Estimation of enhanced low dose rate sensitivity mechanisms using temperature switching irradiation on gate-controlled lateral PNP transistor

The mechanisms occurring when the switched temperature technique is applied,as an accelerated enhanced low dose rate sensitivity(ELDRS)test technique,are investigated in terms of a specially designed gate-controlled lateral PNP transistor(GLPNP)that used to extract the interface traps(Nit)and oxide trapped charges(Not).Electrical characteristics in GLPNP transistors induced by ^(60)Co gamma irradiation are measured in situ as a function of total dose,showing that generation of Nit in the oxide is the primary cause of base current variations for the GLPNP.Based on the analysis of the variations of Nit and Not,with switching the temperature,the properties of accelerated protons release and suppressed protons loss play critical roles in determining the increased Nit formation leading to the base current degradation with dose accumulation.Simultaneously the hydrogen cracking mechanisms responsible for additional protons release are related to the neutralization of Not extending enhanced Nit buildup.In this study the switched temperature irradiation has been employed to conservatively estimate the ELDRS of GLPNP,which provides us with a new insight into the test technique for ELDRS.

Micro-Tuber Production in Diploid and Tetraploid Potato after Gamma Irradiation of in Vitro Cuttings for Mutation Induction

Micro-tubers are important propagules in potato breeding and potato production, and they are also dormant and easily transported and therefore good targets for mutation induction in potato mutation breeding. A prerequisite for mutation breeding is to determine optimal mutation treatments. Therefore, radio-sensitivity tests of a tetraploid and a diploid potato to gamma irradiation were undertaken. Effects of different gamma sources on radio-activity were also studied. In vitro potato cuttings were gamma irradiated using a wide dose range (0, 3, 6, 9, 12, 15 and 20 Gy). The irradiated cuttings were then cultured to induce micro-tubers directly in vitro. Micro-tuber morphotypes were assessed after irradiation of cuttings using three gamma sources with emission activities of 1.8, 7.07 and 139 Gy/min. The diploid species (Solanum verrucosum) was more radio-sensitive than the tetraploid cultivar Desirée (Solanum tuberosum). Gamma dose rates had significant influences on subsequent micro-tuber production at various mutant generations. Effects included reductions in the number, size and weight of micro-tubers produced. Gamma dose was more lethal for the diploid potato genotype and micro-tubers produced were small compared to those produced by the tetraploid genotype after irradiation. Different treatments are recommended for diploid and tetraploid potato irradiation in producing large mutant micro-tuber populations. The mutant micro-tuber populations may then be screened for interesting mutations/trait for both genetics and plant breeding purposes.

Study on Fractionated Total Body Irradiation before Hematopoietic Stem Cell Transplantation

OBJECTIVE To observe the dose and the complicationsfrom total body irradiation before hematopoietic stem celltransplantation.METHODS This study involved 312 patients with total bodyirradiation before hematopoietic stem cell transplantation. Theywere entered into the treated research from May 1999 to October2005. All patients had received the irradiation from ^(60)Co of anabsorbed dose rate of (5.2 ± 1.13) cGy/min. The total dose of TBIwas 7～12 Gy, 1 f/d × 2 d. A high-dose rate group (≥10 Gy) included139 cases and a low-dose rate group (< 10 Gy) included 173 cases.RESULTS The probability of acute gastrointestinal reactionsin the high-dose rate group was more compared with that in thelow-dose rate group. The differences for other reactions, such ashematopoietic reconstitution and graft survival rate, between thetwo groups were insignificant.CONCLUSION Using fractional total body irradiation at a doserate of 5 cGy/min, with a total dose of 7～12 Gy, 1 f/d × 2 d , withthe lung receiving under 7.5 Gy is a safe and effective pretreatmentfor hematopoietic stem cell transplantation.

Effect of dose rate on the characteristics of dislocation loops in palladium:In-situ TEM analysis during 30 keV H_(2)^(+)irradiation

Ion irradiation is usually used to simulate neutron irradiation to accelerate the evaluation of the irradia-tion behavior of reactor materials.However,the validity of using a high damage rate of ion irradiation to simulate a low damage rate of neutron irradiation has always been a controversial topic.Here,the effect of two dose rates(2.94×10^(-6) and 7.35×10^(-5) dpa s^(-1))on the characteristics and evolution of dislo-cation loops in palladium was studied in situ during 30 keV H2+irradiation using transmission electron microscopy.The dose rate obviously affected the nucleation rate and growth rate of dislocation loops,the types(Frank loops or perfect loops)of dislocation loops,and the irradiation hardening and total damage obtained from the product of average loop size and loop density.At the same irradiation dose,a high dose rate would lead to high loop density,small average loop size,low loop growth rate,and low irra-diation hardening and damage induced by loops in pure Pd.Meanwhile,it was found for the first time that a high dose rate was beneficial to the generation of perfect dislocation loops.The effect of dose rate was attributed to the different dynamic equilibrium results between the effective generation rate of point defects and their absorption rate by existing sinks.The present results show that the effect of dose rate should be considered when using ion irradiation to simulate neutron irradiation to evaluate the irradiation damage to materials.

