Cover illustration: The observed X-ray diffuse scattering in the (h0l) section of
1,3-dibromo-2,5-diethyl-4,6-dimethylbenzene. Courtesy of T. R. Welberry and B. D. Butler. |

- research papers
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- laboratory notes
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*J. Appl. Cryst.* (1995). **28**, 69-77 [doi:10.1107/S0021889894008812]

**Synopsis:** An approximation is found for the number of reflections for trajectories that are transmitted by a cylindrical channel illuminated by a beam with a square angular divergence from
a rectangular neutron guide. The results are compared with those for a numerical simulation.

*J. Appl. Cryst.* (1995). **28**, 78-85 [doi:10.1107/S0021889894009222]

**Synopsis:** The gyration components of ammonium Rochelle salt are measured using a universal polarimeter. The dispersion of the gyration is given over the wavelength range 350-650 nm.

*J. Appl. Cryst.* (1995). **28**, 86-95 [doi:10.1107/S0021889894009696]

**Synopsis:** A new procedure is described for the integration of diffraction peaks on imaging plates. The new `seed-skewness' method is shown to lead to more reliable intensities, especially
for the weaker reflections.

*J. Appl. Cryst.* (1995). **28**, 96-104 [doi:10.1107/S0021889894009714]

**Synopsis:** The crystal structure of an approximant quasicrystal with a giant unit cell is refined.

*J. Appl. Cryst.* (1995). **28**, 105-114 [doi:10.1107/S0021889894010095]

**Synopsis:** Numerical and analytical methods are used for determining the resolution function for small-angle neutron scattering. Effects of beam-stop shadowing are also considered.

*J. Appl. Cryst.* (1995). **28**, 115-120 [doi:10.1107/S002188989401037X]

**Synopsis:** A Rietveld X-ray analysis is developed where the background scattering is described with equations based on physical principles.

*J. Appl. Cryst.* (1995). **28**, 121-126 [doi:10.1107/S0021889894010381]

**Synopsis:** The degree of crystallinity in semicrystalline materials has been determined with a Rietveld analysis with an internal approach based on Rietveld's method.

*J. Appl. Cryst.* (1995). **28**, 127-140 [doi:10.1107/S0021889894010629]

**Synopsis:** A preferred-orientation analysis for powder diffraction data is proposed based on an extension of the Wilson-plot intensity analysis in order to correct integrated intensities for
structure determination.

*J. Appl. Cryst.* (1995). **28**, 141-145 [doi:10.1107/S0021889894010113]

**Synopsis:** The structure refinement and estimation of various models of vacancy ordering in -Fe_{2}O_{3} were performed. Attention is paid to the superstructure orientation with respect to well developed planes of microcrystals that depend
on the precursor.

*J. Appl. Cryst.* (1995). **28**, 146-159 [doi:10.1107/S0021889894009027]

**Synopsis:** The method described, based on the `column-like' crystal model, can be applied to both single-and multiple-order reflections. The experimental diffraction peak is fitted by a sum
of elementary components represented by interference functions.

*J. Appl. Cryst.* (1995). **28**, 160-167 [doi:10.1107/S0021889894010071]

**Synopsis:** An analytical approximation is derived for easy calculation of the X-ray reflectivity pattern in low-reflectance multilayers. It allows the identification of pattern features most
sensitive to certain structural parameters (average layer thicknesses and external and internal roughness).

*J. Appl. Cryst.* (1995). **28**, 168-188 [doi:10.1107/S0021889894010083]

**Synopsis:** X-ray topographic methods are used to examine the influence of the paraelectric-to-ferroelectric phase transformation on the crystal perfection of single crystals of ammonium
sulfate.

*J. Appl. Cryst.* (1995). **28**, 189-195 [doi:10.1107/S0021889894010149]

**Synopsis:** X-ray scattering intensities of the primary alcohols were measured with transmission and reflection methods. The radial distribution functions were calculated and a fitting
procedure was used to obtain individual atomic distances and coordination numbers.

*J. Appl. Cryst.* (1995). **28**, 196-205 [doi:10.1107/S0021889894007867]

**Synopsis:** An efficient two-dimensional X-ray detector based on direct imaging of an X-ray-sensitive phosphor with a high-resolution (1024 × 1024) charge-coupled device (CCD) array has
been constructed and characterized. High detective quantum efficiency is obtained without an intensification stage.

*J. Appl. Cryst.* (1995). **28**, 206-208 [doi:10.1107/S0021889894011015]

**Synopsis:** Yttria-tetragonal zirconia polycrystal (Y-TZP), which has sometimes been assumed to be single-phase tetragonal, is shown to contain substantial (10-20%) quantities of cubic
zirconia as the phase diagram predicts. The conclusions from previous studies have been examined in the light of this result.

*J. Appl. Cryst.* (1995). **28**, 209-222 [doi:10.1107/S0021889894010617]

**Synopsis:** An analytical calculation of the three-dimensional resolution function for a small-angle neutron scattering set-up has been performed by application of phase-space analysis and
Gaussian approximations.

*J. Appl. Cryst.* (1995). **28**, 223 [doi:10.1107/S0021889894010137]

**Synopsis:** A rigorous proof of restrictions on rotation, inversion and roto-reflection axes in crystals in three dimensions is presented using transformation matrices, also that the traces
of similar matrices are identical.

*J. Appl. Cryst.* (1995). **28**, 224-225 [doi:10.1107/S0021889894010125]

**Synopsis:** A device is described that is useful for the recovery and re-exposure of frozen crystals and for data collection from frozen crystals at different orientations.

*J. Appl. Cryst.* (1995). **28**, 225-227 [doi:10.1107/S002188989401277X]

**Synopsis:** A brief description of a 3D graphics simulation program for single-crystal diffractometry is presented. The program displays both - and -type diffractometers with a zero-dimensional (conventional) counter or a two-dimensional
area detector and simulates the process of data collection.

*J. Appl. Cryst.* (1995). **28**, 228-236 [doi:10.1107/S002188989400991X]

**Synopsis:** *LAUEGEN* is an X-windows-based program for carrying out the initial data-processing stages for Laue X-ray diffraction data. It has facilities for
Laue simulations, image display and crystal orientation determination and refinement.

*J. Appl. Cryst.* (1995). **28**, 236-242 [doi:10.1107/S0021889894009908]

**Synopsis:** *XDL_VIEW* is an easy-to-use X-windows-based toolkit for crystallographic and more general applications. It has interfaces for both Fortran and C.

*J. Appl. Cryst.* (1995). **28**, 242-243 [doi:10.1107/S0021889894011891]

**Synopsis:** A simple innovation that allows convenient parallel crystallization trials of multiple samples using hanging drops is described.

*J. Appl. Cryst.* (1995). **28**, 243 [doi:10.1107/S0021889894012653]

**Synopsis:** A modification to a standard X-ray beam tunnel that eliminates absorption of X-rays by air is described.

*J. Appl. Cryst.* (1995). **28**, 244 [doi:10.1107/S0021889894013397]

**Synopsis:** *FHKL* is a menu-driven X-windows program to compute structure factors, dielectric susceptibilities, absorption coefficients and crystal rocking
curves, taking into account dispersion corrections, thermal agitation and polarization.

*J. Appl. Cryst.* (1995). **28**, 244-245 [doi:10.1107/S0021889894014172]

**Synopsis:** The program *BREADTH* calculates coherent domain sizes and lattice strains according to the `simplified' and `double-Voigt' integral-breadth
methods.

*J. Appl. Cryst.* (1995). **28**, 245-246 [doi:10.1107/S0021889895000999]

*J. Appl. Cryst.* (1995). **28**, 246 [doi:10.1107/S0021889895099626]

*J. Appl. Cryst.* (1995). **28**, 246 [doi:10.1107/S0021889895099614]

*J. Appl. Cryst.* (1995). **28**, 246 [doi:10.1107/S0021889895099602]

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