| 1. |
- Angerbjörn, Anders, et al.
(författare)
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Dietary Variation in Arctic Foxes (Alopex-Lagopus) - an Analysis of Stable Carbon Isotopes
- 1994
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Ingår i: Oecologia. ; 99:3-4, s. 226-232
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Tidskriftsartikel (refereegranskat)abstract
- We used stable carbon isotopes to analyse individual variation in arctic fox diet. We extracted collagen from bones (the lower jaw), and measured stable carbon isotopes. The foxes came from three different localities: Iceland, where both microtines and reindeer are rare; west Greenland, where microtines are absent; and Sweden, where seat analyses showed the primary food to be microtine rodents and reindeer. The Icelandic samples included foxes from both coastal and inland habitats, the Swedish sample came from an inland area, and the Greenland sample from coastal sites. The spatial variation in the isotopic pattern followed a basic division between marine and terrestrial sources of protein. Arctic foxes from inland sites had delta(13)C values of -21.4 (Ice land) and -20.4 parts per thousand (Sweden), showing typical terrestrial values. Coastal foxes from Greenland had typical marine Values of -14.9 parts per thousand, whereas coastal foxes from Iceland had intermediate values of -17.7 parts per thousand. However, there was individual variation within each sample, probably caused by habitat heterogeneity and territoriality among foxes. The variation on a larger scale was related to the availability of different food items. These results were in accordance with other dietary analyses based on seat analyses. This is the first time that stable isotopes have been used to reveal individual dietary patterns. Our study also indicated that isotopic values can be used on a global scale.
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| 2. |
- Karlsson, Anders, et al.
(författare)
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Transient wave propagation in gyrotropic media
- 1992
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Ingår i: Invariant inbedding and inverse problems. - 0898713056 ; , s. 77-89
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- In this paper transient electromagnetic wave propagation in an inhomogeneous, cold plasma is considered. It is assumed that a constant magnetic induction is present and that the plasma is spatially inhomogeneous in the direction of the magnetic induction. Losses in the plasma are modeled with a collision frequency ν. The direct problem, which is to calculate the reflected and transmitted responses of the plasma, is considered in this paper. Special attention is paid to the precursor effects in the plasma and several examples of precursor effects in an inhomogeneous plasma are showed.
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| 3. |
- Karlsson, Anders, et al.
(författare)
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Wave splitting and imbedding equations for a spherically symmetric dispersive medium
- 1992
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Ingår i: Invariant inbedding and inverse problems. - 0898713056 ; , s. 103-113
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- The direct problem of time dependent electromagnetic scattering in the dispersive sphere is solved by a wave splitting technique. The electric field is expanded in a series involving vector spherical harmonics, leading to a system of wave equations for each term. These systems are reduced to scalar wave equations for each term, which are solved via reflection operators. Some preliminary numerical results are presented.
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