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.

Effects of UV-B irradiation on isoforms of antioxidant enzymes and their activities in red alga Grateloupia filicina(Rhodophyta)

Macroalgae in a littoral zone are inevitably exposed to UV-B irradiance. We analyzed the effects of UV-B on isoenzyme patterns and activities of superoxide dismutase （SOD）, peroxidase （POX）, catalase （CAT）, and ascorbate peroxidase （APX） of red algae Grateloupia filicina （Lamour.） C. Agardh. The activities of SOD, CAT, and APX changed in response to UV-B in a time- and dose-dependent manner. POX activity increased significantly under all three UV-B treatments. The enzymatic assay showed three distinct bands of SODI （Mn-SOD）, SODII （Fe-SOD）, and SODIII （CuZn-SOD） under a low （Luv） and medium （Muv） dose of UV-B irradiation, while SODI and SODIII activities decreased significantly when exposed to a high dose of UV-B irradiation （Huv）. The activity of POX isoenzymes increased significantly after exposure to UV-B, which is consistent with the total activity. In addition, a clear decrease in activity of CATIV was detected in response to all the three doses of UV treatments. Some bands ofAPX isoenzyme were also clearly influenced by UV-B irradiation. Correspondingly, the daily growth rate declined under all the three exposure doses, and was especially significant under Muv and Huv treatments. These data suggest that, although the protection mechanisms of antioxidant defense system are partly inducible by UV-B to prevent the damage, G.filicina has incomplete tolerance to higher UV-B irradiation stress.

Effect of UV-B irradiation on interspecific competition between Ulva pertusa and Grateloupia filicina

We report the effect of UVoB irradiation （9.6 kJ m-2 day^-） on interspecific competition between two species of macroalgae, Ulva pertusa （U） and Grateloupiafilicina （G）, in co-culture. Growth of U. pertusa and G. filicina was inhibited by UV-B irradiation in mono-culture and specific growth rate （μ） declined as a result. Interspecific competition between U. pertusa and G filicina was closely related to the initial weights when co-cultured. When initial ratios of U. pertusa （U） to G filicina （G） were U：G=I.2：I and 1：1, U. pertusa was the dominant algae. When the initial U：G ratio was 1：1.2, G. filicina was competitively dominant in the earlier stage, but U. pertusa grew faster, superseding G. filicina in the later stage. At initial ration U：G = 1：1.4, G. filicina was predominant. Under UV-B irradiation, the competitive ability of G filicina was weakened and the interspecific competitive balance favored U. pertusa, which suggests that G. filicina was more sensitive to UV-B irradiation. We also probed the potential allelopathic effects between the two species, which led to mutual growth inhibition.

The effects of enriched C0_(2) and enhanced UV-B radiation on ultrastructure of Dunaliella salina, singly and in combination

The effects of ambient CO2/ambient UV-B, enriched CO2/ambient UV-B, ambient CO2/enhanced UV-B, and enriched CO2/enhanced UV-B on the ultrastructure of Dunaliella salina were investigated. （1） The ultrastructure of D..salina cell in the control experiment showed that the arrangement of thylakoid lamellae was regular, and there were many large starch grains among the thylakoid lamellae. A prominent well-developed pyrenoid was found in the middle of the chloroplast. Nucleus envelope and nucleolus were clearly observed. The Golgi apparatus accompanied by numerous vesicles with a compact arrangement of cisternae and the peripheral tips of the cisternae were swollen to a size comparable to that of some of the associated vesicles. （2） The ultrastructure of D. salina cell in enriched CO2 showed that the arrangement of thylakoid was regular and the lamellae were vivid. Developed pyrenoids were found in the low-CO2-grown cells, but not in the high-CO2-grown cells. The mitochondria cristae were vivid. The arrangement of Golgi apparatus was compact. （3） The ultrastructure of D. salina cell in enhanced UV-B showed that the thylakoid was dissolved and the cells had a less developed pyrenoid or no detectable pyrenoid. Part of the nucleus envelope was dissolved. The number ofmitochondria was increased and some mitochondria cristae were disintegrated. The starch grains were broken apart into many small starch grains. The Golgi apparatus with a loose arrangement ofcistemae and the peripheral tips of the Golgi cistemae were not especially swollen, with several large associated vesicles. （4） The ultrastructure of D. salina cell in the enriched CO2/enhanced UV-B showed that part of the thylakoid and nucleus envelopes of some cells were dissolved. The pyrenoid was larger than that of the enhanced UV-B. There were many mitochondria between stroma and chloroplast membrane, but mitochondria cristae were partly dissolved. Many small starch grains were accumulated in cells. The starch sheath was broken into several discontinuous starch grains with different sizes. The arrangement of Golgi apparatus was loose. Above all, although the enriched CO2 can alleviate the damage induced by the UV-B radiation, the effects of experimental UV-B radiation were larger than the effects of actual UV-B radiation, the damage induced by the UV-B radiation was so severe, therefore, CO2 enrichment could not restore the ultrastructure to the control level.

