Image contrast reduction mechanism in full‐field optical coherence tomography

Correct interpretation of image contrast obtained with full‐field optical coherence tomography (FFOCT) technique is required for accurate medical diagnosis applications. In this work, first, the characteristics of microscopic structures of tissue that generate the contrast in en‐face tomographic image obtained with FFOCT are discussed. Then an overview is given of the parameters that affect image contrast. Finally, the contrast correction factor for correct image interpretation and the contrast limits to practical FFOCT systems are outlined.     

The structure and continuous stoichiometry change of 1DTbBrx@SWCNTs

HRTEM and HAADF STEM of 1DTbBr_x@SWCNT meta‐nanotubes reveal three structural modifications of 1D nanocrystals within single wall carbon nanotube channels attributed to a different stoichiometry of the guest crystal. For SWCNTs with diameters D_m > 1.4 nm a most complete tetragonal unit cell is observed. When crystallization occurs inside SWCNT with D_m < 1.4 nm 1D TbBr_x crystal deforms a nanotube to elliptical shape in cross section. In this case the 1D crystal unit cell becomes monoclinic, with possible loss of a part of bromine atoms. Two modifications of a monoclinic unit cell appear. One of them is characterized by single or pair vacancies in the structure of the 1D crystal. Another structure is explained by peripheral and central bromine atoms loss. An appearance of such modifications can be stimulated by electron irradiation. The loss of bromine atoms is in agreement with chemical analysis data. Electronic properties of obtained meta‐nanotubes are investigated using optical absorption and Raman spectroscopy. It is shown that intercalation of terbium bromide into SWCNTs leads to acceptor doping of SWCNTs. According to local EDX analysis and elemental mapping this doping can arise from significant stoichiometry change in 1D nanocrystal indicating an average Tb:Br atomic ratio of 1:2.8 ± 0.1.     

Far‐reaching geometrical artefacts due to thermal decomposition of polymeric coatings around focused ion beam milled pigment particles

Focused ion beam and scanning electron microscope (FIB‐SEM) instruments are extensively used to characterize nanoscale composition of composite materials, however, their application to analysis of organic corrosion barrier coatings has been limited. The primary concern that arises with use of FIB to mill organic materials is the possibility of severe thermal damage that occurs in close proximity to the ion beam impact. Recent research has shown that such localized artefacts can be mitigated for a number of polymers through cryogenic cooling of the sample as well as low current milling and intelligent ion beam control. Here we report unexpected nonlocalized artefacts that occur during FIB milling of composite organic coatings with pigment particles. Specifically, we show that FIB milling of pigmented polysiloxane coating can lead to formation of multiple microscopic voids within the substrate as far as 5 μm away from the ion beam impact. We use further experimentation and modelling to show that void formation occurs via ion beam heating of the pigment particles that leads to decomposition and vaporization of the surrounding polysiloxane. We also identify FIB milling conditions that mitigate this issue.     

Ultra‐thin resin embedding method for scanning electron microscopy of individual cells on high and low aspect ratio 3D nanostructures

The preparation of biological cells for either scanning or transmission electron microscopy requires a complex process of fixation, dehydration and drying. Critical point drying is commonly used for samples investigated with a scanning electron beam, whereas resin‐infiltration is typically used for transmission electron microscopy. Critical point drying may cause cracks at the cellular surface and a sponge‐like morphology of nondistinguishable intracellular compartments. Resin‐infiltrated biological samples result in a solid block of resin, which can be further processed by mechanical sectioning, however that does not allow a top view examination of small cell–cell and cell–surface contacts. Here, we propose a method for removing resin excess on biological samples before effective polymerization. In this way the cells result to be embedded in an ultra‐thin layer of epoxy resin. This novel method highlights in contrast to standard methods the imaging of individual cells not only on nanostructured planar surfaces but also on topologically challenging substrates with high aspect ratio three‐dimensional features by scanning electron microscopy.     

Free and open‐source automated 3‐D microscope

Open‐source technology not only has facilitated the expansion of the greater research community, but by lowering costs it has encouraged innovation and customizable design. The field of automated microscopy has continued to be a challenge in accessibility due the expense and inflexible, noninterchangeable stages. This paper presents a low‐cost, open‐source microscope 3‐D stage. A RepRap 3‐D printer was converted to an optical microscope equipped with a customized, 3‐D printed holder for a USB microscope. Precision measurements were determined to have an average error of 10 μm at the maximum speed and 27 μm at the minimum recorded speed. Accuracy tests yielded an error of 0.15%. The machine is a true 3‐D stage and thus able to operate with USB microscopes or conventional desktop microscopes. It is larger than all commercial alternatives, and is thus capable of high‐depth images over unprecedented areas and complex geometries. The repeatability is below 2‐D microscope stages, but testing shows that it is adequate for the majority of scientific applications. The open‐source microscope stage costs less than 3–9% of the closest proprietary commercial stages. This extreme affordability vastly improves accessibility for 3‐D microscopy throughout the world.     

Iodine potassium iodide improves the contrast‐to‐noise ratio of micro‐computed tomography images of the human middle ear

High‐resolution imaging of middle‐ear geometry is necessary for finite‐element modeling. Although micro‐computed tomography (microCT) is widely used because of its ability to image bony structures of the middle ear, it is difficult to visualize soft tissues – including the tympanic membrane and the suspensory ligaments/tendons – because of lack of contrast. The objective of this research is to quantitatively evaluate the efficacy of iodine potassium iodide (IKI) solution as a contrast agent. Six human temporal bones were used in this experiment, which were obtained in right‐left pairs, from three cadaveric heads. All bones were fixed using formaldehyde. Three bones (one from each pair) were stained in IKI solution for 2 days, whereas the other three were not stained. Samples were scanned using a microCT system at a resolution of 20 μm. Eight soft tissues in the middle ear were segmented: anterior mallear ligament, incudomallear joint, lateral mallear ligament, posterior incudal ligament, stapedial annular ligament, stapedius muscle, tympanic membrane and tensor tympani muscle. Contrast‐to‐noise ratios (CNRs) of each soft tissue were calculated for each temporal bone. Combined CNRs of the soft tissues in unstained samples were 6.1 ± 3.0, whereas they were 8.1 ± 2.7 in stained samples. Results from Welch's t‐test indicate significant difference between the two groups at a 95% confidence interval. Results for paired t‐tests for each of the individual soft tissues also indicated significant improvement of contrast in all tissues after staining. Relatively large soft tissues in the middle ear such as the tympanic membrane and the tensor tympani muscle were impacted by staining more than smaller tissues such as the stapedial annular ligament. The increase in contrast with IKI solution confirms its potential application in automatic segmentation of the middle‐ear soft tissues.     

Fine structure characterization of martensite/austenite constituent in low‐carbon low‐alloy steel by transmission electron forward scatter diffraction

Transmission electron forward scatter diffraction and other characterization techniques were used to investigate the fine structure and the variant relationship of the martensite/austenite (M/A) constituent of the granular bainite in low‐carbon low‐alloy steel. The results demonstrated that the M/A constituents were distributed in clusters throughout the bainitic ferrite. Lath martensite was the main component of the M/A constituent, where the relationship between the martensite variants was consistent with the Nishiyama–Wassermann orientation relationship and only three variants were found in the M/A constituent, suggesting that the variants had formed in the M/A constituent according to a specific mechanism. Furthermore, the Σ3 boundaries in the M/A constituent were much longer than their counterparts in the bainitic ferrite region. The results indicate that transmission electron forward scatter diffraction is an effective method of crystallographic analysis for nanolaths in M/A constituents.     

太阳能空气源复合多功能热泵系统的试验研究

构建了一种多功能直膨式太阳能与空气源复合的热泵系统。在常州的冬季及春季分别对试验样机的运行特性进行研究。试验结果表明:系统在冷暖联供的工况下,即同时产生生活热水和冷冻水,整个过程平均COP为6.0;在冬季,太阳辐射强度为354 W/m~2时,系统制生活热水平均COP为4.32;模拟系统供暖,即将循环水从40℃加热至45℃时,测试结果中最低COP为5.07。在春季,太阳辐射强度为856 W/m~2时,系统制生活热水平均COP为5.78。夏季时,系统同时生产冷热水用于生活热水和供冷的需求;冬季时,由于太阳能的辐射,提高了系统的蒸发温度,热泵的性能因此得到提升。     

结合SVM后验概率的散料料位识别试验研究

提出了一种散料装车料位的图像检测方法,该方法将待处理料堆图像分为若干不重叠的子块,对各子块进行了同态滤波、二值化及二值共生矩阵纹理特征提取,并根据纹理特征对各子块进行了分类识别。在识别过程中,提出了一种基于SVM及其后验概率的料堆识别方法,建立了位于交界位置子块的SVM后验概率与其中料堆目标所占比例的关系模型,并将仅采用SVM对子块识别后的料位拟合结果与其后验概率输出相结合,在这些交界位置子块内进行了进一步的图像分割。试验结果表明,所提出的方法与仅采用SVM子块识别的料堆轮廓及料位拟合误差相比,分别减小42%和56%,平均误差分别为0.4517pixel和0.2586pixel,在MATLAB下每帧处理需0.2s。     

Load performance analysis of three‐pad fixing pad aerodynamic journal bearings with parabolic grooves

Three‐pad fixing pad aerodynamic journal bearings (TPFPAJBs) have been widely used in precision instruments due to their low friction, high stability and non‐pollution. In order to improve the load performance of TPFPAJBs, parabolic grooves are opened in the bearing pad surfaces. By opening parabolic grooves in various bearing pad surfaces, the effects of the orientation angle, distance, width and depth of the grooves on the load performance of micro‐grooved TPFPAJBs can be investigated. The numerical results show that the location of the micro‐grooved bearing pads can greatly affect the load performance of micro‐grooved TPFPAJBs. When the given bearing pad surface is grooved, the effects of the bearing number and width‐to‐diameter ratio on the load performance of micro‐grooved TPFPAJBs can be studied. The bearing number and width‐to‐diameter ratio are observed to have significant influences on the load performance of micro‐grooved TPFPAJBs. Copyright © 2015 John Wiley & Sons, Ltd.