Approximations in the Dynamical Theory of Electron Diffract

1978 ◽  
Vol 36 (3) ◽  
pp. 218-229
Author(s):  
S.S. Sheinin
Keyword(s):  
Electron Microscopy ◽  
Electron Diffraction ◽  
Quantitative Information ◽  
Dynamical Theory ◽  
Image Contrast ◽  
Academic Interest ◽  
Crystalline Materials ◽  
The Past ◽  
The Subject ◽  
Electron Microscopist

The last twenty years have seen a remarkable development in electron microscopy of crystalline materials. This development has, quite naturally, been stimulated by the continuing quest of the electron microscopist for more information about the structure of his specimens and it is not surprising, therefore, that the more qualitative observations of the past have been supplemented by techniques which permit higher resolution, more quantitative information to be extracted. The fundamental role played by the dynamical theory of electron diffraction in this development requires no emphasis on my part. As is true with all physical theories, however, the dynamical theory itself has been the subject of continued development and investigation. This work is not simply of academic interest but has been an important, and in fact necessary, concomitant of the developments in the electron microscopy of crystals referred to above. The reason for this can be easily understood when it is recalled that the form of the dynamical theory used in image contrast calculations has many approximations embodied in it.

The Diagnosis of Viral Disease by Electron Microscopy

1982 ◽  
Vol 40 ◽  
pp. 270-273
Author(s):  
William B. McCombs ◽  
Cameron E. McCoy
Keyword(s):  
Electron Microscopy ◽  
Hospital Stay ◽  
Viral Infections ◽  
Medical Profession ◽  
Bacterial Pathogens ◽  
Viral Disease ◽  
Viral Pathogens ◽  
Academic Interest ◽  
The Past

Recent years have brought a reversal in the attitude of the medical profession toward the diagnosis of viral infections. Identification of bacterial pathogens was formerly thought to be faster than identification of viral pathogens. Viral identification was dismissed as being of academic interest or for confirming the presence of an epidemic, because the patient would recover or die before this could be accomplished. In the past 10 years, the goal of virologists has been to present the clinician with a viral identification in a matter of hours. This fast diagnosis has the potential for shortening the patient's hospital stay and preventing the administering of toxic and/or expensive antibiotics of no benefit to the patient.

John Maxwell Cowley 1923 - 2004

2006 ◽  
Vol 17 (2) ◽  
pp. 227
Author(s):  
A. F. Moodie ◽  
J. C. H. Spence
Keyword(s):  
Electron Microscopy ◽  
Electron Diffraction ◽  
Electron Scattering ◽  
Scanning Transmission Electron Microscopy ◽  
High Resolution Electron Microscopy ◽  
Dynamical Theory ◽  
X Rays ◽  
Transmission Electron ◽  
Resolution Electron ◽  
Scanning Transmission

John Cowley contributed significantly to all of the fields that relate to electron diffraction and electron microscopy, and helped to found not a few of them. His name is associated in particular with n-beam dynamical theory, high-resolution electron microscopy, scanning transmission electron microscopy, instrumental design, and the application of the techniques of electron scattering to structure analysis. His experimental work was not, however, confined to the scattering of electrons: to take but one instance, his seminal work on the theory of short-range order was stimulated initially by his experiments using X-rays, and it was only later that he extended the technique to include electron diffraction. Finally, to all those who practise the techniques of scattering electrons, X-rays, or neutrons in the study of solids, liquids or gases, his book Diffraction Physics remains not only eminently readable but authoritative.

Dynamical Aspects of Electron Diffraction

1977 ◽  
Vol 35 ◽  
pp. 26-29
Author(s):  
C. J. Humphreys
Keyword(s):  
Electron Microscope ◽  
Electron Diffraction ◽  
Materials Science ◽  
50Th Anniversary ◽  
Current Work ◽  
Crystalline Materials ◽  
Second Look ◽  
Gradual Development ◽  
The Subject

In this year of the 50th Anniversary of Electron Diffraction it seems particularly appropriate that a significant amount of the current work in dynamical electron diffraction is devoted to taking a second look at some of the more fundamental aspects of the subject. In 1927 electron diffraction was demonstrated experimentally and in 1928 the first formulation of the theory was given. The next thirty years saw the gradual development of the electron microscope and of diffraction theories applied to perfect crystals (for example, 4 to 7). In the last twenty years an enormous expansion of the theory and the practice of electron diffraction and microscopy has occurred in materials science, largely stemming from the discovery that dislocations could be imaged in the electron microscope (8,9). Most of this work has been concerned with studying the distribution and the nature of defects in crystalline materials.

