1,834 research outputs found
La percepción pública de los políticos, los partidos y la política, y uso de medios de comunicación
La reputación de los políticos se ha reducido en muchos países, y en España se han convertido en el tercer problema más importante según los ciudadanos. La influencia de los medios de comunicación sobre este deterioro ha suscitado un interesante debate. Algunos autores atribuyen a los medios la responsabilidad principal del desprestigio; mientras que otros niegan la influencia directa negativa de los media. Este artículo, basado en una encuesta propia realizada en Navarra (España), investiga la relación entre la percepción pública de los políticos, los partidos políticos y la política, y el nivel de uso de los medios de difusión. El análisis de los datos permite concluir que el uso más intenso de los medios está asociado con percepciones menos negativas y más moderadas sobre políticos, partidos y política
High-pressure Raman spectroscopy and lattice-dynamics calculations on scintillating MgWO4: A comparison with isomorphic compounds
Raman scattering measurements and lattice-dynamics calculations have been
performed on magnesium tungstate under high pressure up to 41 GPa. Experiments
have been carried out under a selection of different pressure-media. The
influence of non-hydrostaticity on the structural properties of MgWO4 and
isomorphic compounds is examined. Under quasi-hydrostatic conditions a phase
transition has been found at 26 GPa in MgWO4. The high-pressure phase has been
tentatively assigned to a triclinic structure similar to that of CuWO4. We also
report and discuss the Raman symmetries, frequencies, and pressure coefficients
in the low- and high-pressure phases. In addition, the Raman frequencies for
different wolframites are compared and the variation of the mode frequency with
the reduced mass across the family is investigated. Finally, the accuracy of
theoretical calculations is systematically discussed for MgWO4, MnWO4, FeWO4,
CoWO4, NiWO4, ZnWO4, and CdWO4.Comment: 36 pages, 9 figures, 4 table
DIAGNÓSTICO DE INDICADORES DE CALIDAD FÍSICO-QUÍMICA DEL AGUA EN AFLUENTES DEL RÍO ATOYAC - DIAGNOSIS OF INDICATORS OF PHYSICAL-CHEMICAL QUALITY OF WATER IN AFFLUENTS OF THE ATOYAC RIVER
En la Región de Texmelucan, Pue., las principales fuentes de agua para riego provienen del deshielo de los volcanes y de pozos profundos; estas fuentes satisfacen las necesidades de agua del área agrícola de Texmelucan y sus alrededores. Sin embargo, alrededor de 350 productores también emplean aguas residuales para regar sus cultivos. Se evaluaron algunos parámetros que inciden en la calidad físico-química del agua cuando se utiliza con fines de riego (pH, CE, Ca2+, Mg2+, K+, PO42-, SO42-, CO32-, HCO3-, Na+, B y Cl-). Se realizó un muestreo aleatorio en 28 puntos, en afluentes del cauce del Río Atoyac, donde se tomaron muestras de agua para realizar el análisis físico-químico correspondiente. Los resultados muestran que la CE osciló entre 0 y 0.875 dS m-1; el 64.28% correspondió a aguas de baja salinidad y bajo contenido de sodio (clase C1S1), el 28.57% a aguas con salinidad media y bajo contenido de sodio (clase C2S1) y el 7.15% a aguas de salinidad alta y bajo contenido de sodio (clase C3S1). En promedio, el Ca (0.98 meq L-1) y Mg (1.11 meq L-1) estuvieron presentes en mayor concentración, lo que modificó favorablemente los valores de la relación de adsorción de sodio (RAS). Los iones bicarbonato (HCO3-) en el agua presentaron una media de 1.83 meq L-1. La concentración de Cl-, HCO3-, CO3-2, B y SO4-2 no ha afectado a los cultivos establecidos y la concentración de PO42- es un aporte significativo a los cultivos. Estos resultados indican que la región de Texmelucan, Pue., tiene agua apta para el riego desde el punto de vista físico-químico; sin considerar el contenido de metales pesados ni análisis biológicos de la misma
ATLAS silicon module assembly and qualification tests at IFIC Valencia
ATLAS experiment, designed to probe the interactions of particles emerging
out of proton proton collisions at energies of up to 14 TeV, will assume
operation at the Large Hadron Collider (LHC) at CERN in 2007. This paper
discusses the assembly and the quality control tests of forward detector
modules for the ATLAS silicon microstrip detector assembled at the Instituto de
Fisica Corpuscular (IFIC) in Valencia. The construction and testing procedures
are outlined and the laboratory equipment is briefly described. Emphasis is
given on the module quality achieved in terms of mechanical and electrical
stability.Comment: 23 pages, 38 EPS figures, uses JINST LaTeX clas
Forward SCT Module Assembly and Quality Control at IFIC Valencia
