bluuebunny/crossref_metadata_2025_split huggingface dataset:
Changes induced in the ultrastmcture of the cytoplasmic and intracytoplasmic membranes of several Gram‐positivebacteria by variations in OsO4 fixation
Authors: Silva M. T. 
Published: August 2011

SUMMARYSeveral Gram‐positivebacteria, belonging to different genera, fixed by the complete Ryter‐Kellenberger procedure exhibited asymmetric membranes and prominent, tubular or vesicular, intracytoplasmic membrane systems (mesosomes). When the prefixation step was omitted mesosomes were not generally observed in three of the four bacteria studied. Fixation under conditions of Ca2+ deficiency resulted in symmetric membranes and lamellar mesosomes. From the data available it is difficult to conclude which, if any, of these different patterns of membrane ultrastructure is real.
The cohesive failure of wood studied with the scanning electron microscope
Authors: Borgin Karl 
Published: August 2011

SummaryThe purpose of the present investigation was to establish the value and suitability of the scanning electron microscope for research on the mechanism of fracture and cohesive failure of the structure of wood. Wood samples, mainly consisting of various pines, were stressed to the point of failure in tension and shear parallel or perpendicular to the main fibre direction. The rate of loading and the temperature were varied between wide limits. The fractured surfaces were studied and gave the following results:(1) In tension parallel to the grain, fissures developed between the microfibrils in the cell walls causing the wood to rupture perpendicular to the longitudinal axis of the fibres. At both high and low temperatures the matrix, in which the microfibrils are embedded, and to a much lesser extent the middle lamella between the fibres failed by plastic flow when the external load was applied very slowly. Under such conditions strands or bundles of microfibrils were pulled out and fractured in an irregular pattern. Cohesive failure in tension caused by sudden impact was characterized by limited slippage of microfibrils and a near brittle failure of the embedding matrix. A remarkable clean cleavage approaching a true brittle failure was observed when the wood was stressed rapidly perpendicular to the grain.(2) Cohesive failure when the wood was exposed to shear along the grain and tension across the grain, showed clearly that the weakest part of the ultrastructure of wood under such conditions was the bonds between parallel strands of microfibrils which were pulled out with little resistance from the matrix. However, the adhesion between the middle lamella and the cell wall or the middle lamella itself failed when the wood was exposed to cleavage parallel to the grain. If the process of cleaving was carried out extremely fast, as in the machining of wood, the rheological properties of the middle lamella did not allow for plastic deformation with subsequent failure, and the bulk structure of the wood tissue behaved almost as a homogeneous material.The use of the scanning electron microscope for the study of the structure of wood under stress and the mechanism of its cohesive failure can supply information which seems to be unobtainable by any other method.
Scanning electron microscopy of plant cuticles
Authors: Baker E. A. , Parsons Elizabeth 
Published: August 2011

SummaryThe scanning electron microscope (SEM) has been used to examine the structure of a wide range of different plant cuticles. The extent to which wax deposits may be damaged by mechanical abrasion in the preparative stage and by the electron probe during the scanning processes has been investigated. Techniques have been developed for the examination of the constitution of complex wax deposits and in particular of their underlying structure. Methods of preparation of isolated cuticular membranes for study by scanning electron microscopy are described. The value of wet mounting for membranes which are subject to shrinkage during drying is discussed.
High‐resolution electron microscopy of high‐modulus carbon fibres*
Authors: Crawford D. , Johnson D. J. 
Published: August 2011

SummaryHigh‐resolution electron‐microscope images of high‐modulus carbon‐fibre fragments have been recorded under conditions which allow resolution of the individual 0.34 nm graphite layer planes. Extinction bands previously observed at low resolution are now seen to originate from several different structural features. Single bands are caused by lattice distortion due to non‐basal edge dislocations and low‐angle boundaries of tilt or twist character; periodic bands are the result of Moiré effects from overlapping or interlinked crystallites. Accurately controlled tilting experiments give further insight into the complex interlinked nature of the crystallites and the results are summarized in terms of a model which is also capable of explaining the partial recrystallization observed with boron doping.
Improvements to the functional design of the Roberts and Trevan type culture chamber
Authors: Friend J. V. 
Published: August 2011

SummaryThe design of the body of the cell‐culture chamber developed by Roberts & Trevan (1961) has been modified. The original chamber consists of two cover‐glasses separated by a silicone ring held together by three small screws in an aluminium alloy housing. This type of metal and method of clamping has several disadvantages. The new type of chamber, made of stainless steel which is hard‐wearing and resistant to chemicals, also includes an improved rapid method for clamping the component parts together under pressure without the danger inherent in the original of cracking the coverglasses.
Strengthening mechanisms in high strength structural steels*
Authors: Orr J. 
Published: August 2011

SummaryThe factors controlling the strength and impact properties of predominantly ferritic structural steels including solid‐solution strengthening, ferrite‐grain size and precipitation strengthening, have been discussed. It has been shown how individual factors can be combined to give strong‐tough structural steels. Examples of commercial and experimental steels with high strength and good impact properties have been given.
An improved apparatus for perfusion fixation with automatic pressure control
Authors: Gil Joan , Weibel Ewald R. 
Published: August 2011

SummaryA method and equipment are described which allows vascular‐perfusion fixation for electron microscopy under controlled pressure conditions. Hydrostatic pressure can be kept constant during fixation by automatic adjustment of the flow rate of a peristaltic pump which is governed by a fully automatic remote‐control device. Colloid osmotic pressure of the perfusates must also be adjusted to assure adequate balance of the pressures in the tissue at physiological levels.
A new stereo‐adaptor for use with the scanning electron microscope
Authors: Unsworth A. , Hepworth A. 
Published: August 2011

SummaryA description is given of a new specimen carriage and specimen holder, for use with the scanning electron microscope, to facilitate the preparation of accurate stereo‐micrographs. A detailed calibration procedure shows the apparatus to be extremely reproducible, and giving errors of less than 2% in reported stereo‐measurements.
A distortion‐free low‐magnification stage for the Hitachi HU‐11B electron microscope
Authors: Thompson D. W. , Heap P. F. , Chapman S. K. 
Published: August 2011

SummaryA low‐magnification stage is described which facilitates the production of distortion‐free images in the Hitachi HU‐11B electron microscope in the range × 150–2000. The construction and method of operation of the device together with its advantages and potential uses in the material and biological sciences are considered.
Periodic acid‐Schiff‐phosphotungstic acid as an electron histochemical method for ultrathin sections
Authors: Horobin R. W. , Hague Annette 
Published: August 2011

SummaryStructures which are regarded as ‘PAS positive’ may be strongly and selectively stained for electron microscopy in ultrathin sections by using the following procedure. Tissues were fixed by buffered osmium tetroxide or by glutaraldehyde followed by postfixation in osmium tetroxide. After dehydration the fixed tissues were embedded in butyl methacrylate‐methyl methacrylate (10:1 v/v). Other embedding media do not give successful results. Ultrathin sections were cut and mounted on formvar‐coated gold grids. The sections were treated with 1% w/v periodic acid in aqueous alcohol (water‐ethanol 1:1 v/v) for 10 min, washed in water for 2–3 min, then treated with Schiff reagent for 20 min. The Schiff reagent was made according to the method of de Tomasi and allowed to age for 3–5 h. The sections were then washed in two changes of water for 3–5 min each, dried in air, stained in 1% w/v aqueous phosphotungstic acid for 1.5 h then rinsed in water for 2–3 min.
Preliminary studies of the effects of DMSO on histochemical reactions
Authors: Ward P. , Smith Audrey U. 
Published: August 2011

