bluuebunny/crossref_metadata_2025 huggingface dataset:
The application of image pickup and storage‐display techniques to the high resolution electron microscope
Authors: Catto C. J. D. , Smith K. C. A.
Published: August 2011

The advantages of using image‐intensifiers and other image pickup systems as an aid to the observation of the image in the electron microscope have been known for many years, and a review of a number of the systems employed so far is presented here. The additional advantages to be gained by the use of a sensitive TV pickup tube in conjunction with a storage tube are discussed, with particular reference to a proposed system for use with a high voltage, high resolution, electron microscope. It is shown that the prime limitation to the signal‐to‐noise ratio obtainable in the image pickup‐display chain is due to the noise in the electron microscope signal itself, and that with the proposed pickup and storage tube arrangement a field of 800 by 600 picture points, with adequate signal‐to‐noise ratio, should be obtainable for a current density of 10−9 A/m2 in the image plane of the microscope if an integration period of about 3 s is used.
An observation on the metallizing of specimens for scanning electron microscopy using cathode sputtering
Authors: Simmens S. C.
Published: August 2011

Abnormal metallizing behaviour, occasionally observed during the cathode sputtering of gold onto specimens for scanning electron microscopy, is explained in terms of the decomposition of hydrocarbon vapour.
The effect of variations in objective focal length on electron microscope performance
Authors: Lovell D. J. , Chapman S. K.
Published: August 2011

Standard specimens were examined in a transmission electron microscope with a top entry stage. Using a range of objective focal lengths, measurements of contrast, resolution and magnification range were made. Focal lengths up to 14 mm were examined. The contrast was found to increase with increasing focal length, being twelve and a half times greater at 14 mm focal length than at the normal high resolution mode of 2 mm focal length. Resolution, determined by the fresnel fringe method decreased from 0·3 nm to 3·5 nm. The photographic image magnification was reduced from × 1000– × 500,000 at 2 mm focal length to ×100‐× 50,000 at 14 mm focal length.
A distortion‐free map for use with electron channelling patterns
Authors: Stott D. E. , Wise M. L. H. , Hutchinson W. B.
Published: August 2011

It is shown that by making a map of channelling patterns on the surface of a sphere, the long range distortions inevitably present in planar maps can be avoided. The construction and use of the map is described.
A simple technique for the rapid preparation of freeze‐fracture replicas of plant nuclei
Authors: Severs N. J. , Jordan E. G.
Published: August 2011

A rapid method of extracting nuclei in high yield from small quantities of plant material, for freeze‐fracture studies is described. The nuclei are gently isolated directly into buffered glutaraldehyde which ensures good preservation of ultrastructure. Removal of the cell wall allows rapid glycerination of the specimen and faster cleaning of the replica.
A container for handling small specimens during preparation and examination in the scanning electron microscope (SEM)
Authors: Taylor Peter G.
Published: August 2011

The difficulties of handling small specimens of < 1 mm3 are considerably reduced when the specimens are placed in a small container designed to be compatible with the dimensions of the preparatory instrumentation and of the microscope. The container described is unaffected by solvents used in the preparation of specimens for scanning electron microscopy.
Single atom image contrast: conventional dark‐field and bright‐field electron microscopy
Authors: Chiu Wah , Glaeser Robert M.
Published: August 2011

Single atom image intensities are calculated for bright‐field and various dark‐field modes, including the ideal beam stop, a wire beam stop, tilted illumination and a displaced aperture. Comparisons of scattering amplitudes and elastic scattering cross‐sections are made with different object potentials and scattering formulations. The image contrast for one mercury atom (Z = 80) on a column of carbon atoms (Z = 6) as the substrate is also discussed for both the bright‐field and the various dark‐field situations. A list of abbreviations to be used in the text is shown below.
A wet stage modification to a scanning electron microscope
Authors: Robinson V. N. E.
Published: August 2011

A modification to the vacuum system of a JSM2 scanning electron microscope has enabled hydrated specimens to be placed inside the specimen chamber of the instrument and to be surrounded by water vapour at a pressure up to approximately 1.3 kPa (10 Torr). The surface topography was observed by detecting the backscattered electrons using a wide angle backscattered electron detector placed close to the specimen. The microscope was operated in the normal scanning mode which allowed the examination of the surface topography of the specimens, whilst still retaining the depth of focus which is a feature of the SEM.

