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| 2. |
- Hansson, Lars-Anders, et al.
(författare)
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Consumption patterns, complexity and enrichment in aquatic food chains
- 1998
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Ingår i: Royal Society of London. Proceedings B. Biological Sciences. - : The Royal Society. - 1471-2954. ; 265:1399, s. 901-906
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Tidskriftsartikel (refereegranskat)abstract
- The interactions between consumers and prey, and their impact on biomass distribution among trophic levels, are central issues in both empirical and theoretical ecology. In a long-term experiment, where all organisms, including the top predator, were allowed to respond to environmental conditions by reproduction, we tested predictions from `prey-dependent' and `ratio-dependent' models. Prey-dependent models made correct predictions only in the presence of strong interactors in simple food chains, but failed to predict patterns in more complex situations. Processes such as omnivory, consumer excretion, and unsuitable prey-size windows (invulnerable prey) increased the complexity and created patterns resembling ratio-dependent consumption. However, whereas the prey-dependent patterns were created by the mechanisms predicted by the model, ratio-dependent patterns were not, suggesting that they may be right for the wrong reason'. We show here that despite the enormous complexity of ecosystems, it is possible to identify and disentangle mechanisms responsible for observed patterns in community structure, as well as in biomass development of organisms ranging in size from bacteria to fish.
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| 3. |
- Hansson, Lars, et al.
(författare)
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Eye and Body Movements Characterized by Synchronized Sampling
- 1998
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- An example of a result from a long-term cooperation with Lund University (together with professor Roland Akselsson at the Department of Ergonomics and Aerosol Technology) there some of the authors. (Engström) gained extensive grants (EU-financing and Wallenberg Stifelsen regarding equipment as well as other founding from e.g. the Swedish Work Environment Found). This publication was a result of the just mentioned EU-financing.
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| 4. |
- Hansson, Lars, et al.
(författare)
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Mannequin Properties Desired for Ergonomic Evaluation of Car Interiors
- 1998
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- An example of a result from a long-term cooperation with Lund University (together with professor Roland Akselsson at the Department of Ergonomics and Aerosol Technology) there some of the authors. (Engström) gained extensive grants (EU-financing and Wallenberg Stifelsen regarding equipment as well as other founding from e.g. the Swedish Work Environment Found). This publication has emanated from an EU-financed research project.
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| 6. |
- Al-Karadaghi, Salam, et al.
(författare)
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Crystal structure of ferrochelatase: the terminal enzyme in heme biosynthesis
- 1997
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Ingår i: Structure. - 0969-2126. ; 5:11, s. 1501-1510
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: The metallation of closed ring tetrapyrroles resulting in the formation of hemes, chlorophylls and vitamin B12 is catalyzed by specific enzymes called chelatases. Ferrochelatase catalyzes the terminal step in heme biosynthesis by inserting ferrous ion into protoporphyrin IX by a mechanism that is poorly understood. Mutations in the human gene for ferrochelatase can result in the disease erythropoietic protoporphyria, and a further understanding of the mechanism of this enzyme is therefore of clinical interest. No three-dimensional structure of a tetrapyrrole metallation enzyme has been available until now. RESULTS: The three-dimensional structure of Bacillus subtilis ferrochelatase has been determined at 1.9 A resolution by the method of multiple isomorphous replacement. The structural model contains 308 of the 310 amino acid residues of the protein and 198 solvent molecules. The polypeptide is folded into two similar domains each with a four-stranded parallel beta sheet flanked by alpha helices. Structural elements from both domains build up a cleft, which contains several amino acid residues that are invariant in ferrochelatases from different organisms. In crystals soaked with gold and cadmium salt solutions, the metal ion was found to be coordinated to the conserved residue His 183, which is located in the cleft. This histidine residue has previously been suggested to be involved in ferrous ion binding. CONCLUSIONS: Ferrochelatase seems to have a structurally conserved core region that is common to the enzyme from bacteria, plants and mammals. We propose that porphyrin binds in the identified cleft; this cleft also includes the metal-binding site of the enzyme. It is likely that the structure of the cleft region will have different conformations upon substrate binding and release.
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| 7. |
- Andersson, LM, et al.
(författare)
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Vibrational wave packet dynamics in NaK : The A (1)Sigma(+) state
- 1999
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Ingår i: Chemical Physics. - 0301-0104 .- 1873-4421. ; 241:1, s. 43-54
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Tidskriftsartikel (refereegranskat)abstract
- A combined experimental and theoretical study of the vibrational wave packet dynamics for the NaK molecule in the A (1)Sigma(+) state is presented. The experiment utilises a 790 nm one-colour femtosecond pump-probe scheme with detection of a previously nor reported dissociation pathway of the 3 (1)Pi(+) state, leading to the Na(3p) + K(4s) product channel. The dissociation is suggested to proceed via either collisionally mediated processes or a molecular cascading process via the 4 (1)Sigma(+) state, which crosses several states correlating to the Na(3p) + K(4s) limit. Time-dependent quantum mechanical calculations are used for studying the dynamics in detail. Simulations are performed both for 790 nm and for 766 nm, to relate also to earlier studies. The previous interpretations of the probe processes are revised. Inclusion of vibrational and rotational temperature effects are shown to be crucial for explaining the shape of the signal and the vibrational period, and leads to excellent agreement with the experiments.
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| 8. |
- Axelsson, Tony, 1969, et al.
(författare)
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Theoretical debate and archaeological periodicals - incomparable?
- 1995
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Ingår i: Current Swedish Archaeology. - 1102-7355. ; 1995:3, s. 145-154
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Tidskriftsartikel (refereegranskat)abstract
- In the following article the authors will discuss the relationship between what Björn Myhre proposes as the current state of theory within Scandinavian archaeology and compare his interpretation with the issues presented in some of the Scandinavian archaeological periodicals. The discussion is based on project work carried out by students at the Dept. of Archaeology, Göteborg University. The authors of this article analyse the results of this project to see if "the post-modern period" is reflected in articles published during the period 1980-1994
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| 9. |
- Bergman, Eva, et al.
(författare)
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Synthesis of theoretical and empirical experineces from nutrient and cyprinid reductions in Lake Ringsjön
- 1999
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Ingår i: Hydrobiologia. - 0018-8158. ; 404, s. 145-156
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Tidskriftsartikel (refereegranskat)abstract
- The reduction in external phosphorus load to Lake Ringsjön during the 1980s, did not result in improved water transparency during the following ten-year period. Furthermore, a fish-kill in the Eastern Basin of the lake, in addition to a cyprinid reduction programme (biomanipulation; 1988–1992), in contrast to theory, did not lead to any increase in zooplankton biomass or size. This absence of response in the pelagic food chain may have been attributed to the increase in abundance of YOY (0+) fish, following the fish reduction programme. Despite the lack of effect on zooplankton, there was a decrease in phytoplankton biomass, a change in species composition and an increase in water transparency following biomanipulation. In 1989, one year after the fish-kill in Eastern Basin, the Secchi depth (summer mean) increased from 60 cm to 110 cm. In the following years, water transparency increased further, despite an increase in phosphorus loading. An unexpected effect of the biomanipulation was an increase in benthic invertebrate and staging waterfowl abundances, which occurred 2–4 years after fish reduction. Hence, the response in the benthic community following biomanipulation was considerably stronger than in the pelagic community. A likely explanation is that reduction in abundance of the benthic feeding fish species bream (Abramis brama), strongly affected the benthic invertebrate fauna. In this paper, we present what we believe happened in Lake Ringsjön, and which processes are likely to have been important at various stages of the restoration process.
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