摘要:

Atomic force microscopy (AFM), in various versions, has had major impact as a surface structural and spectroscopic tool since its invention in 1986. At its present state of development, however, the interpretation of AFM images is limited by the current state of methodologies for calibration over the wide dynamic range of magnification. Also, the parameters of individual tips, as well as the generic characteristics of different kinds of tips, affect both the quality of the images and their interpretation. Finally, the very nature of the tip‐to‐surface interaction will generate artefacts, in addition to those associated with tip shape, which need to be fully understood by the practitioners of force microscopy. This project seeks to address and shed light on some of these issues.Polystyrene beads deposited on mica substrates form hexagonal close‐packed layers. The unit cell parameters are suitable for calibration of the AFM in the lateral plane, while the perpendicular spacing of the layers is appropriate for calibration along the vertical axis. Using different size fractions, it is straightforward to determine the extents of linearity, orthogonality, thermal and instrumental drifts over distances from 100 nm to tens of micrometres. The present results show that the methodologies for contact mode operation can be adapted to noncontact modes.It is known that an AFM image arises from a convolution of surface topography and tip shape, and is mediated by the interaction. In principle it is possible to carry out a deconvolution, if we have complete knowledge about two of the three elements (i.e. tip, surface and interaction). In practice we rarely have the requisite information. Prominent artefacts will occur when the characteristic parameters of the tip are comparable to those of the surface topography, and/or if there is a variable strength, or extent of localization, of the interaction. The present results demonstrate artefacts due to effects of geometry as well as inte

ISSN:0022-2720    

DOI:10.1046/j.1365-2818.1996.74351.x

出版商:Blackwell Science Ltd    

年代:1996

数据来源: WILEY

摘要:

Rat liver sinusoidal endothelial cells (LEC) contain fenestrae, which are clustered in sieve plates. Fenestrae control the exchange of fluids, solutes and particles between the sinusoidal blood and the space of Disse, which at its back side is flanked by the microvillous surface of the parenchymal cells. The surface of LEC can optimally be imaged by scanning electron microscopy (SEM), and SEM images can be used to study dynamic changes in fenestrae by comparing fixed specimens subjected to different experimental conditions. Unfortunately, the SEM allows only investigation of fixed, dried and coated specimens. Recently, the use of atomic force microscopy (AFM) was introduced for analysing the cell surface, independent of complicated preparation techniques. We used the AFM for the investigation of cultured LEC surfaces and the study of morphological changes of fenestrae. SEM served as a conventional reference.AFM images of LEC show structures that correlate well with SEM images. Dried‐coated, dried‐uncoated and wet‐fixed LEC show a central bulging nucleus and flat fenestrated cellular processes. It was also possible to obtain height information which is not available in SEM. After treatment with ethanol or serotonin the diameters of fenestrae increased (+6%) and decreased (−15%), respectively. The same alterations of fenestrae could be distinguished by measuring AFM images of dried‐coated, dried‐uncoated and wet‐fixed LEC. Comparison of dried‐coated (SEM) and wet‐fixed (AFM) fenestrae indicated a mean shrinkage of 20% in SEM preparations. In conclusion, high‐resolution imaging with AFM of the cell surface of cultured LEC can be performed on dried‐coated, dried‐uncoated and wet‐fixed LEC, which was hitherto only possible with fixed, dried and coated preparations in SEM and transmission

ISSN:0022-2720    

DOI:10.1046/j.1365-2818.1996.72348.x

出版商:Blackwell Science Ltd    

年代:1996

数据来源: WILEY

摘要:

A method for precisely locating points on large surfaces during SEM examination and for finding corresponding points on matching surfaces (such as those resulting from the fracture of a solid body) is described. This method also allows for the repeated examination of specific points during subsequent SEM sessions after the specimen has been removed and replaced in the SEM. The method is based on a coordinate transformation between the SEM stage coordinates and specimen coordinate systems defined by arbitrarily chosen reference points on the specimen.

ISSN:0022-2720    

DOI:10.1046/j.1365-2818.1996.69349.x

出版商:Blackwell Science Ltd    

年代:1996

数据来源: WILEY

摘要:

Environmental scanning electron microscopy has been used to study ‘wet’ polymer latex films. Comparison of the results obtained by imaging in nitrogen and nitrous oxide gas and water vapour has provided insight into a variety of different contrast phenomena. Notably, it was found that edge definition and fine features could be enhanced by imposing further saturated vapour conditions at the hydrated film surface. Furthermore, by imaging at subzero temperatures in the presence of nitrogen, it was shown that beam damage could be reduced in such sensitive polymeric samp

