Human population effects on genetic diversity of salmonid fishes     

Ole A. Mathisen 《GeoJournal》1996,40(1-2):165-169

Almost all members of the Pacific Salmon have an anadromous life history with reproduction, egg development and juvenile feeding taking place in freshwater. This makes salmon vulnerable to human activities like logging, dam building, agricultural irrigation and hatchery activities. Initially the effect was local and minor in nature. Lately with expanded pen farming and ocean ranching of salmon, some species like pinks and chums, are being moved between streams or from one location to another on a scale not anticipated earlier. The interaction of enhanced and wild stocks of salmon is potentially reducing genetic diversity, which universally is considered necessary for maintaining healthy stocks of salmon. A possible solution is to establish salmon sanctuaries without any enhancement activities.Presented at the XVIII Pacific Science Congress, Beijing, China S4: Freshwater 9 June, 1995 Presentation Number S4-7309P-06.  相似文献   

Strong gravitational lensing by spiral galaxies     

Ole Mo¨ller  & A. W. Blain 《Monthly notices of the Royal Astronomical Society》1998,299(3):845-850

We investigate gravitational lensing using a realistic model of disc galaxies. Most of the mass is contained in a large spherical isothermal dark matter halo, but the potential is modified significantly in the core by a gravitationally dominant exponential disc. The method used is adapted from a very general multilens ray-tracing technique developed by Mo¨ller. We investigate the effects of the disc-to-halo mass ratio, the disc scalelength, the disc inclination to the line of sight and the lens redshift on two strong-lensing cross-sections: the cross-section for multiple imaging and the cross-section for large magnifications, in excess of a factor of 10. We find that the multiple-imaging cross-section can be enhanced significantly by an almost edge-on Milky Way disc compared with a singular isothermal sphere (SIS) in individual cases; however, when averaged over all disc inclinations, the cross-section is only increased by about 50 per cent. These results are consistent with other recent work. The presence of a disc, however, increases the inclination-averaged high-magnification cross-section by an order of magnitude compared with a SIS. This result has important implications for magnification bias in future lens surveys, particularly those in the submillimetre waveband, where dust extinction in the lensing galaxy has no effect on the brightness of the images.  相似文献   

IAG Newsletter     

Ole Baltazar Andersen 《Journal of Geodesy》1998,72(6):364-371

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Reactions of Cl Atoms with Selected VOCs: Kinetics, Products and Mechanisms   总被引：1，自引：0，他引：1  

Gaia Fantechi  Niels R. Jensen  Ole Saastad  Jens Hjorth  Jozef Peeters 《Journal of Atmospheric Chemistry》1998,31(3):247-267

The reactions of isoprene, MBO (2-methyl-3-buten-2-ol) and toluene with chlorine atoms have been studied at 298 ± 5 K and 740 ± 5 Torr with the use of FTIR spectroscopy. Major products of the isoprene-Cl reaction and of the MBO-Cl reaction have been identified and quantified, and reaction mechanisms have been tentatively proposed in order to explain the products formed. The reaction between isoprene and Cl atoms yields mainly HCl, formyl chloride, formic acid, methylglyoxal (pyruvic aldehyde), CO and CO2, while the MBO-Cl reaction forms acetone, HCl, formyl chloride, formic acid, CO, CO2. As products from the reaction between toluene and Cl we identified and quantified HCl and benzaldehyde. The rate constants for the reactions of isoprene and toluene with Cl atoms have also been determined using a relative rate method. The measured values are: kisoprene = (5.5 ± 1.0) × 10–10 cm3 molecule–1 s–1 and ktoluene = (5.6 ± 1.3) × 10–11 cm3 molecule–1 s–1. Atmospheric lifetimes have been estimated from these values.  相似文献   

Cod in fjords and coastal waters of North Norway: distribution and variation in length and maturity at age   总被引：1，自引：3，他引：1  

Berg  Erik; Albert  Ole Thomas 《ICES Journal of Marine Science》2003,60(4):787-797

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Relationships between the geometric dimensions and biomass of schools   总被引：1，自引：1，他引：1  

Misund  Ole Arve; Aglen  Asgeir; Beltestad  Arvid K.; Dalen  John 《ICES Journal of Marine Science》1992,49(3):305-315

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Improved mapping of schooling fish near the surface: comparison of abundance estimates obtained by sonar and echo integration     

Misund  Ole Arve; Aglen  Asgeir; Hamre  Johannes; Ona  Egil; Rottingen  Ingolf; Skagen  Dankert; Valdemarsen  John Willy 《ICES Journal of Marine Science》1996,53(2):383-388

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Seabed shear stress and bedload transport due to asymmetric and skewed waves   总被引：1，自引：0，他引：1  

David Gonzalez-Rodriguez  Ole Secher Madsen   《Coastal Engineering》2007,54(12):914-929

A simple conceptual formulation to compute seabed shear stress due to asymmetric and skewed waves is presented. This formulation generalizes the sinusoidal wave case and uses a variable friction factor to describe the physics of the boundary layer and to parameterize the effects of wave shape. Predictions of bed shear stresses agree with numerical computations using a standard boundary layer model with a k–ε turbulence closure. The bed shear stress formulation is combined with a Meyer-Peter and Müller-type formula to predict sheet flow bedload transport under asymmetric and skewed waves for a horizontal or sloping bed. The predictions agree with oscillatory water tunnel measurements from the literature.  相似文献   

Adaptive behaviour of herring schools in the Norwegian Sea as revealed by high-resolution sonar   总被引：1，自引：6，他引：1  

Pitcher  Tony J.; Misund  Ole Arve; Ferno  Anders; Totland  Bjorn; Melle  Vebjorn 《ICES Journal of Marine Science》1996,53(2):449-452

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Ecology of haddock (Melanogrammus aeglefinus L.) in the Norwegian Deep     

Albert  Ole Thomas 《ICES Journal of Marine Science》1994,51(1):31-44

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