320 research outputs found
Near UV-Blue Excitable Green-Emitting Nanocrystalline Oxide
Green-emitting Eu-activated powders were produced by a two-stage method consisting of pressure-assisted combustion synthesis and postannealing in ammonia. The as-synthesized powders exhibited a red photoluminescence (PL) peak located at λ = 616 nm when excited with λ = 395 nm UV. This emission peak corresponds to the 5 D 0 → 7 F 2 transition in Eu 3+ . After annealing in ammonia, the PL emission changed to an intense broad-band peak centered at λ = 500 nm, most likely produced by 4f 6 5d 1 → 4f 7 electronic transitions in Eu 2+ . This green-emitting phosphor has excitation band in the near UV-blue region (λ = 300-450 nm). Xray diffraction analysis reveals mainly the orthorhombic EuAlO 3 and Al 2 O 3 phases. Transmission electron microscopy observations showed that the grains are formed by faceted nanocrystals (∼4 nm) of polygonal shape. The excellent excitation and emission properties make these powders very promising to be used as phosphors in UV solid-state diodes coupled to activate white-emitting lamps
Estimación de la mortalidad atribuible a gripe estacional en España. Temporadas 1980-2008.
El objetivo de este estudio es estimar los excesos de mortalidad atribuibles a gripe estacional por grupos de edad, durante el período 1980-2008 en España, según las causas de mortalidad por "gripe y neumonía", "circulatorias y respiratorias" o "todas las causas". Se aplicó un modelo de regresión cíclica (Serfling modificado) a los datos de mortalidad obtenidos del Instituto Nacional de Estadística (INE), estimándose los excesos de defunciones mensuales atribuidas a gripe en períodos de circulación viral, con respecto a un nivel basal de mortalidad esperada en ausencia de actividad gripal, para los grupos de causas y de edad planteados. Para todas las temporadas y grupos de causas, más del 90% de los excesos de defunciones atribuibles a gripe estacional se produjeron en el grupo de mayores de 64 años. Se estimó una tasa media anual de excesos de defunciones por gripe y neumonía de 2,68 (IC 95%: 2,65; 2,71) defunciones/100.000 habitantes
Effect of Ni on MCM-41 in the Adsorption of Nitrogen and Sulfur Compounds to Obtain Ultra-Low-Sulfur Diesel
Adsorption of heterocyclic sulfur and nitrogen compounds like dibenzothiophene (DBT) and quinoline (Q), respectively, was carried out using mesostructured adsorbent MCM-41 and Ni/MCM-41 in calcined (C) and reduced (R) form. These materials were proved in a batch adsorption system using a model fuel diesel: a mixture of dodecane, DBT and Q with the same concentrations of ppmw of sulfur and nitrogen at 313 K and atmospheric pressure. When MCM-41 was impregnated with Ni, an important modification of the adsorption properties was observed, for example, the uptake of DBT was increased and this adsorption was twice in Ni/MCM-41 in reduce form than in the calcined form. On the other hand, for the nitrogen adsorption of Q diminished by 62 and 58%, considering Ni/MCM-41 in reduce form and in calcined form as adsorbent, respectively. This is a significant achievement regarding the desulfurization and denitrogenation, especially for commercial diesel without pretreatment. Moreover, the kinetic results were adjusted with second order considering Q as nitrogen and DBT as sulfur molecule. Data fitting for Q was achieved better by the Langmuir model for all materials than the Freundlich model, meanwhile the experimental adsorption data of DBT was fitted to the Freundlich model for Ni/MCM-41 calcinated and reduced form
Plan de Erradicación de la Poliomielitis. Vigilancia de Parálisis Flácida Aguda. España, 2013
Pese a los enormes avances conseguidos hacia la erradicación mundial de la poliomielitis, aún quedan tres países con circulación endémica de poliovirus salvaje y brotes de polio paralítica en áreas previamente libres de polio, como Siria y varios países de África. Debido a esto la Organización Mundial de la salud (OMS) ha declarado que la extensión internacional de la transmisión del poliovirus
salvaje, es un Evento de Salud Pública de Importancia Internacional (ESPII) y que para su control se necesita una repuesta internacional coordinada.
En las zonas del mundo ya declaradas libres de polio (Europa 2002) hay que asegurar altos niveles de inmunidad en la población, mantener sistemas de vigilancia eficaces y planes nacionales de respuesta capaces de interrumpir la transmisión tras una eventual importación del virus de la polio. Además, en una situación de dispersión internacional, la vacunación y el control de viajeros procedentes de zonas del mundo con casos de polio cobra especial importancia.
En este contexto y debido al flujo de personas entre España y zonas el mundo donde hay circulación de poliovirus, no se puede descartar la reintroducción del virus en nuestro país. Aunque las altas coberturas de vacunación reducen el riesgo de transmisión, hay que mantener activos los sistemas de vigilancia de poliovirus, particularmente la vigilancia de PFA, para poder identificar
importaciones y establecer a tiempo medidas de control
Stellar populations of galaxies in the ALHAMBRA survey up to . II. Stellar content of quiescent galaxies within the dust-corrected stellar masscolour and the colourcolour diagrams
Our aim is to determine the distribution of stellar population parameters
(extinction, age, metallicity, and star formation rate) of quiescent galaxies
within the rest-frame stellar masscolour and colourcolour diagrams
corrected for extinction up to . These novel diagrams reduce the
contamination in samples of quiescent galaxies owing to dust-reddened galaxies,
and they provide useful constraints on stellar population parameters. We set
constraints on the stellar population parameters of quiescent galaxies
combining the ALHAMBRA multi-filter photo-spectra with our SED-fitting code
MUFFIT, making use of composite stellar population models. The extinction
obtained by MUFFIT allowed us to remove dusty star-forming (DSF) galaxies from
the sample of red galaxies. The distributions of stellar population
parameters across these rest-frame diagrams are revealed after the dust
correction and are fitted by the LOESS method to reduce uncertainty effects.
Quiescent galaxy samples defined via classical diagrams are typically
contaminated by a % fraction of DSF galaxies. A significant part of the
galaxies in the green valley are actually obscured star-forming galaxies
(%). Consequently, the transition of galaxies from the blue cloud to
the red sequence, and hence the related mechanisms for quenching, seems to be
much more efficient and faster than previously reported. The rest-frame stellar
masscolour and colourcolour diagrams are useful for constraining
the age, metallicity, extinction, and star formation rate of quiescent galaxies
by only their redshift, rest-frame colours, and/or stellar mass. Dust
correction plays an important role in understanding how quiescent galaxies are
distributed in these diagrams and is key to performing a pure selection of
quiescent galaxies via intrinsic colours.Comment: (37 pages, 29 figures, accepted for publication in A&A
Considerations for COVID-19 management in reception centers for refugees, asylum seekers, and migrants, Spain 2020
Shortly after the declaration of the COVID-19 pandemic, governments around the world were urged to leave no population behind. Following a COVID-19 risk evaluation in a refugee and asylum seekers reception center, in September 2020, we considered the priorities of managing COVID-19 in these settings. We encourage actions on four fronts to reduce the COVID-19 associated burden amongst these vulnerable populations based on our interviews, observations and recommendations: (i) decongestion, (ii) facilitated testing, (iii) screening for symptoms and (iv) targeted public health and risk communication.S
The ALHAMBRA survey: evolution of galaxy spectral segregation
We study the clustering of galaxies as a function of spectral type and
redshift in the range using data from the Advanced Large
Homogeneous Area Medium Band Redshift Astronomical (ALHAMBRA) survey. The data
cover 2.381 deg in 7 fields, after applying a detailed angular selection
mask, with accurate photometric redshifts [] down to
. From this catalog we draw five fixed number density,
redshift-limited bins. We estimate the clustering evolution for two different
spectral populations selected using the ALHAMBRA-based photometric templates:
quiescent and star-forming galaxies. For each sample, we measure the real-space
clustering using the projected correlation function. Our calculations are
performed over the range Mpc, allowing us to find a
steeper trend for Mpc, which is especially clear for
star-forming galaxies. Our analysis also shows a clear early differentiation in
the clustering properties of both populations: star-forming galaxies show
weaker clustering with evolution in the correlation length over the analysed
redshift range, while quiescent galaxies show stronger clustering already at
high redshifts, and no appreciable evolution. We also perform the bias
calculation where similar segregation is found, but now it is among the
quiescent galaxies where a growing evolution with redshift is clearer. These
findings clearly corroborate the well known colour-density relation, confirming
that quiescent galaxies are mainly located in dark matter halos that are more
massive than those typically populated by star-forming galaxies.Comment: 14 pages, 9 figures, accepted by Ap
The ALHAMBRA survey: Accurate merger fractions by PDF analysis of photometric close pairs
Our goal is to develop and test a novel methodology to compute accurate close
pair fractions with photometric redshifts. We improve the current methodologies
to estimate the merger fraction f_m from photometric redshifts by (i) using the
full probability distribution functions (PDFs) of the sources in redshift
space, (ii) including the variation in the luminosity of the sources with z in
both the selection of the samples and in the luminosity ratio constrain, and
(iii) splitting individual PDFs into red and blue spectral templates to deal
robustly with colour selections. We test the performance of our new methodology
with the PDFs provided by the ALHAMBRA photometric survey. The merger fractions
and rates from the ALHAMBRA survey are in excellent agreement with those from
spectroscopic work, both for the general population and for red and blue
galaxies. With the merger rate of bright (M_B <= -20 - 1.1z) galaxies evolving
as (1+z)^n, the power-law index n is larger for blue galaxies (n = 2.7 +- 0.5)
than for red galaxies (n = 1.3 +- 0.4), confirming previous results.