This note discusses the assembly and the quality control tests of 282 forward detector modules for the ATLAS Semiconductor Tracker assembled at the Instituto de Fisica Corpuscular (IFIC) in Valencia. The construction and testing procedures are outlined and the laboratory equipment is briefly described. Emphasis is given on the module quality achieved in terms of mechanical and electrical stability
Azimuthal asymmetry in the risetime of the surface detector signals of the Pierre Auger Observatory
The azimuthal asymmetry in the risetime of signals in Auger surface detector
stations is a source of information on shower development. The azimuthal
asymmetry is due to a combination of the longitudinal evolution of the shower
and geometrical effects related to the angles of incidence of the particles
into the detectors. The magnitude of the effect depends upon the zenith angle
and state of development of the shower and thus provides a novel observable,
, sensitive to the mass composition of cosmic rays
above eV. By comparing measurements with predictions from
shower simulations, we find for both of our adopted models of hadronic physics
(QGSJETII-04 and EPOS-LHC) an indication that the mean cosmic-ray mass
increases slowly with energy, as has been inferred from other studies. However,
the mass estimates are dependent on the shower model and on the range of
distance from the shower core selected. Thus the method has uncovered further
deficiencies in our understanding of shower modelling that must be resolved
before the mass composition can be inferred from .Comment: Replaced with published version. Added journal reference and DO
The Pierre Auger Observatory III: Other Astrophysical Observations
Astrophysical observations of ultra-high-energy cosmic rays with the Pierre
Auger ObservatoryComment: Contributions to the 32nd International Cosmic Ray Conference,
Beijing, China, August 201
Measurement of the Depth of Maximum of Extensive Air Showers above 10^18 eV
We describe the measurement of the depth of maximum, Xmax, of the
longitudinal development of air showers induced by cosmic rays. Almost four
thousand events above 10^18 eV observed by the fluorescence detector of the
Pierre Auger Observatory in coincidence with at least one surface detector
station are selected for the analysis. The average shower maximum was found to
evolve with energy at a rate of (106 +35/-21) g/cm^2/decade below 10^(18.24 +/-
0.05) eV and (24 +/- 3) g/cm^2/decade above this energy. The measured
shower-to-shower fluctuations decrease from about 55 to 26 g/cm^2. The
interpretation of these results in terms of the cosmic ray mass composition is
briefly discussed.Comment: Accepted for publication by PR
A search for point sources of EeV photons
Measurements of air showers made using the hybrid technique developed with
the fluorescence and surface detectors of the Pierre Auger Observatory allow a
sensitive search for point sources of EeV photons anywhere in the exposed sky.
A multivariate analysis reduces the background of hadronic cosmic rays. The
search is sensitive to a declination band from -85{\deg} to +20{\deg}, in an
energy range from 10^17.3 eV to 10^18.5 eV. No photon point source has been
detected. An upper limit on the photon flux has been derived for every
direction. The mean value of the energy flux limit that results from this,
assuming a photon spectral index of -2, is 0.06 eV cm^-2 s^-1, and no celestial
direction exceeds 0.25 eV cm^-2 s^-1. These upper limits constrain scenarios in
which EeV cosmic ray protons are emitted by non-transient sources in the
Galaxy.Comment: 28 pages, 10 figures, accepted for publication in The Astrophysical
Journa
Reconstruction of inclined air showers detected with the Pierre Auger Observatory
We describe the method devised to reconstruct inclined cosmic-ray air showers
with zenith angles greater than detected with the surface array of
the Pierre Auger Observatory. The measured signals at the ground level are
fitted to muon density distributions predicted with atmospheric cascade models
to obtain the relative shower size as an overall normalization parameter. The
method is evaluated using simulated showers to test its performance. The energy
of the cosmic rays is calibrated using a sub-sample of events reconstructed
with both the fluorescence and surface array techniques. The reconstruction
method described here provides the basis of complementary analyses including an
independent measurement of the energy spectrum of ultra-high energy cosmic rays
using very inclined events collected by the Pierre Auger Observatory.Comment: 27 pages, 19 figures, accepted for publication in Journal of
Cosmology and Astroparticle Physics (JCAP
- …