| 1. |
- Frederiksen, Lise, et al.
(författare)
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A multivariate approach to plant community distribution in the coastal dune zonation of NW Denmark
- 2006
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Ingår i: Phytocoenologia. - 0340-269X. ; 36:3, s. 321-342
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Tidskriftsartikel (refereegranskat)abstract
- A near-natural coastal dune system in NW Jutland, Denmark was investigated. The area contains a gradient in natural soil mobility with the highest values in dynamic white dunes dominated by Ammophila arenaria, and low mobility in fixed decalcified dune heath with Empetrum nigrum and Calluna vulgaris. A total of 267 plots was investigated and presence of mosses and rooted vascular plants recorded. Cluster analysis identified five communities: white dune, grey dune, outer dune heath, inner dune heath and humid dune heath. These communities were ordered along two main axes in a Detrended Correspondence Analysis (DCA). The relationship between DCA axes and several environmental variables, including soil characteristics and Ellenberg indicator values, were investigated by correlation. Two major complex gradients underlying compositional variation were identified; one short coenocline with an underlying steep gradient in habitat maturity, soil stability and nutrient-limited productivity, and one longer gradient in water-limited productivity and peat accumulation only applying to the older successional stages. Distance from the coast was an important correlate of several of the measured variables. Microclimatic indices, i.e. heat index and wind index, had limited value as descriptors of community patterns as they were not correlated with the DCA axes or with other environmental variables. However, within communities the microclimatic indices correlated with several explanatory variables.
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| 2. |
- Golod, Taras, et al.
(författare)
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Nb-PtNi-Nb Josephson junctions made by 3D FIB nano-sculpturing
- 2009
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Ingår i: Journal of Physics, Conference Series. - : IOP Publishing. - 1742-6588 .- 1742-6596. ; 150 (2009):052062
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Tidskriftsartikel (refereegranskat)abstract
- We use Focused Ion Beam (FIB) for fabrication of nano-scale Superconductor-Ferromagnet-Superconductor (SFS) Josephson junctions, aiming to achieve a uniform, mono-domain state in the F-layer within the junction. We employ a Pt1-xNix alloy, characterized by the perfect solubility of the two components, for obtaining a homogeneous diluted ferromagnet. We perform a systematic analysis of both chemical composition, and ferromagnetic properties of Pt1—xNix thin films for different Ni—concentrations. The nano-scale homogeneity of the Pt1—xNix films is confirmed by energy dispersive X-ray spectroscopy. The Curie temperature of Pt1—xNix films decreases in a non-linear manner with Ni concentration. We observe that the critical current density of Nb — Pt1—xNix — Nb junctions decreases non-monotonously with increasing Ni-concentration: at x 30% it exhibits a minimum, which we attribute to switching into the π state as a function of Ni-concentration.
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| 3. |
- Nygren, Mats, et al.
(författare)
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The effect of Mg doping on the thermoelectric performance of Zn4Sb3 : International Conference on Thermoelectrics
- 2008
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Ingår i: Institute of Electrical and Electronics Engineers. - 1094-2734. ; , s. 382-385
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Tidskriftsartikel (refereegranskat)abstract
- The effect of Mg doping of Zn4Sb3 on thermal and thermoelec. properties has been studied on 4 samples with a doping degree ranging from 0.1 to 2 at.% Mg, and compared to a pure, undoped sample. Lab. X-ray powder diffraction shows that all samples are pure single phase materials as further evidenced with higher confidence by Rietveld refinement of high resoln. synchrotron powder diffraction of the as synthesized 1 at.% and 2 at.% Mg doped samples. Zn4Sb3 undergoes a transition from the room temp. disordered phase to an ordered ' phase, going over an intermediate phase; differential scanning calorimetry show only small effects of doping on the phase transition temp. Phys. properties have been evaluated from 2-400 K for all samples. Some phys. property parameters are affected by doping, but no immediate improvement of ZT was achieved by the doping procedure. The reason for this is discussed in relation to differences in sample compaction.
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| 4. |
- Pedersen, Birgitte L., et al.
(författare)
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The effect of Mg doping on the thermoelectric performance of Zn4Sb3
- 2009
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Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 105:1, s. 13517-
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Tidskriftsartikel (refereegranskat)abstract
- Cation doping studies of high performance thermoelectric (ZnSb3)-Sb-4 have so far focused on elements with larger electronegativity than Zn. Mg has a lower electronegativity than Zn, and, in the present paper, the effect of Mg doping of Zn4Sb3 on phase transition temperatures and thermal and thermoelectric properties have been studied on five samples with a doping degree ranging from 0.1 to 2 at. % Mg. The results are compared with data obtained for a pure, undoped sample. Laboratory x-ray powder diffraction shows that all samples are single phase materials as further evidenced with higher confidence by Rietveld refinement of high resolution synchrotron powder diffraction of as synthesized 1 and 2 at. % Mg doped samples. Multitemperature synchrotron powder diffraction and differential scanning calorimetry reveal a significant effect of Mg-doping on the low temperature phase transitions in one sample (0.5 at. % Mg), whereas the other samples showed only small or no effect. Physical properties have been evaluated from 2-400 K for all samples. Some physical property parameters are affected by doping but no immediate improvement of ZT was achieved. The reason for this is discussed in relation to differences in sample compaction.
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