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- Aben, Ralf C. H., et al.
(författare)
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Cross continental increase in methane ebullition under climate change
- 2017
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Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 8
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Tidskriftsartikel (refereegranskat)abstract
- Methane (CH4) strongly contributes to observed global warming. As natural CH4 emissions mainly originate from wet ecosystems, it is important to unravel how climate change may affect these emissions. This is especially true for ebullition (bubble flux from sediments), a pathway that has long been underestimated but generally dominates emissions. Here we show a remarkably strong relationship between CH4 ebullition and temperature across a wide range of freshwater ecosystems on different continents using multi-seasonal CH4 ebullition data from the literature. As these temperature-ebullition relationships may have been affected by seasonal variation in organic matter availability, we also conducted a controlled year-round mesocosm experiment. Here 4 degrees C warming led to 51% higher total annual CH4 ebullition, while diffusion was not affected. Our combined findings suggest that global warming will strongly enhance freshwater CH4 emissions through a disproportional increase in ebullition (6-20% per 1 degrees C increase), contributing to global warming.
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- Aharonian, Felix, et al.
(författare)
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Solar abundance ratios of the iron-peak elements in the Perseus cluster
- 2017
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Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 551:7681, s. 478-
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Tidskriftsartikel (refereegranskat)abstract
- The metal abundance of the hot plasma that permeates galaxy clusters represents the accumulation of heavy elements produced by billions of supernovae(1). Therefore, X-ray spectroscopy of the intracluster medium provides an opportunity to investigate the nature of supernova explosions integrated over cosmic time. In particular, the abundance of the iron-peak elements (chromium, manganese, iron and nickel) is key to understanding how the progenitors of typical type Ia supernovae evolve and explode(2-6). Recent X-ray studies of the intracluster medium found that the abundance ratios of these elements differ substantially from those seen in the Sun(7-11), suggesting differences between the nature of type Ia supernovae in the clusters and in the Milky Way. However, because the K-shell transition lines of chromium and manganese are weak and those of iron and nickel are very close in photon energy, highresolution spectroscopy is required for an accurate determination of the abundances of these elements. Here we report observations of the Perseus cluster, with statistically significant detections of the resonance emission from chromium, manganese and nickel. Our measurements, combined with the latest atomic models, reveal that these elements have near-solar abundance ratios with respect to iron, in contrast to previous claims. Comparison between our results and modern nucleosynthesis calculations(12-14) disfavours the hypothesis that type Ia supernova progenitors are exclusively white dwarfs with masses well below the Chandrasekhar limit (about 1.4 times the mass of the Sun). The observed abundance pattern of the iron-peak elements can be explained by taking into account a combination of near-and sub-Chandrasekhar-mass type Ia supernova systems, adding to the mounting evidence that both progenitor types make a substantial contribution to cosmic chemical enrichment(5,15,16).
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- Brusk, J., et al.
(författare)
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DEAL – Dialogue Management in SCXML for Believable Game Characters
- 2007
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Ingår i: Proceedings of the 2007 Conference on Future Play, Future Play '07. - New York, New York, USA : ACM Press. - 9781595939432 ; , s. 137-144
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Konferensbidrag (refereegranskat)abstract
- In order for game characters to be believable, they must appear to possess qualities such as emotions, the ability to learn and adapt as well as being able to communicate in natural language. With this paper we aim to contribute to the development of believable non-player characters (NPCs) in games, by presenting a method for managing NPC dialogues. We have selected the trade scenario as an example setting since it offers a well-known and limited domain common in games that support ownership, such as role-playing games. We have developed a dialogue manager in State Chart XML, a newly introduced W3C standard, as part of DEAL -- a research platform for exploring the challenges and potential benefits of combining elements from computer games, dialogue systems and language learning.
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- Carstensen, Anna-Maria, 1982, et al.
(författare)
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Exploring the dynamics of remotely detected fluorescence transients from basil as a potential feedback for lighting control in greenhouses
- 2016
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Ingår i: Acta Horticulturae. - 0567-7572. - 9789462611092 ; 1134, s. 375-383
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Tidskriftsartikel (refereegranskat)abstract
- Optimizing artificial lighting control in industrial scale greenhouses has a potential for increased crop yields, energy savings and production timing. One possible component in controlling greenhouse lighting is continuous and accurate measurement of plant photosynthetic performance. A widely used tool for measuring photosynthetic performance non-invasively is chlorophyll fluorescence. For the purpose of automatic control, remote sensing of fluorescence is favourable, since it provides an aggregated measure for a large canopy area. However, adaptation of traditional fluorescence methodologies to remote sensing is problematic since they are based on the analysis of fluorescence intensities and therefore sensitive to distance and morphology. Other problems with using traditional methods remotely in a greenhouse are a need for dark adaption and use of saturating light. This paper presents a novel concept for the detection of photosynthetic performance based on the dynamics of remotely sensed light induced fluorescence signals. The dynamics of the fluorescence signal is insensitive to distance and morphology and hence provide a good basis for remote detection of photosynthetic performance. Through experiments we have explored how the dynamics of the time-varying fluorescence signal from basil plants was affected by light intensity, light acclimation and light induced stress. This was done by first identifying a dynamic model by transient analysis and then applying frequency analysis on the model. We conclude that the capacity of basil plants to use a certain light intensity was reflected by how fast and how complex the dynamics are. These results show that an identified resonance peak frequency is a potential indicator of plants' ability to adapt to light, which could be a valuable feedback signal for lighting control in greenhouses.
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