Yoshiyuki Hirano¹, Kanta Nambu¹, Tsukasa Aso², Masanori Hara³ and Susumu Fujiwara⁴
1 Department of integrated health sciences, Graduate school of medicine, Nagoya University, Japan
2 Electronics and Computer Engineering, National Institute of Technology, Toyama College, Japan
3 Faculty of Science, Academic Assembly, University of Toyama, Japan
4 Faculty of Materials Science and Engineering, Kyoto Institute of Technology, Japan

Abstract
Ionizing radiation induces DNA damage both directly and indirectly through hydroxyl radicals (·OH) generated by water radiolysis. The indirect action involves hydrogen abstraction from deoxyribose, leading to DNA damage such as base release and strand breaks. The probability of such events depends on the accessibility of specific hydrogen atoms to ·OHradicals. Previous computational studies have examined naked DNA fragments; however, the effect of nucleosomal organization has not been addressed. Here, we performed molecular dynamics (MD) simulations usingLAMMPS(Large-scale Atomic Molecular Massively Parallel Simulator) to evaluate the accessibility of ·OHradicals to deoxyribose hydrogens in both 12-bp naked B-typeDNAand nucleosomal DNA containing histone proteins. The accessibility to the hydrogens increased, following the order H1′≈H2′≈H3′＜H4′＜H5′, consistent with previous studies. Accessibility was approximately proportional to the solvent accessible surface area (SASA), supporting SASA as a practical predictor of accessibility even in base-dependent differences were observed. In nucleosomal DNA, accessibility of hydrogens facing the histone core was significantly reduced compared to solvent-facing hydrogens, despite comparable SASA values. This reduction suggests that histones physically hinder ·OHradical penetration. These findings highlight the importance of considering protein–DNA complexes when modeling indirect radiation effects.

https://doi.org/10.1088/1402-4896/ae3446
ACCEPTED FOR PUBLICATION :6 January 2026

Shun Fukagawa ^a, Tsukasa Aso ^b, Yuya Tanbo ^b, Yoshiyuki Hirano ^c, Susumu Fujiwara ^d, Masanori Hara ^e

a Advanced Course, National Institute of Technology, Toyama College, Imizu 9330293, Japan
b Electronics and Computer Engineering, National Institute of Technology, Toyama College, Imizu 9330293, Japan
c Department of integrated health sciences, Graduate school of medicine, Nagoya University, Nagoya 4618673, Japan
d Faculty of Materials Science and Engineering, Kyoto Institute of Technology, Kyoto 6068585, Japan
e Faculty of Science, Academic Assembly, University of Toyama, Toyama 9308555, Japan

Abstract
Accurate simulation of radiation-induced DNA damage requires geometry models that preserve atomic structure while satisfying Geant4-DNA constraints. We present PDBDNAConv, a modular software suite that provides an automated pipeline for converting Protein Data Bank (PDB) structures into simulation-ready geometries. The software reconstructs hierarchical DNA models based on atomic structure using ellipsoidal approximation categorized for sugar, phosphate, and base moieties in nucleotide to reduce geometric complexes. Geometric overlaps are automatically detected and resolved to ensure valid geometry construction. Structured output is serialized in JSON format for interoperability and seamless integration into Geant4-DNA simulations. The exported JSON files are loadable by an example Geant4-DNA application through developed geometry construction classes that enable atomic-scale analysis of direct and indirect DNA damage.

https://doi.org/10.1016/j.softx.2026.102746
Accepted:21 May 2026

Ichiro Nishii ^a, Tomone Suganuma ^a, Takahiko Horiai ^b, Yuui Yokota ^c , Masao Yoshino ^c, Makoto Nakajima ^a, Masanori Hara ^d, Keisuke Shigemori ^a, Kohei Yamanoi ^a

a Institute of Laser Engineering, The University of Osaka, 2-6 Yamadaoka, Suita, Osaka, 565-0871, Japan
b National Institute of Advanced Industrial Science and Technology (AIST), 1-1-1 Higashi, Tsukuba, Ibaraki, 305-8565, Japan
c Institute for Materials Research, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai, Miyagi, 980-8577, Japan
d Faculty of Science, Academic Assembly, University of Toyama, 3190 Gofuku, Toyama, 930-8555, Japan

