AFM picking-up manipulation of the metaphase chromosome fragment by using the tweezers-type probe

We have studied the development of a new procedure based on atomic force microscopy (AFM) for the analysis of metaphase chromosome. The aim of this study was to obtain detailed information about the specific locations of genes on the metaphase chromosome. In this research, we performed the manipulation of the metaphase chromosome by using novel AFM probes to obtain chromosome fragments of a smaller size than the ones obtained using the conventional methods, such as glass microneedles. We could pick up the fragment of the metaphase chromosome dissected by the knife-edged probe by using our tweezers-type probe.     

应用X射线光刻的微针阵列及掩模板补偿

提出了一种聚甲基丙烯酸甲酯(PMMA)微针的微细加工工艺,该工艺基于PCT技术,结合X射线以及光刻掩模制作三维微结构。通过移动LIGA掩模板曝光来加工微立体PMMA结构,其加工形状取决于X光光刻掩模板吸收体的形状。实验显示,最终的结构形状并非完全与掩模板上吸收体的形状一致。如果不对X光光刻掩模板的吸收体形状进行补偿,即会使被加工的微结构侧面变形,从而影响微针的性能。分析了微针阵列侧面变形的原因,认为这种变形是由于显影时间与曝光量之间的非线性关系导致结构形状与曝光量分布不完全一致造成的。利用PCT方法制作的PMMA微针其长度为100～750μm,直径为30～150μm,针尖的直径最小可达100nm。通过对LIGA掩模板上的吸收体图形进行适当的补偿,使吸收体图形从中空的双直角三角形变为中空的半椭圆图形,增强了带沟道的微注射针阵列的强度。     

FIB preparation and SEM investigations for three-dimensional analysis of cell cultures on microneedle arrays

We report the investigation of the interfaces between microneedle arrays and cell cultures in patch-on-chip systems by using Focused Ion Beam (FIB) preparation and Scanning Electron Microscopy (SEM). First, FIB preparations of micro chips are made to determine the size and shape of the designed microneedles. In this essay, we investigate the cell-substrate interaction, especially the cell adhesion, and the microneedle's potential cell penetration. For this purpose, cross-sectional preparation of these hard/soft hybrid structures is performed by the FIB technology. By applying the FIB technology followed by high-resolution imaging with SEM, new insights into the cell-substrate interface can be received. One can clearly distinguish between cells that are only in contact with microneedles and cells that are penetrated by microneedles. A stack of slice images is collected by the application of the slice-and-view setup during FIB preparation and is used for three-dimensional reconstruction of cells and micro-needles.     

ON THE NATURE OF MACHINING CRACKS IN GROUND CERAMICS: PART I: SRBSN STRENGTHS AND FRACTOGRAPHIC ANALYSIS

Machining cracks in ground sintered reaction-bonded silicon nitride (SRBSN) rods and bars were analyzed by fractographic techniques. Grinding flaw sizes were as small as 12 µm and as large as 80 µm and correlated strongly with grinding direction and wheel grit size. Some grinding treatments had no deleterious effect on strength since the machining cracks were very small and fracture occurred from the material's inherent flaws. The telltale signs of machining damage may be detected with conventional low power optical microscopy using simple fractographic techniques. The telltale signs are summarized in a new series of schematic drawings which will aid pattern recognition for engineers and fractographers.     

ON THE NATURE OF MACHINING CRACKS IN GROUND CERAMICS: PART I: SRBSN STRENGTHS AND FRACTOGRAPHIC ANALYSIS

ABSTRACT

Machining cracks in ground sintered reaction-bonded silicon nitride (SRBSN) rods and bars were analyzed by fractographic techniques. Grinding flaw sizes were as small as 12 µm and as large as 80 µm and correlated strongly with grinding direction and wheel grit size. Some grinding treatments had no deleterious effect on strength since the machining cracks were very small and fracture occurred from the material's inherent flaws. The telltale signs of machining damage may be detected with conventional low power optical microscopy using simple fractographic techniques. The telltale signs are summarized in a new series of schematic drawings which will aid pattern recognition for engineers and fractographers.     

