PubMed Health⌕ Search

Biomedical subjects

D Watkin

Publications and source records attributed to D Watkin.

9 recordsLinked to original sources
PubMed2001

Structure of manganese diacetate tetrahydrate and low-temperature methyl-group dynamics.

We have determined the crystal structure of manganese(II) diacetate tetrahydrate at 300 and 14 K by single-crystal neutron diffraction. Proton density distributions for each of the three crystallographically distinct methyl groups have been calculated by Fourier difference. At room temperature the observed densities are those of quasi-free rotors. At low temperature rather well localized protons are observed. Inelastic neutron scattering measurements performed with single crystals allow us to assign each of the three tunnelling lines to a particular crystal site. Classical molecular dynamics simulations give density distributions in qualitative agreement with the observations. With quantum mechanics proton distributions can be represented with rotational wavefunctions convoluted with static distributions of librational coordinates. The effective rotational potentials are temperature dependent.

Journal Article↗
PubMed2000

Uequiv: its past, present and future.

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.

Journal Article↗
PubMed1995

How many trainees are needed in general surgery? A computer model to facilitate planning.

As a consequence of the reduction in junior doctors' hours, the intention to shorten training and the freedom of Trusts to appoint additional consultants, the requirement for trained surgeons has increased sharply. Whether this consultant expansion will be sustained, so as to reach the target of one general surgeon to 30,000 population, is uncertain. To improve the planning of the number of trainees in this unstable environment, a computer model has been established for the numbers of higher surgical trainees (HSTs) and consultants. Using a series of scenarios the model demonstrates that the existing number of HST posts, with a six-year duration of training, cannot deliver the intended 1767 consultant posts until about 2016. The target can be reached in 2009 by shortening HST to five years or by the conversion of visiting registrar posts to career HST; both measures combined can achieve the target by 2006. Thus urgent action is needed to increase the output of HSTs in general surgery. In view of the uncertain demand for additional consultants, the number of trainees, in each year of HST, should be monitored frequently. The number entering training may then be adjusted appropriately.

Computer Simulation↗
PubMed1988

Invasive amoebiasis: an unusual presentation.

A 63 year old Asian woman who presented with three week's abdominal pain was found to have a hard right iliac fossa mass and rectal ulceration. Profuse rectal bleeding necessitated a laparotomy. An inflammatory paracaecal mass with fistulae involving appendix, small bowel, and bladder was excised with exteriorisation of the bowel ends. Microscopy showed invasive amoebae. Re-anastomosis was successfully done after treatment with metronidazole and diloxanide. There are no previous reports of a paracaecal amoeboma with fistulae to either the appendix, or urinary bladder.

Amebiasis↗