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- Cornelissen, C, et al.
(författare)
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Global change and arctic ecosystems : is lichen decline a function of increases in vascular plant biomass?
- 2001
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Ingår i: Journal of Ecology. - : Wiley. - 0022-0477 .- 1365-2745. ; 89:6, s. 984-994
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Tidskriftsartikel (refereegranskat)abstract
- 1 Macrolichens are important for the functioning and biodiversity of cold northern ecosystems and their reindeer-based cultures and economics. 2 We hypothesized that, in climatically milder parts of the Arctic, where ecosystems have relatively dense plant canopies, climate warming and/or increased nutrient availability leads to decline in macrolichen abundance as a function of increased abundance of vascular plants. In more open high-arctic or arctic-alpine plant communities such a relationship should be absent. To test this, we synthesized cross-continental arctic vegetation data from ecosystem manipulation experiments simulating mostly warming and increased nutrient availability, and compared these with similar data from natural environmental gradients. 3 Regressions between abundance or biomass of macrolichens and vascular plants were consistently negative across the subarctic and mid-arctic experimental studies. Such a pattern did not emerge in the coldest high-arctic or arctic-alpine sites. The slopes of the negative regressions increased across 10 sites as the climate became milder (as indicated by a simple climatic index) or the vegetation denser (greater site above-ground biomass). 4 Seven natural vegetation gradients in the lower-altitude sub- and mid-arctic zone confirmed the patterns seen in the experimental studies, showing consistent negative relationships between abundance of macrolichens and vascular plants. 5 We conclude that the data supported the hypothesis. Macrolichens in climatically milder arctic ecosystems may decline if and where global changes cause vascular plants to increase in abundance. 6 However, a refining of our findings is needed, for instance by integrating other abiotic and biotic effects such as reindeer grazing feedback on the balance between vascular plants and lichens.
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| 5. |
- Jacobson, H, et al.
(författare)
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Doping-Related Strain in n-Doped 4H-SiC Crystals
- 2003
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Ingår i: Silicon Carbide and Related Materials 2002. ECSCRM 2002. 4th European Conference on Silicon Carbide and Related Materials, 2-5 Sept. 2002 , Linkoping, Sweden. ; , s. 269-272
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Konferensbidrag (refereegranskat)
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| 6. |
- Jemt, Torsten, 1950, et al.
(författare)
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A comparison of laser-welded titanium and conventional cast frameworks supported by implants in the partially edentulous jaw: a 3-year prospective multicenter study.
- 2000
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Ingår i: The International journal of prosthodontics. - 0893-2174. ; 13:4, s. 282-8
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Tidskriftsartikel (refereegranskat)abstract
- PURPOSE: The purpose of this prospective multicenter study was to evaluate and compare the clinical performance of laser-welded titanium fixed partial implant-supported prostheses with conventional cast frameworks. MATERIALS AND METHODS: Forty-two partially edentulous patients were provided with Brånemark system implants and arranged into 2 groups. Group A was provided with a conventional cast framework with porcelain veneers in one side of the jaw and a laser-welded titanium framework with low-fusing porcelain on the other side. The patients in group B had an old implant prosthesis replaced by a titanium framework prosthesis. The patients were followed for 3 years after prosthesis placement. Clinical and radiographic data were collected and analyzed. RESULTS: Only one implant was lost, and all prostheses were still in function after 3 years. The 2 framework designs showed similar clinical performance with few clinical complications. Only one abutment screw (1%) and 9 porcelain tooth units (5%) fractured. Four prostheses experienced loose gold screws (6%). In group A, marginal bone loss was similar for both designs of prostheses, with a mean of 1.0 mm and 0.3 mm in the maxilla and mandible, respectively. No bone loss was observed on average in group B. No significant relationship (P > 0.05) was observed between marginal bone loss and placement of prosthesis margin or prosthesis design. CONCLUSION: The use of laser-welded titanium frameworks seems to present similar clinical performance to conventional cast frameworks in partial implant situations after 3 years.
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| 8. |
- Lessem, Jan, et al.
(författare)
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Are cardiac transplant patients more likely to have periodontitis? A case record study.
- 2002
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Ingår i: Journal of the International Academy of Periodontology. - 1466-2094. ; 4:3, s. 95-100
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Tidskriftsartikel (refereegranskat)abstract
- In several large epidemiological studies chronic periodontitis has been implicated as an additional risk factor, independent of other risk factors, for the development of ischaemic heart disease. The underlying mechanism is thought to be a localised infection giving rise to an inflammatory host response, and some experimental data agree with this hypothesis. Recently, however, some studies have questioned the post dated relationship between the two diseases. The current case-record study was undertaken to evaluate the prevalence of chronic periodontitis and the severity of such periodontal disease in a heart transplant population, assuming the latter represented a relatively severely compromised cardiovascular patient population. The study demonstrated that 76% of the patients had various degrees of periodontal disease prior to undergoing a heart transplant. Thus, it is possible that a relationship between cardiovascular disease and periodontal disease exists, but further, large intervention studies will be needed to confirm such a conclusion.
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| 9. |
- Lessem, Jan, et al.
(författare)
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Are cardiac transplant patients more likely to have periodontitis? A case record study.
- 2002
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Ingår i: Journal of the International Academy of Periodontology. - : FDI World Dental Press Ltd. - 1466-2094. ; 4:3, s. 95-100
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Tidskriftsartikel (refereegranskat)abstract
- In several large epidemiological studies chronic periodontitis has been implicated as an additional risk factor, independent of other risk factors, for the development of ischaemic heart disease. The underlying mechanism is thought to be a localised infection giving rise to an inflammatory host response, and some experimental data agree with this hypothesis. Recently, however, some studies have questioned the post dated relationship between the two diseases. The current case-record study was undertaken to evaluate the prevalence of chronic periodontitis and the severity of such periodontal disease in a heart transplant population, assuming the latter represented a relatively severely compromised cardiovascular patient population. The study demonstrated that 76% of the patients had various degrees of periodontal disease prior to undergoing a heart transplant. Thus, it is possible that a relationship between cardiovascular disease and periodontal disease exists, but further, large intervention studies will be needed to confirm such a conclusion.
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| 10. |
- Lindquist, O.P.A., et al.
(författare)
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Ordinary and extraordinary dielectric functions of 4H- and 6H-SiC from 3.5 to 9.0 eV
- 2001
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 78:18, s. 2715-2717
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Tidskriftsartikel (refereegranskat)abstract
- We report ordinary (??c axis) and extraordinary (??c axis) dielectric function data of 4H- and 6H-SiC from 3.5 to 9.0 eV. These data, which were obtained by with spectroscopic ellipsometry, are also compared to recently reported ab initio calculations. Critical point energies were found using real and reciprocal space analysis. © 2001 American Institute of Physics.
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