Protective effects of melatonin against low- and high-LET irradiation

To investigate the protective effects of melatonin against high-LET ionizing radiation, V79 Chinese hamster cells were irradiated with 100 keV/mu m carbon beam. Parallel experiments were performed with 200 kV X-rays. To avoid the impact from extra solvents, melatonin was dissolved directly in culture medium. Cells were cultured in melatonin medium for 1 hr before irradiation. Cell inactivation was measured with conventional colony forming assay, medium containing 6-thioguanine was used for the selection of mutants at hprt locus, and the cell cycle was monitored by flow cytometry. Both carbon beam and X-rays induced cell inactivation, hprt gene mutation and cell cycle G2 block dose-dependently. But carbon beam showed stronger effects as indicated by all three endpoints and the relative biological effectiveness (RBE) was 3.5 for cell killing (at 10% survival level) and 2.9 for mutation induction (at 5 x 10(-5) mutants/ cell level). Melatonin showed protective effects against ionizing radiation in a dose-dependent manner. In terms of cell killing, melatonin only increased the survival level of those samples exposed to 8Gy or larger of X-rays or 6 Gy or larger of carbon beam. In the induction of hprt mutation and G2 block, melatonin reduced such effects induced by carbon beam but not by X-rays. The results suggest that melatonin reduces the direct interaction of particles with cells rather than an indirect interaction. Further studies are required to disclose the underlying mechanisms.

Three-body force rearrangement effect on single particle properties in neutron-rich nuclear matter

We extend the Brueckner-Hartree-Fock (BHF) approach to include the three-body force (TBF) rearrangement contribution in calculating the neutron and proton single particle (s.p.) properties in isospin asymmetric nuclear matter. We investigate the TBF rearrangement effect on the momentum-dependence of neutron and proton s.p. potentials, the isospin splitting and especially its density dependence of the neutron and proton effective masses, and the isospin symmetry potential in neutron-rich nuclear matter by adopting the realistic Argonne V-18 two-body nucleon-nucleon interaction supplemented with a microscopic TBF. We find that at low densities, the TBF rearrangement effect is fairly weak, whereas the TBF induces a significant rearrangement effect on the s.p. properties at high densities and large momenta. The TBF rearrangement contribution to s.p. potential is shown to be repulsive, and it reduces considerably the attraction of the BHF s.p. potential. The repulsion from the TBF rearrangement turns out to be strongly momentum dependent at high densities and high momenta. As a consequence, it enhances remarkably the momentum dependence of the proton and neutron s.p. potentials and reduces the neutron and proton effective masses. At low densities, the TBF rearrangement effect on symmetry potential is almost negligible, while at high densities, it enlarges sizably the symmetry potential. At high enough densities, it may even change the high-momentum behavior of symmetry potential. In both cases, with and without including the TBF rearrangement contribution, the predicted neutron effective mass is larger than the proton one in neutron-rich matter within the BHF framework; i.e., the predicted isospin splitting of the proton and neutron effective masses in neutron-rich matter is such that m(n)(*)>= m(p)(*), in agreement with the recent Dirac-BHF predictions. The TBF rearrangement contribution reduces remarkably the magnitude of the proton-neutron effective mass splitting at high densities. At high enough densities, inclusion of the TBF rearrangement contribution even suppresses almost completely the effective mass splitting.

Production cross section of neutron cluster from the reaction of light neutron rich nuclei

Within the Boltzmann-Langevin equation, the neutron cluster production cross sections in the reactions induced by Be-14, He-8, He-6, Li-11, B-17, Be-11, C-19 on C-12 at 35MeV/u were studied. The experimental data for (4)n production cross section from Be-14+C-12 at 35MeV/u can be reproduced. It is found that the production cross section of neutron cluster is large in the reaction that the projectile has more halo nucleons. And the projectiles with big mass number are easy to produce the neutron cluster, when they have the same number of halo nucleons. The neutron cluster is probably mainly from the halo nucleons of projectile.

