bluuebunny/crossref_metadata_2025_split huggingface dataset:
Stereo pairs of bright‐field micrographs via Wiener‐type inverse filtering
Authors: Khosla Deepak , Holmes Timothy J. 
Published: August 2011

SUMMARYIn a three‐dimensional (3‐D) image data set obtained through optical sectioning, each two‐dimensional (2‐D) segment is blurred by out‐of‐focus information from neighbouring focal planes superimposed on the in‐focus segments from that plane. Instead of attempting to remove this redundant information over the full 3‐D data set, we have developed a technique for restoring stereoscopic views. In this paper we describe the implementation of a Wiener‐type inverse filtering method for generating stereo pairs of bright‐field micrographs. A theoretical optical transfer function valid under certain simplifying approximations has been used in implementing this filtering technique. In developing this method the slice theorem of computed tomography is used. In this way the image reconstruction problem is reduced to one of processing 2‐D arrays rather than 3‐D arrays and the problem of restoring missing Fourier components within the missing‐cone region is circumvented. Limited experimentation with real micrographs shows that the approach provides images that display an effective increased depth of field and 3‐D attributes of the specimen, even though some of the underlying assumptions on which this method is based are difficult to verify explicitly. The method can be implemented with a relatively fast execution time on 386‐SX computers.
Depth discrimination in scanned heterodyne microscope systems
Authors: Somekh Michael G. 
Published: August 2011

SUMMARYThe optical transfer function of several scanning microscope systems is derived, using a physically intuitive approach. The technique allows a wide range of systems to be modelled with only minor modifications to the basic formulation.The results are then used to determine the response of various scanning microscopes for objects both in and out of the focal plane. The possibility of performing extended‐focus phase imaging in heterodyne microscopes by scanning the sample along the optical axis is also examined. This mode of operation should allow measurements of minute topographical and phase variations on tilted or warped samples with the same lateral resolution as would be obtained when the sample is in focus throughout the entire scan.
Computer‐assisted realignment of light micrograph images from consecutive section series of cat cerebral cortex
Authors: Rydmark M. , Jansson T. , Berthold C.‐H. , Gustavsson T. 
Published: August 2011

SUMMARYTwo computer‐ and image‐analysis‐based procedures for realignment of images of consecutive light micrographs of nerve tissue (cat motor cortex) have been developed. One procedure (CENT) was interactive, employing the subjective overall ‘best fit’ of two images to each other and the other (AUTOCENT) was based on an automatic comparison of two images (image thresholding and binary comparison). Images of light micrographs of several hundred consecutive sections were realigned using the interactive and the automatic methods. The interactive procedure was easy to use; realignment of an image took only a few minutes in the hands of an experienced operator and should be easy to implement on commercially available smaller computers like PCs and workstations, but the realignment was possibly disturbed by the operator's subjective expectancy of regular forms. The automatic procedure realigned 1–4 images per hour, might be implemented on smaller computers if the programming is made more efficient, was probably objective and restored the ‘true position of images’.
Optimum recording conditions in scanning microscopes
Authors: Damm Tobias , Wilhelmi Bernd 
Published: August 2011

SUMMARYThe measuring process in the scanning microscope is analysed. The distortion of the recorded image due to finite diameter of the probe (laser spot, electron beam, nanometre tip) and due to the limited temporal response of the recording system is estimated. The influence of noise on the accuracy of the recorded image is considered. Optimum recording conditions such as choice of scan velocity and response time of the registration device are discussed with respect to minimum total error.
Experimental confirmation of super‐resolution in coherent confocal scanning microscopy using optical masks
Authors: Young M. R. , Jiang S. H. , Davies R. E. , Walker J. G. , Pike E. R. , Bertero M. 
Published: August 2011

SUMMARYExperimental results are presented which demonstrate super‐resolution in a coherent scanning microscope. The microscope has a special optical mask, a Fourier lens and detector pin‐hole to carry out optical processing of the image. The form of the special mask was calculated using the theory of singular systems.
Optical modifications enabling simultaneous confocal imaging with dyes excited by ultraviolet‐ and visible‐wavelength light
Authors: BLITON C. , LECHLEITER J. , CLAPHAM D. E. 
Published: August 2011

SUMMARYOptical modifications to a confocal scanning laser microscope are described which allow simultaneous fluorescence imaging of living specimens excited by ultraviolet (UV)‐ and visible‐wavelength light. Modifications to a Bio‐Rad MRC 600 Lasersharp confocal microscope include the introduction of UV‐path‐specific lenses and a specially designed UV transmitting eyepiece and tube lens. Upon UV excitation these modifications provide similar resolution and field flatness when compared with visible confocal microscopy. The UV‐path‐specific optics could be adjusted to correct for varying amounts of longitudinal chromatic aberration in commercially available objectives. Eyepiece and tube lenses were chromatically corrected for UV through visible wavelengths to minimize lateral chromatic error. With these modifications, UV‐wavelength light may be used to excite ratioing dyes to quantify intracellular ion concentrations, or as an energy source to release caged compounds in a spatially restricted volume, while simultaneously imaging with dyes excited by visible‐wavelength light.
A method for spatio‐temporal (4‐D) data representation in confocal microscopy: application to neuroanatomical plasticity
Authors: KRIETE A. , WAGNER H.‐J. 
Published: August 2011

SUMMARYThis paper describes a new method for data representation and visualization in four dimensions (three dimensions plus time). Sequential volumes, exhibiting morphological activity, are acquired non‐invasively with a confocal scanning laser microscope, where each data set corresponds to a time sample. A pipelined processing includes packing of volumes and specific volume rendering techniques. Subsequent processing in HIS (hue, intensity, saturation) colour space combines functional, packed images with shaded three‐dimensional views. As a result, even subtle changes in morphology become visible and computational time is saved. Experimental findings obtained from investigations of synaptic plasticity in cultured retinal tissue are reported.
A synchrotron X‐ray study of the changes occurring in the corneal stroma during processing for electron microscopy
Authors: FULLWOOD N. J. , MEEK K. M. 
Published: August 2011

SUMMARYUsing a high‐intensity synchrotron X‐ray source, the structural changes occurring in the corneal stroma were monitored during each stage of several different processing runs for the transmission electron microscope (TEM) and scanning electron microscope (SEM). The parameters studied were interfibrillar spacing, intermolecular spacing, D‐periodicity and fibril diameter.The processing schedule that produced the least changes in spacings for TEM specimens involved extended fixation in glutaraldehyde followed by low‐temperature embedding in Lowicryl K4M resin. However, interfibrillar material was better preserved after embedding in LR White resin or Nanoplast.Almost every processing stage for electron microscopy produced significant changes in one or more structural parameters in the cornea. Glutaraldehyde fixation significantly increased the intermolecular spacings, while resin infiltration and resin polymerization each resulted in shrinkage of all the spacings monitored. Critical‐point drying for SEM specimens resulted in considerable shrinkage in all three spacings, but was still preferable to air drying, which caused reduction in the order of the fibril packing, resulting in loss of the interfibrillar X‐ray pattern. Perhaps the most drastic effect was caused by post‐fixation in osmium tetroxide, which resulted in loss of the intermolecular pattern, and also increased the amount of shrinkage in the interfibrillar spacings and the D‐periodicity which occurred during later stages of processing.
Glucose alone does not completely hydrate bacteriorhodopsin in glucose‐embedded purple membrane
Authors: PERKINS G. A. , BURKARD F. , LIU E. , GLAESER R. M. 
Published: August 2011

SUMMARYGlucose embedding is a simple and highly effective method for preparing biological macromolecules for high‐resolution electron microscopy. The investigation of conditions that can trap the M‐state intermediate in the bacteriorhodopsin (bR) photocycle has revealed, however, that when glucose‐embedded bR is prepared at ambient humidity, it does not fully retain the capability to execute a proper photocycle. However, ‘native’ photocycle properties are returned after glucose‐embedded samples are equilibrated at 81% relative humidity. Equilibration at relative humidities significantly higher than 81% causes glucose to dissolve in its own water of hydration, resulting in samples that may be too thick to be suitable for electron microscopy. The results obtained with bR indicate that caution should be taken with other biological specimens, and it cannot be assumed that glucose‐embedded biological macromolecules retain completely their native, hydrated structure, even when high‐resolution electron diffraction patterns are obtained. Equilibration of such samples at high humidity may generally be a worthwhile precaution when using the glucose‐embedding technique.
Grid‐specimen interactions: factors affecting copper nanocluster formation on polymer thin films
Authors: BURNS J. L. , SPONTAK R. J. 
Published: August 2011

