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171.
H. Wollenberger 《辐射效应与固体损伤》2013,168(1-3):155-160
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Paulius Grigaravičius Karl Otto Greulich Prof. Dr. Shamci Monajembashi Dr. 《Chemphyschem》2009,10(1):79-85
We show how a technique developed within the framework of physics and physical chemistry—in a true interdisciplinary approach—can answer questions in life sciences that are not solvable by using other techniques. Herein, we focus on blood‐pressure regulation and DNA repair in ageing studies. Laser microbeams and optical tweezers are now established tools in many fields of science, particularly in the life sciences. A short glimpse is given on the wide field of non‐age‐research applications in life sciences. Then, optical tweezers are used to show that exerting a vertical pressure on cells representing the inner lining of blood vessels results in bursts of NO liberation concomitant with large changes in cell morphology. Repeated treatment of such human umbilical vein endothelial cells (HUVEC) results in stiffening, a hallmark of manifest high blood pressure, a disease primarily of the elderly. As a second application in ageing research, a laser microbeam is used to induce, with high spatial and temporal resolution, DNA damages in the nuclei of U2OS human osteosarcoma cells. A pairwise study of the recruitment kinetics of different DNA repair proteins reveals that DNA repair starts with non‐homologous end joining (NHEJ), a repair pathway, and may only after several minutes switch to the error‐free homologous recombination repair (HRR) pathway. Since DNA damages—when incorrectly repaired—accumulate with time, laser microbeams are becoming well‐used tools in ageing research. 相似文献
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连续CO2激光对红外窗口材料损伤研究 总被引:4,自引:0,他引:4
研究了连续CO2激光对几种红外窗口材料的表面损伤特性,研究表明,损伤机制在于杂质缺陷吸收造成的热冲击应力破坏。深入研究了杂质缺陷密度、焦斑与材料损伤阈值的关系,并建立了一个损伤模型。同时分析了热冲击应力破坏方式。 相似文献
176.
P. Galinetto M. Marinone D. Grando G. Samoggia F. Caccavale A. Morbiato M. Musolino 《Optics and Lasers in Engineering》2007,45(3):380
In this work we report on micro-Raman analysis on lithium niobate (LN) substrates in order to study the compositional homogeneity of the crystals and to clear up the effects of etching and polishing processes on the surface of wafers and crystals.The fact that the linewidth of some Raman modes scale with the composition of LN crystals, together with the use of a confocal microscope, allowed a three-dimensional determination of the sample stoichiometry and of the crystalline quality. This local tool can supply additional information, which can be complementary to the electro-optic coefficients, carefully measured as well in order to check functional parameters.Raman spectra from buried regions were obtained on as-grown, etched and polished crystals and wafers. The depth profile of the peak energy and the linewidth of the Raman mode at 872 cm−1 indicate that mechanical processing of surfaces causes, in some cases, structural modifications till a depth of 15 μm. 相似文献
177.
A stochastic theory for the cumulative fatigue damage of structural components with random fatigue strength under random loading is proposed on the basis of Stratonovich-Khasminskii theorem. The analytical solutions for the probability densities of the cumulative fatigue damage and fatigue life and for the reliability function are given for steel and reinforced concrete components with constant fatigue strength subject to a narrow band stationary Gaussian stress process with zero mean. The results agree very well with those of digital simulation. It is noted that the theory can be applied, in principle, to both metallic and non-metallic materials, narrow band and wide band stress process, and adapted to a sequence ofn, stationary stress processes or quasi-stationary stress process. The scatter and degradation of fatigue strength and the inspection maintenance can also be incorporated into the theory. 相似文献
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详细分析了不同形状断裂试件及小范围屈服模型裂纹端部的损伤演化,提出了韧性断裂的宏观起裂相当于裂尖前方一特征位置处的损伤达到一临界值。利用此模型获得了与实验相一致的宏观断裂韧性及与约束无关的理论断裂韧性。 相似文献
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