Microdosimetric Evaluation on the Metallic Nanoparticle-Mediated Dose Enhancement in Radiotherapeutic Proton Irradiation

Monte Carlo simulations are performed on the dosimetric effect of metallic nanoparticles in a clinical proton irradiation.With an in-water hitting model of a single nanoparticle,the secondar.y electrons dose,deposited around the particle surface,is calculated for the proton irradiations in a typical spread-out Bragg peak.The dose enhancement,as the ratio of electron doses from the target particle and background water,is evaluated for the dependence on the depth of hitting,particle size,elements,coating material and thickness.The results indicate a significant dose enhancement on the particle surface within-200 nm,but a fast decay in further distance.The dose enhancement presents a consistency along the spread-out Bragg peak,a positive dependence on both the particle size and electron density,but a strong attenuation by surface coating.Particle cluster may increase the incdividual dose enhajncement by electron crossfire,but is only noticeable in a compact case.The dose enhancement potentiates a radiosensitization use of metallic nanoparticles in clinical proton therapy,but challenqging meanwhile with the narrow ranqge of enhancement effect.

The effects of ^(60)Co γ-ray irradiation on the DC characteristics of enhancement-mode AlGaN/GaN high-electron-mobility transistors

The effects of ^60Co γ-ray irradiation on the DC characteristics of AlGaN/GaN enhancement-mode high-electron- mobility transistors （E-mode HEMTs） are investigated. The results show that having been irradiated by^60Co γ-rays at a dose of 3 Mrad （Si）, the E-mode HEMT reduces its saturation drain current and maximal transconductance by 6% and 5%, respectively, and significantly increases both forward and reverse gate currents, while its threshold voltage is affected only slightly. The obvious performance degradation of E-mode A1GaN/GaN HEMTs is consistent with the creation of electronegative surface state charges in the source-gate spacer and gate-drain spacer after being irradiated.

Different Doses of the Enhanced UV-B Radiation Effects on Wheat Somatic Cell Division

Being sessile, plants are continuously exposed to DNA-damaging agents presenting in the environment such as ultraviolet (UV). Sunlight acts as an energy source for photosynthetic plants;hence, avoidance of UV radiations (namely, UV-A, 315 - 400 nm;UV-B, 280 - 315 nm;and UV-C, 1 group: 4.05 kJ&#8226m-2&#8226d-1, B2 group: 10.08 kJ&#8226m-2&#8226d-1, B3 group: 7.05 kJ&#8226m-2&#8226d-1, B4 group: 23.02 kJ&#8226m-2&#8226d-1) treatment wheat, then, explored on the growth of wheat root and wheat root tip cell of chromosome aberration effect. In wheat, root-tip cells were observed with confocal laser scanning microscopy (CLSM), the results showed that low doses of B1 group (4.05 kJ&#8226m-2&#8226d-1) promoted the growth of wheat root and cell mitosis frequency. But high dose of B2 group (10.08 kJ&#8226m-2&#8226d-1), B3 group (17.05 kJ&#8226m-2&#8226d-1), B4 group (23.02 kJ&#8226m-2&#8226d-1) inhibited the growth of wheat root tip, and made crooked growth of wheat root, and inhibited the wheat root tip cell mitotic frequency and processed that induce root tip cells of wheat produce all kinds of aberration of chromosome in the interphase containing “multiple nucleoli nuclei”, “incomplete nuclei”, “long round nuclei”, “bean sprouts nucleus”. In mitosis M period contains “dissociative chromosome”, “chromosome bridge”, “adhesion chromosome”, “multi-bundle divide”, “nuclear anomalies”. After, high doses of enhanced UV-B radiation treatment, most of the cell cycle anomaly concentrated in mitosis interphase. In mitosis M period, with UV-B radiation dose enhanced chromosome aberration rate was on the rise and the aberration types also increasing.

Ultraviolet irradiation induced oxidative stress and response of antioxidant system in an intertidal macroalgae Corallina officinalis L.

The response of the antioxidant defense system of an intertidal macroalgae Corallina officinalis L.to different dosages of UV-B irradiation was investigated.Results showed that superoxide dimutase （SOD） and peroxidase （POX） increased and then maintained at a relatively stable level when subjected to UV-B irradiation.Catalase （CAT） activity under medium dosage of UV-B irradiation （Muv） and high dosage of UV-B irradiation （Huv） treatments were significantly decreased.Ascorbate peroxidase （APX） activity first remained unaltered and then increased in Huv treatment.In addition,the assay on isozymes was carried out using non-denaturing polyacrylamide gel electrophoresis （PAGE）.The activities of some SOD isoforms were altered by UV-B.Two new bands （POX V and POX VII） appeared upon exposure to all three UV-B dosages.CAT III activity was increased by low dosage of UV-B irradiation （Luv）,whereas CAT III and CAT IV disappeared when the alga was exposed to Muv and Huv.Two bands of APX （APX VI and APX VII） were increased and a new band （APX X） was observed under Huv exposure.H 2 O 2 and thiobarbituric acid reacting substance （TBARS） increased under Muv and Huv treatments.Overall,UV-B protection mechanisms are partly inducible and to a certain extent sufficient to prevent the accumulation of damage in C.officinalis.

The Distribution and Morphology Alterations of Microfilaments and Microtubules in Mesophyll Cells and Root-Tip Cells of Wheat Seedlings under Enhanced Ultraviolet-B Radiation

The distribution and morphology alterations of microfilaments and microtubules in the mesophyll cells and root-tip cells of wheat seedlings, which had been radiated by enhanced ultraviolet-B (10.08 KJ·m-2·d-1), were examined through the confocal laser scanning microscope (Model FV1000, Olympus, Japan). Microtubule was labeled with an indirect immunofluorescence staining method, and microfilament was labeled with fluorescein isothiocyanate-phalloidin (FITC-Ph) as probes. The results indicated that microtubules in mesophyll cells, compared with the controls, would be depolymerized significantly, and dispersed randomly showing some spots or short rods in the cytoplasm, under the enhanced UV-B radiation condition. The microtubule bundles tended to be diffused, and the fluorescence intensity of that significantly decreased. The distribution pattern of microfilaments, which usually arranged parallelly in control cells, was broken up by enhanced UV-B radiation. We further investigated the distribution and morphology of microtubules in root-tip cells during every stage of cell division, and found that these aberrant phenomena of microtubules were often associated with abnormal cell division. Our findings suggested that the distribution, morphology and structure of cytoskeleton in mesophyll cells and root-tip cells of wheat seedlings would be affected by enhanced UV-B radiation, which might be related to abnormal cell division caused by enhanced UV-B radiation as an extracellular signal.

