bluuebunny/crossref_metadata_2025_split huggingface dataset:
Isolation and preparation of colonies grown on soft agar for ultrastructural investigation
Authors: Safa Ahmad R. , Tseng Michael T. 
Published: August 2011

SUMMARYPreparation of cell colonies grown on soft agar for electron microscopic examination is tedious. Mechanical damage to cells can occur during the process of colony removal. A procedure which permits rapid colony removal and preserves the integrity of the individual colony for ultrastructural examinations is described in this paper.
Enhancement of contrast in living and fixed specimens by the use of fibre optics
Authors: Burgess Ann M. C. 
Published: August 2011

SUMMARYA method is described which enhances the contrast of living and fixed specimens examined with the stereomicroscope. It consists of immersing the ends of flexible fibre optic light sources together with the specimen in the fluid used for examination. It is reported that not only does this method increase the contrast of living specimens but that it may also be applied to specimens being prepared as thin sections or freeze fracture surfaces for examination with the transmission electron microscope. A further method of enhancement of contrast is suggested which involves the fitting of light filters of complementary colours, one to each of the fibre optic light sources, before immersion with the specimen.
Recent improvements to the Cambridge University 600 kV High Resolution Electron Microscope
Authors: Smith David J. , Camps R. A. , Freeman L. A. , Hill R. , Nixon W. C. , Smith K. C. A. 
Published: August 2011

SUMMARYSeveral recent modifications to the Cambridge University 600 kV HREM have resulted in increased levels of performance and greater operating efficiency. Changes include new Permendur pole‐pieces with a reduced gap leading to improved aberration coefficients, and an attachment to the tilt/shift supplies which facilitates accurate beam alignment. Resolution figures include: (a) an axial CTF extending, without zeros, beyond 1·8 Å at 575 kV; (b) tilted beam CTFs extending beyond 1·1 Å; and (c) lattice fringes of 0·72 Å spacing.
Combining accurate defocus with low‐dose imaging in high resolution electron microscopy of biological material
Authors: Wrigley N. G. , Brown Elaine , Chillingworth R. K. 
Published: August 2011

SUMMARYHigh resolution (< 2 nm) electron microscopy of biological specimens requires three exacting conditions to be met simultaneously: (a) fine specimen detail must be protected from destruction by the electron beam (low dose), (b) the electron optics must be adjusted to be capable of imaging that detail interpretably (accurate defocus), and (c) a suitable field of interest must be identified. We describe a method encompassing all three with an 80% success rate using only minor modifications to a transmission electron microscope, and no expensive on‐line computing.
HREM and STEM of defects in multiply‐twinned particles
Authors: Marks L. D. , Smith David J. 
Published: August 2011

SUMMARYThe structure of defects in multiply‐twinned particles has been studied in detail using high‐resolution lattice imaging, dark field and microdiffraction techniques. Icosahedral particles with sizes greater than about 15 nm were found to contain defects, in the form of stacking fault loops parallel with the external surface, which were extremely difficult to detect by conventional amplitude contrast techniques. Microdiffraction mappings correlated with these results, showing large rotations of the face‐centred cubic segments. Results for decahedral particles indicated the presence of stacking faults running adjacent to, and parallel with, the twin boundaries. Microdiffraction maps confirmed that the particle structure was face‐centred cubic, and also verified that the apparent epitaxy of these particles was highly variable. Models for the defects are proposed and discussed, and the relative merits of HREM and STEM for elucidating structural details in small particles is briefly considered. Finally, the potential for direct imaging at surfaces, as demonstrated by some recent images, is discussed.
Electron microscopy of frozen hydrated sections of vitreous ice and vitrified biological samples
Authors: McDowall A. W. , Chang J.‐J. , Freeman R. , Lepault J. , Walter C. A. , Dubochet J. 
Published: August 2011

SUMMARYThe preparation and high resolution observation of frozen hydrated thin sections has been studied by transmission electron microscopy (TEM and STEM) on model systems, including pure water, protein solutions, catalase crystals, myelin sheath and various tissues. The state of the ice is determined by electron diffraction. Mass measurement in the electron microscope is used to determine section thickness and control hydration. An adequate depth of vitrified material for sectioning can be obtained from many biological suspensions or untreated tissues. Frozen hydrated sections around 100 nm thick can be produced under optimal conditions from vitreous ice or from vitrified biological samples. Sectioning, transfer and observation in the electron microscope is feasible without alteration of the sample hydration or its initial vitrification. Biological structures can be preserved and observed down to 10 nm. Under favourable working conditions, specimen compression during sectioning and electron beam damage are the factors limiting high resolution observations.
Fresnel fringe contrast of faceted voids within gem‐quality diamond
Authors: Hutchison J. L. , Bursill L. A. 
Published: August 2011

SUMMARYThe topology of faceted void‐like defects (‘voidites’) in gem‐quality type la diamonds has been revealed by high resolution phase‐contrast electron microscopy. Interpretation of the images in terms of a Fresnel contrast mechanism allows the defects to be identified as octahedral in shape. Image contrast is sensitive to defocus and other parameters, and Fresnel fringe interference effects may generate ‘superlattice’‐like contrast.
Instrumental requirements for high resolution imaging
Authors: Herrmann K.‐H. 
Published: August 2011

SUMMARYThe resolution of modern transmission electron microscopes reaches the physical limits imposed by lens aberrations and energy width. One of the many conditions to be fulfilled, the alignment of illuminating and imaging beam onto the coma‐free objective axis, is particularly discussed here since axial coma cannot be detected by the usual resolution‐checking methods. Space consumption of specimen stages prevents the full utilization of the magnetic saturation limit only in the 100 keV range. With higher energies, this handicap is obviated, and some additional advantages can be gained which promote material investigations at atomic resolution, and which are presently utilized in instrumental research projects. High resolution with biological specimens has up to now been unsuccessful because of radiation damage. Optimum utilization of all electrons scattered at the specimen must thus be given priority over optical resolution. Important instrumental requirements are minimum exposure beam control, imaging modes with high collection efficiency, and recording devices with high detection quantum efficiency connected on‐line to image processors. A remarkable decrease in beam sensitivity of organic crystals, by more than one order, has been found by cooling the specimen down to 4 K which, by the use of superconducting lenses, can be combined with both ultra high vacuum and the stability requirements for high resolution. Yet up to now, such protection has not been achieved with He cryostates in conventional lenses, perhaps because a temperature increase even of only a few degree K is harmful.Purely magnetic imaging energy filters are about to be developed to a high optical quality but have been employed so far in only a few high resolution instruments. Such filters allow removal of the inelastic background and thus improvement of contrast of images of low‐Z specimens, particularly in the dark field mode.Finally, some ‘non‐conventional’ projects have made progress. Correction of spherical and chromatic aberration by multipole lenses offers a chance to improve remarkably the resolution in the 100 keV range, to extend the bandwidth of phase contrast transfer and to obtain highly resolved information about inelastic images when an energy filter is also applied. Electron holography provides possibly useful large area phase contrast, particularly if the electron energy is decreased, which may be of great benefit in investigations of unstained specimens.
Air‐drying of human leucocytes for scanning electron microscopy using the GTGO procedure
Authors: Gamliel Haim , Gurfel Dorit , Leizerowitz Rachel , Polliack Aaron 
Published: August 2011

SUMMARYThe utilization of tannic acid and guanidine hydrochloride as mordants for better osmium binding has been shown to serve as an excellent alternative to metal coating of organ tissue specimens for scanning electron microscopy (SEM). The present report describes the GTGO procedure, a modification of the TAO technique introduced by Murakami et al. (1977, 1978), which we have found successful for the preparation of air dried peripheral blood leucocytes for SEM studies. Air dried, GTGO‐treated leucocytes show excellent preservation of surface features with minimal cell shrinkage. When critical point dried, GTGO‐treated cells are examined, they also show less shrinkage than cells prepared with standard glutaraldehyde fixation and critical point drying. The potential application of this air drying procedure (GTGO‐AD) to other soft biological specimens is currently under investigation. This technique is recommended as a new and effective air drying procedure for the successful preparation of cells for SEM.
Visualization of skin appendages by scanning electron microscopy
Authors: Tsuji Takuo 
Published: August 2011

