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At least 397 records · Page 22Linked to original sources
PubMed1998

Applications of Ion Microscopy and In Situ Electron Microscopy to the Study of Electronic Materials and Devices.

: We discuss the application of ion microscopy and in situ electron microscopy to the study of electronic and optical materials and devices. We demonstrate how the combination of in situ transmission electron microscopy and focused ion beam microscopy provides new avenues for the study for such structures, enabling extension of these techniques to the study of dopant distributions, nanoscale stresses, three-dimensional structural and chemical reconstruction, and real-time evolution of defect microstructure. We also discuss in situ applications of thermal, mechanical, electrical, and optical stresses during transmission electron microscopy imaging.

Journal Article↗
PubMed2004

Analysis of environmental particles by atomic force microscopy, scanning and transmission electron microscopy.

Due to their large specific surface and their abundance, micro and nano particles play an important role in the transport of micropollutants in the environment. Natural particles are usually composed of a mixture of inorganic amorphous or crystalline material (mainly FeOOH, Fe(x)Oy, Mn(x)Oy and clays) and organic material (humics and polysaccharides). They all tend to occur as very small particles (1-1,000 nm in diameter). Most natural amorphous particles are unstable and tend to transform with time towards more crystalline forms, either by aging or possibly, by dissolution and re-crystallization. Such transformations affect the fate of sorbed micropollutants and the scavenging properties are therefore changed. As these entities are sensitive to dehydration (aggregation, changes in the morphology), it is highly important to observe their morphology in their natural environment and understand their composition at the scale of the individual particles. Also for the understanding and optimization of water treatment technologies, the knowledge of the occurrence and behavior of nano-particles is of high importance. Some of the possible particle analysis methods are presented: aggregation processes, biomineralization, bacterial adhesion, biofilms in freshwaters, ferrihydrite as heavy metals remover from storm water. These examples demonstrate the capabilities and focus of the microscopes. Atomic Force Microscopy (AFM) allows to analyze the particles in their own environment, meaning in air or in the water. Thus, native aspects of particles can be observed. As well, forces of interactions between particles or between particles and other surfaces such as membranes will be highly valuable data. Scanning Electron Microscopy (SEM) and for higher lateral resolution, Transmission Electron Microscopy (TEM) allow measurement of the morphology and composition. Especially, TEM coupled with Electron Energy Loss Spectroscopy (TEM-EELS) is a powerful technique for elemental analysis. Finally, general guidelines for the effective use of microscopic techniques are provided.

Bacteria↗
PubMed1977

Studies on the embryogenesis of the tapeworm Shipleya inermis Fuhrmann, 1908 using transmission and scanning electron microscopy.

Scanning electron micrographs (SEM) are shown of the scolex, microtrichs, and the submucosal capsule formed by the worm. The course of development of the outer capsule and the outer envelope from the early preoncosphere to the mature oncosphere is followed by SEM and (in part) transmission electron microscopy. Three phases of development of the outer envelope (OE) were noted: (1) early preoncosphere with OE with a relative smooth outer surface, (2) the development of surface lamellae and (3) the formation of a dendritic area distal to the lamellae; all of the organelles appear to be secretory. Stereoscopic pairs of cryofractured developmental stages are used to aid understanding of the OE. Transmission electron micrographs are used to corroborate the SEM micrographs.

Cestoda↗
PubMed1997

Detection of mineral density on the surface of mouse parietal bones: backscattered electron imaging of low accelerating voltage scanning electron microscopy.

