Electronic effects on radiation damage inα-iron:A molecular dynamics study

Iron(Fe)-based alloys,which have been widely used as structural materials in nuclear reactors,can significantly change their microstructure properties and macroscopic properties under high flux neutron irradiation during operation,thus,the problems associated with the safe operation of nuclear reactors have been put forward naturally.In this work,a molecular dynamics simulation approach combined with electronic effects is developed for investigating the primary radiation damage process inα-Fe.Specifically,the influence of electronic effects on the collision cascade in Fe is systematically evaluated based on two commonly used interatomic potentials for Fe.The simulation results reveal that both electronic stopping(ES)and electron-phonon coupling(EPC)can contribute to the decrease of the number of defects in the thermal spike phase.The application of ES reduces the number of residual defects after the cascade evolution,whereas EPC has a reverse effect.The introduction of electronic effects promotes the formation of the dispersive subcascade:ES significantly changes the geometry of the damaged region in the thermal spike phase,whereas EPC mainly reduces the extent of the damaged region.Furthermore,the incorporation of electronic effects effectively mitigates discrepancies in simulation outcomes when using different interatomic potentials.

Low-Dose Gamma Radiation Fields Decrease Cell Viability, Damage DNA, and Increase the Expression of Hsp70 and p53 Proteins in Human Leukocytes

Ionizing radiations are tools in diagnosis and treatment of diseases. Leukopenia from exposure to ionizing radiation has been reported. Due to their radiosensitivity, leukocytes are a biological model to analyze cell damage. Therefore, cell viability, DNA damage, and Hsp70 and p53 expression in human leukocytes exposed to low-dose gamma radiation fields from a 137Cs source were evaluated. A decrease in cell viability, DNA damage and an increase in the expression of Hsp70 and p53 proportional to the radiation dose received was found, which was 0.2, 0.4, 0.6, 0.8 and 1.0 mGy.

Typical Cell Signaling Response to Ionizing Radiation: DNA Damage and Extranuclear Damage

To treat many types of cancer, ionizing radiation （IR） is primarily used as external-beam radiotherapy, brachytherapy, and targeted radionuclide therapy. Exposure of tumor cells to JR can induce DNA damage as well as generation of reactive oxygen species （ROS） and reactive nitrogen species （RNS） which can cause non-DNA lesions or extracellular damage like lipid perioxidation. The initial radiation-induced cell responses to DNA damage and ROS like the proteolytic processing, as well as synthesis and releasing ligands （such as growth factors, cytokines, and hormone） can cause the delayed secondary responses in irradiated and unirradiated bystander cells through paracrine and autocrine pathways.

Surface Etching and DNA Damage Induced by Low-Energy Ion Irradiation in Yeast

Bio-effects of survival and etching damage on cell surface and DNA strand breaks were investigated in the yeast saccharomyces cerevisiae after exposure by nitrogen ion with an energy below 40 keV. The result showed that 16% of trehalose provided definite protection for cells against vacuum stress compared with glycerol. In contrast to vacuum control, significant morpho- logical damage and DNA strand breaks were observed, in yeast cells bombarded with low-energy nitrogen, by scanning electron microscopy （SEM） and terminal deoxynucleotidyl transferase- mediated dUTP nick end labeling （TUNEL） immunofluorescence assays. Moreover, PI （propidium iodide） fluorescent staining indicated that cell integrity could be destroyed by ion irradiation. Cell damage eventually affected cell viability and free radicals were involved in cell damage as shown by DMSO （dimethyl sulfoxide） rescue experiment. Our primary experiments demonstrated that yeast cells can be used as an optional experimental model to study the biological effects of low energy ions and be applied to further investigate the mechanism（s） underlying the bio-effects of eukaryotic cells.

Damage to DNA of effective microorganisms by heavy metals:Impact on wastewater treatment

The research is to test the damage to DNA of effective microorganisms(EMs)by heavy metal ions As3+,Cd2+,Cr3+,Cu2+,Hg2+, Pb2+,and Zn2+,as well as the effects of EM bacteria on wastewater treatment capability when their DNA is damaged.The approach applied in this study is to test with COMET assay the damage of EM DNA in wastewater with different concentrations of heavy metal ions As3+,Cd2+,Cr3+,Cu2+,Hg2+,Pb2+,Zn2+,as well as the effects of EM treated with As3+,Cd2+,Cr3+,Cu2+,Hg2+,Pb2+,and Zn2+ on COD degradin...

