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Suchecki K.,Royal Netherlands Academy of Arts and science KNAW | Suchecki K.,Erasmus University Rotterdam | Suchecki K.,Campus University Illes Balears | Salah A.A.A.,UVA | And 3 more authors.
Advances in Complex Systems | Year: 2012

Wikipedia, as a social phenomenon of collaborative knowledge creation, has been studied extensively from various points of view. The category system of Wikipedia, introduced in 2004, has attracted relatively little attention. In this study, we focus on the documentation of knowledge, and the transformation of this documentation with time. We take Wikipedia as a sample of knowledge in general and its category system as an aspect of the structure of this knowledge. We investigate the evolution of the category structure of the English Wikipedia from its birth in 2004 to 2008. We treat the category system as if it is a hierarchical Knowledge Organization System, capturing the changes in the distributions of the top categories. We investigate how the clustering of articles, defined by the category system, matches the direct link network between the articles and show how it changes over time. We find the Wikipedia category network mostly stable, but with occasional reorganization. We show that the clustering matches the link structure quite well, except short periods preceding the reorganizations. © 2012 World Scientific Publishing Company. Source


Jimenez Zoma N.J.,National Autonomous University of Mexico | Guerrero L.F.,Metropolitan Autonomous University | Jove F.,UVA
Vernacular Architecture: Towards a Sustainable Future - Proceedings of the International Conference on Vernacular Heritage, Sustainability and Earthen Architecture | Year: 2015

At the region of Los Altos Chiapas, in Cristóbal de las Casas, in southern Mexico, the predominant construction system since immemorial times has been adobe. One of the most interesting technical resources for the production is the use of pine needles (Pinus oocarpa) as a strategy to stabilizing the earth. To evaluate in a systematic way their qualities we are developing several studies for its characterization, focused on structural strength, capillary absorption and moisture resistance present of adobe's stabilized with pine needles in different dosages, layout and dimension. To have a properly supported protocol characterization was developed an experimental plan in the laboratory of the School of Architecture, University of Valladolid which is detailed in this paper. © 2015 Taylor & Francis Group. Source


Paranicas C.,APL | Roussos E.,MPS | Krupp N.,MPS | Kollmann P.,MPS | And 8 more authors.
Planetary and Space Science | Year: 2012

We characterize the relative importance of energetic electrons and protons to the weathering of five of the inner satellites of Saturn. To do this, we present data from the Magnetospheric Imaging Instrument on the Cassini spacecraft, some of which is averaged over the whole mission to date. We also compute averaged proton and electron energy spectra relevant to the distances of these inner satellites. Where data are available, we estimate the power per unit area into a satellites surface. For electron energy deposition into satellite leading hemispheres, we find the power per unit area is greatest at Mimas and falls off with distance from Saturn. Using fluxes of 150 MeV protons detected within the sweeping corridors of Mimas and Enceladus, we find the corresponding deposition would be about 2×10 8 and 3.7×10 7 eV/cm 2 s. © 2011 Elsevier Ltd. All rights reserved. Source


Johnston K.C.,UVA | Yan G.,University of Virginia
Stroke | Year: 2011

Background and Purpose-The Acute Physiology, Age, Chronic Health Evaluation score for critically ill patients has provided a method of predicting outcome using major physiological variables. We hypothesized that a physiology score for stroke patients (Acute Physiology of Stroke Score [APSS]) when added to a validated clinical prediction model would improve outcome prediction. Methods-The APSS was developed and validated using multivariable logistic regression. It was added to a previously validated clinical model to assess for increased area under the curve in predicting 3-month outcome. Results-The bootstrap-validated bias-corrected area under the curve for just the APSS predicting alive/dead at discharge was 0.753. The clinical model area under the curve ranged from 0.77 to 0.88 and the addition of the APSS resulted in areas under the curve of 0.77 to 0.89. Conclusions-These data suggest that the APSS is related to 3-month clinical outcome in patients with ischemic stroke. However, the APSS adds no clinically relevant additional predictive value when added to our previously validated clinical prediction model. © 2011 American Heart Association, Inc. Source


Magge R.,Massachusetts General Hospital | Magge R.,Brigham and Womens Hospital | Lau B.C.,UVA | Soares B.P.,University of California at San Francisco | And 6 more authors.
American Journal of Neuroradiology | Year: 2013

BACKGROUND AND PURPOSE: Parameters other than luminal narrowing are needed to predict the risk of stroke more reliably, particularly in patients with <70% stenosis. The goal of our study was to identify clinical risk factors and CT features of carotid atherosclerotic plaques, in a retrospective cohort of patients free of stroke at baseline, that are independent predictors of incident stroke on follow-up. MATERIALS AND METHODS: We identified a retrospective cohort of patients admitted to our emergency department with suspected stroke between 2001-2007 who underwent a stroke work-up including a CTA of the carotid arteries that was subsequently negative for acute stroke. All patients also had to receive a follow-up brain study at least 2 weeks later. From a random sample, we reviewed charts and imaging studies of patients with subsequent new stroke on follow-up as well as those who remained stroke-free. All patients were classified either as "new carotid infarct patients" or "no-new carotid infarct patients" based on the Causative Classification for Stroke. Independently, the baseline CTA studies were processed using a custom, CT-based automated computer classifier algorithm that quantitatively assesses a set of carotid CT features (wall thickness, plaque ulcerations, fibrous cap thickness, lipid-rich necrotic core, and calcifications). Univariate and multivariate statistical analyses were used to identify any significant differences in CT features between the patient groups in the sample. Subsequent ROC analysis allowed comparison to the classic NASCET stenosis rule in identifying patients with incident stroke on follow-up. RESULTS: We identified a total of 315 patients without a new carotid stroke between baseline and follow-up, and 14 with a new carotid stroke between baseline and follow-up, creating the main comparison groups for the study. Statistical analysis showed age and use of antihypertensive drugs to be the most significant clinical variables, and maximal carotid wall thickness was the most relevant imaging variable. The use of age ≥75 years, antihypertensive medication use, and a maximal carotid wall thickness of at least 4 mm was able to successfully identify 10 of the 14 patients who developed a new incident infarct on follow-up. ROC analysis showed an area under the ROC curve of 0.706 for prediction of new stroke with this new model. CONCLUSIONS: Our new paradigm of using age ≥75 years, history of hypertension, and carotid maximal wall thickness of >4 mm identified most of the patients with subsequent new carotid stroke in our study. It is simple and may help clinicians choose the patients at greatest risk of developing a carotid infarct, warranting validation with a prospective observational study. Source

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