Automatic analysis of G-banded human chromosomes by fast scanning microscope photometry. I. Basic principles and computer control

A high resolution scanning microscope photometry system has been developed for use with standard G-banded chromosome preparations. Various alternative scanning methods and their limitations are reviewed. The computer algorithms which we use are described for the manipulation of the digitized image as produced by the microscope photometer; these include noise reduction and contrast enhancement as well as altering the orientation of the chromosome.     

Incident light microscopy of normal and transformed cultured fibroblasts stained with Coomassie blue R250

Incident light microscopy of fibroblasts stained with Coomassie blue R250 results in images of the cytoskeleton with a similar high contrast to those obtained by specific immunofluorescence microscopy. This technique is especially useful for the routine visualization of the cytoskeleton of transformed cells.     

LED光源照明微投影仪系统的设计

随着LCOS技术的发展,投影仪趋于微型化,而投影系统的分辨力也不断提高,因此对投影仪的光源系统的要求就越来越高,希望得到高强度以及光学扩展量小的光束。采用两个LED面光源作为投影仪的照明光源,使用包括了与偏振光转换系统耦合的光棒以及照明透镜的FF光学系统,使光源发出的光得到充分的均匀,并尽量地会聚在LCOS上。模拟结果表明,该照明系统达到了所要求的照度,并且整个系统结构简单,非常紧凑。     

Construction of a Cerenkov light source

A radiation source has been developed and implemented from Cerenkov emission that is intended to provide an intense continuum from the infrared to 600 A. Parasitic use of the primary electron beam at the Stanford Linear Accelerator Center (SLAC) together with a novel optical geometry for light collection can give a focused and tunable ultraviolet beam with 10(4) kW/m(2)sr brightness, 10(-2) spectral purity, and with the pulsed, 5 ps time structure of the SLAC electron beam. Measurements of emission characteristics in the visible part of the spectrum correlate closely with the predicted performance.     

Frequency-domain fluorescence microscopy with the LED as a light source

We describe a frequency-domain lifetime fluorometer based on a microscope and a modulated light-emitting diode (LED) excitation source (370/460 nm), which operates in the frequency range 120 Hz–250 MHz. We collected multifrequency phase and modulation fluorescence responses from cellular areas as small as 10–15 µm in diameter. We also collected fluorescence lifetime data from cells stained by a lipophilic coumarin sensitized europium fluorophore, Coum-Eu, with a millisecond lifetime, and Ru(bpy)₂phe-C₁₂, with microsecond lifetime. Nanosecond lifetimes from native nuclei stained with SYTO 14 and SYTO 16 probes were measured as well. We demonstrate that a simple LED excitation source can, for many applications, successfully replace complex and expensive laser systems, which have been used for cellular frequency-domain lifetime measurements. As the LEDs are very stable with low noise, it will be possible to image even smaller sample areas using brighter LEDs. With availability of modulated LEDs emitting at several wavelengths covering almost the entire visible spectrum it is easy to assemble a system for the fluorophore of choice. The ability to select an excitation source for a given fluorophore and low price make such an excitation source even more practical.     

铝质滤波片在微聚焦钨靶X射线源相衬成像中的应用研究

实验室建立了以钨靶为光源的微聚焦X射线相衬成像系统,为减少应用过程中微聚焦光源的多色性对系统成像质量的影响,使用一系列不同厚度的铝质滤波片对弱吸收材料聚丙烯吸管进行微聚焦X射线相衬成像的研究。结果说明铝质滤波片能够改善成像质量,且随着铝质滤波片厚度的增加图像中物体的边缘特征的衬度呈指数衰减。为铝质滤波片在钨靶微聚焦X射线相衬成像系统中的应用提供了经验。     

Electron microscopy of tRNA crystals. I. Thin crystals negatively stained with uranyl acetate

The first attempt to study crystal structures of tRNA by electron microscopy is described. Sufficiently thin crystals were prepared from yeast tRNAphe. The thickness of the thinnest was estimated at 130 A corresponding to a bilayer of the molecules. The L-shaped structure seemed to be maintained even after the negative staining with uranyl acetate. Optically filtered images from electron micrographs were compared with those simulated from the drawing of the molecular model by optical transform. The results suggest that the observed images reflect the real molecular arrangements within the crystal lattice although the shape of tRNA molecules seems to be somewhat modified by the uneven staining.     

星上LED定标光源的可行性研究

对发光二极管作星上定标光源的可行性进行了分析研究.测量了LED的工作稳定性,对LED做了开合试验,讨论了它的电流特性.在真空环境下,分析了LED的冷热特性和抗辐射性能.结果表明,LED持续点燃1 200 h的衰减量＜1.2X;其开合重复性很好,但存在10～15 min的不稳定性;改变电流会引起LED发光强度和波长不同程度的变化;温度的变化也同样会影响LED的发光强度、正向偏压以及峰值波长.真空状态下,由于传输介质不同,LED的发光强度会有所增加,但其封装材料真空挥发产生的影响不大;在抗辐射外壳的保护下,空间辐射对LED发光强度的影响不超过0.5%/a.经过分析讨论,证明将LED应用于星上定标是可行的.     

动态光源位置及照度控制系统的研制

为了加强对动态光源的控制,利用LabVIEW的比例-积分-微分(PID)控制方法,研制了动态光源的位置及照度控制系统。该系统通过控制电机改变光源的位置,采用LabVIEW的PID控制及参数自整定模块对输出电流进行控制,以改变动态光源的照度。研究表明,该系统可有效控制动态光源的位置及照度,在用于检测摄像机动态范围时,能有效提高检测效率及检测精度。     

Nanoscale optical imaging of chromosomes with apertureless microscopy.

Near-field optical structure of the centromere region of undyed polytene chromosomes has been observed using an apertureless near-field optical microscope that detects the intensity of light scattered from an atomic force microscope tip under laser illumination. The centromere is of primary importance to the functioning of the chromosome in the cell during cell division. It is also particularly interesting for structural/optical studies since its DNA repeat sequences are highly conserved among organisms and it is possible that they play a part in the centromere self assembly (Clark and Wall 1996).     

高平坦度的三级双泵浦结构C+L波段超荧光光源

为了使掺铒光纤超荧光光源C波段与L波段光谱匹配良好,实现高平坦度的C+L波段宽带光源,提出了一种三级双泵浦光源结构。首先,使用三段不同型号、不同长度的掺铒光纤,两个980nm激光二极管,波分复用器,隔离器以及3dB耦合器构成的光纤环形镜搭建宽带光源实验装置;然后,通过不断优化三段掺铒光纤的长度,调节两级抽运源功率获得高平坦度C+L波段光源输出;最后对其产生机理进行分析。实验结果表明,当三段掺铒光纤的长度分别为11.5m、53m和6.5m,两级抽运源功率分别为65mW和115mW时,输出光谱的3dB带宽为75.68nm,在1543～1603nm波段光谱的平坦度±1.3dB(不加任何滤波器的条件下)。获得的高平坦度C+L波段宽带光源可以更好地满足光纤传感、光纤通信系统等领域的应用要求。     

Phase and amplitude contrast in electron microscopy of stained biological objects.

For biological objects negatively stained with heavy atom material, electron microscope images show best contrast for image detail on the scale of 10--20 A when a small objective aperture is used. In images taken under the optimum phase contrast imaging conditions of Scherzer, the required image detail is lost in unwanted noise. Both of these conditions may be described in terms of phase contrast imaging for a thin phase object. Calculations of image intensities and noise are reported for a model object consisting of heavy and light atoms randomly distributed to simulate a negatively stained protein molecule. The results are consistent with experimental observations.     

