| 1. |
- Joelsson, L. M T, et al.
(författare)
-
Kinetic isotope effects of 12CH3D+OH and 13CH3D+OH from 278 to 313K
- 2016
-
Ingår i: Atmospheric Chemistry and Physics. - : Copernicus GmbH. - 1680-7316 .- 1680-7324. ; 16:7, s. 4439-4449
-
Tidskriftsartikel (refereegranskat)abstract
- Methane is the second most important long-lived greenhouse gas and plays a central role in the chemistry of the Earth's atmosphere. Nonetheless there are significant uncertainties in its source budget. Analysis of the isotopic composition of atmospheric methane, including the doubly substituted species 13CH3D, offers new insight into the methane budget as the sources and sinks have distinct isotopic signatures. The most important sink of atmospheric methane is oxidation by OH in the troposphere, which accounts for around 84% of all methane removal. Here we present experimentally derived methane+OH kinetic isotope effects and their temperature dependence over the range of 278 to 313K for CH3D and 13CH3D; the latter is reported here for the first time. We find kCH4/kCH3D Combining double low line 1.31 ± 0.01 and kCH4/k13CH3D Combining double low line 1.34 ± 0.03 at room temperature, implying that the methane+OH kinetic isotope effect is multiplicative such that (kCH4/k13CH4)(kCH4/kCH3D) Combining double low line kCH4/k13CH3D, within the experimental uncertainty, given the literature value of kCH4/k13CH4 Combining double low line 1.0039 ± 0.0002. In addition, the kinetic isotope effects were characterized using transition state theory with tunneling corrections. Good agreement between the experimental, quantum chemical, and available literature values was obtained. Based on the results we conclude that the OH reaction (the main sink of methane) at steady state can produce an atmospheric clumped isotope signal (δ(13CH3D) Combining double low line ln([CH4][13CH3D]/[13CH4][CH3D])) of 0.02 ± 0.02. This implies that the bulk tropospheric δ(13CH3D) reflects the source signal with relatively small adjustment due to the sink signal (i.e., mainly OH oxidation).
|
|
| 2. |
|
|
| 3. |
|
|
| 4. |
|
|
| 5. |
|
|
| 6. |
- Hasselqvist-Ax, I, et al.
(författare)
-
Experiences among firefighters and police officers of responding to out-of-hospital cardiac arrest in a dual dispatch programme in Sweden: an interview study
- 2019
-
Ingår i: BMJ open. - : BMJ. - 2044-6055. ; 9:11, s. e030895-
-
Tidskriftsartikel (refereegranskat)abstract
- The objective of this study was to explore firefighters’ and police officers’ experiences of responding to out-of-hospital cardiac arrest (OHCA) in a dual dispatch programme.DesignA qualitative interview study with semi-structured, open-ended questions where critical incident technique (CIT) was used to collect recalled cardiac arrest situations from the participants’ narratives. The interviews where transcribed verbatim and analysed with inductive content analysis.SettingThe County of Stockholm, Sweden.ParticipantsPolice officers (n=10) and firefighters (n=12) participating in a dual dispatch programme with emergency medical services in case of suspected OHCA of cardiac or non-cardiac origin.ResultsAnalysis of 60 critical incidents was performed resulting in three consecutive time sequences (preparedness, managing the scene and the aftermath) with related categories, where first responders described the complexity of the cardiac arrest situation. Detailed information about the case and the location was crucial for the preparedness, and information deficits created stress, frustration and incorrect perceptions about the victim. The technical challenges of performing cardiopulmonary resuscitation and managing the airway was prominent and the need of regular team training and education in first aid was highlighted.ConclusionsParticipating in dual dispatch in case of suspected OHCA was described as a complex technical and emotional process by first responders. Providing case discussions and opportunities to give, and receive feedback about the case is a main task for the leadership in the organisations to diminish stress among personnel and to improve future OHCA missions.
|
|
| 7. |
- Joelsson, Lars Magnus T., et al.