SUMMARYAll transmission electron microscopy (TEM) studies require the use of grids to support thin films or sections of specimens within the microscope. These grids are presumed to remain inert during sample loading and analysis, an assumption which becomes questionable when on‐the‐grid processing methods are employed to probe the response of a specimen to a particular stimulus, such as temperature increase. Uniform dispersions of nanoclusters were observed to develop on and undergo chemical complexation with thin cast films of a poly(siloxaneimide) copolymer supported on various copper grids during thermal annealing at temperatures of up to 200°C. The thermal conditions which promoted nanocluster formation were investigated. Experiments designed to elucidate the mechanism by which these nanoclusters develop revealed that cuprous oxide (Cu2O) from the copper support grids is deposited on these imide‐bearing films from the vapour phase.
Scan speed limit in atomic force microscopy
Authors: BUTT H.‐J. , SIEDLE P. , SEIFERT K. , FENDLER K. , SEEGER T. , BAMBERG E. , WEISENHORN A. L. , GOLDIE K. , ENGEL A. 
Published: August 2011

SUMMARYThe scan speed limit of atomic force microscopes has been calculated. It is determined by the spring constant of the cantilever k, its effective mass m, the damping constant D of the cantilever in the surrounding medium and the stiffness of the sample. Techniques to measure k, k/m and D/m are described. In liquids the damping constant and the effective mass of the cantilever increase. A consequence of this is that the transfer function always depends on the scan speed when imaging in liquids. The practical scan speed limit for atomic resolution in vacuum is 0·1 μm/s while in water it increases to about 2 μm/s due to the additional damping of cantilever movements. Sample stiffness or damping of cantilever movements by the sample increase these limits. For soft biological materials imaged in water at a desired resolution of 1 nm the scan speed should not exceed 2 μm/s.
A simple modification to the LKB 7800 series Knifemaker and a balanced‐break method to prepare glass knives for cryosectioning
Authors: WEBSTER P. 
Published: August 2011

SUMMARYA novel method of using the LKB 7800 series Knifemaker to produce glass knives using a balanced break is described. The method produces knives of sufficient quality to section aldehyde‐fixed, sucrose‐cryoprotected, frozen biological material in a cooled cryochamber of an ultramicrotome. The modifications to the Knifemaker are minimal and, if required, the machine can be returned easily to its normal state after use.
Numerical apertures of light microscope objectives
Authors: LEHMANN W. , WACHTEL A. 
Published: August 2011

SUMMARYThe numerical aperture of light‐microscope objectives is measured via the exit angle of the rear lens towards the image space, and the magnification of the objective. The method is reliable because of its simplicity and is independent of special instrumentation such as apertometers. Results from eight commercially available objectives indicate fair agreement of nominal data with measured data for the magnifications, but not for all numerical apertures.
Microstructure‐property relationships in silicate‐matrix composites
Authors: LEWIS M. H. , DANIEL A. M. , CHAMBERLAIN A. , PHARAOH M. W. , CAIN M. G. 
Published: August 2011

SUMMARYElectron microscopy and associated analytical spectroscopic techniques have been used to characterize interfaces in SiC‐fibre/silicate‐matrix composites. Interface structure, formed via reaction during hot‐press fabrication, is a function of time, temperature, matrix composition and fibre type. Interfaces with Nicalon or Tyranno fibres vary from amorphous carbon in fine precipitated form to continuous graphitic layers.Interface behaviour in a stressed composite, and hence the matrix microcracking stress, is a sensitive function of microstructure. Interface debond and shear properties have been assessed using indent‐based ‘push‐down’ and ‘push‐through’ tests using a specially developed instrument within a scanning electron microscope. This uses piezoload measurement and translation, and is capable of dynamic image recording of the indentation sequence.Interface micromechanical (indent) measurements have been correlated with structure and macromechanical response in bend testing for a range of fibre/matrix types, processing and post‐processing thermal treatments. An example is also given of interfaces prepared by fibre precoating.
Acoustic microscopy of ceramic‐fibre composites
Authors: BRIGGS G. A. D. , LAWRENCE C. W. , SCRUBY C. B. 
Published: August 2011

