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991.
褶合光谱法考察羟自由基清除剂对紫外照射致DNA变异的作用 总被引:1,自引:1,他引:0
采用褶合光谱法考察了紫外线UV A ,UV B ,UV C导致的DNA变异 ,并以褶合光谱差谱值的形式量化表达DNA细微突变的程度。DNA受UV A ,UV B ,UV C作用后 ,差谱值依次增大 ,表明变异程度增大 ;添加二甲亚砜、甘露醇等羟自由基清除剂以后 ,在UV A ,UV B ,UV C作用下 ,差谱值有不同程度的降低 ,呈现一定的抑制变异作用。尽管DNA的变异程度有所区别 ,但它们的差谱点分布区域相似 ,提示UV A ,UV B ,UV C导致的DNA变异类型可能相似 ,两种羟自由基清除剂抑制DNA变异的作用机制也可能相似 相似文献
992.
紫外辐射对小牛胸腺DNA水溶液影响的拉曼光谱研究 总被引:3,自引:0,他引:3
报道了小牛胸腺DNA水溶液经9,20,40min紫外辐射的拉曼光谱图,紫外线的辐射照度为1868W·m-2。实验结果表明波长为2537nm的紫外光在起主要作用的紫外辐射对DNA的损伤是严重的,短短10min的紫外辐射就使1094cm-1这个强峰分裂成几个小峰,说明DNA的构象受到破坏,DNA的构型发生变化,部分单双键发生了断裂,出现了各种各样由于DNA键断裂产生的多核苷酸;4种碱基均受到不同程度的影响,碱基间的氢键造成断裂,其中嘧啶、嘌呤碱基受到的损伤较为严重;紫外辐射对脱氧核糖也产生了破坏。另外,该实验也表明,在水溶液中,DNA以B型结构为主,局部的A型结构仍然存在。 相似文献
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To improve DMFC (direct methanol fuel cell) performance, a new method using ultrasonic radiation is proposed and a novel DMFC structure is designed and fabricated in the present paper. Three ultrasonic transducers (piezoelectric transducer, PZT) are integrated in the flow field plate to form the ultrasonic field in the liquid fuel. Ultrasonic frequency, acoustic power, and methanol concentration have been considered as variables in the experiments. With the help of ultrasonic radiation, the maximum output power and limiting current of cell can be independently increased by 30.73% and 40.54%, respectively. The best performance of DMFC is obtained at the condition of ultrasonic radiation (30 kHz and 4 W) fed with 2 M methanol solution, because both its limiting current and output power reach their maximum value simultaneously (222 mA and 33.6 mW, respectively) under this condition. These results conclude that ultrasonic can be an alternative choice for improving the cell performance, and can facilitate a guideline for the optimization of DMFC. 相似文献
997.
The effects of UV synchrotron radiation on deoxyribonucleic acid (DNA) cast films have been systematically investigated by vacuum ultraviolet and infrared spectrophotometry as a function of irradiation time. Cast DNA films exposed at 140 nm (8.85 eV) for different irradiation times, revealed consistent changes in their VUV spectra which indicate a decrease of thymine groups and an increase of π → π* transition spectral signature associated with the CO group of the open sugar chain. This result was corroborated by a decrease in CO stretching vibration at 1061 cm−1 observed in the infrared spectra. Both these results are consistent with the creation of single strand breaks in the deoxyribose component of DNA molecule and a decrease in the phosphate groups. It was also shown that UV radiation is effective in damaging the thymine groups involved in Hoogsteen base pairing with adenine. The analysis of the infrared data suggests that the usual spectroscopic fingerprints of DNA denaturation are not necessarily a reliable measure of DNA damage. 相似文献
998.
利用同步辐射CT (SR-CT)技术, 在氮化硅陶瓷样品烧结过程中对其进行实时投影成像, 并应用滤波反投影算法和数字图像处理技术, 得到了样品在整个烧结过程中内部微结构演化的二维和三维重建图像, 实现了对陶瓷固相烧结过程实时、无损的观测. 通过重建图像清晰观测到了陶瓷样品在烧结三个阶段中颗粒接触、烧结颈形成、晶粒和气孔长大、气孔球化并收缩等烧结现象; 统计了样品在不同烧结时刻的孔隙率, 得到了孔隙率随烧结时间对数的变化曲线, 并根据曲线分析了样品在不同烧结时刻致密化速率的变化, 得到了烧结中期孔隙率和时间对数的线性关系. 实验的结果和现有烧结理论相吻合, 并为进一步完善烧结理论提供了有效的实验数据. 相似文献
999.
Walter N.L. dos Santos Geovani C. Brandão Lindomar A. Portugal Jorge M. David Sérgio L.C. Ferreira 《Spectrochimica Acta Part B: Atomic Spectroscopy》2009
This paper proposes the use of photo-oxidation with UV radiation/H2O2 as sample pretreatment for the determination of iron and manganese in wines by flame atomic absorption spectrometry (FAAS). The optimization involved the study of the following variables: pH and concentration of buffer solution, concentrated hydrogen peroxide volume and irradiation time. The evaluation of sample degradation was monitored by measuring the absorbance at the maximum wavelength of red wine (530 nm). Using the experimental conditions established during the optimization (irradiation time of 30 min, oxidant volume of 2.5 mL, pH 10, and a buffer concentration of 0.15 mol L− 1), this procedure allows the determination of iron and manganese with limits of detection of 30 and 22 μg L− 1, respectively, for a 5 mL volume of digested sample. The precision levels, expressed as relative standard deviation (RSD), were 2.8% and 0.65% for iron and 2.7% and 0.54% for manganese for concentrations of 0.5 and 2.0 mg L− 1, respectively. Addition/recovery tests for evaluation of the accuracy were in the ranges of 90%–111% and 95%–107% for iron and manganese, respectively. This digestion procedure has been applied for the determination of iron and manganese in six wine samples. The concentrations varied from 1.58 to 2.77 mg L− 1 for iron and from 1.30 to 1.91 mg L− 1 for manganese. The results were compared with those obtained by an acid digestion procedure and determination of the elements by FAAS. There was no significant difference between the results obtained by the two methods based on a paired t-test (at 95% confidence level). 相似文献
1000.
Post-blast detection of traces of explosives by means of Fourier transform infrared spectroscopy 总被引:1,自引:0,他引:1
A. Banas K. Banas M. Bahou H.O. Moser L. Wen P. Yang Z.J. Li M. Cholewa S.K. Lim Ch.H. Lim 《Vibrational Spectroscopy》2009,51(2):168-176
Samples obtained from debris after explosions of about 30 g of energetic materials were analyzed by means of Fourier transform infrared (FTIR) spectroscopy using both, Globar and synchrotron infrared radiation at the ISMI beamline of the Singapore synchrotron light source (SSLS). Low- and high-strength-of-explosion blasts were performed during each test run with the same explosive material. From the spectroscopic measurements, traces of unreacted explosives were found on more than 200 different materials that served as sample catchers in the explosions.The integrality of the experiments done confirmed that FTIR spectroscopy is a sufficiently sensitive method to detect traces of explosives in post-blast residues even of high-strength explosions. The method requires only a minimal amount of sample and enables accurate and very fast identification of the presence of explosive material. Finally, the synchrotron radiation infrared source provided one order of magnitude higher sensitivity compared to the conventional Globar source. 相似文献