SUMMARYSlices of mammalian kidney were treated with concentrations of dimethyl sulphoxide (DMSO) theoretically high enough to protect living cells against damage during freezing and thawing. The blocks were cooled slowly to −45°C and then quenched in liquid nitrogen. Sections were cut at −45°C and post‐fixed in various reagents. They were stained for lysosomal and mitochondrial enzymes. Cellular and tissue morphology was better preserved than in tissue which had been treated by conventional histochemical freezing methods. The staining of the enzymes was satisfactory and the localization of mitochondrial enzymes, in particular, was sharper.
An investigation of some organic chemicals as cathodoluminescent dyes using the scanning electron microscope
Authors: De Mets M. , Lagasse A. 
Published: August 2011

SUMMARYThirty‐three organic chemicals have been investigated for their cathodoluminescent properties under standard conditions in the scanning electron microscope. The results are classified according to the luminescent yield of these substances and to the decrease of the luminescence after the specimen was scanned for a given time at magnifications of about × 1700 and × 3500 (beam effect). The relationship between molecular structure and luminescent yield, and the origin of the beam effect are difficult to describe. Reference has been made to data obtained from scintillation‐counting studies.
Localization in the electron microscope by acid phosphatase of casein particles in lactating mammary glands of rats
Authors: Tan W. C. , Livingston D. C. , Gilbert J. D. , Young Stretton 
Published: August 2011

SUMMARYCaseins are phosphoproteins and contain phosphate in monoester form; acid phosphatase is a specific hydrolysing enzyme for such phosphate monoesters; and electron‐dense particles of lead phosphate can be precipitated from a solution containing lead by the hydrolysed phosphate radical. We have made use of these facts to verify that the previously described ‘protein droplets’ located within the vacuoles of mammary epithelial cells contain phosphoprotein. Since these protein particles respond to an enzyme having Phosphomonoesterase activity at the correct pH it seems likely that they contain phosphate monoester in their structure and that they are therefore most likely to be casein particles.The method appears to have applications in the study of lactating mammary glands and the secretory activity of mammary tumours.
Lanthanum as an intracellular stain
Authors: Bannister L. H. 
Published: August 2011

SUMMARYIn mouse and fish olfactory mucosæ, lanthanum has been found to penetrate various intracellular components of cells including the endoplasmic reticulum, mitochondria, microvilli, microtubules and cilia, outlining their substructure in negative contrast when seen in sectioned specimens.Structural details approaching those seen in disrupted negatively stained material were observed in sections, suggesting that intracellular lanthanum staining may prove a useful tool in morphological studies.
Field‐ion microscopy of iron‐molybdenum solid solutions
Authors: Papazian J. M. 
Published: August 2011

SUMMARYThe average density of bright spots in the (200) region of field‐ion microscope images is found to be related to the nominal molybdenum composition in a series of iron‐molybdenum alloys containing 1/2 to 5 weight percent molybdenum. The bright spot density is found to be proportional to the square of the tip radius and is thus linearly related to the surface area. This indicates that a correlation between the observed bright spot density and a bulk property is permissable. The bright spot density is also found to increase approximately linearly with molybdenum content, at least up to 3% molybdenum. Observation of specimens with similar amounts of molybdenum in solid solution but different nitrogen contents shows that the observed correlation is independent of the nitrogen content. Similarly, it is shown that the correlation is also independent of carbon content. Thus, it is concluded that the bright spot density is directly related to the amount of molybdenum in solid solution and can be used as a measure of the local molybdenum concentration. The nature of the bright spot contrast is discussed and is shown to be consistent with a current theory of image formation.
The use of the scanning electron microscope for comparing the structure of weak and strong egg shells
Authors: King N. R. , Robinson D. S. 
Published: August 2011

SUMMARYA scanning electron microscopic investigation has been made of the radial fracture surfaces of both weak and strong egg shells. Generally in weak and thin egg shells the mammillae were of irregular shape, very porous, frequently not attached to the outer shell membrane fibres and were cleaved both radially and transversally during fracture.
Optical shadowing in the electron microscope
Authors: Haydon Glen B. , Lemons Ross A. 
Published: August 2011

