National Institutes for Quantum and Radiological Science and Technology
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Practical rule for trimming the DFT-1/2 self-interaction: Band gap, absolute band alignment, and defect properties of semiconductors
No full textIn recent years, density functional theory (DFT) for material design and discovery has gained significant interest. Traditional approximations with the DFT, like the local density approximation (LDA), tend to underestimate band gaps. On the other hand, the Heyd-Scuseria-Ernzerhof (HSE) method provides better accuracy for band gaps but at a high computational cost. In 2008, Ferreira et al. introduced the DFT-1/2 method, which improves band gap predictions at a computational cost similar to LDA. This method adjusts the valence band energy levels by applying Self-Interaction Correction at the local potential level. The extent of this correction is determined by a parameter called 'cutoff,' which must be self-consistently calculated. Although DFT-1/2 is computationally efficient, it requires extra effort in parameter tuning. Moreover, it may not accurately predict band gaps for certain materials, such as narrow-gap semiconductors. Variations like DFT-1/4 or shDFT-1/2 have been developed to address this issue, providing more accurate band gaps for these materials but reducing accuracy for others. Therefore, choosing the optimal method is essential and material-dependent. To overcome these empirical challenges, we introduce a novel parameter-free approach in the framework of DFT-1/2 (parameter-free DFT-1/2). Unlike the original DFT-1/2, which requires an additional self-consistent field (SCF) loop to determine the cutoff radius that maximizes the band gap, our proposed method calculates the cutoff radius directly from the crystal structure, thus eliminating the need for the extra SCF loop. We validated the performance of parameter-free DFT-1/2 by calculating key electronic properties such as band gaps, effective masses, ionization energies, and electron affinities. We also assessed defect levels in the charge transition states of a silicon point defect in silicon carbide (SiC) for the first time. The results demonstrate that parameter-free DFT-1/2 can reproduce spin density with accuracy comparable to HSE and that parameter-free DFT-1/2 is also effective for predicting charge transition levels in defects.journal articl
Combined in situ quick X-ray absorption fine structure and X-ray diffraction systems for ultra-high temperature metal oxides
No full textStructural analysis using synchrotron radiation, such as X-ray diffraction (XRD) and X-ray absorption fine structure (XAFS), is an effective means of investigating physical properties of materials at high temperatures in order to experimentally clarify their physical properties. However, accurate temperature measurements above 2,800 K are difficult, complicating the assessment of structural changes in materials. This study addresses these issues by employing a newly developed furnace capable of reaching 2,800 K and performing in situ rapid XAFS and XRD measurements. These advances will improve our understanding of metal oxides at melting points and provide valuable insights into their behavior under extreme conditions.journal articl
Implementation and 3D extension of dose reconstruction strategies from prompt-gamma emissions in proton therapy
No full textObjective. Range and dose monitoring with secondary radiation can help minimizing the issues of range uncertainties in proton cancer therapy. Prompt gammas (PGs) have been widely investigated as a promising secondary radiation for in vivo verification. Since it can be argued that for a proper delivery of the intended treatment the most desirable quantity to assess is the dose distribution in vivo, this work aims at the reconstruction of the delivered proton dose from distributions of PG radiation. Approach. Some techniques have already been proposed in the literature to reconstruct the dose from a distribution of detected secondary radiation, mostly positron emitters. Among them, very promising methods are the analytical deconvolution approach, the evolutionary algorithm and the maximum-likelihood expectation-maximization (MLEM) algorithm. Herein, the feasibility of the application of these approaches to PG distributions at emission