bluuebunny/crossref_metadata_2025_split huggingface dataset:
Limitations in the X‐ray microanalysis of thin foils in a scanning transmission electron microscope
Authors: Doig P. , Flewitt P. E. J. 
Published: August 2011

SUMMARYThe X‐ray microanalysis of thin foils has been investigated using a scanning transmission electron microscope fitted with an energy dispersive spectrometer. Thin foils prepared from an iron‐nickel and an aluminium‐zinc‐magnesium‐copper alloy have been observed and analysed. For foil thicknesses between 200 and 300 nm the X‐ray intenstiy ratios are consistent with X‐ray absorption characteristics. For regions less than 200 nm thickness the measured intensity ratios increase by up to a factor of 5. These results have been explained in terms of a solute enriched or depleted surface layer developed during the preparation procedure.
Freeze‐fracturing of monolayers (capillary layers) of cells, membranes and viruses: some technical considerations
Authors: Nermut M. V. , Williams Lynn D. 
Published: August 2011

SUMMARYA novel hinged device for freeze‐fracturing of cell monolayers in the Balzers freeze‐etch unit is described. It is economical on biological material and enables oriented adsorption of sheet‐like membrane fragments.For freeze‐fracturing ‘by hand’ a monolayer is formed on a positively charged piece of mica (with polylysine) and this is covered with another piece of mica, thin brass plate or filter paper. Such a sandwich is frozen in liquid nitrogen and fractured by means of forceps. Several modifications of this technique as well as practical examples are described. Among possible applications are: negative staining of intramembranous protein particles; chemical or physical analyses of single membrane leaflets; identification of protein complexes by immunoelectron microscopy, etc.
Semiconductor material assessment by scanning electron microscopy*
Authors: Davidson S. M. 
Published: August 2011

SUMMARYConsiderable strides have been made in the application of the cathodoluminescent and beam‐induced current modes of operation of the scanning electron microscope to the high resolution characterization of semiconductor materials. These techniques can be used to measure parameters such as resistivity, carrier concentration, mobility, composition, diffusion length, minority carrier lifetime, luminescence efficiency, dislocation density and temperature from regions of semiconductors as small as one micron across. The theoretical and experimental factors which limit the range of values over which measurements are possible and the accuracy attainable are discussed in detail. Each technique is illustrated by recent experimental results.
The modulation contrast microscope: principles and performance
Authors: Hoffman Robert 
Published: August 2011

SUMMARYThe modulation contrast microscope produces an image of high contrast and resolution. The image has a three‐dimensional appearance wherein a rounded object appears dark on one side, bright on the other with grey in between against a grey background. The performance features are optical sectioning, directionality, high resolution and control of contrast and coherence. A bright field microscope is converted to the modulation contrast microscope by adding the modulator, a special amplitude filter, in the objective. A slit aperture part of which is polarized is placed before the condenser. Below this is a rotatable polarizer. The modulator processes light from opposite gradients oppositely, that is brighter for one and darker for the other; thereby preserving the sign. The diffraction theory has been extended to show that gradient image intensity is the intensity of the zero order and when modified by the modulator creates a high contrast image.The modulation contrast microscope is simple and easy to adjust. It is useful in reflected and transmitted light systems, with plastic and glass vessels as well as in combination with fluorescence systems and polarization techniques. There is virtually no limit to the type of specimen that can be studied.
Scanning electron microscopy of freeze‐dried aortic elastin
Authors: Grut W. , Edwards J. , Evans E. J. 
Published: August 2011

SUMMARYAs part of a larger project aimed at clarifying some of the uncertainties that exist concerning the structural basis for an explanation of the mechanical behaviour of elastin, an examination was made of purified porcine aortic elastin under the scanning electron microscope. In order to avoid structural changes caused by impregnation with organic solvents, specimens were prepared directly from their water‐saturated state by either air‐drying or freeze‐drying processes. Comparison of the results obtained by these techniques demonstrates that freeze‐drying of elastin has the advantage of enhancing fine detail, minimizing distortion and reducing specimen shrinkage.
The restoration of damaged Philips electron microscope specimen holders used in the high‐resolution stage
Authors: Maxwell M. H. , McFarlane J. B. 
Published: August 2011

