bluuebunny/crossref_metadata_2025_split huggingface dataset:
A routine flat embedding method for electron microscopy of microorganisms allowing selection and precisely orientated sectioning of single cells by light microscopy
Authors: Reymond Olivier L. , Pickett‐Heaps Jeremy D. 
Published: August 2011

SUMMARYA simple method is described to embed material in resin, in the form of microscope slides, to observe it with high resolution light microscopy, to select, orient and section it for TEM. This method can be applied to many kinds of material but is particularly useful for the study of rare or tiny plant or animal microorganisms from field or culture. A diamond scriber, translucent hydrosoluble resin release agent, translucent and smooth resin stubs and a longitudinally perforated block‐holder for ultramicrotome are the specific tools of this method.
Calibration of transmission electron microscopic mass determination using objects with known mass distribution
Authors: Linders P. W. J. , Stols A. L. H. , Stadhouders A. M. 
Published: August 2011

SUMMARYAn improved calibration procedure is described for dry mass determination methods, that are based on microdensitometry of transmission electron micrographs. Polystyrene latex spheres, that are supposed to have a homogeneous mass distribution, are used for the calibration procedure. By computer fitting of the theoretically expected mass distribution to the distribution measured in a line through the centre of a sphere, a mass calibration factor is obtained. The number of measurements required for a predetermined calibration accuracy can be decreased considerably as compared to other calibration methods. Accurate calibration and reproducible adjustment of the electron optical magnification are required.
Electron trajectory‐linked phenomena in thin foil X‐ray microanalysis
Authors: Jones I. P. , Nicholls A. W. 
Published: August 2011

SUMMARYThe methods of calculating electron trajectories are reviewed. Approximate methods may be necessary because of computing time problems on small computers. The various situations in microanalysis where electron trajectories are important are discussed in turn. It appears that the single scattering theory of Goldstein et al. (1977) is useful for situations dominated by high scattering angle events whereas the Gaussian theory of Doig et al. (1981a) may be appropriate to multiple low angle scattering. This type of calculation might turn out to be unnecessary if coincident counting techniques are exploited.
Prospects for improvement in EDX microanalysis
Authors: Statham P. J. 
Published: August 2011

SUMMARYThere is still considerable room for improvement in the EDX technique, particularly for the analysis of thin samples in transmission electron microscopes. Further research is required to characterize changes which are introduced during specimen preparation and a technique for mass thickness determination has to be established which is both accurate and convenient to implement. Since detector efficiency is difficult to predict at low energies, a suitable standard sample needs to be found which produces X‐ray peaks suitable for establishing fixed points on the detector efficiency curve. With current technology, there are several instrumental improvements which can be realized, most of which centre around the use of time‐variant pulse‐processing circuitry and reduction of electronic noise. Problems of overload with high‐voltage microscopes can be minimized, resolution improved and pile‐up rejection made more effective so that higher data rates can be accommodated. With the beryllium vacuum window removed, detection of boron is possible provided the influence of electronic noise is minimized but further investigation is still required into the physics of interactions in the first 100 nm layer of the detector.
Procedures for focusing, stigmating and alignment in high resolution electron microscopy
Authors: Saxton W. O. , Smith David J. , Erasmus S. J. 
Published: August 2011

SUMMARYSeveral different approaches to the alignment, stigmating and focusing of a high resolution electron microscope are evaluated theoretically and experimentally. Ambiguities in the interpretation of diffractograms are pointed out which make it necessary to explore a range of incident beam directions before the correct alignment can be established. The variation of image contrast with the imaging conditions is examined in detail, and its global minimization is shown to be a reliable criteria for adjustment of all parameters. Recommendations are made as to the best procedures to adopt in various circumstances, and a computer‐controlled procedure based on the image contrast is described which sets all parameters automatically in less than a minute.
A high‐resolution electron microscopic study of defects in sodium β′″‐alumina
Authors: Hull R. , Smith David J. , Humphreys C. J. 
Published: August 2011

