Social information use and the evolution of unresponsiveness in collective systems

Animal groups in nature often display an enhanced collective information-processing capacity. It has been speculated that natural selection will tune this response to be optimal, ensuring that the group is reactive while also being robust to noise. Here, we show that this is unlikely to be the case. By using a simple model of decision-making in a dynamic environment, we find that when individuals behave rationally and are subject to selection based on their accuracy, optimality of collective decision-making is not attained. Instead, individuals overly rely on social information and evolve to be too readily influenced by their neighbours. This is due to a classic evolutionary conflict between individual and collective interest. The result is a sub-optimal system that is poised on the cusp of total unresponsiveness. Individuals in the evolved group exhibit delayed reactions to changes in the environment, before responding with rapid, socially reinforced transitions, reminiscent of familiar human and animal social systems (markets, stampedes, fashions, etc.). Our results demonstrate that behaviour of this type may not be pathological, but instead could represent an evolutionary attractor for such collective systems.     

A simplified model for estimating population-scale energy impacts of building envelope air tightening and mechanical ventilation retrofits

Changing the air exchange rate of a home affects the annual thermal conditioning energy. Large-scale changes to air exchange rates of the housing stock can significantly alter the residential sector's energy consumption. However, the complexity of existing residential energy models is a barrier to the accurate quantification of the impact of policy changes on a state or national level. The Incremental Ventilation Energy (IVE) model introduced here combines the output of simple air exchange models with a limited set of housing characteristics to estimate the associated change in energy demand of homes. The IVE model was designed specifically to enable modellers to use existing databases of housing characteristics to determine the impact of ventilation policy change on a population scale. The IVE model estimates of energy change when applied to US homes with limited parameterization are shown to be comparable to the estimates of a well-validated, complex residential energy model.     

The architecture of the British Mandate in Iraq: nation-building and state creation

This paper seeks to examine and contextualise the architecture and infrastructure projects developed by the British during the occupation of Iraq in the First World War and the Mandate period that immediately followed. Relying heavily on military-political events for its structure and underlying narrative, the paper demonstrates how architecture, planning and ‘development’ were integral to the act of creating the new state and were very much part of the colonisers’ vision to create a nation in their own image. Works were deployed to imbue a sense of collective belonging and national identity through the creation of new town plans, as well as through institutions such as museums and universities. A certain dissonance emerges between the infrastructure and prestige projects, with the latter presenting an imagined and fabricated notion of Iraqi history, blended with a grandiose colonial style imported from India, and designed predominantly by James M. Wilson. The infrastructure projects began with sanitation improvements, road and rail installation, and expansion of the Basra docklands to attract international shipping and for the export of oil. Further building projects undertaken by the Public Works Department included a large number of administrative buildings called serais. Built at strategic locations, they were deployed as multi-functional centres for justice, taxation and land registration as well as places where local devolved empowerment was instigated. Iraqi architecture from this period has been largely overlooked in the emerging global histories of architecture, yet it offers an important view of the quandaries that faced late British colonial architecture in its attempts to respond to, and reflect changing and hostile political conditions.     

The Limehouse Link: the architectural and cultural history of a monumental road tunnel in London's Docklands

In the Docklands area of London lies the ‘Limehouse Link’, a dual-bore road tunnel used by around 80,000 cars each day. A monumental and highly expensive piece of construction, the Limehouse Link has nonetheless received almost no attention from architectural historians or others concerned with the history of construction, engineering or urban development.

This article provides an introduction to the Limehouse Link, explaining some of the fundamental characteristics of its construction and position in London's urban landscape. More importantly, the article then considers how one might understand an everyday yet monumental construction such as this: a tunnel without obvious aesthetic form, design intent or symbolic meaning, but which nonetheless has an undeniable presence in the city. The Limehouse Link is therefore interpreted in terms of the car driver's immersive experience of the tunnel, more active constructions of this experience through sensory qualities of sound, representations of the tunnel in different media and art, ways of knowing the history of Limehouse, and, in particular, as a kind of aesthetic experience. The article concludes that driving through the Limehouse Link is to engage in a different way of knowing the postmodern city.     

Tropical Architecture and the West Indies: from military advances and tropical medicine,to Robert Gardner-Medwin and the networks of tropical modernism

The history of modern Tropical Architecture has largely focused on the region of West Africa, however this paper demonstrates that additional strains were being developed elsewhere, preceding the African examples. Indeed, Tropical Architecture, far from being a mid-twentieth century phenomenon, has a much longer history, stretching back into the colonial settlements of the eighteenth century and continued by the tropical medicine contributions of the early twentieth century, particularly in the British West Indies. This paper considers some of these early examples, before investigating the work produced by Robert Gardner-Medwin, along with his small team that included Leo De Syllas and Gordon Cullen, during the Second World War in the West Indies. Their work there as part of the ‘development and welfare’ programme was considered, ‘building research’, concerned with materials, pragmatic decisions and housing, and, whilst it was unacknowledged at the time, was clearly indebted to the earlier military and hygiene models. Nevertheless, the work they undertook was highly influential in the development of modern tropical architecture, and in particular the buildings that were later produced in West Africa: it helped to formalise this canon, and unified the previously fragmented and disparate out-workings of the Metropolis. Gardner-Medwin, therefore, can be considered an agent of Empire, a key-player in the extension of British architects operating as the knowledge makers, not only in the period of colonial rule, but crucially, afterwards. This is further manifest through his involvement in UN housing missions to South East Asia and his contribution to the Tropical Architecture Conference held at University College, London, in 1953.     

