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Yoshimoto, Masataka*; Tamura, Kazuhisa; Watanabe, Kenta*; Shimizu, Keisuke*; Horisawa, Yuhei*; Kobayashi, Takeshi*; Tsurita, Hanae*; Suzuki, Kota*; Kanno, Ryoji*; Hirayama, Masaaki*
Sustainable Energy & Fuels (Internet), 8(6), p.1236 - 1244, 2024/03
Times Cited Count：0 Percentile：0.01(Chemistry, Physical)Photo-rechargeable systems, which can efficiently convert and store solar energy into chemical energy within single devices, are essential to harness sunlight effectively. Photo-(de)intercalation plays a pivotal role in the functionality of photorechargeable systems. Nevertheless, the photo-(de)intercalation process has not been conclusively confirmed owing to potential interference from side reactions, such as the decomposition of liquid electrolytes and the elution of electrode materials. In this study, we successfully demonstrated photo-responsive Li
-deintercalation using an all-solid-state thin-film battery comprised of epitaxially-grown anatase TiO
doped with Nb (a-TiO:Nb) as the cathode. Under light irradiation, Li-deintercalation occurred and was subsequently reversibly intercalated into a-TiO:Nb during discharge.
Watanabe, Kenta*; Horisawa, Yuhei*; Yoshimoto, Masataka*; Tamura, Kazuhisa; Suzuki, Kota*; Kanno, Ryoji*; Hirayama, Masaaki*
Nano Letters, 24(6), p.1916 - 1922, 2024/02
Times Cited Count：2 Percentile：98.52(Chemistry, Multidisciplinary)Electrochemistry has extended from reactions at solid/liquid interfaces to those at solid/solid interfaces. In this study, we achieve the stable photoelectrochemical reaction at the semiconductor-electrode/solid-electrolyte interface in Nb-doped anatase-TiO (a-TiO:Nb)/Li
PO
(LPO)/Li all-solid-state cell. The oxidative currents of a-TiO:Nb/LPO/Li increase upon light irradiation when a-TiO:Nb is located at a potential that is more positive than its flat-band potential. The photoelectrochemical reaction at the semiconductor/solid-electrolyte interface is driven by the same principle as that at semiconductor/liquid-electrolyte interfaces. Thus, we extend photoelectrochemistry to all-solid-state systems composed of solid/solid interfaces.
Kai, Takeshi; Toigawa, Tomohiro; Ukai, Masatoshi*; Fujii, Kentaro*; Watanabe, Ritsuko*; Yokoya, Akinari*
Journal of Chemical Physics, 158(16), p.164103_1 - 164103_8, 2023/04
New insight into water radiolysis and photolysis is indispensable in the dramatic progress of sciences and technologies in various research areas. In the radiation field, reactive hydrated electrons are considerably produced along radiation tracks. Although the formation results from a transient dynamic correlation between ejected electrons and water, the individual mechanisms of electron thermalization, delocalization, and polarization are unknown. Using a dynamic Monte Carlo code, we show herein that the ejected electrons are immediately delocalized by molecular excitations in parallel with phonon polarization and gradually thermalized by momentum transfer with an orientation polarization in a simultaneous manner. Our results show that these mechanisms heavily depend on the intermolecular vibration and rotation modes peculiar to water. We expect our approach to be a powerful technique for connecting physical and chemical processes in various solvents.
Watanabe, Jin*; Araki, Yasufumi; Kobayashi, Koji*; Ozawa, Akihiro*; Nomura, Kentaro*
Journal of the Physical Society of Japan, 91(8), p.083702_1 - 083702_5, 2022/08
Times Cited Count：4 Percentile：63.4(Physics, Multidisciplinary)We investigate magnetic orderings on kagome lattice numerically from the tight-binding Hamiltonian of electrons, governed by the filling factor and spin-orbit coupling (SOC) of electrons. We find that even a simple kagome lattice model can host both ferromagnetic and noncollinear antiferromagnetic orderings depending on the electron filling, reflecting gap structures in the Dirac and flat bands characteristic to the kagome lattice. Kane-Mele- or Rashba-type SOC tends to stabilize noncollinear orderings, such a magnetic spirals and 120-degree antiferromagnetic orderings, due to the effective Dzyaloshinskii-Moriya interaction from SOC. The obtained phase structure helps qualitative understanding of magnetic orderings in various kagome-layered materials with Weyl or Dirac electrons.
