| 1. |
- Johnsson, Anna, 1975, et al.
(författare)
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Bioligand-mediated partitioning of radionuclides to the aqueous phase
- 2008
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Ingår i: Journal of Radioanalytical and Nuclear Chemistry. - : Springer Science and Business Media LLC. - 0236-5731 .- 1588-2780. ; 277:3, s. 637-644
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Tidskriftsartikel (refereegranskat)abstract
- The aqueous-phase partitioning of 59Fe, 147Pm, 234Th and 241Am by complexing compounds from subsurface bacteria has previously been studied in the presence of quartz sand. In this study the aqueous-phase partitioning of pico- to submicromolar amounts of 59Fe, 147Pm, 234Th and 241Am was analyzed in the presence of TiO2 and exudates from three species of subsurface bacteria: Pseudomonas fluorescens, Pseudomonas stutzeri, and Shewanella putrefaciens. All were grown under aerobic conditions and P. stutzeri and S. putrefaciens were grown under anaerobic conditions as well. The supernatants of the aerobic and anaerobic cultures were collected and radionuclide was added. TiO2, with BET surface area of 49.9 m2·g-1, was added to the supernatant radionuclide mix, and the pH was adjusted to approximately 8. After incubation, the amount of radionuclide in the liquid phase of the samples and controls was analyzed using scintillation method. Two types of values were calculated: solution% = the activity maintained in solution relative to the total activity, and Q-values = the quotient between the activity in samples and the activity in controls. Aerobic supernatants had solution% values between 89% and 100% for 59Fe and between 18 and 43% for 234Th. The solution% values for 241Am and 147Pm were less than 2% overall, but the Q-values were between 34 and 115 times more 241Am in bacterial supernatants than in controls. The corresponding values for 147Pm ranged from 6 to 20 times more than in the control. The solution% values for all elements in the presence of anaerobic supernatants were below 2%, but the Q-values clustered around 7 for 59Fe and ranging from 2 to 29 for 234Th, indicated that anaerobic supernatants partitioned these elements to the aqueous phase. Both aerobic and anaerobic supernatants tested positive for complexing compounds when analyzed, using the Chrome Azurol S assay. Complexation with excreted organic ligands is most likely the reason for the higher amounts of metals in samples than in the controls. Hence, aerobically and anaerobically excreted organic ligands seem able to influence the mobility of radionuclides in aerobic and anaerobic environments contaminated with these compounds.
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| 2. |
- Lundell, Anna-Carin, 1976, et al.
(författare)
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Increased levels of circulating soluble CD14 but not CD83 in infants are associated with early intestinal colonization with Staphylococcus aureus
- 2007
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Ingår i: Clin Exp Allergy. ; 37:1, s. 62-71
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Soluble forms of the monocyte marker CD14 and the mature dendritic cell marker CD83 are plasma proteins with immunoregulatory functions. The physiological stimulus for their production is unclear and their possible role in allergy development is unknown. METHODS: We measured the plasma levels of soluble CD14 (sCD14) and soluble CD83 (sCD83) in 64 Swedish children in relation to intestinal bacterial colonization pattern in a prospective birth cohort. Soluble CD14 and sCD83 levels were quantified by enzyme linked immunosorbent assay in plasma obtained at birth and at 4, 18 and 36 months of age. All major aerobic and anaerobic bacteria were quantified in faecal samples obtained regularly over the first 8 weeks of life. Clinical allergy and IgE levels were evaluated at 18 months of age. RESULTS: Soluble CD14 in plasma increased during the first 18 months of life while sCD83 peaked at 4 months of age. Children who were perinatally colonized with Staphylococcus aureus had significantly higher levels of sCD14 in plasma at 4 months of age relative to non-colonized children. The levels of sCD14 were unrelated to colonization with Escherichia coli, other enterobacteria, enterococci, clostridia, Bacteroides, bifidobacteria or lactobacilli. Further, children with food allergy by 18 months tended to have lower levels of sCD14 than healthy children. Plasma levels of sCD83 were not related to either bacterial colonization pattern or allergy development. CONCLUSIONS: Perinatal colonization with S. aureus may trigger the occurrence of sCD14 in plasma, which may influence development of the infantile immune system and risk of allergy development.
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| 3. |
- Moro, Elena, et al.
(författare)
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Long-Term Results of a Multicenter Study on Subthalamic and Pallidal Stimulation in Parkinson's Disease
- 2010
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Ingår i: Movement Disorders. - : Wiley. - 0885-3185. ; 25:5, s. 578-586
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Tidskriftsartikel (refereegranskat)abstract
- We report the 5 to 6 year follow-up of a multicenter study of bilateral subthalamic nucleus (STN) and globus pallidus internus (GPi) deep brain stimulation (DBS) in advanced Parkinson's disease (PD) patients. Thirty-live STN patients and 16 GPi patienis were assessed at 5 to 6 years after DBS surgery. Primary outcome measure was the stimulation effect on the motor Unified Parkinson's Disease Rating Scale (UPDRS) assessed with a prospective cross-over double-blind assessment without medications (stimulation was randomly switched on or off). Secondary outcomes were motor UPDRS changes with unblinded assessments in off- and on-medication states with and without stimulation, activities of daily living (ADL), anti-PD medications, and dyskinesias. In double-blind assessment, both STN and GPi DBS were significantly effective in improving the motor UPDRS scores (STN. P < 0.0001, 45.4%; GPi, P = 0.008, 20.0%) compared with of regardless of the sequence of stimulation. In open assessment. both STN- and GPi-DBS significantly improved the off-medication motor UPDRS when compared with before surgery (STN. P < 0.001, 50.5%; GPi, P = 0.002, 35.6%). Dyskinesias and ADL were significantly improved in both groups. Anti-PD medications were significantly reduced only in the STN group. Adverse events were more frequent in the STN group. These results confirm the long-term efficacy of STN and GPi DBS advanced PD. Although the surgical targets were not randomized, there was a trend to 1 better outcome of motor signs in the STN-DBS patients and fewer adverse events in the GPi-DBS group. (C) 2010 Movement Disorder Society
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| 4. |
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| 5. |
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| 6. |
- Aneheim, Emma, 1982, et al.