Abstract
Tritium in water is difficult to monitor because the low-energy beta particles emitted by tritium are strongly selfabsorbed. Although liquid scintillation counting provides high sensitivity, it requires sample preparation and generates radioactive organic liquid waste, limiting its suitability for on-site continuous monitoring. In this study, we investigated the inorganic single-crystal scintillator (La,Gd)₂Si₂O₇:Ce (Ce:La-GPS) for tritiated water measurements. The as-grown sample showed long-term afterglow that increased the count rate in the region of interest for tritium detection, but air annealing at 1200 ℃ suppressed the afterglow to the background level. The annealed sample exhibited a light output of approximately 35,000 photons/MeV and an energy resolution of 5.5% at 662 keV under ¹³⁷Cs gamma-ray excitation. Immersion measurements in tritiated water showed a linear counting response, with a minimum detectable activity of 3.85 MBq/L for a 600 s measurement. These results indicate that Ce:La-GPS is a promising solid scintillator for high-activity tritiated water monitoring, while application to low-level monitoring will require increasing the effective scintillator surface area.

https://doi.org/10.1016/j.optmat.2026.118252
Accepted:10 June 2026

Joshua Ashley ^a,Yuji Hatano ^b, Kiyohiro Yabuuchi ^c, Masanori Hara ^d,Tsukasa Aso ^e, Enrique Jimenez-Melero ^f

a Department of Materials, Engineering Building A, The University of Manchester, Oxford Road, M13 9P, Manchester, M13 9PL, UK
b Department of Quantum Science and Energy Engineering, Graduate School of Engineering, Tohoku University, 6-6-01-2, Aza-Aoba, Aramaki, Aoba-ku, Sendai, 980-8579, Miyagi Prefecture, Japan
c International Research Center for Nuclear Materials Science, Tohoku University, 2145-2 Narita-cho, Oarai-machi, Higashiibaraki-gun, 311-1313, Ibaraki Prefecture,Japan
d Hydrogen Isotope Research Centre, University of Toyama, 3190 Gofuku, Toyama, 930-8555, Toyama Prefecture, Japan
e Department of Electronics and Computer Engineering, National Institute of Technology, Toyama College, Toyama, 939-8045, Toyama Prefecture, Japan
f School of Metallurgy and Materials, University of Birmingham, Edgbaston, Birmingham, B15 2TT, UK

Abstract
While tungsten is still considered the material of choice for plasma-facing components in future tokamak fusion devices, a number of issues with its use remain when the synergistic loadings imposed by the fusion plasma are taken into account. Significant among these is the potential for irradiation induced damage structures to act as high energy traps for the scarce and radioactive hydrogen isotope tritium. We have experimentally simulated the plasma facing material environment by performing 1 MeV helium irradiation at 300 ℃ to a peak dose of ∼0.5 dpa, followed by deuterium-tritium gas exposure at 400 ℃ for five hours on tungsten-molybdenum alloys and a reference tungsten sample. Tritium retention has been measured using both imaging plate analysis and Beta-ray X-ray Spectrometry. Our results indicate that tritium trapping and retention is significantly enhanced by prior helium irradiation, with a close correspondence between the helium ion irradiation damage profile and the depth at which tritium is retained. Furthermore, we have found that molybdenum alloying can substantially mitigate this effect, decreasing tritium retention by almost half for an alloy of 39 at.% molybdenum, compared to the reference tungsten sample. This effect is discussed with reference to the damage structures resulting from helium ion irradiation and their trapping energies.
https://doi.org/10.1016/j.jnucmat.2026.156761
Accepted:24 May 2026

Makoto I. Kobayashi ^a,b, Masanori Hara ^c, Tsukasa Aso^d, Naofumi Akata ^e, Miyuki Yajima ^a,b

a National Institute for Fusion Science, National Institutes of Natural Sciences, 322-6 Oroshi, Toki, Gifu, 509-5292, Japan
b The Graduate University for Advanced Studies, SOKENDAI, 322-6 Oroshi, Toki, Gifu, 509-5292, Japan
c Hydrogen Isotope Research Center, University of Toyama, 3190 Gofuku, Toyama-shi, Toyama, 930-8555, Japan
d National Institute of Technology, Toyama College, 13 Hongo-machi, Toyama-shi, Toyama, 939-8630, Japan
e Hirosaki University, 1 Bunkyo-cho, Hirosaki, Aomori, 036-8560, Japan

