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Sökning: WFRF:(Fransson Mattias)

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1.
  • Akselsson, Cecilia, et al. (författare)
  • The influence of N load and harvest intensity on the risk of P limitation in Swedish forest soils
  • 2008
  • Ingår i: Science of the Total Environment. - : Elsevier BV. - 1879-1026 .- 0048-9697. ; 404, s. 284-289
  • Tidskriftsartikel (refereegranskat)abstract
    • Nitrogen (N) is often considered to be the major factor limiting tree growth in northern forest ecosystems. An increased N availability, however, increases the demand for other nutrients such as base cations and phosphorous (P) which in turn may change which nutrient is the limiting factor. If P or base cations become limiting, N will start to leach which means a risk of increased eutrophication of surface waters. As many studies focus on base cations, this study instead aims at estimating P budgets on a regional scale for different harvesting scenarios relevant for Swedish conditions. P budget calculations were carried out for 14,550 coniferous sites from the Swedish National Forest Inventory, as weathering+deposition–harvesting–leaching. Three scenarios with different harvest intensities were used: 1) no harvesting, 2) stem harvesting and 3) wholetree harvesting. The input data were derived from measurements and model results. The P budget estimates indicate that harvesting, especially whole-tree harvesting, result in net losses of P in large parts of Sweden. The highest losses were found in southern Sweden due to high growth rate in this area. In the whole-tree harvesting scenario the losses exceeded 1 kg ha−1 y−1 on many sites. N budget calculations on the same sites indicate that N generally accumulates in the whole country and especially in the southern parts. Consequently, the N and P budget calculations indicate that the forests in southern Sweden are in a transition phase from N-to P-limitation to growth. This transition will proceed as long as the accumulation of N continues. These results are important in a sustainable forestry context, as a basis for assessing the risk of future N leaching, and in designing recommendations for abatement strategies of N deposition and for application of wood ash recycling and N fertilization.
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2.
  • Alveteg, Mattias, et al. (författare)
  • On the Calculation and Interpretation of Target Load Functions
  • 2007
  • Ingår i: Water, Air, & Soil Pollution: Focus. - : Springer Science and Business Media LLC. - 1573-2940 .- 1567-7230. ; 7:1-3, s. 385-390
  • Tidskriftsartikel (refereegranskat)abstract
    • In this study critical load functions and target load functions of nitrogen and sulphur deposition with respect to acidity and minimum base cation to aluminium ratio were calculated with the SAFE model using three different averaging strategies: (1) averaging based on current forest generation, (2) averaging based on next generation and (3) averaging based on the entire simulation period. From the results it is evident that although target load calculation and indeed critical load calculation is straight forward, there is a problem in translating a predicted recovery according to the target load calculation back to a site-specific condition. We conclude that a policy strategy for emission reductions that ensures recovery, according to calculated target load functions, is likely to be beneficial from an ecosystem point of view. However, such a strategy may not be sufficient to achieve actual non-violation of the chemical criteria throughout the seasonal or rotational variations. To address this issue we propose a method for calculating dynamic critical loads which ensures that the chosen criteria is not violated.
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3.
  • Belting, Mattias, et al. (författare)
  • Glypican-1 is a vehicle for polyamine uptake in mammalian cells. A pivotal role for nitrosothiol-derived nitric oxide.
  • 2003
  • Ingår i: Journal of Biological Chemistry. - 1083-351X. ; 278:47, s. 47181-47189
  • Tidskriftsartikel (refereegranskat)abstract
    • Polyamines (putrescine, spermidine, and spermine) are essential for growth and survival of all cells. When polyamine biosynthesis is inhibited, there is up-regulation of import. The mammalian polyamine transport system is unknown. We have previously shown that the heparan sulfate (HS) side chains of recycling glypican-1 (Gpc-1) can sequester spermine, that intracellular polyamine depletion increases the number of NO-sensitive N-unsubstituted glucosamines in HS, and that NO-dependent cleavage of HS at these sites is required for spermine uptake. The NO is derived from S-nitroso groups in the Gpc-1 protein. Using RNA interference technology as well as biochemical and microscopic techniques applied to both normal and uptake-deficient cells, we demonstrate that inhibition of Gpc-1 expression abrogates spermine uptake and intracellular delivery. In unperturbed cells, spermine and recycling Gpc-1 carrying HS chains rich in N-unsubstituted glucosamines were co-localized. By exposing cells to ascorbate, we induced release of NO from the S-nitroso groups, resulting in HS degradation and unloading of the sequestered polyamines as well as nuclear targeting of the deglycanated Gpc-1 protein. Polyamine uptake-deficient cells appear to have a defect in the NO release mechanism. We have managed to restore spermine uptake partially in these cells by providing spermine NONOate and ascorbate. The former bound to the HS chains of recycling Gpc-1 and S-nitrosylated the core protein. Ascorbate released NO, which degraded HS and liberated the bound spermine. Recycling HS proteoglycans of the glypican-type may be plasma membrane carriers for cargo taken up by caveolar endocytosis.
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7.
  • Belting, Mattias, et al. (författare)
  • Tumor attenuation by combined heparan sulfate and polyamine depletion.
  • 2002
  • Ingår i: Proceedings of the National Academy of Sciences. - 1091-6490. ; 99:1, s. 371-376
  • Tidskriftsartikel (refereegranskat)abstract
    • Cells depend on polyamines for growth and their depletion represents a strategy for the treatment of cancer. Polyamines assemble de novo through a pathway sensitive to the inhibitor, alpha-difluoromethylornithine (DFMO). However, the presence of cell-surface heparan sulfate proteoglycans may provide a salvage pathway for uptake of circulating polyamines, thereby sparing cells from the cytostatic effect of DFMO. Here we show that genetic or pharmacologic manipulation of proteoglycan synthesis in the presence of DFMO inhibits cell proliferation in vitro and in vivo. In cell culture, mutant cells lacking heparan sulfate were more sensitive to the growth inhibitory effects of DFMO than wild-type cells or mutant cells transfected with the cDNA for the missing biosynthetic enzyme. Moreover, extracellular polyamines did not restore growth of mutant cells, but completely reversed the inhibitory effect of DFMO in wild-type cells. In a mouse model of experimental metastasis, DFMO provided in the water supply also dramatically diminished seeding and growth of tumor foci in the lungs by heparan sulfate-deficient mutant cells compared with the controls. Wild-type cells also formed tumors less efficiently in mice fed both DFMO and a xylose-based inhibitor of heparan sulfate proteoglycan assembly. The effect seemed to be specific for heparan sulfate, because a different xyloside known to affect only chondroitin sulfate did not inhibit tumor growth. Hence, combined inhibition of heparan sulfate assembly and polyamine synthesis may represent an additional strategy for cancer therapy.
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8.
  • Benson, Mikael, 1954, et al. (författare)
  • Inverse relation between nasal fluid Clara Cell Protein 16 levels and symptoms and signs of rhinitis in allergen-challenged patients with intermittent allergic rhinitis.
  • 2007
  • Ingår i: Allergy. - : Wiley. - 0105-4538 .- 1398-9995. ; 62:2, s. 178-83
  • Tidskriftsartikel (refereegranskat)abstract
    • BACKGROUND: Decreased levels of the anti-inflammatory Clara Cell Protein 16 (CC16) are found in intermittent allergic rhinitis (IAR) and asthma. In asthma this decrease has been associated with hyperreactivity and the A38G single nucleotide polymorphism (SNP). The aim of this study was to examine if IAR is associated with signs and symptoms of rhinitis and the A38G SNP. METHODS: Nasal fluid CC16 was analyzed in 20 patients with IAR before allergen challenge and 1 and 6 h after challenge, and from 28 healthy controls. The A38G SNP was analyzed in 80 patients with IAR and 106 controls. Nasal biopsies were obtained from three subjects in each group for immunohistochemical analysis of CC16. RESULTS: In the allergen-challenged patients symptoms and rhinoscopic signs of rhinitis increased after 1 h and normalized after 6 h. In contrast, nasal fluid CC16 decreased 1 h after allergen challenge and returned to baseline after 6 h. Nasal fluid CC16 levels did not differ from controls before and 6 h after challenge. Immunohistochemical investigation showed intense CC16 staining in the nasal epithelium of both patients before season and healthy controls, but weak staining in symptomatic patients during season. No significant association between the A38G SNP and IAR was found. CONCLUSION: There was an inverse relation between nasal fluid CC16 levels and symptoms and signs of rhinitis in allergen-challenged patients with IAR. However, there was no association between IAR and the A38G SNP.
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9.
  • Berglund, Malin, et al. (författare)
  • Myringoplasty Outcomes From the Swedish National Quality Registry
  • 2017
  • Ingår i: The Laryngoscope. - : John Wiley & Sons. - 0023-852X .- 1531-4995. ; 127:10, s. 2389-2395
  • Tidskriftsartikel (refereegranskat)abstract
    • OBJECTIVES/HYPOTHESIS: Data from patients registered for myringoplasty during 2002 to 2012 in the Swedish National Quality Registry for Myringoplasty.STUDY DESIGN: Both conventional myringoplasty and fat-graft techniques were used aimed at healing the tympanic membrane in noninfected ears.METHODS: Analysis was performed on data in a national database collected from 32 ear, nose, and throat clinics. Surgical procedures and outcomes, and patient satisfaction from a questionnaire were studied.RESULTS: The database was comprised of 3,775 surgical procedures, with follow-up available for analysis. One-third were children under the age of 15 years. The most common indication for surgery was infection prophylaxis. The overall healing rate of the tympanic membrane after surgery was 88.5%, with a high mean patient satisfaction. Complications registered were postoperative infection, tinnitus, or taste disturbance that occurred in 5.8% of patients.CONCLUSIONS: Swedish results for a large number of patients who completed myringoplasty are presented. The success rate in this study is comparable to other studies, and good patient-reported outcome measures of myringoplasty are presented. Databases for surgical procedures and clinical audits are systematic processes for continuous learning in healthcare. This study shows that clinical databases can be utilized to analyze national results of surgical procedures.LEVEL OF EVIDENCE: 2b Laryngoscope, 127:2389-2395, 2017.
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10.
  • Berglund, Malin, 1970, et al. (författare)
  • Tinnitus and taste disturbances reported after myringoplasty: Data from a national quality registry
  • 2019
  • Ingår i: Laryngoscope. - : Wiley. - 0023-852X .- 1531-4995. ; 129:1, s. 209-215
  • Tidskriftsartikel (refereegranskat)abstract
    • © 2018 The American Laryngological, Rhinological and Otological Society, Inc. Objectives/Hypothesis: Postoperative tinnitus and taste disturbances after myringoplasty are more common than previously reported. Study Design: This study was a retrospective analysis of prospectively collected data from the Swedish National Quality Registry for Myringoplasty. Methods: The analysis was performed on extracted data from all counties in Sweden collected from database A from 2002 to 2012 and database B from 2013 to 2016. Tinnitus and taste disturbance complications 1 year after myringoplasty were analyzed in relation to gender, age, procedure, and success rate. In database A, physicians reported tinnitus and taste disturbances. In database B, patients reported the complications. Results: A major difference was found when the complications were reported by physicians compared to when the complications were reported by patients. In database A, tinnitus was reported in 1.2% of the patients and taste disturbances in 0.5%. In database B, the frequencies were 12.3% and 11.2%, respectively. Tinnitus and taste disturbances were more frequent after conventional myringoplasty compared to those after fat grafting and were more frequent after primary compared to those after revision surgery when reported by physicians. Patients, however, reported the same frequency of tinnitus after fat graft myringoplasty compared to that after conventional myringoplasty (12.0% vs. 12.6%) and fewer taste disturbances after revision surgery. In follow-up assessments, complications persisted after surgery over a long time period. Conclusion: Tinnitus and taste disturbances are more common after myringoplasty when patients report their symptoms than when physicians report the symptoms. Level of Evidence: 2b. Laryngoscope, 2018.
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11.
  • Bogefors, J., et al. (författare)
  • Nod1, Nod2 and Nalp3 receptors, new potential targets in treatment of allergic rhinitis?
  • 2010
  • Ingår i: Allergy. European Journal of Allergy and Clinical Immunology. - : Wiley-Blackwell. - 0105-4538 .- 1398-9995. ; 65:10, s. 1222-1226
  • Tidskriftsartikel (refereegranskat)abstract
    • BACKGROUND: Recently, a new set of pattern-recognition receptors, the nucleotide-binding oligomerization domain (Nod)-like receptors (NLRs), have emerged. Their activation, either by allergens or microbes, triggers an inflammatory response. The knowledge about NLRs in human airways is limited.AIM OF THE STUDY: To investigate presence of NLRs in the human nose of healthy individuals and patients with intermittent allergic rhinitis outside and during pollen season.METHODS: The expression of Nod1, Nod2, and Nalp3 in nasal biopsies was determined with real-time RT-PCR and immunohistochemistry. Cultured primary human nasal epithelial cells (HNECs) were analyzed using real-time RT-PCR and flow cytometry to further verify the presence of NLRs in the epithelium.RESULTS: Immunohistochemical analysis revealed presence of Nod1, Nod2, and Nalp3 in the nasal epithelium. This was corroborated in cultured HNECs. Patients suffering from symptomatic allergic rhinitis exhibited lower Nod1 and Nalp3 mRNA levels than both controls and patients during pollen season. Nod2 expression was found in all specimens tested, but no differences were seen between the three groups.CONCLUSION: Nod1, Nod2, and Nalp3 receptors were found to be present in the human nose. The expression of Nod1 and Nalp3 were down-regulated during pollen season among patients with allergic rhinitis. This opens up for new insights and novel therapeutic strategies in inflammatory airway disease.
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12.
  • Cheng, Fang, et al. (författare)
  • APP/APLP2 expression is required to initiate endosome-nucleus-autophagosome trafficking of glypican-1-derived heparan sulfate.
  • 2014
  • Ingår i: Journal of Biological Chemistry. - 1083-351X. ; 289:30, s. 20871-20878
  • Tidskriftsartikel (refereegranskat)abstract
    • Anhydromannose (anMan)-containing heparan sulfate (HS) derived from the proteoglycan glypican-1 (Gpc-1) is generated in endosomes by an endogenously or ascorbate induced SNO-catalyzed reaction. Processing of the amyloid precursor protein (APP) and APP-like protein 2 (APLP2) by β- and γ-secretases into amyloid beta (Aβ) and Aβ-like peptides also takes place in these compartments. Moreover, anMan-containing HS suppresses the formation of toxic Aβ assemblies in vitro. We show by using deconvolution immunofluorescence microscopy with an anMan-specific monoclonal antibody as well as 35S-labeling experiment that expression of APP/APLP2 is required for ascorbate-induced transport of HS from endosomes to the nucleus. Nuclear translocation was observed in wild-type mouse embryonic fibroblasts (Wt-MEF), Tg2576 MEF and N2a neuroblastoma cells but not in APP-/- and APLP2-/- MEF. Transfection of APP-/- cells with a vector encoding APP restored nuclear import of anMan-containing HS. In Wt-MEF and N2a neuroblastoma cells exposed to β- or γ-secretase inhibitors, nuclear translocation was greatly impeded, suggesting involvement of APP/APLP2 degradation products. In Tg2576 MEF, the β-inhibitor blocked transport but the γ- inhibitor did not. During chase in ascorbate-free medium, anMan-containing HS disappeared from the nuclei of Wt-MEF. Confocal immunofluorescence microscopy showed that they appeared in acidic, LC3-positive vesicles in keeping with an autophagosomal location. There was increased accumulation of anMan-containing HS in nuclei and cytosolic vesicles upon treatment with chloroquine indicating that HS was degraded in lysosomes. Manipulations of APP expression and processing may have deleterious effects upon HS function in the nucleus.
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13.
  • Cheng, Fang, et al. (författare)
  • Hypoxia induces NO-dependent release of heparan sulfate in fibroblasts from the Alzheimer mouse Tg2576 by activation of nitrite reduction.
  • 2016
  • Ingår i: Glycobiology. - : Oxford University Press (OUP). - 1460-2423 .- 0959-6658. ; 26:6, s. 623-634
  • Tidskriftsartikel (refereegranskat)abstract
    • There is a functional relationship between the heparan sulfate proteoglycan glypican-1 and the amyloid precursor protein of Alzheimer disease. In wild-type mouse embryonic fibroblasts, expression and processing of the amyloid precursor protein is required for endosome-to-nucleus translocation of anhydromannose-containing heparan sulfate released from S-nitrosylated glypican-1 by ascorbate-induced, nitrosothiol-catalyzed deaminative cleavage. In fibroblasts from the transgenic Alzheimer mouse Tg2576 there is increased processing of the amyloid precursor protein to amyloid-β peptides. Simultaneously, there is spontaneous formation of anhydromannose-containing heparan sulfate by an unknown mechanism. We have explored the effect of hypoxia on anhydromannose-containing heparan sulfate formation in wild-type and Tg2576 fibroblasts by deconvolution immunofluorescence microscopy and flow cytometry using an anhydromannose-specific monoclonal antibody and by (35)SO4-labeling experiments. Hypoxia prevented ascorbate-induced heparan sulfate release in wild-type fibroblasts, but induced an increased formation of anhydromannose-positive and (35)S-labeled heparan sulfate in Tg2576 fibroblasts. This appeared to be independent of glypican-1 S-nitrosylation as demonstrated by using a monoclonal antibody specific for S-nitrosylated glypican-1. In hypoxic wild-type fibroblasts, addition of nitrite to the medium restored anhydromannose-containing heparan sulfate formation. The increased release of anhydromannose-containing heparan sulfate in hypoxic Tg2576 fibroblasts did not require addition of nitrite. However, it was suppressed by inhibition of the nitrite reductase activity of xanthine oxidoreductase/aldehyde oxidase or by inhibition of p38 mitogen-activated protein kinase or by chelation of iron. We propose that normoxic Tg2576 fibroblasts maintain a high level of anhydromannose-containing heparan sulfate production by a stress-activated generation of nitric oxide from endogenous nitrite. This activation is enhanced by hypoxia.
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14.
  • Cheng, Fang, et al. (författare)
  • Nitric oxide-dependent processing of heparan sulfate in recycling S-nitrosylated glypican-1 takes place in caveolin-1 containing endosomes.
  • 2002
  • Ingår i: Journal of Biological Chemistry. - 1083-351X. ; 277:46, s. 44431-44439
  • Tidskriftsartikel (refereegranskat)abstract
    • We have previously demonstrated intracellular degradation of the heparan sulfate side-chains in recycling glypican-1 by heparanase and by deaminative cleavage at N-unsubstituted glucosamine with nitric oxide derived from intrinsic nitrosothiols [see Ding, K., Mani, K., Cheng, F., Belting, M. and Fransson, L.-. (2002) J. Biol. Chem., 277, xxx-xxx; prepub M203383200]. To determine where and in what order events take place, we have visualized, by using confocal laser-scanning immunofluorescence microscopy, glypican-1 variants in unperturbed cells or arrested at various stages of processing. In unperturbed proliferating cells, glypican-1 was partly S-nitrosylated. Intracellular glypican-1 was enriched in endosomes, colocalized significantly with GM-1 ganglioside, caveolin-1 and Rab9-positive endosomes, and carried side-chains rich in N-unsubstituted glucosamine residues. However, such residues were scarce in cell-surface glypican-1. Brefeldin A-arrested glypican-1, which was non-S-nitrosylated and carried side-chains rich in N-unsubstituted glucosamines, colocalized extensively with caveolin-1 but not with Rab9. Suramin, which inhibits heparanase, induced the appearance of S-nitrosylated glypican-1 in caveolin-1-rich compartments. Inhibition of deaminative cleavage did not prevent heparanase from generating heparan sulfate oligosaccharides that colocalized strongly with caveolin-1. Growth-quiescent cells displayed extensive NO-dependent deaminative cleavage of heparan sulfate generating anhydromannose-terminating fragments which were partly associated with acidic vesicles. Proliferating cells generated such fragments during polyamine uptake. We conclude that recycling glypican-1 that is associated with caveolin-1-containing endosomes undergoes sequential N-desulfation/N-deacetylation, heparanase cleavage, S-nitrosylation, NO-release and deaminative cleavage of its side-chains in conjunction with polyamine uptake.
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15.
