Extended search for point sources of neutrinos below and above the horizon: Covering energies from TeV to EeV with IceCube

Point source searches with neutrino telescopes like IceCube are normally restricted to one hemisphere, due to the selection of up-going events as a way of rejecting the atmospheric muon background. In this work we show that the down-going region above the horizon can be included in the search by suppressing the background through energy-sensitive selection procedures. This approach increases the reach to the EeV regime of the signal spectrum, which was previously not accessible due to the absorption of neutrinos with energies above a PeV inside the Earth. We present preliminary results of this analysis, which for the first time includes up-going as well as down-going muon events in a combined approach. We used data collected with IceCube in a configuration of 22 strings. No significant excess above the atmospheric background is observed. While other analyses provided results for the Northern hemisphere, this new approach extends the field of view to a large part of the Southern sky, which was previously not covered with IceCube.Comment: 4 pages, 1 figure. To be published in the proceedings of the 2nd Heidelberg workshop "High-Energy Gamma-rays and Neutrinos from Extra-Galactic Sources", 2009 (Journal of Modern Physics D

Do semantic features capture a syntactic classification of compounds? Insights from compositional distributional semantics

Classifying compound words has been the ultimate goal of much research in for- mal linguistics. A popular, cross-linguistically applicable classification (Bisetto & Scalise 2005) distinguishes three main types of compounds, namely Subordinate, Attributive, and Coordinate on the basis of the underlying syntactic relation be- tween the compound elements. Similar tripartitions have also been proposed in cognitive psychology by works exploring conceptual combination. Focusing on the type of semantic interpretation assigned to novel combinations, three main classes have been traditionally described, namely Relation-linking, Property-mapping, and Hybrid or Conjunctive (see Wisniewski 1996). Based on these commonali- ties, we conjecture that syntax-based compound types might also be explained by means of the semantic properties of the compound and its constituents. Using a compositional model of distributional semantics (cDSM), we show that (a) the con- tribution of each constituent in determining the meaning of the compound and (b) the semantic similarity between the two constituent words are significant pre- dictors of these classes. These findings suggest that the various compound types identified by syntactic criteria can also be predicted by means of semantic features. On the one hand, this confirms the validity of the proposed linguistic categoriza- tion. On the other hand, we bring further evidence proving the effectiveness of cDSMs in describing linguistic phenomena

Experimental evaluation of isentropic efficiency in turbocharger twin-entry turbines

Turbocharging plays a fundamental role not only in improving the performance of automotive engines, but also in reducing the fuel consumption and exhaust emissions of spark-ignited biofuel, diesel, liquid, and gaseous engines. Dedicated experimental investigations on turbochargers are therefore needed to evaluate a better understanding of its performance. The availability of experimental information on the steady flow performance of the turbocharger is an essential requirement to optimize the matching calculation. It is interesting to know the isentropic efficiency of the turbine in order to improve the coupling with the engine, in particular it is difficult to identify the definition of the turbine efficiency through a direct evaluation. In a radial turbine, the isentropic efficiency, evaluated directly starting from the measurement of the thermodynamic quantities at the inlet and outlet sections, can be affected by significant errors. This inaccuracy is mainly related to the incorrect evaluation of the turbine outlet temperature, due to the non-uniform distribution of the flow field in the measurement section. For this purpose, a flow conditioner was installed downstream the turbine. Tests were performed at different values of the rotational speed, and in quasi-adiabatic conditions. The flow field downstream the de-coupler was analysed through a hand-made three-hole probe with an exposed junction thermocouple inserted in the pipe with different protrusions. Thanks to this experimental campaign, it was possible to measure pressure, velocity, mass flow and temperature profiles necessary to examine the homogeneity of the flow field. As the turbocharger is fitted with a twin entry turbine, the thermodynamic quantities have been properly taken into account referring to each sector