Phosphore, calcium, silicium et fer dans des cristaux, extraits de graines sèches de Raphanus

Samples were taken from dry seeds of radish and fixed in glutaraldehyde. Ultrathin sections were observed without contrasting treatment. From cotyledonary parenchyma, it was possible to obtain powders or prints, which were observed by transmission electron microscopy. They showed several types of crystals. In the ultrathin sections of parenchyma cells, the crystals are included in globoids. Electron probe microanalysis with a wavelength dispersive spectrometer (Camebax microprobe) showed that they were rich in P, Ca, and Mg. In the powders and the prints, several polymorphic crystals, of varied sizes, were observed; these were sensitive to the electron beam. Some have relatively high ratios in Ca, lower ratios of S, and other elements, such as Si. Others possessed high ratios of Si with other elements, such as Ca and Al. The latter were less dense, more stable under the beam and their average diameter was smaller. Other crystals were smaller (some tenths of a micrometre). They were electron dense and very stable. Some of these were rich in Fe and could contain other elements (among others Si, Ca and P).

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Simplifying Electron Beam Channeling in Scanning Transmission Electron Microscopy (STEM)

Microscopy and Microanalysis ◽

10.1017/s143192761700068x ◽

2017 ◽

Vol 23 (4) ◽

pp. 794-808 ◽

Cited By ~ 6

Author(s):

Ryan J. Wu ◽

Anudha Mittal ◽

Michael L. Odlyzko ◽

K. Andre Mkhoyan

Keyword(s):

Electron Microscopy ◽

Transmission Electron Microscopy ◽

Electron Beam ◽

Angular Distribution ◽

Electron Probe ◽

Scanning Transmission Electron Microscopy ◽

Probe Intensity ◽

Scanning Transmission Electron ◽

Transmission Electron ◽

Scanning Transmission

AbstractSub-angstrom scanning transmission electron microscopy (STEM) allows quantitative column-by-column analysis of crystalline specimens via annular dark-field images. The intensity of electrons scattered from a particular location in an atomic column depends on the intensity of the electron probe at that location. Electron beam channeling causes oscillations in the STEM probe intensity during specimen propagation, which leads to differences in the beam intensity incident at different depths. Understanding the parameters that control this complex behavior is critical for interpreting experimental STEM results. In this work, theoretical analysis of the STEM probe intensity reveals that intensity oscillations during specimen propagation are regulated by changes in the beam’s angular distribution. Three distinct regimes of channeling behavior are observed: the high-atomic-number (Z) regime, in which atomic scattering leads to significant angular redistribution of the beam; the low-Zregime, in which the probe’s initial angular distribution controls intensity oscillations; and the intermediate-Zregime, in which the behavior is mixed. These contrasting regimes are shown to exist for a wide range of probe parameters. These results provide a new understanding of the occurrence and consequences of channeling phenomena and conditions under which their influence is strengthened or weakened by characteristics of the electron probe and sample.

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Techniques for Transmission Electron Microscopy of Fiber-Matrix Interfaces in Aluminum Alloy-Boron Composites by Ion Erosio

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100065079 ◽

1971 ◽

Vol 29 ◽

pp. 204-205

Author(s):

G. G. Shaw

Keyword(s):

Electron Microscopy ◽

Transmission Electron Microscopy ◽

Aluminum Alloy ◽

Electron Beam ◽

Pure Aluminum ◽

Ion Milling ◽

Transmission Electron ◽

Fiber Matrix ◽

Ion Erosion ◽

Row Of Fibers

The morphology and composition of the fiber-matrix interface can best be studied by transmission electron microscopy and electron diffraction. For some composites satisfactory samples can be prepared by electropolishing. For others such as aluminum alloy-boron composites ion erosion is necessary.When one wishes to examine a specimen with the electron beam perpendicular to the fiber, preparation is as follows: A 1/8 in. disk is cut from the sample with a cylindrical tool by spark machining. Thin slices, 5 mils thick, containing one row of fibers, are then, spark-machined from the disk. After spark machining, the slice is carefully polished with diamond paste until the row of fibers is exposed on each side, as shown in Figure 1.In the case where examination is desired with the electron beam parallel to the fiber, preparation is as follows: Experimental composites are usually 50 mils or less in thickness so an auxiliary holder is necessary during ion milling and for easy transfer to the electron microscope. This holder is pure aluminum sheet, 3 mils thick.