  • Cheng, Fang, et al. (författare)
  • Nucleolin is a nuclear target of heparan sulfate derived from glypican-1
  • 2017
  • Ingår i: Experimental Cell Research. - : Elsevier BV. - 0014-4827. ; 354:1, s. 31-39
  • Tidskriftsartikel (refereegranskat)abstract
    • The recycling, S-nitrosylated heparan sulfate (HS) proteoglycan glypican-1 releases anhydromannose (anMan)-containing HS chains by a nitrosothiol-catalyzed cleavage in endosomes that can be constitutive or induced by ascorbate. The HS-anMan chains are then transported to the nucleus. A specific nuclear target for HS-anMan has not been identified. We have monitored endosome-to-nucleus trafficking of HS-anMan by deconvolution and confocal immunofluorescence microscopy using an anMan-specific monoclonal antibody in non-growing, ascorbate-treated, and growing, untreated, wild-type mouse embryonic fibroblasts and hypoxia-exposed Alzheimer mouse Tg2576 fibroblasts and human U87 glioblastoma cells. In all cells, nuclear HS-anMan targeted a limited number of sites of variable size where it colocalized with DNA and nucleolin, an established marker for nucleoli. HS-anMan also colocalized with ethynyl uridine-tagged nascent RNA and two acetylated forms of histone H3. Acute hypoxia increased the formation of HS-anMan in both Tg2576 and U87 cells. A portion of HS-anMan colocalized with nucleolin at small discrete sites, while most of the nucleolin and nascent RNA was dispersed. In U87 cells, HS-anMan, nucleolin and nascent RNA reassembled after prolonged hypoxia. Nucleolar HS may modulate synthesis and/or release of rRNA.
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16.
  • Ding, Kan, et al. (författare)
  • Copper-dependent autocleavage of glypican-1heparan sulfate by nitric oxide derived fromintrinsic nitrosothiols.
  • 2002
  • Ingår i: Journal of Biological Chemistry. - 1083-351X. ; 277:36, s. 33353-33360
  • Tidskriftsartikel (refereegranskat)abstract
    • Cell-surface heparan sulfate proteoglycans facilitate uptake of growth-promoting polyamines [ [Belting, M., Borsig, L., Fuster, M.M., Brown, J.R., Persson, L., Fransson,L.-. and Esko, J.D. (2002) Proc. Natl. Acad. Sci. U.S.A., 99, 371-376] ]. Increased polyamine uptake correlates with an increased number of positively charged N-unsubstituted glucosamine units in the otherwise polyanionic heparan sulfate chains of glypican-1. During intracellular recycling of glypican-1 there is an NO-dependent deaminative cleavage of heparan sulfate at these glucosamine units, which would eliminate the positive charges [ [Ding, K., Sandgren, S., Mani, K., Belting, M. and Fransson, L.-. (2001) J. Biol. Chem., 276, 46779-46791] ]. Here, using both biochemical and microscopic techniques, we have identified and isolated S-nitrosylated forms of glypican-1 as well as low-charged glypican-1 glycoforms containing heparan sulfate chains rich in N-unsubstituted glucosamines. The latter were converted to high-charged species upon treatment of cells with 1 mM L-ascorbate, which releases NO from nitrosothiols, resulting in deaminative cleavage of heparan sulfate at the N-unsubstituted glucosamines. S-nitrosylation and subsequent deaminative cleavage were abrogated by inhibition of a Cu 2+ /Cu + -redox cycle. Under cell-free conditions, purified, S-nitrosylated glypican-1 was able to autocleave its heparan sulfate chains when NO-release was triggered by L-ascorbate. The heparan sulfate fragments generated in cells during this auto-catalytic process contained terminal anhydromannose residues. We conclude that the core protein of glypican-1 can slowly accumulate NO as nitrosothiols while Cu 2+ is reduced to Cu +. Subsequent release of NO results in efficient deaminative cleavage of the heparan sulfate chains attached to the same core protein while Cu + is oxidized to Cu 2+.
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17.
  • Ding, Kan, et al. (författare)
  • Modulations of glypican-1 heparan sulfate structure by inhibition of endogenous polyamine synthesis. Mapping of spermine-binding sites and heparanase, heparin lyase, and nitric oxide/nitrite cleavage sites
  • 2001
  • Ingår i: Journal of Biological Chemistry. - 1083-351X. ; 276:50, s. 46779-46791
  • Tidskriftsartikel (refereegranskat)abstract
    • Cell surface heparan sulfate proteoglycans facilitate uptake of growth-promoting polyamines (Belting, M., Persson, S., and Fransson, L.-A. (1999) Biochem. J. 338, 317-323; Belting, M., Borsig, L., Fuster, M. M., Brown, J. R., Persson, L., Fransson, L.-A., and Esko, J. D. (2001) Proc. Natl. Acad. Sci. U. S. A., in press). Here, we have analyzed the effect of polyamine deprivation on the structure and polyamine affinity of the heparan sulfate chains in various glypican-1 glycoforms synthesized by a transformed cell line (ECV 304). Heparan sulfate chains of glypican-1 were either cleaved with heparanase at sites embracing the highly modified regions or with nitrite at N-unsubstituted glucosamine residues. The products were separated and further degraded by heparin lyase to identify sulfated iduronic acid. Polyamine affinity was assessed by chromatography on agarose substituted with the polyamine spermine. In heparan sulfate made by cells with undisturbed endogenous polyamine synthesis, free amino groups were restricted to the unmodified, unsulfated segments, especially near the core protein. Spermine high affinity binding sites were located to the modified and highly sulfated segments that were released by heparanase. In cells with up-regulated polyamine uptake, heparan sulfate contained an increased number of clustered N-unsubstituted glucosamines and sulfated iduronic acid residues. This resulted in a greater number of NO/nitrite-sensitive cleavage sites near the potential spermine-binding sites. Endogenous degradation by heparanase and NO-derived nitrite in polyamine-deprived cells generated a separate pool of heparan sulfate oligosaccharides with an exceptionally high affinity for spermine. Spermine uptake in polyamine-deprived cells was reduced when NO/nitrite-generated degradation of heparan sulfate was inhibited. The results suggest a functional interplay between glypican recycling, NO/nitrite-generated heparan sulfate degradation, and polyamine uptake.
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18.
  • Ding, Kan, et al. (författare)
  • N-unsubstituted glucosamine in heparan sulfate of recycling glypican-1 from suramin-treated and nitrite-deprived endothelial cells. mapping of nitric oxide/nitrite-susceptible glucosamine residues to clustered sites near the core protein
  • 2001
  • Ingår i: Journal of Biological Chemistry. - 1083-351X. ; 276:6, s. 3885-3894
  • Tidskriftsartikel (refereegranskat)abstract
    • We have analyzed the content of N-unsubstituted glucosamine in heparan sulfate from glypican-1 synthesized by endothelial cells during inhibition of (a) intracellular progression by brefeldin A, (b) heparan sulfate degradation by suramin, and/or (c) endogenous nitrite formation. Glypican-1 from brefeldin A-treated cells carried heparan sulfate chains that were extensively degraded by nitrous acid at pH 3.9, indicating the presence of glucosamines with free amino groups. Chains with such residues were rare in glypican-1 isolated from unperturbed cells and from cells treated with suramin and, surprisingly, when nitrite-deprived. However, when nitrite-deprived cells were simultaneously treated with suramin, such glucosamine residues were more prevalent. To locate these residues, chains were first cleaved at linkages to sulfated l-iduronic acid by heparin lyase and released fragments were separated from core protein carrying heparan sulfate stubs. These stubs were then cleaved off at sites linking N-substituted glucosamines to d-glucuronic acid. These fragments were extensively degraded by nitrous acid at pH 3.9. When purified proteoglycan isolated from brefeldin A-treated cells was incubated with intact cells, endoheparanase-catalyzed degradation generated a core protein with heparan sulfate stubs that were similarly sensitive to nitrous acid. We conclude that there is a concentration of N-unsubstituted glucosamines to the reducing side of the endoheparanase cleavage site in the transition region between unmodified and modified chain segments near the linkage region to the protein. Both sites as well as the heparin lyase-sensitive sites seem to be in close proximity to one another.
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19.
  • Ekman, Anna-Karin, et al. (författare)
  • Nasal Challenge with LPS Stimulates the Release of Macrophage Inflammatory Protein 1 alpha
  • 2009
  • Ingår i: International Archives of Allergy and Immunology. - : S. Karger AG. - 1423-0097 .- 1018-2438. ; 149:2, s. 154-160
  • Tidskriftsartikel (refereegranskat)abstract
    • Background: Bacterial infections can cause a variety of airway diseases. Toll-like receptors (TLRs) directly respond to the presence of microbes and partake in the innate immune defense. TLR4 is activated by lipopolysaccharide (LPS), and has been detected in sinonasal tissue, epithelial cells and various inflammatory cells. Macrophage inflammatory protein 1 alpha (MIP-1 alpha) is a chemokine released during the inflammatory process. The present study investigated the potential role and regulation of MIP-1 alpha in LPS-induced nasal inflammation. Methods: Thirty-two healthy individuals were intranasally challenged with LPS or vehicle. Nasal lavage was performed, followed by a nasal biopsy. Inflammatory cells were counted, MIP-1 alpha levels analyzed and expression of MIP-1 alpha mRNA in biopsies quantified. Neutrophils isolated from peripheral blood were treated with LPS and effects on MIP1 alpha release, cell survival, and the involved signal pathways, were investigated. Results: LPS challenge caused an increase of MIP-1 alpha in nasal lavage. No corresponding change in mRNA expression was seen in nasal biopsies, suggesting the increase was not due to epithelial synthesis. Neutrophil numbers increased after LPS provocation. Treatment of isolated neutrophils with LPS delayed neutrophil apoptosis and resulted in a time-and concentration-dependent release of MIP-1 alpha, which was reduced by inhibitors of transcription and of nuclear factor (NF)-kappa B, protein kinase C (PKC) and p38 MAPK pathways. Conclusions: Nasal LPS challenge results in release of MIP-1 alpha. The release most likely originates from recruited neutrophils, via NF-kappa B-, PKC-and p38 MAPK-dependent pathways. LPS stimulation delayed neutrophil apop tosis. MIP-1 alpha may constitute an important mediator in neutrophilic airway disease. Copyright (C) 2009 S. Karger AG, Basel
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20.
