| 1. |
- Sandin, Per, et al.
(author)
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Precautionary defaults - A new strategy for chemical risk management
- 2004
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In: Human and Ecological Risk Assessment. - : Informa UK Limited. - 1080-7039 .- 1549-7860. ; 10, s. 1-18
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Journal article (peer-reviewed)abstract
- In order to give adequate support to risk managers, new risk assessment methods should be developed that are (1) scientifically sound, (2) simplified, and (3) suited for precautionary risk management. In this Perspective we propose that the notion of a precautionary default can be a useful tool in the development of such methods. A precautionary default is a cautious or pessimistic assumption that is used in the absence of adequate information and that should be replaced when such information is obtained. Furthermore, we point out some promising research areas for the development of such indicators, viz. connections between chemical characteristics such as persistence and effect parameters, monitoring of contaminants in polar regions, monitoring of contaminants in breast milk, application of results from (human) toxicology in ecotoxicology and vice versa, (eco) toxicological test systems that are sensitive to effects on reproduction, and the application of bioinformatic methods to complex data, both in genomic research and in ecotoxicology. We conclude that precautionary decision-making does not require less science, but to the contrary it requires more science and improved communication between scientists and risk managers.
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| 2. |
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| 3. |
- Bergman, Annika, et al.
(author)
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The western Swedish BRCA1 founder mutation 3171ins5; a 3.7 cM conserved haplotype of today is a reminiscence of a 1500-year-old mutation
- 2001
-
In: European Journal of Human Genetics. - : Nature Publishing Group. - 1018-4813 .- 1476-5438. ; 9:10, s. 787-793
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Journal article (peer-reviewed)abstract
- The most recurrent BRCA1/BRCA2 mutation in Sweden is the BRCA1 mutation 3171ins5. In the western part of Sweden this mutation accounts for as much as 77% of identified mutations in these two genes. Our aim was to analyse in detail the haplotype and founder effects of the 3171ins5 and furthermore attempt to estimate the time of origin of the mutation. In the study we included eighteen apparently unrelated families with hereditary breast and/or ovarian cancer. At least one individual in each family had previously tested positive for the 3171ins5 mutation. Polymorphic microsatellite markers were used for the haplotype analyses. The markers were located within or flanking the BRCA1 gene spanning a region of 17.3 cΜ. We found several different haplotypes both for disease alleles and for the normal alleles. However, a conserved haplotype of 3.7 cΜ was observed in the 3171ins5 carriers spanning over four markers located within or very close to the BRCA1 gene. As this haplotype was not present in any of the normal controls it is highly likely that this is a mutation identical by descent, i.e. a true founder. The results from the haplotype analyses were used to estimate the age of the mutation. Estimations based on the Pexcess and linkage disequilibrium gives a first appearance of the mutation sometime around the 6th century, approximately 50 generations ago.
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| 4. |
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| 5. |
- Bergman, Mats A., et al.
(author)
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Large investments in the pulp and paper industry : A count-data regression analysis
- 2002
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In: Journal of Forest Economics. - : Now Publishers Inc.. - 1104-6899 .- 1618-1530. ; 8, s. 29-52
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Journal article (peer-reviewed)abstract
- This paper analyses the effects of price and market size variables on the investment propensities in the pulp and paper industry. A panel of 15 European countries in the time period 1988-1997 is used in the regression analysis. We find the wages, the USD/ECU exchange rate, the price of paper and the installed production capacity to be the main determinants of large investments in this industry. Our measure of market size has no - or only very small - effects.
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| 6. |
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| 7. |
- Bergman, Mats, 1964-, et al.
(author)
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Strategic investments in the pulp and paper industry : a count data regression analysis
- 2000
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Reports (other academic/artistic)abstract
- The effects of price and market size variables on the investment propensities in the pulp and paper industry are analyzed. A panel of 15 European countries for the time period 1984 - 1997 is used in the regression analysis. We find that the wages, the $US/ECU$ exchange rate, the price of paper and the installed production capacity are the main determinants of strategic investments in this industry. There are no - or only very small - effects from our measures of market size.
