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- Ebbesson, Lars, et al.
(författare)
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Daily endocrine profiles in parr and smolt Atlantic salmon.
- 2008
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Ingår i: Comparative Biochemistry and Physiology A. - : Elsevier BV. - 1531-4332 .- 1095-6433. ; 151, s. 698-704
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Tidskriftsartikel (refereegranskat)abstract
- To elucidate possible mechanisms behind the endocrine control of parr-smolt transformation, the daily plasma profiles in thyroid hormones (TH; free thyroxine (FT(4)), total thyroxine (TT(4)), and total 3,5,3'-triiodothyronine (TT(3))), growth hormone (GH) and cortisol were studied in Atlantic salmon parr and smolts under simulated-natural winter (8 L:16D) and spring (16.5 L:7.5D) photoperiods, respectively. Overall, TT(4), TT(3) and GH levels were higher in smolts than in parr, whereas FT(4) levels fluctuated within the same range in parr and smolts. Significant diurnal changes in plasma TH were present in parr. Both FT(4) and TT(4) levels increased during the photophase and decreased during the scotophase, while TT(3) levels followed an inverse pattern. Growth hormone showed no significant changes in parr. Changes in FT(4), TT(4), GH, and cortisol, but not TT(3), levels, were observed in smolts with peak levels during both the photophase and scotophase for FT(4), TT(4) and GH. Plasma cortisol was not assayed in parr but in smolts the peaks were associated with dusk and dawn. In addition to the general increases in TH, GH and cortisol, the distinct endocrine differences in nighttime levels between parr in the winter and smolts in the spring suggest different interactions between TH, GH, cortisol and melatonin at these different time points. These spring scotophase endocrine profiles may represent synergistic hormone interactions that promote smolt development, similar to the synergistic endocrine interactions shown to accelerate anuran metamorphosis. The variations in these diurnal rhythms between parr and smolts may represent part of the endocrine mechanism for the translation of seasonal information during salmon smoltification.
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| 2. |
- Ekström, Henrik, et al.
(författare)
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Nanometer-thick films of titanium oxide acting as electrolyte in the polymer electrolyte fuel cell
- 2007
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Ingår i: Electrochimica Acta. - : Elsevier BV. - 0013-4686 .- 1873-3859. ; 52:12, s. 4239-4245
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Tidskriftsartikel (refereegranskat)abstract
- 0–18 nm-thick titanium, zirconium and tantalum oxide films are thermally evaporated on Nafion 117 membranes, and used as thin spacer electrolyte layers between the Nafion and a 3 nm Pt catalyst film. Electrochemical characterisation of the films in terms of oxygen reduction activity, high frequency impedance and cyclic voltammetry in nitrogen is performed in a fuel cell at 80 ◦C and full humidification. Titanium oxide films with thicknesses up to 18 nm are shown to conduct protons, whereas zirconium oxide and tantalum oxide block proton transport already at a thickness of 1.5 nm. The performance for oxygen reduction is higher for a bi-layered film of 3 nm platinum on 1.5 or 18 nm titanium oxide, than for a pure 3 nm platinum film with no spacer layer. The improvement in oxygen reduction performance is ascribed to a higher active surface area of platinum, i.e. no beneficial effect of combining platinum with zirconium, tantalum or titanium oxides on the intrinsic oxygen reduction activityis seen. The results suggest that TiO2 may be used as electrolyte in fuel cell electrodes, and that low-temperature proton exchange fuel cells could be possible using TiO2 as electrolyte.
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| 4. |
- Ekström, Wilhelmina, et al.
(författare)
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Functional outcome in treatment of unstable trochanteric and subtrochanteric fractures with the proximal femoral nail and the Medoff sliding plate
- 2007
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Ingår i: Journal of Orthopaedic Trauma. - 0890-5339 .- 1531-2291. ; 21:1, s. 18-25
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Tidskriftsartikel (refereegranskat)abstract
- Objective: To compare outcome between the proximal femoral nail (PFN) and the Medoff sliding plate (MSP) in patients with unstable trochanteric or subtrochanteric fractures. Methods: This was a consecutive prospective randomized clinical study. In all, 203 patients admitted to two university hospitals with an unstable trochanteric or a subtrochanteric fracture type were included. Surgery was performed with a short intramedullary nail or a dual-sliding plate device. Follow up visits occurred at 6 weeks, 4 months, and 12 months. Functional outcome was measured by walking ability, rising from a chair, curb test, and additional assessments of abductor strength, pain, living conditions, and complications. Results: The ability to walk 15 m at 6 weeks was significantly better in the PFN group compared to the MSP group with an odds ratio 2.2 (P = 0.04, 95% confidence limits 1.03-4.67). No statistical difference in walking ability could be found between trochanteric and subtrochanteric fractures. The major complication rate (8% in the PFN group and 4% in the MSP group) did not differ statistically (P = 0.50) but reoperations were more frequent in the PFN group (9%) compared to the MSP group (1%; P < 0.02). Conclusions: There were no major differences in functional outcome or major complications between the treatment groups. Reasons other than the operated fracture seem to be equally important in determining the long-term functional ability of the patients in our study. An advantage with the MSP was the lower reoperation rate.
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| 5. |
- Gao, Weiming, et al.