Integrating the merger rate over cosmic time, we find that the average number
of mergers per galaxy since z = 1 is N_m = 0.57 +- 0.05 for red galaxies and
N_m = 0.26 +- 0.02 for blue galaxies. Our new methodology exploits
statistically all the available information provided by photometric redshift
codes and provides accurate measurements of the merger fraction by close pairs
only using photometric redshifts. Current and future photometric surveys will
benefit of this new methodology.Comment: Submitted to A&A, 15 pages, 15 figures, 6 tables. Comments are
welcome. Close pair systems available at
https://cloud.iaa.csic.es/alhambra/catalogues/ClosePairs
The ALHAMBRA survey : Estimation of the clustering signal encoded in the cosmic variance
The relative cosmic variance () is a fundamental source of
uncertainty in pencil-beam surveys and, as a particular case of count-in-cell
statistics, can be used to estimate the bias between galaxies and their
underlying dark-matter distribution. Our goal is to test the significance of
the clustering information encoded in the measured in the ALHAMBRA
survey. We measure the cosmic variance of several galaxy populations selected
with band luminosity at as the intrinsic dispersion in
the number density distribution derived from the 48 ALHAMBRA subfields. We
compare the observational with the cosmic variance of the dark
matter expected from the theory, . This provides an
estimation of the galaxy bias . The galaxy bias from the cosmic variance is
in excellent agreement with the bias estimated by two-point correlation
function analysis in ALHAMBRA. This holds for different redshift bins, for red
and blue subsamples, and for several band luminosity selections. We find
that increases with the band luminosity and the redshift, as expected
from previous work. Moreover, red galaxies have a larger bias than blue
galaxies, with a relative bias of . Our results
demonstrate that the cosmic variance measured in ALHAMBRA is due to the
clustering of galaxies and can be used to characterise the affecting
pencil-beam surveys. In addition, it can also be used to estimate the galaxy
bias from a method independent of correlation functions.Comment: Astronomy and Astrophysics, in press. 9 pages, 4 figures, 3 table
The ALHAMBRA survey : band luminosity function of quiescent and star-forming galaxies at by PDF analysis
Our goal is to study the evolution of the band luminosity function (LF)
since using ALHAMBRA data. We used the photometric redshift and the
band selection magnitude probability distribution functions (PDFs) of those
ALHAMBRA galaxies with mag to compute the posterior LF. We
statistically studied quiescent and star-forming galaxies using the template
information encoded in the PDFs. The LF covariance matrix in
redshift-magnitude-galaxy type space was computed, including the cosmic
variance. That was estimated from the intrinsic dispersion of the LF
measurements in the 48 ALHAMBRA sub-fields. The uncertainty due to the
photometric redshift prior is also included in our analysis. We modelled the LF
with a redshift-dependent Schechter function affected by the same selection
effects than the data. The measured ALHAMBRA LF at and the
evolving Schechter parameters both for quiescent and star-forming galaxies
agree with previous results in the literature. The estimated redshift evolution
of is and , and of is
and . The measured faint-end slopes are and . We find a significant
population of faint quiescent galaxies, modelled by a second Schechter function
with slope . We find a factor decrease in the
luminosity density of star-forming galaxies, and a factor
increase in the of quiescent ones since , confirming the continuous
build-up of the quiescent population with cosmic time. The contribution of the
faint quiescent population to increases from 3% at to 6% at .
The developed methodology will be applied to future multi-filter surveys such
as J-PAS.Comment: Accepted for publication in Astronomy and Astrophysics. 25 pages, 20
figures, 7 table
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