Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Electron Probe Microanalysis”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 379 records · Page 21Linked to original sources
PubMed1962

Electron microscopy and x-ray scanning microanalysis of needle biopsy material from human liver.

A study has been made of the fine structure of hepatic parenchymal cells of human biopsy material in a case of pancreatic tumor with obstructive jaundice. Dense particles about 60 A in diameter have been found in the cytoplasm, which are considered to be ferritin molecules by electron microscopy. They are encountered throughout the cytoplasmic matrix and are often aggregated in electron-transparent areas, most of which are enclosed by an apparently single-layered membrane. Identification of the elemental iron has been pursued by the application of the x-ray scanning microanalyser which reveals a quantitative value within 1.0 per cent of the pure iron sample. The use of x-ray scanning microanalysis enables one to obtain accurate data from extremely small and precisely defined volumes of biological specimens.

Biopsy↗
PubMed1979

Quantitative electron probe X-ray microanalysis of electrolyte elements within epithelial tissue compartments.

The electron probe X-ray microanalysis of 1-micron thick frozen-hydrated sections provides a method to measure local concentrations of electrolyte elements (and H2O) in and around the cells in situ with an analytical spatial resolution of better than 0.2 micron and a sensitivity limit better than 10 mM with a standard error of less than 10%. Our microprobe studies on several epithelia transporting isotonic fluids have provided strong evidence that the electrolyte concentration in the interspaces suspected to be the sites of solute-solvent coupling may, on average, be as much as 35% more than in the bathing fluid. There also appear to be distinct concentration gradients in interspaces, the profiles of which differ according to the tissue geometry but particularly according to the location of the leaky cell junctions, suggesting that the osmotic equilibration of the transported fluid may require substantial mass flow through the junctions. In addition, there is evidence a) that the major electrolytes in the cytoplasm of the epithelial cells are not uniformly distributed but may have distinct axial and radial concentration gradients that depend on active solute transport (e.g., that abolished by ouabain); b) that in some epithelia (e.g., rabbit ileum) there is a peripheral cytoplasmic zone that may support fast convective flow for transcellular fluxes; c) that the extracellular structures like the glycocalyx and basement membrane preferentially sequester potassium (and calcium) and could have a non-zero reflection coefficient; and d) that in normal cells, nuclei have ionic composition similar to that of the circumnuclear cytoplasm.

Animals↗
PubMed1979

Application of electron probe X-ray microanalysis to calcification studies of bone and cartilage.

The use of electron probe x-ray microanalysis in previous studies of bone and cartilage has been reviewed with emphasis on the results which have contributed to some of the current concepts of the mechanism of mineralization in these tissues. A number of investigations continuing in the author's laboratory utilizing high spatial resolution x-ray microanalysis and anhydrous methods of specimen preparation are described, including aspects concerning the derivation of calibration curves from synthetic calcium phosphate solids, qualitative and quantitative analyses of calcium and phosphorus in bone from embryonic chicks and in growth plate cartilage from rats, and the role of organically-bound phosphorus in mineralizing tissues. The data obtained have helped identify brushite, CaHPO4-2H2O, as the major crystalline solid phase of calcium phosphate in the earliest mineral deposits of bone tissue, brushite and poorly crystalline hydroxyapatite in bone mineral of increasing age, and poorly crystalline hydroxyapatite in the most mature mineral portions of the tissue. Growth plate cartilage examination has revealed calcium and phosphorus in single mitochondrial granules within chondrocytes and in certain extracellular particles distinct from matrix vesicles. These results have provided important information about the possible roles of cells, extracellular components, and the organic matrix in the regulation of mineralization and about the composition, structure, and organization of the mineral phase as a function of progressively increasing age and maturation of the tissues studied.

Animals↗
PubMedDate not supplied

The effect of fast secondary electrons on x-ray microanalysis in the scanning electron microscope.

In this paper, the effect of fast secondary electrons (FSE), which result from inelastic scattering of incident electrons, on the characterization of materials in the scanning electron microscope are investigated with the aid of Monte Carlo simulations. The effect of FSE on x-ray microanalysis of light elements is investigated. A full description of the Monte Carlo simulations of FSE in solids is given.

Boron↗
PubMed2005

Synthesis of mesoporous aluminophosphate (AlPO) and investigation of zirconium incorporation into mesoporous AlPOs.

