Oxidation-induced nanolite crystallization triggered the 2021 eruption of Fukutoku-Oka-no-Ba, Japan.

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.

Geological records of transient fluid drainage into the shallow mantle wedge.

Pore fluid pressure on subduction zone megathrusts is lowered by fluid drainage into the overlying plate, affecting subduction zone seismicity. However, the spatial and temporal scales of fluid flow through suprasubduction zones are poorly understood. We constrain the duration and velocity of fluid flow through a shallow mantle wedge based on the analyses of vein networks consisting of high-temperature serpentine in hydrated ultramafic rocks from the Oman ophiolite. On the basis of a diffusion model and the time-integrated fluid flux, we show that the channelized fluid flow was short-lived (2.1 × 10-1 to 1.1 × 101 years) and had a high fluid velocity (2.7 × 10-3 to 4.9 × 10-2 meters second-1), which is close to the propagation velocities of seismic events in present-day subduction zones. Our results suggest that the drainage of fluid into the overlying plate occurs as episodic pulses, which may influence the recurrence of megathrust earthquakes.

[A Survey of the Use of Direct Oral Anticoagulants in Patients' Possession at the Time of Hospitalization].

The dose of direct oral anticoagulants (DOACs) must be determined based on package insert recommendations. There are reports on the rate of inappropriate DOAC dose usage defined as a dose deviating from the approved dose in the package insert but no reports on factors that led to such deviations. Thus, patients who were admitted to the Suzuka Kaisei Hospital between 1 April 2016 and 31 March 2017 were chosen as subjects. Moreover, the factors that during hospitalization led to dose deviation from the package-insert DOAC dose were retrospectively examined. The characteristics of patients administered doses deviating from the package insert were compared with those of patients in the appropriate-dose group. The finding was that the proportion concomitantly administered antiplatelet agents was higher in the underdose group. In contrast, deviations from the recommended dose did not occur when DOACs were combined with CYP3A4 inhibitors or P-glycoprotein (P-gp) inhibitors. It was suggested that increase in the risk of hemorrhage by antiplatelet agents in combination with oral anticoagulants could explain deviations from the stipulated DOAC dose. In addition, a higher proportion of patients in the overdose group showed depressed Ccr, and gastrointestinal bleeding. In future, it will be necessary to propose principle-based dose changes for patients administered doses deviating from the package insert. If an underdose is administered, it is important to make a dose change that takes the concomitant drugs into consideration.

A surface sensitive hard X-ray spectroscopic method applied to observe the surface layer reduction reaction of Co oxide to Co metal.

A simple and easy surface sensitive spectroscopic method using hard X-rays has been developed and applied to observe the surface oxide reduction reaction. The method named TREXS, Total REflection X-ray Spectroscopy, records the total reflection of incident X-rays at sample surfaces. The surface reduction reaction of Co oxide (Co3O4) to Co metal was successfully observed by in situ TREXS measurements with a surface sensitivity of ∼2 nm. The in situ TREXS measurements were performed under H2 flow of N2 balanced atmospheric pressure with increasing temperature. This method, in situ TREXS, will be a suitable and powerful tool to observe a variety of surface chemical reactions and consequently to understand catalytic processes under realistic operating conditions.

Azimuthal-rotation sample holder for molecular orientation analysis.

In this study, an azimuthal-rotation sample holder compatible with scanning transmission X-ray microscopy was developed. This holder exhibits improvement in the accuracy of rotation angles and reduces the displacement of the rotation axes during azimuthal rotation by using a crossed roller bearing. To evaluate the performance of the holder, the authors investigated the dependence of the optical density around the C K-edge absorption of π-orbital-oriented domains in natural spherical graphite on the rotational angle by using linearly horizontally and vertically polarized undulator radiation. Based on the dependence of the optical density ratio between C 1s → π* and 1s → σ* excitation on the polarization angle of the X-rays, the average two-dimensional orientation angle of the π orbital in each position in a natural spherical graphite sample was visualized.