(författare)
-
Tailored chemical mechanisms for simulation of urban air pollution
- 2018
-
Ingår i: WIT Transactions on Ecology and the Environment. - 1746-448X. ; 230, s. 165-176
-
Tidskriftsartikel (refereegranskat)abstract
- A semi-stochastic, statistical reduction method for chemical kinetic schemes based on the ant colony optimization method, is developed for atmospheric chemistry simulations. The prime application is coupled dynamic and chemistry models for simulation of the dispersion and reactivity of chemical species on street scale, i.e. the modelling of urban air pollution in street canyons. The method is designed so that it will optimize the reduction process for any simulation case, as given by user-specific inputs, such as initial concentrations of reactive species, temperature, humidity, residence time, and solar radiation. These inputs will correspond to, or be deduced from, actual variables such as season, time-of-day, geographic location, proximity to volatile organic carbon or nitrogen oxides sources (e.g. forests, roads, industry, harbours etc.) and their source strengths, weather, composition of vehicle fleet, and traffic load inside the street canyon. The method is evaluated against three box model case studies (laboratory and atmospheric simulations) previously described in the literature. The method reduces the mechanism sizes with 62.5%, 84.7%, and 97.7% respectively, retaining the average accuracy for the prediction of the target compound (O3, NO2, and NO) concentrations by 94.1%, 90.3%, and 91.2% respectively. These preliminary results illustrate the potential for the method. Further developments, such as inclusion of lumping or short-cutting of reaction paths, can be considered.
|
|
| 8. |
- Joelsson, L. M.T., et al.
(författare)
-
Tailored reduced kinetic mechanisms for atmospheric chemistry modeling
- 2019
-
Ingår i: Atmospheric Environment. - : Elsevier BV. - 1352-2310. ; 213, s. 675-685
-
Tidskriftsartikel (refereegranskat)abstract
- Reduced chemical kinetic mechanisms are essential for atmospheric chemistry modeling where the use of explicit kinetic schemes is too computationally demanding. By tailoring mechanisms to specific cases, the size of the mechanism can be kept small, without significant loss of accuracy in predictions of selected species’ concentrations. In the present work, we present small kinetic mechanisms tailored to specific cases, using a novel method. The reduced mechanisms are generated by applying the method to several cases previously described in the literature and their performance in box model simulations are evaluated. The characteristics of the reduced mechanisms are examined. In addition, the method's sensitivity towards time scales, choice of trace gas species of interest, and NOx regime are investigated. The reduced mechanisms include 10%–30% of all the reactions in the relevant subset of the detailed chemical mechanism. Simulations with the reduced mechanisms typically yield no loss in accuracy of ozone concentration predictions and less than a 10% accuracy loss for the concentration predictions of nitrogen oxides for the cases over as long as five simulated days. Mechanisms generated to predict the concentrations of few species, over short time scales, in high NOx conditions, and with no isoprene, generally include fewer reactions than mechanisms generated to predict the concentrations of several species, over long time scales, in lowNOx, isoprene rich conditions.
|
|
| 9. |
|
|
| 10. |
- Pettersson, Gunilla, et al.
(författare)
-
Upgrading the strength properties of sheets from hardwood high yield pulps
- 2018
-
Ingår i: Pan Pacific Fibre Value Chain Conference 2018, Proceedings. - : Appita Inc.. - 9780975746998 ; , s. 142-147
-
Konferensbidrag (refereegranskat)abstract
- In the current paper it is shown that tensile and compression strength of sheets from hardwood high yield pulps (HYP), which has been manufactured at a low energy input in refining, can be multiplied by improving the fibre-fibre bond strength and the number of contact areas between fibre surfaces in the sheet structure. At fibre surface treatment with cationic starch the properties are improved at almost preserved bulk (i.e., preserved density). Remarkable improvements are achieved at densification of the sheet structures by pressing in a hot press nip at temperatures well above the softening temperature of wet lignin. The former technique is above all to prefer in manufacturing of middle plies in paperboard composites, whereas the latter technique is of special interest in manufacturing of packaging papers with high demands upon strength. For instance, it is shown in the paper how tensile index on sheets of CTMP from birch (CSF 480 ml) can be enhanced from 20 to 50 kNm/kg and compression index (SCT) from 10 to 35 kNm/kg by the tested techniques.
|
|
