2005年 第22卷 第2期
Status of theoretical studies on superheavy nuclei is simply reviewed.We investigate the influence of nuclear deformation on halflives of α decay for
long lifetime nuclei beyond 208Pb. The range of the validity of relativistic meanfield model is analyzed and discussed. The conservation of parity in αdecay, clusterradioactivity, and spontaneous fission of nuclei is stressed. New views on the properties of superheavy nuclei are presented.
采用IBM模型研究了^142-164Dy核的低能正宇称态的能谱和电磁跃迁。应用U(5)→SU(3)的简化哈密顿量较好地描述了它们的能谱和电磁跃迁。研究结果表明，该核基本属于U(5)→SU(3)的过渡核Spectra and E2 transition rates for the eveneven 142-164Dy isotopes are studied in the framework of the interacting boson model. A schematic Hamiltonian capable of describing their spectra and transition is used. It is found that the eveneven 142-164Dy isotopes are in the transition from U(5)to SU(3) dynamical symmetry.
It is systematically observed that the B(M1)/B(E2) plots with the increasing of rotational frequency, behaves as a socalled parabolalike shape in the π h11/2 νi13/2 bands of rareearth doubly odd nuclei (i.e., the B(M1)/B(E2) ratios increase rapidly after a certain rotational frequency). Such a phenomenon is discussed based on the formula of magnetic dipole reduced transition probability deduced from the Cranking Shell Model and Particle Rotor Model respectively. It is pointed out that, the occurrence of this behavior is closely related to the alignment nature of the νi 13/2 quasineutron. The increasing of B(M1)/B(E2) occurring at large frequency approaching the second BC crossing can be understood as mainly resulted from the mixing of wave function with the 4 quasiparticle band caused by the band crossing. Insight into the angular momentum coupling scheme between the quasiparticles and collective core in the πh11/2 νi 13/2 structures of rareearth doubly odd nuclei is gained by analyzing the increasing behavior of B(M1)/B(E2) ratios occurring at low rotational frequency.
From the spinorial form of the Lorentzforce equation, the problems about axial electric field and axial magnetic field of charge motion in electromagnetic fields, as well as planewave pulse and Larmor power have been discussed in this paper. These problems are the foundation of studying the autoresonance laser accelerator (ALA).
： In CSRe electron cooling device， a special electron gun which can produce variable profile electron beam with different size and density distribution was adopted for decreasing ion losses. Electrostatic bending device was used for reducing electron beam losses and improving vacuum condition. The instability of the electron beam is suppressed because the secondary electrons from collector would come back to the collector in the same orbit finally. Longitudinal magnetic field with parallelism better than 10-4 was achieved by adopting of independent high precise solenoid coils at cooling section. In this case， the r.m.s deviations of the transverse magnetic field at cooling section in horizontal and vertical direction are 3.298×10-5 and 2.458×10-5 respectively. The characters of the gun and collector were investigated. The results were presented and indicate that it achieves the design purpose very well.
载能团簇离子进入固体时， 由于集体相互作用，在入射路径上产生非常高的能量沉积密度。 实验发现， 载能团簇离子的作用结果并不等于团簇中各原子独立作用的总和， 而是具有非线性效应。 就二次离子发射而言， 这种非线性通常与团簇的能量、 团簇的大小、 离子的电荷态以及靶物质的结构有关。 通过研究二次离子发射有助于理解载能团簇离子与物质相互作用过程中的能量沉积与释放机制。
Using energetic cluster as projectile is a unique way to produce simultaneous impacts of several atoms and deposit extremely high energy density in a very small area. The cluster impingement on solids has exhibited some nonlinear effects not presented in collisions of individual atoms with those solids. The study of the secondary ion emissions can give insight into the energy deposition and relaxation steps of the clustersolid interaction. The dependence of the yields of secondary ion emission induced by clusters on the energy of clusters,cluster sizes,charge states and material structures of the targets was reviewed in this paper.
The responses of two extended neutron rein counters as function of neutron energy was ca1cuated Monte Carlo code，MCNPx，was applied in the calculations．Isotropic neutron incidence was employed．The results show that the neutron response is independent on thickness of lead 1aver at low energies，and it is clearly increased with thickness of lead layer at high energies．Although tt1e shape of the response curve does not completely agree with the H (10) curve in ICRP 74 report ，the resuhs obtained give good bases for the practical use of the new instrument in high—energy neutron fields
DNA is considered to be the most important and sensitive target in biological systems. In addition to the base damage, DNA strand breaks are the major lesion in the genome due to exposure to ionizing radiation. Mutation can be introduced to DNA as a result of enzymatic processing of DNA lesions or postirradiation replication. However, the mechanisms of radiationinduced mutations are not well clarified at the molecular level. To study the effect on the simple plasmid DNA of heavy ion is even predominant or more feasible.
