A quantum Hall Mach-Zehnder interferometer far beyond the equilibrium

We experimentally realize quantum Hall Mach-Zehnder interferometer which operates far beyond the equilibrium. The operation of the interferometer is based on allowed intra-edge elastic transitions within the same Landau sublevel in the regime of high imbalances between the co-propagating edge states. Since the every edge state is definitely connected with the certain Landau sublevel, the formation of the interference loop can be understood as a splitting and a further reconnection of a single edge state. We observe an Aharonov-Bohm type interference pattern even for low-size interferometers. This novel interference scheme demonstrates high visibility even at millivolt imbalances and survives in a wide temperature range.Comment: As accepted by PR

Transverse rectification in density-modulated two-dimensional electron gases

We demonstrate tunable transverse rectification in a density-modulated two-dimensional electron gas (2DEG). The density modulation is induced by two surface gates, running in parallel along a narrow stripe of 2DEG. A transverse voltage in the direction of the density modulation is observed, i.e. perpendicular to the applied source-drain voltage. The polarity of the transverse voltage is independent of the polarity of the source-drain voltage, demonstrating rectification in the device. We find that the transverse voltage $U_{y}$ depends quadratically on the applied source-drain voltage and non-monotonically on the density modulation. The experimental results are discussed in the framework of a diffusion thermopower model.Comment: 8 pages, 9 figures, published in PR

Monitoring of activated sludge settling ability through image analysis : validation on full-scale wastewater treatment plants

In recent years, a great deal of attention has been focused on the research of activated sludge processes, where the solid–liquid separation phase is frequently considered of critical importance, due to the different problems that severely affect the compaction and the settling of the sludge. Bearing that in mind, in this work, image analysis routines were developed in Matlab environment, allowing the identification and characterization of microbial aggregates and protruding filaments in eight different wastewater treatment plants, for a combined period of 2 years. The monitoring of the activated sludge contents allowed for the detection of bulking events proving that the developed image analysis methodology is adequate for a continuous examination of the morphological changes in microbial aggregates and subsequent estimation of the sludge volume index. In fact, the obtained results proved that the developed image analysis methodology is a feasible method for the continuous monitoring of activated sludge systems and identification of disturbances.Empresa de Águas, Efluentes e Resíduos de Braga, Portugal - EM (AGERE)Fundação para a Ciência e a Tecnologia (FCT

Options for Producing a Warm-Water Fish in the UK: limits to "Green-Growth"?

This paper explores the development of a sustainable production system for tilapia and the research implications involved with ensuring commercial viability of such a system for UK farmers. The tilapia is a warm water fish with firm texture, white flesh and mild taste quite similar to a cod or haddock. Whilst tropical in origin it is thought to be highly suitable for low cost aquaculture in temperate zones with the potential to be a more sustainable source of food with fewer environmental impacts than other substitutes. Drawing on a literature review and findings from technical trials the paper will review and compare two production systems - novel Activated Suspension Technology (AST) and conventional Recirculating Aquaculture Systems (RAS) - considering their feasibility in terms of potential and financial viability for scaling up to commercial production of tilapia and their environmental and sustainability benefits. The review concludes that AST based only on microbial floc is currently uncompetitive with RAS in a UK context although the approach has benefits that might be incorporated in a new generation of mixed systems. Refinement of such systems needs to occur with potential adopters and could be part of diversification of mixed farms. Such development might further enhance the ethical values of fish produced in small-scale, modular RAS

Quantitative image analysis for the characterization of microbial aggregates in biological wastewater treatment : a review

Quantitative image analysis techniques have gained an undeniable role in several fields of research during the last decade. In the field of biological wastewater treatment (WWT) processes, several computer applications have been developed for monitoring microbial entities, either as individual cells or in different types of aggregates. New descriptors have been defined that are more reliable, objective, and useful than the subjective and time-consuming parameters classically used to monitor biological WWT processes. Examples of this application include the objective prediction of filamentous bulking, known to be one of the most problematic phenomena occurring in activated sludge technology. It also demonstrated its usefulness in classifying protozoa and metazoa populations. In high-rate anaerobic processes, based on granular sludge, aggregation times and fragmentation phenomena could be detected during critical events, e.g., toxic and organic overloads. Currently, the major efforts and needs are in the development of quantitative image analysis techniques focusing on its application coupled with stained samples, either by classical or fluorescent-based techniques. The use of quantitative morphological parameters in process control and online applications is also being investigated. This work reviews the major advances of quantitative image analysis applied to biological WWT processes.The authors acknowledge the financial support to the project PTDC/EBB-EBI/103147/2008 and the grant SFRH/BPD/48962/2008 provided by Fundacao para a Ciencia e Tecnologia (Portugal)