Abstract
Due to the extremely short penetration depth of tritium beta rays, their direct detection remains challenging. This study demonstrates direct detection of low-energybeta particles from tritium decay using a novel outer-layer scintillation (OLS) fiber, consisting of a surface scintillation layer, a cladding layer, and a wavelengthshifting core. In addition, enhanced photon collection efficiency using a fiber-bundle configuration is demonstrated. Tritium beta-ray detection was verified using a graphite plate containing tritium. By inserting a thin plastic film to selectively attenuate beta particles, pulse-height spectra of the OLS fiber were compared with and without the film. A significant increase in the count rate in the low pulse-height region was observed without the film, clearly indicating the detection of low-energy beta particles. Although a fraction of scintillation photons generated in the outer layer does not reach or get absorbed by the wavelength-shifting core in a single fiber, such escaped photons can be partially recovered by the adjacent fibers within the fiber-bundle configuration. This so-called fiber-bundle effect was examined using external scintillation photons emitted from a piece of OLS fiber irradiated with alpha particles. An increase in the detected signal was observed when the piece of OLS fiber on the alpha particle source was placed near the fiber bundle, despite the absence of direct optical coupling, indicating that scintillation photons generated in the piece of fiber were captured by adjacent fibers within the fiber bundle. These results demonstrate that OLS fiber bundles provide an effective approach to real-time, in situ monitoring of tritium in aqueous environments, with improved detection efficiency through enhanced photon collection.

https://doi.org/10.1016/j.radmeas.2026.107771
Accepted:14 July 2026

Kazuto Sazawa ¹, Hanae Koyama ¹, Yusuke Yamazaki ¹, Yoshiki Hara ¹, Nozomi Kohama ², Yustiawati Yustiawati ³ and Hideki Kuramitz ¹,

1 Department of Natural and Environmental Sciences, Faculty of Science, University of Toyama, 3190 Gofuku, Toyama 930-8555, Japan
2 Hydrogen Isotope Science Research Center, University of Toyama, 3190 Gofuku, Toyama 930-8555, Japan
3 Research Center for Limnology and Water Resources, National Research and Innovation Agency, Jl. Raya Jakarta-Bogor Km. 46, Cibinong, Bogor 16911, Indonesia

Abstract
Charge-transfer-type fluorochromes, which exhibit shifts in fluorescence intensity and emission wavelength in response to solvent polarity changes, have been widely employed to investigate solute–solvent interactions. Humic substances (HSs) are naturally occurring macromolecular organic acids derived from plant residues, with structural properties that vary depending on their origin and environmental conditions. The polarity of HSs is closely associated with the mobility and toxicity of environmental pollutants, making their chemical characterization essential. In this study, we developed a rapid and straightforward method to characterize HS polarity using fluorescent solvatochromism. The fluorescence peak shifts of four dyes—8-anilino-1-naphthalenesulfonic acid (ANS), acridine orange (AO), methylene blue (MB), and Rhodamine B (RhB)—were evaluated in the presence of humic acids (HAs), a major component of HSs. To assess environmental variability, a total of twelve HS samples were tested, including HSs derived from soils of different origins, compost, commercial reagents, and standard reference materials. Among these, AO and MB exhibited distinct spectral shifts without overlapping with the intrinsic fluorescence of HAs. Notably, MB displayed a consistent blue shift dependent on HA concentration, with the most stable response observed at 5 mg/L. The magnitude of this shift was significantly correlated with UV–Vis parameters associated with the aromaticity, humification degree, and polarity of HSs. Overall, this study demonstrates that MB-based fluorescent solvatochromism can function as an empirical and facile indicator for assessing the structural and microenvironmental characteristics of HSs, providing a rapid and complementary screening approach for HSs extracted and purified from environmental samples.

https://doi.org/10.3390/s26010107
Accepted:20 December 2025