bluuebunny/crossref_metadata_2025 huggingface dataset:
Recent advances in automatic image analysis using a television system
Authors: Cole M. , Bond C. P.
Published: August 2011

Image analysis, in the context of this paper, comprises the extraction of quantitative geometric and densitometric data from images produced by optical and electron microscopes or any other imaging system. Typical measurements include area percentages, intersect counts, feature counts, size distributions and integrated density determinations. Much of the stereological work is still performed by manual methods, but technological progress in recent years has considerably promoted the use of automatic image analysing devices. This paper describes recent developments in scanner performance and the correction of shading errors which allow reliable densitometric measurement. In addition, the previous geometric capabilities have been extended to include feature selection by pattern recognition criteria.
Apparatus for time‐lapse cinemicrography
Authors: Dawson Mary , Matthews J. E.
Published: August 2011

An apparatus for time‐lapse cinemicrography of living cells is described. It has an advantage over earlier apparatus in that it makes use of a microscope light source which can operate in both steady running and flash conditions. This enables setting up of the microscope and subsequent photography to be carried out with one light source, with consequent optimum illumination during photography. The light source is attached to a modified, inverted, phase‐contrast microscope, and the camera used is a modified 16 mm cine camera.
On the relationship between the modes of image formation in scanning microscopy and conventional microscopy
Authors: Welford W. T.
Published: August 2011

With a non‐resolvable scanning spot, scanning microscopy provides images identical to images in partially coherent illumination in a conventional microscope. If the spot is resolvable the higher spatial frequencies in the scanning image are filtered out.
Photometrie measurements of grain density in autoradiographs
Authors: Rogers A. W.
Published: August 2011

A technique is described for measuring the grain densities in areas of emulsion from 10 to 200 μm2, using vertical incident illumination which converts the silver grains into bright specks on a black background. The light reflected by the silver grains in the measuring area is integrated with a photometer to give a reading that is directly proportional to the number of grains present over a wide range of densities. Speeds of 200 counts/h can be maintained on suitable material throughout a working day without loss of accuracy. The characteristics of the method, the selection of equipment, and some sources of artefacts are discussed.
Purity and stability of radiochemical tracers in autoradiography
Authors: Evans E. Anthony
Published: August 2011

Autoradiography is used as a means of ‘visualizing’ the results of tracer investigations; it gives a measure of ‘events’ which have already occurred. This paper discusses some of the problems peculiar to radiochemicals which should be clearly recognized prior to the application of autoradiographic techniques and the interpretation of the data obtained.

Many of the problems described in this paper are concerned with tritium compounds which are particularly valuable and widely used for studies involving high resolution autoradiography. The physical (nuclear) properties of tritium, the low maximum beta energy (18 keV) of the radiation and the high maximum specific activity (29 Ci/mg atom of hydrogen), makes tritium the ideal isotope for determining the precise localization of compounds, drugs and hormones for example, in biological specimens.

Refinements in autoradiographic techniques which have been developed in recent years have permitted high sensitivity in the detection of the tracer. While the importance of using compounds of known radiochemical purity for any tracer investigation is widely recognized, it is necessary to ensure that the data obtained is related to the radiochemical tracer compound and is not a consequence of the presence of radiochemical impurities. In this paper are therefore described some of the problems which can arise using impure tracer compounds and their effects on the interpretation of autoradiographs. The methods for the determination of purity, for example chromatographic, isotope dilution analysis, autoradiographic and spectroscopic methods are discussed together with some of the difficulties associated with these analytical techniques.

The instability of radiochemicals on storage prior to their use is now a well documented phenomenon; it is a particularly severe problem with compounds used in high resolution autoradiographic studies because of the high molar specific activities which are necessary. Factors which determine the rate of self‐decomposition are discussed, such as the molar specific activity of the compounds, the energy of the radiation and the storage conditions selected for the compound. Current methods for minimizing self‐decomposition of radiochemicals are discussed and illustrated by examples.

When using tritium compounds, the integrity of the tritium label is often related to the position of the tritium atom(s) in the tracer compound. However, many of the methods used for the preparation of tritium compounds can yield products in which the specificity of the labelling is uncertain. The importance of the specificity of labelling in such tracers in relation to the interpretation of autoradiographic data is therefore also discussed.
High efficiency development procedures for nuclear emulsions*
Authors: Rechenmann R. V. , Wittendorp E.
Published: August 2011

The development procedure of nuclear emulsions has been submitted to a systematic study. Each factor involved in this complex procedure has been considered separately.

