| 1. |
- Hagfeldt, A., et al.
(författare)
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A system approach to molecular solar cells
- 2004
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Ingår i: Coordination chemistry reviews. - : Elsevier BV. - 0010-8545 .- 1873-3840. ; 248:13-14, s. 1501-1509
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Forskningsöversikt (refereegranskat)abstract
- This paper gives an overview of the research and development of dye-sensitized solar cells (DSC) within the Swedish research program 'Angstrom Solar Center'. A path towards low production cost is the development of a continuous process, which allows the production of solar cells in large volumes and with a high productivity. We have developed a deposition method for the production of the mesoporous TiO2, electrode layer that is based on compression of a powder film at room temperature. This technique allows us to use flexible substrates-a prerequisite fora continuous process. A novel interconnect technology, compatible with a continuous production process, is described. Stability data of plastic DSC, exposed to indoor light for more than 10,000 h, demonstrates the possibility for the technology to be explored for various types of indoor applications. Optimization of the DSC is a challenging task as it is a complex highly interacting molecular system. A system approach is proposed, where the complete DSC is investigated with a series of measurement techniques ('toolbox') that allows the study of the internal processes under relevant conditions. Two examples of such techniques are given.
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| 2. |
- Bertilson, Michael, et al.
(författare)
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Laboratory soft-x-ray microscope for cryotomography of biological specimens
- 2011
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Ingår i: Optics Letters. - 0146-9592 .- 1539-4794. ; 36:14, s. 2728-2730
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Tidskriftsartikel (refereegranskat)abstract
- Soft-x-ray cryotomography allows quantitative and high-resolution three-dimensional imaging of intact unstained cells. To date, the method relies on synchrotron-radiation sources, which limits accessibility for researchers. Here we present a laboratory water-window microscope for cryotomography. It is based on a lambda = 2.48nm liquid-jet laser-plasma source, a normal-incidence multilayer condenser, a 30nm zone-plate objective, and a cryotilt sample holder. We demonstrate high-resolution imaging, as well as quantitative tomographic imaging, of frozen intact cells. The reconstructed tomogram of the intracellular local absorption coefficient shows details down to similar to 100nm.
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| 3. |
- Bladh, K., et al.
(författare)
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An approach to analyse human reliability during refuelling outage of a nuclear power plant
- 2007
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Ingår i: Proc. of Enlarged Halden Programme Group Meeting.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Human reliability analysis (HRA) constitutes a central role in the probabilistic safety assessment (PSA) for the low power and shutdown period of a nuclear power plant. This is because a large number of operative and maintenance activities take place during a refuelling outage when the plant, to a great extent, is disassembled, maintained, and then reassembled back to operational mode. The paper presents the HRA approach used in the shutdown PSA for Forsmark 1/2 and 3 nuclear power units in Sweden. Challenges of the analysis comprises handling the large scope of activities to be analysed, development and use of a quantification method consistent with the full power PSA, and integration of HRA with the “technical” part of PSA. Experiences from the analysis and results will also be discussed.
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| 4. |
- Boschloo, Gerrit, et al.
(författare)
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Optimization of dye-sensitized solar cells prepared by compression method
- 2002
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Ingår i: Journal of Photochemistry and Photobiology A. - 1010-6030 .- 1873-2666. ; 148:03-jan, s. 11-15
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Tidskriftsartikel (refereegranskat)abstract
- Nanostructured TiO2 films have been deposited onto conducting glass and on flexible conducting plastic substrates using a compression technique. Dye-sensitized solar cells prepared from Degussa P25 TiO2 powder, red dye (Ru(dcbpy)(2)(SCN)(2)) or black dye (Ru(tcterpy)(SCN)(3)) and an electrolyte containing LiI and I-2 in 3-methoxypropionitrile were tested using standard photoelectrochemical techniques. The average overall efficiency of small open cells sensitized with the red dye on plastic substrates was 4.5% (100W m(-2)). In a direct comparison, red and black dye gave about the same efficiencies. For both dyes, addition of 4-tert-butylpyridine to the electrolyte resulted in a decreased IPCE response in the whole spectral range, with a specific decrease in the red region, which is attributed to a shift in the conduction band edge of the nano structured TiO2.
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| 5. |
- Constantinidis, Ioannis, et al.
(författare)
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Non-invasive evaluation of alginate/poly-L-lysine/alginate microcapsules by magnetic resonance microscopy
- 2007
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Ingår i: Biomaterials. - : Elsevier BV. - 0142-9612 .- 1878-5905. ; 28:15, s. 2438-2445
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Tidskriftsartikel (refereegranskat)abstract
- In this report, we present data to demonstrate the utility of H-1 MR microscopy to non-invasively examine alginate/poly-L-lysine/ alginate (APA) microcapsules. Specifically, high-resolution images were used to visualize and quantify the poly-L-lysine (PLL) layer, and monitor temporal changes in the alginate gel microstructure during a month long in vitro culture. The thickness of the alginate/PLL layer was quantified to be 40.6 +/- 6.2 mu m regardless of the alginate composition used to generate the beads or the time of alginate/PLL interaction (2, 6, or 20 min). However, there was a notable difference in the contrast of the PLL layer that depended upon the guluronic content of the alginate and the alginate/PLL interaction time. The T-2 relaxation time and the apparent diffusion coefficient (ADC) of the alginate matrix were measured periodically throughout the month long culture period. Alginate beads generated with a high guluronic content alginate demonstrated a temporal decrease in T-2 over the duration of the experiment, while ADC was unaffected. This decrease in T-2 is attributed to a reorganization of the alginate microstructure due to periodic media exchanges that mimicked a regular feeding regiment for cultured cells. In beads coated with a PLL layer, this temporal decrease in T-2 was less pronounced suggesting that the PLL layer helped maintain the integrity of the initial alginate microstructure. Conversely, alginate beads generated with a high mannuronic content alginate (with or without a PLL layer) did not display temporal changes in either T-2 or ADC. This observation suggests that the microstructure of high mannuronic content alginate beads is less susceptible to culture conditions.
