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Nakanishi, Yohei*; Shibata, Motoki*; Sawada, Satoshi*; Kondo, Hiroaki*; Motokawa, Ryuhei; Kumada, Takayuki; Yamamoto, Katsuhiro*; Mita, Kazuki*; Miyazaki, Tsukasa*; Takenaka, Mikihito*
Polymer, 306, p.127209_1 - 127209_7, 2024/06
Times Cited Count：1 Percentile：61.21(Polymer Science)Kitazato, Kohei*; Milliken, R. E.*; Iwata, Takahiro*; Abe, Masanao*; Otake, Makiko*; Matsuura, Shuji*; Takagi, Yasuhiko*; Nakamura, Tomoki*; Hiroi, Takahiro*; Matsuoka, Moe*; et al.
Nature Astronomy (Internet), 5(3), p.246 - 250, 2021/03
Times Cited Count：51 Percentile：96.49(Astronomy & Astrophysics)Here we report observations of Ryugu's subsurface material by the Near-Infrared Spectrometer (NIRS3) on the Hayabusa2 spacecraft. Reflectance spectra of excavated material exhibit a hydroxyl (OH) absorption feature that is slightly stronger and peak-shifted compared with that observed for the surface, indicating that space weathering and/or radiative heating have caused subtle spectral changes in the uppermost surface. However, the strength and shape of the OH feature still suggests that the subsurface material experienced heating above 300 
C, similar to the surface. In contrast, thermophysical modeling indicates that radiative heating does not increase the temperature above 200 C at the estimated excavation depth of 1 m, even if the semimajor axis is reduced to 0.344 au. This supports the hypothesis that primary thermal alteration occurred due to radiogenic and/or impact heating on Ryugu's parent body.
Kitazato, Kohei*; Milliken, R. E.*; Iwata, Takahiro*; Abe, Masanao*; Otake, Makiko*; Matsuura, Shuji*; Arai, Takehiko*; Nakauchi, Yusuke*; Nakamura, Tomoki*; Matsuoka, Moe*; et al.
Science, 364(6437), p.272 - 275, 2019/04
Times Cited Count：284 Percentile：99.69(Multidisciplinary Sciences)The near-Earth asteroid 162173 Ryugu, the target of Hayabusa2 sample return mission, is believed to be a primitive carbonaceous object. The Near Infrared Spectrometer (NIRS3) on Hayabusa2 acquired reflectance spectra of Ryugu's surface to provide direct measurements of the surface composition and geological context for the returned samples. A weak, narrow absorption feature centered at 2.72 micron was detected across the entire observed surface, indicating that hydroxyl (OH)-bearing minerals are ubiquitous there. The intensity of the OH feature and low albedo are similar to thermally- and/or shock-metamorphosed carbonaceous chondrite meteorites. There are few variations in the OH-band position, consistent with Ryugu being a compositionally homogeneous rubble-pile object generated from impact fragments of an undifferentiated aqueously altered parent body.
Sawada, Shinichi; Yamaguchi, Daisuke; Putra, A.; Koizumi, Satoshi*; Maekawa, Yasunari
Polymer Journal, 45(8), p.797 - 801, 2013/08
Times Cited Count：10 Percentile：30.97(Polymer Science)The nanoscale structures of graft-type polymer electrolyte membranes based on poly(ethylene-co-tetrafluoroethylene) (ETFE) films were investigated using a small-angle neutron scattering (SANS) technique. For comparison, SANS measurements were also performed on two precursor materials, the original ETFE film and polystyrene (PS)-grafted films. The SANS profiles of the grafted films showed shoulder peaks at a d-spacing of approximately 30 nm, which were attributed to the PS grafts introduced into the amorphous phases between the ETFE lamellar crystals. In the ETFE PEMs, the spacing of the polystyrene sulfonic acid (PSSA) grafts and ETFE crystals increased because the graft regions were enlarged by the volume of the attached sulfonic acid groups. Interestingly, the graft / crystal stack spacing in the PEMs did not increase from the dry- to fully-hydrated states. This finding implies restricted water absorption in the PSSA grafts between the ETFE lamellar crystals.
