bluuebunny/crossref_metadata_2025_split huggingface dataset:
Signal‐to‐noise ratio in confocal microscope systems
Authors: Sheppard C. J. R. , Gu Min , Roy Maitreyee 
Published: August 2011

SUMMARYThe effects of various system parameters on the imaging performance of confocal microscopy are discussed, including the effects of pinhole size, type of detector and imaging algorithms on signal‐to‐noise ratio. Careful consideration of these parameters allows the microscope user to obtain the best performance for particular applications.
High‐resolution imaging of chromosome‐related structures by atomic force microscopy
Authors: Grooth Bart G. De , Putman Constant A. J. 
Published: August 2011

SUMMARYAn atomic force microscope (AFM) was combined with a conventional optical microscope. The optical microscope proved to be very convenient for locating objects of interest. In addition, the high‐resolution AFM image can be compared directly with the traditional optical image. The instrument was used to study chromosome structures. High‐resolution chromosome images revealed details of the 30‐nm chromatide structure, confirming earlier electron microscopic observations. Chromosomes treated with trypsin revealed a banding pattern in height which is very similar to the optical image observed after staining with Giemsa. Furthermore, it is shown that the AFM can be used to locate DNA probes on in situ hybridized chromosomes. Images of the synaptonemal complex isolated from rat spermatocytes revealed details that improve the understanding of the three‐dimensional structure of this protein.
Quick‐freezing of cultured cardiac cells in situ with special attention to the mitochondrial ultrastructure
Authors: Dalen Helge , Lieberman Melvyn , LeFurgey Ann , Scheie Paul , Sommer Joachim R. 
Published: August 2011

SUMMARYA new method has been developed which allows quick‐freezing in situ of primary, cardiac cell cultures grown to confluence on gas‐permeable membranes (Petriperm dishes). Small pieces of the growth substratum, with rhythmically beating myocardial cells, were slam‐frozen, without cryoprotectants, against the surface of a helium‐cooled copper block at approximately 16 K. The quality of the cellular cryopreservation, as judged by ultrastructural criteria, was studied in freeze‐substituted specimens processed for transmission electron microscopy. The ultrastructure of cryofixed cardiac cells was compared with that of unfrozen, chemically fixed samples. The severity of cryodistortions increased progressively with increasing distance from the point of first impact. Of particular interest were the dramatic alterations of the mitochondrial ultrastructure. The concept that the reticular and the outer mitochondrial membranes are intimately and strongly associated was clearly demonstrated. Optimally frozen material revealed cryopreserved ultrastructure of high quality. The method described appears to offer an ideal model system for correlating the information gained by phase‐contrast microscopy of living cell cultures with the ultrastructure of the same samples fixed in situ by chemical or physical techniques. Cryofixation would be particularly useful for studying dynamic cellular processes associated with physiological and pathophysiological conditions, e.g. metabolic inhibition, anoxia and substrate deprivation.
Real‐time three‐dimensional tracking of fast‐moving microscopic objects
Authors: Teunis P. F. M. , Bretschneider F. , Machemer H. 
Published: August 2011

SUMMARYAnaxial illumination has been used so far for either enhancement of visual acuity, or three‐dimensional (3‐D) measurements of static objects. Here we report the use of anaxial illumination for 3‐D tracking of fast‐moving objects, with only slight modifications to the standard microscope. To achieve this, we have investigated highspeed recording of stereoscopic images in two different set‐ups.
The accurate alignment of energy‐dispersive X‐ray detectors for quantitative microanalysis
Authors: Nicholson W. A. P. , Craven A. J. 
Published: August 2011

SUMMARYModern collimator design for energy‐dispersive X‐ray detectors requires very accurate positioning of the crystal/collimator assembly in order to achieve the maximum solid angle of collection for the irradiated volume on the specimen. Thus it is important to have a method of checking the alignment of the detector when mounted on the microscope and under vacuum. This paper describes a number of techniques, principally X‐ray mapping, for performing such an alignment check. These techniques are applicable to windowless detectors as well as to those with integral windows which will support atmospheric pressure. Methods of obtaining the non‐standard modes of microscope operation suitable for this task are described, and some suggestions are made for ways of moving the crystal/collimator assembly and monitoring this movement while it is in progress.
Mathematical morphology: from two dimensions to three dimensions
Authors: Meyer F. 
Published: August 2011