The optimum development time is determined by the maximum of the signal/noise ratio curve. It depends strongly on the other parameters involved in the developing process: temperature, type of emulsion, radiation, developer, etc.

New treatment procedures for nuclear emulsions have been established. They are based on the following additional hypothesis concerning the corpuscular latent image: the image formed in the microcrystals consists partly of stable sub‐specks which are not developable, even by total developers. These sub‐germs would render the microcrystals developable if they are ‘activated’, i.e. if their electron levels are lowered by physical or physico‐chemical means.

Activation by gold combined with a forced chemical development has proven to give results which are highly reproducible and homogeneous throughout the emulsion layer. Whatever the type of emulsion used and for most chemical developers, this procedure results always in a strong increase in the number of grains developed together with a remarkable stability of the chemical fog. The intensification effect increases when the grain size, the sensitivity of the emulsions and the mean energy released in a grain by a charged particle decreases. The amplification effect becomes more important when the redox potential of the developer diminishes (in absolute value).

In light and electron microscope autoradiography, the gain in efficiency resulting from these studies permits the amount of radio‐elements used or the exposure times to be reduced in a ratio varying from 1/5 to 1/20, if compared with classical methods. Moreover, the increased probability of development of the ‘first grain hit’ results in a better resolution.
The dimensions and numbers of small vesicles in blood capillary endothelium in the hind legs of dogs, and their relation to vascular permeability
Authors: Casley‐Smith J. R. , Clark Helen I.
Published: August 2011

The dimensions and numbers of vesicles were determined in the blood capillary endothelium of the gastrocnemii muscle of dogs. These results permitted more accurate calculations of the number of vesicles crossing the endothelium in one direction/sec/(μm2 (∼6·2), and of the median vesicular attachment time (∼8 sec). The probability of fusion occurring when a vesicle contacts a plasma membrane (α= 0·004) was unchanged: hence it was concluded, from the mean cellular width (0·21 μm) and the calculated cytoplasmic viscosity (∼0·1 poise), that ∼49% of the vesicles starting from one side reached the other one, and that their median transit time was ∼1 sec.
Tri‐dimensional structure of the forming face of the Golgi apparatus as seen in the high voltage electron microscope after osmium impregnation of the small nerve cells in the semilunar ganglion of the trigeminal nerve
Authors: Rambourg A. , Marraud A. , Chretien Monique
Published: August 2011

When rat trigeminal ganglia were osmicated for 45 h at 40°C in a 1% unbuffered aqueous solution of osmium tetroxide, only the one saccule located on the forming face of the Golgi stacks was impregnated with osmium. This staining property was therefore utilized to examine with the high voltage electron microscope the tri‐dimensional structure of the forming face of the Golgi apparatus of the small nerve cells using sections whose thickness ranged from 1 to 7 μm.

In 1 μm thick sections, the osmicated ‘saccules’ actually consist of tubular polygonal networks scattered throughout the pericaryon. As the thickness of sections is progressively increased, these networks are seen to interconnect and form the so‐called ‘appareil réticulaire interne’ initially described by Golgi (1898a) in the light microscope. Stereoscopic analysis of 5–7 μm thick sections clearly demonstrates that the saccules located on the forming face of the Golgi stacks are in fact a continuous convoluted structure made up of a tubular polygonal network.
High voltage electron transmission microscopy of pyrolytic silicon carbide coatings from nuclear fuel particles
Authors: Hudson B. , Sheldon B. E.
Published: August 2011

One design concept for a gas cooled fast reactor fuel element utilizes directly cooled coated fuel particles. The fission product retention barrier is a pyrolytic SiC layer approximately 50 μm thick and 1 mm diameter. Knowledge of the structure of this material and its irradiation performance after high neutron doses is vital to the success of such reactors.

