Government by experiment? Global cities and the governing of climate change

In this paper, we argue for an approach that goes beyond an institutional reading of urban climate governance to engage with the ways in which government is accomplished through social and technical practices. Central to the exercise of government in this manner, we argue, are ‘climate change experiments’– purposive interventions in urban socio-technical systems designed to respond to the imperatives of mitigating and adapting to climate change in the city. Drawing on three different concepts – of governance experiments, socio-technical experiments, and strategic experiments – we first develop a framework for understanding the nature and dynamics of urban climate change experiments. We use this conceptual analysis to frame a scoping study of the global dimensions of urban climate change experimentation in a database of 627 urban climate change experiments in 100 global cities. The analysis charts when and where these experiments occur, the relationship between the social and technical aspects of experimentation and the governance of urban climate change experimentation, including the actors involved in their governing and the extent to which new political spaces for experimentation are emerging in the contemporary city. We find that experiments serve to create new forms of political space within the city, as public and private authority blur, and are primarily enacted through forms of technical intervention in infrastructure networks, drawing attention to the importance of such sites in urban climate politics. These findings point to an emerging research agenda on urban climate change experiments that needs to engage with the diversity of experimentation in different urban contexts, how they are conducted in practice and their impacts and implications for urban governance and urban life

WALK THE PIPELINE: Urban infrastructure landscapes in Bengaluru's long twentieth century

Walking reveals how urban infrastructure lends identity to the urban landscape. This article focuses on the oldest water pipeline in the city of Bengaluru, India. A series of vignettes trace the linear trajectory of the walk both in terms of the spatial orientation of the pipeline, and its trajectory through time. Through space, the pipeline connects the centre of the city with its suburbs, tracking differential and sometimes invisible patterns of urbanization that follow the city's sprawl. Through time, the pipeline connects water narratives, from nostalgic notions of precolonial management to the contemporary construction of scarcity. The use of walking as a methodological tool draws attention to the subsumed and often invisible experiences of inequity in various parts of the city. The pipeline is a maker of urban stories alongside routine practices and larger strategic projects of urban development. While the pipeline enables the provision of water, the neighbourhoods it passes through are sometimes excluded from the service it provides. Strategic projects have attempted to control water resources following different ways of imagining the city. Still, such urban imaginations coexist with a more extensive set of everyday practices that engage with the pipeline in the urban landscape

Electrical characterization of atomic-layer-deposited hafnium oxide films from hafnium tetrakis(dimethylamide) and water/ozone: Effects of growth temperature, oxygen source, and postdeposition annealing

The electrical properties of HfO2-based metal-insulator- semiconductor capacitors have been systematically investigated by means of I-V and C-V characteristics, admittance spectroscopy, deep level transient spectroscopy, conductance transient, and flat band voltage transient techniques. Attention is also given to the study of the temperature dependence of the leakage current. HfO2 films were grown on p-type silicon substrates by atomic layer deposition using hafnium tetrakis(dimethylamide) as hafnium precursor, and ozone or water as oxygen precursors. The growth temperature ranged from 150 to 350 °C. Low growth temperatures prevent decomposition and high growth rate, as well as high contamination levels. As a result, the leakage current is lower for lower deposition temperatures. Some of the deposited samples were submitted to a postdeposition annealing at 650 °C in N2 atmosphere, showing a decrease in the leakage current and an increase in the equivalent oxide thickness (EOT), whereas interfacial state density increases and defect density inside the dielectric bulk decreases. Regarding dielectric reliability, in our experimental conditions, HfO 2 layers grown at 150 °C exhibit the largest EOT and breakdown voltage. The electrical behaviour is clearly linked with structural properties, and especially with the formation of an interfacial layer between the HfO 2 layer and the silicon substrate, as well as with the presence of several impurities. © 2013 American Vacuum Society.Peer Reviewe

Magnetic stress as a driving force of structural distortions: the case of CrN

We show that the observed transition from rocksalt to orthorhombic P$_{nma}$ symmetry in CrN can be understood in terms of stress anisotropy. Using local spin density functional theory, we find that the imbalance between stress stored in spin-paired and spin-unpaired Cr nearest neighbors causes the rocksalt structure to be unstable against distortions and justifies the observed antiferromagnetic ordering. This stress has a purely magnetic origin, and may be important in any system where the coupling between spin ordering and structure is strong.Comment: 4 pages (two columns) 4 figure

Monte Carlo simulation of subsurface ordering kinetics in an fcc-alloy model

Within the atom-vacancy exchange mechanism in a nearest-neighbor interaction model we investigate the kinetics of surface-induced ordering processes close to the (001) surface of an fcc A_3B-alloy. After a sudden quench into the ordered phase with a final temperature above the ordering spinodal, T_f > T_sp, the early time kinetics is dominated by a segregation front which propagates into the bulk with nearly constant velocity. Below the spinodal, T_f < T_sp, motion of the segregation wave reflects a coarsening process which appears to be slower than predicted by the Lifschitz-Allen-Cahn law. In addition, in the front-penetrated region lateral growth differs distinctly from perpendicular growth, as a result of the special structure of antiphase boundaries near the surface. Our results are compared with recent experiments on the subsurface ordering kinetics at Cu_3Au (001).Comment: 10 pages, 9 figures, submitted to Phys. Rev. B, in prin

Energy levels distribution in supersaturated silicon with titanium for photovoltaic applications

In the attempt to form an intermediate band in the bandgap of silicon substrates to give it the capability to absorb infrared radiation, we studied the deep levels in supersaturated silicon with titanium. The technique used to characterize the energy levels was the thermal admittance spectroscopy. Our experimental results showed that in samples with titanium concentration just under Mott limit there was a relationship among the activation energy value and the capture cross section value. This relationship obeys to the well known Meyer-Neldel rule, which typically appears in processes involving multiple excitations, like carrier capture/emission in deep levels, and it is generally observed in disordered systems. The obtained characteristic Meyer-Neldel parameters were Tmn = 176 K and kTmn = 15 meV. The energy value could be associated to the typical energy of the phonons in the substrate. The almost perfect adjust of all experimental data to the same straight line provides further evidence of the validity of the Meyer Neldel rule, and may contribute to obtain a deeper insight on the ultimate meaning of this phenomenon. (C) 2015 AIP Publishing LLC

Giant multicaloric response of bulk Fe49Rh51

We report on the multicaloric response of the Fe49Rh51 alloy under the combined application of hydrostatic pressure and magnetic field. Experimental data are complemented by a mean field model that takes into account the interplay between structural and magnetic degrees of freedom. A large multicaloric strength has been found for this alloy, and it is shown that a suitable combination of pressure and magnetic field enables the sign of the entropy change to be reversed and thus the multicaloric effect can be tuned from conventional to inverse. It is also shown that an extended temperature window for the multicaloric effect can be achieved by taking advantage of the coupling between structure and magnetism which enables a cross response of the alloy under the application of different external fields. Mean field calculations remarkably reproduce experimental results

2 MeV electron irradiation effects on the electrical characteristics of metal-oxide-silicon capacitors with atomic layer deposited Al<inf>2</inf>O <inf>3</inf>, HfO<inf>2</inf> and nanolaminated dielectrics

The effects of 2 MeV electron irradiation on the electrical characteristics of atomic layer deposited (ALD) high permittivity (high-k) layers of Al 2O3, HfO2 and a nanolaminate of them are evaluated. Metal-oxide-semiconductor capacitors with a nominal dielectric physical thickness of 10 nm were fabricated on different p-type and n-type silicon substrates. The capacitance-voltage (C-V) and current-voltage (I-V) characteristics of the different structures are analyzed as a function of electron irradiation. A progressive negative shift of the C-V characteristics is observed with increasing electron irradiation, indicating the generation of effective positive charges. Similar generation rates for effective trapped charges and interface states are obtained for all the different high-k dielectric layers studied. The hysteresis of the C-V curves after irradiation increases in the case of Al2O3 samples, for HfO 2 decreases while the irradiation has little impact on the hysteresis of the nanolaminate stack. A progressive increase of the leakage current with electron irradiation dose is observed for all the studied dielectrics. The analysis of the current-voltage characteristics measured at different temperatures point to Poole-Frenkel as the dominant conduction mechanism. Under the studied conditions, no impact of electron irradiation fluence on dielectric breakdown voltage has been appreciated. © 2012 Elsevier Ltd. All rights reserved.Peer reviewe

Transformative capacity and local action for urban sustainability.

There is a consensus about the strategic importance of cities and urban areas for achieving a global transformation towards sustainability. While there is mounting interest in the types of qualities that increase the capacity of urban systems to attain deep transformations, empirical evidence about the extent to which existing institutional and material systems exhibit transformative capacity is lacking. This paper thereby seeks to determine the extent to which sustainability initiatives led by local governments and their partners reflect the various components that the literature claims can influence the emergence of transformative capacity as a systemic property of urban settings. Using an evaluative framework consisting of ten components of transformative capacity and associated indicators, the specific objective is to identify patterns in these initiatives regarding the presence of individual components of transformative capacity and their interrelations with other components. The analysis of 400 sustainability initiatives reveals thin evidence of transformative capacity. When detected, evidence of transformative capacity tended to emerge in relation to wider processes of institutional- and social-learning and initiatives that linked outcomes to a city-wide vision of planning and development. However, instances of such initiatives were rare. This widespread lack of evidence for transformative capacity raises concerns that this set of attributes normalised in the literature is in fact rarely found in sustainability action on the ground