(författare)
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A TBP/BTBP-based GANEX Separation Process. Part 1: Feasibility
- 2010
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Ingår i: Solvent Extraction and Ion Exchange. - : Informa UK Limited. - 0736-6299 .- 1532-2262. ; 28:4, s. 437-458
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Tidskriftsartikel (refereegranskat)abstract
- A GANEX (Group ActiNide EXtraction) separation system for transmutation has been developed. In this separation process the actinides should be extracted as a group from the lanthanides and the fission and corrosion/activation products. This can be achieved by combining BTBP (bis-triazine-bipyridine) with TBP (tri-butyl phosphate) in cyclohexanone. From 4M nitric acid this organic system extracts the actinides (log(DAm) = 2.19, log(DPu) = 2.31, log(DU) = 1.03, log(DNp) = 0.53) and also separates them from the lanthanides (log(DLa) = -2.0, log(DCe) = -1.72, log(DNd) = -1.05, log(DSm) = -0.18, log(DEu) = -0.02). One problem encountered is that some of the fission and corrosion products are also extracted. The new system however still looks feasible.
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| 7. |
- Aneheim, Emma, 1982, et al.
(författare)
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A TBP/BTBP-based GANEX Separation ProcessPart 2: Ageing, Hydrolytic, and Radiolytic Stability
- 2011
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Ingår i: Solvent Extraction and Ion Exchange. - : Informa UK Limited. - 0736-6299 .- 1532-2262. ; 29:2, s. 157-175
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Tidskriftsartikel (refereegranskat)abstract
- The waste from nuclear power plants worldwide has to be isolated from man and his environment for about 100,000 years to equal the levels of natural uranium. If, however, the long-lived actinides could be separated from the spent fuel and transmuted, then the isolation time could be shortened to about 1,000 years. This does, however, require the selective separation of the actinides from the rest of the waste. Several processes exist for such a separation, of which one is the Group ActiNide Extraction (GANEX) process. A novel GANEX process has been developed at the Chalmers University of Technology utilizing the properties of already well known extractants by combining BTBP and TBP into one solvent. The stability provided by this GANEX solvent towards ageing, hydrolysis, and radiolysis has been investigated. The results show that the actinide distribution ratios are maintained after a long duration of contact with strong nitric acid. The solvent has also been found to be stable towards radiolysis up to 200 kGy in contact with 4 M nitric acid.
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| 8. |
- Aneheim, Emma, 1982, et al.
(författare)
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Development of a Novel GANEX Process
- 2010
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Ingår i: ACS Symposium Series. - Washington, DC : American Chemical Society. - 1947-5918 .- 0097-6156. ; 1046, s. 119-130
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Konferensbidrag (refereegranskat)abstract
- The waste from nuclear power plants has to be isolated from man and his environment for about 100,000 years to be considered safe. It has been suggested that if the long-lived actinides could be separated from the spent fuel and transmuted, the isolation time could be shortened to about 1,000 years. This, however, requires selective separation of parts of the waste. The partitioning for transmutation research in Europe has for the major part taken place within several European Union Framework Programmes. Within the projects NEWPART, PARTNEW and EUROPART a process scheme for the partitioning of nuclear waste from the PUREX process was developed. The scheme includes the DIAMEX, SANEX and SESAME-processes among which both the DIAMEX and SANEX process has been successfully tested on genuine spent fuel. However, in the latest EU Project ACSEPT, which started in 2008, another approach towards partitioning is being investigated. This is the so called GANEX (Group ActiNide EXtraction) process. In the GANEX process all the actinides in the dissolved spent fuel are extracted as a group and hence separated from the lanthanides as well as the rest of the fission and corrosion/activation products. A novel GANEX process has been developed at Chalmers university of Technology in Sweden. This new process utilizes the properties of already well known extractants by combining BTBP and TBP into one solvent. The system is able to extract U, Np, Pu and Am from strong nitric acid and simultaneously separate these elements from the lanthanides. This is done with sufficiently high distribution ratios and separation factors without the need for any redox control.
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| 9. |
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| 10. |
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| 11. |
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| 12. |
- Brachmann, Cole, 1993, et al.
