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Manganese is a candidate for the ionizing radiation-responsive long-lived signals of irradiated food samples detected by electron spin resonance spectroscopy
No full textWhen foods are exposed by ionizing radiation, unpaired electrons can become radiation-induced radicals. Electron spin resonance spectroscopy (ESR) can detect unpaired electrons. Therefore, ESR can only be used to detect persistent radicals that exist in irradiated foods for long periods. That is, only foods containing long-lived radicals are suitable as detection targets for ESR. When radicals in wet irradiated food samples were measured by ESR, manganese(II)-like signals were observed. To clarify the dose responses of Mn in active centre of enzymes, the Mn2+ solution was mixed with a chelator of hexadentate ligands and measured after γ-irradiation. The chelator suppressed signals from Mn2+, but signals appeared after γ-irradiation. The irradiation-induced degradation of Mn-SOD was affected by enzyme concentration. Furthermore, the degradation of Mn-SOD was proceeded during the post-irradiation period. These results suggested that one of long-lived ESR signals of irradiated foods comes from unpaired electrons of transition metal Mn.journal articl
Dynamic PET Imaging of Elesclomol-Facilitated Copper Delivery in Ischemic Stroke Rats
No full textCopper is an essential trace element that is required at optimal levels to support physiological functions in the cerebrovascular system. Copper deficiency reduces vascular elasticity, potentially worsening the ischemic stroke. Epidemiological evidence has linked higher copper intake with reduced stroke risk. This study aimed to investigate Elesclomol (ES) as a vector for delivering copper to the brain in models of ischemic stroke. 64Cu-ES showed excellent serum stability in vitro. PET/CT imaging revealed that 64Cu-ES exhibited longer brain retention compared to 64Cu-ATSM, likely due to its higher lipophilicity. Ex vivo biodistribution results were consistent with the imaging data. In normal SD rats, 64Cu-ES showed the highest uptake in the cingulate cortex, followed by the striatum, cerebral cortex, hippocampus, thalamus, and pons, with the lowest levels in the cerebellum and amygdala. In ischemic SD rats, there was no significant difference in the 64Cu-ES uptake between the ischemic region and the contralateral side up to 24 h post-administration. These results provide direct evidence that ES can facilitate delivery of copper to the brain, supporting its potential as a therapeutic candidate for copper supplementation in ischemic stroke patients.journal articl
Numerical study on a novel method for the plasma vertical position control using non-axisymmetric coils in JT-60SA
No full textA numerical investigation explored the feasibility of controlling the plasma vertical position using non-axisymmetric coils in JT-60SA. Non-axisymmetric coils offer an alternative to conventional axisymmetric in-vessel coils, addressing challenges in installation and maintenance, particularly in the context of the Japanese DEMO reactor. However, the main concern with using non-axisymmetric coils is the potential generation of locked modes, and the consumption of control margins for other control actions such as edge localized mode suppression. To address such challenges„ we developed control logic to maximize accessible elongation while simultaneously minimizing coil currents. To assess controllability, we employed a magnetohydrodynamic equilibrium control simulator (MECS) and used vacuum magnetic field analysis. We demonstrated that with the application of non-axisymmetric coils, the plasma elongation was extended from 1.75 which was achieved with superconducting poloidal field (SCPF) coils to 1.95, even in the presence of a minor Ip disruption. We also found that an error field correction coil (EFCC) could control during full discharge from ramp-up to ramp-down. The impact of non-axisymmetric magnetic fields on locked modes was evaluated using a three-mode error index (BTMEI ), revealing that n = 1 perturbations remained within acceptable limits (BTMEI ⩽ 0.05 mT) in most scenarios.journal articl
Carbon-ions, protons or photons for head and neck cancer radiotherapy–an in silico planning study
