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PubMed1989

FORTRAN source listing for simulating three-dimensional convergent beam patterns with absorption by the Bloch wave method.

The FORTRAN source code is given for a computer program that calculates the two-dimensional intensity distribution in convergent-beam transmission electron microdiffraction (CBED) patterns from perfect crystals. The program uses the eigenvalue or Bloch-wave method. It allows three-dimensional dynamical diffraction, and so includes all higher-order Laue zone effects without approximation. No symmetry reduction is included. The program accepts noncentrosymmetric or centrosymmetric crystal structures and allows absorption corrections to be included. It uses the "EISPACK" subroutines for the diagonalisation of a general complex matrix. Up to 100 CBED disks may be included. The code is also available via "Bitnet."

Electron Probe Microanalysis↗
PubMed1992

The influence of lens chromatic aberration on electron energy-loss spectroscopy quantitative measurements.

An investigation has been made into the effect of chromatic aberrations of a pre-spectrometer lens system on quantitative elemental analysis by electron energy loss spectroscopy (EELS). In transmission electron microscopy (TEM) diffraction mode, the measured effects are typically 150-330 times larger than if only objective-lens chromatic aberration were important. We discuss several methods of avoiding errors arising from chromatic aberration, including selection of a suitable optical mode (dependent on the desired spatial resolution), adjustment of the TEM imaging system so as to focus the system for a chosen energy loss, and analysis of a large area of a uniform specimen.

Electron Probe Microanalysis↗
PubMed1993

Electron microscopy of materials at the University of Birmingham.

The School of Metallurgy and Materials has traditionally put transmission electron microscopy (TEM) in the forefront of its research interests and, through support from SERC and from the university, has always had the facility to carry out state of the art electron microscopy of materials. In this brief review some of the topics where TEM has played a central role in recent work in Birmingham will be described so that it will be seen just how central to the work in Birmingham TEM has been.

Alloys↗
PubMed1993

Environmental scanning electron microscope (ESEM) evaluation of crystal and plaque formation associated with biocorrosion.

The biofilm attributed to Desulfovibrio vulgaris growing in the presence of ferrous metals was examined with an environmental scanning electron microscope. This novel microscope produced images of iron sulfide colloids and other iron containing structures that had not been reported previously. A plaque composed of iron sulfide enveloped the surface of the corroding metal while crystals containing magnesium, iron, sulfur, and phosphorus were present in the culture where corrosion was in progress. A structure resembling the tubercule found in aerobic corrosion was observed on stainless steel undergoing biocorrosion and the elements present in this structure included sulfur, iron, chloride, calcium, potassium, and chromium.

Biodegradation, Environmental↗
PubMed1994

Electron and atomic force microscopic investigations of lead selenide crystals grown under monolayers.

Lead selenide (PbSe) particulate films, composed of highly oriented, equilateral triangular crystals, have been in situ generated by the exposure of arachidic-acid- (AA) monolayer-coated aqueous lead nitrate [Pb(NO32] solutions to hydrogen selenide (H2Se). The AA coated PbSe films, at different stages of their growth, were transferred to solid substrates and characterized by transmission electron microscopy (TEM), electron diffraction, and atomic force microscopy (AFM). The epitaxial growth of PbSe crystals has been rationalized in terms of matching the [111] plane of crystalline PbSe and the (100) plane of the hexagonally close-packed AA monolayer. The parallel alignment of the < or = 110 > and < or = 001 > axes and the perpendicular alignment of the < or = 110 > axis to the monolayer have been suggested to be responsible for the observed formation of rod-like PbSe particles. The presence of a negatively charged monolayer has been found to be an essential requirement for the oriented growth of PbSe crystals.

Crystallization↗
PubMed1995

Development and application of a dry ultramicrotomy technique for the preparation of galvanneal sheet coatings.

The formability of galvanneal steel sheets used in the automotive industry is influenced by the presence and distribution of brittle and difficult to distinguish Zn-Fe intermetallics in the coating. Characterization of these intermetallics requires a high spatial resolution technique such as analytical transmission electron microscopy (ATEM). Sample preparation by ion milling is impossible due to iron redeposition, and traditional ultramicrotomy using water affects the coating chemistry. A technique based on dry ultramicrotomy has therefore been developed. To optimize the technique, different parameters (knife angle, cutting medium, thickness setting on the ultramicrotome, cutting speed) have been investigated for the preparation of galvanneal coatings and pure A1 sections. Results show that dry cutting does not affect the coating chemistry but shortens the life of the knife. Knife quality (cleanliness, sharpness and absence of defects) is a major factor to obtain good dry sections. The best results for the more ductile pure A1 are obtained with a 35 degrees knife whilst for the harder galvanneal coating it is recommended to use a 55 degrees knife. These results suggest that the sectioning mechanism for the harder material involves more a cleavage-fracture mechanism whilst a greater amount of shear is involved when sectioning relatively ductile A1. The optimum parameters for sectioning galvanneal coatings are established and results obtained by parallel electron energy loss spectrum imaging and energy dispersive X-ray spectrometry in the TEM are given. This study shows that with a good control of all the sectioning parameters it is possible to obtain good sections repeatedly and rapidly.

Electron Probe Microanalysis↗
PubMedDate not supplied

Evaluation of the effect of lichens on ceramic roofing tiles by scanning electron microscopy and energy-dispersive spectroscopy analyses.

The effect of the actions of some lichens on the quality of ceramic roofing tiles was investigated in view of textural and microstructural changes considering their biocorrosion resistance. Two types (extruded and pressed) of the real ceramic roofing tiles aged 6 to 10 years, as well as the ceramic model systems formed with the additives of the specific chemical composition Cu-slag powder (10 wt%) and CuO powder (1 wt%), treated with various concentrations of oxalic acid (0.01 wt%, 0.1 wt%, and 4 wt%) were investigated. The thalli of lichen (Verrucaria nigrescens) growth on ceramic roofing tile were examined by scanning electron microscopy (SEM) and energy-dispersive spectroscopy (EDS). Investigation by SEM and EDS gave information regarding the ultrastructure characteristics of the thallus and the lichen-ceramic tile contact zone, allowing the observation of the hyphal penetration and filling up of the fissures and cracks by the lichens' hyphae. The CuO as the raw mixture additive changed the quality of the surface of the ceramic model systems as it has increased resistance to oxalic acid actions. The textural changes in the ceramic model systems and the formation of the identified destructive crystal phase, whewellite, were slowed down. The fundamental interactions between lichens and ceramic materials of the model systems have been identified as physico-chemical processes based on oxalic acid actions, which could cause ceramic matrix deterioration and consequently aging of ceramic roofing tile systems.

Biodegradation, Environmental↗
PubMed1983

Siliceous deposits in human urinary calculi--an E. M. study.

Silica calculi in man are extremely rare; only 12 cases have been reported. In an electron microscopic study of human urinary stones, siliceous deposits were encountered in three out of 180 stones as a discrete component of stones. There were no histories of magnesium trisilicate administration in these cases. Morphology of the deposits was distinctive from any other components of the stones and bore some resemblance to animal silica calculi. Siliceous deposits in human urinary stones appear to be more common than generally recognized.

Electron Probe Microanalysis↗
PubMed1994

Effect of delay in cryofixation on the elemental composition of biopsies and post mortem specimens of the thyroid gland.

