Non-destructive elemental analysis of lunar meteorites using a negative muon beam

Chiu, I.-H.; 寺田 健太郎*; 大澤 崇人; Park, C.*; 竹下 聡史*; 三宅 康博*; 二宮 和彦*

Meteoritics & Planetary Science, 58(9), p.1333 - 1344, 2023/09

https://doi.org/10.1111/maps.14059

We report the result of a non-destructive elemental analysis of lunar meteorites using a negative muon beam at J-PARC. An experimental system of six Ge semiconductor detectors and a newly designed He analysis chamber (to enable quantitative analysis of Al) was used to provide a high signal-to-noise ratio for the detection of major elements from lunar rocks (Mg, Si, Fe, O, Ca, and Al). We performed a Monte Carlo simulation to determine the chemical compositions at two sides and the center of a sample (at depths of 0.33 and 0.96 mm below the sample surface, respectively) of the lunar meteorite DEW 12007. These results indicate that the three interior regions of DEW 12007 are likely to be 55.8:44.2, 51.4:48.6, and 54.4:45.6 wt% mixtures of anorthositic and basaltic clasts, respectively. This study is the first quantitative analysis of a heterogeneous meteorite interior using a negative muon beam. As elemental analysis using a muon beam is non- destructive and highly sensitive to light elements, including C, N, and O, the protocols established in this study are applicable to initial characterization of returned samples from the South Pole of the Moon.

Non-destructive elemental analysis of lunar materials with negative muon beam at J-PARC

Chiu, I.-H.; 寺田 健太郎*; 大澤 崇人; Park, C.*; 竹下 聡史*; 三宅 康博*; 二宮 和彦*

Journal of Physics; Conference Series, 2462, p.012004_1 - 012004_6, 2023/03

https://doi.org/10.1088/1742-6596/2462/1/012004

今までの10年間で、負のミュオンビームを使用した非破壊元素分析が進歩しつつある。この方法では、サンプルに損傷を与えることなく、バルク材料の元素組成を決定するために使用できる。本研究では、ステンレス製の分析チャンバーに設置されたNWA482隕石の負ミュオン照射実験を行った。分析チャンバーにはヘリウムガスが充填され、空気散乱ミュオンによるバックグラウンド信号が抑制された。試料中のAl, Fe, Ca, Mg, Si, OからのミュオンX線は、分析チャンバーの周囲に配置された6つのゲルマニウム半導体検出器を使用して検出された。サンプルのX線自己吸収効果を補正するために、さらにGeant4ツールキットによるモンテカルロシミュレーションを使用した。シミュレーションからの補正を導入し、ミュオンX線測定の定量分析を行った。その結果、NWA482データに基づいて隕石中の各元素の分析感度を調べることに成功した。

Misassigned neutron resonances of Nd and stellar neutron capture cross sections

片渕 竜也*; 松橋 泰平*; 寺田 和司; 井頭 政之*; 水本 元治*; 廣瀬 健太郎; 木村 敦; 岩本 信之; 原 かおる*; 原田 秀郎; et al.

Physical Review C, 91(3), p.037603_1 - 037603_5, 2015/03

https://doi.org/10.1103/PhysRevC.91.037603

Time-of-flight spectra of the neutron capture events of Nd were measured using a spallation neutron source at the Japan Proton Accelerator Research Complex. The first six resonances of Nd reported in a previous work were not observed. The experimental results and cross-search of resonance energies in nuclear data libraries suggested that resonances of impurity nuclide Pr have been mistakenly assigned as Nd in the previous experiment. To investigate the impact of non-existence of the resonances to the s-process nucleosynthesis model, the Maxwellian averaged neutron capture cross sections with and without the misassigned resonances were compared.

Cross section measurement of Sn using ANNRI-NaI(Tl) spectrometer at J-PARC

廣瀬 健太郎; 古高 和禎; 原 かおる; 原田 秀郎; 木村 敦; 北谷 文人; 小泉 光生; 中村 詔司; 大島 真澄; 藤 暢輔; et al.

JAEA-Conf 2013-002, p.173 - 178, 2013/10

https://doi.org/10.11484/jaea-conf-2013-002

The cross section for Sn reaction has been measured in the neutron energy from 1eV to 1keV using the ANNRI-NaI(Tl) spectrometer at J-PARC/MLF. The sample used in the present experiment was metal tin enriched in Sn by 87%. The impurities of Sn and Sn were 9.3% and 3%, respectively. In the data analysis, the background of the frame-overlap neutrons and the scattered neutrons were subtracted. Comparison with the evaluation of JENDL-4.0 and ENDF/B-VII.1 will be presented in the poster session.

A Generalized conformational energy function of DNA derived from molecular dynamics simulations

山崎 智*; 寺田 透*; 清水 謙多郎*; 河野 秀俊; 皿井 明倫*

Nucleic Acids Research, 37(20), p.e135_1 - e135_9, 2009/09

https://doi.org/10.1093/nar/gkp718

Proteins recognize DNA sequences by two different mechanisms. The first is direct readout, in which recognition is mediated by direct interactions between the protein and the DNA bases. The second is indirect readout, which is caused by the dependence of conformation and the deformability of the DNA structure on the sequence. Various energy functions have been proposed to evaluate the contribution of indirect readout to the free-energy changes in complex formations. We developed a new generalized energy function to estimate the dependence of the deformability of DNA on the sequence. This function was derived from molecular dynamics (MD) simulations previously conducted on B-DNA dodecamers, each of which had one possible tetramer sequence embedded at its center. By taking the logarithm of the probability distribution function (PDF) for the base-step parameters of the central base-pair step of the tetramer, its ability to distinguish the native sequence from random ones was superior to that with the previous method that approximated the energy function in harmonic form. From a comparison of the energy profiles calculated with these two methods, we found that the harmonic approximation caused significant errors in the conformational energies of the tetramers that adopted multiple stable conformations.

Neutronics experiments for DEMO blanket at JAERI/FNS

佐藤 聡; 落合 謙太郎; 堀 順一; Verzilov, Y. M.; Klix, A.; 和田 政行*; 寺田 泰陽*; 山内 通則*; 森本 裕一*; 西谷 健夫

Nuclear Fusion, 43(7), p.527 - 530, 2003/07

https://doi.org/10.1088/0029-5515/43/7/303

原研FNSのDT核融合中性子線源を用いて、原型炉ブランケットに関する中性子工学実験を行った。ブランケット内トリチウム生成実験とシーケンシャル反応断面積測定実験を行った。「ブランケット内トリチウム生成実験」核融合原型炉の増殖ブランケット模擬体系積分実験を実施し、生成トリチウムに対する測定値と計算値の比較・検討を行った。モンテカルロ中性子輸送計算コードMCNPと核データJENDL-3.2による計算値は実験値より1.2~1.4倍過大評価であり、その原因解明のために、ベリリウムの(n, 2n)反応の二重微分断面積については再検討の必要性を示す結果が得られた。「シーケンシャル反応断面積測定実験」冷却水からの反跳陽子による冷却水配管表面のシーケンシャル反応率を、鉄,銅,チタン,バナジウム,タングステン,鉛に対して測定した。冷却水配管表面のシーケンシャル反応率は、材料自身のシーケンシャル反応率に比べて、一桁以上増加することを明らかにした。

D-T中性子照射による低放射化フェライト鋼F82Hの放射化特性の実験的研究

寺田 泰陽*; 落合 謙太郎; 佐藤 聡; 和田 政行*; Klix, A.; 山内 通則*; 堀 順一; 西谷 健夫

JAERI-Research 2002-019, 70 Pages, 2002/10

JAERI-Research-2002-019.pdf:8.47MB

低放射化フェライト鋼 F82Hは核融合炉の有力な構造材料である。核融合中性子源FNSを用いて、F82Hの放射化特性を得ることを目的として原型炉ブランケット模擬体系に対するD-T中性子照射試験を行い、F82Hシート,クロム箔,タングステン箔における放射性核種56Mn,54Mn,51Cr,187Wの生成反応率を測定した。併せて、評価済み核データJENDL-3.2とFENDL/E-2.0を用いてモンテカルロ輸送コードMCNPによる計算値との比較検討を行った。計算結果は、56Mn,54Mn,51Crともに10~20%程度の精度で測定結果と一致した。しかし、タングステンに関しては、30~40%の精度であることがわかった。また、タングステンの放射化断面積に使用する核データによって大きく計算結果が変わり、タングステンの中性子捕獲反応の共鳴領域における断面積評価に核データによって相違があることを示唆する結果となった。

