bluuebunny/crossref_metadata_2025_split huggingface dataset:
Abel type integral equations in stereology: I. General discussion
Authors: Jakeman A. J. , Anderssen R. S. 
Published: August 2011

SUMMARYIn developing numerical methods for the solution of computational problems of an involved and pragmatic nature, as occur for example in stereology, the approach should be first to classify the distinct types of numerical problems which arise. If available, appropriate results from numerical analysis can then be used to develop stable numerical processes for their solution. In fact, many of the results relating to the construction of basic numerical methods, such as spectral methods for the stable differentiation of experimental data and product integration methods for the evaluation of integrals with oscillatory and singular integrands, have been resolved. Thus, we are now in a position to apply the above approach to the more complex computational problems which arise in stereology.Many of these problems belong to one of the following two classes: (i) the solution of integral equations of Abel type; and (ii) the solution of some numerical differentiation problem.In Part I of this paper, we illustrate the generality in stereology of the Abel type integral equation and numerical differentiation formulations. As well, we derive the specific properties required in Part II which is mainly concerned with the construction of stable computational methods for (i). Included among these properties are the explicit inversion formulae which are known for general Abel type integral equations. It is these inversion formulae which we use to construct stable computational methods.Often, when estimates for linear properties of the solutions of (i) and (ii) are required, the numerical solution of (i) and (ii) can be circumvented by estimating the linear properties directly from the given observational data. In deriving such estimates, use of the properties of the Abel type integral equation and differentiation formulations plays an essential role. Because of the close connection between such estimation problems and (i) and (ii), the estimation of linear properties from truncated observational data is also examined in Part I.
The ultrastructural localization of calcium in the avian shell gland
Authors: Solomon Sarah E. , Fryer J. R. , Baird T. 
Published: August 2011

SUMMARYFluctuating concentrations of calcium in the blood supplying the avian shell gland are not reflected at tissue level. Analyses of oviducal mucosa throughout the laying cycle show that the concentration of calcium remains relatively unaltered even at peak activity thereby implying a rapid transfer process. These experiments describe the use of potassium pyroantimonate as a localizing agent. The precipitate produced by injecting the latter via the aorta was identified as calcium pyroantimonate by electron diffraction and the efficiency of the precipitant estimated by neutron activation analysis of eggshells present in the shell gland at the time of operation. Results indicate that calcium is transferred across the surface epithelial cells of the shell gland (tubular and pouch regions). Its localization in the former is taken as an indication of the involvement of this region in the production of the mammillary mantle.
The Denver Universal Microspectroradiometer (DUM): II. Computer configuration and modular programming for radiometry
Authors: Galbraith W. , Geyer Sharon B. , David G. B. 
Published: August 2011

SUMMARYThis paper describes and discusses for microscopists and spectroscopists the choice of computer equipment and the design of programs used in the Denver Universal Microspectroradiometer (DUM). This instrument is an accurate computerized photon‐counting microspectrophotometer, microspectrofluorimeter and microrefractometer. The computer is used to control the operation of the system, to acquire radiometric data of various kinds, and to reduce, analyse and output the data in a readily usable form.Since the radiometer was designed to carry out many kinds of measurements in a variety of micro‐ and macroscopic specimens, and since different methods of microscopy or spectroscopy have to be combined in various ways for the study of any one specimen, no single master‐program could fulfil efficiently all foreseeable requirements. Therefore, the programming developed is interactive, modular, hierarchical and hybrid. Modular interactive programming makes it possible for almost any kind of main program, applicable to almost any kind of measurement, to be assembled quickly from a collection of hierarchical subroutines. Main programs are short and composed mainly of Fortran statements calling subroutines; subroutines, in turn, automatically call other subroutines over many levels. The subroutines are independently written and optimized for maximum operational efficiency in the computer system used, or for maximum ease of transfer to other systems.This approach to programming enables someone unfamiliar with computer languages to operate the radiometric system from the console of the CRT terminal. The writing of new main programs, by linking groups of existing subroutines, requires only a minimum acquaintance with Fortran; only the writing and revision of subroutines requires programming experience.Differences and similarities in the method of computer operation between the present system and other computerized radiometers are briefly discussed.
A universal metal and carbon evaporation accessory for electron microscopy techniques and a method for obtaining repeatable evaporations of platinum carbon
Authors: Harris W. J. 
Published: August 2011

SUMMARYA simple accessory has been designed which can be used for all types of metal or carbon evaporation in either an upwards or downwards direction as required. A method of preparing platinum carbon rod sources which makes possible successive repeatable evaporations of platinum carbon is also described.
Radiation damage in electron microscopy of organic materials: effect of low temperatures
Authors: Salih S. M. , Cosslett V. E. 
Published: August 2011