stage is assessed with simulated mono- and polyenergetic proton beams, irradiating homogeneous and inhomogeneous phantoms, and a realistic case of a head and neck (H&N) tumor patient. Main results. The accuracy of the reconstructed dose is evaluated via comparison with the corresponding simulated ground truth dose distributions using different metrics. For the case of 1D reconstruction on phantoms, the ΔR80, ΔR50 and ΔR10, with ΔR% being the difference of the positions at the % of the dose maximum in the distal fall-off region between the simulated and reconstructed curves, are always less or of the order of 1 mm in absolute value. For 3D reconstruction on phantoms and on the H&N case, the γ(1%/1 mm) passing rate is always above or equal to 97%. Significance. This study demonstrates the applicability of the analytical deconvolution, the evolutionary and the MLEM algorithms to dose reconstruction from PG emissions, providing a step forward toward the final goal of real-time verification of the dose delivery for real-time adaptive particle therapyjournal articl
myCRP, cysteine-rich protein in the yesso scallop Mizuhopecten, is a novel high-molecular weight Cd-binding protein
No full textHeavy metal bioaccumulation in marine organisms is a critical concern for the oceanic environment and food safety. Scallops, as filter-feeding bivalves, accumulate cadmium (Cd) in their midgut gland to toxic concentrations that may pose risks to human health. Despite extensive research on Cd bioaccumulation in the Yesso scallop Mizuhopecten yessoensis, a major Cd-binding protein has not yet been functionally characterized. In this study, we used high-performance liquid chromatography coupled with inductively coupled plasma mass spectrometry (HPLC-ICP-MS) to isolate Cd-binding proteins, and identified myCRP, a novel high-molecular-weight Cd-binding protein. myCRP contains a cysteine-rich sequence, resembling metallothionein Cd-binding motifs, and is expressed exclusively in the midgut gland. Cd-binding assays demonstrated that myCRP binds Cd in a dose-dependent manner. Immunostaining revealed the presence of a small cluster of myCRP-containing cells in the connective tissue surrounding digestive tubules in the midgut gland. Synchrotron radiation X-ray fluorescence (SR-XRF) analyses showed the distribution of Cd throughout the entire midgut gland tissue. We conclude that myCRP is partly responsible for Cd binding in the midgut gland. Our findings clarify a new mechanism of Cd-binding in marine organisms from both biological and molecular perspectives.journal articl
S-PARAMETERS LIVE MEASUREMENT FOR THE MULTIPORT RF COMPONENTS: APPLICATIONS TO THE CIRCULATOR AND THE LIPAC RFQ CAVITY
No full textThe Linear IFMIF Prototype Accelerator (LIPAc) is designed to provide extremely high averaged intensity deuteron beam 125mA-CW up to 9MeV for the fusion material examination. For accelerating the high-current beam, 1.2MW of 175MHz RF power is required to drive the RF Quadrupole (RFQ) cavity with 8 RF input ports. Towards CW, we need to accumulate the dissipation for several RF/beam loading in each component. To understand the condition of the high power components and improve the control of them, it is important to analyze the thermal dynamics characterized by the S-parameters depending on the dissipation related with the DC. In this study, we try to make a semi-analytical model of the S-parameters for arbitral dissipation conditions, and trial of the application to the circulator as the three ports device.conference pape
Quantum Beam-Based Elemental Analysis for Biological Trace Element Research
No full textChemical information of tissue and cellular elements, such as elemental distribution, localization, composition, and chemical status, is required for understanding biological trace elements. Quantum beam-based elemental analyses, such as particle induced X-ray emission (μPIXE) and synchrotron radiation X-ray fluorescence (SR-μXRF) analysis with microprobe, are promising research tactics for such purposes. μPIXE is excellent for detecting light elements, and imaging of biomatrix elements such as sulfur and phosphorus enables us to obtain the distribution and localization of target elements corresponding to the cell structure [1]. Synchrotron radiation X-ray fluorescence analysis (SR-XRF) is a special analysis at large