中能碳离子束对不同贯穿深度上黑色素瘤B16细胞的辐照存活效应

测量了49．30MeV/u及经脊形过滤器展宽的Bragg峰的74.55MeV/u^12C离子束在不同贯穿深度上辐射后黑色素瘤B16细胞的存活率。结果显示,在以存活为终点的B16细胞生物学效应与碳离子束能量沉积同步增大。即Bragg或展宽的Bragg峰区内细胞存活率远低于离子束入射或出射通道处的细胞存活率。通过实验测量与剂量平均LET结合的线性平方模型理论计算存活曲线的比较,发现在实验测量误差范围内两者符合较好。提示：剂量平均LET结合线性平方模型可能是预测中能重离子束贯穿深度上B16细胞存活效应的一种有效的方法。     

重离子照射野均匀度对细胞存活率影响的理论研究

为了给重离子治癌装置的照射野均匀度的确定提供依据,从理论上研究了重离子照射野均匀度对细胞存活率的影响,以细胞存活率曲线的线性平方模型为基础,导出了受不均匀重离子照射野照射时的细胞存活率与剂量的关系式,利用这个关系式讨论了照射野均匀度对细胞存活率的影响,结果表明,受不均匀照射野照射时的细胞存活率要比受理想的均匀照射野照时的细胞存活率大,均匀度越差细胞存活率越大;当实际照射野均匀度＞95％时,方可将实际的照射野作为理想的均匀照射野来处理,因此,重离子治癌装置的照射野均匀度应＞95％,同时指出,在对不同的实验室所得到的细胞存活率曲线进行比较时,应考虑不同的实验室的重离子照射野的均匀度的一致性。     

重离子辐照对红酵母的诱变作用

应用重离子加速器的 5 0MeV/u12 C6+ 重离子对胡萝卜素生产菌 -红酵母(RhodotorulaRYStrain )进行辐照处理 ,经酵母发酵实验 ,发现 5 0MeV/u12 C6+ 重离子对胡萝卜素生产菌———红酵母具有诱变作用 ,并初步筛选到产胡萝卜素有较大变化的辐照变异菌株 ,为工业上利用重离子对胡萝卜素生产菌进行诱变育种展现新的前景     

重离子辐照对红酵母的诱变作用

应用重离子加速器的50MeV／u^12C^6 重离子对胡萝卜素生产菌-红酵母(Rhodotorula RY Strain)进行辐照处理,经酵母发酵实验,发现50MeV／u^12C^6 重离子对胡萝卜素生产菌-红酵母具有诱变作用。初步筛选到了胡萝卜素产量有变化的辐照变异菌株,并对这些辐照变异菌株进行了RFLP(限制性片段长度多态性)和RAPD(随机扩增DNA多态性)分析,这些工作为工业上利用重离子对胡萝卜素生产菌进行诱变育种展现了新的前景。     

不同LET碳离子对V79细胞辐射敏感性的影响

以中国仓鼠肺V79细胞为材料,利用兰州近代物理研究所重离子研究装置（HIRFL）产生的碳离子,研究了不同线性能量传递（LET）的重离子对体外培养细胞的存活效应,并与γ射线的结果作了比较。结果表明,不同LET碳离子引起细胞失活效应由大到小的顺序依次为125、200、700keV/μm。碳离子表现为无肩区的存活曲线,属单靶单击模型,γ射线表现为有肩区的存活曲线,属多靶单击模型。LET值为125、200、700keV/μm时得到的失活截面分别为35、12、8μm^2。当细胞存活比率为0.1和0.37,在LET为125keV/μm时得到相对生物学效应（RBE）值为1.47和2.19。     

重离子辐照诱导DNA双链断裂的剂量率效应

利用不同剂量率的50MeV/u^12C^6 辐照B16黑色素瘤细胞的脱蛋白DNA,采用脉冲场凝胶电泳技术对DNA双链断裂（DSB）的诱导和片段的分布进行了研究。结果发现,在剂量率分别为3Gy/min和30Gy/min的情况下,DNA片段释放百分比（PR）都随着剂量的增加而增加,并在超过一定剂量之后趋于相似的准阈值;3Gy/min辐照诱导DSB的产额为0.40DSBs(100Mbp.Gy）,30Gy/min辐照诱导的DSB产额准确值无法得到;30Gy/min辐照诱导DSB的截面为2.14μm^2,是3Gy/min的3.1掊。所有结果都表明剂量率越高,诱导DSB越有效。另外,3Gy／min辐照诱导DSB片段在－860kbp处有一个片段峰,而30Gy/min没有,说明剂量率可以影响DSB片段的分布。     