This modification has enabled a resolution of approximately 0.2 μm to be obtained from biological specimens partially immersed in water at temperatures just above 0°C.
Photographic aspects of scanning electron microscopy
Authors: Malin D. F.
Published: August 2011

Factors governing photographic image quality in the scanning electron microscope are discussed with particular reference to the commonly used EXA camera on the Cambridge Stereoscan IIa. It is shown that the small image on the medium speed film suffers considerable loss of information due to the turbid nature of the photographic emulsion. Inexpensive modifications to the oscilloscope camera supplied with the Stereoscan are described which enable the superior quality of a larger format to be utilized. Appropriate settings of the brightness and contrast controls of the image tube with respect to the photographic system is discussed and the results illustrated in a series of micrographs.
Preparation of nematodes for scanning electron microscopy
Authors: Green C. D. , Stone A. R. , Turner R. H. , Clark S. A.
Published: August 2011

Nematodes from the orders Tylenchida and Rhabditida were fixed and processed in several different ways for examination with the scanning electron microscope (SEM). Four processes produced good preparations of fixed nematodes. Drying from acetone was the simplest of these techniques and most useful for regions of the tylenchid nematodes supported by skeletal tissue. Critical point drying, a more complicated procedure, gave good preparations but they required special care in processing. Nematodes infiltrated with glycerol and a conducting agent were the most life‐like but were difficult to examine. Specimens infiltrated with an epoxy resin looked natural and this was the most promising process tried.
Contrast enhancement by changing the objective lens focal length
Authors: Misell D. L.
Published: August 2011

Recent experimental results on the variation of resolution and contrast of electron microscope images with objective lens focal length are compared with theory. Whereas there is agreement between theory and experiment for the normal range of focal lengths (2–6 mm), the experimental results indicate a far higher image contrast and inferior image resolution than predicted by theory for a very long focal length objective (12–14 mm).
Preparation of cultured cells for SEM: air drying from organic solvents
Authors: Albrecht R. M. , Rasmussen D. H. , Keller C. S. , Hinsdill R. D.
Published: August 2011

Air evaporation from organic solvents of differing polarities and surface free energies was used in the preparation of cultured murine peritoneal macrophages for scanning electron microscopy (SEM). The surface structural features of these cells were compared to the surfaces of similar cells prepared by the critical‐point procedure. In general, all organic solvents produced a marked collapse of cell structure resulting in an increase in surface irregularity. Fracture surfaces and sharply defined contours including numerous flaps and ridges were characteristic of the non‐polar solvent dehydrated samples. Polar solvent dehydrated samples, including those dried from solvents of low surface free energy, exhibited a secondary flowing and settling of the cell membrane. Primary collapse was apparent but cell contours were smoothed and rounded. Overall cell shape and cell‐to‐cell relationships were retained regardless of solvent type.

It is suggested that solvent evaporation may prove useful in certain cases, though investigators are advised to use caution when interpreting the results obtained by such procedures.
An aid to understanding differential interference contrast microscopy: computer simulation
Authors: Galbraith W. , David G. B.
Published: August 2011

Differential interference contrast (DIC) microscopy has been widely used for many years. However, many biologists employ DIC inefficiently and frequently misinterpret the resulting images. In an effort to improve the standard of use, a method of simulating DIC microscopy on the cathode‐ray tube (CRT) and x–y plotter of a computer was therefore developed. This paper describes the program and gives examples of its application, emphasizing some common errors of operation of the DIC microscope and interpretation of the image.

Simulations are made for objects of negligible thickness, and in one azimuth of the microscope at a time. The method shows clearly the profiles of the phases and amplitudes of the interfering waves obtained for a variety of objects and demonstrates unequivocally the kinds of images obtained. It is possible to show very quickly how the image changes as instrumental parameters, such as phase‐bias, amplitude‐ratio, extinction factor, and beam‐splitter shear are altered.

Simulation was found useful as a tool to learn DICM and as an aid to the interpretation of complicated images obtained with real objects. Examples of common errors in adjusting the microscope and interpreting images are given in this paper.

The simulation program was developed for the computer of the Denver Universal Microspectroradiometer (David & Galbraith, 1975; Galbraith et al., 1975), but it can be used on a number of compatible computing systems. The program construction is explained to enable comparable programs to be written for different computers.
The nature of defocus fringes in scanning‐transmission electron microscope images
Authors: Joy David C. , Maher Dennis M. , Cullis Anthony G.
Published: August 2011

Experimental observations have been made of the fringe contrast which appears at the terminating edges of thin objects in defocused, scanning‐transmission electron micrographs. In general only a single bright fringe is present and the displacement and width of this fringe was found to vary linearly with defocus, indicating the contrast does not result from simple‐Fresnel diffraction. A model for this contrast, based on the refraction of incident electrons by the object edge, is shown to explain the observed results.
Wholebody autoradiography: a β‐radioluminescence method for detecting tritium
Authors: Farebrother D. A. , Creasy Dianne M.
Published: August 2011

A method of increasing the sensitivity of X‐ray film for the wholebody autoradiography of tritiated compounds is described. Thirty micrometre sections are sprayed with a scintillator, Diphenyl oxazole (PPO) and exposed to light sensitive (screen) X‐ray film at −70°C. The method permits a substantial reduction in the required dose of tritium and of the period of exposure of tissue sections.
Two‐Shockley unfaulting of two‐ and three‐layer faulted defects
Authors: Ronander E. , Kritzinger S.
Published: August 2011

