Himawari‐8, a next‐generation geostationary meteorological satellite, was launched on 7 October 2014 and became operational on 7 July 2015. The advanced imager on board Himawari‐8 is equipped with 16 ...observational bands (including three visible and three near‐infrared bands) that enable retrieval of full‐disk aerosol optical properties at 10 min intervals from geostationary (GEO) orbit. Here we show the first application of aerosol optical properties (AOPs) derived from Himawari‐8 data to aerosol data assimilation. Validation of the assimilation experiment by comparison with independent observations demonstrated successful modeling of continental pollution that was not predicted by simulation without assimilation and reduced overestimates of dust front concentrations. These promising results suggest that AOPs derived from Himawari‐8/9 and other planned GEO satellites will considerably improve forecasts of air quality, inverse modeling of emissions, and aerosol reanalysis through assimilation techniques.
Key Points
Next‐generation geostationary meteorological satellite Himawari‐8 launched on 7 October 2014
Himawari‐8 provides full‐disk aerosol optical properties at 10 min intervals from geostationary orbit
Promising results of aerosol assimilation experiment on Himawari‐8 retrievals
Groundmass pyroxene crystals in pumice from the 1914 eruption of Sakurajima in Japan show varied combinations of crystallographic faces (i.e., ‘tracht’). To investigate whether the groundmass ...pyroxene tracht depends on magma decompression conditions, we performed isothermal single–step decompression experiments on hydrous Sakurajima dacite magma. The magma was held under water–saturated conditions at 920 °C, 120 MPa, and oxygen fugacity conditions no more oxidizing than one log unit above Ni–NiO equilibrium for 24 h. Then, a control experiment was immediately quenched, whereas others were decompressed to final pressures of 20, 10, or 5 MPa and held for 3 h before quenching. Groundmass pyroxenes in the control experiment and that quenched at 20 MPa showed octagonal shapes, whereas those decompressed to lower pressures characteristically had hexagonal shapes. Some pyroxenes in the 20 MPa experiment were hexagonal near plagioclase crystals because plagioclase crystallization locally increased the supersaturation of pyroxene in the melt. We conclude that the tracht of groundmass pyroxenes changes from octagonal to hexagonal as the degree of effective undercooling increases and thus reflects the decompression history of a magma during its ascent in a volcanic conduit.
Groundmass crystals indicate syneruptive magmatic conditions, and thus their crystal size distributions (CSDs) are used to infer magma ascent histories. Three-dimensional (3D) CSDs are most commonly ...estimated from two-dimensional (2D) observations and plotted against long-axis length, L (hereafter referred to as "L-plot CSDs"). However, L-plot CSDs have two significant problems: the error because of the conversion from 2D to 3D and a lowered sensitivity to changes in the degree of effective undercooling (ΔTeff), which arises because a crystal's growth rate varies with ΔTeff most strongly along its long dimension. Although these problems can result in false interpretations of magma ascent dynamics, there has been little discussion of the influence of the size criteria on CSDs. In this study, we investigated which 3D size criterion i.e., long (L), intermediate (I), or short (S) axis length is optimum for 2D-estimated CSDs of groundmass crystals from two perspectives: (1) conformity with the actual distributions, and (2) the sensitivity of CSD slopes to the magma ascent conditions in the conduit. We observed groundmass pyroxene crystals in pumice clasts from sub-Plinian and Vulcanian eruptive phases during the 2011 eruption of Shinmoedake (andesitic volcano, Japan) by using synchrotron radiation-based X-ray computed nanotomography (SR-XCT) and field-emission scanning electron microscopy (FE-SEM) and reinvestigated the crystallization kinetics of pyroxene nanolites ranging in width from a few hundred nanometers to 1 µm. The SR-XCT observations provided the detailed 3D shapes and 3D CSDs (CT-CSDs) of these nanolites directly. The FE-SEM observations allowed us to estimate 3D aspect ratios (S:I:L) and CSDs (SEM-CSDs). L-plot SEM-CSDs, acquired using the program CSDCorrections, were used to calculate S-plot SEM-CSDs and I-plot SEM-CSDs. We compared the data from FE-SEM with those from SR-XCT to evaluate the accuracy of 3D aspect ratios and CSDs estimated from 2D data. The L-plot SEM-CSDs from the sub-Plinian pumice sample showed significant inconsistencies with the CTCSD, a result of the difficulty in estimating representative 3D aspect ratios from 2D observations for elongated groundmass crystals. In contrast, the S- and I-plot SEM-CSDs kept the effect of aspect ratio to a minimum and preserved their actual slopes, except for a vertical discrepancy between the CSDs. Moreover, the slopes of S- and I-plot CSDs of the nanolites differed more markedly between the two eruptive styles (by ∼20% more) than those of L-plot CSDs. For estimating magma ascent dynamics, we propose that the optimum method for acquiring SEM-CSDs is to measure the cross-sectional widths of crystals and convert the resulting 2D data set into S-plot CSDs. Our new finding that the 3D shapes and CSDs of pyroxene nanolites differ according to eruptive style means that nanolites indicate distinct differences in ascent histories at the shallow conduit: increasing ΔTeff just before sub-Plinian eruptions and decreasing ΔTeff before Vulcanian eruptions. Given the similarity in CSDs of micro-lites, our results suggest that eruptive style was determined in the shallow conduit. Monitoring the condition of the shallow conduit may contribute to predicting the time evolution of eruptive activity.