重离子治癌中剂量分布均匀度对肿瘤控制率的影响

为了把握重离子治癌中剂量分布的不均匀性对疗效的影响,我们研究了肿瘤控制率随剂量分布均匀度的变化。受不均匀重离子照射野照射时的细胞存活率理论与肿瘤控制率理论相结合,计算了一个假设肿瘤模型在不均匀剂量分布条件下的肿瘤控制率。结果表明：在相同的总剂量照射下,剂量分布均匀度越差肿瘤控制率越低。因此,在实际的治疗中,剂量分布均匀度应尽可能好于95％。     

利用直流辉光放电等离子体改善聚氯乙烯细管内表面亲水性的研究

采用低气压氩气直流辉光放电等离子体对PVC细管内表面进行了处理,使其内表面亲水性得到显著改善,且处理效果均匀.处理时间越长PVC细管内表而的水接触角越小.经过处理后的PVC细管放置室内大气环境后内表面的水接触角出现退化,72小时以后基本稳定,稳定后的内表面水接触角显著好于未经处理的PVC细管.     

Investigation on pulsed discharge mode in SF6-C2H6 mixtures

The non-chain chemical HF(DF)laser is one of the most powerful electrically-driven lasers operating in mid-infrared,in which SF6-C2H6 mixtures are often used as lasering media.Due to the electronegativity of SF6,the discharge in SF6-C2H6 presents a complicated discharge mode.To achieve reproducible pulsed laser output,pulsed discharge in SF6-C2H6 mixtures is investigated for discharge mode using plane electrodes assisted by array pre-ionization spark pins in cathode surface.Firstly,two modes can be distinguished.One mode is called the selfsustained volume discharge(SSVD),which is characterized by spatial uniformity in the discharge gap and pulse to pulse repeatability.On the contrary,another mode includes random arc passages in the discharge gap and therefore cannot conduct lasering.By varying discharge conditions(gap voltage,gas pressure,etc)two discharge modes are observed.Secondly,the holding scope of the SSVD mode is analyzed for the optimal mixture ratio of 20:1,and the boundary tend of the holding scope of SSVD indicates there exists maximum gas pressure and maximum charging voltage for SSVD.Finally,the peak current of SSVD relates positively to charging voltage,while negatively to gas pressure,from which it is drawn that synchronous electron avalanches initiated by the sliding array overlap spatially into SSVD and thus SSVD is essentially an α ionization avalanche.     

Photographic Study on Spark Discharge Generated by a Nanosecond High-Voltage Pulse over a Water Surface

Spark discharge generated by a nanosecond positive high-voltage pulse over a water surface at atmospheric pressure in air was studied using a high speed camera system.Faint streamers form near the pin electrode and propagate towards the water surface.The time for the streamer propagating across the air gap was estimated to be about 50 ns to 60 ns with a propagation velocity of~1.3×10~5 m/s.It was found that the water conductivity and the gap distance have no significant effect on the propagation velocity of the streamer.After the streamers touch the water surface a brilliant spark channel forms across the air gap.The maximum diameter at the middle of the spark channel is about 1 mm,and approximately contracts with a radical velocity of about 2.0×10~3 m/s.No significant dependence of the maximum diameter and decay velocity of the spark channel on the water conductivity and the gap distance were recognized in the present work.The maximum conduction current for a gap distance of 5 mm is significantly larger than that for a gap distance of 10 mm at the same water conductivity,and shows an increasing tendency with increasing water conductivity for a fixed gap distance.Based on the maximum conduction current,the effect of water conductivity and gap distance on the electron density of the spark discharge plasma at the peak current was investigated.Within the range studied,the electron density in the spark channel is about 10~(15)cm~(-3)and increases with water conductivity at a fixed gap distance.