191 research outputs found
Fast and Accurate Coarsening Simulation with an Unconditionally Stable Time Step
We present Cahn-Hilliard and Allen-Cahn numerical integration algorithms that
are unconditionally stable and so provide significantly faster
accuracy-controlled simulation. Our stability analysis is based on Eyre's
theorem and unconditional von Neumann stability analysis, both of which we
present. Numerical tests confirm the accuracy of the von Neumann approach,
which is straightforward and should be widely applicable in phase-field
modeling. We show that accuracy can be controlled with an unbounded time step
Delta-t that grows with time t as Delta-t ~ t^alpha. We develop a
classification scheme for the step exponent alpha and demonstrate that a class
of simple linear algorithms gives alpha=1/3. For this class the speed up
relative to a fixed time step grows with the linear size of the system as N/log
N, and we estimate conservatively that an 8192^2 lattice can be integrated 300
times faster than with the Euler method.Comment: 14 pages, 6 figure
Dynamic Phase Transitions in Cell Spreading
We monitored isotropic spreading of mouse embryonic fibroblasts on
fibronectin-coated substrates. Cell adhesion area versus time was measured via
total internal reflection fluorescence microscopy. Spreading proceeds in
well-defined phases. We found a power-law area growth with distinct exponents
a_i in three sequential phases, which we denote basal (a_1=0.4+-0.2), continous
(a_2=1.6+-0.9) and contractile (a_3=0.3+-0.2) spreading. High resolution
differential interference contrast microscopy was used to characterize local
membrane dynamics at the spreading front. Fourier power spectra of membrane
velocity reveal the sudden development of periodic membrane retractions at the
transition from continous to contractile spreading. We propose that the
classification of cell spreading into phases with distinct functional
characteristics and protein activity patterns serves as a paradigm for a
general program of a phase classification of cellular phenotype. Biological
variability is drastically reduced when only the corresponding phases are used
for comparison across species/different cell lines.Comment: 4 pages, 5 figure
Self-directed self-management interventions to prevent or address distress in young people with long-term physical conditions: a rapid review.
Background: Comorbid distress in adolescents and young adults with physical longâ
term conditions (LTCs) is common but can be difficult to identify and manage. Selfâ
directed selfâmanagement interventions to reduce distress and improve wellbeing
may be beneficial. It is unknown, however, which intervention characteristics are
successful in supporting young people. This rapid review aimed to identify
characteristics of selfâdirected selfâmanagement interventions that aimed, in whole
or part, to address distress, wellbeing or selfâefficacy in this population.
Methods: A systematic search was conducted for relevant controlled studies in six
databases. Data on study settings, population, intervention characteristics, outcome
measures, process measures and summary effects were extracted. The risk of bias
was assessed using the Cochrane Risk of Bias tool v1, and the strength of evidence
was rated (informed by Grading of Recommendations, Assessment, Development
and Evaluations). Patient and public involvement members supported the review
process, including interpretation of results. The rapid review was registered with
PROSPERO (ID: CRD42021285867).
Results: Fourteen studies were included, all of which were randomised trials.
Heterogeneity was identified in the health conditions targeted; type of intervention;
outcome measures; duration of intervention and followâup. Three had distress,
wellbeing or selfâefficacy as their primary outcome. Four modes of delivery were
identified across interventionsâwebsites, smartphone applications, text messages
and workbooks; and within these, 38 individual components. Six interventions had a significant benefit in mental health, wellbeing or selfâefficacy; however, intervention
characteristics were similar for beneficial and nonâbeneficial interventions.
Conclusions: There is a paucity of interventions directly targeting distress and
wellbeing in young people with physical LTCs. In those identified, the heterogeneity
of interventions and study design makes it difficult to identify which characteristics
result in positive outcomes. We propose the need for highâquality, evidenceâbased
selfâmanagement interventions for this population; including (1) more detailed
reporting of intervention design, content and delivery; (2) robust process evaluation;
(3) a core outcome set for measuring mental health and wellbeing for selfâ
management interventions and (4) consistency in follow up periods.