•MOVPE grown N-polar AlN layer without hexagonal hillocks or step bunching.•Optimum growth conditions were different for 1-deg-off and 4-deg-off substrates.•N-polar AlN exhibits hexagonal hillocks or ...step-flow growth.
We present the effect of miscut angle of SiC substrates on N-polar AlN growth. The N-polar AlN layers were grown on C-face 4H-SiC substrates with a miscut towards 〈1¯100〉 by metal-organic vapor phase epitaxy (MOVPE). The optimal V/III ratios for high-quality AlN growth on 1° and 4° miscut substrates were found to be 20,000 and 1000, respectively. MOVPE grown N-polar AlN layer without hexagonal hillocks or step bunching was achieved using a 4H-SiC substrate with an intentional miscut of 1° towards 〈1¯100〉. The 200-nm-thick AlN layer exhibited X-ray rocking curve full width half maximums of 203 arcsec and 389 arcsec for (002) and (102) reflections, respectively. The root mean square roughness was 0.4 nm for a 2 μm×2μm atomic force microscope scan.
Nanometer-sized crystals (nanolites) play an important role in controlling eruptions by affecting the viscosity of magmas and inducing bubble nucleation. We present detailed microscopic and ...nanoscopic petrographic analyses of nanolite-bearing and nanolite-free pumice from the 2021 eruption of Fukutoku-Oka-no-Ba, Japan. The nanolite mineral assemblage includes biotite, which is absent from the phenocryst mineral assemblage, and magnetite and clinopyroxene, which are observed as phenocrysts. The boundary between the nanolite-bearing brown glass and nanolite-free colorless glass is either sharp or gradational, and the sharp boundaries also appear sharp under the transmitted electron microscope. X-ray absorption fine structure (XAFS) analysis of the volcanic glass revealed that the nanolite-free colorless glass records an oxygen fugacity of QFM + 0.98 (log units), whereas the nanolite-bearing brown glass records a higher apparent oxygen fugacity (~ QFM + 2). Thermodynamic modelling using MELTS indicates that higher oxygen fugacities increase the liquidus temperature and thus induced the crystallization of magnetite nanolites. The hydrous nanolite mineral assemblage and glass oxygen fugacity estimates suggest that an oxidizing fluid supplied by a hot mafic magma induced nanolite crystallization in the magma reservoir, before the magma fragmentation. The oxidation-induced nanolite crystallization then enhanced heterogeneous bubble nucleation, resulting in convection in the magma reservoir and triggering the eruption.
Schematic illustration of OANS model (for Graphical Abstract).
•Highly reproducible magnetic field effect (MFE) on heterogeneous photocatalysis.•Various parameters related to MFE revelation and ...perturbation are discussed.•A model for MFE involving dissolved oxygen (DO) is presented (OANS model).
Magnetic field effect (MFE) on heterogeneous photocatalysis is investigated, using mostly ZnO powder and methylene blue (MB) solution. Reproducibility with errors less than 2% is obtained with our newly-developed in-situ measurement system. Multiple parameters are involved in MFE phenomena. MFE magnitude depends on magnetic field intensity, while other parameters are also important, including: initial MB concentration, settling time of solution, and level/state of dissolved oxygen (DO). Short-range-order, or very-short-range-order diffusion in the Helmholtz layer just outside powder appears responsible for MFE. Accordingly, powder surface conditions, e.g. H2O, CO2 adsorption, significantly influence MFE, and magnetic adsorption appears correlated. Temperature-dependent MFE and magneto-hydrodynamic effect on photocatalytic silver reduction/deposition are also observed for the first time.