  • Ekman, A. -K., et al. (författare)
  • Systemic Up-Regulation of TLR4 Causes Lipopolysaccharide-Induced Augmentation of Nasal Cytokine Release in Allergic Rhinitis
  • 2012
  • Ingår i: International Archives of Allergy and Immunology. - : S. Karger AG. - 1423-0097 .- 1018-2438. ; 159:1, s. 6-14
  • Tidskriftsartikel (refereegranskat)abstract
    • Background: Allergic rhinitis is a systemic disorder, and it is clinically well recognized that it can be aggravated by infection. Activation of the innate immune system constitutes a critical element in the process. Toll-like receptors (TLRs) comprise a part of the innate immune system, and lipopolysaccharide (LPS)-induced activation of TLR4 represents bacterial-induced interactions in various model systems. The present study examines how TLR2 and TLR4 expression is affected by symptomatic allergic rhinitis, and if LPS added upon allergen affects nasal cytokine release. Methods: In patients with pollen-induced allergic rhinitis and healthy non-allergic volunteers, nasal lavage (NAL), peripheral blood and bone marrow were sampled before and during the pollen season. TLR2 and TLR4 expression was determined flow cytometrically. Changes in the TLR receptor expression pattern were evaluated by a nasal challenge with allergen followed by LPS, or vice versa. Symptoms along with cells and cytokines in NAL were analyzed. Results: TLR4 expression increased in leukocytes in NAL, peripheral blood and bone marrow during symptomatic allergic rhinitis. A similar increase was seen for TLR2 in neutrophils in blood. Nasal challenge with allergen followed by LPS augmented the release of IL-4, IL-5, IL-10, IL-13, IFN-gamma and TNF-alpha. Conclusion: A systemic up-regulation of TLR4 in symptomatic allergic rhinitis may explain why LPS preceded by allergen increases nasal cytokine release. Copyright (C) 2012 S. Karger AG, Basel
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21.
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22.
  • Ergon, Mattias, 1967-, et al. (författare)
  • Light curve and spectral modelling of the type IIb SN 2020acat. Evidence for a strong Ni bubble effect on the diffusion time
  • 2024
  • Ingår i: Astronomy and Astrophysics. - 0004-6361 .- 1432-0746. ; 683
  • Tidskriftsartikel (refereegranskat)abstract
    • We use the light-curve and spectral synthesis code JEKYLL to calculate a set of macroscopically mixed type IIb supernova (SN) models, which are compared to both previously published and new late-phase observations of SN 2020acat. The models differ in the initial mass, in the radial mixing and expansion of the radioactive material, and in the properties of the hydrogen envelope. The best match to the photospheric and nebular spectra and light curves of SN 2020acat is found for a model with an initial mass of 17 M⊙, strong radial mixing and expansion of the radioactive material, and a 0.1 M⊙ hydrogen envelope with a low hydrogen mass fraction of 0.27. The most interesting result is that strong expansion of the clumps containing radioactive material seems to be required to fit the observations of SN 2020acat both in the diffusion phase and in the nebular phase. These Ni bubbles are expected to expand due to heating from radioactive decays, but the degree of expansion is poorly constrained. Without strong expansion, there is a tension between the diffusion phase and the subsequent evolution, and models that fit the nebular phase produce a diffusion peak that is too broad. The diffusion-phase light curve is sensitive to the expansion of the Ni bubbles because the resulting Swiss-cheese-like geometry decreases the effective opacity and therefore the diffusion time. This effect has not been taken into account in previous light-curve modelling of stripped-envelope SNe, which may lead to a systematic underestimate of their ejecta masses. In addition to strong expansion, strong mixing of the radioactive material also seems to be required to fit the diffusion peak. It should be emphasized, however, that JEKYLL is limited to a geometry that is spherically symmetric on average, and large-scale asymmetries may also play a role. The relatively high initial mass found for the progenitor of SN 2020acat places it at the upper end of the mass distribution of type IIb SN progenitors, and a single-star origin cannot be excluded.
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23.
  • Ergon, Mattias, et al. (författare)
  • Monte-Carlo methods for NLTE spectral synthesis of supernovae
  • 2018
  • Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 620
  • Tidskriftsartikel (refereegranskat)abstract
    • We present JEKYLL, a new code for modelling of supernova (SN) spectra and lightcurves based on Monte-Carlo (MC) techniques for the radiative transfer. The code assumes spherical symmetry, homologous expansion and steady state for the matter, but is otherwise capable of solving the time-dependent radiative transfer problem in non-local-thermodynamic-equilibrium (NLTE). The method used was introduced in a series of papers by Lucy, but the full time-dependent NLTE capabilities of it have never been tested. Here, we have extended the method to include non-thermal excitation and ionization as well as charge-transfer and two-photon processes. Based on earlier work, the non-thermal rates are calculated by solving the Spencer-Fano equation. Using a method previously developed for the SUMO code, macroscopic mixing of the material is taken into account in a statistical sense. To save computational power a diffusion solver is used in the inner region, where the radiation field may be assumed to be thermalized. In addition, a statistical Markov-chain model is used to sample the emission frequency more efficiently, and we introduce a method to control the sampling of the radiation field, which is used to reduce the noise in the radiation field estimators. Except for a description of JEKYLL, we provide comparisons with the ARTIS, SUMO and CMFGEN codes, which show good agreement in the calculated spectra as well as the state of the gas. In particular, the comparison with CMFGEN, which is similar in terms of physics but uses a different technique, shows that the Lucy method does indeed converge in the time-dependent NLTE case. Finally, as an example of the time-dependent NLTE capabilities of JEKYLL, we present a model of a Type IIb SN, taken from a set of models presented and discussed in detail in an accompanying paper. Based on this model we investigate the effects of NLTE, in particular those arising from non-thermal excitation and ionization, and find strong effects even on the bolometric lightcurve. This highlights the need for full NLTE calculations when simulating the spectra and lightcurves of SNe.
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24.
  • Ergon, Mattias, et al. (författare)
  • Optical and near-infrared observations of SN 2011dh-The first 100 days
  • 2014
  • Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 562, s. A17-
  • Tidskriftsartikel (refereegranskat)abstract
    • We present optical and near-infrared (NIR) photometry and spectroscopy of the Type IIb supernova (SN) 2011dh for the first 100 days. We complement our extensive dataset with Swift ultra-violet (UV) and Spitzer mid-infrared (MIR) data to build a UV to MIR bolometric lightcurve using both photometric and spectroscopic data. Hydrodynamical modelling of the SN based on this bolometric lightcurve have been presented in Bersten et al. (2012, ApJ, 757, 31). We find that the absorption minimum for the hydrogen lines is never seen below similar to 11 000 km s(-1) but approaches this value as the lines get weaker. This suggests that the interface between the helium core and hydrogen rich envelope is located near this velocity in agreement with the Bersten et al. (2012) He4R270 ejecta model. Spectral modelling of the hydrogen lines using this ejecta model supports the conclusion and we find a hydrogen mass of 0.01-0.04 M-circle dot to be consistent with the observed spectral evolution. We estimate that the photosphere reaches the helium core at 5-7 days whereas the helium lines appear between similar to 10 and similar to 15 days, close to the photosphere and then move outward in velocity until similar to 40 days. This suggests that increasing non-thermal excitation due to decreasing optical depth for the gamma-rays is driving the early evolution of these lines. The Spitzer 4.5 mu m band shows a significant flux excess, which we attribute to CO fundamental band emission or a thermal dust echo although further work using late time data is needed. The distance and in particular the extinction, where we use spectral modelling to put further constraints, is discussed in some detail as well as the sensitivity of the hydrodynamical modelling to errors in these quantities. We also provide and discuss pre- and post-explosion observations of the SN site which shows a reduction by similar to 75 percent in flux at the position of the yellow supergiant coincident with SN 2011dh. The B, V and r band decline rates of 0.0073, 0.0090 and 0.0053 mag day(-1) respectively are consistent with the remaining flux being emitted by the SN. Hence we find that the star was indeed the progenitor of SN 2011dh as previously suggested by Maund et al. (2011, ApJ, 739, L37) and which is also consistent with the results from the hydrodynamical modelling.
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25.
  • Ergon, Mattias, 1967- (författare)
  • SN 2011dh and the progenitors of Type IIb supernovae
  • 2015
  • Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • Core-collapse supernovae (SNe) are the observed events following the collapse of the core of evolved massive stars. The gravitational energy released creates a powerful shock that disrupts the star and ejects the heated material into the surrounding circumstellar medium. The observed properties depend on the mass lost by the star, e.g. through stellar winds or mass transfer in binary systems, and the subject of this thesis is the class of Type IIb SNe, which are thought to have lost most, but not all of their hydrogen envelopes. A quite unique set of observations has recently been obtained for the Type IIb SN 2011dh, which was followed to more than a thousand days after the explosion, and observed by several groups at a wide range of wavelengths. In this work, the bulk portion of the ultraviolet to mid-infrared observations, as well as pre-explosion images of the progenitor star, are presented, discussed, and analysed. Lightcurve and spectral modelling of the SN observations, presented in this and related works, all suggest a progenitor of modest initial mass (<15 solar masses) with an extended and low-mass hydrogen envelope, consistent with what is found from the pre-explosion observations. Although mass-loss rates for single stars are uncertain, they are likely too weak to expel the hydrogen envelope for stars in this mass range. Therefore, an appealing alternative is mass-loss by Roche-lobe overflow in a binary system, as was likely the case for the Type IIb SN 1993J. Post-explosion observations have revealed a blue compact companion star blended with the fading SN 1993J, and a similar result has been claimed for SN 2011dh. The fact that some SNe arise from binary systems is not surprising given the large binary fraction observed for massive stars, and in this work, a grid of hydrodynamical SN models is used to infer modest initial masses (<15 solar masses) for most Type IIb SNe documented in the literature, suggesting that binary systems actually dominate the production of Type IIb SNe.
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26.
