bluuebunny/crossref_metadata_2025_split huggingface dataset:
Primary considerations for image enhancement in high‐pressure scanning electron microscopy
Authors: Farley A. N. , Shah J. S. 
Published: August 2011

SUMMARYIn the preceding paper the effect of the primary beam scattering on contrast in high‐pressure SEM techniques such as moist‐environment ambient‐temperature SEM and environmental SEM was examined. Here, the effect of the scattering of the emissive components on the image formation and contrast in high‐pressure SEM was considered and evaluated experimentally. A specimen current amplifier was used to detect the absorbed current signal together with the ionic signal components generated by the emissive and primary electrons. It was shown that space charge accumulations of ionic carriers can build up above the specimen when imaging in the presence of a gas and that this can act to suppress the secondary electron emission. The ionic carrier concentration is also discussed. Full image contrast can be restored by the application of an electric bias field above the specimen surface. Since ionic charge carriers contribute to the signal current, new image‐contrast mechanisms were considered and a theoretical model for contrast generation is therefore proposed. The predictions of this model were tested experimentally for a specimen substrate of uniform emissivity under varying electric bias field strengths. It was also found that under sufficiently high electric fields low‐energy charge carriers gain enough energy to ionize the host gas molecules and therefore multiply the signal current. Micrographs are presented to illustrate these image formation processes as a function of electrode bias. The new detection system successfully extends the signal information of high‐pressure SEM and a range of applications is discussed to exploit these possibilities.
How fine a surface crack can you see in a scanning acoustic microscope?
Authors: Briggs G. A. D. , Jenkins P. J. , Hoppe M. 
Published: August 2011

SUMMARYSurface cracks can be detected with great sensitivity in an acoustic microscope, even when the width of the crack is much less than the acoustic wavelength. This is because of the strong excitation and scattering of Rayleigh waves. Cracks in a variety of materials, including cracks from indents in several different ceramics, have been studied by acoustic microscopy, and the results compared with images from light and scanning electron microscopes. No crack or part of a crack that was seen by the other two techniques failed to be seen by acoustic microscopy. The contrast of a crack in an acoustic microscope showed no sign of fading as the crack became thinner towards its tip, and diffraction from tips suggests that they are acoustically well‐defined points on the surface. Although theoretically the acoustic contrast from a crack might be expected to diminish when the crack width is smaller than the shear‐wave decay length in the fluid, in practice this is so small that for many purposes it may be considered that there is almost no limit to how fine a crack can be and still be detected in an acoustic microscope.
A new non‐linear pseudo‐Laplacian filter for enhancement of secondary electron images
Authors: Oho Eisaku , Ogihara Akinori , Kanaya Koichi 
Published: August 2011

SUMMARYA simple, yet effective, non‐linear pseudo‐Laplacian filter has been newly developed to enhance secondary electron (SE) images. This filter is a combination of the second derivative along the direction of the local gradient and a non‐linear weight factor. The filter can successfully enhance SE images without the undesirable effects of noise which are often seen in conventional Laplacian filtered images. Hence, the processed results with high image quality can make original SE images easier to interpret. The effectiveness is especially useful in low‐voltage scanning electron microscopy, because SE images taken at low voltages are not so likely to have good image sharpness.
An improved technique for flattening semithin sections of epoxy‐embedded tissues used for high‐resolution light microscopy
Authors: Sierra Felix , Hegele‐Hartung Christa , Beier Henning M. 
Published: August 2011

SUMMARYThe usefulness of sodium ethoxide as an agent for flattening thick sections (0.5‐2.0μm) of epoxy‐embedded material was studied. It was found that sodium ethoxide conditioned by its resin‐resolving properties leads to elimination of folds and crumples known to be present to various degrees in sections of resin‐embedded tissue. Two minutes of incubation leads to a complete section flattening without any damage to the cellular structures. With regard to large sized sections of epoxy‐embedded tissue, this simple and fast method represents an improvement in the production of useful and qualitatively satisfactory sections for high‐resolution light microscopy
Letter to the Editor
Authors: van Heel Marin 
Published: August 2011

