高能质子-质子碰撞中反物质产生的能量依赖性

用部分子和强子级联模型与动力学约束相空间组合模型模拟高能质子-质子碰撞,得到反粒子和粒子的比值及相关数据,研究了高能质子-质子碰撞中反物质产生的能量依赖性。研究发现:在高能质子-质子碰撞中反粒子和粒子的比值随着质心能量的增加而增加;当质心能量大于200 Ge V时,其比值逐渐趋近1;而不同的正反粒子的平均横动量随着质心能量的增加都快速增加。我们用模型模拟得到的结果与已有的STAR、ALICE等实验组的数据基本一致。

The Effect of Some Effective Quantities to Electronic Stopping Power

The dependences of effective quantities Z＊, Zt,/＊, （effective number of electrons for ionization and for quasi-molecule, effective mean excitation energy） on the incident ion energy have been studied for a pervious stopping power calculation method, and Bohr stripping criterion and quasi-molecule criterion in this regard have been discussed in some details. The effect of effective quantities to the obtained stopping power results is investigated by calculating stopping powers. The contributions to stopping power from the modified LSS and Bethe formulas have been calculated separately and compared in graphs of stopping power. The stopping power for lithium ions in the intermediate and higher energy region is found to be dominant due to excitation-ionization whereas quasi molecule criterion is dominant in the lower energy region.

应用Geant4模拟EBT3胶片的能量响应和质子射程测量

目的计算EBT3胶片吸收剂量的能量依赖性,展示EBT3胶片测量质子吸收剂量时的误差。方法在临床光子和质子能量照射范围内逐步增加射线束能量,应用Geant4计算EBT3胶片吸收剂量与同体积水吸收剂量的差异,并与理论结果进行比对。结果对于光子和质子来说,EBT3胶片吸收剂量能量依赖性与理论结果一致的分界线分别为100 keV和11 MeV;光子和质子能量高于相应值时EBT3胶片能量依赖性与理论结果保持一致,低于相应值时EBT3胶片能量依赖性与理论结果无关;计算EBT3胶片测量质子布拉格峰和50%剂量点与实际位置的差异,最大误差小于1%。结论对较高能量区间内的质子和光子来说,EBT3胶片吸收剂量能量依赖性可忽略;对低能量区间的质子和光子,EBT3胶片吸收剂量能量依赖性差异较大,应给予重点关注。EBT3胶片测量的质子布拉格峰和50%剂量点与实际位置基本一致。

Surface effects on large deflection of nanowires

Surface effects play an important role in the mechanical behavior of nanosized structural elements owing to the increased ratio of surface area to volume. The surface effects on the large deflection of nanowires were considered. Both geometric nonlinearity in finite deformation and surface effects at nanoscale were taken into account to analyze the bending of nanowires subjected to a concentrated force. For simply supported beams and clamped-clamped beams, the influence of surface effects and geometric nonlinearity were discussed in detail. It is found that both surface effects and geometric nonlinearity tend to decrease the deflection of bending nanowires and thus increase the effective elastic modulus of nanowires. Surface effects yield the size dependent behavior of nanowires.

P-糖蛋白表达对胃癌预后的影响

目前,化疗仍然是治疗胃癌的重要手段。由P-糖蛋白介导的多药耐药现象是导致化疗失败的重要原因。P-糖蛋白是一种能量依赖性的药物输出泵,能降低药物的细胞毒作用。许多研究证明,P-糖蛋白的表达与肿瘤的疗效和预后有关,但对胃癌预后的影响尚未见报道。本文采用LSAB法研究P-糖蛋白在41例中的表达,并探讨其与胃癌预后的关系。

Deformation dependence of symmetry energy coefficients of nuclei

Based on the semi-classical Thomas-Fermi approximation together with the Skyrme energy-density functional, we study the deformation dependence of symmetry energy coefficients of finite nuclei. The symmetry energy coefficients of nuclei with mass number A = 40, 100, 150, 208 are extracted from two-parameter parabola fitting to the calculated energy per particle. We find that the symmetry energy coefficients decrease with the increase of nuclear quadrupole deformations, which is mainly due to the isospin dependence of the difference between the proton and neutron surface diffuseness. Large deformations of nuclei can cause the change of the symmetry energy coefficient by about 0.5 Me V and the influence of nuclear deformations on the symmetry energy coefficients is more evident for light and intermediate nuclei.