SUMMARYA method for SEM visualization of skin appendages and elastic fibres around them is described. Skin sections were autoclaved for 4 h and followed by fixation, dehydration and xylol‐air drying. Using this method, the three‐dimensional architectural details of each type of skin appendage and related elastic fibre network were demonstrated.
A method for the detection of amyloid in human tissue embedded in epon using a combination of polarizing light microscopy and electron microscopy
Authors: Cottell David C. 
Published: August 2011

SUMMARYThis paper describes a method for demonstrating amyloid in human tissue embedded in epon using a combination of congo red staining and polarizing microscopy. The method involves the removal of the embedding medium from semi‐thin sections prior to staining with congo red and examination in the polarizing microscope. Typical apple green birefringence was detected in areas of amyloid deposition; these areas were mapped for selective trimming and ultra‐thin sections taken serially were examined in the electron microscope. The method was found to be reliable, easy to use and particularly of value as a sampling procedure prior to investigation in the electron microscope.
Morphometric studies of the spleen of the hypoxic mouse
Authors: Clegg E. J. 
Published: August 2011

SUMMARYAdult male mice were exposed for periods of up to 7 days at atmospheric pressures of either 72 or 52 kPa (540 or 390 mm mercury). Changes in body weights, spleen weights and red and white splenic pulp weights were compared with those in normoxic controls.Contrary to expectation, spleen weights and amounts of red pulp were greater (in terms of experimental‐control differences) in the animals kept at 72 kPa, suggesting that at 52 kPa loss of overall fitness reduced the adaptive erythropoietic response. However, in view of the fact that increased erythropoiesis has disadvantages as well as advantages, the lesser response at the lower pressure may not be wholly disadvantageous.Coefficients of variation of the spleen variables examined showed a tendency to decrease in the animals at 72 kPa, but rose markedly at 52 kPa. This finding was interpreted as indicating that at 72 kPa spleen and red pulp changes are adaptive, but at 52 kPa they indicate an overall relative failure of adaptive mechanisms, with consequent reduced somatic fitness.
Commercial image analysers and the characterization of microscopical images
Authors: Bradbury S. 
Published: August 2011

SUMMARYThis review surveys some of the current approaches to the characterization of microscopical images using commercially available image analysers. The role of image pre‐processing and segmentation is considered, together with the characterization of images by optical density, as well as size and shape.The newer analysers are capable of investigating relationships between grey‐levels in small areas of the image (‘texture‐analysis’); some of the descriptive approaches in this latter field are briefly outlined.
Standards for quantitative energy dispersive X‐ray microanalysis of biological cryosections: validation and application to studies of myocardium
Authors: Hagler Herbert K. , Lopez Linda E. , Flores Jesse S. , Lundswick Rebecca J. , Buja L. Maximilian 
Published: August 2011

SUMMARYThe preparation of a comprehensive set of gelatin‐glycerol‐salt standards for quantitation of diffusible ions in ultrathin cryosectioned tissue is described. This set of standards serves two basic functions. The first is to calibrate the X‐ray analytical system so that peak‐to‐continuum ratios obtained from test specimens may be converted to elemental concentrations. The second is to provide a known set of elemental concentrations which can be used to check the performance of the preparative and analytical steps involved in thin section biological X‐ray microanalysis. The application of these standards and techniques for cryoultramicrotomy and analysis of myocardial tissue also is described.
Vascular smooth muscle orientation in straight portions of human cerebral arteries
Authors: Walmsley James G. 
Published: August 2011