SUMMARYAs measured by the life‐time of their electron diffraction patterns, the radiation sensitivity of anthracene and coronene at 500 kV is reduced by a factor of three to four at liquid helium temperature in comparison to room temperature. Forl‐valine the ratio is about 1·8 but there is a wide variation in the results, possibly due to differences in crystal thickness. The end‐dose at 20°K for valine is equivalent to 13 electrons/Å2; for anthracene and coronene it is about 600 electrons/Å2at room temperature. The variation of end‐dose with temperature shows that at least two mechanisms must be involved in damage to such compounds, possibly concerning the breaking of intermolecular and intramolecular bonds, respectively.
Electron microscopy of monomolecular films*
Authors: Neuman Ronald D. 
Published: August 2011

SUMMARYCalcium stearate monomolecular films were examined by electron microscopy using replica techniques. The effects of two evaporants, palladium and platinum, on the structure of Langmuir‐Blodgett monolayers and multilayers were investigated. The fine structure appears to be altered unless precautions are taken to minimize the radiation heat transfer during the shadow‐casting procedure. The structural features of deposited monolayers are also influenced by the underlying solid substrate.
Topographic intensity profiles in the scanning electron microscope—cubes
Authors: George E. P. , Robinson V. N. E. 
Published: August 2011

SUMMARYTwo‐dimensional Monte Carlo computations have been used to predict the backscattered and secondary electron intensity profiles when a plane surface has a square of side d standing out from it. This was taken as a model for a gold cube of dimensions d situated on a thick gold substrate. This latter situation has been approximately reproduced experimentally and the predicted intensity profiles show quite good agreement with the observed intensity profiles for a range of values of the dimension d.
Cathodoluminescence of biological molecules, macromolecules and cells
Authors: Barnett W. A. , Wise M. L. H. , Jones E. C. 
Published: August 2011

SUMMARYCathodoluminescence observations on biological compounds are compared with previously established data from ultra violet and visible light excitation studies. The comparison demonstrates that the same molecules are responsible for the luminescence properties of macromolecules independent of the type of exciting radiation. Natural cathodoluminescence was also observed from cells. Moreover, advantages gained by the absorption of strongly cathodoluminiscent dyes into cells are demonstrated.
Distilled glutaraldehyde: its use in an improved fixation regime for cell suspensions
Authors: Gillett R. , Jones G. E. , Partridge T. 
Published: August 2011

SUMMARYA method is described for the sequential fixation of cell suspensions, suitable for use at room or culture temperatures. Though an adequate method for fixing cell suspensions does exist in the literature (Hirsch & Fedorko, 1968), it involves the use of a mixed glutaraldehyde–osmium tetroxide fixative. Since these two components inter‐react, this method has many drawbacks.Previously described weaknesses of a sequential fixation regime (Hirsch & Fedorko, 1968; Jones, Yeh & Hirsch, 1972) with glutaraldehyde and osmium tetroxide have been overcome by the use of vacuum distilled glutaraldehyde as the primary fixative. The results, using a mixed glutaraldehyde–osmium tetroxide fixative and using the two components sequentially on a variety of cell types, are compared. The advantages of a sequential fixation made possible by the use of vacuum distilled glutaraldehyde rather than commercial glutaraldehyde are discussed.
The observation of crystalline materials in the scanning electron microscope (SEM)
Authors: Joy David C. 
Published: August 2011

SUMMARYContrast effects from electron channelling in crystalline solids can be observed in the scanning electron microscope by the correct choice of operating conditions. The crystallographic symmetry and orientation of specimen areas as small as 1 μm in diameter can be determined, and detailed quantitative information obtained about the density, nature and position of defects contained within the crystal structure. The backscattered, absorbed current and transmitted electron signals may all be used. With anticipated improvements in instrumentation the technique will be capable of providing all the information currently supplied by the more complex procedures of transmission electron microscopy.
Preparing sections of skeletal muscle for transmission electron analytical microscopy (TEAM) of diffusible elements
Authors: Sjöström Michael , Thornell Lars‐Eric 
Published: August 2011

SUMMARYComparative morphological examination and elemental analysis were carried out in structural compartments of sections of skeletal muscles. These had been prepared either by conventional plastic embedding technique or by various methods of cryo‐ultramicrotomy. The analyses were performed in a Philips EM 301 with an Edax energy‐dispersive X‐ray spectrometer.Spectra obtained from sections of plastic‐embedded muscle depended on the reagents used for fixation and staining and were absent if these were omitted. Brief fixation with glutaraldehyde resulted in gross ionic changes, and sectioning of frozen material with trough liquid led to extraction of elements. Sections cut from unfixed and frozen muscle without trough liquid showed numerous peaks. (Mg, P, S, Cl, K, Ca). In the superficial parts of the fibres of freeze‐dried sections reproducible spectral differences were found between different structures. Thus, rapid freezing of unfixed tissue, dry cutting in the frozen state, and freeze‐drying should be the procedure of choice if data on diffusible ions are desired.
Tungsten coating—a method of improving glass microtome knives for cutting ultrathin sections
Authors: Roberts I. M. 
Published: August 2011

