Enhanced performance in fluorene-free organometal halide perovskite light-emitting diodes using tunable, low electron affinity oxide electron injectors.

Fluorene-free perovskite light-emitting diodes (LEDs) with low turn-on voltages, higher luminance and sharp, color-pure electroluminescence are obtained by replacing the F8 electron injector with ZnO, which is directly deposited onto the CH3NH3PbBr3 perovskite using spatial atmospheric atomic layer deposition. The electron injection barrier can also be reduced by decreasing the ZnO electron affinity through Mg incorporation, leading to lower turn-on voltages.The authors would like to acknowledge funding from the Cambridge Commonwealth, European and International Trusts, Rutherford Foundation of New Zealand, A*STAR National Science Scholarship, Girton College Cambridge, Gates Cambridge Scholarship, EPSRC (Reference: EP/G060738/1), the ERC Advanced Investigator Grant, Novox, ERC-2009-adG 247276 and Cambridge Display Technology.This is the final version of the article. It was first published by Wiley at http://onlinelibrary.wiley.com/doi/10.1002/adma.201405044/abstract

Poor-Grade Aneurysmal Subarachnoid Hemorrhage: Risk Factors Affecting Clinical Outcomes in Intracranial Aneurysm Patients in a Multi-Center Study

Objective: Patients with poor-grade aneurysm subarachnoid hemorrhage (SAH) have commonly been considered to have a poor prognosis. The objective of this study was to investigate the independent risk factors affecting clinical outcomes in intracranial aneurysm patients with poor-grade aneurysm subarachnoid hemorrhage (aSAH) underwent different intervention therapies.Methods: A multicenter observational registry of 324 poor-grade aSAH patients treated at tertiary referral centers from October 2010 to March 2012 were enrolled in this study. The clinical data including patient characteristics on admission and during treatment course, treatment modality, aneurysm size and location, radiologic features, signs of cerebral herniation (dilated pupils), and functional neurologic outcome were collected. Clinical outcomes were assessed via a modified Rankin Scale at 12 months. Multivariate logistic regression models were used to develop prognostic models. The area under the receiver operator characteristic curves (AUC) and Hosmer-Lemeshow tests were used to assess discrimination and calibration. WAP score was developed to predict risk of poor outcome.Results: Older age, female gender, ventilated breathing status, non-reactive pupil response, pupil dilation, lower GCS score, a WFNS grade of V, intraventricular hemorrhage, a higher Fisher grade, a higher modified Fisher grade, and conservative treatment were calculated to be associated with a relatively poor outcome. Multivariate analyses revealed that older age, lower Glasgow coma scale score (GCS), the absence of pupillary reactivity, higher modified Fisher grade, and conservative treatment were independent predictors of poor outcome, showed good discrimination and calibration. Patients with WFNS grade V, older age and non-reactive pupillary reactivity were predicted to have a poor outcome by WAP risk score.Conclusions: A simple WAP risk score had good discrimination and calibration in the prediction of outcome. The risk score can be easily measured and may complement treatment decision-making

Efficient light-emitting diodes based on nanocrystalline perovskite in a dielectric polymer matrix.

Electroluminescence in light-emitting devices relies on the encounter and radiative recombination of electrons and holes in the emissive layer. In organometal halide perovskite light-emitting diodes, poor film formation creates electrical shunting paths, where injected charge carriers bypass the perovskite emitter, leading to a loss in electroluminescence yield. Here, we report a solution-processing method to block electrical shunts and thereby enhance electroluminescence quantum efficiency in perovskite devices. In this method, a blend of perovskite and a polyimide precursor dielectric (PIP) is solution-deposited to form perovskite nanocrystals in a thin-film matrix of PIP. The PIP forms a pinhole-free charge-blocking layer, while still allowing the embedded perovskite crystals to form electrical contact with the electron- and hole-injection layers. This modified structure reduces nonradiative current losses and improves quantum efficiency by 2 orders of magnitude, giving an external quantum efficiency of 1.2%. This simple technique provides an alternative route to circumvent film formation problems in perovskite optoelectronics and offers the possibility of flexible and high-performance light-emitting displays.The authors acknowledge funding from the Gates Cambridge Trust, the Singapore National Research Foundation (Energy Innovation Programme Office), the KACST-Cambridge University Joint Centre of Excellence, the Royal Society/Sino-British Fellowship Trust, and the Engineering and Physical Sciences Research Council, UK. We also thank Dr. Alessandro Sepe for helpful discussions of the XRD data.This is the final version of the article. It first appeared from ACS via http://dx.doi.org/10.1021/acs.nanolett.5b0023

Highly-Efficient Perovskite Nanocrystal Light-Emitting Diodes Enabled by a Universal Cross-linking Method

This work was supported by the EPSRC [Grant numbers EP/M005143/1, EP/J017361/1 and EP/G037221/1]. G.L. thanks Gates Cambridge Trust for funding. F.W.R.R. is grateful for financial support from CNPq [Grant number 246050/2012-8]. N.J.L.K.D. thanks the Cambridge Commonwealth European and International Trust, Cambridge Australian Scholarships and Mr Charles K. Allen for financial support. F.W.R.R., F.D.P. and C.D. acknowledge funding from the ERC under grant number 259619 PHOTO-EM. C.D. acknowledges financial support from the EU under grant number 312483 ESTEEM2. F.G. acknowledges financial support from the Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linköping University.This is the final version of the article. It first appeared from Wiley via https://doi.org10.1002/adma.20160006

Size-Dependent Photon Emission from Organometal Halide Perovskite Nanocrystals Embedded in an Organic Matrix.