SUMMARYThis note describes how damaged Philips electron microscope specimen holders may be repaired simply and cheaply. The damaged part is replaced by a length of 18‐gauge syringe needle which is silver‐soldered into position. This simple and rapid repair caused no subsequent electrical distortion.
Fast freezing device
Authors: Sitte H. , Fell H. , Hölbl W. , Kleber H. , Neumann K. 
Published: August 2011

SUMMARYA fast freezing device for cryofixation of biological material, without cryoprotection, has been developed based on metal freezing (Van Harreveld et al., 1964, 1974) combined with preceding sectioning (Bernard & Krigman, 1974; Van Harreveld & Fifkova, 1975) as well as freeze sectioning and freeze‐etch replication (Dempsey & Bullivant, 1976).
Cutting work in thick section cryomicrotomy
Authors: Saubermann Albert J. , Riley William D. , Beeuwkes Reinier 
Published: August 2011

SUMMARYThe forces during cryosectioning were measured using miniature strain gauges attached to a load cell fitted to the drive arm of the Porter‐Blum MT‐2 cryomicrotome. Work was calculated and the data normalized to a standard (1 mm × 1 mm × 0·5 μm) section. Thermal energy generated was also calculated. Five parameters were studied: cutting angle, thickness, temperature, hardness, and block shape. Force patterns could be divided into three major groups thought to represent cutting (Type I), large fracture planes > 10 μm in length (Type II), and small fracture planes < 10 μm in length (Type III). Type I and Type II produced satisfactory sections. Work in cutting ranged from an average of 78·4 μJ to 568·8 μJ. Cutting angle and temperature had the greatest effect on sectioning. Heat generated would be sufficient to cause through‐section melting for 0·5 μm thick sections assuming the worst possible case, namely that all heat went into the section without loss. Presence of a Type II pattern (large fracture pattern) is thought to be presumptive evidence against thawing.
Frozen‐surface replicas of rat bladder luminal membrane
Authors: Severs N. J. , Hicks R. M. 
Published: August 2011

SUMMARYA method for preparing replicas of the luminal surface of frozen, unfractured but deep‐etched whole bladder tissue using a Bullivant type II device is described. A small piece of glutaraldehyde‐fixed (uncryoprotected) rat bladder is rinsed in distilled water, mounted luminal side uppermost on a specimen holder and rapidly frozen by immersion in liquid nitrogen (cooled below its boiling point in a vacuum) or by contact with a copper block at liquid nitrogen temperature. The specimen is processed in the type II device without fracturing and ‘deep‐etched’ by allowing a longer period than usual to elapse before shadowing. The results are assessed with reference to the appearance of the luminal membrane in standard freeze‐fracture replicas, and some preliminary observations on the structure of the normal luminal membrane and its counterpart in bladder tumours are presented.
Electron diffraction on frozen hydrated polysaccharides
Authors: Chanzy H. , Guizard C. , Vuong R. 
Published: August 2011

SUMMARYElectron diffraction data were obtained on three different frozen hydrated polysaccharide specimens: pustulan single crystals, algal cell wall fragments consisting of β, 1–3 xylan, and fungal microfibrils of β,1–3 glucan. For pustulan, the diffraction pattern yields two of the crystalline lattice parameters of this polymer: a = 2·44 nm and b= 1·77nm. The results with β,1–3 xylan and β,1–3 glucan are identical to already known X‐ray data, but also provide information on the molecular orientation at the micrometre level. In all three cases the hydrated electron diffraction diagrams are compared with the corresponding diagrams of the dried specimen.
Beam heating of a moderately thick cold stage specimen in the SEM/STEM
Authors: Talmon Yeshayahu , Thomas Edwin L. 
Published: August 2011

