bluuebunny/crossref_metadata_2025_split huggingface dataset:
Unbiased estimation of particle density in the tandem scanning reflected light microscope
Authors: Howard V. , Reid S. , Baddeley A. , Boyde A. 
Published: August 2011

SUMMARYThe tandem scanning reflected light microscope has the property of being able to obtain information from ‘inside’ solid objects by taking a thin optical section at the focal plane of the objective lens. This plane can be focused up and down through the specimen.We describe an unbiased 3‐D counting rule for the TSRLM, which is applied to the estimation of osteocyte lacunar density in whole bone. This is shown to be an extremely efficient way of making such an estimate. Further possibilities for the application of the microscope in the field of stereology are discussed.
Manufacture and tests of objective zone plates for use in a scanning transmission X‐ray microscope
Authors: Michette A. G. , Burge R. E. 
Published: August 2011

SUMMARYA method of making high resolution zone plates for use as the focusing elements in soft X‐ray microscopy is briefly described. Tests carried out on these zone plates indicate a first‐order diffraction efficiency of ∼0.3% rather than the calculated value of ∼0.9%. This indicates that the zones are not positioned as accurately as expected, a conclusion also drawn from tests at optical wavelengths on electron micrographs of the zone plates. Modifications to the manufacturing method to enable zone plates with improved imaging properties to be made are described.
The detective quantum efficiency of the scintillator/photomultiplier in the scanning electron microscope
Authors: Oatley C. W. 
Published: August 2011

SUMMARYThe efficiency of a scintillator for use with a photomultiplier in a scanning electron microscope has, in the past, been specified by its detective quantum efficiency (DQE). It is shown that this is likely to give misleading results since the DQE is the product of two factors, each of which may be influenced by the properties of the photomultiplier. It is further shown that there is reason to mistrust the theoretical basis on which the measurement of DQE rests. It is suggested that a better method of specifying the merit of a scintillator/photomultiplier system is by the mean number of electrons per pulse reaching the first dynode of the photomultiplier. A description is given of the way in which this quantity, ϕ, can be determined. Results of measurements of DQE and of ϕ for three commonly used scintillators are recorded.
Astigmatism correction and determination of resolving power in the SEM
Authors: Smith K. C. A. 
Published: August 2011

SUMMARYSome of the early work carried out on the first scanning instrument constructed in the Cambridge University Engineering Department is recalled. The methods then used for astigmatism correction and the determination of resolving power are described and contrasted with later developments, particularly those relating to the use of on‐line digital computer techniques.
Assessment of electron irradiation damage to biomolecules using the Patterson function
Authors: Misra Manoj , Egerton R. F. 
Published: August 2011

SUMMARYA method for the assessment of electron radiation damage to 5‐iodouracil is described which involves the use of the Patterson function. Changes in Patterson maps computed from the electron diffraction patterns recorded at increasing electron irradiation have been related to structural and chemical damage to 5‐iodouracil. The process of radiation damage is also discussed in terms of a disorder parameter which was found to increase with increasing irradiation.
Dilute aldehyde treatment on aldehyde‐fixed cells for observing chromosomes in situ with the scanning electron microscope
Authors: Maruyama Keizo 
Published: August 2011

SUMMARYA new preparation method is introduced to reveal intracellular structures in the scanning electron microscope and its application to mitotic cells in root meristems of Vicia faba is demonstrated. The root tips are fixed with a mixture of formaldehyde and glutaraldehyde and the fixed tissues are frozen and fractured in liquid nitrogen. They are then incubated successively in dilute solutions of aldehyde (formaldehyde or glutaraldehyde) and osmium tetroxide. By this treatment, the excess cell‐matrix is removed from the fractured surface of the cell, and a deep view into the cell‐interior can be obtained with the scanning electron microscope. Varied levels of substructure are observed on the surface of chromosomes.
Glycol methacrylate embedding in histotechnology: factors which influence the evolution of heat during polymerization at room temperature
Authors: Gerrits P. O. , Leeuwen M. B. M. van 
Published: August 2011

