National Institutes for Quantum and Radiological Science and Technology
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X線透過法における 散乱線特性と線量評価の検討
No full text1. はじめにX線透過法による非破壊検査は、コンクリート内部の鉄筋や電線管などの埋設物を非破壊で確認できるため、建築現場で広く利用されている。X線を使用する管理区域では被ばく管理の一環としてサーベイメータによる線量当量率の測定が行われている。非破壊検査では、作業者被ばくの主因としてコンクリート等で散乱したX線が考えられる。散乱X線はエネルギーが変化するため、測定結果に影響を与える可能性がある。本研究ではX線透過法を模擬した作業場における光子フルエンススペクトル及び線量当量率を実測し、被ばく管理に係る測定上の注意点を抽出した。2. X線透過法の模擬及び散乱線の測定方法X線透過法を模擬するため、コンクリート板（600mm×600mm×200mm）に対して、1 mの位置にある携帯型X線発生装置 RIX-200MC（トーレック製）（管電圧200kV、管電流3mA）を用いてX線を照射した。CdTeスペクトロメーター（EMFジャパン製EMF-123型）で実測した波高スペクトルと検出器の応答関数からアンフォールディング処理により、光子フルエンススペクトルを求めた。線量当量率は、電離箱式サーベイメータAE-133B（応用技研製）（H *(10),H ’(3), H ’(0.07)）、電離箱式サーベイメータICS-1323（アロカ製）（H *(10)のみ）、シンチレーション式サーベイメータTCS-1172（アロカ製）（H *(10)のみ）の3機種で測定した。3. 結果及び抽出された測定上の注意点 測定された光子フルエンススペクトルを右図に示す。鉛と錫の特性X線ピーク、タングステン（ターゲット材）の特性X線の後方散乱ピーク、コンクリートで散乱された連続X線の成分が見られ、そのフルエンス平均エネルギーは65 keVであった。 AE-133Bによる線量当量率測定ではH *(10): 29.5 mSv/h、H ’(3): 32.5 mSv/h、H ’(0.07) : 32.5 mSv/hとなり、測定値に大きな差がないことからH *(10)の測定で適切な管理を出来ることが判明した。また、ICS-1323でもH *(10): 33.2 mSv/hが得られ、電離箱式サーベイメータの機種による差異は十分に小さかった。一方、シンチレーション式サーベイメータであるTCS-1172の測定ではH *(10): 7.92 μSv/hとなった。これは、低エネルギー光子がカウントされていないことに加え、X線がパルス照射されているためパイルアップが生じて正しい測定結果が得られなかったと考えられる。よって、X線透過法作業時の線量当量率の測定では適切なサーベイメータの種類を選択する必要があることが確かめられた。日本保健物理学会第58回研究発表会conference poste
Pressure-Induced Charge Amorphisation in BiNiO3
No full text電子の秩序または無秩序は材料特性の基本であり、物質のさまざまな状態への単純な類似点も与える。結晶に類似した電荷秩序絶縁体状態は、多くの混合価数の材料で観察されている。加熱するとこの状態は融けて電荷液体相（金属）となり、多くの場合、興味深い関連した物理や機能を伴う。 今回、BiNiO3で観測された結晶材料における圧力誘起電荷アモルファス化について報告する。journal articl
Nonlinear Hall effect in bilayer WTe2 induced by strong laser field
No full textThe geometric nature of Bloch electrons has recently come into focus of studies in nonlinear optics. In this regard, the Weyl semimetals, with their significant Berry curvature at Weyl nodes, are of particular interest. The recently discovered nonlinear Hall phenomena in Weyl semimetals (mainly 2nd order responses), provide a unique avenue to explore the topological properties of emergent quantum materials [1]. While previous studies in nonlinear optics have explored various mechanisms in Weyl semimetals, such as Bloch oscillations, intraband motions, and high harmonic generation, the relationship between nonlinear Hall phenomena and nonlinear optics remains unexamined.
Our study presents the first investigation of the relationship between nonlinear Hall effects and nonlinear optical responses in Weyl Dirac nodes, ranging from perturbative to nonperturbative regimes. Focusing on the mid-infrared frequency range, we probe the effects of intensity and frequency dependence, including energy cutoffs and the interplay between interband and intraband processes, using time-dependent first-principles formalismjournal articl
Application of the spectral determination method to unified gamma-, beta- and X-ray spectra
No full textSo far we have developed the innovative radioactivity quantification technique of spectral determination method (SDM) based on the first principle that a γ-ray spectrum obtained for a sample is a linear superposition of individual spectra of the radioactive nuclides included in the sample. We have applied this method to spectra measured with Ge, NaI detectors and liquid scintillation counter (LSC) and demonstrated that the determination uncertainty of the SDM was better than those of previous peak analysis methods for the spectra obtained from a sample including 8 or 9 radionuclides.
In the present study we extended the SDM to apply to a unified spectrum composed of LSC and Ge detector, and the number of nuclides has been increased to 40. The new SDM code was named as SDM-LG. We selected 40 radionuclides from possible radionuclides included in nuclear debris and radioactive wastes in the environment which were produced by the nuclear accident in Fukushima in March. 2011. We carried out LSC and Ge measurements for 17 and 7 nuclides, respectively. The rest of the standard spectra among the 40 nuclides have been derived by simulation calculations utilizing the Geant 4.10.3 Monte Carlo simulation tool kit. The derived LSC and Ge spectra for each nuclide were unified to a single spectrum and the 40 sets of the composed spectra were completed as a unified data base.
We studied the determination accuracy of the SDM-LG analysis by examining a composed spectrum made of 40 radionuclides with equal intensities (Each has a radioactivity fraction of 2.5%.). The SDM result shows that the relative determination uncertainties of 35 nuclides are below 20%. It is also indicated that by removing 3 interfering nuclides the determination accuracy of the other 37 nuclides could be improved.journal articl
Development of L10-ordered FePt with low damping and large perpendicular magnetic anisotropy by engineering the nanostructure
No full textTHz spintronics is an emergent area of research aimed at bridging the gap between fifth- and sixth-generation wireless telecommunications by utilizing spintronic devices such as magnetic spin torque oscillators as a source of low powered THz emission. The realization of such devices using ferromagnetic metal thin films however requires magnetic materials with both large perpendicular magnetic anisotropy (PMA) and low Gilbert damping constants. In this Letter, we report on the development of L10-ordered FePt with an effective Gilbert damping constant as low as 0.033. Using time-resolved magneto-optical Kerr effect, we characterized the magnetization dynamics of continuous L10-ordered FePt grown on MgO and SrTiO3 substrates. By changing the substrate on which FePt is grown, the lattice mismatch and subsequent number of misfit dislocations at the interface and L10-ordering can be controlled. We found that fewer misfits and improved ordering in FePt lead to a reduced Gilbert damping constant due to reduced electron scattering but that FePt grown on SrTiO3 also shows robust perpendicular magnetic anisotropy. Importantly, these results demonstrate the ability to control the damping in FePt and similar materials by changing the number of misfit dislocations at the interface and the smaller damping in FePt opens up the possibility of using this material in spintronic
materials in the THz wave range.journal articl
An 211At-labeled alpha-melanocyte stimulating hormone peptide analog for targeted alpha therapy of metastatic melanoma
No full textPurpose: Patients who develop metastatic melanoma have a very poor prognosis, and new treatments are needed to improve the response rates. Melanocortin-1 receptor (MC1R) is a promising target for radionuclide therapy of metastatic melanoma, and alpha-melanocyte stimulating hormone (α-MSH) peptide analogs show high affinities to MC1Rs. Because targeted alpha therapy (TAT) can be a desirable treatment for metastatic melanoma, this study aimed to develop an 211At-labeled α-MSH peptide analog for TAT of metastatic melanoma.
Methods: We designed an α-MSH analog labeled with 211At using neopentyl glycol scaffold via a hydrophilic linker. Preliminary studies using 125I-labeled α-MSH analogs were performed to identify suitable hydrophilic linkers. Then, [211At]NpG-GGN4c was prepared using a procedure similar to that of the 125I-labeled counterpart, [125I]NpG-GGN4b. The biodistribution profile of [211At]NpG-GGN4c in B16F10 tumor-bearing mice was compared with that of [125I]NpG-GGN4b. B16F10 tumor-bearing mice were treated with a single dose of vehicle or [211At]NpG-GGN4c (1 or 0.4 MBq).
Results: The D-Glu-D-Arg linker was identified as the optimal hydrophilic linker because of its high affinity for MC1R and good biodistribution profile, especially with low accumulation in the liver and intestine. [211At]NpG-GGN4c showed tumor accumulation comparable to that of [125I]NpG-GGN4b and maintained the tumor radioactivity retention from 1 to 3 h postinjection. [211At]NpG-GGN4c exhibited a dose-dependent inhibitory effect on B16F10 xenograft growth without apparent body weight loss.