Incident particle range dependence of radiation damage in a power bipolar junction transistor

The characteristic degradations in silicon NPN bipolar junction transistors（BJTs） of type 3DD155 are examined under the irradiations of 25-MeV carbon（C）,40-MeV silicon（Si）,and 40-MeV chlorine（Cl） ions respectively.Different electrical parameters are measured in-situ during the exposure of heavy ions.The experimental data shows that the changes in the reciprocal of the gain variation（（1/β）） of 3DD155 transistors irradiated respectively by 25-MeV C,40-MeV Si,and 40-MeV Cl ions each present a nonlinear behaviour at a low fluence and a linear response at a high fluence.The（1/β） of 3DD155 BJT irradiated by 25-MeV C ions is greatest at a given fluence,a little smaller when the device is irradiated by 40-MeV Si ions,and smallest in the case of the 40-MeV Cl ions irradiation.The measured and calculated results clearly show that the range of heavy ions in the base region of BJT affects the level of radiation damage.

Protective Effect of Dimethyl-4,4'-Dimethoxy-5,6,5',6'-Dimethylene Dioxybiphenyl-2,2'-Dicarboxylate (DDB) against Carcinogen-Induced Rat Liver Nuclear DNA Damage

The protective effect of DDB against carcinogen-induced DNA damage was examined in the present investigation. Preincubation of rat liver nuclei with DDB (1 mmol.L-1) resulted in 60% inhibition of binding of 3H-benzo (a) pyrene to nuclear DNA. Unscheduled DNA synthesis (UDS) induced by aflatoxin BI (10^(-7) mol.L-1) in freshly isolated rat hepatocytes was also inhibited by DDB (10^(-6)-10^(-3)mol.L-1). Oral administration of DDB at 200 mg.kg-1 once daily for 3 d induced a significant increase of liver cytosol glutathione-S-transferase and microsomal UDPG-transferase activity in mice. These results indicate that DDB is able to directly or indirectly antagonize certain carcinogen-induced DNA damages.

Effect of UV Radiation and Other Abiotic Stress Factors on DNA of Different Wild Plant Species Grown in Three Successive Seasons in Alpine and Subalpine Regions

Plants in natural ecosystems are exposed to a combination of UV radiation,ionizing radiation(IR)and other abiotic factors.These factors change with the altitude.We investigated DNA alterations of some wild plants of different plant families in natural ecosystems at three altitudes in Rila Mountain,Bulgaria(1500,1782,and 2925 m above sea level(a.s.l.)exposed to UV radiation,IR and other abiotic stresses,to assess the tolerance of plant species to the changing environmental conditions in three successive growth seasons.For this purpose,physicochemical,cytogenetic,and molecular methods were applied.DNA damage was assessed by micronucleus test and molecular method comet assay adapted and applied by us to wild plant species from Onagraceae,Rosaceae,Boraginaceae,Saxifragaceae,Orobanchaceae,Asteraceae and Poaceae families,growing at three different altitudes.Variability in the DNA sensitivity and the level of tolerance was observed among the plant species in response to combined abiotic factors assessed by induced DNA damage and gross beta activity.The studied representatives of Poaceae were less susceptible than the other studied species at all three altitudes and showed close level of DNA injuries to that of unaffected control plant grown in laboratory conditions.The lower levels of DNA damage of these wild plant species corresponded to their lower ability to accumulate radionuclides.There was a particularly pronounced low level of DNA injuries in the plant species at the highest altitude.The level of DNA damage showed correlation with the values of some abiotic environmental factors.The results would contribute to the elucidation of the extent of adaptation of plant species to the continuously changing environment and would be useful in selecting sensitive herbaceous monitor species for environmental impact assessment at mountain and alpine sites.

Bulk and surface damages in complementary bipolar junction transistors produced by high dose irradiation

Two complementary types NPN and PNP of bipolar junction transistors （BJTs） were exposed to higll dose of neutrons and gamma rays. The change in the base and collector currents, minority carriers lifetime, and current gain factor/3 with respect to the dose were analyzed. The contributions of the base current according to the defect types were also reported. It was declared that the radiation effect of neutrons was almost similar between the two transistor types, this effect at high dose may decrease the value of/3 to less than one. The Messenger-Spratt equation was used to describe the experimental results in this case. However, the experimental data demonstrated that the effect of gamma rays was generally higher on NPN than PNP transistors. This is mainly attributed to the difference in the behavior of the trapped positive charges in the SiO2 layers. Meanwhile, this difference tends to be small for high gamma dose.

