ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1992.tb03244.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

SUMMARYA new method using probabilistic models is used to study the growth of WC grains in WC‐Co cermets. Two different models are tested: a Boolean model and a two‐colour mosaic model. The Boolean Poisson model is the simplest for describing and predicting material evolution, and depends only on two independent parameters. They allow the estimation of the connectivity numbers and, moreover, are used to determine the type of reaction which controls the WC‐Co coarsening kin

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1992.tb03245.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

SUMMARYThis paper presents an application of automatic image analysis to the morphometry of ceramic sheets. The sheets can be characterized by granulometrie and stereological texture parameters of the granular and the porous phases. Grey level granulometry, automatic thresholding and filtering have thus been used. The results show that the morphology of green sheets is strongly dependent on the ball‐milling condition

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1992.tb03246.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

SUMMARYIn this study, Leydig cell numbers in control and atrophied testes (induced via subcutaneous implants of testosterone plus 17β estradiol for 16 weeks; TE‐implanted) of rats, estimated via the fractionator method (independent of any assumptions) were compared to those estimated via the disector (unbiased, but dependent on shrinkage) and Floderus (assumes spherical particles, dependent on shrinkage) methods. Estimates of Leydig cell numbers in control rats produced by all three stereological methods were similar. In rats with atrophied testes, both the fractionator and the disector methods produced significantly lower (P<0.01; 47% and 41 % with fractionator and disector, respectively) Leydig cell number estimates per testis than in the controls. By contrast, the estimates of Leydig cell number in atrophied testes derived via the Floderus equation were not significantly different from those of controls, but larger than those obtained via the fractionator and the disector methods. These results suggested that the assumptions of the Floderus method were violated in the atrophied rat testes.Why was the Floderus method of estimating Leydig cell number applicable to control rats but not to the TE‐implanted rats? In an attempt to answer this question the diameter measurement together with its correction factor used in the Floderus equation (i.e.D + t − 2H)was also derived from the data collected for the disector method. The values forD + t − 2Hused in the Floderus method and also calculated via the disector method were found to be identical in controls, but for the TE‐implanted rats a 32% lower value was obtained with the Floderus equation when compared to the disector. These findings suggested that this estimation error caused an overestimation of Leydig cell numbers in the TE‐implante

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1992.tb03247.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

SUMMARYA method of image reconstruction which can be used in ultrastructural morphology when a number of comparable structures are available is described. The method is suitable for quasi‐regular arrays of objects, and an extension of it allows the average of equivalent objects which could be orientated at random to be obtained. When dealing with crystalline arrays it is first necessary to obtain a leakage‐free pattern in which the coarse distortions are suppressed; this pattern is then filtered to obtain a reference. When dealing with several individual objects which must be brought to the same orientation and enlargement, one of the objects is fixed as a reference. In both cases the distortions relative to the reference are eliminated by an iterative process, making a final average possible. In crystalline arrays this method enhances the bandwidth of the pattern in a way that can be estimated quantitatively by figures of merit. Two examples of reconstructions are reported and discussed: a ctenophore macrocilium, regarded as a crystalline structure, and a sectioned flagellum of an insect sperma

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1992.tb03248.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

SUMMARYThe resolution of an optical microscope is considerably less in the direction of the optical axis(z)than in the focal plane(x‐yplane). This is true of conventional as well as confocal microscopes. For quantitative microscopy, for instance studies of the three‐dimensional (3‐D) organization of chromosomes in human interphase cell nuclei, the 3‐D image must be reconstructed by a point spread function or an optical transfer function with careful consideration of the properties of the imaging system. To alleviate the reconstruction problem, a tilting device was developed so that several data sets of the same cell nucleus under different views could be registered. The 3‐D information was obtained from a series of optical sections with a Zeiss transmission light microscope Axiomat using a stage with a computer‐controlled stepping motor for movement in the z‐axis. The tilting device on the Axiomat stage could turn a cell nucleus through any desired angle and also provide movement in thex‐ydirection.The technique was applied to 3‐D imaging of human lymphocyte cell nuclei, which were labelled byin situhybridization with the DNA probe pUC 1.77 (mainly specific for chromosome 1). For each nucleus, 3‐D data sets were registered at viewing angles of 0°, 90° and 180°; the volumes and positions of the labelled regions (spots) were calculated. The results also confirm that, in principle, any angle of a 2p geometry can be fixed for data acquisition with a high reproducibility. This indicates the feasibility of axiotomographical mic

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1992.tb03249.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

SUMMARYThis paper discusses the imaging of thin organic films in scanning optical microscopes using both differential phase contrast and confocal modes. The Lang‐muir‐Blodgett technique is used to deposit thin films of controllable thickness. Step structures in these films are considered and theoretical models of the imaging are compared with experimental data. The model provides a measurement of film parameters such as thickness and permittivity. The differential phase contrast mode is also proposed as a simple method of assessment of film qual

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1992.tb03250.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

SUMMARYTo avoid problems with electrostatic charging, electrically conductive specimen support films or coatings must be used when observing non‐conductive organic specimens by electron microscopy. At room temperature, microscopists typically use either carbon films or carbon‐coated plastic films as specimen substrates. Such films have also been adopted for low‐temperature microscopy. Recent measurements have shown that conventional carbon films have high electrical resistivity at low temperature. Thin titanium films have been used to provide improved electrical conductivity, but the structure of titanium films is excessively granular for high‐resolution electron microscopy. With the hope of solving both problems, thin films of Ti88Si12have been produced using a standard evaporation system. The deposited films are amorphous, as shown by electron microscopy, electron diffraction and differential scanning calorimetry. The electrical conductivity of the binary alloy films is nearly as high as that of pure titanium films. Therefore, these films appear to be appropriate substrates for low‐temperature electron m

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1992.tb03251.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

SUMMARYThe suitability of cathodoluminescence (CL) measurements for differentiating between different paint pigments is demonstrated with an example of a combined energy‐dispersive X‐ray (EDX) and CL analysis of different zinc oxide (ZnO) pigments in a paint fragment where the EDX spectra are virtually identical, but where the CL spectra show significant differences. Consequently, it is possible to distinguish different pigments on the basis of CL spectra and monochromatic CL microgra

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1992.tb03252.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

SUMMARYThe progressive lowering of temperature (PLT) method of embedding for electron microscope immunolabelling has been examined with the objective of formulating a standardized protocol which can be applied to a wide variety of samples. The methods described cover fixation, processing of samples by the PLT method, embedding in Lowicryl HM20 and subsequent immunolabelling. Each of the steps in the fixation and embedding protocol has been assessed for its potential to retain both morphology and antigenicity. Comparison of samples embedded in Lowicryl K4M and HM20 at −25°C indicate an increased membrane contrast in HM20 sections, and a further improvement in morphology when samples were embedded in HM20 at −50°C rather than at −25°C. The results of applying the methods described are demonstrated in a range of samples of both mammalian and botanical origin, which includes solid tissues, cells in suspension, and cells grownin vitroas a monolayer culture and embeddedin situ. Samples processed by this method have been immunolabelled using a wide range of antibodies recognizing nuclear, cytoplasmic, cell membrane and extracellular matrix

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1992.tb03253.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY