| 1. |
|
|
| 2. |
|
|
| 3. |
- Axelsson, H, et al.
(författare)
-
Measurement of Aromatic-hydrocarbons With the DOAS Technique
- 1995
-
Ingår i: Applied Spectroscopy. - : SAGE Publications. - 1943-3530 .- 0003-7028. ; 49:9, s. 1254-1260
-
Tidskriftsartikel (refereegranskat)abstract
- Long-path DOAS (differential optical absorption spectroscopy) in the ultraviolet spectral region has been shown to be applicable for low-concentration measurements of light aromatic hydrocarbons. However, because of spectral interferences among different aromatics as well as with oxygen, ozone, and sulfur dioxide, the application of the DOAS technique for this group of components is not without problems. This project includes a study of the differential absorption characteristics, between 250 and 280 nm, of twelve light aromatic hydrocarbons representing major constituents in technical solvents used in the automobile industry. Spectral overlapping between the different species, including oxygen, ozone, and sulfur dioxide, has been investigated and related to the chemical structure of the different aromatics. Interference effects in the DOAS application due to spectral overlapping have been investigated both in quantitative and in qualitative terms, with data from a field campaign at a major automobile manufacturing plant.
|
|
| 4. |
|
|
| 5. |
- Callaghan, Terry, et al.
(författare)
-
Multi-Decadal Changes in Tundra Environments and Ecosystems : Synthesis of the International Polar Year-Back to the Future Project (IPY-BTF)
- 2011
-
Ingår i: Ambio. - : Springer Science and Business Media LLC. - 0044-7447 .- 1654-7209. ; 40:6, s. 705-716
-
Tidskriftsartikel (refereegranskat)abstract
- Understanding the responses of tundra systemsto global change has global implications. Most tundraregions lack sustained environmental monitoring and oneof the only ways to document multi-decadal change is toresample historic research sites. The International PolarYear (IPY) provided a unique opportunity for such researchthrough the Back to the Future (BTF) project (IPY project#512). This article synthesizes the results from 13 paperswithin this Ambio Special Issue. Abiotic changes includeglacial recession in the Altai Mountains, Russia; increasedsnow depth and hardness, permafrost warming, andincreased growing season length in sub-arctic Sweden;drying of ponds in Greenland; increased nutrient availabilityin Alaskan tundra ponds, and warming at mostlocations studied. Biotic changes ranged from relativelyminor plant community change at two sites in Greenland tomoderate change in the Yukon, and to dramatic increasesin shrub and tree density on Herschel Island, and in subarcticSweden. The population of geese tripled at one sitein northeast Greenland where biomass in non-grazed plotsdoubled. A model parameterized using results from a BTFstudy forecasts substantial declines in all snowbeds andincreases in shrub tundra on Niwot Ridge, Colorado overthe next century. In general, results support and provideimproved capacities for validating experimental manipulation,remote sensing, and modeling studies.
|
|
| 6. |
|
|
| 7. |
- Emanuelsson, Eva U., et al.
(författare)
-
Formation of anthropogenic secondary organic aerosol (SOA) and its influence on biogenic SOA properties
- 2012
-
Ingår i: Atmospheric Chemistry and Physics Discussions. - : Copernicus Publications. - 1680-7367 .- 1680-7375. ; 12:8, s. 20311-20350
-
Tidskriftsartikel (refereegranskat)abstract
- Secondary organic aerosol (SOA) formation from mixed anthropogenic and biogenic precursors has been studied exposing reaction mixtures to natural sunlight in the SAPHIR chamber in Jülich, Germany. Several experiments with exclusively anthro- 5 pogenic precursors were performed to establish a relationship between yield and organic aerosol mass loading for the atmospheric relevant range of aerosol loads of 0.01 to 10 μgm−3. The yields (0.5–9 %) were comparable to previous data and further used for the detailed evaluation of the mixed biogenic and anthropogenic experiments. For the mixed experiments a number of different oxidation schemes were addressed. The 10 reactivity, the sequence of addition, and the amount of the precursors influenced the SOA properties. Monoterpene oxidation products, including carboxylic acids and dimer esters were identified in the aged aerosol at levels comparable to ambient air. OH radicals were measured by Laser Induced Fluorescence, which allowed for establishing relations of aerosol properties and composition to the experimental OH dose. Further 15 more, the OH measurements in combination with the derived yields for anthropogenic SOA enabled application of a simplified model to calculate the chemical turnover of the anthropogenic precursor and corresponding anthropogenic contribution to the mixed aerosol. The estimated anthropogenic contributions were ranging from small (8 %) up to significant fraction (>50 %) providing a suitable range to study the effect of aerosol 20 composition on the aerosol volatility (volume fraction remaining at 343 K: 0.86–0.94). The anthropogenic aerosol had higher oxygen to carbon ratio O/C and was less volatile than the biogenic fraction. However, in order to produce significant amount of anthropogenic SOA the reaction mixtures needed a higher OH dose that also increased O/C and provided a less volatile aerosol. A strong positive correlation was found between 25 changes in volatility and O/C with the exception during dark hours where the SOA volatility decreased while O/C did not change significantly. This change in volatility under dark conditions is likely due to chemical or morphological changes not affecting O/C.
|
|
| 8. |
- Emanuelsson, Eva U., et al.
