| 1. |
- Mases, Mattias, et al.
(författare)
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In situ electrical conductivity and Raman study of C60 tetragonal polymerat high pressures up to 30 GPa
- 2010
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Ingår i: Physica status solidi. B, Basic research. - : Wiley. - 0370-1972 .- 1521-3951. ; 274:11/12, s. 3068-3071
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Tidskriftsartikel (refereegranskat)abstract
- Theory predicts that tetragonal polymeric C60 will undergo a phase transition into a metallic phase at pressures around 20 GPa. Raman and structural experiments at high pressures confirmed formation of a new phase above 20 GPa although the question about its electrical properties was still open. We report on the first simultaneous in situ study of vibrational and electrical properties of two-dimensional (2D) tetragonal C60 polymer at pressures up to 30 GPa in a diamond anvil cell (DAC) specially designed for this purpose. Our results reveal an anomaly in Raman spectra and a drop in electrical resistance of the sample at 20-25 GPa. We tentatively associate this anomalous behaviour with a phase transition into the conductive phase although its metallic character is yet to be proven.At high pressures the Raman spectra exhibit a high degree of disorder. Upon pressure release the order was partially restored and, more importantly, a significant amount of the initial 2D polymeric phase was recovered.
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| 2. |
- Schäfer, Rudolf, et al.
(författare)
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Analyzer-free, intensity-based, wide-field magneto-optical microscopy
- 2021
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Ingår i: Applied Physics Reviews. - : American Institute of Physics (AIP). - 1931-9401. ; 8:3
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Tidskriftsartikel (refereegranskat)abstract
- In conventional Kerr and Faraday microscopy, the sample is illuminated with plane-polarized light, and a magnetic domain contrast is generated by an analyzer making use of the Kerr or Faraday rotation. Here, we demonstrate possibilities of analyzer-free magneto-optical microscopy based on magnetization-dependent intensity modulations of the light. (i) The transverse Kerr effect can be applied for in-plane magnetized material, as demonstrated for an FeSi sheet. (ii) Illuminating that sample with circularly polarized light leads to a domain contrast with a different symmetry from the conventional Kerr contrast. (iii) Circular polarization can also be used for perpendicularly magnetized material, as demonstrated for garnet and ultrathin CoFeB films. (iv) Plane-polarized light at a specific angle can be employed for both in-plane and perpendicular media. (v) Perpendicular light incidence leads to a domain contrast on in-plane materials that is quadratic in the magnetization and to a domain boundary contrast. (vi) Domain contrast can even be obtained without a polarizer. In cases (ii) and (iii), the contrast is generated by magnetic circular dichroism (i.e., differential absorption of left- and right-circularly polarized light induced by magnetization components along the direction of light propagation), while magnetic linear dichroism (differential absorption of linearly polarized light induced by magnetization components transverse to propagation) is responsible for the contrast in case (v). The domain-boundary contrast is due to the magneto-optical gradient effect. A domain-boundary contrast can also arise by interference of phase-shifted magneto-optical amplitudes. An explanation of these contrast phenomena is provided in terms of Maxwell-Fresnel theory.
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| 3. |
- Warren, Wesley C, et al.
(författare)
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The genome of a songbird
- 2010
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Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 464:7289, s. 757-762
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Tidskriftsartikel (refereegranskat)abstract
- The zebra finch is an important model organism in several fields with unique relevance to human neuroscience. Like other songbirds, the zebra finch communicates through learned vocalizations, an ability otherwise documented only in humans and a few other animals and lacking in the chicken-the only bird with a sequenced genome until now. Here we present a structural, functional and comparative analysis of the genome sequence of the zebra finch (Taeniopygia guttata), which is a songbird belonging to the large avian order Passeriformes. We find that the overall structures of the genomes are similar in zebra finch and chicken, but they differ in many intrachromosomal rearrangements, lineage-specific gene family expansions, the number of long-terminal-repeat-based retrotransposons, and mechanisms of sex chromosome dosage compensation. We show that song behaviour engages gene regulatory networks in the zebra finch brain, altering the expression of long non-coding RNAs, microRNAs, transcription factors and their targets. We also show evidence for rapid molecular evolution in the songbird lineage of genes that are regulated during song experience. These results indicate an active involvement of the genome in neural processes underlying vocal communication and identify potential genetic substrates for the evolution and regulation of this behaviour.
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