| 1. |
- Steeneken, P. G., et al.
(författare)
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Crossing the gap from p- to n-type doping : Nature of the states near the chemical potential in La2-xSrxCuO4 and Nd2-xCexCuO4-delta
- 2003
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Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 90:24
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Tidskriftsartikel (refereegranskat)abstract
- We report on an x-ray absorption and resonant photoemission study on single crystals of the high-T-c cuprates La2-xSrxCuO4 and Nd2-xCexCuO4-delta. Using an intrinsic energy reference, we find that the chemical potential of La2-xSrxCuO4 lies near the top of the La2CuO4 valence band whereas in Nd2-xCexCuO4-delta it is situated near the bottom of the Nd2CuO4 conduction band. The data clearly establish that the introduction of Ce in Nd2CuO4 results in electrons being doped into the CuO2 planes. We infer that the states closest to the chemical potential have a Cu 3d(10) singlet origin in Nd2-xCexCuO4-delta and a 3d(9) (L) under bar singlet origin in La2-xSrxCuO4.
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| 2. |
- Panaccione, G., et al.
(författare)
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Coherent peaks and minimal probing depth in photoemission spectroscopy of Mott-Hubbard systems
- 2006
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Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 97:11
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Tidskriftsartikel (refereegranskat)abstract
- We have measured hard x-ray photoemission spectra of pure vanadium sesquioxide (V2O3) across its metal-insulator transition. We show that, in the metallic phase, a clear correlation exists between the shakedown satellites observed in the vanadium 2p and 3p core-level spectra and the coherent peak measured at the Fermi level. Comparing experimental results and dynamical mean-field theory calculations, we estimate the Hubbard energy U in V2O3 (4.20 +/- 0.05 eV). From our bulk-sensitive photoemission spectra we infer the existence of a critical probing depth for investigating electronic properties in strongly correlated solids.
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| 3. |
- Tjernberg, Oscar, et al.
(författare)
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Electrons, holes, and spin in Nd2-xCexCuO4-delta
- 2003
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 67:10
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Tidskriftsartikel (refereegranskat)abstract
- The spin nature of the states at the top of the valence band in Nd2CuO4 and Nd1.85Ce0.15CuO4-delta has been investigated with spin polarized resonant photoemission. A clear Zhang-Rice singlet state is observed at the top of the valence band in the undoped compound showing that the parent compound of this electron doped superconductor is similar to the parent compounds of hole doped cuprate superconductors. Upon doping, the stability of the singlet is destroyed and the optimum doped compound Nd1.85Ce0.15CuO4-delta does not display any well-separated singlet state. These results indicate that hole contribution to the superconductivity in this system is not important in contrast to what has previously been suggested on the bases of transport measurements.
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| 4. |
- Horio, M., et al.
(författare)
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Three-Dimensional Fermi Surface of Overdoped La-Based Cuprates
- 2018
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Ingår i: Physical Review Letters. - : American Physical Society. - 0031-9007 .- 1079-7114. ; 121:7
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Tidskriftsartikel (refereegranskat)abstract
- We present a soft x-ray angle-resolved photoemission spectroscopy study of overdoped high-temperature superconductors. In-plane and out-of-plane components of the Fermi surface are mapped by varying the photoemission angle and the incident photon energy. No k(z) dispersion is observed along the nodal direction, whereas a significant antinodal k(z) dispersion is identified for La-based cuprates. Based on a tight-binding parametrization, we discuss the implications for the density of states near the van Hove singularity. Our results suggest that the large electronic specific heat found in overdoped La2-xSrxCuO4 cannot be assigned to the van Hove singularity alone. We therefore propose quantum criticality induced by a collapsing pseudogap phase as a plausible explanation for observed enhancement of electronic specific heat.
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| 5. |
- Panaccione, G., et al.
(författare)
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Analysis of surface-bulk screening competition in the electron-doped Nd2-xCexCuO4 cuprate using x-ray photoemission spectroscopy
- 2008
-
Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 77:12
-
Tidskriftsartikel (refereegranskat)abstract
- We report core level and valence band photoemission results obtained for Nd2-xCexCuO4 (x = 0.15) single crystals and films by using both soft and hard x rays, hence, with tunable depth sensitivity. When using hard x rays only, we observe distinct and energy separated structures in the main 2p(5)3d(9)L peak of Cu 2p(3/2) and 2p(1/2) core levels, including the well screened features located at the high kinetic energy side, which were recently reported by Taguchi et al. [Phys. Rev. Lett. 95, 177002 (2005)]. By varying the photoelectron takeoff angle, we analyze the difference in the screening properties between surface and bulk, and we demonstrate the depth dependence of the electronic properties by following the evolution of the bulk-related peak. The possible influence of the surface conditions on the Cu 2p spectral features is also discussed.
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| 6. |
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| 7. |
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| 8. |
- Brookes, N. B., et al.
(författare)
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Detection of Zhang-Rice singlets using spin-polarized photoemission
- 2001
-
Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 8723:23
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Tidskriftsartikel (refereegranskat)abstract
- From a spin-resolved photoemission study on the Bi2Sr2CaCu2O8+delta superconductor, we show experimentally that the first ionization state is of nearly pure singlet character. This is true both above and below the superconducting transition and in the presence of doping and band formation. This provides direct support for the existence and stability of Zhang-Rice singlets in high-temperature superconductors, justifying the ansatz of single-band models. Moreover, we establish this technique as an important probe for a wide range of cuprates and strongly correlated materials.
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| 9. |
- Ekström, Madeleine, 1984-, et al.
(författare)
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Evaluation of internal thermal barrier coatings for exhaust manifolds
- 2015
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Ingår i: Surface & Coatings Technology. - : Elsevier. - 0257-8972 .- 1879-3347. ; 272, s. 198-212
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Tidskriftsartikel (refereegranskat)abstract
- Seven different thermal barrier coatings (TBC) intended for coating the inside of an exhaust manifold to reduce its material temperature were studied. They comprised five plasma-sprayed (mullite, forsterite, La2Zr2O7, 8YSZ, and nanostructured 8YSZ) and two sol-gel composite (one sprayed and one dipped) coatings, which were examined for their thermal insulation properties and oxidation and spallation resistance. Thermal cyclic tests in air and in exhaust gas in a diesel test engine showed that thermal expansion mismatch between substrate and TBC was most crucial for TBC lifetime. Moreover, thermal modeling indicated that it is possible to reduce the material temperature by 50 °C, which is important for improving the fatigue life of exhaust manifolds. This reduction can be obtained with a 0.2 mm thick TBC with thermal conductivity close to 0.1 W/m K, or a 3–6 mm thick TBC with thermal conductivity 1.5–3 W/m K.
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| 10. |
- Ghiringhelli, G., et al.
(författare)
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Probing the singlet character of the two-hole states in cuprate superconductors
- 2002
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Ingår i: Physica. B, Condensed matter. - 0921-4526 .- 1873-2135. ; 312, s. 34-35
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Tidskriftsartikel (refereegranskat)abstract
- Using spin-resolved resonant photoemission we have probed the singlet vs. triplet character of the two-hole state in the layered cuprates Bi2Sr2CaCu2O8+delta La2-xSrxCuO4 and Sr2CuO2Cl2. The combination of the photon circular polarization with the photoelectron spin detection gives access to the character of the photoemission final states, which correspond to the two-hole configurations localized at a (CuO4) site. In particular, the lowest energy state is found to have a very high singlet character in all the measured compounds. This can be considered as a strong indication of the existence and stability of the so-called Zhang-Rice singlets in the layered cuprates.
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| 11. |
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| 12. |
- Hosia, W., et al.
(författare)
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Folding into a ß-Hairpin Can Prevent Amyloid Fibril-Formation
- 2004
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Ingår i: Biochemistry. - : American Chemical Society (ACS). - 0006-2960 .- 1520-4995. ; 43:16, s. 4655-4661
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Tidskriftsartikel (refereegranskat)abstract
- The tetrapeptide KFFE is one of the shortest amyloid fibril-forming peptides described. Herein, we have investigated how the structural environment of this motif affects polymerization. Using a turn motif (YNGK) or a less rigid sequence (AAAK) to fuse two KFFE tetrapeptides, we show by several biophysical methods that the amyloidogenic properties are strongly dependent on the structural environment. The dodecapeptide KFFEAAAKKFFE forms abundant thick fibril bundles. Freshly dissolved KFFEAAAKKFFE is monomeric and shows mainly disordered secondary structure, as evidenced by circular dichroism, NMR spectroscopy, hydrogen/deuterium exchange measurements, and molecular modeling studies. In sharp contrast, the dodecapeptide KFFEYNGKKFFE does not form fibrils but folds into a stable ß-hairpin. This structure can oligomerize into a stable 12-mer and multiples thereof, as shown by size exclusion chromatography, sedimentation analysis, and electrospray mass spectrometry. These data indicate that the structural context in which a potential fibril forming sequence is present can prevent fibril formation by favoring self-limiting oligomerization over polymerization.
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| 13. |
- Nylén, H., et al.