SUMMARYIn a recent paper Frank et al. (1988; J. Microsc. 150, 99–115) proposed the use of a hybrid clustering technique to sort macromolecular images. In contrast to the claims made in that paper, however, the proposed technique is less sophisticated than the enhanced hierarchical ascendant classification technique proposed by us a few years earlier. The hybrid approach will lead to partitions which are less optimal in terms of minimizing the total intra‐class variance for a predetermined number of classes, irrespective of whether the data show distinct clusters or, rather, possess a quasi‐continuous intrinsic structure.
Three‐dimensional reconstruction of porous media from serial section data
Authors: Kwiecien M. J. , Macdonald I. F. , Dullien F. A. L. 
Published: August 2011

SUMMARYSoftware has been developed, with the aid of data for a Berea sandstone sample, to partition the irregular, interconnected pore space of a porous medium into its constituent pores. Output includes the sizes (volumes) of the individual pores, the sizes (area and radii of curvature) of the individual necks (windows) between the pores, the order in which the pores and necks are connected, and the degree of interconnectedness.Data are entered into the computer by digitizing a series of closely spaced serial sections of a pore cast of the sandstone. The pixels represent either rock matrix or pore space which are represented in binary format by ′0′ and ′1′, respectively. Each pixel is assumed to be the top surface of an associated volume element (voxel).The data array is analysed from seven orientations. For each orientation, a feature map is created which identifies the interconnected pore channels through the array. Then a set of potential necks is identified by locating local minima in the radius of curvature of pore space features along the pore channels.The seven sets of local minima are merged, overlaps among the minima are identified, and a consistent set of non‐overlapping necks is created by systematically deleting the larger overlapping minima. The necks are then ‘closed’ and the data set re‐analysed to identify each cluster of pore space voxels bound by rock matrix and ‘closed’ necks as a pore.
Mechanisms of detection and imaging in the ESEM
Authors: Danilatos G. D. 
Published: August 2011

SUMMARYFor proper understanding of image formation using charge carriers, it is shown that signal detection by means of induction must be considered. This explains the possibility of imaging insulators as well as other phenomena especially in the conditions of the environmental scanning electron microscope. In addition, a basic principle and method to separate the secondary and backscattered electrons is demonstrated.
The measurement and calculation of the X‐ray spatial resolution obtained in the analytical electron microscope
Authors: Michael J. R. , Williams D. B. , Klein C. F. , Ayer R. 
Published: August 2011

SUMMARYThe X‐ray microanalytical spatial resolution is determined experimentally in various analytical electron microscopes by measuring the degradation of an atomically discrete composition profile across an interphase interface in a thin‐foil of Ni‐Cr‐Fe. The experimental spatial resolutions are then compared with calculated values. The calculated spatial resolutions are obtained by the mathematical convolution of the electron probe size with an assumed beam‐broadening distribution and the single‐scattering model of beam broadening. The probe size is measured directly from an image of the probe in a TEM/STEM and indirectly from dark‐field signal changes resulting from scanning the probe across the edge of an MgO crystal in a dedicated STEM. This study demonstrates the applicability of the convolution technique to the calculation of the microanalytical spatial resolution obtained in the analytical electron microscope. It is demonstrated that, contrary to popular opinion, the electron probe size has a major impact on the measured spatial resolution in foils < 150 nm thick.
A rapid preparation method for ultrastructural investigations of conifer needles
Authors: Ebel B. , Hamelmann U. , Nieß C. 
Published: August 2011