The limited role for Carbon Capture and Storage (CCS) technologies in a sustainable Australian energy future

There is considerable debate regarding the potential role of Carbon Capture and Storage (CCS) technologies in reducing Australia's greenhouse emissions. The latest climate change science suggests that major (60% or more by 2050), rapid (peaking within 20 years) cuts in global emissions may be required to avoid dangerous climate change. There are a number of existing abatement options including energy efficiency, various renewable energy technologies, nuclear power and fuel switching to natural gas; as well as emerging options including CCS. We outline a simple technology assessment framework for policymakers to evaluate these different options given the climate change imperative. This framework includes technology status, delivered energy services, present and possible future costs, potential scale of abatement, potential speed of deployment and other possible social outcomes. Application of this framework to CCS suggests that it should be considered as a promising, but still somewhat unproven, option that potentially offers very significant abatement potential and good integration into the existing energy industry. There are, however, some outstanding questions regarding its effectiveness and safety, its abatement is likely to come at significant cost, and it is unlikely to be able to make a significant contribution for well over a decade. The Australian policy implications are that while government support for R&D and Demonstration of CCS is appropriate and should in our view be expanded, the major priority should be to support greater deployment of existing abatement options including energy efficiency, efficient gas-fired generation and cogeneration and renewable energy. Such policy support is noticeably lacking at present.     

Systematic Control of the Orientation of Organic Phosphorescent Pt Complexes in Thin Films for Increased Optical Outcoupling

Orienting light‐emitting molecules relative to the substrate is an effective method to enhance the optical outcoupling of organic light‐emitting devices. Platinum(II) phosphorescent complexes enable facile control of the molecular alignment due to their planar structures. Here, the orientation of Pt(II) complexes during the growth of emissive layers is controlled by two different methods: modifying the molecular structure and using structural templating. Molecules whose structures are modified by adjusting the diketonate ligand of the Pt complex, dibenzo‐(f,h)quinoxaline Pt dipivaloylmethane, (dbx)Pt(dpm), show an ≈20% increased fraction of horizontally aligned transition dipole moments compared to (dbx)Pt(dpm) doped into a 4,4′‐bis(N‐carbazolyl)‐1,1′‐biphenyl, CBP, host. Alternatively, a template composed of highly ordered 3,4,9,10‐perylenetetracarboxylic dianhydride monolayers is predeposited to drive the alignment of a subsequently deposited emissive layer comprising (2,3,7,8,12,13,17,18‐octaethyl)‐21H,23H‐porphyrinplatinum(II) doped into triindolotriazine. This results in a 60% increase in horizontally aligned transition dipole moments compared to the film deposited in the absence of the template. The findings provide a systematic route for controlling molecular alignment during layer growth, and ultimately to increase the optical outcoupling in organic light‐emitting diodes.     

A survey of scheduling metrics and an improved ordering policy for list schedulers operating on workloads with dependencies and a wide variation in execution times

This paper considers the dynamic scheduling of parallel, dependent tasks onto a static, distributed computing platform, with the intention of delivering fairness and quality of service (QoS) to users. The key QoS requirement is that responsiveness is maintained for workloads with a wide range of execution times (minutes to months) even under transient periods of overload. A survey of schedule QoS metrics is presented, classified into those dealing with responsiveness, fairness and utilisation. These metrics are evaluated as to their ability to detect undesirable features of schedules. The Schedule Length Ratio (SLR) metric is shown to be the most helpful for measuring responsiveness in the presence of dependencies. A novel list scheduling policy called Projected-SLR is presented that delivers good responsiveness and fairness by using the SLR metric in its scheduling decisions. Projected-SLR is found to perform equally as well in responsiveness, fairness and utilisation as the best of the other scheduling policies evaluated (Shortest Remaining Time First/SRTF), using synthetic workloads and an industrial trace. However, Projected-SLR does this with a guarantee of starvation-free behaviour, unlike SRTF.     

Efficient,high photostability,high brightness,co-polymer solid state dye lasers

Abstract

We report an investigation of the laser beam quality, efficiency and photostability of rhodamine 590 solid state dye lasers with hosts based upon 2-hydroxyethylmethacrylate and methylmethacrylate P(HEMA:MMA) co-polymers and modified methylmethacrylate (MPMMA) polymers with ethanol and dimethylsulphoxide additives. Highest efficiencies were obtained with MPMMA, with slope efficiencies of up to 44% (corresponding to 61% optical-optical conversion) measured for ethanolic MPMMA. P(HEMA:MMA) hosts gave superior photostability, with the highest normalized photostability of 240 GJ mol^?1 obtained for a P(HEMA:MMA) 1:1 rod. A simple resonator has been used to compensate the effects of thermal lensing and pump mode-mismatch, resulting in optimized beam quality for MPMMA lasers.