摘要:

SUMMARYThe Si(Li) detector, with its relatively high collection solid angle, has brought X‐ray microanalysis within the operating current limits of both SEMs and transmission microscopes. At present, the main deficiencies arise in the low‐energy region of the spectrum, below about 2 keV. Here, detection efficiency falls off because of absorption in the entrance window, peaks invariably overlap and pile‐up rejection is less effective. High‐energy photons generated in transmission microscopes are responsible for new spectral artefacts and problems of overload. While computer processing of spectra can correct for most artefacts, background and peak overlaps, accuracy is fundamentally limited by counting statistics and the overall stability of the spectrometer. The technique will therefore benefit from improved design of both electronic circuitry and components. For example, advances in FET design may bring a substantial reduction in electronic noise which will not only improve resolution at low energies, but will also improve discrimination between small pulses and noise so that pile‐up rejection can be more effective. This will be most important when a very thin entrance window is used to permit observation down to the C Kα energy (282 eV) although the hazards involved in such ‘windowless' operation still limit its application. The stability of detection efficiency with time has been exploited in methods which attempt to remove the need for repetitive standardization of the spectrometer and new techniques have been developed for the analysis of thin films, particles and rough surfaces which make use of information contained in the bremsstrahlu

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1981.tb01276.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

SUMMARYAn apparatus to ion beam sputter‐coat SEM samples has recently become available. The equipment uses a small saddle‐field ion source to sputter deposit metals on to samples. This eliminates the surface artefacts seen at high magnifications on samples coated by diode sputtering. Ion beam sputtering has also been used to shadow samples for CTEM and has been found to result in a grain size of 1.2 nm.This technique isolates the specimens from the high‐energy plasma and thus little or no heating of the sample occurs. The removal of the SEM samples from the high‐energy plasma and the use of diffusion pump vacuum conditions to prevent contamination are suggested as reasons for the improved coating quality over diode spu

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1981.tb01277.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

SUMMARYThe purpose of the present paper is twofold. Firstly, to compare the accuracy per unit cost achieved by two different methods of subsampling micrographs from sections of a material for stereology when the sections cannot be analysed as a whole at the required magnification. Secondly, to illustrate, by means of real data, the application of some of the methods and formulae proposed in the companion paper (Cruz‐Orive&Weibel, 1981) for estimating ratios at the electron microscopic level.The final estimates of a same ratio obtained by either subsampling method (namelysystematic(SQ) andsystematic area‐weightedquadrats (SAWQ)) agreed in the mean and they were about equally precise. The former fact indicates that the new SAWQ method is at least as reliable as the SQ method as far as bias is concerned. The latter result is a consequence of the well‐known fact that subsampling is relatively unimportant in two‐stage sampling. Yet, SAWQ subsampling enjoys definite practical advantages over other subsampling methods in certain sit

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1981.tb01278.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

SUMMARYThe possibility of using sodium tetraphenyl boron (TPB) as a precipitant for the ultrastructural localization of K+was examined using bothin vitroandin vivostudies. Because TPB salts are soluble in the usual dehydrating agents, glutaraldehyde‐urea was used for embedding. When Na TPB was introduced to the tissue together with OsO4, good cytoplasmic preservation was achieved, and deposits containing K were located within the cytoplasm and vacuoles. However, these deposits cannot be distinguished visually, so that X‐ray microanalysis is necessary to confirm the presence o

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1981.tb01279.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

SUMMARYBronchial biopsies from ten subjects, including five smokers, have been examined using light microscopic morphometry. The biopsies were free from identifiable disease. Using manual point counting and a Quantimet 720 image analysing computer, a number of parameters were measured. Computer‐based cluster analysis of seven of these parameters associated the subjects into three groups: visual inspection of the sections achieved the same separation. Four subjects (non‐smokers) had normal epithelia: four subjects (one non‐smoker, three smokers) showed mucous cell hyperplasia: two subjects (smokers) had squamous cell metaplasia. Three parameters in conjunction contained sufficient information to characterize accurately the histological appearance of the epithelia: the epithelial thickness, the volume density of intracellular mucus and the number of nuclear profiles per unit area of sectioned epithelium. Reduction of these three parameters to a linear plot closely approximated a similar reduction of the original seven parameters. These three parameters can be measured rapidly, either manually or by the Quantimet. The linear representation of these parameters provides a reproducible and objective basis for comparing specimens of bronchial epith

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1981.tb01280.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

SUMMARYTechniques utilizing Feulgen, azure B bromide, methyl green‐pyronin, gallocyanin chromalum and cresyl violet stains have been modified and adapted for visualizing nucleic acids in 0.5–2.0 μm sections of tissues embedded in glycol methacrylate (GMA). Methods for evaluating the stain specificity for DNA and RNA using deoxyribonuclease and ribonuclease digestions, aldehyde blocking, and acid extractions are also described. The specificity of the stains in GMA embedded tissues is comparable to that reported for paraffin‐embedded t

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1981.tb01281.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

SUMMARYA scanning X‐ray microradiographic system is described with which it is possible to measure the X‐ray absorption in a 1 mm × 1 mm area of a section in about 27 h at a resolution of 20 μm with a reproducibility of about ± 1.5%. This system has advantages over photographic methods for certain quantitative investigations. The results can be presented in various forms including contour maps and half‐tone pictures and this is illustrated with a radiograph of a section of a carious lesion in denta

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1981.tb01282.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

SUMMARYDifferent multistage fixation procedures patterned after the procedure described by Reedy (1976) have been evaluated with regard to preservation of subfllament structural organization along the length of the vertebrate skeletal myosin filament. The criteria used for evaluation of structural preservation include (a) the precision of subfllament organization as reflected by the quality of the optical diffraction patterns obtained from images of transverse sections of the myosin filament and (b) the clarity with which structural differences in serial transverse sections along the myosin filament could be defined.

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1981.tb01283.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

SUMMARYA procedure forin situliquid propane jet‐freezing of unfixed and unglycerinated monolayer cell cultures is described. We have used the method to study monolayer cultures of rat Sertoli cells and human monocytes. The described procedure gives a cooling rate during specimen freezing high enough to yield adequately frozen specimens even in the absence of any cryo‐protectant. Use of the procedure therefore eliminates artefacts usually caused by cell fixation and addition of cryoprotecti

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1981.tb01284.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

SUMMARYA new stain is described that combines the mordanting and preservative effects of tannic acid with very strong staining, particularly of plasma membranes. The staining is sufficiently intense in some cell types to reveal frequent links between the outer and the inner leaflet of the plasma membrane.

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1981.tb01285.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY