Improving the interpretation of high-resolution images

1991 ◽  
Vol 49 ◽  
pp. 654-655
Author(s):  
D. Van Dyck
Keyword(s):  
A Priori ◽  
Quantitative Interpretation ◽  
Future Prospects ◽  
X Ray Diffraction ◽  
X Ray ◽  
Recent Developments ◽  
High Resolution Images ◽  
The Individual ◽  
Technological Improvements ◽  
Structural Research

We are living in a very exciting period for structural research using HREM. Indeed, the possibility to “see” the individual atoms of which matter is constituted seems within reach. Recent technological improvements allow to obtain a resolution of about 0.1 nm. However, the potential power of the technique is still severely limited by the problem of quantitative interpretation of the images. For instance, the use of computer simulation images requires much a priori knowledge which makes HREM very dependent on other techniques. The situation can be compared with the early days of X-ray diffraction. Recent developments make it possible to retrieve the object structure directly from the electron micrographs. We will discuss future prospects in this direction.

scholarly journals Electronic Excitations and Radiation Damage in Macromolecular Crystallography

Crystals ◽  
2018 ◽  
Vol 8 (7) ◽  
pp. 273 ◽  
Author(s):  
José Brandão-Neto ◽  
Leonardo Bernasconi
Keyword(s):  
Chemical Information ◽  
X Rays ◽  
Electronic Excitations ◽  
Macromolecular Crystallography ◽  
X Ray Diffraction ◽  
X Ray ◽  
Atomic Structures ◽  
Successful Approach ◽  
Structural Research

Macromolecular crystallography at cryogenic temperatures has so far provided the majority of the experimental evidence that underpins the determination of the atomic structures of proteins and other biomolecular assemblies by means of single crystal X-ray diffraction experiments. One of the core limitations of the current methods is that crystal samples degrade as they are subject to X-rays, and two broad groups of effects are observed: global and specific damage. While the currently successful approach is to operate outside the range where global damage is observed, specific damage is not well understood and may lead to poor interpretation of the chemistry and biology of the system under study. In this work, we present a phenomenological model in which specific damage is understood as the result of a single process, the steady excitation of crystal electrons caused by X-ray absorption, which acts as a trigger for the bulk effects that manifest themselves in the form of global damage and obscure the interpretation of chemical information from XFEL and synchrotron structural research.

Strain Measurement by X-ray Diffraction Methods

1949 ◽  
Vol 1 (3) ◽  
pp. 211-224
Author(s):  
G. B. Greenough
Keyword(s):  
Strain Measurement ◽  
Plastic Anisotropy ◽  
Stress And Strain ◽  
Routine Method ◽  
X Ray Diffraction ◽  
Strain Measurements ◽  
X Ray ◽  
The Past ◽  
Polycrystalline Metals ◽  
The Individual

SummaryMany papers have been written on the measurement of strain by X-ray diffraction methods and on the interpretation of these strains in terms of stresses. Whereas, during the past few years, the experimental methods of determining the strains have. remained largely unchanged, research has shown that the older techniques for calculating stresses from strains are not always valid.In this paper an attempt is made to describe some of the principles of strain measurement by X-ray diffraction methods to those who are unfamiliar with the methods. The types of stress and strain systems which may exist in polycrystalline metals are then considered, particular attention being paid to the effect of the elastic and plastic anisotropy of the individual crystals. Some indication is given as to how the earlier methods of interpreting X-ray strain measurements should be modified, but no rigid routine method is proposed for use in a general case.

scholarly journals Electronic Excitations and Radiation Damage in Macromolecular Crystallography

2018 ◽  
Author(s):  
José Brandão-Neto ◽  
Leonardo Bernasconi
Keyword(s):  
Chemical Information ◽  
X Rays ◽  
Electronic Excitations ◽  
Macromolecular Crystallography ◽  
X Ray Diffraction ◽  
X Ray ◽  
Atomic Structures ◽  
Successful Approach ◽  
Structural Research

Macromolecular crystallography at cryogenic temperatures has so far provided the majority of the experimental evidence that underpins the determination of the atomic structures of proteins and other biomolecular assemblies by means of single crystal X-ray diffraction experiments. One of the core limitations of the current methods is that crystal samples degrade as they are subject to X-rays, and two broad groups of effects are observed: global and specific damage. While the currently successful approach is to operate outside the range where global damage is observed, specific damage is not well understood and may lead to poor interpretation of the chemistry and biology of the system under study. In this work, we present a phenomenological model in which specific damage is understood as the result of a single process, the steady excitation of crystal electrons caused by X-ray absorption, which acts as a trigger for the bulk effects that manifest themselves in the form of global damage and obscure the interpretation of chemical information from XFEL and synchrotron structural research.

