National Institutes for Quantum and Radiological Science and Technology
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Application of non-integer-n RMP coil current waveform for ELM control in JA DEMO
No full textWe have studied the resonant magnetic perturbation (RMP) coil concept for edge localized mode (ELM) suppression in JA DEMO, a design concept of a steady-state tokamak demonstration reactor, based on the vacuum magnetic model. We investigate the RMP coil layout and current pattern that are effective for ELM suppression and the coil current required for ELM suppression including the pedestal height dependence. We examine the effect of RMPs on the trigger of magnetohydrodynamic instabilities, divertor footprints, and alpha-particle loss. When the currents of the RMP coils in a toroidal row are determined to match non-integer-n sinusoidal waveforms, compared to the cases using integer-n waveforms, we demonstrate that (a) the coil current required for ELM suppression is reduced, (b) the range of plasma conditions under which ELM can be suppressed is widened, (c) the amplitudes of m/n = 2/1 and 3/2 perturbation fields are smaller than the locked mode scaling, (d) the increase in alpha-particle loss is an acceptable level in terms of the plasma heating deterioration and the divertor heat load, and (e) special localization is not seen in the divertor strike points and lost alpha-particle incident positions. Here, n(m) is the toroidal (poloidal) mode number. Utilizing non-integer-n current waveforms is advantageous for ELM control by RMP in DEMO.journal articl
A theoretical study of non-adiabatic processes in the photodissociation of the palladium dichloride anion, PdCl2–
No full textWe theoretically investigate photodissociations of the gas-phase palladium dichloride anion, PdCl2-. Visible photodissociation mass spectrometry revealed that the main dissociation channel yields chloride anion (PdCl + Cl-), but our previous calculations based on a linear-geometry model did not explain the observation. In this study bent geometries are considered and absorption spectra and potential energies are calculated using the MRCI method. It is found that the computational results agree with the observed absorption spectrum and dissociation product. It is worth noting that non-adiabatic transitions between excited-state potential curves are found to play a key role in the photodissociation process.journal articl
A Novel mGluR1-Targeted Radiotheranostic Strategy for Lesion Imaging and Tumor Control in Melanoma and Pancreatic Cancer
No full textTargeting metabotropic glutamate receptor 1 (mGluR1), a key regulator of glutamine metabolism frequently overexpressed in cancers, is a promising strategy for cancer treatment and management (Xie L, et al. Cell Rep Med. 2023). Here, we engineered a mGluR1-targeted radiotheranostic strategy integrating positron emission tomography (PET) with targeted α-particle therapy (TAT) using a novel small-molecule pair, β⁺-emitting 11C-IMTM and α-emitting 211At-AMTM, to identify and eradicate refractory cancers, including melanoma and pancreatic cancer. The radioligand pair, 11C-IMTM and 211At-AMTM, was designed and synthesized based on the mGluR1 structure (Wu H, et al. Science. 