Continuous Low-dose-rate Irradiation of Iodine-125 Seeds Inhibiting Perineural Invasion in Pancreatic Cancer

Background：Perineural invasion （PNI） is a histopathological characteristic of pancreatic cancer （PanCa）.The aim of this study was to observe the treatment effect of continuous low-dose-rate （CLDR） irradiation to PNI and assess the PNI-related pain relief caused by iodine-125 （125I） seed implantation.Methods：The in vitro PNI model established by co-culture with dorsal root ganglion （DRG） and cancer cells was interfered under 2 and 4 Gy of 125I seeds CLDR irradiation.The orthotopic models of PNI were established,and 125I seeds were implanted in tumor.The PNI-related molecules were analyzed.In 30 patients with panCa,the pain relief was assessed using a visual analog scale （VAS）.Pain intensity was measured before and 1 week,2 weeks,and 1,3,and 6 months after 125I seed implantation.Results：The co-culture of DRG and PanCa cells could promote the growth of PanCa cells and DRG neurites.In co-culture groups,the increased number of DRG neurites and pancreatic cells in radiation group was significantly less.In orthotopic models,the PNI-positive rate in radiation and control group was 3/11 and 7/11;meanwhile,the degrees of PNI between radiation and control groups was significant difference （P 〈 0.05）.At week 2,the mean VAS pain score in patients decreased by 50% and significantly improved than the score at baseline （P 〈 0.05）.The pain scores were lower in all patients,and the pain-relieving effect was retained about 3 months.Conclusions：The CLDR irradiation could inhibit PNI of PanCa with the value of further study.The CLDR irradiation could do great favor in preventing local recurrence and alleviating pain.

Dose rate effects on shape memory epoxy resin during 1 Me V electron irradiation in air

The effects of 1 Me V electron irradiation in air at a fixed accumulated dose and dose rates of 393.8,196.9,78.8,and 39.4 Gy s^(-1)on a shape memory epoxy(SMEP)resin were studied.Under low-dose-rate irradiation,accelerated degradation of the shape memory performance was observed;specifically,the shape recovery ratio decreased exponentially with increasing irradiation time(that is,with decreasing dose rate).In addition,the glass transition temperature of the SMEP,as measured by dynamic mechanical analysis,decreased overall with decreasing dose rate.The dose rate effects of 1 Me V electron irradiation on the SMEP were confirmed by structural analysis using electron paramagnetic resonance(EPR)spectroscopy and Fourier transform infrared(FTIR)spectroscopy.The EPR spectra showed that the concentration of free radicals increased exponentially with increasing irradiation time.Moreover,the FTIR spectra showed higher intensities of the peaks at 1660 and 1720 cm^(-1),which are attributed to stretching vibrations of amide C=O and ketone/acid C=O,at lower dose rates.The intensities of the IR peaks at 1660 and 1720 cm^(-1) increased exponentially with increasing irradiation time,and the relative intensity of the IR peak at 2926 cm^(-1)decreased exponentially with increasing irradiation time.The solid-state13 C nuclear magnetic resonance(NMR)spectra of the SMEP before and after 1 Me V electron irradiation at a dose of 1970 k Gy and a dose rate of 78.8 Gy s^(-1) indicated damage to the CH_(2)–N groups and aliphatic isopropanol segment.This result is consistent with the detection of nitrogenous free radicals,a phenoxy-type free radical,and several types of pyrolytic carbon radicals by EPR.During the subsequent propagation process,the free radicals produced at lower dose rates were more likely to react with oxygen,which was present at higher concentrations,and form the more destructive peroxy free radicals and oxidation products such as acids,amides,and ketones.The increase in peroxy free radicals at lower dose rates was thought to accelerate the degradation of the macroscopic performance of the SMEP.

