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The “Fani Maoré” eruption off the coasts of Mayotte has been intensively monitored by applying methods similar to those used for subaerial eruptions. Repeated high-resolution bathymetric surveys and dredging, coupled with petrological analyses of time-constrained samples, allowed tracking the evolution of magma over the whole submarine eruptive sequence. Indeed, after one year of direct ascent (Phase 1), basanitic magma switched to a different pathway that sampled a tephri-phonolitic subcrustal reservoir (Phase 2). Later, the magma pathway shifted again in the crust resulting in a new eruption site located 6 km northwest of the main edifice (Phase 3). The petrological signature of lava flows reveals both an evolution by fractional crystallization and syn-eruptive mixing with a tephri-phonolitic magma.We demonstrate that high-flux eruption of large volumes of basanitic magma from a deep-seated reservoir can interact with shallower reservoirs and remobilize eruptible magma. This has significant hazards implications with respect to the capacity of such large eruptions to reactivate shallow-seated inactive reservoirs from a transcrustal magmatic system that could be located potentially at a distance from the high-flux eruptive site.

Self-doped CuS nanoparticles (NPs) were successfully synthesized via microwave-assisted polyol process to act as co-catalysts to TiO2 nanofiber (NF)-based photoanodes to achieve higher photocurrents on visible light-assisted water electrolysis. The strategy adopted to perform the copper cation sulfidation in polyol allowed us to overcome the challenges associated with the copper cation reactivity and particle size control. The impregnation of the CuS NPs on TiO2 NFs synthesized via hydrothermal corrosion of a metallic Ti support resulted in composites with increased visible and near-infrared light absorption compared to the pristine support. This allows an improved overall efficiency of water oxidation (and consequently hydrogen generation at the Pt counter electrode) in passive electrolyte (pH = 7) even at 0 V bias. These low-cost and easy-to-achieve composite materials represent a promising alternative to those involving highly toxic co-catalysts. [ABSTRACT FROM AUTHOR]

The structural, microstructural, and magnetic properties of ~5‐nm‐sized Co0.6Zn0.4Fe2 − xGdxO4 nanoparticles were investigated in order to evaluate their capability to enhance the magnetic resonance imaging contrast as high magnetization agents. A focus was made on the solubility of Gd3+ cations within the spinel lattice. By coupling X‐ray diffraction to X‐ray fluorescence spectroscopy, we demonstrated that only a limited fraction of Gd3+ can substitute Fe3+ ions into the whole crystal structure and does not exceed 6 at.‐%. At this concentration, the room temperature (27°C) saturation magnetizations of the prepared superparamagnetic nanocrystals were found to be close to 80 emu g−1. Coating these nanoparticles with hydrophilic dopamine ligands leads to the formation of ~50‐nm‐sized clusters in water. As a consequence, relatively high r2/r1 ratios of transverse to longitudinal proton relaxivities and high r2 values were measured in the resulting colloids at physiological temperature (37°C) for an applied magnetic field of 1.41 T: 33 and 188 mM−1 sec−1, respectively, for the richest system in gadolinium. Moreover, after incubation with healthy human model cells (fibroblasts) at doses as high as 10 μg mL−1, they induce neither cellular death nor acute cellular damage making the engineered probes particularly valuable for negative magnetic resonance imaging contrasting. [ABSTRACT FROM AUTHOR]

The optical properties of airborne mineral dust depend on its mineralogy, size distribution, shape, and might vary between different source regions. To date, large differences in refractive index values found in the literature have not been fully explained. In this paper we present a new dataset of complex refractive indices (m=n‒ik) and single scattering albedos (SSA) for 19 mineral dust aerosols over the 370–950 nm range in dry conditions. Dust aerosols were generated from natural parent soils from eight source regions (Northern Africa, Sahel, Middle East, Eastern Asia, North and South America, Southern Africa, and Australia). These were selected to represent the global scale variability of the dust mineralogy. Dust was re‒suspended into a 4.2 m3 smog chamber where its spectral shortwave scattering (βsca) and absorption (βabs) coefficients, number size distribution, and bulk composition were measured. The complex refractive index was estimated by Mie calculations combining optical and size data, while the spectral SSA was directly retrieved from βsca and βabs measurements. Our results show that the imaginary part of the refractive index (k) and the SSA largely vary from sample to sample, with values for k in the range 0.001 to 0.009 at 370 nm and 0.0003 to 0.002 at 950 nm, and values for SSA in the range 0.70 to 0.96 at 370 nm and 0.95 to 0.99 at 950 nm. In contrast, the real part of the refractive index (n) is mostly source (and wavelength) independent, with an average value between 1.48 and 1.55. The sample‒to‒sample variability in our dataset of k and SSA is mostly related to differences in the dust’s iron content. In particular, a wavelength‒dependent linear relationship is found between the magnitude of k and SSA and the mass concentrations of both iron oxide and total elemental iron. As an intrinsic property of matter, k is independent of size. When the iron oxide content exceeds > 3 %, the SSA linearly decreases with increasing fraction of coarse particles at short wavelengths (< 600 nm). [ABSTRACT FROM AUTHOR]