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Effects of High-Energy Ions on Synthetic Quartz

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100095972 ◽

1972 ◽

Vol 30 ◽

pp. 544-545

Author(s):

Joseph J. Comer ◽

Charles Bergeron ◽

Lester F. Lowe

Keyword(s):

Electron Microscopy ◽

Transmission Electron Microscopy ◽

Electron Beam ◽

High Energy ◽

Transmission Electron ◽

Kikuchi Lines ◽

High Energy Ions ◽

Diffraction Patterns ◽

Dauphiné Twinning ◽

Beam Damage

Using a Van De Graaff Accelerator thinned specimens were subjected to bombardment by 3 MeV N+ ions to fluences ranging from 4x1013 to 2x1016 ions/cm2. They were then examined by transmission electron microscopy and reflection electron diffraction using a 100 KV electron beam.At the lowest fluence of 4x1013 ions/cm2 diffraction patterns of the specimens contained Kikuchi lines which appeared somewhat broader and more diffuse than those obtained on unirradiated material. No damage could be detected by transmission electron microscopy in unannealed specimens. However, Dauphiné twinning was particularly pronounced after heating to 665°C for one hour and cooling to room temperature. The twins, seen in Fig. 1, were often less than .25 μm in size, smaller than those formed in unirradiated material and present in greater number. The results are in agreement with earlier observations on the effect of electron beam damage on Dauphiné twinning.

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Magnesium and sulfur in mast cell and basophil granules of lower vertebrates in relation with histamine

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100132613 ◽

1992 ◽

Vol 50 (2) ◽

pp. 1596-1597

Author(s):

Kenichi Takaya

Keyword(s):

Electron Microscopy ◽

Transmission Electron Microscopy ◽

Mast Cell ◽

Mast Cells ◽

Tree Frog ◽

X Ray ◽

Transmission Electron ◽

Scanning Transmission ◽

Fresh Frozen ◽

Ultrathin Sections

Mast cell and basophil granules of the vertebrate contain heparin or related sulfated proteoglycans. Histamine is also present in mammalian mast cells and basophils. However, no histamine is detected in mast cell granules of the amphibian or fish, while it is shown in those of reptiles and birds A quantitative x-ray microanalysis of mast cell granules of fresh frozen dried ultrathin sections of the tongue of Wistar rats and tree frogs disclosed high concentrations of sulfur in rat mast cell granules and those of sulfur and magnesium in the tree frog granules. Their concentrations in tree frog mast cell granules were closely correlated (r=0.94).Fresh frozen dried ultrathin sections and fresh air-dried prints of the tree frog tongue and spleen and young red-eared turtle (ca. 6 g) spleen and heart blood were examined by a quantitative energy-dispersive x-ray microanalysis (X-650, Kevex-7000) for the element constituents of the granules of mast cells and basophils. The specimens were observed by transmission electron microscopy (TEM) (80-200 kV) and followed by scanning transmission electron microscopy (STEM) under an analytical electron microscope (X-650) at an acceleration voltage of 40 kV and a specimen current of 0.2 nA. A spot analysis was performed in a STEM mode for 100 s at a specimen current of 2 nA on the mast cell and basophil granules and other areas of the cells. Histamine was examined by the o-phthalaldehyde method.

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The use of an energy-filtering electron microscope to reduce chromatic aberration in images of thick biological specimens

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100142116 ◽

1986 ◽

Vol 44 ◽

pp. 88-91

Author(s):

L. D. Peachey ◽

J. P. Heath ◽

G. Lamprecht

Keyword(s):

Electron Microscopy ◽

Transmission Electron Microscopy ◽

Electron Beam ◽

Cross Section ◽

Electron Scattering ◽

Chromatic Aberration ◽

Image Resolution ◽

Incident Electron Energy ◽

Energy Filtering ◽

Transmission Electron

Biological specimens of cells and tissues generally are considerably thicker than ideal for high resolution transmission electron microscopy. Actual image resolution achieved is limited by chromatic aberration in the image forming electron lenses combined with significant energy loss in the electron beam due to inelastic scattering in the specimen. Increased accelerating voltages (HVEM, IVEM) have been used to reduce the adverse effects of chromatic aberration by decreasing the electron scattering cross-section of the elements in the specimen and by increasing the incident electron energy.

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