synchrotron radiation facilities, but by using high-energy excitation X-rays, it is possible to detect heavy metals (tin, uranium, cesium, cadmium, etc.) at trace levels in tissues [2-4]. By combining PIXE and SR-XRF, element distribution dynamics from light to heavy elements can also be investigated [3, 4]. Furthermore, combining elemental imaging with X-ray absorption fine structure (XAFS) provides information on the chemical form of the localized elements in the tissues [3]. Application to blood and urine droplet specimens is also expected for contamination monitoring and medical applications. This symposium will present examples of these analyses.References:[1] Shino Homma-Takeda et al., Minerals 2021; 11: 191.[2] Shino Homma-Takeda et al., Nucl. Intr. Meth. Phys. Res. B 2005; 231: 333-337.[3] Shino Homma-Takeda et al., Int. J. Mol. Sci. 2019; 20: 4677-4687.[4] Haruko Yakumaru et al., Eur. Phys. J. Plus (in press).conference pape
Major histocompatibility complex class I chain-related gene A and B expression induced by heavy ion beam irradiation in cervical cancer cells
No full textMajor histocompatibility complex class I chain-related gene A and B (MIC) are transmembrane glycoproteins to function as a ligand for human NKG2D that is a main activating receptor of NK cells. MIC are minimally expressed on normal cells, but frequently upregulated via viral infection, cellular stress signals, and malignant transformation. NKG2D recognizes MIC, resulting in the activation of NK cells. Recent progress on radiation biophysics has shown that radiation can modulate anti-tumor immunity in host irradiated via regulation of immune recognition protein expression on cancer cells. The aim of this study is to investigate the effects of heavy ions beam irradiation on membrane MIC expression in human cervical cancer cells. We used HEK293 cells stably overexpressing HPV-E6 or E7 oncoproteins and 5 human cervical cancer cell lines in this study. Carbon ions beam irradiation (CIR, 290 MeV/n; LET, ∼70 keV/μm, mono peak), a beam of heavy ion beams, was performed at the in-house synchrotron accelerator that is able to produce carbon ion beams. Irradiated doses ranged from 0 to 10 Gy of carbon-ions. Cell membrane MIC expression was evaluated by flowcytometry using an anti-MIC antibody. MIC expression was upregulated in HPV-E6 or E7 overexpressing HEK293 cells and 5 human cervical cancer cells in a dose-dependent manner. HPV16-positive human cervical cancer Caski and cells showed a remarkable upregulation of MIC expression after CIR. Other cervical cell lines (ME-180, HeLa, SiHa, and C33A) showed a modest upregulation. E6- or E7-overexpressing HEK293 cells exhibited a considerable induction of MIC after CIR. We investigated the impact of DNA damage responses on HIR-mediated MIC upregulation using drug inhibitors of proteins that are involved in DNA damage responses. Both pharmacological Chk1 inhibition and ATM inhibition cancelled CIR-mediated MICA/B upregulation in HPV oncoprotein-positive HEK293 cells. The results indicated that ATM/ATR pathways were involved in MIC upregulation on HPV-positive cells including cervical cancer cells. These findings support the favorable combination of MICA/B-targeted therapy with heavy ion therapy against cervical cancers.AACR ANNUAL MEETING 2025conference poste
ダイバータプラズマ中の衝突過程とストライク点位置がトカマク運転領域に及ぼす影響
No full text核融合炉の実現に向けて、ダイバータ熱負荷の低減は最重要課題の一つである。ダイバータプラズマ解析のために、周辺プラズマ統合コードSONICが開発されており、近年新たにイオン–原子間で生じる大角度散乱と、中性粒子同士の衝突過程が実装された。これらの衝突過程がプラズマ・中性粒子輸送に及ぼす影響を定量的に明らかにするとともに、ストライク点の位置がダイバータ熱負荷、ひいてはJT-60SAの運転領域に及ぼす影響を評価する。第42回 プラズマ・核融合学会 年会conference presentatio
Development of fluorine-free anionic polymer electrolyte membranes using aromatic hydrocarbon polymers by radiation-induced graft polymerization and their alkaline resistance.
No full text亜鉛蓄二次電池用高分子電解質膜の開発を目的に、高温での機械特性および耐久性に優れた芳香族炭化水素であるポリエーテルエーテルケトン（PEEK）を用い、アニオン伝導性基の前駆体であるクロロメチルスチレン(CMS)の放射線グラフト重合を検討した。結晶化度11%の市販PEEK膜を50℃18時間ジオキサン中に浸漬することで、高分子構造を制御した膜は、所定の溶媒を用いることでグラフト重合反応が進行し、既成のアニオン伝導膜と同等性能を得ることができた。15th conference of Aseanian Membrane Societyconference poste
赤外自由電子レーザーとファイバーレーザーとの同期のための位相同期システムの評価
No full text中赤外自由電子レーザー(FEL)のキャリアエンベロープ位相(CEP)を安定化させるため、CEP安定シードレーザーを外部からFELへ導入する。そのためには、シードレーザーとFELを同期させる必要がある。本研究では、レーザー発振器を高周波信号と同期させるシステムを採用し、その構築と同期試験を実施した。本発表では、レーザーと高周波信号の同期システムの概要とこれまでの試験結果について報告する。第22回日本加速器学会年会conference poste