bluuebunny/crossref_metadata_2025_split huggingface dataset:
Order‐disorder phenomena in aggregations of particles of sizes and shapes which vary randomly within limits
Authors: Moore Richard E. M. 
Published: August 2011

SUMMARYWhen particles of randomly varied sizes and shapes within limits are aggregated, the expectation is that their disorder will increase as particles are added. But, depending on how disorder is measured, this is not necessarily so. It is shown mathematically that a maximum to the degree of disorder exists, and moreover, that this maximum can only be maintained by highly specialized sequences of particles thereafter. Consequently, it is probable that the degree of disorder, having first increased, will then decrease. As the degree of disorder falls, it becomes more probable that it will increase, so that the expectation is for the degree of disorder to oscillate as particles are added. If sampling sections pass through these more ordered regions the impression can arise that the structure is ordered, whereas the structure may in fact be random.
Graphic stereo‐reconstruction of serial sections
Authors: Yamada Munesato , Yoshida Shuji 
Published: August 2011

SUMMARYSerial histological sections may be graphically reconstructed in the form of paired ‘stereo‐maps’ for observation with a stereoscope. Comfortable stereo‐vision is obtained if the contour lines which produces grades are laterally parallaxed to an appropriate degree. Since the technique is advantageous and its procedures are simple in practice, it will be applied in a number of investigations. The basis of the technique is that the parallax is achieved by staggering one of the half‐maps with a micrometer at the rate of one‐tenth the section interval, which gives rise to perspective in the stereo‐vision. Some fundamental conditions, involved in procedures as well as observation, were investigated in order to consider the nature of the final image. Thus, it has proved to be a satisfactory representation. Other than the primary reconstruction, which is observed at right angles to the sectional plane, a method to convert the viewing direction, or the profile cartography, has been developed, so that we are able to observe sectioned structures practically from any direction.
Analysis of dendrite patterns by use of an adaptive scan system*
Authors: Wyss Urs R. 
Published: August 2011

SUMMARYA scanning procedure is described by which means morphometric parameters of dendrite tree structures may be collected with low operator interaction. The system requires a small computer with 4K core and interfacing to A/D and D/A converters, a scanning oscilloscope, a standard microscope and a photo‐multiplier tube. Modular, or local pattern information is sampled on a circular scan raster, and standardized patterns specified in terms of the number of dendrite processes scanned. These modular patterns are linked together to map a chord approximation of the object. Branches out of focus are recognized and the stage adjusted by remote control of a stepping motor. The paper records a pilot study, performed at the Department of Anatomy, University of Rochester, N. Y.
A computerized method of determining the number of synaptic contacts in a volume of cerebral cortex*
Authors: West Mark J. , Coleman Paul D. , Wyss Urs R. 
Published: August 2011

SUMMARYA computerized flying‐spot scanning device has been used to count the number of synaptic contacts in neural tissue stained with ethanolic phosphotungstic acid (E‐PTA). The ability of the computer to idealize the irregular synaptic contacts as solid disks by modifying the information gleaned from scanning the preparation allows the stereological principle of Weibel & Gomez to be used to calculate the number of E‐PTA stained synaptic contacts per unit volume of tissue. This technique represents a significant improvement over the time necessary for making similar quantitative determinations manually.
Measurement and stereological size analysis of sized spheres
Authors: Timčák Gejza M. , Jones Meurig P. 
Published: August 2011

SUMMARYAccurately sized copper spheres were dispersed in a ‘putty‐like’ Araldite in an attempt to achieve a random spatial distribution. Random sections were then cut through the hardened Araldite and the exposed copper circles were measured by two types of instruments; one measured the diameter of the copper circles whilst the other measured random chords across the circles.The experimental results are compared with the results of a computer simulation of the sectioning of randomly positioned spheres.
Computer techniques in the analysis of field‐ion micrographs
Authors: Youle A. , Davies D. M. , Dury B. L. , Schwartz D. M. , Taylor D. M. , Ralph B. 
Published: August 2011

SUMMARYThe computer techniques at present used in the extraction and analysis of data from field‐ion micrographs are described. These techniques are divided into three categories: simulation of field‐ion images, the analysis of particle sizes and the determination of precipitate shapes and interface topography. The theory and techniques of each are described, together with examples of their use.
Perspectives of application of quantitive television microscopy to earth sciences
Authors: Pinault J. L. , Prevosteau J. M. , Williams D. G. 
Published: August 2011