Public Contribution: Seven young people with an LTC were involved throughout the
rapid review, from the development of the review protocol where they informed the
focus and aims, with a central role in the interpretation of findings.peer-reviewe
The economic burden of stroke care in England, Wales and Northern Ireland: using a national stroke register to estimate and report patient level health economic outcomes in stroke
Healthcare professionalsâ priorities for training to identify and manage distress experienced by young people with a stoma due to inflammatory bowel disease: a consensus study using online nominal group technique
Young people with a stoma due to inflammatory bowel disease (IBD) commonly experience distress; however, this is not always well managed in clinical settings. More effective support may/is likely to reduce the possibility of individuals experiencing sustained distress, which may engender depression or anxiety. This study aimed to gain consensus among a multidisciplinary group of healthcare professionals (HCPs) on priorities for training in the identification and management of distress in this population. One of the authors is a young person with a stoma. Design Participants were recruited through Twitter (X) and the researchersâ clinical/research contacts. Two consensus group meetings were conducted using Nominal Group Technique, involving participants generating, discussing and rating on a Likert scale, topics for inclusion in an HCP training package. Setting Online video conferencing. Participants were located across England, with one based in the USA. Participants Nineteen HCPs participated: three general practitioners, three stoma nurses, two IBD nurses, nine clinical psychologists and two gastroenterologists. Results Twenty-five topics were generated by participants; 19 reached consensus of â„80%, that is, a mean of â„5.6 on a 7-point Likert scale. These included: recognising and validating different levels of, and variation in, distress; tackling stigma and normalising having a stoma; everyday practicalities of stoma management, including food and sleep; opening and holding conversations about stoma-related distress; considering the impact of different cultural beliefs on adaptation after stoma surgery; training in simple techniques for gauging the patientâs distress during clinical encounters; having conversations about body image; and myth-busting common fears, such as odour. Conclusions This study is the first to identify HCP training priorities for managing stoma-related distress in young people. Consensus was reached for 19 topics, reflecting the varied needs of young people with a stoma. Findings will inform development of a training package for HCPs treating young people with IBD and a stoma.peer-reviewe
Anisotropic Coarsening: Grain Shapes and Nonuniversal Persistence
We solve a coarsening system with small but arbitrary anisotropic surface
tension and interface mobility. The resulting size-dependent growth shapes are
significantly different from equilibrium microcrystallites, and have a
distribution of grain sizes different from isotropic theories. As an
application of our results, we show that the persistence decay exponent depends
on anisotropy and hence is nonuniversal.Comment: 4 pages (revtex), 2 eps figure
A systematic review of machine learning models for predicting outcomes of stroke with structured data
Background and purposeMachine learning (ML) has attracted much attention with the hope that it could make use of large, routinely collected datasets and deliver accurate personalised prognosis. The aim of this systematic review is to identify and critically appraise the reporting and developing of ML models for predicting outcomes after stroke.MethodsWe searched PubMed and Web of Science from 1990 to March 2019, using previously published search filters for stroke, ML, and prediction models. We focused on structured clinical data, excluding image and text analysis. This review was registered with PROSPERO (CRD42019127154).ResultsEighteen studies were eligible for inclusion. Most studies reported less than half of the terms in the reporting quality checklist. The most frequently predicted stroke outcomes were mortality (7 studies) and functional outcome (5 studies). The most commonly used ML methods were random forests (9 studies), support vector machines (8 studies), decision trees (6 studies), and neural networks (6 studies). The median sample size was 475 (range 70-3184), with a median of 22 predictors (range 4-152) considered. All studies evaluated discrimination with thirteen using area under the ROC curve whilst calibration was assessed in three. Two studies performed external validation. None described the final model sufficiently well to reproduce it.ConclusionsThe use of ML for predicting stroke outcomes is increasing. However, few met basic reporting standards for clinical prediction tools and none made their models available in a way which could be used or evaluated. Major improvements in ML study conduct and reporting are needed before it can meaningfully be considered for practice
Young peopleâs priorities for the self-management of distress after stoma surgery due to inflammatory bowel disease: a consensus study using online nominal group technique
Abstract Introduction: The aim of this study was to gain consensus among young people with a stoma due to inflammatory bowel disease (IBD) on the priorities for the content of an intervention for the self-management of stoma-related distress. The current identification and management of distress in young people with a stoma is often sub-optimal in clinical settings and there is a need for improved support resources.Methods: Two consensus group meetings were carried out via online video conferencing, using Nominal Group Technique. Participants generated, rated on a Likert scale and discussed, topics for inclusion in a future self-management intervention.Results: Nineteen young people, aged 19-33, with a stoma due to IBD took part in one of two group meetings. Participants were located across England, Scotland, and Northern Ireland. Twenty-nine topics were generated by participants, seven of which reached consensus of >80%, that is, a mean of >5.6 on a 7-point Likert scale. These were: receiving advice from young people with lived experience of stoma surgery; advice on/ addressing concerns about romantic relationships, sex and intimacy; information about fertility and pregnancy related to stoma surgery; stoma âhacksâ, e.g. useful everyday tips regarding clothing, making bag changes easier etc.; reflecting on and recognising own emotional response to surgery; tips on managing the stoma during the night; and processing trauma related to the illness and surgery journey.Conclusions: Findings extend previous research on young peopleâs experiences of stoma surgery, by generating consensus on young peoplesâ priorities for managing distress related to surgery and living with a stoma. These priorities include topics not previously reported in the literature, including the need for information about fertility and pregnancy. Findings will inform the development of a self-management resource for young people with an IBD stoma and have relevance for the clinical management of stoma-related distress in this population.<br/
Associations Between 30-Day Mortality, Specialist Nursing, and Daily Physician Ward Rounds in a National Stroke Registry
Background and Purpose- Well-organized stroke care is associated with better patient outcomes, but the most important organizational factors are unknown. Methods- Data were extracted from the Sentinel Stroke National Audit Programme of adults with acute stroke treated in stroke hospitals in England and Wales between April 2013 and March 2015. Multilevel models with random intercepts for hospitals were used to estimate the association of each variable with 30-day mortality to estimate the impact of admission to differently organized hospitals. Results- Of the 143â578 patients with acute stroke admitted to 154 hospitals, 14.4% died within 30 days of admission. In adjusted analyses, admission to hospitals with higher ratios of nurses trained in swallow screening was associated with reduced odds of death ( P=0.004), and admission to hospitals with daily physician ward rounds was associated with 10% lower odds of mortality compared with less-frequent ward rounds (95% CI, 0.82-0.98; P=0.013). Number of stroke admissions and overall ratio of registered nurses on duty at weekends were not found to be independently associated with mortality after adjustment for other factors. Conclusions- If these associations are causal, an extra 1332 deaths annually in England and Wales could be saved by hospitals providing care associated with a ratio of nurses trained in swallow screening of at least 3 per 10 beds and daily stroke physician ward rounds
Earthquake Input Motions and Seismic Site Response in a Centrifuge Test Examining SFSI Effects
This paper describes the ground motion selection process and reports observed seismic site response and SFSI effects during a dynamic centrifuge test (Test-1). The centrifuge test is the first in a series of tests examining the effects of SFSI in dense urban environments. The objective of Test-1 is to examine SFSI effects for two structures that are located a significant distance apart and essentially isolated. The model structures represent a three-story building founded on spread footings and a nine-story structure founded on a threestory basement. The structures are sited on a dry, dense bed of Nevada Sand. The centrifuge model is subjected to a series of shaking events that represent near-fault and âordinaryâ ground motions at a site in Los Angeles. Results show that site periods degrade as ground motion intensity increases with more pronounced degradation observed for near-fault ground motions as compared with ordinary ground motions. Additionally, the results indicate the importance of kinematic effects of embedded structures when considering SFSI effects
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