Conclusion: [211At]NpG-GGN4c showed dose-dependent efficacy against B16F10 xenografts, suggesting that [211At]NpG-GGN4c is a promising TAT agent for treating metastatic melanoma.journal articl
Operational regime and confinement property of JT-60SA L-mode plasma in the first plasma operation phase
No full textCharacteristics and operational regimes of electron density, electron temperature, and energy confinement have been investigated in the JT-60SA first plasma operation phase. Working gases for these plasma discharges are hydrogen (H2) and helium (He). A plasma current Ip of 1.2 MA has been achieved at a toroidal magnetic field BT of 2 T. In Ip = 1 MA, the operational regimes of a line-averaged electron density ￣ne are 2.7 × 10^18 ? 5.2 × 10^18 m^?3 for the He-gas injected plasma and 2.5 × 10^18 ? 6.5 × 10^18 m^?3 for the H2-gas injected plasma. A maximum electron temperature in this operation phase is 2.0 keV in the core region in the case of He-gas-injection and 1.13-MW electron cyclotron resonant heating (ECH). A global energy confinement time τE of L-mode divertor plasmas for both the He-gas-injected and H2-gas-injected plasmas strongly depends on the total input power. In the similar total input power regimes, τE increases with an increase in ￣ne, leading to the possibility of these plasmas in the linear ohmic confinement regime. The global energy confinement time of the H2-gasinjected plasmas, which is in the range of 100 - 200 ms, is compared with the ITER89-P scaling law, resulting in τE being on and a little below the scaling. The dependence of τE on ￣ne matches the neo-Alcator scaling law and reaches the ITER89-P scaling law in higher-density plasma in the case of the similar total input power regimes.journal articl
Evaluation of the Gly-Phe-Lys Linker to Reduce the Renal Radioactivity of a [64Cu]Cu-Labeled Multimeric cRGD Peptide
No full textRadiometal-labeled peptide-based radiopharmaceuticals (RLPB-radiopharmaceuticals) are promising for cancer imaging and targeted radiotherapy; however, their effectiveness is often compromised by the high retention of nonspecific radioactivity in the kidneys due to renal excretion pathways. Current strategies to address this issue have limitations, highlighting the need for innovative approaches to improve targeting specificity and therapeutic efficacy. We aimed to evaluate the applicability of the Gly-Phe-Lys (GFK) tripeptide, a renal brush border (RBB) enzyme-cleavable linkage, to reduce renal radioactivity in RLPB-radiopharmaceuticals using the integrin-targeting radiopeptide [64Cu]Cu-cyclam-RAFT-c(-RGDfK-)4 ([64Cu]Cu-cyclam-RaftRGD). We designed and synthesized the model compound [64Cu]Cu-cyclam-GFK(benzoyl [Bz]), its predictive metabolites, and GFK-incorporated [64Cu]Cu-cyclam-RaftRGD derivatives [64Cu]Cu-cyclam-GFK-RaftRGD and [64Cu]Cu-cyclam-GFK(beta-alanine [βA])3-RaftRGD. In vitro studies showed that dual radiometabolites, namely, [64Cu]Cu-cyclam-G and [64Cu]Cu-cyclam-GF, were simultaneously released from [64Cu]Cu-cyclam-GFK(Bz) by different RBB enzymes, whereas both RaftRGD derivatives released only [64Cu]Cu-cyclam-GF. When injected into mice, [64Cu]Cu-cyclam-GFK(Bz) and the two RaftRGD derivatives led to the urinary excretion of [64Cu]Cu-cyclam-G and [64Cu]Cu-cyclam-GF, respectively. PET imaging and biodistribution studies showed the increased rates of reduction in renal radioactivity levels for the two RaftRGD derivatives compared to the parental [64Cu]Cu-cyclam-RaftRGD (e.g., PET: 1 to 24 h postinjection, 73.0 ± 2.3 and 75.6 ± 1.8 vs 43.0 ± 4.5%, p < 0.0001; biodistribution: 3 to 24 h, 61.1 and 74.4 vs 22.8%). Taken together, these results indicate that the designed renal cleavage occurred in vivo. We also noted the steric interference of the RaftRGD moiety on enzyme access, the spacer effect of the trimeric βA sequence (reduced steric hindrance), and the altered radiopharmacokinetics (e.g., initially increased renal accumulation) of the RaftRGD compounds upon linker incorporation. These findings provide important insights into the chemical design of RLPB-radiopharmaceuticals with reduced renal retention based on the RBB strategy.journal articl
Utilities of ionic liquid extraction with astatine ions and its extraction mechanism
No full textPresent study is the first attempt on the application of ionic liquid (IL) for the extraction of 211At with the 7.21-h-half-life in targeted alpha-particle therapy. We produced the nuclide to investigate utilities of several ionic liquids, namely, [C4mim][Tf2N], [C6min][Tf2N], [C8mim][Tf2N], [C8mim][PF6], and [C8mim][BF4] in solvent extraction and back extraction for the practical application of a 211Rn/211At generator. Astatine extraction with ionic liquids was investigated in detail in this study, and the extraction mechanism was elucidated for the first time.journal articl
Quaternary ammonium-functionalized polysilsesquioxanes for antifogging coating
No full textAiming to develop antifogging materials with enhanced antifogging
properties and scratch resistance, polysilsesquioxane films
containing quaternary ammonium groups were prepared via a sol?
gel reaction and quaternization. Owing to their high water uptake,
scratch hardness, and transparency, the prepared quaternary
ammonium-functionalized polysilsesquioxane films are promising
for application in antifogging coatings.journal articl