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21.
Influence of AlN buffer layer thickness on structural properties of GaN epilayer grown on Si (111) substrate with AlGaN interlayer 下载免费PDF全文
We present the growth of GaN epilayer on Si (111)
substrate with a single AlGaN interlayer sandwiched between the GaN
epilayer and AlN buffer layer by using the metalorganic chemical
vapour deposition. The influence of the AlN buffer layer thickness
on structural properties of the GaN epilayer has been investigated
by scanning electron microscopy, atomic force microscopy, optical
microscopy and high-resolution x-ray diffraction. It is found that
an AlN buffer layer with the appropriate thickness plays an important
role in increasing compressive strain and improving crystal quality
during the growth of AlGaN interlayer, which can introduce a more
compressive strain into the subsequent grown GaN layer, and
reduce the crack density and threading dislocation density in GaN
film. 相似文献
22.
运用灰色系统GM(1,1)模型进行预测时,模拟精度和预测精度是关注的焦点.对原始数据构造缓冲算子和进行完整的前期检验,运用等维灰数递补的动态建模方法,针对误差建立残差修正模型,都可以提高预测的可信度.通过归纳建模各阶段可能出现的典型问题以及解决方法,以期对建立优化模型有所帮助.最后建立GM(1,1)模型预测天津滨海机场货邮吞吐量. 相似文献
23.
《Analytical letters》2012,45(6):451-465
Abstract The influence of the composition of buffer solutions on fluoride analyses by the fluoride ion selective electrode was studied. Residual fluoride content of reagents was observed to restrict the use of some buffers and reagents in low-level work. The optimum pH for low-level fluoride determinations was found to be around 5, which can be maintained by a sodium acetate-acetic acid buffer. Of the complexing agents studied, citrate was observed to be the most efficient masking agent for aluminum, but this ability depended strongly on ligand concentration. Citrate was also effective in masking iron (III) and magnesium ions. Tris (hydroxymethyi) aminomethane showed a similar ability to complex aluminum at a pH around 8. However, at this pH the hydroxyde ion interferes in fluoride analysis below 0.1 ppm [fbar]. 相似文献
24.
Sulfated glycosaminoglycans were labeled with biotin to study their interaction with cells in culture. Thus, heparin, heparan sulfate, chondroitin 4-sulfate, chondroitin 6-sulfate and dermatan sulfate were labeled using biotin-hydrazide, under different conditions. The structural characteristics of the biotinylated products were determined by chemical (molar ratios of hexosamine, uronic acid, sulfate and biotin) and enzymatic methods (susceptibility to degradation by chondroitinases and heparitinases). The binding of biotinylated glycosaminoglycans was investigated both in endothelial and smooth muscle cells in culture, using a novel time resolved fluorometric method based on interaction of europium-labeled streptavidin with the biotin covalently linked to the compounds. The interactions of glycosaminoglycans were saturable and number of binding sites could be obtained for each individual compound. The apparent dissociation constant varied among the different glycosaminoglycans and between the two cell lines. The interactions of the biotinylated glycosaminoglycans with the cells were also evaluated using confocal microscopy. We propose a convenient and reliable method for the preparation of biotinylated glycosaminoglycans, as well as a sensitive non-competitive fluorescence-based assay for studies of the interactions and binding of these compounds to cells in culture. 相似文献
25.
采用单源化学气相沉积(SSCVD)法,在石英衬底上以Au为缓冲层,Zn4(OH)2(O2CCH3)6.2H2O为固相源制备ZnO薄膜。SEM和XRD测试ZnO薄膜的微结构,结果表明:相对于SiO2衬底上生长的ZnO薄膜,Au/SiO2衬底上生长的ZnO薄膜具有较好的结晶质量和表面平整度;对制备ZnO薄膜的衬底温度进行了工艺优化,结果表明:500℃时制备的ZnO薄膜颗粒大小均匀,结晶质量较好;通过荧光光谱仪对Au/SiO2衬底上的ZnO薄膜进行光致发光(PL)谱测试,ZnO薄膜在400nm出现紫光发射峰,而没有出现与缺陷相关的深能级发射峰,表明ZnO薄膜具有较好的结晶质量。 相似文献
26.
