| 1. |
- Berg, K. E., et al.
(författare)
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Covalently linked ruthenium(II)-manganese(II) complexes : Distance dependence of quenching and electron transfer
- 2001
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Ingår i: European Journal of Inorganic Chemistry. - 1434-1948 .- 1099-1948. ; 2001:4, s. 1019-1029
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Tidskriftsartikel (refereegranskat)abstract
- Continuing our development of artificial models for photosystem II in green plants, a series of compounds have been prepared in which a RU(bpy)(3)(2+) photosensitizer is covalently Linked to a manganese(II) electron donor. In addition to a trispicolylamine Ligand, two other manganese Ligands, dipicolylamine and aminodiacetic acid, have been introduced in order to study Ligands that are appropriate for the construction of manganese dimers with open coordination sites for the binding of water. Coordination equilibria of the manganese ions were monitored by EPR. The interactions between the ruthenium and manganese moieties were probed by flash photolysis, cyclic voltammetry and steady-state and time-resolved emission measurements. The quenching of the Ru-II excited state by Mn-II was found to be rapid in complexes with short Ru-Mn distances. Nevertheless, each Run species could be photo-oxidized by bimolecular quenching with methylviologen, and the subsequent electron transfer from Mn-II to Ru-III could be monitored.
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| 2. |
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| 3. |
- Fahlander, Claes, et al.
(författare)
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Excited States in 103Sn: Neutron Single-particle Energies with Respect to 100Sn
- 2001
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Ingår i: Physical Review C (Nuclear Physics). - 0556-2813 .- 1089-490X. ; 63:2
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Tidskriftsartikel (refereegranskat)abstract
- Gamma-ray lines from Sn-103 have been identified for the first time using EUROBALL and ancillary detectors. The level scheme of Sn-103 has been established by means of particle-gated gamma gamma coincidences. The energy spacing between the g(7/2) and d(5/2) neutron single-particle orbitals is determined from the excited states in Sn-103.
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| 4. |
- Gullbrand, Jessica, et al.
(författare)
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High-order Cartesian grid method for calculation of incompressible turbulent flows
- 2001
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Ingår i: International Journal for Numerical Methods in Fluids. - : Wiley. - 0271-2091 .- 1097-0363. ; 36:6, s. 687-709
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Tidskriftsartikel (refereegranskat)abstract
- A high-order wall treatment is proposed and implemented into a Cartesian grid method and the wall treatment is evaluated for incompressible turbulent flows. The Cartesian grid method employs a sequence of locally refined, uniformly spaced, Cartesian grids. In order to achieve a high-order accuracy, a wall treatment procedure has been developed for arbitrarily shaped geometries. The procedure consists of high-order Lagrangian polynomial interpolations and extrapolations for determining the dependent variables around the wall boundaries. The wall treatment procedure and the Cartesian grid method are used together with a highly efficient multi-grid acceleration method and a local grid refinement strategy for optimal distribution of the grid points. The high-order Cartesian grid method is evaluated using test functions as well as for laminar and turbulent flows. The proposed approach maintains the high-order discretization and yields high-order accuracy of the numerical results. Large eddy simulation of a turbulent swirling flow indicates that the high-order wall treatment leads to significantly different results from those calculated using a low-order piecewise constant wall description. The differences in the results are smaller at a low level of turbulence near the inlet region, but become significant in the region far away from the inlet where the turbulence is more intense. In the latter situation the effect of the wall treatment is as important as the choice of the subgrid scale stress model.
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| 5. |
- Hammarstrom, L., et al.
(författare)
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A biomimetic approach to artificial photosynthesis : Ru(II)-polypyridine photo-sensitisers linked to tyrosine and manganese electron donors
- 2001
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Ingår i: Spectrochimica Acta Part A - Molecular and Biomolecular Spectroscopy. - 1386-1425 .- 1873-3557. ; 57:11, s. 2145-2160
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Forskningsöversikt (refereegranskat)abstract
- The paper describes recent advances towards the construction of functional rr mics of the oxygen evolving complex in photosystem II (PSII) that are coupled to photoinduced charge separation. Some key principles of PSII and artificial systems for light-induced charge accumulation are discussed. Systems are described where biomimetic electron donors - manganese complexes and tyrosine - have been linked to a Ru(II)-polypyridine photosensitiser. Oxidation of the donors by intramolecular electron transfer from the photo-oxidised Ru(III) complex has been studied using optical flash photolysis and EPR experiments. A step-wise electron transfer Mn-2(III,III) --> tyrosine --> Ru(III) has been demonstrated, in analogy to the reaction on the donor side of PSII Electron transfer from the tyrosine to Ru(III) was coupled to tyrosine deprotonation. This resulted in a large reorganisation energy and thus a slow reaction rate, unless the tyrosine was hydrogen bonded or already deprotonated. A comparison with analogous reactions in PSH is made. Finally, light-induced oxidation of a manganese dimer linked to a Ru(II)-photosensitiser has been observed. Preliminary results suggest the possibility of photo-oxidising manganese dimers in several steps, which is an important advancement towards water oxidation.
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| 6. |
- Harnefors, Lennart, et al.