Specimens oriented both parallel and perpendicular to the radius can be prepared from the shells by ion beam sputtering. The defect structure and preferred orientation of the coatings is being investigated. The high voltage electron beam is being utilized to measure the atomic displacement energy and to simulate fast neutron damage at temperatures relevant to reactor conditions.
Application of high voltage electron microscopy to low‐temperature radiation damage studies in metals
Authors: Urban K.
Published: August 2011

The paper briefly reviews the advantages of high voltage electron microscopy applied to low temperature radiation damage studies. Such studies may be performed inside the microscope provided a high resolution specimen cooling stage is available. The main features of a new type of cooling stage used in the experiments relevant to this paper are outlined. The applicability of the stage for post‐irradiation annealing experiments is emphasized.

During electron irradiation to high doses at 8°K the formation of defect clusters was observed in nickel and copper. This is accompanied by pronounced changes in the diffraction pattern. Post‐irradiation annealing of samples irradiated at 8°K produces defect clusters which can be identified as dislocation loops.
High voltage electron microscope studies of void nucleation in nickel
Authors: Harbottle J. E. , Norris D. I. R.
Published: August 2011

The influence of dislocation behaviour on void formation in the high voltage electron microscope (HVEM) has been predicted theoretically and confirmed by experiment. The probability of void nucleation has been computed as a function of the radial distance from a dislocation line in a finite cylinder of material. The observation of strings of voids associated with dislocation lines supports the predictions of the model. Void formation in the HVEM is closely related to the detailed microstructural changes that occur immediately upon electron irradiation, and a good correlation is obtained between the initial interstitial loop density and subsequent swelling by electrons. A minimum foil thickness is necessary for void growth in the HVEM, otherwise the surfaces dominate and the dislocation density always remains low.
Defect structure of PAN‐based carbon fibres
Authors: Burnay S. G. , Sharp J. V.
Published: August 2011

A 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

The 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

Thin 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

When 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

Hydration 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

The 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

The 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

The 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

In 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

Nematodes 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

Red 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

Cell 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

In‐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

A 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

Hydrogen‐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

Stereological 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

The 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

A 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.
The usefulness of disposable syringes in the electron microscope laboratory
Authors: Mehta Rajendra
Published: August 2011

A method of handling, storing and transporting mixed liquid resin using disposable injecting syringes is described. The method gives no adverse effect and specimen blocks are cut with the same ease as when prepared from a fresh mixture. The procedure is simple and is well suited for the electron microscope laboratory.
A method for the rapid removal of sugars and salts from virus preparations on electron microscope grids
Authors: Webb M. J. W.
Published: August 2011

An elution method for the rapid removal of solutes from virus preparations mounted on carbon coated electron microscope grids. Other uses of the method, including negative staining, are noted.
Weak‐beam observation of dislocation loops in silicon
Authors: Bicknell R.
Published: August 2011

Weak‐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 {110} antiphase boundary energy of NiAl
Authors: Campany R. G. , Loretto M. H. , Smallman R. E.
Published: August 2011

A 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

Coupled 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.
Resolution of dense dislocation networks using the weak‐beam technique
Authors: Nordlander I. , Thölë A.
Published: August 2011

The weak‐beam technique has been used to investigate dislocation networks, which were too dense to be resolved in bright field where only Moiré‐type fringes were found.
Dislocation networks in tungsten carbide studied by the weak‐beam technique
Authors: Johannesson T. , Lehtinen B.
Published: August 2011

Dislocation 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

For 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

A 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

The 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

In 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.
A technique for microtome sectioning of charcoal
Authors: Cousins W. J.
Published: August 2011

Sectioning of charcoal is extremely difficult since the knife usually shatters the section into minute fragments. In order to prevent such shattering it is necessary to both infiltrate the charcoal with a hard wax and to support the section during cutting with adhesive cellulose tape.
Field‐ion microscopy of interphase interfaces
Authors: Hildon A. , Howell P. R. , Page T. F. , Ralph B.
Published: August 2011

This 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

A 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

The 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

The 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.
Stereo‐scanning electron microscopy of desmids
Authors: Pickett‐Heaps Jeremy D.
Published: August 2011

Stereo‐pairs of scanning electron micrographs are presented of two species of Staurastrum, one species of Cosmarium and two species of Micrasterias, including the triradiate, diploid variant of M. thomasiana. Techniques for processing these cells are discussed and some typical morphological variations encountered in cultures are illustrated; the methods are reasonably quick and reliable and may prove useful in taxonomic studies of desmids.
High voltage electron microscopy of environmental reactions
Authors: Flower H. M.
Published: August 2011

