bluuebunny/crossref_metadata_2025_split huggingface dataset:
Simultaneous confocal recording of multiple fluorescent labels with improved channel separation
Authors: CARLSSON K. , ÅSLUND N. , MOSSBERG K. , PHILIP J. 
Published: August 2011

Confocal microscopes are often used to study specimens labelled with fluorophores. A commonly used method for simultaneous recording of the distribution of multiple fluorophores is to divide the fluorescent light emitted by the specimen into different wavelength regions using dichroic and bandpass filters. These different wavelength regions are then distributed to multiple detectors. However, the broad and overlapping spectra of commonly used fluorophores often result in considerable crosstalk between channels. A new technique, intensity‐modulated multiple‐beam scanning (IMS) microfluorometry, can be used to reduce this cross‐talk substantially.The IMS technique is implemented with two laser beams of different wavelengths, intensity‐modulated at different frequencies, which illuminate the specimen simultaneously. The two laser wavelengths predominantly excite one fluorophore each. Fluorescent light from the specimen is divided into two wavelength regions (red and green) which are detected by two photomultiplier tubes. The output signals from the photomultiplier tubes are connected to lock‐in amplifiers. The effect of using modulated laser beams, in combination with lock‐in amplifiers, is strongly to reduce cross‐talk between the channels. The performance of the IMS technique using various types of specimen is compared with the results obtained using the conventional multi‐detector method.
Standard performance criteria for analytical electron microscopy
Authors: ZEMYAN S. M. , WILLIAMS D. B. 
Published: August 2011

SummaryUsers of analytical electron microscopy lack easy‐to‐use standards for assessing the consistency and quality of analytical performance. We propose using a Cr thin film of known thickness to measure three important characteristics related to performance: the Cr Kα peak‐to‐background (P/B) ratio, the X‐ray spectrometer relative efficiency, and the spectrometer energy resolution. We used a Cr specimen to determine the instrumental factors which influence the P/B ratio, finding that the highest P/B ratios are achieved in scanning transmission mode at the highest available accelerating voltage. We present values of the P/B ratio, and the detector relative efficiency and energy resolution which can be used for comparison in other laboratories using the standard film.
Regression methods for automated colour image classification and thresholding
Authors: BREEN E. J. 
Published: August 2011

SummaryRegression methods are used to perform automated image thresholding and colour pixel classification. This is done by considering threshold levels and pixel classification labels as pattern attributes. A regression equation that performs a mapping from the J dimensional feature‐pattern space to the K dimensional attribute space is derived. The approach is non‐parametric and deterministic, hence no assumptions about the statistical properties of the input patterns or images need be made. Initially a known set of input patterns with associated attributes are used to constitute a training set. A mapping function is then determined from the training patterns and used for estimating attribute values from unknown input patterns, such as images.
Surface ultrastructure of olfactory receptor sense hairs in the silkmoth, Antheraea pernyi
Authors: POPOV V. I. , NIKONOV A. A. , AGAFONOVA N. K. , FESENKO E. E. 
Published: August 2011

SummaryThe fine structure of silkmoth sense hair surfaces has been investigated by freeze etching with Pt/C rotary shadowing. To do this, the hydrophobic layer in the cuticle was removed using 20–25% methanol or ethanol. Freeze‐etch patterns of sense hair surfaces, as well as the pore structure and pore distribution, are shown. The hair surface has a nonhelical ‘band’ structure, in which every ‘band’ lies at an oblique angle with respect to the axis of the hair. Each ‘band’ is separated from its neighbour by a 30‐nm step. The average density of pores is 11·3 + 2·4 pores μm−2. Freeze‐etch patterns of the single and multiple pore tubules are shown. Evidence for direct contact between the pore tubule and dendrite membrane of an olfactory receptor neuron is presented.
Agar standards for quantitative X‐ray microanalysis of resin‐embedded plant tissues
Authors: FRITZ E. , JENTSCHKE G. 
Published: August 2011

SummaryCalibration standards for quantitative X‐ray microanalysis of resin‐embedded plant tissue were prepared by adding 6600 mM KC1 to 5% agar. Agar blocks with an edge length of 1–2 mm were rapidly frozen, freeze‐dried and embedded in styrene‐methacrylate. Dry sections 1 μm thick were mounted on adhesive‐coated grids. Apart from fine‐scale inhomogeneities caused by ice crystal formation, the KC1 is evenly distributed in the agar blocks. The peak‐to‐continuum values of K and Cl were highly linearly correlated to the K and Cl contents over the whole concentration range.
Differential imaging in confocal microscopy
Authors: WILSON T. , JUŠKAITIS R. , TAN J. B. 
Published: August 2011

SummaryA coherent detection system using a two‐mode optical fibre is described which permits confocal, differential amplitude contrast and differential phase contrast images to be obtained simultaneously from a scanning optical microscope. The direction of differentiation may be chosen arbitrarily. The differential imaging modes possess an optical sectioning property.
A new method to correlate acoustic spectroscopic microscopy (30 MHz) and light microscopy
Authors: VAN DER STEEN A. F. W. , THIJSSEN J. M. , VAN DER LAAK J. A. W. M. , EBBEN G. P. J. , DE WILDE P. C. M. 
Published: August 2011

SummaryA powerful new method is used to investigate the correlation between light microscopic and acoustic properties of biological tissues. Specimens of liver were sectioned into successive slices, 250 μm and 10 μm thick. The thick sections were investigated acoustically, the thin sections by means of light microscopy. Markers that could be detected and located, both optically and acoustically, were used to find and reconstruct corresponding regions in the acoustic and optical sections (2·5 × 2·5 mm).Parameter images were reconstructed from the sections investigated acoustically. The acoustic parameters were attenuation at 30 MHz, the slope of the attenuation spectrum (between 10 and 50 MHz), backscattering at 30 MHz, the slope of the backscattering spectrum (between 10 and 50 MHz) and the local ultrasound velocity. Acoustic images were obtained in the frequency range from 10 to 50 MHz, yielding a lateral resolution of about 50 μm.The sections for light microscopy were stained according to the Goldner trichrome staining technique. The histological composition was determined quantitatively, using digital image segmentation techniques. The percentage of collagen‐rich fibrous tissue, luminal structure and interstitial spaces, and the number of nuclei were calculated for regions of 250 × 250 μm. These histological features were correlated with the acoustic parameters obtained from the corresponding regions in adjacent sections. It was thus possible to find the histological components responsible for acoustic parameters.
Three‐dimensional reconstruction of the human renal glomerulus
Authors: PRESTON K. , JOE B. , SIDERITS R. , WELLING J. 
Published: August 2011

SummaryThe capillary bed of the human renal glomerulus is one of the more complex capillary structures in the human body. This paper illustrates three‐dimensional reconstruction of the capillary bed from serial sections. It shows that, although traditional methods of three‐dimensional rendering by computer fail to handle the complexities of the capillary structure, new methods based on filtering using three‐dimensional mathematical morphology are capable of revealing previously unseen details. This is done at the expense of eliminating fine structure (small capillaries). An error analysis allows the degree to which fine details are lost to be estimated.
Computer‐simulated high‐resolution transmission electron microscopy (HRTEM) in tourmaline
Authors: FERROW E. A. 
Published: August 2011

SummaryThe contrast distributions observed in high‐resolution transmission electron microscopy (HRTEM) images of tourmaline depend on the types and magnitudes of the exchange components present and on the degree of atom overlap along the direction of observation. Furthermore, the fractional atomic coordinates in tourmalines are valid only for the specific specimen refined. These properties make the interpretation of experimental HRTEM images of tourmaline using image simulation if not impossible at least extremely difficult. A correct interpretation of experimental HRTEM images of tourmaline is possible provided the structural refinement data on the same crystal are available. Nevertheless, it is possible to interpret the experimental HRTEM images of tourmaline if the composition of the structural model chosen during image simulations approximates the composition of the specimen studied by electron microscopy. A good control of the composition of the specimen studied and an appropriate choice of a structural model for image simulation are therefore as important as properly controlling specimen thickness, specimen tilt, beam tilt and objective lens defocus.
Thick bone section preparation using a silicon‐rubber‐based sealant
Authors: COX H. , WALKER C. , HOWARD C. V. 
Published: August 2011

