bluuebunny/crossref_metadata_2025_split huggingface dataset:
Defect structure of PAN‐based carbon fibres
Authors: Burnay S. G. , Sharp J. V. 
Published: August 2011

SUMMARYA range of internal defects has been observed by high voltage microscopy in carbon fibres prepared from polyacrylonitrile (PAN). In type I fibres, large elongated cavities up to ∼ 3 μm in diameter are found, often associated with particulate inclusions and occur with a frequency of ∼ 2/mm of fibre. In ion thinned type I fibres where smaller defects are visible, a higher density of defects (approx. 1000/mm of fibre, mean size 86 nm) has been observed both in sections from the centre of the fibre and close to the surface. These smaller defects are also visible in type II fibres (heat treated to ∼ 1500°C) and in this case ∼ 70% of the defects are observed to contain small particulate inclusions.A high density of small voids (mean size 20 nm) is observed in type II fibres particularly in the vicinity of larger defects. These voids appear slightly diffuse in type II fibre and disappear during the graphitization heat treatment. They are also not seen in oxidized fibre, but in fibre heat treated to 500°C they are clearly visible, indicating that they are formed during the temperature range 220–500°C where considerable gas evolution occurs.The effect of these defects on fibre strength is discussed and the observed defect size related to expected crack lengths on the basis of a Griffith relationship.
High voltage electron microscopy of environmental reactions
Authors: Flower H. M. 
Published: August 2011

SUMMARYThe development of environmental cells for transmission electron microscopy is briefly reviewed. The advantages of increased penetrating power and large available space for specimen stages associated with high voltage microscopes are demonstrated. The effect of specimen‐electron beam interactions are considered and the applications of the high voltage microscope to in situ studies of chemical reactions and biological material in the wet state are discussed.
In situ deformation of molybdenum thin foils
Authors: Vesely D. 
Published: August 2011

SUMMARYThin foils of pure molybdenum single crystals with selected surface orientations and tensile axes were tested on a double‐tilt straining stage using a microscope operating at 800 keV. Studies were made of the propagation of screw and edge dislocations, slip geometry, dislocation multiplication and formation of dislocation tangles. Special attention was paid to the influence of the surface on dislocation motion and the comparison of observed effects with those of bulk material.
In situ observations of precipitation and recrystallization with a 1 MeV electron microscope
Authors: Lehtinen Börje , Robets William 
Published: August 2011

SUMMARYWhen fitted with a heating stage and suitable equipment for continuous image recording, the high voltage electron microscope is a powerful tool for the direct observation of recrystallization and precipitation in thin metal foils. However, the behaviour of thin specimens is sometimes not even qualitatively typical of bulk material. For example, true precipitation from supersaturated solid solution can only be observed if vacancies play no significant part in the process as in iron‐nitrogen alloys. In this case, the formation of the intermediate precipitates, α“—Fe8N, and the equilibrium phase, γ—Fe4N, is qualitatively and in some respects quantitatively typical of bulk material even in very thin foils. However, extensive electron displacement damage should be avoided because it seriously retards precipitate growth.It is shown elsewhere (Roberts & Lehtinen, 1972) that true bulk recrystallization is only possible in thick areas of an electron microscope specimen. This is confirmed for several metals in the present work. The critical specimen thickness for bulk behaviour is generally between 3–800 nm depending the degree of cold work etc.; this concurs with earlier heating‐stage experiments at 100 kV in which true recrystallization was not observed.
Applications of the NPL Environmental cell for use in the AEI EM7 1 Mev electron microscope
Authors: Allinson D. L. , Loveday M. S. , Gosnold A. W. O. 
Published: August 2011

SUMMARYHydration of alite and tricalcium silicate has been investigated in the NPL environmental cell. In the presence of free water in the cell the hydration reactions occur at a very rapid rate when subjected to electron bombardment and the resulting hydrates cannot be regarded as being typical of the bulk reaction.Specimens have also been hydrated in a controlled environment external to the cell and subsequently examined in the cell with a humid atmosphere. In addition, the same specimen areas were examined in high vacuum and it was found that there were no obvious changes in the morphology of the hydrates.Fungi spores have been examined at atmospheric pressure in the cell and the microstructure of the spore attachments has been studied. The results also indicate that the surface morphology previously determined from replicas is essentially correct.
In situ observation of dissolution of cementite in steel
Authors: Nemoto Minoru 
Published: August 2011

