Shohei Yamashita
A5018702208- Astro and Planetary Science
- Isotope Analysis in Ecology
- Planetary Science and Exploration
- Catalytic Processes in Materials Science
- Catalysis and Oxidation Reactions
- Geological and Geochemical Analysis
- Evacuation and Crowd Dynamics
- High-pressure geophysics and materials
- Astrophysics and Star Formation Studies
- Social Robot Interaction and HRI
- Electron and X-Ray Spectroscopy Techniques
- Advanced Chemical Sensor Technologies
- Metallurgical Processes and Thermodynamics
- Mass Spectrometry Techniques and Applications
- Corrosion Behavior and Inhibition
- Pigment Synthesis and Properties
- Nuclear Physics and Applications
- Metal Alloys Wear and Properties
- Indoor Air Quality and Microbial Exposure
- Metal and Thin Film Mechanics
- Clay minerals and soil interactions
- Advancements in Photolithography Techniques
- Robotic Path Planning Algorithms
- Catalysts for Methane Reforming
- Gas Sensing Nanomaterials and Sensors
High Energy Accelerator Research Organization
2020-2025
The Graduate University for Advanced Studies, SOKENDAI
2020-2023
The University of Tokyo
2022
Hiroshima City University
2019-2021
Osaka University
2020
Ritsumeikan University
1992-2017
Nagoya University
2012-2013
Institute for Environmental Sciences
2010-2011
University of Shizuoka
2007-2011
Shizuoka Institute of Science and Technology
2010
Samples of the carbonaceous asteroid Ryugu were brought to Earth by Hayabusa2 spacecraft. We analyzed 17 samples measuring 1 8 millimeters. Carbon dioxide-bearing water inclusions are present within a pyrrhotite crystal, indicating that Ryugu's parent formed in outer Solar System. The contain low abundances materials at high temperatures, such as chondrules and calcium- aluminum-rich inclusions. rich phyllosilicates carbonates, which through aqueous alteration reactions temperature, pH,...
Samples of the carbonaceous asteroid (162173) Ryugu were collected and brought to Earth by Hayabusa2 spacecraft. We investigated macromolecular organic matter in samples found that it contains aromatic aliphatic carbon, ketone, carboxyl functional groups. The spectroscopic features are consistent with those chemically primitive chondrite meteorites experienced parent-body aqueous alteration (reactions liquid water). morphology carbon includes nanoglobules diffuse associated phyllosilicate...
Context. The current period is conducive to exploring our Solar System's origins with recent and future space sample return missions, which provide invaluable information from known System asteroids comets Hayabusa2 mission of the Japan Aerospace Exploration Agency (JAXA) recently brought back samples surface Ryugu carbonaceous asteroid. Aims. We aim identify different forms chemical composition organic matter minerals that constitute these primitive objects, shed light on origins. Methods....
Abstract We have conducted a NanoSIMS-based search for presolar material in samples recently returned from C-type asteroid Ryugu as part of JAXA's Hayabusa2 mission. report the detection all major grain types with O- and C-anomalous isotopic compositions typically identified carbonaceous chondrite meteorites: 1 silicate, oxide, O-anomalous supernova ambiguous phase, 38 SiC, 16 grains. At least two grains are graphites, whereas several moderate C anomalies probably organics. The silicate was...
The carbonaceous asteroid Ryugu has been explored by the Hayabusa2 spacecraft to elucidate actual nature of hydrous asteroids. Laboratory analyses revealed that samples from are comparable unheated CI chondrites; however, reflectance spectra and CIs do not coincide. Here, we demonstrate sample reproduced heating Orgueil chondrite at 300°C under reducing conditions, which caused dehydration terrestrial weathering products reduction iron in phyllosilicates. Terrestrial accounts for spectral...
Abstract The infrared spectral characteristics of organic‐rich acid residues prepared from Ryugu samples returned by the JAXA Hayabusa2 mission generally match those unheated carbonaceous chondrite meteorites, but are richer in methyl and methylene functional groups have higher CH 2 /CH 3 ratios. Moreover, two distinct outlier phases found; one with N‐H groups, likely amides, a second phase containing less nitrogen. Such organic matter might indicate pristine nature freshly collected reflect...
Context . The JAXA Hayabusa2 mission returned well-preserved samples collected from the carbonaceous asteroid Ryugu, providing unique non-terrestrially weathered a known parent body. Aims This work aims to provide better understanding of formation and evolution primitive asteroidal matter by studying fine scale association organic minerals in Ryugu samples. We characterized IR nanospectroscopy using infrared photothermal (AFM-IR) technique. technique overcomes diffraction limit (of several...
