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| 2. |
- Holmqvist, Cecilia, et al.
(författare)
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Josephson current through a precessing spin
- 2009
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Ingår i: Journal of Physics, Conference Series. - : IOP Publishing. - 1742-6588 .- 1742-6596. ; 150
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Tidskriftsartikel (refereegranskat)abstract
- A study of the dc Josephson current between two superconducting leads in thepresence of a precessing classical spin is presented. The precession gives rise to a time-dependenttunnel potential which not only creates different tunneling probabilities for spin-up and spin-down quasiparticles, but also introduces a time-dependent spin-flip term. In particular, westudy the effects of the spin-flip term alone on the Josephson current between two spin-singletsuperconductors as a function of precession frequency and junction transparency. The systemdisplays a steady-state solution although the magnitude and nature of the current is indeedaffected by the precession frequency of the classical spin.
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| 4. |
- Holmqvist, Niklas, et al.
(författare)
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Low levels of persistent organic pollutants (POPS) in New Zealand eels reflect isolation from atmospheric sources
- 2006
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Ingår i: Environmental Pollution. - : Elsevier BV. - 0269-7491. ; 141:3, s. 532-538
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Tidskriftsartikel (refereegranskat)abstract
- Polychlorinated biphenyls (PCBs) and organic pesticides (i.e., DDTs) were measured in long finned eels (Anguilla dieffenbachii) in 17 streams on the west coast of South Island, New Zealand. Very low levels of PCBs and low levels of ppDDE were found. The concentrations of PCBs and ppDDE were not correlated within sites indicating that different processes determined the levels of the two pollutants in New Zealand eels. The PCBs probably originate from atmospheric transport, ppDDE levels are determined by land use and are higher in agriculture areas. The low contamination level of these aquatic systems seems to be a function of a low input from both long and short-range transport as well as few local point sources. No correlation could be found between lipid content and persistent organic pollutants (POPs) concentration (as shown in previous studies) in the eels which could be explained by low and irregular intake of the pollutants.
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| 6. |
- Teber, S., et al.
(författare)
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Josephson current through a precessing classical spin
- 2009
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Ingår i: Physica. B, Condensed matter. - : Elsevier BV. - 0921-4526 .- 1873-2135. ; 404, s. 527-529
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Tidskriftsartikel (refereegranskat)abstract
- A study of the dc Josephson current between two superconducting leads in the presence of a precessingclassical spin is presented. The precession gives rise to a time-dependent tunnel potential which notonly implies different tunneling probabilities for spin-up and spin-down quasiparticles, but introducesalso a time-dependent spin-flip term. We provide an exact general analytic solution for the out-of-equilibrium steady-state permanent current between two spin-singlet superconductors as a functionof the superconducting phase difference, the precession frequency and for arbitrary junction transparency.As an application we focus on the effects of the spin-flip term alone and show that the magnitude andnature of the Josephson current are indeed strongly affected by the precession of the classical spin.
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| 7. |
- Thorn, Colin E., et al.
(författare)
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Comparison of radiocarbon dating of buried paleosols using arbuscular mycorrhizae spores and bulk soil samples
- 2009
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Ingår i: The Holocene. - : SAGE Publications. - 0959-6836 .- 1477-0911. ; 19:7, s. 1031-1037
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Tidskriftsartikel (refereegranskat)abstract
- Ten paleosols from four separate soil pits located in Karkevagge, a glaciated trough in Swedish Lapland, were dated using radiocarbon. Each soil was dated using both conventional bulk soil organic material (SOM) and a pure sample of arbuscular mycorrhizae (AM) fungal spores. The latter are produced by ubiquitous mycorrhizal fungi associated with the roots of many plant genera and may be viewed as a fossil material that has not interacted with any soil constituent subsequent to its emplacement in the soil - at a time presumed to mark the cessation of a favorable soil-forming environment. Regional deglaciation is presumed to have been about 10 000 BP, while a cosmogenic exposure date obtained from the valley floor in Karkevagge dated at 13 100 +/- 1638 BP. The youngest paleosol, buried at similar to 6 cm in soil pit M3, produced a spore date of 0-281 cal. yr BP (1 sigma). However, bulk SOM dates of the same paleosol A horizon gave widely divergent dates and varied with the sample pretreatment, ie, the combustion temperature and the acid-base treatment. For example, the bulk SOM dates for that paleosol ranged from a post-bomb date of 0-314 cal. yr BP (1 sigma) to 2366-2710 cal. yr BP (1 sigma) when subjected to different pretreatments (acid only, acid-base-acid) and the ignition temperatures (400, 800, or 900 degrees C). The oldest paleosol in the set, buried at similar to 61 cm in soil pit M6, dated at 5479-5698 cal. yr BP (1 sigma) using spores, but beyond calibration using bulk SOM. The spore dates were all within the range to be expected of postglacial paleosols, but the bulk SOM dates were frequently beyond the generally accepted time of deglaciation. In addition, all of the spore dates followed a conventional age/depth pattern while the bulk SOM dates did not. There are known possible sources of geogenic carbon contamination in Karkevagge which may well account for the obviously invalid older bulk SOM dates. An additional complication is that the spore dates vary somewhat with their density and diameter. However, where other types of fossil or charcoal are unavailable it appears that the enormously broad distribution of spores and their lack of interaction within the soil and persistence may well offer the prospect of an unusually useful radiocarbon dating medium within paleosols.
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