bluuebunny/crossref_metadata_2025_split huggingface dataset:
Stereology of tubular structures
Authors: Baddeley A. , Averback P. 
Published: August 2011

SUMMARYThe morphology of a tubular structure can be characterized, in at least some of its important respects, through stereological methods. We study the geometric meaning of standard stereological quantities when applied to tubular structures, with particular regard to their curvature or tortuosity. Measures defined specifically in relation to tubular structures are also introduced for practical use. The ideal smooth bent cylinder, used here, is not realistic but provides general principles from which a more specialized investigation should be developed. The emphasis is placed on simple counting methods of measurement, specifically the tangent counts introduced by DeHoff, and counts of section profiles exhibiting a particular character (such as ‘figure‐eights’). These measures convey information about the tortuosity of tubular structures, whereas the standard indices Vv, Sv, Mv give no information about tortuosity. Some data from human testicular tubules are discussed.
Dislocation structures in fatigued polycrystalline stainless steel
Authors: Fielding S. E. , Stobbs W. M. 
Published: August 2011

SUMMARYThe dislocation structures produced in polycrystalline Fe‐25Cr as a result of push‐pull fatigue are described with reference to the Schmid factors of the active slip systems in different grains. The activity of the structures is discussed in relation to an etch which is indicative of localized shear activity. The ladder and labyrinth structures seen are compared with those which form in f.c.c. material.
The metallographic characteristics of fatigue cracks in the titanium alloy IMI829 at 400°C and 600°C
Authors: Hamdy M. M. , Noble B. , Waterhouse R. B. 
Published: August 2011

SUMMARYHigh temperature fatigue tests under fluctuating axial tension were carried out on the alloy in the fully heat treated condition, the microstructure consisting of a β matrix containing colonies of aligned α‐platelets. Fatigue cracks were initiated by fretting at temperatures of 400°C and 600°C. A detailed metallographic examination has been made of the fretted region and the resulting fatigue crack and these characteristics have been related to the microstructure of the alloy. At test temperatures of 400°C the fatigue cracks initially propagated at right angles to the α‐platelets but where their orientation was unfavourable, propagation also occurred parallel to the α‐platelets. At test temperatures of 600°C the initial direction of crack propagation was independent of the microstructure.
Digital image processing of combined SEM and EDX signals
Authors: Bauer B. , Schwarz H. , van Thanh Nguyen 
Published: August 2011

SUMMARYDue to the complexity of biological tissue and man‐made materials, the limits of light microscopy in quantitative image analysis are often reached. The scanning electron microscope provides a much higher resolution in such situations, especially when using the low noise secondary electrons signal. However, secondary electrons are sensitive to topography rather than to the elements constituting the specimen. This effect usually makes discrimination of distinct phases or objects by simple grey value thresholding difficult or even impossible.The additional information given by an energy dispersive X‐ray system is the step to overcome this problem. The combination of both signals—grey level and energy dispersive information—leads to a masking procedure which eliminates image sections, not belonging to the phase under investigation, from the evaluation.
A method for mapping localized displacement fields in boundaries
Authors: Donovan P. E. , Stobbs W. M. 
Published: August 2011

SUMMARYA new method is described for the initial characterization of the displacement fields of defects on boundaries. This approach can be applied to defects and boundaries which cannot easily be modelled, since it involves the comparison of known with unknown fields. An application of the technique to the study of a bcc/fcc phase boundary in a steel is also described.
Structures of insoluble carbon in tars and pitches
Authors: Kremer Henry A. , Cukier Samuel 
Published: August 2011