Radiation effects on MOS and bipolar devices by 8 MeV protons,60 MeV Br ions and 1 MeV electrons

The radiation effects of the metal-oxide-semiconductor （MOS） and the bipolar devices are characterised using 8 MeV protons, 60 MeV Br ions and 1 MeV electrons. Key parameters are measured in-situ and compared for the devices. The ionising and nonionising energy losses of incident particles are calculated using the Geant4 and the stopping and range of ions in matter code. The results of the experiment and energy loss calculation for different particles show that different incident particles may give different contributions to MOS and bipolar devices. The irradiation particles, which cause a larger displacement dose within the same chip depth of bipolar devices at a given total dose, would generate more severe damage to the voltage parameters of the bipolar devices. On the contrary, the irradiation particles, which cause larger ionising damage in the gate oxide, would generate more severe damage to MOS devices. In this investigation, we attempt to analyse the sensitivity to radiation damage of the different parameter of the MOS and bipolar devices by comparing the irradiation experimental data and the calculated results using Geant4 and SRIM code.

A Monte Carlo Simulation of Radiation Damage of SiC and Nb Using JA-IPU Code

MC （Monte Carlo） simulation code, JA-IPU is used to study radiation damage of SiC irradiated to spallation neutron and AmBe neutron spectra. The code is based on the major physical processes of radiation damage on incorporation of atomic collision cascade and limited to 10 MeV neutron energy. A phenomenological relation for radiation swelling is also derived. Based on the calculation of swelling, DPA （displacement per atom）, defect production efficiency and effective threshold energy, Efff from the data of MC simulation, SiC is inferred to be a highly radiation resistant material when compared with Nb and Ni metals which are used in composition of several reactor steels. Experimental results of hill-hock density measured using AFM （atomic force microscopy）, also confirm radiation resistant behavior of SiC.

The DNA damage and regulatory strategy in hematopoietic stem cells after irradiation exposure:Progress and challenges

The hematopoietic system is susceptible to ionizing radiation(IR),which can cause acute hematopoietic failure or long-term myelosuppression.As the most primitive cells of the hematopoietic hierarchy,hematopoietic stem cells(HSCs)maintain lifelong hematopoietic homeostasis and promote hematopoietic regeneration during stress.Numerous studies have shown that nuclear and mitochondrial genomes are the main targets of radiation injury in HSCs.More importantly,the damage of DNA may trigger a series of biological responses that largely determine HSC fate following IR exposure.Although some essential pathways and factors involved in DNA injury and damage in HSCs have been revealed,a comprehensive understanding of the biological effects of radiation on HSCs still needs to be improved.This review focuses on recent insights into the molecular mechanisms underlying DNA damage and repair in HSCs after IR.Then summarize corresponding regulatory measures,which may provide a reference for further research in this field.

Effect of Low Level Subchronic Microwave Radiation on Rat Brain

Objective The present study was designed to investigate the effects of subchronic low level microwave radiation （MWR） on cognitive function, heat shock protein 70 （HSP70） level and DNA damage in brain of Fischer rats. Methods Experiments were performed on male Fischer rats exposed to microwave radiation for 90 days at three different frequencies： 900, 2800, and 2450 MHz. Animals were divided into 4 groups： Group I： Sham exposed, Group I1： animals exposed to microwave radiation at 900 MHz and specific absorption rate （SAR） 5.953 x 10-4 W/kg, Group II1： animals exposed to 1800 MHz at SAR 5.835 x 20-4 W/kg and Group IV： animals exposed to 2450 MHz at SAR 6.672 x 10-4 W/kg. All the animals were tested for cognitive function using elevated plus maze and Morris water maze at the end of the exposure period and subsequently sacrificed to collect brain tissues. HSP70 levels were estimated by ELISA and DNA damage was assessed using alkaline comet assay. Results Microwave exposure at 900-2450 MHz with SAR values as mentioned above lead to decline in cognitive function, increase in HSP70 level and DNA damage in brain. Conclusion The results of the present study suggest that low level microwave exposure at frequencies 900, 2800, and 2450 MHz may lead to hazardous effects on brain.

