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論文

Classifying and assembling two-dimensional X-ray laser diffraction patterns of a single particle to reconstruct the three-dimensional diffraction intensity function; Resolution limit due to the quantum noise

徳久 淳師*; 高 潤一郎*; 河野 秀俊; 郷 信広*

Acta Crystallographica Section A, 68(3), p.366 - 381, 2012/05

 被引用回数:19 パーセンタイル:81.39(Chemistry, Multidisciplinary)

A new two-step algorithm is developed for reconstructing three-dimensional diffraction intensity of a globular biological macromolecule from many experimentally measured quantum-noise limited two-dimensional (2D) X-ray laser diffraction patterns, each for unknown orientation. First step is a classification of 2D patterns into groups according to similarity of direction of incident X-ray with respect to the molecule and an averaging within each group to reduce the noise. Second is a detection of common intersecting circles between the signal-enhanced 2D patterns to identify their mutual location in the 3D wave-number space. The newly developed algorithm enables to detect signal for classification in such a noisy experimental photon-count data as low as $$sim$$0.1 photons per effective pixel. Wavenumber of such a limiting pixel determines the attainable structural resolution. From this fact, resolution attainable by this new method of analysis as well as two important experimental parameters, the number of 2D patterns to be measured (load for detector) and the number of pairs of 2D patterns to be analyzed (load for computer), are derived as a function of intensity of incident X-ray and quantities characterizing the target molecule.

論文

Anomalous metallic state in the vicinity of metal to valence-bond solid insulator transition in LiVS$$_{2}$$

片山 尚幸*; 内田 正哉*; 橋爪 大輔*; 新高 誠司*; 松野 丈夫*; 松村 大樹; 西畑 保雄; 水木 純一郎; 竹下 直*; Gauzzi, A.*; et al.

Physical Review Letters, 103(14), p.146405_1 - 146405_4, 2009/10

 被引用回数:49 パーセンタイル:87.07(Physics, Multidisciplinary)

三角格子を持ち、価電子結合固体状態を持つことで知られるLiVS$$_{2}$$とLiVSe$$_{2}$$について研究を行った。金属と強相関系絶縁体の境目にあるLiVS$$_{2}$$は、金属から価電子結合固体絶縁体への転移を305Kにて示した。金属-絶縁体転移の近傍で価電子結合固体状態が観測されたことは、価電子結合固体状態を考える際の電子の遍歴性の重要さを示している。高温金属層に見られる擬ギャップ状態についても議論を行った。また、LiVSe$$_{2}$$は2Kまで金属状態であった。

論文

Growth of ferroelectric bismuth lanthanum nickel titanate thin films by RF magnetron sputtering

小舟 正文*; 福島 浩次*; 山路 徹*; 多田 英人*; 矢澤 哲夫*; 藤澤 浩訓*; 清水 勝*; 西畑 保雄; 松村 大樹; 水木 純一郎; et al.

Journal of Applied Physics, 101(7), p.074110_1 - 074110_6, 2007/04

 被引用回数:8 パーセンタイル:34.47(Physics, Applied)

高周波マグネトロンスパッタリングにより、Pt(100)/MgO(100)基板上に作製したビスマスランタンニッケル酸化物薄膜(Bi$$_{1-x}$$La$$_{x}$$)(Ni$$_{0.5}$$Ti$$_{0.5}$$)O$$_{3}$$(BLNT)のエピタキシャル成長、構造特性、誘電特性について、X線回折、透過型電子顕微鏡、ヒステリシスループ測定によって調べられた。強誘電的BLNTはx$$geq$$0.3でc軸配向し、単結晶の正方晶構造が現れる。c/aはLaの濃度が増えるにつれて1.004から1.028に変化する。成長方向の周りに4回対称性が見られた。X線異常散乱とX線吸収スペクトルの結果より、Biはペロブスカイト構造のAを+3価で占有していることが確かめられた。12$$mu$$C/cm$$^{2}$$の大きな残留分極の値が得られた。

口頭

新クロスオーバ研究,7; 放射光を用いた核燃料模擬物質セリアの重イオン照射効果の研究

大野 裕隆*; 前田 修大*; 中川 将*; 図子 善大*; 岩瀬 彰宏*; 馬場 祐治; 平尾 法恵*; 石川 法人; 知見 康弘; 左高 正雄; et al.

no journal, , 

核燃料中の核分裂片による損傷を評価するために、UO$$_{2}$$の模擬物質CeO$$_{2}$$への重イオン照射効果をX線吸収分光法により評価した。3keV Ar照射実験及び放射光を利用したX線吸収分光測定の結果、照射によって弾性的はじき出しを介して酸素がはじき出され、Ceの電荷が4+から3+に変化することを明らかにした。

口頭

単分子X線回折像からの立体構造決定法の理論的研究

徳久 淳師; 高 潤一郎; 森林 健悟; 乙部 智仁; 甲斐 健師; 中村 龍史; 福田 祐仁; 河野 秀俊; 郷 信広

no journal, , 

A promising tool for 3D-structural determination from a single-molecule without crystallized is X-ray free electron lasers (XFELs), which are now under construction in Europe, USA and Japan, independently. Our final goal is to develop a computational method for the determination of single-molecule 3D-strucures and to suggest feasible parameters of the target molecule and the XFEL device. When a molecule is irradiated by a coherent X-ray pulse with an ultrashort duration time and an extremely high intensity, a continuous diffraction pattern (2D speckle pattern) is observed. It is necessary to collect many 2D speckle patterns from different orientations of the molecule to obtain information sufficient for the structure determination. In the meeting, we present our strategy for determining 3D structures of biomolecules and suggest some critical parameters of the XFEL device and the target molecules required for realizing the 3D structure determination.

口頭

Theory of single molecule imaging by X-ray free-electron laser

徳久 淳師; 高 潤一郎; 河野 秀俊; 郷 信広*

no journal, , 

New light sources of X-ray free-electron laser (XFEL) are under construction in Europe, USA and Japan. XFEL offers a new possibility in imaging single biological macromolecules. Our goal is to develop a computational method for the determination of molecule 3D structures from diffraction intensity data by XFEL. A straight forward procedure would be (1) to classify and average 2D diffraction patterns to improve the S/N ratio, (2) to obtain a 3D diffraction pattern by determining the relative positions of averaged-2D-images and (3) to retrieve the phases and construct the 3D structure using the over-sampling method. One of the big problems is the quantum noise resulting from the extremely weak intensity of elastically diffracted X-ray. Algorithms for structure determination must be developed to process the experimental data immersed in the quantum noise. In this meeting we report detailed procedures of analysis of experimental diffraction intensity data to be obtained 3D structure.

口頭

Estimation of attainable structural resolution by computer simulation for single biomolecule imaging with X-ray Free Electron Laser

徳久 淳師*; 甲斐 健師; 高 潤一郎*; 河野 秀俊; 郷 信広*

no journal, , 

XFEL can potentially offer a new mean for single biomolecule 3D-imaging. Measured intensity, which is a 2D diffraction pattern per one observation without phase information is extremely weak even using XFEL because sample is a single molecule in a single shot and incident intensity of XFEL cannot make stronger than a certain intensity due to suppress molecule decay. Under such experimental conditions, we consequently have to use extremely weak signals effectively to reconstruct a 3D molecule structure using multiply measured many 2D diffraction patterns. We have developed a two-step algorithm for reconstructing a 3D diffraction intensity data from many experimentally measured, quantum-noise limited 2D patterns of single molecule with unknown orientation. Once a 3D diffraction intensity data of a molecule obtained, the 3D structure can be obtained by applying oversampling method to the data. The developed algorithm enables us to detect as low as 0.1 photons per an effective pixel as signal for the classification in such a noisy experimental photon-count data. Theoretically, wave-number of a pixel giving such a limiting photon-count defines the attainable structural resolution.

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