Backscattered electron SEM imaging of cells and determination of the information depth

Backscattered electron imaging of HT29 colon carcinoma cells in a scanning electron microscope was studied. Thin cell sections were placed on indium‐tin‐oxide‐coated glass slides, which is a promising substrate material for correlative light and electron microscopy. The ultrastructure of HT29 colon carcinoma cells was imaged without poststaining by exploiting the high chemical sensitivity of backscattered electrons. Optimum primary electron energies for backscattered electron imaging were determined which depend on the section thickness. Charging effects in the vicinity of the SiO₂ nanoparticles contained in cell sections could be clarified by placing cell sections on different substrates. Moreover, a method is presented for information depth determination of backscattered electrons which is based on the imaging of subsurface nanoparticles embedded by the cells.     

共振扫描显微成像中的图像畸变校正

设计了一种校正算法用于校正双光子荧光显微镜等高速扫描成像系统中共振振镜扫描导致的图像畸变。首先对共振振镜的扫描运动建立模型,推导出非线性扫描的运动公式,进而得到图像畸变公式;然后对一块朗奇光栅样品扫描成像,设计了多峰高斯拟合算法得到光栅所有条纹的宽度变化并通过最小二乘法将条纹宽度数据拟合成一条畸变曲线;最后利用畸变曲线对图像进行校正。结果表明:采用提出的校正算法可使系统最大畸变减小到传统正弦校正方法的1/3,相对畸变减小到1/5,校正效果比传统的正弦校正法提高了2倍。由于提出的曲线拟合校正算法不用增加额外的光路,且不需要切割边缘图像,故显示了极好的图像使用效率和校正效果。     

窄角锥束CT的改进扫描方式

基于圆形扫描轨道的FDK算法因其机械实现简单、算法效率高，已成为目前主要使用的三维锥束CT重建算法。但在工业CT（ICT）中，当探测器面阵的尺寸较小、射线束的水平张角较小，而待检测的工件较大时，单圆扫描的FDK重建算法受到限制。为解决小尺寸探测器检测大尺寸工件问题，本文研究了一种大步距平移加小分度旋转的扫描方式。与Ⅱ代锥束CT比，这种改进的扫描方式既可以节省扫描时间，数据的冗余量也比较少。仿真实验结果表明，这种改进的扫描方式具有良好的空间分辨率和密度分辨率。     

Kinetics of Melt Crystallization of a Sunflower Oil‐Based Polyunsaturated Fatty Acid Mixture

Important parameters like supercooling and cooling rates affecting the melt crystallization of a polyunsaturated fatty acid (PUFA) mixture obtained from sunflower oil were investigated and compared via high‐resolution polarized‐light microscopy. PUFA was thermally characterized in a differential scanning calorimeter and the significant liquid‐solid‐phase transition temperatures determined were then implemented in the development of specific temperature profiles. Analyzed between two glass slides, induction times were found to decrease with low crystallization temperatures and the number of nuclei per unit area increased with higher supercooling and cooling rates. A comparison between the linear crystal growth rates of pure standards of each of the main fatty acids present in the PUFA mixture and the PUFA mixture itself indicated that the latter is much slower than that of each of its pure components.     

Influence of very long aging on the relaxation behavior of flame‐retardant printed circuit board epoxy composites under mechatronic conditions

Very long aging times, up to 15,100 h (629 days) at 110°C, were achieved on flame‐retardant printed circuit board laminates commonly used in automotive design. This composite was fabricated from glass fibers embedded in an epoxy resin. Aging was performed in an oven under an air atmosphere at a temperature lower than the glass‐transition temperature. Temperature‐modulated differential scanning calorimetric analysis was used to investigate the influence of such aging on the glass‐transition phenomena. A new amorphous phase appeared during aging. By extending the analysis to samples collected at different thicknesses, we demonstrated the existence of a time‐dependent gradient of the properties. A skin–core structure was evidenced, and this slowed down oxidation and allowed physical aging to occur in the bulk sample. An exponential law described the variations of the glass‐transition of the new external compound. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 786‐792, 2013     

Internal structure of bitumen/polymer/wax ternary mixtures for warm mix asphalts

Polymer modified asphalts (PMA) and warm mix asphalts (WMA) are technologies widely adopted in the paving industry. The first one is well established, while the second one is relatively new, but rapidly growing since it guarantees economic and environmental advantages. Until now PMA and WMA have been used disjointedly, but it would be useful to combine them to keep the advantages of both. One of the adopted solutions to obtain a warm effect is the addition of waxes to the asphaltic binder. Therefore, a “warm mix polymer modified asphalt” may be potentially obtained with a ternary asphalt/polymer/wax system. However, the final warm effect and performances of the binder will depend on the interactions between the three components. A preliminary investigation was done by mixing asphalt, styrene‐butadiene‐styrene block copolymer and a wax chosen among the following three categories: paraffinic, partially oxidized and maleic anhydride functionalized. The morphological and calorimetric analyses and solubility tests allowed identifying different behaviors depending on the wax type, which may preferentially interact either with the asphalt or with the polymer, thus influencing the whole binder structure. With regard to the ternary mixes, it was found that: (i) the paraffinic wax preferentially resides in the polymer‐rich phase, and slightly enhances the asphalt‐polymer compatibility; (ii) the partially oxidized wax prefers the asphaltene‐rich phase and reduces the compatibility; (iii) it is not clear where the functionalized wax is located, but it has a considerable compatibilizing effect and strongly alters the colloidal equilibrium of the asphalt‐polymer blend. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

A novel method of studying the collapsed cell of eucalyptus wood using X-ray CT scanning

Abstract

Collapse is the severest defect for collapse-prone species used as solid wood product materials. Previous study focused on the morphological structures by scanning electron microscopy (SEM) to observe the change of the collapsed cells during the drying processes. The multi planar reconstruction by X-ray computed tomography (CT) scanning provided a new method for cell microstructure observation. In this study, cell collapse of Eucalyptus urophylla were observed by SEM and X-ray CT scanning during the continuous and intermittent drying process. The cell shapes, cell types, cell collapsed quantities and the shrinkage curves were determined. The results demonstrated that layered scanning technique by X-ray CT scanning provided a top-down approach to investigate the structure in depth at different layers in a fast and nondestructive way. Compared with SEM observation, this approach emphasized more specific aspects and information for collapse quantitative analysis. Quantitative analysis of collapsed cells by X-ray CT scanning not only indicated the cell deformation but quantified the extent of cells collapse. The shrinkage rate was also measured by calculating the areas change in porosity at tissue level before and after drying through X-ray CT scanning. It indicates that intermittent drying process may decrease the extent of cell collapse or accelerate the recovery of collapsed cells. These results further confirm that the X-ray CT scanning provides another effective method for wood cell collapse study at the morphological level.     

The effect of thermal annealing on the adherence of Al2O3 films deposited by LP-MOCVD on several high alloy steels

Thin alumina films, deposited at 280°C on several high alloy steels by low-pressure metal-organic chemical vapor deposition (LP-MOCVD), were annealed at 0.17 kPa in a nitrogen atmosphere for 2, 4, and 17 h at 600 and 800°C. Film adhesion was studied by scanning scratch testing (SST) and Auger electron spectroscopy (AES). The best adhesion properties were obtained with commercial oxide dispersion-strengthened (ODS) high-temperature alloys, especially PM 3030. Among the 'normally' high alloy stainless steels, type AISI-321 showed the best adhesion. The other stainless steel-alumina combinations exhibited a reduced critical load, L_c, after thermal treatment. Alumina on ODS alloys exhibited an increased adhesion. AES studies revealed that this increase could be explained by: (1) the presence of sulfur-trapping elements, preventing segregation of sulfur at the interface; and (2) titanium and carbon enrichment at the interface, resulting in an anchoring effect between the oxide and the substrate.     

Production of microparticles from milk fat products using the Supercritical Melt Micronization (ScMM) process

The ScMM (Supercritical Melt Micronization) process was applied for the production of microparticles from anhydrous milk fat (AMF) and a diacylglycerol-based modified milk fat (D-AMF). Both fats were able to dissolve ca. 30 wt% CO₂ in the studied pressure and temperature ranges, being the CO₂ amount slightly higher for AMF. A melting point depression was observed in both systems in the presence of CO₂. Two powder morphologies were obtained (spherical hollow particles and a mass sponge-like broken particles) depending on the ScMM process conditions. The concentration of CO₂ in the fat melt was the main process variable affecting the particle morphology, followed by the temperature of the melt. The small broken particles originated from the breakage of spherical fat particles that solidified before all CO₂ could escape from the atomized droplets. While the hollow spheres had a tendency to agglomerate, the broken microparticles constituted a free-flowing powder as long as they were stored at low temperatures (up to −18 °C). Both types of particles have a potential for being incorporated in refrigerated or frozen food products as a structuring agent.