DNA损伤效应主动监测的抗氧化基因缺失微生物传感器的构建及性能评价

目的活性氧基团(ROS)水平升高会引起生物体的DNA氧化损伤,监测DNA的氧化损伤程度,能够实现ROS损伤效应的有效评价。基于微生物传感器监测DNA损伤效应可以定量评价氧化损伤程度,但微生物本身具有的ROS清除机制,会影响监测灵敏度。本研究旨在敲除细菌ROS清除机制的关键基因,构建抗氧化基因缺失微生物传感器,实现对DNA损伤效应的灵敏监测,评价ROS对生物体的损伤效应。方法本研究基于λ-Red同源重组的方法敲除细菌抗氧化损伤相关基因ahpCF、katE与katG,构建抗氧化基因缺失微生物传感器,并评价传感器对萘啶酮酸钠和紫外照射的响应。结果成功构建ΔahpCF、ΔahpCF/ΔkatE与ΔahpCF/ΔkatE/ΔkatG三种抗氧化基因缺失的微生物传感器,工程菌ΔahpCF/ΔkatE/ΔkatG对DNA损伤试剂萘啶酮酸钠的响应灵敏度最高,检测限为0.40μmol/L,另外,1.80 min的紫外照射(254 nm)可诱导工程菌产生显著的荧光表达效应。结论本研究构建了抗氧化基因缺失微生物传感器,实现了对DNA损伤试剂和紫外照射等DNA损伤效应的主动灵敏监测,可为未来空间辐射效应的评价提供一种主动、有效、灵敏的潜在监测方法。

低剂量电离辐射对人淋巴细胞氧化应激及DNA损伤的影响

目的:探讨低剂量^(137)Cs γ射线照射后正常人淋巴细胞(AHH-1)是否产生氧化应激及DNA损伤,并引发DNA修复。方法:以剂量率为8.32 mGy/min的^(137)Cs γ射线照射AHH-1细胞,剂量分别为0(未照射)、0.01、0.02、0.05、0.075、0.1和0.2 Gy,照射后分别培养1、24、48和72 h。采用CCK-8试剂盒检测细胞存活率变化;丙二醛(MDA)、超氧化物歧化酶(SOD)和活性氧(ROS)试剂盒检测细胞氧化损伤水平;免疫荧光方法分析γH2AX和53BP1焦点形成情况;实时荧光定量PCR方法检测DNA损伤修复相关基因CDKN1A、DDB2和POLH的mRNA表达水平变化。结果:与未照射组相比,照射后24和48 h,各剂量组细胞存活率显著增强(P<0.05);照射后48 h,MDA水平和SOD活性在0.2 Gy剂量组发生显著变化(P<0.05);0.02~0.075 Gy和0.2 Gy剂量组ROS相对荧光强度显著升高(P<0.05);0~0.2 Gy γ射线照后1 h,γH2AX和53BP1焦点数量随剂量增加而增加,且具有明显的剂量-效应关系(P<0.01);与未照射组相比,照射后48 h,DDB2和POLH mRNA相对表达水平显著升高,差异具有统计学意义(P<0.05)。结论:低剂量电离辐射引起人淋巴细胞产生氧化应激和DNA损伤,并促进DNA损伤修复相关基因在转录水平发生改变。

The characteristics of DNA repair synthesis induced by DNA polymerase β in hepatoma cells after γ rays irradiation

AIM To investigate the effects of DNA repair synthesis induced by DNA polymerase β in hepatoma cells after γ ray irradiation. METHODS Cell nuclei were prepared from SMMC LTNM hepatoma which is a transplanted human liver cancer born on nude mice. Samples were irradiated with 60 Co γ rays at different doses or dose rates. N ethylmaleimide (NEM) and ddTTP were used as selective inhibitors to DNA polymerases. The reaction of DNA repair synthesis was carried out with the selective inhibitor test. RESULTS It was found that the 3H TTP incorporation in irradiated nuclei or calf thymus DNA was significantly higher than that in the non irradiated ones, under the conditions of DNA polymerase α or γ being inhibited. When NEM and ddTTP which selectively inhibits DNA polymerase β both existed in the DNA repair synthesis reaction mixture, the 3H TTP incorporation in irradiated DNA did not significantly increased. Furthermore, 3H TTP incorporation into DNA of SMMC LTNM hepatoma nuclei was higher than that of normal hepatocyte nuclei ( P <0 01). The DNA repair synthesis induced by DNA polymerase β reacted more fast in hepatoma nuclei than in hepatocyte nuclei. CONCLUSION The effects of DNA repair synthesis induced by DNA polymerase β in some tumor cells might be stronger than that in normal cells, which may facilitate the cells to repair DNA damages from radiation.