SummaryA method has been developed, using a silicon‐rubber‐based sealant, which allows 2–3‐mm‐thick specimens to be maintained in a protected fluid environment for a number of months, without risk of dehydration. Following this, the specimen can be retrieved, stained, embedded and sectioned further. For example, 2‐mm‐thick sections of fixed unstained bone are easily examined by means of epi‐illuminated polarized light and fluorescence microscopies using either conventional or confocal optics. The method could easily be extended to other tissues, for example brain tissue.
Application of confocal laser microscopy and three‐dimensional Voronoi diagrams for volume and surface estimates of interphase chromosomes
Authors: EILS R. , BERTIN E. , SARACOGLU K. , RINKE B. , SCHRÖCK E. , PARAZZA F. , USSON Y. , ROBERT‐NICOUD M. , STELZER E. H. K. , CHASSERY J.‐M. , CREMER T. , CREMER C. 
Published: August 2011

SUMMARYThis study demonstrates the use of Voronoi tessellation procedures to obtain quantitative morphological data for chromosome territories in the cell nucleus. As a model system, chromosomes 7 and X were visualized in human female amniotic fluid cell nuclei by chromosomal in situ suppression hybridization with chromosome‐specific composite probes. Light optical serial sections of 18 nuclei were obtained with a confocal scanning laser fluorescence microscope. A three‐dimensional (3‐D) tessellation of the image volumes defined by the stack of serial sections was then performed. For this purpose a Voronoi diagram, which consists of convex polyhedra structured in a graph environment, was built for each nucleus. The chromosome territories were extracted by applying the Delaunay graph, the dual of the Voronoi diagram, which describes the neighbourhood in the Voronoi diagram. The chromosome territories were then described by three morphological parameters, i.e. volume, surface area and a roundness factor (shape factor). The complete evaluation of a nucleus, including the calculation of the Voronoi diagram, 3‐D visualization of extracted territories using computer graphic methods and parameterization was carried out on a Silicon Graphics workstation and was generally completed within 5 min. The geometric information obtained by this procedure revealed that both X‐ and 7‐chromosome territories were similar in volume. Roundness factors indicated a pronounced variability in interphase shape for both pairs of chromosomes. Surface estimates showed a significant difference between the two X‐territories but not between chromosome 7‐territories.
PHOEBE, a prototype scanning laser‐feedback microscope for imaging biological cells in aqueous media
Authors: WONG T. L. , SABATO S. L. , BEARDEN A. 
Published: August 2011

SUMMARYBased on the principle of laser‐feedback interferometry (LFI), a laser‐feedback microscope (LFM) has been constructed capable of providing an axial (z) resolution of a target surface topography of ∼ 1 nm and a lateral (x, y) resolution of ∼ 200 nm when used with a high‐numerical‐aperture oil‐immersion microscope objective. LFI is a form of interferometry in which a laser's intensity is modulated by light re‐entering the illuminating laser. Interfering with the light circulating in the laser resonant cavity, this back‐reflected light gives information about an object's position and reflectivity. Using a 1‐mW He–Ne (λ = 632·8 nm) laser, this microscope (PHOEBE) is capable of obtaining 256 × 256‐pixel images over fields from (10 μm × 10 μm) to (120 μm × 120 μm) in ∼ 30 s. An electromechanical feedback circuit holds the optical pathlength between the laser output mirror and a point on the scanned object constant; this allows two types of images (surface topography and surface reflectivity) to be obtained simultaneously. For biological cells, imaging can be accomplished using back‐reflected light originating from small refractive‐index changes (> 0·02) at cell membrane/water interfaces; alternatively, the optical pathlength through the cell interior can be measured point‐by‐point by growing or placing a cell suspension on a higher‐reflecting substrate (glass or a silicon wafer). Advantages of the laser‐feedback microscope in comparison to other confocal optical microscopes include: the simplicity of the single‐axis interferometric design; the confocal property of the laser‐feedback microscope (a virtual pinhole), which is achieved by the requirement that only light that re‐enters the laser meeting the stringent frequency, spatial (TEM00), and coherence requirements of the laser cavity resonator mode modulate the laser intensity; and the improved axial resolution, which is based on interferometric measurement of optical amplitude and phase rather than by use of a pinhole as in other types of confocal microscopes.
Microstructure and thermo‐mechanical stability of a low‐oxygen Nicalon fibre
Authors: BERGER M. H. , HOCHET N. , BUNSELL A. R. 
Published: August 2011

