On the mechanisms governing gas penetration into a tokamak plasma during a massive gas injection

A new 1D radial fluid code, IMAGINE, is used to simulate the penetration of gas into a tokamak plasma during a massive gas injection (MGI). The main result is that the gas is in general strongly braked as it reaches the plasma, due to mechanisms related to charge exchange and (to a smaller extent) recombination. As a result, only a fraction of the gas penetrates into the plasma. Also, a shock wave is created in the gas which propagates away from the plasma, braking and compressing the incoming gas. Simulation results are quantitatively consistent, at least in terms of orders of magnitude, with experimental data for a D 2 MGI into a JET Ohmic plasma. Simulations of MGI into the background plasma surrounding a runaway electron beam show that if the background electron density is too high, the gas may not penetrate, suggesting a possible explanation for the recent results of Reux et al in JET (2015 Nucl. Fusion 55 093013)

Self-Reported Wisdom and Happiness: An Empirical Investigation

Possible tensions between wisdom and happiness have been extensively debated in philosophy. Some regard wisdom as the 'supreme part of happiness', whereas other think that a more accurate and wiser view on reality might reduce happiness. Analyzing a Dutch internet survey of 7037 respondents, we discovered that wisdom and happiness were modestly positively related. Wisdom, measured with the Three-Dimensional Wisdom Scale (3D-WS), explained 9.2% of the variation in hedonic happiness. The correlation with the reflective dimension of wisdom was the strongest. In addition, wisdom was more important for happiness among adults with only an elementary education. Our results suggest that happiness and wisdom do not conflict

Structure and conductivity of new fluorite-type Bi2O3-Er2O3-PbO materials.

Fluorite-type fcc phases have been synthesised in the system Bi2O3-Er2O3-PbO by solid state reaction, and a partial air-quenchable domain of the fluorite-type phase has been established. Some of these materials display high oxide ion conductivities, notably (BiO1.5)(0.80)(ErO1.5)(0.11)(PbO)(0 09) and (BiO1.5)(0.85)(ErO1.5)(0.12)(PbO)(0.03), which have conductivities of 0.49 and 0.72 S cm(-1) at 750 degrees C, respectively, placing them among the most conductive Bi2O3-based materials. Conductivity was found to increase with increasing Pb2+/Er3+ ratio and decreasing (Er3+ + Pb2+)/Bi3+ ratio. Positional disorder in the oxide ion sublattice was characterised by neutron powder diffraction. At room temperature, the oxide ion sublattice appeared to be completely disordered, with oxide ions only in 32f and 48i sites, and changes in occupancy with increasing Pb2+/Er3+ and (Er3+ + Pb2+)/Bi3+ ratios were not significant. At 700 degrees C, there appeared to be oxide ions in 8c sites for the material (BiO1.5)(0.80)(ErO1.5)(0.11)(PbO)(0 09), with a correspondingly smaller occupancy of the 32f sites, whilst the occupancy of the 48i sites had not changed significantly. © 2007, Elsevier Ltd

Kinetics of the thermally-induced structural rearrangement of γ-MnO<inf>2</inf>

This work presents a temperature-dependent and time-resolved X-ray and neutron diffraction study of the thermally induced structural rearrangement of γ-MnO2. Here, we study electrochemically prepared γ-MnO2, the manganese dioxide phase used in the majority of battery applications, which we find to be ∼64% ramsdellite [a = 4.4351(6) Å, b = 9.486(2) Å, c = 2.8128(7) Å, and V = 118.33(3) Å3] and ∼36% pyrolusite [a = 4.718(3) Å, c = 2.795(2) Å, and V = 62.22(8) Å3]. Taking a deeper look at the kinetics of the structural rearrangement, we find two steps: a fast transition occurring within 4-8 min with a temperature-dependent ramsdellite to pyrolusite transformation (rate constant 0.11-0.74 min-1) and a slow transition over 4 h that densifies (with changes in unit cell and volume) the ramsdellite and pyrolusite phases to give structures that appear to be temperature-independent. This effectively shows that γ/β-MnO2 prepared in the range of 200-400°C consists of temperature-independent structures of ramsdellite, unit cell a = 4.391(1) Å, b = 9.16(5) Å, c = 2.847(1) Å, and V = 114.5(6) Å3, and pyrolusite, unit cell a = 4.410(2) Å, c = 2.869(2) Å, and V = 55.79(4) Å3, with a temperature-dependent pyrolusite fraction between 0.45 and 0.77 and increasing with temperature. Therefore, we have linked the temperature and time of heat treatment to the structural evolution of γ-MnO2, which will aid the optimization of γ/β-MnO2 as used in Li-primary batteries

An investigation of the mechanisms of goethite, hematite and magnetite-seeded Al(OH)(3) precipitation from synthetic Bayer liquor

The precipitation of Al(OH)3 from synthetic Bayer liquor at 70 degrees C seeded with goethite, hematite and magnetite particles was investigated in order to gain insight into the nucleation and growth mechanisms in the presence of these materials. A combination of characterisation techniques was employed including conductivity analysis, particle size analysis, electron microscopy and in situ synchrotron X-ray diffraction. The magnetite seed was less active for promoting Al(OH)(3) precipitation than the goethite and hematite, based on a comparison of the induction time before the onset of measurable precipitation. For each seed material, the early stages of precipitation were characterised by relatively slow deposition of gibbsite on the seed particles. Precipitation then proceeded via a two-stage mechanism, where gibbsite and small amounts of bayerite and nordstrandite precipitated concurrently. The outcomes of this investigation have implications for the nucleation and growth of scale on mild steel process equipment, and are also relevant for alumina reversion which causes significant process losses through uncontrolled precipitation. (C) 2011 Elsevier B.V. All rights reserved

In situ formation of reactive sulfide precursors in the one-pot, multigram synthesis of Cu2ZnSnS4 nanocrystals

Herein we outline a general one-pot method to produce large quantities of compositionally tunable, kesterite Cu2ZnSnS4 (CZTS) nanocrystals (NCs) through the decomposition of in situ generated metal sulfide precursors. This method uses air stable precursors and should be applicable to the synthesis of a range of metal sulfides. We examine the formation of the ligands, precursors, and particles in turn. Direct reaction of CS2 with the aliphatic primary amines and thiols that already constitute the reaction mixture is used to produce ligands in situ. Through the use of 1H and 13C nuclear magnetic resonance, Fourier transform infrared spectroscopy, and optical absorption spectroscopy, we elucidate the formation of the resulting oleyldithiocarbamate and dodecyltrithiocarbonate ligands. The decomposition of their corresponding metal complexes at temperatures of ∼100 °C yields nuclei with a size of 1–2 nm, with further growth facilitated by the decomposition of dodecanethiol. In this way the nucleation and growth stages of the reaction are decoupled, allowing for the generation of NCs at high concentrations. Using in situ X-ray diffraction, we monitor the evolution of our reactions, thus enabling a real-time glimpse into the formation of Cu2ZnSnS4 NCs. For completeness, the surface chemistry and the electronic structure of the resulting CZTS NCs are studied. © 2013, American Chemical Society

X-ray reflectometry studies on the effect of water on the surface structure of [C(4)mpyr][NTf2] ionic liquid.

The effect of water on the surface structure of 1-butyl-1-methylpyrrolidinium trifluoromethylsulfonylimide [C(4)mpyr][NTf2] ionic liquid was investigated using X-ray reflectometry. The measured reflectivity data suggests a significant amount of water is adsorbed at the surface, with the first layer from the gas (nitrogen)-liquid phase boundary mainly occupied by a mixture of cations and water. Beyond the cation + water layer, the scattering length density increases towards the bulk value, indicating a decreasing amount of water and cations, and/or an increasing amount of anions. The orientation of the butyl chain of cation at the phase boundary and the population of water at the surface were described based on results from an independent molecular dynamics (MD) simulation. We show that the presence of water in the ionic liquid has a non-monotonic effect on the overall thickness of the surface. At low water content, the addition of water does not change the surface thickness since water is mainly present in the bulk. As the water content increases, the surface swells before eventually shrinking down close to the solubility limit of water. The non-monotonic surface thickness is used to explain the anomalous trend of surface tension in ionic liquid-water mixtures reported in the literature. © 2009, Royal Society of Chemistr

Non-injection synthesis of Cu2ZnSnS4 nanocrystals using a binary precursor and ligand approach

We present a non-injection, one-pot synthesis of kesterite Cu2ZnSnS4 (CZTS) nanocrystals (NCs) that allows for multi-gram yields with precise control of the NCs’ metal composition. This is enabled through the selective use of a binary sulfur precursor and ligand reaction mixture, which acts to decouple the nucleation and growth stages. © 2013, The Royal Society of Chemistry