Time-resolved scanning Kelvin probe microscopy (SKPM) and Raman microscopy have been used to investigate processes occurring at the interface between indium tin oxide (ITO) electrodes and inkjet printed polyethylenedioxythiophene: polystyrene sulphonic acid (PEDOT:PSS). SKPM reveals a slow, reversible polarisation process (time constant ∼12s) occurring at the electrodes caused by the drift of Na+ and∕or H+ ions in the polymer. Raman microscopy shows that the resulting field enhancement at the electrodes increases the concentration of holes in the polymer at the anode, while at the cathode there is a significant reduction in hole concentration. Such effects have implications for both the short- and long-term stability of devices utilising PEDOT:PSS.
A new particulate composite material has been assessed with regard to the design of an ‘isoelastic’ or ‘modulus matched’ hip prosthesis. Three different prototype designs were assessed, each of which consisted of a femoral component made from the composite material, attached to a metal ball via a metal ‘spike’ insert. The prototypes varied in terms of the detailed shape of the spike, which was modified in the light of photoelastic stress analysis, so as to produce a more acceptable stress distribution to the composite material in the proximal region. Prototypes were made by hand moulding and by transfer moulding; both methods produced defects of various kinds. Simulation tests were conducted using a model of the proximal femur constructed from glass fibre composite, cyclically loaded in a servo-hydraulic testing machine. Though some difficulties were experienced with defective mouldings, especially for the transfer moulding process, a clear improvement was demonstrated for the final (Mark III) design. The fatigue endurance of this prototype was similar to that of conventional metal prostheses tested under similar conditions. Fatigue crack propagation tests were carried out on samples of the composite material to establish its propagation threshold. These results were combined with a finite element stress analysis and fracture mechanics theory to estimate the critical crack length for fatigue in this prosthesis. It was thus possible to specify the maximum safe size of defect that could be tolerated in use.
Abstract This account describes a rapid and accurate fusion technique of X‐ray fluorescence analysis that is based on the method of Norrish and Hutton, 1 but modified from the latter in a number of respects to enable more rapid preparation and processing of samples without any loss of accuracy. The technique allows a wide range of materials to be analysed including silicate rocks and minerals, cements, bricks, carbonates, evaporites, soils and some ores.
Bone is an elementary component in the human skeleton. It protects vital organs, regulates calcium levels and allows mobility. As a result of daily activities, bones are cyclically strained causing microdamage. This damage, in the form of numerous mi
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