| 1. |
- BLOMQVIST, Peter, et al.
(författare)
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PLANKTON AND WATER CHEMISTRY IN LAKE NJUPFATET BEFORE AND AFTER LIMING
- 1995
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Ingår i: CANADIAN JOURNAL OF FISHERIES AND AQUATIC SCIENCES. - 0706-652X. ; 52:3, s. 551-565
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Tidskriftsartikel (refereegranskat)abstract
- Moderately acidified Lake Njupfatet was studied during 2 consecutive years, before and after liming (calcite), and compared with corresponding data from six reference lakes. After liming, the concentration of total phosphorus in the lake water decreased b
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| 2. |
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| 3. |
- Gustafsson, Bengt, et al.
(författare)
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KI emission from envelopes around N-type stars : Spectroscopic observations and interpretations
- 1997
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Ingår i: Astronomy and Astrophysics. - 0004-6361. ; 318:2, s. 535-542
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Tidskriftsartikel (refereegranskat)abstract
- Circumstellar envelopes around three bright N-type stars, R Scl, X TrA, and V Aql have been detected in emission in resonance lines from K I. This radiation, which is most probably scattered photospheric radiation, was first found spectroscopically, but has later been imaged with choronagraphic and polarimetric techniques. In the present paper, which is the first in a series, the spectroscopic K I observations are discussed. From the observations of the K I 769.9 nm emission we find systemic and expansion velocities in fair agreement with those obtained from the CO millimetre lines. We find a decline of the emission with distance from the star, in rough agreement with the assumption of a constant expansion velocity, mass-loss rate and K I abundance.Our mass loss estimates from the K I line observations agree rather well with those obtained from CO (rangning from 1/4 to 1/1 of the CO mass loss), which suggest that a considerable fraction of the potassium stays neutral through the envelope. This puts strong upper limits on the photoionizing chromospheric UV emission from the stars. Some indirect indications that the envelopes have inhomogeneous structures, clumps, are discussed.
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| 4. |
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| 5. |
- Olofsson, Hans, et al.
(författare)
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A thin molecular shell around the carbon star TT Cyg
- 1998
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Ingår i: ASTRONOMY AND ASTROPHYSICS. - : SPRINGER VERLAG. - 0004-6361. ; 330:1, s. L1-L4
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Tidskriftsartikel (refereegranskat)abstract
- Interferometric CO(J=1 --> 0 and 2 --> 1) observations reveal a remarkably thin shell of molecular gas around the carbon star TT Cyg, width/radius less than or similar to 1." 3/34 " approximate to 0.04. It expands at approximate to 13 km s(-1), and contai
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| 6. |
- Olofsson, Hans, et al.
(författare)
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Larger eggs in resident brown trout living in sympatry with anadromous brown trout
- 1999
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Ingår i: ECOLOGY OF FRESHWATER FISH. - : MUNKSGAARD INT PUBL LTD. - 0906-6691. ; 8:2, s. 59-64
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Tidskriftsartikel (refereegranskat)abstract
- Freshwater resident brown trout (Salmo trutta L.) in the stream Jorlandaan (southwestern Sweden) had larger eggs (range of actual mean egg wet weights, 65.9-108.5 mg) than both sympatric migratory trout (76.8-84.2 mg) and trout from five other Swedish str
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| 7. |
- Olofsson, Hans
(författare)
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Reproductive pattern and offspring performance in brown trout (Salmo trutta)
- 1999
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis deals with how reproductive traits and reproductive behaviour in femalebrown trout (Salmo trutta) are linked to offspring performance.In the small stream Tullviksbäcken, the choice of spawning sites was stronglyinfluenced by short-term fluctuations in stream flow and by substrate quality. Coarsegravel gives high egg and alevin survival and was preferred, but substrate selectivityvaried among years. Stream accessibility in the autumn, as determined by fluctuations instream flow and sea level, affected both the number of spawners and the timing ofspawning.In Tullviksbäcken, the distribution of stocked trout two months after emergence wasbest explained by a mathematical model that considered fry to consist of one componentwith resident behaviour and one component with dispersive behaviour. This is opposedto the general view that fry dispersal behaviour is uniform within populations. Dispersionfrom the redds was spatially limited and this may be an adaptation to poor survival farfrom the redds. Initially small sibling trout appeared to be more dispersive than wereinitially large siblings. Egg size had no general effect on fry performance in localaggregations, and trout survival was not affected by differences in egg size. Thus, theprevailing 'bigger-is-better' paradigm concerning larval fish performance wascontradicted. However, initially large trout appeared to be favoured in stream sectionswith high biomass of underyearling trout and good growth opportunities, and it issuggested that selection for initial size may occur locally.Resident trout in the stream Jörlandaån had relatively larger eggs than both sympatric migratory trout and trout from five other Swedish streams. The fitness in residentJörlandaån females is probably enhanced by the production of extremely large offspring, possibly through increased fry survival relative the more numerous fry descending from larger migratory parents.In conclusion, redd-site selection is important for egg and alevin survival but also forjuvenile performance, because fry will not disperse far from their original redd andselection pressures may vary locally. Female egg production strategies may also influenceoffspring survival. Thus, the presented results demonstrate a strong coupling betweenfemale reproductive pattern and offspring performance in brown trout.
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