A fast and robust numerical scheme for solving models of charge carrier transport and ion vacancy motion in perovskite solar cells

Drift-diffusion models that account for the motion of both electronic and ionic charges are important tools for explaining the hysteretic behaviour and guiding the development of metal halide perovskite solar cells. Furnishing numerical solutions to such models for realistic operating conditions is challenging owing to the extreme values of some of the parameters. In particular, those characterising (i) the short Debye lengths (giving rise to rapid changes in the solutions across narrow layers), (ii) the relatively large potential differences across devices and (iii) the disparity in timescales between the motion of the electronic and ionic species give rise to significant stiffness. We present a finite difference scheme with an adaptive time step that is posed on a non-uniform staggered grid that provides second order accuracy in the mesh spacing. The method is able to cope with the stiffness of the system for realistic parameters values whilst providing high accuracy and maintaining modest computational costs. For example, a transient sweep of a current-voltage curve can be computed in only a few minutes on a standard desktop computer.Comment: 22 pages, 8 figure

Systematic derivation of a surface polarization model for planar perovskite solar cells

Increasing evidence suggests that the presence of mobile ions in perovskite solar cells can cause a current-voltage curve hysteresis. Steady state and transient current-voltage characteristics of a planar metal halide CH$_3$NH$_3$PbI$_3$ perovskite solar cell are analysed with a drift-diffusion model that accounts for both charge transport and ion vacancy motion. The high ion vacancy density within the perovskite layer gives rise to narrow Debye layers (typical width $\sim$2nm), adjacent to the interfaces with the transport layers, over which large drops in the electric potential occur and in which significant charge is stored. Large disparities between (I) the width of the Debye layers and that of the perovskite layer ($\sim$600nm) and (II) the ion vacancy density and the charge carrier densities motivate an asymptotic approach to solving the model, while the stiffness of the equations renders standard solution methods unreliable. We derive a simplified surface polarisation model in which the slow ion dynamic are replaced by interfacial (nonlinear) capacitances at the perovskite interfaces. Favourable comparison is made between the results of the asymptotic approach and numerical solutions for a realistic cell over a wide range of operating conditions of practical interest.Comment: 32 pages, 7 figure

IonMonger: a free and fast planar perovskite solar cell simulator with coupled ion vacancy and charge carrier dynamics

Details of an open-source planar perovskite solar cell simulator, that includes ion vacancy migration within the perovskite layer coupled to charge carrier transport throughout the perovskite and adjoining transport layers in one dimension, are presented. The model equations are discretised in space using a finite element scheme and temporal integration of the resulting system of differential-algebraic equations is carried out in MATLAB. The user is free to modify device parameters, as well as the incident illumination and applied voltage. Time-varying voltage and/or illumination protocols can be specified, e.g. to simulate current-voltage sweeps, or to track the open-circuit conditions as the illumination is varied. Typical simulations, e.g. current-voltage sweeps, only require computation times of seconds to minutes on a modern personal computer. An example set of hysteretic current-voltage curves is presented

Speaking-up for patient safety: A scoping narrative review of international literature and lessons for radiography in Ghana and other resource-constrained settings

Objectives Employees ‘speaking-up’, or raising concerns about unsafe practices, has gained traction across healthcare, however, the topic has not been widely discussed within radiography generally or within resource-constrained healthcare settings. A systematic scoping narrative review identified the experiences of radiographers in speaking-up about safety concerns, which was extended to healthcare professionals more broadly. The scope of the review was further extended to cover speaking-up in non-healthcare resource-constrained settings in Africa. Key findings Sixty-three studies were included in the review. The majority originated from westernised and/or higher resource health systems, with a dearth of literature from Africa and other resource-constrained settings. Several studies identified barriers and enablers confronting healthcare workers wishing to speak-up. While ‘speaking-up’ as a concept has gained international interest, most studies are, however, focussed on nursing and medical practice contexts, overlooking other healthcare professions, including radiography. The findings are synthesised into a series of key lessons for healthcare and radiography practitioners in Ghana and other resource-constrained settings. Conclusion The topic has been largely overlooked by policy makers, both within healthcare generally and specifically within radiography in Ghana. This is particularly concerning given the many complexities and risks inherent to radiography. A radiography and a healthcare workforce lacking in voice is poorly positioned to improve workers' safety and patient safety. More generally, promoting speaking up could enhance Ghana's ambitions to deliver a high-quality health care system and Universal Health Coverage (UHC) in the future. Implications for practice National and regional policy makers need to implement speaking-up processes and procedures reflecting the lessons of the literature review, such as ensuring no detriment as result of speaking-up and making staff feel that their concerns are not futile. Speaking-up processes should be implemented by individual organisations, alongside staff training and monitoring

The volume of liver irradiated during modern free-breathing breast radiotherapy: implications for theory and practice

