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Query: UMLS:C0276640 (TEM)
 20,729 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The nucleus pulposus of cat intervertebral disc was examined after staining glycosaminoglycans with Alcian Blue and the results correlated with TEM X-ray probe microanalysis. In unstained sections a difference in copper levels between tissues and resin was detected. In tissue stained with Alcian blue before embedding, the copper levels were slightly increased and the morphological appearance of the intercellular material was amorphous. In sections restained after cutting, the relative levels of copper in the resin were considerably increased and tissue levels were significantly higher than in the resin. Moreover, the morphology of the intercellular material was altered from a rather amorphous material to a network. Sulphur levels behaved in similar manner to copper levels but any correlation between the elements was due to factors unrelated to glycosaminoglycan staining and probably resulted from contaminating sulphur.
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PMID:Correlation between Alcian Blue stainig of glycosaminoglycans of cat nucleus pulposus and TEM x-ray probe microanalysis. 8 31

The results of ultrastructural studies and transmission electron microscope microanalysis of two Scenedesmus strains experimentally exposed to copper sulfate are presented. A fine-structural examination of the cells revealed the presence of nuclear inclusions in the form of central dense-core complexes. Cytoplasmic structures resembling the intranuclear inclusions were occasionally found in the cells. TEM-X-ray microanalysis of these structures has provided evidence that the inclusions contain copper. It is concluded that their presence may be regarded as a detoxifying mechanism.
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PMID:Intranuclear complexes in a copper-tolerant green alga. 125 45

This paper describes four investigations of the olfactory mucosa of the brown trout: 1) the ultrastructure of the olfactory mucosa as revealed by scanning (SEM), conventional transmission (TEM), and high voltage (HVEM) electron microscopy; 2) light and electron-microscopic investigations of retrograde transport of the tracer macromolecule horseradish peroxidase (HRP) when applied to the cut olfactory nerve; 3) SEM and TEM investigations of the effects of olfactory nerve transection on cell populations within the olfactory epithelium; and 4) ultrastructural investigations of reversible degeneration of olfactory receptors caused by elevated copper concentrations. The trout olfactory epithelium contains five cell types: ciliated epithelial cells, ciliated olfactory receptor cells, microvillar olfactory receptor cells, supporting cells, and basal cells. The ciliated and microvillar olfactory receptor cells and a small number of basal cells are backfilled by HRP when the tracer is applied to the cut olfactory nerve. When the olfactory nerve is cut, both ciliated and microvillar olfactory receptor cells degenerate within 2 days and are morphologically intact again within 8 days. When wild trout are taken from their native stream and placed in tanks with elevated copper concentrations, ciliated and microvillar cells degenerate. Replacement of these trout into their stream of origin is followed by morphologic restoration of both types of olfactory receptor cells. Ciliated and microvillar receptor cells are primary sensory bipolar neurons whose dendrites make contact with the environment; their axons travel directly to the brain. Consequently, substances can be transported directly from the environment into the brain via these "naked neurons." Since fish cannot escape from the water in which they swim, and since that water may occasionally contain brain-toxic substances, the ability to close off--and later reopen--this anatomic gateway to the brain would confer a tremendous selective advantage upon animals that evolved the "brain-sparing" capacity to do so. Consequently, the unique regenerative powers of vertebrate olfactory receptor neurons may have their evolutionary origin in fishes.
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PMID:Ultrastructural neurobiology of the olfactory mucosa of the brown trout, Salmo trutta. 139 70

TEM and SAED studies were conducted to clarify a difference in age-hardening mechanism with changes of gold content in Au-Cu-Ag ternary alloys, 18K, 16K, and 14K gold alloys, for which the ratio of copper to silver remained at 65 to 35 in weight. Age-hardening in the 18K alloy was attributed to the formation of the AuCu I type ordered platelets on the matrix (100). In the 16K and 14K alloys, a periodic antiphase domain structure of the AuCu II type ordered phase made a major contribution to age-hardening. An alternating coarse lamellar structure was formed by the mechanism of discontinuous precipitation in the 16K alloy, while a modulated structure by spinodal decomposition was observed in the 14K alloy.
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PMID:Difference in age-hardening mechanism in dental gold alloys. 694 48

Surface-covered nanometer-sized CuO/Al2O3, CuO-ZnO/Al2O3, and CuO/ZnO catalysts were prepared by phase transfer with carboxylate. The surface-covered structure was studied using XPS, XRD, TEM, and high-resolution electron microscope. The results indicated that amorphous CuO and ZnO were dispersed on the surface of nanometer-sized Al2O3 particles in catalysts CuO-ZnO/Al2O3 and CuO/Al2O3, respectively. The thickness of its surface layer is about several angstroms. No spinel structure was found in the catalyst. The particle size of the surface-covered CuO/Al2O3 catalyst was about 2-3 nm. Al2O3 in the catalyst was amorphous. Surface-covered material CuO in the catalyst with low CuO content was also armophous. A large amount of copper carboxylate resulted in crystalline CuO and Cu2O. The protective ability of carboxylate to sol particles differs from the metal element of carboxylate. Copyright 1997 Academic Press. Copyright 1997Academic Press
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PMID:Preparation and Characterization of Surface-Covered Nanometer-Sized Catalyst by Carboxylate Phase Transfer 939 14