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| 8. |
- Bergman, Per
(author)
-
Atherosclerosis of the ascending aorta as a risk factor for stroke after cardiac surgery : a study based on epiaortic ultrasound
- 2004
-
Doctoral thesis (other academic/artistic)abstract
- Postoperative stroke is a dreaded problem in cardiac surgery and atherosclerosis of the ascending aorta (AAA) is an important risk factor. The risk from calcified AAA, the extent and the topography of the disease in the development of stroke was evaluated. We also determined the most important risk factors for aortic embolization of particles with an intra-aortic filter. Moreover, we studied if conversion from a planned on-pump coronary artery bypass grafting (CABG) to off-pump coronary artery bypass (OPCAB) affected the incidence of postoperative stroke. Furthermore, we investigated if preoperative computer tomograpy (CT) was comparable with introperative epiaortic ultrasound to diagnose AAA. Finally, we evaluated the relationship between the topography of aortic atherosclerosis and the incidence of late stroke after coronary surgery. Methods: Epiaortic ultrasound (EPI) was performed before surgical manipulation to evaluate the ascending aorta in all patients. In 921 patients the presence of calcification, location of atheroma, extent of the disease and clinical variables including postoperative stroke were recorded prospectively. In 40 consecutive patients undergoing CABG, intraaortic filters were inserted before aortic clamping and extracted after end of cardiopulmonary bypass (CPB). In 28 consecutive patients with extensive AAA, 15 patients were converted from on-pump CABG to OPCAB. Thirteen (13) patients with similar disease who underwent on-pump CABG were used as a control. In 20 patients undergoing CABG, preoperative CT evaluation of the ascending aorta was compared with intraoperative epiaortic ultrasound findings. The ascending aorta was divided into 12 segments per patient giving in total 240 segments to compare. 611 patients undergoing CABG were followed for late stroke. The extent of atherosclerotic disease in the ascending aorta and aortic arch was evaluated with EPI and transesophageal echocardiography. The mean follow-up time was 5.5±1.7 years (range 0-8 years) and covered 3358 patient-years. Results: 26% of the patients had AAA and in 44.4% of them more than one of 12 possible segments was involved. AAA was found to be the most important predictive factor for postoperative stroke. The incidence of stroke was 1.8% in patients without, and 8.7% in patients with AAA (p<0.0001). The middle-lateral segment was found to be an independent predictive factor for postoperative stroke, with a relative risk of 26% (p=0.04) When using the intra-aortic filter, all patients had particles in the filters, in average 10.5 (SD 5.4). The most important independent risk factor for particles was number/grade of atheromas (p<0.01). When OPCAB surgery was performed, Y-grafts and the non-touch technique of the ascending aorta were used more often with than without OPCAB than in the on-pump group (47% and 73% vs. 0% and 0%, p<0.01). The incidence of stroke with OPCAB was 0% as compared with 31% in the on-pump group (p=0.03). In comparison with CT, epiaortic ultrasound detected atherosclerosis in 16.7±2.4% of the segments, which was significantly higher than with CT (p<0.03). There was a low reliability between the two methods with Kappa Coefficients of 0.45 or lower. The 5-year stroke-free survival rates for patients without aortic disease, those with less than 50% of the ascending aorta diseased and those with more than 50% affected were 95.3±0.9%, 91.8±2.1% and 65.0±14.6%, respectively (p<0.0001). The distal-left side of the ascending aorta was associated with a 5-fold increase in 5-year stroke rate. Conclusions: Patients with AAA had an 8.7% incidence of postoperative stroke. The risk depended on presence, location and extent of AAA. Atherosclerosis is the most important risk factor for embolization of particles from the ascending aorta during CABG. OPCAB preferably without manipulation of the ascending aorta reduces the incidence of stroke in patients with severe disease of the ascending aorta. CT is inferior to EPI in diagnosing extent and location of atherosclerosis of the ascending aorta. AAA stands out as a predictor of late stroke and the extent of the disease in the distal part and lesser curvature of the ascending aorta seem to be of particular importance.
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| 9. |
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| 10. |
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| 11. |
- Bergman, Stefan, 1959-, et al.
(author)
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Chronic musculoskeletal pain, prevalence rates, and sociodemographic associations in a Swedish population study
- 2001
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In: Journal of Rheumatology. - Toronto : Journal of Rheumatology Publishing Co. Ltd.. - 0315-162X .- 1499-2752. ; 28:6, s. 1369-1377
-
Journal article (peer-reviewed)abstract
- OBJECTIVE: To estimate the prevalence of chronic regional and widespread musculoskeletal pain in a sample of the general adult population and study the association to age, sex, socioeconomic class, immigration, and housing area.METHODS: A cross sectional survey with a postal questionnaire to 3928 inhabitants on the west coast of Sweden.RESULTS: The age and sex adjusted prevalence of chronic regional pain (CRP) was 23.9% and chronic widespread pain (CWP) 11.4% among 2425 subjects who responded to the complete questionnaire. Odds ratio (OR) for CWP showed a systematic increasing gradient with age and was highest in the age group 59-74 yrs (OR 6.36, 95% CI 3.85-10.50) vs age group 20-34 yrs. CWP was also associated with female sex (OR 1.91, 95% CI 1.41-2.61), being an immigrant (OR 1.83, 95% CI 1.22-2.77), living in a socially compromised housing area (OR 3.05, 95% CI 1.48-6.27), and being an assistant nonmanual lower level employee (OR 1.92, 95% CI 1.09-3.38) or manual worker (OR 2.72, 95% CI 1.65-4.49) vs being an intermediate/higher nonmanual employee. OR for CRP showed a systematic increasing gradient with age and was highest in the age group 59-74 yrs (OR 2.22, 95% CI 1.62-3.05) vs age group 20-34 yrs. CRP was also associated with being a manual worker (OR 1.63, 95% CI 1.19-2.23) vs being an intermediate/higher nonmanual employee.CONCLUSION: Chronic musculoskeletal pain is common in the general population. Sociodemographic variables were overall more frequently and strongly associated with CWP than with CRP, which indicates different pathophysiology in the development or preservation of pain in the 2 groups.
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| 12. |
- Bergman, Vivi, et al.
(author)
-
Urinary excretion of 8-hydroxydeoxyguanosine and malondialdehyde after high dose radiochemotherapy preceding stem cell transplantation
- 2004
-
In: Free Radical Biology & Medicine. - : Elsevier BV. - 0891-5849 .- 1873-4596. ; 36:3, s. 300-306
-
Journal article (peer-reviewed)abstract
- The urinary excretion of the hydroxylated DNA base 8-hydroxydeoxyguanosine (8-OHdG) and the lipid peroxidation product malondialdehyde (MDA) was monitored in 11 patients with hematological malignancies undergoing total body irradiation and high-dose chemotherapy preceding bone marrow transplantation. Nine patients showed a prompt increase in urinary 8-OHdG (8-25 times the initial baseline level) on days 0-7 after irradiation onset, the excretion then decreased during the aplastic period and increased again when engraftment took place (in 7 patients). A significant positive correlation was found between urinary 8-OHdG and whole blood leukocyte count, both on day 5 (p = .04, r = .72) and on day 22 (p = .009, r = .80) after irradiation onset. One patient who lacked the first peak of 8-OHdG excretion showed low blood leukocyte counts (less than 2×109/l) before therapy onset, this patient, however, later had a successful engraftment and then also showed considerable increases in both 8-OHdG excretion and leukocyte count. These observations suggest leukocytes play a part in the excretion of 8-OHdG after conditioning therapy preceding bone marrow transplantation. As opposed to the biphasic 8-OHdG excretion, the excretion of MDA showed a single peak appearing on days 11-19 after radiochemotherapy onset, i.e., during the period in which the patients suffered from cytopenia, mucositis, and other side effects of the treatment. It is suggested, therefore, that these clinical manifestations are associated with increased lipid peroxidation. Altogether, these findings illustrate the utility of serial urinary samples for monitoring oxidative stress due to conditioning therapy in clinical practice. They also demonstrate that different oxidative stress markers may behave quite differently regarding their appearance in the urine after whole-body oxidative stress.
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| 13. |
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| 14. |
- Chakhunashvili, Alexander, 1974, et al.
(author)
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Variation Mode and Effect Analysis
- 2004
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In: Annual Reliability and Maintainability Symposium, 2004, Los Angeles, CA.. - 0780382153
-
Journal article (peer-reviewed)
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| 15. |
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| 16. |
- Gustafsson, Fredrik, et al.
(author)
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Particle Filters for Positioning, Navigation and Tracking
- 2001
-
Reports (other academic/artistic)abstract
- A framework for positioning, navigation and tracking problems using particle filters (sequential Monte Carlo methods) is developed. It consists of a class of motion models and a general non-linear measurement equation in position. A general algorithm is presented, which is parsimonious with the particle dimension. It is based on marginalization, enabling a Kalman filter to estimate all position derivatives, and the particle filter becomes low-dimensional. This is of utmost importance for high-performance real-time applications. Automotive and airborne applications illustrate numerically the advantage over classical Kalman filter based algorithms. Here the use of non-linear models and non-Gaussian noise is the main explanation for the improvement in accuracy. More specifically, we describe how the technique of map matching is used to match an aircraft's elevation profile to a digital elevation map, and a car's horizontal driven path to a street map. In both cases, real-time implementations are available, and tests have shown that the accuracy in both cases is comparable to satellite navigation (as GPS), but with higher integrity. Based on simulations, we also argue how the particle filter can be used for positioning based on cellular phone measurements, for integrated navigation in aircraft, and for target tracking in aircraft and cars. Finally, the particle filter enables a promising solution to the combined task of navigation and tracking, with possible application to airborne hunting and collision avoidance systems in cars.
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| 17. |
- Gustafsson, Fredrik, et al.
(author)
-
Particle Filters for Positioning, Navigation and Tracking
- 2002
-
In: IEEE Transactions on Signal Processing. - : Institute of Electrical and Electronics Engineers (IEEE). - 1053-587X .- 1941-0476. ; 50:2, s. 425-437
-
Journal article (peer-reviewed)abstract
- A framework for positioning, navigation and tracking problems using particle filters (sequential Monte Carlo methods) is developed. It consists of a class of motion models and a general non-linear measurement equation in position. A general algorithm is presented, which is parsimonious with the particle dimension. It is based on marginalization, enabling a Kalman filter to estimate all position derivatives, and the particle filter becomes low-dimensional. This is of utmost importance for high-performance real-time applications. Automotive and airborne applications illustrate numerically the advantage over classical Kalman filter based algorithms. Here the use of non-linear models and non-Gaussian noise is the main explanation for the improvement in accuracy. More specifically, we describe how the technique of map matching is used to match an aircraft's elevation profile to a digital elevation map, and a car's horizontal driven path to a street map. In both cases, real-time implementations are available, and tests have shown that the accuracy in both cases is comparable to satellite navigation (as GPS), but with higher integrity. Based on simulations, we also argue how the particle filter can be used for positioning based on cellular phone measurements, for integrated navigation in aircraft, and for target tracking in aircraft and cars. Finally, the particle filter enables a promising solution to the combined task of navigation and tracking, with possible application to airborne hunting and collision avoidance systems in cars.
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| 18. |
- Hallén, Anders., et al.
(author)
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Ion implantation of silicon carbide
- 2002
-
In: Nuclear Instruments and Methods in Physics Research Section B. - 0168-583X .- 1872-9584. ; 186, s. 186-194
-
Journal article (peer-reviewed)abstract
- Ion implantation is an important technique for a successful implementation of commercial SiC devices. Much effort has also been devoted to optimising implantation and annealing parameters to improve the electrical device characteristics. However, there is a severe lack of understanding of the fundamental implantation process and the generation and annealing kinetics of point defects and defect complexes. Only very few of the most elementary intrinsic point defects have been unambiguously identified so far. To reach a deeper understanding of the basic mechanisms SiC samples have been implanted with a broad range of ions, energies, doses, etc., and the resulting defects and damage produced in the lattice have been studied with a multitude of characterisation techniques. In this contribution we will review some of the results generated recently and also try to indicate where more research is needed. In particular, deep level transient spectroscopy (DLTS) has been used to investigate point defects at very low doses and transmission electron microscopy (TEM) and Rutherford backscattering spectrometry (RBS) are used for studying the damage build-up at high doses.
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| 19. |
- Harati Zadeh, Hamid, 1964-, et al.
(author)
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Photoluminescence study of Si-doped GaN/Al0.07Ga0.93N multiple quantum wells with different dopant position
- 2004
-
In: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 84:25, s. 5071-5073
-
Journal article (peer-reviewed)abstract
- The Si-doped GaN/Al0.07Ga0.93N multiple quantum wells (MQW) were investigated, using photoluminescence (PL) and time-resolved (PL) measurements. The influence of Si doping on the emission energy and recombination dynamics of the MWQs were also investigated, with different dopant position in the wells. It was observed that the redshifted emission of the MQWs was attributed to the self-energy shift of the electron states due to the correlated motion of the electrons exposed to the fluctuating potential of the donor ions. It was also observed that the PL decay time of the sample was ∼760 ps, at low temperature.
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| 20. |
- Johansson, Per, 1973, et al.
(author)
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Beyond Root-Cause Analysis
- 2002
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In: 48th Reliability and Maintainability Symposium.
-
Conference paper (peer-reviewed)
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| 21. |
- Karlsson, Eva, 1977, et al.
(author)
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Large CO Ratio Variations in the NGC 2146
- 2004
-
In: in Proceedings of "The Neutral ISM in Starburst Galaxies", Marstrand, June 2003, eds. Aalto S., Huettemeister S., Pedlar A., Astronomical Society of the Pacific Conf. Series, San Francisco. - 1583811826 ; , s. 158-159
-
Conference paper (peer-reviewed)
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| 22. |
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| 23. |
- Lindell, Lisa, et al.
(author)
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Prevalence of fibromyalgia and chronic widespread pain
- 2000
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In: Scandinavian Journal of Primary Health Care. - Abingdon : Taylor & Francis. - 0281-3432 .- 1502-7724. ; 18:3, s. 149-153
-
Journal article (peer-reviewed)abstract
- OBJECTIVE: To explore the prevalence of fibromyalgia and chronic widespread musculoskeletal pain in a general population using the criteria of the American College of Rheumatology from 1990.DESIGN: Structured interview and clinical examination, including tender-point count and pain threshold measured with a dolorimeter, of subjects with suspected chronic widespread musculoskeletal pain.SETTING: The general population in south-west Sweden 1995-1996.SUBJECTS: 303 individuals with suspected chronic widespread pain were identified in a previously defined cohort containing 2425 men and women aged 20-74 years. 202 individuals were invited and 147 agreed to participate.MAIN OUTCOME MEASURES: Tenderpoint count, pain threshold and prevalence of chronic widespread pain and fibromyalgia.RESULTS: The prevalence of fibromyalgia was estimated to 1.3% (95% CI 0.8-1.7; n = 2425) and that of all chronic widespread pain to 4.2% (95% CI 3.4-5.0; n = 2425). The mean pain threshold measured with a dolorimeter was lower in subjects with chronic widespread pain (p < 0.01) and correlated with the number of tender points (r = -0.59, p < 0.01) but could not be used to distinguish the subjects with fibromyalgia.CONCLUSION: Compared to other studies, fibromyalgia and chronic widespread musculoskeletal pain seemed to be relatively rare conditions in the south-west of Sweden.
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| 24. |
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| 25. |
- Monemar, Bo, 1942-, et al.
(author)
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Influence of polarization fields and depletion fields on photoluminescence of AlGaN/GaN multiple quantum well structures
- 2003
-
In: Physica status solidi. B, Basic research. - : Wiley. - 0370-1972 .- 1521-3951. ; 237:1, s. 353-364
-
Journal article (peer-reviewed)abstract
- We report on a detailed study of low temperature photoluminescence (PL) in Al0.07Ga0.93N/GaN multiple quantum wells (MQWs). The structures were grown on sapphire with the conventional low temperature AlN nucleation layer and thick GaN buffer layer. Several sets of 5 QW MQW samples were studied, one set with Si doping in the barriers up to or above the metallic limit. Nominally undoped MQW samples were also studied. The spectral behaviour of the doped samples was strongly affected by the near surface depletion field, causing overlap of different spectra from non-equivalent QWs. The QWs closest to the surface are presumably inactive in some samples, due to a very high depletion field. For the case of undoped samples, on the other hand, the near surface QWs are active and most prominent in the PL spectra. The structure from discrete well width variations is here resolved in the PL spectra. The results demonstrate that for structures with no additional capping layer both the depletion field and the polarisation fields need to be considered in the interpretation of experimental data. The theoretically estimated fields in this work are consistent with the experimental spectra. The presence of localisation even in the case of metallic samples, as observed by a constant PL decay time independent of doping, is discussed in terms of penetration of the hole wave functions into the AlGaN barriers. This localisation is also manifested in a sizeable LO phonon coupling strength in all samples studied.
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| 26. |
- Monemar, Bo, et al.
(author)
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Optical investigation of AlGaN/GaN quantum wells and superlattices
- 2004
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In: Physica status solidi. A, Applied research. - : Wiley. - 0031-8965 .- 1521-396X. ; 201:10, s. 2251-2258
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Journal article (peer-reviewed)abstract
- We report a detailed optical study of several sets of multiple quantum wells (MQWs) in the AlGaN/GaN system, as well as AlN/GaN superlattice (SL) structures. In this study all materials were grown by MOCVD, as opposed to most previous studies where MBE was employed. In undoped MQWs discrete photoluminescence (PL) peaks related to discrete well width fluctuations by one full c lattice parameter are clearly observed. In doped samples this effect appears to be screened. While the recombination process in undoped samples is excitonic, in MQWs doped with Si above about 5 x 10(18) cm(-3) free electrons (a 2DEG) are dominant, and the PL process is a free electrons-localized hole transition at low temperatures. The hole localization prevails up to very high n-doping, as was previously observed in bulk GaN. The hole localization is demonstrated via several experiments, including results on PL transient decay times and LO phonon coupling. Near surface band bending, due mainly to dopant depletion in doped structures or interaction with surface states in case of higher Al content in barriers, influences the distribution of electron filling among the QWs, making a detailed modeling of the spectral shape somewhat ambiguous. It is found that AlN barriers promote a strong room temperature PL signal from the QWs, as opposed to the case with AlGaN barriers.
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| 27. |
- Monemar, Bo, et al.
(author)
-
Photoluminescence of InGaN/GaN and AlGaN/GaN multiple quantum well structures : Role of depletion fields and polarization fields
- 2003
-
In: Physica status solidi. A, Applied research. - Weinheim, Germany : Wiley-VCH Verlagsgesellschaft. - 0031-8965 .- 1521-396X. ; 195:3, s. 523-527
-
Journal article (peer-reviewed)abstract
- We report on low temperature photoluminescence (PL) in InxGa1-xN multiple quantum wells (MQWs) with x in the range 0.1 and highly Si doped barriers of In0.01Ga0.99N. The MQW was placed either in the near surface depletion field or at the n-side depletion field of a pn-junction. At low temperatures the PL and electroluminescence (EL) spectra are quite different at no, low, or reverse bias, the PL appearing at higher energy. At high forward bias a spectral component at the EL position appears in PL. This proves a strong influence of the depletion field on the optical spectra. Preliminary results are also reported for Al0.07Ga0.93N/GaN structures, with near surface MQWs with 5 QWs, both Si-doped and nominally undoped. These structures show clear spectral features related to nonequivalent QWs in a graded depletion field.
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| 28. |
- Nordlund, Per-Johan, et al.
(author)
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A Framework for Particle Filtering for Positioning, Navigation and Tracking
- 2001
-
In: Proceedings of the 11th IEEE Signal Processing Workshop on Statistical Signal Processing. - : IEEE. - 0780370112 ; , s. 34-37
-
Conference paper (peer-reviewed)abstract
- A framework for positioning, navigation and tracking problems using particle filters (recursive Monte Carlo methods) is developed. Automotive and airborne applications, approached in this framework, have proven a numerical advantage over classical Kalman filter based algorithms. Here the use of non-linear measurement models and non-Gaussian measurement noise is the main explanation for the improvement in accuracy, and models for relevant sensors are surveyed.
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| 29. |
- Olofsson, Henrik, 1972, et al.
(author)
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Odin water mapping in the Orion KL region
- 2003
-
In: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 402, s. L47-L54
-
Journal article (peer-reviewed)abstract
- New results from water mapping observations of the Orion KL region using the submm/mm wave satellite Odin (2.1\arcmin beam size at 557 GHz), are presented. The ortho-H2O \jkktrans{1}{1}{0}{1}{0}{1} ground state transition was observed in a 7arcminx 7arcmin rectangular grid with a spacing of 1\arcmin, while the same line of H218O was measured in two positions, Orion KL itself and 2\arcmin south of Orion KL. In the main water species, the KL molecular outflow is largely resolved from the ambient cloud and it is found to have an extension of 60\arcsec-110\arcsec. The H2O outflow profile exhibits a rather striking absorption-like asymmetry at the line centre. Self-absorption in the near (or ``blue'') part of the outflow (and possibly in foreground quiescent halo gas) is tentatively suggested to play a role here. We argue that the dominant part of the KL H218O outflow emission emanates from the compact (size ~ 15\arcsec) low-velocity flow and here estimate an H2O abundance of circa 10-5 compared to all H2 in the flow - an order of magnitude below earlier estimates of the H2O abundance in the shocked gas of the high-velocity flow. The narrow ambient cloud lines show weak velocity trends, both in the N-S and E-W directions. H218O is detected for the first time in the southern position at a level of ~ 0.15 K and we here estimate an H2O abundance of (1-8) x 10-8. Odin is a Swedish-led satellite project funded jointly by the Swedish National Space Board (SNSB), the Canadian Space Agency (CSA), the National Technology Agency of Finland (Tekes), and the Centre National d'Études Spatiales (CNES, France). The Swedish Space Corporation (SSC) was the industrial prime contractor and is also responsible for the satellite operation.
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| 30. |
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| 31. |
- Persson, Per, et al.