The time between the excision and cryofixation of a biopsy is most important regarding its elemental composition as demonstrated by an investigation of the thyroid glands of rats and pigs. Biopsies taken and cryofixed immediately served as control specimens. Biopsies that were allowed to stand at room temperature for 20 min before cryofixation and specimens cryofixed at 1 h post mortem were also investigated. Significant changes in the ion concentration of the cells and colloid were apparent in biopsies in which cryofixation was delayed for 20 min and in thyroids cryofixed 1 h post mortem. It was demonstrated that redistribution of electrolytes occurs within 1h post mortem and that similar changes occur in biopsies allowed to stand for 20 min at room temperature before cryofixation. The results stress the importance of immediate cryofixation after surgical excision of a biopsy. This is especially important since numerous elemental changes due to delayed cryofixation resemble those which occur in pathological processes.

Animals↗
PubMed1995

An electron probe X-ray microanalytical study of bone mineral in osteogenesis imperfecta.

A semiquantitative electron probe X-ray microanalytical (XRMA) technique, in conjunction with transmission electron microscopy, was used to compare the calcium to phosphorus (Ca/P) molar ratios in calcium phosphate standards of known composition, in normal bone and in bone from patients with osteogenesis imperfecta (OI). Using a modified routine processing and resin embedding schedule, the measured Ca/P molar ratio of calcium phosphates standards of known composition were found to correlate well with the Ca/P molar ratio based on their respective chemical formulae. This technique was then used to compare the Ca/P molar ratio in normal human bone and in OI bone. The Ca/P ratio values for normal bone (Ca/P = 1.631) correlated well with those for chemically prepared hydroxyapatite (Ca/P = 1.602), but in bone from OI patients, the Ca/P molar ratio was significantly lower (Ca/P = 1.488). This study has shown that there is a lower Ca/P molar ratio in OI bone compared with normal, matched bone. This suggests that the mineral deviates from the carbanoapatite usually found in bone. Isomorphous substitutions in the carbanoapatite lattice could account for this although this study has neither proved nor disproved this. The altered bone mineral is another factor that could contribute to the increased fracture rate observed in OI.

Bone Density↗
PubMed1991

Maturation-related changes in mass and elemental contents of secretory granules as measured by electron-microprobe.

The relationship between granule density, protein content, and Ca and S contents were studied in two secretory granule fractions, from parotid glands of the rat, previously shown to constitute different stages in granule maturation. The density of the lighter fraction was between 1.133 and 1.142 g/ml, while that of the heavier fraction was greater than 1.142 g/ml. The mean protein content of the denser granules was 12% greater than that of the lighter granules (P less than 0.03), while the dry-mass elemental concentrations in the two granule fractions were unchanged. These results indicate that protein is added to granules during the maturation process (presumably by vesicular traffic), and that the resulting increase in granule density is not driven simply by decrease in water content and/or increased concentrations of inorganic Ca or S in the granules. The elemental concentration values also indicate that the diffusible elements permeate the granule membrane during the fractionation procedures.

Animals↗
PubMed1987

The structure, composition, formation and possible functions of calcareous corpuscles in Trilocularia acanthiaevulgaris Olsson 1867 (Cestoda, Tetraphyllidea).

Mature calcareous corpuscles in the juvenile (stomach) worms of Trilocularia acanthiaevulgaris comprise a number of concentric lamellae interspersed with areas of flocculent material. Each lamella is composed of a pair of membranous rings to which amorphous, non-crystalline material is attached. The process of corpuscle formation is intracellular, beginning with the autophagic break-down of the cytoplasm to produce a central vacuole within a parenchymal cell. The vacuole enlarges until only a thin layer of cytoplasm remains at the periphery and the nucleus is displaced to one end of the cell. Paired, concentrically arranged membranes are laid down beneath the peripheral cytoplasmic layer and eventually occlude the central vacuole. X-ray analysis of the corpuscles indicates the presence of calcium, phosphorus, sulphur, zinc and molybdenum, with the major peaks representing calcium, phosphorus and sulphur. Calcium appears to be bound to the lamellae rather than associated with the material between lamellae. The possible functions of the corpuscles are discussed in relation to the biology of T. acanthiaevulgaris and its developmental sequence in the dogfish gut.