HREM and FEG TEM were emphasized and extensively used to follow the most subtle changes in the structure and composition of ball-milled Cu, Fe-Cu, and thermally decomposed Fe60Cu40. Some significant results are obtained and summarized as follows: HREM shows that the deformation of ball-milled copper proceeds mainly by twinning and shear bands (SBs) formation. The nano-grains formed during ball milling (BM) contain a high density of dislocations. The grain boundaries (GBs) of nanocrystalline (NC) Cu prepared by BM are ordered, curved, and strained, but disordering, lattice distortion, and nanovoids in local regions were frequently observed. Nanoscale composition analysis on mechanically alloyed Fe16Cu84 shows that the average Fe content in both the interior of grains and the GBs is close to the designed composition, which proves that a supersaturated solid solution has really formed. However, the Fe content is rather inhomogeneous between the larger and smaller grains, which infers the inhomogeneous mixing of Fe and Cu during mechanical alloying (MA). NC structure and the mechanical force-enhanced fast diffusion are the reasons of the formation of supersaturated solid solutions in immiscible systems with positive enthalpy of mixing. HREM observations carried out with the thermally decomposed Fe60Cu40 solid solution show that the Nishiyama (N-W) or Kurdyumov-Sachs (K-S) orientation relationships exist between alpha-Fe and Cu. Energy dispersive X-ray spectra (EDXS) results show that the Cu content in these alpha-Fe grains reaches as high as 9.5 at.% even after heating to 1,400 degrees C, which is even higher than the maximum solubility of Cu in gamma-Fe at 1,094 degrees C.
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PMID:Microstructure investigations of ball milled materials. 950 23

A site-specific technique for cross-section transmission electron microscopy specimen preparation of difficult materials is presented. A focused ion beam was used to slice an electron transparent membrane from a specific area of interest within a bulk sample. Micromanipulation lift-out procedures were then used to transport the electron-transparent specimen to a carbon-coated copper grid for subsequent TEM analysis. The FIB (focused ion beam) lift-out technique is a fast method for the preparation of site-specific TEM specimens. The versatility of this technique is demonstrated by presenting cross-sectioned TEM specimens from several types of materials systems, including a multi-layered integrated circuit on a Si substrate, a galvanized steel, a polycrystalline SiC ceramic fiber, and a ZnSe optical ceramic. These specimens have both complex surface geometry and interfaces with complex chemistry. FIB milling was performed sequentially through different layers of cross-sectioned materials so that preferential sputtering was not a factor in preparing TEM specimens. The FIB lift-out method for TEM analysis is a useful technique for the study of complex materials systems for TEM analysis.
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PMID:Applications of the FIB lift-out technique for TEM specimen preparation. 963 46

: Reconstruction of the Cu(001) surface due to oxygen gas impingement on a clean copper surface was directly observed by in situ UHV-TEM. Strain contrast between differently oriented surface reconstruction domains, assumed to be radical2 x 2 radical2 R45, were clearly visible by this method. The reconstruction precedes the nucleation of Cu2O islands. When Cu2O islands were partially reduced and then re-oxidized, a dwell time before formation of Cu2O was noted, demonstrating that a reconstructed Cu-O surface monolayer is necessary before oxide formation.
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PMID:Surface Reconstruction and Oxide Nucleation Due to Oxygen Interaction with Cu(001) Observed by In Situ Ultra-High Vacuum Transmission Electron Microscopy. 976 71

A prepration technique for nanometer particles, namely the replacing solvent drying technique, was developed. The main process of the technique including replacement of water in gel with special organic solvent and the removal of the solvent by distillation. No collapse of gel structure took place because of low interface tension between water and the solvent as well as low surface tension of the solvent. Where special apparatus and strictly limited preparation conditions were not necessary. The technique is noted for its low preparation cost and high universality. Titanium oxide and copper borate were prepared using the technique and were characterized using XRD, nitrogen physical adsorption, TEM, and small angle X-ray scattering. Results indicated that the titanium oxide and copper borate possessed particle sizes of 7-10 and 7-20 nm as well as a specific surface area of 235 m2/g and 360 m2/g, respectively. The specific surface area were even much higher than that of the samples prepared using supercritical drying technique. Copyright 1998 Academic Press.
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PMID:Replacing Solvent Drying Technique for Nanometer Particle Preparation. 984 79

For a weak phase/weak amplitude object the information transfer in the imaging process of TEM is described by the common formalism of the contrast transfer function (CTF). So far the effects of inelastic scattering were not accounted for in this formalism. In conventional imaging they were simply neglected. In energy filtering TEM (EFTEM), where removal of inelastic electrons leads to higher specimen contrast, they were modelled by a global increase of the elastic amplitude contrast. Thus, the description of inelastic and elastic scattering was mixed. Here a new ansatz is proposed which treats elastic and inelastic contrast transfer separately by adding an inelastic contribution to the scattering potentials. In EFTEM this has the effect of adding a filter contrast which depends on the characteristics of the inelastic scattering. For samples with dominant plasmon loss the additional filter contrast is restricted to low resolution. Because of its strong dependence on the nature of the inelastic scattering process, the filter contrast cannot in general be unified with the conventional elastic amplitude contrast. The modified CTF theory for EFTEM was tested experimentally on a variety of samples. Images of amorphous layers of copper, aluminium, and carbon films, as well as zero-loss images of proteins embedded in amorphous ice were evaluated. The values of the parameters of the additional filter contrast were determined for carbon film and proteins embedded in vitrified ice. Comparison of different CTF models used to reconstruct 3D volumes from zero-loss images confirmed that best agreement with the atomic model is attained with the new, modified CTF theory.
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PMID:Zero-loss image formation and modified contrast transfer theory in EFTEM. 1078 45


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