SUMMARYA technique of embedding, sectioning and analysis has been developed for studying the orientation and proportional composition of smooth muscle in the straight portions of human major cerebral arteries. Various distortions, which occurred during processing and sectioning, were measured quantitatively. Nerve fibres were implanted as a reference frame within the paraffin block containing an arterial bifurcation. The nuclei of smooth muscle have been treated as three‐dimensional vectors of cellular orientation. The projected length in the plane of the section and the section thickness were used to define section pitch. To relate these vectors to the overall geometry of cerebral arteries they were transformed such that the resultant pitch would be the same as that observed if the sections were cut normal to the arterial longitudinal axis. Matrix transformations of nuclear vectors were of the expansion and Eulerian forms. The average pitch for the five sections from three straight portions was −0.22° ± 2.36 (SD of five means) with a range between −2.8° and 3.2°. Because this pitch is small it is possible to use 6.9 μm thick longitudinal and mid‐plane sections of straight arteries to obtain estimates of proportional composition. Stereological point counting was used to determine that smooth muscle comprised 72.0% ± 4.76 (SD for ten segments) of the tunica media in cerebral arteries.
Indentation analysis: applications in the strength and wear of brittle materials
Authors: Lawn B. R. , Hockey B. J. , Richter H. 
Published: August 2011

SUMMARYSome recent developments in the principles and applications of indentation fracture in brittle materials are surveyed. Attention is focused on ‘sharp’ indenters, for which precursor ‘plasticity’ is an essential element of the crack development. A major consequence of this plasticity is a residual contact stress field which exerts a dominant influence on ensuing mechanical behaviour. This influence is discussed in relation to strength and wear properties of brittle ceramics. Emphasis is placed on the advantages of the indentation method as a means of producing controlled cracks for evaluating material fracture parameters and for gaining insight into flaw micromechanics.
Field emission, developments and possibilities
Authors: van der Mast K. D. 
Published: August 2011

SUMMARYThe overall performance of any electron microscope is to a great extent determined by the electron source. For example, the current acceptance of the STEM concept is due to the stimulation provided by field emission sources, which made it possible to image single atoms in the STEM.The field emission source remains the electron source with the highest brightness and the lowest energy spread. As a consequence, considerable research and engineering work has been and is still being conducted in a number of important areas. These areas include: (i) the mechanisms which determine the beam current stability; (ii) the electron‐electron interactions which lead to beam spreading and an increase of the energy spread; (iii) various types of emitters such as bare tungsten tips, oxygen processed tips, zirconium coated tips, carbon emitters, carbon coated tungsten emitters and even solid state emitters; (iv) the lifetime limiting factors, e.g. inclusions, ion bombardment and flashovers effects; (v) different types of optical systems for field emission guns, e.g. choice of magnetic and/or electrostatic lenses at high voltage potential in UHV systems, and special magnetic lenses just below the anode; (vi) field emission guns operating at higher kV's, up to 1·6 MeV.Because analytical work in the smallest possible volumes is a growing area of scientific interest, the demand for field emission sources which are reliable, easy to operate and stable will continue.
The use of a digitizing frame store in microscopy
Authors: Agar A. W. 
Published: August 2011

SUMMARYA digitizing frame store giving real time read out of the image for TV or slow scan rates is now available. This equipment has a number of applications in both optical and electron microscopy. Examples of results obtained by linkage to a low light level TV system are given showing that use of the frame store yields image information not otherwise available. Other possibilities of the system are indicated.
The role of specimen and instrumental parameters in STEM‐EDS X‐ray microanalysis of thin foils
Authors: Doig P. , Flewitt P. E. J. 
Published: August 2011

SUMMARYThe optimization of STEM‐EDS X‐ray microanalysis within thin metal foils can be achieved by control of the instrumental and specimen variables. The contribution of incident electron probe size, accelerating voltage and sampling frequency together with the specimen variable of foil thickness are discussed with reference to typically enountered microstructural features.
Microscopy of sclerotinites in the coal beds of the central part of the Appalachian coal field, U.S.A
Authors: Thompson Carolyn L. , Lyons Paul C. , Finkelman Robert B. , Brown Floyd W. , Hatcher Patrick G. 
Published: August 2011