SUMMARYThe method discussed here for preparing conifer needles for transmission electron microscopy combines three important components in a new way: chilling (273 K) during fixation to prevent autolysis, HEPES buffer to protect cytoplasm against washing out and VCD/HXSA as an ultralow viscid and therefore rapidly infiltrating medium. Ultrastructural analysis of Picea abies and Pinus silvestris shows very satisfactory tissue preservation.
Assessment of particle retention and clearance in the intrapulmonary conducting airways of hamster lungs with the fractionator1
Authors: Geiser Marianne , Cruz‐Orive Luis M. , Hof Vinzenz Im , Gehr Peter 
Published: August 2011

SUMMARYA modified version of the fractionator was used to estimate the total number of polystyrene microspheres retained in the airways of hamster lungs at two different time points after inhalation. A systematic three‐stage subsampling procedure with known sampling fractions was adopted. First, each lung was cut into slices, from which primary disectors were sampled systematically with a known sampling fraction. From each primary disector, smaller sub‐disectors were subsampled, and the corresponding sampling fraction was estimated by point counting. Finally, a few particles were counted at the microscopic level in the sub‐disectors, and the final estimate of total particle number (which is unbiased irrespective of any tissue deformations) was easily computed as a product of the counted number times the reciprocal of the successive sampling fractions. The error variance of each estimate was assessed from the data using a new estimator.An average of 6% of the deposited particles were retained on the epithelial surface of the intrapulmonary conducting airways shortly after the inhalation, from which at least one‐third was already phagocytosed by macrophages. After 24 h, an average of 87% of the particles retained shortly after the inhalation had been cleared. The proportion of particles ingested by macrophages had increased to at least 87%, in three out of four animals studied.
An introduction to singular systems with applications to confocal scanning microscopy
Authors: Pike E. R. , Davies R. E. , Walker J. G. , Young M. R. 
Published: August 2011

SUMMARYAn introduction to both the classical and the singular‐systems theory of resolution is given. Singular‐system analysis is applied to the case of the coherent confocal scanning microscope. Ultimate resolution is predicted to be half the Rayleigh distance. The results of a low‐numerical‐aperture experiment are presented and compared with the theory. The predicted increase in resolution is accurately found.
Imaging in scanning microscopes with slit‐shaped detectors
Authors: Wilson T. , Hewlett S. J. 
Published: August 2011

SUMMARYWe consider the imaging in scanning microscopes employing point and slit‐shaped detectors in both the bright‐field and fluorescent mode. In particular we consider the three‐dimensional aspects of the imaging and show inter alia that acceptable, albeit asymmetrical, images result from a slit detector system at low levels of defocus. The situation becomes worse as the defocus is increased although acceptable extended‐focus and isometric images are still possible in some cases.
High‐resolution electron microscopy of human enamel crystals
Authors: Brès E. F. , Voegel J.‐C. , Frank R. M. 
Published: August 2011

SUMMARYThe structure of enamel crystals obtained from four human premolars has been studied by high‐resolution electron microscopy (HREM) in the [0001], [***2110], [***1540], [***0110] and [***1213] crystallographic directions at various microscope defocus and crystal thickness values. The resolution obtained has not previously been reported for human enamel crystals. In all cases, it was possible to match the experimental images to images calculated using the atomic positions of mineral hydroxyapatite. However, a deviation from hexagonal symmetry characterized by marked (***1010) planes of intensity different from the one of the (***3030) and {***1010}‐type planes was observed. In this work, we present an improvement of Scherzer resolution of 0.25‐0.20 nm over previous work on biological enamel crystals. This improvement of resolution has permitted the incorporation of crystallographic reflections of higher spatial frequencies into the imaging process of the microscope and has led to a more precise structure determination of the crystals studied.
Transmission electron microscopy of lead scandium tantalate thin‐films
Authors: Reaney I. M. , Barber D. J. 
Published: August 2011

