1,721,023 research outputs found
Astrophysical sources for the observed electron and positron axcess at high energy with AMS-02 experiment.
Full text linkCosmic ray electrons and positrons represent only _ 1% of the total particles which reach the Earth. The standard scenario predicts that the main component of the electron spectrum is the one produced by supernova remnants, while positrons are supposed to be mainly originated from the decay of muons produced by cosmic ray interactions with the interstellar medium. In the last years, space born experiments, like AMS-02, have detected an anomalous electron and positron abundance with respect to the theoretical model predictions, for energy above _ 10 GeV, where the solar modulation e_ects are negligible. This di_erence, between data and model prediction, shows an extra contribution suggesting an equal amount for both electrons and positrons. These kinds of particles, with an initial energy of 100 GeV, can travel at most for _ 2 kpc; thus, a source of electron-positron pairs is expected inside this region. We studied the contribution from Vela-X Pulsar Wind Nebula starting from its photon spectrum; a di_usion model is applied from the source up to the Solar System and the propagated spectra are compared with the AMS-02 data. Above 100 GeV, Vela-X is the main candidate to contribute to the observed excess and it could give an anisotropic signal in the arrival cosmic ray directions
Development and validation of a prognostic model for predicting the risk of allopurinol-induced severe cutaneous adverse reactions: a retrospective new-user cohort study using linked primary care, hospitalisation, and mortality data
No full textBackground Allopurinol, the most prescribed urate-lowering drug, is a known cause of severe cutaneous adverse reactions. We aimed to develop and validate a model to assess the risk of allopurinol-induced severe cutaneous adverse reactions in adults newly prescribed allopurinol. Methods In this retrospective new-user cohort study, we developed and validated a prognostic model using primary care, hospitalisation, and mortality data extracted from the UK Clinical Practice Research Datalink (CPRD) primary care database, for the period Jan 1, 2001, to March 29, 2021. Data from CPRD Aurum was used for model development and data from and CPRD GOLD was used for model validation. Adults (aged ≥18 years) residing in England who were newly prescribed allopurinol were followed up for 100 days to assess whether a severe cutaneous adverse reaction was recorded in hospitalisation or mortality records. Risk predictors included in the model were age, sex, ethnicity, chronic kidney disease stage, initial allopurinol dose, ischaemic heart disease, and heart failure. The primary outcome was to predict the 100-day risk of allopurinol-induced severe cutaneous adverse reactions in people newly prescribed allopurinol. We developed the model using multivariable Cox regression and pseudo-values, followed by penalisation and external validation. We assessed calibration, discrimination, and clinical utility in the risk range of 0·0001 to 0·003. People with lived experience of allopurinol use or gout were not involved in developing this research question, but will be involved in the dissemination of results. Findings 225 761 patients newly prescribed allopurinol were registered in the CPRD Aurum database (development cohort) and 173 812 were included in the study. 44 630 (25·7%) of 173 812 patients were female, 129 182 (74·3%) were male, 154 323 (88·8%) were White, and the mean age was 63·9 years (SD 15·0). Of the patients newly prescribed allopurinol with data in the CPRD GOLD database (validation cohort), 55 395 patients were screened and 41 610 were included in the study. 10 829 (26·0%) of 41 610 patients were female, 30 781 (74·0%) were male, 37 242 (89·5%) were White and the mean age was 64·4 years (SD 14·9). 63 (0·04%) severe cutaneous adverse events occurred in 173 812 patients in the development cohort and 16 (0·04%) occurred in 41 610 patients in the validation cohort. Age (adjusted hazard ratio 1·03 [95% CI 1·01–1·06]), chronic kidney disease stages 3, 4, and 5 (2·24 [1·20–4·17] for stage 3; 6·65 [2·90–15·23] for stage 4; 18·85 [6·32–56·19] for stage 5), initial allopurinol dose of 300 mg or higher (5·99 [3·56–0·08]), South Asian ethnicity (5·35 [2·37–12·07]), and other Asian ethnicity (5·63 [1·34–23·61]) were associated with the 100-day risk of allopurinol-induced severe cutaneous adverse reactions. In the development dataset, after optimism-adjustment, the model's explained variation (Royston and Sauerbrei's R2D) was 0·50 and Harrell's C was 0·82. In the validation dataset, the calibration slope was 0·93 (95% CI 0·18–1·68), the R2D was 0·44 (95% CI 0·20–0·62), and Harrell's C was 0·79 (95% CI 0·71–0·88). The model had clinical utility across the prespecified risk range. Interpretation We developed and validated a prognostic model for the 100-day risk of an allopurinol-induced severe cutaneous adverse reaction with good predictive performance and clinical utility. This model could be used to inform the choice of urate-lowering drugs. Funding University of Nottingham
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
Pulsar Wind Nebulae as a source of the observed electron and positron excess at high energy: The case of Vela-X
No full textAbstractWe investigate, in terms of production from pulsars and their nebulae, the cosmic ray positron and electron fluxes above ∼10 GeV, observed by the AMS-02 experiment up to 1 TeV. We concentrate on the Vela-X case. Starting from the gamma-ray photon spectrum of the source, generated via synchrotron and inverse Compton processes, we estimated the electron and positron injection spectra. Several features are fixed from observations of Vela-X and unknown parameters are borrowed from the Crab nebula. The particle spectra produced in the pulsar wind nebula are then propagated up to the Solar System, using a diffusion model. Differently from previous works, the omnidirectional intensity excess for electrons and positrons is obtained as a difference between the AMS-02 data and the corresponding local interstellar spectrum. An equal amount of electron and positron excess is observed and we interpreted this excess (above ∼100 GeV in the AMS-02 data) as a supply coming from Vela-X. The particle contribution is consistent with models predicting the gamma-ray emission at the source. The input of a few more young pulsars is also allowed, while below ∼100 GeV more aged pulsars could be the main contributors
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
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
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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