Modelling the interaction of dust with longwave (LW) radiation is still a challenge due to the scarcity of information on the complex refractive index of dust from different source regions. In particular, little is known on the variability of the refractive index as a function of the dust mineralogical composition, depending on the source region of emission, and the dust size distribution, which is modified during transport. As a consequence, to date, climate models and remote sensing retrievals generally use a spatially-invariant and time-constant value for the dust LW refractive index. In this paper the variability of the mineral dust LW refractive index as a function of its mineralogical composition and size distribution is explored by in situ measurements in a large smog chamber. Mineral dust aerosols were generated from nineteen natural soils from Northern Africa, Sahel, Middle East, Eastern Asia, North and South America, Southern Africa, and Australia. Soil samples were selected from a total of 137 samples available in order to represent the diversity of sources from arid and semi-arid areas worldwide and to account for the heterogeneity of the soil composition at the global scale. Aerosol samples generated from soils were re-suspended in the chamber, where their LW extinction spectra (2-16 µm), size distribution, and mineralogical composition were measured. The generated aerosol exhibits a realistic size distribution and mineralogy, including both the sub- and super-micron fractions, and represents in typical atmospheric proportions the main LW-active minerals, such as clays, quartz, and calcite. The complex refractive index of the aerosol is obtained by an optical inversion based upon the measured extinction spectrum and size distribution. Results from the present study show that the LW refractive index of dust varies greatly both in magnitude and spectral shape from sample to sample, following the changes in the measured particle composition. The real part (n) of the refractive index is between 0.84 and 1.94, while the imaginary part (k) is ~ 0.001 and 0.92. For instance, the strength of the absorption at ~ 7 and 11.4 µm depends on the amount of calcite within the samples, while the absorption between 8 and 14 µm is determined by the relative abundance of quartz and clays. A linear relationship between the magnitude of the refractive index at 7.0, 9.2, and 11.4 µm and the mass concentration of calcite and quartz absorbing at these wavelengths was found. We suggest that this may lead to predictive rules to estimate the LW refractive index of dust in specific bands based on an assumed or predicted mineralogical composition, or conversely, to estimate the dust composition from measurements of the LW extinction at specific wavebands. Based on the results of the present study, we recommend using refractive indices specific for the different source regions, rather than generic values, in climate models and remote sensing applications. Our observations also suggest that the refractive index of dust in the LW does not change due to the loss of coarse particles by gravitational settling, so that a constant value could be assumed close to sources and during transport. The results of the present study also clearly suggest that the LW refractive index of dust varies at the regional scale. This regional variability has to be characterized further in order to better assess the influence of dust on regional climate, as well as to increase the accuracy of satellite retrievals over regions affected by dust. We make the whole dataset of the dust complex refractive indices obtained here available to the scientific community by publishing it in the supplementary material to this paper. [ABSTRACT FROM AUTHOR]

We report the synthesis of yttrium iron garnet ( YIG) combining soft chemistry route, namely the polyol process, and spark plasma sintering ( SPS) technique. The polyol process produced an intermediary amorphous phase containing both iron and yttrium cations in the desired ratio. They were annealed at 400°C in air to decompose the organic content of the reaction (polyol and acetate). To achieve the garnet phase, the polyol-obtained precursor was subjected to reactive SPS treatment at a temperature of 750°C, far below the typical temperatures (1350°C) used in the classic solid-state reaction process. In 15 min pure and high-density Y3 Fe5 O12 ceramic, with about 100 nm sized crystalline grains, was obtained. We report as well the characterization of the initial amorphous phase and the obtained YIG by X-ray diffraction, scanning electron microscopy, Fourier-transform infrared spectroscopy, 57 Fe Mössbauer spectrometry, and magnetization measurements. [ABSTRACT FROM AUTHOR]

Abstract: Spark plasma sintering (SPS) was used to sinter gas-atomized Zr57Cu20Al10Ni8Ti5 amorphous powder. Systematic analyses were performed to study particle size and annealing time effects on the parts structure and properties. Partial devitrification and particles welding were observed and correlated to particle size and thermal conditions. Mechanical testing, through compression and micro-hardness, reveals that the sintered parts show strength similar to a quenched bulk metallic glass and damaging before failure. However, the pulsed current input does not seem the most relevant way to sinter amorphous powders: during the sintering initial stages (when necks are small), excessive over-heating is generated in the vicinity of particles necks, and is responsible for partial devitrification; further current input at large necks leads to complete densification. Effects of the stress, the thermo- and electro-transports on the sintering are evaluated to provide a better understanding of the SPS mechanisms of densification of metallic glasses. [ABSTRACT FROM AUTHOR]

An alternative route for metal hydrogenation has been investigated: cold plasma hydrogen implantation on polyol-made transition metal nanoparticles. This treatment applied to a challenging system, Ni-H, induces a re-ordering of the metal lattice, and superstructure lines have been observed by both Bragg-Brentano and grazing incidence X-ray diffraction. The resulting intermetallic structure is similar to those obtained by very high-pressure hydrogenation of nickel and prompt us to suggest that plasma-based hydrogen implantation in nanometals is likely to generate unusual metal hydride, opening new opportunities in chemisorption hydrogen storage. Typically, almost isotropic in shape and about 30 nm sized hexagonal-packed Ni 2 H single crystals were produced starting from similarly sized cubic face-centred Ni polycrystals.