Time lapse video microscopy using an animation control unit

A system for time lapse video microscopy incorporating an edit recorder and animation control unit is described, allowing both colour recording, forward and reverse playback without synchrony bars, and the identification of each individual frame recorded. This is achieved by using the edit recorder, controlled by the animation unit to produce continuous series of insert edits using the preroll facility of the recorder. A feature of this system is the preview of the last hour' s recording which is constantly played as the preroll of the edit recorder. Tissue culture flasks modified for stable focus are also described.     

Radial gas-permeability measurement in cement-based materials under steady-state flow

An innovative apparatus guided by a proposed theoretical-model was developed for evaluating the radial gas-permeability of cement-based materials under steady-state flow. The testing condition is of higher inlet-gas pressure in an annular concrete cavity to monitor the pressure decrease over time. The gas-tightness for the cavity was effectively enhanced and quantitatively characterized by an ingenious silicone-rubber washer with embedded flexible sensors. The radial gas-permeabilities of the annular concrete with different water-to-cement (w/c) ratios of 0.35–0.55 were measured using various inlet-gas pressures (1.0 bar–30.0 bars) and compared to those obtained by the traditional axial-direction method. The results show that the concrete gas permeability in radial-direction reaches stable permeability zone (SPZ) with inlet-gas pressure exceeding 6.0 bars, which is faster than the SPZ with inlet-gas pressure exceeding 15.0 bars of the axial-direction gas permeability obtained by the traditional method. Under the same inlet-gas pressures of 6.0 bars–10.0 bars, the intrinsic permeability values in the radial and axial directions are near to each other with the standard deviations of 2.83%~9.90% while the apparent permeability values in the radial direction are lower than those in the axial direction by reductions of 3.69%~21.89%. The evolution of apparent gas permeability in radial-direction obeys well the typical model with the low coefficients of variation from 1.01% to 12.55%, indicating that the as-obtained apparatus combined with the proposed theoretical-model can quantitatively and accurately evaluate the radial-direction gas permeability of cement-based materials.     

Interferometry-based Kolsky bar apparatus

A new experimental approach of the Kolsky bar system using optical interferometry is presented for determination of dynamic behavior of materials. Conventional measurements in the Kolsky bar system are based on recording the strain histories on the incident and transmitter bars with two strain gauges, and require good adhesion between the gauge and the bar. We suggest an alternative approach, based on measuring the actual velocities of the bars by using fiber-based velocity interferometry. Two fiber focusers illuminate the bars at a small angle and collect reflected Doppler-shifted light, which is interfered with a reference beam. Velocities are calculated from short-time Fourier transform and phase-based analysis, and the dynamic stress-strain curve is derived directly from the measured velocity traces. We demonstrate that the results coincide with those obtained by conventional strain gauge measurements. The new method is non-intervening and thus not affected by bar impacts, making it more robust and reliable than strain gauges.     

The compaction of powder metallurgy bars using high voltage electrical discharges

A new compaction process for the production of high density powder metallurgy (P/M) bars is suggested using a high voltage electrical discharge followed by rotary swaging. This paper gives practical details concerning the production of P/M bars from iron powder by electrical discharge, and endeavours to describe the mechanism of density increase. Experimental results for determining the effect of various parameters are presented.     

Straightness evaluation using inclinometers with a pair of offset bars

To evaluate the straightness of large objects, the use of an inclinometer is advantageous because it requires neither straight shape references nor transferring mechanisms. Herein, we consider adopting it for precise (with greater accuracy than 1 mm) evaluation of the straightness of linear particle accelerators (linacs) that are several hundred meters long or longer. In this study, the straightness evaluation of a 206-m-long part of the KEK injector linac was demonstrated using inclinometers with a pair of cantilevers called offset bars. The offset bars were adopted to extend the evaluation length by avoiding obstacles that block the evaluation path. Errors caused by the offset bars can be eliminated by reversal measurement considering the slope angles of the offset bars. The derived straightness corresponded with those derived by an alignment telescope and a laser-based alignment system within several millimeters and partly within several hundred micrometers. The reproducibility of slope angles for an arbitrary measurement point was 15 μrad at standard deviation. This corresponds to a standard deviation of 0.47 mm for straightness, with a total evaluation length of 500 m and measurement intervals of 2 m. The results indicate that our newly devised method is applicable for evaluating the straightness.     