(författare)
-
Formation of anthropogenic secondary organic aerosol (SOA) and its influence on biogenic SOA properties
- 2013
-
Ingår i: Atmos. Chem. Phys.. - : Copernicus Publications. - 1680-7324. ; 13:5, s. 2837-2855
-
Tidskriftsartikel (refereegranskat)abstract
- Secondary organic aerosol (SOA) formation from mixed anthropogenic and biogenic precursors has been studied exposing reaction mixtures to natural sunlight in the SAPHIR chamber in Jülich, Germany. In this study aromatic compounds served as examples of anthropogenic volatile organic compound (VOC) and a mixture of α-pinene and limonene as an example for biogenic VOC. Several experiments with exclusively aromatic precursors were performed to establish a relationship between yield and organic aerosol mass loading for the atmospheric relevant range of aerosol loads of 0.01 to 10 μg m−3. The yields (0.5 to 9%) were comparable to previous data and further used for the detailed evaluation of the mixed biogenic and anthropogenic experiments. For the mixed experiments a number of different oxidation schemes were addressed. The reactivity, the sequence of addition, and the amount of the precursors influenced the SOA properties. Monoterpene oxidation products, including carboxylic acids and dimer esters were identified in the aged aerosol at levels comparable to ambient air. OH radicals were measured by Laser Induced Fluorescence, which allowed for establishing relations of aerosol properties and composition to the experimental OH dose. Furthermore, the OH measurements in combination with the derived yields for aromatic SOA enabled application of a simplified model to calculate the chemical turnover of the aromatic precursor and corresponding anthropogenic contribution to the mixed aerosol. The estimated anthropogenic contributions were ranging from small (≈8%) up to significant fraction (>50%) providing a suitable range to study the effect of aerosol composition on the aerosol volatility (volume fraction remaining (VFR) at 343 K: 0.86–0.94). The aromatic aerosol had higher oxygen to carbon ratio O/C and was less volatile than the biogenic fraction. However, in order to produce significant amount of aromatic SOA the reaction mixtures needed a higher OH dose that also increased O/C and provided a less volatile aerosol. The SOA yields, O/C, and f44 (the mass fraction of CO2+ ions in the mass spectra which can be considered as a measure of carboxylic groups) in the mixed photo-chemical experiments could be described as linear combinations of the corresponding properties of the pure systems. For VFR there was in addition an enhancement effect, making the mixed aerosol significantly less volatile than what could be predicted from the pure systems. A strong positive correlation was found between changes in volatility and O/C with the exception during dark hours where the SOA volatility decreased while O/C did not change significantly. Thus, this change in volatility under dark conditions as well as the anthropogenic enhancement is due to chemical or morphological changes not affecting O/C.
|
|
| 9. |
|
|
| 10. |
- Herlitz, Johan, et al.
(författare)
-
Mortality and morbidity during a period of 2 years after coronary artery bypass surgery in patients with and without a history of hypertension
- 1996
-
Ingår i: Journal of Hypertension. - : Lippincott Williams & Wilkins, Ltd.. - 0263-6352 .- 1473-5598. ; 14:3, s. 309-314
-
Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVE: To describe mortality and morbidity during a period of 2 years after coronary artery bypass grafting (CABG) in relation to a history of hypertension. PATIENTS: All patients in western Sweden in whom CABG was undertaken between June 1988 and June 1991 and in whom simultaneous valve surgery was not performed were included in the study. DESIGN: A prospective 2-year follow-up study. RESULTS: Patients with a history of hypertension (n = 777) differed from patients without such a history (n = 1348) in that the proportion of women was higher, they were older and more frequently had a history of congestive heart failure, diabetes mellitus, renal dysfunction, cerebro-vascular disease, intermittent claudication and obesity, and the number of smokers and patients with previous CABG was lower. They were also more likely to develop post-operative cerebrovascular complications and signs of myocardia damage. Patients with hypertension tended to have increased mortality during the first 30 days after CABG and the late mortality (between day 30 and 2 years) was significantly higher than in non-hypertensive participants. Whereas the development of myocardial infarction was similar in both groups, the hypertensive study participants more frequently developed stroke during 2 years of follow-up. In a multivariate analysis including age, sex, history of different cardiovascular diseases, smoking, ejection fraction, and the occurrence of three-vessel disease, hypertension did not emerge as an independent predictor of death in the early or late phase or during a total of 2 years of follow-up. CONCLUSION: Among CABG patients, those with a history of hypertension have a different pattern of risk factors. They have a higher mean age, include a higher proportion of women and have a higher prevalence of congestive heart failure, diabetes mellitus, renal dysfunction, cerebro-vascular disease, intermittent claudication, and obesity. They also have an increased frequency of immediate post-operative complications and an increased 2-year mortality, even if a history of hypertension was not an independent predictor of death during 2 years of follow-up.
|
|