rangeIwase, Hiroki*; Sawada, Shinichi; Yamaki, Tetsuya; Koizumi, Satoshi; Onuma, Masato*; Maekawa, Yasunari
Macromolecules, 45(22), p.9121 - 9127, 2012/11
Times Cited Count：19 Percentile：53.01(Polymer Science)Fundamental understanding of the structure-property relationship of polymer electrolyte membranes (PEM) is prerequisite for a material design satisfying PEM performance requirement. Small-angle scattering in a wide- range was observed by focusing small-angle neutron scattering (FSANS), small-angle neutron scattering (SANS), and small-angle X-ray scattering (SAXS). The hierarchical structure of the PEM was characterized as being composed of conducting layers (graft domains) in lamellar stacks with 48-57 nm spacing on the surfaces of 480 nm diameter crystallites and ultra-small structures with a 1.7 nm correlation distance of the sulfonic acid groups in the conducting layers. From the change in the SAXS profiles as a function of grafting degrees, it was revealed that the graft domains around the crystallites were connected with the adjoining domains and thus, the PEMs with a higher degree of grafting had conductivity higher than that of Nafion.
and Au+Au collisions at 
= 200 GeVAdare, A.*; Afanasiev, S.*; Aidala, C.*; Ajitanand, N. N.*; Akiba, Yasuyuki*; Al-Bataineh, H.*; Alexander, J.*; Aoki, Kazuya*; Aphecetche, L.*; Aramaki, Y.*; et al.
Physical Review C, 83(4), p.044912_1 - 044912_16, 2011/04
Times Cited Count：10 Percentile：52.22(Physics, Nuclear)Measurements of electrons from the decay of open-heavy-flavor mesons have shown that the yields are suppressed in Au+Au collisions compared to expectations from binary-scaled collisions. Here we extend these studies to two particle correlations where one particle is an electron from the decay of a heavy flavor meson and the other is a charged hadron from either the decay of the heavy meson or from jet fragmentation. These measurements provide more detailed information about the interaction between heavy quarks and the quark-gluon matter. We find the away-side-jet shape and yield to be modified in Au+Au collisions compared to collisions.
Iwase, Hiroki*; Sawada, Shinichi; Yamaki, Tetsuya; Maekawa, Yasunari; Koizumi, Satoshi
International Journal of Polymer Science, 2011(2011), p.301807_1 - 301807_7, 2011/00
Times Cited Count：12 Percentile：37.14(Polymer Science)Preirradiation graft polymerization of styrene in a poly(tetrafluoroethylene) (PTFE) film was examined by time-resolved small-angle neutron scattering (SANS). A crosslinked PTFE film, thickness of which is about 50
m, was irradiated by 
-ray and immersed in a mixed solvent of styrene monomer and toluene. SANS elucidated that graft polymerization proceeds by two reaction processes (I) and (II). In process (I) at 0
200 min, graft polymerization occurs at an interface between crystalline and amorphous PTFE domains and the grafted polystyrene segregates from PTFE, forming a thin layer with a sharp interface. In process (II) at 200600 min, grafted PS layer starts to bridge between crystalline domains. At the end of process (II), 40% of total crystalline PTFE domain is covered by the grafted PS chains.
Nishiyama, Satoshi*; Onishi, Yuzo*; Sawada, Atsushi; Yano, Takao*
Doboku Gakkai Rombunshu, C, 65(4), p.776 - 788, 2009/10
This paper describes the simulation method to explain the mechanism of the permeability characteristics of specimens with single discontinuties under shear through shear-flow coupling tests, showing that on the shear stress-displacement curve obtained by the constant normal load testing, the water flowing through the discontinuties have different transmissibility-aperture width relation before or after the yield range. As a technique to serve this purpose, the lattice gas method, which is to substitute the fluid with particles and repeat letting them collide. With this technique, the factors of surface structure of discontinuties that determine the shear/permeability characteristics are identified.