Mesoporous aluminophosphate materials with variable amounts of zirconium have been synthesized at room temperature using a nonionic surfactant tri-block copolymer (PEO(20)PPO(70)PEO(20)) as the structure-directing agent. Powder X-ray diffraction of as-synthesized and calcined AlPO and ZrAlPO mesoporous materials shows a single broad peak near 2theta = 2.5 degrees, indicative of the average pore-pore correlation distance. Electron probe microanalysis shows that the ratio of P/Al in the powders is approximately 0.5, far lower than 1.0 for an ideal aluminophosphate framework. XRD, TEM, and N2 adsorption data indicate that the calcined samples consist of wormlike tubular materials having surface areas >350 m2/g and pores in the mesopore range. Electron spin resonance (ESR) studies of the gamma-irradiated and evacuated ZrAlPO samples show signals due to Zr3+ that increase with Zr content in addition to signals due to framework defects (i.e., V centers) and H atoms. The line shape and g values observed for Zr3+ are best explained as arising from a trivalent zirconium ion situated at the framework tetrahedral sites.

Journal Article↗
PubMed1980

Progress in electron energy loss analysis for biological specimens.

Recent work, both experimental and theoretical has clarified the range of applicability, optimum conditions of operation and limits of detection of the EELS technique. Its chief use is for microanalysis of light elements (Z < 10). For heavier elements, however, it also has an important advantage over X-ray methods in requiring lower electron exposure of the specimen for given signal strength.

Electron Probe Microanalysis↗
PubMed2000

Electron probe X-ray microanalysis of cultured myogenic C2C12 cells with scanning and scanning transmission electron microscopy.

Heterogeneity of the elemental content of myogenic C2C12 cultured cells was studied by electron probe X-ray microanalysis (EPXMA) with scanning (SEM EPXMA) and scanning transmission electron microscopy (STEM EPXMA). The best plastic substrate for growing cells was Thermanox. For STEM EPXMA, a Formvar film coated with carbon was found to be suitable substrate. The cells examined by scanning transmission electron microscopy showed great heterogeneity in their elemental content in comparison with the cells examined in the scanning electron microscope despite of an almost identical preparation procedure for EPXMA. Nevertheless the K/Na ratios obtained from both methods of EPXMA were very close (4.1 and 4.3). We conclude that the observed discrepancy in the elemental content obtained by the two methods may be due to differences in instrumentation and this must be taken into account when planning a comparative study.

Animals↗
PubMed1988

Membrane and cytoplasmic structure at synaptic junctions in the mammalian central nervous system.

Application of rapid freezing, freeze substitution fixation, and freeze fracture techniques to the study of synaptic junctions in the mammalian central nervous system has revealed new aspects of synaptic structure that are consistent with and partially explicate advances in synaptic biochemistry and physiology. In the axoplasm adjacent to the presynaptic active zone, synaptic vesicles are linked to large spectrin-like filamentous proteins by shorter proteins that resemble synapsin I in morphology. This mesh of presynaptic filamentous proteins serves to concentrate synaptic vesicles in the vicinity of the active zone. The affinity with which the vesicles are bound by the mesh is probably modulated by the extent of phosphorylation at specific sites on the constituent filamentous proteins, and changes in the binding affinity result in changes in transmitter release. The structural organization of the postsynaptic density in Purkinje cell dendritic spines consists of very fine strands with adherent, heterogeneous globular proteins. Some of these globular proteins probably correspond to protein kinases and their substrates. The postsynaptic density, positioned at the site of the maximal depolarization caused by synaptic currents, apparently serves as a supporting framework for a variety of proteins, which respond to and transduce postsynaptic depolarization. At least two classes of filamentous protein fill the cytoplasm of spines with a complex mesh, which presumably contributes to maintenance of the spine shape. Membrane bound cisterns are a ubiquitous feature of Purkinje cell dendritic spines. Studies of rapidly frozen tissue with electron probe microanalysis and elemental imaging reveal that these cisterns take up and sequester calcium, which is derived from the extracellular space, and which probably enters the spine as part of the synaptic current.

Animals↗
PubMed1998

Improved quantitative electron probe X-ray microanalysis of biological cryosections using an EDS germanium detector and a super-atmosphere thin window (SuperATW).

