Natalie is implementing a scattering model for chemical groups which behave as “hindered rotors” to the base Fortran code of the CRYSTALS software. The representation requires fewer parameters and is more physically realistic than current models. Look out for better trifluoromethyl groups in future!

Natalie does not have a favourite programming language, believing instead that we should use the appropriate tool for the problem being solved. In her spare time she is a keen cross-country runner and has completed over 170 parkruns.

*J. Appl. Cryst.* (2004), **37**, 545-550. Â Â [ doi:10.1107/S0021889804009847 ]

The program *CRYSTALS* [Betteridge, Carruthers, Cooper, Prout & Watkin (2003). *J. Appl. Cryst.* **36**, 1487] has been extended to include an option for the refinement of a continuous electron density distribution lying along a line, a ring or on the surface of a sphere. These additional non-atomic electron distributions can be refined in any combination with traditional anisotropically distributed spherical atoms, including the refinement of `partial’ atoms overlapping with the special electron distributions.

Electronic reprints

Publisherâ€™s copy

*Acta Cryst.* (2000), B**56**, 747-749. Â Â [ doi:10.1107/S0108768100008466 ]

The reporting of *U*_{equiv} and its standard uncertainty has a chequered history. In spite of the recommendation of the IUCr Commission on Journals that authors use the definition of *U*_{equiv} of their own choice, possibly without standard uncertainties, there still seems to be some confusion amongst referees and editors about the status of this derived parameter. It is shown that neither of the common definitions are very useful, and that the standard uncertainty computed from the refinement normal matrix is almost worthless. A potential alternative derived parameter is proposed.