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Results for “Electron Probe Microanalysis”

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At least 811 records · Page 45Linked to original sources
PubMed1992

Visualization and initial characterization of the titanium boundary of the bone-implant interface of osseointegrated implants.

A simple procedure has allowed consistent visualization of the titanium boundary of the bone-implant interface of osseointegrated titanium implants at the electron microscope level. This was accomplished by embedding the intact bone-implant specimen block with low-viscosity resin prior to removal of the device in preparation for sectioning. The titanium boundary consisted of either a thin, compact amorphous electron dense layer, a broad layer of dense amorphous granules, or both. This material was removed by decalcification in formic acid (prior to embedding) and did not diffract electrons (ie, was noncrystalline). Scanning-transmission electron microscopy-EDX analysis indicated the presence of titanium, calcium, and phosphorus in the electron dense material. Field emission scanning electron microscopy-EDX dot-mapping analysis confirmed the presence of these elements and mapped them to the same locations at the implant-interface boundary.

Animals↗
PubMed1992

Surface analysis of an original Brånemark implant and three related clones.

Selected surface characteristics of screw-type titanium dental implants from four different manufacturers were evaluated. Considerable differences in surface and near-surface contaminants were demonstrated. The fixture treated with radiofrequency glow discharge (plasma) demonstrated the thinnest titanium oxide layer and the cleanest surface.

Dental Implants↗
PubMed1990

Shark tooth morphogenesis. An SEM and EDX analysis of enameloid and dentin development in various shark species.

The study provides a survey of shark tooth morphogenesis based on SEM and EDX analyses of whole tooth families in six shark species. The teeth, demonstrating different stages of development, were acid-etched and coated with palladium. Calcium content was determined semi-quantitatively by using the palladium coating as an internal standard. Due to the rapid development of the enameloid, all major events took place in the two or three youngest teeth of a tooth family. Enameloid appeared to develop as a transformation of the peripheral part of the dental papilla. Mineralization started immediately. Based on morphological criteria the middle zone of the enameloid was established at an early stage, excluding the possibility of an unambiguous centrifugal or centripetal direction of growth. Substantial mineral increase first occurred in the middle zone, spreading from the tooth tip toward the base. Dentin formed after the enameloid was completely established. Dentin formation started basally as a direct prolongation of the enameloid cap, then spreading toward the tooth tip, first along the edges. It is concluded that shark enameloid has a mesenchymal background, but a role played by the inner dental epithelium can not be excluded.

Amelogenesis↗
PubMed1987

X-ray microscopy and X-ray imaging.

Within a framework of an overview of the current status and potential of X-ray microscopy, a description is given of the development of the King's College scanning instrument which produced its first images in September, 1986. The instrument was mounted on the newly-built undulator beam line at the UK Science and Engineering Research Council's SRS synchrotron. There are consequently three sites worldwide where high-resolution X-ray microscopes with zone-plate optics are in operation. The other sites are BESSY-Berlin and NSLS-Brookhaven.

Animals↗
PubMed1985

Progress in element analysis on a high-voltage electron microscope.

X-Ray microprobe (XMA) and electron energy-loss (EELS) spectrometers have been installed on the high-voltage electron microscope (HVEM). The probe size has been measured and background reduction is in progress for XMA and EELS as are improvements in electron optics for EELS and sensitivity measurements. XMA is currently useful for qualitative analysis and has been used by several investigators from our laboratory and outside laboratories. However, EELS background levels are still too high for meaningful results to be obtained. Standards suitable for biological specimens are being measured, and a library for quantitative analysis is being compiled.

Animals↗
PubMed1981

The effect of monobasic sodium phosphate on statolith synthesis in aurelia.

The effect of monobasic sodium phosphate on statolith synthesis in Aurelia metamorphosing in artificial sea water (ASW) and in low sulfate ASW was determined. Phosphate enhances statolith synthesis in organisms metamorphosing in ASW and restores statolith numbers to normal or above in organisms developing in low sulfate ASW. A small amount of sulfate must be present in the medium along with phosphate during the time period of statolith synthesis for normal statolith formation. Apparently, neither sulfate nor phosphate is stored in the organisms during early strobilation for later use in statolith synthesis because pre-treatment of either ion in early strobilation followed by treatment with the other ion does not result in statolith formation. Calcifying vesicles of the rhopalia of organisms from low sulfate ASW are normal in number, acid phosphatase activity, and in ability to initiate mineralization (by forming minute statoliths). While phosphate is not incorporated directly into the statoliths, it contributes to an efficient uptake of calcium and sulfur into the cells and/or calcifying vesicles, stimulating growth of calcium sulfate dihydrate statoliths. The high efficiency of the phosphate effect in enhancing statolith synthesis intracellularly demonstrates that phosphate acts at the cellular level in the jellyfish calcification process and emphasizes that phosphate probably plays multiple roles in the calcification of higher organisms.

Animals↗
PubMedDate not supplied

Electron microscopy of tRNA crystals. I. Thin crystals negatively stained with uranyl acetate.

The first attempt to study crystal structures of tRNA by electron microscopy is described. Sufficiently thin crystals were prepared from yeast tRNAphe. The thickness of the thinnest was estimated at 130 A corresponding to a bilayer of the molecules. The L-shaped structure seemed to be maintained even after the negative staining with uranyl acetate. Optically filtered images from electron micrographs were compared with those simulated from the drawing of the molecular model by optical transform. The results suggest that the observed images reflect the real molecular arrangements within the crystal lattice although the shape of tRNA molecules seems to be somewhat modified by the uneven staining.

Crystallography↗