A solar water heater for remote communities

The RADG has been developing a solar water heater suitable for use in remote areas. The original inspiration for this project was to provide hot water for remote Aboriginal communities. It was felt that a regular and plentiful supply of hot water would encourage showering and laundering and hence improve personal hygiene. Electric, fuel burning and solar water heaters are currently used in some communities. Solar water heaters are attractive for remote areas because they stand alone i.e. they require no external fuel source. Wood has traditionally been used as a fuel by Aboriginal people, but in permanent communities the demand on this resource may have a large impact on the environment. Solar water heaters can help to reduce this demand

On-site wastewater reuse technology options in Australia

Domestic wastewater reuse is currently not permitted anywhere in Australia but is widely supported by the community, promoted by researchers, and improvised by up to 20% of householders. Its widespread implementation will make an enormous contribution to the sustainability of water resources. Integrated with other strategies in the outdoor living environment of settlements in arid lands great benefit will be derived. This paper describes six options for wastewater reuse under research by the Remote Area Developments Group (RADG) at Murdoch University and case studies are given where productive use is being made for revegetation and food production strategies at household and community scales. Pollution control techniques, public health precautions and maintenance requirements are described. The special case of remote Aboriginal communities is explained where prototype systems have been installed by RADG to generate windbreaks and orchards. New Australian design standards and draft guidelines for domestic greywater reuse produced by the Western Australian state government agencies for mainstream communities are evaluated. It is recommended that dry composting toilets be coupled with domestic greywater reuse and the various types available in Australia are described. For situations where only the flushing toilet will suffice the unique "net composting" system can be used and this also is described. A vision for household and community-scale on-site application is presented

Single-photon exchange interaction in a semiconductor microcavity

We consider the effective coupling of localized spins in a semiconductor quantum dot embedded in a microcavity. The lowest cavity mode and the quantum dot exciton are coupled and close in energy, forming a polariton. The fermions forming the exciton interact with localized spins via exchange. Exact diagonalization of a Hamiltonian in which photons, spins and excitons are treated quantum mechanically shows that {\it a single polariton} induces a sizable indirect exchange interaction between otherwise independent spins. The origin, symmetry properties and the intensity of that interaction depend both on the dot-cavity coupling and detuning. In the case of a (Cd,Mn)Te quantum dot, Mn-Mn ferromagnetic coupling mediated by a single photon survives above 1 K whereas the exciton mediated coupling survives at 15 K.Comment: 4 pages, 3 figure

Sustainable urban biophilia: The case of greenskins for urban density

Green infrastructure ameliorates the urban heat island effect, contributes positively to liveability and enables sustainability in higher density urban environments. Greenskins (living architectures) are a more specific form of green infrastructure, including green walls and green roofs, for dense urban areas. These offer a new approach for sustainable urban biophilia and some forms can be built using the ecological design principles of constructed wetlands. The paper compares findings from two urban centres in warm Mediterranean climates. In general from Adelaide, South Australia and more specifically from university collaborative projects on particular technical and social parameters necessary to sustain Greenskins in dense urban conditions in Fremantle, Western Australia. Results from trials of a prototype greywater Greenskin using vertical constructed wetland cells are reported. Through an experimental investigation of designing living green walls in urban Fremantle, this paper challenges the conventional "triple-bottom-line" approach to sustainable dense urban systems by addressing the greater aesthetic needs of sustainability and its thinking. Here landscape aesthetics looks to the collaborative fields of urban design, environmental engineering and landscape architecture to design new urban biophilic experiences and restorative landscapes for regenerative cultural pleasure, ecological responsibility, environmental stewardship and intellectual gain

Transport properties of a two impurity system: a theoretical approach

A system of two interacting cobalt atoms, at varying distances, was studied in a recent scanning tunneling microscope experiment by Bork et. al.[Nature Phys. 7, 901 (2011)]. We propose a microscopic model that explains, for all experimentally analyzed interatomic distances, the physics observed in these experiments. Our proposal is based on the two-impurity Anderson model, with the inclusion of a two-path geometry for charge transport. This many-body system is treated in the finite-U slave boson mean-field approximation and the logarithmic-discretization embedded-cluster approximation. We physically characterize the different charge transport regimes of this system at various interatomic distances and show that, as in the experiments, the features observed in the transport properties depend on the presence of two impurities but also on the existence of two conducting channels for electron transport. We interpret the splitting observed in the conductance as the result of the hybridization of the two Kondo resonances associated with each impurity.Comment: 5 pages, 5 figure