SUMMARYThe mechanisms of dissolution of cementite particles in steel have been studied in situ by high voltage electron microscopy. This method permits direct, continuous observations of the process and provides new information which has not been obtained without this technique. During dissolution of cementite particles in austenite at about 770°C, dislocation helices, loops and complex dislocation configurations are formed from the interfaces of the particles. Dissolution of cementite in ferrite during decarburization at about 700°C also causes the formation and movement of dislocations. However, in contrast to the case of dissolution in austenite, the emission of dislocation loops and helices has not been observed. The migration of crystallographic and noncrystallographic interfaces has been observed during the ferrite to austenite transformation. The noncrystallographic interface is apparently attracted to the cementite particles. The migration rate of the noncrystallographic interfaces is five to ten times faster than that of the crystallographic interface.
Direct observation of discontinuous precipitation in Al‐28at%Zn
Authors: Ramaswamy V. , Butler E. P. , Swann P. R. 
Published: August 2011

SUMMARYThe cellular precipitation occurring in an Al–28at%Zn alloy has been followed in situ using a hot stage in the high voltage electron microscope. The cellular reaction starts at grain boundaries and after a period of accelerated growth, a linear growth rate is established. The interlamellar spacing and the rate of growth vary as a function of temperature and the results have been analysed on the basis of the Turnbull theory of cellular precipitation which suggests that the cell boundary diffusion is the rate controlling factor in this system.
The response of photographic materials to electrons with particular reference to electron micrography
Authors: Farnell G. C. , Flint B. 
Published: August 2011

SUMMARYThe response of photographic emulsion layers to electron beam exposures is reviewed in simple terms, particularly for those energies used in conventional electron micrography. Emphasis is placed on the way many features of response are determined by the fact that a single electron serves to render several grains developable. In particular it is shown that the contrast is independent of emulsion/developer combination, the granularity is uniquely related to the speed, and the signal/noise ratio increases with exposure irrespective of the conditions leading to exposure increase. Demonstrations of these aspects are presented. Factors governing image spread are also outlined. The dependence of the minimum magnification for observation of details of a given size on this property is discussed.
Statistical analysis of transformations leading to normal distribution of measurements of the peripheral glomerular basement membrane
Authors: Gundersen H. J. G. , ØSterby R. 
Published: August 2011

SUMMARYIn a morphometric study of the peripheral glomerular basement membrane distribution curves of true membrane thickness were obtained. The measurements were made on photomontages of total glomerular cross‐sections.The distributions were always markedly right‐skewed. A transformation leading to normal distributions was sought. Transformation of basement membrane thickness T to was found to be optimal.The arithmetic mean, Th, of this reciprocal transformation was applied in the statistical analysis of the very earliest stages of diabetic glomerulopathy. It is also meaningful as regards the physiological role of the basement membrane as a filtration barrier.
Preparation of biological material for scanning electron microscopy by critical point drying from water miscible solvents
Authors: Turner R. H. , Green C. D. 
Published: August 2011

SUMMARYNematodes and mildew‐infected barley leaves when examined in the scanning electron microscope after critical point drying (CPD) from sulphur dioxide (critical temperature 157–7°C) showed no obvious physical damage, but the specimens had a surface deposit which was probably heat damaged natural waxes. The nematode Caenorhabditis elegans and clover roots (Trifolium subterraneum) showed no physical or heat damage after CPD from monochlorodifluoromethane (Freon 22, critical temperature 96°C). The hyphæ and conidia of unfixed mildew on barley were damaged after CPD from Freon 22, probably due to the Freon extracting lipids from the cell walls. Freon 22 was preferred for most specimens as it is cheap, easy to get and not very toxic.
High voltage electron microscopy of cellular changes in the wet state
Authors: Clarke J. A. , Ward P. R. , Salsbury A. J. 
Published: August 2011