The principles of butterfiy‐unfaulting of Frank dislocation loops, i.e. unfaulting by the simultaneous action of two Shockley partial dislocations (Swart & Kritzinger, 1974a), are applied to two‐layer faulted defects in thin foils of quenched aluminium to explain the structure and contrast behaviour of some dislocation configurations observed by transmission electron microscopy. Direct electron microscope evidence is presented for the butterfiy‐unfaulting of three‐layer faulted defects in the same specimens. Positive evidence is furnished that Shockley partial dislocations can be nucleated at sites in the stacking fault other than the hexagon corners of the defects.
A standard field area frame for use in automatic image analysis
Authors: Alston R. L. , Stanbridge L.
Published: August 2011

Thin, copper electroformed microcomponents have been used to provide standard field area frames for comparative cell counting techniques using automatic image analysis. The design of the frames and the technique for using them is outlined.
Methods for the measurement of polarization optical properties: I. Birefringence
Authors: Taylor D. Lansing , Zeh Robert M.
Published: August 2011

A simple birefringence detection system has been developed that can be used with any standard polarizing microscope. A Foster prism is utilized in separating the orthogonal components of the resultant linearly polarized light coming from a properly oriented λ/4 plate. The light intensities of the orthogonal components are measured simultaneously and a mathematical manipulation yields a direct read‐out of phase retardation (nm). The theory and practical use of this technique is discussed, as well as the present and future applications.
Modes of chromatin packing in Feulgen‐stained normal and malignant uro‐epithelial cell nuclei, and in lymphocytes, in relation to DNA content
Authors: Boss J. M. N. , Feneley R. C. L. , Mays R. G. W.
Published: August 2011

By a two‐step method of histogram densitometry it was found that the inhomogeneity of distribution of chromatin within a nucleus was similar in normal and malignant human bladder epithelium and in lymphocytes, despite the grossly abnormal range of DNA content of the carcinoma nuclei.
Modifications to an LKB Pyramitome
Authors: Dingemans K. P. , Lettinga K. P.
Published: August 2011

Modifications to an LKB Pyramitome and Target Marker are described which considerably increase both the accuracy and speed when preselected areas are trimmed out from larger tissue blocks. The modifications include: (a) a better viewing system which facilitates the movement of the specimen and the knife with respect to each other; (b) a movable light source which makes it possible to obtain a reflection image of the front face of the block in which many structural details are visible; (c) the possibility of introducing to the Target Marker system polaroid micrographs of light microscopic sections rather than the sections themselves. On the micrographs, the selected area and other desired features of the section can easily and clearly be marked; (d) a selected area marker with which the area to be trimmed out can be marked mechanically on the block with great accuracy; (e) various modifications to knobs, controls, etc., all aimed at higher speed and accuracy and greater convenience for the user. Whereas its basic working principles have remained unchanged, the modified instrument is much better suited for routinely executed high‐precision work than the original version.
A technique for electron microscope autoradiography (and X‐ray microanalysis) of diffusible substances using freeze‐dried fresh frozen sections
Authors: Baker J. R. J. , Appleton T. C.
Published: August 2011

Several attempts have been made over the past few years to localize diffusible radioactive substances in tissues at the electron microscope level. The procedures employed hitherto have involved one or more aspects of the methods used in tissue preparation for conventional electron microscopy and as such are unlikely to be universally applicable for all classes of diffusible substance. The present paper shows that the use of ultrathin frozen sections of fresh unembedded biological material permits the ultrastructural localization by autoradiography and X‐ray microanalysis of highly soluble electrolytes.
Problems associated with particulate contamination of cell cultures with relation to ultra‐thin sectioning techniques
Authors: Smith K. , Luther P. D.
Published: August 2011

Hard foreign particles encountered in centrifuged pellets of cell cultures and other biological material can interfere with ultra‐thin sectioning. Factors which influence the presence of this contamination are considered and a technique is recommended for cell cultures which overcomes these difficulties.
A resin slide technique to select fixed embedded cells for transmission electron microscopy
Authors: Sigee D. C.
Published: August 2011

A simple technique is described to resection, for electron microscopy, 2–6 μm sections that have been observed under the light microscope. The technique can be used to select cells on the basis of light microscope ultrastructure, histochemistry and autoradiography prior to electron microscopy.
Making fusible metal casts of previously fixed lung material
Authors: Boyd R. B. , Coalson R. E.
Published: August 2011

A technique has been developed which will permit fusible metal (Wood's metal) casts to be made of lung tissue previously fixed by formalin inflation.
An improved method for photographing fluorescent human chromosomes*
Authors: Verma Ram S. , Dosik Harvey
Published: August 2011

In the photography of sequentially QFQ and RFA banded chromosomes, the fading problem can be solved by reducing exposure time. This can be accomplished by choosing the right light source, filter combinations, type of film and developer. Three different systems were employed to record the exposure time during photography. A ‘Vertical Illuminator III RS’ with a 50 w/AC mercury burner equipped with 400–490, BG 12–BG 38 excitation filters and 510 barrier filter was found to be the most efficient and satisfactory. QFQ banded chromosomes can be photographed within 3–5 s and RFA banded chromosomes within 10–15 s with this system.
Image processing of electron micrographs of deformed filaments
Authors: Fraser R. D. B. , MacRae T. P. , Suzuki E. , Davey C. L.
Published: August 2011