Introduction Incidental liver irradiation during breast radiotherapy can increase the risk of second primary malignancy and induce adverse inflammatory states. This study establishes the volume of liver irradiated during free-breathing breast radiotherapy. Novel associations between liver dose-volume data and systemic interleukin-6 soluble receptor and blood counts are evaluated. Methods The volume of liver within the 10%, 50% and 90% isodose was determined for 100 women with stage 0 to II breast carcinoma undergoing 40Gy in 15 fractions over three weeks tangential irradiation. Blood counts and interleukin 6 soluble receptor concentration were recorded before, during and four weeks after radiotherapy. Dose-volume data for right-sided treatments was associated with longitudinal measures at bivariate and multivariable levels. Results A maximum of 226cm3 (19%), 92 cm3 (8%) and 62 cm3 (5%) of the liver was irradiated within the 10%, 50% and 90% isodose. Liver irradiation was almost exclusively a feature of the 52 right-sided treatments and was strongly correlated with breast volume (ρ = 0.7, p < 0.0001). Liver V10% was significantly associated with interleukin-6 soluble receptor concentration four weeks post-radiotherapy (beta = 0.38, p = 0.01) after controlling for theoretical confounding variables. Conclusion Up to 8% of the liver is irradiated within the primary beam during local right-sided breast radiotherapy. Select use of a deep inspiration breath hold technique would reduce this volume, and minimise the risk of radiation-induced malignancy and acute systemic elevation of inflammatory interleukin 6 soluble receptor

Targeted molecular characterization shows differences between primary and secondary myelofibrosis

INTRODUCTION: In BCR-ABL1-negative myeloproliferative neoplasms, myelofibrosis (MF) is either primary (PMF) or secondary (SMF) to polycythemia vera or essential thrombocythemia. MF is characterized by an increased risk of transformation to acute myeloid leukemia (AML) and a shortened life expectancy. METHODS: Because natural histories of PMF and SMF are different, we studied by targeted next generation sequencing the differences in the molecular landscape of 86 PMF and 59 SMF and compared their prognosis impact. RESULTS: PMF had more ASXL1 (47.7%) and SRSF2 (14%) gene mutations than SMF (respectively 27.1% and 3.4%, P = .04). Poorer survival was associated with RNA splicing mutations (especially SRSF2) and TP53 in PMF (P = .0003), and with ASXL1 and TP53 mutations in SMF (P &lt; .0001). These mutations of poor prognosis were associated with biological features of scoring systems (DIPSS and MYSEC-PM score). Mutations in TP53/SRSF2 in PMF or TP53/ASXL1 in SMF were more frequent as the risk of these scores increased. This allowed for a better stratification of MF patients, especially within the DIPSS intermediate-1 risk group (DIPSS) or the MYSEC-PM high risk group. AML transformation occurred faster in SMF than in PMF and patients who transformed to AML were more SRSF2-mutated and less CALR-mutated at MF sampling. CONCLUSIONS: PMF and SMF have different but not specific molecular profiles and different prognosis depending on the molecular profile. This may be due to differences in disease history. Combining mutations and existing scores should improve prognosis assessment

Radiological-pathological correlation of pleomorphic liposarcoma of the anterior mediastinum in a 17-year-old girl

Liposarcoma is a soft-tissue sarcoma typically seen in adults. It is extremely rare in children. It most often occurs in the extremities or in the retroperitoneum. We present a very rare case of an anterior mediastinal liposarcoma of the pleomorphic subtype in a 17-year-old girl, along with radiological and pathological correlation. The location, patient age and histological subtype are exceedingly uncommon for this tumor

Patient prioritisation of impact items to develop the patient‐reported impact of dermatological diseases ( PRIDD ) measure: European Delphi data

Background: The Global Research on the Impact of Dermatological Diseases (GRIDD) project is developing a patient‐reported measure of the impact of dermatological disease on the patient's life called Patient Reported Impact of Dermatological Diseases (PRIDD). We developed a list of 263 potential impact items through a global qualitative interview study with 68 patients. We next conducted a Delphi study to seek consensus on which of these items to prioritize for inclusion in PRIDD. This study aims to explore patterns in demographic (e.g. country) and clinical variables (e.g. disease group) across the impacts ranked as most important to European dermatology patients. Methods: We conducted a modified, two rounds Delphi study, testing the outcomes from the previous qualitative interview study. Adults (≥18 years) living with a dermatological disease were recruited through the International Alliance of Dermatology Patient Organizations' (GlobalSkin) membership network. The survey consisted of a demographic questionnaire and 263 impact items and was available in six languages. Quantitative data were collected using ranking scales and analysed against a priori consensus criteria. Qualitative data were collected using free‐text responses and a Framework Analysis was conducted. European data were obtained, and descriptive statistics, including multiple subgroup analyses, were performed. Results: Out of 1154 participants, 441 Europeans representing 46 dermatological disease from 25 countries participated. The results produced a list of the top 20 impacts reported by European patients, with psychological impacts accounting for the greatest proportion. Conclusion: This study identified what patients consider to be the most important issues impacting their lives as a result of their dermatological disease. The data support previous evidence that patients experience profound psychological impacts and require psychological support. The findings can inform research, clinical practice and policy by indicating research questions and initiatives that are of most benefit to patients