351 research outputs found

    Runaway Events Dominate the Heavy Tail of Citation Distributions

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    Statistical distributions with heavy tails are ubiquitous in natural and social phenomena. Since the entries in heavy tail have disproportional significance, the knowledge of its exact shape is very important. Citations of scientific papers form one of the best-known heavy tail distributions. Even in this case there is a considerable debate whether citation distribution follows the log-normal or power-law fit. The goal of our study is to solve this debate by measuring citation distribution for a very large and homogeneous data. We measured citation distribution for 418,438 Physics papers published in 1980-1989 and cited by 2008. While the log-normal fit deviates too strong from the data, the discrete power-law function with the exponent γ=3.15\gamma=3.15 does better and fits 99.955% of the data. However, the extreme tail of the distribution deviates upward even from the power-law fit and exhibits a dramatic "runaway" behavior. The onset of the runaway regime is revealed macroscopically as the paper garners 1000-1500 citations, however the microscopic measurements of autocorrelation in citation rates are able to predict this behavior in advance.Comment: 6 pages, 5 Figure

    The emerging zika virus epidemic in the Americas: Research priorities

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    On February 1, 2016, the World Health Organization declared a “public health emergency of international concern” regarding neurological disorders associated with the rapid emergence of Zika virus (ZIKV) in the Americas. Since being detected in Brazil in early 2015, ZIKV has spread extensively, with most countries in Latin America and the Caribbean now reporting local transmission of the virus. An association between congenital ZIKV infection and birth defects, most prominently microcephaly, has prompted intense concern among health officials and the public

    Variation in paranasal pneumatisation between Mid-Late Pleistocene hominins

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    There is considerable variation in mid-late Pleistocene hominin paranasal sinuses, and in some taxa distinctive craniofacial shape has been linked to sinus size. Extreme frontal sinus size has been reported in mid-Pleistocene specimens often classified as Homo heidelbergensis, and Neanderthal sinuses are said to be distinctively large, explaining diagnostic Neanderthal facial shape. Here, the sinuses of fossil hominins attributed to several mid-late Pleistocene taxa were compared to those of recent H. sapiens. The sinuses were investigated to clarify differences in the extent of pneumatisation within this group and the relationship between sinus size and craniofacial variation in hominins from this time period. Frontal and maxillary sinus volumes were measured from CT data, and geometric morphometric methods were used to identify and analyse shape variables associated with sinus volume. Some mid

    Search for black holes and other new phenomena in high-multiplicity final states in proton-proton collisions at root s=13 TeV

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    Search for high-mass diphoton resonances in proton-proton collisions at 13 TeV and combination with 8 TeV search

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    Search for heavy resonances decaying into a vector boson and a Higgs boson in final states with charged leptons, neutrinos, and b quarks

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    Measurement of the mass difference between top quark and antiquark in pp collisions at root s=8 TeV

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    Search for leptophobic Z ' bosons decaying into four-lepton final states in proton-proton collisions at root s=8 TeV

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    Vascular endothelial growth factor (VEGF), transforming growth factor beta (TGFbeta), angiostatin, and endostatin are increased in radiotherapy-induced gastrointestinal toxicity

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    Radiotherapy-induced gut toxicity (RIGT) is a debilitating effect of radiotherapy for cancer, often resulting in significant diarrhoea and pain. Previous studies have highlighted roles of the intestinal microvasculature and matrix metalloproteinases (MMPs) in the development of RIGT. We hypothesized vascular mediators would be significantly altered in a dark agouti (DA) rat model of RIGT. Additionally, we aimed to assess the effect of MMP-2 and -9 inhibition on the response of tumour-associated microvascular endothelial cells (TAMECs) to radiation.Dark Agouti (DA) rats were administered 2.5 Gy abdominal irradiation (3 times/week over 6 weeks). Vascular endothelial growth factor (VEGF), transforming growth factor beta (TGFβ), von Willebrand factor (VWF), angiostatin, and endostatin expression was assessed at 3, 6 and 15 weeks. Additionally, DA rat mammary adenocarcinoma tumour-associated microvascular endothelial cells (TAMECs) were used to assess the effects of radiation (12 Gy) and the MMP inhibitor SB-3CT on MMP, VEGF, and TGFβ expression, and cell viability.VEGF mRNA expression was significantly increased in the colon at week 15 (p = 0.0012), and TGFβ mRNA expression was significantly increased in both the jejunum and colon at week 3 (p = 0.0280, and p = 0.0310, respectively). Endostatin immunostaining was significantly increased at week 3 (p = 0.0046), and angiostatin at 3 and 6 weeks (p = 0.0022, and p = 0.0135, respectively). MMP-2 and -9 mRNA and total protein levels were significantly increased following irradiation of TAMECs. Although this increase was significantly attenuated by SB-3CT, it did not significantly alter endothelial cell viability or VEGF and TGFβ mRNA expression.Findings of this study support the involvement of VEGF, TGFβ, angiostatin, endostatin, and MMP-2 in the pathobiology of RIGT. However, the relationship between these mediators is complex and needs further investigation to improve understanding of their therapeutic potential in RIGT.Romany L. Stansborough, Emma H. Bateman, Noor Al-Dasooqi, Joanne M. Bowen, Anthony Wignall, Dorothy M. Keefe, Ann S. Yeoh, Richard M. Logan, Eric E. K. Yeoh, Andrea M. Stringer and Rachel J. Gibso
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