437 research outputs found
Identifying eroded Messinian deposits on the Maltese Islands by gypsum Sr isotopes
International audienceEvaporite sediments are known to have formed during the Messinian high salinity crisis that has been recognized in many Mediterranean areas. This event was however never identified on the Maltese Islands. In this study, a Sr isotopic characterization of gypsum, found as secondary minerals in the Oligocene-Miocene formations of Malta and Gozo is performed. The 87Sr/86Sr values are discussed on the basis of comparison with the surrounding rock Sr isotopic signature. The data outline two distinguishable 87Sr/86Sr ratios for gypsum according to their facies. Most of crack-infilling mineral data suggest a downward fluid circulation in the Miocene sediment associated with interaction in the currently outcropping limestones. Some gypsum crystals found as crystallized spherules show significantly lower 87Sr/86Sr ratios, close to those defined in the literature for Messinian evaporate sediments. Taken together, this may suggest that an evaporate formation of Messinian age had in the past covered the present-day sedimentary sequence in Malta and Gozo
Production of topological defects at the end of inflation
Hybrid inflation within supersymmetric grand unified theories, as well as
inflation through brane collisions within braneworld cosmological models, lead
to the formation of one-dimensional defects. Observational data, mainly from
the cosmic microwave background temperature anisotropies but also from the
gravitational wave background, impose constraints on the free parameters of the
models. I review these inflationary models and discuss the constraints from the
currently available data.Comment: 9 pages, Invited talk in the Conference "Challenges in Particle
Astrophysics" -- 6th Rencontres du Vietnam, Hanoi (Vietnam) 6-12 Aug. 200
Fundamentation, design and validation of a questionnaire: “Profile of the university student in research training”
La formación investigativa es un proceso sistematizado que involucra prácticas y actores diversos en la
adquisición y desarrollo de competencias de investigación. El objetivo del artículo es explicar la fundamentación teórica,
diseño y validación un instrumento de medición en Instituciones de Educación Superior Veracruzanas. Dentro del presente
se describe lo siguiente: 1) La introducción del documento; 2) El estado del arte sobre las competencias de investigación
de los estudiantes en educación superior y su participación en las actividades relacionadas con la investigación; 3) Diseño
del instrumento con su respectiva matriz de operacionalización; 4) Validación del instrumento propuesto, que incluye su
piloteo y juicio por expertos. Durante el proceso de validación participaron 74 estudiantes universitarios voluntarios de
diversos semestres. Los materiales utilizados fueron: formatos de consentimiento, así como un cuestionario
autoadministrado diseñado en google forms. Como parte de los resultados, se confirmó la fundamentación, diseño, validez
de contenido y confiabilidad del instrumento de medición. Para fortalecer el instrumento se propone una segunda prueba
pilotoResearch training is a systematized process that involves diverse practices and actors in the acquisition
and development of research skills. The objective of the article is to explain the theoretical foundation, design and
validation of a measuring instrument in Veracruzanas Higher Education Institutions. The following describes: 1) The
introduction of the document; 2) The state of the art on the research competencies of students in higher education and
their participation in research-related activities; 3) Design of the instrument with its respective operationalization matrix;
4) Validation of the proposed instrument, which includes its piloting and trial by experts. During the validation process, 74
voluntary university students from different semesters participated. The materials used were: consent formats, as well as
a self-administered questionnaire designed in google forms. As part of the results, the rationale, design, content validity and
reliability of the measuring instrument were confirmed. To strengthen the instrument, a second pilot test is propose
Constraints on Supersymmetric Grand Unified Theories from Cosmology
Within the context of SUSY GUTs, cosmic strings are generically formed at the
end of hybrid inflation. However, the WMAP CMB measurements strongly constrain
the possible cosmic strings contribution to the angular power spectrum of
anisotropies. We investigate the parameter space of SUSY hybrid (F- and D-
term) inflation, to get the conditions under which theoretical predictions are
in agreement with data. The predictions of F-term inflation are in agreement
with data, only if the superpotential coupling is small. In
particular, for SUSY SO(10), the upper bound is \kappa\lsim 7\times 10^{-7}.
This fine tuning problem can be lifted if we employ the curvaton mechanism, in
which case \kappa\lsim 8\times 10^{-3}; higher values are not allowed by the
gravitino constraint. The constraint on is equivalent to a constraint
on the SSB mass scale , namely M \lsim 2\times 10^{15} GeV. The study of
D-term inflation shows that the inflaton field is of the order of the Planck
scale; one should therefore consider SUGRA. We find that the cosmic strings
contribution to the CMB anisotropies is not constant, but it is strongly
dependent on the gauge coupling and on the superpotential coupling
. We obtain g\lsim 2\times 10^{-2} and \lambda \lsim 3\times
10^{-5}. SUGRA corrections induce also a lower limit for .
Equivalently, the Fayet-Iliopoulos term must satisfy \sqrt\xi \lsim
2\times 10^{15} GeV. This constraint holds for all allowed values of .Comment: 32 pages, 7 figures. To match published versio
Scalar Multiplet Dark Matter
We perform a systematic study of the phenomenology associated to models where
the dark matter consists in the neutral component of a scalar SU(2)_L n-uplet,
up to n=7. If one includes only the pure gauge induced annihilation
cross-sections it is known that such particles provide good dark matter
candidates, leading to the observed dark matter relic abundance for a
particular value of their mass around the TeV scale. We show that these values
actually become ranges of values -which we determine- if one takes into account
the annihilations induced by the various scalar couplings appearing in these
models. This leads to predictions for both direct and indirect detection
signatures as a function of the dark matter mass within these ranges. Both can
be largely enhanced by the quartic coupling contributions. We also explain how,
if one adds right-handed neutrinos to the scalar doublet case, the results of
this analysis allow to have altogether a viable dark matter candidate,
successful generation of neutrino masses, and leptogenesis in a particularly
minimal way with all new physics at the TeV scale.Comment: 43 pages, 20 figure
Supergravity based inflation models: a review
In this review, we discuss inflation models based on supergravity. After
explaining the difficulties in realizing inflation in the context of
supergravity, we show how to evade such difficulties. Depending on types of
inflation, we give concrete examples, particularly paying attention to chaotic
inflation because the ongoing experiments like Planck might detect the tensor
perturbations in near future. We also discuss inflation models in Jordan frame
supergravity, motivated by Higgs inflation.Comment: 30 pages, invited review for Classical and Quantum Gravity, published
versio
Aquatic Organic Matter in the Seine Basin: Sources, Spatio-Temporal Variability, Impact of Urban Discharges and Influence on Micro-pollutant Speciation
International audienc
The astrometric Gaia-FUN-SSO observation campaign of 99 942 Apophis
Astrometric observations performed by the Gaia Follow-Up Network for Solar
System Objects (Gaia-FUN-SSO) play a key role in ensuring that moving objects
first detected by ESA's Gaia mission remain recoverable after their discovery.
An observation campaign on the potentially hazardous asteroid (99 942) Apophis
was conducted during the asteroid's latest period of visibility, from
12/21/2012 to 5/2/2013, to test the coordination and evaluate the overall
performance of the Gaia-FUN-SSO . The 2732 high quality astrometric
observations acquired during the Gaia-FUN-SSO campaign were reduced with the
Platform for Reduction of Astronomical Images Automatically (PRAIA), using the
USNO CCD Astrograph Catalogue 4 (UCAC4) as a reference. The astrometric
reduction process and the precision of the newly obtained measurements are
discussed. We compare the residuals of astrometric observations that we
obtained using this reduction process to data sets that were individually
reduced by observers and accepted by the Minor Planet Center. We obtained 2103
previously unpublished astrometric positions and provide these to the
scientific community. Using these data we show that our reduction of this
astrometric campaign with a reliable stellar catalog substantially improves the
quality of the astrometric results. We present evidence that the new data will
help to reduce the orbit uncertainty of Apophis during its close approach in
2029. We show that uncertainties due to geolocations of observing stations, as
well as rounding of astrometric data can introduce an unnecessary degradation
in the quality of the resulting astrometric positions. Finally, we discuss the
impact of our campaign reduction on the recovery process of newly discovered
asteroids.Comment: Accepted for publication in A&
Lactate Regulates Metabolic and Proinflammatory Circuits in Control of T Cell Migration and Effector Functions
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