SUMMARYRed blood cells and bacteria have been viewed under the high voltage transmission electron microscope, using a controlled environment chamber. Red cell changes on introduction of an agglutinating serum into the environment and bacterial changes on addition of an antibiotic, were observed. The results are compared with those obtained by phase contrast light microscopy and the potentialities of the system discussed.
Use of post‐polymerization whole block staining with Azure 11 to identify in situ embedded cultured cells for electron microscopy
Authors: Nelson Barry K. , Flaxman B. Allen 
Published: August 2011

SUMMARYCell cultures, embedded at the surface of an Araldite block, can be stained after polymerization by immersing the block in an aqueous solution of 0.1% Azure II with 1% sodium borate for 10 min at 60°C. Visibility of the embedded cells is thereby considerably enhanced and cells of interest can be readily selected for subsequent electron microscopic examination. The cutting quality and ultra‐structure of such treated material are unaltered.
Enhanced contrast in electron microscopy of unstained biological material
Authors: Johnson H. M. , Parsons D. F. 
Published: August 2011

SUMMARYIn‐focus phase contrast electron microscopy has been investigated for the enhancement of bulk contrast (i.e. the contrast of large regions) of model biological specimens. Carbon film phase plates, of measured thickness, were introduced into the back focal plane of the objective lens. Image contrast was determined from Faraday‐cage intensity measurements. A contrast enhancement was observed but was measured to be less than that obtained using a very small objective aperture. This was attributed to the smaller proportion of elastic scattering and the limited spatial frequency region over which the phase contrast transfer function was uniform. Electron beam interferometry established the ability of the phase plates to preserve the coherence of the beam traversing them. Carbon granularity, of specific dimensions, was significantly enhanced by the phase plate in accordance with the phase contrast transfer function and this enhanced granularity dominated the images of biological specimens.
The computation of particle size‐shape distributions in transmission microscopy
Authors: Skillman David C. 
Published: August 2011

SUMMARYA method has been developed, and a computer program written, to correct measurements of particle length and width for the effects of section thickness and swelling in the preparation of sectioned samples for transmission microscopy. The method is applied to the system of silver particles in gelatin, and the resulting calculated extinction spectra are compared with those observed and calculated without correction. Improved correlations show that the method is useful.
Hydrogen‐ion image features of tempered martensite
Authors: Ranganathan B. N. , Grenga Helen E. 
Published: August 2011

SUMMARYHydrogen‐ion microscopy has been used to study first and third stage tempered ferrous martensite. Both ε‐carbide and cementite particles resulting from the tempering process appeared dark in the images. The image characteristics of the matrix phases in these specimens were intermediate between those of pure iron and as‐quenched ferrous martensite. The sharpness of the (111) zone lines and the ‘butterfly’ pattern in {110} regions, the development of high index planes and the regularity of low index net plane edges decreased continuously with increasing carbon content of the matrix phase. The effects of carbon content and lattice strain on specimen geometry, field evaporation, hydrogen etching and field ionization are discussed. It is suggested that carbon atoms in random solid solution lead to an irregular evaporation, similar to that previously proposed for other solid solution alloys, and that the irregular evaporation is enhanced by the associated lattice strain and hydrogen etching process. The irregular end form thus produced lacks the sharp image features found in the smoother end form of the pure metal.
A specimen scanner for stereology with the electron microscope
Authors: Fulker M. J. 
Published: August 2011

SUMMARYStereological methods which involve the use of test grid systems with electron micrographs suffer from a basic limitation that the magnification used has to be a compromise between high magnification for good visibility of image detail and low magnification for good sampling. The electron microscope scanning stage described avoids this difficulty since high magnification imposes no limitation on the sampling of the specimen and in practice can be used for situations where test grid methods become impractical.
A simple method to estimate the true diameter of synaptic vesicles
Authors: Froesch Dieter 
Published: August 2011