Role of indirect readout in protein-DNA recognition assessed by a Bayesian approach

山崎 智*; 福井 一彦*; 河野 秀俊; 清水 謙多郎*; 皿井 明倫*; 寺田 透*

no journal, , 

Sequence-specific recognition of DNA by proteins plays a critical role in regulating gene expression. Accurate recognition is achieved by a combination of two different mechanisms. The first is direct readout, in which recognition is mediated by direct interactions between the protein and the DNA bases. The second is indirect readout, which is caused by the sequence-dependence of the conformation and deformability of the DNA structure. In our previous study, the contributions of indirect readout to binding affinity were evaluated for every tetrameric step in given protein-DNA complex structures. Using sequence-structure threading, potential energy differences between native and non-native tetrameric sequences for given tetrameric step conformation were compared. These potential energy functions were derived from the probability distribution function of its tetrameric step conformations calculated from trajectories of MD simulations of free DNAs which include all 136 types of tetramers. This gave good agreement with some experimental results, but shortage of structural sampling made the accurate estimation of distribution function difficult. In this work, we estimate the probability of occurrence of each tetrameric step sequence on given tetrameric step conformation using a Bayesian approach using the same structural dataset. We apply this approach to known protein-DNA complex structures, and assess the performance of predicting the sequence region where indirect readout makes important contribution to the binding affinity.

A New method for evaluating the specificity of indirect readout in protein-DNA recognition

山崎 智*; 寺田 透*; 河野 秀俊; 清水 謙多郎*; 皿井 明倫*

no journal, , 

Sequence-specific recognition of DNA by proteins plays a critical role in regulating gene expression. The accurate recognition of target sequences in the genome can be achieved by a combination of two different mechanisms: the direct readout through the direct interactions between protein and DNA bases; and the indirect readout through the sequence-dependent conformation and/or deformability of DNA structure. While the specificity of direct readout has been well characterized, it is rather difficult to assess the contribution of indirect readout to the specificity. In order to quantify the specificity of indirect readout, we have developed a new method. First, we used Bayesian statistics to derive the probability of a particular sequence for a given DNA structure using ensembles obtained by molecular dynamics (MD) simulations of DNAs containing all 136 unique tetramer sequences. Secondly, we used the information entropy to quantify the specificity of indirect readout. We applied this method to protein-DNA complexes of known structures to examine its validity. We could correctly predict those regions where experiments suggested the involvement of indirect readout, and could indicate new regions where the indirect readout mechanism can make major contributions to the recognition. The present probability/entropy-based approach has advantage over the previous energy-based approach in that the trajectories of MD simulation can be directly converted into the probability of sequence and the specificity of indirect readout without any approximation to the distributions in the conformational ensembles of DNA, and would serve as a powerful tool to study the mechanism of protein-DNA recognition.

パルスレーザー分光分析と狭隘部分ファイバスコープ観察の複合化

西村 昭彦; 伊東 富由美; 寺田 隆哉; 冨吉 健太郎; 岡 潔

no journal, , 

原子力分野におけるレーザープロセスの適用を進めている。特に、プラントの検査補修及び廃止措置において、超短パルスレーザーから高出力CWレーザーにかけて、各々のレーザー光と物質の特性に合わせた工学応用分野を推進している。高経年化する軽水炉の保守保全技術として、ナノ秒パルスレーザーを組み込んだ小型可搬の検査補修装置が有用である。これまで、レーザー光と画像の伝送を双方向に行える複合型光ファイバとナノ秒パルスレーザーを組合せることで、狭隘部分の観察とパルスレーザー分光分析がその場で行える装置概念について報告した。プラズマ生成が有効となる10GW/cm領域では、レーザー光伝送のための光学材料の耐性が装置開発の制限となる。現在、複合型光ファイバとパルスレーザー及び小型レーザートーチの組合せにより、配管内部を観察しレーザー分光が可能な試作機の開発に成功した。低クロム鋼,銅,アルミニウムなどの金属片をサンプルとして、元素分析のデモンストレーションに成功した。