(författare)
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O KVV Auger emission versus resonant photoemission at the O K edge of high-Tc superconductors
- 1998
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Ingår i: Physica C: Superconductivity and its Applications. - 0921-4534. ; 300:3-4, s. 161-170
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Tidskriftsartikel (refereegranskat)abstract
- Photoelectron spectroscopy results on single crystals of the superconductors Bi2Sr2CaCu2O8,Bi2Sr 2CuO6, Ba0.6K0.4BiO3 and the semiconductor Ba0.9K0.1BiO3 are reported for the photon energy region around the O K absorption threshold. The development of the O-KVV Auger structure has been carefully monitored as a function of photon energy. A non-monotonic behavior displaying a feature at a constant binding energy of about 14 eV was found for Bi2Sr2CaCu2O8 and Bi2Sr2CuO6 in a narrow photon energy region of 1 eV at the main edge of the O K absorption spectrum around 530 eV. The corresponding enhancement, connected with the autoionization of O 2 p states, is absent in Ba1-xKxBiO3 in contrast to Bi2Sr2CaCu2O8 and Bi2Sr2CuO6. The resonant enhancement is more pronounced for Bi2Sr2CuO6 as compared to Bi2Sr2CaCu2O8, which can be explained by a lower charge carrier concentration in the former case, leading to a more localized nature of intermediate O 2 p states. The model parameters Cu d-d and O p-p Coulomb interactions and the charge transfer energy Δ are estimated from the experiments.
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| 14. |
- Polley, Craig, et al.
(författare)
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Observation of topological crystalline insulator surface states on (111)-oriented Pb1-xSnxSe films
- 2014
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 89:7, s. 075317-
-
Tidskriftsartikel (refereegranskat)abstract
- We present angle-resolved photoemission spectroscopy measurements of the surface states on in-situ grown (111) oriented films of Pb1-xSnxSe, a three-dimensional topological crystalline insulator. We observe surface states with Dirac-like dispersion at (Gamma) over bar and (M) over bar in the surface Brillouin zone, supporting recent theoretical predictions for this family of materials. We study the parallel dispersion isotropy and Dirac-point binding energy of the surface states, and perform tight-binding calculations to support our findings. The relative simplicity of the growth technique is encouraging, and suggests a clear path for future investigations into the role of strain, vicinality, and alternative surface orientations in (Pb,Sn)Se solid solutions.
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| 15. |
- Qvarford, M, et al.
(författare)
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Photoemission and x-ray absorption study of superconducting and semiconducting Ba1-xKxBiO3 single crystals
- 1996
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Ingår i: Physical Review B Condensed Matter. - 0163-1829 .- 1095-3795. ; 54:9, s. 6700-6707
-
Tidskriftsartikel (refereegranskat)abstract
- Semiconducting Ba0.9K0.1BiO3 and superconducting Ba0.6K0.4BiO3 single crystals cleaved in situ have been studied by core level and valence band photoelectron spectroscopy and O K edge x-ray absorption spectroscopy. It was found that the general shape of the valence band spectrum agrees with the shape predicted by band structure calculations, but the intensity near the Fermi level, was lower in the experimental spectrum as compared to the calculated. The O K edge spectra showed that the metallic phase is not related to the presence of doping inducted O 2p holes. This property of Ba1-xKxBiO3 shows that the semiconductor-metal transition of this system is of a different nature than that of the hole doped cuprate high-T-c superconductors. The core level photoemission spectra of the cations showed a small asymmetry for Ba0.9K0.1BiO3. Corresponding spectra for Ba0.6K0.4BiO3 showed a larger asymmetry resulting in a resolved high binding energy shoulder in the Bi 4f spectrum. The origin of this feature is discussed.
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| 16. |
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| 17. |
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| 18. |
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| 19. |
- Andersen, J., et al.
(författare)
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The soft X-ray laser project at MAX IV
- 2017
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Ingår i: IPAC 2017 - Proceedings of the 8th International Particle Accelerator Conference. - : Joint Accelerator Conferences Website - JACoW. - 9783954501823 ; , s. 2760-2762
-
Konferensbidrag (refereegranskat)abstract
- A Soft X-ray Laser (SXL) beamline utilising FEL technology is being designed for the Short Pulse Facility (SPF) at the MAX IV Laboratory. A conceptual design study has been started following on the scientific case already prepared in collaboration between several Swedish Universities and driven by a strong (Swedish) user demand. The baseline goal of the SXL beamline is to generate intense and short pulses in the range 1-5 nm (0.2-1 keV). The system is building on the MAX IV linac system, already today providing 100 fs 3 GeV and pulses compressed to 100 fs for other applications within the SPF. As a special feature we foresee a variety of pump-probe capabilities.
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| 20. |
- Arafat, Yasir, 1985, et al.
(författare)
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Experience from real tests on multiple smart meter switching
- 2015
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Ingår i: IEEE PES Innovative Smart Grid Technologies Conference Europe.
