摘要:

SUMMARYSIMS matrix effects (mass interferences, sputter yield variations and practical ion yield variations) were evaluated in freeze‐fractured, freeze‐dried cultured cells at the ∼0.5 μm spatial resolution of the Cameca IMS‐3f ion microscope. Cell lines studied include normal rat kidney (NRK), 3T3 mouse fibroblast, L6 rat myoblast, chinese hamster ovary (CHO) and rat kangaroo kidney (PtK2) cells. High mass resolution studies indicated that the secondary ion signals of H—, C—, O—, Na+, Mg+, CN—, P—, S—, Cl—, K+and Ca+were free from major mass interferences. However, a large mass interference was observed for nitrogen at mass 14. No significant sputtering yield difference between the nuclear and cytoplasmic compartments of the cells studied was observed. The subcellular distributions of the major (H, C, N and O) and minor (P, S, K, Cl, Na, Mg and Ca) matrix elements were found to be largely homogeneous with the exception of Ca, which was observed mainly in the cell cytoplasm. Practical ion yield variations were compared by three different approaches: (i) by the use of cells doped with known electrolyte concentrations, (ii) by quantitative ion implantation, and (iii) by analysis of the same cell with both electron probe and ion microscope. Each approach indicated an absence of significant practical ion yield differences between the nuclear and cytoplasmic regions of these specimens. These observations indicate that secondary ion signals in this type of sample are not significantly affected by local matrix effect variations. Hence, qualitative imaging of such specimens provides a true representation of subcellular elemental distribtions. These observations should allow the development of quantitative ion imaging methodologies and enhance the applicability of ion microscopy

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1987.tb02869.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

SUMMARYSamples of aluminium‐lithium alloys have been observed by scanning ion microscopy and analysed by secondary ion mass spectrometry. The high signal‐to‐noise ratio of the positive secondary lithium ion opens up the possibility of both high resolution imaging and microanalysis of lithium distributions in aluminium and other materials. Some of the problems encountered due to sample preparation are discussed and ion images of both the artefacts and the true lithium distribution are

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1987.tb02870.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

SUMMARYSpecifically stained features in microscopic images rarely have a unique range of grey levels which would permit selection of the features by simple thresholding. The spaces between features and immediately surrounding them are often as dark or darker than the more lightly stained features. An algorithm for minima equalization which facilitates the extraction and segmentation of such features was designed and is explained in intuitive terms. It is applied to the analysis of cross‐sections of peripheral myelinated nerve fibres. It is shown that the binary image obtained can be combined with a gradient image to give a binary image which accurately reflects the thickness of the myelin in the original image. Using silver‐impregnated nerve endings and bile canaliculi stained for thiamine pyrophosphatase, binary images like those prepared manually from thick specimens using a camera lucida can be obtained using the minima equalization procedure. The image processor is used to develop a composite image by combining images at various focal planes through the thick specimen. This image is then processed to obtain the binary im

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1987.tb02871.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

SUMMARYAutomatic setting of discriminator thresholds to select features from grey‐scale images is desirable to reduce variations due to operator variability, and to adapt to changing illumination or sample characteristics. This can be carried out in several ways. One locates minima in the original brightness histogram. For images in which minima are absent or poorly defined other techniques are preferred. Settings that minimize the change in total feature area or perimeter with changes in the threshold setting are suitable for a wide variety of images. After processing to extract edges a fixed percentage of the number of pixels in the image may be usefu

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1987.tb02872.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

SUMMARYWe have attempted to measure the O/Ni inner‐shell cross‐section ratios from a sample of NiO using EELS in an electron microscope. The results lay within roughly 10% of the predictions of both the hydrogenic and Hartree‐Slater theories. However, the data showed a spread of around 20% which may have been caused by artefacts introduced during the specimen prepar

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1987.tb02873.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

SUMMARYWe have measured the relationship between the input and output pulse rates for an EELS pulse counting system. Two simple formulae for predicting the behaviour of such a system are compared with the data. One is for a system which has extendible deadtime. The other is for the counting system which has non‐extendible deadtime. The latter provides agreement with our experimental results over the range 0–20

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1987.tb02874.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

SUMMARYMonte Carlo calculation of slow secondary electrons (SE) has been performed with a hybrid model of the exponential decay law and cascade process. The contributions of both valence electron excitation and core electron excitation have been considered. The calculated yield, energy distribution, angular distribution and depth distribution for Au, Ag and Cu (28 keV, at normal incidence) are in agreement with the experimental results and better than those previously reported.

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1987.tb02875.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

SUMMARYUnder the assumption of homogeneity and isotropy, this paper solves the problem of determining spatial curvature distributions of fibre processes from curvatures of projection curves from thin sections. As an example, a sample of dislocation lines in a hot‐rolled Fe‐Ni alloy is discus

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1987.tb02876.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

SUMMARYSchabtach (1974) developed a process for making ‘thin’ (i.e. self‐cleaning) apertures for electron microscopes. Several improvements in this process are described, the most important of which is the deposition of a heavy metal by DC sputtering rather than by evaporation, making the process much e

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1987.tb02877.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1987.tb02878.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY