Bayesian uncertainty evaluation applied to the tilted-wave interferometer.

The tilted-wave interferometer is a promising technique for the development of a reference measurement system for the highly accurate form measurement of aspheres and freeform surfaces. The technique combines interferometric measurements, acquired with a special setup, and sophisticated mathematical evaluation procedures. To determine the form of the surface under test, a computational model is required that closely mimics the measurement process of the physical measurement instruments. The parameters of the computational model, comprising the surface under test sought, are then tuned by solving an inverse problem. Due to this embedded structure of the real experiment and computational model and the overall complexity, a thorough uncertainty evaluation is challenging. In this work, a Bayesian approach is proposed to tackle the inverse problem, based on a statistical model derived from the computational model of the tilted-wave interferometer. Such a procedure naturally allows for uncertainty quantification to be made. We present an approximate inference scheme to efficiently sample quantities of the posterior using Monte Carlo sampling involving the statistical model. In particular, the methodology derived is applied to the tilted-wave interferometer to obtain an estimate and corresponding uncertainty of the pixel-by-pixel form of the surface under test for two typical surfaces taking into account a number of key influencing factors. A statistical analysis using experimental design is employed to identify main influencing factors and a subsequent analysis confirms the efficacy of the method derived.

'Finally, I could breathe': the utility and impact of a diagnosis of obsessive compulsive disorder.

BACKGROUND: The diagnosis of obsessive compulsive disorder (OCD) is characterised by intrusive thoughts leading to compulsions to alleviate anxiety. However, research is lacking on impact post-diagnosis. Some research suggests diagnosis may benefit treatment access, but potentially leads to higher levels of stigma and altered self-identity. AIMS: The present study assessed the utility (treatment access and problem identification) and impact (stigma, personal wellbeing or social identity) of receiving a diagnosis of OCD. METHOD: Semi-structured interviews with 12 individuals who had received a diagnosis of OCD were conducted between February and April 2020, then transcribed and analysed using theoretical thematic analysis. RESULTS: Participants reported positive impacts of diagnosis on both 'utility' and 'impact'. CONCLUSIONS: The diagnosis of OCD was helpful for participants in making their symptoms tangible, providing relief and hope for recovery. Non-diagnostic or alternative frameworks should aim to meet this need. Future research may wish to identify how this understanding of disorders vary between different diagnoses, especially in terms of stigma and personal wellbeing.