SUMMARYAfter a discussion of the best grid for the digitization of three‐dimensional (3‐D) images, two grids are retained for which the approximations of the elementary disc are respectively the cuboctahedron and the rhombododecahedron. These are used to derive the formulae for the basic Minkowski measures. The extension from 2‐D to 3‐D is demonstrated to be straightforward for most transformations of mathematical morphology, and covers almost all practical situations.
Colour confocal reflection microscopy using red, green and blue lasers
Authors: Cogswell C. J. , Hamilton D. K. , Sheppard C. J. R. 
Published: August 2011

SUMMARYTo obtain colour reflected confocal images we have incorporated three lasers (HeNe: 633 nm; NdYAG: 532 nm; HeCd: 442 nm) and three photomultiplier detectors into our on‐axis scanning system then adjusted the registration of the simultaneous output signals to produce full‐colour images on a video monitor. Colour confocal images were produced from multi‐stained fixed tissue as well as from natural pigments in fresh plant material. Rayleigh scattering properties of immunogold‐labelled specimens were studied to show how variations in colour response can be utilized to identify subwavelength gold particles. Colour stereo pairs were produced to illustrate the accuracy with which the three‐laser microscope system can record depth information without incurring problems due to chromatic aberration effects.
Confocal‐line microscopy
Authors: Benedetti P. A. , Evangelista V. , Guidarini D. , Vestri S. 
Published: August 2011

SUMMARYThe confocal‐line (CL) technique combines some of the characteristics of confocal‐scanning microscopy with those of conventional‐imaging methods. It is based on the introduction of line‐shaped illumination and linear image detection, as an alternative to the current confocal‐point (CP) approach. Although confocal only in one dimension, the proposed solution offers performance and features adequate to a variety of biological and non‐biological applications and is also adaptable to an increased number of microscopical observations and measurements. The absence of moving components in the optical path and the use of electronic linear imagers permits flexible and fast operation that appears particularly relevant in many fields of basic and applied research. For instance, transmission, reflection and emission images can simultaneously be collected from the same area of the specimen, with slight adjustments to the optical setup. Useful extensions of CL microscopy to the field of spectral imaging are obtained with the introduction of a slit, a polychromator and an area detector, substituting for the linear imager. Prototype instrumentation has been constructed working from the cited principles and some tests have been performed on selected applications.
Comparison of in vivo and ex vivo cellular structure in rabbit eyes detected by tandem scanning microscopy
Authors: Jester James V. , Petroll W. Matthew , Garana Randa M. R. , Lemp Michael A. , Cavanagh H. Dwight 
Published: August 2011

SUMMARYUsing the tandem scanning microscope, in vivo confocal microscopic images of living eyes were compared to images obtained from ex vivo, freshly enucleated or fixed tissue in the rabbit. In the normal cornea, microscopic details of the superficial epithelium, basal lamina, stromal fibrocyte nuclei, nerves and endothelial cell borders were easily discernible. Removal of the eye from the intact animal resulted in loss of detail with distortion of the normal structural interrelationships within the corneal stroma whilst enhancing details of the corneal epithelium. Formalin fixation further enhanced details of the basal and suprabasal corneal epithelial cell nuclei and the stromal fibrocyte cell borders whilst inducing prominent brightly reflecting folds in the thickened stroma with concomitant enhancement of the edge contrast of the collagen lamellae. These changes appeared to be related, in part, to hydration of the cornea and artefactual pooling of water between structures that may enhance reflectivity by increasing the difference between the refractive index of the cellular and extracellular elements. We conclude that microscopic examination of ex vivo preparations of corneal tissue, although providing increased resolution similar to conventional light microscopic techniques, significantly altered the normal structural relationships and could lead to erroneous measurements of the physiological properties of the tissue as compared to in vivo microscopy of undisturbed, intact tissue.
Measuring the surface area of a cell by the method of the spatial grid with a CSLM—a demonstration
Authors: Howard C. Vyvyan , Sandau Konrad 
Published: August 2011

