| 1. |
- Kleimark, Jonatan, 1982, et al.
(författare)
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Mechanistic Investigation of Iron-Catalyzed Coupling Reactions
- 2009
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Ingår i: ChemCatChem. - : Wiley. - 1867-3880 .- 1867-3899. ; 1:1, s. 152-161
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Tidskriftsartikel (refereegranskat)abstract
- The mechanism of the iron-catalyzed cross-coupling of aryl electrophiles with alkyl Grignard reagents is studied by a combination of GC monitoring, Hammett competition experiments, and DFT calculations. The reaction follows a pathway where an FeI complex, formed in situ, reacts in a rate-limiting oxidative addition with the aryl electrophile. A rapid thermoneutral transmetalation from a Grignard reagent occurs either before or after the oxidative addition, with little to differentiate between the two pathways. A reductive elimination of the resulting alkyl aryl FeIII complex closes the catalytic cycle. Iron in lower oxidation states can act as a competent precatalyst by oxidation into the FeI-FeIII cycle. FeII complexes can give FeI catalysts through reductive elimination of a bimetallic complex. Added ligands, dilution, and powerful aryl electrophiles all serve to increase the stability of the active catalyst, presumably by counteracting oligomerization of low-valent iron.
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| 5. |
- Hedenås, Henrik, et al.
(författare)
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Conservation of epiphytic lichens : Significance of remnant aspen (Populus tremula) trees in clear-cuts
- 2007
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Ingår i: Biological Conservation. - Barking : Applied Science Publishers. - 0006-3207 .- 1873-2917. ; 135:3, s. 388-395
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Tidskriftsartikel (refereegranskat)abstract
- In the boreal forest landscape, aspen has been effectively selected against in favour of conifers. The decrease in aspen is of particular concern since it has more host-specific species associated with it than any other boreal tree species. Recently forest management systems have begun to include green-tree retention in order to maintain structural diversity. We initiated this study in order to investigate whether retained aspen trees provide suitable habitats for epiphytic lichens and, if so, whether this varies according to species characteristics, such as morphology and photobiont. We chose to investigate the abundance and vitality of five species: three foliose cyanobacterial lichens (Collema curtisporum, Collema furfuraceum and Leptogium saturninum) and two crustose green-algal lichens (Biatora epixanthoides and Mycobilimbia carneoalbida). These lichens were examined on aspen within forest stands and on remnant aspen in clear-cuts at eight localities, in northern Sweden. Our results show that the response to exposure following clear-felling differs between species according to their morphology. The two crustose lichens were more abundant in the forest stands compared to the clear-cuts. In the clear-cuts, they mainly occurred on the northern sides of the trunks. Even 24 years after cutting, the three cyanolichens were equally or even more abundant on trees in the clear-cuts than in the forest stands. However, they were mainly found on the northern sides of the remnant aspen. We suggest that remnant aspen trees may function as suitable substrate and as stepping stones for colonisation of new stands, at least for the cyanolichens studied here.
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| 6. |
- Hedström, Lars, 1977-, et al.
(författare)
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Description and modelling of the solar–hydrogen–biogas-fuel cell system in GlashusEtt
- 2004
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Ingår i: Journal of Power Sources. - : Elsevier BV. - 0378-7753 .- 1873-2755. ; :131, s. 340-350
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Tidskriftsartikel (refereegranskat)abstract
- The need to reduce pollutant emissions and utilise the world's available energy resources more efficiently has led to increased attention towards e.g. fuel cells, but also to other alternative energy solutions. In order to further understand and evaluate the prerequisites for sustainable and energy-saving systems, ABB and Fortum have equipped an environmental information centre, located in Hammarby Sjostad, Stockholm, Sweden, with an alternative energy system. The system is being used to demonstrate and evaluate how a system based on fuel cells and solar cells can function as a complement to existing electricity and heat production. The stationary energy system is situated on the top level of a three-floor glass building and is open to the public. The alternative energy system consists of a fuel cell system, a photovoltaic (PV) cell array, an electrolyser, hydrogen storage tanks, a biogas burner, dc/ac inverters, heat exchangers and an accumulator tank. The fuel cell system includes a reformer and a polymer electrolyte fuel cell (PEFC) with a maximum rated electrical output of 4 kW(el) and a maximum thermal output of 6.5 kW(th). The fuel cell stack can be operated with reformed biogas, or directly using hydrogen produced by the electrolyser. The cell stack in the electrolyser consists of proton exchange membrane (PEM) cells. To evaluate different automatic control strategies for the system, a simplified dynamic model has been developed in MATLAB Simulink. The model based on measurement data taken from the actual system. The evaluation is based on demand curves, investment costs, electricity prices and irradiation. Evaluation criteria included in the model are electrical and total efficiencies as well as economic parameters.
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| 7. |
- Hedström, Lars, et al.
