Landing gear for a 'silent' aircraft

The Silent Aircraft Initiative aims to provide a conceptual design for a large passenger aircraft whose noise would be imperceptible above the background level outside an urban airfield. Landing gear noise presents a significant challenge to such an aircraft. 1/10th scale models have been examined with the aim of establishing a lower noise limit for large aircraft landing gear. Additionally, the landing gear has been included in an integrated design concept for the 'Silent' Aircraft. This work demonstrates the capabilities of the closed-section Markham wind tunnel and the installed phased microphone arrays for aerodynamic and acoustic measurements. Interpretation of acoustic data has been enhanced by use of the CLEAN algorithm to quantify noise levels in a repeatable way and to eliminate side lobes which result from the microphone array geometry. Results suggest that highly simplified landing gears containing only the main struts offer a 12dBA reduction from modern gear noise. Noise treatment of simplified landing gear with fairings offers a further reduction which appears to be limited by noise from the lower parts of the wheels. The importance of fine details and surface discontinuities for low noise design are also underlined.

Probing the location of displayed cytochrome b562 on amyloid by scanning tunnelling microscopy.

Amyloid fibres displaying cytochrome b562 were probed using scanning tunnelling microscopy (STM) in vacuo. The cytochromes are electron transfer proteins containing a haem cofactor and could, in principle, mediate electron transfer between the tip and the gold substrate. If the core fibres were insulating and electron transfer within the 3D haem network was detected, then the electron transport properties of the fibre could be controlled by genetic engineering. Three kinds of STM images were obtained. At a low bias (<1.5 V) the fibres appeared as regions of low conductivity with no evidence of cytochrome mediated electron transfer. At a high bias, stable peaks in tunnelling current were observed for all three fibre species containing haem and one species of fibre that did not contain haem. In images of this kind, some of the current peaks were collinear and spaced around 10 nm apart over ranges longer than 100 nm, but background monomers complicate interpretation. Images of the third kind were rare (1 in 150 fibres); in these, fully conducting structures with the approximate dimensions of fibres were observed, suggesting the possibility of an intermittent conduction mechanism, for which a precedent exists in DNA. To test the conductivity, some fibres were immobilized with sputtered gold, and no evidence of conduction between the grains of gold was seen. In control experiments, a variation of monomeric cytochrome b562 was not detected by STM, which was attributed to low adhesion, whereas a monomeric multi-haem protein, GSU1996, was readily imaged. We conclude that the fibre superstructure may be intermittently conducting, that the cytochromes have been seen within the fibres and that they are too far apart for detectable current flow between sites to occur. We predict that GSU1996, being 10 nm long, is more likely to mediate successful electron transfer along the fibre as well as being more readily detectable when displayed from amyloid.

Guidewire retention following central venous catheterisation: a human factors and safe design investigation.

BACKGROUND: Central Venous Catheterisation (CVC) has occasionally been associated with cases of retained guidewires in patients after surgery. In theory, this is a completely avoidable complication; however, as with any human procedure, operator error leading to guidewires being occasionally retained cannot be fully eliminated. OBJECTIVE: The work described here investigated the issue in an attempt to better understand it both from an operator and a systems perspective, and to ultimately recommend appropriate safe design solutions that reduce guidewire retention errors. METHODS: Nine distinct methods were used: observations of the procedure, a literature review, interviewing CVC end-users, task analysis construction, CVC procedural audits, two human reliability assessments, usability heuristics and a comprehensive solution survey with CVC end-users. RESULTS: The three solutions that operators rated most highly, in terms of both practicality and effectiveness, were: making trainees better aware of the potential guidewire complications and strongly emphasising guidewire removal in CVC training, actively checking that the guidewire is present in the waste tray for disposal, and standardising purchase of central line sets so that differences that may affect chances of guidewire loss is minimised. CONCLUSIONS: Further work to eliminate/engineer out the possibility of guidewires being retained is proposed.