PMMA光纤辐照特性研究

分析了聚合物光纤在辐照环境下的物理化学变化,实验研究了聚甲基丙烯酸甲脂（PMMA）光纤在不同剂量的γ射线辐照下的辐照损伤和恢复特性,测量了PMMA光纤在可见光波段的辐照光谱和恢复光谱以及在638 nm的辐照前后透过率及辐照损伤.测量结果表明,光纤的辐照损伤和恢复都有波长相关性,辐照剂量低于5 kGy,PMMA光纤在整个可见光波段的辐照损伤情况差别不大,辐照剂量超过5 kGy,PMMA光纤在400 nm~550 nm波段的辐照损伤比600 nm~800 nm的辐照损伤要严重.     

核材料辐照损伤协同效应的研究北大核心CSCD

通过拉曼光谱、沟道背散射、原子力显微镜、透射电子显微镜、红外光谱等一系列测试手段对Zr O2,Si C和ODS钢三种核材料的多束辐照行为进行表征,研究离子束的协同效应对核材料辐照损伤的影响。Zr O2双束辐照肿胀和损伤是两个单束辐照的线性叠加,Si C双束同时辐照的拉曼光谱比双束先后辐照有更大的主峰半高宽的变化,ODS钢的三束辐照有最大的肿胀和硬化。综合分析得出双束同时辐照比先后辐照具有更明显的协同效应,三束辐照ODS钢的损伤最严重,比三个单束损伤之和大,Si离子与He,H的协同效应最明显。多束辐照能较好地模拟实际反应堆中的辐照环境。这些研究结果对于核材料在实际反应堆中的中子辐照行为具有一定的参考意义。     

不锈钢辐射损伤随温度和剂量的变化(英文)

用重离子辐照模拟和正电子湮没寿命技术研究了改进型316L不锈钢在21 和33 dpa辐照剂量下的辐照损伤在室温到802 °C温度范围随辐照温度变化和室温下0—100 dpa剂量范围随辐照剂量变化. 在580 °C左右实验观察到辐照肿胀峰， 在21 和33 dpa辐照剂量下相应的空位团分别由14和19个空位组成， 尺度分别为0.68 和0.82 nm. 空位团尺寸随辐照剂量增加， 在100 dpa时空位团由8个空位组成， 尺度为0.55 nm. 实验结果表明， 在改进型316L不锈钢中辐照损伤随辐照温度变化更灵敏.     

真空紫外辐照对MQ增强硅橡胶热性能及光学性能的影响

 采用空间综合辐照模拟设备研究了真空紫外辐照对MQ增强加成型硅橡胶的表面形貌、质量损失、热性能及光学性能的影响。试验结果表明：真空紫外辐照后,硅橡胶表面出现损伤裂纹,随辐照剂量的增加,裂纹的数量增多;真空紫外辐照后,硅橡胶的质量有所损失,其质损率随辐照剂量的增加而增加;真空紫外辐照后硅橡胶的耐热性随辐照剂量的增加先增加而后下降;真空紫外辐照对硅橡胶材料的体膨胀/收缩变形影响不大,但对材料的光学性能有较大影响,随着辐照剂量的增加,材料的光学透过率下降。     

碲镉汞焦平面光伏器件的实时γ辐照效应研究

对碲镉汞长波和中波焦平面光伏器件进行了实时γ射线辐照效应研究,通过辐照过程中实时测试器件的电流-电压特性,发现随着辐照剂量的增加,中波器件比长波器件表现出更好的抗辐照能力.对于长波器件,随着辐照剂量的增大,能够反映器件性能的零偏电阻逐渐降低;对于中波器件,零偏电阻随着辐照剂量的增加无固定变化趋势,辐照效应主要表现在电阻-电压曲线随着辐照剂量增加出现越来越明显的扰动.根据光伏器件的暗电流机理,对长波器件的电阻-电压曲线进行数值拟合,发现辐照引起少子产生-复合寿命逐渐降低,缺陷密度逐渐增大,主要影响的电流机理 关键词： γ辐照 辐照效应 光伏器件 碲镉汞     

