Laue techniques

The use of Lorentz and polarization factors not corresponding exactly to the Laue technique probably introduces no appreciable error.) The parameter accordingly has the value... 

The advantages of the difference Laue technique is that wavelength and position dependent corrections are not needed except in the case of significant change in the mass absorbtion coefficient during the course of the experiment (eg. the binding of heavy atoms). A modified difference Laue method was exploited by Faber et al. (1987) in the determination of the positions of the heavy atom binding sites in crystals of xylose isomerase. 

As with neutron powder methods, both monochromatic and time-of-flight (Laue) techniques have been used for single-crystal neutron studies. Such studies are much less numerous, however, as a result of the difficulty of compressing suitably sized (>1 mm ) single-crystal sample to the required pressure while maintaining the crystal quality. The piston cylinder cell design of Me Whan and others [128] has been used at the ILL reactor source for a number of neutron structural studies to... 

Because the amplitude of the lattice distortion in the Peierls insulator is very small, the X-ray scattering associated with it is weak. Furthermore the one-dimensional nature of this distortion gives rise to diffuse Bragg planes instead of the usual well-defined Bragg reflections. These two facts have led to the development of a special diffuse X-ray photographic technique often referred to as the monochromatic Laue technique or XDS (for X-ray diffuse scattering) (64). 

One exception is the so-called Laue technique, in which white radiation is employed to produce diffraction patterns from stationary single crystals. 

In conclusion is should be emphasised that time-resolved studies like those described here provide information on stereochemical pathways rather than kinetics. This reflects the obvious point that individual molecules are not free but are in an environment where they interact with other molecules. However, it should be emphasised that, as is well illustrated by kinetic studies using for example Laue techniques in protein crystallography where the crystal environment is typically more ordered than in a crystalline fiber, the molecular environment in a fiber is not necessarily any less functionally meaningful than that of many kinetic studies in solution. 

The Laue technique is aimed squarely at reducing the minimum x-ray exposure, which determines the time resolution in a time-resolved crystallographic experiment. The Laue technique yields the lowest possible exposure time, that is typically two orders of magnitude less than the corresponding monochromatic oscillation exposure time [20] a large volume of reciprocal space is stimulated simultaneously, which is... 

Very recently, phase transitions in single crystals of the hormone, insulin, have been induced by variation in zinc concentration, and the Laue technique has been used to monitor the change in diffraction intensities at 10 minute intervals over a period of several hours [41]. 

The revival of the Laue technique has been made possible by the polychromatic nature of the emitted spectrum and the associated high brightness. The study of time resolved phenomena in biological structures (as well as chemistry and solid state physics) with this method is a major research and development effort that is under way. 

Key words Perovskite/Twiniming/Laue Technique/Solid Oxide Fuel Cells... 

Laue technique. The diffracted beams produce a pattern consisting of an array of spots. It is used to orient single crystals (with an accuracy in a range of 0.3° to 1°) prior to cutting and polishing. 

Initial assessment of the outcome of a crystal growth experiment is usually carried out by Laue X-ray diffraction. Chemical etching (when possible) can reveal grain boundaries but the extent of a single grain is usually confirmed by XRD. The Laue technique can also provide an indication of crystal quality from the shape and nature of the individual spots. Often this is as far as characterisation proceeds, particularly where the intermetallic compounds are concerned. 

Different X-ray diffraction techniques for single crystal starting from Laue techniques to rotation/oscillation and finally to Weissenberg techniques are discussed along with the interpretation and the advantages and limitations. These techniques which are systematically introduced and discussed are essential for imderstanding the inside of structure and their arrangements in a crystal. 

The Laue techniques used for this purpose can give a picture of the whole changing structure, but the time resolution still restricts it to slow changes (seconds rather than milliseconds). A much faster resolution is obtained from records of single reflections in diffraction patterns of active muscle fibres after electrical stimulation (Huxley Faruqi, 1983). 

The use of well collimated and high intensity synchrotron radiation beams is essential to reach the necessary time intervals without losing the statistical significance in the observed diffracted intensities. The white beam Laue technique has already been proven to facilitate studies down to the picosecond time regime for studies such as recombination of CO in myoglobin after flash photolysis. Nanosecond resolution has been obtained in a study of laserannealing of defects in a silicon crystal. 

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