SUMMARYBenzoyl peroxide is widely applied as an initiator–accelerator system in combination with tertiary amines for the polymerization of water‐miscible methacrylates. However, this system is very sensitive to the ambient temperature and the evolution of exothermic heat is, especially at room temperature (293 K), difficult to control. Temperatures involved may increase beyond 373 K. A linear correlation between a graded series of benzoyl peroxide (0.2–1.0 g% benzoyl peroxide/glycol methacrylate) and the maximum temperature within the polymerizing plastic was established using a commercially‐available embedding system. Commercially‐available glycol methacrylates contain various concentrations of inhibitor in order to prevent spontaneous polymerization of the monomer. We tested a series of 200–300–400–800 ppm of the inhibitor hydroquinone and found a significant influence exerted upon the maximum temperature and the moment at which the maximum temperature was reached. Supplementary addition of inhibitors to the GMA monomer may effect a decrease of the maximum temperature within polymerizing GMA mixtures. Possibilities for standardizing the polymerization of glycol methacrylate by means of the benzoyl peroxide/tertiary amine initiator–accelerator system at room temperature are discussed.
Improved vacuum evaporation unit for beryllium coating for biological X‐ray microanalysis
Authors: Marshall A. T. , Carde D. , Kent M. 
Published: August 2011

SUMMARYAn improved vacuum evaporator is described for coating frozen‐hydrated biological samples with beryllium for X‐ray microanalysis. The evaporator permits repeated coatings without bringing the main chamber to atmospheric pressure and ambient temperature. The use of a glass sleeve in the evaporation chamber facilitates cleaning.
The relative merits of various cooling methods
Authors: Bald W. B. 
Published: August 2011

SUMMARYThree different methods of rapidly cooling specimens prior to microscopical analysis are currently in use, namely, slamming, plunging and spraying.The heat transfer processes and specimen cooling rates which are theoretically achievable by each method are discussed and compared with some of the published experimental data.For the slamming method it is concluded that very little improvement in specimen freezing will be achieved by pre‐cooling the block below about 20 K and where pure silver is the most efficient block material.The highest cooling rates and best microscopy by either the plunging or spraying method will be achieved using nitrogen at supercritical pressures. At subcritical pressures propane will produce the best results for metal samples whereas ethane is superior to propane for exposed biological specimens.Future experimental work which relates ice crystal size to cooling rate must be based on the cooling rate at the instant of freezing or nucleation and not on some average cooling rate.
An inexpensive device for freeze drying and plastic embedding tissues at low temperatures
Authors: Lyon R. , Appleton J. , Swindin K. J. , Abbot J. J. , Chesters J. 
Published: August 2011

SUMMARYThe preparation of biological tissues for electron microscopy by rapid freezing retains the original localization of ions and molecules. A reproducible freezing regime was established by quenching tissues in liquid propane according to the method of Elder et al. (1981). Tissue was thereafter freeze dried in a custom built freeze drying device with a liquid nitrogen cooled stage to prevent ice recrystallization during drying. The device was also designed to allow the vacuum embedding of tissue in low temperature resin such as Lowicryl® and polymerization in situ. This paper describes the design of the device and an example of its use in the freeze drying of cartilage. The results show that minimal ice damage occurs to the chondrocytes and that intracellular organelles are clearly visible. The regime described may prove a useful and pragmatic alternative to cutting tissue in the frozen state. Translocation of elements is unlikely except perhaps in the case of very labile elements such as Na and K, but this remains to be fully elucidated.
Phase separation in frozen erythrocyte membrane preparations
Authors: Finean J. B. , Hutchinson A. , Mills D. 
Published: August 2011

SUMMARYThe reversible formation of a lipid‐like phase in frozen preparations of erythrocyte membranes has been studied by X‐ray diffraction and by electron microscopy of freeze‐fracture replicas. The observations provide strong evidence for lateral migration or displacement at specific temperatures of intra‐membrane particles. This creates large areas of particle‐free membranes which fracture preferentially so as to dominate the freeze‐fracture image.
Normalization of light element X‐ray intensities for surface topography effects in frozen‐hydrated biological bulk samples
Authors: Marshall A. T. , Condron R. J. 
Published: August 2011

SUMMARYX‐rays from light elements (Z=6–12) experience marked absorption in biological or organic matrices. Consequently surface tilt has a strong effect on X‐ray intensity. Using epoxy resin models with well‐defined surface tilt variations the effect of tilt on potassium, sodium and oxygen X‐ray intensities has been examined and methods for normalizing intensities for tilt effects have been investigated.With an energy dispersive X‐ray detector having a high (40°) take‐off angle, samples, having local tilt variations from 20° from the horizontal towards the detector to 20° away from the detector, can be analysed for potassium using peak intensities without loss of accuracy. Little loss in accuracy is experienced for sodium over the tilt range of 10° towards the detector to 10° away from the detector. Under these conditions peak to background (P/BG) ratios offer little advantage over simple intensity values.Sodium absorption in frozen‐hydrated biological samples is about 10% greater than in epoxy resin whilst potassium absorption is similar in both samples. It is assumed therefore that the foregoing conclusions also hold for frozen‐hydrated samples.X‐ray peak intensity to backscattered electron (P/BE) ratios provide a means of normalizing peak intensities from light elements for surface tilt effects. This is a particularly useful method for oxygen intensities because P/BG ratios cannot be obtained with any facility at the present time. Oxygen P/BE ratios provide a means of obtaining intracellular water concentrations in fractured frozen‐hydrated biological bulk samples, where surface tilt varies. Sodium intensities can also be normalized in this way.
X‐ray microanalytical resolution in frozen‐hydrated biological bulk samples
Authors: Marshall A. T. , Condron R. J. 
Published: August 2011

SUMMARYIn coated frozen‐hydrated gelatin gels the backscattered electron yield does not increase during electron irradiation as it does in uncoated samples. Neither is the backscattered electron yield greater from coated frozen‐hydrated gels than that from more conductive organic samples. This is interpreted as indicating that a significant distortion of the electron interaction volume, due to the development of a space charge, does not occur in electron irradiated frozen‐hydrated gelatine gels when they are coated with a conducting coat.The depth resolution as estimated from models of biological samples in the form of frozen‐hydrated photographic film and frozen‐hydrated sections of gelatine gel is consistent with that computed from X‐ray depth distribution curves, i.e. close to 2.0 μm at 15 kV. Lateral resolution was estimated from photographic film to be close to 2.0 μm also, at 15 kV.
Toughening of hot pressed beta‐alumina using zirconia additions prepared from zirconate, tartrate and carbonate precursor materials
Authors: Binner J. G. P. , Stevens R. , Tan S. R. 
Published: August 2011

SUMMARYThe development of second phase zirconia precipitates in a beta‐alumina matrix has been achieved using chemical reactions which occur during the firing process. The degree of success of each of several fabrication routes has been evaluated by use of toughness measurements and electron microscopy techniques. Approximately half of the routes yielded ∼90% retention of tetragonal zirconia, resulting in an approximate doubling of the Mode 1 critical stress intensity factor (K1c).
The characterization of interfacial structures in the oxidation of Fe and FeNiCr alloys by edge‐on transmission electron microscopy
Authors: Newcomb S. B. , Stobbs W. M. 
Published: August 2011

SUMMARYA wide range of scaling processes can occur during the high temperature oxidation of FeCr alloys. Here we discuss the relative merits of using alternative transmission electron microscopical (TEM) techniques, as applied to edge‐on foils, for characterizing some of the different diffusional and microstructurally limited processes which occur, in particular at oxide and metal‐oxide boundaries. We give results for interfaces in wüstite, which is formed very rapidly on pure iron, as well as for the more protective FeCr spinels and sesquioxides, as grown on FeNiCr alloys in both air and 1%C0–C02.
Resolution in low voltage scanning electron microscopy
Authors: Joy David C. 
Published: August 2011