A new Link energy-dispersive GEM detector with SuperATW window was tested for quantitative electron probe microanalysis of low calcium and sodium concentrations ([Ca], [Na]) in intracellular compartments of cardiac myocytes. We compare Ca profiles with high count statistics and similar peak area collected under the same conditions with either a Be-windowed Si and a Ge SuperATW detector. The height of the Ca peak was increased by 7%, the full width at half-maximum height was reduced by 9% with the Ge detector. The counts statistics of the Ca K alpha peak improved by 9% and the partial overlap with the K K beta peak was better deconvoluted. We calculate [Ca] and errors of the single measurement in mitochondria of guinea-pig cardiac myocytes from spectra acquired with a Si or Ge detector. For identical analysis conditions, the [Ca] were identical; however, with the Ge SuperATW detector, the calculated error of the single measurement was only 1/2.7 of that calculated from measurements with the Si detector. We compare the peak area of identical [Na] in spectra collected with the Be-windowed Si detector and Ge SuperATW detector. The peak area was significantly higher with the SuperATW Ge than with the Si detector and Be window, whereas the continuum in the range 4-10 keV was comparable, demonstrating the improved sensitivity for low atomic elements such as Na of the Ge SuperATW detector. [Na] and errors of the single measurement in mitochondria of quiescent guinea-pig cardiac myocytes were calculated from spectra acquired with the Si or the Ge detector. The use of the Ge SuperATW detector improved the detectability limit for sodium by more than 80% and reduced the error of the single measurement by a factor of 7-8.

Animals↗
PubMed2006

WDS versus silicon drift detector EDS: a case report for the comparison of quantitative chemical analyses of natural silicate minerals.

Electron probe microanalysis (EPMA) is an essential analytical approach to determine elemental concentrations of various solid specimens quantitatively in mineralogical, petrological and materials research. Either wavelength dispersive X-ray (WDS) or energy dispersive X-ray (EDS) spectrometric techniques can collect the characteristic X-rays generated from each element in the specimen by an incident electron beam in order to define chemical constituents. Although WDS has been the preferred technique because of its higher spectral resolution and ability to detect trace elements, new generation EDS systems with silicon drift detectors (SDD), equipped with thin windows and integrated digital processing electronics, are claimed to approach the WDS throughput. In this study, we compared the analytical capability of a SDD EDS system with respect to WDS equipped systems on natural silicate minerals. For this purpose, natural rock samples, in which the silicate minerals present had already been analysed by various WDS systems, were chosen to compare these results with the ones acquired with a SDD EDS system. SDD EDS yielded satisfactory results for major elements (Na, Mg, Al, Si, K, Ca, Ti, Mn and Fe) compared with the results of the same minerals obtained by various WDS systems.

Journal Article↗
PubMed1997

Influence of rapid heating with infrared radiation on RF magnetron-sputtered calcium phosphate coatings.

This study evaluated the effect of rapid heating with infrared radiation on the physico-chemical and morphological properties of radio frequent (RF) magnetron-sputtered calcium phosphate (Ca-P) coatings. About 2.5 microm thick Ca-P coatings were deposited on titanium disks and cylinders. These specimens were left untreated or were heat treated by infrared radiation at 300, 400, 500, 600, and 700 degrees C for 4, 7, 11, 17, and 24 s. Subsequently, the specimens were immersed in simulated body fluid (SBF) for 1 day, 1 week, and 5 weeks. X-ray diffraction measurements showed that heating at 500 degrees C or higher resulted in an increase of coating crystallinity. In addition, FT-IR measurements revealed the appearance of OH peaks in the spectra of samples treated at 500-700 degrees C. Electron probe microanalysis showed that after 5 weeks of immersion about 40-50% of the coatings heat treated at 500 and 600 degrees C was maintained. The coatings heat treated at 700 degrees C showed no dissolution at all. On the other hand, as-coated and 300 degrees C treated films were dissolved within 1 day. Scanning electron microscopy of the samples showed that directly after heat treatment no apparent cracks were present in the coatings. On the basis of these findings, we conclude that rapid heating with infrared radiation around 600 degrees C is the best heat treatment for RF magnetron-sputtered coatings.

Biocompatible Materials↗
PubMed1976

[Biophsical study of dental tissues under the effect of a local strontium application].

Microradiographic and electronmicroscopic observations show that topical application of concentrated strontium chloride solution on an abraded dentinal surface caused the formation in the dentine of very compact superficial layer composed of fine granules and with a high degree of radiodensity. This layer not only forms a continuous deposit on the superficial zone, but also penetrates and fills the canclicules to a certain distance. A barrier is thus created, diminishing the permeability of the dentine, which would explain the desensitization of the tooth. Electron probe microanalysis and X-ray diffraction studies show that the fundamental mechanism of the formation of strontium deposits is an exchange with the calcium fo the dentinal tissue, and recrystallization in the form of strontium apatite.