不同剂量率下锗硅异质结双极晶体管电离损伤效应研究

对于相同制作工艺的NPN锗硅异质结双极晶体管(SiGe HBT), 在不同辐照剂量率下进行⁶⁰Co γ射线的辐照效应与退火特性的研究. 测量结果表明, 两种辐照剂量率下, 随着辐照总剂量增加, 晶体管基极电流增大, 共发射极电流放大倍数降低, 且器件的辐照损伤、性能退化与辐照剂量率相关, 低剂量率下辐照损伤较高剂量率严重. 在经过与低剂量率辐照等时的退火后, 高剂量率下的辐照损伤仍较低剂量率下的损伤低, 即待测SiGeHBT具有明显的低剂量率损伤增强效应(ELDRS). 本文对相关的物理机理进行了探讨分析. 关键词： 锗硅异质结双极晶体管 低剂量率辐照损伤增强 辐照效应     

中子辐照诱导钨再结晶的模拟研究

钨作为未来聚变堆偏滤器靶板的候选材料,需要长期服役在高温且受到高能中子辐照的严峻环境,这将导致钨发生中子辐照诱导再结晶,从而提高钨发生沿晶脆断的可能性,威胁偏滤器的运行安全,因此研究中子辐照诱导钨再结晶的物理机制具有重要意义.然而,与最近高通量同位素反应(HFIR)堆高温下中子辐照实验观察到的结果相比,目前考虑辐照增强再结晶驱动力效应的模型低估了中子辐照对再结晶的影响,结果表明仍有其他效应影响再结晶过程.基于此,本文在假设晶界迁移率与自体扩散系数成正比的前提下,引入辐照增强晶界迁移因子(R),建立了新的辐照诱导再结晶动力学模型.模拟结果显示,在综合考虑辐照增强再结晶驱动力和晶界迁移效应后,模型计算出的850℃下达到一半再结晶分数所需要的时间(t_X=0.5)和HFIR堆中子辐照实验结果相符,这表明辐照增强晶界迁移效应是影响辐照诱导再结晶现象的重要因素之一.另外,模型研究了不同辐照温度下钨的t_X=0.5.结果表明辐照与未辐照的t_X=0.5差别随温度升高而逐渐下降.这是因为随着温度的升高,辐照缺陷复合加剧,辐照缺陷对再结晶驱动...     

高功率厘米波辐照黄粉虫幼虫和草坪热效应研究

 建立了高功率厘米波辐照平台,测定了黄粉虫幼虫和草坪的表面温升及黄粉虫幼虫致死百分率。实验结果表明,高功率厘米波辐照过程中黄粉虫幼虫温度与辐照时间呈一定函数关系;草坪温度与辐照时间也呈一定函数关系,但两者不同。由实验结果拟合得到了辐照过程中黄粉虫幼虫表面温升与辐照时间之间的关系和黄粉虫幼虫致死百分率与辐照时间及致死百分率与温度的函数关系。实验观察了不同时间厘米波辐照对草坪的影响。观察结果表明温度超过一定数值时,厘米波辐照将损伤草坪。采用图像处理方法得到了草坪损伤的量化结果,并进一步得到了草坪损伤程度与辐照温度的函数关系。     

质子辐照对MQ硅树脂增强的加成型硅橡胶质损及热性能的影响

 采用空间综合辐照模拟设备研究了100 keV和150 keV能量的质子辐照对MQ硅树脂增强的加成型硅橡胶的损伤及其对硅橡胶热性能的影响。试验结果表明：质子辐照后，硅橡胶表面出现损伤裂纹，随辐照能量和剂量的增加，裂纹的数量增多，裂纹增大；质子辐照后，硅橡胶的质量有所损失，其质损率随辐照能量和剂量的增加而增加；质子辐照后硅橡胶的耐热性随辐照剂量的增加先略有增加而后下降，经辐照后的硅橡胶在玻璃态和玻璃转变区的温度区间内收缩率降低，而在高弹态的温度区间内膨胀率增加。     

超深亚微米互补金属氧化物半导体器件的剂量率效应

对0.18 μm互补金属氧化物半导体(CMOS)工艺的N型金属氧化物半导体场效应晶体管(NMOSFET)及静态随机存储器(SRAM)开展了不同剂量率下的电离总剂量辐照试验研究. 结果表明: 在相同累积剂量, SRAM的低剂量率辐照损伤要略大于高剂量率辐照的损伤, 并且低剂量率辐照损伤要远大于高剂量率辐照加与低剂量率辐照时间相同的室温退火后的损伤. 虽然NMOSFET 低剂量率辐照损伤略小于高剂量率辐照损伤, 但室温退火后, 高剂量率辐照损伤同样要远小于低剂量率辐照损伤. 研究结果表明0.18 μm CMOS工艺器件的辐射损伤不是时间相关效应. 利用数值模拟的方法提出了解释CMOS器件剂量率效应的理论模型.     

Comparison of seasonal and yearly average indoor radon levels using CR-39 detectors

In order to assess the effect of long term exposure, CR-39 based radon dosimeters were exposed to indoor radon in the drawing rooms (living room) of 200 selected houses of the districts of Swabi, Mardan and Charsadda in the North West Frontier Province (NWFP) as well as in the Mohmand and Bajuar Agencies of the federally administered tribal areas (FATA), Pakistan. Dosimeters were exposed to the indoor radon during each season as well as throughout the year. From the measured indoor radon data it was observed that seasonal yearly average value were higher than that of the 12 months average indoor radon concentration values. The overall seasonal average was found to be 13% higher than that of the 12 months exposed CR-39 based dosimeters. However after the removal of the worst differences, seasonal average remains only 8 % higher than the 12 months averaged value.     

Study of zinc-induced changes in lymphocyte membranes using atomic force microscopy,luminescence, and light scattering methods

Changes in the surface structure of lymphocyte membranes exposed to various concentrations of zinc ions are studied. It is found by atomic force microscopy that increasing the concentration of zinc ions leads to a reduction in the correlation length of the autocorrelation function of the roughness profile of a lymphocyte compared to control samples; this may indicate the existence of fine structure in the membrane surface. Fluorescence markers are used to observe a reduction in the microviscosity of the lipids in the outer monolayer of the lipid bilayer after lymphocytes are exposed to Zn ions, as well as the exposure of phosphatidylserine on the surface membrane, and the oxidation of HS-groups of membrane proteins. Calculations of the absorption coefficients of lymphocytes modified with zinc reveal the existence of absorption bands owing to the formation of metal-protein complexes and zinc oxide nanoparticles. These results indicate significant changes in the structural and functional state of lymphocyte membranes exposed to zinc ions.     

Effects of chronic ozone (O3) exposure on vocal-fold mucosa in bonnet monkeys

Effects of ambient ozone (O₃) on the respiratory tract have been frequently reported. However, little is known regarding possible effects of chronic exposure to O₃ on the larynx or on vocal-fold mucosa. In this study, six bonnet monkeys were exposed to 1 ppm O₃ 8 h per day, 5 days per week, for 3 months. Three of the monkeys' larynges were examined 4 h after exposure, and three were examined 9 months after exposure. Tissues were subjected to histological staining and morphometric quantification. Results revealed increased thickness of epithelial and connective tissue components of vocal-fold mucosa in the 4-h group and connective tissue changes that persisted in mucosa examined 9 months after exposure. Additional changes indicative of hyperplasia and disorganization of epithelial and connective tissue, as well as disruption of glands and vessels, were also noted in tissues examined at both postexposure intervals. Implications of the data for the larynx and voice quality in humans exposed to similar environmental toxins are discussed.     

Response of hydrogen bonding to low-intensity 50 Hz electromagnetic field in typical proteins in bi-distilled water solution

Samples of hemoglobin and bovine serum albumin in different bi-distilled water solutions were exposed to a 50?Hz electromagnetic field at the intensity of 1?mT to investigate the response of hydrogen bonding to the applied field after exposure of 3?h by means of Fourier Transform Infrared spectroscopy. Spectral analysis evidenced a significant decrease in the absorbance signal of the Amide I vibration in exposed samples of hemoglobin and bovine serum albumin water solutions. In addition, Fourier self-deconvolution analysis and min-max normalization applied in the mid-infrared region to exposed and unexposed hemoglobin samples revealed a significant increase in the absorbance signal of the Amide II band and an up-shift toward the high energies of 1.5?cm^?1 after exposure. Similar findings were observed after exposure of bovine serum albumin. These results can be easily explained assuming that hydrogen bonding in the secondary structure of these proteins in bi-distilled water solutions was enhanced after exposure to 50?Hz electromagnetic field.     

Evaluation of the morphological changes in the lungs of BALB/c mice after inhalation of spherical and rod-shaped titanium nanoparticles

Titanium nanoparticles are widely used by industry in consumer products such as sunscreens and some cosmetic products due to their specifically engineered properties. Some of these properties may, however, increase the toxicity of the nanoparticles which in turn may affect human and environmental health. Therefore, it is of utmost importance to study the possible effects of these particles through in vivo studies, which might produce different results than in vitro cell studies. The current study aimed to investigate the possible remodelling in the lungs of BALB/c mice by means of light and transmission electron microscopy after inhalation of spherical and rod-shaped titanium nanoparticles at two different concentrations. The focus of this paper was to demonstrate whether whole body exposure to different concentrations of the said nanoparticles could induce an inflammatory response in the lungs and no inter particle comparison was done or retention investigated. Animals were divided into five experimental groups: control, high and low concentration groups exposed to the spherical-shaped particles, as well as high and low concentration groups exposed to the rod-shaped particles. Histological and ultrastructural changes, typical of an inflammatory response, were noted in the lungs of the exposed animals. These changes were not observed in the lungs of the control animals. It can be concluded from this study that titanium nanoparticles may cause inflammatory reactions in the lungs of animals exposed through inhalation, as indicated by the presence of inflammatory cells and congestion of inter-alveolar areas. This has implications for individuals who may be potentially exposed during the production and use of titanium nanoparticles.     

γ射线辐照人类正常肝细胞染色体损伤的动态修复

应用早熟染色体凝集技术对人类正常肝脏细胞经γ射线照射导致的染色体损伤后48h内的动态修复过程进行了研究。结果显示:照射后原初染色单体断裂和等点染色单体断裂数随着照射剂量的增加而增多，染色单体断裂显著多于等点染色单体断裂；经过24h的继续培养，这两种类型的损伤都有不同程度的修复，约50％染色单体断裂得到修复，而等点染色单体断裂的修复率最多为15％；经过48h的照射后培养，染色体损伤的水平与24h相比没有显著差异。说明肝细胞经γ射线照射后染色体损伤的主要形式是染色单体断裂，易于修复；虽然等点染色单体断裂数量较少，但修复困难。由此表明，等点染色体断裂是细胞经γ射线照射后死亡和癌变的一个重要因素。We employed the prematurely chromosome condensation （PCC） technique to investigate the 48 h kinetic repair of normal human liver cell line L02 exposed to γ-rays. The results showed that chromatidtype and isochromatid-type breaks increased with the dose at 0 h measured by PCC, the number of chromatid-type breaks was several times more than that of isochromatid-type breaks. Further 24 h incubationafter exposed to irradiation, both of these two type breaks decreased in different extent, 50% for chromatid-type one, change of the the main type easy to repair. 15% for isochromatid-type one at most, respectively. chromosome breaks compared with that of 24th h（p〉 0. 05 of the chromosome breaks was chromatid-type after exposed 48th h, there was a slightly ）. These results revealed that to low LET rays, also, it was Though the isochromatid-type breaks was obvioously less than that of the chromatid-type one, it was difficult to repair. It implied that the isochromatid-type breaks was the important factor causing cell death and canceration when cells were exposed to irradiations.     

