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Relaxation Property and Stability Analysis of the Quasispecies Models

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Communications in Theoretical Physics 2009年第10期52卷 726-734页

作者： FEGN Xiao-Li LI Yu-Xiao GU Jian-Zhong ZHUO Yi-Zhong School of Physical Engineering Zhengzhou University Zhengzhou 450052 China Center for Computational and System Biology Institute of Biophysics Chinese Academy of Science Beijing 100101 China china Institute of Atomic Energy P.O. Box 275（18） Beijing 102413 China Center of Theoretical Nuclear Physics National Laboratory of Heavy Ion Accelerator of Lanzhou Lanzhou 730000 China

The relaxation property of both Eigen model and Crow-Kimura model with a single peak fitness landscape is studied from phase transition point of view. We first analyze the eigenvalue spectra of the replication mutation matrices. For sufficiently long sequences, the almost crossing point between the largest and seeond-largest eigenvalues locates the error threshold at which critical slowing down behavior appears. We calculate the critical exponent in the limit of infinite sequence lengths and compare it with the result from numerical curve fittings at sufficiently long sequences. We find that for both models the relaxation time diverges with exponent 1 at the error （mutation） threshold point. Results obtained from both methods agree quite well. From the unlimited correlation length feature, the first order phase transition is further confirmed. Finally with linear stability theory, we show that the two model systems are stable for all ranges of mutation rate. The Igigen model is asymptotically stable in terms of mutant classes, and the Crow-Kimura model is completely stable.

关键词： relaxation time critical exponent error threshold

Application of the SCC method to the multi-O(4) model:The collective Hamiltonian

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Science china(Physics,Mechanics & Astronomy) 2009年第10期52卷 1518-1529页

作者： KOBAYASI Masato Department of Physics Graduate School of ScienceKyoto University Advancesoft Center for Collaborative ResearchUniversity of Tokyo

The collective Hamiltonian up to the fourth order for a multi-O(4) model is derived for the first time based on the self-consistent collective-coordinate(SCC) method,which is formulated in the framework of the time-dependent Hartree-Bogoliubov(TDHB) *** collective Hamiltonian is valid for the spherical case where the HB equilibrium point of the multi-O(4) model is spherical as well as for the deformed case where the HB equilibrium points are *** validity is tested numerically in both the spherical and deformed *** simulations indicate that the low-lying states of the collective Hamiltonian and the transition amplitudes among them mimic fairly well those obtained by exactly diagonalizing the Hamiltonian of the multi-O(4) *** numerical results for the deformed case imply that the "optimized RPA boundary condition" is also valid for the well-known η*,η expansion around the unstable HB point of the multi-O(4) *** these illuminate the power of the SCC method.

关键词： self-consistent collective-coordinate method multi-O(4) model time-dependent Hartree-Bogoliubov theory collective Hamiltonian

Determination of the Astrophysically Relevant ~6Li(n,γ)~7Li Cross Sections from the ~7Li(~6Li,~7Li)~6Li Elastic-Transfer Reaction

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Plasma Science and Technology 2012年第5期14卷 364-366页

作者：苏俊李志宏郭冰白希祥李志常刘建成王友宝连钢曾晟王宝祥颜胜权李云居李二涛樊启文柳卫平 china Institute of Atomic Energy

Angular distributions for the 7^Li（6^Li, 7^Li）6^Li elastic-transfer reaction have been measured with the Q3D magnetic spectrograph at the HI-13 tandem accelerator of Beijing, china. The neutron spectroscopic factors of 7^Li are derived by comparing the calculated differential cross sections, which are obtained through the distorted-wave Born approximation （DWBA） calculation, to the experimental data. And these spectroscopic factors are then used to deduce the direct capture cross sections in 6^Li（n, γ）TLi at energies of astrophysical relevance.

关键词： elastic-transfer reaction spectroscopic factor Big Bang nucleosynthesis

Breakup Effect of Weakly Bound Projectile on the Barrier Distribution Around Coulomb Barrier

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Plasma Science and Technology 2012年第5期14卷 390-392页

作者：贾会明林承键张焕乔刘祖华喻宁杨峰徐新星贾飞吴振东张世涛 china Institute of Atomic Energy

The excitation function of quasi-elastic （QEL） scattering at a backward angle has been measured for 9^Be＋208^Pb. The barrier distribution was extracted by means of the first derivative of the measured excitation function and calculated with the coupled-channel model. The present work shows that the experimental barrier distribution extracted from QEL scattering is shifted to the low energy side by 1.5 MeV as compared with the theoretical one. This energy discrepancy indicates that breakup is important in the colliding processes of the weakly bound nucleus system.

关键词： quasi-elastic scattering barrier distribution coupled-channel model

Indirect Measurement of Astrophysical ^(13)C(α,n)^(16)O S-Factors

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Plasma Science and Technology 2012年第5期14卷 357-359页

作者：郭冰李志宏李云居苏俊白希祥陈永寿樊启文金孙均李二涛李志常连钢刘鑫刘建成舒能川王宝祥王友宝颜胜权曾晟柳卫平庞丹阳 M. LUGARO J. BUNTAIN china Institute of Atomic Energy School of Physics and State Key Laboratory of Nuclear Physics and Technology Peking University Center for Stellar and Planetary Astrophysics Monash University

The 13^C（a, n）160 reaction is believed to be the main neutron source reaction for the s-process in asymptotic giant branch （AGB） stars. The astrophysical S-factors of this reaction have been determined based on an evaluation of the a spectroscopic factor of the 1/2＋ subthreshold state in 17^O （Ex = 6.356 MeV） by using the 13^C（11^B, 7^Li）17^O a transfer reaction. Our result confirms that the 1/2＋ subthreshold resonance is dominant for the 13^C（a, n）16^O reaction at low energies of astrophysical interest.

关键词： transfer reaction elastic scattering s-process

Experimental Study of Two-Alpha Emission from High-Lying Excited States of ^(17,18)Ne

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Plasma Science and Technology 2012年第5期14卷 371-374页

作者：徐新星林承键贾会明杨峰贾飞吴振东张世涛刘祖华张焕乔徐瑚珊孙志宇王建松胡正国王猛陈若富张雪荧李琛雷祥国徐治国肖国青 china Institute of Atomic Energy Institute of Modern Physics Chinese Academy of Sciences

The experiments of two-alpha emission from 17,18^Ne excited levels were performed at the HIRFL-RIBLL facility of the Institute of Modern Physics, Lanzhou. The beams of 17^Ne at the energy of 49.9 MeV/u and lSNe at 51.8 MeV/u bombarded a 197Au target to populate excited states of 17,18^Ne via Coulomb excitation. Complete kinematics measurements were achieved by the detectors of a silicon strip and CsI＋PIN array. The experimental results combined with simple MC simulations show the characteristic of sequential two-alpha emission via 140 excited states for lSNe. The results of two-alpha emission from 17^Ne are preliminary and need further analyses.

关键词： two-alpha emission Coulomb excitation complete kinematics measurements,sequential emission

Excited States in ^18Ne Studied via ^17F＋p

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Chinese Physics Letters 2010年第3期27卷 96-99页

作者：金孙均王友宝王宝祥白希祥方晓郭冰李二涛李云居李志宏连钢苏俊颜胜权曾晟姚泽恩柳卫平 china Institute of Atomic Energy PO Box 275(46) Beijing 102413 School of Nuclear Science and Technology Lanzhou University Lanzhou 730000

The elastic resonance scattering of ^17F＋p is studied in inverse kinematics via a thick-target method. The excitation function for ^17F＋p elastic scattering is obtained within the energy interval of Ec.m ≈ 0.4-1.7 MeV. The experimental excitation function is analyzed with a multilevel R-matrix code MULTI7, and the proton widths are deduced. The α decay from 6.15 MeV 1- state in 18Ne is observed, which is critical to the 14O（α, p）17F reaction as the main breakout route from CNO cycle to rp-process in supernovae and x-ray bursts.

关键词： Nuclear physics Astrophysics and astroparticles

Neutron Spectroscopic Factors of ^7Li and Astrophysical ^6Li（n,γ）^7Li Reaction Rates

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Chinese Physics Letters 2010年第5期27卷 54-57页

作者：苏俊李志宏郭冰白希祥李志常刘建成王友宝连钢曾晟王宝祥颜胜权李云居李二涛樊启文柳卫平 china Institute of Atomic Energy PO Box 275(10) Beijing 102413

Angular distributions of the ^7Li（^6Li, ^6Li）^7Li elastic scattering and the ^7Li（^6Li, ^7Lig.s.）^6Li, ^7Li（^6Li, ^7Li0.48）^6Li transfer reactions at Ec.m. = 23.7 MeV are measured with the Q3D magnetic spectrograph. The optical potential of ^6Li ＋ ^7Li is obtained by fitting the elastic scattering differential cross sections. Based on the distorted wave Born approximation （DWBA） analysis, spectroscopic factors of ^7Li =^6Li n are determined to be 0.73 ± 0.05 and 0.90 ± 0.09 for the ground and first exited states in ^7Li, respectively. Using the spectroscopic factors, the cross sections of the ^6 Li（n, γ0,1）^7 Li direct neutron capture reactions and the astrophysical ^6Li（n, γ）^7 Li reaction rates are derived.

关键词： Spectral analysis

Yrast Properties of Dysprosium Isotopes in the Double Mid-Shell Region

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Chinese Physics Letters 2010年第1期27卷 78-81页

作者：邹文华顾建中 School of Nuclear Engineering and Technology East China Institute of Technology Fuzhou 344000 china Institute of Atomic Energy PO Box 275(18) Beijing 102413 Center of Theoretical Nuclear Physics National Laboratory of Heavy Ion Accelerator of Lanzhou Lanzhou 730000

The yrast bands of the even-even dysprosium isotopes 164-174Dy are calculated up to high angular momentum 34h based on the projected shell model. Our calculations are in good agreement with the experiments quantitatively. They predict that an energy minimum of the first 2＋ state in these isotopes exists around the neutron mid-shell N=104, implying the maximum collectivity in 66170Dy104, however, the energy ratio R4=E（4＋1）/E（2＋1） reaches a saturation at N=102. Meanwhile, the back-bending plots of these yrast bands are examined carefully. It is found that the sharpness of the back-bending has a gradual shift along the dysprosium isotopic chain, namely, the slope of the back-bending becomes steeper as the neutron number increases except for an irregularity of a decreasing dip angle in the double mid-shell nucleus 170Dy. We suggest that 170Dy undergoes a dual alignment with midshell high-j protons and neutrons aligning simultaneously at spin I≈16h, which probably results in the distinctive back-bending behavior.

关键词： DYSPROSIUM ISOTOPES ANGULAR momentum (Nuclear physics) ENERGY levels (Quantum mechanics) NEUTRONS NUCLEAR models