Backscattered electron (BSE) imaging of scanning electron microscopy (SEM) was applied to a study on the mineral density of the bone surface. The neonatal and adult mouse parietal bones freed of the periosteum and covering cells were examined in a field emission scanning electron microscope equipped with a high sensitivity BSE detector at 1-30 kV accelerating voltages. The mineral density of the bone surface was observable in BSE images at 5 kV accelerating voltage while only the topographic structures of the surface were obtained under an accelerating voltage less than 5 kV. As the accelerating voltages increased from 5 kV, the bright areas were extended, probably due to the imaging of the calcified bone matrix under the uncalcified osteoid. The bone surface is usually divided into smooth and rough areas according to its irregularities. BSE images at 5 kV clearly showed that the smooth areas were further divided into dark and bright areas which apparently corresponded to the uncalcified osteoid and calcified bone matrix, respectively. Bright granules, about 1.0-3.0 microns in diameter, were sometimes observed at the border between the osteoid and calcified bone matrix; these granular calcified areas were regarded as the calcifying front forming the calcified bone matrix from the osteoid. The present study demonstrated that the distribution of the osteoid on the mouse parietal bone surface changes depending on age: the osteoid occupied a large area in the parietal bone surface in neonatal mice, but was small in adult mice. Thus, low accelerating voltage SEM using BSE provides new information on the distribution of the osteoid and the bone matrix calcification under both normal and pathological conditions.

Aging↗
PubMed1984

Structure and composition of microcalcifications in benign and malignant lesions of the breast: study by light microscopy, transmission and scanning electron microscopy, microprobe analysis, and X-ray diffraction.

Microcalcifications previously located by radiography were extracted from 25 fresh specimens obtained from patients who had undergone tumorectomy or systematized mammary exeresis. Two principal types of microcalcifications were distinguished: Type I microcalcifications were amber in color and generally crystalline on scanning electron microscopy, with only one calcium peak on microprobe analysis; x-ray diffraction revealed that weddellite was involved. Type II microcalcifications were whitish, nonbirefringent under polarized light, and generally ovoid or fusiform, with two peaks, one calcium and the other phosphorus, on microprobe analysis; these microcalcifications were composed of calcium phosphate, the most characteristic form of which is hydroxyapatite, in the form of needles arranged in rosettes on transmission electron microscopy. Type I microcalcifications were observed in four of eight benign breast lesions, in two of three in situ lobular carcinomas, and in no intraductal adenocarcinomas or infiltrating carcinomas. Type II microcalcifications were present in all infiltrating carcinomas and intraductal adenocarcinomas; they were also found in benign lesions (four of eight) and even associated with type I microcalcifications in one in situ lobular carcinoma. There are, therefore, no "benign" or "malignant" microcalcifications; however, the presence of weddellite is a strong indication that a lesion is benign or, at most, an in situ lobular carcinoma.

Adenocarcinoma↗
PubMed1992

Abnormal collagen fibril structure as studied by electron microscopy.

Transmission electron microscopy has emerged as an ideal tool for the study and diagnosis of various disorders that involve collagen, since the information obtained by this technique is at the ultrastructural level. Structural alterations of collagen fibrils brought about by these disorders are discussed. The positive staining pattern of such fibrils is also investigated. In addition, this review describes how quantitative studies of electron-optical images from abnormal collagen fibrils can lead to information about the changes produced by collagen defects which relate to molecular or fibril architecture.

Animals↗
PubMed2001

Retinopathy of Great Pyrenees dogs: fluorescein angiography, light microscopy and transmitting and scanning electron microscopy.

OBJECTIVE: Investigation of the pathogenesis of Great Pyrenees retinopathy. ANIMALS: One male and two female puppies of parents who were affected with Great Pyrenees retinopathy and one 4-year-old affected adult male Great Pyrenees dog. PROCEDURE: The puppies were examined daily from 7 weeks of age by indirect ophthalmoscopy and their fundi were photographed until the lesions were static. Fluorescein angiography was completed at 7 weeks of age, within 24 h of detection of ophthalmoscopic lesions, and then weekly. The eyes of a 4-year-old and two 20-week-old puppies were examined with light microscopy, and transmitting and scanning electron microscopy. RESULTS: Blocked choroidal fluorescence was detected at 7 weeks of age. The blocked fluorescence enlarged, when the characteristic serous retinal detachments developed at 11 weeks of age. The detachments enlarged in size and number until the puppies were approximately 20 weeks old. Fluorescein pooling confirmed the presence of transient retinal pigment epithelial detachments. Leakage of dye into serous retinal detachments was not detected in this study. Light microscopy and transmitting and scanning electron microscopy confirmed the presence of multifocal serous retinal detachments with focal retinal degeneration that extended to the inner nuclear layer in a 4-year-old dog. The retinal detachments were accompanied by hypertrophy, hyperplasia, increased pigmentation, and vacuolation of the retinal pigment epithelium. CONCLUSIONS AND CLINICAL RELEVANCE: Great Pyrenees retinopathy is manifested by multifocal serous retinal and retinal pigment epithelial detachments. These detachments are similar to those noted with central serous retinopathy of humans. The sudden development of multifocal retinal and retinal pigment epithelial detachments, and the serous nature of these detachments, supports a theory that they develop secondary to focal secretion and absorption defects in retinal pigment epithelial cells. Given the age of the puppies when the blocked choroidal fluorescence was noted and maturation of the dog retina at 8 weeks postpartum, this retinopathy is considered to be a retinal pigment epithelial dysplasia. This unique inherited retinopathy offers an opportunity to study retinal pigment epithelial secretion.

