Institution
University of Johannesburg
Education•Johannesburg, South Africa•
About: University of Johannesburg is a education organization based out in Johannesburg, South Africa. It is known for research contribution in the topics: Population & Tourism. The organization has 8070 authors who have published 22749 publications receiving 329408 citations. The organization is also known as: UJ.
Topics: Population, Tourism, Large Hadron Collider, Adsorption, Higher education
Papers published on a yearly basis
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SLAC National Accelerator Laboratory1, Kansas State University2, Istituto Nazionale di Fisica Nucleare3, University of Trieste4, University of Padua5, University of Maryland, College Park6, Goddard Space Flight Center7, University of Turin8, École Polytechnique9, Instituto Politécnico Nacional10, INAF11, Agenzia Spaziale Italiana12, United States Naval Research Laboratory13, University of Montpellier14, University of Bologna15, University of Udine16, Stanford University17, Hiroshima University18, University of London19, École Normale Supérieure20, Paris Diderot University21, University of Tokyo22, University of Iceland23, University of Gothenburg24, Max Planck Society25, University of Botswana26, University of Johannesburg27, Ames Research Center28, Jagiellonian University29, Sea Mammal Research Unit30, Catalan Institution for Research and Advanced Studies31, Spanish National Research Council32
TL;DR: In this article, the authors observed minute-scale variability suggests a very compact emission region at hundreds of Schwarzschild radii from the central engine in conical jet models, where a minimum bulk jet Lorentz factor of 35 is necessary to avoid both internal gamma-ray absorption and super-Eddington jet power.
Abstract: On 2015 June 16, Fermi-LAT observed a giant outburst from the flat spectrum radio quasar 3C 279 with a peak $>100$ MeV flux of $\sim3.6\times10^{-5}\;{\rm photons}\;{\rm cm}^{-2}\;{\rm s}^{-1}$ averaged over orbital period intervals. It is the historically highest $\gamma$-ray flux observed from the source including past EGRET observations, with the $\gamma$-ray isotropic luminosity reaching $\sim10^{49}\;{\rm erg}\;{\rm s}^{-1}$. During the outburst, the Fermi spacecraft, which has an orbital period of 95.4 min, was operated in a special pointing mode to optimize the exposure for 3C 279. For the first time, significant flux variability at sub-orbital timescales was found in blazar observations by Fermi-LAT. The source flux variability was resolved down to 2-min binned timescales, with flux doubling times less than 5 min. The observed minute-scale variability suggests a very compact emission region at hundreds of Schwarzschild radii from the central engine in conical jet models. A minimum bulk jet Lorentz factor ($\Gamma$) of 35 is necessary to avoid both internal $\gamma$-ray absorption and super-Eddington jet power. In the standard external-radiation-Comptonization scenario, $\Gamma$ should be at least 50 to avoid overproducing the synchrotron-self-Compton component. However, this predicts extremely low magnetization ($\sim5\times10^{-4}$). Equipartition requires $\Gamma$ as high as 120, unless the emitting region is a small fraction of the dissipation region. Alternatively, we consider $\gamma$ rays originating as synchrotron radiation of $\gamma_{\rm e}\sim1.6\times10^6$ electrons, in magnetic field $B\sim1.3$ kG, accelerated by strong electric fields $E\sim B$ in the process of magnetoluminescence. At such short distance scales, one cannot immediately exclude production of $\gamma$ rays in hadronic processes.
233 citations
01 Dec 2014
TL;DR: In this paper, a measurement of the production processes of the recently discovered Higgs boson is performed in the two-photon final state using 4.5 fb(-1) of proton-proton collisions data at root s = 7 TeV and 20.4 GeV.