Watching Photochemistry Happen: Recent Developments in Dynamic Single-Crystal X-Ray Diffraction Studies

2020 ◽  
Author(s):  
Lauren E. Hatcher ◽  
Mark R. Warren ◽  
Anuradha R. Pallipurath ◽  
Lucy K. Saunders ◽  
Jonathan M. Skelton
Keyword(s):  
Single Crystal ◽  
X Ray Diffraction ◽  
X Ray ◽  
Recent Developments

scholarly journals X-ray diffraction method application to assess the energy losses on explosive-rock contact under various blasting

2020 ◽  
Vol 168 ◽  
pp. 00051
Author(s):  
Ihor Kratkovskyi ◽  
Ernest Yefremov ◽  
Kostyantyn Ishchenko ◽  
Sergo Khomeriki
Keyword(s):  
Rock Fracture ◽  
Diffraction Method ◽  
Optical Systems ◽  
Energy Losses ◽  
X Ray Diffraction ◽  
X Ray ◽  
Wave Nature ◽  
Diffraction Patterns ◽  
The Individual ◽  
Granulometric Characteristics

The dissipative energy losses of the explosion on the explosive-rock contact are usually evaluated with comparative analysis of the particle size distribution of finely dispersed fractions (0-100 microns). The more tiny particles contained in the destruction products, the higher there is a level of energy loss during the explosion. Fine dust granulometric characteristics are determined by processing the mass measurements data of the individual smallest particles sizes when decoding microphotographs obtained by a microscope. However due to the chromatic aberrations due the wave nature of light and the optical systems imperfection, it is not possible to reliably estimate the mass and granulometric characteristics particles of micron size. X-ray diffraction method for studying ultrafine rock fracture products makes it possible to estimate the dissipative energy losses on explosive-rock contact based on the reflected X-ray beam total intensity in diffractograms. In order to establish the effectiveness of methods for reducing the level of dissipative energy losses of an explosion, X-ray diffraction patterns of finely dispersed fracture products of rock samples under various conditions of dynamic loading are analyzed (using different charge designs, attenuating the rocks by the action of a surfactant, and the force action of a different gradient stress field).

scholarly journals Interfacial Structure of Lattice Mismatched bcc(110)/bcc(110) Transition Metal Superlattices

1993 ◽  
Vol 307 ◽  
Author(s):  
Eric E. Fullerton ◽  
S. M. Mini ◽  
A. S. Bommannavar ◽  
C. H. Sowers ◽  
S. N. Ehrlich ◽  
...  
Keyword(s):  
Lattice Strain ◽  
Structural Model ◽  
Interfacial Structure ◽  
X Ray Diffraction ◽  
X Ray ◽  
Lattice Strains ◽  
The Individual ◽  
Structural Characterizations ◽  
Modulation Wavelength ◽  
Coherent Interfaces

ABSTRACTWe present structural characterizations of a series of sputtered Fe/Nb and V/Nb superlattices by high-angle x-ray diffraction. Diffraction scans were performed with the scattering vector at various angles (χ) with respect to the layers. χ=0° diffraction spectra (normal to the layers) were fitted to a general structural model to determine the (110) lattice strains, interfacial disorder and interdiffusion. χ>0° spectra probe the lattice strain of the individual layers and the in-plane interfacial coherence. Both systems form incoherent interfaces above a critical modulation wavelength (ΛC). At ΛC, the Fe/Nb system undergoes a crystalline-to-amorphous transition while the V/Nb forms in-plane coherent interfaces.

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