SUMMARYThe spatial grid is a method for estimating the surface area of particles. A stack of perfectly registered sections is the essential prerequisite for its use. The confocal scanning light microscope provides such a stack by optical sectioning. The spatial grid method is briefly described and applied to an osteocyte lacuna in dry mineralized human mandible. This type of cell was chosen because of its very complex shape. The variance of the area estimate is studied and compared with the results of a simulation.
Amplification and noise in high‐pressure scanning electron microscopy
Authors: DURKIN R. , SHAH J. S. 
Published: August 2011

SUMMARYHigh‐pressure scanning electron microscopy (HPSEM) is a promising new family of techniques. The present knowledge of these techniques is reviewed and a new set of criteria developed for optimizing signal detection in HPSEM with a view to preserving specimen integrity. For this purpose, amplification of contrast signals generated in HPSEM was examined by computing the effect of ionization over a range of pressures and biasing fields, routinely used for this technique. The influence of secondary ionization due to ion impact was included in the calculations. To check the calculated results, the experiments were performed in the HPSEM apparatus in a nitrogen atmosphere. A divergence between the experimental values and the calculated values was found. This was removed by taking into account the effect of recombination of charge carriers. Inductive currents generated in the HPSEM environment are transient and do not affect the conclusions of this study. The gas pressure, biasing fields and beam current for preserving specimen integrity and obtaining good micrographs were selected from the data. Experimental measurements of noise are reported, and criteria for optimizing the signal‐to‐noise ratio for performing HPSEM are discussed. The application of these criteria has shown that specimen current detection can be more advantageous than other methods and configurations of detection and was capable of obtaining high/medium‐resolution micrographs.
Optimizing microstructure in spray‐formed and squeeze‐cast metal‐matrix composites
Authors: CANTOR B. 
Published: August 2011

SUMMARYThis paper discusses the methods of optimizing microstructure in the manufacture of spray‐formed and squeeze‐cast A‐ and Ti‐based metal–matrix composites (MMCs) for a range of automotive and aerospace applications. Three specific MMC material/process/product combinations are considered: spray‐formed/extruded Al alloy/SiC particulate‐reinforced MMCs for aerospace structural components; squeeze‐cast Al alloy/SiC particulate‐ and Al2O3 fibre‐reinforced MMCs for automotive components; and spray‐formed/diffusion‐bonded Ti alloy/SiC fibre‐reinforced MMCs for aeroengine components. Important features, which are emphasized in each case, are (i) using specific end applications to define desirable property and therefore microstructural goals; (ii) understanding the underlying process physics to control the resulting mechanisms of microstructural development; and (iii) using numerical modelling and associated experimental validation to allow subsequent implementation of process control systems.
Interface compatibility in Nicalon‐fibre reinforced metal and ceramic composites
Authors: SCOTT V. D. , BLEAY S. M. , CHAPMAN A. R. , LOVE G. 
Published: August 2011

SUMMARYMicrostructural characteristics of the fibre–matrix interface of two composite systems which utilize Nicalon fibre reinforcement are analysed and discussed.An Al‐based composite produced by liquid‐metal infiltration was found to contain crystals of aluminium carbide and alumina at the fibre–matrix interface, which produced a strong interfacial bond, restricted fibre pullout, and resulted in an essentially brittle composite.A ceramic‐matrix composite based upon calcium aluminosilicate and produced by hot pressing exhibited substantial fibre pullout during testing; microstructural analysis of the interface showed the presence of a C‐rich layer. Treatment of the composite in air over a range of temperatures (600–1200°C) progressively oxidized the carbon and formed silica ‘bridges' between fibre and matrix, which resulted in increased brittleness.Electron‐probe microanalysis combined with electron microscopy of the Nicalon fibre showed that approximately half the material consisted of microcrystalline β‐SiC and the remainder was free carbon and silicon oxycarbide. Thus the carbon constituent was largely responsible for carbide formation in the Al‐based material, which restricted fibre pullout, whilst free carbon, plus the additional free carbon formed by chemical reaction between silicon carbide in the fibre and the calcium aluminosilicate matrix, provided the interfacial carbon layer which gave enhanced fibre pullout in the ceramic‐based composite; the decreased fibre pullout and increased brittleness of the latter after heat treatment in air could thus be explained by the removal of the carbon layer and the development of silica bridges between fibre and matrix.
Microstructural observations of reaction zones in Ti‐based metal‐matrix composites
Authors: LORETTO M. H. , JOHNSON T. P. 
Published: August 2011