The effect of the scalar-isovector meson field on hyperon-rich neutron star matter

We investigate the effect of the calar-isovector delta-meson field on the equation of state (EOS) and composition of hyperonic neutron star matter, and the properties of hyperonic neutron stars within the frame work of the relativistic mean field theory. The influence of the delta-field turns out to be quite different and generally weaker for hyperonic neutron star matter as compared to that for npe mu neutron star matter. We find that inclusion of the delta-field enhances the strangeness content slightly and consequently moderately softens the EOS of neutron star matter in its hyperonic phase. As for the composition of hyperonic star matter, the effect of the delta-field is shown to shift the onset of the negatively-charged (positively-charged) hyperons to slightly lower (higher) densities and to enhance (reduce) their abundances. The influence of the delta-field on the maximum mass of hyperonic neutron stars is found to be fairly weak, where as inclusion of the delta-field turns out to enhance sizably both the radii and the moments of inertia of neutron stars with given masses. It is also shown that the effects of the delta-field on the properties of hyperonic neutron stars remain similar in the case of switching off the Sigma hyperons.

两种保护剂对C离子诱导小鼠急性肝损伤的应答；Response of Two Protective Agents to Acute Injury Induced by ~(12)C~(6+) Ions in Mouse Liver

比较了N-乙酰半胱氨酸(NAC)及乙酰左旋肉毒碱(ALCAR)对12C6+离子照射小鼠的损伤效应,并探讨了其可能的作用机制。利用4Gy剂量的12C6+离子束对预先给予NAC(100mg/kg)和ALCAR(100mg/kg)保护的昆明小鼠进行单次全身照射。随后检测肝组织中总抗氧化能力(TAC)、DNA单链断裂和细胞凋亡率。结果显示,与照射对照组相比,提前给予NAC和ALCAR均极显著地增强了肝组织的抗氧化能力(P<0.001),减轻了12C6+离子导致的肝组织中DNA断裂(P<0.001)和细胞凋亡(P<0.001)。此外,还发现ALCAR组抗重离子辐照损伤的能力显著地高于NAC组(P<0.05)。实验结果提示了NAC和ALCAR可通过抵御组织内的氧化胁迫,阻止DNA链的断裂和细胞的凋亡,实现对C离子辐照损伤的保护效应。而且ALCAR比NAC可能更适合成为有潜力、有希望的抗C重离子辐射药物。

Recent Progress in Constraining the Equation of State of Dense Neutron-Rich Nuclear Matter with Heavy-Ion Reactions

The nuclear symmetry energy E-sym(rho) is the most uncertain part of the Equation of State (EOS) of dense neutron-rich nuclear matter. In this talk, we discuss the underlying physics responsible for the uncertain E-sym(rho) especially at supra-saturation densities, the circumstantial evidence for a super-soft E-sym(rho) from analyzing pi(-)/pi(+) ratio in relativistic heavy-ion collisions and its impacts on astrophysics and cosmology.

Radiosensitivity to high energy iron ions is influenced by heterozygosity for Atm, Rad9 and Brca1

Loss of function of DNA repair genes has been implicated in the development of many types of cancer. In the last several years, heterozygosity leading to haploinsufficiency for proteins involved in DNA repair was shown to play a role in genomic instability and carcinogenesis after DNA damage is induced, for example by ionizing radiation. Since the effect of heterozygosity for one gene is relatively small, we hypothesize that predisposition to cancer could be a result of the additive effect of heterozygosity for two or more genes critical to pathways that control DNA damage signaling, repair or apoptosis. We investigated the role of heterozygosity for Aim, Rad9 and Brad on cell oncogenic transformation and cell survival induced by 1 GeV/n Fe-56 ions. Our results show that cells heterozygous for both Aim and Rad9 or A tin and Brca1 have high survival rates and are more sensitive to transformation by high energy iron ions when compared with wild-type controls or cells haploinsufficient for only one of these proteins. Since mutations or polymorphisms for similar genes exist in a small percentage of the human population, we have identified a radiosensitive sub-population. This finding has several implications. First, the existence of a radiosensitive sub-population may distort the shape of the dose response relationship. Second, it would not be ethical to put exceptionally radiosensitive individuals into a setting where they may potentially be exposed to substantial doses of radiation. (C) 2010 COSPAR. Published by Elsevier Ltd. All rights reserved.