ORDERING AND ORDERING TRANSITIONS IN CONFINED LIQUID CRYSTALS

1993 ◽  
Vol 07 (28) ◽  
pp. 1785-1808 ◽  
Author(s):  
G.P. CRAWFORD ◽  
J.W. DOANE
Keyword(s):  
Liquid Crystals ◽  
Liquid Crystalline ◽  
Finite Size ◽  
Finite Size Effects ◽  
Crystalline Materials ◽  
The Past ◽  
Ordering Transitions ◽  
The Subject ◽  
Liquid Crystalline Materials ◽  
Confined Liquid Crystals

A resurgence of interest in confined liquid crystals has taken place over the past few years because of the availability of well-defined and random-type matrices that can be used to constrain liquid crystalline materials to submicrometer spaces. The main driving force behind many of the studies on confined liquid crystals is their relevance to electrically controllable light-scattering devices. Apart from their electrooptic importance, confined liquid crystals introduce many fascinating surface and finite-size effects which are the subject of this review.

Canadian Mortgages Regarded as a Field for the Investment of the Funds of British Life Assurance Companies, with Some General Notes on Canadian Indebtedness

1915 ◽  
Vol 49 (1) ◽  
pp. 33-89
Author(s):  
Arthur Digby Besant
Keyword(s):  
Academic Interest ◽  
Distant Future ◽  
The Past ◽  
Life Assurance ◽  
Financial Conditions ◽  
The Subject ◽  
The Moment ◽  
Past Summer

In the course of the past summer I visited Canada, partly with a view to investigating upon the spot the opportunities which the Dominion might afford for mortgage investments, and partly in order to gain, at first hand, knowledge of the general financial conditions of the country.The subject is one of great importance, and although the outbreak of war may have rendered all questions of new investments of purely academic interest for the moment, yet I hope that the following notes will be of interest to the Institute, and may be turned to some practical use in a not distant future.

Electron Diffraction and TEM Studies of Y1Ba2Cu3O7−x

1987 ◽  
Vol 99 ◽  
Author(s):  
R. Pérez ◽  
J. G. Pérez-Ramírez ◽  
M. Avalos ◽  
J. Reyes ◽  
L. Martinez ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Electron Diffraction ◽  
Optical Microscopy ◽  
Image Contrast ◽  
Zone Axis ◽  
Twin Boundaries ◽  
Boundary Area ◽  
Transmission Electron ◽  
The Common

ABSTRACTOptical microscopy and transmission electron microscopy show that most of the crystalline grains in Y1Ba2Cu3O7−x superconducting specimens have large number of twins. These bands of different image contrast have similar microdiffraction patterns. However the diffraction conditions are different and correspond to different tilts of the crystalline grains along one of the zone axis. HREM images of these twin boundaries indicate that the boundary area has appreciable dimensions and both matrix and twin crystals show the existence of a superstructure with double of the common periodicity obtained under [001] diffraction conditions.

Electron Diffraction by an Optical Grating

1969 ◽  
Vol 27 ◽  
pp. 154-155
Author(s):  
G. H. Curtis ◽  
R. P. Ferrier
Keyword(s):  
Electron Microscopy ◽  
Electron Diffraction ◽  
Small Angle ◽  
Diffraction Gratings ◽  
Image Contrast ◽  
Optical Diffraction ◽  
Diffraction Angle ◽  
Optical Grating ◽  
Carbon Replicas

Carbon replicas of optical diffraction gratings can be used, not only for magnification calibration in electron microscopy, but also as angular standards in small-angle electron diffraction. These replicas are usually shadowed with a heavy material to improve image contrast, but we acquired some unshadowed samples (kindly supplied by Mr. R.H. Alderson of AEI Ltd,) for the experiments described below. The gratings are cross-ruled with 2,160 lines per mm to give a spacing of 463 nm and a diffraction angle of about 9 microradians at U=80KV.

Atomic Imaging of the Amorphous State

1981 ◽  
Vol 39 ◽  
pp. 106-109
Author(s):  
J.M. Gibson
Keyword(s):  
High Resolution ◽  
Amorphous Materials ◽  
Amorphous State ◽  
Quantitative Information ◽  
Lattice Image ◽  
Perfect Lattice ◽  
High Resolution Images ◽  
The Subject ◽  
The Difference ◽  
Electron Microscopist

When an electron microscopist takes a high resolution image of an amorphous object, perhaps he has something in common with a pianist who tackles a complex atonal sonata. Both efforts could represent a pinnacle of achievement for the performer and his instrument but the pianist's audience may not immediately recognize the difference if a monkey were to walk over the keys. To stretch the analogy, a perfect lattice image could be equated to a faultless rendition of a Haydn Sonata: aesthetically satisfying but predictable. One conclusion from a decade's work on the subject (see a recent review by Howie) is that high resolution images from amorphous samples are not easily interpreted directly. One can learn more about the atomic arrangement in amorphous materials from such images if one treats them rather as quantitative information about the local scattering properties than pictures.

Intensity distribution of electron diffraction pattern from Ti-14Wt%Mo alloy containing ωphase plate crystal

1990 ◽  
Vol 48 (4) ◽  
pp. 986-987
Author(s):  
Mitsuhiro Awaji ◽  
Hatsujiro Hashimoto ◽  
Eiichi Sukedai ◽  
Fumio Akao
Keyword(s):  
Electron Microscopy ◽  
Electron Microscope ◽  
Electron Diffraction ◽  
Electron Diffraction Pattern ◽  
Dynamical Theory ◽  
Β Phase ◽  
Ω Phase ◽  
Microscope Images ◽  
Phase Crystal ◽  
Diffraction Patterns

The study of ω-phase in various alloys such as Ti-Mo, Ti-Cr, Zr-Nb etc. have been carried out so far by electron diffraction and electron microscopy. However, the shape of ω-phase particles has not been fully clarified yet. This is due to the facts that ω-phase is formed in ω-phase crystal, and rather difficult to obtain isolated crystal particles and also that w-phase is produced only by the displacement of atoms in characteristic directions which makes no contrast in the electron microscope images projected along this directions and hence the crosssectional shape can not be studied. Since the intensity of electron diffraction patterns is very sensitive to the amount of ω-phase existing in β-phase, its thickness dependence has been studied in the present paper by using multi-slice dynamical theory of electron diffraction for the various thickness combination of the ω- and β-phases so that the thickness and location of ω-phase can be seen.

Plan-view microstructures of Co/Ru bilayers

1995 ◽  
Vol 10 (6) ◽  
pp. 1539-1545 ◽  
Author(s):  
G.Z. Pan ◽  
A. Michel ◽  
V. Pierron-Bohnes ◽  
P. Vennéguès ◽  
M.C. Cadeville
Keyword(s):  
Electron Microscopy ◽  
High Resolution ◽  
Electron Diffraction ◽  
High Resolution Electron Microscopy ◽  
Image Contrast ◽  
Misfit Dislocations ◽  
Double Diffraction ◽  
Plan View ◽  
Resolution Electron ◽  
Diffraction Patterns

Plan-view microstructures of two Co/Ru bilayers with a composition of [Co12ÅRu45Å]2 and [Co40ÅRu35Å]2 have been studied by conventional and high resolution electron microscopy. Large differences in electron diffraction and image contrast between the two bilayers were observed, which are recognized as the microstructural variations during the relaxation of large coherent planar strains when the Co layers wet coherently or semicoherently the Ru layers. For the [Co12ÅRu45Å]2 bilayer, the Co layers are unrelaxed from the Ru layers; only one set of electron diffraction patterns was observed, and the image consists of three types of contrasts which are closely related with either the generation and movement of misfit dislocations or large coherent strains. For the [Co40ÅRu35Å]2 bilayer, the Co layers are relaxed basically from the Ru layers; two sets of electron diffraction patterns with double diffraction spots were observed, and the image consists of small irregular areas with moiré fringe dots.

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