| 1. |
- Corvellec, Hervé, et al.
(författare)
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Action nets for waste prevention
- 2015
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Ingår i: Waste Management and Sustainable Consumption: Reflections on Consumer Waste. - 9781138797253 ; , s. 88-101
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Bokkapitel (refereegranskat)
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| 2. |
- Ekström, Sanna, et al.
(författare)
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A possible role of ground-based microorganisms on cloud formation in the atmosphere
- 2010
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Ingår i: Biogeosciences. - : Copernicus GmbH. - 1726-4170 .- 1726-4189. ; 7:1, s. 387-394
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Tidskriftsartikel (refereegranskat)abstract
- The formation of clouds is an important process for the atmosphere, the hydrological cycle, and climate, but some aspects of it are not completely understood. In this work, we show that microorganisms might affect cloud formation without leaving the Earth’s surface by releasing biological surfactants (or biosurfactants) in the environment, that make their way into atmospheric aerosols and could significantly enhance their activation into cloud droplets. In the first part of this work, the cloud-nucleating efficiency of standard biosurfactants was characterized and found to be better than that of any aerosol material studied so far, including inorganic salts. These results identify molecular structures that give organic compounds exceptional cloud-nucleating properties. In the second part, atmospheric aerosols were sampled at different locations: a temperate coastal site, a marine site, a temperate forest, and a tropical forest. Their surface tension was measured and found to be below 30 mN/m, the lowest reported for aerosols, to our knowledge. This very low surface tension was attributed to the presence of biosurfactants, the only natural substances able to reach to such low values. The presence of strong microbial surfactants in aerosols would be consistent with the organic fractions of exceptional cloud-nucleating efficiency recently found in aerosols, and with the correlations between algae bloom and cloud cover reported in the Southern Ocean. The results of this work also suggest that biosurfactants might be common in aerosols and thus of global relevance. If this is confirmed, a new role for microorganisms on the atmosphere and climate could be identified.
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| 3. |
- Ekström, Sanna, et al.
(författare)
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Biosurfactants as CCN : comparison between on-line and off-line measurements
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- We are presenting the CCN properties for the bacterial compounds rhamnolipid and surfactin, which are extremely strong surfactants. Three organic:sodium chloride mixtures with mass percentages of 80:20, 50:50 and 20:80 were measured for each biosurfactant. Both on-line Cloud Condensation Nuclei Counter (CCNC) and off-line osmolality combined with surface tension measurements were performed to obtain two sets of critical supersaturations for various dry particle diameters. The critical supersaturations measured by the CCNC were systematically higher than the corresponding supersaturations derived from osmolality/surface tension measurements. A simple surface partitioning-adaption was applied to the off-line data and resulted in a correlation with the results from CCNC measurements for both mixtures with 20 wt% biosurfactant and the 50 wt% rhamnolipid mixture but not for the mixtures with 80 wt% biosurfactant and the 50 wt% surfactin mixture. An explanation can be unreliable CCNC results from the surfactin mixtures as we suspect poor dissolvement of the organic crystals. The choice of the assumed biosurfactant density also has an effect which should not be ignored. However, this indicate that the experimental method using osmolality and surface tension measurements together with a simple surface partitioning model can be used for strongly surfactant compounds as long as they do not dominate the particle mass. We also conclude that biosurfactants in mixed potential CCN particles can activate at relatively low supersaturation compared to other organic mixtures. Still, the critical supersaturation increases with increasing surfactant fraction.
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| 4. |
- Ekström, Sanna, et al.
(författare)
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First direct measurements of the CCN properties of 2-methyltetrols and polyols
- 2008
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Ingår i: Geophysical Research Abstracts.
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Konferensbidrag (refereegranskat)abstract
- 2-methyltetrols and polyols have received a lot of attention in recent years. 2-methyltetrols have been found in aerosols in various regions are believed to be formed by the oxidation of isoprene. Polyols are produced by fungi and have been measuredin large concentrations in aerosols. The main reason of interest of both 2-methyltetrols and polyols as efficient cloud condensation nuclei (CCN) is due to their high solubility.This presentation will report for the first time the experimental determination of complete Köhler curves for 2-methyltetrols (2-methylerythritol and 2-methylthreitol), C3 to C6 polyols (glycerol, erythritol, arabitol, and mannitol), and for comparison theiranalogue di-acids (malonic acid, succinic acid and, adipic acid). The original Köhler equations were determined from osmolality and tensiometry measurements of the compounds both in water and salt solutions (sodium chloride and ammonium sulphate).The results indicate that the polyols generally have similar CCN properties as the dicarboxylic acids. The critical supersaturation for aerosol particles with a 30 nm radius were: 2-methyltetrol; 0.68%, mannitol; 0.62%, arabitol; 0.60%, 2-methylerythritol;0.57%, erythritol; 0.56%, glycerol; 0.53%, adipic acid; 0.52%, succinic acid; 0.49%, and malonic acid; 0.44%. Mixtures of salts had lower critical supersaturation than water solutions, especially for the polyols. One exception was 2-methylerythritol, which interestingly was less efficient as CCN in salt solutions.The CCN efficiency of the polyols is believed to result mostly from their large water affinity, enforcing the Raoult effect, while organic acids lower the Kelvin effect. The very large solubility of polyols compared to the di-acids mean that they could positive effect in the initial phase of the droplet growth while the di-acids cannot. 2-methyltetrols were found to have both a Kelvin and a Raoult effect.In addition, these results establish for the first time that the 3-dimensional structure of molecules can have an effect on their CCN properties. The two isomers of the 2-methyltetrols have significantly different CCN properties that are also influencedoppositely in the presence of salts.