SUMMARYRodlets from fusain and carbominerite bands or lenses in bituminous coal beds of the central part of the Appalachian coal field in the eastern United States were studied in three dimensions using both light microscopy and scanning‐electron microscopy (SEM). Infrared studies and chemical analyses complemented reflectance measurements. The rodlets are found strati‐graphically from the Pocahontas no. 3 coal bed (Pocahontas Formation, Lower Pennsylvanian or Namurian B & C) to the Washington coal bed (Washington Formation, Lower Permian). The most common rodlets are noncellular, range in diameter from 60 to 440 μm, and, when polished, have the relief and high reflectances typical of the inertinite maceral group. They have characteristic notches, ovoid shapes, distinctive fracture patterns, dense (oxidized) rims, vesicles, cavities and canals, some of which contain minerals (tentatively identified by SEM semiquantitative X‐ray and infrared analyses). Some rodlets show a cellular cast on their longitudinal surfaces. Due to different exposures in variously‐oriented polished sections, this type of rodlet is classified as sclerotinite of the inertinite maceral group. Comparison of the sclerotinites from the central part of the Appalachian coal field with the fusinitized resin rodlets from coal and coal balls of the Illinois basin (Kosanke & Harrison, 1957) and with the ‘sclerotioids’ of the St Rose no. 5 coal of Nova Scotia indicates that they represent the same bodies. All are interpreted to be rodlets of resinous origin belonging to one or more of the genera of medullosan seed ferns of Carboniferous and Permian age. We suggest using the existing terms ‘resino‐sclerotinite’ and ‘fungo‐sclerotinite’ for two distinct maceral varieties of the inertinite maceral group because of their distinguishing properties and their different paleobotanical origins. Two types of cellular rodlets, woody splinters and sclerenchyma strands, are also documented in this study because of their close association with the resino‐sclerotinites of the central part of the Appalachian coal field.
A comparison of optical properties of carbonized sporinite and vitrinite concentrates of coals of the same rank
Authors: Goodarzi F. 
Published: August 2011

SUMMARYThis paper reports a systematic study of variation of morphological and optical properties of low and medium rank sporinites (carbon = 830 and 87.1% d.a.f.) and vitrinites (carbon = 79.6 and 86.6% d.a.f.) of same coals carbonized over temperatures ranging from 300 to 950°C for 1 h at a heating rate of 5°C/min in an atmosphere of nitrogen. Contrasts are drawn between the molecular structure of carbonized residues of sporinites and vitrinites of the same coal based on variation of morphological and optical properties. For the same carbonization conditions, carbonized residues of sporinites eventually develop better ordered molecular structures than do the carbonized vitrinites, due to the greater level of fluidity of sporinite than vitrinite.
Graphitizability of carbonaceous materials as studied by TEM and X‐ray diffraction
Authors: Oberlin A. , Oberlin M. 
Published: August 2011

SUMMARYProgressive graphitization is measured from X‐ray patterns by the probability P for finding a carbon layer pair reaching the graphite order in the solid. TEM studies show that all carbons (whether graphitizing or not) contain small basic structural units less than 10 Å both in thickness and in diameter which acquire, locally, a preferred parallel orientation during the carbonization process, i.e. at the end of tar release. However, tilt and twist boundaries remain between adjacent units which create wrinkled layers. All the materials are porous; from microporous if the orientation is less than 50–100 Å (non‐graphitizing carbons) to macroporous if the preferred orientation is due to coalesced mesophase spheres (graphitizing carbons). For graphitization to occur it is necessary to have small basic structural units distributed in large areas of preferred orientation. Graphitization occurs only after a sudden elimination of the defects situated at the boundaries between two adjacent structural units, i.e. after development of perfect two dimensional order by dewrinkling and stiffening of the carbon layers (turbostratic structure made of large layers). If both Lamax and Lcmax are too small (micropores) graphitization is impossible. There is a continuous range of materials extending between those with the smallest regions possessing the same molecular orientations (non‐graphitizing carbons) and the largest (graphitizing carbons). A nearly continuous increase of P (from P = 0 to P = 0.8) was found by studying a great variety of kerogens, coals and asphalts. For a given sample, the maximum possible value of P depends only on the size of the oriented areas which itself depends only on the elemental composition at the very moment of its production. There is an opposite influence of the hydrogenated functional groups and the cross‐linking functional groups such as oxygen, sulphur and nitrogen.