The shear viscosity (η) and entropy density (s) are studied for the central Au+Au collisions with the help of a microscopic transport model,namely the isospin-dependent quantum molecular dynamic model (IQMD).Employ the formula given in Ref.[1],η is calculated as a time dependent variable for different incident energies from 40 MeV/u to 120 MeV/u and the energy dependence of η/s of nuclear matter in the most compressed stage in collision process is displayed.
Shear viscosity (η) is a basic transport coefficient of the medium.In this work,we calculate shear viscosity to entropy density ratio (η/S) of an equilibrated system in intermediate energy heavy ion collisions within the framework of the Boltzmann-Uehling-Uhlenbeck model (BUU) model.After the equilibration of Au + Au system at central collision in a fixed volume is reached,temperature,pressure and energy density are extracted by the phase space information and then η/S is calculated using the Green-Kubo formulas.The results show that η/S drops with the incident energy and its value is not so drastically different from the RHIC results.
Assuming a core plus valence nucleon structure, one-nucleon removal reaction is investigated within the framework of few-body Glauber theory. Fermi-type distribution is used for the core density, while the wavefunction of the valence nucleon is calculated by solving the single particle eigenvalue problem of the Schrdinger equation with the Woods-Saxon potential. The parallel momentum distribution (P//) of the fragments is calculated for isotopes with 3 < Z < 18. A remarkable scaling property is observed from the dependence of the dimensionless quantity Rv2/Rc2 on the full width at half maximum of the parallel momentum distribution (FWHMP//). Rv2/Rc2 is a measure of the exotic extent of the nuclear halo. Based on the obtained scaling law, FWHMP// can be used as an experimental observable to extract Rv2/Rc2 and measure the exotic extent for the nuclear halo.
With large-scale production and application at large scale, carbon nanotubes (CNTs) may cause ad-verse response to the environment and human health. Thus, study on bio-effects and safety of CNTs has attracted great attention from scientists and governments worldwide. This report briefly summa-rizes the main results from the in vitro toxicity study of CNTs. The emphasis is placed on the descrip-tion of a variety of factors affecting CNTs cytotoxicity, including species of CNTs, impurities contained, lengths of CNTs, aspect ratios, chemical modification, and assaying methods of cytotoxicity. However, experimental information obtained thus far on CNTs' cytotoxicity is lacking in comparability, and some-times there is controversy about it. In order to assess more accurately the potential risks of CNTs to human health, we suggest that care should be taken for issues such as chemical modification and quantitative characterization of CNTs in cytotoxicity assessment. More importantly, studies on physical and chemical mechanisms of CNTs' cytotoxicity should be strengthened; assaying methods and evaluating criteria characterized by nanotoxicology should be gradually established.
ZHU Ying1,2 & LI WenXin1 1 Laboratory of Nano-biology and Medicine, Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201800, China
The correlation between neutron-to-proton yield ratio (Rnp) and neutron skin thickness (δnp) in neutron-rich projectile induced reactions is investigated within the framework of the Isospin-Dependent Quantum Molecular Dynamics (IQMD) model. The density distribution of the Droplet model is embedded in the initialization of the neutron and proton densities in the present IQMD model. By adjusting the diffuseness parameter of neutron density in the Droplet model for the projectile, the relationship between the neutron skin thickness and the corresponding Rnp is obtained. The results show strong linear correlation between Rnp and δnp for neutron-rich Ca and Ni isotopes. It is suggested that Rnp may be used as an experimental observable to extract δnp for neutron-rich nuclei, which is very interesting in the study of the nuclear structure of exotic nuclei, the equation of state (EOS) of asymmetric nuclear matter and neutron-rich matter in astrophysics, etc.
The isoscaling behavior in the reaction system of 58,64Ni + 9Be has been studied by using the heavy-ion phase-space exploration(HIPSE) model. The extracted isoscaling parameters α and β for both heavy and light fragments for HIPSE model calculations are in good agreement with recent experimental data. The investigation shows that the parameters in the HIPSE model have some effect on the isoscaling parameter. The isoscaling parameters for hot and cold fragments have been extracted.