基于X-ray光刻的微针阵列及掩膜版补偿

提出了一种聚甲基丙烯酸甲酯（PMMA）微针的微细加工工艺,即基于PCT技术,结合X射线以及光刻掩膜版制作三维微结构。通过移动LIGA掩膜版曝光的方法,可以加工微立体PMMA结构,其加工的形状取决于X光光刻掩膜版吸收体的形状。实验发现,最终的结构形状并非完全与掩膜版上吸收体的形状相一致。如果不对X光光刻掩膜版的吸收体形状进行补偿,将会导致被加工的微结构侧面变形,从而影响微针的性能。本文分析了引起微针阵列侧面的变形的原因,其中主要原因是由于显影时间与曝光量之间的非线性关系,导致结构形状与曝光量分布不完全一致,造成微针结构侧面变形。同时,通过对LIGA掩膜版上的吸收体图形进行适当的补偿,即将吸收体图形从中空的双直角三角形变为中空的半椭圆图形,这样使得带沟道的微注射针阵列的强度得到增强。     

基于主动轮廓线模型的棒材自动计数方法的实现

针对棒材集捆后的特点,提出了一种基于主动轮廓线模型及数字图像处理的计数方法。首先利用主动轮廓线模型将棒材从背景中分离出来,然后利用图像分割、边缘提取及数学形态学来实现棒材的计数。     

Fatigue growth simulation for cracks in notched and unnotched round bars

Fatigue crack growth for various cracks in both unnotched and notched round bars is directly modelled by using an automated numerical technique, which calculates the stress intensity factors at a set of points on the crack front through the three-dimensional finite element method and then applies an appropriate fatigue crack growth law to this set of points to obtain a new crack front. This technique also has the capability of automatic remeshing so that the crack propagation can conveniently be followed. The crack geometries modelled in the present paper include a small internal crack near the free boundary and several initially part-elliptical or irregular surface cracks in a smooth round bar under tension, a surface crack in different semi-circularly notched bars under both tension and bending, a surface crack initiated from the root of a V-notched bar and an initially twin crack configuration within a smooth tension bar. Some fatigue growth characteristics relevant to each type of cracks are also revealed. It is demonstrated that the fatigue growth analyses of various cracks commonly occurring in bars can reliably be made by using the automated finite element technique proposed.     

Probability calculus for quantitative HREM. Part I: Monte-Carlo and point cloud techniques

A new approach to a central question of modern high-resolution electron microscopy (1-IREM) is presented: How precisely can we locate atom positions in crystal defects using computer-controlled structure retrieval algorithms? The purpose is not just to give error bars for the determined atomic column positions, but to derive estimations for the continuous probability functions. In the first part of this two-part paper, we present techniques which analyse point clouds of fluctuating fit-results for atom coordinates. The point clouds are obtained in a first approach from multiple input images differing in noise, commonly known as Monte-Carlo error estimation. Furthermore, we exploit the response obtained during a global optimisation-based refinement process for which all the trial structures are evaluated resulting in a second type of point cloud. In comparison, the Monte-Carlo-type technique turns out to be the most robust one. Using examples from current research on SrTiO3-bicrystals and Cu-Al2O3 interfaces, we study two largely different crystallographic and statistical situations.     