Araki, Yasufumi; Watanabe, Jin*; Nomura, Kentaro*
Journal of the Physical Society of Japan, 90(9), p.094702_1 - 094702_9, 2021/09
Times Cited Count：1 Percentile：15.5(Physics, Multidisciplinary)While nodal-line semimetals with magnetism have been theoretically predicted and experimentally observed in a few compounds, idea on the relation between the magnetic order and the electronic structure is still limited. We theoretically explore the electronic structure in bulk and boundary of such a magnetic nodal-line state by introducing magnetism in topological Dirac semimetal (TDSM). TDSMs, such as 
and 
,are characterized by a pair of spin-degenerate Dirac points protected by rotational symmetries of crystals. By introducing local magnetic moments coupled to the electron spins in the lattice model of TDSM, we show that the TDSM can turn into either a Weyl semimetal or a nodal-line semimetal, which is determined by the orbital dependence in the exchange coupling and the direction of magnetization formed by the magnetic moments. In this magnetic nodal-line semimetal state, we find zero modes with drumhead-like band structure at the boundary that are characterized by the topological number of 
. Those zero modes are numerically demonstrated by introducing magnetic domain walls in the lattice model.
Kai, Takeshi; Yokoya, Akinari*; Fujii, Kentaro*; Watanabe, Ritsuko*
Hoshasen Kagaku (Internet), (106), p.21 - 29, 2018/11
It is thought to that the biological effects such as cell death or mutation are induced by complex DNA damage which are formed by several damage sites within a few nm. As the prediction of complex DNA damage at an electron track end, we report our outcomes. These results indicate that DNA damage sites comprising multiple nucleobase lesions with a single strand breaks can be formed by multiple collisions of the electrons within 1 nm. This multiple damage site cannot be processed by base excision repair enzymes. Pre-hydrated electrons can also be produced resulting in an additional base lesion over a few nm from the multi-damage site. This clustered damage site may be finally converted into a double strand break. These DSBs include another base lesion(s) at their termini that escape from the base excision process and which may result in biological effect. Our simulation is useful to reveal phenomena involved in radiation physico-chemistry as well as the DNA damage prediction.
Kai, Takeshi; Yokoya, Akinari*; Ukai, Masatoshi*; Fujii, Kentaro*; Toigawa, Tomohiro; Watanabe, Ritsuko*
Physical Chemistry Chemical Physics, 20(4), p.2838 - 2844, 2018/01
Times Cited Count：22 Percentile：76(Chemistry, Physical)It is thought that complex DNA damage which induces in radiation biological effects is formed at radiation track end. Thus, the earliest stage of water radiolysis at the electron track end was studied to predict DNA damage. These results indicate that DNA damage sites comprising multiple nucleobase lesions with a single strand breaks can therefore be formed by multiple collisions of the electrons within three base pairs (3bp) of a DNA strand. This multiple damage site cannot be processed by base excision repair enzymes. However, pre-hydrated electrons can also be produced resulting in an additional base lesion more than 3bp away from the multi-damage site. This clustered damage site may be finally converted into a double strand break (DSB) when base excision enzymes process the additional base lesions. These DSBs include another base lesion(s) at their termini that escape from the base excision process and which may result in biological effects such as mutation in surviving cells.
Kai, Takeshi; Yokoya, Akinari*; Fujii, Kentaro*; Watanabe, Ritsuko*
Yodenshi Kagaku, (8), p.11 - 17, 2017/03
It is thought to that the biological effects such as cell death or mutation are induced by complex DNA damage which are formed by several damage sites within a few nm. We calculated dynamic behavior of secondary electrons produced by primary electron and positon of high energy in water whose composition ratio is similar to biological context. The secondary electrons induce the ionization or electronic excitation near the parent cations. The decelerated electrons about 10% are distributed to their parent cations by the attractive Coulombic force. From the results, we predicted the following formation mechanism for the complex DNA damage. The electrons ejected from DNA could induce the ionization or the electronic excitation within the DNA. The electrons attracted by the Coulombic force are pre-hydrated in water layer of the DNA. The pre-hydrated electrons could induce to the DNA damage by dissociative electron transfer. As the results, the complex DNA damage with 1 nm could be formed by the interaction of not only the primary electron or positon but also the secondary electrons.
