Morphology, structure and electronic properties of CdTe surfaces studied by scanning tunneling microscopy

A scanning tunneling microscope has been used to study the surface properties of CdTe crystals. Coupled with scanning tunneling spectroscopy (STS) and atomic force microscopy, the surface morphology, structure and electronic properties of CdTe and CdZnTe surfaces have been studied. We have systematically investigated the three low index surface planes of the cubic crystal, that is the {100}, {110} and {111} surface planes. In addition, wet chemically treated surfaces were also examined. Clean surfaces were prepared in ultra-high vacuum conditions using argon ion sputtering and annealing. For each surface we imaged and recorded the surface reconstructions and morphologies. For the (100) surface, a mixed c(2x2)+(2x1) surface phase was found, where steps on the surface were found to preferentially align along directions. For the (110) surface, tunneling spectroscopy was used to investigate the surface electronic structure of the (1x1) reconstruction. Using theoretical calculations of the tunneling current, we were able to match theory to experiment and discern the various vacuum tunneling processes for both n-type and semi-insulating material. For the (111) surface, a (2x2) reconstruction consisting of a cadmium vacancy structure was found. For the (-1-1-1) surface, a very disordered c(8x4) reconstruction was observed, consisting of a complicated tellurium terminated chain structure. For both faces, a large amount of faceting was observed to occur with the facets formed by {311} planes. Finally, wet chemically treated surfaces, important for the construction of many semiconductor devices, were investigated. Here the change in surface morphology for a variety of different common surface preparation methods was observed and, using STS, various surface electronic states were identified

Team strategic philosophy: requiem for the infinite game

Deliberate accountability has arrived in the medical arena, producing an age of reward for measured performance, and belief in publicizing metrics to ensure clarity, with winning defined as hitting targets, whereby staff are incentivised by arbitrary objectives. Finite game theory declares that players are known, rules are fixed, and the objective agreed, but infinite game theory asserts that players are both known and unknown, rules are changeable, and the objective is to perpetuate the game; these standards are clearly at odds and risk real world chaos in global universal medical education and clinical outcomes and functioning. Five principles are necessary to lead an infinite game: first, a fair basis, such that sacrifices for its advancement are promoted; second, a trusting blame-free team culture and environment; third, competitors viewed as worthy rivals, rather than adversaries, promoting healthy competition; fourth, existential flexibility when faced with credible evidence; and finally, transformational leadership; including infinite game theory into healthcare planning may be difficult, but the potential rewards are surely worth the existential fight

Children’s gaze behaviour at real-world and simulated road crossings

Children and older adults are overrepresented in pedestrian accidents (Department for Transport, 2010a, 2010b). Gaze behaviour is cited as a contributing factor in the majority of such accidents (Department for Transport, 2010a, 2010b); however, remarkably little is known about how children, adults and older adults control their gaze during either real or simulated road-crossing tasks. Because evidence suggests that behaviour in the laboratory may not accurately reflect that in more realistic situations (Dicks et al., 2010; ‘t Hart et al., 2009), this thesis used a real-world, active road-crossing task to compare, for the first time, how pedestrians across the lifespan direct their gaze during real road crossing. A total of 70 participants took part in the studies: 42 children (mean age 8.6 yrs, SD = 0.4); 14 young adults (mean age 24.1 yrs, SD = 4.5) and 14 older adults (mean age 70.7 yrs, SD = 4.1). In the first experiment, participants were escorted on a short walk while wearing a mobile eye tracker and asked to cross the roads along the way when they felt it was safe to do so. Gaze behaviour during the last 3 seconds before crossing the road at a signalised crossing was analysed. Both children and older adults directed their gaze significantly less often to traffic-relevant features (such as the road and vehicles) than young adults. However, their gaze patterns were very different. Older adults looked more at the ground ahead of them, which most likely reflects a functional adaptation to reduce the risk of tripping and falling as falls represent a serious risk in this population (Jensen, 1999). Children fixated traffic-irrelevant features more, which may indicate poorer attentional control or insufficient practice or experience. A serendipitous finding from this study was that the presence of a distractor (ice cream) acted to further draw attention away from the direction of oncoming vehicles in the sample of children. Based on these findings, a subsequent aim of the thesis was to explore whether two road-crossing training interventions (Crossroads and Safety Watch) would improve the amount of time children fixated traffic-relevant features of the environment: neither programme was found to have a significant impact on gaze behaviour compared to the control condition (no intervention). Another aim of the thesis that followed from the results of the first experiment was to further examine the attentional control of gaze behaviour in children. Two simulated road-crossings were purposely developed in the laboratory, allowing more controlled investigation of gaze behaviour at (simulated) signalised and unsignalised crossings, with and without a non-spatial secondary task (counting in threes). It was found that the addition of this secondary task affected children’s gaze behaviour in one of the simulation types but not the other. This demonstrated that cognitive processes are context dependent and not invariant across conditions. In light of the growing concern raised with respect to the use of artificial laboratory settings and tasks, the final aim of this thesis was to compare gaze behaviour of children under three display conditions: monitor simulation, projector simulation, and real-world; the results suggested that behaviour in the laboratory did not correspond with real-world behaviour. In real road-crossing situations, children looked significantly more often at the ground ahead of them (walkway) and at lights and signs than when performing in the “monitor” or “projector” simulations. These findings further emphasise the context-dependence of cognition and behaviour. This thesis contributes to the argument that a real-world setting provides rich and meaningful data and that, although the laboratory setting has certain methodological advantages, transfer of laboratory findings to the real-world context cannot be assumed. Similarly, road-crossing skills trained in a simulated setting (on a computer) do not appear to transfer to the real-world context. This thesis therefore advocates a real-world approach to the research and training of behaviour and underlying cognitive processes