Animals↗
PubMed1981

Mycosis fungoides: diagnostic criteria based on quantitative electron microscopy.

Quantitative electron microscopy can provide objective measurements of nuclear atypia in lymphoid cells in skin biopsies during early stages of infiltration of the skin as part of inflammatory or neoplastic processes. This potentially provides a method for establishing reproducible criteria for determining whether an individual skin biopsy represents mycosis fungoides or is unlikely to represent mycosis fungoides. To investigate such criteria, quantitative electron microscopic studies of skin biopsies from 109 patients were performed. Seventy-seven patients had benign disorders, 16 patients had early mycosis fungoides, and 16 patients had controversial lesions. Measurements were made of lymphocyte nuclear profile perimeter and areas in electron micrographs. A nuclear contour index was calculated. On the basis of the mean degree of nuclear convolution alone, mycosis fungoides was not adequately distinguished from benign disorders. Better discrimination was achieved when the proportion of cells with a anuclear contour index of 9.0 or more was considered as an additional actor. When statistical methods were used to select discriminating factors, the best electron microscopic discrimination between benign and mycosis fungoides groups occurred when the proportion of cells with a nuclear contour index of 7 or more and the proportion of cells with a nuclear profile area greater than 30 sq. micrometer. were used together. Nomograms are presented which demonstrate the use of these criteria for a given case.

Aged↗
PubMed2006

Nanometric crystal defects in transmission electron microscopy.

Transmission electron microscopy (TEM) is revisited in order to define methods for the identification of nanometric defects. Nanometric crystal defects play an important role as they influence, generally in a detrimental way, physical properties. For instance, radiation-induced damage in metals strongly degrades mechanical properties, rendering the material stronger but brittle. The difficulty in using TEM to identify the nature and size of such defects resides in their small size. TEM image simulations are deployed to explore limits and possible ways to improve on spatial resolution and contrast. The contrast of dislocation loops, cavities, and a stacking fault tetrahedra (SFT) are simulated in weak beam, interfering reflections (HRTEM), and scanned condensed electron probe (STEM) mode. Results indicate that STEM is a possible way to image small defects. In addition, a new objective aperture is proposed to improve resolution in diffraction contrast. It is investigated by simulations of the weak beam imaging of SFT and successfully applied in experimental observations.

Crystallization↗
PubMed1995

Histology and electron microscopy of fucosidosis of the skin. Subtle clues to diagnosis by electron microscopy.

Fucosidosis is an autosomal recessive inborn error of metabolism in which fucose-containing glycolipids, glycoproteins, and oligo- and polysaccharides accumulate in tissues as a consequence of alpha-L-fucosidase deficiency. Since the detection of this entity in 1966 several cases have been described, but until now investigations of clinically uninvolved skin have not been performed. In this study we have investigated clinically normal skin obtained from a patient with fucosidosis and his healthy sister, by light and electron microscopy, to determine whether normal skin in this condition yields clues that may have prognostic relevance. We found "empty"- appearing storage vesicles in melanocytes, endothelial cells, sweat glands, and fibroblasts in the skin.

Child, Preschool↗