SummaryA new Nicalon SiC‐based fibre, characterized by a low oxygen content (0–5% wt) has been studied. The absence in this fibre of a continuous Si–C–O phase, which characterized the previous NLM 202 series of fibres, induces larger mean sizes for the constituents: the fibre is composed of β‐SiC grains 5–20 run in diameter and turbostratic aggregates of carbon 2–5 nm in diameter. The fibre is seen to be suffer at room temperature (E= 300 GPa) and stronger due to a reduction in critical defects thanks to improvements in processing conditions. The Young's modulus remains almost stable up to 1473 K in air and above this temperature the core of the fibre exhibits continuous grain growth up to 1773 K, but without the degradation that occurred in the previous generation of fibres. Fibre strength was seen to be lowered when compared to room temperature values even when exposed in air to temperatures of 1073 K. A comparable fall is not seen with the NLM 202 fibres until 1273 K and this difference is attributed to the oxidation of the carbon‐rich surface of the new fibre. SiC is oxidized at higher temperatures, inducing, above 1473 K, the growth of a silica layer on the surface, with defects at the glass/ceramic interface. The large discrepancies between the good thermo‐mechanical characteristics in inert atmosphere and the behaviour in air may be reduced if a coating resistant to oxidation could be applied to the fibre.
Environmental ageing effects in a silicon carbide fibre‐reinforced glass‐ceramic matrix composite
Authors: PLUCKNETT K. P. , SUTHERLAND S. , DANIEL A. M. , CAIN R. L. , WEST G. , TAPLIN D. M. R. , LEWIS M. H. 
Published: August 2011

SummaryA silicon carbide fibre‐reinforced glass‐ceramic composite, based upon a BaO–MgO–Al2O3–SiO2 (BMAS) matrix, has been used for a study of microstructural stability (specifically interface stability) after environmental exposure at elevated temperature. Characterization of the as‐received material demonstrated the presence of a thin ‘carbon‐rich’ interfacial layer between fibre and matrix, as typically observed in glass‐ceramic/silicon carbide fibre composite systems. Samples have been subjected to heat‐treatments in an oxidizing atmosphere at temperatures between 723 and 1473 K, for up to 500 h. Intermediate‐temperature ageing, between 873 and 1073 K, results in strong fibre/matrix bonding, with consequent degradation of strength and composite ‘ductility’. This is due to oxidative removal of the carbon interfacial layer and subsequent oxidation of the fibre surface, forming a silica bridge. Carbon is retained at higher ageing temperatures due to the formation of a protective surface oxide scale at exposed fibre ends. Attempts to pretreat the BMAS composite at high temperature (1273–1473 K), designed to inhibit intermediate‐temperature degradation via the formation of silica plugs at exposed fibre ends, has given mixed results due to the high residual porosity content in these materials, allowing paths of ‘easy’ oxygen ingress to be retained.
Synthesis of silicon carbide ceramics from a polysilastyrene at low temperatures
Authors: McMILLAN S. M. , BROOK R. J. 
Published: August 2011

SummaryThe conventional route for preparation of silicon carbide ceramics is by the use of pressureless sintering, hot pressing, or hot isostatic pressing of silicon carbide starting powders. High sintering temperatures (2073–2473 K) and the addition of sintering additives are normally used to enhance densification. These sintering additives, however, form second phases at grain boundaries which impair the mechanical properties of the material, particularly at high temperatures. It is therefore desirable that new processing routes are developed that overcome these difficulties. A proposed route is to use a polymeric pressure which can provide a Silicon carbide matrix as binding agent for silicon carbide powders, thus making the requirement for high temperatures and sintering additives unnecessary. This paper reports observations of the direct transformation of a polymeric precursor into amorphous Si–C, and crystalline SiC at low temperatures, and the use of this precursor as a binder for the production of SiC powder/ex‐precursor SiC composites.
A comparison of the microstructure of silicon nitride‐silicon carbide composites made with and without deoxidized starting material
Authors: TURAN S. , KNOWLES K. M. 
Published: August 2011