SUMMARYA high‐resolution electron‐microscopic study of sodium β′″‐alumina, a polytype of the more‐widely‐studied sodium β‐ and β″‐alumina, has been undertaken using the 600 kV instrument at Cambridge University. Images revealed the loss of sodium‐containing planes, which had caused crystals to collapse and shear into defect layers. A model for the structure of these defects is proposed, based on the use of computed images and by comparison with high‐resolution images of silver β″‐alumina.
The relative accuracy of axial and non‐axial methods for the measurement of lattice spacings
Authors: Hall D. J. , Self P. G. , Stobbs W. M. 
Published: August 2011

SUMMARYThe various different transmission electron microscopical techniques available for the measurement of lattice spacings are discussed, and the limited situations under which lattice fringe spacing measurement is the most appropriate approach are considered. The relative accuracy of measurements on images obtained under axial and non‐axial conditions is further considered, and the generally greater accuracy of the latter technique demonstrated. Further results on the use of the method for the measurement of the carbon content of retained austenite in a dual phase steel are included.
Optimizing the cooling block for the quick freeze method
Authors: Bald W. B. 
Published: August 2011

SUMMARYIt is important for future ultrastructural preservation studies to freeze biological specimens as rapidly as possible. Finite element numerical techniques have been used to compare different cooling block materials used in the quick freeze ‘slamming’ method. It is concluded that a pure silver block at an optimum initial temperature of about 15.6 K will produce the quickest cooling and will give rates approximately 50% higher than if the block were initially cooled to 4.2 K.A copper block will produce the fastest cooling rates when the block is initially at liquid nitrogen temperature of 77.3 K provided the section being studied is taken no more than about 30 μm from the specimen‐block interface.Composite metal blocks can further reduce the total specimen cooling time compared to a mono‐block at the same initial temperature but the cooling rate near the interface will be slower.Future methods for specifying cooling rates within thin biological samples should be standardized and must be based on a combination of finite element numerical analysis and the measured temperature at the rear surface of the sample. Thermal contact resistance between cooling block and specimen and between specimen and the rear face temperature sensor must be minimal.
On the preparation of specimens from multifilamentary Nb3Sn superconducting wires for transmission electron microscopy
Authors: Hascicek Y. S. , Nourbakhsh S. , Goringe M. J. 
Published: August 2011

SUMMARYA set of techniques for preparing transmission electron microscope specimens from sections of thin (≤ 1 mm overall diam.) multifilamentary wires (filaments being approximately 5 μm diam.) are described. Results illustrating the successful uniform thinning of the several phases present in ‘bronze‐route’ Nb3Sn are shown.
Radiation damage to lyophilized mineral solutions during electron probe analysis: quantitative study of chlorine loss as a function of beam current‐density and sample mass‐thickness
Authors: Roy Andre F. Le , Roinel Nicole 
Published: August 2011

SUMMARYThe quantitative effects of beam current‐density and sample mass‐thickness on the loss of chlorine which occurs from lyophilized solutes of micro‐droplets of mineral salt solutions irradiated in an electron probe analyser were studied. Results are reported for chlorine loss from lyophilized deposits with mass‐thickness varying between 5 and 50 mg mm−2 for NaCl salts and 5 and 80 mg mm−2 for KCl salts. Electron accelerating voltage was kept constant at 15 kV. The range of beam current‐density (I/S, current/sample surface area) was from 0.1 to 1.5 A mm−2. Samples were irradiated for 1200 s. The results show that under some conditions there is a period of stable chlorine signal before chlorine loss occurs. This is observed between 0.1 and 1 A mm−2, for a period which can last several hundred seconds depending on beam current‐density and sample mass‐thickness. For each value of I/S, however, no stable chlorine signal can be observed for samples whose mass‐thickness exceeds a value negatively correlated with I/S. The curves of decrease of characteristic chlorine X‐ray signal (expressed as per cent of count rate in the initial counting interval) versus irradiation time can be fitted by the sum of two exponentials with half lives T1 and T2. In NaCl, T1 and T2 values are highly correlated with I/S but not with mass‐thickness. In KCl, T1 is correlated only with mass‐thickness and T2 only with I/S. Mixing plasma with mineral solutions prevents chlorine loss.
Staining plastic sections
Authors: Horobin Richard W. 
Published: August 2011