SUMMARYThe quantitative application to earth sciences of the recent techniques of opto‐electronic methods has become possible not only thanks to new methods of sample preparation, to analysis at all levels of magnification, to progress in image analysis, but also to the mathematical formulation and evaluation of data. At the level of the light microscope (thin slice, polished section) this methodology is applicable to porous media, to powder granulometry, and to an analysis of metallic ores. As a special case, we have treated an example of the modal analysis of eight phases in an ore considered difficult from the point of view of identification and separation of the phases. At the macroscopic or geological level, we have tried to determine the hydraulic diameter of fissures and cracks, that is their orientation, working on a structural survey by simple application of stereological functions.
A general method of calculating particle size distributions
Authors: Schwartz D. M. 
Published: August 2011

SUMMARYA general nonparametric approach to estimating the true distribution of particle sizes from either light or electron micrographs of particles of known shape is described. This method can deal with any arbitrary shape and fixed or random orientations, it assumes that the observed distribution is obtained by recording the maximum observed diameters of the particles under study. As examples, the method is applied to the distributions of both cubic particles observed in an optical metallographic specimen and spherical particles observed in a transmission electron microscope specimen.
A comparison of several methods for stereological determination of the numbers of organelles per unit volume of cytoplasm
Authors: Mayhew T. M. 
Published: August 2011

SUMMARYGranules in electron micrographs of normal rat peritoneal macrophages were analysed using a number of stereological procedures currently available for estimating the numbers of discrete particles from measurements made on random sections. The distinction between the various procedures was dependent upon the nature of the parameters derived from micrograph samples, and upon the degree to which particle shape and size distribution coefficients were incorporated within the mathematical derivations. Whilst all methods were found to produce similar estimates of granule number per unit volume of macrophage cytoplasm, two procedures demonstrated a greater degree of flexibility of application. It is concluded that these two methods may possess important advantages when quantitating experimental systems exhibiting alterations in particle morphology.
A theory of field‐ion imaging: II. On the origin of site‐current variations*
Authors: Forbes Richard G. 
Published: August 2011

SUMMARYExperimental evidence demonstrates the incompleteness of the usual rate constant explanation of field‐ion image appearance, and suggests that gas distribution effects may be the dominant influence on image contrast, certainly in some circumstances. Further evidence shows that gas concentration variations across the surface would not be given by any simple formal rule. However, significant features of image behaviour in the helium‐on‐tungsten system can be rationalized by closer examination of gas behaviour during and after accommodation. For the normal imaging range a provisional working rule is suggested, that regional contrast may be primarily determined by supply‐and‐capture effects, but local contrast by a tendency for local gas equilibria to be established.
Use of vibratory polishing for the location of ion‐bombardment induced voids in metal foils
Authors: Mazey D. J. , Hudson J. A. , Francis S. , Whitton J. L. 
Published: August 2011

SUMMARYThe technique of vibratory polishing has been successfully applied to the controlled removal of surfaces for examination of ion‐irradiation damage structure in nickel, a nickel‐based alloy, and stainless steel. The application of this technique to the study of voids formed in localized layers in nickel and stainless steel during high dose 20 MeV carbon ion irradiation is described. Transmission electron microscopy observations of the vibratory polished surfaces reveal mechanical damage in the form of linear tracks (∼ 100 nm wide) which are produced by the abrasive Al2O3 particles used for polishing. These tracks do not prevent observation of irradiation damage structure. An example is shown of a thin (∼ 100 nm edge thickness) foil produced entirely by this mechanical polishing process. It is proposed that this technique will be equally applicable to the preparation of transmission electron microscope specimens from a wide range of metals, from alloys containing second‐phase particles and from ceramics, glasses and oxides which are not amenable to preparation by chemical or electro‐polishing.
Electron microscope measurements: A digital read‐out across the intermediate lens
Authors: Yodaiken Ralph E. 
Published: August 2011

SUMMARYIn order to ensure reproducibility of magnification and to determine the accuracy of figures taken from the magnification meter on the side of a Siemens electron microscope, a sensitive voltmeter with a digital read‐out was put in the intermediate as well as the objective and projector lens circuits. The microscope was calibrated on different days and the results of the magnification measurements taken from the scale were compared with the results obtained using the read‐out system. The conclusions underline the necessity for exercising caution in interpreting magnification figures and suggest a relatively inexpensive method of improving reproducibility.
Recent advances in automatic image analysis using a television system
Authors: Cole M. , Bond C. P. 
Published: August 2011

SUMMARYImage analysis, in the context of this paper, comprises the extraction of quantitative geometric and densitometric data from images produced by optical and electron microscopes or any other imaging system. Typical measurements include area percentages, intersect counts, feature counts, size distributions and integrated density determinations. Much of the stereological work is still performed by manual methods, but technological progress in recent years has considerably promoted the use of automatic image analysing devices. This paper describes recent developments in scanner performance and the correction of shading errors which allow reliable densitometric measurement. In addition, the previous geometric capabilities have been extended to include feature selection by pattern recognition criteria.
Apparatus for time‐lapse cinemicrography
Authors: Dawson Mary , Matthews J. E. 
Published: August 2011