2014), both sharing the same small-molecule backbone (Xie L, et al. J Nucl Med. 2020). The diagnostic and therapeutic efficacy, as well as safety, were evaluated in xenograft mouse models of localized and metastatic melanoma and pancreatic cancer. Mechanistic studies were performed to elucidate the antitumor effects of the mGluR1-targeted TAT. 11C-IMTM PET clearly visualized primary and metastatic melanoma lesions, while α-particles from 211At-AMTM anchored to mGluR1 to downregulate this oncoprotein, which is subsequently internalized to trigger cancer cell senescence via the p21–caveolin-1 pathway. In mice with localized and metastatic melanoma, a single dose of 211At-AMTM induced a >86% reduction in tumor volume and a twofold increase in survival. Moreover, complete eradication of pancreatic cancer was observed in 46.67% (7/15) of treated mice, without significant toxicity. This mGluR1-targeted radiotheranostic strategy, 11C-IMTM PET-guided 211At-AMTM TAT, represents a novel and effective approach for the diagnosis and treatment of melanoma and pancreatic cancer, and provides new insights into clinical development and application of approaches targeting cancer-specific metabolic vulnerabilities.A3 Foresight Joint Meeting in OISTconference presentatio
Structural basis of hydride and proton transfer reactions revealed by the detection of hydrogen atoms in mammalian NADH-cytochrome b5 reductase
No full textMany structural studies have been reported for ferredoxin:NADP+ reductase family members, but an experimental validation of the catalytic hydride and proton transfer steps through a direct detection of the involved hydrogen atoms has not been achieved so far. Here, we determined high-resolution X-ray and neutron crystal structures of NADH-cytochrome b5 reductase, which acts as an electron supplier for various metabolic processes and mediates hydride and proton transfer reactions via its FAD and NADH cofactors. The X-ray structures identify the FADH--NAD+ and FAD-NADH complexes based on the electron densities of the hydrogen atoms bound to the cofactors. The neutron structures determined at different pD-values show a difference in the protonation state of the histidine residue in the hydrogen-bond network from FAD to the protein surface. The observation of the hydrogen atoms reveals the structural basis for the hydride and proton transfer reactions catalyzed by NADH-cytochrome b5 reductase.journal articl
Experimental validation of a Fisher information–based predictive framework for dose and time optimization in PET-guided online adaptive proton therapy
No full textObjective: The range determination uncertainty (σ_est) based on positron emission tomography (PET) imaging, which stems from the Poisson statistics of the detected signal, can be theoretically predicted using Fisher information. This study aims to experimentally validate a Fisher information–based predictive framework that optimizes the irradiation dose and measurement time required for reliable range verification in PET-guided online adaptive proton therapy.Approach: First, we defined a precision criterion of 1.5σ_est<2 mm for reliable range verification. Then, using polyethylene, water, and a head and neck phantom, we determined the minimum measurement time—calculated in 2-s increments—required to satisfy this criterion at given irradiation doses (0.5 Gy and 0.1 Gy) based on Fisher information. For each condition, 5,000 PET images were generated from the measurement datasets, and the maximum likelihood estimation method was independently applied to each to determine the standard deviation of the measured range (σ_meas). Finally, the values of σ_meas were compared with those of σ_est to validate the predictive framework.Main results: The values of σ_meas and σ_est showed consistent agreement (within approximately 0.5 mm), regardless of target properties, dose levels, and measurement times. Furthermore, the measured range uncertainty satisfied the pre-defined precision criterion of 1.5σ_meas<2 mm under almost all of the tested conditions.Significance: This study provides the first experimental validation of the Fisher information–based predictive framework for PET-based range verification. The findings offer a rationale for integrating this framework into PET-guided online adaptive proton therapy, which will potentially enable reliable range verification with the minimum pre-irradiation dose and measurement time.journal articl