(författare)
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Experimental results from a 5 kW PEM fuel cell stackoperated on simulated reformate from highly dilutedhydrocarbon fuels: Efficiency, dilution, fuel utilisation,CO poisoning and design criteria
- 2009
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Ingår i: International journal of hydrogen energy. - : Elsevier BV. - 0360-3199 .- 1879-3487. ; :34, s. 1508-1514
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Tidskriftsartikel (refereegranskat)abstract
- The present article analyses the effects of dilute biogas on efficiency, fuel utilisation, dynamics, control strategy, and design criteria for a polymer electrolyte fuel cell (PEFC) system. The tested fuel compositions are exemplified by gas compositions that could be attained within various Swedish biofuel demonstration projects. Experimental data which can serve as a basis for design of PEFC biogas systems operating in load-following, or steady-state mode, are reported for a 5 kW PEFC stack.
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| 8. |
- Hedström, Lars, et al.
(författare)
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Key factors in planning a sustainable energy future including hydrogen and fuel cells
- 2006
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Ingår i: Bulletin of Science, Technology & Society. - : SAGE Publications. - 0270-4676 .- 1552-4183. ; 26:4, s. 264-277
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Tidskriftsartikel (refereegranskat)abstract
- In this article, a number of future energy visions, especiallythose basing the energy systems on hydrogen, are discussed.Some often missing comparisons between alternatives, from asustainability perspective, are identified and then performedfor energy storage, energy transportation, and energy use invehicles. It is shown that it is important to be aware of thelosses implied by production, packaging, distribution, storage,and end-use of hydrogen when suggesting a "hydrogen economy."It is also shown that for stationary electric energy storage,fuel cell electrolyzers could be feasible. Zero-tailpipeemissionvehicles are compared. The battery electric vehicle has thehighest electrical efficiency, but other requirements implythat plug-in hybrids or fuel cell hybrids might be a betteroption in some types of vehicles. Finally, a simplified exampleis applied to the overall results and used to discuss the needsand nature of an energy system based on intermittent energysources.
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| 9. |
- Hedström, Per, 1963-
(författare)
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Skönhet och skötsamhet : Konstnärliga utsmyckningar i svenska skolor 1870-1940
- 2004
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis is about the permanent artistic decoration of Swedish school buildings during the period 1870–1940. Its main aim is to examine the ideals and values which the works installed can be said to convey. It takes its starting point in the major movement for the decoration of schools in Sweden that began around 1900, and that was part of a broader recognition of the importance of public art in the country.The thesis analyses the basic thinking behind the move to install art in schools. In Sweden, discussion on the subject was initiated by the writings and lectures of Carl G. Laurin and Ellen Key. The most important argument for the artistic decoration of schools was the general ennobling influence of art. Art represented beauty, and was thus associated with goodness and truth.The study covers some eighty permanent schemes, or individual works, in Swedish schools, created between 1877 and 1940. They are discussed, first, in a thematic section, with a focus on the different types of subject matter represented, and second, in a number of case studies. Among the subjects dealt with in the thematic analysis are characteristic themes such as sport and outdoor recreation and scenes reflecting school activities. Many of the works portray well-behaved children and young people, who are held up as good examples.The nine case studies analyse individual schemes in greater depth. They include examples that reflect the specific cultures and ideologies of, for instance, higher public grammar schools and girls’ schools. An important aspect of the case studies is their analysis of the reception of the schemes. The reviews examined include discussions of what types of subject were appropriate in art for children and young people.One conclusion drawn in the thesis is that a broader aim of the artistic decoration of schools seems to have been to mould a sense of identity. The images created depict children and young people themselves, regional landscapes and regional and national history.
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| 10. |
- Norman, Holly, et al.
(författare)
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Myofibrillar protein and gene expression in acute quadriplegic myopathy
- 2009
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Ingår i: Journal of the Neurological Sciences. - : Elsevier BV. - 0022-510X .- 1878-5883. ; 285:1-2, s. 28-38
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Tidskriftsartikel (refereegranskat)abstract
- The dramatic muscle wasting, preferential loss of myosin and impaired muscle function in intensive care unit (ICU) patients with acute quadriplegic myopathy (AQM) have traditionally been suggested to be the result of proteolysis via specific proteolytic pathways. In this study we aim to investigate the mechanisms underlying the preferential loss of thick vs. thin filament proteins and the reassembly of the sarcomere during the recovery process in muscle samples from ICU patients with AQM. Quantitative and qualitative analyses of myofibrillar protein and mRNA expression were analyzed using SDS-PAGE, confocal microscopy, histochemistry and real-time PCR. The present results demonstrate that the transcriptional regulation of myofibrillar protein synthesis plays an important role in the loss of contractile proteins, as well as the recovery of protein levels during clinical improvement, myosin in particular, presumably in concert with proteolytic pathways, but the mechanisms are specific to the different thick and thin filament proteins studied.
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