Nanoscale crack initiation and propagation in carbon fiber/epoxy composites using synchrotron: 3D image data.

Crack initiation and propagation in carbon fiber-reinforced plastic (CFRP) was observed in situ under the application of an opening load using nanoscopic synchrotron radiation X-ray computed tomography (nanoscopic SR X-CT) at a high spatial resolution of ∼50 nm. Two datasets of reconstructed and segmented images were produced in typical regions, namely in the thin and thick epoxy regions where the resin thickness between the adjacent carbon fibers was small and large, respectively. This novel study presents the first non-destructive three-dimensional (3D) visualization of resin deformation behavior around crack tips, and provides a valuable and unique insight for the future design of CFRPs.

Nanoscopic origin of cracks in carbon fibre-reinforced plastic composites.

Voids and cracks can fatally degrade structural materials such as metals and ceramics but are tolerated in carbon fibre-reinforced plastic (CFRP) composites if monitored to prevent their growth to a critical size. Thus, the use of CFRPs as aeronautical structural materials requires an understanding of microscopic crack formation. However, this crack-formation mechanism remains unclear because experimental difficulties have hindered studies of relevant phenomena that occur before crack formation. Herein, we report high-resolution (~50 nm) and non-destructive three-dimensional observations of crack initiation and propagation under applied stress. This evaluation reveals that voids and cracks do not simply result from local stresses but instead occur largely through two competing nanoscale mechanisms, namely, fibre/plastic interface debonding and in-plastic crack initiation. Therefore, nanoscopic insights into these heterogeneities are essential for controlling crack initiation and determining reasonable safety margins for CFRP composite use.

Microstructural deformation process of shock-compressed polycrystalline aluminum.

Plastic deformation of polycrystalline materials under shock wave loading is a critical characteristic in material science and engineering. However, owing to the nanosecond time scale of the shock-induced deformation process, we currently have a poor mechanistic understanding of the structural changes from atomic scale to mesoscale. Here, we observed the dynamic grain refinement of polycrystalline aluminum foil under laser-driven shock wave loading using time-resolved X-ray diffraction. Diffraction spots on the Debye-Scherrer ring from micrometer-sized aluminum grains appeared and disappeared irregularly, and were shifted and broadened as a result of laser-induced shock wave loading. Behind the front of shock wave, large grains in aluminum foil were deformed, and subsequently exhibited grain rotation and a reduction in size. The width distribution of the diffraction spots broadened because of shock-induced grain refinement and microstrain in each grain. We performed quantitative analysis of the inhomogeneous lattice strain and grain size in the shocked polycrysalline aluminum using the Williamson-Hall method and determined the dislocation density under shock wave loading.

In situ TREXS Observation of Surface Reduction Reaction of NiO Film with ∼2 nm Surface Sensitivity.

X-ray absorption fine structure (XAFS) spectroscopy is one of the most widely used methods at synchrotron radiation facilities. XAFS gives us information on chemical states and local structures. Fundamentally, XAFS is bulk sensitive, not surface sensitive. If a surface sensitive XAFS method was available, surface chemical reactions can be observed under realistic conditions. Here, we report the development and present status of a type of surface sensitive x-ray spectroscopy, which is named total reflection x-ray spectroscopy, TREXS.

Finding Degradation Trigger Sites of Structural Materials for Airplanes Using X-Ray Microscopy.

Macroscopic properties of carbon fiber-reinforced plastic (CFRP) and environmental barrier coating (EBC), widely used for airplanes, can be deteriorated by local cracks or degradation ("trigger sites"). We have tried to find these trigger sites using x-ray microscopy (XM), which can provide the 2D or 3D images of the chemical states and microstructures. Crack initiation in CFRP was observed in a non-destructive manner in multi-scales (nm-mm). 3D chemical-state mapping of Yb in EBC was achieved with high resolution (<50 nm). In addition to XM, in-situ observations at high temperatures were conducted for obtaining complementary information. X-ray absorption spectroscopy (XAS) and x-ray diffraction (XRD) analysis were performed simultaneously up to 1773 K. Dynamic XAS with short time-resolution (<10 ns) was conducted to investigate changes in the local structure of metal. These approaches can help us identify degradation trigger sites in the materials.

