Capillary Behavior of Binary Liquid Mixtures Near Criticality: Rise and Kinetics

In three different phase-separated binary liquid mixtures we have observed stationary capillary rises in which the meniscus curvature is inconsistent with the sign of the rise. This ‘‘inverted-meniscus’’ configuration occurs within approximately 50 mK of the mixture’s critical temperature and shows no sign of decay after much longer than the characteristic time for relaxation. We also report experiments showing that perturbation of the wetting layer inside the capillary tube can dramatically affect the capillary rise. This motivates three scenarios in which the behavior of the wetting layer foils an equilibrium capillary rise measurement of the contact angle and produces an inverted meniscus

Expanding Economic Perspectives for Sustainability in Urban Water and Sanitation

The economic principles and tools that are commonly applied to recover costs for urban water and sanitation arise from the dominant perspective of neo-classical economics, with its emphasis on ‘full cost pricing’ based on the ‘user pays’ principle. Kumudini Abeysuriya, Cynthia Mitchell and Juliet Willetts examine two other qualitatively different economic perspectives to demonstrate how they lead to different approaches: ecological economics takes a more holistic approach explicitly committed to sustainability, while Buddhist economics brings ethics to the fore and opens the possibility for cooperation between the various actors in creating solutions to benefit individuals, society and the environment. We propose a set of interconnected guiding principles based on an expanded economic perspective that integrates all three perspectives, to enable water and sanitation services for developing countries to align with sustainability. Development (2008) 51, 23–29. doi:10.1057/palgrave.development.1100442