SUMMARYGlass knives for ultramicrotomy were considerably improved by coating the cutting edge with a film of evaporated tungsten metal. Knives treated by this method gave up to ten times as many acceptable sections as uncoated glass knives. They could also cut thinner sections and harder tissues than ordinary glass knives, and eliminated some of the cutting artefacts produced by them. No explanation for this improvement was found although several possibilities were examined.
Detection of ultra‐soft X‐rays with a variable geometry proportional counter fitted to a transmission electron microscope (TEM)
Authors: Armigliato A. , Bentini G. G. , Ruffini G. 
Published: August 2011

SUMMARYThe ability of an end‐window variable geometry flow proportional counter to detect the ultrasoft BeK and SiL X‐ray lines induced by the electron beam of a transmission electron microscope (TEM) has been demonstrated. This counter has been used in the current work in the energy dispersive mode, and has been equipped with a Formvar window about 400 nm thick, aluminized on both sides with a layer of 65 nm total thickness. X‐ray peaks generated by specimens of other light elements such as boron, carbon, oxygen, fluorine and aluminium, and detected with this technique, are also reported. In the case of the BK line, the counting rate obtained with this detector has been evaluated and compared with that of a crystal spectrometer equipped with a conventional side‐window flow proportional counter. Finally, a linear relationship between X‐ray energy and detected pulse height was found for the lines examined, i.e. from the SiL up to the SiK X‐rays.
Lipid losses during processing of cardiac muscle for electron microscopy
Authors: Ward Barbara J. , Gloster Josephine A. 
Published: August 2011

SUMMARYThe lipid retaining properties of several methods of processing tissue for electron microscopy (EM) have been assessed quantitatively.Guinea‐pig hearts were perfused in vitro at 37°C with 3H‐oleic acid bound to albumin. The hearts were fixed by perfusion with 4% glutaraldehyde in 0.1 M cacodylate buffer. Pieces of left ventricle and interventricular septum were removed., weighed and processed for EM. The fluids used at each stage of processing were monitored for loss of radioactive lipid by scintillation counting. Lipids were extracted from the processed tissue immediately before the embedding stage using a mixture of chloroform: methanol (2:1 v/v). Counts from processed tissue were compared with counts from tissue extracted directly after perfusion fixation in order to monitor subsequent losses during processing.A modified version of Epon processing, omitting 100% ethanol, acetone or propylene oxide, gave a lipid retention of only 20.6%. The addition of para‐phenylenediamine to the procedure did not improve the retention although this has been shown to be a useful stain for intracellular lipid. Water soluble Durcupan which does not involve ethanol or acetone dehydration has an average retention of 63% with 100% recovery while the lesser known polymer GACH, a mixture of glutaraldehyde and carbohydrazide used both for dehydration and embedding showed a lipid retention of 82% of the counts recovered although recovery was only 69%.An attempt was made to determine which classes of lipids were present in the tissue after perfusion fixation using thin layer chromatography. It was found that the presence of any of the processing fluids affected the polarity of the lipids and their rates of migration on thin layer plates.
Contrast enhancement of negatively stained macromolecules and biomembranes by single sideband phase contrast interference
Authors: Harris J. R. , Kerr J. 
Published: August 2011

SUMMARYA straightforward procedure is described for the production of contrast enhancement of negatively stained macromolecules and biological membranes by single sideband phase contrast interference (electron optical shadowing). The instrumental adjustment required to produce this type of phase contrast illumination is readily achieved by beam deflection from the strioscopic (dark field) mode. Part of the hollow cone of electrons from the annular condenser aperture that are unscattered by the specimen are permitted to pass through the objective aperture and interfere with the scattered beam. The electron optical shadowing effect is produced because only one side of the unscattered beam is used. Careful adjustment of the beam tilt control, with the ability to tilt in any azimuth, allows optimal illumination conditions to be achieved. The results presented show the increased image contrast obtained using as specimens the purified cylindrical macromolecule from human erythrocyte membranes, purified nuclear envelopes and collagen fibres.
Section diameter method for non‐spherical objects
Authors: Chang K. S. , Dullien F. A. L. 
Published: August 2011

SUMMARYA theory of section diameter method has been developed for simply connected convex objects randomly distributed and oriented in three‐dimensional space. All objects have been assumed to be of a similar geometrical shape and they differ only in size. No geometrical symmetry is assumed in the most general case considered, however, considerable simplifications are obtained if the objects have certain symmetry properties. Solution of the integral equations giving the size distribution of two‐dimensional features in the sections presupposes the knowledge of a function which is determined entirely by the geometry of the objects. This function may be found, in principle, by parallel sectioning many identical bodies of random orientations in space.
The influence of the embedding medium when staining for electron microscopy: the penetration of stains into plastic sections
Authors: Horobin Richard W. , Tomlinson Annette 
Published: August 2011