UV-B辐射增加对燕麦产量及其构成因素影响研究

在大田条件下通过采用人工UV-B灯管模拟来增加太阳光辐射量5%和10%对燕麦品种-巴燕4号的有关性状的影响进行了研究。结果表明,UV-B辐射增加能显著降低燕麦种子产量,产量下降的主要原因是每穗粒数和单位面积穗数下降,粒重的变化未达到显著水平。比较燕麦同一花位的粒重,UV-B辐射增加导致燕麦粒重显著下降,同时导致粒重较低的高花位籽粒数减少。青藏高原上来自太阳紫外辐射量的增加可能会影响燕麦的繁殖能力。

全球环境变化使植物体对增强UV-B辐射信号的感受和传导

据国际上的最新研究成果 ,论述了在全球环境变化引起的UV -B辐射过程中 ,植物对UV -B信号的感受和传导机理 ,其中包括细胞中UV -B信号受体 ,各种信号分子 (诸如活性氧、水杨酸、茉莉酸、乙烯和一氧化氮等 )的级联放大传递以及对于基因表达活性的影响 ,提出了UV -B胁迫信号传递的信号分子级联模型 ,从而为有效防护环境变化引起的UV

Effects of UV-B radiation and different light repair conditions on the early development of the tetraspores of Chondrus ocellatus Holm

The effects of exposure to UV-B radiation, 280-315 nm, and dark or dark repair conditions on the early development of Chondrus ocellatus Holm collected from Qingdao coast were studied under the laboratory condition. After being exposed to different doses [0, 36, 72, 108, 144 and 180 J/（m2.d）] of UV-B radiation, one treatment of tetraspores were put back to normal culture condition （PAR）, the other treatment were put into dark condition to repair for 2 h. During the cultivation, the diameter of the tetraspores were recorded every 4 d till the 50th day when vertical branches formed in all treatments. Then at the 50th day, CPDs, phycoerythrin, chlorophyll a and MAAs （Palythine and asterina-330） were measured. The results showed that low doses UV-B radiation could significantly accelerate the growth rate of the rate reduced gradually with UV-B radiation keep on tetraspores of C. ocellatus and the growth increasing. The variation trend of both the phycoerythrin and chlorophyll a concentration reduced significantly （P 〈0.05） once given the UV- B radiation. Under UV-B stress, the CPDs were induced, and the concentrations of CPDs were significant low in dark repair groups. The data of MAAs analyzed by LC/MS in the tetraspores of C. ocellatus suggested that there were two MAAs formed （palythine and asterina-330） after UV-B radiation induced, and low dose of UV-B irradiation could significantly induced the concentration of MAAs. From the growth and development state of the tetraspores, negative effects of UV-B radiation on the dark repair groups were more serious than PAR.

Unraveling the mystery of enhanced cell-killing effect around the Bragg peak region of a double irradiation source^(9)C-ion beam

An enhanced cell-killing effect at the penetra- tion depths around the Bragg peak of a β-delayed particle decay 9C-ion beam has been observed in our preceding ra- diobiological experiments in comparison with a therapeutic 12C beam under the same conditions, and RBE values of the 9C beam were revealed to be higher than those of the comparative 12C beam by a factor of up to 2. This study is aimed at investigating the biophysical mechanisms underlying the important experimental phenomenon. First of all, a model for calculating the stopping probability density of the experimentally applied 9C beam is worked out, where all determinants such as the initial momentum spread of the 9C beam, the fluence attenuation with penetration depth due to the projectile-target nuclear reaction and the energy strag- gling effect are taken into account. On the basis of the calcu- lated 9C-ion stopping distribution, it has been found that the area corresponding to the enhanced cell-killing effect of the 9C beam appears at the stopping region of the incident 9C ions. The stopping 9C-ion density in depth, then, is derived from the calculated probability density. Moreover, taking entrance dose 1 Gy for the 9C beam as an example, the aver- age stopping 9C-ion numbers per cell at various depths are deduced. Meanwhile, the mean lethal damage events induced by the 9C and comparative 12C beams at the depths with al- most equal dose-averaged LETs are derived from the meas- ured cell surviving fractions at these depths for the 9C and 12C beams. Under the condition of the same absorbed doses, there are indeed good agreements between the average stop- ping 9C-ion number pre cell and the difference of the mean lethal damage events between the 9C and 12C beams at the depths of similar dose-averaged LETs. It can be inferred that if a 9C ion comes to rest in a cell, the cell would undergo dy- ing. In view of the decay property of 9C nuclide, clustered damage would be caused in the cell by the emitted low-energy particles. Therefore, the results achieved in this work can be taken as indirect evidence supporting that damage cluster is more efficient in leading to cell lethality.