甘肃省某石煤提钒企业伴生放射性污染的调查及分析

本文对甘肃省石煤资源的伴生矿物天然放射性核素的活度浓度水平以及开发利用过程中产生的辐射问题进行了调查,石煤伴生矿放射性主要来自铀系核素238 U和226 Ra,部分矿区的^(238)U和^(226)Ra的放射性活度浓度的平均水平超过了1 Bq/g。并对甘肃省某石煤提钒企业的测量数据,评估了工作人员以及公众接受的照射剂量率,分析了放射性污染以废水、废气、放射性固体废物等形式向环境转移的可能性。最后对石煤伴生放射性矿现存的各类放射性污染问题提出相应的建议。

我国掌握可控核聚变高约束先进控制技术

8月25日下午,新一代人造太阳“中国环流三号”取得重大科研进展,首次实现100万安培等离子体电流下的高约束模式运行,再次刷新我国磁约束聚变装置运行纪录,突破了等离子体大电流高约束模式运行控制、高功率加热系统注入耦合、先进偏滤器位形控制等关键技术难题,是我国核聚变能开发进程中的重要里程碑,标志着我国磁约束核聚变研究向高性能聚变等离子体运行迈出重要一步。

脉冲低剂量率照射联合累及野调强放疗治疗食管癌的临床疗效

目的探讨脉冲低剂量率照射联合累及野调强放疗治疗食管癌的临床疗效。方法选取2019年1月至2020年3月于盐城市第二人民医院放疗科行放疗的50例初治食管癌患者作为研究对象,按照随机数字表法分为实验组与对照组,每组25例。对照组采用累及野调强放疗方法,实验组采用脉冲低剂量率联合累及野调强放疗方法,比较两组近期疗效和放疗不良反应发生率及局部控制、转移情况。结果实验组近期治疗总有效率为92.0%,对照组为88.0%,两组比较差异无统计学意义。两组≤2级与≥3级骨髓抑制、放射性食管炎发生率比较差异无统计学意义;实验组≤2级放射性肺炎发生率高于对照组,≥3级放射性肺炎发生率低于对照组,差异有统计学意义(P<0.05)。两组局部复发、区域淋巴结转移、远处转移发生率比较差异无统计学意义。结论脉冲低剂量率照射联合累及野调强放疗与累及野调强放疗治疗初治食管癌疗效相当,均可出现骨髓抑制、放射性食管炎情况,但脉冲低剂量率照射联合累及野调强放疗可降低放射性肺炎发生率和严重程度,优势明显。

miniSCIDOM: a scintillator-based tomograph for volumetric dose reconstruction of single laser-driven proton bunches

Laser plasma accelerators(LPAs)enable the generation of intense and short proton bunches on a micrometre scale,thus offering new experimental capabilities to research fields such as ultra-high dose rate radiobiology or material analysis.Being spectrally broadband,laser-accelerated proton bunches allow for tailored volumetric dose deposition in a sample via single bunches to excite or probe specific sample properties.The rising number of such experiments indicates a need for diagnostics providing spatially resolved characterization of dose distributions with volumes of approximately 1 cm^(3) for single proton bunches to allow for fast online feedback.Here we present the scintillator-based miniSCIDOM detector for online single-bunch tomographic reconstruction of dose distributions in volumes of up to approximately 1 cm^(3).The detector achieves a spatial resolution below 500μm and a sensitivity of 100 mGy.The detector performance is tested at a proton therapy cyclotron and an LPA proton source.The experiments’primary focus is the characterization of the scintillator’s ionization quenching behaviour.

双极晶体管不同剂量率的辐射效应和退火特性

对不同类型和型号的国产及进口双极晶体管的不同剂量率的辐照效应及退火特性进行了研究。结果表明:在辐照的剂量率范围内,无论是国产还是进口的双极晶体管,都有明显的低剂量率辐照损伤增强现象,且NPN管比PNP管的明显。文中对引起双极器件辐照损伤差异的机理进行了探讨。

^(60)Coγ射线辐照对小麦种子根尖细胞有丝分裂的影响

采用3种不同剂量的60Coγ射线,对3个不同小麦品种种子进行了辐照试验,对其引起的细胞学效应进行了研究。结果表明,低剂量的60Coγ射线辐照对小麦根尖细胞的有丝分裂有正反两种效应,但随着γ射线剂量的增加,根尖细胞有丝分裂指数呈不同程度的下降趋势;60Coγ射线辐照能诱发根尖细胞的染色体畸变和核畸变,出现染色体桥、染色体断片、微核等多种畸变类型,并且随辐照剂量的增加,染色体畸变率、微核率也相应增加,与辐照剂量之间呈正相关;另外,不同小麦品种对60Coγ射线的辐射敏感性不同,在所选的3个品种中,郑引1号较敏感,长武131次之,陕合6号最弱。

工艺条件对双极晶体管低剂量率辐射损伤增强效应的影响

对具有相同制作工艺但NPN管的发射极面积不同以及LPNP管发射极掺杂浓度相异的两种不同类型的国产双极晶体管,在不同剂量率下进行辐射效应和退火特性研究。结果表明:晶体管类型不同,对高低剂量率的辐照响应也相异;不同发射极面积的NPN管的结果显示,发射极面积越小,损伤越大;不同掺杂浓度的LPNP管的结果则表明,轻掺杂的发射极比重掺杂的具有更高的辐射敏感性。对各种实验现象的损伤机理进行了较详细的分析。

