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

Energy Filtered Transmission Electron Microscopy (EFTEM) has been used to study nucleic acids localization in unstained thin sections of virus-infected cells. For this purpose, phosphorus maps (P-maps) have been obtained by applying the N-windows Egerton model for background subtraction from data acquired by a non-dedicated TEM Jeol 1200EXII equipped with a post-column PEELS Gatan 666-9000 and a Gatan Image Filter (GIF-100). To prevent possible errors in the evaluation of elemental maps and thus incorrect nucleic acid localization, we have studied different regions of swine testis (ST) cells with similar local density containing either high concentration of nucleic acids (condensed chromatin and ribosomes) or a very low concentration (mitochondria). Special care was taken to optimize the sample preparation conditions to avoid as much as possible the traditional artifacts derived from this source. Selection of the best set of pre-edge images for background fitting was also considered in order to produce "true P-maps". A new software for interactive processing of images series has been applied to estimate this set. Multivariate Statistical Analysis was used as a filtering tool to separate the "useful information" present in the inelastic image series (characteristic signal) from the "non-useful information" (noise and acquisition artifacts). The reconstitution of the original image series preserving mainly the useful information allowed the computation of P-maps with improved signal-to-noise ratio (SNR). This methodology has been applied to study the RNA content of maturation intermediate coronavirus particles found inside infected cells.
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PMID:Optimization of phosphorus localization by EFTEM of nucleic acid containing structures. 974 88

Using single crystal V2O5 as a sample, we tested the performance of the new aberration corrected GATAN spectrometer on a monochromatised 200 kV FEG FEI (S)TEM. The obtained V L and O K ELNES were compared with that obtained in a common GATAN GIF and that in the new spectrometer, without monochromatised beam. The performance of the new instrumentation is impressive: recorded with an energy-resolution of 0.22 eV, the V L(3) edge reveals all the features due to the bulk electronic structure, that are also revealed in near-edge X-ray absorption fine structure (NEXAFS) with a much higher energy-resolution (0.08 eV). All features of the ELNES and NEXAFS are in line with a theoretical spectrum derived from band-structure calculations.
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PMID:High resolution EELS using monochromator and high performance spectrometer: comparison of V2O5 ELNES with NEXAFS and band structure calculations. 1289 95

The oxidation state of iron oxide nanoparticles was determined using the two principally different technical realisations of energy filtering TEM, in one case using the JEOL 3010 equipped with a LaB6 cathode and a post-column GIF and in the second, the newly designed LIBRA 200FE equipped with an corrected in-column 90 degrees energy filter and a field emission gun (Schottky emitter). The samples studied were oxide-coated iron nanoparticles, and iron oxide inclusions in feldspars in granites. Five possible candidates exist for the iron-oxide phases: FeO, alpha-Fe2O3 (hematite), gamma-Fe2O3 (maghemite), Fe3O4 (magnetite) or alpha-FeO(OH) (goethite). Fingerprinting the O K-edge ELNES allows to distinguish between oxide phases with the same stochiometry and enables to make a first selection of possible candidates. The additional determination of the chemical composition allows unique identification of the phase present. For the oxide coated iron nanoparticles the most probable iron oxide phase of the shell is maghemite, which was additionally confirmed by HRTEM studies. The second studied system were iron oxide needles in alkali feldspar, where we obtained hematite as the most probable phase. There we additionally demonstrated the drastic changes of the ELNES of the O K-edge for the alkali feldspar and iron oxide needle by spatially resolved EELS.
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PMID:Determination of the oxidation state for iron oxide minerals by energy-filtering TEM. 1646 25