A timely reminder of technical limitations

Peer reviewedPublisher PD

Twist transition of nematic hyperbolic hedgehogs

Stability of an idealized hyperbolic hedgehog in a nematic liquid crystal against a twist transition is investigated by extending the methodology of Rüdinger and Stark [Liq. Cryst. 26, 753 (1999)], where the hedgehog is confined between two concentric spheres. In the ideal hyperbolic-hedgehog the molecular orientation is assumed to rotate proportionally with respect to the inclination angle, θ (and in the opposite sense). However, when splay, k11, and bend, k33, moduli differ this proportionality is lost and the liquid crystal deforms relative to the ideal with bend and splay. Although slight, these deformations are shown to significantly shift the transition if k11/k33 is small. By increasing the degree of confinement the twist transition can be inhibited, a characteristic both hyperbolic and radial hedgehogs have in common. The twist transition of a hyperbolic defect that accompanies a particle is found to be well predicted by the earlier stability analysis of a thick shell

Frequency domain laser velocimeter signal processor: A new signal processing scheme

A new scheme for processing signals from laser velocimeter systems is described. The technique utilizes the capabilities of advanced digital electronics to yield a smart instrument that is able to configure itself, based on the characteristics of the input signals, for optimum measurement accuracy. The signal processor is composed of a high-speed 2-bit transient recorder for signal capture and a combination of adaptive digital filters with energy and/or zero crossing detection signal processing. The system is designed to accept signals with frequencies up to 100 MHz with standard deviations up to 20 percent of the average signal frequency. Results from comparative simulation studies indicate measurement accuracies 2.5 times better than with a high-speed burst counter, from signals with as few as 150 photons per burst

An evaluation of specialist mentoring for university students with autism spectrum disorders and mental health conditions

Mentoring is often recommended to universities as a way of supporting students with autism spectrum disorders (ASD) and/or mental health conditions (MHC), but there is little literature on optimising this support. We used mixed-methods to evaluate mentees’ and mentors’ experiences of a specialist mentoring programme. Mentees experienced academic, social and emotional support, although subtle group differences emerged between students with ASD and MHC. The quality of the mentee-mentor relationship was especially important. Mentors also reported benefits. Thematic analysis identified that effective mentoring requires a tailored partnership, which involves a personal relationship, empowerment, and building bridges into the university experience. Mentoring can effectively support students with ASD and/or MHC, but this is highly dependent on the development of tailored mentee-mentor partnerships