Effect of heterozygous deletions on phenotypic changes and dosage compensation in Arabidopsis thaliana
No full textHeterozygous deletions, which include a large number of genes, are often caused by the induction of mutations. The induction of gene dosage compensation should be considered when assessing the effects of heterozygous deletions on phenotypic changes. This mechanism is known to balance the expression levels of genes with different copy numbers in sex chromosomes, but it is also known to operate in autosomes. In the present study, 12 Arabidopsis thaliana BC1 mutants with heterozygous deletions were produced by crossing wild-type Col-0 plants with mutants induced by heavy ion beams. The sizes of the deletions ranged from 50.9 kb to 2.03 Mb, and the number of deleted genes ranged from 8 to 92. Nine of the 12 BC1 mutants showed phenotypic changes in fresh weight 14 days after cultivation or during the flowering period. RNA-sequencing (RNA-seq) analyses of 14-day-old leaves, 40-day-old leaves, and flower buds showed that dosage compensation did not occur in any stage or tissue tested. These results indicate that heterozygous deletions cause phenotypic changes owing to the absence of dosage compensation.journal articl
高速・高精度な頭部PET体動補正法の開発
No full text頭部PET撮像中の被験者の体動は画像の空間分解能を劣化させるため、適切な体動補正が不可欠である。従来技術であるフレーム法では、撮像データを一定時間間隔で分割して再構成することでフレーム画像を生成し、各フレーム画像間のレジストレーション（画像位置合わせ）によりモーションを推定する。この手法は追加装置を必要とせず、取り扱いが容易であるというのが最大の利点である。しかし、フレーム分割位置が一定間隔に固定されており、体動の発生タイミングが考慮されていないため、単一フレーム内に複数の動きが含まれるケースが生じやすく、モーション推定精度の低下が問題となっていた。一方で、同時計数イベントが発生した検出器対を結ぶ反応線の中心点を短時間間隔で平均化することで、Center of Distribution（CoD）と呼ばれる指標が算出できる。CoDは実際の体動と高い相関を有することが知られており、我々はこの特性を利用して、体動の発生タイミングに応じたフレーム分割を行う適応的フレーム分割法を開発した[1]。本手法により、フレーム内の動きを単一に抑えた、必要最小限のフレーム分割が可能となった。しかし、フレーム分割位置を最適化しても、画像間のレジストレーションに基づいてモーション推定を行うという基本的な方針は変わらない。レジストレーション処理は計算コストが高く、適応的フレーム法によってフレーム数を最小限に抑えた場合でも、解析には数時間程度の計算が必要であった。そこで本研究では、画像空間における画素値分布の解析に基づき、頭部の位置および姿勢を直接推定する新たな手法を提案する。本手法ではレジストレーション処理を必要とせず、従来法と比較して大幅な計算時間の短縮が期待できる。次世代PET研究会2026conference poste
量子センサ計測技術が拓く生体ナノ・マイクロ計測の新展開
No full text第8回Q-LEAPシンポジウムにて「量子センサ計測技術が拓く生体ナノ・マイクロ計測の新展開」の演題でポスター発表を行う。第8回Q-LEAPシンポジウムconference poste
一塩基編集技術を利用した代謝型グルタミン酸受容体の in vivo 化学遺伝学的制御法の開発
No full text脳内に存在する受容体の働きは、学習や記憶といった脳機能と深く結びついている。薬剤により動物個体中の受容体を阻害し、行動への影響を評価する手法は、この関係を解明するうえで有用である。しかし、薬剤は全身に拡散するため、作用する脳領域を制御することは困難である。我々は化学遺伝学に着目し、阻害剤が作用しない変異型受容体を用いることで、特定領域の標的受容体のみを阻害する手法の開発を進めている。これまでに、全脳に広く発現する代謝型グルタミン酸受容体 1 型(mGlu1) を小脳選択的に阻害することに成功している。一方、本手法では変異型受容体を発現するマウスの新規作製が必要であり、多大な時間を要する。現在、一塩基編集技術を用いてマウスの内在性遺伝子を後天的に編集することで、この課題の解決を目指している。本発表では、一塩基編集に基づく新規変異体の設計とそれによる mGlu1 の化学遺伝学的制御の進捗について報告する。日本化学会第106春季年会（2026）conference presentatio
Spin-lattice relaxation for point-node–like s-wave superconductivity in f-electron systems
No full textIn this study, we examined the temperature dependence of the spin-lattice relaxation using an f-d-p model, which is an effective model of UTe2. Solving the linearized Eliashberg equation in the f-d-p model based on third-order perturbation theory, we obtain a point-node–like s-wave pairing state. Our result shows that the Hebel-Slichter-peak in the point-node–like s-wave pairing state is smaller than that in the isotropic s-wave pairing state. However, the Hebel-Slichter peak remains robust even in the point-node–like s-wave pairing state, and the point-node–like s-wave state is inconsistent with the results of nuclear magnetic resonance measurements.conference pape