11,041 research outputs found

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    How many Ultra High Energy Cosmic Rays could we expect from Centaurus A?

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    The Pierre Auger Observatory has associated a few ultra high energy cosmic rays with the direction of Centaurus A. This source has been deeply studied in radio, infrared, X-ray and γ\gamma-rays (MeV-TeV) because it is the nearest radio-loud active galactic nuclei. Its spectral energy distribution or spectrum shows two main peaks, the low energy peak, at an energy of 10−210^{-2} eV, and the high energy peak, at about 150 keV. There is also a faint very high energy (E ≥\geq 100 GeV) γ\gamma-ray emission fully detected by the High Energy Stereoscopic System experiment. In this work we describe the entire spectrum, the two main peaks with a Synchrotron/Self-Synchrotron Compton model and, the Very High Energy emission with a hadronic model. We consider pγ\gamma and pppp interactions. For the pγ\gamma interaction, we assume that the target photons are those produced at 150 keV in the leptonic processes. On the other hand, for the pp interaction we consider as targets the thermal particle densities in the lobes. Requiring a satisfactory description of the spectra at very high energies with pγ\gamma interaction we obtain an excessive luminosity in ultra high energy cosmic rays (even exceeding the Eddington luminosity). However, when considering pp interaction to describe the γ\gamma-spectrum, the obtained number of ultra high energy cosmic rays are in agreement with Pierre Auger observations. Moreover, we calculate the possible neutrino signal from pp interactions on a Km3^3 neutrino telescope using Monte Carlo simulations.Comment: Accepted in Ap

    Study of TeV variability of Mrk 421 from 3 years of monitoring with the Milagro Observatory

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    The Milagro experiment was a TeV gamma-ray observatory designed to continuously monitor the overhead sky in the 0.1-100 TeV energy range. It operated from 2000 and 2008 and was characterized by a large field of view (∼\sim 2 sr) and a high duty cycle (≥\geq 90%\%). Here we report on the long-term monitoring of the blazar Mrk 421 with Milagro over the period from September 21, 2005 to March 15, 2008. We present a study of the TeV variability of the source and provide upper limits for the measured flux for different time scales, ranging from one week up to one year.Comment: 3 pages, 2 figures. Paper to appear in the Proceedings of the Thirteen Marcel Grossmann Meeting, held in Stockholm, Sweden, on July 2012, World Scientific, Singapore, in pres

    Sequential modular position and momentum measurements of a trapped ion mechanical oscillator

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    The non-commutativity of position and momentum observables is a hallmark feature of quantum physics. However this incompatibility does not extend to observables which are periodic in these base variables. Such modular-variable observables have been suggested as tools for fault-tolerant quantum computing and enhanced quantum sensing. Here we implement sequential measurements of modular variables in the oscillatory motion of a single trapped ion, using state-dependent displacements and a heralded non-destructive readout. We investigate the commutative nature of modular variable observables by demonstrating no-signaling-in-time between successive measurements, using a variety of input states. In the presence of quantum interference, which we enhance using squeezed input states, measurements of different periodicity show signaling-in-time. The sequential measurements allow us to extract two-time correlators for modular variables, which we use to violate a Leggett-Garg inequality. The experiments involve control and coherence of multi-component superpositions of up to 8 coherent, squeezed or Fock state wave-packets. Signaling-in-time as well as Leggett-Garg inequalities serve as efficient quantum witnesses which we probe here with a mechanical oscillator, a system which has a natural crossover from the quantum to the classical regime.Comment: 6 pages, 3 figures and supplemental informatio

    Finding the Imagined Motherland in China: the Italian experience in Tianjin

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    Nearly one hundred years ago, from 25 to 27 September, 1910 a Conference of =Orientalist-Geographers` was held to commemorate the =apostle and geographer of China`, the Jesuit Father Matteo Ricci (1552-1610). This event took place three hundred years after his death, in his native town, Macerata (Anonymous, 1911, 1). On that occasion, two of the invited speakers, Mr E. A. Perogio and Mr L. Sborlino, chose as the focus of their speeches =Italians and Government in China` (Italiani e Governo in Cina) and =The Royal Italian Concession of Tien-Tsin`, respectively. By this stage, nearly fifty years had passed since the complex and problematic creation of the newly unified Italian State, and significantly, only nine years had elapsed after the official acquisition from the Qing Government of the territory destined to become the Italian concession (yizujie), that has been re-baptised today as Italianstyle scenic neighbourhood (yishi fengqingqu)

    Diffuse cosmic rays shining in the Galactic center: A novel interpretation of H.E.S.S. and Fermi-LAT gamma-ray data

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    We present a novel interpretation of the γ\gamma-ray diffuse emission measured by Fermi-LAT and H.E.S.S. in the Galactic center (GC) region and the Galactic ridge (GR). In the first part we perform a data-driven analysis based on PASS8 Fermi-LAT data: we extend down to few GeV the spectra measured by H.E.S.S. and infer the primary cosmic-ray (CR) radial distribution between 0.1 and 3 TeV. In the second part we adopt a CR transport model based on a position-dependent diffusion coefficient. Such behavior reproduces the radial dependence of the CR spectral index recently inferred from the Fermi-LAT observations. We find that the bulk of the GR emission can be naturally explained by the interaction of the diffuse steady-state Galactic CR sea with the gas present in the Central Molecular Zone. Although our results leave room for a residual radial-dependent emission associated with a central source, the relevance of the large-scale background prevents from a solid evidence of a GC Pevatron.Comment: 5 pages, 3 figures, accepted for publication in Physical Review Letter

    Ethical and medico-legal remarks on uterus transplantation: may it solve uterine factor infertility?

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    Uterus transplantation was firstly tested with animal trials sixty-five years ago. Despite several successful attempts in human subjects, the different procedures still lay at the experimental stage, in need of further studies and investigations before they can be considered as standard clinical practices. Uterus transplant cannot be regarded as a life-saving procedure, but rather a method to restore woman ability to procreate, when lost, thus improving her quality of life. Uterus transplant is a complex surgical procedure and presents significant health threats. Medical staff should therefore always obtain informed consent from patients, emphasizing such risks. Before that, women undergoing uterine transplants should be thoroughly informed about the hazards inherent to the procedure and especially about the dangers of immunosuppressant drugs, administered after the surgery which may injure the fetus, eventually formed in the restored organ and even lead to its death, thus nullifying the purpose of the transplant itself. Therefore, the risk-benefit ratio of uterus transplantation needs to be carefully assessed and described
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