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| 5. |
- Ekström, Sanna, et al.
(författare)
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Of Bacteria and clouds: when microbial substances trigger cloud formation in Earth’s atmosphere
- 2008
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Ingår i: American Geophysical Union Fall Meeting 2008.
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Konferensbidrag (refereegranskat)abstract
- This presentation reports the discovery that substances produced by microorganisms might trigger the formation of cloud in the atmosphere, at least under certain conditions.The Cloud Condensation Nuclei (CCN) efficiency of substances produced by microorganisms (bacteria, fungi, micro-algae …) that are common at Earth’s surface and in the oceans were studied. Their Köhler curves were determined experimentally by surface tension and osmometry measurements and found to have much lower critical supersaturations than any material studied so far, including inorganic salts.The presence of these substances was evidenced in aerosols from four different origins (coastal, marine, temperate forest, and Amazonian forest) by LC/MS/MS analyses and by their unique signature on the surface tension. These substances lowered the surface tension of the aerosols below 40 mN/m, allowing them to be activated into cloud droplets before inorganic particles.Microorganisms would thus be able to control cloud formation in Earth’s atmosphere under certain conditions. This would explain many previous observations such as correlations between algae bloom and cloud cover. Most importantly, this work identifies a potentially important component of Earth’s hydrological cycle and a new direct link between biosphere and climate.
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| 6. |
- Ekström, Sanna, et al.
(författare)
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The Cloud Condensation Nuclei (CCN) properties of 2-methyltetrols and C3-C6 polyols from osmolality and surface tension measurements
- 2009
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Ingår i: Atmospheric Chemistry And Physics. - : Copernicus GmbH. - 1680-7316 .- 1680-7324. ; 9:3, s. 973-980
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Tidskriftsartikel (refereegranskat)abstract
- A significant fraction of the organic material in aerosols is made of highly soluble compounds such as sugars (mono-and polysaccharides) and polyols such as the 2-methyltetrols, methylerythritol and methyltreitol. Because of their high solubility these compounds are considered as potentially efficient CCN material. For the 2-methyltetrols, this would have important implications for cloud formation at global scale because they are thought to be produced by the atmospheric oxidation of isoprene. To investigate this question, the complete Kohler curves for C3-C6 polyols and the 2-methyltetrols have been determined experimentally from osmolality and surface tension measurements. Contrary to what was expected, none of these compounds displayed a higher CCN efficiency than organic acids. Their Raoult terms show that this limited CCN efficiency is due to their absence of dissociation in water, this in spite of slight surface-tension effects for the 2-methyltetrols. Thus, compounds such as saccharides and polyols would not contribute more to cloud formation than other organic compounds studied so far. In particular, the presence of 2-methyltetrols in aerosols would not particularly enhance cloud formation in the atmosphere, in contrary to recently suggested
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| 7. |
- Ekström, Sanna, et al.
(författare)
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The Cloud Condensation Nuclei (CCN) properties of 2-methyltetrols and C3–C6 polyols from osmolality and surface tension measurements (Discussion paper)
- 2008
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Ingår i: Atmospheric Chemistry and Physics Discussion. - : Copernicus GmbH. - 1680-7367. ; 8:5, s. 17237-17256
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Tidskriftsartikel (refereegranskat)abstract
- A significant fraction of the organic material in aerosols is made of highly soluble compounds such as sugars (mono- and polysaccharides) and polyols, including the 2-methyltetrols, methylerythritol and methyltreitol. The high solubility of these compounds has brought the question of their potentially high CCN efficiency. For the 2-methyltetrols, this would have important implications for cloud formation at global scale because they are thought to be produced by the atmospheric oxidation of isoprene. To investigate this question, the complete Köhler curves for C3–C6 polyols and the 2-methyltetrols have been determined experimentally from osmolality and surface tension measurements. Contrary to what expected, none of these compounds displayed a critical supersaturation lower than those of inorganic salts or organic acids. Their Raoult terms show that this limited CCN efficiency is due to their absence of dissociation in water, this in spite of slight surface-tension effects for the 2-methyltetrols. Thus, compounds such as sugars and polyols would not contribute more to cloud formation in the atmosphere than any other organic compounds studied so far. In particular, the presence of 2-methyltetrols in aerosols would not particularly enhance cloud formation in the atmosphere, contrary to what has been suggested.