Identification of chemical modification in single human keratinocyte cells exposed to low doses of chlorpyriphos by Raman micro‐spectroscopy

Raman micro‐spectroscopy can be used to investigate biological single cells exposed to different chemicals. Since chronic exposure at low doses of pesticides can promote several diseases, the investigation of cellular changes induced by exposure to non‐cytotoxic doses of pesticides is of increasing interest. The efficiency of Raman micro‐spectroscopy to detect chemical modification in normal human keratinocytes induced by exposure to non‐cytotoxic doses of chlorpyriphos, an organophosphate pesticide present in many plant‐protection products, was investigated. Such modification affects mainly proteineous components (both single amino acids and amide linkages between amino acids) of the nucleus, cellular membranes and cytoplasm as well as the nucleic acid component of the nucleus. Chemical modifications are already detectable after 24 h exposure of keratinocytes at a chlorpyriphos concentration of 10⁻⁶ M , which is three orders of magnitude lower than the cytotoxic concentration (10⁻³ M ). Heavy damage to the lipid component occurs after exposure to the nearly cytotoxic concentration (10⁻⁴ M ). Atomic force microscopy images of keratinocyte cells exposed for 24 h to various chlorpyriphos concentrations show a progressive deterioration of the morphology of cellular membrane as the chlorpyriphos concentration increases. The results of this work may have wide applications in the monitoring of molecular changes in single human cells exposed to toxic agents. Copyright © 2010 John Wiley & Sons, Ltd.     

Dispersion of laser droplets using H+ ions and annealing effect on pulsed laser deposited nickel ferrite thin films

Nickel ferrite thin films were deposited by a pulsed laser deposition (PLD) technique on silicon substrate at room temperature in a vacuum of 5×10⁻⁵ mbar. The films were subjected to different annealing temperatures from 300–900°C and were also exposed to single shot energetic hydrogen ions using a Dense Plasma Focus (DPF) device. The changes induced in the films exposed at different distances from the top of the anode were investigated. The structural, morphological and magnetic properties of the annealed and exposed samples were investigated. X-ray diffraction (XRD) studies reveal the presence of a single phase of nickel ferrite after annealing. SEM micrographs indicate an increase in the grain size, both on annealing as well as on exposure to hydrogen ions. Annealing and hydrogen ion irradiation induced an enhancement in the magnetic moments. Laser droplets which are inherent in films deposited by laser ablation were found to be dispersed as a result of single shot hydrogen ion irradiation from the DPF.     

Life of Artemia under very high pressure

The experiment on the search for life under very high pressure done for small animal tardigrades has been extended to a plankton, Artemia. It was found that cysts, or dried eggs, of Artemia remain alive after being exposed to a very high hydrostatic pressure of 7.5 GPa for 42 h. We are convinced that at least two kinds of small animals are still alive after being exposed to such high hydrostatic pressure of 7.5 GPa, which corresponds to the pressure at the depth of about 180 km below the surface of the Earth, i.e., Mantle pressure. The results of the present investigation suggest the possibility that Artemia, as well as tardigrade may have traveled through outer space in a large meteorite, and reached the Earth alive from another planet or galaxy.     

Effect of high pressure on mesophilic starters for cheesemaking

In the experiment, the effect of pressurization on the survival as well as acidifying and proteolytic activity of mesophilic commercial starters used for cheesemaking was studied. The samples were exposed to a single and a double (after 24 h) pressurization in the range of 200-800 MPa, for 15 minutes, at 20 °C. Analyses were performed immediately after the processing as well as after 1, 2, and 3 weeks of storage at 4 °C. A double processing at 600 and 800 MPa caused an irreversible reduction in the number of microorganisms, inhibited the process of milk acidification but preserved approximately 20% of the initial proteolytic activity of the bacterial enzymes.