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- Baden, Susanne P., 1952, et al.
(författare)
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Shift in seagrass food web structure over decades is linked to overfishing
- 2012
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Ingår i: Marine Ecology-Progress Series. - : Inter-Research Science Center. - 0171-8630 .- 1616-1599. ; 451, s. 61-73
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Tidskriftsartikel (refereegranskat)abstract
- Empirical field studies in seagrass have revealed that overgrowth by filamentous algae which reduces seagrass growth can be explained by a top-down cascading effect caused by declines in top predators, which is enforced by eutrophication. On the Swedish west coast, 60% of the seagrass has disappeared since the 1980s. We hypothesised that overfishing, responsible for a >90% decline in the cod stock, and the 4 to 8 times increase in nutrient load since the 1930s have altered the seagrass structure and function during recent decades. We used quantitative samples from the 1980s and 2000s and analysed the trends in abundance of the 4 feeding guilds: top predatory fish, intermediate predatory fish, crustacean omnivores and mesoherbivores. Since the 1980s, the commercial catch of gadoids on the Swedish west coast has decreased by >90 %, and here we found that the biomass of top predators (gadoids and trout) that forage in seagrass has decreased by approximately 80%. In contrast, the biomass of intermediate predatory fish (gobids and sticklebacks) has increased 8 times during summer and 11 times during autumn, while mesoherbivores (idoteids and gammarids >7 mm) have more or less disappeared from the seagrass bed. We thus found clear evidence that a shift in seagrass food web structure has taken place over the last 3 decades. Combining these findings with our recent empirical results from field cage experiments in the Skagerrak seagrass, where we manipulate top-down and bottom-up regulation, we conclude that lack of grazers in concert with eutrophication most likely contributed to the overgrowth by filamentous algae and disappearance of the seagrass on the Swedish west coast.
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| 2. |
- Bergman, Jan, et al.
(författare)
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Oxidative Ring Expansion of Spirocyclic Oxindole Derivatives
- 2014
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Ingår i: Journal of Organic Chemistry. - : American Chemical Society (ACS). - 0022-3263 .- 1520-6904. ; 79:19, s. 9065-9073
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Tidskriftsartikel (refereegranskat)abstract
- Oxidation of the spirocyclic oxindole derivative, isamic acid 1, led to decarboxylation and ring expansion to quinazolino[4,5-b]quinazoline-6,8-dione 7 rather than, as previously believed, its isomer 6. The structure of 7 was confirmed by X-ray crystallography. Condensation of isatin (indole-2,3-dione) and 2-aminobenzamide led to the spirocyclic molecule, spiro[3H-indole-3,2'(1H)quinazoline]-2,4'(1H,3H)dione 8, which was also identified as an intermediate in the oxidation of isamic acid. Mild hydrolysis of 7 gave the 10-membered molecule 22. Isamic acid could easily be converted to N-nitrosoisamic acid, which when heated in ethanol underwent a ring expansion to a hydroximino derivative, 38, of compound 6. The structure of 38 was confirmed by X-ray crystallography.
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| 3. |
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| 4. |
- Svensson, Robert, et al.
(författare)
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CFD simulations of the Cutting extinguisher
- 2014
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Rapport (refereegranskat)abstract
- Developing tactics for extinguishing fires located in civil structures is needed. Nowadays, the most commonly procedure employed by most fire brigades when extinguishing fires located in the interior of buildings, consists in sending a unit of firefighters inside the structure spraying water on the surface of the burning fuels. This procedure has enormous caveats since it leads to the unavoidable necessity of exposing personal to situations where risks to their personal safety are major. An alternative to these tactics consists on using the Cutting extinguisher which in principle allows combating a fire by injecting water mist into the burning building without the necessity of entering it. This work studies the capabilities and limitations of the Cutting extinguisher when used for fire-fighting activities in conventional and idealised civil structures by the aid of computerised simulations and experimental data. The simulations were done using Fire Dynamics Simulator (FDS) which is an open-source code for modelling well-ventilated fires while experimental data was obtained from idealised and controlled fires and experiments. Findings of this study suggest that the Cutting extinguisher is effective for combating fires of moderated size in confinements using less water than traditional methods by reducing the relative concentration of oxygen in the room instead of by cooling the fuels as traditional methods do. The high velocity of the jet induces mixing in the confinement, enhancing the interaction of droplets with hot combustion products and promoting the vaporisation of the injected water. Furthermore, the induced momentum to the gases in the room together with the vaporisation of the injected water reduces the overall gas temperature inside the structure.
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