Electron micrographs of filaments are frequently unsuitable for image processing because they are not perfectly straight. Even minor departures from straightness result in appreciable deterioration of the Fourier transform and analysis of periodicities and subsequent image processing becomes difficult. A procedure is described for recovering the projection of a straight filament from that of an imperfectly straight filament.
Correction of stereological parameters from biased samples on nucleated particle phases
Authors: Orive Luis‐M. Cruz
Published: August 2011

Stereologists are aware that the experimental evaluation of component volume fractions and surface‐to‐volume ratios are subject to systematic errors whenever the requirements for cell identification impose the necessity for component‐biased sectioning. Mathematical corrections of biased volume proportion data have recently been published; these corrections assume that the components under analysis are spherical, and that the nucleated particle phase is monodispersed.

In this report, general methods for obtaining corrections of biased nuclear volume fraction data are set out for polydispersed phases of nucleated particles, in terms of the relevant shapes and joint size distribution of nucleus and cell; the scope and limitations of these methods are thereby discussed.

Explicit corrections of an immediate applicability are obtained, together with their standard errors, for monodispersed phases where nucleus and cell are two dissimilar biaxial ellipsoids (spheroids). When nucleus and cell are two concentric and similar convex bodies of a certain class—to which triaxial ellipsoids belong—the corrections are shown to be very simple.

The corrections for the spheroid–spheroid systems are easily accessible with the aid of a small programmable calculator, whereas those for the sphere–spheroid models are directly obtainable from two nomograms.
Correction of stereological parameters from biased samples on nucleated particle phases
Authors: Orive Luis‐M. Cruz
Published: August 2011

General formulations for correcting component‐biased S/V estimates on poly‐dispersed phases of nucleated particles are set out. Direct application of these corrections to monodispersed phases where nucleus and cell are spheroids, yield explicit corrections. As a rule, the corrected specific surface area of the containing bodies equals the product of the nuclear‐biased estimate times a correction coefficient, which is bigger than one, and depends upon the shape of the components and the relative volume of nucleus‐in‐cell. Reference curves which allow a rapid obtention of the correction factor, are provided.

Simple formulae for correcting biased surface density and surface‐to‐volume ratio estimates other than the specific surface area, are also given, together with the standard errors of the corrected parameters.
A programmable flying‐spot microscope and picture preprocessor
Authors: Eccles M. J. , McCarthy B. D. , Proffitt D. , Rosen D.
Published: August 2011

A description is given of a system comprising a general purpose computer (PDP‐8E) and a special purpose computer controlling a flying‐spot microscope. Under program control, the system extracts data from a field of view on the microscope slide. Various operating features of the system are detailed and a general account is given of its design and construction. Experience of using the system is briefly discussed.
The spatial and grey‐level resolution of flying‐spot microscopes
Authors: Eccles M. J. , McCarthy B. D. , Proffitt D. , Rosen D.
Published: August 2011

An analysis is presented of the optimum number of points per line at which a flying‐spot microscope might work when used in a digital mode, and also of the maximum number of levels of light intensity which may be detected at any one point. In actual instruments, the parameters which appear in the resulting formulae will be determined by engineering considerations. In a practical case used as illustration, the upper limits are 563 points per line and eighty intensity levels at maximum microscope magnification (× 1200).
Compensator transducer increases ease, accuracy, and rapidity of measuring changes in specimen birefringence with polarization microscopy
Authors: Salmon E. D. , Ellis G. W.
Published: August 2011

An instrument has been designed to improve substantially the efficiency and convenience of measuring specimen birefringence retardation (BR) with a conventional Brace‐Köhler compensator. The design is based on the precise transduction of the angular position of the compensator's vernier dial to an easily visible red‐illuminated display on a digital voltmeter. The instrument display is accurate to within 0.1° over a range of ± 25° in the compensator vernier dial position which is similar to the precision obtainable with an ordinary vernier and the Brace‐Köhler method of measuring BR of biological specimens. For convenience in data reduction the display can also be read directly in nanometre units, with a similar precision for specimen BR in the range of 5 nm or less which is typical of birefringent fine structures in living cells.
Goethe's four microscopes in Weimar
Authors: Otto Ludwig
Published: August 2011

Four microscopes that belonged to Johann Wolfgang von Goethe (1749–1832) are preserved in the instrument collection of the Goethe‐Haus, Weimar, D.D.R.; these are described and illustrated. The four instruments are: a simple and compound microscope by George Adams Sr, a compound microscope by L. F. Dellebarre, an unsigned solar microscope, and a universal microscope after W. F. von Gleichen‐Russworm.
EM autoradiography of non‐sectioned biological material
Authors: Haworth R. A. , Chapman J. A.
Published: August 2011

Methods of EM autoradiography suitable for the study of non‐sectioned biological material deposited on a support film from suspension are described. The methods, which include modified procedures for specimen support and emulsion preparation, may also have advantages for the study of any specimen where physical separation of specimen and emulsion is desirable.

