Turbulent transport by diffusive stratified shear flows: from local to global models. Part II: Limitations of local models

This paper continues the systematic investigation of diffusive shear instabilities initiated in Part I of this series. In this work, we primarily focus on quantifying the impact of non-local mixing, which is not taken into account in Zahn's mixing model \citep{Zahn92}. We present the results of direct numerical simulations in a new model setup designed to contain coexisting laminar and turbulent shear layers. As in Part I, we use the Low P\'eclet Number approximation of \citet{Lign1999} to model the evolution of the perturbations. Our main findings are twofold. First, turbulence is not necessarily generated whenever Zahn's nonlinear criterion \citep{Zahn1974} $J{\rm Pr} < (J{\rm Pr})_c$ is satisfied, where $J=N^2/S^2$ is the local gradient Richardson number, ${\rm Pr} = \nu/ \kappa_T$ is the Prandtl number, and $(J{\rm Pr})_c \simeq 0.007$. We have demonstrated that the presence or absence of turbulent mixing in this limit hysteretically depends on the history of the shear layer. Second, Zahn's nonlinear instability criterion only approximately locates the edge of the turbulent layer, and mixing beyond the region where $J{\rm Pr} < (J{\rm Pr})_c$ can also take place in a manner analogous to convective overshoot. We found that the turbulent kinetic energy decays roughly exponentially beyond the edge of the shear-unstable region, on a lengthscale $\delta$ that is directly proportional to the scale of the turbulent eddies, which are themselves of the order of the Zahn scale (see Part I). Our results suggest that mixing by diffusive shear instabilities should be modeled with more care than is currently standard in stellar evolution codes.Comment: Submitted to Ap

Outcome Reporting in Randomized Trials for Shoulder Disorders: Literature Review to Inform the Development of a Core Outcome Set

Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/141827/1/acr23254_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/141827/2/acr23254.pd

Vitamin D and subsequent all-age and premature mortality: a systematic review

&lt;br&gt;Background: All-cause mortality in the population &#60; 65 years is 30% higher in Glasgow than in equally deprived Liverpool and Manchester. We investigated a hypothesis that low vitamin D in this population may be associated with premature mortality via a systematic review and meta-analysis.&lt;/br&gt; &lt;br&gt;Methods: Medline, EMBASE, Web of Science, the Cochrane Library and grey literature sources were searched until February 2012 for relevant studies. Summary statistics were combined in an age-stratified meta-analysis.&lt;/br&gt; &lt;br&gt;Results: Nine studies were included in the meta-analysis, representing 24,297 participants, 5,324 of whom died during follow-up. The pooled hazard ratio for low compared to high vitamin D demonstrated a significant inverse association (HR 1.19, 95% CI 1.12-1.27) between vitamin D levels and all-cause mortality after adjustment for available confounders. In an age-stratified meta-analysis, the hazard ratio for older participants was 1.25 (95% CI 1.14-1.36) and for younger participants 1.12 (95% CI 1.01-1.24).&lt;/br&gt; &lt;br&gt;Conclusions: Low vitamin D status is inversely associated with all-cause mortality but the risk is higher amongst older individuals and the relationship is prone to residual confounding. Further studies investigating the association between vitamin D deficiency and all-cause mortality in younger adults with adjustment for all important confounders (or using randomised trials of supplementation) are required to clarify this relationship.&lt;/br&gt

An empirical study using permutation-based resampling in meta-regression

<p>Abstract</p> <p>Background</p> <p>In meta-regression, as the number of trials in the analyses decreases, the risk of false positives or false negatives increases. This is partly due to the assumption of normality that may not hold in small samples. Creation of a distribution from the observed trials using permutation methods to calculate <it>P </it>values may allow for less spurious findings. Permutation has not been empirically tested in meta-regression. The objective of this study was to perform an empirical investigation to explore the differences in results for meta-analyses on a small number of trials using standard large sample approaches verses permutation-based methods for meta-regression.</p> <p>Methods</p> <p>We isolated a sample of randomized controlled clinical trials (RCTs) for interventions that have a small number of trials (herbal medicine trials). Trials were then grouped by herbal species and condition and assessed for methodological quality using the Jadad scale, and data were extracted for each outcome. Finally, we performed meta-analyses on the primary outcome of each group of trials and meta-regression for methodological quality subgroups within each meta-analysis. We used large sample methods and permutation methods in our meta-regression modeling. We then compared final models and final <it>P </it>values between methods.</p> <p>Results</p> <p>We collected 110 trials across 5 intervention/outcome pairings and 5 to 10 trials per covariate. When applying large sample methods and permutation-based methods in our backwards stepwise regression the covariates in the final models were identical in all cases. The <it>P </it>values for the covariates in the final model were larger in 78% (7/9) of the cases for permutation and identical for 22% (2/9) of the cases.</p> <p>Conclusions</p> <p>We present empirical evidence that permutation-based resampling may not change final models when using backwards stepwise regression, but may increase <it>P </it>values in meta-regression of multiple covariates for relatively small amount of trials.</p

Effect of Left Atrial Function Index on Late Atrial Fibrillation Recurrence after Pulmonary Vein Isolation