-
Konferensbidrag (refereegranskat)abstract
- Smart Meters (SMs) offer remote switching functionalities to the Distribution System Operators (DSOs). The DSO can switch the breaker of the SM of any customer remotely whenever needed. The DSOs are currently applying this technique for customers typically one by one when customers are changing their addresses or when contracts are terminated. The breaker functionalities of the SMs could be used for multiple customers, thereby opening up new possibilities to balance electricity consumption and production. How the technology has been functioning in practice has, however, not been fully investigated with regard to multiple SM switching. In this paper, the experience from real tests on simultaneous multiple SM switching is presented. The tests have been conducted to observe the effect of SM switching on power quality (PQ). Power Quality Meters (PQMs) had been used both at the substation as well as the customer level to measure the PQ during SM switching. This paper presents the results by showing current measurements during switching ON and OFF of multiple SMs belonging to each substation.
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| 21. |
- Arafat, Yasir, 1985, et al.
(författare)
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Field test on multiple Smart Meter switching to study the effect on power quality at customers level
- 2015
-
Ingår i: 2015 IEEE Eindhoven PowerTech, PowerTech 2015. - : IEEE conference proceedings. - 9781479976935
-
Konferensbidrag (refereegranskat)abstract
- Smart Meters (SMs) are undergoing an increasing deployment all over the world and have been introduced to several regions. The SMs generally have remotely accessible breakers which offer remote switching functionalities to the Distribution System Operators (DSOs). The DSOs have the possibility of using this unique functionality of SMs for various future applications, e.g., switching some loads during peak loads crisis or outage management during natural disasters. Under these conditions, the DSO can disconnect selected customers by using SM switching while continuing power supply to risk customers and emergency service providers. During multiple SM switching, the power quality (PQ) of the connected loads might be affected. This paper presents results on the impact of multiple SM switching at customer level. Data are used from a field test on multiple SM switching from a DSO in Sweden. The number of customers in this test was higher compared to the previous two tests of the work. Moreover, all customers in the selected test area were not switched in this test. Almost half of the customers in the test area were disconnected remotely using SMs while the other half of the customers remained connected with power supply to investigate the impact of SMs switching in a different way. This work observed some transient events during the SMs switching. Voltage quality was stable during the test except some flickering effects beyond the limit.
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| 22. |
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| 23. |
- Berntsen, Magnus H., et al.
(författare)
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A spin- and angle-resolving photoelectron spectrometer
- 2010
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Ingår i: Review of Scientific Instruments. - : AIP Publishing. - 0034-6748 .- 1089-7623. ; 81:3
-
Tidskriftsartikel (refereegranskat)abstract
- A new type of hemispherical electron energy analyzer that permits angle and spin resolved photoelectron spectroscopy has been developed. The analyzer permits standard angle resolved spectra to be recorded with a two-dimensional detector in parallel with spin detection using a mini-Mott polarimeter. General design considerations as well as technical solutions are discussed and test results from the Au(111) surface state are presented.
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| 24. |
- Chang, J., et al.
(författare)
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Electronic structure near the 1/8-anomaly in La-based cuprates
- 2008
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Ingår i: New Journal of Physics. - : IOP Publishing. - 1367-2630. ; 10
-
Tidskriftsartikel (refereegranskat)abstract
- We report an angle-resolved photoemission study of the electronic structure of the pseudogap state in La1.48Nd0.4Sr0.12CuO4 (T-c < 7 K). Two opposite dispersing Fermi arcs are the main result of this study. Several scenarios that can explain this observation are discussed.
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| 25. |
- Chang, Johan, et al.
(författare)
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When low- and high-energy electronic responses meet in cuprate superconductors
- 2007
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 75:22, s. 224508-
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Tidskriftsartikel (refereegranskat)abstract
- The existence of coherent quasiparticles near the Fermi energy in the low-temperature state of high-temperature superconductors has been well established by angle-resolved photoemission spectroscopy (ARPES). We present a study of La1.83Sr0.17CuO4 in the superconducting state and report an abrupt change in the quasiparticle spectral function, as we follow the dispersion of the ARPES signal from the Fermi energy to 0.6 eV. The interruption in the quasiparticle dispersion separates coherent quasiparticle peaks at low energies from broad incoherent excitations at high energies. We find that the boundary between these low-energy and high-energy features exhibits a cosine-shaped momentum dependence, reminiscent of the superconducting d-wave gap. Further intriguing similarities between characteristics of the incoherent excitations and quasiparticle properties suggest a close relation between the electronic response at high and low energies in cuprate superconductors.
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| 26. |
- Dziawa, P., et al.