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| 8. |
- Ekström, Sanna, 1980-
(författare)
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The influence of biogenic organic compounds on cloud formation
- 2010
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Aerosols and clouds provide the largest uncertainty in the atmospheric radiation budget. The main focus of this thesis was to investigate the ability of organic compounds in aerosol particles to form clouds, and more specifically those emitted by living organisms. The cloud forming properties of the highly water-soluble methyltetrols and polyols, which are compounds produced by plants and fungi that are common in aerosol, were studied. All compounds and their salt mixtures have a moderate potential to serve as cloud condensation nuclei (CCN). They are thus not likely to have a significant global impact on cloudiness. The potential presence of surfactants released by microorganisms was investigated for aerosols sampled at different locations. Very low surface tension values were measured for these aerosol extracts (30 mN/m), which implies that these aerosols have good CCN properties and indicate the presence of biosurfactants. Their occurrence in aerosols still needs to be confirmed directly by chemical identification. Reactions of organic compounds in sulfate salt solutions exposed to UV-light were studied and found to produce surface active compounds. Thus, mixed sulfate/organic aerosol could have more favourable CCN properties after exposure to light than when kept in the dark. The surface active compounds were proposed to be long-chained organosulfates with hydrophilic and hydrophobic parts, similar to other amphiphilic surfactants. Mixtures of salt and strong surfactants formed by bacteria were studied using two different techniques for determining their CCN properties. There were inconsistencies between the two methods which could be accounted for by surface partitioning. The studied mixtures were determined to be good potential CCN material in both techniques. All these aspects require further investigation, but if the impact of strong biogenic surfactants on cloud formation is confirmed, a new link between living organisms and climate would be identified.
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| 9. |
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En båge genom tiden - ritualer kring en göteborgshistoria. Om Flickläroverket i Artisten
- 2024
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Samlingsverk (redaktörskap) (övrigt vetenskapligt/konstnärligt)abstract
- 1929 bildades Göteborgs första Högre allmänna läroverk för Flickor – Flickläroverket som fick en byggnad 1935 i det kulturella centrumet, Götaplatsen. Efter några år som Kjellbergska gymnasiet, sedan Komvux, blev byggnaden del av Artisten, Högskolan för scen och musik, HSM 1992. Byggnaden har burit kvinnors utbildning, konst och kultur över många generationer, en minneskedja som nu är bruten. Boken - En båge genom tiden – ritualer kring en göteborgshistoria – en konst- och forskningsantologi – är resultatet av de offentliga minnesdagar där de deltagande drygt 200 kvinnorna (70– 97 år) som varit elever på Flickläroverket, studenter vid Artisten, konstnärer och forskare – bidrog till och deltog i gestaltande ritualer, minnesrum, dans, utställningar och samtal som gav liv åt en utbildningskultur och konst som berört samhället i generationer. I boken bidrar ett 20-tal Göteborgsbaserade konstnärer och forskare med olika perspektiv på byggnadens poetiska, sociala och konstnärliga dimensioner. Bland annat beskrivs återskapandet av Bågdansen, som dansades varje år vid Lucia mellan 1934-1972. Här beskrivs även den medie-debatt som ledde till räddningen av målningen Dansen av Nils Nilsson från 1935 och hur nedtagningen gick till. Tillsammans med ett rikt foto- och bildmaterial, filmdokumentationer och ett ljudarkiv utgör boken ett tidsdokument där konst fungerar som minnesbärare över tid och rum.
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| 10. |
- Islam, M. Shahidul, et al.
(författare)
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In situ activation of the type 2 ryanodine receptor in pancreatic beta cells requires cAMP-dependent phosphorylation
- 1998
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Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 0027-8424 .- 1091-6490. ; 95:11, s. 6145-6150
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Tidskriftsartikel (refereegranskat)abstract
- Molecular mechanisms that regulate in situ activation of ryanodine receptors (RY) in different cells are poorly understood. Here we demonstrate that caffeine (10 mM) released Ca2+ from the endoplasmic reticulum (ER) in the form of small spikes in only 14% of cultured fura-2 loaded beta cells from ob/ob mice. Surprisingly, when forskolin, an activator of adenylyl cyclase was present, caffeine induced larger Ca2+ spikes in as many as 60% of the cells. Forskolin or the phosphodiesterase-resistant PKA activator Sp-cAMPS alone did not release Ca2+ from ER. 4-Chloro-3-ethylphenol (4-CEP), an agent that activates RYs in other cell systems, released Ca2+ from ER, giving rise to a slow and small increase in [Ca2+]i in beta cells. Prior exposure of cells to forskolin or caffeine (5 mM) qualitatively altered Ca2+ release by 4-CEP, giving rise to Ca2+ spikes. In glucose-stimulated beta cells forskolin induced Ca2+ spikes that were enhanced by 3,9-dimethylxanthine, an activator of RYs. Analysis of RNA from islets and insulin-secreting betaTC-3-cells by RNase protection assay, using type-specific RY probes, revealed low-level expression of mRNA for the type 2 isoform of the receptor (RY2). We conclude that in situ activation of RY2 in beta cells requires cAMP-dependent phosphorylation, a process that recruits the receptor in a functionally operative form.
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