SUMMARYThe problem of estimating the full diameter of synaptic vesicles from the diameter of their profiles in section is approached by calculating the respective difference in simulated size distributions. This difference increases linearly to the quotient Da/T (the ‘apparent’ mean diameter and the thickness of section). Knowing Da/T the observer can add the corresponding percentage proportion given in this paper to the measured mean diameter (Da) in order to get the ‘true’ diameter in a vesicle population.
Scanning electron microscopy of the internal cellular structure of plants
Authors: Bole Barbara , Parsons Elizabeth 
Published: August 2011

SUMMARYA technique is described in which the scanning electron microscope (SEM) has been used to study the internal cellular organization of the plant organs and the interaction of the plant with the environment. Transverse surfaces were revealed by fracturing quick frozen specimens and freeze‐drying the fragments. The greater depth of focus of the SEM compared with the optical microscope enabled the production of clear, realistic micrographs with a three‐dimensional appearance.
Weak‐beam observation of dislocation loops in silicon
Authors: Bicknell R. 
Published: August 2011

SUMMARYWeak‐beam microscopy has been used to examine the dislocation loops formed when ion implanted silicon is annealed in the temperature range 900–1300 K. The extinction distances of about 10 nm, resulting from the use of large deviation parameters S' enable stacking fault fringes of 4nm spacing to be resolved in faulted loops. The projected shape of the dislocation loops and the variable contrast along the perimeter of the bounding partial dislocation enables the habit planes of the dislocation loops to be determined from inspection. These together with the width of the dislocation image, which is about 3 nm enables the type of loop to be characterized completely from a single micrograph.
The determination of the 1/2<lll> {110} antiphase boundary energy of NiAl
Authors: Campany R. G. , Loretto M. H. , Smallman R. E. 
Published: August 2011

SUMMARYA value for the 1/2 <111> {110} antiphase boundary (APB) energy in stoichiometric NiAl has been obtained by employing the weak‐beam technique to resolve the separation of the two 1/2 <111> partial dislocations composing the <111 superdislocation.A separation of 4·5 nm is obtained corresponding to an APB energy of 200 ± 40 mJ m−2 (erg cm2).
The application of weak‐beam imaging to studies of small dislocational loops
Authors: Perrin R. C. , Eyre B. L. 
Published: August 2011

SUMMARYCoupled differential equations for calculating diffracted ands tranmitted intensities from thin crystals have been solved numerically for many beam diffracting conditions. This approach has been used to enable us to study weak‐beam dark‐field images from small circular edge dislocation loops. The exact displacement field around such loops has been calculated using isotropic elasticity theory. Crystal orientations have been chosen to obtain single systematic rows of low order reflections and loop images have been calculated for different combinations of strong and weak beams. Although emphasis has been placed on investigating the application of weak beam imaging to determine the nature of small loops (diam. < 10 nm) a preliminary study has also been made of g.b = 0 residual images. The calculated images have been compared with experimental weak beam images of small loops in neutron irradiated molybdenum.
Dislocation networks in tungsten carbide studied by the weak‐beam technique
Authors: Johannesson T. , Lehtinen B. 
Published: August 2011

SUMMARYDislocation networks in tungsten carbide (WC) have been studied in the HVEM. The nodes of the network have been resolved by using the weak‐beam technique in the high voltage electron microscope. They consist of parallel partial dislocations, which are concluded to have Burgers vectors of the type b = 1/6 <20<23>.
Contrast and resolution from biological objects examined in the electron microscope with particular reference to negatively stained specimens
Authors: Horne R. W. 
Published: August 2011

SUMMARYFor the practical biologist applying electron microscopy to the study of biological macromolecules, there are serious problems in obtaining high resolution images showing detail below 2.5–3.0 nm. The limitation in resolution from biological specimens can be attributed to support film thickness and granularity, specimen preparation, irradiation damage, focusing effects and possible contamination in the electron beam. Specimens possessing repeating features can be analysed and averaged by optical diffraction and image reconstruction methods which offer some improvement to the signal to noise ratio. The above problems, with particular reference to irradiation damage, still impose the basic limitation for high resolution applications. When considered together they offer formidable difficulties in practical terms in attempting to make full use of the potential resolving power of modern electron microscopes.
Electron diffraction analysis and techniques for studying polypeptides and other polymers
Authors: Baldwin J. P. , Bradbury E. M. , McLuckie I. F. 
Published: August 2011

