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| 2. |
- Lindgren, Stig-Åke, 1950, et al.
(författare)
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Coverage-dependent frequency for Li-atom vibrations on Cu(111)
- 1996
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Ingår i: Physical Review B. - 2469-9969 .- 2469-9950. ; 54:15, s. 10912 - 10916
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Tidskriftsartikel (refereegranskat)abstract
- Electron-energy-loss spectra recorded for monolayer amounts of Li adsorbed on Cu(111) show a loss peak associated with Li vibrations perpendicular to the substrate. The loss energy shifts from 38 meV at low coverage to 43 meV at 0.3 ML and remains constant for coverages between 0.3 and 0.5 ML. The loss intensity passes a maximum at a Li coverage of 0.15 ML and gradually decreases such that it is difficult to resolve a loss peak at coverages above 0.5 ML. The high loss energy indicates that the adatom resides on the surfaces rather than in substitutional sites. The frequency shift is much too large to be explained by dipole-dipole interactions. The above results are obtained with the evaporation source loaded with the natural Li isotope mixture (92.6% 7Li, 7.4% 6Li). Measurements with 6Li show that the increase of the vibration frequency with increasing coverage is not an isotope effect.
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| 4. |
- Carlsson, Anna K, 1966, et al.
(författare)
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Shifts and widths of metal-overlayer quantum-well states near EF observed by photoemission
- 1994
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Ingår i: Physical Review B - Condensed Matter and Materials Physics. - 2469-9950 .- 2469-9969. ; 50:12, s. 8926 - 8929
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Tidskriftsartikel (refereegranskat)abstract
- Photoelectron energy spectra reveal discrete valence-electron states in the range 0–220 meV above EF for 1–3 atomic layers of Na on Cu(111). Apart from a stepwise dependence on the number of atomic Na layers the energy of the quantum-well states depends in a gradual manner on how full the layer is. The states are as well defined in energy as comparable surface states producing peak widths (50–90 meV), which depend on temperature and coverage.
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| 5. |
- Råberg, Lars, et al.
(författare)
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On the adaptive significance of stress-induced immunosuppression
- 1998
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Ingår i: Royal Society of London. Proceedings B. Biological Sciences. - : The Royal Society. - 1471-2954 .- 0962-8452. ; 265:1406, s. 1637-1641
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Forskningsöversikt (refereegranskat)abstract
- We approach the field of stress immunology from an ecological point of view and ask: why should a heavy physical workload, for example as a result of a high reproductive effort, compromise immune function? We argue that immunosuppression by neuroendocrine mechanisms, such as stress hormones, during heavy physical workload is adaptive, and consider two different ultimate explanations of such immunosuppression. First, several authors have suggested that the immune system is suppressed to reallocate resources to other metabolic demands. In our view, this hypothesis assumes that considerable amounts of energy or nutrients can be saved by suppressing the immune system; however, this assumption requires further investigation. Second, we suggest an alternative explanation based on the idea that the immune system is tightly regulated by neuroendocrine mechanisms to avoid hyperactivation and ensuing autoimmune responses. We hypothesize that the risk of autoimmune responses increases during heavy physical workload and that the immune system is suppressed to counteract this.
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| 6. |
- Svensson, Erik, et al.
(författare)
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Energetic stress, immunosuppression and the costs of an antibody response
- 1998
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Ingår i: Functional Ecology. - : Wiley. - 1365-2435 .- 0269-8463. ; 12:6, s. 912-919
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Tidskriftsartikel (refereegranskat)abstract
- 1. Recently, there has been much interest in physiological trade-offs between parasite resistance and fitness-related traits such as secondary sexual characters or reproductive effort. More specifically it has been suggested that (i) energetically costly activities may suppress the immune system and (ii) that this immunosuppression is caused by costly immune defences competing with other bodily demands for scarce resources, e.g. energy. 2. The possibility was investigated of an energetically based trade-off between humoral (antibody-based) immunocompetence and other costly activities, by immunizing Blue Tits, Parus caeruleus, with novel antigens (proteins) thereby inducing antibody responses, and performing two experiments. In experiment i, one group of birds was subjected to cold stress, thereby increasing their daily energy expenditure and the effect on immune responsiveness was investigated. In experiment 2, the basal metabolic rate (BMR) of immunized birds was measured to investigate the energetic costs of mounting the antibody responses. 3. In experiment I, birds subject to increased energy turnover had significantly lower antibody responses, consistent with the hypothesis that environmental stress could suppress immunocompetence. However, in experiment 2 the energetic costs of these antibody responses were found to be low and at most 8-13% of BMR, indicating that adaptive resource allocation of energy was an unlikely explanation for the lowered immune responsiveness in the cold stress treatment (experiment 1). 4. It is concluded that our data provide some support to the idea that there may be a trade-off between immunocompetence and energetically costly activities such as thermoregulation, reproduction or mate attraction, although this trade-off may not necessarily be based on energy or nutrient limitation (i.e. resource allocation models). Two non-energetic explanations are briefly discussed, one adaptive and one non-adaptive, that could explain the immunosuppression in our study as well as in other behavioural and ecological contexts.
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