| 511. |
- Jonsson, K., et al.
(författare)
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Effect of sorption kinetics on the transport of solutes in streams
- 2001
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Ingår i: Science of the Total Environment. - 0048-9697 .- 1879-1026. ; 266:03-jan, s. 239-247
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Tidskriftsartikel (refereegranskat)abstract
- To provide an appropriate description of the transport of a reactive substance in a stream, it is important to include a kinetic description of sorption in a transport model. In this study, first-order sorption kinetics was taken into account in both the transient storage zone and the stream water, and analytical expressions for relative error in statistical moments of the residence time PDF, resulting from disregarding sorption kinetics, were derived. The sorption rate coefficient in the water was found to influence the error in the expected value, and the error was found to approach infinity as the travel distance or sorption rate coefficient approaches zero. The sorption rate coefficient in the storage zone influences only higher-order moments. For sufficiently long distances, the error in the variance was found to be more pronounced when sorption kinetics in the storage zone was disregarded, than when sorption kinetics in the stream water was disregarded. Parameter values from a tracer experiment with Cr-51 revealed that the relative error in the variance could be more than 100%, if sorption kinetics in the storage zone is disregarded.
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| 512. |
- Jonsson, K., et al.
(författare)
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Hyporheic exchange of reactive and conservative solutes in streams - tracer methodology and model interpretation
- 2003
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Ingår i: Journal of Hydrology. - : Elsevier BV. - 0022-1694 .- 1879-2707. ; 278:04-jan, s. 153-171
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Tidskriftsartikel (refereegranskat)abstract
- A transient storage model is evaluated using results from a tracer experiment, where a conservative and a reactive tracer (H-3 and Cr-51(III)) were injected simultaneously and monitored in stream water and bed sediment. About 76% of the chromium was lost from the stream water on the reach 30 km downstream of the injection point directly after the passage of the pulse in the flowing water. The bed sediment hosted the main part of the retained chromium. The time to washout 75% of the maximum solute uptake in the sediment was similar to 85 times longer for chromium than for tritium (i.e. similar to 45 days). It was possible to describe the sediment-water exchange with a diffusive flux formulation that could be evaluated using tritium breakthrough curves in the stream water or the tritium inventory breakthrough curves in the sediment. This experiment revealed further that observations of chromium concentrations in the sediment were essential for the quantifying of sorption properties, as it was not possible to catch accurately the time scale of sorption within the duration of the breakthrough curves in the stream water. There was a clear need for a rate-limited description of the sorption of chromium in the sediment. We found that a first-order kinetic description of the sorption process could acceptably describe the breakthrough curves in both the stream water and the bed sediment.
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| 513. |
- Jonsson, Karin, et al.
(författare)
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Hyporheic Exchange of Reactive and Conservative Solutes in Streams - Tracer Methodology and Model Interpretation
- 2003
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Ingår i: Journal of Hydrology. - 0022-1694 .- 1879-2707. ; 278:1-4, s. 153-171
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Tidskriftsartikel (refereegranskat)abstract
- A transient storage model is evaluated using results from a tracer experiment, where a conservative and a reactive tracer (3H and 51Cr(III)) were injected simultaneously and monitored in stream water and bed sediment. About 76% of the chromium was lost from the stream water on the reach 30 km downstream of the injection point directly after the passage of the pulse in the flowing water. The bed sediment hosted the main part of the retained chromium. The time to washout 75% of the maximum solute uptake in the sediment was ∼85 times longer for chromium than for tritium (i.e. ∼45 days). It was possible to describe the sediment-water exchange with a diffusive flux formulation that could be evaluated using tritium breakthrough curves in the stream water or the tritium inventory breakthrough curves in the sediment. This experiment revealed further that observations of chromium concentrations in the sediment were essential for the quantifying of sorption properties, as it was not possible to catch accurately the time scale of sorption within the duration of the breakthrough curves in the stream water. There was a clear need for a rate-limited description of the sorption of chromium in the sediment. We found that a first-order kinetic description of the sorption process could acceptably describe the breakthrough curves in both the stream water and the bed sediment.
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| 514. |
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| 515. |
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| 516. |
- Jónsson, Kristján, et al.
(författare)
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Perioperative stroke and survival in coronary artery bypass grafting patients: a SWEDEHEART study
- 2022
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Ingår i: European Journal of Cardio-Thoracic Surgery. - : Oxford University Press (OUP). - 1010-7940 .- 1873-734X. ; 62:4
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Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVES Perioperative stroke is a severe complication of cardiac surgery. We assessed the incidence of stroke over time, the association between stroke and mortality and identified preoperative factors independently associated with perioperative stroke, in a large nationwide cardiac surgery population. METHODS All patients who underwent coronary artery bypass grafting in Sweden 2006-2017 were included in a registry-based observational cohort study based on prospectively collected data. Multivariable logistic and Cox regression models were used to assess associations between perioperative stroke and mortality and to identify factors associated with stroke. The median follow-up was 6 years (range 0-12). RESULTS There were 441 perioperative strokes in 36 898 patients. The mean incidence was 1.2% and decreased marginally over time [adjusted odds ratio (OR) 0.97 per year (95% confidence interval 0.94-1.00), P = 0.035]. Stroke patients had a higher overall mortality risk during follow-up [adjusted hazard ratio 2.30 (2.00-2.64), P < 0.001], with the highest risk during the first 30 postoperative days [adjusted hazard ratio (7.29 (5.58-9.54), P < 0.001]. The strongest independent preoperative factors associated with stroke were prior cardiac surgery [adjusted OR 2.89 (1.40-5.96)], critical preoperative condition [adjusted OR 2.55 (1.73-3.76)], previous stroke [adjusted OR 1.77 (1.35-2.33)], preoperative angina requiring intravenous nitrates [adjusted OR 1.67 (1.28-2.17)], peripheral vascular disease [OR 1.63 (1.25-2.13)] and advanced age [OR 1.05 (1.03-1.06) per year]. CONCLUSIONS The incidence of perioperative stroke after coronary artery bypass grafting has remained stable. Patients with perioperative stroke had a markedly higher adjusted risk of death early after surgery. The risk declined over time but remained higher during the entire follow-up period.