(författare)
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Topological crystalline insulator states in Pb1-xSnxSe
- 2012
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Ingår i: Nature Materials. - 1476-1122 .- 1476-4660. ; 11:12, s. 1023-1027
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Tidskriftsartikel (refereegranskat)abstract
- Topological insulators are a class of quantum materials in which time-reversal symmetry, relativistic effects and an inverted band structure result in the occurrence of electronic metallic states on the surfaces of insulating bulk crystals. These helical states exhibit a Dirac-like energy dispersion across the bulk bandgap, and they are topologically protected. Recent theoretical results have suggested the existence of topological crystalline insulators (TCIs), a class of topological insulators in which crystalline symmetry replaces the role of time-reversal symmetry in ensuring topological protection(1,2). In this study we show that the narrow-gap semiconductor Pb1-xSnxSe is a TCI for x = 0.23. Temperature-dependent angle-resolved photoelectron spectroscopy demonstrates that the material undergoes a temperature-driven topological phase transition from a trivial insulator to a TCI. These experimental findings add a new class to the family of topological insulators, and we anticipate that they will lead to a considerable body of further research as well as detailed studies of topological phase transitions.
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| 27. |
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| 28. |
- Falkevall, Annelie, et al.
(författare)
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Degradation of the amyloid beta-protein by the novel mitochondrial peptidasome, PreP
- 2006
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Ingår i: Journal of Biological Chemistry. - 0021-9258 .- 1083-351X. ; 281:39, s. 29096-29104
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Tidskriftsartikel (refereegranskat)abstract
- Recently we have identified the novel mitochondrial peptidase responsible for degrading presequences and other short unstructured peptides in mitochondria, the presequence peptidase, which we named PreP peptidasome. In the present study we have identified and characterized the human PreP homologue, hPreP, in brain mitochondria, and we show its capacity to degrade the amyloid beta-protein (Abeta). PreP belongs to the pitrilysin oligopeptidase family M16C containing an inverted zinc-binding motif. We show that hPreP is localized to the mitochondrial matrix. In situ immuno-inactivation studies in human brain mitochondria using anti-hPreP antibodies showed complete inhibition of proteolytic activity against Abeta. We have cloned, overexpressed, and purified recombinant hPreP and its mutant with catalytic base Glu(78) in the inverted zinc-binding motif replaced by Gln. In vitro studies using recombinant hPreP and liquid chromatography nanospray tandem mass spectrometry revealed novel cleavage specificities against Abeta-(1-42), Abeta-(1-40), and Abeta Arctic, a protein that causes increased protofibril formation an early onset familial variant of Alzheimer disease. In contrast to insulin degrading enzyme, which is a functional analogue of hPreP, hPreP does not degrade insulin but does degrade insulin B-chain. Molecular modeling of hPreP based on the crystal structure at 2.1 A resolution of AtPreP allowed us to identify Cys(90) and Cys(527) that form disulfide bridges under oxidized conditions and might be involved in redox regulation of the enzyme. Degradation of the mitochondrial Abeta by hPreP may potentially be of importance in the pathology of Alzheimer disease.
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| 29. |
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| 30. |
- Finazzi, M., et al.
(författare)
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Multiatomic resonant photoemission spectroscopy on CuO and NiO : Observation of antiresonant behavior
- 2000
-
Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 62:24, s. R16215-R16218
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Tidskriftsartikel (refereegranskat)abstract
- The intensity of the O 1s core photoemission peak has been measured for CuO and NiO as the photon energy is scanned across the L-3 absorption edge of the metal ion. In CuO, the O 1s peak shows a typical antiresonant behavior, with a sizable decrease of its cross section at photon energies below the Cu L-3 threshold. No detectable effect is observed for NiO. The CuO data are well reproduced by a multiatom resonant photoemission model based on resonant light scattering.
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| 31. |
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| 32. |
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| 33. |
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| 34. |
- Ghiringhelli, G., et al.
(författare)
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3d spin-orbit photoemission spectrum of nonferromagnetic materials : The test cases of CoO and Cu
- 2002
-
Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 66:7
-
Tidskriftsartikel (refereegranskat)abstract
- The x-ray photoemission spectrum of the valence states of 3d transition-metal systems is spin polarized when using circularly polarized photons. The integral of the spin-orbit spectrum is proportional to the expectation value of the angular part of the 3d spin-orbit operator in the initial state. We show that this quantity can be used to get an estimate of the atomic orbital moment. While the measurement is sensitive to the magnetization axis, it does not require a net macroscopic magnetization nor the presence of a long-range magnetic order, and is therefore suitable for any transition-metal systems being antiferromagnetic or paramagnetic or magnetically disordered. In the case of full 3d shell the integral of the spin-orbit spectrum is zero, but the spectral shape can give a direct estimate of the 3d spin-orbit energy splitting DeltaE(SO). We have used Cu and CoO to experimentally test this technique. As expected Cu provides a vanishing result for , whereas for Co2+ in CoO we find =1.36h at 0 K. On the other hand we find DeltaE(SO)similar or equal to280 meV for Cu.
