Determination of the Burgers vector of a dislocation from equal-thickness fringes observed with a plane wave of X-rays

IntroductionA simple and accurate technique to determine the Burgers vector of a dislocation has become feasible with the advent of HVEM. The conventional image vanishing technique(1) using Bragg conditions with the diffraction vector perpendicular to the Burgers vector suffers from various drawbacks; The dislocation image appears even when the g.b = 0 criterion is satisfied, if the edge component of the dislocation is large. On the other hand, the image disappears for certain high order diffractions even when g.b ≠ 0. Furthermore, the determination of the magnitude of the Burgers vector is not easy with the criterion. Recent image simulation technique is free from the ambiguities but require too many parameters for the computation. The weak-beam “fringe counting” technique investigated in the present study is immune from the problems. Even the magnitude of the Burgers vector is determined from the number of the terminating thickness fringes at the exit of the dislocation in wedge shaped foil surfaces.

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Problems in Thin-Film X-ray Quantification

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100135897 ◽

1990 ◽

Vol 48 (2) ◽

pp. 458-459

Author(s):

J N Chapman ◽

W A P Nicholson

Keyword(s):

Thin Film ◽

Specimen Thickness ◽

X Rays ◽

Characteristic Peak ◽

Local Composition ◽

X Ray ◽

Measured Ratio ◽

Path Lengths ◽

Composition Changes

Energy dispersive x-ray microanalysis (EDX) is widely used for the quantitative determination of local composition in thin film specimens. Extraction of quantitative data is usually accomplished by relating the ratio of the number of atoms of two species A and B in the volume excited by the electron beam (nA/nB) to the corresponding ratio of detected characteristic photons (NA/NB) through the use of a k-factor. This leads to an expression of the form nA/nB = kAB NA/NB where kAB is a measure of the relative efficiency with which x-rays are generated and detected from the two species.Errors in thin film x-ray quantification can arise from uncertainties in both NA/NB and kAB. In addition to the inevitable statistical errors, particularly severe problems arise in accurately determining the former if (i) mass loss occurs during spectrum acquisition so that the composition changes as irradiation proceeds, (ii) the characteristic peak from one of the minority components of interest is overlapped by the much larger peak from a majority component, (iii) the measured ratio varies significantly with specimen thickness as a result of electron channeling, or (iv) varying absorption corrections are required due to photons generated at different points having to traverse different path lengths through specimens of irregular and unknown topography on their way to the detector.

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Using the parallel tempering algorithm to overcome complex problems in structure determination of inorganic materials with laboratory X-rays

Zeitschrift für Kristallographie Supplements ◽

10.1524/zksu.2006.suppl_23.9 ◽

2006 ◽

Vol 2006 (suppl_23_2006) ◽

pp. 9-14 ◽

Cited By ~ 3

Author(s):

T. Bataille ◽

N. Mahé ◽

E. Le Fur ◽

J.-Y. Pivan ◽

D. Louer

Keyword(s):

Structure Determination ◽

Inorganic Materials ◽

Parallel Tempering ◽

X Rays ◽

Complex Problems

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Determination of the Vertical Dimension and the Position of the Occlusal Plane in a Removable Prosthesis Using Cephalometric Analysis and Golden Proportion

Applied Sciences ◽

10.3390/app11156948 ◽

2021 ◽

Vol 11 (15) ◽

pp. 6948

Author(s):

Gabriele Cervino ◽

Sergio Sambataro ◽

Chiara Stumpo ◽

Salvatore Bocchieri ◽

Fausto Murabito ◽

...

Keyword(s):

Vertical Dimension ◽

Occlusal Plane ◽

X Rays ◽

Common Procedure ◽

Lower Incisor ◽

Golden Proportion ◽

The Face ◽

Removable Prosthesis ◽

Edentulous Patients

The aim of this study is to demonstrate the use and the effectiveness of cephalometry and golden proportions analysis of the face in planning prosthetic treatments in totally edentulous patients. In order to apply this method, latero-lateral and posterior-anterior X-rays must be performed in addition to the common procedure. Two main concerns for totally edentulous patients are the establishment of the vertical dimension and the new position of the occlusal plane. The divine proportion analysis was carried out by the use of a golden divider. The prosthetic protocol was divided into three steps and a case was selected for better understanding. Referring to the golden relations, if the distance from the chin to the wing of the nose is 1.0, the distance from the nose to eye is 0.618. This proportion is useful and effective in determining the correct prosthetic vertical dimension. The incisal margin of the lower incisor must be positioned between Point A (A) and protuberance menti (Pm) according to the gold ratio 0.618 of the total height A-Pm. Posteriorly the occlusal plane must be placed 2 mm below the divine occlusal plane (traced from the incisal margin of lower incisors to Xi point). A prosthesis made in accordance with cephalometric parameters and divine proportions of the face helps to improve the patient’s aesthetics, function and social personality.

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Determination of the Efficiency of Production of X-Rays

Journal of the Röntgen Society ◽

10.1259/jrs.1918.0014 ◽

1918 ◽

Vol 14 (54) ◽

pp. 33-33

Author(s):

P. T. Weeks

Keyword(s):

X Rays

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Electronic Excitations and Radiation Damage in Macromolecular Crystallography

Crystals ◽

10.3390/cryst8070273 ◽

2018 ◽

Vol 8 (7) ◽

pp. 273 ◽

Cited By ~ 1

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.

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