Nishiyama, Satoshi*; Uehara, Shinichi*; Yano, Takao*; Saito, Ryuhei*; Uchida, Masahiro; Sawada, Atsushi; Takebe, Atsuji
JNC TY8400 2005-007, 70 Pages, 2005/03
JNC-TY8400-2005-007.pdf:2.24MB
None
Otsuka, Jiro; Yasui, Hisatoshi*; Yoshida, Kazuo*; ; Koyagishi, Naoki; SASAKI, Kazuhito; Sawada, Makoto
JNC TN4410 2004-001, 31 Pages, 2004/06
JNC-TN4410-2004-001.pdf:4.19MB
None
Yamaki, Tetsuya; Motokawa, Ryuhei; Iwase, Hiroki*; Sawada, Shinichi; Asano, Masaharu; Koizumi, Satoshi; Maekawa, Yasunari
no journal, ,
The nanometer-to-micrometer hierarchical structure of crosslinked-polytetrafluoroethylene(PTFE)-based electrolyte membranes was investigated by combined SANS and SAXS analyses. As the SANS results demonstrated, the grafting reaction was found to occur in a PTFE amorphous layer between rigid lamellar crystals and, however, a main reaction field was the outside of the lamellae, which would determine proton conductivity of the membranes. The SAXS peak at Q
= 3.8 nm
would be due to the ionic clusters of approximately 1.7 nm in diameter, which basically appeared smaller than that of Nafion. The phase-separated domain including them grew large by connecting with each other toward high ion exchange capacities.
Yamaki, Tetsuya; Motokawa, Ryuhei; Iwase, Hiroki*; Sawada, Shinichi; Asano, Masaharu; Koizumi, Satoshi; Maekawa, Yasunari
no journal, ,
The nanometer-to-micrometer hierarchical structure of cPTFE-based electrolyte membranes was investigated by SANS and SAXS and transmission electron microscopy observation. The grafting reaction was found to occur in a PTFE amorphous layer between rigid lamellar crystals and, however, a main reaction field was the outside of the lamellae, which would determine proton conductivity of the membranes. The ionic clusters basically appeared smaller than that of Nafion, and the phase-separated domain including them grew large by connecting with each other toward high ion exchange capacities. This morphological change was accompanied by an increase in the self-diffusion coefficient of protons representing proton conductivity.
Yamaki, Tetsuya; Motokawa, Ryuhei; Iwase, Hiroki*; Sawada, Shinichi; Asano, Masaharu; Koizumi, Satoshi; Maekawa, Yasunari
no journal, ,
The nanometer-to-micrometer hierarchical structure was investigated by small-angle neutron/X-ray scattering (SANS/SAXS) analysis, a dissipative particle dynamics (DPD) simulation, and transmission electron microscopy (TEM) observation and then discussed in relation to proton conductivity. In a macroscopic scale, the grafting reaction was found to occur in a PTFE amorphous layer between rigid lamellar crystals and, however, a main reaction field was the outside of the lamellae, which would determine proton conductivity of the membranes. The microscopically-aggregated ionic clusters basically appeared smaller than that of Nafion, and the phase-separated domain including them grew large by connecting with each other toward high ion exchange capacities. This morphological change was accompanied by an increase in the self-diffusion coefficient of protons mainly representing proton conductivity.
Koizumi, Satoshi; Maekawa, Yasunari; Yamaki, Tetsuya; Sawada, Shinichi; Iwase, Hiroki*
no journal, ,
no abstracts in English
Sawada, Shinichi; Yamaguchi, Daisuke; Putra, A.; Koizumi, Satoshi; Maekawa, Yasunari
no journal, ,
In order to develop the novel polymer electrolyte membranes (PEMs) with high performances, it is important to clarify the structures of conventional PEMs. In this study, we investigated the structures of the radiation grafted PEMs based on poly(ethylene-co-tetrafluoroethylene) (ETFE) films by a small angle neutron scattering (SANS) technique. From the SANS profile, the shoulder peak was observed at the wave number q
=0.16nm. This result suggest that the domains containing poly(styrene sulfonic acid) (PSSA) graft chains should exist at constant intervals, corresponding to the correlation distance L=2
/q=39 nm. The distance of ETFE lamellar stacks was reported to 27 nm, which is somewhat close to L. This indicates that the PSSA graft chains were introduced in the interfacial regions in lamellar stacks.