(författare)
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Herbivore-shrub interactions influence ecosystem respiration and biogenic volatile organic compound composition in the subarctic
- 2023
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Ingår i: Biogeosciences. - 1726-4170 .- 1726-4189. ; 20, s. 4069-4086
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Tidskriftsartikel (refereegranskat)abstract
- Arctic ecosystems are warming nearly 4 times faster than the global average, which is resulting in plant community shifts and subsequent changes in biogeochemical processes such as gaseous fluxes. Additionally, herbivores shape plant communities and thereby may alter the magnitude and composition of ecosystem respiration and biogenic volatile organic compound (BVOC) emissions. Here we determine the effect of large mammalian herbivores on ecosystem respiration and BVOC emissions in two southern and two northern sites in Swedish Scandes, encompassing mountain birch (LOMB) and shrub heath (LORI) communities in the south and low-herb meadow (RIGA) and shrub heath (RIRI) communities in the north. Herbivory significantly altered BVOC composition between sites and decreased ecosystem respiration at RIGA. The difference in graminoid cover was found to have a large effect on ecosystem respiration between sites as RIGA, with the highest cover, had 35 % higher emissions than the next highest-emitting site (LOMB). Additionally, LOMB had the highest emissions of terpenes, with the northern sites having significantly lower emissions. Differences between sites were primarily due to differences in exclosure effects and soil temperature and the prevalence of different shrub growth forms. Our results suggest that herbivory has a significant effect on trace gas fluxes in a productive meadow community and that differences between communities may be driven by differences in shrub composition. Copyright:
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| 13. |
- Börjesson Sandén, Fredrik, 1995, et al.
(författare)
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Effects of boric acid on volatile tellurium in severe accident conditions
- 2024
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Ingår i: Annals of Nuclear Energy. - 0306-4549 .- 1873-2100. ; 200
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Tidskriftsartikel (refereegranskat)abstract
- Boric acid is used in light-water nuclear reactors to control the reactor and is expected to be present as part of the chemistry of a severe accident. Therefore, its influence on other prominent species expected in an accident must be investigated. One such species is tellurium. In the present study, tellurium is volatized, and boric acid is dissolved and injected into the system as a means of studying the interaction between it and tellurium. The experiments were evaluated with ICP-MS and XPS. Results suggest that while there is no direct interaction, boric acid still affects the tendency for tellurium to oxidize. In general, less oxidation was detected in the presence of boric acid than in its absence, especially at high temperatures. The species formed upon oxidation was determined to be TeO2. Since tellurium metal is more volatile than TeO2, this may have implication in a wider severe accident context.
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| 14. |
- Cedborg, Anna I. Hardemark, et al.
(författare)
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Co-ordination of spontaneous swallowing with respiratory airflow and diaphragmatic and abdominal muscle activity in healthy adult humans
- 2009
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Ingår i: Experimental Physiology. - : Wiley. - 1469-445X .- 0958-0670. ; 94:4, s. 459-468
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Tidskriftsartikel (refereegranskat)abstract
- Co-ordination of breathing and swallowing is essential for normal pharyngeal function and to protect the airway. To allow for safe passage of a bolus through the pharynx, respiration is interrupted (swallowing apnoea); however, the control of airflow and diaphragmatic activity during swallowing and swallowing apnoea are not fully understood. Here, we validated a new airflow discriminator for detection of respiratory airflow and used it together with diaphragmatic and abdominal electromyography (EMG), spirometry and pharyngeal and oesophageal manometry. Co-ordination of breathing and spontaneous swallowing was examined in six healthy volunteers at rest, during hypercapnia and when breathing at 30 breaths min(-1). The airflow discriminator proved highly reliable and enabled us to determine timing of respiratory airflow unambiguously in relation to pharyngeal and diaphragmatic activity. During swallowing apnoea, the passive expiration of the diaphragm was interrupted by static activity, i.e. an 'active breath holding', which preserved respiratory volume for expiration after swallowing. Abdominal EMG increased throughout pre- and post-swallowing expiration, more so during hyper- than normocapnia, possibly to assist expiratory airflow. In these six volunteers, swallowing was always preceded by expiration, and 93 and 85% of swallows were also followed by expiration in normo- and hypercapnia, respectively, indicating that, in man, swallowing during the expiratory phase of breathing may be even more predominant than previously believed. This co-ordinated pattern of breathing and swallowing potentially reduces the risk for aspiration. Insights from these measurements in healthy volunteers and the airflow discriminator will be used for future studies on airway protection and effects of disease, drugs and ageing.
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| 15. |
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| 16. |
- Cedborg, Anna I Hårdemark, et al.
(författare)
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Pharyngeal Function and Breathing Pattern during Partial Neuromuscular Block in the Elderly: Effects on Airway Protection.
- 2014
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Ingår i: Anesthesiology. - 1528-1175. ; 120:2, s. 312-325
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Tidskriftsartikel (refereegranskat)abstract
- Intact pharyngeal function and coordination of breathing and swallowing are essential for airway protection and to avoid respiratory complications. Postoperative pulmonary complications caused by residual effects of neuromuscular-blocking agents occur more frequently in the elderly. Moreover, elderly have altered pharyngeal function which is associated with increased risk of aspiration. The purpose of this study was to evaluate effects of partial neuromuscular block on pharyngeal function, coordination of breathing and swallowing, and airway protection in individuals older than 65 yr.
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| 17. |
- Chen, Lingjing, et al.
