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- Nyberg, L, et al.
(författare)
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Water transit times and flow paths from two line injections of 3H and 36Cl in a microcatchment at Gårdsjön, Sweden
- 1999
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Ingår i: Hydrological Processes. - 0885-6087. ; 13:11, s. 1557-1575
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Tidskriftsartikel (refereegranskat)abstract
- To investigate groundwater transit times and flow paths in shallow till soil, within an acidification study at Gardsjon, Sweden, two line injections of Cl-36 and H-3 Were made in groundwater during 1992. The first injection in January, when the two tracers were injected at the same depth, gave tracer transit times from injection line to outlet of some hours due to a runoff event on the first day. The subsequent recession period left a considerable amount of tracer in the unsaturated zone, which had transit times that ranged from weeks to months. Tracer recovery at the outlet was 78% for H-3 and 47% for Cl-36. Cl retention was indicated. The second injection in November, when H-3 was injected at 30 cm depth and 36C1 at 60 cm depth, gave recoveries of 96% for H-3 and 83% for Cl-36. Apart from an advective flow-dependent tracer transport, very fast tracer pulses occurred. The velocities for those pulses were of the order of tens of metres per hour. Highest tracer concentrations were observed in the superficial soil layers, which suggest that these layers were the dominant flow paths.
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| 6. |
- Magnuson, Ann, et al.
(författare)
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The role of cytochrome b559 and tyrosineD in protection against photoinhibition during in vivo photoactivation of Photosystem II
- 1999
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Ingår i: Biochimica et Biophysica Acta (BBA) - Bioenergetics. - Elsevier. - 0005-2728. ; 1411:1, s. 180-191
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Tidskriftsartikel (refereegranskat)abstract
- In vivo photoactivation of Photosystem II was studied in the FUD39 mutant strain of the green alga Chlamydomonas reinhardtii which lacks the 23 kDa protein subunit involved in water oxidation. Dark grown cells, devoid of oxygen evolution, were illuminated at 0.8 μE m-2&#;s-1 light intensity which promotes optimal activation of oxygen evolution, or at 17 μE m-2&#;s-1, where photoactivation compete with deleterious photodamage. The involvement of the two redox active cofactors tyrosineD and cytochrome b559 during the photoactivation process, was investigated by EPR spectroscopy. TyrosineD on the D2 reaction center protein functions as auxiliary electron donor to the primary donor P680+ during the first minutes of photoactivation at 0.8 μE m-2&#;s-1 (compare with Rova et al., Biochemistry, 37 (1998) 11039-11045.). Here we show that also cytochrome b559 was rapidly oxidized during the first 10 min of photoactivation with a similar rate to tyrosineD. This implies that both cytochrome b559 and tyrosineD may function as auxiliary electron donors to P680+ and/or the oxidized tyrosine&#;Z on the D1 protein, to avoid photoinhibition before successful photoactivation was accomplished. As the catalytic water-oxidation successively became activated, TyrosineD remained oxidized while cytochrome b559 became rereduced to the equilibrium level that was observed prior to photoactivation. At 17 μE m-2&#;s-1 light intensity, where photoinhibition competes significantly with photoactivation, tyrosineD was very rapidly completely oxidized, after which the amount of oxidized tyrosineD decreased due to photoinhibition. In contrast, cytochrome b559 became reduced during the first 2 min of photoactivation at 17 μE m-2&#;s-1. After this, it was reoxidized, returning to the equilibrium level within 10 min. Thus, during in vivo photoactivation in high-light cytochrome b559 serves two functions. Initially, it probably oxidizes the reduced primary acceptor pheophytin, thereby relieving the acceptor side of reductive pressure, and later on it serves as auxiliary electron donor, preventing donor-side photoinhibition.
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| 7. |
- Rova, Maria, et al.
(författare)
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Coupled Activation of the Donor and the Acceptor Side of Photosystem II during Photoactivation of the Oxygen Evolving Cluster
- 1998
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Ingår i: Biochemistry. - American Chemical Society. - 0006-2960. ; 37:31, s. 11039-11045
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Tidskriftsartikel (refereegranskat)abstract
- Photoactivation of photosystem II has been studied in the FUD 39 mutant of Chlamydomonas reinhardtii that lacks the 23 kDa extrinsic subunit of photosystem II. We have taken advantage of the slow photoactivation rate of FUD 39, earlier demonstrated in Rova, E. M., et al. (1996) J. Biol. Chem. 271, 28918-28924, to study events in photosystem II during intermediate stages of the process. By measuring the EPR multiline signal, the decay of the variable fluorescence after single flashes, and electron transfer from water to the QB site, we found a good correlation between the building of a tetrameric Mn cluster, longer recombination times between QA- and the donor side of photosystem II, and the achievement of water splitting ability. An increased rate of electron transfer from QA- to the QB site on the acceptor side of photosystem II, mainly due to enhanced efficiency of binding of QB to its site, was found to precede the building of the Mn cluster. We also showed that TyrD was oxidized simultaneously with this increase in electron-transfer rate. Thus, it appears that photoactivation is sequential, with an increased rate of electron transfer on the acceptor side occurring together with the oxidation of TyrD in the first step, followed by the assembly of the Mn cluster. We suggest that a conformational change of photosystem II is induced early in the photoactivation process facilitating electron transfer from the primary donor to the acceptor side. As a consequence, TyrD, an auxiliary electron donor to P680+/TyrZ, is oxidized. That this occurs before the Mn cluster is fully functional serves to protect photosystem II against donor side induced photodamage.
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| 8. |
- Bäccman, C., et al.
(författare)
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Expectations of romantic relationsships: : A comparison between homosexual and heterosexual men with regard to Baxter´s criteria.
- 1999
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Ingår i: Social Behavior and Personality. - Palmerston North. - 0301-2212. ; 27:4, s. 363-347
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Tidskriftsartikel (refereegranskat)abstract
- According to Baxter (1986) every relationship has rules which must be followed. If at least one of these rules is broken, it gives the individual the right to breadup the relationship. Baxter identified eight such rules or criteria. The aim of the present study was to investigate whether or not the expectations of romantic relationships held by homosexual men can be linked to Baxter's criteria. Data were obtained through a questionnaire addressed to 31 homosexual men and 50 heterosexual men. Results indicated that Baxter's criteria can be linked to expectations of romantic relationships held by men regardless of sexual orientation, and that age and experience are more reliable predictors than is sexual orientation.
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- Dahlström, M
(författare)
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The production of child care services in Sweden- uneven development and local solutions
- 1997
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Ingår i: Service Industries Journal. - Florence, Kentucky : Routledge. - 0264-2069. ; 17:1, s. 28-50
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Tidskriftsartikel (refereegranskat)abstract
- This article deals with the production and regional development of child care services in Sweden. The production of social services outside the home is discussed in relation to labour market needs and equal opportunities. Staffing, organisation and extension of child care services, as well as restructuring trends are dealt with. The services studied are characterised by local solutions. Reasons for local variations are discussed with special references to labour market factors, political tradition and level of urbanisation. No single factor can explain the variations. Explanations have to be found in the specific local mix of factors.
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