Abstract: A measurement of the production processes of the recently discovered Higgs boson is performed in the two-photon final state using 4.5 fb(-1) of proton-proton collisions data at root s = 7 TeV and 20.3 fb(-1) at root s = 8 TeV collected by the ATLAS detector at the Large Hadron Collider. The number of observed Higgs boson decays to diphotons divided by the corresponding Standard Model prediction, called the signal strength, is found to be mu = 1.17 +/- 0.27 at the value of the Higgs boson mass measured by ATLAS, m(H) = 125.4 GeV. The analysis is optimized to measure the signal strengths for individual Higgs boson production processes at this value of m(H). They are found to be mu(ggF) = 1.32 +/- 0.38, mu(VBF) = 0.8 +/- 0.7, mu(WH) = 1.0 +/- 1.6, mu(ZH) = 0.1(-0.1)(+3.7), and mu t (t) over barH = 1.6(-1.8)(+2.7), for Higgs boson production through gluon fusion, vector-boson fusion, and in association with a W or Z boson or a top-quark pair, respectively. Compared with the previously published ATLAS analysis, the results reported here also benefit from a new energy calibration procedure for photons and the subsequent reduction of the systematic uncertainty on the diphoton mass resolution. No significant deviations from the predictions of the Standard Model are found.
233 citations
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TL;DR: In this article, the authors examine key developments in recent tourism mobilities research, arguing that tourism is not just a form of mobility like other forms of mobility but that different mobilities inform and are informed by tourism.
233 citations
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TL;DR: This article conducted a systematic review of the tourism and adaptation literature prior to 2012 and concluded that adaptation studies in tourism have so far had a limited focus on community perceptions, which in general has been an area of major interest in tourism research.
Abstract: The relationship between tourism and changing climate has been discussed and studied for a relatively long time in tourism research. Over the past 15 years, more focused studies have begun to appear, and especially recently, the issue of adaptation has been emphasised as an urgent research need in tourism and climate change studies. This paper is based on a systematic review of the tourism and adaptation literature prior to 2012. It discusses adaptation challenges, the dimensions of vulnerability in a tourism context and the implications of such studies on communities. By dividing the current adaptation studies into business; consumer; destination; and policy- and framework-focused theme areas and traditions, the paper concludes that adaptation studies in tourism have so far had a limited focus on community perceptions, which in general has been an area of major interest in tourism research. More emphasis on community-based research in relation to tourism and climate change allows highly contextual adapta...
232 citations
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TL;DR: In this article, the authors used the ATLAS detector at the Large Hadron Collider (LHC) to measure inclusive jet and dijet cross sections in proton-proton collisions at a centre-of-mass energy of 7 TeV using the anti-kT algorithm.
Abstract: Inclusive jet and dijet cross sections have been measured in proton-proton collisions at a centre-of-mass energy of 7 TeV using the ATLAS detector at the Large Hadron Collider. The cross sections were measured using jets clustered with the anti-kT algorithm with parameters R=0.4 and R=0.6. These measurements are based on the 2010 data sample, consisting of a total integrated luminosity of 37 inverse picobarns. Inclusive jet double-differential cross sections are presented as a function of jet transverse momentum, in bins of jet rapidity. Dijet double-differential cross sections are studied as a function of the dijet invariant mass, in bins of half the rapidity separation of the two leading jets. The measurements are performed in the jet rapidity range |y|<4.4, covering jet transverse momenta from 20 GeV to 1.5 TeV and dijet invariant masses from 70 GeV to 5 TeV. The data are compared to expectations based on next-to-leading order QCD calculations corrected for non-perturbative effects, as well as to next-to-leading order Monte Carlo predictions. In addition to a test of the theory in a new kinematic regime, the data also provide sensitivity to parton distribution functions in a region where they are currently not well-constrained.
230 citations
Authors
Showing all 8414 results
Name | H-index | Papers | Citations |
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Vinod Kumar Gupta | 165 | 713 | 83484 |
Arnold B. Bakker | 135 | 506 | 103778 |
Trevor Vickey | 128 | 873 | 76664 |
Ketevi Assamagan | 128 | 934 | 77061 |
Diego Casadei | 123 | 733 | 69665 |
Michael R. Hamblin | 117 | 899 | 59533 |
E. Castaneda-Miranda | 117 | 545 | 56349 |
Xiaoming Li | 113 | 1932 | 72445 |
Katharine Leney | 108 | 459 | 52547 |
M. Aurousseau | 103 | 403 | 44230 |
Mika Sillanpää | 96 | 1019 | 44260 |
Sahal Yacoob | 89 | 408 | 25338 |
Evangelia Demerouti | 85 | 236 | 49228 |
Lehana Thabane | 85 | 994 | 36620 |
Sahal Yacoob | 84 | 399 | 35059 |