SUMMARYAs the energy of an electron beam is reduced, the range falls and the secondary electron yield rises. A low voltage scanning electron microscope can therefore, in principle, examine without damage or charging samples such as insulators, dielectrics or beam sensitive materials. This paper investigates the way in which the choice of beam energy affects the spatial resolution of a secondary electron image. It is shown that for samples which are thin compared to the electron range, the edge resolution and contrast in the image improve with increasing beam energy. In samples that are thicker than the electron range, the resolution can be optimized at either high or low energies, but low energy operation will produce images of higher contrast. At an energy of 2 keV or less beam interaction limited resolutions of the order of 3 nm should be possible.
Point cathodes for use in virtual source electron optics
Authors: Tuggle D. W. , Li J. Z. , Swanson L. W. 
Published: August 2011

SUMMARYA comparison is made for three point cathodes which are used in an electron gun forming a virtual rather than real source. The three cathodes operate in the field emission (FE), thermal‐field (TF) and Schottky emission (SE) regimes. A low angular intensity is chosen for this comparison, typical of an SEM as contrasted to an electron‐beam lithography system application. Energy spread, virtual source size and current fluctuations are compared.
Thermal field emission for low voltage scanning electron microscopy
Authors: Orloff J. 
Published: August 2011

SUMMARYLow voltage scanning electron microscopy is a technique of great importance to the semiconductor industry, where inspection and testing of non‐conductive devices must be done at ∼ 1 keV beam energy. In order to perform scanning electron microscopy for inspection at high speed, improved cathodes are required in order to achieve good resolution at low energy with high beam current, the chromatic spread in the electron beam is shown to be the limiting factor in the SEM and a comparison of thermionic, field emission and Schottky cathodes is made to determine which can provide the best performance. It is concluded that a thermal field emission or Schottky, cathode is superior to either conventional field emission or thermionic cathodes.
The pair correlation function for point and fibre systems and its stereological determination by planar sections*
Authors: Hanisch Karl‐Heinz , König Dieter , Stoyan Dietrich 
Published: August 2011

SUMMARYTraditional stereology consists nearly completely in the determination of particle size distributions and mean values such as Vv and Sv. However, for the description of the ‘inner’ structure of random structures second‐order characteristics such as the pair correlation function or reduced second moment function are useful. In the present paper stereological estimation of second‐order quantities for centres of random sphere systems and for random fibre systems are considered. In the case of sphere systems stereological formulae are given which connect the pair correlation function of the sphere centres with quantities available from planar, linear and thin sections. For random fibre systems some exact and approximate stereological methods are suggested which enable the determination of second‐order quantities from planar and thin intersections.
The stabilization of labile configurations of plant cytoplasm by freeze‐substitution
Authors: McCully M. E. , Canny M. J. 
Published: August 2011

SUMMARYThe system of elongated, vacuole‐like structures that are seen in phase‐contrast images of living plant cytoplasm, which has been called the pleomorphic canalicular system, has been shown previously to be distorted and vesiculated by conventional fixation methods. The stabilization of this labile structure in tomato hair cells by freeze‐substitution is described. Structural features of the freeze‐substituted cytoplasm as seen in whole mounts of resin‐embedded cells resemble closely those of the living cells.
The structure of the stalk surface layer of a brine pond microorganism: correlation averaging applied to a double layered lattice structure
Authors: Kessel Martin , Radermacher Michael , Frank Joachim 
Published: August 2011

SUMMARYThe surface layer of the stalk of a prosthecate halophilic microorganism is a periodic array (space group p3ml) comprised of electron dense trimers with a centre to centre spacing of 9.0nm. The structure is reminiscent of E. coli porin. We have demonstrated that the method of correlation averaging can be effectively used to separate overlapping lattices, and that this results in a higher fidelity reconstruction, when compared to the established method of Fourier filtration. Two statistical methods are used to determine the resolution of the correlation average as a function of the number of ‘windows’ averaged, (i) The phase residual of spatial frequencies in Fourier space is computed between independently obtained subaverages, and (ii) a new method of Q factor analysis examines the cumulative vector sum in Fourier space as a function of the number of windows averaged. Both methods give a resolution of 1/2.1−nm.
High resolution electron microscopy of interfaces in chlorinated phthalocyanine molecular crystals
Authors: Fryer J. R. , Smith David J. 
Published: August 2011