In recent years, organometal halide perovskite materials have attracted significant research interest in the field of optoelectronics. Here, we introduce a simple and low-temperature route for the formation of self-assembled perovskite nanocrystals in a solid organic matrix. We demonstrate that the size and photoluminescence peak of the perovskite nanocrystals can be tuned by varying the concentration of perovskite in the matrix material. The physical origin of the blue shift of the perovskite nanocrystals’ emission compared to its bulk phase is also discussed.D.D. acknowledges the Department of Physics, University of Cambridge and the KACST-Cambridge University Joint Centre of Excellence for financial support. G.L. thanks the Gates Cambridge Trust for support. Q.S. acknowledges the Imperial College Junior Research Fellowship. J.L.M.D. acknowledges ERC Advanced Investigator Grant, Novox, ERC-2009-adG247276. This work was supported by the Engineering and Physical Sciences Research Council, UK.This is the final published version. It first appeared at http://pubs.acs.org/doi/abs/10.1021/jz502615e

Bright light-emitting diodes based on organometal halide perovskite.

Solid-state light-emitting devices based on direct-bandgap semiconductors have, over the past two decades, been utilized as energy-efficient sources of lighting. However, fabrication of these devices typically relies on expensive high-temperature and high-vacuum processes, rendering them uneconomical for use in large-area displays. Here, we report high-brightness light-emitting diodes based on solution-processed organometal halide perovskites. We demonstrate electroluminescence in the near-infrared, green and red by tuning the halide compositions in the perovskite. In our infrared device, a thin 15 nm layer of CH3NH3PbI(3-x)Cl(x) perovskite emitter is sandwiched between larger-bandgap titanium dioxide (TiO2) and poly(9,9'-dioctylfluorene) (F8) layers, effectively confining electrons and holes in the perovskite layer for radiative recombination. We report an infrared radiance of 13.2 W sr(-1) m(-2) at a current density of 363 mA cm(-2), with highest external and internal quantum efficiencies of 0.76% and 3.4%, respectively. In our green light-emitting device with an ITO/PEDOT:PSS/CH3NH3PbBr3/F8/Ca/Ag structure, we achieved a luminance of 364 cd m(-2) at a current density of 123 mA cm(-2), giving external and internal quantum efficiencies of 0.1% and 0.4%, respectively. We show, using photoluminescence studies, that radiative bimolecular recombination is dominant at higher excitation densities. Hence, the quantum efficiencies of the perovskite light-emitting diodes increase at higher current densities. This demonstration of effective perovskite electroluminescence offers scope for developing this unique class of materials into efficient and colour-tunable light emitters for low-cost display, lighting and optical communication applications.This is the author accepted manuscript and will be under embargo until 3/2/15. The final version is published in Nature Nanotechnology: http://www.nature.com/nnano/journal/vaop/ncurrent/full/nnano.2014.149.html

Postgraduate ethics training programs: a systematic scoping review

BACKGROUND: Molding competent clinicians capable of applying ethics principles in their practice is a challenging task, compounded by wide variations in the teaching and assessment of ethics in the postgraduate setting. Despite these differences, ethics training programs should recognise that the transition from medical students to healthcare professionals entails a longitudinal process where ethics knowledge, skills and identity continue to build and deepen over time with clinical exposure. A systematic scoping review is proposed to analyse current postgraduate medical ethics training and assessment programs in peer-reviewed literature to guide the development of a local physician training curriculum. METHODS: With a constructivist perspective and relativist lens, this systematic scoping review on postgraduate medical ethics training and assessment will adopt the Systematic Evidence Based Approach (SEBA) to create a transparent and reproducible review. RESULTS: The first search involving the teaching of ethics yielded 7669 abstracts with 573 full text articles evaluated and 66 articles included. The second search involving the assessment of ethics identified 9919 abstracts with 333 full text articles reviewed and 29 articles included. The themes identified from the two searches were the goals and objectives, content, pedagogy, enabling and limiting factors of teaching ethics and assessment modalities used. Despite inherent disparities in ethics training programs, they provide a platform for learners to apply knowledge, translating it to skill and eventually becoming part of the identity of the learner. Illustrating the longitudinal nature of ethics training, the spiral curriculum seamlessly integrates and fortifies prevailing ethical knowledge acquired in medical school with the layering of new specialty, clinical and research specific content in professional practice. Various assessment methods are employed with special mention of portfolios as a longitudinal assessment modality that showcase the impact of ethics training on the development of professional identity formation (PIF). CONCLUSIONS: Our systematic scoping review has elicited key learning points in the teaching and assessment of ethics in the postgraduate setting. However, more research needs to be done on establishing Entrustable Professional Activities (EPA)s in ethics, with further exploration of the use of portfolios and key factors influencing its design, implementation and assessment of PIF and micro-credentialling in ethics practice. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s12909-021-02644-5

Robust estimation of bacterial cell count from optical density

Optical density (OD) is widely used to estimate the density of cells in liquid culture, but cannot be compared between instruments without a standardized calibration protocol and is challenging to relate to actual cell count. We address this with an interlaboratory study comparing three simple, low-cost, and highly accessible OD calibration protocols across 244 laboratories, applied to eight strains of constitutive GFP-expressing E. coli. Based on our results, we recommend calibrating OD to estimated cell count using serial dilution of silica microspheres, which produces highly precise calibration (95.5% of residuals <1.2-fold), is easily assessed for quality control, also assesses instrument effective linear range, and can be combined with fluorescence calibration to obtain units of Molecules of Equivalent Fluorescein (MEFL) per cell, allowing direct comparison and data fusion with flow cytometry measurements: in our study, fluorescence per cell measurements showed only a 1.07-fold mean difference between plate reader and flow cytometry data