In a study of the growth of 125I‐labelled collagen fibrils reconstituted from solution in vitro, these procedures have allowed the production of EM autoradiographs which show a high resolution and are free from stress artefacts and chemography.
High‐resolution autoradiography as a tool for the localization of nucleic acid synthesis and distribution in the mammalian cell nucleus
Authors: Fakan Stanislav
Published: August 2011

Several examples of the application of high resolution autoradiography to the study of nucleic acid distribution in ultrathin sections of fixed and plastic embedded or frozen material are presented.

Newly‐synthesized DNA, labelled by very short pulses of 3H‐thymidine is found to be localized throughout the nucleus.

In the blastomeres of early mouse embryos developing after fertilization by 3H‐thymidine‐labelled spermatozoa, the labelled paternal DNA is distributed non‐homogeneously in the nucleus.

Finally some results obtained by using a cytochemical enzymatic technique for visualization of DNA directly in ultrathin sections of fixed and embedded cells are demonstrated.

Concerning the distribution of RNA, perichromatin localization of rapidly transcribed RNA is described in different cell systems. This label can be attributed to perichromatin fibrils. In cells labelled for longer periods of time, sometimes followed by prolonged postincubations, a residual label is always found over the nucleus. Clusters of interchromatin granules are usually only weakly labelled or unlabelled. These structures probably contain a limited amount of rather slowly labelled RNA.

The present results are discussed in the context of some biochemical evidence and of the data described by other investigators.
Proliferative characteristics of epithelial cells in the pregnant rat uterus
Authors: Peel Sandra , Liddiard Barbara
Published: August 2011

In the pregnant rat, killed at about mid gestation and 1 h after injection of tritiated thymidine, 40% of the cells in the epithelium lining the uterine lumen at the implantation site were labelled. Between implantation sites fewer than 20% of the surface epithelial cells were labelled. A series of rats was given tritiated thymidine on day 12 of pregnancy and killed at intervals in the next 30 h. A percentage labelled mitoses analysis of the epithelium between implantation sites (interconceptual) and within the implantation site (conceptual) showed that cells in either region spent 7 h in DNA synthesis and 1.5 h in the G2 + ½ mitosis phases. The epithelial cells in the conceptual region spent 1.5 h in the G1 + ½ mitosis phases whereas cells in interconceptual regions spent at least 11.5 h in these phases. The average cycle times of cells in conceptual regions was 10 h: in interconceptual regions minimum cycle time was 20 h and the average appeared to be considerably longer. The grain count of the epithelial cells in the conceptual region was rapidly reduced during the 30 h after injection of tritiated thymidine suggesting successive rounds of cell division. In contrast the grain count distribution of cells in interconceptual regions changed only slowly during this time. The percentage of labelled epithelial cells was determined in the animals killed up to 30 h after injection of tritiated thymidine. In both conceptual and interconceptual regions these percentages increased initially as labelled cells produced labelled progeny. In the conceptual region the increase was not maintained after 7 h as cells initially in G1 divided to give unlabelled progeny. In the interconceptual region the increase in the percentage of labelled cells continued for 14 h; thereafter the percentage did not significantly alter.

The interpretation of these results is discussed in relation to the differences in the kinetic characteristics of the epithelial cells in the two regions and in relation to the morphology of the epithelium lining the uterus during pregnancy.
A copper block method for freezing non‐cryoprotected tissue to produce ice‐crystal‐free regions for electron microscopy
Authors: Dempsey G. P. , Bullivant S.
Published: August 2011

A wide variety of plant and animal tissues were prepared for electron microscopy by freeze‐substitution, after rapid freezing on a liquid nitrogen cooled copper block by the van Harreveld method. Measurements were made of ice crystal size versus depth in tissues that had not been treated with any cryoprotectants. Ice crystal size increased exponentially with depth. It was confirmed that a narrow surface band (approximately 12 μm) was frozen sufficiently rapidly to prevent the formation of electron microscopically‐visible ice crystals.
Multiple‐Shockley unfaulting of single‐layer faulted defects
Authors: Ronander E. , Kritzinger S.
Published: August 2011

The general principles laid down by Swart & Kritzinger (1974a) in a paper dealing with the unfaulting of Frank dislocation loops by the simultaneous action of two shearing Shockley dislocations are applied to explain the structure and electron diffraction contrast behaviour of certain complex single‐layer dislocation configurations observed in quenched aluminium and dilute Al‐Mg alloys. In these cases the simultaneous operation of three Shockley dislocations is employed. It is also demonstrated that adequate stresses, such as those encountered during annealing at temperatures ∼150°C, serve to transform butterfly hexagons to normal hexagonal prismatic dislocation loops, confirming the expectation that the butterfly defects are in a metastable state.
A method for preparing absolute standards for quantitative calibration and measurement of section thickness with X‐ray microanalysis of biological ultrathin specimens in EMMA
Authors: Chandler J. A.
Published: August 2011