(författare)
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Work Loss Duration and Predictors Following Rectal Cancer Treatment among Patients with and without Prediagnostic Work Loss
- 2016
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Ingår i: Cancer Epidemiology, Biomarkers and Prevention. - 1055-9965 .- 1538-7755. ; 25:6, s. 987-994
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Tidskriftsartikel (refereegranskat)abstract
- Background: The number of working-age rectal cancer survivors is increasing due to early detection and improved treatment. However, work loss duration and predictors among them have not been studied thoroughly. Methods: We identified 3,438 patients with stage I-III rectal cancer, 18 to 61 years of age in the Swedish Colorectal Cancer Register 1996-2009. Information on work loss due to sick leave or disability pension was collected from 2 years before diagnosis to 5 years after (until December 31st, 2013). Incidence rate ratios (IRR) of work loss were estimated in a negative binominal model by clinical characteristics for the 1st and 2nd-5th years after diagnosis. Patients were stratified by prediagnostic work loss. Results: Patients without prediagnostic work loss (74%) experienced median 147 days (25th and 75th percentile: 55 and 281) of work loss during the 1st year after diagnosis. Work loss rates (2nd-5th years) were significantly increased among relapse-free patients diagnosed in stage III [IRR = 1.92; 95% confidence interval (CI), 1.52-2.43], operated with abdominoperineal resection (IRR = 1.26; 95% CI, 1.03-1.56), and treated with neoadjuvant (chemo) radiotherapy (IRR = 1.46; 95% CI, 1.06-2.02). Patients with prediagnostic work loss (26%) experienced median 336 days (25th and 75th percentile: 183 and 365) of work loss during the 1st year, and rates did not vary clinically till 5 years. Conclusion: Without prediagnostic work loss, disease-and treatment-related factors could help identify rectal cancer patients in need of early interventions to facilitate return to work. Impact: Clinical awareness around prediagnostic and postdiagnostic work loss and individualized cancer rehabilitation programs should be emphasized among cancer survivors.
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| 18. |
- Christensen, Torben, et al.
(författare)
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Factors controlling large scale variations in methane emissions from wetlands
- 2003
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Ingår i: Geophysical Research Letters. - 0094-8276 .- 1944-8007. ; 30:7
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Tidskriftsartikel (refereegranskat)abstract
- [1] Global wetlands are, at estimate ranging 115-237 Tg CH4/yr, the largest single atmospheric source of the greenhouse gas methane (CH4). We present a dataset on CH4 flux rates totaling 12 measurement years at sites from Greenland, Iceland, Scandinavia and Siberia. We find that temperature and microbial substrate availability (expressed as the organic acid concentration in peat water) combined explain almost 100% of the variations in mean annual CH4 emissions. The temperature sensitivity of the CH4 emissions shown suggests a feedback mechanism on climate change that could validate incorporation in further developments of global circulation models.
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| 19. |
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| 20. |
- Ekberg, Anna
(författare)
-
Den arktiska tundran värmer
- 2002
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Ingår i: Biologen: medlemsblad för Biologilärarnas förening. - 0345-1127.
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Tidskriftsartikel (populärvet., debatt m.m.)
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| 21. |
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| 22. |
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| 23. |
- Ekberg, Anna, et al.
(författare)
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Isoprene emission from Sphagnum species occupying different growth positions above the water table
- 2011
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Ingår i: Boreal Environment Research: An International Interdisciplinary Journal. - 1239-6095. ; 16:1, s. 47-59
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Tidskriftsartikel (refereegranskat)abstract
- Isoprene emission from Sphagnum species naturally growing at different positions above the water table were measured in a subarctic peatland and at monoliths from a temperate bog. Our objectives were to investigate (1) whether emission rates were species and/or moisture dependent, and (2) whether short-term temperature history had an influence on emission capacity. We expected greater emission capacities in moist than dry growing conditions, and from species adapted to wet habitats. We also expected that higher emission capacities would be found in response to elevated temperatures. Average peak growing season isoprene emission capacities (standardized to 20 degrees C and PAR 1000 mu mol m(-2) s(-1)) at the subarctic site were 106 and 74 mu g C m(-2) h(-1) from a S. balticum wet lawn and a S. balticum dry hummock/palsa, respectively. Emission capacities correlated strongly with gross primary productivity (GPP) and the average air temperature of the 48 hours prior to measurement (T-48), but the effect of T-48 seemed to be partly masked by the influence of GPP when moisture was not limiting. The laboratory experiments suggested that a typical hummock species, S. rubellum had higher capacity for isoprene emission than a typical lawn species S. magellanicum. Instantaneous emission rates increased with temperature, but no effect of temperature history was discernible. Sphagnum mosses are known to emit substantial amounts of isoprene, but in this study we also showed significant inter-species differences in emission capacity. The results imply that climate change induced alterations of peatland hydrology may change the total ecosystem isoprene source strength, as individual species adapt to new growth conditions or as a consequence of species succession.
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| 24. |
- Ekberg, Anna, et al.
(författare)
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Isoprene emission from wetland sedges
- 2009
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Ingår i: Biogeosciences. - 1726-4189. ; 6:4, s. 601-613
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Tidskriftsartikel (refereegranskat)abstract
- High latitude wetlands play an important role for the surface-atmosphere exchange of carbon dioxide (CO2) and methane (CH4), but fluxes of biogenic volatile organic compounds (BVOC) in these ecosystems have to date not been extensively studied. This is despite BVOC representing a measurable proportion of the total gaseous C fluxes at northern locations and in the face of the high temperature sensitivity of these systems that requires a much improved process understanding to interpret and project possible changes in response to climate warming. We measured emission of isoprene and photosynthetic gas exchange over two growing seasons (2005-2006) in a subarctic wetland in northern Sweden with the objective to identify the physiological and environmental controls of these fluxes on the leaf scale. The sedge species Eriophorum angustifolium and Carex rostrata were both emitters of isoprene. Springtime emissions were first detected after an accumulated diurnal mean temperature above 0 degrees C of about 100 degree days. Maximum measured growing season standardized (basal) emission rates (20 degrees C, 1000 mu mol m(-2) s(-1)) were 1075 (2005) and 1118 (2006) mu g Cm-2 (leaf area) h(-1) in E. angustifolium, and 489 (2005) and 396 (2006) mu g Cm(-2)h(-1) in C. rostrata. Over the growing season, basal isoprene emission varied in response to the temperature history of the last 48 h. Seasonal basal isoprene emission rates decreased with leaf nitrogen (N), which may be explained by the typical growth and resource allocation pattern of clonal sedges as the leaves age. The observations were used to model emissions over the growing season, accounting for effects of temperature history, links to leaf assimilation rate and the light and temperature dependencies of the cold-adapted sedges.