Kai, Takeshi; Yokoya, Akinari*; Ukai, Masatoshi*; Fujii, Kentaro*; Watanabe, Ritsuko*
Journal of Physical Chemistry A, 120(42), p.8228 - 8233, 2016/10
Times Cited Count：18 Percentile：62.22(Chemistry, Physical)Low energy secondary electrons produced by an ionizing radiation in a living cell may involve in formation of complexed DNA damage. We performed theoretical study for numerical calculation of dynamic behavior of the electrons to imply a formation of radiation damage to DNA. The decelerating electrons are gradually attracted to their parent cations by the Coulombic force within hundreds of fs, and about 12.6 % of electrons are finally distributed within 2 nm from the cations. The collision fraction of the ionization and excitation within 1 nm from the cation was estimated to be about 40 %. From those analyses, we suggested a process of DNA damage that the secondary electrons may cause highly localized lesions around a cation in DNA molecule through additional dissociative electron transfer as well as the ionization or the excitation if the electrons are ejected from DNA. The localized damage may involve ultimately in biological effects such as cell death or mutation induction.
Kai, Takeshi; Yokoya, Akinari*; Fujii, Kentaro*; Watanabe, Ritsuko*
Hoshasen Kagaku (Internet), (102), p.49 - 56, 2016/00
Behavior analysis of low energy electrons in liquid water provides the fundamentals for successive radiation chemistry, and it makes analysis of DNA damage implication involved in the electrons possible. We have progressed theoretical studies for radiation physicochemical process of water to clear the role of secondary electrons damage to DNA. The process has included many unknown factors for the DNA damage so far. We implied a newly formation process of unrepair DNA damage produced by the secondary electrons. We report our outcomes separately in three manuscripts entitled "Recent progress of radiation physicochemical process (first, second, third parts)". In this second part, we show calculated results of thermalization lengths and times of electrons in water to verify a dynamic Monte Carlo code developed in this study. From the calculated results, we also report our prediction, which are different from previous one, for thermalization and pre-hydration processes.
Si investigated by decay spectroscopy of AlSteiger, K.*; Nishimura, Shunji*; Li, Z.*; Gernh
user, R.*; Utsuno, Yutaka; Chen, R.*; Faestermann, T.*; Hinke, C.*; Kr
cken, R.*; Nishimura, Mitsuki*; et al.
European Physical Journal A, 51(9), p.117_1 - 117_9, 2015/09
Times Cited Count：10 Percentile：57.61(Physics, Nuclear)no abstracts in English
Yokoya, Akinari; Fujii, Kentaro; Ushigome, Takeshi; Shikazono, Naoya; Urushibara, Ayumi; Watanabe, Ritsuko
Radiation Protection Dosimetry, 122(1-4), p.86 - 88, 2006/12
Times Cited Count：11 Percentile：60.07(Environmental Sciences)We have studied yields of DNA damages induced by soft X-rays obtained from a conventional soft X-ray machine in a LET region between 
-rays and ultrasoft X-rays. Practically soft X-rays with a broad energy spectrum emitted from a target of heavy metal, such as tungsten, have been widely used not only for radiobiological experiments but also for medical application such as mammography. Radiation weighting factors for these soft X-rays have been assigned to be 1 by ICRP. However, the fraction of a large number of low energy photons in the spectrum (below several tens keV) provided by bremsstrahlung is expected to be more effective for DNA damage induction than -rays since low energy photo- and Auger electrons predominantly ejected in consequence of a photoelectric effect can produce dense clusters of ionization/excitation on DNA molecules. We have examined the yield of DNA strand breaks induced by white soft X-rays (150 kVp, tungsten target). Yields of base lesions revealed by base excision repair enzymes will be also presented.
Yokoya, Akinari; Shikazono, Naoya; Urushibara, Ayumi; Fujii, Kentaro; Akamatsu, Ken; Watanabe, Ritsuko
Hoshasen Seibutsu Kenkyu, 40(2), p.168 - 184, 2005/06
Ionizing radiation causes modifications in a DNA molecule depending on the characteristic tack-structure in which two or more isolated lesions arise in a few nm scale (1 or 2 helical turn of DNA), known as "clustered DNA damage". These clustered DNA damages could be distinct from those by reactive oxygen species (ROS) endogenously induced on their severity of induction of biological effects such as mutation. However, the studies on the nature and repair mechanism of clustered DNA damage have still been behind because of the technical difficulties on determination of the chemical structure and yield. This article reviews some experimental evidences of the clustered DNA damages in this research field, as well as our recent progress on the studies on the clustered DNA damages using both molecular biological techniques and synchrotron spectroscopic method.
