4,244 research outputs found

    Neutrinos from supernovae: experimental status and perspectives

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    I discuss the state of the art in the search for neutrinos from galactic stellar collapses and the future perspectives of this field. The implications for the neutrino physics of a high statistics supernova neutrino burst detection by the network of detectors operating around the world are also reviewed.Comment: 19 pages, 12 figures. Extended version of talk given at IInd International Workshop on Matter, Anti-Matter and Dark Matter, Trento (Italy), 29-30 October 2001. A reduced version will appear in Int. J. of Mod. Phys.

    Thermal hadron production in high energy collisions

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    It is shown that hadron abundances in high energy e+e-, pp and p{\bar p} collisions, calculated by assuming that particles originate in hadron gas fireballs at thermal and partial chemical equilibrium, are in very good agreement with the data. The freeze-out temperature of the hadron gas fireballs turns out to be nearly constant over a large center of mass energy range and not dependent on the initial colliding system. The only deviation from chemical equilibrium resides in the incomplete strangeness phase space saturation. Preliminary results of an analysis of hadron abundances in S+S and S+Ag heavy ion collisions are presented.Comment: 10 pages, 1 .eps figure, talk given at the Strangeness and Quark Matter 97 conferenc

    Mineral oil paraffins in jute bags and cocoa butter

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    Jute bags and cocoa butter (CB) were analysed by gas chromatography (GC-FID/MS) to detect and quantify mineral oil saturated hydrocarbons (MOSH). Extraction clean-up on silica gel SPE (10 g/60 ml) was developed, as a unique sample preparation step for the determination of linear and branched n-alkanes in the range C14 to C31. The size of CB sample (500 mg) was sufficient for the detection of batching oil at levels of 2 mg kg−1, with satisfactory recovery and repeatability. MOSH from batching oil form a hump of unresolved components and the shape reflect balanced molecular-mass distribution between even and odd carbon atoms (from C14 to C22n-alkanes), expressed with the Carbon Preference Index (CPI=∑odd homologs/∑even homologs). Contaminated raw CB extracted from cocoa beans, transported and stored in jute bags during 2000 and 2001, showed MOSH (average 42 mg kg−1). However, only the 7.5% of the samples analysed of deodorized CB from 2007 to 2009 contained MOSH −1. High CPI values (>1.26) were attributed to natural hydrocarbons with a strong predominance of odd-numbered paraffins, situated between C22 and C31n-alkanes (average 31.7±5.37 mg kg−1). The results confirmed that MOSH components below n-C20 were fully eliminated by the deodorization process

    Positioning systems in Minkowski space-time: from emission to inertial coordinates

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    The coordinate transformation between emission coordinates and inertial coordinates in Minkowski space-time is obtained for arbitrary configurations of the emitters. It appears that a positioning system always generates two different coordinate domains, namely, the front and the back emission coordinate domains. For both domains, the corresponding covariant expression of the transformation is explicitly given in terms of the emitter world-lines. This task requires the notion of orientation of an emitter configuration. The orientation is shown to be computable from the emission coordinates for the users of a `central' region of the front emission coordinate domain. Other space-time regions associated with the emission coordinates are also outlined.Comment: 20 pages; 1 figur

    On the degrees of freedom of a semi-Riemannian metric

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    A semi-Riemannian metric in a n-manifold has n(n-1)/2 degrees of freedom, i.e. as many as the number of components of a differential 2-form. We prove that any semi-Riemannian metric can be obtained as a deformation of a constant curvature metric, this deformation being parametrized by a 2-for

    Overlooked impacts and challenges of the new European discard ban

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    Discards are the portion of animal and plant material in the catch that is dumped back at sea. The Common Fisheries Policy plan proposed by the European Commission for 2014-2020 presents a controversial goal: to enforce the landing of fishing discards as a measure to encourage their reduction. This historical and political decision will shape the future of the fishing exploitation in European Seas. Discards generated by European fleets are not negligible, and its reduction is an ecological, socioeconomical and moral imperative. However, it must be achieved through the reduction in discards at source and the promotion of selective and non-destructive gears. We argue it is doubtful that this discard ban will result in an effective reduction of discards. The proposed measure may, in fact, negatively affect ecosystems at all levels of biological hierarchy by disregarding the Ecosystem-Based Approach to Fisheries and the Precautionary Principle. It could negatively impact several species by increasing fishing mortality, also commercial species if discards are not accounted in the total allowable catch. Communities preying on discards will likely be affected. The role discards currently play in the energy turnover of current ecosystems will be modified and should be fully evaluated. The landing of discards will likely generate new markets of fishmeal due to the growing demands for marine living resources. The ban will require substantial public investment to deal with technical problems on board and to control and enforce. Therefore, this measure should be only implemented after rigorous scientific and technical studies have been developed
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