The work function of titanium and selected metals in vacuum

The work functions of titanium films have been measured at room temperature with a scanning probe version of the Kelvin-Zisman dynamic capacitor. The values for the clean surfaces of films deposited onto a gold substrate at 2.10-9 torr lay between 4.5 and 6.0 eV. The surface potentials of hydrogen were positive apparently due to penetration of the adsorbed hydrogen atom with a partial negative ionicity below the surface electronic plane. The maximum surface potential increased approximately linearly with the initial work function and varied between 0.26 and 1.30 eV. A surface potential model was proposed which attempted to account for dissociative adsorption of molecular hydrogen and solution of adsorbed atomic hydrogen. The time dependant changes of the surface potential were consistent with the theoretical predictions and the activation energy for solution of atomic hydrogen was derived to be between 0.7 and 1.5 Kcal gr-atom-1. The work function and surface potential of rapidly deposited films at 1.10-7 torr onto a silver substrate behaved similarly to those above and mass spectrometric analysis of the residual gas provided evidence for a predominant adsorption of hydrogen. Slowly deposited films at this pressure onto a silver substrate, however, possessed a low work function between 2.5 and 3.8 eV which broadly encompassed the range of values recently published by others for thin titanium films deposited apparently under similar conditions. The low values apparently arise from impurities. The surface potential of the residual gas adsorbate was negative on contaminated films and the time dependant changes were of a similar form to those of purer films. These results were discussed in relation to the hydrogen surface potential model and the adsorption of other gases. The work function of two polished stainless steel electrodes were 4.65 + 0.10 eV at 1.10-7 torr and 5.60 + 0.10 eV (after baking) at 2.10-9 torr. The work function was reversibly decreased by illumination, prolonged exposure to hydrogen and by applied electrostatic fields; it was reversibly increased by an incident electron current. These effects are interpreted as the result of an oxide layer on the steel surface. Theoretical models are proposed which attempt to account for these as due to changes in the density of surface states at a semiconducting oxide surface. The results are generally consistent with the theoretical predictions with the exception of the field effect. The effect of stray capacitive coupling on contact potential measurements was experimentally investigated. The results were partially consistent with the predictions of a model which is proposed. These effects are shown to be a major source of error if simple precautionary measures are not taken to avoid them

Patient-initiated switching between private and public inpatient hospitalisation in Western Australia 1980 – 2001: An analysis using linked data

BACKGROUND: The aim of the study was to identify any distinct behavioural patterns in switching between public and privately insured payment classifications between successive episodes of inpatient care within Western Australia between 1980 and 2001 using a novel 'couplet' method of analysing longitudinal data. METHODS: The WA Data Linkage System was used to extract all hospital morbidity records from 1980 to 2001. For each individual, episodes of hospitalisation were paired into couplets, which were classified according to the sequential combination of public and privately insured episodes. Behavioural patterns were analysed using the mean intra-couplet interval and proportion of discordant couplets in each year. RESULTS: Discordant couplets were consistently associated with the longest intra-couplet intervals (ratio to the average annual mean interval being 1.35), while the shortest intra-couplet intervals were associated with public concordant couplets (0.5). Overall, privately insured patients were more likely to switch payment classification at their next admission compared with public patients (the average rate of loss across all age groups being 0.55% and 2.16% respectively). The rate of loss from the privately insured payment classification was inversely associated with time between episodes (2.49% for intervals of 0 to 13 years and 0.83% for intervals of 14 to 21 years). In all age groups, the average rate of loss from the privately insured payment classification was greater between 1981 and 1990 compared with that between 1991 and 2001 (3.45% and 3.10% per year respectively). CONCLUSION: A small but statistically significant reduction in rate of switching away from PHI over the latter period of observation indicated that health care policies encouraging uptake of PHI implemented in the 1990s by the federal government had some of their intended impact on behaviour

Strategic alliances and their impacts on the container shipping industry

The thesis deals with the evolution of container shipping route networks over a ten-year span from 1989 to 1999. The network evolution is shown to be a direct result of globalization, with a decline in the number of direct routes serving only two maritime ranges and a proliferation of multi-range services. A particular development has been the establishment of Strategic Alliances. Today, the industry has restructured itself around five major groupings. This paper provides an explanation for the establishment of such alliances and their influence. In particular the New World Alliance and its members will be examined in the thesis