  • Ergon, Mattias, 1967-, et al. (författare)
  • Spectral modelling of Type IIb supernovae Comparison with SN 2011dh and the effect of macroscopic mixing
  • 2022
  • Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 666
  • Tidskriftsartikel (refereegranskat)abstract
    • We use the new non-local-thermodynamical-equilibrium (NLTE) light curve and spectral synthesis code JEKYLL to evolve a macro-scopically mixed ejecta model of a Type IIb supernova (SN) originating from a star with an initial mass of 12 M⊙ through the photospheric and nebular phase. The ejecta model is adopted from earlier work and has a mass of 1.7 M⊙, has a kinetic energy of 0.7 foe, and contains 0.075 M⊙ of 56Ni. The macroscopic mixing is simulated through a statistical representation of ejecta fragmented into small clumps but spherically symmetric on average. We compare our model with SN 2011dh and find that both the spectra and the light curves are well reproduced in both the photospheric and nebular phase, although there are also some differences. Our work further strengthens the evidence that this SN originated from a star with an initial mass of ~12 M⊙ that had lost all but a tiny (<0.1 M⊙) fraction of its hydrogen envelope, strongly suggesting a binary origin. We also investigate the effects of the macroscopic mixing by comparing macroscopically and microscopically mixed models and by varying the clumping geometry. In the photospheric phase, we find strong effects on the effective opacity in the macroscopically mixed regions, which affects the model light curves. The diffusion peak is considerably narrower (rise time decreased by 11%) in the macroscopically mixed case and differs strongly (rise time decreased by 29%) if the radioactive material in the helium envelope is allowed to expand more than in our standard model. The effect is mainly geometrical and is driven by the expansion of the clumps that contain radioactive material, which tend to decrease the effective opacity. In the limit of optically thick clumps, the decrease is roughly given by the product of the (volume) expansion and filling factors for the radioactive material, and in our models values up to ~8 are explored. These findings have implications for light curve modelling of stripped-envelope SNe in general, and the effect would increase the estimated ejecta masses. In the nebular phase, we find strong effects on the collisional cooling rates in the macroscopically mixed regions, which affects lines driven by collisional cooling, in particular the [Ca II] 7291, 7323 Å and [O I] 6300, 6364 Å lines. The effect is mainly related to differences in composition between macroscopically and microscopically mixed ejecta. As these lines are often used for mass determinations, this highlights the importance of how and to what extent the calcium- and oxygen-rich material is mixed. As shown in this and earlier work, both NLTE and macroscopic mixing are essential ingredients for accurately modelling the light curves and spectra of Type IIb SNe throughout their evolution.
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27.
  • Ergon, Mattias, et al. (författare)
  • The Type IIb SN 2011dh : Two years of observations and modelling of the lightcurves
  • 2015
  • Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 580
  • Tidskriftsartikel (refereegranskat)abstract
    • We present optical and near-infrared (NIR) photometry and spectroscopy as well as modelling of the lightcurves of the Type IIb supernova (SN) 2011dh. Our extensive dataset, for which we present the observations obtained after day 100, spans two years, and complemented with Spitzer mid-infrared (MIR) data, we use it to build an optical-to-MIR bolometric lightcurve between days 3 and 732. To model the bolometric lightcurve before day 400 we use a grid of hydrodynamical SN models, which allows us to determine the errors in the derived quantities, and a bolometric correction determined with steady-state non-local thermodynamic equilibrium (NLTE) modelling. Using this method we find a helium core mass of 3.1+0.7-0.4 M⊙ for SN 2011dh, consistent within error bars with previous results obtained using the bolometric lightcurve before day 80. We compute bolometric and broad-band lightcurves between days 100 and 500 from spectral steady-state NLTE models, presented and discussed in a companion paper. The preferred 12 M⊙ (initial mass) model, previously found to agree well with the observed spectra, shows a good overall agreement with the observed lightcurves, although some discrepancies exist. Time-dependent NLTE modelling shows that after day ~600 a steady-state assumption is no longer valid. The radioactive energy deposition in this phase is likely dominated by the positrons emitted in the decay of 56Co, but seems insufficient to reproduce the lightcurves, and what energy source is dominating the emitted flux is unclear. We find an excess in the K and the MIR bands developing between days 100 and 250, during which an increase in the optical decline rate is also observed. A local origin of the excess is suggested by the depth of the He I 20 581 Å absorption. Steady-state NLTE models with a modest dust opacity in the core (τ = 0.44), turned on during this period, reproduce the observed behaviour, but an additional excess in the Spitzer 4.5 μm band remains. Carbon-monoxide (CO) first-overtone band emission is detected at day 206, and possibly at day 89, and assuming the additional excess to bedominated by CO fundamental band emission, we find fundamental to first-overtone band ratios considerably higher than observed in SN 1987A. The profiles of the [O I] 6300 Å and Mg I] 4571 Å lines show a remarkable similarity, suggesting that these lines originate from a common nuclear burning zone (O/Ne/Mg), and using small scale fluctuations in the line profiles we estimate a filling factor of ≲0.07 for the emitting material. This paper concludes our extensive observational and modelling work on SN 2011dh. The results from hydrodynamical modelling, steady-state NLTE modelling, and stellar evolutionary progenitor analysis are all consistent, and suggest an initial mass of ~12 M⊙ for the progenitor.
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28.
  • Fransson, Claes, et al. (författare)
  • HIGH-DENSITY CIRCUMSTELLAR INTERACTION IN THE LUMINOUS TYPE IIn SN 2010jl : THE FIRST 1100 DAYS
  • 2014
  • Ingår i: Astrophysical Journal. - 0004-637X .- 1538-4357. ; 797:2
  • Tidskriftsartikel (refereegranskat)abstract
    • Hubble Space Telescope and ground-based observations of the Type IIn supernova (SN) 2010jl are analyzed, including photometry and spectroscopy in the ultraviolet, optical, and near-IR bands, 26-1128 days after first detection. At maximum, the bolometric luminosity was similar to 3 x 10(43) erg s(-1) and even at 850 days exceeds 10(42) erg s(-1). A near-IR excess, dominating after 400 days, probably originates in dust in the circumstellar medium (CSM). The total radiated energy is greater than or similar to 6.5x10(50) erg, excluding the dust component. The spectral lines can be separated into one broad component that is due to electron scattering and one narrow with expansion velocity similar to 100 km s(-1) from the CSM. The broad component is initially symmetric around zero velocity but becomes blueshifted after similar to 50 days, while remaining symmetric about a shifted centroid velocity. Dust absorption in the ejecta is unlikely to explain the line shifts, and we attribute the shift instead to acceleration by the SN radiation. From the optical lines and the X-ray and dust properties, there is strong evidence for large-scale asymmetries in the CSM. The ultraviolet lines indicate CNO processing in the progenitor, while the optical shows a number of narrow coronal lines excited by the X-rays. The bolometric light curve is consistent with a radiative shock in an r(-2) CSM with a mass-loss rate of M similar to 0.1 M(circle dot)yr(-1). The total mass lost is greater than or similar to 3 M-circle dot. These properties are consistent with the SN expanding into a CSM characteristic of a luminous blue variable progenitor with a bipolar geometry. The apparent absence of nuclear processing is attributed to a CSM that is still opaque to electron scattering.
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29.
  • Fransson, Erik, 1990, et al. (författare)
  • Dynasor - A Tool for Extracting Dynamical Structure Factors and Current Correlation Functions from Molecular Dynamics Simulations
  • 2021
  • Ingår i: Advanced Theory and Simulations. - : Wiley. - 2513-0390. ; 4:2
  • Tidskriftsartikel (refereegranskat)abstract
    • Perturbative treatments of the lattice dynamics are widely successful for many crystalline materials; however, their applicability is limited for strongly anharmonic systems, metastable crystal structures and liquids. The full dynamics of these systems can, however, be accessed via molecular dynamics (MD) simulations using correlation functions, which includes dynamical structure factors providing a direct bridge to experiment. To simplify the analysis of correlation functions, here the dynasor package is presented as a flexible and efficient tool that enables the calculation of static and dynamical structure factors, current correlation functions as well as their partial counterparts from MD trajectories. The dynasor code can handle input from several major open source MD packages and thanks to its C/Python structure can be readily extended to support additional codes. The utility of dynasor is demonstrated via examples for both solid and liquid single and multi-component systems. In particular, the possibility to extract the full temperature dependence of phonon frequencies and lifetimes is emphasized.
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30.
  • Fransson, J.E.S., et al. (författare)
  • Detection of clear-cuts using ALOS PALSAR satellite images
  • 2008
  • Ingår i: Proceedings of the European Conference on Synthetic Aperture Radar, EUSAR. - 2197-4403. ; 1-4
  • Konferensbidrag (refereegranskat)abstract
    • The objective of this study is to make a first evaluation of the possibilities to detect forest clear-cuts using high-resolution ALOS PALSAR FBD (Fine Beam Dual polarization) satellite images. New operational applications for mapping of changes in forest cover are of interest for government authorities in Sweden and in other countries with similar needs. The study was conducted in southern Sweden and included seven old coniferous stands located on flat terrain. Three of the stands were clear-felled and the remaining stands were left untreated for reference. Altogether, six PALSAR FBD images (look angle 34.3°, HH- and HV-polarization) acquired during the summer and fall seasons were analyzed. The difference in backscattering coefficient between the reference and the clear-felled stands was on average 2.4 dB and 2.9 dB for the HH- and HV-polarization, respectively. When comparing the backscattering coefficient before and after clear-felling the drop was found to be 1.7 dB and 2.3 dB for the HH- and HV-polarization, respectively.
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31.
  • Fransson, Liisa, et al. (författare)
  • A regional perspective on present and future soil chemistry at 16 Swedish forest sites
  • 2005
  • Ingår i: Water, Air and Soil Pollution. - : Springer Science and Business Media LLC. - 1573-2932 .- 0049-6979. ; 162:1-4, s. 89-105
  • Tidskriftsartikel (refereegranskat)abstract
    • Assessing the timescales of recovery, by the use of dynamic models, will be used as input to the policy process to abate acidification. In this study the multilayer dynamic soil chemistry model SAFE was applied to 16 forest sites in Sweden, covering a sulfur deposition gradient of 1.2-11 kg S/ha/yr. Soil samples were collected at all sites and the pH and sulfate concentration dependent isotherm, used for modeling sulfate adsorption in SAFE, was parameterized for every site. A new way of implementing the nutrient uptake distribution in SAFE was developed, which allows the uptake distribution between layers in the rooting zone to vary with time, depending on the availability of base cations in the individual layers. Model output was compared to measurements of base cation concentration, total inorganic Al, pH and Bc/Al both site-by-site and cumulatively for all sites, and the usefulness of these comparisons is discussed from a policy viewpoint. Future projections of recovery show that the overall recovery, expressed as minimum Bc/Al ratio > 1 in the rooting zone, is slow. Assuming full implementation of the UNECE LRTAP Gothenburg Protocol and no further emission reductions thereafter, 44% of the modeled sites still have a Bc/Al ratio below 1 in 2100 in some soil layer within the rooting zone.