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| 35. |
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| 36. |
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| 37. |
- Grishin, Michael A., et al.
(författare)
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Anisotropy of electron structure at InAs(111) surfaces by laser pump-and-probe photoemission spectroscopy
- 2005
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Ingår i: Surface Science. - : Elsevier BV. - 0039-6028 .- 1879-2758. ; 574:1, s. 89-94
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Tidskriftsartikel (refereegranskat)abstract
- The electronic structure and the electron dynamics of the clean InAs(111)A 2 x 2 and the InAs(111)B 1 x 1 surfaces have been studied by laser pump-and-probe photoemission spectroscopy. Normally unpopulated electron states above the valence band maximum (VBM) are filled on the InAs(111)A surface due to the conduction band pinning above the Fermi level (E-F). Accompanied by the downward band banding alignment, a charge accumulation layer is confined to the surface region creating a two dimensional electron gas (2DEG). The decay of the photoexcited carriers above the conduction band minimum (CBM) is originated by bulk states affected by the presence of the surface. No occupied states were found on the InAs(111)B 1 x 1 surface. This fact is suggested to be due to the surface stabilisation by the charge removal from the surface into the bulk. The weak photoemission intensity above the VBM on the (111)B surface is attributed to electron states trapped by surface defects. The fast decay of the photoexcited electron states on the (111)A and the (111)B surfaces was found to be tau(111A) less than or equal to 5 ps and tau(111B) less than or equal to 4ps, respectively. We suggest the diffusion of the hot electrons into the bulk is the decay mechanism. (
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| 38. |
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| 39. |
- Henningsson, Anna J., 1972-, et al.
(författare)
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Laboratory diagnosis of Lyme neuroborreliosis: a comparisonof three CSF anti-Borrelia antibody assays
- 2014
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Ingår i: European Journal of Clinical Microbiology and Infectious Diseases. - : Springer Publishing Company. - 0934-9723 .- 1435-4373. ; 33, s. 797-803
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Tidskriftsartikel (refereegranskat)abstract
- The diagnosis of Lyme neuroborreliosis (LNB) requires the detection of intrathecal synthesis of Borrelia-specific antibodies, but in very early disease, the sensitivity may be low. We compared the performance of the second-generation IDEIA Lyme Neuroborreliosis test (Oxoid), based on purified native flagellum antigen, with two newly developed tests based on several recombinant antigens for the diagnosis of LNB. Patients investigated for LNB during 2003 through 2007 were included (n = 175); 52 with definite LNB, four with possible LNB and 119 non-LNB patients. Serum and cerebrospinal fluid (CSF) were analysed with the IDEIA Lyme Neuroborreliosis (Oxoid), VIDAS Lyme IgG (bioMérieux) and recomBead Borrelia IgM and IgG (Mikrogen) assays. Intrathecal antibody indices (AIs) were calculated according to the manufacturers’ protocols. The IDEIA test performed with an overall sensitivity (IgM and IgG AIs taken together) of 88 % and a specificity of 99 %. The VIDAS test showed a sensitivity of 86 % and a specificity of 97 %. An overall sensitivity of 100 % and a specificity of 97 % were achieved by the recomBead test. We conclude that the three assays performed equally well regarding specificity, but our data suggest an improved diagnostic sensitivity with the recomBead Borrelia test.
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| 40. |
- Jayamanne, M, et al.
(författare)
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Development of a two-dimensional liquid chromatography system for isolation of drug metabolites
- 2010
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Ingår i: Journal of Pharmaceutical and Biomedical Analysis. - : Elsevier BV. - 0731-7085 .- 1873-264X. ; 51:3, s. 649-657
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Tidskriftsartikel (refereegranskat)abstract
- The separation, isolation and identification of drug metabolites from complex endogenous matrices like urine, plasma and tissue extracts are challenging tasks. Metabolites are usually first identified by mass spectrometry and tentative structures proposed from product ion spectra. In many cases mass spectrometry cannot be used to determine positional isomers and metabolites have to be fractionated in microgram amounts for analysis by NMR. To overcome the difficulties associated with separation and isolation of drug metabolites from biological matrices, a new two-dimensional liquid chromatography system has been developed. The retention times of 45 acidic, basic and neutral compounds were determined on liquid chromatographic columns with different stationary phases in order to identify two columns with highly different selectivity to be used for two-dimensional liquid chromatography. Drug metabolites of three model compounds were first generated in vitro with liver microsomes and then compared with potential metabolites formed by oxidation with hydrogen peroxide catalyzed by meso-tetra (4-sulphonatophenyl) porphine (porphine). The results showed that the porphine system could be used as a complementary system for the generation of phase I microsomal metabolites with high yield of some metabolites in a less complex matrix. The two-dimensional liquid chromatography system was used to separate and isolate microsomal and porphine generated drug metabolites in off-line and on-line mode. Finally, to verify the utility of the developed system, urine samples were spiked with metabolite standards of model compounds for separation in the two-dimensional system. Excellent separations were obtained with an amide column in the first dimension and a pentafluorophenylpropyl (PFPP) column in the second dimension. The metabolites were successfully separated from each other as well as from the complex biological matrix. The results demonstrate the applicability of the system for fractionation of drug metabolites but it could also be used in many other analytical purposes, especially for basic compounds. Trace levels of metabolites were successfully separated in the on-line mode which failed in the off-line mode.