Animals↗
PubMed1988

Na transport compartment in rabbit urinary bladder.

Electron microprobe analysis was used to determine cellular electrolyte concentrations in rabbit urinary bladder. Under control conditions the mean cellular electrolyte concentrations were for Na 11.6 +/- 2.0, for K 124.1 +/- 15.3, and for Cl 26.0 +/- 5.1 mmol/kg wet weight. The dry weight content was 19.0 +/- 2.0 g/100 g. Inhibition of the Na/K-pump with ouabain resulted in drastic changes of the cellular element concentrations. Similar changes also occurred when in addition to ouabain the apical side was kept Na-free. In all epithelial layers the Na and Cl concentrations increased by 90 and 30 mmol/kg wet weight, whereas the K concentration and the dry weight content decreased by 90 mmol/kg wet weight and 6 g/100 g wet weight, respectively. With Na-free choline-Ringer's solution on the basal side ouabain led to a decrease in the K concentration by about 60 mmol/kg wet weight while the Na and Cl concentrations remained unchanged. These data indicate that the basolateral membrane is permeable to Na, choline, Cl, and K. Nystatin produced drastic changes in the cellular electrolyte concentrations when Na- or Rb-sulfate Ringer's solutions were present on the apical side. With Na-sulfate Ringer's solution the Na concentration increased by about 25, the Cl concentration by 30 mmol/kg wet weight and the dry weight content decreased by 4.5 g/100 g, respectively. With Rb-Ringer's solution about 20 mmol/kg wet weight of the cellular K was exchanged against Rb. The concentration changes were identical in all epithelial layers supporting the idea that the rabbit urinary bladder represents a functional syncytium with regard to the transepithelial Na transport.

Animals↗
PubMed1982

Calcium and magnesium binding to thin and thick filaments in skinned muscle fibres: electron probe analysis.

Electron probe analysis of ultrathin cryosections with high spatial resolution was used to determine in situ the concentrations of Ca2+ and Mg2+ bound in the absence of ATP to myofilaments in the I and A-bands of skinned frog skeletal muscle. At 2.2 x 10(-11) M Ca2+ and 2.7 x 10(-9) M Mg2+, the inexchangeably bound Mg2+ in the I-band was equivalent to the amount of divalent cations known to be inexchangeably bound to F-actin, while the Ca2+ bound to the I-band was not significantly above zero. The bound Mg2+ in the I-band was not exchangeable with Ca2+ even when the skinned fibres were exposed to 10 mM Ca2+ solution. These results clearly indicate that Mg2+, rather than Ca2+, is the divalent cation bound to F-actin in the thin filaments in situ. In the presence of 1 mM Mg2+, the exchangeable Ca2+ bound to the I-band was increased as a function of the free Ca2+, while that in the A-band was not significantly changed with [Ca2+] up to 2 x 10(-5) M, and increased to approximately 0.8 mol Ca2+ per mol myosin at 10(-4) M Ca2+. At a saturating free Ca2+ in Tris-Cl solution, the bound Ca2+ content (2-3 mol Ca2+ per mol troponin) of the nonoverlapping I-band was unexpectedly low; the replacement of Tris with Na+ enhanced Ca2+ binding to the level equivalent to 3-4 mol Ca2+ per mol troponin. The depressant effect of Tris on Ca2+ binding was greater in the absence of Mg2+. High concentrations of Tris also reduced the maximum tension induced by 10(-4) M Ca2+ buffered with 10 mM EGTA. At 1.3 x 10(-7) M Ca2+, thought to be close to the cytoplasmic free Ca2+ in resting muscle, the I-band bound a significant amount of Ca2+: equivalent to about 1 mol Ca2+ per mol troponin. In rabbit myofibrils there was a significant amount (approximately 1.5 mol/mol myosin) of Ca2+ bound by the A-band at a free Ca2+ of 10(-4) M.

Animals↗