SUMMARYAn apparatus for time‐lapse cinemicrography of living cells is described. It has an advantage over earlier apparatus in that it makes use of a microscope light source which can operate in both steady running and flash conditions. This enables setting up of the microscope and subsequent photography to be carried out with one light source, with consequent optimum illumination during photography. The light source is attached to a modified, inverted, phase‐contrast microscope, and the camera used is a modified 16 mm cine camera.
Photometrie measurements of grain density in autoradiographs
Authors: Rogers A. W. 
Published: August 2011

SUMMARYA technique is described for measuring the grain densities in areas of emulsion from 10 to 200 μm2, using vertical incident illumination which converts the silver grains into bright specks on a black background. The light reflected by the silver grains in the measuring area is integrated with a photometer to give a reading that is directly proportional to the number of grains present over a wide range of densities. Speeds of 200 counts/h can be maintained on suitable material throughout a working day without loss of accuracy. The characteristics of the method, the selection of equipment, and some sources of artefacts are discussed.
Purity and stability of radiochemical tracers in autoradiography
Authors: Evans E. Anthony 
Published: August 2011

SUMMARYAutoradiography is used as a means of ‘visualizing’ the results of tracer investigations; it gives a measure of ‘events’ which have already occurred. This paper discusses some of the problems peculiar to radiochemicals which should be clearly recognized prior to the application of autoradiographic techniques and the interpretation of the data obtained.Many of the problems described in this paper are concerned with tritium compounds which are particularly valuable and widely used for studies involving high resolution autoradiography. The physical (nuclear) properties of tritium, the low maximum beta energy (18 keV) of the radiation and the high maximum specific activity (29 Ci/mg atom of hydrogen), makes tritium the ideal isotope for determining the precise localization of compounds, drugs and hormones for example, in biological specimens.Refinements in autoradiographic techniques which have been developed in recent years have permitted high sensitivity in the detection of the tracer. While the importance of using compounds of known radiochemical purity for any tracer investigation is widely recognized, it is necessary to ensure that the data obtained is related to the radiochemical tracer compound and is not a consequence of the presence of radiochemical impurities. In this paper are therefore described some of the problems which can arise using impure tracer compounds and their effects on the interpretation of autoradiographs. The methods for the determination of purity, for example chromatographic, isotope dilution analysis, autoradiographic and spectroscopic methods are discussed together with some of the difficulties associated with these analytical techniques.The instability of radiochemicals on storage prior to their use is now a well documented phenomenon; it is a particularly severe problem with compounds used in high resolution autoradiographic studies because of the high molar specific activities which are necessary. Factors which determine the rate of self‐decomposition are discussed, such as the molar specific activity of the compounds, the energy of the radiation and the storage conditions selected for the compound. Current methods for minimizing self‐decomposition of radiochemicals are discussed and illustrated by examples.When using tritium compounds, the integrity of the tritium label is often related to the position of the tritium atom(s) in the tracer compound. However, many of the methods used for the preparation of tritium compounds can yield products in which the specificity of the labelling is uncertain. The importance of the specificity of labelling in such tracers in relation to the interpretation of autoradiographic data is therefore also discussed.
High efficiency development procedures for nuclear emulsions*
Authors: Rechenmann R. V. , Wittendorp E. 
Published: August 2011

SUMMARYThe development procedure of nuclear emulsions has been submitted to a systematic study. Each factor involved in this complex procedure has been considered separately.The optimum development time is determined by the maximum of the signal/noise ratio curve. It depends strongly on the other parameters involved in the developing process: temperature, type of emulsion, radiation, developer, etc.New treatment procedures for nuclear emulsions have been established. They are based on the following additional hypothesis concerning the corpuscular latent image: the image formed in the microcrystals consists partly of stable sub‐specks which are not developable, even by total developers. These sub‐germs would render the microcrystals developable if they are ‘activated’, i.e. if their electron levels are lowered by physical or physico‐chemical means.Activation by gold combined with a forced chemical development has proven to give results which are highly reproducible and homogeneous throughout the emulsion layer. Whatever the type of emulsion used and for most chemical developers, this procedure results always in a strong increase in the number of grains developed together with a remarkable stability of the chemical fog. The intensification effect increases when the grain size, the sensitivity of the emulsions and the mean energy released in a grain by a charged particle decreases. The amplification effect becomes more important when the redox potential of the developer diminishes (in absolute value).In light and electron microscope autoradiography, the gain in efficiency resulting from these studies permits the amount of radio‐elements used or the exposure times to be reduced in a ratio varying from 1/5 to 1/20, if compared with classical methods. Moreover, the increased probability of development of the ‘first grain hit’ results in a better resolution.
The dimensions and numbers of small vesicles in blood capillary endothelium in the hind legs of dogs, and their relation to vascular permeability
Authors: Casley‐Smith J. R. , Clark Helen I. 
Published: August 2011

