The Imaging of Crystal Structures and Crystal Defects

The problem of "understandinq" electron microscope imaqes becomes more acute as the resolution is improved. The naive interpretation of an imaqe as representinq the projection of an atom density becomes less and less appropriate. We are increasinqly forced to face the complexities of coherent imaqinq of what are essentially phase objects. Most electron microscopists are now aware that, for very thin weakly scatterinq objects such as thin unstained bioloqical specimens, hiqh resolution imaqes are best obtained near the optimum defocus, as prescribed by Scherzer, where the phase contrast imaqe qives a qood representation of the projected potential, apart from a lack of information on the lower spatial frequencies. But phase contrast imaqinq is never simple except in idealized limitinq cases.

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Experimental Determination of the Imaging Properties of a 200 kV Electron Microscope

Australian Journal of Physics ◽

10.1071/ph860071 ◽

1986 ◽

Vol 39 (1) ◽

pp. 71 ◽

Cited By ~ 8

Author(s):

SR Glanvill ◽

AF Moodie ◽

HJ Whitfield ◽

IJ Wilson

Keyword(s):

Electron Microscope ◽

Phase Contrast ◽

Spherical Aberration ◽

Minimum Phase ◽

Amorphous Films ◽

Great Precision ◽

Spatial Frequencies ◽

Imaging Properties ◽

Microscope Stage

Optical transforms from a through focal series of images of amorphous films of Ge were used to measure the spatial frequencies of maximum and minimum phase contrast of a specific 200 kV lEOL electron microscope. This information was used to determine precise values for the spherical aberration coefficient and defect of focus. Under the appropriate conditions of lens excitation the spherical aberration coefficient was found to be as low as 0�94 mm. Other image defects revealed with great precision were associated with astigmatism, beam divergence and specimen drift in the microscope stage. Quantitative examples illustrating these effects are discussed.

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Observation of biological macromolecules using various electron microscopic methods

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100081711 ◽

1978 ◽

Vol 36 (2) ◽

pp. 170-171

Author(s):

Mitsuo Ohtsuki ◽

Michael Sogard

Keyword(s):

Electron Microscope ◽

Phase Contrast ◽

Image Interpretation ◽

Density Lipoprotein ◽

Biological Macromolecules ◽

Contrast Effects ◽

Biological Structure ◽

Electron Microscopic ◽

Structural Investigations ◽

Staining Techniques

Structural investigations of biological macromolecules commonly employ CTEM with negative staining techniques. Difficulties in valid image interpretation arise, however, due to problems such as variability in thickness and degree of penetration of the staining agent, noise from the supporting film, and artifacts from defocus phase contrast effects. In order to determine the effects of these variables on biological structure, as seen by the electron microscope, negative stained macromolecules of high density lipoprotein-3 (HDL3) from human serum were analyzed with both CTEM and STEM, and results were then compared with CTEM micrographs of freeze-etched HDL3. In addition, we altered the structure of this molecule by digesting away its phospholipid component with phospholipase A2 and look for consistent changes in structure.

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Defects in Crystals

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100100962 ◽

1968 ◽

Vol 26 ◽

pp. 244-245

Author(s):

Kenneth R. Lawless

Keyword(s):

Electron Microscope ◽

Point Defects ◽

Surface Defects ◽

Chemical Properties ◽

Material Point ◽

Crystal Defects ◽

Defects In Crystals ◽

Irradiation Effects ◽

Normal Lattice ◽

Line Defects

One of the most important applications of the electron microscope in recent years has been to the observation of defects in crystals. Replica techniques have been widely utilized for many years for the observation of surface defects, but more recently the most striking use of the electron microscope has been for the direct observation of internal defects in crystals, utilizing the transmission of electrons through thin samples.Defects in crystals may be classified basically as point defects, line defects, and planar defects, all of which play an important role in determining the physical or chemical properties of a material. Point defects are of two types, either vacancies where individual atoms are missing from lattice sites, or interstitials where an atom is situated in between normal lattice sites. The so-called point defects most commonly observed are actually aggregates of either vacancies or interstitials. Details of crystal defects of this type are considered in the special session on “Irradiation Effects in Materials” and will not be considered in detail in this session.

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New challenges to image processing posed by cryo-Electron microscopy of single particles

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100086416 ◽

1991 ◽

Vol 49 ◽

pp. 422-423

Author(s):

Joachim Frank

Keyword(s):

Electron Microscopy ◽

Phase Contrast ◽

Particle Orientation ◽

Single Particles ◽

Contrast Transfer Function ◽

Virtual Absence ◽

Cryo Electron Microscopy ◽

Spatial Frequencies ◽

New Challenges ◽

Particle Images

Compared with images of negatively stained single particle specimens, those obtained by cryo-electron microscopy have the following new features: (a) higher “signal” variability due to a higher variability of particle orientation; (b) reduced signal/noise ratio (S/N); (c) virtual absence of low-spatial-frequency information related to elastic scattering, due to the properties of the phase contrast transfer function (PCTF); and (d) reduced resolution due to the efforts of the microscopist to boost the PCTF at low spatial frequencies, in his attempt to obtain recognizable particle images.

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Sintering Process of Nd:YAG Transparent Ceramic

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.281.475 ◽

2013 ◽

Vol 281 ◽

pp. 475-479

Author(s):

Bo Wang ◽

Quan Xi Cao ◽

Guang Xu ◽

Sen Tian

Keyword(s):

Grain Size ◽

Electron Microscope ◽

Scanning Electron Microscope ◽

Crystal Structures ◽

Heating Rate ◽

Optical Transmittance ◽

Sintering Process ◽

X Ray ◽

Polycrystalline Ceramics ◽

Scanning Electron

1.0at% Nd:YAG polycrystalline ceramics were sintered at 1420°C, 1500°C, 1600°C and 1730°C respectively by different heating rate (1°C/min and 5°C/min). The crystal structures were indexed by X-ray diffractometer (XRD). The microstructure and the grain size of the samples were characterized by scanning electron microscope (SEM). The optical transmittance spectra of the samples were measured using V-570 UV spectrophotometer. The sintering process of Nd:YAG ceramics and the effect of heating rate on the microstructure of samples have been investigated.

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Phase Contrast Aberration Corrected Electron Microscope for Phase Plate Imaging

Microscopy and Microanalysis ◽

10.1017/s1431927610057740 ◽

2010 ◽

Vol 16 (S2) ◽

pp. 534-535 ◽

Cited By ~ 2

Author(s):

E Majorovits ◽

B Barton ◽

G Benner ◽

C Dietl ◽

W Kühlbrandt ◽

...

Keyword(s):

Electron Microscope ◽

Phase Contrast ◽

Phase Plate ◽

Aberration Corrected

Extended abstract of a paper presented at Microscopy and Microanalysis 2010 in Portland, Oregon, USA, August 1 – August 5, 2010.

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THE SUBMICROSCOPIC ORGANIZATION OF AXON MATERIAL ISOLATED FROM MYELIN NERVE FIBERS

Journal of Experimental Medicine ◽

10.1084/jem.98.3.269 ◽

1953 ◽

Vol 98 (3) ◽

pp. 269-276 ◽

Cited By ~ 20

Author(s):

E. De Robertis ◽

C. M. Franchi

Keyword(s):

Electron Microscopy ◽

Electron Microscope ◽

Phase Contrast ◽

Nerve Fibers ◽

Myelinated Nerve ◽

Myelinated Nerve Fibers ◽

Dense Granules ◽

Small Clusters ◽

Membranous Material ◽

The Way

A technique has been developed for the extrusion of axon material from myelinated nerve fibers. This material is then compressed and prepared for observation with the electron microscope. All the stages of preparation and purification of the axon material can be checked microscopically and in the present paper they are illustrated with phase contrast photomicrographs. Observation with the electron microscope of the compressed axons showed the presence of the following components: granules, fibrils, and a membranous material. Only the larger granules could be seen with the ordinary microscope. A considerable number of dense granules were observed. Of these the largest resemble typical mitochondria of 250 mµ by 900 mµ. In addition rows or small clusters of dense granules ranging in diameter from 250 to 90 mµ were present. In several specimens fragments of a membrane 120 to 140 A thick and intimately connected with the axon were found. The entire axon appeared to be constituted of a large bundle of parallel tightly packed fibrils among which the granules are interspersed. The fibrils are of indefinite length and generally smooth. They are rather labile structures, less resistant in the rat than in the toad nerve. They varied between 100 and 400 A in diameter and in some cases disintegrated into very fine filaments (less than 100 A thick). The significance is discussed of the submicroscopic structures revealed by electron microscopy of the material prepared in the way described.

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On Bridging the Gap in Cytology Between the Light and Electron Microscopes by Some Combined Observations on Snail Neurones

Journal of Cell Science ◽

10.1242/jcs.s3-105.70.139 ◽

1964 ◽

Vol s3-105 (70) ◽

pp. 139-162

Author(s):

S. M. McGEE-RUSSEL

Keyword(s):

Electron Microscope ◽

Phase Contrast ◽

Nile Blue ◽

Ultra Violet ◽

Object A ◽

Snail Neurones ◽

Cross Correlations ◽

Electron Microscopes ◽

Microscopy Data ◽

Dark Ground

Discrepancies between observations made with the light microscope only, and with the electron microscope only, can be clarified by using both instruments to study exactly the same section of the same object. A simple technique for doing this is outlined. Direct, phase-contrast, ‘anoptral’ phase-contrast, dark-ground, interference, and ultra-violet microscopy can all be used. When applied to snail neurones this technique of combined observations reveals intracellular organelles which have not previously been differentiated. These organelles are positively identified by criteria appropriate to each instrument. By combined observations it is possible to see the ‘Golgi apparatus’ in preparations stained only with Nile blue, by direct microscopy. Data obtained by combined observations are considered in relation to the previous literature. Unequivocal cross-correlations between the light and the electron microscope go a long way towards explaining past difficulties.

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