Feedback dew-point sensor utilising optimally cut plastic optical fibres

A plastic optical fibre reflectance sensor that makes full use of the critical angle of the fibres is implemented to monitor dew formation on a Peltier-cooled reflector surface. The optical configuration permits isolation of optoelectronic components from the sensing head and better light coupling between the reflector and the detecting fibre, giving a better signal of the onset of dew formation on the reflector. Continuous monitoring of the rate of change in reflectance as well as the absolute reflectance signals, the use of a novel polymethyl-methacrylate-coated hydrophobic film reflector on the Peltier element and the application of feedback around the point of dew formation, further reduces the possibility of contamination of the sensor head. Under closed-loop operation, the sensor is capable of cycling around the point of dew formation at a frequency of 2.5 Hz.

Shifting sand, shifting livelihoods? Reflections on a coastal gold rush in Ghana

Artisanal and small-scale mining (ASM) is often characterised as rush-type activity undertaken by people looking to ‘get-rich quick’. An alternative view posits ASM as poverty-driven activity which provides a valuable source of employment to a rural population where agriculture has failed to provide an adequate income. Against this dichotomy, this article critically reviews the short-lived, but high profile, gold rush which occurred on the beaches of Elmina, a fishing town in Ghana’s Central Region. At its peak, more than 1000 people, including local fishermen and career miners from the Western Region and Eastern Region of the country, were mining on the beaches. Drawing on interviews with miners and local business owners, the analysis explores the dynamics of the rush and its implications for understanding the ASM sector in Ghana. The discussion highlights the challenges associated with managing resources in dynamic and heterogeneous contexts, reconciling separate and conflicting sectoral priorities and the need to go beyond simplified and dualistic representations of the sector.