SummaryTwo different types of silicon carbide (SiC) matrix composites, with either 10 wt% or 20 wt% silicon nitride (Si3N4) reinforcement, were fabricated to investigate the effect of pretreatment on the resulting composite micro‐structure. The first type of composite was prepared from as‐received α‐SiC and α‐Si3N4 powders, while the second type was prepared from powder compacts that had been deoxidized to eliminate surface silica on the powder particles. The composites were hot isostatically pressed in tantalum cans at 2373 K for 1h under a pressure of 200 MPa. Density measurements showed that full theoretical density was achieved for the composites prepared from the as‐received powders, while much lower densities were obtained for the composites prepared from the deoxidized green compacts. Almost all of the α‐SiC transformed into β‐SiC, and almost all the α‐Si3N4 transformed into α‐Si3N4 in the composites made from the as‐received powders, while in the composites made from the deoxidized material the α‐SiC remained untransformed and both α‐Si3N4 and β‐Si3N4 phases were present in significant quantities. High‐resolution transmission electron microscopy and Fresnel fringe imaging were used to identify the grain boundary and interphase boundary structure. Most interfaces were found to be covered with ≅ 1 nm thick amorphous intergranular films in the composites prepared from as‐received powders, whereas most interfaces were found to be free of such amorphous intergranular films in the composites prepared from the deoxidized material. Taken together, the presence of intergranular films at the interfaces and the results from density measurements are consistent with the densification and reverse α → β‐SiC transformation taking place in the composites made from as‐received powders by a liquid‐phase sintering route. An incomplete liquid‐phase sintering mechanism is also able to explain the microstructure observed in the composites made from the deoxidized material.
Microstructural origins of corrosion in a 20% SiCp/2124 aluminium alloy metal matrix composite
Authors: IMESON D. , BARTLETT D. L. 
Published: August 2011

SummaryThe microstructure of a metal matrix composite (MMC) consisting of 20 wt% 3 μm SiC particles in a 2124 Al alloy matrix has been examined and the relationship to corrosion pitting processes investigated. Standard bulk corrosion tests show that the MMC forms a higher density of pits than the unreinforced alloy, although the overall performance is similar as the pits are shallower. In a new addition to conventional characterization techniques, transmission electron microscopy samples have been directly subjected to ‘flash’ corrosion treatment and subsequently examined. This technique is shown to be effective in studying the initiation of pits. The SiC particles and the widespread 9 intermetallic precipitates are shown to play little, if any, role. A sparse population of features introduced during powder processing and consolidation procedures, probably linked with strong magnesium segregation, is suggested to be responsible for pit initiation.
Ion microprobe studies of reactions in squeeze‐cast aluminium alloy matrix composites
Authors: SONI K. K. , KANG H. G. , GRANT P. S. , CANTOR B. , ADRIAENS A. G. , GAVRILOV K. L. , MOGILEVSKY R. , LEVI‐SETTI R. , TSENG M. W. , WILLIAMS D. B. 
Published: August 2011

SummaryAn ion microprobe with high lateral resolution has been used to study the chemical reactions at the fibre/matrix interface of metal–matrix composites. During the squeeze‐casting process, the Al–Si–Mg matrix reacts with the preform made of Saffil fibres (96% Al2O3, 4% SiO2). The reaction occurs mainly between the silica binder and Mg from the matrix according to SiO2 + 2Mg = 2MgO + Si. A continuous layer of MgO was formed around the fibres, even on surfaces that were not covered by the silica binder. Possible reasons are discussed for the formation of MgO in areas where binder coating was missing. In such areas, Mg reduces SiO2 that is contained in the fibre. However, the fibres (A12O3) are not attacked by Mg. In the isolated case of fibres that were completely uncoated, no reaction products were observed at the interface. The presence of silica binder seems to be an essential requirement for this reaction to occur. When squeeze‐casting is performed with sufficiently high melt temperature, Al from the matrix also reduces silica.
Preliminary confocal scanning laser microscopy study of fluid inclusions in quartz
Authors: PETFORD N. , MILLER J. A. , RANKIN A. H. 
Published: August 2011

SummaryThe initial results of the first dedicated confocal scanning laser microscopy (CSLM) study of fluid inclusions in quartz are presented. CSLM imaging of a large inclusion shows the quartz crystal to contain numerous small (< 1 μm), highly reflective inclusions arranged along planes in at least two directions that are not readily visible in transmitted light. The technique allows measurements to be made of the angular intersection and orientation of the planes in both two and three dimensions. Results suggest that larger inclusions (> 10 μm) occur where two planes of small inclusions intersect, and that the shape of the large inclusions is controlled by the angular relationship between intersecting planes.