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- Andersson, Erik, et al.
(författare)
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Accumulation and degradation of dead-end metabolites during treatment of soil contaminated with polycyclic aromatic hydrocarbons with five strains of white-rot fungi
- 1996
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Ingår i: Applied Microbiology and Biotechnology. - 1432-0614. ; 46:5-6, s. 647-652
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Tidskriftsartikel (refereegranskat)abstract
- The white-rot fungi Trametes versicolor PRL 572, Trametes versicolor MUCL 28407, Pleurotus ostreatus MUCL 29527, Pleurotus sajor-caju MUCL 29757 and Phanerochaete chrysosporium DSM 1556 were investigated for their ability to degrade the polycyclic aromatic hydrocarbons (PAH) anthracene, benz[a]anthracene and dibenz[a,h]anthracene in soil. The fungi were grown on wheat straw and mixed with artificially contaminated soil. The results of this study show that, in a heterogeneous soil environment, the fungi have different abilities to degrade PAH, with Trametes showing little or no accumulation of dead-end metabolites and Phanerochaete and Pleurotus showing almost complete conversion of anthracene to 9,10-anthracenedione. In contrast to earlier studies, Phanerochaete showed the ability to degrade the accumulated 9,10-anthracenedione while Pleurotus did not. This proves that, in a heterogeneous soil system, the PAH degradation pattern for white-rot fungi can be quite different from that in a controlled liquid system.
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- Andersson, Maria, 1965-
(författare)
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Cooperation in local electricity markets : modelling of technical measures
- 1997
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis presents a system analysis for co-operation in local electricity markets including distributors and customers. The purpose of co-operation is to minimise the system cost of local markets by introducing system measures, such as end-use measures and municipal co-generation plants. Co-operation will strengthen the position of local markets in the national as well as future international electricity markets. With end-use measures local markets will achieve flexibility, additional reserve capacity and ability to avoid sudden large costs for peak loads. Biomass-fired cogeneration plants can become of great importance in an international market. In Sweden there is a simultaneous demand for electricity and district heating, many local markets already include district heating systems and there are major forest areas which can contribute with renewable fuel. The system analysis is partly based on the simulation model (INDSIM) and the linear programming model (MODEST). The simulation model has been further developed (STRATO) to include calculation of system costs. Shadow price analysis has been developed in order to study incentives for system measures. Calculation procedures have been developed that describe cooperation between distributor and customer. Six case studies of a selection of real, existing local markets in Sweden are presented. The studies show the potential economical effects of co-operation measured by system costs and shadow prices. Co-operation has been considered between demand- and supply-side, electricity- and district heating systems and also between different time periods. In a typical local market with 90 000 inhabitants, if end use measures are introduced without cooperation the system cost of the distributor will increase by 14 million SEK for a time period of 25 years. If instead end-use measures are introduced in co-operation, together with a biomass-fired cogeneration plant, the system cost of the local market will be reduced by 444 million SEK. Furthermore, the use of biomass in the local market is increased from 36 to 72 % while the use of oil is decreased from 34 to 1%. Another case study of another local market (50 000 inhabitants) shows that end-use measures will reduce the system cost (excluding investment costs) of an industry by 50 % corresponding to 1.3 million SEK for one year. The end-use measures imply reduced power demand during peak load periods in the local market and increased power demand during non- peak load periods.
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- Andersson, Tomas
(författare)
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Thermal shock and thermal fatigue in ceramic materials
- 1997
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis concerns thermal stress fracture in ceramicmaterials. The work describes a new technique for determiningthe thermal shock resistance of brittle materials as well asexperimental results and thermal stress simulations.A new indentation-quench method to the determine theresistance of ceramics to thermal shock and thermal cycling isdescribed. The method defines a critical temperaturedifference, ΔTc, from the amount of extension and propagation ofsmall Vickers cracks. Statistically significant data areobtained by studying a large number of cracks in each specimen.Few test specimens are thus required. Another advantage withthe method is that no specific specimen shape is required. Themethod can therefore be used directly on complex shapedcomponents. This is important since the thermal shockresistance of a material is highly dependent on its size andshape.The new method is used to determine the thermal shockresistance for several materials. The materials are rankedaccording to their value of ΔTc. The ranking from quenches into water at roomtemperature is compared with that from quenches into boilingwater. The results show that the thermal conductivity of thematerials becomes of large importance when the materials aresubjected to slower quenching rates in boiling water, while thevalues of ΔTcis more dependent on the mechanical properties forquenches into water at room temperature. The resistance to tenthermal cycles close to the ΔTcof the materials is investigated. Thesecomparisons show that milder quenching conditions gives alarger crack extension. Milder quenches give longer durationtimes of the thermal stresses. The cracks will thus have longertimes to find weak paths in the microstructure. Furthermore itis shown that a finely distributed toughening phase ispreferable in thermal cycling conditions.Thermal stresses are simulated in flat plates subjected tosymmetric cooling in order to estimate the effect of severalimportant thermal shock variables. The simulated conditions aresimilar to those met by alumina in quench tests. A thermaldiffusivity, with negative temperature dependence is found toincrease the thermal stresses significantly for thinner platesizes, whereas the effects for thicker plates are small. Theeffect of the statistical distribution of fracture strengths isshown to give a larger scatter in thermal shock resistance forthin specimens than for thick ones.Keywords:Thermal shock, thermal stress, thermalfatigue, indentation, SiC-whisker-reinforced alumina, waterquench, cooling rate, thermal diffusivity.
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| 9. |
- Fischer, Håkan, et al.
(författare)
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Brain correlates of an unexpected panic attack: a human positron emission tomographic study
- 1998
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Ingår i: NEUROSCIENCE LETTERS. - : ELSEVIER SCI IRELAND LTD. - 0304-3940. ; 251:2, s. 137-140
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Tidskriftsartikel (refereegranskat)abstract
- Previous brain imaging studies on symptom provocation in panic anxiety have used either drug-infusions or sensory related stimulation to induce panic attacks. We here report positron emission tomographic measurements of regional cerebral blood flow (rCBF
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