(author)
-
Structural defects in electrically degraded 4H-SiC PiN diodes
- 2002
-
In: Materials Science Forum, Vols. 389-393. ; , s. 423-426
-
Conference paper (peer-reviewed)abstract
- Triangular structural defects, occasionally generated during long term operation of 4H-SiC pin diodes, are known to negatively affect the forward characteristics of the diode. We have used synchrotron white beam X-ray topography, scanning electron microscopy, in situ cathodo luminescence and transmission electron microscopy for characterizing the structure and formation mechanisms of such defects. It is shown from high-resolution images that the defect results from glide slip on the (0001) basal plane. The defect consists of a stacking fault bound by two partial dislocations with Burgers vectors 1/3<11 (1) over bar0> and 1/3<01 (1) over bar0>. The fault is a means for stress relaxation in the epilayer, near the contact layer using an existing dislocation as a nucleation source.
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| 32. |
- Reginski, K, et al.
(author)
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Investigations of optical properties of active regions in vertical cavity surface emitting lasers grown by MBE
- 2002
-
In: Thin Solid Films. - 0040-6090 .- 1879-2731. ; 412:1-2, s. 107-113
-
Journal article (peer-reviewed)abstract
- The design of the vertical cavity surface emitting lasers (VCSELs) needs proper tuning of many different optical parameters of those structures. So, the optimisation of the VCSELs requires deep understanding of optical processes occurring in the active regions of such lasers. In a series of MBE processes, active regions of VCSELs as well as the whole VCSELs were grown. The active regions of the VCSEL structures were designed for lambda = 1000 nm and 980 nm emission. They consisted of a pair of distributed Bragg reflectors (DBRs) composed of AlAs and GaAs quarter wavelength layers and a cavity made of GaAs. The cavities contained one or several quantum wells (QWs) made of In0.2Ga0.8As. To optimise the optical characteristics of the active regions, several experimental methods have been applied. The Bragg reflectors and the whole microcavities were investigated by optical reflectivity. For selective excitation of a QW in a cavity active layer, a Ti-sapphire tuneable laser has been used. The fine tuning between the QW emission and the cavity Fabry-Perot resonance has been investigated by photoluminescence at varying temperatures of the sample. For monitoring the temporal evolution of the luminescence from the active region of the laser, time-resolved spectroscopy has been employed. The combination of many methods of optical investigations enabled a comprehensive characterisation and as a result an optimisation of the whole laser structure. (C) 2002 Elsevier Science B.V. All rights reserved.
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| 33. |
- Shubina, Tatiana, et al.
(author)
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Intrinsic electric fields in N-polarity GaN/AlxGa1-xN quantum wells with inversion domains
- 2003
-
In: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 67:19
-
Journal article (peer-reviewed)abstract
- GaN/AlGaN quantum wells (QWs) of dominant N polarity with inversion domains (IDs), grown by molecular-beam epitaxy, have been studied. Two-band photoluminescence (PL), with the lower-energy band and an additional absorption edge related to the IDs, is observed in these QWs due to a difference in strain, electric field, and well width in the regions of different polarities. A time-resolved PL study reveals additionally strong inhomogeneity of the electric fields among the IDs. The intrinsic electric fields in the structures are relatively small-their maximal estimated value of 180 kV/cm is among the lowest ever reported. The low-scale electric fields indicate likely polarization deterioration in the N-polarity structures. These conditions are favorable for bright PL up to room temperature in 8-9-nm-wide wells.
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| 34. |
- Shubina, Tatiana, et al.
(author)
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Nanometric-scale fluctuations of intrinsic electric fields in GaN/AlGaN quantum wells with inversion domains
- 2002
-
In: Physica status solidi. B, Basic research. - 0370-1972 .- 1521-3951. ; 234:3, s. 919-923
-
Journal article (peer-reviewed)abstract
- Strain and electric field fluctuations in regions of different polarities in GaN/AlGaN quantum well (QW) structures of dominant N-polarity with inversion domains (IDs) split the photoluminescence (PL) emission into two bands. Micro-PL and time-resolved PL studies reveal strong inhomogeneity of the array of the IDs, where essential parameters, such as strain, electric fields, and sizes are fluctuating quantities. We demonstrate also that the ID formation decreases the intrinsic electric field magnitudes.
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| 35. |
- Shubina, Tatiana, et al.
(author)
-
Optical properties of GaN/AlGaN quantum wells with inversion domains
- 2003
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In: Physica status solidi. A, Applied research. - : Wiley. - 0031-8965 .- 1521-396X. ; 195:3, s. 537-542
-
Journal article (peer-reviewed)abstract
- Two-band photoluminescence (PL) and respective absorption and reflection features are observed in GaN/AlGaN MBE-grown quantum well (QW) structures of dominant N polarity with inversion domains (IDs). The PL bands are related to transitions in the regions of different polarity, characterized by different strain and electric fields. A micro-PL study reveals sharp and narrow (1.5-2.5 meV) PL lines placed between the bands, which are tentatively attributed to recombination at localization sites associated with intersections of the QWs with the domains. Additionally, we demonstrate that the ID formation decreases the overall strength of the intrinsic electric fields in the QW structures.
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| 36. |
- Shubina, Tatiana, et al.