A call for a round robin study of XAFS stability and platform dependence at synchrotron beamlines on well defined samples.

Round robin studies have been used across fields of science for quality control testing and to investigate laboratory dependencies and cross-platform inconsistencies as well as to drive forward the improvement of understanding of experimental systems, systematic effects and theoretical limitations. Here, following the Q2XAFS Workshop and Satellite to IUCr Congress 2017 on `Data Acquisition, Treatment, Storage - quality assurance in XAFS spectroscopy', a mechanism is suggested for a suitable study across XAFS (X-ray absorption fine-structure) beamlines and facilities, to enable each beamline to cross-calibrate, provide representative test data, and to enable collaborative cross-facility activities to be more productive.

The challenge of constructing an international XAFS database.

The present state of XAFS databases, particularly in Japan, and proposals for future directions are presented. International collaboration is important for enlarging the database for further development of XAFS spectroscopy.

Prediction of tortuosity, permeability, and pore radius of water-saturated unconsolidated glass beads and sands.

Tortuosity, permeability, and pore radius, which are parameters in the Biot model, are important for analyzing the elastic wave propagation in water-saturated unconsolidated marine sands. In this study, the formation factor and permeability are measured for 34 kinds of water-saturated glass beads and sands with uniformly sized grains and 73 kinds of water-saturated sands with distributed sized grains. Using these measured data, the empirical equations for the formation factor, cementation exponent, and tortuosity are obtained. The pore shape factor, k0, in the Kozeny-Carman model and pore shape factor, a, in the Revil-Cathles (RC) model are derived. The Hazen, Kozeny-Carman, and RC models are compared for the measured permeability results. Furthermore, the relationship between the tortuosity and permeability is shown. Finally, the ratio of the effective pore radius to effective mean grain diameter is derived.

Non-empirical identification of trigger sites in heterogeneous processes using persistent homology.

Macroscopic phenomena, such as fracture, corrosion, and degradation of materials, are associated with various reactions which progress heterogeneously. Thus, material properties are generally determined not by their averaged characteristics but by specific features in heterogeneity (or 'trigger sites') of phases, chemical states, etc., where the key reactions that dictate macroscopic properties initiate and propagate. Therefore, the identification of trigger sites is crucial for controlling macroscopic properties. However, this is a challenging task. Previous studies have attempted to identify trigger sites based on the knowledge of materials science derived from experimental data ('empirical approach'). However, this approach becomes impractical when little is known about the reaction or when large multi-dimensional datasets, such as those with multiscale heterogeneities in time and/or space, are considered. Here, we introduce a new persistent homology approach for identifying trigger sites and apply it to the heterogeneous reduction of iron ore sinters. Four types of trigger sites, 'hourglass'-shaped calcium ferrites and 'island'- shaped iron oxides, were determined to initiate crack formation using only mapping data depicting the heterogeneities of phases and cracks without prior mechanistic information. The identification of these trigger sites can provide a design rule for reducing mechanical degradation during reduction.

X-ray analyzer-based phase-contrast computed laminography.

X-ray analyzer-based phase-contrast imaging is combined with computed laminography for imaging regions of interest in laterally extended flat specimens of weak absorption contrast. The optics discussed here consist of an asymmetrically cut collimator crystal and a symmetrically cut analyzer crystal arranged in a nondispersive (+, -) diffraction geometry. A generalized algorithm is given for calculating multi-contrast (absorption, refraction and phase contrast) images of a sample. Basic formulae are also presented for laminographic reconstruction. The feasibility of the method discussed was verified at the vertical wiggler beamline BL-14B of the Photon Factory. At a wavelength of 0.0733 nm, phase-contrast sectional images of plastic beads were successfully obtained. Owing to strong circular artifacts caused by a sample holder, the field of view was limited to about 6 mm in diameter.