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| 41. |
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| 42. |
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| 43. |
- Lu, Jun, et al.
(författare)
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Ebsulfur is a benzisothiazolone cytocidal inhibitor targeting the trypanothione reductase of Trypanosoma brucei
- 2013
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Ingår i: Journal of Biological Chemistry. - 0021-9258 .- 1083-351X. ; 288:38, s. 27456-27468
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Tidskriftsartikel (refereegranskat)abstract
- Trypanosoma brucei is the causing agent of African trypanosomiasis. These parasites possess a unique thiol redox system required for DNA synthesis and defense against oxidative stress. It includes trypanothione and trypanothione reductase (TryR) instead of the thioredoxin and glutaredoxin systems of mammalian hosts. Here, we show that the benzisothiazolone compound ebsulfur (EbS), a sulfur analogue of ebselen, is a potent inhibitor of T. brucei growth with a favorable selectivity index over mammalian cells. EbS inhibited the TryR activity and decreased non-protein thiol levels in cultured parasites. The inhibition of TryR by EbS was irreversible and NADPH-dependent. EbS formed a complex with TryR and caused oxidation and inactivation of the enzyme. EbS was more toxic for T. brucei than for Trypanosoma cruzi, probably due to lower levels of TryR and trypanothione in T. brucei. Furthermore, inhibition of TryR produced high intracellular reactive oxygen species. Hydrogen peroxide, known to be constitutively high in T. brucei, enhanced the EbS inhibition of TryR. The elevation of reactive oxygen species production in parasites caused by EbS induced a programmed cell death. Soluble EbS analogues were synthesized and cured T. brucei brucei infection in mice when used together with nifurtimox. Altogether, EbS and EbS analogues disrupt the trypanothione system, hampering the defense against oxidative stress. Thus, EbS is a promising lead for development of drugs against African trypanosomiasis.
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| 44. |
- Matt, C. E., et al.
(författare)
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Direct observation of orbital hybridisation in a cuprate superconductor
- 2018
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Ingår i: Nature Communications. - : Nature Publishing Group. - 2041-1723. ; 9
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Tidskriftsartikel (refereegranskat)abstract
- The minimal ingredients to explain the essential physics of layered copper-oxide (cuprates) materials remains heavily debated. Effective low-energy single-band models of the copper-oxygen orbitals are widely used because there exists no strong experimental evidence supporting multi-band structures. Here, we report angle-resolved photoelectron spectroscopy experiments on La-based cuprates that provide direct observation of a two-band structure. This electronic structure, qualitatively consistent with density functional theory, is parametrised by a two-orbital (d(x2-y2) and d(z2)) tight-binding model. We quantify the orbital hybridisation which provides an explanation for the Fermi surface topology and the proximity of the van-Hove singularity to the Fermi level. Our analysis leads to a unification of electronic hopping parameters for single-layer cuprates and we conclude that hybridisation, restraining d-wave pairing, is an important optimisation element for superconductivity.
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| 45. |
- Matt, C. E., et al.
(författare)
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Electron scattering, charge order, and pseudogap physics in La1.6-xNd0.4SrxCuO4 : An angle-resolved photoemission spectroscopy study
- 2015
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - : American Physical Society. - 1098-0121 .- 1550-235X. ; 92:13
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Tidskriftsartikel (refereegranskat)abstract
- We report an angle-resolved photoemission study of the charge stripe ordered La1.6-xNd0.4SrxCuO4 (Nd-LSCO) system. A comparative and quantitative line-shape analysis is presented as the system evolves from the overdoped regime into the charge ordered phase. On the overdoped side (x = 0.20), a normal-state antinodal spectral gap opens upon cooling below 80 K. In this process, spectral weight is preserved but redistributed to larger energies. A correlation between this spectral gap and electron scattering is found. A different line shape is observed in the antinodal region of charge ordered Nd-LSCO x = 1/8. Significant low-energy spectral weight appears to be lost. These observations are discussed in terms of spectral-weight redistribution and gapping originating from charge stripe ordering.