(author)
-
Peculiarities of exciton-polaritons in GaN at different polarizations studied by mu-photoluminescence spectroscopy
- 2002
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In: Physica status solidi. A, Applied research. - 0031-8965 .- 1521-396X. ; 190:1, s. 205-211
-
Journal article (peer-reviewed)abstract
- We report on polariton properties in high quality thick GaN grown by hydride vapor phase epitaxy on c-sapphire. A strong fine is observed in the vicinity of the A exciton in T-polarization (k perpendicular to c, E parallel to the c-axis) by micro-photoluminescence (mu-PL). Comparison of the mu-PL and mu-reflectance spectra confirms the internal origin of the polariton emission. In the samples with low density of residual donors the enhancement of the a-polarized component is induced mostly by interbranch scattering which occurs, possibly., due to the complex structure of the exciton-polariton branches at k perpendicular to c. The Gamma(1)-Gamma(5) exciton splitting in the C band is determined by the mu-reflectance as similar to1 meV.
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| 37. |
- Sjögren, M., et al.
(author)
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Antifouling activity of brominated cyclopeptides from the marine sponge Geodia barretti
- 2004
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In: Journal of Natural Products. - : American Chemical Society (ACS). - 0163-3864 .- 1520-6025. ; 67:3, s. 368-372
-
Journal article (peer-reviewed)abstract
- In this work, we show the potent antifouling effects of two compounds, barettin (cyclo[(6-bromo-8-entryptophan)arginine]) (1), isolated as a Z/E mixture (87/13), and 8,9-dihydrobarettin (cyclo[(6-bromotryptophan)arginine]) (2), isolated from the marine sponge Geodia barretti. The compounds were isolated guided by their ability to inhibit the settlement of cyprid larvae of the barnacle Balanus improvisus, and their structures were determined by means of mass spectrometry, NMR, and quantitative amino acid analysis. The activities of these brominated diketopiperazine-like cyclic dipeptides are in the range of antifouling agents in use today, as shown by their EC50 values of 0.9 and 7.9 muM, respectively. However, contrary to today's antifouling agents, the effects of barettin and 8,9-dihydrobarettin are nontoxic and reversible. A small set of synthetic analogues, including L-arginine, L-tryptophan, 5-bromo-D,L-tryptophan, 6-bromo-D,L-tryptophan, and 6-fluoro-D,L-tryptophan, were tested for possible structure-activity relationships. None of these compounds showed any effect at a concentration of 10 muM. We hypothesize that the isolated compounds are part of the sponge's chemical defense to deter fouling organisms. This theory is supported by the fact that barettin is found in water exposed to living specimens of G. barretti in concentrations that completely inhibit barnacles from settling.
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| 38. |
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| 39. |
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| 40. |
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| 41. |
- Svanberg, Christer, 1970, et al.
(author)
-
Secondary relaxation in confined and bulk propylene carbonate
- 2003
-
In: Europhysics Letters. - : IOP Publishing. - 0295-5075 .- 1286-4854. ; 64:3, s. 358-363
-
Journal article (peer-reviewed)abstract
- Dielectric loss spectra of propylene carbonate in bulk and dissolved in a polymer matrix are investigated with focus on the currently debated excess wing. The spatial restrictions caused by the polymer matrix slow down the main structural (α) relaxation, while the excess wing continuously transforms towards a shoulder with increasing spatial restrictions. We show that the excess wing in a consistent manner can be described by a secondary relaxation with only a weak dependence of the concentration of polymer. Thus the results imply that the excess wing is due to a secondary relaxation submerged in the α-relaxation.
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| 42. |
- Svensson, BG, et al.
(author)
-
Doping of silicon carbide by ion implantation
- 2001
-
In: Materials Science Forum, Vols. 353-356. - : Trans Tech Publications Inc.. - 9780878498734 - 0878498737 ; , s. 549-554, s. 549-554
-
Conference paper (peer-reviewed)abstract
- A brief survey is given of some recent results on doping of 4H- and 6H-SiC by ion implantation. The doses and energies used are between 10(9) and 10(15) cm(-2) and 100 keV and 5 MeV, respectively, and B and Al ions (p-type dopants) are predominantly studied. After low dose implantation (less than or equal to 10(10) cm(-2)) a strong compensation is observed in n-type samples and this holds irrespective of implantation temperature up to 600 degreesC. However, at higher doses (10(14)-10(15) Al/cm(2)) the rate of defect recombination (annihilation) increases substantially during hot implants (greater than or equal to 200 degreesC) and in these samples one type of structural defect dominates after past-implant annealing at 1700-2000 degreesC. The defect is identified as a dislocation loop composed of clustered interstitial atoms inserted on the basal plane in the hexagonal crystal structure. Finally, transient enhanced diffusion (TED) of ion-implanted boron in 4H-samples is discussed.
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| 43. |
- Wiklund, Per, et al.
(author)
-
Alkylation and acylation of basic salts of anthranilic acid
- 2004
-
In: Tetrahedron Letters. - : Elsevier BV. - 0040-4039 .- 1359-8562. ; 45:5, s. 969-972
-
Journal article (peer-reviewed)abstract
- The O-nucleophilicity of basic anthranilic acid salts was documented, analyzed, and utilized in synthesis. Specifically substitutions leading to esters instead of secondary amines, and formation of anthranilic acid anhydrides were studied.
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| 44. |
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| 45. |
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| 46. |
- Wiklund, Per, et al.
