| 1. |
- Hustad, J.E., et al.
(författare)
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Reactivity measurements of coke particles in five different flow reactors
- 1990
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Ingår i: Rivista dei Combustibili. - 0370-5463. ; 44:10, s. 257-267
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Experiments on reactivity of 128 μm coke particles in the gas temperature range from 1150 K to 1370 K have been performed in five different flow reactors in the Nordic countries and all the results were calculated by the shrinking particle model. The activation energy is found to be 25 kcal/mol indicating combustion control by the combined effects of chemical kinetic and pore diffusion (zone II combustion). The overall apparent reaction order was found to be 1.0
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| 2. |
- Kiorboe, T., et al.
(författare)
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Intensive aggregate formation with low vertical flux during an upwelling-induced diatom bloom
- 1998
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Ingår i: Limnology and Oceanography. - 0024-3590. ; 43:1, s. 104-116
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Tidskriftsartikel (refereegranskat)abstract
- The surfaces of most pelagic diatoms are sticky at times and may therefore form rapidly settling aggregates by physical coagulation. Stickiness and aggregate formation may be particularly adaptive in upwelling systems by allowing the retention of diatom populations in the vicinity of the upwelling center. We therefore hypothesized that upwelling diatom blooms are terminated by aggregate formation and rapid sedimentation. We monitored the development of a maturing diatom (mainly Chaetoceros spp.) bloom in the Benguela upwelling current during 7 d in February. Chlorophyll concentrations remained consistently high during the observation period (similar to 500 mg Chi m(-2)) and phytoplankton grew at an average specific rate of 0.25 d(-1). The diatoms were extraordinarily sticky, with stickiness coefficients of up to 0.40, which is the highest ever recorded for field populations. Combined with estimates of turbulent shear in the ocean such stickiness coefficients predict very high specific coagulation rates (0.3 d(-1)). In situ video observation demonstrated the occurrence of abundant diatom aggregates with surface water concentrations between 1,000 and 3,000 ppm. Despite the very high concentration of aggregates, vertical fluxes of phytoplankton were very low, with fractional losses <0.005 d(-1), and the aggregates thus seemed to be near neutrally buoyant. Losses due to copepod grazing were also low (similar to 0.025 d(-1)). Most of the aggregates were colonized by the heterotrophic dinoflagellate Noctiluca scintillans that feed upon diatoms in the aggregates. The system appeared to be in near steady state; specific diatom growth rate, coagulation rate, and loss rate due to N, scintillans feeding were all of the same magnitude (0.25-0.3 d(-1)) and the latter two varied in concert. Our observations provide only partial support for the population retention hypothesis because aggregate buoyancy and N, scintillans grazing efficiently reduced the vertical flux of aggregates in this system.
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| 3. |
- Selander, Erik, 1973, et al.
(författare)
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Solid phase extraction and metabolic profiling of exudates from living copepods
- 2016
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Ingår i: Peerj. - : PeerJ. - 2167-8359. ; 4
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Tidskriftsartikel (refereegranskat)abstract
- Copepods are ubiquitous in aquatic habitats. They exude bioactive compounds that mediate mate finding or induce defensive traits in prey organisms. However, little is known about the chemical nature of the copepod exometabolome that contributes to the chemical landscape in pelagic habitats. Here we describe the development of a closed loop solid phase extraction setup that allows for extraction of exuded metabolites from live copepods. We captured exudates from male and female Temora longicornis and analyzed the content with high resolution LC-MS. Chemometric methods revealed 87 compounds that constitute a specific chemical pattern either qualitatively or quantitatively indicating copepod presence. The majority of the compounds were present in both female and male exudates, but nine compounds were mainly or exclusively present in female exudates and hence potential pheromone candidates. Copepodamide G, known to induce defensive responses in phytoplankton, was among the ten compounds of highest relative abundance in both male and female extracts. The presence of copepodamide G shows that the method can be used to capture and analyze chemical signals from living source organisms. We conclude that solid phase extraction in combination with metabolic profiling of exudates is a useful tool to develop our understanding of the chemical interplay between pelagic organisms.
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