2,014 research outputs found

    PanDA Workload Management System Meta-data Segmentation

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    AbstractThe PanDA (Production and Distributed Analysis) workload management system (WMS) was developed to meet the scale and complexity of LHC distributed computing for the ATLAS experiment. PanDA currently distributes jobs among more than 100,000 cores at well over 120 Grid sites, supercomputing centers, commercial and academic clouds. ATLAS physicists submit more than 1.5M data processing, simulation and analysis PanDA jobs per day, and the system keeps all meta-information about job submissions and execution events in Oracle RDBMS. The above information is used for monitoring and accounting purposes. One of the most challenging monitoring issues is tracking errors that has occurred during the execution of the jobs. Current meta-data storage technology doesn‚Äôt support inner tools for data aggregation, needed to build error summary tables, charts and graphs. Delegating these tasks to the monitor slows down the execution of requests.We will describe a project aimed at optimizing interaction between PanDA front-end and back-end, by meta-data storage segmentation into two parts ‚Äď operational and archived. Active meta-data are remained in Oracle database (operational part), due to the high requirements for data integrity. Historical (read-only) meta-data used for the system analysis and accounting are exported to NoSQL storage (archived part). New data model based on usage of Cassandra as the NoSQL backend has been designed as a set of query-specific data structures. This allowed to remove most of data preparation workload from PanDA Monitor and improve its scalability and performance. Segmentation and synchronization between operational and archived parts of jobs meta-data is provided by a Hybrid Meta-data Storage Framework (HMSF). PanDA monitor was partly adopted to interact with HMSF. The operational data queries are forwarded to the primary SQL-based repository and the analytic data requests are processed by NoSQL database. The results of performance and scalability tests of HMSF-adopted part of PanDA Monitor shows that presented method of optimization, in conjunction with a properly configured NoSQL database and reasonable data model, provides performance improvements and scalability

    Plasmon channels in the electronic relaxation of diamond under high-order harmonics femtosecond irradiation

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    We used high order harmonics of a femtosecond titanium-doped sapphire system (pulse duration 25 fs) to realise Ultraviolet Photoelectron Spectroscopy (UPS) measurements on diamond. The UPS spectra were measured for harmonics in the range 13 to 27. We also made ab initio calculations of the electronic lifetime of conduction electrons in the energy range produced in the UPS experiment. Such calculations show that the lifetime suddenly diminishes when the conduction electron energy reaches the plasmon energy, whereas the UPS spectra show evidence in this range of a strong relaxation mechanism with an increased production of low energy secondary electrons. We propose that in this case the electronic relaxation proceeds in two steps : excitation of a plasmon by the high energy electron, the latter decaying into individual electron-hole pairs, as in the case of metals. This process is observed for the first time in an insulator and, on account of its high efficiency, should be introduced in the models of laser breakdown under high intensity

    ‚ÄúCommunist Muslims‚ÄĚ : The USSR and the people's democratic party of Afghanistan's conversion to Islam, 1978‚Äď1988

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    Soviet leaders sent troops into Afghanistan in December 1979 to support a friendly Marxist-Leninist regime in its conflict against a popular insurgency and help it build a new society. When the Soviet troops withdrew nine years later, they left behind a state that had none of the nominal characteristics of a Soviet-type Communist country. During the war, the People's Democratic Party of Afghanistan had discarded Marxism-Leninism and turned to Islam. This article examines how, with Moscow's support, the Afghan Communists Islamicized their discourse and policies as they tried to gain support from the population and co-opt insurgent fighters

    The allure of Jihad : the de-territorialization of the war in the North Caucasus

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    Published online: 22 October 2020Insurgents in the North Caucasus switched from the al-Qaedaaffiliated Imarat Kavkaz to the Islamic State after 2014. Although this transition was partially the result of Imarat Kavkaz’s military defeat, it has also settled two decades of tension over ideology. It signalled the victory of Salafi-jihadism over a nationally rooted (radical) Islamism and led to a break between the insurgents and the Caucasian context. This de-territorialization of grievances for the war has in turn increased the threat of radical Islamist violence for Russia

    Photoconductivity and Photoemission of Diamond Under Femtosecond Vuv Irradiation

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    In order to gain some insight on the electronic relaxation mechanisms occuring in diamond under high intensity laser excitation and/or VUV excitation, we studied experimentally the pulsed conductivity induced by femtosecond VUV pulses, as well as the energy spectra of the photoelectrons released by the same irradiation. The source of irradiation consists in highly coherent VUV pulses obtained through high order harmonic generation of a high intensity femtosecond pulse at a 1.55 eV photon energy (titanium-doped sapphire laser). Harmonics H9 to H17 have been used for photoconductivity (PC) and harmonics H13 to H27 for photoemission experiments (PES). As the photon energy is increased, it is expected that the high energy photoelectrons will generate secondary e-h pairs, thus increasing the excitation density and consequently the PC signal. This is not what we observe : the PC signal first increases for H9 to H13, but then saturates and even decreases. Production of low energy secondary e-h pairs should also be observed in the PES spectrum. In fact we observe very few low energy electrons in the PES spectrum obtained with H13 and H15, despite the sufficient energy of the generated free carriers. At the other end (H21 and above), a very intense low energy secondary electron peak is observed. As a help to interprete such data, we realized the first ab initio calculations of the electronic lifetime of quasiparticles, in the GW approximation in a number of dielectrics including diamond. We find that the results are quite close to a simple "Fermi-liquid" estimation using the electronic density of diamond. We propose that a quite efficient mechanism could be the excitation of plasmons by high energy electrons, followed by the relaxation of plasmons into individual e-h pairs

    Study of Spin and Decay-Plane Correlations of W Bosons in the e+e- -> W+W- Process at LEP

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    Data collected at LEP at centre-of-mass energies \sqrt(s) = 189 - 209 GeV are used to study correlations of the spin of W bosons using e+e- -> W+W- -> lnqq~ events. Spin correlations are favoured by data, and found to agree with the Standard Model predictions. In addition, correlations between the W-boson decay planes are studied in e+e- -> W+W- -> lnqq~ and e+e- -> W+W- -> qq~qq~ events. Decay-plane correlations, consistent with zero and with the Standard Model predictions, are measured
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