艾里光束的产生及对微小粒子的操作

近年来,艾里光束因具有横向加速、无衍射以及自愈等独特性质引起了人们的广泛关注。该光束的光场振幅分布遵从艾里函数,并满足类似薛定谔型的波动方程。从理论和实验、线性和非线性、应用等多个方面对它进行研究。从理论上阐述了艾里光束产生的原理,用相位空间光调制器从实验上产生了艾里光束。在此基础上,采用瑞利近似方法,重点分析了在一维艾里光束作用下,粒子所受的光学散射力、梯度力以及粒子所受的光学散射力和梯度力与粒子半径、折射率的关系。     

The STEM approach to the imaging of surfaces and small particles

The characteristics of scanning transmission electron microsopy, which make it a particularly powerful tool for the study of surfaces and small crystals, include the serial nature of the image signal which makes it amenable to recording and image processing procedures, the possibility of correlating the image data with microdiffraction patterns and microanalysis of chosen small regions and the possibilities for combining several different image signals obtained simultaneously. Images obtained from surfaces using reflected diffraction beams may be very sensitive to variations of surface structure but the resolution, depth of focus and contrast of the images are strongly dependent on the nature of the surface and the aperture sizes used in the microsope. Microdiffraction patterns may be obtained from small surface features. Electron energy loss analyses of the diffracted beams provides sensitive indications on surface electron excitations. Microdiffraction patterns obtained in transmission from regions of 1–5 nm diameter provide valuable information on the structure and defects of small crystals, such as those of platinum and gold which are of interest in relation to the study of catalysts.     

小数控车床加工大模具工件的刀具改进

就在经济型数控车床上加工模具工件中存在的装夹、车削方法、表面接刀、车刀选择及编程方法等技术问题,提出在实际加工中用改进刀具、加工方法及程序处理等措施去解决问题.     

The dimensions and numbers of small vesicles in cells, endothelial and mesothelial and the significance of these for endothelial permeability

Measurements were made of the diameters, numbers and other parameters of small, smooth-surfaced vesicles in the endothelium of blood capillaries and lymphatics, and in the mesothelial cells of the diaphragms of mice. Some measurements were also made on the aortic endothelium. With a few exceptions, there were no morphological differences between the various sites. It was found that between 25% and 35% of the non-nuclear cell volume was composed of vesicles, whose membranes accounted for about 55% of their volumes. Their internal volumes were ～ 70,000 nm³, totalling ～ 0·04 μm³/μm² of luminal surface area. For each 1 μm² there were ～ 135 vesicles attached to each surface membrane of the cell, and between ～ 200 and ～ 350 vesicles lying free in the cytoplasm. There was probably a slight amount of shrinkage during the preparation of the material, and the true linear dimensions were probably ～ 105% of those actually observed. Thus the values for the internal volumes were probably ～ 85,000 nm³ and ～005 μm³ respectively; the vesicular numbers were probably ～ 125 attached to each surface and between ～ 175 and ～ 300 free. The vesicles attached to the plasma membranes often had quite long stalks; these were estimated to be ～ 30 nm at the moment of rupture. Thus the vesicles must be released an appreciable distance away from the membrane. This modifies the conclusions of Shea & Karnovsky (1966), since it can now be shown that Brownian movement alone is capable of accounting for the release of the vesicles, their movements within the cells and their transportation of material. By combining these results with others estimating the endothelial permeability coefficients, it can be calculated that the average free lifetime of a vesicle is ～1½ sec, from union with one plasma membrane to the next. It can also be shown that the average time of such an attachment is ～ 2½ sec. There are many possible sources of error relating to these measurements; they must only be regarded as tentative. It appears likely, however, that they are of about the correct order of magnitude as they accord well with other data.     