Watanabe, Ritsuko; Yokoya, Akinari; Fujii, Kentaro; Saito, Kimiaki
International Journal of Radiation Biology, 80(11-12), p.823 - 832, 2004/11
Times Cited Count：15 Percentile：68.07(Biology)no abstracts in English
Kai, Takeshi; Yokoya, Akinari*; Ukai, Masatoshi*; Fujii, Kentaro*; Watanabe, Ritsuko*; Yonetani, Yoshiteru*; Toigawa, Tomohiro; Sato, Tatsuhiko
no journal, ,
It is very important to study water radiolysis by electrons because the study are applied to fields involved in atomic industry and radiotherapy, the study is also useful to predict radiation damage to DNA in a living cell. In this study, we calculated deceleration process of secondary electrons produced by ionization at a primary electron track end, at which a primary and secondary electrons densely deposit those energies to water, to understand the earliest process of water radiolysis. From the results, the secondary electrons distributed 10 nm from parent cations at 300 fs, and the mean energy of the electrons reached 0.7 eV. At this timescale, we indicated that the energy distribution shows the non-equilibrium state strongly, and fraction of the electrons energy below 0.1 eV is more than 10
. The results may indicate a new insight of the formation of prehydrated electrons due to the extremely low energy electrons.
Kai, Takeshi; Toigawa, Tomohiro; Ukai, Masatoshi*; Fujii, Kentaro*; Watanabe, Ritsuko*; Yokoya, Akinari*
no journal, ,
Fundamental studies of water radiolysis by radiation and laser irradiation are applied to atomic industry, and provide useful fundamental insights to understanding of radiation DNA damage. We developed a code to simulate dynamic behavior of electrons produced in water by energy deposition at energies, also performed theoretical study for the behaviors. The spatial probability distributions of the electrons depend on the deposition energies, also show the exponential or Gaussian types. We also show calculated results of energy probability distributions of the electrons. We found that the distributions below 100 meV are gradually close to Maxwell distribution with the temporal evolution, while the distributions above 100 meV not depend on the temporal evolution due to effect of Coulombic field of the parent cation. The findings provide significant insights to a connection radiation physics and radiation chemistry.
Watanabe, Jin*; Araki, Yasufumi; Nomura, Kentaro*
no journal, ,
no abstracts in English
Osawa, Takahito; Ninomiya, Kazuhiko*; Nakamura, Tomoki*; Takahashi, Tadayuki*; Terada, Kentaro*; Yurimoto, Hisayoshi*; Noguchi, Takaaki*; Okazaki, Ryuji*; Yabuta, Hikaru*; Naraoka, Hiroshi*; et al.
no journal, ,
I report on the muonic X-ray analysis experiment conducted at J-PARC from 2020 to 2021, in which the analytical method was significantly developed through four preliminary experiments and successfully analyzed samples from the asteroid Ryugyu in July 2021. The experimental process is described from a radiochemical point of view.
Si
Mn
Matsukawa, Yoshitaka*; Watanabe, Daiki*; Tsurekawa, Sadahiro*; Abad, N. M.*; Muta, Hiroaki*; Yoshida, Kenta*; Kasada, Ryuta*; Yamaguchi, Masatake; Kumano, Hideki*; Endo, Minako*
no journal, ,
It is now generally believed that when a light water reactor is operated for nearly 80 years, Ni-Si-Mn ternary intermetallic compounds such as the G phase and the 
phase precipitate in the pressure vessel steel, which contribute to irradiation embrittlement. We have started a basic study focusing on the relationship between these compounds and diffusion coefficients. In order to investigate the characteristics of interdiffusion at the precipitate/matrix interface of pressure vessel steels, bulk materials of the compounds were prepared by arc melting and bonded to bulk materials of pure iron to produce so-called diffusion pairs. In this report, we describe our findings for the G phase.