Specimen thickness is determined using X‐ray microanalysis in conjunction with atomic absorption spectrophotometry. Specimens of evaporated metal films and standards comprising fixed concentrations of elements (such as potassium) in organic media are used to determine elemental concentrations of endogenous elements in embedding resin, from which section thickness can also be determined. The method finally depends only on the single measurement of X‐ray emission of such an element in the specimen. Calibration of the X‐ray detector over the energy range with mineral salts enables the standard to be used for the quantitative analysis of any element under investigation.
A simple method to measure resolution on micrographs
Authors: Dubochet Jacques
Published: August 2011

A method for rapid measurement of the resolution of a microscope by finding the smallest distance between pairs of points that appear on two successive micrographs is described. The method based on the visualization of moiré pattern gives the same result as other tests with a precision sufficient for routine checks. Neither a special instrument nor time consuming training are required.
Low temperature preparation of pteridophyte spores and sporangia for SEM
Authors: Spicer R. A. , Sengupta S. , Phillips L.
Published: August 2011

Low temperature fracturing of spores and sporangia followed by freeze‐drying has enabled detailed observations to be made of developing spores within the sporangia as well as of the internal features of spores.
Observations on the production of frozen‐dried thin sections for electron microscopy using unfixed fresh liver, fast‐frozen without cryoprotectants
Authors: Spriggs T. L. B. , Wynne‐Evans Daphne
Published: August 2011

Thin sections of unfixed liver, fast‐frozen without cryoprotectants, have been cut using conditions under which momentary thawing of the sections is unlikely to occur. A transfer stage which facilitates this procedure is described. Sections show hole damage probably due to ice‐crystal formation during the freezing process and have well defined edges, but despite hole damage, some morphological features of the cell are discernible. Presumptive mitochondria appear smaller in frozen sections than in conventional Araldite sections. Sections devoid of hole damage have indistinct edges and are presumed to have undergone transient thawing. Carbon coating of freeze‐dried sections to exclude atmospheric moisture during transference of sections to the electron microscope (EM) appear unnecessary as regards preservation of morphological structure. The results are discussed in relation to the limitations of the method and the potential value of the technique.
A study of the structure of reverse osmosis membranes by means of the scanning electron microscope
Authors: Mossa G.
Published: August 2011

Reverse osmosis, or hyperfiltration, is a desalination process that uses membranes through which brackish or sea water is passed under pressure. The desalination properties of the cellulose acetate reverse‐osmosis membranes are due to their particular structure.

A study was made of the structure of the Loeb‐Sourirajan type cellulose acetate membranes by means of the scanning electron microscope (SEM). The specimens were prepared as follows: the samples were freeze‐dried and then fractured by applying a bending stress at liquid nitrogen temperature.

Different results were obtained depending on which of the two surfaces of the membrane had been subject to bending stress. The scanning micrographs of membrane cross‐sections confirmed (Gittens et al., 1973), a three‐layer structure of the membranes: a first dense layer which is responsible for desalination, a second layer, and a porous sub‐layer which is a very good natural support for the dense one. The asymmetric morphology of the membrane was correlated with its particular transport properties. A study was also made of the influence that the conditions of preparation exerted on the structure of cellulose acetate asymmetric membranes; the micrographs confirmed that the evaporation step has a marked effect on the membrane morphology. The technique has been extended to observe the recently perfected, anisotropic polyamide membranes.
Atomic number intensity profiles in the scanning electron microscope—gold and aluminium
Authors: Robinson V. N. E. , George E. P.
Published: August 2011

Monte Carlo computations were used to calculate the backscattered and secondary electron intensity profiles associated with a gold slice and gold cube in an aluminium matrix. The gold slice in an aluminium matrix was produced experimentally and the theoretical profiles show good agreement with the experimental profiles.
An efficient spectroscopic detection system for cathodoluminescence mode scanning electron microscopy (SEM)
Authors: Steyn J. B. , Giles† P. , Holt D. B.
Published: August 2011

A detection system for analytical cathodoluminescence (CL) mode scanning electron microscopy (SEM) is described. This incorporates a cold stage, an efficient light collector, a monochromator and a photomultiplier and used the photon counting technique. The efficiency of the component subsystems was optimized and calibrated, and the performance of alternative light collecting and monochromating equipment is compared. The operation of the photon counter is discussed. The digital output of the photon counter was fed into a multichannel scaler and thence to a computer. This was used to correct the observed count rate with the calibrated spectral variations in the performance of the detection system.

Spectra obtained at both room temperature and liquid nitrogen temperacure and monochromatic and panchromatic SEM micrographs are given as examples illustrating the value of this technique.

