| 1. |
- Carlsson, Ella, et al.
(författare)
-
Mass composition of the escaping plasma at Mars
- 2006
-
Ingår i: Icarus. - : Elsevier BV. - 0019-1035 .- 1090-2643. ; 182:2, s. 320-328
-
Tidskriftsartikel (refereegranskat)abstract
- Data from the Ion Mass Analyzer (IMA) sensor of the ASPERA-3 instrument suite on Mars Express have been analyzed to determine the mass composition of the escaping ion species at Mars. We have examined 77 different ion-beam events and we present the results in terms of flux ratios between the following ion species: CO2+/O+ and O-2(+)/O+. The following ratios averaged over all events and energies were identified: CO2+/O+ = 0.2 and O-2(+)/O+ = 0.9. The values measured are significantly higher, by a factor of 10 for O-2(+)/O+, than a contemporary modeled ratio for the maximum fluxes which the martian ionosphere can supply. The most abundant ion species was found to be O+, followed by O-2(+) and CO2+. We estimate the loss of CO2+ to be 4.0 x 10(24) s(-1) (0.29 kg s(-1)) by using the previous measurements of Phobos-2 in our calculations. The dependence of the ion ratios in relation to their energy ranges we studied, 0.3-3.0 keV, indicated that no clear correlation was found.
|
|
| 2. |
- Sundqvist, Bertil, et al.
(författare)
-
Physical properties of pressure polymerized C60
- 1996
-
Ingår i: Proceedings of the Symposium on Recent Advances in the Chemistry and Physics of Fullerenes and Related Materials. - Pennington, NJ : Electrochemical Society, Incorporated. - 1566771625 ; , s. 1014-1028
-
Konferensbidrag (refereegranskat)
|
|
| 3. |
- Andersson, K, et al.
(författare)
-
Colloidal rare earth elements in a boreal river: Changing sources and distributions during the spring flood
- 2006
-
Ingår i: Geochimica Et Cosmochimica Acta. - : Elsevier BV. - 0016-7037 .- 1872-9533. ; 70:13, s. 3261-3274
-
Tidskriftsartikel (refereegranskat)abstract
- Variations in the physico-chemical speciation of the rare earth elements (REE) have been investigated in a subarctic boreal river during an intense spring flood event using prefiltered (< 100 mu m) samples, cross-flow (ultra)filtration (CFF), flow field-flow fractionation (FIFFF), and diffusive gradients in thin films (DGT). This combination of techniques has provided new information regarding the release and transport of the REE in river water. The colloidal material can be described in terms of two fractions dominated by carbon and iron, respectively. These two fractions, termed colloidal carrier phases, showed significant temporal changes in concentration and size distribution. Before the spring flood, colloidal carbon concentrations were low, the colloids being dominated by relatively large iron colloids. Colloidal concentrations increased sharply during the spring flood, with smaller carbon colloids dominating. Following the spring flood, colloidal concentrations decreased again, smaller carbon colloids still dominating. The REE are transported mainly in the particulate and colloidal phases. Before the spring flood, the REE composition of all measured fractions was similar to local till. During the spring flood, the REE concentrations in the colloidal and particulate fractions increased. The increase was most marked for the lighter REE, which therefore showed a strong enrichment when normalized to local till. Following the spring flood, the REE concentrations decreased again and reverted to a distribution similar to local till. These changes in the concentration and distributions of carbon iron and REE are interpreted in terms of changing hydrological flow paths in soil and bedrock which occur during the spring flood. (c) 2006 Elsevier Inc. All rights reserved.
|
|
| 4. |
- Gustafsson, Ö., et al.
(författare)
-
Evaluation of the collection efficiency of upper ocean sub-photic-layer sediment traps : A 24-month in situ calibration in the open Baltic Sea using 234Th
- 2004
-
Ingår i: Limnology and Oceanography. - : Wiley. - 1541-5856. ; 2:2, s. 62-74
-
Tidskriftsartikel (refereegranskat)abstract
- The collection efficiency of cylindrical sediment traps of common design was assessed in situ for more than 2 y in an offshore shelf regime using the 234Th proxy and simultaneously collected hydrological and biogeochemical parameters. The traps were found to systematically record an undertrapping bias of 234Th by, on average, a factor of three (range 0.8 to 10). Seasonal variations in trapping efficiency were related to the seasonally varying ballasting properties of the settling particle pool. Sediment trap 234Th fluxes agreed within a factor of two of the estimated 234Th export from the overlying surface waters in the winter-spring periods in both 1999 and 2000 and appeared related to a particle pool that included, presumably rapidly sinking, mineral particles and diatom tests acting as ballast. In contrast, discrimination against slowly settling organic-rich aggregates of apparent exudate origin resulted in undertrapping of 234Th by factors of three to ten throughout the summerfall seasons. These data are consistent with hydrodynamic predictions that the collection efficiency of sinking particles is inversely related to their intrinsic settling velocities. Recognition of changing particle composition along a settling velocity spectrum combine with carbon mass balance restrictions to suggest that these 234Th-based collection efficiencies, ranging from 0.1 to 1, may not be directly applicable to "correct" sediment trap fluxes of other components, such as organic carbon. However, the 234Th-derived insights of settling-velocity-related undertrapping may beneficially be taken into account when interpreting trap records both in studies of biogeochemical element fluxes and in phytoplankton ecology
|
|
| 5. |
- Hedberg, P. A. Mikael, et al.
