强激励单透镜的象差特性及其在离子源能散测量中的应用

一、相空间中的等角等高曲线族对于强激励单透镜,因象差展开式中的高阶项不能忽略,故计算与分析的工作量均变大,且展开法的结果也不直观。而象面相空间中的等角等高曲线族可以反映出直至高阶的几何象差的总体作用,我们可惜此在任选的物面与接收平面之间进行任意发射图形的变换。     

^137Cs事故受照人员外周血淋巴细胞染色体畸变的随访观察

本文报道了３６例在５个月内多次受到＾１３７Ｃｓγ射线源照射受照人员的细胞遗传学随访观察结果。结果表明，在照后１年和５年，各类染色体型畸变明显高于对照组，差异显著或非常显著。由于非稳定性畸变的不断丢失。在照后５年，染色体畸变率比照后１年明显降低，但此时畸变细胞率和累积剂量之间仍存在正相关关系。     

一种利用精密全站仪实施跨江水准测量的方法

在跨江水准测量原理基础上,提出一种利用精密全站仪实施大跨距跨江水准测量的方法,并结合长江隧道工程介绍了具体的作业方法和量测结果。通过实际量测结果分析证明,该方法可以消除球气差影响。     

Observation of lens aberrations for very high-resolution electron microscopy. I. Theory

Least-squares fitting methods are described, currently the most accurate known, for determining the imaging aberrations and other important parameters. The data required are either the image displacement or the image diffractogram shape (or both), as a function of injected beam tilt; the analysis is largely common to the two cases. Explicit solutions are given for some simple cases (e.g. coma-free alignment on the basis of three images only) and some promising developments are considered; the relevant aberration theory is set out in detail. Experimental work reported in a companion paper has confirmed the presence of threefold astigmatism at significant levels, but has not shown any evidence of other higher order aberrations.     

Effects of aberrations and specimen structure in conventional, confocal and two-photon fluorescence microscopy

Specimen-induced aberrations cause a reduction in signal levels and resolution in fluorescence microscopy. Aberrations also affect the image contrast achieved by these microscopes. We model the effects of aberrations on the fluorescence signals acquired from different specimen structures, such as point-like, linear, planar and volume structures, when imaged by conventional, confocal and two-photon microscopes. From this we derive the image contrast obtained when observing combinations of such structures. We show that the effect of aberrations on the visibility of fine features depends upon the specimen morphology and that the contrast is less significantly affected in microscopes exhibiting optical sectioning. For example, we show that point objects become indistinguishable from background fluorescence in the presence of aberrations, particularly when imaged in a conventional fluorescence microscope. This demonstrates the significant advantage of using confocal or two-photon microscopes over conventional instruments when aberrations are present.     

Measuring and correcting aberrations of a cathode objective lens

In this paper I discuss several theoretical and practical aspects related to measuring and correcting the chromatic and spherical aberrations of a cathode objective lens as used in Low Energy Electron Microscopy (LEEM) and Photo Electron Emission Microscopy (PEEM) experiments. Special attention is paid to the various components of the cathode objective lens as they contribute to chromatic and spherical aberrations, and affect practical methods for aberration correction. This analysis has enabled us to correct a LEEM instrument for the spherical and chromatic aberrations of the objective lens.     

Determination of analytical expansion from numerical field data

We introduce a method of calculation of the analytical expansion of the field near the axis that is based on an application of Green's theorem. The approach is demonstrated on an example of a round electrostatic unipotential lens with field computed by the finite-element method and results are compared to methods of Hermite polynomials and wavelet transformation which are used in electron optics. The work is motivated by application to calculations of aberration coefficients where the high order axial field derivatives must be known.     

Aberration measurement in HRTEM: implementation and diagnostic use of numerical procedures for the highly precise recognition of diffractogram patterns

The precise characterisation of the instrumental imaging properties in the form of aberration parameters constitutes an almost universal necessity in quantitative HRTEM, and is underlying most hardware and software techniques established in this field. We focus in this paper on the numerical analysis of individual diffractograms as a first preparatory step for further publications on HRTEM aberration measurement. The extraction of the defocus and the 2-fold astigmatism from a diffractogram is a classical pattern recognition problem, which we believe to have solved in a near-optimum way concerning precision, speed, and robustness. The newly gained measurement precision allows us to resolve fluctuations of the defocus and the 2-fold astigmatism and to assess thereby the optical stability of electron microscopes. Quantitative stability criteria are elaborated, which may serve as helpful guidelines for daily work as well as for microscope acceptance tests.     

Toxicological evaluation of commercial mineral water bottled in polyethylene terephthalate: a cytogenetic approach with Allium cepa

The aim of this study was to ascertain the possible toxicological effects of chemicals released into mineral water packaged in polyethylene terephthalate (PET) bottles. Two commercial mineral waters, bottled both in PET and glass and stored under different conditions, were examined using the Allium cepa     

A new high-aperture glycerol immersion objective lens and its application to 3D-fluorescence microscopy

High‐resolution light microscopy of glycerol‐mounted biological specimens is performed almost exclusively with oil immersion lenses. The reason is that the index of refraction of the oil and the cover slip of ~1.51 is close to that of ~1.45 of the glycerol mountant, so that refractive index mismatch‐induced spherical aberrations are tolerable to some extent. Here we report the application of novel cover glass‐corrected glycerol immersion lenses of high numerical aperture (NA) and the avoidance of these aberrations. The new lenses feature a semi‐aperture angle of 68.5°, which is slightly larger than that of the diffraction‐limited 1.4 NA oil immersion lenses. The glycerol lenses are corrected for a quartz cover glass of 220 µm thickness and for a 80% glycerol‐water immersion solution. Featuring an aberration correction collar, the lens can adapt to glycerol concentrations ranging between 72% and 88%, to slight variations of the temperature, and to the cover glass thickness. As the refractive index mismatch‐induced aberrations are particularly important to quantitative confocal fluorescence microscopy, we investigated the axial sectioning ability and the axial chromatic aberrations in such a microscope as well as the image brightness as a function of the penetration depth. Whereas there is a significant decrease in image brightness associated with oil immersion, this decrease is absent with the glycerol immersion system. In addition, we show directly the compression of the optic axis in the case of oil immersion and its absence in the glycerol system. The unique advantages of these new lenses in high‐resolution microscopy with two coherently used opposing lenses, such as 4 Pi‐microscopy, are discussed.