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Recent HERMES Results on DVCS from Proton and Nuclear Targets

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原子核物理评论 2009年第S1期26卷 124-128页

作者： YE Hong-xue,MAO Ya-jun (school of physics and State Key Laboratory of Nuclear physics and Technology,peking university,beijing 100871,China) school of physics and State Key Laboratory of Nuclear physics and Technology Peking UniversityBeijing 100871China

Spin structure is one of the fundamental subjects in the study of nucleon structure. Recently it is found that Generalized Parton Distributions(GPDs) are related to the total angular momentum carried by partons,which offers a possible solution to the spin puzzle in the first time. We get access to certain GPDs by looking at the azimuthal angle asymmetries attributed to the interference between Deeply Virtual Compton Scattering(DVCS) and Bethe-Heilter processes in HERMES experiment. By measuring the asymmetry with respect to transverse target polarization from proton target,a model-dependent constraint on Ju vs Jd is obtained. Another worldwide unique channel is nuclear DVCS. The preliminary results on asymmetries with respect to beam spin and beam charge are reported.

关键词： GPDs DVCS TTSA nuclear DVCS

An eSnake model for medical image segmentation

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Progress in Natural Science:Materials International 2005年第5期15卷 424-429页

作者： Lv Hongyu1, YUAN Kehong2, BAO Shanglian1, ZU Donglin1 and DUAN Chaijie1*(1. The Research Center for Tumor Diagnosis and Therapeutical physics & beijing Key Laboratory of Medical physics and Engineering, beijing 100871, China 2. Key Laboratory of Pure and Applied Mathematics, school of Mathematical Sciences, peking university, beijing 100871, China) The Research Center for Tumor Diagnosis and Therapeutical physics & beijing Key Laboratory of Medical physics and Engineering Beijing 100871 China Key Laboratory of Pure and Applied Mathematics School of Mathematical Sciences Peking University Beijing 100871 China

A novel scheme of external force for detecting the object boundary of medical image based on Snakes (active contours) is introduced in the paper. In our new method, an electrostatic field on a template plane above the original image plane is designed to form the map of the external force. Compared with the method of Gradient Vector Flow (GVF), our approach has clear physical meanings. It has stronger ability to conform to boundary concavities, is simple to implement, and reliable for shape segmenting. Additionally, our method has larger capture range for the external force and is useful for medical image preprocessing in various applications. Finally, by adding the balloon force to the electrostatic field model, our Snake is able to represent long tube-like shapes or shapes with significant protrusions or bifurcations, and it has the specialty to prevent Snake leaking from large gaps on image edge by using a two-stage segmentation technique introduced in this paper. The test of our models proves that our methods are robust, precise in medical image segmentation.

关键词： image segmentation eSnake external force electrostatic field balloon force.

NUMERICAL APPLICATION OF THE RECURSION METHOD TO THE ELECTRONIC STRUCTURE OF C60

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原子与分子物理学报 1997年第3期 25-29页

作者： Lu Jing Zhang LiyuanDepartment of physics, peking university, beijing 100871, P.R.China

采用Ｒｅｃｕｒｓｉｏｎ方法计算了Ｃ６０分子的能态密度，所得的能隙、能级的简并度及顺序与ＬＤＡ方法或者解析方法得到的结果吻合。

关键词： C60 电子结构

Optical data storage in nonphotosensitive media by femtosecond laser pulses

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Progress in Natural Science:Materials International 2007年第8期17卷 877-880页

作者： Li Yan~(**) Liu Dayong Dou Yanping Yang Hong and Gong Qihuang (State Key Laboratory for Mesoscopic physics and Department of physics,peking university,beijing 100871,China) State Key Laboratory for Mesoscopic physics Department of Physics Peking University Beijing 100871 China

Ultrashort lasers have become powerful tools by inducing extremely nonlinear effects in a wide variety of materials. Femtosecond laser data storage in non-photosensitive media is promising for its high density and fast *** reviewed the progress of three types of femtosecond laser storage in transparent materials:three-dimensional bit-oriented storage by micro-voids,holographic data storage by two beam interference and storage by computer-generated holograms.

关键词： femtosecond laser three-dimensional data storage holographic data storage computer-generated hologram

β-decay studies of the neutron-rich ^(18,21)N isotopes

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Science China(physics,Mechanics & astronomy) 2011年第S1期54卷 53-60页

作者： HUA Hui, LI ZhiHuan, YE YanLin, JIANG Dongxing, LOU JianLing, LI XiangQing & XU FuRong school of physics and State Key Laboratory of Nuclear physics and Technology, peking university, beijing 100871, China 1. school of physics and State Key Laboratory of Nuclear physics and Technology Peking University Beijing 100871 China

The β-decay studies of neutron-rich 18,21N isotopes have been performed using β-n, β-γ, and β-n-γ coincidence methods. The 18,21N ions were produced by the fragmentation of the 22Ne and 26Mg beams, respectively, on a thick beryllium target. The time of flight of the emitted neutrons following the β-decay of 18,21N was measured by a neutron detector system with wide energy detection range and low-energy detection threshold. In addition, several clover germanium detectors were used to detect the β-delayed γ-rays. The half-lives of the β-decays of 18N and 21N were determined to be (619±2) ms and (82.9±7.5) ms, respec tively. Several new β-delayed neutron groups were observed with a total branching ratio of (6.98±1.46)% and (90.5±4.2)% for 18N and 21N, respectively. The level schemes of 18O and 21O were deduced. The experimental Gamow-Teller β-decay strengths of 18N and 21N to these levels were compared with the shell model calculations.

关键词： β-delayed neutron decay 18 21N neutron detector system branching ratio Gamow-Teller strength

Effects of diffusion time and diffusion gradient strength on the mean diffusivity of water molecules in healthy human brain

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Progress in Natural Science:Materials International 2006年第7期16卷 706-711页

作者： GAO Song, WANG Xiaoying and BAO Shanglian ( Laboratory of Medical physics & Engineering, peking university, beijing 100871, China Department of Radiology, The First Affiliated Hospital of peking university, beijing 100034, China) peking Univ Lab Med Phys & Engn Beijing 100871 Peoples R China peking Univ Affiliated Hosp 1 Dept Radiol Beijing 100034 Peoples R China

Diffusion time and diffusion gradient strength are two important parameters of pulsed gradient spin echo (PGSE) that is the most commonly used method in diffusion-weighted magnetic resonance imaging. However, the effects of the diffusion time on the mean diffusivity (MD) in previous studies are controversial. In this study, a new experimental protocol was designed to evaluate the effects of the two parameters on the results of PGSE. It was found that MD decreased significantly with the increased diffusion time or increased diffusion gradient strength, which cannot be explained by the previous theories. Through theoretical analysis, we found the flaw in the pulsed gradient spin echo (PGSE) method, which is the explanation for the controversial results of diffusion time obtained by oth- ers.

关键词： diffusion time diffusion gradient strength diffusion-weighted imaging diffusion tensor imaging mean diffusivity.

Identifying the northernmost summer monsoon location in East Asia

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Progress in Natural Science:Materials International 2007年第7期17卷 812-820页

作者： Hu Haoran~1 Qian Weihong~(2**) (1.Institute of Plateau Meteorology,CMA,Chengdu 610071,China 2.Monsoon and Environment Research Group,school of physics,peking university,beijing 100871,China) [a]Institute of Plateau Meteorology CMA Chengdu China [b]Monsoon and Environment Research Group School of Physics Peking University Beijing China

An integrated index which can be used to indicate the advance of subtropical summer monsoon in East Asia has been proposed in this *** index was comhined by three variables including precipitation,wind and pseudo-equivalent potential tempera- *** northernmost summer monsoon location(NSML)was identified by using this index *** was found that the NSML ex- perienced an interdecadal shift in the period 1977—1979 based on the annual index analysis from 1961 to 2001.A comparison of the NSML with other four summer monsoon indices has also been *** result showed that the NSML could well represent the interan- nual and interdecadal variability of summer monsoon precipitation in North China(beyond 35°N),while other four indices could well indi- cate the precipitation anomalies of East Asian summer monsoon along the Yangtze River valley(around 30°N).

关键词： subtropical summer monsoon northernmost location index,interdecadal variability East Asia

Polyelectrolyte Complexes and Coacervates Formed by De novo-Designed Peptides and Oligonucleotide

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Chinese Journal of Polymer Science 2024年第9期42卷 1333-1340,I0007页

作者： Tian-Hao ren De-Hai Liang beijing National Laboratory for Molecular Sciences Department of Polymer Science and Engineering and the Key Laboratory of Polymer Chemistry and Physics of the Ministry of EducationCollege of Chemistry and Molecular EngineeringPeking UniversityBeijing100871China

The liquid-liquid phase separation of biopolymers in living cells contains multiple interactions and occurs in a dynamic *** the regulation mechanism is still a *** this work,we designed a series of peptides(XXLY)_(6)SSSGSS and studied their complexation and coacervation behavior with single-stranded ***“X”and“Y”are varied to combine known amounts of charged and non-charged amino acids,together with the introduction of secondary structures and pH *** show that the electrostatic interaction,which is described as charge density,controls both the strength of complexation and the degree of chain relaxation,and thus determines the growth and size of the *** hydrophobic interaction is prominent when the charges are ***,the secondary structures of peptides exhibit profound effect on the morphology of the phases,such as solid phase to liquid phase *** study gains insight into the phase separation under physiological *** is also helpful to create coacervates with desirable structures and functions.

关键词： Polyelectrolyte complex Coacervate Peptides Secondary structure Electrostatic interaction

A modified soft docking method for proteins and peptides

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Chinese Chemical Letters 1997年第7期8卷 615-618页

作者： Jun Mei WANG Li Rong CHEN Fan JING Xiao Jie XU(Department of chemistry and Weixin Institute of Natural Medicine,peking university, beijing 100871)(Department of Technical physics, peking university, beijing 100871)(Department of Biophysics, university beijing UNIV DEPT CHEM BEIJING 100871 PEOPLES R CHINA beijing UNIV WEIXIN INST NAT MED BEIJING 100871 PEOPLES R CHINA beijing UNIV DEPT TECH PHYS BEIJING 100871 PEOPLES R CHINA UNIV ROCHESTER DEPT BIOPHYS ROCHESTER NY 14642 USA

A modified two-stage soft-docking procedure was developed for the theoretic researches on the recognition of protein-protein or protein-peptide complexes. Some systems have been used to test our program and the result... 详细信息

关键词： A modified soft docking method for proteins and peptides