Plasmid pUC18 DNA was prepared and irradiated by neon beam (7.199 MeV/u). The fragment distributions were determined by quantifying the ethidium bromide fluorescence. It can be seen that the shape of the intensity distributions is vastly different for the used radiation Dose. The distribution produced shows an excess of fragments particularly in 3 000 and 10 000 Gy the size range between 20—40 kbp and 20—50 bp. This clustering of doublestranded fragments might be influenced by the higher order chromatin structure of genomic DNA. If so, DNA loop structures could correspond to the size range for which we observed DSB clustering. Further studies aim at elucidating the heterogeneity of DSB induction within the genome and investigate the influence of chromatin structure on the nonrandom fragment distribution.
We investigate the radiation response of hepatoma cells SMMC-7721 by premature chromosome condensation (PCC) technique. A dose-dependent increase in radiation-induced chromatid/isochromatid breaks was observed in G1 and G2 phase respectively. A good relationship was found between cell survival and chromatin breaks.
以低剂量γ射线(0.05 Gy)预照射人肝癌细胞hep G2， 8 h后再用高剂量(3 Gy)照射， 测定了细胞的克隆存活率和细胞周期。 结果表明， 低剂量辐射预处理可诱导hep G2细胞产生克隆存活适应性反应， 并且有助于细胞通过G2/M期阻滞； 低剂量辐射诱导的克隆存活适应性反应与增强的通过细胞周期阻滞的能力之间有一定的相关性。
Human hepatoma cells hep G2 were irradiated with 3 Gy of γray 8 hours after primed with 0.05 Gy of γray， thereafter，cell survival and cell cycle were determined. The results indicated that both survival adaptive response and the enhanced ability to overcome G2/M arrest could be induced by preirradiation with low dose of γray. It is suggested that there is a certain correlation between the survival adaptive response and the enhanced ability to overcome cell cycle arrest.
目前肿瘤基因治疗尚存在许多问题, 距临床应用还有相当的距离, 但是在传统的放疗、化疗和手术治疗的基础上, 辐射与基因治疗的有机结合在肿瘤治疗中却显示出可喜的前景。综述了近年来这一领域的研究进展, 探讨了这一疗法对肿瘤治疗的应用前景。
Although tumor gene therapy has a distance to clinical use due to some problems, the combination of irradiation and gene therapy holds much promise in cancer therapy based on the traditional radiotherapy, chemotherapy and surgery. We have termed this therapeutic radiogenic therapy. This review focuses on the group of radiogenic therapy that are either： ⑴ improvement of gene transfer efficiency by irradiation; ⑵ radiotherapy combined with cytokines gene delivery or enhancement of the immunity of tumor cells by transgene; ⑶ directly stimulated by radiation to produce either directly or indirectly cytotoxic agents; ⑷ increasing of radiosensitivity in gene therapy; ⑸ radioprotective gene therapyenhances radiation tumor killing effect while protecting the normal tissue and organs with transgene using transfer vector.
综述了DNA辐射损伤导致的细胞阻遏于G1期以及在该时期对DNA的修复活动， 提出了较大剂量辐射诱导的三磷酸腺苷不足导致细胞凋亡的假说， 并分析了细胞走向凋亡与修复的辨正关系。
DNA damage induced by irradiation，which makes the cell arrested at G1 stage and DNA repair being activated in this stage，are summarized. It is proposed that the deficiency of adenosine triphosphate which is induced by the larger irradiation dose, induces cell apoptosis. And the relationship of cell selecting repair and apoptosis is also analyzed.
凋亡素是一种抗癌因子， 能以非p53依赖性途径诱导不同类型人肿瘤细胞的凋亡， 不受Bcl2的抑制作用， 且对正常细胞不起作用。 根据凋亡素的肿瘤特异性， 可将其作为一种极具潜力的抗肿瘤生物制剂， 在人体内大量传递给肿瘤细胞， 有选择性地根除肿瘤细胞。 论述了凋亡素抗肿瘤细胞的作用机理， 并对其应用现状、 前景及进一步研究的主要问题予以简要评述。Apoptin is an anticancer gene. It can induce p53independent，Bcl2insensitive type of apoptosis in various human tumor cells，and fails to induce programmed cell death in normal cell. Because of having tumor specificity， apoptin can be transferred enough to tumorcell in vivo，selectly kill the tumor as a potential antitumor biological preparation. In this paper， we provide a brief review on the anticancer mechanism of apoptin， current status and application prospect， and the main issues in apoptin studies.