ABSTRACT
A new category of articles - Raw Data Letters - is introduced to IUCrData.
ABSTRACT
A working group on data format standardization for X-ray absorption spectroscopy (XAS) has recently formed under the auspices of the International X-ray Absorption Society and the XAFS Commission of the International Union of Crystallography. This group of beamline scientists and XAS practitioners has been tasked to propose data format standards to meet the needs of the world-wide XAS community. In this report, concepts for addressing three XAS data storage needs are presented: a single spectrum interchange format, a hierarchical format for multispectral X-ray experiment, and a relational database format for XAS data libraries.
ABSTRACT
Weissenberg screens and a translating cassette have been employed to allow an imaging plate to collect 30 scans per readout. In this configuration the imaging plate functions as a curved one-dimensional position-sensitive detector and, by changing the sample angle for each of the scans, two-dimensional images were produced in reciprocal space. This method of data collection leads to a reduction in scan time compared with methods based on a scintillation detector, particularly for asymmetric reflections. The data-collection method was tested using InGaN/GaN/AlN multilayers on sapphire substrates, since these exhibit broad features in reciprocal space. The geometry of the scans in reciprocal space required the data to be interpolated onto a Cartesian grid. Several interpolation schemes were investigated, with the results compared with the reciprocal space maps collected using a triple-axis scheme with a point detector. The quality of the interpolated reciprocal space maps depends upon the size and shape of the feature in reciprocal space, the interpolation method used, and the step size of the sample rotation. The method can be extended to three dimensions without an increase in data-collection time.
ABSTRACT
The triclinic superstructure of a small crystal of LiCa(2)Nb(3)O(10), lithium dicalcium triniobium decaoxide, has been investigated by synchrotron X-ray diffraction. The unit cell is an almost rectangular parallelepiped, although there is a 0.245 degrees offset from orthogonality for beta. The structure essentially belongs to a homologous series of Li[Na(n-3)Ca(2)Nb(n)O(3n+1)] with n = 3, where the moiety in square brackets has a perovskite-type slab structure. The superstructure has a doubled unit-cell volume with respect to the tetragonal aristotype. The NbO(6) octahedra are rotated about axes parallel to [110] by approximately 10 degrees. Adjacent slabs are connected by Li atoms and are geometrically related by 4(2) pseudosymmetry lying parallel to c. There are twice as many sites as Li atoms, providing a variation of population at these Li sites.
ABSTRACT
Adaptive Behavior Scale (ABS) Part One ratings by one rater who completed the entire scale was compared with the composite rating by a group of raters, each of whom completed only a portion of the ABS. Individual and composite ratings were obtained for 40 retarded clients. In using total scores, we found that composite ratings were significantly higher than individual ratings.