Gritty Surface Sample Holder Invented To Obtain Correct X-ray Absorption Fine Structure Spectra for Concentrated Materials by Fluorescence Yield.

A gritty surface sample holder has been invented to obtain correct XAFS spectra for concentrated samples by fluorescence yield (FY). Materials are usually mixed with boron nitride (BN) to prepare proper concentrations to measure XAFS spectra. Some materials, however, could not be mixed with BN and would be measured in too concentrated conditions to obtain correct XAFS spectra. Consequently, XAFS spectra will be incorrect typically with decreased intensities of the peaks. We have invented the gritty surface sample holders to obtain correct XAFS spectra even for concentrated materials for FY measurements. Pure Cu and CuO powders were measured mounted on the sample holders, and the same spectra were obtained as transmission spectra of properly prepared samples. This sample holder is useful to measure XAFS for any concentrated materials.

Grain-size dependence of shear wave speed dispersion and attenuation in granular marine sediments.

The author has shown that measured shear wave speed dispersion and attenuation in water-saturated silica sand can be predicted by using a gap stiffness model incorporated into the Biot model (the BIMGS model) [Kimura, J. Acoust. Soc. Am. 134, 144-155 (2013)]. In this study, the grain-size dependence of shear wave speed dispersion and attenuation in four kinds of water-saturated silica sands with different grain sizes is measured and calculated. As a result, the grain-size dependence of the aspect ratio in the BIMGS model can be validated and the effects of multiple scattering for larger grain sizes are demonstrated.

Clinical practice guidelines for therapeutic drug monitoring of arbekacin: a consensus review of the Japanese Society of Chemotherapy and the Japanese Society of Therapeutic Drug Monitoring.

Arbekacin (ABK) was approved and widely used in Japan for treatment of patients infected with MRSA, and TDM was introduced in clinical practice. The Japanese Society of Chemotherapy and the Japanese Society of Therapeutic Drug Monitoring decided to develop a clinical practice guidelines for TDM of ABK for the following reasons. First, although the daily dose of 150-200 mg was approved in Japan, recent PK-PD studies revealed that higher serum concentration is required to achieve better clinical efficacy and several findings concerning the usefulness of higher dosage regimen have obtained recently. Second, although maximal concentrations that obtained immediately after the end of administration (Cmax) was generally adopted, the serum concentration at 1 h after initiation of administration [peak serum concentration (Cpeak)] proved to be more suitable as an efficacy indicator of aminoglycosides. Lastly, as ABK is approved only in Japan, no international practice guideline for TDM has not been available in ABK to date. This guideline evaluated the scientific data associated with serum ABK monitoring and provided recommendations based on the available evidence. Potential limitations of this guideline, however, include the findings that few prospective clinical trials of TDM of ABK are available in the treatment of MRSA infections and that most of the published literature describes observational studies.

Shear wave speed dispersion and attenuation in granular marine sediments.

The reported compressional wave speed dispersion and attenuation could be explained by a modified gap stiffness model incorporated into the Biot model (the BIMGS model). In contrast, shear wave speed dispersion and attenuation have not been investigated in detail. No measurements of shear wave speed dispersion have been reported, and only Brunson's data provide the frequency characteristics of shear wave attenuation. In this study, Brunson's attenuation measurements are compared to predictions using the Biot-Stoll model and the BIMGS model. It is shown that the BIMGS model accurately predicts the frequency dependence of shear wave attenuation. Then, the shear wave speed dispersion and attenuation in water-saturated silica sand are measured in the frequency range of 4-20 kHz. The vertical stress applied to the sample is 17.6 kPa. The temperature of the sample is set to be 5 °C, 20 °C, and 35 °C in order to change the relaxation frequency in the BIMGS model. The measured results are compared with those calculated using the Biot-Stoll model and the BIMGS model. It is shown that the shear wave speed dispersion and attenuation are predicted accurately by using the BIMGS model.