The effect of fluorocarbon tails on the phase behaviour of some Schiff's base liquid crystals

Several new liquid crystalline compounds comprising Schiff's-base cinnamate cores and fluorocarbon alkoxy tails of varying lengths have been synthesized and characterized. The thermal properties of these materials are compared to those of their hydrocarbon analogues. The results show that fluorination stabilizes the crystalline phase, quite unexpectedly destabilizes the S_c phase, and for two of the compounds produces extraordinarily stable S_A phases.     

Electrophoretic and computer analysis of skeletal muscle used for cardiac assistance.

Skeletal muscle has an inherent plasticity which allows it to undergo fibre type transformation when induced by a specific stimulus. Electrical stimulation has been used here to induce transformation of a predominantly fast type skeletal muscle towards a slow, more fatigue-resistant phenotype, which is more suitable for use in long-term cardiac assistance. Muscle samples from animals electrically stimulated for periods up to 6 months have been analysed by electrophoresis for myosin heavy chain (MHC) and myosin light chain (MLC) fast and slow isoforms. Densitometry and computer analysis have been used to determine the pattern of transformation of the different myosin subunits over this time period. MHC and MLC 2 fast to slow isoform switching preceded that of the alkali light chains (MLC1 and MLC3). After 3 months of stimulation the MHC slow isoform was found to have doubled in concentration relative to the unstimulated control muscle and by 4 months accounted for almost 50% of the total MHC content. The slow isoform accounted for 75% of the MLC2 after 4 months of stimulation. The protein products of mRNA isolated from stimulated muscle samples, translated in vitro and separated by electrophoresis, showed that transformation at the mRNA level preceded that at the protein level. By 2-4 weeks of stimulation MLC2 slow isoform mRNA represented over 60% of the total MLC2 mRNA population. An understanding of the molecular structure of muscle during transformation provides insight into its haemodynamic performance in cardiac assistance.     

Catheter microelectrode assembly for in-vivo and in-vitro voltammetric analysis of body fluids

An electrode assembly suitable for voltammetric analysis of very small sample volumes, in vitro or (vivo), has been constructed inside a catheter. Well-defined differential pulse current peaks have been obtained for acetaminophen, chlorpromazine and ascorbic acid at the submillimolar concentration level. Voltamperograms recorded for rhesus monkey blood in vivo and in vitro were similar.     

A study of the fracture mechanisms in pristine silica fibres utilising high speed imaging techniques

The 40 kg test masses of the Advanced LIGO interferometric gravitational wave detector will each be suspended on four fibres fabricated from Heraeus Suprasil synthetic silica glass. The ultimate tensile breaking stress and fracturing process of loaded silica fibres was investigated in order to develop the technology required to suspend the test mass in a robust and safe manner. The majority of the fibres in this study were pulled by hand in a H₂ ? O₂ flame; for comparison, fibres were also pulled on a CO₂ laser machine. Carefully prepared fibres were shown to be pristine, i.e. free of surface cracks. Such fibres exhibited breaking strengths as high as 5 ? 6 GPa. To analyse the mechanisms of fracture a high speed photographic setup was developed in addition to the use of a high speed video camera. The pristine fibres break in the zone of maximal stress as expected in the model of flawless fibres. Some fibres break at a lower stress and these fractures occur at the fibre ends. This type of fracture is related to the thermal stress induced by local heating which was used to align the fibre in the test structure. The most likely fracture mechanism is based on a thermo-kinetic approach.     

A monolithic resonant terahertz sensor element comprising a metamaterial absorber and micro‐bolometer

In this article a monolithic resonant terahertz sensor element with a noise equivalent power superior to that of typical commercial room temperature single pixel terahertz detectors and capable of close to real time read‐out rates is presented. The detector is constructed via the integration of a metamaterial absorber and a micro‐bolometer sensor. An absorption magnitude of 57% at 2.5 THz, a minimum NEP of and a thermal time constant of 68 ms for the sensor are measured. As a demonstration of detector capability, it is employed in a practical Nipkow terahertz imaging system. The monolithic resonant terahertz detector is readily scaled to focal plane array formats by adding standard read‐out and addressing circuitry enabling compact, low‐cost terahertz imaging.