(author)
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Synthesis of 1,4-benzodiazepine-3,5-diones
- 2004
-
In: Journal of Organic Chemistry. - : American Chemical Society (ACS). - 0022-3263 .- 1520-6904. ; 69:19, s. 6371-6376
-
Journal article (peer-reviewed)abstract
- Even though benzodiazepines have a strong position in medicinal chemistry, very few synthetic routes to 1H-1,4-benzodiazepine-3,5(2H,4H)-diones have ever been published and the claimed products have often been poorly characterized. Through the present work several 1H-1,4-benzodiazepine-3,5(2H,4H)-diones have become available from N-carbamoylmethylanthranilic acids. The required ring closures were achieved only when the amino groups of the starting materials were substituted with electron withdrawing groups such as acetyl, alkyloxycarbonyl, or nitroso. During the synthetic work a novel ring contraction rearrangement from a 1-nitroso-1H-1,4-benzodiazepine-3,5(2H,4H)-dione to a 3H-quinazoline-4-one was observed. The proposed mechanism involves elimination of HNO followed by a proton-mediated loss of CO. The 1-nitrosated 1,4-benzodiazepinediones could be separately denitrosated to the corresponding amino compounds.
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| 47. |
- Wiklund, Per
(author)
-
Synthesis of heterocycles from anthranilic acid and its derivatives
- 2004
-
Doctoral thesis (other academic/artistic)abstract
- Anthranilic acid (2-aminobenzoic acid, Aa) is the biochemical precursor to the amino acid tryptophan, as well as a catabolic product of tryptophan in animals. It is also integrated into many alkaloids isolated from plants. Aa is produced industrially for production of dyestuffs and pharmaceuticals. The dissertation gives a historical background and a short review on the reactivity of Aa. The synthesis of several types of nitrogen heterocycles from Aa is discussed. Treatment of anthranilonitrile (2-aminobenzonitrile, a derivative of Aa) with organomagnesium compounds gave deprotonation and addition to the nitrile triple bond to form amine-imine complexed dianions. Capture of these intermediate with acyl halides normally gave aromatic quinazolines, a type of heterocyclic compounds that is considered to be highly interesting as scaffolds for development of new drugs. When the acyl halide was a tertiary 2-haloacyl halide, the reaction instead gave 1,4-benzodiazepine-3-ones via rearrangement. These compounds are isomeric to the common benzodiazepine drugs (such as diazepam, Valium®) which are 1,4-benzodiazepine-2-ones. Capture of the dianions with aldehydes or ketones, led to 1,2-dihydroquinazolines. Unsubstituted imine anions could be formed by treatment of anthranilonitrile with diisobutylaluminium hydride. Also in this case capture with aldehydes gave 1,2-dihydroquinazolines. Several different dicarboxylic acid derivatives of Aa were treated with dehydrating reagents, and the resulting products were more or less complex 1,3-benzoxazinones, one of which required X-ray crystallography confirm its structure. During the work on preparation of N-substituted derivatives of Aa, necessary for synthesis of 1,4-benzodiazepine-3,5-diones, it was noted that many of the obtained products were in fact not N-substituted, but O-substituted. This challenged the established notion that Aa reacts nucleophilically at the N-terminal under most conditions. Several grave errors in the recent literature were revealed. In 1976 researchers from the group that originally developed the common benzodiazepine drugs published a retraction of a claim of synthesis of a benzodiazepine by Gärtner in 1904. They found that the method actually gave a 6-membered ring system, not a 7-membered 1,4-benzodiazepine-3,5-dione as originally claimed. Because the 1,4-benzodiazepine skeleton is highly interesting as a scaffold for development of new drugs, a few publications on synthesis of this target has appeared. However, repetition of several of the described syntheses failed to yield the poorly described products. Studies on how to ring close N-carbamoyl derivatives of Aa were undertaken. It became clear that Umpolung of the substrates by N-derivatisation was a necessary prerequisite for ring closure. The introduction of the N-nitroso group was developed to this end, leading to N1-nitroso substituted 1,4-benzodiazepine-3,5-diones. The nitroso group could be removed after ring closure. Heating of one of these compounds induced a ring contraction rearrangement. A proposed mechanism involves elimination of HNO (nitrosyl) and proton mediated loss of CO.
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| 48. |
- Zhao, Q.X., et al.
(author)
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Dynamic properties of radiative recombination in p-type d-doped layers in GaAs
- 2001
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In: Physical Review B. - : American Physical Society. - 2469-9950 .- 2469-9969. ; 63
-
Journal article (peer-reviewed)abstract
- We present an optical study of thin Zn-doped GaAs layers embedded in bulk GaAs, grown by metal-organic vapor-phase-epitaxy by means of stationary and time-resolved optical spectroscopy. The concentration of the Zn acceptors was aimed at 2×1020/cm3 in 4-nm-wide doping regions. The intensity of the optical radiative transition (so called the F emission) appearing in photoluminescence spectra was found to be related to holes confined at doping regions. The F emission shows a strong dependence on excitation intensity and temperature. The energy position varies from 1.46 to 1.49 eV as the excitation density changes from about 40 mW/cm2 to 23 W/cm2. The dynamic properties of the F-emission band have been studied by time-resolved spectroscopy. The F emission shows a nonexponential decay character. The decay time of the F emission exhibits a strong dependence on the detection energy within the F-emission band. The decay time becomes longer as the detection energy is redshifted.
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