Neutron dose measurement in carbon ion radiation therapy at HIRFL (IMP)

For radiation protection purposes, the neutron dose in carbon ion radiation therapy at the HIRFL (Heavy Ion Research Facility in Lanzhou) was investigated. The neutron dose from primary C-12 ions with a specific energy of 100 MeV/u delivered from SSC was roughly measured with a standard Anderson-Broun rem-meter using a polyethylene target at various distances. The result shows that a maximum neutron dose contribution of 19 mSv in a typically surface tumor treatment was obtained, which is less than 1% of the planed heavy ion dose and is in reasonable agreement with other reports. Also the gamma-ray dose was measured in this experiment using a thermo luminescent detector.

Two-quasiparticle K-isomeric states in strongly deformed neutron-rich Nd and Sm isotopes: a projected shell-model analysis

Motivated by recent spectroscopy data from fission experiments, we apply the projected shell model to study systematically the structure of strongly deformed, neutron-rich, even-even Nd and Sm isotopes with neutron number from 94 to 100. We perform calculations for rotational bands up to spin I = 20 and analyze the band structure of low-lying states with quasiparticle excitations, with emphasis given to rotational bands based on various negative-parity two-quasiparticle (2-qp) isomers. Experimentally known isomers in these isotopes are described well. The calculations further predict proton 2-qp bands based on a 5(-) and a 7(-) isomer and neutron 2-qp bands based on a 4(-) and an 8(-) isomer. The properties for the yrast line are discussed, and quantities to test the predictions are suggested for future experiment.

CONSISTENT THREE-BODY FORCE WITH BONN B POTENTIAL AND NEUTRON STAR STRUCTURE

Microscopic three-nucleon force consistent with the Bonn B two-nucleon potential is constructed, which includes Delta(1232), Roper, and nucleon-antinucleon excitation contributions. Recent results for the choice of the meson parameters are discussed. The forces are used in Brueckner calculations and the saturation properties of nuclear matter are determined. At the high densities,the nuclear equation of state and the symmetry energy are calculated. The corresponding neutron star mass-radius relations are presented.

TRITON-(HE)-H-3 RELATIVE AND DIFFERENTIAL FLOWS AND THE HIGH DENSITY BEHAVIOR OF NUCLEAR SYMMETRY ENERGY

Using a transport model coupled with a phase-space coalescence after-burner we study the triton-He-3 relative and differential transverse flows in semi-central Sn-132 + Sn-124 reactions at a beam energy of 400 MeV/nucleon. We find that the triton-He-3 pairs carry interesting information about the density dependence of the nuclear symmetry energy. The t-He-3 relative flow can be used as a particularly powerful probe of the high-density behavior of the nuclear symmetry energy.

Effects of pH on the Interactions and Conformation of Bovine Serum Albumin: Comparison between Chemical Force Microscopy and Small-Angle Neutron Scattering

The conformation of bovine serum albumin (BSA), as well as its interactions with negatively charged mica surfaces in saline solutions of different pH values, have been studied by small-angle neutron scattering (SANS) and chemical force microscopy (CFM), respectively. A new approach to extract the contribution of elementary interactions from the statistically averaged force-extension curves through self-consistent fitting was proposed and used to understand the effects of pH on the interactions and conformation of BSA in saline solutions. When pH increases, the SANS results reveal that the sizes of BSA molecules increase slightly, while the statistical analysis of the CFM results shows that the averaged pull-off force for the elongation monotonously decreases. The decrease of pull-off force with the increase of pH results from the decrease in the strength of hydrogen bonding and the number of interaction pairs, as well as the slight increase of the strength of van der Waals interaction. When pH approaches the isoelectric point (pI) of BSA, results from both SANS and CFM suggest a loss of long-range interactions in BSA molecules. Our results also suggest that the force-extension curve is mainly contributed by the van der Waals interaction. The combination of SANS and CFM provides new insight to understand the interactions and conformation of BSA molecules

Investigation of sol-gel transition in Pluronic F127/D2O solutions using a combination of small-angle neutron scattering and Monte Carlo simulation

Physical gelation in the concentrated Pluronic F127/D2O solution has been studied by a combination of small-angle neutron scattering (SANS) and Monte Carlo simulation. A 15% F127/D2O solution exhibits a sol-gel transition at low temperature and a gel-sol transition at the higher temperature, as evidenced by SANS and Monte Carlo simulation studies. Our SANS and simulation results also suggest that the sol-gel transition is dominated by the formation of a percolated polymer network, while the gel-sol transition is determined by the loss of bound solvent. Furthermore, different diffusion behaviors of different bound solvents and free solvent are observed. We expect that this approach can be further extended to study phase behaviors of other systems with similar sol-gel phase diagrams.