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| 25. |
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| 26. |
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| 27. |
- Ekberg, Anna, et al.
(författare)
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Peatlands and bogs
- 2005
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Ingår i: Encyclopedia of the Arctic. - 157958439X ; , s. 1601-1602
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Bokkapitel (övrigt vetenskapligt/konstnärligt)
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| 28. |
- Ekberg, Anna, et al.
(författare)
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Rhizospheric influence on soil respiration and decomposition in a temperate Norway spruce stand
- 2007
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Ingår i: Soil Biology & Biochemistry. - : Elsevier BV. - 0038-0717. ; 39:8, s. 2103-2110
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Tidskriftsartikel (refereegranskat)abstract
- Assessments of terrestrial carbon fluxes require a thorough understanding of links between primary production, soil respiration and carbon loss through drainage. In this study, stem girdling was used to terminate autotrophic soil respiration including rhizosphere respiration and root exudation in a temperate Norway spruce stand. Rates of soil respiration and dissolved organic carbon (DOC) formation were measured in the second year after girdling, comparing an intact plant rhizosphere continuum with an exclusive decomposer system. The molecular and isotopic composition of DOC in the soil solution was analysed with a coupled Py-GC/MS-C-IRMS system to distinguish between the carbon sources of dissolved carbon. Pyrolysis products were grouped according to their precursor origins: polysaccharides, proteins or of mixed origin (mainly derivates of lignins and proteins). When dead roots became available for decomposition, rates of heterotrophic soil respiration in girdling plots peaked at 6.5 mu mol m(-2) s(-1), comparable to peak rates of total soil respiration (autotrophic and heterotrophic) in control plots, 6.1 mu mol m(-2) s(-1). A significant response of soil respiration to temperature was found in control plots only, showing that an unlimiting supply of organic substrates for microbial respiration may mask any temperature effects. The enhanced decomposition in girdled plots was further supported by the isotopic composition of DOC in soil solution; all three precursor groups became isotopically enriched as the growing season progressed (polysaccharides by 2.3 parts per thousand, proteins by 1.9 parts per thousand, mixed origin group by 2.2 parts per thousand). This indicates a trophic level shift due to incorporation of organic substrate into the microbial food chain. In the control plots' mixed origin fraction, the isotopic composition changed over time from a signature resembling that of lignin (-28.9 parts per thousand) to one similar of the protein fraction (-25.7 parts per thousand). Significant temporal changes of structural DOC composition occurred in the girdling plots only. These results suggest that changes in the microbial community and in decomposition rates occurred in both girdled and control plots in the following ways: (i) increased substrate availability (dead roots) gave rise to generally enhanced performance of the decomposer community in girdled plots, (ii) root-derived exudates probably contributed to enhanced decomposition of recalcitrant lignin in the control plots and (iii) the structural composition of DOC seemed to be more a result of decomposition than of plant root exudation in all plots. (C) 2007 Elsevier Ltd. All rights reserved.
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| 29. |
- Ekberg, Anna, et al.
(författare)
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Soil respiration
- 2005
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Ingår i: Encyclopedia of the Arctic. - 157958439X ; , s. 1928-1929
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Bokkapitel (övrigt vetenskapligt/konstnärligt)
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| 30. |
- Ekberg, Anna, et al.
(författare)
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Wetlands and methane emission
- 2005
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Ingår i: Encyclopedia of Soil Science. - 0849338301 ; , s. 1905-1908
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Bokkapitel (övrigt vetenskapligt/konstnärligt)
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| 31. |
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| 32. |
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| 33. |
- Ekberg, Christian, 1967, et al.
(författare)
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Thermodynamics of Dissolution for Bis(triazine)-Bipyridine-Class Ligands in Different Diluents and Its Reflection on Extraction
- 2010
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Ingår i: Journal of Chemical & Engineering Data. - : American Chemical Society (ACS). - 0021-9568 .- 1520-5134. ; 55:11, s. 5133-5137
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Tidskriftsartikel (refereegranskat)abstract
- Hydrochemical separation processes are one of the methods used for the treatment of spent nuclear fuel. Solvent extraction is also used in many other non-nuclear applications like the mining industry. In the nuclear case, hydrochemical separation processes are already employed in the world today for the recovery of uranium and plutonium. The method is however also considered for future separation systems for use in combination with the transmutation of the minor actinides. In a hydrochemical separation process the two phases are the pregnant (usually) aqueous feed and the organic phase comprising a diluent together with one or more extractants. One such class of extractants developed for partitioning and transmutation purposes is the bis(triazine)-bipyridine-type (BTBP) molecules. When assessing the feasibility and loading properties of such an extraction system, the solubility of the ligands is of the outmost importance. The understanding of whether the dissolution is enthalpically or entropically driven will also help the understanding of the differences in extraction observed between various diluents and temperatures. In this paper the enthalpy and entropy of dissolution of the BTBP-class ligands have been determined for different diluents. It has also been shown that it is possible to predict the extraction behavior of these molecules in the selected diluent once the solubility is known.
