David Keen

Abstract:

We investigate the structures of H(3)Co(CN)(6) and D(3)Co(CN)(6) and their temperature dependence using a combination of advanced neutron and x-ray diffraction techniques. Lattice parameter refinements show marked temperature- and isotope-dependent effects in the thermal expansion behaviour. Reverse Monte Carlo modelling of neutron total scattering data characterizes the distribution of D atom positions in the deuterated compound; analysis of these distributions reveals that the two N-H/D bonds become increasingly different with increasing temperature, suggesting a mechanism for the observed thermal expansion anomalies. We discuss these results in the context of the previous crystallographic, spectroscopic and theoretical results for H(3)Co(CN)(6) and 'super-short' N···H···N systems in general.

Abstract:

Background

Musculoskeletal injuries (MSIs) persist as the leading category of occupational injury in health care. Limited evidence exists regarding MSIs for occupations other than direct patient care providers. An evaluation of the risks, causes and activities associated with MSIs that includes non-patient care health care occupations is warranted.

Aims

To examine the risks and causes of time-loss MSIs for all occupations in health care.

Methods

Workers employed by a health region in British Columbia were followed from April 2007 to March 2008 using payroll data; injuries were followed using an incidence surveillance database. Frequency and rates were calculated for all occupational injuries and MSIs and relative risks (RRs) were computed using Poisson regression. Causes and occupational activities leading to MSIs were tabulated for direct care occupations and non-patient care occupations.

Results

A total of 944 injuries resulting in time-loss from work were reported by 23 742 workers. Overall, 83% injuries were musculoskeletal. The two occupations showing highest RR of MSIs relative to registered nurses were facility support service workers [RR = 3.16 (2.38-4.18), respectively] and care aides [RR=3.76 (3.09-4.59)]. For direct patient care occupations, the leading causes of MSIs were awkward posture (25%) and force (23%); for non-patient care occupations were force (25%) and slip/fall (24%). Patient handling activities accounted for 60% of all MSIs for direct care occupations. For non-patient care occupations, 55% of MSIs were due to material/equipment handling activities.

Conclusions

Prevention efforts for MSIs should be directed to non-patient care occupations as well and consider their occupation-specific causes and activities.

Abstract:

Conversion of aldo to keto sugars by the metalloenzyme D-xylose isomerase (XI) is a multistep reaction that involves hydrogen transfer. We have determined the structure of this enzyme by neutron diffraction in order to locate H atoms (or their isotope D). Two studies are presented, one of XI containing cadmium and cyclic D-glucose (before sugar ring opening has occurred), and the other containing nickel and linear D-glucose (after ring opening has occurred but before isomerization). Previously we reported the neutron structures of ligand-free enzyme and enzyme with bound product. The data show that His54 is doubly protonated on the ring N in all four structures. Lys289 is neutral before ring opening and gains a proton after this; the catalytic metal-bound water is deprotonated to hydroxyl during isomerization and O5 is deprotonated. These results lead to new suggestions as to how changes might take place over the course of the reaction.