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32.
  • Fransson, Liisa, et al. (författare)
  • Parameterization and evaluation of sulfate adsorption in a dynamic soil chemistry model.
  • 2003
  • Ingår i: Environmental Pollution. - 0269-7491. ; 124:1, s. 119-125
  • Tidskriftsartikel (refereegranskat)abstract
    • Sulfate adsorption was implemented in the dynamic, multi-layer soil chemistry model SAFE. The process is modeled by an isotherm in which sulfate adsorption is considered to be fully reversible and dependent on sulfate concentration as well as pH in soil solution. The isotherm was parameterized by a site-specific series of simple batch experiments at different pH (3.8–5.0) and sulfate concentration (10–260 mol l−1) levels. Application of the model to the Lake Gårdsjön roof covered site shows that including sulfate adsorption improves the dynamic behavior of the model and sulfate adsorption and desorption delay acidification and recovery of the soil. The modeled adsorbed pool of sulfate at the site reached a maximum level of 700 mmol/m2 in the late 1980s, well in line with experimental data.
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33.
  • Fransson, Liisa, et al. (författare)
  • The effect of changes in natural and anthropogenic deposition on modelling recovery from acidification.
  • 2003
  • Ingår i: Hydrology and Earth System Sciences. - 1607-7938. ; 7:5, s. 766-776
  • Tidskriftsartikel (refereegranskat)abstract
    • The mufti-layer dynamic soil chemistry SAFE model was used to study the dynamics of recovery in the F1 catchment at Lake Gardsjon, Sweden. The influence of (F) sulphate adsorption, and (2) changes in marine deposition, oil model predictions of recovery was studied. Sulphate adsorption/desorption in SAFE is modeled by all isotherm in which sulphate adsorption is dependent oil both the sulphate concentration and the pH in the soil solution. This isotherm was parameterised for the B-horizon of F1 for the sulphate concentration range 10-260 mumol(-1) and the pH range 3.8-5.0. Sulphate adsorption/desorption as the only soil process involving sulphate is adequate to predict sulphate in run-off at F1. Adding the process caused time-delays in sulphate concentration in run-off of only 1-2 years. which was Much shorter than previously seen in the adjacent G1 catchment. The location of Lake Gardsjon. approximately 15 km inland from the Swedish west coast, ensures that the marine deposition to the area is high. Model Output showed that the temporal variation in marine deposition has a considerable impact oil the run-off-chemistry. Such changes in marine deposition are difficult to foresee and their influence on modelled run-off-chemistry, can be large when soils start to recover as the previously high concentrations of anthropogenic sulphate in the soil solution decrease.
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34.
  • Fransson, Liisa, et al. (författare)
  • The importance of including the pH dependence of sulfate adsorption in a dynamic soil chemistry model
  • 2004
  • Ingår i: Water, Air and Soil Pollution. - 1573-2932. ; 154:1-4, s. 349-356
  • Tidskriftsartikel (refereegranskat)abstract
    • Sulfate adsorption is an important process when modeling the dynamics of recovery from acidification. In the dynamic soil chemistry model SAFE sulfate adsorption is modeled by a pH and sulfate concentration dependent isotherm. This isotherm has been parameterized by fitting it to data from batch experiments on soil samples using multiple linear regression. The soil samples were from the B-horizon from three sites, two from the Lake Gardsjon area in south-west Sweden and one from southern Poland. The pH dependency of sulfate adsorption is important. The batch experiments show that the adsorbed amount, at a specific sulfate concentration, increases considerably with decreasing pH. This implies that the adsorbed pool of anthropogenic sulfate in soils may remain fairly high during the recovery phase. Although a decrease of sulfate concentration is commonly seen, the modeled pH increase is often slow, and thus delays in the modeled desorption of anthropogenic sulfate can be expected.
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35.
  • Fransson, Lars-Åke, et al. (författare)
  • Novel aspects of glypican glycobiology.
  • 2004
  • Ingår i: Cellular and Molecular Life Sciences. - : Springer Science and Business Media LLC. - 1420-9071 .- 1420-682X. ; 61:9, s. 1016-1024
  • Forskningsöversikt (refereegranskat)abstract
    • Mutations in glypican genes cause dysmorphic and overgrowth syndromes in men and mice, abnormal development in flies and worms, and defective gastrulation in zebrafish and ascidians. All glypican core proteins share a characteristic pattern of 14 conserved cysteine residues. Upstream from the C-terminal membrane anchorage are 3–4 heparan sulfate attachment sites. Cysteines in glypican-1 can become nitrosylated by nitric oxide in a copper-dependent reaction. When glypican-1 is exposed to ascorbate, nitric oxide is released and participates in deaminative cleavage of heparan sulfate at sites where the glucosamines have a free amino group. This process takes place while glypican-1 recycles via a nonclassical, caveolin-1-associated route. Glypicans are involved in growth factor signalling and transport, e.g. of polyamines. Cargo can be unloaded from heparan sulfate by nitric oxide-dependent degradation. How glypican and its degradation products and the cargo exit from the recycling route is an enigma.
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36.
  • Fransson, Mattias, et al. (författare)
  • A role for neutrophils in intermittent allergic rhinitis
  • 2004
  • Ingår i: Acta Otolaryngol. - : Informa UK Limited. - 0001-6489 .- 1651-2251. ; 124:5, s. 616-20
  • Tidskriftsartikel (refereegranskat)abstract
    • OBJECTIVE: In patients with intermittent allergic rhinitis, allergen challenge may induce both early- and late-phase responses. The aim of this study was to examine the correlation between inflammatory cells in the nasal lavage fluid and clinical parameters following pollen challenge. MATERIAL AND METHODS: Nasal lavage fluids were obtained from 29 patients with intermittent allergic rhinitis before and 1 and 6 h after allergen provocation, representing the control, early and late phases, respectively. Symptom and rhinoscopic scores were registered on the same occasions. Inflammatory cells were determined in the nasal fluid. RESULTS: The early phase was characterized by increased symptom scores, rhinoscopic signs of oedema and secretion and neutrophilia. In the late phase, symptom scores had diminished, but the signs of ongoing secretion remained. Both the total nasal symptom score and the secretion score correlated with the number of neutrophils in lavage fluids at 1 h. The eosinophil count did not increase during the early or late phases. CONCLUSION: A single allergen provocation induces an early-phase response dominated by neutrophils, with secretion being the only clinical sign remaining during the late phase. The increase in neutrophil numbers correlated with the registration of secretory symptoms. The presented data indicate a role for neutrophils in intermittent allergic rhinitis and their relation with secretory parameters makes it intriguing to speculate that neutrophils may function as promoters of nasal secretion.
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37.
  • Fransson, Mattias, et al. (författare)
  • Expression of Toll-like receptor 9 in nose, peripheral blood and bone marrow during symptomatic allergic rhinitis.
  • 2007
  • Ingår i: Respiratory research. - : Springer Science and Business Media LLC. - 1465-993X .- 1465-9921. ; 8
  • Tidskriftsartikel (refereegranskat)abstract
    • BACKGROUND: Allergic rhinitis is an inflammatory disease of the upper airway mucosa that also affects leukocytes in bone marrow and peripheral blood. Toll-like receptor 9 (TLR9) is a receptor for unmethylated CpG dinucleotides found in bacterial and viral DNA. The present study was designed to examine the expression of TLR9 in the nasal mucosa and in leukocytes derived from different cellular compartments during symptomatic allergic rhinitis. METHODS: The study was based on 32 patients with seasonal allergic rhinitis and 18 healthy subjects, serving as controls. Nasal biopsies were obtained before and after allergen challenge. Bone marrow, peripheral blood and nasal lavage fluid were sampled outside and during pollen season. The expression of TLR9 in tissues and cells was analyzed using immunohistochemistry and flow cytometry, respectively. RESULTS: TLR9 was found in several cell types in the nasal mucosa and in different leukocyte subpopulations derived from bone marrow, peripheral blood and nasal lavage fluid. The leukocyte expression was generally higher in bone marrow than in peripheral blood, and not affected by symptomatic allergic rhinitis. CONCLUSION: The widespread expression of TLR9 in the nasal mucosa along with its rich representation in leukocytes in different compartments, demonstrate the possibility for cells involved in allergic airway inflammation to directly interact with bacterial and viral DNA.
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38.
  • Fransson, Mattias, et al. (författare)
  • Lipopolysaccharide-induced down-regulation of uteroglobin in the human nose.
  • 2007
  • Ingår i: Acta Oto-Laryngologica. - : Informa UK Limited. - 1651-2251 .- 0001-6489. ; 127:3, s. 285-291
  • Tidskriftsartikel (refereegranskat)abstract
    • Conclusion. Lipopolysaccharide (LPS) challenge of the human nose has the capacity to reduce the amount of natural anti-inflammatory proteins, such as uteroglobin. Objectives. Nasal challenge with LPS, an activator of innate immunity, has been shown to increase the amount of pro-inflammatory mediators in nasal lavage fluid. Uteroglobin is a newly described anti-inflammatory mediator that is secreted in the nose. This study examined the effect of nasal LPS application on the level of uteroglobin in nasal lavage fluid as well as on the expression of uteroglobin in nasal mucosa. Materials and methods. Thirty-eight volunteers were challenged nasally with either 50 mu g LPS or vehicle; 6 h later, nasal lavage fluid was collected and a nasal biopsy was obtained. Levels of uteroglobin, albumin and the pro-inflammatory mediators interleukin (IL)-6 and IL-8 were analysed in the lavage fluids using enzyme-linked immunosorbent assays (ELISAs). Biopsies were used for either quantification of uteroglobin mRNA by real-time PCR or for localization of the corresponding protein with immunohistochemistry. Results. The uteroglobin level decreased in nasal lavage fluid following LPS challenge, whereas the levels of IL-6 and albumin increased. Uteroglobin was mainly seen in the respiratory epithelium and its mRNA expression decreased as a consequence of the LPS challenge.