Discovery of Highly Excited Long-Lived Isomers in Neutron-Rich Hafnium and Tantalum Isotopes through Direct Mass Measurements

A study of cooled Au-197 projectile-fragmentation products has been performed with a storage ring. This has enabled metastable nuclear excitations with energies up to 3 MeV, and half-lives extending to minutes or longer, to be identified in the neutron-rich nuclides Hf-183,Hf-184,Hf-186 and Ta-186,Ta-187. The results support the prediction of a strongly favored isomer region near neutron number 116.

Rotation alignment in neutron-rich Cr isotopes: A probe of deformed single-particle levels across N=40

Recent experiments have reached the neutron-rich Cr isotope with N = 40 and confirmed enhanced collectivity near this subshell. The current data focus on low-spin spectroscopy only, with little information on the states where high-j particles align their spins with the system rotation. By applying the projected shell model, we show that rotation alignment occurs in neutron-rich even-even Cr nuclei as early as spin 8 (h) over bar h and, owing to shell filling, the aligning particles differ in different isotopes. It is suggested that observation of irregularities in moments of inertia is a direct probe of the deformed single-particle scheme in this exotic mass region.

Identification of a quasiparticle band in very neutron-rich Zr-104

The high spin levels of a very neutron-rich Zr-104 nucleus have been reinvestigated by measuring the prompt. rays in the spontaneous fission of Cf-252. The ground-state band has been confirmed. A new sideband has been identified with a band-head energy at 1928.7 keV. The projected shell model is employed to investigate the band structure of Zr-104. The results of calculated levels are in good agreement with the experimental data, and suggest that the new band in Zr-104 may be based on the neutron nu 5/2(-)[532] circle times nu 3/2(+)[411] configuration.

Iron XII to XXII spectra measurements between 250 and 400 angstrom

This paper reports laboratory measurements of the spectrum of the most abundant transition Fe ions in the universe. Spectrum of iron of low-lying excited states has been observed in the wavelength range 250-400 angstrom at Chinese Institute of Atomic Energy on the HI-13 tandem accelerator with beams of 130 MeV. A number of spectral lines have been mainly classified as transitions of magnesium-, sodium-, neon-, fluorine-like ions. A total of 54 lines have been measured. Most of them have been mainly ascribed to 3s3p(k)-3p(k+1), 3s(2)3p(k)-3s3p(k+1), 2p(5)3s-2p(5)3p, 3s3d-3p3d and 2p(5)3p-2p(5)3d resonance transitions. These spectral lines have been identified, among which 21 are new and accurately measured. The analysis of the spectra was based on a comparison with other experimental results and calculated values. (c) 2010 Elsevier Ltd. All rights reserved.

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.

Influence of iron promoter on catalytic properties of Rh-Mn-Li/SiO2 for CO hydrogenation

The effect of iron promoter on the catalytic properties of Rh-Mn-Li/SiO2 catalyst in the synthesis Of C-2 oxygenates from syngas was investigated by means of the following techniques: CO hydrogenation reaction, temperature-programmed reduction (TPR), temperature-programmed desorption and reaction of adsorbed CO (CO-TPD and TPSR) and pulse adsorption of CO. The results showed that the addition of iron promoter could improve the activity of the catalysts. Unexpectedly, the yield of C-2 oxygenates increased greatly from 331.6 up to 457.5 g/(kg h) when 0.05% Fe was added into Rh-Mn-Li/SiO2 catalyst, while no change in the selectivity to C-2 oxygenates was observed. However, the activity and selectivity Of C-2 oxygenates were greatly decreased if the Fe amount exceeded 1.0%. The existence of a little iron decreased the reducibility of Rh precursor, while the reduction of Fe component itself became easier. CO uptake decreased with increasing the quantity of Fe addition. This phenomenon was further confirmed by CO-TPD results. The CO-TPD and TPSR results showed that only the strongly adsorbed CO could be hydrogenated, while the weakly adsorbed CO was desorbed. We propose that Fe is highly dispersed and in close contact with Rh and Mn; such arrangements were responsible for the high yield Of C-2 oxygenates. (C) 2002 Elsevier Science B.V. All rights reserved.