| 1. |
- Martinsson, Johan, et al.
(författare)
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Evaluation of delta C-13 in Carbonaceous Aerosol Source Apportionment at a Rural Measurement Site
- 2017
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Ingår i: Aerosol and Air Quality Research. - : Taiwan Association for Aerosol Research. - 1680-8584 .- 2071-1409. ; 17:8, s. 2081-2094
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Tidskriftsartikel (refereegranskat)abstract
- The stable isotope of carbon, C-13, has been used in several studies for source characterization of carbonaceous aerosol since there are specific signatures for different sources. In rural areas, the influence of different sources is complex and the application of delta C-13 for source characterization of the total carbonaceous aerosol (TC) can therefore be difficult, especially the separation between biomass burning and biogenic sources. We measured delta C-13 from 25 filter samples collected during one year at a rural background site in southern Sweden. Throughout the year, the measured delta C-13 showed low variability (-26.73 to -25.64%). We found that the measured delta C-13 did not correlate with other commonly used source apportionment tracers (C-14, levoglucosan). delta C-13 values showed lower variability during the cold months compared to the summer, and this narrowing of the delta C-13 values together with elevated levoglucosan concentrations may indicate contribution from sources with lower delta C-13 variation, such as biomass or fossil fuel combustion. Comparison of two Monte Carlo based source apportionment models showed no significant difference in results when delta C-13 was incorporated in the model. The insignificant change of redistributed fraction of carbon between the sources was mainly a consequence of relatively narrow range of delta C-13 values and was complicated by an unaccounted kinetic isotopic effect and overlapping delta C-13 end-member values for biomass burning and biogenic sources.
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| 2. |
- Azeem, Hafiz Abdul, et al.
(författare)
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Towards the isolation and estimation of elemental carbon in atmospheric aerosols using supercritical fluid extraction and thermo-optical analysis
- 2017
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Ingår i: Analytical and Bioanalytical Chemistry. - : Springer Science and Business Media LLC. - 1618-2642 .- 1618-2650. ; 409:17, s. 4293-4300
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Tidskriftsartikel (refereegranskat)abstract
- Air-starved combustion of biomass and fossil fuels releases aerosols, including airborne carbonaceous particles, causing negative climatic and health effects. Radiocarbon analysis of the elemental carbon (EC) fraction can help apportion sources of its emission, which is greatly constrained by the challenges in isolation of EC from organic compounds in atmospheric aerosols. The isolation of EC using thermo-optical analysis is however biased by the presence of interfering compounds that undergo pyrolysis during the analysis. EC is considered insoluble in all acidic, basic, and organic solvents. Based on the property of insolubility, a sample preparation method using supercritical CO2 and methanol as co-solvent was developed to remove interfering organic compounds. The efficiency of the method was studied by varying the density of supercritical carbon dioxide by means of temperature and pressure and by varying the methanol content. Supercritical CO2 with 10% methanol by volume at a temperature of 60 °C, a pressure of 350 bar and 20 min static mode extraction were found to be the most suitable conditions for the removal of 59 ± 3% organic carbon, including compounds responsible for pyrolysis with 78 ± 16% EC recovery. The results indicate that the method has potential for the estimation and isolation of EC from OC for subsequent analysis methods and source apportionment studies.
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| 3. |
- Birgersson, Simon, et al.
(författare)
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Flexibility and Function of Distal Substrate-Binding Tryptophans in the Blue Mussel β-Mannanase MeMan5A and Their Role in Hydrolysis and Transglycosylation
- 2023
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Ingår i: Catalysts. - 2073-4344. ; 13:9
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Tidskriftsartikel (refereegranskat)abstract
- β-Mannanases hydrolyze β-mannans, important components of plant and microalgae cell walls. Retaining β-mannanases can also catalyze transglycosylation, forming new β-mannosidic bonds that are applicable for synthesis. This study focused on the blue mussel (Mytilus edulis) GH5_10 β-mannanase MeMan5A, which contains two semi-conserved tryptophans (W240 and W281) in the distal subsite +2 of its active site cleft. Variants of MeMan5A were generated by replacing one or both tryptophans with alanines. The substitutions reduced the enzyme’s catalytic efficiency (kcat/Km using galactomannan) by three-fold (W281A), five-fold (W240A), or 20-fold (W240A/W281A). Productive binding modes were analyzed by 18O labeling of hydrolysis products and mass spectrometry. Results show that the substitution of both tryptophans was required to shift away from the dominant binding mode of mannopentaose (spanning subsites −3 to +2), suggesting that both tryptophans contribute to glycan binding. NMR spectroscopy and molecular dynamics simulations were conducted to analyze protein flexibility and glycan binding. We suggest that W240 is rigid and contributes to +2 subsite mannosyl specificity, while W281 is flexible, which enables stacking interactions in the +2 subsite by loop movement to facilitate binding. The substitutions significantly reduced or eliminated transglycosylation with saccharides as glycosyl acceptors but had no significant effect on reactions with alcohols.
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| 4. |
- Genberg, Johan, et al.
(författare)
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Sealed Glass Tube Combustion of mu g-Sized Aerosol Samples
- 2013
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Ingår i: Radiocarbon. - 0033-8222. ; 55:2-3, s. 617-623
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Tidskriftsartikel (refereegranskat)abstract
- It is important to evaluate each step in radiocarbon analysis to ensure that the whole process is as efficient and accurate as possible. Aerosol filter samples contain a myriad of carbonaceous compounds with varying resistance to oxidation. Complete combustion of the sample is thus of great importance to ensure that the graphitized sample is representative of the original filter sample. We have evaluated sealed tube combustion of mu g-sized aerosol samples using different types and amounts of reagents. Successful analysis of aerosol samples as small as 20 mu g C was possible following small changes to our standard on-line method. The sealed tube combustion method performs well for standard samples containing 11 mu g C.
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| 5. |
- Genberg, Johan, et al.
(författare)
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Source apportionment of carbonaceous aerosol in southern Sweden
- 2011
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Ingår i: Atmospheric Chemistry and Physics. - : Copernicus GmbH. - 1680-7316 .- 1680-7324. ; 11:22, s. 11387-11400
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Tidskriftsartikel (refereegranskat)abstract
- A one-year study was performed at the Vavihill background station in southern Sweden to estimate the anthropogenic contribution to the carbonaceous aerosol. Weekly samples of the particulate matter PM10 were collected on quartz filters, and the amounts of organic carbon, elemental carbon, radiocarbon (14C) and levoglucosan were measured. This approach enabled source apportionment of the total carbon in the PM10 fraction using the concentration ratios of the sources. The sources considered in this study were emissions from the combustion of fossil fuels and biomass, as well as biogenic sources. During the summer, the carbonaceous aerosol mass was dominated by compounds of biogenic origin (80%), which are associated with biogenic primary and secondary organic aerosols. During the winter months, biomass combustion (32%) and fossil fuel combustion (28%) were the main contributors to the carbonaceous aerosol. Elemental carbon concentrations in winter were about twice as large as during summer, and can be attributed to biomass combustion, probably from domestic wood burning. The contribution of fossil fuels to elemental carbon was stable throughout the year, although the fossil contribution to organic carbon increased during the winter. Thus, the organic aerosol originated mainly from natural sources during the summer and from anthropogenic sources during the winter. The result of this source apportionment was compared with results from the EMEP MSC-W chemical transport model. The model and measurements were generally consistent for total atmospheric organic carbon, however, the contribution of the sources varied substantially. E.g. the biomass burning contributions of OC were underestimated by the model by a factor of 2.2 compared to the measurements.
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| 6. |
- Gilardoni, S., et al.
(författare)
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Better constraints on sources of carbonaceous aerosols using a combined C-14 - macro tracer analysis in a European rural background site
- 2011
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Ingår i: Atmospheric Chemistry and Physics. - : Copernicus GmbH. - 1680-7324. ; 11:12, s. 5685-5700
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Tidskriftsartikel (refereegranskat)abstract
- The source contributions to carbonaceous PM2.5 aerosol were investigated at a European background site at the edge of the Po Valley, in Northern Italy, during the period January-December 2007. Carbonaceous aerosol was described as the sum of 8 source components: primary (1) and secondary (2) biomass burning organic carbon, biomass burning elemental carbon (3), primary (4) and secondary (5) fossil organic carbon, fossil fuel burning elemental carbon (6), primary (7) and secondary (8) biogenic organic carbon. The mass concentration of each component was quantified using a set of macro tracers (organic carbon OC, elemental carbon EC, and levoglucosan), micro tracers (arabitol and mannitol), and C-14 measurements. This was the first time that C-14 measurements covered a full annual cycle with daily resolution. This set of 6 tracers, together with assumed uncertainty ranges of the ratios of OC-to-EC, and the reference fraction of modern carbon in the 8 source categories, provides strong constraints to the source contributions to carbonaceous aerosol. The uncertainty of contributions was assessed with a Quasi-Monte Carlo (QMC) method accounting for the variability of OC and EC emission factors, the uncertainty of reference fractions of modern carbon, and the measurement uncertainty. During winter, biomass burning composed 64% (+/- 15%) of the total carbon (TC) concentration, while in summer secondary biogenic OC accounted for 50% (+/- 16%) of TC. The contribution of primary biogenic aerosol particles was negligible during the entire year. Moreover, aerosol associated with fossil sources represented 27% (+/- 16%) and 41% (+/- 26%) of TC in winter and summer, respectively. The contribution of secondary organic aerosol (SOA) to the organic mass (OM) was significant during the entire year. SOA accounted for 30% (+/- 16 %) and 85% (+/- 12 %) of OM during winter and summer, respectively. While the summer SOA was dominated by biogenic sources, winter SOA was mainly due to biomass burning and fossil sources. This indicates that the oxidation of semi-volatile and intermediate volatility organic compounds co-emitted with primary organics is a significant source of SOA, as suggested by recent model results and Aerosol Mass Spectrometer measurements. Comparison with previous global model simulations, indicates a strong underestimate of wintertime primary aerosol emissions in this region. The comparison of source apportionment results in different urban and rural areas showed that the sampling site was mainly affected by local aerosol sources during winter and regional air masses from the nearby Po Valley in summer. This observation was further confirmed by back-trajectory analysis applying the Potential Source Contribution Function method to identify potential source regions.
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| 7. |
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| 8. |
- Hambraeus, Mette, et al.
(författare)
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Functional outcome and health-related quality of life in patients with sacrococcygeal teratoma – a Swedish multicenter study
- 2019
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Ingår i: Journal of Pediatric Surgery. - : Elsevier BV. - 0022-3468 .- 1531-5037. ; 54:8, s. 1638-1643
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Tidskriftsartikel (refereegranskat)abstract
- Background/Purpose: The aims of this study were to evaluate bowel and urinary tract function, to identify predictors for dysfunctional outcome and to evaluate health-related quality-of life (QoL) in patients treated for sacrococcygeal teratomas (SCT). Methods: Medical records of patients with SCT born between 1985 and 2015 treated at three Swedish pediatric surgical centers were reviewed. Questionnaires regarding urinary tract function, bowel function and QoL were sent to patients and parents. Different QoL instruments were used for the different age groups. Results: Totally 85 patients were identified. Four patients died in the neonatal period. Forty-nine patients answered the questionnaires (60%). Median age at follow-up was 8.9 years (range 3.6–28.8). Bowel dysfunction was reported by 36% and urinary tract dysfunction by 46% of the patients. Univariate analysis revealed that urinary tract dysfunction correlated with gestational age (p = 0.018) and immature histology (p = 0.008), and bowel dysfunction correlated with gestational age (p = 0.016) and tumor size (p = 0.042). Low gestational age was an independent predictor for both urinary tract and bowel dysfunction. Good or very good QoL was reported by 56% of children aged 4–7 years, 90% of children aged 8–17 years and 67% of the adults. Conclusion: Although a considerable proportion of bowel and urinary tract dysfunction was found, the reported QoL was good in a majority of the patients with SCT. Low gestational age was found to be a predictor for bowel- and urinary tract dysfunction. Level of Evidence: Level III.