Abrasive flow machining (AFM) finishing of conformal cooling channels created by selective laser melting (SLM)

Conformal cooling channels are widely adopted in the mold industry because of rapid and uniform cooling during injection molding. These complicated cooling channel geometries become feasible via selective laser melting (SLM) technology. However, the SLM fabricated internal channel surface shows high surface roughness of about 10 μm Ra. This rough surface can cause stress concentration, reducing the fatigue life of the mold. Therefore, the objective of this study is to investigate the surface finish of the SLM fabricated conformal channels by abrasive flow machining (AFM), which is widely used in the surface finishing of internal channels. To fulfill this objective, a combination of single/multiple and straight/helical channels for conformal cooling channel geometries are employed. Seven different types of conformal cooling channels (ø3mm) inside the bar are fabricated using SLM. The bar is put in the AFM fixture, and the internal channels are polished by flowing AFM media (ULV50%-54) through the channel at the same extrusion pressure of 80 bars for ten cycles. Fourteen bars (seven before AFM and seven after AFM) are machined to have the internal channel surfaces exposed for surface roughness measurement. Surface topographies of the exposed surfaces of seven types of internal channels are obtained using focus variation microscopy. The areal roughness parameters, such as arithmetical mean height (Sa) on the internal channel surfaces before and after AFM. By comparing SLM as-built conformal channel surfaces with AFM finished ones, AFM is shown to be effective in improving all SLM conformal cooling channels’ arithmetical mean height, Sa. Areal roughness parameters, such as developed interfacial area ratio (Sdr), root mean square gradient (Sdq), reduced peak height (Spk), reduced valley height (Svk), and skewness (Ssk), on those internal surfaces, were found to be sensitive to surface finishing by AFM.     

Discharge characteristics of a trench weir

Trench weirs are commonly adopted in boulder streams for diverting water for use in hydropower, irrigation and water supply schemes etc. Here, a trench is built across the river below its bed level. The top level of this trench is covered with bars to prevent the entry of sediment into the trench. Discharge characteristics of this weir apart from flow conditions also depend on the geometric characteristics of the bars used. Generally round bars are used, however, from a structural consideration, flat bars are preferred over round bars as flat bars have more flexural rigidity. In the present paper, the results of an experimental study on the discharge characteristics of a trench weir consisting of flat bars under free and submerged flow conditions are reported.     

Preparation of flat carbon support films

Wrinkling of carbon support films is known to limit the resolution of electron microscopy images of protein two-dimensional crystals. The origin of carbon wrinkling during preparation of the support films was investigated by reflected light microscopy. We observed that carbon films go through several states during their preparation. While dried carbon films have a tendency to be wrinkled, a flat state is observed transiently before complete drying. This state could be stabilized by the addition of sugars or tannic acid to the embedding medium. An alternative method for preparing flat carbon films was developed, in which a sandwich is formed by two symmetrical carbon films positioned on both sides of a grid. The formation of sandwiched carbon films was facilitated by the use of grids with thin bars. The carbon sandwich films were flat, stable, and easily and reproducibly prepared.     

采用D-S证据推理的电机转子故障诊断

提出了采用D-S(Dempster-Sharer)证据理论对感应电机转子断条故障进行识别的故障诊断方法.基于小波包变换的频率划分特性,对定子三相电流信号进行小波包分解,利用节点系数的均方根值构建电机转子故障的特征矢量(证据体);利用明氏距离测度构造基本可信度分配函数,求取证据体对转子故障所赋予的基本概率分配函数值,然后根据D-S证据融合规则进行融合处理,实现了对电机转子故障的准确识别.试验结果表明,该方法可实现转子断条故障的可靠诊断.     

基于虚拟示波器的涡流应力测量装置研制

为将涡流阻抗法应用于金属构件应力的快速测量,基于改进的矢量伏安法,采用虚拟示波器技术,研制出一套测量参数可控的便携式阻抗测量装置。实验测试了信号平均次数、电路采样电阻等对涡流传感器阻抗-频率特性曲线测量精度的影响规律,在优化参数条件下,研制的阻抗测量装置与Agilent 4294a的测试结果较为一致,相对偏差在±5%范围。将便携式装置应用于金属杆件的涡流应力测量:先后对45号钢杆和LY12铝合金直杆进行拉伸实验,测量粘贴于直杆上涡流传感器的阻抗变化,回归分析得到阻抗变化率与拉力的直线拟合方程(拟合优度大于0.9)。实验结果表明,基于虚拟示波器的阻抗测量装置可以基于涡流测力原理,实现金属构件应力的快速、有效测量。