National Institutes for Quantum and Radiological Science and Technology
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高強度レーザー照射水素クラスターターゲットからの準単色100 MeV超陽子線加速の加速メカニズム
No full text高強度レーザーJ-KAREN-Pのアップグレード後の最初の実験において、マイクロメートルスケールの水素クラスターターゲットを用い、準単色100 MeVの陽子線加速を実現した。講演では、三次元粒子コードシミュレーションを用いた加速機構について議論する。特に、クラスターサイズ、レーザー集光強度、レーザー照射位置に着目し、実験データと比較するレーザー学会学術講演会第46回年次大会conference presentatio
研究フォーラムでの講演
No full text結晶構造解析によって取得した精密な構造情報を基盤に、タンパク質機能および薬理作用の分子機構を解明する知見を紹介する。本発表では、炎症性サイトカインとその阻害剤にフォーカスした内容を発表した。研究者をつなぐ研究フォーラム ～ライフサイエンスの交差点～conference presentatio
New Findings in the Visualization of Subepithelial Melanoma or Pseudoprogression-Like Phenomena in Oral Mucosal Melanoma During Carbon-Ion Radiation Therapy
No full text口蓋粘膜悪性黒色腫に対して行われた炭素イオン線治療によって観察された偽進行（Pseudoprogression）、あるいは上皮下病変が可視化された現象を報告したjournal articl
Influence of magnetic fields generated by a magnetized ferritic first wall on surface heat loads from plasma heat flux along magnetic field lines
No full textLocalized concentrations of plasma heat flux (comprising charged particles moving along magnetic field lines) can result in excessive thermal loads whose peak values may exceed several MW/m2, e.g. at the edges of blanket modules. Such conditions are undesirable and have motivated the development of heat load analysis methods, including magnetic field line tracing within the vacuum vessel (VV), as established in our previous work. In JA DEMO, reduced-activation ferritic martensitic steel is employed for the first wall (FW) due to its superior resistance to neutron irradiation. Here, the strong magnetic field in JA DEMO magnetizes the FW, thereby altering the magnetic field configuration in VV and affecting plasma equilibrium. This modified equilibrium, in turn, influences the magnetization vector in FW. Accurate prediction of magnetic field distribution in VV and the heat load distribution on the FW thus necessitates consideration of this mutual interaction between the magnetized FW and the plasma equilibrium. To address this, a computational code capable of evaluating the effect of FW magnetization under JA DEMO-like conditions is developed. The code iteratively computes a three-dimensional MHD equilibrium consistent with the magnetic field generated by the magnetized FW (Bm). Subsequently, plasma heat flux and heat load distributions on the FW are calculated via the magnetic field line tracing. Although Bm is relatively weak and it induces unnoticeable changes in plasma equilibrium, it significantly alters the heat load distribution compared to cases neglecting Bm. In this research, three distinct patterns of Bm influence are identified: (1) cumulative effect of weak Bm altering field line trajectories, (2) strong Bm modifying field line orbit, and (3) strong Bm directly attracting field lines toward the FW. Future work will focus on identifying the specific conditions under which these effects become significant.journal articl
Investigation of functional hot spot residues of enzyme by real-time monitoring of enzymatic reaction by NMR and computational experiments
No full textFavipiravir is an anti-influenza prodrug that is metabolized to its phosphoribosylated form, favipiravir-ribofuranosyl-5′-monophosphate (favipiravir-RMP), by human endogenous enzyme hypoxanthine-guanine phosphoribosyltransferase (HGPRT). This enzymatic reaction is the rate-determining step in generating the active form of favipiravir, making it important to understand the molecular mechanisms underlying the HGPRT-catalyzed RMP-modification of favipiravir. However, the pharmacokinetics of this reaction have not been fully elucidated, despite X-ray crystallographic studies on the HGPRT-favipiravir complex. Here, we identified functional hot-spot residues in HGPRT that play important roles in the enzymatic conversion of favipiravir to favipiravir-RMP. Real-time monitoring of the HGPRT reaction via ligand-observed solution NMR experiments, biochemical mutagenesis of HGPRT, and computational calculations and molecular dynamics simulations, allowed us to investigate the free binding energetics and structural properties of the interaction between HGPRT and favipiravir-RMP. This powerful hybrid experimental strategy allows the identification of functional hot-spot residues in the enzyme and provide complementary structural biological information. This approach could be universally applicable to investigating drug-protein interaction modes.journal articl
Equilibrium flow-induced bifurcation between quasi-steady and bursty dynamics of ballooning mode turbulence
No full textEdge-localized modes (ELMs) are burst-like transport events observed in the edge region of tokamak plasmas, typically driven by pressure- driven instabilities such as the ballooning mode. Understanding nonlinear dynamics of ELMs is essential for future devices such as ITER. In this study, we conduct nonlinear simulations of the resistive ballooning mode turbulence using the reduced two-fluid model that includes both the heating and the neoclassically induced equilibrium flow. In the absence of the equilibrium flow, the system exhibits the quasi-steady turbulent dynamics, while the inclusion of the equilibrium flow triggers the repetitive bursts. These bursts are triggered by the formation and decay of the intermediate-scale vortices, whose radial extent and lifetime are regulated by the flow shear through nonlinear interactions. The dependence of the burst dynamics on the flow strength is non-monotonic, indicating complex nonlinear interactions between the mean flow and turbulent vortices. These findings reveal the mechanism by which the equilibrium flow modulates the burst dynamics and the vortex size selection in the ELM-like phenomena.journal articl
Dopamine shapes brain metastate dynamics
No full textDopamine’s influence on large-scale network dynamics, especially on the default mode network (DMN), remains uncertain, as fMRI studies have produced mixed results. One likely contributor to these discrepancies is reliance on traditional functional connectivity analyses, which typically derive a single metric (e.g., the Pearson correlation coefficient) from the entire time series and thus fail to capture network dynamics. To address this issue, we combined a dopaminergic challenge (mazindol, a dopamine transporter [DAT] reuptake inhibitor), PET, resting-state fMRI, and hidden Markov modeling (HMM) to characterize time-varying alterations in human large-scale functional networks following acute DAT blockade. We found that mazindol-induced increases in endogenous dopamine altered the balance between the brain’s functional “metastates,” two recurrent higher-order network configurations that each encompass multiple HMM-derived brain states. Mazindol increased the time participants spent in an internally oriented cognitive metastate and decreased the time spent in a sensorimotor–perceptual metastate, with the DMN showing the most pronounced lengthening. In exploratory analyses, declines in [¹¹C]raclopride binding, a PET index of D2 dopamine receptor availability reflecting increased striatal extracellular dopamine levels, tended to show a positive correlation with the prolongation of these cognitive states. These findings indicate that dopamine is closely linked to shifts from sensorimotor and perceptual to cognitive brain metastates, potentially underpinning the prioritization of internally oriented over externally driven psychological processes. Our results highlight the importance of dynamic, time-resolved connectivity approaches for understanding neuromodulatory actions in the human brain and suggest that dopamine helps regulate the dynamic balance between functionally competing large-scale brain networks.conference pape
Real-Time Tracking of Flexible Markers in Low-Contrast Fluoroscopy Using a Deep Neural Network Trained Solely on Synthetic Data
No full textIn radiation therapy, fiducial markers implanted in a pa-tient’s body are tracked using X-ray fluoroscopy to estimatetumor positions. However, flexible markers, such as GoldAnchor® (Naslund Medical AB, Sweden), deform within thebody, making conventional template matching challenging.While deep learning offers a promising solution, the ex-tensive collection and annotation of clinical data requiredfor training pose a significant barrier to adoption. To ad-dress this, we propose a tracking framework that utilizes alightweight Siamese CNN trained exclusively on syntheticfluoroscopy images. Our method generates synthetic datasimulating diverse marker deformations under low-contrastand high-noise conditions, employs dynamic programmingfor stable initial detection, and performs real-time trackingwith a particle filter. In evaluations using clinical data, ourmethod achieves a tracking accuracy of 0.42 ± 0.12 pixelsfor prostate cancer cases and 0.97 ± 0.53 pixels for pan-creatic cancer cases. This significantly outperforms con-ventional methods, particularly in challenging low-contrastpancreatic cancer cases. With TensorRT optimization, theframework achieves a processing speed of 3.8 ms/frame.This work presents a practical solution for high-accuracytracking, reducing data collection costs and facilitating theuse of deep learning in clinical applications.journal articl
Multichannel highly sensitive diamond quantum magnetometer
No full textWe demonstrate a highly sensitive real-time magnetometry method at two measurement points. This magnetometry method is based on the frequency-division multiplexing of continuous-wave optically detected magnetic resonance. We use two ensembles of nitrogen-vacancy (NV) centers separated by 3.6 mm to measure a magnetic field. A different bias field is applied to the two NV ensembles to resolve the resonance peak for each ensemble in the frequency space and enables the multiplexed magnetometry at the two points. The sensitivities achieved at the measurement points are 21 pT/Hz‾‾‾√ and 22 pT/Hz‾‾‾√. The proposed magnetometry method can be expanded to include more measurement points and shorter spacing. The capability of real-time measurement at numerous points with short spacing and high sensitivity is beneficial for various applications, including biomagnetic sensing, geophysical research, and material science.journal articl
Nano light-source generation by electron beam irradiation of CsPbBr3/Cs4PbBr6 composites
No full textPrecise allocation of nano light-sources in photonic integrated circuits is essential for the development of next-generation optical technologies such as optical nano-circuits, quantum information processing, and quantum communication. However, controlling the position of such light sources is a challenging task. We here show that halide perovskite nanoparticle light sources can be generated at the desired positions by electron beam. We applied cathodoluminescence spectroscopy to CsPbBr3/Cs4PbBr6 composites produced by thermal evaporation and discovered that the intensity of green light emission from the CsPbBr3 nanoparticles increased with electron beam irradiation. Furthermore, by taking advantage of the high spatial resolution and controllability of the electron beam, we demonstrate nano-light source patterning on the film.journal articl