SUMMARYUsing a sectioned‐section procedure it was found that only a few structures, e.g. the connective tissue elements, were deeply penetrated by phosphotungstic acid (PTA) and uranyl acetate (UA). Reynold's lead citrate appeared to penetrate more generally. Using stains selective for the embedding medium, and also observing the surfaces of shadowed sections, it was concluded that structures readily penetrated by polar stains were only poorly infiltrated by non‐polar embedding media. It is argued that this differential infiltration leading to differential penetration by polar stains largely controls the pattern of staining of ultrathin sections by PTA and UA.
X‐ray analysis without the need for standards
Authors: Nasir M. J. 
Published: August 2011

SUMMARYA technique has been developed for X‐ray analysis using energy dispersive solid state detectors commonly used with electron microprobes or scanning electron microscopes (SEM). This technique does not require the use of analysed standard alloys, instead the elemental peaks are directly compared to each other and simple corrections applied to convert these to weight percentages. A new empirical table for X‐ray fluorescence yields for the L X‐ray spectra is also given in this article.
Scanning electron microscopy of renal vascular casts
Authors: Bielke S. R. , Nagle R. B. , Trump B. F. , Bulger R. E. 
Published: August 2011

SUMMARYThe use of Cementex to form casts of the renal vascular system is described. These casts are useful in delineating the vascular microarchitecture of the kidney including that of the glomerular capillaries, but do not appear to reproducibly reflect physiological vascular tone. The postglomerular vascular system is often incompletely filled using this technique. The amount of filling can be altered by the techniques used in cast preparation. The effect of perfusion pressure, concentration of Cementex, fixation, and type of colour additive are compared with respect to the cast structure.
A new metachromatic stain technique for paraffin‐embedded neural tissue using thionin
Authors: Eichler Victor B. , Taylor Patricia W. 
Published: August 2011

SUMMARYA metachromatic staining procedure which differentiates Nissl substance in neuron cell bodies, neuropil area, and axonic fibres of passage with distinct colours with no counterstaining has been developed for paraffin‐embedded tissue utilizing thionin stain. Frozen sections of neural tissue fixed in formalin may also be satisfactorily stained by this procedure, and both paraffin‐embedded and frozen sections have been found to retain the distinct colours for a year with little fading. Since metachromatic staining of paraffin‐embedded neural tissue has not been successfully achieved before, the following procedure will be especially valuable for studying small vertebrate brains, or other central nervous tissue which must be processed by the paraffin method.
Improved resolution in cathodoluminescent microscopy of biological material
Authors: Haggis G. H. , Bond E. F. , Fulcher R. G. 
Published: August 2011

SUMMARYThis paper continues work reported in an earlier paper† on modification of a Cambridge Stereoscan Mk IIA to improve the quality of cathodoluminescent micrographs of biological material. In the work presently described the microscope gun has been offset laterally by 2 mm, to prevent light from the filament passing down through the column to the specimen chamber. The electron beam is brought onto the column axis by deflection coils. This modification effectively eliminates background light in the chamber, and a full parabolic mirror is fitted to maximize light collection. Results for yeasts and wheat seed sections are described.
The application of optical microscopy to studies of dust filtration: II. Specimen preparation techniques for analysing the distribution of dusts in filter fabrics
Authors: Rothwell E. , Bickham D. R. 
Published: August 2011

SUMMARYMicroscopic examination of dust cakes supported on filter fabrics is limited by difficulties in preparing useful sections by impregnating in cold setting resins; cake movement and sedimentation of dust particles result in sections which are not representative of the initial materials. An evaporator‐condenser assembly has been designed to enable sections to be prepared in which the fibres and dust particles are retained in their initial locations. Specimens of dust cakes supported on filter fabrics are placed in a thermal gradient in this assembly and a volatile monomer is condensed from the vapour phase on to dust particles and fibres of the fabrics. In situ polymerization effectively cements individual dust particles to each other and to the supporting fabric. After this treatment, specimens are vacuum impregnated in cold setting resin and sectioned by established techniques.
Molecular image of copper phthalocyanine
Authors: Murata Y. , Fryer J. R. , Baird T. 
Published: August 2011

SUMMARYThe structure of copper phthalocyanine has been studied by high resolution transmission electron microscopy (TEM). To reduce radiation damage, the technique of minimal beam exposure has been used together with X‐ray film for recording the image. This resulted in very noisy micrographs but optical averaging clearly revealed the molecular shape of the copper phthalocyanine, and also showed that a slight discrepancy exists between the averaged image, and the model structure which had been assumed to be isomorphous with platinum phthalocyanine.