An incorrect caption to Fig. 11 was printed in this paper which was published in the Journal of Microscopy, Vol. 97, Pts 1/2, pp. 171–190. The correct caption should read ‘Unstained glutaraldehyde‐fixed 3T3 cell (bright‐ and dark‐field pair) showing mitochondria (arrowed). In wet specimens the mitochondria appear broader (possibly due to damage) and scatter electrons less strongly than the surrounding material.’
Wetting agents for biological electron microscopy
Authors: Gregory D. W. , Pirie B. J. S.
Published: August 2011

The most frequently used method of enabling aqueous suspensions of small, particulate, biological specimens to spread on the hydrophobic support films required for electron microscopy, is to add a surface‐active compound to the suspensions. The requirements of an ideal wetting agent for use in this situation are outlined. The polypeptide bacitracin has been found to meet all these requirements, and it is superior to the commonly‐used bovine serum albumin (BSA) in several respects. Bacitracin molecules are much smaller than those of BSA, and unlike BSA molecules they are not visualized by negative staining. Thus bacitracin produces a very even background against which the fine details of a specimen can be more easily interpreted. It facilitates the penetration of negative stain into small crevices and it produces a smaller halo of negative stain around specimen particles. Its use for spreading electron dense specimens is also demonstrated. Bacitracin is compatible with at least five commonly‐used negative stains, namely ammonium molybdate, potassium phosphotungstate (KPT), potassium silicotungstate, sodium tungstate and uranyl acetate. It is also biologically acceptable for use with a wide range of specimens. There is no evidence of bacitracin causing damage to specimens examined representing macromolecules, animal, plant and bacterial viruses, bacteria and subcellular organelles.
A computer system for the measurement of cell and nuclear sizes*
Authors: Cowan W. M. , Wann F.
Published: August 2011

A semi‐automated system has been developed for the measurement of cell (perikaryal), nuclear and nucleolar areas. The system consists essentially of a Graf/Pen data tablet (with its associated acoustical stylus and tablet electronics), an optical input system such as a camera lucida, and a small digital computer. The perikaryal, nuclear and nucleolar outlines are traced in sequence with the stylus which, on contacting the tablet surface, emits a high frequency acoustic wave that is sensed by X and Y strip microphones along the left and upper edges of the tablet. The acoustic signal is converted by a simple program into a series of X and Y coordinates which are sampled at several points around the perimeter of the profile. When the stylus tip re‐enters a 1 mm stationary window set up around the starting point, the measurement is automatically terminated and the data for this profile is printed out and stored in memory for subsequent statistical analysis. The system has an overall accuracy of about 1% and in practice it has been possible to measure objects at least ten times more rapidly than by any of the other currently available methods. The hardware and software features of the system are detailed and a number of additional uses for the system are described.
A practical device for processing Polaroid 55 P/N film used with scanning electron microscopes
Authors: Thurston E. Laurence , Scott James R. , McKee Thomas R.
Published: August 2011

A device to improve the awkward handling and processing of Polaroid type 55 P/N film used with scanning electron microscopes can be constructed from Plexiglass and 1, 2 dichloroethane.
A fine‐sieve processing container for use in critical point drying
Authors: Scott J. R. , Thurston E. L. , McKee T. R.
Published: August 2011

A container to hold specimens during dehydration and critical point drying can be constructed from a 100 mesh screen cylinder and a BEEM embedding capsule.
The application of cryo‐ultramicrotomy in the study of the fine structure of myofilaments
Authors: Sjöström M. , Thornell L. E. , Cedergren E.
Published: August 2011

The possibility of using sections obtained by cryo‐ultramicrotomy in the study of the fine structure of myofilaments was explored. Heart and skeletal muscles were stabilized for 5–15 min in 2.5% glutaraldehyde. Neither cryo‐protection, encapsulation nor any other chemical treatment preceded the freezing in Freon‐12 cooled by liquid nitrogen. ‘Wet’ sectioning was performed using dimethyl sulphoxide (50% in water) in the knife trough. The sections were stained using either positive or negative contrasting techniques.