SUMMARYThe interaction between Ti‐alloy matrices and ceramic particulate and fibres in Ti‐based metal‐matrix composites (MMCs) is reviewed. It is concluded that the stability of surface‐treated SiC fibres is adequate for some applications of MMCs, but no other fibres have yet been developed which are useful additions to Ti alloys. Although there is less interest at this stage in particulate‐reinforced Ti MMCs, there are two ways in which useful particulate MMCs could be developed. First, the approach used in fibre‐reinforced composites, of using special coating techniques to stabilize the particulate against any reaction with the matrix. Second, either C or B additions could be used, both of which give rise to particulate phases which are stable in the presence of a Ti matrix, and which can therefore be manufactured using a wider range of process routes than is possible for other composites. The significance of these conclusions with regard to the ability to shape particulate composites into final products is briefly discussed.
Raman microscopy of fibres and composites
Authors: DAY R. J. , YOUNG R. J. 
Published: August 2011

SUMMARYSome of the progress made in using Raman microscopy to examine the structure and micromechanics of polymer and inorganic fibres is reviewed. Examples of how the technique has been used to verify some of the theories of composite reinforcement are then given. Finally, a specific example of how Raman microscopy has been used, in conjuction with other approaches, to understand the micromechanics of the microbond test, which is often used to measure interfacial shear strength in composite systems, is presented.
Scanning ion microprobe analysis of composite materials
Authors: WILLIAMS D. B. , SONI K. K. , TSENG M. W. , CHABALA J. M. , LEVI‐SETTI R. 
Published: August 2011

SUMMARYApplications of scanning ion imaging with high lateral resolution in the microchemical investigation of metal – and ceramic‐matrix composites are described. The technique, which combines a scanning ion microprobe with secondary ion mass spectrometry (SIMS), is ideally suited to the study of complex, multicomponent composite structures. Most elements can be detected with good sensitivity, enabling the determination of spatial distributions for major and minor elements. Analytical images obtained with this technique reveal unprecedented chemical information about interfacial segregation and interdiffusion phenomena. As examples, the characterization of both ceramic–matrix (Al borate–SiC) and metal–matrix (Ni alloy–Al2O3) composite materials is described.
The use of microscopy in the evaluation of fibre‐matrix interfacial properties
Authors: PITKETHLY M. J. 
Published: August 2011

SUMMARYMicroscopy plays an important role in the evaluation of the micromechanical properties of fibre‐matrix interfaces. The methods rely on the use of microscopy to undertake each test successfully. Physical parameters are evaluated quantitatively and the interface morphology is assessed qualitatively. This paper reviews the use of microscopy in evaluating the fibre–matrix interfacial properties of composites.
Characterization of subsurface damage in ceramic‐matrix composites by confocal scanning laser microscopy
Authors: POWELL K. L. , YEOMANS J. A. , SMITH P. A. 
Published: August 2011

SUMMARYThe techniques of confocal scanning laser microscopy (CSLM) and reflected‐light microscopy (RLM) have been combined in a study of the subsurface damage in continuous‐fibre reinforced ceramic‐matrix composites (CMCs).The damage was induced by subjecting a composite to Vickers hardness indentation tests and single‐particle impacts. The subsurface damage was viewed conventionally by RLM at specific depths, following material removal by standard metallographic techniques. Mechanical sectioning, however, is time‐consuming and may introduce artefacts in the crack patterns. Consequently CSLM was employed to provide a rapid, non‐destructive analysis of the subsurface damage.In the classic description of elastic‐plastic indentation of monolithic ceramics, there are two major types of crack: radial cracks, which grow out from the elastic‐plastic boundary perpendicular to the surface, and lateral cracks, which are on planes approximately parallel to the surface. In CMCs radial cracks were found to be restricted to the near‐surface region. Lateral cracks, however, were located a few micrometres from the free surface.Preliminary analysis of damage about impact sites by mechanical sectioning and CSLM has shown that the crack patterns are similar to those observed in indentation fracture. The topographical‐mapping facility of the CSLM has been used to detail the radius of damage about an impact site, which has been found to increase with increasing impact velocity.
Silicon carbide/SRBSN composites
Authors: RAZZELL A. G. , LEWIS M. H. 
Published: August 2011