低能离子辐照生物体存活率剂量效应的质量效应模型

低能离子束诱变的主要特点是其具有质量沉积效应。本文立足于“双链断裂”学说，从质量沉积效应出发，认为注入离子通过各种沉积方式形成的沉积产物对ＤＮＡ双链或单链的断裂具有修复或增强作用，由此导出低能氮离子辐照中生物体存活率的剂量效应模型：，并将之称为质量效应模型。该模型很好地拟合了过去的模型所不能拟合的多种生物体的存活率剂量效应曲线。同时还对其应用范围进行了分析。

食管癌外照射综合高剂量率后装治疗价值的探讨

目的 :探讨食管癌外照射加腔内后装治疗的价值及后装治疗合适的每次剂量与总剂量。方法 :1992年 10月至 1993年 5月 112例经病理证实的食管癌患者 ,外照射加腔内照射 5 2例 ,单纯外照射 60例 ,分组比较。并将综合组的剂量分组进行生存率的比较。结果 :综合组的 1、3、5年生存率分别为 73 %、3 2 .7%、2 3 % ;对照组的 1、3、5年生存率分别为 4 1.6%、18.3 %、8.3 %。经统计学处理有明显差异。其中病变长度小于或等于 5cm外照射加后装的病例 1、3、5年生存率比单纯外照射明显增高 ,统计学有显著性差异。而长度大于 5cm的病例 ,两组病人差别不大。结论 :外照射综合高剂量率后装治疗对病灶小于或等于 5cm的食管癌可明显提高疗效。掌握后装剂量是提高生存率的关键。外照射 60Gy后再加腔内后装 5Gy/次 ,总量

不同偏置对NPN双极晶体管的低剂量率电离辐照损伤的影响

对NPN双极晶体管进行了低剂量率下不同偏置条件的电离辐射实验。结果表明,不同偏置条件下的低剂量率辐射损伤具有明显差异。基-射结反向偏置时,其过剩基极电流最大,电流增益衰减最为显著。而基-射结正向偏置时,过剩基极电流和电流增益衰减都最小。讨论了出现这种结果的内在机制。

高速CMOS电路电离辐照损伤的剂量率效应

对国产加固６４ＨＣ０４高速ＣＭＯＳ电路进行了不同剂量率的辐照响应和室温退火特性研究。探讨了５４ＨＣ０４电路在不同剂量率辐照下的损伤机理和失效模式的差异及其对高速ＣＭＯＳ电路在辐射环境中应用可靠性的影响。

双极电压比较器低剂量率辐照损伤增强效应的变温辐照加速评估方法

对3款同种型号不同公司生产的双极电压比较器进行了高、低剂量率及变温辐照的60 Coγ辐照实验。结果表明:偏置电流和电源电流为双极电压比较器辐射敏感参数,失调电压仅在工作偏置条件下为辐射敏感参数;由于工艺不同,不同公司的双极电压比较器存在辐射响应差异,而同一公司的双极电压比较器在不同偏置条件下的辐照损伤趋势亦不同;变温辐照加速评估方法不仅可鉴别上述不同公司的双极电压比较器在不同偏置条件下的剂量率效应,而且能很好地模拟和保守地评估其低剂量率下的辐照损伤。

瞬时电离辐射剂量率对BiMOS运放输出扰动时间的影响

对两种不同类型BiMOS运算放大器(JFET-Bi,PMOS-Bi)γ瞬时电离辐射效应进行研究。结果显示,BiMOS运放瞬时辐射扰动时间随剂量率变化呈现出一定的规律性,在剂量率较低情况下扰动时间随剂量率指数增长,剂量率较高时,扰动时间呈现出饱和特性。另外,输入信号不同,输出扰动时间随剂量率的变化也会有差异。

食管癌体外加HDR腔内放疗疗效分析

1992年5月～1994年12月体外放疗50～60Gy／5～6周加高剂量率（HDR）腔内放疗10～15Gy／4～6；k／5～9天，2.5Gy／次，Bid治疗食管鳞癌56例（综合组），与同期单纯体外放疗60～70Gy／6．5～7周52例（对照组）比较。综合组1、2年生存率和2年局控率分别为76．8％、51．8％和63．5％。明显高于对照组的42．3％、28．8％和32．6％。食管X线片示病变长度≤7cm和无食管轴向异常者，综合组3年生存率分别42．3％和40．9％，明显高于对照组的14．8％和14．3％。综合组食管瘘发生率为3．6％，晚期食管良性狭窄率为7．4％。