The results showed that sections prepared by cryo‐ultramicrotomy permit high resolution studies, especially if negatively stained. By eliminating several steps of specimen preparation that destroy the native configuration of biopolymers, the method promises to make it possible to study well‐preserved myofilaments and their fine structure, both in longitudinal and cross‐section, in situ. It is not yet certain, however, that new sources of artefacts are not introduced.
A preliminary field‐ion atom‐probe investigation of competitive carbide formation in ferritic steels
Authors: Youle A. , Turner P. J. , Ralph B.
Published: August 2011

A combined field‐ion microscope and field‐ion atom‐probe study has been made of the early stages of precipitation in an Fe—V—Mo—C alloy. Crystallo‐graphic analysis showed that precipitates based on both molybdenum and vanadium carbide structures were present. Atom probe analysis showed that individual carbides ∼15 nm in size contained both molybdenum and vanadium, while for smaller sizes a considerable amount of iron was present in the precipitates.
Morphometrics of living specimens. A methodology for the quantitative three‐dimensional study of growing microscopic embryos
Authors: Prothero John W. , Tamarin Arnold , Pickering Ruth
Published: August 2011

A methodology is described which permits quantitative three‐dimensional studies of growing microscopic (and substantially transparent) animals to be made. The methodology has been applied in a limited way to the study of blastula formation in sand dollar embryos. A preliminary analysis has been made of the errors likely to arise (see Appendix).

It was observed that the total blastomeric (cellular) volume decreased somewhat at the time of the second cleavage, and that the volume of the blastocoel simultaneously increased by about the same amount. It is suggested on the basis of this and other evidence that the blastocoel material is initially secreted by the blastomeres and that the blastocoel may subsequently innate, perhaps as a result of the imbibition of fluid from the extrablastular space. Further study will be required to confirm or invalidate this hypothesis.

A study of plexiglas reconstructions suggests that formation of the blastular epithelium is the result of a coordinated pattern of cell cleavages and cell displacements. It is suggested that cell displacements may be the result of localized intracellular constrictions and/or changes in surface adhesion. Further study will also be required to confirm or invalidate this hypothesis.

The methodology described in this paper is considered to be complementary to one previously described by Hou, Veress & Prothero (1970) for application to similar problems at the macroscopic level of resolution.
A comparative survey of techniques for preparing plant surfaces for the scanning electron microscope
Authors: Parsons Elizabeth , Bole Barbara , Hall D. J. , Thomas W. D. E.
Published: August 2011

A comparative investigation of techniques for the preparation of soft botanical tissue for the scanning electron microscope has been carried out using the leaves and petals of Pelargonium zonale as test specimens. Twelve different preparative procedures involving combinations of fixation, dehydration, air drying, freeze drying, critical point drying, coating methods, replicas and a temperature controlled specimen stage were tested.
The preparation of small, particulate specimens by critical point drying: application for scanning electron microscopy
Authors: Lung Ben
Published: August 2011

A procedure is described using round glass cover‐slips as supports for preparing specimens by critical point drying for the scanning electron microscope. Also described is the construction of a plastic Teflon holder to facilitate handling of the cover‐slips.
Preparation of tough, fibrous material for examination in the scanning electron microscope
Authors: Barlow John R.
Published: August 2011

A simple method has been devised which minimizes distortion of fibrous material during the cutting needed for examination of cross‐sections in the SEM. Camphene, suggested for use in ‘freeze‐drying’ at room temperature (Watters & Buck, 1971) is used as an embedding material with a surrounding layer of ice for reinforcement and sectioning can then be carried out. The technique has been successfully applied to hides and skins in several stages of processing to leather, i.e. in both wet and dry initial states.
Suppression of lattice periods in vermiculite single crystal specimen supports for high resolution electron microscopy*
Authors: Baumeister W. , Hahn M. H.
Published: August 2011

Easy preparation of thin crystalline specimen supports for high resolution electron microscopy has been achieved by thermic exfoliation of vermiculite. The thinnest layers obtained appear to be 1·8 nm thick and show the expected hexagonal array with a 0·46 nm lattice spacing. This periodic background could be suppressed either by optical filtering or by putting a zero crossing of the respective transfer function of the electron microscope objective over the diffraction spots of the crystal.