338 research outputs found
Los documentales cientÃficos como instrumentos de formación ciudadana para hacer frente a la situación de emergencia planetaria
El propósito de este trabajo es presentar los primeros resultados de una investigación en torno a la atención prestada por la educación cientÃfica al uso de los documentales en las clases de ciencias y, en particular, para dar a conocer la actual situación de emergencia planetaria y promover la implicación en la construcción de un futuro sostenible. Con ese objeto hemos estudiado la atención prestada por la educación cientÃfica a los documentales, mediante una búsqueda exhaustiva en veinte revistas de educación cientÃfica a lo largo de los diez últimos años. Asà mismo, hemos analizado el contenido de 42 documentales cientÃficos de amplia difusión. Los resultados muestran un escaso aprovechamiento de los documentales en la enseñanza, pero, a la vez, una notable potencialidad para incorporar las relaciones CTSA y, muy concretamente, la problemática de la sostenibilidad
Integral equation mei applied to three-dimensional arbitrary surfaces
The authors present a new formulation of the integral equation of the measured equation of invariance (MEI) as a confined field integral equation discretised by the method of moments, in which the use of numerically derived testing functions results in an approximately sparse linear system with storage memory requirements and a CPU time for computing the matrix coefficients proportional to the number of unknowns.Peer ReviewedPostprint (published version
The young stellar population of NGC 4214 as observed with HST. I. Data and methods
We present the data and methods that we have used to perform a detailed
UV-optical study of the nearby dwarf starburst galaxy NGC 4214 using
multifilter HST/WFPC2+STIS photometry. We explain the process followed to
obtain high-quality photometry and astrometry of the stellar and cluster
populations of this galaxy. We describe the procedure used to transform
magnitudes and colors into physical parameters using spectral energy
distributions. The data show the existence of both young and old stellar
populations that can be resolved at the distance of NGC 4214 (2.94 Mpc) and we
perform a general description of those populations.Comment: 33 pages, 9 figures, and 8 table
Biosensors in Rehabilitation and Assistance Robotics
Robotic developments in the field of rehabilitation and assistance have seen a significant increase in the last few years [...
Migration of mineral oil aromatic hydrocarbons (MOAH) from cardboard containers to dry food and prediction tool
This research aimed to study the migration of mineral oil aromatic hydrocarbons (MOAH) from primary carton packages to dry foods, using 16 aromatic hydrocarbons as model substances, covering a wide range of molecular masses and chemical structures. Migration experiments were performed using modified polyphenylene oxide as a food simulant and couscous and polenta as dry foods. The migration tests were carried out to simulate storage at room temperature for long periods and in hot food containers as the worst scenario. Multivariate analysis algorithms were applied to correlate and group the migration of model substances, and a partial least squares regression (PLSR) model was built to predict the worst-case migration. The results showed strong correlations in the migration patterns of the model substances, based on their volatility, food matrix, migration time and temperature. Different behaviour between the migration of the most volatile and the heaviest model substances was observed
The ACS Nearby Galaxy Survey Treasury VII. The NGC 4214 Starburst and the Effects of Star Formation History on Dwarf Morphology
We present deep Hubble Space Telescope Wide Field Planetary Camera 2 (WFPC2)
optical observations obtained as part of the ACS Nearby Galaxy Survey Treasury
(ANGST) as well as early release Wide Field Camera 3 (WFC3) ultra-violet and
infrared observations of the nearby dwarf starbursting galaxy NGC 4214. Our
data provide a detailed example of how covering such a broad range in
wavelength provides a powerful tool for constraining the physical properties of
stellar populations. The deepest data reach the ancient red clump at M_F814W
-0.2. All of the optical data reach the main sequence turnoff for stars younger
than ~300 Myr, and the blue He burning sequence for stars younger than 500 Myr.
The full CMD-fitting analysis shows that all three fields in our data set are
consistent with ~75% of the stellar mass being older than 8 Gyr, in spite of
showing a wide range in star formation rates at the present day. Thus, our
results suggest that the scale length of NGC 4214 has remained relatively
constant for many Gyr. As previously noted by others, we also find the galaxy
has recently ramped up production, consistent with its bright UV luminosity and
its population of UV-bright massive stars. In the central field we find UV
point sources with F336W magnitudes as bright as -9.9. These are as bright as
stars with masses of at least 52-56 M_sun and ages near 4 Myr in stellar
evolution models. Assuming a standard IMF, our CMD is well-fitted by an
increase in star formation rate beginning 100 Myr ago. The stellar populations
of this late-type dwarf are compared with those of NGC 404, an early-type dwarf
that is also the most massive galaxy in its local environment. The late-type
dwarf appears to have a similar high fraction of ancient stars, suggesting that
these dominant galaxies may form at early epochs even if they have low total
mass and very different present-day morphologies.Comment: 17 pages, 10 figures, accepted for publication in Ap
Stable cycling in quasi-linkage equilibrium:fluctuating dynamics under gene conversion and selection
Genetic systems with multiple loci can have complex dynamics. For example,
mean fitness need not always increase and stable cycling is possible. Here, we
study the dynamics of a genetic system inspired by the molecular biology of
recognition-dependent double strand breaks and repair as it happens in
recombination hotspots. The model shows slow-fast dynamics in which the system
converges to the quasi-linkage equilibrium (QLE) manifold. On this manifold,
sustained cycling is possible as the dynamics approach a heteroclinic cycle, in
which allele frequencies alternate between near extinction and near fixation.
We find a closed-form approximation for the QLE manifold and use it to simplify
the model. For the simplified model, we can analytically calculate the
stability of the heteroclinic cycle. In the discrete-time model the cycle is
always stable; in a continuous-time approximation, the cycle is always
unstable. This demonstrates that complex dynamics are possible under
quasi-linkage equilibrium.Comment: 35 pages, 6 figure
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