SUMMARYMany of the difficulties of staining plastic embedded tissues for light and electron microscopy derive from physical exclusion of hydrophilic staining reagents by hydrophobic embedding media. Structures which stain most intensely with hydrophilic reagents usually contain less hydrophobic plastic than do non‐staining structures. Such incomplete infiltration is apparently caused by exclusion of viscous, hydrophobic monomers by physically dense and/or well hydrated tissue elements. In keeping with this, generalized staining of tissues embedded in hydrophobic media does occur when hydrophobic reagents are used. Staining of plastic‐free structures with single hydrophilic reagents or with sequences of such reagents, is, however, largely rate‐controlled.The surprising similarity of hydrophilic and hydrophobic plastic embedding media is discussed.Limits of this simple model are explored, with a consideration of the roles of fixative and of monomer‐tissue reactions.
Exocrine glands and protein secretion: a stereological viewpoint
Authors: Cope G. H. 
Published: August 2011

SUMMARYThe exocrine pancreas and the parotid salivary gland have been widely used as models for studying the synthesis, intracellular transport and discharge of exportable proteins. This article briefly reviews quantitative morphological (stereological) studies which have been made of these glands and assesses their contribution to our understanding of the secretory process. A general stereological profile of these glands is presented and the way in which their morphology changes during development is outlined. Detailed consideration is given to the granule population of the cells, particularly the way in which granules are formed and discharged as a result of secretory stimuli. The membrane content of secretory cells and membrane dynamics during the secretory cycle are also examined. Throughout, the emphasis is placed on the interpretation of stereological data rather than on the methods themselves.
The microvascular cast as a three‐dimensional tissue skeleton: visualization of rapid morphological changes in tissues of the rat uterus
Authors: Rogers P. A. W. , Gannon B. J. 
Published: August 2011

SUMMARYA new interpretation of microvascular corrosion casting is described using examples from casts of the rat uterus taken during the oestrous cycle and early pregnancy. The casts are considered as representing a three‐dimensional model of the tissue vascular space; this characteristic model or tissue skeleton is used to demonstrate transient morphological changes that may be difficult to visualize by other techniques, that may be obscured by other structures, or destroyed by conventional aldehyde fixation procedures. This new application, when supplemented by conventional histology to determine vessel distribution within the tissue and to confirm observations first made by casting, provides a technique for visualizing three‐dimensional morphological changes in tissues that is accurate, relatively simple and far more rapid than the laborious method of histological serial sectioning and three‐dimensional tissue reconstruction.
Quantitative serial sectioning analysis: preview
Authors: DeHoff R. T. 
Published: August 2011

SUMMARYQuantitative serial sectioning analysis provides all of the geometric information that is available from ordinary stereological analysis. In addition, it circumvents the weaknesses inherent in geometric models that are used to estimate distribution functions and topological properties. It further makes accessible some geometric aspects of microstructures that are not available stereologically, even with model assumptions. At the present state of the art it requires a prodigious effort to prepare and analyse a single sample from a single specimen. However, the current generation of image analysing computers already has the capability for automating data collection and analysis, and there is reasonable potential for automating the sample preparation procedure. Quantitative serial sectioning analysis would render obsolete all of the elegant geometrical probability arguments of stereology. Is it the wave of the future?
Distribution‐free estimation of sphere size distributions from slabs showing overprojection and truncation, with a review of previous methods
Authors: Cruz‐Orive L. M. 
Published: August 2011