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| 517. |
- Jonsson, Kristina, 1967-
(författare)
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Practices for the Living and the Dead : Medieval and Post-Reformation Burials in Scandinavia
- 2009
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The main themes of the thesis are burial customs and social identities, and how medieval and post-Reformation graves can provide information on such as age structures, phases in life, gender relations and social organization. The study is based on nine groups of Scandinavian material, and it comprises four case studies. The first one deals with social zoning in medieval cemeteries and how age and gender structures varied within and between different social strata. The second concerns ‘atypical’ medieval burials, such as graves in which individuals have been buried in a deviant or peripheral position; and it also focusses on burials of the sick and the impaired. The third case study examines two mainly medieval burial practices: the use of charcoal and burial rods, and possible interpretations of their inclusion in graves. The fourth study deals with post-Reformation burial customs; how they differ from the medieval ones and what notions may have caused the changes in practice. It is concluded that in the Early Middle Ages, social identity was to a large extent intermingled with group identity. Towards the twelfth century, the social boundaries were sharpened and burial customs emphasizing personal aspects such as gender, age and body developed. A person’s biological status was a major factor in determining gender and social identities, and thereby also social status. In the Late Middle Ages the inner burial customs became more homogeneous, probably as a result of new religious beliefs and ecclesiastical restrictions. After the Reformation, social differences in burial prevailed, and above all the memorials displayed and shaped social identities. The inner burial customs became more varied again, displaying a ‘revival’ of old customs. This was most likely caused by changes in religious practices: since the Church no longer provided comforting and protective ritualistic practices they were instead performed before the funeral by the next of kin.
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| 518. |
- Jonsson, K., et al.
(författare)
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Sorption behavior and long-term retention of reactive solutes in the hyporheic zone of streams
- 2004
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Ingår i: Journal of environmental engineering. - : American Society of Civil Engineers (ASCE). - 0733-9372 .- 1943-7870. ; 130:5, s. 573-584
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Tidskriftsartikel (refereegranskat)abstract
- This paper analyzes the transport of sorbing solutes by extending the advective storage path model developed for longitudinal transport of inert solutes in streams coupled with flow-induced uptake in the hyporheic zone. Independent observations of a conservative (H-3) and a reactive (Cr-51) tracer in both the stream water and the hyporheic zone were used to differentiate between hydraulic and sorption processes. The method of temporal moments was found to be inadequate for parameter determination, whereas fitting versus the entire tracer breakthrough curves with special emphasis on the tail indicates that the proposed model could be used to represent both conservative and reactive transport. Information on the tracer inventory of the conservative tracer in the hyporheic zone was found to be of vital importance to the evaluation of the hydraulic exchange. A model evaluation based on stream water data alone can yield predictions of a wash-out in the hyporheic zone that deviates markedly from the observed wash-out. This prohibits long-term predictions of the wash-out from the hyporheic zone as well as the evaluation of sorption properties. The sorption in the hyporheic zone was found to follow a two-step model, where the first step is instantaneous and the second kinetic. A model with a single-step sorption process could not reproduce the observed breakthrough curves. An evaluation of the relative importance of including sorption kinetics in solute stream transport models is elucidated by means of the analytical expressions for the temporal moments. The omission of the kinetics in the second sorption step in the hyporheic zone will result in relative errors in the moments of second order or higher. The error will increase with decreasing residence time in the hyporheic zone. Especially, long-term predictions of the wash-out from the hyporheic zone require consideration of the rate-limited sorption.
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| 519. |
- Jonsson, Karin, et al.
(författare)
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Sorption Behaviour and Long-term Retention of Reactive Solute in the Hyporheic Zone of Streams
- 2004
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Ingår i: Journal of environmental engineering. - 0733-9372 .- 1943-7870. ; 130:5, s. 573-584
-
Tidskriftsartikel (refereegranskat)abstract
- This paper analyzes the transport of sorbing solutes by extending the advective storage path model developed for longitudinal transport of inert solutes in streams coupled with flow-induced uptake in the hyporheic zone. Independent observations of a conservative (3H) and a reactive (51Cr) tracer in both the stream water and the hyporheic zone were used to differentiate between hydraulic and sorption processes. The method of temporal moments was found to be inadequate for parameter determination, whereas fitting versus the entire tracer breakthrough curves with special emphasis on the tail indicates that the proposed model could be used to represent both conservative and reactive transport. Information on the tracer inventory of the conservative tracer in the hyporheic zone was found to be of vital importance to the evaluation of the hydraulic exchange. A model evaluation based on stream water data alone can yield predictions of a wash-out in the hyporheic zone that deviates markedly from the observed wash-out. This prohibits long-term predictions of the wash-out from the hyporheic zone as well as the evaluation of sorption properties. The sorption in the hyporheic zone was found to follow a two-step model, where the first step is instantaneous and the second kinetic. A model with a single-step sorption process could not reproduce the observed breakthrough curves. An evaluation of the relative importance of including sorption kinetics in solute stream transport models is elucidated by means of the analytical expressions for the temporal moments. The omission of the kinetics in the second sorption step in the hyporheic zone will result in relative errors in the moments of second order or higher. The error will increase with decreasing residence time in the hyporheic zone. Especially, long-term predictions of the wash-out from the hyporheic zone require consideration of the rate-limited sorption.
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| 520. |
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