SUMMARYPreliminary results are reported on the examination of lead scandium tantalate (PST) ferroelectric thin‐films by transmission electron microscopy (TEM). The samples were grown on sapphire substrates by the solution‐gel route and were examined in both plan and transverse section.Scanning electron micrographs of the surface of the samples of PST on sapphire showed that the PST films were invariably cracked. TEM examination of the PST on sapphire in plan section revealed that two distinct distributions of PST grains had grown on the sapphire (100 and 1500 nm diameter) and that nucleation of PST on the sapphire surface was associated with surface flaws and dislocations. TEM samples prepared in transverse section revealed that ordering of the Sc and Ta cations was greater at the PST‐sapphire interface than within the interior of the thin‐film. Small crystallites of an unidentified second phase were also observed to have formed in the centres of PST grains.
Low‐temperature scanning electron microscopy in biology
Authors: Read Nick D. , Jeffree Christopher E. 
Published: August 2011

SUMMARYA review of low‐temperature scanning electron microscopy (LTSEM) with regard to preparation protocols, specimen preservation, experimental approaches, and high‐resolution studies, is provided. Preparative procedures are described and recent developments in methodologies highlighted. It is now well established that LTSEM, for most biological specimens, provides superior specimen preservation than does ambient‐temperature SEM. This is because frozen‐hydrated samples retain most or all of their water, are rapidly immobilized and stabilized by cryofixation, and are not exposed to chemical modification or solvent extraction. Nevertheless, artefacts in LTSEM are common and most arise because frozen‐hydrated specimens contain water. LTSEM can be used as a powerful experimental tool. Advantages of employing LTSEM for this purpose and ways in which it can be used for novel experimentation are discussed. The most exciting development in recent years has been high‐resolution LTSEM. The advantages, problems and requirements for this approach are defined.
Low‐temperature scanning electron microscopy of birch leaves after exposure to ozone
Authors: SCHEIDEGGER C. , GÜNTHARDT‐GOERG M. , MATYSSEK R. , Hatvani P. 
Published: August 2011

SUMMARYComparison of different harvesting and preparation pathways showed that low‐temperature SEM is an adequate method to conserve the stomatal aperture for SEM. Both critical point drying and freeze drying cause considerable artefacts.Exposure to site‐relevant concentrations of ozone led to reduced width of the stomatal aperture. Moreover, unetchable droplet‐like exudates were found on the outer face of mesophyll cells of leaves where the trees had been exposed to ozone. These exudates were later followed by collapsed mesophyll cells and ended in necrotic zones before premature leaf loss.
Radiation damage in dry and frozen hydrated organic material
Authors: Lamvik M. K. 
Published: August 2011

SUMMARYElectron‐induced radiation damage can cause errors in interpreting electron micrographs. Radiation damage is distinguished from contamination (polymerization of hydrocarbons) and etching (radiolysis in the presence of water), both of which can be controlled by a proper specimen environment in the microscope. While temperature has little effect on the primary interactions of fast electrons with matter, most secondary radiation‐damage processes are temperature dependent. Because damage mechanisms differ so greatly among materials, there is no simple factor by which specimen stability is improved as a function of temperature (some cases improve fivefold, others improve 100‐fold). While some specimens are stable to almost arbitrarily high doses, some tests reveal damage at 1 e/nm2. This paper surveys damage rates and temperature dependencies of various materials as a guide for future electron microscopic studies of organic specimens.
Freeze‐substitution and the preservation of diffusible ions
Authors: Edelmann Ludwig 
Published: August 2011

SUMMARYFreeze‐substitution of biological material in pure acetone followed by low‐temperature embedding in the Lowicryls K11M and HM23 yields stable preparations well suited for sectioning and subsequent morphological and microanalytical studies. Transmission electron microscopy of dry‐cut sections shows that diffusible cellular thallium ions (Tl+) of Tl+‐loaded muscle are localized at similar protein sites in freeze‐substituted as in frozen‐hydrated preparations. A comparison of X‐ray micro‐analytical data obtained from freeze‐dried cryosections and sections of freeze‐substituted normal (potassium‐containing) muscle shows that K+ ion retention in the freeze‐substituted sample is highly dependent on the freeze‐substitution procedure used; so far, in the best case, about 67% of the cellular K+ is retained after freeze‐substitution in pure acetone and low‐temperature embedding. It is concluded that the retention of diffusible cellular ions is dependent on their interactions with cellular macromolecules during the preparative steps and that ion retention may be increased by further optimizing freeze‐substitution and low‐temperature embedding.
Cryosputtering—a combined freeze‐drying and sputtering method for high‐resolution electron microscopy
Authors: Lindroth Margaretha , Fredriksson Bengt‐Arne , Bell Paul B. 
Published: August 2011