SUMMARYA distribution‐free method is presented for unfolding the size distribution of an aggregate of disjoint opaque spherical particles in a translucent medium, from the circular profiles observed in the orthogonal projection of sections of a certain thickness through the medium. This situation pertains especially to light and transmission electron microscopy.The model accounts for overprojection (or ‘Holmes effect’) due to section thickness, and for two forms of truncation (or ‘missing profiles’ mechanisms), simultaneously. The profile data may be grouped into an arbitrary class system, chosen by the user, and the procedure can be programmed in a medium‐size desk calculator.In order to incorporate the above features, however, we had to choose a finite‐difference unfolding algorithm, the advantages and disadvantages of which are discussed early in the paper in the context of the main alternative unfolding procedures hitherto available.The performance of the method is tested against three sets of real data previously analysed by a maximum likelihood method (Keidinget al., 1972).
Unbiased linear property estimation for spheres, from sections exhibiting overprojection and truncation
Authors: Clarke K. R. , Moore M. N. 
Published: August 2011

SUMMARYIn the biological sciences, stereological techniques are frequently used to infer changes in structural parameters (volume fraction, for example) between samples from different populations or subject to differing treatment regimes. Non‐homogeneity of these parameters is virtually guaranteed, both between experimental animals and within the organ under consideration. A two‐stage strategy is then desirable, the first stage involving unbiased estimation of the required parameter, separately for each experimental unit, the latter being defined as a subset of the organ for which homogeneity can reasonably be assumed. In the second stage, these point estimates are used as data inputs to a hierarchical analysis of variance, to distinguish treatment effects from variability between animals, for example.Techniques are therefore required for unbiased estimation of parameters from potentially small numbers of sample profiles. This paper derives unbiased estimates of linear properties in one special case—the sampling of spherical particles by transmission microscopy, when the section thickness is not negligible and the resulting circular profiles are subject to lower truncation. The derivation uses the general integral equation formulation of Nicholson (1970); the resulting formulae are simplified, algebraically, and their efficient computation discussed. Bias arising from variability in slice thickness is shown to be negligible in typical cases.The strategy is illustrated for data examining the effects, on the secondary lysosomes in the digestive cells, of exposure of the common mussel to hydrocarbons. Prolonged exposure, at 30 μg 1−1 total oil‐derived hydrocarbons, is seen to increase the average volume of a lysosome, and the volume fraction that lysosomes occupy, but to reduce their number.
Morphometric study of the development of Purkinje cell dendritic trees in the mouse using vertex analysis
Authors: Sadler Martin , Berry Martin 
Published: August 2011

SUMMARYVertices are the points in an arborescence which interconnect segments and comprise terminal or pendant vertices (Vp), nodal or branching points and the root point. Branching points may be dichotomous (Vd) or trichomtomous (Vt), etc., and are subdivided into distinct two‐dimensional topological entities according to the number of terminal vertices they drain, i.e. Vds comprise primary vertices (Va), connecting two Vps; secondary vertices (Vb), connecting one Vp and one Vd or one Vt; and tertiary vertices (Vc), connecting either two Vds, two Vts or one Vt and one Vd. The four types of Vt (Va‘, Vb’, Vc‘, Vd’) similarly connect three, two, one and zero Vps respectively. Each Vt may be transformed into two Vds thus, Va' = Va + Vb; Vb’ = Va/3 + 4Vb/3 + Vc/3; Vc' = Vb + Vc and Vd’ = 2Vc. Analysis proceeds by transforming mixed trees containing varying proportions of Vds and Vts into entirely dichotomous branching structures. The topology is then defined by the Va Vb ratio which has a unique value according to the mode of growth and the frequency of Vts.Vertices are ordered by a centrifugal technique. The frequency distribution of vertices of different order allow the changes in growth characteristics and in remodelling to be detected within particular regions of the tree. Metrical parameters are readily incorporated into the analysis since all vertices are interconnected by segments of finite length and are given the same order magnitude as the vertex they drain.The analytical capabilities of the method are exemplified by its application to the study of growth and plasticity in the dendritic trees of Purkinje cells in the mouse. Growth is defined in metrical and topological terms and sites of reorganization within the mature tree are identified.
Vascular smooth muscle orientation in curved branches and bifurcations of human cerebral arteries
Authors: Walmsley James G. 
Published: August 2011