A model is proposed, whereby, in the volume in close proximate to the powder, electrostatic potential and the corresponding magnetic flux would be perturbed, resulting in the appearance of a net Lorentz force on paramagnetic DO, which is essentially responsible for various MFE phenomena (OANS model). DO could be involved with (i) formation of DO-dye complex, (ii) modifying powder adsorption layer, (iii) scavenging rate of excited electrons, (iv) spin chemistry involving singlet–triplet conversion, and (v) manifestation of magneto-hydrodynamic effect. Simultaneous multiple mechanisms are suggested for MFE.
•Achievement of high-quality N-polar AlN growth by MOVPE on 4H-SiC.•Optimum growth conditions were vastly different for N-polar and Al-polar AlN.•N-polar AlN exhibited either hexagonal hillocks or ...step-flow growth.
We present a comprehensive study on metal-organic vapor phase epitaxy growth of N-polar and Al -polar AlN on 4H-SiC with 4° miscut using constant growth parameters. At a high temperature of 1165 °C, N-polar AlN layers had high crystalline quality whereas the Al-polar AlN surfaces had a high density of etch pits. For N-polar AlN, the V/III ratio below 1000 forms hexagonal hillocks, while the V/III ratio over 1000 yields step bunching without the hillocks. 1-μm-thick N-polar AlN layer grown in optimal conditions exhibited FWHMs of 307, 330 and 337 arcsec for (0 0 2), (1 0 2) and (2 0 1) reflections, respectively.
The composition dependence of transition temperatures on quaternary Co-Fe-Ni-Ga melt-spun alloys with constant Ga content are examined. A few at.% of Fe replacement for Co in Co50Ni22Ga28 drastically ...reduce martensitic transformation temperature (TM) whereas ferromagnetic transition temperature (Tc) remains above 400 K. Increasing Ni instead of Co in Fe doped specimen can raise TM around room temperature again. Further increase of Fe content with this manner, the alloys finally connected to ternary Ni-Fe-Ga of ferromagnetic shape memory region. The martensitic transition start temperature (MS) of Co-Fe-Ni-Ga28 alloys show good correlation with the valence electron ratio (e/a). The MS vs e/a plot clearly shows that trend lines are separated for each Fe content, and intervals of trend lines seem to be proportional to Fe content at lower Fe region. The Tc and saturation magnetization of Co-Fe-Ni-Ga28 alloys show almost linear relation with magnetic valence Zm.
•Compositions of Co-Fe-Ni-Ga alloys which connect between ferromagnetic shape memory region of Co-Ni-Ga and Ni-Fe-Ga.•Martensite transformation temperatures are almost proportional to electron to atom ratio.•The trend lines are separated for each Fe contents.
Double Shockley-type stacking faults (2SSFs) formed in 4H-SiC epitaxial films with a dopant concentration of 1.0 × 1016 cm−3 were characterized using grazing incident X-ray topography and ...high-resolution scanning transmission electron microscopy. The origins of 2SSFs were investigated, and it was found that 2SSFs in the epitaxial layer originated from narrow SFs with a double Shockley structure in the substrate. Partial dislocations formed between 4H-type and 2SSF were also characterized. The shapes of 2SSFs are related with Burgers vectors and core types of the two Shockley partial dislocations.
We calculate transverse spin susceptibility in the linear response method based on the ground states determined in the quasiparticle self-consistent GW (QSGW) method. Then we extract spin-wave (SW) ...dispersions from the susceptibility. We treat bcc Fe, hcp Co, fcc Ni, and B2-type FeCo. Because of the better description of the independent-particle picture in QSGW, calculated spin stiffness constants for Fe, Co, and Ni give much better agreement with experiments in QSGW than those in the local density approximation (LDA); the stiffness for Ni in LDA is two times greater than in experiment. For Co, both acoustic and optical branches of SWs agree with experiment. As for FeCo, we have some discrepancy between the spin stiffness in QSGW and that in experiment. We may need further theoretical and experimental investigations on the discrepancy.
PDF
