1015 research outputs found

    Interplay of valence states and magnetic interactions in the perovskite system LaNi1–xRhxO3

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    We report on the structural, magnetic and electronic properties of Rh substituted LaNiO3, LaNi1–xRhxO3 (0 ​≤ ​x ​≤ ​1). Increased Rh contents are associated with increased structural distortion, and we observe a phase transformation and an immiscibility gap between 0.15 ​≤ ​x ​≤ ​0.25, separating the R-3c and Pnma perovskite structure regimes. Structural evaluation by synchrotron X-ray diffraction, X-ray absorption spectroscopy and DC magnetic measurements suggest variations in oxidation state for the B-site cations, with Ni(II)/Rh(IV), in addition to Rh(III), dominating for high Rh-contents. Although ordering of Ni(II)/Rh(IV) is possible, no B-site ordering between Ni and Rh is observed for any composition. A metal-to-insulator transition occurs upon Rh-substitution, correlating with the structural transition. DC- and AC magnetic measurements reveal that several of the compositions are magnetically frustrated with both antiferro- and ferromagnetic behaviour at low temperatures. The antiferromagnetic interactions are dominating, while the ferromagnetic interactions increase with increasing Rh-content, to a maximum at x ​= ​0.80 and x ​= ​0.90 in LaNi1–xRhxO3. The mixed valence states are assumed to contribute with a ferromagnetic super-exchange interaction between Ni(II) and Rh(IV).acceptedVersio

    Monitoring of environmental contaminants in freshwater ecosystems 2020 – Occurrence and biomagnification

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    This program, «Monitoring of environmental contaminants in freshwater ecosystems and single species in large Norwegian lakes”, has covered sampling and determination of environmental contaminants by analyses of organisms in an aquatic, pelagic food web of Lake Mjøsa, and in the top predator in Lake Femunden. Samples of different trophic levels, from epipelagic zooplankton to the top predator brown trout, were collected during the late stages of the growth season in 2020. In this report, the status of contamination in the food web, trends and biomagnification potential of various environmental contaminants is discussed.publishedVersio

    Upward and downward two-phase flow of in a pipe: Comparison between experimental data and model predictions

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    In order to deploy capture and storage (CCS) systems to mitigate climate change, it is crucial to develop reliable models for design and operational considerations. A key element of the system is the interface between transportation and storage, namely the injection well, where various transient scenarios involving multiphase flow will occur. In the literature there are very few data relevant for validation of vertical multiphase flow models for . Hence in this work, we present measurements of liquid holdup, pressure drop and flow regime for upward and downward flow of in a pipe of inner diameter 44mm at a pressure of 6.5MPa, a condition relevant for -injection wells. The experimental results indicate that the flow is close to no-slip. We have compared the experimental data to predictions by well-known models for phase slip and frictional pressure drop, and the results show that overall, the best model is the simplest one – the fully homogeneous approach, in which no slip is assumed and the friction is calculated simply by employing gas-liquid mixture properties in the single-phase friction model. Keywords carbon dioxideinjectionvertical flowfrictionliquid holdupfluid dynamicsthermodynamicspublishedVersio

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