SUMMARYThe dimensions and numbers of vesicles were determined in the blood capillary endothelium of the gastrocnemii muscle of dogs. These results permitted more accurate calculations of the number of vesicles crossing the endothelium in one direction/sec/(μm2 (∼6·2), and of the median vesicular attachment time (∼8 sec). The probability of fusion occurring when a vesicle contacts a plasma membrane (α= 0·004) was unchanged: hence it was concluded, from the mean cellular width (0·21 μm) and the calculated cytoplasmic viscosity (∼0·1 poise), that ∼49% of the vesicles starting from one side reached the other one, and that their median transit time was ∼1 sec.
Tri‐dimensional structure of the forming face of the Golgi apparatus as seen in the high voltage electron microscope after osmium impregnation of the small nerve cells in the semilunar ganglion of the trigeminal nerve
Authors: Rambourg A. , Marraud A. , Chretien Monique 
Published: August 2011

SUMMARYWhen rat trigeminal ganglia were osmicated for 45 h at 40°C in a 1% unbuffered aqueous solution of osmium tetroxide, only the one saccule located on the forming face of the Golgi stacks was impregnated with osmium. This staining property was therefore utilized to examine with the high voltage electron microscope the tri‐dimensional structure of the forming face of the Golgi apparatus of the small nerve cells using sections whose thickness ranged from 1 to 7 μm.In 1 μm thick sections, the osmicated ‘saccules’ actually consist of tubular polygonal networks scattered throughout the pericaryon. As the thickness of sections is progressively increased, these networks are seen to interconnect and form the so‐called ‘appareil réticulaire interne’ initially described by Golgi (1898a) in the light microscope. Stereoscopic analysis of 5–7 μm thick sections clearly demonstrates that the saccules located on the forming face of the Golgi stacks are in fact a continuous convoluted structure made up of a tubular polygonal network.
High voltage electron transmission microscopy of pyrolytic silicon carbide coatings from nuclear fuel particles
Authors: Hudson B. , Sheldon B. E. 
Published: August 2011

SUMMARYOne design concept for a gas cooled fast reactor fuel element utilizes directly cooled coated fuel particles. The fission product retention barrier is a pyrolytic SiC layer approximately 50 μm thick and 1 mm diameter. Knowledge of the structure of this material and its irradiation performance after high neutron doses is vital to the success of such reactors.Specimens oriented both parallel and perpendicular to the radius can be prepared from the shells by ion beam sputtering. The defect structure and preferred orientation of the coatings is being investigated. The high voltage electron beam is being utilized to measure the atomic displacement energy and to simulate fast neutron damage at temperatures relevant to reactor conditions.
Application of high voltage electron microscopy to low‐temperature radiation damage studies in metals
Authors: Urban K. 
Published: August 2011

SUMMARYThe paper briefly reviews the advantages of high voltage electron microscopy applied to low temperature radiation damage studies. Such studies may be performed inside the microscope provided a high resolution specimen cooling stage is available. The main features of a new type of cooling stage used in the experiments relevant to this paper are outlined. The applicability of the stage for post‐irradiation annealing experiments is emphasized.During electron irradiation to high doses at 8°K the formation of defect clusters was observed in nickel and copper. This is accompanied by pronounced changes in the diffraction pattern. Post‐irradiation annealing of samples irradiated at 8°K produces defect clusters which can be identified as dislocation loops.
High voltage electron microscope studies of void nucleation in nickel
Authors: Harbottle J. E. , Norris D. I. R. 
Published: August 2011

SUMMARYThe influence of dislocation behaviour on void formation in the high voltage electron microscope (HVEM) has been predicted theoretically and confirmed by experiment. The probability of void nucleation has been computed as a function of the radial distance from a dislocation line in a finite cylinder of material. The observation of strings of voids associated with dislocation lines supports the predictions of the model. Void formation in the HVEM is closely related to the detailed microstructural changes that occur immediately upon electron irradiation, and a good correlation is obtained between the initial interstitial loop density and subsequent swelling by electrons. A minimum foil thickness is necessary for void growth in the HVEM, otherwise the surfaces dominate and the dislocation density always remains low.