基于过程控制的机载高光谱定标光源的快速稳定恒流源研制

定标光源的稳定性及稳定速度直接影响机载高光谱仪光谱辐射定标的准确性和效率。为实现定标光源的快速稳定,提出并设计了基于数字过程控制的恒流源快速稳定调节方法和系统。该快速稳定恒流源系统,在场效应管恒流源的基础上,加入数字过程控制环节,弥补场效应管恒流源反馈振荡调节及系统热稳定时间长的不足。快速稳定调节方法分为能够快速产生热量的大预置值启动快速预热、减小过冲振荡现象的缓冲快稳和输出稳定电流的模拟闭环稳流三阶段。快速稳定恒流源与场效应管恒流源对比实验表明:输出1 500.00 mA电流,纹波系数达到1?的时间由670 s缩短到66 s;作为标准光源中卤钨灯的驱动电路,上电2 min后连续测量20 min获得的400～2 500 nm光谱数据全谱平均基线漂移由0.5%降低到0.06%。     

Electron microscopy of tRNA crystals: I. Thin crystals negatively stained with uranyl acetate

The first attempt to study crystal structures of tRNA by electron microscopy is described. Sufficiently thin crystals were prepared from yeast tRNA^phe. The thickness of the thinnest was estimated at 130 Å corresponding to a bilayer of the molecules. The L-shaped structure seemed to be maintained even after the negative staining with uranyl acetate. Optically filtered images from electron micrographs were compared with those simulated from the drawing of the molecular model by optical transform. The results suggest that the observed images reflect the real molecular arrangements within the crystal lattice although the shape of tRNA molecules seems to be somewhat modified by the uneven staining.     

微光夜视系统试验中微光应力源的模拟

针对微光夜视系统可靠性试验的需要,在实验室准确模拟微光夜视系统在自然条件下所受的光应力具有重大意义。野外自然微光主要由月光、星光、大气辉光及杂散光经多次漫反射而成,所以在不同的环境条件下形成的自然微光不同。为模拟出不同的微光应力源,在试验过程中需要改变平行光管出瞳处的光照度,并使其对微光夜视系统的作用与自然微光对微光夜视系统的作用相当。在实验室条件下,当平行光管的视场大于微光夜视系统的视场时,通过改变光源光照度的办法即可改变平行光管出瞳处的光照度,从而实现自然微光应力源的精确模拟,并通过实验验证了该方法的可行性。     

荧光粉浓度和温度对激光混合荧光投影光源发光特性的影响

光源是投影显示系统的核心组成部件。激光投影光源具有亮度高、寿命长和色域广等特点,但存在成本较高和散斑现象的问题。将激光结合激发荧光作为投影机光源,可以有效降低成本并解决散斑问题。通过将钇铝石榴石(YAG)荧光粉和激光单元结合制成混合光源,研究了不同荧光粉质量分数及工作温度对混合光源发光特性的影响。实验结果表明,光源的亮度和色度坐标值均随着荧光粉质量分数的增大而提高,而荧光粉的转化效率随着工作温度的升高而降低。研究结果验证了激光–荧光混合作为投影机用光源的可行性,不仅降低了整机的制造成本,解决了激光光源存在的散斑问题,而且降低了对光源光学元件加工的精度要求,提升了量产的制成能力。     

被动型CPT原子钟光源系统的设计与实现

简要介绍了相干布局数囚禁(CPT)原子钟的机理,分析了典型的CPT原子钟的系统构成.在此基础上,针对CPT原子钟的特点,以Rb原子钟为设计对象,设计并制作了一种可出射稳定激光频率并能与其他CPT原子钟相兼容的光源系统.该光源系统采用热电致冷器(TEC)对激光器进行温度控制,利用直接数字频率合成(DDS)技术和锁定放大(LIA)技术实现激光器光频稳定.测试结果表明,光源系统温度对波长的控制精度为0.001 2 nm,在此条件下,系统可以很好地完成激光光频的锁定.