Synthetic factors affecting the stability of methylammonium lead halide perovskite nanocrystals.

Lead halide perovskite nanocrystals (PNCs) have emerged as promising candidates for use in optoelectronic devices. Significant focus has been directed towards optimising synthetic conditions to obtain PNCs with tunable emission properties. However, the reproducible production of stable PNC dispersions is also crucial for fabrication and scale-up of these devices using liquid deposition methods. Here, the stability of methylammonium lead halide (MAPbX3 where X = Br, I) PNCs produced via the ligand-assisted reprecipitation process is explored. We have focussed on understanding how different combinations of specific synthetic factors - dilution, halide source and ratio as well as capping-ligand concentration - affect the stability of the resultant PNC dispersion. Photoluminescence spectroscopy, transmission electron microscopy and dynamic light scattering studies revealed that subtle changes in the reaction conditions lead to significant changes in the particle morphology and associated optical properties, often with catastrophic consequences on stability. This study highlights the importance of designing PNC dispersions in order to make more efficient and reliable optoelectronic devices.This project has received funding from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (grant agreement No. 818762 - SPECTRACON)

Adaptive strategies used by surgical teams under pressure:an interview study among senior healthcare professionals in four major hospitals in the United Kingdom

BackgroundHealthcare systems are operating under substantial pressures, and often simply cannot provide the standard of care they aspire to within the available resources. Organisations, managers, and individual clinicians make constant adaptations in response to these pressures, which are typically improvised, highly variable and not coordinated across clinical teams. The purpose of this study was to identify and describe the types of everyday pressures experienced by surgical teams and the adaptive strategies they use to respond to these pressures.MethodsWe conducted interviews with 20 senior multidisciplinary healthcare professionals from surgical teams in four major hospitals in the United Kingdom. The interviews explored the types of everyday pressures staff were experiencing, the strategies they use to adapt, and how these strategies might be taught to others.ResultsThe primary pressures described by senior clinicians in surgery were increased numbers and complexity of patients alongside shortages in staff, theatre space and post-surgical beds. These pressures led to more difficult working conditions (e.g. high workloads) and problems with system functioning such as patient flow and cancellation of lists. Strategies for responding to these pressures were categorised into increasing or flexing resources, controlling and prioritising patient demand and strategies for managing the workload (scheduling for efficiency, communication and coordination, leadership, and teamwork strategies).ConclusionsTeams are deploying a range of strategies and making adaptations to the way care is delivered. These findings could be used as the basis for training programmes for surgical teams to develop coordinated strategies for adapting under pressure and to assess the impact of different combinations of strategies on patient safety and surgical outcomes

Phase Behaviour and Composition in the Formamidinium-Methylammonium Hybrid Lead Iodide Perovskite Solid Solution

The phase and structural behaviours of the hybrid perovskites FAxMA1−xPbI3as a function of composition and temperature have been determined.</p

Testing metallicity indicators at z~1.4 with the gravitationally lensed galaxy CASSOWARY 20

We present X-shooter observations of CASSOWARY 20 (CSWA 20), a star-forming (SFR ~6 Msol/yr) galaxy at z=1.433, magnified by a factor of 11.5 by the gravitational lensing produced by a massive foreground galaxy at z=0.741. We analysed the integrated physical properties of the HII regions of CSWA 20 using temperature- and density-sensitive emission lines. We find the abundance of oxygen to be ~1/7 of solar, while carbon is ~50 times less abundant than in the Sun. The unusually low C/O ratio may be an indication of a particularly rapid timescale of chemical enrichment. The wide wavelength coverage of X-shooter gives us access to five different methods for determining the metallicity of CSWA 20, three based on emission lines from HII regions and two on absorption features formed in the atmospheres of massive stars. All five estimates are in agreement, within the factor of ~2 uncertainty of each method. The interstellar medium of CSWA 20 only partially covers the star-forming region as viewed from our direction; in particular, absorption lines from neutrals and first ions are exceptionally weak. We find evidence for large-scale outflows of the interstellar medium (ISM) with speeds of up 750 km/s, similar to the values measured in other high-z galaxies sustaining much higher rates of star formation.Comment: 18 pages, 11 figures, accepted for publication in MNRA

In vitro permeation and biological activity of punicalagin and zinc (II) across skin and mucous membranes prone to Herpes simplex virus infection

Coadministration of pomegranate rind extract (PRE) and zinc (II) ions has recently been reported as a potential new topical treatment for Herpes simplex virus (HSV) infections. In the current work we examined the in vitro topical delivery of punicalagin (major phytochemical of PRE) and zinc from hydrogels across epithelial membranes that can become infected with HSV. Porcine epidermal, buccal and vaginal mucous membranes were excised and mounted in Franz diffusion cells and dosed with a simple hydrogel containing PRE and zinc sulphate (ZnSO4). The permeation of punicalagin and zinc were determined by HPLC and ICPMS respectively; punicalagin was also determined in the basal layers by reverse tape stripping. Receptor phases from the epidermal membrane experiment were also used to challenge HSV-1 in Vero host cells, and ex vivo porcine skin was used to probe COX-2 modulation. Punicalagin and zinc permeated each of the three test membranes, with significantly greater amounts of both delivered across the epidermal membrane. The amounts of punicalagin permeating the buccal and vaginal membranes were similar, although the amount of zinc permeating the vaginal membrane was comparatively very large – it is known that zinc interacts with vaginal mucosa. The punicalagin recovered by reverse tape stripping of the epidermal, buccal and vaginal membranes gave 0.47 ± 0.016, 0.45 ± 0.052 and 0.51 ± 0.048 nM cm− 2 respectively, and were statistically the same (p < 0.05). A 2.5 log reduction was achieved against HSV-1 using diffusion cell receptor phase, and COX-2 expression was reduced by 64% in ex vivo skin after 6 h. Overall, a hydrogel containing 1.25 mg mL− 1 PRE and 0.25 M ZnSO4 was able to topically deliver both the major bioactive compound within PRE and Zn (II) across all membranes and into the site specific region of Herpes simplex vesicular clusters, while maintaining potentiated virucidal and anti-inflammatory properties. This novel therapeutic system therefore has potential for the topical treatment of HSV infections

Phase Behavior and Substitution Limit of Mixed Cesium-Formamidinium Lead TriIodide Perovskites

The mixed cation lead iodide perovskite photovoltaics show improved stability following site substitution of cesium ions (Cs+) onto the formamidinium cation sites (FA+) of (CH(NH2)2PbI3 (FAPbI3) and increased resistance to formation of the undesirable ∂-phase. The structural phase behavior of Cs0.1FA0.9PbI3 has been investigated by neutron powder diffraction (NPD), complemented by single crystal and power X-ray diffraction and photoluminescence spectroscopy. The Cs-substitution limit has been determined to be less than 15%, and the cubic α-phase, Cs0.1FA0.9PbI3, is shown to be synthesizable in bulk and stable at 300 K. On cooling the cubic Cs0.1FA0.9PbI3, a slow, second-order cubic to tetragonal transition is observed close to 290 K, with variable temperature NPD indicating the presence of the tetragonal β-phase, adopting the space group P4/mbm between 290 and 180 K. An orthorhombic phase or twinned tetragonal phase is formed below 180 K, and the temperature for further transition to a disordered state is lowered to 125 K compared to that seen in phase pure α-FAPbI3 (140 K). These results demonstrate the importance of understanding the effect of cation site substitution on structure–property relationships in perovskite materials

Equal Footing of Thermal Expansion and Electron–Phonon Interaction in the Temperature Dependence of Lead Halide Perovskite Band Gaps

Lead halide perovskites, which are causing a paradigm shift in photovoltaics, exhibit an atypical temperature dependence of the fundamental gap: it decreases in energy with decreasing temperature. Reports ascribe such a behavior to a strong electron–phonon renormalization of the gap, neglecting contributions from thermal expansion. However, high-pressure experiments performed on the archetypal perovskite MAPbI₃ (MA stands for methylammonium) yield a negative pressure coefficient for the gap of the tetragonal room-temperature phase, which speaks against the assumption of negligible thermal expansion effects. Here we show that for MAPbI₃ the temperature-induced gap renormalization due to electron–phonon interaction can only account for about 40% of the total energy shift, thus implying thermal expansion to be more if not as important as electron–phonon coupling. Furthermore, this result possesses general validity, holding also for the tetragonal or cubic phase, stable at ambient conditions, of most halide perovskite counterparts

CHoosing Active Role Models to INspire Girls (CHARMING): protocol for a cluster randomised feasibility trial of a school-based, community-linked programme to increase physical activity levels in 9-10-year-old girls.

BACKGROUND: In the UK, there is evidence that girls' physical activity tends to decline to a greater extent than boys as they enter adolescence. 'Role models' could play a vital role in inspiring girls to become or remain physically active. The CHARMING Programme is a primary school-based community linked role-model programme, co-developed in 2016, with children, parents, schools and wider stakeholders. It involves different types of physical activity delivered for 1-h each week by a community provider and peer role models (e.g. older girls from secondary schools) joining in with the sessions. The programme ultimately aims to increase and sustain physical activity levels among 9-10-year-old girls. This study aims to assess the feasibility and acceptability of the CHARMING Programme and of evaluating it using a randomised trial. METHODS: This study is a feasibility cluster randomised controlled trial, with embedded process evaluation and health economic evaluation. Approximately 90 Year 5 (i.e. 9-10-year-old) girls will be recruited across six primary schools in Mid-South Wales. Participating schools will be allocated to the programme: control on a 2:1 basis; four intervention schools will run the CHARMING Programme and two will continue with usual practice. A survey and accelerometer will be administered at baseline and repeated at 12 months. Interviews and focus groups will be conducted post-intervention delivery. The primary aim is to assess feasibility of a future randomised trial via the recruitment of schools, participants and role models; randomisation; retention; reach; data collection completion rates; programme adherence; and programme fidelity, views on intervention acceptability and programme barriers and facilitators. Secondary aims are to evaluate established physical activity outcome measures for children plus additional health economic outcomes for inclusion in a future full-scale trial. DISCUSSION: The results of this study will inform decisions on whether and how to proceed to a full-scale evaluation of the effectiveness and cost-effectiveness of the CHARMING Programme to improve or sustain physical activity. TRIAL REGISTRATION: ClinicalTrials.gov ISRCTN36223327. Registered March 29, 2021