John S. Reid

Pharmacists: A resource for general practice?

A postal questionnaire seeking the views of all Grampian general practitioners (n=314) to a proposed wider role for pharmacists obtained an 85 per cent response rate. The questionnaire consisted of prescribing related and general tasks compiled from the recommendations of the joint working partys report “Pharmaceutical care: the future for community pharmacy” and those identified by a local GP and pharmacist while working on a joint study.

ABSFAC: a program for the calculation of the absorption during scattering in multifaceted crystals and similar samples

ABSFAC is a FORTRAN program that rapidly and efficiently calculates the absorption factor, T, in multifaceted convex crystals and in other materials whose shape can be modeled by a convex polyhedron. The program also calculates derivatives of T with respect to small outward movements of the polyhedron faces and the mean path length for the scattered rays. Although written for X-ray scattering, the programme is relevant to other scattering provided the underlying assumptions are valid. The program uses a mathematically exact method for calculating quantities from given sample shape data. The size of any numerical error (typically of the order of 1 in 1014) that arises during the calculation is estimated by the program and is much less than the uncertainty in specifying the scattering geometry. Excellent accuracy is obtained for a very wide range of absorption coefficients. An option within the program permits storing of the calculated geometrical factors for any one orientation of the sample and scattering vector, so that the absorption can be rapidly recalculated for different values of the absorption constant. This is particularly relevant for energy dispersive scattering. The program can also calculate the absorption in samples that are only partly illuminated by the incident beam.

Reciprocal-space mapping of synthetic and natural diamond

High-resolution reciprocal-space maps of synthetic and natural diamonds have been recorded for the first time on the new six-circle diffractometer at the Synchrotron Radiation Source of the Daresbury Laboratory, UK. Variations in lattice spacing (typically 10 ppm) have been measured within specific growth sectors of synthetic diamonds as well as lattice tilts (typically 1 arcmin). Similar measurements have been made on diamonds containing strain-producing metallic inclusions. Platelet radii in a natural diamond have also been estimated, giving results (such as 140 A) agreeing with measurements from other techniques.

Synchrotron radiation flux at experimental stations

Abstract A FORTRAN 77 program is described that will estimate the flux and polarisation available to synchrotron radiation users whose experimental stations receive the direct synchrotron emission. The radiation pattern is integrated over the finite aperture of the entrance pupil of the apparatus, assumed rectangular and centred axially on the emission cone. Allowance is made for the finite source size and the angular spread of source trajectories on the assumption that the bending field is uniform. Use is made of NAg Fortran library mathematical subroutines for quadrature and for evaluation of Airy functions.

James Clerk Maxwell 150 years on

This paper is the preface to a special Issue of Phil. Trans. R. Soc. A reporting selected proceedings of the international conference marking the 150th anniversary of James Clerk Maxwells professorial debut at Marischal College, Aberdeen. Following an introduction to Marischal College, a brief historical note summarizes Maxwells life prior to his entering the college as professor of natural philosophy. The preface provides a short summary of the event and overviews the contributed papers devoted to subjects covering a wide range of Maxwells research interests and their modern developments. The mixture of review and research papers reflects both the fundamental importance and the diverse applicability of Maxwells works in electromagnetics, colour science, dynamics and kinetics. Acknowledgements are given to the individuals and bodies who made the conference the success that it was.

SRS station 16.3: high-resolution applications

Abstract Station 16.3 is a high-resolution X-ray diffraction beamline at Daresbury Laboratory Synchrotron Radiation Source. The data presented demonstrate the high-resolution available on the station utilising the recently commissioned four-reflection Si 1xa01xa01 monochromator and three-reflection Si 1xa01xa01 analyser. For comparison, a reciprocal space map of the two-bounce Si 1xa01xa01 monochromator and two-bounce analyser is also shown. Operation of the station is illustrated with examples for silicon, and for diamond. Lattice parameter variations were measured with accuracies in the part per million range and lattice tilts at the arc second level (DuMond, Phys. Rev. 52 (1937) 872).

Single-phonon X-ray scattering

Abstract Title of program : SPHZB86 Catalogue number : AALZ Program obtainable from : CPC Program Library, Queens University of Belfast, N. Ireland (see application form in this issue) Computer : Honeywell 66/80; Installation : University of Aberdeen Operating system : GCOS8 Programming language used : FORTRAN 77 High speed storage required : 37 Kwords, plus eigendata file No. of bits in a word : 36 Peripheral used : lineprinter No. of lines in combined program and test deck : 1710

James Clerk Maxwell's Scottish chair

This account of Maxwell as professor of natural philosophy at Marischal College, Aberdeen, fills in many details that have been left out of Maxwells biographies. It discusses the degree programme that Maxwell taught on, the nature of his colleagues, the type of student he had in his classes and the range of activities involved in his teaching. Evidence is cited that Maxwell was an enthusiastic and effective teacher, contrary to the often repeated but thinly supported view to the contrary. Following a brief summary of Maxwells research interests while at Aberdeen, the myth that Maxwell was sacked from the University of Aberdeen is exploded and the detail of why he moved on is spelt out.

David Gill FRS (1843–1914): The Making of a Royal Astronomer:

David Gill was an outstanding astronomer over several decades at the end of the nineteenth and into the early twentieth century. He was famous for his observational accuracy, for his painstaking attention to detail, and for his hands-on knowledge of the fine points of astronomical instrumentation. Astronomy, though, was a second professional career for David Gill. This account maps out the surprising and unusual path of David Gill’s life before he became Her Majesty’s Astronomer at the Cape of Good Hope. It covers aspects of his education, his horological career, his employment by Lord Lindsay to oversee the Dunecht observatory, his personal expedition to Ascension Island and his appointment as Her Majesty’s Astronomer at the age of 34. The account includes local detail and images not found in the main biography of David Gill. It ends with some detail of Gill’s continuing interest in clocks after his appointment.

Diffuse scattering from large-angle, thermally induced, orientational disorder in molecular crystals

Large-angle rotational motion (libration) characteristic of molecular solids has not been properly included in many scattering calculations because of the need to develop scattering theory through small-angle approximations. A simple but effective approach to calculating the influence of large-angle librations on the thermal disorder scattering given by molecular solids is to treat the molecules as independent librators, each in a harmonic potential well, using the mathematics appropriate for large-angle rotations. The resulting probability distribution for angular misorientations is Gaussian and this distribution can be used to smear the molecular form factor, enabling the librational influence on the scattering to be calculated. It is shown how to apply this direct approach quite generally and by way of examples the technique is used with the molecular solids sulfur hexafluoride (SF(6)), adamantane (C(10)H(16)) and buckminsterfullerene (C(60)). For these materials, the molecular Fourier transform (i.e. the molecular form factor) have been calculated in selected planes in reciprocal space, followed by the separate effects of librational and translational smearing. It is found that the librational smearing produces a large effect on the form factor, particularly at larger scattering vectors, that is not sensitive to approximations in the argument. Additionally, the Debye-Waller effect of vibrational motion is included in the calculations, showing quantitatively the decreasing influence of vibrations on the scattering with increasing scattering vector. Both effects illustrate with pedagogic clarity how different processes modify the basic molecular scattering.