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| 6. |
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| 7. |
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| 8. |
- Grant, S. C., et al.
(författare)
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Alginate assessment by NMR microscopy
- 2005
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Ingår i: Journal of materials science. Materials in medicine. - : Springer Science and Business Media LLC. - 0957-4530 .- 1573-4838. ; 16:6, s. 511-514
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Tidskriftsartikel (refereegranskat)abstract
- Alginate hydrogels have long been used to encapsulate cells for the purpose of cell transplantation. However, they also have been criticized because they fail to consistently maintain their integrity for extended periods of time. Two issues of critical importance that have yet to be thoroughly addressed concerning the long-term integrity of alginate/poly-L-lysine/alginate microcapsules are: (i) are there temporal changes in the alginate/poly-L-lysine interaction and (ii) are there temporal changes in the alginate gel structure. NMR microscopy is a non-invasive analytical technique that can address these issues. in this report, we present data to demonstrate the utility of H-1 NMR microscopy to (i) visualize the poly-L-lysine layer in an effort to address the first question, and (ii) to observe temporal changes in the alginate matrix that may represent changes in the gel structure.
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| 9. |
- Hendrikse, Natalie M., et al.
(författare)
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Exploring the therapeutic potential of modern and ancestral phenylalanine/tyrosine ammonia-lyases as supplementary treatment of hereditary tyrosinemia
- 2020
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Ingår i: Scientific Reports. - : Nature Research. - 2045-2322. ; 10:1
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Tidskriftsartikel (refereegranskat)abstract
- Phenylalanine/tyrosine ammonia-lyases (PAL/TALs) have been approved by the FDA for treatment of phenylketonuria and may harbour potential for complementary treatment of hereditary tyrosinemia Type I. Herein, we explore ancestral sequence reconstruction as an enzyme engineering tool to enhance the therapeutic potential of PAL/TALs. We reconstructed putative ancestors from fungi and compared their catalytic activity and stability to two modern fungal PAL/TALs. Surprisingly, most putative ancestors could be expressed as functional tetramers in Escherichia coli and thus retained their ability to oligomerize. All ancestral enzymes displayed increased thermostability compared to both modern enzymes, however, the increase in thermostability was accompanied by a loss in catalytic turnover. One reconstructed ancestral enzyme in particular could be interesting for further drug development, as its ratio of specific activities is more favourable towards tyrosine and it is more thermostable than both modern enzymes. Moreover, long-term stability assessment showed that this variant retained substantially more activity after prolonged incubation at 25 °C and 37 °C, as well as an increased resistance to incubation at 60 °C. Both of these factors are indicative of an extended shelf-life of biopharmaceuticals. We believe that ancestral sequence reconstruction has potential for enhancing the properties of enzyme therapeutics, especially with respect to stability. This work further illustrates that resurrection of putative ancestral oligomeric proteins is feasible and provides insight into the extent of conservation of a functional oligomerization surface area from ancestor to modern enzyme.
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| 10. |
- Holmberg, J. -E, et al.
(författare)
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Nordic experience and experiments of modeling digital I&C systems in PSA
- 2012
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Ingår i: 8th International Topical Meeting on Nuclear Plant Instrumentation, Control, and Human-Machine Interface Technologies 2012, NPIC and HMIT 2012. ; , s. 278-290
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Konferensbidrag (refereegranskat)abstract
- The OECD/NEA CSNI Working Group on Risk Assessment (WGRisk) has set up a task group called DIGREL to develop a taxonomy of failure modes of digital components for the purposes of probabilistic safety assessment (PSA). A parallel Nordic activity carried out a prestudy where a comparison of Nordic experiences and a literature review were performed. The study showed a wide range of approaches and solutions to the challenges given by digital I&C, and also indicated that no state-of-the-art currently exists. An existing simplified PSA model has been complemented with fault tree models for a four-redundant distributed protection system in order to study and demonstrate the effect of design features and modelling approaches. The model has been used to test the effect of CCF modelling, fail-safe principle and voting logic. The example shows that even rather simple I&C design leads to rather complex model despite of the fact that many things have been simplified and only a few protection signals are considered. One lesson from the example is that the Alpha factor model should be used to model CCF: s instead of the Beta factor model. Two options were developed to the comparison of different fail-safe principles. The role of detectable and undetectable failure modes with respect to the failed versus spurious actuations can be clearly seen in the results, showing the importance to model these features in PSA.
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