The factors governing the performance of the system are discussed. The forms of noise in the signal and in the detection system are described and the means for minimizing, avoiding or correcting for them are dealt with. Sources of spurious signals in the SEM are treated.
Form and distribution of actin and myosin in non‐muscle cells: A study using cultured chick embryo fibroblasts
Authors: Buckley I. K. , Raju T. R.
Published: August 2011

Attempting to throw light on the mechanical basis of movement of non‐muscle (cf. muscle) cells, the present work aims to determine the form and distribution of actin and myosin in chick embryo fibroblasts. These cells were cultured on formvar, fixed in glutaraldehyde then osmium tetroxide vapours, dehydrated, critical‐point dried and examined, in tow, in the electron microscope (EM). Stereoscopic pairs of micrographs were studied to define more exactly the form and distribution of cytoplasmic filaments topographically associated with deformations of the cell surface and with organelle movements through the cytoplasm. Permeating the cytoplasm, interconnecting long and short filaments closely surrounded all organelles, linked with microtubules and polyribosomes and joined to the plasma membrane. These filaments, which varied greatly in width (2–13 nm) were closely associated with large numbers of ‘comma‐shaped’ globoid bodies of ∼15 nm diameter. Attempting to establish the identity, form and distribution of cytoplasmic myosin, cultured cells were extracted with a cold (4°C) glycerol/pyrophosphate solution for 24 h before being fixed and critical‐point dried. EM examination of these cells revealed a residual three‐dimensional network of branching and anastomosing 4–13 nm diameter smooth filaments, devoid of fine (2 nm) filaments and globoid bodies. Examination of fixed, critical‐point dried, skeletal muscle heavy meromyosin showed globoid structures similar in form and size to the globoid bodies found in cultured fibroblasts. Similarly fixed and critical‐point dried paracrystals of actin, polymerized in the presence of Mg2+, appeared as branching interconnecting filaments which, in form and dimensions, resembled the network filaments observed in pyrophosphate‐extracted cells. It is concluded that the pyrophosphate‐extractable globoid bodies found in cultured fibroblasts represent monomers of myosin, that the broader filaments to which these attach represent actin in Mg2+ paracrystalline form and that the various subcellular movements are brought about by interactions between the two, analogous to those occurring in muscle cells.
Field‐ion microscopy of segregation to planar imperfections
Authors: Howell P. R. , Fleet D. E. , Hildon A. , Ralph B.
Published: August 2011

This paper investigates the segregation of solute to planar imperfections using field‐ion microscopy. Two major systems have been analysed, namely the segregation of chromium to grain boundaries in a tungsten‐chromium alloy, and the segregation of niobium to stacking faults in a cobalt‐niobium alloy.

In both cases, the solute distributions within the planar faults were quantitatively analysed, and a strong tendency towards clustering of the niobium solute within the stacking faults of the cobalt alloy was observed.
Examining water trees in polythene using a flexible light source
Authors: Fursey Anita
Published: August 2011

A battery powered flexible surgical light can be used as an inexpensive light source for transmission microscopy through 2 mm thick walls of polythene cups, where it is not possible to use a conventional condenser. With ASA 400 film photographic exposure times are 5–10 s. The illuminator has been used to study water trees in polythene.
Peculiar artefacts after fixation with glutaraldehyde and osmium tetroxide
Authors: Kuthy Enikö , Csapó Zsolt
Published: August 2011

Peculiar electron dense granules were observed, in otherwise well preserved structures of the heart muscle and kidney of the rat after a 5–10 min perfusion, a 2 h fixation in the modified Karnovsky solution, followed by a postfixation in Millonig buffer containing 1% OsO4. The granules appeared most frequently on membranes, the surface of the red blood cells and in pinocytotic vacuoles, in stained and unstained sections alike. No artefacts were produced when the same buffer was used for both pre‐ and postfixation, or when the postfixative contained Veronal buffer.
Stereology of parallel, straight, circular cylinders
Authors: Elias Hans
Published: August 2011

New stereological formulae are developed to quantify an array of straight, parallel, circular cylinders. The problem arose through the necessity to determine the average length and surface density of the crypts of the large intestine. These crypts or glands have the shape of test tubes.
Improved specimen lighting in ultramicrotomy by painting reflective surfaces on specimen blocks
Authors: Mollenhauer Hilton H.
Published: August 2011

Specimen lighting for ultramicrotomy can be improved by painting reflective surfaces on the ends of the specimen blocks. A convenient paint for this purpose is the white correction fluid commonly used by secretaries to cover typing errors.
The presentation of three‐dimensional reconstructions from serial sections
Authors: Jordan E. G. , Saunders A. M.
Published: August 2011

A simple and effective way is described for showing particular structures in serial sections. By using waterproof inks and acetate sheets supported on a frame immersed in water and illuminated from beneath, the information from up to sixty sections can be easily visualized. This technique is particularly useful for displaying enclosed structures and by a suitable choice of colours enables special emphasis to be given to selected components. The information can be recorded simply through stereo photography.
Estimating aggregate and overall characteristics from thick sections by transmission microscopy
Authors: Miles R. E.
Published: August 2011