SUMMARYA variety of ceramic‐fibre composites has been studied by acoustic microscopy, at 1·9 GHz with a resolution of 0·8 μm. The materials studied were Nicalon‐reinforced borosilicate glass, SiC fibres in a magnesium–aluminosilicate matrix and a calcium‐aluminosilicate matrix, and SiC monofilaments in a Ti–6Al–4V matrix. In all the specimens the contrast was dominated by strong excitation of Rayleigh waves in the surface. This gave strong contrast from different phases, and revealed interfaces and cracks by characteristic crack patterns. Quantitative agreement between observed and calculated fringe patterns was found, and values of shear and Young's modulus were measured. In the SiC monofilament specimens, various stages of progressive deterioration as a result of thermal ageing treatments were observed.
TEM observations of SiC‐SiC composites with a carbon interphase layer annealed in air at high temperatures
Authors: SEBIRE‐LHERMITTE I. , GOMINA M. , VICENS J. 
Published: August 2011

SUMMARYSiC–SiC composites with a carbon interphase layer have been annealed in air at high temperature (800–1400°C) in order to determine the oxidation mechanism. Transmission electron microscopy and high‐resolution electron microscopy observations have been performed on thin slices of oxidized specimens. Observations show that, with oxidation above 800°C, the carbon interphase can be replaced totally by a thick silica layer, in agreement with previous work. However, in many cases the modified interphase is heterogeneous. The turbostratic carbon structure disappears and the carbon interphase layer is partially replaced by an amorphous silica layer found preferentially at the contact zone between the fibres and the carbon layer. A very thin silica layer can also be observed on the matrix side at the matrix‐fibre interfaces. Some decohesion appears in areas where carbon is still present. For short‐duration exposures, decohesion occurs between the fibres and the carbon interphase layer.
The microstructure of silicon carbide (Nicalon) fibre reinforced silicon carbide ceramic‐matrix composites heat treated in vacuo and in pure oxygen
Authors: VINE W. J. , STEEDS J. W. 
Published: August 2011

SUMMARYSilicon carbide (Nicalon) fibre reinforced SiC composites have been heat treated in vacuo and in pure oxygen environments at 1400°C for 100 h. The response of the microstructure and, in particular, of the interface between fibre, carbon interlayer and SiC matrix components has been studied. Microstructural modifications were observed by transmission electron microscopy, using imaging, electron energy‐loss spectroscopy and electron diffraction techniques, and fibre stoichiometries were determined using a scanning Auger microprobe.Recrystallization of Nicalon fibres within composites heat treated in vacuo was found to result from decomposition of the metastable silicon oxy‐carbide phase found in the fibres. No significant changes to the pyrolytic carbon interlayer were observed. Fibre recrystallization was considered to embrittle the composite.Samples heat treated in oxygen showed no appreciable fibre recrystallization. Study of interlayers in such aged samples often revealed decohesions, holes and narrow silica layers. In the most extreme cases, complete displacement of carbon by SiO2 was found and such interfaces were identified as silica and α‐cristobalite. Interfacial modifications were considered to be responsible for the retention of the small β‐SiC grain size in Nicalon fibres and were also considered to be deleterious to the mechanical properties.
A microstructural investigation of deformation in fine SiC particulate‐ and whisker‐reinforced aluminium‐matrix composites
Authors: BARLOW C. Y. , HANSEN N. , LIU Y. L. 
Published: August 2011

SUMMARYAluminium‐based composites, reinforced with low volume fractions of whiskers and small particles, have been formed by a powder route. The materials have been tested in tension, and the microstructures examined using transmission electron microscopy. The whisker composites showed an improvement in flow stress over the particulate composites, and this was linked to an initially enhanced work‐hardening rate in the whisker composites. The overall dislocation densities were estimated to be somewhat higher in the whisker composites than the particulate composites, but in the early stages of deformation the distribution was rather different, with deformation in the whisker material being far more localized and inhomogeneous. This factor, together with differences in the internal stress distribution in the materials, is used to explain the difference in mechanical properties.
The microstructures of locally reinforced squeeze‐cast Al‐alloy metal‐matrix composites
Authors: KANG H. G. , ZHANG D. L. , CANTOR B. 
Published: August 2011

