4,282 research outputs found

    Critical Reception since 1900

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    Geofísica ambiental: técnicas no destructivas para el reconocimiento de zonas contaminadas por vertidos

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    Industrial countries face the consequences of decades of inappropiate handling of hazardous waste. The dumping of al1 types of hazardous materials has been ongoing in most industrialised countries for hundreds of years. Large quantities of industrial and other waste material have been buried in landfill sites. A relatively large number of these lack reliable man-made or natural geological barriers and toxic fluids are scaping and polluting the groundwater. The problem is greatly aggravated when a soil covenng is placed over the waste and there is no information about the dumping practices used in the past. One of the first tasks in any remedial action is to delineate the physical extent of the sites and its encroachment into the surrounding area. Test borings and limited excavations are very valuable but the information obtained is not continuous and dheir destructive nature makes it possible that waste could inadvertently be released during the probing phase. In this regard, both borehole drilling and excavation are very dangerous to workers and the environment and expensive and tedious to conduct.Many of these problems may be alleviated by using a geophysical assisted system approach to determine where the pollutants will go in the subsurface, gain more complete understanding of site conditions and asses the optimal placement of exploration drills and monitonng wells. At hazardous waste sites, the main objectives must commonly include:- Determine the presence, location, distribution, depth and composition of possible buried wastes.- Determine the presence and extent of contaminant and leachate plumes within the unsaturated and saturated zones.- Characterise and asses the local (and regional) geohydrologic regime for groundwater flow paterns, recharge areas and localised permeable pathways

    Coupled Geophysical and Hydrogeochemical Characterization of a Coastal Aquifer as Tool for a More Efficient Management (Torredembarra, Spain)

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    The aquifers of the Spanish Mediterranean coast are generally subjected to intense exploitationto meet the growing water supply demands. The result of the exploitation is salinizationdue to the marine saltwater intrusion, causing a deterioration in the quality of the water pumped,limiting its use for community needs, and not always being well delimited. To prevent deterioration,a groundwater control network usually allows precise knowledge of the areas affected by saltwaterintrusion but not the extent of the saline plumes. Moreover, the characterization of aquifer systemsrequires a model that defines the geometry of aquifer formations. For this objective, we integratedhydrogeological, hydrogeochemical, and electrical resistivity subsoil data to establish a hydrogeologicalmodel of the coastal aquifer of Torredembarra (Tarragona, NE Spain). In this research, wehave carried out a regional and local-scale study of the aquifer system to define the areas prone tobeing affected by saline intrusion (electrical resistivity values below 10 Wm). The obtained resultscould be used as a support tool for the assessment of the most favorable areas for groundwaterwithdrawal, as well as enabling the control and protection of the most susceptible areas to be affectedby saltwater intrusion.</p

    Constraints on the χ_(c1) versus χ_(c2) polarizations in proton-proton collisions at √s = 8 TeV

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    The polarizations of promptly produced χ_(c1) and χ_(c2) mesons are studied using data collected by the CMS experiment at the LHC, in proton-proton collisions at √s=8  TeV. The χ_c states are reconstructed via their radiative decays χ_c → J/ψγ, with the photons being measured through conversions to e⁺e⁻, which allows the two states to be well resolved. The polarizations are measured in the helicity frame, through the analysis of the χ_(c2) to χ_(c1) yield ratio as a function of the polar or azimuthal angle of the positive muon emitted in the J/ψ → μ⁺μ⁻ decay, in three bins of J/ψ transverse momentum. While no differences are seen between the two states in terms of azimuthal decay angle distributions, they are observed to have significantly different polar anisotropies. The measurement favors a scenario where at least one of the two states is strongly polarized along the helicity quantization axis, in agreement with nonrelativistic quantum chromodynamics predictions. This is the first measurement of significantly polarized quarkonia produced at high transverse momentum