The random spatial structure considered is the union X of an aggregate of random opaque convex particles in transparent space, the particle centroids being sited at the points of a homogeneous Poisson process. The model is thus the union of an aggregate of non‐necessarily‐convex disjoint regions. Expressions are derived for the fundamental stereological quantities VV, SV, KV (integrated mean curvature density) and GV (integrated gaussian curvature density) for X; and for AA, LA and CA (integrated curvature density) for the projection of a slice of thickness t of this model onto a plane parallel to the slice, where t may take any non‐negative value. The estimates relevant to transmission microscopy suggested by this theory are presented.
Recognition and classification of structure by means of stereological methods in neurobiology
Authors: Bernroider Gustav
Published: August 2011

The problem of measuring fine structure of individual particles without losing information on largescale characteristics of particle arrangement is discussed. With the help of stereological and pattern recognition methods a possible solution of this important problem is introduced. The domain specimen for which the brain serves as an example is characterized by two main properties. One of them being the position dependent ‘aggregate characteristics’ (distribution of neurons within the specimen), the other position invariant ‘single cell characteristics’ (structural properties of single neurons). It is shown that by simultaneous observation both properties together cannot be detected with sufficient accuracy by conventional methods. This is the decisive problem of ‘correlation microscopy’. The method described in this paper is based on selection of the most informative variables and selection of subdomains (e.g. sections and reference planes). This results in a very general probabilistic concept in modern stereology, offering solutions to complex structure classification problems in biology.
Quantitative characterization of wood microstructure
Authors: Steele James H. , Ifju Geza , Johnson Jay A.
Published: August 2011

Stereological countings were applied to transverse sections of closely related and widely different species of hardwoods for quantitative characterization. Anatomical elements, such as the wall and lumen of vessels, fibres, and ray cells, were distinguished. Volume fraction, average size, average spacing, aspect ratios for oriented features, and size distribution parameters were then calculated. Sampling fields were strategically and systematically located within growth rings for characterization of the spatial distribution of the anatomical elements.

Initially five species: paper birch, yellow birch, sugar maple, aspen, and sassafras cross‐sections were subjected to quantitative stereological analysis. The two birch species were anatomically very similar, and somewhat similar to the sugar maple. Sassafras was very different in structure from the other three species studied. Aspen was typical diffuse‐porous wood.

The initial results were promising, and revealed certain subtle distribution patterns never before recognized. Second, all species including those which were very similar, were recognized by quantitative expression of their structural elements. Third, the method provided quantitative descriptions of the structural characteristics. It is expected that stereological analysis of wood structure will be used for prediction of properties and utilization potentials of the various species, as well as for their identification.
Ultrastructural effects of performic acid oxidation of epoxy‐embedded tissue with and without early uranyl staining
Authors: Heath Everett
Published: August 2011

Epoxy‐embedded blocks of glutaradehyde and OsO4 fixed adenohypophyseal tissue were immersed in performic acid, rinsed and sectioned for electron microscopy. Sections exhibited a general image intensity equivalent to control sections but their stainability with both uranyl acetate and lead citrate stains was increased. It was concluded that osmium was not removed by performic acid oxidation.

Membranes of endoplasmic reticulum and the Golgi apparatus were not visible, and other components (acidophil granules, in particular) were markedly distorted in shape after oxidation. Such changes, however, were not evident in specimens previously exposed to uranyl acetate during ethanol dehydration.
Using simultaneous three colour X‐ray mapping and digital‐scan‐stop for rapid elemental characterization of coal combustion by‐products
Authors: Pawley James B. , Fisher Gerald L.
Published: August 2011

A system is described for rapid, simultaneous three colour elemental mapping with a scanning electron microscope (SEM) and an energy dispersive X‐ray analyser. The technique, which uses a SEM scanning at TV rate, minimizes the disadvantages of long scan times such as inefficient use of linear amplifier and observable dead‐time shadowing. The system also employs a digital scan‐stop assembly utilizing a light pen to rapidly and reproducibly direct the beam to an object of choice for spot‐mode analysis. Application of the system to analysis of fine particulates with emphasis on fly ash derived from coal‐fired electric power plants is discussed. Chemical heterogeneity of fine particles in standard reference material fly ash and in phagocytized fly ash within pulmonary macrophages is demonstrated.

This system combines the morphologic capability of the SEM with X‐ray multielement mapping to provide a needed tool for particulate source identification.
Reduction of background due to backscattered electrons in energy‐dispersive X‐ray microanalysis
Authors: Hall T. A.
Published: August 2011

When energy‐dispersive X‐ray microanalysis is practised in a scanning electron microscope, most of the spectral background may come from electrons entering the detector. This background can be eliminated by deflecting magnets. Alternatively, the electrons can be blocked by a plastic film but only at the cost of suppression of the low‐energy end of the X‐ray spectrum.