SUMMARYOptical shadowing offers a valuable technique for the study of many transmission electron microscope specimens. Simply blocking half of the illumination with the objective aperture produces an image with a striking shadowed effect which gives a distinctly three‐dimensional appearance to the specimen's surface topography. Theoretical analysis shows that this is due primarily to a discrimination between electrons refracted in opposite directions, and that the characteristic features of the effect are successfully explained by a refraction model. The capability of visualizing surface topography is applicable up to the full resolving power of the instrument and accordingly opens many new avenues of investigation.
Some observations on the filaments of frozen‐etched striated muscle
Authors: Willison J. H. M. , Cocking E. C. , Lawrie R. A. 
Published: August 2011

SUMMARYFrozen‐etched rabbit psoas muscle and locust flight muscle are illustrated. The myofibril structure of striated muscle as seen by freeze‐etching is wholly compatible with the well‐established interdigitating sliding filament model. A major difficulty in interpretation arises from the detailed appearance of projecting myofilaments which arise when myofibrils lie obliquely to the fracture plane. They appear to be surrounded by a grey halo, with a light central spot, but without sufficient projection to account for the length of the shadow. The grey halo consists of undissolved myosin released from the replicated projecting myofilament during the drying of the replica following cleaning. It may be removed by recleaning. The surface tension forces involved in removing the myosin from its casing, however, cause the case itself to be destroyed, leaving a phantom shadow. The light, central spot is a resultant hole in the replica. Thick and thin filaments are found in longitudinally fractured myofibrils. There is a close correspondence with the images of frozen‐etched muscle from previous work.
Negative staining of viruses
Authors: Nermut M. V. 
Published: August 2011

SUMMARYSeveral techniques and procedures of negative staining are described and compared from the point of view of both ‘drying’ and ‘specific staining’ artefacts. These are shown on examples from several virus species. The ‘drying artefacts’ can be prevented using the freeze‐drying technique or reduced using ‘paper‐filtration’, ‘pseudoreplication’ or the Kleinschmidt techniques. The ‘specific staining’ artefacts can be avoided by using another stain which does not affect the structure under study. Different ways are shown to stain the surface or the interior of virus particles.
Quantitative analysis of scanning electron micrographs
Authors: Hilliard J. E. 
Published: August 2011

SUMMARYScanning electron microscopy (SEM) provides a considerably greater depth of field than optical microscopy at the same magnification. It is therefore particularly suitable for the examination of specimens with irregular surfaces.This review of procedures for quantitative measurements on SEM images falls into two parts. The first deals with mensuration; that is, with the determination of the lengths, dihedral angles and other properties of specific features in the image. Particular emphasis is given to means of correcting for non‐linearity and other distortions caused by instrumental defects. The second part considers the analysis for bulk properties such as volume fraction and boundary area per unit volume. In the case where observations are made on a planar section, these properties can be determined by use of the standard stereological relationships after making a computable correction (where necessary) for the tilt of the specimen and non‐linearities in the scan. However, for irregular surfaces (for example, those produced by fracture) rigorous estimations are not possible without certain assumptions which, unfortunately, are in many cases unrealistic.
Stereology and structuring elements
Authors: Serra J. 
Published: August 2011

SUMMARYAn object's quantitative analysis is not purely objective. On the contrary, it results from the interaction of a structuring element chosen by the observer, with the object to be analysed. After defining this relation in a quantitative way (hit‐or‐miss transformation), and recalling its probabilistic interpretation (Matheron, 1971) some examples of structuring elements are given:The couple of points which measures the covariances matrix. It allows harmonic analysis and the solving of sample problems.The segment which measures the chord distribution, and leads to the stereo‐logical parameter ‘the star’.The parallel segments doublet, which measures curvature radius distribution and the number of particles in the two‐dimensional space.The hexagon, which measures bi‐dimensional granulometries, etc.These measurements have been made on the texture analyser, built by us especially for that purpose. As a conclusion, we give an application of structuring elements to clustering measurements.
Multi‐dimensional perspectives on stereology
Authors: Miles R. E. 
Published: August 2011

SUMMARYThe structures of primary concern in Part A are varieties—the generalization in higher dimensions of smooth curves and surfaces. Fixed orientation random s‐sections (s‐dimensional flat sections) of a fixed t‐variety (t‐dimensional variety) in Rd (d‐dimensional space) are considered in Section 2. The t‐variety induces a density‐cum‐orientation distribution which is related to corresponding sectional quantities. The by now classical basic formula; of stereology are all special cases of the simple multi‐dimensional formula (2.16). Next (Section 3), statistics of the variety of intersection of several statistically homogeneous random varieties are related to the corresponding statistics of the parent varieties.Part B is concerned with the analysis by random s‐sections of fixed aggregates of t‐dimensional opaque particles (i.e. varieties for 1 ≤ t ≤ d — 1, domains for t = d) embedded within an opaque specimen. Fixed orientation random sections are considered in Section 5, and isotropically oriented ones in Sections 6–10. It is shown in Section 7 that the mean particle ‘caliper diameter’, a key quantity, may in theory be estimated by isotropic slice sectioning. The theory is particularly rich when the particles are convex, witness the arrays of useful formula; in Sections 8–10. Crofton's remarkable ‘second theorem’ comes into its own in Section 9, permitting simple estimates from isotropic test lines of mean area squared to mean perimeter (when d = 2) and mean volume squared to mean surface area (when d = 3); in fact, the formulæ of Sections 7–9 suggest estimates for both mean and variance of the areas (when d = 2) and volumes (when d = 3) of aggregates of embedded convex particles. Further results for aggregates of convex polytopes are given in Section 10. Certain general considerations and principles relating to estimation from random sections in the practical cases, i.e. d ≤ 3, are included in the final Section 11.Equations which are the specializations of multi‐dimensional formulæ to the practical cases are asterisked. A feature is the attention given to the proper probabilistic specification of random sections through the specimen, a matter that seems largely to have been ignored.
Rasterable pointsets
Authors: Giger Hans 
Published: August 2011

SUMMARYA very general class ℛ of pointsets is introduced which is named rasterable.The term ‘rasterable’ designates the important property of these pointsets that they can be represented by the raster of those points of a lattice belonging to the pointset. This representation concerns the Minkowski measures and has to be interpreted in a statistical sense.It is shown that the directional Minkowski measures for rasterable pointsets can be interpreted as coefficients of the expansion of the corresponding correlation function. It follows that the well‐known Wiener spectrum of a two‐dimensional texture, which equals the Fourier transformation of a reduced correlation function, does not preserve the topological properties of the pointset.The described representability of a pointset by a point picture may clarify the property of the pointset to be ‘normal’ in the common sense of the word. If one knows the pathological appearances in the theory of pointsets this clarification is of special interest.
A generalization of the concept of size
Authors: Delfiner P. 
Published: August 2011

SUMMARYThe size of a set is defined without ambiguity as a ratio of homothety with an elementary set having the same shape. In order to generalize this, we compare the object studied with the elements of the family {λB} of the homothetics of B. The size λ of a particular element B is going to act as a measure of the object.If the latter is made up of individualized elements, we can calculate the size of each one and construct the size histogram, assuming for example that the size of a connex component C according to B is the size of the largest B included in C. (Examples: inscribed circle radius, maximum intercept.) For any object (alveolar lung space, pore system), the size at each point x is defined as the largest λB included in the object and containing x. The set of points x of a given size λ is related to the opening with respect to λB. This geometrical transformation of opening has mathematical properties similar to those of the sieving process, and is the basis of the size distribution concept as generalized by mathematical morphology.In the plane, the texture analyser allows the above measurements.