| 1. |
- Aasmundtveit, K.E., et al.
(författare)
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Structural ordering in phenyl-substituted polythiophenes
- 2000
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Ingår i: Macromolecules. - : American Chemical Society (ACS). - 0024-9297 .- 1520-5835. ; 33:15, s. 5481-5489
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Tidskriftsartikel (refereegranskat)abstract
- Various substituted poly(phenylthiophene)s have been studied by X-ray diffraction. They are semicrystalline, with very different degrees of crystallinity. Those with para-substituted phenyl groups have a low degree of crystallinity, whereas those with ortho-substituted phenyl groups are more crystalline. The most crystalline materials in this study have two equally long substituents on the phenyl ring, one at the ortho position and the other at the ortho or meta position on the opposite side of the phenyl ring. Poly(3-(2,5-dioctylphenyl)thiophene) (PDOPT) was most thoroughly studied, and a structural model is proposed. The structure of PDOPT is quite different from previously studied substituted polythiophenes in that the octyl side chains are directed normal to the thiophene planes. In this way, the conjugated polymer chains are kept separated from each other. Solution-cast and spin-cast PDOPT films are anisotropic, with the octyl side chains oriented normal to the film surface in both cases. This is contrary to the situation for poly(3-alkylthiophene)s, where solution-cast and spin-cast films orient in different ways.
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| 2. |
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| 3. |
- Baev, A, et al.
(författare)
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Picturing molecular femtosecond processes through an ultra-fast controllable X-ray shutter
- 2003
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Ingår i: Chemical Physics. - 0301-0104 .- 1873-4421. ; 289, s. 51-56
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Tidskriftsartikel (refereegranskat)abstract
- We show that frequency detuning in a resonant X-ray scattering experiment acts as an X-ray camera shutter by regulating the duration time of the scattering process. The camera shutter can be used to select processes at different time scales for observation. This is illustrated by a resonant Auger study of the ultra-fast dissociation of the core-excited HF molecule. We present experimental results and first principle simulations of the molecular fraction in the resonant Auger spectra of HF which is a dynamical parameter that well illustrates X-ray shutter controlled dissociation.
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| 4. |
- Björklund, Henrik, et al.
(författare)
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Controlled Linear Programming: Boundedness and Duality
- 2004
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Computer supported work is often stressful and inadequate computer sys-tems and poor usability contribute to the problem. Still the work situation, and work environment of users are seldom considered when developing computer systems, and it is difficult to incorporate the ideas of User Centred Systems Design (UCSD) in practice. Hence, this research addresses the dif-ficulty in integrating usability, UCSD and occupational health issues in IT systems development in order to improve the resulting work situation and well-being of users. How do basic values and perspectives of stakeholders in systems development projects affect the work with UCSD, usability and users’ health issues in the organisations studied?This research aims at influencing systems development in practice; hence, research is carried out in real life settings with an action research approach. Data is gathered and analysed with a qualitative research approach with in-terview studies, meetings with stakeholders, analysis of documentation, ob-servations and field studies. The theoretical framework adheres to situated action, participatory design, and UCSD that stresses the importance of in-volving users in the design process.This research shows that several basic values and perspectives affect sys-tems development and hinder the usability work, for example, the perspec-tive on user representatives, the value of rationality and objectivity, and the perspective underpinning descriptions and discourse on work. Moreover, this research indicates that the strong business values of automation, efficiency and customer satisfaction shape the development of new technology, and ultimately the tasks and work practices of the civil servants. In short, the studies show that there are some contradictions in business values and the implementation of user-centred systems design, usability and health issues in systems development.Attitudes and perspectives are not easily changed, and change comes gradually. In these organisations, we continuously discuss the integration of health issues in systems development, and by introducing and changing the models of systems development these will hopefully enable communication and change forwards of new perspectives and values. However, a focus on models alone is insufficient and therefore we need to develop a systematic approach to include reflection and new perspectives. Perhaps the reflection itself would help us see our values and perspectives and to alter them?
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| 5. |
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| 6. |
- Bueno, AM, et al.
(författare)
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Influence of chemical bonds on the lifetime of the molecular-field-split 2p levels in H2S
- 2003
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Ingår i: Physical Review A (Atomic, Molecular and Optical Physics). - 1050-2947. ; 67, s. 22714:1-7
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Tidskriftsartikel (refereegranskat)abstract
- Different lifetime broadenings in molecular-field-split 2p core levels in H2S are predicted theoretically and are identified in an experimental investigation of the S 2p Auger electron spectrum. The measurements were performed for the transition to the vibrationally resolved X(1)A(1) ground state of H2S2+. The lifetimes of the 3e(1/2) and 5e(1/2) levels of the 2p ionized molecule are found to be 64 and 74 meV, respectively. This unambiguous determination of the lifetime difference of 10+/-1 meV is only possible as the 4e(1/2)-->X(1)A(1)(2b(1)(-2)) decay channel that overlaps the 5e(1/2)-->X(1)A(1)(2b(1)(-2)) channel is practically suppressed in Auger decay in H2S. The lifetime difference is confirmed by ab initio calculations. A theoretical analysis shows that it results from the mutual orientation of the core hole in the intermediate states and the valence electron density in the sulfur 3p orbitals. Both are strongly influenced by the chemical bond. Thus the observed effect is the direct result of a fundamental property of molecular electronic structure.
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| 8. |
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| 9. |
- Chen, LC, et al.
(författare)
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Excitation transfer in polymer photodiodes for enhanced quantum efficiency
- 2000
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Ingår i: Advanced Materials. - 0935-9648 .- 1521-4095. ; 12:15, s. 1110-
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Tidskriftsartikel (refereegranskat)abstract
- The realization of polymer solar cells is the driving force behind this research. In an idea inspired by photosynthesis, the authors have constructed efficient bilayer photodiodes by a well-chosen combination of conjugated polymers (see Figure) in the donor layer. Forster energy transfer within the donor layer allows the absorbed light to be channeled to the C-60 acceptor layer, improving the total photoconversion of the blend device.
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| 10. |
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