(författare)
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Binuclear iron-sulfur complexes with bidentate phosphine ligands as active site models of Fe-hydrogenase and their catalytic proton reduction
- 2007
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Ingår i: Inorganic Chemistry. - : American Chemical Society (ACS). - 0020-1669 .- 1520-510X. ; 46:6, s. 1981-1991
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Tidskriftsartikel (refereegranskat)abstract
- The displacement of CO in a few simple Fe(I)-Fe(I) hydrogenase model complexes by bisphosphine ligands Ph2P-(CH2)(n)-PPh2 [with n = 1 (dppm) or n = 2 (dppe)] is described. The reaction of [{mu-(SCH2)(2)CH2}Fe-2(CO)(6)] (1) and [{mu-(SCH2)(2)N(CH2CH2CH3)}Fe-2(CO)(6)] (2) with dppe gave double butterfly complexes [{mu-(SCH2)(2)CH2}Fe-2(CO)(5)(Ph2PCH2)](2) (3) and [{mu-(SCH2)(2)N(CH2CH2CH3)}Fe-2(CO)(5)(Ph2PCH2)](2) (4), where two Fe2S2 units are linked by the bisphosphine. In addition, an unexpected byproduct, [{mu-(SCH2)(2)N(CH2CH2CH3)}Fe-2(CO)(5){Ph2PCH2CH2(Ph2PS)}] (5), was isolated when 2 was used as a substrate, where only one phosphorus atom of dppe is coordinated, while the other has been converted to PS, presumably by nucleophilic attack on bridging sulfur. By contrast, the reaction of 1 and 2 with dppm under mild conditions gave only complexes [{mu-(SCH2)(2)CH2}Fe-2(CO)(5)(Ph2PCH2PPh2)] (6) and [{mu-(SCH2)(2)N(CH2CH2CH3)}Fe-2(CO)(5)(Ph2PCH2PPh2)] (8), where one ligand coordinated in a monodentate fashion to one Fe2S2 unit. Furthermore, under forcing conditions, the complexes [{mu-(SCH2)(2)CH2}Fe-2(CO)(4){mu-(Ph2P)(2)CH2}] (7) and [{mu-(SCH2)(2)N(CH2CH2CH3)}Fe-2(CO)(4){mu-(Ph2P)(2)CH2}] (9) were formed, where the phosphine acts as a bidentate ligand, binding to both the iron atoms in the same molecular unit. Electrochemical studies show that the complexes 3, 4, and 9 catalyze the reduction of protons to molecular hydrogen, with 4 electrolyzed already at -1.40 V versus Ag/AgNO3 (-1.0 V vs NHE).
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| 7. |
- Jónsdóttir, Kristín
(författare)
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Studies of Unusual Seismicity and Long Period Events at the Glacier Overlain Katla Volcano, Iceland
- 2009
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Earthquake catalogues are usually dominated by diffusive behaviour consistent with the Omori law of aftershocks. This is investigated in terms of waiting times, i.e. the time between successive events in a time-sorted earthquake catalogue. The theoretical waiting time probability distribution for the Omori law is derived and shown to predict the numerically produced Omori aftershock sequence well. These results enhance our understanding of aftershock processes and demonstrate that previous waiting time interpretations were severely flawed.Iceland earthquake catalogues are studied in terms of waiting times. Omori aftershock sequences are shown to predict most datasets well but there are some significant exceptions. One of these is data from the glacier covered Katla volcano in South Iceland, with few aftershocks. This dataset can be further split into two geographical groups: Several hundred volcano-tectonic earthquakes occurring within the caldera, reaching depths down to 15 km, and thousands of emergent low frequency earthquakes with a poorly defined shallow source in Goðabunga, in the western part of Katla. These events are investigated further.The lp events at Goðabunga have been recorded for decades and show a clear seasonal and climate-related correlation where their number increases in the autumn as well as during warmer years. Many of them form groups with very with similar waveforms. New broad-band seismic data suggests that the lp events originate in a steep outlet glacier covering Katla. Here, ice movement leads to ice falls over the steep escarpment, and we now believe that the lp events are generated by large ice falls rather than being related to gas or magma movements within the volcano, and are not precursors to an eruption as previously suspected. This observation probably has major significance for hazard estimation at the many ice-covered volcanoes around the world.We report near-field (vlp) signals simultaneous with the largest lp events. Our data is partly consistent in character with surface deformation (displacement and tilt) due to the ice movements. However, in line with results from elsewhere, the magnitudes of the observed effects are large relative to those from mathematical modelling. Our analysis suggests that the signal is not an instrumental artefact. Possible explanations are discussed.
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| 10. |
- Ryen, Øyvind, et al.
(författare)
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Strengthening mechanisms in solid solution aluminum alloys
- 2006
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Ingår i: Metallurgical and Materials Transactions. A. - : Springer Science and Business Media LLC. - 1073-5623 .- 1543-1940. ; 37A:6, s. 1999-2006
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Tidskriftsartikel (refereegranskat)abstract
- A number of commercial and high-purity non-heat-treatable aluminum alloys are investigated in this work. It is found that both magnesium and manganese in solid solution give a nearly linear concentration dependence of the strength at a given strain for commercial alloys. This deviates from high-purity AlMg binary alloys, where a parabolic concentration dependence is found. Mn in solid solution is found to give a considerably higher strengthening effect per atom than Mg, both in terms of yield stress and initial work hardening rate. This strengthening effect is stronger comparing commercial grades to high-purity alloys. This enhanced strengthening is believed to be a synergy or clustering effect caused by interaction between Mn atoms and trace elements, probably silicon, in solid solution.
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