SUMMARYPreparing cellular structures for visualization by high‐resolution scanning electron microscopy (SEM) is a multi‐step process which includes fixation, dehydration, drying and metal coating. Drying and metal coating are limiting for high‐resolution work. Commonly, the dried samples are exposed to the air before they are inserted into a metal coating apparatus, thereby exposing them to moisture and the accompanying risk of rehydration, which may cause changes in the supramolecular structure. We have modified a freeze‐dryer to accommodate a magnetron sputtering head, in order to sputter‐coat the frozen‐dried samples while still in the drying chamber in the cold, a process we call cryosputtering. A layer of 1·5 nm of tungsten was cryosputtered onto whole mounts of cytoskeletons from detergent‐extracted human glioma cells or fibroblasts and the specimens were examined by high‐resolution SEM and transmission electron microscopy (TEM). To reduce the effects of backstreaming oil from the vacuum system, a turbomolecular pump backed by a two‐stage rotary vane pump was connected to the drying‐coating chamber. This pump system provides a high vacuum, making it possible to dry the specimens at — 90°C/183 K, thus reducing the risk for recrystallization of water. Furthermore, the high vacuum minimizes the negative effects of contaminants, which can be deposited onto the specimen surface and affect the quality of the metal coat formed during sputtering.
Preparation of ultrathin amorphous ice films for cryo‐electron microscopy
Authors: Jakubowski U. , Mende M. 
Published: August 2011

SUMMARYElectron microscopy of biological macromolecules embedded in vitrified ice films suffers from serious problems caused by excessive inelastic scattering, beam‐induced movements of the specimen, deformation of the molecules by adsorption at the water‐air interface and insufficient mechanical stability of the films. We have built an environmental chamber to control temperature and humidity independently in order to produce ultrathin water films (< 20 nm) spanning holes with diameters of 20 μm to 1 mm. The surface tension of the water films was reduced by adding lipid monolayers, thus prolonging the usable time for thinning of the film and avoiding adsorption artefacts in the embedded material. After cryofixation in ethane a carbon film was evaporated on each side of the specimen to stabilize the ultrathin ice—lipid film. Mechanical stability and charging effects could successfully be reduced by this preparation method. Collapsing water films could be cryofixed and the shape of the hole was analysed. By the eccentricity of the elliptical holes an estimation could be made of the burst velocity of the rim of the hole and of the cooling rate of the cryofixation process.
Image analysis and processing of an imperfect two‐dimensional crystal: the surface layer of the archaebacterium Sulfolobus acidocaldarius re‐investigated
Authors: Lembcke G. , Dürr R. , Hegerl R. , Baumeister W. 
Published: August 2011

SUMMARYThe surface layer of the archaebacterium Sulfolobus acidocaldarius has been re‐investigated exploring various image analysis and image processing strategies. Straightforward correlation averaging correcting for translational disorder only, and lattice unbending in conjunction with filtration in the Fourier domain gave equivalent results. Careful examination of cross‐correlation functions as well as multivariate statistical analysis of individual unit cells revealed the existence of interpenetrating domains with intrinsic p3 symmetry but rotated with respect to each other by 60° and separated by twin boundaries. Non‐discriminative averaging over twinned crystal patches generates a higher (p6) class of symmetry emphasizing the importance of selective averaging.