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41.
本文结合分子动力学方法和动力学蒙特卡罗方法, 研究了单个粒子入射硅引起的位移损伤缺陷的产生和演化过程; 基于Shockley-Read-Hall理论计算了单个粒子入射引起的位移损伤缺陷导致的泄漏电流增加及其演化过程, 比较了缺陷退火因子与泄漏电流退火因子之间的差异, 并将计算结果与实验值进行了对比. 结果表明, 计算泄漏电流时, 仅考虑一种缺陷的情况下缺陷退火因子与泄漏电流退火因子相同, 考虑两种缺陷类型情况下二者在数值上有所区别, 但缺陷退火因子仍能在一定程度上反映泄漏电流的退火行为. 分子动力学模拟中采用Stillinger-Weber势函数和Tersoff势函数时缺陷退火因子和泄漏电流退火因子与实验结果一致, 基于Stillinger-Weber势函数的计算结果与实验值更为接近. 相似文献
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Stage-I fatigue cracks are commonly described by the model of Bilby, Cottrell and Swinden (BCS model). However, since several experimental investigations have shown a dislocation-free zone (DFZ) in front of crack-tips, it is necessary to validate the new DFZ model and to examine the deviations to the BCS model. Therefore, the dislocation density distribution is derived from height profiles of slip lines in front of stage-I fatigue cracks in CMSX4® single crystals measured by contact-mode atomic force microscopy. This is possible, because the cracks are initiated at notches milled by focused ion beam technique directly on slip planes with a high Schmid factor. Consequently, the directions of the Burgers vectors are well known; it is possible to calculate the dislocation density distributions from the height profiles. The measured distributions are compared to the calculated distribution function of the DFZ model proposed by Chang et al. The additionally measured microscopic friction stress of the dislocations is then used to calculate the influence of grain boundaries on the dislocation density distribution in front of stage-I cracks. The calculation is done by the extended DFZ model of Shiue et al. and compared with the measured distribution function in polycrystalline specimens. Finally, the crack-tip sliding displacement as a measure for the crack propagation rate is compared for the DFZ model and the BCS model with the experimentally revealed values. The important result: the often used BCS model does not reflect the experimental measurements. On the contrary, the DFZ model reflects the measurements at stage-I cracks qualitatively and quantitatively. 相似文献
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Toehold‐initiated Rolling Circle Amplification for Visualizing Individual MicroRNAs In Situ in Single Cells 下载免费PDF全文
Ruijie Deng Dr. Longhua Tang Qianqian Tian Dr. Ying Wang Lei Lin Prof. Dr. Jinghong Li 《Angewandte Chemie (International ed. in English)》2014,53(9):2389-2393
The ability to quantitate and visualize microRNAs (miRNAs) in situ in single cells would greatly facilitate the elucidation of miRNA‐mediated regulatory circuits and their disease associations. A toehold‐initiated strand‐displacement process was used to initiate rolling circle amplification of specific miRNAs, an approach that achieves both stringent recognition and in situ amplification of the target miRNA. This assay, termed toehold‐initiated rolling circle amplification (TIRCA), can be utilized to identify miRNAs at physiological temperature with high specificity and to visualize individual miRNAs in situ in single cells within 3 h. TIRCA is a competitive candidate technique for in situ miRNA imaging and may help us to understand the role of miRNAs in cellular processes and human diseases in more detail. 相似文献
46.
A Supercharged Fluorescent Protein as a Versatile Probe for Homogeneous DNA Detection and Methylation Analysis 下载免费PDF全文
Chunyang Lei Dr. Yan Huang Prof. Dr. Zhou Nie Jun Hu Lijun Li Guoyan Lu Yitao Han Prof. Dr. Shouzhuo Yao 《Angewandte Chemie (International ed. in English)》2014,53(32):8358-8362
Supercharged proteins are a new class of functional proteins with exceptional stability and potent ability to deliver bio‐macromolecules into cells. As a proof‐of‐principle, a novel application of supercharged proteins as a versatile biosensing platform for nucleic acid detection and epigenetics analysis is presented. Taking supercharged green fluorescent protein (ScGFP) as the signal reporter, a simple turn‐on homogenous method for DNA detection has been developed based on the polyionic nanoscale complex of ScGFP/DNA and toehold strand displacement. This assay shows high sensitivity and potent ability to detect single‐base mismatch. Furthermore, combined with bisulfite conversion, this ScGFP‐based assay was further applied to analyze site‐specific DNA methylation status of genomic DNA extracted from real human colon carcinoma tissue sample with ultrahigh sensitivity (4 amol methylated DNA). 相似文献
47.