研究了壬基酚聚氧乙烯醚(NPEO-10)在3种具有不同比表面积和孔径大小的超高交联树脂上的吸附行为与机理.3种超高交联树脂对壬基酚聚氧乙烯醚的吸附量受它们的比表面积和孔径大小以及溶液温度的影响.壬基酚聚氧乙烯醚在3种超高交联树脂上的吸附等温线可以用Langmuir和双Langmuir模型很好地拟合,而用Freundlich模型拟合则效果不好,但这些拟合曲线都具有相似的形状.热力学分析表明吸附过程主要表现为吸附质分子的疏水部分和吸附剂表面的作用以及吸附质分子在其表面形成胶束状的聚集体,即分散的、单层及双层聚集体的混合分布.吸附动力学曲线中的两个平台也证明了吸附过程存在单层和双层聚集体.脱附研究为实现超高交联树脂吸附分离水溶液中的壬基酚聚氧乙烯醚提供了合适的操作条件. 相似文献
27.
Zhi Zeng Marina Hincapie Brian B. Haab Samir Hanash Sharon J. Pitteri Steven Kluck Jason M. Hogan Jacob Kennedy William S. Hancock 《Journal of chromatography. A》2010,1217(19):3307-3315
Protein glycosylation represents one of the major post-translational modifications and can have significant effects on protein function. Moreover, changes in the carbohydrate structure are increasingly being recognized as an important modification associated with cancer etiology. In this report, we describe the development of a proteomics approach to identify breast cancer related changes in either concentration and/or the carbohydrate structures of glycoprotein(s) present in blood samples. Diseased and healthy serum samples were processed by an optimized sample preparation protocol using multiple lectin affinity chromatography (M-LAC) that partitions serum proteins based on glycan characteristics. Subsequently, three separate procedures, 1D SDS-PAGE, isoelectric focusing and an antibody microarray, were applied to identify potential candidate markers for future study. The combination of these three platforms is illustrated in this report with the analysis of control and cancer glycoproteomic fractions. Firstly, a molecular weight based separation of glycoproteins by 1D SDS-PAGE was performed, followed by protein, glycoprotein staining, lectin blotting and LC–MS analysis. To refine or confirm the list of interesting glycoproteins, isoelectric focusing (targeting sialic acid changes) and an antibody microarray (used to detect neutral glycan shifts) were selected as the orthogonal methods. As a result, several glycoproteins including alpha-1B-glycoprotein, complement C3, alpha-1-antitrypsin and transferrin were identified as potential candidates for further study. 相似文献
28.
Natalini B Marinozzi M Sardella R Macchiarulo A Pellicciari R 《Journal of chromatography. A》2004,1033(2):363-367
The chromatographic resolution of enantiomeric amino acids is accomplished on a reversed phase column using aqueous mobile phase containing the chiral reagent N,N-dimethyl-S-phenylalanine-Cu(II). The separation is a result of the whole interaction between the diastereomeric complex surface and the mixed stationary phase realized by the dynamic coating of the RP-18 carbon chains layer. The elution order seems to be related to the different water coordination capability on copper ion in the formation of the mixed ternary complexes. 相似文献
29.
Wang-bing Zhang Xin-an Yang Yuan-yuan Ma Hai-xia Zhu Shang-bing Wang 《Microchemical Journal》2011,97(2):201-206
The determination of trace concentrations of Hg in water samples by the use of electrolytic cold vapor generation (ECVG) system and AFS was studied. Several buffer solutions were used and the detection limits with these systems were found to be by a factor of 1–2 lower than in the conventional electrolytic cold vapor generation system. Comparing with the traditional inorganic acid, phosphate buffer solution (PBS) increased the signal intensity of Hg vapor from electrolytic generation on Pt cathode and reduced the impact of cathode erosion on the stability of signal intensity. Moreover, buffer solution has better interference tolerance. The effects of the electrolytic conditions and interference ions on the ECVG have been studied. Under optimized conditions and with PBS as catholyte the detection limit for Hg was found to be 0.27 ng L−1. The relative standard deviation was 2.8% for 11 consecutive measurements of 1 μg L−1 Hg. This method has been applied in the determination of inorganic Hg in Yangtze River water. 相似文献
30.