(författare)
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Torque-Maximizing Field-Weakening Control : Design, Analysis, and Parameter Selection
- 2001
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Ingår i: IEEE Transactions on Industrial Electronics. - : Institute of Electrical and Electronics Engineers (IEEE). - 0278-0046 .- 1557-9948. ; 48:1, s. 161-168
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Tidskriftsartikel (refereegranskat)abstract
- The torque-maximizing field-weakening controlscheme proposed by Kim and Sul is developed further. Theperformance under imperfect field orientation conditions isinvestigated, and it is shown that an overestimated—rather thanan underestimated—model leakage inductance should be used. Aslightly modified algorithm, which offers better robustness andreduced computational complexity, is presented. The importance,for good performance, of combining the scheme with currentand speed controllers featuring antiwindup and improved disturbancerejection is emphasized. The dynamics of the resultingclosed-loop system are analyzed. Obtained in the process are rulesfor selection of all controller parameters, allowing tuning withouttrial-and-error steps. Good performance of the resulting systemis verified experimentally.
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| 7. |
- Morfeldt, E, et al.
(författare)
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Isolated hypervariable regions derived from streptococcal M proteins specifically bind human C4b-binding protein : implications for antigenic variation.
- 2001
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Ingår i: Journal of Immunology. - : The American Association of Immunologists. - 0022-1767 .- 1550-6606. ; 167:7, s. 3870-7
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Tidskriftsartikel (refereegranskat)abstract
- Antigenic variation in microbial surface proteins represents an apparent paradox, because the variable region must retain an important function, while exhibiting extensive immunological variability. We studied this problem for a group of streptococcal M proteins in which the approximately 50-residue hypervariable regions (HVRs) show essentially no residue identity but nevertheless bind the same ligand, the human complement regulator C4b-binding protein (C4BP). Synthetic peptides derived from different HVRs were found to retain the ability to bind C4BP, implying that the HVR corresponds to a distinct ligand-binding domain that can be studied in isolated form. This finding allowed direct characterization of the ligand-binding properties of isolated HVRs and permitted comparisons between different HVRs in the absence of conserved parts of the M proteins. Affinity chromatography of human serum on immobilized peptides showed that they bound C4BP with high specificity and inhibition experiments indicated that different peptides bound to the same site in C4BP. Different C4BP-binding peptides did not exhibit any immunological cross-reactivity, but structural analysis suggested that they have similar folds. These data show that the HVR of streptococcal M protein can exhibit extreme variability in sequence and immunological properties while retaining a highly specific ligand-binding function.
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| 8. |
- Palacz, M., et al.
(författare)
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Investigations of Neutron Deficient Nuclei Close to 100Sn with EUROBALL
- 2001
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Ingår i: Acta Physica Polonica. Series B: Elementary Particle Physics, Nuclear Physics, Statistical Physics, Theory of Relativity, Field Theory. - 0587-4254 .- 1509-5770. ; 32, s. 999-1003
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Tidskriftsartikel (refereegranskat)abstract
- Excited states of nuclei in the vicinity of Sn-100 have been studied using: the EUROBALL detector array. Gamma-ray lines from Sn-103 have been identified for the first time, and a level scheme of low-lying excited states of Sn-103 has been established. New constraints on energies of single particle orbitals with respect to the Sn-100 core are obtained.
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| 9. |
- Revstedt, Johan, et al.
(författare)
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Handling complex boundaries on a Cartesian grid using surface singularities
- 2001
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Ingår i: International Journal for Numerical Methods in Fluids. - 0271-2091 .- 1097-0363. ; 35:2, s. 125-150
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Tidskriftsartikel (refereegranskat)abstract
- This paper considers flow around arbitrarily shaped objects. The boundary conditions on the solid boundaries have been applied by replacing the boundary with a surface force distribution on the surface, such that the required boundary conditions are satisfied. The velocity on the boundary is determined by interpolation or by local (Gaussian space) average. The source terms are determined iteratively as part of the solution. They are then averaged and are smoothed out to nearby computational grid points. The method has been applied both to test problems as well as to more complex engineering problems, where there are not many real competitive alternatives to the proposed method. Simulations of creeping flow around a sphere were studied in order to evaluate the performance of different, competitive approaches of imposing boundary conditions. Using local averaging first-order accuracy is obtained; this can be improved by using a Lagrangian polynomial instead, although the convergence is then considerably slower. Simulations of flows around spheres in the Reynolds number range 1-1000 have been carried out. Finally, the approach was used to describe the impellers in a turbine agitated mixer. For these cases, the results show overall good agreement with other computational and experimental results.
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| 10. |
- Salek, Pawel, et al.
(författare)
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Dynamical suppression of atomic peaks in resonant dissociative photoemission
- 2001
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Ingår i: Chemical Physics Letters. - 0009-2614 .- 1873-4448. ; 343:3-4, s. 332-338
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Tidskriftsartikel (refereegranskat)abstract
- Resonant excitation to the F1s-sigma* dissociative state in hydrogen fluoride gives a photoelectron spectrum where the spectator part contains strong atomic lines but a participator part where such lines are lacking. We demonstrate that this contrasting behaviour between the two parts is due to a strong dynamical suppression of the resonant contribution, making direct main state photoionization the dominating channel even at resonant conditions.
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