SUMMARYPrimary or True QIs, and also the so‐called ‘dirt’ were separated from seven tar sources available in Canada from four different steel companies, by filtering hot tar solution of quinoline and other good solvents. After washing with quinoline and acetone and drying, the filter cake was examined under scanning electron microscope (SEM) and analysed for inorganic impurities by wave length and energy dispersive X‐ray spectrometers. A limited amount of work was carried out on a production pitch blend, utilizing optical microscopy.After the filtration process, the filtrates which represented the QI free tars were subjected to distillation at atmospheric pressure and various pitches were prepared with a softening point range of 70–100°C. The pitches were dissolved in quinoline and analysed for QIs. The small amount of QI from each pitch was extracted and dispersed with solvent onto a microscope slide. The samples then were subjected to SEM and in one case to optical microscope studies; the sizes and shapes of the QIs were determined and compared with the QIs originally found in the individual tars. Photographs have been taken during the scanning work to record findings which have been considered typical and demonstrative of the findings.In order to gather further information on the role of QI in tars and pitches, particle size distribution was determined of QI extracted from a tar and a production pitch by a Coulter Counter.
The microscopy of mesophase formation and of anisotropic cokes produced from solvent‐refined coals
Authors: Davis Alan , Hoover David S. , Wakeley Lillian D. , Mitchell Gareth D. 
Published: August 2011

SUMMARYThermal processing of coal and coal products can lead to the formation of ordered carbons through the mesophase mechanism. The performance characteristics of metallurgical coke may be improved by the extent of this ordering; however, in the direct hydroliquefaction of coals the objective is to make species of low molecular weight, and coking is an undesirable retrograde reaction. This study is concerned with fundamental mechanisms of coke formation and their roles in these two processes.Most studies of mesophase formation have involved the heat treating of samples followed by quenching and examination at room temperature. This project has used hot‐stage microscopy and the production of a 16‐mm colour film to study the dynamics of mesophase growth and coalescence.Various solvent‐refined coal (SRC) and SRC fractions were carbonized in gold tubes at 450°C and 34.5 MPa, and the pyridine‐insoluble fractions (semi‐coke) examined microscopically. Greater molecular mobility, manifested by lower proportions of anisotropic carbon and larger domain sizes, was evident for SRCs which had undergone more extensive hydrogenation at the pilot plant, and for SRC fractions of lower functionality.The performance of metallurgical coke in the blast furnace can be related to its inherent carbonaceous structure. Coals which give cokes of marginal quality include low‐rank bituminous coals which form an optically isotropic coke. One method of improving the carbon ordering in these cokes is the use of a carbonizing additive. In this study SRC was used as the additive, giving improvements in the coke structure and microstructure.
Microscopy of porosity in metallurgical cokes
Authors: Patrick J. W. 
Published: August 2011

SUMMARYThe importance of the porous structure of coke in industrial usage has been recognized for many years but the difficulties involved in determining by manual microscopic methods, quantitative details of the structure precluded comprehensive and detailed studies. With the advent of computerized image analysis systems it has become possible to overcome many of the practical difficulties associated with the determination of structural data for a material as heterogeneous as metallurgical coke. Techniques based on reflected light microscopy and automatic image analysis have been developed to the extent that representative and reliable structural characterization of coke can be achieved. The data so obtained have been used to derive strength/structure relationships which enable coke strength to be predicted with a standard error comparable with that of the experimental determination and the structural characterization now offers an additional means of defining coke quality with potentially significant industrial applications.
Evaluation and interpretation of grain density autoradiographs by reflectance photometry
Authors: Mai J. K. , Krauthausen I. , Jennissen J.‐J. 
Published: August 2011

SUMMARYThe tritium content of nervous tissue sections is calculated from grain‐density of autoradiographs without loss in anatomical information. The calculation is not based on determination of (expected) grain numbers but on photometric measurements (SKphot), interpreted as the result of the function of exposure time (T) and incorporated activity (β): SKphot = f (T, β).As experimental radiation standards homologous material (optic nerve preparations) with different activities determined by liquid scintillation counting has been used. Exposure times between 12 h and 28 weeks for these preparations with known radioactivities yielded a set of curves (nomogram) relating photometric values to exposure times. At any given exposure time the knowledge of photometric readings and related radioactivities within that set of curves enabled the development of a function covering all photometer readings within the range of the nomogram. Thus, any photometric reading could be correlated to the corresponding radioactivity.Such a function has been applied for the transformation of photometric values obtained from particular brain‐section areas exposed for 16 weeks. Since the results are given in Bq, they may be related and, if necessary, corrected to results obtained by other tritium detection methods.Terminology used in the text: experimental radiation source = experimental standards prepared from optic nerve sections; standard radiation source = polymer reference source.
Sampling problems in an heterogeneous organ: Quantitation of relative and total volume of pancreatic islets by light microscopy
Authors: Kroustrup J. P. , Gundersen H. J. G. 
Published: August 2011

SUMMARYIn stereological studies analysis of sampling variances is used for optimizing the sampling design. In organs with a heterogeneous distribution of the phase of interest the analysis of sampling variances can be undertaken only if the observed variance between sections is distributed into the fraction which is due to random variation and the fraction which is due to the heterogeneity. In the present example (pancreatic islet volume estimated by light microscopic point‐counting) the density of islets showed a linear increase along the axis of the organ. By analysis of sampling variances it was calculated that the most efficient number of sections (cut perpendicular to the organ) was considerably lower when the isolated contribution from the random variation was considered.The total islet volume was obtained by the product of the fractional islet volume and the pancreatic weight. Analysis of sampling variances of the total islet volume was performed by including the variance contribution from the individual pancreatic weights to the variance of the group mean total islet volume. Due to a negative correlation between the fractional volume and organ weight the total islet volume in the group of animals was more precisely estimated than the fractional islet volume.The methods used for dealing with the heterogeneity of the organ and for estimating sampling variances of total structural quantities generalize to a large number of stereological studies in biology.
A new method for unfolding sphere size distributions
Authors: Taylor C. C. 
Published: August 2011

SUMMARYSpherical particles are embedded in an opaque matrix. Circular profiles with radii X1,…, Xn are then observed from a cross‐section. To estimate the distribution of the particle sizes a two‐stage method is proposed. The probability density of the profile radii is statistically estimated by a smooth, piecewise quartic polynomial, and then an inversion formula is used. The method has some advantages over existing techniques in that the estimate is continuous, is quite straightforward computationally and it involves a less subjective choice of statistical parameters. In the case of several types of distributions, the procedure performed well for simulated data.
Specimen holder improvements for the study of amphibian skin pigmentation
Authors: Hedin C. Anders 
Published: August 2011

SUMMARYA skin specimen holder was constructed permitting nearly identical experimental conditions during in vitro spectrophotometry and photomicrography of amphibian skin melanocytes. The specimen holder was made of non‐corrosive steel thread and made to fit a spectrophotometer cuvette and the light microscope stage. The improvements were compared to earlier constructions.
The current status of fixation for electron microscopy: A review
Authors: Bullock Gillian R. 
Published: August 2011

SUMMARYChemical fixation of cells has been used extensively in different fields of electron microscopy. The type of fixation can be selected to maximize retention of different cell constituents where morphology is of prime interest. For techniques such as immunocytochemistry and autoradiography, a compromise between morphology and retention of antigenicity or radiolabel has to be reached. By careful choice of fixative, buffer and other physical parameters, optimum results can be obtained for both animal and plant tissues. Emphasis has been put on more recent developments in technique.
The use of high‐voltage electron microscopy and semi‐thick sections for examination of cyanobacterial thylakoid membrane arrangements
Authors: Nierzwicki‐Bauer S. A. , Balkwill D. L. , Stevens S. E. 
Published: August 2011

SUMMARYHigh‐voltage electron microscopy (HVEM) of semi‐thick sections was evaluated as a technique for studying thylakoid membrane arrangements in cyanobacterial cells. Semi‐thick sections (0·25 μm) provided important information that was relatively difficult or impractical to obtain by viewing either randomly or serially cut thin sections. Specifically, the semi‐thick sections were better suited for visualizing (i) overall thylakoid arrangements and (ii) interconnections between the thylakoids and the cytoplasmic membrane. By comparison, randomly cut thin sections frequently yielded deceptively incomplete or inconsistent data in regard to these specific features. Tilting of thick sections about two perpendicular axes served to improve the clarity of complex membranous intersections and other cell features.
A method differentiating between bacterial adhesiveness and invasiveness in cell culture monolayer
Authors: Bukholm Geir , Johansen B. V. , Namork Ellen 
Published: August 2011