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| 46. |
- Mazidi, Peyman, et al.
(författare)
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A Performance and Maintenance Evaluation Framework for Wind Turbines
- 2016
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Konferensbidrag (refereegranskat)abstract
- In this paper, a data driven framework forperformance and maintenance evaluation (PAME) of windturbines (WT) is proposed. To develop the framework, SCADAdata of WTs are adopted and several parameters are carefullyselected to create a normal behavior model. This model which isbased on Neural Networks estimates operation of WT andaberrations are collected as deviations. Afterwards, in order tocapture patterns of deviations, self-organizing map is applied tocluster the deviations. From investigations on deviations andclustering results, a time-discrete finite state space Markov chainis built for mid-term operation and maintenance evaluation.With the purpose of performance and maintenance assessment,two anomaly indexes are defined and mathematically formulated.Moreover, Production Loss Profit is defined for PreventiveMaintenance efficiency assessment. By comparing the indexescalculated for 9 WTs, current performance and maintenancestrategies can be evaluated, and results demonstrate capabilityand effectiveness of the proposed framework.
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| 47. |
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| 48. |
- Mazidi, Peyman, et al.
(författare)
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Wind Turbine Prognostics and Maintenance Management based on a Hybrid Approach of Neural Networks and Proportional Hazards Model
- 2017
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Ingår i: Journal of Risk and Reliability. - : Sage Publications. - 1748-006X .- 1748-0078. ; 231:2, s. 121-129
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Forskningsöversikt (refereegranskat)abstract
- This paper proposes an approach for stress condition monitoring and maintenance assessment in wind turbines(WT) through large amounts of collected data from supervisory control and data acquisition (SCADA) system. Theobjectives of the proposed approach are: to provide a stress condition model for health monitoring, to assess the WT’smaintenance strategies, and to provide recommendations on current maintenance schemes for future operations ofthe wind farm. At first, several statistical techniques, namely Principal component analysis, Pearson, Spearman andKendall correlations, mutual information, regressional ReliefF and decision trees are used and compared to assessthe data for dimensionality reduction and parameter selection. Next, a normal behavior model is constructed by anartificial neural network which performs condition monitoring analysis. Then, a model based on mathematical form ofProportional hazards model is developed where it represents stress condition of the WT. Finally, those two modelsare jointly employed in order to analyze the overall performance of the WT over the study period. Several cases areanalyzed with a five-year SCADA data and maintenance information is utilized to develop and validate the proposedapproach.
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| 49. |
- Medarde, M., et al.
(författare)
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Low-temperature spin-state transition in LaCoO3 investigated using resonant x-ray absorption at the CoK edge
- 2006
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 73:5
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Tidskriftsartikel (refereegranskat)abstract
- LaCoO3 displays two broad anomalies in the DC magnetic susceptibility chi(DC), occurring, respectively, around 50 K and 500 K. We have investigated the first of them within the 10 K < T < RT temperature range using Co K alpha(1) x-ray absorption spectroscopy (XAS) in the partial fluorescence yield mode. In contrast with previous O K-edge XAS reports, our data show the existence of abrupt changes around 50 K which can be nicely correlated with the anomaly in chi(DC). To our knowledge, this is the first time that a clear, quantitative relationship between the temperature dependence of the magnetic susceptibility and that of the XAS spectra is reported. The intensity changes in the preedge region, which are consistent with a transition from a lower to a higher spin state, have been analyzed using a minimal model including the Co 3d and O 2p hybridization in the initial state. The temperature dependence of the Co magnetic moment obtained from the estimated e(g) and t(2g) occupations could be satisfactorily reproduced. Also, the decrease of the Co 3d and O 2p hybridization by increasing temperature obtained from this simple model compares favorably with the values estimated from thermal evolution of the crystallographic structure.
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| 50. |
- Mizokawa, T., et al.
(författare)
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Spin-orbit coupling in the Mott insulator Ca2RuO4
- 2001
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Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 8707:7
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Tidskriftsartikel (refereegranskat)abstract
- O 1s x-ray absorption study of the Mott insulator Ca2RuO4 shows that the orbital population of the 4d t(2g) band dramatically changes with temperature. In addition, spin-resolved circularly polarized photoemission study of Ca2RuO4 shows that a substantial orbital angular momentum is induced in the Ru 4d t(2g) band. Based on the experimental results and model Hartree-Fock calculations, we argue that the cooperation between the strong spin-orbit coupling in the Ru 4d t(2g) band and the small distortion of the RuO6 octahedra causes the interesting changeover of the spin and orbital anisotropy as a function of temperature.
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