Search results for "GAM"
showing 10 items of 5334 documents
Mapping research on legacy of mega sporting events: structural changes, consequences, and stakeholder evaluations in empirical studies
2019
Findings from empirical studies on the legacy of hosting a mega sporting event are inconclusive. This paper considers empirical studies published in English language peer-reviewed journals between ...
Historical and Technical Notes on Aqueducts from Prehistoric to Medieval Times
2013
The aim of this paper is to present the evolution of aqueduct technologies through the millennia, from prehistoric to medieval times. These hydraulic works were used by several civilizations to collect water from springs and to transport it to settlements, sanctuaries and other targets. Several civilizations, in China and the Americas, developed water transport systems independently, and brought these to high levels of sophistication. For the Mediterranean civilizations, one of the salient characteristics of cultural development, since the Minoan Era (ca. 3200-1100 BC), is the architectural and hydraulic function of aqueducts used for the water supply in palaces and other settlements. The M…
Predicting hospital associated disability from imbalanced data using supervised learning.
2019
Hospitalization of elderly patients can lead to serious adverse effects on their functional capability. Identifying the underlying factors leading to such adverse effects is an active area of medical research. The purpose of the current paper is to show the potential of artificial intelligence in the form of machine learning to complement the existing medical research. This is accomplished by studying the outcome of hospitalization of elderly patients as a supervised learning task. A rich set of features characterizing the medical and social situation of elderly patients is leveraged and using confusion matrices, association rule mining, and two different classes of supervised learning algo…
Beta Decay Studies of Neutron Rich Nuclei Using Total Absorption Gamma-ray Spectroscopy and Delayed Neutron Measurements
2010
International audience; A complete characterisation of the β-decay of neutron-rich nuclei can be obtained from the measurement of β-delayed gamma rays and, whenever the process is energetically possible, β-delayed neutrons. The accurate determination of the β-intensity distribution and the β-delayed neutron emission probability is of great relevance in the fields of reactor technology and nuclear astrophysics. A programme for combined measurements using the total absorption gamma-ray spectroscopy technique and both neutron counters and neutron time-of-flight spectrometers is presented.
Hints of an axion-like particle mixing in the GeV gamma-ray blazar data?
2013
Axion-Like Particles (ALPs), if exist in nature, are expected to mix with photons in the presence of an external magnetic field. The energy range of photons which undergo strong mixing with ALPs depends on the ALP mass, on its coupling with photons as well as on the external magnetic field and particle density configurations. Recent observations of blazars by the Fermi Gamma-Ray Space Telescope in the 0.1-300 GeV energy range show a break in their spectra in the 1-10 GeV range. We have modeled this spectral feature for the flat-spectrum radio quasar 3C454.3 during its November 2010 outburst, assuming that a significant fraction of the gamma rays convert to ALPs in the large scale jet of thi…
Why Have Many of the Brightest Radio-loud Blazars Not Been Detected in Gamma-Rays by Fermi?
2015
We use the complete MOJAVE 1.5 Jy sample of active galactic nuclei (AGNs) to examine the gamma-ray detection statistics of the brightest radio-loud blazars in the northern sky. We find that 23% of these AGNs were not detected above 0.1 GeV by the Fermi-LAT during the four-year 3FGL catalog period partly because of an instrumental selection effect and partly due to their lower Doppler boosting factors. Blazars with synchrotron peaks in their spectral energy distributions located below 10^(13.4) Hz also tend to have high-energy peaks that lie below the 0.1 GeV threshold of the LAT, and are thus less likely to be detected by Fermi. The non-detected AGNs in the 1.5 Jy sample also have significa…
Relativistic simulations of black hole-neutron star coalescence: the jet emerges
2014
We perform magnetohydrodynamic simulations in full general relativity (GRMHD) of a binary black hole-neutron star on a quasicircular orbit that undergoes merger. The binary mass ratio is 3:1, the black hole initial spin parameter $a/m=0.75$ ($m$ is the black hole Christodoulou mass) aligned with the orbital angular momentum, and the neutron star is an irrotational $\Gamma=2$ polytrope. About two orbits prior to merger (at time $t=t_B$), we seed the neutron star with a dynamically weak interior dipole magnetic field that extends into the stellar exterior. At $t=t_B$ the exterior has a low-density atmosphere with constant plasma parameter $\beta\equiv P_{\rm gas}/P_{\rm mag}$. Varying $\beta$…
Binary neutron star mergers: a jet engine for short gamma-ray bursts
2016
We perform magnetohydrodynamic simulations in full general relativity (GRMHD) of quasi-circular, equal-mass, binary neutron stars that undergo merger. The initial stars are irrotational, $n=1$ polytropes and are magnetized. We explore two types of magnetic-field geometries: one where each star is endowed with a dipole magnetic field extending from the interior into the exterior, as in a pulsar, and the other where the dipole field is initially confined to the interior. In both cases the adopted magnetic fields are initially dynamically unimportant. The merger outcome is a hypermassive neutron star that undergoes delayed collapse to a black hole (spin parameter $a/M_{\rm BH} \sim 0.74$) imme…
The Gamma-Ray Emitting Radio-Loud Narrow-Line Seyfert 1 Galaxy PKS 2004-447 II. The Radio View
2015
Gamma-ray detected radio-loud narrow-line Seyfert 1 (g-NLS1) galaxies constitute a small but interesting sample of the gamma-ray loud AGN. The radio-loudest g-NLS1 known, PKS 2004-447, is located in the southern hemisphere and is monitored in the radio regime by the multiwavelength monitoring program TANAMI. We aim for the first detailed study of the radio morphology and long-term radio spectral evolution of PKS 2004-447, which are essential to understand the diversity of the radio properties of g-NLS1s. The TANAMI VLBI monitoring program uses the Australian Long Baseline Array (LBA) and telescopes in Antarctica, Chile, New Zealand, and South Africa to monitor the jets of radio-loud active …
Radio and gamma-ray properties of extragalactic jets from the TANAMI sample
2016
Using high-resolution radio imaging with VLBI techniques, the TANAMI program has been observing the parsec-scale radio jets of southern (declination south of -30{\deg}) gamma-ray bright AGN simultaneously with Fermi/LAT monitoring of their gamma-ray emission. We present the radio and gamma-ray properties of the TANAMI sources based on one year of contemporaneous TANAMI and Fermi/LAT data. A large fraction (72%) of the TANAMI sample can be associated with bright gamma-ray sources for this time range. Association rates differ for different optical classes with all BL Lacs, 76% of quasars and just 17% of galaxies detected by the LAT. Upper limits were established on the gamma-ray flux from TAN…