functionals (e.g., B3LYP) are capable of accurate predictions of structure, thermodynamics, and reactivity of such systems, there are situations and systems for which the magnitude of the SIE can be large, and for which the effects can be severe for the modeling of chemical reactivity. The largest energetic effect reported here is the artificial stabilization of a catalyst-substrate complex by as much as 18 kcal/mol. Also, the disappearance of significant energy barriers for hydrogen atom transfer in certain systems are reported. In line with earlier work, it is found that the magnitude of the SIE is related to the energetics of electron transfer between the metal catalyst and the substrate molecule. It is suggested that these problems might be circumvented by the inclusion of counterions or point charges that would alter the energetics of electron transfer. It is also pointed out that the effects of SIE in the modeling of transition metal reactivity need to be investigated further.
  •  
49.
  •  
50.
  • Johansson, Adam Johannes, 1976-, et al. (författare)
  • Quantum chemical modeling of the oxidation of dihydroanthracene by the biomimetic nonheme iron catalyst [(TMC)Fe-IV(O)](2+)
  • 2007
  • Ingår i: The Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 111:33, s. 12397-12406
  • Tidskriftsartikel (refereegranskat)abstract
    • Hybrid density functional theory has been employed to model the oxidation of dihydroanthracene (DHA = C14H12) to anthracene (C14H10) by the biomimetic iron complex [(TMC)Fe-IV(O)](2+) (TMC = 1,4,8,11-tetramethyl-1,4,8,11-tetraazacyclotetradecane). Experimentally, the reaction has been studied in a solution of the reactants and the counterion trifluoroacetate (CF3CO2) in the solvent acetonitrile (CH3CN). Depending on the concentration of trifluoroacetate, different coordination situations have been observed by NMR spectroscopy. The complexity of the chemical environment offers a challenging modeling problem, and five different models were initially considered. The effects of the coordination of either a counterion or a solvent molecule were found to be rather small. The reaction was found to be a two-step process in which the first step is rate-limiting. The free energy of activation (Delta G) for the first H-abstraction was found to be between 14.5 and 16.9 kcal mol(-1) depending on the model, in reasonable agreement with experimental data. The second step has a much lower free-energy barrier, found to be completely entropic in origin. In all models, the system is found to have a triplet ground state in the Fe-IV(O) reactant. A spin-crossing of the triplet and quintet potential energy surfaces occurs before the first transition state, and the system is found to end up in the Fe-II quintet state, releasing a water molecule and the anthracene product. Because of the formation of the aromatic anthracene molecule, the reaction is very exothermic.
  •  
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