SUMMARYA mathematical model for the electron beam heating problem of thick specimens (thickness less than the electron range) in the cold stage of SEM/STEM is proposed, and an analytic solution for the problem is provided. The use of the model is demonstrated by calculating the maximum temperature rise in a red blood cell mounted on a metallized polymer film, for a large range of operating conditions. With a probe size of 20 nm and probe current of less than 10 nA the temperature rise was found to be on the order of 5 K. This temperature rise increases proportionally to the probe current if all other variables are kept constant. Although the amount of energy dissipated in thick specimens is large relative to thin films, temperature rise can be minimized by mounting the thick sample on a metal stub or on a metallized film thus providing large heat transfer area through a high thermal conductivity substrate. Of course our calculations only have meaning if the specimen is in good thermal contact with the underlying support.
Bright field and hollow cone dark field electron microscopy of palladium catalysts
Authors: Freeman L. A. , Howie A. , Treacy M. M. J. 
Published: August 2011

SUMMARYThe usefulness of hollow cone dark field imaging for the study of Pd catalyst particles on γ‐alumina substrates is investigated. By varying the depth of the specimen in the objective lens field, different Bragg reflections can be conveniently selected. Typically, about 70% of the particles appear in either the 111 or 200 Bragg reflections. Rather more particles can be visible in bright field because of other Bragg reflections as well as absorption effects. Size distributions in bright field and dark field are compared.
Photoelectron microscopy of cell surfaces
Authors: Dam Rudy J. , Nadakavukaren Karen K. , Griffith O. Hayes 
Published: August 2011

SUMMARYPhotoelectron micrographs of fixed, unstained, uncoated chicken embryo fibroblasts and the absolute photoelectron quantum yields in the 180–230 nm wavelength band of l‐fucose, d‐galactose, d‐glucose, n‐acetyl‐d‐glucosamine, and the sucrose polymer Ficoll are reported. The quantum yields of the saccharides are low compared to the reference dye, phthalocyanine, and fall in the same range as those previously measured for amino acids and membrane phospholipids. Photoelectron micrographs of the unstained and uncoated cells exhibit considerable surface detail. The photoelectron quantum yield data and the micrographs indicate that surface relief is the dominant source of contrast.
A device for dark field microphotography at low magnifications
Authors: Holzgraefe M. , Wolff J. R. 
Published: August 2011

SUMMARYA simple illumination system is described that can be easily adapted to a laboratory stereomicroscope allowing for low power high contrast dark field surveying. The system uses commercially available fibre optic lamps, standard bright field objectives and produces a large, evenly illuminated field suitable for photography.
The analysis of fibre distributions in fibre reinforced materials*
Authors: Stroeven Piet 
Published: August 2011

SUMMARYDifferent spacing factors and various orientation efficiency factors, applied to characterize the spatial distribution of the (steel) fibres in fibre reinforced cementitious materials, cannot constitute a sound basis for a mutual comparison of experiments or for an evaluation of experiments in a fracture mechanical sense.This paper therefore presents a complete framework, based on geometrical probability theory, providing the investigator with methods to obtain three‐dimensional information from two‐dimensional images produced by X‐ray radiography. In this approach the fibres are assumed to be disposed in such a way that on the average a partially planar‐oriented structure is obtained. In addition, because of their high aspect ratio, the fibres are considered to be lineal features.Two methods are elaborated, i.e. the feature counting technique and the method of directed secants. These operations have to be performed in the projection plane. Both methods yield data on the degree of inhomogeneity (segregation) and the degree of orientation (anisometry), as well as on spacing and orientation efficiency. By substituting design data in the presented formulae, this framework can also serve to characterize the spatial properties of the fibre structure in the designed mix.The application of the theory is illustrated with the help of data that confirm the occurrence of segregation and preferred orientation effects due to vibration of the specimens.
Fifty‐nine tetrakaidecahedra as grain models
Authors: Hucher Monique , Grolier Jacques 
Published: August 2011