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| 34. |
- Ekberg, Christian, 1967, et al.
(författare)
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Using At-211 as internal alpha radiolysis source allowing for simple detection of radiolysis products
- 2010
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Ingår i: Radiation Physics and Chemistry. - : Elsevier BV. - 1879-0895 .- 0969-806X. ; 79:4, s. 454-456
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Tidskriftsartikel (refereegranskat)abstract
- The determination of radiolysis products is an important field both for the basic understanding of the radiolysis process and for process development. The latter case mainly dealing with processes for handling radioactive wastes. There are several kinds of radiolysis processes that originate from the different kinds of radiation. Gamma rays and high-energy beta has a high ability to penetrate barriers while alpha irradiation in principle has to be performed with the radiation emitting nuclide inside the actual sample. This can be a problem since most laboratories able to identify radiolysis products cannot handle alpha contaminated samples. In this paper we suggest the use of At-211 as internal alpha emitting radionuclide. Due to its short half-life and decay to more or less stable daughters the radiolysis products may be examined using normal equipment without causing contamination.
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| 35. |
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| 36. |
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| 37. |
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| 38. |
- Espegren, Fredrik, 1989, et al.
(författare)
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Tellurium transport in the RCS under conditions relevant for severe nuclear accidents
- 2021
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Ingår i: Progress in Nuclear Energy. - : Elsevier BV. - 0149-1970. ; 139
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Tidskriftsartikel (refereegranskat)abstract
- In the case of a severe nuclear power plant accident, tellurium is one of the more problematic and volatile fission products. If released it could become a health issue as it decays to iodine which accumulates in the thyroid gland. Research exists, that indicates tellurium likely interacts with caesium under severe accident conditions, thus it is important to further explore related phenomenon. In this work, tellurium was exposed to high temperature under oxidizing and inert conditions simulating severe accident conditions with and without airborne caesium iodide to determine the effect on the tellurium source term. The effect of caesium iodide was noticeable on tellurium transport behaviour in the gas phase under oxidizing and inert conditions. Under humid oxidizing conditions with caesium iodide, no significant impact on the total aerosol mass transport was noticed. However, less tellurium was transported through the model primary circuit and a potentially new compound was observed on the filter located after this model. Comparing inert dry to humid with caesium iodide showed an increase in the total aerosol mass transport whereas there was a decrease noticed of the tellurium reaching the filter after the model primary circuit. In the latter case, new unidentified compound(s) correlated to caesium, iodine and tellurium were observed on the filter located after the model. In this work, evidence was found that tellurium behaviour will be affected by caesium iodide under the investigated conditions. Moreover, it seems that under inert conditions the formed compounds may be stable at close to ambient temperatures. Unlike under oxidizing conditions, where dissociation likely occurred.
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| 39. |
- Fagerlind, Anna-Carin, et al.
(författare)
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Experience of work-related flow : Does high decision latitude enhance benefits gained from job resources?
- 2013
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Ingår i: Journal of Vocational Behavior. - : Elsevier. - 0001-8791 .- 1095-9084. ; 83:2, s. 161-170
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Tidskriftsartikel (refereegranskat)abstract
- Flow is an experience of enjoyment, intrinsic motivation and absorption, which may occur in situations involving high challenges and high skill utilization. This study investigated the likelihood of experiencing work-related flow in relation to the job strain categories of the demand–control model, and to job resources such as social capital and an innovative learning climate. A questionnaire was sent out to employees in nine Swedish organizations (n = 3667, 57% response rate). Binary logistic regression analysis was performed. The results show that active jobs, low-strain jobs, a high degree of social capital and innovative learning climate increased the likelihood of experiencing work-related flow. In jobs with high decision latitude, regardless of demands, there was an increased likelihood to benefit from social capital and an innovative learning climate. The results emphasize the importance of autonomy and skill utilization, to enable the use of additional job resources in order to promote work-related flow and well-being at work.
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| 40. |
- Fagerlind Ståhl, Anna-Carin, et al.
(författare)
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Associations between organisation of work, work conditions, work-relatedf low and performance: a multilevel analysis
- 2015
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- The aim of this study is to investigate how organisation of work in terms of sociotechnical characteristics and use of tools inspired by lean production, and psychosocial conditions at the workplace, are associated with work-related flow and performance.A questionnaire including questions concerning work organisation, psychosocial work conditions, work-related flow and self-rated performance was sent to employees in ten Swedish organisations; 4442 people (56%) responded. Multilevel logistic regression analyses were used in order to investigate organisation of work and work conditions in relation to work-related flow and performance. In addition, the association between work-related flow and performance was investigated.Our results show that a high degree of lean tool use in combination with a low degree of sociotechnical characteristics was negatively associated with work-related flow but positively associated with performance. When decision latitude, social capital, and innovative learning climate were included in the model, the association was no longer significant in relation to work-related flow, but remained and was strengthen in relation to performance. Work-related flow had a positive association with performance.The conclusion is that work-related flow and work conditions that enable individual and collective skill use are important for increased performance. When lean tools are used to a high degree, good decision latitude, social capital and innovative learning climate buffer negative effects on health, and increase performance.
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| 41. |
- Fagerlind Ståhl, Anna-Carin, et al.