Exploiting the orbital motion of water particles for energy extraction from waves

In wave motion, the water particles are known to follow orbital paths. This orbital motion was used to drive five-bladed Savonius rotors. Experiments were performed on an array of four rotors placed in a two-dimensional (2-D) wave channel. The flow around the rotors was documented using particle image velocimetry measurements. The submergence of the rotors and the distance between them were varied, and the rotational speeds of the rotors (N_n) were recorded at different wave frequencies. It was found that rotational speeds increased with an increase in the wave frequency, as it amplified the wave height that increased the kinetic energy of the particles in their orbital motion. The rotational speeds decreased when the distance between the rotors increased. High rotational speeds are recorded when the array of the rotors is placed close to the water surface at the smallest centre-to-centre distance between the rotors.     

应用小波包能量谱及SVM的安瓿内浮类异物识别

目的：为了解决安瓿内漂浮物与悬浮物的识别问题,本文提出了一种基于小波包能量谱的特征提取及支持向量机的识别方法。方法：首先通过图像序列差分及点检测分割提取杂质存在区图像作为目标区;然后将目标区沿安瓿瓶轴线方向逐行叠加形成一维信号;对一维信号进行小波包分解,采用主成分分析方法提取小波包分解特征向量中独立主成分;以小波包特征向量中独立主成分的能量谱作为异物类型特征;将提取的特征作为支持向量机的输入向量,采用序列最小优化方法实现训练样本快速分类。实验过程中选择不同类型的核函数和相应参数进行训练和测试。结果：实验结果显示,相对于传统BP网络,SVM在将识别用时减少近60%,识别精度提高了35%。结论：能够满足在生产中对浮类杂质的提取和快速识别的要求。     

应用不同功率电动机驱动的大型立式车铣复合加工中心工作台

介绍了应用不同功率电动机驱动的大型立式车铣复合加工中心工作台的具体结构和工作原理.     

On the size of small protein particles determined by electron microscopy of unidirectionally shadowed freeze-etched preparations

The influence exerted by the thickness of the deposited metal layer and the ionic strength of the solution on the apparent size of particles of bovine serum albumin in unidirectionally shadowed freeze-etch preparations of spray-frozen specimens was investigated. It appeared that the size increase due to shadowing is nearly twice the thickness of the deposited metal layer. Apparent particle size was shown to increase linearly with the inverse square root of the ionic strength of the solution. At ionic strength 0·001 the particles appeared about 30% larger than at infinite ionic strength.     

An electron energy loss spectrometer designed for studies of electronic energy losses and spin waves in the large momentum regime

Based on 143° electrostatic deflectors we have realized a new spectrometer for electron energy loss spectroscopy which is particularly suitable for studies on surface spin waves and other low energy electronic energy losses. Contrary to previous designs high resolution is maintained even for diffuse inelastic scattering due to a specific management of the angular aberrations in combination with an angle aperture. The performance of the instrument is demonstrated with high resolution energy loss spectra of surface spin waves on a cobalt film deposited on the Cu(100) surface.     

Detection of sulfur in fixed and embedded rat peritoneal mast cell granules by X-ray energy dispersive spectroscopy

Purified rat peritoneal mast cells contained 3.3 × 10^?5 gm SO₄ and 2.2 × 10^?8 gm Ca/10⁶ cells. The molar ratio of S/Ca in the whole cell was 600:1. Frozen thin sections of unfixed mast cells contained only sulfur (S) in the granules when examined by X-ray energy dispersive spectroscopy (EDS). Mast cells fixed in 3% glutaraldehyde and 1.5% formaldehyde in 75% ethanol (Et/Ald) or in mixed buffered aldehydes and embedded in Epon 812 or the low viscosity resin diepoxyoctane (DEO) contained S in all granules and Ca in some of the granules measured. Neither element was found in the nucleus, cytoplasm, or resin. Isolated, Et/Ald fixed and embedded granules also contained S. The presence of Ca in the granules was artifactual in that the Ca was absorbed from water in the trough of the diamond knife and/or from the filter paper used to blot the sections dry. This phenomenon was investigated further. Sections of Et/Ald fixed and embedded mast cells were incubated with 5 × 10^?6 to 10^?2 M CaCl₂. Ca was detectable in 100% of the granules incubated at concentrations ≥ 10^?4 M and reached a constant S/Ca ratio of 2.0 at concentrations ≥ 10^?3 M. Ca was not detectable in the nucleus, cytoplasm, or resin at 10^?2 M. A plot of S versus Ca counts from the granules of cells incubated with 10^?2 M CaCl₂ was linear with a slope of 2.0 and a correlation coefficient of 0.88. Et/Ald fixed cells incubated with distilled H₂O had fewer granules containing Ca, 10%, than unincubated cells, 77%. Further, H₂O removed all Ca from Et/Ald fixed cells embedded in DEO. These studies show that S, which is present as SO₄ on the proteoglycan heparin, is readily detectable by X-ray EDS in fixed and embedded cells. An artifact of the technique is that weak anionic sites, which are most probably carboxyl groups on the proteoglycan, can bind the divalent cation Ca and cause spurious localization.     

