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Fluid flow in subduction zones is one of the essential factors of seismic activity in subduction zones. However, the timescale of fluid flow and fluid flow velocity in subduction zones is unclear. In this study, we report antigorite veins with brucite-rich reaction zones in the crust-mantle transition zone of the Oman ophiolite and estimate the timescale and fluid flow velocity during vein formation.In this study, we observed 28 samples in the lower crust to upper mantle section obtained from the Oman Drilling Project Hole CM1A (Kelemen et al., 2020). The lithology of borehole CM1A consists of lower crust (0-160 m depth), crust-mantle transition zone (160-310 m depth), and mantle section (310-404 m depth), which were mainly composed of altered gabbroic rocks (olivine gabbro, troctolite: 5-95% altered) and completely serpentinized dunite and 70-100% serpentinized harzburgite, respectively. Antigorite-chrysotile (Atg-Ctl) vein network was found in dunite at 160-180 m in Hole CM1A. The matrix of the dunite (lizardite, brucite, and magnetite) is cut by antigorite-chrysotile (Atg-Ctl) vein network. Trace element analysis using LA-ICP-MS revealed that the Atg-Ctl vein is enriched in As and Sb compared to the matrix lizardite, suggesting that the Atg-Ctl veins were formed by fluids interacting with subducting sediments. Some of the Atg-Ctl veins are accompanied by brucite-rich reaction zones. The brucite-rich reaction zone was developed at both sides of the antigorite veins with widths of 0.5 – 4 mm. Elemental mapping of the reaction zone using EPMA and TEM show sharp reaction front at scale from micro- to nano- meter.Mass balance calculations and thermodynamic considerations of the reaction zone suggest that the formation of the reaction zone was caused by the removal of silica from the host rock during the precipitation of antigorite in the veins. Based on a diffusion model, we estimated the fluid activity is short-lived (2.1 × 10–1 to 1.1 × 101 yr), and the fluid flow velocity of 2.7 × 10–3 to 4.9 × 10–2 m s-1, which is much faster than those observed for the intact mantle and crustal rocks. This fluid flow velocity along the fractures within the mantle wedge is similar to the observed propagation velocities of seismic events in subduction zones. These results suggest that fluid flow in the overlying plate occurs as episodic pulses as observed as the migration of seismicity in the present subduction zones.

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 × 10 1 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.

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.

An azimuthal-rotation sample holder, with improvements in the rotation-angle accuracy and rotation-axes displacement during azimuthal rotation, was developed for molecular-orientation analysis using scanning transmission X-ray microscopy., 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.

Fluid flow in subduction zones is related to geological processes such as seismic and volcanic activities. However, the timescale of fluid flow and its flux in the supra-subduction setting is unclear. In this study, we report the novel texture of the antigorite veins with a brucite-rich reaction zone in dunite in the crust-mantle transition zone of the Oman ophiolite, and investigated the timescale and time-integrated fluid flux during the vein formation.The antigorite veins occur in the drilling cores of serpentinized dunite in the crust-mantle transition zone taken from the Oman Drilling Project CM1 site (Wadi Zeeb, Northern Sharqiyah). The dunite samples are completely serpentinized and consist mainly of lizardite, brucite, magnetite, and Cr-rich spinel and are cut by the antigorite vein networks and later chrysotile. These features indicate that the antigorite veins formed at the stage of obduction of the Oman ophiolite. The antigorite veins, which are distinct by ‘bright’ networks by X-ray CT due to magnetite, occur preferentially in dunite (at 160 – 313 m along the CM1A). The veins are filled with a mixture of randomly orientated antigorite crystals and fine chrysotile. Some antigorite vein contains fragments of the host rock. The brucite-rich reaction zone was developed at both sides of the antigorite veins with a thickness of 0.5 – 4 mm. The reaction zone is composed of brucite (39.4 area%), chrysotile (59.3 area%), and magnetite (1.3 area%). The microtexture of the reaction zone indicates the brucite silicification after the brucite reaction zone formation. Mass balance and thermodynamic calculation suggest that silica was leached from the host rock lizardite during antigorite vein crystallization, resulting in the formation of the brucite reaction zone. Given solution chemistry and the amount of leached SiO2 during vein formation, the time-integrated fluid flux was estimated to be 105 - 106 m3(fluid) m-2(rock). A diffusion-controlled model suggests that the reaction zone was formed in a short time, ~10-1 - 100 years. These results suggest that a large amount of high-temperature fluid passed through the fracture network over several hundred meters in a short time at the earlier stage of the obduction of the Oman ophiolite.

A void formation at nanoscale and a crack initiation at micrometer scale in CFRP during a tensile test were investigated by means of positron annihilation and X-ray computed tomography (X-CT). Free volumes in bisphenol-A epoxy resin in CFRP were probed, and a mean diameter of free volumes at room temperature was determined to be 0.49 nm. The crack initiation and propagation in the CFRP sample was observed by in-situ measurements of X-CT during a tensile test. For the sample after the tensile test, free volumes with a mean diameter of 0.70 nm were introduced near fractures locations. In the same locations, the density of free volumes which intrinsically existed in the polymer resins decreased. Thus, the introduction of the free volumes was attributed to breaks in molecular chains upon fracture and a resultant agglomeration of intrinsic free volumes in the polymer matrix.

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.