Operando time-resolved soft x-ray absorption spectroscopy (TR-SXAS) is an effective method to reveal the photochemical processes of metal complexes in solutions. In this study, we have developed TR-SXAS measurement system for observing various reactions solutions by combination laser pump pulses with probe from synchrotron radiation. For evaluation system, measured nitrogen K-edge (XAS) spectra aqueous iron phenanthroline during a photoinduced spin transition process. The decay process high...
We report the H, C, and N isotopic compositions of microscale (0.2 to 2 µm) organic matter in samples asteroid Ryugu Orgueil CI carbonaceous chondrite. Three regolith particles Ryugu, returned by Hayabusa2 spacecraft, several fragments were analyzed NanoSIMS imaging. The distributions from two different collection spots are closely similar each other samples, strengthening proposed Ryugu-CI chondrite connection. Most individual sub-μm grains have within error bulk values, but 2–10 % them...
A simple method for screening indoor emission sources of carbonyl compounds developed previously by the authors was used this study. The new device, which is called “emission cell simultaneous multisampling” (ECSMS), flux sampling volatile from surfaces building and furnishing materials in situ. Indoor concentrations various rooms at a school residential Shizuoka, Japan, were investigated 2006 using techniques. In several rooms, formaldehyde exceeded air quality guideline value (100 µg m −3...
Dodecavanadate, [V12 O32 ]4- (V12), possesses a 4.4 Å cavity entrance, and the shows unique electrophilicity. Owing to high polarizability, Br2 was inserted into V12, inducing inversion of one VO5 square pyramids form (Br2 )]4- (V12(Br2)). The molecule polarized showed peak at 185 cm-1 in IR spectrum. reaction V12(Br2) toluene yielded bromination ring, showing electrophilicity molecule. Compound also reacted with propane, n-butane, n-pentane give brominated alkanes. Bromination selectivity...
The X-ray absorption fine structure (XAFS) spectroscopy was used to analyze the chemical state conversion of Ni species in SiO2-supported catalysts which were prepared by impregnation me...
Abstract We report a Fourier transform infrared analysis of functional groups in insoluble organic matter (IOM) extracted from series 100–500 μm Ryugu grains collected during the two touchdowns February 22 and July 11, 2019. IOM most samples is very similar to primitive CI, CM, CR chondrites, shows that extent thermal metamorphism regolith was, at best, limited. One sample displays chemical signatures consistent with mild heating, likely due asteroidal collision impacts. also lower carbonyl...
The reaction mechanism of reduction processes NiO supported on silica has been clarified by means the time-resolved dispersive XAFS (DXAFS) technique. shows two-phase changes. first corresponds to metallic Ni particle, and sintering formed particles occurs in second step. process is composed surface particle successive oxygen diffusion from core surface. first-order kinetics suggests that latter rate-determining conditional rate constants indicate atoms relatively faster for lower loading.
Abstract Alteration minerals in one of the Martian meteorite nakhlites, Yamato (Y) 000802, were studied to understand alteration process and conditions. Mn‐precipitates are discovered between altered plagioclase grains Y 000802. consist hausmannite ( ), manganite (γ‐Mn 3+ OOH), rhodochrosite (Mn 2+ CO 3 a trace amount Mn 4+ O 2 mineral. Jarosite ) is also found. dissolved from olivine contributes formation Mn‐precipitates. A weakly acidic‐neutral fluid containing olivine, was into fluid. The...
Nanomaterial-based humidity sensors hold great promise for water vapor detection because of their high sensitivity and fast response/recovery. However, the condensation in nanomaterial films remains unclear from a physicochemical perspective. Herein, silica nanoparticle was physicochemically analyzed to bridge abovementioned gap. The morphology surface-adsorbed molecules characterized using infrared absorption spectroscopy soft X-ray spectroscopy, effect RH on amount adsorbed observed quartz...
The oxidation property of SiO2-supported small Ni particle has been studied by means the in-situ XAFS method. with average diameter 4 nm supported on SiO2 was prepared sol-gel XANES spectrum metallic clearly different from that bulk Ni. exposure diluted O2 gas at room temperature promoted surface Ni(0) particle. During programmed process, quantitatively oxidized to NiO, and lower ca. 200 °C than larger radius 17 impregnation