SUMMARYIn order to differentiate between bacterial adhesiveness and invasiveness in cell culture monolayers, a method is reported which enables the same specimen to be examined by both scanning electron microscopy and Nomarski interference contrast microscopy. The source of error made by statistical variation when the two microscopical techniques are used individually is thus avoided.
An acidic silver staining method for synaptonemal complexes under light microscopy
Authors: Fernandez‐Piqueras José , Castaño Carlos Sentis , Garcia E. Rojo , Campos A. Rodriguez 
Published: August 2011

SUMMARYA simple method is presented by which synaptonemal complexes (SCs) can be visualized under bright field microscopy. Staining was accomplished with a silver nitrate solution adjusted to pH 3–3·5 with formic acid, after an acidic fixation. This method is suitable for the demonstration of SCs, centromeres and NOR regions in both mammalian (Rattus norvegicus, ‘Wistar’) and orthopteran spermatocytes (Steropleurus martorelli complex). Results suggest that pretreatment with solutions of alkaline pH are not needed for demonstrating SCs, and that the silver impregnation may also operate when the proteinaceous lateral elements of the SC are subjected to low pH conditions. Differential staining of the X chromosome during meiosis in Orthoptera, and a core‐like structure in the chromosomes during the more condensed stages of meiosis and mitosis can also be shown.
Acoustic beam position monitor for microanalysis of particles in the 10 nm range in a TEM‐SCAN system
Authors: Sørensen Ole , Andersen Jesper Refslund 
Published: August 2011

SUMMARYThis paper describes the principle and use of a simple equipment which makes it possible to keep the electron beam in the centre of a small particle analysed by X‐ray microanalysis in a STEM system. A deviation from the correct beam position introduced by drift or other deficiencies is monitored by an audible change in a sound frequency and corrected for by a convenient manual operation.
An interference technique for measuring the thickness of semi‐thin and thick sections
Authors: Robertson W. M. , Storey B. , Griffiths B. S. 
Published: August 2011

SUMMARYAn interference method is described for measuring section thickness in the range 0·3–45 μm. An incident illumination objective incorporating a beam splitter and adjustable reference mirror is used to generate interference fringes by reflection from the upper surfaces of sections on glass slides. Sections do not require a reflective coating. The lateral displacement of the zero‐order fringe generated using white light is measured in terms of sodium light fringes and photographic enlargement of the fringes allows measurement to ± 30 nm. The method is simple in operation and allows rapid assessment of any local distortions over the entire section area.
Caveat on the use of alloys for surface replication
Authors: Williamson Francis A. , Pillinger Raymond N. 
Published: August 2011

SUMMARYSome replicas of plant cell surfaces produced by platinum/palladium evaporation were of very poor quality. Scanning electron microscope X‐ray microanalysis showed that only Pd was evaporated from the Pt/Pd alloy, leaving the Pt on, or alloyed with, the tungsten filament used for evaporation.
Alteration of cartilage matrix morphology with histological processing
Authors: Cole Madison B. 
Published: August 2011