Background: Although the rates of catheter ablation (CA) for atrial fibrillation (AF) are rapidly increasing, there are few predictors of outcome to help inform appropriate patient selection for this procedure. Traditional echocardiographic measures of atrial structure do not significantly reclassify risk of AF recurrence over and above the clinical risk factors. Left Atrial Function Index (LAFI) is a rhythm-independent measure of atrial function. We hypothesized that baseline LAFI would relate to AF recurrence after CA. Methods: Pre-procedural echocardiograms from 170 participants, who underwent CA for AF and were enrolled in the UMMC AF Treatment Registry, were analyzed. LAFI was calculated by a previously validated formula. Primary outcome was late or clinically significant AF recurrence 3-12 months after CA. Baseline clinical, laboratory and echocardiographic variables were compared between the recurrence and non-recurrence groups. Results: Study participants were middle aged (60+/10 years) and had a moderate-to-severe burden of cardiovascular comorbidities. 78 participants (46%) experienced late AF recurrence. Mean LAFI was 0.26+/-0.18. In multivariate analysis, lower LAFI was independently associated with the risk of recurrence (0.23 in recurrence group vs 0.29 in non-recurrence group, p \u3c 0.01). Predictive value of LAFI for AF recurrence was similar to CHADS2 score (c-statistic 0.60 vs 0.58, p 0.76). In subgroup of patients with persistent AF, LAFI predicted AF recurrence more strongly than CHADS2 score (c-statistic: 0.79 vs 0.58, p 0.02). Conclusions: In our cohort of 170 participants with AF undergoing index CA ablation, we observed that LAFI related to late AF recurrence after CA, independent of the traditional risk factors. Since LAFI can be calculated from almost any traditional echocardiographic recording, our findings suggest that LAFI may help guide therapeutic decision-making regarding application of CA, particularly among challenging patients with symptomatic persistent AF

Patients' experience of shoulder disorders: a systematic review of qualitative studies for the OMERACT Shoulder Core Domain Set.

OBJECTIVES:To describe the experiences (including symptoms and perceived impacts on daily living) of people with a shoulder disorder. METHODS:Systematic review of qualitative studies. We searched for eligible qualitative studies indexed in Ovid MEDLINE, Ovid Embase, CINAHL (EBSCO), SportDiscus (EBSCO) and Ovid PsycINFO up until November 2017. Two authors independently screened studies for inclusion, appraised their methodological quality using the Critical Appraisal Skills Programme checklist, used thematic synthesis methods to generate themes describing the experiences reported by participants and assessed the confidence in the findings using the Grading of Recommendations Assessment, Development and Evaluation Confidence in Evidence from Reviews of Qualitative research (GRADE-CERQual) approach. RESULTS:The inclusion criteria were met by eight studies, which included 133 participants (49 females and 84 males) with either rotator cuff disease, adhesive capsulitis, proximal humeral fracture, shoulder instability or unspecified shoulder pain. We generated seven themes to describe what people in the included studies reported experiencing: pain; physical function/activity limitations; participation restriction; sleep disruption; cognitive dysfunction; emotional distress; and other pathophysiological manifestations (other than pain). There were interactions between the themes, with particular experiences impacting on others (e.g. pain leading to reduced activities and sleep disruption). Following grading of the evidence, we considered it likely that most of the review findings were a reasonable representation of the experiences of people with shoulder disorders. CONCLUSION:Patients with shoulder disorders contend with considerable disruption to their life. The experiences described should be considered by researchers seeking to select the most appropriate outcomes to measure in clinical trials and other research studies in people with shoulder disorders

SYNTHESYS+ Virtual Access - Report on the Ideas Call (October to November 2019)

The SYNTHESYS consortium has been operational since 2004, and has facilitated physical access by individual researchers to European natural history collections through its Transnational Access programme (TA). For the first time, SYNTHESYS+ will be offering virtual access to collections through digitisation, with two calls for the programme, the first in 2020 and the second in 2021. The Virtual Access (VA) programme is not a direct digital parallel of Transnational Access - proposals for collections digitisation will be prioritised and carried out based on community demand, and data must be made openly available immediately. A key feature of Virtual Access is that, unlike TA, it does not select the researchers to whom access is provided. Because Virtual Access in this way is new to the community and to the collections-holding institutions, the SYNTHESYS+ consortium invited ideas through an Ideas Call, that opened on 7th October 2019 and closed on 22nd November 2019, in order to assess interest and to trial procedures. This report is intended to provide feedback to those who participated in the Ideas Call and to help all applicants to the first SYNTHESYS+Virtual Access Call that will be launched on 20th of February 2020.This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. The attached file is the published pdf

CONSORT Harms 2022 statement, explanation, and elaboration: updated guideline for the reporting of harms in randomized trials.

Randomized controlled trials remain the reference standard for healthcare research on effects of interventions, and the need to report both benefits and harms is essential. The Consolidated Standards of Reporting Trials (the main CONSORT) statement includes one item on reporting harms (i.e., all important harms or unintended effects in each group). In 2004, the CONSORT group developed the CONSORT Harms extension; however, it has not been consistently applied and needs to be updated. Here, we describe CONSORT Harms 2022, which replaces the CONSORT Harms 2004 checklist, and shows how CONSORT Harms 2022 items could be incorporated into the main CONSORT checklist. Thirteen items from the main CONSORT were modified to improve harms reporting. Three new items were added. In this article, we describe CONSORT Harms 2022 and how it was integrated into the main CONSORT checklist and elaborate on each item relevant to complete reporting of harms in randomized controlled trials. Until future work from the CONSORT group produces an updated checklist, authors, journal reviewers, and editors of randomized controlled trials should use the integrated checklist presented in this paper