Determination of Residual Stress from Two-Dimensional Diffraction Patterns

1984 ◽  
pp. 47-57 ◽  
Author(s):  
Giancarlo M. Borgonovi
Keyword(s):  
Residual Stress ◽  
Two Dimensional ◽  
Diffraction Patterns

Electron Crystallographic Determination of the Structure of Bacteriorhodopsin

1990 ◽  
Vol 48 (1) ◽  
pp. 90-91
Author(s):  
R. Henderson ◽  
J.M. Baldwin ◽  
T.A. Ceska ◽  
E. Beckman ◽  
F. Zemlin ◽  
...  
Keyword(s):  
High Resolution ◽  
Proton Pump ◽  
Three Dimensional ◽  
Atomic Resolution ◽  
Two Dimensional ◽  
New Methods ◽  
Density Map ◽  
Diffraction Patterns

The light driven proton pump bacteriorhodopsin (bR) occurs naturally as two-dimensional crystals. A three-dimensional density map of the structure, at near atomic resolution, has been obtained by studying the crystals using electron cryo-microscopy to obtain diffraction patterns and high resolution micrographs (1).New methods have been developed for analysing micrographs from tilted specimens, incorporating the methods previously developed for untilted specimens that enable large areas to be analysed and corrected for distortions. Data from 72 images, from both tilted and untilted specimens, have been analysed to produce the phases of 2700 independent Fourier components of the structure. The amplitudes of these components have been accurately measured from 150 diffraction patterns. Together, these data represent about half of the full three-dimensional transform to 3.5 Å. The distribution of the data which is included in the map is shown in fig. 1. For specimen tilts up to around 20° the data is essentially complete. For higher tilts the data is more sparsely sampled, and is at present about half complete.

Structure of Membrane Proteins Revealed by Electron Crystallography

2000 ◽  
Vol 6 (S2) ◽  
pp. 234-235
Author(s):  
K. Mitsuoka
Keyword(s):  
Membrane Proteins ◽  
Structure Determination ◽  
Two Dimensional ◽  
Asymmetric Unit ◽  
Electron Crystallography ◽  
Aquaporin 1 ◽  
Diffraction Patterns ◽  
2D Crystals

Because membrane proteins are localized in a continuous lipid bilayer in the native environment, the situation of membrane proteins in the two-dimensional (2D) crystals is quite similar to the environment in vivo. Thus, electron crystallography using 2D crystals is one of the suitable techniques for structure determination of membrane proteins at atomic or near-atomic resolution. Here we describe the structures of the two membrane proteins, bacteriorhodopsin and aquaporin-1, which were solved by electron crystallography at 2.5 and 4.0 Å resolution, respectively.Bacteriorhodopsin (bR) is a light-driven proton pump found in Halobacterium salinarium. The atomic model of the protein was first proposed by electron crystallography and we improved the resolution of the structure determination up to 3.0 Å by collecting 366 electron diffraction patterns and 129 images. The resulted map showed not only a bR molecule but also eight surrounding lipids in the asymmetric unit.

Automatic determination of diffuse-peak positions and the centre of a diffraction pattern

1999 ◽  
Vol 32 (2) ◽  
pp. 332-335 ◽  
Author(s):  
S. J. Wilkinson ◽  
D. W. L. Hukins
Keyword(s):  
Annulus Fibrosus ◽  
Gaussian Function ◽  
Two Dimensional ◽  
X Ray Diffraction ◽  
X Ray ◽  
Oriented Molecules ◽  
Beam Stop ◽  
Diffraction Patterns ◽  
Good Agreement

Correlation with a two-dimensional Gaussian function was used to locate the positions of diffuse peaks in X-ray diffraction patterns. The centre of a pattern was defined as the centroid of the image of the undeflected beam, found by convolution with a two-dimensional Gaussian function. These methods were implemented using the IDL programing language. They were tested on diffraction patterns from systems containing oriented molecules of the protein collagen: collagen tape, elastoidin spicules and annulus fibrosus of intervertebral disc. Specimens were dusted with quartz to calibrate the diffraction patterns. These patterns were recorded on film, using a semi-transparent beam stop to obtain an image of the undeflected beam, and digitized at a resolution of 105 µm. Intermolecular spacings, calculated from the distance between a peak and the centre of a pattern, were in good agreement with those determined previously.

Neutron Residual Stress Measurements on Rail Sections for Different Production Conditions

2004 ◽  
Author(s):  
Vladimir Luzin ◽  
Jeffrey E. Gordon ◽  
Thomas Gnaupel-Herold ◽  
Henry J. Prask
Keyword(s):  
Residual Stress ◽  
Stress State ◽  
Residual Stresses ◽  
Two Dimensional ◽  
Strain Measurements ◽  
Stress Measurements ◽  
Triaxial Stresses ◽  
The Difference ◽  
Production Conditions