SUMMARYAn interlacunar network in the extracellular matrix of femoral head articular cartilage of neontal rats was seen by light microscopy to: (1) consist of elements, 0·5 μm thick, which occurred as individual elements, as bundles of elements, and as fused elements, (2) stain intensely with toluidine blue, methylene blue, and safranin O, and (3) connect chondrocytes by inserting on the chondrocyte capsules which were composed of morphologically and cytochemically similar material. By electron microscopy, the single elements were seen to be composed of thicker, denser staining areas of the honeycomb appearing matrix and the fused elements appeared as non‐membrane bound channels containing granular material.Articular cartilage was processed using combinations of fixatives, dehydrating agents, and embedding media. Regardless of fixation, demineralization, or embedding, the network was not seen after dehydration of the cartilage with methanol, ethanol, acetone or tert‐butanol but was seen after dehydration with aqueous solutions of glycol methacrylate, propylene oxide, 2‐propanol or 2,2‐dimethoxypropane. Network visualization following a variety of methods demonstrated that no single fixative, dehydrating agent, or embedding medium caused its formation. The presence of the network in different cartilage zones, its consistent morphology by light and electron microscopy, the uniformity of the elements in their connection with the chondrocytes, and presence in fresh‐frozen sections suggest the network may be real, but rigorous evidence for its existence in vivo is still required.Since cartilage morphology was altered by histological methods, especially dehydration, common methods used in studying connective tissue matrix should be evaluated to determine their effect on matrix morphology.
The application of scanning transmission electron microscopy (STEM) to the study of thin anodic films on nickel and nickel‐molybdenum alloys
Authors: Moriya M. , Ives M. B. 
Published: August 2011

SUMMARYAnodized thin‐film samples of nickel, molybedenum and a nickel‐13 w/o molybdenum alloy have been analysed by scanning transmission electron microscopy, using selected area diffraction, microdiffraction and X‐ray micro‐analysis.Thin‐film samples were obtained by ion thinning with argon and by electropolishing in acetic acid‐perchloric acid. Electropolishing is the preferred technique for these studies, producing a surface with roughness on a scale of 1 nm.The anodized films on nickel and nickel 13 w/o molybdenum alloy exhibit a rugosity with a ‘particle’ size of 3 nm. The crystal structure of the films is similar to f.c.c. nickel oxide.Molybdenum enrichment was detected in the anodized alloy surfaces but there is no electron diffraction evidence for a crystalline molybdenum oxide. The electron diffraction pattern from anodized pure molybdenum suggests that the surface film is amorphous.
A method for exposing the internal anatomy of small and delicate tissues for correlated SEM/TEM studies using polyethylene glycol embedding
Authors: Nagele R. G. , Doane K. J. , Lee H. , Wilson F. J. , Roisen F. J. 
Published: August 2011

SUMMARYA method for preparing and handling large, clean, distortion‐free cut surfaces through small and delicate tissues for correlated SEM/TEM examination is described. In this method, tissues are fixed according to conventional protocols; however, instead of critical‐point‐drying after fixation, tissues are first embedded in polyethylene glycol (PEG), a water‐soluble waxy solid. Tissue blocks are easily oriented and sectioned to the desired regions, immersed in a solvent to remove PEG, critical‐point‐dried, and examined with an SEM. The same tissue blocks can be reworked for TEM by immersing in propylene oxide and embedding in an epoxy resin.
Some recent experience with the scanning electron microscope in corrosion research
Authors: Stott F. H. 
Published: August 2011

SUMMARYCorrosion and oxidation are the results of chemical reaction between a solid surface (such as of a metal or alloy) and its environment, to form a corrosion product. The product may adhere to the surface, thereby usually providing some protection from further attack, or may be removed from it (e.g. by volatilization or by dissolution in the environment). In either case this leads to changes in topography, morphology and, often, composition of the surface. Study of such changes can provide considerable information and assistance in the determination of the mechanisms of degradation. Scanning electron microscopy with associated microanalysis has thus enabled significant advances to be made in understanding many corrosion and oxidation processes. The progress attained in several areas where the technique has played a major part but has been extended to its maximum capabilities is discussed and related to the particular advantages and limitations of scanning electron microscopy in this field. One such area is the study of high‐temperature corrosion processes. Here, the high resolution and depth of focus of the instrument have provided detailed information on the microstructure of high‐temperature oxide and other corrosion‐product scales and underlying alloy. For instance, the sizes and distributions of pores in the scales give important insight into the possibility of growth mechanisms involving gas‐phase transport within the scales themselves. Associated microanalysis can assist in identification of rate‐determining layers and of other localized diffusion paths which can short‐circuit bulk lattice diffusion.