Study on Enhancement Effect of Cavitation Caused by HIFU Piezoelectricity Transducer

An orthogonal ultrasonic irradiation system consisting of HIFU with frequency at 1.05 MHz combined with ultrasound with frequency at 28 kHz was applied in this paper.Effect of cavitation was detected by pH-value measurement and conductance measurement.The result shows that the effect of cavitation caused by ultrasound with frequency at 28 kHz is greatly enhanced by HIFU piezoelectricity transducer with frequency at 1.05 MHz.

Enhancement of pulsed laser ablation assisted with continuous wave laser irradiation

Continuous wave(CW) laser irradiation is employed to enhance the pulsed laser ablation of silicon and stainless steel(316 L)samples. Different surface temperatures generated by the CW laser irradiation are set as the initial working circumstance for the pulsed laser ablation. The diameter and depth of laser-ablated craters are measured to study threshold fluence, pulse incubation coefficient and ablation rate under different surface temperatures. Numerical simulation employing Heat Transfer in Solid and Deformed Geometry Interface modules in COMSOL is performed to estimate ablation rate theoretically based on Hertz-Knudsen equation. The realized crater-related data are analyzed to further obtain their dependences on surface temperature. The parametric and morphological studies indicate that the weakened plasma shielding effect and thermal diffusion in the ablated region induced by the CW laser irradiation lead to the enhanced pulsed laser ablation significantly.

增强型GaNHEMT器件5MeV质子辐照试验研究

氮化镓器件凭借优异的性能在抗辐照应用领域备受关注,为探究不同结构的氮化镓器件抗质子辐照能力,开展了对增强型Cascode级联结构和P-GaN栅结构GaN高电子迁移率晶体管(High Electron Mobility Transistor,HEMT)器件的5MeV质子辐照试验,分析器件电学特性退化规律,并明确其质子辐照效应损伤机制。试验发现,质子辐照注量越大,Cascode结构器件阈值电压负漂越严重,同时饱和漏极电流增加越显著,当质子注量大于1×10^(13) p∙cm^(-2)时,器件电学特性退化程度开始降低。对于P-GaN栅结构GaN HEMT而言,辐照后电学特性退化规律与Cascode结构器件截然相反,且退化程度明显小于Cascode结构器件,表明增强型Cascode结构器件对质子辐照更加敏感。结合低频噪声测试,发现随辐照注量的增加,Cascode结构器件噪声功率谱密度先增加后保持稳定,其变化规律与电学特性退化情况相吻合。分析认为,5 MeV质子辐照诱导发生电离损伤使Cascode结构器件内部级联的Si基金属-氧化物-半导体场效应晶体管(Metal-Oxide-Semiconductor Field Effect Transistor,MOSFET)栅氧化层产生了更多的氧化物陷阱电荷与界面态陷阱电荷,是Cascode结构器件对质子辐照敏感的主要原因。研究结果对GaN功率器件加固设计和航天应用器件选型具有一定的参考价值。

利用激光辐照AgCl纳米立方体制备表面增强拉曼散射基底的方法

利用激光辐照AgCl纳米立方体,通过析出Ag纳米颗粒制备了表面增强拉曼散射(surface-enhanced Raman scattering,SERS)基底。利用水热法合成AgCl纳米立方体,随后利用波长为633 nm的激光进行辐照,AgCl纳米立方体表面会析出Ag纳米颗粒。利用场发射扫描电子显微镜对辐照后的样品进行形貌表征,同时采用对氨基硫酚(PATP)探索Ag@AgCl样品的SERS灵敏度。结果发现,随着辐照功率增大或者辐照时间增加,析出的Ag颗粒数量增多并且尺寸增大,因此获得的SERS基底的灵敏度得到增强。研究结果为制备SERS基底提供了一种比较简便的方法。

Ethylene Production and 1-Aminocyclopropane-l-Carboxylate （ACC） Synthase Gene Expression in Tomato （ L ycopsicon esculentum Mill.） Leaves Under Enhanced UV-B Radiation

Tomato （Lycopslcon esculentum Mill.） plants grown in a greenhouse were irradiated with two different levels of UV-B, namely 8.82 （T1） and 12.6 kJ/m^2 per day （T2）. Ethylene production, 1-aminocyclopropane-1-carboxylate （ACC） content, 1-（malonylamino） cyclopvopane-1-carboxylic acid （MACC） content, gene expression of ACC aynthase （EC 4.4.1.14）, and ACC oxidase activity in tomato leaves were determined. The results Indicated that ACC content, the activity of ACC synthase and ACC oxidase, and ethylene production Increased continuously under low doses of UV-B radiation, whereas at high doses of radiation these parameters Increased during the first 12 d and then started to decrease. The MACC content increased continuously over 18 d under both doses of UV-B irradiation. The changes in ACC content, ACC synthaae activity, ACC oxidase activity, the transcriptional level of the ACC synthase gene, and ethylene production were consistent with each other, suggesting that ACC synthase was the key enzyme in ethylene biosynthesis and that ethylene production in tomato leaf tissues under UV-B radiation could be regulated by the expression of the ACC synthase gene. The results also indicate that the change in ethylene metabolism may be an adaptive mechanism to enhanced UV-B radiation.

Giant enhancement of photoluminescence emission in monolayer WS_(2)by femtosecond laser irradiation

Monolayer transition metal dichalcogenides have emerged as promising mat erials for opt oelectTonic and nanophotonic devices.However,the low photoluminescence(PL)quantum yield(QY)hinders their various potential applications.Here we engineer and enhance the PL intensity of monolayer WS_(2)by femtosecond laser irradiation.More than two orders of magnitude enhancement of PL intensity as compared to the as-prepared sample is determined.Furthermore,the engineering time is shortened by three orders of magnitude as compared to the improvement of PL intensity by continuous-wave laser irradiation.Based on the evolution of PL spectra,we attribute the giant PL enhancement to the conversion from trion emission to exciton,as well as the improvement of the QY when exciton and trion are localized to the new-formed defects.We have created microstructures on the monolayer WS_(2)based on the enhancement of PL intensity,where the engineered structures can be stably stored for more than three years.This flexible approach with the feature of excellent long-term storage stability is promising for applications in information storage,display technology,and opto electronic devices.

MgF_(2)/Lumogen复合薄膜抗辐照损伤效应研究

为研究MgF_(2)/Lumogen复合薄膜应用于真空紫外探测的高能辐照损伤特性,以300 W高能1064 nm连续激光进行辐照。通过改变激光功率和扫描速率,调控膜层受激光辐照的能量和时间,并测试辐照前后薄膜光致发光强度、荧光衰减、透过率等光信号性能。结果表明,在能量密度0.58~2.94 W/mm2、扫描速率50~10 mm/min激光辐照后,深紫外160 nm激发的荧光响应强度衰减了1%~61%,近紫外273 nm激发的荧光响应强度衰减了1%~21%,可见光500~700 nm透过率衰减了2%~3%。对比单层Lumogen薄膜的辐照损伤结果以及复合薄膜的热传导分析,MgF_(2)薄膜对Lumogen具有减反增透作用的同时还具有一定的抗辐照损伤能力。