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| 9. |
- Hasserius, Johan, et al.
(författare)
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Treatment and Patient Reported Outcome in Children with Hirschsprung Disease and Concomitant Congenital Heart Disease
- 2017
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Ingår i: BioMed Research International. - : Hindawi Limited. - 2314-6133 .- 2314-6141. ; 2017
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Tidskriftsartikel (refereegranskat)abstract
- Purpose. Congenital heart disease (CHD) is reported to be associated with Hirschsprung disease (HD). The aim was to evaluate any differences between children with HD with and without CHD, respectively, with regard to patient characteristics, medical care, and patient reported bowel function. Method. This is a retrospective chart study and a cross-sectional long-term follow-up of patients older than 4 years old, including all children with HD operated on with transanal endorectal pull-through (TERPT) at a tertiary center of pediatric surgery. Information about patient characteristics, diagnostics, surgery, and medical care was compiled. At long-term follow-up, bowel function was assessed by Bowel Function Score. Results. Included were 53 HD-patients, 13 with CHD and 40 without CHD. Children with CHD more commonly presented with failure to thrive; 4 (23%) compared to those without CHD (0%) (p<0.01). In the long-term follow-up, including 32 patients (6 with CHD), constipation was more commonly reported by children with CHD 5 (83%) than by children without CHD 4 (27%) (p=0.01). No differences were shown in the other parameters such as fecal control and incontinence. Conclusion. HD-patients with CHD more commonly presented with failure to thrive and more frequently reported constipation than HD-patients without CHD. The findings indicate that HD-patients with CHD might need special consideration in their initial care and long-term follow-up.
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| 10. |
- Hedbys, Josefine, et al.
(författare)
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Children with Hirschsprung's Disease and Syndromes with Cognitive Dysfunction : Manifestations, Treatment, and Outcomes
- 2019
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Ingår i: The Surgery Journal. - : Georg Thieme Verlag KG. - 2378-5128 .- 2378-5136. ; 5:3, s. 103-109
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Tidskriftsartikel (refereegranskat)abstract
- Introduction To assess differences in initial symptoms, treatments, and bowel function between children with Hirschsprung's disease (HD) with or without a cognitive dysfunction (CD). Materials and Methods The study included children with HD who underwent transanal endorectal pull-through. A retrospective chart review was performed to collect data on patient characteristics, diagnosis, and treatment. Data on bowel symptoms in children older than 4 years without a colostomy were compiled during a cross-sectional, patient-reported follow-up. Results Fifty-three children with HD were included; of these, 12 (23%) had CD. The median birth weight was lower, frequency of vomiting as the presenting symptom was lower, and time until the first contact with a pediatric surgeon was higher in children with CD than in those without (3,295 vs. 3,623 g, p = 0.013; 28 vs. 66%, p = 0.02; and 4 days vs. 1 day, p = 0.048, respectively). At follow-up, 5 (15%) of 33 children aged over 4 years had CD. More children without CD had some ability to hold back defecation and sense the urge to defecate than those with CD ( p = 0.002 and p = 0.001, respectively). Conclusion HD children who have CD present with different initial symptoms, have a delay in the first consultation with a pediatric surgeon, and experience poorer bowel function outcomes than HD children without CD. Therefore, HD children with CD should receive special attention in both clinical practice and research.
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