(författare)
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Lean production tools and decision latitude enable conditions for innovative learning in organizations : a multilevel analysis
- 2015
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Ingår i: Applied Ergonomics. - : Elsevier. - 0003-6870 .- 1872-9126. ; 47, s. 285-291
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Tidskriftsartikel (refereegranskat)abstract
- The effect of lean production on conditions for learning is debated. This study aimed to investigate how tools inspired by lean production (standardization, resource reduction, visual monitoring, housekeeping, value flow analysis) were associated with an innovative learning climate and with collective dispersion of ideas in organizations, and whether decision latitude contributed to these associations. A questionnaire was sent out to employees in public, private, production and service organizations (n = 4442). Multilevel linear regression analyses were used. Use of lean tools and decision latitude were positively associated with an innovative learning climate and collective dispersion of ideas. A low degree of decision latitude was a modifier in the association to collective dispersion of ideas. Lean tools can enable shared understanding and collective spreading of ideas, needed for the development of work processes, especially when decision latitude is low. Value flow analysis played a pivotal role in the associations.
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| 42. |
- Fagerlind Ståhl, Anna-Carin, 1982-
(författare)
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Live long and prosper : Health-promoting conditions at work
- 2015
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The aim of this thesis is to contribute with knowledge concerning health-promoting conditions at work, and to investigate how individual, workplace and organisational conditions are interrelated. In the thesis, work-related flow, i.e. an experience of motivation, absorption and work enjoyment, is used as a holistic notion of occupational health. In Paper I, work-related flow is investigated in relation to decision latitude, social capital and an innovative learning climate at work. Paper II investigates whether the use of tools inspired by lean production, such as standardisation and value stream mapping, is positively associated with conditions for innovative learning in organisations. The aim of Paper III is to identify conditions for health and performance in organisation and at work; further, to investigate the association between work-related flow and performance. Paper IV reports on a longitudinal investigation of workrelated flow in relation to lean tool use and conditions at the workplace. The empirical material is based on data from 10 organisations, including 4442 employees. Papers I-III are cross-sectional, whereas Paper IV is longitudinal. Papers II-IV utilise multilevel analyses.The results show that decision latitude, social capital and an innovative learning climate are associated with an increase in work-related flow (Papers I, III & IV), and with performance (Paper III). Individuals’ decision latitude enables an increased benefit from the social capital and innovative learning climate at work (Paper I). The effect of tools inspired by lean production on work-related flow (Papers III & IV), and on conditions for innovative learning (Paper II) differs, depending on which tools are used, and on workplace conditions. These tools enable innovative learning mainly where decision latitude is low (Paper II), and it is primarily the lean tool value stream mapping which has the potential to create an arena for innovative learning (Paper II) and work-related flow (Paper IV).It is concluded that the individual is embedded in a social work context that has the potential to strengthen the ability to act with motivation, absorption and enjoyment. In order to utilise collective healthpromoting conditions at work, individuals need to have authority to make their own decisions and use their skills. The effect of tools inspired by lean production depends on the specific tools that are used, and on individuals’ decision latitude at work. Their potential to enable innovative learning is most evident for employees who have few opportunities for autonomous decision-making and skill use in their work. For those with a high degree of decision latitude, the use of lean tools has a smaller effect. Work-related flow may in itself serve as a resource that improves performance and increases engagement in health-promoting work conditions. In order to promote health as well as performance, work needsto be organised so that employees have opportunities to decide over their own work, and utilise their skills, individually and collectively within the workgroup.
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| 43. |
- Fagerlind Ståhl, Anna-Carin, et al.
(författare)
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The effect of lean tool use and work conditions on employee health : a longitudinal multilevel study
- 2015
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Objectives: Although lean production is an increasingly common approach to increase the efficiency of organisations, its effect on employee health is not clear. This longitudinal study investigates the effect of lean tool use and work conditions on work-related flow. Flow is a measure of health that reflects the experience of intrinsic motivation, absorption and work enjoyment.Methods: A questionnaire was sent to employees in seven organisations on two occasions with an interval of two years (n =1722). Multilevel linear regression analyses were used in order to investigate the association between the use of lean tools (i.e. standardisation, value stream mapping, visual monitoring, housekeeping and resource reduction), decision latitude, social capital, and innovative learning climate at baseline, and work-related flow at follow-up.Results: In multivariate analyses, adjusted for flow at baseline, use of lean tools was positively associated with work-related flow at follow-up. When the tools were investigated separately, only value stream mapping remained significant after adjustment for work conditions and flow at baseline. Social capital and decision latitude were positively associated with flow at follow-up. Flow at baseline and follow-up were strongly associated.Conclusions: The extent to which lean tool use has an effect on employee health depends on which tools are used. Work conditions that support learning, such as decision latitude and social capital, are associated with a longitudinal increase in the experience of work-related flow, and are important for gaining health-promoting benefits from the use of lean tools.
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| 44. |
- Fermvik, Anna, 1978, et al.
(författare)
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Influence of dose rate on the radiolytic stability of a BTPB solvent for actinide(III)/lanthanide(III) separation
- 2009
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Ingår i: Radiochimica Acta. - : Walter de Gruyter GmbH. - 0033-8230. ; 97:6, s. 1-6
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Tidskriftsartikel (refereegranskat)abstract
- The recently developed ligand MF2-BTBP dissolved in cyclohexanone is a promising solvent for the group separation of trivalent actinides(III) from the lantha-nides(III). Its high stability against nitric acid has been demonstrated recently. Since the solvent is also exposed to a continuously high radiation level in the counter current process, the radiolytic stability of the solvent was examined in this study. Irradiation experiments were carried out up to an absorbed dose of 100 kGy and the effect of the dose rate was investigated. The extraction behaviour for An(III)/Ln(III) separation was studied after radiolysis for evaluation. It was found that during high dose rate irradia-tion the extraction efficiency for both Am(III) and Eu(III) decreased significantly with increasing absorbed dose, whereas during the low dose rate irradiation the extraction efficiencies remained more or less at the same level.