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39.
  • Fransson, Mattias (författare)
  • Toll-like Receptors in Allergic Rhinitis
  • 2006
  • Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • Allergic rhinitis is an inflammatory disorder with the characteristic symptoms itching, sneezing, secretion and blockage upon allergen contact. In addition to the local inflammation in the nose, there is a systemic component that influences peripheral blood, bone marrow and lungs. The immune system is conventionally divided into innate and acquired (adaptive) immunity. The former is important in the early phase of the defense against previously unknown intruders, since there is a delay of 4-7 days for a full function of the adaptive immunity. Repeated encounters with the same antigen will result in a faster and more effective response of the adaptive immunity. Development of allergic airway inflammation is traditionally related to T helper type 2 (Th2) lymphocytes and their production of inflammatory cytokines as a part of the adaptive immunity, but recent data suggest that the innate immunity might also have a role in this process. Toll-like receptors (TLRs) have emerged as key receptors of the innate immune system but information about their role in allergy and airway inflammation is so far limited. The aims of the present study were to investigate the expression of TLR2, TLR3, TLR4 and TLR9 in the nose, peripheral blood and bone marrow, and to find out if pollen encounter affects the local and systemic expression of these proteins. The effects of nasal provocation with lipopolysaccharide (LPS), a ligand to TLR4, were investigated and the functional activity of TLR3 in eosinophils was explored in a series of in vitro experiments. In the six studies included in this thesis, a total of 111 patients with allergic rhinitis and 55 healthy volunteers were investigated. Samples of nasal mucosa, nasal lavage fluid, peripheral blood and bone marrow were examined using enzyme-linked immunosorbent assay (ELISA), real-time polymerase chain reaction (RT-PCR), immunohistochemistry and flow cytometry. TLR2, TLR3, TLR4 and TLR9 were found in the nasal epithelium and in inflammatory cells in the submucosa, and TLR2, TLR4 and TLR9 were expressed in neutrophils in nasal lavage fluid. In bone marrow, TLR2, TLR3, TLR4 and TLR9 were found in neutrophils, eosinophils, monocytes and immature granulocytes. These TLRs also appeared in peripheral blood, except for the absence of TLR3 in neutrophils. In addition, TLR9 was seen in basophils and lymphocytes. Generally, the leukocyte expression of TLRs was higher in nasal lavage fluid compared to bone marrow, where it in turn was higher than in peripheral blood. Stimulation of isolated eosinophils with the TLR3 agonist polyinosinic-polycytidylic acid (poly(I:C)), resulted in an enhanced expression of CD11b and release of interleukin (IL)-8, involving the intracellular pathways of p38 mitogen-activated protein kinase (MAPK) and nuclear factor kappa B (NF-?B). Nasal provocation with the TLR4 ligand LPS resulted in leukocyte recruitment and increase in IL-6 and albumin in nasal lavage fluid after 6 hours. In addition, it caused a reduction in the tissue expression and the nasal lavage fluid levels of the anti-inflammatory mediator uteroglobin. Nasal pollen challenge in allergic patients resulted in an increased amount of neutrophils in nasal lavage fluid after one hour and an increased expression of TLR2, TLR3 and TLR4 in the nasal epithelium after 24 hours. Patients with seasonal allergic rhinitis had an activated expression of TLR4 in neutrophils, eosinophils and monocytes in peripheral blood during pollen season. Similarly, an activated expression of TLR4 was found in immature granulocytes and neutrophils in bone marrow and in neutrophils in nasal lavage fluid. The expression of TLR3 in eosinophils decreased in peripheral blood and bone marrow during pollen season, whereas the expression of TLR9 was not affected by allergen exposure. The present findings that pollen-induced upper airway inflammation affects the expression of TLRs locally and systemically, support the idea of a role for the innate immune system during symptomatic allergic rhinitis.
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40.
  • Fransson, Mattias, et al. (författare)
  • Up-regulation of Toll-like receptors 2, 3 and 4 in allergic rhinitis
  • 2005
  • Ingår i: Respiratory Research. - : Springer Science and Business Media LLC. - 1465-9921 .- 1465-993X. ; 6:100
  • Tidskriftsartikel (refereegranskat)abstract
    • BACKGROUND: Toll-like receptors enable the host to recognize a large number of pathogen-associated molecular patterns such as bacterial lipopolysaccharide, viral RNA, CpG-containing DNA and flagellin. Toll-like receptors have also been shown to play a pivotal role in both innate and adaptive immune responses. The role of Toll-like receptors as a primary part of our microbe defense system has been shown in several studies, but their possible function as mediators in allergy and asthma remains to be established. The present study was designed to examine the expression of Toll-like receptors 2, 3 and 4 in the nasal mucosa of patients with intermittent allergic rhinitis, focusing on changes induced by exposure to pollen. METHODS: 27 healthy controls and 42 patients with seasonal allergic rhinitis volunteered for the study. Nasal biopsies were obtained before and during pollen season as well as before and after allergen challenge. The seasonal material was used for mRNA quantification of Toll-like receptors 2, 3 and 4 with real-time polymerase chain reaction, whereas specimens achieved in conjunction with allergen challenge were used for immunohistochemical localization and quantification of corresponding proteins. RESULTS: mRNA and protein representing Toll-like receptors 2, 3 and 4 could be demonstrated in all specimens. An increase in protein expression for all three receptors could be seen following allergen challenge, whereas a significant increase of mRNA only could be obtained for Toll-like receptor 3 during pollen season. CONCLUSION: The up-regulation of Toll-like receptors 2, 3 and 4 in the nasal mucosa of patients with symptomatic allergic rhinitis supports the idea of a role for Toll-like receptors in allergic airway inflammation.
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41.
  • Fransson, Nathalie, et al. (författare)
  • Emissionsfaktorer för bränslen till el- och värmeproduktion
  • 2020
  • Rapport (övrigt vetenskapligt/konstnärligt)abstract
    • Projektet har tagit fram uppdaterade och aktuella emissionsfaktorer (växthusgasutsläpp) och primärenergifaktorer för biogas, HVO, RME och energitorv som används till el- och värmeproduktion för svenska förhållanden. Emissionsfaktorerna redovisas i g koldioxid-ekvivalenter per MJ bränsle och primärenergi som MJ per MJ bränsle. Resultaten baseras på publicerade data och har valts ut med hjälp av uppsatta kriterier i Miljöfaktaboken 2011. För HVO, RME och biogas redovisas emissionsfaktorer uppdelade på utsläpp från energiomvandling respektive utsläpp från produktion och distribution. För torv tillämpas en metod där torvens nettoutsläpp från hela livscykeln beräknas och visar på ett spann baserat på vilken typ av mark som tas i bruk, efterbehandling av marken samt val av tidsperspektiv. Rapporten visar att den åtgärdsareal som behövs för att kompensera årliga utsläpp av energitorv skördad på en hektar varierar stort. Den minsta arealen som krävs är 1,2–1,4 ha om åtgärden är att återväta tidigare jordbruksmark till sjöliknande förhållanden för att kompensera för utsläpp som uppstått då torv skördats från näringsrik torvmark utan skog. För andra markexempel och åtgärder kan arealen som behövs för att kompensera utsläppen uppgå till 200 ha. Två olika synsätt för miljövärdering av rökgaskondensering lyfts fram i rapporten, ett bokföringsperspektiv och ett konsekvensperspektiv.
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42.
  • Fransson, Susanne, 1975, et al. (författare)
  • p37δ is a new isoform of PI3K p110δ that increases cell proliferation and is overexpressed in tumors
  • 2012
  • Ingår i: Oncogene. - : Nature Publishing Group. - 0950-9232 .- 1476-5594. ; 31:27, s. 3277-3286
  • Tidskriftsartikel (refereegranskat)abstract
    • The phosphatidylinositol 3-kinases (PI3Ks) regulate cell growth, proliferation and survival, and are frequently affected in human cancer. PI3K is composed of a catalytic subunit, p110, and a regulatory subunit, p85. The PI3K catalytic subunit p110δ is encoded by PIK3CD and contains p85- and RAS-binding domains, and a kinase domain. Here we present an alternatively spliced PIK3CD transcript encoding a previously unknown protein, p37δ, and demonstrate that this protein is expressed in human ovarian and colorectal tumors. p37δ retains the p85-binding domain and a fraction of the RAS-binding domain, lacks the catalytic domain, and has a unique carboxyl-terminal region. In contrast to p110δ, which stabilizes p85, p37δ promoted p85 sequestering. Despite the truncated RAS-binding domain, p37δ bound to RAS and we found a strong positive correlation between the protein levels of p37δ and RAS. Overexpressing p37δ, but not p110δ, increased the proliferation and invasive properties of HEK-293 cells and mouse embryonic fibroblasts. Cells overexpressing p37δ showed a quicker phosphorylation response of AKT and ERK1/2 following serum stimulation. Ubiquitous expression of human p37δ in the fruit fly increased body size, DNA content and phosphorylated ERK1/2 levels. Thus, p37δ appears to be a new tumor-specific isoform of p110δ with growth-promoting properties.
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43.
  • Fransson, Åsa, 1971, et al. (författare)
  • Characterization of fractured crystalline rock: two Swedish in situ field experiments
  • 2014
  • Ingår i: 1st International Discrete Fracture Network Engineering Conference, 20-22 oct 2014, Vancouver, Canada.
  • Konferensbidrag (refereegranskat)abstract
    • Construction of a nuclear waste repository requires information and an understanding of the fractured rock. The Swedish concept for nuclear waste deposition that is currently being developed by the Swedish Nuclear Fuel and Waste Management Co (SKB) includes a natural barrier in the form of crystalline rock, and engineered barriers in the form of bentonite and a copper canister. This paper aims to present two in situ field experiments: the first is the Large fractures experiment and the second is BRIE, the Bentonite Rock Interaction Experiment. Important issues include possible deformation (shearing) of fractures and deformation zones influencing the localization of canisters, and fluid flow, resulting in hydration of the bentonite. The aim of Large fractures is to further develop strategies and integrated investigation and modelling methodology for the identification and characterization of geological structures to ensure that (size) determination of large fractures or minor deformation zones to a greater extent can be based on real properties and to a lesser degree on a criterion related to the existence of a full perimeter fracture – tunnel intersection. BRIE is a field experiment which addresses the hydraulic interaction between the system components of compacted bentonite and the near-field host rock composed of hard and fractured bedrock. The above experiments are presented in terms of investigations performed to obtain discrete fracture descriptions. Grouting of fractures intersecting the investigation borehole of the Large fractures experiment was designed based on field data and a decrease in flow from above 200 liters/min to below 1 liter/min was achieved. The magnitude of the transmissivity of the fracture/deformation zone that was grouted indicates a large fracture size. This is also indicated by the ongoing integrated interpretation (geology, hydrogeology and geophysics). Results from BRIE show that hydration is uneven and is controlled by the main conductive fracture, highlighting the need for a relevant fracture description.