SUMMARYA catalogue of the Schlegel graphs of all the three‐valent tetrakaidecahedra with faces having at least four edges and at most six edges is presented. These fifty‐nine polyhedra can be used for all purposes in stereology, either as morphological models of grains in microscopic studies of all kinds of materials where the unit cells are supposed in equilibrium, for the experimental and theoretical study of three‐dimensional packing and non‐packing problems or as a conceptual basis for the theoretical frequency computation of occurrences of the different types of polygons in materials observed in slides or polished sections.
A simple low‐cost critical point dryer with continuous flow dehydration attachment
Authors: Brown J. N. 
Published: August 2011

SUMMARYA simple low‐cost critical point dryer with continuous flow dehydration attachment is described. By using the critical point pressure chamber for all fluid exchanges, loss of material and air‐drying artefacts due to specimen handling are reduced. An operating schedule that allows the optimum path around the critical point process to be followed is proposed.
Application of fluorescence microscopy in coal petrology and oil exploration
Authors: Teichmuller M. , Wolf M. 
Published: August 2011

SUMMARYFluorescence microscopy of polished surfaces allows more satisfactory study and identification of the hydrogen‐rich constituents (liptinites) that are the precursors of petroleum and which, in soft brown coals, fine‐grained clastic and carbonate sediments can hardly be detected using normal reflected light. Diagnostic properties of liptinites and lipoid substances are their colour, intensity and variation of fluorescence (both colour and intensity) during irradiation which may allow distinction of organic and inorganic constituents in coals and bituminous shales. Fluorescence properties also change with increasing degree of diagenesis (‘rank’) of organic matter, although organic constituents cease to fluoresce beyond the medium‐volatile, bituminous‐rank stage. In this paper fluorescence microscopy as a means of studying the rank of coaly and lipoid substances in sedimentary rocks is discussed after a brief description of the method. The influence of facies on fluorescence properties is considered and the relative merits of fluorescence and reflectance measurements in different parts of the rank range are discussed. The importance of fluorescence microscopy in petroleum exploration is also emphasized. Finally, consideration is given to the future of fluorescence microscopy in relation to the ‘bituminization range’ of coalification which has important implications to both petroleum generation and to the coking and hydrogenation of coals.
The variation of the microhardness and reflectance of coal under conditions of oxidation simulating weathering
Authors: Nandi B. N. , Ciavaglia L. A. , Montgomery D. S. 
Published: August 2011

SUMMARYThis investigation indicated that different types of microhardness impressions were obtained on different ranks of coal by the Vickers microhardness test and that oxidation transformed the plastic state of fresh vitrinite into an elastic state. The transformation occurred rapidly in high volatile coals, but more severe oxidation was required to cause this change in low volatile coals. Reflectance also increased with oxidation. As oxygen penetrated a coal particle, it produced changes in the microhardness impressions and in the reflectance which were rather abrupt at some point between the outer surface and the centre. The microhardness impressions combined with the reflectance data were capable of defining the boundary where rapid transition from the plastic to elastic state occurred. Movement of this boundary made it possible to follow the oxygen penetration into coal particles.
‘Large’ and ‘small’ nuclear pore complexes: The influence of glutaraldehyde
Authors: Willison J. H. M. , Rajaraman R. 
Published: August 2011