A microcomputer program in “BASIC” for the accurate determination of the height of small particles

A formula is derived to enable the calculation of the true height of an object, such as a shadowed latex bead, from electron micrographs. Knowing only the angle of shadowing and the length of the evaporated shadow, and by substituting these values in the derived formula, a microcomputer may be programmed to carry out the necessary computations. An example of such a microcomputer program is given. The correct determination of the height of particles by electron microscopy using the shadowing technique is one of the most accurate methods available for the determination of small particle height.     

Correlation method for processing speckle patterns of dynamic light scattering by small particles based on spatial averaging of data

A correlation method for processing dynamic light scattering patterns resulting from laser radiation propagation through solutions and suspensions is proposed which is based on spatial averaging of measurement data on the correlation functions of the intensity of light scattered by small particles.     

Elastic contact between rough surfaces: Effect of roughness at large and small wavelengths

The area and pressure distribution in elastic contacts between frictionless, nonadhesive surfaces is studied as a function of load and surface geometry using finite element calculations. Surfaces that follow self-affine scaling on all resolved scales are compared to surfaces with cutoffs at small and large length scales, and experimental surfaces that are not self-affine. In all cases the true area of contact is proportional to load and inversely proportional to elastic modulus and the mean slope of the surface. The constant of proportionality κ is nearly constant and lies between analytic predictions. Large wavelength cutoffs lead to a small increase in κ, a homogeneous distribution of contacts at large scales, and limit the size of the largest connected regions. Small wavelength cutoffs lead to local redistributions in pressure that decrease the probability of low and high local pressures.     

Cranz-Schardin camera with a large working distance for the observation of small scale high-speed flows

The Cranz-Schardin camera utilizes a Q-switched Nd:YAG laser and four single CCD cameras. Light pulse energy in the range of 25 mJ and pulse duration of about 5 ns is provided by the laser. The laser light is converted to incoherent light by Rhodamine-B fluorescence dye in a cuvette. The laser beam coherence is intentionally broken in order to avoid speckle. Four light fibers collect the fluorescence light and are used for illumination. Different light fiber lengths enable a delay of illumination between consecutive images. The chosen interframe time is 25 ns, corresponding to 40 × 10(6) frames per second. Exemplarily, the camera is applied to observe the bow shock in front of a water jet, propagating in air at supersonic speed. The initial phase of the formation of a jet structure is recorded.     

The dimensions and numbers of small vesicles in blood capillary endothelium in the hind legs of dogs, and their relation to vascular permeability

The dimensions and numbers of vesicles were determined in the blood capillary endothelium of the gastrocnemii muscle of dogs. These results permitted more accurate calculations of the number of vesicles crossing the endothelium in one direction/sec/(μm² (～6·2), and of the median vesicular attachment time (～8 sec). The probability of fusion occurring when a vesicle contacts a plasma membrane (α= 0·004) was unchanged: hence it was concluded, from the mean cellular width (0·21 μm) and the calculated cytoplasmic viscosity (～0·1 poise), that ～49% of the vesicles starting from one side reached the other one, and that their median transit time was ～1 sec.