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| 45. |
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| 46. |
- Fermvik, Anna, 1978, et al.
(författare)
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Radiolysis of C5-BTBP in cyclohexanone irradiated in the absence and precence of an aqueous phase
- 2012
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Ingår i: Radiochimica Acta. - : Walter de Gruyter GmbH. - 0033-8230 .- 2193-3405. ; 100:4, s. 273-282
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Tidskriftsartikel (refereegranskat)abstract
- Spent nuclear fuel contains many highly ra-dioactive species; hence solvents used in reprocessing willbe subjected to radiolysis. In this study, solvents containingone of the BTBP molecules intended for the separation oftrivalent actinides and lanthanides, the so called C5-BTBP,have been subjected to radiolysis and hydrolysis. We presenthere that this compound shows a dramatic decrease in bothdistribution ratios and separation factor when irradiated withhigher doses up to 50 kGy; particularly in the presence ofan aqueous phase. Furthermore, fast hydrolytic degradation isobserved, which significantly contributes to the overall degreeof decomposition. This is supported by speciation studies per-formed by HPLC and LC-MS methods. Proposed structuresof the highest-yield degradation products are presented andthey seem to confirm previously drawn structures for theseproducts. From these studies it can be concluded that thepresence of nitric acid or nitrate during irradiation leads tohigher content of species containing keto groups.
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| 47. |
- Fermvik, Anna, 1978, et al.
(författare)
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Radiolysis of solvents containing C5-BTBP: identification of degradation products and their dependence on absorbed dose and dose rate
- 2009
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Ingår i: Dalton Transactions. - 1477-9226 .- 1477-9234. ; 32, s. 6421-6430
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Tidskriftsartikel (refereegranskat)abstract
- Solvents intended for the separation of trivalent actinides from trivalent lanthanides in spent nuclear fuel have been irradiated with gamma-radiation. The solvents initially contained 0.005 M C5-BTBP dissolved in either hexanol or cyclohexanone and they were exposed to doses up to 20 kGy. Identification of degradation products was done using atmospheric pressure chemical ionization-mass spectrometry (APCI-MS). Structures were suggested for a number of degradation products and the relative intensity of the peaks in the MS spectra was estimated. It was clear that the content of the original molecule, C5-BTBP, decreased with dose, while the content of the various degradation products increased. It was also shown that both the choice of diluent and the dose rate (Gy/h) affect the amount of degradation products formed. A degradation scheme was proposed for the radiolytic degradation of C5-BTBP.
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| 48. |
- Fermvik, Anna, 1978, et al.
(författare)
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Radiolytic Degradation of Heterocyclic Nitrogen Containing Ligands from Low Dose-Rate Gamma Sources
- 2010
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Ingår i: ACS Symposium Series. - Washington, DC : American Chemical Society. - 1947-5918 .- 0097-6156. ; 1046, s. 215-229
-
Konferensbidrag (refereegranskat)abstract
- Chemical processes intended for the separation of various elements in used nuclear fuel will inetvitably take place in an environment exposed to ionizing radiation. Solutions used in liquid-liquid extraction processes must therefore be resistant towards radiolysis. This study presents a collection of radiolysis experiments with BTP and BTBP type molecules carried out at Chalmers University of Technology over a period of several years. The molecules both aim to extract trivalent actinides into an organic phase while leaving lanthanides in the aqueous phase. Detailed knowledge about the radiolysis behavior of BTP and BTBP type molecules can enhance the design of new, more radiolytically stable extractants and facilitate any future implementation of triazine containing ligands in an industrial process. Results show that many factors, e.g. dose rate and diluent composition, influence the radiolytic stability of these molecules. There are also strong indications that the radiolysis products of the BTBP ligand are still able to coordinate and extract metal ions, effectively altering the chemical equilibrium constants.
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| 49. |
- Fermvik, Anna, 1978, et al.
(författare)
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Semi-quantitative and quantitative studies on the gamma radiolysis of C5-BTBP
- 2011
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Ingår i: Radiochimica Acta. - : Walter de Gruyter GmbH. - 0033-8230. ; 99:2, s. 113-119
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Tidskriftsartikel (refereegranskat)abstract
- An industrial liquid liquid extraction process for reprocessing of spent nuclear fuel will inevitably lead to radiolysis of the phases, since the process streams contain highly radioactive species. Solvents containing one of the BTBP (6,6'-bis(5,6-dialkyl-[1,2,4]-triazin-3-yl)-2,2'-bipyridine) molecules intended for the separation of trivalent actinides (An) from lanthanides (Ln), the so called C5-BTBP, have shown a dramatic decrease in both distribution ratios and An/Ln separation factor when irradiated; hence, the molecule is highly unstable towards radiolysis. HPLC-, APCI(+)-MS and LC-MS analyses were performed on irradiated solvents containing initially 0.005 M C5-BTBP dissolved in either hexanol or cyclohexanone. The decrease in concentration of starting molecule as well as the increase in concentration of various degradation products were studied with quantitative and semi-quantitative measurements. Structures were suggested for the degradation products produced in highest yields and these were compared to previously proposed structures for the same products.
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| 50. |
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