ISSN:0022-2720    

DOI:10.1046/j.1365-2818.1996.67341.x

出版商:Blackwell Science Ltd    

年代:1996

数据来源: WILEY

摘要:

When defects are imaged using weak beam techniques it is common to use a higher beam convergence than when they are imaged under strong two beam conditions because of the way specimen drift limits the exposure times that can be used. It is demonstrated that, for a typical illumination system, as the convergence is increased the range of tilt across the probed area is also increased. This can affect the weak beam imaging behaviour of a defect, and the α‐fringe contrast of thin twins is examined in this context. The contrast changes in the field of view associated with the local variation in tilt are discussed in relation to the degree to which the relative effects of convergence on α‐fringe and thickness fringe contrast can be qualitatively understood kinematically. However, some effects, such as the observed increase in α‐fringe contrast at moderate convergence, are more difficult to model but are also potentially of greater concern in the characterization of the differences in contrast to be expected for intrinsic and extrinsic faults as well as f

ISSN:0022-2720    

DOI:10.1046/j.1365-2818.1996.31368.x

出版商:Blackwell Science Ltd    

年代:1996

数据来源: WILEY

摘要:

A suitable procedure is presented to characterize the neighbourhood in disperse micro‐structures by measuring the Delaunay neighbour distances and neighbour numbers. Results are discussed from simulation experiments with three germ‐grain models, regular arrangements and a seam‐like model. A plot of variation coefficients is suggested to differentiate between various random distributions of part

ISSN:0022-2720    

DOI:10.1046/j.1365-2818.1996.93374.x

出版商:Blackwell Science Ltd    

年代:1996

数据来源: WILEY

摘要:

Direct measurement of absorption spectra for minute areas (2 μm ×2 μm) in a dried mammalian cell was attempted using X‐ray contact images of a whole cell. The wavelength region used ranged from 1.5 to 10 nm covering the absorption edges of the major cellular elements. The measurements were achieved taking advantage of synchrotron radiation as a tuneable light source and an electronic zooming tube as an X‐ray detector with a high spatial resolution. The spectra in every intracellular area exhibited marked absorption changes at the absorption edges of carbon, nitrogen and oxygen, while minor but significant changes for iron and calcium were observed, particularly in the cytoplasmic areas. These results reveal the different spatial distributions of the constituent elem

ISSN:0022-2720    

DOI:10.1046/j.1365-2818.1996.71347.x

出版商:Blackwell Science Ltd    

年代:1996

数据来源: WILEY

摘要:

Eight different commercially available fluorescent dyes (fluorochromes) were tested for suitability for use in low‐viscosity epoxy resin. Dyes were compared based on solubility in different solvents and epoxy resin and a numerical criterion for each dye's fluorochromicity. The two best dyes, based upon the brightness of each dye after illumination by a UV source, were Hostasol Red GG and Hostasol Yellow 3G. These two dyes in epoxy resin were used to visualize impregnation and remnant porosity in porous superconductor ceramic pellets. The impregnant was either cured epoxy or a low melting point allo

ISSN:0022-2720    

DOI:10.1046/j.1365-2818.1996.94375.x

出版商:Blackwell Science Ltd    

年代:1996

数据来源: WILEY

摘要:

The dark‐field diffraction contrast of helical nanotubes (NTs) is shown to be asymmetric when an NT is tilted at appropriate angle with respect to the incident electron beam. This phenomenon was used for the chirality determination of multi‐shell NTs observed in MoS2layered compound. Both kinds of NT — helical and non‐helical — were found. In the case of helical NTs only right‐hand chirality w

ISSN:0022-2720    

DOI:10.1046/j.1365-2818.1996.96377.x

出版商:Blackwell Science Ltd    

年代:1996

数据来源: WILEY

摘要:

Recently developed statistical methods for analysing orientation data are presented and applied here in a study of the precision by which crystal orientations can be measured from electron backscattering patterns. The use of these methods allows a direct comparison to be made between the precision obtained with manually and automatically localized bands, which is important owing to a more and more widespread use of fully automatic analysis of electron backscattering patterns. Curves which show how the precision depends on the pattern quality and on the number of bands used for the orientation measurements are presented for both manually and automatically localized bands. Typical values for the relative precision of crystal orientations measured from electron backscattering patterns are shown to be of the order of 0.5° for manually localized bands and 0.75° for automatically localized bands, when about 10 bands are used for the measurements. In a more realistic situation where a careful operator is willing to localize four to five bands in each pattern, the precision of the measured crystal orientations is similar to that obtained for automatically localized band

ISSN:0022-2720    

DOI:10.1046/j.1365-2818.1996.95376.x

出版商:Blackwell Science Ltd    

年代:1996

数据来源: WILEY