Feng-Shou Zhang

Nuclear symmetry energy at subnormal densities from measured nuclear masses

The symmetry energy coefficients for nuclei with mass number A = 20-250 are extracted from more than 2000 measured nuclear masses. With the semiempirical connection between the symmetry energy coefficients of finite nuclei and the nuclear symmetry energy at reference densities, we investigate the density dependence of the symmetry energy of nuclear matter at subnormal densities. The obtained results are compared with those extracted from other methods.

125I labelling of human serum albumin and fibrinogen and a study of protein adsorption properties on the surface of titanium oxide film

In order to detect the surface concentration of proteins adsorbed on a solid surface for selecting blood compatible materials, a gentle iodination reagent, Iodogen, was used to label human serum albumin and fibrinogen, and has been applied to the study of protein adsorption properties on a plate of titanium oxide film. The yields of the labelled albumin and fibrinogen are 69.7% and 49.6%. The results of adsorption show that [125I]HSA and [125I]HFG are efficacious at the surface concentration detection and can be used to investigate the protein adsorption properties of a solid material.

Understanding transport simulations of heavy-ion collisions at 100A and 400A MeV: Comparison of heavy-ion transport codes under controlled conditions

Transport simulations are very valuable for extracting physics information from heavy-ion-collision experiments. With the emergence of many different transport codes in recent years, it becomes important to estimate their robustness in extracting physics information from experiments. We report on the results of a transport-code-comparison project. Eighteen commonly used transport codes were included in this comparison: nine Boltzmann-Uehling-Uhlenbeck-type codes and nine quantum-molecular-dynamics-type codes. These codes have been asked to simulate Au + Au collisions using the same physics input for mean fields and for in-medium nucleon-nucleon cross sections, as well as the same impact parameter, the similar initialization setup, and other calculational parameters at 100 A and 400 A MeV incident energy. Among the codes we compare one-body observables such as rapidity and transverse flow distributions. We also monitor nonobservables such as the initialization of the internal states of colliding nuclei and their stability, the collision rates, and the Pauli blocking. We find that not completely identical initializations may have contributed partly to different evolutions. Different strategies to determine the collision probabilities and to enforce the Pauli blocking also produce considerably different results. There is a substantial spread in the predictions for the observables, which is much smaller at the higher incident energy. We quantify the uncertainties in the collective flow resulting from the simulation alone as about 30% at 100 A MeV and 13% at 400 A MeV, respectively. We propose further steps within the code comparison project to test the different aspects of transport simulations in a box calculation of infinite nuclear matter. This should, in particular, improve the robustness of transport model predictions at lower incident energies, where abundant amounts of data are available.

Dynamical analysis on heavy-ion fusion reactions near Coulomb barrier

The shell correction is proposed in the improved isospin dependent quantum molecular dynamics (ImIQMD) model, which plays an important role in heavy-ion fusion reactions near Coulomb barrier. By using the ImIQMD model, the static and dynamical fusion barriers, dynamical barrier distribution in the fusion reactions are analyzed systematically. The fusion and capture excitation functions for a series of reaction systems are calculated and compared with experimental data. It is found that the fusion cross sections for neutron-rich systems increase obviously, and the strong shell effects of two colliding nuclei result in a decrease of the fusion cross sections at the sub-barrier energies. The lowering of the dynamical fusion barriers favors the enhancement of the sub-barrier fusion cross sections, which is related to the nucleon transfer and the neck formation in the fusion reactions.

On the formation of transient (Na19)2 and (Na20)2 cluster dimers from molecular dynamics simulations

Abstract By using distance-dependent tight-binding molecular dynamics simulations, we discuss the possibilities to form (Na 19 ) 2 and (Na 20 ) 2 cluster dimers in sodium cluster-cluster collisions. In the case of Na 19 +Na 19 , we show that the formation of a prolate dimer-like (Na 19 ) 2 may depend on the initial relative orientations of the colliding clusters. A similar study for Na 20 +Na 20 does not seen to show the same dependence on the initial orientations in the formation of the (Na 20 ) 2 cluster dimer.

Boltzmann-Langevin equation, dynamical instability and multifragmentation

Abstract By using simulations of the Boltzmann-Langevin equation which incorporates dynamical fluctuations beyond usual transport theories and by coupling it with a coalescence model, we obtain information on multifragmentation in heavy-ion collisions. From a calculation of the 40 Ca+ 40 Ca system, we can compute with confidence physical observables related to recent multifragmentation data.

Production of heavy neutron-rich nuclei in transfer reactions within the dinuclear system model

The dynamics of nucleon transfer processes in heavy-ion collisions is investigated within the dinuclear system model. The production cross sections of nuclei in the reactions 136Xe+208Pb and 238U+248Cm are calculated, and the calculations are in good agreement with the experimental data. The transfer cross sections for the 58Ni+208Pb reaction are calculated and compared with the experimental data. We predict the production cross sections of neutron-rich nuclei Eu, Tb, Ho, and based on the reaction 176Yb+238U. It can be seen that the production cross sections of the neutron-rich nuclei 165Eu, 169Tb, 173Ho, and 181Yb are 2.84 ?b, 6.90 ?b, 46.24 ?b, and 53.61 ?b, respectively, which could be synthesized in experiment.

Isospin dependence of radial flow in heavy-ion collisions at intermediate energies

Within the framework of an isospin-dependent quantum molecular dynamics model, the radial flows from the central collisions of Ba-124 + Ba-124 and Sn-124 + Sn-124 are studied at different incident energies. It is found that the more neutron-rich system exhibits smaller radial flow and it is shown that the radial flow is sensitive to the nucleon-nucleon cross sections and independent of the nuclear symmetry energy. It suggests that the experimental measurement of the radial flow for reaction systems with different ratios of neutron to proton provide a novel recipe for determining the isospin dependent in-medium nucleon-nucleon cross sections

Vibrational properties of sodium microclusters

The structural and vibrational properties of Na-n (n = 2-8) The structural and vibrational properties of Na-n (n = 2-8)

Detection of Changes in DNA Methylation Induced by Low-Energy Ion Implantation in Arabidopsis thaliana

Abstract This study evaluated changes in DNA methylation in Arabidopsis thaliana plants grown from seeds implanted with low-energy N+ and Ar+ ions. Methylation-sensitive amplified polymorphism (MSAP) testing revealed altered DNA methylation patterns after ion implantation at doses of 1 × 1014 to 1 × 1016 ions/cm2. Comparison of the MSAP electrophoretic profiles revealed nine types of polymorphisms in ion-implanted seedlings relative to control seedlings, among which four represented methylation events, three represented demethylation events, and the methylation status of two was uncertain. The diversity of plant DNA methylation was increased by low-energy ion implantation. At the same time, total genomic DNA methylation levels at CCGG sites were unchanged by ion implantation. Moreover, a comparison of polymorphisms seen in N+ ion-implanted, Ar+ ion-implanted, and control DNA demonstrated that the species of incident ion influenced the resulting DNA methylation pattern. Sequencing of eight isolated fragments that showed different changing patterns in implanted plants allowed their mapping onto variable regions on one or more of the five Arabidopsis chromosomes; these segments included protein-coding genes, transposon and repeat DNA sequence. A further sodium bisulfite sequencing of three fragments also displayed alterations in methylation among either different types or doses of incident ions. Possible causes for the changes in methylation are discussed.