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44.
  •  
45.
  • Freyhult, Lisa, 1977-, et al. (författare)
  • Working with context rich problems to teach problem solving
  • 2017
  • Ingår i: Transforming patterns through the scholarship of teaching and learning.
  • Konferensbidrag (refereegranskat)abstract
    • The ability to solve problems is an important ability for scientists as well as engineers and something we identify as a key competence for our students. Problem solving is often examined but still students complain about the difficulty of the examination, describing the problems as more difficult than the problems they have encountered previously.Our study suggests that our students often use inefficient strategies for problem solving, like pattern matching or trying to find a mathematical formula that fits the situation. It is clear that these strategies will not work and they become less and less useful the further the students get in their education.To train problem solving and to prepare students to handle unknown problems and situations cooperative problem solving and context rich problems have been identified as efficient strategies [1,2]. These methods have specifically been used in early courses in mechanics and similar experiences with open ended but shorter problems have been described in [3,4,5]. We have applied these strategies in a more advanced course in Lagrangian mechanics. Students perceive this topic as somewhat abstract and disconnected from everyday experience and lack a clear relevance to their professional role. We describe our work as a team of teachers and our experience introducing a new methodology in the course with the goal to teach in a way that discourages inefficient problem solving strategies.ReferencesHeller, P och Heller, K (2010) Cooperative Problem Solving in Physics A User’s ManualHeller, P, Keith, R och Andersson (1992), Teaching problem solving through cooperative grouping. Part 1: Group versus individual problem solving, S, Am. J. Phys. 60, 627; Heller, P och Hollabaugh, M (1992), Teaching problem solving through cooperative grouping. Part 2: Designing problems and structuring groups, Am. J. Phys. 60, 637Maloney, D., Research on problem solving in physics, in D. Gabel (ed.) (1994), Handbook of research in science teaching and learning, New YorkWedelin, D., Adawi, T., Jahan T. and Andersson, S., (2015), Investigating and developing engineering students’ mathematical modelling and problem-solving skills, European Journal of Engineering Education, 40:5, pp. 557-572Wedelin, D. och Adawi, D. (2015), Warming up for PBL: a course in mathematical modelling and problem solving for engineering students Högre utbildning Vol. 5, No. 1, pp. 23-34 
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46.
  • Gren, Martin, 1989, et al. (författare)
  • Modeling of vibrational and configurational degrees of freedom in hexagonal and cubic tungsten carbide at high temperatures
  • 2021
  • Ingår i: Physical Review Materials. - 2475-9953. ; 5:3
  • Tidskriftsartikel (refereegranskat)abstract
    • Transition metal carbide is a class of materials characterized by high hardness, high melting points, and low chemical reactivity. It is widely used in industrial applications involving exposure to elevated temperatures, aggressive media, and heavy loads, and is thus of technological and industrial importance. In this paper the high-temperature thermodynamic properties of tungsten carbide, WC, is studied. At most temperatures below melting, WC assumes a hexagonal structure with essentially no vacancies (δ-WC). Only at very high temperatures (around 3000 K), WC crystallizes in the cubic rocksalt structure (γ-WC), which is more common for the transition metal carbides and in the case for WC can contain up to 40% carbon vacancies. At lower temperatures, γ-WC can, however, form as thin interfacial structures or nanoparticles. Hence, the thermodynamic properties of both γ-WC and δ-WC are of relevance. Here, we conduct a first-principles density-functional theory based computational investigation of the γ-WC and δ-WC phases, which requires modeling of high carbon vacancy concentrations at high temperatures. The configurational degrees of freedom are modeled with an alloy cluster expansion and sampled through Monte Carlo simulations. To account for the dynamic instability of the cubic γ-WC phase at low temperatures, the vibrational degrees of freedom are treated using effective harmonic models constructed from ab initio molecular dynamics simulations. Finally, we obtain a part of the W-C phase diagram in reasonably quantitative agreement with experimental data.
  •  
47.
  • Ho, Anna Y. Q., et al. (författare)
  • Evidence for Late-stage Eruptive Mass Loss in the Progenitor to SN2018gep, a Broad-lined Ic Supernova : Pre-explosion Emission and a Rapidly Rising Luminous Transient
  • 2019
  • Ingår i: Astrophysical Journal. - : American Astronomical Society. - 0004-637X .- 1538-4357. ; 887:2
  • Tidskriftsartikel (refereegranskat)abstract
    • We present detailed observations of ZTF18abukavn (SN2018gep), discovered in high-cadence data from the Zwicky Transient Facility as a rapidly rising (1.4 +/- 0.1 mag hr(-1)) and luminous (M-g,M- peak = -20 mag) transient. It is spectroscopically classified as a broad-lined stripped-envelope supernova (Ic-BL SN). The high peak luminosity (L-bol greater than or similar to 3 x 10(44) erg s(-1)), the short rise time (t(rise) = 3 days in g band), and the blue colors at peak (g-r similar to -0.4) all resemble the high-redshift Ic-BL iPTF16asu, as well as several other unclassified fast transients. The early discovery of SN2018gep (within an hour of shock breakout) enabled an intensive spectroscopic campaign, including the highest-temperature (T-eff greater than or similar to 40,000 K) spectra of a stripped-envelope SN. A retrospective search revealed luminous (M-g similar to M-r approximate to -14 mag) emission in the days to weeks before explosion, the first definitive detection of precursor emission for a Ic-BL. We find a limit on the isotropic gamma-ray energy release E-gamma,E- iso < 4.9 x 10(48) erg, a limit on X-ray emission L-X < 10(40) erg s(-1), and a limit on radio emission nu L-v less than or similar to 10(37) erg s(-1). Taken together, we find that the early (< 10 days) data are best explained by shock breakout in a massive shell of dense circumstellar material (0.02 M-circle dot) at large radii (3 x 10(14) cm) that was ejected in eruptive pre-explosion mass-loss episodes. The late-time (> 10 days) light curve requires an additional energy source, which could be the radioactive decay of Ni-56.
  •  
48.
  • Jerkstrand, A., et al. (författare)
  • Late-time spectral line formation in Type IIb supernovae, with application to SN 1993J, SN 2008ax, and SN 2011dh
  • 2015
  • Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 573
  • Tidskriftsartikel (refereegranskat)abstract
    • We investigate line formation processes in Type IIb supernovae (SNe) from 100 to 500 days post-explosion using spectral synthesis calculations. The modelling identifies the nuclear burning layers and physical mechanisms that produce the major emission lines, and the diagnostic potential of these. We compare the model calculations with data on the three best observed Type IIb SNe to-date - SN 1993J, SN 2008ax, and SN 2011dh. Oxygen nucleosynthesis depends sensitively on the main-sequence mass of the star and modelling of the [O I] lambda lambda 6300, 6364 lines constrains the progenitors of these three SNe to the M-ZAMS = 12-16 M-circle dot range (ejected oxygen masses 0.3-0.9 M-circle dot), with SN 2011dh towards the lower end and SN 1993J towards the upper end of the range. The high ejecta masses from M-ZAMS greater than or similar to 17 M-circle dot progenitors give rise to brighter nebular phase emission lines than observed. Nucleosynthesis analysis thus supports a scenario of low-to-moderate mass progenitors for Type IIb SNe, and by implication an origin in binary systems. We demonstrate how oxygen and magnesium recombination lines may be combined to diagnose the magnesium mass in the SN ejecta. For SN 2011dh, a magnesium mass of 0.02-0.14 M-circle dot is derived, which gives a Mg/O production ratio consistent with the solar value. Nitrogen left in the He envelope from CNO burning gives strong [N II] lambda lambda 6548, 6583 emission lines that dominate over Ha emission in our models. The hydrogen envelopes of Type IIb SNe are too small and dilute to produce any noticeable H alpha emission or absorption after similar to 150 days, and nebular phase emission seen around 6550 angstrom is in many cases likely caused by [N II] lambda lambda 6548, 6583. Finally, the influence of radiative transport on the emergent line profiles is investigated. Significant line blocking in the metal core remains for several hundred days, which affects the emergent spectrum. These radiative transfer effects lead to early-time blueshifts of the emission line peaks, which gradually disappear as the optical depths decrease with time. The modelled evolution of this effect matches the observed evolution in SN 2011dh.
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49.
  •  
50.
  • Jerkstrand, A., et al. (författare)
  • The progenitor mass of the Type IIP supernova SN 2004et from late-time spectral modeling
  • 2012
  • Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 546, s. A28-
  • Tidskriftsartikel (refereegranskat)abstract
    • SN 2004et is one of the nearest and best-observed Type IIP supernovae, with a progenitor detection as well as good photometric and spectroscopic observational coverage well into the nebular phase. Based on nucleosynthesis from stellar evolution/explosion models we apply spectral modeling to analyze its 140-700 day evolution from ultraviolet to mid-infrared. We find a M-ZAMS = 15 M-circle dot progenitor star (with an oxygen mass of 0.8 M-circle dot) to satisfactorily reproduce [Oi] lambda lambda 6300, 6364 and other emission lines of carbon, sodium, magnesium, and silicon, while 12 M-circle dot and 19 M-circle dot models under-and overproduce most of these lines, respectively. This result is in fair agreement with the mass derived from the progenitor detection, but in disagreement with hydrodynamical modeling of the early-time light curve. From modeling of the mid-infrared iron-group emission lines, we determine the density of the Ni-bubble to rho(t) similar or equal to 7 x 10(-14) x (t/100 d)(-3) g cm(-3), corresponding to a filling factor of f = 0.15 in the metal core region (V = 1800 km s(-1)). We also confirm that silicate dust, CO, and SiO emission are all present in the spectra.
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