SUMMARYCeramic‐matrix composites have been produced using unidirectionally aligned Textron SCS‐6 fibres in a sintered reaction‐bonded matrix. A tape‐casting technique was used to produce a prepreg sheet that could be cut and stacked to form a layup. Al2O3 and Y2O3 were used as sintering aids, final sintering being carried out in a hot press at 1700°C.Matrix, fibre and interfacial microstructure has been characterized using analytical microscopical techniques. X‐ray mapping of the carbon and silicon distribution at the fibre–matrix interface was carried out, and evidence of reaction between the outer carbon‐rich layer of the fibre and the matrix was found.Micromechanical behaviour of interfaces has been investigated and compared with interfacial microstructure and macromechanical properties.
Structure and composition of interfaces in an aluminium metal‐matrix composite
Authors: GOURBILLEAU F. , RUTERANA P. , NOUET G. 
Published: August 2011

SUMMARYThe microstructure of a 2024 type aluminium alloy, reinforced with 13 vol.% SiC particles, and made by a spray technique, has been investigated by transmission electron microscopy and X‐ray microanalysis in the as‐extruded and T6 conditions. High resolution electron microscopy studies and energy‐dispersive X‐ray spectrometry microanalysis were performed on the interfaces between the SiC particles and the metal matrix. The interfaces were found to be abrupt: some exhibit an amorphous layer, rich in oxygen; in many others, silver‐rich crystallites have grown coherently on the SiC particles.
The measurement of local plastic deformation in a metal‐matrix composite by electron back‐scatter patterns
Authors: WILKINSON A. J. , GONZALEZ G. , DINGLEY D. J. 
Published: August 2011

SUMMARYHigh dislocation densities in the matrices of metal‐matrix composites (MMCs) contribute to the strengthening of particulate MMCs, whilst heterogeneous nucleation of precipitates at these defects can cause marked differences in the age hardening of many matrix alloys. Electron back‐scatter patterns (EBSPs) and transmission electron microscopy (TEM) have been used to examine the dislocation distribution in continuous‐fibre SiC/Al alloy MMCs. TEM observations showed dislocation densities as high as 3 times 1014m−2, with a marked increase as thinner matrix regions were observed. From EBSP measurements on bulk specimens, a much lower dislocation density of 2 times 1012 m−2 was estimated. To resolve this discrepancy, EBSP measurements were made from thinned TEM specimens and these showed that the dislocation density had increased during specimen thinning. However, both TEM and EBSP measurements from unreinforced matrix material prepared for TEM using the same procedures showed no such increase in dislocation density. Redistribution of internal stresses during thinning of the composite to a transparent foil must therefore be the cause of the observed rise in dislocation density. The EBSP technique was demonstrated to be an excellent means of examining the distribution of plastic deformation in MMCs. It was concluded that TEM measurements of dislocation densities in continuous‐fibre MMCs can be erroneously high.
Microstructural characterization in diffusion‐bonded SiC/Ti–6Al–4V composites
Authors: GUO Z. X. , DERBY B. 
Published: August 2011

SUMMARYThe microstructural evolution during the diffusion bonding consolidation of a Ti–6Al–4V/SiC fibre composite was investigated by optical, scanning and transmission electron microscopy. The effects of processing parameters, particularly temperature, on the microstructures of the matrix and the fibre and their bonding were considered. Processing at too high a temperature can result in growth of SiC crystals in the fibre in addition to rapid interfacial reaction, while interfacial bonding cannot be established if the temperature is too low. Various defects can be caused by inadequate fabrication practices. These include micro‐pores, matrix‐cracking, cracking, bending and impingement of fibres, and heterogeneous fibre distribution. Methods for avoiding these are discussed. A defect‐free and uniformly distributed fibre composite can only be achieved by optimizing the processing parameters (such as temperature, pressure, time and cooling rate) and adequately combining fibre spacing and matrix thickness with accurate fibre alignment.