Solid lubricants are used to lubricate the mechanical equipment of various spacecraft and launch vehicles. Tungsten disulfide (WS2) is one of the solid lubricants that can be used in a variety of applications at elevated temperatures in outer space. In this study, WS2 coatings on a metal disc were applied via the shot peening method using WS2 powder (diameter of 2.0 μm). Friction experiments were carried out to investigate the friction characteristics of WS2 using a pin-on-disc-type rotary tribometer at high temperature in a vacuum. The friction coefficients of the WS2 shot peening coating were extremely low at room temperature and increased with the test temperature. Nevertheless, WS2 coatings demonstrated superior frictional properties at elevated temperatures and thus they are applicable at 400 °C in vacuum. All WS2 specimens showed a preferred orientation of the (0002) basal plane parallel to the disc surface. Atomic arrangements of the second nearest neighbor atoms were distorted from the original sites during the wear process. The room temperature friction tests of the shot peened WS2 specimen, annealed at 400 °C, demonstrated that the friction coefficients of the specimen with a higher degree of planar alignment on the (0002) plane were larger than those of the specimens with planner imperfections. Lattice defects such as stacking faults and dislocations assisted in the sliding motions of the adjacent sulfur atoms on the (0002) plane by extremely low shear stress.

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.

The mechanical properties of carbon fibers (CFs) can be controlled by their internal structures such as the distribution of &pi, orbital-oriented domains, as well as the diameter and cross-sectional shape of the fiber. In this study, we investigated the carbon chemical structure maps of commercial polyacrylonitrile (PAN)- and pitch-based CFs using scanning transmission X-ray microscopy to evaluate the differences in the distribution of &pi, orbital-oriented domains. The graphene sheets in the PAN-based CFs have a fiber texture that is aligned along the fiber direction and randomly oriented within the cross section. The domain sizes within the cross section are less than the resolution limit (i.e., 50 nm). By contrast, the graphene sheets in the pitch-based CFs are aligned parallel to each other and form aggregates with a size ranging from approximately 100 nm to 1 &mu, m within the cross sections. They form 200&ndash, 300-nm stripes along the CF axis in the longitudinal sections.

The initial stage of degradation process of yttria partially stabilized zirconia thermal barrier coatings during heating at 1000–1450 K were observed in situ by transmission electron microscopy. The observation directly demonstrated that the formation of several kinds of oxides and resulting void growth started above 1000 K in the bond-coat layer near the interface with the thermally grown oxide layer, leading to the development of voids over the entire interface due to void coalescence. Such development of voids corresponds to the generation and propagation of thermally grown cracks, i.e., to the initial spallation of the coating.

The present situation of the XAFS database in Japan and a proposal for the construction of an international collaboration XAFS database are presented., 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.

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, k 0, 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.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, k 0, 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.

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.

The corrosion of metal and alloy under a wet environment includes a series of process: ionization of constituent elements by electron transfer reaction (oxidation) at the solid/liquid interface between a solution and a metal surface, and dissolution of metal into the solution, diffusion of the dissolved ions, and formation of hydroxides. These reactions progress depending on the environments near the interface, which change with the progress of the corrosion reaction itself. One of the most important environments is the concentration distribution of chemical species near the solid/liquid interface that is different from that of uniform corrosion. This is the case of pitting corrosion, and it is difficult to understand its mechanism by only using ex situ observation technique. Therefore, an in situ measurement technique with time and spatial resolution is required. In this study, an unique cell for an in situ electrochemical-XAFS measurement was developed to observe diffusion behavior of dissolved ions and reactions among them near the solid/liquid interface. Figure shows the schematic diagram of an in situ electrochemical cell [1], which can detect the state of dissolved metal ions in a minute space simulating pitting corrosion. The X-ray absorption spectrum (XAS) measurement was performed using the cell. The change in concentrations and structures of dissolved ions were measured at different distances from the solid/liquid interface as a function of reaction time. A sheet of SUS304 (Cr 18 %, Ni 8 %) with a thickness of 200 μm was used as a sample, and worked as an electrode. LiBr aqueous solution (1.0 M) was used as an electrolyte. A typical measurement of corrosion was carried out by applying potential of 0.8 V vs. Ag/AgCl on the specimen. The size of an X-ray beam was set to 500 μm (horizontal) × 90 μm (vertical) (FWHM). As the corrosion progressed, the interface shifted to –Z direction (Fig.), but the shape of the interface, the metal surface shape, along the horizontal direction remained sufficiently smooth compared with the beam size. XAS for Fe, Cr, and Br K-edges were measured by the transmission geometry using QXAFS technique at BL-9A of Photon Factory (PF), High Energy Accelerator Research Organization (KEK). The X-ray absorption spectrum changed according to the progression of the corrosion reaction. From the spectrum, the change of absorption (Δμt) at the energy of white line at different distances from the solid/liquid interface as a function of the reaction time: t was obtained.These results showed that the absorption of Fe rapidly increases at the early stage of reaction and as the reaction advances, the change in the absorption becomes small and reaches an equilibrium state. It was also shown that the absorption change also heavily depends on the distance from the interface. The same measurements were also performed for Cr and Br. These results will be discussed by paying a special attention to the relationship of the concentration change of Fe, Cr, and Br and their coordination structures. References [1] M. Kimura, et al., J. Synchrotron Rad., 8, 487 (2001). Figure 1

To obtain the best possible performance from engineering materials, it is necessary to optimize their intrinsic properties, the processing involved in their production, and their performance in actual applications. To this end, the concept of the “materials science tetrahedron” was proposed [1]. Subsequently, an important environmental aspect, proposed by Doyama (1988), was added to the concept, giving a “materials science octahedron,” which has since been a guideline for R&D in the field of engineering materials (Figure 1). The structure of engineering materials governs the properties, process, and performance of these materials. Synchrotron radiation has been widely used to successfully reveal structural information and its relationship to properties, performance, processing, and environment.

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.

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.