SUMMARYAliquots of lymphocyte cell suspensions were pretreated according to the following three schedules before freeze fracturing: (a) prefixed with 2% glutaraldehyde before infiltration with 25% glyercol in medium RPMI‐1640; (b) frozen in medium RPMI‐1640 without additional pretreatment; and (c) frozen after pretreatment with 25% glycerol in medium RPMI‐1640. The diameters of the fractured nuclear pore complexes of cells prefixed with glutaraldehyde were normally distributed within the range 70–120 nm (median 90 nm). The nuclear envelopes of 66–75% of cells processed through schedules b and c, which omitted glutaraldehyde fixation, had 70–120 nm diameter pores, while the remainder had pores with diameters in the range 120–175 nm. The large pores were structurally similar to the smaller pores except for their dimensions. These results indicate that glutaraldehyde gives rise to shrinkage of the larger pores to the minimum, smaller, diameter. Apparent orifices of at least 30 nm diameter were sometimes observed at the centres of these large pore complexes. We propose that the variation in pore diameters may indicate opening and closure of this orifice, and that the widely reported ‘central granule’ of the nuclear pore complex corresponds with the orifice in a closed configuration.
Detection of Concanavalin A receptors by affinity to peroxidase and iron dextran by scanning and transmission electron microscopy and X‐ray microanalysis
Authors: Baccetti Baccio , Burrini Anna G. 
Published: August 2011

SUMMARYA method of cell surface mapping has been developed on spermatozoa. Concanavalin A binding sites have been simultaneously revealed both by peroxidase DAB reaction and by iron dextran coupling. The areas are examined in scanning and transmission electron microscopes and submitted to electron probe X‐ray microanalysis.
Staining reticulin in beef dorsal lymph nodes for electron microscopy
Authors: Voyle C. A. 
Published: August 2011

SUMMARYReticulin has been classically identified by virtue of its argyrophilia, as observed by light microscopy. The similarity between reticulin and collagen has been a matter for considerable discussion. This paper describes the application of a silver‐staining procedure which demonstrates the fine structure of these fibres when studied by electron microscopy, giving a direct indication of the morphological identity of the argyrophilic structures, i.e. reticulin, with collagen. Beef lymph node tissue was used for this study.
Signal to noise enhancement in dark field electron micrographs of vasopressin: filtering of arrays of images in reciprocal space
Authors: Ottensmeyer F. P. , Andrew J. W. , Bazett‐Jones D. P. , Chan A. S. K. , Hewitt J. 
Published: August 2011

SUMMARYA technique for filtering arrays of images of dispersed molecules is presented which takes advantage of the crystallographic properties of regular arrays and the rapidity of optical treatment. A filter in reciprocal space consisting of perforations in a square or rectangular lattice, as determined by the image arrangement, reduces noise and averages the images simultaneously by transmitting only regularly recurring image structure. The filter is universal for all image contents and introduces no additional biases. The signal to noise improvement approaches √N for N independent images of the same molecule in the same configuration. The procedure, which is simple, rapid and inexpensive, is demonstrated with the aid of dark field electron micrographs of the protein vasopressin and combined with iodination of that molecule to elucidate its structure.
Optical properties of graphite
Authors: Kwiecinska B. , Murchison D. G. , Scott E. 
Published: August 2011

SUMMARYReflectances of natural surfaces of fresh graphite peels parallel to the (0001) plane have been measured throughout the visible spectrum using only slightly modified microphotometric equipment and measuring procedures. There is satisfactory agreement between the level and trends of reflectances of graphites from different metamorphic environments throughout the spectrum, the maximum relative difference in the most difficult conditions in the blue region being approximately 4%. There is less good agreement between the dispersion curves of derived refractive and absorptive indices for which the maximum relative difference is as high as 12% in the red region. At 546 nm, the wavelength at which optical data in organic petrology are principally reported, relative errors below 1% for all the optical parameters were attained between samples. Values of Rair = 31.40%, Roil = 17.85%, n = 2.49 and k = 0.61 compare well with other recent estimates and although there is still not complete agreement between laboratories, the true constants for graphite at this wavelength must lie close to these values. The use of semi‐graphites as metamorphic indicators in a scale with graphite as the end‐point is considered, as are the implications on such a scale of the current use of natural surfaces for reflectance measurement, because of an inability of many laboratories to produce specularly polished surfaces of semi‐graphites and graphites of high uniform quality.