Mini-Publics as an innovation in spatial governance

Mini-publics—deliberative fora made up of randomly selected, representative groups of citizens—have attracted considerable interest as a means of resolving perceived weaknesses in existing forms of governance. In this paper, we consider the use of a mini-public or citizens’ assembly to constitute an ad hoc governance space based on the Travel to Work Area of Cambridge in the United Kingdom rather than working within the existing local government boundaries within which transport infrastructure is usually governed. Through this case study, we explore the question of embedding mini-publics in the wider processes of policy and decision-making. More specifically this is the question of the extent to which they ought to be permitted to inform and even assume responsibility for local-level transport policy decisions. We argue that, if they are to become more widely used, then it will be necessary to understand the practices associated with such democratic experiments and their potential to transform existing governance networks in contested areas of spatial policy

Electron localisation in static and time-dependent one-dimensional model systems

Electron localization is the tendency of an electron in a many-body system to exclude other electrons from its vicinity. Using a new natural measure of localization based on the exact manyelectron wavefunction, we find that localization can vary considerably between different ground-state systems, and can also be strongly disrupted, as a function of time, when a system is driven by an applied electric field. We use our new measure to assess the well-known electron localization function (ELF), both in its approximate single-particle form (often applied within density-functional theory) and its full many-particle form. The full ELF always gives an excellent description of localization, but the approximate ELF fails in time-dependent situations, even when the exact Kohn-Sham orbitals are employed.Comment: 7 pages, 4 figure

Energy versus electron transfer in organic solar cells: a comparison of the photophysics of two indenofluorene: fullerene blend films

In this paper, we compare the photophysics and photovoltaic device performance of two indenofluorene based polymers: poly[2,8-(6,6,12,12-tetraoctylindenofluorene)-co-4,7-(2,1,3-benzothiodiazole] (IF8BT) and poly[2,8-(6,6,12,12-tetraoctylindenofluorene)-co-5,5-(40,70-di-2-thienyl-20,10,30-benzothiodiazole] (IF8TBTT) blended with [6,6]-phenyl C61 butyric acid methyl ester (PCBM). Photovoltaic devices made with IF8TBTT exhibit greatly superior photocurrent generation and photovoltaic efficiency compared to those made with IF8BT. The poor device efficiency of IF8BT/PCBM devices is shown to result from efficient, ultrafast singlet F€orster energy transfer from IF8BT to PCBM, with the resultant PCBM singlet exciton lacking sufficient energy to drive charge photogeneration. The higher photocurrent generation observed for IF8TBTT/PCBM devices is shown to result from IF8TBTT’s relatively weak, red-shifted photoluminescence characteristics, which switches off the polymer to fullerene singlet energy transfer pathway. As a consequence, IF8TBTT singlet excitons are able to drive charge separation at the polymer/fullerene interface, resulting in efficient photocurrent generation. These results are discussed in terms of the impact of donor/acceptor energy transfer upon photophysics and energetics of charge photogeneration in organic photovoltaic\ud devices. The relevance of these results to the design of polymers for organic photovoltaic applications is also discussed, particularly with regard to explaining why highly luminescent polymers developed for organic light emitting diode applications often give relatively poor performance in organic photovoltaic devices

Role of long-range exact exchange in polaron charge transition levels: The case of MgO

Predicting the degree of localization and calculating the trapping energies of polarons in insulators by density functional theory (DFT) is challenging. Hybrid functionals are often reparametrized to obtain accurate results and the a priori selection of these parameters is still an open question. Here we test the accuracy of several range-separated hybrid functionals, all reparametrized to produce an accurate band gap, by calculating the charge transition levels (CTLs) of experimentally well-studied hole polaron defect centers in MgO. We show that the functional with screened long-range exact exchange is moderately but consistently more accurate than functionals which do not include long-range exact exchange. We provide evidence that the source of the improved accuracy is the eigenvalue associated with the valence band maximum of the bulk material. We discuss the extent to which this accuracy relates to Koopmans' compliance of the defect energy level

What are the Characteristics of Respondents using Different Devices in Mixed-device Online Surveys? Evidence from Six UK Surveys

There is a move towards online data collection across the world. Online survey response is complicated by respondents using different devices. So far, no research has been conducted in the UK to study characteristics of people using different devices in mixed‐device online surveys. This analysis uses all publicly available UK social surveys with an online component: Understanding Society Innovation Panel, Community Life Survey, European Social Survey, 1958 National Child Development Study and the Second Longitudinal Study of Young People in England. Descriptive analysis and logistic regressions are used to explore significant correlates of device use in online surveys. The results of bivariate analysis suggest that age, gender, marital status, employment, religion, household size, children in household, household income, number of cars and frequency of internet use are significantly associated with device used across surveys. The associations with age, gender, employment status, household size and education are consistent with the findings from other countries. The knowledge about respondents' characteristics using different devices in online surveys in the UK will help to understand better the response process in online surveys and to target certain subgroups more effectively. It is also important for designs of online surveys, understanding of data quality and post‐survey adjustments

Materials-to-applications evaluation framework: assessing memristor technologies for neural network implementations

Practical needs in technology capability assessment for extremely low-energy neuromorphic computing is addressed via a novel development/analysis concept integrating atomic-level material modeling, statistical simulations of charge transport in a device material stack and verification of the modeling scheme against measurements emulating circuitry operation conditions for applications in specific neural networks (NN). This multi-scale concept - from materials to applications - directly links materials to their electrical properties, and the latter to NN algorithms. Such link enables identifying structural features controlling device characteristics and the range of operation conditions delivering performance targets for a given technology implementation. In comparison to widely employed memristor analyses primarily based on TCAD-type methodology with adjustable phenomenological parameters, the proposed approach allows to deliver feedback on favorable material compositions and cell architecture/dimensions to modify memristor fabrication process. Implementation of this technology evaluation approach to carbon nanotube (CNT) memristors enables identifying structural and operation conditions delivering optimal performance ahead of actual circuitry fabrication

Light-intensity and thickness dependent efficiency of planar perovskite solar cells: charge recombination versus extraction

Photoactive layer thickness is a key parameter for optimization of photovoltaic power conversion efficiency (PCE), yet its impact on charge extraction and recombination hasn’t been fully understood in perovskite solar cells (PSCs). Herein we find that in planar PSCs the perovskite thickness yielding maximal PCE is strongly light-intensity dependent. Whilst under 1 sun irradiation the PCE is relatively invariant for perovskite thicknesses between 250 to 750 nm, at lower light intensities (0.1–0.5 sun) the thickest devices yield strongly enhanced PCE, but at higher light intensities (>1 sun) the thinnest devices give optimal PCE. Our results unravel that increased perovskite thickness leads to enhanced light absorption, reduced interfacial recombination at open circuit but greater bimolecular recombination losses at short circuit thus is suitable for devices working under weak illumination, typical of many real-world applications. Reducing perovskite thickness, however, shows the contrast trend and is suitable for PSCs working under concentrated illumination