This study is focused on numerical investigation on fracture behaviors of carbon black (CB) and silica filled elastomeric composites. Finite element analysis (FEA) in compliance with multi-specimen method is used to calculate J-integral and geometry factor of the rubber composites up to a displacement of 20 mm for single edge notch in tension (SENT) and double edge notch in tension (DENT) specimens. An empirical relationship between crack tip opening displacement (CTOD) and crack advancement is established depending on notch to width ratio (NWR). The stress contours across the notches for SENT and DENT specimens is discussed briefly. It is found that fracture propagation resistance of CB filled elastomer is 125% more than that of silica filled elastomer. Although, Silica filled elastomer have good tensile strength and crosslink density but it fails to replace carbon black in terms of fracture properties. The critical J-integral for CB filled elastomer is 18.7% and 32.2% more than silica filled elastomer for SENT and DENT specimens respectively. The effect of specimen type on various fracture properties is also explored. The factor of safety is found to be significantly more in case of CB filled elastomers making them less vulnerable to crack propagation and catastrophic failure. 相似文献
48.
对中学化学学生实验活动中产生的气体污染物进行测试,得到不同通风条件下化学实验室内部空气污染物的数据。结果表明,中学化学学生分组实验产生的主要气体污染物有苯、甲苯、甲醛、氨气等,实验过程中如不采取任何通风措施,实验室气体污染物的浓度短时间内会急剧升高,所以采取有效措施对实验室内部空气污染物进行消除是非常必要的。目前中学化学实验室配备的通风设备以桌面排风设备为主,相比于自然通风的环境,学生实验时开启桌面排风设备,能够有效降低实验产生的气体污染物浓度。 相似文献
49.
Fast growing technology and requirements for testing of different types of materials and devices require new methods and systems
for investigation of their parameters. Among the quantities of high interest are shape, deformation, roughness, local materials
constants, displacement, and strain fields of elements under load. In the paper, we present novel solutions for digital holographic
cameras, which allow for remote monitoring and measurement of the above mentioned quantities at small mechanical objects or
at restricted areas of interest at big structures. The systems have compact design, “black box” measurement approach, and
allows for fast and accurate measurements performed directly at the element and often in outdoor environment. The principles
of digital and optoelectronic reconstruction and phase manipulation are described together with the exemplary measurement
results obtained by means of the cameras presented. 相似文献
50.
This paper studies the problem of a functionally graded piezoelectric circular plate subjected to a uniform electric potential
difference between the upper and lower surfaces. By assuming the generalized displacements in appropriate forms, five differential
equations governing the generalized displacement functions are derived from the equilibrium equations. These displacement
functions are then obtained in an explicit form, which still involve four undetermined integral constants, through a step-by-step
integration which properly incorporates the boundary conditions at the upper and lower surfaces. The boundary conditions at
the cylindrical surface are then used to determine the integral constants. Hence, three-dimensional analytical solutions for
electrically loaded functionally graded piezoelectric circular plates with free or simply-supported edge are completely determined.
These solutions can account for an arbitrary material variation along the thickness, and thus can be readily degenerated into
those for a homogenous plate. A numerical example is finally given to show the validity of the analysis, and the effect of
material inhomogeneity on the elastic and electric fields is discussed.
Supported by the National Natural Science Foundation of China (Grant Nos. 10472102 and 10432030) and the Specialized Research
Fund for the Doctoral Program of Higher Education of China (Grant No. 20060335107) 相似文献