Yamaki, Tetsuya; Motokawa, Ryuhei; Iwase, Hiroki*; Sawada, Shinichi; Asano, Masaharu; Koizumi, Satoshi; Maekawa, Yasunari
no journal, ,
The nanometer-to-micrometer hierarchical structure of cPTFE-based electrolyte membranes was investigated by SANS or SAXS analysis, DPD simulation and transmission electron microscopy observation. The grafting reaction was found to occur in a PTFE amorphous layer between rigid lamellar crystals and, however, a main reaction field was the outside of the lamellae, which would determine proton conductivity of the membranes. The ionic clusters basically appeared smaller than that of Nafion, and the phase-separated domain including them grew large by connecting with each other towards high ion exchange capacities. This morphological change was accompanied by an increase in the self-diffusion coefficient of protons representing proton conductivity.
Yamaki, Tetsuya; Motokawa, Ryuhei; Iwase, Hiroki; Sawada, Shinichi; Asano, Masaharu; Koizumi, Satoshi; Maekawa, Yasunari
no journal, ,
Novel electrolyte membranes for PEFC applications were developed by the radiation-induced grafting of styrene into crosslinked polytetrafluoroethylene (PTFE) films and subsequent sulfonation. We performed here small-angle neutron scattering (SANS) analysis to investigate their structure and proton conductive properties. The crosslinked-PTFE electrolyte membranes exhibited a SANS pattern being entirely different from Nafion's: an intense small-angle upturn in intensity and no well-defined peak. This demonstrates that they will possess the structural properties which cannot be rationalized by the so far presented models.
Tran, D. T.; Sawada, Shinichi; Hasegawa, Shin; Putra, A.; Yamaguchi, Daisuke; Oba, Yojiro*; Koizumi, Satoshi; Onuma, Masato*; Maekawa, Yasunari; Katsumura, Yosuke*
no journal, ,
We investigated the structure of the ethylene-co-tetrafluoroethylene (ETFE) based radiation-grafted polymer electrolyte membranes (PEMs) by the small-angle X-ray scattering (SAXS) method. From SAXS profile for the base ETFE film, a lamellar structure with spacing of 23 nm was observed. For the styrene-grafted film and PEM, the lamellar spacing measured by SAXS profiles were 30 and 33 nm, respectively. This can be explained by that the grafted regions were introduced into the amorphous phases in the lamellar structures, thereby extending the lamellar spacing.
Koizumi, Satoshi; Iwase, Hiroki; Sawada, Shinichi; Yamaki, Tetsuya; Maekawa, Yasunari
no journal, ,
no abstracts in English
Iwase, Hiroki; Koizumi, Satoshi; Hashimoto, Takeji; Sawada, Shinichi; Yamaki, Tetsuya; Maekawa, Yasunari
no journal, ,
The structures of crosslinked-polytetrafluoroethylene (PTFE) electrolyte membranes prepared using both radiation-induced crosslinking and graft polymerization of styrene were analyzed by small-angle neutron scattering (SANS) with contrast variation methods. The contrast variation methods were applied to determine a partial scattering function 
of graft chains. The reflects the ion-channel structures in the membranes. We found that the size of the ion-channel structure was about 10 times larger than that of Nafion. Combing with the previous results of our SANS studies for synthetic process of the crosslinking PTFE electrolyte membranes, we concluded that the size of the ion-channel structures is closely related with the size and the arrangement of microcrystals induced by radiation-induced crosslinking.