No full textTo compare dose to the organ at risk (OAR) and target coverage of carbon-ion beam, protons, and photons for patientswith head and neck cancer. Treatment plans for carbon-ion pencil beam scanning (C-PBS) (64 Gy (RBE) in 16 fractions),proton pencil beam scanning (P-PBS), and volumetric modulated arc therapy (VMAT) (70 Gy in 35 fractions for P-PBSand VMAT) were generated and compared using different dose constraints per treatment modality. Dose metrics (e.g.D95,V20) were analyzed. Statistical significance was assessed by the Wilcoxon signed-rank test. Also, we investigatedhowmany normal tissues were irradiated above the constraint after achieving the planning goals (pass rate) in the OARs.C-PBS outperformed P-PBS and VMAT in PTV coverage (p=0.01 for both); however, P-PBS and VMAT did not dif-fer substantially from each another (p=0.35). C-PBS was superior in limiting the dose to the OAR. The pass rates forC-PBS, P-PBS, and VMAT were 94%, 81%, and 69%, respectively. C-PBS demonstrated superior performance comparedto VMAT and P-PBS in terms of dose conformation to the target volume and normal tissue sparing, and achieved thehighest pass rate in meeting dose constraints.journal articl
レーザー励起過程の理論開発とシミュレーション
No full textレーザー加工過程の理解ためにモデル構築および第一原理シミュレーションによる物理過程の解析を行ってきた。その成果の概要を講演し、破壊過程の理論研究の現状について解説する。RIKEN-RAP and QST-KPSI Joint Seminarconference presentatio
High-resolution TOF-DOI detectors with diode-based multiplexing for brain PET
No full textFor brain dedicated positron emission tomography (PET), time-of-flight (TOF) and depth-of-interaction (DOI) information is essential to improve PET image quality. In addition, signal multiplexing is required to reduce the number of data acquisition channels thereby reducing cost. Last year, we developed a TOF-PET detector with a diode-based row-column multiplexing (RC mux) circuit. However, the detector lacks DOI information, and the crystal pitch was large (3.2 mm). Here, we present the CLS (crosshair light sharing) detector with diode-based multiplexing for brain-dedicated TOF-DOI PET development. The CLS detector consists of fast-LGSO crystal 14×14 array (crystal pitch=1.6 mm, thickness=15 mm) and SiPM 8×8 array (S14160-3050HS, pixel pitch=3.2 mm) (Fig. 1(a)). Custom-made RC mux circuits were used to reduce the SiPM channels from 64 into 16 (8 x-position + 8 y-position) with diode and resistor materials, respectively (Fig. 1(b-c)). The multiplexed analog signals were digitized by using PETsys TOFPET2 ASIC modules with an energy window of 440-560 keV (Fig. 2(a)). The effects of the RC mux circuits on the CTR were evaluated (Fig. 2(b)), and the diode-based multiplexing did not degrade the CTR (378 ps), whereas the resistor-based multiplexing degraded the CTR by 34% (572 ps). In conclusion, the diode-based RC multiplexing is a cost-effective solution for the development of brain-dedicated TOF-DOI PET systems.2026年第７３回応用物理学会春季学術講演会conference presentatio
Characterization of radioactive carbon ion beams using optical imaging technique
No full textOptical imaging is a cost-effective technique to characterize of physical properties of heavy ion beams. However, optical imaging has not been used for radioactive carbon ion beams. Since radioactive ion beams have larger momentum spreads (i.e. energy spreads) than those of conventional stable ion beams, the physical properties should be carefully measured during quality control. Here, we propose optical imaging for quality control of radioactive 11C ion beams with different momentum spreads (i.e. energy spreads). A polymethyl methacrylate (PMMA) phantom (10.0 × 10.0 × 9.9 cm3) was irradiated by 11C ion beams (200 MeV/u) with three different momentum acceptances (M.As) of 1%, 2% and 4% corresponding to the energy spreads of 1.8, 2.9, and 5.0 MeV/u, respectively (Fig. 1(a)). We obtained luminescence and Cerenkov images using an optical imaging system during and after irradiation, which were used for estimations of the Bragg peak position and energy spread, respectively (Fig. 1(b)). The Bragg peak position was estimated by using luminescence imaging with a maximum error of 0.5 mm (Fig. 2(a)). The full width at half maximum (FWHM) of the Cerenkov signals was linearly increased with the M.A (Fig. 2(b)). The positional difference between the Bragg peak and Cerenkov peak was also increased with the M.A. In conclusion, the optical imaging technique is a cost-effective solution to characterize the physical properties of 11C ion beams for beam quality control.2026年第７３回応用物理学会春季学術講演会conference presentatio
