1,720,984 research outputs found
Are higher operator volumes for unprotected left main stem percutaneous coronary intervention associated with improved patient outcomes?: A survival analysis of 6724 procedures from the British Cardiovascular Intervention Society National Database
No full textBackground: The relationship between operator volume and survival after unprotected left main stem percutaneous coronary intervention (uLMS-PCI) is poorly defined. Methods: Data from the British Cardiovascular Intervention Society national PCI database were analyzed for all uLMS-PCI procedures performed in England and Wales between 2012 and 2014 and 4 quartiles of annualized uLMS-PCI volume (Q1-Q4) generated. Individual logistic regressions were performed for 12-month mortality to quantify the independent association between operator quartile and outcomes. Results: In total, 6724 uLMS-PCI procedures were analyzed with a negatively skewed distribution and an annualized median of 3 procedures per year. Operator volume ranged from 1 to 54 uLMS-PCI procedures/year. Within Q1, 347 operators performed a median of 2 procedures/year (interquartile range, 1-3); in Q2, 134 operators performed a median of 5 procedures/year (interquartile range, 4-6); in Q3, 59 operators performed a mean of 10 procedures/year (interquartile range, 8-12); and in Q4, 29 operators performed a mean of 21 procedures/year (interquartile range, 17-29). Higher volume operators undertook uLMS-PCI in patients with greater comorbid burden and performed more complex procedures compared with lower operator volumes. Adjusted in-hospital survival (odds ratio, 0.39 [95% CI, 0.24-0.67]; P<0.001), in-hospital major adverse cardiac and cerebral events (odds ratio, 0.41 [95% CI, 0.27-0.62]; P<0.001), and 12-month survival (odds ratio, 0.54 [95% CI, 0.39-0.73]; P<0.001) were lower in Q4 operators compared with Q1 operators. A close association between operator volume/case and superior 12-month survival was observed (P<0.001). The lower volume threshold of minimum operator uLMS-PCI volume associated with improved survival was ≥16 cases/year. Conclusions: These data suggest that operator volume is an important factor in determining outcome after uLMS-PCI.</p
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Operator volumes and in-hospital outcomes: an analysis of 7,740 rotational atherectomy procedures from the BCIS national database
No full textObjectives
The aims of this study were to use a national percutaneous coronary intervention (PCI) registry to study temporal changes in procedure volumes of PCI using rotational atherectomy (ROTA-PCI), the patient and procedural factors associated with differing quartiles of operator ROTA-PCI volume, and the relationship between operator ROTA-PCI volumes and in-hospital patient outcomes.
Background
Whether higher operator volume is associated with improved outcomes after ROTA-PCI is poorly defined.
Methods
Data from the British Cardiovascular Intervention Society national PCI database were analyzed for all ROTA-PCI procedures performed in the United Kingdom between 2013 and 2016. Individual logistic regressions were performed to quantify the independent association between annual operator ROTA-PCI volume and in-hospital outcomes.
Results
In total, 7,740 ROTA-PCI procedures were performed, with a negatively skewed distribution and an annualized operator volume median of 2.5 procedures/year (range: 0.25 to 55.25). Higher volume operators undertook more complex procedures in patients with greater comorbid burdens than lower volume operators. A significant inverse association was observed between operator ROTA-PCI volume and in-hospital mortality (odds ratio [OR]: 0.986/case; 95% confidence interval (CI): 0.975 to 0.996; p = 0.007) and major adverse cardiac and cerebral events (OR: 0.983/case; 95% CI: 0.975 to 0.993; p < 0.001). Additionally, lower rates of emergency cardiac surgery (OR: 0.964/case; 95% CI: 0.939 to 0.991; p = 0.008), arterial complications (OR: 0.975/case; 95% CI: 0.975 to 0.982; p < 0.001) and in-hospital major bleeding (OR: 0.985/case; 95% CI: 0.977 to 0.993; p < 0.001) were associated with higher ROTA-PCI operator volume. Sensitivity analyses in several subgroups demonstrated a consistency of improved outcomes as annual ROTA-PCI volume increased. An annual volume of <4 ROTA-PCI procedures/year was observed to be associated with increased major adverse cardiac and cerebral events, with 239 of 432 operators (55%) not exceeding this threshold.
Conclusions
In-hospital adverse outcomes occurred less frequently as ROTA-PCI operator volume increased. These data suggest that operator volume is an important factor determining outcome after ROTA-PCI
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
High breakdown inference for mixed linear models
No full textMixed linear models are used to analyze data in many settings. These models have in most cases a multivariate normal formulation. The maximum likelihood estimator (MLE) or the residual MLE (REML) are usually chosen to estimate the parameters. However, the latter are based on the strong assumption of exact multivariate normality. Welsh and Richardson (1997) have shown that these estimators are not robust to small deviations from the multivariate normality. This means, in practice, that a small proportion of data (even only one) can drive the value of the estimates on their own. We present some of the most used models in the analysis of variance. We introduce the mixed linear model formulation and see that in most cases it is possible to extract independent subvectors of observation. The structure of the covariance matrix is derived for a great variety of models. Since the model is multivariate, we propose in this thesis a high breakdown multivariate robust estimator for very general mixed linear models, that include, for example, covariates. This robust estimator belongs to the class of S-estimators (Rousseeuw and Yohai 1984) from which we can derive the asymptotic properties for inference. We also use it as a diagnostic tool to detect outlying subjects. We derive the estimating equation defining the high breakdown estimator and we describe how it can be computed via a simple iterative algorithm. We study the behavior of the robust estimator through an extensive simulation study. It is compared to the maximum likelihood estimator under a great variety of configuration implying different models, different contamination patterns and different samples size. We also discuss the advantages of this estimator and illustrate its performance with the analysis of four datasets. We also consider robust inference for multivariate hypotheses as an alternative to the classical F-test by using a robust score type test statistic proposed by Heritier and Ronchetti (1994) and study its properties by means of simulations and real data analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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