Rail sectioning with subsequent neutron diffraction experiments has been used to assess residual stresses in the rails. In this study we present the results of neutron stress measurements performed at the NIST Center for Neutron Research (NCNR) on rail sections from rails that were produced under various conditions. Specifically, these are air-cooled, air-cooled and roller-straightened, head-hardened and head-hardened and roller-straightened. More significantly, a head-hardened and roller-straightened rail was also studied after service to elucidate evolution of the service-induced residual stresses. In the latter case both a transverse-cut slice and the central region of a 0.53 m long piece were studied. Measurements on this piece are the first in which triaxial stresses have been determined for an intact rail. Neutron strain measurements with 3×3×3 mm3 spatial resolution were successfully employed for transversally cut slices to verify the difference in the stress state depending on the production process. Although examination of slices allows determination of only two-dimensional stresses in the plane of the slice, additional measurements on obliquely-cut slices, which were also carried out, and utilization of FEM gives the possibility of reconstructing the full triaxial stress distribution. Together, these approaches provide a better understanding of rail fabrication and the possibility of improving the durability and safety of rails in the future.

scholarly journals Determination of Local Strains in a Neighborhood of Cracks in a Welded Seam of Ni-Cr-Fe According to the Power Fourier Spectrum of Kikuchi Patterns

2018 ◽  
Vol 19 (4) ◽  
pp. 307-312 ◽  
Author(s):  
M.D. Borcha ◽  
M.S. Solodkyi ◽  
S.V. Balovsyak ◽  
I.M. Fodchuk ◽  
A.R. Kuzmin ◽  
...  
Keyword(s):  
Fourier Transform ◽  
Gaussian Noise ◽  
Fourier Spectrum ◽  
Electron Backscatter Diffraction ◽  
Two Dimensional ◽  
Electron Backscatter ◽  
Diffraction Patterns ◽  
Welded Seam ◽  
Backscatter Diffraction

A discrete two-dimensional Fourier transform and the power Fourier spectrum are used for determination of average strains near cracks in a welded seam of Ni-Cr-Fe alloy. The alignment of Kikuchi images with the help of genetic algorithms and subtraction of white Gaussian noise made it possible to more fully take into account the influence of instrumental factors on the formation of electron backscatter diffraction patterns.

Inelastic Electron Scattering from Valence Electrons in Aluminum

1976 ◽  
Vol 34 ◽  
pp. 462-463
Author(s):  
P. E. Batson ◽  
C. H. Chen ◽  
J. Silcox
Keyword(s):  
Electron Scattering ◽  
Single Scattering ◽  
Three Dimensions ◽  
Inelastic Electron ◽  
Weak Beam ◽  
Scattering Spectrum ◽  
Valence Electrons ◽  
Diffraction Patterns ◽  
Electronic Scattering

We wish to report in this paper measurements of the inelastic scattering component due to the collective excitations (plasmons) and single particlehole excitations of the valence electrons in Al. Such scattering contributes to the diffuse electronic scattering seen in electron diffraction patterns and has recently been considered of significance in weak-beam images (see Gai and Howie) . A major problem in the determination of such scattering is the proper correction for multiple scattering. We outline here a procedure which we believe suitably deals with such problems and report the observed single scattering spectrum.In principle, one can use the procedure of Misell and Jones—suitably generalized to three dimensions (qx, qy and #x2206;E)--to derive single scattering profiles. However, such a computation becomes prohibitively large if applied in a brute force fashion since the quasi-elastic scattering (and associated multiple electronic scattering) extends to much larger angles than the multiple electronic scattering on its own.

STEM and ELS Observation of Early Oxide Formation on the Surface of Cr Thin Films

1980 ◽  
Vol 38 ◽  
pp. 412-413
Author(s):  
Fumio Watari ◽  
J. M. Cowley
Keyword(s):  
Thin Films ◽  
Optical System ◽  
Room Temperature ◽  
Oxide Formation ◽  
Initial Nucleation ◽  
Diffraction Patterns ◽  
Relationship Of ◽  
Multiple Twinning ◽  
Moderately High Temperature

STEM coupled with the optical system was used for the investigation of the early oxidation on the surface of Cr. Cr thin films (30 – 1000Å) were prepared by evaporation onto the polished or air-cleaved NaCl substrates at room temperature and 45°C in a vacuum of 10−6 Torr with an evaporation speed 0.3Å/sec. Rather thick specimens (200 – 1000Å) with various preferred orientations were used for the investigation of the oxidation at moderately high temperature (600 − 1100°C). Selected area diffraction patterns in these specimens are usually very much complicated by the existence of the different kinds of oxides and their multiple twinning. The determination of the epitaxial orientation relationship of the oxides formed on the Cr surface was made possible by intensive use of the optical system and microdiffraction techniques. Prior to the formation of the known rhombohedral Cr2O3, a thin spinel oxide, probably analogous to γ -Al203 or γ -Fe203, was formed. Fig. 1a shows the distinct epitaxial growth of the spinel (001) as well as the rhombohedral (125) on the well-oriented Cr(001) surface. In the case of the Cr specimen with the (001) preferred orientation (Fig. 1b), the rings explainable by spinel structure appeared as well as the well defined epitaxial spots of the spinel (001). The microdif fraction from 20A areas (Fig. 2a) clearly shows the same pattern as Fig. Ia with the weaker oxide spots among the more intense Cr spots, indicating that the thickness of the oxide is much less than that of Cr. The rhombohedral Cr2O3 was nucleated preferably at the Cr(011) sites provided by the polycrystalline nature of the present specimens with the relation Cr2O3 (001)//Cr(011), and by further oxidation it grew into full coverage of the rest of the Cr surface with the orientation determined by the initial nucleation.

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