EUV Spectroscopic Analysis of Highly Charged Kr24+ Ion for Impurity Seeding Studies in Fusion Plasmas via Electron-Impact Excitation and Collisional-Radiative Modeling
No full textThis study presents a spectroscopic investigation of Kr24+ ion, generated via a krypton impurity seeding experiment in the Large Helical Device, aimed at supporting Extreme Ultraviolet (EUV) diagnostics of high-temperature fusion plasma. EUV spectral lines corresponding to fine-structure transitions among the 2p63s2, 2p63s3p, 2p63s3d, and 2p63p2 configurations were observed in the 12–25 nm wavelength range. To systematically analyze the measured emission lines, extensive relativistic atomic structure calculations were carried out over a broad configuration space, spanning more than 40 configurations, including core-excited and correlation-dominated states up to n ≤ 7 and ℓ ≤ 4. Bound-state wave functions were obtained using the relativistic many-body perturbation theory and configuration interaction method, implemented via the Flexible Atomic Code. Parallel calculations based on the relativistic multiconfiguration Dirac-Hartree-Fock method with configuration interaction were performed using the GRASP-2018 code to ensure numerical consistency. This article presents fine-structure-resolved excitation energies and transition parameters, including oscillator strengths and transition probabilities, for the relevant spectroscopic configurations up to 3ℓ. Moreover, electron impact excitation and ionization cross-sections from the ground state (2p63s2 1S0) as well as from selected excited states to higher-lying levels were calculated using the relativistic distorted wave method from the respective thresholds over a wide energy range. The corresponding Maxwellian averaged rate coefficients for excitation, de-excitation, ionization, and three-body recombination were evaluated over fusion-relevant electron temperatures. The results are presented for the prominent spectroscopic transitions up to 3ℓ. These complete atomic and electron-collision datasets were incorporated into a suitable collisional-radiative model, accounting for the dominant population and depopulation processes, including electron impact excitation, de-excitation, ionization, radiative decay, and three-body recombination. The theoretically modeled EUV spectrum, calculated at ne=5.5 × 1019 m-3 and Te=578 eV, shows good agreement with experimental observations, validating the accuracy of the calculated atomic structure, and electron-collision parameters. The resulting atomic dataset and modeling framework enable detailed spectral analysis of highly charged Kr24+ ion under magnetically confined fusion plasma conditions.journal articl
JT-60SAにおけるミリ波ドップラー反射計アンテナの電磁力解析
No full textJT-60SAに敷設予定のミリ波ドップラー反射計は、2026年後半のメンテナンス期間での設置に向けて設計が進められている。アンテナのプラズマへの接近性を高めるため、ステンレス製導波管を水平ポートから真空容器内へ挿入する構造としており、プラズマ崩壊時にはアンテナ先端部に大きな電磁力が作用すると想定される。そこで、核融合科学研究所技術部では、プラズマ崩壊時に発生する渦電流に起因する電磁力の時刻歴応答解析と構造解析を実施し、構造上の問題点の有無を検討した。R7年度核融合科学研究所技術研究会conference presentatio
抗酸化物質のラジカル消去反応に対する水および重水の影響
No full text目的：抗酸化物質は、ラジカル性活性酸素種に水素原子を供与することで、これらのラジカルを消去することが知られている。その水素移動反応には、一段階で水素原子が移動するhydrogen atom transfer (HAT)機構や、電子移動とプロトン移動が段階的に進行するelectron transfer followed by proton transfer (ET-PT)またはproton-coupled electron transfer (PCET)機構が知られている。これらの反応経路は、溶媒などの反応環境の影響を受けることが示されている。1) 本研究では、活性酸素種のモデルとして2,2-ジフェニル-1-ピクリルヒドラジル(DPPH)ラジカルを用い、アセトニトリル(MeCN)中での抗酸化物質との反応に対し、水(H2O)および重水(D2O)がどのような影響を及ぼすかを速度論的に検討した。方法：反応はAgilent 8453フォトダイオードアレイ紫外可視分光光度計およびユニソクRSP-1000-02NM型ストップトフロー分光測定装置を用いて追跡した。結果および考察：MeCN中25 ℃において、水溶性ビタミンE類縁体であるTroloxとDPPHラジカルをストップトフロー法で反応させ、DPPHラジカル由来の519 nmの吸収減衰から二次反応速度kを1.8 × 10^2^ M^-1^ s^-1^と決定した。10% (v/v)のH2Oを添加すると、k値は2.7 × 10^2^ M^-1^ s^-1^に増大した。一方、10% (v/v)のD2Oを添加すると、k値は7.4 × 10 M^-1^ s^-1^に低下した。(+)-カテキンとDPPHラジカルとの反応では、10%H2Oの添加時にk値は1.7 × 10 M^-1^ s^-1^から1.8 × 10^2^ M^-1^ s^-1^に増大し、10%D2Oの添加時には1.7 × 10^3^ M^-1^ s^-1^とさらに増大した。本研究では、抗酸化物質としてアスコルビン酸誘導体やコーヒー酸についても同様の検討を行い、さらにH2O/D2Oの代わりに酢酸および重酢酸を添加した反応系についても速度論的影響を比較した。これらの結果を併せて報告する。1) Nakanishi I., Shoji Y., Ohkubo K., Fukuhara K., Ozawa T., Matsumoto K., Fukuzumi S. J. Clin. Biochem. Nutr., 68, 116 (2021).日本薬学会第146年会conference presentatio