X射线激活氧化应激诱导DNA损伤及HaCaT发生细胞早衰研究

目的:探索不同剂量X射线照射人永生化角质形成细胞(HaCaT)后导致细胞氧化应激水平变化、DNA损伤及细胞早衰的发生。方法:对HaCaT进行X射线照射,根据照射剂量将其分为0 Gy组、5 Gy组和10 Gy组,使用2,7-二氯荧光素二乙酸酯(DCFH-DA)荧光探针检测细胞内活性氧(ROS)水平,并用比色法测定细胞内脂质过氧化产物丙二醛(MDA)含量和超氧化物歧化酶(SOD)活性。利用免疫荧光染色检测不同剂量X射线照射后HaCaT中的磷酸化组蛋白2A变异体(γ-H2AX)焦点变化。使用细胞计数试剂盒-8(CCK-8)试剂盒检测不同剂量X射线照射HaCaT后对细胞增殖的影响,采用β-半乳糖苷酶染色检测早衰细胞比例。利用蛋白免疫印迹法检测X射线照射后p21、p53蛋白表达变化。结果:X射线照射HaCaT后24 h,5 Gy组、10 Gy组均较0 Gy组2',7'-二氯荧光素(DCF)荧光强度显著增加,MDA含量较0 Gy组显著升高,而SOD活性较0 Gy组显著下降,3组比较差异均有统计学意义(F=38.35、92.22、5.22,P<0.05)。照射后1 h,γ-H2AX焦点变化呈剂量依赖性显著增加,与0 Gy组相比差异均有统计学意义(F=129.3,P<0.05)。X射线照射HaCaT后6、24和48 h,5 Gy组、10 Gy组均较与0 Gy组相比细胞增殖能力降低,3组比较差异均有统计学意义(F=116.41、62.20、34.29,P<0.01),β-半乳糖苷酶活性增高,其差异均有统计学意义(F=1629.22,P<0.01)。不同剂量X射线照射HaCaT后72 h,5 Gy组和10 Gy组p21、p53蛋白表达量升高,3组比较差异均有统计学意义(F=104.4、66.69,P<0.01)。结论:电离辐射可诱导HaCaT细胞发生氧化应激和DNA损伤同时引起细胞早衰的发生。

Radiation-hardened property of single-walled carbon nanotube film-based field-effect transistors under low-energy proton irradiation

Strong C-C bonds,nanoscale cross-section and low atomic number make single-walled carbon nanotubes(SWCNTs)a potential candidate material for integrated circuits(ICs)applied in outer space.However,very little work combines the simulation calculations with the electrical measurements of SWCNT field-effect transistors(FETs),which limits further understanding on the mechanisms of radiation effects.Here,SWCNT film-based FETs were fabricated to explore the total ionizing dose(TID)and displacement damage effect on the electrical performance under low-energy proton irradiation with different fluences up to 1×1015 p/cm2.Large negative shift of the threshold voltage and obvious decrease of the on-state current verified the TID effect caused in the oxide layer.The stability of the subthreshold swing and the off-state current reveals that the displacement damage caused in the CNT layer is not serious,which proves that the CNT film is radiation-hardened.Specially,according to the simulation,we found the displacement damage caused by protons is different in the source/drain contact area and channel area,leading to varying degrees of change for the contact resistance and sheet resistance.Having analyzed the simulation results and electrical measurements,we explained the low-energy proton irradiation mechanism of the CNT FETs,which is essential for the construction of radiation-hardened CNT film-based ICs for aircrafts.

Effect of bias condition on heavy ion radiation in bipolar junction transistors

The characteristic degradations in a silicon NPN bipolar junction transistor （BJT） of 3DG142 type are examined under irradiation with 40-MeV chlorine （C1） ions under forward, grounded, and reverse bias conditions, respectively. Different electrical parameters are in-situ measured during the exposure under each bias condition. From the experimental data, a larger variation of base current （IB） is observed after irradiation at a given value of base-emitter voJtage （VBE）, while the collector current is slightly affected by irradiation at a given VBE. The gain degradation is affected mostly by the behaviour of the base current. From the experimental data, the variation of current gain in the case of forward bias is much smaller than that in the other conditions. Moreover, for 3DG142 BJT, the current gain degradation in the case of reverse bias is more severe than that in the grounded case at low fluence, while at high fluence, the gain degradation in the reverse bias case becomes smaller than that in the grounded case.

DNADam ageEffectsofHydroxyapatiteUltrofinePowderonW-256 Sarcom a Cells and Lym phocytes in Rats

To explore the anticancer mechanism and DNA damages of hydroxyapatite ultrofine powder (HAUFP) on lymphocytes of rats, DNA damages in W 256 sarcoma cells and lymphocytes of rats were measured by single cell gel electrophoresis (SCGE). The results showed that HAUFP damaged DNA of W 256 sarcoma cells obviously but only cause slight damage of DNA of lymphocytes in rats. It is suggested that HAUFP selectively damaged DNA of tumor cells with only mild damage of lymphocyte DNA. HAUFP has powerful anticancer effect and little genetic toxicity.