Monolayer MoS2 strained to 1.3% with a microelectromechanical system

We report on a modified transfer technique for atomically thin materials integrated onto microelectromechanical systems (MEMS) for studying strain physics and creating strain-based devices. Our method tolerates the non-planar structures and fragility of MEMS, while still providing precise positioning and crack free transfer of flakes. Further, our method used the transfer polymer to anchor the 2D crystal to the MEMS, which reduces the fabrication time, increases the yield, and allowed us to exploit the strong mechanical coupling between 2D crystal and polymer to strain the atomically thin system. We successfully strained single atomic layers of molybdenum disulfide (MoS2) with MEMS devices for the first time and achieved greater than 1.3% strain, marking a major milestone for incorporating 2D materials with MEMS We used the established strain response of MoS2 Raman and Photoluminescence spectra to deduce the strain in our crystals and provide a consistency check. We found good comparison between our experiment and literature.Published versio

Isolas of 2-Pulse Solutions in Homoclinic Snaking Scenarios

Homoclinic snaking refers to the bifurcation structure of symmetric localised roll patterns that are often found to lie on two sinusoidal “snaking” bifurcation curves, which are connected by an infinite number of “rung” segments along which asymmetric localised rolls of various widths exist. The envelopes of all these structures have a unique maximum and we refer to them as symmetric or asymmetric 1-pulses. In this paper, the existence of stationary 1D patterns of symmetric 2-pulses that consist of two well-separated 1-pulses is established. Corroborating earlier numerical evidence, it is shown that symmetric 2-pulses exist along isolas in parameter space that are formed by parts of the snaking curves and the rungs mentioned above

Existence of stationary fronts in a system of two coupled wave equations with spatial inhomogeneity

We investigate the existence of stationary fronts in a coupled system of two sine-Gordon equations with a smooth, "hat-like" spatial inhomogeneity. The spatial inhomogeneity corresponds to a spatially dependent scaling of the sine-Gordon potential term. The uncoupled inhomogeneous sine-Gordon equation has stable stationary front solutions that persist in the coupled system. Carrying out a numerical investigation it is found that these inhomogeneous sine-Gordon fronts loose stability, provided the coupling between the two inhomogeneous sine-Gordon equations is strong enough, with new stable fronts bifurcating. In order to analytically study the bifurcating fronts, we first approximate the smooth spatial inhomogeneity by a piecewise constant function. With this approximation, we prove analytically the existence of a pitchfork bifurcation. To complete the argument, we prove that transverse fronts for a piecewise constant inhomogeneity persist for the smooth "hat-like" spatial inhomogeneity by introducing a fast-slow structure and using geometric singular perturbation theory

Reliability of GRBAS evaluation of voice quality in children who have a history of airway reconstruction surgery and how this compares to parental report of voice-related quality of life

Voice evaluation includes laryngoscopy, perceptual judgement of voice quality, evaluation of respiratory function, acoustic analysis of the voice signal and patient reported subjective impact of voice on quality of life. This is recommended in adults (Dejonkere et al 2001) and children (Cohen et al 2012). Perceptual evaluation of voice often follows the CAPE-V (ASHA 2002) or GRBAS (Hirano 1981). Children requiring laryngotracheal reconstruction (LTR) surgery tend to have this procedure during infancy, where subglottic stenosis forms following intubation in medically fragile or premature infants. Clinicians require reliable measures, particularly where there is a degree of subjectivity. Aspects of the CAPE-V show a high degree of reliability in rating of severity, pitch, breathiness and roughness (Krival et al 2007, Kelchner et al 2008). UK clinicians favour the GRBAS though there is little published information about reliability in a paediatric population. Comparison of clinician perceptual evaluation with patient report shows weak agreement in adults (Karnell et al 2006) reinforcing the need for both measurements. The extent to which the same is the case in children needs further exploration