(författare)
-
Measurements and Simulations of the Flow Distribution in a Down-Scaled Multiple Outlet Spillway with Complex Channel
- 2024
-
Ingår i: Water. - : Multidisciplinary Digital Publishing Institute (MDPI). - 2073-4441. ; 16:6
-
Tidskriftsartikel (refereegranskat)abstract
- Measurements of mass flow through a three-outlet spillway modeled after a scaled-down spillway were conducted. The inlet and channel leading up to the outlets were placed to lead the water toward the outlet at an angle. With this, measurements of the water level at three locations were recorded by magnetostrictive sensors. The volumetric flow rates for each individual outlet were recorded separately to study the differences between them. Additionally, Acoustic Doppler Velocimetry was used to measure water velocities close to the outlets. The conditions changed were the inlet volume flow rate and the flow distribution was measured at 90, 100, 110, and 200 L per second. Differences between the outlets were mostly within the error margin of the instruments used in the experiments with larger differences shown for the 200 L test. The results produced together with a CAD model of the setup can be used for verification of CFD methods. A simulation with the k-epsilon turbulence model is included and compared to earlier experiments and the new experimental results. Larger differences are seen in the new experiments. Differing inlet conditions are assumed as the principal cause for the differences seen.
|
|
| 6. |
- Hedberg, P. A. Mikael, 1989-, et al.
(författare)
-
Numerical modelling of flow in parallel spillways
- 2020
-
Ingår i: Proceedings of the 8th IAHR International Symposium on Hydraulic Structures ISHS2020. - : The University of Queensland.
-
Konferensbidrag (refereegranskat)abstract
- Mathematical modelling of single spillways is well documented in literature. For parallel spillways however, there is a lack of documented, verified, and validated cases. Here, in this article, ANSYS-CFX is used to simulate the flow over three parallel ogee-crested spillways. For mesh size verification, a grid convergence study is performed by Richardson extrapolation. The turbulence model chosen for this simulation is the k-ε model and the volume of fluid method is used to simulate the water-air interface. This article details the models ability to accurately predict flow distribution at the spillways, and the water levels. The mesh is kept relatively coarse at the channel inlet with increased mesh density at the spillways. The results are validated against experimental data from Vattenfall AB, R&Ds laboratories. The geometry and boundary conditions of the experiment are tailored for CFD. The flow rate of each spillway is measured separately with high accuracy, and for several different inlet volumetric flows. The simulation results lie within the error estimates of the measuring tools used in the experiments, within ±1%. The volume flow rate differences between the three outlets is very small, within ±1%.
|
|
| 7. |
- Ingri, Johan, et al.
(författare)
-
Hydrogeochemistry of sulfur isotopes in the Kalix River catchment, northern Sweden
- 1997
-
Ingår i: Applied Geochemistry. - 0883-2927 .- 1872-9134. ; 12:4, s. 483-496
-
Tidskriftsartikel (refereegranskat)abstract
- The 34S-to-32S ratio in dissolved SO4 has been studied in the Kalix River, Northern Sweden, and its catchment. Weekly sampling over 17 months revealed temporal variations from +5.3‰ up to +7.4‰ in the δ34S values in the river. Snow and rain samples showed lower δ34S values (average +5.6‰ and +5.0‰, respectively). The atmosphere is the major source for S in surface waters in the catchment, and the heavier δ34S values in the river are a result of SO4 reduction within the catchment. Most of the temporal variations in the δ34S value in the river are caused by a mixing of water from the mountain areas (relatively light δ34S) and the woodland. The δ34S value is relatively heavy in the woodland tributaries because of bacterial SO4 reduction in peatland areas influenced by groundwater. The highest δ34S values were measured during the spring flood, in June and in November. These heavy δ34S values are related to different types of water with diverse origins. The heavy δ34S values coinciding with the early spring flood originate from peatland areas in the woodland. Relatively heavy δ34S values (up to +14.4‰) were registered in mire water. Smaller variations of the δ34S value during summer and early autumn most likely were caused by the input of ground-mire water during heavy rains. A correlation between increased TOC concentrations and increased δ34S values was observed. The heavy δ34S values in June and November probably originate from SO4 reduction in bottom water and sediments in lakes within the catchment. Bottom water, enriched in 34S---SO4, was transported in the river during the spring and autumn overturn.
|
|
| 8. |
- Räisänen, Petri, et al.