SUMMARYMolecular images of chlorinated copper phthalocyanine have shown the arrangement of molecules at the interface between two crystals. Mismatch does not cause distortion or recrystallization for low index junctions but for more irregular interfaces strain causes alteration of the molecular tilt angle and accommodation of the mismatch by the formation of edge dislocations whose Burger's vectors are parallel to the interface.
A sample preparation for quantitative determination of magnesium in individual lymphocytes by electron probe X‐ray microanalysis
Authors: Hook Gregory R. , Elin Ronald J. , Hosseini Jeanette M. , Swyt Carol , Fiori Charles E. 
Published: August 2011

SUMMARYWe present a sample preparation method for measuring magnesium in individual whole lymphocytes by electron probe X‐ray microanalysis. We use Burkitt's lymphoma cells in culture as the test sample and compare X‐ray microanalysis of individual cells with atomic absorption analysis of pooled cell populations. We determine the magnesium peak‐to‐local continuum X‐ray intensity ratio by electron probe X‐ray microanalysis and calculate a mean cell magnesium concentration of 39± 19 mmol/kg dry weight from analysis of 100 cells. We determine a mean cell magnesium concentration of 34 ±4 mmol/kg dry weight by atomic absorption analysis of pooled cells in three cell cultures. The mean cell magnesium concentrations determined by the two methods are not significantly different. We find a 10% coefficient of variation for both methods of analysis and a 30% coefficient of variation in magnesium concentration among individual cells by electron probe X‐ray microanalysis. We wash cells in ammonium nitrate for microanalysis or in buffered saline glucose for atomic absorption analysis. We find cells washed in either solution have the same cell viability (85%), recovery (75%), cell volume (555 μm3) and cytology. We air dry cells on thin film supports and show by magnesium X‐ray mapping that magnesium is within the cells. We conclude that: (a) our microanalysis cell preparation method preserves whole intact lymphocytes; (b) there is no systematic difference in results from the two methods of analysis; (c) electron probe X‐ray microanalysis can determine the variation in magnesium concentration among individual cells.
Measurement of the optical thickness of transparent tissue layers
Authors: Gahm Thomas , Witte Siegfried 
Published: August 2011

SUMMARYThe method of Due de Chaulnes was employed to determine the mechanical and optical thickness, as well as the refractive index, of transparent tissue layers in living specimens. To this end the reproducible accuracy of the method and its dependence on the adjustment in focusing and on the numerical aperture of the objective was evaluated on test specimens using the procedures of transmitted light, phase‐contrast (PC), and differential interference contrast (DIC) microscopy. The best working conditions were then applied to the actual measurements.
Characterization of defects in semiconductors by combined application of SEM(EBIC) and SDLTS*
Authors: Heydenreich J. , Breitenstein O. 
Published: August 2011

SUMMARYBesides the characterization of the geometrical structure of defects in semiconductors by TEM the estimation of their electrical activity is of importance. SEM(EBIC) and SDLTS (scanning deep level transient spectroscopy) are especially suitable for this purpose; they allow the inspection of electronic properties with a spatial resolution in the micron‐range. On the one hand, SEM(EBIC) yields information on the recombination efficiency of defects in the crystal volume adjacent to a pn junction or a Schottky barrier; on the other hand, SDLTS enables the detection to be carried out of the distribution and the energetic levels of deep level defects lying in the space charge region. Accordingly, the combined application of these techniques is very promising for investigating physical processes implying an inhomogeneous incorporation of deep level defects in semiconductor crystals.In comparison to the widely used SEM(EBIC) technique SDLTS has only rarely been applied, a fact that is due to the high detection sensitivity necessary for measuring capacity transients. The application of a highly sensitive (10—6 pF) micro‐computer‐controlled SDLTS system in combination with a conventional EBIC system allows a reliable inspection of semiconductor materials and devices, based on A3B5 compounds and on silicon. A typical application of the above technique is the investigation of the impurity distribution around extended crystal defects, like dislocations and precipitates, to study their gettering activity.