Dental Enamel↗
PubMed1982

[Uranium concentration by crustacea: A structural, ultrastructural and microanalytical study by secondary ion emission and electron probe X ray microanalysis].

Experimental intoxications were performed on the Crayfish Pontastacus leptodactylus using hydrosoluble uranium nitrate. Investigations demonstrate that Crustacea are able to concentrate both uranium main radioactive isotopes 238U and 235U within the cuticle, gill epithelium, midgut gland (= hepatopancreas) and macrophagic hemocytes. The storage occurs within nucleus and lysosomal system where uranium is precipitated in the form of an unsoluble phosphate. The proposed hypothesis for the metal extrusion is the following: residual bodies containing the uranium precipitates are extruded into the extracellular space where they are absorbed, by phagocytosis, by the macrophagic hemocytes.

Animals↗
PubMed2005

Preparation and multicolor electrochromic performance of a WO3/tris(2,2'-bipyridine)ruthenium(II)/polymer hybrid film.

A tungsten trioxide (WO(3))/tris(2,2'-bipyridine)ruthenium(II) ([Ru(bpy)(3)](2+); bpy=2,2'-bipyridine)/poly(sodium 4-styrenesulfonate) (PSS) hybrid film was prepared by electrodeposition from a colloidal triad solution containing peroxotungstic acid (PTA), [Ru(bpy)(3)](2+), and PSS. A binary solution of [Ru(bpy)(3)](2+) and PTA (30 vol % ethanol in water) gradually gave an orange precipitate, possibly caused by the electrostatic interaction between the cationic [Ru(bpy)(3)](2+) and the anionic PTA. The addition of PSS to the binary PTA/[Ru(bpy)(3)](2+) solution remarkably suppressed this precipitation and caused a stable, colloidal triad solution to form. The spectrophotometric measurements and lifetime analyses of the photoluminescence from the excited [Ru(bpy)(3)](2+) ion in the colloidal triad solution suggested that the [Ru(bpy)(3)](2+) ion is partially shielded from electrostatic interaction with anionic PTA by the anionic PSS polymer chain. The formation of the colloidal triad made the ternary [Ru(bpy)(3)](2+)/PTA/PSS solution much more redox active. Consequently, the rate of electrodeposition of WO(3) from PTA increased appreciably by the formation of the colloidal triad, and fast electrodeposition is required for the unique preparation of this hybrid film. The absorption spectrum of the [Ru(bpy)(3)](2+) ion in the film was close to its spectrum in water, but the photoexcited state of the [Ru(bpy)(3)](2+) ion was found to be quenched completely by the presence of WO(3) in the hybrid film. The cyclic voltammogram (CV) of the hybrid film suggested that the [Ru(bpy)(3)](2+) ion performs as it is adsorbed onto WO(3) during the electrochemical oxidation. An ohmic contact between the [Ru(bpy)(3)](2+) ion and the WO(3) surface could allow the electrochemical reaction of adsorbed [Ru(bpy)(3)](2+). The composition of the hybrid film, analyzed by electron probe microanalysis (EPMA), suggested that the positive charge of the [Ru(bpy)(3)](2+) ion could be neutralized by partially reduced WO(3)(-) ions, in addition to Cl(-) and PSS units, based on the charge balance in the film. The electrostatic interaction between the WO(3)(-) ion and the [Ru(bpy)(3)](2+) ion might be responsible for forming the electron transfer channel that causes the complete quenching of the photoexcited [Ru(bpy)(3)](2+) ion, as well as the formation of the ohmic contact between the [Ru(bpy)(3)](2+) ion and WO(3). A multicolor electrochromic performance of the WO(3)/[Ru(bpy)(3)](2+)/PSS hybrid film was observed, in which transmittances at 459 and 800 nm could be changed, either individually or at once, by the selection of a potential switch. Fast responses, of within a few seconds, to these potential switches were exhibited by the electrochromic hybrid film.

Journal Article↗
PubMed2004

Application of FIB microsampling technique to long-period ordered TiAl single crystal with composition gradient.

Metastable long-period superstructures in an L10-TiAl single crystal with a composition gradient were observed successfully by transmission electron microscopy with a focused ion beam (FIB) microsampling technique. The composition gradient from 54.7 to 75 at.% Al with approximately 6 microm width was detected by electron probe microanalysis and foil specimens containing the composition-gradient area were fabricated by the FIB microsampling method. The foil specimens clearly exhibit sequential changes in long-period superstructure depending on the Al concentration.

Alloys↗