(författare)
-
High but stable incidence of adult-onset asthma in northern Sweden over the last decades
- 2021
-
Ingår i: Erj Open Research. - : European Respiratory Society (ERS). - 2312-0541. ; 7:3
-
Tidskriftsartikel (refereegranskat)abstract
- Background The prevalence of asthma has increased both among children and adults during the latter half of the 20th century. The prevalence among adults is affected by the incidence of asthma not only in childhood but also in adulthood. Time trends in asthma incidence have been poorly studied. Aims The aim of this study was to review the incidence of adult-onset asthma from 1996 to 2006 and 2006 to 2016 and compare the risk factor patterns. Methods In the Obstructive Lung Disease in Northern Sweden (OLIN) studies, two randomly selected population-based samples in the 20-69-year age group participated in postal questionnaire surveys about asthma in 1996 (n=7104, 85%) and 2006 (n=6165, 77%). A 10-year follow-up of the two cohorts with the same validated questionnaire was performed, and 5709 and 4552 responded, respectively. Different definitions of population at risk were used in the calculations of asthma incidence. The protocol followed a study performed between 1986 and 1996 in the same area. Results The crude incidence rate of physician-diagnosed asthma was 4.4 per 1000 person-years (men 3.8, women 5.5) from 1996 to 2006, and 4.8 per 1000 person-years (men 3.7, women 6.2) from 2006 to 2016. When correcting for possible under-diagnosis at study entry, the incidence rate was 2.4 per 1000 personyears from 1996 to 2006 and 2.6 per 1000 person-years from 2006 to 2016. The incidence rates were similar across age groups. Allergic rhino-conjunctivitis was the main risk factor for incident asthma in both observation periods (risk ratio 2.4-2.6). Conclusions The incidence of adult-onset asthma has been stable over the last two decades and has remained at a similar level since the 1980s. The high incidence contributes to the increase in asthma prevalence.
|
|
| 9. |
|
|
| 10. |
- Andersson, Joel, et al.
(författare)
-
Evolution of structures and hydrothermal alteration in a Palaeoproterozoic supracrustal belt : Constraining paired deformation–fluid flow events in an Fe and Cu–Au prospective terrain in northern Sweden
- 2020
-
Ingår i: Solid Earth. - : Copernicus publications. - 1869-9510 .- 1869-9529. ; 11:2, s. 547-578
-
Tidskriftsartikel (refereegranskat)abstract
- An approximately 90 km long Palaeoproterozoic supracrustal belt in the northwestern Norrbotten ore province (northernmost Sweden) was investigated to characterize its structural components, assess hydrothermal alteration–structural geology correlations, and constrain a paired deformation–fluid flow evolution for the belt. New geological mapping of five key areas (Eustiljåkk, Ekströmsberg, Tjårrojåkka, Kaitum West, and Fjällåsen–Allavaara) indicates two major compressional events (D1 and D2) have affected the belt, with each associated with hydrothermal alteration types typical for iron oxide–apatite and iron oxide Cu–Au systems in the region. Early D1 generated a regionally distributed, penetrative S1 foliation and oblique reverse shear zones that show a southwest-block-up sense of shear that formed in response to NE–SW crustal shortening. Peak regional metamorphism at epidote–amphibolite facies broadly overlaps with this D1 event. Based on overprinting relationships, D1 is associated with regional scapolite ± albite, magnetite + amphibole, and late calcite alteration of mafic rock types. These hydrothermal mineral associations linked to D1 structures may form part of a regionally pervasive evolving fluid flow event but are separated in this study by crosscutting relationships.During D2 deformation, folding of S0–S1 structures generated F2 folds with steeply plunging fold axes in low-strain areas. NNW-trending D1 shear zones experienced reverse dip-slip reactivation and strike-slip-dominated movements along steep, E–W-trending D2 shear zones, producing brittle-plastic structures. Hydrothermal alteration linked to D2 structures is a predominantly potassic–ferroan association comprising K-feldspar ± epidote ± quartz ± biotite ± magnetite ± sericite ± sulfides. Locally, syn- or post-tectonic calcite is the main alteration mineral in D2 shear zones that intersect mafic rocks. Our results highlight the importance of combining structural geology with the study of hydrothermal alterations at regional to belt scales to understand the temporal–spatial relationship between mineralized systems. Based on the mapping results and microstructural investigations as well as a review of earlier tectonic models presented for adjacent areas, we suggest a new structural model for this part of the northern Fennoscandian Shield. The new model emphasizes the importance of reactivation of early structures, and the model harmonizes with tectonic models presented by earlier workers based mainly on petrology of the northern Norrbotten area.
|
|
