The Dynamics of a Meandering River

We present a statistical model of a meandering river on an alluvial plane which is motivated by the physical non-linear dynamics of the river channel migration and by describing heterogeneity of the terrain by noise. We study the dynamics analytically and numerically. The motion of the river channel is unstable and we show that by inclusion of the formation of ox-bow lakes, the system may be stabilised. We then calculate the steady state and show that it is in agreement with simulations and measurements of field data.Comment: Revtex, 12 pages, 2 postscript figure

Externally validated prediction models for pre‐eclampsia:systematic review and meta‐analysis

Objective: This systematic review and meta‐analysis aimed to evaluate the performance of existing externally validated prediction models for pre‐eclampsia (PE) (specifically, any‐onset, early‐onset, late‐onset and preterm PE). Methods: A systematic search was conducted in five databases (MEDLINE, EMBASE, Emcare, CINAHL and Maternity & Infant Care Database) and using Google Scholar/reference search to identify studies based on the Population, Index prediction model, Comparator, Outcome, Timing and Setting (PICOTS) approach until 20 May 2023. We extracted data using the CHARMS checklist and appraised the risk of bias using the PROBAST tool. A meta‐analysis of discrimination and calibration performance was conducted when appropriate. Results: Twenty‐three studies reported 52 externally validated prediction models for PE (one preterm, 20 any‐onset, 17 early‐onset and 14 late‐onset PE models). No model had the same set of predictors. Fifteen any‐onset PE models were validated externally once, two were validated twice and three were validated three times, while the Fetal Medicine Foundation (FMF) competing‐risks model for preterm PE prediction was validated widely in 16 different settings. The most common predictors were maternal characteristics (prepregnancy body mass index, prior PE, family history of PE, chronic medical conditions and ethnicity) and biomarkers (uterine artery pulsatility index and pregnancy‐associated plasma protein‐A). The FMF model for preterm PE (triple test plus maternal factors) had the best performance, with a pooled area under the receiver‐operating‐characteristics curve (AUC) of 0.90 (95% prediction interval (PI), 0.76–0.96), and was well calibrated. The other models generally had poor‐to‐good discrimination performance (median AUC, 0.66 (range, 0.53–0.77)) and were overfitted on external validation. Apart from the FMF model, only two models that were validated multiple times for any‐onset PE prediction, which were based on maternal characteristics only, produced reasonable pooled AUCs of 0.71 (95% PI, 0.66–0.76) and 0.73 (95% PI, 0.55–0.86). Conclusions: Existing externally validated prediction models for any‐, early‐ and late‐onset PE have limited discrimination and calibration performance, and include inconsistent input variables. The triple‐test FMF model had outstanding discrimination performance in predicting preterm PE in numerous settings, but the inclusion of specialized biomarkers may limit feasibility and implementation outside of high‐resource settings. © 2023 The Authors. Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of International Society of Ultrasound in Obstetrics and Gynecology

WOmen's Action for Mums and Bubs (WOMB) trial protocol: a non-randomized stepped wedge implementation trial of participatory women's groups to improve the health of Aboriginal and Torres Strait Islander mothers and children in Australia

Introduction: In Australia, there have been improvements in Aboriginal and Torres Strait Islander maternal health, however inequities remain. There is increasing international evidence illustrating the effectiveness of Participatory Women's Groups (PWGs) in improving Maternal and Child Health (MCH) outcomes. Using a non-randomized, cluster stepped-wedge implementation of a complex intervention with mixed methods evaluation, this study aims to test the effectiveness of PWGs in improving MCH within Indigenous primary care settings in Australia and how they operate in various contexts. Methods: This study takes place in ten primary health care services across Australia and involves the recruitment of existing PWGs or the setting up of new PWGs. Services are paired based on geography for practical reasons and two services commence the PWG intervention at three monthly intervals, with the initial four services being those with existing women's groups. Implementation of the PWGs as an intervention involves training local facilitators of PWG groups, supported engagement with local MCH data through workshops, PWGs identifying and prioritizing issues and strengths and co-implementing solutions with health services. Outcomes are measured with yearly MCH audits, a cost-effectiveness study, and process evaluation of community participation and empowerment. Discussion: This study is the first to formally implement and quantitatively, yet with contextual awareness, measure the effect of applying a community participation intervention to improve the quality of Aboriginal and Torres Strait Islander MCH in Australia. Findings from this work, including detailed theory-producing qualitative analysis, will produce new knowledge of how to facilitate improved quality of MCH care in Indigenous PHC settings and how to best engage community in driving health care improvements.Karen Carlisle, Catrina Felton-Busch, Yvonne Cadet-James, Judy Taylor, Ross Bailie, Jane Farmer, Megan Passey, Veronica Matthews, Emily Callander, Rebecca Evans, Janet Kelly, Robyn Preston, Michelle Redman-MacLaren, Haylee Fox, Adrian Esterman, Merrick Zwarenstein and Sarah Larkin

The N3RO trial: a randomised controlled trial of docosahexaenoic acid to reduce bronchopulmonary dysplasia in preterm infants < 29 weeks’ gestation

Background: Bronchopulmonary dysplasia (BPD) is a major cause of mortality and long-term respiratory and neurological morbidity in very preterm infants. While survival rates of very preterm infants have increased over the past two decades there has been no decrease in the rate of BPD in surviving infants. Evidence from animal and human studies has suggested potential benefits of docosahexaenoic acid (DHA), an n-3 long chain polyunsaturated fatty acid, in the prevention of chronic lung disease. This randomised controlled trial aims to determine the effectiveness of supplementary DHA in reducing the rate of BPD in infants less than 29 weeks’ gestation. Methods/design: This is a multicentre, parallel group, randomised, blinded and controlled trial. Infants born less than 29 weeks’ gestation, within 3 days of first enteral feed and with parent informed consent are eligible to participate. Infants will be randomised to receive an enteral emulsion containing DHA or a control emulsion without DHA. The DHA emulsion will provide 60 mg/kg/day of DHA. The study emulsions will continue to 36 weeks’ postmenstrual age (PMA). The primary outcome is BPD as assessed by the requirement for supplemental oxygen and/or assisted ventilation at 36 weeks’ PMA. Secondary outcomes include the composite of death or BPD; duration of respiratory support and hospitalisation, major neonatal morbidities. The target sample size is 1244 infants (622 per group), which will provide 90 % power to detect a clinically meaningful absolute reduction of 10 % in the incidence of BPD between the DHA and control emulsion (two tailed α =0.05). Discussion: DHA supplementation has the potential to reduce respiratory morbidity in very preterm infants. This multicentre trial will provide evidence on whether an enteral DHA supplement reduces BPD in very preterm infants

Reliability and Responsibility: a Theory of Endogenous Commitment

A common assumption in Political Science literature is policy commitment: candidates maintain their electoral promises. We study its validity and we prove that is an costless electoral is an effective way of transmitting information to voters. We investigate the responsiveness of policies to electoral promises depending on politicians' motivations. The results are robust to relevant equilibrium refinements