SUMMARYTwo approaches were developed for determining reference axes and positions associated with bending tubular arteries and bifurcations from the human middle cerebral branching system. In the region of the bifurcation the orientation of groups of two‐dimensional nuclear vectors was determined by the method of roses and average alignment. The reference axes and positions for these groups were determined from physical reconstructions of two bifurcations. The overall pattern in the bifurcation region was found to be random but there were significant differences between group orientations. The three‐dimensional arterial direction vectors for three sections, from the bending arteries of one bifurcation, were determined. By taking the dot product of the three‐dimensional nuclear vectors and these direction vectors, the pitch of individual nuclei was determined. The average pitch was 2.45° ± 3.20 (SD for N = 8) with the largest mean pitch (6.14°) in the branch with the greatest curvature. Possible use of the three‐dimensional approach for determination of smooth muscle orientation at bifurcations is discussed in general terms.
Introduction to the microscopy of erosion
Authors: Hutchings M. 
Published: August 2011

SUMMARYErosion of materials by the impact of small solid particles, by the impact of liquid drops and by cavitation in a liquid is discussed. Erosion arising from these three sources is described, terminology is defined, and the methods available for erosion testing in the laboratory are reviewed. A brief discussion is presented of the microscopical techniques which have been used to study erosion, and some of their advantages and drawbacks are outlined.
Microstructural studies of the temperature‐dependence of deformation structures around hardness indentations in ceramics
Authors: Naylor M. G. S. , Page T. F. 
Published: August 2011

SUMMARYVarious light microscopy and SEM techniques have been used to study the temperature dependence of deformation structures around hardness indentations in highly brittle ceramics (including single crystals of silicon and silicon carbide and polycrystalline forms cf SiC, Si3N4 and B4C). Nomarski differential interferometry has enabled slip steps to be resolved around high‐temperature indentations, allowing identification of the dominant slip systems and measurement of the extent of surface plasticity as a function of temperature. The occurrence of indentation fracture as a function of both temperature and specimen microstructure was studied by SEM methods (including stereo imaging), Nomarski differential interferometry and polarized reflection light microscopy. Generally, radial and lateral crack sizes increased with increasing temperature, due to increasing residual stresses around indentations caused by increasing indentation plasticity. Examples of microstructural control of crack paths are given for various single crystal and polycrystalline materials.
Current uses of fluorescence microscopy in coal petrology
Authors: Crelling John C. 
Published: August 2011

SUMMARYFluorescence analysis of the liptinite maceral content of various U.S. coal seams has shown that these macerals are consistently under‐counted in conventional white‐light analysis. Fluorescence analysis revealed a greater variety of liptinite macerals as well as a large amount of fluorescing vitrinite in all of the coals studied. However, pseudovitrinite was not observed to fluoresce. Textures and structures not visible in normal viewing are also seen in fluorescence analysis. Quantitative spectral analysis of single coals has shown that most liptinite macerals can be both petrographically and statistically separated on the basis of fluorescence parameters, with the wavelength at maximum intensity and the red/green quotient being the most significant. In coals of the Illinois Basin, one or more forms of fluorinite, resinite, sporinite and cutinite can be distinguished.As the rank of the coal increases, the fluorescence intensity decreases and the spectral maxima shift toward longer wavelengths. In some Rocky Mountain coals these effects occur at a much lower rank (<0.85% reflectance) than in the coals of the Appalachian Basin. Similar changes in fluorescence properties have also been found in naturally weathered coals. Fluorescence analysis of resinite‐rich Rocky Mountain coals has shown that two major forms of resinite are present; one is the ‘normal’ resinite, and the other is a much more abundant fissure‐filling resinite that carries coal xenoliths, shows flow structure, and has a spectral maximum well below that of the ‘normal’ resinite.