SUMMARYLocally reinforced metal‐matrix composites (MMCs) have been manufactured by squeeze casting an A357 Al alloy into a die containing a reinforcement insert of either steel, an A356/10 vol.% SiCp MMC, or a 20 vol.% Al2O3 short‐fibre preform. The temperatures of the Al‐alloy matrix, reinforcement insert and die were monitored continuously during squeeze casting, and the microstructures of the ascast MMCs were examined. Application of high pressure caused intimate contact along the insert‐matrix interface with refinement of the matrix microstructure. There was little bonding between the matrix and the steel insert, while good bonding was obtained between the matrix and the A356/SiCp MMC insert, which was partially melted at the interface. The Al2O3 short‐fibre preform insert was fully infiltrated at high pressure, with a band of high Si content in the matrix microstructure near the interface.
Heterogeneous fibre microstructures and their influence on failure
Authors: ZYWICZ E. , KINNEY J. H. , SATTLER M. L. , BREUNIG T. M. , NICHOLS M. C. 
Published: August 2011

SUMMARYA detailed microscopic, experimental and micromechanical evaluation of fibre damage initiation in a unidirectional aluminium matrix‐silicon carbide fibre (SCS‐8TM) composite has been performed for a monotonic load sequence. The salient fibre features include a 33‐μm‐diameter monofilament turbostratic carbon (C) core, a ∼ 1·5‐μm pyrolytic C layer, an interior sheath of β‐phase silicon carbide (SiC) crystallites imbedded in an amorphous C matrix, and an exterior sheath of radially orientated β‐SiC. Quantitative microscopy shows that the interior sheath's surplus C varies smoothly from ∼ 35% by volume near the core to zero at the mid‐radius. The multi‐phase structure of the fibre produces an internal mechanical stiffness that increases with distance from the core, and thus peak stresses result in the exterior sheath. X‐ray tomographic microscopy (XTM) reveals that cores fracture randomly, without failure of the surrounding SiC, at stress levels above half the ultimate strength of the composite. Three‐dimensional XTM reconstructions show planar, non‐planar and spiral cracks in the failed fibre, suggesting multiple and competing initiation mechanisms. Qualitative fracture assessments suggest that flaws near the C core grow outward in a curved manner through the SiC–C and planar beyond the mid‐radius, whereas cracks originating near the fibre–matrix interface favour planar trajectories inward across the whole fibre.
The microstructure of spray‐formed Ti‐6Al‐4V/SiCf metal‐matrix composites
Authors: ZHAO Y. Y. , GRANT P. S. , CANTOR B. 
Published: August 2011

SUMMARYSpray‐forming is a possible manufacturing route for the fabrication of Ti alloy fibre‐reinforced metal‐matrix composites (MMCs) because high rates of alloy‐droplet cooling on impact with the fibres prevent excessive fibre‐matrix reaction. Ti–6Al–4V matrix MMC monotapes containing TiB2‐coated SiC fibres have been manufactured by electric‐arc spray‐forming, and the key MMC microstructural characteristics in the as‐sprayed monotapes have been investigated by optical and scanning electron microscopy. Fibre infiltration increases with decreasing spraying distance, decreasing atomizing gas pressure and increasing arc current, because of higher temperatures in the Ti alloy spray droplets on impact with the fibres. Too much binder in the fibre preform leads to poor fibre–matrix contact, while removing the binder leads to the fibres becoming misaligned during spraying.
Comparison of interfaces in Ti composites reinforced with uncoated and TiB2/C‐coated SiC fibres
Authors: GUO Z. X. , DERBY B. , CANTOR B. 
Published: August 2011

SUMMARYInterfaces play an important role in determining the mechanical properties of composite materials. The interfaces established between a titanium‐alloy matrix (Ti‐6Al‐4V) and uncoated and TiB2/C‐coated SiC fibres are analysed by scanning electron microscopy, transmission electron microscopy and X‐ray techniques. Emphasis is placed upon the interfacial morphology and microstructure, identification of reaction products, and the stability of the coating layer. Complex multi‐reaction layers are observed frequently in the interfacial zones. Previous, often contradictory, reports about the interlayers are reviewed. Experimental observation demonstrates that the type and distribution of interlayers vary in a given system, due to prolonged treatment of the samples at temperature. The formation and distribution of the interlayers are discussed further, with respect to these and previous findings. Methods of reducing interfacial reactivity are discussed.