摘要:

SUMMARYSubmicrometre holes in a gold film are illuminated with coherent low‐energy electrons in the low‐energy electron point‐source microscope. The images are interpreted as holograms and simulated using the Fresnel‐Kirchhoff formula. A reconstruction scheme yields the wave front at the object, in good agreement with transmission electron microscope images of the same hole structures. Laser experiments of similarly shaped, but scaled appropriately, hole structures reveal the same f

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1995.tb03597.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

SUMMARYIn electron energy‐loss spectroscopy (EELS) elemental quantification, the measured intensity ratio has been observed to change with thickness (t) when a collector aperture is used. This change has been shown semi‐quantitatively to be a result of elastic scattering. In this paper, a method based on the elastic Lenz model is used to correct for the effects of elastic scattering in amorphous materials. The validity of the Lenz model is confirmed by studying the zero‐loss component of EEL spectra recorded from several amorphous materials as a function of thickness and collection angle. The experimental data are found to be consistent with calculations based on the Lenz model and Poisson statistics. Based on these calculations, a simple scheme is proposed to obtain the important scattering parameterst/Λe, where Λeis the elastic mean free path, and θ0, the characteristic angle of elastic scattering, with adequate accuracy from the low‐loss data. These values are then used to correct for the effect of elastic scattering in core‐edge quantification. The procedure is applied to Al2O3and good agreement with experimental data up tot= 2Λeis found; beyond 2Λethe method can serve as a part

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1995.tb03598.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

SUMMARYMicrostructural developments in discontinuously reinforced aluminium composites have been monitored during a variety of thermo‐mechanical treatments. The material, made by powder blending or casting, followed by extrusion, contains particulate or short‐fibre alumina in a matrix of commercial purity aluminium. Attention is centred on the distribution of reinforcement, the fine alumina particles derived from the prior oxide layers on the aluminium powder, and the effects that these inclusions have on cavitation, recovery and recrystallization processes. Optical metallography, by viewing anodized sections in polarized light, is used to reveal grain and coarse subgrain structures. Scanning electron microscopy has also been employed to reveal fine oxide stringers, cavities and (in backscattered mode) fine subgrain structures. The emphasis in this paper is on the type of information that can be obtained for these materials from careful application of standard microscopy techniq

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1995.tb03599.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

SUMMARYA general formulation for the secondary fluorescence correction is presented. It is intended to give an intuitive appreciation for the various factors that influence the magnitude of the secondary fluorescence correction, the specimen geometry in particular, and to serve as a starting point for the derivation of quantitative correction formulae. This formulation is primarily intended for the X‐ray microanalysis of electron‐transparent specimens in the analytical electron microscope (AEM).The fluoresced intensity,IYX, is expressed relative to the primary intensity of the fluorescing element,IY, rather than to that of the fluoresced element,IX, as has been customary for microanalysis. The importance of this choice ofIYas a reference intensity for the electron‐transparent specimens examined in the AEM is discussed. The various factors entering the secondary fluorescence correction are grouped into three factors, representing the dependencies of the correction on specimen composition, X‐ray fluorescence probability and specimen geometry. In principle, an additional factor should be appended to account for the difference in detection efficiencies of the fluoresced and fluorescing X‐rays; however, this factor is shown to be within a few per cent of unity for practical applications of the secondary fluorescence correction. The absorption of secondary X‐rays leaving the specimenen routeto the detector is also accounted for through a single parameter.In the limit that the absorption of secondary X‐rays is negligible, the geometric factor has the simple physical interpretation as the fractional solid angle subtended by the fluoresced volume from the perspective of the analysed volume. Studies of secondary fluorescence in the published literature are compared with this physical interpretation. It is shown to be qualitatively consistent with Reed's expression for secondary fluorescence in the electron probe microanalyser and with the specimen‐thickness dependence of the Nockolds expression for the parallel‐sided thin foil. This interpretation is also used to show that the ‘sec α’ dependence on specimen tilt in the latter expression is erroneous and should be omitted. The extent to which extrapolation methods can be used to correct for secondary fluorescence is also discussed. The notion that extrapolation methods, by themselves, can be used to correct for secondary fluorescence is refuted. However, extrapolation methods greatly facilitate secondary fluorescence correction for wedge‐shaped specimens when used in conjunction

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1995.tb03600.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

