Numerical Solution for the Extrapolation Problem of Analytic Functions.

In this work, a numerical solution for the extrapolation problem of a discrete set of n values of an unknown analytic function is developed. The proposed method is based on a novel numerical scheme for the rapid calculation of higher order derivatives, exhibiting high accuracy, with error magnitude of O(10-100) or less. A variety of integrated radial basis functions are utilized for the solution, as well as variable precision arithmetic for the calculations. Multiple alterations in the function's direction, with no curvature or periodicity information specified, are efficiently foreseen. Interestingly, the proposed procedure can be extended in multiple dimensions. The attained extrapolation spans are greater than two times the given domain length. The significance of the approximation errors is comprehensively analyzed and reported, for 5832 test cases.

An analysis of retractions of dental publications.

OBJECTIVES: To comprehensively report on the characteristics of retracted publications in the field of dentistry. METHODS: We searched MEDLINE (via PubMed), PubMed Central, Web of Science and Google Scholar databases for dental retracted articles from database inception to 02 July 2018. In addition, we scanned the search engine Google Scholar, and the website, Retraction Watch (www.retractionwatch.com), for retracted dental articles. Two researchers independently screened titles, abstracts and full text of search results. Descriptive data was collected on each retracted article including reason for retraction, study type, journal impact factor, and time between publication and retraction. Regression models were used to evaluate the association between journal impact factor and retraction characteristics. RESULTS: A total of 138 retractions of dental articles were included. Reasons for retraction were misconduct (N = 100, 72.5%), with the most frequently reported misconduct being overlap/plagiarism and innacurate/falsified conducting and reporting (N = 53, 38.4%). In vitro (N = 39, 28.3%), case reports (N = 29, 21%) and narrative reviews (N = 19, 13.8%) were study design most frequently identified in retracted articles. The median time between article publication and date of retraction notice was 1 year (interquartile-range [IQR] = 0-2 years). More than half of the retracted articles (n = 82, 59.4%) were cited post-retraction. A retracted article reporting a randomized controlled trial was more likely to appear in journal with higher impact factor than a retracted case report (mean difference [MD] = 2.2; 95% confidence interval [CI] = 1.2,3.1. Articles retracted after 2012 were likely to appear in journals with a lower impact factor (MD=-1.3; 95%CI=-1.8, 0.8). CONCLUSIONS: Research misconduct is the main reason for retraction of dental articles. A substantial proportion of these articles were still being cited after their retraction. CLINICAL SIGNIFICANCE: This report of dental retraction articles informs that more transparency is needed with data reporting in dentistry to improve writing practices in dentistry. A more complete report of retractions and their causes would provide more accurate information to inform researchers and editors to avoid or reduce future cases of retractions. More complete and accurate reporting would increase the overall trust in dental research.

A survey of prevalence of narrative and systematic reviews in five major medical journals.

BACKGROUND: Systematic reviews may provide less biased evidence than narrative reviews because they observe a strict methodology, similarly to primary studies. Hence, for clinical research questions, systematic reviews should be the study design of choice. It would be important to evaluate the prevalence and characteristics of narrative and systematic reviews published in prominent medical journals. Researchers and clinicians give great value to articles published in such scientific journals. This study sought to evaluate the prevalence and characteristics of narrative and systematic reviews in the five highest-ranked general medical journals and investigate the associations among type of review, number of citations, and impact factor (IF). METHODS: We surveyed the five highest-ranked medical journals (The New England Journal of Medicine, The Lancet, The Journal of the American Medical Association, The BMJ, and Annals of Internal Medicine) for narrative and systematic reviews published between June 2015 and June 2016. We independently selected and extracted the data from the reviews by strictly following the pre-determined eligibility criteria (Systematic and narrative reviews that focused on the management of diseases). We conducted regression analyses to investigate the associations among review type, number of citations, and IF. We also descriptively reported narrative reviews containing some methodology that might be reproducible. RESULTS: Two hundred seventy-five reviews were included: 75 (27%) systematic; 126 (46%) narrative with some methodology reported, and 74 (27%) narrative reviews. In comparison to systematic reviews, narrative reviews were more frequently published in journals with higher IF (risk ratio [RR] = 1.114 (95% CI 1.080 to 1.149). Systematic reviews received more citations than narrative reviews (group formed by narrative and narrative with some methodology reported (RR = 0.985 95% CI 0.978 to 0.991). CONCLUSIONS: Non-systematic evidence is the most prevalent type of evidence in reviews published in the five highest-ranked general medical journals. Narrative reviews were more frequently published in journals with higher IF. We recommend that journals limit their space for narrative information, and to address clinical research questions, these journals consider publishing systematic evidence exclusively.

Emergence of large scale structure in barotropic ß-plane turbulence.

In this Letter, we use a nonequilibrium statistical theory, the stochastic structural stability theory (SSST), to show that an extended version of this theory can make predictions for the formation of nonzonal as well as zonal structures (lattice and stripe patterns) in forced homogeneous turbulence on a barotropic ß plane. Comparison of the theory with nonlinear simulations demonstrates that SSST predicts the parameter values for the emergence of coherent structures and their characteristics (scale, amplitude, phase speed) as they emerge and at finite amplitude. It is shown that nonzonal structures (lattice states or zonons) emerge at lower energy input rates of the stirring compared to zonal flows (stripe states) and their emergence affects the dynamics of jet formation.