SUMMARYA review of electron diffraction studies of polypeptide structures is given together with a discussion of the methods for obtaining diffraction patterns without serious specimen damage by electrons. Electron diffraction studies of poly‐β‐benzyl‐L‐aspartate show that diffraction intensities can be used quantitatively to determine polypeptide structures and the advantages of these studies in observing high angle meridional reflections are shown up by the observation of a novel structure in the unheated left handed helical form of the polypeptide. A large catalogue of techniques for preparing orientated films of polypeptides suitable for electron diffraction investigations makes the technique a powerful one for studying these structures. Polypeptides are shown to be useful for studying electron beam damage in protein‐like materials.
The possibilities for electron diffraction in biology
Authors: Murray R. T. 
Published: August 2011

SUMMARYThe techniques whereby an electron microscope may be used to observe the low angle electron diffraction pattern from crystallized macromolecules are described. A discussion is then presented of the advantages and disadvantages of the technique relative to X‐ray diffraction, high resolution electron microscopy and optical diffraction or computer analysis of electron micrographs.
Stereoscopy of cylindrical objects in the scanning electron microscope
Authors: Hepworth A. , Sikorski J. 
Published: August 2011

SUMMARYIn order to obtain accurate measurements of the topography of surfaces using the scanning electron microscope some form of stereoscopy is generally necessitated. One technique has already been described elsewhere (Unsworth & Hepworth, 1971) along with a detailed calibration procedure using polymer monofilaments as standard specimens.Because of the special case they represent, the present paper justifies the use of such specimens (with an almost perfect circular cross‐section) on both theoretical and practical grounds. Further, since the monofilaments possess a known geometry, conclusions are possible regarding some sources of distortion of the stereo‐image.
Field‐ion microscopy of interphase interfaces
Authors: Hildon A. , Howell P. R. , Page T. F. , Ralph B. 
Published: August 2011

SUMMARYThis paper considers the relationship between the bulk matching of plane stacks abutting an interphase interface and the resultant matching of plane rings seen in the field‐ion image. An image contrast model is developed whereby the interfacial parameters may be deduced from field‐ion investigations and the methods of data acquisition and handling are considered.
The fibrous components of bovine ligamentum nuchae observed in the scanning electron microscope
Authors: Finlay J. B. , Steven F. S. 
Published: August 2011

SUMMARYA combination of enzymes have been employed to remove certain components of the adult bovine ligament sequentially. The course of this sequential enzymic dissection has been followed by scanning electron microscopy. We have been able to define the organization of elastic fibres embedded in matrix of collagen fibrils. The elastic fibres themselves appear to be made up from an amorphous core of elastin surrounded by a knitted sheath; the latter probably contains a mixture of collagen together with an unidentified protein component.
Scanning electron microscopy of etched Epon extraocular muscle sections*
Authors: Pachter B. R. , Davidowitz J. , Zimmer B. , Breinin G. M. 
Published: August 2011

SUMMARYThe internal fine structure of extraocular muscle cells was observed with scanning electron microscopy. One micrometre Epon sections were etched with an iodine acetone solution. When adhered to carbon coated glass, such specimens may be viewed without surface coating. Such preparations provide information about the fibrillar organization of the muscle fibre, as well as its transverse tubular system and M line.
An improved method for the scanning electron microscopy of spermatozoa
Authors: Baccetti B. , Burrini A. G. 
Published: August 2011

SUMMARYThe authors carried out this research on an SEM technique and obtained a good preservation of spermatozoa. Among the many fixatires tested, potassium di‐chromate mixed with osmium tetroxide and NaCl gave the best results. Generally, a rapid freeze drying of the fixed material, after a treatment with dimethylsul‐phoxide, isopentane and liquid nitrogen improves the general standard of preservation.