SUMMARYThe performance characteristics of two sets of triple‐band epifluorescence filters have been evaluated for use with digitally enhanced fluorescence microscopy. Use of such filters, at most, requires movement of the excitation filter, while the dichroic and emission filters remain fixed, allowing multi‐wavelength imaging to be performed on standard microscopes. The dyes appropriate for use with these particular filters include Texas Red (TR), Bodipy (BD), FITC and Cascade Blue (CB), four fluorophores now commonly conjugated to both immunochemical probes and other proteins and lipids of biological interest. Good spectral separation existed for most experimental conditions allowing accurate localization of the different fluorophores during multi‐wavelength imaging. Anomalous responses were observed during near‐UV excitation at high concentration for some dyes. Scanning spectrofluorometry demonstrated that concentration‐dependent spectral shifts occurred, resulting in large increases in near‐UV absorbance. Despite the complexity of concentration and dye‐interaction effects, quantitative measurements of dye concentration could be made, even in regions of multiple dye co‐localization. Therefore, multi‐band pass filters are an additional valuable approach for performing quantitative fluorescence mi

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1995.tb03601.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

SUMMARYThe selective staining of nucleolar acidic proteins by silver dyes (AgNOR technique) is a promising tool to discriminate malignant cells from benign cells in tumour pathology. Until now, the existing methods to measure the distribution of the AgNOR proteins were performed in two‐dimensional space. Confocal scanning laser microscopy (CSLM) and progress in computer sciences make it possible to image biological specimens in three dimensions. We have used these techniques to develop a method to discriminate cells by comparing the three‐dimensional (3‐D) spatial distribution of the AgNOR proteins. The distribution of the AgNOR proteins was described by the following measurements: the volume fraction of the nucleus occupied by the AgNOR‐stained aggregates, the distances between the aggregates, their number per nucleus, the distance of each aggregate from the nuclear border and their anisotropy. CSLM was used to acquire simultaneously the 3‐D data set of the nucleus (confocal fluorescence) and the 3‐D data set of the location of the AgNOR proteins (brightfield transmission). Two biases, due to the different modes of microscopy and the silver labelling technique, had to be taken into account in the evaluation of the measurements. A preliminary study on three lines of lymphocytic cells shows that these parameters are discriminatory. Thus, this method makes it possible to combine two different modes of scanning laser microscopy for a 3‐D quantitative analysis and is potentially useful for assessing the spatial distribution of AgNOR proteins in tum

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1995.tb03602.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

SUMMARYA new confocal scanning beam system (MACROscope) that images very large‐area specimens is described. The MACROscope uses a telecentric, f‐theta laser scan lens as an objective lens to image specimens as large as 7·5 cm × 7·5 cm in 5 s. The lateral resolution of the MACROscope is 5 μm and the axial resolution is 200 μm. When combined with a confocal microscope, a new hybrid imaging system is produced that uses the advantages of small‐area, high‐speed, high‐resolution microscopy (0·2 μm lateral and 0·4 μm axial resolution) with the large‐area, high‐speed, good‐resolution imaging of the MACROscope. The advantages of the microscope/MACROscope are illustrated in applications which include reflected‐light confocal images of biological specimens, DNA sequencing gels, latent fingerprints and photoluminescence

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1995.tb03603.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

SUMMARYThe three‐dimensional point spread function (3‐D PSF) of an optical system in image space is distinguished from the 3‐D PSF in object space and the relation between the two 3‐D PSFs is derived. By using this relation one 3‐D PSF can be easily obtained from the other. The 3‐D PSFs are given in a single integral expression, which can be computed numerically. The results of this study can be used in 3‐D image processing for microscopy and have been applied to the analysis of the diffusion of fluorescent molecules in a 3‐

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1995.tb03604.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

SUMMARYThis paper deals with constant time algorithms computing the propagation function ofX, assumed to be a simply connected planar set. This function, extensively used for object measurements and shape characterization, is defined as the geodesic distance to the furthest point inX, where the geodesic distance between two points inXis the lower bound of the length of paths entirely lying insideXand linking the two points. When the plane is equipped with a distance derived from a regularn‐sided polygon (distances on image lattices), efficient algorithms for the propagation function are based on the following remark: the furthest points to any point inXmay have only a few possible locationsY.In this paper, it is shown that, as in the convex case, there exists a setYwith at mostnelements, giving rise to constant time algorithms. Algorithms designed to compute this setYand an implementation for the square lattice equipped with the four‐connectivity distance, by means of at most seven geodesic balls, whatever the shape ofX, are descri

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1995.tb03605.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

SUMMARYTwo specimen holders for use in scanning electron microscopy (SEM) of insect and other specimens glued to triangular cardboard points are described. They have important advantages over standard metal stub mounts. Diverse, precisely orientated, viewing angles are possible using single specimens, which can afterwards be re‐pinned for return to the collectio

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1995.tb03606.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY