Hidden polymorphism of FAPbI3 discovered by Raman spectroscopy

Formamidinium lead iodide FAPbI3 can be used in its cubic, black form as a light absorber material in single junction solar cells. It has a band gap 1.5 eV close to the maximum of the Shockley Queisser limit, and reveals a high absorption coefficient. Its high thermal stability up to 320 C has also a downside, which is the instability of the photo active form at room temperature RT . Thus, the black amp; 945; phase transforms at RT with time into a yellow non photo active amp; 948; phase. The black phase can be recovered by annealing of the yellow state. In this work, a polymorphism of the amp; 945; phase at room temperature was found as synthesized amp; 945;i , degraded amp; 945; amp; 948; and thermally recovered amp; 945;rec . They differ in the Raman spectra and PL signal, but not in the XRD patterns. Using temperature dependent Raman spectroscopy, we identified a structural change in the amp; 945;i polymorph at ca. 110 C. Above 110 C, the FAPbI3 structure has undoubtedly cubic Pm[3 with combining macron]m symmetry high temperature phase amp; 945;HT . Below that temperature, the amp; 945;i phase was suggested to have a distorted perovskite structure with Im[3 with combining macron] symmetry. Thermally recovered FAPbI3 amp; 945;rec also demonstrated the structural transition to amp; 945;HT at the same temperature ca. 110 C during its heating. The understanding of hybrid perovskites may bring additional assets in the development of new and stable structure

Unsettling planning theory

Recent political developments in many parts of the world seem likely to exacerbate rather than ameliorate the planetary-scale challenges of social polarization, inequality and environmental change societies face. In this unconventional multi-authored essay, we therefore seek to explore some of the ways in which planning theory might respond to the deeply unsettling times we live in. Taking the multiple, suggestive possibilities of the theme of unsettlement as a starting point, we aim to create space for reflection and debate about the state of the discipline and practice of planning theory, questioning what it means to produce knowledge capable of acting on the world today. Drawing on exchanges at a workshop attended by a group of emerging scholars in Portland, Oregon in late 2016, the essay begins with an introduction section exploring the contemporary resonances of ‘unsettling’ in, of and for planning theory. This is followed by four, individually authored responses which each connect the idea of unsettlement to key challenges and possible future directions. We end by calling for a reflective practice of theorizing that accepts unsettlement but seeks to act knowingly and compassionately on the uneven terrain that it creates

Rents, knowledge and neo-structuralism: transforming the productive matrix in Ecuador

This paper explores the relationship between ground rent, production and knowledge in Ecuador’s neo-structuralist, state-led project to transform the productive matrix. Based upon insights from the Marxian approach to the critique of political economy, we interrogate how neo-structuralism has conceptualised the relationship between ‘natural resource income’ and ‘knowledge-based’ economic development. The paper argues that a rent-theoretical perspective, which takes seriously the regional unfolding of uneven geographical development in Latin America, can highlight the limits of a national development plan conceived according to the logic of Schumpeterian efficiency. In doing so, the paper identifies the contradictory relationship between natural resource exports, state-led ‘knowledge’-based development and capital accumulation. On this basis the paper offers a historically and empirically informed critical analysis of selective import substitution industrialisation and vanguard science and technology strategies designed to transition Ecuador away from primary resource dependence

Deconstructing spatial planning: reinterpreting the articulation of a new ethos for English local planning

This article reviews recent debates about the emergence of “spatial planning” as a new ethos for English planning, suggesting that continued uncertainty around the term's use is partly caused by a failure to consider its emergence as the product of a contested political process. Drawing on an interpretive approach to policy analysis, the article goes on to show how this new organizing principle is a complex articulation of different and potentially contradictory reform impulses. The result is to destabilize the concept of spatial planning, showing how it has been constructed as an “empty signifier”, an unstable and tension-filled discursive stake in an ongoing politics of reform. Finally, it is argued that this has significant implications for the ways in which implementation success and failure should be understood and for analysis of planning reform initiatives and systems more widely

Structural characterization of Cu2SnS3 and Cu2 Sn,Ge S3 compounds

Cu2SnS3 CTS and Cu2Sn0.83Ge0.17S3 CTGS compounds were successfully prepared by a powder technology using a combination of mechanical alloying MA and spark plasma sintering SPS . Structural, compositional and optical properties were studied. A true alloy with composition similar to the starting constituents was formed after 2 h of MA at 400 rpm. Subsequently, SPS was performed at 600 C for 5 min under a pressure of 50 MPa. The Cu Sn Ge composition ratios of the MA and SPS materials, determined by wavelength dispersive X ray spectroscopy, are in the range of 1.84 1.94. Rietveld refinements of the powder X ray diffraction data show a good agreement with the monoclinic crystal structure already for the MA materials. No structural changes were observed after SPS. Raman measurements coincide with XRD results in the identification of the characteristic peaks from phonon vibrational modes of monoclinic CTS phase. Band gaps between 1.24 eV and 1.34 eV were determined by diffuse reflectance for the mechanically alloyed and sintered sample

Intranasal sodium citrate in quantitative and qualitative olfactory dysfunction: results from a prospective, controlled trial of prolonged use in 60 patients

Objectives!#!We have previously shown that treatment with intranasal sodium citrate may be beneficial in post-infectious olfactory dysfunction. Sodium citrate reduces free intranasal calcium and is, therefore, thought to prevent calcium-mediated feedback inhibition at the level of the olfactory receptor. We aimed to determine whether treatment with a 2-week course of intranasal sodium citrate improves quantitative olfactory function in patients with post-infectious impairment. We also aimed to determine whether sodium citrate is beneficial in treating qualitative olfactory dysfunction.!##!Methods!#!We performed a prospective, controlled study. Patients applied intranasal sodium citrate solution to the right nasal cavity for 2 weeks. The left nasal cavity was untreated and, therefore, acted as an internal control. Monorhinal olfactory function was assessed using the 'Sniffin' Sticks' composite 'TDI' score, before and after treatment. The presence of parosmia and phantosmia was also assessed.!##!Results!#!Overall, there was a significant increase in TDI after treatment (using the best of right and left sides). Treatment with sodium citrate did not significantly improve quantitative olfactory function, compared to control. The proportion of patients reporting parosmia did not change significantly after treatment. However, there was a significant reduction in the proportion of patients reporting phantosmia, at the end of the study period.!##!Conclusions!#!Treatment with intranasal sodium citrate for a period of 2 weeks does not appear to improve quantitative olfactory function in patients with post-infectious impairment, compared to control. It may, however, be beneficial in treating phantosmia, which should be further addressed in future work